基于PIV测试的风轮主要声源区域雷诺应力特征分析

为了获悉风轮主要声源区域的流动机理,在风洞开口段,在不同风速和尖速比下,文章对风轮展向X/C=0.5区域不同相对弦长处的流场进行了PIV测试。测试结果表明:由于翼型表面发生流动分离导致流体速度脉动,雷诺应力迅速增加,使叶片与来流相互作用产生压力脉冲;随着相对弦长的增加,雷诺应力均有不同程度的增大,当X/C为0.4~0.8时,雷诺应力的变化最为明显;对比不同风速、尖速比、相对弦长处的雷诺应力数据发现,随着尖速比的增加,雷诺应力增大最明显的区域向前缘移动,流动分离位置提前,而风速变化对流动分离位置没有影响;发生流动分离后的主要声源区域的雷诺应力呈现单峰值,流体脉动程度较剧烈;对比不同工况下主要声源最大声压级和X/C=1处中心最大雷诺应力值发现,两者变化趋势一致且易受尖速比变化的影响。文章以实验测试的方法揭示了风轮主要声源区域雷诺应力表现的流动特征,研究成果对于叶片的优化设计和降噪方法的改进提供了可行的解决思路。

Analysis of reynolds stress characteristics of main sound source region of wind wheel based on PIV test

In order to understand the flow mechanism in the main sound source area,PIV test was carried out on the flow field with different relative string strengths in the wind wheel spreading r/R=0.5 area at the opening section of the wind tunnel with different wind speed and tip speed ratio.The results show that the main sound source is the fluid velocity pulsation caused by flow separation on the airfoil surface,and the Reynolds stress increases rapidly,which causes the interaction between the blade and the incoming flow to produce pressure pulse.The measurement results also show that with the increase of relative chord length,the Reynolds stress increases to different degrees,and the change of Reynolds stress is most obvious between X/C=0.4 and X/C=0.8.By comparing the Reynolds stress data of different wind speed,sharp speed ratio and relative string length,it is found that the region with the increase of wind speed and the increase of Reynolds stress is the most obvious to move to the front edge,and the flow separation position is in advance,while the change of sharp speed ratio has no effect on the flow separation position.After flow separation,the Reynolds stress in the main sound source region shows a single peak value,and the fluid pulsation degree is more intense.By comparing the maximum sound source SPL and the maximum Reynolds stress at the center of X/C=1 under different working conditions,it is found that the two have the same change trend and are significantly affected by the change of wind speed.In this paper,the flow characteristics of Reynolds stress in the maximum sound source area of the wind turbine are revealed by means of experimental test.