Numerical investigation of the effect of the blade type and the chord length on the performance of the vertival axis wind turbines

Vertical axis wind turbines (VAWT) convert the wind energy into the electrical energy like horizontal axis wind turbines. But there are some differences and also advantages. VAWTs can be used in urban areas where flow behavior is mostly turbulent and unsteady. They can work with wind from all directions. Airfoil aerodynamic is one of the important factors that affect the performances of the VAWTs. Airfoil aerodynamic is depend on blade shape, blade number, chord length and rotor diameter. These parameters are important for designing and producing an H-Darrieus VAWT. In this thesis; at first, different blade types were analyzed by changing the angle of attack at steady state with FLUENT 6.3. Secondly; the performance of a three bladed VAWT was analyzed with ANSYS-FLUENT 14.0 by changing the chord length and the rotor diameter of the turbine. In the first part of the thesis, NACA 0012, 0018, 0021 and 0024 airfoils were analyzed at 0, 3, 6, 9, 12 and 16 degree angle of attacks. The analyses have shown that the increase at angle of attack causes an increase in the lift coefficient until a certain angle for all airfoil types. But, it was found that the increment was more significant for the drag coefficient at 12, 16 degree angle of attacks. This is a factor that decreases the performance. It is understood from the analyses that NACA 0012 creates more lift in comparison to NACA 0018, 0021 and 0024. Also, the ratio between the lift and the drag is higher than the other profiles for NACA 0012. The aerodynamic performance of NACA 0012 is better than the other airfoils, but thin airfoils can be structurally weak. So NACA 0018 was chosen for the three bladed turbine analyses. After completing the preliminary analyses; the power coefficients were found for NACA 0018 airfoil at 0.3, 0.6, 0.8, 1.2 solidities and different tip speed ratios. Maximum power coefficient was found to be 0.56 at 0.8 solidity and 2.25 tip speed ratio. The widest range of power coefficient was found at 0.3 solidity.