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

Jet mill is an apparatus that produces superfine powder and is widely used in various industries. In this work, a new supersonic target jet mill based on aerodynamic theory is presented according to the flow field of a traditional jet mill. An annular supersonic flow produced by an annular converging-diverging nozzle is used to entrain the central particle flow by the shear mechanism in this new supersonic target jet mill. Then, the particle beam concentrating in the flow center impacts the target with high kinetic energy after the entrainment of the supersonic flow. An apparatus of the annular supersonic target jet mill was created to validate the theoretical design. Two types of experiments were implemented to estimate its performance. The validation experiments confirmed that the gas speed in the collision chamber was approximately 600 m/s and the supersonic flow could deliver a kinetic energy of approximately 180 J/s to the particles. The particle size reduction of boroncarbide (B₄C) and silica (Si) in the collision tests showed that the accelerated particles concentrated in the supersonic flow center collided on the targets precisely with high collision energy.