Research On Aerodynamic Characteristics And Blade Surface Structure Optimization Of Wind Turbine Under Yaw Flow

Wind turbines in the atmospheric environment were operated in a yaw state,resulting in a reduction in the wind energy capture rate of the wind wheel,and will seriously affected the service life of the wind turbine.Therefore,it was of great significance to studied the aerodynamic characteristics and flow field characteristics of wind turbines under yaw conditions.This paper analyzes the aerodynamic characteristics of wind turbines operating under yaw conditions through the combination of theoretical analysis methods,external field monitoring methods,comparative verification methods and numerical simulation methods of turbulence,and the convex hull drag reduction theory was used to optimize its blade surface structure.The main research content includes the following aspects:(1)Study the aerodynamic characteristics and flow field characteristics of horizontal axis wind turbines under rated operating conditions.the result shows:Under rated operating conditions,the speed loss along the radial direction quickly recovered at the hub position,and the speed loss along the axial flow field recovered and slows down with increasing distance.The loss of speed in the tower shadow area caused the tangential and normal forces on the blade to decrease.Through the DES method,the change law of the aerodynamic characteristics of the wind turbine was obtained,The fluctuation of aerodynamic load was lessed than 1%,At the same time,along the radial direction of the blade at 0.6R,the flow field of the tower and the blade had the strongest mutual influence.(2)Study the aerodynamic characteristics of wind turbines in yaw conditions,the result shows:During the change of yaw,When?(28)30~?,the growth rate of Average yaw force was 28.6%,The maximum average value of the yaw moment,And the period fluctuation was the largest;When the yaw angle??30~?,During the period,the pitching force and pitching moment drop sharply at the trough,and the amplitude change increases,The range of the reverse flows area was sharply reduced,And form a large area of low-speed wake diffusion area behind it,The pressure on the blade pressure surface drops sharply.In different wind speed conditions.The yaw force_zF and yaw momentM_z show an increasing trend with increasing wind speed,The maximum growth rate was reached at a yaw angle of 30°;The pitching momentM_x increases with wind speed,When the yaw angle was 30°,Its growth rate reached its maximum.(3)Adopt NACA 0012 airfoil model,Study the drag reduction characteristics of convex hull non-smooth surface structure on airfoil,the result shows:Hemispherical convex hull structure,The optimal convex hull height was 0.004C,The convex hull structure had a better drag reduction effect at the angle of attack,When the interval ratio of the convex hull structure was 3,The airfoil reached a maximum drag reduction rate of 12.69%,The maximum rate of increase was 7.44%;When the maximum drag reduction effect of the streamlined convex hull structure was 14°,The drag reduction rate was 17.39%.(4)Study the optimization of convex hull structure to improve the operation stability and power of wind turbines,the result shows:According to the blade airfoil structure characteristics,hemispherical convex hull was used.The distribution range and arrangement of convex hull structure were determined according to the distribution area of turbulent flow energy on the blade surface.When running without yaw,After the convex hull structure was added,the area of wind energy utilization in the wind turbine flow field was expanded;The separation point of the blade surface moves towards the trailing edge;The turbulent flow energy distribution on the suction surface of the blade was uniform,Enhance its output power and operating stability;After attaching the convex hull.The yaw moment and pitch moment peak value change was more than 30%;Wind turbine torque and thrust have been increased by 14.717%and 5.412%,And as the wind speed increases,the amount of lifting tends to be stable.During yaw operation,After attaching convex hull structure.The average value,maximum value and minimum value of the yaw moment had been reduced:35.18%,21.78%,64.27%,The growth rate of wind turbine torque and thrust was 22.75%,8.84%,And the power output stability was good.