Research And Improvement Of Dynamic Stall On H-type Wind Turbine Blades

As a new type of wind power equipment,H-type wind turbines have gradually attracted great attention.Compared with the horizontal axis wind turbines,H-type wind turbines have many advantages in fabrication,operation,and maintenance.Straight-blades are manufactured more easily,and they can capture winds in any direction without complicated yaw devices.Important components such as gearboxes and engines are installed on the ground,moreover,the impact on the environment is small,and it is more convenient to combine with the modern urban life.However,the current aerodynamic analysis and design theory of the H-type wind turbine is not complete,and the leaf-momentum theory is difficult to calculate the large-scale flow separation problem occurring on the H-type wind turbine blades.The existing dynamic stall model cannot accurately reflect the performance of the airfoil.The influence of the airfoil parameters on the dynamic stall performance is not clear.All of these problems have brought difficulties to the analysis and design of the H-type wind turbine.This paper takes the NACA 4-dig,which is the common airfoil of H-type wind turbine,as the research object,introducing the relevant theories of the airfoil and simplifying the dualactuation disk according to the operating characteristics of the H-type wind turbine.The influence of the main parameters of the H-type wind turbine airfoil on the dynamic stall performance under different tip speed ratios was studied by numerical simulation.Finally,a special vortex generator for the blade of H-type wind turbine was designed.By the wind tunnel test,the effect of vortex generators on the dynamic stall of the blade was verified.The main contents of this paper include:According to the unsteady aerodynamic characteristic of the H-type wind turbine,the double multiple streamtube model is simplified,and dynamic stall models(such as B-L and MIT model)are improved.Comparing the calculated results of the two improved models with the experimental data,a new dynamical stall model with high accuracy is obtained.The numerical simulation has been used to study the flow conditions of the airfoil,observing the generation,development,separation,mutual induction and reattachment of the airfoil surface vortex.The characteristics of the airfoil with different thickness and camber at different tip speed ratios were compared,and the influence of the basic geometric parameters of the airfoil on the dynamic stall performance was analyzed.At low tip speed ratios,increasing the airfoil camber and thickness can improve the tangential force coefficient;when the tip speed ratio is high,the small camber((?)≤4%)and thin airfoil((?)≤10%)have better aerodynamic performance.Vortex generators dedicated to the H-type wind turbine blade was designed,the installation method of the vortex generator on the blade was determine by the operating characteristics of the H-type wind turbine.The dynamic aerodynamic characteristics of the vertical axis wind turbine blade with vortex generators was verified by wind tunnel experiments.The vortex generator has a particularly obvious improvement effect at low tip speed ratios(λ≤2).At that time,the peak lift coefficient increased by 37.5%.The research in this paper provides guidance for the design of special blades for H-type wind turbines.Applying the vortex generator to the H-type wind turbine blade has achieved good results in improving the stall performance of the blade.