The VSI crusher considered in this study has been designed particularly for the use of crushing aggregates. The material enters through a feed hopper and tube onto the centre of a high-speed rotating table. Impellors attached to the table eject the material at high velocity onto the surrounding stationary anvils. The crushing properties of such a device, as well as the wear on the impellors and anvils, are critically related to the velocity distribution of the ejected particles.
courtesy Magotteaux SA
This numerical study using DEM concentrated on the particle motion produced by the impellors; the anvils were not considered. A total of 4,000 polydisperse particles was considered, with a size ratio of 8. The flow rate in the cylindrical feed tube is 110 kg/s. The rotation speed of the table and impellors is 1000 rpm.
Shown below are two views of the numerical simulation results. These animations indicate the mechanism of radial accelaration of the particles as a result of contact with the impellors. The particles leave the impellors at a high radial velocity in excess of 60 m/s.
The temporal averages of particle number density and velocity shown in the plots below provide a more quantitative evaluation. A large number of particles have trajectories close to the rotating table surface. In addition, the numerical results indicate that size segregation occurs, with large particles ejected from the impellors at a greater distance from the rotating table surface.