Numerical study on the influence mechanism of inlet distortion on the stall margin in a transonic axial rotor

Abstract

A numerical study is conducted to investigate the influence of inlet flow condition on tip leakage flow (TLF) and stall margin in a transonic axial rotor. A commercial software package FLUENT, is used in the simulation. The rotor investigated in this paper is ND_TAC rotor, which is the rotor of one-stage transonic compressor in the University of Notre Dame. Three varied inlet flow conditions are simulated. The inlet boundary condition with hub distortion provides higher axial velocity for the incoming flow near tip region than that for the clean inflow, while the incoming main flow possesses lower axial velocity near the tip region at tip distortion inlet boundary condition. Among the total pressure ratio curves for the three inlet flow conditions, it is found that the hub distorted inlet boundary condition improves the stall margin, while the tip distorted inlet boundary condition deteriorates compressor stability. The axial location of interface between tip leakage flow (TLF) and incoming main flow (MF) in the tip gap and the axial momentum ratio of TLF to MF are further examined. It is demonstrated that the axial momentum balance is the mechanism for interface movement. The hub distorted inflow could decrease the axial momentum ratio, suppress the movement of the interface between TLF and MF towards blade leading edge plane and thus enhance compressor stability.