Bifurcation behavior in homogeneous-heterogeneous combustion: II. Computations for stagnation-point flow

Abstract

Bifurcation analysis of ignition and extinction of combustion in stagnation-point flow was carried out for conditions when both homogeneous and heterogeneous reactions can occur. A technique based on the bifurcation theory and the shooting algorithm is developed, which permits fast and efficient tracking of bifurcation in these systems. The influences of the different parameters on the ignition and extinction behavior were investigated by assuming (1) only catalytic surface (heterogeneous) reaction, (2) only homogeneous reaction on a hot inert surface, and (3) both surface and homogeneous reactions. The coupling effects of the homogeneous and heterogeneous reactions are clearly demonstrated. It is shown that the heterogeneous reaction dominates the system behavior at the lower temperature while both homogeneous and heterogeneous reactions play important role at higher temperature. It is predicted that the homogeneous ignition temperature is higher with surface reaction than without surface reaction. However, homogeneous-heterogeneous reactions expand the stabilized operating regions with high reaction rates compared with either heterogeneous or homogeneous reaction alone. The numerical results for propane and for methane oxidation on platinum foil also show good qualitative agreement with the experimental results of Part I of this article, which include the two types of ignition, extinction and autothermal behavior of homogeneous-heterogeneous reactions.