Acoustic attenuation panel for aircraft for engine nacelle
An aircraft turbojet engine air intake structure includes an air intake lip provided with a first acoustic attenuation panel which contains a structuring skin and, as an acoustic absorption material, a porous material fastened on the skin. The air intake structure also includes a pneumatic de-icing compartment defined by the lip and by an inner partition. The first acoustic attenuation panel is of the type including an open-cell porous material which is capable of resisting a temperature of up to 200° C. and having high heat conductivity.
1. An air intake structure for an aircraft turbojet engine, the air intake structure comprising:
an air intake lip provided with at least a first acoustic attenuation panel comprising a structuring skin and, as acoustic absorption material, a porous material fastened on said skin,
wherein the air intake structure comprises a pneumatic de-icing compartment defined in particular by said lip and by an inner partition, said inner partition closing said pneumatic de-icing compartment and comprising a return being fastened on a common sheet, and said first acoustic attenuation panel is an open-cell porous material capable of resisting a temperature of up to 200° C. and having high heat conductivity,
wherein a centering member directly connected to a shroud is fastened on the common sheet partially covering said first acoustic attenuation panel on an opposite side to said structuring skin.
2. The panel according to claim 1 , wherein the material forming said porous material comprises at least one of:
a porous material formed by a superposition of layers of porous materials with different characteristics, in the direction of the thickness of the panel, and
a porous material formed by a juxtaposition of blocks of porous materials with different characteristics, in the direction parallel to the middle plane of the panel.
3. The panel according to claim 1 , wherein said porous material includes cavities comprising through cavities and blind cavities, wherein said cavities comprise cavities with walls oriented substantially perpendicular to the middle plane of said panel and cavities with walls that are inclined relative to the middle plane of said panel.
4. The panel according to claim 1 , wherein said structuring skin includes perforations.
5. The air intake structure according to claim 1 , further comprising stiffeners being fastened on said structuring skin.
6. The air intake structure according to claim 5 , comprising a resistive layer attached on the stiffeners, wherein said resistive layer comprises a wire mesh or a perforated skin, or by a combination of those two elements,
wherein said structuring skin and/or said stiffeners and/or said resistive layer are formed in material comprising at least one of metal alloys, ceramics, metal matrix composites, ceramic matrix composites.
7. The air intake structure according to claim 1 , wherein said first acoustic attenuation panel is fastened to an inside of said air intake lip by an upstream maintenance sheet and a downstream maintenance sheet, and said inner partition is fastened on said downstream maintenance sheet.
8. The air intake structure according to 1 , further comprising a second acoustic attenuation panel fastened to an inside of the air intake lip downstream of said inner partition, separated from said first panel by a joint made of an open-cell porous material able to resist a temperature of up to 400° C. and having a low heat conductivity.
9. The air intake structure according to claim 8 , wherein said second acoustic attenuation panel is chosen in the group comprising a panel with porous material and open cells, capable of resisting temperatures of up to 120° C., and a honeycomb structure panel.
10. The air intake structure according to claim 8 , wherein said first panel, said joint made from porous material and said second panel are covered by the common sheet.
11. The air intake structure according to claim 1 , wherein the air intake lip forms a single-piece assembly with an outer wall of the air intake structure, said single-piece assembly being able to slide relative to a fan case of the turbojet engine.
12. The air intake structure according to claim 1 , wherein the structure of said porous material is chosen from the group comprising foams, expanded materials, felts, aggregates of small elements, and the material forming said porous material is chosen from the group comprising metal, polymer, ceramic, composite materials, and carbon foam, said material being itself chosen from the group comprising materials resisting temperatures of up to 200° C., materials resisting temperatures up to 400° C., materials resisting temperatures up to 600° C., and materials resisting temperatures up to 800° C.