An asymptotic analysis of catalytic ignition in a stagnation-point flow

Abstract

The catalytic ignition of a gaseous combustible mixture in a planar stagnation-point flow is studied. The heterogeneous reaction mechanism is modelled by two dissociative adsorption-desorption reactions for both reactants, a surface reaction of the Langmuir-Hinshelwood type and the desorption reaction of the adsorbed product. Using asymptotic techniques based on the large activation energy of the desorption of the most efficient adsorbed reactant, the critical conditions for ignition are obtained in closed form, showing the full parametric dependence on this critical process. A direct comparison with the global one-step surface reaction shows that the reaction order of the most efficient adsorbed reactant has to be negative with its value depending on the dissociative adsorption of the reactant. The overall activation energy also depends strongly on the dissociative character of the adsorption processes of both reactants.