ACOUSTIC PANEL FOR AN AIRCRAFT TURBOMACHINE

Abstract

The invention relates to an acoustic panel (17) comprising at least: - a first box (18) comprising a first honeycomb structure (20) having acoustic cells open at at least one of their ends and a first porous acoustic structure (22) arranged on the first honeycomb structure (20) and closing the end of the acoustic cells, - a second box (19) comprising a second honeycomb structure (21) having acoustic cells open at at least one of their ends and a second porous acoustic structure (23) arranged on the second honeycomb structure (21) and closing the end of the acoustic cells, the first and second boxes (18, 19) being arranged next to each other and fixed to each other, characterized in that the first porous acoustic structure (22) covers at least part of the second honeycomb structure (21) in an overlap zone (30). Abbreviated figure: figure 4

Description

Title of the invention: ACOUSTIC PANEL FOR AN AIRCRAFT TURBOMACHINE Technical field of the invention

[0001] The invention relates to the field of acoustic panels for aircraft turbomachinery.

[0002] The invention relates in particular to the field of acoustic panels having a sandwich structure. Technical background

[0003] An aircraft turbomachine typically has a longitudinal axis. It includes, for example, from upstream to downstream in the direction of gas flow along the longitudinal axis, a fan, a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine, a low-pressure turbine, and a gas exhaust nozzle.

[0004] The blower allows the intake of an airflow that divides into at least a primary airflow and a secondary airflow. The primary airflow passes through an annular primary channel of the turbomachine, while the secondary airflow is directed towards an annular secondary channel surrounding the primary channel.

[0005] The primary airflow is compressed within the compressors. The compressed air is then mixed with a fuel and burned within the combustion chamber. The combustion gases pass through the turbines and then escape through the nozzle, the cross-section of which allows these gases to be accelerated to generate propulsion.

[0006] The blower typically comprises a rotating disc about its longitudinal axis and blades mounted on the disc. The blades are surrounded by a blower housing centered on the longitudinal axis and designed to retain the blades in case of damage, for example, to the blades.

[0007] The fan housing is typically surrounded by a nacelle that protects the fan. Such a fan is said to be enclosed. The fan may also be unenclosed. In this example, the fan blades are not surrounded by a housing.

[0008] The turbomachine may further include an intermediate casing located downstream of the blower casing.

[0009] Turbomachinery is a significant source of noise pollution, and there is a strong demand to reduce this type of pollution. To this end, it has been proposed to equip certain turbomachine components, such as the fan and intermediate casings and / or the nacelle, with acoustic panels in order to reduce the noise generated. by turbomachinery.

[0010] An acoustic panel is typically sectorized and comprises a plurality of adjacent acoustic boxes connected together to form the acoustic panel. The acoustic panel thus comprises at least a first box and a second box facing each other and connected together.

[0011] Each first and second box comprises, respectively, first and second honeycomb structures, each comprising a plurality of acoustic cells. Each first and second box further comprises, respectively, first and second porous acoustic structures arranged on the first and second honeycomb structures, which dissipate most of the acoustic energy. The porous acoustic structures are generally in contact with the airflow in which the noise to be attenuated propagates. Thus, the porous acoustic structures have small perforations to minimize the impact on the airflow, and therefore to improve the aerodynamic performance of the turbomachine. The acoustic panel may comprise one or more solid surfaces located along the face opposite the porous acoustic structures of the honeycomb structures.

[0012] Document WO-A1-2021 / 084206 describes such a box in which the honeycomb structure is connected to the porous acoustic structure by interlocking their respective materials, for example during a molding step of the box. Such a box thus has the advantage of being able to be manufactured in a single piece.

[0013] While offering numerous manufacturing advantages, such acoustic panels present many challenges. Indeed, there are no solutions for connecting the acoustic panel's cells without reducing its aeroacoustic performance. In fact, gaps between the cells generally generate acoustic and aerodynamic losses. Furthermore, acoustic panels may include connecting elements between the cells that tend to create surface defects, which also lead to significant acoustic losses and disrupt the secondary airflow, thus degrading the turbomachine's aerodynamic performance.

[0014] There is therefore a need to provide an acoustic panel for an aircraft turbomachine which has at least two acoustic boxes connected together, whose acoustic and aerodynamic properties are improved. Summary of the invention

[0015] To this end, the invention proposes an acoustic panel for an aircraft turbomachine, the acoustic panel comprising at least:

[0016] - a first box comprising a first alveolar structure including acoustic cells open at at least one end and a first porous acoustic structure arranged on the first alveolar structure and closing the end of the acoustic cells,

[0017] - a second box comprising a second honeycomb structure comprising acoustic cells open at at least one end and a second porous acoustic structure arranged on the second alveolar structure and closing the end of the acoustic cells,

[0018] the first and second boxes being arranged next to each other and fixed to each other.

[0019] The acoustic panel is remarkable in that the first porous acoustic structure covers at least in part the second alveolar structure in an overlap zone.

[0020] Thus, according to the invention, the first porous acoustic structure overlaps the second alveolar structure in the overlap zone.

[0021] Thanks to such an overlap or cover, the first and second boxes of the acoustic panel can be connected together by maximizing the surface continuity between the first and second porous acoustic structures and thus minimizing the surface defects of the acoustic panel.

[0022] The overlap of the second box by the first porous acoustic structure makes it possible to do away with the surface connecting elements linking the boxes together.

[0023] This helps to limit disturbances in the airflow within the channel containing the acoustic panel, thereby improving the aerodynamic performance of the turbomachine. Furthermore, this configuration minimizes the acoustic losses of the acoustic panel of the invention.

[0024] The invention may comprise one or more of the following features, taken individually or in combination with each other:

[0025] - the first porous acoustic structure is fixed to the second box,

[0026] - the overlap zone has an elongated shape along the edges of the first and second boxes and extends in particular over a width between 1 mm and 50 mm, advantageously between 1 mm and 30 mm and preferably between 5 mm and 15 mm,

[0027] - a device for attaching the first porous acoustic structure to the second box, preferably located in the overlap zone,

[0028] - the fastening device comprises a first band fixed to the first structure porous acoustic material and a second strip attached to the second box and cooperating with the first strip by clipping.

[0029] - the first strip comprises first longitudinal tabs between which are inserted from the second longitudinal tabs of the second strip,

[0030] - the first porous acoustic structure is glued to the second box, preferably tiellement on at least part of the overlap area,

[0031] - a seam connects the first porous acoustic structure to the second box, the with the seam preferably located in the overlap area,

[0032] - the first porous acoustic structure also partially covers the second porous acoustic structure in the overlapping area,

[0033] - the second porous acoustic structure and the second alveolar structure they take a silking, the height of the first and second boxes being equal in the overlap zone,

[0034] - the first and second porous acoustic structures have edges on the side at side by side or opposite each other in the overlapping zone,

[0035] - the first and second caissons respectively comprise a first and second perforated acoustic structures located sandwiched respectively between the first and second porous acoustic structures and the first and second alveolar structures,

[0036] - the second perforated acoustic structure comprises at least one reinforcement arranged between the first and second porous acoustic structures and the first and second alveolar structures supporting the first and second porous acoustic structures in the overlap zone,

[0037] - the first and second porous acoustic structures comprise a lattice. Brief description of the figures

[0038] Other features and advantages will become apparent from the following description of non-limiting embodiments of the invention with reference to the accompanying drawings in which:

[0039] [Fig. 1] is a schematic longitudinal cross-sectional representation of half an aircraft turbomachine,

[0040] [Fig.2] is a schematic perspective representation of an acoustic panel according to the invention,

[0041] [Fig.3] is a schematic perspective representation of a first or second box equipping the acoustic panel of [Fig.2],

[0042] [Fig. 4] is a cross-sectional representation along the X-axis of an acoustic panel according to an embodiment of the invention,

[0043] [Fig. 5] is a cross-sectional representation along the X-axis of an acoustic panel according to another embodiment of the invention,

[0044] [Fig. 6] is a cross-sectional representation along the X-axis of an acoustic panel according to another embodiment of the invention,

[0045] [Fig. 6a] is a cross-sectional representation along the X-axis of an acoustic panel according to another embodiment of the invention,

[0046] [Fig.7] is a perspective representation of a fastening device that can be implemented in the acoustic panel of [Fig.2],

[0047] [Fig.8] is a top view of a connection between the first and second porous structures in the overlap zone according to an embodiment of the invention,

[0048] [Fig.9] is a cross-sectional view along the X axis of a connection between the first and second porous structures in the overlap zone according to an embodiment of the invention. Detailed description of the invention

[0049] An example of a turbomachine 1 for an aircraft is shown in [Fig. 1]. The turbomachine 1 extends around and along a longitudinal axis A.

[0050] In the present application, the terms "upstream" and "downstream" are defined with respect to the direction of gas flow in the turbomachine 1 along the longitudinal axis A.

[0051] The terms “axial”, “axially”, “radial”, “radially” are defined with respect to the longitudinal axis A.

[0052] The terms "internal", "interior", "internally", "external", "exterior", "externally", are defined with respect to the distance from the longitudinal axis A along an axis Z extending radially with respect to the longitudinal axis A.

[0053] The turbomachine 1 is preferably a turbojet, for example a twin-spool, twin-spool turbojet. It comprises, from upstream to downstream, a fan 2, at least one compressor such as a low-pressure compressor 3 and a high-pressure compressor 4, a combustion chamber 5, at least one turbine such as a high-pressure turbine 6 and a low-pressure turbine 7, and an exhaust nozzle.

[0054] The low-pressure and high-pressure compressors 3, 4 and the high-pressure and low-pressure turbines 6, 7 each comprise at least one rotor. The rotor of the low-pressure compressor 3 is connected to the rotor of the low-pressure turbine 7 by a low-pressure shaft 8, and the rotor of the high-pressure compressor 4 is connected to the rotor of the high-pressure turbine 6 by a high-pressure shaft 9. The high-pressure shaft 9 is arranged coaxially around the low-pressure shaft 8. The low-pressure and high-pressure shafts 8, 9 are centered on the longitudinal axis A.

[0055] The fan 2 comprises a rotating disc about the longitudinal axis A and blades 10 evenly distributed about the longitudinal axis A and extending radially from the disc. The fan 2 further comprises a fan shaft (not shown) connected to the low-pressure shaft 8 via, for example, a speed reducer.

[0056] The blower 2 allows the aspiration of an airflow F which divides into an airflow primary Fl and a secondary airflow F2. The primary airflow Fl passes through an annular primary vein vl of the turbomachine 1 and the secondary flow F2 flows into an annular secondary vein v2 of the turbomachine 1. The secondary vein v2 surrounds the primary vein vl.

[0057] The primary flow Fl is compressed within the low pressure compressor 3 and then the high pressure compressor 4. The compressed air is then mixed with a fuel and burned within the combustion chamber 5. The gases from the combustion pass through the high pressure and low pressure turbines 6, 7. The gases finally escape through the nozzle whose cross-section allows the acceleration of these gases to generate propulsion.

[0058] According to one example, the fan 2 is of the shrouded type. The turbomachine 1 thus further comprises a fan casing 11. The fan casing 11 is annular and centered on the longitudinal axis A. It is arranged around the blades 10 of the fan 2. The fan casing 11 delimits a portion of the secondary flow v2.

[0059] According to another example, the blower 2 is of the unshrouded type. The blades 10 of the blower 2 are therefore not surrounded by a casing.

[0060] The turbomachine 1 further includes an intermediate casing 12. The intermediate casing 12 is arranged downstream of the fan casing 11. It is connected to the fan casing 11 for example by flanges.

[0061] The intermediate casing 12 is centered on the longitudinal axis A and comprises an inner ferrule 13 and an outer ferrule 14 connected by arms 15. The outer ferrule 14 is annular and centered on the longitudinal axis A. It is arranged coaxially around the inner ferrule 13. The outer ferrule 14 delimits with the inner ferrule 13 a portion of the secondary vein v2.

[0062] The turbomachine 1 further comprises a nacelle 16. The nacelle 16 is arranged around the fan and intermediate housings 11, 12.

[0063] In order to reduce the noise pollution generated by the turbomachine 1, the turbomachine 1 comprises at least one and advantageously a plurality of acoustic panels 17. Each acoustic panel 17 is advantageously capable of absorbing acoustic energy over a frequency range between 300 Hz and 3000 Hz.

[0064] Each acoustic panel 17 can extend over an angular sector or have an annular shape centered on the longitudinal axis A, or extend axially or radially. Each acoustic panel 17 can be attached and fixed inside the fan casing 11 and / or inside the outer shell 14 of the intermediate casing 12 and / or inside the nacelle 16 or any element of the turbomachine 1 requiring acoustic treatment such as a thrust reverser.

[0065] With reference to [Fig. 2], each acoustic panel 17 is sectorized or multi-part. It thus comprises a plurality of boxes, in particular at least a first box 18 and a second box 19 adjacent or situated next to each other, for example along the longitudinal axis A or around the longitudinal axis A or in a radial direction, and connected together to form the acoustic panel 17. Each box 18, 19 thus forms a sector or part of the acoustic panel 17.

[0066] The first and second boxes 18, 19 may have a substantially polygonal shape, for example square or rectangular. The first and second boxes 18, 19 have two parallel or substantially parallel longitudinal edges 18a, 19a extending along a first direction X and two parallel or substantially parallel transverse edges 18b, 19b extending along a second direction Y perpendicular to the first direction X. The longitudinal and transverse edges 18a, 19a, 18b, 19b also extend along a third direction Z perpendicular to the first and second directions X, Y. The directions X, Y, Z form an orthonormal coordinate system.

[0067] The length L of the acoustic panel 17 or of each box 18, 19 is measured along the first direction X. The width L' of the acoustic panel 17 or of each box 18, 19 is measured along the second direction Y. The height or thickness H of the acoustic panel 17 or of each box 18, 19 is measured along the third direction Z.

[0068] The longitudinal edges 18a, 19a or transverse edges 18b, 19b are located next to each other or are adjacent. They may be joined or separated from each other by a determined distance.

[0069] The first and second caissons 18, 19 each have a sandwich structure.

[0070] Each first and second box 18, 19 comprises respectively first and second honeycomb structures 20, 21, first and second porous acoustic structures 22, 23 and advantageously first and second perforated acoustic structures 24, 25 located between the first and second honeycomb structures 20, 21 and the first and second porous acoustic structures 22, 23. The first and second honeycomb structures 20, 21, the first and second porous acoustic structures 22, 23 and advantageously the first and second perforated acoustic structures 24, 25 are thus stacked along the third direction Z.

[0071] Each first and second box 18, 19 may further comprise first and second solid skins (not shown) opposite the first and second porous acoustic structures 22, 23. The first and second honeycomb structures 20, 21 are thus arranged sandwiched between the first and second solid skins and the first and second perforated acoustic structures 24, 25, respectively. The first and second solid skins may be formed by the housing supporting the acoustic panel 17 or by separate skins of this housing. The first and second solid skins reflect sound waves to attenuate noise.

[0072] When the acoustic panel 17 is mounted in the turbomachine 1, the first and second porous acoustic structures 22, 23 face the air stream in which the acoustic waves propagate, for example the secondary air stream v2 and the first and second alveolar structures 20, 21 are located towards the supporting structure of the turbomachine 1, such as the nacelle, in the opposite direction of the air stream.

[0073] With reference to [Fig. 3], the first and second honeycomb structures 20, 21 each comprise acoustic cells 26. The acoustic cells 26 form Helmholtz resonators. The acoustic cells 26 are separated from each other by peripheral walls 27. Each acoustic cell 26 has, for example, a polygonal cross-section, such as a square, rectangle, or hexagon. The cross-section of the acoustic cells 26 may differ from one acoustic cell 26 to another. Each acoustic cell 26 is open at each end and has an internal cavity 28 opening on either side of the acoustic cell 26. The internal cavities 28 are separated by the peripheral walls 27.

[0074] The peripheral walls 27 extend preferentially along the third direction Z from the perforated acoustic structure 24, 25.

[0075] The first and second honeycomb structures 20, 21 may also include fastening systems allowing the acoustic panel 17 to be connected to the supporting structure of the turbomachine 1, such as the nacelle 16, the blower housing 11 or the intermediate housing 12.

[0076] Advantageously, the first and second alveolar structures 20, 21 have a height between 10 mm and 80 mm, in particular between 12 mm and 50 mm as measured along the third direction Z. Advantageously, the peripheral walls 27 of the first and second alveolar structures 20, 21 have a thickness between 0.5 mm and 5 mm, in particular between 1 mm and 3 mm as measured along the third direction Z.

[0077] The first and second alveolar structures 20, 21 comprise for example a metallic material such as aluminium, in particular an aluminium alloy selected from the 6000 series or a polymeric material selected for example from thermoplastics or composites.

[0078] The first and second perforated acoustic structures 24, 25 are respectively located between the first and second porous acoustic structures 22, 23 and the first and second alveolar structures 20, 21. The first and second perforated acoustic structures 24, 25 each comprise perforations 29. Preferably, the perforations 29 are regularly distributed within the first and second perforated acoustic structures 24, 25. The perforations 29 communicate with the cavities 28 of the acoustic cells 26. Preferably, a group of four The perforations 29 communicate with a cavity 28 of an acoustic cell 26. The perforations 29 have, for example, a substantially polygonal cross-section, for example square and / or rectangular and / or hexagonal and / or a circular cross-section. The perforations 29 have a dimension, for example, greater than or equal to 1 mm, in particular greater than or equal to 2 mm.

[0079] Advantageously, the first and second perforated acoustic structures 24, 25 have a thickness less than the thickness of the first and second alveolar structures 20, 21. The thickness of the first and second perforated acoustic structures 24, 25 is preferably between 0.5 mm and 3 mm.

[0080] The first and second perforated acoustic structures 24, 25 advantageously comprise a material identical or different from the material of the first and second honeycomb structures 20, 21. The first and second perforated acoustic structures 24, 25 comprise, for example, a metallic material such as aluminium, in particular an aluminium alloy selected from the 6000 series or a polymeric material selected, for example, from thermoplastics or composites.

[0081] According to an advantageous embodiment, the first and second perforated acoustic structures 24, 25 and the first and second alveolar structures 20, 21 form a single piece.

[0082] The first and second porous acoustic structures 22, 23 each have a polygonal shape, for example, square or rectangular. The first and second porous acoustic structures 22, 23 each have transverse edges 22', 23' extending along the second direction Y. The transverse edges 22', 23' of the first and second porous acoustic structures 22, 23 are thus parallel to the transverse edges 18b, 19b of the first and second alveolar structures 20, 21. The first and second porous acoustic structures 22, 23 further comprise longitudinal edges extending along the first direction X and aligned along the third direction Z with the longitudinal edges of the first and second alveolar structures 20, 21.

[0083] The first and second porous acoustic structures 22, 23 advantageously comprise a mesh, also called a grid or mesh. The first and second porous acoustic structures 22, 23 comprise, for example, woven or non-woven yarns. The first and second porous acoustic structures 22, 23 preferably comprise a thermoplastic polymeric material. The thermoplastic material is, for example, selected from polyaryletherketones (PAEKs) such as polyetherketone (PEK), polyetheretherketone (PEEK), or polyetherketone-neketone (PEKK), or polyacrylonitrile (PAN). According to another example, the first and second porous acoustic structures 22, 23 comprise a metallic material such as aluminum or a ceramic material.

[0084] The first and second porous acoustic structures 22, 23 each comprise holes or openings. The holes are regularly distributed in the first and second porous acoustic structures 22, 23. The holes have, for example, a diameter on the order of a micrometer.

[0085] The first and second porous acoustic structures 22, 23 each have a thickness, measured along the third direction Z, of between 0.1 mm and 2 mm, advantageously between 0.1 mm and 1 mm, and preferably between 0.3 mm and 0.8 mm. The thickness of the first porous acoustic structure 22 is advantageously equal to the thickness of the second porous acoustic structure 23.

[0086] The first porous acoustic structure 22 is located on the first alveolar structure 20, the first perforated acoustic structure 24 being able to be intercalated between the first porous acoustic structure 22 and the first alveolar structure 20. The first porous acoustic structure 22 thus closes one end of the acoustic cells 26. The opposite end of the acoustic cells 26 can be closed by the solid skin.

[0087] The second porous acoustic structure 23 is located on the second alveolar structure 21, the second perforated acoustic structure 25 being able to be intercalated between the second porous acoustic structure 23 and the second alveolar structure 21. The second porous acoustic structure 23 thus closes one end of the acoustic cells 26. The opposite end of the acoustic cells 26 can be closed by the solid skin.

[0088] The first and second porous acoustic structures 22, 23 can close all or some of the acoustic cells 26 of the first and second alveolar structures 20, 21 respectively.

[0089] With reference to figures 4 to 6, according to the invention, the first porous acoustic structure 22 also covers at least part of the second box 19 in an overlap zone 30. In particular, according to the invention, the first porous acoustic structure 22 covers at least part of the second alveolar structure 21 in the overlap zone 30.

[0090] The overlap zone 30 represents the area in which the first porous acoustic structure 22 and the second alveolar structure 21 overlap or are superimposed. The overlap zone 30 advantageously extends over a width of between 1 mm and 50 mm, advantageously between 1 mm and 30 mm, and preferably between 5 mm and 15 mm, as measured along the first direction X.

[0091] The overlap zone 30 has an elongated shape along the second direction Y. It thus extends along the transverse edges 18b, 19b. The overlap zone 30 therefore has a length equal to the width L' of the acoustic panel 17 and / or the first and second boxes 18, 19.

[0092] According to a first embodiment illustrated in Figures 4 and 5, the first porous structure 22 also covers the second porous acoustic structure 23 in the overlap zone 30. Thus, the first and second porous structures 22, 23 overlap in the overlap zone 30. According to this embodiment, the first and second porous structures 22, 23 each have a longitudinal end 22a, 23a extending along the second direction Y. The longitudinal end 22a of the first porous structure 22 overlaps the longitudinal end 23a of the second porous structure 23. The longitudinal end 23a of the second porous structure 23 is thus sandwiched between the longitudinal end 22a of the first porous structure 22 and the second alveolar structure 21 or the second perforated acoustic structure 25.The width of the longitudinal ends 22a, 23a as measured along the first direction X defines the overlap zone 30.

[0093] According to a preferred embodiment illustrated in [Fig. 5], the second porous acoustic structure 23 has a chamfer or step 31. The chamfer 31 connects the longitudinal end 23a of the second porous acoustic structure 23 to the rest of the second porous acoustic structure 23. This chamfer 31 creates a height reduction in the surface of the longitudinal end 23a of the second porous acoustic structure 23. This reduction eliminates the need for a gap between the first and second chambers 18, 19. Indeed, it eliminates the need for a step between the first porous acoustic structure 22 and the second porous acoustic structure 23, thus ensuring surface continuity. This limits disturbances in the secondary airflow F2 and therefore improves the aerodynamic performance of the turbomachine 1.Preferably, the height of step 31 is equal to or substantially greater than the thickness of the first porous acoustic structure 22. Thanks to step 31, the height of the first and second boxes 18, 19 is equal to or substantially equal in the overlap zone 30.

[0094] Corollarily, according to this embodiment, the second alveolar structure 21 and possibly the second perforated acoustic structure 25 also have a step 32 aligned with the step 31 of the second porous acoustic structure 23 along the third axis Z.

[0095] According to one embodiment of the invention, the overlap zone 30 has a sound resistance equal to or substantially equal to the sound resistance of the first and second porous acoustic structures 22, 23 as measured outside the overlap zone 30. Preferably, the longitudinal end 22a, 23a of one of the first and second porous acoustic structures 22, 23 has a sound resistance lower than the sound resistance of the first and second porous acoustic structures 22, 23 as measured outside the overlap zone 30. Preferably, the longitudinal end 23a of the second The porous acoustic structure 23 exhibits a lower acoustic resistance than the acoustic resistance of the first and second porous acoustic structures 22, 23 as measured outside the overlap zone 30. Thus, the longitudinal end 22a of the first porous acoustic structure 22 exhibits an acoustic resistance equal to or substantially equal to the acoustic resistance of the first and second porous acoustic structures 22, 23 as measured outside the overlap zone 30. This allows the aerodynamic appearance of the surface of the acoustic panel 17 to be maintained within the overlap zone 30 and ensures a constant acoustic resistance of the first and second boxes 18, 19 despite the overlap zone 30.

[0096] According to a second embodiment illustrated in [Fig. 6], the transverse edges 22', 23' of the first and second porous acoustic structures 22, 23 are opposite each other or side by side in the overlap zone 30. The transverse edges 22', 23' may be contiguous or separated. This embodiment has the advantage of eliminating the need for a step or joint in the second porous acoustic structure 23 and in the second alveolar structure 21, and of ensuring surface continuity without the need for a joint in the second porous acoustic structure 23. This makes it possible to limit disturbances in the secondary airflow F2 and thus improve the aerodynamic performance of the turbomachine 1 while facilitating the manufacturing process of the acoustic panel 17.

[0097] With reference to [Fig. 6a], according to an example of the second embodiment, the second perforated acoustic structure 25 of the second enclosure 19 comprises at least one reinforcement 25' located sandwiched between the second honeycomb structure 21 and the first and second porous acoustic structures 22, 23. The reinforcement 25' thus supports the first and second longitudinal ends 22a, 23a. The reinforcement 25' may comprise a material identical to that of the second perforated acoustic structure 25 or to the second honeycomb structure 21. The reinforcement 25' is, for example, metallic.

[0098] Preferably, the first porous acoustic structure 22 is fixed to the second box 19 in the overlap zone 30. The first porous acoustic structure 22 is fixed in the overlap zone to the second porous acoustic structure 23 and / or to the second honeycomb structure 21 and / or to the second perforated acoustic structure 25.

[0099] According to a first embodiment, the acoustic panel 17 comprises at least one attachment device 33 for the first and second boxes 20, 21. A plurality of attachment devices 33 can be arranged in the acoustic panel 17. Preferably, the attachment device 33 is located in the overlap area 30. The attachment device 33 is, for example, fixed to the first and second boxes 18, 19 by sewing, gluing or even welding.

[0100] According to a first embodiment illustrated in [Fig. 7], the fastening device 33 comprises a first band 34 attached to the first porous acoustic structure 22 and a second band 35 attached to the second box 19. The second band 35 can be attached to the second porous acoustic structure 23 and / or to the second honeycomb structure 21 and / or to the second perforated acoustic structure 25. The first and second bands 34, 35 are preferably located in the overlap zone 30. The first and second bands 34, 35 can be attached to the transverse edges 22', 23' of the first and second porous acoustic structures 22, 23. The first and second bands 34, 35 preferentially extend over the entire width of the overlap zone 30 along the first direction X. They have an elongated shape along the second direction Y. They preferentially extend along the entire edges transverse 18b, 19b along the second direction Y.They have a thickness of between 0.5 mm and 5 mm, advantageously between 1 mm and 2 mm as measured along the third direction Z. Such a thickness makes it possible to limit the disturbances in the airflow and therefore to preserve the aerodynamic performance of the turbomachine 1.

[0101] Advantageously, the first strip 34 may include perforations. The perforations advantageously have a diameter equal to the diameter of the holes in the first and second porous acoustic structures 22, 23. Such an embodiment makes it possible to improve the acoustic properties of the acoustic panel 17 by limiting acoustic losses.

[0102] The first and second strips 34, 35 cooperate together by clipping. In particular, the first and second strips 34, 35 respectively comprise first and second tabs 36, 37 having an elongated shape along the second direction Y. The first tabs 36 are inserted between the second tabs 37. The first and second tabs 36, 37 are thus nested within each other.

[0103] According to another example not shown, the first band 34 comprises hooks and the second band 35 comprises loops cooperating with the hooks. The first and second bands 34, 35 form a hook-and-loop fastener.

[0104] According to a second embodiment, the first porous acoustic structure 22 is glued to the second box 19 in at least part of the overlap area 30. The first porous acoustic structure 22 can be glued to the second porous acoustic structure 23 or to the second honeycomb structure 21 or to the second perforated acoustic structure 25.

[0105] According to a first embodiment, the first porous acoustic structure 22 is heat-bonded to the second box 19.

[0106] According to a second embodiment, the first porous acoustic structure 22 is glued to the second box 19 by means of an adhesive.

[0107] According to a third embodiment, and with reference to figures 8 and 9, the first porous acoustic structure 22 and the second box 19 are connected together by a seam 38.

[0108] According to the embodiment of [Fig.8], the first porous acoustic structure 22 and the second porous acoustic structure 23 are sewn together, preferably over at least part of the overlap area 30.

[0109] According to the embodiment of [Fig.9], the first porous acoustic structure 22 is sewn to the second alveolar structure 21 preferably over at least part of the overlap area 30.

[0110] The seam 38 can be of the simple type, open, open topstitched, overlocked, on edge, topstitched, English or even folded over.

[0111] The seam 38 can be made using a bonding thread. The seam 38 can be made using a straight stitch, a reverse straight stitch, a triple stitch, or any other type of stitch.

[0112] The seam 38 extends over the entire width L' of the acoustic panel 17 or of the first and second boxes 18, 19.

[0113] Such types of fixing make it possible to connect the boxes 18, 19 of the acoustic panel 17 together while limiting the surface defects inside the acoustic panel 17 which faces the air stream in which the acoustic panel 17 is located. This makes it possible to limit the disturbances of the airflow and thus to improve the aerodynamic performance of the turbomachine.

[0114] Also, such types of fixing make it possible to limit the spaces between the porous acoustic structures 22, 23 and therefore to reduce acoustic losses.

[0115] The fixing examples are not limited to the positions described above. The fixing methods for the juxtaposed boxes 18, 19 can be carried out along longitudinal or transverse directions, or at an angle, or even in broken lines, depending on the needs of integration, assembly, and installation of the boxes in the acoustic panel 17.

Claims

Demands

1. Acoustic panel (17) for an aircraft turbomachine (1), the acoustic panel (17) comprising at least: - a first box (18) comprising a first honeycomb structure (20) having acoustic cells (26) open at at least one of their ends and a first porous acoustic structure (22) arranged on the first honeycomb structure (20) and closing the ends of the acoustic cells (26), - a second box (19) comprising a second honeycomb structure (21) having acoustic cells (26) open at at least one of their ends and a second porous acoustic structure (23) arranged on the second honeycomb structure (21) and closing the ends of the acoustic cells (26), the first and second boxes (18, 19) being arranged next to each other and fixed to each other,characterized in that the first porous acoustic structure (22) at least partially covers the second alveolar structure (21) in an overlap zone (30).

2. Acoustic panel according to the preceding claim, characterized in that the first porous acoustic structure (22) is fixed to the second box (19).

3. Acoustic panel according to any one of the preceding claims, characterized in that the overlap area (30) has an elongated shape along edges (18b, 19b) of the first and second boxes (18, 19) and extends in particular over a width between 1 mm and 50 mm, advantageously between 1 mm and 30 mm and preferably between 5 mm and 15 mm.

4. Acoustic panel according to any one of the preceding claims, characterized in that it further comprises an attachment device (33) of the first porous acoustic structure (22) to the second box (19), preferably located in the overlap zone (30).

5. Acoustic panel according to the preceding claim, characterized in that the fastening device (33) comprises a first strip (34) fixed to the first porous acoustic structure (22) and a second strip (35) fixed to the second box (19) and cooperating with the first strip (34) by clipping.

6. Acoustic panel according to the preceding claim, characterized in that the first strip (34) comprises first longitudinal tabs (36) between which second longitudinal tabs (37) of the second strip (35) are inserted.

7. Acoustic panel according to any one of claims 1 to 3, characterized in that the first porous acoustic structure (22) is glued to the second box (19), preferably on at least part of the overlap area (30).

8. Acoustic panel according to any one of claims 1 to 3, characterized in that a seam (38) connects the first porous acoustic structure (22) to the second box (19), the seam (38) being preferably located in the overlap zone (30).

9. Acoustic panel according to any one of the preceding claims, characterized in that the first porous acoustic structure (22) also partially covers the second porous acoustic structure (23) in the overlap zone (30).

10. Acoustic panel according to the preceding claim, characterized in that the second porous acoustic structure (23) and the second alveolar structure (21) comprise a soffit (31, 32), the height of the first and second box (18, 19) being equal in the overlap zone (30).

11. Acoustic panel according to any one of claims 1 to 7, characterized in that the first and second porous acoustic structures (22, 23) have edges (22', 23') side by side or opposite each other in the overlap zone (30).

12. Acoustic panel according to the preceding claim, characterized in that the first and second boxes (18, 19) respectively comprise a first and second perforated acoustic structures (24, 25) located sandwiched respectively between the first and second porous acoustic structures (22, 23) and the first and second alveolar structures (20, 21).

13. Acoustic panel according to the preceding claim, characterized in that the second perforated acoustic structure (25) comprises at least one reinforcement (25') arranged between the first and second porous acoustic structures (22, 23) and the first and second alveolar structures (20, 21) and supporting the first and second porous acoustic structures (22, 23) in the overlap zone (30).

14. Acoustic panel according to any one of the preceding claims cédentes, characterized in that the first and second porous acoustic structures (22, 23) comprise a lattice.

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