Boundary Layer Ignition of Hydrogen-Air Mixtures in Supersonic Flows

Due to viscous heating spontaneous ignition of a supersonic flow of premixed combustible gases can occur in boundary layers. This process is studied numerically for a hydrogen-air mixture in the case of a laminar boundary layer over a flat plate. In a previous study the main structure of the reacting flow was given as well as a first mapping of the ignition conditions versus boundary conditions. In the present work computations are performed in order to further specify the controlling mechanisms and parameters of such a boundary layer ignition. We emphasize more precisely i) the elementary steps of the chemical process which effectively control the ignition ii) the unusual role played by the equivalence ratio of the mixture iii) the influence of the Soret effect (species transport due to temperature gradients).