Experimental investigation on dynamic diffusion characteristics and mechanism of liquid kerosene jet in supersonic high-enthalpy inflow

This study investigates the dynamic diffusion characteristics and mechanisms of liquid kerosene jets in supersonic high-enthalpy flows. Experiments were conducted on the ground directly connected scramjet combustor test rig with a high-speed schlieren system at injection pressures of 0.44 MPa, 0.60 MPa, and 0.78 MPa. The dynamic development of kerosene diffusion was analyzed based on the grayscale values of schlieren images, further revealing the underlying diffusion mechanisms. Results show that kerosene diffusion in supersonic high-enthalpy flows involves two stages: diffusion development and steady-state oscillation. Increasing injection pressure significantly accelerates diffusion and expands its range. Higher inertia lowers the main oscillation frequency but increases oscillation energy by enhancing turbulent energy exchange and phase-change disturbances. The oscillation mode shifts from small-scale, high-frequency fluctuations near the nozzle, caused by gas–liquid shear instability, to large-amplitude, low-frequency oscillations downstream due to phase-change expansion. The diffusion process and distribution result from the dynamic interplay of jet momentum, aerodynamic heating, and phase-change effects. These findings are significant for improving fuel mixing and combustion efficiency.