Effect of Tip Clearance on Casing Boundary Layer in an Isolated Axial Compressor Rotor : 2nd Report, Variation with Inlet Boundary Layer Thickness

Abstract

The detailed flow measurements were done in an isolated axial compressor rotor with various tip clearances, and the development of the casing boundary layer through the rotor was investigated for various inlet boundary layer thicknesses. The flow behavior for the thick inlet boundary layer was distinguished from the case of the thin inlet boundary layer at an off-design condition, in spite of almost the same incidence angle near the blade-tip. As the inlet boundary layer is thicker, a leakage vortex becomes slightly stronger but isn't so strong as that at the off-design condition. The input work changes little in comparison with that for the thin inlet boundary layer at the design condition, while the output work increases by the uniforming action of blades. Therefore, the thicker the inlet boundary layer is, the higher the blade-tip efficiency calculated from the integral parameters of the casing boundary layer.