Title: PERFORMANCE EVALUATION OF A 2MW WIND TURBINE BLADE
Abstract: In previous works an in-house MatLab program based on the Glauert Blade Element Theory allowed the design of an optimum geometry for a 2 MW wind turbine blade. Although the analytical theory may be considered reliable for the steady state condition of a factual wind velocity, the same approach does not apply to conditions of higher velocities closer to stall. An important necessity is the evaluation of the blade behavior in a wide range of velocities values. The present work is intended to evaluate the performance of wind turbine blades using a CFD method. A preliminary model has been created. Initial results reveal a great sensitivity to the mesh quality and refinement. A prediction of torque and power response can be accomplished. Analytical solutions of optimum wind turbines blades are available tools that can be used to extract the maximum power from a given wind situation (Burton, 2001). The geometry of the blade can be obtained to provide the maximum Cp from a wind site, considered a proper average wind A complete design of a wind generator is a complex problem that includes the design of an optimum blade and many other issues like the tower design. Wind towers have to be designed according to three basic criterions: (a) Stress levels; (b) Buckling; and (c) Mechanical Vibrations. For the two preliminary criteria, essentially, an adequate wind loads evaluation has to be accomplished. Nevertheless, for the vibration evaluation, the correct blade rotational velocities have to be properly predicted. The tower vibration stability is strongly associated to the rotational velocity range of the blades in all working conditions. A blade must be optimum at the, so called, wind speed. Usually, the wind generator is allowed to work between a cut-in wind speed and a cut-out wind While the rotational velocity of the blade can be accurately predicted by analytical models, the same rotational velocity cannot be properly predicted for wind speeds below and above the rated wind Particularly for high wind speeds, the phenomenon of stall can be manifested. In such case, the ideal fluid hypothesis, which is the basis of most common analytical solutions, has to be abandoned to give way to more sophisticated theories. The CFD method is a well know technique applied in the solution of more complex fluid problems. A performance evaluation of a wind turbine rotor is one of these difficulties. Therefore, this work has the goal of presenting a preliminary model of performance of a 2MW wind turbine blade using the CFD technique. 2. THE BLADE Beforehand, the blade geometry was obtained by using the Blade Element Method (BEM) according with earlier works of Menezes and Donadon (2008, 2009). Numerical results obtained for the blade geometry has been treated in the SolidWorks CAD software. An illustration of the blade configuration is shown in Fig. 1. The wind turbine has three blades equally spaced along the circumferential direction. For the present work, the aerodynamic characteristic curves in terms of lift coefficient versus angle of attack and drag coefficient versus angle of attack of a four digit NACA 44** was taken into account. The adopted criterion for choosing the best airfoil for the wind turbine blade is based on how much aerodynamic power the airfoil can effectively generate and transfer to the wind turbine shaft for a given operating condition. This quantity is measured by the power coefficient p C which is
Publication Year: 2010
Publication Date: 2010-01-01
Language: en
Type: article
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