Stator Modification Methods for Diagonal Flow Fans to Achieve Noise Reduction of Rotor-Stator Interaction

The effect of three noise reduction methods for rotor-stator interaction in diagonal flow fans was studied. The unsteady flow field and directivity of tonal noise were obtained by numerical simulation based on computational fluid dynamics (CFD) and the Ffowcs Williams and Hawkings (FW-H) method; the baseline model was tested in a semi-anechoic chamber. The generation mechanism and location of noise were investigated. In addition, the characteristics of tonal noise at blade-passing frequency (BPF) were studied, along with its harmonics. The results show that the tonal noise at 1 BPF dominates the overall sound pressure level. Proper rotor-stator spacing, a large forward-leaned angle, and a large backward-swept angle are beneficial to reduce tonal noise. Also, the noise reduction effect is related to the low amplitude and to the phase shift caused by the pressure response of the rotor wake impinging on stator surfaces, especially near the leading edge at 1 BPF.