臺灣博碩士論文加值系統

本研究係利用計算流體力學與熱傳學之原理配合數值方法完成相關之氣動力數值模擬工作，前處理以ICEM/CFD套裝軟體完成薄膜冷卻渦輪葉片數種三維內、外通道流場幾何外形之建構及格點製作，輔以CFX4.3計算器軟體進行其氣動力、熱傳特性求解，最後藉由FIELDVIEW 以及TECPLOT後處理軟體作定量及定性之流場可視化處理及分析。
本研究係將葉片模型上下壁面設定為週期邊界，並忽略間隙渦流（tip vortex）效應之影響，將模型正面簡化為對稱面，以期模擬出實際渦輪轉子之三維流場。而研究重點則在於針對四種不同構型之薄膜冷卻葉片，模擬與分析其不同吹出比對流場及葉片表面絕熱薄膜冷卻效率分佈之影響。
研究結果發現薄膜冷卻構型對流場及絕熱薄膜冷卻效率分佈較吹出比之效應顯著。本研究三種不同薄膜冷卻構型之高壓渦輪葉片，因凹面（壓力面）存在有較高之正向壓力，以致無論採蓮蓬頭式冷卻孔或冷卻槽之方式設計，都無法達到適當之薄膜冷卻效果；於凸面（吸入面）上，可發現具蓮蓬頭之渦輪葉片構型，其絕熱冷卻效率趨勢較緩和且覆蓋之區域較廣，而採用頭端冷卻槽設計之葉片構型，則受次流場與端牆效應之影響，其冷卻效率於葉片弦長 後即有明顯之遞減現象，且冷卻薄膜所能覆蓋之區域亦較小。另增加吹出比雖可改善其絕熱冷卻效率，但無法改變流場之特性之影響。

The present study is aimed to study the film-cooling effectiveness problem by employing the computational fluid dynamic（CFD）technique. The computational simulation has been performed using four kind of commercial software packages, the grid generator, ICEM/CFD, the solver, CFX4.3, and the flowfield visualible /analysis tools, TECPLOT and FIELDVIEW.
There are four different structure multiblock grid systems that are generated to simulate the complicated, three-dimensional turbine flowfield. These grids differ mainly in the cooling hole shape and location, especially in the regions of leading edge and trailing edge. In additional to the grid systems, this thesis also studied the effect of two various coolant-to- freestream blowing ratios, 0.8 and 1.2.
For the given parameters, the coolant geometry parameter has great influence than the blowing ratio on the distribution of adiabatic cooling- effectiveness. Result on the pressure side, it show just little film-cooling effect near the ejection hole, as the reason of great front pressure gradient. On the suction side, the cooling-effectiveness of the head-shower cooling blade is better than the blade with three rows of slot cooling model. Present study clearly exhibits the effect of secondary flow and the endwall on the film-cooling behavior of turbine blade. The complicate flow structures caused by the interaction of coolant flow and mainstream are also presented.

1.前言
1.1研究目的與動機
1.2文獻回顧
1.3薄膜冷卻效能與熱傳係數之探討
2.網格系統
2.1物理幾何外型
2.2網格分佈情況
2.3週期邊界網格之設計
2.4網格加密情況
3.數學模式
3.1統御方程式
3.2紊流模式
3.3本研究所採用之紊流模式
4.邊界條件處理
4.1入口邊界條件
4.2物體壁面邊界條件
4.3相鄰區塊邊界條件
4.4週期性之流場邊界條件
4.5背壓邊界條件
5.結果與討論
5.1入口流0度攻角之渦輪葉片流場之分析
5.2入口流角度效應對渦輪葉片流場影響之分析
5.3不同形式之冷卻孔及吹出比對薄膜冷卻效率分佈之影響分析
5.3.1 具蓮蓬頭設計之絕熱薄膜冷卻效率分佈
5.3.2 具蓮蓬頭及尾端冷卻噴槽設計之絕熱薄膜冷卻效率分佈
5.3.3 具頭端冷卻噴槽及尾端冷卻噴槽設計之絕熱薄膜冷卻效率分佈
5.4薄膜冷卻葉片三維溫度場與薄膜冷卻效率分佈分析
6.結論

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