Influence of thermal radiation on laminar coal-dust flames

A numerical simulations study was performed to examine the influence of thermal radiation on the propagation of coal dust flames. The compressible reacting Navier-Stokes equations coupled to a Eulerian granular multiphase flow model were solved. The geometrical setup consists of a channel with one open end filled with a coal-dust and air mixture. No-slip, adiabatic boundary conditions are used on the top and bottom walls of the channel. Detailed chemical reactions were used to describe the combustion of coal and volatiles. Thermal radiation was included for by solving the radiation transfer equation using a third-order filtered spherical harmonics approximation. The coal dust is ignited with high temperature products placed near the open end of the channel. The flame then propagates stably towards the closed end of the channel. Computational results show that thermal radiation produces a significant preheating effect in the reactants. The results also show that radiation has a large effect on the morphology of the flame. In some cases, a cusp-like flame shape formed when radiation was included, while neglecting thermal radiation produced a completely different flame shape.