CFD-DEM simulation of AP particle transport and breakage in a feed pipe

Abstract

The jet mill achieves particle refinement and classification through the shear collisions between high-speed airflow and particles, effectively meeting the demand for multi-scale ammonium perchlorate (AP) in composite solid propellants. However, the flow dynamics of the two-phase fine grinding system during the jet milling process still require further investigation. This paper employs the CFD-DEM method to analyze the dynamic behavior of the feed gas flow, the dynamic transmission of polyhedral particles, and the fracture mechanics of the true particles. The Ab-T10 model regards the particles as a single entity that is instantaneously decomposed into fragments by the Voronoi fracture algorithm after the impact energy accumulation is higher than the breakage energy. The visualization results show that the feed gas flow is subsonic inside the Venturi tube and reaches the sonic state at the nozzle outlet. As the jet continues to penetrate, the flow rate initially increases before subsequently decreasing. The increase of surface curvature will reduce the proportion of multi-stage collisions of particles, and it is difficult for the wall to form a long-term retardation of particle motion. The collision of low-curvature particles results in a greater normal contact force and a longer residence time on the wall, which can potentially cause mechanical damage to the feed pipe. Upon colliding with the wall, multiple large-scale cracks form in the initial deformation area, causing the original particles to break down into multi-scale fragments. The wall blocking reduces the velocity of the micro-particle fragments and forms a stable broken flow structure.