波浪前缘静子叶片对高速轴流风扇单音噪声的影响

航空发动机压气机噪声与大型风洞压缩机噪声问题日益凸显，相关研究机构迫切需求新的降噪手段以指导大型叶轮机械降噪设计。为了探索波浪前缘静子叶片在大型叶轮机械降噪中的应用前景，采用非定常雷诺平均Navier-Stoke（URANS）方程与FW-H方程混合方法对基准静子叶片和3种波浪前缘静子叶片的降噪效果进行了数值模拟，研究对象静子来流平均马赫数约为0.49，基于静子叶片弦长的雷诺数约为1 040 000。数值预测结果显示：波浪前缘静子叶片可以显著降低高速轴流风扇单音噪声，但会对风扇的气动性能产生少许不利影响；相较于基准静子叶片，3种波浪前缘静子叶片可以在1BPF时降低风扇入口声功率级0.97~1.5 dB，2BPF时降低风扇入口声功率级2.89~4.9 dB，3BPF时降低风扇入口声功率级3.32~4.72 dB；同时，总压比降低0.1%~0.8%，等熵效率降低0.1%~0.3%。进一步研究表明：不同频率下声源振幅和相位关系是风扇单音噪声强度的主要影响因素，总的来说，幅值的增加会降低声源强度，然而通过改变声源相位关系的降噪方式则需要兼顾径向模态与波长两个方面。

Tonal noise reduction of a high-speed single axial fan with wavy leading-edge stator

It is an urgent need for related research institutes to find new methods to guide large impeller mechanical noise reduction design when the noise problem of aero-engine and large wind tunnel compressor is becoming more and more prominent. To explore the application prospect of the wavy leading-edge stator for noise reduction of large turbomachinery, the noise reduction effect of the base stator and three kinds of wavy leading-edge stator are numerically simulated by the hybrid method of Unsteady Reynolds-Averaged Navier-Stokes (URANS) equation and FW-H equation. The inflow averaged Mach number at leading-edge of stator is about 0.49, and the corresponding stator blade chord based Reynolds number is about 1 040 000. Numerical prediction results show that the wavy leading-edge stator can substantially reduce the fan tonal noise but have certain adverse effects on the fan aerodynamic performance. Compared with base blade, the fan inlet sound power level could be reduced by about 0.97-1.5 dB at 1BPF, 2.89-4.9 dB at 2BPF, and 3.32-4.72 dB at 3BPF by using those wavy leading-edge stators, while the total pressure ratio reduced by about 0.1%~0.8%, and the isentropic efficiency reduced by about 0.1%~0.3%. Further study shows that the amplitude and phase relationship of sound source at different frequencies are the main influencing factors for fan tonal noise. In general, the sound source intensity will reduce with the increase of amplitude. However, the noise reduction method by changing the phase relationship of the sound source needs to balance both the radial mode and the wavelength.