Abstract: 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.

Key words: wavy leading-edge blade, tonal noise, acoustic analogy theory, fan, FW-H equations, hybrid method, noise reduction