Abstract: The discrete element method(DEM)was employed to simulate motion and mixing of polydisperse particles in a rotary drum. The effects of eccentricity on partition of particle system and its regional variation,change of large particle velocity and mixing degree of polydisperse particles were studied. Results showed that the rolling regime is divided three areas in the eccentric drum,particle system,the stagnant layer,the active layer and the vortex core. There is no actual vortex core,the shape and position of the "moving vortex core" are periodically changed with the rotation of the drum in the eccentric drum. In the center drum,the velocity of large particles in the stagnant layer is basically equal in different particle motion period. But in the eccentric drum,the two uniform velocity of the large particle in the two adjacent stagnant layer is unequal. The change of large particle velocity is more obvious with increasing eccentricity. The eccentricity has little effect on contact result of polydisperse particles. The variation of contact numbers of polydisperse particles is similar to that of the damping vibration curve in the mixing process.

Key words: discrete element method, eccentric drum, polydisperse particles, moving vortex core

摘要： 采用离散单元法（DEM），对5种粒径颗粒在滚筒内的运动混合进行数值模拟，研究了偏心距对滚筒内颗粒体系分区及区域变化、大颗粒速度变化和多粒径颗粒混合程度的影响。结果表明；非偏心滚筒内处于滚落运动模式的颗粒体系分为3个区域：平流层、活动层和涡心；偏心滚筒内不存在实际的涡心，随着滚筒转动，“移动涡心”的形状大小和位置都在周期性变化。在不同颗粒运动周期中，非偏心滚筒内的大颗粒在平流层中的匀速度基本相等；而在偏心滚筒内，大颗粒在相邻两次平流层中的两次匀速度基本都不相等，且偏心距越大的滚筒内，颗粒匀速度的变化越明显。偏心距基本不影响滚筒内多粒径颗粒的接触效果，多粒径颗粒在滚筒内的混合过程中，接触数的变化类似阻尼振动曲线变化。

关键词: 离散单元法, 偏心滚筒, 多粒径颗粒, 移动涡心