Numerical Study of Combustion and Pollutants Formation in Inert Nonhomogeneous Porous Media

Abstract

Combustion in inert porous media offers an interesting and promissing route towards high power density, high power dynamic range and very low emission of pollutants such as NOx and CO. This work assumes one dimensional combustion in a porous burner but considers the detailed reaction mechanism of methane/air, 27 species and 73 reactions, and also the conductive heat transfer of solid matrix and radiative heat transfer in the porous media. In this work, we present a numerical study which show the effects of excess air ratio, thermal power, solid conductivity and radiative heat transfer on the combustion and pollutants formation in inert nonhomigeneous porous media. It was concluded that NO and CO emission depend mainly on the excess air ratio and thermal power. The peak flame temperature is reduced with the reduction of th solid conductivity resulting in a decrease of NO emission. This important conclusion means that NO emission can be decreased through the utilization of porous medium with small solid conductivity. Radiative heat transfer is also important for the combustion and heat transfer in porous media. The flame can be stabilized easily at the interface between two different porosity ceramic blocks due to the radiative heat feedback. In addition the predicted gas and solid temperatures were compared and discussed with reported measurements of centre line temperature in a cylindrical porous burner. Special emphasis was given to the predicted pollutants formation and their comparison with experiments. The good agreement with experimental observations suggests that the numerical model is an excellent tool to investigate combustion and pollutants formation in porous media as well as to achieve optimised porous combustion designs.