Aerodynamic Damping Characteristic Analysis And Optimization Of Horizontal Axis Wind Turbine

The system stabilization of wind turbine is becoming increasingly important, and the problem is attracted more and more attention. With this, supported by the project of China National Natural Science Foundation, named"The Stall Characteristic Analysis of Wind Turbine Based on Dynamic Aerodynamics"(No. 50676053), and by the key project of Guangdong Province Natural Science Foundation , named"The Stall Aerodynamic Damping Characteristic Analysis of Wind Turbine Based on Dynamic Aerodynamics"(No. 07118378), the aerodynamic damping characteristic in stall which is related to the instability of the wind turbine system is researched in this paper. The aerodynamic damping characteristic mainly concerns the influence of aerodynamic loading on the structure vibration in stall condition.The three-dimensional stochastic turbulent wind model and dynamic stall model of the airfoil are modified, to start with, the fundamental research of aerodynamic damping characteristic carried out, then, the accurate external input conditions for research on aerodynamic damping characteristic is provided. Based on these results, by theoretically analyzing steady aerodynamic forces on an airfoil section of the wind turbine blade, combining with the blade modal analysis of the structural dynamics, an effective model for analyzing steady aerodynamic damping of wind turbine airfoil sections and blade is established. And also all the key parameters which affect the change of aerodynamic damping are researched,Taking the negative aerodynamic damping which can easily initiate stall vibration of blade as the key point of the research, a concrete modified method for improving the aerodynamic damping characteristic of blade in stall condition is proposed.Then,aerodynamic damping characteristic is studied in time domain. As the initial conditions, the history of wind velocities from the 3D turbulent wind model, the time traces of angle of attack, lift coefficients and drag coefficients of every airfoil section belong to the blade from the dynamic stall model are imported into steady-state aerodynamic damping models, thus, steady-state single airfoil section and single blade aerodynamic damping models are converted into dynamic models.Making use of the results and experiences from the research on dynamic aerodynamic damping of single blade, the global system aerodynamic damping model and the relevant analysis method are set up, is based on the comprehensive consider of the modified 3D turbulence model of the wind field, the dynamic stall model of blade, the dynamic aerodynamic damping model of blade, the structural dynamics model of blade, the modal synthesis technique of overall unit structural dynamics and the full system transient process model of wind turbine. The aerodynamic stall characteristic and dynamic responses of blade based on the dynamic aerodynamics are analyzed and calculated.Taking the negative aerodynamic damping which can easily initiate stall vibration of blade as the key point of the research, using the full system aerodynamic damping calculation model and analysis method, the dynamic loads of blade are exported. Then, combing with the finite element analysis software ABAQUS, the mechanism of damage caused by stall-induced vibrations of blade is analyzed.At the end of the paper, the aerodynamic damping models are introduced into the conventional optimum design model of blade, a detailed flow of vibration restraining design and modification of wind turbine is developed. Finally, an optimum design model for the blade of wind turbine which seeks for excellent aerodynamic characteristic and aerodynamic damping characteristic is developed. An effective method for wind turbine vibration restraining optimum design and fault diagnosis are provided.