Numerical study of the effects of material properties on flame stabilization in a porous burner

Development of porous burners has been encouraged by lower emission standards as well as the advantages these burners offer; such as fuel flexibility, the ability to operate at low equivalence ratios, and effective flame speeds greater than the laminar flame speed. Although a burner may be constructed from a single section of porous media, a burner consisting of two sections with different characteristics has received significant attention in the last decade. Through proper selection of the properties of the two sections, the interface between the two sections serves as a flame holder preventing flashback for a range of conditions. In this paper, we present the results from a one-dimensional computational study on flame stabilization in a two section porous burner. The stable operating limits are predicted for a range of equivalence ratios and are compared to experimental values. A parametric study, in which the properties of the two sections are varied independently, is presented. The results indicate that matrix properties significantly affect the stable operating range. In addition, the upstream section acts primarily as a flashback arrestor and for the widest operating range, it should have a low conductivity, low volumetric heat transfer coefficient, and high radiative extinction coefficient. The downstream section acts primarily to recirculate heat through the matrix; it should have a high conductivity, high volumetric heat transfer coefficient, and an intermediate radiative extinction coefficient. (C) 2003 The Combustion Institute. All rights reserved.