Power Performance Assessment Of Straight-bladed Vertical Axis Wind Turbines In Turbulent Flows By Wind Tunnel Testing

With the large-scale exploitation of traditional fossil fuels,energy crisis and other issues greatly affect human life,hence,the demand for renewable energy such as wind energy is increasing.Among them,wind turbines are one of the main tools of wind energy utilization.In the field of wind energy utilization,vertical axis wind turbines(VAWTs)are used in cities due to low noise,high performance,and easy maintenance.This study carries out multi-parameter optimization of the aerodynamic performance of VAWTs by wind tunnel testing.In this study,a prototype of VAWT was made.The prototype was mainly composed of three parts: the fan-the test system-the supporting tower.The test system consisted of a speed torque sensor,a hysteresis brake and a supporting frame.On the one hand,the system ensured that the rotation of the wind turbine was freely transferred to the torque and speed sensor and the hysteresis brake;on the other hand,the system transferred the weight of the wind turbine to the support frame instead of the torque sensor,ensuring that the sensor measured the torque and speed accurately.In the paper,the grid was used to generate uniform turbulence,and the grid was used to simulate the wind field.Three turbulence intensities of 5.1%,10.9% and14.6% were successfully debugged.Four parameter levels of aspect ratio,pitch angle,solidity and airfoil were selected.After that,parametric studies were conducted in turbulent flows,and the influences of each parameter on the power performance of VAWTs were obtained: With the increase of the aspect ratio,the rated tip speed ratio(TSR)and power coefficient increased.The increase in solidity could effectively improve the power coefficient of VAWTs,whereas the rated TSR decreased.Negative pitch angles improved the power coefficient while positive pitch angles were found to deteriorate the overall efficiency.The aerodynamic performance of VAWT with the airfoil NACA0018 was better than that of VAWT with the NACA4418 airfoil.Turbulence intensity was observed to improve the aerodynamic performance.Taguchi method as a robust design approach was used.The design goal was to maximize the power coefficient of VAWTs.Four design parameters of wind turbine aspect ratio,pitch angle,solidity and turbulence intensity were selected to obtain a four-factor four-level design.The range analysis method was applied to the results of orthogonal working conditions.The order of the influence of each design parameter on the power performance was obtained: pitch angle>solidity>aspect ratio>turbulence intensity.A generalized additive model was applied to the results of Taguchi method.And the interaction of various influencing parameters was analyzed to predict the results of the conditions under the complete horizontal combination test.Finally,the results of parametric studies,the results of Taguchi design method and the prediction results of the generalized additive model were compared,supplemented and verified.The results provided a reference for the selection and layout of WAWT parameters.