One-piece acoustic component with misaligned acoustic cells

Abstract

One-piece acoustic component with misaligned acoustic cells The invention relates to a one-piece acoustic component (120) comprising a plurality of hollow acoustic elements (121) having a shape that gradually narrows between a base (121a) and a vertex (121b), the bases (121a) of the hollow acoustic elements (121) being connected to each other by connecting edges (123), the acoustic component (120) being characterized in that it comprises a plurality of partitions (122) connecting the hollow acoustic elements (121) so as to form acoustic cells extending between the hollow acoustic elements (121), the vertices (121b) of the hollow acoustic elements (121) comprising an opening (121c) leading into at least one acoustic cell, so that only one opening (121c) of hollow acoustic element (121) leads into each acoustic cell. Figure for the summary: Fig. 2

Description

Title of the invention: One-piece acoustic component with misaligned acoustic cells. Technical field

[0001] The present invention relates to the general field of acoustic attenuation panels. It relates more particularly to acoustic panels used to reduce noise produced in aircraft propulsion assemblies such as in the nacelle, the fan, the compressor(s), the turbine(s), the nozzle(s), and in particular in the vicinity of the fan: air intake, fan casing or secondary flow channel. Previous technique

[0002] Acoustic attenuation panels typically consist of a plate or skin with an acoustic surface permeable to the acoustic waves to be attenuated and a solid reflective plate or skin, known as the "closing plate," with a multicellular body positioned between these two surfaces. The multicellular body is generally composed of a series of partitions, for example, in the shape of a honeycomb, delimiting a plurality of cells. As is well known, such panels form Helmholtz-type resonators that attenuate acoustic waves within a certain frequency range, the height of the cavities allowing the selection of the targeted frequency band. Acoustic attenuation panels of this type are described in particular in US patent 5,912,442 and GB patent 2,314,526. Thus, the lower the frequency bands to be attenuated, the greater the height of the cavities will be.

[0003] These acoustic attenuation panels, limited to simple cell shapes such as NIDA-type honeycomb cells, are not suitable for absorbing very low frequencies due to the required cavity height and resulting bulk. This is particularly true for acoustic attenuation panels found in turbojet engines with slower rotational speeds and / or with a reduction gear between the fan and the turbine, where the frequencies to be absorbed are between 200 Hz and 400 Hz and where the available space is limited.

[0004] One solution for handling low frequencies without using an excessively thick multicellular body is to place hollow acoustic elements, for example open truncated cones, within the cells of the multicellular body. Such hollow acoustic elements are described in particular in documents FR 3 082 987, FR 3 127 713, FR 3 129 022 and FR 3 129 315.

[0005] To manufacture such an acoustic panel, it is therefore necessary to assemble the acoustic skin with an acoustic component formed by the hollow acoustic elements, the hollow acoustic elements with the multicellular body and the multicellular body with the possible closing skin.

[0006] This assembly presents several drawbacks. First, inserting the hollow acoustic elements into the cells of the multicellular body can be tricky. The cells or hollow acoustic elements may be irregular or misaligned, and the multicellular body may be too rigid. Furthermore, assembling the acoustic component with the multicellular body requires either the application of glue and its curing in an autoclave, or welding, both of which are relatively expensive operations. Finally, the distance between the hollow acoustic elements and the closing skin can be difficult to control. An unsuitable distance between the hollow acoustic elements and the closing skin can lead to a reduction in the acoustic panel's performance. All these drawbacks are further amplified when producing double-curved acoustic panels.Indeed, the positioning of the elements relative to each other and their assembly are even more delicate to implement when producing double-curved acoustic panels. Description of the invention

[0007] The present invention aims to remedy at least the aforementioned drawbacks.

[0008] To this end, the invention proposes a one-piece acoustic component comprising a plurality of hollow acoustic elements having a shape that gradually narrows between a base and a top, the bases of the hollow acoustic elements being connected to each other by connecting edges, the acoustic component being characterized in that it comprises a plurality of partitions connecting the hollow acoustic elements so as to form acoustic cells extending between the hollow acoustic elements, the tops of the hollow acoustic elements comprising an opening leading into at least one acoustic cell, so that only one opening of the hollow acoustic element leads into each acoustic cell.

[0009] Thus, the hollow acoustic elements and acoustic cells are made in a single piece. This eliminates the problems associated with assembling the acoustic elements with a multi-cell body. Furthermore, the hollow acoustic elements are no longer each positioned inside a cell. In this geometry, each acoustic cell extends between several hollow acoustic elements. The shape and dimensions of the hollow acoustic elements are therefore easier to control, as is the distance between the top of the hollow acoustic elements and the closing skin. is controlled. Moreover, the presence of partitions between the hollow acoustic elements allows for their mechanical reinforcement. The acoustic cells thus formed are airtight.

[0010] According to a particular embodiment of the invention, the partitions extend from the bases of the hollow acoustic elements to a lower edge, the lower edges of the partitions being present at the same level as the tops of the hollow acoustic elements.

[0011] Thus, when the acoustic component is assembled with a closing skin or placed against a wall, the lower edges of the partitions and the tops of the hollow acoustic elements come into contact with the closing skin or the wall. Therefore, the distance between the hollow acoustic elements and the closing skin or the wall is very well controlled.

[0012] According to another particular embodiment of the invention, the tops of the hollow acoustic elements comprise a chimney, the openings of the tops of the hollow acoustic elements being present on said chimneys.

[0013] Thus, the control of the dimensions of the acoustic component and the homogeneity of the acoustic protection are improved.

[0014] According to another particular embodiment of the invention, the acoustic cells have a quadrilateral cross-section. In particular, the acoustic cells may have a square cross-section.

[0015] Indeed, such a cell shape is simpler to manufacture and allows for particularly satisfactory acoustic attenuation.

[0016] According to another particular embodiment of the invention, the bases of the hollow acoustic elements are hexagonal in shape.

[0017] According to another particular embodiment of the invention, the hollow acoustic elements extend in rows along first and second intersecting directions, the partitions extending along said first and second directions.

[0018] The invention also proposes an acoustic panel comprising an acoustic component as described above and comprising an acoustic skin disposed in contact with the bases of the hollow acoustic elements.

[0019] The invention also provides an acoustic panel comprising an acoustic component as described above and including a closing skin disposed in contact with the tops of the hollow acoustic elements and the bottom edges of the partitions. Such an acoustic panel may also include an acoustic skin disposed in contact with the bases of the hollow acoustic elements.

[0020] In addition, the invention relates to an aircraft propulsion assembly comprising at least one acoustic panel as described above. Brief description of the drawings

[0021] [Fig.1] Fig.1 is a schematic exploded perspective view of an acoustic panel comprising an acoustic component according to the invention.

[0022] [Fig.2] Fig.2 is a detailed perspective view of the acoustic component of the [Fig.l].

[0023] [Fig.3] Fig.3 is a schematic perspective view of the acoustic panel of the [Fig.l], Description of the implementation methods

[0024] Figures 1 to 3 illustrate an acoustic panel 100 comprising in order an acoustic skin 110, an acoustic component 120 and a closing skin 130.

[0025] The acoustic skin 110 has the function of allowing the sound waves to be attenuated to pass through the acoustic panel 100. For this purpose, the acoustic skin 110 comprises a plurality of perforations 111, as illustrated in figures 1 and 2. The acoustic skin 110 can have a thickness of between 1 mm and 5 mm, for example 2 mm.

[0026] The acoustic skin 110 can be produced in a well-known manner by stamping, by automated fiber placement (AFP), or by automated tape laying (ATL). Other processes can also be used to manufacture the acoustic skin 110, such as manual laying.

[0027] The acoustic skin 110 can be made of a thermoplastic material, for example, a thermoplastic matrix composite material comprising fibers. The fibers can be made of carbon, glass, or aramid. The acoustic skin 110 may not comprise fibers. The thermoplastic matrix can be made, for example, of polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyphenylene sulfide (PPS), polyethersulfone (PESU), or polycarbonate (PC).

[0028] The closing skin 130 corresponds to a solid surface designed to reflect sound waves entering the acoustic panel 100. The closing skin 130 may be a constituent element of the acoustic panel, as in the example described here, or correspond to a surface of an object, for example, an aircraft engine. In the latter case, the acoustic panel does not have a closing skin and is mounted directly onto the surface of the object.

[0029] The closure skin 130 can be produced in a well-known manner by stamping, by automated fiber placement (AFP), or by automated tape laying (ATL). Other processes can also be used to manufacture the closure skin. 130. For example, the closure skin can be pre-cooked and then glued onto the multicellular body, or it can be formed and cooked directly onto the multicellular body.

[0030] The closing skin 130 may be made of a composite material comprising fibers, for example, a composite material based on carbon fibers impregnated with a thermoplastic or thermosetting resin. The closing skin 130 may not comprise fibers. The closing skin 130 may comprise all the types of fibers and all the types of matrix described previously for the acoustic skin 110. The closing skin 130 may also comprise other types of fibers and other types of matrix than those described previously.

[0031] The acoustic component 120 comprises a plurality of hollow acoustic elements 121, each having a shape that gradually narrows between a base 121a and an apex 121b. The hollow acoustic elements 121 are connected to each other by one or more connecting edges 123. The connecting edges 123 comprise an upper face, situated on the same plane as the bases 121a of the hollow acoustic elements 121, and a lower face opposite the upper face. The bases 121a of the hollow acoustic elements 121 and the upper faces of the connecting edges 123 define a first assembly face of the acoustic component 120. The first assembly face of the acoustic component 120 may be intended to be assembled in contact with the acoustic skin 110.

[0032] In the example shown in Figures 1 to 3, the hollow acoustic elements 121 have a funnel shape. However, it does not depart from the scope of the invention if the hollow acoustic elements have, for example, a conical, spiral, or pyramidal shape. In the example shown in Figures 1 to 3, the hollow acoustic elements 121 exhibit symmetry. However, it does not depart from the scope of the invention if the hollow acoustic elements are asymmetrical.

[0033] The hollow acoustic elements 121 may include a chimney, as illustrated in Figures 1 to 3. Such a chimney is located at the apex 121b of the hollow acoustic elements 121. The chimney represents the apex 121b of the hollow acoustic element 121. Such a chimney may have a height of between 3 and 10 mm, preferably 5 mm. The height of the chimney allows contact after assembly of the acoustic panel between said chimney and the closing skin. The outlet area of ​​the chimney is smaller than the inlet area of ​​the chimney. The ratio between the outlet area of ​​the chimney and the inlet area of ​​the chimney is lower than the ratio between the inlet area of ​​the hollow acoustic element 121 and the inlet area of ​​the chimney. Openings 121c may be located on the chimneys.

[0034] In the example illustrated in Figures 1 to 3, the bases 121a of the hollow acoustic elements 121 have a hexagonal shape. Of course, it remains within the scope of the invention if the bases 121a have another shape, for example, a circular or square shape. Similarly, in the example illustrated in Figures 1 to 3, the vertices 121b of the hollow acoustic elements 121 have a hexagonal shape. Of course, it remains within the scope of the invention if the vertices 121b have another shape, for example, a circular or square shape.

[0035] The hollow acoustic elements 121 may have a wall thickness of between 0.25 mm and 2 mm. Preferably, the hollow acoustic elements 121 have a thickness of less than 1 mm, for example between 0.3 mm and 0.5 mm.

[0036] Preferably, the base 121a of the hollow acoustic elements 121 is contained within a circle with a diameter between 5 mm and 50 mm. In particular, the base 121a of the hollow acoustic elements 121 is contained within a circle with a diameter between 8 mm and 20 mm. Preferably, the apex 121b of the hollow acoustic elements 121 is contained within a circle with a diameter between 1 mm and 10 mm. In particular, the apex 121b of the hollow acoustic elements 121 is contained within a circle with a diameter between 2 mm and 5 mm.

[0037] The height of the hollow acoustic elements 121 between the base 121a and the top 121b can be between 10 mm and 50 mm. In particular, the height of the hollow acoustic elements 121 can be between 20 mm and 30 mm.

[0038] The acoustic component 120 further comprises a plurality of partitions 122. The partitions 122 connect the hollow acoustic elements 121 to one another. The partitions 122 form acoustic cells. The acoustic cells are delimited by the partitions 122 and by the walls of the hollow acoustic elements 121.

[0039] The partitions 122 extend widthwise from one hollow acoustic element 121 to another. Of course, the partitions 122 located at the edge of the acoustic component 120 may be connected to only one hollow acoustic element 121. The partitions 122 extend heightwise from a lower edge 122b to the bases 121a of the hollow acoustic elements 121. Thus, the partitions 122 extend heightwise between an upper end 122a and a lower edge 122b. The upper ends 122a of the partitions 122 are located at the junction between the bases 121a of the hollow acoustic elements 121 and the partitions 122.

[0040] Preferably, the partitions 122 extend to the level of the tips of the peaks 121b of the hollow acoustic elements 121. Thus, the lower edges 122b of the partitions 122 are preferably located at the same level as the tips of the peaks 121b of the hollow acoustic elements 121. Consequently, the height of the partitions 122 is preferably identical to the distance between the base 121a and the tip of the peak 121b of the hollow acoustic elements 121.

[0041] The partitions 122 form a network of ribs. The partitions 122 form a network connecting the hollow acoustic elements 121 to each other. Preferably, four partitions 122 extend from each hollow acoustic element 121. In this configuration, the hollow acoustic elements 121 located at the edge of the acoustic component 120 may be in contact with fewer than four partitions. Thus, preferably, four partitions 122 extend from each hollow acoustic element 121 not located at the edge of the acoustic component 120. According to an unillustrated variant, six partitions may extend from each hollow acoustic element. In particular, six partitions may extend from each hollow acoustic element not located at the edge of the acoustic component. According to another unillustrated variant, eight partitions may extend from each hollow acoustic element.In particular, eight partitions can extend from each hollow acoustic element not located at the edge of the acoustic component. It should be noted that the more partitions there are, the better the mechanical strength of the acoustic component 120 will be.

[0042] In the configuration where only four partitions 122 extend from each hollow acoustic element 121, the hollow acoustic elements 121 comprise a single opening 121c leading into a single acoustic cell. In configurations where more than four partitions 122 extend from each hollow acoustic element 121, for example, six or eight partitions, the opening 121c of the hollow acoustic elements 121 leads into several acoustic cells simultaneously, so that a single hollow acoustic element 121 leads into each acoustic cell. The openings 121c can then be divided by one or more partitions 122 to allow them to lead simultaneously into several acoustic cells.

[0043] The lower edges 122b of the partitions 122 form a second assembly face of the acoustic component 120. The second assembly face of the acoustic component 120 can be intended to be assembled in contact with the closing skin 130. Preferably, the lower edges 122b of the partitions 122 and the tops 121b of the hollow acoustic elements 121 form the second assembly face of the acoustic component 120. Thus, in the acoustic panel 100, the lower edges 122b of the partitions 122 and the tops 121b of the hollow acoustic elements 121 are in contact with the closing skin 130.

[0044] In the example illustrated in Figures 1 to 3, the acoustic cells have a parallelogram cross-section. Of course, it does not depart from the scope of the invention if the acoustic cells have a cross-section of another shape, for example a triangular or a square cross-section.

[0045] The partitions 122 may have a thickness of between 0.5 mm and 1 mm. The partitions 122 are preferably thicker than the walls of the hollow acoustic elements 121.

[0046] The vertices 121b of the hollow acoustic elements 121 comprise an opening 121c leading into at least one acoustic cell. The vertex 121b of each hollow acoustic element 121 comprises a single opening 121c leading into a single acoustic cell. Preferably, a single opening 121c of vertex 121b of the hollow acoustic element 121 leads into each acoustic cell. Thus, each acoustic cell is preferably associated with a single opening 121c of the hollow acoustic element 121. Conversely, the same hollow acoustic element 121 can lead into several acoustic cells via the opening 121c of that hollow acoustic element.

[0047] Preferably, the openings 121c extend from the tip of the apex 121b of the hollow acoustic elements 121. The openings 121c can be laterally delimited by two partitions 122. The acoustic component 120 can be produced in a well-known manner by additive manufacturing, for example by filament deposition, laser sintering, or photopolymerization. The acoustic component 120 can also be produced in a well-known manner by injection molding, injection-compression molding, or stamping.

[0048] The acoustic component 120 can also be produced using a well-known injection-compression method with a thermoplastic material. Injection-compression involves injecting the material into a partially open mold. Thus, even if the material solidifies, the channels become less obstructed. Once the material is distributed throughout the mold, it is completely closed by a closing force to return to the correct dimensions. This allows for thinner wall thicknesses for the acoustic elements 121 and partitions 122 than with a conventional injection molding process.

[0049] The acoustic component 120 can also be produced in a well-known manner by injection molding with temperature control of a thermoplastic material. Injection molding with temperature control of the mold consists of controlling the temperature of the mold or the tooling by means of a mold temperature control system, for example with a heat transfer fluid or with air.

[0050] Preferably, the acoustic component 120 is made of a thermoplastic material. For example, the acoustic component 120 can be made of polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyphenylene sulfide (PPS), polyethersulfone (PESU), or polycarbonate (PC). Polyetherimide (PEI) and polyethersulfone (PESU) are particularly suitable for this application. The acoustic component 120 can be made of a filled or unfilled thermoplastic material.

[0051] The acoustic component 120 can also be made of thermosetting material, in particular if it is manufactured by filament deposition or by photopolymerization.

[0052] The acoustic component 120 can be "flat," meaning that the bases 121a of the hollow acoustic elements lie in the same plane. The acoustic component 120 can also be curved, meaning that the bases 121a of the hollow acoustic elements lie on the same curved surface. The acoustic component 120 can have a single curvature or a double curvature.

[0053] The acoustic skin 110 can be attached to the acoustic component 120 by bonding or welding. Pretreatment can be carried out on the first assembly face of the acoustic component 120 before assembly with the acoustic skin 110, in order to facilitate said assembly. For example, the first assembly face of the acoustic component 120 can be degreased, sanded, and / or plasma-treated before assembly with the acoustic skin 110.

[0054] Similarly, the closing skin 130 can be attached to the acoustic component 120 by bonding or welding. Pretreatment can be carried out on the second mounting face of the acoustic component 120 before assembly with the closing skin 130, in order to facilitate said assembly. For example, the second mounting face of the acoustic component 120 can be degreased, sanded, and / or plasma-treated before assembly with the closing skin 130.

[0055] In the example illustrated in Figures 1 to 3, the acoustic panel 100 comprises only an acoustic skin 100, an acoustic component 120, and a closing skin 130. It is thus a single-degree-of-freedom (SDoF) acoustic panel. Of course, the invention remains within the scope of the invention if the acoustic panel comprises several acoustic components as described above. Nor does the invention depart from the scope of the invention if the acoustic panel also comprises one or more multicellular bodies. The acoustic panel may also include intermediate acoustic skins separating different layers of said acoustic panel. Thus, the first assembly face and / or the second assembly face of the acoustic component as described above may be in contact with an intermediate acoustic skin separating two layers of the acoustic panel.Therefore, the acoustic component as described above can be used in two-degree-of-freedom acoustic panels, known as "2DoF".

[0056] The acoustic panel 100 can for example be used for acoustic attenuation in an aircraft nacelle or engine, for a blade platform, for an aeronautical sleeve.

[0057] The expression "between ... and ..." should be understood as including the bounds.

Claims

Demands

1. A one-piece acoustic component (120) for an aircraft propulsion assembly comprising a plurality of hollow acoustic elements (121) having a shape that gradually narrows between a base (121a) and a top (121b), the bases (121a) of the hollow acoustic elements (121) being connected to each other by connecting edges (123), the acoustic component (120) being characterized in that it comprises a plurality of partitions (122) connecting the hollow acoustic elements (121) so as to form acoustic cells extending between the hollow acoustic elements (121), the tops (121b) of the hollow acoustic elements (121) comprising an opening (121c) leading into at least one acoustic cell, such that only one opening (121c) of the hollow acoustic element (121) leads into each acoustic cell.

2. Acoustic component (120) according to claim 1, wherein the partitions (122) extend from the bases (121a) of the hollow acoustic elements (121) to a lower edge (122b), the lower edges (122b) of the partitions (122) being present at the same level as the tops (121b) of the hollow acoustic elements (121).

3. Acoustic component (120) according to claim 1 or 2, wherein the peaks (121b) of the hollow acoustic elements (121) comprise a chimney, the openings (121c) of the peaks (121b) of the hollow acoustic elements (121) being present on said chimneys.

4. Acoustic component (120) according to any one of claims 1 to 3, wherein the acoustic cells have a quadrilateral cross-section.

5. Acoustic component (120) according to any one of claims 1 to 4, wherein the bases (121a) of the hollow acoustic elements (121) are hexagonal in shape.

6. Acoustic component (120) according to any one of claims 1 to 5, wherein the hollow acoustic elements (121) extend in rows along first and second intersecting directions, the partitions (122) extending along said first and second directions.

7. Acoustic panel (100) for an aircraft propulsion assembly comprising an acoustic component (120) according to any of claims 1 to 6 and comprising an acoustic skin (110) disposed in contact with the bases (121a) of the hollow acoustic elements (121).

8. Acoustic panel (100) comprising an acoustic component (120) according to claim 2 or according to any one of claims 3 to 6 related to claim 2 and comprising a closing skin (130) disposed in contact with the tops (121b) of the hollow acoustic elements (121) and the bottom edges (122b) of the partitions (122).

9. Acoustic panel (100) according to claim 8, further comprising an acoustic skin (110) disposed in contact with the bases (121a) of the hollow acoustic elements (121).

10. Aircraft propulsion assembly comprising at least one acoustic panel (100) according to any one of claims 7 to 9.

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