Aero -acoustics Calculation and Noise Reducing Techniques of Multi -Blade Centrifugal Fan

摘要

Based on software of computational fluid dynamics FLUENT, an efficient and feasible numerical method (CFD/CAA) for calculating the aerodynamic noise of the multi -blade centrifugal fan is developed. This method is applied in the numerical simulation of three-dimensional flow field and sound field, and the results are analyzed in order to research the main aerodynamic noise source and strength of the multiblade centrifugal fan, which can provide lots of useful information for noise reducing. According to theoretical analysis and numerical analysis, some proposals are provided to reduce the aerodynamic noise with the method of numerical calculation. Vortex noise can be reduced mainly through the optimization of the geometric parameters of the impeller, volute and installing a rotation diffuser in the outlet of the impeller. Discrete noise can be reduced mainly by changing the form of volute tongue, such as the use of sloping volute tongue and gradient volute tongue. In the meantime, the experimental tests are carried out on the two improved fans, one is designed with optimized inlet and outlet blade angle, and the other is installed a rotation diffuser in the outlet The test results show that the noise of the improved fan is reduced by a certain degree compared with the prototype with tiny change on the performance.