Catalyzed combustion of H 2/air mixtures in a flat plate boundary layer: II. Numerical model

Abstract

A computer program has been developed to solve the boundary layer equations for laminar flow over a heated catalytic plate with H 2/air combustion. The objectives are to investigate the importance of homogeneous as opposed to surface reactions during high-temperature surface catalyzed combustion and to determine the roles of heat and mass transfer and their effect on the combustion process. Realistic transport properties and a detailed kinetic mechanism have been included in the program. Results are presented for the combustion of H 2/air at an equivalence ratio of 0.1 during flow over a noncatalytic plate with a surface temperature of 1100K. The results indicate the existence of an initial region near the plate leading edge in which radical concentrations increase with little associated heat release, and a downstream region where heat release due to gas phase combustion results in a significant increase in thermal boundary layer thickness. Boundary conditions are formulated for a catalytic surface and the resulting calculations show that surface reaction has a strong quenching effect on the initiation of gas phase combustion in the boundary layer due to removal of H 2 near the plate surface and quenching of radical species generated in the gas phase. This results in a significant reduction in gas phase heat release rates and a smaller increase in thermal boundary layer thickness than found with a noncatalytic surface.