| Permanent-magnet direct drive wind turbine, without gearbox compared to doubly-fed wind turbine and the rotor directly coupled with the generator, has advantages of simple structure, high efficiency, low noise and low maintenance costs, so it is becoming the trend of wind power technology. In order to reduce costs, improve overall performance and ensure reliability of operation, the Strength analysis and checking of wind turbine key components should be conducted. Based on wind turbine aerodynamics, structural dynamics, strength analysis theory and modern design methods and according to GL, IEC, EuroCode3 and other wind turbine standards, the thesis analyzed and conducted systematic research on the mainframe structure of large-scale permanent magnet direct drive wind turbine. It lays foundation for wind turbine key components design and optimization, and has a high theoretical and practical value.The main contents of the thesis are as follows:â‘ Established the Wind turbine analysis model by Bladed software, and according to GL standard requirement, calculated the extreme and fatigue load exerted on the mainframe structure under all load cases.â‘¡clarified the structural characteristics and force circumstance of the mainframe structure; and according to the static and dynamic related theories of finite element analysis(FEA), built the FEA model of mainframe structure, analyzed its static and dynamic characteristics, and obtained its stress distribution, inherent frequency and vibration model which provided base for further fatigue analysis.â‘¢Adopted the method of All-life (S-N) analysis, adhering to Miner cumulative damage law, calculated the fatigue damage of the mainframe structure in 20-year design life under all load cases; Moreover, investigated the amendment of S-N curve and the methodology of load spectrum.â‘£In order to study the nonlinear characteristics of bolt connection, applied contact FEA method to analyze the static strength and fatigue life of all the coupled bolts and parts; and summarized the fatigue analysis method of high strength bolts when taking account of preload. |
