US 2003/0146296 A1Published application

Active noise reducing nozzle

OwnerLuis Manuel Braga Da Costa Camposinventor

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Abstract

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, ondulated 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.

a nozzle whose perimeter can be divided into sectors of two types:

sectors I for which noise reduction is sought, because they correspond to the directions of populated areas, into which sound radiation should be reduced,
and sectors II corresponding to directions in which there is no population or noise sensitive beings or structures, so that no noise reduction is sought, and even increased sound radiation may be harmless,
so that different treatment is given to the two types of sectors, namely:
in the sectors I, where noise reduction is sought, the nozzle lip is active, i.e. moves in and out relative to the axis, in an oscillatory motion, driven by actuators commanded by a control system so as to make the shear layer more irregular and turbulent, or left in free motion, thus scattering back a larger fraction of the sound from sources inside the jet, and spreading the sound which is transmitted outside over a wider range of directions and frequencies;
and also, in the sectors I where noise reduction is sought the nozzle lip may be smooth, or may have corrugations, undulations and/or vortex generators, to enhance the sound scattering effects and reduce sound transmission further,
whereas in the sectors II where noise reduction is not sought and increased sound radiation is harmless, the nozzle lip is smooth and fixed, to produce a thin shear layer, which allows as much as possible of the acoustic energy in the jet to exit in harmless directions, with the operation of the nozzle being scheduled over time, so that:
when noise reduction is needed, the movable nozzle lip sectors are driven by the actuators in the most suitable way, or left in free motion, to achieve maximum noise reduction;
whereas when noise reduction is not needed, the movable nozzle lip sections are fixed in the position which minimizes thrust loss and causes no increase in fuel consumption, also saving actuator power, wear of mechanisms and fatigue of structures,
and furthermore, similar mode of operation applying to any number of nozzles, coaxial or not, circular or not, including nozzles of nacelles containing several engines, and applications to any type of vehicle (air, land, sea) in a moving, fixed or deployable installation (powerplant, factory, etc . . . )

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Facts

Application

10/060,808Filed 1 Feb 2002

Published

7 Aug 2003

Term ends

Not estimatedThe source records don’t support an estimate.

Classification8 codes

B64D 33/06
Of exhaust outlets or jet pipes: silencing exhaust or propulsion jets
F02K 1/386
Introducing air inside the jet: mixing devices in the jet pipe, e.g. for mixing primary and secondary flow
F02K 1/44
Plants characterised by the form or arrangement of the jet pipe or nozzle; Jet pipes or nozzles peculiar thereto: nozzles having means, e.g. a…
F02K 1/48
Nozzles having means for adding air to the jet or for augmenting the mixing region between the jet and the ambient air, e.g. for silencing:…

Abstract

Claims1