Aerodynamic performance and noise level of AC (Air-Conditioner) indoor unit fan system has always been receiving much concern. But most previous studies have been focused on aerodynamic performance and noise level, and less attention is paid to the noise radiation problem. It is essential to identify and quantify the noise radiation, so as to control and reduce the noise level effectively.
The objective of the present investigation is to identify the influential factors of the Blade Passing Frequency (BPF) noise radiation and investigate noise directivity distribution of two double-suction centrifugal flow fans with different fan blades used in AC indoor unit. A hybrid numerical approach is developed for predicting the unsteady fan flow and noise radiation. Unsteady fan flow is solved by Detached Eddy Simulation (DES) method. Then the areoacoustic calculation is performed based on the predicted unsteady flow field, and the obtained results are used as dipole source inputs in acoustic Finite Element Model (FEM) for predicting the noise radiation of the centrifugal fans.
Experimental tests of aerodynamic and aeroacoustic performance are conducted respectively for the fan. A comparison is made between the experimental and measured results. It is demonstrated that the predicted aeroacoustic and noise radiation both agree with the measured ones and the fan blade geometry is much influential to acoustic prediction. Finally, directivity of BPF noise radiation to noise level is evaluated for two different fans.