WO2022117968A1 - Variable-height multicellular acoustic-attenuation panel - Google Patents

Variable-height multicellular acoustic-attenuation panel Download PDF

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Publication number
WO2022117968A1
WO2022117968A1 PCT/FR2021/052186 FR2021052186W WO2022117968A1 WO 2022117968 A1 WO2022117968 A1 WO 2022117968A1 FR 2021052186 W FR2021052186 W FR 2021052186W WO 2022117968 A1 WO2022117968 A1 WO 2022117968A1
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WO
WIPO (PCT)
Prior art keywords
acoustic
cells
rows
acoustic cells
row
Prior art date
Application number
PCT/FR2021/052186
Other languages
French (fr)
Inventor
Marc VERSAEVEL
Davi SILVA DE VASCONCELLOS
Thomas VANDELLOS
Eric Conete
Original Assignee
Safran Nacelles
Safran Ceramics
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Safran Nacelles, Safran Ceramics filed Critical Safran Nacelles
Publication of WO2022117968A1 publication Critical patent/WO2022117968A1/en

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Classifications

    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
    • B32B3/10—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material
    • B32B3/12—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material characterised by a layer of regularly- arranged cells, e.g. a honeycomb structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/14—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by a layer differing constitutionally or physically in different parts, e.g. denser near its faces
    • B32B5/145—Variation across the thickness of the layer
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02K—JET-PROPULSION PLANTS
    • F02K1/00—Plants characterised by the form or arrangement of the jet pipe or nozzle; Jet pipes or nozzles peculiar thereto
    • F02K1/78—Other construction of jet pipes
    • F02K1/82—Jet pipe walls, e.g. liners
    • F02K1/827—Sound absorbing structures or liners
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/162—Selection of materials
    • G10K11/168—Plural layers of different materials, e.g. sandwiches
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
    • B32B2262/10—Inorganic fibres
    • B32B2262/105—Ceramic fibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
    • B32B2262/10—Inorganic fibres
    • B32B2262/106—Carbon fibres, e.g. graphite fibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/10—Properties of the layers or laminate having particular acoustical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
    • B64D33/00—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for
    • B64D33/02—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for of combustion air intakes
    • B64D2033/0206—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for of combustion air intakes comprising noise reduction means, e.g. acoustic liners
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
    • B64D33/00—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for
    • B64D33/04—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for of exhaust outlets or jet pipes
    • B64D33/06—Silencing exhaust or propulsion jets
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2250/00—Geometry
    • F05D2250/70—Shape
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2260/00—Function
    • F05D2260/96—Preventing, counteracting or reducing vibration or noise
    • F05D2260/963—Preventing, counteracting or reducing vibration or noise by Helmholtz resonators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2300/00—Materials; Properties thereof
    • F05D2300/60—Properties or characteristics given to material by treatment or manufacturing
    • F05D2300/603—Composites; e.g. fibre-reinforced
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T50/00—Aeronautics or air transport
    • Y02T50/60—Efficient propulsion technologies, e.g. for aircraft

Definitions

  • the present invention relates to the general field of acoustic attenuation structures. It relates more particularly to acoustic attenuation structures or panels used to reduce the noise produced in aircraft engines such as in gas turbines or their exhaust.
  • acoustic attenuation structures In order to reduce the noise in the exhaust ducts of gas turbines, it is known to provide the surfaces of the elements delimiting these ducts with acoustic attenuation structures. These structures typically consist of a first multi-perforated skin permeable to the acoustic waves that it is desired to attenuate and of a second solid reflecting skin, a core, such as a honeycomb or a honeycomb structure, being placed between these two skins. In a well-known manner, the cores of such structures form Helmholtz-type resonators which make it possible to attenuate the acoustic waves produced in the conduit within a certain range of frequencies.
  • acoustic attenuation structures are preferably made of composite material (fibrous reinforcement densified by a matrix) rather than metallic material.
  • the acoustic cells are limited to shapes of simple cells such as those of the cells of a classic N-type IDA® structure.
  • the cells located upstream and downstream will be of variable height because it is necessary to manage the passage from the non-acoustic zones (monolithic skins) to the acoustic zone. . This is particularly true for parts made of composite materials where these zones of variable height are called chamfers.
  • chamfers are short when the panel is thin (20mm to 30mm) but for significant heights (for example of the order of 150mm to 250mm), the majority of the acoustic zone of the exhaust is made up of zones of chamfers. There is therefore only a short central zone at the desired constant height, the rest being of variable height experienced, and of height less than the nominal target acoustic height.
  • the acoustic cells have variable heights between them, for example when the cells present at the level of a chamfer have a height lower than the height of the cells present outside the chamfer, a shift in the frequency range of the sound waves is observed. processed, this offset corresponding to an increase in the processed frequencies.
  • the acoustic emissions at the level of the exhaust part in the new architectures of aeronautical engines have frequencies included in the low frequencies.
  • Combustion noises related to pressure fluctuations in the combustion chamber of the engine have frequencies typically between 400 Hz and 1000 Hz.
  • the present invention proposes a multicellular acoustic attenuation panel comprising several rows of acoustic cells, each row extending in a circumferential direction, each acoustic cell being delimited by a wall extending in height in a radial direction, characterized in that at least the acoustic cells of one or more first rows of cells have a cross-section greater than the cross-section of the acoustic cells of one or more second rows of acoustic cells and in that said acoustic cells of the first row or rows of acoustic cells have a wall height less than the wall height of the acoustic cells of the second row or rows of acoustic cells.
  • wall height we mean a height which can be constant for a given acoustic cell or an average height of an acoustic cell when the wall height of the cell varies.
  • the acoustic cells of the first row or rows of acoustic cells have an internal volume equivalent to the internal volume of the acoustic cells of the second row or rows of acoustic cells.
  • the frequency shift between all the acoustic cells is thus reduced to a minimum.
  • equivalent internal volume is meant here a difference in volume of less than 30%, preferably less than 10%, and more preferably a difference in volume of zero.
  • each acoustic cell has a volume configured to capture sound waves having a frequency between 400 Hz and 1000 Hz.
  • the rows of acoustic cells are juxtaposed to each other from upstream to downstream in an axial direction, the row of acoustic cells present upstream of the plurality of rows of acoustic cells and the row of acoustic cells present downstream of the plurality of rows of acoustic cells have a lower wall height than the wall height of the acoustic cells of the other row(s) of cells.
  • the invention also relates to an acoustic attenuation structure of at least partially annular or semi-annular shape comprising an acoustic skin and a closing skin delimiting between them an annular or semi-annular volume comprising a multicellular acoustic attenuation panel according to the invention.
  • the acoustic skin, the closure skin and the multicellular acoustic attenuation panel are made of composite material comprising a fibrous reinforcement densified by a matrix.
  • the acoustic skin and the closure skin are made of composite material comprising a fibrous reinforcement densified by a matrix, while the multicellular acoustic attenuation panel is made of metallic material.
  • the invention also relates to:
  • an aeronautical gas turbine engine comprising an ejection cone according to the invention or an ejection nozzle according to the invention.
  • Figure 1 is a schematic perspective view of an exhaust cone of an aeronautical engine exhaust system in accordance with one embodiment of the invention
  • Figure 2 is a schematic sectional view of the acoustic attenuation structure present in the upstream part of the ejection cone of Figure 1
  • Figure 3 is another schematic sectional view of the acoustic attenuation structure present in the upstream part of the ejection cone of Figure 1
  • Figure 4 is a schematic top view showing the section of the acoustic cells of the acoustic attenuation structure present in the upstream part of the exhaust cone of Figure 1,
  • Figure 5 is a schematic perspective view of an exhaust cone of an aeronautical engine exhaust system according to another embodiment of the invention.
  • Figure 6 is a schematic top view showing the section of the acoustic cells of the acoustic attenuation structure present in the upstream part of the exhaust cone of Figure 5.
  • a particular but non-exclusive field of application of the invention is that of the exhaust systems of aeronautical gas turbine engines such as those used in airplanes or helicopters. These exhaust systems comprise in particular a nozzle and an ejection cone defining between them an ejection channel for the exhaust gases.
  • FIG. 1 shows an exhaust cone 100 of a gas turbine engine exhaust system in accordance with one embodiment of the invention.
  • the ejection cone 100 has a shape of revolution around an axial direction D and comprises, from upstream to downstream in the axial direction D, an upstream part 110 incorporating an acoustic attenuation structure 200 and a downstream part 120 finalizing the aerodynamic line.
  • the ejection cone is here made of composite material, for example ceramic matrix composite (CMC) for reasons of temperature resistance.
  • CMC ceramic matrix composite
  • the end of the upstream part 110 of the cone has a metal fixing flange 130 forming part of the motor casing (not shown in FIG. 1) or intended to be fixed on the latter.
  • the parts in CMC material are formed by a fibrous reinforcement in refractory fibers (carbon or ceramic) which is densified by a ceramic matrix, in particular carbide, nitride, refractory oxide,...
  • CMC materials are Oxide/Oxide materials (oxide fiber and oxide matrix such as alumina, mulite, alumino-silicate matrix), C-SiC (carbon fiber reinforcement and silicon carbide matrix), SiC-SiC materials and CC/SiC materials (mixed carbon/silicon carbide matrix).
  • Oxide/Oxide materials oxide fiber and oxide matrix such as alumina, mulite, alumino-silicate matrix
  • C-SiC carbon fiber reinforcement and silicon carbide matrix
  • SiC-SiC materials and CC/SiC materials mixed carbon/silicon carbide matrix
  • the upstream part 110 of the ejection cone 100 comprises an acoustic attenuation structure 200 which is constituted in the example described here by a structural internal skin 210, a multicellular acoustic attenuation panel 220 and an acoustic external skin 230.
  • outer skin 230 delimits the inner surface of the exhaust gas flow path.
  • the outer skin 230 also has perforations 231 to allow the entry of the acoustic waves to be attenuated into the attenuation structure while the inner skin 210 is solid so as to reflect these waves.
  • the multicellular panel 220 comprises several rows of acoustic cells each extending along a circumferential direction (D c ).
  • the multicellular panel 220 comprises five rows of acoustic cells 240, 250, 260, 270 and 280 each extending in an annular manner in a circumferential direction D c , the rows of acoustic cells 240, 250, 260 , 270 and 280 being juxtaposed with each other from upstream to downstream in the axial direction D A , the row 240 being located the most upstream while the row 280 is located the most downstream of the rows of acoustic cells.
  • Each acoustic cell is delimited by a wall which extends in height in a radial direction DR between the inner and outer skins 210 and 230 and in a circumferential direction D c .
  • the acoustic cells 240, 250, 260, 270 and 280 are each respectively delimited by a wall 241, 251, 261, 271 and 281 so as to form boxes capable of damping the acoustic waves which it is desired to attenuate.
  • the wall delimiting the acoustic cells of a row for example the wall 241 , has a common portion with the wall of the acoustic cells of the adjacent row, for example with the wall 251 .
  • the acoustic cells 240, 250, 260, 270 and 280 each respectively have a wall height H 241 , H 251 , H 26 I , H 2 71 and H 2 8i . More specifically, the most upstream acoustic cells 240 and the acoustic cells 280 furthest downstream respectively have wall heights H 2 4i and H 281 lower than the wall heights H 251 , H 26 iet H 271 respectively of the acoustic cells 250, 260 and 270 which are located between the acoustic cells 240 and 280.
  • the wall heights H 241 , H 251 , H 26 I, H 271 and H 28 I which are parallel to the radial direction D R vary depending on whether one moves in the axial direction D A of the ejection cone 100 in particular because of the variable profile of the internal skins 210 and external skin 230 defining the shape of the acoustic attenuation structure 200.
  • the wall heights H 241 and H 28 I are significantly lower than the wall heights H 25 I, H 26 I and H 27 I due to the presence of an upstream chamfer CAM and a downstream chamfer CAV-
  • the acoustic attenuation structure 200 comprising the internal and external skins 210 and 230 being made of composite material, it is difficult to form sudden changes in slopes in particular at the level of the internal skin so as to form a recess allowing to immediately obtain a suitable housing depth for the acoustic cells.
  • the wall heights of each row of acoustic cells being variable depending on whether one moves in an axial direction D A , in particular at the level of the chamfers C A M and C A v, the wall heights H 241 , H 251 , H 26 I, H 271 and H 281 described here correspond to an average wall height for each acoustic cell.
  • the acoustic cells of one or more rows of cells having a wall height lower than the wall height of the acoustic cells of one or more other rows have a cross-section greater than the cross-section of the acoustic cells from where other rows of cells.
  • the rows of acoustic cells 240 and 280 which have wall heights H 241 and H 281 significantly lower than the wall heights H 25 I, H 26 I and H 27 I of the rows of acoustic cells 250, 260 and 270 are formed so as to present sections S 240 and S 28 o in cross section greater than the cross sections S250, S 26 o and S 270 of the acoustic cells 250, 260 and 270 (FIG. 4).
  • the section of the acoustic cells is enlarged by increasing their length in the axial direction D A , the width of the cells in the circumferential direction D c being constant between the rows of acoustic cells.
  • the acoustic cells 240 and 280 have lengths L 240 and L 280 greater than the lengths L 25 o, L 26 o and L 27 o of the acoustic cells 250, 260 and 270 in the axial direction D A .
  • the section of the acoustic cells having a lower height can of course be adapted by increasing both the length and the width of the cells.
  • the acoustic cells 240 and 280 have wall heights H 24 I and H 28 I of 95 mm while the acoustic cells 250, 260 and 270 have wall heights H 251 , H 26 I and H 271 of 150 mm.
  • the acoustic cells 240 and 280 have lengths L 240 and L 280 twice as large as the lengths L 25 o, L 26 o and L 270 of the acoustic cells 250, 260 and 270 according to the axial direction D A .
  • the acoustic cells 240 and 280 have a volume of approximately 3.7 liters while the acoustic cells 250, 260 and 270 have a volume of approximately 2.9 liters.
  • the frequency shift of the attenuation peak between the acoustic cells 240 and 280, on the one hand, and the acoustic cells 250, 260 and 270, on the other hand, is only 100Hz.
  • the acoustic cells may have different geometries from those represented in FIG. 4.
  • the cells may in particular have polygonal, rectangular, spherical, etc. shapes.
  • the choice of the dimension or dimensions to be increased in order to adapt the section of cells having a lower height depends on the geometry of the cells.
  • Figure 5 shows another example of an exhaust cone 400 of a gas turbine engine exhaust system in accordance with one embodiment of the invention which comprises as previously described has a shape of revolution around an axial direction D and comprises, from upstream to downstream along the axial direction D A , an upstream part 410 integrating an acoustic attenuation structure 300 and a downstream part 420 finalizing the aerodynamic line.
  • the ejection cone is here made of a composite material, for example of a ceramic matrix composite (CMC) for temperature resistance reasons.
  • CMC ceramic matrix composite
  • the upstream part 410 of the ejection cone 400 comprises an acoustic attenuation structure 300 which is constituted in the example described here by a structural internal skin 310, a multicellular acoustic attenuation panel 320 and an acoustic external skin 330 delimiting the internal surface of the exhaust gas flow path and also having perforations 331 in order to allow the entry of the acoustic waves to be attenuated into the attenuation structure while the internal skin 310 is solid so as to reflect these waves.
  • the multicellular panel 320 comprises several rows of acoustic cells each extending along a circumferential direction (D c ).
  • the multicellular panel 320 comprises five rows of acoustic cells 340, 350, 360, 370 and 380 each extending in an annular manner in a circumferential direction D c , the rows of acoustic cells 340, 350, 360 , 370 and 380 being juxtaposed with each other from upstream to downstream in the axial direction D A , the row 340 being located the most upstream while the row 380 is located the most downstream of the rows of acoustic cells.
  • the 340, 350, 360, 370 and 380 acoustic cells differ from the 240, 250, 260, 270 and 280 acoustic cells previously described in that they have a rectangular shape.
  • Each acoustic cell is delimited by a wall which extends in height in a radial direction D R between the inner and outer skins 310 and 330 and in the circumferential direction D c . More specifically, the acoustic cells 340, 350, 360, 370 and 380 are each respectively delimited by two adjacent walls 341, 351, 361, 371, 381 and 391 in the circumferential direction D c and by two adjacent walls 321 in the axial direction D so as to form boxes capable of damping the acoustic waves which it is desired to attenuate.
  • the acoustic cells of or the rows of cells having a wall height lower than the wall height of the cells acoustic cells of one or more other rows have a cross section greater than the cross section of the acoustic cells of the other row or rows of cells.
  • the rows of acoustic cells 340 and 380 which have wall heights significantly lower than the wall heights of the rows of acoustic cells 350, 360 and 370 are formed so as to present sections S 340 and S 38 o in cross section greater than the cross sections S 35 o, S 36 o and S 37 o of the acoustic cells 350, 360 and 370 (FIG. 6).
  • the section of the acoustic cells is enlarged by increasing their length in the axial direction D A .
  • the acoustic cells 240 and 280 have lengths L 240 and L 28 o greater than the lengths L 250 , L 26 o and L 270 of the acoustic cells 250, 260 and 270 in the axial direction D A .
  • the section of the acoustic cells having a lower height can of course be adapted by increasing both the length and the width of the cells.
  • the acoustic attenuation structure and, consequently, the multicellular panel which composes it has an at least partially annular or semi-annular shape.
  • the impact of the reduction in wall height on the overall volume of each cell is limited so as to have acoustic cells which have an equivalent internal volume in order to reduce as much as possible the frequency shift between all the acoustic cells.
  • equivalent internal volume is meant here the volume difference between the acoustic cells of one row relative to another row, this volume difference being less than 30%, preferably less than 10%, and more preferably nil or close to 0%. This preserves for acoustic cells with a lower wall height the ability to attenuate low frequencies.
  • the acoustic cells of upper cross-sectional section and of lower wall height have an internal volume equivalent to the internal volume of the other acoustic cells.
  • the frequency shift in the acoustic attenuation between the different rows of acoustic cells is minimized.
  • the acoustic attenuation structure according to the invention can correspond to a part of revolution and be produced in a single part or from a plurality of annular sectors assembled with each other.
  • the acoustic attenuation structure of the invention can in particular be integrated into an aeronautical engine exhaust cone as described above and/or even into an ejection nozzle of an aeronautical engine exhaust system.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Building Environments (AREA)
  • Exhaust Silencers (AREA)

Abstract

A multicellular acoustic-attenuation panel (220) comprises several rows of acoustic cells (240, 250, 260, 270, 280) each extending in a circumferential direction (DC), each acoustic cell being delimited by a wall (241, 251, 261, 271, 281) extending height-wise in a radial direction (DR). Acoustic cells (240, 280) of some rows of cells have a cross-sectional area greater than the cross-sectional area of the acoustic cells of other rows of cells (250, 260, 270) and a wall height that is less than the wall height of the acoustic cells of the other rows of cells.

Description

Description Description
Titre de l'invention : PANNEAU MULTICELLULAIRE D'ATTENUATION ACOUSTIQUE A HAUTEUR VARIABLE Title of the invention: MULTICELLULAR SOUND ATTENUATION PANEL WITH VARIABLE HEIGHT
Domaine Technique Technical area
La présente invention se rapporte au domaine général des structures d'atténuation acoustiques. Elle concerne plus particulièrement les structures ou panneaux d'atténuation acoustique utilisés pour réduire les bruits produits dans les moteurs d’avion comme dans les turbines à gaz ou échappement de ceux-ci. The present invention relates to the general field of acoustic attenuation structures. It relates more particularly to acoustic attenuation structures or panels used to reduce the noise produced in aircraft engines such as in gas turbines or their exhaust.
Technique antérieure Prior technique
Afin de réduire le bruit dans les conduits d'échappement des turbines à gaz, il est connu de doter les surfaces des éléments délimitant ces conduits de structures d'atténuation acoustique. Ces structures sont typiquement constituées d'une première peau multi-perforée perméable aux ondes acoustiques que l'on souhaite atténuer et d'une deuxième peau pleine réfléchissante, une âme, tel qu'un nid d'abeille ou une structure alvéolaire, étant disposée entre ces deux peaux. De façon bien connue, les âmes de telles structures forment des résonateurs de type Helmholtz qui permettent d'atténuer dans une certaine gamme de fréquences les ondes acoustiques produites dans le conduit. In order to reduce the noise in the exhaust ducts of gas turbines, it is known to provide the surfaces of the elements delimiting these ducts with acoustic attenuation structures. These structures typically consist of a first multi-perforated skin permeable to the acoustic waves that it is desired to attenuate and of a second solid reflecting skin, a core, such as a honeycomb or a honeycomb structure, being placed between these two skins. In a well-known manner, the cores of such structures form Helmholtz-type resonators which make it possible to attenuate the acoustic waves produced in the conduit within a certain range of frequencies.
Dans des domaines techniques où le gain de masse est une préoccupation constante, comme en aéronautique, les structures d'atténuation acoustique sont de préférence réalisées en matériau composite (renfort fibreux densifié par une matrice) plutôt qu’en matériau métallique. In technical fields where mass gain is a constant concern, such as aeronautics, acoustic attenuation structures are preferably made of composite material (fibrous reinforcement densified by a matrix) rather than metallic material.
Le document US 9 631 519 décrit une structure d’atténuation acoustique dont les peaux et l’âme sont formés à partir de matériaux composites permettant un gain de masse par rapport aux matériaux métalliques habituellement utilisés. Document US 9,631,519 describes an acoustic attenuation structure whose skins and core are formed from composite materials allowing a saving in mass compared to the metallic materials usually used.
Cependant, dans les structures d’atténuation acoustique de l’art antérieur, les cellules acoustiques sont limitées à des formes de cellules simples telle que celles des alvéoles d’une structure classique de type N IDA®. En général, on cherche à avoir une hauteur de cellules acoustiques constante sur la longueur de la pièce. Cela est possible pour des hauteurs faibles (par exemple de l’ordre de 20mm à 30mm), notamment pour les pièces métalliques. Cependant, pour des hauteurs importantes (par exemple plus de 50mm), les cellules situées à l'amont et à l'aval seront de hauteur variable car il est nécessaire de gérer le passage des zones non acoustiques (peaux monolithiques) à la zone acoustique. C'est particulièrement vrai pour des pièces réalisées en matériaux composite où ces zones de hauteur variable sont appelées chanfreins. Ces chanfreins sont courts quand le panneau est mince (20mm à 30mm) mais pour des hauteurs importantes (par exemple de l’ordre de 150mm à 250mm), la majorité de la zone acoustique de l'échappement se retrouve constituée de zones de chanfreins. On n'a donc qu'une courte zone centrale à la hauteur constante voulue, le reste étant de hauteur variable subie, et de hauteur inférieure à la hauteur acoustique cible nominale. However, in the acoustic attenuation structures of the prior art, the acoustic cells are limited to shapes of simple cells such as those of the cells of a classic N-type IDA® structure. In general, we seek to have a constant height of acoustic cells over the length of the room. This is possible for low heights (for example of the order of 20mm to 30mm), in particular for metal parts. However, for significant heights (for example more than 50mm), the cells located upstream and downstream will be of variable height because it is necessary to manage the passage from the non-acoustic zones (monolithic skins) to the acoustic zone. . This is particularly true for parts made of composite materials where these zones of variable height are called chamfers. These chamfers are short when the panel is thin (20mm to 30mm) but for significant heights (for example of the order of 150mm to 250mm), the majority of the acoustic zone of the exhaust is made up of zones of chamfers. There is therefore only a short central zone at the desired constant height, the rest being of variable height experienced, and of height less than the nominal target acoustic height.
Lorsque les cellules acoustiques présentent entre elles des hauteurs variables, par exemple lorsque les cellules présentes au niveau d’un chanfrein ont une hauteur inférieure à la hauteur des cellules présentes en dehors du chanfrein, on observe un décalage de la plage de fréquences des ondes sonores traitées, ce décalage correspondant à une augmentation des fréquences traitées. When the acoustic cells have variable heights between them, for example when the cells present at the level of a chamfer have a height lower than the height of the cells present outside the chamfer, a shift in the frequency range of the sound waves is observed. processed, this offset corresponding to an increase in the processed frequencies.
Or, les émissions acoustiques au niveau de la partie d’échappement dans les nouvelles architectures de moteurs aéronautiques ont des fréquences comprises dans des basses fréquences. Les bruits de combustion liés aux fluctuations de pression dans la chambre de combustion du moteur ont des fréquences comprises typiquement entre 400 Hz et 1000Hz. However, the acoustic emissions at the level of the exhaust part in the new architectures of aeronautical engines have frequencies included in the low frequencies. Combustion noises related to pressure fluctuations in the combustion chamber of the engine have frequencies typically between 400 Hz and 1000 Hz.
Il existe, par conséquent, un besoin pour permettre de contrôler la plage de fréquence des ondes sonores à atténuer, et ce avec des cellules acoustiques de hauteurs variables dans la zone de traitement acoustique. There is therefore a need to make it possible to control the frequency range of the sound waves to be attenuated, and this with acoustic cells of variable heights in the acoustic treatment zone.
Exposé de l’invention Disclosure of Invention
A cet effet, la présente invention propose un panneau multicellulaire d’atténuation acoustique comprenant plusieurs rangées de cellules acoustiques, chaque rangée s’étendant suivant une direction circonférentielle, chaque cellule acoustique étant délimitée par une paroi s’étendant en hauteur suivant une direction radiale, caractérisé en ce qu’au moins les cellules acoustiques d’une ou plusieurs premières rangées de cellules présentent une section en coupe transversale supérieure à la section en coupe transversale des cellules acoustiques d’une ou plusieurs deuxièmes rangées de cellules acoustiques et en ce que lesdites cellules acoustiques de la ou les premières rangées rangée de cellules acoustiques présentent une hauteur de paroi inférieure à la hauteur de paroi des cellules acoustiques de la ou les deuxièmes rangées de cellules acoustiques. To this end, the present invention proposes a multicellular acoustic attenuation panel comprising several rows of acoustic cells, each row extending in a circumferential direction, each acoustic cell being delimited by a wall extending in height in a radial direction, characterized in that at least the acoustic cells of one or more first rows of cells have a cross-section greater than the cross-section of the acoustic cells of one or more second rows of acoustic cells and in that said acoustic cells of the first row or rows of acoustic cells have a wall height less than the wall height of the acoustic cells of the second row or rows of acoustic cells.
Par « hauteur de paroi », on entend une hauteur qui peut être constante pour une cellule acoustique donnée ou une hauteur moyenne d’une cellule acoustique lorsque la hauteur de paroi de la cellule varie. By “wall height”, we mean a height which can be constant for a given acoustic cell or an average height of an acoustic cell when the wall height of the cell varies.
En agrandissant la section des cellules ayant une hauteur de parois réduite, on limite l’impact de la réduction de hauteur de paroi sur le volume global de chaque cellule. On préserve ainsi pour les cellules acoustiques ayant une hauteur de paroi plus faible la capacité d’atténuer les basses fréquences. By enlarging the section of the cells having a reduced wall height, the impact of the reduction in wall height on the overall volume of each cell is limited. This preserves for acoustic cells with a lower wall height the ability to attenuate low frequencies.
Selon une caractéristique particulière du panneau de l’invention, les cellules acoustiques de la ou les premières rangées de cellules acoustiques présentent un volume interne équivalent au volume interne des cellules acoustiques de la ou les deuxièmes rangées de cellules acoustiques. On réduit ainsi au maximum le décalage fréquentiel entre toutes les cellules acoustiques. Par « volume interne équivalent », on entend ici une différence de volume inférieure à 30%, de préférence inférieure à 10%, et plus préférentiellement une différence de volume de nulle. According to a particular characteristic of the panel of the invention, the acoustic cells of the first row or rows of acoustic cells have an internal volume equivalent to the internal volume of the acoustic cells of the second row or rows of acoustic cells. The frequency shift between all the acoustic cells is thus reduced to a minimum. By "equivalent internal volume" is meant here a difference in volume of less than 30%, preferably less than 10%, and more preferably a difference in volume of zero.
Selon une autre caractéristique particulière du panneau de l’invention, chaque cellule acoustique présente un volume configuré pour capter des ondes sonores ayant une fréquence comprise entre 400 Hz et 1000 Hz. According to another particular characteristic of the panel of the invention, each acoustic cell has a volume configured to capture sound waves having a frequency between 400 Hz and 1000 Hz.
Selon une autre caractéristique particulière du panneau de l’invention, les rangées de cellules acoustiques sont juxtaposées les unes aux autres d’amont en aval suivant une direction axiale, la rangée de cellules acoustiques présente en amont de la pluralité de rangées de cellules acoustiques et la rangée de cellules acoustiques présente en aval de la pluralité de rangées de cellules acoustiques présentent une hauteur de paroi inférieure à la hauteur de paroi des cellules acoustiques de la ou les autres rangées de cellules. L’invention a également pour objet une structure d’atténuation acoustique de forme au moins partiellement annulaire ou semi-annulaire comprenant une peau acoustique et une peau de fermeture délimitant entre elles un volume annulaire ou semi-annulaire comprenant un panneau multicellulaire d’atténuation acoustique selon l’invention. According to another particular characteristic of the panel of the invention, the rows of acoustic cells are juxtaposed to each other from upstream to downstream in an axial direction, the row of acoustic cells present upstream of the plurality of rows of acoustic cells and the row of acoustic cells present downstream of the plurality of rows of acoustic cells have a lower wall height than the wall height of the acoustic cells of the other row(s) of cells. The invention also relates to an acoustic attenuation structure of at least partially annular or semi-annular shape comprising an acoustic skin and a closing skin delimiting between them an annular or semi-annular volume comprising a multicellular acoustic attenuation panel according to the invention.
Selon une caractéristique particulière de la structure de l’invention, la peau acoustique, la peau de fermeture et le panneau multicellulaire d’atténuation acoustique sont en matériau composite comprenant un renfort fibreux densifié par une matrice. According to a particular characteristic of the structure of the invention, the acoustic skin, the closure skin and the multicellular acoustic attenuation panel are made of composite material comprising a fibrous reinforcement densified by a matrix.
Selon une autre caractéristique particulière de la structure de l’invention, la peau acoustique et la peau de fermeture sont en matériau composite comprenant un renfort fibreux densifié par une matrice tandis que le panneau multicellulaire d’atténuation acoustique est en matériau métallique. According to another particular characteristic of the structure of the invention, the acoustic skin and the closure skin are made of composite material comprising a fibrous reinforcement densified by a matrix, while the multicellular acoustic attenuation panel is made of metallic material.
L’invention concerne également : The invention also relates to:
- un cône d’éjection de moteur aéronautique comprenant une structure d’atténuation acoustique selon l’invention. - an ejection cone for an aeronautical engine comprising an acoustic attenuation structure according to the invention.
- une tuyère d’éjection de moteur aéronautique comprenant une structure d’atténuation acoustique selon l’invention. - an aeronautical engine exhaust nozzle comprising an acoustic attenuation structure according to the invention.
- un moteur aéronautique à turbine à gaz comprenant un cône d’éjection selon l’invention ou une tuyère d’éjection selon l’invention. - an aeronautical gas turbine engine comprising an ejection cone according to the invention or an ejection nozzle according to the invention.
- un aéronef comprenant au moins un moteur selon l’invention. - an aircraft comprising at least one engine according to the invention.
Brève description des dessins Brief description of the drawings
[Fig. 1] La figure 1 est une vue schématique en perspective d’un cône d’éjection d’un système d’échappement de moteur aéronautique conformément à un mode de réalisation de l’invention, [Fig. 1] Figure 1 is a schematic perspective view of an exhaust cone of an aeronautical engine exhaust system in accordance with one embodiment of the invention,
[Fig. 2] La figure 2 est une vue schématique en coupe de la structure d’atténuation acoustique présente dans la partie amont du cône d’éjection de la figure 1 , [Fig. 3] La figure 3est une autre vue schématique en coupe de la structure d’atténuation acoustique présente dans la partie amont du cône d’éjection de la figure 1 , [Fig. 2] Figure 2 is a schematic sectional view of the acoustic attenuation structure present in the upstream part of the ejection cone of Figure 1, [Fig. 3] Figure 3 is another schematic sectional view of the acoustic attenuation structure present in the upstream part of the ejection cone of Figure 1,
[Fig. 4] La figure 4 est une vue schématique de dessus montrant la section des cellules acoustiques de la structure d’atténuation acoustique présente dans la partie amont du cône d’éjection de la figure 1 , [Fig. 4] Figure 4 is a schematic top view showing the section of the acoustic cells of the acoustic attenuation structure present in the upstream part of the exhaust cone of Figure 1,
[Fig. 5] La figure 5 est une vue schématique en perspective d’un cône d’éjection d’un système d’échappement de moteur aéronautique conformément à un autre mode de réalisation de l’invention, [Fig. 5] Figure 5 is a schematic perspective view of an exhaust cone of an aeronautical engine exhaust system according to another embodiment of the invention,
[Fig. 6] La figure 6 est une vue schématique de dessus montrant la section des cellules acoustiques de la structure d’atténuation acoustique présente dans la partie amont du cône d’éjection de la figure 5. [Fig. 6] Figure 6 is a schematic top view showing the section of the acoustic cells of the acoustic attenuation structure present in the upstream part of the exhaust cone of Figure 5.
Description des modes de réalisation Description of embodiments
Un domaine particulier mais non exclusif d’application de l’invention est celui des systèmes d’échappement de moteurs aéronautiques à turbine à gaz telles que ceux utilisés dans les avions ou hélicoptères. Ces systèmes d’échappement comprennent en particulier une tuyère et un cône d’éjection délimitant entre eux un canal d’éjection pour les gaz d’échappement. A particular but non-exclusive field of application of the invention is that of the exhaust systems of aeronautical gas turbine engines such as those used in airplanes or helicopters. These exhaust systems comprise in particular a nozzle and an ejection cone defining between them an ejection channel for the exhaust gases.
La figure 1 représente un cône d’éjection 100 d’un système d’échappement de moteur à turbine à gaz conformément à un mode de réalisation de l’invention. Le cône d’éjection 100 présente une forme de révolution autour d’une direction axiale D et comprend de l’amont vers l’aval suivant la direction axiale D une partie amont 110 intégrant une structure d’atténuation acoustique 200 et une partie aval 120 finalisant la ligne aérodynamique. Le cône d’éjection est ici réalisé en matériau composite, par exemple en composite à matrice céramique (CMC) pour des raisons de tenue à la température. L’extrémité de la partie amont 110 du cône comporte une bride de fixation métallique 130 faisant partie du carter du moteur (non représenté sur la figure 1 ) ou destinée à être fixé sur celui-ci. Figure 1 shows an exhaust cone 100 of a gas turbine engine exhaust system in accordance with one embodiment of the invention. The ejection cone 100 has a shape of revolution around an axial direction D and comprises, from upstream to downstream in the axial direction D, an upstream part 110 incorporating an acoustic attenuation structure 200 and a downstream part 120 finalizing the aerodynamic line. The ejection cone is here made of composite material, for example ceramic matrix composite (CMC) for reasons of temperature resistance. The end of the upstream part 110 of the cone has a metal fixing flange 130 forming part of the motor casing (not shown in FIG. 1) or intended to be fixed on the latter.
De façon bien connue, les pièces en matériau CMC sont formées par un renfort fibreux en fibres réfractaires (carbone ou céramique) qui est densifié par une matrice céramique, notamment carbure, nitrure, oxyde réfractaire,.... Des exemples typiques de matériaux CMC sont les matériaux Oxyde/Oxyde (fibre oxyde et matrice oxyde comme par exemple matrice alumine, mulite, alumino-silicate), C-SiC (renfort en fibres de carbone et matrice en carbure de silicium), les matériaux SiC-SiC et les matériaux C-C/SiC (matrice mixte carbone/carbure de silicium). La fabrication de pièces en composite CMC est bien connue. In a well-known way, the parts in CMC material are formed by a fibrous reinforcement in refractory fibers (carbon or ceramic) which is densified by a ceramic matrix, in particular carbide, nitride, refractory oxide,... Typical examples CMC materials are Oxide/Oxide materials (oxide fiber and oxide matrix such as alumina, mulite, alumino-silicate matrix), C-SiC (carbon fiber reinforcement and silicon carbide matrix), SiC-SiC materials and CC/SiC materials (mixed carbon/silicon carbide matrix). The manufacture of CMC composite parts is well known.
La partie amont 1 10 du cône d’éjection 100 comprend une structure d’atténuation acoustique 200 qui est constituée dans l’exemple décrit ici par une peau interne structurale210, un panneau multicellulaire d’atténuation acoustique 220 et une peau externe acoustique 230. La peau externe 230 délimite la surface interne de la veine d’écoulement des gaz d’échappement. La peau externe 230 présente en outre des perforations 231 afin de permettre l’entrée des ondes acoustiques à atténuer dans la structure d’atténuation tandis que la peau interne 210 est pleine de manière à réfléchir ces ondes. The upstream part 110 of the ejection cone 100 comprises an acoustic attenuation structure 200 which is constituted in the example described here by a structural internal skin 210, a multicellular acoustic attenuation panel 220 and an acoustic external skin 230. outer skin 230 delimits the inner surface of the exhaust gas flow path. The outer skin 230 also has perforations 231 to allow the entry of the acoustic waves to be attenuated into the attenuation structure while the inner skin 210 is solid so as to reflect these waves.
Le panneau multicellulaire 220 comprend plusieurs rangées de cellules acoustiques s’étendant chacune suivant une direction circonférentielle (Dc). Dans l’exemple décrit ici, le panneau multicellulaire 220 comprend cinq rangées de cellules acoustiques 240, 250, 260, 270 et 280 s’étendant chacune de manière annulaire suivant une direction circonférentielle Dc, les rangées de cellules acoustiques 240, 250, 260, 270 et 280 étant juxtaposées les unes aux autres d’amont en aval suivant la direction axiale DA, la rangée 240 étant située le plus en amont tandis que la rangée 280 est située le plus en aval des rangées de cellules acoustiques. The multicellular panel 220 comprises several rows of acoustic cells each extending along a circumferential direction (D c ). In the example described here, the multicellular panel 220 comprises five rows of acoustic cells 240, 250, 260, 270 and 280 each extending in an annular manner in a circumferential direction D c , the rows of acoustic cells 240, 250, 260 , 270 and 280 being juxtaposed with each other from upstream to downstream in the axial direction D A , the row 240 being located the most upstream while the row 280 is located the most downstream of the rows of acoustic cells.
Chaque cellule acoustique est délimitée par une paroi qui s’étend en hauteur suivant une direction radiale DR entre les peaux interne et externe 210 et 230 et suivant une direction circonférentielle Dc. Plus précisément, les cellules acoustiques 240, 250, 260, 270 et 280 sont chacune respectivement délimitées par une paroi 241 , 251 , 261 , 271 et 281 de manière à former des caissons aptes à amortir les ondes acoustiques que l’on souhaite atténuer. La paroi délimitant les cellules acoustiques d’une rangée, par exemple la paroi 241 , a une portion commune avec la paroi des cellules acoustiques de la rangée adjacente, par exemple avec la paroi 251 . Each acoustic cell is delimited by a wall which extends in height in a radial direction DR between the inner and outer skins 210 and 230 and in a circumferential direction D c . More specifically, the acoustic cells 240, 250, 260, 270 and 280 are each respectively delimited by a wall 241, 251, 261, 271 and 281 so as to form boxes capable of damping the acoustic waves which it is desired to attenuate. The wall delimiting the acoustic cells of a row, for example the wall 241 , has a common portion with the wall of the acoustic cells of the adjacent row, for example with the wall 251 .
Comme illustrées sur les figures 2 et 3, les cellules acoustiques 240, 250, 260, 270 et 280 présentent chacune respectivement une hauteur de paroi H241, H251, H26I, H271 et H 28i . Plus précisément, les cellules acoustiques le plus en amont 240 et les cellules acoustiques 280 le plus en aval présentent respectivement des hauteurs de paroi H24i et H281 inférieures aux hauteurs de paroi H251, H26iet H271 respectivement des cellules acoustiques 250, 260 et 270 qui sont situées entre les cellules acoustiques 240 et 280. As illustrated in FIGS. 2 and 3, the acoustic cells 240, 250, 260, 270 and 280 each respectively have a wall height H 241 , H 251 , H 26 I , H 2 71 and H 2 8i . More specifically, the most upstream acoustic cells 240 and the acoustic cells 280 furthest downstream respectively have wall heights H 2 4i and H 281 lower than the wall heights H 251 , H 26 iet H 271 respectively of the acoustic cells 250, 260 and 270 which are located between the acoustic cells 240 and 280.
Dans l’exemple décrit ici, les hauteurs de paroi H241, H251, H26I, H271 et H28I qui sont parallèles à la direction radiale DR varient suivant que l’on se déplace dans la direction axiale DAdu cône d’éjection 100 notamment en raison du profil variable des peaux interne 210 et peau externe 230 définissant la forme de la structure d’atténuation acoustique 200. In the example described here, the wall heights H 241 , H 251 , H 26 I, H 271 and H 28 I which are parallel to the radial direction D R vary depending on whether one moves in the axial direction D A of the ejection cone 100 in particular because of the variable profile of the internal skins 210 and external skin 230 defining the shape of the acoustic attenuation structure 200.
Toujours dans l’exemple décrit ici, les hauteurs de parois H241 et H28I sont significativement inférieures aux hauteurs de paroi H25I, H26I et H27I en raison de la présence d’un chanfrein amont CAM et d’un chanfrein aval CAV- La structure d’atténuation acoustique 200 comprenant les peaux interne et externe 210 et 230 étant en matériau composite, il est difficile de former des changements de pentes brutaux notamment au niveau de la peau interne de manière à former un décrochement permettant d’obtenir immédiatement une profondeur de logement adaptée pour les cellules acoustiques. En effet, à la différence d’un matériau métallique, un changement de pente brutal, par exemple par formation d’un angle à 90°, entraîne la formation de plissures et ou de décollements locaux dans le matériau composite qui réduisent la résistance mécanique de la structure. C’est pourquoi les changements de pente dans le profil d’une pièce de révolution en matériau composite comprennent de préférence des chanfreins plutôt que des angles marqués. Still in the example described here, the wall heights H 241 and H 28 I are significantly lower than the wall heights H 25 I, H 26 I and H 27 I due to the presence of an upstream chamfer CAM and a downstream chamfer CAV- The acoustic attenuation structure 200 comprising the internal and external skins 210 and 230 being made of composite material, it is difficult to form sudden changes in slopes in particular at the level of the internal skin so as to form a recess allowing to immediately obtain a suitable housing depth for the acoustic cells. Indeed, unlike a metallic material, a sudden change in slope, for example by forming a 90° angle, leads to the formation of creases and/or local detachments in the composite material which reduce the mechanical resistance of the structure. This is why the changes in slope in the profile of a part of revolution made of composite material preferably include chamfers rather than marked angles.
Les hauteurs de parois de chaque rangée de cellules acoustiques étant variables suivant que l’on se déplace dans une direction axiale DA, en particulier au niveau des chanfreins CAM et CAv, les hauteurs de paroi H241, H251, H26I, H271 et H281 décrites ici correspondent à une hauteur moyenne de paroi pour chaque cellule acoustique. The wall heights of each row of acoustic cells being variable depending on whether one moves in an axial direction D A , in particular at the level of the chamfers C A M and C A v, the wall heights H 241 , H 251 , H 26 I, H 271 and H 281 described here correspond to an average wall height for each acoustic cell.
Conformément à l’invention, les cellules acoustiques de ou les rangées de cellules présentant une hauteur de paroi inférieure à la hauteur de paroi des cellules acoustiques d’une ou plusieurs autres rangées présentent une section en coupe transversale supérieure à la section transversale des cellules acoustiques de la ou les autres rangées de cellules. Dans l’exemple décrit ici, les rangées de cellules acoustiques 240 et 280 qui présentent des hauteurs de parois H241 et H281 significativement inférieures aux hauteurs de paroi H25I, H26I et H27I des rangées de cellules acoustiques 250, 260 et 270 sont formées de manière à présenter des section S240 et S28o en coupe transversale supérieure aux sections transversales S250, S26o et S270 des cellules acoustiques 250, 260 et 270 (figure 4). Dans l’exemple décrit ici, la section des cellules acoustiques est agrandie en augmentant leur longueur dans la direction axiale DA, la largeur des cellules suivant la direction circonférentielle Dc étant constante entre les rangées de cellules acoustiques. En d’autres termes, les cellules acoustiques 240 et 280 présentent des longueurs L240 et L28O supérieures aux longueurs L25o, L26o et L27o des cellules acoustiques 250, 260 et 270 suivant la direction axiale DA. La section des cellules acoustiques ayant une hauteur plus faible peut bien entendu être adaptée en augmentant à la fois la longueur et la largeur des cellules. According to the invention, the acoustic cells of one or more rows of cells having a wall height lower than the wall height of the acoustic cells of one or more other rows have a cross-section greater than the cross-section of the acoustic cells from where other rows of cells. In the example described here, the rows of acoustic cells 240 and 280 which have wall heights H 241 and H 281 significantly lower than the wall heights H 25 I, H 26 I and H 27 I of the rows of acoustic cells 250, 260 and 270 are formed so as to present sections S 240 and S 28 o in cross section greater than the cross sections S250, S 26 o and S 270 of the acoustic cells 250, 260 and 270 (FIG. 4). In the example described here, the section of the acoustic cells is enlarged by increasing their length in the axial direction D A , the width of the cells in the circumferential direction D c being constant between the rows of acoustic cells. In other words, the acoustic cells 240 and 280 have lengths L 240 and L 280 greater than the lengths L 25 o, L 26 o and L 27 o of the acoustic cells 250, 260 and 270 in the axial direction D A . The section of the acoustic cells having a lower height can of course be adapted by increasing both the length and the width of the cells.
A titre d’exemple non limitatif, les cellules acoustiques 240 et 280 présentent des hauteurs de parois H24I et H28I de 95 mm tandis que les cellules acoustiques 250, 260 et 270 présentent des hauteurs de paroi H251, H26I et H271 de 150 mm. En outre et conformément à l’invention, les cellules acoustiques 240 et 280 présentent des longueurs L240 et L280 deux fois plus importantes que les longueurs L25o, L26o et L270 des cellules acoustiques 250, 260 et 270 suivant la direction axiale DA. Ainsi, dans le mode de réalisation illustré, les cellules acoustiques 240 et 280 présentent un volume d’environ 3,7 litres tandis que les cellules acoustiques 250, 260 et 270 présentent un volume d’environ 2,9 litres. Le décalage fréquentiel du pic d’atténuation entre les cellules acoustiques 240 et 280, d’une part, et les cellules acoustiques 250, 260 et 270, d’autre part, n’est que de 100Hz. By way of non-limiting example, the acoustic cells 240 and 280 have wall heights H 24 I and H 28 I of 95 mm while the acoustic cells 250, 260 and 270 have wall heights H 251 , H 26 I and H 271 of 150 mm. In addition and in accordance with the invention, the acoustic cells 240 and 280 have lengths L 240 and L 280 twice as large as the lengths L 25 o, L 26 o and L 270 of the acoustic cells 250, 260 and 270 according to the axial direction D A . Thus, in the illustrated embodiment, the acoustic cells 240 and 280 have a volume of approximately 3.7 liters while the acoustic cells 250, 260 and 270 have a volume of approximately 2.9 liters. The frequency shift of the attenuation peak between the acoustic cells 240 and 280, on the one hand, and the acoustic cells 250, 260 and 270, on the other hand, is only 100Hz.
Les cellules acoustiques peuvent présenter des géométries différentes de celles représentées sur la figure 4. Les cellules peuvent notamment présenter des formes polygonales, rectangulaires, sphériques, etc. Le choix de la ou les dimensions à augmenter pour adapter la section de cellules ayant une hauteur plus faible est fonction de la géométrie des cellules. The acoustic cells may have different geometries from those represented in FIG. 4. The cells may in particular have polygonal, rectangular, spherical, etc. shapes. The choice of the dimension or dimensions to be increased in order to adapt the section of cells having a lower height depends on the geometry of the cells.
La figure 5 représente un autre exemple d’un cône d’éjection 400 d’un système d’échappement de moteur à turbine à gaz conformément à un mode de réalisation de l’invention qui comprend comme décrit précédemment présente une forme de révolution autour d’une direction axiale D et comprend de l’amont vers l’aval suivant la direction axiale DA une partie amont 410 intégrant une structure d’atténuation acoustique 300 et une partie aval 420 finalisant la ligne aérodynamique. Le cône d’éjection est ici réalisé en matériau composite, par exemple en composite à matrice céramique (CMC) pour des raisons de tenue à la température. Figure 5 shows another example of an exhaust cone 400 of a gas turbine engine exhaust system in accordance with one embodiment of the invention which comprises as previously described has a shape of revolution around an axial direction D and comprises, from upstream to downstream along the axial direction D A , an upstream part 410 integrating an acoustic attenuation structure 300 and a downstream part 420 finalizing the aerodynamic line. The ejection cone is here made of a composite material, for example of a ceramic matrix composite (CMC) for temperature resistance reasons.
La partie amont 410 du cône d’éjection 400 comprend une structure d’atténuation acoustique 300 qui est constituée dans l’exemple décrit ici par une peau interne structurale 310, un panneau multicellulaire d’atténuation acoustique 320 et une peau externe acoustique 330 délimitant la surface interne de la veine d’écoulement des gaz d’échappement et présentant en outre des perforations 331 afin de permettre l’entrée des ondes acoustiques à atténuer dans la structure d’atténuation tandis que la peau interne 310 est pleine de manière à réfléchir ces ondes. The upstream part 410 of the ejection cone 400 comprises an acoustic attenuation structure 300 which is constituted in the example described here by a structural internal skin 310, a multicellular acoustic attenuation panel 320 and an acoustic external skin 330 delimiting the internal surface of the exhaust gas flow path and also having perforations 331 in order to allow the entry of the acoustic waves to be attenuated into the attenuation structure while the internal skin 310 is solid so as to reflect these waves.
Le panneau multicellulaire 320 comprend plusieurs rangées de cellules acoustiques s’étendant chacune suivant une direction circonférentielle (Dc). Dans l’exemple décrit ici, le panneau multicellulaire 320 comprend cinq rangées de cellules acoustiques 340, 350, 360, 370 et 380 s’étendant chacune de manière annulaire suivant une direction circonférentielle Dc, les rangées de cellules acoustiques 340, 350, 360, 370 et 380 étant juxtaposées les unes aux autres d’amont en aval suivant la direction axiale DA, la rangée 340 étant située le plus en amont tandis que la rangée 380 est située le plus en aval des rangées de cellules acoustiques. The multicellular panel 320 comprises several rows of acoustic cells each extending along a circumferential direction (D c ). In the example described here, the multicellular panel 320 comprises five rows of acoustic cells 340, 350, 360, 370 and 380 each extending in an annular manner in a circumferential direction D c , the rows of acoustic cells 340, 350, 360 , 370 and 380 being juxtaposed with each other from upstream to downstream in the axial direction D A , the row 340 being located the most upstream while the row 380 is located the most downstream of the rows of acoustic cells.
Les cellules acoustiques 340, 350, 360, 370 et 380 diffèrent des cellules acoustiques 240, 250, 260, 270 et 280 décrites précédemment en ce qu’elles présentent une forme rectangulaire. The 340, 350, 360, 370 and 380 acoustic cells differ from the 240, 250, 260, 270 and 280 acoustic cells previously described in that they have a rectangular shape.
Chaque cellule acoustique est délimitée par une paroi qui s’étend en hauteur suivant une direction radiale DR entre les peaux interne et externe 310 et 330 et suivant la direction circonférentielle Dc. Plus précisément, les cellules acoustiques 340, 350, 360, 370 et 380 sont chacune respectivement délimitées par deux parois adjacentes 341 , 351 , 361 , 371 , 381 et 391 suivant la direction circonférentielle Dc et par deux parois adjacentes 321 suivant la direction axiale D de manière à former des caissons aptes à amortir les ondes acoustiques que l’on souhaite atténuer. Each acoustic cell is delimited by a wall which extends in height in a radial direction D R between the inner and outer skins 310 and 330 and in the circumferential direction D c . More specifically, the acoustic cells 340, 350, 360, 370 and 380 are each respectively delimited by two adjacent walls 341, 351, 361, 371, 381 and 391 in the circumferential direction D c and by two adjacent walls 321 in the axial direction D so as to form boxes capable of damping the acoustic waves which it is desired to attenuate.
Conformément à l’invention, les cellules acoustiques de ou les rangées de cellules présentant une hauteur de paroi inférieure à la hauteur de paroi des cellules acoustiques d’une ou plusieurs autres rangées présentent une section en coupe transversale supérieure à la section transversale des cellules acoustiques de la ou les autres rangées de cellules. Dans l’exemple décrit ici, les rangées de cellules acoustiques 340 et 380 qui présentent des hauteurs de parois significativement inférieures aux hauteurs de paroi des rangées de cellules acoustiques 350, 360 et 370 sont formées de manière à présenter des section S340 et S38o en coupe transversale supérieure aux sections transversales S35o, S36o et S37o des cellules acoustiques 350, 360 et 370 (figure 6). Dans l’exemple décrit ici, la section des cellules acoustiques est agrandie en augmentant leur longueur dans la direction axiale DA. En d’autres termes, les cellules acoustiques 240 et 280 présentent des longueurs L240 et L28o supérieures aux longueurs L250, L26o et L270 des cellules acoustiques 250, 260 et 270 suivant la direction axiale DA. La section des cellules acoustiques ayant une hauteur plus faible peut bien entendu être adaptée en augmentant à la fois la longueur et la largeur des cellules. According to the invention, the acoustic cells of or the rows of cells having a wall height lower than the wall height of the cells acoustic cells of one or more other rows have a cross section greater than the cross section of the acoustic cells of the other row or rows of cells. In the example described here, the rows of acoustic cells 340 and 380 which have wall heights significantly lower than the wall heights of the rows of acoustic cells 350, 360 and 370 are formed so as to present sections S 340 and S 38 o in cross section greater than the cross sections S 35 o, S 36 o and S 37 o of the acoustic cells 350, 360 and 370 (FIG. 6). In the example described here, the section of the acoustic cells is enlarged by increasing their length in the axial direction D A . In other words, the acoustic cells 240 and 280 have lengths L 240 and L 28 o greater than the lengths L 250 , L 26 o and L 270 of the acoustic cells 250, 260 and 270 in the axial direction D A . The section of the acoustic cells having a lower height can of course be adapted by increasing both the length and the width of the cells.
La structure d’atténuation acoustique et, par conséquent, le panneau multicellulaire qui la compose présente une forme au moins partiellement annulaire ou semi- annulaire. The acoustic attenuation structure and, consequently, the multicellular panel which composes it has an at least partially annular or semi-annular shape.
En agrandissant la section des cellules ayant une hauteur de parois réduite, on limite l’impact de la réduction de hauteur de paroi sur le volume global de chaque cellule de manière à avoir des cellules acoustiques qui présentent un volume interne équivalent afin de réduire au maximum le décalage fréquentiel entre toutes les cellules acoustiques. Par « volume interne équivalent >>, on entend ici la différence de volume entre les cellules acoustiques d’une rangée par rapport à une autre rangée, cette différence de volume étant inférieure à 30%, de préférence inférieure à 10%, et plus préférentiellement nulle ou proche de 0%. On préserve ainsi pour les cellules acoustiques ayant une hauteur de paroi plus faible la capacité d’atténuer les basses fréquences. By enlarging the section of the cells having a reduced wall height, the impact of the reduction in wall height on the overall volume of each cell is limited so as to have acoustic cells which have an equivalent internal volume in order to reduce as much as possible the frequency shift between all the acoustic cells. By "equivalent internal volume" is meant here the volume difference between the acoustic cells of one row relative to another row, this volume difference being less than 30%, preferably less than 10%, and more preferably nil or close to 0%. This preserves for acoustic cells with a lower wall height the ability to attenuate low frequencies.
Selon une caractéristique particulière de l’invention, les cellules acoustiques de section en coupe transversale supérieure et de hauteur de paroi inférieure présentent un volume interne équivalent au volume interne des autres cellules acoustiques. Dans ce cas, on réduit au maximum le décalage fréquentiel dans l’atténuation acoustique entre les différentes rangées de cellules acoustiques. La structure d’atténuation acoustique selon l’invention peut correspondre à une pièce de révolution et être réalisée en une seule pièce ou à partir d’une pluralité de secteurs annulaires assemblés les uns avec les autres. According to a particular characteristic of the invention, the acoustic cells of upper cross-sectional section and of lower wall height have an internal volume equivalent to the internal volume of the other acoustic cells. In this case, the frequency shift in the acoustic attenuation between the different rows of acoustic cells is minimized. The acoustic attenuation structure according to the invention can correspond to a part of revolution and be produced in a single part or from a plurality of annular sectors assembled with each other.
La structure d’atténuation acoustique de l’invention peut être notamment intégré à un cône d’éjection de moteur aéronautique comme décrit ci-avant et/ou encore à une tuyère d’éjection d’un système d’échappement de moteur aéronautique. The acoustic attenuation structure of the invention can in particular be integrated into an aeronautical engine exhaust cone as described above and/or even into an ejection nozzle of an aeronautical engine exhaust system.

Claims

Revendications Claims
[Revendication 1] Panneau multicellulaire d'atténuation acoustique (220) comprenant plusieurs rangées de cellules acoustiques (240, 250, 260, 270,[Claim 1] Multi-cell acoustic attenuation panel (220) comprising several rows of acoustic cells (240, 250, 260, 270,
280), chaque rangée s'étendant suivant une direction circonférentielle (Dc), chaque cellule acoustique étant délimitée par une paroi (241, 251, 261, 271,280), each row extending in a circumferential direction (D c ), each acoustic cell being delimited by a wall (241, 251, 261, 271,
281) s'étendant en hauteur suivant une direction radiale (DR), les cellules acoustiques (240, 280) d'une ou plusieurs premières rangées de cellules acoustiques présentant une section en coupe transversale (S24o, S2so) supérieure à la section en coupe transversale (S25o, S2ÔO, S27o) des cellules acoustiques d'une ou plusieurs deuxièmes rangées de cellules acoustiques (250, 260, 270) et en ce que lesdites cellules acoustiques de la ou les premières rangées de cellules acoustiques présentent une hauteur de paroi (H24I, H28I) inférieure à la hauteur de paroi (H25I, H26I, H27I) des cellules acoustiques de la ou les deuxièmes rangées de cellules acoustiques, caractérisé en ce que les rangées de cellules acoustiques (240, 250, 260, 270, 280) sont juxtaposées les unes aux autres d'amont en aval suivant une direction axiale (DA) et dans lequel la rangée de cellules acoustiques (240) présente en amont de la pluralité de rangées de cellules acoustiques et la rangée de cellules acoustiques (280) présente en aval de la pluralité de rangées de cellules acoustiques présentent une hauteur de paroi (H24I, H28I) inférieure à la hauteur de paroi (H25I, H26I, H27I) des cellules acoustiques de la ou les autres rangées de cellules. 281) extending in height in a radial direction (DR), the acoustic cells (240, 280) of one or more first rows of acoustic cells having a cross section (S 24 o, S 2 so) greater than the cross-sectional section (S 25 o, S 2 ÔO, S 27 o) of the acoustic cells of one or more second rows of acoustic cells (250, 260, 270) and in that said acoustic cells of the first or first rows of acoustic cells have a wall height (H 24 I, H 28 I) lower than the wall height (H 25 I, H 26 I, H 27 I) of the acoustic cells of the second row or rows of acoustic cells, characterized in that the rows of acoustic cells (240, 250, 260, 270, 280) are juxtaposed to each other from upstream to downstream in an axial direction (D A ) and in which the row of acoustic cells (240) present upstream of the plurality of rows of acoustic cells and the row of cells The acoustic cells (280) present downstream of the plurality of rows of acoustic cells have a wall height (H 24 I, H 28 I) lower than the wall height (H 25 I, H 26 I, H 27 I) of the acoustic cells of the other row(s) of cells.
[Revendication 2] Panneau selon la revendication 1, dans lequel les cellules acoustiques (240, 280) de la ou les premières rangées de cellules acoustiques présentent un volume interne équivalent au volume interne des cellules acoustiques de la ou les deuxièmes rangées de cellules acoustiques (250, 260, 270). [Claim 2] Panel according to claim 1, in which the acoustic cells (240, 280) of the first row or rows of acoustic cells have an internal volume equivalent to the internal volume of the acoustic cells of the second row or rows of acoustic cells ( 250, 260, 270).
[Revendication 3] Panneau selon la revendication 1 ou 2, dans lequel chaque cellule acoustique (240, 250, 260, 270, 280) présente un volume configuré pour capter des ondes sonores ayant une fréquence comprise entre[Claim 3] Panel according to claim 1 or 2, in which each acoustic cell (240, 250, 260, 270, 280) has a volume configured to pick up sound waves having a frequency between
400 Hz et 1000 Hz. 400Hz and 1000Hz.
[Revendication 4] Structure d'atténuation acoustique (200) de forme au moins partiellement annulaire comprenant une peau acoustique (230) et une peau de fermeture (210) délimitant entre elles un volume annulaire ou semi- annulaire comprenant un panneau multicellulaire d'atténuation acoustique (220) selon l'une quelconque des revendications 1 à 3. [Claim 4] Acoustic attenuation structure (200) of at least partially annular shape comprising an acoustic skin (230) and a closure skin (210) defining between them an annular or semi-annular volume comprising a multicellular attenuation panel acoustic (220) according to any one of claims 1 to 3.
[Revendication 5] Structure selon la revendication 4, dans laquelle la peau acoustique (230), la peau de fermeture (210) et le panneau multicellulaire d'atténuation acoustique (220) sont en matériau composite comprenant un renfort fibreux densifié par une matrice. [Claim 5] Structure according to claim 4, in which the acoustic skin (230), the closing skin (210) and the multicellular acoustic attenuation panel (220) are made of a composite material comprising a fibrous reinforcement densified by a matrix.
[Revendication 6] Structure selon la revendication 4, dans laquelle la peau acoustique (230) et la peau de fermeture (210) sont en matériau composite comprenant un renfort fibreux densifié par une matrice tandis que le panneau multicellulaire d'atténuation acoustique (220) est en matériau métallique.[Claim 6] Structure according to claim 4, in which the acoustic skin (230) and the closure skin (210) are made of a composite material comprising a fibrous reinforcement densified by a matrix, while the multicellular acoustic attenuation panel (220) is made of metallic material.
[Revendication 7] Cône d'éjection (100) de moteur aéronautique comprenant une structure d'atténuation acoustique (200) selon l'une quelconque des revendications 4 à 6. [Claim 7] An aeroengine exhaust cone (100) comprising an acoustic attenuation structure (200) according to any one of claims 4 to 6.
[Revendication 8] Tuyère d'éjection de moteur aéronautique comprenant une structure d'atténuation acoustique selon l'une quelconque des revendications 4 à 6. [Claim 8] Aircraft engine exhaust nozzle comprising an acoustic attenuation structure according to any one of claims 4 to 6.
[Revendication 9] Moteur aéronautique à turbine à gaz comprenant un cône d'éjection selon la revendication 7 ou une tuyère d'éjection selon la revendication 8. [Claim 9] An aero gas turbine engine comprising an exhaust cone according to claim 7 or an exhaust nozzle according to claim 8.
[Revendication 10] Aéronef comprenant au moins un moteur selon la revendication 9. [Claim 10] Aircraft comprising at least one engine according to claim 9.
PCT/FR2021/052186 2020-12-04 2021-12-02 Variable-height multicellular acoustic-attenuation panel WO2022117968A1 (en)

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