Numerical study and optimization of a porous burner with annular heat recirculation

Abstract

Low calorific gases (LCGs) can be completely combusted by preheating the reactant gases and increasing the reaction rates through heat recirculation. In this study, three different arrangements of porous media were numerically investigated, and the effects of the firing rate and LCG heat value on the flame temperature, flame-stability limits, and pollutant emissions were evaluated. The results showed that flame-stability limits are lower for arrangement structure C in the combustion chamber, which is effective for heat recirculation from the flame to the preheating zone. The burner with radially increasing and gradually varying porous media has lower flame-stability limits than those with radially decreasing and gradually varying porous media. In contrast, the burner with higher axially increasing and gradually varying porous media has lower flame-stability limits. Moreover, CO emissions decrease with increasing heat value of the LCG, which is an opposite trend to that of the corresponding firing rate of the flame-stability limits for different arrangements.