| Since the second industrial revolution,over exploitation of fossil energy has resulted in the shortage of energy supply and environmental pollution.In order to solve the above problems,people began to widely use wind energy and other clean and renewable energy.As the main means to obtain wind energy,wind turbine has made great progress in recent years.At present,there are more and more researches on the structure of wind turbine.The main components of wind turbine structure are tower,blade and generator set.Tower is the main force bearing component of random loads such as wind and earthquake.In order to obtain more wind energy,the wind turbine is built higher and higher,the tower is more and more slender,and the generator is more and more heavy,the resulting effect and tower geometric nonlinearity will more and more significantly affect the dynamic response of wind turbine structure.As the main component of bearing wind load,the aeroelastic problem of blade is more prominent.When the wind speed is high,the aerodynamic damping may amplify the dynamic response of blade,resulting in aerodynamic instability and even fracture,which seriously affects the safe operation of blade.In order to study the above problems,the main contents and research methods of this paper are as follows:(1)In order to study the structural effect and geometric nonlinearity of wind turbine,a theoretical model of wind turbine structure is established based on continuous beam.Secondly,the nonlinear control equation of variable cross-section beam considering geometric nonlinearity is derived by using the principle of virtual work.The partial differential equations considering the effect of wind turbine structure and geometric nonlinearity of tower are obtained by simplifying the equation.The differential quadrature method and generalized differential quadrature method are used to discretize the partial differential equations,and the ordinary differential equations are obtained.Finally,the time domain integral method is used to solve the ordinary differential equations to obtain the response of wind turbine structure under wind and earthquake.The results show that: in the range of small deformation,the influence of tower geometric nonlinearity on the dynamic response of wind turbine structure can be ignored,the influence of gravity second-order effect on the dynamic response is more obvious,the softer the site soil is,the greater the influence of gravity second-order effect is;the influence of vertical earthquake effect on horizontal seismic response can be ignored;with the increase of tower deformation,the number of tower is smaller The effect of he non-linear is increasing gradually,and the tower appears stiffening with deformation.(2)In order to study the bending and torsional flutter of wind turbine blade under shutdown condition,the classical bending and torsional flutter analysis model of continuous beam is adopted.Based on the unsteady aerodynamic force of Theo Dawson,the partial differential equation of bending and torsional flutter of blade under shutdown condition is firstly given.Secondly,the torsional vibration partial differential equation is discretized by differential quadrature method,and the bending vibration partial differential equation is discretized by generalized differential quadrature method,and the flutter eigenvalue equation is obtained.Finally,the flutter wind speed and flutter frequency of the blade are obtained by solving the eigenvalue equation,and the results are verified with the results obtained by the traditional Galerkin method.The results show that the flutter analysis results of the three node differential quadrature method and the generalized differential quadrature method can meet the requirements of engineering calculation accuracy;in order to improve the flutter wind speed,the blade section center of gravity and elasticity should be adjusted The axis should be as close as possible.(3)In order to study the aerodynamic stability of a rotating wind turbine blade,a two degree of freedom constant cross-section rotating continuous beam model was adopted.Based on the Greenberg aerodynamic model,the aeroelastic partial differential equations of blade shimmy/flutter in the rotating state were given.Secondly,the generalized differential quadrature method is used to discretize the equation,and the aerodynamic ordinary differential equations are obtained.Finally,given the parameters of a wind turbine blade,the complex eigenvalue analysis method and time domain integration method are combined to study the aerodynamic stability of blade shimmy / flutter.The results show that: the highorder modes of blade shimmy / flutter are prone to aerodynamic instability,comparatively speaking,the flutter aerodynamic stability changes greatly with the wind speed,and the shimmy is small;appropriately increasing the blade speed is helpful to improve the aerodynamic stability of the blade. |
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