超细颗粒在碰撞凝并作用下的尺寸分布变化

Change of Particle Size Distribution of the Ultr-Fine Particles Undergoing Coagulation

对于燃烧过程中生成的超细颗粒,其自身的布朗运动引起的细颗粒之间的碰撞以及与较大颗粒之间的碰撞是改变其尺寸分布的主要因素．基于矩方法,对颗粒的初始分布作出一个合理的正态对数分布假设,研究了超细颗粒在碰撞凝并作用下的颗粒尺寸分布的变化情况．并将所得到的结果与仅仅考虑细颗粒之间碰撞的结果进行对比．数值结果表明,在同时考虑两种碰撞时,布朗凝并碰撞的自保持特性发生了一定的变化;与仅仅考虑细颗粒之间的碰撞凝并时相比,颗粒初始的不均匀程度对最终的颗粒分布的影响增强,成为一个必须考虑的因素．

For the sub-micro particles generated in the combustion process, the main reason for the change of their size distribution is the coagulations caused by their Brownian motion. These coagulations of sub-micro particles include both the coagulation of particles among themselves and with bigger particles. Based on Moment Method, this article first gives particles a reasonable log-normal size distribution, then predicts the ciistribution extent when particles undergoing coagulations. And these results are compared with those when only coagulation among the sub-micro particles are considered. It shows that when both kinds of coagulation are considered, something has changed in the self-preserved characters of Brownian coagulation. Compared with the case when only coagulation among sub-micro particles is considered, the initial poly-disperse character has much stronger effects on the final particle size distribution and becomes an important factor that must be considered.