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

The catalytic ignition of a gaseous combustible mixture in a planar stagnat ion-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 reacti on 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 comparis on 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 d epending on the dissociative adsorption of the reactant. The overall activa tion energy also depends strongly on the dissociative character of the adso rption processes of both reactants.