Performance improvement and noise reduction analysis of multi-blade centrifugal fan imitating long-eared owl wing surface

Abstract

This research was inspired by the long-eared owl's ability to fly silently. For the first time in this study, a wind turbine blade is designed to mimic the wing surface and the leading edge of the long-eared owl. The commonly used two-dimensional blade profile in previous studies is replaced by a more effective three-dimensional profile. This change leads to improved aerodynamic performance of the multi-blade centrifugal fan and reduced noise levels. The airfoil and leading edge profile parameters of the long-eared owl were extracted and utilized. These parameters were used to develop a fitting formula based on their correlation. This formula facilitated the design and optimization of a bionic blade (B-Blade). The results indicate a 4.1% enhancement in the maximum flow rate compared to the original blade fan, alongside a noise reduction of 1.3 dB(A) under identical static pressure conditions. An examination of the internal flow, noise, and sound source characteristics of both fan types was conducted, elucidating the aerodynamic noise mechanism. Fan noise propagation showed pronounced dipole sound source traits. The sound source area at the B-Blade fan's inlet and the volute tongue was more compact, leading to a decrease in mid-low frequency discrete noise. The sound source intensity was also diminished. The B-Blade fan also ameliorated the flow distribution at the impeller outlet, reducing the unstable interaction between the impeller and volute tongue, thereby effectively diminishing noise.