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STUDIES ON UTILIZATION OF CNG AND BIODIESEL BLEND IN A COMPRESSION IGNITION ENGINE USING

EXHAUST GAS RECIRCULATION

by

SUNIL KUMAR MAHLA Centre for Energy Studies

Submitted

in fulfillment of the requirement of the degree of Doctor of Philosophy

to the

INDIAN INSTITUTE OF TECHNOLOGY, DELHI

APRIL 2007

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Dedicated To

My 91elored Parents

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CERTIFICATE

The thesis entitled "STUDIES ON UTILIZATION OF CNG AND BIODIESEL BLEND IN A COMPRESSION IGNITION ENGINE USING EXHAUST GAS RECIRCULATION" being submitted by Mr. Sunil Kumar Mahla to the Indian Institute of Technology, Delhi for the award of the degree of Doctor of Philosophy, is a record of bona fide research work carried out by him. He has worked under our supervision, and has fulfilled the requirement for the submission of this thesis, which has attained the standard required for a Ph.D. degree of the institute. The results presented in this thesis have not been submitted elsewhere for the award of any degree or diploma.

Date:

IQ

— — 2-0 6--

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Prof. L.M. Das Prof. M.K.G. Babu

Centre for Energy Studies, Head, Centre for Energy Studies, Indian Institute of Technology, Indian Institute of Technology,

New Delhi-110016 New Delhi-110016

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ACKNOWLEGEMENTS

First, I would like to thank my supervisor's Prof. L.M. Das and Prof. M.K.G.

Babu for providing me the opportunity to work on this research project which is a form of doctoral thesis. Their time spent to advice me, helped to establish a base of knowledge and experience for this study. I have learned a great deal from their wisdom and wit. Thanks for their support and encouragement given to me. I would like to thank Prof. J.P. Subhramanyam, Mechanical Engineering Department for their valuable suggestions from time to time. I would also like to thank Prof. T.S. Bhatti, Prof. (Mrs.) M.G. Dastidar for participating in my thesis committee and for their helpful comments.

Thanks are also extended to fellow research scholars Mr. B. Baiju, Mr. R.T.

Naik, Mr. Pradeepta Sahoo, Mr. Dilip Bora, and Mr. Sudhir Ghai for assisting me throughout the research work.

I also appreciate the help and cooperation of Mr. Attar Singh, Mr. G.P. Singh and other staff members Mr. Rakesh Kumar, Mr. Mohit Khanna and Mr. Varinder Singh for their help in carrying out experiments. Special thanks to Mr. Kundan Singh for their help in numerous ways besides my research work.

I would like to express my sincere thanks to the staff of IDDC workshop for their help in fabrication work. I am also thankful to Mr. Manjit Singh, Textile Department for giving me support in difficult times.

Finally, to my family, without whom I could not have been accomplished all I have to this day, thank you with all my heart.

New Delhi (SUNIL 1 AR MAHLA)

April 2007

ii

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ABSTRACT

In this work, experiments were carried out to determine the performance, combustion and emissions characteristics of dual fuel engine using small quantities of compressed natural gas (CNG) in a compression ignition engine primarily fuelled with a B20 blend of jatropha biodiesel. The engines, which utilizes both the gaseous fuel, and liquid pilot fuel is referred to dual fuel engine. The primary usage of dual fuel system is to minimize the consumption of diesel and reducing the pollutants formation. B20 blend of biodiesel was chosen as it is optimum based on the trade-off of smoke and NOx emissions. A single cylinder air cooled direct injection commercial diesel engine was chosen for present research work. The B20 blend was injected into the diesel engine as that of the conventional diesel engine. The CNG flow rate was varied on energy substitution basis (0— 80%) and data were recorded at different loading points i.e. 20%, 40%, 60%, 80% and 100% of brake power. All the experiments were performed at constant speed of 1500 rev/min. Test results were compared with baseline diesel operation.

Results show that there was a slight increase in brake thermal efficiency with small amount of natural gas substitution in both the pilot fuels. This is due to improved combustion and better utilization of fuel. Smoke opacity was reduced in dual fuel operation as natural gas contains less impurities and smoke is only associated due to liquid pilot fuel. There was an increase in HC and CO emissions at light load conditions. With CNG induction, due to increase in combustion temperature at full load there was also an increase in NOx emission in both the pilot fuels.

However, NOx cannot be reduced by dual fuelling. Moreover, dual fuel operation inevitably suffers from poor performance and higher emissions at light

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CONTENTS

Page No.

Certificate

Acknowlgements ii

Abstract ili

Contents

List of Figures x

List of Plates XV

List of Tables xvi

Nomenclature xvii

Chapter: 1 INTRODUCTION 1-16

1.1 General Introduction 1

1.2 Alternative Fuels 2

1.3 Benefits of Natural gas as a Transportation fuel 4

1.4 Dual fuel engines 6

1.5 Pollutant formation in diesel engine 9

1.5.1 Particulate Matter Emissions 10

1.5.2 Nitric Oxides emissions 12

1.6 Biodiesel 13

1.7 Exhaust gas recirculation 15

1.7.1 Definition of exhaust gas recirculation percent 16

Chapter: 2 REVIEW OF LITERATURE 18-38

2.1 Fundamentals of diesel engines 18

2.2 CNG Utilization in Transportation Sector 20

2.3 Literature Survey of Dual Fuel engines 22

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2.3.1 2.4 2.5

Historical Perspective and Applications Diesel Engine Fuelled with Natural gas Biodiesel-An Introduction

Page No.

22 23 27

2.5.1 Transesterification Process 28

2.5.2 Advantages of Biodiesel 29

2.5.3 Disadvantages of Biodiesel 30

2.5.4 Emissions from Biodiesel fueled diesel engine 31 2.6 Exhaust Gas Recirculation- NOx Emission Reduction Method 32

2.6.1 EGR in dual fuel engines 34

2.7 Conclusions from Literature Review 35

2.8 Need for Present Work 36

2.9 Statement of the Problem 37

Chapter: 3 BIODIESEL PRODUCTION METHODOLOGY

39-51

3.1 Production of Biodiesel 39

3.2 Stages of Process 39

3.3 Testing of Biodiesel fuel properties 44

3.4 Measured Fuels Properties 45

3.4.1 Viscosity 45

3.4.2 Heating Value 46

3.4.3 Density 48

3.4.4 Flash Point 48

3.4.5 Cloud Point 49

3.4.6 Pour Point 49

3.5 Fuel properties 51

vi

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Chapter: 4

4.1 4.2 4.3 4.4 4.5

EXPERIMENTAL TEST RIG DEVELOPMENT &

Page No.

52-61

52 52 54 54 56

METHODOLOGY

Introduction Engine

Natural Gas Delivery Exhaust Gas Recirculation Instrumentation

4.5.1 Pressure Transducer and Magnetic Pickup 56

4.5.2 Engine Speed 56

4.453 Air Flow Measurement 56

4.5.4 Temperature Measurement 56

4.6 Fuel Supply System 57

4.6.1 Liquid Fuel Supply 57

4.6.2 Gaseous Fuel Supply 57

4.7 Exhaust Emissions Analysis System 58

4.8 Experimental Procedures 59

4.8.1 Preliminary work 59

4.8.2 Experimental Procedure for EGR and CNG Substitution 60

Chapter: 5 RESULTS AND DISCUSSION 62-138

5.1 Introduction 62

5.2 Experimental Approach 62

5.3 Combustion Calculations 63

5.4 Exhaust Gas Recirculation 64

5.5 Measured data repeatability and accuracy 66

5.6 Diesel-EGR Mode (Pilot Fuel-Diesel) 67

5.7 EGR Substitution (with B20 & Diesel pilot fuels) 71

5.7.1 Combustion characteristics 78

5.8 Dual Fuel Mode (Pilot Fuel-Diesel & B20) 81

5.8.1 Maximum substitution of CNG 81

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loads. To resolve these problems, the effect of exhaust gas recirculation (EGR) was investigated. In natural aspirated engine there is a limit of the substitution of air as minimum air-fuel ratio is required for complete combustion. Therefore, maximum of 14% EGR and maximum of 44% natural gas by energy substitution corresponding to knock limited power output was used. Higher smoke level limits the maximum amount of EGR while knocking and power deration limits the maximum amount of natural gas substitution.

Various combustion parameters such as peak cylinder pressure, heat release rate and maximum rate of pressure rise were evaluated with the help of pressure-crank diagrams generated with the data acquisition system fitted to the engine. In dual operation the high heat release rates promotes the NOx formation due to rapid combustion. The peak cylinder gas pressure diagrams showed that dual fuel operation along with EGR suppresses the cylinder pressure and increases the delay period. This is mainly because of oxygen depletion and high specific heat capacity of overall air- fuel mixture.

In conclusion, the utilization of compressed natural gas and B20 blend of jatropha biodiesel along with induction of EGR was helpful in reducing the NOx-

smoke emission without deteriorating the performance parameters.

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5.8.2 5.8.3 5.8.4

Dual Fuel Operation with B20 Pilot Fuel

Effect of dual fuel operation on Emission Characteristics Effect of dual fuel operation on PerformanceCharacteristics

Page No.

81 82 87

5.9 Comparison of pilot fuels 89

5.9.1 Performance characteristics 89

5.9.2 Emission characteristics 93

5.9.3 Effect on Combustion characteristics 98

5.10 Maximum Substitution of EGR along with dual fuel operation 101 5.10.1 Combustion characteristics of dual fuel operation along with EGR 111 5.11 Effect of different percentage of EGR substitution on emission

characteristics of dual fuel operation (Pilot Fuel-Diesel)

114

5.12 Results of tests at different brake mean effective pressure 120

5.13 Comparison of all test fuels 127

5.14 Relative change in performance and emission parameters 133

Chapter: 6 CONCLUSIONS AND RECOMMENDATIONS

139-143

6.1 Conclusions 139

6.2 Recommendations 143

References

144-148

Appendices

APPENDIX 1: Engine Technical Specifications APPENDIX 2: Alternator Specifications

APPENDIX 3: Natural gas fractional analysis

APPENDIX 4: Specifications of Pressure Transducer APPENDIX 5: Pressure Transducer Calibration APPENDIX 6: Specifications of Charge Amplifier APPENDIX 7: Specifications of CNG Rotameter

viii

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APPENDIX 8: Specifications of Oscilloscope

APPENDIX 9: Technical Data of AVL DiGas Gas Analyzer (Model 4000) APPENDIX 10: Technical Data of AVL Smoke Meter (Model 437)

ix

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