Analysis of circumferential skew effect on rotor/stator interaction noise reduction

The rotor/stator interaction noise as a type of the dipole sound source is generated from the pressure fluctuation on the stator vanes. The noise is one of the main noise sources in multistage turbomachines such as axial compressors and fans. In the paper, the effect of circumferential skewed angle on the rotor/ stator interaction tone noise reduction was studied. The Ffowcs-Williams and Hawkings (FW-H) acoustics model showed that the amplitude of pressure fluctuation on the stator vanes was the main impacting factor of the interaction noise when the sound source was compact. Consequently, the pressure fluctuation on the stator vanes was calculated using computational fluid dynamics (CFD) method to study the relationship between the circumferential skewed angles and the amplitude of pressure fluctuation at BPF (blade passing frequency) and its harmonics. The research results concluded that the test fan with circumferential backward skew rotor blades and backward skew stator vanes could reduce the amplitude compared against other test fans. The sound pressure levels (SPLs) of the interaction tone noise calculated using the FW-H acoustics model also supported the conclusion