Gas turbine exhaust having reduced jet noise

Patent metadata

Field	Value
Publication number	US-10280871-B2
Application number	US-201615204415-A
Country	US
Kind code	B2
Filing date	Jul 7, 2016
Priority date	Feb 28, 2012
Publication date	May 7, 2019
Grant date	May 7, 2019

Abstract

A nacelle exhaust nozzle having a deployable noise-reducing component is described. The noise-reducing component includes an annular perforated sleeve coinciding with the inner nacelle loft line and circumscribing a mixed exhaust gas flow exiting the nacelle. The annular perforated sleeve is radially spaced apart from of a displaceable wall of an inflatable envelope that is displaceable between a deployed position, wherein noise-reduction is active, and a retracted position, wherein noise-reduction is inactive. When the inflatable envelope is pressurized, portions of the displaceable wall project through openings in the perforated sleeve and into the exhaust gas flow to form a rough surface at the loft line which causes a reduction in noise level. The portions of the displaceable wall that project through the openings in the perforated sleeve when the inflatable enveloped is pressurized include a plurality of dimples formed on the inner wall and forming the rough surface.

First claim

The invention claimed is:

1. A gas turbine engine comprising an engine core 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 deployable noise-reducing component therewithin, the noise-reducing component including an annular perforated sleeve positioned to coincide with an inner nacelle loft line and circumscribing a mixed exhaust gas flow exiting the nacelle, the annular perforated sleeve being radially spaced apart from of a displaceable wall of an inflatable envelope, the displaceable wall being radially displaceable between a deployed position wherein noise-reduction is active and a retracted position wherein noise-reduction is inactive, the displaceable wall being displaced from the retracted position to the deployed position when the inflatable envelope is pressurized thereby forcing portions of the displaceable wall to project through 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 which causes a reduction in the noise level of the gas turbine engine, wherein the portions of the displaceable wall that project through the openings in the perforated sleeve when the inflatable enveloped is pressurized include a plurality of dimples formed on the inner wall, the plurality of dimples being aligned with and protruding through the openings in the perforated sleeve to form said rough surface.

2. The gas turbine engine as defined in claim 1 , wherein a pressurized inlet is in fluid communication with the inflatable envelope.

3. The gas turbine engine as defined in claim 1 , wherein at least the displaceable wall of the inflatable envelope is deformable.

4. The gas turbine engine as defined in claim 3 , wherein deformation of regions of the displaceable wall aligned with the openings in the perforated sleeve and forced therethrough by the pressurization of the inflatable envelope forms said plurality of dimples on the displaceable wall.

5. 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.

6. The gas turbine engine as defined in claim 5 , 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.

7. A gas turbine engine comprising an engine core 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, 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, the annular perforated sleeve defining a plurality of spaced-apart openings therein, 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 when the cavity is pressurized to inflate the inflatable envelope, a plurality of dimples on the inner wall protrude through the openings in the perforated sleeve and into the exhaust gas flow to form a rough surface on the inner surface of the nacelle exhaust nozzle and thereby reducing a level of jet noise produced, and wherein when said inner wall is retracted upon depressurization of the inflatable envelope, the dimples are to withdrawn from the exhaust gas flow via the openings in the perforated sleeve.

8. The gas turbine engine as defined in claim 7 , 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.

9. The gas turbine engine as defined in claim 8 , 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.

10. The gas turbine engine as defined in claim 7 , wherein at least the inner wall of the inflatable envelope is deformable.

11. The gas turbine engine as defined in claim 10 , wherein deformation of regions of the inner wall aligned with the openings in the perforated sleeve and forced therethrough by the pressurization of the inflatable envelope forms said plurality of dimples on the inner wall.

12. A method for reducing the level jet noise produced by a gas turbine engine having an engine nacelle from which an exhaust gas flows, comprising pressurizing an inflatable portion of an exit nozzle of the engine nacelle using a pressurized fluid, to displace an inner wall of the inflatable portion radially inwardly such that projecting portions thereof protrude into the exhaust gas flow -at a 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 projecting portions that protrude into the exhaust gas flow when the inflatable portion is pressurized include dimples formed on the inner wall; restricting the pressurized fluid to the inflatable portion at a cruise altitude so that flight will proceed at the cruise altitude with the projecting portions retracted from the loft line and withdrawn 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, wherein the inner wall is deformable, the step of protruding the projecting portions into the exhaust gas flow further comprising deforming the inner wall by pressurizing the inflatable portion and forcing regions of the inner wall aligned with corresponding openings in a perforated sleeve located radially inwardly of the inner wall, thereby forming the plurality of dimples on the inner wall.

13. The method as defined in claim 12 , further comprising using a control system to pressurize the inflatable portion when noise-reduction is desired and depressurize the envelope when reduced fuel consumption is more desired than noise-reduction.

14. The method as defined in claim 13 , further comprising using the control system to vary the pressure within said envelope to actively control the jet noise level during operation of the gas turbine engine.

Assignees

• Pratt & Whitney Canada

Inventors

• Joshi Ninad
• Girard Gaetan

Classifications

• Y02T50/671

  Cross-Sectional Technologies · mapped topic

• F02K1/827 Primary

  Sound absorbing structures or liners · CPC title

• F01D25/30

  Exhaust heads, chambers, or the like · CPC title

• F05D2300/516

  Surface roughness · CPC title

• F05D2260/96

  Preventing, counteracting or reducing vibration or noise · CPC title