초록 ▼

A nozzle where the sector into which noise reduction is sought (the direction of populated areas) has a moving lip, driven by actuators in an oscillatory, periodic or sinusoidal motion, around the mid position, to and from the axis, so as to cause the shear layer to become more irregular and turbule

A nozzle where the sector into which noise reduction is sought (the direction of populated areas) has a moving lip, driven by actuators in an oscillatory, periodic or sinusoidal motion, around the mid position, to and from the axis, so as to cause the shear layer to become more irregular and turbulent, thus enhancing scattering effects on the sound of internal sources, including back reflection into the jet, widening the directivity pattern and spreading the acoustic energy into a broader spectrum, so as to reduce the acoustic energy transmitted in these sensitive directions; the nozzle lip may also be corrugated, undulated or have vortex generators, in the sector over which noise reduction is sought. In all other sectors, for which noise radiation is of no concern, even if enhanced, the nozzle lip is smooth and fixed, leading to a thin shear layer, across which sound is more easily, so that acoustic energy exits from the jet in these harmless directions. The active nozzle need only be actuated at times when noise reduction is needed, e.g. a take-off and landing; at all other times, when noise reduction is not needed, e.g. in cruise flight, the nozzle is not active, i.e. is fixed in the mid-position, to save actuator power, and wear and fatigue of moving mechanisms; also, this position, minimizes any thrust loss or increase in fuel consummation, in cruise flight.

대표청구항 ▼

1. An active exhaust nozzle for a gas turbine engine comprising a primary exhaust nozzle having a central axis and an exit end; the exit end having two sectors, a first noise reducing sector and a second noise transmission sector; the noise reducing sector being formed by a hinged section which

1. An active exhaust nozzle for a gas turbine engine comprising a primary exhaust nozzle having a central axis and an exit end; the exit end having two sectors, a first noise reducing sector and a second noise transmission sector; the noise reducing sector being formed by a hinged section which allows a lip of the section, located at the exit end, to oscillate towards and away from the central axis; an active noise reduction means for actuating the hinged section of the first noise reducing sector to make the exhaust shear layer irregular and turbulent, thus scattering parts of the sound from sources inside the gas turbine engine and spreading the sound to a range of directions corresponding to the noise transmission sector, over a wide range of frequencies; and, a controller for actuating the active noise reduction means during operation when reduced noise is required in the direction defined by the noise reducing section. 2. The active exhaust nozzle for a gas turbine engine according to claim 1, wherein the noise reducing sector has corrugations, undulations or vortex generators. 3. The active exhaust nozzle for a gas turbine engine according to claim 1, wherein the lip of the noise reducing sector is smooth. 4. The active exhaust nozzle for a gas turbine engine according to claim 1, wherein the noise transmission sector has exit lip, which is smooth.