Analysis of compressing and shearing behavior of powders in high-speed elliptical-rotor-type powder mixer (HEM)

This paper describes the analysis of behavior of powder being compressed and sheared by a rotor in a high-speed elliptical-rotor-type powder mixer (HEM). Two kinds of two-dimensional simplified dynamics models are proposed to analyze the powder behavior under conditions in which the maximum external force acts on the powders. Each of these models express the phenomena in which the powder layer slides on the vessel wall after it causes plastic deformation, and the rotor compresses the powder layer dynamically. The model equations contain both the operating conditions of HEM and the physical properties of powder as parameters, and are used to estimate the stresses acting on the powders while the HEM is operated. Good agreement between the experimental data and the calculated value of the torque acting on the rotor shaft during the mixing operation is obtained. It is clarified from the calculation that the powder layer is compressed dynamically in the minimum clearance region, and the powder layer in the other region is forced out of the minimum clearance region. The results obtained in this study indicate that adequate selection of the operating conditions of HEM enable achievement of precise control of stress acting on a powder of arbitrary physical properties.