This is the textbook for the master's course Combustion and Fuels that the author teaches at the Louvain School of Engineering of UCLouvain. Read More
This is the textbook for the master's course Combustion and Fuels that the author teaches at the Louvain School of Engineering of UCLouvain. The subjects contained herein are the following: origin and composition of fossil fuels, stoichiometry and thermochemistry of combustion, chemical kinetics, governing equations of reacting flows, laminar premixed flames and turbulent premixed flames. Emphasis is placed on the presentation and analysis of the basic concepts and physico-chemical mechanisms underpinning combustion. Further, particular attention has been paid to render these notes self-contained. A list of review questions and exercises has been included at the end of each chapter. This book is intended for master’s or advanced undergraduate students in engineering, physics, chemistry or applied mathematics. It is assumed that the reader is familiar with the basic notions of thermodynamics and fluid mechanics.
Foreword 9
1 Introduction 11
1.1 Classification of the various types of combustion . . . . . . . . 12
1.2 Phenomenology of combustion . . . . . . . . . . . . . . . . . . 13
1.3 Review questions and exercises . . . . . . . . . . . . . . . . . . 15
2 Origin and composition of fuels 17
2.1 The fossilization process . . . . . . . . . . . . . . . . . . . . . . 17
2.2 Composition of fossil fuels . . . . . . . . . . . . . . . . . . . . . 20
2.3 Analysis of the composition of complex fuels . . . . . . . . . . . 22
2.3.1 Proximate analysis . . . . . . . . . . . . . . . . . . . . . 22
2.3.2 Ultimate analysis . . . . . . . . . . . . . . . . . . . . . . 23
2.4 Review questions and exercises . . . . . . . . . . . . . . . . . . 24
3 Stoichiometry of combustion 25
3.1 Principal steps of combustion . . . . . . . . . . . . . . . . . . . 25
3.2 Generalized balance equation . . . . . . . . . . . . . . . . . . . 27
3.3 Complete and stoichiometric combustion . . . . . . . . . . . . . 34
3.4 Carbon-monoxide and excess-air coefficients . . . . . . . . . . . 35
3.5 The Ostwald diagram . . . . . . . . . . . . . . . . . . . . . . . 38
3.6 Optimization of the air supply . . . . . . . . . . . . . . . . . . 41
3.7 Combustion pollutants . . . . . . . . . . . . . . . . . . . . . . . 47
3.8 Review questions and exercises . . . . . . . . . . . . . . . . . . 49
4 Thermochemistry of combustion 53
4.1 Basic concepts of thermodynamics . . . . . . . . . . . . . . . . 53
4.2 Mixtures of ideal gases . . . . . . . . . . . . . . . . . . . . . . . 62
4.3 Heat of combustion . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.3.1 Combustion under constant pressure . . . . . . . . . . . 65
4.3.2 Combustion under constant volume . . . . . . . . . . . 68
4.4 Heating value of fuels . . . . . . . . . . . . . . . . . . . . . . . 70
4.5 Calculation of the heating value . . . . . . . . . . . . . . . . . . 71
4.5.1 Gaseous fuels . . . . . . . . . . . . . . . . . . . . . . . . 72
4.5.2 Liquid fuels . . . . . . . . . . . . . . . . . . . . . . . . . 73
4.5.3 Solid fuels . . . . . . . . . . . . . . . . . . . . . . . . . . 75
4.6 Adiabatic flame temperature . . . . . . . . . . . . . . . . . . . 77
4.7 Thermal efficiency of combustion . . . . . . . . . . . . . . . . . 79
4.8 Review questions and exercises . . . . . . . . . . . . . . . . . . 82
5 Chemical kinetics of combustion 85
5.1 Reaction rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.2 Collision theory . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
5.3 Elementary reactions . . . . . . . . . . . . . . . . . . . . . . . . 91
5.4 Steady-state approximation . . . . . . . . . . . . . . . . . . . . 95
5.5 Chain and chain-branching reactions . . . . . . . . . . . . . . . 99
5.5.1 Chain reactions . . . . . . . . . . . . . . . . . . . . . . . 99
5.5.2 Chain-branching reactions . . . . . . . . . . . . . . . . . 101
5.6 Reactions mechanisms of common fuels . . . . . . . . . . . . . 106
5.6.1 The H2/O2 system . . . . . . . . . . . . . . . . . . . . . 106
5.6.2 The CO/O2 system . . . . . . . . . . . . . . . . . . . . 109
5.6.3 The C/O2 system . . . . . . . . . . . . . . . . . . . . . 109
5.6.4 The CH4/O2 system . . . . . . . . . . . . . . . . . . . . 110
5.7 Global reaction mechanisms . . . . . . . . . . . . . . . . . . . . 112
5.8 Review questions and exercises . . . . . . . . . . . . . . . . . . 114
6 Governing equations of reacting flows 119
6.1 Mass balance law . . . . . . . . . . . . . . . . . . . . . . . . . . 119
6.2 Species-concentration balance law . . . . . . . . . . . . . . . . . 120
6.3 Momentum balance law . . . . . . . . . . . . . . . . . . . . . . 122
6.4 Energy balance law . . . . . . . . . . . . . . . . . . . . . . . . . 124
6.5 The resulting governing system . . . . . . . . . . . . . . . . . . 127
6.6 Low-Mach-number approximation . . . . . . . . . . . . . . . . . 128
6.6.1 The physical meaning of incompressibility . . . . . . . . 128
6.6.2 Nondimensionalization of the equations . . . . . . . . . 130
6.6.3 Perturbation of the equations . . . . . . . . . . . . . . . 133
6.6.4 The resulting system . . . . . . . . . . . . . . . . . . . . 135
6.7 Review questions and exercises . . . . . . . . . . . . . . . . . . 137
7 Laminar premixed flames 139
7.1 Basic characteristics . . . . . . . . . . . . . . . . . . . . . . . . 140
7.2 Simplified laminar-flame theory . . . . . . . . . . . . . . . . . . 141
7.3 Flame speed and thickness dependencies . . . . . . . . . . . . . 148
7.4 Extinction and ignition . . . . . . . . . . . . . . . . . . . . . . 149
7.4.1 Extinction analysis . . . . . . . . . . . . . . . . . . . . . 150
7.4.2 Ignition analysis . . . . . . . . . . . . . . . . . . . . . . 152
7.5 Flammability limits . . . . . . . . . . . . . . . . . . . . . . . . 154
7.6 Review questions and exercises . . . . . . . . . . . . . . . . . . 155
8 Turbulent premixed flames 157
8.1 Basic concepts of turbulence . . . . . . . . . . . . . . . . . . . . 157
8.1.1 Direct Numerical Simulation . . . . . . . . . . . . . . . 161
8.1.2 Reynolds averaging . . . . . . . . . . . . . . . . . . . . . 162
8.1.3 Large Eddy Simulations . . . . . . . . . . . . . . . . . . 166
8.2 Characteristics of turbulent premixed flames . . . . . . . . . . . 168
8.3 Flamelet regime . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
8.4 Thin-reaction-zone regime . . . . . . . . . . . . . . . . . . . . . 174
8.5 Broken-reaction-zone regime . . . . . . . . . . . . . . . . . . . . 177
8.6 Flame stabilization . . . . . . . . . . . . . . . . . . . . . . . . . 178
8.7 Concluding remark . . . . . . . . . . . . . . . . . . . . . . . . . 179
8.8 Review questions and exercises . . . . . . . . . . . . . . . . . . 179
Bibliography 181
Index 183