Research Of Corner Vanes Technique On Low Pressure Loss

In wind tunnel applications corner pressure losses are often one of the main contributors to the overall pressure drop in the tunnel circuit. If can minimize losses associated with the flow in corners, it will lower the wind tunnel movement power and then lowering the total pressure loss of wind tunnel, thus, has significantly effect on the exaltation of efficiency. At the low pressure loss guide vanes research aspect, great progress has been made in the research under the condition of upstream uniformity. But in the wind tunnel, the corner upstream is usually distributed by the model asymmetrical. The actual performance when upstream and guide vane deviating from designing angle of attack is our main concern and research purpose. Moreover, the CARDC is constructing the 5.5m×4m Low Turbulence Aeroacoustic Wind Tunnel. In that wind tunnel research to manufacture process, how to minimize the pressure loss of each corner, thus lower the tunnel circuit pressure loss is an importance project. This paper research is conducted on the low pressure loss guide vane needing of 5.5m×4m Low Turbulence Aeroacoustic Wind Tunnel. The point of research is the actual performance and influence of guide vane when corner upstream is asymmetry or there is model existed and upstream is distributed so upstream and guide vane is deviating from designing angle of attack.This research includes two parts. At first, three types of turning vane airfoils(a thin 1/4-circle shape with straight prolongation at the heading and trailing edge, a circular-arc shape and a controlled-diffusion shape named SA070.61) have been evaluated in the first corner of a 0.1-scale model of CARDC's proposed 5.5m×4m Low Turbulence Aeroacoustic Wind Tunnel. Each type of guide vane was set of different setting angle. Flow surveys of pressure were taken for both the first corner and fan section to determine their respective losses. Second, take the experimenting corner (guide vane) configuration of research as the physics model, carry on the numerical simulation research, to thoroughly understand the geography solution guide vane flow field, and to further analyze the reason of different guide vane has the different function.Conclusions from the study are as follows:The result of experiment shows that, SA070.61 guide vane corresponding the overall corner loss was about 10 percent of inlet dynamic pressure, corresponding the overall wind tunnel circuit loss was about 34 percent of the test section's dynamic pressure and the effect of the vane's installation angle is little to pressure loss. The circular-arc shape guide vane corresponding the overall corner loss was about 18 percent of the inlet dynamic pressure, corresponding the overall wind tunnel circuit loss was about 34.5 percent of the test section's dynamic pressure and the pressure loss changes with the installation angle is also not affected. The thin 1/4-circle shape guide vane corresponding the overall corner loss was above 18 percent of the inlet dynamic pressure, corresponding the overall wind tunnel circuit loss was above 34.7 percent of the test section's dynamic pressure, but, the pressure loss changes with the installation angle is significantly. As a whole, the SA070.61 guide vane has the best aerodynamic performance, the circular-cir shape guide vane is better and the thin 1/4-circle shape guide vane is the worst. The experiment result illustrates that the SA070.61 has also lower pressure loss coefficient when upstream is asymmetrical distributing and can be introduced to wind tunnel.The performance of different type of guide vane and installation of the angle, numerical results and experiments coincide well.Detail of more overall corner flow field are studied by numerical simulation and some useful result is obtained. First, different from condition of uniformity free upstream, downstream of corner is more even than upstream and the two-dimensional pressure loss coefficient is larger than three-dimensional pressure loss coefficient. This difference is decreased while calculating from the inlet and outlet of the core part of install the guide vanes. The second is because of the three-dimensional influence of the wall boundary, at guide vane near the tail, it will form the obvious eddy structure, makes all three types of guide vanes expressed a common trend: The central neighborhood appears a static pressure peak on suction side, which would cause separation on the suction side; And this phenomenon can be connected with the trend of the loss distribution along the flow direction together. The third is SA070.61 vane carry on good static pressure distribution on the suction side, but circular-cir vane and thin 1/4-circle vane's static pressure distribution all presenting'W', having two static pressure peaks. This phenomenon can be connected with that SA070.61 having lower pressure loss coefficient together. Also the pressure distribution of SA070.61 vane surface changes little impact with the installation of angle, but the circular-cir and thin 1/4-circle are bad.