Dynamic Analysis And Structure Optimization Of Large Wind Turbine Blades

Due to the energy crisis and environmental pollution, renewable energy, especially wind power industry is developing rapidly. With the progress of wind power technology, the installed capacity and the radius of wind turbine is increasing. Besides, the shape of blade is more complex. In order to get more wind energy resources and ensure safety, aerodynamic and structure performance of wind turbine blade is very important. Although the wind power industry is growing rapidy in China, the core design and manufacturing technology has not yet been mastered. The main contents of this paper are as follows:1. Aerodynamic shape design of wind turbine blade. The aerodynamic theories of wind turbine blades were summarized. Betz, Schmitz, Glauert and Wilson methods were used to design 1.5MW wind turbine blades. Combining with the design results of the four theoretical models, the best design model was chosed.2. Geometric shape correction and aerodynamic performance anslysis. Due to the aerodynamic design theory only considering how to get more wind power, but ignoring the structural performance and processability, the three polynomial fitting method was usd for geometric shape correction of wind turbine blades. The whole wind turbine model was built and the electrical power under every working condition was calculated with GH Bladed software. The results satisfied the design goals.3. Finite element modeling and structure analysis of wind turbine blade. Based on the coordinate transformation theory, the original two-dimensional coordinate data of airfoils was convert to the three-dimensional coordinate data. Then, the finite element model of wind turbine blade was built with software ANSYS. The loads of the wind turbine blade under the steady flow condition were calculated with GH Bladed software. Vibration frequencies of blades under working wind speeds were analysed, and the results revealed how rotational speed of blades affected frequency characteristics; Through the strength and stiffness characteristics analysis of wind turbine blade under different wind speeds, The stress and deformation distribution under dangerous working condition was calculated; The stability of blades on dangerous working conditions was studied, and the failure location was predicted.4. Structure optimization and fatigue life calculation. By choosing the thickness of three materials as optimization variables, blade weight as optimization goal, the structure optimal mathematical model of blade was established under the condition of constraint blade strength and displacement. It succeeded in reducing the blade weight by using the finite element method combining with the optimization algorithm. While the blades are often subject to alternating loads, so S-N curve and Miner cumulative damage theory were chosed to calculate the fatigue life of FRP blades. The caiculation result proved the feasibility of optimization design.