• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to an acoustic attenuation panel provided for a turbojet, comprising an acoustic front skin (22) comprising perforations, then a central structure formed of partitions arranged perpendicularly to form cells, the front skin (22) and the central structure form the integrally formed panel (20), which is provided to directly cover a surface of a turbojet element (30) forming a rear skin closing the cells of the central structure rearwardly.
    公开号:FR3058762A1
    申请号:FR1663073
    申请日:2016-12-21
    公开日:2018-05-18
    发明作者:Marc VERSAEVEL；Marc Ginefri；Jeremy QUESNEL；Fabrice Provost；Wouter Balk；Sebastien Louchard；Loic Herve Le Boulicaut
    申请人:Safran Nacelles SAS；Safran SA；
    IPC主号:
    专利说明:

    © Publication number: 3,058,762 (to be used only for reproduction orders) (© National registration number: 16 63073 ® FRENCH REPUBLIC
    NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY
    COURBEVOIE © Int Cl 8 : F02 C 7/24 (2017.01), G 10 K 11/168, B 32 B 3/12
    A1 PATENT APPLICATION
    ©) Date of filing: 21.12.16. © Applicant (s): SAFRAN — FR and SAFRAN © Priority: 14.11.16 FR 1660978. NACELLES Simplified joint-stock company - FR. @ Inventor (s): VERSAEVEL MARC, GINEFRI MARC, QUESNEL JEREMY, PROVOST FABRICE, BALK (43) Date of public availability of the WOUTER, LOUCHARD SEBASTIEN and LE BOULI- request: 18.05.18 Bulletin 18/20. CAUT LOÏC. ©) List of documents cited in the report preliminary research: Refer to end of present booklet (© References to other national documents ® Holder (s): SAFRAN, SAFRAN NACELLES Company related: by simplified actions. ©) Extension request (s): © Agent (s): CABINET GERMAIN & MAUREAU.
    104) ACOUSTIC MITIGATION PANEL INCLUDING A FRONT SKIN AND A CENTRAL STRUCTURE.
    FR 3,058,762 - A1 _ The subject of the invention is an acoustic attenuation panel intended for a turbojet engine, comprising an acoustic front skin (22) comprising perforations, then a central structure formed by partitions arranged perpendicularly to constitute cells, the front skin (22) and the central structure form the panel (20) made in one piece, which is intended to directly cover a surface of an element of the turbojet engine (30) forming a rear skin closing the rear cells of the central structure.
    i
    ACOUSTIC MITIGATION PANEL COMPRISING A FRONT SKIN AND A CENTRAL STRUCTURE
    The present invention relates to the technical field of acoustic attenuation panels, intended in particular to equip internal surfaces of turbojet engines for aircraft, as well as aircraft turbojet engines equipped with such acoustic panels.
    The turbojets have internal surfaces for aerodynamically guiding gases which may be cold at the inlet or outlet of a cold stream, or hot at the outlet of combustion.
    To reduce the noise emitted by the turbojet engine in operation, a known type of acoustic panel, presented in particular in document EP-B12291840, comprises an acoustic front skin facing the flow comprising micro-perforations, a central acoustic structure constituting a core having partitions arranged perpendicularly separating cells forming a honeycomb, and a back skin.
    In general, the skins of the acoustic panels are fixed to the central structure by gluing.
    The front skin receiving the sound waves has gas passages formed by the perforations, opening into resonant cavities formed by the closed cells of the central structure, to constitute Helmholtz resonators achieving attenuation of the acoustic emissions coming from the turbojet engine.
    In particular by choosing the dimensions of the cells of the central structure, in particular the height, one obtains from an input of sound waves by the perforations, a reflection of these waves on the back skin which returns them towards the perforations of the front skin. In this way an acoustic intensity attenuation is obtained for frequency ranges by visco-thermal effect at the perforations of the acoustic skin.
    In particular, it is sought to cover as much as possible the internal aerodynamic surfaces receiving sound waves with acoustic panels to reduce the noise emissions from aircraft.
    However, these acoustic panels comprising the central structure bonded to the two highly rigid skins constitute relatively heavy and expensive assemblies. In addition, they are suitable for covering large areas, but are ill-suited for effectively covering small areas.
    Indeed, the central honeycomb structure is generally chamfered at the edge of the part in order to connect the acoustic skin and the back skin. The chamfered area is less efficient from an acoustic point of view. This type of loss is minimal on large panels, but not on small parts.
    The present invention aims in particular to solve these problems presented by the prior art.
    To this end, it proposes an acoustic attenuation panel intended for a turbojet engine, comprising an acoustic front skin comprising perforations, then a central structure formed of partitions arranged perpendicularly to constitute cells, this panel being remarkable in that the skin before and the central structure form the panel made in one piece, which is intended to directly cover a surface of an element of the turbojet engine forming a rear skin closing the cells of the central structure towards the rear.
    An advantage of this acoustic attenuation panel is that the surface of the element of the turbojet engine forming the rear skin of the acoustic panel, this eliminates the specific rear skin which is generally provided at the rear of the acoustic panels to close the cells. With the specific back skin less, the mass of the acoustic panels is reduced, as well as the costs.
    In addition, the manufacture of these acoustic panels having no back skin, having the cells open towards the rear, is easier to carry out, in particular by molding.
    The acoustic attenuation panel according to the invention may include one or more of the following characteristics, which can be combined with one another.
    Advantageously, the panel comprises punctual fixing means on the surface of the carrier element. In this way it is easier to get rid of slight deformations of the support element or of the acoustic panel.
    In this case, the point-type fastening means may include fixing tabs arranged parallel to the surface of the carrier element.
    Advantageously, the point fixing means are arranged on the external contour of the acoustic panel. In this case, we can cover a large area of the panel with the acoustic skin.
    Advantageously, the panel is designed to present, after its assembly, a clearance between the base of the partitions and the surface of the support element. This game allows to accept small geometric deformations of the load-bearing element or of the panel.
    In this case, the play is advantageously between 0.5 and 1.5 mm.
    In particular, the cells of the central structure may have contours forming quadrilaterals in the plane of the skin before.
    Advantageously, the closed cells of the central structure have, in the plane of the front skin, dimensions of less than 60 mm.
    Advantageously, the panel is formed in one piece by the molding of a synthetic material. This process makes it possible to economically produce panels with a surface having complex shapes.
    The invention also relates to an aircraft turbojet engine comprising acoustic attenuation panels comprising any one of the preceding characteristics.
    Other characteristics and advantages of the invention will emerge on reading the description which follows, given solely by way of example, with reference to the following appended figures:
    Figure 1 is a diagram of a turbojet engine having in axial section different surfaces receiving an acoustic treatment;
    Figure 2 is a diagram showing in cross section an acoustic attenuation panel according to the invention;
    Figures 3 and 4 show an acoustic panel according to the invention, seen successively from the front side and from the rear side;
    Figure 5 is a side view of this acoustic panel; and FIG. 6 is a graph obtained by measurements, presenting as a function of the frequency the acoustic attenuation obtained with a panel according to the prior art and a panel according to the invention.
    For the sake of clarity, identical or similar elements are identified by identical reference signs in all of the figures.
    Figure 1 shows a turbofan engine arranged along a main axis A, receiving on surfaces of interior load-bearing elements of acoustic attenuation panels, in order to partially absorb the sound waves received on these surfaces.
    The surface facing the axis A of the contour of the cold air inlet 2 is treated in particular, the surfaces facing the axis 4 and towards the outside 6 of the cold air stream of the double flow, and the surfaces facing the axis 8 and towards the outside of the hot gas ejection flow.
    FIG. 2 shows an acoustic panel 20, comprising on a side conventionally called the front side, indicated by the arrow "AV", an acoustic front skin 22 having perforations. Internal partitions 24 are arranged below the front skin 22, perpendicular to this skin. Fixing supports 28 are arranged on the contour of the panel 20.
    In order to limit the manufacturing steps, and therefore the cost of the part, the entire panel 20 is produced in one go, for example by injection of thermoplastic material into a mold forming the negative of the part.
    The tabs 2 come into contact with the surface of the carrier element 30 to be fixed thereto, the partitions 24 being slightly offset from this surface, with a minimum clearance 36 of the order of 1mm.
    The clearance 36 makes it possible to ensure that with small deformations with respect to a theoretical curvature, of the complete acoustic panel 20 and of the entire surface of the support element 30, one nevertheless obtains a frank support on limited points formed by the fixing lugs 28 ensuring a good tightening on this element, and a good positioning of the aerodynamic surface of the front skin 22 in the vein of the nacelle, without being hindered by the partitions 24 of the internal structure which could press on this surface if no play was planned.
    Advantageously, the fixing lugs 28 are arranged outside the aerodynamic guide surface, so as to cover this surface with a maximum of acoustic front skin 22 to optimize the sound attenuation.
    FIGS. 3, 4 and 5 show an acoustic panel 20 formed in one piece by the molding of a thermoplastic material, having a generally triangular shape having a point 32.
    One can in particular use any type of thermoplastic material, but also thermosetting materials formed by molding. It is also possible to provide for manufacturing the panel 20 with a rapid prototyping process, comprising a three-dimensional printing enabling the part to be formed without a mold.
    The top of the acoustic panel 20 has the acoustic front skin
    22. The underside of this front skin 22 has a central structure composed of partitions 24 arranged perpendicularly, forming a grid having substantially square quadrilaterals, which cover the entire perforated surface of this skin.
    The acoustic panel 20 has an outer contour 26 having on the sides and on the front tip 32 of the tabs 28 also formed by the molding of the material. Some tabs 28 are connected to the outer contour 26 by reinforcement triangles 34 providing them with substantial rigidity.
    The molding of the acoustic panel 20 is facilitated by the complete opening of the cells towards the rear, which in particular makes it possible to form a mold comprising two parts connecting along a joint plane parallel to this panel, forming for one the outer side of the front skin 22, and for the other the interior side as well as all of the partitions 24.
    During the molding of the acoustic panel 20, minimum clearance 36 is provided for on all of the partitions 24 and of the external contour 26, relative to the base of the tabs 28, to facilitate mounting on the surface of the support element 30. In this way, the precision constraints on the overall shape of the acoustic panel 20 are limited during its molding, which facilitates its manufacture and reduces costs.
    It will be noted that by this molding principle, parts with small dimensions and low masses can be easily produced, compared to conventional panels using a honeycomb structure receiving a skin bonded on both sides.
    In addition, the clearance 36 formed at the rear of all the closed cells of the central structure, allows evacuation of liquids entering the acoustic panel 20 by the perforations of the front skin 22, in particular water, or possibly fuel in the event of failure. By providing a liquid evacuation circuit comprising the sets 36, one avoids an accumulation which could in the case of water form ice filling the closed cells and reducing the efficiency of the acoustic attenuation, or of fuel which could then ignite.
    To obtain a good level of acoustic attenuation, the perforations of the front skin 22 preferably represent between 5 and 15% of the active surface of this skin, and advantageously around 10%. In addition, for a good level of attenuation up to the frequency of 3000 Hz, the section of the cells in the front skin plane 22 is advantageously inscribed in a square having a side of 50 mm.
    The perforations of the front skin 22 are advantageously carried out directly during the molding of the acoustic panel 20, which makes it possible to avoid the essential drilling phase for conventional composite structures including a honeycomb.
    The distribution of the perforations and the pitch between these perforations can be variable depending on the shape of the part, to obtain the best distribution without having a loss between the closed cells.
    FIG. 6 shows, as a function of the frequency F of a sound wave expressed in Hertz, a first acoustic attenuation curve 40 expressed in decibels, obtained by measurements on an acoustic panel according to the prior art, comprising the partitions 24 of the closed cells which completely join a back skin of this panel, without interposed play.
    A second curve 42 presents the acoustic attenuation obtained by measurements on an acoustic panel 20 according to the invention, comprising the partitions of the closed cells 24 having a clearance of 1 mm relative to the surface of a support element 30 receiving this panel.
    The theory on Helmholtz resonators requires cells which are in principle entirely closed, comprising partitions 24 joining the rear skin of the acoustic panel.
    It is unexpectedly observed that the acoustic attenuation performance of the panel according to the invention is almost equivalent for a frequency between 700 (A) and 2000Hz (B), and slightly less by less than 1 dB below the value A , and above the value B.
    The acoustic performance of the panel according to the invention is reduced marginally, with panels which are very economical to manufacture, and which can easily be adapted to small surfaces having complex shapes, which makes it possible to increase the covered surface area. to improve the acoustic attenuation on a turbojet.
    The invention is described in the foregoing by way of example. It is understood that a person skilled in the art is able to carry out different variant embodiments of the invention without going beyond the ambit of the invention.
    权利要求:
    Claims (10)
    [1" id="c-fr-0001]
    1. Acoustic attenuation panel provided for a turbojet engine, comprising an acoustic front skin (22) comprising perforations, then a central structure formed by partitions (24) arranged perpendicularly to constitute cells, characterized in that the front skin (22 ) and the central structure form the panel (20) made in one piece, which is intended to directly cover a surface of an element of the turbojet engine (30) forming a rear skin closing the cells of the central structure towards the rear .
    [2" id="c-fr-0002]
    2. Attenuation panel according to claim 1, characterized in that it comprises punctual fixing means (28) on the surface of the carrier element (30).
    [3" id="c-fr-0003]
    3. Attenuation panel according to claim 2, characterized in that the punctual fixing means (28) comprise fixing lugs arranged parallel to the surface of the carrier element (30).
    [4" id="c-fr-0004]
    4. Attenuation panel according to claim 2 or 3, characterized in that the point fixing means (28) are arranged on its outer contour (26).
    [5" id="c-fr-0005]
    5. Attenuation panel according to any one of the preceding claims, characterized in that it is designed to present, after its assembly, a clearance (36) between the base of the partitions (24) and the surface of the support element ( 30).
    [6" id="c-fr-0006]
    6. Attenuation panel according to claim 5, characterized in that the clearance (36) is between 0.5 and 1.5mm.
    [7" id="c-fr-0007]
    7. Attenuation panel according to any one of the preceding claims, characterized in that the cells of the central structure have in the plane of the front skin (22), contours forming quadrilaterals.
    [8" id="c-fr-0008]
    8. Attenuation panel according to any one of the preceding claims, characterized in that the closed cells of the central structure have in the plane of the front skin (22), dimensions less than 60mm.
    [9" id="c-fr-0009]
    9. Attenuation panel according to any one of the preceding claims, characterized in that it is formed in one piece by the molding of a synthetic material.
    [10" id="c-fr-0010]
    10. Aircraft turbojet characterized in that it comprises acoustic attenuation panels according to any one of the preceding claims.
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    同族专利:
    公开号 | 公开日
    FR3058672B1|2019-05-10|
    FR3058672A1|2018-05-18|
    FR3058762B1|2020-09-25|
    WO2018087502A1|2018-05-17|
    US20190264614A1|2019-08-29|
    EP3538752A1|2019-09-18|
    EP3538752B1|2020-06-10|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    JPH03248835A|1990-02-28|1991-11-06|Yokohama Rubber Co Ltd:The|Manufacture of honeycomb made of synthetic resin|
    JPH06126853A|1992-10-21|1994-05-10|Hirokazu Dezuki|Production of honeycomb structure|
    US5785919A|1994-06-30|1998-07-28|Short Brothers Plc|Method of manufacture of structual cellular components|
    FR2811129A1|2000-06-30|2002-01-04|Short Brothers Plc|NOISE MITIGATION PANEL, MANUFACTURING METHOD, UNITS INCLUDING THE PANEL|
    EP2291840B1|2008-06-25|2016-01-13|Aircelle|Acoustic panel for an ejector nozzle|
    FR2989310B1|2012-04-11|2014-04-04|Aircelle Sa|METHOD FOR MANUFACTURING SANDWICH PANEL COMPOSITE WITH ALVEOLAR SOUL|FR3100570A1|2019-09-09|2021-03-12|Safran Nacelles|Structural and / or acoustic panel comprising a U-shaped closing flange oriented towards the interior of the panel, and method of manufacturing such a panel|
    FR3102882B1|2019-10-31|2021-11-12|Safran Nacelles|Acoustic attenuation panel and its manufacturing processes|
    US20210239073A1|2020-02-03|2021-08-05|Rohr, Inc.|Thrust reverser door and method for making same|
    法律状态:
    2017-11-23| PLFP| Fee payment|Year of fee payment: 2 |
    2018-05-18| PLSC| Publication of the preliminary search report|Effective date: 20180518 |
    2019-11-20| PLFP| Fee payment|Year of fee payment: 4 |
    2020-11-20| PLFP| Fee payment|Year of fee payment: 5 |
    2021-11-17| PLFP| Fee payment|Year of fee payment: 6 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1660978|2016-11-14|
    FR1660978A|FR3058672B1|2016-11-14|2016-11-14|THRUST REVERSING SHUTTER, AND METHOD OF MANUFACTURING|
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