Investigation of the aerodynamic performance and noise suppression characteristics for a voluteless centrifugal fan with bionic serrated trailing edges

Bionic serrated blades with three configurations for a voluteless centrifugal fan are proposed to improve the aerodynamic performance and suppress the noise, including triangular serrated blade (T-BLE), square serrated blade (S-BLE) and semi-circular serrated blade (C-BLE). The improved delayed detached eddy turbulence model and Ffowcs Williams-Hawkings acoustic model are employed to deal with the flow fields and acoustic characteristics. The models are first validated by comparing the experimental results and simulation data in terms of the aerodynamic and noise tests. Then, a comprehensive analysis of flow field characteristics and acoustic performance of a voluteless fan is conducted. Results indicate that the aerodynamic performance of serrated blades decreases due to the reduced air-exhaust area, with the T-BLE showing a 1.6% reduction. The improvement in wake flow pattern, vortex formation and separation for triangular serrations is pronounced. The serration designs significantly suppress primary tonal noise at the 13th blade passing frequency and other broadband noise. The total sound pressure levels of the T-BLE, S-BLE and C-BLE decrease by 6.27 dB, 4.06 dB and 5.14 dB, respectively. The serration structures inhibit noise generation and propagation by weakening periodic unsteady interactions between wake vortices and stationary flow. In general, the T-BLE achieves better noise reduction while maintaining the same aerodynamic performance.