Numerical Study On Aerodvnamics Of The Blades With Serrated Trailing-edge

With the stand-alone wind turbine capacity of large-scale, the tip speed increases as the length of wind turbine blades increase, which makes it a problem to be solved to reduce the level of wind turbines noise. Passive airfoil edge treatments such as serrations have shown great potential for providing noise reductions, and the method to add trailing edge serrations on the blades has been developed to reduce the wind turbine noise. Many studies indicate both theoretically and experimentally that to add trailing-edge serrations on the blades is an effective way to decrease the aerodynamic noise radiated into the far field. However the investigations of the aerodynamic performance for the airfoil and blade with trailing-edge serrations have not been widely conducted, the method is too new and immature to be applied to the engineering project. The prediction of the aerodynamics of serrated trailing-edge blades is an urgent desire. The aviation of aerodynamics, the load and the power captured of serrated trailing-edge blades has been predicted and analyzed by numerical simulations in this paper, and the results will perform as references in aerodynamics and load for low-noise blades with trailing-edge serrations in the future.Airfoils with three different serrated trailing edges, a flat-plat trailing-edge and without any trailing edge extensions are studied at angles of attack ranging from0°to17°and the results are analyzed and compared. It is found that the serrations with different shapes have different influences on the aerodynamics of airfoil certain trailing-edge serrations can improve the lift of airfoil before stall and have a better comprehensive aerodynamic performance than the initial airfoil at low-to-moderate angles of attack. A row of counter-rotating vortex pairs are generated as a result of the introduction of trailing edge serrations, and the vortices alter the structure of the trailing vortex systems, reduce the coherence of vortex in span-wise and so reduce the noise radiation.In order to institute the affection of trailing edge serrations on the entire wind turbine blade, we simplified the serrated trailing edge into a flat-plat extension to avoid the difficulty in the grid generation on the serrations. The flow condition on the blade surface, the force distribution along the blade, the blade root bending moments, the axial thrust force on the wind turbine and the power coefficient are studied after the numerical simulation on the blade with simplified flat-plate trailing edge, and it is found that the flap-plate trailing edge has little influence on blade surface flow, but enhance the forces and bending moments on the blade and improve the power coefficient. For the accurate aerodynamic performance and load predictions on the wind turbine serrated trailing-edge blade, the commercial software called GH Bladed, which based on the theory of blade element momentum (BEM), is employed to study the wind turbine model that used the2D serrated trailing-edge airfoils aerodynamic data. What can be drawn from the comparative analysis is that serrated trailing-edge blade has higher energy capture efficiency than initial blade in the variable-speed and variable-pitch control strategy, and improved the annual electricity production at different annual average wind speed. What’s more, in the entire wind turbine operation region, the tip speed of serrated trailing-edge blade is lower than the one of initial blade, which is of great significance for the wind turbine noise reduction. But the negative aspect of serrated trailing-edge is the increase of thrust force on the turbine.Wind tunnel experiments are designed to have a further study on the aerodynamics of the2D serrated trailing-edge airfoils and to test and verify the results of numerical simulation. The parameters of the wind tunnel and experiment devices are introduced first. Then the experimental programs are formulated and some preparatory work has been done.