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 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 units such as in the nacelle, the fan, the compressor(s), the turbine(s), the nozzle(s), and in particular near the fan: air intake, fan casing or secondary flow channel. Prior art

[0002] Acoustic attenuation panels are typically made up of an acoustic surface plate or skin permeable to the acoustic waves that are to be attenuated and a reflective solid plate or skin called a "closing plate", a multicellular body being arranged between these two skins. The multicellular body is generally made up of a set of partitions, for example in the form of a honeycomb, delimiting a plurality of cells. In a well-known manner, such panels form Helmholtz-type resonators which make it possible to attenuate the acoustic waves in a certain frequency range, the height of the cavities making it possible to choose the targeted frequency band. Acoustic attenuation panels of this type are described in particular in documents US 5,912,442 and GB 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 those of the cells arranged in a honeycomb of the NIDA type are not suitable for very low frequencies to be absorbed due to the height of the required cavities and the resulting bulk. This is particularly the case for acoustic attenuation panels present in turbojets with slower rotation speeds and / or with a reducer between the fan and the turbine, for which the frequencies to be absorbed are between 200 Hz and 400 Hz and for which the possible bulk is limited.

[0004] One solution for processing low frequencies without resorting to an excessively thick multicellular body is to place hollow acoustic elements, for example open cone truncates, in 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 thus 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 has several drawbacks. First, inserting the hollow acoustic elements into the cells of the multicellular body can be tricky. Indeed, the cells or hollow acoustic elements may be irregular or misaligned, and the multicellular body may be too rigid. In addition, assembling the acoustic component with the multicellular body requires either the application of glue and its autoclave curing, or welding, which are relatively expensive operations. Finally, the distance between the hollow acoustic elements and the closing skin can be difficult to control. However, an unsuitable distance between the hollow acoustic elements and the closing skin can lead to a reduction in the performance of the acoustic panel. All these drawbacks are further amplified when double-curved acoustic panels are produced.Indeed, the positioning of the elements in relation to each other and their assembly are even more delicate to implement for the production of double-curved acoustic panels. Statement of the invention

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

[0008] To this end, the invention provides 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 opening into at least one acoustic cell, so that only one hollow acoustic element opening opens into each acoustic cell.

[0009] Thus, the hollow acoustic elements and the acoustic cells are made in a single piece. This eliminates the problems associated with assembling the acoustic elements with a multicellular body. In addition, the hollow acoustic elements are no longer each positioned inside a cell. Indeed, in this geometry, each acoustic cell extends between several hollow acoustic elements. The shape and dimensions of the hollow acoustic elements are thus easier to control, and the distance between the top of the hollow acoustic elements and the closing skin is controlled. In addition, the presence of partitions between the hollow acoustic elements makes it possible to mechanically reinforce said hollow acoustic elements. The acoustic cells thus formed are watertight.

[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. Thus, 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 section. In particular, the acoustic cells may have a square section.

[0015] Indeed, such a cell shape is simpler to manufacture and allows 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 provides an acoustic panel comprising an acoustic component as described above and comprising an acoustic skin arranged 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 comprising a closing skin arranged in contact with the tops of the hollow acoustic elements and the lower edges of the partitions. Such an acoustic panel may also comprise an acoustic skin arranged in contact with the bases of the hollow acoustic elements.

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

[0021] [Fig.l] [Fig.l] is an exploded schematic 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 [Fig.l], Description of the embodiments

[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 inside the acoustic panel 100. For this purpose, the acoustic skin 110 comprises a plurality of perforations 111, as illustrated in FIGS. 1 and 2. The acoustic skin 110 may 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 automatic fiber placement known as “AFP” for “Automated Fiber Placement”, or by automatic tape draping known as “ATL” for “Automated Tape Laying”. Other methods can also be used to manufacture the acoustic skin 110, such as manual draping.

[0027] The acoustic skin 110 may be made of thermoplastic material, for example a composite material with a thermoplastic matrix comprising fibers. The fibers may be carbon, glass or aramid. The acoustic skin 110 may not comprise fibers. The thermoplastic matrix may 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 intended to reflect the 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 directly mounted on the surface of the object.

[0029] The closure skin 130 can be produced in a well-known manner by stamping, by automatic fiber placement known as “AFP” for “Automated Fiber Placement”, or by automatic tape draping known as “ATL” for “Automated Tape Laying”. Other methods can also be used to manufacture the closure skin. 130. For example, the closing skin may be pre-baked and then assembled by gluing onto the multicellular body, or may be formed and baked 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 a top 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, located 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 have 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 comprise a chimney, as illustrated in Figures 1 to 3. Such a chimney is present at the top 121b of the hollow acoustic elements 121. The chimney “represents” the top 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 exit area of ​​the chimney is smaller than the entry area of ​​the chimney. The ratio between the exit area of ​​the chimney and the entry area of ​​the chimney is smaller than the ratio between the entry area of ​​the hollow acoustic element 121 and the entry area of ​​the chimney. The openings 121c may be located on the chimneys.

[0034] In the example illustrated in Figures 1 to 3, the bases 121a of the acoustic elements hollow 121 have a hexagonal shape. It is of course not departing from 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 tops 121b of the hollow acoustic elements 121 have a hexagonal shape. It is of course not departing from the scope of the invention if the tops 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 included in a circle whose diameter is between 5 mm and 50 mm. In particular, the base 121a of the hollow acoustic elements 121 is included in a circle whose diameter is between 8 mm and 20 mm. Preferably, the top 121b of the hollow acoustic elements 121 is included in a circle whose diameter is between 1 mm and 10 mm. In particular, the top 121b of the hollow acoustic elements 121 is included in a circle whose diameter is between 2 mm and 5 mm.

[0037] The height of the hollow acoustic elements 121 between the base 121a and the top 121b may be between 10 mm and 50 mm. In particular, the height of the hollow acoustic elements 121 may 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 each other. 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 in width from one hollow acoustic element 121 to another. Of course, the partitions 122 located at the edge of the acoustic component 120 may only be connected to a single hollow acoustic element 121. The partitions 122 extend in height from a lower edge 122b to the bases 121a of the hollow acoustic elements 121. Thus, the partitions 122 extend in height 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 end of the tops 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 ends of the tops 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 end of the top 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 disposed at the edge of the acoustic component 120. According to a variant not illustrated, six partitions may extend from each hollow acoustic element. In particular, six partitions may extend from each hollow acoustic element not disposed at the edge of the acoustic component. According to another variant not illustrated, eight partitions may extend from each hollow acoustic element. In particular, eight partitions may extend from each hollow acoustic element not disposed at the edge of the acoustic component.It should be noted that the more partitions there are, the more the mechanical strength of the acoustic component 120 will be improved.

[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 opening 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 opens into several acoustic cells simultaneously, so that a single hollow acoustic element 121 opens into each acoustic cell. The openings 121c can then be divided by one or more partitions 122 to allow them to open 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 may 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 section. It is of course not outside the scope of the invention if the acoustic cells have a section of another shape, for example a triangular section or a square 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 tops 121b of the hollow acoustic elements 121 comprise an opening 121c opening into at least one single acoustic cell. The top 121b of each hollow acoustic element 121 comprises a single opening 121c opening into a single acoustic cell. Preferably, a single opening 121c of the top 121b of the hollow acoustic element 121 opens into each acoustic cell. Thus, each acoustic cell is preferably associated with a single opening 121c of the hollow acoustic element 121. On the other hand, the same hollow acoustic element 121 may open into several acoustic cells via the opening 121c of this hollow acoustic element.

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

[0048] The acoustic component 120 can also be produced in a well-known manner by injection-compression of a thermoplastic material. Injection-compression consists of injecting the material into a half-open mold. Thus, even if the material sets, the channels become less obstructed. When the material is distributed throughout the mold, the latter is completely closed by a closing force to return to the correct dimension. This makes it possible to obtain wall thicknesses for the acoustic elements 121 and the partitions 122 that are thinner than with a conventional injection process.

[0049] The acoustic component 120 can also be produced in a well-known manner by injection with control of the temperature of the tooling of a thermoplastic material. Injection with control of the temperature of the tooling consists of controlling the temperature of the tooling or the mold by means of a system for controlling the temperature of the tooling, 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 may 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 may be made of a filled or unfilled thermoplastic material.

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

[0052] The acoustic component 120 may be “flat”, that is to say that the bases 121a of the hollow acoustic elements belong to the same plane. The acoustic component 120 can also be curved, that is to say that the bases 121a of the hollow acoustic elements belong to the same curved surface. The acoustic component 120 can have a single curvature or a double curvature.

[0053] The acoustic skin 110 may be fixed by gluing or welding to the acoustic component 120. A pretreatment may 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 may be degreased, sanded and / or plasma treated before assembly with the acoustic skin 110.

[0054] Similarly, the closing skin 130 may be fixed by gluing or welding to the acoustic component 120. A pretreatment may be carried out on the second assembly face of the acoustic component 120 before assembly with the closing skin 130, in order to facilitate said assembly. For example, the second assembly face of the acoustic component 120 may 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 one acoustic skin 100, one acoustic component 120 and one closing skin 130. It is thus an acoustic panel with a single degree of freedom known as “SDoF” for “Single Degree of Freedom” in English. It is of course not departing from the scope of the invention if the acoustic panel comprises several acoustic components as described above. It is also not departing from the scope of the invention if the acoustic panel further comprises one or more multicellular bodies. The acoustic panel may also comprise intermediate acoustic skins separating different stages of said acoustic panel. Thus, the first assembly face and / or the second assembly face of the acoustic component as described above may be arranged in contact with an intermediate acoustic skin separating two stages of the acoustic panel.Therefore, the acoustic component as described above can be used in two-degree-of-freedom, so-called “2DoF” acoustic panels.

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

[0057] The expression “between ... and ...” must be understood as including the limits.

Claims

Claims

1. A one-piece acoustic component (120) for an aircraft propulsion system comprising a plurality of hollow acoustic elements (121) having a shape that gradually tapers 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) opening into at least one acoustic cell, such that a single opening (121c) of the hollow acoustic element (121) opens into each acoustic cell.

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

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

5. An 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. An 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 unit comprising an acoustic component (120) according to any one of claims 1 to 6 and comprising an acoustic skin (110) arranged in contact with the bases (121a) of the hollow acoustic elements (121).

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

9. An 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.

Images