Flow characterization of non-spherical particles based on DEM-PPM method

doi:10.16085/j.issn.1000-6613.2024-0677

Abstract

Abstract:

Simplifying particle shapes to spheres in simulations can lead to significant discrepancies between simulations and real-world scenarios. The polyhedral particle method (PPM) offers more accurate geometric representation and collision detection. This study modeled non-spherical particles using PPM coupled with the discrete element method (DEM), incorporating the non-spherical Ganser drag coefficient and the Di Felice drag model, resulting in the Di Felice-Ganser drag model suitable for non-spherical particles. The DEM-PPM method was employed to simulate the flow of non-spherical particles in a bubbling fluidized bed and analyze their motion characteristics. A comparison between the motion of non-spherical and spherical particles in the fluidized bed revealed distributions of particle count, particle velocity, and particle rotational velocity, along with the Lacey mixing index over time. Results indicated that the bed height of cylindrical particles was greater than that of spherical particles, and the rotational velocity of cylindrical particles significantly exceeded that of spherical particles. Spherical particles exhibited a more uniform distribution, whereas cylindrical particles tended to aggregate. With increasing bed height, the velocity and rotational velocity of cylindrical particles increased. Cylindrical particles predominantly accumulated on the sides, displaying higher velocities and rotational speeds. When the number of cylindrical particles in each bed layer reached a certain threshold, further increases led to reduced particle velocity and rotational speed, and increased drag force. The generation and breakup of bubbles enhanced the mixing of cylindrical particles, resulting in better mixing efficiency within the fluidized bed.

Key words: polyhedral method, non-spherical particles, discrete element method, bubbling fluidized bed, numerical simulation

摘要：

将颗粒形状简化为球形进行模拟会导致模拟与实际情况相差较大，多面体法（polyhedral particle method，PPM）能够提供更准确的几何表示和碰撞检测，基于离散单元法（discrete element method，DEM）耦合PPM法对非球形颗粒建模，结合非球形Ganser曳力系数耦合Di Felice曳力模型，采用适用于非球形颗粒的Di Felice-Ganser曳力模型。本文基于DEM-PPM方法模拟非球形颗粒在鼓泡流化床内的流动并分析其运动特性。对比非球形颗粒与球形颗粒在流化床中的运动过程，得到非球形颗粒和球形颗粒的颗粒数量、颗粒速度及颗粒旋转速度的分布，并计算各时刻的Lacey混合指数。结果表明，圆柱颗粒床层高度大于球形颗粒的床层高度，且圆柱颗粒的旋转速度远高于球形颗粒旋转速度。在球形颗粒的运动过程中，颗粒分布较为均匀，而在圆柱颗粒的运动过程中，颗粒更易于聚集。随着流化床高度的增加，圆柱颗粒的速度和旋转速度逐渐增大。圆柱颗粒在两侧分布较多，且两侧颗粒具有较大的速度与旋转速度。流化床中各层圆柱颗粒数量到达一定数量造成颗粒堆积后，随着颗粒数量的增加，颗粒速度和颗粒旋转速度减小，颗粒所受曳力增大。气泡的产生和破碎会促进圆柱颗粒混合，圆柱颗粒在流化床内混合效果较好。

关键词: 多面体法, 非球形颗粒, 离散单元法, 鼓泡流化床, 数值模拟

CLC Number:

TK229

CHEN Juhui, ZHANG Qian, LI Dan, LI Weikang, CHEN Ke, ZHOU Huan, ZHURAVKOV Michael, LAPATSIN Siarhel, JIANG Wenrui. Flow characterization of non-spherical particles based on DEM-PPM method[J]. Chemical Industry and Engineering Progress, 2025, 44(6): 3382-3392.

陈巨辉, 张谦, 李丹, 李魏康, 陈轲, 周欢, ZHURAVKOV Michael, LAPATSIN Siarhel, 姜文锐. 基于DEM-PPM方法的非球形颗粒流动特性[J]. 化工进展, 2025, 44(6): 3382-3392.

Figures/Tables 15

References 25

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名称	参数
球形颗粒直径/mm	1.2
圆柱颗粒等体积直径/mm	1.2
圆柱颗粒直径/mm	0.92
圆柱颗粒高度/mm	1.38
颗粒密度/kg·m^-3	1000
颗粒数	9240
恢复系数	0.97
摩擦系数	0.1
弹性模量	1.2×10⁵
泊松比	0.33
气体密度/kg·m^-3	1.205
气体黏度/Pa·s	1.8×10^-5
流化床宽/mm	44
流化床深/mm	10
流化床高/mm	120
气速/m·s^-1	0.9
CFD时间步长/s	1×10^-4
DEM时间步长/s	1×10^-6

名称	参数
球形颗粒直径/mm	1.2
圆柱颗粒等体积直径/mm	1.2
圆柱颗粒直径/mm	0.92
圆柱颗粒高度/mm	1.38
颗粒密度/kg·m^-3	1000
颗粒数	9240
恢复系数	0.97
摩擦系数	0.1
弹性模量	1.2×10⁵
泊松比	0.33
气体密度/kg·m^-3	1.205
气体黏度/Pa·s	1.8×10^-5
流化床宽/mm	44
流化床深/mm	10
流化床高/mm	120
气速/m·s^-1	0.9
CFD时间步长/s	1×10^-4
DEM时间步长/s	1×10^-6