Parametric analysis of Joukowski airfoil for 10-kW horizontal axis windmill

Abstract

Small wind turbines are mainly used in rural areas, farms and isolated communities. These machines are supposed to be able to work within a wide range of wind speeds and usually are not equipped with pitching control mechanisms. The main objective of this study is to investigate Joukowski airfoil as an alternative for use in small power windmills (compared with the Solar Energy Research Institute, SERI airfoil as a reference) and investigate the effects on the aerodynamic performance caused by varying the tip–speed ratio and the number of blades as well as the use of blades composed of multiple airfoils. The SERI airfoils were treated using Xfoil software while the Joukowski airfoils were calculated by analytical transformation and then treated by Xfoil to estimate the aerodynamic characteristics for the different operating conditions. The data from the selected airfoils were used in a home-built numerical code based on the blade element momentum (BEM) theory. Predictions from this numerical code were compared with available experimental and numerical results to validate the numerical code. The validated code was then used to investigate parametrically two rotors of 10 kW each and verify the effects of varying the blade geometry and the tip–speed ratio on the aerodynamic loads. The Joukowski blades show higher values of torque and power at low speeds and the short chord makes these blades light and easy to startup when compared with the SERI airfoil.