- 學位論文
通過降維法加速篩板洗滌器中 顆粒清除的三維流場建模
Accelerating 3D Flow Modeling for the Particles Scavenging in a Sieve Plate Scrubber via Dimension Reduction
摘要
本研究建立了一個篩板洗滌器的計算流體動力學（CFD）模型,用以預測其顆粒去除效率。該模型亦能模擬出擴散及慣性機制交互作用而產生的粒子清除效率U型曲線。然而,於流場中跟蹤粒子的計算相當複雜,且硬體設備效能需求高,若使用三維(3D)流場結構來進行建模的試誤將花費大量時間,這將不利於找到適當的模型設置及洗滌塔設計。 為降低軟體計算的複雜性及時長,本研究提出了降維法來簡化三維流場至二維(2D)流場,用以分析連續流場施予粒子的力在不同的組合下,對粒子清除效率的影響。降維法及用戶自定義模型的合理性是通過2D及3D流場的泡沫密度的一致性來進行驗證。其中,流體施予粒子的力組合在2D流場中被分析,模擬結果顯示除了拖曳力之外,還應包含其他力(例如:升力,壓力梯度力,虛擬質量力等),才能正確地模擬篩板上的粒子流動情形。該力組合亦使得模擬在各種操作條件下,得到與文獻中實驗數據相符的結果。出乎意料地,該模型預測出粒徑由0.1至3.0μm的顆粒去除效率呈現U形曲線,且該現象無法由關係式預測而得。本文的最後, 使用具有與2D模型相同設置的3D模型來驗證兩者清除效率的一致性。結果表明, 2D模型與3D模型的粒子清除效率預測結果相當接近。
並列摘要
In this thesis, a computational fluid dynamics (CFD) model of a sieve plate scrubber was built to predict its particle-removal efficiency and predict the U-shaped curve of the particle-removal efficiency as particles became smaller. Due to the complexity of particle tracking, it takes considerable time to simulate the model by using a three-dimensional (3D) structure, which is not conducive to finding the appropriate setting of particle forces. Instead, this work presented a dimension-reduction method to estimate the particle force setting by using a two-dimensional (2D) structure. The rationality of the dimension-reduction method and user-defined function was validated by the consistency in froth density for both 2D and 3D models at various air-inlet velocities. Furthermore, the result of the particle forces setting showed that besides the drag force, other forces, such as the lift force, pressure-gradient force, gravity force, and virtual mass force, should be employed in the CFD model to predict the particle-removal efficiency of the sieve plate scrubber. The prediction results of the 2D model remarkably match the particle-removal efficiency results of experimental data from the literature for various gas velocities and particle sizes. In addition, the model predicts the U-shaped curve of the particle-removal efficiency for the particle-diameter range from 0.1 to 3.0μm. Furthermore, a 3D model with the setting of the particle forces as in the 2D model was used to validate the consistency between the 2D and 3D models. The result showed that the particle-removal efficiency of the 3D model was considerably close to the prediction results of the 2D model.