Research On Bend-twist Coupling Characteristics And Lightweight Design Of Large Wind Turbine Blade

With the increasement of blade size,the flexibity,mass and loads of blade also become larger.The blade with bend-twist coupling(BTC)effect will twist as it bends under the wind load,which alleviates the aerodynamic force as a result of changing the angle of attack.The BTC characteristics are researched from the angle of numerical solution,and the mass of blade is reduced on this basis,which contribute to the realization of large-scale wind turbine and the reduction of levelized cost of energy.The main research and results of the paper are as follows:(1)Nonlinear time domain aeroelastic simulations of the full wind turbine are performed using servo-aero-elastic solver hGAST.In hGAST solver,the full wind turbine is considered as components of blades,drive train and tower in the multibody framework.The aerodynamic loads of BTC blade are calculated based on the BEM theory.Calculating the extreme load in the root of blade according the design load cases of IEC 61400,which consider the aerodynamic load,centrifugal force and gravity of blade,to prepare for the lightweight design of blade.(2)The geometry of cross section and material layup of large wind turbine baldes are complicated.In this paper,the detaild 3D finite element model of DTU 10 MW wind turbine is built from bottom-up by using the parametric design language APDL.This method improves the modeling speed and reflects the structural deformation and stress in detail.Next,the model is verified through mass and modal comparison.(3)The BTC is accomplished by introducing an offset angle on the plies of material over the spar caps of the blade.Evaluate the effect of plies offset angle and coupling area on the maximum tip twist angle.Next,the influence of BTC on natural frequency is analyzed.(4)Reduction of mass is investigated by decreasing the material thickness with uniform coefficient,while observing the stress levels of BTC blade.It was found that when the material thickness of 5 degree and 10 degree laminated blades decreased by 5% and 8%,respectively,the stress curve fitted well with the stress curve of the baseline blade,and correspondingly,the blade quality also decreased by 5% and 9%,respectively.The ultimate strength check and modal check are carried out on the blade after the material reduction to ensure that the blade meets the ultimate strength requirements and there will be no resonance accident.The content of this research make contribute to the load and mass reduction of wind turbine blade,which is significant for the realization of large scale wind turbine.