Research On Aerodynamic Performance Of Straight-Bladed Vertical Axis Wind Turbine With B-Spline Curved Wind Gathering Devices

With the increasingly serious international fossil energy crisis and environmental pollution problems,green energy such as wind power has become a research hotspot for countries based on the present and looking to the future.Since small wind turbines are suitable for remote areas such as rural areas,they have always been a research hotspot.In order to improve the static starting characteristics of the straight-bladed vertical axis wind turbine（SB-VAWT）and increase the dynamic output power of the wind turbine,this paper proposes a wind gathering devices（WGD）with a convex streamline profile based on the B-Spline curve generation method,which is installed at the top and bottom of the wind rotor respectively.It is used to increase the flow rate of incoming wind and optimize the distribution of the flow field near the wind wheel,so that the wind wheel can absorb more wind energy and achieve the characteristics of easier startup and higher energy output.The research mainly takes the WGD as the object,optimizes the design parameters of the convex streamline WGD,takes the average starting moment and average power coefficient of the SB-VAWT as the research goal,and adopts the research method combining numerical simulation and wind tunnel test.The content and research conclusions are as follows:（1）Using the shrinking nozzle model,SB-VAWT with a B-Spline curved WGD is proposed,and the five main structural parameters of the WGH are optimized.Using the quadratic orthogonal rotation test design and response surface analysis,the average starting moment of the wind rotor is used as the screening index,and the SB-VAWT equipped with WGD with different structural parameters are calculated through numerical simulation,and the average starting moment index is obtained.The regression equation is obtained by variance analysis,and finally the best parameter combination of the WGD is obtained:the gap distance between the wind gathering device and the wind wheelΔL=60mm,the bottom circle radius of the WGD R₁=412mm,the top circle radius of the wind gathering device R₂=542mm,the inlet The angleα₁=19°and the exit angleα₂=23°.（2）The WGD and the SB-VAWT are used to form a wind-gathering type wind turbine.Taking this as the research object,the combination of numerical simulation and wind tunnel test is used to study the effect of the WGD on the VAWT.The effect of the VAWT on the start-up performance and power output.The results show that the B-Spline curved WGD can greatly improve the start-up performance and power output of the SB-VAWT,and the wind speed with the best lifting effect is U=5m/s.When U=5m/s,the average increase percentage of the starting moment coefficient of the wind-gathering wind turbine is 24.7%.Whenφ=80°,the average starting moment coefficient increases the most,up to 38.8%;whenφ=100°,the average starting moment coefficient reaches the peak value,which can be increas ed by a maximum of 31.2%compared with the VAWT.The optimal tip speed ratio of the wind-gathering wind turbine reaches2.0,which corresponds to the peak average power coefficient at this wind speed.Compared with the VAWT,the peak average power coefficient is increased by 51.7%.The average percentage increase in power coefficient reached 41.3%.（3）The pressure field analysis and velocity field analysis of the two wind turbines with and without the WGD are carried out,and the optimization mechanism of the B-Spline curve WGD on the starting performance and power output of the SB-VAWT is summarized.For the blade:Improve the pressure distribution of the blade,increase the pressure difference on the ventral back of the blade to increase the pressure gradient,so that the blade is subjected to greater aerodynamic force;Optimize the position of the pressure distribution to generate more effective positive moment;Reduce the resistance of the leading edge of the blade and increase the Trailing edge thrust.For the flow channel in the WGD:reduce the energy loss caused by the vortex generated by the blades;increase the gas velocity near the blades and inside the wind turbine when the wind turbine rotates,reduce the flow velocity of the wake,and increase t he energy density of the incoming flow.Combining the above two reasons,the B-Spline curved WGD optimizes the aerodynamic characteristics of the SB-VAWT in all directions.In this study,it is verified that the B-Spline curved WGD can significantly improve the aerodynamic performance of the SB-VAWT through a combination of numerical simulation and wind tunnel test.The proposed WGD with B-Spline curve has a certain reference value for the application and development of small and medium-sized SB-VAWT in areas where wind resources are scarce,uneven distribution of wind resources and low wind speed.