本文關鍵詞：風對氣溶膠粒子粒徑演化過程影響的數值模擬　出處：《北京交通大學》2017年碩士論文　論文類型：學位論文

  更多相關文章： 大氣環(huán)境 氣溶膠粒子 混凝 粒徑分布

【摘要】：生活在中國北方城市的人們近幾年普遍感受到,霧霾的發(fā)生頻率在不斷增加,特別是在2013年其出現頻率之多、持續(xù)時間之長、污染程度之重都創(chuàng)下了歷史記錄。面對大氣環(huán)境不容忽視的嚴峻挑戰(zhàn),我們必須重視對霧霾問題的相關研究。雖然風對霧霾污染物的去除是顯而易見的,其作用機理主要是通風輸送作用和混凝成長作用,但是本文以氣溶膠粒子的成長過程進行數值模擬計算,研究了風對氣溶膠粒子的成長與去除作用。本研究模擬在一個密閉的空間內,均勻且不斷地注入氣溶膠粒子,注入的粒子通過混凝作用,其粒徑隨著時間呈一定的變化規(guī)律。研究采用的是Hounslow混凝動力學模型,布朗碰撞核選用了 Fuchs建立的過渡區(qū)混凝核,模擬采用MATLAB軟件。首先通過粒子的數目分布模擬與前人所作的研究進行比對,檢驗了求解方法和計算程序的可靠性;緊接著模擬了在不同條件下的球形粒子和分形粒子的粒徑分布演變,得出了在純布朗作用下粒子的粒徑演變規(guī)律,即注入源對球形粒子和分形粒子的粒徑增長均起到了促進作用,其中,排放源對促進分形粒子的粒徑增長效果更為顯著;最后分別從剪切作用和通風作用兩個方面進行模擬研究,討論了風對球形粒子粒徑演變的影響規(guī)律,得出剪切作用加快了粒子的混凝進程,而剪切和通風共同作用下粒徑的增長最終會達到一個穩(wěn)定值,且在一定范圍內隨著通風速率逐漸增大,粒徑增長到達穩(wěn)定值的時間越短,這是因為風對霧霾的水平搬運作用。
[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.
【學位授予單位】：北京交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：X513

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本文編號：1347493