具有中心淨氣柱的虛擬衝擊器之設計與應用

A Virtual Impactor with Clean Air Core: Design and Application

本研究設計構造一個具有中心淨氣柱的虛擬衝擊器，使用兩組加速噴嘴及收集孔，其進入總氣流量可從7到85lpm，可選擇的截取直徑範圍從10到40μm，此虛擬衝擊器具有幾近100%的微粒分離效率以及非常低的微粒損失。此外，本研究應用所設計之虛擬衝擊器進一步去除細小的氣膠，避免因微粒小於偵測極限所成之疊合誤差（Coincidence Errors）及假數微粒（Phantom Particles），因此增加氣動微粒粒徑計APS的量測準確性。本文亦將討論改良式虛擬衝擊器的理論與設計準則。

A virtual impactor with clean air core was designed, fabricated, and tested. This improved virtual impactor was demonstrated to have nearly 100% particle separation efficiency and little wall loss. The inlet total flow rate could be ranged from 7 to 85 lpm and the selectable cut-point diameter varied from 10 to 40μm. The improved virtual impactor employed two sets of acceleration nozzle and collection probe. The clean air core was shown to totally eliminate fine particle contamination in the collection probe. The theory and design of virtual impactors would be discussed. The improved virtual impactor was successfully employed to remove fine particles which were below the lower detection limit of Aerodynamic Particle Sizer (APS) and, therefore, reduced the phantom particles and coincidence errors of APS measurements. The experimental data showed that the APS measurement data was more accurate without phantom particles and coincidence errors.