Modelling Diesel Combustion (eBook)

Acknowledgments 8
Preface 9
Contents 11
1 Introduction 14
Role of Internal Combustion Engines 14
Developments in DI Diesel Engines 15
Modelling of Combustion in DI Diesel Engines 19
References 20
2 Phenomenology of Diesel Combustion and Modelling 21
Combustion Model 22
Ignition delay 22
Heat release 23
Models based on fluid dynamics 23
Phenomenological models 23
Zero-dimensional models 24
Emission Models 26
Theme of the Book 29
3 Experiments 34
Studies in a Bomb 34
Engine – bomb similarity 36
Vaporisation studies 37
Combustion studies 38
Real Engine Studies 40
4 Turbulent Structure of the Diesel Spray 49
Vaporising Spray 49
Free jet region 49
Jet penetration and entrainment of air 56
Combusting Sprays 59
Summary of the Model for Vapourising and Combusting Sprays 63
Modern View of the Vaporising and Burning Spray 65
5 Ignition Delay in a Diesel Engine 69
Definition and Measurement of Ignition Delay 70
Classical Model for Ignition Delay and Its Extension to Other Fuels 71
Validation of classical model 72
Phenomenological Model of Ignition Delay 73
Mechanism of ignition delay 73
Spray formation 74
Mass transfer 77
Reactions 78
Ignition delay 80
Extent of reaction within the spray 80
Turbulence 82
Computations 82
Validation of the model 82
Effect of orifice size 83
Effect of injection quantity 83
Effect of Cetane number 84
Effect of volatility 84
Summary 85
References 87
6 Heat Transfer 89
Heat Transfer Across the Walls 89
Heat Transfer Coefficient at the Wall Where the Spray Impinges 90
Heat Transfer from Spray to the Wall 91
References 92
7 Heat Release in Indirect Injection Engines 93
Description of the Phenomenological Model 94
Combustion model 94
Heat transfer 100
Gas exchange model 100
Friction power 100
Calculation procedure 100
Experimental Technique 100
Results and Discussions 101
Conclusions 104
References 107
8 Mixing Correlations for Smoke and Fuel Consumption of Direct Injection Engines 108
Characteristic Parameter for Air Fuel Mixing in a Cross Flow 109
The concept of useful air 110
Calculation of momentum of injected fuel 112
Calculation of momentum of useful air 115
Characteristic mixing parameter of an engine 115
Validation of the Mixing Parameter 116
Input data for the validation of the correlation 116
Results 117
Conclusion 120
References 120
9 Heat Release in Direct Injection Engines 122
Heat Release Rate in Diesel Engines 123
Single dimensional models 123
Multidimensional models 123
Mixing controlled combustion 124
Model for Mixing Controlled Combustion 126
Regimes of combustion in a modern DI diesel engine 126
Two factors affecting heat release rate 127
k-e theory 128
Modified k-e model 128
Input rate and dissipation rate of turbulent kinetic energy of fuel spray 129
Energy input 129
Calculation of fuel injection rate 130
Energy dissipation 131
Density of turbulent energy 131
Modelling three regimes of heat release rate 132
Steps to calculate heat release rate using the new model 133
Step 1: Prediction of impingement and loss in kinetic energy 133
Step 2: Computation of factors of rate of heat release 134
Step 3: Resultant rate of heat release 134
Experimental Validation 134
Heat release rate from the experiments 134
Engines A9, B9 and C9 134
Engine D9 135
Estimation of heat transfer across the walls 135
Results 135
Parametric studies of Engine A9 135
Base data at rated 100% load and 2,700 rpm 137
Other loads and speeds 137
Study of Engine-B9 138
Engine-C9 and Engine-D9 138
Engine-E9 138
Discussions 139
Summary 144
References 145
10 Hydrocarbons from DI Diesel Engines 146
Injection characteristics and the indicated diagrams 147
HC Model 148
Spray structure 148
Ignition delay 148
Fuel injected during delay 149
Over-leaned fuel air mixture 149
Fuel effusing the injector sac 150
Other sources of hydrocarbons 150
Formation of unburned hydrocarbons 150
Predicting HC in the Exhaust 152
HC and fuel injected during delay 152
Specific HC in the exhaust 153
Phenomenological model 153
Discussions 154
Summary 155
References 155
11 Hydrocarbon Emissions from Spark Ignition Engines 156
Description of the Engine Model 158
Breathing 158
Combustion 159
HC emissions 161
The contribution of ring crevice to HC emission 164
Oxidation of HC during exhaust 164
Solution procedure 164
Comparison of the Model Prediction with Engine Experiments 165
Conclusions 173
References 174
12 Smoke from DI Diesel Engines 176
Phenomenon of Soot Formation 177
Application to Engine Conditions 180
Correlating smoke: phenomenon with spray characteristics 182
Benchmarking with well known smoke model 194
Transient conditions 195
References 196
13 Oxides of Nitrogen from Direct Injection Diesel Engines 198
Exhaust Gas Recirculation (EGR) 203
Phenomenology of Oxides of Nitrogen 204
Effect of EGR 206
Effect of oxygen in the fuel 208
References 210
Before detachment 201
After detachment 202
Phenomenon of Heat Transfer 203
14 Particulate Matter from Direct Injection Diesel Engines 211
Phenomenology of Particulate Matter (PM) 211
Validation of Correlation 213
ReferencesCartillieri W, 214
15 Multi-dimensional Modelling of DieselCombustion: Review 215
Basic Approach 216
Turbulence Modelling 218
RANS models 218
Large Eddy simulation (LES) 219
Spray and Evaporation Modelling 220
Spray models 221
Evaporation models 224
Combustion Modelling 226
Shell/CTC model 226
Direct integration of chemical kinetics 228
Pollutant Emissions Modelling 231
NOx modelling 231
Soot modelling 233
CO and UHC modelling 234
Heat Transfer Modelling 235
Efficient Multi-dimensional Simulation of Diesel Engine Combustion with Detailed Chemistry 237
Adaptive multi-grid chemistry (AMC) model 237
Mesh-independent spray models 241
Code parallelization 244
CFD Codes for Engine Simulation 246
Open source codes 247
Commercial software 249
Future and Challenge 249
References 250
16 Multi-dimensional Modelling of DieselCombustion: Applications 255
Case Studies 256
Study of UHC/CO emissions trends 256
Study of engine size-scaling relationships for a light-duty and a heavy-duty diesel engine 269
Results and discussion 276
Optimisation of a heavy-duty engine at low- and high-loads 280
Results and discussion 284
References 289
Appendices 291
Appendix I: Estimation of Products of Combustion from the Interferogram 291
Appendix II: Estimation of Concentration of Fuel Vapour in the Vapourising and Combusting Spray from the Interferogram 292
Appendix III: Estimation of Mass and Heat Transfer Functions 293
Appendix IV: Vapour Pressure of Diesel and Fuels A & B and B*
Appendix V: Calculation of Tangential Velocity of Air in the Piston Cavity from the Inlet Swirl Number 294
Appendix VI: Momentum of Useful Air of the Three Different Combustion Cavities Described in Kuo et al. (1988) 294
Appendix VII: Momentum of Useful Air for Engines A8, B8, C8 and D8 295
Appendix VIII: Estimation of Spray Properties andImpingement Parameters 296
Appendix IX: Calculation of Fuel Injection Rate 298
Appendix X: Influence of Nozzle Features 299
Appendix XI: Henry’s Constant Hc for Fuel (n-Octane) in Oil 300
Appendix XII: Evaluation of gF* and gG* 301
Appendix XIII: In-Cylinder Oxidation of HC 302
Appendix XIV: Estimation of Wall Surface Temperature 305
Appendix XV: Experimental Data on HC Emissions from DI Diesel Engines 306
References 307
Index 309