滚筒端面对颗粒物料轴向混合过程影响的离散模拟

基于离散单元法模拟了仅颜色存在差异的两组分颗粒物料在轴径比0.3的窄滚筒中的轴向混合过程，滚筒的左侧端面固定，右侧端面可随侧壁旋转。结果表明，不同物料装载量和滚筒转速下，在达到完全混合状态前，黄红颗粒物料初始轴向界面处可能出现3种不同的径向结构：黄?红结构、红?黄?红结构和红?黄结构。红?黄?红结构和红?黄结构工况下，固定端面一侧还可出现更复杂的多层三明治结构。径向结构源自滚筒端面效应导致的颗粒轴向对流，颗粒轴向速度在切向截面上的分布决定了径向结构的类型。

Discrete simulation of influence of drum end-wall on axial mixing behavior of granular material

Drum has been widely used to handle granular materials in various industries such as mining, metallurgy and chemical engineering. Thorough understanding of the complex flow behavior of granular material is critical to the design, optimization and scale-up of drum apparatus. A rather short rotating drum with the ratio of axial length to diameter equal to 0.3 was focused in this work. By performing discrete element method (DEM) simulations, the axial mixing process of binary granular material in such short drum was investigated. The drum was asymmetrically operated with the left end-wall fixed and the other rotated with side wall. The particles only differed in color (yellow versus red). The yellow and red particles were initially arranged side by side axially. The simulation results indicated that the system inevitably went through a radial segregation state before attaining the full mixing state. Depending on the filling degree and rotating speed, there could be three types of radial pattern at the initial axial interface of yellow and red materials: yellow?red, red?yellow?red and red?yellow. As to cases of the latter two structures, a more complex multi-layer sandwich type radial segregation pattern could be observed in the half side close to the fixed end wall. The analyses of the axial flow structure demonstrate that the occurrence of radial pattern can be ascribed to the end-wall effect: due to the asymmetrical operation of end-walls, clear axial convection structure was formed. And the exact distribution of particle axial velocity in the transverse cross-section determined the type of radial segregation.