臺灣博碩士論文加值系統

本研究透過風洞實驗，針對透孔率50%之透孔盤模型於均勻來流下進行尾流逐點量測，分析其速度分布、紊流強度、動量通量、等氣動力特性，而藉由改變模型旋轉速度，賦予尾流旋轉特性，探討透孔盤模型旋轉所造成之尾流特性及發展情況，並與風機模型之特徵比較，觀察旋轉之透孔盤模型是否可以模擬風機尾流的旋轉特性。

改變模型轉速後，尾流明顯擴張，原先靜止時於翼尖產生之特徵，隨著剪力層外移，由Y/D=±0.5擴展到Y/D=±1以外，且各特徵大小變得更強烈。由渦度分布能看出尾流流場正在旋轉，並且與模型旋轉方向相反。透孔盤模型對尾流造成的紊流強度相當高，也加快了尾流的回速，由於透孔盤不像風機模型有葉片根部構造，因此部分於翼根特性無法模擬呈現，但在橫向和縱向速度方面，在一定轉速之上，可以表現出和風機模型相近的趨勢，雖然傳遞範圍不是很遠，約在X/D=2~3範圍內，

本研究亦有以六力平衡儀量測透孔盤與風機模型推力並計算推力係數，做為動量理論和圓盤理論計算結果的參考標準。以兩種一維動量理論方程式計算時，透孔盤模型以式(3-4-1)於X/D=2~3所得結果誤差較小，而風機模型則較適合以式(3-4-2)做計算，另外以二維風速剖面計算模型整體推力係數時，可更精準貼近六力平衡儀之量測結果。而根據尾流風速剖面計算的圓盤理論，考慮圓盤內尾流域速度平均，取X/D=2~3的位置較合適。

當模型旋轉時，無論是葉片模型或是透孔盤模型，翼尖位置能譜中的高能量會出現在轉子旋轉頻率的倍頻上，而主頻會顯現在1倍旋轉頻率或是與葉片數相關之倍頻上，當透孔盤靜止時，因模型沒有旋轉頻率，圖中亦沒見到局部高能量出現，只能觀察到Inertial subrange斜率-5/3的趨勢。

透孔盤旋轉後可以看見部分風速剖面、渦度等方面旋轉特性，但因圓盤轉動轉動造成的劇烈擾動，使得尾流範圍擴大，翼尖位置發生的特徵外移，影響到對於相同尺寸風機模型的特徵位置判斷，圓盤內的特性變化也較為強烈，分析上較為複雜，而擴張的尾流會影響各種距離上的判斷，無法精確制定風機的架設距離，整體而言模型上有極大改善空間。

This paper examines experimentally the wake characteristics of porosity 50% porous disk models using hot-wire anemometer in a uniform free stream condition for the wind tunnel study. The porous disks, based on the actuator disk theory, are used for studying the characteristics of wind turbine wake some distance downstream. And make the disks rotating to compare with wind turbine models’ results, investigating whether the disks can model the wind turbines or not.

When the disks with rotation, the wake expands evidently. The characteristics at the tip also move out from Y/D=±0.5 to the positions around Y/D=±1, and the distribution becomes stronger than the profile when the disks are stationary. From vorticity distribution, it can be observed that the wake flow field is also rotating, and its direction is opposite to the model. In the experiment the turbulent intensity is quit high from the porous disks, and it makes the velocity recover faster. Because porous disks do not have the parts of blade root, they cannot model characteristics of wind turbines at root. There are similar tendencies for spanwise and vertical velocity, but they cannot transfer too far, it is about at X/D=2~3.

The thrust coefficient of porous disc model obtained by actuator disc theory, momentum theory, and compared with the results measured by force balance. 2D momentum theory is confirmed more accurate to calculate thrust for whole disk model. Power spectral density for every model can observe slope of -5/3, when the models are rotating, including porous disk and turbine models, there are some peaks observed on the spectrum, and the main frequency will locate at the rotating frequency or its multiple related to blade numbers.

摘要 I
致謝 XI
目錄 XII
表目錄 XIV
圖目錄 XV
符號說明 XXI
第一章 緒論 1
1-1 前言 1
1-2 研究動機與目的 2
1-3 文獻回顧 3
第二章 實驗設備與架設 8
2-1 開放式低速風洞 8
2-2 壓力校正器 8
2-3 皮托管及壓力感測器 8
2-4 熱線探針與熱線測速儀 9
2-5 資料擷取系統 10
2-6 六力平衡儀 11
2-7 雷射感測器[39] 11
2-8 透孔盤模型 12
2-9 實驗架設 12
第三章 分析方法與理論 14
3-1 風機的物理特性 14
3-2 圓盤理論(actuator disk theorem) 15
3-3 轉盤理論(rotor disk theorem) 16
3-4 動量理論(momentum theorem) 17
3-5 渦度 18
3-6 紊流頻譜 18
第四章 結果與討論 20
4-1 透孔盤模型靜止時的尾流分析比較 20
4-2 透孔盤模型旋轉時的尾流分析比較 23
4-3 模型A尾流之旋轉特性探討 26
4-4 三葉與四葉風機模型 27
4-5 模型推力係數差異比較 31
4-6 能譜分析 37
第五章 結論與未來建議 39
5-1 結論 39
5-2 未來建議 40
第六章 參考文獻 42
第七章 圖表 46
7-1 表格 46
7-2 圖片 52

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