臺灣博碩士論文加值系統

本研究採用數值模擬的方式，搭配田口法在不同文氏管幾何尺寸下找出空氣吸入量最佳的尺寸組合。流場利用計算流體力學軟體 FLUENT進行模擬，而最佳幾何參數尺寸組合則採用田口法分析。針對前段距離L、喉部直徑D2、後段距離L2做探討，瞭解在文氏管內流場的變化情形及不同尺寸組合的空氣吸入量。
研究結果顯示當流體經過文氏管喉部時，由於流速的加快、壓力減少，進而自動吸入連接管路的空氣，形成空氣與水的液氣混合流。當水流過喉部進入漸擴區因重力作用及空氣擠壓，使得水流漸漸往下沉，此現象一直發展到文氏管尾端。同時因壁面阻力作用，使得水帶動空氣迴流產生渦流現象。
而藉由FLUENT的流場模擬與田口法的幾何參數分析，發現更改後段距離L2能有效增加空氣吸入量。在本研究所設定幾合參數尺寸範圍內，當尺寸組合為前段距離L=10mm、喉部直徑D2=2mm、 後段距離L2=70mm，可獲得最大空氣吸入量為3.47e-5 kg/sec。且經由驗證得知最佳實驗值落在預測值區間內，證明參數分析結果合理。

In this study, the geometric parameter combination for optimal air intake was found by numerical simulation and Taguchi method under different Venturi geometry sizes. The flow field was simulated by FLUENT, a computational fluid dynamics (CFD) software, and the optimal geometric parameter combination was analyzed by Taguchi method. The changes of the flow field in Venturi tube and the air intake amount of different size combinations were studied in terms of the distance L in the front section, throat diameter D2 and distance L2 in the back section.
The results show that when the fluid flows through the throat of the Venturi, the air connected to the tube is automatically sucked in due to the acceleration of the fluid flow and the reduction of pressure, and a mixture of air and water is formed. When the water flow through the throat into the expansion section due to the gravity and air extrusion effects make the water gradually sinking, this phenomenon has been developed to the end of a Venturi tube. At the same time, due to the resistance of the wall, the water drives the air both to flow back and produce a recirculation.
By flow field simulation with FLUENT and geometric parameter analysis with Taguchi method, it is found that changed distance L2 can effectively increase the mass flow rate of intake air. Within the range of several parameter sets in this study, when the size combination is L=10mm in the front, D2=2mm in the throat, and L2=70mm in the back, the maximum intake air can be obtained as 3.47e-5kg/sec. It is also proved that the optimal experimental value falls within the predicted range, which proves that the result of parameter analysis is reasonable.

摘 要......................i
Abstract..................ii
誌謝......................iii
目錄 .................iv
表目錄 ..................vi
圖目錄 .................vii
符號說明....................x
第一章 緒論.................1
1.1 前言....................1
1.2 文獻回顧............... 3
1.3 研究動機................8
1.4 研究目的................9
1.5 論文架構................9
第二章 理論分析.............10
2.1 物理模型................10
2.2 紊流模式................12
2.3 壁面函數................14
2.4 邊界條件................15
2.4.1 入口邊界條件..........15
2.4.2 出口邊界條件..........16
2.4.3 壁面邊界條件..........16
2.5 分析求解流程............16
2.6 網格獨立性測試...........18
2.7 時間步距大小測試.........19
2.8 數值模擬驗證.............20
第三章 田口法品質工程.........22
3.1 品質工程發展歷史.........22
3.2 參數設計的程序...........23
3.3 品質特性.................24
3.4 田口法選擇因子............25
3.5 田口直交表...............26
3.6 變異數分析...............27
第四章 結果與討論 .............30
4.1數值模擬分析............... 30
4.2田口法分析................. 48
4.2.1田口法資料分析.............48
4.2.2變異數分析................51
4.2.3確認實驗結果...............52
4.2.4最佳幾何參數組合之數值模擬.. 53
第五章 結論與建議................63
5.1結論........................63
5.2未來研究方向之建議............64
參考文獻........................65
Extended Abstract...........68

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