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EP-3259125-B1 - ACOUSTIC LINERS AND METHOD OF SHAPING AN INLET OF AN ACOUSTIC LINER

EP3259125B1EP 3259125 B1EP3259125 B1EP 3259125B1EP-3259125-B1

Inventors

  • ROACH, ANDREW MICHAEL
  • CEDAR, RICHARD DAVID
  • DAVIES, STEVEN THOMAS
  • DEPUY, Timothy Richard
  • HOWARTH, GRAHAM FRANK
  • MARTINEZ, Michael Moses

Dates

Publication Date
20260506
Application Date
20150218

Claims (13)

  1. An acoustic liner (20) for a turbine engine (12), comprising: a support layer (22) that includes a set of partitioned cavities (28) with open faces; a perforated sheet (24) that includes a set of perforations (30) with corresponding inlets, the perforated sheet operably coupled to the support layer such that perforations (30) are in overlying relationship with the open faces to form paired perforations and cavities that define acoustic resonator cells; and a coating (40) applied to the perforated sheet (24) on a surface (49) of the perforated sheet (24) distal from the support layer (22), the coating (40) having a portion arranged to be upstream relative to a generally forward-to-aft bypass airflow path (18) of the turbine engine (12), the portion having a reducing thickness (42) to define a transition area leading up to the inlets, so as to modify the geometry into the perforations (30) to improve the flow of acoustic energy into the acoustic resonator cells; wherein the perforations have a 90 degree transition angle at the inlets relative to an upper surface of the perforated sheet and the portion with the reducing thickness increases the transition angle to greater than 90 degrees.
  2. The acoustic liner (20) of claim 1 wherein the reducing thickness includes a continuously reducing thickness.
  3. The acoustic liner (20) of claim 1 wherein the reducing thickness includes a linear step-wise reducing thickness.
  4. The acoustic liner (20) of claim 1 wherein the portion with the reducing thickness forms a radius upstream of the inlet.
  5. The acoustic liner (20) of claim 1 wherein the portion with the reducing thickness forms a taper upstream of the inlet.
  6. The acoustic liner (20) of claim 1 wherein the portion with the reducing thickness forms a chamfer upstream of the inlet.
  7. The acoustic liner (20) of claim 1 wherein the perforations are between 0.1 and 0.25 millimeters (0.005 and 0.010 inches) in diameter.
  8. The acoustic liner (20) of claim 1 wherein the perforated sheet includes a composite material.
  9. The acoustic liner (20) of claim 1 wherein the coating includes at least one of a fluoropolymers, polymers, hydrophobic, icephobic, low friction, or anti-erosion coating.
  10. The acoustic (20) liner of claim 9 wherein the coating is at least one of a sprayed coating or a vapor deposited coating.
  11. The acoustic liner (20) of claim 1 further includes an imperforate sheet supported by the support layer on an opposite side of the support layer than the perforated sheet.
  12. A method of shaping an inlet of an acoustic liner (20), the method comprising: providing a support layer (22) having a set of partitioned cavities (28) with open faces; providing a perforated sheet (24) having a set of perforations (30) corresponding to cavities in the set of partitioned cavities, such that perforations (30) are in overlying relationship with the open faces to form paired perforations (30) and cavities (28) that define acoustic resonator cells; and applying a coating (40) to the perforated sheet (24) on a surface (49) of the perforated sheet (24) distal from the support layer (22), and forming a portion of the coating (40) with a reducing cross section (42) leading up to the perforation along an air flow direction across the acoustic liner in a generally forward-to-aft bypass airflow path (18) of the turbine engine (12), the portion of the coating (40) formed with a reducing cross section (42) defining a transition area leading up to the perforation, so as to modify the geometry into the perforations (30) to improve the flow of acoustic energy into the acoustic resonator cells; wherein the perforations have a 90 degree transition angle at the inlets relative to an upper surface of the perforated sheet and the portion with the reducing thickness increases the transition angle to greater than 90 degrees.
  13. The method of claim 12, wherein the coating (40) is sprayed in a direction relative to the perforated sheet (34) to form an acute angle relative to the perforated sheet.

Description

BACKGROUND OF THE INVENTION Contemporary aircraft engines can include acoustic attenuation panels in aircraft engine nacelles to reduce noise emissions from aircraft engines. These acoustic attenuation panels generally have a sandwich structure comprising liners enclosing a cellular honeycomb-type inner structure. EP 1 071 072 A2 discloses an acoustic liner for suppressing noise in aircraft engines, especially turbofan gas engines, said liner comprising a support layer having a multiplicity of partitioned cavities, preferably a honeycomb; an imperforate layer on a back side of said support layer; a perforated face sheet attached to the face side of said support layer and having a plurality of perforations formed therein; and a coating of an erosion-resistant material applied to one side of said perforated sheet and optionally to said perforation walls. BRIEF DESCRIPTION OF THE INVENTION In one aspect, an embodiment of the invention relates to an acoustic liner having a support layer that includes a set of partitioned cavities with open faces, a perforated sheet that includes a set of perforations with corresponding inlets, the perforated sheet supported by the support layer such that perforations are in overlying relationship with the open faces to form paired perforations and cavities that define acoustic resonator cells, and a coating applied to the perforated sheet and having a portion, at least upstream relative to the through air flow of the inlets, with a reducing thickness to define a transition area leading up to the inlets. In another aspect, an embodiment of the invention relates to a method of shaping an inlet of an acoustic liner, the method includes applying a coating to the perforated sheet to form a portion of the coating with a reducing cross section leading up to the inlet along an air flow direction across the acoustic liner. SUMMARY OF INVENTION The invention shall be specified by the appended set of claims. BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: FIG. 1 is a schematic view of an aircraft engine assembly with a portion of the outer nacelle cut away for clarity.FIG. 2 is a detail view of section A of the acoustic panel of FIG. 1 illustrating a partitioned support structure with facing and backing sheets.FIG. 3 is perspective view of the acoustic panel of FIG. 1 with portions of the support structure and facing sheet removed for clarity.FIG. 4 is a sectional view showing a coating applied to the perforated sheet of FIG. 3 according to an embodiment of the invention.FIGS. 5A - 5C illustrate a coating applied to a perforated sheet according to embodiments of the invention. DESCRIPTION OF EMBODIMENTS OF THE INVENTION FIG. 1 illustrates an aircraft engine assembly 10 having a turbine engine 12, a fan assembly 13, and a nacelle 14. Portions of the nacelle 14 have been cut away for clarity. The nacelle 14 surrounds the turbine engine 12 and has an inlet section 17 that defines an inlet 19 open to ambient air and an annular airflow path or annular bypass duct 16 through the aircraft engine assembly 10 to define a generally forward-to-aft bypass airflow path as schematically illustrated by the arrow 18. The turbine engine 12 can have a fan section 21 that includes an annular fan case 23 and an aft duct 25 of a thrust reverser (not shown). The fan section can be provided within the nacelle wherein the fan section 21 is in fluid communication with the inlet 19. An annular acoustic panel 20 is provided within the nacelle in at least a portion of the inlet 19 or the fan section 21. The acoustic panel 20 forms a liner for attenuating noise in the aircraft engine assembly 10 and defines the through air flow. FIG. 2 shows a detailed view of the annular acoustic panel of FIG. 1. The annular acoustic panel 20 includes an open framework 22 disposed between an imperforate backing sheet 26 and a front perforated sheet 24. The open framework 22 forms a support layer having a set of partitioned cavities or cells 28 with open faces. Including that the open framework 22 has open faces on opposing front and rear sides of the open framework 22. In this manner, the open framework 22 forms a set of cells 28 in the open spaces between the open framework 22, the backing sheet 26, and the perforated sheet 24. As illustrated more clearly in FIG. 3, the cells 28 formed by the open framework 22 disposed between the backing sheet 26 and the perforated sheet 24 each have a predetermined volume defined by the geometry of the open framework 22 and the spacing between the backing sheet 26 and the perforated sheet 24. The open framework 22 can include a honeycomb structure wherein the cells have six walls formed by the open frame work 22, a top wall formed by the backing sheet 26 and a bottom wall formed by the perforated sheet 24. The backing sheet 26 can be impervious with respect to air. More specifically, the backing sheet 26 can be an imperforate sheet supported by the support layer or open framework 22 on an oppo