Premixed flame response to unsteady strain-rate and curvature

The interaction of a premixed stoichiometric methane-air flame with a counter-rotating vortex-pair is studied using a skeletal C{sub 1} chemical description of the reaction process. The focus is on the modification to flame structure and dynamics due to unsteady strain-rate and curvature. The detailed description of flame structure and dynamics in response to unsteady flow is necessary to establish relevant extinction criteria in unsteady multi-dimensional flow, which, based on recent experimental evidence, may be significantly different from those of steady one-dimensional counterflow stagnation flames. Present results suggest that the increasing unsteady tangential strain-rate causes modification of flame structure that leads to reduced reaction rates of key chain-branching reactions which are active on the products side of the flame. This causes a reduction in the concentrations of active radicals, such as H, OH, and O, which are necessary for the breakdown of hydrocarbons on the reactants side of the flame