Fan case treatment.

摘要

To enhance stall margin without degrading engine performance the case (14) of the fan (10) of a fan-jet engine is treated by incorporating a passageway to remove flow from the main flow stream (A). The location and amount of the low momentum flow relative to the rotor being removed is critical. The flow is removed at a judicious location downstream of the leading edge (32) of the rotor blade (18) and returned at a judicious location upstream of the point of removal. The amount of removed flow must be no greater than 8% of the total flow in the fan rotor. Anti-swirl vanes (38) in the passageway and discreetly sized inlet and outlet passages (34,36) of the passageway return the flow to the main stream at an increased velocity. The intake is so designed that it selectively removes only the weak low momentum flow relative to the rotor and encourages the strong mainstream flow to remain in the main gas stream.