Large eddy simulation on flow characteristics of powder fuel in a cavity combustor

Based on the Large Eddy Simulation (LES) method, this paper provides a detailed investigation into the effects of powder fuel particle size, injection velocity, and incoming flow velocity on the powder fuel mixing characteristics within the combustion chamber of a scramjet. The study shows that smaller particles (2, 5 μm) tend to flow near the wall and enter the cavity, while larger particles remain closer to the main flow region. The residence time of particles in the cavity area (approximately 1 ms) is longer than that of particles outside the cavity (about 0.4 ms). For 2 μm and 5 μm particles, their trajectories cover the low-velocity recirculation zone inside the cavity, extending their residence time through a recirculation mechanism. At the same time, small particles (2, 5 μm) induce significant fluctuations in the shear layer profile, and their motion is more easily influenced by the vortical structures of the flow field. The particle mass fraction reaches about 0.9 near the injection point but decreases rapidly downstream, dropping to approximately 0.1–0.3 in the main flow region. Increasing the injection velocity enhances the penetration depth of the particle jet, whereas raising the incoming flow Mach number reduces the particle residence time. Meanwhile, the increased momentum of the incoming flow makes it more difficult for the particle jet to penetrate the main flow region, resulting in noticeable jet deflection. This study provides a theoretical basis for the further design of powder fuel injection strategies.