Otimização do efeito sweep da turbina eólica NREL-Phase VI, através de CFD e da construção de metamodelos

Abstract

This work presents an optimization procedure through the variation of the sweep curve of a two bladed Horizontal Axis Wind Turbine, previously tested by the National Renewable Energy Laboratory (NREL). The simulation was conducted using unstructured mesh on whole domain, steady state with multiple reference frames: a moving reference frame around the rotor, and a steady reference frame on the far field region. The turbulence model was the 𝑘 − 𝜔 𝑆𝑆𝑇, the coupling algorithm was the SIMPLE, and the discretization scheme was the first order upwind for the moment. It was also conducted a grid indepence study and a validation with experimental data from NREL Phase VI, using the moment as the control variable, whereby it was concluded that the numerical method was validated for a range of wind speeds from 5 m/s to 16 m/s. In addition, it has been also made an integration of processes of geometry generation, mesh generation and simulation, aiming to optimize the power coefficient of the blades, by means of introducing the sweep angle on the geometry of the blades. The parameters of sweep, such as radial position of sweep start, maximum displacement of the tip and the exponent of the curve, were chosen as the design variables, and varied during the optimization process through genetic algorithm, with the power coefficient being the objective function. As a result of the optimization process, it was possible to obtain two optimized geometries for the blade, one with forward sweep with an increase of 4,49% on the power coefficient; and another one with backward sweep, which has resulted in an increase of 5,62% on power coefficient. Both cases were tested for a wind speed of 11 m/s, which was the speed with the highest moment within the stable range of operation. Furthermore, it was built a metamodel, aiming to fastly get a better optimum point. The optimization with metamodel has yielded a turbine with 5,93% more 𝐶𝑝 in comparison with the baseline turbine. Moreover, both geometries yielded greater power coefficients for all wind speeds between 10 m/s and 15 m/s.