摘要

題目：探討三顆/四顆垂直軸風機之排列及計算三顆風機陣列之功率
研究生：劉家宏
指導教授：黃啟鐘

人類消耗石化能源的同時，也將大量二氧化碳自地底釋放於空氣之中，導致溫室效應加重，造成極端氣候。石化能源的另一隱憂為全球石油儲藏量，研究指出，全球石油蘊藏量僅能再供應人類大約50至100年左右，故再生能源的發展刻不容緩。
本文使用之垂直軸風機類型為直立葉片垂直軸風機 (SB-VAWT)，包含三片NACA0015翼型之葉片，弦長為0.4公尺，風機旋轉半徑為1.25公尺，利用GAMBIT所建立之風機幾何外型，以商業軟體ANSYS 16.0進行流場計算。
本研究共分為兩階段進行，第一階段以田口法探討三顆/四顆風機系統之配置，選用之的參數如下：第二顆風機與第三顆風機間間距 (B)、第三顆風機與水平軸之間距 (H) ，並且考量是否放置第四顆風機，經由分析後得出結果如下，（一）三個因子對於輸出功率之影響力由大至小：第三顆風機與X軸之間距 > 第二顆風機與第三顆風機間間距 > 放置第四顆風機，（二）最佳之組合為B = 4.5d、H = 2.165d，未放置第四顆風機，（三）優化後之風機系統的平均功率係數相較於雙顆風機系統提升2.65%；相對於單顆風機則提升12.88%；第二階段，吾人變動三顆風機陣列之B值(第二顆風機與第三顆風機間間距)，經由計算結果得出，（一）當B值為6倍風機直徑距離時，平均功率係數相較於田口法所預測之風機系統提升2.86%，（二）在特定B值範圍下(4.5 < B < 7.5)，因風機間良好之交互作用，可獲得較高之功率係數，本研究更進一步將此配置下之第三顆風機的旋轉方向變更為順時針旋轉，得出之結果顯示第三顆風機之功率係數遠低於相同配置下逆時針旋轉之第三顆風機。接著，根據田口法所得之因子影響力，將間距B固定且維持三顆風機配置，探討第三顆風機與水平軸之間距對風機系統之影響。

The power output of three/ four SB-VAWTs is simulated numerically. Each turbine consists of three vertically aligned NACA0015 turbine blades separated apart by an angle of 120º. Each 2.5m diameter VAWT has a chord length of 0.4 m. The freestream velocity is 8 m/sec and tip speed ratio (TSR) is 2. In the 1st stage, three operating factors including: the distance between the 3rd turbine and x axis (H) ; the distance between the 2nd turbine and the 3rd turbine (B) and placing the 4th turbine, along with two levels are taken into consideration to account for their influences on the performance of the turbine system with Taguchi method. An orthogonal array of L4(23) is designed. The influence strength order of each factor is featured by H > B > placing the 4th turbine, indicating that the factors H play a crucial role in determining power output. Moreover, the analysis of the signal-to-noise suggests that the combination of the three factors for optimum operation conditions is located at B=4.5, H=2.165, w/o placing the 4th turbine.
In the second part of the research, we adjust the value of B based on Taguchi-optimized three VAWTs array. The result shows that the averaged power coefficient reaches peak when B=6. Comparing with the single wind turbine, the mean power output of the three turbines system is enlarged by 16.11%. Compared to the dual wind turbine system, the mean power output of the three turbine system is enlarged by 5.59%. Besides, in the specific range between B=4.5 and B=7.5, three turbine array gain extra power from positive interaction. Then, we fixed the value B and H at 6 and 2.165, respectively, and changing the rotating direction of the 3rd turbine from counterclockwise (CCW) to clockwise (CW). The result showed that Cp3 in CCW rotating direction is much higher than that in CW rotating direction, meant to that the CCW 3rd VAWT leads to better performance.

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