Large-eddy Simulations of Transverse Jet Mixing and Flame Stability in Supersonic Crossflow

Large-eddy simulations (LES) combined with the partially stirred reactor (PaSR) combustion model are employed to investigate the turbulent mixing, combustion mode, and flame stability of a sonic hydrogen jet injecting into high-enthalpy supersonic crossflow at three momentum flux ratios J, in other words, 0.71, 2.11, and 4.00, respectively. The LES accuracy in terms of the turbulent kinetic energy, power spectra density, and subgrid Damköhler number is carefully addressed against various LES resolution criteria and the experimental mean pressure distribution on the upper wall. The ignition processes with autoignition and shock compression effects are identified and analyzed. At J=0.71, the shock-induced ignition occurs behind the reflected shock wave, and the combustion heat release is dominated by the premixed combustion. While for the high jet-to-crossflow momentum flux ratios, for example, J=2.11 and 4.00, ignition happens around the jet orifice due to the strong bow shock and reflected shock effects, and the combustion heat releases are dominated by the nonpremixed combustion. Furthermore, the mechanisms of flame stabilization, local extinction, and reignition in the transverse jet combustion in supersonic crossflow are further analyzed with the chemical explosive mode analysis.