Inviscid spatial stability of a compressible mixing layer. Part 2. The flame sheet model

We report the results of an inviscid spatial stability calculation for a compressible reacting mixing layer. The limit of infinite Damkohler number is taken and the diffusion flame is approximated by a flame sheet. Results are reported for the phase speeds of the neutral waves and maximum growth rates of the unstable waves as a function of the parameters of the problem: the ratio of the temperature of the stationary stream to that of the fast stream, the Mach number of the fast stream, the heat release per unit mass fraction of the reactant, the equivalence ratio of the reaction, and the frequency of the disturbance. These results are compared to the phase speeds and growth rates of the corresponding non-reacting mixing layer. We show that the addition of combustion has important, and complex, effects on the flow stability. In particular, we show that the flow can become absolutely unstable with a sufficient amount of heat release.