前缘锯齿对边界层不稳定噪声的影响

Effect of leading-edge serrations on boundary layer instability noise

为探索仿生学前缘锯齿结构的降噪规律,试验研究了低雷诺数到中等雷诺数（Re=（2~8）×10~5）不同攻角状态下9种前缘锯齿结构对叶片层流边界层不稳定噪声的影响。研究表明：前缘锯齿可以减弱甚至完全抑制边界层不稳定噪声,降噪效果对锯齿振幅和锯齿波长均比较敏感,锯齿振幅越大、波长越小,降噪效果越好,降噪量可达30dB;前缘锯齿结构可以诱导产生流向涡,影响叶片下游边界层流动,破坏声学反馈回路;前缘锯齿对边界层不稳定噪声峰值频率没有影响。

In order to explore the noise reduction law of the bionics leading-edge serrations,the effect of nine leading-edge serrations on blade laminar boundary layer instability noise has been investigated experimentally at low to moderate Reynolds number（Re=（2-8）×10~5）and different angle of attacks.It can be concluded that leading-edge serrations can decrease and even totally suppress blade laminar boundary layer instability noise.The noise reduction effect is very sensitive to both serration amplitude and serration wavelength,and the blade with larger amplitude and smaller wavelength has better noise reduction effect,which can reach a maximum of 30 dB.The noise reduction mechanism is attributed to the stream-wise vortices induced by the leading-edge serrations,which can affect blade downstream boundary layer flow and then destroy the acoustic feed-back loop.The leading-edge serrations have no effect on the instability noise peak frequency.