Key parameters on combustion characteristics in a rocket-aided ramjet engine under Mach 6 flight conditions

The rocket-aided ramjet engine integrates high-thrust rocket engines into the flow passage of the ramjet, effectively broadening the operating speed range and altitude capability of the ramjet. This integration enables rapid thrust modulation and stable mode transitions. To enhance the understanding of turbulent combustion organization within rocket-aided ramjet engines and to better devise combustion organization strategies, numerical simulations were conducted using the Reynolds-Averaged Navier-Stokes method to investigate the influence of key parameters, including the number of fuel injection holes, equivalence ratios, injection positions, and rocket mass flow rates, on engine combustion characteristics and performance under Mach 6 flight conditions. The results indicate that, under the research conditions of this paper, in pure ramjet mode, a configuration with 12 fuel injection holes can achieve superior overall performance. As the fuel injection equivalence ratio increases, the heat release area in the combustor expands, but combustion efficiency and specific impulse decrease. Advancing the fuel injection location enhances mixing, and simultaneously alters the core heat release region. When the rocket is ignited and its mass flow rate is set to 0.2 kg/s, the engine's thrust increases by 53%, while the specific impulse decreases by 48%. As the rocket mass flow rate increases, the engine's overall performance gradually shifts toward a rocket-dominated mode.