涡流空气分级流场中团聚体破碎规律研究

doi:10.11949/0438-1157.20240470

摘要/Abstract

摘要：

为探究颗粒团聚体在分级机流场内的破碎规律，基于软球模型研究了涡流空气分级流场中团聚体破碎行为及组成团聚体的单颗粒粒径、单颗粒数和团聚体形状对团聚体破碎的影响。结果表明：团聚体进入分级流场后在流体曳力的作用下先发生变形随后破碎；颗粒越小，其组成的团聚体团聚性越强；球形团聚体团聚性最强，圆柱体团聚体次之，立方体团聚体团聚性最弱；组成团聚体的单颗粒数越多，其在分级流场中完全解团所需时间越长，当团聚体大到一定程度时可能无法完全解团则被收集为粗粉，导致“鱼钩效应”。因此，通过优化流场延缓团聚体沉降或对粉体原料预分散处理有利于团聚体解团。

关键词: 涡流空气分级机, 软球模型, 破碎, 计算流体力学, 粉体, 数值模拟

Abstract:

To probe into the fragmentation laws of particle aggregate in the flow field of the classifier. Based on the soft sphere model, the fragmentation behavior of aggregate in turbo air classification flow field and the effects of single particle size, single particle number, and shape of aggregates on aggregate fragmentation are studied. The results show that: aggregates undergo deformation and then fragmentation under the action of drag force after entering the classification flow field. The smaller the single particles, the stronger the agglomerates they form. Spherical aggregates have the strongest aggregation, followed by cylindrical aggregates, and cubic aggregates have the weakest aggregation. The more single particles that make up the agglomerates, the longer it takes for them to completely disagglomerate in the classification flow field. When the agglomerates are large enough, they may not be completely disagglomerated and are collected as coarse powder, resulting in the“fishhook effect”. Thus, completely fragmentation of aggregates can be promoted by optimizing the flow field to retard aggregates settling or pre-dispersion treatment for the raw materials.

Key words: turbo air classifier, soft sphere model, fragmentation, computational fluid dynamics, powders, numerical simulation

中图分类号:

TQ 028.8

刘克润, 于源. 涡流空气分级流场中团聚体破碎规律研究[J]. 化工学报, 2024, 75(10): 3477-3487.

Kerun LIU, Yuan YU. Study of aggregate fragmentation laws in turbo air classification flow field[J]. CIESC Journal, 2024, 75(10): 3477-3487.

图/表 16

图1 涡流空气分级机结构示意图1—进风口;2—蜗壳;3—导风叶片;4—转笼;5—细粉出口;6—撒料盘

Fig.1 Structural diagram of a turbo air classifier

表1 数值模拟参数设置

Table 1 Parameter settings in the numerical simulation

参数	数值
空气动力黏度μ/(Pa·s)	1.83×10^-5
空气密度 $ρ$ /(kg·m^-3)	1.205
颗粒密度 $ρ p$ /(kg·m^-3)	2700
杨氏模量E/GPa	2
泊松比 $μ q$	0.2
时间步长δt/s	10^-8
Hamaker常数A/J	5×10^-19[28]
颗粒表面能 $γ$ /(J·m^-2)	0.0826^[29]
进口风速/(m·s^-1)	12
转笼转速/(r·min^-1)	1200

表1 数值模拟参数设置

Table 1 Parameter settings in the numerical simulation

参数	数值
空气动力黏度μ/(Pa·s)	1.83×10^-5
空气密度 $ρ$ /(kg·m^-3)	1.205
颗粒密度 $ρ p$ /(kg·m^-3)	2700
杨氏模量E/GPa	2
泊松比 $μ q$	0.2
时间步长δt/s	10^-8
Hamaker常数A/J	5×10^-19[28]
颗粒表面能 $γ$ /(J·m^-2)	0.0826^[29]
进口风速/(m·s^-1)	12
转笼转速/(r·min^-1)	1200

图2 团聚体释放位置示意图

Fig.2 Schematic diagram of the release locations of aggregates

图3 三个不同位置释放的团聚体在分级流场中不同时刻的形态变化

Fig.3 The morphological changes of aggregates released in different locations at different time in classification flow field

图4 由4个颗粒组成的团聚体形成的不同接触数

Fig.4 Contact numbers formed by aggregate composed of four particles

图5 团聚体在分级流场中的接触率随时间变化情况

Fig.5 The changes of contact rate of aggregates in classification flow field

图6 团聚体在分级流场中的团聚率随时间变化情况

Fig.6 The changes of aggregation rate of aggregates in classification flow field

图7 团聚体单颗粒组成示意图

Fig.7 Schematic diagram of an aggregate composed of single particles

图8 团聚体内单颗粒受曳力情况

Fig.8 Drag force on the single particles in an aggregate

图9 团聚体内单颗粒相对位置变化情况

Fig.9 The changes of relative position of the single particle in an aggregate

图10 不同粒径单颗粒组成的团聚体示意图

Fig.10 Schematic diagram of aggregates composed of single particles with different particle sizes

图11 不同粒径单颗粒组成的团聚体的团聚率ξ和接触率Lk随时间变化情况

Fig.11 The changes of the aggregation rate ξ and contact rate Lk of aggregates with different single particle sizes

图12 不同颗粒数组成的团聚体示意图

Fig.12 Schematic diagram of aggregates composed of different particle numbers

图13 不同颗粒数组成的团聚体的团聚率ξ和接触率Lk随时间变化情况

Fig.13 The changes of aggregation rate ξ and contact rate Lk of aggregates with different particle numbers

图14 立方体、圆柱体及球形团聚体示意图

Fig.14 Schematic diagram of cubic, cylindrical, and spherical aggregates

图15 三种形状的团聚体的团聚率ξ和接触率Lk随时间变化情况

Fig.15 The changes of aggregation rate ξ and contact rate Lk for three different shapes of aggregates

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