Wall ramp-induced flow modulation in a two-strut hydrogen-fueled scramjet: a numerical study

Abstract Stable combustion in scramjet engines is difficult to achieve because the airflow remains supersonic, leaving very little time for fuel and air to mix and react. To address this challenge, the present study numerically investigates the effect of combining double wall ramps with a semi-circular trailing-edge half-wedge strut fuel injector. The performance of this combined configuration is compared with cases using only wall ramps and only a strut injector. Three different axial positions of the ramp were selected, based on previous research, to examine how location influences flow structure and combustion characteristics ramp. Two-dimensional RANS simulations using the SST k–ω turbulence model were performed, and the numerical method was validated against experimental data from the DLR scramjet combustor. The results indicate that increasing the ramp height reduces excessive shock-shear layer interaction, while proper downstream ramp placement improves flame stabilization and accelerates fuel–air mixing. The best-performing configuration (Case C-3 mm) achieved nearly complete combustion within about 47 % of the combustor length. However, this improvement in combustion efficiency is accompanied by increased total pressure loss. These findings highlight the need to balance enhanced combustion performance with pressure recovery to maintain overall engine efficiency.