Computational Comparison Between an Elliptic and a Boundary Layer Formulation for Methane/Air Combustion Above a Heated Non-Catalytic Surface

Abstract

A fully two-dimensional elliptic model with a detailed gas phase reaction mechanism for the combustion of premixed fuel (CH₄) and air, over a non-catalytic, non-permeable plate is presented. By comparing solutions for ignition distances and species profiles predicted by the elliptic and boundary layer models, a criteria, based on the equivalence ratio and the wall temperature was obtained, which can be used to determine when the boundary layer approximation is valid. For low equivalence ratios (φ<0.4), no difference (except in the vicinity of the leading edge) was observed between the predictions of the two models at downstream distances from the leading edge of the plate for wall temperatures up to 1580 K. For high equivalence ratios (03=0.4) and for wall temperatures above 1300 K, the predictions differed significantly. The boundary layer model always predicted a thicker reaction zone.

Keywords:

• Catalytic combustion
• numerical modeling