STUDY OF DYNAMIC BEHAVIOR OF NANOMETER-SIZED AEROSOL PARTICLES AND ION CLUSTERS

纳米气溶胶颗粒和离子团簇的动态行为研究

基本信息

批准号：
08650896
负责人：
KOUSAKA Yasuo
金额：
$ 1.47万
依托单位：
OSAKA PREFECTURE UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

In this research, dynamic behavior of nanometer-sized aerosol particles and ion clusters was studied by measuring with the differential mobility analyzer (DMA) combined with a condensation nucleus counter (CNC) or an electrometer (EM) as a particle detector. The results obtained can be summarized below. At the first year, a theoretical and experimental study of mobility shift in the case of extremely fine particles requiring low electric fields for their classification when performing aerosol size measurements with the DMA has been carried out. As a result, it was made clear that the mobility shift is due to (i) diffusive mixing of trajectories of different-sized particles, and (ii) the existence of a space-charge field in addition to the applied field. Furthermore, the most important results can be summarized thus : (i) particles smaller than the average are classified at voltages smaller than the ideal ; (ii) particles larger than the average are classified at voltages larger than th … More e ideal ; (iii) larger aerosol concentrations lead to larger shifts ; (iv) mobility shifts occur even at low aerosol concentrations due to Brownian diffusion effects ; and (v) mobility shifts are important only in the first DMA,and can be safely neglected for the second. At the second year, particle size measurement were done using a tandem DMA system to accurately determine the size of the particles on the basis of the results of the first year. Penetration of nanometer-sized particles through a wire screen and a laminar flow tube has been carried out. The results obtained can be summarized thus : (i) the presence of electrical charges in the particles do not affect their penetration behavior ; (ii) the existing theories, Cheng and Yeh for wire screens and Gormley and Kennedy for tubes, are accurate for particles with Stokes-Einstein diameter down to 2nm ; and (iii) particles do not rebound from the metallic surfaces, i.e., all the particle-metal collisions are effective, Furthermore, an experimental study of charging and neutralization of aerosol particles by bipolar air ions has been carried out. As a result, if adequate value of ion mobility and mass are chosen, our experimental results agree very well with Fuchs'theory for particles larger than about 3nm. In the size range below 3nm, deviations are considerable and abrupt. Less

在这项研究中，通过用降低迁移率分析仪（DMA）与凝结核电计数器（CNC）或电气机（EM）作为粒子探测器结合使用，研究了纳米尺寸的气溶胶颗粒和离子簇的动态行为。获得的结果可以总结下面。在第一年，对使用DMA进行气溶胶尺寸测量值时需要低电场进行分类的情况下，对迁移率转移的理论和实验研究进行了研究。结果，很明显迁移率移动是由于（i）不同大小颗粒的轨迹的不同混合，以及（ii）除了应用领域外，还存在空间荷尔兰的场。此外，可以总结最重要的结果：（i）小于平均值的颗粒在小于理想的电压下分类；（ii）大于平均值的颗粒的分类在大于……更理想的电压下；（iii）较大的气溶胶浓度导致较大的变化；（iv）即使在较低的气溶胶浓度下，由于布朗的差异效应，迁移率转移也会发生。（v）移动性转移仅在第一个DMA中很重要，并且可以安全地忽略第二个DMA。在第二年，使用串联DMA系统进行粒度测量，以根据第一年的结果准确确定颗粒的尺寸。已经对纳米尺寸的颗粒穿透了电线筛和层流管。因此，可以总结所获得的结果：（i）颗粒中存在电荷不会影响其穿透行为；（ii）现有的理论，用于金属丝网的Cheng和Yeh，Gormley和Kennedy用于试管，对于Stokes-Einstein直径降至2nm的颗粒对于颗粒是准确的；（iii）颗粒不会从金属表面反弹，即，所有粒子金属碰撞都是有效的，此外，还进行了双极气离子对气溶胶颗粒充电和中和的实验研究。结果，如果选择了足够的离子迁移率和质量值，我们的实验结果与大于3nm的颗粒的富奇理论非常吻合。在3nm以下的尺寸范围内，出发率相当大且突然。较少的