An Experimental Investigation of Contoured Leading Edges for Secondary Flow Loss Reduction

Abstract

Experimental results are presented which provide mass averaged total pressure loss coefficient measurements for three different turbine airfoil leading edge configurations. A baseline (Langston) configuration, a leading edge bulb, and a leading edge fillet were tested in a large-scale, low aspect ratio, high turning linear cascade. Results show that while the fillet geometry reduced overall loss by approximately 7%, the bulb did not exhibit a loss reduction. For the fillet, overall turning was slightly reduced, while for the bulb turning increased slightly. Thus, the bulb shows potential for increasing airfoil loading without an associated loss penalty. Contour plots of total pressure loss coefficient and vorticity are presented for all geometries and the major differences between each are discussed. Through investigation of pitch averaged loss profiles it is found that the area of greatest reduction differs between the bulb and fillet, leading to the possibility that the mechanisms through which each is affecting the flow may be different. This provides hope that the best features of each may potentially be combined to determine an optimum shape for secondary flow loss reduction.