Study On Piezoelectric Ceramic Layout And Flutter Suppression Of Large Wind Turbine Blades

The large scale of wind turbine makes the blade aeroelastic problem become the main cause of blade fatigue damage and shortened service life.In recent years,the application of piezoelectric material in the field of active control has effectively solved this problem.In order to study the influence of piezoelectric ceramics on the dynamic stability of blades,this work takes 8MW wind turbine as the research object on the basis of the existing flutter's control research.The effect of piezoelectric ceramic on blade flutter was studied by adding piezoelectric ceramic sheet to the layer.Moreover,the applicability of piezoelectric material to flexible structure with variable thickness is discussed by building dynamic experimental platform of cantilever beam.The specific contents are as follows:1.The aerodynamic design of 8MW wind turbine blade is carried out based on BEM theory.Numerical simulation is used to verify the correctness of the designed blade and the aerodynamic performance of the blade under rated operating conditions.The results showed that the axial force of blade increased first and then decreased from blade root to blade tip and reached the maximum value near 72 m,while the tangential force did not change significantly on the whole.The velocity diffusion in the xz plane gradually deepens with the distance to the center of the hub and spreads almost to the entire static domain in 2D.The pressure difference between the upper and lower surfaces of the blade increases with the radius.2.Wind turbine blades under five schemes were designed for the placement of piezoelectric ceramic sheets and the effect of piezoelectric cera mics on the blade structure and performance was studied.The results show that the natural frequency of the blade can be increased by laying piezoelectric material.Under the action of static load,all five kinds of blades can increase the blade stiffness and decrease the maximum tip displacement.The best solution is to lay the piezoelectric ceramics all along the blade.Under the transient load,all five kinds of blades can effectively reduce the amplitude of blade tip and the time needed to reach steady state.The piezoelectric material laid at 40% ~ 1 of the blade has the best flutter inhibition effect.3.The influence of piezoelectric material on the characteristics of the cantilever with equal and varying thickness is analyzed by introducing the piezoelectric ceramic sheet into the experimental study of the cantilever.The results show that under the static load,the displacement and strain of the free end of the cantilever with equal or varying thickness after the addition of the piezoelectric ceramic are obviously reduced.Under dynamic load,the vibration of the cantilever beam gradually changes from low-frequency large amplitude motion to high-frequency small amplitude motion with the increase of excitation frequency.Moreover,large voltage can better reduce the vibration amplitude within the voltage range that the piezoelectric ceramic sheet can withstand.This work studies the active control of piezoelectric material applied to wind turbine blades.The reasonable laying scheme of the piezoelectric ceramics and its antiflutter effect on the blades are obtained.It provides reference for flutter active control and safe operation of large wind turbine.