A Large Eddy Simulation Study on Hydrogen Microjets in Hot Vitiated Crossflow

Abstract

Abstract In this paper, the results of a large eddy simulation (LES) study on hydrogen microjets (dj ~ 0.5 mm) injected into a hot (1600 K) vitiated crossflow at different angles?namely, normal (90°) and inclined jet (30°), are presented. The goal is to explore the effects of injection angle on coherent turbulent structure formations, flame-vortex interactions, and wall heat flux contributions. The LES identifies the presence of the horseshoe vortex, the shear layer vortices (SLV), and the counter-rotating vortex pair (CVP), along with the shedding of spanwise-symmetry hairpin vortices in both the normal and inclined jets. The structures in the latter, however, appear more convoluted. In the near field, SLV-induced flow is crucial for mixing and flame propagation on the windward side of the jet, stabilized by autoignition near the jet exits. A flame-shear layer offset is observed here. In the far field, CVP dominates hot vitiated crossflow entrainment, driving flame propagation and heat and species transfer to the leeward side near the injection wall. In the wake region, combustion remains closer to the normal jet exit due to a stronger recirculation zone, resulting in higher wall heat fluxes. The mean wall heat flux values of both the normal and inclined jets decrease and approach each other with moving away from the jet exit in the streamwise direction. The present LES study results are compared to experimental data from the literature by considering instantaneous hydroxide (OH) fields and mean wall heat fluxes.