Role of hub-corner-separation on rotating stall in an axial compressor

A 3D computation was conducted to investigate the role of hub-corner-separation on the rotating stall in a low-sliced axial compressor. It is generally known that tip leakage flow plays an important role in stall inception. However. not much attention has been paid to the role of hub-corner-separation on the rotating stall although it is a common flow feature in an axial compressor operating near the stall point. During our time-accurate unsteady simulation, we suspected that hub-corner-separation might be a trigger for the rotating stall. After an asymmetric disturbance is initiated at hub-corner-separation, this disturbance is transferred to the tip leakage flows and grows to become an attached stall cell. which adheres to the blade passage and rotates at the same speed as the rotor. When the attached stall cell reaches it critical size, it moves along the blade row and becomes the rotating stall. The rotating speed of the stall cell decreases to 79% of the rotor so the stall cell rotates in the opposite direction to the rotor in the rotating frame.