Integrated Design Of Structure And Materials Of Honeycomb Core In The Main Beam Of Vertical Axis Wind Turbine Blad

The increasing demand for low-cost energy all over the world have greatly promoted the development of the wind energy.Wind turbine is widely used as the device to convert wind energy into electric energy,and its blade is the key component to capture wind energy.During operation of the wind turbine,the blade is subjected to the moment of swing,shimmy and torsion due to the aerodynamic force,gravity,inertia force and other loads,while the main beam bears most of the shear load generated by the three moments.Honeycomb core has the advantages of light weight,high specific strength and high specific stiffness,and filling it in the main beam cavity along the blade span can effectively improve the overall stiffness and bearing performance of the blade.The mechanical properties of the honeycomb core are determined by the material distribution and the geometry and arrangement of cells.Thus,the integrated design of structure and material of honeycomb core has important theoretical significance and engineering application value to improve the structural performance of blade.The main research work and results of this paper are as follows:(1)The equivalent elastic modulus and Poisson’s ratio of the cell are derived by the Castigliano theorem.The honeycomb core is uniformly divided into several substructure columns along the axial,and the stiffness matrixes of the substructures are obtained by Finite Element Method(FEM).The super-element stiffness matrixes are established using the static condensation,and are assembled according to the node number to obtain the global stiffness matrix of the honeycomb core.The structural deformation of the honeycomb core is calculated under the shear load and compared with that from ANSYS software.The multi-objective structural optimization model,in which the number of the substructures,the angle of the cell and the ratio of splitter width to inclined wall length are taken as design variables,is solved using the improved Particle Swarm Optimization(PSO)to maximize the equivalent elastic modulus and minimize the structure deformation,and the static and dynamic characteristics of original and optimized honeycomb cores are analyzed.The results show that after the optimization,the maximum displacement,stress and strain obviously decrease,and the harmonic displacement is maximum when the excitation frequency is equal to the second-order natural frequency.(2)The analytical relations between the size and shape control factors and equivalent elastic constants are established using the energy method.The stiffness matrixes of substructures formed by uniform division of the honeycomb core are calculated using the FEM.The static condensation technology reorganizing the substructure stiffness matrix is integrated with the structural stiffness equation to calculate the deformation of the honeycomb core under shear loads.A multi-objective optimization model taking the size and shape control factors as design variables is solved using the improved PSO to maximize the equivalent elastic moduli and minimize the structural deformation.The results are compared with those from the collaborative technology of MATLAB and ANSYS,and the static,modal and harmonic response analysis are performed on original and optimized honeycomb cores.The results show that the stiffness,strength and stability of the honeycomb core obtained by using the optimization method of geometry and non-uniform arrangement for cells considering size effect are significantly higher than those before optimization.(3)The topology optimization technology based on improved SIMP interpolation model is applied to obtain the material distribution in the design domain.The functional relationship between the geometric parameters of cells and the density of topological elements in the substructure of the honeycomb core is established based on the local relative density mapping,and the structural deformation of honeycomb core is obtained by the static condensation technique and FEM.The multi-objective structural optimization model,in which the size and shape control factors and the topological element density are taken as design variables is solved using the improved PSO to maximize the equivalent elastic modulus and minimize the structure deformation and design domain flexibility.The original and optimized honeycomb core are filled into the vertical axis wind turbine blade by ANSYS software respectively,and the variation laws of static and dynamic characteristics of the blade are studied.The results show that the integrated design of structure and material for the honeycomb core filled in the cavity between webs can effectively improve the stiffness,bearing performance and stability of the blade.