符合可呼吸性粉塵曲線之慣性衝擊器研發

Development of a Personal Inertial Impactor for Respirable Dust Sampling

本研究探討使用多孔聚酯泡綿及多孔金屬片作為個人粉塵分徑之慣性衝擊器的採樣介質時，在不同噴嘴直徑及不同採樣流量下慣性衝擊器的微粒貫穿曲線。研究結果顯示，具有多孔聚酯泡綿收集板慣性衝擊器的微粒貫穿曲線較多孔金屬片收集板慣性衝擊器的微粒貫穿曲線為平緩，並且具有較小的截取氣動直徑。此外，使用多孔介質為收集板的慣性衝擊器的微粒貫穿率會隨著採樣流量的增加而減少。這是因為較多氣流貫穿進入多孔介質內部，導致微粒收集效率提高。本研究利用數值方法模擬多孔聚酯泡綿收集板慣性衝擊器的流場、微粒運動軌跡及微粒貫穿曲線。結果顯示，靠近中心線的氣流流線，較容易貫穿進入多孔聚酯泡綿內部，遠離中心線的氣流流線則不容易進入多孔聚酯泡綿內部。對於較小粒徑微粒而言，由於微粒的慣性力較小，微粒的運動軌跡接近於氣流流線，然而對於較大粒徑微粒，微粒軌跡偏離相對應的氣流流線。數值模擬多孔聚酯泡綿收集板慣性衝擊器的微粒貫穿曲線與實驗數據有良好的一致性。研究結果顯示，當噴嘴直徑為 0.36cm，採樣流量為 1.9L/min 時，多孔聚酯泡綿收集板慣性衝擊器的微粒貫穿曲線非常接近可呼吸性粉塵曲線。

This research investigated the particle penetration curves of inertial impactors using porous foam and porous metal discs as impaction substrates under different nozzle diameters and sampling flow rates. The penetration curve of impactors with the porous foam is less sharp than those with porous metal discs. The impactor with porous foam has a smaller cut-off aerodynamic diameter. In addition, the particle penetration of impactors with porous substrates is reduced with an increase in the sampling flow rate. This is because more air penetrates into the porous substrates, resulting in higher particle collection efficiency. Numerical simulations were conducted to simulate flow field and particle trajectory, and to obtain the penetration curve of impactors with porous foam. The result shows that the streamline close to the centre line penetrates into the porous foam, while the streamline far away from the centre line is not apt to penetrate more easily. For small particles, because the inertial force of the particle is relatively small, the particle trajectory approaches the streamline; but for large particles, the particle trajectory deviates from the corresponding streamline. There is good agreement between the numerical results and the experimental data for the particle penetration of impactors with porous foam. The result shows that when the nozzle diameter is 0.36 cm and the sampling rate is 1.9 lpm, the penetration curve of the impactor with porous foam can be close to the respirabe dust curve.