In the first part of this thesis, the blade element momentum theory is applied to design a blade of a conventional horizontal axis wind turbine. In this method, the aerodynamic coefficients are adopted from experimental measurements of a specified airfoil. Then, the geometric distribution of the blade is calculated at different cross sections. This includes chord length, twist angle and the flow relative wind angle along the blade. In order to adopt the most efficient airfoils for a particular application, the power coefficient is calculated for 10 different airfoils types and the results are compared and analyzed. Also, to enhance the wind turbine performances, instead of using one type of airfoils from hub to tip, three different airfoil geometries, are adopted. In the hub region, NACA63-215 is used while in the middle part Riso A1-24 and in the outer part of the blade FX63-137 is selected. The performance of the designed blade is compared well with some reliable results in this field. In the second part of this study, the three-dimensional fluid flow simulations are carried out for the designed blade using ANSYS CFX software package. In this study, a moving reference frame is used for the rotating system. Also, the shear stress traort turbulence model was employed with the boundary layer type mesh near the blade surface. In order to ensure accuracy of the numerical simulations, the simulated results are validated with some experimental data and other numerical solutions. In the third part of this study, using an iterative inverse design method, the aerodynamic performance of airfoils is enhanced for the designed blade. In the inverse design, the aerofoil geometry is altered to produce a given pressure distribution over the aerofoil surfaces through an iterative procedure In this work, the inverse design method is applied for the designed blade airfoil sections using the moving boundaries in the software package. Pressure distribution on the airfoil surfaces are calculated by solving the flow field around the blade sections in CFX flow solver. The CFX provides with the designer the ability to design the blade for any flow reg ime, with suitable turbulence modeling and the computational speed is relatively high. To evaluate the optimum design after the inverse design approach, the symmetrical airfoil NACA0012 geometry is considered as the geometry of target. The pressure distribution is obtained using the numerical solution. Then, the obtained distribution of pressure is imposed to different initial guess airfoil geometry. The results of inverse design method were converged to the NACA0012 in all cases which proofs suitability and accuracy of this optimization technique. Next, the pressure distribution in an asymmetric airfoil FX63-137 at 6 degrees angle of attack is modified in such a way that no separation can occur over the upper airfoil surface and the blade can withstand additional loads. The obtained optimum airfoil geometry has proved a better pressure distribution and 3.8 percent enhancement in lift to drag ratio compared with the initial FX63-137 aerofoil. Moreover, the new airfoil geometry produces 5.4 percent higher lift coefficient value than the initial airfoil. Finally, the improved airfoils are used in a new blade to investigate the power performance of the new blade. The results indicate 2.3 percent increase of the power coefficient compared with the initial blade and the aerodynamic performance of the wind turbine blades are improved. However, the structural properties of the wind turbine blades are not investigated here. Keywords: BEM method, CFX ANSYS, horizontal axis wind turbine, optimum blades, the inverse method.
