Unsteady behavior of tip clearance flow in an axial flow compressor rotor at near stall condition

In order to uncover the unsteady behavior of tip clearance flow in an axial flow compressor rotor at near stall condition and its associated flow mechanism, three-dimensional steady and unsteady flow simulations were conducted to analyze the internal flow fields in an axial flow compressor rotor. To validate the numerical results, the predicted total and elemental performance was compared with the available experimental data, and good agreement was achieved. The convergence history of the unsteady simulations at near stall condition showed that parameters, especially rotor efficiency and torque acting on blade, got nearly periodic fluctuation, and the period was about 2.5 blade passing time. By further analyzing the instantaneous flow structure near rotor tip, it was found that tip leakage vortex broken down at near stall condition. The interaction of the breakdown of tip leakage vortex, main flow and the tip leakage flow from the adjacent blade formed another distinct vortex, which was named as tip secondary vortex. The cyclical motion of this vortex was the main source of the periodic variation of the flow total parameters.