以計算流體力學電腦模擬輔助氣膠捕捉式衝擊器之設計研究

Computational Fluid Dynamics Modelling Assisted Design of Aerosol Trap Impactors

吳浩維(Hau-Wei Wu)

指導教授 ： 張幼珍

元智大學/工程學院/化學工程與材料科學學系/碩士(2005年)

摘要

本研究主要目的在利用計算流體力學套裝軟體－FLUENT來建構及驗證一個類似Biswas and Flagan (1988)實驗中所使用的氣膠捕捉式衝擊器的三維數值模型。模型驗證工作包括找出適當疏密度且計算有效率的網格、檢查物理模型裡的 pressure far field 對噴流音速流場與流速與微粒收集效率的影響、以及利用具有適當網格與物理參數設定的數值模型來模擬並與Biswas and Flagan (1988)的實驗數據進行比較。結果顯示模擬結果與實驗結果在最大和最小粒徑時都相當接近，Stk0.5=0.2和0.6，然而在Stk0.5=0.4時結果相差高達30%。
本研究最終目的在利用驗證過的模型來探討不同設計參數包括噴流到收集杯開口的距離、收集杯深度、收集杯開口的直徑、收集杯的直徑、對氣膠捕捉式衝擊器效能的影響。初步結果顯示，所有參數中，收集杯深度對收集效率的影響最大。

關鍵字

氣膠 ； 捕捉式衝擊器 ； 計算流體力學 ； 衝擊器設計研究 ； 收集效率

並列摘要

The main objective of this research is to utilize the computation fluid dynamics (CFD) package-FLUENT (Fluent, Inc., USA) to develop and validate a 3-dimensional CFD model for aerosol trap impactors. The model adopts a design resemble that of Biswas and Flagan (1988). Simulation were performed to validate the model by optimizing the mesh scheme, and to examine the effect of pressure far field setting on sonic jet velocity as well collection efficiency. The optimized model was validated against experiment by Biswas and Flagan (1988). Simulation results were found to agree with both the largest and the smallest particles sizes or Stk0.5 = 0.2 and 0.6, significant under-estimation, up to 30%, was found for Stk0.5 = 0.4. An investigation of design parameters including jet-to-cup opening distance, cup depth, cup opening diameter, and cup diameter on trap impactor performance was performed. Among the parameters investigated here, cup depth was found to affect collection efficiency most significantly.

並列關鍵字

aerosol ； computational fluid ； impactor design ； collection efficiency ； dynamics ； trap impactor

參考文獻

1. Asgharian, B., & Godo M. N. (1997). Transport and deposition of spherical particles and fibers in an improved virtual impactor. Aerosol Science and Technology, 27, 499~506.

2. Biswas, P., & Flagan, R. C. (1988). The particle trap impactor. Journal of Aerosol Science, 19, 113~121.

3. Brach, R. M., & Dunn, P. F. (1998). Models of rebound and capture for oblique microparticle impacts. Aerosol Science and Technology, 29, 379~388.

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6. Chen, B. T., & Yeh, H. C. (1987). An improved virtual impactor: design and performance. Journal of Aerosol Science, 18, 203~214.