Abstract:

Microscopic particles are not only the main cause of haze but also can carry toxic substances that can be adsorbed into the human lungs, posing a threat to human health. Heterogeneous condensation technology, considered as one of the most promising dust removal technologies, effectively enhances the efficiency of gas-solid separation by forming a liquid film on the particle surface. However, the collision and coalescence mechanisms of micrometer-level wet particles are not yet fully understood. Therefore, this study focused on micrometer-level condensable wet particles and established a model that integrates two-phase flow, continuous surface tension, and overlapping grids to investigate the dynamic changes of particles and liquid bridges during the collision process. By analyzing the effects of surface tension coefficient, liquid film thickness, and relative velocity before collision on particle collision behavior, the study summarized the laws of particle dynamics during collision and the energy dissipation situation, providing a theoretical basis for improving the aggregation effect of wet particles and enhancing dust removal performance. The results indicated that in normal collisions, wet particles followed a motion pattern of liquid film deformation, rebound, coalescence, or separation. Moreover, reducing the surface tension coefficient and liquid film thickness while increasing collision velocity led to an increase in the height of the liquid bridge. As for energy dissipation, pressure resistance and energy loss caused by surface tension were the dominant factors, while energy loss due to viscous resistance can be neglected.

Key words: microscale, condensable particles, collision, numerical simulation, energy dissipation

摘要：

微细颗粒不仅是造成雾霾的主要原因，还会携带可吸附有毒物质进入人体肺部，危害人体健康。异质凝结技术作为最有前景的除尘技术之一，通过在颗粒表面形成液膜有效提高了气固分离效率。然而，目前对微米级湿颗粒的碰撞和聚并机制尚未完全明确。本文针对微米级可凝结湿颗粒，基于Fluent软件构建了耦合两相流动、连续表面张力模型和重叠网格的模型，研究微米级湿颗粒碰撞过程中颗粒和液桥的动态变化过程。通过分析表面张力系数、液膜厚度和碰撞前相对速度对颗粒碰撞行为的影响，总结了碰撞过程颗粒动力学变化规律及能量耗散情况，为改善湿颗粒的聚合效果和提升除尘性能提供了理论基础。结果表明，湿颗粒在法向碰撞中遵循液膜变形、反弹和聚并或分离的运动模式。同时，减小液膜表面张力系数、减小液膜厚度、提高碰撞前相对速度都会使液桥高度增加。在动能耗散方面，压差阻力和表面张力引起的能量损失是主导因素，而黏性阻力的能量损失可忽略不计。

关键词: 微尺度, 可凝结颗粒物, 碰撞, 数值模拟, 能量耗散