Integration of a fan flutter damper in an engine casing
An acoustic treatment panel intended to be disposed on at least one wall of a turbojet in contact with a fluid flow, the panel comprising a first sheet, a second sheet parallel to the first sheet and having a first face intended to be in contact with a fluid flow and a second face facing the first sheet, and acoustic treatment cells extending between the first and second sheets and each including an enclosure and a cavity delimited by the enclosure. The enclosure of each cell comprises two openings facing one another, at least one of the openings being coincident with an opening of the enclosure of an adjacent cell.
1. An acoustic treatment panel intended to be disposed on at least one wall of a turbojet in contact with a fluid flow, the panel comprising a first sheet, a second sheet parallel to the first sheet and having a first face intended to be in contact with a fluid flow and a second face facing the first sheet, and acoustic treatment cells extending between the first and second sheets and each including an enclosure and a cavity delimited by the enclosure,
the enclosure of each cell comprising two openings facing one another, at least one of the openings being coincident with an opening of the enclosure of an adjacent cell,
wherein the second sheet comprises a non-porous portion covering at least one first acoustic treatment cell and at least one porous portion disposed facing the at least one second acoustic treatment cell and comprising at least one perforation passing through the thickness of the second sheet and allowing the sound waves to gain access to at least one second acoustic treatment cell and to said at least one first acoustic treatment cell via the openings.
2. The acoustic treatment panel according to claim 1 , wherein said cells are disposed in mutually parallel rows and the openings of the cells of the same row are aligned in the direction of the row to define a propagation channel for sound waves passing through the openings of the cells of the row.
3. The acoustic treatment panel according to claim 2 , wherein at least one row comprises acoustic treatment cells including at least one additional opening communicating with a cell of an adjacent row.
4. The acoustic treatment panel according to claim 1 , wherein each acoustic treatment cell comprises a cylindrical cavity with a hexagonal base delimited by an enclosure including six walls extending between the first sheet and the second sheet.
5. The acoustic treatment panel according to claim 4 , wherein each opening extends over 10% to 95% of the surface of the wall on which the opening is formed.
6. The acoustic treatment panel according to claim 5 , wherein each opening covers more than 25% of the surface of the wall on which the opening is formed.
7. The acoustic treatment panel according to claim 1 , wherein the openings have the same geometric shape.
8. The acoustic treatment panel according to claim 1 , wherein each opening is formed by a plurality of openings.
9. The acoustic treatment panel according to claim 1 , wherein the second sheet comprises a plurality of perforations and necks each secured to one of said perforations and protruding from the second face of the second sheet between a first aperture and a second aperture.
10. The acoustical treatment panel according to claim 1 , wherein the acoustic treatment cells disposed facing the at least one perforation of the second sheet each comprise a horn extending inside the enclosure of the cell between a first aperture secured to the second sheet and a second aperture smaller than the first aperture.
11. The acoustic treatment panel according to claim 1 , wherein the length in the axial direction of said portion of the sheet is less than the height of the cells disposed facing said portion.
12. A turbojet comprising a nacelle provided with at least one wall comprising at least one acoustic treatment panel according to claim 1 .
13. The turbojet according to claim 12 , wherein at least one acoustic treatment panel comprises sound wave propagation channels, each acoustic treatment cell comprises a cylindrical cavity with a hexagonal base delimited by an enclosure including six walls extending between the first sheet and the second sheet, each opening extends over 10% to 95% of the surface wall on which the opening is formed, each opening covers more than 25% of the surface of the wall on which the opening is formed, and the turbojet defines an axial direction corresponding to the axis of rotation of the turbines, the propagation channels being aligned in directions not parallel to the axial direction of the turbojet.