Wind energy is a kind of clean and renewable energy. Wind power is the most mature and fastest growing power generation technology in renewable energy. Global wind power installed capacity has maintained high-speed growth of more than double digits for more than ten consecutive years, and the proportion of offshore wind power in wind energy utilization is increasing rapidly. In recent years, with the continuous development of offshore wind power in the deep sea areas, floating wind turbines have gradually attracted the attention of companies and researchers.
Under the combined effects of offshore wind and waves, the oscillatory motion of floating wind turbines is very significant. The oscillating movement of the unit will have an important influence on the safe operation and aerodynamic characteristics of the floating wind turbine. At the same time, because the floating platform and the mooring system are coupled with the hydrodynamic load and the structural dynamic load of the system and the aerodynamic load of the wind wheel, it brings great difficulties for the accurate simulation and evaluation of the floating wind turbine. . Since 2002, researchers from Bulder, Lee, Wayman, Vijfhuizen, Henderson, Withee, Fulton, and Nielsen have conducted feasibility studies on some preliminary designs of floating wind turbines. In 2006, Jonkman et al. of the American Renewable Energy Laboratory (NREL) established a fully coupled model of “pneumatic-hydrodynamic-control-structure†for floating wind turbines and designed three floating platforms.
Three kinds of floating wind turbines
In order to obtain the dynamic response characteristics and aerodynamic characteristics of floating wind turbines, the wind turbine blade R&D team of the Institute of Engineering Thermophysics, Chinese Academy of Sciences, calculated and analyzed the dynamic response of a variety of typical floating wind turbines under a series of wind and wave conditions. Summarizes the laws of motion of floating wind turbines and the changing rules of blade angle of attack.
The study found that the swaying movement is the most important form of exercise, and the mean value of the sway is mainly affected by the wind speed, and the amplitude of the sway is mainly affected by the wave height. According to the variation law of blade angle of attack of floating wind turbine, the numerical simulation of the two-dimensional dynamic stall characteristics of thick airfoil is studied. The study found that the lift coefficient of thick airfoil basically has no dynamic stall effect, and the dynamic stall effect of drag coefficient and pitching moment coefficient is very strong. The oscillating motion not only causes changes in the aerodynamic characteristics of the wind wheel, but also causes interaction between the wind turbine and the wake, thereby changing the wake characteristics of the wind turbine. In order to study the wake characteristics of floating wind turbines under oscillating conditions, the research team has improved the actuating line method widely used in the study of wind turbine wakes and established a two-dimensional brake line model. The calculation results show that the newly established model has Higher accuracy and can reduce computing time by about 10%.
Based on the dynamic response characteristics of floating wind turbines, the research team designed a swing test bench that simulates the oscillating motion of floating wind turbines in a wind tunnel, and performed a series of steady and unsteady experimental studies on model wind turbines. Wind turbine power and load fluctuation characteristics under conditions.
Wind tunnel experimental device diagram and wind turbine power fluctuation curve
The above research work was supported by the National Natural Science Foundation of China's project “Study on the Three Dimensional Flow and Dynamic Stall Characteristics of Floating Wind Turbines†(No. 50976117). The relevant research results have been published in the Journal of Engineering Thermophysics (2013, 34 ( 7): 1256-1261).
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