Abstract
Flow fields at the rotor tip region in a low-speed axial-flow fan were experimentally and computationally investigated to clarify the flow mechanism behind a modal stall inception pattern. The behavior of tip leakage flow at the modal stall inception was different from that at the spike stall inception. The interface between the incoming flow, tip leakage flow, and end-wall backflow did not parallel to the rotor leading edge plane. Leading edge separation occurred when the tip leakage vortex broke down. This separation grew and formed three-dimensional separation vortex, which stood on the suction side near the leading edge. We concluded from these results that this three-dimensional separation vortex influenced on the initiation of the modal disturbance.
