高旋轉數下45°肋條於三角形冷卻通道中不同方位角之熱傳研究

Abstract

本論文藉由內部冷卻的實驗方法探討旋轉效應對於裝置有肋條的正三角形通道(Dh=2.9㎝)表面各區域其熱傳效果，並報告方位角對熱傳效果的影響。兩種不同的肋條排列方式：45°肋條及V型肋條排列方式分別置於翼前緣與翼後緣表面，其肋條高度與水力直徑比(e/Dh)為0.085，不同肋條間距與高度比(P/e)則為9。本次實驗藉由測試不同的雷諾數(15000及25000)和旋轉速度(0~330 rpm)，其旋轉數(Ro)及浮力數(Bo)分別可達到0.65和0.5左右。方位角對於熱傳效果的改變，可透過測試三種不同方位角(90°、112.5°、及135°)的紐賽數比值與旋轉數和浮力數之分佈圖清楚呈現。實驗結果顯示，方位角影響此三角形通道之局部熱傳分佈，且在翼前緣區域其熱傳效果隨方位角由90°上升至135°時而有大幅的提升。但翼前緣區域在45°肋條排列方式時，其熱傳效果對於旋轉效應並不明顯，而在V型肋排列方式時，其紐賽數比值則隨旋轉數的增加而逐漸上升。

This thesis presents an experimental study of heat transfer in an equilateral triangular cooling channel (Dh=2.9㎝) with ribs, and also reports the heat transfer variation due to different channel orientations. Two different rib arrangements are studied: 45° angled ribs and V-shaped ribs. The ribs are put on the leading and trailing surface. The rib height to hydraulic diameter ratio (e/Dh) is 0.085 and the rib pitch to height ratio (P/e) is 9. By varying the Reynolds numbers (15000 and 25000) and the rotational speeds (0~330 rpm), the corresponding rotation number and buoyancy number goes from 0-0.65 and 0-0.5 respectively. For each rib case, three channel orientations (90°,112.5°, and 135°) with respect to the plane of rotation are tested. The Nusselt number ratio distribution with rotation number and buoyancy number are presented. The result shows that that the effect of channel orientation influences local heat transfer distribution inside this triangular channel, and the heat transfer is enhanced obviously on turbine blade leading edge region when the channel orientation increases from 90° to 135°.