Porous radiant burners are widely used in industry to provide a uniform source of heat flux with reduced emissions. Such burners have provided high rates of heat transfer by radiation while preventing flame flashback. The work to be presented relates to the modeling of the combustion process in a double-layered flat porous burner. The burner employs a low porosity layer on the upstream side and high porosity layer on the downstream side of the homogenous fuel-air mixture flow.
The nonequilibrium model is adopted. The energy equations for the gas and solid media are solved numerically with a one step reaction (Arrhenius type) energy release rate for the gas-phase. The solid phase is considered to be non-reactive. The thermophysical properties of the gas and solid phases are assumed to be functions of temperature. The effects of thermal conductivity and thickness of the layers on the flame stabilization within the porous medium and radiant energy output are investigated and discussed. The high thermal conductivity layer diffuses heat and thus has significant effects on the flame location and flame temperature. However, the high thermal conductivity of the layer also contributes to a decrease in the radiant energy. It was found that generally the flame stabilizes at the interface between the two layers. When the thermal conductivity of the upstream low porosity layer was too low (e.g. 0.1 W/m.K), the flame was stabilized within the low porosity layer.