Research On Intelligent Blade Suppression Flutter Of Large Wind Turbines

Blade is one of the key parts of wind turbine.Nowadays,the development of wind turbines tends to build large wind turbines.Because of the large wind turbine sweeping area of large units,more wind energy can be captured for wind turbines.The increasing wind wheel makes the blades more slender.When the wind wheel rotates,the blades that will bear complex air loads will be accompanied by a large number of aeroelastic problems.The coupling of wind load and blade deformation produces unstable self excited vibration,which is caused by the gradual increase of the coupling effect,and is called flutter.The blade of the 8MW wind turbine is taken as the research object.Through the analysis of the aeroelastic stability of the blade,it is concluded that the blade can suppress the flutter by increasing the blade stiffness and damping.A large intelligent blade is designed by embedding piezoelectric fiber into the glass fiber composite layer.Electric load is applied to the piezoelectric fiber layer of intelligent blade,and the inverse piezoelectric effect is produced by piezoelectric material,so that the stiffness and damping of blade can be controlled within a certain range.Finally,through the establishment of intelligent blade structural model and Simulation of the model,the results of comparison and analysis verify the feasibility of intelligent blade to suppress flutter.The verification feasibility details are as follows:In this thesis,the aerodynamic shape of 8MW wind turbine is designed,and the blade and wind basin model is established by using Solidworks software.The flow field operation is carried out by the ANSYS software Fluent module,and the pressure of the blade surface under the action of multiple wind speeds is obtained as the preload of static and transient structural analysis.Based on the aerodynamic shape of the designed blade,the structure model was built,and Solidworks software was used to construct the blade model including the blade web,beam cap and the front and back edge.The model is introduced into the Mechanical APDL module of ANSYS software,and the structure model is defined by unit definition,material selection and layer design.Finally,the finite element structure model of the blade is established.According to the modal analysis of the finite element model,the first eight blade modes and their natural modes are obtained.The excitation and vibration characteristics of the blades are used as the basis for the electric load of the piezoelectric action layer.After introducing the preload to the blade structure model,the static structure is calculated.The displacement of every degree of freedom before and after the electric load is applied and the distribution of the stress of the blade is compared,and the change of the stiffness and stress of the blade is analyzed.The dynamic structure is calculated by applying gust load and periodic electric load on the blade.The displacement value of each degree of freedom,the peak value of the torsion angle and the vibration attenuation are compared,and the effect of the reverse piezoelectric effect on the damping of the blade is analyzed.The innovative points of this thesis include :the design of a 8MW large wind turbine intelligent blade with a piezoelectric layer;the structural analysis exerts the pre load from the numerical simulation flow field,and the structural model uses the piezoelectric coupling method to carry out steady analysis and transient analysis.Finally,the intelligent blade designed by the method of embedding the piezoelectric layer under the composite layer of the large wind turbine blade can be used to control the stiffness and damping of the blade by applying the electric load to the piezoelectric layer,and the conclusion that the blade flutter suppression is effectively suppressed.