To improve aerodynamic performance and reduce noise for a split air conditioner outdoor unit fan, a hybrid method is developed, which combines the Computational Fluid Dynamics (CFD) flow simulation with Computational Aero Acoustics (CAA) noise analysis, where Large Eddy Simulation (LES) model and Ffowcs Williams-Hawkings (FW-H) acoustic analogy model are solved respectively for the unsteady flow characteristics and far field noise solutions. Experimental tests are conducted respectively for fan aerodynamic performance and acoustic behavior, with the aerodynamic performance test rig and semi-anechoic room. Numerical results demonstrates that the main dipole sound sources are located mainly on the blade trailing edge and tip surface, and shroud and casing inner surface, such a distribution is caused by fluctuations in instantaneous pressure associated with rotor-stator interaction. The casing dipole sources contribute largely to the total noise of the fan, and are the main causes for fan noise. It is demonstrated both numerically and experimentally that modifications of impeller blade geometry are effective to reduce the fan noise. Two redesign schemes, the concaved-trailing edge and flanging outer-edge blades, are used, but the latter is more effective in reducing the fan noise as well as shaft power simultaneously. The predicted SPL agrees well with the measured results at the fundamental frequency of the highest intensity, and the hybrid method used in the present study is justified.

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