Sound attenuation apparatus and method

Patent metadata

Field	Value
Publication number	US-9587563-B2
Application number	US-201514804867-A
Country	US
Kind code	B2
Filing date	Jul 21, 2015
Priority date	Jul 21, 2015
Publication date	Mar 7, 2017
Grant date	Mar 7, 2017

Abstract

An aircraft auxiliary power unit sound attenuation apparatus includes a perforated body having a center aperture through which exhaust fluid passes, a backing member outwardly offset from the perforated body, a plurality of connecting members coupling the perforated body to the backing member to form a locally reacting sound attenuation member having a plurality of channels spanning outwardly from the perforated body to the backing member, and a bulk absorber disposed in each of the plurality of channels where the bulk absorber is in fluid communication with the exhaust fluid, where the locally reacting sound attenuation member is in fluid communication with an auxiliary power unit of an aircraft so that the plurality of channels are oriented in a direction crossing a pressure drop direction of an exhaust fluid flow passing through the center aperture and each channel circumscribes the center aperture.

First claim

What is claimed is:

1. An aircraft auxiliary power unit sound attenuation apparatus comprising:
a perforated body having a center aperture through which exhaust fluid passes;
a backing member outwardly offset from the perforated body;
a plurality of connecting members coupling the perforated body to the backing member to form a locally reacting sound attenuation member having a plurality of channels spanning outwardly from the perforated body to the backing member;
at least one septum layer disposed between the perforated body and backing member where the at least one septum layer divides each channel into at least two portions; and
a bulk absorber disposed in each of the plurality of channels where the bulk absorber is in fluid communication with the exhaust fluid;
wherein the locally reacting sound attenuation member is in fluid communication with an auxiliary power unit of an aircraft so that the plurality of channels are oriented in a direction crossing a pressure drop direction of an exhaust fluid flow passing through the center aperture and each channel circumscribes the center aperture.

2. The aircraft auxiliary power unit sound attenuation apparatus of claim 1 , wherein each channel has a width in the direction crossing the pressure drop direction of the exhaust fluid, the width of each channel is configured such that the width prevents sound propagation inside the channel substantially parallel to a surface of the channel in the direction of the pressure drop direction of the exhaust fluid.

3. The aircraft auxiliary power unit sound attenuation apparatus of claim 1 , further comprising a liquid drainage path in one of the at least two portions of a respective channel.

4. The aircraft auxiliary power unit sound attenuation apparatus of claim 1 , wherein each of the plurality of connecting members extends radially from the perforated body so as to form a wall of a respective channel where the wall has a circumferentially extending sinewave configuration that undulates in a circumferential direction around the perforated body.

5. The aircraft auxiliary power unit sound attenuation apparatus of claim 1 , wherein the locally reacting sound attenuation member has a longitudinal axis that extends along the direction of exhaust fluid flow and each of the plurality of connecting members circumferentially extends substantially linearly around the longitudinal axis.

6. The aircraft auxiliary power unit sound attenuation apparatus of claim 1 , wherein the locally reacting sound attenuation member has a longitudinal axis that extends along the direction of exhaust fluid flow and the plurality of connecting members forms a truss core that circumferentially extends around the longitudinal axis.

7. The aircraft auxiliary power unit sound attenuation apparatus of claim 1 , wherein the plurality of channels are oriented in a direction that is substantially normal to the pressure drop direction of the exhaust fluid flow.

8. The aircraft auxiliary power unit sound attenuation apparatus of claim 1 , wherein the perforated body includes perforations that place the bulk absorber in each channel in fluid communication with the exhaust fluid flow.

9. The aircraft auxiliary power unit sound attenuation apparatus of claim 1 , further comprising a first bulk absorber disposed in one of the at least two portions of a respective channel and a second bulk absorber, that is different than the first bulk absorber, disposed in another of the at least two portions of the respective channel.

10. An aircraft auxiliary power unit comprising:
an exhaust outlet;
a locally reacting sound attenuation member in fluid communication with the exhaust outlet, the locally reacting sound attenuation member including
a perforated body having a center aperture through which exhaust fluid passes,
a backing member outwardly offset from the perforated body,
a plurality of connecting members coupling the perforated body to the backing member to form a locally reacting sound attenuation member having a plurality of channels spanning outwardly from the perforated body to the backing member;
at least one seam layer disposed between the perforated body and backing member where the at least one septum layer divides each channel into at least two portions; and
a bulk absorber disposed in each of the plurality of channels where the bulk absorber is in fluid communication with the exhaust fluid;

wherein the locally reacting sound attenuation member is in fluid communication with the exhaust outlet so that the plurality of channels are oriented in a direction crossing a pressure drop direction of an exhaust fluid flow passing through the center aperture and each channel circumscribes the center aperture.

11. The aircraft auxiliary power unit of claim 10 , wherein each channel has a width in the direction crossing the pressure drop direction of the exhaust fluid, the width of each channel is configured such that the width prevents sound propagation inside the channel substantially parallel to a surface of the channel in the direction of the pressure drop direction of the exhaust fluid.

12. The aircraft auxiliary power unit of claim 10 , wherein the locally reacting sound attenuation member further includes a liquid drainage path in one of the at least two portions of a respective channel.

13. The aircraft auxiliary power unit of claim 10 , wherein each of the plurality of connecting members extends radially from the perforated body so as to form a wall of a respective channel where the wall has a circumferentially extending sinewave configuration that undulates in a circumferential direction around the perforated body.

14. The aircraft auxiliary power unit of claim 10 , wherein the locally reacting sound attenuation member has a longitudinal axis that extends along the direction of exhaust fluid flow and each of the plurality of connecting members circumferentially extends substantially linearly around the longitudinal axis.

15. The aircraft auxiliary power unit of claim 10 , wherein the locally reacting sound attenuation member has a longitudinal axis that extends along the direction of exhaust fluid flow and the plurality of connecting members forms a truss core that circumferentially extends around the longitudinal axis.

16. The aircraft auxiliary power unit of claim 10 , wherein the plurality of channels are oriented in a direction that is substantially normal to the pressure drop direction of the exhaust fluid flow.

17. The aircraft auxiliary power unit of claim 10 , wherein at least one of the perforated body and the backing member includes an access panel that is configured for passage of the bulk absorber through the access panel to provide access to the bulk absorber in each channel.

18. The aircraft auxiliary power unit of claim 10 , further comprising a first bulk absorber disposed in one of the at least two portions of a respective channel and a second bulk absorber, that is different than the first bulk absorber, disposed in another of the at least two portions of the respective channel.

19. A method for aircraft auxiliary power unit sound attenuation, the method comprising:
flowing fluid in an exhaust outlet of an aircraft auxiliary power unit;
receiving at least a portion of the fluid in perforations of the exhaust outlet so that the portion of the fluid flows through the perforations into at least one radial channel of the exhaust outlet where the at least one radial channel is divided into at least two portions by at least one septum layer disposed within the at least on

Assignees

• Boeing Co

Inventors

• Nesbitt Eric H
• Lan Justin H
• Bhat Thonse R S
• Rust Charles W

Classifications

• F02C7/045

  having provisions for noise suppression · CPC title

• B64D33/06 Primary

  Silencing exhaust or propulsion jets · CPC title

• B64C1/40

  Sound or heat insulation {, e.g. using insulation blankets} · CPC title

• B64D2041/002

  Mounting arrangements for auxiliary power units (APU's) · CPC title

• B64D41/00

  Power installations for auxiliary purposes · CPC title