| Fan is one of the core department of the wind tunnel section, performance of the fan have a major impact on the wind tunnel's. In addition to the aerodynamic efficiency of fan has influence on energy saving, the fan noise has a direct impact on the background noise of test section. Typically, using a fan as dynamic segment, the fan's noise is the main source of noise in some wind tunnel. At present, China Aerodynamics Research & Development Center is building low turbulence aeroacoustic wind tunnel, in the development of the process, how to increase fan's efficiency and reduce the fan's noise is an important topic of the aerodynamic design of this wind tunnel. This paper will setting in the needs of low turbulence aeroacoustic wind tunnel reduces the fan noise and carrying out arbitrary vortex design in fan design application.This paper's study mainly includes two parts. First of all, arbitrary vortex design method and free vortex design method were used to design aerodynamic parameters of the two fan system separately, and then compare the two fan system's performance through the numerical simulation.This paper introduces the design process of arbitrary vortex method and free vortex method, firstly. Free vortex design assumptions to flow axial speed equal everywhere, as well as air passes through the fan along the different radial height after the pressure rise is equal. Under these assumptions, we can infer flow rotate speed in different positions is inversely proportional to the distance of the rotation away from the fan blade section to the axis. In the arbitrary vortex design, on the assumption that axial velocity along the radial flow is unfixed, flow rotate speed along the radial rotation is not must a inversely proportional. Therefore, the arbitrary vortex design method can have a more well-distributed axial speed at outlet of fan system by regulating the rotate speed distribution. The more well-distributed speed of the fan exit can improve the aerodynamic performance of diffuse section. In addition, the arbitrary vortex method gives the fan blade more accurate lift coefficient distribution, which could guarantee adequate surge-to-stall margin and improve the fan aerodynamic and acoustic performance.In the numerical simulation, the fan of low turbulence aeroacoustic pilot wind tunnel is used as physical model. First, taking the fan made by Shanghai fan factory for example, by comparison with the experimental data we can verify the reliability of the numerical simulation. We use the aerodynamic parameters of the two fan systems, which were designed by arbitrary vortex method and free vortex method, to establish the fan physical model. In this paper, we use 9 numerical simulation conditions totally, corresponding to the wind speed in closed test section 100m / s, wind speed in closed test section 130m / s, wind speed in open test section 100m / s, and the state correspond to the arbitrary vortex and the free vortex fan base installation angle, and each increase of 4°blade installation angle. The result of numerical simulation indicate: compared to the free vortex method, the arbitrary vortex fan minish the separation on the tip and root of blade, get a more well-distributed axial speed distribution at the outlet of fan system. And the efficiency of blade is increased by arbitrary vortex method. These results show the arbitrary vortex method is feasible in design of large wind tunnel, especially the wind tunnel which has the need of acoustics test. |
PDF Full Text Request