ACOUSTIC SANDWICH PANEL WITH IMPROVED MOUNTING

Abstract

Acoustic panel (30) comprising a first skin (31) and a second skin (32) extending on either side of an acoustic core (33), the acoustic panel (30) also having a flank (34) connecting the first skin (31) and the second skin (32), one of the first skin (31) and the second skin (32) comprising an opening (35) leading to a cavity (36) formed in the acoustic core (30), a first fastening component (37, 40) extending into the cavity (36) in the immediate vicinity of an inner face (34.1) of the flank (34). Assembly of such a panel (30) on a flange. Propulsion assembly comprising such a panel (30). Figure for the abstract: Fig. 5

Description

Title of the invention: ACOUSTIC SANDWICH PANEL WITH IMPROVED MOUNTING Technical field of the invention

[0001] The present invention relates to the field of acoustic insulation sandwich panels, and more specifically to the implementation of such panels in turbojet nacelles.

[0002] It relates more specifically to the junction of an air inlet on the nacelle housing, also called the blower housing in the case of a twin-flow turbomachine.

[0003] The invention applies to all turbomachine designs, for example turbojets with a fan driven directly by a low-pressure body, driven indirectly by a reducer, single-body, twin-body, single-flow and twin-flow turbojets. Prior art

[0004] In a turbomachine, here a central axis AX turbojet, air is admitted, following a longitudinal direction parallel to the AX axis, into an inlet sleeve to pass through a fan comprising a series of rotating blades before splitting into a central primary flow which circulates in a so-called primary airflow circulation channel and a secondary flow surrounding the primary flow.

[0005] The primary flow is compressed by stages of compressors before reaching a combustion chamber, after which it expands as it passes through turbines, before being discharged, generating thrust. The secondary flow, on the other hand, is propelled directly by the blower to generate the main thrust.

[0006] The turbofan engine also includes a nacelle that supports the turbofan engine components and provides the connection between the turbofan engine and the aircraft. The nacelle includes a fan casing on the upstream end of which is attached an air inlet—also called an air inlet lip. The air inlet conventionally comprises an annular structure and a substantially transverse rear bulkhead that connects an inner radial fairing and an outer radial fairing of the annular structure. Aircraft noise reduction requirements have led to the installation of acoustically treated panels to define the inner radial fairing (the one in contact with the inlet airflow) of the air inlet.

[0007] These sandwich-type panels are generally composite structures consisting of two rigid outer skin layers (most often made of aluminum or composite materials) and a lightweight central core, often made of materials such as foam or honeycomb. Acoustic treatments applied The aim of these panels is to improve their noise attenuation performance, which is crucial for passenger comfort and compliance with environmental regulations.

[0008] There are three main types of acoustically treated sandwich panels: SDOF (Single Degree of Freedom) panels, 2DOF (Double Degree of Freedom) panels, and multilayer panels.

[0009] Single-degree-of-freedom (SDOF) sandwich panels are designed with a single acoustic resonance mechanism. These panels consist of two skin layers and a homogeneous core. Their acoustic performance is determined primarily by the core density and the skin thickness. These panels are simple to manufacture and are often used in applications where moderate noise attenuation is sufficient.

[0010] 2DOF (double degree of freedom) sandwich panels incorporate two acoustic resonance mechanisms, thus offering improved attenuation performance over a wider frequency range. This type of panel generally comprises two layers of different cores separated by an intermediate layer, which allows for the effective treatment of low and high frequencies. 2DOF panels are more complex to manufacture but offer significant advantages in terms of noise reduction.

[0011] Multilayer sandwich panels comprise several layers of cores and skins, allowing for very fine acoustic control. These structures can be customized to meet specific noise attenuation needs at different frequencies. Their manufacturing complexity is high, but they offer the best acoustic performance among sandwich panel types.

[0012] The skins of sandwich panels are generally made from composite or metallic materials. Composite materials often consist of carbon or glass fibers impregnated with resin, while metallic skins are typically made of aluminum or titanium. Manufacturing the skins requires shaping processes such as vacuum molding, autoclaving, or thermoforming.

[0013] The cores, for their part, can be made from materials such as polymer foam, honeycomb structures, or cellular materials. Polymer foam is manufactured by molding or extrusion, while honeycomb structures are obtained by lamination and expansion. Cellular materials can be produced by extrusion or injection molding.

[0014] The sandwich panel components are generally assembled by bonding, using structural adhesives capable of maintaining the mechanical and acoustic integrity of the structure. Assembly methods may include pressing. Hot bonding, vacuum bonding, and the use of mechanical fasteners are employed to enhance adhesion. Some panels may also incorporate a metallic honeycomb core brazed onto metal skins.

[0015] Traditionally, sandwich panels are joined together using specific bonding or welding techniques, ensuring structural and acoustic continuity. The adhesives used must offer excellent resistance to fatigue and to the operating environments of the aeronautics industry.

[0016] For connections between sandwich panels and non-sandwich elements (such as monolithic metal or composite structures), bonding, bolting, or riveting techniques can be used. For the latter two techniques, a flanged assembly is created, comprising a first flange and a second flange whose respective connecting faces are brought into contact. A bolt or rivet is inserted through aligned holes in the two flanges and then exerts a joining force on the bearing faces of each flange opposite the connecting faces.

[0017] For parts of revolution, shaping these flanges requires bending the outer radial skin to meet the inner radial skin, and, at a distance from this joint, bending the inner radial skin at ninety degrees to create the flange. This creates an area devoid of acoustic core, the axial length of which corresponds at least to the length of the screw, rivet, or clamping or riveting tool. This area reduces the surface area of ​​the sandwich panel that is acoustically treated. Finally, shaping the flange and joining the skins involve complex and costly panel manufacturing techniques. Presentation of the invention

[0018] The present invention aims to improve the acoustic insulation of a composite panel structure assembled with an element of a different nature and to reduce the costs of such an assembly.

[0019] To this end, an acoustic panel is provided comprising a first skin and a second skin extending on either side of an acoustic core, the acoustic panel also having a side connecting the first and second skins. According to the invention, one of the first and second skins comprises an opening leading to a cavity formed in the acoustic core, a first fastening component extending into the cavity in the immediate vicinity of an inner face of the side.

[0020]

[0021] According to other specific, non-exclusive and optional embodiments of the invention:

[0022] - the acoustic panel is in the shape of a sector of a piece of revolution;

[0023] - the light is a portion of a ring sector and the first component of fastening is a counter-flange sector;

[0024] - the counter flange sector includes at least one tapped portion;

[0025] - the light is circular and / or the first fastening component is a nut barrel;

[0026] - the flank extends orthogonally to the first skin and / or the second skin;

[0027] - the fastening component includes a first fairing which extends into the light to become a continuation of the first skin.

[0028]

[0029] The invention also relates to an assembly of an acoustic panel as defined above on a flange of an element, in which the side comprises an outer face opposite the inner face, the outer face being in contact with a bonding face of the flange, a second fixing component extending through the flange and the side to cooperate with the first fixing component and apply a bearing force of the flange on the side.

[0030] Advantageously, the side comprises an outer face opposite the inner face, the outer face being in contact with a connecting face of the flange, a second fastening component extending through the flange and the side to cooperate with the first fastening component and apply a bearing force of the flange on the side, and wherein the element comprises a second fairing which extends into the light to come into continuity with the first skin.

[0031] The invention also relates to a propulsion assembly comprising a turbojet engine and a nacelle comprising an assembly of an acoustic panel as defined above.

[0032]

[0033] Other features and advantages of the invention will become apparent from the following description of particular, non-limiting embodiments of the invention. Brief description of the figures

[0034] The invention will be better understood upon reading the following description, given by way of non-limiting example, and made with reference to the figures which represent:

[0035] [Fig-1] [Fig.1] is a schematic cross-sectional representation of a turbojet engine equipped with an acoustic panel according to the invention;

[0036] [Fig.2] [Fig.2] is a partial schematic representation in detail section of an air inlet equipped with an acoustic panel according to a first embodiment of the invention;

[0037] [Fig.3] [Fig.3] is a schematic perspective representation of a panel acoustics according to a first embodiment of the invention;

[0038] [Fig.4] [Fig.4] is a partial schematic cross-sectional detail representation of a assembly including the acoustic panel of [Fig.2] without the fixing components;

[0039] [Fig. 5] [Fig. 5] is a partial schematic cross-sectional detail representation of a assembly including the acoustic panel of [Fig.2] provided with the fixing components;

[0040] [Fig.6] [Fig.6] is a partial schematic cross-sectional detail representation of a assembly comprising an acoustic panel according to a second embodiment of the invention and which is devoid of the fixing components;

[0041] [Fig.7] [Fig.7] is a partial schematic cross-sectional detail representation of a assembly comprising an acoustic panel according to the second embodiment of the invention provided with the fixing components;

[0042] [Fig.8] [Fig.8] is a partial schematic cross-sectional detail representation of an assembly comprising an acoustic panel according to a third embodiment of the invention and which is devoid of the fixing components;

[0043] [Fig.9] [Fig.9] is a partial schematic cross-sectional detail representation of a assembly comprising an acoustic panel according to the third embodiment of the invention provided with the fixing components;

[0044] [Fig. 10] [Fig. 10] is a partial schematic cross-sectional detail representation of an assembly comprising an acoustic panel according to a fourth embodiment of the invention and which is devoid of the fixing components;

[0045] [Fig. 11] [Fig. 11] is a partial schematic cross-sectional detail representation of an assembly comprising an acoustic panel according to the fourth embodiment of the invention provided with the fixing components;

[0046] [Fig. 12] [Fig. 12] is a partial schematic cross-sectional detail representation of an assembly comprising an acoustic panel according to a fifth embodiment of the invention provided with the fixing components;

[0047] [Fig. 13] [Fig. 13] is a partial schematic cross-sectional detail representation of an assembly comprising an acoustic panel according to a sixth embodiment of the invention provided with the fixing components;

[0048] [Fig. 14] [Fig. 14] is a partial schematic cross-sectional detail representation of an assembly comprising an acoustic panel according to a seventh embodiment of the invention provided with the fixing components. Description of the implementation methods

[0049] With reference to Figures 1 and 2, a propulsion assembly 1000 comprises a turbomachine, here a turbojet generally designated 1, in which an airflow 100 is admitted, following a longitudinal direction parallel to the axis AX of rotation of the turbomachine 1, into an inlet sleeve 2 to pass through a fan comprising a series of rotating blades 3.

[0050] Part of the airflow 100 is compressed by compressor stages 4 and 5 before reaching a combustion chamber 6, after which it expands as it passes through turbines 7, before being discharged, generating thrust. The remainder of the airflow 100 is propelled directly by the fan to generate the main thrust.

[0051] In this text, the terms "internal" and "external" are used with reference to the position or orientation relative to the axis of rotation of the turbines 7.

[0052] In this text, the terms "upstream" and "downstream" are used with reference to the position or orientation of an element with respect to the direction of flow of the airflow 100 in the turbojet 1.

[0053] As a preliminary matter, an axial direction is defined, a radial direction which is orthogonal to the axial direction and a circumferential / tangential direction which is orthogonal to the axial and radial directions.

[0054] The turbojet engine 1 also includes a nacelle 8 which supports the components of the turbojet engine 1 and provides its connection to an aircraft (not shown). The nacelle 8 includes a fan casing 9, the upstream end of which includes, in particular, an upstream casing flange 20 to which an air inlet 10 is attached. The upstream flange 20 includes a web 21 which extends radially outwards from the casing 9. The web 21 has an upstream connecting face 22 and a downstream bearing face 23. A plurality of holes 24 extend through the web 21 to connect the connecting face 22 and the bearing face 23.

[0055] The air inlet 10 includes an annular structure 11 with longitudinal axis coinciding with the AX axis and includes an internal fairing 12 and an external fairing 13.

[0056] As seen in [Fig.2], the internal fairing 12 delimits a radially external wall 15 of a circulation vein 16 of the airflow 100. The internal fairing 12 is, here, made of a sandwich-type acoustic panel 30.

[0057] In the following description, the parts being parts of revolution or sectors of such parts, only a section will be described, it being understood that such a section is classically repeated according to a rotation about longitudinal axis AX.

[0058] With reference to Figures 2 to 5, the acoustic panel 30 is here in the shape of a right cylinder and comprises a first inner skin 31 and a second outer skin 32 extending on either side of an acoustic core 33. The panel 30 also has a downstream side 34 connecting the inner skin 31 and the outer skin 32. The skin The internal structure 31 includes a slot 35—here an annular slot—made in the internal skin 31 and opening into a cavity 36—here an annular groove—made in the acoustic core 33. A counter flange 37, formed in the form of two half counter flanges 37.1 and 37.2, each describing a counter flange sector of approximately 180 degrees, extends into the cavity 36 in the immediate vicinity of an inner face 34.1 of the side 34. As can be seen in Figures 3 and 5, the counter flange 37 includes a first fairing 38 that extends into the slot 35 to become continuous with the internal skin 31, along an axial direction. The counter flange 37 includes a connecting face 39.1 that faces the inner face 34.1 of the side 34 and a bearing face 39.2 to which nuts 39.3 are welded.

[0059] The manufacture of panel 30 can be carried out according to the following steps:

[0060] - internal skin forming 31;

[0061] - forming of the external skin 32;

[0062] - forming of the acoustic core 33;

[0063] - flank forming 34;

[0064] - assembly and securing of skins 31 and 32 with the flank 34 and the core 33 according to methods known to a person skilled in the art;

[0065] - machining of light 35.

[0066] Alternatively, the realization of the light 35 can take place prior to the forming of the inner skin 31.

[0067] The assembly of the panel 30, equipped with the counter flange 37, on the flange 20 of the housing 9 is done by bringing into contact an outer face 34.2 of the side 34, which is opposite the inner face 34.1, with the connecting face 22 of the flange 20. A counter-drilling of the side 34 is then carried out using the flange 20 as a template. Alternatively, the side 34 was pre-drilled during the manufacture of the panel 30, either before or after the side 34 was assembled onto the skins 31 and 32. Screws 90 are then inserted into the holes 24 to extend through the flange 20 and the side 34. The screws 90 then cooperate with the nuts 39.3 and tightening the screws 90 into the nuts 39.3 allows a bearing force to be applied to the face 39.2 of the counter-flange 37 and to the face 23 of the flange 20 to assemble the flange 20 onto the side 34, and thus connect the air inlet 10 to the housing 9.

[0068] This results in a simple, reliable clamping assembly that is economical to implement and optimizes the acoustic protection surface area. Finally, using a reduced number of parts, the invention ensures continuity of the internal fairing of the channel 16.

[0069] Elements identical or analogous to those previously described shall bear a numerical reference identical to that in the following description of the second, third, fourth, fifth, sixth and seventh embodiments of the invention.

[0070] According to a second embodiment of the invention shown in figures 6 and 7, the opening 35 extends to the outer face 34.2 and the housing 9 includes a second fairing 28 which projects axially from the wall 21 to extend into the opening 35 and become continuous with the inner skin 31. The assembly of the panel 30 onto the flange 20 is carried out in the same manner as described above.

[0071] According to a third embodiment of the invention shown in Figures 8 and 9, the opening 35 is formed in the outer skin 32 and is annular in shape. The opening 35 leads to the cavity 36—here an annular groove—formed in the acoustic core 33 to accommodate the counter flange 37. Assembly onto the flange 20 is carried out in the same manner as described above. The counter flange 37 is, in this case, without a fairing because the opening 35 in the outer skin preserves the continuity of the inner skin 31.

[0072] According to a fourth embodiment of the invention shown in Figures 10 and 11, the opening 35 is formed in the outer skin 32 by a core drilling extending in a substantially radial direction. The opening 35 is circular and the cavity 36 is in the form of a right cylinder with a radial axis. A barrel nut 40 extends into the cavity 36 such that its threaded portion 41 extends axially. As can be seen in Figures 10 and 11, the radially external face 42 of the nut 40 extends into the opening 35 to become continuous with the outer skin 32. The radially internal face 43 of the nut 40 comes into contact with a radially external face 31.1 of the skin 31.

[0073] This results in a simple, reliable clamping assembly that is economical to implement and optimizes the acoustic protection surface area. Indeed, core drilling uses common and inexpensive tools. The inner skin 31 is preserved, and the use of multiple barrel nuts 40 further optimizes the surface area of ​​the acoustic panel 30, which provides effective acoustic protection.

[0074] According to a fifth embodiment represented in [Fig.

[12] , the inner skin 31 has, at its connection with the side 34, an annular recess 50 formed by means of a radially external offset of the inner skin 31. An additional flange 60 has a substantially L-shaped cross-section comprising a web 61 extending substantially radially and axially projecting from which a wing 62 extends upstream of the web 61. The wing 62 extends into the recess 50 and is fixed to the panel 30 by means of radial screws 63. The side 34 extends at a non-zero distance from the upstream bearing face 64 of the web 61 to define an annular housing 65. The annular housing 65 is open at its radially external edge to accommodate the counter-flange 37. The web 61 includes a plurality of holes 66 arranged to face the holes 24 of the flange 20.

[0075] The assembly of the panel 30, equipped with the counter-flange 37, onto the flange 20 of the housing 9 is achieved by bringing into contact a downstream contact face 67 of the web 61, which is opposite the upstream support face 64, with the contact face 22 of the flange 20. The holes 66 of the additional flange 60 then face the holes 24 of the flange 20. Screws 90 are then inserted into the holes 24 to extend through the flange 20 and the holes 66 of the additional flange 60. The screws 90 then cooperate with the nuts 39.3, and tightening the screws 90 into the nuts 39.3 allows a bearing force to be applied to the face 39.2 of the counter-flange 37 and to the face 23 of the flange 20 to achieve an assembly of the flange 20. on the additional flange 60 of panel 30.

[0076] According to a sixth embodiment shown in [Fig. 13], the wing 62 of the additional flange 60 extends opposite the outer skin 32 and is fixed to the panel 30 by screwing with radial screws 63 into the outer skin 32. The side 34 extends to a non-zero distance from the upstream bearing face 64 of the web 61 to define an annular housing 65. The annular housing 65 is, according to this sixth embodiment, open at its radially internal edge to accommodate the counter flange 37.

[0077] The counter flange 37 includes a fairing 38 which extends in continuity with the inner skin 31, in an axial direction, to connect the face 34.2 of the side 34 and the face 22 of the flange 20 and ensure continuity of the fairing of the vein 16. The assembly of the panel 30 on the flange 20 is carried out in the same manner as described above.

[0078] According to a seventh embodiment shown in [Fig. 14], the wing 62 of the additional flange 60 extends opposite the outer skin 32 and is fixed to the panel 30 by screwing with radial screws 63 into the outer skin 32. The side 34 extends to a non-zero distance from the upstream bearing face 64 of the web 61 to define an annular housing 65. The annular housing 65 is, according to this sixth embodiment, open at its radially internal edge to accommodate the counter flange 37.

[0079] The housing 9 includes a fairing 28 which projects axially from the wall 21 to extend to the face 34.2 of the side 34 and to be continuous with the inner skin 31.

[0080] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0081] In particular,

[0082] - although here the acoustic panel is in the shape of a straight cylinder and thus describes a sector of a cylinder of three hundred and sixty degrees, the invention also applies to other configurations of the acoustic panel such as for example an acoustic panel in the shape of a sector of a cylinder of ninety degrees, four sectors then being necessary to define the complete cylindrical envelope of the air inlet;

[0083] - although here the light is an annular light and thus describes a sector of a three-hundred-sixty degree ring, the invention also applies to other configurations of the light such as for example a light in the shape of a sector of an eighty-degree ring, four sectors then being implemented to achieve the fixing of the air inlet;

[0084] - although here the counter-bridle is made in the form of two half counter-bridles describing each a counter-flange sector of one hundred and eighty degrees, the invention also applies to other configurations of the first fastening component such as for example a counter-flange made in the form of four counter-flange sectors each describing a counter-flange sector of approximately eighty degrees, four sectors then being implemented to make the counter-flange;

[0085] - although here the light is circular in shape and produced by coring, the invention also applies to other forms of light such as polygonal or non-circular light in order to block a rotation of the barrel on itself around a radial axis;

[0086] - although here the flange receives welded nuts, the invention also applies to Other methods for equipping a counter flange with threaded portions include, for example, making threaded bores in the counter flange body or adding cage nuts.

[0087] - although here the panel includes a counter flange provided with threaded holes for to achieve a connection by clamping using screw / nut type elements, the invention applies equally to other types of first fixing component and second fixing component such as for example a riveted assembly in which the counter-flange is devoid of threads;

[0088] - although here the panel is assembled onto the crankcase flange using screws, The invention also applies to other types of second fastening components such as rivets.

[0089] - although here the panel according to the invention has been described in application to an entrance air, the invention also applies to other types of structures such as for example a downstream portion of the vein;

[0090] - although here the internal fairing defines the internal wall of a circulatory vein of air, the invention also applies to an internal fairing which would partially define such a vein, such as for example an internal fairing connected to another element which would also contribute to the definition of the vein;

[0091] - although here the crankcase and air intake flanges are described as being circular elements of revolution, the invention also applies to flanges composed of a plurality of crown sectors;

[0092] - although here the assembly of the air inlet onto the crankcase is carried out using two flat flanges bolted or riveted together, the invention also applies to other flanged type assemblies such as screwed flanges or flanges with conical sides;

[0093] - although here the invention has been described in application to a propulsion system including a twin-spool turbojet engine, the invention also applies to propulsion assemblies comprising other types of turbomachinery such as for example a propulsion assembly comprising a single-spool turbojet engine.

Claims

Demands

1. Acoustic panel (30) comprising a first skin (31) and a second skin (32) extending on either side of an acoustic core (33), the acoustic panel (30) also having a side (34) connecting the first skin (31) and the second skin (32), one of the first skin (31) and the second skin (32) comprising a light (35) opening into a cavity (36) made in the acoustic core (30), a first fixing component (37, 40) extending into the cavity (36) in the immediate vicinity of an inner face (34.1) of the side (34).

2. Acoustic panel (30) according to claim 1, wherein the acoustic panel (30) is in the shape of a sector of a part of revolution.

3. Acoustic panel (30) according to claim 2, wherein the light (35) is a portion of a ring sector and the first fixing component (37, 40) is a counter flange sector.

4. Acoustic panel (30) according to claim 3, wherein the counter-flange sector comprises at least one threaded portion.

5. Acoustic panel (30) according to claim 1 or 2, wherein the light (35) is circular and / or the first fixing component (37, 40) is a barrel nut (40).

6. Acoustic panel (30) according to any one of the preceding claims, wherein the side (34) extends orthogonally to the first skin (31) and / or the second skin (32).

7. Acoustic panel (30) according to any one of the preceding claims, wherein the fixing component (37, 40) comprises a first fairing (38) which extends into the light (35) to become continuous with the first skin (31).

8. Assembly of an acoustic panel (30) according to any one of the preceding claims on a flange (20) of an element (9), wherein the side (34) comprises an outer face (34.2) opposite the inner face (34.1), the outer face (34.2) being in contact with a connecting face (22) of the flange (20), a second fastening component (90) extending through the flange (20) and the side (34) to cooperate with the first fastening component (37) and apply a bearing force of the flange (20) on the side (34).

9. Assembly of an acoustic panel (30) according to any one of claims 1 to 7 on a flange (20) of an element (9), wherein the side (34) comprises an outer face (34.2) opposite the inner face (34.1), the outer face (34.2) being in contact with a connecting face (22) of the flange (9), a second fastening component (90) extending through the flange (20) and the side (34) to cooperate with the first fastening component (37) and apply a bearing force of the flange (20) on the side (34), and wherein the element (9) comprises a second fairing (28) which extends into the opening (35) to become continuous with the first skin (31).

10. Propulsion assembly comprising a turbojet (1) and a nacelle (8) comprising an assembly of an acoustic panel (30) according to claim 8 or 9.

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