Mixing layer ignition of hydrogen

A theoretical analysis is given for the high-temperature ignition in a laminar mixing layer between hydrogen and air at the high temperatures characteristic of supersonic combustion. We analyze the most important practical case where the temperature of the air stream is higher than that of the hydrogen stream. In this case, the chemical reactions responsible for ignition occur in the air side of the mixing layer, where the mixture is lean. A simplified reduced mechanism is found to describe the ignition process. The radicals OH and H follow the steady-state approximation while the radical O is the chain branching species following an autocatalytic reaction with moderately large activation energy. Numerical results of the governing equations for large values of the activation energy are presented and from a symplified analysis, we obtain a closed form solution of the ignition distance as a function of the physicochemical parameters.