本論文針對風力發電機的發電效率及尾流特性進行了研究。其研究方法是藉由風洞實驗以檢測縮尺風力渦輪機，過程中使用眼鏡蛇探針風速計來取得風速資料，功率方面則利用風渦輪的發電轉子再接出電導線即可觀測其發電電流值。在實際風力發電場中，下游風渦輪機的效率會受到上游渦輪機的尾流所影響，為了避免該影響，將渦輪機的前後距離拉大是一種方法。本研究將關注另一種方式，即調整上游風機的偏航角，使其的尾流具有偏移效應、避開下游風機的位置，其中本文將探討不同偏航角所對應的尾流偏移與發電功率。在實驗中用了以下獨立變數：風渦輪機的不同偏航角與發電電路中加載不同電阻負載值(這進而影響風渦輪機的葉片轉速)。本研究分了三個case進行討論，(1)在風洞風速為6.1m s-1的流速下，以角度每隔5度由-45到45度的偏航角條件及兩組電阻(22與521歐姆)進行發電效率的實驗、(2)沿襲case1的變數設定並取幾個特徵偏航角進行尾流的量測(角度間隔改為15度)，及其(3)承襲case2，取其中的負偏航角的案例並且分別提升入流速度，測試不同風速所帶來的影響。其結果顯示，最大功率輸出出現在無偏航條件下和電阻較低的電路中，最大功率係數約為0.23。發電量隨著渦輪機偏航角的增加而減小，負偏航角條件略微比正偏航角條件快速減小。當偏航角的大小增加到15,30和45度時，無因次化的功率輸出降低到90-96％，68-79％，20-55％。尾流量測結果顯示出，在增大的偏航角條件下尾流速度降減小、速度降區域對下游的延伸提早結束，並且造成尾流有偏移現象，在偏航角-30°至30°之內，尾流的偏移角與偏航角成正比，而在大偏航角（±45°）條件時，尾流偏移不僅不會增大反而減小。另外垂直速度、湍流強度和動量通量與偏航角條件成反比，也就是當偏航角提升其尾流特性愈不明顯。另一方面，尾流特性由負載電路中的電阻值改變，其中電阻值越小，可以獲得明顯的流向速度降、尾流偏轉、垂直速度和湍流強度。最後，入流的風速幾乎不影響(無因次化的)尾流特性，也就是說，包含我們所關注的尾流速度大小、尾流偏移角幾乎只與偏航角有關。總結以上，風渦輪機設置偏航角將使其發電效率下降，然而後方尾流速度將有所提升，並且尾流的偏移現象能使得速度降區域遠離正後方的下游位置，風力發電場的單位面積將能有更大的利用，這些結果或許可以在風力發電場設置時納入考量。

A wind-tunnel experiment was carried out to examine the power generation efficiency of a stand-alone miniature wind turbine and its wake characteristics under different yaw conditions. The yaw conditions involved the variability of yaw angle from -45° to 45° with an angle interval of 5 degrees for power generation measurement under the same freestream inflow velocity of 6.1 m s-1. Two resistors were used in the series circuit to study changes in the blade angular speed and power generation in the different yaw conditions. As expected, the maximum power output appears at the non-yaw condition and in the circuit with a lower resistor, with a maximum power coefficient approximately 0.23. The amount of power generation decreases with the magnitude increase of the turbine yaw angle, with a slightly fast reduction in the negative yaw angle condition. The normalized power output decreases to 90-96%, 68-79%, 20-55% as the magnitude of the yaw angle increases to 15, 30, and 45. The turbine wake characteristics at those yaw angle magnitudes are investigated through collecting the complex wake velocity components with the calibration-free cobra probe. The turbulence statistics showed that the wake velocity deficit is decreased under the increased yaw angle condition, and its deflecting angle is proportional to the yaw condition within the yaw angle -30° to 30°. The other wakes deflecting not only does not increase instead decreases under the large yaw angle (±45°). Also, the vertical velocity, turbulence intensity, and momentum flux are inversely proportional to yaw angle conditions. On the other hand, the wake characteristic is changed by the resistance value in the loaded circuit where the smaller the resistance value can obtain the obvious streamwise velocity deficit, wake deflection, vertical velocity, and turbulence intensity.

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