Large Eddy Simulation of a Premixed Flame in Hot Vitiated Crossflow With Analytically Reduced Chemistry

This numerical study deals with a premixed ethylene–air jet at 300 K injected into a hot vitiated crossflow at 1500 K and atmospheric pressure. The reactive jet in crossflow (RJICF) was simulated with compressible 3D large eddy simulations (LES) with an analytically reduced chemistry (ARC) mechanism and the dynamic thickened flame (DTF) model. ARC enables simulations of mixed combustion modes, such as autoignition and flame propagation, that are both present in this RJICF. 0D and 1D simulations provide a comparison with excellent agreement between ARC and detailed chemistry in terms of autoignition time and laminar flame speed. The effect of the DTF model on autoignition was investigated for varying species compositions and mesh sizes. Comparisons between LES and experiments are in good agreement for average velocity distributions and jet trajectories; LES remarkably capture experimentally observed flame dynamics. An analysis of the simulated RJICF shows that the leeward propagating flame has a stable flame root close to the jet exit. The lifted windward flame, on the contrary, is anchored in an intermittent fashion due to autoignition flame stabilization. The windward flame base convects downstream and is “brought back” by autoignition alternately. These autoignition events occur close to a thin layer that is associated with radical build-up and that stretches down to the jet exit.