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 cellular structure (20) comprising acoustic cells open at at least one of their ends and a first porous acoustic structure (22) arranged on the first cellular structure (20) and closing the end of the acoustic cells, - a second box (19) comprising a second cellular structure (21) comprising acoustic cells open at at least one of their ends and a second porous acoustic structure (23) arranged on the second cellular 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) at least partially covers the second cellular structure (21) in an overlapping zone (30). Abstract 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 turbomachines.

[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 comprises, 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 suction of an air flow dividing at least into a primary air flow and a secondary air flow. The primary air flow passes through an annular primary vein of the turbomachine while the secondary air flow is directed towards an annular secondary vein surrounding the primary vein.

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

[0006] The blower typically comprises a movable disc rotating about the longitudinal axis and blades mounted on the disc. The blades are surrounded by a fan casing centered on the longitudinal axis and intended to retain the blades in the event of damage, for example, to the blades.

[0007] The fan casing is typically surrounded by a nacelle that protects the fan. Such a fan is said to be shrouded. The fan can also be unshrouded. In this example, the fan blades are not surrounded by a casing.

[0008] The turbomachine may further comprise an intermediate casing located downstream of the fan casing.

[0009] Turbomachines are 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 components of the turbomachine such as the fan and intermediate casings and / or the nacelle with acoustic panels in order to reduce the noise generated. by turbomachines.

[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 alveolar structures each comprising a plurality of acoustic cells. Each first and second box further comprises respectively first and second porous acoustic structures arranged respectively on the first and second alveolar structures and which dissipate most of the acoustic energy. The porous acoustic structures are generally in contact with the air flow in which the noise to be attenuated propagates. Thus, the porous acoustic structures have small perforations in order to minimize the impact on the flow of the air flow, 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 alveolar 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 material, for example during a step of molding the box. Such a box thus has the advantage of being able to be manufactured in a single piece.

[0013] Although presenting numerous advantages in terms of manufacturing, such acoustic panels present numerous challenges. Indeed, there are no solutions for connecting the boxes of the acoustic panel to each other without reducing the aeroacoustic performance of the acoustic panel. Indeed, there are generally gaps between the boxes which generate acoustic and aerodynamic losses. Also, the acoustic panels may comprise members for connecting the boxes to each other which tend to generate surface defects which also lead to significant acoustic losses and disrupt the flow of the secondary air flow thus degrading the aerodynamic performance of the turbomachine.

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

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

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

[0017] - a second chamber comprising a second alveolar structure comprising acoustic cells open at at least one of their ends 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 chambers being arranged side by side and fixed to each other.

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

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

[0021] By means of such overlapping or covering, the first and second boxes of the acoustic panel can be connected together while maximizing surface continuity between the first and second porous acoustic structures and thus minimizing surface defects of the acoustic panel.

[0022] The overlapping of the second box by the first porous acoustic structure makes it possible to do without the surface connecting members connecting the boxes together.

[0023] This makes it possible to limit disturbances to the flow of the airflow in the vein in which the acoustic panel is located and therefore to improve the aerodynamic performance of the turbomachine. In addition, thanks to such a configuration, the acoustic losses of the acoustic panel of the invention are limited.

[0024] The invention may comprise one or more of the following features, taken in isolation from one another or in combination with one another:

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

[0026] - the overlapping area has an elongated shape along edges of the first and second boxes and extends in particular according to 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 attachment device comprises a first strip attached to the first structure porous acoustics and a second strip fixed to the second box and cooperating with the first strip by clipping,

[0029] - the first strip comprises first longitudinal tabs between which insert second longitudinal tabs of the second strip,

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

[0031] - a seam connects the first porous acoustic structure to the second box, the seam being preferentially located in the overlap zone,

[0032] - the first porous acoustic structure also partly covers the second porous acoustic structure in the covering area,

[0033] - the second porous acoustic structure and the second alveolar structure com take a bedding, the height of the first and second boxes being equal in the covering area,

[0034] - the first and second porous acoustic structures have side-by- side or facing each other in the covering area,

[0035] - the first and second boxes respectively comprise a first and second perforated acoustic structures located in sandwich 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 honeycomb structures and supporting the first and second porous acoustic structures in the overlap area,

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

[0038] Other characteristics and advantages will emerge from the following description of non-limiting embodiments of the invention with reference to the appended drawings in which:

[0039] [Fig.l] is a schematic representation in longitudinal section of a half 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 sectional representation along the X axis of an acoustic panel according to one embodiment of the invention,

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

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

[0045] [Fig.6a] is a 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 of the first and second porous structures in the overlap zone according to an embodiment of the invention,

[0048] [Fig.9] is a sectional view along the X axis of a connection of 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.l]. The turbomachine 1 extends around and along a longitudinal axis A.

[0050] In the present application, the terms “upstream” and “downstream” are defined in relation to the direction of circulation of the gases in the turbomachine 1 along the longitudinal axis A.

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

[0052] The terms "internal", "interior", "internally", "external", "externally", "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-flow 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 a gas exhaust nozzle.

[0054] The low- and high-pressure compressors 3, 4 and the high- and low-pressure turbines 6, 7 each include 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- and high-pressure shafts 8, 9 are centered on the longitudinal axis A.

[0055] The blower 2 includes a rotating movable disk around the longitudinal axis A and blades 10 regularly distributed around the longitudinal axis A and extending radially from the disk. The blower 2 further includes a blower shaft (not shown) connected to the low-pressure shaft 8 through a speed reducer for example.

[0056] The blower 2 allows the suction of an air flow F dividing into an air flow primary air flow Fl and a secondary air flow F2. The primary air flow 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 F1 is compressed within the low pressure compressor 3 then the high pressure compressor 4. The compressed air is then mixed with a fuel and burned within the combustion chamber 5. The gases resulting from the combustion pass through the high pressure and low pressure turbines 6, 7. The gases finally escape through the nozzle, the cross-section of which 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 vein v2.

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

[0060] The turbomachine 1 further comprises 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 shell 13 and an outer shell 14 connected by arms 15. The outer shell 14 is annular and centered on the longitudinal axis A. It is arranged coaxially around the inner shell 13. The outer shell 14 delimits with the inner shell 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 casings 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 may 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 may 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 located 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 a 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 in a first direction X and two parallel or substantially parallel transverse edges 18b, 19b extending in a second direction Y perpendicular to the first direction X. The longitudinal and transverse edges 18a, 19a, 18b, 19b also extend in a third direction Z perpendicular to the first and second directions X, Y. The directions X, Y, Z form an orthonormal reference frame.

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

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

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

[0070] Each first and second box 18, 19 respectively comprises first and second alveolar 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 alveolar structures 20, 21 and the first and second porous acoustic structures 22, 23. The first and second alveolar 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 alveolar structures 20, 21 are thus arranged in a sandwich respectively between the first and second solid skins and the first and second perforated acoustic structures 24, 25. The first and second solid skins may be formed by the casing carrying the acoustic panel 17 or by skins distinct from this casing. The first and second solid skins make it possible to reflect the sound waves to attenuate the 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 alveolar structures 20, 21 each comprise acoustic cells 26. The acoustic cells 26 form Helmholtz resonators. The acoustic cells 26 are delimited from one another by peripheral walls 27. Each acoustic cell 26 has, for example, a polygonal cross-section, for example square, rectangular or even hexagonal. 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 of its ends and has an internal cavity 28 opening out on either side of the acoustic cell 26. The internal cavities 28 are delimited by the peripheral walls 27.

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

[0075] The first and second honeycomb structures 20, 21 may also comprise fixing systems making it possible to connect the acoustic panel 17 to the supporting structure of the turbomachine 1, such as the nacelle 16, the fan casing 11 or even the intermediate casing 12.

[0076] Advantageously, the first and second alveolar structures 20, 21 have a height of 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 of 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 cellular structures 20, 21 comprise, for example, a metallic material such as aluminum, in particular an aluminum alloy chosen from the 6000 series or a polymeric material chosen, 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 in 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 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 to or different from the material of the first and second cellular structures 20, 21. The first and second perforated acoustic structures 24, 25 comprise, for example, a metallic material such as aluminum, in particular an aluminum alloy chosen from the 6000 series or a polymeric material chosen, 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 part.

[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' which extend in 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 cellular structures 20, 21. The first and second porous acoustic structures 22, 23 further comprise longitudinal edges which extend in the first direction X and which are aligned in the third direction Z with the longitudinal edges of the first and second cellular structures 20, 21.

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

[0085] The first and second porous acoustic structures 22, 23 each comprise a thickness as measured along the third direction Z of between 0.1 mm and 2 mm, advantageously of between 0.1 mm and 1 mm and preferably of 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 interposed between the first porous acoustic structure 22 and the first alveolar structure 20. The first porous acoustic structure 22 thus closes one of the ends 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 interposed between the second porous acoustic structure 23 and the second alveolar structure 21. The second porous acoustic structure 23 thus closes one of the ends 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 may close all or some of the acoustic cells 26 of the respective first and second honeycomb structures 20, 21.

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

[0090] The overlap zone 30 represents the zone in which the first porous acoustic structure 22 and the second alveolar structure 21 overlap or superimpose. 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 of 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 overlapping zone 30. Thus, the first and second porous structures 22, 23 overlap in the overlapping zone 30. According to this embodiment, the first and second porous structures 22, 23 each have a longitudinal end 22a, 23a which extends in 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 groove or a 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 recess in the surface of the longitudinal end 23a of the second porous acoustic structure 23. This recess makes it possible to eliminate a gap between the first and second boxes 18, 19. Indeed, it makes it possible to eliminate a step between the first porous acoustic structure 22 and the second porous acoustic structure 23 and thus to ensure surface continuity. This makes it possible to limit disturbances to the flow of the secondary air flow F2 and therefore to improve the aerodynamic performance of the turbomachine 1.Preferably, the height of the step 31 is equal to or is substantially greater than the thickness of the first porous acoustic structure 22. Thanks to the step 31, the height of the first and second boxes 18, 19 is equal or substantially equal in the overlap zone 30.

[0094] Correlatively, 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 an acoustic resistance equal or substantially equal to the acoustic 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 an acoustic resistance lower than the acoustic 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 porous acoustic structure 23 has an acoustic resistance lower 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 has an acoustic resistance equal 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 makes it possible to maintain the aerodynamic appearance of the surface of the acoustic panel 17 in the overlap zone 30 and to maintain 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 at a distance from each other. This embodiment has the advantage of avoiding a step or a groove in the second porous acoustic structure 23 and in the second cellular structure 21 and of guaranteeing surface continuity without the need to make a groove in the second porous acoustic structure 23. This makes it possible to limit disturbances to the flow of the secondary air flow F2 and therefore to 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 exemplary embodiment of the second embodiment, the second perforated acoustic structure 25 of the second box 19 comprises at least one reinforcement 25' located in a sandwich between the second cellular 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 the second perforated acoustic structure 25 or to the second cellular 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 alveolar 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 may be arranged in the acoustic panel 17. Preferably, the attachment device 33 is located in the overlap zone 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 exemplary embodiment illustrated in [Fig.7], the attachment 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. The second strip 35 can be fixed to the second porous acoustic structure 23 and / or to the second cellular structure 21 and / or to the second perforated acoustic structure 25. The first and second strips 34, 35 are preferably located in the overlap zone 30. The first and second strips 34, 35 can be fixed to the transverse edges 22', 23' of the first and second porous acoustic structures 22, 23. The first and second strips 34, 35 preferably extend over the entire width of the overlap zone 30 in the first direction X. They have an elongated shape in the second direction Y. They preferably extend all along the transverse edges 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 disturbances to the flow of the air flow and therefore to preserve the aerodynamic performance of the turbomachine 1.

[0101] Advantageously, the first strip 34 may comprise 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 illustrated, the first strip 34 comprises hooks and the second strip 35 comprises loops cooperating with the hooks. The first and second strips 34, 35 form a self-gripping type fastener.

[0104] According to a second embodiment, the first porous acoustic structure 22 is bonded to the second box 19 in at least a portion of the overlapping zone 30. The first porous acoustic structure 22 may be bonded to the second porous acoustic structure 23 or to the second alveolar structure 21 or to the second perforated acoustic structure 25.

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

[0106] According to a second exemplary embodiment, the first porous acoustic structure 22 is bonded 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 overlapping zone 30.

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

[0110] The seam 38 can be simple, open, open topstitched, overlocked, overstitch, topstitched, English or even folded type.

[0111] The seam 38 may be made using a connecting thread. The seam 38 may be made using a straight stitch, a reverse straight stitch, a triple stitch or any other type of sewing 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 attachment 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 is located 17. This thus makes it possible to limit the disturbances of the air flow and therefore 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 methods of fixing the juxtaposed boxes 18, 19 can be carried out in longitudinal or transverse directions, or at an angle, or even in broken lines depending on the needs of integration, assembly, installation of the boxes in the acoustic panel 17.

Claims

Claims

1. Acoustic panel (17) for an aircraft turbomachine (1), the acoustic panel (17) comprising at least: - a first box (18) comprising a first cellular structure (20) comprising acoustic cells (26) open at at least one of their ends and a first porous acoustic structure (22) arranged on the first cellular structure (20) and closing the end of the acoustic cells (26), - a second box (19) comprising a second cellular structure (21) comprising acoustic cells (26) open at at least one of their ends and a second porous acoustic structure (23) arranged on the second cellular structure (21) and closing the end 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 overlapping 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 overlapping zone (30) has an elongated shape along edges (18b, 19b) of the first and second boxes (18, 19) and extends in particular with a width of 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 a device (33) for attaching 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 attachment 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 overlapping zone (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 preferentially 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 partly covers the second porous acoustic structure (23) in the overlapping area (30).

10. The acoustic panel according to the preceding claim, characterized in that the second porous acoustic structure (23) and the second alveolar structure (21) comprise a dovetail joint (31, 32), the height of the first and second chambers (18, 19) being equal in the overlapping area (30).

11. The 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 facing each other in the overlapping area (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 structure (24, 25) located sandwiched respectively between the first and second porous acoustic structure (22, 23) and the first and second alveolar structure (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. An acoustic panel according to any one of the preceding claims- preceding, characterized in that the first and second porous acoustic structures (22, 23) comprise a lattice.

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