An innovative 3D-CFD-Approach towards Virtual Development of Internal Combustion Engines

Cover......Page 1
An Innovative 3D-CFDApproach
towards
Virtual Development
of Internal Combustion
Engines......Page 4
ISBN 9783834815408......Page 5
Acknowledgments......Page 8
Table of Contents......Page 10
Abstract......Page 16
Zusammenfassung......Page 20
Roman Symbols......Page 24
Greek Symbols......Page 31
Subscripts and Abbreviations......Page 32
1.2 The Fascination of Internal Combustion Engines......Page 36
1.3.1 Development Targets of Internal Combustion Engines in the Past......Page 37
1.3.3 Development Targets of Internal Combustion Engines in the Future......Page 39
1.3.3.3 Hybridization......Page 40
1.3.3.5 Alternative Fuels......Page 41
1.4 How to Face the Complexity of Future Internal- Combustion-Engines......Page 43
2 Simulation of Internal Combustion Engines......Page 45
2.1.1 One Tool for the Simulation of the Entire Engine?......Page 46
2.1.1.1 Mechanical Numerical Analysis......Page 47
2.1.1.2 Engine Operating Cycle Analyses......Page 48
2.1.2 The Future Challenge: an improved Integration of Simulation Tools......Page 50
2.2 Today’s Repartition of the Resources in Engine Development......Page 52
2.3 Introduction to Engine Processes Modeling in the Simulation of the Operating Cycle......Page 56
3.1 Energy-Balance of the Combustion Chamber......Page 60
3.2 Energy-Balance of the Entire Engine......Page 61
3.3 The Role of Engine Energy-Balance in the Engine Development Process......Page 63
4.1 Introduction......Page 64
4.2 Fundamental Equations......Page 66
4.4 Engine Modeling (Engine-Specific Models)......Page 67
4.4.1 Modeling of the Thermo-Physical Properties of the Working Fluid......Page 68
4.4.3 Modeling of the Combustion Process......Page 69
4.4.3.1 Empirical Models......Page 70
4.4.3.2 Quasi-dimensional Models......Page 75
4.5 Two Approaches in the Calculation of the Real Working-Process......Page 78
4.5.2 Combustion Profile Calculation - Pressure Profile Supply......Page 79
4.6 The Role of Real Working-Process Analysis in the Engine Development Process......Page 80
5.1 Introduction......Page 83
5.2 Engine Layout and Conservation Equations......Page 84
5.3 The Role of the 1D-CFD-Simulation in the Engine Development Process......Page 85
6 Three-Dimensional Simulation (3D-CFD Simulation)......Page 87
6.1.1 Mass Conservation Equation......Page 88
6.1.3 Momentum Conservation Equation (Navier-Stokes’ Equation)......Page 89
6.2 Engine Modeling......Page 90
6.2.1.1 Modeling of the Thermo-physical Properties of the Working Fluid......Page 91
6.2.1.2 Modeling of Non-Convective Processes......Page 92
6.2.1.3 Turbulence Modeling......Page 94
6.2.1.4 Combustion Models......Page 101
6.2.2 Introduction to Engine-Specific 3D-CFD-Models......Page 102
6.3 Discretization Practices (Numerical Implementation)......Page 103
6.3.1.1 Low-Order Differencing Scheme – Upwind Differencing (UD)......Page 105
6.4 The Role of the 3D-CFD-Simulation in the Engine Development Process......Page 106
7.1 An innovative Fast-Response 3D-CFD-Tool: QuickSim......Page 108
7.1.1 Fast Analysis......Page 109
7.1.1.2 Mesh Discretization for LES Simulations......Page 111
7.1.1.3 Mesh Discretization for QuickSim Simulations......Page 112
7.1.2 Reliable Calculation......Page 113
7.1.3 User-Friendliness......Page 114
7.1.4 Clear Representation of the Results......Page 115
7.1.5.1 Processor Utilization for QuickSim Simulations......Page 116
7.2.1 Simulation of several successive Engine Operating Cycles......Page 117
7.2.2 Extension of the 3D-CFD-Domain up to a Full-Engine Simulation......Page 119
7.2.3 The Simulation of a Flow Test-Bench......Page 122
7.3 Summary of the QuickSim Features......Page 124
7.4 QuickSim’s Calculation Layout......Page 125
8.1 Introduction......Page 129
8.2.1 One-Step Fuel-Oxidation Reaction Mechanism......Page 130
8.2.2 The Reality: More than Thousand Intermediate Products......Page 132
8.3 Traditional Approach......Page 134
8.4 QuickSim’s Approach: Few Species for the Description of the Working Fluid......Page 135
8.4.1 QuickSim’s Approach: A universally-valid Chemical Reaction Scheme for the Description of Burned Gas......Page 140
8.4.1.1 Chemical Equilibrium Assumption......Page 142
8.4.1.2 The proposed Chemical Reaction Scheme......Page 143
8.4.1.3 A “frozen” Composition at low Temperatures......Page 145
8.4.1.4 Results: The Chemical Composition of Burned Gas......Page 146
8.4.2 QuickSim’s Approach: Conclusive Modeling of the Thermodynamic Properties of Burned Gas......Page 149
8.4.2.1 Heat Release at the Flame Front and Post-Oxidation of Exhaust Gas with Fresh Gas......Page 151
8.4.2.2 Heat Exchange due to Dissociation Effects and Post-Oxidation within Exhaust Gas......Page 153
8.4.2.3 Combustion Conversion Efficiency......Page 156
9.1 Introduction......Page 158
9.2 Flame Propagation Modeling (Weller Model)......Page 161
9.3.1 Numerical Implementation of the Flame Propagation Model......Page 163
9.3.2 Numerical Inconsistencies at the Flame Front......Page 166
9.3.2.1 Expedients for the Numerical Inconsistencies at the Flame Front......Page 168
9.3.3 Local Two-Zones Model......Page 169
9.3.4 Ignition Model......Page 174
9.3.5 Final Implementation Procedure......Page 176
9.4 Results......Page 178
10.1 Introduction......Page 180
10.1.1 Phenomena Understanding, Calculation Approach and Considerations......Page 181
10.2.1 The Wall Function Approach......Page 183
10.2.2 Low Reynolds Number Models......Page 185
10.2.3 Phenomenological Heat-Transfer Models in the Real Working-Process Analysis (WP)......Page 186
10.2.3.2 Woschni’s Correlation......Page 187
10.2.3.4 Bargende’s Correlation......Page 188
10.2.4 Comparison between the 3D-CFD-Heat-Transfer (Wall- Function Model) and the Real Working-Process Analysis......Page 190
10.2.4.1 Sensitivity Analysis of the 3D-CFD-Heat-Transfer calculated with a Wall-Function Model......Page 193
10.2.5 QuickSim’s Approach: A new Phenomenological Heat- Transfer Model in the 3D-CFD-Simulation......Page 197
10.2.5.1 The Heat-Transfer during the Working Cycle......Page 198
10.3 Results......Page 204
10.4 Influence of 3D-CFD-Heat-Transfer-Models on the Engine Energy-Balance......Page 206
11.2 The Hardware: a turbocharged CNG Race-Engine......Page 209
11.3 Setting of the 3D-CFD-Simulation......Page 211
11.3.1 Initial Conditions and Properties of the Working Fluid......Page 213
11.3.2 Boundary Conditions......Page 214
11.4 CNG-Injector Model......Page 216
11.4.1 Traditional Gas Injection Modeling......Page 218
11.4.2 Gas Injection Modeling in QuickSim......Page 219
11.5.1 3D-CFD-Simulation excluding the Fuel Injectors......Page 221
11.5.2 3D-CFD-Simulation including the Fuel Injectors......Page 224
11.6 Extension of the 3D-CFD-Domain: One Cylinder with the Airbox......Page 229
11.6.1 Between Predictability and Results Consistency......Page 230
11.6.1.1 QuickSim’s Improved Approach: The integrated 0D- and1D-CFD Simulationof the missing Cylinders......Page 231
11.7 3D-CFD-Simulation of the Full Engine......Page 234
11.7.1 Results and 3D-CFD-Flow Field Investigations on the Full Engine......Page 235
11.7.1.1 Mixture Formation......Page 237
11.7.1.2 Residual Gas Distribution......Page 242
11.7.1.3 Turbulence......Page 244
11.7.1.4 Combustion......Page 246
11.7.2 Result Comparison among different Operating Conditions......Page 248
11.8 The Simulation of successive Operating Cycles......Page 250
11.9 Result Comparison among the different Extensions of the 3D-CFD-Domain......Page 253
12 Conclusion......Page 255
13 Outlook......Page 257
A.1 Vector and Matrix Analysis......Page 260
B.1 Thermodynamic Properties of the Working Fluid......Page 262
References......Page 274