Influence of jet-to-crossflow pressure ratio and combustor width on performance of a hydrogen fueled scramjet

Abstract

In the development of hypersonic propulsion systems, efficient mixing of gaseous jets in supersonic cross-stream has been facing formidable challenges for over a decade. This paper presents a numerical analysis of a non-reacting scramjet (Supersonic Combustion Ramjet) combustor flow field by solving the two-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations coupled with the Menter SST k-ω model. The focus of this study is to investigate the effects of jet-to-crossflow pressure ratio and combustor width on various performance parameters such as mixing efficiency, total pressure recovery, and mass-flux-weighted Mach number. Accordingly, gaseous jets of hydrogen are injected from two opposite walls on finite parallel streams of air with rearward-facing step configurations. The jet-to-crossflow pressure ratio is varied as 4.5, 9.0, 13.5, and 18.0 while the combustor widths of 40, 50, and 60 mm are considered for the present investigation. Particular emphasis is placed on the utilization of internal shock waves to enhance the combustor performance in lieu of the conventional methods of using shock generators. The insight physics of fuel-air mixing under the influence of internal shocks is also explained. The results reveal that proper shock utilization can improve the overall performance and reduce the overall dimension of the combustion chamber. For the jet-to-crossflow pressure ratio of 4.5, around 10% higher mixing efficiency and 15% greater total pressure recovery are achieved without choking the internal flow when the combustor width is reduced from 60 to 40 mm.