非对称锯齿结构对叶片气动声学性能的影响

INFLUENCE OF ASYMMETRIC SAWTOOTH STRUCTURE ON AEROACOUSTIC PERFORMANCE OF BLADE OF WIND TURBINE

为降低水平轴风力机叶片的气动噪声,受鸮类静音飞行能力的启发,提取鸮类翅膀羽毛的非对称锯齿结构,并重构于风力机叶片尾缘处。采用大涡模拟(LES)和FW-H方程对改型叶片和原型叶片的流场及声场特性分别进行研究。同时通过改变非对称锯齿尾缘的结构参数,以探究不同锯齿夹角、锯齿宽度和锯齿间距对非对称锯齿尾缘的降噪效果的影响。结果显示:非对称锯齿尾缘具有较好的降噪效果,尤其是在低频和中频区域,总声压级最多可降低10 dB。当锯齿夹角分别为30°、40°和50°时,随着锯齿夹角的增加,噪声声压级在多数方位角下呈增加的趋势;锯齿宽度分别为10、12.5和15 mm时,随着锯齿宽度的增加,噪声声压级在多数方位角下明显降低;锯齿间距的改变,对0°方位角下的噪声声压级影响显著。而从涡分布图中可发现,非对称锯齿尾缘未改变叶片表面涡脱落的位置,但会减小涡结构和涡强度,增大涡间距,从而抑制噪声的产生。

To reduce the aerodynamic noise of horizontal axis wind turbine blade,inspired by the quiet flight ability of owls,the asymmetric sawtooth structure of owl wing feather was been extracted and reconstructed for the trailing edge of wind turbine blade.Large eddy simulation(LES)and FW-H equation were used to analyze the flow field and sound field characteristics of the modified blade and the prototype blade.Meanwhile,the noise reduction efficiency of the blade with asymmetric sawtooth trailing edge under different structural parameters were explored.The changing structural parameters include sawtooth angle,sawtooth width and sawtooth space.The results show that the asymmetric sawtooth trailing edge has excellent effect on noise reduction,especially in the low and intermediate frequency regions.The overall sound pressure level can be reduced by 10 dB at most.When the sawtooth angle is 30°,40°and 50°,with the increase of the sawtooth angle,the sound pressure level shows an increasing trend in most azimuth angles.When the sawtooth width is 10mm,12.5 mm and 15 mm,with the increase of the saw tooth width,the sound pressure level decreases significantly in most azimuths.The change of saw tooth spacing has a significant impact on the noise sound pressure level at 0°azimuth angle.From the vortex distribution,it can be found that the asymmetric sawtooth trailing edge does not change the position of vortex shedding on the blade surface,but it will reduce the vortex structure and vortex intensity,increase the vortex spacing,so as to suppress the generation of noise.