Investigations on Flow Characteristics, Surface Loadings and Performances of Vertical Axis Wind Turbine

不同葉片傾角之垂直軸風機性能分析

陳建章(Chien-Chang Chen) ； 郭正雄(Cheng-Hsiung Kuo)

《中國機械工程學刊》 33卷4期 (2012/08) Pp. 327-339

https://doi.org/10.29979/JCSME.201208.0006

摘要

本文是以探討在風速為10m/s下，二維垂直軸風機的三個葉片為NACA0012時，葉片傾角變化為±10度對於風機效能的影響。藉由計算流體力學套裝軟體Ansys/Fluent及UDF法計算風機葉片所承受風的推力轉換成風機葉片轉速且紀錄風機每一個葉片在每一個瞬間所承受的水平與垂直兩方向的分力、扭力以便於風機效能分析。本研究結論如下：1.當葉片傾角為正值且葉片位於上風區時，葉片會提供系統正扭力（逆時針方向旋轉）；反之，葉片傾角為負值時，則是葉片要在下風區方能提供正扭力給於系統。2.當葉片傾角變化從10度減至-10度時，系統旋轉一圈輸出扭力peak值所對應之方位角會往較小方位角偏移。3.當葉片傾角為5度時，垂直軸風力機會有較佳效率輸出。4.當葉片傾角為-10度時，垂直軸風力機會有較佳自我啟動能力。

並列摘要

This study simulates the unsteady flow structures around the small-size vertical axis wind turbines (VAWT) with three straight blades. The software Ansys/Fluent is employed. The effects of collective variations of the blade pitch angle on the surface loadings, the moment coefficients, the self-starting ability and the power coefficient are addressed and discussed. The VAWT system is driven to rotate from rest by the coming wind with a uniform speed 10 m/s, and the pitch angle varies within ±10°. The blade profile is NACA 0012. While the pitch angle is positive, the CCW rotation of the VAWT system is primarily provided by an individual blade advancing on the upwind side. On the contrary, at negative pitch angles, the CCW rotation of the VAWT system is provided mainly by the blade advancing on the downwind side. The distributions of moment coefficients, contributed by all three blades, shift toward small φ while the pitch angle decreases from θ = 10° to. θ = -10° These trends are in synchronization with those of CX and CY. The primary positive peak value of CM reaches the maximum at the pitch angle θ = 5°; and the magnitudes are comparable and mostly positive (CCW) within one complete revolution for the case θ=10°. While the pitch angle decreases from θ=5° to θ=-10°, the peak magnitude of CM decreases significantly, the interval (or azimuthal portion) of negative moment extends wider and the negative value of CM increases within one complete revolution. Within -10°≦θ ＜ 5°, the enlargement of negative CM, significant reduction of positive CM and longerinterval (or larger azimuthal portion) of negative values of CM are the main reason responsible for the retardation of the rotating speed and thus the reduction of the power coefficients of the VAWT system. The self-starting ability is the best at the pitch angle θ=-10° and is degraded monotonously from θ =-10° to θ=10°.

並列關鍵字

VAWT ； collective pitch-angle variation ； self-start ability ； power coefficient