Characteristics of a Cavity-Stabilized Hydrogen Jet Flame in a Model Scramjet Combustor

The characteristics of a hydrogen jet flame in a one-sided divergent scramjet combustor are investigated using both experiments and large-eddy simulations. Optical observations provide macroscopic insight into the typical flow structures and reaction zone. The combustor operates in a cavity-stabilized combustion mode, in which a stable flame is anchored in the cavity shear layer and spreads into the jet wake. Particular attention is paid to the effect of turbulence on hydrogen combustion, which is often difficult or impossible to measure experimentally. Therefore, a high-fidelity simulation of sonic hydrogen jet injection into a scramjet combustor is conducted to provide a detailed description of the three-dimensional unsteady reacting flow. Autoignition occurs along the windward jet boundary, but the flame cannot be sustained due to the high local scalar dissipation rate. Two pairs of large-scale recirculation zones are generated in the cavity. Reflux with a long-flow residence time entrains hot intermediate products into the cavity, which continuously ignite the mixture in the jet wake. Then, the steady turbulent diffusion flame governs the combustion downstream of the cavity, and a large amount of chemical heat is released close to the stoichiometric mixture fraction.