Optimal Design And Fluid-structure Analysis Of Small Wind Turbine Blades

Wind energy is favored by people as a clean and pollution-free renewable energy source.The research and development of wind turbines have a positive significance for China's economic and social development.This paper takes small wind turbines that can be used in cities as the research object,and uses the method of correction coefficient to improve the blade shape parameters,so as to improve the overall aerodynamic performance of the wind turbine.In this paper,based on Wilson theory and the theory of leaf element momentum correction,a theoretical model of wind turbine blade design is established.The NACA63-215 airfoil is suitable for medium and low speed wind conditions,based on the local optimal principle of wind energy utilization coefficient,perform optimization calculation through software such as Matlab,and obtain the induction factor at different radius of the blade.The chord length and torsion angle are used to build a solid model of3-8 blades of 6 different wind turbine blades.The shape parameters of the blade are optimized,which improves the output power of the wind turbine and the structural strength of the blade.The NACA63-215 airfoil was used as the original airfoil design of the blade,and the effects of various turbulence models,Reynolds number,blade angle of attack,relative thickness and other factors on the aerodynamic performance of the airfoil were analyzed by numerical calculation.The results show that under the operating conditions of small wind turbines,the results obtained by the S-A turbulence model are more consistent with the results provided by the literature.At the same time,it was found that the flow field of the wind turbine airfoil affected by the angle of attack will change significantly.When the angle of attack is 0°,the velocity field and the pressure field of the upper and lower surfaces of the airfoil are symmetrically distributed;when the angle of attack is 8°,the airfoil In the front section,there is a clear negative pressure area,and the pressure on the lower surface of the airfoil is higher than that on the upper surface.At an angle of attackof 16°,the negative pressure area moves significantly toward the front of the airfoil,and a separation vortex appears at the tail,causing a boundary layer separation.When the angle of attack is fixed,the greater the Reynolds number,the greater the airfoil lift coefficient and the smaller the drag coefficient.When the angle of attack is lower than8°,the relative thickness of the airfoil has little effect on the lift resistance of the airfoil;when the angle of attack is higher than 8°,the larger the relative thickness,the larger the airfoil lift coefficient and the smaller the drag coefficient.The numerical calculation method was used to analyze the aerodynamic performance of six different numbers of wind turbine blades,and the effects of wind speed,wind turbine blade number and rotation speed on wind turbine output power,torque,wind energy utilization coefficient and other aerodynamic parameters were obtained.The output power of the wind turbine increases approximately exponentially with the increase of wind speed.The output power of the 6 and 7 blade wind turbines changes more significantly than the wind turbines with other blades;the output torque of the wind turbine increases with the speed and then decreases,and a certain wind speed corresponds to a optimal speed to meet the requirements of the largest wind energy utilization factor.The analysis of the wind turbine flow field shows that the energy loss of the front and back of the 6 and 7 blade wind turbine is greater.At this time,the energy conversion efficiency of the 6 and 7 blade wind turbine is higher.Using the two-way fluid-solid coupling method,through numerical calculations,the flow field distribution of the wind turbines with different blade numbers in the fluid and solid domains in the limited channel is obtained.Study the flow field changes of wind turbines at different blade numbers,speeds,and moments.The results show that the blade deformation will affect the fluctuation of the flow field,and the flow field of the even-numbered blade wind turbine is more stable than that of the odd blade.Stress and strain analysis of wind turbine blades: The total deformation of wind turbine blades increases with the increase of the number of blades,the total deformation of 8-blade wind turbines is the largest;the equivalent stress of 7-blade wind turbines is the largest.At the same time,under the action of the coupling force formed by centrifugal force and aerodynamic force,the greater the speed,the greater the stress and strain of the blade.The results show that the prestress frequency is not much different from the natural frequency at rest,and the blade has no obvious prestress effect.