Numerical analysis and optimization of a horizontal axis wind turbine blade

The global energy demand has been continuously rising due to the technological developments and the population growth. Therefore it is of great importance to meet the energy need in sustainable energy sources due to the decrease in fossil fuel reserves and the negative effects of these fuels on the environment. As a promising source for sustainable energy, wind turbines turn the kinetic energy of wind into electrical energy. In this work, the effects of wind turbine blade design parameters such as airfoil geometry, angle of attack, blade angle, tip speed ratio (λ) and blade length on aerodynamic performance were investigated based on a new proposed two-stage blade design optimization method using ANSYS Workbench platform and SOLIDWORKS software. In the first stage, for validation of CFD analysis, the lift force coefficient (CL) values of standard NACA 63-415 airfoil were calculated using Spalarat Almaras and SST k-ω turbulence models were compared with the experimental CL values for various angles of attack (0˚-20˚) at 1.6x106 Reynolds number. Since the SST k-ω turbulence model fits the experimental data better, this model was used for all calculations in the thesis. Then, NCAY 10, NCAY 20 and NCAY 30 wing profiles were produced by reducing the lower surface of the standard NACA 63-415 airfoil by 10%, 20% and 30%, respectively. It was observed that the new airfoils improved the aerodynamic performance compared to the standard NACA 63-415 airfoil, and the maximum CL/CD (lift force coefficient / drag force coefficient) value was obtained with the NCAY 30 airfoil at approximately 7° angle of attack. In the second stage, optimum chords and twist angles were calculated at 1 m intervals along the blade length and a solid blade model was generated for the standard NACA 63-415 airfoil using SOLIDWORKS. The results of this blade model showed that torque and power values enhanced an increase in λ and blade length and a decrease in blade angle. Then, the influence of the blade surface geometry on the turbine performance were scrutinized by using new produced blade models such as NACA 63-415, NCAY 30 and NCAYÜY 30 (reducing the lower and upper surfaces of the standard NACA 63-415 by 30%) for angle attack of 7°, λdesign = 7 and blade length of 20 m at 4-16 m/s wind speeds. The results indicated that power coefficient (Cp) values increased with an increase in wind speed for all blade models. The highest Cp value of 0.511 was obtained in the NCAYÜY 30 blade model at a wind speed of 16 m/s and this blade model augmented Cp value by 10.62% compared to the standard NACA 63-415 blade model. Besides, NCAYÜY 30 blade model increased pressure at the lower surface of the blade and the blade velocity near the tip of the blade compared to other models. NCAYÜY 30 blade model increased the maximum blade velocity by 7.2% in comparison to NACA 63-415 blade model. It is thought that the blade geometry optimization method developed in this work will help future research related to wind turbine design.