Materials and Technologies for a Green Environment 9815051229, 9789815051223

Table of contents :
Cover
Title
Copyright
End User License Agreement
Contents
Preface
List of Contributors
Renewable Energy Generation Using a NovelGeothermal-Solar Hybrid Power Plant UsingRORC
Energy Harvesting Through ThermoelectricGenerators
Solar Electric Vehicle Charging and GridInteraction: An Integrated Module
A Review of the Current Challenges on the Issues of Scramjet Combustion Engines
Namrata Bordoloi1, K. M. Pandey1,*, K. K. Sharma1 and Dharmendra Sapariya2
1. INTRODUCTION
1.1. Principle of Scramjet
1.2. The Need for Scramjet
1.4. Advantages and Disadvantages
2. CHALLENGES IN DESIGNING A SCRAMJET ENGINE
3. LITERATURE REVIEW
3.1. Studies Conducted Experimentally
3.2. Studies Conducted both Experimentally and Numerically
3.3. Studies Conducted Numerically
4. FUTURE SCOPE
CONCLUSION
CONSENT FOR PUBLICATION
CONFLICT OF INTEREST
ACKNOWLEDGEMENT
REFERENCES
Review of the Role of Geometrical Modification ofScramjet Combustor on PerformanceCharacteristics
Subject Index
Back Cover

Citation preview

Materials and Technologies for a Green Environment Edited by Santhanam Harikrishnan

Department of Mechanical Engineering, Kings Engineering College, Chennai, India

Materials and Technologies for a Green Environment Editor: Santhanam Harikrishnan ISBN (Online): 978-981-5051-21-6 ISBN (Print): 978-981-5051-22-3 ISBN (Paperback): 978-981-5051-23-0 © 2023, Bentham Books imprint. Published by Bentham Science Publishers Pte. Ltd. Singapore. All Rights Reserved. First published in 2023.

BSP-EB-PRO-9789815051216-TP-183-TC-05-PD-20230323

BENTHAM SCIENCE PUBLISHERS LTD.

End User License Agreement (for non-institutional, personal use) This is an agreement between you and Bentham Science Publishers Ltd. Please read this License Agreement carefully before using the book/echapter/ejournal (“Work”). Your use of the Work constitutes your agreement to the terms and conditions set forth in this License Agreement. If you do not agree to these terms and conditions then you should not use the Work. Bentham Science Publishers agrees to grant you a non-exclusive, non-transferable limited license to use the Work subject to and in accordance with the following terms and conditions. This License Agreement is for non-library, personal use only. For a library / institutional / multi user license in respect of the Work, please contact: [email protected].

Usage Rules: 1. All rights reserved: The Work is the subject of copyright and Bentham Science Publishers either owns the Work (and the copyright in it) or is licensed to distribute the Work. You shall not copy, reproduce, modify, remove, delete, augment, add to, publish, transmit, sell, resell, create derivative works from, or in any way exploit the Work or make the Work available for others to do any of the same, in any form or by any means, in whole or in part, in each case without the prior written permission of Bentham Science Publishers, unless stated otherwise in this License Agreement. 2. You may download a copy of the Work on one occasion to one personal computer (including tablet, laptop, desktop, or other such devices). You may make one back-up copy of the Work to avoid losing it. 3. The unauthorised use or distribution of copyrighted or other proprietary content is illegal and could subject you to liability for substantial money damages. You will be liable for any damage resulting from your misuse of the Work or any violation of this License Agreement, including any infringement by you of copyrights or proprietary rights.

Disclaimer: Bentham Science Publishers does not guarantee that the information in the Work is error-free, or warrant that it will meet your requirements or that access to the Work will be uninterrupted or error-free. The Work is provided "as is" without warranty of any kind, either express or implied or statutory, including, without limitation, implied warranties of merchantability and fitness for a particular purpose. The entire risk as to the results and performance of the Work is assumed by you. No responsibility is assumed by Bentham Science Publishers, its staff, editors and/or authors for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products instruction, advertisements or ideas contained in the Work.

Limitation of Liability: In no event will Bentham Science Publishers, its staff, editors and/or authors, be liable for any damages, including, without limitation, special, incidental and/or consequential damages and/or damages for lost data and/or profits arising out of (whether directly or indirectly) the use or inability to use the Work. The entire liability of Bentham Science Publishers shall be limited to the amount actually paid by you for the Work.

General: 1. Any dispute or claim arising out of or in connection with this License Agreement or the Work (including non-contractual disputes or claims) will be governed by and construed in accordance with the laws of Singapore. Each party agrees that the courts of the state of Singapore shall have exclusive jurisdiction to settle any dispute or claim arising out of or in connection with this License Agreement or the Work (including non-contractual disputes or claims). 2. Your rights under this License Agreement will automatically terminate without notice and without the

need for a court order if at any point you breach any terms of this License Agreement. In no event will any delay or failure by Bentham Science Publishers in enforcing your compliance with this License Agreement constitute a waiver of any of its rights. 3. You acknowledge that you have read this License Agreement, and agree to be bound by its terms and conditions. To the extent that any other terms and conditions presented on any website of Bentham Science Publishers conflict with, or are inconsistent with, the terms and conditions set out in this License Agreement, you acknowledge that the terms and conditions set out in this License Agreement shall prevail. Bentham Science Publishers Pte. Ltd. 80 Robinson Road #02-00 Singapore 068898 Singapore Email: [email protected]

BSP-EB-PRO-9789815051216-TP-183-TC-05-PD-20230323

CONTENTS PREFACE ................................................................................................................................................ i LIST OF CONTRIBUTORS .................................................................................................................. ii CHAPTER 1 RENEWABLE ENERGY GENERATION USING A NOVEL GEOTHERMALSOLAR HYBRID POWER PLANT USING RORC ........................................................................... K. C. Ramya, S. Sheeba Rani, S. Sivaranjani and R. Vinoth Kumar 1. INTRODUCTION ...................................................................................................................... 1.1. Renewable Energy ........................................................................................................... 2. LITERATURE SURVEY .......................................................................................................... 3. METHODOLOGY ..................................................................................................................... 4. GOVERNING EQUATIONS .................................................................................................... 4.1. Thermal Design of the Hybrid Power Plant ..................................................................... 4.2. Solar Design of the Hybrid Power Plant .......................................................................... 5. RESULTS AND DISCUSSION ................................................................................................. 5.1. Geothermal Fluid Mass Flow Rate .................................................................................. 5.2. RORC Working Fluid Mass Flow ................................................................................... 5.3. Influence of Parameters on the Condenser ...................................................................... CONCLUSION ............................................................................................................................... FUTURE SCOPE ............................................................................................................................ CONSENT FOR PUBLICATION ................................................................................................ CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. REFERENCES ............................................................................................................................... CHAPTER 2 ENERGY HARVESTING THROUGH THERMOELECTRIC GENERATORS A.D. Dhass, Ganesh Babu L., Raghuram Pradhan, G.V.K Murthy and M. Sreenivasan 1. INTRODUCTION ...................................................................................................................... 1.1. Peltier Effect .................................................................................................................... 1.2. Thomson Effect ................................................................................................................ 1.3. Figure of Merit ................................................................................................................. 2. TYPES OF THERMO ELECTRIC GENERATORS ............................................................. 2.1. Fossil Fuel Generators ..................................................................................................... 2.2. Solar Source Generators .................................................................................................. 2.3. Nuclear-fueled Generators ............................................................................................... 2.4. Semiconductor Materials for Thermoelectric Generators ................................................ 2.5. Environmental Extremes .................................................................................................. 3. WASTE HEAT RECOVERY ................................................................................................... 4. MICROGENERATION ............................................................................................................ 5. HARVESTING MICROPOWER ............................................................................................. 6. THERMO ELECTRIC GENERATORS & COOLERS ........................................................ 6.1. Thermo Electric Cooler (TEC) ........................................................................................ 6.2. Air Conditioning Systems for Vehicles ........................................................................... 7. THERMO ELECTRIC MATERIALS ..................................................................................... 7.1. Inorganic TE Materials .................................................................................................... 7.2. Organic TE Materials ....................................................................................................... 7.3. Hybrid TE Materials ........................................................................................................ 7.4. Polymers acts as TE Materials ......................................................................................... 7.5. Advanced TE Materials ................................................................................................... 7.6. Bulk Binary Semiconductors ...........................................................................................

1 2 2 8 13 15 18 19 21 21 23 25 25 27 27 27 27 27 32 32 34 34 34 35 35 35 35 36 36 38 39 42 42 42 45 46 46 46 47 48 49 49

7.7. Complex Inorganic Structures ......................................................................................... 7.8. Oxide Thermoelectrics ..................................................................................................... 7.9. Thin Film Materials ......................................................................................................... 8. OPTIMAL DESIGN ................................................................................................................... 9. HYBID THERMO ELECTRIC GENERATORS ................................................................... 9.1. Solar Powered Thermoelectric Refrigerator .................................................................... 10. ENERGY HARVESTING ....................................................................................................... 11. PERFORMANCE AND MEASUREMENT OF THERMO ELECTRIC GENERATORS 12. MICRO SCALE APPLICATIONS ......................................................................................... 13. MACRO SCALE APPLICATIONS ....................................................................................... CONCLUSION ............................................................................................................................... NOMENCLATURE ....................................................................................................................... CONSENT FOR PUBLICATION ................................................................................................ CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. REFERENCES ...............................................................................................................................

49 49 50 50 52 53 54 56 59 59 60 60 61 61 61 61

CHAPTER 3 SOLAR ELECTRIC VEHICLE CHARGING AND GRID INTERACTION: AN INTEGRATED MODULE ..................................................................................................................... 67 D. Muruganandam, J. Jayapriya, P.K. Chidambaram and B. Karthik Anand 1. INTRODUCTION ...................................................................................................................... 68 1.1. Advantages of Electric Vehicles Over ICE Vehicles ...................................................... 69 1.2. Disadvantages of Electric Vehicles over ICE Vehicles ................................................... 69 2. SOLAR POWER CHARGING ................................................................................................. 70 2.1. Energy flow & Management ............................................................................................ 72 2.2. Solar Power Grid .............................................................................................................. 74 2.3. The Power Electronics Components and their Configuration for the Solar .................... 78 2.4. Importance of Photo Voltaic Panel as an Energy Source for EVs ................................... 83 2.5. Clean Photovoltaic Energy and Battery Vehicles: Initiatives Taken by Law-making Authorities and Industry/Institutions ...................................................................................... 84 2.6. Future of Renewable Photo Voltaic Power Generation ................................................... 85 3. ELECTRIC VEHICLE SMART GRID INTEGRATION ..................................................... 86 3.1. Smart Charging for a Reliable and Resilient Grid ........................................................... 86 3.2. A Typical Sizing Methodology of ESS ........................................................................... 87 3.3. Sizing of Battery and the Converter Definition ...................................................................... 88 3.4. Number of EVs for Charging .................................................................................................. 88 3.5. Battery Charging ..................................................................................................................... 89 3.6. Commercial and Personal Vehicles ........................................................................................ 89 3.7. Charging Scenario with Respect to the Location .................................................................... 89 3.8. Charging Scenario with Respect to Timings .......................................................................... 90 3.9. Battery Capacity of Vehicles .................................................................................................. 90 3.9.1. Wireless Battery-operated Electric Vehicle Charging .................................................. 91 3.10. Smart Charging ....................................................................................................................... 93 3.11. Smart Charging Functioning ................................................................................................... 94 3.12. Load Balancing ....................................................................................................................... 94 3.13. V2G Definition ....................................................................................................................... 95 4. SECOND LIFE OF BATTERIES ...................................................................................................... 98 4.1. Retired EV Batteries: How They can be Re-used or Recycled? ............................................... 98 4.2. Opportunities for Second Life Batteries .................................................................................. 100 DISCUSSION AND CONCLUSION .................................................................................................... 101

CONSENT FOR PUBLICATION ................................................................................................ CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. REFERENCES ...............................................................................................................................

101 101 101 101

CHAPTER 4 A REVIEW OF THE CURRENT CHALLENGES ON THE ISSUES OF SCRAMJET COMBUSTION ENGINES ............................................................................................. Namrata Bordoloi, K. M. Pandey, K. K. Sharma and Dharmendra Sapariya 1. INTRODUCTION ...................................................................................................................... 1.1. Principle of Scramjet ........................................................................................................ 1.2. The Need for Scramjet ..................................................................................................... 1.3. Advantages and Disadvantages ........................................................................................ 2. CHALLENGES IN DESIGNING A SCRAMJET ENGINE .................................................. 3. LITERATURE REVIEW .......................................................................................................... 3.1. Studies Conducted Experimentally .................................................................................. 3.2. Studies Conducted both Experimentally and Numerically .............................................. 3.3. Studies Conducted Numerically ...................................................................................... 4. FUTURE SCOPE ........................................................................................................................ CONCLUSION ............................................................................................................................... CONSENT FOR PUBLICATION ................................................................................................ CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. REFERENCES ...............................................................................................................................

104 105 107 107 108 109 110 117 121 140 141 141 141 141 141

CHAPTER 5 REVIEW OF THE ROLE OF GEOMETRICAL MODIFICATION OF SCRAMJET COMBUSTOR ON PERFORMANCE CHARACTERISTICS .................................. Kumari Ambe Verma1, K. M. Pandey1,*, K.K. Sharma1 and Dhiren R. Patel2 .................... 1. INTRODUCTION ...................................................................................................................... 2. SCRAMJET GEOMETRICAL MODIFICATION ................................................................ 2.1. Combustor Geometry ....................................................................................................... 2.1.1. Combustor Wall Transverse Fuel Injection ........................................................ 2.1.2. Combustor Wall Cavity with Strut Fuel Injection ............................................... 2.2. Fuel Injector Geometrical Modifications ......................................................................... 2.2.1. Modified Strut or Multi Struts ............................................................................. 2.2.2. Flame Stabilization Analysis: Ideal Strut or altered Injection Strategy ............. 3. SCRAMJET PERFORMANCE CHARACTERISTICS ANALYSIS ................................... 3.1. Supplementary Fuel (Mixed) Implications ...................................................................... 3.2. Different Fuels ................................................................................................................. 3.3. Variable Inflow Condition ............................................................................................... 3.4. Different Computational Model ....................................................................................... SUMMARY AND CONCLUDING REMARKS ......................................................................... CONSENT FOR PUBLICATION ................................................................................................ CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. REFERENCES ...............................................................................................................................

150 150 150 151 151 152 153 155 155 158 161 161 162 163 165 169 170 170 170 170

104

SUBJECT INDEX .................................................................................................................................... 179

i

PREFACE I am pleased to introduce the book titled "Materials and Technologies for a Green Environment". It comprises five chapters, covering different subjects of energy harvesting, biofuel, electric vehicle and Scramjet. All the chapters discuss the fundamentals and the recent developments in their respective subjects. This book could be beneficial to graduates, post-graduates, and researchers as it could cater to their needs. Suggestions and comments from the readers are invited in order to improve the quality of the next edition.

Prof. Santhanam Harikrishnan Kings Engineering College Chennai India

ii

List of Contributors A.D. Dhass

Department of Mechanical Engineering, IITE, Indus University, Gujarat, India

B. Karthik Anand

Department of Mechanical Engineering, Newprince Shri Bhavani College of Engineering and Technology, Chennai, Tamil Nadu, India

D. Muruganandam

Department of Mechanical Engineering, Sri Venkateswaraa College of Technology, Tamil Nadu, India

Dharmendra Sapariya Department of Mechanical Engineering, IITE, Indus University, Ahmedabad, Gujarat, India Dhiren R. Patel

Mechanical Engineering Department, IITE, Indus University, Ahmedabad, Gujarat, India

Ganesh Babu L.

Mechatronics Engineering, Tishk International University, Erbil, Iraq

G.V.K. Murthy

Department of Electrical and Electronics Engineering, PACE Institute of Technology and Sciences, Ongole-523272, India

J. Jayapriya

Department of Mechanical Engineering, Sri Venkateswaraa College of Technology, Tamil Nadu, India

K.C. Ramya

Department of Electrical and Electronics Engineering, Sri Krishna College of Engineering and Technology, Coimbatore, India

K. M. Pandey

Department of Mechanical Engineering, National Institute of Technology, Silchar, Assam, India

K. K. Sharma

Department of Mechanical Engineering, National Institute of Technology, Silchar, Assam, India

Kumari Ambe Verma

Department of Mechanical Engineering, National Institute of Technology, Silchar, Assam, India

M. Sreenivasan

Department of Mechanical Engineering, PACE Institute of Technology and Sciences, Ongole-523272, India

Namrata Bordoloi

Department of Mechanical Engineering, National Institute of Technology Silchar, Assam, India

P.K. Chidambaram

Department of Mathematics, Sathyabama Institute of Science and Technology, Chennai, Tamil Nadu, India

Raghuram Pradhan

Department of Mechanical Engineering, PACE Institute of Technology and Sciences, Ongole-523272, India

R. Vinoth Kumar

Department of Electrical and Electronics Engineering, New Horizon College of Engineering, Bengaluru, India

S. Sivaranjani

Department of Electrical and Electronics Engineering, Sri Krishna College of Engineering and Technology, Coimbatore, India

S. Sheeba Rani

Department of Electrical and Electronics Engineering, Sri Krishna College of Engineering and Technology, Coimbatore, India

Materials and Technologies for a Green Environment, 2023, 1-31

1

CHAPTER 1

Renewable Energy Generation Using a Novel Geothermal-Solar Hybrid Power Plant Using RORC K. C. Ramya1,*, S. Sheeba Rani1, S. Sivaranjani1 and R. Vinoth Kumar2 Department of Electrical and Electronics Engineering, Sri Krishna College of Engineering and Technology, Coimbatore, India 2 Department of Electrical and Electronics Engineering, New Horizon College of Engineering, Bengaluru, India 1

Abstract: A recent survey of energy consumption indicates that there has been exponential growth in the need for renewable energy and also for curbing the growth of fossil fuel reserves. To meet this future need, renewable energy sources are being explored. In this paper, we have proposed a Recuperative Organic Rankine Cycle that operates in conjunction with air-cooled condensers. Solar energy is said to be an energy source that varies periodically, unlike geothermal energy which is available round the clock, to generate electricity continuously. Hence it is a highly recommended source to meet the growing demands for electricity globally. A major contribution to geothermal power development is the progress in Organic Rankine Cycles. These plants are best known for their ability to curb harmful gas emissions, especially that of noncondensable gases. There is a significant growth in geothermal power owing to the ORC (Organic Ranking Cycle) power units that are implemented. In this methodology, the working fluid of ORC is made to go through an evaporator where a hot turbine is used to heat the liquid. In this process, the temperature of the preheated liquid is further increased with the aid of solar energy. This heat generated thus is further converted into electricity when the turbine unit causes the expansion of the fluid. Finally, an aircooled condenser is used to condense the final exhaust of the turbine. Combining the two powerful forms of renewable energy (solar and geothermal), it is possible to generate power in such a way that the need for power begins to drop from its peak that it has achieved already. The simulated results define the decline in energy consumption of condensers based on the minimum heat transfer area of the condenser as well as the minimum power consumption of the fans.

Keywords: Duct curve, Geothermal-solar power generation, Hybrid power plant, Renewable energy, Recuperative Organic Ranking Cycle. * Corresponding author K.C. Ramya: Department of Electrical and Electronics Engineering, Sri Krishna College of Engineering and Technology, Coimbatore, India; Email: [email protected]

Santhanam Harikrishnan (Ed.) All rights reserved-© 2023 Bentham Science Publishers

2 Materials and Technologies for a Green Environment

Ramya et al.

1. INTRODUCTION 1.1. Renewable Energy As the planet becomes more populated, the demand for energy also increases subsequently at a very fast pace. In recent times, this demand for energy is met with the help of fuels based on fossil. However, the use of these carbon-based fuels resulted in air quality deterioration, increased pollution and global warming. In May 2018, a report by WHO stated that about 90% of people all over the world are breathing polluted air. Because of this, there is a need for renewable energy sources and governments across the globe are investing heavily in this aspect. The Clean Energy future is made possible through the invention of renewable energy. In the beginning, energy was highly dependent on fossil fuels. However, due to the emission of carbon and other impurities that had harmful effects on the environment, there has been much need for cleaner energy usage. The introduction of wind and solar generation was a ground breaking invention that paved the way to a better and healthier atmosphere. This was further improved by the introduction of renewable energy. Renewable energy is commonly referred to as clean energy as it is generated from natural processes or sources. Though the use of natural sources as energy is thought of to be a novel concept, we have been using them for various aspects like transportation, heating, and so on. The sun has been used since ancient times to keep us warm during the day and further to kindle fire and provide warmth during the night. Similarly, windmills have been used to grind grain and wind has been used for a long period of time to sail boats. However, during the past few centuries, the invention of many energy sources such as fracking gas and coal has led to a more polluted environment. These types of energy sources are known as non-renewable sources. These types of energy take a longer time to replenish and are available for only a limited period of time. Most non-renewable energy sources will have a harmful impact on human health and will also cause harm to the environment. Some known impacts are: drilling of oil performed using fracking might result in water pollution and cause earthquake, while a coal power plant will make the air smell foul. The following are some of the renewable energy sources that are being used by us: • Wind Energy: One of the most ancient ways of producing electricity is the use of wind as a source of energy. The turbines are built high and as the blades of the turbine turn, electricity is produced using an electric generator. It is also one of the cheapest forms of energy and accounts for about 23% of the total energy produced.

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 3

• Solar Energy: Solar energy has been used for a long period of time by us for various purposes like drying fruits, staying warm, and growing crops. Energy from the sun is used in many ways to power devices, and to warm water. Solar cells, also known as photovoltaic cells are built of a base metal plate of either steel or aluminum. These cells convert sunlight into electricity directly. • Geothermal Energy: As the radioactive particles begin to decay slowly, in rocks at the earth’s centre, they will be as hot as the surface of the sun, resulting in a natural hot spring. An underground well is dug up that acts as a hydrothermal resource, which can be used to create electricity. • Biomass Energy: Trees, waste wood, crops, carcasses of animals, and withered plants are used to make biomass. Chemical energy is liberated in the form of heat from burning biomass. This in turn can be used to generate electricity. Though this form of energy is considered to be a cleaner and greener alternative, it still produces a large amount of carbon emissions. • Hydroelectric Power: The source of hydroelectric power is water which descends rapidly from a higher end to the foot of the river. This force of water can be converted into electricity. • Ocean: Though the production of tidal energy through the waves of the ocean is currently in an experimental phase, it still remains a good option to harness power. According to energy statistics 2020, a report released by the Ministry of Statistics and Programme Implementation, Government of India, there is an abrupt increase in the use of renewable resources of energy in India. The report states that about 28.18 GW of electricity is generated using solar power, which is a 12.23% increase from the previous year. This is also reflected in decreasing the cost of solar electricity, thereby attracting more people to use the same. Estimated potential of renewable energy sources is tabulated in Table 1. Here Jammu & Kashmir, Maharashtra and Rajasthan are the states that contribute highly to using renewable energy in India. Table 1. Usage of Renewable Sources in India. State

Use of Renewable Energy

Andra Pradesh

8%

Gujarat

11%

Himachal Pradesh

3%

4 Materials and Technologies for a Green Environment

Ramya et al.

(Table 1) cont.....

State

Use of Renewable Energy

Jammu & Kashmir

10%

Karnataka

8%

Madhya Pradesh

7%

Maharashtra

10%

Odisha

3%

Rajasthan

15%

Tamil Nadu

5%

Telangana

2%

Uttar Pradesh

2%

Others

16%

A survey of the renewable energy potential across the different states of India indicates that the major source of renewable energy used is solar energy followed closely by wind power as shown in Fig. (1). However, there are many more sources of energy that are still progressing and the use of hybrid geothermal and solar energy is still in the experimentation process.

7%

25%

Small Hydro Power 42% Biomass Power 40%

Solar Wind Power Others

68%

Cogeneration Bagasse 12% Waste to Energy 6%

Waste to Energy

Fig. (1). Renewable Energy Potential.

6%

Solar energy is said to be an energy source that varies periodically unlike geothermal energy which is available round the year to generate electricity continuously. Hence it is a highly recommended source to meet the growing demand for electricity globally. Moreover, the cost of generating electricity from the geothermal resource is reasonable, making it a good choice for the production mix. Except in certain volcanic countries, the use of high enthalpy, and high-

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 5

temperature geothermal resources have been explored vastly all over the world. A major contribution to geothermal power development is the progress in Organic Rankine Cycles. These plants are best known for their ability to control harmful gas emissions, especially that of non-condensable gases. There is a significant growth in geothermal power owing to the ORC (Organic Ranking Cycle) power units that are being implemented. As the accumulation of atmospheric carbon dioxide increases, there is much need to initiate the production of electricity using non-fossil energy sources. Hence renewable and nuclear energy sources are experimented with to provide a large part of global electric power in the days to come. However, solar and wind sources which are renewable are not available on a regular continuous basis and hence will not be able to meet the demand for fluctuating electric power. Fig (2) represents the duck curves or U-shaped demand curves which indicate the imbalance in the supply and demand of electricity because of renewable energy sources’ higher penetration. When this occurs, there is a possibility for time-shift and augmentation of electric power demand to increase such that it causes an imbalance. This figure represents the power demand during a peak summer afternoon in India. The demand for electricity is currently being met by electricity sources like wind, nuclear, coal, hydro and natural gas power plants along with a small input from the solar power plant. Fig. (2). also represents the amount of electricity required when the electricity generated from solar energy contributes to 15%, 25% and 35% of the total energy. This indicates that during the day time, solar energy can be used to the maximum while energy from other sources can be minimized so that during the night when there is no solar power available, the electricity demand can be met by other sources of energy. This effect will cause a huge impact on the already existing coal and nuclear power plant units which will find it difficult to adjust their supply of electricity based on the requirement, making it almost impossible and inefficient.

6 Materials and Technologies for a Green Environment

Ramya et al.

Fig. (2). Duct Curve.

To address this duck curve issue, the optimal solution would be to take advantage of geothermal energy which is available continuously and solar energy which is available during the daytime when the demand for electric power is high. Moreover, the use of hybrid geothermal and solar power plants will prove to be an excellent method to generate high electricity to meet the peak electric demand. Recently a patent was submitted introducing a system that uses solar power during the time that it was available and further uses geothermal energy during the other time to balance the demand. However, the demand for electricity in the morning hours is not as high as at other times, and this results in duck curves. Ever since the invention of geothermal power generation, it has been experimented in hybrid combination with a number of other power plants because of the many advantages that it has to offer. Geothermal energy has a number of advantages over other types of renewable energy sources. They can operate at a lower cost when compared with other energy systems. Soil is said to have better heating capacity when compared to air which is proven by the fact that the temperature of soil that is deep inside the ground is quite low. As the temperature of the soil at a depth of 20m or more is

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 7

constant, it results in the earth being cool during summer and warm during winter. Hence in order to control the temperature of air, 3 different types of ground heat exchangers are designed. The types of configuration will vary depending on the available soil and space considerations (Fig. 3).

Fig. (3). (a) Vertical configuration (b) Horizontal configuration.

• Spiral Configuration: This type of configuration is a combination of both vertical and horizontal types for optimal thermal performance. • Horizontal Configuration: The depth of this configuration is less than 1.5 m. • Vertical Configuration: The depth of this configuration is greater than 50 m. In general, a grout material made up of a mixture of bentonite and sand or cement surrounds the ground heat exchanger. This is done in order to improve heat transfer and protect groundwater. The major reason for using geothermal energy is because of its low operating cost as well as its minimal effect on the environment in comparison to the other operating plants. This chapter is categorized into the following sections: • Section 2 gives a brief outline of all power plants and their implementation and usage since their introduction.

8 Materials and Technologies for a Green Environment

Ramya et al.

• Section 3 describes the proposed unit that uses Organic Rankine Cycle that operates in conjunction with air-cooled condensers. • The results are recorded and the comparative charts are drawn explaining the implementation of the system along with appropriate graphical support. • A conclusion is drawn and a brief suggestion for future work is also recommended. 2. LITERATURE SURVEY All energy sources have their own weaknesses. Because of this, a proper combination of renewable energy sources will go a long way in rectifying this problem and further serve to be a good source. One of the recent hybrid technologies is combining geothermal and solar energy to provide a new source of energy which is more advantageous than the two used individually. Geothermal energy is important as it is not restricted by constraints like time, season, and condition and can be used without any interruption. But, since the temperature of the liquids released is very low, it will result in decreasing the plant’s efficiency while making it a more expensive option. On the other hand, solar energy has been used by us for a very long time and is a clean and free source of energy. The drawback is the cost price at which solar energy devices are sold in the market. This has boosted the usage of energy sources like natural gas and crude oil which are available at cheaper rates. Another major drawback of using solar energy is that the sun is not always shining brightly and is greatly dependent on factors like the position in the sky, climatic changes and time. This will have a great impact on the output of energy which will change regularly. Moreover, the use of a single energy source will require high investment in constructing the plant as well as an increase in the requirement of the area. Taking these aspects into consideration, it is found that a combination of geothermal energy and solar energy will prove to be an excellent source of renewable energy in terms of efficiency and economy. Moreover, it is also possible to get rid of the disadvantages of solar and geothermal energy when they are operated separately, and also this combination can convert the heat produced by means of a thermodynamic cycle. Some of the investigations made in studies are outlined in this literature survey. A study [1] experimented with geothermal fluid by applying it to double and single evaporator configurations. He observed that there were both advantages and disadvantages while heating geothermal fluids directly. The advantage is that it resulted in reducing the heat exchangers and also increased the rate at which

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 9

steam was flowing in the solar collectors. This also decreased the cost price dramatically. However, the disadvantage is that there is high possibility that salt could not be deposited in the fluid. Hence, in another study [2], Tempesti et al. used the simulation of geothermal and solar energy simultaneously and observed their output in work production and micro heat environment. In this work, the organic fluid that is used is initially pre-heated before it is sent to the evaporator. To superheat this fluid, solar fluid is given for evaporation. Both geothermal and solar resources are available in places where water is limited. This is especially the case when the level of groundwater in a particular area is less due to excessive usage for agricultural and urban applications. This is also the major reason why air conditioners are preferred as they do not require water and take the humidity from the air. In a study [3] Greenhut analyzed the ORC configuration using geothermal energy as the source along with the combined usage of both geothermal and solar energy. It was observed that there was a noticeable improvement in the functionality of the system when a combination of the two sources is used. Similarly [4] Astolfi et al. used a hybrid stimulator to analyze the organic regenerative supercritical Rankine cycle. Here heating of the fluid is done initially at 150°C with geothermal fluid. This fluid is then sent to reheat the ORC fluid. Experimental analysis indicated that there is almost a 5% increase in the efficiency of the system. In another research work, Zhou et al. [5] studied the performance of the hybrid system with ORC in two subcritical and supercritical conditions. In fact, it was also suggested that it is possible to boost the generation of power by 19% by combining solar energy and geothermal power plant. Zhou also analyzed the price of power production [6] and found that using this methodology, cost consideration can be dramatically reduced up to 20-%. Ghasemi et al. did a survey on the hybrid plant and individual plants wherein a part of the working fluid was heated using the solar energy source along with a vaporizer [7]. It showed that the energy efficiency and output efficiency of the system increased by 3.4% and 5.5%, respectively. In a study [8], Ming et al. studied the technical and physical capacity of various technologies that are used to fight climate change by cooling the earth using longwave radiation. These technologies were used to generate power that will in turn help to produce renewable energy. Similarly in another study [9], the authors describe how vastly renewable energy has developed. However, the actual implementation of the use of renewable energy like wind and solar energies is far from reaching its full potential, around the world. This growth of renewable energy has a number of advantages, some of which are as follows:

10 Materials and Technologies for a Green Environment

Ramya et al.

• It reduces disasters caused due to fossil energy resources and also the risks. • It increases the employment of local labour. • It helps sustainable development. • It provides diversified resources of energy generation, thereby enhancing the existing system of energy production. • It improves environment and reduces the emission of harmful gases like carbon dioxide. According to the global status report [10] in 2014, the contribution of geothermal energy was very low when compared with other power generating capacities. It was observed that about one-third of the total renewable power capacity was contributed by hydropower and solar photovoltaic sources while about 17% was contributed by other renewable sources collectively (except hydropower which increased by 4% since the previous year). Geothermal energy also offers a number of advantages that surpass wind and solar systems. Some of the advantages are as follows: • It has high thermal efficiency. • Holds less ecological effect and land use. • It has more than 90% capacity and is highly stable. • Has base-load power and is not affected by weather. In a study [11], the author introduced a hybrid geothermal-solar model which was an additional arrangement with the already existing flashing unit. Based on the observations, it was noticed that it was possible to produce more power during peak hours with the help of parabolic collectors that quickened the rate of mass flow to create vapor. In another study [12, 13], the authors describe the use of geothermal energy in two ways: power generation and direct use. In a study [14], an interview was conducted with 26 persons inclusive of local government officials, inn managers, and developers. It indicated that the stagnant growth of geothermal power was mainly because of the political [15], technical [16] and financial risks [17] involved. Moreover, Evan et al. [18] surveyed all the different methods of generating renewable electricity and identified that the most sustainable source of energy is wind power followed by photovoltaic cells, hydropower and finally

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 11

geothermal [19 - 22]. Table 2 indicates the total percentage of power installed and used for various resources. Table 2. Comparison of Global resources during 2014-2019. Resource Installed Increase (TW)

Energy

Resource

% Total Power Installed

Geothermal

67

158.5

1.10

12

0.21

Hydro

15955

1.6

125

1000

17.44

Wind

1700

20.3

159

318

5.55

Photovoltaic

6500

49.9

116

139

2.42

In many countries, geothermal power generation is growing at a very slow rate and in the study by [23] Wang et al., it was recorded that during a period of 5 years from 2008 to 2013, the power generation system of geothermal, hydro, wind and photovoltaic varied in different parts of the world as seen in Table 3. About a quarter of the total global demand for energy is likely to be accounted for by India between 2020 and 2040. However, this demand may be met by coal which indicates that there will be a significant increase in carbon dioxide [24 26]. Though there is an increase in gas production in India, it is still not sufficient to meet the demands of the total energy required [27]. Hence the proposed hybrid power plant will go a long way in helping us meet the demand for power in the future. Based on the survey on the power consumption that will be required and the power generated currently, the following observations are made: • By 2040, India’s population [28 - 31] would have doubled which indicates that there will be a significant rise in the income per capita. • By 2040, the demand for energy consumption would have reached 156% of its current consumption as the population expands exponentially, resulting in India becoming one of the leading nations that demand a vast supply of energy [32]. • A 60 percent growth in the demand for primary energy will be seen within two decades in order to meet the demand resulting in a 220% increase in power generation. • There will be a steady increase in power generated through the nuclear plant accounting for 4% of the power generation [33]. • The total carbon dioxide emitted by 2040 will be twice the quantity emitted in

12 Materials and Technologies for a Green Environment

Ramya et al.

2020 resulting in an increase from 8% to 16% in the global emission analysis. • The energy produced by solar power plants will observe a rise from 30 Mtoe consumed today to 400 Mtoe in 2040. However, this renewable energy production will not be enough [34] to meet the consumer requirement. Hence a call will continue to contribute 85 percentage of power generated during 2040. • Hence as a result of this India's carbon emission rate will continue to be 60% over the global average despite it is likely to decline [35] by 30% in 2040. • Hence the total carbon dioxide emitted in 2040 in India will see an increase to 14% from its current 7% [36]. During the past few decades, a number of hybrid solar-geothermal power [37, 38] generations have been introduced with varying configurations such as the following: • Geothermal Preheating Configuration: In this model, a steam Rankine cyclebased power plant that works on thermal and solar power is examined. Here the feed water is heated using geothermal energy [39]. • Solar Preheating configuration: In this model, the brine is preheated using solar energy, thereby elevating the dryness fraction and the brine temperature [40]. • Solar superheating configuration: In this model, the working fluid is superheated using solar energy and is then sent to the geothermal power cycle. During the past few decades, a number of hybrid power systems have come into existence and each carry its own advantages and disadvantages [41, 42]. A brief summary of the different solar-geothermal power generation concepts is provided in Table 3. Table 3. Comparison of various Solar-Geothermal Power Generation Plants. Geothermal power plant and its location

Hybridization Approach and operating mode

Working fluid

Power Cycle

Temperature

Existing Models Husavic, Iceland

Working fluid superheat mode.

NH3-H2O mixture

Geothermal Kalina Cycle

125°C

Ahuachapan geothermal field, USA

Increasing the brine’s vapour by preheating the brine.

Steam

Geothermal flash plant

154°C

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 13

(Table 3) cont.....

Geothermal power plant and its location

Hybridization Approach and operating mode

Working fluid

Power Cycle

Temperature

Cerro Prieto, Mexico

Increasing the brine’s vapour by preheating the brine.

Steam

Geothermal double flash plant

300°C

USA

Brine preheat mode.

Isobutane

A subcritical geothermal binary plant.

154.5°C

7-unit dual cycle binary plant (USA)

Brine preheat, working fluid superheat mode.

Isopentance

Subcritical dual cycle geothermal binary plant.

132.2°C

Hypothetical Models Hypothetical, USA

Working fluid superheat mode

NH3-H2O mixture

Dual Temperature geothermal cycle

150°C

Hypothetical, USA

Geothermal feedwater preheating mode

Steam

Solar steam Rankine cycle

95-300°C

Hypothetical Chile

Solar energy used to reheat liquid fraction of brine and vapour fraction.

Steam

Single-flash geothermal plant

250°C

Hypothetical, Italy and USA

Working fluid superheat mode.

R-134a

Supercritical geothermal binary plant

150°C

Hypothetical, Australia

Working fluid superheat mode.

Isopentane

Subcritical geothermal binary plant

180°C

Hypothetical USA

Brine preheat mode and Working fluid superheat mode.

Supercritical geothermal flash-binary plant

Supercritical geothermal flash/binary plant

150°C

3. METHODOLOGY Fig. (4) represents the process flow diagram of the proposed hybrid geothermalsolar plant. In this methodology, the working fluid is superheated with the help of solar energy. There are two main components in the hybrid plant:

14 Materials and Technologies for a Green Environment

Ramya et al.

Fig. (4). Proposed Geothermal-Solar Power Plant.

• The solar heating system is made up of solar collectors, a solar pump and the super heater. • The geothermal ORC power cycle is built with the binary arrangement. Here the working fluid of RORC is made to go through an evaporator where hot brine is used to heat the liquid. In this process, the temperature of the preheated liquid is further increased with the aid of solar energy. This heat thus generated is further converted into electricity when the turbine unit causes the expansion of the fluid [43]. Finally, an air-cooled condenser is used to condense the final exhaust of the turbine. The table below (Table 4) gives a summary of the key parameters and the conditions in which they are used during the simulation analysis.

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 15

Table 4. Various Parameters Used. Parameters

Value

Optical efficiency of solar collectors

75%

Minimum temperature approach of the heat exchangers

10 °C

Minimum temperature of solar heat transfer fluid

390 °C

Solar heat transfer fluid

Therminol, VP-1

Design point solar irradiance

1000 W/m3

Ambient temperature range

5-44 °C

Isentropic efficiency of turbine

80%

Pump efficiency

70%

Organic working fluid

Isopentane

Production well flow rate

50 Kg/s

In order to analyse the performance of the hybrid plant, the input to the model is sent using the meteorology data gathered during the entire year on an hourly basis. 4. GOVERNING EQUATIONS The laws of energy conservation and mass should be applied to each and every component of the system in order to analyze the proposed system under thermodynamics. There are some assumptions that we need to consider before using any equation, which are as follows: • The geothermal fluid used is in a saturated liquid state. • Both the pump and turbine are adiabatic. • Both the pump and turbine - have a specific and fixed isentropic yield. • Kinetic and potential energy is ignored. • The power plant is made to operate in a steady state condition. Taking these assumptions into consideration [44], the following two equations represent energy balance and mass conservation: 𝑄 − 𝑊 = ∑ 𝑚𝑜𝑢𝑡 ℎ𝑜𝑢𝑡 − ∑ 𝑚𝑖𝑛 ℎ𝑖𝑛

(1)

16 Materials and Technologies for a Green Environment

Ramya et al.

(2)

σ ݉௢௨௧ ൌ σ ݉௜௡

Here h represents enthalpy and m represents the mass flow rate of the fluid. Similarly, W and Q represent the output work and input heat at the control volume border. The subscripts ‘out’ and ‘in’ are used to represent the out and input of the system. Fig. (5) gives the incident angle of sunlight and how the working fluid is heated in the proposed methodology.

Collector

Sunlight

Aperture

Receiver

. ○

Normal

Fig. (5). Incident Angle of sunlight.

Based on these two equations, the following components are examined in the following manner: The heat efficiency of the cycle can be represented as the following equation (3) ߟ௡ ൌ

ௐ೙೐೟ ொ೔೙

(3)

A typical ORC working in this condition will hold a net power output that is represented as follows:

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 17

ܹ௣௔ ൌ ܹ௖௢௡ ൅ ܹ௣

ܹ௡௘௧ ൌ ܳ௜௡ െ ܳ௢௨௧ ൌ ܹ௖௢௡ ൅ ܹ௣

(4)

(5)

The input heat can be determined using the following equation: ܳ௖௢௡ ൌ ݉௪௙ ሺ݄ଵ െ ݄௡ ሻ

(6)

Similarly, the efficiency of the system with respect to the work done can be expressed using the following equations: ߟ௧ ൌ

ܹ௧ ݄௡ିଶ െ ݄௡ିଵ ൌ ܹ௡ିଵǡ௧ ݄௡ିଶ െ ݄௡ିଵǡ௧

ܹ௧ ൌ ݉௪௙ ሺ݄௡ିଶ െ ݄௡ିଵ ሻ

(7) (8)

The input heat along the evaporator and recuperator is expressed as follows:

ܳ௘௩௔ ൌ ݉௪௙ ሺ݄௔ െ ݄௕ ሻ

(9) (10)

ܳ௥௘௖ ൌ ݉௪௙ ሺ݄௕ െ ݄௖ ሻ

Here the subscripts represent total power consumption in Wpa and work required in the isentropic state as Ws.p while Ws.t represents the word done by turbine output. The input heat provided to the power station can be denoted as Qin such that it is the total sum of both solar heat Qsolar as well as heat from a geothermal source,Qgeo. The geothermal source’s input energy can be represented as given below: ܳ௚௘௢ ൌ ݉௚௘௢ ሺ݄ூௐ െ ݄௣ௐ ሻ

(11)

Here hpW and hIW represent the enthalpy of geothermal fluid in the production well and injection well. Similarly, the rate of flow of mass of the geothermal fluid is represented by mgeo.

18 Materials and Technologies for a Green Environment

Ramya et al.

4.1. Thermal Design of the Hybrid Power Plant The heat that is dissipated from the air-cooled condenser [45], which is represented by Qaircooler as shown in the following equation: (12)

ܳ௔௜௥௖௢௢௟௘௥ ൌ ሺ݉௖௣ οܶሻ௔௜௥ ൌ ሺ݉௖௣ οܶሻ௪௙

Here the subscripts air and wf represent the fluid in the outdoor atmosphere and tube respectively while the change in output and input temperature is represented as ∆T. This equation can be further elaborated as: (13)

݉௔௜௥ ܿ௣௔௜௥ ‫ܶݏ‬௔௜௥ ൌ ܷ ൈ ݀‫ ܣ‬ൈ ‫ ܦܶܯܮ‬,

where m represents mass and the suffix represents the corresponding factors while LMTD denotes logarithmic mean temperature difference such that: It is observed that the overall heat transfer coefficient is U which is assumed based on the fact that the tubes’ outer surface is the only part having fins. Hence ‘U’ can be determined from the equation: ‫ ܦܶܯܮ‬ൌ

ଵ ௎

ு

ଵ

ு೔

௛೔

ൌ ቀ ್ቁ

ு

ௗೝ

ு೔

ଶ௞ೢ

൅ ቀ ್ቁ ܴ௙௜ ൅

ሺο்ಹ೚೟ ିο்಴೚೗೏ ሻ

(14)

୪୬ሺο்ಹ೚೟ ିο்಴೚೗೏ ሻ

݈݊

ௗೝ ௗ೔

ு

ோ೑೚

ு೟

ఎబ

൅ ቀ ್ቁ

ு

ଵ

ு೟

ఎబ ௛బ

൅ ቀ ್ቁ

൅ ܴ௖

(15)

where ‫ ܦܶܯܮ‬ൌ

ଵ ௎

ு

ଵ

ு೔

௛೔

ൌ ቀ ್ቁ

ு

ௗೝ

ு೔

ଶ௞ೢ

൅ ቀ ್ቁ ܴ௙௜ ൅

ሺο்ಹ೚೟ ିο்಴೚೗೏ ሻ

(14)

୪୬ሺο்ಹ೚೟ ିο்಴೚೗೏ ሻ

݈݊

ௗೝ ௗ೔

ு

ோ೑೚

ு೟

ఎబ

൅ ቀ ್ቁ

ு

ଵ

ு೟

ఎబ ௛బ

൅ ቀ ್ቁ

൅ ܴ௖

(15)

Here η0 represents the total surface efficiency while heat transfer is denoted by h0. Similarly, kw is assigned to the tube wall’s heat conduction coefficient, meanwhile the heat resistance of fouling and contact heat resistance between the wall and fins are represented by Rfo and Rc, respectively. On the other hand, the

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 19

total thermal surface, the outside of the tube without fins and the inner side of the tube are represented by Hi, Hb and Ht, respectively. In equation (14), both the diameter of the outer tube as well as that of the fins are considered to be equivalent. 4.2. Solar Design of the Hybrid Power Plant In order to determine…efficiency of the absorption (?)………………, we need to find the solar heat energy during different months, days and hours, using a parabolic trough collector. The solar energy used is represented as Qsolar and Qabs represents the total energy absorbed by the parabolic trough collector. ܳ௔௕௦ ൌ ‫ܦ‬Ǥ ߟ௔௕௦ ‫ܣ‬Ǥ ‫ן‬

(16)

Where ηabs is the efficiency of the absorption by the collector is, ∝ is the tube’s absorption and A is the collector’s area. Moreover, the direct normal irradiance is denoted using ‘D’ [46, 47]. This is nothing but the amount of solar energy that is not spread or absorbed by the atmosphere on reaching the earth’s surface. ߟ௔௕௦ ൌ ݁ଵ ݁ଶ ݁ଷ ݁ସ ݁ହ ݁଺ ߩ௖௟ ߢ߬

(17)

τ is the transmittance coefficient, ρcl is the clean mirror coefficient and e1,e2,e3,e4,e5 and e6 are the different optimal parameters. The incident angle modifier is represented by κ which can be further calculated using the formula: ߢ ൌ ܿ‫ ߠݏ݋‬൅ ͲǤͲͲͲͺͺͶߠ െ ͲǤͲͲͲͲͷ͵͸ͻߠ ଶ

(18)

In this equation, θ is the irradiance angle or the incident angle. It is the angle between the normal vector of the earth’s surface and the sun’s irradiance. Based on the position of the sun, this angle will vary accordingly with respect to collectors’ rotation [48, 49]. In order to determine this irradiance angle during any time of the day, the following equation is used: ܿ‫ ߠݏ݋‬ൌ ඥሺܿ‫ߠݏ݋‬௭ ሻଶ ൅ ሺܿ‫ߜݏ݋‬ሻଶ Ǥ ሺ‫߱݊݅ݏ‬ሻଶ

(19)

ܿ‫ߠݏ݋‬௭ ൌ ‫ߜ݊݅ݏ‬Ǥ ‫ ߮݊݅ݏ‬൅ ܿ‫ߜݏ݋‬Ǥ ܿ‫߱ݏ݋‬Ǥ ܿ‫߮ݏ݋‬

(20)

20 Materials and Technologies for a Green Environment

Ramya et al.

where φ is the collector’s latitude location δ is the declination angle ω is the hour angle and θz is the solar zenith angle (equal to 23.45°sin B) It is worth noting that the heat absorbed and used by the collector is different since a small amount of energy that is absorbed is wasted by radiation, conduction, displacement and heat transfer. Thus, the parabolic trough collector’s heat can be represented as: (21)

ܳ௟௢௦௦ ൌ ܳ௔௕௦ ൌ ܳ௨௦௘ ൌ ܳ௦௢௟௔௥

Table 5 represents the optical parameters of the solar model implemented in the proposed hybrid model. Table 5. Optical Parameters. Parameters

Value

e1

0.974

e2

0.994

e3

0.98

e5

(1+e4)/2

e4

Rfρcl

e6

0.96

ρcl

0.93

Rf

0.87

τ

0.935

α

0.95

A

100

L

100

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 21

5. RESULTS AND DISCUSSION 5.1. Geothermal Fluid Mass Flow Rate Thermodynamic analysis is made for finding out the various flow rates of geothermal fluid mass, in order to determine the performance of the proposed power plant based on geothermal fluid mass flow rate. At the strike of noon, the experimentation is observed for a period of 6 different days. Accordingly the net output power, the condensers’ consumption power and the turbine output power are recorded as shown in Fig. (6).

Fig. (6). Net output power for geothermal working fluid mass flow rate at varying weather conditions.

Fig. (6) indicates that there is a rise in the net output power when a rise in in the geothermal fluid mass flow rate is observed. However, this increase observed during the hot months of the year seems to drop due to the higher need for power consumption. It is also recorded that the power consumption of air cooled condensers and the turbines’ output also shows an increasing number directly proportional to the increase in geothermal fluid mass flow rate, because of the high ambient temperature as shown in Figs. (7 & 8).

22 Materials and Technologies for a Green Environment

Ramya et al.

Fig. (7). Condensers consumption power for geothermal working fluid mass flow rate at varying weather conditions.

Fig. (8). Turbine Output Power for geothermal working fluid mass flow rate at varying weather conditions.

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 23

5.2. RORC Working Fluid Mass Flow To further establish the effect of RORC working fluid mass flow rate, thermal analysis is made by varying the rate of flow in the proposed power plant. Observations indicate that both geothermal as well as solar sources are used to provide the RORC heat. But for both sources the conditions are maintained at a constant level indicating that the RORC evaporator also holds a constant heat value. Fig. (9) represents the condenser’s consumption power for the working fluid mass flow rate at different weather conditions.

Fig. (9). Condensers consumption power for ORC working fluid mass flow rate at varying weather conditions.

This impact can be seen in Fig. (10) where the output power of the turbine increases while the air cooled condenser power consumption begins to decrease due to the heat transfer that occurs in the RORC evaporator as a constant. This is also the reason why increasing the flow rate of RORC working fluid mass will result in a dip in the temperature which will further have an impact on the contentious inlet fluid enthalpy, for decreasing the power consumed by the

24 Materials and Technologies for a Green Environment

Ramya et al.

condenser. Moreover, it is observed that this trend continues during all the hot months with minute changes that do not have any significant impact on the overall performance.

Fig. (10). Net Power Output for ORC working fluid mass flow rate at varying weather conditions.

Fig. (11). Turbines output power for ORC working fluid mass flow rate at varying weather conditions.

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 25

On the other hand, there is a definite change observed in the output power of the turbine due to an increase in the RORC fluid mass flow ratio. It is observed that when there is an increase in ORC fluid mass flow ratio, there is also a decrease in enthalpy as shown in Fig. (11) (which is still higher than that of the increasing fluid mass flow rate). 5.3. Influence of Parameters on the Condenser The proposed work provides a clear picture of the impact of the various parameters on the condensers designed. It is also worth noticing that these parameters are used to improve the efficiency of the air cooled condenser. The parameters involved are listed in Table 6. The initial step in the thermal design takes into consideration the following parameters Table 6. Influence of Parameters.

● ● ● ● ●

Parameter

Value

Altitude of Unit

1639 m

RORC Working Fluid Mass Flow

724 kg/s

RORC Working Fluid Type

Isolutane

Input Pressure of RORC Working Fluid

546 kPa

Inlet Vapor Fraction of RORC Working Fluid

0.51

RORC Working Fluid Temperature

40.3 °C (Inlet)/ 40.5 °C (Outlet)

Inlet Air Temperature

21.8 °C

Air velocity Total tubes present in every row Number of tube rows Fin Thickness Length of the tube

Taking into consideration a number of parameters such as total heat transfer coefficient, tube side pressure drop, airside pressure drop and fan's driver, these parameters are observed under varying conditions. During this process, the heat transfer rate is maintained constant. CONCLUSION The proposed methodology studies the working model of a hybrid geothermalsolar power plant. Parabolic trough collectors are used for power plant cycle

26 Materials and Technologies for a Green Environment

Ramya et al.

hybridization. Efficient operational parameters like turbine pressure ratio, geothermal fluid mass flow, working fluid mass flow and working fluid type during cold as well as hot months were analysed. In order to further improve the hybrid geothermal solar power plants' performance, cooling level of the condenser was also examined with respect to the design parameters. It has been found that the following aspects were considered during the thermal design of air cooled condenser • During summer time, the hybridized power plant using solar collectors and geothermal cycle shows a noticeable improvement in the output performance. It also indicates the proposed hybrid power plant is an optimal choice in order to produce more energy. According to the observed results it was found that during the months of July and June, the net output power was recorded to be 0.77 MW and 0.37 MW respectively. The ambient temperature results in higher power during July and slightly lower power in June. • 2-butane, Normal butane, Isobutene and isobutane are the four types of RORC working fluids considered. It was found that isobutane has the best characteristics while normal butane and 2-butane showed lesser performance. It was also observed that the isobutane's GWP is lesser than normal butane and is also found to be identical to that of Isobutene. Hence the fluid that is chosen for the proposed hybrid geothermal solar plant is isobutane. • The simulation results of the geothermal solar power plant implicated that there is a significant increase in the net power output when there is a positive change in the input temperature of the condenser. For example, when the input temperature rises from -5 to 0°C, an increase of 0.108% is observed in the condenser power while a decrease of 0.25% is seen in the net output power. This is due to the fact that the pressure is minimal when the ambient temperature of the condenser is less than 5°C. Moreover, pressure grows to increase during high temperatures resulting in decreasing the turbine's net power output. • In this proposed methodology, an exhaustive method has been formulated using the important parameters for measurement and an application of the same is made in the design to determine the efficiency and operation of the air-cooled condenser. The observed results indicate that in application with a minimum power consumption, the parameters like fin thickness, number of tubes and air velocity are minimum when compared with an application involving less heat transfer area.

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 27

FUTURE SCOPE The proposed methodology offers a reliable hybrid geothermal solar hybrid power plant that provides more power to be utilized by the consumers. However, work can still be done to reduce the size of the power plant by making the features smaller or by integrating some of the components such that it is easier to build the power plant suitable for all locations. One of the biggest drawbacks of this power plant is that the amount of power generated will vary during the hot and the cold months. This is mainly because of the fact that solar energy which is available for a prolonged period of time during the hot months will result in more power generation when compared with the solar power available during the cold months. Future work can also be done on integrating more sources of power so that a significant increase in the power produced is observed. CONSENT FOR PUBLICATION Not applicable. CONFLICT OF INTEREST The authors declare no conflict of interest, financial or otherwise. ACKNOWLEDGEMENT Declared none. REFERENCES [1]

Y. Chen, J. Wang, and P.D. Lund, "Sustainability evaluation and sensitivity analysis of district heating systems coupled to geothermal and solar resources", Energy Convers. Manage., vol. 220, p. 113084, 2020. [http://dx.doi.org/10.1016/j.enconman.2020.113084]

[2]

D. Tempesti, G. Manfrida, and D. Fiaschi, "Thermodynamic analysis of two micro CHP systems operating with geothermal and solar energy", Appl. Energy, vol. 97, pp. 609-617, 2012. [http://dx.doi.org/10.1016/j.apenergy.2012.02.012]

[3]

A.D. Greenhut, "Modeling and analysis of hybrid geothermal-solar thermal energy conversion systems", Massachusetts Institute of Technology, 2009.

[4]

M. Astolfi, L. Xodo, M.C. Romano, and E. Macchi, "Technical and economical analysis of a solar–geothermal hybrid plant based on an Organic Rankine Cycle", Geothermics, vol. 40, no. 1, pp. 58-68, 2011. [http://dx.doi.org/10.1016/j.geothermics.2010.09.009]

[5]

C. Zhou, E. Doroodchi, and B. Moghtaderi, "An in-depth assessment of hybrid solar–geothermal power generation", Energy Convers. Manage., vol. 74, pp. 88-101, 2013. [http://dx.doi.org/10.1016/j.enconman.2013.05.014]

[6]

C. Zhou, "Hybridisation of solar and geothermal energy in both subcritical and supercritical Organic Rankine Cycles", Energy Convers. Manage., vol. 81, pp. 72-82, 2014. [http://dx.doi.org/10.1016/j.enconman.2014.02.007]

28 Materials and Technologies for a Green Environment

Ramya et al.

[7]

H. Ghasemi, E. Sheu, A. Tizzanini, M. Paci, and A. Mitsos, "Hybrid solar–geothermal power generation: Optimal retrofitting", Appl. Energy, vol. 131, pp. 158-170, 2014. [http://dx.doi.org/10.1016/j.apenergy.2014.06.010]

[8]

S.K. Chou, K.J. Chua, J.C. Ho, and C.L. Ooi, "On the study of an energy-efficient greenhouse for heating, cooling and dehumidification applications", Appl. Energy, vol. 77, no. 4, pp. 355-373, 2004. [http://dx.doi.org/10.1016/S0306-2619(03)00157-0]

[9]

Y. Feng, Y. Zhang, B. Li, J. Yang, and Y. Shi, "Sensitivity analysis and thermoeconomic comparison of ORCs (organic Rankine cycles) for low temperature waste heat recovery", Energy, vol. 82, pp. 664677, 2015. [http://dx.doi.org/10.1016/j.energy.2015.01.075]

[10]

M. Khaljani, "R. KhoshbakhtiSaray, K. Bahlouli, Comprehensive analysis of energy,exergy and exergo-economic of cogeneration of heat and power in a combined gasturbine and organic Rankine cycle", Energy Convers. Manage., vol. 97, pp. 154-165, 2015. [http://dx.doi.org/10.1016/j.enconman.2015.02.067]

[11]

T.Z. Ming, R. de Richter, W. Liu, and S. Caillol, "Fighting global warming by climate engineering: is the Earth radiation management and the solar radiation management any option for fighting climate change?", Renew. Sustain. Energy Rev., vol. 31, pp. 792-834, 2014. [http://dx.doi.org/10.1016/j.rser.2013.12.032]

[12]

V.P. Sethi, and S.K. Sharma, "Survey of cooling technologies for worldwide agricultural greenhouse applications", Sol. Energy, vol. 81, no. 12, pp. 1447-1459, 2007. [http://dx.doi.org/10.1016/j.solener.2007.03.004]

[13]

V.P. Sethi, and S.K. Sharma, "Survey and evaluation of heating technologies for worldwide agricultural greenhouse applications", Sol. Energy, vol. 82, no. 9, pp. 832-859, 2008. [http://dx.doi.org/10.1016/j.solener.2008.02.010]

[14]

H. Ghasemi, M. Paci, A. Tizzanini, and A. Mitsos, "Modeling and optimization of a binary geothermal power plant", Energy, vol. 50, pp. 412-428, 2013. [http://dx.doi.org/10.1016/j.energy.2012.10.039]

[15]

D. Madan, P. Mallesham, S. Sagadevan, and C. Veeramani, "Renewable energy scenario in Telangana", Int. J. Ambient Energy, vol. 41, no. 10, pp. 1110-1117, 2020. [http://dx.doi.org/10.1080/01430750.2018.1501737]

[16]

S.A. Ansari, M. Kazim, M.A. Khaliq, and T.A.H. Ratlamwala, "Thermal analysis of multigeneration system using geothermal energy as its main power source", Int. J. Hydrogen Energy, vol. 46, no. 6, pp. 4724-4738, 2021.

[17]

A. Paulillo, L. Cotton, R. Law, A. Striolo, and P. Lettieri, "Geothermal energy in the UK: The lifecycle environmental impacts of electricity production from the United Downs Deep Geothermal Power project", J. Clean. Prod., vol. 249, p. 119410, 2020. [http://dx.doi.org/10.1016/j.jclepro.2019.119410]

[18]

A. Evans, V. Strezov, and T.J. Evans, "Assessment of sustainability indicators for renewable energy technologies", Renew. Sustain. Energy Rev., vol. 13, no. 5, pp. 1082-1088, 2009. [http://dx.doi.org/10.1016/j.rser.2008.03.008]

[19]

K.P. Tsagarakis, L. Efthymiou, A. Michopoulos, A. Mavragani, A.S. Anđelković, F. Antolini, M. Bacic, D. Bajare, M. Baralis, W. Bogusz, S. Burlon, J. Figueira, M.S. Genç, S. Javed, A. Jurelionis, K. Koca, G. Ryżyński, J.F. Urchueguia, and B. Žlender, "A review of the legal framework in shallow geothermal energy in selected European countries: Need for guidelines", Renew. Energy, vol. 147, pp. 2556-2571, 2020. [http://dx.doi.org/10.1016/j.renene.2018.10.007]

[20]

H.X. Li, D.J. Edwards, M.R. Hosseini, and G.P. Costin, "A review on renewable energy transition in Australia: An updated depiction", J. Clean. Prod., vol. 242, p. 118475, 2020.

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 29

[http://dx.doi.org/10.1016/j.jclepro.2019.118475] [21]

N. Jocić, J. Müller, T. Požar, and D. Bertermann, "Renewable Energy Sources in a Post-Socialist Transitional Environment: The Influence of Social Geographic Factors on Potential Utilization of Very Shallow Geothermal Energy within Heating Systems in Small Serbian Town of Ub", Appl. Sci. (Basel), vol. 10, no. 8, p. 2739, 2020. [http://dx.doi.org/10.3390/app10082739]

[22]

M. Alibaba, R. Pourdarbani, M.H.K. Manesh, G.V. Ochoa, and J.D. Forero, "Thermodynamic, exergo-economic and exergo-environmental analysis of hybrid geothermal-solar power plant based on ORC cycle using emergy concept", Heliyon, vol. 6, no. 4, p. e03758, 2020. [http://dx.doi.org/10.1016/j.heliyon.2020.e03758] [PMID: 32382674]

[23]

A. Mahmoudan, F. Esmaeilion, S. Hoseinzadeh, M. Soltani, P. Ahmadi, and M. Rosen, "A geothermal and solar-based multigeneration system integrated with a TEG unit: Development, 3E analyses, and multi-objective optimization", Appl. Energy, vol. 308, p. 118399, 2022. [http://dx.doi.org/10.1016/j.apenergy.2021.118399]

[24]

E. Wang, H. Zhang, B. Fan, and Y. Wu, "Optimized performances comparison of organic Rankine cycles for low grade waste heat recovery", J. Mech. Sci. Technol., vol. 26, no. 8, pp. 2301-2312, 2012. [http://dx.doi.org/10.1007/s12206-012-0603-4]

[25]

J. Wang, Z. Yan, M. Wang, M. Li, and Y. Dai, "Multi-objective optimization of an organic Rankine cycle (ORC) for low grade waste heat recovery using evolutionary algorithm", Energy Convers. Manage., vol. 71, pp. 146-158, 2013. [http://dx.doi.org/10.1016/j.enconman.2013.03.028]

[26]

G. Shu, L. Liu, H. Tian, H. Wei, and G. Yu, "Parametric and working fluid analysis of a dual-loop organic Rankine cycle (DORC) used in engine waste heat recovery", Appl. Energy, vol. 113, pp. 11881198, 2014. [http://dx.doi.org/10.1016/j.apenergy.2013.08.027]

[27]

J. Wang, J. Wang, X. Bi, and X. Wang, "Performance simulation comparison for parabolic trough solar collectors in China", Int. J. Photoenergy, vol. 2016, pp. 1-16, 2016. [http://dx.doi.org/10.1155/2016/9260943]

[28]

M.F. Ezzat, and I. Dincer, "Energy and exergy analyses of a new geothermal–solar energy based system", Sol. Energy, vol. 134, pp. 95-106, 2016. [http://dx.doi.org/10.1016/j.solener.2016.04.029]

[29]

A. Colmenar-Santos, E. Palomo-Torrejón, F. Mur-Pérez, and E. Rosales-Asensio, "Thermal desalination potential with parabolic trough collectors and geothermal energy in the Spanish southeast", Appl. Energy, vol. 262, p. 114433, 2020. [http://dx.doi.org/10.1016/j.apenergy.2019.114433]

[30]

Z. Qiao, Y. Cao, P. Li, X. Wang, C.E. Romero, and L. Pan, "Thermoeconomic analysis of a CO2 plume geothermal and supercritical CO2 Brayton combined cycle using solar energy as auxiliary heat source", J. Clean. Prod., vol. 256, p. 120374, 2020. [http://dx.doi.org/10.1016/j.jclepro.2020.120374]

[31]

A.A. Ananno, M.H. Masud, P. Dabnichki, and A. Ahmed, "Design and numerical analysis of a hybrid geothermal PCM flat plate solar collector dryer for developing countries", Sol. Energy, vol. 196, pp. 270-286, 2020. [http://dx.doi.org/10.1016/j.solener.2019.11.069]

[32]

F. Calise, F.L. Cappiello, M. Dentice d’Accadia, and M. Vicidomini, "Francesco LiberatoCappiello, Massimo Denticed’Accadia, and Maria Vicidomini. “Thermo-economic analysis of hybrid solargeothermal polygeneration plants in different configurations.”", Energies, vol. 13, no. 9, p. 2391, 2020. [http://dx.doi.org/10.3390/en13092391]

[33]

S. Waseem, T.A.H. Ratlamwala, Y. Salman, and A.A. Bham, "Geothermal and solar based

30 Materials and Technologies for a Green Environment

Ramya et al.

mutligenerational system: A comparative analysis", Int. J. Hydrogen Energy, vol. 45, no. 9, pp. 56365652, 2020. [http://dx.doi.org/10.1016/j.ijhydene.2019.06.135] [34]

M. Temiz, and I. Dincer, "A unique ocean and solar based multigenerational system with hydrogen production and thermal energy storage for Arctic communities", Energy, vol. 239, p. 122126, 2022. [http://dx.doi.org/10.1016/j.energy.2021.122126]

[35]

O.B.E.K. Mokrani, M.R. Ouahrani, M.H. Sellami, and L. Segni, "Experimental investigations of hybrid: geothermal water/solar chimney power plant", Energy Sources A Recovery Util. Environ. Effects, pp. 1-18, 2020. [http://dx.doi.org/10.1080/15567036.2020.1810830]

[36]

J.D. Liang, B.H. Huang, Y.C. Chiang, and S.L. Chen, "Experimental investigation of a liquid desiccant dehumidification system integrated with shallow geothermal energy", Energy, vol. 191, p. 116452, 2020. [http://dx.doi.org/10.1016/j.energy.2019.116452]

[37]

M. Norouzi, M. Yeganeh, and T. Yusaf, "Landscape framework for the exploitation of renewable energy resources and potentials in urban scale (case study: Iran)", Renew. Energy, vol. 163, pp. 300319, 2021.

[38]

X. Chen, H. Zhou, Z. Yu, W. Li, J. Tang, C. Xu, Y. Ding, and Z. Wan, "Thermodynamic and economic assessment of a PEMFC-based micro-CCHP system integrated with geothermal-assisted methanol reforming", Int. J. Hydrogen Energy, vol. 45, no. 1, pp. 958-971, 2020. [http://dx.doi.org/10.1016/j.ijhydene.2019.10.176]

[39]

S. Kavian, C. Aghanajafi, H. Jafari Mosleh, A. Nazari, and A. Nazari, "Exergy, economic and environmental evaluation of an optimized hybrid photovoltaic-geothermal heat pump system", Appl. Energy, vol. 276, p. 115469, 2020. [http://dx.doi.org/10.1016/j.apenergy.2020.115469]

[40]

Gutiérrez-Negrín, "Luis CA, Ismael Canchola Félix, José M. Romo-Jones, and José L. Quijano-León. “Geothermal energy in Mexico: update and perspectives", Proceedings, Proceedings World Geothermal Congress, 2020

[41]

P.A. Østergaard, N. Duic, Y. Noorollahi, H. Mikulcic, and S. Kalogirou. "Sustainable development using renewable energy technology". vol. 146, pp. 2430-2437, 2020,

[42]

M.R. Karlsdottir, J. Heinonen, H. Palsson, and O.P. Palsson, "High-Temperature Geothermal Utilization in the Context of European Energy Policy—Implications and Limitations", Energies, vol. 13, no. 12, p. 3187, 2020. [http://dx.doi.org/10.3390/en13123187]

[43]

R. Liu, L. He, X. Liang, X. Yang, and Y. Xia, "Is there any difference in the impact of economic policy uncertainty on the investment of traditional and renewable energy enterprises? – A comparative study based on regulatory effects", J. Clean. Prod., vol. 255, p. 120102, 2020. [http://dx.doi.org/10.1016/j.jclepro.2020.120102]

[44]

Salim, Abdalla Mahmoud, and ImadAlsyouf. "Renewable Energy in the United Arab Emirates: Status and Potential." In: 2020 Advances in Science and Engineering Technology International Conferences (ASET), pp. 1-5. IEEE., 2022,

[45]

R. Maali, and T. Khir, "Performance analysis of different orc power plant configurations using solar and geothermal heat sources", Int. J. Green Energy, vol. 17, no. 6, pp. 349-362, 2020. [http://dx.doi.org/10.1080/15435075.2020.1731517]

[46]

Z. Li, S. Khanmohammadi, S. Khanmohammadi, A.A.A.A. Al-Rashed, P. Ahmadi, and M. Afrand, "3-E analysis and optimization of an organic rankine flash cycle integrated with a PEM fuel cell and geothermal energy", Int. J. Hydrogen Energy, vol. 45, no. 3, pp. 2168-2185, 2020. [http://dx.doi.org/10.1016/j.ijhydene.2019.09.233]

Geothermal-Solar Hybrid Power Plant

Materials and Technologies for a Green Environment 31

[47]

D.U. Lawal, and N.A.A. Qasem, "Humidification-dehumidification desalination systems driven by thermal-based renewable and low-grade energy sources: A critical review", Renew. Sustain. Energy Rev., vol. 125, p. 109817, 2020. [http://dx.doi.org/10.1016/j.rser.2020.109817]

[48]

M.K. Ouzza and A. Aattache, Geothermal Energy: A New Source of Energy for Heating NetworksICREEC 2019. Springer: Singapore. pp. 661-672, 2020. [http://dx.doi.org/10.1007/978-981-15-5444-5_83]

[49]

M.V. Kljajić, A.S. Anđelković, V. Hasik, V.M. Munćan, and M. Bilec, "Shallow geothermal energy integration in district heating system: An example from Serbia", Renew. Energy, vol. 147, pp. 27912800, 2020. [http://dx.doi.org/10.1016/j.renene.2018.11.103]

32

Materials and Technologies for a Green Environment, 2023, 32-66

CHAPTER 2

Energy Harvesting Generators

Through

Thermoelectric

A.D. Dhass1,*, Ganesh Babu L.2, Raghuram Pradhan3, G.V.K Murthy4 and M. Sreenivasan3 Department of Mechanical Engineering, IITE, Indus University, Gujarat, India Mechatronics Engineering, Tishk International University, Erbil, Iraq 3 Department of Mechanical Engineering, PACE Institute of Technology and Sciences, Ongole523272, India 4 Department of Electrical and Electronics Engineering, PACE Institute of Technology and Sciences, Ongole-523272, India 1 2

Abstract: Thermoelectric generator (TEG) converts waste heat energy from automobiles into valuable electrical power and has no moving parts compared to conventional thermoelectric motors. The functioning of TEG is dependent on the design and the material used. TEGs are classified as small and medium power outputs. Small power outputs are in the range between 5 μW to 1W, and high power outputs are higher than 1W in a TEG. Thermoelectric power generators offer fast, economical storage methods for wearable and mobile applications. Macro heat waste application is recovered through in-house, industrial and solid waste. Moreover, an immense amount of waste fuel, such as recycling and power plants, is emitted from the industry; this can be utilized in a useful manner by TEGs. This chapter discusses the TEG study of the fundamental operating principles, TEG products, micro applications and energy generation techniques.

Keywords: Applications, Energy storage, Heat engines, Power generation, Thermoelectric generator, Waste heat recovery. 1. INTRODUCTION The majority of the operating expense of a gas turbine is due to turbine fuel, and much energy is lost from the flue gas after combustion to the atmosphere. Up to 40% of the fuel is released from exhaust energy. The technology of semicondCorresponding author A.D. Dhass: Department of Mechanical Engineering, IITE, Indus University, Gujarat, India; E-mail: [email protected]

*

Santhanam Harikrishnan (Ed.) All rights reserved-© 2023 Bentham Science Publishers

Thermoelectric Generators

Materials and Technologies for a Green Environment 33

uctors helps to solve energy problems by procuring waste heat sources [1, 2]. The immensity of the global energy is calculated to be the product of effective thermal energy-saving technologies that can conserve atmospheric energy as heat, generating approximately 40% or less. Thermo-energy waste can improve the power efficiency of the electricity base. The gas turbine, vehicle exhaust, steam and method of production produce waste thermal energy and transform it into energy using a thermoelectrical generator [3]. In recent years, the principal objective has been to increase energy production to improve its economy, methods of transport and quality. Researchers and commercial activities have in particular, tried to enhance resource efficiency through improved energy systems performance since the energy crisis [4]. The energy costs (oil, gas and charcoal) have risen at unpredictable rates over recent years. Consequently, renewable energy is more conventional in producing electricity, since it produces lower emissions. By converting heat energy, the device is converted into electric power. It is suitable for space exploration and satellite exploration and for devices that are unmanned. Modern electrical systems include photovoltaic cells, piezo-electric modules for human motion and thermoelectric heat modules. The aim is to provide electricity efficiency to the human organism with its limited resources [5]. The schematic diagram of the conversion of ambient energy into electrical energy is shown in Fig. (1). The energy supply (solar, mechanical, thermostat, RF) is converted into electrical energy. In order to store extracted power, the energy storage device is almost always required. Since the charge energy and the storage area have different voltage levels, it is necessary to have a voltage controller. Electrical charge typically includes one or more sensors, an RF transceiver, and a microcontroller that wirelessly transmits the sensed information [6]. Input Energy Source: Light, Mechanical, Thermal

Transducer (Solar PV cell, piezo electric, thermo electric generator)

Electrical Energy

Energy storage element

Fig. (1). Schematic Diagram of Ambient Energy is converted to Electrical Energy [6].

Junction

Load (Sensors)

34 Materials and Technologies for a Green Environment

Dhass et al.

1.1. Peltier Effect The Peltier effect is a phenomenon where heat is absorbed at a link between materials; heat is released at a different intersection, as shown in Fig. (2), when a current (I) flows through the material [7, 8],

Cold

Hot Junction

Current

Voltage Fig. (2). Schematic diagram of Peltier effect [8].

The Peltier effect is used to describe the sum of QP for heat absorption and heat release in the following equation [9]: QP

– ab .I

(1)

1.2. Thomson Effect The Thomson effect is a phenomenon where heat is absorbed or emitted as the current passes through the material. Thomson effect is expressed in the following equation as quantities of heat (QT) absorption or heat discharge per unit volume [9]: QT

WJ

dT dl

(2)

1.3. Figure of Merit A Figure of merit (ZT) shall be a number used in comparison with its alternatives to differentiate between systems, devices or processes. Figure of merits are also

Thermoelectric Generators

Materials and Technologies for a Green Environment 35

used in engineering to determine their relative utility in relation to particular materials and/or devices. The thermoelectric value remains a proven instrument for the evaluation of thermoelectrical materials [10],

ZT

S2 T Uk

(3)

2. TYPES OF THERMO ELECTRIC GENERATORS The connection scheme of thermoelectric generator differ by the type of heat source and thermal sink, energy usage and intended use. Between 1955 and 1965, substantial progress was made in semiconductor materials and electrical contacts, increasing the scope of practical application. Much equipment needs a power supply to convert the generator output into operating voltage. 2.1. Fossil Fuel Generators A number of heat sources have been used by generators like natural gas, propane, butane, diesel, forest fuel and jet. Commercial units typically have a power range of 10-100 watts. These products are used to prevent electrolysis corrosion of metal pipelines and marine structures in distant applications, such as navigation support, data collection systems, communication, and cathode-resistant applications [11]. 2.2. Solar Source Generators Solar thermal energy generators have been successfully utilized to power small irrigation pumps in remote and underdeveloped regions worldwide. Solar thermoelectric generators have been developed for the supply of orbital electricity to spacecraft, but are struggling to cope with efficient silicon solar cells of less weight. In orbital thermal control systems, however, both heat pump and power generation systems have been considered. Thermoelectric heating from the sound side of the spacecraft generates electricity for other thermo electrical equipment in the dark areas of the spacecraft and the thermal body discharge [12]. 2.3. Nuclear-fueled Generators Due to the relative high immune content of thermoelectric equipment and the length of its components, nuclear generators provide a useful energy source

36 Materials and Technologies for a Green Environment

Dhass et al.

designed for a wide range of unforeseen, remote functions. Thermoelectric radioisotopes produce electricity for each wind monitoring station, deep-sea data acquisition, various warning and communication systems and aerial systems. A low-performance generator for thermo-isotope pacemakers has also been developed and used in 1970. Radioisotope thermoelectric generators are used to generate 10-6 to 100 watts power [13]. 2.4. Semiconductor Materials for Thermoelectric Generators Three materials (Bi2Te3, PbTe and SiGe) are typically used in thermoelectric generators. Many materials are currently being studied, but are not available for preparing thermoelectric generators. Fig. (3) shows the internal structure of the TEG module, which consists of a heat supply as the input source and generates electrical energy as an output, remaining heat dissipated to the atmosphere [14].

Fig. (3). Internal structure of TEG module [16].

2.5. Environmental Extremes In extreme environmental applications, where power is important, thermocouple generators are sometimes used. Since thermoelectric generators do not have

Thermoelectric Generators

Materials and Technologies for a Green Environment 37

moving parts, they are extremely reliable. These extreme applications also use radiological heat from sources such as Plutonium-238 (Fig. 4) [15]. These include shelves, mars rovers, mountain energy, Antarctic power generation (Fig. 5), lights and nuclear pacemakers (Fig. 6). The thermal sinks, offshore platforms, dams, electricity and navigation assistants all form extreme areas for thermal energy generators, which are commonly used as non-radiological thermal sources.

Fig. (4). Plutonium Pellet [17].

Fig. (5). Antarctica Thermoelectric Generator [17].

38 Materials and Technologies for a Green Environment

Dhass et al.

Fig. (6). Thermoelectric Generator Pacemaker [17].

3. WASTE HEAT RECOVERY Waste heat is characterized as heat loss under environmental conditions. This heat is the by-product of all conversion methods. The unwanted heat released from the thermal power plant and gas power plant is shown in Figs. (7 and 8). The use of any fossil fuels available leads to losses of up to 72%. Such heat is emitted into or lost in the atmosphere. In order to recycle this waste heat, all conversion processes are made more efficient [18].

Fig. (7). Waste heat released from power plant [19].

Thermoelectric Generators

Materials and Technologies for a Green Environment 39

Fig. (8). Waste Heat released from a Gas power plant [19].

4. MICROGENERATION Applications for thermo-electric micro generators can be utilized by very low heat or a change in temperature from air to heat source, or if the thermoelectric generator alone is very low. This leads to thermoelectric generators for micro watts and milli watts (Fig. 9).

Fig. (9). Energy Harvesting from Body Heat [20].

Systems include the Wireless Sensor Network, IoT (Internet of Things), body-fuel wristwatches, torch fuel, and heat fuel control systems can be used for micro generation systems. The combined heat and power or chip (including cogeneration) is the method of collecting energy from a heat source and making

40 Materials and Technologies for a Green Environment

Dhass et al.

use of excess thermal energy to produce heating, heating room or preheating. Heat generators, for example biomass cookers, campers and barbecues have a high difference in temperature (∆T) which increases the efficiency of the thermoelectric power generator. Concentrated solar power for thermoelectric generator (Fig. 10) produces a huge temperature difference between the source and sink of TEGs [21]. Table 1 shows the merits and demerits of the commonly used TEG power generation system. Table 1. Merits and demerits of TEG power generation system [22]. Merits

Demerits

1.Cost Savings 2.Huge Time Savings 3.Better Product Design 4.Reliability 5. Quiet 1. Thermoelectric generators are less effective to convert electricity than 6. No Greenhouse Gases any other technology. 7. Wide Range of Fuel Sources 8. Scalability 9. Mountable in Any Orientation 10. Direct Energy Conversion 11. Compact Size

Fig. (10). Concentrated Solar system for Thermoelectric Generator.

Thermoelectric Generators

Materials and Technologies for a Green Environment 41

A greater figure of merit value (ZT) is important for energy generation and a ZT>1.5 is crucial for waste recycling. The ZT value was typically lower than 1 in the early development period while the material progression suggested a ZT value of 2 to 3. Fig. (11) demonstrates ZT values for various energy sources [23].

Fig. (11). Variation of TEM [23].

Thermoelectric materials and manufacturing architecture are the main core of the TEGs preparation. The first stage is the synthesis of thermoelectric materials with their ingredients usually by ball moldings. The steps for TEG development are shown in Fig. (12). Another method of processing thermoelectric powder is by melting, while changes in the process lead to phase and microstructure variations. Then synthetic powders are produced by moving the heating or sintering plasma spark, and then into thermoelectric forces. Several TEGs are available and only bismuth telluride and germanium are used. The manufacture of polymer, oxide and silicone reduces the use of germanium greatly and thereby reduces the cost of the raw materials [24].

42 Materials and Technologies for a Green Environment

Dhass et al.

Fig. (12). Typical manufacturing process of TEG [25].

5. HARVESTING MICROPOWER The ability to generate very low thermal semi-conductivity ensures that heat generation is low in energy. Because of the thermal scarcity of thermoelectric substrate parallel to the disposal plane, it loses some efficiency but gains the thermoelectrical elements' density and length, producing 5V at a temperature drop of 10 K. An excellent example of thermostatic strength removal is the thermoelectrical bracelet that uses thin bulk electronic devices [26]. 6. THERMO ELECTRIC GENERATORS & COOLERS Low power generation is considered to be less than 1W of TEG electricity generation (from 5 μW to 1W). The QHg is equilibrated with Fourier (QFourier) heat tubing, Peltier (Qpeltier) and Qjoule heat at the hot cross junctions [27]. 6.1. Thermo Electric Cooler (TEC) TEC is a powerful heat pump that uses Peltier in heating removal system in electronic packaging. The prevalent heat pump is powerful and increases commercial and industrial development [28]. In terms of the effects on current load, geometric measurements, intermediate section length and heat resistance, finite-element coolers are tested for

Thermoelectric Generators

Materials and Technologies for a Green Environment 43

refrigeration efficiency and response time. It has been demonstrated that thermoelectric coolers (TEC) size and cross-sectional area length have improved TEC efficiency. The maximum temperature difference of 1000 W / cm2 or a simple millisecond response time can be achieved for those conditions. The thermoelectric micro cooler has a three-dimensional system shown in Fig. (13) [30].

Fig. (13). TEC with a heat-generating chip [29].

The TEC systems are theoretically investigated for optimizing issues, such as exchange of the TEC heating device in electronic cooling. The schematic diagram of the TEC system is shown in Fig. (14). The thermodynamics analysis [31] is as follows,

Fig. (14). The schematic of a TEC system [31].

44 Materials and Technologies for a Green Environment

Dhass et al.

QPeltier  QFourier  QJoule

QHg

(4)

Where as, QPeltier

QFourier

Q Joule

D g IThg

k g (Thg  Tcg )

(5)

I 2Rg 2

The energy balance of thermo electric generator is,

Q Hg

ª I 2 Rg º n g «D g IThg  k g Thg  Tcg  » 2 »¼ «¬

Q Cg

ª I 2Rg º n g «D g ITcg  Thg  Tcg  » 2 »¼ «¬

(6)

The power output, Po

Q

Hg

>

 QCg

n g D g I Thg  Tcg  I 2 R g

Rl  Load Resistance

I 2 Rl

@

(7)

Thermoelectric Generators

Materials and Technologies for a Green Environment 45

 L  p Lp  Rg   n n   A p   An

Rg=Sum of the resistance of the thermoelectric legs Thermal conductance k A k p Ap  kg   n n   L p   Ln

(8)

6.2. Air Conditioning Systems for Vehicles The use of the TEC system as an alternative to standard Air conditioning (AC) systems for an automotive system has two main advantages: it conforms to R134a and provides ventilation in selected areas instead of the entire cabin. The inherent advantages of TEC systems, on the other hand, made automobile air conditioning systems an adequate option. However, conventional automotive air conditioning systems with the same input power were stated to be five times higher than TEC, in ambient temperatures between 25oC and 30oC. Recent interest in TEC technology was demonstrated in growing automotive systems requirements [32]. Fig. (15) shows the time reaction between the output voltage, the output power and the TEG power. The heating module will maintain a continuous current and voltage as well as an increasingly high-temperature supply of power to the load. The system time is roughly four sec at a time. The spacing time is a little longer with an efficient heating tube [33].

()LJ ) contd.....

46 Materials and Technologies for a Green Environment

Dhass et al.

Fig. (15). Temporal response of the thermoelectric module [33].

7. THERMO ELECTRIC MATERIALS The TEG is based on three composite parameters relating to the material's thermoelectric properties, electro-resistance and thermo-conductance. The ZT values of TE materials are proportional to the Seebeck coefficient, which at a certain concentration achieves high thermo-electric effectiveness [34]. The classifications of different TEG materials are shown in Fig. (16). TEGs are the first kinds of items that are inorganic compost (Bismuth-Telluride), tin selenide (SnSe), and lead Telluride (PbTe). The second form refers to the polymerized TE substances (PODOT: PSS): poly (SYRENE sulfonate), polyaniline (PANI), or polypropylene (PPY), respectively). BiTe – PEDOT – is a synthetic TE substance made from an inorganic compound and a polymer conductive additive doped from an organic material mixture. BiTe: PEDOT: Certain TE materials are available in 2 ZT labs, some ZT for 3 or more [35]. 7.1. Inorganic TE Materials The ZT maximum value of generated TE inorganic materials remained standardized for most applications until mid-1990, which was not enough. However, advancement in research, technology and information on the risks of fossil fuels has led to a need to improve the quality of TE materials [36]. 7.2. Organic TE Materials In recent decades, the reduction of the ZT values and their increased growth have neglected organic thermoelectric materials, such as polymers, carbon nanotubes

Thermoelectric Generators

Materials and Technologies for a Green Environment 47

(CNTs), and graphites. As inorganic TE materials can, however, attenuate the cost-effectiveness and recyclability of organic TE materials. It is hard to lower the standard thermal conductivity of organic materials further [37]. Intermetallics

Skutterudites

Clathrates

Half-Heusler (HH) alloys

Oxides

Rare earth chalcogenides Thermoelectric Materials Zintl-phase materials

Pnicogens

Nitrides

Carbon nanomaterials

Graphene

Electronically conducting polymers

Nanocomposites

Fig. (16). Classifications of Different Thermoelectric Materials [34].

7.3. Hybrid TE Materials Present TE materials have ZT values less than 1 while the TE value is 3 or higher and this is to be accomplished by ZT materials. These materials need conductivity and a Seebeck factor, while low thermal conduction to improve the TE efficiency. The production of hybrid TE composites is thus a simple strategy by combining classic TE materials into inorganic and organic form [38]. Seebeck coefficient of electrical resistivity (Fig. 17): both features fall under the ZT. As a higher density symbol, the power factor is encrypted. This is

48 Materials and Technologies for a Green Environment

Dhass et al.

accompanied by the colours of the family of materials. The axis is the same as the Jonker plot (where the Seebeck coefficient is drawn against the tube), but its implementation is still very distinct. For the impact analysis of a carrier concentration into a single material, Jonker compounds are widely used [39].

Fig. (17). Seebeck co-efficient of various materials with effect on electrical resistivity [39].

7.4. Polymers Acts as TE Materials Polymers like TE materials gained a lot of attention recently because of their quick manufacturing methods and their low cost of materials. The key carbon part, however, is available in polymers and the use of polymers in electronic equipment is therefore more economical and advantageous. The properties of various TEG polymers are given in Table 2. Thermally low polymers are ideal for TE applications [40]. Table 2. Properties of various TEG polymers [40].

S. No. 1

Polymer

Conductivity (σ) S/cm

Seebeck coefficient (S) µV/K

Thermal Conductivity (κ) W/mK

Polyacetylene

1.53 × 10−3– 2.85 × 104

0.5–1077

--

Thermoelectric Generators

Materials and Technologies for a Green Environment 49

(Table 2) cont.....

Polymer

Conductivity (σ) S/cm

Seebeck coefficient (S) µV/K

Thermal Conductivity (κ) W/mK

2

poly(p-phenylene vinylene)

10-5

7

7.2 × 10-11

3

Polyaniline

7000

7

5.1 × 10-2

4

poly(2,7-carbazolenevinylne)

5 × 10-3

230

8.0 × 10-5

5

poly(2,5-dimethoxyphenylenevinylene)

46.3

39.1

--

S. No.

7.5. Advanced TE Materials In the field of materials design, TE materials analyses have posed problems through chemical sciences and physical concepts of the robust state of complex structural / properties relations of complex solids. If it is difficult to do or to dope a material with minimum thermo power, ZT = 1 [41]. 7.6. Bulk Binary Semiconductors Metals typically form weak TE materials when the basic electronic structure of the belt is formed. The majority of early TE research therefore favored semiconductors. To achieve optimum electrical-thermal conductivity, materials should have extremely low mobility (1.019 cm-3), and significantly affect mobility for the crystal structure and bonding [42]. 7.7. Complex Inorganic Structures The low-temperature substances may be analysed as pentatellurides (such as ZrTe5, and HfTe5,) of a low-dimensional, semi-reductive or semi-metallic doped layer. The compounds are equal to Bi2Te3, except that there are different layers between the Vander Waals. In the lower temperature range (< 250 C), doped pentatellurides are of very high intensity (beyond and beyond the ideally dosed solid solution of Bi2Te3). There is relatively high thermal conductivity. In order to achieve success in TEs, the structure of these materials should be modified [43]. 7.8. Oxide Thermoelectrics The strong ionic nature of TE applications has received relatively little attention; the intensive orbital overlap leading to clustered electrons with low transport mobility has resulted in a limited bandwidth. This changed in NaCo2O4, a closely related, layered oxide, whereby strong TE properties were discovered

50 Materials and Technologies for a Green Environment

Dhass et al.

unexpectedly. Then it is crystallized into an unfitting structure based on TE's remarkable findings with NaCo2O4 and oxide levels, including Ca3Co4O9 and Bi2Sr3Co2Oy. It is relatively solid for n-type (ZT 0.3 at 1,000 K) doped ZnO [Al 0.02, Zn 0.980] [44]. 7.9. Thin Film Materials Some situations rely on the thermodynamic stability of phases for research approaches on bulk materials, while film deposition may lead to mechanical design steps with new characteristics. In Atomic well systems (0-D, 1-D, 2-D), the electronic properties of the basic material have been improved by using physical containers in atomic and nano-heat structures [45]. 8. OPTIMAL DESIGN The electrical field E→ produced in the thermoelectric material is given by the temperature gradient [46], o

E

o

D’T  U J

(9)

The Peltier effect, which explains the thermoelement heat flux q→, is expressed in [46] o

o

DT J  k’T

q

(10)

The second term here describes the thermal conductivity of the thermal conduction k [46] o

’. q

o o

J .E

(11)

0

(12)

’ V

(13)

o

’. J o

E

Express legislation on energy efficiency, current stability and electric potential

Thermoelectric Generators

Materials and Technologies for a Green Environment 51

oscillations. By means of these partial differential equation solutions, five equations and five unknown variables can be achieved simultaneously with the finite element process. The equations for TEG is [47],

Q1

n1 h1 A1 Tf1  T1

Q2

n 2 h2 A2 T2  Tf 2

I

(14)

D T1  T2 RL  R

Power output W Efficiency K

W Q1

Q1  Q 2

(15) (16)

Fig. (18) shows the effect of the thermocouple span and maximum duration on the conversion efficiency. The increase in dimension would also help to improve thermal conductivity. The ideal lens ratio, which corresponds to optimum efficiency, is determined by calculating the thermo elements. Since the overall time increases, the amount of power decreases, the lower heat intake decreases the effects as the thermocouples become shorter. Productivity increases first and then decreases with an increase in total life.

52 Materials and Technologies for a Green Environment

Dhass et al.

Fig. (18). Variation of efficiency with length ratio q and total length of thermoelements L for T1 ¼ 600 K and T2 ¼ 300 K [48].

9. HYBID THERMO ELECTRIC GENERATORS Solar radiations are absorbed in the salt tank and raise the temperatures in the salt and lake. Both the sole and the basin grow temperate, which releases the vapour evaporates. The distribution of water vapour into the condensing chamber also simplifies solar distillation and further increases solar evaporation. The hot side of the TEG is thermally related to the organic-photovoltaic thermoelectric (OPV), which absorbs transferred sunlight and waste from the solar absorption bladder. It absorbs the solar absorber blade. Due to the electrical interaction sequences in both points, the TEG output results in the OPV output as the TEG results in the upright temperature gradient [49].

K pv

Pout

Voc I sc FF

Pin

I sun S

By definition, the fill factor FF is given by [50],

(17)

Thermoelectric Generators

Materials and Technologies for a Green Environment 53

FF = (Vmax × Imax)/(Voc × Isc)

(18)

Variations in the output power, voltage and current are due to the change in heat side temperatures. For example, when TEG permitted heat side (350°C) and minimum permissible temperature on the cold side (30oC) and therefore maximum allowable temperature variation (320oC), total output power of 21.7 W was obtained [50]. 9.1. Solar Powered Thermoelectric Refrigerator In solar powered thermoelectric refrigerator, thermocouples are connected on all surfaces of the inside wall of the fridge. Thermocouples are connected to the data logger as shown in Fig. (19). The processes should be continued when the solar pans are refused from the solar load controller in order to evaluate the battery bank capabilities. For efficient operation of the 52 W electric solar cooler, 45.7A, 17.5 V and 100W solar modules, 4 x12V and 100Ah lead acid battery, 12 A and 24V charging control and 24V and 150W inverter are required. In order to maximize electricity generation, the pictorial range should be horizontally oriented at 15oC, installed to the south. The photovoltaic range's maximum output is 230 W. It showed that the battery bank would act as an energy provider for three independent days. The cooler has maintained the temperature of the cooling room at 1 to 7oC and the average temperature is 4 oC. After shutdown, the warm-up time to normalize cooled temperatures is about four hours. The cooler is not a vapour compression cooler but because of its lack of control, ecological performance and noise. The cooler body isolation and the efficiency of its heat exchanger can boost performance of the cooler. The photovoltaic-powered thermoelectric refrigerator cannot be opened for more than 30 seconds [51].

54 Materials and Technologies for a Green Environment

Dhass et al.

Fig. (19). Schematic diagram of the structure of thermoelectric refrigerator [51].

10. ENERGY HARVESTING The principle of “energy selection,” which allows us to make free use of energy, such as sunlight, atmospheric temperature, or vibration in road transport, has recently been implemented (Fig. 20). The 16 PV cells have been divided into four separate areas depending on the position of the body. The PV cells are attached to the same field parallel to operate at the same power point and ideally at the maximum power point. The instrument proposed removes the need to avoid diodes and reduces the number of electricity management systems, as all photovoltaic cells almost have complete control. Body heat TEGs are a major problem at low voltage [52].

Thermoelectric Generators

Materials and Technologies for a Green Environment 55

Fig. (20). Energy Harvesting Applications [52].

In recent years, the combination of low performance RF technology with highperformance microcontrollers has led to various new applications such as cable sensors (Fig. 21).

Fig. (21). Components of an intelligent remote sensor system [53].

56 Materials and Technologies for a Green Environment

Dhass et al.

The low power conversion factor can be controlled by a range of integrated boost converters. The converting system needs much work, since power sources can be very weak or reduced, but also with a high conversion efficiency and very low quiet current [53]. Mechanical vibration is an environmental source of energy that converts electricity. The use of an electrically polarized piezoelectric material for pressure and/or for the electromagnetic spiral of atmosphere vibration generates electrical power. Electrical and mechanical transducers of energy are piezoelectric materials. In cases of mechanical tension of piezoelectric material, an electrical charge occurs in the material and a voltage is produced in the piezoelectric material when the voltage is applied (Fig. 22).

Fig. (22). Schematic view of harvester attached accelerometer [54].

A pioneering regenerative absorber device is proposed to the electromagnetic energy collector, using a mechanical motion correction mechanism, which transforms an oscillating vibration into electrical energy. A 15 mph system prototype of a 15 watt power supplied 15.4 watts during road trials on a paved road at the Chevrolet suburban suspension [55]. 11. PERFORMANCE AND MEASUREMENT OF THERMO ELECTRIC GENERATORS Fig. (23) shows, in line with complex thermal conditions, power outputs, voltage and current. The power output is maximized at peak RL. If the temperature difference in cool to warm TEGs declines, the efficiency of power generation also improves significantly. In Fig. (23), the hot lateral temperature rises from 343 to 373 K significantly, with major changes in temperature and performance [57].

Thermoelectric Generators

Materials and Technologies for a Green Environment 57

(a)

(b)

(c) Fig. (23). TEG performance (a) voltage output; (b) current output and (c) power output [56].

The power supply in the P-H segment curves with high thermo electrical generator voltage is decreased as performance decreases (Fig. 24). These are not the optimal working environments. The best working position for a generator of thermal power is to be in the P-h segment with a negative spot [58],

K t Km P>Pm

(19)

58 Materials and Technologies for a Green Environment

Dhass et al.

Fig. (24). Efficiency versus dimensionless power output [58].

Fig. (25) illustrates Tc/Th= 0.5 and TEG standard values in the generalized performance characteristics. The maximum power output occurs at RL/R = 1 resistance level predicted.

Fig. (25). Generalized TEG performance for TcTh/=0.5 and ZT=1 [59].

Thermoelectric Generators

Materials and Technologies for a Green Environment 59

12. MICRO SCALE APPLICATIONS Thermoelectric generators offer an easy and cost-effective energy storage system for the usable or mobile application. This does not make it possible to use rigid inorganic semi-constructors and substrates for applications that require significant mechanical stability [60]. A new strategy will be developed to decentralize the combined output of heat and energy using small and micro biomass. There is predestined thermoelectric power and large heat volumes are enough to minimize usage. The basic device makes it possible for automated biomass furnace operators, such as fuel from the storage and heating water unload, independently of the grid. Additional energy can also be supplied by the integrated system to transmit a grid or other electrical device [61]. In the production process of manufacturing plants, the industry needs sensors to be successful. The sensors are needed to work for a few watts. The power of the sensor is equivalent to the life cycle of the sensor. The key power source for sensors is the battery. The battery adaptation issue is also recognised and costly in some industrial applications due to its severe protection and geographical limits, access constraints, nuclear power, military or secure data centres. Manufacturers construct and operate multiple watt generator sensors independently of electronic sensors such as micro space generators [62]. Thermoelectric micro equipment for the energy generation of waste heaters is a recent publication for the implementation of an electronic device. This device includes a heat pipe substratum that is extracted in a high-temperature environment (for example, diamonds or other high-temperature materials) during thermal contact. When the device is functional, heat is transferred from the high area to the heat conduit and the heat to the electricity generator. In that patent, Bi2Te3 alloy is based on the thermal contact with the thermocouple substrate. The low temperature range on the other side of the thermoelectric panel is opposite to the high temperatures [63]. 13. MACRO SCALE APPLICATIONS Macro waste heat applications cover vehicles for residential, industrial and solid waste. Recent research activities also focus on the use of industrial waste heat generated thermoelectric energies. The potential progress here is reflected by the use of post-efficient thermal electrical materials that can resist higher temperatures at a viable cost from various industrial heating sources. Another method is the development of new thermoelectric assembly geometries and configurations. New thermoelectrically flexible devices should be built to make them effective and more suitable for use with more thermo setters [64].

60 Materials and Technologies for a Green Environment

Dhass et al.

A primary source of electricity is the concentration and distribution through grids. However, some fields are still not electrified. In certain cases, grid connectivity is not the best choice in development countries and greener options are being explored. Self-generating energy is of different importance for both developing and developed countries. While TEG is mainly used for energy production only, it can also be used for combined heating and power systems in most recent businesses [65]. CONCLUSION A power and waste heat storage system was considered a great success. The power generated is generally limited to low microwaves. The energy produced is limited. The advantages of no moving parts and no difficulty, quiet low maintenance and environmental impacts can be accomplished easily and effectively with the aid of solid state generators. Thermal conductivity will decrease overall power output and therefore increase the Seebeck coefficient of conductivity and electricity. It offers easy, efficient heat collection power management solutions for the generation of wireless sensors and others. NOMENCLATURE S

Seebeck coefficient with a dimension (V/K)

πab

Peltier coefficient when Material A and Material B is joined and I is current.

τ

Thomson coefficient

J

current density

∆T

temperature dependence,

k

thermal conductivity,

T

absolute temperature

Q

Heat

α

Seebeck coefficient

I

Current

T

Temperature

k

Thermal Conductance

R

Electrical Resistance

n

n-type material

p

p-type material

L

Length

A

Area

Thermoelectric Generators

Materials and Technologies for a Green Environment 61

ρ

Electrical Resistivity

hg

Hot Junction of Thermoelectric generator

Hg

Hot side of Thermoelectric generator

g

Generator

cg

Cold Junction of Thermoelectric generator

Cg

Cold side of Thermoelectric generator

l

Load

n

number of thermocouple

h1, h2

thermal conductance

A1, A2

Area of inlet and outlet thermocouple.

T1, T2

inlet and outlet temperature

T∞1,T∞2 atmospheric temperature of inlet and outlet conditions α

seebeck co-efficient

Voc

open circuit voltage

Isc

short-circuit current

FF

Fill factor

φsun

solar radiation intensity

Vmax

maximum voltage

Imax

maximum current

ηm

efficiency at maximum power output

Pm

dimensionless power output at maximum efficiency.

CONSENT FOR PUBLICATION Not applicable. CONFLICT OF INTEREST The authors declare no conflict of interest, financial or otherwise. ACKNOWLEDGEMENT Declared none. REFERENCES [1]

J. Tervo, A. Manninen, R. Ilola, and H. Hänninen, State-of-the-art of thermoelectric materials processing, properties and applications. VTT Technical Research Center of Finland, Vuorimiehentie, 2009.

[2]

N. Enjamuri, and S. Darbha, "Solid catalysts for conversion of furfural and its derivatives to alkanediols", Catal. Rev., Sci. Eng., vol. 62, no. 4, pp. 566-606, 2020.

62 Materials and Technologies for a Green Environment

Dhass et al.

[http://dx.doi.org/10.1080/01614940.2020.1744327] [3]

Y. Yang, S. Wang, and Y. Zhu, "Evaluation method for assessing heat transfer enhancement effect on performance improvement of thermoelectric generator systems", Appl. Energy, vol. 263, p. 114688, 2020. [http://dx.doi.org/10.1016/j.apenergy.2020.114688]

[4]

D. Champier, "Thermoelectric generators: A review of applications", Energy Convers. Manage., vol. 140, pp. 167-181, 2017. [http://dx.doi.org/10.1016/j.enconman.2017.02.070]

[5]

G. Chen, Y. Li, M. Bick, and J. Chen, "Smart textiles for electricity generation", Chem. Rev., vol. 120, no. 8, pp. 3668-3720, 2020. [http://dx.doi.org/10.1021/acs.chemrev.9b00821] [PMID: 32202762]

[6]

M. Soni, and R. Dahiya, "Soft eSkin: distributed touch sensing with harmonized energy and computing", Philos. Trans.- Royal Soc., Math. Phys. Eng. Sci., vol. 378, no. 2164, p. 20190156, 2020. [http://dx.doi.org/10.1098/rsta.2019.0156] [PMID: 31865882]

[7]

L.C. Ding, N. Meyerheinrich, L. Tan, K. Rahaoui, R. Jain, and A. Akbarzadeh, "Thermoelectric power generation from waste heat of natural gas water heater", Energy Procedia, vol. 110, pp. 32-37, 2017. [http://dx.doi.org/10.1016/j.egypro.2017.03.101]

[8]

https://instrumentationtools.com/peltier-effect-theory/ Retrived on 25/05/2020

[9]

Y. Shinohara, O. Umezawa. "Thermoelectric Power Generation from Waste Heat". In: L. Martínez, O. Kharissova, B. Kharisov (eds) Handbook of Ecomaterials. Springer, Cham, pp. 961-979, 2019. [http://dx.doi.org/10.1007/978-3-319-68255-6_14]

[10]

G.J. Snyder, and A.H. Snyder, "Fig. of merit ZT of a thermoelectric device defined from materials properties", Energy Environ. Sci., vol. 10, no. 11, pp. 2280-2283, 2017. [http://dx.doi.org/10.1039/C7EE02007D]

[11]

R. Decher, Direct Energy Conversion: fundamentals of electric power production. vol. 3. Oxford University Press on Demand, 1997.

[12]

R.K. Singal, and M. Tabatabaian, Direct Energy Conversion Technologies. Stylus Publishing, LLC, 2019.

[13]

https://www.britannica.com/technology/thermoelectric-power-generator Retrived on 25/05/2020

[14]

A. Piggott, "Detailed transient multiphysics model for fast and accurate design, simulation and optimization of a thermoelectric generator (TEG) or thermal energy harvesting device", J. Electron. Mater., vol. 48, no. 9, pp. 5442-5452, 2019. [http://dx.doi.org/10.1007/s11664-019-06952-x]

[15]

https://ThermoelectricSolutions.com/how-thermoelectric-generators-work Retrived on 26/05/2020

[16]

N. Jaziri, A. Boughamoura, J. Müller, B. Mezghani, F. Tounsi, and M. Ismail, "A comprehensive review of Thermoelectric Generators: Technologies and common applications", Energy Rep., vol. 6, no. Suppl 7, pp. 264-287, 2019.

[17]

J.B. Labegorre, Synthèse et caractérisation de matériaux oxydes et oxylfures pour applications thermoélectriques, 2018.

[18]

C.J. An, Y.H. Kang, H. Song, Y. Jeong, and S.Y. Cho, "High-performance flexible thermoelectric generator by control of electronic structure of directly spun carbon nanotube webs with various molecular dopants", J. Mater. Chem. A Mater. Energy Sustain., vol. 5, no. 30, pp. 15631-15639, 2017. [http://dx.doi.org/10.1039/C7TA02509B]

[19]

G. Li, D. Zhu, Y. Zheng, and W. Guo, "Mesoscale combustor-powered thermoelectric generator with enhanced heat collection", Energy Convers. Manage., vol. 205, p. 112403, 2020. [http://dx.doi.org/10.1016/j.enconman.2019.112403]

Thermoelectric Generators

Materials and Technologies for a Green Environment 63

[20]

L. Dudzinski, J. Hamley, P. McCallum, C. Sandifer, T.J. Sutliff, and J.F. Zakrajsek, "NASA’s Radioisotope Power Systems Program Status", 12th International Energy Conversion Engineering Conference 2014, p. 3462.

[21]

S.J. Kim, J.H. We, and B.J. Cho, "A wearable thermoelectric generator fabricated on a glass fabric", Energy Environ. Sci., vol. 7, no. 6, pp. 1959-1965, 2014. [http://dx.doi.org/10.1039/c4ee00242c]

[22]

K. Imasato, S.D. Kang, and G.J. Snyder, "Exceptional thermoelectric performance in Mg 3 Sb 0.6 Bi 1.4 for low-grade waste heat recovery", Energy Environ. Sci., vol. 12, no. 3, pp. 965-971, 2019. [http://dx.doi.org/10.1039/C8EE03374A]

[23]

P.M. Kumar, Babu, A. Subramanian, A. Bandla, N. Thakor, S. Ramakrishna, and H. Wei, "The Design of a Thermoelectric Generator and Its Medical Applications", Designs, vol. 3, no. 2, p. 22, 2019. [http://dx.doi.org/10.3390/designs3020022]

[24]

K. Fukuda, Y. Sato, and T. Kajihara, "U.S. Patent No. 6,274,802. Washington, DC: U.S. Patent and Trademark Office", 2001.

[25]

J. Paradiso, P. Dutta, H. Gellersen, and E. Schooler, "Guest editors’ introduction: Smart energy systems", IEEE Pervasive Comput., vol. 10, no. 1, pp. 11-12, 2011. [http://dx.doi.org/10.1109/MPRV.2011.4]

[26]

M. Hamid Elsheikh, D.A. Shnawah, M.F.M. Sabri, S.B.M. Said, M. Haji Hassan, M.B. Ali Bashir, and M. Mohamad, "A review on thermoelectric renewable energy: Principle parameters that affect their performance", Renew. Sustain. Energy Rev., vol. 30, pp. 337-355, 2014. [http://dx.doi.org/10.1016/j.rser.2013.10.027]

[27]

S.B. Riffat, and X. Ma, "Thermoelectrics: a review of present and potential applications", Appl. Therm. Eng., vol. 23, no. 8, pp. 913-935, 2003. [http://dx.doi.org/10.1016/S1359-4311(03)00012-7]

[28]

S. Twaha, J. Zhu, Y. Yan, and B. Li, "A comprehensive review of thermoelectric technology: Materials, applications, modelling and performance improvement", Renew. Sustain. Energy Rev., vol. 65, pp. 698-726, 2016. [http://dx.doi.org/10.1016/j.rser.2016.07.034]

[29]

A. Elghool, F. Basrawi, T.K. Ibrahim, K. Habib, H. Ibrahim, and D.M.N.D. Idris, "A review on heat sink for thermo-electric power generation: Classifications and parameters affecting performance", Energy Convers. Manage., vol. 134, pp. 260-277, 2017. [http://dx.doi.org/10.1016/j.enconman.2016.12.046]

[30]

A. Majumdar, "Helping chips to keep their cool", Nat. Nanotechnol., vol. 4, no. 4, pp. 214-215, 2009. [http://dx.doi.org/10.1038/nnano.2009.65] [PMID: 19350027]

[31]

T. Gong, Y. Wu, L. Gao, L. Zhang, J. Li, and T. Ming, "Thermo-mechanical analysis on a compact thermoelectric cooler", Energy, vol. 172, pp. 1211-1224, 2019. [http://dx.doi.org/10.1016/j.energy.2019.02.014]

[32]

C.T. Hsu, G-Y. Huang, H-S. Chu, B. Yu, and D-J. Yao, "Experiments and simulations on lowtemperature waste heat harvesting system by thermoelectric power generators", Appl. Energy, vol. 88, no. 4, pp. 1291-1297, 2011. [http://dx.doi.org/10.1016/j.apenergy.2010.10.005]

[33]

L. Zhu, H. Tan, and J. Yu, "Analysis on optimal heat exchanger size of thermoelectric cooler for electronic cooling applications", Energy Convers. Manage., vol. 76, pp. 685-690, 2013. [http://dx.doi.org/10.1016/j.enconman.2013.08.014]

[34]

R. Gonzalez, and C. Maronde, "Automotive thermoelectric HVAC development and demonstration project", California Energy Commission, pp. 10-10, 2010.

[35]

M. Fisac, F.X. Villasevil, and A.M. López, "Design of a thermoelectric generator with fast transient

64 Materials and Technologies for a Green Environment

Dhass et al.

response", Renew. Energy, vol. 81, pp. 658-663, 2015. [http://dx.doi.org/10.1016/j.renene.2015.03.080] [36]

C. Gayner, and K.K. Kar, "Recent advances in thermoelectric materials", Prog. Mater. Sci., vol. 83, pp. 330-382, 2016. [http://dx.doi.org/10.1016/j.pmatsci.2016.07.002]

[37]

S. Lee, S. Kim, A. Pathak, A. Tripathi, T. Qiao, Y. Lee, H. Lee, and H.Y. Woo, "Recent progress in organic thermoelectric materials and devices", Macromol. Res., vol. 28, no. 6, pp. 531-552, 2020. [http://dx.doi.org/10.1007/s13233-020-8116-y]

[38]

M.S. Hossain, T. Li, Y. Yu, J. Yong, J.H. Bahk, and E. Skafidas, "Recent advances in printable thermoelectric devices: materials, printing techniques, and applications", RSC Advances, vol. 10, no. 14, pp. 8421-8434, 2020. [http://dx.doi.org/10.1039/C9RA09801A] [PMID: 35497831]

[39]

M. Wang, P. Baek, A. Akbarinejad, D. Barker, and J. Travas-Sejdic, "Conjugated polymers and composites for stretchable organic electronics", J. Mater. Chem. C Mater. Opt. Electron. Devices, vol. 7, no. 19, pp. 5534-5552, 2019. [http://dx.doi.org/10.1039/C9TC00709A]

[40]

H. Yao, Z. Fan, H. Cheng, X. Guan, C. Wang, K. Sun, and J. Ouyang, "Recent development of thermoelectric polymers and composites", Macromol. Rapid Commun., vol. 39, no. 6, p. 1700727, 2018. [http://dx.doi.org/10.1002/marc.201700727] [PMID: 29356234]

[41]

H. Jin, J. Li, J. Iocozzia, X. Zeng, P.C. Wei, C. Yang, N. Li, Z. Liu, J.H. He, T. Zhu, J. Wang, Z. Lin, and S. Wang, "Hybrid Organic–Inorganic Thermoelectric Materials and Devices", Angew. Chem. Int. Ed., vol. 58, no. 43, pp. 15206-15226, 2019. [http://dx.doi.org/10.1002/anie.201901106] [PMID: 30785665]

[42]

M.W. Gaultois, T.D. Sparks, C.K.H. Borg, R. Seshadri, W.D. Bonificio, and D.R. Clarke, "Datadriven review of thermoelectric materials: performance and resource considerations", Chem. Mater., vol. 25, no. 15, pp. 2911-2920, 2013. [http://dx.doi.org/10.1021/cm400893e]

[43]

N.T. Kemp, A.B. Kaiser, C.J. Liu, B. Chapman, O. Mercier, A.M. Carr, H.J. Trodahl, R.G. Buckley, A.C. Partridge, J.Y. Lee, C.Y. Kim, A. Bartl, L. Dunsch, W.T. Smith, and J.S. Shapiro, "Thermoelectric power and conductivity of different types of polypyrrole", J. Polym. Sci., B, Polym. Phys., vol. 37, no. 9, pp. 953-960, 1999. [http://dx.doi.org/10.1002/(SICI)1099-0488(19990501)37:93.0.CO;2-L]

[44]

T.M. Tritt, "Thermoelectric phenomena, materials, and applications", Annu. Rev. Mater. Res., vol. 41, no. 1, pp. 433-448, 2011. [http://dx.doi.org/10.1146/annurev-matsci-062910-100453]

[45]

R.R. Heikes and R.W. Ure. Thermoelectricity. Science and engineering". Interscience Publishers: New York, London, 1961.

[46]

M.G. Kanatzidis, S.D. Mahanti, T.P. Hogan, Ed., Chemistry, Physics and Materials Science of Thermoelectric Materials: Beyond Bismuth Telluride. Plenum: New York, 2003. [http://dx.doi.org/10.1007/978-1-4419-9278-9]

[47]

M. Ohtaki, T. Tsubota, K. Eguchi, and H. Arai, "High‐temperature thermoelectric properties of (Zn 1−x Al x )O", J. Appl. Phys., vol. 79, no. 3, pp. 1816-1818, 1996. [http://dx.doi.org/10.1063/1.360976]

[48]

L.D. Hicks, and M.S. Dresselhaus, "Effect of quantum-well structures on the thermoelectric Fig. of merit", Phys. Rev. B Condens. Matter, vol. 47, no. 19, pp. 12727-12731, 1993. [http://dx.doi.org/10.1103/PhysRevB.47.12727] [PMID: 10005469]

[49]

B. Jang, S. Han, and J.Y. Kim, "Optimal design for micro-thermoelectric generators using finite

Thermoelectric Generators

Materials and Technologies for a Green Environment 65

element analysis", Microelectron. Eng., vol. 88, no. 5, pp. 775-778, 2011. [http://dx.doi.org/10.1016/j.mee.2010.06.025] [50]

H. Lee, "Optimal design of thermoelectric devices with dimensional analysis", Appl. Energy, vol. 106, pp. 79-88, 2013. [http://dx.doi.org/10.1016/j.apenergy.2013.01.052]

[51]

X. Jia, and Y. Gao, "Optimal design of a novel thermoelectric generator with linear-shaped structure under different operating temperature conditions", Appl. Therm. Eng., vol. 78, pp. 533-542, 2015. [http://dx.doi.org/10.1016/j.applthermaleng.2014.12.011]

[52]

D. Narducci, P. Bermel, B. Lorenzi, N. Wang, and K. Yazawa, Hybrid Photovoltaic–Thermoelectric Generators: Materials Issues.Hybrid and Fully Thermoelectric Solar Harvesting. Springer: Cham, 2018, pp. 103-116. [http://dx.doi.org/10.1007/978-3-319-76427-6_6]

[53]

A.A. Anitha, J. Jayakumar, and L.G. Asirvatham, "Performance analysis of (Bi2Te3-PbTe) hybrid thermoelectric generator", International Journal of Power Electronics and Drive Systems, vol. 8, no. 2, p. 917, 2017.

[54]

R. Saidur, H. H. Masjuki, M. Hasanuzzaman, T. M. I. Mahlia, C. Y. Tan, J. K. Ooi, and P. H. Yoon. "Performance investigation of a solar powered thermoelectric refrigerator". Int. J. Mech. Mater. Eng. vol. 3, no. 1, pp. 7-16, 2008.

[55]

S. Roudy, and L. Frechette. "Energy scavenging and nontraditional power sources for wireless sensor networks," In: I. Stojmenovic (Ed.) Handbook of Sensor Networks: Algorithms and Architectures. John Wiley & Sons 2005.

[56]

T.V. Galchev, J. McCullagh, R.L. Peterson, and K. Najafi, "Harvesting traffic-induced vibrations for structural health monitoring of bridges", J. Micromech. Microeng., vol. 21, no. 10, p. 104005, 2011. [http://dx.doi.org/10.1088/0960-1317/21/10/104005]

[57]

Z. Li, L. Zuo, J. Kuang, and G. Luhrs, "Energy-harvesting shock absorber with a mechanical motion rectifier", Smart Mater. Struct., vol. 22, no. 2, p. 025008, 2013. [http://dx.doi.org/10.1088/0964-1726/22/2/025008]

[58]

H.S. Han, Y.H. Kim, S.Y. Kim, S. Um, and J.M. Hyun, "Performance measurement and analysis of a thermoelectric power generator", In: 2010 12th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems. IEEE, pp. 1-7, 2010. [http://dx.doi.org/10.1109/ITHERM.2010.5501389]

[59]

M. Alhawari, B. Mohammad, H. Saleh, and M. Ismail, Energy Harvesting Sources, Models, and Circuits.Energy Harvesting for Self-Powered Wearable Devices. Springer: Cham, 2018, pp. 7-35. [http://dx.doi.org/10.1007/978-3-319-62578-2_2]

[60]

J. Chen, and C. Wu, "Analysis on the performance of a thermoelectric generator", J. Energy Resour. Technol., vol. 122, no. 2, pp. 61-63, 2000. [http://dx.doi.org/10.1115/1.483163]

[61]

A. Elarusi, N. Illendula, and H. Fagehi, "Performance Prediction of Commercial Thermoelectric Cooler Modules using the Effective Material Properties". J. Elec. Mater., vol. 44, pp. 2157-2165, 2015.

[62]

J.P. Rojas, D. Singh, S.B. Inayat, G.A.T. Sevilla, H.M. Fahad, and M.M. Hussain, "Micro and nanoengineering enabled new generation of thermoelectric generator devices and applications", ECS J. Solid State Sci. Technol., vol. 6, no. 3, pp. N3036-N3044, 2017. [http://dx.doi.org/10.1149/2.0081703jss]

[63]

W. Moser, S. Aigenbauer, M. Heckmann, G. Friedl, and H. Hofbauer, Micro-scale CHP based on biomass–intelligent heat transfer with thermoelectric generators. BIOENERGY: Jyväskylä, Finland, 2007.

[64]

A.R.M. Siddique, S. Mahmud, and B.V. Heyst, "A review of the state of the science on wearable

66 Materials and Technologies for a Green Environment

Dhass et al.

thermoelectric power generators (TEGs) and their existing challenges", Renew. Sustain. Energy Rev., vol. 73, pp. 730-744, 2017. [http://dx.doi.org/10.1016/j.rser.2017.01.177] [65]

R.R. Nimbalkar, and S.S. Kshirsagar, "Thermoelectric power generation as an alternative green technology of energy harvesting", Int. J. Adv. Comput. Res., vol. 3, no. 3, p. 368, 2013.

Materials and Technologies for a Green Environment, 2023, 67-103

67

CHAPTER 3

Solar Electric Vehicle Charging Interaction: An Integrated Module

and

Grid

D. Muruganandam1,*, J. Jayapriya2, P.K. Chidambaram3 and B. Karthik Anand4 Department of Mechanical Engineering, Adhi College of Engineering and Technology, Tamilnadu, India 2 Department of Mathematics, Sathyabama Institute of Science and Technology, Chennai, Tamilnadu, India 3 Department of Mechanical Engineering, Newprince Shri Bhavani College of Engineering and Technology, Chennai, Tamil Nadu, India 4 Sathyabama Institute of Science and Technology, Chennai, Tamilnadu, India 1

Abstract: Electric mobility is one of the key technologies for the replacement of nonrenewable energy sources in the long term; creating new markets, opportunities, and new technologies, as the old energy order comes to an end with the evolution of new ones. With the passing of around two centuries, electric vehicle technology has developed to different levels across the globe. Norway has the highest percentage of electric vehicles, while China has the highest number of electric vehicles sold per year in the world. India is catching up with electric vehicle penetration. As per 2018 data, 49% of the total vehicles sold in Norway were electric. In 2019, China registered the maximum number of electric vehicles sold – 1.15 million vehicles. The key advantages of e-mobility are a reduction in GHG emissions, a reduction in the dependency on fossil fuels, higher efficiency compared to ICE vehicles, fewer noise emissions, and the flexibility of EVs becoming a platform for collaborative development of autonomous cars and shared mobility and MaaS. The key challenges are the total cost of ownership, charging infrastructure, reliance on the imported content and parts, customer acceptance of EVs, vehicle range anxiety and battery manufacturing, and availability of raw materials. This research investigates in detail the opportunities created by technologies such as solar-powered vehicle charging, the second life of traction battery, smart grid integration, connected and autonomous CAVE and vehicle light-weighting to enable e-mobility as a more commercial means of transportation.

Keywords: CAVE, GHG, ICE vehicles, MaaS. * Corresponding author D. Muruganandam: Department of Mechanical Engineering, Sri Venkateswaraa College of Technology, Tamil Nadu, India; E-mail: [email protected]

Santhanam Harikrishnan (Ed.) All rights reserved-© 2023 Bentham Science Publishers

68 Materials and Technologies for a Green Environment

Muruganandam et al.

1. INTRODUCTION A disruptive innovation is an innovation that creates a new market and a value network and eventually disrupts an existing market and value network, displacing established market-leading firms, products, and alliances. There was a disruption in computer technology that started in 1970s and ended with a revolution in speed, structure, communication and size as shown in Fig. (1). 1970s Computer

Main Frame

1980s 2000

Personal computers

Fig. (1). Tipping point and disruptions.

Similar to the computer technology disruption, the first working electric motor and electric vehicle was built by Thomas Davenport, an American from Vermont, in 1834. It was a small locomotive that used two electromagnets, a pivot and a battery. There were other inventors like Robert Anderson of Scotland (1830s) who had created a fully electric carriage. The evolved architecture EV is shown in Fig. (2).

Fig. (2). Electric vehicle architecture.

EV disruptions that are going to be the tipping point are, 1) Big data for decisions (expected to be commonplace by 2023 - 2025); 2) Autonomous cars (by 2026 - 2027);

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 69

3) Artificial Intelligence and decision-making (also, by 2030); 4) Connected vehicles (by 2030). Before delving into the challenges and opportunities in EVs, it is worthwhile to look into the advantages and disadvantages of EVs. 1.1. Advantages of Electric Vehicles Over ICE Vehicles The total cost of ownership of an electric vehicle (EV) is lesser in comparison to a conventional fuel vehicle. Typical life of a battery is around 8 to 10 years, after which it will still find uses in storage and other less complex applications. Electric vehicles (EV) have relatively fewer moving parts, i.e., 75 to 80% less compared to the internal combustion engine vehicles. Due to the above characteristics, electric vehicles are easily adoptable for implementing autonomous technologies which results in autonomous driving. They also reduce emissions to help the environment (less pollution, renewable energy, eco-friendly materials). The battery cost is also expected to be half of the current price in the next 5 years. 1.2. Disadvantages of Electric Vehicles over ICE Vehicles The affordability of electric vehicles will be of great concern at least for another decade till the prices of batteries become cheaper. In order to decide on the right technology for charging, numerous studies have been undertaken and many are still in progress in understanding the different modes of charging. Customers have options for night charging, home charging, public charging station, charging on the go, wireless charging, swappable solutions, opportunity charging, charging on malls and restaurants and charging at gas stations. The right technology needs are to be made standard. The investment for the charging stations is seen to be higher and subsidies are being provided for using the charging stations. Mergers and acquisitions of market leaders by sustaining business giants are slowly changing the scenario, but are time bound. The majority of the vehicle OEMs in the EV horizon are also in the process of establishing their standard chargers, taking into account customer requirements. With countries going to end the non-renewable sources in respective years as given in Fig. (3), the e-mobility enablers are to be implemented on a holistic basis to have a seamless integration.

70 Materials and Technologies for a Green Environment

Country Norway

Muruganandam et al.

Year by which non-renewable sources of energy will be banned 2025

Iceland, Ireland, Israel. Denmark UK, Sri Lanka, Spain, France, Canada, Portugal Costa Rica

2030 2035 2040 2050

Fig. (3). Countries and year of ban on sale of non renewable fuels.

These technologies for enablers are below but are not limited to: • Solar powered vehicle charging. • Second life EV batteries • Smart grid integration • Connected and autonomous vehicles - CAVE • Vehicle light weighting. 2. SOLAR POWER CHARGING In Europe for the 01st time in the previous decade, the percentage of cars that got registered, reversed in July 2020. In January 2011, the percentage was 55% diesel, 44% gasoline and 1% electric. In July 2020, it was 50% gasoline, 25% diesel, 20 to 22% electric and the rest shared by others. There is a paradigm shift in the energy generation landscape at the global level and investments are happening in the space of solar power generation. As per expert predictions, for the next decade, renewable energy sources (solar energy and wind power) will be the primary source for powering EVs. The transportation and mobility ecosystem considers solar powered EV charging as one of the game changing technologies and also as a need of the hour for effective energy management. Vehicles powered by solar energy through different forms, are summarized below:

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 71

1. Roof-top solar panels – These are mobile solar charging systems. The panels fixed on the vehicles keep powering the batteries. 2. Fixed solar powered charging installation – The solar energy is trapped, converted into the form of electricity used in electric vehicles. The stations interact with the EVs, grids and storage systems at the ground. Data is also exchanged with the help of cloud networks. Solar energy is being used as storage, supplementary to the main grid and also as a power source on its own. Though the investment is very high, it will be a onetime investment and also well spread across a period of 20 to 25 years. Countries in the tropical region have been tapping into solar energy effectively and efficiently. In India, there are projects installed to produce approximately 36 gigawatts of solar power. India’s earlier target was to produce 175 gigawatt by 2022, which is now revised to 100 gigawatts by the solar energy corporation of India (SECI). SECI is responsible for creating various solar energy projects. In the first half of 2020, SECI awarded a mega project to the Adani group for creating an 8 giga watt plant. The Kamuthi solar farm, is a fully functioning solar project in Tamil Nadu, India, which has been operational since 2016 with a capacity of 648 megawatts at full utilisation. It can produce electricity capable of powering a maximum of 1,50,000 homes. The return on investment of the project will be covered in a few years, with one–time installation and capital expenditure taken care of in the next 20-25 years. The abundance of solar power being tapped in PV enabled EV charging station is explained in several studies, including [1, 2]. The complete system is divided into 4 areas. The end user has the interfacing functionalities for more visibility on the system. Information is exchanged based on the user’s interaction with the system. The power management blocks interact with the grids and batteries. The central controller controls the data flow, exchanging data with networks and monitors the CAN. The final block includes physical devices like chargers, blue tooth devices, etc. More details are shown in Fig. (4).

72 Materials and Technologies for a Green Environment

Muruganandam et al.

Fig. (4). Solar energized EV charging - functional blocks.

The computational functions drive on the background. The central controller monitors the computational functions. 2.1. Energy flow & Management The system has three sources of energy exchange: 1. Solar panels 2. Power grid 3. Battery The most significant among the three are solar cells and panels. The sizing estimation is made considering the fact that a few kilowatts is to be generated, at the minimum. A panel would typically produce at rated irradiance, approximately 150W/square meter. The solar panels provide energy through the MPPT (maximum power point tracking) module. Since the solar energy is not constant throughout the day, there can be an inbuilt logic in order for the whole system to maximise the power throughout a period of time. MPPT or maximum power point tracking is an algorithm that is used for extracting maximum available power from PV module under certain conditions. The voltage at which PV module can produce maximum power is called

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 73

maximum power point. Maximum power varies with solar radiation, ambient temperature and solar cell temperature. A solar charge controller is embedded with MPPT algorithm to maximize the amount of current going into the battery from the photo voltaic (PV) module. MPPT is like a DC-to-DC converter which operates by taking DC input from PV module, changing it to AC and converting it back to a different DC voltage and current to exactly match the PV module to the battery. Solar power management system is explained in [3]. Typically, a solar panel similar to the roof of a car will develop 300 to 400 watts of electricity. A study about S2V (solar-to-vehicle) systems explores this in detail, elaborating on the effectiveness of solar-powered vehicles [4]. A schematic representation is provided in Fig. (5). The design of an electric vehicle powered by solar calls involves making all body surfaces suitable for impregnating solar panels on the body(roof, hood, panels) and exterior of the electric car. A case study on the determination of a number of solar panels required for a given vehicle configuration is provided in Table 1 below.

Fig. (5). Solar roof panels on the roof, hood and rear windows. Table 1. Solar roof panels calculation for electric vehicle charging. S. No.

Parameters

Case I (250W Panel

Case II (400W Panel)

Remarks

1

Average power delivery from solar panel / month

30 to 40 kWh

30 to 40kwh

-

2

Average power delivery from solar panel /day

1 kWh

1.16kwh

-

100KW motor 32kwh battery

A. Considering a vehicle range of 200kms b. Energy consumption will be (0.32/200) ~ 0.16kwh/km

3

An electric vehicle passenger carrier powertrain

100KW motor 32kwh battery

Passenger electric vehicle static under sun during day 4

Average hours where sun will be available in a day

7 hours

7 hours

-

74 Materials and Technologies for a Green Environment

Muruganandam et al.

(Table 1) cont.....

S. No.

Parameters

Case I (250W Panel

Case II (400W Panel)

Remarks

5

Wattage of solar panel required

4.5kw

4.5kw

(32 kWh /7hours)

6

Number of panels req.On veh. To charge battery to 100% after complete drain.

18

11.25

11.25

Scenario when the passenger electric vehicle is running in the day 7

Typical driving range of customer daily

100kms

100kms

-

8

Time, vehicle need to run with to cover the 100 kms

1 hour

1 hour

Vehicle max speed considered as 100kmph

9

Based on research, a. For every hour of vehicle running under sun, it generates 5 to 6 miles, b. Additional energy created due to this running (10 X 0.16kwh/km)

1.6kw

1.6kw

-

10

So total number of panels that will be required including this running in

(4.5 - 1.6)/ 0.25 = 11.6 ~ 12

(4.5 -1.6)/0.40 = 7.25 ~8

-

Hourly solar irradiation data is used for estimating power generated from each solar panel. The following formulation is used: S’=A’ * I’ *η’

(1)

S’ =amount of power generated by solar panel A’=area of solar panel exposed I’= the solar panel irradiation Η’=efficiency of the solar panel 2.2. Solar Power Grid A functional working diagram of a solar power grid is provided in Fig. (6). The maximization of the energy from the system is the main intent. However, as the intensity of the solar is not uniform, during the OFF periods of power generation, the energy from grid will be utilized. For this, bi-directional inverters are being used. For PV sizing, several approaches have been already explored. The more optimal approach is to match the power demand of EV load. Simplified and direct load profiles are developed by taking peak value with assumed efficiency of components.

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 75

Fig. (6). A functional working diagram of solar power grid.

PPV = pevp / (η ACC × ηinv ×ηdcc × ηmm × ηdic × ηasl)

(2)

Where, PPV - panel power sizing, kW PEV p - peak power of one EV, kW Ηacc – 95 to 98% (efficiency of AC cable) Ηinv – 90 to 95% (efficiency of inverter) Ηdcc – 95 to 99% (efficiency of DC cable) Ηmm – 95 to 99% (efficiency of panels after module mismatch) Ηdic – 95 to 99% (efficiency after diodes & connections loss) Ηasl – 90 to 95% (efficiency after annual soling loss). Solar collectors placed on the parking area are linked to the grid through smart meters/4way meters/bi denominated equivalent meters, along with the EVs. The equivalent metering which is followed in personal home usage shall be deployed in the case of EVs. During the daytime, the production of solar energy is seen to be the highest in the afternoon whereas the consumption is at the peak in the morning, evening and night. So the excess produced is fed back into the grid. During peak load, the grid provides the necessary power with EVs, the same

76 Materials and Technologies for a Green Environment

Muruganandam et al.

strategy is being followed. A study has been done on the various modes of energy flow [5]. Fig. (7) represents a typical energy flow in the PV and grid systems.

Fig. (7). Energy interaction between the PV and the grid.

Different types of charging models are being explored currently. The real-time charging model is one in which EVs get charged simultaneously while the photovoltaic power is generated. Another charging model makes use of a system equipped with a mobile charging unit. The real-time charge is always the primary load, which is the electricity demand that must be served according to a particular schedule. The mobile charging unit or source is a deferrable load, which is the electricity demand that can be served at any time within a certain time span and the exact timing is flexible. The total energy involved in this system is the sum of the energy generated by solar photo voltaic cells and the energy from grid. The contribution is 50 to 55% from PV and 50 to 45% from grid. There is a marginal excess production of energy compared to the demand. The inverter converts the DC power from PV to AC. The rectifier converts the AC power to DC and moves it to the vehicle. The excess in production is summation of the losses on inverter, rectifier and the surplus. Inverters and rectifiers have efficiencies between 85% and 90% in terms of system-wise operation.

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 77

The total energy loss in the converter accounts for ~10% of the total energy produced. Any partial transfer/shifting of load from DC to AC will further reduce the energy losses attributed from the converter. Power clipping is carried out by inverter when more DC power is generated than the capacity of the inverter. In order to protect the inverter, there may be reduction in the DC current and increase of the DC voltage, thereby reducing the DC power. Alternately, the inverter locks the AC output values. This effect is pronounced if there is a DC/AC ratio to the tune of 1.3~1.5/1. Interestingly this phenomena has an impact on the power generation capacity of the entire photovoltaic system. So high DC /AC ratio is seen as an opportunity for optimized system energy generation especially for solution providers with long term investment and returns. The system also has an in-built capability to manage the inverter. When power from solar PV is in higher proportion than capacity of inverter, some parts of PV power is discharged to the battery in buck mode of voltage by bidirectional controlled DC-DC converter. This eliminates the need for power clipping phenomena and also ensures no major limitations in terms of inverter capacity as losses are reduced. In the other way, when solar PV production is lower than inverter capacity, power from battery is diverted into the grid through same bidirectional DC-DC converter in boost mode of voltage. Avoiding power clipping losses by inverter having high DC-to-AC loading ratio in grid connected solar PV plant using battery energy storage system is explained in [6]. The third source and the sink/storage is the battery. Lithium-ion battery cells have high energy density, high efficiency batteries, long life span and also have very high cycle life. They lend itself well to quick charging, very high depth of discharge and very high volumetric efficiency. It is possible to house these batteries underground. The nominal voltage of 3.2V in lithium ion is an input for the charge controller. Lithium-ion battery’s characteristics of high energy density is an added advantage. The advanced charge controller monitors power. It senses the voltage from energy generated from panel, modulates the current and keeps it at maximum power point. The function of charge controller is very important. It plays the role of converting the solar energy from solar panel into the voltage for the battery to charge. So, selection of charge controller is critical and will be in line with the type of battery cell which may be lithium ion or lead acid. The charge controller works when enough light and voltage are produced. When there is no sufficient light, the charge controller goes on OFF mode. The inefficiency of the simple type is that it cannot use the peripheral power available in the morning and afternoon. The controller can interface through different types of communication. The CAN bus allows the microcontroller to communicate without any central computer. Modbus

78 Materials and Technologies for a Green Environment

Muruganandam et al.

is one more communication protocol used for transmitting data between master devices and slave devices. Each master device is coded with a number and gives an order for getting information to the slave devices. Modbus transmission is in simple words and is versatile to be incorporated in a very broad list of devices supplied by different manufacturers. Analysis of charge controllers in a typical solar charging system is discussed in detail in [7]. Fig. (8) represents the power system architecture:

Fig. (8). The power system architecture.

2.3. The Power Electronics Components and their Configuration for the Solar DC–AC inverter gets utilised when vehicles go for slow charging and where AC is needed. The DC –AC inverter also feeds back the energy into the grid, when there is an imbalance or less demand. During DC fast charging, there will be a high demand for voltage and current. In this condition, the controller decides what needs to be configured. The DC bus provides charge to the DC-DC converter. The configuration of DC (with buck mode /boost mode) converter is made in such a manner to take care of both fast charging and AC slow charging. Based on research, it is understood that the efficiency of the inverter is approximated around 93- 94%. Also, there is a need of system sizing to the compact level. Nowadays, researchers/organisations are finding more interest in silicon carbide

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 79

devices-due to their small size, ability to lessen power loss, and adaptability to high temperatures. Solar vehicle charging has been explained in detail in the abstract [8]. RS485 is of high-speed protocol that enables a distance of approximately 1200m transfer wise. It does not use the concept of slave and master and helps facilitate communication between driver and receivers through the differential signal. The master central controller is the most powerful tool in the station. Its function starts from identification, and engagement of the consumer and goes till the vehicle is charged to the required SOC levels. It is a cluster of high-performance computing, connectivity and sensing. The major functionalities are as follows: 1. User interface: The user connects with the application of any of the NFC technologies. The NFC (near field technologies) enables data transfer within a few cms (less than 10cms). Antenna is fixed on the device through which digital data gets exchanged. Smart cards are also used. Each smart card has a microprocessor or microcontroller that senses the type of data. The only drawback of smart cards is the security breach. 2. Power management: The MPPT has a system with a DC-DC converter which optimizes the system voltage to deliver maximum power. The maximisation of power is done by three techniques/methods. In method 1, there is a linear correlation assumed between open circuit voltage and voltage at maximum. By monitoring open circuit voltage from array voltage, the voltage at peak power tracking can be established. Though it is simple, the establishment of a correlation constant is very complex. In the second technique, the PV array voltage is measured. There is a comparison done between the measured PV output power and the earlier one. Based on the difference in positive or negative direction, the decision will be taken to disturb it on increase or decrease mode. There are also methods that use fuzzy logic in the MPPT controller. Details of MPPT are provided in Fig. (9). In the third method, instead of fixed step external stimuli, variable stimuli are used based on changing environmental PV array measurement. The functioning of the MPPT algorithm in this application is explained in a study [5].

80 Materials and Technologies for a Green Environment

Muruganandam et al.

Fig. (9). MPPT.

3. Connectivity: The station is always in access and control with coordinated management unit. The interaction between the station and CMU deals with reporting of data and diagnosis at defined intervals of time. For connectivity, wireless is to be taken forward as a futuristic option. For remote control, recent trends are in favour of the IOT monitoring system. In IOT along with artificial intelligence (AI), the failure of the set up can be predicted in advance. Since lots of manual movements /efforts are reduced, a positive impact on greenhouse emissions decreases. There are attempts to make realtime remote monitoring customised for individual applications. The data captured is communicated/shared with cloud. The local computer can download from the cloud. 4. Protections, diagnostics and fault reporting: There should be a standard evaluation criterion using fault detection and reporting. The system has to identify and locate faults, so that the problematic modules can be replaced. Since the response needs to be within a fraction of seconds, the system has superior protection units. These protection units immediately get alert /disturbances if there are excess voltage, excess current, short circuits, thunder strikes, severe lightening, high temperatures, etc. Reporting of the issues by systems on a realtime basis will reduce the downtime and in turn the operational cost.

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 81

5. Communication, protocol between EV battery, systems and charging equipment: Severity and complexities in the equipment make communication difficult. The battery monitoring system (BMS) of vehicle getting charged helps in ensuring that the cells are under monitoring and are not stressed too much. The BMS needs to communicate to the controller of the solar powered charging system and also to the motor controller and vehicle controller to ensure a balanced charging. The accurate cost, maintainability of the BMS is important in selection. The charging gadgets connect with the battery management system of the electric vehicle either through the strong bus standard which enables systems to talk or by the conductor itself. Information on vehicle battery is exchanged between the two interfaces during charging. a. Voltage of the cells b. Current in the cell c. Temperature encountered d. SOC e. Internal resistance of the cells Thus, BMS is a fail-safe device which helps in avoiding failure of the system. It is based on monitoring, even at instances that disconnect the battery during charging. With the help of communication/data sharing in the power lines, the normal power grid is turned into a smart grid. Since the power line communication cables are intended for power transmission, there is a limitation in the frequency of data getting transmitted. High frequency transmissions are limited. Data transmission rate is typically in the range between 1 kilobyte/sec to 100-150kilobyte/sec. This range will be suitable for data control and data gathering instances. The PLCs perform real time monitoring and share the billing information to customers regarding charging [9]. In Fig. (10), the different aspects of interaction provided between EV and PV are shown.

82 Materials and Technologies for a Green Environment

Muruganandam et al.

Fig. (10). PV and EV charging.

Interface: EV charging infrastructure should incorporate a human-machine interface (HMI) that provides an interface between the charging station and the electric vehicle. Provision to real-time data and analytics associated with the charging process get created. HMI provides multiple functions at a solar charging station. The operators could see the data in the systems, tracking units, and check whether there are any alarms in the systems and monitor the produced power from the systems. The HMI may be installed at the station locally or managed remotely. For bigger projects, a dedicated station is recommended. Solar charging stations and an analysis of their effectiveness in a power distribution system when including variables like HMIs, are presented in a detailed manner [10]. 6. EV battery charging equipment: Charging levels for electric vehicles are classified by society of automotive engineers (SAE) into 3 levels: level 1, level 2

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 83

and fast charge. The infrastructure and equipment are accordingly installed/provided along with the vehicle. The levels define the charging power. Solar power charging qualifies for level I. Level 1 charging: Level 1 charging comes with 120V circuit up to 1.4 to 1. 5kw. The slow rate calls either around 1.4kilowatts or around 2.3kilowatts. It typically takes 8 to 10 hours or even more.This type of charging will be conducted during night, when the vehicle is not used much. If seen comprehensively, level 1 charging is normally done at home from 10 pm onwards till early morning (with regular hardware provided along with EV) and in workplaces when the vehicle usage is the least [11]. When the vehicle is slowly charged, the entire power can be drawn from solar power. As per estimation if the electric vehicle is charged at approximately 3 kilowatts of power, then roughly 2.5kilowatts can be taken from solar power and the rest 0.5kilowatts of power from the external grid (this is considering the transmission losses). If the vehicle charging is up to level 2, the ultimate aim of the charging is to strike a balance between the solar charging and grid capacity utilisation. If the charging goes to level 2, may be 3KW, half of the same will be drawn from the grid. If charging starts moving beyond that, say 6 to 8KW, most of the energy would be shared from the grid. But this comes at an inflated cost. So, to keep it optimal, timer arrangement is set by means of which the charging happens only during the maximum solar output. These phenomena can also be enabled by a relay which gets switched on when there is surplus solar energy available. 2.4. Importance of Photo Voltaic Panel as an Energy Source for EVs Various cities across the world are installing solar powered charging stations, the reasons for this growth are multiple. In India, the plan is approximately to have EV solar charging station for every 100kms. The installation of the EV solar charger station is not under licensing and is considered as a service. Public partnership involvement is being encouraged. The following tangible benefits make solar more competitive. 1. More than three fourth of a solar panel module can be recycled. Recycled products can be reused in less stressed applications. China is leading in the utilisation and implementation of solar energy worldwide. Nearly 30+ countries across the globe have got nearly more than 1-gigawatt solar capacity. 2. Typically, the useful life of a solar panel manufactured is between 25 to 30 years. Conventional batteries and inverters are needed to be repaired or replaced after 7-10 years of application commencement.

84 Materials and Technologies for a Green Environment

Muruganandam et al.

3. Developments in technology enable solar energy to create new milestones in terms of power generation, capacity, and levels of affordability and economics of scale. 4. Photovoltaic push is a major cleaner option for fuelling electric cars, especially in the low voltage category. This will be giving an additional 30 miles or more. 5. Solar panels installed at homes, workplaces, restaurants, companies, and farms can augment the reduction of electricity costs through a monitored charging schedule. In India, MNRE (ministry of non-renewable energy) approved kits prove useful for doing the same. 6. Investments and costs of solar installations have reduced over the period, attracting more initiatives and public partnerships to make the joint venture and invest in this sustainable energy. In India, the cost of solar panels 250W is INR 7000 approximately. While the price per watt is INR 28 to 30. 7. A 1KW solar system off the grid is priced at INR 80000 to INR 90000. This comes with a warranty of 4 to 5 years. 2.5. Clean Photovoltaic Energy and Battery Vehicles: Initiatives Taken by Law-making Authorities and Industry/Institutions Over the past few decades, law authorities and agencies, automotive bodies and start-ups have joined hands to increase the penetration of solar and electric vehicle charging. Tax cuts, discounts, loans, social awareness, motivational strategies, and concessions for manufacturing within country are playing key roles in bringing all stakeholders together. Below is a glimpse of some of the initiatives taken by various countries and their governments in the move towards solar charging. 1. The United States of America: National agencies to work with leading institutes to explore the market-driven opportunities of integrating solar energy generation and scheduled electric vehicle charging. 2. China: Leading solar equipment manufacturers are a building solar production base, estimated to be more than $700 million in the eastern part of country. In EV developments, the PV manufacturers are collaborating with auto manufacturers to create an eco-system with sustainability. Polysilicon manufacturing is on a critical path and the excess reserves are used in automotive as inventory [12]. 3. India: Plans to achieve between 175 to 200 gigawatts (GW) of renewable energy capacity in the next 2 years. Half of the planned initiative is to be sourced

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 85

from solar energy. Solar-powered charging stations are being installed both by law making authorities, public sectors and technology solution providers. 4. Netherlands: Environmental assessment agency recently estimated the country could reach 27 GW of installed PV capacity by 2030. Since 2013, the residential solar sector in the Netherlands has grown annually by double-digit rate and accounted for around 80% of installed capacity until 2016. 5. Canada: The solar electricity sector success is based on the growth of the Ontario solar market. Ontario has developed a globally recognized solar market sector which is one of the top 20 solar electricity markets in the world. Incentives are being provided while the user goes off the grid. 2.6. Future of Renewable Photo Voltaic Power Generation Industry experts are of the view that rooftop solar charging stations/vehicles are going to pick up in the next 5 years. Many manufacturers are working on roadworthy prototypes. Solar energy will be an alternative source of power, and only to address the excessive demand for electricity. Indian government is speeding up power generation through renewable sources and has come up with a rooftop solar policy. According to international agencies’ study, India has started more investment in solar photovoltaic (PV) solutions compared to fossil fuels for the generation of electricity from 2018 onwards. Large-scale tenders (with fewer restrictions, more transparency, lower taxes, lower operating costs, and auctions with more public private involvements) have contributed to faster renewable energy development at rapidly decreasing prices. In 2019, India generated a power to the tune of capacity 350GW and above, which included 80 to 85GW of grid-connected renewable electricity. By 2030, India targets to generate 450 to 500GW of electricity from renewable energy sources. The prices of battery and PV solar cells have been coming down. Generation of electricity from solar alternatives has emerged as a long-term solution for the near future. But to have an optimum utilisation of solar energy, EV charging needs to be self-sustained too. Finally, the consumer needs to pay the price of migrating to different (batteryoperated or hybrid) electric mobility solutions. The government and energy suppliers should focus more on building the network of electric vehicle infrastructure such as charging stations and transformers across different landscapes. In practical terms, the investment being done in these infrastructures is also being shared with end users which is what transforms into the cost of using

86 Materials and Technologies for a Green Environment

Muruganandam et al.

charging stations. The availability of space is also a critical challenge considering the rapid urbanisation and movement of the human population towards cities. 3. ELECTRIC VEHICLE SMART GRID INTEGRATION The EV battery packs have a dedicated BMS, which monitors the states of the individual cells in terms of voltage, current and temperature. The circuit has an individual BMS, a controller converter and a bidirectional power converter. This arrangement prevents the battery from being overloaded by external load requests. The BMS monitors state of individual cells, and sends a request to the inverter to reduce the power, controlling the power flow to and from the battery, in order to protect the battery from being overloaded by an external load request. The bidirectional inverter is able to control the power flow to and from the battery within the specified limitations using its integrated control panel and also by external communications [13]. 3.1. Smart Charging for a Reliable and Resilient Grid It has been proved that if charging in an EV goes uncontrolled, it may result in up to 1.5 to 2 times the peak load in residential areas. Smart charging and its impact on typical residential areas are discussed in detail in [14, 15]. A typical electric vehicle user always has to face the prospect of range anxiety. The range can be extended by any of the following means. Solution 1 is to have a greater number of batteries which increase the energy /power density. But this solution comes with excess weight addition, extra cost and recyclability concerns. Solution 2 is to have enhanced charging infrastructure increasing the charging rate i.e., fast charging. This also needs proper interfacing with the grid. Solution 2 is better in terms of economy and time to charge. As recent trends point out, globally there are networks which dynamically adapt to changing electrical demands and conditions. These networks use algorithm that adjusts the speed of the charge for individual EVs based on several factors, such as the number of vehicles plugged in at a given time, other energy demands on the system, and available power from different energy sources. This allows the laboratory to avoid peak-demand charges. It also reduces the amount of electrical infrastructure required, which helps mitigate installation, operation, and maintenance costs. Optimal sizing of stationary energy storage systems (ESS) is required to reduce the peak load and increase the profit of fast charging stations. Sequential sizing of battery and converter or fixed-size converters are also being considered. But with sequential sizing or fixed-converter, sizes may result in less or oversizing. Simultaneous sizing of battery and converter shall overcome the under /oversizing issues. For simulation purposes, the parameters such as number of estimated EVs

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 87

that will arrive in for charging, charging levels, probability of the vehicles returning for charging, etc. can be used. 3.2. A Typical Sizing Methodology of ESS The power demand of the fast-charging station is estimated as in the equation given below: Total load of EV @ given time t = summation of each EV load. = ¦Charging level of evn in kW) x (time interval in Hours) x (probability of evn returning For charging) x (probability of evn requiring Recharge in return) ………………….2

Commercial vehicles need charging on daily basis, whereas personal use vehicles require charging every 2 or 3 days depending on the usage. The electrical load needs are classified into 2 categories. The primary load will be the vehicle directly charging. Secondary loads comprise charging of the electric vehicles coming back from the office to home and getting charged at home. Though the secondary charge may have different timings, it adds to the peak load of the grid. For a system to function in an effective manner, the ESS has to be functional in an optimal manner. The ESS cost comprises 3 factors with a summation of the annual operation cost of ESS, the penalty of buying power from the grid during peak hours and the cost for exchanging power of the grid. The main advantage of EV fast chargers is their ability to charge vehicles quickly. But electricity demand charges incurred during peak periods can significantly impact costs for fast-charging applications. One of the best options is to explore the use of stationary energy storage systems to mitigate demand charges. Cost of buying power in a day pbuy/day = (power tariff during the time of use in day) x (Power taken from grid) Cost of buying power in a year pbuy/year = pbuy/day xtotal no. Of respective days of use in A year. Cost of selling power in a day psell/day = (power tariff during the time of use in day) x (Power sold to grid) Cost of selling power in a year psell/year = psell/dayxtotal no. Of respective days of use in A year. Annual trading price of the grid = ∑ pbuy/year - psell/year ………………. 6

Cost of paying penalty for buying power during peak loads penalty day =(power tariff as penalty/day) x (power borrowed from grid)

88 Materials and Technologies for a Green Environment

Muruganandam et al.

Cost of paying penalty for buying power during peak loads /year is penaltyyear = ∑penalty day x no. of respective days in a year. ……………………………………… 7 The cost of the energy storage system = cost of power conversion system + cost of battery+ cost of maintenance cost+cost of all supporting elements to deliver the power…8 There shall be power balance at a given point of time. The decision whether to buy or sell is dependent on the time of usage price. The power will be bought during low price intervals and sold at higher price intervals. The power balance equation will be Pbuy/day + power discharged from ESS = total EV load+psell/day+power charged to ESS…9

For a smart grid to be efficient, the influencing parameters are to be controlled and optimised. The following parameters influence the functioning of the system. Several studies explore the power capacity and net revenue involved in a V2G system with a power grid [16, 17]. 3.3. Sizing of Battery and the Converter Definition Battery size and specifications of the converter decide the optimisation of the grid model. During this cycle, parameters of the battery such as SOC, charging rate, and discharging rate shall be maintained within the limits. Considering the power balance equation, the more the number of EVs, the higher is the size of the battery, but not necessarily for the converter size. The increase in the battery size is augmented by the fact that more charging (slow and fast) takes place during off peak hours and more discharging takes place in the peak hours (during the day and evening). Hence, the battery and converter sizing are independent and are simultaneous deliverables. 3.4. Number of EVs for Charging With a greater number of EVs, there will be an exponential need for power which calls for buying more power from the grid. More purchase results in more penalty. As a result, the buying penalty will be dominant over the investment cost of ESS. So, the power balance equation will opt for increasing the size of the ESS as load profile at different charging locations differs during the day. The most optimal solution will be to compensate between the investment cost of energy storage system and the peak load buying amount. This is explained in great detail in a study [18].

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 89

3.5. Battery Charging Charging of the battery has a direct impact on the ESS. To keep the investment cost of ESS within limits, if the business model of the charging station goes for low utilisation of battery i.e., charging not from 0 to 100%, but only between 30 to 70%/80%, then the size of battery and converter gets reduced. But the model will not be able to utilise energy of the battery though the investment of ESS is less. This increases the cost of buying power. 3.6. Commercial and Personal Vehicles The charging station caters to the needs of both commercial vehicles and personal vehicles. Commercial vehicles work all around the weekdays, while the personal vehicles are also active on weekends. With an increase in the number of vehicles used for transportation and logistics, the size of the electricity storage unit reduces. As for the load increase, the converter size typically gets unaffected. The following graphs give the peak load distribution due to EVs in different countries in different continents. India: By 2025, the penetration of EVs will be competitive compared to conventional IC engine vehicles due to the falling prices of the battery. A prediction for 2025 and 2030 is provided in Table 2. Table 2. Prediction for 2025 and 2030 on number of EVs to be sold.

S. No. Category of Vehicles

2025 (Percentage of EVs in Total Vehicles Sold)

2030 (Percentage of EVs in Total Vehicles Sold)

1

Passenger vehicles

15 to 20%

30 to 35%

2

Commercial vehicles

5 to 10%

10 to 15%

3

2 wheelers

25 to 30%

45 to 50%

4

3 wheelers

10 to 15%

25 to 30%

3.7. Charging Scenario with Respect to the Location Different vehicles prefer location-wise charging. In electric 2 wheelers, most of the time charging happens at residence. For applications like buses, trucks, charging happens during the off hours in operations at the stations, malls, stoppage points, etc. The same is highlighted in Table 3.

90 Materials and Technologies for a Green Environment

Muruganandam et al.

Table 3. Typical preferred location of charging. S. No.

Category of Vehicles

Location of Charging

1

Passenger vehicles

Non-commercial vehicles are charging in different scenarios: a) Charging @ station: 60 to 90% b) Charging @ home: 20 to 30%

2

Commercial vehicles

Only charging @ charging station

3

2 wheelers

Charging mostly@home and very rarely @ charging station

4

3 wheelers

Charging both @ home and @ charging station

3.8. Charging Scenario with Respect to Timings Charging time varies for the commercial and passenger vehicles. Home charging is preferred by electric 2 wheelers. For commercial vehicles, daytime charging is advisable considering the application. Preferred time for charging is shown in Table 4. Table 4. Typical preferred time of charging. S. No.

Category of Vehicles

Most Preferred Time of Charging

1

Commercial vehicles

Morning: 6am to 9am (45%) Evening: 9pm to 1200am (45%) During the day: 7am to 7pm (10%)

2

Passenger vehicles

Home charging: 7pm to 10am. Every hour addition of vehicles from 8pm onwards.

3

2 wheelers

Between 8pm to 11pm

4

3 wheelers

Electric 3W /auto – 7pm to 12am / 7am to 10pm

3.9. Battery Capacity of Vehicles Typically, the battery capacity of the vehicles ranges from 2 kWh to 125 kWh as per the vehicle application. Based on the vehicle manufacturer’s configurations, there will be additional power sources. The battery capacity is also configured in such a way as to avail the regulatory benefits. This is shown in Table 5. Considering all the above scenarios and based on the studies, the following is predicted in India.

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 91

Table 5. Typical battery capacity rating of vehicles. S. No.

Category of Vehicles

Battery Capacity (kWh)

1

Passenger vehicles

Approximately 30 to 35kwh

2

Commercial vehicles

Approximately 100 to 125kwh

3

2 wheelers

Approximately 2 to 2.5kwh

4

3 wheelers

Approximately 3.5kwh to 4.5kwh

1) Considering the Indian temperature which goes beyond 40 deg celsius in most of the summer and other conditions, the performance of the battery storage system is to be considered to be of utmost importance, and should be studied in detail. 2) Off period charging to be encouraged for the user. 3) Initiative to be provided more on the conversion to hybrid, so that the stress on the grid will be reduced. 4) Generating power from waste to add on to the renewable energy solutions. 5) Focus & fast track the solar charging stations project. 6) Time of use (TOU) tariff strategy to be used to discourage EV users from charging during the peak load conditions. 7) Infrastructure development for grid. 8) The charging at home to be monitored remotely. The home charging is to be allowed only if it is not affecting the peak load of the grid. With predicted EVs opting for plug-in charging, there will be an additional 27GW requirement needed from the grid. For this growth, there has to be an increase in the generation. The barriers and challenges in vehicle to grid optimization in India is discussed in a study [19]. The extra power required for considering the EV charging is shown in Table 6. 3.9.1. Wireless Battery-operated Electric Vehicle Charging In the developed countries, power requirement for demand in home is considered to be 2 to 2.5kw. With normal EVs, going on 6 to 8 kW for charge storage, charging EVs by home charging only adds further load to the grid. By adding dynamic wireless charging, the EV user can use continuous charging during the drive which in turn reduces the size of the batteries. But the challenge is to enable the required hardware, communication, and control strategies to be competitive on cost compared to DC charging technologies. Details are provided in Fig. (11).

92 Materials and Technologies for a Green Environment

Muruganandam et al.

Table 6. Additional Grid Power required for Electric Vehicle Charging by 2025.

Cont Power

W

Power

Road

Fig. (11). Wireless charging of electric vehicle.

Inductive charging is being used in wireless transfer. Charge is transferred though the air gap of the magnetic coils.The EV needs to be in close proximity to the charging coil. The primary magnet will be on the ground and the secondary magnet on the vehicle and power is coupled using flux. The magnetic field is designed and shaped in such a manner that it is within the boundary of the vehicle and the flux is not interfering with the outside objects including human beings. Foreign object detection and living object protection features are getting incorporated. Much of the standardisation work is happening on the wireless EV charging. Standards such as J2954 define the safety and electromagnetic limits, testing, and efficiency and interoperability targets [20]. The following criteria are under study for designing an optimised system.

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 93

1) Identification and classification of roadway classes to be electrified. 2) Identification and location of roadway charging segment. 3) Defining the levels of charging power. 4) Making the system versatile for interoperability to serve all ranges of vehicle classes. 5) Definition of battery capacity to charge-sustaining operation for long-distance travel. 6) Applicability for shared automated electric vehicles. Different OEMs are working in collaboration, in order to make this technology affordable and cost competitive with regular charging technology. Power transferred= coupling factor x √vaprimary*vasecondary ……………………………………………

If the coupling factor is less, more va(volt-ampere) factor is to be considered for ensuring the power transfer. The misalignment in manual parking will be corrected in the future by guided systems. In case of commercial vehicles with bigger sizes, the secondary magnetics is made larger to ensure proper coupling. The trade-off with bigger secondary magnetics is that it brings limitation to the sensitivity of misalignment and emissions which will be significant in case of vehicle being in stationery or moving condition. In the current scenario, secondary magnetics involve limited power electronics. In the future, with advancements, the secondary magnetics will need to be with three-phase coils. There will be independent energisation of these coils respectively. However, there are challenges in relation to the design of the road and materials on the road for the implementation of inductive charging. Research is being conducted for the inductive charging on the coupling factors, and optimisation of pads on the primary and secondary and on the road construction side. 3.10. Smart Charging EVs are considered as batteries on wheels. Charging during the peak load remains one of the main challenges. Smart charging is a way of improving efficiency in the system. The independence of an electric vehicle does not depend only on the capacity of batteries packaged, but is also affected by the temperature of the operating environment, the selection of control methodology, the consumption of the auxiliary devices on board, and driver’s operational pattern. With V2G

94 Materials and Technologies for a Green Environment

Muruganandam et al.

applications, the electric car ideally behaves as a large mobile battery set-up powered by renewable energy produced and managed in a bidirectional manner. Based on needs, the available energy is shared from the home to the car or the network or vice versa with an economic advantage and return for those who supply it. In these smart grids of the future, cars become an essential link in the clean energy value chain. 3.11. Smart Charging Functioning In developed countries, as practiced, smart charging requires the EV driver to install a mobile app. The RFID tag should be shown to the charger. Alternatively, payment shall be done with a credit or debit card. Once the charging event is activated, the system connects the EV driver and charging point together. An advanced enabler of smart charging is vehicle-to-grid (V2G). The technology allows the vehicle control unit to “interact” with other networks, using the traction battery which is connected like an energy storage system. The EV requires alignment and integration with the electrical system so that communication between the vehicle, network and charging media is complete. The economic benefits of a V2G technology heavily depend on the strategies of charging and vehicle aggregation, as showcased in [21, 22]. 3.12. Load Balancing Load balancing is a smart charging feature where a charging station is operated by many charging points at a single location. Operating a charging source requires that the source shall be able to cover the cumulative EV load. One study uses innovative and revolutionary techniques to manage multi-microgrid load balancing through EV charging networks [23]. The load balancing distributes the available capacity in proportionality to all charging stations. In the following way, load balancing is implemented. Power source rating maximum (@ building location) = X amperes available. In parking lot of a building, there is a charging station, which has sockets that have Y amp Y amp > X amp. When only 1 EV comes for charging, it is charged with an X amp. When the 2nd EV comes for charging, the charging is reduced to X/2 with limitations in place.

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 95

The critical factors for smart charging are dynamic pricing, charging infrastructure and standardisation, interoperability, commonised data for vehicle drivers, consumers, service providers or aggregators, ancillary service, etc. .

IEC 62056 is a set of standards for electricity metering data exchange by the international electrotechnical commission. COSEM or companion specification for energy metering, includes a set of specifications that defines the transport and application layers of the DLMS protocol. Trends propose IEC 62056 protocol to enhance communications between substations. Automation systems use technical requirements of the protocol for sharing data, messages to the networks and control systems like load balance controller. In some of the cases, extensions will be used for interactions with various V2G. 3.13. V2G Definition Vehicle-to-grid technology provides excess power from the EV into the smart grid. V2G, which is also known as vehicle-grid integration (VGI), can help the energy grid supply electricity during peak hours. This is also called smart charging as shown and explained in Fig. (12). It creates an extra power source when weather-dependent renewable energy sources are not available. This type of technology can help meet clean energy goals such as targeting zero-carbon emissions by 2045. It can also provide an added benefit to consumers by potentially lowering the cost of electric vehicle ownership. The owner sells back excess power from his vehicle in order to offset other expenses. This type of setup is established across the globe.

Fig. (12). Smart charging.

Automobile manufacturers have been quick to adopt this technology, as showcased by EV-focused companies like Tesla, building V2G-based

96 Materials and Technologies for a Green Environment

Muruganandam et al.

supercharging stations, in large numbers [24]. Nissan Leaf is one type of electric car which is capable of bidirectional energy flow. While parked, it is able to make enough money to recover the charge of a DC fast charger. It has been established in UK and Japan where users save an average of $1,200. There are scenarios where the electric car’s battery is connected to the electrical lines, in-house. In case of a power shut down, it can be a source of lighting. This is one of the most attractive consumer scenarios for vehicle-to-grid (V2G) technology. People are viewing V2G as a means to help secure the grid and lower down operating costs. V2G is not futuristic and is a commonly used technology in the western world and other developed countries. A detailed analysis of benefits of vehicle-to-grid technology to a power system is done in a study [25, 26]. Vehicle-grid integration (VGI) helps in making an energy grid more resilient. It supplies electricity during times of peak use. This will happen especially when renewable energy resources are not available, such as at night when solar panels do not generate power, but most of the EVs are parked and are idle. In states like California, strong incentives are being provided to consumers to purchase electric vehicles. Intelligent and unidirectional “V1G” systems that flow energy only towards the vehicle battery can cut off the tap during peak traffic on the grid. The idea of smart charging gives manufacturers lots of opportunities regarding how smart charging of a vehicle can be executed. The solution of “EVBox” comes with three features. The first one is the dynamic load balance as explained above. Another feature called hub/satellite is designed to collect information and data from all connected charging stations that further stores it in a cloud-based system called back office at a remote location. Station A (hub) collects information from the rest of the stations (satellites). The data is then processed by the system to give the user-specific information about the charging sessions. The third and last feature of this particular solution is called “peak shaving” and is designed to avoid the charging to exceed the maximum capacity of the power source. As soon as the system notices that the charging is exceeding the maximum capacity available, it will automatically decrease the charging power or pause the charging. These characteristics are shown in Fig. (13). The peak shaving as shown in Fig. (14) can be in terms of switching off of the less essential equipment or having energy storage systems in terms of solar panels or re distributing the peak loads into the off-peak time. The best strategy will be

Solar Electric Vehicle Charging

Materials and Technologies for a Green Environment 97

worked out considering the economy and operating flexibility of the system. The next solution is the intelligent electric vehicle charging system. The system depends on the electricity cost and the charge requirement strategy. The data is collected and communicated in the system. The user takes the final decision on when it should be charged. Charging will be encouraged automatically, when the cost is low and during the off-peak hours. GPS system is used to locate the power outlet locations.

Power Need /Distribution (MW/KW)

Load Distribution Representation 30 25 20 15 10 5 0 9am

12pm

2pm

4pm

8pm

Time of the Day

Fig. (13). Peak Need Vs Time of the Day.

Power Need /Distribution (MW/KW)

Load Distribution Representation – Peak Shaving 30 25

20 15 10

5 0

9am

12pm

2pm

4pm

8pm

Time of the Day Fig. (14). Peak shaving.

The last smart solution is to charge with solar panel and the battery storage systems. There is a mobile app which is connected to the charger via internet. This connects the charger to the solar panel. This also opens up the communication with the entire solar charging community. If there is less charge in one of the chargers, then the power demand is met by other chargers for the balance. Solar electric charging model is explained in a study [28].

98 Materials and Technologies for a Green Environment

Muruganandam et al.

4. SECOND LIFE OF BATTERIES As per the study and research done, the first generation of batteries will be getting retired and by 2030, there will be a huge set of retired batteries. Projection is that by 2030, there will be approximately 5 to 6 million getting retired. By energy capacity, this will be approximately 250gwh to 300gwh/year. For usage in automotive application for EV, the available energy capacity shall be equal to or more than 80% and the self-discharge rate shall be less than 5%. The second life batteries can be used in less stressful applications, where the life can be typically between 200 to 500 cycles [27]. 4.1. Retired EV Batteries: How They can be Re-used or Recycled? Recycling processes for Li-ion chemistry batteries are growing. There is no regulation for the recycled performance. Hence there is no guarantee on the second-life batteries. As there is no regulation, there are variations in the regionwise with respect to performance. China leads the second battery supply by energy and demography wise followed by the United States and other European countries. Currently only 4 ms inside the engine. Fig. (7a) is the OH distribution near the fuel injectors, in which the open space in the center denotes a flame holding strut installed in the combustor. Fig. (7c) is the OH distribution just downstream of the strut and (Fig. 6f) is that at the exit of the engine. The fuel was injected from the top wall of the combustor. The simulation results indicated that due to the high Mach number auto-ignition occurred. But at the regions of high pressure, it did not allow the flame to get stable initially. Also, the combustion efficiency was increased slowly and due to the presence of small flame structures, there was an abrupt increase in combustion efficiency. Fig. (8)

Scramjet Combustion Engines

Materials and Technologies for a Green Environment 125

shows the two curves of experimental data representing a hysteresis effect, and depend on the engine test sequence. The weak combustion mode is believed to be associated with a “detached flame,” or “flow-reactor-type combustion,” and the intensive combustion mode is believed to be associated with an “attached flame” stabilized at the backward facing step. The combustion efficiency at the exit of the engine is a function of Ø and shows that combustion efficiency is inversely proportional to Ø . This information is useful to optimize the design of the fuel injector (size, pitch, location) and to optimize the geometries of struts to assure rapid mixing for Ø > 0.3 This can be concluded from the results that the performance of the scramjet engine can be very sensitive in the upstream region of the flow. Thus, optimization techniques should be carefully selected. cowl strut

sidewall flow

(a)

(b)

(c)

(d)

(e)

(f)

topwall air

air diffusion flame

H2

H2

H2

(a) x = 0.84 m

(b) x = 0.9 m

(c) x = 0.97 m

air

air

air

H2

H2 (d) x = 1.20 m

(e) x = 1.50 m

H2 (f) x = 1.80 m

Fig. (7). Flame structures in the upstream and downstream regions of the engine.

126 Materials and Technologies for a Green Environment

Bordoloi et al.

Fig. (8). Comparison of measured and computed thrusts.

Huang and Yan [63] modeled a dual-mode scramjet combustor to understand the ram-to- scram transition mechanism. The simulation was carried out using Ansys Fluent. In the study the boundary conditions at the entrance were varied. It was observed that the model operated as ramjet for lower Mach numbers and as the Mach number was increased the process changed to scramjet operation. During the transition, there was the formation of a shock train with an increase in the jet to crossflow pressure ratio. This rise in pressure ratio was due to increased velocity. Thus, the pressure ratio should be high to work in the scramjet mode for the considered model. It can be concluded that the results would be beneficial in designing the flow dynamics of a scramjet engine. Mahto et al. [64] considered a parallel cavity hydrogen-fuelled scramjet combustor to study the effect of length to depth ratio and Mach number at the inlet on the combustor performance. The model considered was in good accord with the experimental work conducted by Yang et al. [65]. It was indicated that the shock waves formed were in good agreement with the desired results. The length to depth ratio can be an important parameter for combustion characteristics. After many hits and trial methods, based on the considered inlet conditions, the optimal L/D was 7. The recirculation region was formed in the cavity and no shock train was formed at this ratio. Also, stable combustion was achieved for Mach numbers ranging between 2-2.5. For Mach 2.5, the combustion efficiency was the maximum. A similar study was conducted by Choubey and Pandey [66] to study the influence of inlet boundary conditions on a double

Scramjet Combustion Engines

Materials and Technologies for a Green Environment 127

cavity. In this study the inlet Mach number was varied and its effect was studied. It was found that at for low Mach numbers the shock wave formation was limited only to the combustion region, which was insufficient for the combustion to occur. But due to the presence of the cavity, residence time was increased and combustion was taking place. The contours of the mass fraction indicated that due to the injection of H2 boundary layer separation occurred and the pressure was increased. Thus, it can be concluded from both the studies that the presence of cavities in the combustor resulted in the formation of a high-pressure region that helps in enhancement of the combustion in a scramjet engine. Soni and De [67] attempt to understand the mixing behavior of the flow by using different strut geometries. Two different configurations along with two fuels were considered. The model considered was in good accord with the experimental work conducted by Gerlinger and Brüggemann [39]. The results indicated that due to lip thickness there was a difference in the reattachment region. Also, out of the two fuels, hydrogen was considered best for the strut geometry. The SS configuration with hydrogen as fuel provides better spreading of the jet in comparison to the others. If the diameter of the jet was increased by 2 mm there would be no efficient mixing. Also, efficient mixing results in pressure decay. Dharavath et al. [68] studied an ethylene-fuelled scramjet combustor computationally. In the study, the fuel was injected in the opposite direction of the airflow. The model considered was in good agreement with experimental work conducted by Xiao et al. [69]. The results include the Mach number and pressure contours along the central plane. It was seen that oblique shock waves were generated at the strut forefront and middle wall. The pressure on the walls increased. This increase was due to the combustion of the fuel. Also, wall pressure was increasing due to the increase in the ER. Le et al. [70] modeled a CWG scramjet combustor as described by Yakar and Gany [71] for estimating the regression of the fuel, boundary condition, mass flow rate, etc. It was understood from the simulated results that two recirculation regions were formed, such as a low-speed recirculation region and a high-speed recirculation region. The recirculation region resulted in the formation of the shear layer. Due to the injection of the rich fuel into the combustor, pyrolysis of the fuel occurs. The combustion efficiency of the model was around 75%. Thus it can be concluded from the results that using the appropriate fuel for the combustion process will yield better performance. Kummitha [72] modeled a modified DLR scramjet combustor and studied its effect on the dynamics of the flow. Fig. (9) shows modified scramjet combustor that contained circular and triangular bumps. Also, attempts were made to find the

128 Materials and Technologies for a Green Environment

Bordoloi et al.

appropriate turbulence model by comparing the commonly used turbulence models such as SST K-omega and standard K- ε model. Both the models were applied to standard DLR boundary conditions. On comparing the results of both the models, the K-omega model yielded better results. (a) Air inlet Ma=2

30 120

50

Fuel inlet Ma = 1

62

340 (b) Air inlet Ma=2

Circular bumps

30 120

50

62

Fuel inlet Ma = 1 340

(c) Air inlet Ma=2 120 50

triangular bumps

30

Fuel inlet Ma = 1

62

340

Fig. (9). Scramjet computational domains (a) basic and standard DLR Scramjet model, (b) DLR scramjet model with circular bump inserts and (c) DLR scramjet model with triangular bump inserts.

The pressure and velocity profiles for both triangular and circular bumps were studied. The simulated results indicated that due to the presence of bumps, the pressure at the lower wall was increased, which caused a decrease in the ignition delay period. Also, from the temperature profile, it can be estimated that the highest temperature and good combustion occurred for circular bumps when compared with the triangular bumps. Fig. (10) shows mixing efficiency and combustion efficiency for three models.

Scramjet Combustion Engines

Materials and Technologies for a Green Environment 129

The combustion efficiency was also the highest for circular bumps. Another study was conducted by Kummitha [73] where the standard DLR scramjet combustor was modified by introducing a uniform zigzag surface, small parabola shaped cavities and bumps at the lower wall of the combustion chamber. All the same boundary conditions were adopted. The simulated results indicate that the introduction of parabola geometry results in the formation of more shock waves and hence promotes the generation of a recirculation area. The modified geometry acts as a cavity which can be helpful for flame holding and increasing resident time. All the other geometries increased the shock wave formation. On comparing all the geometries, the zigzag geometries yielded the highest combustion efficiency than the other two geometries. Thus, the modified version of the DLR scramjet combustor enhances the combustion efficiency.

Fig. (10). (a) Mixing efficiency, (b) combustion efficiency of three models.

Manna et al. [74] considered a 3D kerosene injected strut-based scramjet combustor model for estimating flow dynamics. In the study, the K-ε model was used for turbulence modeling and Lagrangian Particle Tracking Method was employed to characterize the flow. The flow simulations were observed for ER=1.0. The simulated results indicated that there was an increase in pressure and temperature due to the combustion of kerosene. However, the pressure and temperature decreased gradually as the flow underwent expansion. At a distance of L/D=0.14, there was a sudden rise in pressure due to the formation of a shock wave. Also, on studying the mass fractions, at the middle portion of the combustor, there was an increase in CO2 and an increase in O2 and a large amount of fuel was unburnt. The combustion efficiency of the combustion was around 69%. Thus it can be concluded that a considerable amount of fuel remains unburnt, which in turn affects combustion efficiency. Future studies must be conducted to find ways to reduce the percentage of unburnt fuel.

130 Materials and Technologies for a Green Environment

Bordoloi et al.

Cho ubey and Pandey [75] considered a two strut combustor model for a different angle of attack -3°, 0°,+3°. The CFD model considered the same boundary conditions as that of the earlier studies. It simulated that the CFD results were in good agreement with the experimental results. A shock wave was generated at the forefront due to which the mixing was also enhanced. The performance of the combustor was affected by the angle of attack. By changing the angle of attack, combustion efficiency can be enhanced. It was also observed that the highest temperature at the recirculation zone was achieved at 0° angle of attack. A similar study was conducted by Pandey et al. [76], where the angle of attack considered was -5°, 0°,+5 °, and -4°,0°,+4° along with parallel fuel injection. On studying the results, it was found that for the negative angle of attack, the shock train was displaced and ignition delay was shorter. Due to the shorter ignition delay, combustion was efficient. Also, the highest temperature at the recirculation was achieved for the negative angle of attack. Another study was conducted by Choubey and Pandey [77] on a modified version of the scramjet model described by Rabadan et al. [78] for a different angle of attack (-3°,0°,+3°). The results of the ignition delay are affected by the angle of attack. Out of the considered angle of attack, -3° showed the shorted ignition delay and +3° showed the longest ignition delay. Also, the highest temperature at the recirculation was achieved for the negative angle of attack. Almost the same results were observed for all the studies. Thus, it can be concluded the angle of attack can be an important parameter for determining better combustion in a scramjet engine. Wang et al. [79] modeled a 3D hydrogen-fuelled dual cavity-based scramjet combustor to the combustion dynamics. The study considered LES modeling to address the stated problem. The model was simulated using Fluent. On studying the results it was found that between the cavities a high-pressure region was formed. This was due to the interaction of the bow shock wave. The jet penetration height was decreased and the recirculation region was made larger. Due to the recirculation region, the resident time was increased hence causes efficient mixing of the fuel. Berglund and Fureby [80] modeled a 3D hydrogen-fuelled strut-based scramjet combustor to study the combustion characteristics using LES simulations. The results showed the formation of an oblique shock wave at the forefront of the strut which was reflected in the walls of the combustor. Due to the injection of the fuel, the boundary layer formed at the walls are affected. This causes the temperature to increase. Also as a result of LES simulations and due to fuel injection, at the recirculation region, the pressure was increased, shear layers were formed at the wedge. Due to the formation of the shear layer, ignition becomes more prominent. Thus it can be concluded that LES simulations help in predicting combustion characteristics more clearly and precisely.

Scramjet Combustion Engines

Materials and Technologies for a Green Environment 131

Kummitha et al. [81] considered a 3D modified strut induced scramjet engine to enhance mixing and efficiency. The result shows that the formation of oblique shock waves at the forefront of the strut that was reflected at the walls of the combustor. Also due to the fuel injection position of the fuel, an extra shock wave was generated at the boundary layer separation. At this point, there was an increase in pressure. By introducing a double strut causes the early formation of the shock. Also on studying the profiles of velocities, it was observed that the pressure energy was converted to kinetic energy increases as it moves downstream. The combustion efficiency of the double strut model was 67%. Thus, it was concluded that the double strut model did not yield good combustion efficiency. Choubey et al. [82] modeled a three-strut scramjet combustion configuration to find the optimal H2 injection condition. A 2D model was considered and simulated using Ansys Fluent 14. The simulated results indicated that the formation of eddies and vortices near the wall of the combustor. Due to the injection of fuel, the oblique shock wave was generated. This wave was reflected from the combustor walls increasing the temperature. The recirculation region was formed downstream due to heat release causing the temperature to rise. The maximum temperature in the recirculation region was 2950K. Also, the combustion efficiency was 92% for the three strut model as compared to the standard single strut model. Another study was conducted by Kummitha et al. [83] in two cavity-based scramjet combustors. The cavity models have a ramped cavity and a spherical cavity that were simulated using computational software Ansys FLUENT 16. Similar to the above study oblique shock waves were formed which are reflected in the combustor walls. The ramped and spherical cavity model, the expansion shock waves were generated at the leading and trailing edge of the cavity. Also, it was found that the ramped cavity exhibits the highest combustion efficiency than the spherical cavity. Thus, it can be concluded that the introduction of multiple struts and different geometrical cavities in the combustor enhanced the performance of the scramjet engine. Table 2. Summary of studies conducted numerically.

Authors

Year

Place

Oevermann 2000 Germany [19] Mitani and 2004 Kaochi [62] Berglund and Fureby [80]

Japan

2007 Sweden

Model Used

Fuel Type

Mach No

Flame Holder

Fuel Injection

Validation Paper Name

2 equ. K-ε

Hydrogen

Air=2; Fuel=1

Strut

Strut

Waidmann et al. [55]

K-ε

Hydrogen

Air=4 to 8; Fuel=6

Strut

Strut

……..

LES

Hydrogen

Air=2 Fuel=1

Strut

Strut base

Oevermann [19]

132 Materials and Technologies for a Green Environment

Bordoloi et al.

(Table 2) cont.....

Year

Place

Model Used

Fuel Type

Mach No

Flame Holder

Fuel Injection

Validation Paper Name

Le et al. [70] 2008

China

SST K- omega

HTPB

Air=1.6; Fuel=1

CWG

……

Yakar and Gany [71]

Authors

Kumaran and Babu [52]

2009

India

one equation, Hydrogen Spalart–Allmaras

Air=2.5 Fuel=1

Strut

Strut

Tomioka et al. [53]

Kumaran and Babu [54]

2010

India

one equation, Kerosene Spalart–Allmaras

Air=2.5 Fuel=1

Strut

Strut

Tomioka et al. [53]

Pandey and Sivasakthivel 2011 [59]

India

K-ε

Air=2 Fuel=1

Strut

Strut

Oevermann [19]

Cacere et al. 2011 [57]

Italy

LES, sub grid

Combustor entrance

Frost et al [58]

Pandey and Thagavel 2011 [84]

India

K- ε

Hydrogen

Strut

Strut

Waidmann et al.

Manna et al. 2012 [74]

India

K-ε

Kerosene Air=6.5; Fuel=2

Strut

Strut wall

…………

Pandey and 2013 Nath [85]

India

K- ε

Hydrogen

Strut

Strut

Waidmann et al. [55]

Wang et al. 2014 [79]

China

LES

Hydrogen Air=2.5; Fuel=1

Dual Cavity

wall

Wang et al. [42]

Pandey and 2014 Roga [86]

India

LES

Hydrogen

Air=2; Fuel=1

Ramp

…….

Pandey and 2014 Roga [87]

India

SST K-ω

Hydrogen

Air=2; Fuel=6

Cavity

Wall

……..

Pandey et al. 2015 [76]

India

K-ε

Hydrogen

Air=6 Fuel=2

Strut

Strut with circular injector;

Oevermann [19]

Dharavath et 2015 al. [68]

India

SST K- omega

Ethylene

Air= 6; Fuel=1

Strut

strut wall

Xiao et al. [69]

Choubey and 2015 Pandey [77]

India

SST K- omega

Hydrogen

Air=7 Fuel= 2

Strut

Strut

Rabadan et al. [78]

Mahto et al. 2016 [64]

India

K-ε

Hydrogen

Air=2.5 Fuel=1

Cavity

Wall

Yang et al. [65]

Choubey and 2016 Pandey [88]

India

SST K-omega

Hydrogen

Air=2.5 Fuel=1

2- Strut

Strut

Oevermann [19]

Air=2; Fuel=1

Strut

Sturt

Oevermann [19]

3- strut

Strut

Oevermann [19]

Sturt

Sturt

Oevenmann [19]

Hydrogen

Hydrogen Air=2.79 Fuel=1 ………. Air=2; Fuel=1

Air=2; Fuel=1

Kummitha [73]

2016

India

SST K omega

Hydrogen

Choubey et al. [89]

2016

India

SST K- omega

Hydrogen Air=2.5; Fuel=1

Huang and Yan [63]

2016

China

SST K- omega

Hydrogen

Air=1; Fuel=4 to 7

Scramjet Combustion Engines

Materials and Technologies for a Green Environment 133

(Table 2) cont.....

Flame Holder

Fuel Injection

Validation Paper Name

3-strut

Three strut

Waidmann et al.

Air=2 Fuel1,2 = 2.3

Strut

Strut

Gerlinger and Brüggemann [39]

Hydrogen

Air=2.5 Fuel=1

3- Strut

Strut

Oevermann [19]

SST K- omega

Hydrogen

Air =2 Fuel=1

Strut

Strut

Oevermann [19]

India

SST K- omega

Hydrogen

Air =2 Fuel=1

Strut

Strut wall

Oevermann [19]

India

SST K-ω

Hydrogen Air=2.5 Fuel =1

2-Strut

two strut

Waidmann et al. [55]

Fuel Type

Authors

Year

Place

Model Used

Choubey et al. [75]

2016

India

2 equation Komega

Soni and De 2017 [67]

India

2 equ K-ε

Hydrogen and Ethylene

Choubey et al. [61]

2017

India

SST K- omega

Kummitha [72]

2017

India

Kummitha et 2017 al. [81] Choubey and 2017 Pandey [80]

Mach No

Hydrogen Air=2.5 Fuel =1

Dixit et al. [56]

2017

India

K-ε

Hydrogen

Air=2 Fuel=1

…….

Pylon

Oevermann [19]

Choubey et al. [90]

2017

India

SST K-ω

Hydrogen

Air=2; Fuel=1

Multi strut

Multi Strut

Waidmann et al. [55]

Kummitha et 2018 al. [83]

India

SST K- ω

Hydrogen

Air =2 Fuel=1

Cavity

Cavity wall

Oevermann [19]

Kummitha et 2018 al. [91]

India

SST K-ω

Hydrogen

Air =2 Fuel=1

Cavity

Cavity wall

Oevermann [19]

Choubey and 2018 Pandey [66]

India

K-ε

Hydrogen

double cavity

Waidmann et al. [55]

Choubey and 2018 Pandey [60]

India

SST K -ω

Hydrogen Air=2.5 Fuel =1 …….

4-wall

Waidmann et al. [55]

Kummitha et 2018 al. [92]

India

SST K-ω

Hydrogen

Air =2; Fuel=1

Cavity

Cavity wall

Oevermann [19]

Kummitha et 2018 al. [83]

India

SST K-ω

Hydrogen

Air=2; Fuel=1

Cavity Strut+Cavity

Waidmann et al. [55]

Verma et al 2020 [93]

India

K- ε

Hydrogen

Air= 2; Fuel=1

Strut

Strut

Waidmann et al. [55]

Verma et al. 2020 [94]

India

SST K-ω

Hydrogen

Air-2; Fuel=1

Strut

Strut+Wall

Waidmann et al. [55]

Verma et al. 2020 [95]

India

K- ε 2 equation Hydrogen

Air=2; Fuel=1

Strut

Strut

Waidmann et al. [55]

Kummitha et XXX al. [96]

India

Air=2; Fuel=1

Wavy wall strut

Strut

Waidmann et al. [55]

SST K-ω

Hydrogen

Air=1.7,1.9,2.2.3; Double Fuel=1 Cavity

Kummitha et al. [91] considered a modified DLR scramjet combustor to understand the dynamics of the flow. The strut models considered were the rocket

134 Materials and Technologies for a Green Environment

Bordoloi et al.

and double arrow strut. The variation of density was studied for both the models. It can be observed that there was a decrease in the density of the wake region of the strut for both models. In the case of the rocket strut, the oblique shock wave was formed at the forefront of the stru,t which caused the pressure to rise. On the other hand, due to the two strut models vortices are formed between the shock waves. But for both the models the velocities were almost equal. Also, there was a rise in temperature as the reaction was taking place in the wake regions. But the amount of fuel injection in the case of the rocket strut was greater as compared with the other. Due to the geometry of the double-headed strut early ignition occurred due to the formation of two recirculation regions. However, on comparing the combustion efficiency for both the geometries, it was concluded that the rocket strut was superior to the other. Another study was conducted by Kummitha et al. [92] by introducing cavities to understand the effect of passive and directed fuel injection. It was observed that the introduction of cavities created more shock waves and a larger recirculation zone also shifted the shear layer formation into the mainstream. The simulated results were also viewed for passive and direct fuel injection into the wavy wall of the cavity. It was observed that an additional mixing layer was developed due to direct fuel injection into the cavity, which in turn resulted in efficient mixing as compared to any passive technique. Both study conclue that adding more shock waves to the flow field and using direct fuel injection improve the performance of the scramjet combustor. Choubey et al. [89] attempted to increase the overall performance of the scramjet engine by using multi-strut geometry. This multi-strut geometry refers to the presence of three struts which was a modification of the DLR scramjet combustor to reduce the risk of thermal chocking in the combustor. Due to the geometry of the strut, shock waves, eddies and vortices were generated. The fuel injection from the upper wall of the combustor resulted in the formation of oblique shock at the forefront of the strut geometry. The waves were reflected in the combustor walls thereby increasing the temperature and forming of the recirculation region. Due to this region, the heat release combustion occurred in the combustion reacting the temperature to 2950K. For the considered scramjet model, the combustion efficiency was around 92%. Thus, introducing struts into combustion promotes the formation of shock waves and combustion. Verma et al. [93] investigated the combustor performance of a wedged-shaped scramjet combustor using Ansys Fluent software. To acknowledge the combustion performance, temperature, and Mach number distribution of the model were studied. The results indicated that with the variation of inlet velocity, the locale of the incident shock wave formation changed. With the increase in inlet free stream velocity, the injected fuel from the strut becomes parallel to the incoming air. While studying the performance parameters, it was found that the

Scramjet Combustion Engines

Materials and Technologies for a Green Environment 135

combustion efficiency for Mach 3.0 was found to be superior to the other Mach numbers considered. Thus, it was concluded that the combustion model considered was valid for Mach number 3.0 as it showed enhanced combustion efficiency than the other Mach numbers. Verma et al. [94] investigated the mixing performance of the combustor to understand the effects of transverse fuel injection on a parallel fuel injection system. The results indicated that at 10mm length in the axial direction, there was efficient mixing of fuel and air was observed. While at the same location, when applied with only parallel fuel injection, the combustor showed a mixing efficiency of 86%. On studying the contours of pressure, the author found that the combustion occurred at a length of 103mm, while the combustion efficiency observed was less. Thus the study conclude that introducing transverse fuel injection in a parallel fuel injection scramjet combustor enhances the mixing but combustion efficiency was observed less. Verma et al. [95] simulated a hydrogen-fuelled strut based scramjet combustor to understand the effect of the combustion characteristics of the combustor. The model in the study is a slight modification of the DLR experiment. The goal of the study was to find the optimum boundary condition for a single Mach number. To achieve the same different profiles and variations of different variables were studied. Fig. (11) shows the combustion efficiency comparison between all five models at different temperatures. The temperature profiles for the model shows that in the downstream direction, there was an increase in the temperature; a uniform flow pattern was observed. Fig. (12) Combustion efficiency comparison between the two models at constant temperature 833 K. The performance parameters reveal that the combustion efficiency was found as 93% at 833K and 115 299 Pa temperature and pressure respectively. Thus, it can be concluded that the modified model is valid for Mach number 1.

Fig. (11). Combustion efficienncy at 1 bar incoming air.

136 Materials and Technologies for a Green Environment

Bordoloi et al.

Fig. (12). Combustion efficiency at 833K air temperature.

Pandey and Nath [85] investigated the flame holding mechanism on 2D strut based scramjet combustor by using different types of strut injectors. In the study, two different types of injectors were used such as strut with the circular injector and Strut with alternating wedge injectors. The results indicated that the alternating wedge injectors a uniformly formed mixing region from the strut than the other injectors. For the alternating wedge injectors, minimum pressure loss was observed with high propulsion efficiency. However, for strut with circular injectors. More appropriate combustion efficiency was found. While studying the different profiles it was identified that for the strut with circular injectors, for the efficient combustion process, a longer combustion chamber length was required as compared to the other one. Thus it was concluded from the results the alternating wedged injectors showed better combustion than the strut with circular injectors. Pandey and Roga [86] numerically studied a scramjet combustor model with ramped injectors to understand the flow structure of scramjet combustion by using the K-epsilon turbulence model. The simulation results were found using computational software Ansys Fluent. The results show that at the recirculation region, the maximum temperature was found which occurred due to the expansion of the generated shock, losses of the fuel jet and wave-jet interaction. The temperature was slightly reduced on moving downstream. During the combustion process, the highest temperature observed was 2096K. Pandey and Roga [97] studied a cavity-based scramjet combustor to understand the inlet-combustion interaction and flow structure at flight Mach number 6. The results of the study indicate that due to high heat release in the combustion process, the reacting cases produced modified shock waves. The study also reveals that due to the cavity

Scramjet Combustion Engines

Materials and Technologies for a Green Environment 137

based scramjet combustor; a recirculation region was produced, which produces a stable flame holding. This enhanced the process of combustion. Thus it can be concluded from the study the process of combustion and the structure of the shock waves formed are affected by the flight Mach number and the geometry of the combustor. The presence of cavity in the combustor enhances combustion efficiency. Choubey et al. [90] introduced a multi-strut hydrogen injection system in the scramjet combustor to understand the overall performance of the combustor. The simulation was initiated with three struts such as three wedgedshaped struts for Mach 2.5. The simulated results were compared with the single strut model that was considered for validation. The multi-strut model showed superior performance than the single strut model. Due to the geometry, the multistrut model provided better scope for injection of hydrogen, which improved the combustion process. The multi-strut model showed a maximum temperature of 2950K approximately at the recirculation region. Also, the combustion efficiency for the same was obtained as 92%, which was higher than the single strut model. Thus, the multi strut model was valid for the considered inlet boundary conditions. Kummitha et al. [96] compared two different strut models to understand the effect on the flow field of the scramjet combustor. The combustor model is a modification of the DLR experiment; the modification was made by introducing a wavy wall strut fuel injector in the combustion chamber. The modification was made with the motive of producing more oblique shock waves. In the study, the profile of pressure, temperature and velocity were studied for both the models to understand the internal flow structure. The results of the simulation show that the leading curved edge of the redesigned strut model generated multiple oblique shock waves than the basic DLR strut. While studying the pressure and temperature profile for the wavy wall model, high pressure and temperature were observed at the entrance of the combustion chamber as compared with the basic strut model. Thus, it can be concluded that the introduction of the modification in the basic DLR model shows an enhanced performance of the scramjet combustor. Pandey and Thangavel [84] investigated the combustion and mixing performance for different types of strut injection in the combustor. The strut injectors used in the study were namely strut with a circular injector and strut with a planer injector. The results of the simulation show that minimum pressure loss, better mixing and combustion efficiency were observed for strut with planer injector as compared to the other model. It was identified that the strut with circular injector required more combustor length for efficient combustion as compared to the other. However, for both models, high static pressure values were observed in non-reacting cases. The reason identified for this high pressure was maybe due to impingement of reflected shock waves or due to expansion of the shock waves at

138 Materials and Technologies for a Green Environment

Bordoloi et al.

the walls. A subsonic region was also observed at the symmetry, which can be eliminated by proper combustor design. Thus, it can be concluded from the study that proper design of the combustor region may require the changes in formation of the subsonic region. Kummitha et al. [98] studied the behavior of the internal flow for different cavitybased flame holders in the combustor. The numerical analysis was carried out using Ansys Fluent 16.0 tool, the turbulence in the model was addressed by using the SST K-ω model. The model considered was a slight modification of the basic DLR model. The cavities used in the study were namely spherical and stepped cavities. On studing the profiles for temperature and pressure, the results show that more recirculation regions, vortices and shock waves formed for both the cavity due to their geometry. This improved the fuel-air mixing. The presence of cavities in the DLR strut model improves the performance of the combustor. Additionally, a rise in pressure and temperature was also observed the cavity models irrespective of boundary separation. The stepped cavities showed better performance in the combustor as compared to the circular cavity. Fig. (13) shows pressure rise develops an acoustic wave and propagates along the upstream of the cavity and impacts at the front wall of the cavity and develops vortices, which grow as the flow towards trailing edge of the cavity. From the pressure profiles, it was observed that the rate of conversion of pres- sure energy into kinetic energy is more for the case of standard DLR scramjet combustor due to less drag coefficient as compared to the other two models. The crest points in the pressure profiles indicate the impinging of shock waves at the walls of the combustion chamber.

Fig. (13). Pressure variation at (a) lower wall of the combustor (Y = 0) and (b) middle of the combustor (Y = 25 mm).

Fig. (14) shows the temperature profiles of all the models at different locations along the length of the scramjet combustor. From the observation of temperature

Scramjet Combustion Engines

Materials and Technologies for a Green Environment 139

and velocity profiles, it is identified that the velocity is less and temperature is high at the middle of the combustor as compared to the nearest locations of 380 the combustor walls, it is due to the existence of drag force in between combustor walls and supersonic air stream and the presence of combustion process at the middle of the combustor respectively. If, we observe the temperature profile it is found that the temperature of the flow stream has increased from x = 120 mm to x = 275 mm due to the enhancement of turbulent mixing along the 385 flow direction in the combustion chamber. From the comparison of standard and cavity models, it is differentiated that the temperature of the main stream which is entered into the cavity has been increased due to the development of acoustic wave (compression wave) and multiple reflections in between molecules and cavity walls. 0.06 (a)

Numerical-DLR Spherical cavity

Step cavity

0.04

0.04

0.03

0.03

0.02

0.02

0.01

0.01

0.00 0.06

Experimental

Numerical-DLR Spherical cavity

Step cavity

Increase in temperature due to the presence of cavity flame holder

0.00 400

600

800 1000 1200 1400 1600 1800 2000

400

Temperature(K) (c)

600

0.06

800

1000 1200 1400 1600 1800 2000 Temperature(K)

(d)

Experimental

Numerical-DLR Spherical cavity

0.05

Experimental

Numerical-DLR Spherical cavity

0.05

Step cavity

Step cavity

0.04

0.03

0.03

Y(m)

0.04

0.02

0.02

0.01

0.01

0.00

(b)

0.05

Y(m)

Y(m)

0.05

Y(m)

0.06

Experimental

400

600

800 1000 1200 1400 1600 1800 2000 Temperature(K)

0.00

400

600

800 1000 1200 1400 1600 1800 2000 Temperature(K)

Fig. (14). Cross stream temperature profiles at different locations (a) x = 120 mm (b) x = 136 mm (c) x = 167 mm and (d) x = 275 mm.

From the review of literature, it can be concluded that the performance of the scramjet engine depends on the fuel injection mechanics, flow dynamics, combustion schemes, combustor design, type of flame holders, etc. For enhancing the combustion phenomenon, literature shows the usage of computational formulation software such as Ansys FLUENT, etc. to address the complex

140 Materials and Technologies for a Green Environment

Bordoloi et al.

turbulent flow dynamics arising due to the hypersonic velocities. Researchers have also used computational software to understand the combustion flame stabilization techniques, boundary interaction with the shock waves as the combustion process in a scramjet can be very complex. Based on the literature, it was observed that the objectives of the researchers were to find an appropriate scramjet combustor design that could produce a stable flame, minimize pressure loss and efficient utilization of the fuel supplied. 4. FUTURE SCOPE Various numerical, computational and experimental databases of the recent years are shown in the literature review provides insights about the recent development of the scramjet engines. It can be observed that the performance of the scramjet engine depends on fuel injection mechanisms such as transverse and parallel fuel injection systems, flame stabilization mechanism, design of the flame holder such as cavities, struts etc., type of fuel used, etc. From the literature review it can be estimated that a number of research has been conducted on the introduction of different types of cavities, strut in the combustor. The presence of struts and cavities in the combustor leads to the formation of more shock waves and recirculation regions which enhance the combustion efficiency. The literature also addresses the use of transverse and parallel fuel injection systems in the combustor. However, very less focus has been found in the literature that addresses the use of pylons [99, 100], back facing step [101, 102], ramp [103], shock generator [104]. The implementation of these geometries in the combustor can be beneficial for the combustion process thereby improving the combustion efficiency of the scramjet engine. From the literature review, it can also be observed that most of the computational studies indicate the usage of K-ε and K-omega turbulence model. However, fewer studies are found in the literature that use the LES as the turbulence model. The flow inside the combustor is turbulent and complex. The combustion occurs at a supersonic speed, which is completed in milliseconds. The K-ε and K-omega model holds good up to a certain limit and also fails to address the physics behind the formation of the complex eddies. Thus, by using LES modelling may address the complex turbulent flow in the combustor, also may provide better perceptive of the complex physics of the flow that remained unsolved with the other two turbulence models. Due to the hypersonic speed of the scramjet, the combustion process is very fast [105]. A large amount of fuel is exhausted unburnt. In future studies, innovative fuel injection techniques must be designed keeping in mind the supersonic combustion process that may result in proper utilization of the fuel. Young researchers may consider adapting hybrid fuel injection systems,

Scramjet Combustion Engines

Materials and Technologies for a Green Environment 141

introducing back-facing stepped struts or cavities in the combustor. From the literature it is found that back facing stepped produces smaller recirculation region and has the capability to receive more fuel, which is beneficial for the engine. CONCLUSION This paper reviews the fundamental principles, current status, challenges and the future scope of a scramjet engine. The manuscript also draws attention to the experimental studies and computational models that have been conducted by various researchers around the globe. It has been noted that the combustion in a scramjet engine is due to the high flow velocity which has a considerable effect on the mixing performance. Many studies are conducted on different parameters that affect the performance of the scramjet engine. However, the proper understanding of flow dynamics is yet to be reviewed. Although advances have been made in the field of research that addresses the complex turbulence, shock waves, boundary layer formation, separation and its interaction with the flow, the outstanding issues remain. Particularly in the direction of physiochemical processes, mixing of fuel-air, eddy and vortex formation in the flow, there is efficient usage of fuel. It is of utmost importance to understand these issues for proper modelling. It can be concluded that more innovative developments and techniques must be modelled to solve the issue in the flow occurring inside supersonic combustion. Therefore, an intense review of the fundamental techniques and mechanisms is necessary for the future advancements of the scramjet engine. CONSENT FOR PUBLICATION Not applicable. CONFLICT OF INTEREST The authors declare no conflict of interest, financial or otherwise. ACKNOWLEDGEMENT Declared none. REFERENCES [1]

J. Tishkoff, J. Drummond, T. Edwards, and A. Nejad, Future directions of supersonic combustion research - Air Force/NASA workshop on supersonic combustion, 2013. [http://dx.doi.org/10.2514/6.1997-1017]

[2]

A. M. Bonanos, "Scramjet Operability Range Studies of an Integrated Aerodynamic-Ram-Injector/Plasma-Torch Igniter with Hydrogen and Hydrocarbon Fuels", 2005.

142 Materials and Technologies for a Green Environment

Bordoloi et al.

[3]

A. Ferri, Selected papers on advanced design of air vehicles., 1977.

[4]

A. Ben-Yakar, and R.K. Hanson, "Cavity Flame-Holders for Ignition and Flame Stabilization in Scramjets: An Overview", J. Propuls. Power, vol. 17, no. 4, pp. 869-877, 2001. [http://dx.doi.org/10.2514/2.5818]

[5]

E.T. Curran, "Scramjet Engines: The First Forty Years", J. Propuls. Power, vol. 17, no. 6, pp. 11381148, 2001. [http://dx.doi.org/10.2514/2.5875]

[6]

R.S. Fry, "A Century of Ramjet Propulsion Technology Evolution", J. Propuls. Power, vol. 20, no. 1, pp. 27-58, 2004. [http://dx.doi.org/10.2514/1.9178]

[7]

E. J. Efsic, Supersonic Combustion ramjet propulsion engines. Embry-Riddle Aeronautical University Extended Campus, September 2002.

[8]

K. M. Busa, and J. M. D. M. S. Brown, Characteristics for Scramjet Engine Control, 2016.

[9]

W. Heiser, D. Pratt, D. Daley, and U. Mehta, Hypersonic Airbreathing Propulsion. American Institute of Aeronautics and Astronautics, Inc.: Washington, DC, 1994. [http://dx.doi.org/10.2514/4.470356]

[10]

B.J. Matkowsky, and D.O. Olagunju, "Pulsations in a Burner-Stabilized Premixed Plane Flame", SIAM J. Appl. Math., vol. 40, no. 3, pp. 551-562, 1981. [http://dx.doi.org/10.1137/0140046]

[11]

A. Ben-Yakar, and R. Hanson, "Cavity flameholders for ignition and flame stabilization in scramjets Review and experimental study", 34th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, vol. 17, 1998. [http://dx.doi.org/10.2514/6.1998-3122]

[12]

C.C. Rasmussen, S.K. Dhanuka, and J.F. Driscoll, "Visualization of flameholding mechanisms in a supersonic combustor using PLIF", Proc. Combust. Inst., vol. 31, no. 2, pp. 2505-2512, 2007. [http://dx.doi.org/10.1016/j.proci.2006.08.007]

[13]

C. Fureby, K. Nordin-Bates, K. Petterson, A. Bresson, and V. Sabelnikov, "A computational study of supersonic combustion in strut injector and hypermixer flow fields", Proc. Combust. Inst., vol. 35, no. 2, pp. 2127-2135, 2015. [http://dx.doi.org/10.1016/j.proci.2014.06.113]

[14]

D.J. Micka, and J.F. Driscoll, Combustion characteristics of a dual-mode scramjet combustor with cavity flameholder, 2009. [http://dx.doi.org/10.1016/j.proci.2008.06.192]

[15]

M.B. Sun, Z-G. Wang, J.H. Liang, and H. Geng, "Flame Characteristics in Supersonic Combustor with Hydrogen Injection Upstream of Cavity Flameholder", J. Propuls. Power, vol. 24, no. 4, pp. 688-696, 2008. [http://dx.doi.org/10.2514/1.34970]

[16]

T. Kouchi, C. P. Goyne, R. D. Rockwell and J. C. Mcdaniel. "Focusing-schlieren Visualization in A Dualmode Scramjet". Exp Fluids vol. 56, 211, 2015. [http://dx.doi.org/10.1007/s00348-015-2081-9]

[17]

S. Nakaya, Y. Hikichi, Y. Nakazawa, K. Sakaki, M. Choi, M. Tsue, M. Kono, and S. Tomioka, "Ignition and supersonic combustion behavior of liquid ethanol in a scramjet model combustor with cavity flame holder", Proc. Combust. Inst., vol. 35, no. 2, pp. 2091-2099, 2015. [http://dx.doi.org/10.1016/j.proci.2014.07.023]

[18]

C. Fureby, "LES for Supersonic Combustion". AIAA Paper, 2012-5979, Sept, 2012. [http://dx.doi.org/10.2514/6.2012-5979]

[19]

M. Oevermann, "Numerical investigation of turbulent hydrogen combustion in a SCRAMJET using

Scramjet Combustion Engines

Materials and Technologies for a Green Environment 143

flamelet modeling", Aerosp. Sci. Technol., vol. 4, no. 7, pp. 463-480, 2000. [http://dx.doi.org/10.1016/S1270-9638(00)01070-1] [20]

L. Tian, L. Chen, Q. Chen, F. Li, and X. Chang, "Quasi-One-Dimensional Multimodes Analysis for Dual-Mode Scramjet", J. Propuls. Power, vol. 30, no. 6, pp. 1559-1567, 2014. [http://dx.doi.org/10.2514/1.B35177]

[21]

S. Torrez, N. Scholten, D. Micka, J. Driscoll, M. Bolender, D. Doman, and M. Oppenheimer, "A Scramjet Engine Model Including Effects of Precombustion Shocks and Dissociation", Am. Inst. Aeronaut. Astronaut, no. July, pp. 1-22, 2008. [http://dx.doi.org/10.2514/6.2008-4619]

[22]

X. Fan, G. Yu, J. Li, X. Lu, X. Zhang, and C.J. Sung, "Combustion and ignition of thermally cracked kerosene in supersonic model combustors", J. Propuls. Power, vol. 23, no. 2, pp. 317-324, 2007. [http://dx.doi.org/10.2514/1.26402]

[23]

H.B. Gu, L. Chen, and X. Chang, "Experimental investigation on the cavity-based scramjet model", Sci. Bull. (Beijing), vol. 54, no. 16, pp. 2794-2799, 2009. [http://dx.doi.org/10.1007/s11434-009-0460-4]

[24]

R. Masumoto, S. Tomioka, K. Kudo, A. Murakami, K. Kato, and H. Yamasaki, "Experimental Study on Combustion Modes in a Supersonic Combustor", J. Propuls. Power, vol. 27, no. 2, pp. 346-355, 2011. [http://dx.doi.org/10.2514/1.B34020]

[25]

R.D. Rockwell Jr, C.P. Goyne, W. Haw, R.H. Krauss, J.C. McDaniel, and C.J. Trefny, "Experimental Study of Test-Medium Vitiation Effects on Dual-Mode Scramjet Performance", J. Propuls. Power, vol. 27, no. 5, pp. 1135-1142, 2011. [http://dx.doi.org/10.2514/1.B34180]

[26]

M.B. Sun, C. Gong, S.P. Zhang, J.H. Liang, W.D. Liu, and Z.G. Wang, "Spark ignition process in a scramjet combustor fueled by hydrogen and equipped with multi-cavities at Mach 4 flight condition", Exp. Therm. Fluid Sci., vol. 43, pp. 90-96, 2012. [http://dx.doi.org/10.1016/j.expthermflusci.2012.03.028]

[27]

D.B. Le, C.P. Goyne, R.H. Krauss, and J.C. McDaniel, "Experimental Study of a Dual-Mode Scramjet Isolator", J. Propuls. Power, vol. 24, no. 5, pp. 1050-1057, 2008. [http://dx.doi.org/10.2514/1.32591]

[28]

Z. Wang, M. Sun, H. Wang, J. Yu, J. Liang, and F. Zhuang, "Mixing-related low frequency oscillation of combustion in an ethylene-fueled supersonic combustor", Proc. Combust. Inst., vol. 35, no. 2, pp. 2137-2144, 2015. [http://dx.doi.org/10.1016/j.proci.2014.09.005]

[29]

Y. Tian, S. Yang, J. Le, T. Su, M. Yue, F. Zhong, and X. Tian, "Investigation of combustion and flame stabilization modes in a hydrogen fueled scramjet combustor", Int. J. Hydrogen Energy, vol. 41, no. 42, pp. 19218-19230, 2016. [http://dx.doi.org/10.1016/j.ijhydene.2016.07.219]

[30]

Z. Zhong, Z. Wang, M. Sun, and H. Wang, "Combustion characteristics in a supersonic combustor with ethylene injection upstream of dual parallel cavities", Proc. Inst. Mech. Eng. Part G J. Aerosp. Eng., vol. 230, no. 13, pp. 2515-2522, 2016. [http://dx.doi.org/10.1177/0954410016629495]

[31]

Z. Cai, X. Zhu, M. Sun, and Z. Wang, "Experiments on flame stabilization in a scramjet combustor with a rear-wall-expansion cavity", Int. J. Hydrogen Energy, vol. 42, no. 43, pp. 26752-26761, 2017. [http://dx.doi.org/10.1016/j.ijhydene.2017.09.059]

[32]

Z. Cai, J. Zhu, M. Sun, and Z. Wang, "Spark-enhanced ignition and flame stabilization in an ethylenefueled scramjet combustor with a rear-wall-expansion geometry", Exp. Therm. Fluid Sci., vol. 92, pp. 306-313, 2018. [http://dx.doi.org/10.1016/j.expthermflusci.2017.12.007]

144 Materials and Technologies for a Green Environment

Bordoloi et al.

[33]

"Y. hang Wang, W. yan Song, and D. yong Shi, “Investigation of flameholding mechanisms in a kerosene-fuelled scramjet combustor,”", Acta Astronaut., vol. 140, no. September, pp. 402-408, 2017. [http://dx.doi.org/10.1016/j.actaastro.2017.09.010]

[34]

Z. Cai, X. Zhu, M. Sun, and Z. Wang, "Experimental Study on the Combustion Process in a Scramjet Combustor with a Rear-Wall-Expansion Geometry", J. Aerosp. Eng., vol. 31, no. 5, p. 04018077, 2018. [http://dx.doi.org/10.1061/(ASCE)AS.1943-5525.0000911]

[35]

J. Li, G. Zhu, O. Yan, W. Li, S. Zhang, and F. Qin, "Experimental investigation on upstream fuel injection technique of RBCC scramjet mode", Appl. Therm. Eng., vol. 154, pp. 450-457, 2019. [http://dx.doi.org/10.1016/j.applthermaleng.2019.03.097]

[36]

J. Li, K. Wang, G. Jiao, J. Luo, and W. Song, "Experimental Study on Mode Transition in a DualMode Scramjet Combustor", Combust. Sci. Technol., vol. 24, no. 5, pp. 1-19, 2019. [http://dx.doi.org/10.1080/00102202.2019.1594800]

[37]

Y. Tian, X. Zeng, S. Yang, F. Zhong, and J. Le, "Experimental study on the effect of equivalence ratio and injector position on flow structure and flame development in the scramjet combustor", Aerosp. Sci. Technol., vol. 82-83, pp. 9-19, 2018. [http://dx.doi.org/10.1016/j.ast.2018.08.026]

[38]

Q. Liu, D. Baccarella, W. Landsberg, A. Veeraragavan, and T. Lee, "Cavity flameholding in an optical axisymmetric scramjet in Mach 4.5 flows", Proc. Combust. Inst., vol. 37, no. 3, pp. 3733-3740, 2019. [http://dx.doi.org/10.1016/j.proci.2018.08.037]

[39]

P. Gerlinger, and D. Bruggemann, "Numerical Investigation of Hydrogen Strut Injections into Supersonic Airflows", J. Propuls. Power, vol. 16, no. 1, pp. 22-28, 2000. [http://dx.doi.org/10.2514/2.5559]

[40]

Q. Yang, K. Chetehouna, N. Gascoin, and W. Bao, "Experimental study on combustion modes and thrust performance of a staged-combustor of the scramjet with dual-strut", Acta Astronaut., vol. 122, pp. 28-34, 2016. [http://dx.doi.org/10.1016/j.actaastro.2016.01.002]

[41]

R. Milligan, D. Eklund, J. Wolff, T. Mathur, and M. Gruber, "Dual Mode Scramjet Combustor", Analysis of Two Configurations, no. January, pp. 1-19, 2010. [http://dx.doi.org/10.2514/6.2010-751]

[42]

M. Wang, M. Wang, Hongbo; Wang Zhenguo; Sun, “Experimental study of oscillations in a scramjet combustor with cavity flameholders,” Exp. Therm. Fluid Sci., vol. 45, pp. 259–263, 2013, [http://dx.doi.org/1037//0033-2909.I26.1.78]

[43]

J.V.S. Moorthy, B. Rajinikanth, B.V.N. Charyulu, and G. Amba Prasad Rao, "Effect of ramp-cavity on hydrogen fueled scramjet combustor", Propulsion and Power Research, vol. 3, no. 1, pp. 22-28, 2014. [http://dx.doi.org/10.1016/j.jppr.2014.01.001]

[44]

Z.J. Denman, V. Wheatley, M.K. Smart, and A. Veeraragavan, Fuel injection and mixing in a Mach 8 hydrocarbon-fuelled scramjet. 20th Australasian Fluid Mechanics Conference, Perth, Australia, 5 – 8 December 2016. Perth, Australia: Australasian Fluid Mechanics Society, 2016.

[45]

Z.J. Denman, V. Wheatley, M.K. Smart, and A. Veeraragavan, "Supersonic combustion of hydrocarbons in a shape-transitioning hypersonic engine", Proc. Combust. Inst., vol. 36, no. 2, pp. 2883-2891, 2017. [http://dx.doi.org/10.1016/j.proci.2016.08.081]

[46]

J. Zhang, J. Chang, C. Kong, H. Qiu, and W. Bao, "Flame oscillation characteristics in a kerosene fueled dual mode combustor equipped with thin strut flameholder", Acta Astronaut., vol. 161, no. May, pp. 222-233, 2019. [http://dx.doi.org/10.1016/j.actaastro.2019.05.037]

[47]

J. Ye, D. Shi, W. Song, G. Li, Z. Zhang, and Z. Hu, "Investigation of turbulence flow characteristics in

Scramjet Combustion Engines

Materials and Technologies for a Green Environment 145

a dual-mode scramjet combustor using hydroxyl tagging velocimetry", Acta Astronaut., vol. 157, no. August, pp. 276-281, 2019. [http://dx.doi.org/10.1016/j.actaastro.2018.12.040] [48]

J. Zhang, J. Chang, W. Shi, W. Hou, and W. Bao, "Combustion stabilizations in a liquid kerosene fueled supersonic combustor equipped with an integrated pilot strut", Aerosp. Sci. Technol., vol. 77, pp. 83-91, 2018. [http://dx.doi.org/10.1016/j.ast.2018.02.035]

[49]

J. Zhang, J. Chang, J. Ma, Y. Wang, and W. Bao, "Investigations on flame liftoff characteristics in liquid-kerosene fueled supersonic combustor equipped with thin strut", Aerosp. Sci. Technol., vol. 84, pp. 686-697, 2019. [http://dx.doi.org/10.1016/j.ast.2018.11.017]

[50]

J. Zhang, J. Chang, J. Ma, C. Zhang, and W. Bao, "Investigation of flame establishment and stabilization mechanism in a kerosene fueled supersonic combustor equipped with a thin strut", Aerosp. Sci. Technol., vol. 70, no. May, pp. 152-160, 2017. [http://dx.doi.org/10.1016/j.ast.2017.08.005]

[51]

J. Zhang, J. Chang, J. Ma, Y. Zhang, and W. Bao, "Local and global flame characteristics in a liquid kerosene fueled supersonic combustor equipped with a thin strut", Aerosp. Sci. Technol., vol. 76, pp. 49-57, 2018. [http://dx.doi.org/10.1016/j.ast.2018.02.007]

[52]

K. Kumaran, and V. Babu, "Investigation of the effect of chemistry models on the numerical predictions of the supersonic combustion of hydrogen", Combust. Flame, vol. 156, no. 4, pp. 826-841, 2009. [http://dx.doi.org/10.1016/j.combustflame.2009.01.008]

[53]

S. Tomioka, A. Murakami, K. Kudo, and T. Mitani, "Combustion Tests of a Staged Supersonic Combustor with a Strut", J. Propuls. Power, vol. 17, no. 2, pp. 293-300, 2001. [http://dx.doi.org/10.2514/2.5741]

[54]

K. Kumaran, P.R. Behera, and V. Babu, "Numerical Investigation of the Supersonic Combustion of Kerosene in a Strut-Based Combustor", J. Propuls. Power, vol. 26, no. 5, pp. 1084-1091, 2010. [http://dx.doi.org/10.2514/1.46965]

[55]

F. Alff, U. Brummund, W. Clauss, M. Oschwald, J. Sender and W. Waidmann. Experimental Investigation of the Combustion Process in a Supersonic Combustion Ramjet (SCRAMJET) Combustion Chamber, 1994.

[56]

S. Kumar Dixit, "Mathematical Modeling and Analysis of Different Type of Fuel Injector in Scramjet Engine Using CFD Simulation in Fluent", Int. J. Res. Appl. Sci. Eng. Technol., vol. V, no. II, pp. 379389, 2017. [http://dx.doi.org/10.22214/ijraset.2017.2056]

[57]

D. Cecere, A. Ingenito, E. Giacomazzi, L. Romagnosi, and C. Bruno, "Hydrogen/air supersonic combustion for future hypersonic vehicles", Int. J. Hydrogen Energy, vol. 36, no. 18, pp. 1196911984, 2011. [http://dx.doi.org/10.1016/j.ijhydene.2011.06.051]

[58]

A. Paull, M. Frost, and H. Alesi, https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20000037 781.pdf HyShot-T4 Supersonic Combustion Experiments. Report for NAG-1-2113, 2000.

[59]

K.M. Pandey, and T. Sivasakthivel, "CFD Analysis of Mixing and Combustion of a Hydrogen Fueled Scramjet Combustor with a Strut Injector by Using Fluent Software", IACSIT Int. J. Eng. Technol., vol. 3, no. 5, pp. 466-453, 2011. [http://dx.doi.org/10.7763/IJET.2011.V3.268]

[60]

G. Choubey, and K.M. Pandey, "Effect of different wall injection schemes on the flow-field of hydrogen fuelled strut-based scramjet combustor", Acta Astronaut., vol. 145, no. January, pp. 93-104, 2018.

146 Materials and Technologies for a Green Environment

Bordoloi et al.

[http://dx.doi.org/10.1016/j.actaastro.2018.01.034] [61]

K.M. Pandey, G. Choubey, F. Ahmed, D.H. Laskar, and P. Ramnani, "Effect of variation of hydrogen injection pressure and inlet air temperature on the flow-field of a typical double cavity scramjet combustor", Int. J. Hydrogen Energy, vol. 42, no. 32, pp. 20824-20834, 2017. [http://dx.doi.org/10.1016/j.ijhydene.2017.07.026]

[62]

T. Mitani, and T. Kouchi, "Flame structures and combustion efficiency computed for a Mach 6 scramjet engine", Combust. Flame, vol. 142, no. 3, pp. 187-196, 2005. [http://dx.doi.org/10.1016/j.combustflame.2004.10.004]

[63]

W. Huang, and L. Yan, "Numerical investigation on the ram–scram transition mechanism in a strutbased dual-mode scramjet combustor", Int. J. Hydrogen Energy, vol. 41, no. 8, pp. 4799-4807, 2016. [http://dx.doi.org/10.1016/j.ijhydene.2016.01.062]

[64]

N.K. Mahto, G. Choubey, L. Suneetha, and K.M. Pandey, "Effect of variation of length-to-depth ratio and Mach number on the performance of a typical double cavity scramjet combustor", Acta Astronaut., vol. 128, pp. 540-550, 2016. [http://dx.doi.org/10.1016/j.actaastro.2016.08.010]

[65]

Y. Yang, Z. Wang, M. Sun, H. Wang, and L. Li, "Numerical and experimental study on flame structure characteristics in a supersonic combustor with dual-cavity", Acta Astronaut., vol. 117, pp. 376-389, 2015. [http://dx.doi.org/10.1016/j.actaastro.2015.09.005]

[66]

G. Choubey, and K.M. Pandey, "Effect of variation of inlet boundary conditions on the combustion flow-field of a typical double cavity scramjet combustor", Int. J. Hydrogen Energy, vol. 43, no. 16, pp. 8139-8151, 2018. [http://dx.doi.org/10.1016/j.ijhydene.2018.03.062]

[67]

R.K. Soni, and A. De, "Investigation of strut-ramp injector in a Scramjet combustor: Effect of strut geometry, fuel and jet diameter on mixing characteristics", J. Mech. Sci. Technol., vol. 31, no. 3, pp. 1169-1179, 2017. [http://dx.doi.org/10.1007/s12206-017-0215-0]

[68]

M. Dharavath, P. Manna, and D. Chakraborty, "Numerical exploration of mixing and combustion in ethylene fueled scramjet combustor", Acta Astronaut., vol. 117, pp. 305-318, 2015. [http://dx.doi.org/10.1016/j.actaastro.2015.08.014]

[69]

Y. Xiao, W. Song, L. Chen, D. Wang, and J. Le, "Investigations on ethylene combustion in a scramjet combustor using resistance heaters", Proc. Inst. Mech. Eng. Part G J. Aerosp. Eng., vol. 222, no. 3, pp. 411-416, 2008. [http://dx.doi.org/10.1243/09544100JAERO317]

[70]

D.B. Le, C.P. Goyne, R.H. Krauss, and J.C. McDaniel, "Numerical study on solid-fuel scramjet combustor with fuel-rich hot gas", J. Propuls. Power, vol. 24, no. 5, pp. 1050-1057, 2008. [http://dx.doi.org/10.2514/1.32591]

[71]

A. Ben-Yakar, and A. Gany, Experimental study of a solid fuel scramjet, 1994. [http://dx.doi.org/10.2514/6.1994-2815]

[72]

O.R. Kummitha, "Numerical analysis of hydrogen fuel scramjet combustor with turbulence development inserts and with different turbulence models", Int. J. Hydrogen Energy, vol. 42, no. 9, pp. 6360-6368, 2017. [http://dx.doi.org/10.1016/j.ijhydene.2016.10.137]

[73]

O.R. Kummitha, "Numerical analysis of passive techniques for optimizing the performance of scramjet combustor", Int. J. Hydrogen Energy, vol. 42, no. 15, pp. 10455-10465, 2017. [http://dx.doi.org/10.1016/j.ijhydene.2017.01.148]

[74]

P. Manna, M. Dharavath, P.K. Sinha, and D. Chakraborty, "Optimization of a flight-worthy scramjet combustor through CFD", Aerosp. Sci. Technol., vol. 27, no. 1, pp. 138-146, 2013.

Scramjet Combustion Engines

Materials and Technologies for a Green Environment 147

[http://dx.doi.org/10.1016/j.ast.2012.07.005] [75]

G. Choubey, and K.M. Pandey, "Effect of variation of angle of attack on the performance of two-strut scramjet combustor", Int. J. Hydrogen Energy, vol. 41, no. 26, pp. 11455-11470, 2016. [http://dx.doi.org/10.1016/j.ijhydene.2016.04.048]

[76]

K.M. Pandey, S. Roga, and G. Choubey, "Numerical investigation on hydrogen-fuelled scramjet combustor with parallel strut fuel injector at a flight mach number of 6", J. Appl. Fluid Mech., vol. 9, no. 3, pp. 1215-1220, 2016. [http://dx.doi.org/10.18869/acadpub.jafm.68.228.24082]

[77]

G. Choubey, and K.M. Pandey, "Numerical studies on the performance of scramjet combustor with alternating wedge-shaped strut injector", Int. J. Turbo Jet Engines, vol. 34, no. 1, pp. 1-12, 2017. [http://dx.doi.org/10.1515/tjj-2015-0048]

[78]

E. Rabadan Santana, and B. Weigand, Numerical Investigations of Inlet-Combustor Interactions for a Scramjet Hydrogen-fuelled engine at a Mach Flight Number of 8. September, pp. 1–13, 2012. [http://dx.doi.org/10.2514/6.2012-5926]

[79]

H. Wang, Z. Wang, M. Sun, and N. Qin, "Large eddy simulation of a hydrogen-fueled scramjet combustor with dual cavity", Acta Astronaut., vol. 108, pp. 119-128, 2015. [http://dx.doi.org/10.1016/j.actaastro.2014.12.008]

[80]

D.B. Le, C.P. Goyne, R.H. Krauss, and J.C. McDaniel, "LES of supersonic combustion in a scramjet engine model", J. Propuls. Power, vol. 24, no. 5, pp. 1050-1057, 2008. [http://dx.doi.org/10.2514/1.32591]

[81]

O.R. Kummitha, L. Suneetha, and K.M. Pandey, "Numerical analysis of scramjet combustor with innovative strut and fuel injection techniques", Int. J. Hydrogen Energy, vol. 42, no. 15, pp. 1052410535, 2017. [http://dx.doi.org/10.1016/j.ijhydene.2017.01.213]

[82]

G. Choubey, and K.M. Pandey, "Effect of different strut + wall injection techniques on the performance of two-strut scramjet combustor", Int. J. Hydrogen Energy, vol. 42, no. 18, pp. 1325913275, 2017. [http://dx.doi.org/10.1016/j.ijhydene.2017.04.024]

[83]

O.R. Kummitha, K.M. Pandey, and R. Gupta, CFD analysis of a scramjet combustor with cavity based flame holders, 2018. [http://dx.doi.org/10.1016/j.actaastro.2018.01.005]

[84]

S. Thangavel, and K..M.Pandey;, “CFD Analysis of Scramjet Combustor Using Strut with Circular and Planer Injector,” 2017.

[85]

K. M. N. N. Pandey, Numerical Simulation of a Hrodrogen fuled scramjet combustor at Mach 1.5 using sturt Injecotrs at Mach 2.47 air speed, .

[86]

K.M. Pandey, and S. Roga, "CFD analysis of scramjet combustor with non-premixed turbulence model using ramp injector", Appl. Mech. Mater., vol. 555, pp. 18-25, 2014. [http://dx.doi.org/10.4028/www.scientific.net/AMM.555.18]

[87]

K.M. Pandey, and S. Roga, CFD Analysis of Hypersonic Combustion of H 2 -fuelled Scramjet Combustor with Cavity Based Fuel Injector at Flight Mach 6. vol. 656, pp. 53–63, 2014. [http://dx.doi.org/10.4028/www.scientific.net/AMM.656.53]

[88]

G. Choubey, and K.M. Pandey, "Investigation on the effects of operating variables on the performance of two-strut scramjet combustor", Int. J. Hydrogen Energy, vol. 41, no. 45, pp. 20753-20770, 2016. [http://dx.doi.org/10.1016/j.ijhydene.2016.09.157]

[89]

K.M. Pandey, and G. Choubey, "Computational simulation on the performance of Scramjet combustor using Multi-strut circular shaped injector", 52nd AIAA/SAE/ASEE Joint Propulsion Conference pp. 19, 2016. [http://dx.doi.org/10.2514/6.2016-5097]

148 Materials and Technologies for a Green Environment

Bordoloi et al.

[90]

G. Choubey, K.M. Pandey, A. Maji, T. Deshmukhya, and A. Debbarma, ScienceDirect Computational Investigation of Multi-Strut Injection of Hydrogen in a Scramjet Combustor, vol. 4, pp. 2608-2614, 2017.

[91]

O.R. Kummitha, K.M. Pandey, and R. Gupta, "Numerical analysis of hydrogen fuelled scramjet combustor with innovative designs of strut injector", Int. J. Hydrogen Energy, vol. 45, no. 25, pp. 13659-13671, 2020. [http://dx.doi.org/10.1016/j.ijhydene.2018.04.067]

[92]

O.R. Kummitha, K.M. Pandey, and R. Gupta, "Optimization of scramjet performance with different fuel injection techniques and flame holder cavities", Acta Astronaut., vol. 152, pp. 908-919, 2018. [http://dx.doi.org/10.1016/j.actaastro.2018.09.026]

[93]

K.A. Verma, K.M. Pandey, M. Ray, and K.K. Sharma, "The numerical analysis of combustion performance of a wedge shaped strut-based scramjet combustor", Therm. Sci. Eng. Prog., vol. 20, p. 100714, 2020. [http://dx.doi.org/10.1016/j.tsep.2020.100714]

[94]

K.A. Verma, K.M. Pandey, and K.K. Sharma, Computational investigation of mixing performance on the effects of innovative transverse fuel injection system in parallel fuel injection based scramjet combustor. Materials Today Proceedings, vol. 38, part 5, pp. 2452-2456, 2021. [http://dx.doi.org/10.1016/j.matpr.2020.07.388]

[95]

K.A. Verma, K.M. Pandey, and K.K. Sharma, "Impact of parametric variation on combustion characteristics of hydrogen‐fueled strut based scramjet combustor at supersonic speed", Int. J. Energy Res., vol. 44, no. 14, pp. 11807-11826, 2020. [http://dx.doi.org/10.1002/er.5822]

[96]

O.R. Kummitha, K.M. Pandey, and R. Gupta, "Numerical investigation of wavy wall strut fuel injector for hydrogen fueled scramjet combustor", Int. J. Hydrogen Energy, vol. 44, no. 60, pp. 32240-32253, 2019. [http://dx.doi.org/10.1016/j.ijhydene.2019.10.147]

[97]

K.M. Pandey, and S. Roga, "CFD Analysis of Scramjet Combustor with Non-Premixed Turbulence Model Using Ramp Injector", Appl. Mech. Mater., vol. 555, pp. 18-25, 2014. [http://dx.doi.org/10.4028/www.scientific.net/AMM.555.18]

[98]

O.R. Kummitha, K.M. Pandey, and R. Gupta, "CFD analysis of a scramjet combustor with cavity based flame holders". Acta Astronaut., vol. 144, pp. 244–253, 2018. [http://dx.doi.org/10.1016/j.actaastro.2018.01.005]

[99]

M. Vishwakarma, and A. Vaidyanathan, "Experimental study of mixing enhancement using pylon in supersonic flow", Acta Astronaut., vol. 118, pp. 21-32, 2016. [http://dx.doi.org/10.1016/j.actaastro.2015.09.011]

[100] H. Takahashi, Q. Tu, and C. Segal, "Effects of Pylon-Aided Fuel Injection on Mixing in a Supersonic Flowfield", J. Propuls. Power, vol. 26, no. 5, pp. 1092-1101, 2010. [http://dx.doi.org/10.2514/1.48393] [101] W. Huang, L. Ma, M. Pourkashanian, D.B. Ingham, S. Luo, J. Liu, and Z. Wang, "Flow-Field Analysis of a Typical Hydrogen-Fueled Dual-Mode Scramjet Combustor", J. Aerosp. Eng., vol. 25, no. 3, pp. 336-346, 2012. [http://dx.doi.org/10.1061/(ASCE)AS.1943-5525.0000136] [102] W. Huang, L. Jin, L. Yan, and J. Tan, "Influence of jet-to-crossflow pressure ratio on nonreacting and reacting processes in a scramjet combustor with backward-facing steps", Int. J. Hydrogen Energy, vol. 39, no. 36, pp. 21242-21250, 2014. [http://dx.doi.org/10.1016/j.ijhydene.2014.10.073] [103] J. S. and E. U. of T. Schumacher, “Numerical Simulation of Cantilevered Ramp Injector Flow Mixing,” 2000.

Scramjet Combustion Engines

Materials and Technologies for a Green Environment 149

[104] M. Barzegar Gerdroodbary, D.D. Ganji, and Y. Amini, "Numerical study of shock wave interaction on transverse jets through multiport injector arrays in supersonic crossflow", Acta Astronaut., vol. 115, pp. 422-433, 2015. [http://dx.doi.org/10.1016/j.actaastro.2015.06.002] [105] A. Idris, M. Saad, H. Zare-Behtash, and K. Kontis, "Luminescent measurement systems for the investigation of a scramjet inlet-isolator", Sensors (Basel), vol. 14, no. 4, pp. 6606-6632, 2014. [http://dx.doi.org/10.3390/s140406606] [PMID: 24721773]

150

Materials and Technologies for a Green Environment, 2023, 150-178

CHAPTER 5

Review of the Role of Geometrical Modification of Scramjet Combustor on Performance Characteristics Kumari Ambe Verma1, K. M. Pandey1,*, K.K. Sharma1 and Dhiren R. Patel2 1 2

Department of Mechanical Engineering, National Institute of Technology, Silchar, Assam, India Mechanical Engineering Department, IITE, Indus University, Ahmedabad, Gujarat, India Abstract: The current scenario in the field of aviation is focused on hypersonic-speed vehicles. To achieve the required performance, engines have to be designed in such a way that their outcome should be maximum. Nowadays high-speed performance engines have utilized a type of air-breathing engine amongst which, the scramjet is found appropriate. However, the engine can only perform under atmospheric area because the supersonic combustion ramjet engine utilizes the atmospheric air as an oxidizer. Nonetheless, engines do not comprise any rotating or moving parts. So, to complete the mixing and chemical kinetics, engine geometry has special dimensions. The present chapter is focused on a rigorous review of the geometrical modification of the combustor and fuel injector. The impact of mixed fuel, different types of working fuels, and variable inflow conditions have been explored to uncover the beneficial effects on scramjet combustion performance. Since numerous authors have explored different aspects of the ongoing challenges in scramjet hence a summary has been drawn to acquire a suitable model for future work.

Keywords: Combustion Characteristics, Fuel Injection Strategy, Geometrical Modification, Inflow Conditions, Supplementary Fuels. 1. INTRODUCTION A supersonic combustion ramjet engine is a type of air-breathing engine, which performs all the thermodynamic processes at the supersonic speed level. Any kind of air-breathing engine utilizes the incoming free stream atmospheric air to participate inside the combustor for the completion of chemical kinetics. As shown in Fig. (1), the Scramjet engine comprises three major sections i.e., a converging inlet, a combustor, and a diverging nozzle. The respective four Corresponding author K. M. Pandey: Department of Mechanical Engineering, National Institute of Technology, Silchar, Assam, India; E-mail: [email protected] *

Santhanam Harikrishnan (Ed.) All rights reserved-© 2023 Bentham Science Publishers

Role of Geometrical Modification

Materials and Technologies for a Green Environment 151

processes of every engine are compression, combustion, expansion, and exhaust. However, the behavioral impact will change by changing the working conditions of the engine and also its applications [1 - 3]. The specialty of scramjet can be identified by looking at its geometrical configuration i.e., no moving or rotating parts are utilized for completion of the all the processes. So, to create a desirable environment inside the respective section of the scramjet, several approaches are used. Fuel injection strategy and mixing approach in the supersonic combustor can be considered as a leading parameter for achieving higher combustion efficiency and stability [4 - 6]. Through various experimental and numerical investigations of a supersonic combustor, different aspects of ongoing challenges have been performed by many authors, few major considerations have been categorized as follows:

Fig. (1). Scramjet Engine Model.

2. SCRAMJET GEOMETRICAL MODIFICATION The scramjet engine comprises an isolator, a fuel injection system, a combustion chamber, and an exhaust nozzle. Since all the thermodynamic processes of the scramjet engine are completed in the restricted length of the scramjet. Hence the modifications in the combustor geometry and fuel injection implication have a major influence on the desirable outcome. 2.1. Combustor Geometry The supersonic combustion ramjet engine does not involve any moving parts. Therefore, Combustor geometry should be designed in such a way that a beneficial environment arises to complete the mixing between incoming fuel and air. During the combustion process, chemical kinetics should evolve rapidly to

152 Materials and Technologies for a Green Environment

Verma et al.

create a stable flame entirely. To keep in mind the above phenomena, the belowmentioned subsections are drawn: 2.1.1. Combustor Wall Transverse Fuel Injection A numerical investigation of a two-strut scramjet combustor was performed by Gautam Choubey and K. M. Pandey [7, 8] to explore the effect of a wall transverse fuel injector. Four different cases were compared and among them, two struts with lower wall transverse fuel injectors at two subsequent locations were found appropriate in regards to mixing performance because fuel penetration was identified deeper in the same case so it leads to better combustion. The same author has also examined the double cavity scramjet combustor [9] by numerical investigation. Eight different sets of the investigation were performed by changing incoming fuel and air boundary conditions. The author concluded that the highpressure regimes near the cavity could help to create a favorable environment for mixing and stable combustion. An experimental investigation has been performed in the supersonic flow field with a cavity present at the combustor wall. Since the presence of a wall cavity has been identified as a flame holder in the supersonic flow regimes. Yueming Yuan et al. [10] approached a similar investigation by changing incoming boundary conditions. To uncover the flame behavior near the cavity, temperature and equivalence ratio were scrutinized. The author identified four different locations at which flame was seen stabilized i.e. inside the cavity domain, shear layer around the wall cavity, near jet wake, and also in the oscillation region generated between jet wake and cavity. A strong correlation was recognized that the flame balance in the turbulence regions could be affected by temperature and the global equivalence ratio. O. R. Kummitha et al. [11] optimized the cavity geometry and wall fuel injection position to explore the flow field characteristics. The author concluded that the geometry design is responsible to increase the thickness of the recirculation region and also shear mixing layer growth. Nonetheless, an additional upper wall cavity was found helpful toward combustion stability. The computational investigation was performed by Wei Huang et al. [12] to explore mixing augmentation by utilizing a novel step at the lower combustor wall. The combined effect of oblique shock wave and the influence of jet location and jet pressure ratio were examined. A conclusion has been drawn by the author that to lengthen the residence time, oblique shock waves were found suitable nonetheless larger jet pressure ratio was responsible to create a recirculation region near the novel wall step. Hence the above combination can be further promoted for mixing enhancement. K. M. Pandey et al. [13, 14] numerically investigated wall cavity scramjet combustors at higher air Mach numbers. A further performance was also done by utilizing

Role of Geometrical Modification

Materials and Technologies for a Green Environment 153

changing fuel pressure and air temperature. Higher fuel pressure creates a large vortex structure near the cavity and the higher air temperature further shifts the location of oblique shock waves. A numerical investigation of the scramjet combustor by utilizing the cavity at the lower wall was performed by Dai Jian et al. [15] by utilizing the additional grooves on the aft cavity walls. With and without grooves arrangement with different aft wall angles were compared to undergo the flow field characteristics behavior near the fuel injector. Enhanced stream-wise vortices in the downstream combustor were recognized nonetheless the presence of grooves augments the shear effect, which was found beneficial in terms of downstream mixing. A numerical investigation was performed by utilizing different lower wall transverse fuel locations by K. A. Verma et al. [16, 17] to explore the combustion efficiency. As shown in Fig. (2), four separate locations were modeled to identify the appropriate position of the wall fuel injector, author concluded that the location 68 mm ahead of the strut placed in the middle was found suitable. Nonetheless, two distinct zones were also seen i.e. rapid change in chemical kinetics and gradual consumption of incoming fuel. N. Bordoloi et al. [18] numerically investigated the effect of incoming air Mach number in a cavity-based scramjet combustor. The impact of Mach number was identified on the location of oblique shock waves and distribution of fuel downstream.

Fig. (2). Combustion Efficiency [16].

2.1.2. Combustor Wall Cavity with Strut Fuel Injection Better combustion performance is highly influenced by creating appropriate disturbance which can be acquired with the help of shock waves and their interaction with upcoming jet wake. A numerical investigation was performed by Li Yan et al. [19] by using two separate cases i.e. single strut arrangement and

154 Materials and Technologies for a Green Environment

Verma et al.

strut with cavity arrangement. Nonlinear dual-mode combustion characteristics were also analyzed. Transition mode reflected nonlinear pressure plot nonetheless scram to ram mode provided stabilized flow field in the strut with cavity arrangement. Lei LIAO et al. [20] introduced a wall cavity to explore the effect of jet-to-cross-flow pressure ratio on combustion performance with the help of a computational fluid dynamics solver. Hydrogen was selected as a working fuel. The author concluded that the increase in jet to cross-flow pressure is a cause of reduction in the performance and half of the pressure ratio was found appropriate. Computational fluid dynamics analysis was performed by utilizing a strut with cavity arrangement by O. R. Kummitha et al. [21]. To stabilize the combustion near the fuel injector, the wall cavity was identified as beneficial regarding the residence time of mixed fuel and air. The sudden appearance of the recirculation region around the cavity and reflected shock waves were found beneficial in terms of the flame holder. K. Sathiyamoorthy et al. [22] utilized an experimentally strut with a cavity combustor model to explore the impact of pressure oscillation. Kerosene and pilot hydrogen were utilized as working fuels. A cold flow experiment was done to get insights into the occurrence of pressure oscillation. The cavity aspect ratio between two tandem struts in the streamwise direction dominated the pressure oscillation modes. The author concluded that this arrangement could be responsible for the better mixing however passive control device is needed to stabilize the flame. A numerical investigation was performed by utilizing a wall cavity in the parallel fuel injection strut-based combustor by K. A. Verma et al. [23]. Two separate models i.e. with and without cavity model were compared with variable incoming Mach numbers. The author concluded that higher combustion efficiency was identified in wall cavity arrangements. Dual mode scramjet combustor was experimentally investigated by Chenin Zhang et al. [24] to explore the flow field characteristics. Ramjet and scramjet modes are essentially present in dual-mode scramjet combustion however the author observes one more intermitted mode. Hence three consequent modes are scramjet mode, weak ramjet mode, and ramjet mode. Scramjet mode often affects the boundary layer. The weak boundary layer effect was eliminated by changing the location of the fuel injection. Also, backpressure was improved. Dongqing Zhang and Wenyan Song [25] utilized kerosene to perform experimental investigation through cone-shaped struts, cavities, and also a combination of both. Cone strut solely is not beneficial for better ignition and flame stabilization. Backpressure flow at the isolator entrance could be eliminated by using a shorter cone strut arrangement. In the sole cavity, the arrangement does not allow to use of a wide range of equivalence ratios. However, the author concluded that the larger range

Role of Geometrical Modification

Materials and Technologies for a Green Environment 155

of equivalence ratio could be utilized by using a combination of cone-strut with cavity arrangement. 2.2. Fuel Injector Geometrical Modifications Fuel injection strategy can be various types [26] while taking about scramjet combustors because the pattern of the flow field is highly influenced by the fuel entry. The geometrical modification aspect is one of those, where a significant positive outcome can be seen. To get the stabilized flame in the supersonic flow field, a Followed literature review has been done. 2.2.1. Modified Strut or Multi Struts S. Aravind et al. [27] explained the impact of an improved strut injection scheme by introducing extra disturbances in terms of vortices. The vortices in the highspeed flow field increase the turbulence intensity, which leads to enhanced mixing. The numerical investigation was performed by using a two-dimensional non-premixed combustion model. Obtained plots from the computational investigation show the completion of mixing hydrogen as a fuel in the air a bit earlier compared with the conventional strut. As shown in Fig. (3), more than 95% of the mixing was completed with a reduction in 15mm length in the improved strut. The obtained performance shows the reduction in combustor length. The author has identified a wider reaction zone by observing contour plots of mass fraction and temperature. Rahul Kumar Soni et al. [28] examined two different strut geometry with various jet spacing effects to get improved mixing characteristics. A numerical approach was taken to complete the observation and it has perceived that flow physics was exclusively different for both strut designs with constant jet spacing. Nevertheless, straight strut (SS) has well near field mixing performance among all the activities done. The same author explained the involvement of vortices ahead of the strut and Kelvin-Helmholtz (K-H) instability was seen with the help of density gradient and vortices contours. Enhancement of mixing and diffuse was identified by the interaction between the K-H structure and vortices shed. Therefore, it can be summarized that large-scale vortices act as a major role in supersonic mixing.

156 Materials and Technologies for a Green Environment

Verma et al.

1

Combustion efficiency

0.8 Strut Modified strut 0.6

0.4

0.2

0 50

100

150

200

X-coordinate

250

300

Fig. (3). Combustion efficiency plot for basic and modified strut injection configuration in the streamwise direction [27].

O. R. Kummitha et al. [29, 30] numerically investigated the supersonic scramjet combustor by utilizing hydrogen as a working fluid through innovative fuel injectors such as rocket-shaped, double arrow, and wavy strut walls. In all the cases, better mixing and combustion performance were identified through a large number of vortex formations and also boundary layer separation can act as an instigator for better performance. Nonetheless, a large number of oblique shock waves could be introduced by creating sharp edges in the working geometry. Modification of strut is nowadays common to fulfill the performance gap. Shaohua Zhu et al. [31] introduced a wedge at the trailing side of the strut and confirmed that it provides an additional vortex effect with increased mixing and combustion efficiency nonetheless author assured that the reduced total pressure loss has also been seen. Kerosene was selected to complete the combustion and a two-step chemical reaction was performed for numerical simulation. Cold flow condition has been done to understand that first, the mixing performance afterward hot flow simulation has entertained. To get appropriate thrust with improved pressure recovery Stephen M. Neill and Apostolos Pesyridis [32] investigated different injection strategies with modified wedge-shaped struts. From the results, it was found that a polygonal injector is better compared to a circular one. A parallel injection is more suitable for pressure recovery in the place of a transverse. By going through all investigations by the author, the twin strut arrangement is suitable for higher thrust. In the end, it was resolved that a hydrogen-based parallel fuel injector with a modified strut combustor can achieve the hypersonic flight speed with satisfactory performance.

Role of Geometrical Modification

Materials and Technologies for a Green Environment 157

K. M. Pandey et al. [33, 34] utilized numerical investigation to get explore the combustion performance by using different shapes of a fuel injector. Two different, circular and planer-modified struts were examined, and concluded that the planer-shaped strut provides higher performance compared to the circular. The author also studied ramp-based scramjet combustors [34]. The recirculation region was identified higher temperature region due to the presence of shock wave expansion, and wave jet interaction. A dual crossed strut was selected to examine the combustion performance by using kerosene as a fuel in the dual-staged scramjet combustor by Zhang Yan et al. [35]. Surrogated n-decane fuel has been selected for reaction. The inflow equivalence ratio was found great impact on the thermal throat location. The location of the thermal throat was moving downstream as the equivalence ratio was reducing. No impact was observed on the combustor thrust due to the equivalence ratio, however, tremendous changes in the combustor thrust were observed due to the hysteresis mode transition. Multi-strut fuel injection was adopted by Gautam Choubey et al. [36] to examine numerically supersonic combustors. To suppress thermal choking during high-speed flow, a multi-strut fuel injection arrangement was found beneficial nonetheless improved turbulence mixing could also be identified. Yann Hendrik Simsont and Peter Gerlinger [37] examined the cooling effect of strut injectors by external and internal flow fields. By analyzing the temperature plot of the strut solid body, the author concluded that the active cooling technique is more acceptable for this kind of supersonic combustion and the parallel injection technique is more suitable. Two strut-based combustors were numerically observed by Gautam Choubey and K.M. Pandey [38] to explain the strut geometry effect over the performance of combustion. The author appreciates the multi-strut-based combustor compared with a single one. The effect of lip height was found to be a major parameter for increased combustion performance nonetheless transverse distance between both struts and the location of the strut relative to the entrance section was also responsible for the same. Maximized combustion can be reached by creating overlap between the divergence point and intersectional point central to both struts. The length of the single strut was analyzed numerically by K. A. Verma et al. [39]. By enlarging the blunt end wedge-shaped strut face, an additional shockwave was recognized which was further involved to improve the mixing performance. The design of the scramjet combustor was also reviewed by the same author [40]. A numerical investigation has been performed to identify optimal geometry with improved fuel injection by P. Nithish Reddy and K. Venkatasubbaiah [41] to get increased combustion efficiency. To avoid a sudden fall of Mach number, a

158 Materials and Technologies for a Green Environment

Verma et al.

divergence angle is available. To get higher combustion efficiency, various angles were analyzed and found that the 3º divergence angle at a top wall was more appropriate. Incoming pressure and temperature is the key parameter to get better performance. Based on geometry observation, two strut-based fuel injection-based combustor has better combustion efficiency as compared to a single strut. The author suggested that asymmetric structure is good for enhanced mixing and combustion nonetheless height and divergence angle of the combustor wall are key parameters for combustor geometry. Strut geometry and location of strut w.r.t. combustor entry have been considered by Wei Huang [42] to investigate the effect of the same on combustion efficiency. By changing the radius of the strut tip, there was no considerable effect identified on combustion performance nonetheless location of the strut has played a significant role in combustion efficiency. Combustion efficiency was obtained at 96.2% at the location where the generated shock wave due to the leading edge of a strut, overlaps with the divergence point of the upper wall. This can be considered a key parameter during the designing of strut-based supersonic combustor arrangement. Numerical observation has been completed by W Bao et al. [43] to change the swept angle of a strut. A small modification in any geometry can lead to higher changes in performance. The swept angle was started from 0 to 75-degree angle. Reduction in total pressure loss and drag coefficient has been identified up to 60 degrees of swept angle. By going above this, a weaker shock wave was found also with total a pressure loss. Qiongyao Qin et al. [44] numerically investigated the traditional strut by modifying the rear section of a strut. The enlarged additional part was added to the traditional strut to examine the flame stabilization. Nonetheless, the novel section creates a high temperature and pressure combustion segment in the nearby region. Chunlei Li et al. [45] introduced a modified strut named a backward-facing step. A numerical investigation was performed by adopting a modified two-strut arrangement. The optimization suggests that the height of a backward-facing step is responsible to affect the combustion efficiency as well as the total pressure loss downstream. 2.2.2. Flame Stabilization Analysis: Ideal Strut or altered Injection Strategy In the supersonic flow field, turbulence will unquestionably appear and the disturbance can be seen in the form of vortices. The baroclinic effects are responsible to generate a large number of vortices and this is found beneficial with regard to mixing between fuel and incoming free stream air. Nonetheless, unregimented pressure lines in the flow field and the different density gradients could be the cause of the generation of vortices. Donggang Cao et al. [46] experimentally investigated the jet flame to understand the jet flame behavior and

Role of Geometrical Modification

Materials and Technologies for a Green Environment 159

its propagation in the flow field. The interaction among jet flame with flow field shock provides a beneficial environment for baroclinic effects, which further enhances the mixing. The dynamics behind better mixing utilizing vortices are connected through the mass transfer between jet spacing to the shear layer and vice-versa. A numerical investigation was utilized to explore the effect of largescale vortices and shear layers on the mixing performance by Rahul Kumar Soni and Ashoke De [47]. Two different-shaped struts have been utilized to create different sizes of vortices. The height of the strut lip in addition to velocity gradients was found responsible to produce vortices. Nonetheless mixing layer growth and mixing efficiency are also correlated with the size of vortices. The effect of streamlined vortices created by the strut during supersonic combustion at a variable equivalence ratio has been explored by Toshihiko Hiejima [48]. The point at which shock waves with vortex interacted, boosted burning performance was seen. Furthermore, this interaction is also helpful for flame holding as well as combustion enhancement. As shown in Fig. (4), the brief flow behavior behind the strut has been evaluated by Donggang Cao et al. [49]. The mixing layer during combustion was observed in three parts initial stage, the quick-developing stage, and the fully developed stage. Shock wave nearer to the fuel injector was recognized as boosting phenomena for early-stage fuel-air mixing due to vortices generated by the turbulence. Numerous types of the shockmixing layer were analyzed during the development of the flow field. During shock wave generation, it is quite difficult to reduce pressure loss. So increased pressure loss is found a major challenge in the present supersonic combustion scenario. inlet

wall injector

strut

injector

periodic

outlet

wall outlet

inlet

strut

Fig. (4). Schematic of the computational Domain.

wall

160 Materials and Technologies for a Green Environment

Verma et al.

The supersonic air-fuel combustion jet flame stability mechanism has been explained by Lisa Bouheraoua et al. [50]. To avoid resolution issues, the author selected three different meshes. Non-premixed large eddy simulation-based model was found good agreement with the experimental data. Highly unstable flames cause diamond shock near the burner. These shocks were found helpful in mixing and also it controls the auto-ignition process. The experimental observation was carried out by Junlong Zhang et al. [51] to examine flame stabilization and combustion establishment. Three stages were observed during combustion where the first was the establishment stage, then the stabilization stage was identified as the second, and the last one was the extinction stage. Variation in the equivalence ratio also shows the different styles of flame propagation. The flame was initially seen downstream then it proceeded with upstream as the equivalence ratio was low. Similarly for a higher value of equivalence ratio, Firstly, flame was generated in the recirculation zone and then propagate downstream. Flame stabilization analysis was carried out experimentally by Felix J. Förster et al. [52]. Staged fuel injection was introduced, i.e. strut and ramp. To understand the flow physics of the flow field, wall pressure information, schlieren imaging, and flame visualization were applied. Distinct and stable flame shapes were recognized at an intermitted zone of supersonic and dual-mode combustors. To understand the effect of streamwise vortices, the geometry and trajectory of the combustor have been explored by K. M. Pandey et al. [53] with the help of a numerical solver. Nonetheless, the author also considered different angles of attack in parallel fuel injection strategy with hypersonic speed. Flow characteristics and combustion characteristics were explained and shock structure is affected by the geometry and trajectory of the combustor and also flight Mach number. Nevertheless shorter ignition delay was identified as a negative angle of attack. L. Maddalena et al. [54] explored the vortex dynamics through a reduced-order model. This model is often helpful to explore the vortex structures. The entire work was focused on the co-rotating vortices merging process and also a study of counter-rotating vortex pairs. Much experimental design has been chosen and found a similar pattern of plume visualization, and vortex-plume interactions. L. Abu-Farhan et al. [55] investigated the hydrogen-based single-stage injection with the help of a central wedge-shaped strut and compared it with a multi-stage injection technique i.e. wall injection. Numerical simulation has been carried out through ANSYS CFX-12 code. Unstructured tetrahedral grids were carried out to generate appropriate mesh for getting better flow field visualization and performance of the combustor. At the end of all observations, the formation of vortices with the addition of bow shock waves was identified in multi-stage injection nonetheless it indicated enhanced mixing between the fuel and an

Role of Geometrical Modification

Materials and Technologies for a Green Environment 161

oxidizer. To improve the supersonic mixing S. Sujith et al. [56] selected three different types of struts with variable ramp angles at the trailing edge. And also seven different trailing ramp angles were analyzed through numerical simulation. Additional streamwise vortices have been generated with alternative trailing ramp angles and identified better mixing at 14.04 degrees. To augment the mixing performance of a dual combustor ramjet engine, Chuan Sun et al. [57] utilized a co-flow jets arrangement. To separate the incoming fuel and air, one straight splitter plate was utilized. To compare the mixing performance of the engine, sinusoidal-shaped splitter plates with different amplitudes were simulated. The nature of the flow field became more turbulent due to the formation of vortices, it occurred due to the huge production of expansion waves. Since the non-uniform waves further decline other reflected waves hence the strength of the vortices becomes lesser. Therefore, the selection of the amplitude of the sinusoidal splitter plate highly influences the mixing behavior. 3. SCRAMJET PERFORMANCE CHARACTERISTICS ANALYSIS As stated earlier, the combustion process in Scramjet occurs at supersonic speeds and the engine. Any type of engine performance is evaluated by its combustion performance characteristics [59, 60]. The selection of appropriate working fuel [58, 61] and inflow conditions of air and fuel are highly influencing parameters to reach their maximum performance. This section comprises four different aspects to explore and discuss in detail the future scope. 3.1. Supplementary Fuel (Mixed) Implications Since the single working fuel has widely been utilized in supersonic combustion ramjet engines, however the effect of multiple fuel utilization is not performed extensively. To fill the gap, single vs. multiple fuel injection approaches were performed by Sugang Ma et al. [62]. Combinations of hydrogen and hydrocarbon fuels were selected in supersonic flow to uncover the combustion performance by utilizing numerical investigation. Two separate tests were done to compare sole hydrogen fuel with mixed hydrocarbon fuels. The shorter distance was identified to get full mixing in mixed fuel, however a significant drop was identified in the combustion performance plot for the same model. Nonetheless weaker combustion intensity was recognized by adding mixed hydrocarbon fuel in supersonic flow regimes. To understand the mode transition process of a dualmode combustor, Rui Xue et al. [63] selected a few parameters equivalence ratio, incoming temperature, and pilot hydrogen. The vanished high-pressure zone near

162 Materials and Technologies for a Green Environment

Verma et al.

the fuel injector by reducing the kerosene equivalence ratio is observed during mode transition. A weaker shock train is also identified near this zone. So heat release zone concentrates near the cavity. Shear layer thickness increased again when the temperature was changed at the same equivalence ratio. The overall heat release becomes more distributed using pilot hydrogen. Jianping Li et al. [64] utilized kerosene and pioneer hydrogen fuels for getting appropriate flame stabilization methods by changing the incoming Mach number in addition to the total temperature. The experimental observation was performed by three different injection techniques by utilizing different timings of ignition control. Hydrogen was nominated to guide the kerosene where two different locations were used for kerosene injection i.e. simultaneously and sequentially. In the absence of pioneer hydrogen, kerosene alone was unable to burn stable. Nonetheless, the presence of a spray block was found favorable to burn kerosene alone however it created back pressure which further destroyed the inflow condition. The author concluded that the selection of an appropriate fuel injection technique for kerosene at a lower range of Mach number can surely affect the flame stabilization, nevertheless the appropriate design of the combustor suggestions has also been identified. 3.2. Different Fuels Rahul Kumar Soni and Ashoke De [65] selected the two different fuels to observe the effect on the geometry of the fuel injector. The Lip thickness of both struts i.e. straight and taper was analyzed and a dissimilar type of reattachment region was seen, however, this region is often helpful for mixing. Based on the mole fraction profile, hydrogen was found a better candidate for straight strut compared with other fuels i.e. ethylene. So straight strut is a more prominent geometry for fuel spreading nonetheless higher fuel jet diameter was responsible for reduced mixing phenomena. Malsur Dharavath et al. [66] solely selected ethylene as a working fluid in the supersonic flow regimes with the help of both reacting and nonreacting cases to analyze the performance characteristics. The effect of shocks on fuel penetration was also examined. The total pressure loss in both cases was calculated. The effect of the equivalence ratio on the wall pressure plot was identified and this is due to a larger heat release. An experimental investigation was performed by Jichao Hua et al. [67] by utilizing a strut and flush wall fuel injection approach with kerosene as a working fuel. Combustion performance was evaluated by varying fuel feeding ratio among the wall and strut nonetheless separate strut mode and strut with wall mode were also examined. The author concluded that the strut mode enhances the combustion performance, however, the lesser wall temperature gradient was identified in

Role of Geometrical Modification

Materials and Technologies for a Green Environment 163

strut-wall mode due to wall fuel injection, which displayed a wall film cooling effect. Experimental observation has been conducted by Wen Bao et al. [68] to explain the behavior of central fuel injection with the help of a strut. Liquid kerosene has been selected as a fuel and also additional pilot oxygen was injected through the orifice at the end of the strut. The behavior of the central sprayed fuel has been found noticeable. A stable flame near the center has been recognized due to the pilot oxygen placed ahead of the strut. This technique is quite helpful to organize the incoming mainstream. Nonetheless, central injection is gaining more attention in supersonic combustion due to its wide range of equivalence ratios. Tristan Vanyai et al. [69] utilized an axisymmetric supersonic combustor model to explore combustion modes by using ethylene as a working fuel. Multiple ranges of flight Mach number were performed to get insights into combustion modes. In all the sets of experiments, three consecutive combustion modes i.e. scram-mode, jet wake, and dual-mode were identified. In the scram mode, a ringlike structure in an axisymmetric manner was seen however broken and dissimilar structures were observed at various locations. All the cross-sectional OH radical distributions were captured well with the help of planar laser-induced fluorescence (PLIF) signal. 3.3. Variable Inflow Condition Computational analysis has been performed by Kun Wu et al. [70] to identify the flame stabilization modes, with the help of variable incoming temperature and overall equivalence ratio of DLR-based combustor. At relatively low-temperature conditions, the attached zone (Flame Stabilization) was identified, and also the recirculation zone after the wedge-shaped strut plays a major role in combustion stabilization. Similarly for high-temperature inflow conditions, a lifted flame mode was encountered. There was no significant variation observed due to the overall equivalence ratio over flame stabilization. Gautam Choubey and K. M. Pandey [71] numerically investigated the effect of parametric variation by utilizing two strut scramjet combustors. Three different cases i.e. divergence angle, strut tip radius, and also its half angle were selected to examine their effects. Enhanced combustion performance was identified by changing the divergence angle and half angle of the strut from 5 to 8 degrees. However, the reduction was seen in the combustion plot by changing the strut tip. Rajiv R. Shenoy et al. [72] explored the suitable fuel injection strategy with an appropriate fuel injector for different hypersonic flow conditions. Three different types of fuel injectors i.e. strut, ramp, and flush wall have been exhaustively comprehended with the help of a numerical-based solver. As three of the injectors are having their benefits as the strut injector is useful for its core injection inside

164 Materials and Technologies for a Green Environment

Verma et al.

the flow field. Similarly, a ramp is mostly used to generate large counter-rotating vortices. Thrust augmentation can be attained by flush wall injectors. In the end, the author summarized that the strut-type injector is most appropriate for mixing and combustion efficiency for a higher value of Mach number. The variable air-inflow condition was carried out to investigate flame stabilization by Fei Qin et al. [73]. For a lower temperature of the air, flame stability was improved however at the same time combustion intensity was reduced. During moderate temperatures, shock waves were found helpful to stabilize the flame, however, this failed at higher temperature values. By comparing the two different techniques of fuel injection i.e. strut and cavity, the simplicity flame stabilized location was seen in strut-based fuel injection. Shao-Hua Zhu and Xu Xu [74], experimentally investigated dual-mode scramjet with the help of two-stage. The author varies the inflow Mach number as well as the temperature to understand the flow characteristics. A higher value of temperature with a lower Mach number was found beneficial to activate flame flashback. Wall pressure profile and flame both were found continuous and oscillating at higher Mach number. K. M. Pandey et al. [75, 76] numerically investigated scramjet combustors at different incoming air and fuel Mach numbers. Better combustion performance was recognized at a higher air Mach number with the help of flow distribution alteration and temperature rise. Wei Huang and Li Yan [77] numerically evaluated the dual-mode combustor model by changing the inlet condition of an isolator, jet-to-cross flow pressure ratio, and injection techniques. From the observation, it was found that pressure ratio and inlet condition are the major parameters of ram-to-scram mode transition, however, there was no major effect available due to the injection technique. A larger pressure ratio difference was identified to affect the upstream flow speed of the strut nonetheless upstream separation zone was also affected by the pressure ratio. Near the tip of the strut, the first thermal chocking was recognized. The incoming boundary condition is a major parameter for supersonic combustion, however, to reach desirable demand, higher incoming temperatures often play a major role. This parameter often ablates the strut material. To reduce the problem, frequent cooling of wedge shape fuel injectors is needed. To overcome this problem, Yan-Bin Xiong et al. [78] introduced a transpiration cooling technique by using a metal porous strut. A numerical investigation was performed to get insights into the impact of parametric variation on the supersonic combustion performance by K. A. Verma et al. [79, 80]. Change of any particular incoming boundary condition was found to correlate with the velocity profile plot. Higher incoming air temperature with static pressure near atmospheric conditions was identified as optimum for the

Role of Geometrical Modification

Materials and Technologies for a Green Environment 165

selected combustor model. FAN ZhouQin et al. [81] explored the supersonic combustion flamelet model. To understand the effect of the flamelet model, theoretical analysis has been performed. The flamelet model was recognized as appropriate in premixed combustion for all flight Mach numbers due to less instability in the recirculation and shear layer zone. Similarly for non-premixed combustion, high Mach numbers are not appropriate for the flamelet model. Understanding the flame-holding mechanism of strut-based supersonic combustor has been completed numerically by Huang Wei et al. [82] with the help of parametric variation. The variation is done in two ways, first in the reaction mechanism and second in the variation in the pressure and the temperature of the fuel. Minor variation was seen in by changing the chemical reaction mechanism. However, the shock waves move towards the exit of the combustor just by increasing the incoming pressure and temperature of the fuel. This situation also leads to the disappearance of separation. 3.4. Different Computational Model Turbulent combustion interaction of hydrogen-fueled combustor for high Mach number with the help of the eddy dissipation model (EDM) has been explored computationally by J.J.O.E Hoste et al. [83]. EDM was identified better for nearwake regions compared with far-wake regions due to the kinetic limit of the model. In the end, the author concluded that this model is not appropriate for future simulation and improved model is required to predict the far field wake region. Kun Wu et al. [84] analyzed large eddy simulation based on all chemistry treatment methods i.e. tabulation of dynamic adaptive chemistry (TDAC), dynamic adaptive chemistry (DAC), detailed mechanism, and global skeletal mechanism methods to get the improve chemistry fidelity for flame stabilization and efficient computational performance. Thermochemical radicals have been well predicted by DAC/TDAC method. The global performance of the engine can be identified by the global skeletal mechanism method nonetheless TDAC method is more suitable for supersonic combustion numerical simulation. Large eddy simulation (LES) modeling took a high computational cost compared with Reynolds-Averaged Navier-Stokes (RANS) based models for supersonic combustion simulation. Junsu Shin and Hong-Gye Sung [85] selected a zonal hybrid RANS/LES modeling framework to understand the vortices effect over the mixing layer through changing fuel injector numbers. To couple the both RANS and LES zone, the Author elected an SEM interface connection and identified that a growing number of fuel injectors influence the mixing shear layer and create the additional coherent vortices downstream however, no major changes were found in velocity and temperature plots. Hybrid RANS/LES model has been taken to

166 Materials and Technologies for a Green Environment

Verma et al.

analyze the supersonic combustion through Junsu Shin and Hong-Gye Sung [86]. Near to combustion domain, LES modeling has been performed and the incoming far field has been solved by the RANS model by utilizing a hybrid RANS/LES framework-based model. Comparisons have been performed within two fuels i.e. hydrogen and cracked kerosene. Cracked kerosene is collected by methane and ethylene catalytic. And it has been identified that surrogate kerosene is more susceptible in the direction of flame quenching. Non-premixed supersonic combustion evaluation has been performed with the help of LES based solver coupled with the Eulerian Stochastic Fields (ESF) model and also compared with the well-stirred reactor (WSR) model. Flame stabilization and its structure were examined by the LES-ESF model method. It was found that the flame stabilization and re-ignition were affected by the recirculation zone. Oscillation of recirculation can be a governing factor for stabilizing the flame and local extinction under the observed conditions commented on by Cheng Gong et al. [87]. Qing Li and Zhenguo Wang [88] selected a large eddy simulation coupled with dynamic mode decomposition (DMD) to investigate the instabilities of combustion. The unevenness was strongly observed in OH and HO2 fields. This unsteadiness was entirely related to waking region instability. The velocity plot can show the dynamics of this region clearly. Junsu Shin and Hong-Gye Sung [89] investigated reacting and nonreacting flow with the help of two different turbulence models and two spatial discretization methods to identify the appropriate model. For non-reacting flow, there was no important observation found. However, better temperature plots were found by using Delayed Detached Eddy Simulation (IDDES) based turbulence model. The WENO-spatial discretization method combined with the IDDES-based turbulence model has been found best for reacting flow fields. Cao Changmin et al. [90] selected the LES - probability density function based on two different models i.e. β and δ function to observe the combustion and flow field characteristics. Nonetheless, to get proper results of flow structure, the adaptive mesh refinement (AMR) technique was used. Reaction rate rescaling was done through pressure in a thermo-chemistry table to reflect the compressibility effects. Better statistical results were attained by the β-function model compared with the δ-function. Fuel stabilization was identified in the central recirculation bubble. Guo-Yan Zhao et al. [91] examined a modified flamelet model for supersonic non-premixed combustion with different pressure. Hybrid RANS/LES method was chosen to carry out this analysis. The author improved the premixed condition of the previous work to a non-premixed condition, this modified model improved the accuracy of the chemical source term and pressure plot. The same model has been tested over two different combustor geometries and found improved results with a wide range of pressure.

Role of Geometrical Modification

Materials and Technologies for a Green Environment 167

The LES model has been performed by Yann Moule et al. [92] to understand the effect of micro-mixing through finite-rate chemistry and a partially stirred reactor. Nonetheless, flame structure and stability of flame have also been explained with the abilities of an unsteady partially stirred reactor. In the end, it was identified that the local temperature was increased due to the first diamond shock. These occurrences commonly help in flame stabilization because they are a primary source of heat release. The LES-based model with two different combustion models has been tested to observe the behavior of supersonic flow, mixing, and combustion performance through C. Fureby et al. [93]. Two-step global mechanism over seven-step reduction mechanics was together analyzed. A better agreement with experimental data was observed in LES-PaSR Model. In the entire observation, it was found that most of the heat release was done in the wake region due to a lack of mixing through shear layers. Malsur Dharavath et al. [94] selected the (k-ɛ) turbulent model for the evaluation of the thermochemical of hydrogen-air combustion. Non-reacting flows based plots through experiment were seen in good agreement with numerical observation. Weaker shock waves were realized in reacting flows, nonetheless over-predicted data was recognized in far-field velocity, also 12% maximum deviation was seen in temperature plots. The author suggested that detailed chemical kinetics are essentially required to resolve the present problem while plotting temperature graphs. Changing the boundary layer thickness of the combustor shows a shorter reaction zone. However, any turbulent model is appropriate to predict the combustion and mixing process. Combustion performance was experimentally analyzed by varying inflow conditions such as local equivalence ratio, a mass flow rate of fuel, and incoming boundary conditions [100]. Two staged strut was selected for dual mode combustor by Shaohua Zhu et al. [95] also to understand the flame propagation and stabilization. Stabilized flame in the recirculation region was observed at low inflow enthalpy conditions. The escaped flame was observed at a lean fuel flow rate. Similarly, flame stabilization near the separated boundary layer zone at the wall was identified at higher incoming enthalpy furthermore hysteresis phenomena were also seen in the pressure graph. Qingchun Yang et al. [96] scrutinized staged combustors with the help of dual struts to understand the combustion modes experimentally. Strut placed in the first stage gave improved engine performance at subsonic combustion mode and the second stage is useful for supersonic combustion mode. Nevertheless thrust produced by the engine is also affected by the combustion modes. Combustion performance was analyzed by using a different angle of attachment of incoming air inside the combustor by Gautam Choubey and K.M. Pandey [97]. Three different angles of attack were chosen to understand the performance of two

168 Materials and Technologies for a Green Environment

Verma et al.

strut-based strut combustors. The author found that the smallest ignition delay was identified at zero angles of attack nonetheless efficiency was found higher for this arrangement. Zhi-Wei Huang et al. [98] numerically and experimentally both explored the combustion oscillation of rocket-based combined cycle combustors. At the initial stage of an unsteady shear layer formed by rocket jet and incoming air, it was thin and after further movement, it got thickened and wrinkled. A lowspeed recirculation zone with a sudden expansion arrangement was generated due to the main strut. Over-expanded rocket jet was found as a key parameter for mixing and combustion. Zhi-Wei Huang et al. [99] selected a Partially Stirred Reactor (PaSR), sub-grid combustion model, to analyze the combustion mode and flame configuration. 27steps, 9 species-based multistep reactions were selected for chemical kinetics. LES – Compressible solver has opted to conduct all simulations. Combustion was identified in the non-premixed mode and this mode is signified by turbulent mixing in the shear layer area. Nonetheless stabilized flame in the combustor was mostly identified due to auto-ignition compared with the propagation of flame. Flame stability and combustion efficiency can be easily modified by using the appropriate fuel injection and mixing strategy suggested by C. Fureby et al. [101]. Experimental and numerical investigation was performed to understand the effect of self-ignition, mixing, and flow stabilization mechanisms through the modified strut. LES-based finite rate chemistry model has been chosen to conduct numerical simulation and found appropriate similarities with the experiment. Longitudinal vortices play a major role to enhance combustion performance, this has been seen in modified wedge-shaped struts compared with conventional. Mode transition of combustion in strut-based combustor has been evaluated through experimental observation by Qingchun Yang et al. [102]. Three different combustion modes have been explored i.e. scramjet mode, weak ramjet mode, and strong ramjet mode. A sudden increase in thrust was observed during scramjet to weak ramjet transition mode, nonetheless, thermal chocking was also seen at the exit of the combustor section. From weak ramjet to strong ramjet mode, a sudden reduction in thrust was identified and also thermal chocking was analyzed near the fuel supply. Flow field characteristics were abruptly changed during mode transitions. The Center strut fuel injector strategy has been followed to get stable combustion by Wen Bao et al. [68]. Novelty can be identified in the leading part of the strut, where orifices were created to inject oxygen. Due to this, stable local flame was identified in a dual-mode scramjet combustor. Flame intensity can easily be controlled by oxygen amount. At the end of the experimental observation, the author found that a very less amount of oxygen was needed for further combustion stabilization.

Role of Geometrical Modification

Materials and Technologies for a Green Environment 169

SUMMARY AND CONCLUDING REMARKS The present article has gone through various aspects of supersonic combustion ramjet engine performance analysis. The role of jet position and combustor geometrical modification has a greater impact on the overall analysis of scramjet. Since numerous authors have explored different aspects of the ongoing challenges in scramjet hence the following summary has been drawn to acquire a suitable model for future work. • In all the cases, better mixing and combustion performance were identified through a large number of vortex formations and also boundary layer separation can act as an instigator for better performance. Nonetheless, a large number of oblique shock waves can be introduced by creating sharp edges in the working geometry. The baroclinic effects are responsible to generate a large number of vortices and this is found beneficial regarding mixing. The vortices in the highspeed flow field increase the turbulence intensity, which leads to enhanced mixing. Enhancement of mixing is identified by the interaction between the K-H structure and the vortices shed. So, it can be summarized that large-scale vortices act as a major role in supersonic mixing. An asymmetric structure is good for enhanced mixing and combustion nonetheless height and divergence angle of the combustor wall are key parameters for combustor geometry. • By going through all investigations, the twin strut arrangement is suitable for higher thrust. In the end, it is determined that a hydrogen-based parallel fuel injector with a modified strut combustor can achieve hypersonic flight speed with satisfactory performance. The location of the thermal throat was moving downstream as the equivalence ratio was reducing. No impact was observed on the combustor thrust due to the equivalence ratio, however, tremendous changes in the combustor thrust are observed due to the hysteresis mode transition. • The dynamics behind better mixing utilizing vortices are connected through the mass transfer between jet spacing to the shear layer and vice-versa. The nature of the flow field became more turbulent due to the formation of vortices, it occurred due to the huge production of expansion waves. Since the non-uniform waves further decline other reflected waves, hence the strength of the vortices becomes lesser. So, the selection of the amplitude of the sinusoidal splitter plate highly influences the mixing behavior. • Highly unstable flames cause diamond shock near the burner. These shocks were found helpful in mixing and also control the auto-ignition process. The flame was initially seen downstream then it proceeds with upstream as the equivalence ratio was low. Similarly for a higher value of equivalence ratio, firstly flame was generated in the recirculation zone and then propagated downstream. Many

170 Materials and Technologies for a Green Environment

Verma et al.

arrangements can be responsible for better mixing, however, passive control device is needed to stabilize the flame. A strong correlation is recognized that the flame balance in the turbulence regions can be affected by temperature and the global equivalence ratio. • Shock wave nearer to the fuel injector is recognized as boosting phenomena for early-stage fuel-air mixing due to vortices generated by the turbulence. Numerous types of shock-mixing layers have been analyzed during the development of the flow field. During shock wave generation, it is quite difficult to reduce pressure loss. So increased pressure loss is found a major challenge. • The incoming boundary condition is a major parameter for supersonic combustion, however, to reach desirable demand, higher incoming temperatures often play a major role. This parameter often ablates the fuel injector material. To reduce the problem, frequent cooling of wedge shape fuel injectors is needed. The minor wall temperature gradient is identified in strut-wall mode due to wall fuel injection, which displayed a wall film cooling effect. • Flame intensity can easily be controlled by oxygen amount. Nonetheless stabilized flame in the combustor can be generally identified due to auto-ignition compared with the propagation of flame. The smallest ignition delay has been identified at zero angles of attack nonetheless efficiency was found higher for this arrangement. • A sudden increase in thrust has been observed during scramjet to weak ramjet transition mode nonetheless thermal chocking can also be seen at the exit of the combustor section. From weak ramjet to strong ramjet mode, a sudden reduction in thrust is identified and also thermal chocking is analyzed near the fuel supply. Flow field characteristics abruptly change during mode transitions. CONSENT FOR PUBLICATION Not applicable. CONFLICT OF INTEREST The authors declare no conflict of interest, financial or otherwise. ACKNOWLEDGEMENT Declared none. REFERENCES [1]

T. Vanyai, S. Brieschenk, M. Bricalli, T. Sopek, and T.J. McIntyre, "Thermal compression effects

Role of Geometrical Modification

Materials and Technologies for a Green Environment 171

within a fundamental, hydrogen-fuelled scramjet", Aerosp. Sci. Technol., vol. 110, p. 106499, 2021. [http://dx.doi.org/10.1016/j.ast.2021.106499] [2]

Z. Du, C. Shen, W. Huang, L. Yan, J. Liang, and G. Choubey, "Parametric study on mixing augmentation mechanism induced by cantilevered ramp injectors in a shock-induced combustion ramjet engine", Aerosp. Sci. Technol., vol. 108, p. 106413, 2021. [http://dx.doi.org/10.1016/j.ast.2020.106413]

[3]

Y. Jiang, R. Moradi, A.M. Abusorrah, M.R. Hajizadeh, and Z. Li, "Effect of downstream sinusoidal wall on mixing performance of hydrogen multi-jets at supersonic flow: Numerical study", Aerosp. Sci. Technol., vol. 109, p. 106410, 2021. [http://dx.doi.org/10.1016/j.ast.2020.106410]

[4]

C. Zhang, J. Chang, Y. Zhang, Y. Wang, and W. Bao, "Flow field characteristics analysis and combustion modes classification for a strut/cavity dual-mode combustor", Acta Astronaut., vol. 137, pp. 44-51, 2017. [http://dx.doi.org/10.1016/j.actaastro.2017.03.023]

[5]

M. Faheem, A. Khan, R. Kumar, S. Afghan Khan, W. Asrar, and A.M. Sapardi, "Experimental study on the mean flow characteristics of a supersonic multiple jet configuration", Aerosp. Sci. Technol., vol. 108, p. 106377, 2021. [http://dx.doi.org/10.1016/j.ast.2020.106377]

[6]

J. Dai, and C. Huang, "Secondary fuel jet strategies on mixing enhancement performance of rocketbased combined cycle engine", Acta Astronaut., vol. 178, pp. 285-295, 2021. [http://dx.doi.org/10.1016/j.actaastro.2020.09.028]

[7]

G. Choubey, and K.M. Pandey, "Effect of different strut + wall injection techniques on the performance of two-strut scramjet combustor", Int. J. Hydrogen Energy, vol. 42, no. 18, pp. 1325913275, 2017. [http://dx.doi.org/10.1016/j.ijhydene.2017.04.024]

[8]

G. Choubey, and K.M. Pandey, "Effect of different wall injection schemes on the flow-field of hydrogen fuelled strut-based scramjet combustor", Acta Astronaut., vol. 145, pp. 93-104, 2018. [http://dx.doi.org/10.1016/j.actaastro.2018.01.034]

[9]

G. Choubey, and K.M. Pandey, "Effect of variation of inlet boundary conditions on the combustion flow-field of a typical double cavity scramjet combustor", Int. J. Hydrogen Energy, vol. 43, no. 16, pp. 8139-8151, 2018. [http://dx.doi.org/10.1016/j.ijhydene.2018.03.062]

[10]

Y. Yuan, T. Zhang, W. Yao, X. Fan, and P. Zhang, "Characterization of flame stabilization modes in an ethylene-fueled supersonic combustor using time-resolved CH* chemiluminescence", Proc. Combust. Inst., vol. 36, no. 2, pp. 2919-2925, 2017. [http://dx.doi.org/10.1016/j.proci.2016.07.040]

[11]

O.R. Kummitha, K.M. Pandey, and R. Gupta, "Optimization of scramjet performance with different fuel injection techniques and flame holder cavities", Acta Astronaut., vol. 152, pp. 908-919, 2018. [http://dx.doi.org/10.1016/j.actaastro.2018.09.026]

[12]

W. Huang, H. Wu, Z. Du, L. Yan, and G. Choubey, "Design exploration on the mixing augmentation induced by the oblique shock wave and a novel step in a supersonic flow", Acta Astronaut., vol. 180, pp. 622-629, 2021. [http://dx.doi.org/10.1016/j.actaastro.2020.12.058]

[13]

K.M. Pandey, G. Choubey, F. Ahmed, D.H. Laskar, and P. Ramnani, "Effect of variation of hydrogen injection pressure and inlet air temperature on the flow-field of a typical double cavity scramjet combustor", Int. J. Hydrogen Energy, vol. 42, no. 32, pp. 20824-20834, 2017. [http://dx.doi.org/10.1016/j.ijhydene.2017.07.026]

[14]

K.M. Pandey, and S. Roga, "CFD analysis of hypersonic combustion of H2-fueled scramjet combustor with cavity based fuel injector at flight Mach 6", Appl. Mech. Mater., vol. 656, pp. 53-63, 2014.

172 Materials and Technologies for a Green Environment

Verma et al.

[http://dx.doi.org/10.4028/www.scientific.net/AMM.656.53] [15]

D. Jian, Z. Qiuru, and H. Chao, "Numerical investigation of cavity-induced enhanced supersonic mixing with inclined injection strategies", Acta Astronaut., vol. 180, pp. 630-638, 2021. [http://dx.doi.org/10.1016/j.actaastro.2021.01.012]

[16]

K. Ambe Verma, K. Murari Pandey, M. Ray, and K. Kumar Sharma, "Effect of transverse fuel injection system on combustion efficiency in scramjet combustor", Energy, vol. 218, p. 119511, 2021. [http://dx.doi.org/10.1016/j.energy.2020.119511]

[17]

K.A. Verma, K.M. Pandey, and K.K. Sharma, "Computational investigation of mixing performance on the effects of innovative transverse fuel injection system in parallel fuel injection based scramjet combustor", Mater. Today Proc., 2020.

[18]

N. Bordoloi, D. Alontseva, K.M. Pandey, and K.K. Sharma, "The performance of a scramjet combustor with cavity for Mach numbers 2.25, 2.52 and 2.75 with hydrogen as a fuel", Mater. Today Proc., vol. 45, pp. 6615-6622, 2021. [http://dx.doi.org/10.1016/j.matpr.2020.11.794]

[19]

L. Yan, L. Liao, W. Huang, and L. Li, "Nonlinear process in the mode transition in typical strut-based and cavity-strut based scramjet combustors", Acta Astronaut., vol. 145, pp. 250-262, 2018. [http://dx.doi.org/10.1016/j.actaastro.2018.01.061]

[20]

L. Liao, L. Yan, W. Huang, and L. Li, "Mode transition process in a typical strut-based scramjet combustor based on a parametric study", J. Zhejiang Univ. Sci. A, vol. 19, no. 6, pp. 431-451, 2018. [http://dx.doi.org/10.1631/jzus.A1700617]

[21]

O.R. Kummitha, K.M. Pandey, and R. Gupta, "CFD analysis of a scramjet combustor with cavity based flame holders", Acta Astronaut., vol. 144, pp. 244-253, 2018. [http://dx.doi.org/10.1016/j.actaastro.2018.01.005]

[22]

K. Sathiyamoorthy, T.H. Danish, J. Srinivas, and P. Manjunath, "Experimental investigation of supersonic combustion in a strut-cavity based combustor", Acta Astronaut., vol. 148, pp. 285-293, 2018. [http://dx.doi.org/10.1016/j.actaastro.2018.05.014]

[23]

K.A. Verma, K.M. Pandey, and K.K. Sharma, "Effect of wall cavity with combined fuel injection technique in scramjet combustor with CFD", Mater. Today Proc., 2021.

[24]

Y. Tian, W. Shi, M. Guo, Y. Liu, C. Zhang, and J. Le, "Investigation of combustion characteristics in a hydrogen-fueled scramjet combustor", Acta Astronaut., vol. 186, pp. 486-495, 2021. [http://dx.doi.org/10.1016/j.actaastro.2021.06.021]

[25]

D. Zhang, and W. Song, "Experimental study of cone-struts and cavity flameholders in a kerosenefueled round scramjet combustor", Acta Astronaut., vol. 139, pp. 24-33, 2017. [http://dx.doi.org/10.1016/j.actaastro.2017.06.025]

[26]

K.A. Verma, K.M. Pandey, and K.K. Sharma, Study of Fuel Injection Systems in Scramjet Engine—A Review. Recent Advances in Mechanical Engineering. pp. 931-940, 2021. [http://dx.doi.org/10.1007/978-981-15-7711-6_92]

[27]

S. Aravind, and R. Kumar, "Supersonic combustion of hydrogen using an improved strut injection scheme", Int. J. Hydrogen Energy, vol. 44, no. 12, pp. 6257-6270, 2019. [http://dx.doi.org/10.1016/j.ijhydene.2019.01.064]

[28]

R.K. Soni, and A. De, "Role of jet spacing and strut geometry on the formation of large scale structures and mixing characteristics", Phys. Fluids, vol. 30, no. 5, p. 056103, 2018. [http://dx.doi.org/10.1063/1.5026375]

[29]

O.R. Kummitha, K.M. Pandey, and R. Gupta, "Numerical analysis of hydrogen fueled scramjet combustor with innovative designs of strut injector", Int. J. Hydrogen Energy, vol. 45, no. 25, pp. 13659-13671, 2020. [http://dx.doi.org/10.1016/j.ijhydene.2018.04.067]

Role of Geometrical Modification

Materials and Technologies for a Green Environment 173

[30]

O.R. Kummitha, K.M. Pandey, and R. Gupta, "Numerical investigation of wavy wall strut fuel injector for hydrogen fueled scramjet combustor", Int. J. Hydrogen Energy, vol. 44, no. 60, pp. 32240-32253, 2019. [http://dx.doi.org/10.1016/j.ijhydene.2019.10.147]

[31]

S. Zhu, X. Xu, and Q. Yang, "Application of the vortex effects induced by the trailing wedge to enhance the mixing and combustion in the strut-based scramjet", Appl. Therm. Eng., vol. 140, pp. 604614, 2018. [http://dx.doi.org/10.1016/j.applthermaleng.2018.05.084]

[32]

S. Neill, and A. Pesyridis, "Modeling of Supersonic Combustion Systems for Sustained Hypersonic Flight", Energies, vol. 10, no. 11, p. 1900, 2017. [http://dx.doi.org/10.3390/en10111900]

[33]

K.M. Pandey, and S. Thangavel, "CFD Analysis of Scramjet Combustor Using Strut with Circular and Planer Injector", ASME International Mechanical Engineering Congress and Exposition, 2011 pp. 1521-1529, 2011. [http://dx.doi.org/10.1115/IMECE2011-62310]

[34]

K.M. Pandey, and S. Roga, "CFD analysis of scramjet combustor with non-premixed turbulence model using ramp injector", Appl. Mech. Mater., vol. 555, pp. 18-25, 2014. [http://dx.doi.org/10.4028/www.scientific.net/AMM.555.18]

[35]

Z. Yan, Z. Shaohua, C. Bing, and X. Xu, "Hysteresis of mode transition in a dual-struts based scramjet", Acta Astronaut., vol. 128, pp. 147-159, 2016. [http://dx.doi.org/10.1016/j.actaastro.2016.07.025]

[36]

G. Choubey, K.M. Pandey, A. Maji, T. Deshmukhya, and A. Debbarma, "Computational investigation of multi-strut injection of hydrogen in a scramjet combustor", Mater. Today Proc., vol. 4, no. 2, pp. 2608-2614, 2017. [http://dx.doi.org/10.1016/j.matpr.2017.02.115]

[37]

Y.H. Simsont, and P. Gerlinger, "High order numerical simulation of the thermal load on a lobed strut injector for scramjet applications", Int. J. Numer. Methods Fluids, vol. 82, no. 7, pp. 417-436, 2016. [http://dx.doi.org/10.1002/fld.4224]

[38]

G. Choubey, and K.M. Pandey, "Effect of parametric variation of strut layout and position on the performance of a typical two-strut based scramjet combustor", Int. J. Hydrogen Energy, vol. 42, no. 15, pp. 10485-10500, 2017. [http://dx.doi.org/10.1016/j.ijhydene.2017.03.014]

[39]

K.A. Verma, K.M. Pandey, and K.K. Sharma, "Numerical investigation of variation of combustion efficiency of scramjet combustor with change in length of wedge shaped strut blunt end", Test Eng Manage, vol. 82, pp. 7800-7806, 2020.

[40]

K.A. Verma, K.M. Pandey, and K.K. Sharma, "Computational investigation on design of scramjet combustor–A review", Int. J. Recent Technol. Eng., vol. 7, no. 6, pp. 544-548, 2019.

[41]

P. Nithish Reddy, and K. Venkatasubbaiah, "Numerical investigations on development of scramjet combustor", J. Aerosp. Eng., vol. 28, no. 5, p. 04014120, 2015. [http://dx.doi.org/10.1061/(ASCE)AS.1943-5525.0000456]

[42]

W. Huang, "Investigation on the effect of strut configurations and locations on the combustion performance of a typical scramjet combustor", J. Mech. Sci. Technol., vol. 29, no. 12, pp. 5485-5496, 2015. [http://dx.doi.org/10.1007/s12206-015-1150-6]

[43]

W. Bao, Y. Zong, J. Chang, and T. Cui, "Effects of strut swept angle on the drag of scramjet", Proc. Inst. Mech. Eng. Part G J. Aerosp. Eng., vol. 226, no. 4, pp. 455-466, 2012. [http://dx.doi.org/10.1177/0954410011409658]

[44]

Q. Qin, R. Agarwal, and X. Zhang, "A novel method for flame stabilization in a strut-based scramjet

174 Materials and Technologies for a Green Environment

Verma et al.

combustor", Combust. Flame, vol. 210, pp. 292-301, 2019. [http://dx.doi.org/10.1016/j.combustflame.2019.08.038] [45]

C. Li, X. Chen, Y. Li, O. Musa, L. Zhu, and W. Li, "Role of the backward-facing steps at two struts on mixing and combustion characteristics in a typical strut-based scramjet with hydrogen fuel", Int. J. Hydrogen Energy, vol. 44, no. 52, pp. 28371-28387, 2019. [http://dx.doi.org/10.1016/j.ijhydene.2019.09.023]

[46]

D. Cao, G. He, F. Qin, and D. Michaels, "Local supersonic and subsonic combustion mode transition in a supersonic jet flame", Proc. Combust. Inst., vol. 37, no. 3, pp. 3723-3731, 2019. [http://dx.doi.org/10.1016/j.proci.2018.06.213]

[47]

R.K. Soni, and A. De, "Investigation of mixing characteristics in strut injectors using modal decomposition", Phys. Fluids, vol. 30, no. 1, p. 016108, 2018. [http://dx.doi.org/10.1063/1.5006132]

[48]

T. Hiejima, "Effects of streamwise vortex breakdown on supersonic combustion", Phys. Rev. E, vol. 93, no. 4, p. 043115, 2016. [http://dx.doi.org/10.1103/PhysRevE.93.043115] [PMID: 27176398]

[49]

D. Cao, G. He, F. Qin, X. Wei, L. Shi, B. Liu, and Z. Huang, "LES study on flow features of the supersonic mixing layer affected by shock waves", Int. Commun. Heat Mass Transf., vol. 85, pp. 114123, 2017. [http://dx.doi.org/10.1016/j.icheatmasstransfer.2017.04.019]

[50]

L. Bouheraoua, P. Domingo, and G. Ribert, "Large-eddy simulation of a supersonic lifted jet flame: Analysis of the turbulent flame base", Combust. Flame, vol. 179, pp. 199-218, 2017. [http://dx.doi.org/10.1016/j.combustflame.2017.01.020]

[51]

J. Zhang, J. Chang, J. Ma, C. Zhang, and W. Bao, "Investigation of flame establishment and stabilization mechanism in a kerosene fueled supersonic combustor equipped with a thin strut", Aerosp. Sci. Technol., vol. 70, pp. 152-160, 2017. [http://dx.doi.org/10.1016/j.ast.2017.08.005]

[52]

F.J. Förster, N.C. Dröske, M.N. Bühler, J. von Wolfersdorf, and B. Weigand, "Analysis of flame characteristics in a scramjet combustor with staged fuel injection using common path focusing schlieren and flame visualization", Combust. Flame, vol. 168, pp. 204-215, 2016. [http://dx.doi.org/10.1016/j.combustflame.2016.03.010]

[53]

K.M. Pandey, S. Roga, and G. Choubey, "Computational analysis of hypersonic combustor using strut injector at flight mach 7", Combust. Sci. Technol., vol. 187, no. 9, pp. 1392-1407, 2015. [http://dx.doi.org/10.1080/00102202.2015.1035371]

[54]

L. Maddalena, F. Vergine, and M. Crisanti, "Vortex dynamics studies in supersonic flow: Merging of co-rotating streamwise vortices", Phys. Fluids, vol. 26, no. 4, p. 046101, 2014. [http://dx.doi.org/10.1063/1.4871022]

[55]

L. Abu-Farah, O.J. Haidn, and H.P. Kau, "Numerical simulations of single and multi-staged injection of H2 in a supersonic scramjet combustor", Propulsion and Power Research, vol. 3, no. 4, pp. 175186, 2014. [http://dx.doi.org/10.1016/j.jppr.2014.12.001]

[56]

S. Sujith, T.M. Muruganandam, and J. Kurian, "Effect of trailing ramp angles in strut-based injection in supersonic flow", J. Propuls. Power, vol. 29, no. 1, pp. 66-78, 2013. [http://dx.doi.org/10.2514/1.B34532]

[57]

C. Sun, N.S. Rayeni, M. Moghimihanjani, R. Moradi, and Z. Li, "Effect of sinusoidal splitter on mixing performance of co-flow jets of hydrogen and air inside dual-combustor ramjet", Acta Astronaut., vol. 180, pp. 211-217, 2021. [http://dx.doi.org/10.1016/j.actaastro.2020.12.036]

[58]

Z. Huang, G. He, S. Wang, F. Qin, X. Wei, and L. Shi, "Simulations of combustion oscillation and

Role of Geometrical Modification

Materials and Technologies for a Green Environment 175

flame dynamics in a strut-based supersonic combustor", Int. J. Hydrogen Energy, vol. 42, no. 12, pp. 8278-8287, 2017. [http://dx.doi.org/10.1016/j.ijhydene.2016.12.142] [59]

K. Wu, P. Zhang, W. Yao, and X. Fan, "Numerical investigation on flame stabilization in DLR hydrogen supersonic combustor with strut injection", Combust. Sci. Technol., vol. 189, no. 12, pp. 2154-2179, 2017. [http://dx.doi.org/10.1080/00102202.2017.1365847]

[60]

F. Shan, L. Hou, Z. Chen, J. Chen, and L. Wang, "Linearized correction to a flamelet-based model for hydrogen-fueled supersonic combustion", Int. J. Hydrogen Energy, vol. 42, no. 16, pp. 11937-11944, 2017. [http://dx.doi.org/10.1016/j.ijhydene.2017.02.100]

[61]

Z. Huang, G. He, F. Qin, D. Cao, X. Wei, and L. Shi, "Large eddy simulation of combustion characteristics in a kerosene fueled rocket-based combined-cycle engine combustor", Acta Astronaut., vol. 127, pp. 326-334, 2016. [http://dx.doi.org/10.1016/j.actaastro.2016.06.016]

[62]

S. Ma, F. Zhong, and X. Zhang, "Numerical study on supersonic combustion of hydrogen and its mixture with Ethylene and methane with strut injection", Int. J. Hydrogen Energy, vol. 43, no. 15, pp. 7591-7599, 2018. [http://dx.doi.org/10.1016/j.ijhydene.2018.03.007]

[63]

R. Xue, M. Xu, C. Bai, C. Weng, and C. Xu, "Study on transient process of mode transition in a scramjet combustor with pilot hydrogen", Int. J. Energy Res., vol. 42, no. 7, pp. 2481-2493, 2018. [http://dx.doi.org/10.1002/er.4030]

[64]

J. Li, K. Wang, G. Jiao, Z. Liao, and W. Song, "Ignition and combustion characteristics of supersonic combustor under flight Mach number 2.6–3.8", Fuel, vol. 283, p. 118960, 2021. [http://dx.doi.org/10.1016/j.fuel.2020.118960]

[65]

R.K. Soni, and A. De, "Investigation of strut-ramp injector in a Scramjet combustor: Effect of strut geometry, fuel and jet diameter on mixing characteristics", J. Mech. Sci. Technol., vol. 31, no. 3, pp. 1169-1179, 2017. [http://dx.doi.org/10.1007/s12206-017-0215-0]

[66]

M. Dharavath, P. Manna, and D. Chakraborty, "Numerical exploration of mixing and combustion in ethylene fueled scramjet combustor", Acta Astronaut., vol. 117, pp. 305-318, 2015. [http://dx.doi.org/10.1016/j.actaastro.2015.08.014]

[67]

J. Hu, J. Chang, W. Bao, Q. Yang, and J. Wen, "Experimental study of a flush wall scramjet combustor equipped with strut/wall fuel injection", Acta Astronaut., vol. 104, no. 1, pp. 84-90, 2014. [http://dx.doi.org/10.1016/j.actaastro.2014.07.012]

[68]

W. Bao, J. Hu, Y. Zong, Q. Yang, M. Wu, J. Chang, and D. Yu, "Combustion characteristic using O 2 -pilot strut in a liquid-kerosene-fueled strut-based dual-mode scramjet", Proc. Inst. Mech. Eng. Part G J. Aerosp. Eng., vol. 227, no. 12, pp. 1870-1880, 2013. [http://dx.doi.org/10.1177/0954410012464455]

[69]

T. Vanyai, W.O. Landsberg, T.J. McIntyre, and A. Veeraragavan, "OH visualization of ethylene combustion modes in the exhaust of a fundamental, supersonic combustor", Combust. Flame, vol. 226, pp. 143-155, 2021. [http://dx.doi.org/10.1016/j.combustflame.2020.11.037]

[70]

K. Wu, P. Zhang, W. Yao, and X. Fan, "Computational realization of multiple flame stabilization modes in DLR strut-injection hydrogen supersonic combustor", Proc. Combust. Inst., vol. 37, no. 3, pp. 3685-3692, 2019. [http://dx.doi.org/10.1016/j.proci.2018.07.097]

[71]

G. Choubey, and K.M. Pandey, "Investigation on the effects of operating variables on the performance of two-strut scramjet combustor", Int. J. Hydrogen Energy, vol. 41, no. 45, pp. 20753-20770, 2016.

176 Materials and Technologies for a Green Environment

Verma et al.

[http://dx.doi.org/10.1016/j.ijhydene.2016.09.157] [72]

R.R. Shenoy, T.G. Drozda, A.T. Norris, R.A. Baurle, and J.P. Drummond, "Comparison of Mixing Characteristics for Several Fuel Injectors at Mach 8 and 15 Hypervelocity Flow Conditions", 2018 Joint Propulsion Conference p. 4540, 2018. [http://dx.doi.org/10.2514/6.2018-4540]

[73]

F. Qin, Z. Huang, G. He, S. Wang, X. Wei, and B. Liu, "Flame stabilization mechanism study in a hydrogen-fueled model supersonic combustor under different air inflow conditions", Int. J. Hydrogen Energy, vol. 42, no. 33, pp. 21360-21370, 2017. [http://dx.doi.org/10.1016/j.ijhydene.2017.06.237]

[74]

S.H. Zhu, and X. Xu, "Experimental study on flame transition in a two-stage struts dual-mode scramjet", J. Aerosp. Eng., vol. 30, no. 5, p. 06017002, 2017. [http://dx.doi.org/10.1061/(ASCE)AS.1943-5525.0000740]

[75]

K.M. Pandey, S. Roga, and G. Choubey, "Numerical investigation on hydrogen-fueled scramjet combustor with parallel strut fuel injector at a flight mach number of 6", J. Appl. Fluid Mech., vol. 9, no. 3, pp. 1215-1220, 2016. [http://dx.doi.org/10.18869/acadpub.jafm.68.228.24082]

[76]

K.M. Pandey, and B. Nath, "Numerical simulation of a hydrogen fueled scramjet combustor at Mach 1.5 using strut injectors at Mach 2.47 air speed", ASME International Mechanical Engineering Congress and Exposition, vol. 56178, 2013. [http://dx.doi.org/10.1115/IMECE2013-66036]

[77]

W. Huang, and L. Yan, "Numerical investigation on the ram–scram transition mechanism in a strutbased dual-mode scramjet combustor", Int. J. Hydrogen Energy, vol. 41, no. 8, pp. 4799-4807, 2016. [http://dx.doi.org/10.1016/j.ijhydene.2016.01.062]

[78]

Y.B. Xiong, Y.H. Zhu, and P.X. Jiang, "Numerical simulation of transpiration cooling for sintered metal porous strut of the scramjet combustion chamber", Heat Transf. Eng., vol. 35, no. 6-8, pp. 721729, 2014. [http://dx.doi.org/10.1080/01457632.2013.837790]

[79]

K.A. Verma, K.M. Pandey, and K.K. Sharma, "Impact of parametric variation on combustion characteristics of hydrogen-fueled strut based scramjet combustor at supersonic speed", Int. J. Energy Res., vol. 44, no. 14, pp. 11807-11826, 2020. [http://dx.doi.org/10.1002/er.5822]

[80]

K.A. Verma, K.M. Pandey, M. Ray, and K.K. Sharma, "The numerical analysis of combustion performance of a wedge shaped strut-based scramjet combustor", Therm. Sci. Eng. Prog., vol. 20, p. 100714, 2020. [http://dx.doi.org/10.1016/j.tsep.2020.100714]

[81]

Z. Fan, W. Liu, M. Sun, Z. Wang, F. Zhuang, and W. Luo, "Theoretical analysis of flamelet model for supersonic turbulent combustion", Sci. China Technol. Sci., vol. 55, no. 1, pp. 193-205, 2012. [http://dx.doi.org/10.1007/s11431-011-4659-7]

[82]

W. Huang, Z. Wang, S. Luo, and J. Liu, "Parametric effects on the combustion flow field of a typical strut-based scramjet combustor", Chin. Sci. Bull., vol. 56, no. 35, pp. 3871-3877, 2011. [http://dx.doi.org/10.1007/s11434-011-4823-2]

[83]

J.J.O.E. Hoste, M. Fossati, I.J. Taylor, and R.J. Gollan, "Characterisation of the eddy dissipation model for the analysis of hydrogen-fuelled scramjets", Aeronaut. J., vol. 123, no. 1262, pp. 536-565, 2019. [http://dx.doi.org/10.1017/aer.2018.169]

[84]

K. Wu, F. Contino, W. Yao, and X. Fan, "On the application of tabulated dynamic adaptive chemistry in ethylene-fueled supersonic combustion", Combust. Flame, vol. 197, pp. 265-275, 2018. [http://dx.doi.org/10.1016/j.combustflame.2018.08.012]

Role of Geometrical Modification

Materials and Technologies for a Green Environment 177

[85]

J. Shin, and H.G. Sung, "Zonal Hybrid Reynolds-Averaged Navier–Stokes/Large-Eddy Simulation of a Hydrogen-Fueled Scramjet Combustor", AIAA J., vol. 56, no. 6, pp. 2322-2335, 2018. [http://dx.doi.org/10.2514/1.J056707]

[86]

J. Shin, and H.G. Sung, "Combustion characteristics of hydrogen and cracked kerosene in a DLR scramjet combustor using hybrid RANS/LES method", Aerosp. Sci. Technol., vol. 80, pp. 433-444, 2018. [http://dx.doi.org/10.1016/j.ast.2018.03.006]

[87]

C. Gong, M. Jangi, X.S. Bai, J.H. Liang, and M.B. Sun, "Large eddy simulation of hydrogen combustion in supersonic flows using an Eulerian stochastic fields method", Int. J. Hydrogen Energy, vol. 42, no. 2, pp. 1264-1275, 2017. [http://dx.doi.org/10.1016/j.ijhydene.2016.09.017]

[88]

Q. Li, and Z. Wang, "Dynamic mode decomposition of turbulent combustion process in DLR scramjet combustor", J. Aerosp. Eng., vol. 30, no. 5, 2017.04017034 [http://dx.doi.org/10.1061/(ASCE)AS.1943-5525.0000747]

[89]

J. Shin, and H.G. Sung, "Numerical Simulation of Hydrogen Combustion in Model SCRAMJET Combustor Using IDDES Framework", 20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference, 2015 p. 3625, 2015. [http://dx.doi.org/10.2514/6.2015-3625]

[90]

C. Cao, T. Ye, and M. Zhao, "Large eddy simulation of hydrogen/air scramjet combustion using tabulated thermo-chemistry approach", Chin. J. Aeronauti., vol. 28, no. 5, pp. 1316-1327, 2015. [http://dx.doi.org/10.1016/j.cja.2015.08.008]

[91]

G.Y. Zhao, M.B. Sun, J.S. Wu, and H.B. Wang, "A flamelet model for supersonic non-premixed combustion with pressure variation", Mod. Phys. Lett. B, vol. 29, no. 21, p. 1550117, 2015. [http://dx.doi.org/10.1142/S0217984915501171]

[92]

Y. Moule, V. Sabelnikov, and A. Mura, "Highly resolved numerical simulation of combustion in supersonic hydrogen–air coflowing jets", Combust. Flame, vol. 161, no. 10, pp. 2647-2668, 2014. [http://dx.doi.org/10.1016/j.combustflame.2014.04.011]

[93]

C. Fureby, E. Fedina, and J. Tegnér, "A computational study of supersonic combustion behind a wedge-shaped flameholder", Shock Waves, vol. 24, no. 1, pp. 41-50, 2014. [http://dx.doi.org/10.1007/s00193-013-0459-2]

[94]

M. Dharavath, P. Manna, and D. Chakraborty, "Thermochemical exploration of hydrogen combustion in generic scramjet combustor", Aerosp. Sci. Technol., vol. 24, no. 1, pp. 264-274, 2013. [http://dx.doi.org/10.1016/j.ast.2011.11.014]

[95]

S. Zhu, X. Xu, and P. Ji, "Flame stabilization and propagation in dual-mode scramjet with staged-strut injectors", AIAA J., vol. 55, no. 1, pp. 171-179, 2017. [http://dx.doi.org/10.2514/1.J054974]

[96]

Q. Yang, K. Chetehouna, N. Gascoin, and W. Bao, "Experimental study on combustion modes and thrust performance of a staged-combustor of the scramjet with dual-strut", Acta Astronaut., vol. 122, pp. 28-34, 2016. [http://dx.doi.org/10.1016/j.actaastro.2016.01.002]

[97]

G. Choubey, and K.M. Pandey, Effect of variation of angle of attack on the performance of two-strut scramjet combustor. Int J Hyd Energy vol 41, no. 26, pp. 11455-11470, 2016.

[98]

Z.W. Huang, G.Q. He, F. Qin, R. Xue, X.G. Wei, and L. Shi, "Combustion oscillation study in a kerosene fueled rocket-based combined-cycle engine combustor", Acta Astronaut., vol. 129, pp. 260270, 2016. [http://dx.doi.org/10.1016/j.actaastro.2016.09.024]

[99]

Z.W. Huang, G.Q. He, F. Qin, and X.G. Wei, Large eddy simulation of flame structure and combustion mode in a hydrogen fueled supersonic combustor. Int J Hyd Energy vol 40, no. 31, pp.

178 Materials and Technologies for a Green Environment

Verma et al.

9815-9824, 2015. [100] K.A. Verma, S. Kapayeva, K.M. Pandey, and K.K. Sharma, "The recent development of supersonic combustion ramjet engines for augmentation of the mixing performance and improvement in combustion Efficiency: A review", Mater. Today Proc., vol. 45, pp. 7058-7062, 2021. [http://dx.doi.org/10.1016/j.matpr.2021.01.879] [101] C. Fureby, K. Nordin-Bates, K. Petterson, A. Bresson, and V. Sabelnikov, "A computational study of supersonic combustion in strut injector and hypermixer flow fields", Proc. Combust. Inst., vol. 35, no. 2, pp. 2127-2135, 2015. [http://dx.doi.org/10.1016/j.proci.2014.06.113] [102] Q. Yang, J. Hu, J. chang, Y. Zong, and W. Bao, "Experimental study on combustion mode transition effects in a strut-based scramjet combustor", Proc. Inst. Mech. Eng. Part G J. Aerosp. Eng., vol. 229, no. 4, pp. 764-771, 2015. [http://dx.doi.org/10.1177/0954410014539288]

Materials and Technologies for a Green Environment, 2023, 179-183

179

SUBJECT INDEX A Adaptive mesh refinement (AMR) 166 Aerospace technology 104 Air 2, 6, 7, 25, 26, 105, 108, 113, 117, 118, 122, 123, 131, 132, 133, 154, 161 clean 113 polluted 2 Antarctic power generation 37 Artificial intelligence 69, 80 Automotive engineers 82

B Battery 81, 91, 97, 100 monitoring system (BMS) 81, 100 storage systems 91, 97 Biomass 3 burning 3 energy 3

C Carbon dioxide 5, 10, 11, 12 atmospheric 5 total 11, 12 Carbon nanotubes 46 Cars 67, 68, 70, 84, 94 autonomous 67, 68 electric 84 CAVE, autonomous 67 CFD-based hypersonic research 109 Charge 33, 56, 76, 77, 78, 86, 92, 96, 97 electrical 33, 56 real-time 76 Charging stations 69, 71, 82, 83, 85, 86, 89, 90, 94 public 69 Chemical energy 3 Chevrolet suburban suspension 56 Chip, heat-generating 43

Coal power plant 2 Combustion 104, 105, 107, 108, 109, 110, 111, 114, 116, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 134, 135, 137, 138, 139, 140, 151, 153, 158, 166, 167, 168 chamber 105, 107, 122, 123, 124, 125, 126, 129, 137, 138, 139, 151 dynamics 116, 130 efficiency 123, 124, 125, 126, 127, 128, 129, 130, 131, 134, 135, 137, 140, 153, 158 hydrogen-air 167 oscillation 168 Combustion process 105, 106, 107, 108, 113, 121, 124, 127, 136, 137, 139, 140 supersonic 140 Combustor 113, 119, 153 kerosene-fuelled 119 pressure 113 wall cavity 153 Computational fluid dynamics (CFD) 109, 112, 154 Condensers 1, 8, 14, 18, 21, 24, 25, 26 air-cooled 1, 8, 14, 18, 26 cooled 21, 25, 26 Condensers consumption power for 22, 23 geothermal 22 ORC 23 Condensing chamber 52 Conductivity, electrical-thermal 49 Cooled condenser power consumption 23 Cooler 43, 53 electric solar 53 thermoelectric micro 43 vapour compression 53

D Demand side management (DSM) 99 Devices 33, 34, 35, 42, 59, 71, 78, 79, 93, 105 auxiliary 93

Santhanam Harikrishnan (Ed.) All rights reserved-© 2023 Bentham Science Publishers

180 Materials and Technologies for a Green Environment

blue tooth 71 chemical propulsive 105 electrical 59 electronic 42, 59 energy storage 33 Dynamic 165, 166 adaptive chemistry (DAC) 165 mode decomposition (DMD) 166

E Economical storage methods 32 Eddy dissipation model (EDM) 165 Electrical and mechanical transducers of energy 56 Electricity 1, 2, 3, 4, 5, 6, 35, 36, 37, 40, 59, 60, 71, 73, 85, 95 energy grid supply 95 generator 59 grid-connected renewable 85 sources 5 Electric power 5, 6, 33 global 5 Electric vehicle 67, 92 charging 92 technology 67 Electrolysis corrosion 35 Emissions 1, 2, 3, 5, 10, 69, 80, 93 carbon 3 greenhouse 80 harmful gas 1, 5 Energy 1, 2, 3, 4, 5, 8, 10, 11, 12, 19, 32, 33, 36, 56, 59, 60, 74, 76, 84, 85, 86, 87, 88, 89, 96, 131, 138 charge 33 consumption 1, 11 conserve atmospheric 33 converting heat 33 electrical 33, 36, 56 kinetic 131, 138 solar heat 19 storage systems (ESS) 86, 87, 88, 89, 96 suppliers 85 sustainable 84 waste heat 32 waste thermal 33 Energy generation 10, 32, 41, 59, 70 landscape 70 techniques 32 Energy sources 1, 2, 4, 5, 8, 41, 67, 86, 95

Santhanam Harikrishnan

non-renewable 2, 67 nuclear 5 weather-dependent renewable 95 Engine vehicles 69, 89, 101 internal combustion 69, 101 Equipment 35, 48, 81, 83, 96 electrical 35 electronic 48 thermoelectric 35 Eulerian stochastic fields (ESF) 166

F Field 49, 50, 60, 92, 109, 141, 150, 166 electrical 50 magnetic 92 Flame 108, 109, 110, 113, 114, 115, 118, 119, 120, 121, 123, 124, 125, 159, 160, 164, 166, 167, 168, 169, 170 detached 125 heated 115 intensity 168, 170 oscillation 118, 119, 121 propagation process 120 quenching 114, 166 stability 108, 114, 119, 164, 167 steady 110 Flame stabilization 108, 109, 114, 115, 116, 120, 121, 140, 158, 160, 162, 163, 164, 165, 166, 167 analysis 158, 160 mechanisms 115, 140 Flux, thermoelement heat 50 Fraction 12, 13, 80 dryness 12 vapour 13 Fuel 2, 35, 38, 46, 67, 70, 85, 105, 108, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 127, 131, 132, 133, 140, 162 carbon-based 2 forest 35 fossil 2, 38, 46, 67, 85 gaseous ethylene 117 injecting 116 kerosene 110, 111 pioneer hydrogen 162 renewable 70

Subject Index

Fuel injection 105, 108, 117, 118, 120, 122, 130, 131, 132, 133, 134, 135, 139, 151, 154 transverse 135 mechanics 139 system 105, 120, 151 Fuel injector geometrical modifications 155

G Gas(es) 8, 10, 11, 32, 33, 35, 69, 110 harmful 10 hot 110 natural 8, 35 production 11 stations 69 turbine 32, 33 Gasoline 70 Geothermal 8, 9, 12, 15, 17 fluid 8, 9, 15, 17 kalina cycle 12 Geothermal power 1, 5, 12 cycle 12 development 1, 5 Geothermal-solar power 1, 14 generation 1 plant 14 Greenhouse gases 40

H Heat 7, 16, 18, 20, 23, 34, 35, 37, 38, 39, 42, 134 absorption 34 discharge 34 efficiency 16 generation 42 loss 38 pump 35, 42 radiological 37 release combustion 134 resistance 18, 42 source 35, 39 transfer 7, 18, 20, 23 Heating 2, 8, 9, 40, 41, 42, 60 combined 60 geothermal fluids 8 removal system 42 High-speed 114

Materials and Technologies for a Green Environment 181

framing flame luminosity 114 High-speed photography 113, 119, 121 and pressure 119 Human-machine interface (HMI) 82 Hybid thermo electric generators 52 Hydrocarbon fuels 108, 110, 113, 119, 161 Hydrogen 108, 113, 114, 115, 116, 117, 118, 119, 122, 123, 127, 131, 132, 133, 161, 162, 165 combustion of 108, 116 fueled combustor 165 gaseous 108, 113, 118 Hydroxyl tagging velocimetry (HTV) 119 Hypersonic 106, 163 flow conditions 163 research engine (HRE) 106

I Ignition ratio 115 Injection techniques 162, 164 Injectors, kerosene-fuelled 116 IOT monitoring system 80

K Kerosene 116, 162 burning stage 116 equivalence ratio 162 injection 162 Kinetic and potential energy 15

M Macro 59 scale applications 59 waste heat applications 59 Mass 121, 127, 129, 155, 159, 169 fraction 121, 127, 129, 155 transfer 159, 169 Mechanical 56 tension 56 transducers 56 vibration 56 Micro scale applications 59 Mobility technology 101 Modbus transmission 78

182 Materials and Technologies for a Green Environment

N Natural hot spring 3

O

Santhanam Harikrishnan

co-rotating vortices merging 160 fuel-burning 112 natural 2 thermodynamic 150, 151 Properties 48, 49, 50, 108 electronic 50

Omega ethylene air 132 Operation 26, 86, 89, 93, 105, 107 charge-sustaining 93 Organic 1, 5, 8, 52 photovoltaic thermoelectric 52 rankine cycles 1, 5, 8 Oscillations, low-frequency 114 Oxide thermoelectrics 49

R

P

S

Partially stirred reactor (PaSR) 168 Photo voltaic (PV) 71, 73, 76, 81, 82, 85 Planar laser-induced fluorescence (PLIF) 163 Plants, hybrid geothermal solar 26 Polluted environment 2 Power 1, 3, 9, 10, 11, 12, 21, 26, 27, 32, 35, 36, 56, 57, 59, 60, 71, 74, 76, 77, 83, 84, 85, 87, 88, 94, 96 advanced charge controller monitors 77 consumption 11, 21 condenser 26 electrical 32, 56 generation 9, 10, 11, 27, 32, 56, 74, 84, 85 hybrid solar-geothermal 12 hydroelectric 3 nuclear 59 photovoltaic 76 predestined thermoelectric 59 source 27, 56, 71, 85, 94, 96 thermal 57 Power plants 1, 5, 6, 7, 11, 15, 18, 19, 21, 23, 26, 27, 32, 38, 39 gas 38, 39 geothermal solar 26 hybrid 1, 11, 18, 19, 26, 27 natural gas 5 thermal 38 Pressure oscillation 154 Probability density function (PDF) 109, 166 Process 1, 2, 14, 25, 34, 38, 41, 53, 69, 98, 105, 112, 110, 150, 151, 160 conversion 38

Scramjet 115, 126, 136 combustion 115, 136 operation 126 Scramjet combustor 113, 120, 123, 126, 127, 130, 131, 136, 153 cavity-based 130, 131, 136, 153 ethanol-fuelled cavity-induced 113 ethylene-fuelled 127 hydrogen-fuelled 123, 126 kerosene-fuelled 120 Scramjet engine 104, 105, 106, 107, 108, 109, 110, 111, 119, 123, 124, 125, 126, 140, 141, 151 hydrocarbon-fuelled 119 Sensors 33, 59 electronic 59 Solar 1, 3, 5, 8, 12, 27, 35, 52, 70, 71, 72, 73, 74, 78, 81, 82, 83, 84, 85, 91, 97 absorption bladder 52 cells 3, 72 charge controller 73 geothermal power generation plants 12 mobile 71 photovoltaic 85 radiations 52, 73 reliable hybrid geothermal 27 source generators 35 thermal energy generators 35 Solar energy 3, 4, 5, 6, 8, 9, 12, 13, 19, 70, 71, 72, 83, 84, 85 devices 8 generation 84

Renewable energy 1, 2, 3, 4, 8, 9, 33, 69, 94 Resources 3, 5, 10, 11, 99 fossil energy 10 renewable 3 temperature geothermal 5

Subject Index

source 9 Solar power 5, 6, 12, 70, 74, 75 generation 70 grid 74, 75 plants 5, 6, 12 Sonic condition 117 Stability, thermodynamic 50 Storage systems, stationary energy 86, 87 Stream, supersonic air 139 Strut 117, 120, 121, 122, 123, 124, 131, 132, 133, 134, 135, 136, 137, 140, 154, 155, 157, 158, 162, 163, 164, 168 based combustors 154, 157, 168 hydrogen-fuelled 135 injectors 136, 137, 157, 163 wedged-shaped 137 Supersonic combustion 104, 105, 107, 115, 157, 159, 163, 164, 165, 166, 170 Supersonic combustor 109, 110, 112, 114, 119, 123, 151, 157 ethylenefuelled 114 fuelled cavity 109 Systems 11, 14, 35, 45, 55, 60, 77, 88 automobile air conditioning 45 automotive 45 automotive air conditioning 45 intelligent remote sensor 55 photovoltaic 77 power conversion 88 power generation 11, 35 solar heating 14 waste heat storage 60

T TDAC method 165 Techniques 119, 140, 164 combustion flame stabilization 140 molecular tagging 119 transpiration cooling 164 Technology 104 air-breathing propulsion 104 hypersonic 104 TEG 40, 42 electricity generation 42 power generation system 40 Thermal 48, 50, 51, 60 conduction 50 conductivity 48, 50, 51, 60 Thermo electric 35, 42, 43, 45, 56

Materials and Technologies for a Green Environment 183

cooler (TEC) 42, 43, 45 generators 35, 56 Thermoelectric 32, 35, 36, 40, 41, 43 coolers 43 forces 41 heating 35 power generators 32, 40 radioisotopes 36 Thermoelectric refrigerator 53, 54 photovoltaic-powered 53 powered 53 Turbine, hot 1 Turbulence intensity 155, 169 Turbulent 117, 120, 122, 140, 161, 169 diffusion flames 122 flow dynamics 140 Schmidt number 117 viscosity 120

V Vehicle 69, 81, 95, 96 battery 81, 96 drivers 95 grid integration (VGI) 95, 96 OEMs 69 Voltage controller 33

W Wall fuel injection 163, 170 Waste 32, 52, 59, 91 fuel 32 solid 32, 59 Waste heat 32, 38, 39, 59 industrial 59 recovery 32, 38 Waste recycling 41 Well-stirred reactor (WSR) 166 Wind 2, 5 energy 2 sources 5 Wireless 39, 92 sensor network 39 transfer 92