Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
TWO-DIMENSIONAL NUMERICAL ANALYSIS OF A VERTICAL AXIS WIND TURBINE USING SLIDING MESH
Submission Author:
Kaio Lourenço Teixeira Barbosa , MA
Co-Authors:
Kaio Lourenço Teixeira Barbosa, Glauber Cruz
Presenter: Kaio Lourenço Teixeira Barbosa
doi://10.26678/ABCM.COBEM2021.COB2021-0154
Abstract
The growing energy demand has accelerated the need to discover new renewable energy sources, which tend to supply electricity consumption. Some of these sources, specially, wind energy, enabled the development of several research and projects in the area of power optimization of wind generators, including small turbines. Consequently, studies of new rotor configurations need to be considered, using experimental and numerical approaches to obtain greater efficiencies in harnessing the winds. In this sense, a rotor modeling strategy focusing on the microgeneration of electrical energy from the wind matrix is shown. For obtaining a better performance and efficiency of the generator at low speeds, the attack angle in the variable pitch of the propeller was evaluated and validated. The attack angle directly influences the performance of the blades and, consequently, in the energy generation. Initially, the model developed was analytically compared to the commercial vertical axis models, analyzing the NACA 0018 profile (chord dimensions: 250 and 375 mm), for using in Vertical Axis Wind Turbines (VAWT). A numerical analysis using Computational Fluid Dynamics (CFD) for the analysis of the flow field (unsteady state), considering several angular positions and blades opening was also performed. Results for three propeller inclinations (7.5°, 9° and 10. 5°) and wind flow velocities (4, 8 and 12 m s-1) were obtained. Other important factor considered in this study was the turbulence model. In this analysis, it was adopted the realizable k-epsilon model with treatment on the walls for the discretized model and the shear stress transport (SST) formulation that combines the k-ω formulation in the inner parts of the boundary layer, making a directly usable down to the wall through the viscous sublayer, hence the SST k-ω model can be used as a Low-Reynolds turbulence model without any extra damping functions. The SST formulation also changes to a k-ε behavior in the free-stream, avoiding the common k-ω problem. From this analysis, it was possible to adjust some geometric parameters for the rotor, aiming to increase the power coefficients for wind turbines under low velocities, providing an increase of approximately 20% in the power coefficient compared to a fixed-pitch wind turbine, these values of 0.003 kW to 0.45 kW of power coefficient were obtained within the range of 4 to 12 m / s.
Keywords
NACA profile, Vertical Axis Wind Turbine - VAWT, Computational Fluid Dynamics - CFD, Numerical analysis
