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

1)确定超音速虚拟冲击器作为纳米颗粒分离器和浓缩器的最佳几何形状：数值研究了带拉瓦尔喷嘴的超音速二分采样器作为分离器或喷嘴截面形状（矩形和圆形）的性能、喷嘴出口与颗粒收集探头入口间隙以及探头几何形状对分离特性的影响。分析了沿喷嘴壁和中心的鞘层流动对分离特性和颗粒壁损失的影响。设计了超声速二分采样器，使其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。收集探头入口到驻激波的距离越小，与颗粒的截止尺寸有关。护套气流提高了分离锐度，减少了颗粒壁损失。2)设备设计及性能调查：根据调查结果设计的设备1)安装并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。湿度对水溶性较高的气态多环芳烃化合物影响显著。3)纳米颗粒分离器和选矿厂的改进：在2)的基础上对设计进行了改进和改进。调整了喷嘴几何形状和探头几何形状。4)总结：根据所得结果，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200-300nm，圆形喷嘴的最小截止尺寸为50-80nm。由于超声速流的高度饱和状态，气态多环芳烃化合物和有机碳被有效地收集在下游。水蒸气在超声速流动中凝结，在水滴上收集了水溶性较高的Nap、Ace、Phe等气态多环芳烃化合物。将气态化合物在过饱和状态下的沉积或冷凝与沉积成水滴相结合，采用预设技术可以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