纤维表面气溶胶粒子沉积与反弹行为数值模拟

Numerical simulation of particles deposition and rebound on fiber surface

在单纤维表面粉尘树枝生长随机模拟基础上,采用Dahneke碰撞反弹模型分析纤维过滤中气溶胶粒子碰撞反弹行为。讨论捕集体近壁区粒子碰撞反弹运动特性及其对沉积物形态结构和过滤单元捕集效率的影响。研究结果表明:随着粒子直径增大,粒子与纤维表面的碰撞反弹频率增大;输送粒子与沉积粒子发生多次碰撞反弹后仍有可能被捕集;所有过滤工况下,粒子碰撞反弹频率增大,均将导致沉积物向紧密结构演变;引入粒子碰撞反弹作用后,较低拦截参数下过滤单元捕集效率随沉积量的变化关系呈现出两阶段性特征,各阶段的变化关系仍满足近似线性,而较高拦截参数下过滤单元捕集效率随沉积量的变化关系未出现此特征;在相同黏附能下,多分散粒子的捕集效率均高于单分散粒子情形。

The growing process of particle dendrites on a single fiber was simulated by the Monte Carlo stochastic simulation technique.The behavior of aerosol particles collision,adhesion and rebound on surface of collectors（fiber or deposited particles） was therefore analysed using collision/rebound model developed by Dahneke.Particles rebound characteristics in near field of collectors,and effects on morphology of particle deposit and collection efficiency of filter element by particles rebound were investigated.The results indicate that the increase of particles diameters leads to the increase of the collision frequency,and the particles which experience multiple rebound upon with deposited particles are possibly captured.Increasing the collision frequency results in transition of the deposit from being rather dendritic and open to compact structures for all studied filtration conditions.Considering the mechanics of particles collision and rebound,two steps may be distinguished in evolution of the collection efficiency of filter element with deposit aspect for the higher value of the interception number.During the two steps,the evolution is linear,while it is not noticed for a smaller interception number.The collection efficiency for polydisperse particles is higher than that of monodisperse particles at the same adhesion energy.