Numerical Analysis of Strut and Cavity Configurations for Improved Combustion Efficiency in Scramjet Engines

This study presents a numerical investigation into the synergistic effects of combined strut and cavity-based hydrogen injection on combustion performance within a supersonic combustion ramjet combustor. A wedge-type strut injector and a ramped cavity (20 mm × 10 mm), located 78 mm downstream from the inlet within a 300 mm × 50 mm rectangular channel, are employed as dual fuel injection mechanisms. The computational fluid dynamics simulations are conducted using the shear stress transport turbulent kinetic energy-specific turbulent dissipation rate turbulence model in conjunction with a finite-rate/eddy-dissipation combustion model to resolve complex flow–chemistry interactions. Model predictions are validated against experimental data from the German Aerospace Center, confirming accurate representation of shock–flame interactions and species distributions. The integrated strut–cavity configuration demonstrates significant enhancements in local recirculation, fuel–air mixing, and overall combustion efficiency—achieving an approximate 15% improvement over the strut only case. Moreover, unburned H2 mass fraction is markedly reduced, indicating improved combustion completeness. These results highlight the potential of hybrid fuel injection strategies for advancing flame stabilization and thermal performance in hypersonic air-breathing propulsion systems.