軸流ファンにおける小スケール失速セルの発生点近傍での動翼先端流れ場(流体工学,流体機械)

Abstract

Rotor tip flow-field in a low-speed axial-flow fan was investigated by steady numerical simulations to elucidate inception mechanisms of rotating stall initiated from a short length-scale stall cell. Tip leakage flow interacts with the incoming flow at the maximum pressure-rise point. Backflow from the trailing edge is initiated at the tip near the stall inception point and develops at the stall inception point. The interface between the tip leakage flow and the incoming flow becomes parallel to the leading edge plane near the stall inception point and moves upstream of the rotor leading edge at the stall inception point. Moreover, the tip leakage flow spills from the leading edge at the stall inception point. Tip-leakage vortex breakdown occurs and induces the three-dimensional separation on the suction surface of the rotor blade near the stall inception point. At the stall inception point, this separation grows into a three-dimensional separation vortex, which crosses the rotor passage near the trailing edge. It is concluded from the numerical results that the three-dimensional separation vortex and the spillage of tip leakage flow affect the inception of the short length-scale stall cell.