Resumo:
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.
