考虑小攻角影响H型风轮变桨方法研究

STUDY ON VARIABLE PITCH STRATEGY OF H-TYPE VAWT CONSIDERING EFFECT OF MINIMUM ANGLE OF ATTACK

升力型立轴风轮叶片气动特性随方位角变化而变化,可通过变桨来改善。与传统变桨思路相反,采用在小攻角区域大角度变桨,在大攻角区域小角度变桨,以重点改善小攻角区域性能为出发点来提高风轮整体性能的变桨思路。以NACA0012翼型2 m高和2 m旋转直径的两叶片H型风轮为研究对象,基于双盘面多流管模型,分析和比较在最佳尖速比5时变桨前后攻角、切向力系数、能量密度的分布及其变化规律,验证新变桨方案效果。研究结果表明:变桨后上盘面攻角、切向力系数、能量密度的高性能覆盖面积明显增大。在上盘面,攻角和切向力系数呈梯形分布;在下盘面原极大值两侧形成了新的更大的极大值区域,攻角呈W分布,切向力系数呈M分布。

The aerodynamic performance of the blade of lift type vertical axis wind turbine(VAWT)changes versus azimuth angle;variable pitch technology can upgrade the blade performance.Contrary to the mind of traditional variable pitch technologies,the new proposed by the paper emphasizes on the performance improvement of azimuth corresponding to small angle of attack,employs a big pitch angle in small angle of attack zone and a small pitch angle even zero in big angle of attack position,the aim of the new pitch technology is also to improve the performance of VAWT.A H-type VAWT employing NACA0012 aerofoil and 2 m height and 2 m rotation diameter is considered as research objective.Based on double disks multistream tubes model,the variation rules of angle of attack,tangential force coefficient and power density are analyzed and compared between the conditions of fixed pitch and variable pitch at tip speed ratio 5,the purpose of which is to validate the effect of the new technology.The research results showed that in the variable pitch condition,the zones with big values of angle of attack,torque coefficient and power density are amplified.The distributions of angle of attack and torque coefficient appear shapes of trapezoid in upstream disk;while in downstream disk,two new maximum points are created,the distribution of angle of attack shows shape of'W',the distribution of torque coefficient shows'M'shape.