Study of Tip Flows in High Hub-to-Tip Ratio Axial Compressors at Low Speed With Varying Tip Gaps, Inflow Conditions and Tip Shapes

Abstract

The present study involves simulation of a single compressor rotor with a high hub-to-tip ratio blade. The study includes the effect of variation of tip gap, of tip shapes and of inlet axial velocity profiles, with inflows simulated similar to that of a typical rear stage environment of a multi-stage axial compressor. Numerical studies were carried out on a baseline rotor blade (without sweep or dihedral) and then on blades with sweep and dihedral applied at the tip region of the rotor. Simulation of these part-span sweep and dihedral shapes are done to study their effects on blade tip leakage flow. Results show that sweep and dihedral, in some cases, produce favorable tip flows, improving blade aerodynamics. Positive dihedral caused weakening of tip leakage vortex at design point as well as at peak pressure point. Negative dihedral may help postpone stall at the high pressure, low flow operation. Backward sweep weakened tip vortex at the design point. Contrary to some of the studies reported earlier forward sweep, when applied at the tip region, showed performance deterioration over the most of the operating range of the high hub-to-tip rotor.

Effects of the Shock Wave Structure on the Tip Clearance Leakage Flow in Transonic Compressor Rotors

“…Tip clearance flow and its mixing with main flow and spanwise transport flow, including the interaction with shock waves in supersonic or transonic rotors, form a complex three-dimensional flow [1]. Studies show that the flow loss in the tip region accounts for approximately one-third of the total loss of the compressor, so the rotor tip region is a high loss region, usually also the stall initiation region [2][3][4][5][6][7]. The tip region of the rotor is the only region with high flow loss regardless of whether the pressure ratio is high or low [8,9].…”