Abstract: A noise controlling device (12) is used for controlling noise in a turbo-fan engine (10). The engine includes an entrance (22) for ingesting air, and a fan rotor (18) connected to a spinner (20) in the interior of the engine. The fan rotor faces the forward side of the engine. A ring (24) is connected to the interior of the engine, with the ring being located between the engine entrance and the forward side of the fan rotor. The inner periphery of the ring faces the spinner, with the ring surrounding the spinner in substantial coaxial alignment therewith. An acoustic lining (26) is disposed around the inner and outer peripheries of the ring.

Abstract: This invention is an improvement to a turbofan engine intended to reduce fan noise caused by the interaction of the rotor with secondary flow generated by the inlet guide vanes. A portion of the air flowing through the engine is removed from the fan duct from a region between the inlet guide vanes and the rotor and near the outer periphery of the fan duct by a system of bleed ducts. The ducts have one or more openings in the fan casing. The system may also include means for controlling the flow through the bleed ducts and means for injecting high energy flow into the bleed ducts to assist in ejecting the bleed flow.