Effects of lifted fuel injection using an upstream ramp of a cavity on scramjet combustion

Abstract

A scramjet combustor (RSC) incorporating two ramps and a cavity was proposed. The leading edge of the cavity of a normal single-cavity scramjet combustor (SSC) was chamfered downward, and two ramps were arranged on the chamfered surface. Fuel was ejected from the ramp and injected vertically into a supersonic flow. The combustion fields of the RSC and SSC fueled by ethylene at an inlet Mach number of 2 were examined using a validated numerical simulation method. Furthermore, the effects of the lifted fuel injection by the upstream ramp of the cavity in the RSC on scramjet combustion and its mechanisms were analyzed. The combined effects of the chamfered surface and ramp increased the penetration height of the ethylene jet by 48%. This in turn facilitated the ethylene in obtaining oxygen from above and below during the combustion reaction. The low-speed wake region of the ramp was conducive to the successful ignition of ethylene, and the streamwise vortex behind the ramp accelerated the oxygen supply and flame propagation in the lower part of the ethylene jet. The ethylene jet obtained sufficient oxygen from its surroundings to participate in the combustion reaction, and a combustion efficiency of 99% was achieved at the combustor outlet. Compared to the SSC, the RSC achieved a 25% increase in the combustion efficiency and a 2% decrease in the total pressure loss at the combustor outlet. Hence, this study established that lifted fuel injection by the upstream ramp of the cavity can significantly improve the combustion performance of a scramjet combustor. Therefore, further studies and optimization of this novel configuration are required.