Analysis of collision energy of bead media in a high-speed elliptical-rotor-type powder mixer using the discrete element method

In a high-speed elliptical-rotor-type powder mixer (HEM), to which zirconia beads are added to aid stress transmission, the energy generated during the bead-to-bead, bead-to-rotor and bead-to-vessel wall collisions has been analyzed. The motion of beads in the HEM was expressed by a simplified quasi-two-dimensional (2D) model adopting the discrete element method (DEM), so that actual physical properties can be used in the model calculation and the calculation time is reduced. Comparison between the calculated and experimental results has proved that the quasi-2D model can adequately express the motion of beads within the practical range of application. By using the collision energy obtained from the model calculation, the local temperature rise on the contact surface of a bead in a collision was estimated surprisingly to exceed several thousand degrees Kelvin under severe operating conditions. It has been found that the net energy applied to the particles is several percent of the increased kinetic energy of beads in the bead-to-rotor collision.