基于CFD-DEM模腔填充过程中颗粒分离行为分析

Analysis of particle separation behavior during cavity filling process based on CFD-DEM

为综合分析不同工况下三元颗粒混合物填充模腔的分离行为,采用计算流体力学-离散单元法(CFD-DEM),模拟高密度、无黏性颗粒混合物填充模具过程,并研究送料速度、颗粒生成方式、送料机构壁面斜度、模具形状与深度以及环境空气等多种因素对其分离行为的影响。结果表明,增加送料机构行进速度,可在行进方向上显著抑制大粒径颗粒的分离行为,降幅高达71%,而在其他方向上对其分离行为的影响较小;降低送料机构壁面斜度、适当加大模具深度均能提高颗粒混合物在模腔内的分布均匀度;分层生成方式产生的颗粒混合物,位于中间层颗粒群的分离行为受到显著抑制,分离指数最小仅为0.8;模腔内的空气会在颗粒填充时发生逸散从而迟滞细颗粒的运动,使得约40%的细颗粒在局部区域集聚,不利于颗粒混合物在模具内的均匀分布。

In order to comprehensively analyze the separation behavior of the ternary particle mixture filling the mold cavity under different working conditions, the computational fluid dynamics-discrete element method(CFD-DEM) was used to simulate the process of filling the mold with a high-density, non-viscous particle mixture. The effects of various factors such as feeding speed, particle generation method, wall inclination of feeding mechanism, mold shape and depth, and ambient air on its separation behavior were studied. The results show that increasing the travel speed of the feeding mechanism can significantly inhibit the separation behavior of large-sized particles in the travel direction, and the drop rate is as high as 71%, while the effect on the separation behavior in other directions is small. Reducing the wall slope of the feeding mechanism and appropriately increasing the depth of the mold can improve the distribution uniformity of the particle mixture in the mold cavity. For the particle mixture produced by the layered generation method, the separation behavior of the particle group located in the middle layer is significantly suppressed, and the minimum separation index is only 0.8. The air in the mold cavity will escape when the particles are filled, which will retard the movement of the fine particles, causing about 40% of the fine particles to accumulate in the local area, which is not conducive to the uniform distribution of the particle mixture in the mold.