Abstract: Particle mixing and segregation are ubiquitous in industrial processes, with their dynamic behavior being governed by both equipment geometry and particle attributes. Using the discrete element method (DEM), this study investigates the mixing characteristics of granular materials in a horizontal drum. Three quantitative metrics as the contact-based separation index, steady-state separation index, and average mixing rate are introduced to systematically evaluate the combined effects of drum width, particle density ratio, and particle size ratio on axial mixing performance under a constant drum diameter. The results demonstrate that the average mixing rate decreases with increasing drum width, but increases with higher density and size ratios. At a fixed drum width, mixing uniformity deteriorates as the density or size ratio increases. Both density and size differences induce radial and axial segregation, with radial segregation intensifying as these ratios increase. Notably, size difference also triggers axial segregation, the degree of which rises markedly with drum width. Kinetic analysis reveals that the higher radial kinetic energy compared to axial kinetic energy is the key reason for the superior radial mixing rate. Furthermore, the shear effect at the end-walls is identified as crucial for inducing axial particle flow. The differential impact of drum width on systems with density versus size differences stems from the distinct synergistic actions of buoyancy and percolation segregation mechanisms.

Key words: particle mixing, drum width, discrete element method, mixing characteristics

摘要： 颗粒的混合与分离广泛存在于工业生产中，这种混合和分离的动态过程通常受到装置尺寸和颗粒属性的影响。采用离散单元法对水平转筒内颗粒物质的混合特性进行模拟，利用以颗粒接触为基础的分离指数、稳态分离指数和平均混合速率三个参数，系统地评估在恒定转筒直径下，转筒宽度和颗粒密度比、尺寸比对颗粒轴向混合特性的综合影响。结果表明，颗粒系统的平均混合速率随转筒宽度增加而降低，随颗粒密度比和尺寸比增加而增加。转筒宽度固定时，颗粒混合均匀度随密度比和尺寸比增大而减弱。颗粒密度和尺寸差异会诱发颗粒系统的径向和轴向偏析，且径向偏析程度均随二者增大而加剧；尺寸差异还会引发轴向偏析，转筒宽度越大，偏析程度越高。动力学分析显示，颗粒系统的径向动能高于轴向动能是径向平均混合速率优于轴向的关键原因，而端壁剪切效应是诱发颗粒轴向流动的关键。密度比与尺寸比对颗粒轴向混合的影响随转筒宽度变化呈现差异，源于二者分别由浮力主导和渗透主导的偏析机制不同。

关键词: 颗粒混合, 转筒宽度, 离散单元法, 混合特性