Aerodynamic Performance of Multi-Blade Centrifugal Fan with Bionic Blades Inspired by C-Type Start of Cyprinidae

Inspired by the high-efficiency swimming posture of cyprinid C-type escape reaction and the characteristics of eddy-current around the fish body, the bionic blades are designed to improve the aerodynamic performance and reduce the noise of a multi-blade centrifugal fan. Firstly, the reverse engineering method is used to obtain the center line equation and horizontal profile equation of cyprinidae in C-type starting posture, and bionic equally-thick blades are designed and optimized based on the C-type middle-arc. Through the comparison of numerical calculation and experimental results of fan aerodynamic performance, bionic equally-thick blades with the optimal installation angle (O-BETBs) are obtained. After applying the O-BETB to the prototype fan, the fan flow-rate increases by 6.8% while the noise decreases by 0.5 dB(A). Further, the reconstructed geometric profile of fish body is coupled into the O-BETB to obtain a coupled bionic blade (CBB) to further improve the aerodynamic performance of the multi-blade centrifugal fan. The results show that the flow-rate of a CBB fan is increased by 8. 3% while the noise is reduced by 1. 1 dB(A). The flow field analysis shows that the coupled blade with bionic middle arc and fish body contour has better guidance effect at the leading edge inlet angle and blade profile, and the low-speed separation vortex in the inter-blade channel is significantly smaller than that of the other two impellers; The wake vortex shedding at the trailing edge causes the weakest degree of air flow heterogeneity, which alleviates the unsteady interaction of the wake with the volute tongue and with the volute. Analysis of sound field characteristics shows that the aerodynamic noise of the multi blade centrifugal fan is mainly concentrated in the middle and low frequency bands. The reduced noise of CBB fans in the middle and low frequency bands is also mainly attributed to the use of the CBB, the suppression of separation vortex in impeller channel, the weakening of unsteady interaction between wake and volute wall, and the effective control of sound pressure pulsation on the blade surface and volute tongue. © 2022 Xi'an Jiaotong University. All rights reserved.