Development of Technology for Separation and Enrichment of Nano-Aerosol Particles

1)确定了超音速虚拟冲击器作为纳米粒子分离器和浓缩器的最佳几何形状：数值研究了拉瓦尔喷管的超音速二分采样器作为分离器的性能、喷嘴截面形状(矩形和圆形)、喷嘴出口与粒子收集探头入口之间的间隙以及探头几何形状对分离特性的影响。分析了沿喷管壁面和中心的鞘流对分离特性和颗粒壁面损失的影响。超音速二分取样器的设计目的是使流动类似于停滞流动，在喷嘴出口和收集探头入口之间提供明显的驻波。收集探头入口处到驻波的距离越小，与颗粒的截止尺寸有关。鞘气流提高了分离锐度，降低了颗粒…。更多的壁面损失2)设备的设计和性能的调查：根据调查的结果设计的设备1)配备了在环境空气中对气态多环芳烃的分离性能和行为进行了研究。3)纳米粒子分离器和浓缩器的改进：根据实验结果对装置进行了改进和改进。4)总结：根据研究结果，提出了超音速冲击器的设计准则。在常压条件下，矩形喷嘴的截止尺寸为200-300 nm，圆形喷嘴的最小截止尺寸为50-80 nm。由于超音速流动高度饱和，气态多环芳烃化合物和有机碳被有效地收集在超音速流动下游。水蒸气在超音速流动中凝结，水滴上聚集了溶解度较高的气态多环芳烃化合物Nap、Ace、Phe。将气态化合物在过饱和状态下的沉积或冷凝与水滴的沉积相结合，利用预置技术可以有效地收集气态化合物。较少

1)Determination of optimal geometry of supersonic virtual impactor as a nano-particle separator and concentrator : A supersonic dichotomous sampler with a Laval nozzle was numerically investigated into its performance either as a separator or a shape of nozzle cross-section (rectangular and circular), clearance between nozzle exit and particle collection probe inlet, and probe geometry on the separation characteristics were simulatively investigated. The effect of sheath flow along the nozzle wall and center on the separation characteristics and the particle wall loss were also analyzed. The supersonic dichotomous sampler was designed to make the flow as similar to the stagnation flow, which provided a distinct standing shock wave between the nozzle exit and the collection probe inlet. The smaller distance from the collection probe inlet to the standing shock wave was related to the cutoff size of particle. The sheath air flow improved the separation sharpness and reduced the particle … More wall loss.2)Devising of equipment and investigation into performance : The devise designed as the result of the investigation 1) was equipped and the separation performance and behavior of gaseous PAHs were investigated using the ambient air. Influence of humidity was shown to be significant for gaseous PAHs compounds with higher water solubility.3)Improvements of nano-particle separator and concentrator : The devise was modified and improved based on the results 2). The nozzle geometry and probe geometry were adjusted.4)Summary : According to obtained results, the guideline for the design of supersonic impactor was proposed. The cutoff size of the rectangular nozzle is 200-300nm under the ambient pressure condition while the circular nozzle has 50-80nm of the minimal cutoff size. Gaseous PAH compounds and organic carbon was shown to be effectively collected in the downstream of supersonic flow due to the highly saturated condition. The water vapor was condensed in the supersonic flow and gaseous PAH compounds such as Nap, Ace, Phe, which have higher water solubility were collected on the water droplet. Combining the deposition or condensation of gaseous compounds in the supersaturated condition and deposition to water droplets, the gaseous compounds can be effectively collected using the preset technique. Less