Research on the mixing characteristics of a cavity based supersonic combustion chamber coupled with secondary recirculation jets

In this study, a numerical study has been conducted on the mixing augmentation performance of the secondary recirculation jet in a scramjet engine. The impact of secondary recirculation jets with varying ramp angles and jet modes on the mixing effect has been investigated. The combustion chamber uses a cavity connected to the recirculation device. This structure has not been used in previous studies of secondary recirculation jets. The presence of cavities makes combustion more stable, so this paper will study the flow and mixing under chemical reactions. The three-dimensional compressible Reynolds-averaged Navier-Stokes equation and the two-equation shear stress transport k-omega turbulence model are employed. The mixture adopts the ethylene/air. The findings demonstrate that the secondary recirculation jet can accelerate fuel mixing, induce boundary layer separation, and contribute to the formation of counter-vortex pairs. The secondary recirculation jet improves mixing efficiency and reduces mixing length by at least 20%. It will also increase the total pressure loss, but outlet total pressure can be reduced by 7.6%. The secondary recirculation jet reduces penetration by about 20%. A ramp angle of 20 degrees combines best with the recirculation jet, while the penetration depth and total pressure are highest at a 10 degrees ramp angle. Double injection can reduce the total pressure loss caused by the secondary recirculation jet, increasing the total outlet pressure by 5.4%, but it reduces the mixing efficiency and increases the mixing length by 26.5% compared to single injection.