Characteristics of a Scramjet Combustor with Fluidic Oscillator Fuel Injection

This study proposes a fuel injection scheme based on a fluidic oscillator to enhance fuel mixing in a scramjet combustor. Numerical simulations, incorporating a seven-step hydrogen-air reaction mechanism and the eddy dissipation concept model, were conducted to investigate the cold-flow characteristics, combustion behavior, and overall performance of the combustor under the influence of the fluidic oscillator. The combustor inlet conditions were set at Mach 2.0, total pressure of 659 kPa, and total temperature of 1,350 K, with hydrogen as the fuel (total pressure: 200 kPa, total temperature: 300 K) at an equivalence ratio of 0.328. The results indicate that, under cold-flow conditions, the fluidic oscillator reduces the scale of the recirculation zone near the jet root, weakens the wave system intensity within the combustor, delays the shock wave/boundary layer interaction, decreases total pressure loss, increases the outlet Mach number, and enhances both the energy of the fuel jet and the low-frequency oscillations within the cavity. Under combustion conditions, flame evolution progresses through four stages: wall-ignition, shear-layer combustion, near-wall quenching, and stable combustion. The fluidic oscillator increases the temperature inside the cavity, expands its recirculation zone, suppresses the development of the recirculation zone on the upper wall, increases the core flow velocity and flow area, and enhances the low-frequency oscillation intensity at both the injection orifice and the cavity. High-frequency pressure oscillations induced at the orifice outlet have a limited impact on the cavity. In terms of combustor performance, the fluidic oscillator significantly improves combustion efficiency while reducing pressure loss.