The Study Of Internal Flow Field And Aerodynamic Noise Characteristics On Contra-Rotating Fan

Because of Contra-rotating fan's special structure and superior performance, Contra-rotating fan is used extensively in such as engineering field of boiler, tunnel and mine, but noise problems are always troubling researchers and users. This paper sets a Mine Used Contra-rotating fan which model is FBD5.0/2×7.5 as an example, using Solidworks and Gambit to build model. Adopting CFD amongst LES and FFT to accomplish analyzing the unsteady value of three dimensional flow field of fan,and estimating fan aerodynamic noise.Firstly, using arithmetic of SIMPLE and Realizable k- e turbulence model and setting the contra-rotating fan with velocity-inlet and pressure-outlet boundary condition to calculate steady-state numerical result by moving reference frames method.Secondly, setting the convergence of steady numerical calculation as the initial value of unsteady computation, use Moving Mesh and the method of time advance to process numerical iteration calculation. Select the second rotation period which is enough iteration to compare with four different periods( 0.25 T,0.5T, 0.75 T and 1T) of pressure and velocity of two stage impeller rotating regional interference surface.Thirdly, in two stage impeller rotating region, setting 10 level monitors total 30 monitoring points. On condition unsteady calculation that outputting time domain pulse pressure distribution in two steady period, then adopting FFT to get the power spectrum. By means of monitoring each points of pulse frequency domain graph to obtain the pressure pulsation frequency size, fluctuation intensity and frequency characteristics. Compared with every fluctuating trends of monitoring points, in order to be sure about fluid along the radial and axial fan impeller pulse distribution rule.Last, use noise module of Fluent to obtain distribution sound pressure value of the monitoring on frequency change through FW-H on base LES. Introduce Proudman to estimate fan aerodynamic noise sound power, and forecast broadband acoustic source position to find the main noise source area of the fan. It plays an important role in noise estimating and designing for fan.