Chi Jeng Bai

Computational fluid dynamics analysis of the vertical axis wind turbine blade with tubercle leading edge

The performance of a vertical axis wind turbine (VAWT) blade with NACA0015 airfoil section has been investigated using the commercial computational fluid dynamics software ANSYS FluentTM. The Semi Implicit Method for Pressure Linked Equations algorithm is chosen to solve the incompressible Navier-Stokes equations. The k-ω shear stress transport turbulence model was selected for the turbulence flow simulations. The simulation results of lift and drag coefficients between angles of attack of 0° and 40° were first validated with the experimental data in order to confirm the boundary layer distributions. The grid numbers and time step sizes were then examined to confirm the simulation accuracy. To exam the 3D effect, a 2.5D model was additionally developed and compared with 2D model. Finally, the predictions of thrust obtained from the blade with tubercle leading edge were compared with the ones from the straight blade. Overall, the thrusts of VAWT with modified turbine blades were lower than the ones with straight blade. The values of the thrust decreased with increasing amplitudes and decreasing wavelengths, mainly due to the structure of the vortices generated at the leading edge of the turbine blade.

Aerodynamic design and analysis of a 10 kW horizontal-axis wind turbine for Tainan, Taiwan

The purpose of the present study is to develop a small-scale horizontal-axis wind turbine (HAWT) suitable for the local wind conditions of Tainan, Taiwan. The wind energy potential was first determined through the Weibull wind speed distribution and then was adapted to the design of the turbine blade. Two numerical approaches were adopted in the design and analysis of the HAWT turbine blades. The blade element momentum theory (BEMT) was used to lay out the shape of the turbine blades (S822 and S823 airfoils). The geometry of the root region of the turbine blade was then modified to facilitate integration with a pitch control system. A mathematical model for the prediction of aerodynamic performance of the S822 and S823 airfoils, in which the lift and drag coefficients are calculated using BEMT equations, was then developed. Finally, computational fluid dynamics (CFD) was used to examine the aerodynamic characteristics of the resulting turbine blades. The resulting aerodynamic performance curves obtained from CFD simulation are in agreement with those obtained using BEMT. It is also observed that separation flow occurred at the turbine blade root at the tip speed ratios of 5 and 7.

The effects of sinusoidal leading edge of turbine blades on the power coefficient of horizontal-axis wind turbine (HAWT)

ABSTRACT In order to improve the aerodynamic performance of horizontal-axis wind turbine (HAWT), a sinusoidal shape is applied to turbine blade. In this study, four types of modified blades were chosen based on variations in amplitude and wavelength of protuberance along the leading edge. Compared with the baseline model, the power coefficients (Cp) of HAWT with modified blades were improved, especially at low tip speed ratios. At low wind speed (V = 6 m/s), blades with short wavelength obtain significant improvement in Cp compared with the baseline model. As wind speed increases, this improvement decreases. In addition, turbine blade with large amplitude and long wavelength obtains better Cp values at higher wind speeds than lower ones, which have a great potential to be more superior at relatively higher wind speeds.