風力渦輪機機艙與發電機散熱模擬分析

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姓名

謝承穎(Cheng-Ying Hesieh) 查詢紙本館藏

畢業系所

機械工程學系

論文名稱

風力渦輪機機艙與發電機散熱模擬分析
(Cooling Simulation of Nacelle and Generator in Wind Turbine)

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摘要(中)

現有2 MW級風力渦輪機在台灣熱帶天候運轉有過熱問題，因此本研究使用FLUENT軟體模擬此類風機的機艙與發電機熱流場，並採用可行之散熱改善方法以降低機艙與發電機的溫度分布，目的為建立出風機散熱改善之參考依據。本文參考實際風機建立簡化之幾何外型，建模包含鼻錐、發電機環狀區域、機艙、冷卻風管等幾何結構，其餘較小的次組件則加以省略。
本文先分析風機機艙（含發電機）熱流場分布，並與實際運轉溫度做比較，由此模擬驗證得知高溫集中於發電機環狀區域，其中最大溫度產生於發電機熱源。受到現有冷卻風管的氣流影響，發電機上部環狀及鼻錐流體區域流動較明顯，其餘區域流動則較為緩慢，此流動分布不均導致機艙（含發電機）溫度無法有效冷卻。
依據數值模擬解，本研究建議三種改善冷卻散熱方法。第一種是提升現有冷卻風管入口流速；第二種是在發電機下部環狀區域另外加裝一個送風導管，第三種則是在現有冷卻風管延伸一個分支管進入發電機下部環狀區域。模擬分析分別比較溫度、速度、壓力分布和各區域流場型態來評估三種散熱方法。第一種方案提升入口冷卻流速可降低發電機上部環狀區域溫度和提昇此區域流速，並且導致整體壓力上升，其餘區域溫度降幅有限。第二種方法單獨加裝冷卻導管，導致發電機上部環狀區域溫度增加，並引入冷卻氣流進入發電機下部區域，有效提升此區域流動分布。第三種方法將冷卻風管延伸分支管，若提升入口流速至12 m/s，整體風機內溫度分布能有效降低，並且提升機艙與發電機的流動，這種方式效果最佳，建議優先考慮安裝。

摘要(英)

Current 2 MW wind turbine encounters an overheat problem in Taiwan’s tropic weather, thus this paper simulates the thermo-fluid field inside nacelle and generator of such wind turbine with FLUENT software and adopts feasible cooling solutions to reduce temperature inside nacelle and generator. The simplified geometry use in simulation is base on a realistic wind turbine, including nose, generator, nacelle and cooling pipe, others smaller sub-components are neglected.
The temperature of nacelle including generator is analyzed first and compared with realistic operating temperature of wind turbine. Based on this validation of simulation, the high temperature area is identified on the region of annular generator with maximum temperature located in the heat source inside the generator. Due to the influence of air flow from existing cooling pipe, large flow motion inside the annular upper region of generator and nose region is predicted, while in the rest region the flow is relatively slow, such uneven flow distribution leads to ineffective cooling for nacelle including generator.
Based on simulation results, three improving cooling options are suggested. First option is to increase inlet velocity of cooling pipe. Second approach is to install another cooling pipe into the annular bottom region of generator. Third option is to extend a branch pipe from the existing cooling pipe into annular bottom region of generator. The result is compare contour of temperature, velocity, pressure, and flow field in wind turbine. Increasing cooling velocity can reduce the temperature and enhance flow of annular upper region of generator, which increase the pressure too, but the temperature drop in other flow region is limited. Installing cooling duct alone can lead to temperature increased in annular upper region of generator, but it can effectively improve flow in annular bottom region of generator. Extended branch pipe from cooling pipe and enhanced velocity to 12 m/s can reduce temperature and increased flow motion inside nacelle and generator. This option is most effective in cooling and should be adopted.

關鍵字(中)

★ 氣冷散熱
★ 發電機
★ 風力渦輪機
★ 計算流體力學

關鍵字(英)

★ Wind turbine
★ Air cooling
★ Computational fluid dynamics
★ Electric generator

論文目次

摘要 i
Abstract ii
致謝 iv
目錄 vi
圖目錄 ix
表目錄 xiv
符號說明 xvi
第一章緒論 1
1.1 前言 1
1.1.1 風力渦輪機 2
1.1.2 現有冷卻裝置介紹 3
1.2 文獻回顧 5
1.2.1 腔體內部自然對流現象研究 6
1.2.2 通風結構之混合對流現象研究 7
1.2.3 散熱相關物理現象研究 8
1.2.4 風機散熱相關技術介紹 10
1.3 研究動機 14
1.4 論文架構 15
第二章數值模擬計算 17
2.1 計算流體力學簡介 17
2.2 FLUENT軟體介紹 18
2.2.1 傳輸方程式：離散及數值計算 19
2.2.2 空間離散 20
2.2.3 壓力基準分離運算流程 20
2.2.4 速度與壓力耦合運算 22
2.3 幾何外型 23
2.4 基本假設 27
2.5 統御方程式介紹 27
2.6 紊流模型介紹 28
2.6.1 標準k-ε紊流模型 28
2.6.2 RNG k-ε紊流模型 29
2.6.3 Realizable k-ε紊流模型 31
2.7 壁面函數方程式介紹 32
2.8 邊界條件 36
2.9 計算方法 39
第三章數值模擬驗證 41
3.1 網格獨立性分析 41
3.1.1 冷卻風管獨立性分析 41
3.1.2 發電機環狀區域獨立性分析 47
3.2 不同紊流模型之差異性 51
3.3 模擬驗證 53
3.3.1 風機實際運轉溫度/風速說明 54
3.3.2 不同對流係數值之溫度比較 58
3.3.3 風機整體模擬分析 62
第四章散熱改善分析評估 73
4.1 散熱改善方法介紹 73
4.2 不同冷卻流速對熱流場變化之比較 75
4.3 導入一冷卻氣流至發電機下部熱流場分析 84
4.3.1 發電機環狀區域加裝送風導管 84
4.3.2 現有冷卻風管加裝分支管延伸至發電機環狀區域 92
第五章結論與建議 105
5.1 結論 105
5.2 未來建議 107
參考文獻 109

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指導教授

吳俊諆(Jun-Chi Wu)

審核日期

2012-7-23

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