SURFACE TRIM FOR ACOUSTIC ABSORPTION

• US 20200130854A1
• Filed: 04/13/2018
• Published: 04/30/2020
• Est. Priority Date: 04/21/2017
• Status: Active Grant

• Current Assignee: Office National D'Etudes et de Recherches Aerospatiales
• Original Assignee: Office National D'Etudes et de Recherches Aerospatiales
• Inventors: SIMON, Frank
• Granted Patent: US 11,524,792 B2
• Time in Patent Office: Days
• CPC Class Codes: B64C 1/40 Sound or heat insulation , e.g. using insulation blankets
• CPC Class Codes: B64D 2033/0206 comprising noise reduction means, e.g. acoustic liners
• CPC Class Codes: B64D 29/00 Power-plant nacelles, fairings, or cowlings nacelles not otherwise provided for B64C
• CPC Class Codes: G10K 11/162 Selection of materials
• CPC Class Codes: G10K 11/172 using resonance effects

Abstract

A surface liner member includes an external wall which is provided with multiple holes, a spacer structure, and tubes which are respectively associated with the holes in the external wall. The surface liner member is intended to be applied to a base surface in order to reduce, by acoustic absorption, an acoustic wave reflected on this base surface. The acoustic absorption efficiency is improved, particularly for frequencies below 500 Hz, by varying the shape of the holes in the external wall such that the ratio of the hole perimeter to the hole area varies. Such a surface liner member may be adapted to form a surface portion of an aircraft engine nacelle, or of a leading edge of an aircraft wing.

Claims

1. Surface liner member (10) intended to be applied to a base surface (SB) in order to reduce, by acoustic absorption, an acoustic wave (OA) reflected on the base surface through the surface liner member, said surface liner member comprising:

an external wall (1) which is provided with multiple holes (2), each hole individually forming an open passage through said external wall;

a spacer structure, which is connected to an inner face (FI) of the external wall (1) and adapted to set a gap (E) between said external wall and the base surface (SB), so as to form at least one acoustic cavity between the inner face of the external wall and the base surface; and

tubes (3), which are connected to the external wall (1) and which extend into the acoustic cavity from the inner face (FI) of said external wall, towards the base surface (SB), each tube being open at two opposite ends of said tube and being dedicated to one of the holes (2) in the external wall with a hole section that is contained in an inner section of the tube at the external wall,

wherein a length of each tube (3) is smaller than the gap (E) between the external wall (1) and the base surface (SB), said tube length being measured in a direction perpendicular to the inner face (FI) of said external wall, so that at least 10% of the gap between the external wall and the base surface, against said base surface, is devoid of tubes,

and characterized in that several of the holes (2) in the external wall (1) have different cross-sectional shapes, such that a quotient of a hole cross-sectional perimeter divided by a hole cross-sectional area varies between at least some of said holes.

2. Surface liner member (10) according to claim 1, wherein at least some of the tubes (3) have respective lengths which are different, each measured in the direction perpendicular to the inner face (FI) of the external wall (1).

3. Surface liner member (10) according to claim 1, wherein each tube (3) extends perpendicularly to the inner face (FI) of the external wall (1).

4. Surface liner member (10) according to claim 1, wherein the length of each tube (3) is less than the gap (E) between the external wall (1) and the base surface (SB), by a distance of between 2 mm and 40 mm, in the direction perpendicular to the inner face (FI) of said external wall.

5. Surface liner member (10) according to claim 1, wherein, for at least one of the tubes (3), the internal cross-section of said tube varies as a function of the distance measured from the inner face (FI) of the external wall (1), along the direction perpendicular to said inner face of the external wall.

6. Surface liner member (10) according to claim 1, wherein a peripheral edge of at least one of the holes (2) is a polygon with more than four sides.

7. Surface liner member (10) according to claim 6, wherein the peripheral edge of at least one of the holes (2) has a fractal pattern of second order or higher than second order.

8. Surface liner member (10) according to claim 1, having a shape adapted to form a surface portion of an aircraft engine nacelle, a portion of a leading edge of an aircraft wing, a portion of an acoustic absorption device for an air conditioning system, or a portion of a blower inner wall.

9. Surface liner member (10) according to claim 1, wherein one end of the spacer structure which is opposite to the external wall (1) is adapted to be bonded to the base surface (SB).

10. Method for manufacturing a surface liner member (10) which is in accordance with any one of the preceding claims, wherein the tubes (3), are formed by a method of three-dimensional printing or injection molding from the inner face (FI) of the external wall (1).

11. Surface liner member (10) according to claim 2, wherein each tube (3) extends perpendicularly to the inner face (FI) of the external wall (1).

12. Surface liner member (10) according to claim 2, wherein the length of each tube (3) is less than the gap (E) between the external wall (1) and the base surface (SB), by a distance of between 2 mm and 40 mm, in the direction perpendicular to the inner face (FI) of said external wall.

13. Surface liner member (10) according to claim 3, wherein the length of each tube (3) is less than the gap (E) between the external wall (1) and the base surface (SB), by a distance of between 2 mm and 40 mm, in the direction perpendicular to the inner face (FI) of said external wall.

14. Surface liner member (10) according to claim 2, wherein, for at least one of the tubes (3), the internal cross-section of said tube varies as a function of the distance measured from the inner face (FI) of the external wall (1), along the direction perpendicular to said inner face of the external wall.

15. Surface liner member (10) according to claim 3, wherein, for at least one of the tubes (3), the internal cross-section of said tube varies as a function of the distance measured from the inner face (FI) of the external wall (1), along the direction perpendicular to said inner face of the external wall.

16. Surface liner member (10) according to claim 4, wherein, for at least one of the tubes (3), the internal cross-section of said tube varies as a function of the distance measured from the inner face (FI) of the external wall (1), along the direction perpendicular to said inner face of the external wall.

17. Surface liner member (10) according to claim 2, wherein a peripheral edge of at least one of the holes (2) is a polygon with more than four sides.

18. Surface liner member (10) according to claim 3, wherein a peripheral edge of at least one of the holes (2) is a polygon with more than four sides.

19. Surface liner member (10) according to claim 4, wherein a peripheral edge of at least one of the holes (2) is a polygon with more than four sides.

20. Surface liner member (10) according to claim 5, wherein a peripheral edge of at least one of the holes (2) is a polygon with more than four sides.