以數值模擬研究虛擬衝擊器的設計與氣膠微粒粒徑的純化收集及分類

The Numerical Study of Virtual Impactor Design and Aerosol Sizes Purification /Separation

　　本研究是以數值模擬研究虛擬衝擊器的設計與氣膠微粒粒徑的純化收集及類。本虛擬衝擊器的設計如圖1，氣膠微粒從樣品流進入管道後，由邊鞘流將樣品流做流體聚焦。藉由下游的側邊流使氣膠微粒因垂直方向及水平方向的拖曳力比較，而選擇由垂直方向及水平方向出口達到純化及分離氣膠微粒粒徑的目的。由於氣膠的動量反應時間是非常短的(大約為10-4)，在這樣短的動量反應時間，氣膠微粒是隨著流場所移動。因此虛擬衝擊器的流場對氣膠微粒的分離與純化扮演著很關鍵的因素。在此研究的模擬結果，可將樣品流速與邊鞘流速的比例作無因次的分析，而得到一操作曲線圖，可提供分離或純化氣膠微粒粒徑的操作參數。同時也發現，氣膠微粒粒徑分離的選擇性取決於時間因素，即氣膠微粒在流經右側出口的路徑時間L/V與氣膠微粒在管道移動的時間(D/2)/U比。

關鍵字：氣膠、虛擬衝擊器、數值模擬

ABSTRACT

　　This study is based on numerical simulation of the virtual impactor design and aerosol sizes purification of collection and classification. The design of the virtual impactor is shown in Figure 1. Aerosol particles were introduced from the sample flow channel and focused by the two side of sheath flow. The aerosol were sizes purification and purification due to the drag force compared by the downstream side flow and the main stream. The momentum response time of the aerosol was as short as the order of 10-4. The aerosol will moving with the flow field in such a short momentum response time. Therefore, the flow field of virtual impactor plays a very crucial factor of aerosol particles separation and purification. The simulation results In this study show by non-dimensional the ratio of sample flow and sheath flow will get a curve of operation. The curve of operation could provide the operating parameters aerosol particle size separation or purification. Also found that aerosol particle size selectivity of separation depends on the time factor. The time compared by aerosol flow through the channel of L/V and (D/2)/U.

Kewwords: Aerosol、Virtual Impactor、Numerical Simulation