Turbulent premixed flames

A work on turbulent premixed combustion is timely because of increased concern about the environmental impact of combustion and the search for new combustion concepts and technologies. An improved understanding of lean fuel turbulent premixed flames must play a central role in the fundamental science of these new concepts. Lean premixed flames have the potential to offer ultra-low emission levels, but they are notoriously susceptible to combustion oscillations. Thus, sophisticated control measures are inevitably required. The editors' intent is to set out the modeling aspects in the field of turbulent premixed combustion. Good progress has been made recently on this topic. Thus, it is timely to edit a cohesive volume containing contributions from international experts on various subtopics of the lean premixed flame problem.

Author Notes

Dr. Nedunchezhian Swaminathan is a Lecturer in the Department of Engineering at the University of Cambridge and Director of Studies at Robinson College. He has published more than 90 research articles on turbulent flames and combustion and on the numerical simulation of turbulence and combustion.
K. N. C. Bray is Professor Emeritus in the Department of Engineering at the University of Cambridge. He is the author of numerous refereed research publications. Among his many honors, he was elected a Fellow of the Royal Society.

Preface	p. ix
List of Contributors	p. xi
1 Fundamentals and Challenges	p. 1
1.1 Aims and Coverage	p. 1
1.2 Background	p. 3
1.3 Governing Equations	p. 6
1.3.1 Chemical Reaction Rate	p. 8
1.3.2 Mixture Fraction	p. 9
1.3.3 Spray Combustion	p. 10
1.4 Levels of Simulation	p. 11
1.4.1 DNS	p. 11
1.4.2 RANS	p. 11
1.4.3 LES	p. 12
1.5 Equations of Turbulent Flow	p. 13
1.6 Combustion Regimes	p. 14
1.7 Modelling Strategies	p. 16
1.7.1 Turbulent Transport	p. 17
1.7.2 Reaction-Rate Closures	p. 20
1.7.3 Models for LES	p. 27
1.8 Data for Model Validation	p. 31
References	p. 33
2 Modelling Methods	p. 41
2.1 Laminar Flamelets and the Bray, Moss, and Libby Model	p. 41
2.1.1 The BML Model	p. 42
2.1.2 Application to Stagnating Flows	p. 48
2.1.3 Gradient and Counter-Gradient Scalar Transport	p. 50
2.1.4 Laminar Flamelets	p. 52
2.1.5 A Simple Laminar Flamelet Model	p. 54
2.1.6 Conclusions	p. 60
2.2 Flame Surface Density and the G Equation	p. 60
2.2.1 Flame Surface Density	p. 61
2.2.2 The G Equation for Laminar and Corrugated Turbulent Flames	p. 64
2.2.3 Detailed Chemistry Modelling with FSD	p. 68
2.2.4 FSD as a PDF Ingredient	p. 71
2.2.5 Conclusion	p. 74
2.3 Scalar-Dissipation-Rate Approach	p. 74
2.3.1 Interlinks among SDR, FSD, and Mean Reaction Rate	p. 76
2.3.2 Transport Equation for the SDR	p. 77
2.3.3 A Situation of Reference - Non-Reactive Scalars	p. 78
2.3.4 SDR in Premixed Flames and Its Modelling	p. 81
2.3.5 Algebraic Models	p. 97
2.3.6 Predictions of Measurable Quantities	p. 100
2.3.7 LES Modelling for the SDR Approach	p. 101
2.3.8 Final Remarks	p. 102
2.4 Transported Probability Density Function Methods for Premixed Turbulent Flames	p. 102
2.4.1 Alternative PDF Transport Equations	p. 105
2.4.2 Closures for the Velocity Field	p. 107
2.4.3 Closures for the Scalar Dissipation Rate	p. 108
2.4.4 Reaction and Diffusion Terms	p. 109
2.4.5 Solution Methods	p. 110
2.4.6 Freely Propagating Premixed Turbulent Flames	p. 111
2.4.7 The Impact of Molecular-Mixing Terms	p. 113
2.4.8 Closure of Pressure Terms	p. 114
2.4.9 Premixed Flames at High Reynolds Numbers	p. 121
2.4.10 Partially Premixed Flames	p. 124
2.4.11 Scalar Transport at High Reynolds Numbers	p. 126
2.4.12 Conclusions	p. 130
Appendix 2.A p. 132
Appendix 2.B p. 133
Appendix 2.C p. 134
Appendix 2.D p. 135
References	p. 135
3 Combustion Instabilities	p. 151
3.1 Instabilities in Flames	p. 151
3.1.1 Flame Instabilities	p. 152
3.1.2 Turbulent Burning, Extinctions, Relights, and Acoustic Waves	p. 166
3.1.3 Auto-Ignitive Burning	p. 168
3.2 Control Strategies for Combustion Instabilities	p. 173
3.2.1 Energy and Combustion Oscillations	p. 174
3.2.2 Passive Control	p. 176
3.2.3 Tuned Passive Control	p. 187
3.2.4 Active Control	p. 189
3.3 Simulation of Thermoacoustic Instability	p. 202
3.3.1 Basic Equations and Levels of Description	p. 202
3.3.2 LES of Compressible Reacting Flows	p. 206
3.3.3 3D Helmholtz Solver	p. 215
3.3.4 Upstream-Downstream Acoustic Conditions	p. 219
3.3.5 Application to an Annular Combustor	p. 221
3.3.6 Conclusions	p. 229
References	p. 229
4 Lean Flames in Practice	p. 244
4.1 Application of Lean Flames in Internal Combustion Engines	p. 244
4.1.1 Legislation for Fuel Economy and for Emissions	p. 245
4.1.2 Lean-Burn Combustion Concepts for IC Engines	p. 256
4.1.3 Role of Experiments for Lean-Burn Combustion in IC Engines	p. 304
4.1.4 Concluding Remarks	p. 307
4.2 Application of Lean Flames in Aero Gas Turbines	p. 309
4.2.1 Background to the Design of Current Aero Gas Turbine Combustors	p. 312
4.2.2 Scoping the Low-Emissions Combustor Design Problem	p. 313
4.2.3 Emissions Requirements	p. 314
4.2.4 Engine Design Trend and Effect of Engine Cycle on Emissions	p. 317
4.2.5 History of Emissions Research to C.E. 2000	p. 318
4.2.6 Operability	p. 321
4.2.7 Performance Compromise after Concept Demonstration	p. 323
4.2.8 Lean-Burn Options	p. 324
4.2.9 Conclusions	p. 331
4.3 Application of Lean Flames in Stationary Gas Turbines	p. 335
4.3.1 Common Combustor Configurations	p. 336
4.3.2 Fuels	p. 338
4.3.3 Water Injection	p. 339
4.3.4 Emissions Regulations	p. 340
4.3.5 Available NO x Control Technologies	p. 342
4.3.6 Lean Blowoff	p. 345
4.3.7 Combustion Instability	p. 345
4.3.8 Flashback	p. 348
4.3.9 Auto-Ignition	p. 348
4.3.10 External Aerodynamics	p. 349
4.3.11 Combustion Research for Industrial Gas Turbines	p. 349
4.3.12 Future Trends and Research Emphasis	p. 350
References	p. 351
5 Future Directions	p. 365
5.1 Utilization of Hot Burnt Gas for Better Control of Combustion and Emissions	p. 365
5.1.1 Axially Staged Lean-Mixture Injection	p. 367
5.1.2 Application of the Concept to Gas Turbine Combustors	p. 374
5.1.3 Numerical Simulation towards Design Optimization	p. 375
5.2 Future Directions and Applications of Lean Premixed Combustion	p. 378
5.2.1 LPP Combustors	p. 378
5.2.2 Reliable Models that Can Predict Lift-Off and Blowout Limits of Flames in Co-Flows or Cross-Flows	p. 383
5.2.3 New Technology in Measurement Techniques	p. 386
5.2.4 Unresolved Fundamental Issues	p. 390
5.2.5 Summary	p. 395
5.3 Future Directions in Modelling	p. 396
5.3.1 Modelling Requirements	p. 396
5.3.2 Assessment of Models	p. 398
5.3.3 Future Directions	p. 400
References	p. 401
Nomenclature	p. 407
Index	p. 415

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