后掠叶片锯齿尾缘宽频噪声实验研究

Experimental Study on Broadband Noise Reduction of Swept Blade With Serrated Trailing Edge

本文采用线性传声器阵列分别对具有常规尾缘及锯齿形尾缘的后掠叶片的尾缘噪声进行了实验测量;运用CLEAN-SC数据处理方法精确地识别出叶片尾缘噪声的声学参数。并且基于多组实验结果的对比,深入研究了不同的尾缘锯齿长度、周期、几何比例对后掠叶片尾缘噪声降噪效果的影响。实验结果表明:在低湍流度、自由来流情况下,在总声压级降噪方面,尾缘锯齿长度越大,尾缘噪声的降噪效果愈发明显;尾缘锯齿周期增大,其降噪效果也有不错的改善;针对几何比例相同的尾缘锯齿,其整体尺寸越大,降噪效果越显著。对于特定的后掠叶片而言,一定存在可以使降噪效果达到最优的尾缘锯齿尺寸。在所有实验中,锯齿尾缘的最大降噪量可以达到1.2 dB。“流向型”尾缘锯齿的降噪效果要远优于“对称型”锯齿,且所有“对称型”锯齿均未能进一步降低后掠叶片的尾缘噪声。

In this paper,the trailing edge noise of the swept blade with conventional trailing edge and serrated trailing edges is measured experimentally by linear microphone array;and the acoustic parameters of trailing edge noise of swept blade are accurately identified by the CLEAN-SC algorithm.Based on the comparison of multiple sets of experimental results,the influence of different amplitudes,widths and geometric ratios of the serrated trailing edge of swept blade on the noise reduction effect is studied in depth.The experimental results show that in the case of low turbulence intensity and free upcoming flow,in consideration of overall sound pressure level,the longer the amplitude of serrations,the more obvious the noise reduction effect;the bigger the serration width,the better the noise reduction effect of trailing edge.For the same geometric ratio of the trailing edge serrations,the larger the overall size of serrations,the better performance the trailing edge noise reduction.For a specific swept blade,there must be an optimal size of the serrated trailing edge which can reduce the noise most.In all experiments,the maximum Sound Pressure Level(SPL)reduction is 1.2 dB.Moreover,the noise reduction effect of“stream-wise”trailing edge serration is far better than the“symmetric”serration,and all“symmetric”serrations never have a noise reduction effect.