Abstract: Based on a large eddy simulation (LES) gas-solid two-phase numerical model, this paper conducts a detailed investigation of the mixing characteristics of powder fuel in a supersonic flow field. The study reveals that the flow behavior of particles in the supersonic flow field exhibits significant size dependency. Under distributed particle size conditions, smaller particles tend to adhere to the wall and enter the cavity, while larger particles remain closer to the mainstream region. The residence time of particles entering the leading edge of the cavity (approximately 1 ms) is significantly longer than that of particles bypassing the cavity (approximately 0.4 ms). For 2 μm and 5 μm particles, their trajectories cover the low-speed recirculation zone within the cavity, extending the residence time through a recirculation mechanism. Small-sized particles (2 μm, 5 μm) cause significant fluctuations in the shear layer profile and are more susceptible to the flow field vortex structures: their mass fraction reaches about 0.9 near the injection point but decreases rapidly downstream; the mass fraction distribution in the mainstream region shows obvious discontinuity (typically 0.1–0.3), with a wider distribution compared to larger particles. In contrast, larger particles (20 μm, 40 μm) form a smoother shear layer profile. Increasing the injection velocity slightly enhances the penetration depth of the particle jet but has minimal impact on the overall particle residence time. Increasing the incoming Mach number reduces the particle residence time and causes deflection of the particle jet, driving more particles into the cavity.

Key words: Powder-fueled scramjet, Supersonic flow, Cavity structure, Particle injection, Mixing characteristics