Aerodynamics And Structural Performance Of Blunt Trailing Edge Blades Of Large Wind Turbines

In recent years,with the continuous improvement of the wind power industry,the development of large-scale wind turbines constitutes an inevitable trend.The ever-expanding blade size has led to a growing contradiction between the aerodynamic and structural characteristics of the blade.However,the traditional airfoil has been unable to meet the design requirements of modern wind turbines for low load and light weight.Due to its excellent aerodynamic and structural characteristics,the blunt-tailed edge airfoil has attracted more and more attention and attention from scholars at home and abroad.In order to study the influence of the blunt-tailed edge airfoil on the performance of the wind turbine,this paper uses the NREL 5MW wind turbine as the object to improve the blunt trailing edge of the inner airfoil of the blade.The combination of theoretical analysis and numerical simulation is used to study the effects of the blunt-tailed edge airfoil on the aerodynamic and structural characteristics of the blade.The details and conclusions are as follows:Firstly,the correctness of the model and method used is verified by calculating the rise and drag coefficients of the S809 airfoil under different grid numbers and comparing with the experimental data.On this basis,the symmetrical blunt trailing edge modification of the airfoil in the 40%R(blade radius)of the NREL 5MW wind turbine blade is simulated.Through numerical simulation,it is found that with the increase of the thickness of the tail,the improved airfoil The lift coefficient is gradually increased and the lift-to-drag ratio is increased.The improved blunt-tailed edge airfoil tail has a pair of similar vortices,which causes the airflow at the trailing edge to wash down,changing the distribution of surrounding pressure,reducing the back pressure gradient at the trailing edge of the suction surface,delaying The emergence of flow separation increases the aerodynamic performance of the airfoil.Secondly,the original windfoil of the wind turbine is replaced by the improved best blunt edge airfoil.The two-equation SST k-co model is used to simulate the improved wind turbine and the original wind turbine in Fluent.Under the calculation conditions,the power of the improved wind turbine is higher than that of the original wind turbine;as the wind speed increases,the advantages of the improved wind turbine gradually increase,but the axial force of the blade increases.Through flow field analysis and comparison,it is found that flow separation occurs in both roots of the blade,and secondary flow occurs,but the degree of separation of the improved blade is significantly lower than that of the original blade,and the flow of the blade is improved in the separation zone.The line distribution is more turbulent than the original leaves.Then,the degraded layering scheme is designed for two types of blades.The finite element model is established in ANSYS Mechanical.The unidirectional fluid-solid coupling method is used to analyze and compare the structural performance of the two types of blades under different loads.The results show that compared with the original blade,the tip displacement and total stress of the improved blunt trailing edge blade are reduced;the gain effect of improving the centrifugal force of the blade is higher than that of the original blade.Through the modal analysis,the low-order mode of the blade has a good gain after adopting the blunt-tailed airfoil,so that the resonance can be better avoided.Finally,the factors affecting the performance of the blunt blade,the parameters of the beam cap,are studied.It is found that the thickness of the beam cap has the greatest influence on the structure of all the parameters of the beam cap,and the order of the layer angle has the least influence on the structure.The above conclusions are used to optimize the structure of the blade,reduce the width of the beam cap of the blunt trailing edge airfoil,increase the thickness of the beam cap in the area,and increase the thickness of the blade root and the middle beam cap.After comparison,the quality of the blade is optimized and the structural performance is improved.In this paper,the blunt trailing edge of the 40%R inner airfoil of NREL 5MW wind turbine blade is modified and replaced with the original airfoil.The combination of theoretical analysis and numerical simulation is used to study the two types of wind turbines.The new characteristics of the aerodynamics and structure of the trailing edge blade,and the structural optimization of the blunt trailing edge blade,improve the structural performance and reduce the blade quality,which provides a reference for the design and optimization of the wind turbine.