Assembly of acoustic component sectors

Abstract

The invention relates in particular to the assembly of annular sectors (100) of an annular multi-element acoustic component (10), each sector (100) comprising a plurality of rows of hollow complex acoustic elements (110) each having a shape that steadily narrows between a base and a vertex, each sector (100) comprising a plurality of first rows comprising the same number of hollow complex elements (110) and one or more second rows comprising one hollow complex element (110) less than the first rows, each second row further comprising a male attachment element (121) on one of the assembly edges (102a) and a female attachment element (122) on the other assembly edge (101a), the female attachment element (121) having the same size as a hollow complex element (110) in the assembly direction (Dc).

Description

[0001] Description

[0002] Title of the invention: Assembly of acoustic component sectors

[0003] Technical Field

[0004] The present invention relates to the general field of acoustic structures or panels. It relates more particularly but not exclusively to acoustic attenuation structures used to reduce noise produced in aircraft engines such as in gas turbines or their exhausts.

[0005] Prior art

[0006] Acoustic attenuation structures typically consist 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 multi-element acoustic component and a multi-cellular body being arranged between these two walls. The multi-cellular body is generally constituted by a set of partitions, for example in the form of a honeycomb, and the multi-element acoustic component generally comprises complex hollow acoustic elements, for example cones, arranged in the cells of the multi-cellular body. In a well-known manner, such structures form Helmholtz-type resonators which make it possible to attenuate the acoustic waves in a certain frequency range. Acoustic attenuation structures of this type are described in particular in document FR 3 108 765 A1.

[0007] In most applications of such acoustic structures, for example in aeronautics, the multi-element acoustic component must be lightweight in order to limit the mass of the acoustic structure. In order to produce a lightweight multi-element acoustic component, it is necessary to use manufacturing methods that allow the production of very thin walls, such as injection or stamping at controlled temperature and pressure. However, such methods require specific tools and parameters, which limit the size of the multi-element acoustic components that can be obtained by these methods. However, the acoustic structures may be intended to cover the inner or outer annular surface of large parts or elements, for example a fan casing of an aeronautical engine.Thus, it is necessary to produce the multi-element acoustic component in several annular sectors, then to assemble said multi-element acoustic component sectors on the surface to be covered by mounting them with the multi-cellular body and the acoustic skin, so as to form an annular acoustic structure matching the surface to be covered.

[0008] Fastening devices are used to connect the different sectors of the multi-element acoustic component along the perimeter of the surface to be covered.

[0009] However, the design, positioning and assembly of the various pieces of the acoustic structure can be tricky.

[0010] First, the fastening devices used increase the mass of the acoustic structure and generally represent areas that do not contribute to acoustic attenuation. In addition, the fastening devices used can have an aerodynamic impact by disrupting airflow.

[0011] The positioning of the different pieces of the acoustic structure relative to each other along the perimeter of the surface to be covered can also be complex, especially when the hollow acoustic elements or cells have a hexagonal shape. Indeed, as illustrated in Figure 1, gaps may be present between the different pieces of acoustic structure. These gaps represent areas not covered by the acoustic assembly, which will therefore not be able to fulfill their acoustic attenuation function. Furthermore, without special provisions, the assembly edges between the different sectors may not be complementary, and thus cause additional uncovered areas, as illustrated in Figure 1.

[0012] Furthermore, uncovered areas also create discontinuities in the acoustic treatment, which will modify the structure of the acoustic field by repelling the energy propagating in the annular acoustic structure. Thus, the reduction in acoustic performance is much greater than the reduction in performance due solely to the loss of acoustic functional surface. Conversely, it may be necessary to cut pieces of acoustic structure during assembly to avoid unwanted overlaps between sectors and thus allow assembly. These cuts represent a waste of material and lead to unnecessary costs.

[0013] Finally, uncovered areas and overlaps can decrease the aerodynamic performance of the acoustic structure, disrupting airflow and increasing the drag of the acoustic structure.

[0014] Statement of the invention

[0015] The main aim of the present invention is therefore to enable the assembly of acoustic structures while overcoming at least some of the aforementioned problems.

[0016] To this end, the invention proposes an annular sector of annular multi-element acoustic component extending in an assembly direction between a first assembly edge and a second assembly edge opposite the first assembly edge, the sector comprising a plurality of rows of hollow complex acoustic elements each having a shape gradually narrowing between a base and a top, the hollow complex elements being connected to each other by one or more adjacent edges, each row extending from the first to the second assembly edge in the assembly direction, said sector being characterized in that it comprises a plurality of first rows comprising the same number of hollow complex elements and one or more second rows comprising one hollow complex element less than the first rows,each second row further comprising a male attachment element on one of the assembly edges and a female attachment element on the other assembly edge, the female attachment element having the same dimension as a hollow complex element along the assembly direction.,

[0017] By using annular sectors whose first rows have the same number of hollow acoustic elements and whose second rows comprising the male and female attachment elements have one less hollow acoustic element than the first rows, it is ensured that annular sectors are produced whose first assembly edge is complementary to the second assembly edge. Furthermore, by using a female attachment element having the same dimension as a hollow complex element along the assembly direction, it is ensured that the area occupied by the assembly of a female attachment element with a male attachment element fits perfectly between two adjacent sectors, without altering the complementarity between the edges of said sectors.

[0018] Furthermore, it is no longer necessary to provide an area for the assembly of two neighboring sectors, this function being provided by the attachment elements. Thus, the surface area actually devoted to acoustic attenuation is increased compared to acoustic structures of the prior art not comprising such attachment elements.

[0019] According to a particular embodiment of the invention, the male attachment element has a pierced shape which gradually narrows between a base and a top.

[0020] Thus, the areas not effectively participating in acoustic attenuation due to the assembly of the sectors are further limited, the male attachment element being capable of fulfilling an acoustic attenuation function. More particularly, the male attachment element preferably has a geometric shape identical to that of the complex hollow acoustic elements.

[0021] According to another particular embodiment of the invention, the bases of the hollow complex acoustic elements are hexagonal.

[0022] The assembly of a multi-element acoustic component comprising hexagonal complex hollow acoustic elements is more delicate than in the case of square hollow acoustic elements. Thus, the sectors according to the invention are particularly interesting in the case of hexagonal complex hollow acoustic elements.

[0023] The invention further relates to an annular multi-element acoustic component comprising the assembly of a plurality of annular sectors according to the invention along the assembly direction, each male attachment element of an annular sector of the acoustic component being inserted into a female attachment element of an adjacent sector. Positioning the sectors relative to each other is thus facilitated, the attachment elements serving as markers for the assembly of the sectors relative to each other. Furthermore, the space occupied by the attachment elements is limited and fits perfectly into the assembly between the complex hollow acoustic elements of the different sectors.

[0024] According to a particular embodiment of the invention, all the sectors are identical.

[0025] By "identical sectors" is meant that each sector has the same dimensions, the same shape of complex hollow acoustic elements, the same number of rows of complex hollow acoustic elements, the same number of hollow acoustic elements in each first and second row, the same offset between the rows of complex hollow acoustic elements, the same shape of attachment elements, the same positioning of the attachment elements.

[0026] Thus, the design and manufacturing of the sectors are greatly simplified, and consequently the design and manufacturing of the complete acoustic structure is facilitated.

[0027] The invention also relates to an annular acoustic attenuation structure comprising an annular multi-element acoustic component according to the invention and an annular multi-cellular body, the top of each complex hollow acoustic element of the multi-element acoustic component being inserted into a cell of the multi-cellular body.

[0028] Preferably, the assembly of the male attachment element with the female attachment element is present in a volume between the surface defined by the bases or the edges of the complex hollow acoustic elements and the surface defined by the tops of the complex hollow acoustic elements. Thus, the assembly of the male element with the female element does not generate any excess thickness, which makes it possible not to alter the aerodynamics of the multi-element acoustic component and to facilitate the assembly of said multi-element acoustic component with a possible multicellular body or a possible acoustic skin. According to a particular embodiment of the invention, the acoustic attenuation structure further comprises a perforated acoustic skin, said acoustic skin being in contact with the base of the complex hollow acoustic elements.

[0029] According to another particular embodiment of the invention, the annular multicellular body comprises a plurality of assembled multicellular body annular sectors extending along the assembly direction, the length of the annular sectors of the multicellular body being greater than the length of the annular sectors of the multi-element acoustic component along the assembly direction.

[0030] Indeed, the manufacturing and assembly of the multicellular body presents fewer constraints than the manufacturing and assembly of the multi-element acoustic component, because the manufacturing and assembly tolerances of the multicellular body are less strict than those of the multi-element acoustic component. Thus, in order to limit the number of fixings or manipulations to form the multicellular body, an attempt is made to assemble a limited number of multicellular body sectors. In addition, by using longer multicellular body sectors than the multi-element acoustic component sectors, the robustness of the assembly of the acoustic structure is increased.

[0031] The invention further relates to a method for designing an annular multi-element acoustic component according to the invention, said annular multi-element acoustic component extending around an axial direction and having a determined inner or outer section perimeter, each annular sector of the acoustic component extending in the axial direction between a first circumferential edge and a second circumferential edge, the circumferential edges extending in the assembly direction, the method comprising the following steps:

[0032] - determination of a number of annular sectors of the multi-element acoustic component by rounding up to the next higher integer the ratio of the perimeter of the section of said acoustic component by the maximum theoretical length of an annular sector of the multi-element acoustic component,

[0033] - determination of the length of the circumferential edges of each annular sector of the acoustic component, - determination of a theoretical width along the assembly direction of the hollow complex acoustic elements corresponding to the desired acoustic attenuation,

[0034] - determination of an integer number of hollow complex acoustic elements per first row of each annular sector,

[0035] - determination of a final width following the assembly direction of the hollow complex acoustic elements.

[0036] Thus, the design method according to the invention makes it possible to produce multi-element acoustic components that are easily assembled and with very little clearance between the sectors. Indeed, the invention proposes to slightly adjust the width of the hollow acoustic elements to limit the clearance between the sectors, which ultimately makes it possible to improve the acoustic properties of the annular multi-element acoustic component by reducing the non-functional zones and limiting the discontinuities in the acoustic field. In addition, by ensuring a constant number of hollow complex elements per row, it is ensured that complementary axial edges are obtained at the junction between the annular sectors.

[0037] Finally, the invention provides a method for manufacturing an annular acoustic attenuation structure comprising:

[0038] - the design of an annular multi-element acoustic component as described previously,

[0039] - the manufacture of the annular sectors of said multi-element acoustic component in accordance with the design,

[0040] - assembling the annular sectors of the multi-element acoustic component with each other and with an annular multi-cellular body, so that each complex hollow acoustic element is arranged in a cell of the multi-cellular body,

[0041] - covering the multi-element acoustic component with an acoustic skin so as to form the annular acoustic attenuation structure comprising at least the annular multi-element acoustic component, the annular multi-cellular body and the acoustic skin.

[0042] Brief description of the drawings [Fig. 1] Figure 1 schematically illustrates the assembly of an annular acoustic structure around a cylindrical element without the invention.

[0043] [Fig. 2] Figure 2 is a partial exploded perspective view of an acoustic structure according to an embodiment of the invention comprising a multi-element acoustic component.

[0044] [Fig. 3] Figure 3 is a perspective view of a sector of the multi-element acoustic component of Figure 2 including attachment elements in accordance with one embodiment of the invention.

[0045] [Fig. 4] Figure 4 is a sectional view of two acoustic component sectors assembled according to a first variant.

[0046] [Fig. 5] Figure 5 is a sectional view of two acoustic component sectors assembled according to a second variant.

[0047] [Fig. 6] Figure 6 is a perspective view of the assembly of a multi-element acoustic component different from that illustrated in Figure 1.

[0048] [Fig. 7] Figure 7 is a flowchart describing the method of designing a multi-element acoustic component according to one embodiment of the invention.

[0049] [Fig. 8] Figure 8 schematically illustrates the steps of the design process of Figure 7.

[0050] [Fig. 9] Figure 9 is a partial cross-sectional schematic view of the assembled acoustic structure of Figure 2.

[0051] Description of the embodiments

[0052] Figure 2 illustrates the assembly of an acoustic structure 1 according to the invention on the developable external surface of a large annular part 5 extending around an axial direction D a . It is of course not outside the scope of the invention if the acoustic structure according to the invention is assembled on the developable internal surface of a large annular part 5.

[0053] The annular part 5 may for example be a fan casing of a jet engine, a nacelle of an aircraft turbojet, a fuselage element, a wing element, a platform connecting the blades of a stator or an inner flow separator, also called "IFS" for "inner flow spacer".

[0054] The term "annular" herein describes a shape comprising at least one developable inner or outer surface extending around the axial direction D a and making a complete turn around said axial direction D a , and having a constant section in each plane perpendicular to said axial direction D a . Thus, the term "annular" can describe, for example, a shape having a cylindrical surface of revolution, as illustrated in Figures 1 to 9.

[0055] The annular acoustic structure 1 comprises at least one annular multi-element acoustic component 10 and an annular multi-cellular body 20. The annular multi-cellular body 20 and the annular multi-element acoustic component 10 each extend around the axial direction D a following a circumferential assembly direction D c .

[0056] The multicellular body 20 comprises a plurality of cells 210 distributed in rows and separated by partitions 220 which form a network of ribs. The multicellular body 20 is preferably in contact with the surface to be covered of the part 5. The annular multi-element acoustic component 10 comprises a plurality of complex hollow acoustic elements 110 distributed in rows. In a well-known manner, the annular multi-element acoustic component 10 is inserted into the annular multicellular body 20 so that each complex hollow acoustic element 110 of the multi-element acoustic component 10 is inserted into a cell 210 of the multicellular body 20.

[0057] Preferably, the acoustic structure 1 also comprises an acoustic skin 30 which covers the annular multi-element acoustic component 10. The acoustic skin 30 has the function of allowing the sound waves to be attenuated to pass inside the acoustic structure 1. For this purpose, the acoustic skin 30 comprises a plurality of perforations 31.

[0058] The annular multi-element acoustic component 10 is produced by assembling a plurality of annular sectors 100 of annular multi-element acoustic component 10. Preferably, the annular multi-element acoustic component 10 is mounted sector by sector in the annular multi-cellular body 20.

[0059] Figure 3 illustrates an example of an annular sector 100 of an annular multi-element acoustic component 10.

[0060] The annular sector 100 extends along the circumferential assembly direction D cbetween a first assembly edge 101a and a second assembly edge 102a opposite the first assembly edge 101a. The first assembly edge 101a of the annular sector 100 is intended to be assembled with the second assembly edge of an adjacent annular sector, and the second assembly edge 102a of the annular sector 100 is intended to be assembled with the first assembly edge of an adjacent annular sector.

[0061] The annular sector 100 further extends in the axial direction D a between a first circumferential edge 101c and a second circumferential edge 102c. The first circumferential edge 101c and a second circumferential edge 102c preferably have the same length L c .

[0062] The annular sector 100 of the annular multi-element acoustic component 10 comprises a plurality of complex hollow acoustic elements 110 distributed in rows. Each row of hollow acoustic elements 110 extends along the circumferential assembly direction D c from the first assembly edge 101a to the second assembly edge 102a of the annular sector 100. The complex hollow acoustic elements each have a shape that gradually narrows between a base and a top, the hollow acoustic elements being connected to each other by one or more adjacent edges. The hollow complex acoustic elements have, for example, a pierced truncated cone or pierced truncated pyramid shape, as illustrated in FIGS. 2 to 9. The base of each complex acoustic element 110 is in continuous contact with the base of the adjacent complex acoustic elements 110 so as to form a continuous network of edges.

[0063] The annular sector 100 extends in thickness along a thickness direction D e , perpendicular to the axial direction D a and to the circumferential assembly direction D c , between an upper surface 100a and a lower surface 100b. The upper surface 100a is defined by the bases of the hollow acoustic elements 110 and the lower surface 100b is defined by the tops of the hollow acoustic elements 110. The upper surface 100a is therefore of length L c along the circumferential assembly direction D c .

[0064] The annular sector 100 of annular multi-element acoustic component 10 comprises a plurality of first rows of hollow acoustic elements 110 having the same number n of hollow acoustic elements 110. In the example illustrated in FIG. 3, the number n of hollow acoustic elements 110 of each first row is seven. The annular sector 100 of annular multi-element acoustic component 10 further comprises one or more second rows of hollow acoustic elements 110 having one hollow acoustic element 110 less than the first rows, i.e. the second row(s) of hollow acoustic elements 110 have the same number n-1 of hollow acoustic elements 110. In the example illustrated in FIG. 3, the number n-1 of hollow acoustic elements 110 of each second row is six.

[0065] Each second row of hollow acoustic elements 110 further comprises a male attachment element 121 on one of the assembly edges 101a or 102a of the annular sector 100 and a female attachment element 122 on the other assembly edge 101a or 102a of the annular sector 100. In the example illustrated in FIG. 3, the sector 100 comprises 8 rows of hollow acoustic elements 110, including 6 first rows and 2 second rows.

[0066] The male attachment element 121 of the annular sector 100 is intended to cooperate with the female attachment element of an adjacent annular sector, and the female attachment element 122 of the annular sector 100 is intended to cooperate with the male attachment element of an adjacent annular sector. The cooperation of a male attachment element with a female attachment element is achieved by inserting the male attachment element into the female attachment element. The cooperation of a male attachment element of an annular sector of the multi-element acoustic component 10 with a female attachment element of an adjacent annular sector of the multi-element acoustic component 10 makes it possible to fix said annular sector to the adjacent annular sector. The female attachment element 122 has the same dimension along the circumferential assembly direction D cthan a complex hollow acoustic element 110. Thus, the positioning of the annular sectors relative to each other can be carried out without leaving areas not covered by a complex hollow acoustic element 100 or by a female attachment element 122, the female attachment element 122 into which a male attachment element is inserted completely filling the area between two adjacent annular sectors.

[0067] Preferably, so that the areas covered by the female attachment elements 122 in which male attachment elements are inserted are not lost and can fulfill an acoustic attenuation function, the male attachment elements 121 have a shape similar to that of the complex hollow acoustic elements 110, as illustrated in FIGS. 2 and 3. Thus, the male elements 121 have a pierced shape gradually narrowing between a base and a top, the base of the male elements 121 being located on the same side of the annular sector 100 as the bases of the complex hollow acoustic elements 110 and the top of the male attachment elements 121 being located on the same side of the annular sector 100 as the tops of the complex hollow acoustic elements 110. Preferably, the geometric shape of the base of the male attachment elements 121 is identical to the geometric shape of the bases of the complex hollow acoustic elements 110.Thus, if the bases of the complex hollow acoustic elements 110 have a hexagonal shape, the base of the male attachment elements 121 will preferably be of hexagonal shape.

[0068] In the configuration where the male fastener elements 121 have a shape similar to that of the complex hollow acoustic elements 110, the female fastener elements 122 may have a flat shape pierced by a through hole allowing the insertion and retention of a male fastener element 121, as illustrated in Figures 2 and 3. Preferably, the male fastener element 121 is inserted into the female fastener element by the application of pressure, so that the male fastener element is clamped by the female fastener element. Preferably, the male fastener element is mounted in the female fastener element so that the base of the male fastener element is in contact with the female fastener element.According to a variant illustrated in Figure 4, in the configuration where the male attachment elements 123 have a shape similar to that of the complex hollow acoustic elements 110, the female attachment elements 124 may also have a shape similar to that of the complex hollow acoustic elements 110, that is to say that the female attachment elements 124 have a pierced shape gradually narrowing between a base and a top, the base of the female attachment elements 124 being located on the same side of the annular sector as the bases of the complex hollow acoustic elements 110 and the top of the female attachment elements 124 being located on the same side as the tops of the complex hollow acoustic elements 110.Thus, the male fastener element 123 is mounted in the female fastener element 124 such that the base of the male fastener element 123 is in contact with the base of the female fastener element 124, the shape of the female fastener element 124 clamping the shape of the male fastener element 123 between the base and the top of the male fastener element 123.

[0069] According to another variant illustrated in FIG. 5, the assembly of the male attachment element 125 with the female attachment element 126 is of the snap button type.

[0070] Of course, it does not go beyond the scope of the invention if other male / female attachment methods are used.

[0071] In all configurations, the assembly of the male attachment element with the female attachment element has a dimension along the thickness direction D e less than or equal to the dimension of the other complex hollow acoustic elements 110 along the thickness direction De . In particular, the assembly of the male attachment element with the female attachment element does not pass through the surface formed by the bases or edges of the complex hollow acoustic elements. The assembly of the male attachment element with the female attachment element is present in a volume between the surface defined by the bases or edges of the complex hollow acoustic elements and the surface defined by the tops of the complex hollow acoustic elements.

[0072] Preferably, as illustrated in Figures 2 and 3, all the male attachment elements 121 of the annular sector 100 are located on the second assembly edge 102a and all the female attachment elements 122 of the annular sector 100 are located on the first assembly edge 101a, in order to facilitate the manufacture of the annular sector 100 and the assembly of said sector 100 with the adjacent sectors of multi-element acoustic component.

[0073] However, it does not depart from the scope of the invention when the first assembly edge comprises male and female attachment elements, the second assembly edge then also having female attachment elements on the second rows where the first edge comprises a male attachment element and male attachment elements for the second rows where the first edge comprises a female attachment element.

[0074] Preferably, a second row of hollow acoustic elements 110 is not adjacent to another second row of hollow acoustic elements 110, in order to improve the assembly between them of the annular sectors of the annular multi-element acoustic component 10. Thus, two second rows of hollow acoustic elements 110 of an annular sector 100 are preferably separated by one or more first rows of hollow acoustic elements 110.

[0075] In the case of hollow acoustic elements with a square base, the squares formed by the hollow acoustic elements are arranged side to side, each side of the squares being oriented in the circumferential assembly direction D c or along the axial direction D a . Thus, the length L c of an annular sector 100 of multi-element acoustic component 10 must be understood as the length extending in the circumferential assembly direction D c between the outer side of a square hollow acoustic element of a first row belonging to the first assembly edge and the outer side of a square hollow acoustic element of the same first row belonging to the second assembly edge.

[0076] In the case of circular hollow acoustic elements, the centers of the circles formed by the hollow acoustic elements of the same row are aligned according to the circumferential assembly direction D c. Thus, the length L c of an annular sector 100 of multi-element acoustic component 10 must be understood as the length extending in the circumferential direction D c between the outer side of a circular hollow acoustic element of a first row belonging to the first assembly edge and the outer side of a circular hollow acoustic element of the same first row belonging to the second assembly edge, said length passing diametrically through the circular hollow acoustic elements of the first row at their center. Furthermore, the centers of the circles of the circular hollow acoustic elements of at least one row out of two alternately are aligned along the axial direction D a .

[0077] In the case of hexagonal hollow acoustic elements, as in the examples illustrated in Figures 2 to 9, the hexagons formed by the hollow acoustic elements 110 are arranged side against side, the centers of the hexagons of the hollow acoustic elements 110 of the same row being aligned according to the circumferential assembly direction D c . Thus, the length L c of the annular sector 100 of multi-element acoustic component 10 must be understood as the length extending in the circumferential assembly direction D c between the outer side of a hexagonal hollow acoustic element 110 of a first row belonging to the first assembly edge 101a and extending in the axial direction D a , and the outer side of a hexagonal hollow acoustic element 110 of the same first row belonging to the second assembly edge 102a and extending in the axial direction D a, said length passing through the hexagonal hollow acoustic elements 110 of the first row at their center. Furthermore, the centers of the hexagons of the hollow acoustic elements 110 of every other row alternately are aligned along the axial direction D a .

[0078] The assembly of the annular sectors 100 of multi-element acoustic component following the circumferential assembly direction D c makes it possible to produce the multi-element acoustic component 10. Preferably, all the annular sectors 100 of the multi-element acoustic component are identical, in order to facilitate the manufacture and assembly of said multi-element acoustic component 10.

[0079] By using identical annular sectors 100 of multi-element acoustic component, and having the same number of hollow acoustic elements 110 in each first row as well as one less hollow acoustic element 110 in each second row comprising attachment elements 121 and 122, it is ensured that the assembly edges 101a and 102a of the annular sectors 100 will be complementary. This property of complementarity applies even when the rows of complex hollow acoustic elements are irregularly offset from one another, as illustrated in FIG. 6, which illustrates a multi-element acoustic component 10b comprising a plurality of annular sectors 100b comprising complex hollow acoustic elements 110b. In the example illustrated in FIG. 6, the assembly edges of the annular sectors 100b are indeed complementary at their junction.

[0080] In order to limit the appearance of play or overlap between the annular sectors 100 of the multi-element acoustic component 10, the annular sectors 100 can be designed according to the design method of the invention illustrated in FIGS. 7 and 8.

[0081] The multi-element acoustic component 10 is arranged in contact with the multi-cellular body 20. Thus, the perimeter Pi0 of the upper surface of the multi-element acoustic component 10 must correspond to the perimeter P20 of the upper surface of the multi-cellular body 20 in each plane perpendicular to the axial direction D a in order to avoid clearances or overlaps between the annular sectors 100. The perimeter P10 of the upper surface of the multi-element acoustic component 10 corresponds to the sum of the lengths L cof each sector 100 of the multi-element acoustic component 10. The perimeter P2o of the upper surface of the multicellular body 20 is determined in a well-known manner from the perimeter of the surface to be covered of the part 5 and the desired thickness e2o of the multicellular body 20 along the thickness direction D e .

[0082] In the example illustrated here, the sectors 100 of the multi-element acoustic component 10 are identical, and all have the same length L c along the circumferential assembly direction D c .

[0083] The first step 1000 of designing the multi-element acoustic component 10 makes it possible to determine the number N of annular sectors 100 that said multi-element acoustic component 10 will comprise.

[0084] The maximum achievable length L cmax for the annular sectors 100 of the multi-element acoustic component 10 along the circumferential assembly direction D c is limited and depends on the manufacturing method used for the manufacture of said annular sectors 100. The annular sectors 100 can be produced in a well-known manner by injection or by stamping, preferably at controlled temperature and pressure.

[0085] Thus, the length L c of the annular sectors 100 is less than or equal to the maximum achievable length L cma x imposed by the manufacturing means. However, in order to limit the number N of annular sectors 100 to be assembled and to reduce the number of attachment elements 121 and 122 required, it is desired that the length L c of the annular sectors 100 is as close as possible to the maximum achievable length L cma x-

[0086] Therefore, the number N of sectors 100 of the multi-element acoustic component 10 is determined by rounding up to the next higher integer the ratio of the perimeter Pio of the upper surface of the multi-element acoustic component 10 to be produced by the maximum achievable length L cma x of an annular sector imposed by the manufacturing means. As a reminder, the perimeter Pio of the upper surface of the multi-element acoustic component 10 corresponds to the perimeter P20 of the upper surface of the multi-cellular body 20.

[0087] For example, if the surface of the part 5 to be covered is a cylindrical surface of revolution with radius R5 = 1500 mm and the desired thickness e2o of the multicellular body 20 is 28.6 mm, the perimeter P20 of the upper surface of the multicellular body 20 will be approximately 9600 mm. Thus, the perimeter Pio of the upper surface of the multi-element acoustic component 10 to be produced will be approximately 9600 mm. It is also considered that the maximum achievable length L cma x of an annular sector is 1000 mm. We thus obtain that the number N of sectors 100 of the multi-element acoustic component 10 will be equal to 10.

[0088] The numerical values ​​given here and below, in connection with the description of Figure 7, are given for illustrative purposes only, in order to better understand the advantages of the design method of the invention. They should not be considered as limiting the invention. According to the second step 2000 of designing the annular acoustic structure 10, the length L is determined c of each of the N annular sectors 100, by dividing the perimeter Pw of the upper surface of the multi-element acoustic component 10 to be produced by the number N of sectors 100. In our example, we thus obtain a length L c equal to 960 mm.

[0089] The third step 3000 of designing the multi-element acoustic component 10 makes it possible to determine a theoretical width l c o of each complex hollow acoustic element following the circumferential assembly direction D c . This theoretical width l co corresponds to the theoretical width allowing an optimal reduction of the acoustic waves to be attenuated, in particular in relation to a given frequency range. This theoretical width l c o can be determined by an acoustic study carried out independently of the method described here.

[0090] The theoretical width l c o of a hollow acoustic element corresponds to the distance extending along the circumferential assembly direction D c from the middle of the edge separating the hollow acoustic element from a first adjacent hollow acoustic element of the same row to the middle of the edge separating the hollow acoustic element from the second adjacent hollow acoustic element of the same row.

[0091] In our example, the theoretical width l c o hollow acoustic elements 110 along the circumferential assembly direction D c is estimated at 20 mm.

[0092] The third step 3000 may be performed independently of the first and second steps 1000 and 2000. For example, the first and second steps 1000 and 2000 may also be performed in parallel with the third step 3000.

[0093] The fourth step 4000 of designing the multi-element acoustic component 10 makes it possible to determine an integer number n of hollow acoustic elements 110 in each first row of each annular sector 100. This number n is obtained by rounding to unity the ratio of the length L c circumferential edges 101c and 102c by the theoretical width l c o hollow acoustic elements 110.

[0094] In our example, each annular sector 100 has a length L c of 960 mm and the theoretical width l co is estimated at 18 mm. Thus, we obtain a number n of 53 complex hollow acoustic elements 110 in each first row, or a number of 52 complex hollow acoustic elements 110 in each second row comprising male and female attachment elements 121 and 122.

[0095] As illustrated in Figure 8, it can be seen that at the end of the fourth step 4000 the length of all n complex hollow acoustic elements 110 of a first row may be different from the length L c circumferential edges 101c and 102c. In our example, we can see that there remains a lost space 111 of approximately 6 mm, as illustrated in Figure 8.

[0096] In our example, the 53 complex hollow acoustic elements 110 have a theoretical width l co of 18 mm. Thus, the set of n complex hollow acoustic elements 110 of a first row has a length of 954 mm, i.e. a difference of 6 mm with the length L c of 960 mm. On the scale of the multi-element acoustic component 10 which comprises ten annular sectors 100, these ten lost spaces 111 of approximately 6 mm represent a total lost space of approximately 60 mm in the circumferential direction D c .

[0097] The design method proposed by the invention aims to reduce this wasted space, in order to increase the functional surface area of ​​the annular acoustic structure 1 and to allow easier and lower-cost mounting of the multi-element acoustic component 10.

[0098] Thus, the fifth step 5000 of designing the multi-element acoustic component 10 makes it possible to determine a final width l c complex hollow acoustic elements 110 along the circumferential assembly direction of

[0099] This final width l c is obtained by dividing the length L c circumferential edges 101c and 102c by the number n of complex hollow acoustic elements 110 of each first row of sectors 100.

[0100] The final width l c of a hollow acoustic element corresponds to the distance extending along the circumferential assembly direction D c from the middle of the edge separating the hollow acoustic element from a first adjacent hollow acoustic element of the same row to the middle of the edge separating the hollow acoustic element from the second adjacent hollow acoustic element of the same row. In our example, each annular sector 100 has a length L c of 960 mm and a number n of 53 complex hollow acoustic elements 110 in a first row. Thus, the final width l cof a hollow acoustic element 110 will be 18.1 mm, an increase of 0.1 mm compared to the theoretical width l c o- The difference in width between the theoretical width l c o and the final width l c complex hollow acoustic elements 110 is not high enough to cause a significant decrease in the acoustic performance of the acoustic structure 1. On the other hand, this difference allows a clear improvement in the mounting of the multi-element acoustic component 10 and an improvement in the area and continuity of the functional surface of the acoustic structure 1.

[0101] Using the design method described above, identical annular sectors 100 are produced, allowing very satisfactory mounting of the multi-element acoustic component 10 in the multicellular body 20 around the part 5. The design of identical annular sectors facilitates their manufacture and reduces the associated design and manufacturing costs.

[0102] The design and manufacture of the multi-cell body 20 are less restrictive than the design and manufacture of the multi-element acoustic component 10. Thus, the design of the multi-element acoustic component 10 is preferably first carried out, which then makes it possible to determine the number and dimensions of the cells 210 of the multi-cell body 20, so that each complex hollow acoustic element 110 and each female attachment element 122 corresponds to a cell 210 of the multi-cell body 20.

[0103] Preferably, the multicellular body 20 is also assembled by sectors 200 on the surface to be covered of the part 5, as illustrated in FIG. 8. Since the manufacturing constraints of the multicellular body 20 are low, sectors 200 of the multicellular body 20 are preferably produced of large dimensions in order to use a limited number of sectors 200 of the multicellular body 20. Thus, preferably, the length of the annular sectors 200 of the multicellular body 20 along the circumferential assembly direction D c is greater than the length L c annular sectors 100 of the multi-element acoustic component 10. When the design of the acoustic structure 1 is complete, the said acoustic structure 1 can be manufactured.

[0104] The network of partitions 220 of the multicellular body 20 and the sectors 100 of the multi-element acoustic component 10 can be produced by injection of a thermoplastic or thermosetting material, whether filled or not, by injection-compression of a thermoplastic or thermosetting material, whether filled or not, or by injection with control of the temperature of the tooling of a thermoplastic or thermosetting material, whether filled or not. The acoustic skin 30 can be produced by manual or automatic draping of a composite material with a thermoplastic or thermosetting matrix.

[0105] The thermoplastic material used to manufacture the sectors 100 of the multi-element acoustic component 10 or the network of partitions 220 of the multicellular body 20 may be notably but not exclusively selected from the following materials: polyaryletherketones (PAEK) such as polyetheretherketone (PEEK) and polyetherketoneketone (PEKK), polyetherimides (PEI), polycarbonate (PC), polyphenylene sulfide (PPS), polysulfones (PSU). The thermoplastic material may or may not be filled.

[0106] The network of partitions 220 of the multicellular body 20 can also be obtained using a honeycomb structure, for example made of aluminum or Nomex®.

[0107] The sectors 100 of the multi-element acoustic component 10 or the network of partitions 220 of the multicellular body 20 can be produced directly by being curved along the circumferential assembly direction D c, or can be bent after manufacture, for example by hand or by performing a hot forming operation. Thin complex acoustic elements are more easily deformed than thick acoustic elements.

[0108] Still in the example described here, the sectors 100 of the multi-element acoustic component 10 can be assembled with the multi-cellular body 20 by gluing or welding. The assembly between the sectors 100 of the multi-element acoustic component 10 and the multi-cellular body 20 is greatly facilitated by the self-positioning of the complex acoustic elements 110 with the partitions 220 of the multi-cellular body 20.

[0109] The acoustic skin 30 can be fixed by gluing or welding on the upper portion of the bases of the complex acoustic elements 110.

[0110] Once assembled, the acoustic structure 1 comprises a plurality of complete acoustic cells each formed by a complex acoustic element 110 and the partitions 220 of the multicellular body 20 which surround it, as illustrated in FIG. 9.

[0111] The height Hno of the complex acoustic elements 110 is less than the height H2IO of the cells 210 of the multicellular body 20. More precisely, the height Hn0 of the hollow acoustic elements 110 is between 10% and 99% of the height H210 of the cells 210 along the thickness direction D e . The height Hno can be between 5 mm and 100 mm while the base of each hollow acoustic element 110 can be inscribed in a circle with a diameter between 5 mm and 50 mm. In addition, the hollow complex acoustic elements 110 have a very low thickness Eno, less than 1 mm and typically between 0.3 mm and 0.5 mm.

[0112] It is of course not outside the scope of the invention if the elements making up the annular acoustic structure 1 are produced using different processes or with different materials.

[0113] The annular acoustic structure, the multi-element acoustic component and its sectors as well as the multi-cellular body illustrated in Figures 1 to 9 are simplified, and the number of cells or hollow acoustic elements per row or per sector may vary or be reduced for reasons of simplification of the figures.

[0114] The expression "between" must be understood as including the limits.

Claims

Claims

1. Annular sector (100) of annular multi-element acoustic component (10) extending in an assembly direction (D c ) between a first assembly edge (101a) and a second assembly edge (102a) opposite the first assembly edge (101a), the sector (100) comprising a plurality of rows of hollow complex acoustic elements (110) each having a shape gradually narrowing between a base and a top, the hollow complex elements (110) being connected to each other by one or more adjacent edges, each row extending from the first to the second assembly edge (101a, 102a) along the assembly direction (D c), said sector (100) being characterized in that it comprises a plurality of first rows comprising the same number of hollow complex elements (110) and one or more second rows comprising one hollow complex element (110) less than the first rows, each second row further comprising a male attachment element (121) on one of the assembly edges (102a) and a female attachment element (122) on the other assembly edge (101a), the female attachment element (122) having the same dimension as a hollow complex element (110) along the assembly direction (De).

2. An annular sector (100) of a multi-element acoustic component (10) according to claim 1, wherein the male attachment element (121) has a pierced shape gradually narrowing between a base and a top.

3. An annular sector (100) of a multi-element acoustic component (10) according to claim 1 or 2, wherein the bases of the hollow complex acoustic elements (110) are hexagonal.

4. Annular multi-element acoustic component (10) comprising the assembly of a plurality of annular sectors (100) according to any one of claims 1 to 3 along the assembly direction (D c ), each male attachment element (121) of an annular sector (100) of the acoustic component (10) being inserted into a female attachment element (122) of an adjacent sector.

5. A multi-element acoustic component (10) according to claim 4, wherein all sectors (100) are identical.

6. An annular acoustic attenuation structure (1) comprising an annular multi-element acoustic component (10) according to claim 4 or 5 and an annular multi-cellular body (20), the top of each complex hollow acoustic element (110) of the multi-element acoustic component (10) being inserted into a cell (210) of the multi-cellular body (20).

7. An annular acoustic attenuation structure (1) according to claim 6, said acoustic attenuation structure (1) further comprising a perforated acoustic skin (30), said acoustic skin (30) being in contact with the base of the complex hollow acoustic elements (110).

8. An acoustic attenuation structure according to claim 6 or 7, wherein the annular multicellular body (20) comprises a plurality of annular sectors (200) of assembled multicellular bodies (20) extending along the assembly direction (D c), the length of the annular sectors (200) of the multicellular body (20) being greater than the length of the annular sectors (100) of the multi-element acoustic component (10) along the assembly direction (De).

9. A method of designing an annular multi-element acoustic component (10) according to claim 5, said annular multi-element acoustic component (10) extending around an axial direction (D a ) and having a determined interior or exterior section perimeter (Pio), each annular sector (100) of acoustic component (10) extending in the axial direction (D a ) between a first circumferential edge (101c) and a second circumferential edge (102c), the circumferential edges (101c, 102c) extending in the assembly direction (D c ), the method comprising the following steps: - determination of a number (N) of annular sectors (100) of the multi-element acoustic component (10) by rounding up to the next higher integer the ratio of the perimeter of the section (Pi0) of said acoustic component (10) by the maximum theoretical length (L cm ax) of an annular sector (100) of a multi-element acoustic component (10), - determination of the length (L c ) circumferential edges (101c, 102c) of each annular sector (100) of acoustic component (10), - determination of a theoretical width (l c o) following the assembly direction (D c ) hollow complex acoustic elements (110) corresponding to the desired acoustic attenuation, - determination of an integer number (n) of hollow complex acoustic elements (110) per first row of each annular sector (100), - determination of a final width (l c ) following the assembly direction (D c) hollow complex acoustic elements (110).

10. A method of manufacturing an annular acoustic attenuation structure (1) comprising: - the design of an annular multi-element acoustic component (10) according to claim 9, - manufacturing the annular sectors (100) of said multi-element acoustic component (10) in accordance with the design, - assembling the annular sectors (100) of the multi-element acoustic component (10) with each other and with an annular multi-cellular body (20), so that each complex hollow acoustic element (110) is arranged in a cell (210) of the multi-cellular body (20), - covering the multi-element acoustic component (10) with an acoustic skin (30) so as to form the annular acoustic attenuation structure (1) comprising at least the annular multi-element acoustic component (10), the annular multi-cellular body (20) and the acoustic skin (30).

Images