Radiation Heat Transfer in Combustion Systems

An adequate treatment of thermal radiation heat transfer is essential to a mathematical model of the combustion process or to a design of a combustion system. This paper reviews the fundamentals of radiation heat transfer and some recent progress in its modeling in combustion systems. Topics covered include radiative properties of combustion products and their modeling and methods of solving the radiative transfer equations. Examples of sample combustion systems in which radiation has been accounted for in the analysis are presented. In several technologically important, practical combustion systems coupling of radiation to other modes of heat transfer is discussed. Research needs are identified and potentially promising research topics are also suggested. Nomenclature 1. 2. CONTENTS Introduction Radiative Transfer 2.1. Radiative transfer equation 2.2. Conservati_on of radiant energy equation 2.3. Turbulence/radiative interaction 3. Radiative Properties of Combustion Products 3.1. Radiative properties of combustion gases 3.1.1. Narrow-band models 3.1.2. Wide-band models 3.1.3. Total absorptivity emissivity models 3.1.4. Absorption and emission coefficients 3.l.5. Effect of absorption coefficient on the radiative heat flux predictions 3.2. Radiative properties of polydispersions 3.2.1. Types and shapes of polydispersions 3.2.2. Prediction methods of the particle radiative properties 3.2.3. Simplified approaches 3.2.4. Scattering phase function 3.3. Total properties 4. Solution Methods 4.1. Exact models 4.2. Statistical methods 4.3. Zonal method 4.4. Flux methods 4.4.1. Multiflux models 4.4.2. Moment methods 4.4.3. Spherical harmonics approximation 4.4.4. Discrete ordinates approximation 4.4.5. Hybrid and other methods 4.5. Comparison of methods 5. Applications to Simple Combustion Systems 5.1. Single-droplet and solid-particle combustion 5.2. Contribution of radiation to flame wall-quenching of condensed fuels 5.3. Effect of radiation on one-dimensional char flames 5.4. Radiation in a combusting boundary layer along a vertical wall 5.5. Interaction of convection-radiation in a laminar diffusion flame 5.6. Effect of radiation on a planar, two-dimensional turbulent-jet diffusion flame 5.7. Radiation from flames 5.8. Combustion and radiation heat transfer in a porous medium 6. Applications to Combustion Systems 6.1. Industrial furnaces 6.1.1. Stirred vessel model 6.1.2. Plug flow model 6.1.3. Multi-dimensional models 6.2. Coal-fired furnaces 6.3. Gas turbine combustors 6.4. Internal combustion engines 6.5. Fires as combustion systems 7. Concluding Remarks Acknowledgements References 98 98 100 100 104 104 106 107 107 107 109 109 111 113 114 115 116 119 121 122 122 123 123 124 125 126 127 128 129 130 133 133 133 134 135 136 138 139 140 141 142 143 145 145 146 149 151 151 153 154 154