Numerical studies on improving performance of rotor-67 by blended blade and endwall technique

The paper describes an advanced blading concept for highly loaded turbomachinery, named as Blended Blade and EndWall(BBEW). It implies the following three separate aspects or any of their combinations, i.e. increasing the dihedral between blade surface and endwall as much as possible, increasing the minimum curvature radius of curved transition surface that connects the blade with the endwall, and decreasing the streamwise gradient of the dihedral as the dihedral reduces streamwise. To the knowledge of the authors this is the first approach reported in the open literature that try to control corner separations and horse-shoe vortex(HSV) systematically under the guidance of the Rules of Dihedral (RD). In this paper, BBEW is applied to NASA rotor 67 which is featured by hub corner separation at the suction side and intensive HSV originating from blade leading edge at the hub. Two successive BBEW modifications are made to promote the performance of rotor 67. First, only a curved transition surface is designed to cover the hub corner at the suction side. Emphasis is paid on the streamwise distribution of the minimum curvature radius. Then, the second curved transition surface is added at the leading edge in near hub part. The nearby streamwise gradient of the dihedral is changed from infinity to a finite. Numerical tests showed that the implementation of BBEW had not only nearly eliminated the hub corner separation, but also weakened the leading edge HSV. Performance improvements are observed throughout its operation range. The work presented makes a contribution to a fully 3-D blading methodology for higher aerodynamic loading, engine efficiency and specific thrust.