Structure and extinction of a diffusion flame with chain mechanism in supersonic mixing layer

The structure and extinction of a diffusion flame in supersonic mixing layer were investigated asymptotically in order to determine some of the essential features of the coupling between heat and mass transfer and chemical reaction in scramjet engines. Analysis, based on the three-step chain mechanism of Birkan and Law, was performed by employing large activation-energy asymptotics. Special attention was paid to investigating the interaction of compressibility, viscous heating and chemical mechanism, and their influence on the flame structure and extinction limit. This analysis yielded the same explicit expression as that of Linan. The upper branch of the S curve was obtained and extinction was identified by a rapid decrease of maximum temperature in the flame zone, which resulted in a leakage of the reactants. Both the flame structure and the extinction limit were greatly affected by the Mach number, viscous heating and rates of branching and termination reactions.