Discrete element method based analysis of mixing and collision dynamics in adhesive mixing process
Discrete element method based analysis of mixing and collision dynamics in adhesive mixing process
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DOI：
10.1016/j.ces.2018.06.043
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发表时间：
2018-11
影响因子：
4.7
通讯作者：
Xiaoliang Deng;K. Zheng;R. Davé
中科院分区：
文献类型：
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作者：
Xiaoliang Deng;K. Zheng;R. Davé
当少量的细颗粒与较粗的颗粒混合时，它们往往会形成有序的或粘接的混合物。为了了解细颗粒量和黏聚力对胶粘剂混合过程的影响，采用表面能表示黏聚力的离散元法（DEM）进行了模拟。采用高强度振动混合来考察两个重要且相关的动力学过程；通过分析归一化的细颗粒（FF）和粗颗粒（CF）颗粒接触数以及混合质量，细颗粒脱团聚及其随后与粗颗粒的粘附。发现FF接触随着混合时间的延长而减少，表明在达到平衡之前存在脱团聚现象；而涂层指标CF接触量和混合质量在达到平衡前均有所增加。一个重要的新发现是在平衡状态下细颗粒与粗颗粒的数量服从对数正态分布。达到平衡的FF接触数和混合质量的时间尺度具有可比性，表明解团聚是实现均匀粘合剂混合物的主要因素。正如预期的那样，细颗粒表面能的增加导致混合质量的降低，这是由于更强的团聚体不能被碰撞打破。另一方面，只要碰撞能量大于细颗粒团聚体相应的脱离能量，碰撞率可以决定混合质量。选定的实验结果验证了DEM模拟及其描述胶粘剂混合过程的能力。
When small amounts of fine particles are mixed with coarser particles, they tend to form ordered or adhesive mixtures. In order to understand the effect of fine particle amount and cohesion on the adhesive mixing process, discrete element method (DEM) simulations are carried out in which cohesion is represented by surface energy. High-intensity vibrational mixing was used to examine two important and related dynamic processes; fine particle deagglomeration and their subsequent adhesion to coarse particles, by analyzing normalized fine-fine (FF) and coarse–fine (CF) particle contact numbers, respectively, along with the mixing quality. It is found that FF contacts decreases with the mixing time, indicating deagglomeration, before reaching equilibrium; while CF contacts, an indicator of coating, as well as mixing quality increase before reaching equilibrium. A major new finding is that the number of fine particles per coarse particle at equilibrium follows lognormal distribution. The time scales to reach equilibrium FF contact number and mixing quality are comparable, indicating that deagglomeration is the dominant factor for achieving a uniform adhesive mixture. As expected, increasing surface energy of fine particles leads to decreased mixing quality due to stronger agglomerates that cannot be broken by collisions. On the other hand, collision rate can dictate mixing quality, as long as the collision energy is greater than the corresponding detachment energy of fine particles agglomerates. Selected experimental results validate the DEM simulations and their ability to describe the adhesive mixing process.