Influence Of Airfoil Concave Parameters On Blade Aerodynamic Performance

Fixed pitch Angle rotation stall type wind power generator for wind turbines startup performance,hub of airfoil design installation Angle generally larger,its purpose is to make wind turbine get under low wind speed large torque,when the wind turbines start smoothly,it is the main power of the wind turbines area will move from blade root to leaves,leaf,this will lead to wind turbines after normal boot,Due to the relatively large blade element attack Angle at the blade root,the section near the blade root is more prone to flow separation and even stall,which limits the power capacity of the blade to a certain extent.However,it is found that the airflow on the blade suction surface can be controlled by concaving the airfoil suction surface and selecting the geometrical characteristics and location of the concave surface reasonably.In addition,the convergence location and influence range of the flow around the suction surface can be controlled by selecting the airfoil concave deformation properly.Therefore,this article embarks from the test,in view of the distributed small horizontal axis wind turbine,to enhance the wind turbine aerodynamic performance for the purpose,based on the rotating blade airfoil concave on the suction surface modified,adopts the method of combining experiment and simulation by reasonable selection airfoil geometric feature and position of concave change to achieve control of the blade suction surface air flow,The influence of different concave geometrical characteristics and positions on the aerodynamic performance of rotating wind turbine was investigated.By analyzing the axial Reynolds stress on the suction surface of the rotating blade of the wind turbine,the turning point of the turbulent flow of the suction surface layer of the airfoil under certain working conditions was obtained.The concave position was selected as a reference,and the influence of different concave geometrical characteristics on the aerodynamic travel energy of the wind turbine was investigated.Blade exhibition to the selection of location by a given wind speed and blade speed,get different exhibition to the position of section airfoil Angle of attack,in combination with a turning point in the early stage of the different Angle of attack airfoil position determine the blade suction surface to the flow separation area,with appropriate concave profile and get the aerodynamic performance of concave variable blade lofting and processing the corresponding concave blade,Place in the low speed wind tunnel test end to check the aerodynamic performance improvement.At the wind speed of 7～11m/s,the workability of the concave variable wind turbine and the original wind turbine as well as the flow field changes on the suction surface are compared under different concave variable geometry characteristics.It is found that the concave airfoil with a long axis length of 2.57% chord length and a short axis length of1.54% chord length before and after the ellipse is connected by B-spline curve has the best comprehensive aerodynamic performance among all characteristic geometrical concave blades with a concave blade extending 350 mm from blade root to blade tip,and the average aerodynamic performance is improved by 0.74% compared with the original blade.Maximum aerodynamic performance increased by 3.26%;It is found that the concave vane directly connected with a circular diameter of 1.54% chord length can significantly improve the aerodynamic performance of the blade under the condition of large Angle of attack,but seriously damage the aerodynamic performance under the condition of small Angle of attack.At the same time,after the airfoil is concave,the convergent airflow flowing from blade root to blade tip can be induced to flow regularly in the vicinity of the blade’s suction surface along the spreading direction,thus reducing the energy loss caused by the irregular radial flow of the suction surface caused by the interaction between blade rotation and unstable incoming flow.It is also proved in the experiment that the concave effect near the root of the blade is better than that near the middle and tip of the blade.Finally,it is found that the inductive effect of concave deformation on the transverse flow is also attributed to the effect of delayed transition and extended laminar flow caused by concave deformation on the chord flow.Therefore,when considering the transverse concave deformation,the location of the transverse concave deformation should be selected based on the inductive effect of concave deformation on the chord flow.