Numerical simulation of horizontal fuel injection in supersonic air flow and investigation of the effect of the geometric shape of the wedge surface on mixing performance

One common method for fuel injection in scramjet engines is transverse fuel injection into a supersonic airflow. Given the extremely high air velocities and very short fuel residence time within the scramjet combustor, achieving efficient fuel-air mixing at these high speeds is a critical challenge. Consequently, research into fuel injection and dispersion is a pivotal aspect of scramjet engine design. This study numerically investigates transverse fuel injection into a supersonic airflow. This was achieved by solving the Reynolds-Averaged Navier-Stokes (RANS) equations coupled with the ideal gas equation of state and a two-equation turbulence model . Furthermore, the impact of three distinct fuel injection wedge surface geometries – flat, wavy, and serrated – was examined. Key parameters, including mixing efficiency and total pressure loss, were calculated and compared for these three configurations. The results demonstrate that the wedge surface geometry directly influences fuel injection performance. Specifically, the serrated wedge yielded the highest mixing efficiency (approximately 14.7%) compared to the flat (9%) and wavy (13.4%) wedges, primarily due to the generation of controlled disturbances. However, this increase in efficiency comes at the cost of elevated total pressure loss, reaching 8.4% for the serrated wedge. The numerical model was validated by comparing simulation results with experimental data, showing good agreement. This study indicates that optimal selection of the wedge geometry can establish a suitable balance between mixing efficiency and pressure loss in scramjet combustor design. The findings of this research can serve as a foundation for improving fuel injection system design in supersonic flow applications.