慣性效應影響微粒沉積率之研究

A Study of Inertial Effect on Particle Deposition Rates

蔡瑞益(R. Tsai) ； 張永鵬(Y. P. Chang) ； 梁龍驥(L. J. Liang) ； 涂育麟(Y. L. Tu)

《中原學報》 30卷3期 (2002/09) Pp. 323-329

https://doi.org/10.6358/JCYU.200209.0323

摘要

本文探討氣懸浮微粒在楔形流中受惯性和布朗擴散效應作用時，微粒沉積率所產生之差異，這兩種傳輸機制的交互作用，對微粒附著率具有相當重要性。慣性效應之無因次參數定義為修正史托克數(Stk(下標 x))，修正史托克數是由微粒鬆弛時間與區域流場時間之比值所構成。本文採二維楔形層流模型，制御方程式包括動量及濃度場方程式，在求解的過程中採方塊消去法解動量及濃度場方程式，進而計算微粒附著速度或附著參數。在慣性及擴散效應影響下，當Stk(下標 x)很小時，微粒附著率乃受布朗擴散效應支配，但當Stk(下標 x)增大時擴散效應趨減而慣性效應之影響趨增。另在不角度之楔形板塊，微粒受慣性效應影響情形亦不相同。

關鍵字

楔形流 ； 慣性效應 ； 相似分析法

並列摘要

Combined effects of inertial and Brownian diffusion on particle deposition onto wedges are reported. The two effects are important mechanisms for particle deposition. We introduced the modified Stokes number(Stk(subscript x)), which is defined as the ratio of the characteristic stopping time of a particle to the local flow time, as the dominate parameter to the inertial effect. In this study, the flow was modeled as a two-dimension laminar flow. The governing equations include the conservation of mass, momentum, and particle transport. Similarity method was used to transform these governing equations. The particles transport equation became a nonsimilar form. Box method was used to solve the equations and obtained flow field and particle concentration. The results showed that particle deposition rates are controlled by Brownian diffusion effect for particles of small Stk(subscript x).However, when the particle Stk(subscript x)increases, the inertial effect becomes important and Brownian diffusion effect may be negligible. Also the inertial effects on particle deposition rates for different wedge angles were examined.

並列關鍵字

wedge flow ； inertial effect ； similarity analysis