Numerical Study on Duct Acoustic Modal and Source Flow Structure of Fan Tones With Leaned and Swept Stator

Abstract The present study is focused on the fan tone noise reduction with leaned and swept stator blade. A hybrid URANS/Goldstein’s equations method is used to calculate the unsteady flow and tone noise of a high loaded axial-flow fan. The numerical simulation results show that the fan tone noise will be increased with negative angle lean, while it will be reduced with positive lean angle. The higher the harmonic number, the larger the noise reduction with positive lean angle blade. It is found that when the stator blade sweeps back of 30 degrees, the fan tone noise at the fan inlet can be reduced by 5.5 dB, while the fan tone noise at the fan outlet can be reduced by 9.8dB. It is also found that the combined leaned and swept blade has the largest noise reduction. When the fan stator blade lean angle and sweep angle are both 30 degrees, the fan inlet tone noise can be reduced by 8.5 dB, while the fan outlet tone noise can be reduced by 17dB. The numerical simulation results indicate that the influence of blade lean and sweep on fan mass flow is less than 1% within the scope of this study. The negative lean angle of stator blade can improve the aerodynamic performance, but the positive lean angle of the stator blade will reduce the total pressure ratio and isentropic efficiency of the fan.