An Introduction to Thermodynamic Cycle Simulations for Internal Combustion Engines

Preface xiii 1 Introduction 1 1.1 Reasons for Studying Engines 1 1.2 Engine Types and Operation 2 1.3 Reasons for Cycle Simulations 3 1.3.1 Educational Value 3 1.3.2 Guide Experimentation 3 1.3.3 Only Technique to Study Certain Variables 4 1.3.4 Complete Extensive Parametric Studies 4 1.3.5 Opportunities for Optimization 4 1.3.6 Simulations for Real]time Control 4 1.3.7 Summary 5 1.4 Brief Comments on the History of Simulations 5 1.5 Overview of Book Content 6 2 Overview of Engines and Their Operation 9 2.1 Goals of Engine Designs 9 2.2 Engine Classifications by Applications 10 2.3 Engine Characteristics 11 2.4 Basic Engine Components 12 2.5 Engine Operating Cycles 12 2.6 Performance Parameters 12 2.6.1 Work, Power, and Torque 12 2.6.2 Mean Effective Pressure 15 2.6.3 Thermal Efficiencies 16 2.6.4 Specific Fuel Consumption 17 2.6.5 Other Parameters 17 2.7 Summary 18 3 Overview of Engine Cycle Simulations 19 3.1 Introduction 19 3.2 Ideal (Air Standard) Cycle Analyses 19 3.3 Thermodynamic Engine Cycle Simulations 21 3.4 Quasi]dimensional Thermodynamic Engine Cycle Simulations 22 3.5 Multi]dimensional Simulations 23 3.6 Commercial Products 24 3.6.1 Thermodynamic Simulations 24 3.6.2 Multi]dimensional Simulations 25 3.7 Summary 26 Appendix 3.A: A Brief Summary of the Thermodynamics of the “Otto” Cycle Analysis 29 4 Properties of the Working Fluids 37 4.1 Introduction 37 4.2 Unburned Mixture Composition 37 4.2.1 Oxygen]containing Fuels 40 4.2.2 Oxidizers 41 4.2.3 Fuels 41 4.3 Burned Mixture (“Frozen” Composition) 42 4.4 Equilibrium Composition 43 4.5 Determinations of the Thermodynamic Properties 46 4.6 Results for the Thermodynamic Properties 47 4.7 Summary 61 5 Thermodynamic Formulations 63 5.1 Introduction 63 5.2 Approximations and Assumptions 64 5.3 Formulations 65 5.3.1 One]Zone Formulation 65 5.3.2 Two]Zone Formulation 67 5.3.3 Three]Zone Formulation 72 5.4 Comments on the Three Formulations 77 5.5 Summary 77 6 Items and Procedures for Solutions 79 6.1 Introduction 79 6.2 Items Needed to Solve the Energy Equations 79 6.2.1 Thermodynamic Properties 79 6.2.2 Kinematics 80 6.2.3 Combustion Process (Mass Fraction Burned) 82 6.2.4 Cylinder Heat Transfer 85 6.2.5 Mass Flow Rates 86 6.2.6 Mass Conservation 89 6.2.7 Friction 89 6.2.8 Pollutant Calculations 94 6.2.9 Other Sub]models 94 6.3 Numerical Solution 94 6.3.1 Initial and Boundary Conditions 95 6.3.2 Internal Consistency Checks 96 6.4 Summary 96 7 Basic Results 99 7.1 Introduction 99 7.2 Engine Specifications and Operating Conditions 99 7.3 Results and Discussion 101 7.3.1 Cylinder Volumes, Pressures, and Temperatures 102 7.3.2 Cylinder Masses and Flow Rates 106 7.3.3 Specific Enthalpy and Internal Energy 108 7.3.4 Molecular Masses, Gas Constants, and Mole Fractions 110 7.3.5 Energy Distribution and Work 114 7.4 Summary and Conclusions 116 8 Performance Results 119 8.1 Introduction 119 8.2 Engine and Operating Conditions 119 8.3 Performance Results (Part I)—Functions of Load and Speed 119 8.4 Performance Results (Part II)—Functions of Operating/Design Parameters 129 8.4.1 Combustion Timing 129 8.4.2 Compression Ratio 131 8.4.3 Equivalence Ratio 133 8.4.4 Burn Duration 135 8.4.5 Inlet Temperature 135 8.4.6 Residual Mass Fraction 136 8.4.7 Exhaust Pressure 136 8.4.8 Exhaust Gas Temperature 140 8.4.9 Exhaust Gas Recirculation 142 8.4.10 Pumping Work 145 8.5 Summary and Conclusions 149 9 Second Law Results 153 9.1 Introduction 153 9.2 Exergy 153 9.3 Previous Literature 154 9.4 Formulation of Second Law Analyses 154 9.5 Results from the Second Law Analyses 158 9.5.1 Basic Results 158 9.5.2 Parametric Results 163 9.5.3 Auxiliary Comments 174 9.6 Summary and Conclusions 176 10 Other Engine Combustion Processes 179 10.1 Introduction 179 10.2 Diesel Engine Combustion 179 10.3 Best Features from SI and CI Engines 180 10.4 Other Combustion Processes 181 10.4.1 Stratified Charge Combustion 181 10.4.2 Low Temperature Combustion 181 10.5 Challenges of Alternative Combustion Processes 182 10.6 Applications of the Simulations for Other Combustion Processes 183 10.7 Summary 184 11 Case Studies: Introduction 187 11.1 Case Studies 187 11.2 Common Elements of the Case Studies 188 11.3 General Methodology of the Case Studies 189 12 Combustion: Heat Release and Phasing 191 12.1 Introduction 191 12.2 Engine and Operating Conditions 191 12.3 Part I: Heat Release Schedule 191 12.3.1 Results for the Heat Release Rate 197 12.4 Part II: Combustion Phasing 205 12.4.1 Results for Combustion Phasing 206 12.5 Summary and Conclusions 221 13 Cylinder Heat Transfer 225 13.1 Introduction 225 13.2 Basic Relations 226 13.3 Previous Literature 227 13.3.1 Woschni Correlation 228 13.3.2 Summary of Correlations 229 13.4 Results and Discussion 230 13.4.1 Conventional Engine 230 13.4.2 Engines Utilizing Low Heat Rejection Concepts 241 13.4.3 Engines Utilizing Adiabatic EGR 247 13.5 Summary and Conclusions 250 14 Fuels 253 14.1 Introduction 253 14.2 Fuel Specifications 254 14.3 Engine and Operating Conditions 255 14.4 Results and Discussion 255 14.4.1 Assumptions and Constraints 255 14.4.2 Basic Results 255 14.4.3 Engine Performance Results 259 14.4.4 Second Law Results 266 14.5 Summary and Conclusions 268 Appendix 14.A: Energy and Exergy Distributions for the Eight Fuels at the Base Case Conditions (bmep = 325 kPa, 2000 rpm, ϕ = 1.0 and MBT timing) 269 15 Oxygen]Enriched Air 275 15.1 Introduction 275 15.2 Previous Literature 276 15.3 Engine and Operating Conditions 277 15.4 Results and Discussion 277 15.4.1 Strategy for This Study 278 15.4.2 Basic Thermodynamic Properties 278 15.4.3 Base Engine Performance 280 15.4.4 Parametric Engine Performance 283 15.4.5 Nitric Oxide Emissions 289 15.5 Summary and Conclusions 291 16 Overexpanded Engine 295 16.1 Introduction 295 16.2 Engine, Constraints, and Approach 296 16.2.1 Engine and Operating Conditions 296 16.2.2 Constraints 296 16.2.3 Approach 296 16.3 Results and Discussion 297 16.3.1 Part Load 297 16.3.2 Wide]Open Throttle 304 16.4 Summary and Conclusions 309 17 Nitric Oxide Emissions 311 17.1 Introduction 311 17.2 Nitric Oxide Kinetics 312 17.2.1 Thermal Nitric Oxide Mechanism 312 17.2.2 “Prompt” Nitric Oxide Mechanism 312 17.2.3 Nitrous Oxide Route Mechanism 313 17.2.4 Fuel Nitrogen Mechanism 313 17.3 Nitric Oxide Computations 313 17.3.1 Kinetic Rates 315 17.4 Engine and Operating Conditions 316 17.5 Results and Discussion 317 17.5.1 Basic Chemical Kinetic Results 317 17.5.2 Time]Resolved Nitric Oxide Results 320 17.5.3 Engine Nitric Oxide Results 324 17.6 Summary and Conclusions 329 18 High Efficiency Engines 333 18.1 Introduction 333 18.2 Engine and Operating Conditions 334 18.3 Results and Discussion 336 18.3.1 Overall Assessment 336 18.3.2 Effects of Individual Parameters 343 18.3.3 Emissions and Exergy 347 18.3.4 Effects of Combustion Parameters 351 18.4 Summary and Conclusions 353 19 Summary: Thermodynamics of Engines 355 19.1 Summaries of Chapters 355 19.2 Fundamental Thermodynamic Foundations of IC Engines 356 Item 1: Heat Engines versus Chemical Conversion Devices 356 Item 2: Air]Standard Cycles 357 Item 3: Importance of Compression Ratio 357 Item 4: Importance of the Ratio of Specific Heats 359 Item 5: Cylinder Heat Transfer 360 Item 6: The Potential of a Low Heat Rejection Engine 360 Item 7: Lean Operation and the Use of EGR 361 Item 8: Insights from the Second Law of Thermodynamics 361 Item 9: Timing of the Combustion Process 362 Item 10: Technical Assessments of Engine Concepts 362 19.3 Concluding Remarks 362 Index 363