v TABLE OF CONTENTS SOMMARIO………....i ABSTRACT………...iii TABLE OF CONTENTS………..v LIST OF FIGURES………..ix LIST OF TABLES………..xiii NOMENCLATURE……….…xv 1 INTRODUCTION 1.1. Background and Motivations……….………..1
1.2. Objectives and Approach……….………2
1.3. Outlines of the Thesis……….………..3
SECTION 1 – LITERATURE REVIEW 2 HCCI COMBUSTION 2.1. Introduction……….………7
2.2. Gasoline-Fuelled HCCI Engines……….………9
2.3. Diesel-Fuelled HCCI Engines……….……….9
2.3.1. Premixed HCCI……….……….10
2.3.2. Early Direct-Injection HCCI………..11
2.3.3. Late Direct-Injection HCCI………...11
2.4. Key Operating Parameter for HCCI Control and Operating Range Extension……….12
2.4.1. Intake Air Temperature……….13
2.4.2. Compression Ratio………13
2.4.3. Exhaust Gas Recirculation (EGR) and Residual Gas……….14
2.4.4. Water Injection………...14
2.4.5. Boosting………..15
2.4.6. Fuel Injection Strategy………..15
2.4.7. Additives and Fuel Modifications……….15
2.4.8. Engine Speed……….16
2.5. CO and HC Emissions and their Control……….17
3 CFD SIMULATIONS 3.1. Computational Models for Engine Development………19
3.2. Governing Equations for Turbulent Reacting Flows………..19
3.2.1. Navier-Stokes Equations………..19
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3.3. Chemical Kinetics Application………...25
3.4. Combustion Models………26
3.4.1. Mixing-Controlled Models……….…27
3.4.1.1. Eddy-Break-Up Model……….…27
3.4.1.2. Shell Auto-Ignition Model………...27
3.4.1.3. Characteristic Time Scale Combustion Model…………....28
3.4.2. Flamelet Models……….…28
3.4.2.1. G-Equation Model………...29
3.4.3. PDF Approach………...30
3.5. Other Submodels in Engine Modeling……….31
3.5.1. Spray Model………...31
3.5.1.1. Linearized Instability Sheet Atomization (LISA) Model………...31
3.5.1.2. Kelvin-Helmholtz Rayleigh-Taylor (KH-RT) Model………..33
3.5.1.3. Taylor-Analog-Breakup (TAB) Model………...34
3.5.1.4. Droplet Collision and Coalescence Model………...35
3.5.1.5. Droplet Vaporization Model………35
3.5.1.6. Wall Impingement Model………36
3.5.2. Heat Transfer Model……….36
SECTION 2 – RESEARCH ACTIVITY 4 HCCI/PCCI COMBUSTION ANALISYS 4.1. Introduction………...39
4.2. Numerical Approach………40
4.2.1. MIT PRF Chemical Mechanism………..40
4.3. Spray Characteristics Validation………...40
4.4. Engine Experiments………45
4.4.1. Operating Conditions………....47
4.5. HCCI and PCCI Simulations………..48
4.6. HCCI and PCCI Results………...49
4.7. Summary and Conclusions………53
5 DIESEL/GASOLINE DUAL FUEL COMBUSTION 5.1. Introduction………...55
5.2. Numerical Approach………56
5.2.1. Shell-CTC Model Settings for Dual Fuel Combustion……….56
5.2.2. Dual Fuel Combustion Using Detailed Chemistry and Flame Propagation Approach………..56
5.3. Preliminary Concept Validation……….58
5.3.1. Preliminary Diesel Case Validation……….60
5.3.2. Preliminary Dual Fuel Simulations………..61
5.4. Damkohler Combustion Strategy Validation………...63
5.4.1. Diesel Liftoff-Length Validation……….……..63
5.4.1.1. Conceptual Model of Conventional Diesel Spray Combustion……….…..63
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5.4.2. Validation with Cummins Diesel/Natural Gas
Dual Fuel Experiments………..…..71
5.4.2.1. Reference Engine………71
5.4.2.2. Operating Conditions………..72
5.4.2.3. Diesel/Natural Gas Dual Fuel Combustion………..73
5.5. Diesel/Gasoline Dual Fuel Combustion……….. ……76
5.5.1. Operating Conditions………....76
5.7.2. Results with Medium Engine Speed and Load……….78
5.5.2.1. Injector Type Effect……….78
5.5.2.2. Mixture Composition Effect………81
5.5.2.3. Injection Timing Effect……….83
5.5.2.4. Emission Results……….85
5.5.2.5. Combustion Model Variation………..88
5.5.2.6. Two-Stage Combustion with Late Injection……….92
5.5.3. Results with Low Speed and Load……….93
5.5.3.1. Injector Type Effect……….93
5.5.3.2. Mixture Composition Effect………...96
5.5.3.3 Injection Timing Effect………96
5.5.3.4. Emission Results……….96
5.5.3.5. Combustion Model Variation……….98
5.6. Summary and Conclusions………99
6 NEW CONCEPT DIESEL HCCI COMBUSTION – A PRELIMINARY STUDY 6.1. Introduction………...101
6.2. Concept Validation………101
6.3. Proposed Solutions……….……..107
6.4. Proposed Solutions CFD Analysis……….108
6.5. Conventional Diesel Engine Application………116
6.6. Emission Results………...118
6.7. Injection Process Optimization………122
6.7.1. Operating Conditions………..122
6.7.2. Emissions and HRR Results……….124
6.8. Summary and Conclusions………..127
7 SUMMARY AND CONCLUSIONS 7.1. Introduction……….129
7.2. Summary and Conclusions………..130
7.2.1. HCCI/PCCI Combustion Analysis……….130
7.2.2. Diesel/Gasoline Dual Fuel Combustion………...131
7.2.3. New Concept Diesel HCCI Combustion – A Preliminary Study……….132
APPENDECES APPENDEX A – MIT PRF N-HEPTANE/ISO-OCTANE MECHANISM...137
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APPENDEX C – 1-D SIMULATION SCHEMES FOR THE
PROPOSED SOLUTIONS………..142
