Temperature-Lags and Radiative Transfer in Particle-Laden Gaseous Flames Part I: Steady Planar Fronts

Abstract

We study the steady propagation of a planar flame into a gaseous, flammable premixture uniformly seeded with inert, solid particles of finite heat capacity. We assume that the particles to gas heat capacity ratio is small, the two-phase mixture is a one-velocity continuous medium, the time needed by conduction to heat up the particles is of same magnitude as the transit time in the convection/conduction flame thickness, the convection/conduction to radiation attenuation length ratio is very small, the radiant to convective heat flux ratio is small. Using the techniques of asymptotic expansions in the limit of a large activation energy of the rate of heat release in the gas phase, we obtain the changes in flame structure and burning speed due to the particles, analytically. Three important results of the competition between the radiative exchanges and conductive losses, due to the particles, show up Adding particles can make the flame propagate faster or slower, depending on the particle suspension and the gaseous mixture. The radiative transfer makes the flame much more resistant to quenching by additions of inert particles. For some mixtures, three burning speeds may coexist.