A gas turbine engine has an engine core and an annular by-pass duct, within a surrounding nacelle. An exhaust nozzle of the nacelle includes a selectively deployable noise-reduction section on an inner surface thereof. The noise-reduction section includes an inflatable envelope comprising a fixed ou
A gas turbine engine has an engine core and an annular by-pass duct, within a surrounding nacelle. An exhaust nozzle of the nacelle includes a selectively deployable noise-reduction section on an inner surface thereof. The noise-reduction section includes an inflatable envelope comprising a fixed outer wall and a displaceable inner wall. At least projections on the inner wall are inwardly displaced when the envelope is pressurized and retracted radially outwardly when the envelope is de-pressurized. When the envelope is pressurized, the inner wall includes portions that project to form a rough surface on the inner surface of the nacelle exhaust nozzle. This thickens the boundary layer and reduces the speed of the gas flow at the outer radius of the nozzle, thus reducing the differential velocity with the ambient air, which reduces the gradient throughout the shear layer thus reducing the noise level of the engine.
대표청구항▼
1. A gas turbine engine comprising: an engine core having a core exit nozzle within an annular by-pass duct defined within a surrounding nacelle, the nacelle having an exhaust nozzle at an aft end thereof; a selectively deployable noise-reduction section on an inner surface of the aft end of the nac
1. A gas turbine engine comprising: an engine core having a core exit nozzle within an annular by-pass duct defined within a surrounding nacelle, the nacelle having an exhaust nozzle at an aft end thereof; a selectively deployable noise-reduction section on an inner surface of the aft end of the nacelle exhaust nozzle, said inner surface of the aft end of the nacelle exhaust nozzle being downstream of the core exhaust nozzle and receiving mixed exhaust gas flow, including core engine gas flow and bypass air flow, therethrough, the noise-reduction section including at least one inflatable envelope, projections deployable from the inner wall of the nacelle exhaust nozzle to form a rough surface at the loft line of the inner wall when the envelope is pressurized and the projections are retracted when the envelope is de-pressurized; means are provided to retain the inner wall in the loft line, the so formed rough surface effectively thickens the boundary layer to reduce the speed of the mixed flow of engine exhaust and by-pass air at the outer radius of the nozzle to reduce the differential velocity with the ambient air thus reducing the jet noise level of the engine, wherein the selectively deployable noise-reduction section on the inner surface of the aft end of the nacelle exhaust nozzle, including the inflatable envelope comprising a fixed outer wall and a displaceable inner wall radially spaced apart therefrom, the envelope including metal walls defining a pressurizable cavity and an inlet in fluid communication with the pressurizable cavity, at least a portion of the inner wall being radially inwardly displaced when the envelope is pressurized and retracted radially outwardly when the envelope is de-pressurized; an annular perforated sleeve having a plurality of openings therein and provided on the inner nacelle loft line, radially inwardly of the inner wall, to limit the travel of the inner wall; and wherein the inner wall includes a plurality of pins which are aligned with the plurality of openings in the perforated sleeve, the pins projecting through the openings in the perforated sleeve when the envelope is pressurized to form the rough surface at the loft line of the inner wall of the nacelle exhaust nozzle to thereby thicken the boundary layer and reduce the speed of the mixed flow of engine exhaust and by-pass air at the outer radius of the nozzle to reduce the differential velocity with the ambient air thus reducing the jet noise level of the engine. 2. The gas turbine engine as defined in claim 1, further comprising a control system operable to pressurize the envelope when noise-reduction is desired, and depressurize the envelope when reduced fuel consumption is more desired than noise-reduction. 3. The gas turbine engine as defined in claim 2, wherein said control system is operable to vary the pressure within said envelope to actively control the jet noise level during operation of the gas turbine engine. 4. A gas turbine engine comprising an engine core including a core exhaust nozzle and an annular by-pass duct defined between the engine core and a surrounding nacelle, the nacelle having an exhaust nozzle at an aft end thereof through which exhaust gas flow exits, the nacelle exhaust nozzle having a selectively deployable noise-reducing component therewithin on an inner surface thereof, said inner surface of the nacelle exhaust nozzle being downstream of the core exhaust nozzle and receiving mixed exhaust gas flow, including core engine gas flow and bypass air flow, therethrough, the noise-reducing component including an annular perforated sleeve positioned to coincide with the inner nacelle loft line and circumscribing a mixed exhaust gas flow exiting the nacelle, the annular perforated sleeve being disposed radially inwardly of a displaceable inner wall of an inflatable envelope, the inner wall being radially displaceable between a deployed position wherein noise-reduction is active and a retracted position wherein noise-reduction is inactive, the inner wall being displaced from the retracted position to the deployed position when the inflatable envelope is pressurized thereby forcing a plurality of pins provided on the inner wall to project through corresponding openings in the perforated sleeve and into the exhaust gas flow to form a rough surface at the loft line of the nacelle exhaust nozzle, causing a reduction in the noise level of the gas turbine engine. 5. A gas turbine engine as defined in claim 4, wherein a pressurised inlet is in fluid communication with the inflatable envelope. 6. A gas turbine engine as defined in claim 4, wherein the portions of said inner wall that project through the openings when the inflatable enveloped is pressurized include pins which project from the inner wall and protrude into the mixed exhaust gas flow. 7. The gas turbine engine as defined in claim 4, further comprising a control system operable to pressurize the envelope when noise-reduction is desired, and depressurize the envelope when reduced fuel consumption is more desired than noise-reduction. 8. The gas turbine engine as defined in claim 7, wherein said control system is operable to vary the pressure within said envelope to actively control the jet noise level during operation of the gas turbine engine. 9. A gas turbine engine comprising an engine core including a core exhaust nozzle and an annular by-pass duct defined within a surrounding nacelle, the nacelle having an exhaust nozzle which includes a selectively deployable noise-reduction section on an inner surface thereof, said inner surface of the nacelle exhaust nozzle being downstream of the core exhaust nozzle and receiving mixed exhaust gas flow, including core engine gas flow and bypass air flow, therethrough, the noise-reduction section defining an inflatable envelope comprising a fixed outer wall, a displaceable inner wall radially inward of the fixed outer wall, and an annular perforated sleeve radially inward of the inner wall and facing an exhaust gas flow exiting the exhaust nozzle, at least a portion of the inner wall being radially inwardly displaced when the envelope is pressurized and retracted radially outwardly when the envelope is de-pressurized, wherein the inner wall including a plurality of pins thereon that are aligned with and extend through openings in the perforated sleeve, the pins protruding through the perforated sleeve extending into the exhaust gas flow to form a rough surface on the inner surface of the nacelle exhaust nozzle when the envelope is pressurized, thereby reducing a level of jet noise produced, and wherein said projections being retracted upon depressurization of the envelope such that the inner surface is smooth thereby increasing the level of the jet noise but decreasing fuel consumption. 10. The gas turbine engine as defined in claim 9, further comprising a control system operable to pressurize the envelope when noise-reduction is desired, and depressurize the envelope when reduced fuel consumption is more desired than noise-reduction. 11. The gas turbine engine as defined in claim 10, wherein said control system is operable to vary the pressure within said envelope to actively control the jet noise level during operation of the gas turbine engine. 12. A method for reducing the level jet noise produced by a gas turbine engine having a engine nacelle from which an exhaust gas flows, comprising pressurizing an inflatable portion of an exit nozzle of the engine nacelle to displace an inner wall of the inflatable portion radially inwardly such that a plurality of pins on the inner wall protrude through a plurality of openings formed in an annular perforated sleeve radially inward of the inner wall and facing an exhaust gas flow exiting the exhaust nozzle, the pins extending into the exhaust gas flow at the loft line of the nacelle so as to form a rough surface at the loft line to thereby reduce the exhaust velocity as it mixes with ambient free air shear surrounding the nacelle and thus reduce the level of jet noise produced, wherein the inflatable portion of the exit nozzle of the engine nacelle is downstream of a core exhaust nozzle of the gas turbine engine within the engine nacelle, said inflatable portion of the exit nozzle of the engine nacelle receiving mixed exhaust gas flow, including core engine gas flow and bypass air flow, therethrough; restricting the pressurized air to the inflatable portion at a predetermined altitude so that flight will proceed with the projecting portions retracted from the loft line and withdraw within the exit nozzle of the engine nacelle; and initiating the pressurized fluid to the inflatable portion in preparation for landing thereby re-forming the rough surface within the exit nozzle of the engine nacelle to thereby reduce the level of jet noise produced during landing.
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Clarke James A. ; Parente Charles A., Acoustical and structural microporous sheet.
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