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 9780203757451, 0203757459

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ENGINE OILS AND AUTOMOTIVE LUBRICATION

MECHANICAL ENGINEERING A Series of Textbooks and Reference Books

Editor

L. L. Faulkner Columbus Division, Battelle Memorial Institute and Department o f Mechanical Engineering The Ohio State University Columbus, Ohio

1. 2. 3. 4. 5. 6. 7. 8.

9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.

Spring Designer’s Handbook, Harold Carlson Computer-Aided Graphics and Design, Daniel L. Ryan Lubrication Fundamentals, J. George Wills Solar Engineering for Domestic Buildings, William A. Himmelman Applied Engineering Mechanics: Statics and Dynamics, G. Boothroyd and C. Poli Centrifugal Pump Clinic, Igor J. Karassik Computer-Aided Kinetics for Machine Design, Daniel L. Ryan Plastics Products Design Handbook, Part A : Materials and Compo­ nents; Part B: Processes and Design for Processes, edited by Edward Miller Turbomachinery: Basic Theory and Applications, EarlLogan, Jr. Vibrations o f Shells and Plates, Werner Soedel Flat and Corrugated Diaphragm Design Handbook, Mario Di Giovanni Practical Stress Analysis in Engineering Design, Alexander Blake An Introduction to the Design and Behavior of Bolted Joints, John H. Bickford Optimal Engineering Design: Principles and Applications, James N. Siddall Spring Manufacturing Handbook, Harold Carlson Industrial Noise Control: Fundamentals and Applications,edited by Lewis H. Bell Gears and Their Vibration: A Basic Approach to Understanding Gear Noise, J. Derek Smith Chains for Power Transmission and Material Handling: Design and Applications Handbook, American Chain Association Corrosion and Corrosion Protection Handbook, edited by Philip A. Schweitzer

20. Gear Drive Systems: Design and Application, Peter Lynwander 21. Controlling In-Plant Airborne Contaminants: Systems Design and Calculations, John D. Constance 22. CAD/CAM Systems Planning and Implementation, Charles S. Knox 23. Probabilistic Engineering Design: Principles and Applications, James N. Siddail 24. Traction Drives: Selection and Application, Frederick W. Heilich III and Eugene E. Shube 25. Finite Element Methods: An Introduction, Ronald L. Huston and Chris E. Passerello 26. Mechanical Fastening of Plastics: An Engineering Handbook, Brayton Lincoln, Kenneth J. Gomes, and James F. Braden 27. Lubrication in Practice: Second Edition, edited by W. S. Robertson 28. Principles of Automated Drafting, Daniel L. Ryan 29. Practical Seal Design, edited by Leonard J. Martini 30. Engineering Documentation for CAD/CAM Applications, Charles S. Knox 31. Design Dimensioning with Computer Graphics Applications, Jerome C. Lange 32. Mechanism Analysis: Simplified Graphical and Analytical Tech­ niques, Lyndon 0 . Barton 33. CAD/CAM Systems: Justification, Implementation, Productivity Measurement, Edward J. Preston, George W. Crawford, and Mark E. Coticchia 34. Steam Plant Calculations Manual, V. Ganapathy 35. Design Assurance for Engineers and Managers, John A. Burgess 36. Heat Transfer Fluids and Systems for Process and Energy Applications, Jasbir Singh 37. Potential Flows: Computer Graphic Solutions, Robert H. Kirchhoff 38. Computer-Aided Graphics and Design: Second Edition, Daniel L. Ryan 39. Electronically Controlled Proportional Valves: Selection and Appli­ cation, Michael J. Tonyan, edited by Tobi Goldoftas 40. Pressure Gauge Handbook, AMETEK, U.S. Gauge Division, edited by Philip W. Harland 41. Fabric Filtration for Combustion Sources: Fundamentals and Basic Technology, R. P. Donovan 42. Design of Mechanical Joints, Alexander Blake 43. CAD/CAM Dictionary, Edward J. Preston, George W. Crawford, and Mark E. Coticchia 44. Machinery Adhesives for Locking, Retaining, and Sealing, Girard S. Haviland 45. Couplings and Joints: Design Selection, and Application, Jon R. Mancuso

46. Shaft Alignment Handbook, John Piotrowski 47. BASIC Programs for Steam Plant Engineers: Boilers, Combustion, Fluid Flow, and Heat Transfer, V. Ganapathy 48. Solving Mechanical Design Problems with Computer Graphics, Jerome C. Lange

49. 50. 51. 52.

53. 54. 55.

56. 57. 58. 59. 60.

61. 62. 63. 64. 65. 66. 67. 68.

Plastics Gearing: Selection and Application, Clifford E. Adams Clutches and Brakes: Design and Selection, William C. Orthwein Transducers in Mechanical and Electronic Design, Harry L. Trietley Metallurgical Applications o f Shock-Wave and High-Strain-Rate Phenomena, edited by Lawrence E. Murr, Karl P. Staudhammer, and Marc A. Meyers Magnesium Products Design, Robert S. Busk How to Integrate CAD/CAM Systems: Management and Technol­ ogy, William D. Engelke Cam Design and Manufacture: Second Edition; with cam design software for the IBM PC and compatibles, disk included, Preben W. Jensen Solid-State A C Motor Controls: Selection and Application, Sylves­ ter Campbell Fundamentals of Robotics, David D. Ardayfio Belt Selection and Application for Engineers, edited by Wallace D. Erickson Developing Three-Dimensional CAD Software with the IBM PC, C. Stan Wei Organizing Data for CIM Applications, Charles S. Knox, with contributions by Thomas C. Boos, Ross S. Culverhouse, and Paul F. Muchnicki Computer-Aided Simulation in Railway Dynamics, by Rao V. Dukkipati and Joseph R. Amyot Fiber-Reinforced Composites: Materials, Manufacturing, and De­ sign, P. K. Mallick Photoelectric Sensors and Controls: Selection and Application, Scott M. Juds Finite Element Analysis with Personal Computers, Edward R. Champion, Jr., and J. Michael Ensminger Ultrasonics: Fundamentals, Technology, Applications: Second Edition, Revised and Expanded, Dale Ensminger Applied Finite Element Modeling: Practical Problem Solving for Engineers, Jeffrey M. Steele Measurement and Instrumentation in Engineering: Principles and Basic Laboratory Experiments, Francis S. Tse and Ivan E. Morse Centrifugal Pump Clinic: Second Edition, Revised and Expanded, Igor J. Karassik

69. Practical Stress Analysis in Enineering Design: Second Edition, Revised and Expanded, Alexander Blake 70. An Introduction to the Deisgn and Behavior o f Bolted Joints: Second Edition, Revised and Expanded, John H. Bickford 71. High Vacuum Technology: A Practical Guide, Marsbed H. Hablanian 72. Pressure Sensors: Selection and Application, Duane Tandeske 73. Zinc Handbook: Properties, Processing, and Use in Design, Frank Porter 74. Thermal Fatigue of Metals, Andrzej Weronski and Tadeuz Hejwowski 75. Classical and Modern Mechanisms for Engineers and Inventors, Preben W. Jensen 76. Handbook o f Electronic Package Design, edited by Michael Pecht 77. Shock-Wave and High-Strain-Rate Phenomena in Materials, edited by Marc A. Meyers, Lawrence E. Murr, and Karl P. Staudhammer 78. Industrial Refrigeration: Principles, Design and Applications, P. C. Koelet 79. Applied Combustion, Eugene L. Keating 80. Engine Oils and Automotive Lubrication, edited by Wilfried J. Bartz

Additional Volumes in Preparation

Mechanical Engineering Software Spring Design with an IBM PC, Al Dietrich Mechanical Design Failure Analysis: With Failure Analysis System Software for the IBM PC, David G. Ullman

ENGINE OILS AND AUTOMOTIVE LUBRICATION EDITED BX

WILFRIED J. BARTZ Technische Akademie Esslingen Ostfildern, Germany

CRC Press T a y lo r &. Francis G ro u p

Boca Raton London New York CRC Press is an im p rin t o f th e Taylor & Francis G roup, an in fo rm a business

C R C P ress Taylor & F ra n cis G ro u p 6 0 0 0 B roken S o u n d Parkw ay N W , S u ite 300 B oca R aton, FL 33487-2742 © 1993 by Taylor & F ra n cis G ro u p , LLC C R C P re ss is a n im p r in t o f T ay lo r & F ra n cis G ro u p , a n I n fo rm a b u sin e ss N o c la im t o o rig in a l U.S. G o v e rn m e n t w o rk s T h is b o o k c o n ta in s in fo rm a tio n o b ta in e d fro m a u th e n tic a n d h ig h ly re g a rd e d so u rc e s. R easo n ab le e ffo rts have b e e n m ad e to p u b lish reliab le d a ta a n d in fo rm a tio n , b u t th e a u th o r a n d p u b lis h e r c a n n o t a s su m e re sp o n sib ility for th e v a lid ity o f all m a te ria ls o r th e c o n s e q u e n c e s o f th e ir use. T h e a u th o rs a n d p u b lish e rs have a tte m p te d to tra c e th e c o p y rig h t h o ld e rs o f all m a te ria l r e p r o ­ d u c e d in th is p u b lic a tio n a n d a p o lo g iz e to c o p y rig h t h o ld ers if p e rm iss io n to p u b lish in th is fo rm h a s n o t b e e n o b ta in e d . I f any c o p y rig h t m a te ria l h a s n o t b e e n ac k n o w led g e d p lease w rite a n d let u s k n o w so w e m ay r e c tify in a n y f u tu re re p rin t. E xcept a s p e rm itte d u n d e r U.S. C o p y rig h t Law, n o p a rt o f th is b o o k m ay b e re p rin te d , rep ro d u c e d , tra n s m itte d , o r u tiliz e d in any fo rm by a ny e le c tro n ic , m e c h a n ic a l, o r o th e r m e a n s, n o w k n o w n o r h e re a fte r in v en te d , in clu d in g p h o to co p y in g , m ic ro film in g , a n d re c o rd in g , o r in a ny in fo rm a tio n s to ra g e o r re trie v a l sy ste m , w ith o u t w r itte n p e rm iss io n fro m th e p u b lish e rs. F or p e rm iss io n to p h o to c o p y o r u se m a te ria l e le c tro n ic a lly fro m th is w ork, p lease a c cess w w w .c o p y rig h t.c o m (h ttp ://w w w .co p y rig h t.c o m /) o r c o n ta c t th e C o p y rig h t C le a ra n c e C e n te r, In c. (CCC ), 22 2 R o sew ood D rive, D an v ers, M A 01923, 978 -7 5 0 -8 4 0 0 . C C C is a n o t-fo r-p ro fit o rg a n iz a tio n t h a t p ro v id es lic e n ses a n d r e g is tra tio n fo r a v a rie ty o f u se rs. F or o rg a n iz a tio n s th a t h ave b e e n g r a n te d a p h o to c o p y licen se by th e C C C , a s e p a ra te s y ste m o f p a y m e n t h a s b e e n a rra n g e d . T r a d e m a r k N o tic e : P ro d u c t o r c o rp o r a te n a m e s m ay b e tra d e m a rk s o r re g is te re d tra d e m a rk s , a n d a re u se d o n ly for id e n tific a ­ tio n a n d e x p la n a tio n w ith o u t i n te n t to in frin g e . V is it t h e T a y lo r & F r a n c is W e b s ite a t h ttp ://w w w .ta y lo r a n d f r a n c is .c o m a n d t h e C R C P r e s s W e b s ite a t h ttp ://w w w .c r c p r e s s .c o m

Preface

Lubricants and lubrication techniques are indispensable in the automobile industry. Owing to the special operating conditions, characterized by high tem­ peratures, loads and speeds, lubricants have to cover extreme requirements. Therefore, the necessary properties of these lubricants require appropriate classification, production and form ulation, testing and application as well as expert disposal. This book deals w ith the state o f the art in the field of automotive lubrication, particularly engine lubrication. The different topics are covered by experts from the mineral oil, additive and automobile industries as well as from research institutes, thus providing high standard expert knowledge in any specific area of automotive and engine lubrication. Experts from several countries contributed to this book. In different chapters the following topics are covered: — Film thickness in engine bearings - Base oils for automotive lubricants — Additives and mechanism o f effectiveness — Engine oils and their evaluation - Sludge deposits in gasoline engines - Special aspects of engine lubrication - Two-Stroke-Engine Oils - Tractor lubrication — Gear lubrication — Lubricant influence on ceramic and seal materials This book is characterized by the fact that experts from all over the world gathered and summarized their knowledge, resulting in a general but nevertheless comprehensive presentation of all major aspects of automotive and engine lubrication. This book might be useful to all who are active in the field of automobile tribology and lubrication. Experts from the mineral oil and additive industries can also find new points o f view to supplement their knowledge, as w ill junior scientists and engineers who are introducing themselves to this field of trib o ­ logy and lubrication engineering. In addition, w ith the aid of this book a great number of students of tribology may gain a great deal of useful information.

Prof. W.J. Bartz iii

Table of Contents

Preface

iii

1.

Oil Film Thickness in Engine Bearings

1.1

Measurement of Oil Film Thickness in Big-End Bearings and Its Relevance to Engine Oil Viscosity Classifications

2

T.W. Bates, M.A. Vickars

1.1.1 1.1.2 1.1.2.1 1.1.2.2 1.1.2.3 1.1.3 1.1.3.1 1.1.3.2 1.1.3.3 1.1.3.4 1.1.3.5 1.1.4 1.1.5

1.2

Summary Introduction Experimental Engines Oil Film Thickness Measurement Oils Results Precision MOFT/crankangle curves-general features Effect of Speed and Torque Shear rates in the bearing Effect of viscosity Conclusions Acknowledgements References

2 2 3 3 4 6 6 8 8 10 14 15 20 22 23

Does the Automotive Industry Need a Standard Engine Test to Measure Journal Bearing Oil Film Thickness?

24

J.A. Spearot 1.2.1 1.2.2 1.2.3 1.2.4 1.2.5 1.2.6

Summary Introduction Development of Methods fo r Measuring BO FT Experimental Methods fo r Making BOFT Measurements Effects o f Oil Rheology on Bearing Performance Does the Autom obile Industry Need a Bearing Film Thickness Test?

24 24 26 27 31 41

1.2.7 1.2.8

Is an Industry Engine Bearing Test o f any Sort Needed? References

2.

Base Oils

2.1

Structure of Oils According to Type and Group Analysis of Oils by the Combination of Chroma­ tographic and Spectral Methods

44 44

48

P. Daucik, T. Jakubik, N. Pronayova and B. Zuzi

2.1.1 2.2.2 2.1.3 2.1.4 2.1.5

2.2

Summary Introduction Experimental Results and Discussion Conclusion References

48 48 49 51 57 58

Dependency of Viscometric Properties on Base-Stocks Chemical Structures in Multigrade Crankcase Oils

59

H.H. Abou el Naga and S.A. Bendary 2.2.1 2.2.2 2.2.3 2.2.4 2.2.4.1 2.2.5 2.2.5.1 2.2.5.2 2.2.5.3 2.2.5.3.1 2.2.5.3.2 2.2.5.4 2.2.5.5 2.2.5.6 2.2.6 2.2.7 2.2.8

vi

Abstract Introduction Experimental Statistical Methodology Chemical Variables Results and Discussion Base-Stocks Chemical Structure Variables Change in Viscometric Properties w ith increasing bright-stock content Dependency of Viscometric Propertieson Single Chemical Structures Variables Directions o f Proportionality Magnitude of Dependency Dependency of Viscometric Propertieson Combined Chemical Structure Variables Predictive Statistical Models Correlation via M ultiple Models Summary Acknowledgement References Appendix 1

59 59 62 66 67 69 69 70 75 76 76 88 90 96 98 99 99 101

Determination of Zinc and Calcium in Multigrade Crankcase Oils

1 02

H.H. Abou el Naga, M.M. Mohamed and M.F. el Meneir Abstract Introduction Experimental Results and Discussion Method precision limits Effect o f VI Improvers on Measured Zinc and Calcium Concentrations Effect of Viscosity on Percent Reduction of Measured Concentrations Estimating Correction Factors Via VI Improver Concentration Via Blend Viscosity Explanation of Results Conclusions References

The Characterisation of Synthetic Lubricant Formulations by Field Desorption Mass Spectrometry

102 102 103 107 107 107 110 112

112 113 114 114 115

116

K. Rollins, M. Taylor, J.H. Scrivens and A. Robertson, H. Major Experimental Results and Discussion Conclusions References

117 118 123 124

Tailor Making Polyalphaolefins

125

R.L. Shubkin and M.E, Kerkemeyer D.K. Walters and J.V. Bullen Tailor Making PAO's Introduction Background Results and Discussion Conclusion References

125 125 126 130 144 145

vii

Additives and Mechanism of Effectiveness Engine Oils Additives: A General Overview C.

149

Kajdas

Introduction Engine Oil Properties Properties o f Base Oils Properties Imparted by Additives Types and General Characteristics o f Additives for Engine Oils Description of the Engine Oil Additives General Information Additives Responsible fo r Formation o f Deposits Oxidation Inhibitors Heavy Duty (HD) Additives Detergents Dispersants A lkali Agents Additives Modifying Oil Properties Viscosity Index Improvers Pour Point Depressants Corrosion Inhibitors Other Additives But Tribological Ones Rust Inhibitors Foam Inhibitors Tribological Additives Introduction Friction M odifying Additives Antiwear Additives Extreme Pressure Additives Interactions o f Engine Oil Components References

Effects of NOv on Liquid Phase Oxidation and Inhibition at Elevated Temperatures

149 150 150 150 151 153 153 154 155 157 158 158 159 159 159 160 161 162 162 163 163 163 164 167 169 169 173

177

S. Korcek and M.D. Johnson Blowby Composition Experimental Reactions o f NO and N 0 2 Effects o f Uninhibited Hexadecane Oxidation Effects on Inhibited Hexadecane Oxidation Effects on Inhibited Oxidation o f Preoxidized Hexadecane Summary References Appendix 1 Appendix 2

177 179 180 181 186 192 195 197 198 199

Application of a New Concept to Detergency

200

J.M. Georges, J.L. Loubet, N. Alberola and G. Meille H. Bourgognon, P. Hoornaert and G. Chapelet Abstract Introduction A Coking Experiment Principle o f the Experiment Results Gel Formation and its Consequences Cracking and Overbased Detergent Correlation between the ELF/ECL Coking Test and a Renault 30 TD Engine Test Conclusions References

Overbased Lubricant Detergents — A Comparative Study of Conventional Technology and a New Class of Product

200 200

202 202 203 206 208 209

210 210

212

S.P. O'Connor, J. Crawford, C. Cane Abstract Introduction Review o f Detergent Types General Sulphonates Phenates Salicylates Others Naphthenates Phosphonates A New Class of Overbased Detergent Introduction Properties and Performances Basic Strength Viscosity-Temperature Behaviour Friction Reduction Anti-oxidant Performance Other Bench Tests Reciprocating Rig Wear Test Engine Tests Conclusion Acknowledgement References

212 212 213 213 216 218 219

220 220 220 221 221 222

222 223 223 225 226 227 228 230 230 230

ix

3.5

Synthesis of Additives Based on Olefin-Maleic Anhydride Reactions G.

3.5.1 3.5.2 3.5.3 3.5.4 3.5.5 3.5.6 3.5.6.1 3.5.6.2 3.5.6.3 3.5.7 3.5.8

3.6

231

Deak, L. Bartha and J. Proder

Introduction Materials Methods Olefin-Maleic Anhydride Adducts Olefin-Maleic Anhydride Copolymers Olefin-Maleic Anhydride Reaction Products as Raw Material for Additives in Lubricants Emulsifiers Rust Prevention Pour Point Depressants Conclusions References

Effects of the Structure on Various Performances of Polyisobutenylsuccinimides

231 231 233 233 235 236 236 237 237 240 241

242

K. Endo and K. Inoue

3.6.1 3.6.2 3.6.2.1 3.6.2.2 3.6.3 3.6.3.1 3.6.3.2 3.6.3.3 3.6.3.4 3.6.4 3.6.5

3.7

Abstract Introduction Experimental Materials Apparatus and Procedure Results and Discussions Thermal Stability Oxidation Stability Sludge Preventing Performance Antiwear Performance Conclusion References

242 242 243 243 243 245 245 247 248 251 251 252

Resistance of Ashless Dispersant Additives to Oxidation and Thermal Decomposition

253

L. Bartha and J. Hancsok, E. Bobest 3.7.1 3.7.2 3.7.3 3.7.4 3.7.5

x

Introduction Methods Materials Results and Discussion References

253 253 254 257 262

Anti-Wear Actions of Additives in Solid Dispersion

263

M.F. Morizur and 0 . Teysset Abstract Introduction Experimental Condition Lubricant Friction Tests Results and Discussion Additive decomposition mode in homogeneous phase Behaviour o f additives in the presence of metallic surfaces Adsorptions Isotherms Surface Reactivity Friction Tests Rolling Tests Type of Surface Film Formed in Slip Chemical state of elements at the surface Boundary Films Formed by Hyperbasic Detergents Boundary Film Formed in the Presence o f Potassium Triborate Thickness o f Films Formed on Antagonistic Specimens Results o f Mechanical Tests w ith Pure Slip Friction Properties Formation Rate o f the Boundary Film Wear Interpretation Conclusions References

An Investigation of Effects of Some Motor Oil Additives on the Friction and Wear Behaviour of Oil-soluble Organomolybdenum Compounds

263 263 264 264 266 267 267 269 270 272 275 275 278 278 278 280 281 281 281 283 284 285 285 286

287

D. Wei, H. Song and R. Wang Abstract Introduction Experimental Methods Friction and Wear Test Base Oil and Additives Analysis o f Surface Films Experimental Results and Discussion The Effect o f Additive Concentration Detergent and Dispersant Zinc Dialkyldithiophosphate Rust Inhibitor Influence o f Temperature

287 287 288 288 288 290 290 290 290 292 293 294

xi

3.9.3.3 3.9.3.4 3.9.4 3.9.5

3.10

The Influence o f Oil Change - Running-in Process The Mechanisms o f the Synergistic Effects Between the Molybdenum Compounds and the Calcium Sulfonate Conclusions References

The Study on the Antiwear Action Mechanism of Alkoxy Aluminium in Lubricating Oil

296 299 306 307

308

J. Dong, G. Chen and F. Luo

3.10.1 3.10.2 3.10.3 3.10.4 3.10.5

3.11

Abstract Introduction Performances o f A lko xy Alum inium Antiwear Action Mechanism Conclusion References

308 308 309 311 315 315

Functional Properties of EP-Additive Packages Containing Zn-Dialkyldithiophosphate, Sulphurized EP-Additive and a Metal Deactivator 316 G.S. Cholakov, K.G. Stanulov and I.A. Cheriisky, T. Antonov

3.11.1 3.11.2 3.11.3 3.11.3.1 3.11.3.2 3.11.3.3 3.11.3.4 3.11.4

3.12

Introduction Experimental Details Results and Discussion Lubrication Properties Thermal Stability Thermal Oxidation Stability Performance Related Tests and Ideas for Practical Application References

Relationship between Chemical Structure and Effectiveness of Some Metallic Dialkyl and Diaryldithiophosphates in Different Lubricated Mechanisms

316 317 320 320 324 324 328 333

335

M. Born, J.C. Hipeaux, P. Marchand and G. Parc

3.12.1 3.12.2 3.12.3 3.12.4

xii

Summary Background Introduction Additives Studied Experimental Procedure

335 336 336 338 340

Test Results and Discussion Metallic DTP Four-ball EP Test Four-ball AU Tests FZG EP Tests Single ZnDTP Four-ball EP Tests Four-ball AW Tests FZG EP Tests Combined ZnDTP Four-ball EP Tests FZG EP Tests Conclusion References

344 344 344 347 347 349 349 350 352 354 355 355 355 358

Evaluation of the Antiwear Performance of Aged Oils through Tribological and Physicochemical Tests

359

G. Monteil, A.M. Merillon and J. Lonchampt C. Roques-Carmes Summary Introduction Experimental Lubricants Oxidation Test AC Impedance Technique Tribological Tests Results AC Impedance Spectra Wear Tests Discussion Conclusion References

359 359 360 360 360 361 364 365 365 375 380 381 382

Mathematic Model for the Thickening Power of Viscosity Index Improvers. Application in Engine Oil Formulations

383

H. Bourgognon and C. Rodes, C. Neveu and F. Huby Summary Introduction Background Objective o f the Study Contribution o f Package Components to Viscosity Contribution of Package Components to Viscosity

383 383 383 385 385 385

xiii

3.14.4.2 3.14.5 3.14.5.1 3.14.5.2 3.14.5.3 3.14.5.4 3.14.6 3.14.7

3.15

Analysis o f Packages Used by a Blending Plant Model Describing the Contribution o f Package to Viscosity Model Describing the Contribution of Packages to Viscosity Effect of the Package on the Thickening Power of the Polymer First Model Second Model Conclusion References

Surface Morphology and Chemistry of Reaction Layers Formed Under Wear Test Conditions as Determined by Electron Spectroscopy and Scanning Electron Microscopy

388 390 391 391 396 400 404 405

406

Y. de Vita, I.C. Grigorescu and G.J. Lizardo

3.15.1 3.15.2 3.15.3 3.15.3.1 3.15.3.2 3.15.3.3 3.15.4 3.15.5 3.15.6

4.

Abstract Introduction Experimental Results and Discussion Friction and Wear Behaviour Wear Morphology vs. Friction Coefficient Pattern Comparison o f Worn Surface Morphology between SRV Test Specimens and Valve Lifters Conclusions Acknowledgement References

406 406 407 409 409 413 422 424 425 425

Engine Oils and Their Evaluation/ Engine Lubrication Aspects Engine Oils and Their Evaluation

4.1

The Changing Requirements of the 1980sAutomotive Oil Evaluation by Bench and Field Testing

429

A. Quilley 4.1.1 4.1.2 4.1.2.1 4.1.3

xiv

Introduction Engine Oil Development SG/DB 226.5 vs SF/DB 226.1 Conclusions

429 429 431 435

4.2

An Investigation into theLubricating Engine Oil's Mechanical andChemical Behaviour

436

S.L. A ly, M.O.A. Mokhtar, Z.S. Safar, A.M. Abdel-Magid, M.A. Radwan and M.S. Khader

Part I: Experimental Findings 4.2.1 4.2.2 4.2.2.1 4.2.2.2 4.2.3 4.2.4

Introduction Experimental Work and Results Field Tests Wear Tests Conclusion References (Part I)

436 437 437 440 443 444

Part II: Theoretical Interpretation 4.2.1 4.2.2 4.2.3 4.2.4 4.2.5 4.2.6

Introduction Analysis Application Results and Discussion Conclusion References (Part II)

445 446 447 449 453 453

4.3

Development of Superior EngineOils for Diesel Locomotives in India

455

J.R. Nanda, G.K. Sharma, R.B. Koganti and P.K. Mukhopadhyay R.M. Sundaram

4.3.1 4.3.2 4.3.3 4.3.4 4.3.5 4.3.6 4.3.7 4.3.8

4.4

Abstract Introduction Lubricant Performance Levels Development o f an Indigenous Formulation Development of Multigrade FuelEfficient Railroad Oil Future Activities Acknowledgement Abbreviations References

Very High Shear Rate, High Temperature Viscosity Using the Automated Tapered Bearing SimulatorViscometer

455 455 456 460 465 466 466 468 469

470

T.W. Selby, T.J. Tolton

4.4.1

Abstract Introduction

470 470

xv

4.4.1.1 4.4.1.2 4.4.1.3 4.4.1.4 4.4.2 4.4.2.1 4A.2.2 4.4.3 4.4.3.1 4.4.3.2 4.4.4 4.4.4.1 4.4.4.2 4.4.4.3 4.4.4.4 4.4.4.5 4.4.5 4.4.6 4.4.7

Background Importance o f the Tapered Coaxial Configuration Thermoregulator and Heater Development Effects Continuous or Long-Duration Operation of the TBS Standardization o f the TBS Viscometer ASTM D4863-87 — Relative Rotor Position Method ASTM D4863-90 - Absolute Rotor Position Method Automation o f the TBS Viscometer First Stage — Autom atic Sampling Second Stage - Semi-Automatic Calibration Applications o f the TBS/Automated-TBS Viscometer General Singular Temperature — M ultiple Shear Rate Data Multiple Temperature - M ultiple Shear Rate Data Correlation w ith the "Cross Equation" Correlation w ith Engine Oil-Film Thickness Studies Summary Acknowledgements References

471 -47 2 474 474 475 475 476 478 478 479 481 481 481 484 486 487 487 488 489

Sludge Deposits in Gasoline Cars

4.5

Literature Survey on Sludge Deposits Formation in Gasoline Engines

491

C.D. Neveu, W. Bottcher

4.5.1 4.5.2 4.5.3 4.5.4 4.5.5 4.5.6 4.5.7

4.6

Abstract Introduction Objective o f the Literature Survey Summarized Findings on Sludge Formation Mechanism Analytical Test Methods Causal Factors Conclusions o f the Literature Survey References Appendix 1 Appendix 2 Appendix 3/1: Blotter Spot Test Appendix 3/2: Evaluation Possibilities

491 491 492 492 495 496 497 498 501 505 507 508

Development and Application of an"On the Road" Test Method for the Evaluation of Black Sludge Performance in Gasoline PassengerCars

509

P.G. Carress 4.6.1 4.6.2 XVI

Introduction Test Vehicles

509 509

4.6.3 4.6.4 4.6.5 4.6.6 4.6.7 4.6.8

Test Fuel Manufacturers Oil and Service Recommendations Test Schedule Test Oils Results Conclusions

509 510 510 511 511 511

Special Aspects of Engine Lubrication

4.7

Review of Oil Consumption Aspects of Engines

515

D.C. Roberts

4.7.1 4.7.2 4.7.2.1 4.7.2.2 4.7.2.3 4.7.3 4.7.4 4.7.5

4.8

Abstract 515 Introduction and Overview 516 Factors Affecting Oil Consumption 519 Engine Design 519 Engine Operating Conditions 520 Engine Oil Technology 520 Influence o f Oil Viscosity and V o la tility in Gasoline Engines 524 Conclusions 532 References 534

The Contribution of the Lube Oil to Particulate Emissions of Heavy Duty Diesel Engines

535

P. T ritth a rt, F. Ruhri and W. Cartel I ieri 4.8.1 4.8.2 4.8.3 4.8.4 4.8.5 4.8.5.1 4.8.5.2 4.8.5.3 4.8 .5.4 4.8.5.5 4.8.6 4.8.7 4.8.8 4.8.9

Summary 535 Introduction 535 Particulate Analysis 536 Lube Oil Particulates in Exhaust Emission Tests — Current Position 538 Peculiarities of Lube Oil Particulates 541 The Influence of Cooling Water Temperature 541 Particulate Emission During Motoring 541 Effect o f Sulphur Content of Fuel on Lube Oil Particulates 543 Influence o f Lube Oil Formulation on Particulate Emissions 544 Effect o f Valve Stem Sealing on Particulate Emissions 545 Oil Consumption and Lube Oil Particulates 546 Strategy for Lube Oil Particulate Reduction 550 Summary and Conclusions 551 References 552

xvii

4.9

Gasoline Engine Camshaft Wear: The Culprit is Blow-By

553

J.A. McGeehan and E.S. Yamaguchi 4.9.1 4.9.2 4.9.3 4.9.4 4.9.5 4.9.6 4.9.7 4.9.8 4.9.9 4.9.10 4.9.11 4.9.12 4.9.13 4.9.14 4.9.15 4.9.16

Abstract Introduction Blow-by Caused Engine Deposits in Gasoline-Engines Diverting the Blow-by from the Camshaft Low Wear w ith no Blow-by Search for the Wear-Causing Component inthe Blow-by Blow-by Causes ZnDTP to Deplete Analysis o f the Blow-by N itric Acid Causes Valve-Train Wear Wear can be Controlled in the Presence o f N itric Acid Wear Film Analysed w ith and w ithout Blow-by Metallurgical Analysis Other Studies Relevant to these Findings Conclusions Acknowledgements References

553 553 554 555 558 560 563 563 564 565 568 568 571 573 573 584

4.10

Lubrication Technique of Not Continuously Operating Vehicles

586

A.

Zakar, G. Borsa

References

4.11

Environmental Effects of Crankcase and Mixed Lubrication

596

598

P. van Donkelaar

4.11.1 4.11.2 4.11.3 4.11.4 4.11.5 4.11.6 4.11.6.1 4.11.6.2 4.11.7 4.11.8 4.11.9 4.11.10

xviii

Summary Introduction Basic Requirements o f Engine Lubrication Systems Development o f Engine Lubrication Systems Development o f Engine Lubricants Environmentally Relevant Engine Operating Conditions Lubricant Emissions Lubricant Emissions by Crankcase-Lubricated Engines Lubricant Emissions by Mixed-Lubricated Engines Lubricant Immissions Fate o f Engine Lubricants in the Environment Conclusions References

598 598 599 600 604 605 607 607 610 611 612 613 614

Two-Stroke Engine Oils

Development in Synthetic Lubrication for Air Cooled Two Cycle Engine Oils: Effect of Esters on Lubrication and Tribological Properties D.

616

Moura and J.-P. Legeron

Summary Introduction Two-Stroke Engines and their Conditions of Use Lubricant Choice and Performance Considerations Friction Test Procedure PLINT Friction Machine Cyclinder/Cylinder Tribometer Results Engine Road Tests General Conclusion Acknowledgements References

616 616 616 617 619 619 622 623 624 627 628 628

High Performance Ester-Based Two-Stroke Engine Oils

629

D.

Kenbeek and G. van der Waal

Introduction Lubricant Requirements and Composition Basefluid Additives Classification o f Two-Stroke Lubricants API TC and API TD/TE Test Conditions API TC (ASTM D4859-89) API TD/API TE Synthetic Two-stroke Oils: Engine Test Results Air-cooled Performance According to TSC-1/API TA Air-cooled Performance According to TSC-3/API TC Water-cooled Performance According to TSC-4/API TD (NMMA TC-W) w ith Air-cooled Performance According to API TC Air-cooled Performance in Chainsaw Engines Summary and Conclusions References Appendix

629 630 631 631 632 633 633 633 635 635 636

638 641 643 644 644

xix

Tractor Lubrication Tractor Lubrication

648

D.J. Neadle Summary Introduction Functional Requirements Placed on Tractor Lubricants Engine Lubrication Transmission and Gearbox Rear Axle and Wet Brakes IPTO Hydraulics Specification Requirements Super Tractor Oil Universal Universal Tractor Transmission Oils Tractor Lubricants Super Tractor Oil Universal Universal Tractor Transmission Oil Current and Future Developments

648 649 650 650 651 651 653 653 654 654 655 658 658 659 660

Use of Low Speed FZG Test Methods to Evaluate Tractor Hydraulic Fluids

661

B.M. O'Connor, H. Winter Introduction Experimental Full-Scale T ractor Test Calculation fo r the Full-Scale Tractor Test Calculation o f Contact Stress Estimation o f Film Thickness Establishing FZG Test Conditions Test Stand Test Gears Operating Conditions Test Lubricants Test Results and Discussion Comparison Between Tractor and FZG Test Methods Evaluation o f Current Generation Fluids (Method B) Influence o f Water as a Contaminant (Method C) Influence o f Surface Roughness Summary References Appendix: Symbols and Units

661 662 662 663 663 664 665 665

666 668 671 672 672 675 678 683 684 684 685

Gear Lubrication Performance Characteristics of Sulfur-Phosphorus Type Hypoid Gear Oils

688

S. Watanabe and H. Ohashi

688

Introduction Experimental Axle Gear Tester Test Hypoid Gears Test Oils Procedure Results and Discussion Gear Protection Performance Under High Temperature and High Speed Conditions Load Carrying Properties Under High Speed and Shock Loading Effect o f Hypoid Gear Oils on Axle Break-In Temperature Effect o f Hypoid Gear Oils on Fuel Economy Conclusions References

695 696 699 701 702

The Screening of E.P. Oil Formulas by the Use of a New Hypoid Gear Axle Test

704

689 689 690 690 691 691 691

G. Venizelosand G. Lassau P. Marchand Summary Introduction Objectives and Test Equipment Recalls on the Principle of the CRC L 42 Test Objectives Test Apparatus Selection o f Test Conditions Test Procedure Running In Test Results Severity Level of Test Correlation w ith the CRC L 42 Test Conclusions References

704 704 706 706 707 707 709 713 713 713 715 715 717 718 718

xx i

Automatic Transmission Fluids — State of the Art

719

A.G. Papay Summary Introduction Function and Properties Functions Properties Specifications History Present Future Properties Needing Upgrading Chemistry Old Chemistry Present Chemistry Future Chemistry Needs Comparison in Key Properties Comparison in DEXRON® II and MERCON® Requirements Comparison in Possible DEXRON® III Properties Comparison in Industrial Requirements Japanese ATF Formulations Environmental Considerations vs. Formulation Conclusions References

Prediction of Low Speed Clutch Shudder in Automatic Transmissions Using the Low Velocity Friction Apparatus

719 719 719 719 720 720 720 720 721 721 722 722 722 723 725 725 725 726 728 730 731 731

732

R.F. Watts and R.K. Nibert Introduction Background Experimental Results Effect of Mating Steel Surface Effect of Friction Material Effect o f Load Effect of Temperature Summary References Appendix 1: Standard Test Procedure Appendix 2: Test Results

732 734 736 739 739 741 743 746 747 748 749

Lubricant Influence on Ceramic and Seal Materials

Relation Between Surface Chemistry of Ceramics and Their Tribological Behaviour

752

T.E. Fischer and W.M. Mullins Abstract Introduction Chemical Effects o f Water on Ceramic Tribology Tribochemical Reaction of Ceramics w ith Water Formation o f Lubricious Oxides Chemically Induced Fracture in Oxide Ceramics Interaction w ith Hydrocarbons Boundary Lubrication by Paraffins Adsorption-Induced Fracture Chemical Properties o f Ceramics MgO, A I2O3 , S i0 2 SiC, Si3N4 Z rO j Discussion References

752 752 753 753 755 756 758 758 758 758 759 759 760 760 762

Effect of Hydrogenation Degree of HSN on Various Lubricating Oil Additives Resistance

765

M. Oyama, H. Shimoda, H. Sakakida and T. Nakagawa Introduction Experimental Test Samples and Physical Tests Immersion Test fo r Commercial Lubricating Oils Lubricating Oil Additive Resistance The Determinations o f N, Mg, Ca, P, Cl and S Elements in the Lubricating Oils Tested Results and Discussions Resistance o f Lubricating Oils The Effects o f Unsaturation Degree o f HSN on the Resistance to Oil Additives Analysis o f Additives in Lubricating Oil Conclusions Acknowledgement References

765 767 767 767 767 769 770 770 772 775 777 778 778

xxiii

7.3

Electro-Chemical Investigation of Deposit Formations on Mechanical Seal Surfaces for Diesel Engine Coolant Pumps H.

7.3.1 7.3.2 7.3.3 7.3.3.1 7.3.3.2 7.3.4 7.3.5 7.3.6 7.3.7 7.3.8

779

Hirabayashi, K. Kiryu, K. Okada, A. Yoshino and T. Koga

Summary Introduction Investigations o f Failures Experiments Mechanical Seals Test Procedure Experimental Results Discussions Conclusions Acknowledgement References

779 779 780 785 785 786 787 789 792 792 792

Index

794

The Authors

798

xx iv

1. Oil Film Thickness in Engine Bearings 1.1

Measurement of Oil Film Thickness in Big-End Bearings and Its Relevance to Engine Oil Viscosity Classifications

1.2

Does the Automotive Industry Need a Standard Engine Test to Measure Journal Bearing Oil Film Thickness?

1.1

Measurement of Oil Film Thickness in Big-End Bearings and Its Relevance to Engine Oil Viscosity Classifications

T.W. Bates, Shell Research Ltd., Chester, Great Britain M.A. Vickars, Esso Research Centre, Abingdon, Great Britain

Summary Minimum oil film thickness (MOFT) measurements have been carried out in big-end bearings o f V -6 and in-line four cylinder gasoline engines during engine operation. MOFT decreases w ith increasing crankshaft speed above 2000 r/m in . The most severe, practical, steady-state operation is high-speed cruising. Maximum shear rates are in the region o f 107 s—1 at 4000 r/m in. The dynamic viscosities at a shear rate o f 10® s-1 correlate significantly better w ith mono­ grade MOFT data than w ith multigrade data; the correlation parameters for mono- and multigrade data are also significantly different. Although the dynamic viscosity measurement correlates w ith multigrade data better than the low-shear-rate kinematic viscosity, the differences are not always significant at the 95 % confidence level. Some other rheological parameter or combination of parameters may be better than either kinematic or dynamic viscosities.

1.1.1

Introduction

Until recently, the most widely used method o f measuring journal bearing performance in operating gasoline or diesel engines was to measure bearing weight loss at the end o f a test which inevitably involved operating under severe conditions o f load and speed in order to obtain metal-to-metal contact (1.2). Such tests are the ultimate arbiter for assessing long-term durability perfor­ mance. They are less than ideal, however, fo r studying the effects o f oil rheology on journal bearing performance because of: (a) poor test repeatability; and (b) complications arising from operating under boundary/mixed lubrication condi­ tions where chemical effects o f the dispersant/inhibitor package complicate interpretation o f the results in terms of oil rheology (1,2). Poor repeatability also makes bearing weight loss experiments unsatisfactory fo r studying the effects o f bearing design on performance.

2

A preferred assessment o f journal bearing performance is measurement o f the oil film thickness during engine operation.. The latter is critical since it ensures the bearing is subject to relevant dynamic loadings(as opposed to the use o f tactic­ ally-loaded journal bearing rigs). Moreover, operation of the bearing under fu llfilm hydrodynamic loading ensures only oil rheology effects are involved. Consi­ derable progress has been made in the last ten years in instrumenting bearings of engines to allow measurement o f oil film thickness during operation. Most o f the activity has centred around main bearings (3-9) . Big-end bearings, however, are of more interest because the combination o f smaller bearing area and severe dynamic loadings make them more prone to field failure than main bearings. The problem of making electrical connections to the reciprocating big-end has been overcome by the use o f light-weight, mechanical scissor linkages to support the wires and prevent their premature breakage (10-14). As part o f an extended CEC programme (15-18) into the effects o f oil viscometry on engine performance, the CEC Project Group PL-33 has initiated a study of the relationship between oil rheology and oil film thickness in the big-end bearings of tw o different engines. This study was initiated partly in response to a request from CCMC for further information on the role o f hightemperature, high-shear viscosity (HTHSV) and other Theological properties on bearing performance, and partly to provide information which could be used as input to the debate on HTHSV classifications and lim its in the SAE Viscosity Classification J300. There is considerable interest at the present time in a better characterization o f the high-temperature performance of lubricants than that provided by the present low-shear, kinematic-viscosity limits in SAE J300. This interest stems from the trend towards lower viscosity oils fo r easier low-temperature starting and improved fuel economy. There is a concern that journal bearing durability problems may arise due to possible limitations of the kine­ matic viscosity as a guide to oil-rheological effects and its lack of relevance in terms of temperature and shear rate to critical areas of the engine. In journal bearings fo r instance shear rates in the region 10s s-1 to 107 s-1 occur.

1.1.2

Experimental

1.1.2.1

Engines

The connecting-rod, big-end bearings o f tw o gasoline engines were instrumented. One engine was an in-line, four-cylinder, 2.3 litre, fuel-injected unit (hereinafter referred to as the 2.3I L-4 engine). The ungrooved big-end bearings were o f lead/ bronze on a steel backing. There was a squirt hole in the upper shell fo r lubri­ cation o f the bore. The bearing corresponding to cylinder number 1 (pulley-end) was instrumented. The other engine was a 60 , V-6 , fuel-injected u nit o f 2.8 litre capacity (referred to as the 2.8I V -6 engine). The ungrooved bearing material was copper/lead on a steel backing w ith an overlay of lead/tin. The cylinder of the instrumented bearing was in the middle of the bank. Special big-end bearing shells w ith o u t the normal squirt hole in the upper shell were obtained from the engine manufacturer. Values o f 40 pm and 25 pm were used fo r the radial 3

clearances of the instrumented big-end bearings of the 2.3 litre and 2.8 litre engines, respectively. These are estimated values based on pre-build inform ation. Since the bearings have not been dismantled their present radial clearances are not known precisely. Table 1.1.1 gives further information on the engines and the bearing dimensions. The engines were installed in a test cell, speed and torque being controlled by a dynamometer. Oil temperature was controlled at the gallery by passing the oil through an external oil cooler and electric heater. Table 1.1.1: Test-engine data 2.31 L-4

2.81 V -6

21.5 48.5 32.8 0.44 1.8

16.5 54.0 28.0 0.30 1.4

Big-end bearing dimensions: length diameter area length :diameter ratio shell thickness

, mm , mm , cma , mm

Maximum brake horsepower Maximum torque Bore diameter Stroke Compression ratio

, kW ,N •m , mm , mm

100 at 5100 r/m in 205 at 3500 r/m in 95.5 80.3 9.0:1

110 at 216 at 93 68.5 9.2:1

Radial clearance*

,//m

40

25

5800 4000

r/m in r/m in

★ Estimated fo r the instrumented big-end bearing

1.1 2 .2

Oil Film Thickness Measurement

The oil film thickness in the big-end bearing during engine operation was calculated from measurement o f the total capacitance, C, o f the oil film in the bearing. For a cylindrical bearing and shaft (i. e. no distortion) and in the absence o f cavitation (i. e. uniform dielectric constant o f the oil in the bearing), it can be shown (3) that: MOFT = R(1 - [1 —(kAe/RC)2J°'s ) .

(1)

Here MOFT is the minimum oil film thickness at a given crankshaft position (see Fig. 1.1.1), R is the radial clearance, k the perm ittivity o f free space, A the area o f the bearing and e the dielectric constant o f the oil at the temperature and pressure in the bearing. 4

In order to measure capacitance of the oil film in the bearing, the bearing shell was electrically insulated from the connecting rod by replacing ca. 200 j/m of metal in the bearing housing by an equal thickness o f alumina cera­ mic applied by plasma spraying (see. Fig. 1.1.1). The journal was earthed by means o f copper braid held in tension over a pulley on the end o f the crank­ shaft. The bearing shells and the journal now act as a cylindrical capacitor with the oil film as dielectric.

Figure 1.1.1:

Electrical insulation o f the big-end bearing shell fo r the measure­ ment o f the minimum oil film thickness, MOFT, as a function of crankangle

The oil film capacitance was measured continuously as a function of crank­ shaft angle by a capacitive divider circuit (3) in the case o f the 2.31 L-4 engine and by a transformer ratio arm bridge circuit fo r the 2.81 V -6 engine (12). A check was made (19) that both techniques gave the same capacitance by replacing the ratio-arm circuit by a capacitive divider circuit fo r the 2.8I V -6 engine. The ac voltages applied to the bearing capacitor had frequencies of 100 kHz and 20 kHz fo r the 2.3 litre and 2.8 litre engines, respectively. The output voltage was used to calculate a capacitance by use of a voltage/capa­ citance calibration relationship established by replacing the bearing by a series of fixed capacitors. Further details of the electrical circuits and the data acquisition systems are given elsewhere (3,4,12-14). Electrical connections were made to the reciprocating big-end bearing by screened cables supported by a light-weight, aluminium-alloy, scissor linkage. The linkages were custom built fo r each engine by T&N Technology, Cawston, England and allowed operation at speeds up to 4000 r/m in fo r periods in excess of 200 hours before wire breakage occured. Connections of the wires to the bearing were arranged so that replacement of broken wires could be carried out w itho ut removal o f the big-end bearing cap, thereby ensuring continuity of results. In the case o f the 2.8I V -6 engine, theoretical calculations (20) established that the linkage did not contribute significantly to loading in the bearing. 5

1.1.2.3

Oils

A series of five mono- and sixteen multigrade oils were specially blended fo r this programme. The oils are listed in Table 1.1.2 along w ith their viscosities and dielectric constants. Viscosities were measured at 100°C, 130°Cand 150°C at both low- and high-shear rates (see Table 1.1.2). The low-shear-rate viscosi­ ties were measured in an Ubbelohde viscometer (ASTM Procedure D 445) which yields kinematic viscosities, V ^ IT ), at a temperature T. The high-shear-rate viscosities were measured in a Ravenfield tapered plug viscometer by CEC procedure L-36-A-87. This procedure provides thedynam ic viscosity, V ^ IT , 10*), at a temperature T and a fixed shear rate o f 106 s 1. The oils all contained the same (commercial) dispersant/inhibitor SF/CC performance package. Conventional base oils from a single source were used, all fully-form ulated oils being blended from the same batches o f base oils. The monograde oils covered the four SAE viscosity grades SAE 20, SAE 30, SAE 40 and SAE 50. The sixteen multigrade oils were formulated from four different, commercial, viscosity index (VI) improver types: namely styrene-isoprene (S-l), styrene-butadiene (S-B), olefin copolymer (OCP) and polymethacrylate (PMA). The base oil and VI improver concentrations were determined by the respective supplier o f the VI improver. Each VI improver type was formulated into the follow ing SAE grades: 10W30, 10W40, 15W40 and 20W50. The dielectric constants o f the fresh oils were measured by Southwest Research Institute, San A ntonio, Texas using a brass, cylindrical capacitor and an excitation signal of 100 kHz. Results at 100°C are shown in Table 1.1.2. The mean dielectric constant is 2.13, there being little difference between the oils. A value of 2.1 was used throughout these studies, the effects o f temperature between 100°C and 150°C (13,14) and pressure between atmospheric and 100 MPa (21) being small (i. e. ca. 1 %). Changes o f 1 % in dielectric constant alter MOFT as calculated by Equation (1) by about 1 %.

1.1.3

Results

Voltage/crankangle curves were averaged over sixteen, 720°, engine cycles in order to minimise the effects o f cycle-to-cycle variations. The repeatability is not very sensitive to the number o f cycles averaged, provided it is not less than about eight; sixteen is a somewhat arbitrary, convenient number. Measurements were taken after about one hour o f engine operation to allow temperature equilibrium around the engine to be established. MOFT was determined as a function of crankangle fo r each o f the mono- and multigrade oils at the conditions shown in Table 1.1.3. One o f the SAE 40 oils, RL 153, was used fo r a study o f the effects o f engine speed and torque on MOFT; the engine conditions used are shown in Table 1.1.4. 6

10W30 10W40 15W40 20W50

10W30 S-B 10W40 S-B 15W40 S-B 20W50 S-B

10W30 OCP 10W40 OCP 15W40 OCP 20W50 OCP

10W30 10W40 15W40 20W50

RL156 RL157 RL158 RL159

RL160 RL161 RL162 RL163

RL164 RL165 RL166 RL167

RL168 RL169 RL170 RL171

4.83 6.37 6.22 7.25

11.16 14.70 14.56 18.26

6.44 8.61 8.28 9.74

35.0 35.0 33.5 40.8

4.66 6.06 5.93 6.73

6.27 8.10 8.05 9.26

11.11 14.61 14.83 17.96

31.7 35.7 34.1 45.2

7.36 8.72 9.31 12.10

7.06 8.55 9.32 12.00

4.34 5.15 5.24 6.60

4.17 5.02 5.32 6.43

4.41 5.49 5.54 6.62

7.72 9.66 9.82 12.28

4.62 5.88 5.33 6.47

6.31 8.13 7.65 9.21

11.10 14.78 14.39 18.08

28.6 30.1 30.0 43.9

4.16 4.99 5.16 6.44

7.14 8.54 9.05 12.20

4.78 6.24 5.85 6.78

6.46 8.49 8.11 9.46

11.43 15.21 14.83 18.27

32.0 32.2 31.4 42.8

3.57 4.30 5.47 5.97 7.52

6.48 8.00 11.00 11.74 15.65

3.25 3.83 4.76 5.26 6.33

4.41 5.28 6.74 7.30 9.12

7.98 9.74 12.98 14.33 18.65

nd*^ nd nd nd nd

100°C

130°C

3,27 3.88 3.86 4.78

3.15 3.77 3.94 4.62

3.28 4.06 4.08 4.77

2.16 2.19 2.17 2.17

2.10 2.11 2.12 2.13

2.12 2.12 2.12 2.13

2.11 2.10 2.11 2.12

2.10 2.12 2.12 2.13 2.15

2.62 3.11 3.81 4.20 5.14 3.12 3.74 3.82 4.60

100°C

ec>

150°C

Vd (T,106 ),m P a • s

150°C

130°C

Pa • s

100°C

V ^ IT l.m m ’ /s

CCSa>

a) Cold cranking simulator viscosities. 10 WX, 15 WX and 20 WX measured at —20°C, —15°C, —10°C respectively. b) nd = not determined. c) dielectric constant.

PMA PMA PMA PMA

S-l S-l S-l S-l

None None None None None

SAE SAE SAE SAE SAE

RL151 RL152 RL153 RL154 RL155

20 30 40 40 50

V II Type

SAE Grade

Viscometric and dielectric constant data for mono- and multigrade oils

Oil Code

Table 1.1.2:

Table 1.1.3:

Engine conditions used to measure MOFT o f mono- and m u lti­ grade oils Engine Condition

Engine

Crankshaft Speed r/m in

Torque N • m % max.

Gallery Temperature °C

2.3 litre L-4

I II III IV

2000 2000 3000 3000

45 108 120 120

25 60 60 60

100 100 100 130

2.8 litre V -6

V VI V II

2500 2500 3000

100 100 100

40 40 40

100 130 100

1.1.3.1

Precision

The value o f MOFT obtained by the total capacitance technique can be inde­ terminate w ithin a factor o f two (13-14) due to uncertainty in assigning a precise value to the radial clearance in Equation (1) (see section dealing w ith the enigines). The assumptions o f no-cavitation and no-distortion made in deriving Equation (1) also introduce further uncertainties in the absolute magnitude of MOFT (8,20). These factors must be borne in mind when comparing oil film thickness given in this paper w ith theoretical predictions. The method, however, provides excellent precision in terms o f the magnitude of MOFT. Thus MOFT values fo r repeat tests carried out sequentially are usually w ithin 1 %: excellent repeatability is also obtained between measurements made on different days fo r the same oil at the same engine condition, e. g. such repeat tests have a standard deviation o f less than 3 % fo r the 2.8I V -6 engine. MOFT values fo r in-house reference oils showed no d rift over the period in which measurements were made. 1.1.3.2

MOFT/crankangle curves — general features

Table 1.1.4 shows the results o f the various speed/torque studies on the SAE 40 o il, RL 153. In this table, (MOFT)0 is the minimum value o f MOFT, as deter­ mined from the MOFT/crankangle curve (see Fig. 1.1.2), Gmax is the maximum shear rate (i. e. the shear rate o f M 0 F T )o — see later) and m is the crankangle locating (MOFT)0. (Note that 0° is top-dead-centre o f the firing stroke o f the cylinder corresponding to that of the instrumented bearing.) A (MOFT)0 "re­ su lt" as reported in this paper is the mean of tw o sixteen cycle averages in the case o f the 2.3I L-4 engine and of five such averages fo r the 2.8I V -6 engine. The individual averages were taken over a five to ten minute period.

8

Table 1.1.4:

Effect of torque and crankshaft speed on (MOFT)0 , Gj»,ax< ancl hm . SAE 40 oil RL 153 at a gallery temperature of 100°C 2.81 V -6

Torque Speed (MOFT) q N •m r/min (i m

106Gmax /s

2.3I L-4 m degrees

(MOFT)0 (im

106Gmax /s

m degrees

45 45 45 45 45 45

1500 2000 2500 3000 3500 4000

2.16 1.77 1.33 1.05 0.83 0.56

1.7 2.6 6.2 9.6 14.3 24.3

239 225 414 401 407 403

2.52 2.22 1.88 1.62 nd nd

1.7 2.0 3.2 4.7 nd nd

67 243 261 272 nd nd

120 120 120 120 120 120

1500 2000 2500 3000 3500 4000

nd 1.28 1.14 0.96 0.77 0.39

nd 3.6 5.0 7.3 15.5 34.5

nd 222 222 227 406 408

1.40 1.81 nd 1.46 nd nd

3.1 2.1 nd 5.2 nd nd

59 156 nd 270 nd nd

10 80 120 160 175

2500 2500 2500 2500 2500

1.29 1.26 1.14 1.00 nd

6.4 5.0 5.3 5.9 nd

413 244 233 230 nd

2.04 1.75 1.66 nd 1.54

3.0 3.4 3.6 nd 3.7

264 258 258 nd 247

nd = not determined Fig. 1.1.2 shows a comparison of MOFT/crankangle curves fo r the two engines for an SAE 40 oil at 2500 r/min and 80 N • m torque. These curves are represen­ tative o f those obtained at different speed/torque conditions and fo r different viscosities. The curves fo r the two big-end bearings are remarkably similar. Thus there is a maximum in each of the firing, exhaust and induction strokes and a minimum in each o f the exhaust, induction and compression strokes. The crankangles locating the maxima and minima are very close fo r the two engines, as are their relative heights and depths. The magnitude of MOFT is close fo r the two bearings over some o f the 720° cycle; (MOFT)0 is, however, higher by some 40 % for the 2.3I L-4 big-end bearing than fo r that o f the 2.8I V -6 (i. e. 1.75 jum vs. 1.26 fxm). It is not possible to state whether this difference is real or is due to uncertainties about the correct values o f the radial clearance to be used in Equation (1) - see previous section. Thus if a radial clearance o f 20 /xm, instead of 25 /xm, was assumed in Equation (1) fo r the 2.8I V -6 engine, the calculated value o f (MOFT)0 would be increased to 1.59 (im. This value would be obtained fo r the 2.31 L-4 engine by using a radial clearance o f 44 fxm instead o f 40 /xm. Uncertainties of -t5 fxm are quite possible fo r the radial clearances o f the big-end bearings since they have not been dismantled.

9

6

— "2 5 0 0 r/mln — 80 N.m S A E 40 oil •

10

TEMPERATURE RISE ESTIM ATED FROM SOMMERFELD ANALYSIS. *C

„ '*

. 1

TEMPERATURE RISE PREDICTED FROM REGRESSION ANALYSIS. *C

Figure 1.2.6: A Comparison o f the Temperature Rise in the Bearing Predicted by M ultilinear Regression Analysis w ith that Calculated from Sommerfeld Approximations. Reprinted w ith permission. Copy­ right 1989, Society o f Autom otive Engineers, Inc.

Using the regression equation to calculate bearing oil temperatures and deter­ mining the corresponding viscosities provides the BOFT versus Sommerfeld Number curve shown in Fig. 1.2.7. The assumptions made regarding the Som­ merfeld Number and the amount o f viscous heating produce a high degree o f correlation fo r this series o f single-grade oils. Although the temperature regression equation developed is truly valid only fo r the engine bearing and operating conditions used in this work, it can be used to estimate the tempe­ rature rise in the bearing fo r a series of multigrade oils over the same range o f operating conditions. 36

Figure 1.2.7: Absolute Minimum Oil Film Thickness as a Function of Sommerfeld Number fo r Single-Grade Oils at the Estimated Bearing Oil Temperature. Reprinted w ith permission, Copyright 1989, Society o f Automotive Engineers, Inc.

Spearot, Murphy, and Deysarkar (11) also calculated values for different shear rates associated w ith the test bearing. The two shear rate definitions which were thought might be related to film thickness values in a journal bearing were 1) the maximum shear rate, and 2) the average shear rate in the loaded portion of the bearing. The maximum shear rate occurs at the minimum film thickness point in the bearing and thus the viscosity calculated at such conditions could influence BOFT. The average shear rate in the loaded portion o f the bearing is a variable which reflects the shearing conditions in the entire portion of the oil film which carries the applied load. Thus, it could also influence BOFT. By using the temperature regression equation to calculate the temperature of the oil in the bearing and using these different shear rate definitions, the viscosity of a series o f both single- and multigrade oils were calculated at different bearing operating conditions. Using these viscosities to calculate values o f S, regressions between film thickness and Sommerfeld Number were constructed as shown in Figs. 1.2.8 and 1.2.9. In each o f these figures, (1) provides the raw data, and (b) provides the linear regressions through the data.

37

(b ) R E G R E S S IO N S

«-

S IN Q LE -G R A D E OILS

R l-£ S B 2 _

_

_

M U LTIG R A D E OILS R ' - 0.981__________ 3

-

A B S O LU TE M IN IM U M O IL FILM 3H T H IC K N E S S .

B O T H O IL S R* - 0 .9 8 6

fim

OIL FILM TH IC K N E S S CO R R E C TE D FOR ENGINE D R IF T SO M M ER FELD N U M B E R CO R R E C TE D FOR TE M P E R A TU R E A N D SH EAR RATE 10

—r 13

14

—1— 13

S Q U A R E R O O T OF SO M M ER FELD NU M BER

Figure 1.2.8:

38

Relationship between Bearing Oil Film Thicknessand Sommerfeld Number at an Average Shear Rate. Reprinted w ith permission, Copyright 1989, Society o f Autom otive Engineers, Inc.

(b ) R E G R E S S IO N S

/

S IN G LE -G R A D E OILS (V _ -_ 2 ]9 8 S _ _ _

/

M U LTIG R A D E OILS R1 - 0.070

/ / / /

A B S O LU TE M IN IM U M O IL FILM T H IC K N E S S . Atm

yy yy yy

B O T H O IL S R* - 0 .9 7 9

V OIL FILM TH IC K N E S S C O R R E C TE D FOR ENGINE D R IFT SO M M ERFELD N U M B E R CO R R E C TE D FOR TE M P E R A TU R E A N D SH EAR RATE 2

4

10

12

S Q U A R E R O O T OF SO M M ERFELD NUM BER

Figure 1.2.9:

Relationship between Bearing Oil Film Thickness and Sommer­ feld Number at the Maximum Shear Rate. Reprinted w ith Per­ mission, Copyright 1989, Society o f Automotive Engineers, Inc. 39

In the case o f viscosities based on the average shear rate in the loaded quadrant of the bearing, as shown in Fig. 1.2.8, the film thickness values provided by multigrade oils are statistically indistinguishable from those provided by single­ grade oils at a confidence level o f 95 percent. Using this combination o f tempe­ rature and shear rate conditions, it would be concluded that multigrade oils perform the same as single-grade oils in a journal bearing and that there is no elastic benefit due to the presence o f the high molecular weight polymer in the multigrade form ulation. In the case of viscosities based on the maximum shear rate in the bearing, as shown in Fig. 1.2.9, the film thickness values provided by multigrade oils are greater than those provided by single-grade formulations. The regression curves based on these data are statistically different at the 95 percent confidence level. Although the differences do not appear large, certain multigrade oils, parti­ cularly at low values o f S, provide as much as a 25 percent greater film thickness than single-grade oils at the same value o f S. Using this combination o f tempe­ rature and shear rate conditions, one might conclude that the polymer in m u lti­ grade oil formulations does provide an additional benefit to journal bearing performance over the provided by its viscometry properties. One possible explanation for some additional benefit associated w ith multigrade oils is that of fluid elasticity. The question o f whether or not high molecular weight polymer blended into a multigrade oil could produce sufficient elastic forces to influence bearing operation has been debated fo r many years. As of yet there has been no definitive proof o f such elastic benefits. Bates, Williamson, Spearot, and Murphy (12) attempted to relate bearing film thickness measure­ ments to both viscous and elastic parameters. A multivariable linear regression o f the form :

hm = C0 +C ,t? + C20

(4)

was used where r? and 6 are the viscosity and the relaxation time o f the oil, respectively, caculated at the bearing temperature and maximum shear rate. As shown in Fig. 1.2.10, Equation 4 which gives a predicted film thickness based on fluid properties was fit to a collection o f measured film thickness data for both single- and multigrade oils w ith a reasonable degree o f success (R1 = 0.73). Although this is not absolute proof o f the importance of oil elastic properties, it does lend credibility to theories which include the influence of such effects. The question o f which o f the tw o analyses described in Figs. 1.2.8 and 1.2.9 is correct w ill have to be determined from further research into the operation of journal bearings as well as research on the rheological properties o f engine oils, particularly at high temperatures and shear rates. The numerical solution to bearing design equations fo r both non-Newtonian and elastic fluids should provide an understanding of what characteristic shear rate is required fo r de­

40

fining bearing performance. Coincidentally, the measurement o f oil viscosities and elastic properties at temperatures and shear rates representative o f bearing operation should allow the determination of the relative magnitudes o f these two rheological effects. Research into both o f these areas is a continuing e ffo rt in several laboratories around the world.

PREDICTED OIL FILM TH ICKN ESS, l/un)

Figure 1.2.10: A Comparison o f Measured and Predicted Bearing Oil Film Thicknesses from a Regression Using Viscosity and Relaxation Time Measured at 100°C and at the Maximum Shear Rate in the Bearing as Independent Variables. Reprinted w ith permission, Copyright 1986, Society o f Autom otive Engineers, Inc.

1.2.6

Does the Automobile Industry Need a Bearing Film Thick­ ness Test?

The answer to the central question o f this paper depends entirely on whether or not the film thickness in a journal bearing o f an operating engine can be adequately described by one or more laboratory oil Theological properties measurements. Clearly, if relatively straightforward laboratory measurements are available, there is no justification fo r a more complex, harder to control, more time-consuming and expensive engine test. SAE J300 was originally

41

developed as a table o f oil viscosities from which engine designers could choose an oil suitable fo r use in their engines w itho ut having to evaluate a large number o f oils in engine tests. The concept of such a table o f oil viscometric properties is still valid and desirable. But are the proper rheological measurements which affect bearing oil film thickness known, and can they be easily measured in the laboratory? Although our research has progressed greatly during the last decade, and we now have the capabilities to measure film thickness in bearings more easily than ever be­ fore, it must be said that the exact relationship between oil rheological properties and bearing film thickness fo r multigrade oils is yet to be determined. The data in several publications have demonstrated that the viscosity o f engine oil measured at a temperature and shear rate close to those o f an operating journal bearing is an important factor in bearing performance. No reasonable inter­ pretation o f the existing data would conclude that kinematic viscosity at 100°C relates better to bearing film thickness than does a viscosity measured at bearing temperatures and shear rates. The problem which occurs, however, is that each engine bearing and operating condition is characterized by a different shear rate and temperature. Where 150°C and 10s s—1 might be well suited to describe the operation o f some bearings at certain operating conditions, it is less suited fo r others. Complicating the issue even further is the fact that the characteristic shear rate o f an operating journal bearing is itself a function o f oil viscosity. As oil viscosity increases, film thickness increases and shear rate, in general, decreases. Thus, the selection o f any particular set o f shear rate and temperature conditions at which to specify the viscosity grade o f an engine oil must be viewed as a compromise based on the characteristics o f many engines and many operating conditions. This concept is not w ithout precedent, however. The pum pability specifications in SAE J300 (the Borderline Pumping Temperature, BPT) are based on an average o f the pum pability characteristics o f a set o f widely differing engines. The advancements which have been made over the past decade in measuring the viscosity o f oils at high temperatures and shear rates have also been significant. Although the maximum shear rates at which oil viscosities have been reported measured in the laboratory range from 2 to 5 x 106 s~* (13,14), less than the shear rates which can occur in con-rod bearings (6), these measure­ ments are significant in that a decade ago viscosity determinations at 10* s-1 were considered the lim its o f laboratory capabilities. Regardless o f the value o f shear rate which is identified as being representative o f bearing operation, if the shear rate is produced in an operating engine, it can be reproduced in a laboratory viscometer. Viscosity values may be determined on a relative rather than an absolute basis, but they w ill be determined none-the-less. The other rheological property which may influence journal bearing operation is oil elasticity. Although the relative influence o f this multigrade oil property is still to be verified, the measurements needed to define its effect in engines

42

are available, and the laboratory measurements needed to quantify its magnitude are beginning to be developed. The limited data which have been collected in recent engine bearing studies suggest that the effect of elasticity is additive to that o f any viscosity effect. If this is true, it means that a vis­ cosity classification system based only on measurements of high-temperature, high-shear viscosity would define a level o f minimum performance fo r m ulti­ grade oils. This would provide protection fo r the automotive industry from shear-thinning, non-elastic multigrade oils. If it can be unequivocally demon­ strated that elasticity provides an extra measure of protection fo r certain multigrade formulations, then recognition o f this fact could also be incorpor­ ated into a system such as SAE J300 at a later date. With regard to the problems which might be experienced in developing an engine BOFT test, it is w orth noting that the development o f any "standard" industry engine test is a time-consuming, arduous task. In this instance, potential prob­ lems would arise even in the selection of a test engine. Because the operat­ ing characteristics o f passenger car and heavy-duty engines are radically d iffe r­ ent, it is doubtful that either segment of the industry would accept a BOFT engine test which uses the other's engine. Journal bearings in heavy-duty engines are designed differently and for different objectives as are those in passenger car applications. Even if an engine could be selected to which both segments of the industry agree, the selection of lim its on film thickness to define different viscosity grades o f oil in such a test would present a significant hurdle. BOFT engine tests are excellent tools fo r developing an understanding o f how journal bearings operate in an engine. As a technique for defining different grades of engine oil, however, they should be considered as a last resort after it is demon­ strated that laboratory rheological properties measurements can not do the job adequately. Given the current data regarding the effects of oil rheological properties on bearing oil film thickness in engines, it is the opinion of General Motors Cor­ poration, that including oil viscosities measured at a representative temperature and shear rate in the Viscosity Classification System, SAE J300 is sufficient for providing a measure o f oil high-temperature, high-shear viscometric performance. The engine test procedures which have been developed for research projects designed to study oil rheological effects on bearing performance are very good, and the data collected from them w ill help in the selection of a temperature and shear rate which is representative o f industry bearing characteristics. However, at this time, there is no compelling reason fo r complicating the oil qualification process w ith an engine test designed to measure only journal bearing film thick­ ness.

43

1.2.7

Is an Industry Engine Bearing Test of any Sort Needed?

It has been demonstrated in previous engine studies that bearing wear is a function of both the rheological properties of an oil as well as its chemical characteristics (1). The rheological properties insure a sufficient oil film th ick­ ness when the engine is up to speed and operating at relatively steady conditions. The chemical characteristics protect the bearing during interm ittent contacts between it and the journal which can occur during accelerations, decelerations and each time the engine is started. A t General Motors, we believe the rheolo­ gical properties which are required to insure suitable oil film s during steady engine operation can be provided by the inclusion o f HTHS viscosity specifica­ tions in SAE J300. However, we also realize that there is very little in the remainder o f the oil qualification system which protects bearings based on the chemical characteristics o f the oil. If the industry is to take it upon itself to develop an engine bearing performance test, then we believe that test should evaluate bearing distress and wear rather than oil film thickness. In particular, correlation between bearing wear in a laboratory engine and long-term bearing durability in the field should be the ultim ate objective o f such a test. The com­ bination of viscometric specifications in SAE J300 and the a bility to rank chemistries based on long-term bearing wear would provide the industry w ith an excellent tool for meeting the tw in objectives o f producing high-powered, durable engines while at the same time optimizing corporate fuel economies.

1.2.8 (1) (2) (3)

(4) (5) (6) (7) (8)

44

References

The Relationship Between High-Temperature Oil Rheology and Engine Operation: A Status Report, ASTM Data Series DS-62, ASTM , Philadelphia, PA 19103 (1985). Bassoli, C.; Cornetti, G.; Belei, M.: "A System for Assessing the General Conditions of Lubricated Crankshafts", R IV IS T A A T A T , January (1978). Spearot, J.A.; Murphy, C.K.; Rosenberg, R.C.: "Measuring the Effect of Oil Vis­ cosity on Oil Film Thickness in Engine Journal Bearings", SAE Paper No. 831689 (1983). Craig, R.C.; King Jr., W.H.; Appeldoorn, J.K.: "O il Film Thickness in Engine Bearings - The Bearing as a Capacitor", SAE Paper No. 821250 (1982). Girshick, F.; Craig, R.C.: "O il Film Thickness in a Bearing of a Fired Engine, Part III: The Effects of Lubricant Rheology", SAE Paper No. 831691 (1983). Schilowitz. A.M .; WBters, J.L.: "O il Film Thickness in a Bearing of a Fired Engine - Part IV " . SAE Paper Nol 861561 (1986). Bates, T.W.; Benwell, S.: "Effect of Oil Rheology on Journal Bearing Performance", SEA Paper No. 880679 (1988). Bates, T.W.; Vickars, M.A.: "Measurement of II Film Thickness in Big-End Bearings and Its Relevance to Engine Oil Viscosity Classifications", 3rd CED International Symposium on Performance Evaluation for Automotive Fuels and Lubricants, Paris, April 1 9 -2 1 (1989).

(9)

(10) (11) (12)

(13) (14)

Spearot, J.A.; Murphy, C.K.: " A Comparison of the Total Capacitance and Total Resistance Technique for Measuring the Thickness of Journal Bearing Oil Films in an Operating Engine", SAE Paper No. 880680 (1988). Deysarkar, A .K .: "The Bearing Oil Film Thickness of Single and Multi-Grade Oils — Part I: Experimental Results in a 3.8 L Engine", SAE Paper No. 880681 (1988). Spearot, J.A.; Murphy, C.K.: Deysarkar, A .K .: "Interpreting Experimental Bearing Oil Film Thickness Data", SAE Paper No. 892151 (1989). Bates, T.W.; Williamson, B.; Spearot, J.A.; Murphy, C.K.: " A Correlation Between Engine Oil Rheology and Oil Film Thickness in Engine Journal Bearings", SAE Paper No. 860376 (1986). Tolton, T.: "T he Temporary Viscosity Losses of New and Sheared Multiweight Oil Formulations Characterized at Multiple Shear Rates", SAE Paper N o .890272 (1989). Lodge, A.S.: "Multigrade Oil Elasticity and Viscosity Measurement at High Shear Rates", SAE Paper No. 872043 (1987).

45

2. Base Oils 2.1

Structure of Oils According to Type and Group Analysis of Oils by the Combination of Chromatographic and Spectral Methods

2.2

Dependency of Viscometric Properties on Base-Stocks Che­ mical Structures in Multigrade Crankcase Oils

2.3

Determination of Zinc and Calcium in Multigrade Crankcase Oils

2.4

The Characterisation of Synthetic Lubricant Formulations by Field Desorption Mass Spectrometry

2.5

Tailor Making Polyalphaolefins

2.1

Structure of Oils According to Type and Group Analysis of Oils by the Combination of Chromatographic and Spectral Methods

P. D aucik.T. Jakubik, N. Pronayova and B. Zuzi, Slovak Technical University, Bratislava, Czechoslovakia

Summary In this work was used the rapid preparation-analysis separation o f oils on the chromatographic column w ith recirculation o f the eluant. The basic quantitative data concerning the group composition o f oils have been supplement by analysis o f chromatographic fractions by means o f NMR spectrometry. The analysis results o f group composition o f oils obtained by means o f chromatographic fractionation have been completed w ith the results of NMR spectrometry and mass spectrometry.

2.1.1

Introduction

Knowledge o f the composition o f oil products is a prerequisite o f optim ization o f technological processes and better utilization o f raw materials. Therefore, the requirements fo r a prom pt analysis o f vacuum distillates and residues are still in the foreground o f interest. With increasing boiling p oint o f hydrocarbons the possibility o f their resolution in a m ixture decreases. Therefore, by chroma­ tographic separation o f oils, data on their group composition are obtained. In spite o f the intensive development o f high efficient liquid chromatography problems w ith detection, calibration, recovery, etc. remain unsolved during the separation of oil compounds (1-3), and therefore, also preparative separations are employed (4, 5). Introduction o f spectral methods to the analysis o f oil fractions resulted in a remarkable progress. Their great advantages are reliability o f results, time saving and considerable information. Structural type analysis an information on an average molecule can be obtained from infrared (6 ) or NMR (7, 8 ) spectra. Direct determinations of group composition o f oils by NMR spectrometry (9) are derived from simplifying prerequsites which are not always fu lfille d. The quantitative analysis by mass spectrometry ( 10, 11) provides more information on the group composition o f oils. However, they are more demanding as fo r the instrument calibration, its price and considerable wearing.

48

The combination o f separation and spectral methods always brings the most valuable inform ation on the sample composition. The preparative-analytical methods o f the chromatographic determination of the group composition of oils together w ith the mass and NMR spectrometry are the most efficient modes of oil analysis. The use o f a simple and cheap separation method together w ith the analysis o f fractions obtained ensures reliable quantitative and qualitative data on the sample analyzed.

2.1.2

Experimental

Chroma tography: A sample weighing 1 g was separated by a preparative-analytical method of chromatographic determination o f group composition. The sample was dis­ solved in 5 ml of hexane. A glass column was used (Fig. 2.1.1) which was con­ nected to a boiling flask and cooler. The eluant was evaporated through a side tube of the column and condensed in the cooler. The side tube was used for recycling the eluant on the head o f the column. The column was filled w ith 15 g of alumina and 25 g o f silica gel (bottom layer). Alumina and silica co

60 60

35

34

32

30

27

25

22

20

18

17

BO 3

BO 4

BO 5

BO 6

BO 7

BO 8

BO 9

BO 10

BO 11

BO 12 23

21

20

18

15

13

10

8

6

5

82.05

78.98

77.09

74.33

69.71

6621

62.37

58.82

57.54

55.45

53.83

_ 3

50.22

135 Brt.

9.72

9.48

9.32

9.15

8.75

8.49

8.17

7.88

7.75

7.68

7.44

7.14

Kin. Vis., cSt., 100° C

* A multipurpose additive is incorporated in all form ulations at concentration 7.9 % w t.

60

60

60

60

60

60

60

60

60

37

BO 2

60

Base-Stocks, % w t 300 N

40

150 N



Base Blends: Constituents and Characteristics

BO 1

Base Blends*

Table 2.2.1:

■t* o0 O

96

96

96

97

97

97

98

98

98

99

99

99

VI

2

38.29

10.37 46.86

45.9

16.9

58.3

54.1

BO 12

absolute -1 6 .9 change percent -2 3 .8 change

32.5

32.04

29.79

44.5

41.29

29.02

27.69

58.71

40

55.5

60

27.19

25.51

25.2

24.44

23.52

22.32

22.13

MAR

BO 11

61.71

BO 8

BO 9

37.4

53.42

34.8

33.8

32.5

31

29

TAR

76.6

4.12

9.5

9.1

8.45

8.1

7.9

7.7

7.51

7.26

7.15

7.05

6.81

5.38

DAR

Chemical Groups, % w t

161.7

2.41

3.9

3.36

3.05

2.88

2.7

2.51

2.4

2.34

221

1.93

1.87

1.49

PAR

Base Blends: Chemical Structure Variables

BO 10

64.58

62.6

BO 6

BO 5

BO 7

66.2

65.2

BO 4

69

67.5

BO 2

BO 3

71

BO 1

SAT

Table 2 .2 2 :

118.7

1.08

1.99

1.87

1.77

1.7

1.61

1.53

1.43

1.29

1 26

122

1.12

0.91

- 1 .9 2

- 1 .2 7

64.87

64.96

65.04

65.18

65.31

65.42

65.59

65.7

65.81

65.86

65.97

66.14

Nonhydron. % wt (S+N+O) Cp

5.640

0.54

10.12

10.08

10.05

10.

9.93

9.88

9.81

9.76

9.72

9.7

9.65

9.58

CA

CN

2.02

0.49

24.77

24.74

24.71

24.67

24.6

24.56

24.49

24.45

24.4

24.39

24.34

2428

Mole %

1889

1.07

1.63

1.54

1.44

1.31

1 22

1.16

1.09

0.94

0.78

0.75

0.65

0.56

^m

o> U1

26 26

non-dispersant dispersant

PMA PMA-D

Polyalkylmeth acrylate

Mixed copolymer

11

Polyalkylmeth aery late

(M IX) 1

Mixed copolymer

non-dispersant

13

45

(OCP)2

Olefin copolymer

non-dispersant

solid

highly dispersant

(OCP)1

Olefin copolymer

non-dispersant

5

5.5

3

3.6

12

10.8

1.3

1.02

solid

(MIX12

SBCP

Styrene-butadiene copolymer

non-dispersant

Dose, % wt

Co-Polymer Content, % w t

40

SICP

Styrene-isoprene copolymer

Dispersing A ctivity

highly dispersant

Symbol

Viscosity Index Improvers Characteristics

Copolymer Chemical Structure

Table 2.2.3:

-

Kinematic viscosity o f multigrade blend at 40 and 100° C (V40 & V100).

-

Kinematic viscosity increase (AV) = V — Vo at 40 and 100° C (A V40 & A V100).

-

Viscosity index (VI)

-

V -V o „ Specific viscosity (Vsp) = ------------ at 40 and 100 C (Vsp40 & Vsp 100) Vo

-

V sp100 Thickening tendency (Q) = -----------Vsp40

A computer program was used to explore and derive the statistical relation­ ships between the blends viscometric properties and the chemical structure variables for incorporated base-stocks (14 & 30).

2.2.4

Statistical Methodology

Regression analysis, as a statistical technique, is usually used to examine results and draw conclusions about the functional relationships existing between the independent variables and the dependent responses (14 & 36). Through regres­ sion analysis it is possible to get clear answers about the following three basic questions: Is it so?, To what extent is it so? and Why is it so? Single linear regression analysis can be simply represented by the following equation: V = A + aX Where, V X A a

= = = =

dependent response independent variable equation constant regression constant

In this study V, as dependent response, is one of the tested viscometric proper­ ties fo r formulated crankcase multigrade oils, while X, as independent variable, is one o f the chemical structure variables fo r incorporated base-stocks. As base-stocks contain m ultiple chemical structure variables, such single re­ gression relationships are misleading. It is obvious that no single independent variable can alone explain the performance behaviour o f a formulated blend. Therefore, it is more realistic to use multiple linear regression, which can be represented by the follow ing equation:

66

Y - A + aj X, + a2 X2 . . . + am X m where, — X i, X2 . . . X m are independent variables, i. e. base-stocks chemical structure variables. — a i , a2 . . . am are regression constants. Non-linear regression analysis can also be applied to improve the correlations as obtained via the linear relationships. For each derived model the following statistical factors can be calculated and used to check its confidence and suitability: — F:

a statistical parameter which is taken to assess the whole model signi­ ficance and to be compared w ith the statistical F-Distribution.

— t:

a statistical parameter which is taken to assess the significance o f each partial relation (i. e. w ith each of the independent variables) and to be compared w ith the statistical t-D istribution. Positive t value indi­ cates direct proportionality between Y and X, while negative value shows inverse proportionality. Sign o f t value is similar to that o f F value. It is also possible to use t value fo r the entire model.

— R2 :

the model correlation coefficient.

Models w ith F and t values higher than those listed in the statistical tables for confidence of 99.5 % are the only models to be considered in this study. Any accepted model must also represent a logical physical meaning. References 14 & 30 include more data about the use of statistical methodology.

2.2.4.1

Chemical Variables

In this study the follow ing single chemical structure variables are considered to derive the dependency relationships (i. e. statistical models): Saturates (SAT), total aromatics (TAR), monoaromatics (MAR), diaromatics (DAR), polyaromatics (PAR), total non-hydrocarbons (S+N+O), sulphur percent mole (Sm), paraffinic carbon (Cp), naphthenic carbon (C|yj) and aromatic carbon (C/^). Absolute and percent changes in these single variables by going from oil B01 to oil B012 are listed in Table 2.2.2. Some other combined variables were calculated, either by adding, m ultiplying or dividing of the basic single variables. These derived combined variables are included in the following: 67

6.67

6.57

6.47

6.5

6.68

6.73

0.79

10.51

BO 7

BO 8

BO 9

BO 10

BO 11

BO 12

absolute change

percent change

-

35.34

6.93

80 6

65.05

-

27.42

8.71

23.05

27.17

50.59

23.33 23.84

29.74

23.74

24.43

24.79

26.89

26.78

33.17

45.19

50.39

52.46

-

38.26

7.42

BO 5

-

23.56

40.89

7.42

26.62

BO 4

55.28

7.35

BO 3

27.6

61.44

7.73

BO 2

31.76

77.76

(S+N+O)

7.52

(S+N+O)

(S+N+O)

(TAR)

BO 1

(SAT)

-

-

45.21

72.84

88.27

90.82

89.76

95.24

98.18

101.08

101.2

116

135.2

135.42

147.62

161.11

(S)

(DAR+PAR)

Combined Chemical Structure Variables

(DAR+PAR)

Table 2.2.4:

27.59 27.18

29.2 29.4 29.6

8.969 8.544

0.1115

35.77

59.08

17.24

42.42

44.99

41.75

40.42

38.68

37.77

173.59

63.42

-

12.3 32.49

11.33

6.23

0.1606

3.13

30.76

6.56

10.8

25.77

30.5

6.99

0.143 0.1525

-

25.43

30.24

7.62

0.1313

0.1019

26.14 25.00

29.89

8.15

32

0.1227

0.117

28.31

28.07

10.411

0.096

35.1

37.44

0.08

34.05

28.32

37.42 28.22

41.33 27.93

14.7 12.44

0.077

32.74

38.17

27.63

17.03

(CA+Sm) (Cp /C n )

(cA) (Sm )

(Ca )

(Sm>

12.93

0.068

0.0587

(TAR+S)

31.21

29.18

(S)

(TAR)

(DAR+PAR)/(S+N+0), (TAR)/(S+N+0), (TAR)/(S), (Shti/C a ), (CA/Sm)> an MAR > DAR > PAR > (S+N+O) As percent change: PAR > (S+N+O) > DAR > TAR > MAR > SAT Such high increase in the percent change fo r polyaromatics, non-hydrocarbons and diaromatics is directly related to the increase in bright-stock content. With regard to the chemical structure variables, as percent mole, which sre also listed in Table 2.2.2, it is possible to order the change in them according to the following: 69

As absolute change:

Cp>sm > c A > c N As percent change:

Sm > CA > CN > CP Combined chemical structure variables, as listed in Table 2.2.4, are also changed in steps by increasing bright-stock. Order o f decrease in these variables is ac­ cording to the following: As absolute change:

(DAR + PAR)/S > (SAT)/(S+N+O) > (TAR/S) > TAR/(S+N+0) > (DAR+PAR)/(S+N+0) > (TAR+S). As percent change:

(TAR+S) > SAT/(S+N+0) > (TAR/S) > (DAR+PARJ/S > TAR/(S+N+0) > (DAR+PAR)/(S+N+0) The change in the combined chemical variables, as percent mole, is found to be according to the follow ing order: As absolute change:

(CA + Sm) (Cp/CN) > S m/CA > C A /Sm As percent change:

Sm/CA > < CA +Sm> « V CN> > CA 'Sm 2.2.5.2

Change in Viscometric Properties with increasing bright-stock content

VI improvers were incorporated in the base-blends (B01 - B012 - Table 2.2.1) at the treating rates recommended by their suppliers. The following vis­ cometric properties were measured on the formulated blends: — Kinematic viscosity at 40 & 100° C (V40 & V100). — Kinematic viscosity increase (difference between kinematic visocosity of VI improver containing blend (V) and kinematic viscosity o f neat blend (Vo) a t 40 & 100° C (A V 4 0 & A V 1 0 0 )). — Viscosity index (V. I.)

70

-

Specific viscosity at 40 & 100° C (Vsp 40 & VSp 100). Where, V - Vo Vsp = ---------Vo

-

Thickening tendency (Q). Where, Vsp 100 Q = -----------Vsp 40

Table 2.2.5 includes these viscometric results fo r blends B01 and B012 w ith zero and 23 % w t o f bright-stock respectively. While V40, A V40 & V100, A V100, Vsp 40 and Vsp 100 fo r all blends are increased w ith increasing brightstock, their VI and Q value are decreased. For more illustration Fig. 2.2.1 includes the change in V100 and VI fo r the tested blends against increase in bright-stock. Accordingly, it is clear that oils viscometric properties are re­ markably changed w ith increasing bright-stock. Comparing the absolute changes in these viscometric properties, as listed in Table 2.2.6, w ith the changes in the chemical structure variables, as listed in Table 2.2.2, is also clearly supporting that the limited changes in chemical variables have resulted in great changes in oils viscometric properties. In other words, such comparison clearly shows the high dependency o f oils viscometric properties on chemical structure variables o f base-stock. In general, these viscometric properties are indicating the following: 1. Increase of bright-stock content results in a very wide change in kinematic viscosity at 40 C. It is possible to explain such a change in V40 by the improvement of the blends solvation power due to the increase in their aromaticity as their contents o f bright-stock are increased. 2. The wide increase in A V40 is in analogy to such a remarkable increase in V40. 3. Kinematic viscosity at 100°C for VI improver containing blends w ith zero % w t bright-stock (i. e. based on oil B01) have not been acquired the re­ quirement o f SAE 50 viscosity (16.3 cSt at 100°C). According to Fig. 2.2.1, these blends have acquired the SAE 50 viscosity lim it at the follow ing bright-stock contents: SICP SBCP (OCP)1 (OCP)2

12.8 19.2 4.4 6.2

%wt %wt %wt %wt

(Mix) 1 (Mix)2 PMA PMA-D

20.5 23 11 15

%wt %wt %wt %wt

71

4. Changes in A V100 are limited in comparison to A V40 changes. 5. Due to the increase in the oils solvation power the viscosity index for all blends is decreased.

VISCOSITY

INDEX

IV.I.I

KIN.

VIS.

»T

IOO*C

IVIOOI.

cSl.

6 . Changes in Vsp 40, Vsp 100 and Q value can be considered limited in com­ parison to changes of other viscometric properties. As expected, Q values fo r all blends are decreased w ith increasing bright-stock. While both Vsp 40 and Vsp 100 for all blends are increased, those fo r SICP are decreased. It is d iffic u lt to explain these Vsp results fo r SICP w ith o u t considering its Vsp at other temperatures.

B R IC H T -S T O C K ,

Figure 2.2.1:

72

%

« T .

Change in kinematic viscosity at 100° C and viscosity index w ith increasing bright-stock content

co

4.89

1.096 0.8

0.84

0.849

1.081

Q

1.36

1.22

0.786

1.46

0.926

0.845

122

0.914

119

128

11.88

7.64

10.66

20.38

21.6

17.36

75.95

194 111.95

119.95

0.86

0.91 202

158

0.882

1.245 1.07

1.29 1.17

135

7.66

14.8

62.55

112.77

(OCP)2

Vsp 100

138

8.88

18.6

69.35

0.777 0.685

142

8.38

15.52

64.85

115.07

(OCP)1

Vsp 40

V. 1.

A V100

bright-stock) V 100

A V40

(23 % w t

151.4

1.059

Q

V40

0.966

BO 12

0.913

Vsp 100

V. I.

Vsp 40

128

6.9

bright-stock) V 100

150

12.03

14.04

A V100

39

45.83

A V40

(zero % w t

89.22

SBCP

V40

96.06

SICP

BO 1

Oil

0.936

0.757

0.809

125

7.36

17.08

66.35

148.4

1.018

0.604

0.593

132

4.31

11.45

29.78

80

(MIX)2

0.918

0.693

0.755

122

6.74

16.46

61.95

144

0.929

0.668

0.719

131

4.77

11.91

36.13

86.35

(MIX)2

5.91

1.059

1.035

0.977

141

10.06

19.78

80.15

162.2

1.269

0.941

0.742

1.157

0.868

0.75

141

8.44

18.16

61.55

143.6

1.243

0.828

0.666

157

6.72 163

13.05

33.43

83.65

PMA-D

13.86

37.26

87.48

PMA

Table 2.2.5: Viscometric properties fo r formulated multigrade crankcase oils w ith zero % w t and 23 % w t bright-stock

49.4

36.57

68.78

86.93

81.23

68.4

57.65

74.72

59.95

SBCP

(OCP)1

(OCP12

(MIX)1

(MIX)2

PMA

PMA-D

28.12

42.89

25.82

55.1

36.95

23.52

55.35

SICP

A V40

V40

/I Improver

5.11

5.92

4.55

5.63

5.59

6.08

5.33

4.56

V100

2.53

3.34

1.97

3.05

3

3.5

2.75

1.98

A V100

-

-

-

-

-

-

-

-

VI

16

22

9

7

13

14

9

12

-

0.084

0.235

0.036

0.216

0.119

0.171

0.149

0.067

Vsp 40

-

-

0.041

-

-

-

-

-

-

0.094

0.025

0.154

0.024

0.648

0.101

0.05

Vsp 100

0.086

0.213

0.01

0.082

0.058

0.072

0.033

0.022

Q

Table 2.2.6: Change in viscometric properties fo r formulated multigrade crankcase oils by increasing bright-stock content

According to Table 2.2.6, it is possible to evaluate the response o f the different VI improvers to bright-stock increasing. Such a response is considered in terms of the absolute changes in each viscometric property. The order o f decrease in these responses is found according to the following: high «- response o f V I improver -*■ low V40 AV40

(OCP)1 (MIX) 1

> >

(OCP)2 PMA-D

> >

PMA (MIX)2

> >

SBCP SICP

V100 (OCP)1 AV100 SBCP

> >

PMA PMA-D

> >

(MIX) 1 (MIX)2

> >

(OCP)2 SICP

> >

PMA-D SBCP

> >

(OCP)1 (MIX)2

> >

(OCP)2 (MIX) 1

V. I.

PMA SICP

As the differences in Vsp 40 and Vsp 100 are very close, the ordering o f them in terms of VI improver responses is found not to be significant. With regard to Q values (cf. Table 2.2.5) the order of decrease in them fo r blends based on B012 (with 23 % w t bright-stock) is found according to the following: Q > 1 PMA-D > SICP > PMA, Q < 1 (M lX) 1 > (M1X)2 > SBCP (OCP)2, (i.e. behave as thickeners)

(i.e. behave as VI improvers) > (OCP)1 >

In general these changes for the oils viscometric properties clearly prove the following: 1. The high dependency of oils viscometric properties on base-stocks chemical structures. 2. Response of tested VI improver samples towards change in base-stocks chemical structures is remarkably different.

2.2.5.3

Dependency of Viscometric Properties on Single Chemical Structure Variables

Single linear regression analysis (Y = A + aX) was applied to evaluate the degree of dependency fo r each o f the measured viscometric properties on the chemi­ cal structure variables. It was on mind, at deriving the correlation between viscometric properties and single chemical structure variables, that no single chemical structure can exist alone or affect all viscometric properties w ith the same magnitude of power. Actually the main reasons to carry the single re­ gression analysis are: 1. To define direction of proportionality (as direct or inverse) between visco­ metric properties and each of the chemical structure variables. 75

2. To establish magnitude o f dependency o f each viscometric property on each chemical structure variable. Tables 2.2.7 - 2.2.14 include the F values fo r the derived statistical models between measured viscometric properties and each o f the single and combined chemical structure variables. As the F values for models o f the single chemical variables are extremely high, it is clear the presence o f high dependency o f viscometric properties on most of the single chemical variables. The percent confidence in these models is also very high (over 99.5 %). Exploring directions o f proportionality and magnitude o f dependency according to these models is discussed in the succeeding tw o sections. 2 .2.5.3 .1 D irections o f P ro po rtio na lity Table 2.2.15 includes directions o f proportionality between the different che­ mical structure variables and each o f the measured viscometric properties. In spite of that, these directions o f proportionality can be traced by referring to the trend o f increasing or decreasing o f each chemical variable comparing with each viscometric property, but applying the regression analysis technique has helped in defining them by referring to the sign of the F values fo r each de­ rived model, as listed in Tables 2.2.7 - 2.2.14. It can be seen, according to Table 2.2.15, that all single chemical variables, w ith the exception of SAT and Cp, are at direct proportionality to all visco­ metric properties. With the exception o f V I and Q value which are at inverse proportionality. With regard to SAT and Cp, they are at direct proportionality to VI and Q and at inverse proportionality to the rest o f the viscometric pro­ perties. These observations concerning the direction o f proportionality, agree w ith the previously published conclusions (19, 22 & 25) which have clarified that the viscosity o f V I improver containing blend is increased as the structure of base-stock becomes more aromatic. 2.2.5.3.2

Magnitude o f Dependency

Magnitude o f dependency o f viscometric properties on chemical structure variables can be expressed via considering the F values o f the derived models. The high F value indicates a high degree of dependency and the opposite is also correct. Therefore, it was possible to order the decrease in magnitude o f depen­ dency in terms o f the F values, as listed in Tables 2.2.7 - 2.2.14, fo r each incor­ porated VI improver. Table 2.2.16 includes the order o f decrease in depen­ dency o f the different viscometric properties on the following single chemical groups: SAT, MAR, DAR, PAR and (S+N+O). In this table similar orders for magnitude o f power are put together. 76

(*)

L.C.: low confidence

73 336.4 388

74.4 585.8 753.3

38.9

37.2

Ca /S iti Sm/CA (CA+Sm) (Cp/Cfsj)

64.5 25.4 62.3 74.1

61 30.2 80.3 56.4

178

308.4 302.8 269.4 350.5

174.5 252.3 93.3 49.7 166.2

351

499.4 1342.2 1244.9 704.9

-

-

399.5 499.4 139.5 70.1 369.8

-

A V 40

Combined (TAR/S) TAR/(S+N+0) SAT/(S+N+0) (DAR+PAR)/S (DAR+PAR) (S+N+O) (TAR+S)

Cp Cn Ca Sm

Single SAT MAR PAR DAR (S+N+O)

V 40

-

-

-

59.5 351.3 435.7

296

35.1

49.4 27.4 68.2 472

848.7 817 879.6 412.3

289 435.1 129.8 63.8 288.5

V 100

-

-

-

42.5 169.4 182.7

117.6 55.9 51.4

33

147

135.4 98 48.7 94.4

39.2 38.4 36.5 51.6

32.3 31.8 29.5 24.7 37.7

25.1 -

-

-

VI

31.1

37.7 19.5 43.3 43.9

219 208.4 210.5 184.9

145.3 222 87.5 41.4 120.4

A V 100

Table 2.2.7: F values for dependency relationships (SICP blends)

L.C. L.C. L.C.

L.C.

L.C.

L.C. L.C. L.C. L.C.

L.C. L.C. L.C. L.C.

L.C.C) L.C. L.C. L.C. L.C.

Vsp 40

L.C. L.C. L.C.

L.C.

L.C.

L.C. L.C. L.C. L.C.

L.C. L.C. L.C. L.C.

L.C. L.C. L.C. L.C. L.C.

Vsp 100

L.C. L.C. L.C.

L.C.

L.C.

L.C. L.C. L.C. L.C.

L.C. L.C. L.C. L.C.

L.C. L.C. L.C. L.C. L.C.

Q

64.3 466.6 378.4

65.7 468.1 383.4

CA/Sm Sm/CA (CA+Sm ) (Cp/C|s|)

70.9 585.1 450.7

32.8 416.8

52.7 27.4 82.5 49.5

52.7 27.4 71.9 48.7 -

52.9 29.8 78.9 46.1

428

82.5 2313.3 2436.3 742.8

33.7

15 1271.2 1166.7 574.8

15.4 2014.6 2276.2 580.4

68 585.7 461.2

357.7

31.3

55.3 26.4 68.7 52.7

14.4 869.4 821 742.9

346.2 518.95 140.2 70.1 277.3

A V 100

386.5 525.9 150.7 80.4 432.8

32

386.5 589.9 149.2 72.7 322.8

414.9 561.2 157.6 78.9 416.6

V 100

398.4

-

-

A V 40

Combined TAR/S TAR/S+N+O SAT/S+N+O DAR+PAR/S DAR+PAR S+N+O TAR+S

Cp Cn Ca Sm

DAR (S+N+O)

Single SAT MAR

V 40

Table 2.2.8: F values fo r dependency relationships (SBCP blends)

-

-

-

VI

165.3 88.1 65.3

65.1

35.4

111.3 106 239.5 21.8

21.3 103.9 101.8 84.2

64.5 54 53.2 66.2 124.3

-

-

50.3 160.6 138.8 60.3 120.5 99.4

24.8

44.9 16.1 36 71.7

112 108.3 100.5 163.3

90.5

-

-

89.1 116.9 59.1 34.1 69.1

Vsp 100

78.4

29.5

58 19.4 42.8 75.1

12.8 107.4 94.7 119.5

77.4 95.2 50.4 34.12 69.5

Vsp 40

-

-

-

9.9 7.4 6.8

7

8.7

9.5 8.2 9.3 8.7

5.7 8.5 7.9 7.3

7 7.1 5.8 6.4 7.9

Q

(*) L.C.: low confidence

66.7 354.5 416.5

71.6 455.9 595.4

58.9 331 412.8

81.7 81.8 88.1

127.3

16.6

41

39.6

-

48.9 64 246.8 21.8

109.3 103 109.5 81.9

127.8 79.6 129.7 278 186.7

56.7 26.1 65.8 62.4

61.9 379.5 497.4

29.2

30.8

-

-

VI

46.6 26.3 78.8 55.7

CA/Sm Sm/CA (CA+Sm) (Cp/Cfsj)

58.6 30 70.7 42.1

49 28.6 76.8 42.7

219.7

626.2 671.3 616.9 398

214.6 364.5 92 53.7 203.7

300.2

-

-

A V 100

456

38.4 1754.7 1663.9 536.7

-

-

292.1 452.3 144.3 66.3 321.4

-

V 100

474.6

849.6 822.6 914.1 399.7

1348.2 1300.5 1622.4 459.9

-

-

445.3 696 155.8 76.8 305.7

461.8 651.7 162 80.8 386.1

-

A V 40

Combined TAR/S TAR/S+N+O SAT/S+N+O DAR+PAR/S DAR+PAR S+N+O TAR+S

cp Cn Ca Sm

Single SAT MAR PAR DAR (S+N+O)

V 40

Table 2.2.9: F values fo r dependency relationships ((OCP) 1 blends)

-

-

-

-

25.42 52.6 24.6 27.5

13.5 13.5 13.6 12.2

17.2 14.5 18.2 23.1 15.7

Q

21 19.3 27.6 27

55.5 32.7 52.2 52.5

11.2 12 12.4

17

L.C.

L.C. 10.3 15.6 5.3

-

20.8 27.3 14.6 9.8 18.2

- 20.5 L.C.* L.C. 45.6

-

Vsp 100

23.9

17.8

55.5 13.3 29.3 32.3

53.7 54.2 52.4 52.9

35.4 65.5 38.5 28 42.6

Vsp 40

(*) L.C.: low confidence

69.2 499.8 640.2

68.7 494.9 669.7

CA/Sm Sm/CA (CA+Sm > (Cp/C n )

32.9

54.6 29.3 81.8 48.2

500

-

114.5 475.3 613.4

208.8

49.8

54.6 29.3 125.9 67.5

1593 2387 1735.7 494.9

1564.3 1399.2 1361 607.6

151.6 295.1 326.7

123.7

62.5

123.7 48.4 128.4 91.5

435.8 499.6 419.1 283.2

120.7 133.7 66.1 55.8 218.4

A V 100

203.5 226.9 139.2 80.8 418.5

V 100

483.8 827.1 139.2 80.8 383.2

494.9

33.3

54.2 30.7 84.7 46.3

2371.7 2123 2477.3 610.2

-

-

478.7 695.5 149.9 83.5 458.6

-

A V 40

Combined TAR/S TAR/S+N+O SAT/S+N+O DAR+PAR/S DAR+PAR S+N+O TAR+S

cp Cn Ca Sm

Single SAT MAR PAR DAR (S+N+O)

V 40

-

-

-

VI

Table 2.2.10: F values for dependency relationships ((OCP)2 blends)

222 76 79

157.5

11.1

18.3 12.6 28.3 16.7

81.9 75.1 79.7 80.3

158.9 1622 127 59.9 76

3.3 11.6 5.4 5.2

49.1 45.9 58.8 56

62 13.7 13.8

20.5

L.C.* -

5.1 3.4 7.4 5.5

13.9 13.6 13.7 14.3

20.7 22.1 17.7 14.1 13.5

12

-

-

23

81.9 75.1 79.8 5.1

158.9 1622 127 59.9 76

Q

18.3 12.6 28.3 14.6

-

-

Vsp 100

3.3 8.2 7.2 49.2

51.3 50.8 47 57.5

-

-

48.8 58 29.2 27.3 41.3

-

Vsp 40

267.1 74.5 714 1258.7

35.1 404.9 73.7 730.2 2772

32 551.4 78 1047 3887.7

32.9

524.6

73.1 697.4 2873.04

38.2

60 30 83.1 52.7

63.3 29.6 8 4 .1 6 54.4

64.1 28.8 73 63.4

-

876.6 728.2 — — 734 861.5 —

-

2164.8 2020.2 2234.1 955.6

1396.8 1123 1157.7 1469.5 -

— 259 369.3 — 117.3 — 63.3 — 277 —

-

VI

390.4 532.9 145.7 78 429.8

A V 100

526.8 769.8 166.8 84.1 416.1

V100

58 31.2 86.7 49

2515.5 2081.1 2594.2 917

-

-

504 66 169.3 86.1 509.5

A V 40

-

(*) L.C.: low confidence

CA/Sm Sm/CA (CA+Sm) (Cp /C n )

Combined TAR /S TAR/S+N+O SAT/S+N+O DAR+PAR/S DAR+PAR S+N+O TAR+S

Sm

ca

Cp Cn

Single SAT MAR PAR DAR (S+N+O)

V 40

Table 2.2.11: F values fo r dependency relationships ((M IX) 1 blends)

124.2 73.5 66.6

65.3

32

802 38.9 1042 52.6

73 70.7 70.1 70.1

64.9 63.7 48.3 44 76

-

-

-

106.1 98.8 96.1 132.4

-

L.C. 66.1 65.9 136.3 117.7

125.8 162.7 345.1 213.8

5 9.6 L.C.

L.C.

34.4

44.9

L.C. L.C. L.C. L.C.

L.C.* L.C. L.C. - 5 L.C.

Q

L.C. L.C. L.C. L.C. -

65 77.7 45.5 30.9 74.8

-

Vsp 100

69.6 23.7 45.4 98.6 137.7 31.6 87.5 117.1

159.2 152 139.8 304.6

123.2 133.6 72.1 56.2 126.7

Vsp 40

(*) L.C.: low confidence

65.6 258.5 299.8

67.9 373.7 482.7

CA/Sm Sm/CA (CA+Sm ) (Cp/Cfsj)

68 252.1 315.2

211.1

153.5

255.9

55 36.5 89 45.4

928.1 1294.2 1261.3 277.9

42

-

-

56 131.1 150.3

110.1

47.8

47.7 342 69.7 42.3

281.8 333.7 313.4 137.9

108.9 126.1 61.4 48.9 163.1

A V 100

207.3 237.7 98.3 69.3 350.6

51.6

478.8 608.6 517.5 278.7

-

41.3

-

150.5 209.5 75.2 49.2 199.5

58.2 30 672 61.1

1259.9 1625.9 1698.9 431

249.8 336.7 110.5 65.7 343.5

V 100

56.5 32 79 51.5

-

-

-

A V 40

Combined TAR/S TAR/S+N+O SAT/S+N+O DAR+PAR/S DAR+PAR S+N+O TAR+S

Sm

Cn cA

Cp

Single SAT MAR PAR DAR (S+N+O)

V 40

-

-

-

VI

Table 2.2.12: F values for dependency relationships ((M IX )2 blends)

233 233.8 196.7

742

38.8

129.6 26.4 55.1 179.4

107.8 107 992 209.6

72.8 82.6 51.9 35.8 81.6

-

-

-

10.2 10.7 10.3 8

-

15.5 16.2 16

8 8 8.3

8 8 7.5

6.8 7

L.C.

16.4 11

5.8 6 5.6 7.7

42.3

-

L.C.* L.C. L.C. L.C. L.C.

Q

9.7 L.C. L.C. 22.3 -

7 7.7 5.2 5.3 8.7

-

Vsp 100

8 8.3 8.3 8.8

18.4 8.9 10.9 34.8

15.8 16.9 15.7 15.9

10.9 13.3 7.7 6.3 12.6

Vsp 40

CO GJ

200.4 1426.6 1909.5 565.8

-

55.8 370.9 416.3

63.9 452 622

34.9 140.9 163

45.2 217.2 273.4

24.2

28.7

CA/Sm Sm/C A (CA+Sm) (Cp/Cjsj)

44.4 25.7 69.2 37.2

50.3 30 82.1 40.9

253.7

228 614.6 712.2 475.1

585.9 679 212 90.5 317.8

355.2

-

557.1 627.3 190.3 93.2 475.9

-

603

28.6 19.5 45.6 26.1

123.8 260.1 288.1 161.4

252.9 312.2 138.7 65.5 154.7

576.2

-

-

A V 100

20.2

36.6 24.2 59.3 322

148.1 522.6 522.6 255.7

350.6 436.9 158.9 75.5 249.8

V 100

24.9

-

-

-

A V 40

Combined TAR/S TAR/S+N+O SAT/S+N+O DAR+PAR/S DAR+PAR S+N+O TAR+S

Cn Ca Sm

cP

Single SAT MAR PAR DAR (S+N+O)

V 40

Table 2.2.13: F values fo r dependency relationships (PMA blends)

-

-

-

VI

47.8 127.7 170.5

152.2

29.9

382 30.7 69.3 30.5

89.5 409.2 436.6 139

151.8 161.4 84.8 64.2 187.3

-

-

-

212 60.1 64.5

98

12.9

17.6 12.5 27 16.9

68.5 89.7 92.7 65.6

98.4 113.1 72 41.6 62.6

Vsp 40

22.9 57.5 51.5

18.3 41.2 47.3

14.9 59.8

15.3 132 24.9 14.6

40.9 72.3 73.2 442

60 67.5 43.1 31.9 50

8.9 -

-

-

Q

72.7

19.7 10.3 23.5 18.6

79.6 49.4 50.4 60.2

-

-

72.7 75 69.9 37.3 43.2

-

Vsp 100

2791.7 5529.7 4441.3 660

-

-

74 - - 66.5 - - 512 - - 622 - - 1382

VI

41.9 304.7 91.8 891.88 1214.8

39.1 366.9 83.4 664.4 9712

49.8 235.2 100 583.3 735.6

332.2

812 557.5 183.8

--

225.2 124.4 129.6

74.9

43.3

153.8 86.9 233.6 58.5

1650.5 146.5 2030.5 - - 154.8 1519.1 - - 143.9 1052.1 - - 117.4

294.6 417.9 121.3 68.6 372.8

75.3 32.9 90.7 69

CA/Sm S m /^A (CA+Sm) (Cp/CN )

-

3615.7 6033.7 5249.8 628.1

354.7 447.7 137.4 79.4 528.4

A V 100

66.4 34.8 96.6 55.6

39.5

1158.6 2058 1247 807

228.7 301.7 101.1 64.9 332

81.8 35.7 97.8 73

-

V 100

61.9 34.5 94.3 54.8

-

322.2 410.5 130.5 75.9 470.4

-

A V 40

Combined TAR /S TAR/S+N+O SAT/S+N+O DAR+PAR/S DAR+PAR S+N+O TAR+S

Sm

ca

cp Cn

Single SAT MAR PAR DAR (S+N+O)

V 40

Table 2 2 .1 4 : F values fo r dependency relationships (PMA-D blends)

-

-

-

702 37.8 36

44 45.7 42.3

26.5 22.7

53.7 12.9 22.6 153.5

32.9 332 31 43.5

30.8

-

-

262 31.5 20.1 14.1 25.9

Vsp 100

45.9

89 23.1 33.5 135.3

31.3 33.4 30.4 35.6

22.5 24.7 16.5 15.6 27

Vsp 40

-

-

-

41.5 192 18.8

13.5

29.9

46.1 25.2 26.6 38.9

17.9 19.3 17.8 18.3

13.4 13.6 10.1 12.1 17.3

Q

Table 2.2.15: Proportionality direction between viscometric properties and chemical structure variables

Chemical Variables

Proportionality Direction

Single

Combined

Direct

Inverse

MAR

(S+N+O)

V 40

V. I.

DAR

(TAR+S)

A V 40

Q

PAR

Sm/CA

V 100

TAR

(CA+Sm) (Cp/Cfsj)

A V 100

Cn

Vsp 40

Ca

Vsp 100

Sm

SAT

TAR/S

V. I.

V 40

cp

SAT/(S+N+O)

Q

A V 40

TAR/(S+N+0)

V 100

DAR+PAR/(S+N+0)

A V 100

DAR+PAR/S

Vsp 40

CA/Sm

Vsp 100

85

V 4 0 - A V 4 0 - A V 100 - Vsp 100

SBCP

(0CP)1

V 100

V 100

PMA

SBCP

(OCP)1

V 40 - A V 40 - V 100 - Vsp 40 - Q

V. I.

(MIX)2

PMA-D

V 4 0 - A V 4 0 - V 1 0 0 - A V 100 Vsp 4 0 - Vsp 1 0 0 - V. I.

(OCP12

V 100

V 1 0 0 - A V 1 0 0 - Vsp 100

PMA-D

V 1 0 0 - A V 1 0 0 - Vsp 4 0 - V s p 100

Vsp 100

PMA

(MIX)1

V 4 0 — A V 4 0 — V 100 — A V 1 0 0 — Q

(MIX)1

PMA-D

V 40 - A V 40 - Vsp 40

A V 40

(OCP12

A V 100 - Vsp 40

V 40 - A V 40 - V 100 - A V 100

V 40 - A V 40 Vsp 1 0 0 - Q

SICP

Viscometric Properties

VI Improver

(S+N+O) > MAR > S A T > DAR > PAR

MAR > (S+N+O) > SAT > PAR > DAR

(S+N+O) > MAR > SAT > PAR > DAR

MAR > SAT > (S+N+O) > PAR > DAR

Decrease in magnitude o f power for single chemical groups

Table 2.2.16: Viscometric properties as affected by the single chemical structure variables

According to Table 2.2.16, it is possible to observe and/or conclude the fo l­ lowing: 1. Most o f the viscometric properties fo r blends containing SICP, SBCP, (OCP) 1, (OCP)2 (i. e. all hydrocarbon copolymers) and PMA are highly dependent on MAR. The order o f decrease in magnitude of dependency on the five chemical groups is found according to the following: MAR > SAT > (S+N+O) > PAR > DAR This order clearly expresses the great role of monoaromatic compounds to affect the oils viscometric properties for formulated blends. On the con­ trary, this order shows the relative low magnitude for power fo r PAR and DAR in affecting these properties. This order also explains that the non­ hydrocarbons, in spite of their presence at very low content, affect visco­ metric properties at power higher than those for PAR and DAR, which are presented at higher concentrations (cf. Table 2.2.2). 2. For most of the viscometric properties fo r blends containing the mixed copolymer (S+N+O) > SAT > PAR > DAR. In the case of the other mixed copolymer (M IX)2, the role o f non-hydro­ carbons in affecting its viscometric properties is found to be more powerful than is the case in (MIX11. The order o f decrease in power o f chemical groups for this V I improvers is found according to the following: (S+N+O) > MAR > SAT > PAR > DAR. 3. With blends containing PMA-D, nearly the same order as that for (MIX)2 is found. The only difference is the exchange between DAR and PAR in their positions, i. e. the following order is found: (S+N+O) > MAR > SAT > DAR > PAR. The increasing role for the non-hydrocarbons w ith blends containing the fo l­ lowing VI improvers: ( Ml X) 1, (M IX)2 and PMA-D, can be explained by the presence o f dispersant chemical groups (i. e. nitrogen containing groups), which are attached to the structure of these ester-based copolymers. It is obvious to mention that similar molecules are usually associated free, there­ fore they are showing good solvation power to groups similar to them. Accordingly, these three viscosity index improvers are greatly affected by the change in the non-hydrocarbon content (or type) o f the base-stock che­ mical structures. 4. Most o f the V I and Q value results have showed a great role for the influence of the non-hydrocarbons. 87

5. Most o f the derived relations are supporting the low role o f power fo r the diaromatics (DAR) and polyaromatics (PAR) in affecting the oils visco­ metric properties. In general, the derived statistical models can be valuable in explaining the d if­ ferent behaviours fo r the viscosity index improvers under the influence o f the change in base-stocks chemical structure. With regard to the chemical structure variables, as presented by % mole, possi­ b ility to order dependency o f viscometric properties on them did not show clear agreement, where each V I improver has acquired different order fo r its response to the change in these variables.

2.2.5.4

Dependency of Viscometric Properties on Combined Chemical Struc­ ture Variables

Single linear regression analysis (Y = A + aX) was also applied to evaluate the degreee o f dependency o f viscometric properties on the calculated combined chemical variables, as listed in Table 2.2.4. The F values for the derived statis­ tical models are also listed in Tables 2.2.7 - 2.2.14. According to these F values it is clear that most o f the combined variables are in good correlation w ith the viscometric properties. In other words, measured viscometric proper­ ties showed a high dependency on the combined variables. Directions o f proportionality between the combined variables and viscometric properties are also listed in Table 2.2.15, where they are defined accordinq to the sign of the F values for the derived statistical models (cf. Tables 2.2.7 - 2 .2 .1 4 ). According to these F values, it is also possible to order the decrease in magni­ tude o f dependency o f viscometric properties according to the following: (TAR+S) > SAT/(S+N+O) > T A R /S > (DAR+PAR)/S > (DAR+PAR)/(S+N+0) > T A R /(S + N + 0 ). Most of the measured viscometric properties are found to be strongly affected by the first three variables. (TAR+S), SAT/(S+N+0), (TAR/S). Table 2.2.17 includes the viscometric properties which are affected by each o f these com­ bined variables. Accordingly, it is clear that the combined variable (TAR+S) strongly affected most o f the concerned viscometric properties. This variable is representing the sum o f the tw o most im portant single variables (TAR & S) in the base-stock chemical structure. This variable (TAR+S) was previously postulated and used by Burn and Greig in their valuable study concerning effect o f aromaticity on lubricating oil oxidation (3).

88

Table 2.2.17: Viscometric properties as effected by the combined chemical structure variables VI Improver

Viscometric properties

SICP

V 4 0 - A V 4 0 - V 1 0 0 - A V 100

SBCP

V 4 0 — A V 4 0 — V 1 0 0 — A V 100 Vsp 4 0 - Vsp 100

(OCP)1

V 4 0 - A V 4 0 - V 1 0 0 - A V 100 Vsp 40

(OCP)2

V 40 - A V 40 - V 100 - Vsp 40 V. I . - Q

(Ml X) 1

V 4 0 - A V 4 0 - V 1 0 0 - A V 100

(MIX12

V 4 0 - A V 4 0 - V 1 0 0 - A V 100

PMA

V 4 0 - A V 4 0 - V 1 0 0 - A V 100 Vsp 4 0 - Vsp 1 0 0 - V. 1. - Q

PMA-D

V 4 0 - A V 4 0 - V 1 0 0 - A V 100

SICP

V. I.

SBCP

Q

(M 1X } 1

Vsp 4 0 - Vsp 1 0 0 - V. 1.

(MIX)2

Vsp 4 0 - V . 1.

PMA-D

Vsp 40 — Vsp 100 — Q

SBCP

V. I.

(OCP)I

V. I.

(OCP12

A V 1 0 0 - Vsp 100

(M1X)2

Vsp 100

PMA-D

V. I.

Combined chemical variable

(TAR+S)

(TAR/S)

SAT/(S+N+0)

89

The other two variables SAT/(S+N+0) and TAR/S were also previously success­ fu lly used in explaining some o f the oils performance properties (1,4 , 5 & 14). In general, it might be im portant to explain the oils viscometric properties to draw the attention on these three variables. On the other hand, the order of decrease in dependency o f oils viscometric properties on combined chemical variables, as based on % mole (cf. Table 2.2.4) is found to be according to the follow ing: (CA +Sm) (Cp/CN] > S m/CA > C A/Sm Most of the measured viscometric properties are also found to be strongly affected by these three variables. As listed in Table 2.2.18, the variable (Ca +Sm ) (Cp/Cfsj) strongly affected most o f the viscometric properties, while the other tw o variables affected less properties. These three combined variables were previously developed by Korcek and Jensen in their study concerning the relation between base oil composition and oxidation stability fo r the oils at high temperatures (5). It is the first time to use o f them in explaining the viscometric properties o f base-stocks.

2.2.5.5

Predictive Statistical Models

Most o f the oils viscometric properties have shown high dependency on the tw o combined variables: (TAR+S) and (Ca +Sm) (Cp/C|sj). Therefore, their derived statistical models were used fo r the prediction o f oils viscometric proper­ ties. These models were derived via single regression analysis (Y = A + aX), where Y = X = A = a=

any o f the measured viscometric properties any o f the tw o combined variables, (TAR+S) or (CA+Sm) (Cp/Cfg) equation constant regression constant

Tables 2.2.19 and 2.2.20 include the results fo r A, a and F o f the derived models via (TAR+S) and (CA+Sm) (Cp/Cu) respectively. Tests o f these models w ith other base-stocks, either from local sources or im ­ ported, in the presence o f different V I improvers, have proved their suitability fo r predicting o f the oils viscometric properties at high confidence. Figure 2.2.2 respresents calculated viscometric results via models o f the variable (TAR+S) against observed results fo r the following viscometric properties: Vsp 100 fo r PMA A V 40 fo r (OCP) 1 A V 100 for (MIX) 1

90

Figure 2.2.2-A Figure 2.2.2-B Figure 2.2.2-C

Viscometric properties

SICP

V 4 0 — A V 4 0 — V 100 — A V 100

(OCP)1

V 4 0 - A V 4 0 - V 1 0 0 - A V 100 Vsp 4 0 - V . I . - Q

(OCP)2

V 4 0 - A V 4 0 - V 1 0 0 - A V 100 V. I . - Q

(Ml X) 1

V 4 0 - A V 3 4 0 - V 1 0 0 - A V 100

(MIX)2

V 40 - A V 40 - V 100 - A V 100 Vsp 100

PMA

V 4 0 - A V 4 0 - V 1 0 0 - A V 100 Vsp 4 0 - V. I . - Q

PMA-D

A V 4 0 - V 1 0 0 - A V 100

SBCP

V 4 0 - A V 3 0 - V 1 0 0 - A V 100 Vsp 40 - Vsp 100

R-H-R NEUTRAL DETERGENT (SOAP)

♦ 2Ha0 WATER

Neutral Detergent Production 213

In hydrocarbon solution the neutral detergent molecules act w ith typical ionic surfactant behaviour and tend to form ordered micellar arrangements (see Fig. 3.4.2). Overbased detergents can be made using the acid/base reaction but overbasing is achieved by employing a chemical equivalent excess o f inorganic base (see Fig. 3.4.3). A more common process, however, is the carbonation technique which converts excess inorganic base to metal carbonate. This inorganic carbonate is stabilised by metallic soap to form an oil soluble overbased detergent (see Fig. 3.4.4). The excess basicity is usually considered to be accommodated in the micellar core o f the neutral detergent molecules (see Fig. 3.4.5).

IONIC AMPHIPHILE

ORDERED MICELLE

Figure 3.4.2:

Neutral Detergent Molecular Arrangements

OVERBASING 2 R-H

ORGANIC ACID



nM (0H )j

INORGANIC BASE

Figure 3.4.3:

214

— > R-M-R ( n - 1 ) H (0H )2 ♦ 2HjO

OVERBASED DETERGENT

Overbased Detergent Production

VATER

CARBONATION/OVERBASING 2 R-H

+

ORGANIC ACID

n M(OH)j INORGANIC BASE ( n - l ) C O j (g )

CARBON DIOXIDE

R-H-R (n-l)HCOj CARBONATED OVERBASED DETERGENT

+ (n+l)H,0 VATER

Figure 3.4.4:

Carbonated Overbased Detergent Production

Figure 3.4.5:

Structure o f Carbonated Overbased Detergents

This constitutes the store o f base useful in the neutralisation of potentially harmful acidic components in the combustion chamber and the crankcase. The extent to which a lubricant detergent is overbased can be conveniently determined by either ASTM D2896 (AV) or ASTM D664 (TBN). TBN(Total Base Number) and A V (A lkalinity Value) measure the basic equivalent o f the detergent additive in milligrams o f KOH per gram o f detergent. The TBN value (or AV ) and the % metal w /w give measure o f the concentration of base present in the detergent additive. 215

Another key analytical parameter fo r lubricant detergents is additive viscosity (e.g. viscosity at 100°C), which should always be quoted w ith detergent TBN. Clearly, additives possessing excessively high viscosities are d iffic u lt or impos­ sible to handle during and after manufacture (e.g. during blending operations). Other parameters fo r detergents are often used and include: * Other microanalytical data (e.g. % sulphur) * Metal ratio or basicity index (Bl) * % neutral detergent (% soap) Metal ratio (or basicity index) is a simple ratio of the total metal content to the metal contained in the neutral soap. However, this method o f expressing over­ basing does not give a measure o f the concentration o f base available fo r neutra­ lisation o f harmful acids. The most common types o f lubricant detergent w ill now be reviewed.

3.4.2.2

Sulphonatei

Neutral and overbased sulphonates are derived from organic sulphonic acids. The earliest sulphonic acids were obtained as by-products from white oil manufac­ ture. Removal of the aromatic components o f mineral oil by sulphonation w ith sulphuric acid led to the production o f white oil and a mixed aromatic sulphonic acid stream. Mineral Oil + Sulphuric -*■ Acid

White + Sulphonic Oil Acid M ixture

The sulphonic acid m ixtrue was then neutralised and the resulting salt was separated into oil soluble and water soluble fractions. Sulphonic Acid + MOH -*■ Mixture

M =K,Na

Mahogany + Green Acid Soap Acid Soap oil soluble

water soluble

The mahogany acid derived sulphonates are also known as neutral sulphonates or petroleum sulphonates. However, the increased use of hydrogenation for the production of white oils has led to a reduction in the availability o f the mahogany sulphonic acids.A lter­ native sulphonation feedstocks have been developed and these include: 216

* polydodecy Ibenzenes - obtained as "bottom s'* form the alkylation of benzene to give dodecylbenzene, an intermediate in the production o f house­ hold detergents. * synthetic alkylbenzenes specifically produced for use in the lubricant addi­ tive application (see Fig. 3.4.6). Typical olefins used fo r this route include * branched chain olefins (average chain length >C18) * linear a -o le fin s (average chain length >C 18) A large volume of work has been carried out on processes to neutral and especially overbased sulphonates. The optim um process conditions fo r a parti­ cular target sulphonate depend on the structure o f starting sulphonic acid, the metal salt employed and the nature o f the prom otor used. Structural studies (1 -4 ) on overbased sulphonates confirm a micellar structure w ith the size o f the core (the store of excess base) dependent on TBN ( and % metal content).

ALKYLATION

A LK Y LB E N ZE N E

SULPHONATION

SULPHONIC ACID

Figure 3.4.6:

Synthetic Sulphonic Acid Production

217

3.4.2.3 Phenates The acidic organic substrate used fo r the production o f metal phenates are alkylphenols and sulphurised alkyl phenols (SAP's) (see Fig. 3.4.7). OH OLEFIN

0 ALKYLATION

alkylphenol

SULPHURXSATION

SULPHURISED ALKYLPHENOL (SAP)

Figure 3.4.7:

Sulphurised Alkylphenol Production

The olefin used to alkylate phenol may be branched or linear and is generally o f average chain length o f C9 or more. Sulphurisation of alkyl phenol can be carried out using sulphur halides or sulphur and this process yields a complex SAP m ixture. The average number of sulphur atoms per sulphur bridge (x) is usually more than one and the number o f linked phenol rings (y) is also usually greater than one. This substrate is then reacted w ith the appropriate quantity o f metal base (and optinally carbon dioxide) to produce the target neutral or overbased phenate. Many variations on the process to overbased phenates have been reported (5) and usually involve carbonation to give metal carbonate overbasing. "M ixed detergents" have been produced in which a m ixture o f substrates are used in reaction w ith the metal base e.g. mixed phenate sulphonate overbased detergents. 218

3.4.2.4 Salicylates The substrates used fo r the production o f metal salicylate detergents are alkylsalicylic acids. These are derived from alkyl phenols using the Kolbe-Schmidt reaction (see Fig. 3.4.8).

o

OH

♦ OLEFIN

ALKYLATION OH ALKYLPHENOL

Cr i

KOLBE SCHMIDT REACTION CO,, PRESSURE

COO

O

SODIUM ALKYLPHENOXIDE

No OH

SODIUM ALKYL SALICYLATE

1

ACIDIFICATION

C OOH OH

ALKYLSALICYLIC ACID

0 Figure 3.4.8:

Alkylsalicylic Acid Production

The resulting alkali metal salicylate is usually converted to an alkaline earth salt by metal exchange (e.g. w ith alkaline earth halide salt). As w ith phenates the olefin used to alkylate phenol may be branched or linear (usually C9). The micellar behaviour o f some neutral metal salicylates has been studied (6,7). 219

3.4.2.5 Others 3.4.2.S. 1

Naphthenates

Naphthenate based detergents are derived from naphthenic acid substrates. Naphthenic acids occur in varying quantities in crude oil (0-2.5% ) and are extracted during refining. A typical chemical structure found in naphthenic acid is shown in Figure 3.4.9.

(CHj). C0]H

Figure 3.4.9:

3.4.2.5.2

Typical Structure in Naphthenic Acid

Phosphonates

A common substrate fo r phosphonates is produced by the reaction o f polyisobutene w ith phosphorous pentasulphide where the product has a general formula approximating to that in Figure 3.4.10. The metal employed is usually barium as there are oil solubility problems associated w ith the calcium salts.

n

S R -P

0 P -R

Figure 3.4.10: Phosphonate Production

220

TYPICAL PHOSPHONATB STRUCTURE

3.4.3

A New Class of Overbased Detergent

3.4.3.1

Introduction

A new class of overbased detergent has recently been developed. This novel range o f products offers significant advantages over conventional overbased detergents. In particular the new products possess: (i)

Higher basic strength and greater neutralising power than conventional detergents, prim arily phenates and salicylates.

(ii)

Added performance advantages over conventional products.

The new product range includes: New high TBN phenates New high TBN salicylates New high TBN mixed phenate/sulphonates New high TBN sulphonates Certain o f the products are available on a commercial scale. Evidence to support these claims is presented below. Table 3.4.1: Comparison of Conventional Detergents Property

Phenates

Sulphonates

Salicylates

Phosphonates

Approx. Commercial TBN Range (ASTM D2896)

0 -3 0 0

0 -5 0 0

0 -3 0 0

0 -8 0

H ydrolytic Stability

Good

Moderate

Good

Moderate

Oxidation Stability

Very good Poor

Very good

Good

Thermal Stability

Excellent

Excellent

Excellent

Moderate

Detergency

Good

Good

Excellent

Good

Rust Inhibition

Low

Good

Low

Good

Very good

Good

A n ti- O x i­ dant Effect

Very good None

221

3.4.3.2 Properties end Performence 3.4.3.2.1

Basic Strength

The new detergent product range provides the form ulator w ith a flexible series o f options. See Tables 3.4.2 and 3.4.3. Table 3.4.2:

New Overbased Detergents

Parameter

Range

Metal Type

Ca, Mg

TBN(ASTM D2896)

5 0 -5 0 0

%Metal

1.5-18.0

Basicity Index

1 -1 0

Viscosity cSt at 100°C

5 0 -7 0 0

Table 3.4.3:

New Overbased Detergents

Typical Products

Type

% Ca w/w

New Phenate

14.3

400

300

New Salicylate

14.2

400

250

New Sulphonate

15.7

425

100

Conventional Phenate

9.2

258

300

Conventional Salicylate

10.0

280

160

Conventional Sulphonate

15.3

400

70

222

TBN (ASTM D2896)

V100

The new detergent technology allows the production o f overbased phenates and salicylates o f higher basic strength than has previously been readily available. Consequently, the new phenates and salicylates have a significantly greater neutralising power per unit weight than the conventional products and therefore treatment level in the finished lubricant can be reduced. This permits a greater oil content in the lubricant thereby contributing to oil film reinforcement. Furthermore, the new products possess viscosity properties consistent w ith large-scale handling and blending operations.

3A.3.2.2

Viscosity-Temperature Behaviour

The general move towards more severe operating conditions in marine engines has led to an increase in the significance o f the viscosity index (VI) o f marine oils. The oil must possess a sufficiently high VI to provide an adequate oil film at the higher operating temperatures to prevent scuffing and minimise wear. Additive components o f the new detergent class have been found to make a more significant contribution to lubricant viscosity index than components of the conventional type. This property in demonstrated in Table 3.4.4. Table 3.4.4:

C ontribution to Lubricant V I - Comparative Data

Additive Components

A% VI

New Phenate vs Conventional Phenate

+ 26

New Sulphonate vs Conventional Sulphonate New Salicylate vs Conventional Salicylate

* a typical MCL treatment levels blended into bright stock

3.4.3.2.3

Friction Reduction

An im portant function o f automotive and marine lubricants is to reduce engine friction . This can lead to reduced wear and improved fuel consumption. The new detergent additive have been found to possess markedly improved friction m odification properties over detergents o f the conventional type.

223

This friction reduction property has been demonstrated in 2 types o f rig test which model the contact between piston ring and cylinder bore. These are (i) the pin-on-disc technique and (ii) a technique employing a reciprocating test rig, the C am eron-Plint TE77 frictio n and wear machine. Table 3.4.5 presents pin-on-disc machine results on marine lubricants form u­ lated w ith new and conventional detergent types. A marked reduction in friction is observed fo r the lubricants containing the new components especially fo r the new phenate and sulphonate. Cameron-Plint machine results also indicate improved friction performance fo r the new deter­ gents, w ith the improvement over conventional products increasing w ith increa­ sing temperature (see Fig. 3.4.11).

CAMERON-PLINT FRICTION COEFFICIENTS

FRICTION

C O E F F IC IE N T

FRICTION COEFFICIENT v.TEMPERATURE IN C

TEMPERATURE IN C NEW PHENATE

Figure 3.4.11

224

PHENATE

Table 3.4.5:

Pin-on-Disc Friction Reduction Results

Component

Friction Co-Efficient

New Phenate

0.09

Conventional Phenate

0.14

New Sulphonate

0.08

Conventional Sulphonate

0.12

New Salicylate

0.076

Conventional Salicylate

0.085

%Decrease in Friction Co-Efficient

36

33

11

Components blended into full marine formulations conditions - slow sliding speed, 100° C.

3A.3.2.4

A nti-oxidant Performance

The new detergent components were evaluated in the Rotary Bomb oxidation Test (RBOT, ASTM D2272) which determines anti-oxidant performance in the presence o f water. This refelcts the wet environment in which a marine lubri­ cant has to operate in the field. Table 3.4.6:

Rotary Bomb Oxidation Test Results (ASTM D2272)

Component

Time to 15 PSI Pressure Drop in O j (min)

Base Oil

33, 29

New Phenate

139,137

Conventional Phenate

63,61

Conventional Sulphonate

A

34, 32

Conventional Sulphonate

B

19,32

Test oils blended to 70 TBN in base oil. 225

The results (see Table 3.4.6) show the superior anti-oxidant performance o f the new phenate over conventional phenate. It can be seen that overbased sulpho­ nates perform only as well as or marginally worse than base oil in this test.

314.3.2.5

Other Bench Tests

Representatives o f the new detergent class have been evaluated in a series of standard bench tests to establish comparative performance data against conven­ tional products (see Table 3.4.7). The new phenate and new sulphonate detergents showed improved or equal performance in all tests over conventional products. In particular com patibility o f the new components w ith conventional detergents o f different type was much improved over that fo r 2 conventional detergents o f different type: com patibility (new phenate/conventional sulphonate) > > com patibility (conventional phenate/ conventional sulphonate) Table 3.4.7:

Comparison o f new Detergents w ith Conventional Products in Bench Tests New Phenate o f Conventional Phenate

1. Demulsibility (ASTM D1401) 2. Centrifuge Test Sludge (AF2C5) TBN Loss % 3. Rust Protection (ASTM D665B) 4. Panel Coker (330°) Deposits

improved

-

improved improved

-

improved

-

improved

5. Wear Protection FZG

equal

6. Com patibility w ith conventional Phenate/Sulphonate

much improved

226

New Sulphonate o f Conventional Sulphonate

improved -

much improved

3A.3.2.6

Reciprocating Rig Wear Test

This test was designed to simulate ring/cylinder contact under typical marine engine operating conditions. The test employed high specimen temperatures (250 ) in the presence o f sulphuric acid to simulate the corrosive environment caused by the combustion o f residual fuel oils. Table 3.4.8:

Reciprocating Rig Wear Test Results Marine Formulations Containing new and Conventional Phenate

%Base Removed

H,SO« Added (% W/W)

Total Wear (Microns)

Friction Co-Efficient

New P

Conv.P

New P

Conv. P

New P

Conv.P

0.0

0

0

0

0

0.050

0.101

2.0

56

61

0

0

0.059

0.101

2.5

70.6

77

0

18.2

0.073

0.106

3.0

84.7

91.9

14.5

68.9

0.084

0.108

CAMERON-PLINT MACHINE TEST MARINE FORMULATIONS

WEAR RATE (g m /h )

9

.

8 . 7

.

6 . 5 .

tx x x x ::.-::::::£:':-x£:\£:;

♦ ■

3 .

xjxxxj:;X;:v



x-xxxxxxrxxjx:

2

o ------------ x-x-xJ------------ r.v...x.v. COMYDTTIOML

tC V

PHENATE

PHENATE

Figure 3.4.12 227

The improved performance o f the new overbased phenate over the conventional phenate type can be observed in the results table (Table 3.4.8). The new phenate

is more effective at form ing a boundary film which acts as a barrier to corrosive attack at the surface and reduces the rate o f wear (see Fig. 3.4.12).

3.4.3.2.7

Engine Tests

A representative o f the new detergent class, a highly overbased phenate (400 TBN), has been evaluated in a number o f bench engine tests. These include a Petter AVB Marine Test and the Bolnes Engine Test, specifically designed to evaluate marine formulations. The Petter AVB Marine Test employs a radio-active ring wear measurement technique and candidate oils are evaluated alternately between reference oils over the life o f a cylinder linear. Marine cylinder lubricants (MCLs) formulated w ith the new overbased phenate were found to exhibit equivalent performance to a conventional MCL at equal TBN. Evaluation o f the new phenate in a MCL formulated to 50 TBN led to marginally poorer performance than the 70 TBN reference oil (see Table 3.4.9). The Bolnes Engine Test uses a 3 cylinder marine 2-stroke engine w ith each cylinder separately fed allowing concurrent evaluation o f 3 different oils. Marine formulations (70 TBN) containing the new phenate were found to perform at an equivalent standard to a commercial MCL (70 TBN) in this test, both in terms of total ring weight loss and piston rating. Table 3.4.9:

Petter AVB Marine Test Results

Candidate Oil

Oil TBN

Performance Relative to Reference Oil

A

70

equivalent

A

70

equivalent

C

50

poorer

Candidate Oils A—C contain new phenate Reference oil = commercial marine cylinder lubricant (70 TBN, V10 0 = 18 cSt)

228

excellent very good moderate

very good

excellent

good

low

very good

moderate

Oxidation Stability

Thermal Stability

Detergency

Rust Inhibition

Anti-oxidant Effect

Friction Effect

excellent

excellent

excellent

very good

good

H ydrolytic Stability

400

New Phenate

250

Conv. Phenate

Typical TBN (ASTM D2896)

Property

good

moderate

low

very good

excellent

very good

good

280

Conv. Salicylate

very good excellent

excellent

excellent

430

New Sulphonate

none

good

good

excellent

poor

moderate

400

Conv. Sulphonate

Table 3.4.10: Comparison o f new and Conventional Detergents

excellent

excellent

400

New Salicylate

3.4.4

Conclusion

A new class o f detergent additive has been developed which offers significant improvements in properties and performance over conventional products. New high TBN phenates and salicylates are now available w ith excellent performance credentials. Benefits include improved anti-oxidant, friction reduction and wear control performance. Furthermore, the chemistry associated w ith this new technology is sufficiently flexible to allow the production o f "designer deter­ gents" to meet the requirements o f particular applications.

3.4.5

Acknowledgement

The authors wish to acknowledge the contribution o f Dr. A. Moore (BP Research Sunbury) in designing the bench friction and wear tests and providing data.

3.4.6 (1) (2)

(3)

(4)

(5)

(6) (7)

230

References

Marsh, J.F.: Colloidal Lubricant Additives. Chemistry and Industry (1987), 4 7 0 — 473. Tricaud, C_ Hipeaux, J.C.; Lemerle, J.: Micellar Structure of Alkaline Earth Metal Alkylarylsulphonate Detergents. Ostfildern 1986. P 9.3-1 — 9.3-7. Additives for Lubricants and Operational Fluids. 5th International Colloquium, Technische Aka­ demie Esslingen 1 4 /1 /8 6 — 16/1/86. Ostfildern. Glavati, O.L.; Fialkovskii, R.V.; Marchenko, A .I.; Premyslov. V.Kh.; Alekseev, O .L.: Stabilisation of Colloidal CaCO, Dispersions in Hydrocarbons containing Anionic Furfactants Kolloid Zh (1970), 42, 26—30. Markovic. I.; Ottewill. R.H.; Cebula, D.J.; Field, I.; Marsh, J.F.: Small Angle Neutron Scattering Studies on NorvAqueous Dispersion of Calcium Carbonate Colloid and Polymer Sci. (1984), 262, 6 4 8 -6 5 6 . M orin, S.V.; Pavlova, T .V .: Methods of Preparation of High Alkalinity (Overbased) Additives of the Alkylphenol Type (Review of Patents). Khim. Tekhnol. Topi. Masel (1978). 3. 6 1 -6 3 . Inoue, K.; Watanabe, H.: Micelle Formation in Detergent-Dispersant Additives in Non-aqueous Solutions, J. Japan. Petrol Inst. (1981), 2 4 (2 ), 9 2 —100. Inoue. J.: Carbon-13 Nuclear Magnetic Resonance Study o f Reversed Micellar Struc­ ture of Calcium Dodecylsalicylates in Chloroform. J. Japan, Petrol Inst. (1982), 25(5), 3 3 5 -3 3 9 .

3.5

Synthesis o f Reactions

Additives

Based on

Olefin-Maleic

Anhydride

G. Deak, L. Bartha and J. Proder Veszprem University of Chemical Engineering, Hungary

Alkenyl succinic anhydrides and olefin-maleic anhydride copolymers were syn­ thesized from straight and branched olefins which were reacted w ith alcohols and amines. Some o f these compounds showed rust preventing, pour point depressing or emulsifiying effects in lubricants. Relationships were established between the efficiency and structural properties o f the additives.

3.5.1

Introduction

Many industrial additives, including several o f those used in petroleum pro­ ducts are produced by reacting an olefin - usually alpha olefin - and maleic anhydride. In this reaction either alkenyl succinic anhydride o f maleic anhy­ dride - olefin copolymers are produced depending upon the reaction para­ meters. The potential use of the reaction products depends not only on this difference, but also on the characteristics o f the olefin raw material. According to data in the literature the carbon number o f olefin molecules used in such reactions is w ithin the range 2 to 60, and the structure o f the olefin molecules can be different. Most o f the suggested hydrocarbons are, however, alpha olefins. In the present paper the reaction o f maleic anhydride and various olefins — poly­ ethylene and atactic polypropylene degradation products, crack gasoline oli­ gomers — were investigated and the potential use of the produced anhydrides or copolymers and some o f their derivatives as additives fo r lubricants are evalu­ ated and correlations among the performance and olefin type are tried to be established.

3.5.2

Materials

Since the effects of the olefin structure on the performance o f the anhydrides or copolymers were to be investigated, olefins in a wide molecular mass range having different CH3/CH2 ratio were selected fo r the experiments (Table 3.5.1). Raw materials were mixtures o f hydrocarbons w ith the exception of alpha octadecene. Alpha olefins (AO-X) were commercial products (Fluka, Germany). Mixtures PE-X and APP-X were prepared by thermal degradation o f polyethy­ lene and atactic polypropylene, resp. that was followed by distillation into narrower fractions. Samples KO-X were prepared from a 32 - 112° C cat. crack gasoline by oligomerization and subsequent fractionation.

231

232

(1) (2) (3) (4)

1 2 0 -1 8 2

5 — 58 58

1.1

63 29 91

8

8.2

16—18

AO-16-18

97



97



8.9

18(2)

AO-18

9

68 68

-

1.2

1 8 2 -2 6 0

APP-2

76 76

16 —

2 4 0 -2 8 0 1.7

APP-3

Atactic polypropylene degradates

APP-1

5 76 19 95

Fluka, Germany Carbon number range Determined as in (4) Determined as in (5)

vinylideneE alpha olefins

Boiling rate. °C CH 2/-C H 3 ratioO ) Olefin distribution!4 ) transvinyl-

rroMW ly

transvinylvinylideneE alpha olefins

8.6

14_16 12

u

264 0.50

2500

800 3150 502

— —

15.2 1.8 0.01

> 12

U

250 0.58

3150

800 4000 570

— — —

8.1 2.8 0.07

Formulated Gear Oils SAE 90 API GL-5 Automotive AG M A 5 EP Industrial Reference Experimental Reference Experimental

Beaker Oxidation; - Viscosity Increase, % - Loss o f o il, % — Insoluble in n-heptane, %

Performance Related Test

Table 3.11.9 (continued)

Table 3.11.10:

Standard Requirements for the Selected Performance Re­ lated Tests fo r GL-5 Autom otive (BSSM 14368-82) and AG M A 5 EP Industrial (BSSM 14367-82) Gear Oils BSSM 14368-82 BSSM 14367-82

Kinematic Viscosity, mm2s'1: - A t 40° C - A t 100° C

18 — 2 0 a

200 - 240 -

Viscosity Index, not less than

CD O Q >

Performance Related Test

90a

Copper Corrosion, merits, not higher than

3

u —

u

U

1b

Storage Stability

no separation

no separation

Anticorrosive Properties in the Presence of Dist. Water

no corrosion

no corrosion

"Volkswagen” Corrosion: - on steel bearing — on copper plate, mg, not more than

no change 5

no change 5

Foaming A b ility , cm3 foam (5 min blow /10 min rest), not more than: - A t 25° C - A t 95° C - A t 25° C Demulsibility, not more than: - Total free water, cm3 - Water in oil, % - Emulsion, cm3 Beaker Oxidation, not more than: - Viscosity Increase, % - Loss o f oil, % — Insoluble in n-heptane, % Thermal Oxidation Stability Test (T.O.S.T.), not more than: — Viscosity Increase, % — Insoluble in n-pentane, % - Insoluble in toluene, %

100/0 50/0 100/0

100/0 50/0 100/0

not required

80 2.5 1.0



not required — -

20 5 1

not required 100 3 2



331

Table 3.11.10 (continued) Performance Related Test EP Properties (Four Ball Machine), not less than: - Initial Seizure Load, N - Weld Load, N — Load Wear Index, N EP Properties after Demulsibility Test, decrease o f Weld Load, not greater than Antiwear Properties (Four Ball Machine): — Antiwear Index, N, not less than — Wear Scar Diameter, mm Antiscuffing Properties (FZG Machine), stages, not less than

BSSM 14368-82

800a 4000a 550a

not required

200 —

10c

BSSM 14367-82

700j? 3150° 500

one increment

200 —

12d

a BSSM 9797-82 b BSSM 13134-82 c 130° C; 25,0 m s'1; b = 10 mm d 90° C; 16.6 m s’ 1; b = 20 mm

Since results presented above gave certain hopes for practical application, further investigation was dedicated to formulations which may be useful. In principle, combinations as the ones discussed in this presentation may be experimented fo r a wide variety of lubricating products — metalworking lu­ bricants, hydraulic fluids, stick-slip lubricants, fluids for different transmis­ sions, etc. w ith or w ithout the need of additional additives. Table 3.11.9 presents the results fo r two experimental formulations. The first of the compositions tested fo r some o f the requirements o f the Bulgarian auto­ motive GL-5/90 gear oil specifications did not contain SME, while the second — for application as an industrial 5 EP gear oil — included SME and a smaller amount o f DAPS. As seen from Table 3.11.9, results from previous tests were confirmed in general. Furthermore, properties not tested beforehand - dem ulsibility, foam ability, corrosion on steel under different conditions, etc. — were also satisfactory.

332

However, fu ll implementation o f the present results in practice needs much more extensive testing in conditions closer related to real service, such as, for instance, these required by the US MIL-21058 specification - CRC L-33, L-37, L-42, etc. and then - in fleet tests. Hereunder w ill be summarized only some o f the questions that await their experimental answers: - W ill Zn-DADTP create problems? Certain hopes in this direction give results (reported previously (25)) o f suc­ cessful application o f oils, containing a relatively high amount of Zn-DADTP in gear boxes o f trucks and busses and the fact that even "new generation" borate packages (26) contain similar components (27). - Will lubricating properties satisfy both the CRC L-37 and L-42 requirements? Correlation between results from simple tribometers and these tests seems rather questionable. Still results have been reported that formulations w ith certain Zn-DADTP-s may pass L-37, while sulphurized hydrocarbons w ith radicals similar to those o f DAPS may pass L-42 (16). -

W ill the rather complex and m ultifacted moisture corrosion process in CRC L-33 be successfully dealt with? The hope here is probably the better correlation between corrosion tests and the sim ilarity o f components of the experimental packages w ith the references. These and other similar problems remain to be solved by future investigations.

3 .1 1 .4 R eferen ces (1) (2) (3) (4) (5) (6) (7) (81

Ishchuk, lu.L.: Technology of Plastic Greases. Kiev: Naukova dumka 1986 (in Russian). Report No. K-3845: Presentation of Hydraulic and Gear Lubricants and Additives for Neftochim, Bulgaria. Lubrizol International Laboratories: Hazelwood 1978. Malinovskii, G.T.: Oil Based Lubricating Cooling Fluids for Metal Cutting. Mos­ cow: Himia 1988 (in Russian). Vipper, A.B.: Vilenkin, A.V.; Gaisner. D.A.: Foreign Oils and Additives. Moscow: Himia 1981 (in Russian). Bratkov. A.A. (Editor): Theoretical Foundations of Himmotology. Moscow: Himia 1985 (in Russian). Papay, A .G .; Dinsmore, D.W.: Advances in Gear Additive Technology, Lubrication Engineering, 32 (1976) 5. 2 2 9 -2 3 4 . Papay, A.G.: Gear Lubricant Additive Technology. NLG I Annual Meeting: Chicago October 1974. Rounds. F.G.: Some Effects of Amines on Zn Dialkyldithiophosphate Antiwear Performance as Measured in 4 Ball Wear Tests. ASLE Transaction 24 (1981) 4, 4 3 1 -4 4 0 .

333

(9)

(10) (11) (12)

(13) (14) (15)

(16) (17) (18)

(19)

(20) (21)

(22) (23) (24)

(25)

(26) (27)

Hsu, S.M.; Pei, P.; Ku, C.S.; Lin, R.S.; Hsu, S.T.: Mechanisms of Additive Effective­ ness. Ostfildern 1986. 3.14.1 - 3.14.10. Proc. Additives for Lubricants and Opera­ tional Fluids. Technische Akademie Esslingen. January 1986. Ostfildern. Shirama, S.; Hirata, M.: Effects of Engine Oil Additives on Valve Train Wear, ibid. 4.4.1 - 4 . 4 .1 3 . Rounds, F.G.: Changes in Friction and Wear Performance Caused by Interactions Among Additives, ibid. 4.8.1 — 4.8.21. Barcroft, F .T .; Park, D.: Interactions of Heated Metal Surfaces Between Zn-Dialkyldithiophosphates and Other Lubricating Oil Additives. Wear 108 (1986) 3, 213­ 234. Kuo. L.L.K .; Chao-Yuan Tung: Fuel Economy Engine Oils Via Friction Modifiers. Lubrication Engineering. 44 (1988) 2 ,8 1 —86. Papay, A.G.: Industrial Gear Oils — State of the A rt. ibid. 3, 21 8 —229. Papay, A.G.: Friction Reducers for Engine and Gear Oils — A Review of the State of the Art. Ostfildern 1986. 5.1.1 — 5.1.10. Proc. Additives for Lubricants and Ope­ rational Fluids. Technische Akademie Esslingen. January 1986. Ostfildern. Damrath, Jr., J.G.; Papay, A.G.: Additives for Gear Oils — Function and Interactions, ibid. 4.Z 1 - 4.2.8. Emannuel, N.M.; Denisov, E.; Maizus, Z .K .: Chain Reactions of Oxidation of Hydro­ carbons in Fluid Phase. Moscow: Nauka 1965 (in Russian). Ivanov. SI.: Karshalukov, K.: Manometric Installation for Measuring the Increase and Decrease of Gases in Chemical Reactions with Automatic Keeping of Constant Pressure. Chemistry and Industry (Sofia) (1974) 3 ,1 2 7 —131 (in Bulgarian). Fuels and Lubricating Materials. Compilation of Bulgarian State Standards: Part I. Technical Requirements. Part II. Methods for Analysis. Sofia: Standartizatzia 1983 (in Bulgarian). Vilenkin. A.V.: Oils for Gear Transmissions. Moscow: Himia 1982. Kajdas, C.: Review of AW and EP Working Mechanisms of Sulphur Compounds and Selected Metallo-organic Additives. Ostfildern 1986. 4.6.1 — 4.6.19. Proc. Additives for Lubricants and Operational Fluids. Technische Akademie Esslingen. January 1986. Ostfildern. Kuliev, A.M .: Chemistry and Technology of Additives for Oils and Fuels. Leningrad: Himia 1985 (in Russian). Cholakov, G.S.; Kaishev, K.P.: Storage Stability of Sulphurized Sperm Oil Replace­ ments: I. Origin and Nature o f the Sludge. Wear 96 (1984) 2, 109—119. Kaishev, K .P.; Cholakov, G.S.; Stanulov, K.G.; Shopova, M.D.: Solubility Problems with Sulphurized Sperm Oil Replacement EP Additives; Solubility of Additives in Mineral Base Oil Hydrocarbon Cinstituents. Wear 131 (1989) 3, 3 0 3 -3 1 3 . Klucho. P.; Foltanova, S.: Szucs, L ; Matas. M .: Synthesis, Laboratory and MachineApplication Evaluation and Performance Tests of EP Additives on the Basis of Dialkyldithiophosphoric Acid Metal Salts in Gear Oils. Ostfildern 1986. 4.11.1 4.11.4. Proc. Additives for Lubricants and Operational Fluids. Technische Aka­ demie Esslingen. January 1986. Ostfildern. Adams, J.H.: Borate — A New Generation EP Gear Lubricant. Lubrication Engineer­ ing 33 (1977! 5, 2 4 1 -2 4 6 . Adams, J.H.: US Patent 4 089 790/M ay 16, 1 9 7 a

ACKNO W LED G EM ENT The authors are indebted to: The UNDP-UNESCO Laboratory for Small Scale Organic Products, Higher Institute for Chemical Technology, Sofia: The Committee for Science of Bulgaria and the Petrochemical Combine — Pleven, Bulgaria for their generous support and interest in this work.

334

3.12

Relationship between Chemical Structure and Effectiveness of Some Metallic Oialkyl and Diaryldithiophosphates in Different Lubricated Mechanisms

M. Born, J.C. Hipeaux, P. Marchand and G. Parc Institut Francaisdu P6trole, Rueil-Malmaison, France

Summary The antiwear (AW) and extreme-pressure (EP) properties of some metallic dialkyl and diaryldithiophosphates (MDTP), including zinc, have been studied in different metal/metal contact conditions: four-ball and FZG rigs. We have noted: •

With pure dialkyldithophosphates o f different divalent metals (Zn, Cd, Cu, Pb, Ni, Co) prepared from the same alcohol: -

on the four-ball rig, EP results, expressed in terms o f load-wear index, show that the highest performances are obtained w ith ZnDTP but sta­ tistically the higher the ionic radius o f the metal, the better the perform­ ance. EP results, expressed in terms of weld load, do not show any difference between these MDTP;

— on the four-ball rig, AW results, expressed in terms o f wear scar, show that the highest performances are obtained w ith ZnDTP; beyond a cer­ tain value these performances w ith Zn and Pb are almost independent of the concentration. For the other metallic DTP, there is a very close relationship between performance and concentration; -



on the FZG gear rig, EP-AW results, expressed in terms of failure load stage and specific wear, show that statistically, the higher the ionic ra­ dius o f the metal, the better the performance.

With ZnDTP: — on the four-ball rig, EP results, expressed in terms of load wear index, do not depend on the chemical structure of the alcohol used for synthezised Zn-DTP but if results are expressed in terms o f weld load, better performances are obtained w ith ZnDTP synthezised from secondary al­ cohols. AW results show that the effectiveness o f ZnDTP from secondary al­ cohols is slightly higher when the alcohols used contain less than six carbon atoms. Beyond six carbon atoms in primary or secondary alcohol molecules performances decrease.

335

— on the FZG gear rig, EP-AW results show that performances do not de­ pend on the primary or secondary nature of the alcohols used and that the smaller the hydrocarbon chain o f these alcohols, the better the per­ formances. The results of this w ork indicate that ZnDTP is the most effective o f the MDTP we have studied. For ZnDTP prepared from different alcohols and alkylphenols the performances depend not only on the chemical structure of the addi­ tive but also on contact conditions (kinematic, material types, etc.), and on the criteria considered (seizure load, weld load, wear, etc.).

3.12.1 Background Metallic dialkyl and diaryldithiophosphates, particularly ZnDTP, have been extensively used in lubrication fo r over fo rty years. The advantage of these compounds is that several highly desirable lubrication-related properties such as antioxidant, detergent and more specifically antiwear properties, and to a lesser extend extreme pressure properties (load carrying capacity properties) can all be found in the same molecule. Other non-negligible advantages, from the practical point o f view, include acceptable thermal stability, moderate to xic ity , considerable case o f storage and application, relatively low cost, and great effectiveness fo r a small dose since they are used in lubricants in con­ centrations not exceeding 1.5 weight %. Although their use is decreasing for purely environmental reasons (they tend to deactivate the catalyst in automotive catalytic mufflers since they pass into the exhaust gases in very small quantities along w ith the crank-case oil) they are still one o f the irreplaceable additives in modem lubricating oils and w ill probably continue to be so fo r several years.

3.12.2 Introduction The number o f studies performed for the purpose o f linking the AW and EP properties o f MDTP to their chemical structure is rather limited. Work by Rowe and Dickert (1) on a pin and disc machine has shown that AW effective­ ness, measured in mild sliding conditions, is proportionately higher when the thermal stability o f the MDTP is low. Effectiveness is rated as follows: Ag > Pb > Co > Zn > Cu Moreover, these authors have shown a correlation between the AW properties of the MDTP studied and the ionic radius of the corresponding metals. According to Forbes (2), MDTP load carrying capacities vary considerably. If he is considering wear, he rates effectiveness as follows:

336

Zn > Ni > Fe > Ag > Pb > Sn > Bi and if he is examining extreme pressure, his rating is Ag > Bi > Sb > Ni > Zn No metal can in fact provide all the optim um properties desired, but industrially speaking, the ZnDTPs are recognized as offering the best compromise between the different properties mentioned above. A series of tests carried out by Larson (3) on a Chevrolet LS-5 engine w ith a cam/tappet system has shown that a ZnDTP, derived from tw o secondary al­ cohols, provides greater AW effectiveness when each phosphorus atom is linked to radicals o f the same nature. Forbes, Allum and Silver (4) noted, when studying extreme pressure and using a four-ball rig, that the nature of substitutes for P atoms in ZnDTP had very little influence on performance but that substitutes derived from secondary alcohols did have a slightly positive effect. Jayne and E lliot (5) also studied EP-AW properties of ZnDTP on a four-ball rig and have noted no difference in AW effectiveness at moderate loads bet­ ween ZnDTP derived from primary or secondary alcohols, which coincides w ith the results o f Zamberlin Mikac-Cergolj and Bencetic (6). However, at severe loads, EP properties, expressed in terms o f welding load, are better in the case o f ZnDTP derived from secondary alcohols. Tests carried out by Jayne and E lliot (5) on a Timken rig show that dialkyl ZnDTP have a higher load carrying capacity than diaryls, and that mixtures of alkyls and aryls have an intermediate capacity. Zamberlin's work leads to the same conclusions but in addition it points to the greater effectiveness of ZnDTP derived from secondary alcohols compared to those derived from p ri­ mary alcohols. Tests performed by Rowe and Dickert (1) on a pin and disc rig under mild sliding conditions show that differences in AW effectiveness of the ZnDTP studied are related to their thermal stability, and that the rate o f wear o f the copper pin is higher fo r secondary alcohol than fo r primary alcohol ZnDTP. The diversity of the results obtained by the different authors shows that the EP-AW effectiveness of ZnDTP depends on a number of parameters involved when lubricated surfaces are in contact, i.e.: — — — — —

stress exerted on surfaces types o f movement velocity o f sliding surfaces temperature metallurgy and roughness of lubricated materials 337

and consequently on the measurement method used and perhaps even on the degree o f purity o f the MDTP o f interest. In this paper we propose first to examine the validity o f industrial practices, in other words, to see whether ZnDTP are really the type o f MDTP best suited to reducing wear in lubricated mechanisms. This led us to compare the EP-AW properties of a reference zinc dialkyldithophosphate to those o f different me­ tallic DTPs (prepared w ith the same alcohol as that used for the synthesis of the model ZnDTP) in which each metal atom is oxidized to the same degree, i. e. linked to the same number o f sulfur and phosphorus atoms. Second, we have attempted to point out the relationship between the AW-EP effectiveness o f ZnDTP and the chemical structure o f their organic chains, under different lubrication conditions. In order to ensure the exact composition o f the MDTPs studied and their de­ gree o f p urity, the products were prepared in the laboratory by the tw o most common synthesis methods: -

by double decomposition, or metathesis, in the case o f ZnDTP prepared w ith alcohols containing less than 8 carbon atoms (7); this method pro­ duces very pure metallic DTPs.

— by the zinc oxide method in the case of ZnDTP prepared from alcohols containing at least 8 carbon atoms and those prepared from alkylphenols (8 ).

3.12.3 Additives Studied In order to study only the influence of the nature o f the metal on the EP-AW properties of the metallic DTPs, the products were prepared from 4-methyl 2-pen tanol: "

CH3 (CH3-

I

C H - C H j-

S' C H -O —) j —P C Hj



V S S_

The metals studied were: M = Zn — Cu — Ni — Co — Cd — Pb The physical and chemical characteristics of these products are indicated in Table 3.12.1.

338

Table 3.12.1: Characteristics o f the metaliics DTP studied CH3

S

I

(CH3- C H - C H , - C H - 0 ) j



M

p

ch3

s

Synthesis method = double decomposition M = divalent Metal ELEM ENTAL ANALYSIS Metal

Zn Ni Cu Co Cd Pb

Metal % Mass

Carbon % Mass

Hydrogen % Mass

Obs.

Theory

Obs.

Theory

Obs.

Theory

9.92 8.27 9.65 8.75 15.90 25.80

9.92 8.99 9.65 9.02 15.60 25.85

43.40 44.40 46.20 44.32 42.60 36.02

43.67 44.12 43.80 44.12 40.77 35.96

7.70 7.76 8.45 8.12 7.70 6.52

7.83 7.97 7.91 7.96 7.36 6.49

The ZnDTP studied consisted o f single versions based on a primary or secondary alcohol or an alkylphenol and a combined version based on an equimolecular m ixture o f two alcohols w ith different chemical functions. SINGLE ZnDTP Alcohols used 1-PROPANOL (n-propanol) 2-PROPANOL (iso-propanol) 1-BUTANOL (n-butanol) 2-M ETHYL 1-PROPANOL (iso-butanol) 1-METHYL 1-PROPANOL (2-butanol) iso-PENTANOL 2,2-DIM ETHYL 1-PROPANOL (neo-pentanol) 1-HEXANOL (n-hexanol) 4-M ETHYL 2-PENTANOL CYCLOHEXANOL 2-ETHYL HEXANOL 0 X 0 C8 1-METHYL 1-HEPTANOL (2-octanol)

Alcohols or phenol primary secondary primary primary secondary primary alcohol m ixture primary primary secondary secondary primary primary alcohol m ixture secondary 339

secondary secondary alkylphenol alkylphenol

2,6-DIM ETHYL 4-HEPTANOL 2,6,8-TRIM ETHYL 4-NONANOL NONYLPHENOL DODECYLPHENOL COMBINED ZnDTP

The combined ZnDTP was prepared from an equimolecular mixture o f iso­ propanol (secondary alcohol) and iso-pentanol (primary alcohol). The thermal decomposition temperature o f the ZnDTP was determined by the following method: A 100 neutral solvent mineral oil containing 4.5 10'3 atom-gram of zinc (in the form o f ZnDTP) per 100 g of m ixture is gradually heated at a rate o f 2 - 3 ° C/minute until the product clouds, indicating the thermal decomposition o f the additive. The analytical characteristics o f these compounds are indicated in Tables 3.12.2 and 3.12.3.

3.12.4 Experimental Procedure The EP-AW performances are characterised by a pin-point hertzian contact occurring under rough elastohydrodynamic conditions (EHD) w ith pure sliding and under very high stress. — FZG gear rig test The moving metal surfaces are characterised by a linear hertzian contact occur­ ring under EHD conditions w ith combined sliding and rolling and under very high stress. A mineral ARAMCO 400 neutral solvent base oil was chosen for these two experimental rig tests, their characteristics are as follows: Viscosity at 100° C(mmJ/s) Viscosity index Sulphur content (mass %)

9.51 101

1.1

— Four-ball extreme-pressure test The EP performance assessment tests were carried out in accordance w ith the ASTM D 2782-82 standard method. The principal test characteristics are as follows: Balls: Top ball revolution speed: Sliding speed: Oil temperature: Duration o f tests: 340

100 C6 steel 12.7 mm diameter 1 4 2 5 - 1480 rpm 0.56 - 0.58 m/s 32.5° C 10 seconds

-C -

25*

0

D O * double decomposition I - in d u s tria l m eth o d

C l 0X0

OXO-OCTANOL

9.60

1.47

50.39

49.77

936

8 31

8 31

1.97 49.77 50.03

M 7

737

2-0CTAN0L

C -C-C-C-C-C-C

c

731

734

234

231

194 731 737 43.70 4170

4157 44.10

931

C-C-C-C-

931

9.92

4 -M ETHYL

225 731

1

1

1

DD

DD

DO 195 6.75 175 731

DD

DD

247

225

DD 225

729

729

DD

DD

DO

DD

Q

194

183

184

PC)

SYNTHESIS METHOD

7.43

732

939

4170

4189

931

912

4420

44.60

10.03

10.01

CYCLOHEXANOL

1-HEXANOL

39.71

3937

10.83

39.71

1 01 2

39.67

m o -PENTANOl

1033

2-PENTANOL

I ;

I

C-C-C-C-C-C-

S - r

C

c.j.c.

4

C-C-C-C-

C

C-C-C-C10.87

3 53 6

35.00

1134

1 10 0

ise-BUTANOL

C - f- C -

no-PENTANOL

637

6.40

3 53 6

3530

1134

11.72

2-BUTANOL

c-c-ec

I

637

6.60

3 53 6

3530

1r*

637

5.77 630

2 93 0

2938

1130 1134

1 11 0

5.70

5.70

1130

5.72

Hy4rat*a (X MASS) Tkaary Ota

1-BUTANOL

75X

2 93 0

29.41

1130

1130

Tkaary

Ota

Carbea 1X MASS)

b o -PROPANOL

.

2

Zn

ELEMENTAL ANALYSIS



2a (V MASS) U n a ry

Ota

p

C-C-C-C-

C C -C -

n-PROPANOL

ALCOHOL

• IR

C-C-C-

CORRESPONDING

CHEMICAL STRUCTURE

(RO)2-

Table 3.12.2: Characteristics o f the ZnDTP studied

50*

C•

4-DOOECYLPHENOL®

4-NONYPHENOl®

C0M8IHED

isopropyuc alcohol

131

141

12.09

525

111-TRIMETHYL 4-N0NAN0L IS0AM1UCALCOHOL

6.50

2S-0IMETKYL 4-HEPAHOL®

111

171

1106

HI

750

147

TiliT|

z*(* MASS)

Ob* IJO

DO - double deeom ponlion I • in d u s tr ia l m a th o d contain* 5% mass excess alcohol contains 25% mass fluxing mineral oil for easier handling

c» c

a

0

C»-C

t %

C -C

'c = c

s - e~fiC.-C

4

C-C-

J

\ 7W ISO*

I c-c-c-c-

[

/c-c-c-c-

4

c-c-c

Ct K Cc-c-c'

c ''c c-c-c^

t-i'C

c-c-e-c-c-cc-c c

tin

CORRESPONDING ALCOHOLOH ALKYPHEMOL 2-ETHYl l-HEXANOL

Table 3.12.3: Characteristics o f the ZnDTP studied

6164

34.46

-

5120

Pba**b*r Tb**rr 3.00 306 1 *-- 3 rWM

6350

3451



-

ELEMEHTALAHALYSIS CarbatfAMASS) IbMTT Ob* 4177 50.10

2

Zn

113

141

-

-

SM*taa Tb**ry Ftmi 120 6.00

7.90

654



111

lYjmlHi(%MASS) Tb**ry 0b* Ut 195

>260

>260

195



105

231

TO

OacMaaaiiaa

1

1

00

1

1

00

SYNTHESIS METHOD ©

The criteria used to assess the results were the load-wear index figure (LWI) and the welding load o f the ball. The amount of additives used for these tests was designed to provide an oil w ith following metal contents: [M etal] = 1.52 - 3.04 - 7 . 6 - 15.2 (1 O'3 ) atom gram/kg -

Four-ball wear test

The NF E 48-617 method, whereby a 40 kgf load is normally applied fo r one hour, was supplemented by three successive loads of 60 — 80 — 100 kgf. The criterion used to assess the antiwear (AW) performance o f each additive is the mean wear diameter (d*), i. e. the arithmetic average of the wear dia­ meters for the successive loads o f 40 — 60 — 80 — and 100 kgf. d40 + d60 + d80 + d 100 d*(m m ) = -----------------------------------4 In addition, a mean value is calculated for each metallic DTP, based on the mean wear diameter (d*) corresponding to the arithmetical average of the d* fo r the 4 concentrations studied: _ d*1.52 + d*3.04 + d *7 .6 + d*15.2 d * (m m )= ------------------------------------------------4 Further, these values d * are expressed in terms of relative antiwear effective­ ness e, determined in relation to the performance o f a base oil (e = 0 fo r d*B = 1.90 mm) and to the performance o f an ideal oil whose wear diameter d* would be minimal and would correspond to the average of the compensation diameters d * c for loads o f 40 — 60 — 80 — 100 kgf. The compensation dia­ meters used in the ASTM methods are as follows: 40 kgf

60 kgf

80 kgf

0.33 mm

0.38 mm

0.42 mm

100 kgf 0.46 mm

Consequently d *C =

dc40 + dr 60 + dr 80 + d r 100 —--------- £---------- --------- £------ = 0 .4 0 mm 4

The relative antiwear effectiveness determined by the relation:

343

-

d *B ~ d *X

6”

d‘ B - d *C

X10°

Thus becomes: 1.90 - d * v e=

x 100 1.50

The amount o f additives used was identical to that used fo r EP four-ball rig tests: Metal = 1.52 - 3.40 - 7.6 - 15.2 103 atom-gram/kg — FZG gear rig tests: The tests were based on the CEC-L-07-A-85 method, namely: Gears: Sliding speed: Initial oil temperature:

" A " type 5.56 m/s 90° C

The amount o f additives used was designed to produce an oil w ith the following additive content: Metal = 0.76 - 1.52 - 3.04 - 7.6 10'3 atom-gram/kg The criteria used to assess performance were the failure load stage and the gear specific wear.

3 .1 2 .5

T est R esu lts and D iscu ssion

3.12.5.1

3 .12

Metallic DTP

5.1.1 Four-ball EP test

The EP performance, expressed in terms of Load Wear Index (LWI), show that among the different metallic DTPs studied, those prepared from heavy metals (characterised by a large ionic radius), are statistically more effective than those prepared from metals w ith a lower ionic radius. But ZnDTP is an exception w ith a very high LWI particularly at low concen­ tration (Tables 3.12.4 and 3.12.5). Decreasing order of EP effectiveness is as follows: Zn > Cd > Cu > Pb > Co > Ni

344

EP performances, expressed in terms o f Welding Load, d iffer little from one additive to another. Decreasing order o f effectiveness is as follows: Zn = Cd = Cu > Co = Ni > Pb

Table 3.12.4: Four ball extreme pressure test load wear index versus metal concentration

/ ----------- #--•________ /

zf= 200 5 UJ

5 O < UJ

n M EII

GC

UJ

>


j

^ s j-.

|p » o C l - O J r - P ^

I(to o C l -O W —

r

Zn:

Zn:

Zn:

AB

B

A

Table 3.12.18: FZG extreme pressure test, synergy effect o f combined ZnDTP

Zn C O N C E N T R A T IO N (a to m /k g )

The second part of the study attempts to establish the relationship between the chemical structure of the DTP and their EP-AW effectiveness, based on the results o f rig tests using a considerable number o f compounds. The conclusions reached vary greatly depending on the method o f investigation used. The results of four-ball EP and AU tests (100 C6 steel balls, pinpoint contact during pure sliding) do not point to any relationship between chemical structure and EP properties if performance is based solely on LWI. On the other hand, if the welding load o f the balls is taken into account, the ZnDTP derived from secondary alcohols prove the most effective, whatever the length of the or­ ganic chains linked to the P atoms. ZnDTP derived from primary and secondary alcohols (with low thermal stabi­ lity) have the highest AW properties. When the number of carbon atoms in the organic chain of the alcohols exceeds six, thermal stability increases but AW properties deteriorate. 357

The results o f FZG EP test (hardened, quenched 20 MC 5 steel, combined sliding and rolling) show that EP-AW protection o f transmission mechanisms is greater when the ZnDTP organic chain is shorter, particularly at low con­ centrations, and whatever the nature o f the alcohols used in the synthesis. A m ixture of primary and secondary alcohols produces a combined ZnDTP w ith EP-AW properties close to those o f the best ZnDTP derived from the corresponding pure alcohol. A ll these results and observations complete and confirm what has already been suggested by research w ork, namely that the EP-AW effectiveness of ZnDTP does in fact depend on their chemical structure, and also on the contact conditions in which wear occurs, i. e.: — — — — — — —

type o f contact stress on moving surfaces surface roughness surface movement (sliding, rolling) sliding/rolling ratio lubricating oil temperature etc.

Lastly, when a test rig is used, EP-AW effectiveness also depends on the chosen assessment criteria.

3.12.7 References (1)

(2) (3) (4)

(5) (6)

(7) (8)

358

Rowe, C.N.; Dickert, J J .: The Relation of Antiwear Function to Thermal Stability and Structure for Metal 0,0-dialkylphosphorodithioates. American Chemical Society preprint 10(19651 D 7 1 -D 83. Forbes, E.S.: Antiwear and Extreme-pressure Additives for Lubricants. Tribology (1970) 1 4 5 -1 5 2 . Larson, R.: The Performance of Zinc Dithiophosphates as Lubricating Oil Additives. Scientific lubrication (1958) 12—20. Forbes, E.S.; Allum, K.G.; Silver, K.B.: The Load Carrying Properties of Metal Dithiophosphates: Application of Electron Probe Microanalysis. Institution of Mechanical Engineers. Gothenburg (1969) 188. Jayne, G.J«J.; Elliott, J.S.: The Load Carrying Properties of some Metal Phosphorodithioates. Am. Chem. Soc. preprints (1960) 1 3 9 -1 4 9 . Zamberlin, I.; Mikac-Cergolj, I.; Benecetic, M.: The Effect of the Chemical Structure of Zinc Dithiophosphates on Antiwear and Extreme-pressure Properties of Lubricat­ ing Oils. Nafta (Zagreb) 20 (1069) 3 5 1 -3 5 8 . Brazier, A.D.; Elliott, J.S.: The Thermal Stability of Zinc Dithiophosphates. J. Inst. Petr 53(19671 518, 6 3 -7 6 . Elliott, J.S.; Jayne, G.J J .; Barber, R.I.: Evaluation of Antioxidants for Automotive Lubricants Using the Rotary bomb. Inst. Petrol. London 55, (1969) 544, 2 19—226.

3.13

Evaluation of the Antiwear Performance of Aged Oils through Tribological and Physicochemical Tests

G. Monteit, A.M. Merillon and J. Lonchampt, Peugeot S.A., Voujeaucour,France C. Roques-Carmes, ENSMM, Besancon, France

Summary Extending automotive engine drain intervals requires a good knowledge o f the antiwear level o f lubricant efficiency. These performances are often closely linked to the oxidative degradation o f the oils. Physicochemical analysis and tribological tests were carried out on several oils oxidized by laboratory oxidation tests at different stages. An interesting correlation was found between the antiwear efficiency and some characteristics o f the electrochemical impedance spectra of such oxidized lubricants. A very promising way o f understanding the mechanisms o f wear mitigation by aged engine oils is proposed.

3.13.1 Introduction The trends observed in the recent automotive engine developments have led to a significant increase in the constraints imposed on the lubricants. The new constraints which contribute to a perceptible speeding up o f the effects of the oil aging are, among others: - an increase in the oil drain intervals, - the lowering o f the engine oil consumption and thereby its regeneration, - an increase in the crankcase oil temperatures, - the lowering o f the crankcase capacity... For these reasons and some others, it becomes very important to achieve a better knowledge of the residual ability o f the lubricants to carry out their functions, particularly the antiwear function, during the aging process in field service. Oxidation aging phenomena are mainly responsible fo r the loss of antiwear efficiency which is dramatically critical fo r valve train systems. Consequently, the aim o f the present study is to make its contribution to a better knowledge o f the influence o f the lubricant oxidation upon valve train wear. 359

For this purpose, some tests were carried out on a serial o f lubricants of different levels o f performance. A controlled accelerated aging o f these oils was achieved by a laboratory air oxidation test. That test led to a simulation o f the behaviour of the lubricants in service. Their remaining antiwear efficiency was assessed by means o f different trib o ­ logical tests. Last o f all, an electrochemical impedance spectrum measurement technique was used.

3.13.2 Experimental 3.13.2.1

Lubricants

The main characteristics o f the engine oils used in this work are listed in Table 3.13.1. These oils are mineral oils (B and D), or semi-synthetic (A and C). Each o f the tests presented here has been done on a similar oil batch. Table 3.13.1: Characteristics o f the lubricants under study. Rafarenca of the lubricant

3.13.2.2

SAE

Kinaoatic

Perfonaanea

Srada

viscosity at 100'C (cSt)

Laval

A

10 W 30

11.9

API SF/CO

B

20 W 50

17.9

API SF/CC

C

15 U 50

19.5

API SF/CC

0

10 U 40

14.5

API SF/CC

Oxidation Test

The laboratory method used to oxidize the lubricants is the one currently in service in the laboratories o f Peugeot SA . and other French car manufacturers. It is referred to as the method GFC T021 x 88. Briefly described, it consists in oxidizing in an erlenmeyer a quantity o f 300 ml o f the lubricants to be tested at a temperature o f 160°C and under an air flow o f 10 liters per hour. The oxidation test was performed w ithout any catalytic element. Its duration was variable in our experiments. 360

3.13.2.3

AC Impedance Technique

The AC impedance technique fo r studying the electrochemical properties of the lubricants consists in subjecting the lubricant contained in an electroche­ mical measurement cell to a low level excitation alternative voltage superim­ posed or not at a DC polarisation potential. In the work presented here, the measurement cell is of the tw o electrode type. The AC peak to peak voltage is 140 mv and the bias polarisation voltage is equi­ valent to zero DC, in other words, to the rest potential of the system. The impedance Z o f this electrochemical cell is equal to the ratio voltage/ current. It is measured over a large range o f frequencies (1 mHz to 30 kHz). The detail o f the electrochemical circuit and the different apparatuses is shown on Fig. 3.13.1 and Fig. 3.13.2.

Figure 3.13.1:

Electrochemical impedance measurement test stand

It consists of an electrochemical measurement stand; a potentiostat solartron 1286 (A) controlling the polarisation DC voltage, a frequency response analyser solartron 1250 (B) allowing the generation o f the sinusoidal alternative exci­ tation signals applied to the cell and the analysis o f its response.

361

Cell

Current Voltage

Potentiostat Solartron 1286 (A)

Oscilloscope (01

o

F ilt e r s

IC)

IB)

Frequency

' Analyser

Generator

response analyser Solartron 1250

Disk

(O Computer

Printer

Plotter Figure 3.13.2: Block diagram o f the electrochemical measurement circuit

The response signals are filtered by means o f a computer software driven filte r box (C) and visualized on an oscilloscope (D). The whole electrochemical stand is w holly computerized (E) via a IEE 488 connection. The electrochemical cell used has been specifically b uilt up fo r this study. It is shown on Figures 3.13.3 and 3.13.4. The cell is made o f an insulating material and it can be used w ith oil temperatures up to 130°C. Its design allows the variation and the con­ trol o f the distance between the tw o electrodes down to very low values (25 nm) by means o f a micrometer. The thermostatic regulation is achieved by means of a heating coil immersed in a special compartment o f the cell. A mechanical stirrer allows the temperature to be uniform . A platinum tempe­ rature probe controls its value.

362

Figure 3.13.3: General view o f the components o f the cell

Temperature platinum probe

Electrodes

Micrometer

±

D

-

spring

Plastic tank

•— Molted resin

Figure 3.13.4: Description of the electrochemical cell

The electrodes are made from calibrated metal bars molded by gravity in a special resin.

363

The truncating o f these bars allows two electrodes to be made. Their surfaces are finely diamond polished until a roughness lower than 0.5 fim is achieved. Before each measurement, the electrodes are polished and washed in an ultra­ sonic bath.

3.13.2.4

Tribological Tests

In order to evaluate the antiwear efficiency o f oxidized oils, tw o types o f wear tests have been performed. Firstly, long duration tests (50 hours) on a cam tappet friction simulation rig and secondly on a four-ball machine. The cam tappet wear rig is made o f tw o cams, powered at a constant speed by an electric m otor, in contact w ith two tappets designed as in a real situation on the Peugeot XU engines. Owing to the low quantity o f oxidized oil available (300 m l), the lubricating principle o f this contact has been modified. The cams are lubricated during their rotation by rotating in a small oil bath. The contact load and rotation speed have been respectively set at 83 daN and 2000 t/m n corresponding to an oil bath temperature o f 75°C. This kind o f test has been used taking into account its good correlation w ith the valve train wear results from fired engine bench tests and automotive field tests. In addition, other wear tests have been conducted on the four-ball machine. The test conditions have been determined as follows: load: 30 daN, rotational speed: 1400 t/m n , oil temperature: ambient, test duration: 30 mn. Furthermore, it seemed interesting to us to study the antiwear efficiency o f the oxidized lubricants through the observation o f the growth o f the reactional films on the contacting surfaces. This has been achieved by altering the four-ball machine in order to connect an electric circuit to the balls. This circuit, des­ cribed in reference (1), allows us to observe the electric insulation between the balls, which is directly related to the thickness o f the films. The recording o f the voltage among the balls during the experiments is done by a digital storage oscilloscope. Filtered signals are thus available on a plotter. Let us bear in mind that in such an electric scheme, a short circuit (0 volt) means a metallic contact between balls w ith o u t wear protection films on it, and a fu ll voltage, as is applied, indicate a continuous antiwear film . The wear evaluation on the four ball machine is classically achieved by the measurement o f the wear scar diameter. *

364

3.13.3 Results 3.13.3.1

AC Impedance Spectra

There are only a few papers available in the literature concerning the application of the electrochemical impedance spectrum techniques to the study o f lubrica­ ting oils (2 — 5). Consequently, in order to understand the phenomena observed in this kind o f experiments, some preliminary tests have to be done. More parti­ cularly, some o f them have been related to the study of the influence of speci­ fic parameters.

Influence o f the Inter-electrodes Distance For this serial o f experiments, the electrode material was 35CD4 steel: the oil A oxidized on three levels was chosen as the electrolytes (0.96 and 264 hours of oxidation). Figures 3.13.5a and 3.13.5b show the aspect o f the impedance diagrams plotted in the Nyquist plane o f the oil A after 96 h in the oxidation test for different electrodes spacings. In this w ork, it could be assumed that the electrolyte resistance Re, in our case the lubricant, is represented by the value of the real part o f the impedance at the low frequency lim it o f the first loop (6). Then it is possible to plot the curve illustrating the evolution of this resistance Re w ith respect to the electrode spacing (cf. Figure 3.13.6). It can be seen that the value o f Re increases quite linearly w ith the electrode spacing, whatever the aging level o f the oil. However, if this curve is extrapo­ lated to the null value o f the spacing which is the "short c irc u it" one, a value of Re equal to zero may be found. This is not the case and a residual value o f the resistance is noticed and is different fo r the degree o f oxidation o f the oil as shown in table 3.13.2. This table also contains the values of the specific resistance o f these oils calcu­ lated from the slopes o f the curves in Figure 3.13.6. Likewise, it is possible to assume that the capacitance created by the bulk electrolyte (lubricant) between the electrodes is given by the relation (1).

ee0 S C = ----------------

(1)

1

365

where

ImlZlohms

C :capacitance o f the cell e : dielectric constant o f the lubricant e0 : dielectric constant o f the vacuum S : surface o f the electrodes 1 = electrode spacing Imaginary part

4 8 E 7 -

d=0.03mm

2.46*7

Qacraasing fraqutncy

Re (Z) ohms 2.46-7

ImlZlohms

4,86-7

7, 2 6-7

Real part

Imaginary part

4 . 8 6 7 -

d=0.04mm 2 . 4 E 7 Oacraasing fraquancy

RefZlohms 2 . 4 E 7

4 . 8 E 7

7 . 2 E 7

Real part

ImlZlohms Imaginary part

4.8E-7*

d =0.06 mm

2.4E-7-

0*crta»ing

frtqutcy

Re (Z) ohms UE-7

4. 8 E-7

7.26-7 Real part

1

Figure 3.13.5a:

366

Nyquist plots o f the impedance spectra fo r different elec­ trodes spacings

ImlZlohms Imaginary part < . . 8 E * 7

d = 0.10 m m

2 . 4 E 7

y o■

OKrMiing friqmncy

Re (Z) ohms

Z ' '

2 . 4 E * 7

'

4 . 8 E 7

7 . 2 E * 7

Real Part’

Imaginary part

ImlZlohms 4 . S E 7 -

d=0.13m m

2 , 4 * 7 -

jr

D#cr«sng friquincy

RelZlohms

Z ' 02 , 4 E » 7

4 . 8 E * 7

'

7 . 2 E 7

Real P31^

ImlZlohms Imaginary part 4 , 8 E * 7 -

d = 0 .2 3 m m

2 , 4 E * 7 *

s'

s

/ 0

O w Nsing frtqutncy

Re (Z)ohms

\y '2 , 4 E * 7

'

4 . 8 E 7

'

7 . 2 E 7

Rea* Par*’

2

Figure 3.13.5b:

Nyquist plots o f the impedance spectra fo r different elec­ trodes spacings

In the hypothesis where we consider that the first loop o f the impedance diagram is representative o f the capacitive behaviour o f the electrolyte, relation (2) applies: 1

C = ----------2 jt f Re

(2)

367

Re : electrolyte resistance f : frequency corresponding to the minimum value o f the imaginary part of the impedance. This is equivalent to the frequency position of the summit o f the first loop. Re(Mfl)

100 90 80­ 70­

0 = oilA fresh x=oilA oxidized 96 h •soil A oxidized 264h

60­ 50­



40­



50

. O



20­ 10­

I (mm)

0

1

0,05

Figure 3.13.6:

0,10

1 ' 1 I ' 1

0,15

0,20

0,25

'

'

1 I "electrodes 0,30 spacing

Evolution o f the resistance Re w ith respect to the interelec­ trodes distance

Table 3.13.2: Electric parameters measured on oil A at different oxidation levels Reference of the lubricant

Electrolyte Resistivity

spacing (H (1)

(6 Q.ae)

Dielectric constant

011 A fresh

7

12

5.4

Oil A after 96 h of oxidation

5

S.l

5.6

IS

9.6

6

Oil A after Z64 h of oxidation

368

Extrapolated value o f Re for zero

The curves in Figure 3.13.7 illustrate the dependence o f the capacitance versus the inverse o f the electrodes spacing. One can conclude that relation (1) applies well to the lubricant even if the latter has been aged by oxidation. The calcu­ lated values o f the dielectric constants o f the oils are also listed in table 3.13.2. Capacifance

0,60­

cho -’ fi

• =oil A fresh o=oit A oxidized 96h x =oil A oxidized 264h

0.55­

0,50­ 0,4-5­

0,40' 0,35

0,30' 0.25



0, 20 '

fi v

0,15

0,10­ 0,05-

1/ 1

—l— |— i— |— i — r "i— |

15 20 25 3 0 35 4 Q 45 50 55 6Q 65

Figure 3.13.7:

( m m )

i 1■]— i— T75

qq

85

Evolution of the capacitance C w ith respect to the interelec­ trodes distance

Influence o f the electrode metallurgy The nature of the materials in contact w ith the lubricants in automotive engines is extremely different. Consequently we have tried to evaluate their influence upon the trends o f the impedance diagrams. Different metallurgies have been used in addition to the 35CD4 steel: a GS cast iron and tw o alumi­ nium alloys AS7G0.3 and AS5U3. Only one lubricant has been used as a reference oil in the cell (oil B after 144 hours o f oxidation). The electrodes spacing was set at 0.025 millimeter. The Nyquist diagrams illustrating the results o f these impedancemeasuring conditions are shown on figure 3.13.8. The first loop o f the diagrams is almost not affected by the nature o f the electrode material. The capacitance and resistance values deduced from the characteristics o f the first loop are indicated in table 3.13.3. Bearing in mind the very slight differences noticed, the global behaviour o f the electrolyte can be assumed to be similar.

369

ImlZlohms Imaginary part 4. ae*7-

Electrodes=35CD4 steel

H i g h 2 , 4 £ * 7 - f r * q u t n c y l o o p t

Low f r o q u t n c yl o o p

RelZlohms 2 . 4 E 7

4 8 E * 7

7 . 2 E * 7

Real part

ImlZlohms Imaginary part 4 , 8 E * 7 -

2,4E»7 -

f r o q u t n c y l o o p

Electrodes=AS7G0.3. 'Low

R e lZlohms

2.4e*7

4 8 E * 7

7 . 2 E 7

Real part

Figure 3.13.8: Nyquist plots o f the impedance spectra fo r different electrodes materials

370

Table 3.13.3: Values o f the capacitance and the resistance o f the cell for different electrodes materials El«ctrod« material

Resistance Re (H Q)

Capacitance C (PF)

3SCD4 Steel

22.4

537

GS cast iron

19.2

509

AS7G0.3

21.6

518

AS5U3

20

530

In return, the trends o f the diagrams fo r the low frequencies of excitation, which correspond to the electronic exchange mechanisms at the interfaces, is very d if­ ferent fo r all the tested materials. Two types of diagrams can be drawn, one corresponding to the ferrous materials (cast iron and steel) whose low frequency part is roughly represented by a capacitive loop and the other, corresponding to aluminium-based alloys whose diagram aspects are represented by a low frequency capacitive loop followed by a divergent straight line. Further investigations are needed to explain these phenomena. However, it must be noticed that the reactional mechanisms can be brought out by this technique. In addition, they seem to be different for the ferrous and aluminium based materials. This report is supported by the physicochemical examinations on the surfaces of friction materials which show that the chemical composition o f the reactional films analyzed by XPS were very different fo r these tw o kinds o f materials (7).

Influence o f the level o f Oxidation Oils A and B have been used fo r this study. They have been submitted to d iffe ­ rent durations of the oxidation test (0.50, 96, 144, 200 and 264 hours). The electromechanical cell was set up at two spacings (0.1 and 0.03 mm) at room temperature (23°C). The corresponding diagrams are represented in figure 3.13.9a and 3.13.9b for the large inter-electrodes distance. These diagrams show that the dielectric properties o f the oils are dramatically affected by the degree o f oxidation depending upon the chemical form ulation of the lubricant.

371

ImlZlohms Imaginary part 4.8E.7Oil A :fre sh electrode spacing =0,10 m m

2AE-7

Re (Z)ohms 2 ,tE *7

'

;,8E *7

' 7 , 2 E -7

Real part

Imaginary part

ImlZlohms 4.8E*7H

Oil A oxidized 96h 2 .4 E -7

RelZlohms 2.4E-7

'

4.8E-7

7,2E*7

Real part

ImlZlohms Imaginary part 4,8 E *7-

Oil A oxidized 144h 2 A E *7 -

RelZlohms o

ImlZlohms

' 2 a e *7

a.8E»7

7, 2 e *7

Real part

Imaginary part

4 .B E -7 -

Oil A oxidized 264h 2 .4 E -7 -

RelZlohms 2AE-7 ' 4.8E*7 ' 7,2E*7 ' Real part

1 Figure 3.13.9a:

372

Nyquist plots o f the impedance spectra fo r different oxidation levels

ImlZlohms Imaginary part

Oil B . fresh

t,6 E *7 -

RelZlohms Real part

ImlZlohmsl Imaginary part M E *7 -

Oil 8 .oxidized 144h

2 ,4 E * 7 -

RelZlohms Real part

Oil B .oxidized 200h

RelZlohms "•°E*7 Real part

Figure 3.13.9b:

Nyquist plots o f the impedance spectra fo r different oxidation levels

373

On figure 3.13.10 are represented the variations of Re during the oxidation process. Oil A shows very slight variations o f Re and exhibits a minimum value w ith respect to the oxidation. Conversely, oil B shows a significant increase of this value and exhibits a maximum in the curve. No equivalent plots have been drawn fo r the capacitive behaviour. As a matter o f fact, the variations of the capacitive behaviour are very little affected by the oxidation, at least in the high frequency excitations.

210

200

Resistance Re (Mfi) (electrochemical impedance measurement)

-

150

o = oil A o = oil B 100-

50i □ -i

50 Figure 3.13.10:

100

(hours) ---------------- 1---------------- 1----------------i— — oxidation test

150

200

250

300

Dependance of Re w ith respect to the oxidation duration

A ll the reports given previously show that the value o f Re could be successfully used to evaluate the oil degradation. Thus it is possible to m onitor the variations o f the degradation o f the oil by means o f the simplest electric way: a DC voltage cell. For this purpose we have made such measurements in a specially designed cell w ith stainless steel electrodes. The DC voltage was set to 1v, the electrodes spacing to 0.3 mm in order to measure the global resistance o f the cell. Figure 3.13.11 illustrates the results obtained w ith this device. The relative variation (in percent) o f the resistance o f the cell measured on an oxidized oil w ith respect to the same measurement on the corresponding fresh oil is drawn versus the oxidation time. This total resistance cell is the sum o f the different resistances associated to the bulk electrolyte and to the two electrochemical electrode/lubricant reactions. 374

One can immediately establish that the general trends o f the curves of oils A and B are very similar to the corresponding ones previously drawn w ith the results of the impedance spectrum technique. In addition, it can been seen that the curve trends related to the oxidation behaviour o f oils A.C.D are very close to one another but very different from those o f oil B. In order to translate all these observations into an antiwear performance crite­ rion, some wear tests have been done. The results o f these tests are examined below. (%) Percenfage of variation of Re 400­

Re at oxidation time t xTOO Re fresh oil

a = oil

300­

o

200

A

o r Oil B *= oil C • = oil D

­

100 -

J

Q

a □ (hours) oxidation test -100-1--------------- 1---------------- 1---------------- 1----------------1----------------1----------------T— 0 50 100 150 200 250 3 0 0 duration

Figure 3.13.11:

3.13.3.2

Evolution of the electrolyte resistance during the oxidation process as measured in DC voltage

Wear Tests

Table 3.13.4 collects all the tribological results obtained w ith the different oils which are the subject o f the present work. The wear results on four-ball machine are expressed by the mean value o f the wear scar diameters of three different tests. Wear values resulting from the cam-tappet endurance tests are expressed by the mean value o f the weight loss o f the cams o f two tests (two cams fo r one test). Systematic microscopic observations were made o f the worn faces of cams and tappets w ith different oils to make sure that the wear process involved the same mechanism and differed only in their respective intensity.

375

Table 3.13.4; Physicochemical results on oxidized oils 011 rafaranca Oxidation tost du­ ration (h)

A

Valght loss of cams

TAN Hoar scar (mg K0H dlaaatar {») /9)

Viscosity Viscosity at loo* c at 40* C (cSt) (cSt)

(■9)

0

-

0.34

2.5

11.9

81.8

96

4

0.32

4.5

11.6

82.4

144

1.7

0.36

5.2

12

87

200

2.35

0.36

6

12.9

99.5

264

5

0.87

7

16.6

147.9

0

-

0.34

2.3

17.9

161.4

50

709.6

0.37

-

96

604

0.42

4

16.9

158.7

144

1

5.1

17.3

166.5

200

9.8

0.38

6.4

18.7

189.2

264

16.3

0.38

8.6

25.5

366.6

-

0.33

2.8

19.5

148.8

96

2.9

0.39

4.7

20.2

158.5

144

6

0.40

5.8

21.1

172.8

200

1.9

0.36

6.9

25.1

231.4

264

4.62

0.38

8

37

356.8

0

-

0.34

2.6

14.5

95.7

96

1.4

0.37

4.6

14.7

99.4

144

4.6

0.37

5.3

16.1

111.4

200

5.5

0.38

6.5

19.2

153.2

264

3.1

0.39

B.2

29.4

249.9

-

B

0

C

0

376

-

In this table are also listed the values of the physicochemical characteristics measured on the same oils; the total acid number (TAN: method ASTM D664), the kinematic viscosities at 40 and 100°C, traditionally used to qualify the oil degradation following oxidation tests.

Cam tappet Test Result Figure 3.13.12 shows the evolution o f the wear o f the cams w ith respect to the degree o f oxidation o f the oil. It shows that the general profile o f these curves are very close to those illustrating the evolution o f electrochemical measure­ ments on the oils (cf. figures 3.13.10 and 3.13.11). Two different kinds o f behaviour can be noticed, one related to a progressive increase in wear w ith respect to the oxidative level (oils A , C, D) and the other related to the presence o f the maximum in the wear curve (oil B). (mg) I Weight loss of cams log scale

□ = oil o r Oil x = oil • = oil



A B C D

3-

2

­

o o

1­ *



0 •



E x (hours) oxidation :------- °t--------- 1--------- 1--------- r— test 100 150 200 250 500 duration

1---------

0

50 Figure 3.13.12:

Relation between the wear o f cams and oxidation test duration.

Four-ball Test Results Figure 3.13.13 illustrates the wear results at the end o f the 30 min run. Roughly, the trends visible w ith respect to the oxidation level are the same as those that can be seen at the end o f the endurance test.

377

(mm)

Wear scar diameter

0 ,5 ­

s

0 ,4 -

□ t

0 ,3 :

a = oil o = oil » = oil - = oil

0,2­

A B

C D

0,1(hours) oxidation test

50

Figure 3.13.13:

100

150

200

250

300

N a tio n

Wear scar diameter on four-balls machine versus oxidation duration time.

The relative lack o f correlation between the two tests in not surprising and not very significant. More attention is to be paid to the wear results o f the motored valve train wear which are more closely linked to the real valve train wear prob­ lems o f automotive engines. More interesting is the study o f the form ation o f the reactional films during these four-ball wear tests. Curves in figure 3.13.14 show, fo r all the oils, the evolution o f the contact potential between the balls related to this form ation. A ll the lubricants show a similar trend such as, a lowering o f the insulation state o f the balls corresponding to a slowing down o f the growth kinetic o f the protective layers w ith a progressive increase in the oxidation process. Some o f these film s are very unstable and, moreover, worn out, as is shown by the curves o f oils A oxidized fo r 144 h and oil C fo r 96 h and 144 hours, which are decreasing beyond a certain duration.

378

Fresh

BO (mn)

Figure 3.13.14:

Evolution of the contact potential between the balls during the wear test.

379

3.13.4 Discussion The last results relative to the measurement o f the insulating state o f the balls show a good correlation w ith the antiwear performance o f the oils after oxida­ tion tests evaluated by means o f a cam tappet wear test. The evolution o f this insulation, which can reasonably be considered as represen­ tative of the antiwear activity o f the lubricants (8), allows us to find the two groups o f the oils already identified; oil B showing a maximum o f wear degra­ dation and percentage o f metallic contacts and, on the other hand, oils A , C and D showing a continuous decrease in their insulation state, in the same classification as their wear mitigation performance. These two kinds o f behaviour are the same as the one observed by the electro­ chemical techniques described in paragraph 3.13.2.3. We have already seen that the value o f "global resistance" o f the cell as measured in DC, voltage or the specific resistance Re o f the electrolyte deduced from AC Impedance Spectra exhibited a similar trend, w ith respect to the type and oxidation level o f the lubricants, to the one shown by the wear of cams and the contact resistance between the balls. No other physicochemical value measured on the lubricant during this work was able to reproduce these evolutions. Thus, this electrochemical technique seems to be promising in the study of the oil activity. A number o f other questions appear from the result presented here. Among others, figure 3.13.15 describing the relationship between the relative variation of the resistance Re and the wear o f cams in the endurance test shows that the correlation is not satisfactory enough. This relation becomes notably better if we consider only the results of the measurements made w ith alternative AC excitation voltages. It can be explained by the fact that, w ith this technique, there is no polarisation o f the electrodes perturbing the interfacial system response as w ith DC voltage. As a matter o f fact, the global resistance value o f the cell is a complex para­ meter. The polarisation voltage is often o f a very high level and, consequently, the stationary state o f the system cannot be reached before a long time. Conversely, the AC Impedance measurements do not perturb the system and allow us to separate the electrochemical reaction effects which are affected by the nature o f the electrodes material, the polarisation voltage amplitude. The other discrepancies observed fo r the highest values o f the cam wear might be easily explained by mechanical considerations. In this test, such values can be qualified as "catastrophic wear." and the cam profile is quite completely worn away. Consequently, the acceleration curve and, as a result, the contacting force law, becomes erratic, giving rise to an autocatalytic increase in the wear kinetics. There ist a phenomenon o f "geometrical activation" o f the wear which shifts the curve towards the wear value axis. Mild and medium wear do not suffer from this kind o f problem. 380

(%) 400-

Percentage of variation of Re Re at oxidation time t *100 Re fresh oil

In brackets the same values as determined by the impedance spectrum technique for oil A and 8

300­

□= o= *= •=

oo

200

­ (o)

100

Oil oil oil oil

A B C D

(°o) (o)

( (o ) (H

(a* X □ □ X !D)j (a) LJ □ * X

-100

Figure 3.13.15:

(mg)

weight toss ■ of cams (log scale)

Relation between electrochemical impedance determination o f Re and wear performance

3,13.5 Conclusion It has been shown that the electrochemical techniques applied to the study o f the lubricants allowed a forward-looking evaluation o f their antiwear capability during a laboratory simulated oxidation process. This evaluation is shown to be well assessed by means o f an electrochemical impedance spectrum technique. This method allows us to display the differences in the chemical reactions w ith respect to the oil oxidation fo r various lubricants. For example, the real part component of the impedance measured at high frequencies can already be a very powerful tool fo r such studies. In addition, interesting potentialities o f studying the reactional mechanisms o f the lubri­ cants have been offered by extending these measurements to the low frequency domain. Nevertheless, an im portant work has to be done fo r a better knowledge and understanding of the strictly interfacial reactions between various metal sur­ faces and the active species of lubricants. This research is being carried out.

381

3.13.6 References (1)

(2)

(3)

(4) (5)

( 6)

(7)

(8)

382

Monteil. G.; Lonchampt, J.; Roques-carmes. C.: Etude tribologique du systfeme came-poussoir. Amsterdam 1985. 2.2 p 1—8. Proceedings Eurotrib 85.9.12.09.85. Ecully. Wang, S.; Tung, S.: Electrochemical phenomena in lubricants. I. potential measure­ ments and analysis of metal/additive interactions — 1985 p 6 4 2 -6 4 3 . Extended Ab­ stract No. 431, Fall Meeting o f the Electrochemical Society. Las Vegas 13-18.10.85. Wang, S.; Maheswari, S.; Wang, Y.; Tung, S.: An electrochemical technique for characterizing metal-lubricant interfacial reactions. ASLE transactions 30 (1987) 3, p. 3 9 4 -4 0 Z Wang. S.; Maheswari, S.; Tung, S.: AC Impedance measurements of the resistance and capacitance of lubricants. ASLE transactions 3 0 (1987) 4, p. 4 36—443. Wang, S.; Maheswari, S.; Tung, S.: The nature of electrochemical reactions between several zinc organodithiophosphate antiwear additives and cast iron surfaces. Tri­ bology transactions 31 (1988) 3, p. 381— 389. Barral, G.; Diard, J.P. le Gorrec, B.; Dac T ri, L.; Montella, C.: Impedance de cellules de conductivity I. Determination de plages de frequence de mesure de la conducti­ vity. Journal of applied electrochemistry 15 (1985), p. 913—924. Denizot, D .; Monteil, G.; Roques-Carmes, C.; Lonchampt, J.: A tribological study of synchronizing devices used in car gearboxes. Journal of automobile engineering Part 0 2 .2 0 3 (1 9 8 9 ), p. 1 1 1 -1 1 5 . Cameron, A.: Thick boundary lubrication. Helsinki. 1989 not published. EUROtrib 89 12-15.6.89. Helsinki.

3.14

Mathematic Model fo r the Thickening Power of Viscosity Index Improvers. Application in Engine Oil Formulations

H. Bourgognon and C. Rodes, Centre de Recherche E lf Solaize, Lyon, France C. Neveu and F. Huby, Rohm & Flaas European Operations, Paris, France

Summary It is essential fo r a lubricating oil blender to be able to quantify the contribution of each component entering in the form ulation to the viscosity of the finished product. In this context several studies have been devoted to the modelization of the thickening power of different types o f polymers at both high (100° C and 40° C) and low (— 15° C) temperature in base oils o f various origin and viscosity. To complement these earlier investigations, it is necessary to quantify the effect of the additive package on the viscosity of the form ulation. For this purpose, the effect o f several DI packages of different performance levels has been in­ vestigated in order to derive appropriate mathematical models representing their contribution o f the oil viscosity.

3.14.1 Introduction It is necessary fo r both economical and technical reasons (com patibility w ith seals, thermal stability, . . .) to optimize the composition of an engine oil in order to minimize the quantity o f VI improver and to use the most viscous base oil blend. This is possible in a laboratory w ith no time constraint but it is impossible in a blending plant. The latter is not in a position to adjust the fo r­ mulation to take into account the variability of the components (VI improver, base stocks, DI package). In order to be able in a blending plant to produce oil exhibiting consistent viscosity, it is necessary to develop precise models describing the thickening power o f a polymer and o f a package in various base stocks at different tempe­ ratures.

3.14.2 Background In a previous study (reference 1) it has been shown that the Kraemerand Huggins equations which are normally applicable only in the field of dilute solutions could be used:

383

a) to describe the thickening power o f a PMA V I improver in typical engine oil blends at temperatures ranging between 38° C and 175° C, and b) to provide an estimate o f the intrinsic viscosity o f a PMA polymer in a given solvent and at a given temperature. They are o f the form : LN (VF/V B)=ETA K*c—b eta*(E T A K *c)‘ *2

Kraemer

VF/V B=1+E TAH *c+k, (E T A H *c), , 2

Huggins

VF is the viscosity o f the blend containing c % by weight of polymer in a base oil o f viscosity VB. ETAH and ETAK are the intrinsic viscosities calculated using respectively the Huggins and Kraemer equations. Beta and k are the second order coefficients o f these equations. In addition, the effect o f the solvent (paraffinic mineral o il, solvent refined) on the intrinsic viscosity ETA(T) could be approximated by the equation: ETA (T)=ETA 0(T)*(1—delta(T)*VB) where VB is the solvent viscosity at 100° C and delta(T) is a constant fo r PMA's at temperature T. ETAO(T) corresponds to the intrinsic viscosity of the poly­ mer at temperature T extrapolated to a zero centistoke base oil. In a second study (reference 2), it was shown that the Kraemer and Huggins equations could be used at both 100° C and 40° C outside of the field of d i­ lute solution o f OCP VI improvers, providing one takes into account the d i­ lution oil. A t - 15° C the equations could be simplified fo r the dPMA and OCP VI im ­ prover by neglecting the second order term. The solvency o f the base stock can be represented by a model o f the form : ETA{T)=ETA0(T) * (1 -d e lta (T )* VB+gamma(T) * (d—.88)) where VB is the solvent viscosity at 100° C, delta(T) and gamma(T) are con­ stants for PMA's and OOP's at temperature T and d is the specific gravity of the base oil at 15° C. Finally, ETAO(T) corresponds to the intrinsic viscosity of the polymer at temperature T extrapolated to a zero centistoke base oil o f specific gravity d = 0.88.

384

3.14.3 Objective of the Study In order to optimize the composition o f engine oils in a production plant, it is necessary to complement the previous results by equations which can re­ present: a) the contribution o f a package to the kinematic viscosity at 100° C and 40° C and in the CCS (ASTM D 2602) at - 15° C. b) the effect o f the presence o f a package on the contribution o f the polymer to viscosity and on the solvent power of the base stocks.

3.14.4 Contribution of Package Components to Viscosity A DI package is made of several components which all have a contribution to the blend viscosity. Before embarking on the modelization of the effect on the viscosity of the complete package, we have examined the variability which may result from the fluctuations o f the package composition. For this pur­ pose, we have evaluated: a) the contribution o f each o f the main DI components to the blend viscosity. b) the variability of blends based on samples of packages delivered to a blend­ ing plant.

3.14.4.1

Contribution of Package Components to Viscosity

To define a model describing the contribution of each of the main components of a package to the viscosity o f a lubricant, we have used a greco-latin design. Such a model w ill be simple but sufficient fo r our purpose. We selected 6 components which were combined in such a way that the sum of the concentrations was kept equal to 8 %. The formulations are detailed in Table 3.14.1. V1 et V2 are ashless dispersants, V3 is a ZDTP, V4, V5, V6 are detergents. The analysis of the viscometric data shown in Table 3.14.2 showed that V I, V2 and V3 had the largest influence on the blend viscosity. In order to obtain a more precise model, three additional blends shown in Table 3.14.1 were made. The viscometric data are shown in table 3.14.2.

385

Table 3.14.1: Contribution o f package components to viscosity Blend compo­ sitions

V 4

V 5

V 1

V 2

V 6

V 3

Ref.

Blend 1

5.6

0.48

0.48

0.48

0.48

0.48

92

Blend 2

0.48

5.6

0.48

0.48

0.48

0.48

92

Blend 3

0.48

0.48

5.6

0.48

0.48

0.48

92

Blend 4

0.48

0.48

0.48

5.6

0.48

0.48

92

Blend 5

0.48

0.48

0.48

0.48

5.6

0.48

92

Blend 6

0.48

0.48

0.48

0.48

0.48

5.6

92

Blend 7

1.33

1.33

1.33

1.33

1.33

1.33

92

V 4

V 5

V 1

V 2

V 6

V 3

Ref.

Blend 8

0.48

0.48

3.04

3.04

0.48

0.48

92

Blend 9

0.48

0.48

3.04

0.48

0.48

3.04

92

Blend 10

0.48

0.48

0.48

3.04

0.48

3.04

92

a) Greco-Latin Design

b) Additional blends

386

Table 3.14.2: Contribution o f package components to viscosity viscosimetric data

Viscosity 100° C (cSt)

Viscosity 40° C (cSt)

Blend 1

12.78

81.41

2800

Blend 2

13.07

85.59

2950

Blend 3

13.74

92.15

3200

Blend 4

13.77

91.05

3200

Blend 5

12.36

82.51

2950

Blend 6

11.86

76.11

2700

Blend 7

12.86

84.49

2900

Name

Viscosity - 15° C (cPo)

a) Greco-Latin Design

Name

Viscosity 100° C (cSt)

Viscosity 40° C (cSt)

Viscosity — 15° C (cPo)

Blend 8

13.72

91.72

3100

Blend 9

12.70

82.29

2900

Blend 10

12.67

82.89

2900

b) Additional blends

The complete analysis o f the data enabled us to obtain the following models: KV

100° C =

12.63 + 0.191 *V1 + 0.194*V2

KV

40° C = 8 2.35+ 1.66*V1 + 1.54*V2

DV

—15° C = 2863 + 51.5*V1 + 5 1 .5 *V 2

- 0.187*V3 - 1 .5 * V 3 - 48.5*V3

in which Vi is the concentration in percent weight of component Vi. This model appears to fit correctly the ten data points of our design. However, it should not be valid outside the range o f composition studied.

387

It is interesting to note that: a) the two ashless dispersants V1 and V2 give essentially the same level of viscosity increase. b) each percent o f ZDTP (V3) decreases the viscosity by almost the same amount as each percent o f ashless dispersant increases it. Using these models, we can estimate the effectwhich would result from a 5 % increase and a 5 % decrease o f the concentration o f the ashless dispersants and ZDTP respectively. We have taken, for example, a SAE 15 W 40 containing 5 % of ashless dis­ persants and 1 % o f ZDTP. Increasing the ashless concentration to 5.25 %, re­ ducing the ZDTP content to 0.95 % and rebalancing the package to maintain a treat rate o f 8 % would result in the following increase of viscosity: KV KV DV

100° C increase = 0.06 cSt 40° C increase = 0.5 cSt —15° C increase = 15 cPo

3.14.4.2

Analysis of Packages Used by a Blending Plant

We have obtained 16 and 12 samples o f respectively an SF/CC and an SHPDO package which were retained at the time o f delivery. Using each o f the gasoline package samples, wehave prepared aform ulation using a given base oil m ixt and a givenVI improversample. A similar exercise was repeated w ith the Diesel package samples. The complete results are gathered in Table 3.14.3. The mean viscosity and the standard deviation at 100° C, 40° C and — 15° C have been calculated for each package. It can be seen in Table 3.14.3 that the standard deviation ob­ tained for the Diesel and gasoline packages are essentially identical irrespective of the temperature. Consequently, an average value can be used to estimate at each temperature the variability associated w ith the use o f different DI package deliveries. Standard deviation 100° C = 0.04 cSt Standard deviation 40° C = 0.2 cSt Standard deviation - 1 5 ° C = 110 cPo To each o f these three standard deviations corresponds a variance which can be broken down into: VP: variance due to fluctuation in package composition VB: variance due to the preparation o f the blend VM: variance due to the precision o f the viscosity measurement. 388

o D E iQ. a ? cj

u

CD

*Q *> H Q) O) c c

CD

U CD

CL

CO CO

V CD

-O

in

in ^ ^ f o o io ^ c o o o Q o iin o o c o

'9 m o o i > 0 0 0 0 O O 0 co CNi Iin in ( •o o in in 8 O in 8 8 m (J o «CM CN CO CO CO CO CO CO ( j co co 8 ;

o

o or^crjr^o oo cjo dr^co cor^r^cd cjo od r^

CO CO CO CO CO CO CO CO CO CO CO CO* CO CO CO CO*

o o o o m m o o o o o o o o o o c o c o c o c o c N r - r ^ ^ o o c N C N c n ’- C N ^ t r ^ co co co co ^ co co co co co ^ co

OOCOOOOOCOCOOOOOOOCOOOCOOOOOOOCO

r-_ ro 0 cp ^ o 0 q o » - cq co ip c o _ c o

>

>

>

•c N C O ^ L n io r-o o a ^ O r-c N C O ^ in io

d d d d d d d d d d d o d d d d

COOOOOCOOOCOCOCOCOCOCOCOCOCDCOCX)

COCOOOOOOOOOCOCOCOOOCOOOOOCOGOCO

< o a o o o c o o c o c o c o c o o o a o c o o o o o o io } 0C co ococ ococ ococ ocococ ococ ocococ oco CL CO

co CD o

a) Gasoline package

Knowing that the standard deviation associated w ith the precision o f the vis­ cosity measurement corresponds to approximately:

Standard deviation 100° C = 0.02 cSt Standard deviation 40° C = 0.12 cSt Standard deviation —15° C = 75 cPo it can be concluded that the sum o f the variabilities due to the fluctuations of the package composition and to the preparation o f the blends still accounts fo r more than half o f the variance irrespective o f the temperature. However, we must consider that the residual standard deviations o f the models developed in prior studies are significantly higher than those calculated in this section. Consequently, we w ill neglect in our calculations the variations which could be associated to the variability o f the package.

3.14.5 Model Describing the Contribution of Package to Viscosity In order to define a model which could be used to represent the contribution o f a package to the viscosity as a function o f temperature, we have used data generated according to the follow ing factorial design: Factors

Levels

Base stock origin

3

Package type

SF/CC (8.0 %) SF/CD (11.8%) SHPD (14.5 %)

% PMA

None 6 % in SF/CC and SF/CD formulations 5 % in SHPD form ulation

Temperature

— 15° C, 40° C, 100° C

Considering that the intrinsic viscosity of a polymer depends on the viscosity o f the base o il, we have completed our blending study in three different base oil mixtures having a kinematic viscosity of 8 cSt at 100° C. These base stocks were selected because of the difference in aromatics content and, consequent­ ly, specific gravity as shown below: Base code

Aromatic carbons IR HPLC

B1 B2 B5

21.2 22.9 39.7

390

6.25 5.8 8.4

Specific gravity

.8767 .8720 .8835

3.14.5.1

Model Describing the Contribution of Packages to Viscosity

Our analysis is based on the blends containing no VI improver. The viscometric results are gathered in Table 3.14.4. We have decided to use a model on the Kraemer equation w ith no second term order: LN(VP/VB) = K1*Xp' VP and VB are the viscosity o f the base oil w ith and w itho ut package respective­ ly. Xp' is the concentration of the package corrected fo r the addition o f VI improver according to the formula: Xp' = X p /( 1 0 0 - X V I) w ith: XVI = 6 fo r the SF/CC and SF/CD packages XVI = 5 for the SHPD package Xp = recommended package concentration infu lly formulated

oil.

This correction was made in order to take into account the presence o f a VI improver in the fu lly formulated oil. When using Xp' the relative concentra­ tion o f the package in the base oil plus package only is the same as in the fu lly formulated oils. The values o f K1 for each of the packages and each o f the base oils are detailed in Table 3.14.5. It can be seen that, irrespective o f the temperature, K1 de­ pends significantly on the package type but that it is essentially independent on the base oil origin.

3.14.5.2

Effect of the Package on the Thickening Power of the Polymer

Using the Kraemer and the Huggins equations we have calculated the intrinsic viscosity o f the dPMA polymer for each of the blends at each o f the three temperatures. When the blend contained a package, we use VP (base oil + package) in the equations instead of VB (base oil no package). The results of this exercise are gathered in Table 3.14.6. We completed a vari­ ance analysis which indicated that: a) the package type has a significant effect on the intrinsic viscosity at both 10(T Cand 40° C b) the base stock origin has a significant effect on the intrinsic viscosity at 40° C c) at — 15° C neither the package type nor the base stock origin have a signi­ ficant effect on the intrinsic viscosity. 391

7.99

59.00

B5

14.50

SHPD

57.56

8.01

B2

14.50

SHPD

61.12

8.01

BI

14.50

SHPD

5 9.00

7.99

B5

11.85

SF/CD

57.56

8.01

B2

11.85

SF/CD

61.12

BI

11.85

SF/CD

8.01

B5

8.0

SF/CC

57.56 59.00

8.01

B2

8.00

SF/CC

61.12

VB 40

7.99

8.01

VB 100

B1

Bablend

8.00

Packrate

SF/CC

Package

35

34

48

35

34

48

35

34

48

VBCCS

9.86

9.80

9.77

9.70

9.63

9.68

9.44

9.41

9.42

VP 100

78.17

78.00

80.96

76.93

74.30

79.28

73.08

70.79

75.31

VP 40

55.0

52.5

74.0

54.5

52.0

72.0

47.0

45.0

63.5

VPCCS

Table 3.14.4: Thickening effect o f polymers, effect o f DI package performance level

62 .0 67.0

122.0 127.87

16.10 16.16

69.0

65.0

90.0

59.3

55.0

79.0

VFCCS

88 .5

132.80

124.58

135.56

125.72

117.93

127.89

V F 40

130.18

16.12

17.19

16.92

17.20

16.52

16.41

16.52

V F 100

Table 3.14.5: Thickening effect o f packages K1 100

K1 40

K1 CCS

Mean

Mean

Mean

Package

Bablend

SF/CC

B1

0.0191

0.0245

0.0329

B2

0.0189

0.0243

0.0329

B5

0.0196

0.0251

0.0346

A ll

0.0192

0.0247

0.0335

B1

0.0150

0.0206

0.0322

B2

0.0146

0.0203

0.0337

B5

0.0154

0.0210

0.0351

All

0.0150

0.0206

0.0337

B1

0.0130

0.0183

0.0284

B2

0.0132

0.0199

0.0285

B5

0.0138

0.0184

0.0296

All

0.0133

0.0189

0.0288

SF/CD

SHPD

Bablend

Bablend

393

Table 3.14.6: Thickening effect o f polymers, effect o f DI package performance level

VIITYPE PMAD ETAH CCS

ETAH 100

ETAH 40

0.1834 0.1101

ETAK 100

ETAK 40

0.2066

0.1908 0.0952

ETAK CCS

Package

Bablend

SF/CC

BI

0.2021

B2

0.2000 0.1762

0.0960 0.2045

0.1834

0.0843

B5

0.2013 0.1874

0.1106 0.2058

0.1949

0.0955

B1

0.2073

0.1864

0.1147

0.2120 0.1939

0.0986

B2

0.2031

0.1790 0.1084

0.2076 0.1862

0.0939

B5

0.2064

0.1902

0.1150

0.2110 0.1968

0.0988

B1

0.2145 0.1974

0.1086

0.2193 0.2055

0.0961

B2

0.2126

0.1855 0.0960 0.2174 0.1930 0.0861

B5

0.2117

0.2034

SF/CD

SHPD

0.1125 0.2164

0.2117

0.0991

We have plotted in Figures 3.14.1 to 3.14.3 the dependence of the intrinsic viscosity on the package concentration and base stock origin. It can be seen that: a) the addition o f a package reduces the effect of the base oil origin on the intrinsic viscosity of the polymer especially at 100° C. We w ill, therefore, neglect it in our models. b) at 100° C and 40° C the intrinsic viscosity increases w ith the concentration of DI package sometimes in a nonlinear manner.

394

Legend ■ B1

0 B2_____ • B5 % package Figure 3.14.1:

Effect o f packages on intrinsic viscosity

fS UJ

o a

4—* ca >
- u ) U O u ) - h > OUl/J M EASURED VIS C O SITY CCS M O DEL BASED ON PACKAGE T R E A T RATE A N D ETA HUGGINS

Figure 3.14.9:

Thickening effect o f polymers, effect of DI package perform­ ance level, prediction using the mathematical model

403

1 P

%

Absolute

%

Huggins Kraemer

0.87 0.80

1.23 1.13

1.78 1.45

2.54 2.07

1.7%

40

Huggins Kreamer

2.64 2.66

2.07 2.09

2.19 2.21

1.72 1.73

1%

100

Huggins Kraemer

0.214 0.213

1.29 1.29

0.118 0.113

0.71 0.68

0.6%

-

15

X

X

Absolute

Equation

T

43 O

General average o f 7?

•3

It

Table 3.14.9: Compared model residual standard deviations W ithout package Study CEC

These results can be compared to those which were generated in a previous study (reference 2) in which no package was used but in which the base stock viscosity was variable. It can be seen that at all temperatures, the precision o f the models describing the presence o f the package is not very different from that o f the models we obtained previously.

3.14.6 Conclusion a) It can be concluded that in a first approximation we can neglect the variabi­ lity in thickening power of the package which could be associated to the fluctuation o f the package composition. b) We can represent the contribution of a package to the viscosity using an equation o f the form : LN (VP/VB) = K1*Xp c) We can also take into account the effect of the package on the intrinsic viscosity o f the polymer using the follow ing equation: ETA(T)=ETA0(T)*(1 —alpha(T)*Xp) d) A t — 15° C one can alternatively use an average value o f ETA(T) calculated w ith different packages fo r use in the Kraemer and Huggins equations. e) We have obtained models which can be used to estimate the effect o f a package on viscosity. Their precision is similar to that o f models defined in a previous study in which no package was used (reference 2). f) This study should be complemented by the evaluation o f different polymer chemistries, using base stocks o f different viscosities and at different CCS temperatures. 404

3.14.7 References (1) (21

Neveu, C.; Huby, F.: Solution Properties of Polymeth 8crylate V I Improvers, 5th International Colloquium. 1986, pp 8-3-1/3-3-14. Neveu. C. Huby, F.; Rodes, C.; Bourgognon, H.: Modelisation m8th 6matique du pouvoir epaississant des amfiliorants d'indice de viscosite, lllrd international CEC Symposium (Paris 1989) 11 LM.

405

3.15

Surface Morphology and Chemistry of Reaction Layers Formed Under Wear Test Conditions as Determined by Electron Spectroscopy and Scanning Electron Microscopy

Y. de Vita, I.C. Grigorescu and G.J. Lizardo Intevep S.A., Caracas, Venezuela

A bstract Friction and wear tests were performed in the Optimol SRV unit in the presence o f engine lubricant oils A and B w ith different form ulation at a constant load and at different temperatures. Microanalytical studies on wear were accomplished using photomicrographs. In those samples where the wear scar was not detected by SEM, a digital inter­ ferential optical profiler was employed. The behaviour o f friction coefficient vs. time was analysed and metal-metal contact was detected in some test samples. Under severe wear conditions and lubrication failure, the morphologies o f the wear scars suggested that several wear mechanisms were possible: adhesive, delamination, plowing and oil corrosion. It was observed smooth worn scars formed under continuous lubrication conditions. On the basis o f semiquantitative analysis performed by AES and on the results of other researchers, it could be suggested that on those worn scars, w ith very smooth surface, a glassy compound could be formed w ith amorphous structure containing phosphorus and sulphur as major components. Similitude was observed between the worn area in valve lifte r sides, from a taxi fleet test, run w ith oils A and B, and those corresponding to the SRV test samples morphology. This fact could suggest that the same wear mechanism occurred, as it was described above.

3 .1 5 .1

In trod u ction

Theoretical (1) and experimental research (2) have shown that valve lifters often operate in either the boundary or the partica! elastohydrodynamic (EHD) lub ri­ cation regime. For this reason and in order to assess possible correlation between the results of wear obtained on valve lifters, from a taxi cab fleet test and those from SRV test device, morphological and chemical surface studies have been carried out under boundary lubrication conditions.

406

Much e ffo rt has been directed towards the understanding o f wear mechanism in the presence o f two different lubricant formulations; A and B. Therefore, the present study was conducted to investigate the relationship between the severity of the damaged surface to the variation pattern of friction coefficient versus time, and to state the chemical composition o f the worn surface at a given temperature and a constant load. Finally, the worn areas at the top and at the sides o f two valve lifters from taxi cab test were examined by SEM and EDX.

3 .1 5 .2 E xperim ental The wear experiments were carried out on a modified commercial cylinder plane test device (Optimol SRV), consisting of a small cylinder (15 x 22 mm) scillating on a static plane chip (234 x 7,85 mm). The experimental set-up has been described elsewhere (3). A schematic diagram o f the test equipment appears in Fig. 3.15.1.

Figure 3.15.1: Diagram of the test equipment (3) 407

Both cylinder and test sample were 100CR 6 steel w ith 62—63HRC hardness. The contact surface o f the test fla t specimens were polished to 0.1 jum grit be­ fore tested, while the cylindrical contact surface was grinded as received. Both, cylinders and plane chips, were carefully cleaned in pure acetone. The tests were performed at a constant load of 500 N, oscillation amplitude 1000 mm, temperature range 7 0 - 1 10°C, frequency 50 Hz and time 60 minutes. All of them were controlled piezoelectrically while the friction coefficients were monitored continuously. The friction and wear behaviour o f oils A, B w ith d iffe ­ rent formulations were evaluated. Some inspection properties are given in Table 3.15.1. Table 3.15.1: Properties o f the oils A and B

Properties Viscosity Grade

Method

A

B

-

SAE 10W30

SAE 10W30

Kinematic Viscosity 40°C (cSt) 100°C (cSt)

ASTM D—445

66.21 10.17

86.68 10.39

Sulfated ash (% p)

ASTM D—874

1.02

0.82

0.057 0.131 0.121 0.135 0.463

0.188 0.086 0.097 0.450

Element Content (% p) Mg Ca P Zn S

-

Previously, a repeatability study o f ten run test were performed, and ± 4 % experimental error o f friction coefficients was calculated from standard devia­ tion o f the mean at 95 % confidence level. During the present investigation, all friction coefficient and wear measurements were made in triplicate. The recorded diagrams of friction coefficient-time were studied. The mean value of the steady state friction coefficient was calculated and the "running-in" phase and transitory fluctuations o f this paper were observed. 408

In order to estimate the wear performance, an approximate assessment o f the wear scar was determined by a photographic method. The worn surface morphology was examined by Scanning Electron Microscopy (SEM) (ISI-SS40) and Digital Interferential Optical Profiler. The result was compared w ith the microstructure o f the worn valve lifters from a taxi cab fleet test where oil A and B were used. The chemical composition of the surface layers along the w idth o f the wear scar centre was determined by Energy-Dispersive-Xray Analysis (EDAX—9100) and by Auger Electron Spectroscopy (AES). The AES analysis were performed in the Leybold Heraeus surfaces analyses system at INTEVEP (Energy analyser 11) at 5 x 10 ~ 8 mbar. The electron gun operated at 3KeV. Several areas were selected for depth pro­ file analysis and a Argon ion gun was used at 3KeV, a current o f 10 mA and 10 ~ 6 mbar. The Auger spectra were obtained by digital differentiation o f the intensity spectra. The data were collected at an energy pass o f 200 eV w ith a step energy o f 1eV. Fig. 3.15.10 shows a typical Auger spectra for specimens subjected to a SRV wear test. A semiquantitative approach based on elemental sensitivity factors was employed (4). The atomic concentration Cx may be given by:

Cx

!x/Sx = -------2 Ij/Sj i

where l x is the Auger electron peak-to-peak height fo r a specific Auger transi­ tion, and Sx is the relative elemental sensitivity factor. Additionally, qualitative corrosion tests were performed by immersion of the chip samples in oils A and B, heated at 150°C during six hours. Surface corro­ sion damage was observed by SEM in order to compare it w ith scar morphology.

3 .1 5 .3

R esu lts and D iscussion

3.15.3.1

Friction and Wear Behaviour

In order to study friction and wear, the experiments were carried out in a range o f temperatureso70—110°C fo r oils A and B. It was observed that at temperatures below 70 C both oils presented a similar friction behaviour, while above 100 C the friction coefficient showed a quite different tendency. In oil A it increased while in B it decreased. 409

Fig. 3.15.2 shows the friction coefficient vs. temperature diagram fo r the A and B oils. The friction coefficient o f A is mostly constant into the test temperature range (7 0 -1 10°C). The observed variations fall in the error range. The oil B showed a more evident increment up to 100°C w ith a decreasing tendency at 110°C. o •o a c o *■ 0 ul 110 o

ft iso n

140 -

13S ■

130-

70

SO

SO

100

110

T

Figure 3.15.2: Friction coefficient variation vs. temp., oil A and B

Different patterns o f the friction-tim e trace were recorded during test. Fig. 3.15.3a and 3.15.3b show quasiconstant and slow variation pattern respectively. The friction behaviour is related w ith continuous fluid film lubrication condi­ tions. The Fig. 3.15.3c presents high and dense peaks at the initial stage related by R. Schumacher w ith the "running-in" phase (3). Less frequent transitory peaks appear also during the steady state (Fig. 3.15.3d). As A. Jahanmir states, under unidirectional sliding conditions, this type o f friction coefficient variation corresponds to the metal-metal contact wear induced by the transient fluid film rupture and restoration (5). Further morphological studies on worn scars sam­ ples w ith similar behaviour seems to confirm this assumption, as well as in the case o f the reciprocating sliding. 410

(* C

(c)

Cd 1

Figure 3.15.3: Friction coefficient vs. time a) A-oil, 100°C; b) B-oil, 100°C c) A-oil, 70°C; d) A-oil, 90°C

411

Finally, the friction coefficient increases to values higher than those o f the "running-in" and transitory peaks, and then remains constant. This stage corres­ ponds to the complete rupture o f the flu id film and is associated w ith a high vibration level which stops the test device. The variation o f the wear scar area vs. temperature fo r A and B oils appears in the Fig. 3.15.4. Up to 90°C B oil induces a slightly inferior wear o f the metal sample while, at higher temperature, the A oil shows better behaviour. No parallelism is observed between the friction coefficient and wear (Fig. 3.15.5), as it has been reported by R. Schumacher in similar tests (3). However, in the present case, higher deviation between steady state friction coefficient vs. time and wear-time trace was observed at temperature where transient rupture and restoration o f the fluid film , as well as severe metal-metal wear occurred (oil A80°C and 90°Cand B-90°C).

10 / < 1) oil

c

Figure 4.2.4:

lyuml

Cloaronc*

c (pm)

Variation o f oil side leakage Qg and circumferential flow rate Q w ith radial clearance c

Figures 4.2.1 and 4.2.2 have shown that the lubricant oil is slightly affected by use through its recommended running life and w ithin the range of operating temperature. Figure 4.2.1 gives the values o f the load capacity as a direct func­ tion o f the radial clearance. As general recommendation (2), the oil film th ic k ­ ness should not go below 0.0025 mm or beyond 0.0042 mm fo r main bearings and 0.002 mm to 0.004 mm fo r big end bearings. Flence, for the present engine bearings computations, the range of radial clearances is taken practically to be 0.025 to 0.070 mm and it is further recommended that the clearance should not exceed 0.100 mm even after engine bearings' wear fo r safe running w ithout the probability of oil film failure. Add to this that the choice o f the values of the clearances is based on the concept o f maximum load carrying capacity and minimum power loss w ith minimum side leakage assuming a steady state hydrodynamic solution (4, 12). However, in actual bearings subjected to dy­ namic loadings, the effect o f squeeze action on bearings' performance is ex­ pected to be predominant (13). In this context strict limitations should be put on bearings' wear as excessive increase in radial clearance, as graphs ind i­ cate, would deteriorate the hydrodynamic performance; this is evident by the drop in load capacity under full power or idling speeds using either new or used oils.

451

-3

Clearance

Figure 4.2.5:

c

(jjm)

Variation o f coefficient o f frictio n w ith radial clearance for different eccentricity ratios e

Due to the change in oil viscosity w ith temperatures during engine running, Figure 4.2.2 shows that, even fo r the data o f multigrade oils, the load capacity may vary markedly. Lubricants, due to polymeric additives, are expected to behave non-newtonian as pseudoplastic fluids (n = 1) when new. However, by continuous use the flow behaviour index n may vary. As there is little inform ation and experimental data on the actual behaviour o f lubricants, it has been herein decided to p lot comparative data to show the effect o f flow behaviour index variation on the load capacity values. Figure 4.2.3 gives the possible effects o f mode o f fluid flo w on the load capacity. It is clear that, although the use o f polymeric addi­ tives enhances the viscosity variation w ith temperatures, the use o f non-new­ tonian fluids w ith n < 1 influences the bearing capacity by reducing it. As there is no experimental evidence on the way the viscosity may vary w ith frequent use, depending on type o f additives, base o il, condition o f applica­ tion and possible contaminants, the graphs in Figure 4.2.3 show that dilatent fluids may be more superior than pseudoplastic ones (12). Figures 4.2.4 and 4.2.5 reveal that the radial clearance between bearing sur­ faces has a direct impact on oil flow rate, side leakage and frictional resistance. The increase in radial clearance due to possible engine bearings' wear would require higher rates o f oil delivered to bearings to ensure sufficient oil film form ation w itho ut starvation and to take account o f the side leakage. The coefficient o f friction displays an increasing trend w ith the increase in radial 452

clearance. This situation affects the bearing performance by increasing the power losses which render higher temperature rise w ith a consequential vari­ ation in oil behaviour.

4.2.5

Conclusion

It can be concluded that restrict limitations on oils and hence on engine com­ ponents wear rate should be put forward to assure efficient and longer engine life. The proper assignment o f lubricant properties and flow behaviour (whether newtonian or non-newtonian) and its corresponding working life would not only safeguard the engine aginst excessive wear but would also guarantee high performance w ith minimal power losses. The interaction between lubricant properties and engine wear can be summed up as follows: excessive engine wear due to improper oil properties or prolonged use o f oils would lead to greater bearings' clearances, which in turn lead to reduced load capacity, higher frictional losses and greater oil flow rates.

4.2.6

References

Part II (1) (2) (3)

Braithwaite, E.R.: Lubrication and Lubricants, Amsterdam. Elsevier Pub., 1967. Schilling, A.: Automobile Engine Lubrication. G.B.. Scientific Pub. (GB) Ltd., 1972. Pinkus. O.; Sternlicht, B.: Theory of Hydrodynamic Lubrication, New York, McGrawHill. 1961. (4) Cameron, A.: The Principles o f Lubrication, London, Longmanns Green Ltd., 1966. (5) Mokhtar, M.O.A.; Howarth, R.B.; Davies, P.B.: Wear Characteristics of Plain Hydro­ dynamic Bearings During Repeated Starting and Stopping. ASLE Trans., 20, 1977, 1 9 1 -1 9 4 . (6) Lubricating Oil and Additives-Lubrizon Tech Presentation, Report C-7528, The Lubrizon Corp., April 1983. (7) Dowson. D.; Higgenson, G.R.: Elastohydrodynamic Lubrication, Oxford, Pergamon, 1966. (8) Cheng, H.S.; Sternlich, S.: A Numerical Solution for the Pressure, Temperature and Film Thickness Between Two Infinitely Long Lubricated Rolling and Sliding Cylinders under Heavy Loads, Trans. ASME, Journal of Basic Engineering, 87, 1965, 6 9 5 -7 0 7 . (9) Mokhtar, M .O.A. et.al.: Investigation into the Lubricating Engine Oils' Mechanical and Chemical Properties — I. Experimental Findings, a paper to be presented in the 7th Inter. Colloquium Tribology on Automotive Lubrication, Tech. Akademie Esslingen, January 16-18, 1990, Esslingen (FRG ). (101 Tanner, R .I.: Study of Anti-isothermal Short Journal Bearing with Non-Newtonian Lubricants, Trans ASMEJ. Applied Mechanics, 32, 1965, 7 8 1 -7 8 7 .

453

(11)

(12)

(13)

454

Dien, I.K.; Elrod. H.: A Generalized Steady State Reynolds Equation for NonNewtonian Fluids — With Application to Journal Bearings, Trans. ASME, Journal of Lubrication Tech., 105, 1983, 3 8 5 -3 9 0 . Abdel-Latif, L.A.; Safar, Z.S.; Mokhtar, M.O.A.: Behaviour of Non-Newtonian Lubricants in Rough Bearings Applications, Proc. 14th Leeds/Lyon Symposium on Tribology, INSA, Sept. 8 -1 1 ,1 9 8 7 , Lyon - France. Shawki, G.S.A.; Mokhtar, M.O.A.: Computer Aided Study of Journal Bearing Per­ formance under Cyclic Loads, Part I: Theory, ASME paper no. 71-Vibr-86; Part II: Application. ASME paper no. 71-Vibr-87.

4.3

Development of Superior Engine Oils for Diesel Locomotives in India

J.R. Nanda, G.K. Sharma, R.B. Koganti and P.K. Mukhopadhyay, Indian Oil Corporation Ltd., Faridabad, India R.M. Sundaram, M inistry of Railways, Lucknow, India

Abstract Performance of 1C engines largely depends on their design, operation, main­ tenance and also on the quality o f fuels and lubricants. In this paper the de­ velopment of superior crankcase lubricants w ith a view to enhance the per­ formance o f rail road diesel engines operated by the Indian Railways has been presented. Starting from the '70s w ith LMOA Generation-11 performance level, oil quality has moved up to Generation-IV level oil and subsequently to high TBN Generation-IV oil. In the literature, there are indications o f superior per­ formance multigrade oils particularly w ith respect to fuel economy. Such benefits have also been reported for rail road diesel engines. A programme to draw specifications and develop multigrade lubricants was taken up jo in tly w ith the Indian Railways. Laboratory evaluation o f different V .l. improvers in combination w ith appropriate Dl package was carried out to develop formulations w ith desired and viscometric characteristics including shear stability, temporary viscosity loss (TVL) and high temperature high shear viscosity (HTHSV). Subsequently, candidate oils were evaluated for fuel eco­ nomy in Petter AV-1 followed by test bed evaluation on a stationary locomo­ tive engine w ith load box facility. Field trials are currently ‘under progress for establishing the fuel economy, engine durability, lube oil life and other performance criteria. Fuel economomy data fo r multigrade oils as observed in laboratory and stationary loco engines have been presented.

4.3.1

Introduction

Large scale dieselisation o f the Indian Railways commenced in the early sixties. A t present Indian Railways operate a fleet o f about 3000 diesel locomotives, the m ajority o f which (approx. 87 %) are o f ALCO design. With the advancing technological development in the country, the communication and transport system has also to move at a faster pace. Growth o f tra ffic has been increasing over the years and Indian Railways has to keep pace w ith this. Locomotive engines w ith higher loadings developing higher bmeps impose high mechanical and thermal stress on various engine components including the lubricant which therefore has to withstand severe operating requirements viz: (a) higher temperatures, (b) higher unit loading, (c) corrosive acids and in­ creased level of insolubles on account of higher rate of fuel burning. This has 455

necessitated upgradation o f oil quality over the years like elsewhere in the w orld. Indian Railways which consume about 1.3 m illion tons o f diesel per annum and about 30,000 kl o f crankcase oil have been taking adequate meas­ ures to conserve petroleum products as the expenditure on fuel and lubricants forms a major part o f their working/operating expenses. The objectives of conserving petroleum products are being tackled from all possible directions and some o f the projects which Indian Railways are persuing are as follows ( 1 ). — Optimising Engine design to improve combustion and thermal efficiency including adoption o f well matched piston top profile and ring configu­ ration, better engine-turbo match. — Locomotive design incorporating aerodynamic profile to reduce drag — Track modernization — Driving/operating techniques using microprocessor controls — Fuel and lubricant quality upgradations In this paper, it is intended to cover the efforts undertaken jo in tly by Indian Railways and Indian Oil Corporation to upgrade the lubricant quality over the years from Generation-11 level to Generation-1 V plus High TBN level and to move towards a fuel efficient multigrade 20 W - 40 lubricant.

4.3.2

Lubricant Performance Levels

Major steps in railroad improvements have been categorised by Locomotive Maintenance Officers Association, USA (LMOA) in fo ur groupings called "Generations". Table 4.3.1 gives this classification system. Indian Railways, according to their fleet requirements have been conventional­ ly using two types of lubricants - one for GM-EMD Locos and another for ALCO locos. GM locos require zinc-free oils due to use o f silver bearings in the gudgeon pin area, whereas for ALCO locomotives this restriction on addi­ tive chemistry does not exist. ALCO locomotives have tw o popular models denoted as WDM2 and YDM4, which employ 16 cylinder 251B diesel engine and 6 cylinder 251D diesel engine respectively. The engine characteristics for these tw o models are given in Table 4.3.2.

456

A (7 TBN)

B (7 TBN)

C-1 (10 TBN)

C-2 (10 TBN)

D (13 TBN)

Generation II

Generation II

Generation III

Generation III

Generation IV

Higher alkalinity and dispersancy.

Much higher alkalinity w ith improved dispersancy and detergency.

Improved alkalinity of Generation III and im ­ proved insoluble control of Generation II. Added protection under adverse operating con­ dition.

Improved detergency fo r upper ring belt control deposits

Extended ring sticking pro­ tection in 4 cycle engines.

Higher alkalinity included w ith high detergency package.

Dispersancy first added.

Extended oil filte r life.

Improved base reserved to Group B fo r 2 cylce engines.

Formulation Characteristics

Service Requirements

Pre— 1964 Locomotive Maintenance Officer's Association, U.S.A.

Group (TBN levels by D-2896)

LM DA* Designation

Generation I: * LMDA:

Railroad oil classification

Table 4.3.1:

1976

1975

1968

1968

1964

Introduction Year

Table 4.3.2:

Details o f popular types o f ALCO engines in Indian Railways

Performance Characteristics

WDM2 (16-251B)

VDM4 (6-251D)

Cycle

4-Stroke

4-Stroke

Aspiration

Turbo-super charged w ith charge aircooling

Turbo-super charged w ith charge aircooling

Bore, mm.

228

228

Stroke, mm.

267

267

Compression Ratio

12.5 : 1

12.5 : 1

Horse power (gross) BHP

2600

1350

Power per cylinder BHP

162.5

225

Speed: Full load, rpm. Idle (normal), rpm.

1000 400

1100 400

Piston speed, m/s

8.89

9.78

BMEP, kg/cm2

13.57

17.02

Fuel consumption at full Horse Power, litre/m in.

8.2

4.5

Following is the chronological order of different types of lubricants used in the past by Indian Railways. Prior to 1964, Indian Railways were importing proprietary brands o f lubri­ cating oils as recommended by ALCO/GM. Under the Marketing cum D istri­ butorship Agreement o f Indian Oil w ith Mobil, Indian Railways switched over to the use of Delvac S-140 and Delvac-1140. A fter the expiry o f this agree­ ment in mid 1974, Indian Oil R & D Centre developed Servi RR 402 which was accepted by Indian Railways fo r use in 16-2518 and 6-251D diesel engines after extensive field evaluation extending over a period o f one year in 24 locos in 4 loco sheds. GM-EMD locos in Indian Railways were all these years using Esso's Diol RD-78 which was blended using special Naphtenic MVI base stock (imported). Servo RR 402 was considered to be an interim substitute and the need was felt to have a further superior oil to improve oil life especially of 251D diesel engines. To reduce the wear rate o f engine components on account 458

of high sulphur operation, a high TBN oil to combat the deleterious effects was considered to be the best solution to bring down the maintenance cost. Apart from this advantages in other areas, namely increased filte r life, long oil life, reduced carbonization on power assembly, etc. could also be derived w ith the use o f high TBN oil. Table 4.3.3:

Physico-chemical characteristics of railroad oils Servo RR 4 02 ,40 5 and 407 (Typical Data)

Properties

Servo RR402

Servo RR405

Servo RR407

LMOA Generation

Gen. 11

Gen. Ill

Gen. IV

K. Viscosity, cSt at 40° C at 100° C

168.0 15.90

Viscosity Index Pour Point, °C Flash point, r o c °c TBN(D-2896) mg KOH/g

97 -

15 260

165.6 15.80

171.0 15.90

97

96 -

15 260

-

15 260

8.69

10.91

13.34

Sulphated Ash, % w t

1.10

1.25

1.55

Phosphorus, % w t

0.075

-

-

Zinc, % w t

0.078

-

-

Calcium, % wt

0.28

0.34

0.45

Nitrogen, % w t

0.028

0.060

0.075

Formulation: Base o il, % w t Additive dosage, % vol. Total:

94.05

90.50

86.50

5.95

9.50

13.50

100.00

100.00

100.00

As a result o f jo in t endeavours, tw o products viz. Servo RR 405 and Servo RR 407 were developed by Indian Oil R & D. These products were developed using indigenous paraffinic base stock and zinc free modern railroad additive systems (imported) and could be categorised as Generation-Ill and Generation459

IV levels. The oils were approved by GM-EMD fo r field trials after successful evaluation in their inhouse tests and also met the specification/requirements stipulated by ALCO. Based on GM-EMD's approval and other technical back up, Indian Railways accepted Servo RR 405 and 407 fo r fu ll scale field trials w ith a view to have common form ulation fo r both ALCO and GM-EMD locos. Trials were undertaken on 56 locos fitte d w ith GM-EMD 16-567D3 diesel engines, ALC016-251B and ALCO 6-251D diesel engines fo r a period o f one year at 7 locosheds spread over different zones of the country. Superior per­ formance of these grades fo r various parameters could be clearly established over Servo RR 402 in this trials. Table 4.3.3 gives the typical physico-che­ mical characteristics of these oils — RR 402 , 405 and 407 and Table 4.3.4 lists the percentage of improvements which could be established during the course o f trials w ith the use o f Generation-IV lubricant over Generation-ll lubricant. The benefits include longer oil drain life, filte r life, reduced wear, reduced oil/fuel ratio, improved piston deposit control, better alkalinity re­ tention and reduced level of insolubles. The benefits observed by Indian Rail­ ways w ith the use o f Generation-IV level oil were directionally similar to those reported elsewhere in the world w ith the use of superior q uality lubricants. Table 4.3.4:

Benefits w ith the use o f Servo RR 407 (Gen. IV oil) over Servo RR 402 (Gen. II oil) Field Data

Performance Characteristics

% Improvement 16-251B 6-251D

Liner wear per 100,000 km

21.9

Top ring wear per 100,000 km

61.5

% Lube/Fuel ratio

19.2

Average merit rating Filter life Oil life

-

7.5* 16.0

-

12.9*

4.2

4.9

27.0

12.8 more than double

* Some locomotives have used different combinations o f liners and also from different sources and this has affected the ultim ate wear data. Increased liner wear also seems to be the probable cause o f high oil consumption.

4.3.3

Development of an Indigenous Formulation

On the successful completion o f these trials, Indian Railways started using Servo RR 405 and Servo RR 407 in various regions defined on the basis of sulphur levels in fuel and finally adopted Servo RR 407 as a common oil fo r the integrated operation o f diesel locomotives. Although Indian Railways were 460

fu lly satisfied w ith the performance of these oils, in an e ffo rt to indigenise additive system, hitherto imported, in the years 1981-82 Indian Oil Company started working on a 'component based form ulation' namely Servo RR 409. The following two factors were recognised jo in tly by Indian Oil and Indian Rail­ ways before taking up the development o f Servo RR 409. a) For the integrated operation o f railways in various zones w ith different sulphur level in fuel, higher TBN form ulation to achieve high TBN stabili­ zation would be developed. It was well recognised that TBN provides addi­ tional protection against corrosive wear. 16 TBN form ulation was thus aimed at. b) The m ajority o f locomotives were of ALCO design, hence a zinc based form u­ lation fo r which additive components are locally available w ill be worked out. A zinc based form ulation Servo RR 409 was thus developed and then tried out in 20 locos at 3 locosheds. Typical test data o f Servo RR 409 are given in Table 4.3.5. Percentage improvement as obtained in field trials w ith the use o f Servo RR 409 over Servo RR 407 is listed in Table 4.3.6. Table 4.3.5:

Data on monograde rail road oil Servo RR 409 based on indigen­ ous component-approach developed by Indial Oil fo r railways

Characteristics

Typical Data

K. Viscosity, cSt @ 40° C • @ 100°C

171.13 15.87

Viscosity Index

95

TBN mg KOH/g (D-2896)

16.0

Pour Point, °C

- 18

Colour, ASTM

6.5

Flash Point, COC, °C

254

Sulphated Ash, % w t

2.05

Foam Test (Tendency/Stability) Sequence I Sequence II Sequence 111

20/nil nil/n il 20/nil

Panel Coker Test (300° C) Rating Weight gain, mg.

2 -0 1.04 461

Table 4.3.5: continued Characteristics

Typical Data

CLR L-38 Bearing Weight Loss, mg.

23.9

Petter AV-B test overall Merit Rating

60.4

CAT 1G2 Test % TGF WTD

28 232.3

Oxidation Test (Modified IP-280), (150° C for 150 hours, A ir flow rate 0.5 l/m in.) + 28.71 - 0.60 + 1.26

% Change in K. Viscosity @40° C Weight change in copper fo il, mg. Change in TAN value Dispersancy Test (in-house) 40° C viscosity increase, cSt. w ith 1 % carbon black w ith 2 % carbon black w ith 3 % carbon black Table 4.3.6:

1.0 1.1 0.5

Benefits w ith the use o f Servo RR 409 (Generation IV plus oil) over Servo RR 407 (Generation IV oil) Field Trial Data

Performance Characteristics

% Improvement 16-251B 6-251D

Liner wear per 100,00 km

61.2*

16.75

Top ring wear per 100,000 km

- 2 .7

29.9

% Lube/Fuel ratio

52.7*

-2 4 .3

Average Merit Rating

comparable

Filter life

comparable

Oil life

Comparable

Needs further monitoring.

* Control locomotives have shown abnormal liner wear and hence cannot be taken as representative for comparison. Probably this factor has influenced lube consumption also. 462

EMD8-645E3 EMD 16-645 E3 EMD2-567C

10

11

12

3

3

6

Exxon

General Motors

G ulf Canada Ltd.

Amoco

Amoco

British Rail

1

CRSD 157

9

Chevron

Indian Railways

GE 12-7FDL

9

Chevron

Locomotive on Load Box

40

MRDC — Medium Road Duty Cycle (GM-EMD's)

ALCO 2 51B

Operating Loco­ motive Fleet

DMU's and Class 56

20W-40

15-W-40

20W-40

40

Engine Test Stand

EMD 12-645 E3B 30

20W-40

40

20W-40

20W-40

20W-40

Engine Test Stand

40

40

40

Test Stand

Generator Stand

5.9 3.9

0 -5

Mainline Switcher

Normal Service

6 months

MRDC

MRDC

0.8 0.7—0.9

MRDC 1.3

Idle

Idle

4 -9

Low idle

2 -7

20W-40

40

Test Stand

Low idle

2 -1 3

20W-40

40

Test Stand

MRDC

1.1

40

Locomotive on Load Box

20W-40

Lubricant Viscosity Grade ISAE) Fuel Conditions Test savings Reference %

Locomotive on Load Box

EM D-12-645 E3

EMD 16-645 E3B

Engine

4

Reference

Test Apparatus

Published fuel economy benefits of multigrade engine lubricants in medium speed locomotive engines

Chevron

Company

Tabler4.3.7:

CM 1 O

463

Table 4.3.8:

Requirements of a fuel efficient multigrade railroad oil for Indian Railways

Characteristics

Targets

SAE Grade

20W-40

Appearance

Clear

Colour ASTM

8 max.

K. Viscosity, cSt at 100° C at 40° C

15.5-16.3 Report

Viscosity Index

Report

Apparent viscosity, cP, max. at 10° C by CCS

4500

Apparent viscosity cP (Borderline pumping) at — 15° C by MRV, max.

30,000

TBN (D-2896), mg KOH/g, min.

13

Flash point, °C, COC, min.

225

Pour Point, °C, max.

-2 1

Foaming Tendency/Stability Sequence I Sequence II Sequence III

25/nil 150/nil 25/nil

Diesel Performance, min.

API'CD' level

Shear Stability (Bosch rig)

Stay- in SAE 40 grade

100° C viscosity loss after 30 passes, cSt, min.

i.e. 12.5

High Temperature High Shear Viscosity, cP at 150° C, 10* sec’1, min.

3.5

% Temporary viscosity loss at 150° C, 106 sec'1

Report

Noack test, % Evaporation loss after 1 hour at 250° C, max.

15

464

Table 4.3.8: continued Characteristics

Targets

Oxidation stability, 150 hours at 150° C, 0.5 It air/min. a) % viscosity increase at 40° C. max. b) weight change o f copper fo il, mg max. c) increase in TAN, mg KOH/g, max.

10 10 2.5

Filter plugging test (in-house) time to filte r oil at 17—23°C at 0—2°C

Fuel economy test a) % basic reduction in Petter AV-1 test over RR 409, min. b) Demonstration o f fuel efficiency in stationary loco engine ALCO 251 B fitte d w ith load box, min.

4.3.4

10 % increase max, over standard oil RR 409

2.5

1%

Development of Multigrade Fuel Efficient Railroad Oil

Following the successful development of w holly indigenous Servo RR 409, multigrading of this form ulation was undertaken. Multigrade oils have been found to give significant fuel economy benefits in medium speed railroad en­ gines all over the world. Although friction m odifier (FM) additives have shown promising results on medium speed railroad engines w ith oils containing FM did not, however, show any benefits (3, 4). Some of the published data on fuel economy benefits w ith the use of multigrade engine lubricants in medium speed locomotive engines are listed in Table 4.3.7. Keeping in view the large fuel consumption in the diesel locomotive o f the Indian Railways costing about 8 3.5 billion per annum, development of m u lti­ grade fuel efficient railroad oil was undertaken. In jo in t consultation between Indian Oil Corporation and Indian Railways, the targets o f proposed m ulti­ grade oil were evolved. Table 4.3.8 summarises these requirements. British Rail had pioneered the work on development o f multigrade rail road oils (6,7) and it was agreed to follow a similar approach. It was therefore decided to keep the viscosity at high operating temperature of sump at the same level as that o f the monograde oil. Although lowering o f viscosity is expected to give better fuel economy, yet it was feared at the outset that it may result in in­ creased wear. British Rail had also adopted the same viscosity for multigrade as that of monograde oil at the operating temperature. Since in Indian Rail­ ways sump operating temperatures are about 90 — 95° C, a 20W-40 grade was 465

considered to be appropriate w ith 100° C kinematic viscosity being similar to monograde, i.e. 15.5 to 16.3 cSt. The same D .l. package as in Servo RR 409 was used and a number of V .l. improvers were screened. Table 4.3.9 presents the viscometric data o f a number of formulations w ith different V .l. impro­ vers. The shear stability data on various formulations and the fuel efficiency data in comparison w ith monograde oil determined in Petter AV-1 engines are covered in Table 4.3.10. In our studies all V .l. improvers gave T V L in the range of 10.0 — 13.5. PVL variations are somewhat wider (9.0 — 19.0). The data do not indicate any general correlation between fuel economy and T V L or PVL as claimed by some researchers (2), nevertheless, candidate oil AO-26 gave a fuel efficiency of 4.5 % while satisfying all other requirements. Subse­ quently, test bed trials to determine the fuel economy were undertaken by the Indian Railways in a stationary engine (ALCO 16-251B engine) in Golden Rock Workshop of Southern Railways. The observed fuel economy w ith the use of A0-26 was 5.9 % and 3.9 % for the main line and switcher cycle respectively over the monograde (1). In a subsequent test at the R & D Centre o f Indian Rail­ ways (13), fuel economy o f around 1 % was seen w ith some o f the multigrades. Field trials are currently under progress w ith three multigrade oils in 29 loco­ motives fitted w ith 16-251B and 6-251D diesel engines in 2 locosheds. Except fo r one form ulation which has shown increased viscosity, the other tw o are behaving satisfactorily. Detailed assessment of performance for different para­ meters including fuel savings and lube consumption shall be made on comple­ tion o f trial. Regular adoption o f multigrade railroad oil in Indian Railways is shortly expected once the logistics are worked out including techno-eco­ nomical viabilities.

4.3.5

Future Activities

In future, the follow ing w ill be investigated: (i)

To evaluate and adopt indigenous V .l. improvers.

(ii)

To study the extent o f improvement o f fuel economy w ith the use of FM oils in Indian locomotives.

4.3.6

Acknowledgement

The authors wish to thank the management o f Indian Oil Corporation Limited and Research, Design & Standards Organization (RDSO) o f Indian Railways for publishing this paper.

466

Table 4.3.9:

Formulations

Viscometrics data on candidate multigrade oils using various V .l. improvers Apparent Viscosity cP (CCS) (MRV) @ -1 0 ° C @ -15°C

Kinematic Viscosity cSt @ 40° C

@ 100°C

AO-17

3100

14,905

128.91

15.85

AO-18

3400

17,892

136.51

15.80

AO-19

3600

19.272

137.78

15.81

AO-20

3200

13,769

137.40

15.80

AO-25

4200

18,084

138.56

15.85

AO-26

3400

15,455

131.87

15.80

AO-27*

4200

1,61,112

139.04

15.85

AO-28

3900

17,422

137.66

15.85

Limits for SAE 20W-40 Railroad Oil

4500 max.

30,000 max.



15.5­ 16.3

AO-17, 19, 2 0 ,2 6

Styrene Isoprene Copolymer

AO-19, 2 7,2 8

Olefin Copolymer

AO-25

Styrene Isoprene Copolymer + Styrene ester Copolymer

* does not meet MRV test requirement.

467

Table 4.3.10: Shear stability and fuel economy data on candidate multigrade oils Formulations

% Permanent VISCOSITY LOSS (Boschinjector rig 30 cycle test)

% Temporary VISCOSITY LOSS (Tapered bearing simulator 150° C, 106 Sec'1 Test

% Fuel Economy over RR 409 BASE LINE DATA (Petter AV-1 fuel economy test!

AO-17

9.72

11.69

2.09

AO-18

10.63

9.96

2.29

AO-19

11.32

10.80

3.75

AO-20

9.0

12.96

3.76

AO-25

13.0

12.42

2.13

AO-26

19.0

11.74

4.51

AO-28

11.6

13.50

2.86

4.3.7 TBN CCS MRV cP cSt V .l V .l.I F.M HTHSV PVL TVL MRDC

468

Abbreviations = = = = = = = = = = = =

Total Base Number Cold Cranking Simulator Mini Rotary Viscometer Centipoise Centistokes Viscosity Index Viscosity Index Improver Friction Modifiers High Temperature High Shear Viscosity Permanent Viscosity Loss Temporary Viscosity Loss Medium Road Duty Cycle

4.3.8 (1)

(2)

(3) (4)

(5) 16) (7) (8) (9) (10) (11) (12) (13)

References

Research Designs and Standards Organisation: Development of multigrade lubri­ cant oil for diesel locomotive — Results of satisfactory engine tests conducted at Golden Rock Workshop of Southern Railways. RDSO investigation Report No. M P-295/86, December 1986. Baltersley, J.; Hillier, J.E.: The prediction of lubricant related fuel economy charac­ teristic of gasoline engines by laboratory bench test. Proc. Fuel efficient engine oil for improving the economy of vehicles symposium, Ed. W.J. Bartz, June 1984. Stauffer. R.D.; Zahalka, T.L.: Fuel savings with multigrade engine oils in medium speed diesel engines. Lub. Engg. 40 (1984), 12, 7 44—751. Logan, M.R.; Parker. C.K.; Pallesen, L.C.: Improved fuel economy through lubri­ cant technology in medium speed rail road diesel engines. Lub. Engg. 37th Annual meeting. May 10-13, 1982, Cincinnati, Ohio. Sharma, G.K.; Mukhopadhyay, P.K.: Development of fuel efficient engine oils. Proc. Indo-OAPEC Seminar on Hydrocarbon industry. Feb. 1987, New Delhi. Morley, G.R.; Eland, J.E.; Dunn, British Rail switch of multigrade. Ind. Lubri­ cation and Tribology, July/August 1984, 124—130. Morley, G.R.; Eland, J.E.: Development of fuel efficient multigrade oils for B R traction uses. Report Ref. TR Lub. 2, May 1983. Nanda, J.R.; Kashyap, A.K.: Railroad Diesel Engine Oils, 3rd LAWPSP Symposium, 1982, India. Thomas, F J.; Ahluwalia, J.S.; Shamah, E.: Medium speed diesel engine lubricants, their characgeristics and evaluation. ASME paper no. 84-DGP — 1 7, 1984. Younghouse, E.C.: Lubricants with improved frictional properties for medium speed diesel engine applications. ASME paper No. 82-DGEP-6. 1982. Pratt, T.N .: Discussion of Reference 10. Hamilton, G .D .: Reduced locomotive fuel consumption using a multigrade friction modified engine oil. Annual meeting of ASLE, 1984. Research Designs and Standards Organisation: Evaluation of Fuel economy with the use of multigrade lubricating oil. Engine Development Directorate, RDSO Re­ port No. T R /E D /8 8 /4 August ' 88.

469

4.4

Very High Shear Rate, High Temperature Viscosity Using the Automated Tapered Bearing Simulator-Viscometer

T.W. Selby, Savant Inc.. Midland, USA T.J. Tolton, Dow Corporation, Freeland, USA

A b stract While the automation of the Tapered Bearing Simulator Viscometer (TBS) has been dependent on several state-of-the-art developments, its ability to be used as an absolute viscometer w ith relatively high precision was a first requirement. In view of the ease of changing and measuring shear rates while in operation, the TBS was chosen to produce the data fo r engine bearing oil-film-thickness cor­ relation through use w ith the empirical Cross Equation. Very good correlation is reported in the literature and these results confirm to the use o f the TBS in both automated and non-automated modes. A new test method shows considerable reduction in analysis time and an equally marked improvement in precision. The paper presents the background o f the instrument, the steps o f its auto­ mation, and its application to trenchant problems and new opportunities in the area o f very high shear viscometry.

4.4.1

Introduction

The Tapered Bearing Simulator Viscometer (TBS), shown in Figure 4.4.1, has been used commercially since the early 1980s (Ref. 1, 2). During the inter­ vening years, several changes have been made reflecting developments in the art of temperature control, and its benefit in simplifying and automating the instrument. Much o f this work has been done by the close cooperation o f in­ vestigators in the Tannas Co. and in Savant, Inc. w ith whom both authors have been associated. This paper presents further information on the development o f automation fo r the TBS Viscometer as well as recent information on the original reason fo r its development — correlation between the TBS and the engine bearing. However, fo r full understanding, the paper first presents some o f the back­ ground factors leading to the development o f TBS automation.

470

Figure 4.4.1

4.4.1.1

Background

A number of technical papers have documented the development of the TBS Viscometer (Ref, 1 — 8). Essentially, the instrument was designed w ith a geo­ metry simulating that of the automotive journal bearing since this was one of the important potential applications for information from the instrument. The normally concentric cylinder arrangement fo r rotational viscometers was modified to have a slight taper along the lines o f the Kingsbury Tapered Plug Viscometer (Ref. 9) and particularly, the work of Pike, et. al. (Ref. 10). In the development of the TBS Viscometer, a number o f design requirements were set, the most important of which were to reduce extraneous friction to a minimum in order to increase the sensitivity o f the viscous torque signal. The instrument has always performed well as a true viscometer by showing very linear torque/shear-rate calibration curves and coincident intercepts w ith Newtonian reference oils, as shown in Figure 4.4.2.

471

Indicated Torque P1)

Figure 4.4.2:

4.4.1.2

Newtonian Fluid Performance

Importance of the Tapered Coaxial Configuration

The tapered design was prim arily chosen fo r the development o f the TBS Vis­ cometer to permit vertical displacement o f the rotor and stator and the ability to thereby vary rotor/stator clearances and, thus, shear rate. Adjustment of height was so easy because of the relatively light weight o f the platform hold­ ing the motor that it was quickly found possible to do this while the instru­ ment was running. (As far as is known, at least among commercial viscometers, the TBS is unique in this regard.) As a consequence, relatively early in the use of the instrument, independent studies by one o f the authors and an associate showed (Ref. 3) that the reci­ procal o f torque, 1/t, varied linearly w ith the rotor height, H, as shown in Figure 4.4.3, as Newtonian theory would require. (Much earlier, unknown to Selby and Piasechi (Ref. 3) at the time, Kingsbury (Ref. 9) had demonstrated the same relationship w ith his Tapered Plug Viscometer which provided confir­ mation of the authors work.) This linear relationship o f 1 /t vs. H was found to exist over a fairly broad range of rotor/stator displacement. Thus, this re­ lationship indicated that not only was the TBS Viscometer effectively an ab­ solute Viscometer (an instrument w ith which viscosities can be calculated from the rotor/stator dimensions and rotor speed) but also that temperature effects were demonstrably negligible over a rotor/stator gap ranging up to about 8 microns. From these findings, it was possible to determine the operating shear rate quickly and experimentally on an absolute basis. That is, the theoretical con­ tact height (TCH) o f the rotor and stator could be determined where 1/t became 472

zero. From 1) the TCH, 2) the actual position of the rotor in the stator, and 3) knowledge of the rotor taper, the operating shear rate could be calculated. The unique capacity o f the TBS to determine operating shear rates "o n the run" was an im portant factor in simplifying the calibration of the instrument and automating it, as w ill be shown. Indicated Rotor Depth, mm

Inverse Indieoted Torque ( 1 / T ')

Figure 4.4.3:

Application o f Absolute Method to Determine Rotor/Stator Gap Relationship

Table 4.4.1 (Shear Rate)

7 1 000 s_1 2 000 5 000 10 000 20 000 50 000

(Error)

i l l

23.9% 21.6 17.0 12.8 8.9 4.9

(Error)

(Shear Rate) •

2 — To

7 100 200 500 1 000 2 000

000 s'1 000 000 000 000

.

2.99 % 1.75 0.83 0.47 0.26

473

The presence of two flats on the rotor raised a question about the assumption of absolute viscometry from the mechanical data (Ref. 11). However, a theo­ retical analysis by DuParquet (Ref. 12) indicated that the flats would have negligible effect at shear rates above 500,000 sec"1 where the error would be less than the repeatability of the instrument (see Table 4.4.1). As previously noted, the linearity o f 1/t vs. H in Figure 4.4.3 extends at least to a gap of 8 microns w ith a Correlation Coefficient o f 0.9999+. In the TBS Viscometer, an operating gap of eight microns at 3600 rpm is equivalent to about 440,000 sec'1 which experimentally tends to confirm DuParquet's theoretical work. 4.4.1.3

Thermoregulator and Heater Development Effects

It is perhaps stating the obvious to note that a high level o f temperature control is a necessity for the practice o f viscometry, particularly in high shear visco­ metry. The higher the shear rate, the more care which must be taken by de­ sign o f the viscometer to control the effects o f heat generated by viscous fric ­ tion. In the case of the tapered geometry, higher shear rates are obtained by narrower gaps rather than by higher speeds. For example, the TBS Viscometer works at a gap o f only 3.5 microns to generate a shear rate o f 1,000,000 sec'1 at 3600 rpm. The thinness o f the sheared film thus offers little opportunity fo r heat retention by the fluid and distortion o f the reasonably linear shear gradient across the gap is avoided. (Similarly, heat transfer to the oil film from the stator heater is essentially immediate.) Much thought and e ffo rt has been expended to design the optimum thermo­ regulation for the TBS Viscometer. This e ffo rt has been encouraged by the rapid evolution o f thermoregulators from simple o n /o ff switches, to proportio­ nal bandwidths, to automatic reset, to derivative controls during the last few years and progress is continuing. This evolution has had a major impact on TBS development. Each new advance in thermoregulation has been incoroporated as available and it must be emphasized that the present level o f sim plifi­ cation and automation o f the TBS is significantly dependent on the afore­ mentioned advances in thermoregulator development, as w ill be evident. The heating source has similarly gone through three stages o f m odification as technology progressed. A t present, using modern high capacity heating mem­ branes, heat is applied to the stator rapidly and uniform ly. However, the thin membrane also permits excess heat to be quickly "dum ped" through the mem­ brane as well. 4.4.1.4

Continuous or Long-Duration Operation of the TBS

One o f the field observations made earlier in the development o f the TBS was that over a period o f days or weeks, the indicated contact height determined by the 1/t vs. H relationship increased slowly (the gap became smaller). While the slow change in indicated contact height did not affect the gathering o f data (since the TBS is calibrated daily), the effect was puzzling. 474

A t the outset, the effect was variously attributed to slow expansion o f the wire-wound, flexible shaft coupling the rotor to the m otor, deposits forming in the gap, changes in the housing holding the stator, or some combination. To eliminate the firstmentioned possibility and to decrease the rate o f heat transfer up the relatively thick, wire-wound, flexible shaft, a thin, single-wire, flexible shaft was developed, which, at times, seemed to correct some o f the phenomenon. However, it became obvious that there was a more important factor to be considered. Ultimately, it was found that deposits on the stator wall facing the rotor were the culprit. These deposits apparently formed slowly from decomposition of the base oil and/or additives at the high temperature of viscometric analysis. Certain strong solvents were found to be capable of removing the deposits, after which the TCH would drop back to original value. As a consequence o f this experience and in anticipation o f the long-duration operation o f the TBS Viscometer when automated, special fluids were chosen for reference oils and a so-called "id lin g flu id " was developed by the Mobil Oil Company for specific use in the TBS. This idling oil is recommended for use at any time when the instrument is waiting for further work. Tests have shown that the fluid w ill withstand weeks of exposure at 150° C and full rotor speed w ith insignificant wall effects or operating problems w ith the instrument when again used for viscosity determination. Most im portantly, the TCH re­ mained reasonably constant. Simultaneously w ith the development of the idling fluid, protective circuitry was developed for the TBS viscometer to shut down the unit in the case of overheating or power outages (the latter is important since the TBS Viscometer should not be started up w ith cold fluid in the gap set for operation at 1,000,000 sec'1 ).

4.4.2

Standardization of the TBS Viscometer

4.4.2.1

ASTM D 4863-87 — Relative Rotor Position Method

The initial laboratory utilization o f the TBS Viscometer led to the formation of a Rotational Viscometer Task Force under the leadership of Robert B. Rhodes (Ref. 8) w ithin the appropriate group in the ASTM, namely Committee D2, Subcommittee 7, Section B. Reports on the activities of the Section and the Task Force have been recently published (Ref. 2,8). Essentially, this first method (Ref. 6) employed a relative technique of comparing the viscosities of a Newtonian and a non-Newtonian fluid which at 1,000,000 sec'1 had iden­ tical viscosities. (However, the absolute technique possible w ith the TBS was used to establish the viscosity of the non-Newtonian oil at 10® sec'1.) The roundrobin study gave a repeatability of 3.1 % and a reproducibility of 3.9 % at the 95 % confidence level. The method, unfortunately, required plotting torque, t, versus rotor height, H, curves for the Newtonian and non-Newtonian fluids and interpreting their 475

point o f interception. Such interpretation could be d iffic u lt as shown in Figure 4.4.4. Coupled w ith the limitations of technology at the time (reflected by a manual-reset thermoregulator and a resistance-wired, silicon-rubber pad heater), the method was relatively slow and laborious. A fter the tim e required fo r cali­ bration, relatively few samples (8 to 12) could be run in a day since sampleto-sample turn-around was a minimum o f about 1/2 hour. Indicoted Rotor Depth, mm

Indicoted Torque (T i)

Figure 4.4.4:

Ri Determination

Even this minimum turn-around time was possible, in fact, because the TBS Viscometer was designed so that no sample cleanup is necessary. That is, each sample “ chases" the previous sample from the test cell while the rotor is spin­ ning which helps to speed return to analysis. (However, the "chase" procedure was prim arily chosen to avoid using solvents w ith their attendant problems of solvent contamination, odors, and the serious potential fo r either flash fires or toxic exposure conditions produced by some solvents at high temperatures.) Fifty-m l injections o f each fluid were standard but 30-ml, injected 10-ml at a time — w ith a few seconds pause between injections, was found sufficient to give complete interchange of oils in the shearing zone.

4.4.2.2

ASTM D4863-90 — Absolute Rotor Position Method

It was experimentally found that the reciprocal torque technique also pro­ duced an essentially straight line w ith the non-Newtonian calibration oil. The 476

significance of this finding was that the intercept of the Newtonian and nonNewtonian oil could be easily calculated as a unique point, rather than hand plotted and interpreted. This technical development, coupled w ith the pre­ viously discussed availability o f 1. Advanced thermoregulators which, w ith automatic reset, could handle widely different viscosities, 2. High capacity heaters which don 't block the heat flow from the stator, 3. Idling oil which could be left in the cell for weeks at a time w itho ut adverse effects, and 4. The a bility o f the TBS Viscometer to determine the TCH "o n the run", combined to make possible a faster, simpler method as well as to open the opportunity o f automating the instrument. The new version of the method requires bringing the instrument to operating temperature for about an hour to permit the thorough warming o f the equip­ ment. However, w ith the use o f idling fluid and the safeguards b uilt into the latest models o f the instrument fo r unattended idling and automatic operation, a preferred alternative is to leave the instrument on all the time at operating temperature and w ith the rotor spinning at the desired gap so that the instru­ ment is immediately ready fo r use at any time. Indicoted Rotor Depth, mm

Inverse Indicoted Torque ( t/T i)

Figure 4.4.5:

Reciprocal Torque Intercept Technique for Setting Gap

477

When the instrument is at temperature, the reciprocal torque vs. height .tech­ nique is used to determine both the TCH o f the Newtonian and non-Newtonian oils and their straight-line intercept as shown in Figure 4.4.5. The height o f the rotor is adjusted to this intercept value and the instrument calibrated w ith four Newtonian reference oils. The method requires a modern thermoregula­ tor. Using it, analysis time is now less than 10 minutes fo r sample turn-around. Significantly improved precision was shown when the ASTM round-robin conducted on the method in 1989 gave repeatability o f 0.96 % and a reproduci­ b ility o f 2.59 % at the 95 % confidence level. The method and pertinent in­ form ation on the round-robin is presented in ASTM Research Report D02-1253 (Ref. 13).

4.4.3

Automation of the TBS Viscometer

4.4.3.1

First Stage — Automatic Sampling

With studies showing success in 1. thermoregulation, 2. close heat control w ith o u t operator attendance, 3. simple determination o f the rotor position, 4. obtaining availability o f a stable idling fluid, and 5. the incorporation o f safe, continuous operation,

Figure 4.4.6 478

automation of the TBS Viscometer was now quite feasible. The first step was to set up a programmable sampler, as shown in Figure 4.4.6. This work has been covered in a past paper (Ref. 5). Essentially, the TBS Viscometer was calibrated as usual after which the sampler was activated to progressively ana­ lyse the unknown samples and reference fluids comprising the loaded sampler. In all, the sampler holds 70 tubes of oil. Use of a strip-chart recorder helped in the assimilation o f data.

4.4.3.2

Second Stage — Semi-Automatic Calibration

One of the more technically d iffic u lt parts o f the use o f any viscometer is calibration and, since the TBS Viscometer is usually calibrated (despite its absolute nature), the instrument is no different. While the new (absolute) technique considerably simplified the calibration, there was still a need for even simpler approaches. Fortunately, the microcomputer is just right for such applications and one o f the systems operating in Japan is pictured in Figure 4.4.7.

Figure 4.4.7

479

The second stage o f automating the TBS Viscometer was to semi-automate the calibration. Using the computer keyboard, the operator is asked to ans­ wer certain questions on the computer keyboard regarding sample ide ntifi­ cation and location of calibration fluids on the sampling rack. The computer program then directs the automatic sampler to pick up certain reference oils fo r intercept analysis. When this is accomplished, the program then directs the operator to set the rotor at certain positions to generate necessary data to calculate the intercept of the Newtonian and non-Newtonian reference oils which p lo t is shown on the cathode ray tube (CRT) as pictured in Figure 4.4.8. ■

-— —

I» u .

,r t

w n t w . c« W » < i

M ED IU M ; L = LOW

505

Table 4.5.2 A N A L Y T IC A L TEC H N IQ U E

No. of Refs

REFERENCES

R O U TIN E D R A IN AN A LYS IS Blotter spot Elemental analysis K inematic viscosity T A N & SAN Insolubles (various) Fuel/flash TBN Water/glycol

8 10 11 10 10 7 6 4

7 , 4 1 ,4 8 . 5 1 .5 5 , 5 8 , 60, 69 4, 7. 24, 41, 46, 49, 55, 57, 59, 67 7, 20-21, 24, 28, 53, 62-63, 65-66, 69 6 -7 .2 4 , 28, 30, 40, 59, 63, 65, 69 7 -8 ,2 1 ,2 4 , 59, 62, 65-67, 69 7, 28, 30. 42, 46, 52, 67 7, 28, 30. 36, 63, 69 7. 26, 28, 67

SEPA RATIO N TECHNIQ UES Dial./filter/centrifuge Solvent extraction GC GPC/HPLC

11 7 4 2

8 , 28-29, 32, 40, 42, 48, 51-52, 55, 58

SPECTROSCOPIC METHODS IR

26

2-4. 7, 14. 22, 24, 26. 30, 32-36. 39, 41, 49, 52. 55-56, 58-59, 61, 63, 66, 69 4 2 ,4 6 ,5 1

5 ,8 ,1 8 , 29. 33, 35, 37 45, 6 7 ,6 8 , 69 2 6 ,3 4

UV/vis spectroscopy TLC -IR 13-C NMR and 1-H NMR Mass spectrometry Chemiluminescence

3 2 4 2 1

T H E R M A L M ETHODS TG A volatility T G A -F ID & TGA-GLC TGA-MS/GCMS & TG A -IR R'bottom carbon residue

3 1 1 1

A N A L Y S IS O F INSOLUBLES Optical microscopy Particle size Gravimetric analysis Solubility tests Electrophoresis Electron microscopy

4 3 3 1 2 2

40, 42. 69 41 14, 53 14,51

O TH ER M ETHO DS Carbon-14 tracers Titration Vap. phase osmometry Density Peroxide number Iodine value (unsat'n)

2 4 3 1 1 1

10,31 4 1 ,5 0 , 5 5 .6 5 5 5 ,5 7 ,6 7 46 42 46

506

69 papers reviewed

3

34

5! 2 6 ,4 1 ,5 5 5, 26 45 4, 20, 66

8 8 59

1 4 ,4 8 ,5 1 ,6 6

8 , 20, 28

APPENDIX 3/1 BLOTTER SPOT TEST OBJECTIVE To evaluate the “ residual dispersive power" o f crankcase oil, after subjecting it to heating so that the insoluble products derived from combustion begin to flocculate. MATERIALS Test tubes: 10 x 75 mm — Pyrex Thermostatic bath capable o f holding test tubes and offering sufficient thermal inertia (i. e. a block heater) Thermometer Special paper (French: Durieux n° 122) (British: Whatman Chromo 1) Mount fo r special paper Syringe or disposable pipettes Drying closet or oven METHOD Preparation o f samples Place 2 to 3 cm3 of oil to be examined in a test tube. Heat for 5 min at 240° C in a thermostatic block heater. Allow to cool to room temperature (30 min) Production o f the spot: Place the special paper in its holder (make sure that it is flat) Approximately 20 microlitres (one drop) of the test oil is placed on the paper. It may be necessary to touch the paper lightly w ith the drop o f oil if it does not fail on its own accord.

507

Dry the spots fo r an hour at 80° C, being sure that the paper is flat. (The evo­ lution o f the oil spot stain is accelerated by passage through the drying closet.) The exterior diameter o f the spot should measure 32 to 35 mm. For permanent records, photograph w ithin one hour.

APPENDIX 3/2 E V A LU A TIO N POSSIBILITIES Valuable information can be obtained by comparing blotter spots on oil samples before and after heating at 240° C. Used oil is in good "dispersive'' condition if the distribution of the carbon­ aceous material is uniform before heat treatment. "Residual dispersive power" can be estimated by the oil's reluctance to coagu­ late after heat treatment.

508

4.6

Development and Application of an "On the Road" Test Method for the Evaluation of Black Sludge Performance in Gasoline Passenger Cars

P.G. Carress Adibis — BP Chemicals (Additives) Ltd., Redhill, Great Britain

4.6.1

Introduction

The increasing number o f incidence o f black sludge form ation in the field prompted the author's company to investigate the form ation o f a gasoline car test fleet to reproduce this problem. This paper describes the methods used and the results obtained.

4.6.2

Test Vehicles

Make: Model/Type: Fuel: Engine: Special Features:

4.6.3

Ford Escort 1.3 C.V.H. Gasoline Normally Aspirated Carburettered C.V.H. Transverse Engine — Front Wheel Drive — Overhead Camshaft Hydraulic Followers

Test Fuel

Density at 15°C RON MON Lead Content Existent GHM RVP E 70 E 100 E 180 FBP Benzene Toluene FI A Aromatics Olefins Saturates

mg/m3

g/i mg/100ml bar %V %V %V °C %V %V %V %V %V

795 100.7 88.8 0.15 1 0.68 25.5 39 91.5 221 5.5 7.1 56.5 15.0 28.5 509

%V %V %V

Methanol TBA MTBE

4.6.4

2.9 1.7 0.0

Manufacturers Oil and Service Recommendations

Engine O il:

10W-30 - 15W-30 dependent on temperature, or meeting Ford Specification SSM-2C 9001-A-A Engine Oil Capacity: 4.0 litres (7.0 pts) Engine Oil and Filter change period:

4.6.5

10,000 km

Test Schedule

Engine Preparation: (at each test stage) Engine flushed, filte r replaced, top deck washed clean, rocker cover renewed, test oil added, ignition checks, timing check, tim ing belt replaced carburetter diaphragm replaced, CO corrected, breather system checked and value replaced. Drivers: Ten drivers selected who commute between 5 and 20 miles twice daily, i.e. morning and evening. One driver selected who commutes 70 miles twice daily, i.e. morning, evening and weekends. Driving Cycle: The ten drivers to change cars weekly every Monday. Cars to be driven Monday to Friday on commuter journeys and fo r approx. 300 miles each weekend w ith different drivers. Idle Time: A ll vehicles to be idled fo r 15 minutes mid morning and mid afternoon Test Duration: 10.000 miles (9 cars) 19.000 miles (1 car) Oil Changes: None other than at test start Oil Filter Changes: None Test Oils: A BCD

510

Test Inspection: A t mid point and at test end Photographs: A t mid point and at test end

4.6.6

Test Oils

Oil A Poor CEC Sludge Reference Oil Oil B Good CEC Sludge Reference Oil Oil C SG/CD, DB 226.5 VW 500/505 10V\M0 Oil Oil D SG/CD, DB 226.5 VW 501/505 15W-50 Oil

4.6.7

Results

Figures 1 to 12 inclusive

4.6.8

Conclusions

All vehicles showed the ability to produce black sludge in varying amounts on the low reference oil. Since no two vehicles give exactly the same results the significance of the ratings and photographs should be assessed individually for each vehicle. Other than fo r vehicle C464 TLC which showed a high oil consumption all other vehicles showed similar low oil consumption and therefore this can be discounted as a result influence. Across all six vehicles all test oils except fo r Oil D on vehicle B469 XRH showed better rating results and sludge control than Oil A reference oil. Minimum reference Oil B gave better sludge control than the two test oils. The varying climatic conditions during the tests are effective on the control of black sludge. The used oil analysis and the aging o f the cars are also considered a contributory factor.

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4.7

Review of Oil Consumption Aspects of Engines

D.C. Roberts, Esso Petroleum Co. Ltd., Abingdon, Great Britain

Abstract The key performance feature o f an engine oil readily visible to the motorist or truck driver is its control o f its own consumption. If oil consumption is high it is soon noticed by dip stick checks, oil deposits on parking places, and high levels o f exhaust emissions such as blue smoke. If as a result the oil level in the engine sump gets too low, engine damage w ill result. To most people low oil consumption is synonymous w ith the oil maintaining good engine performance w ith low levels o f engine wear and low running costs. Control o f oil consumption has always been important, but today it is even more so because of its possible adverse effect on exhaust emissions and the life of exhaust catalysts and particulate traps. An oil helps control oil consumption by both its additive chemistry and its physical properties. The additive chemistry helps by minimising piston ring and cylinder liner wear, the prevention o f bore polishing and piston ring sticking, and ensuring oil seals on the valve stems and crankshafts continue to work effective­ ly. Tests to ensure good oil performance in these areas were developed over many years and they are briefly reviewed in the paper. Of the physical properties of an o il, viscosity and volatility are the two key characteristics known to be important in the control of oil consumption. Over many years viscosity per se was held to be the all im portant factor, but w ith the continued trend to lower viscosity oils for improved fuel economy and lubrication at engine start, control of volatility is recognised as the key factor in achieved low oil consumption in today's and tom orrow ’s hotter running engines. The paper reviews the key factors affecting oil consumption and the various tests developed to ensure acceptable levels in service in the field under arduous operating conditions. It also reports on a programme of work investigating the relative influence o f viscosity and volatility o f multigrade oils in different passenger car engine types. The principal findings were that volatility was a more important factor influencing oil consumption than viscosity and that this applied to most passenger car engine types, not just to air-cooled engines. Linear equations were developed fo r each engine type relating oil consumption to fresh oil vo la tility at 375°C (ASTM-D 2887) and fresh oil kinematic viscosity at 100°C. These gave an idea o f the relevant importance o f v o la tility and viscosity in the different engine types tested. 515

4.7.1

Introduction and Overview

Since the O tto and Diesel engines were invented over 100 years ago there has always been concern over their oil consumption. Because o f this, considerable developments in engine design and engine oil technology have taken place in order to minimize oil consumption as, over the years, operating conditions have become increasingly more severe, oil sump capacities have been reduced, and oil change intervals extended up to 20,000 km for gasoline engine passenger cars and 50,000 km fo r heavy duty Dl diesel engines. Engine o il is consumed in an automotive engine in a number o f ways: -

Past the piston rings into the combustion chamber where it is volatilized and/or burnt and passes to atmosphere via the exhaust system.

— Down the inlet and exhaust valve stems into the combustion chamber and/or the exhaust system. — Past the crankshaft and camshaft oil seals into the atmosphere. -

Into the atmosphere or engine air/fuel induction system via the crankcase venting system.

Oil flow past the pistons is largely controlled by the piston o il control ring and its design, but the other piston rings, cylinder wall honing, and the f it o f the pistons in the engine block all play their part. The oil flows down the valve stems and out o f the crankcase via the crankshaft are controlled by valve stem and crankshaft oil seals. In older engine designs most noticeable oil loss was via leaks from the crankcase, particularly via worn crankshaft seals and the air breather, and blue smoke in the exhaust as the result o f stuck piston rings. In modern engines w ith improved crankshaft and valve stem seals, and closed crankcase ventilation system, the reduced amount o f oil that is still consumed is lost mainly via the combustion chamber to the exhaust. The flo w o f oil through the narrow passages presented by the piston oil control ring and the oil seals is largely controlled by the oil's viscosity. However, piston and ring design, cylinder wall honing, and oil seal designs are all important. The amount o f oil that volatilizes in the combustion chamber and other hot parts o f the engine is governed by the temperature and pressure the oil is exposed to and its own vo la tility. As piston rings and cylinder walls wear, cylinder bores become polished, piston rings tend to stick and oil seals harden and become ineffective, their restriction on oil flow into the combustion chamber or the atmosphere diminishes and oil consumption increases. This can be a gradual long term effect but w ith the sudden sticking o f a piston ring or breakage o f an oil seal, oil consumption w ill suddenly rise.

516

It is well known that engine oil technology, particularly additive chemistry, can significantly reduce long-term piston ring wear, cylinder liner wear, and bore polishing. Also it can prevent piston ring sticking and maintain oil seals in good condition. Use o f such technology can help maintain over the life o f the engine excellent control of oil consumption, which is largely governed by the engine o il’s viscosity and volatility fo r a given set o f engine operating conditions. Because engine oil technology can influence oil consumption directly or indi­ rectly in various ways, a number o f different engine and oil seal tests have been developed over the years aimed at specifying engine oils maintaining long engine life and continued good control o f oil consumption. Well known engine tests that look directly at oil consumption control are: 50hr VW 1302 DKA 6/79 A ir Cooled Gasoline Test. 200hr Cummins NTC 400 Turbo Diesel Test. 600hr Mack T6 Turbo Diesel Test. Engine tests which look at secondary factors affecting oil consumption control are: Ring Stick

CEC L-03-A-78 100hr Cortina Test CEC L-35-T-84 50hr VW 1431 Turbo Diesel Test

Liner Wear

CEC-L-17-A-78 216hr OM 616 Diesel Test

Bore Polish

CEC L-27-T-79 200hr Ford Tornado Turbo Diesel Test CEC PL29 300hr OM 364A Turbo Diesel Test

Of the above all but the Cortina and VW 1302 engines are diesel engines. This is because the diesel is more prone to piston ring and liner wear, and bore polishing due to corrosive wear arising from the diesel fuel sulphur content. To guard against oil seal problems CCMC and VW have special seal com patibility require­ ments covering a number of different standardized elastomer materials. These seal requirements are listed in "Appendix 1” . Except fo r the VW 1302 test, where basestock vo la tility is the key factor, engine oil additive chemistry strongly influences the results o f the above engine tests and CCMC/CEC & VW seal tests. To formulate oils to pass these other engine tests and seal tests requires careful selection and balancing o f the detergent, dispersant, anti-wear, anti-oxidant and viscosity index improver chemistries used. Some generalised comments on the engine oil form ulation factors affecting the above engine tests and CCMC/CEC & VW seal tests are as follows:

517

Engine oil vo la tility the key factor affecting oil consumption.

VW 1302

Cumins NTC 400 Likes lower ash (1.0 %), dispersants, and lower viscosity m ulti­ grade oils in preference to monograde oils. Mack T6

Satisfied w ith API CE quality 1.0 % ash oils.

Cortina

Satisfied w ith CCMC Gl quality 1.0 % ash oils.

VW 1431 TD

Requires CCMC PD2 1.5 % ash oils.

OM 616

Satisfied w ith CCMC PD2 quality 1.5 % ash oils.

Ford Tornado

Likes high ash SHPD oils and 15W40 multigrade oils in pre­ ference to monogrades.

OM 364A

Likes high ash SHPD oils.

CEC & VW Seals Sensitive to dispersant type, but also affected be detergent type, sulphur containing additives and certain synthetic basestocks.

Appendix Elastomer Seal Compatibility Requirements—Engine Oils (All tests on fresh engine oils) Limits on Changes in Elastomer Properties

Hardness Units 1.

Volume %

Elongation at Break %

Tensile Strength %

CCMC (CEC L-39-T-87: 168 hours at 150 C) RE1 (Fluorelastomer) 0/+5 0/+5 -6 0 /0

-5 0 /0

RE2 (Acrylate)

—15/+10

RE3 (Silicone) RE4 (Nitrile)

2.

-5 /+ 5 - 2 5 /0 -5 /+ 5

-5 /+ 5 0/+30 -5 /+ 5

-3 5 /+ 1 0 -2 0 /+ 1 0 -5 0 /0

—30/+10 —

20/0

VW (96 hours at 150°C) Fluorelastomer FKM E-281

N /A

N /A

-2 5 /+ 2 5

-2 0 /+ 2 0

Fluorelastomer FP 7501

N /A

N /A

-2 5 /+ 2 5

—20/+15

Fluorelastomer WO 781

N /A

N /A

—15/+10

—10/+15

518

4.7.2

Factors Affecting Oil Consumption

The mechanism o f engine oil consumption is very complex, and there are many factors which influence it. Some factors have a primary influence while others secondary, particularly those affecting the long term changes in oil consumption as the engine ages. These many factors fall into three main categories: Engine Design; Engine Operating Conditions; Engine Oil Technology. 4.7.2.1

Engine Design

Engine Block

- Rigidity and bore diameter - Bore roundness/tolerance - Cylinder wall honing quality

Piston

— Height and stroke - Roundness and tightness in bore - Land and skirt clearances - Secondary motion and maximum tilt angle - Ring positions - Grove width/depth

Piston Rings

— Profiles and tensions - Gaps and side clearances - Oil control ring type and effectiveness

Connecting Rod — Misalignment and twist - Big end/small and offset Crankshaft

- Oil lip seal effectiveness

Cylinder Head

— Valve stem clearance - Effectiveness o f valve stem and camshaft oil seals

Crankcase

— Closed ventilation

By good engine design significant reductions can be made in oil consumption. The typical oil consumption figures o f modern heavy duty diesels are 0.7 but improved designs can achieve as low as 0.2 g/KW (1)*. Today's engine de­ signers are striving to achieve this and lower levels o f oil consumption in moves towards meeting 1991 and 1994 diesel particulate emissions targets. Lower oil consumption w ill also help reduce bore polishing by reducing the build-up of crown land carbon deposits, and this in turn w ill reduce the long term increase in oil consumption as the engine ages. * N u m b tri in parentheala deilgnate reference* at the end o l th e paper.

519

4.7.2.2

Engine Operating Conditions

Severe operating conditions, particularly high speed high temperature oper­ ation of gasoline engines at full load can cause high oil consumption. In diesel the fuel sulphur content can have a long term effect due to liner and ring wear and the build-up of top ring groove deposits. Today's diesel tend to be more prone to wear under high load medium speed operations. The influence o f operating conditions on oil consumption became abundantly clear in Europe in the early 1960s w ith the rapid development o f the autobahn, autoroute, autostrada, and motorway networks. These high speed roads opened up the opportunity fo r a large number o f cars to be driven fo r long periods at high speeds and maximum power. These conditions produced high oil tempera­ tures and often catastrophic damage to the engine prim arily as the result o f high oil consumption. This occurred because the cars at the time were mostly lubri­ cated w ith SAE 10W-30 oils formulated w ith solvent 100 and 150 neutral basestocks o f, by today's standards, high volatility. Such oils had given very satis­ factory lubrication and oil consumption when vehicle speeds were generally 50 to 80 kmh or lower, and maximum power was rarely used. However, once the motorists had the chance to put their feet down on accelerator pedals fo r long periods, trouble was often in store. The situation was saved by the oil industry introducing the high viscosity 20W-50 multigrade oils. Their use spread from the UK, where it was first introduced to satisfy the thirst of the Mini, to all over Europe and beyond. Now 25 years later many motorists still prefer to use them as, in their eyes, SAE 20W-50 is synonymous w ith quality.

4.7.2.3

Engine Oil Technology

The low or improved oil consumption obtained w ith SAE 20W-50 oils, compared to the 1960s SAE 10W-30 oils, was attributed by most people at the time purely to their higher viscosity. However, the penny eventually dropped amongst oil formulators that such oils had significantly lower vo la tility, and that this was really the im portant factor controlling oil consumption, especially in hot running engines. As a result oil companies in the 1970s again began to favour marketing 10W multigrade oils but now formulated w ith improved narrow cut mineral or special non-conventional basestocks that gave finished oil volatilities close to matching that o f the SAE 20W-50 oils. These improved low vo la tility 10W multigrades give low oil consumption in today's lean or fast bum engines even under arduous conditions. This is due to the combination o f tight control on oil volatility together w ith improvements in engine design and engine oil form ulation technology. The latter has led to better control of engine wear, particularly piston ring and liner wear, less tendency to ring sticking, and prolonged oil seal life through the use o f dispersant addtitives and m ultifunc­ tional viscosity index improvers compatible w ith the oil seal elastomers.

520

Volkswagen, w ith their long experience of hot running air-cooled engines and preference fo r monograde SAE 30 or 40 oils, were the first car maker to appre­ ciate the significance o f oil vo la tility as the key factor controlling oil consump­ tion in hot running engines. They have largely led the way in the promotion o f European low viscosity, low volatility fuel efficient oils by the introduction of a very tight oil consumption target o f 0.4 g/kWh in the D KA 79/6 VW 1302 air-cooled engine test. This lim it is one of the key requirements o f their VW 500.00 service fill specification fo r fuel efficient 5W & 10W multigrade oils, and the specification now also includes a severe Noack vo la tility requirement of 13 % maximum and severe oil seal elastomer requirements. CCMC (Committee o f European Common Market Constructors) have followed Volkswagen's lead and have adopted the 13 % maximum vo la tility requirement and seal test requirements w ith other elastomer seal materials fo r their new CCMC G5 service fill specification fo r low viscosity oils. Ford and GM have also recently introduced GC distillation volatility requirements into their latest factory fill requirements, but these are less demanding than the VW/CCMC requirements and equate to approximately 20 % maximum Noack. The Volkswagen & CCMC seal requirements greatly lim it the choice of oil additive chemistries that can be used in engine oil formulations, particularly that o f the dispersant. The Volkswagen & CCMC volatility requirement and the Volkswagen VW 1302 oil consumption requirement rule out the possibility o f formulating 5W and 10W multigrade oils using only conventional mineral basestocks. The lowest vo la tility that can be achieved w ith a 10W40 mineral based oil is 14 to 15% , which gives a typical VW 1302 oil consumption result o f 0.65 g/kWh. Typical Noack volatility and VW 1302 oil consumption results for 10W30 and 10W40 oils with different basestock components are shown in Figs. 4.7.1 and 4.7.2 (2). The 10W30 oil was formulated w ith a conventional solvent 150 neutral basestock; the 10W40 (1965) oil w ith a m ixture o f solvent 100 and 150 basestocks; the 10W40 (1975) w ith a narrow cut solvent 130, and the 10W40 (1985) w ith a narrow cut solvent 140. The last oil met the CCMC G3 15 % maximum volatility requirement but not the VW 1302 oil consumption requirement or the current VW 500.00 and new CCMC G5 13 % maximum vo la tility requirement. To meet these it is necessary to use a part synthetic basestock. Lower volatility and oil consumption can be achieved by going to a fu lly synthetic product. However, it should be noted that some synthetic basestock such as 4 cS PAO are still quite volatile and cannot be used alone to meet the severe vo la tility and oil consumption requirements. In European gasoline engines it is generally true that higher oil viscosity gives lower oil consumption. In European turbo charged DI diesels higher ash SHPD oils give lower bore polishing and hence less tendency fo r oil consumption to increase as the engine ages. There is also evidence that multigrade mineral based oils give lower bore polishing than monograde oils of lower volatility. This is supported by results from Cummins NTC 400 tests (3) depicted in Fig. 4.7.3 that show that multigrade mineral oils give lower oil consumption than mono­ grades and that oil consumption falls as viscosity is reduced. Further Cummins 521

NTC 400 results (3) depicted in Fig. 4.7.4 also show that oil consumption tends to increase as ash content is increased. This is contrary to experience in Euro­ pean engines (Mercedes Benz, Volvo, Scania, DAF, RV1, Perkins Eagle) for which high ash oils (1.8 -2 .0 %) are recommended fo r extended drain service. As far as engine oil technology factors are concerned they can be equivocal and there are no hard and fast rules. What holds fo r one engine type/design does not necessarily hold fo r another, particularly w ith regard to long term effects in Dl Diesels.

L im it s 1 0 W o ila C C M C G1 & G2

E va p o ra tive 2 0 - ­ loss (•/•) 16 -

- C C M C G3 12

-V W

500.00

-

8 4 10W30

10VV40

(1965)

10W40 (1975)

10W40 (1965)

15W40

-M in e r a l B a s e d -

Figure 4.7.1:

10W30 (PART)

10WTO (FULL)

— I l* -S y n th e tlc — |

V o la tility Comparison - Noack, DIN 51581, 250°C fo r 1 Hour

O il 1.5 i c o n su m p tio n (g / k W h )

1.0

-

0.5 -

V W 500.00 Lim it

10W40 (1965)

10W40 (1975)

10W40 (1965)

-M in e r a l B ased -

Figure 4.7.2: 522

15W40

10W30

10W30

(PARTI

(FUU.)

•| I— S y n th e tic — |

Oil Consumption Comparison VW 1302, Test, A ir Cooled Engine: 50 Hour Duration

O il Co n su m ptio n lb/hr

Test Hours

Figure 4.7.3:

Cummins NTC 400, Viscosity Grade Effect, API SF/CE

Oil Consumption lb/hr

Test Hours

Figure4.7.4:

Cummins NTC 400, Effect o f Ash, Wt-%, API SF/CD: 15W-40 523

4.7.3

Influence of Oil Viscosity and Volatility in Gasoline Engines

In 1975 Esso carried out a field test programme at 3 test sites to study the influence o f oil viscosity and vo la tility on oil consumption. 52 gasoline engined cars were used covering volume produced models from Europe, Japan and North America. Four basic engine types were covered: -

4 4 6 8

cylinder cylinder cylinder cylinder

water cooled air cooled water cooled water cooled

and the oil consumption was determined under typical mixed speed driving conditions. The 9 specially prepared multigrade mineral based test oils used, all formulated w ith the same additive package and VI improver system, were 10W30, 10W40 and 10W50 products. For each viscosity grade there were High, Medium, and Low vo la tility variants, w ith KV 100 kinematic viscosities/ASTM D2887 375°C volatilities as shown in Table 4.7.1. Table 4.7.1:

Test Oil Viscosity&Volatil ity Data

High

Medium

Low

10W30: KV100cS % Volatility

12.78 19.0

11.95 6.0

12.15 4.0

10W40: KV100cS % Volatility

16.23 18.0

15.19 6.2

16.01 4.1

10W50: KV100cS % Volatility

20.05 17.5

19.40 6.4

19.43 4.0

The vo la tility was measured by ASTM D2887 because at the time the DIN 51581 Noack Method was not as well established as it is today. Full details o f the test, the test oils and the results are all given in SAE 890726 (4). The results were analysed by multiple linear regression and modelled on the generalised linear equation Oil Cons. = B0 + B , . KV100 + B2 . VO L 375. (1/1000 km) where KV100 is kinematic viscosity cS at 100°C and VO L 375 is % ASTM D2887 volatility at 375°C.

524

The same linear form o f equation was found suitable fo r correlating the data fo r each engine type. Viscosities and volatilities at other temperatures were investigated but the best correlations were obtained using the values shown. No justification was found fo r using anything other than linear viscosity and volatility terms, or for the incorporation of a viscosity/volatility interaction term. The analysis o f all the data produced the following oil consumption equations: Four cylinder air cooled engines Oil consumption = 0.117 - 0.00124 KV100 + 0.00369 VO L 375 Four cylinder water cooled engines Oil consumption = 0.191 - 0.00324 KV100 + 0.0049 VO L 375 Six cylinder water cooled engines

Oil consumption = 0.333 -0.016 KV100 + 0.00412 VOL 375 Eight cylinder water cooled engines Oil consumption = 0.196 - 0.00498 KV100 + 0.00712 VO L 375 The contributions of viscosity and volatility to the oil consumption of the four engine types are shown in the upper and lower parts of Figs. 4.7.5,4.7.6,4.7.7 and 4.7.8. The oil consumption as a function o f volatility fo r oils of 12,15 and 18 cS, corresponding to XW30, 40 and 50 multigrade, are shown in Figs. 4.7.9, 4.7.10, 4.7.11 and 4.7.12. Also shown are confidence bands for each set of lines. The constant terms (B0) in the above equations account for variables other than viscosity and vo la tility held constant during the test programme. The following conclusions can be drawn from Figures 4.7.5 through 4.7.12 over the range of viscosities and volatilities examined. -

For all four engine types tested oil consumption decreased w ith increasing viscosity and increased w ith increasing vo la tility.

-

The influence of viscosity and vo la tility on oil consumption in the four engines types varied as follows:

Viscosity V o latility

4 cyl. A ir Cooled Very low High

4 cyl. Water Cooled Low High

6 cyl. Water Cooled Very High High

8 cyl. Water Cooled Low Very high

525

Viacoiity at 100°C, cSt 12

11 14

15

16

17

18

19

Volatility % Off at 375aC

Figure 4.7.5:

The Separate Contributions o f Viscosity and V o la tility to Oil Consumption in Four Cylinder A ir Cooled Engines Viicoiity at 100°C, cSt

Figure 4.7.6:

526

The Separate Contributions o f Viscosity and V o la tility to Oil Consumption in Four Cylinder Water Cooled Engines

Oil Consumption

Rate, L/1000

Km

Viscosity at 100°C, cSt

Figure 4.7.7:

The Separate Contributions of Viscosity and V o latility to Oil Consumption in Six Cylinder Water Cooled Engines Viscosity at 100°C, cSt 12

13

14

15

16

17

18

19

Volatility % Off at 375°C

Figure 4.7.8:

The Separate Contributions of Viscosity and V o la tility to Oil Consumption in Eight Cylinder Water Cooled Engines 527

Figure 4.7.9:

Oil Consumption as a Function of V o la tility in A ir Cooled Engines

Figure 4.7.10: Oil Consumption as a Function o f V o la tility in Four Cylinder Water Cooled Engines 528

Figure 4.7.11: Oil Consumption as a Function o f V o la tility in Six Cylinder Water Cooled Engines

Figure 4.7.12: Oil Consumption as a Function o f V o la tility in Eight Cylinder Water Cooled Engines 529

-

Viscosity per se at constant vo la tility was only a significant factor in 6 cylinder water cooled engines

— V o la tility per se at constant viscosity was a significant factor in all four engine types, not only in air cooled engines, and had a large effect in the 8 cylinder water cooled engines. The field test findings fo r the 4 cylinder air cooled engines were confirmed by carefully controlled VW 1302 oil consumption bench tests carried out on the 10W30 and 10W50 high and low vo la tility oils used in the field test. These results are shown in Fig. 4.7.13 and show viscosity to have little or no influence, and volatility to be the significant factor. The tw o low vo la tility multigrade oils were close to matching a low vo la tility SAE 30 monograde oil. Analysis of the field test data showed that it was not possible to generate one equation to correlate the data fo r the fo ur engine types tested. However, it is possible to calculate overall weighted fleet averages fo r viscosity and vo la tility effects in multigrade oils in the following manner. Percent Change in Oil Consumption Engine Type

1cS Change in Viscosity

A.4 cyl.A ir Cooled B.4 cyl.Water Cooled C.6 cyl.Water Cooled D.8 cyl.Water Cooled

1 % Change in V o la tility

0.99 1.75 11.94 2.59

2.67 2.51 2.99 3.63.

The test fleet consisted o f 7 type A cars, 18 type B, 4 type C, and 23 type D. Using these numbers gives a weighted fleet average fo r 1 cS change in KV100 viscosity of: 7 (0.99) + 18(1.75) + 4( 11.94) + 23(2.59) = 2 .8 0 % 52 Cars and a weighted fleet average fo r 1 % change in ASTM D2887 375°C vo la tility of: 7 (2.67) + 18(2.51) + 4(2.99) + 23(3.63) = 3.06 % 52 Cars The results o f the above analysis compare well w ith other published data (5) which reported a fleet average change in oil consumption o f 3 % fo r a 1 cS KV100 viscosity change, and 2 % fo r a 1 % change in ASTM 2887 vo la tility at 375°C.

530

T E S T D U R A T IO N

(h )

Figure 4.7.13: VW 1302 Weighed Sump Oil Consumption Test

In the 4 cylinder air and water cooled engines very low vo la tility monograde SAE 30 (K), 40(L) and 50 (N) oils were also evaluated. The results fo r these three oils are compared against the oil consumption results fo r the medium volatility 10W30 (B), 10W40 (E) and 10W50 (H) oils in Figure 4.7.14. In the 4 cylinder water cooled engines the multigrade oils gave significantly lower oil consumption than the monogrades; the reverse was true fo r the 4 cylinder air cooled engines. The lower oil consumption fo r the monograde oils in the 4 cylinder air cooled engines is simple to explain - lower vo la tility, but the better performance fo r the multigrades in the 4 cylinder water cooled engines is an enigma. The Cummins NTC 400 results shown in Fig, 4.7,3 emphasise the point that in certain engines multigrade oils o f lower volatility and viscosity can give lower oil consumption than monograde oils o f higher viscosity and lower volatility.

531

E

x o o o

rj ee e

o

o U

Figure 4.7.14. Multigrade Oils give Lower Oil Consumption than Corresponding Monogrades in Water Cooled Engines, Higher in A ir Cooled.

4.7.4

Conclusions

Engine oil is consumed in a number of different ways and the mechanism is very complex. Many factors affect oil consumption and some have a primary influence and others secondary, particularly those affecting the long term changes in oil consumption as the engine ages. These many factors fall into three main categories: -

Engine Design Engine Operating Conditions Engine Oil Technology

With good engine design low levels o f oil consumption can be achieved, even under arduous operating conditions, but the key to this is engine oil technology. This is particularly so if low levels o f oil consumption are to be maintained as the engine ages.

High viscosity oils were long held to be the cure fo r engines w ith inherently high oil consumption, but now it is seen that it is low volatility rather than high viscosity what is required. Findings regarding oil consumption are also confu­ sing w ith what holds for one engine type is the opposite to what holds for another. This is demonstrated in Fig. 4.7.14 and by the fact that whereas European turbocharged HD diesels rely on high ash SHPD oils to control bore polishing/oil consumption their North American counterparts rely on medium to low ash oils. Engine oil additive chemistry can significantly affect long term increases in oil consumption as the engine ages. Because of growing concerns re oil seal perfor­ mance, the European vehicle makers have recently introduced tough require­ ments which severely restrict the choice dispersants and other additives used in today's engine oil formulations. To meet severe European vo la tility/o il consumption requirements with 5W or 10W multigrade oils, it is necessary to incorporate non-conventional basestocks on a partial basis. An extensive field test involving 52 cars and four gasoline engine types compared the oil consumption performance o f 9 10W30, 10W40 and 10W50 oils o f high, medium, and low vo la tility. Analysis o f the results showed the following fo r the range of oils and cars covered: — For all four engine types there is a linear relation between viscosity and oil consumption, which decreases as viscosity increases. — For 4 cylinder air cooled, 4 cylinder water cooled and 8 cylinder water cooled engines the viscosity effect is small, but it has a large effect in the 6 cylinder water cooled engines tested. — For the 52 cars tested the weighted fleet average figure calculated for percent change in oil consumption fo r a one centistoke change in kine­ matic viscosity at 100°C was 2.8 %. — For all four engine types there is a linear relationship between volatility and oil consumption, which increases as vo la tility increases. — V o la tility was a major factor controlling oil consumption for all four engine types, and was particularly large fo r the 8 cylinder water cooled engines. — The weighted fleet average figure calculated fo r percent change in oil consumption fo r a 1 % change in ASTM D2887 375°C volatility was 3.06 %. This and the result obtained fo r viscosity change compared very favourably w ith the figures quoted from another test.

533

— The oil consumption results fo r the 9 multigrade oils were best correlated w ith an oil consumption model o f the form : Oil Cons. = B0 + B ,. KV100 3 B2. VOL375 (1/1000 km), where B0 . B] and B2 are constants depending on engine type. -

Because o f variations between engine types it was not possible to develop one equation covering all 4. The following 4 equations best covered the oil consumption (OC) data from the field test: — 4 cylinder air-cooled engines OC = 0.117-0.00124 KV100 + 0.00369 V O L 375 — 4 cylinder water-cooled engines OC = 0.191-0.00324 KV100 + 0.0049 V O L 375 — 6 cylinder water-cooled engines OC + 0.333-0.016 KV100 + 0.00412 VO L 375 — 8 cylinder water-cooled engines OC = 0.196-0.00498 KV100 + 0.00712 VO L 375

-

4 .7 .5 (1) (2)

(3) (4) (5)

534

In a comparison o f the multigrade oils against low vo la tility monograde oils o f equal viscosity, the multigrade oils gave higher oil consumption in 4 cylinder air cooled engines, but lower oil consumption in 4 cylinder water cooled engines.

R eferen ces Guertier, R.W.: — Mahle — "Excessive Cylinder Wear and Bore Polishing in Heavy Duty Diesel Engines: Causes and Proposed Remedies", SAE Paper 860165. Roberts, D.C.: - Esso — "W hy Synthetics in Modern Engine Oils?" Stichting Nederlands National Cimite Motorporoven Smeerolie En Brandstoffen Symposium Fuels and Lubricants For Future Cars, Rotterdam. April 1987. O ro nite— "Diesel Engine Oil Technology", February 1988. Carey, L.R.; Roberts, D.C.; Shaub, H.: — Esso/Exxon — "Factors Influencing Engine Oil Consumption in Today's Automative Engines", SAE Paper 890726. Didot, F.E.; Green, E.; Johnson, R.H.: — Sun Oil — ..Volatility and Oil Consumption of SAE 5W-30 Oils, SAE Paper 872126.

4.8

The Contribution of the Lube Oil to Particulate Emissions of Heavy D uty Diesel Engines

P. T rittha rt, F. Ruhri and W. Cartellieri A V L-List Ges.m.b.H, Graz, Austria

4.8.1

Summary

First the analysis o f particulates as practiced in the engine development depart­ ment is introduced, especially to define the quantity o f soluble particulates caused by lube oil. Then, the significance o f lube oil particulates is demonstrated by means of some peculiarities. The major form ation mechanisms and the correlation between lube oil particulate emission and lube oil consumption is demonstrated, from which a strategie fo r oil particulate reduction is de­ rived.

4.8.2

Introduction

Different studies performed by A V L (1—4) and others (5 -1 0 ) already showed the importance o f lube oil as a significant contributor to particulate emissions. The first studies concentrated on particulate emissions o f diesel engines for light vehicles (passenger cars and light trucks) but in the last years the attention was put to heavy duty diesel engines because o f the particulate reductions especially required in the U.S. fo r this engine category, Table 4.8.1. A fter all the experience collected at A V L during the development of diesel engines to meet future particulate lim its, we have to state that the particulate fraction caused by lube oil plays a key role, which finally determines whether development work becomes successful or not. The essential lube oil particulate sources are: — lube oil from the cylinder wall and - lube oil from valve stem lubrication Therfore, these tw o aspects deserve major attention in engine development. In the following it is demonstrated which influences on lube oil particulate emissions are possible and in what direction and magnitude future developments w ill have to be led.

535

Table 4.8.1:

Exhaust emission standards fo r Heavy Duty Diesel engines in Europe and USA

ECE

HC

CO

NOx

Basis 1988

3.5 2.4 (-3 0 % )

14.0 11.2 ( - 2 0 %)

18.0 14.4 (-2 0 % )

Switzerland 1991

1.23

Part. _ —

g/kWh ECE R49 13 Mode-Test

4.9

9.0

0.7

USA 1991

1.3

15.5

5.0

025

1994

1.3

15.5

5.0

0.10

4.8.3

g/HP-hr Transient Test cold 1/7 hot 6/7

Particulate Analysis

A ll particulate fractions mentioned in the following were derived from the scheme in Fig. 4.8.1. The lube oil particulate fraction is the result o f a gas chromatografic analysis which is described in detail in (1). This method is based on the comparison o f the 50 %-boiling point o f organic soluble particulates and the 50 %-boiling point o f various fuel/lube oil-calibrating blends. For the latter only those fuel fractions that boil above 320°C are used, i.e. light fuel fractions are distilled o ff before. This method implies that the molecular distribution of the defined fuel/lube oil calibrating blend stays the same during its change to the particulate phase. Hence, at a given 50 %-boiling point the molecular dis­ tribution o f the organic soluble particulate phase should coincide w ith that o f the calibrating blend. Of course, this is a simplistic and not always correct assumption, since even at lowest loads or during motoring — depending on the absolute size o f the oil particulate portion — remarkable crack reactions may occur. Thus, originally higher boiling lube oil fractions are split into lighter boiling components. In the gas chromotogram these lighter components are then wrongly identified as fuel portions. Therefore, this method leads to an under­ estimation o f the lube oil portion on particulates. Furthermore, the contribution of lube oil to organic insoluble particulate fractions cannot be defined by this method. Despite these shortcomings the fuel/lube oil separation method has successfully detected lube oil particulate problems in engines since its introduction 8 years ago. Due to automation o f gas chromatography laboratory technical analysis can also be kept w ithin reasonable limits. Therefore, this method is conveniently applicable fo r the daily routine work. 536

Figure 4.8.1:

Analysis o f Diesel Particulates (Schematic)

Total - Particulates

Fuel Particulates

Figure 4.8.2:

Lube-OII Particulates

S04 + HzO

Carbon + ?

Topography of Particulate Components from 12 I DI/TCI Heavy Duty Diesel Engine, US-2D Fuel (0.3 % S by Weight) 537

Fig. 4.8.2 shows the topography of particulate components o f a heavy-duty diesel engine (according to the analysis scheme of Fig. 4.8.1). This example presents a typical lube oil particulate problem. In a wide load and speed range lube oil particulates exceed more than half o f the entire particulate emission, while carbon portions (dry soot) play a m inor role fo r this engine because of prior combustion optim ization. Fig. 4.8.2 also shows that sulphates and water present a considerable magnitude when using fuel w ith a high sulphur content (0.3 %).

4.8.4

Lube Oil Particulates in Exhaust Emission Tests — Current Position

The test procedure prescribed fo r exhaust emission tests is primarly essential fo r engine development. In Europe it is the 13-mode-steady test acc. to ECE R49 and in the U.S. it is the transient test (Fig. 4.8.3). The latter requires significant investments for electronic engine and dynamometer control and for exhaust measurement equipment. To reduce the costs fo r engine development, an 8-mode-steady state test is helpful to simulate the transient test. A compa­ rison o f the weighting factors o f points in Fig. 4.8.3 shows that the ECE-test is prim arily settled in the medium speed and the transient test in the upper speed range.

EUROPE

E C E R49 13-Mode Test

Figure 4.8.3:

538

USA

US Heavy Duty Diesel Transient Teat

ML

8-Mode Test for Simulation of Transient Test

Test Procedures fo r Heavy D uty Diesel Engines Time Distribution in Load-Speed Zones

When testing the engine according to ECE R49 and the US-Transient test — depending on the engines type-different results on emissions may occur. Fig. 4.8.4 shows on three combustion-optimized engines of different sizes that in the US-test lube oil particulate emissions are usually higher and therefore, the entire particulate level is increased. This behaviour can also be seen at extremely low oil particulate levels (engine C in Fig. 4.8.4). The increase o f oil particulates is especially distinct on engine A , where the lube oil portion increased from 35 to 43 % o f the total particulate emission. The reason fo r this characteristic lies in the engine's load and speed behaviour (Fig. 4.8.5). As this figure shows, lube oil particulates first increase w ith load to a maximum and decrease then to higher loads to a minimum and then again increase slightly on each engine. With increased speed the maximum generally lies higher and is shifted to lower loads. On engine A the increase w ith speed is especially distinct which explains its high transient test emission, as this test prim arily runs at high speed. These characte­ ristics can be seen even better when comparing the modal lube oil particulate emissions in the 8-mode-test, Fig. 4.8.6. This figure shows that the high speed modes 5 and 6 are prim arily decisive fo r lube oil particulates in the transient test, which are remarkably higher on engine A. This example already indicates that a potential lube oil particulate problem is prim arily a high speed/light load problem, which is manifest only on the transient test because o f its high speed weightings. Therefore, all further investi­ gations prim arily concentrate on the transient test, as most o f the lube oil parti­ culate problems occur during this test procedure. Engine A

Engine B

Engine C

71 DE/TCI 0.14

61 DE/TCI 0.14

111 DE/TCI 0.05 Sulphur content ol Fuel (% by wt)

g/BHPh - 0.30

g/kWh 0.4 "

~ 0.25 in 0.3 *—

0 jf 3 1 °-2 ' n_

-

0.20

ECE

USA USA

0.15 h

ECE

-s o 4+h2o

am

0.10

"Carbon

0.1 - i

0.05

,-Fuel —Lube Oil

Lube Oil Content-

14

35

43

- T 10

13

g/kWh

0.076 0.167

0.015

0.023

gTHP-hr

0,057 0,124

0,011

0,017

Figure 4.8.4:

C ontribution o f Lube Oil to Particulate Emissions ECE = ECE R49 Test; USA = US Diesel Transient Test (A V L 8-Mode Si­ mulation) 539

Intermediate Speed

Rated Speed

I £ 3

bmep •

Figure 4.8.5:

bmep •

bar

bar

Effect o f Speed and Load on Lube Oil Particulate Emissions from D I/TC I Diesel Engines (A ca. 7 I; B ca. 6 I; C ca. 11 I; all 6 Cyl.)

A V I 8-Mode-Simulation el Transient Teet .

^ ta l|i'5 “M6yeEm1sslons

UoU.Nl5.4 o

te>

0.05

m i

o

1

0.04

ft I I J ? | i CL I

0.02

_l

Engine A » Total 0.124 g/HPh B - Total 0.060 g/HPh

B i

£3

T

k

0.03

0.01 0

C -T o ta l 0.017 g/HPh

Efcl=

EL-

fin

£B_

L d

n

Mode No.:

Figure 4.8.6:

540

Modal Lube Oil Particulate Emissions from 8-Mode Test for Engines A , B and C

4.8.5

Peculiarities of Lube Oil Particulates

4.8.5.1

The Influence of Cooling Water Temperature

Fig. 4.8.7 shows the influence of cooling water temperature on lube oil parti­ culate emission in the transient test on two engines. Two variants are shown for engine A - variant 1 at a high level o f lube oil particulates and variant 2 at a very reduced level. It can be seen that on engines w ith a high oil particulate level a reduction in cooling water temperature by 30UC causes lube oil particulates to increase by 35 %. This result is backed-up by the experience that oil consump­ tion increases w ith reduced cylinder wall temperature (higher viscosity, i.e. thicker lubricating film at the cylinder wall) (11). Surprising is the result on the lube oil particulate optimized engine A/variant 2, where no influence o f tempe­ rature exists.

Figure 4.8.7:

4.8.5.2

Effect o f Cooling Water Temperature on Lube Oil Particulates in Transient Test from D I/TC I Diesel Engines

Particulate Emission During Motoring

Fig. 4,8,8 shows particulate emission during motoring on various engines. The corresponding piston displacement as well as the rate o f lube oil particulates in transient test is entered fo r each curve. The particulate rate during motoring corresponds to the lube oil consumption (after ensuring that fuel injection is out of order, as was the case for these tests) during this operation mode. For the first it is striking, that motored particulate emission o f all engines increases w ith speed. The steeper the curve, the higher the lube oil particulate emission in the transient test. This data suggests a correlation of lube oil particulate emissions 541

w ith the rate o f motoring particulates at high speed, as the latter is im portant in the transient test, Fig. 4.8.9. For better comparison o f engines, the particu­ lates rates in Fig. 4.8.9 were normalized by the engine displacement, and the motored particulate value was taken as that o f the engine at rated speed. Fig. 4.8.9 shows that the curves o f high quality engines are close together and the transient test oil particulates increase in a linear manner w ith motoring particulates to a certain level and then go apart. During motoring we found that the exhaust pipes are practically dry in good engines, whilst in engines w ith high motoring particulate rates the exhaust pipes are oil wetted, and in extreme cases oil drips out. It can be concluded that high oil particulate rates derive from a high oil availability on the cylinder wall, i.e. oil is fed into the exhaust system, partly stored on the walls and then evaporated at a higher exhaust temperature and fed into the particulate measuring system. It should be mentioned that during motoring, substantial quantities o f particu­ lates may also derive from leaky turbocharger shaft seals, as comparative measurements w ith and w itho ut turbocharger have shown.

Cepedbr • I

Lub* Q> Perteut*>*» In Treneierrt Teel (hop - t W M r

7,51/0,12 81/ 0,075 101/0,070 111/0,045 101/0,029 6,51/0,035 500

1000

1500 Engine Speed

Figure 4.8.8:

2000 -

2500

3000

rpm

Lube Oil Particulates from Motored Engine Conditions Compared w ith Transient Test Oil Particulates

Condition ol Exhaust System alter Motoring Exhaust System dry 1.2



1

1.0

TS

Z

it

0.8

-1

0.6

|

Exhaust System wet

k

it

0.4

& e

0.2

& 3 0.0 0.0

1.0

2.0

3.0

4.0

Motored Particulate Emissions at Rated Speed • g/h x Liter Displ. (warm Engine - no Injection)

Figure 4.8.9:

4.8.5.3

Lube Oil Particulates in Transient Test as Function o f Oil Parti­ culates from Motoring Test at Rated Speed ( 1 - 2 l/Cyl.; Rated Speed 1800 - 3200 rpm)

Effect of Sulphur Content of Fuel on Lube Oil Particulates

Tests w ith fuel o f different sulphur content showed that particulate emission is reduced by 0.020 +/— 0.004 g/HP-hr in the transient test on an average of various engines fo r each 0.1 weight % sulphur reduction (12). This influence does not only derive from reduced sulfate form ation but also, as Fig. 4.8.10 shows, from the reduction o f lube oil particulates. The average lube oil particu­ late gradient of 0.0062 +/— 0.0033 g/HP-hr and 0.1 w t % fuel sulphur (Fig. 4.8.10) seems to be low, but is still important, if all particulate components ought to be minimised in order to arrive at total particulates o f 0.1 g/HP-hr w itho ut exhaust after treatment. The property o f sulfates to attract hydrocarbons from the gaseous phase and hence, to increase particulate emissions has already been mentioned (13). As our tests show, this effect is prim arily attributable to lube oil particulates.

543

Average Rate of Increase

0.0062 1 0.0033

g/HPh x 0.1 % wt S Displacement:

Fuel-Sulphur Content

- %wt

Figure 4.8.10: Effect of Fuel Sulphur Content on Lube Oil Particulates in Transient Test; DI/TCI Diesel Engines

4.8.5.4

Influence of Lube Oil Formulation on Particulate Emission

In earlier investigations (3) we found a remarkable influence o f the lube oil evaporation characteristics as expressed by the Noack-value on particulate emissions, especially regarding the organis soluble lube oil fraction. These tests have been effected at a relatively high level o f oil particulates. Therefore, further test w ith a lube oil particulate-optimized engine have been effected to see whether the same effect then occurs also. Fig. 4.8.11 shows the result o f these tests w ith 4 different lube oils. It can be seen that the lube oil particulate frac­ tion is influenced only a little w hilst the biggest differences in significant magni­ tudes occur at the organic insolube particulates. In future more attention w ill have to be drawn to this fact.

544

OH Type SAE Density (15*C) Bolling Point 10% *C 50% *C 00% "C Noack(%) Viscosity (cSt) at 40*C 100*C

A 30 0.893

B 40 0.893

C 10W40 0.885

D 10W40 0.854

417 450 503 8-9

458 491 532 3-4

389 412 441 15-20

406 442

90 10.8

153 15.5

93

83 13.8

14.0

500 8-9

Figure 4.8.11: Effect o f Lube Oils on Particulate Emissions 11 I DI/TCI Diesel Engine, U S -2D Fuel

4.8.5.5

Effect of Valve Stem Sealing on Particulate Emissions

Until now this report is based on the assumption that only lube oil of the cylinder lubrication causes the major portion o f oil particulates. But it is also known o f various tests (1 ,6 ,1 4 ) that valve stem sealing can present a significant source fo r lube oil particulates especially at an increased level o f lube oil availa­ b ility on the valve stems. In case of a reduced level (low splash oil, good oil removal) this influence is dramatically diminished. To define the influence o f valve stem sealings at an extremely low level o f lube oil particulates from the cylinder, these sealings were gradually removed in the inlet and outlet area, Fig. 4.8.12. As expected, the component of lube oil particulates increased, but proportionally also the carbon fraction, especially when there was no valve stem sealing mounted at the outlet. Thus, it can be concluded that already small quantities of lube oil which get along the valve stems into the induced air or into the exhaust significantly influence the parti­ culate emission. Experience showed that this influence is higher at four-valve than at two-valve-engines due to the double number o f sealings. Similar effects o f oil admission at inlet and outlet valves are described in (6), but the levels o f oil consumption and oil admission were remarkably higher. Absolutely measured, the effects which are described here are rather low in comparison to those in (6).

545

Figure 4.8.12: Effect of Valve Stem Seals on Particulate Emission 8-Mode Trans. Test Simulation; DI/TCI Diesel Engine, 2 Valves/Cyl., Exhaust Emissions Optimized, Fuel Sulphur Content: 0.05 % by w t.

4.8.6

Oil Consumption and Lube Oil Particulates

A fter all the experiences presented so far, the question arises what connection exists between lube oil consumption and lube oil particulates, especially regar­ ding future targets fo r lube oil consumption. To fo llo w this question, the oil ring tension has been increased by about 40 % at a lube oil optimized engine. Fig. 4.8.14 shows the results regarding oil consumption, oil particulates and inso­ luble particulates in significant points o f the 8-mode-test (mode 1, 5 ,6 ,8 ) , in a 4-mode-cycle (consisting o f these 4 modes) and finally in the transient test. The 4-mode-test should show the accuracy o f projection from the single modes at a cylcic test driven in a 5 minute rhythm . The weighting and sequence of modes were adjusted to approximately reflect the operating mode o f the tran­ sient test, i.e. low idling (mode 1) is fixed w ith 2 minutes duration and all other modes w ith 1 minute, and mode 8 (high load, high torque) follows immediately after idling (mode 1). The percental reduction o f all components due to the increase of oil ring tension is shown in Fig. 4.8.14. The following statements can be derived from the results presented in Figs. 4.8.13 and 4.8.14: -

546

Depending on the load point or operation mode the ratio o f oil consump­ tion to lube oil particulates fluctuates between 2:1 and 15:1. No rule can

be derived from these ratios. Tendenciously the ratio diminishes w ith reduced oil consumption, which means that the magnitude o f reduction in oil consumption does not reflect completely in reduced lube oil parti­ culate emissions. Mode 5 presents an exception. -

In mode 5 (high speed, low load) the reduction of oil consumption results in an overproportional reduction o f lube oil particulates.

-

A t high loads the reduction o f oil consumption prim arily affects the reduction o f insoluble particulates.

-

The projected 4-mode results derived from the single mode results show a relatively good agreement w ith the dynamic 4-mode-results.

-

In the transient test and also in the 4-mode-test the reduction of oil consumption is reflected prim arily in the reduction o f insoluble particu­ lates, whilst lube oil particulate fractions practically remain unchanged.

-

Therefore, it can be concluded that there are no longer any significant oil evaporations and oil feed processes below a certain oil quantity on the cylinder wall, but oil combustion processes forming insoluble particulates (soot, ash) become the dominant mechanism. This experience is in line w ith the earlier mentioned (Fig. 4.8.7) influence of cooling water tempe­ rature on lube oil particulate fractions, which no longer exists at a low level o f oil particulates.

The question arises which oil consumption target is necessary to achieve this unsensitive threshold of oil particulates. For that purpose in Fig. 4.8.15 the lube oil particulate emission in the transient test o f various engines is plotted versus their oil consumption at mode 8. If it is assumed that based on our tests this threshold is at a lube oil particulate value o f 0.03 g/HP-hr, Fig. 4.8.15 shows that an oil consumption of max. 0.19 g/kWh (0.14 g/HP-hr) should be achieved in mode 8. Oil consumption figures o f similar magnitude have been recommended in (9). As the lube oil particulate problem has been identified as one at high speed/low load which is also becoming manifest during motoring, a further criteria, namely motoring particulate emission at rated speed, should be considered. In Fig. 4.8.16 this has been put into relation fo r various engines to their lube oil parti­ culate emission in the transient test. If again the threshold value of 0.03 g/HP-hr for lube oil particulate emission is required, according to Fig. 4.8.16 the mo­ toring particulate value at rated speed should not exceed 0.5 g/h x 1 piston displacement.

547

Q Lube 01 Consumplon

0 Lube Oil Partiouiates | Insoluble Particulates

4 Mode - 4 Mode Test Values calculated from Modes 1 .5 ,6 . B 4 Mode dyn. - 4 Mode Test. Mode Sequence 1. 6.5 ,6 ; Time Intervals 2/1/1/1 Minutes. cycBc

Figure 4.8.13: Effect o f Oil Control Ring Contact Pressure on Oil Consumption and Lube Oil Particulate Emissions 11 I D I/TC I Diesel Engine, Optimized Oil Consumption. 230 kW 11 Uter Ol / TC I Diesel Engine, 230kW, Final Status altar Oil Consumption Optimisation 60 50

40

10

Mode

[5]

1

Oil Consumption

Figure 4.8.14:

548

4 Mods Test Dyn. (1-8-5-6)

Q

Lube Oil Partleulales

Transient Test hot

Insoluble Partlculales

Reduction o f Oil Consumption, Lube Oil Particulates and Inso­ luble Particulate Fraction by a 40 % Increase in Oil Control Ring Contact Pressure

DI/TCI - Diesel Engines, 1-21/Cyl., Rated Speed Range 1800-3200 rpm

1 0

0,1

0,2

0,3

0,4

0,5

1

1

1

1

1

1

1

0

0,1

0,2

0,3

0,4

0,5

0,6

g/HP-hr

1 0,7 g/kWh

Figure 4.8.15: Lube Oil Consumption, Mode 8 (90 % Speed, 95 % Load). Depen­ dency o f (Transient Test) Lube Oil Particulates on Oil Consump­ tion in Mode 8

DI/TCI - Diesel Engines, 1-21/Cyl., Rated Speed Range 1800-3200 rpm

o-P

0,08 -

5*

S| 0.04

0,02

Objective

T-------------- 1-------------- 1 0 1 2 3 4 Particulates from Motoring at Rated Speed - g/h x I Dispi.

Figure 4.8.16: Dependency o f Transient Test Lube Oil Particulates on Parti­ culate Levels from Motoring at Rated Speed

549

4.8.7

Strategy for Lube Oil Particulate Reduction

In view o f gained experience a strategy fo r oil particulate reduction ought to be put in place on 3 levels: 1) Minimization o f oil consumption from the cylinder wall 2) Minimization o f all possible oil entrances into the intake and exhaust system like valve stem seals, turbocharger shaft seals, blow-by return 3) Development o f lube oil according to the latest requirements. Engine producers mainly have to pursue the first two tasks, whereby oil con­ sumption anyway presents a permanent task in engine development. The oil consumption in the cylinder depends on numerous design parameters, which should have certain characteristics to secure the required oil consumption, Fig. 4.8.17. The lube oil performance has to be integrated into all these require­ ments.

MatariSprapartaa Haring praoMi Bor* Distortion

Profile ol CyL Surfoc*

:W

:i ' Piston S F Rings " NngM

31ST

W*or Rot* of CyflmJorsLRln(p ond Ring Q roovM

.

Malarial eelecSer Surtaot trauma* WHpn * ring daatgn

Ring nation

Figure 4.8.17: Criteria and Design Parameters Affecting the Lube Oil Con­ sumption form the Cylinder Wall

550

4.8.8

Summary and Conclusions

These tests have shown that the organic soluble particulate portion caused by lube oil may contribute w ith more than 40 % to the entire particulate emission. On the very same engine, lube oil particulates are generally higher in the UStransient test than in the ECE R49 test, as the US-test puts more weight to higher speeds and is based on a lower load factor, and the lube oil particulate emission generally increases w ith speed. Thus, work fo r optim ization has to be done especially fo r the transient test. The lube oil particulate emission has been prim arily identified as a high speed/ low load problem, which is also manifest during motoring. The lubrication o f valve stems presents a further essential source for lube oil particulates, but sometimes also the shaft sealing o f the turbo charger. The lube oil particulate emission correlates well w ith the particulate emission during motoring at rate speed. This value should be < 0.5 g/h x liter piston displacement to achieve a target o f < 0.03 g/HP-hr lube oil particulates in the transient test. The lube oil consumption at high load necessary to achieve the target o f lube oil particulates in the transient test « 0.03 g/HP-hr) should be < 0.19 g/KLh (0.14 g/HP-hr). A t this low level o f oil consumption a further reduction in oil consumption hardly influences the organic solube particulate phase. But a reduction in the insolube particulate phase can be stated. Also the oil form ulation at a low level of oil consumption primarily influences the insoluble rather than the soluble particulate phase. Therefore, in future the major emphasis has to be put on the insoluble particulate portion deriving from lube oil. In general it can be stated that secondary influences to the lube oil particulate emission, like cooling water temperature or sulphur content o f fuel, are the less distinct the lower the level o f oil consumption. A strategy fo r oil particulate reduction should be put in place on 3 levels: -

Minimization o f oil consumption from the cylinder wall

-

Minimization o f all oil entrances into the intake and exhaust system

-

Development o f lube oils according to the latest requirements.

551

4.8.9 (1)

(2)

(3) (4) (5)

( 6)

(7)

(8) (9)

(10)

(11) (12)

(13) (14)

552

References

Cartellieri, W.; Tritthart, P.: "Particulate Analysis of Light Duty Diesel Engines (ID I & D I) with Particular Reference to the Lube Oil Particulate Fraction", SAE Paper 840418. Cartellieri, W.; Wachter, W.F.: "Status Report on a Preliminary Survey of Strategies to Meet US-1991 HD Diesel Emission Standards Without Exhaust Gas Aftertreat­ ment", SAE Paper 870342. Cartellieri, W j Herzog, P.L.: "Swirl Supported of Quiescent Combustion for 1990's Heavy-Duty DI Diesel Engines — An Analysis", SAE Paper 880342. Cartellieri. W.; Ospelt, W.M.; Landfahrer, K.: "Erfullung der Abgasgrenzwerte von Nutzfahrzueg-Dieselmotoren der 90er Jahre", Motortechn. Zeitschrift 50 (89) 9. Mayer, W J.; Lechmann, D.C.; Hilden, D.C.: "The Contribution of Engine Oil to Diesel Exhaust Particulate Emissions", SAE Paper 800256, also in SAE Proceedings, P-86 "Diesel Combustion and Emissions", 1980. Maurer, M.: "Beeinfiussung der Partikelemission eines Dieseimotors durch das Schmierol", Dissertation (1986), Fakultat fur Maschinenwesen der Rheinisch-Westfalischen Technischen Hochschule Aachen. Springer, K.J.: "Diesel Lube Oils — 4th Dimension of Diesel Particulate Control", ASME Conference on Engine Emissions Technology for the 1990’s, San Antonio, Texas, October 1988. Shore, P.R.: "Advances in the Use of Tritium as a Radiotracer for Oil Consumption Measurement", SAE Paper 881583. Moser, F .X .; Haas, E.; Schlogl, H.: "D ie Partikel-Hurde U.S. 1991: Vergleich der Testverfahren fur Nutzfahrzeugmotoren-Bewaltigung mittels innermotorischer MaSnahmen", 10. Internationales Wiener Motorensymposium, April 1989. Lewinsky, P.M.; Cooke, V.B.; Andrews, C.A.: "Lubrication Oil Requirements for Low Emission Diesel Engines", AVL-Conference "Engine and Environment", Graz, Aug. 1 .- 2 . 1989. Rulfs, H.W.: "Untersuchung des Schmierdlverbrauchs eines aufladbaren Diesei­ motors unter Anwendung eines Radioisotops", VDI-Forschungsheft Nr. 601 (1980). Cartellieri, W.: "D ie Partikelproblematik aus der Sicht der Motorenentwicklung von Nutzfahrzeug-Dieselmotoren", AVL-Conference "M otor und Um w elt", Graz. 1. - 2 . August 1989. Wall, J.C.; Hoekman, S.K.: "Fuel Composition Effects on Heavy-Duty Diesel Par­ ticulate Emissions", SAE Paper 841364. Amano, M.; Sami, H.; Nakogawa, S.: Yoshizaki, H.: "Approaches to Low Emission Levels for Light-Duty Diesel Vehicles". SAE Paper 760211.

4.9

Gasoline Engine Camshaft Wear: The Culprit is Blow-By

J. A. McGeehan and E. S. Yamaguchi Chevron Research Company, Richmond, USA

4.9.1

Abstract

We were able to identify engine blow-by as a primary factor affecting cam­ shaft wear in gasoline engines. Using a 2.3-liter overhead-camshaft engine, we isolated the valve-train oil from the crankcase oil and its blow-by using a separated oil sump. We find that: -

w ith engine blow-by, the camshaft wear was high. w itho ut blow-by, the camshaft wear was low. w ith blow-by piped into the isolated camshaft sump, the wear was high again.

Later studies identified nitric acid as a primary cause o f camshaft wear. It is derived from nitrogen oxides reacting w ith water in the blow-by. But even in the presence of blow-by, camshaft wear can be controlled by the proper se­ lection o f zinc dithiophosphates (ZnDTP) and detergent type.

4.9.2

Introduction

Today's multi-valve gasoline engines rely on tw o or four overhead camshafts for their high performance and fuel economy. One o f the keys to their success is camshaft wear control. But what are the causes o f camshaft wear? An overhead camshaft design allowed us to study the effects o f engine blow ­ by on wear. Simply by isolating the valve-train oil from the crankcase oil and its blow-by, using a separated sump, we could run a fire engine w ith or w ith ­ out blow-by entering the valve-train area. Operating w ith this configuration, we found that: 1. Blow-by affects camshaft wear and ZnDTP structural changes - for example, in its depletion rates. 2. N itric acid is a primary cause of this wear. It is derived from the nitrogen oxides reacting w ith water in the blow-by. 3. The key to low wear — in the presence o f blow-by — is the proper selection of ZnDTP and detergent type. Phosphorus, zinc, and sulfur from the ZnDTP 553

must adsorb, react, and remain as an intact film on the wear surface, in spite of the continuous production o f nitric acid. These findings were derived from a sequence o f tests using a 2.3-liter overheadcamshaft engine, operating at Sequence V-D conditions. This paper is organized in the sequence o f test events which led us to the final conclusions shown above.

4.9.3

Blow by Caused Engine Deposits in Gasoline-Engines

We began this study because o f the lack o f correlation between bench test and engine test results on camshaft wear. We already knew that blow-by was a critical element in deposit form ation. As early as 1932, researchers identified nitric acid and "nitro-hydrocarbons'' in used engine oils, and associated them w ith resin form ation (1 -3 ).* However, Diamond et al. (4), could not produce varnish deposits by intro ­ ducing nitrogen dioxide into a non-fueled, motored engine. Later, Spindt et al. (5), pin-pointed the fact that deposits are caused by the reactions between oxides o f nitrogen and unsaturated fuel constituents. They also found that high nitrogen content resulting from lean combustion mixtures, combined w ith low operating temperatures, caused major varnish deposits. Spindt and Wolf (6) and D im itro ff et al. (7) provided evidence that related engine varnish to certain types o f fuel constituents or their combinations, specifically diolefins, heavy aromafics, and certain naphtenes. Rogers et al. found that low temperature sludge was derived almost exclusively from fuel degradation products. These products arrive in the crankcase lubri­ cant mainly as low molecular weight oil solubles, which then undergo further reactions and are converted into an oil-insoluble form . Rogers also showed that the idling period was significant in increasing sludge deposits (8). Following this research, Quillian et al. (9) demonstrated that varnish and sludge deposits could be significantly reduced by diverting the blow-by from the crankcase oil. Vineyard and Coran (10) also used blow-by diversion to collect the liquid products of blow-by, and to implicate these materials as deposit precursors. Their analysis showed that a^-nitro-nitrates were present in the blow-by. D im itro ff et al. (11) measured NOx (NO, N 0 2) in the blow-by and found that its level was dependent on spark-timing. As a result of this earlier research, later ASTM tests fo r sludge and varnish deposits — VB, VC, V-D, and VE — have operated w ith high blow-by rates, high NOx conditions, low coolant temperatures, and idling cycle, and fuels prone to deposit form ation (12—14).

*

Numbers In parentheses designate reference at end of paper.

554

4.9.4

Diverting the Blow-by from the Camshaft

The Sequence V-D test introduced in 1980 used a 2.3-liter single overheadcamshaft engine (see Figure 4.9.1). In this test, the blow-by rises through the oil drain holes in the cylinder head and exits out the rear end of the rocker cover. The blow-by then passed through an external heat exchanger — main­ tained at engine coolant temperature — and finally exits through the positive crankcase pressure valve (PCV). This valve regulates the amount of blow-by being drawn from the crankcase to the vacuum side of the inlet manifold.

Figure 4.9.1:

Sequence V-D Overhead Camshaft Engine. Camshaft and Cam Follower

This engine configuration made it easy to divert the engine blow-by from the camshaft. Camshaft oil was isolated from crankcase oil by a few simple modi­ fications: 1. Blocking o ff the normal oil drain holes in the cylinder head w ith tapered, threaded plugs, and providing alternative drain holes at the side of the cylin­ der head. Unblocked oil drain holes normally allow blow-by to rise through the valve-train area. 555

2. Blocking o ff the normal oil supply gallery to the camshaft from the crank­ case oil pump w ith a Lee plug and substituting an external oil pump to supply the oil gallery in the cylinder head. 3. Providing a separate external oil sump and pump fo r the valve train. With these changes, we could maintain the valve train oil at normal V-D test temperatures. The combination of frictional heating and cylinder deck heating raised the oil temperature, but we could use a heat exchanger to cool and re­ gulate it (see Figure 4.9.2 and Table 4.9.1). When using the separated oil sump, we could pipe the blow-by from the side o f the crankcase to the fro n t o f the rocker cover. Entering at this location, the blow-by travels the full length o f the valve-train assembly before it exits through the cooling heat exchanger (see Figure 4.9.3).

Follower

Oil Drainage Can Oil Inlet Can ■Oil Outlet Plugged Crankcase Oil Supply Plug to Prevent Blow-By Entering the Head

Figure 4.9.2:

556

Valve-Train and Crankcase Oil Separated in 2.3 L Engine

(Ji CJl -j

750

III

192 Hours

120 (49)

155 (68)

135 (57)

°F (°C)

Camshaft Wear Limits: Average: 0.0010 I nches (0.0254 mm) Maximum: 0.0025 Inches (0.0635 mm)

Test Length:

33.5 (25)

2500

II

1.0 (0.75)

33.5 (25)

2500

1

bhp (kW)

rpm

H jO Out.

120 (49)

187 (86)

1 7 5 (7 9 )

°F (°C)

Oil Gallery,

Temperature

-

1.14

Inlet Air Hum idity, %

-

-

1.8-1.4

Blow-by, cfm

155 (68)

135 (57)

°F (°C)

Temperature.

Blow-by Condenser

Piston Ring End Gaps Increased to 0.051 Inches (1.295 mm)

No Follower Limits

80 (27)

80 (27)

80 (27)

°F (°C)

Inlet Air,

V-D Operating Conditions — Basic Inform ation

Cycle

Table 4.9.1:

46

46

10

°B TD C

Spark Timing,

Blow -By Inlet Separated Oil S Tests O n ly

Cam shaft

Baffle

Figure 4.9.3:

4.9.5

Blow-by Inlet and Outlet in Separated Oil Sump System

Low Wear with no Blow-by

In our earlier research we developed a form ulation which consistently pro­ duced high wear in a normal V-D engine configuration. This oil contained primary ZnDTP at a 0.05 % phosphorus level, in an all-calcium detergent pack­ age. Its sulfated ash was 0.76 %, and its viscosity grade was 10W-30 (we refer to this as Formulation A). Using this oil in these tests, we found that: 1. With blow-by in the normal V-D engine configuration, valve-train wear was high in two separate tests. 2. W ithout blow-by in the separated-oil-sump configuration, valve-train wear was low in tw o separate tests. 3. With blow-by piped in to the separated-oil-sump, valve-train wear was high again (see Figures 4.9.4 — 4.9.6). With the blow-by piped in to the fro n t o f the rocker cover and exiting at the rear, the cam lobe wear became progressively worse toward the rear o f the engine. We assumed that increased wear at the rear was associated w ith in­ creased condensation o f the gas as it traveled from the fron t entry to the rear

558

exit. The rear lobes 7 and 8, which were not covered by the camshaft baffle* and were directly below the cooling condenser, exhibited the greatest wear (see Figure 4.9.6). Although we conducted only one test at this condition, the wear results were the same as those o f a normal V-D test w ith this oil. Cam Lobe Wear, mm (In.) 0.305 ( 0 . 012 )

F o rm u la tio n A

0.254 (0 .0 10 )

0.203 (0.008)

0.152 (0.006)

0.101

-

(0.004)

0.051 ■ (0 .002)

0.000 4 5 Cam Lobe No. Run No. 1

Figure 4.9.4:

'-«>> •! Run No. 2

Normal V-D Cam Lobe Wear

The camshaft baffle is a part added to the normal head assembly. First, the baffle pre­ vented oil normally sprayed through the camshaft feed holes from washing sludge o ff the rocker arm cover. Second, it provided an additional part to rate for varnish (14).

559

Cam Lobe Wear, mm (In.)

BBBB Run No. 1

Figure 4.9.5:

4.9.6

Formulation A

EZZZ3 Run No. 2

No Blow-by in the Valve Train. Separated Oil Sump Configuration

Search for the Wear-Causing Component in the Blow-by

Initially, we ran two experiments to find out what blow-by component causes the wear. In the first experiment, we separated the liquid and gas phases of the blow-by, and returned only the gas phase to the engine. In the second experiment, we returned only the liquid phase to the engine. First Experiment: (Only the gaseous phase returned to the engine.) It is d iffi­ cult to separate the gas phase from the liquid phase due to the small particle sizes. So we decided to try blow-by cooling followed by a series o f filtrations. Consequently, the crankcase blow-by passed sequentially through the following separators: 1. 2. 3. 4.

water-cooled heat exchanger. low speed cyclone filter. high speed cyclone filte r. Balston paper filte r, which removed particles larger than 0.6 micron and is 99 % effective. The filte r element was changed every 24 hours (see Figure 4.9.16).

560

Cam Lobe Wear, mm (In.) Formulation A 0.305(0.012) Max. - 0.244 mm A v g .-0 .1 1 7 mm 0 .2 5 4 (0 .010 )

0 .2 0 3 (0.006)

0.152 (0.006)

0 . 101 (0.004) Mai. Limit

0.051 -

(0.002)

Avg. Limit

0.000. 3

Figure 4.9.6:

4 5 Cam Lobe No.

All the Blow-by Returned to the Valve Train. Separated Oil Sump Configuration

These separators removed 14 quarts (13.2 liters) o f liquid from the blow-by in the 192-hour test. Separation was not complete, however, as evidenced by the lacquer that formed on the inside o f the clear plastic tube connecting the paper filte r to the rocker cover inlet. When only the "gas phase" was returned to the engine, the valve-train wear was low (see Figure 4.9.7). Second Experiment: (Only the liquid phase was returned to the engine.) In this experiment, too, the wear was low. First, we injected the liquid phase in­ to the separated sump at the same rate that it was extracted from the blow ­ by — 60 m L/hr. The camshaft seized in its bearing after 48 hours at test con­ ditions, probably due to the fact there was 32 % water in the oil. However, the cam lobe wear was low. On the next test we decided to inject the liquid phase at a slower rate o f 6 m L/hr. A t this rate o f injection, the test was success­ fu lly run fo r 192 hours w ith low wear (see Figure 4.9.8 and Table 4.9.2). We achieved this result in spite o f the fact there was 2 % water in the oil at the end of the test, which is 10 times the normal water content. Neither of these tw o experiments provided the key to the failure mechanism. But, along w ith the previously completed tests, they provided important in­ form ation on ZnDTP depletion rates in the used oil. 561

Cam Lobe Wear, mm (In.)

Formulation A

Cam Lobe No.

Run No. 1

Figure 4.9.7:

E SS3 Run No. 2

Gas Phase Returned to the Valve Train. Separated Oil Sump Configuration

Cam Lobe Wear, mm (In.)

Formulation A

0.305 Max. - 0.013 mm Avg. - 0.010 mm

(0.012 L 0.254 ‘ (0.010)_

0.203 “ (0.000)

0.152 * (0.006)

0.101 " (0.004) Max. Limit 0.051(0.002) Avq. Limit o.ooo-

b

.

^

b

3

m 4

^

B

e=

B

5

Cam Lobe No.

Figure 4.9.8:

562

Liquid Phase Returned to Valve Train. Separated Oil Sump Configuration

4.9.7

Blow-by Causes ZnDTP to Deplete

It is known that the chemical structure of fresh ZnDTP changes in the engine environment. This change can be monitored by: -

Thin Layer Chromatography (TLC) Fourier Transform-Infrared Spectroscopy (FT-IR) 31 Phosphorus Nuclear-Magnetic Resonance Spectroscopy (31 P-NMR)

ZnDTP's are salts o f esters of dithiophosphoric acids. TLC indicates only the presence or absence o f the intact dithiophosphate anion. In contrast, the FT-IR indicates the changes in the P-O-C and the P=S bonds. 31 P-NMR monitors the ZnDTP conversion to other phosphorus-containing compounds. We used all three o f these techniques. Although these results agreed, the 31 PNMR was the most specific (see Appendix Table 4.9.2). 31 P-NMR allows one to look at the fate o f the ZnDTP during the engine test. The fresh or intact ZnDTP is composed o f tw o distinct phosphorus-containing species — neutral and basic — which are clearly identified in the 31 P-NMR spectrum (see Figure 4.9.15). Any changes in these two signals, or any new signals which appear in the spectrum, indicate that the ZnDTP is being converted to other P-containing compounds. Our 31 P-NMR results clearly demonstrated that only total blow-by causes complete ZnDTP depletion, while its components cause only moderate de­ pletion rates and low cam lobe wear, as summarized below: 1. ZnDTP was fu lly depleted w ithin 24 hours in the presence of total blow ­ by, and the wear was high. 2. ZnDTP remained intact — w ith no structural changes — inthe absence of blow-by, and the wear was low. 3. 65 % of the ZnDTP was depleted after 192 hours in the liquid phase o f the blow-by, and the wear was low.

presence of the

4. 60 % o f the ZnDTP was depleted after 100 hours in the presence of the gaseous phase o f the blow-by, and the wear was low. Blow-by affects both ZnDTP depletion rates and valve-train wear. We therefore analysed the composition o f the blow-by to help elucidate the mechanism of ZnDTP depletion on the resulting wear rates.

4.9.8

Analysis of the Blow-by

The gaseous phase of the blow-by was collected and analysed by high reso­ lution mass spectrometry (HRMS). The HRMS showed NOx (NO and N 0 2 ) in the sample. It also showed C 02, 0 2, and N2. 563

The condensed-liquid phase, which we collected at room temperature, con­ tained approximately 20 % hydrocarbons. Hydrocarbons in the same carbon number range as the fuel accounted fo r 90 % o f this layer, while hydrocarbons (oil) greater than CM were responsible fo r the remaining 10 %. FT-IR analysis showed organic nitrates, but no peroxides. The remainder (80 %) of the liquid phase was analysed by Dionex Ion Chro­ matograph. The identifiable anions were: (10 ppm) (310 ppm) (1300 ppm) Clearly the data shows that N 0 3—1 is the predominant ionic species and sug­ gests that it was derived from the nitrogen oxides reacting w ith water in the blow-by. The aqueous phase was very acidic (pH 2), and we attribute this acidity to n itric acid (H N 0 3).

4.9.9

Nitric Acid Causes Valve-Train Wear

From all these findings, three facts were apparent: 1. Blow-by causes high camshaft wear w ith the specific form ulation used throughout our studies. 2. Only the total blow-by causes ZnDTP to deplete w ithin 24 hours. Its com­ ponents - gas or liquid phases - showed significantly decreased depletion rates, and produced low wear. 3. The predominant anion in the condensed liquid phase o f the blow-by was n o 3- ‘ This, combined w ith the strong acidity o f the liquid phase (pH 2), led us to conclude that nitric acid (H N 0 3) had formed. This strong acid probably gives rise to the rapid change in the ZnDTP structure, and may cause the wear in­ hibitors to become inactive. Our experiment in which we injected the liquid phase only contained 2 to 9 millimoles of strong acid and caused only moderate ZnDTP depletion (see Appendix). These findings led us to the follow ing premise: that it is the con­ tinuous production o f NO^, and its reaction w ith water produced in combustion, that forms enough n itric acid to cause rapid ZnDTP depletion. Consequently, we estimated the total production of nitric acid in the blow-by during the 192-hour test. These calcuations, shown in the Appendix, suggest a total production o f 82 millimoles o f n itric acid. We actually observed 110 millimoles, based on the collection o f 14 quarts o f liquid blow-by. This small amount o f nictric acid may cause ZnDTP depletion by:

564

- Acid-catalyzed hydrolysis and/or — Non-catalyzed hydrolysis. To test our hypothesis that H N 0 3 is the harmful component in the blow-by, we vaporized solutions of n itric acid directly into the valve train and camshaft compartment of the separated-oil-sump configuration. We did one engine test w ith 10 times the 110 millimoles o f nitric acid referred to above. In this test, we observed high wear, in the range fo r this oil in a conventional Sequence V-D test (see Figure 4.9.9).

4.9.10 Wear can be Controlled in the Presence of Nitric Acid Our previous V-D wear results indicated that 0.05 % phosphorus oils can be developed to provide low wear — even in the presence o f blow-by. These results showed that either magnesium or calcium detergents can be used in a low wear form ulation provided the right type o f ZnDTP and detergent is selected (15) (see Figure 4.9.10). With calcium detergent low wear was achieved w ith either secondary or m ix t­ ures of secondary and primary ZnDTP's. In contrast, w ith magnesium deter­ gent, low wear was achieved w ith primary ZnDTP. ZnD TP Typa 0.05% P

J Datargant

Secondary

Calcium

Secondary

Calcium

Primary

Calcium

Primary

Magnaalum

Primary

Calcium

Primary

Magnaalum

Primary

Calcium

Prlmary/Sacondary

Calcium

Primary/Sacondary

Calcium

Cam Lob* Waar, tnehaa « 10"* 0

1

2

3

4

i

5

(

7

8

1----1---- r-

1

1

0

Avg. Waar Max. Waar

T77A

m

0.0254 0.0635

Figure 4.9.10: Sequence V-D Study at 0.05 % P in 0.76 % Ash Formulation. Effect o f Detergents and ZnDTP Types on Wear (15)

565

Figure 4.9.9 and 4.9.11:

3

6

(04)04)

(0.008)

(0.008)

0.254 (0.010)

Avg lanit

3

i . i n . :. 4 S Cam Lobe No.

i x

i.

Cam Lobe Wear, mm (In.) 0.305 Max. • 0.025 mm Awg. *0.018 mm ( 0 . 012)

n

n

.

Formulation B

N itric Acid (10 x 110 Millimoles) Returned to Valve Train. Separated Oil Sump Configuration

4 5 Cam Lobe No.

Formulation A

m

Cam Lobe Wear, mm (In.)

i

566

567

BkmA*f

1 • Normal V-0 Formula A 2 - No Separate Sump Formula A

3

v .v .W

Maximum

iWySiM Mirwrxjm

4

3 * Bbw-by Ratumad Separata Sump Formula A 4 - Gas Phasa Saparala Sump Formula A 5 - Liquid Phasa Separata Sump Formula A

Figure 4.9.12: Summary o f A ll Engine Test Results

0.000

( 0 .002 )

0.051

(0.004)

0.101

0.152 (0.006)

0.203 ■ (0.008)

0.254 (0.010)

(0 .012)

0.305

Cam Lobe Wear, mm (In.)

5

^8888888

8 - 1 0 x IIO M iBm olesH N O j Formula A 7 -1 0 x 110 MiKmoles HNO 3 Formula B

So we selected a low wear form ulation from this matrix and tested it, again using 10 times the 110 millimoles of nitric acid observed in the blow-by. This oil (Formulation B) contained magnesium detergent w ith primary ZnDTP, equal TBN, ash, and viscosity to Formulation A. We observed low valve-train wear comparable to the levels fo r this oil in a conventional Sequence V-D test (see Figures 4.9.11 and 4.9.12). We therefore concluded that the H NOj is definitely the harmful component in the blow-by.

4.9.11 Wear Film Analysed with and without Blow-by The key to low wear in the presence o f blow-by is the proper selection of ZnDTP type. Our previous research in the V-D test indicated that sulfur, zinc, and phosphorus from the ZnDTP must be adsorbed on the camshaft and fo l­ lower to provide a protective wear film. To confirm these previous findings, we used ESCA (Electron Spectroscopy fo r Chemical Analysis) and depth profiling on the surfaces of the followers. In our tests w ith no blow-by, gas phase only, and liquid phase only which pro­ duced low wear films, we found phosphorus in the oxidation state present in the original ZnDTP, sulfur as sulfide, and zinc. In contrast, w ith the blow ­ by piped back to the valve train, there was no sulfur as sulfide and almost no phosphorus. Zinc, however, was present. This agrees w ith normal engine test results which show that low wear films contain phosphorus, sulfur, and zinc, and high wear films lack phosphorus and sulfur (see Figures 4.9.13 and 4.9.17).

4.9.12 Metallurgical Analysis Our previous research (15) also indicated that if a protective wear film is fo r­ med, it w ill protect the integrity o f the camshaft and the follower and provide low wear. We also confirmed these findings in this study. In all the low wear tests, a film containing phosphorus, sulfur, and zinc was present on the surfaces. In these tests the camshaft and its followers were completely intact, exhibiting very low wear. In the high wear test, abrasive wear and scuffing was evident on the followers; and the camshaft subsurface was plastically deformed, w ith fractured carbides at the surface o f the cam lobes (see Figures 4.9.14 and 4.9.18). West et al. postulated that wear in the V-D test is corrosive (16). Analysis of our high wear parts at the end of the test indicates an abrasive wear mecha­ nism. Lack of the proper wear films probably results in a two-body abrasion. We suggest that n itric acid caused corrosion of the cast iron — martensitic m atrix — allowing the unreactive iron carbides to fall out of, or abrade, the follower surface.

568

*

3

Figure 4.9.13

Zn(*2)

1 -.Original Surface 2 -.-2 5 A

Zn(+2)

hxlEL

-1-

3-.40+0.8) - loglog

(j>iqo +0.8)]/0.07616

T M = T O +7400[PVz/ (a -b )]0-, l [X s/ ( 1 ^ . X Ca)] The calculated film thickness, hmjn, for the full-scale tractor planetary gears was 0.008/im for the second (slower speed) stage of the test. The lambda ratio, X = h/Ra, for these gears is very low ( exceeds 1.0. Under these conditions the force required to initiate m otion is larger than that required to maintain sliding. As increasing force is applied to the movable element it eventually overcomes the static coefficient o f friction and begins to move. The acceleration is then opposed by the spring force of the mechanism as well as by friction and viscosity o f the lubricant. These decelerating forces cause the velocity to drop, the friction increases and the movable element again stops. This continual acceleration-deceleration is the source o f stick-slip vibration (7). The stick-slip phenomenon has been modelled mathematically by Friesen (6) w ith the same general conclusion, that is: a sufficiently negative slope of the friction-velocity curve leads to self-excited vibration. This relationship is shown in Figure 6.4.1.

732

Figure 6.4.1:

Velocity (V) — Friction versus Sliding Speed

A phenomenon closely related to stick-slip is dynamic frictional vibration. The fundamental difference between the tw o phenomena is that dynamic frictional vibration results from velocity pulsation w ith o u t actual sticking. If in a decelerating system, friction coefficient is increasing w ith decreasing speed, -6#x/6V (Figure 6.4.1), a self energizing condition exists which ampli­ fies the vibration (7). Clutch systems used in automatic transmissions are susceptible to both types of phenomena, stick-slip and dynamic frictional vibration. However, tru ly continuously slipping clutches, such as those employed in some torque con­ verters and differentials, would only be vulnerable to dynamic frictional vi­ bration (8). Whether a system experiences stick-slip conditions or dynamic frictional vibration depends on the relative sliding rates and system elasticity or spring constant. Many different types o f apparatuses have been constructed to investigate these phenomena. Early investigations o f stick-slip behavior were conducted using a modified m illing machine slideway. Steel surfaces o f various finishes could be moved relative to each other in the presence of various lubricants. Coeffi­ cient of friction could then be determined under different sliding speeds and applied loads. Stick-slip behavior showed up as vibration in this type o f system (3). In the late 1950s the emphasis changed from evaluating steel-on-steel friction behavior to looking at the frictional characteristics o f paper or asbestos based clutch linings running against steel plates. Several different apparatuses appeared and were used to evaluate the low speed frictional characteristics of these clutch systems. A modified four ball wear tester was used to measure coefficient of friction at low speeds. The standard specimen cup was replaced by a chamber supported by an air bearing to provide free rotation. A modified spindle, capable of rotating 0.75 inch diameter clutch segments, was fitted to the machine arbor. The system could be loaded by adding dead weights. Tempe­ rature was controlled by the cup heater and frictional torque measured by a strain gauge arrangement on the cup (7). About 1960, General Motors reported the construction of an appratus designed specifically for the measurement of 733

friction at low sliding speeds under a wide variety o f conditions. This Low Velocity Friction Apparatus (LV FA ) was capable o f measuring frictional proper­ ties o f lubricants using a small annulus o f clutch material. Speed, load and temperature could be varied over a wide range to simulate field operating con­ ditions (9). This apparatus continues in wide use today. A number o f appara­ tuses similar to the General Motors LV F A but on a much larger scale have been constructed fo r measuring low speed friction performance on full size clutch plates (10,11), and even the use o f an entire tractor is reported (6).

6.4.2

Background

The most critical aspect of performance in clutch systems operating at very low sliding speeds is elimination o f shudder caused by stick-slip and dynamic frictional vibration. Figure 6.4.2 shows three friction coefficients (ju) versus velocity curves. Curve 1 ist that observed for a typical lubricant base oil. As speed is decreased friction coefficient remains constant to a certain point and then increases rapidly. In this area of large —5/i/6V shuddering w ill occur. Curve 2 is representative o f a friction modified oil. In this case, as velocity de­ creases so does friction coefficient (a positive 6 ji/6 V ). This system should be free o f shuddering on deceleration. Curve 3 shows a poorly friction modified flu id . Although the performance of this fluid could be generally acceptable, shuddering would occur in the region designated " a " if the clutch system were to operate in or pass through this region. A number of authors have correlated —6 /i/6 V w ith shudder or squawk in actual clutch operation (4, 5, 6 ,9 ,1 1 ).

Figure 6.4.2:

Friction versus Sliding Speed

For the optimum performance and control o f a continuously slipping clutch device, the frictional performance o f the system, frictio n material, mating steel surface, and lubricant must be as constant as possible over a wide range o f operating conditions. Many factors determine the frictional performance 734

400

400

7.1

8.1

7.9

7.6

A

B

C

D

E

300

350

300

8.3

Fluid

cP

cSt

@0°C,

Viscosities

Fluids studied

KV100,

Table 6.4.1:

26,000

41,000

41,500

39,500

37,000

cP

40°C,

0

205

54

275

277

B

10

210

20

590

920

Zn

310

290

180

580

540

P

3,100

4,900

4,200

3,400

2,600

S

0

0

820

0

2,740

Ca

Elements, ppm

50

100

10

0

30

Mg

0

0

0

0

1,990

Ba

120

700

900

100

1,100

N

o f a clutch system; selection o f clutch lining material, the type and finish o f the steel surface against which the clutch runs and the lubricant are all cri­ tical. Ideally, once a clutch system and lubricant are chosen, friction coeffi­ cient would not vary significantly w ith applied load, temperature or sliding velocity. It is the combined goal o f clutch manufacturers and lubricant fo r­ mulators to achieve this type o f performance.

6.4.3

Experimental Results

A ll experimental results reported were obtained on a Low Velocity Friction Apparatus similar to that described by General Motors (9). The specimen cup was modified so that evaporated liquid nitrogen could be passed through it to extend the range o f operating temperatures significantly below ambient. A numer o f combinations o f friction materials, fluids, and mating steel sur­ faces have been studied under a wide range o f loads, speeds and temperatures to assess the friction properties o f the systems and look fo r conditions under which clutch induced shuddering could occur. Table 6.4.1 lists the fluids in­ cluded in this study. Fluids are characterized by their viscometrics and ele­ mental analysis. A ll o f the fluids w ith the exception o f the ‘ Experimental Fluid* are commercially available automatic transmission fluids. Table 6.4.2 lists the friction materials used in the work and gives a brief description of their properties. A ll of the friction materials are currently used in automatic transmissions. Unless otherwise noted all results were obtained by the standard procedure described in Appendix 1. Dynamic friction as used in this discussion is measured at a sliding speed of 100 ft/m in . Static friction is the value observed just as the system comes to rest, i. e. at zero sliding speed. Table 6.4.2:

Clutch Friction Materials*

Material

Clutch Type

M aterial** Density

Particles**

Resin** Content

CFM-1 CFM-2 CFM-3 CFM-4 CFM-5 CFM-6 CFM-7

Lock-Up Band Plate Plate Plate Plate Plate

High Low Low Medium Low Medium Low

Resin None None Resin None Graphite Graphite

High Medium Medium High Moderate High Moderate

* **

736

A ll Materials are Cellulose Based Determined by Optical Microscopy

10

0.08

0.10

0.12

0.14

40

50

60

70

Sliding Speed, ft /min

30

80

Effect o f Steel Mating Surface Fluid A, CFM-3 Friction Material

20

J 4 9 *C

0.16

• o re

1 34*C

1--- 1--- 1--- 1--- 1--- 1--- 1--- r

SAE 1035 STEEL

0.18

0

i

0.20

0.22

0.24

0.26

Figure 6.4.3:

Coefficient of Friction

Sliding Speed, fl/mln

SAE 1010 STEEL

•^1

8

%

10

0.10

0.16

o

0.12

O

Figure 6.4.4:

0.08

0.10

0.14

%

13

93*C

0.20

40

50

60

70

Sliding Speed, fl/min

30

Effect o f Steel Mating Surface Fluid A, CFM-1 F riction Material

20

149"C

34*C

I 022

0

SAE 1035 STEEL

80

1-------1-------1------- 1------- 1------- 1-------1-------r

? u.

0.24

0.26

90

100 0

10

20

40

50

60

70 Sliding Speed. Il/min

30

80

SAE 1010 STEEL

90

100

6.4.4

Effect of Mating Steel Surface

The hardness and surface finish o f the mating steel surface can greatly affect the overall frictional characteristics of a clutch system. Figures 6.4.3 and 6.4.4 show the different friction response achieved when running Fluid A against two steels o f different hardness and surface finish w ith tw o different paper based lining materials. The two steels are typical o f those used in clutch sy­ stems today. The steels referred to as SAE 1035 are generated from a medium carbon steel o f Rockwell hardness 24, tumbled to a 10-15 microinch A A (arith­ metic average) surface finish. This process produces a hard smooth steel sur­ face. The steels referred to as SAE 1010 are generated from a low carbon steel of Rockwell hardness 8, lapped to a 40 microinch A A surface finish. In con­ trast to the SAE 1035 steel described above, this process produces a soft rough steel mating surface. Both systems were run-in fo r 16 hours under a load of 127 psi at room temperature and a sliding speed o f 50 ft/m in . The friction characteristics of the systems were then evaluated. Both friction materials per­ formed quite well w ith the SAE 1035 steel, giving somewhat similar results. The CFM-1 friction material gave lower friction coefficients at 34°C than the CFM-3 material and also showed an area o f potential shuddering at sliding speeds from 10 to 70 ft/m in at 34°C. With the SAE 1010 steel, quite different results were observed w ith the tw o friction materials. The CFM-1 material gave reasonable results w ith the possible exception o f 34°C where again, poten­ tial fo r shuddering existed. The CFM-3 material, which is softer and less dense than the CFM-1 material, was totally consumed during the break-in process. The softer lining material was badly abraded by the rougher steel surface and subsequently gave the very poor curves shown. This example highlights the criticalness of matching the friction material to the steel mating surface to achieve good operation over a range o f temperatures and to yield a system w ith good long term durability.

6.4.5

Effect of Friction Material

To illustrate the different frictional characteristics o f various clutch lining materials, the seven friction materials shown in Table 6.4.2 were run under standard conditions using Fluid B. The full results o f this testing are shown in Appendix 2. None of the lining materials tested produced the extremely high static friction values (0.17 to 0.25) which are sometimes observed w ith modified resin systems. Neither did they produce extremely low dynamic friction coefficients (0.07 to 0.10) which are observed w ith very dense ma­ terials of low porosity. Systems which exhibit very high static friction coeffi­ cients or very low dynamic friction coefficients are predisposed to give stickslip or dynamic frictional vibration. Table 6.4.3 shows the extremes of friction performance obtained w ith Fluid B and the seven friction materials. CFM-1, CFM-3 and CFM-4 gave the most diverse frictional behavior. CFM-1, the most dense material, gave by far the lowest dynamic friction coefficient. This is most likely due to trapping o f oil 739

between the friction material and steel surface. Since the dynamic friction coefficient was very low, the frictio n ratio was P0'*6 hi9h - 1-034.’ This high friction ratio would predict poor stick-slip performance. CFM-3, the ma­ terial o f highest porosity, gave a high dynamic friction coefficient, which in turn gave a low friction ratio This low friction ratio would predict good stick-slip performance. The third friction material, CFM-4, gave very high static and dynamic friction coefficients which in turn produced a high friction ratio. This system would also be predicted to be susceptible to stick-slip be­ havior. Figure 6.4.5 shows the friction coefficient versus sliding speed curves fo r these three friction materials. As discussed, it appears that both CFM-1 and CFM-4 would be capable o f giving stick-slip behavior at low sliding speeds when used w ith Fluid B. Table 6.4.3:

Effect o f Friction Material, Fluid B#

Friction Material

*«d‘ *

Friction Ratio

CFM-1

0.122

0.118

1.034

CFM-3

0.122

0.144

0.847

CFM-4

0.152

0.150

1.013

* **

100°C, 140 psi at 100 ft/m in

FLUID B

Sliding Speed, ft/min SAE 1035 Steel, 140 psi, 100°C Figure 6.4.5:

740

Effect o f Lining Material, Fluid B

6.4.6

Effect of Load

For optimal control, a clutch system would have a constant coefficient of friction under conditions of increasing and decreasing thrust load. This is espe­ cially true fo r continuously slipping clutch devices. To quantify this aspect of performance, model clutch systems can be run on the LV F A under a range of loads and temperatures to determine their response to these changes under actual operating conditions. The thrust load responses o f Fluids B, C, D and E were evaluated using CFM-3 run against an SAE 1035 steel disc. Thrust load was varied from 70 psi to 210 psi and friction torques recorded at 0, 40, 100 and 150 degrees C. The full results o f this testing are included in Appendix 2. Static friction coefficient was found to be quite insensitive to thrust load, but quite sensitive to temperature. The temperature sensitivity w ill be discussed in the next section. Figures 6.4.6 and 6.4.7 show the dynamic friction coefficients obtained w ith this system at 0 and 40 degrees C at a sliding speed o f 100 ft/m in . The effect of changing load was much more pronounced at lower temperatures. In each case the fluids grouped into two types, those that had increasing friction co­ efficient w ith increasing load, Fluids C and D, and those w ith decreasing friction coefficients w ith increasing load. Fluids B and E. The reason fo r these tw o different phenomena is not entirely understood; however, it does not appear to be viscosity related since all o f the fluids have quite similar viscosities at 0°C (see Table 6.4.1).


The growth o f the depositions is promoted by the self-catalytic reaction which is accelerated by the generation o f hydrogen. 2) The countermeasures are considered as follows; =* Decreasing the absolute value of the potential energy due to the inter­ action between the deposition particles and the carbon materials. =» Removing the factors to promote the self-catalytic reaction.

7.3.7

Acknowledgement

The authors wish to express their sincere appreciation to Dr. F. Hirano, Professor Emeritus o f Kyushu University, fo r his valuable advice during this investigation, and to thank the directors o f Eagle Industry Co., Ltd. for permission to publish this paper.

7.3.8 (1) (2)

(3)

792

References

Matsushima, A.: Guide to Automotive Water Pump Seals, SAE (1978) Paper No. 780404. Kiryu, K.; Fukahori, K.; Matsumoto. S.; Shimomura, T.; Hirabayashi, H.: A Status of Sealing Performance of End-Face Type Seals for Water Pumps of Automotive Engines in Japan, SAE (1988) Paper No. 880303. Kiryu, K .; Tsuchiya, K.: Yonehara, Y .; Shimomura, T.; Koga, T.: An Investigation of Deposits Formation and Sealing Surfaces o f Water Pump End Face Seals, STLE, Lubr. Eng. (1988) Vol. 45. 1, 4 9 -5 5 .

(4)

(5) (6) (7) 18)

Kiryu, K.; Tsuchiya, K.; Shimomura, T.; Yanai, T .; Okada, K.; Hirabayashi, H.: The Effect of Coolant Additives and Seal Composition on Performance o f Water Pump Seals o f Automotive Engines, SAE (1989) Paper No. 890609. Pourbaix, M.; Zoubov, N.; Muylder, J.V.: Atlas Dequilibres Electrochimiques a 25°C, Gauthier-Villars & Ceditier Paris (1963). Cubicciotti, D.: Pourbais Diagrams for Mixed Metal Oxide Chemistry of Copper in BWR Water, Corrosion (1988) Vol. 44, No. 12, 8 7 5 -8 8 0 . Devereux, O .F. & Bruyn, P.L.: Interaction of Plane Parallel Double Layers. The M it Press (1963), Cambridge, Mass. Hogg, R.; Healy, T.W.; Fuerstenau, D.W.: Trans., Faraday Soc. (1966) 62, 1638.

793 i

Index

Abrasion 422, 463 Abrasive wear 568, 661 Additive 459 Additive systems 459 Additive viscosity 216 Adhesion 264 Adhesive 406 Adhesive cracks 206 Agricultural single purpose machines 594 Alpha olefin 231 Alumina 756 Alumina ceramic 5, 27 Antagonistic effects 287 Antioxidants 149 Antiseizure function 169 Antiwear 163, 335 Antiwear file 296 Atmospheric corrosion 587 Atomic absorption spectroscopy 102 Auger electron spectroscopy (AES) 290, 409 Barium dinonylnaphthenesulfonate (B a D N ) 293 Barium thiophosphonate detergent (BaTP) 291 Batch reactor 179 Bearing oil film thickness (BOFT) 25 Bench 212 Biodegradation 631 Black sludge 492 Blow by collection 502 Blowby gases 177 Borate 263 Bore polish 517 Boundary 445 Boundary additives 163 Boundary lubrication 616 Brightstock 631 Calcium 102 Calcium carbonate 263 Calcium sulfonate detergent (CaSF) 290 Camshaft baffle 559 Cam-tappet endurance tests 375 Cam tappet wear rig 364 Capacitance 26, 365 Capacitance technique 29 Carboxylate 249 Catalyst 126 Cavitation 30 Chain length 167 Chelate complex 306 Chemiluminescence 179

794

Chemisorption 168 Chromatography 180 Cocatalyst 125 f. Coefficient 732 Coefficient of friction 445 Cohesive cracks 206 Cocking process 200 Color 726 Compatibility 287 Compression 10 Compression strokes 10, 13 Concentration 167 Configuration 167 Correlation coefficients 16 f., 34 Corrosion 586 Corrosion and rust inhibitors 149 Corrosion Inhibitor 151, 589 Corrosion protection 308 Crankshaft B p e e d 15 Cyclanic 49 Decomposition mode 264 Degradation 177 Delamination 406 Deposit build-up 200 Deposit formation 177, 502 Deposition of sludge 242 Deposit precursor 502 Depressant 152 Detergents 149, 151 Differential Scanning Calorimeter (DSC) 253 Dilution oil 384 DI package 383 Direct insertion probe (DIP) method­ ology 116 Dispersancy 242 Dispersant 149, 151 Double decomposition 338 Dowson and Higginson formula 664 DPPH 247 Ductile film 200 Dynamic vibration 732 Eddy current 26 EHD 406 Elaatohydrodynamic lubrication 445 Electronic structure 759 Elongation changes 775 Encapsulation 200 Energy-Dispersive-Xray Analysis (EDAY-9100) 409 Engine tests 212 Environment 336 Equations 383 Ertel and Grubin's formula 715

Ester 616 Evaporation 202 Exhaust 10, 12, 607 Exhaust particulate 608 ExhauBt pipes 542 Exhaust stroke 13 Exhaust valve stems 516 Extraneous friction 471 Extreme pressure (EP) additives 163 Extreme-pressure (EP) properties 335 Fade Test 652 Fatigue corrosion pits 422 Fatigue crack 416 Fatigue strength 278 Field desorption-mass spectrometry (FD-MS) 116 Film thickness 664 Firing stroke 10, 13 Fluid film rupture 413 Foam control 720 Foam inhibitor 149, 152 Formation of thick films 287 Four-ball machine 311 Four ball machine tests 317 Four-ball test 242 Free enthalpy 315 Free radical 180 Friction 732 Friction coefficient 292, 294, 310 Friction curves 294 Friction durability 721 Friction modifiers 149, 163, 465 Friction reduction 287 Friction zone 264 FT-IR 563 Fuel saving motor oils 287 Gas chromatography-mass spectrometry (GC-MS) 116 GC 180 GDS (Glow Discharge Spectroscopy) 272 Green gears 690 Grey-staining 692 Heavy aromate 49 Heavy metals 344 High efficient liquid chromato­ graphy 48 Highly saturated Nitrile Elastomer (HSN) 765 High molecular weight polymer 40 High Speed Deceleration Test 652 High-temperature, high-shear vis­ cosity (HTHSV) 3, 455 Hot tube test 242 HPLC 180 HRMS 50, 563 HTHSV 20 Hydrocarbons (P+N) 49 Hydrocracked mineral oil 125 Hydrodynamic lubrication 700 Hydroperoxide decomposer 247 Hydrophobic film 293

Imino groups 242

Impedance 365 Induction 10, 13 Induction period 287 Induction stroke 12 f., Initial Seizure Load 320 Intergranular fracture 756 Intrinsic viscosity 384 Iodine value 772 Iodometrically 180 Ionic surfactant behaviour 214 IR, NMR 116 Kraemer equation 391 Lacouer precursors 501 Leadfree fuel 430 Leakage 779 Leaks 610 Light aromate 49 Liner wear 517 Load capacity 445 Load-carrying agent 149 Load-carrying capacity 169 Load Wear Indices 320 Locus of minima 31 Low ash additives 632 Low temperature fluidity 721 (PIBBSI) 254 LRMS 50 Zinc dithiophosphates 264 M.102E sludge test 430 Mass spectrometry 48 Matrix interference 102 MAXRD 781 Mean viscosity 388 Metallurgy 167 Metathesis 338 Micelles 242 Micro welds 635 Minimum oil film thickness (MOFT) 2

Mo compounds 694 Molecular weights of polysobutenyl groups 242 Molybdenum dithiocarbamate (MoDTC) 288 Molybdenum dithiophosphate (MoDTP) 288 Multi-channel analysis (MCA) 118 Multigrade crankcase oil 102 Multiple linear regression 66 Nitrate ion 571 Nitric acid 553 Nitrous ion 571 NMR spectrometry 48 Non-linear regression analysis NOx bubbling test 242 NOx emission 629 Nyquist 365 OCP Oil Oil Oil Oil

67

103 changes 610 corrosion 406 drain intervals 359 flow rate 445

795

Olefin chain length 126 Olefin copolymer (OCP), 6 Oligomers 231 Orbital Combustion Process 630 Organometallics 163 Oxidation inhibitor (antioxidant) 151 Oxidation stability 242 Oxidation-thermal stability 721 Panel coking test 242 Paraffinic 49 Peeling test 204 PEMSI 260 Phenates 212 PIBEA 260 PIBMBSI 257 PIBMSI 260 Piston rings 516 Planetary gears 661 Plasma spectroscopy 270 Plastic properties 285 Plowing 406 PMA 103 P-NMR 563 Polar carboxylic groups 635 Polar group 167 Polycyclic aromatic hydrocarbons (PAH) 605 Polymers 383 Polymethacrylate (PMA) 6 Position of double bond 126 Potassium triborate 263 Pour point depressant 149, 237 Protective film 299 Protective lubricanta 586 Pseudoplastic fluids 452 Radical trapper 247 Radical trapping antioxidant 186 Reaction-catalyst 125 R ear

a x le

688

Regression analyse 66 Regression equation 34 Residual mean square, RMS 17 Residual stress 209 Resistance technique 29 Reynold's equation 446 Rig test 224 Ring stick 517 RMS 20 Rubber 765 Running-in phase 408 Rust inhibitor 151 SAE Viscosity Classification J300 3, 24 Salicylates 212 SBCP 103 Scanning Electron Microscopy (SEM) 311 Scissor linkage 5 Scuffing 670 Seal compatibility 721 Sediments 612 Semiconductors 759 Shear stability 455 Shear strength 285

796

Shear stress 160 SICP 103 Side leakage 445 Silicon carbide 755 Silicon nitride 753 Silver bearingB 456 Single and multiple regression ana­ lysis 59 Single linear regresaion 66 Sludge 177 Sludge analysis 501 Sludge binders 494, S03 Sludge deposition 495 Sludge formation 493 Sludge precursora 493 Solubility 242 Sommerfeld Number, S 32, 34 Specific gravity 390 Specific viscosity 59 Speed/torque studies 8 Spin turns 652 Standard deviation 388 Stick-slip 732 Storage engine protecting oil 587 Styrene-butadiene (S-B) 6 Styrene-isoprene (S-l) 6 Sulphonates 212 sulphuric 589 Sulphurised alkyl phenols 218 Sump oil temperature 34 Surfaxe electric charge 789 Synergistic-effect 153, 287 Temperature 126, 167 Temperature moderator 7719 Temporary viscosity loss (TVL) 455 Thermal stability 242 Thermogravimetric analysis 317 Thickening tendency 59 Thin film oxygen uptake test 242 f. Time 126 TLC 563 Transition concentration regions 293 Tribochemical interaction 761 Tribological agent 149, 152 Tribometry 616 Triethoxy aluminium (TEAL) 309 Turbocharger 542 2,6-di-tert-butyl-4-methlyphenol (MPH) 186 Two stroke 616 Valve lifters 406 Varnish 502 VI improver 60 f., 102 Viscosity 59, 515 Viscosity increase 59 Viscosity index 59, 223 Viscosity index improver 60, 102, 149, 151, 149 Viscosity Loss Trapezoids (VLT) 481 Viscous grip 484 Viscous tarque signal 471 Volatility 515 Hater 588 Water vapor 753

Wear protection 721 Wear reduction 287 Wear scar 300 Weld load 320 White layer 692 Whitening 692 XHVI (Extra High VI) fluid 125 XPS 781 XPS (X-ray photon electron spectroscopy 275 X-ray Energy Dispersion Spectro­ scopy (EDX) 311

X-ray fluorescence 270 Yellow metals corrosion 721 Young's modulus 206 Zero centistoke base oil 384 Zeta-potential 789 Zinc 102 Zinc dialkyldithiophosphates 156, 167 Zinc dithiophosphates 242, 264, 553 Zinc free 459 Zirconia 756

797

The Authors

Section 1.1 T.W. Bates Shell Research Ltd., Chester, Great Britain M.A. Vickars Esso Research Centre, Abingdon, Great Britain

Section 2.5 R.L. Shubkin and M.E. Kerkemeyer Ethyl Corporation Baton Rouge, USA D.K. Walters and J.V. Bullen Ethyl Petroleum Additives Ltd. Bracknell, Great Britain

Section 1.2 J.A. Spearot General Motors Research Laboratories Warren, USA

Section 3.1 C. Kajdas Technical University at Radom, Poland

Section 2.1 P. Daucik, T. Jakubik, N. Pronayova and B. Zuzi Slovak Technical University Bratislava, Czechoslovakia

Section 3.2 S. Korcek and M.D. Johnson Ford Motor Company Dearborn, USA

Section 2.2 H.H. Abou el Naga and S.A. Bendary MISR Petroleum Co. Cairo, Egypt Section 2.3 H.H. Abou el Naga, M.M. Mohamed and M.F. el Meneir Research Centre, MISR Petroleum Co. Cairo, Egypt Section 2.4 K. Rollins, M. Taylor, J.H. Scrivens and A. Robertson ICI Wilton Materials Research Centre W ilton Middlesborough, Great Britain H. Major VG Analytical Ltd. Whythenshane, Great Britain

798

Section 3.3 J.M. Georges, J.L. Loubet, N. Alberola and G. Meille Ecole Centralede Lyon, France H. Bourgognon, P. Hoornaert and G. Chapelet Centre de Recherche Elf Solaize Saint-Symphorien d'Ozon, France Section 3.4 S.P. O'Connor BP Chemicals Hull, Great Britain J. Crawford Adibis, Redhill, Great Britain C. Cane Adibis, Hull, Great Britain Section 3.5 G. Deak, L. Bartha and J. Proder Veszprem University of Chemical Engineering, Hungary

Section 3.6 K. Endo and K. Inoue Nippon Oil Company Ltd. Yokohama, Japan Section 3.7 L. Bartha and J. Hancsok Veszprem University of Chemical Engineering, Hungary E. Bobest Komarom Petroleum Refinery Komarom, Hungary Section 3.8 M.F. Morizur and 0 . Teysset Institut Francais du P6trole Rueil-Malmaison, France Section 3.9 D. Wei, H. Song and R. Wang Research Institute o f Petroleum Processing Beijing, P.R. China Section 3.10 J. Dong, G. Chen and F. Luo Institute o f Logistics Engineering Chongquing, P.R. China Section 3.11 G.S. Cholakov, K.G. Stanulov and I.A. Cheriisky Higher Institute o f Chemical Technology Sofia, Bulgaria T. Antonov Petrochemical Combine Pleven, Bulgaria Section 3.12 M. Born, J.C. Hipeaux, P. Marchand and G. Parc Institut Francais du Petrole Rueil-Malmaison, France

Section 3.13 G. Monteil, A.M. Merillon and J. Lonchampt Peugeot S.A. Voujeaucour, France C. Roques-Carmes ENSMM Besancon, France Section 3.14 H. Bourgognon and C. Rodes Centre de Recherche Elf Solaize Lyon, France C. Neveu and F. Huby Rohm & Haas European Operations Paris, France Section 3.15 Y. de Vita, I.C. Grigorescu and G.J. Lizardo Intevep S.A. Caracas, Venezuela Section 4.1 A. Quilley Adibis BP Chemicals (Additives) Ltd. Redhill, Great Britain Section 4.2 Part I + Part 11 S.L. A ly, M.O.A. Mokhtar, Z.S. Safar, A.M. Abdel-Magid, M.A. Radwan and M.S. Khader Cairo University Cairo, Egypt Section 4.3 J.R. Nanda, G.K. Sharma, R.B. Koganti and P.K. Mukhopadhyay Indian Oil Corporation Ltd. Faridabad, India R.M. Sundaram Ministry of Railways Lucknow, India

799

Section 4.4 T.W. Selby Savant Inc. Midland, USA T.J. Tolton Dow Corporation Freeland, USA

Section 4.12 D. Moura and J.-P. Legeron Cofran Research Sari La Rochelle, France Section 4.13 D. Kenbeek and G. van der Waal Unichema International Gouda, The Netherlands

Section 4.5 C.D. Neveu Rohm & Haas European Operations Paris, France W. Bottcher Rohm GmbH Chemische Fabrik Darmstadt, Germany

Section 5.1 D.J. Neadle Small man Lubricants Ltd. West Bromwich, Great Britain

Section 4.6 P.G. Carress Adibis — BP Chemicals (Additives) Ltd. Redhill, Great Britain

Section 5.2 B.M. O'Connor The Lubrizol Corporation W ickliffe, USA H. Winter Technical University Munich Munich, Germany

Section 4.7 D.C. Roberts Esso Petroleum Co. Ltd. Abingdon, Great Britain Section 4.8 P. T ritthart, F. Ruhri and W. Cartellieri A V L-List Ges.m.b.H. Graz, Austria Section 4.9 J.A. McGeehan and E.S. Yamaguchi Chevron Research Company Richmond, USA Section 4.10 A. Zakar Hungarian Hydrocarbon Institute Szazhalombatta, Hungary G. Borsa Danube Refinery Szazhalombatta, Hungary Section 4.11 P. van Donkelaar Greentech Research sprl Essen, Belgium 800

Section 6.1 S. Watanabe and H. Ohashi Tonen K.K. Corporate Saitama, Japan Section 6.2 G. Venizelos and G. Lassau Conservatoire National des A rt et Metiers Paris, France P. Marchand Institut Francais du P6trole Rueil-Malmaison, France Section 6.3 A.G. Papay Ethyl Petroleum Additives Division St. Louis, USA Section 6.4 R.F. Watts and R.K. Nibert Exxon Chemical Company Linden, USA

Section 7.1 T.E. Fischer and W.M. Mullins Stevens Institute o f Technology Hoboken, USA

Section 7.3 H. Hirabayashi, K. Kiryu, K. Okada, A. Voshino and T. Koga Eagle Industry Co. Ltd. Okayama-ken, Japan

Section 7.2 M. Oyama, H. Shimoda, H. Sakakida and T. Nakagawa Nippon Zeon Co. Ltd. Tokyo, Japan

801