Bend-Twist Coupling Characteristics Calculations of 5MW Wind Turbine Blades based on 3D Shell Model

Abstract

Five 5MW wind turbine blades with different ply orientation are modeled based on 3D shell element. The MPC method and a beam element are used in calculating their section stiffness. Bend-twist coupling parameters of the five models are calculated. Results show that section stiffness of wind turbine blade based on 3D shell model has higher efficiency and the accuracy of the method based on 3D shell model is verified. INSTRUCTIONAs a passive means to shape the power curve and reduce loads, bend-twist coupling blades are commonly researched. Researching related to bend-twist coupling blade in the 1990's are summarized in References [1] and pointed that the enough twist-bend coupling can reduce 10% of the fatigue load and improve energy capture. Reference [2] also confirm that bend-twist coupling blade using off-axis carbon in the skin will induce extra twist and alleviate load. Reference [3] design coupled blades where fibers are rotated only on the outboard part of blade and demonstrate this blade can achieve good load mitigation capabilities.According to the slender structure characteristics of the blade, it usually can be simplified as beam model and bend-twist coupling parameter based on beam model is given in Reference [4], obviously, sectional properties are necessary to calculated based on this definition. Analytical method based on the classical laminated plate theory (CLP) in reference [5,6] has a higher efficiency while numerical method based on 2D finite element method in reference [7,8] has a higher accuracy.As a complex structure, blades are composed of several airfoils and made up of anisotropy material and 3D model of blades can more accurate and more truly covers the characteristics of the large blade. In this paper, the 5MW blades with different ply orientation are modeled based on 3D shell element and their section stiffness and bend-twist coupling parameters are calculated.