基于环状超声速气流引射作用的靶式气流磨研究

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

气流磨作为生产超精细粉末的设备在工业界得到了广泛应用。通过数值模拟和试验验证,提出了一种超声速靶式气流磨。该气流磨采用环状超声速气流引射颗粒流,使其达到超声速状态并获得极大动能,以颗粒束形式维持于气流中心,准确碰撞靶头,实现超声速粉碎。对颗粒速度和运动轨迹的两相流数值模拟结果表明:在总压1.5MPa、马赫数3.0的超声速气流引射作用下,粒径为25~1μm的颗粒可加速至440~530m/s,并精准地碰撞靶头。在此基础上,设计制造了超声速靶式气流磨并进行了铁粉粉碎试验和靶头侵蚀试验,结果表明:颗粒具有极大的碰撞能量,且与靶头发生了聚焦式碰撞。

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 25μm to 1μm 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.