一個多階衝擊器內的微粒反彈及溼度的影響研究

Abstract

本研究主要的目的在於探討相對溼度對MOUDI (micro-orifice uniform deposit impactor)多階衝擊器內微粒彈跳造成的微粒濃度分佈影響，而MOUDI入口的溼度控制的方式是以一個Nafion 乾燥器來達成的。以塗敷矽油鋁箔為衝擊板基質的MOUDI為參考標準，若相對溼度低至15%左右，未塗敷基質的MOUDI測得的奈米微粒濃度約高估兩倍左右；相對溼度50%時則會高估一倍以上；但相對溼度提升至77%以上時，奈米微粒幾無高估情形發生。然而在以上三種溼度下，本研究發現未塗敷矽油的MOUDI的細微粒粒徑分佈與塗敷矽油鋁箔的MOUDI並無顯著的差異。若塗敷的鋁箔換成未塗敷的鐵氟龍濾紙時，本研究也發現在不同溼度下使用鐵氟龍濾紙的MOUDI的細微粒粒徑分佈，與塗敷矽油鋁箔的MOUDI並無顯著的差異。在相對溼度25%左右時奈米微粒會高估50%；若將相對溼度提升至100%左右後，未塗敷的鐵弗龍與已塗敷的鋁箔所收集的濃度差異在14%內，大幅改善了微粒彈跳對奈米微粒濃度的影響。

This study aims at investigating the effect of the relative humidity (RH) on particle bounce occurred in the MOUDI (micro-orifice uniform deposit impactor) which influences particle mass distributions. A Nafion dryer was used to control the relative humidity at the inlet of the MOUDI. Using the MOUDI which used coated aluminum (AL) foils as the impaction substrates as a reference standard, it was found that the PM0.1 (or nanoparticle) concentrations measured by the MOUDI which used uncoated AL substrates were overestimated. The nanoparticle concentration was overestimated two times and one time, respectively, when the RH was 15 % and 50 %. When the RH was increased to 77 %, the nanoparticle concentration difference was reduced to below 10 % or the effect of particle bounce was largely eliminated. However, there were no significant differences between the mass distributions of the MOUDI using uncoated AL substrates with those of the MOUDI using coated AL substrates. Using uncoated Teflon filters as the substrates, the measured mass distributions were not significantly different from those of the MOUDI using coated AL substrates either. The nanoparticle concentration was overestimated by 50 % when the RH was about 25 %; the overestimation was reduced below 14 % when the RH was increased to about 100 %. The effect of particle bounce on nanoparticle concentration is reduced substantially using Teflon filters as the substrates of the MOUDI.