Investigation on target jet mill based on the entrainment of the annular supersonic flow

The jet mill widely used in many industrial fields is a kind of apparatus to produce superfine powder. A new supersonic jet mill, whose design is based on numerical simulations and collision experiments, is presented and manufactured. In our design an annular supersonic flow produced by an annular converging-diverging nozzle is used to entrain the central subsonic flow with particles. After the supersonic flow's entrainment, the particle beam concentrated in the flow center impacts on the target accurately with a great kinetic energy. The multiphase numerical studies show that the collision speed of particles of 25 μm to 1 μm in diameter can reach 440 m/s to 530 m/s approximately in the entrainment of the supersonic flow with the Mach number of 3.0 and the total pressure of 1.5 MPa, and particles can precisely collide on the target. The collision experiments implemented in the new-made jet mill manifest the huge collision energy and the precise supersonic collision in the jet mill by the target erosion and the iron particles size reduction.