Geometrically exact discrete-element-method (DEM) simulation on the flow and mixing of sphero-cylinders in horizontal drums

Mixing of Particles in a Rotating Drum with Inclined Axis of Rotation

Various experimental and numerical studies have been carried out to study the mixing processes inside rotating drums with a horizontal axis of rotation in the past, but little effort has been made to investigate the rotating drums with an inclined axis of rotation, though such inclined drums exist in industrial waste management, food processing, power and pharmaceutical industries. To fill this gap, in this work, the discrete element method was used to study the mixing phenomena of a rotating drum for different angles of inclination from 0° to 15°. It was found that for inclined rotating drums, the whole bed Lacey mixing index is higher than that for the horizontal drum by 7.2% when the angle of inclination is 10°. The mixing index is related to the area ratio of the active region to the whole bed and volumetric fill. Increase in volumetric fill would lead to the decrease of the mixing index. The mixing index and area ratio exhibit similar patterns along the length of the drum for different angles of inclination.

Modelling of large-particle-motion–heat-transfer coupling characteristics in rotary kiln based on discrete element method

A three-dimensional numerical simulation of the motion – heat-transfer coupling characteristics of waste tyre particles in a rotary kiln at 773–973 K was performed in this study. The particle dynamics and heat transfer characteristics were solved on a Lagrange grid. The motion model considered particle collisions using a nonslip collision model. Based on the particle motion results obtained, we considered three heat transfer mechanisms: particle–particle collision heat conduction, wall–particle radiation heat transfer, and wall–particle collision heat conduction. Subsequently, we established a mathematical model wherein the heat transfer associated with a particle is determined by its position in each time step, and implemented it on a JAVA platform to perform calculations. Finally, we obtained the temperature of each particle at each moment in the entire process. Further analysis of the simulation results shows that the average temperature and temperature standard deviation is governed by the wall temperature, rotation speed, and particle size.