波浪形前缘降低后掠叶片宽频噪声实验研究

Experimental Study on Broadband Noise Reduction with Wavy Leading Edge for Sweep Blade

关键词:  后掠叶片  波浪形前缘  宽频噪声  干涉  湍流

Key words:  Sweep blade  Wavy leading edge  Broadband noise  Interference  Turbulence

摘要:

为了研究波浪形前缘对后掠叶片湍流干涉噪声的影响，通过放置于叶片上游的倾斜圆柱产生尾迹，圆柱尾迹为各向异性的湍流，之后湍流与叶片相互干涉产生干涉噪声。实验采用的叶型后掠角度为30°，截面为NACA0012翼型。在气流来流速度v分别为30，40，60，70m/s的情况下（基于叶片弦长的雷诺数为3×10⁵~7×10⁵），使用31个麦克风线阵列测量了基准后掠叶片与波浪形前缘叶片对应的叶片湍流干涉噪声。采用Clean-SC算法处理数据，得到不同幅值与波长下后掠叶片前缘噪声信息。实验结果表明，波浪形前缘幅值与波长对总声压级降噪量均有影响，使用最大幅值和最小波长的波浪形前缘降噪效果最好；不同气流速度下，采用相同的波浪形前缘，使用斯特劳哈尔数表征的噪声频谱图变化规律相似。

Abstract:

In order to investigate the blade-turbulence interaction （BTI） noise reduction of a sweep blade with wavy leading edge（WLE） configuration，the noise radiation from the sweep blade leading-edge is generated by the interaction of the blade and incoming anisotropic turbulence which is produced by a rod whose wake impinges onto the downstream blade. The swept blade with swept angle of 30 degrees and constructed by NACA0012 airfoil was experimental investigated in this study. The BTI noise for the swept blade with and without wavy leading edge were measured with the flow speeds of U=30m/s， 40m/s， 60m/s and 70m/s， and the corresponding Reynolds numbers based on the blade chord are in 3×10⁵ ~ 7×10⁵. A linear array of 31 microphones was used in this study to determine the BTI noise of the swept blade. With the Clean-SC approach， clear and quantitative sound radiation results of the leading edge noise source of swept blade with different amplitudes and wavelengths are obtained. It is observed that the OASPL （overall sound pressure level） reduction is sensitive to both the amplitude and wavelength of the WLE. The WLE with the largest amplitude and smallest wavelength can achieve the most considerable OASPL reduction. It is found in this study that the spectra of BTI noise reduction with Strouhal number is almost the same for same WLE under different airflow velocities.