Auto-ignition of near-ambient temperature H2/air mixtures during flame-vortex interaction

Abstract

This paper demonstrates auto-ignition in reactants at approximately 350 K, upstream of curved H 2 /air flame surfaces during flame/vortex interaction. Temperature fields were measured using laser Rayleigh scattering during head-on interactions of toroidal-vortices with stagnation flames. Repeatable ignition occurred along the ring of the vortexslightly towards the center-when it was approximately 1 mm upstream of the wrinkled flame surface. The resultant outwardly propagating toroidal flame led to approximately twice the volumetric heat release rate over the duration of the interaction. The ignition occurred in a region of low fluid dynamic strain rate that was farther from the flame than the region of maximum vorticity. Evidence of additional ignition pockets was found upstream of other flame wrinkles, preferentially near the highest magnitude flame curvatures. Different hypotheses for explaining this observation are discussed. The possibility of substantial heat release driven by auto-ignition and complicated diffusion has implications for reaction rate closure models and transport models used in turbulent combustion simulations.