摘 要

本論文旨在以數值模擬方式探討機車化油器前端節流閥體內，於不同管內徑與閥開度情況下，流量與流場結構變化之情形。在節流閥體彎管流場中，流體會因離心力及壁面效應而在流場中產生二次渦漩流(Secondary Swirl Flow)，再加上內部閥開度不同所引發之尾流(Wake Flow)與迴流(Recirculation Flow)，更加劇流場之複雜性。此外，由於本研究進行分析之個案多達九種，不論網格系統與流場結構均相當複雜，故本論文使用不同之CFD套裝軟體，分別進行網格系統製作與流場模擬分，一方面可加速研究工作之進行，另一方面則可測試不同軟體間介面連結之能力。
本研究使用SIMPLE與SIMPISO數值法則求解結合κ-ε紊流模式之三維依時性全雷諾均值那維爾-史托克方程組，先進行90oL型彎管之網格製作與流場驗證，並與實驗數據相比對，證實本數值模擬程序有一定之精確度後，再進行節流閥體彎管流場之模擬分析工作，分別探討彎管效應與內部閥片啟閉角度對流場結構之影響，期能更精確掌握流場特性，並進一步掌握節流閥體設計與改良之關鍵，以提供後續研究與設計節流閥體之參考。

ABSTRACT

The influences of duct inner diameter and throttle opening ratio on the flow rate and flow structures within a motorcycle carburetor throttle body are investigated in present study. The existences of centrifugal force and wall effect of the bend duct result in the secondary swirling flow except for the mainstream. In addition, the wake flows and the recirculations flows due to the mainstream flows over the throttle body make the flow field more complicated. The test matrix contains nine assembling cases with different duct inner diameter and throttle setting. Two different commercial packages are introduced. One is the grid generator named ICEM and the other is the CFD solver named STAR-CD. The purposes are to accelerate the progress of program and to test the linkage ability between two different packages.
Both the SIMPLE and SIMPISO numerical scheme are applied to solve the time-dependent fully Reynolds-Averaged Navier-Stokes Equations. The numerical method is control-volume-method and the turbulence model isκ-ε turbulent model. A 90o L type bend duct is served as the benchmark to validate the accuracy and reliability of present numerical method. As compared with the experimental data, results show that both approaches meet quite well. Generally, the complicate flow field within the throttle body can be successfully captured by present study.
The present study can be extending to the available tool for the ones who are interested in the development and design of throttle body.

目錄


第一章 前言…………………………………………….…1
1.1研究動機……………………………………………1
1.2文獻回顧……………………………………………3
第二章節流閥體之工作原理與流場描述………...7
2.1工作原理…………………………………………...7
2.2流場描述…………………………………………...8
第三章研究方法……………………………………….13
3.1統御方程式……………………………………….13
3.2無因次化處理…………………………………….16
3.3邊界條件………………………………………….20
3.3.1節流閥體入口與出口邊界條件…………20
(1). 壓力部分……………………………….20
(2). 溫度部分……………………………….20
3.3.2管壁面之固體邊界條件………………….21
3.4數值方法………………………………………….21
3.4.1 The SIMPLE algorithm…………………..22
3.4.2 The PISO algorithm……………………...24
3.4.3 The SIMPISO algorithm…………………27
3.5紊流模式…………………………………………28
第四章格點系統…………………………………35
4.1格點產生方法……………………………………35
4.2格點製作程序…………………………………...36
4.3流場驗證格點……………………………………39
4.4節流閥體格點……………………………………41
第五章結果與討論………………………………44
5.190o圓形彎管流場驗證…………………………..44
5.1.1 層流流場之流場分析與數據比對…………47
5.1.2 紊流流場之流場分析與數據比對…………49
5.2節流閥體流場分析………………………………50
5.2.1計算程序之執行……………………….50
5.2.2節流閥體流場分析…………………….52
5.2.3管徑與流量分析……………………….56
5.2.4閥開度與流量分析…………………….57
第六章結論與建議……………………………………58
6.1結論………………………………………………..58
6.2建議………………………………………………..62
參考文獻………………………………………………….64

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