| With the shortage of fossil energy and the prominence of environmental problems,China practices the concept of green development and is the pioneer of " carbon peak" and " carbon neutrality".As a renewable and pollution-free natural resource in nature,wind energy is used by more and more planning.As a key component of wind turbine to obtain wind energy,the aerodynamic performance and load bearing capacity of blade are the key to the stable and safe operation of wind turbine.At home and abroad,the large-scale wind turbine has been the development trend.The blade size is getting larger and larger,the blade flexibility is reduced,and the load during operation is more complicated.For this reason,domestic and foreign research experts have tried to sweep the wind turbine by referring to the swept characteristics of the aircraft wing.It is found that the swept design can make the wind turbine blade achieve the purpose of load reduction due to the deviation between the pitch axis and the torsion axis of its geometric shape.In order to study the aerodynamic characteristics of swept blade wind turbine under shear flow and the dynamic and static mechanical characteristics of wind turbine blades under this flow condition.In this paper,the NREL 5 MW wind turbine blade is used as the prototype blade.On this basis,two different swept blades(swept 2m blade and swept 4m blade)are designed.The CFD numerical simulation method is used to simulate the two swept blades and straight blades.Under the condition of shear index of 0.2,the aerodynamic forces of the three blades under different inflow and different azimuth angles are compared and analyzed by loading different inflow wind speeds of7m/s,9m/s,11.4m/s,13 m/s,15 m/s and 17 m/s.Using ANSYS Workbench platform,the static and dynamic analysis of the aerodynamic load,centrifugal load and gravity load of the three blades under different inflows is carried out.The main work and research results of this paper are as follows:1.Compared with the NREL 5MW wind turbine design power,the numerical simulation results of the three blades are basically the same under the rated wind speed.At the rated wind speed and above the rated wind speed,due to the adaptive load reduction effect of the swept blade,the wind turbine power of the swept 4m blade is smaller than the design value and the power value of the other two blades.The axial force and circumferential force of three kinds of blades under different wind speeds are analyzed.It is found that the axial force and circumferential force of the wind turbine blade increase with the increase of wind speed at the rated wind speed.After the rated wind speed,due to the pitch effect,the axial force and circumferential force of the blade decrease with the wind speed.In the spanwise direction of the blade,due to the load reduction effect of the swept section,the axial thrust and circumferential force of the swept 4m blade are smaller than those of the other two blades.2.Through the non-prestressed modal analysis of the finite element model,it is found that the modal frequencies of the three blades gradually increase with the increase of the order,and the increase of the subsequent sweep decreases gradually.Through the Campbell diagram,it is clear that the three blades have no intersection with the first-order natural frequency in the speed range,and the 1P and first-order natural frequency of the straight blade,the swept 2m blade and the swept 4m blade are13.45%,11.9% and 10% different from the rated wind speed,respectively,and resonance damage will not occur;through statics research,it is found that under the rated wind speed,the order of displacement of the three blades at different azimuth angles is 0 ° > 90 ° > 270 ° > 180 °.Different from displacement,the maximum stress occurs at 90 ° azimuth angle,and the order of magnitude at different azimuth angles follows : 90 ° > 270 ° > 0 ° > 180 °.3.The modal analysis of the three finite element models under prestress is carried out.The results show that after the prestress is loaded,the stiffness of the blade increases under the action of centrifugal force,and the results are slightly improved compared with the non-prestressed modal results.Secondly,the prestress results of the blade in the half-way rotation of the blade(0°～180°)are :180°> 90°>0°;through the study of the buckling stability of the blade,it is found that with the increase of the wind speed,the buckling factor of the wind turbine blade gradually increases,indicating that the anti-buckling ability of the blade is stronger with the increase of the wind speed,and the buckling factor of the blade is also different at different azimuth angles.By comparison,it is found that the order of magnitude is:180°>90°>0°. |
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