亚微米微粒的捕集技术研究

发布时间：2018-01-16 10:48

本文关键词：亚微米微粒的捕集技术研究　出处：《中国计量大学》2016年硕士论文　论文类型：学位论文

【摘要】：亚微米微粒因具有复杂的运动特性以及荷电特性,使对其捕集造成极大困难,因此有必要对此粒径段颗粒的捕集技术及其效果进行研究。本文在对亚微米微粒的静电捕集理论研究的基础上,采用实验和数值模拟两种方法研究静电捕集技术对亚微米微粒的捕集效果并分析影响捕集效率的各种参数,并对其捕集前后的粒径谱进行对比分析。实验设计搭建静电捕集装置平台,采用快速粒径谱仪和质量浓度测量仪测量颗粒捕集前后的颗粒数量浓度和质量浓度,分析正负离子荷电、极板层数、背景浓度和电压对颗粒捕集效率的影响,以及粒径谱的变化特征。研究表明:负离子荷电后的数量和质量捕集效果都比正离子荷电后的捕集效果要好;增加电极板的层数会明显提高颗粒的捕集效率,但其效率的增加不会成倍的增加,且其增加量逐渐减小;颗粒的捕集效率随着电压的增大先增大后减小,每个极板间距都有一个最佳电压;颗粒的捕集效率与其背景浓度成指数变化关系,其捕集效率在未到达90%之前随着背景浓度增大而快速增加;捕集前的粒径谱成单峰分布,峰值在100nm到200nm之前,捕集后的粒径谱也成单峰分布,但其峰值处较捕集前平滑许多。数值模拟采用Fluent软件对颗粒轨迹进行仿真计算,应用udf编程添加电场力的作用,模拟研究电压和极板间距对颗粒在捕集通道内的运动轨迹的影响。模拟显示,在其它条件相同的情况下,极板间电压越大,颗粒的运动轨迹的偏移量就越大;极板间距越大,颗粒轨迹的偏移量越小;在同一极板间距和同一电压下,颗粒捕集装置对颗粒的偏移量和捕集效率随着粒径的增大成增大的趋势,但粒径在200nm时其捕集效率增加较快,粒径在500nm时,其捕集效率会有所下降。原因是在200nm到500nm之间的颗粒同时受扩散荷电和场致荷电作用并饱和荷电,因此在此段粒径段的荷电量较大。
[Abstract]:It is very difficult for submicron particles to trap because of their complex motion and charge characteristics. Therefore, it is necessary to study the trapping technology and its effect of this particle size segment. This paper is based on the electrostatic trapping theory of submicron particles. The effect of electrostatic trapping on submicron particles was studied by means of experiment and numerical simulation, and various parameters affecting the trapping efficiency were analyzed. And the particle size spectrum before and after trapping was compared and analyzed. The electrostatic trapping device platform was designed and built. The quantity and concentration of particles before and after capture were measured by fast particle size spectrometer and mass concentration measuring instrument. The effects of positive and negative ion charge, plate number, background concentration and voltage on particle trapping efficiency were analyzed. The results show that the quantity and mass trapping effect of negative ion charged is better than that of positive ion charge. Increasing the layer number of the electrode plate can obviously improve the trapping efficiency of particles, but the increase of the efficiency will not increase by many times, and the increasing amount will gradually decrease. The particle trapping efficiency increases first and then decreases with the increase of voltage, and each plate spacing has an optimum voltage. The trapping efficiency of particles is exponentially related to the background concentration, and the trapping efficiency increases rapidly with the increase of background concentration before reaching 90%. The particle size spectrum before capture is a single peak distribution, the peak value is before 100nm to 200nm, and the particle size spectrum after trapping is also a single peak distribution. However, the peak value is much smoother than that before trapping. Fluent software is used to simulate the particle trajectory, and the effect of electric field force is added by udf programming. The effects of voltage and plate spacing on the trajectory of particles in the trapping channel are studied. The simulation results show that the larger the voltage between the poles is, the greater the migration of the particle trajectory is under the same conditions. The larger the polar plate spacing, the smaller the migration of particle trajectories. Under the same plate spacing and same voltage, the migration and the capture efficiency of the particle trapping device increase with the increase of the particle size, but the trapping efficiency increases faster when the particle size is 200 nm. When the particle size is 500nm, the trapping efficiency decreases, because the particles between 200nm and 500nm are simultaneously charged by diffusion charge and field charge and saturated charge. Therefore, the charge at this stage of particle size is larger.
【学位授予单位】：中国计量大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X701.2;X513

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