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  • 學位論文

後掠傾斜與錐形葉片對H-Darrieus垂直軸風力機性能之影響

Influences of swept-back angled and tapered blades on the performance of a H-Darrieus vertical axis wind turbine

指導教授 : 翁輝竹
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摘要


本論文完成葉片幾何外型改變對垂直軸風力機性能之數值分析,主要目的在探討相同尖端速度比下,後掠傾斜葉片與錐形葉片對於小型H-Darrieus垂直軸風力機性能之影響。研究所使用之風力機葉片翼型為NACA0018,轉子直徑0.8 m,高度0.8 m,並使用SST k-omega紊流模型進行模擬分析。首先,本研究進行了模擬驗證,透過與前人研究的實驗及數值模擬數據進行比較,以驗證後續研究所使用的紊流模型及參數設定之可行性與準確性。接著,對於所使用的研究模型進行網格獨立性測試以及時間步長測試,選用較符合時間成本且不失準確性之方案進行後續模擬。最後先對葉片寬長比進行比較分析,再透過加入後掠角及翼縮比的改變,觀察其對於轉子轉換效率及風場之影響,並使用ANSYS-Fluent針對風流經葉片之流線圖及壓力分佈圖等進行分析。 研究結果發現,在葉片的寬長比為0.275時,H-Darrieus垂直軸風力機有最佳轉換效率。藉由觀察流線圖及渦度分布圖發現具有後掠角葉片之風力機能有效減緩動態失速時的氣流分離,以提升風力機之轉換效率,而在高風速下後掠角效應會較低風速情況來的明顯,於本研究風力機,前緣後掠角為2度時皆有最佳性能表現。具有翼縮比之錐形葉片能減緩葉片尖端之渦流產生,從而導致有較高的轉換效率,風速8 m/s時最佳翼縮比為0.95。

並列摘要


This thesis presents a numerical study on the blade geometry change to the vertical axis wind turbine performance. The main purpose is to explore the influences of swept-back angled blade and tapered blade on the performance of a H-Darrieus vertical axis wind turbine at a same tip speed ratio. In this study, the airfoil NACA0018 was used, the rotor diameter and the height were set to 0.8 m, and the SST k-omega turbulence model was used to solve the Navier-Stokes equation and obtain the flow field information. First, the numerical results in this study were compared with previous experimental and numerical studies to verify the feasibility and accuracy of the turbulence model and parameter settings used in subsequent studies. Then, sensitivity tests of grid size and time step were performed to select the best solution with less time cost without losing accuracy. Finally, the blade aspect ratio was compared and analyzed, and then the effect on the conversion efficiency and the wind field by adding the swept-back angle and the tapered ratio were observed, then ANSYS-Fluent was used to analyze the streamline and the pressure distribution. It was found that the H-Darrieus vertical axis wind turbine has the best conversion efficiency when the aspect ratio is 0.275. The wind turbine with swept-back angle blades could effectively suppress the flow separation and delay the dynamic stall in the middle of the blade, which can improve the conversion efficiency of the wind turbine comparing to that of the conventional straight blade. The tapered blade with the tapered ratio could suppress the vortices from the trailing edge and the tip end of the blade, leading to higher conversion efficiency. The best tapered ratio is 0.95 when the wind speed is 8 m/s.

參考文獻


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