Investigation acoustic effect of the convexity-preserving axial flow fan based on Bezier function

The axial flow fan is the major component of air-conditioning outside units, and the noise reduction has always been the main object of the fan researches in the past decades. Many previous researches have concentrated on the noise reduction of the axial flow fan by changing the tip clearance and blade shape of the trailing edge (TE). In this article, a local convexity-preserving structure at leading edge (LE) has been proposed, which is implemented through retrofit design of the original fan blade based on Bezier function method. The effect on the aerodynamic noise of the convexity-preserving of the improved fan B is investigated. To this purpose, the unsteady flow field in the fan is predicted by solving the incompressible Reynolds-averaged Navier-Stokes (RANS) equations with the SST-SAS turbulence model. The result shows that the convexity-preserving structure is beneficial for the noise reduction without decreasing the axial fan performance. Moreover, the noise frequency spectrograms in the far field and sound pressure of 1/3 octave are given by experiment. The noise-reduction effect of improved fan B is verified by comparing the sound pressure lever (SPL) at different frequency bands.