Study On The Influence Of New 3D Guide Vane Attachment On Aerodynamic Performance Of Wind Turbines

Wind energy is one of the clean renewable energy sources with the most potential for large-scale commercial development.In order to enhance the efficiency of wind turbines for harnessing wind energy,blades are gradually evolving towards large-scale development.However,in the transition zone from the blade root to maximum chord length of large wind turbine blades,a thick airfoil with suboptimal aerodynamic performance is typically employed for ensuring the stability of blade structure.Meanwhile,the angle of attack near the blade root of a wind turbine typically ranges from 10° to 30° during operation,resulting in suboptimal aerodynamic performance in the blade root of large-scale wind turbine blades.In this paper,a new type of 3D guide vane attachment is designed to improve the aerodynamic performance of the blade root and increase the output power of the wind turbine by the flow control.The attachment is located on the suction surface of the blade and is installed in the transition area between the blade root and the maximum chord length.When the fluid passes through the guide vane attachment,the attachment will change the flow direction of the fluid,forcing the fluid to deflect towards the suction surface of the blade to inhibit flow separation phenomenon.Firstly,the technical path of aerodynamic analysis of the new 3D guide vane attachment using computational fluid dynamics is explored to provide a reliable scheme for the subsequent numerical simulation research.Taking DTU230 airfoil as the research object,numerical simulation is carried out on the grid with different spanwise lengths in the computational domain,and the results are compared with the experimental data.It is found that with the increase of spanwise lengths in the computational domain,the numerical simulation results are closer to the experimental values.In addition,the influence of the number of chord and spanwise nodes on the calculation results is studied,and the mesh element size of the airfoil is determined to achieve mesh independence.At the same time,the influence of local mesh changes at the attachment site after installation of the guide vane attachment on numerical simulation of airfoil is taken into account.The non-thickness surface mesh of the attachment is transformed into internal flow field mesh.It has been demonstrated that the implementation of mesh encryption at the guide vane attachment exerts negligible influence on the simulation outcomes of airfoil body.Secondly,through the numerical simulation experiment design,the design parameters of guide vane accessory with optimal aerodynamic performance are explored.Taking DTU230 airfoil as the object of study,with Re=3×103 and angle of attack AoA=20°,13 groups of different guide vane accessories were designed with the overall lift-to-drag ratio of the accessory and airfoil as the response value.The effects of three experimental factors,the chord position,the height and the length of the accessory on the overall lift-to-drag ratio were studied.The results of variance analysis of quadratic polynomial regression equation of the whole liftto-drag ratio show that the sensitivity of the whole lift-to-drag ratio to test factors is the chord position of the attachment,the height of the attachment and the length of the attachment in order from large to small.Then,the influence of the chord position and the height of the attachment on the aerodynamic performance of the airfoil is further studied by the control variates.On the one hand,from the perspective of the overall lift-to-drag ratio of the accessory and airfoil,the aerodynamic performance improvement effect is the best when the center of the accessory is located at 0.15 chord.When the attachment height is 0.15 chord length,the overall lift-drag ratio is 87.16%higher than that of the original airfoil.At the same time,the aerodynamic improvement effect of the guide vane attachment at 0.15 chord is relatively stable,and the lift force coefficient,drag coefficient and overall lift-to-drag ratio of the controlled airfoil will not change too much with the change of the height of the attachment.On the other hand,from the Angle of lift-drag ratio of the controlled airfoil,the closer the attachment is to 0.45 chord,the better the optimization effect of the attachment on the airfoil.When the attachment is located at 0.45 chord,the length of accessory is 0.2 chord length and the height of accessory is 0.05 chord length,the lift coefficient of the controlled airfoil reaches the maximum value,increasing by 34%compared with the original airfoil.Meanwhile,the lift-to-drag ratio of the guide vane attachment and the airfoil increases by 80.46%compared with the original airfoil.Finally,based on the research conclusion that adding accessory can improve the aerodynamic performance of the airfoil,the influence of installing guide vane accessory on the aerodynamic performance of wind turbine blades is explored.Taking NREL 5MW wind turbine as the object,the attachment design is based on the characteristics of the flow separation area near the blade root.It is found that the turbine output power increases by 0.32%when the wind speed is 8 m/s and 0.55%when the wind speed is 11.4 m/s after adding the guide vane accessory.Moreover,the aerodynamic performance of the blades far away from the blade root is better,which shows the coupling phenomenon between the three-dimensional rotation effect of wind turbines and the effect of guide vane inhibiting separation flow.In conclusion,through numerical simulation,this paper designs,analyzes,and optimizes a new type of pneumatic attachment applicable to the blade root,which can inhibit flow separation at a large angle of attack,and thus improve the lift-to-drag ratio of the airfoil and aerodynamic performance of the wind turbine,providing reference for the relevant design of wind turbines.