Extinction of counterflow diffusion flames with branching-termination chain mechanisms: Theory and experiment

Abstract

The asymptotic structure and extinction of diffusion flames supported by a chain mechanism consisting of two two-body, thermoneutral, high-activation-energy branching reactions and a three-body, exothermic, zero-activation-energy termination reaction have been analyzed for the model problem of counterflow flames. A unique extinction criterion has been derived which contains a chain extinction limit and a global extinction limit; the latter is identified as Linan's extinction criterion for a one-step overall reaction. A companion experimental study shows that the density-weighted extinction strain rate increases only linearly with increasing pressure, thereby demonstrating weakened pressure dependence due to the influence of the three-body termination reaction.