ANALYSIS OF THERMAL IGNITION IN THE SUPERSONIC MIXING LAYER

Ignition in a laminar supersonic mixing layer between two parallel str eams of initially separated reactants is studied both numerically and through the use of large activation energy asymptotics. The asymptotic analysis provides a description of ignition characteristics over the entire range of system parameters. In particular, it is demonstrated t hat, for small values of viscous heating, the ignition distance scales approximately Linearly with the freestream Mach number, whereas for l arge viscous heating it decreases rapidly due to the temperature-sensi tive nature of the reaction rate. This indicates the potential of usin g local flow retardation to enhance ignition rather than relying solel y on external heating. The asymptotic analysis further identifies seve ral distinct ignition situations, yielding results that compare well w ith those obtained from the full numerical calculation. The effects of flow nonsimilarity are also assessed and are found to be more promine nt for the mixing layer flow in comparison to the flat-plate configura tion studied previously.