风对气溶胶粒子粒径演化过程影响的数值模拟

发布时间：2017-12-28 21:26

本文关键词：风对气溶胶粒子粒径演化过程影响的数值模拟　出处：《北京交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：生活在中国北方城市的人们近几年普遍感受到,雾霾的发生频率在不断增加,特别是在2013年其出现频率之多、持续时间之长、污染程度之重都创下了历史记录。面对大气环境不容忽视的严峻挑战,我们必须重视对雾霾问题的相关研究。虽然风对雾霾污染物的去除是显而易见的,其作用机理主要是通风输送作用和混凝成长作用,但是本文以气溶胶粒子的成长过程进行数值模拟计算,研究了风对气溶胶粒子的成长与去除作用。本研究模拟在一个密闭的空间内,均匀且不断地注入气溶胶粒子,注入的粒子通过混凝作用,其粒径随着时间呈一定的变化规律。研究采用的是Hounslow混凝动力学模型,布朗碰撞核选用了 Fuchs建立的过渡区混凝核,模拟采用MATLAB软件。首先通过粒子的数目分布模拟与前人所作的研究进行比对,检验了求解方法和计算程序的可靠性;紧接着模拟了在不同条件下的球形粒子和分形粒子的粒径分布演变,得出了在纯布朗作用下粒子的粒径演变规律,即注入源对球形粒子和分形粒子的粒径增长均起到了促进作用,其中,排放源对促进分形粒子的粒径增长效果更为显著;最后分别从剪切作用和通风作用两个方面进行模拟研究,讨论了风对球形粒子粒径演变的影响规律,得出剪切作用加快了粒子的混凝进程,而剪切和通风共同作用下粒径的增长最终会达到一个稳定值,且在一定范围内随着通风速率逐渐增大,粒径增长到达稳定值的时间越短,这是因为风对雾霾的水平搬运作用。
[Abstract]:People living in northern cities in recent years generally feel that the frequency of haze is increasing. Especially in 2013, the frequency of occurrence, duration and severity of pollution are all recorded. In the face of the severe challenges that can not be ignored in the atmosphere, we must attach importance to the study of the haze problem. Although the removal of haze pollutants is obvious, the mechanism is mainly the role of ventilation and transportation and coagulation. But in this paper, the growth and removal of aerosol particles are studied by numerical simulation of aerosol particle growth process. This study simulated the uniform and continuous injection of aerosol particles into a confined space, and the particle size of injected particles changed with time. The study adopted the Hounslow coagulation dynamic model, and the Brown collision core selected the transition zone coagulant core established by Fuchs, and simulated the MATLAB software. Compare the first through the simulation of particle distribution and the number of previous work, the reliability test method and calculation program; followed by the simulation of spherical particles and the fractal particle under different conditions of the particle size distribution of particles in the evolution of the pure Brown under the influence of grain size evolution, which is injected into the source of the spherical particles and the fractal particle size growth have played a role in promoting the emission source to promote the fractal particle size growth effect is more significant; the last were simulated from the two aspects of the shearing action and the role of ventilation, influence of wind on the spherical particle size evolution are discussed, that shear. To speed up the process of mixed particle coagulation, and shear and ventilation interaction under the particle diameter growth will eventually reach a stable value, and in a certain range with the ventilation rate gradually increased, the particle size increased to The shorter the time to reach the stability is due to the horizontal transport of the wind to the haze.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X513

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