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

1)超声速虚拟撞击器作为纳米颗粒分离器和浓缩器的最佳几何形状的确定：数值研究了具有拉瓦尔喷嘴的超声速二分采样器作为分离器或喷嘴横截面形状（矩形和圆形）的性能，模拟研究了喷嘴出口与颗粒收集探针入口之间的间隙以及探针几何形状对分离特性的影响。分析了沿喷嘴壁面和中心沿着的鞘流对分离特性和颗粒壁面损失的影响。设计了超声速二分采样器，使流动类似于滞止流，在喷嘴出口和收集探头入口之间提供明显的驻激波。收集探头入口到驻激波的距离越小，与颗粒的截止粒径有关。鞘层气流的引入提高了分离的尖锐度，降低了分离过程中的颗粒 关于我们 2）设备设计和性能研究：根据1）的研究结果设计的设备被装备，并且使用环境空气来研究气态PAHs的分离性能和行为。湿度对水溶性较高的气态多环芳烃化合物有显著影响。3）纳米颗粒分离器和浓缩器的改进：在此基础上对装置进行了改进。对喷管和探头的几何形状进行了调整。4）总结：根据计算结果，提出了超声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，而圆形喷嘴的最小截止尺寸为50- 80 nm。气态多环芳烃化合物和有机碳被证明是有效地收集在下游的超音速流，由于高度饱和的条件。水蒸气在超声速气流中冷凝，水溶性较高的气态多环芳烃化合物如Nap、Ace、Phe等聚集在水滴上。将气态化合物在过饱和条件下的沉积或冷凝与沉积成水滴相结合，可以使用预设技术有效地收集气态化合物。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