Two-stage fuel injection performance of RBCC under scramjet mode

Abstract

Multistage fuel injection is a promising method to improve mixing and combustion in the rocket-based combined-cycle (RBCC) engine operating under scramjet mode. To create an efficient two-stage fuel injection strategy for RBCC engines under scramjet mode, Reynolds-averaged Navier-Stokes-based CFD modeling is performed to analyze the effects of injection from single or multiple walls, fuel equivalence ratio and axial injection position on engine performance. First-stage fuel is injected from the walls of the isolator, whereas a second-stage fuel is injected from pylons. The results obtained reveal that the appropriate axial fuel injection position of the first stage can significantly improve the engine performance under Mach 6. The first-stage fuel injected from multiple walls of the isolator yields a wider low-speed region to enhance fuel/air mixing and combustion compared with fuel injected from a single wall. Fuel injected from multiple walls can cause unstart of inlet at Mach 6, but can achieve a higher specific impulse and combustion efficiency at Mach 7 for an increasing backpressure threshold. The results can contribute to improving the operational reliability of RBCC engines which use two-stage fuel injection technique to achieve a high performance.