Effect of Thickness Distribution on Performance of S‐Cambered Profiles

Abstract

A fully reversible axial flow pump‐turbine is a device that can work as a turbine and as a pump for both forward and reverse directions of flow. These machines find applications in tidal power plants. Double‐cambered S‐shaped profiles are known to be better suited for the blades of such machines; however, information on the aerodynamic characteristics of S‐cambered profiles is very limited. The effect of thickness distribution on the performance of S‐shaped airfoils is considered in this paper. The results obtained from an extensive experimental aerodynamic investigation of three S‐cambered profiles with different thickness distributions are presented. Göttingen 775 and NACA 0010‐66 basic thickness distributions were used to obtain these profiles. The profiles were tested in a wind tunnel in forward and reverse directions of flow. The variation of lift and drag coefficients and that of lift‐to‐drag ratio with angle of attack were obtained. The study showed that among the profiles tested the profile with Göttingen 775 thickness distribution having a maximum thickness at 30% chord is best suited for fully reversible axial pump‐turbine application from the point view of high lift‐to‐drag ratio.