Tonal noise prediction in a small high speed centrifugal fan and experimental validation

This paper presents the work done to establish a methodology that is capable of predicting tonal noise generation in high speed centrifugal fans. The deliverables from this work emphasize on identifying and characterizing the source of tonal noise in the centrifugal fan. Computational fluid dynamics (CFD) modeling was performed using 3-D Detached Eddy Simulation (DES) to compute the unsteady flow field in the fan. The calculated time history of surface data from the CFD is then used in Ffowcs Williams-Hawkings (FW-H) solver to predict the far field noise levels. The predicted aerodynamics and aeroacoustics results are in good agreement with the experimental data acquired from the flow testing facility and the anechoic chamber. The study conducted on the centrifugal fan shows that the aerodynamic interaction between the non-uniform impeller outflow and the leading edge of the diffuser vane is the source of tonal noise generation. The impingement of the jet-wake flow structure from the impeller outflow causes periodical pressure fluctuation on the leading edge of the diffuser vanes which leads to the tonal noise generation at the blade passing frequency (BPF).