- 學位論文
三維垂直軸風力機之氣動力數值探討
Numerical study of Aerodynamic Characteristics in 3D Vertical Axis Wind Turbine
摘要
垂直軸風力機具有較水平軸風力機不受風向轉變影響、架設容易與噪音小等優點，且可安裝於市區、市郊的建築使用，在提倡綠色能源於住宅生活的前提下，垂直軸式風力機成為極具發展潛力的項目。本文以數值模擬方式探討垂直軸風機葉片的氣動力學現象，深入聊解風力機葉片的動態空氣動力流場特性，藉此設計規劃葉片仰角的控制方法，以達成提升性能的目標。 本研究採用具SST K-ω紊流模組並結合滑動網格設計之計算流體有限體積法，探討三維垂直式風機葉片於不同之尖速比時之流場變化以及扭力係數的比較。分析NACA0015翼型之風機葉片並探討三種不同展弦比4、8、12，計算結果顯示在尖速比低於2時，展弦比為4的風機葉片其平均Cq值會較高，反之，在尖速比為高於2時，展弦比為12的風機葉片其平均Cq值則較高。流場變化亦顯示在風機葉片後，而當尖速比增加時，其造成之 渦流較小，模擬結果顯示本研究分析之展弦比為4、8的兩種葉片在尖速比2.1至2.3之間時會產生最佳的Cq值。 本研究接著探討固定俯仰角的影響，分別在尖速比1≦λ≦2上做不同俯仰角度分析其數值，其結果方面顯示不同尖速比時其產生最佳Cq值的固定俯仰角亦不同，在研究範圍內最大增益可達22.6%。本研究亦針對三種Twist型的風機葉片做數值的探討，分別為Asymmetry twist，Symmetry twist center，Symmetry twist tip，結果顯示，Symmetry twist tip 型的風機葉片會有較好的扭力性能，其最大增益在尖速比為1扭轉角10°時，增益為48.9%。 最後本文也在可變俯仰角方面分別在尖速比1≦λ≦2上不同俯仰角的控制來探討其平均Cq值的趨勢，在本研究的結果方面顯示當尖速比1.1時所產生的最大增益可達355.79%，尖速比1.5時最大增益可達148.39%。尖速比2時最大增益可達45.4%。 關鍵詞：垂直軸風力機，三維，數值模擬，twist葉片，俯仰角控制
並列摘要
The vertical axis wind turbines have an advantage over the horizontal axis wind turbines because of many merits such as easy installation, less susceptibility to wind shift and low noise. They are very suitable to be installed in urban and suburban region. The vertical axis-wind turbine have great potential for promoting green energy in residential life. The present study applied numerical simulation to investigate the aerodynamic phenomena of a vertical axis wind turbine to understand the characteristic of flow field in-depth. A control mechanism of the pitch angle control is purposed based on the numerical results to enhance the performance of the wind turbines. This study integrated the SST K-ω turbulence model combined with a sliding mesh design into the computational fluid finite volume method to explore variation of the flow fields and moment coefficient Cq of a three-dimensional vertical wind turbine with 3 NACA0015 blades at different tip speed ratios. Three different aspect ratio of 4, 8 and 8 are studied. The results show that, when the tip speed ratio is less than 2, the blade with aspect ratio 4 has the highest Cq value. On the contrary, when the tip speed ratio is higher than 2, the blade with aspect ratio 8 has the highest Cq value. The numerical flow field also show when the tip speed ratio increases, the vortex induced behind the blade becomes smaller. The simulation results show that the blade with aspect ratio 4 and 8 have the optimal Cq value when the tip speed ratio is between 2.1 and 2.3. This study then studied the effects of a fixed pitch angle on the turbine performance at tip speed ratio. The results show the pitch angle that generate the highest Cm value will vary wish the tip-speed ratio. The maximum increase of Cq reaches 22.6% for the blades with fixed pitch angle. This study also carried out the numerical studies of three twist blade: 1. Anisymmetry twist 2. Symmetric twist cent, 3. Symmetry twist tip. The results show that the symmetric twist tip blade has the better performance in torque, it can increase Cq up to 48.9% with 10° twist angle at tip speed ratio λ=1. Finally, the paper also use the variable pitch angle control mechanism to study their effects on average Cq values at different tip speed ratios. The results show that the proposed pitch control mechanism can increase the Cq values by 377.1% at tip speed ratio 1.1, by 148.39% at λ=1.5 and by 45.4% at λ=2. Keywords：VAWT, 3D, simulation,twist, pitch control
參考文獻
被引用紀錄
延伸閱讀
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