Investigation on combustor performance of a ramp-based solid rocket scramjet with ethylene addition

High combustion efficiency and low total pressure loss are essential for improving the performance of solid rocket scramjets. This study conducted direct-connect experiments to investigate the combustor performance of a ramp-based solid rocket scramjet with ethylene addition, simulating a Mach 6 flight condition with an equivalence ratio of 0.56. Ramps were installed near the exit of the combustor, expected to function as a throat and control the shock train intensity in the isolator. A boron-containing, oxygen-poor gas generator was used to generate a fuel-rich mixture, which was injected into the combustor for further combustion with the inflow air. Wall pressure along the combustor was measured, and other flow parameters were calculated using a one-dimensional analysis method. The experimental results indicate that subsonic combustion occurs within the combustor, and the ramps are confirmed as the throat. Raising the ramp height intensifies the blockage, thereby enhancing the shock train intensity. Ethylene addition boosts the total heat release, further enhancing the shock train intensity. The enhanced shock train increases the temperature and pressure, thereby promoting combustion. Furthermore, the enhanced shock train decreases Mach number, resulting in a reduction in total pressure loss. Therefore, raising the ramp height and adding ethylene both improve thrust and specific impulse. These findings offer novel insights into the design of solid rocket scramjets with high combustion efficiency and low total pressure loss.