Aerodynamic noise prediction of a centrifugal fan considering the volute effect using IBEM

Customer demands for quieter centrifugal fans in the industry have brought their noise to the forefront. It is found that dipole sources on the surfaces of the rotating impeller and volute are the main acoustic noise sources. The volute effect is seen to have a significant influence on the radiation characters of the fan, although this is frequently ignored by previous studies. Hence, the indirect boundary element method (IBEM) is employed to study the noise of an industrial forward-curved centrifugal fan and to take the effect of volute reflection and scattering of the sound wave into consideration. A large eddy simulation (LES) is used to gain reliable pressure fluctuations on the surfaces of volute and rotating blades. Then the FW-H equation and Lowson equation are applied to calculate the dipole sources on the surfaces of the volute and the blades respectively. The predicted aerodynamic noise of the fan with and without the volute is compared to experiment. The results indicate that the pressure fluctuations on the volute surfaces, especially on the tongue surface, are the main dipole source. It is also found that the application of IBEM can improve the prediction accuracy greatly, especially for the blade passing frequency and its higher harmonics.