Abstract
Numerical and experimental studies were carried out to clarify the mechanism behind a modal-type stall inception in a low-speed axial-flow fan. The modal disturbance was experimentally observed in the positive slope region of the pressure-rise characteristics of two rotors. Tip-leakage vortex breakdown was not numerically confirmed in the positive slope region. A three-dimensional separation vortex, which was developed from the leading edge separation or the separation at the mid-chord on the suction surface, was confirmed. The numerical and experimental results show that the three dimensional separation vortex induced by the leading edge separation or the separation at the mid-chord influences the development of the modal disturbance.
