ACOUSTIC PANEL FOR AN AIRCRAFT TURBOMACHINE

Abstract

The invention relates to an acoustic panel (17) for an aircraft turbomachine, the acoustic panel (17) comprising: - a honeycomb structure (18) comprising a plurality of honeycomb cells (21), and - a connecting member (29) for connecting the acoustic panel (17) to a support of the turbomachine, the connecting member (29) comprising an anchoring portion passing through a thickness (e1) of the honeycomb structure (18) and an attachment portion (30) projecting from the honeycomb structure (18), characterized in that the honeycomb structure (18) and the connecting member (29) form a single unit. (Shorthand figure: Figure 3)

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. Technical background

[0002] An aircraft turbomachine includes, for example, from upstream to downstream in the direction of gas flow along a 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.

[0003] The blower allows the intake of an airflow that splits into a primary flow and a secondary flow. The primary flow passes through a primary channel of the turbomachine while the secondary flow is directed towards a secondary channel surrounding the primary channel.

[0004] The primary flow is compressed within the compressors. The compressed air is then mixed with a fuel and burned within the combustion chamber. The gases from the combustion pass through the turbines and then escape through the nozzle, the cross-section of which allows these gases to be accelerated to generate propulsion.

[0005] 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 these blades.

[0006] The fan housing is typically surrounded by a nacelle that protects the fan. Such a fan is said to be enclosed, as opposed to unenclosed fans whose blades are not surrounded by a housing.

[0007] Turbomachinery, and in particular fans, 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 turbomachinery with acoustic panels to reduce the noise generated by the fans.

[0008] An acoustic panel typically has a sandwich structure comprising a first and second skin, between which is arranged a honeycomb structure designed to attenuate sound waves. In the case of an acoustic panel, the second skin typically has holes allowing sound waves to propagate through the honeycomb structure, where they are absorbed.

[0009] The alveolar structure comprises alveolar cells organized, for example, in a honeycomb pattern. Each alveolar cell has a typically hexagonal cross-section and is delimited by walls that define a cavity between them. Each cavity extends through the entire thickness of the alveolar structure and therefore between the first and second layers.

[0010] In order to connect such an acoustic panel to a turbomachine housing, for example to the fan housing, it is known to equip the acoustic panel with a connecting element, also called a fitting. For this purpose, the connecting element is attached to the honeycomb structure of the acoustic panel. The connecting element typically comprises a portion for attaching to the housing that projects from the honeycomb structure. In order to secure this connecting element, the acoustic panel further comprises connecting rods that pass through the honeycomb structure and secure this connecting element.

[0011] These connecting rods generate compressive forces in the acoustic panel that the honeycomb structure must be able to withstand. To resist such a level of compression, the number of honeycomb cells is increased, thereby increasing the compressive strength of the honeycomb structure.

[0012] However, increasing the number of cells in the honeycomb structure of the acoustic panel has drawbacks. Indeed, the greater the number of acoustic cells, the higher the cost of the acoustic panel. Also, such a high density of acoustic cells can introduce defects into the acoustic panel. Furthermore, increasing the number of cells means reducing the size of the cells, which can then neither drain properly nor perform their acoustic function. Acoustic performance is therefore reduced.

[0013] Therefore, there is a need to provide an acoustic panel comprising a honeycomb structure and a connecting element, which is inexpensive, has few structural defects, and whose acoustic performance is improved. Summary of the invention

[0014] To this end, the invention proposes an acoustic panel for an aircraft turbomachine, the acoustic panel comprising:

[0015] - an alveolar structure comprising a plurality of alveolar cells, and

[0016] - a connecting element intended to link the acoustic panel to a support of the turbomachine, the connecting element comprising an anchoring portion passing through a thickness of the alveolar structure and an attachment portion extending in projection from the alveolar structure.

[0017] The acoustic panel is remarkable in that the honeycomb structure and the connecting element form a single unit.

[0018] According to the invention, the connecting element and the alveolar structure thus form a single unit.

[0019] Such a configuration of the acoustic panel allows the connecting element to be attached to the honeycomb structure without intermediate parts. This eliminates the need for connecting rods and thus reduces compressive forces within the honeycomb structure. It is therefore possible to reduce the number of honeycomb cells in the honeycomb structure.

[0020] The acoustic panel according to the invention thus has a low density of alveolar cells compared to acoustic panels having connecting elements linked by connecting rods to the alveolar structure.

[0021] Thanks to the invention, the cost of the acoustic panel is thus reduced and manufacturing defects are limited.

[0022] Furthermore, this low density of alveolar cells allows for an increase in the size of each alveolar cell, thus maximizing the acoustic surface area of ​​the acoustic panel. The acoustic performance of the panel is therefore improved.

[0023] The invention may comprise one or more of the following features, taken individually or in combination with each other:

[0024] - the alveolar structure and / or the connecting element comprise a metallic material or polymeric,

[0025] - the alveolar structure and / or the connecting element comprise the same material, in metallic or polymeric particular

[0026] - the alveolar structure and the connecting element are produced by additive manufacturing,

[0027] - the alveolar structure comprises at least one septum arranged in at least one of the alveolar cells,

[0028] - the connecting element is located in the middle of the alveolar structure,

[0029] - the alveolar cells are distributed around the connecting organ,

[0030] - the attachment portion comprises a clevis and a circular base from which the projecting screed extends,

[0031] - the anchoring portion has a frustoconical internal surface,

[0032] - the internal surface delimits an internal space,

[0033] - alveolar cells exhibit a plurality of shapes in cross-section, for example polygonal, hexagonal,

[0034] - the alveolar structure includes a border located around the alveolar cells. Brief description of the figures

[0035] 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:

[0036] [Fig. 1] is a schematic longitudinal cross-sectional representation of half an aircraft turbomachine,

[0037] [Fig.2] is a schematic cross-sectional representation of an acoustic panel according to the invention,

[0038] [Fig. 3] is a perspective view of the acoustic panel according to the invention,

[0039] [Fig. 4] is a cross-sectional view of the acoustic panel of [Fig. 3] passing through the plan AA shown in [Fig.5],

[0040] [Fig.5] is a top view of [Fig.3]. Detailed description of the invention

[0041] 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.

[0042] In the present application, unless otherwise indicated, the terms "upstream" and "downstream" are defined with respect to the direction of gas flow in the turbomachine 1 along the longitudinal axis A.

[0043] The terms “axial”, “axially”, “radial”, “radially” are defined with respect to the longitudinal axis A.

[0044] The terms "internal", "interior", "internally", "external", "exterior", "externally", are defined with respect to the distance from the longitudinal axis A along an axis Z perpendicular to the longitudinal axis A.

[0045] The turbomachine 1 is, for example, 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.

[0046] The low and high pressure compressors 3, 4 and the high 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 and high-pressure shafts 8, 9 are centered on the longitudinal axis A.

[0047] The blower 2 comprises a rotating disc about the longitudinal axis A and blades 10 extending radially from the disc. The blower 2 further comprises a blower shaft (not shown) connected to the low-pressure shaft 8 via, for example, a speed reducer.

[0048] The blower 2 allows the aspiration of an airflow F which divides into a primary flow Fl and a secondary flow F2. The primary flow Fl passes through a primary vein vl of the turbomachine 1 and the secondary flow F2 flows into a secondary vein v2 of turbomachine 1. The secondary vein v2 surrounds the primary vein vl.

[0049] 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 formed by the combustion pass through the high 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.

[0050] The fan 2 is, for example, 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. The fan casing 11 forms a portion of the secondary flow v2.

[0051] 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.

[0052] The intermediate housing 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.

[0053] The turbomachine 1 can be surrounded by a nacelle 16. The nacelle 16 is arranged around the fan and intermediate housings 11, 12.

[0054] In order to reduce the noise pollution generated by the turbomachine 1, the turbomachine 1 includes at least one and advantageously acoustic panels 17.

[0055] Each acoustic panel 17 is attached and fixed to a support of the turbomachine 1. The support can be the fan casing 11 and / or the outer shell 14 of the intermediate casing 12 and / or the nacelle 16. Any other structure located in a noise zone can constitute a support for the acoustic panel 17.

[0056] With reference to [Fig. 2], each acoustic panel 17 may have a sandwich structure. Each acoustic panel 17 comprises at least one honeycomb structure 18, and advantageously a first skin 19 and a second skin 20. The honeycomb structure 18 is sandwiched between the first and second skins 19, 20. When the acoustic panel 17 is mounted in the turbomachine 1, the second skin 20 is internal and the first skin 19 is external. The second skin 20 faces the secondary vein v2, and the first skin 19 is located opposite the secondary vein v2. The first skin 19 is, in particular, located opposite the support.

[0057] The first and second skins 19, 20 advantageously comprise a composite material. The composite material comprises, for example, a polymer matrix and fibers embedded in the matrix. The matrix polymer is, for example, a thermoset such as an epoxy resin or a thermoplastic such as polyethylene, polypropylene, or a fluoropolymer. The fibers are, for example, carbon, polyamide, polyester, or glass fibers.

[0058] The first and second skins 19, 20 have a thickness for example between 1 mm and 10 mm.

[0059] The second skin 20 includes holes (not shown) for the passage of sound waves. The holes are regularly distributed over the second skin 20. The holes are through holes and have a diameter, for example, between 0.5 mm and 2 mm.

[0060] The honeycomb structure 18 comprises, for example, a polymeric or metallic material. The metallic material is, for example, aluminum, in particular an aluminum alloy selected from the 3000, 5000, or 6000 series. The polymeric material is, for example, selected from thermoplastics such as polyphenylene sulfide (PPS), polyetherimide (PEI), polyetheretherketone (PEEK), or thermosets such as epoxy or phenolic resins.

[0061] The alveolar structure 18 has a general shape, for example pentagonal, and advantageously with rounded edges or corners. It extends along an elongation axis XI between a first end 18a and a second opposite end 18b.

[0062] Advantageously, the honeycomb structure 18 has a thickness el of between 5 mm and 100 mm, and more advantageously between 10 mm and 40 mm. The thickness el of the honeycomb structure 18 is measured along a first direction dl which is parallel to the propagation of sound waves in the honeycomb structure 18. This first direction dl is perpendicular to the elongation axis XI of the honeycomb structure 18. Also, this first direction dl is perpendicular to the longitudinal axis A of the turbomachine 1 when the acoustic panel 17 is mounted in the turbomachine 1.

[0063] The alveolar structure 18 comprises alveolar cells 21. The alveolar cells 21 are adjacent to each other.

[0064] As more clearly seen in [Fig. 3], each alveolar cell 21 has, for example, a polygonal cross-section, for example pentagonal or hexagonal. The cross-section of the alveolar cells 21 differs advantageously from one alveolar cell 21 to another. Thus, some alveolar cells 21 have a substantially triangular shape, other alveolar cells 21 have a pentagonal shape, and other alveolar cells 21 have a parallelepiped, hexagonal, or any other shape.

[0065] Among the alveolar cells 21, at least some of them, for example, have a different size from each other. The size of the cells The alveolar 21 size is between 9 mm and 25 mm. This allows for an increase in the number of alveolar 21 cells in areas where high compressive strength is required, and a reduction in the number of alveolar 21 cells outside these areas by offering larger alveolar 21 cells.

[0066] Each alveolar cell 21 is delimited by peripheral walls 22. The peripheral walls 22 extend over the entire thickness el of the alveolar structure 18. The peripheral walls 22 have a variable thickness. Indeed, the thickness of a peripheral wall 22 can vary relative to the thickness of an adjacent peripheral wall 22 depending on the required mechanical strength. The peripheral walls 22 may be perforated. This allows for the drainage of fluids within the alveolar structure 18.

[0067] Each peripheral wall 22 can thus comprise at least one orifice 23, and for example a plurality of orifices 23. Each orifice 23 can have a general circular, oblong, polygonal, or any other shape. Each orifice has a dimension, for example, between 2 mm and 7 mm, depending on the pressure of the fluid to be drained. Each orifice 23 has an axis that extends, for example, in a direction perpendicular to the first direction dl.

[0068] Some of the peripheral walls 22 can be curved. This allows the shape of the alveolar cells 21 to be adapted to the general shape of the alveolar structure 18.

[0069] At least two of the peripheral walls 22 can form beams 22a. The beams 22a have a thickness e2, measured along a direction perpendicular to the elongation axis XI, greater than the thickness of the other peripheral walls 22. Each of these beams 22a has at least one hole 22b. Each hole 22b has an axis extending along the first direction dl. Each hole 22b therefore has an axis perpendicular to the axis of the holes 23 in the other peripheral walls 22.

[0070] Each alveolar cell 21 further comprises a cavity 24 delimited by the peripheral walls 22. The cavity 24 of each alveolar cell 21 extends over the entire thickness el of the alveolar structure 18.

[0071] With reference to [Fig. 4], the alveolar structure 18 may comprise at least one septum 25 located in a cavity 24 of an alveolar cell 21. Advantageously, each cavity 24 is equipped with at least one septum 25. Advantageously, each cavity 24 is equipped with a plurality of septa 25. Each septum 25 comprises a porous membrane for the passage of sound waves. The porous membrane has, for example, perforations for the passage of sound waves. The perforations are regularly distributed over the membrane. Each perforation has a dimension, for example, between 0.5 mm and 1.5 mm.

[0072] Advantageously, each cavity 24 comprises two septa 25. According to this example, each septum 25 can define, with a transverse wall 22, a passage 26 for sound waves into the cavity 24, the passages 26 being offset along a direction perpendicular to the direction dl of sound wave propagation. This makes it possible to form a baffle in the cavities 24 and thus increase the length of the path traveled by the sound waves through the acoustic cells 21. The absorption of sound waves by the acoustic panel 17 is thus improved.

[0073] The alveolar structure 18 has an alveolar cell density 21 between 1500 / m2 and 11000 / m2.

[0074] The honeycomb structure 18 further includes a border 27. The border 27 extends over the entire thickness el of the honeycomb structure 18. It thus extends along the direction dl parallel to the direction of propagation of sound waves in the acoustic panel 17. The border 27 borders the honeycomb cells 21 or surrounds the honeycomb cells 21.

[0075] The rim 27 has a first face 27a connected to a second face 27b by a first edge 27c, and the second face 27b is connected to a third face 27d by a second edge 27e. Advantageously, the first and third faces 27a, 27d are connected by a V-shaped vertex 27e. The first face 27b is opposite the vertex 27e along the elongation axis XL. Advantageously, the first and third faces 27a, 27d extend from the second 27b in a direction parallel to the elongation axis XI and meet at the vertex 27e.

[0076] According to one example, the rim 27 has openings 28. The openings 28 are, for example, located on the first face 27a or the third face 27d. The openings 28 are aligned along the direction dl. Preferably, the openings 28 are located in a median plane perpendicular to the elongation axis XI and parallel to the first direction dl.

[0077] The honeycomb structure 18 is monobloc. It is advantageously formed from the same material and in one piece. The honeycomb structure 18 is produced by additive manufacturing. The additive manufacturing process is, for example, a filament deposition process, also known by the English acronym FDM for "fused deposition modeling", or a stereolithography process, also known by the acronym SLA, or a selective laser sintering process, also known by the English acronym SLS for "selective laser sintering", or a laser beam melting process, also known by the English acronym LBM for "laser beam melting".

[0078] Each acoustic panel 17 is attached and fixed to the support of the turbomachine 1, such as the blower housing 11 and / or the intermediate housing 12 and / or the nacelle 16. In order to ensure the connection of each acoustic panel 17 to its support, each acoustic panel 17 further includes a connecting member 29.

[0079] The connecting member 29 is located in the middle of the alveolar structure 18, the middle being defined as the point located at an equal distance from the first and third face 27a, 27d and at an equal distance from the second face 27b and the vertex 27e.

[0080] The connecting member 29 extends along and around a central axis X2. The central axis X2 is parallel to the first direction dl and therefore perpendicular to the elongation axis XL. The connecting member 29 comprises an attachment portion 30 and an anchoring portion 31. Preferably, the central axis X2 passes through the middle of the alveolar structure 18.

[0081] The attachment portion 30 extends projecting from the alveolar structure 18 or the first skin 19. The attachment portion 30 comprises a circular base 32 and a cap 33 extending projecting from the circular base 32.

[0082] The yoke 33 has a general U-shape. It comprises a first arm 34 and a second arm 35 parallel to the first arm 34. The first and second arms 35 extend along the first direction d1. The first arm 34 has a first opening 34a and the second arm 35 has a second opening 35a. The first and second openings 34a, 35a have an axis that extends perpendicularly to the central axis X2.

[0083] The circular base 32 is annular and centered on the central axis X2.

[0084] The anchoring portion 31 passes through the thickness el of the alveolar structure 18. In Referring to [Fig. 4], the anchoring portion 31 has a frustoconical annular internal surface 36. This internal surface 36 is centered on the axis of the circular base 32. It flares out in the opposite direction to the attachment portion 30. The anchoring portion 31 is hollow. Thus, the internal surface 36 of the anchoring portion 31 defines a frustoconical annular internal space 37. This internal space 37 is devoid of alveolar cells 21.

[0085] The alveolar cells 21 are distributed around the connecting organ 29. They are thus located around the circular base 32.

[0086] According to the invention, the connecting element 29 forms a single unit with the honeycomb structure 18. This single unit is preferably made of the same material. The connecting element 29 and the honeycomb structure 18 are thus made from a single piece of material. The material of the connecting element 29 and / or the honeycomb structure 18 is preferably a metallic material or a polymeric material. The metallic material is, for example, aluminum, in particular an aluminum alloy selected from the 3000, 5000, or 6000 series. The polymeric material is, for example, selected from thermoplastics such as polyphenylene sulfide (PPS), polyetherimide (PEI), polyetheretherketone (PEEK), or thermosetting materials such as epoxy or phenolic resins.

[0087] The connecting element 29 is preferably produced by additive manufacturing. It is produced simultaneously with the honeycomb structure 18.

[0088] Thanks to this feature, the acoustic panel 17 is free of a connecting rod to link the connecting element 29 to the honeycomb structure 18. This reduces the compressive forces in the honeycomb structure 18, allowing for a reduction in the density of the honeycomb cells 21. With a reduced number of honeycomb cells 21, the acoustic panel 17 is less expensive, simpler, and lighter. Furthermore, by reducing the number of honeycomb cells 21, the size of each honeycomb cell 21 is increased, thus improving the acoustic surface area of ​​the honeycomb structure 18. The acoustic performance of the acoustic panel 17 is therefore enhanced.

[0089] Also, thanks to the additive manufacturing of the connecting element 29 with the alveolar structure 18, it is possible to produce the alveolar cells 21 as close as possible to the connecting element 29. It is also possible to adapt the configuration of the alveolar cells 21, for example, by producing thicker peripheral walls 22 in the area of ​​the connecting element 29 in order to increase compressive strength in highly stressed areas. Conversely, the less stressed areas of the alveolar structure 18 can have larger alveolar cells 21, reducing the overall density of the alveolar cells 21.

[0090] Furthermore, thanks to the invention, it is possible to overcome the phenomenon of marking of the first and second skins 19, 20 which can appear during a co-molding of the acoustic panel 17 in composite material, a phenomenon known as "telegraphing".

[0091] Also, the connecting element 29 integrated into the alveolar structure 18 makes it possible to facilitate possible drilling operations since the drilling areas can be pre-located.

[0092] Thanks to additive manufacturing, it is also easier to integrate the septa 25 into the alveolar structure 18.

Claims

Demands

1. Acoustic panel (17) for an aircraft turbomachine (1), the acoustic panel (17) comprising: - a honeycomb structure (18) comprising a plurality of honeycomb cells (21), and - a connecting member (29) for connecting the acoustic panel (17) to a support (11, 12) of the turbomachine (1), the connecting member (29) comprising an anchoring portion (31) passing through a thickness (el) of the honeycomb structure (18) and an attachment portion (30) extending projecting from the honeycomb structure (18), characterized in that the honeycomb structure (18) and the connecting member (29) form a single unit.

2. Acoustic panel according to the preceding claim, characterized in that the honeycomb structure (18) and / or the connecting member (29) comprise a metallic or polymeric material.

3. Acoustic panel according to any one of the preceding claims, characterized in that the honeycomb structure (18) and the connecting member (29) are made by additive manufacturing.

4. Acoustic panel according to any one of the preceding claims, characterized in that the alveolar structure (18) comprises at least one septum (25) arranged in at least one of the alveolar cells (21).

5. Acoustic panel according to any one of the preceding claims, characterized in that the connecting member (29) is located in the middle of the honeycomb structure (18).

6. Acoustic panel according to any one of the preceding claims, characterized in that the alveolar cells (21) are distributed around the connecting member (29).

7. Acoustic panel according to any one of the preceding claims, characterized in that the attachment portion (30) comprises a screed (33) and a circular base (32) from which the screed (33) extends in projection.

8. Acoustic panel according to any one of the preceding claims, characterized in that the anchoring portion (31) has a frustoconical internal surface (36).

9. Acoustic panel according to the preceding claim, characterized in that the internal surface (36) delimits an internal space (37).

10. Acoustic panel according to any one of the preceding claims, characterized in that the alveolar cells (21) have a plurality of shapes in cross-section, for example polygonal, hexagonal.

11. Acoustic panel according to any one of the preceding claims, characterized in that the alveolar structure (18) comprises a border (27) situated around the alveolar cells (21).

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