Investigation of improved aerodynamic performance of isolated airfoils using CIRCLE method

摘要

The Prescribed suRface Curvature distribution bLade dEsign (CIRCLE) method, proposed by T Korakianitis, is a direct method for designing (or redesigning) high efficiency turbomachinery and fan blades, and isolated airfoils. It was initially introduced to improve the design of high efficiency turbomachinery blades. It is now extended for use with 2D and 3D turbomachinery blades and isolated airfoils. The connection of the profile's leading edge (LE) to the trailing edge (TE), on both sides, is defined using continuity in the surface curvature and its derivatives. Improvements to the aerodynamic performance of the Eppler airfoil are presented in this paper. Improved geometries with continuous curvature have been produced using the CIRCLE method. The performances of Eppler and the redesigned A5 and A6 have been studied using CFD analysis. They are analyzed considering low subsonic flow condition (Reynolds number~10s). These are compared to a previous airfoil A4. The redesigned blades' LE proved favorable as they succeeded in removing pressure 'spikes' on the suction side. Comparative analysis with the original results showed significant aerodynamic improvements. Airfoils A4, A5 and A6 have comparatively thicker TE section compared to Eppler. Despite the changes made to the geometry and continuous curvature distribution in A4, A5 and A6 (from Eppler), there appear a separated region on the suction side at about 60% of the chord downstream from the LE. The new blades exhibit higher aerodynamic efficiencies, in terms of overall lift-to-drag ratio up to 40% than the original. The investigations are performed at on and off design conditions.