Search

EP-4015797-B1 - ATTACHABLE ACOUSTIC PANELS AND METHOD OF MAKING SAME

EP4015797B1EP 4015797 B1EP4015797 B1EP 4015797B1EP-4015797-B1

Inventors

  • WARD, STEPHEN H.

Dates

Publication Date
20260506
Application Date
20211216

Claims (13)

  1. A propulsion assembly (10; 10') comprising: a fan (18) configured to rotate about an axial centerline (12); a fan case system (20) disposed about the fan (18) with respect to the axial centerline (12), the fan case system (20) comprising at least one perforated portion (48) comprising a plurality of holes (50) extending from an interior surface (46) of the fan case system (20) to an exterior surface (44) of the fan case system (20); and at least one acoustic panel (24) mounted to the exterior surface (44) of the fan case system (20) coincident with the at least one perforated portion (48), the at least one acoustic panel (24) comprising a core (26) comprising a plurality of cells (28) extending between a first side (30) of the core (26) and a second side (32) of the core (26) opposite the first side (30) of the core (26), the at least one acoustic panel (24) further comprising a back skin (34) attached to the second side (32) of the core (26), the first side (30) of the core (26) in contact with the exterior surface (44) of the fan case system (20) to form a plurality of resonant cavities (52) defined by the plurality of holes (50), the plurality of cells (28), and the back skin (34), characterized in that the plurality of holes (50) has a hole density (58, 60) which changes in an axial direction from a higher first hole density (58) to a lower second hole density (60) in the axial direction from forward to aft, and in that the plurality of cells (28) has a cell density (62, 64) which changes in the axial direction.
  2. The propulsion assembly (10; 10') of claim 1, wherein the fan case system (20) comprises a fan case portion (38) surrounding the fan (18), an inlet portion (40) mounted to the fan case portion (38) and located at a forward end of the fan case system (20), and a fan duct portion (42) mounted to the fan case portion (38) and located at an aft end of the fan case system (20).
  3. The propulsion assembly (10; 10') of claim 2, wherein the at least one acoustic panel (24) is mounted on either the inlet portion (40) or the fan duct portion (42).
  4. The propulsion assembly (10; 10') of claim 1, 2, or 3, wherein the core (26) and the back skin (34) form a unitary component.
  5. The propulsion assembly (10; 10') of any preceding claim, further comprising a nacelle (14) radially surrounding the fan case system (20), the at least one acoustic panel (24) located between the fan case system (20) and the nacelle (14).
  6. The propulsion assembly (10; 10') of any preceding claim, wherein the at least one acoustic panel (24) is curved in a circumferential direction relative to the axial centerline (12) to correspond to a shape of the exterior surface (44) of the fan case system (20).
  7. The propulsion assembly (10; 10') of claim 6, wherein the core (26) comprises a plurality of walls (36) which define the plurality of cells (28), and each of the plurality of walls (36) are substantially parallel to one another in a direction from the first side (30) of the core (26) to the second side (32) of the core (26).
  8. A method for forming a propulsion assembly (10; 10'), the method comprising: forming a plurality of holes (50) through a fan case system (20) to define at least one perforated portion (48) of the fan case system (20), the plurality of holes (50) extending from an interior surface (46) of the fan case system (20) to an exterior surface (44) of the fan case system (20); forming at least one acoustic panel (24) comprising a core (26) comprising a plurality of cells (28) extending between a first side (30) of the core (26) and a second side (32) of the core (26) opposite the first side (30) of the core (26), the at least one acoustic panel (24) further comprising a back skin (34) attached to the second side (32) of the core (26); and mounting the at least one acoustic panel (24) to the exterior surface (44) of the fan case system (20) coincident with the at least one perforated portion (48), the first side (30) of the core (26) in contact with the exterior surface (44) of the fan case system (20) to form a plurality of resonant cavities (52) defined by the plurality of holes (50), the plurality of cells (28), and the back skin (34), wherein the step of forming the plurality of holes (50) comprises forming the plurality of holes (50) with a hole density (58, 60) that changes in an axial direction from a higher first hole density (58) to a lower second hole density (60) in the axial direction from forward to aft, wherein the step of forming the at least one acoustic panel (24) comprises forming the plurality of cells (28) with a cell density (62, 64) that changes in the axial direction.
  9. The method of claim 8, wherein the step of forming the at least one acoustic panel (24) comprises forming the core (26) and the back skin (34) as a unitary component.
  10. The method of claim 8 or 9, wherein the step of forming the at least one acoustic panel (24) comprises injection molding the at least one acoustic panel (24).
  11. The method of claim 8, 9, or 10, wherein the at least one acoustic panel (24) is curved in a circumferential direction relative to an axial centerline (12) to correspond to a shape of the exterior surface (44) of the fan case system (20).
  12. The method of any of claim 11, wherein the core (26) comprises a plurality of walls (36) which define the plurality of cells (28), and each of the plurality of walls (36) are substantially parallel to one another in a direction from the first side (30) of the core (26) to the second side (32) of the core (26).
  13. The method of any of claims 9 to 12, wherein the step of forming the at least one acoustic panel (24) comprises forming the at least one acoustic panel (24) from a composite material.

Description

BACKGROUND 1. Technical Field This disclosure (invention) relates generally to propulsion assemblies for aircraft, and more particularly to acoustic liners for propulsion assemblies. 2. Background Information Acoustic attenuation panels are known for lining air flow surfaces of aircraft propulsion assemblies. Such acoustic structures are often referred to as acoustic liners. Generally, acoustic liners may include a cellular core covered on its exterior sides by a face skin and, on the opposite side, by a back skin. The face skin may include a plurality of spaced-apart holes or perforations. In this configuration, the cells of the core, covered by the face skin and the back skin, may form resonant cavities that contribute to the dissipation of incident acoustic energy by canceling acoustically reflected waves and/or converting acoustic energy into heat, such as by Helmholtz resonance. There is a need for improved acoustic panels which reduce manufacturing time and cost and improve acoustic panel resiliency while also effectively attenuating propulsion assembly noise. FR 3,059,044 discloses a fan casing for aeronautical turbomachinery. EP 1,336,739 discloses a gas turbine fan casing with containment and noise suppression functions. US 2011/139927 discloses a panel for an air intake of an aircraft nacelle that ensures optimized acoustic treatment and frost treatment. GB 2,391,059 discloses a noise attenuation panel. CN 105,366,060 discloses a lightweight high efficiency low noise duct type four-level electric fan propeller. SUMMARY It should be understood that any or all of the features or embodiments described herein can be used or combined in any combination with each and every other feature or embodiment described herein unless expressly noted otherwise. According to an aspect of the present invention, a propulsion assembly is provided in accordance with claim 1. Optionally, the fan case system includes a fan case portion surrounding the fan, an inlet portion mounted to the fan case portion and located at a forward end of the fan case system, and a fan duct portion mounted to the fan case portion and located at an aft end of the fan case system. Optionally, the at least one acoustic panel is mounted on the inlet portion. Optionally, the at least one acoustic panel is mounted on the fan duct portion. Optionally, the core and the back skin form a unitary component. Optionally,, the propulsion assembly further includes a nacelle radially surrounding the fan case system. The at least one acoustic panel is located between the fan case system and the nacelle. Optionally, the at least one acoustic panel is curved in a circumferential direction relative to the axial centerline to correspond to a shape of the exterior surface of the fan case system. Optionally, the core includes a plurality of walls which define the plurality of cells, and each of the plurality of walls are substantially parallel to one another in a direction from the first side of the core to the second side of the core. According to another aspect of the present invention, a method for forming a propulsion assembly is provided in accordance with claim 8. Optionally, the step of forming the at least one acoustic panel includes forming the core and the back skin as a unitary component. Optionally, the step of forming the at least one acoustic panel includes injection molding the at least one acoustic panel. Optionally, the at least one acoustic panel is curved in a circumferential direction relative to the axial centerline to correspond to a shape of the exterior surface of the fan case system. Optionally, the core includes a plurality of walls which define the plurality of cells, and each of the plurality of walls are substantially parallel to one another in a direction from the first side of the core to the second side of the core. Optionally, the step of forming the at least one acoustic panel includes forming the at least one acoustic panel from a composite material. The present disclosure, and all its aspects, embodiments and advantages associated therewith will become more readily apparent in view of the detailed description provided below, including the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a side, cross-sectional view of an exemplary propulsion assembly, in accordance with one or more embodiments of the present disclosure.FIG. 2 illustrates a side, cross-sectional view of another exemplary propulsion assembly, in accordance with one or more embodiments of the present disclosure.FIG. 3 illustrates a perspective, exploded view of a portion of a fan case system of the propulsion assembly of FIG. 1, in accordance with one or more embodiments of the present disclosure.FIG. 4 illustrates a perspective, exploded view of a portion of a fan case system of the propulsion assembly of FIG. 1, in accordance with one or more embodiments of the present disclosure.FIG. 5 illustrates a perspective, exploded view of a por