Mathematical modeling of porous combustion under various working conditions

Porous burner offers attractive advantages including high combustion performance and power ranges, and approximately zero pollutant emission. In this paper, the thermal behavior of premixed flame of a CH4/air mixture in a porous burner was examined using an unsteady In-house CFD code with an appropriate single reaction mechanism. In this regard, to solve the transient term, an implicit scheme was used, and displacement terms were solved using the upwind methodology. Additionally, the discretized central difference was employed to solve diffusion terms. At first, the results were compared with available published data, and then the influences of various working parameters, including solid matrix conductivity and volumetric heat transfer coefficient, were investigated on the flame structure. Thermal performance of the burner is studied by varying relevant parameters within a practical range. The predicted gas temperature profile near the reaction zone is much broader than that in an adiabatic premixed flame. The effect of volumetric heat transfer coefficient on the temperature profile is investigated. The local gas temperature decreases in the reaction zone and the solid temperature increases in the preheat zone with an increase in convective heat transfer. Also, the corresponding local convective heat transfer rates for different values of volumetric heat transfer coefficient are calculated and compared. Simulation results also indicate that increasing the effective thermal conductivity of the solid will decrease the solid phase temperature downstream of the flame location. Due to high temperature gradients in the solid matrix, its effective thermal conductivity has a significant impact on the conductive heat transfer rates.