Research On Dynamic Modeling And Modal Analysis Of Wind Turbine Blades

With the wind turbine blades being developed towards targets of large size and good flexibility,the dynamic characteristics of the blades have also been changing.Especially in order to avoid the occurrence of resonance,it is very important to calculate the low-order inherent frequency of the blade.In this study,the Largrange equation of the rotating beam was derived by derivative calculations based on the Largrange-Hamilton system of the rotating beam and then the dynamic equation of the wind turbine blade was established.The modality of the blade were analyzed based on the control equation of the rotating beam.The influences of rotational inertia,centrifugal,density of the material and elastic modulus of the material on the inherent frequencies of the blade were studied.The main contents of this study are as follows:The Hamilton principle of the rotating beam can be obtained from the Largrange density by the Lagrange equation of elastic cantilever.The Largrange equation of the wind turbine blade was established by the method of finding the resident value of the Hamilton principle of the rotating beam according to the Largrange-Hamilton system.According to the algorithm of variation derivative and the derivation properties of the Lagrange equation,by deducing the items in the Lagrange equation of the wind turbine blade,the dynamic equation of the wind turbine blade is established.The dynamic equation of the wind turbine blade established by the Lagrange equation in this study is consistent with the equation in existing literature,and thus the effectiveness of the method adopted in this study is proved.By reducing the dynamic equation of the wind turbine blade to the Euler-Berrnoulli beam model,the Euler-Berrnoulli beam model with centrifugal stiffening and the Timoshenko beam model with centrifugal stiffening,and studying the influencing factors of the inherent frequency of the blade,while the frequency calculation result of the Euler-Berrnoulli beam model with centrifugal stiffening terms is slightly higher than the frequency of the Euler-Berrnoulli beam,but the influence of the centrifugal stiffening terms is small;due to the effects of rotational inertia and shear deformation,the centrifugal stiffening.The frequency calculation result of the Timoshenko beam model of the term is lower than that of the Euler-Berrnoulli beam model with the centrifugal stiffening term.Under the same conditions,the reduction of the blade material density and the increase of the elastic modulus will significantly increase the natural frequency of the blade.The study in this paper provides a beneficial reference for the preliminary design and safety evaluation of blade structures.