Study On Aerodynamic Performance Influence Of A Horizontal Axis Wind Turbine Under Dynamic Inflow

Environmental issues caused by the fossil energy and other traditional energy have been one of hot spot problems confronted by various countries worldwide, as the breakthroughs in core issues of new energy technologies, and the policy support for new energy, new energy industry has been rapid development. This paper based on the issues existed in the operation of wind turbine, choose Phase VI wind turbine and a 1.5MW wind turbine as research objects, investigation the change laws about their flow field and aerodynamic performance under the influence of the dynamic inflow.In this paper, the flow field of Phase VI wind turbine has been numerically simulated by CFD(Computational Fluid Dynamics) technology.At the beginning, the accuracy of the numerical method used in this paper has verified by comparing the simulation results with the experimental results;secondly, in order to study the influence of wind speed change rate on the aerodynamic performance of wind turbine, a simplified dynamic wind speed model based on the wind speed change rate has established by analyzing the distribution law of random wind speed, which includes wind speed increasing process and wind speed decreasing process;Thirdly,aerodynamic performance of wind turbine has carried out by simulating the operation under this wind speed model, the differences of aerodynamic performance under two different process has been compared and analyzed, then the mechanism of the three-dimensional rotation effect on wind turbine aerodynamic performance has studied; In the end, we used a extreme operation gust(EOG) model as the dynamic inflow model and study the dynamic stall problems of a 1.5WM wind turbine. The results are as follows:(1) Under the action of dynamic inflow, as the varies with time, we must capture the wind speed value at different times in a very short time, that makes a high-quality requirement for grid. We compare the torques of the wind turbine blades under two variation process of wind speed (increasing and reducing), found that there is no significant difference at a low wind speed change rate, and significant difference appears between two variation process at a high wind speed change rate.According to this, we propose the definition of aerodynamic sensitivity, consider the wind speed change rate as the influence coefficient of wind turbine aerodynamicsensitivity. When ?v/?t?4.23. there is a large difference between the torquecoefficients of two variation process. When ?v/?t?4.23, there is no difference of torque coefficients existed in two variation process.(2) The rotation of wind turbine blade cause the radial flow phenomenon on the limiting streamline of blade suction surface. Stall happens on wind turbine when the wind speed above lOm/s, the larger the wind speed, the more serious the stall. We compare the increasing and reducing process of wind speed, the stall degree is heavier when the wind speed is increasing.(3)By comparing the results with the results of two-dimensional airfoil, dynamic three-dimensional rotation effect makes streamline separation extent reducing near the section on the blade, that cause to stall delay, and results in lift and drag coefficients and critical angle of attack increasing. Under the dynamic process, the lift and drag coefficients show little difference between the wind speed increasing and decreasing processes at low attack angel, but when high attack angel, lift and drag coefficients under the wind speed increasing process are less than that under the wind speed decreasing process.(4) When the wind turbine operating under the EOG model, stall degree decreased gradually from the root to the tip along the blade. By analyzing velocity streamline, found that the dynamic stall degree on same blade element is lower than the static stall degree. The maximum lift and drag coefficients of dynamic stall is higher than that of static stall, the attack angle corresponded to stall decreased from the root to the tip along the blade. If dynamic stall is not considered during the design process of wind turbine, incalculable loss would occur.