RESONATING PATCH AND ACOUSTIC TREATMENT CELL PROVIDED WITH SUCH A PATCH

Abstract

Resonating patch for acoustic treatment comprising a resonant plate, a transducer and an electrical circuit electrically connected to the transducer, the resonant plate comprising a peripheral strip extending along the perimeter of the resonant plate.

The patch comprises cutouts together defining deformable lamellae having at least one end connected to the peripheral strip.

Claims

1. A resonating patch for acoustic treatment for a cell for acoustic treatment of an acoustic panel of a turbomachine of an aircraft, the resonating patch comprising a resonant plate, a transducer and an electrical circuit electrically connected to the transducer, the resonant plate comprising a peripheral strip extending along the perimeter of the resonant plate, wherein the resonant plate comprises cutouts together defining deformable lamellae having at least one end connected to the peripheral strip.

2. The resonating patch for acoustic treatment according to claim 1, wherein the cutouts of the resonant plate are rectilinear cutouts together defining polygonal lamellae.

3. The resonating patch for acoustic treatment according to claim 1, comprising at least two lamellae of different dimensions.

4. The resonating patch for acoustic treatment according to claim 1, wherein the resonant plate has a form entered in a circle of diameter D between 5 and 50 mm, and the lamellae have a length of between 1 and 50 mm.

5. The resonating patch for acoustic treatment according to claim 1, wherein the lamellae comprise a width of between 0.5 and 20 mm.

6. The resonating patch for acoustic treatment according to claim 1, wherein the lamellae have a thickness between 20 μm and 2 mm.

7. The resonating patch for acoustic treatment according to claim 1, wherein the cutouts have a width of between 10 μm and 1 mm.

8. The resonating patch for acoustic treatment according to claim 1, wherein the cutouts are parallel to each other.

9. The resonating patch for acoustic treatment according to claim 1, wherein two adjacent cutouts are devoid of parallelism.

10. The resonating patch for acoustic treatment according to claim 1, wherein the lamellae comprise two ends according to the direction of the length, the two ends being attached to the peripheral strip.

11. The resonating patch for acoustic treatment according to claim 1, wherein the plate comprises material with a high Young's module.

12. The resonating patch for acoustic treatment according to claim 1, wherein the transducer is a piezoelectric transducer comprising a thin layer on the zones of maximal deformations of lamellae, such as at the ends of the lamellae attached to the peripheral strip.

13. The resonating patch for acoustic treatment according to claim 1, wherein the transducer is an electrodynamic transducer comprising a thin layer of an electrically conductive material on the lamellae and a magnet.

14. A cell for acoustic treatment comprising an enclosure, a cavity delimited by the enclosure, and a resonating patch according to claim 1 arranged in the cavity.

15. The cell for acoustic treatment according to claim 14, also comprising a protective grille mounted on an end of the enclosure intended to be opposite a fluidic flow.

16. A panel for acoustic treatment intended to be arranged on at least one wall of a turbojet in contact with a fluidic flow, the panel comprising a first plate, a second plate parallel to the first plate and having a first face intended to be in contact with a fluidic flow and a second face opposite the first plate, wherein it also comprises cells for acoustic treatment according to claim 14 extending between the first and second plates.

17. A turbomachine for an aircraft comprising at least one panel for acoustic treatment according to claim 16.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] FIG. 1 illustrates a sectional view of a turbojet according to an embodiment of the invention, in a longitudinal plane of the turbojet.

[0054] FIG. 2 illustrates a partial perspective view of a panel for acoustic treatment according to an embodiment of the invention.

[0055] FIG. 3 illustrates a schematic perspective view of a cell for acoustic treatment 18 of the core 12 of the panel for acoustic treatment 10 of FIG. 2.

[0056] FIG. 4 illustrates a perspective view of the resonant plate 21 of the resonating patch 20 of the cell 18 of FIG. 3 according to a first embodiment.

[0057] FIG. 5 illustrates a plan view of the resonant plate 21 of FIG. 4 according to a first orientation relative to a fluidic flow.

[0058] FIG. 6 illustrates a plan view of the resonant plate 21 of FIG. 4 according to a second orientation relative to a fluidic flow.

[0059] FIG. 7 illustrates a perspective view of the resonant plate 21 of the resonating patch 20 of the cell 18 of FIG. 3 according to a second embodiment.

[0060] FIG. 8 illustrates a plan view of the resonant plate 21 of FIG. 7 according to a first orientation relative to a fluidic flow.

[0061] FIG. 9 illustrates a plan view of the resonant plate 21 of FIG. 7 according to a second orientation relative to a fluidic flow.

[0062] FIG. 10 illustrates a perspective view of a resonating patch 20 with an electrodynamic transducer 22 according to an embodiment.

[0063] FIG. 11 illustrates a plan view of the resonant plate 21 of the resonating patch 20 according to a third embodiment.

[0064] FIG. 12 illustrates a plan view of the resonant plate 21 of the resonating patch 20 according to a fourth embodiment.

[0065] FIG. 13 illustrates a plan view of the resonant plate 21 of the resonating patch 20 according to a fifth embodiment.

DESCRIPTION OF EMBODIMENTS

[0066] FIG. 1 shows a sectional view of a turbojet 1 according to an embodiment of the invention, in a longitudinal plane of the turbojet 1.

[0067] The turbojet 1 comprises a nacelle 2, an intermediate casing 3 and an internal casing 4. The nacelle 2 and the two casings 3 and 4 are coaxial and define an axial direction D.sub.A and a radial direction D.sub.R. The nacelle 2 defines at a first end an inlet channel 5 of a fluid flow and at a second end, opposite the first end, a discharge channel 6 of a fluid flow. The intermediate casing 3 and the internal casing 4 together delimit a primary vein 7 of a fluid flow. The nacelle 2 and the intermediate casing 3 together delimit a secondary vein 8 of a fluid flow. The primary vein 7 and the secondary vein 8 are arranged according to an axial direction D.sub.A of the turbojet 1 between the inlet channel 5 and the discharge channel 6.

[0068] The turbojet 1 also comprises a fan 9 configured to deliver an airflow F as fluidic flow, the airflow F being divided when exiting from the fan into a primary flow Fp circulating in the primary vein 7 and into a secondary flow Fs circulating in the secondary vein 8.

[0069] The turbojet 1 also comprises panels for acoustic treatment 10 configured to attenuate the acoustic waves emitted by the turbojet 1 before these waves discharge radially to the outside of the nacelle 2 of the turbojet 1.

[0070] Each panel for acoustic treatment 10 is configured to attenuate acoustic waves whereof the frequency belongs to a predetermined range of frequencies. In the embodiment illustrated in FIG. 1, the panels 10 for acoustic treatment are integrated into the nacelle 2, the intermediate casing 3 and the internal casing 4. On the internal casing 4, the panels 10 for acoustic treatment are integrated, on the one hand, on the portion upstream of the intermediate casing 3 according to the axial direction D.sub.A and especially on the portion carrying the fan 9, and on the other hand, on a portion downstream of the intermediate casing 3.

[0071] FIG. 2 shows a partial view in perspective of a panel for acoustic treatment 10 according to an embodiment of the invention.

[0072] In reference to FIG. 2, the panel for acoustic treatment 10 comprises a core 12, an entry layer 14 and a reflecting layer 16.

[0073] In the embodiment illustrated in FIG. 2, the core 12 presents a honeycomb structure. More precisely, the core 12 comprises a plurality of alveolae 18, arranged according to a known honeycomb structure. Each alveola 18 forms a cell for acoustic treatment for absorption of soundwaves having a cylindrical form with hexagonal base. Each cell for acoustic treatment 18 comprises a resonating cavity 180 of cylindrical form with hexagonal base and an enclosure 182 comprising 6 walls 1820 extending between the entry layer 14 and the reflecting layer 16.

[0074] In variants, the alveolar structure of the core 12 could be formed by acoustic cylindrical cells with circular bases, or other, or even any.

[0075] Each alveola 18 terminates on a first face 121 of the core 12 and on a second face 122 of the core 18 located opposite the first face 121. The first face 121 of the core 12 is in contact with the entry layer 14 and is intended to be oriented towards the primary air vein 7 or secondary air vein 8 according to the placement of the panel for acoustic treatment 10. The second face 122 of the core 12 is in contact with the reflecting layer 16 and is intended to be oriented opposite the air vein.

[0076] According to the embodiment, the core 12 can be made of metal, or of composite material such as composite material formed from fibres of carbon or glass embedded in a matrix of hardened resin.

[0077] The entry layer 14 can be a monobloc plate formed by additive manufacturing. The entry layer 14 has a first face 141 in contact with a fluidic flow such as the flow F and a second face 142 opposite the first face 141 and opposite the core 12 and the reflecting layer 16. At least some of the entry layer 14 is porous.

[0078] The reflecting layer 16 is adapted to reflect acoustic waves having a frequency belonging to the predetermined range of frequencies. It is connected to the walls 1820 of the enclosure 182 of the alveolae 18 of the core 12 in the region of its second face 122. It can be fixed to the core 12 by adhesion for example. According to the embodiment, the reflecting layer 16 can be made of metal or composite material such as composite material formed by fibres of carbon or glass embedded in a matrix of hardened resin.

[0079] FIG. 3 illustrates a schematic view in perspective of a cell for acoustic treatment 18 of the core 12 of the panel for acoustic treatment 10 of FIG. 2.

[0080] The cell for acoustic treatment 18 which comprises the resonating cavity 180 delimited by the enclosure 182, here cylindrical with a circular base, also comprising a protective grille 188, a resonating patch 20 inserted inside the resonating cavity 180.

[0081] The protective grille 188 comprises a perforated or micro-perforated structure or a protective wiremesh to reduce direct impact of the flow. This protective grille 188 is mounted on the end of the enclosure 182 intended to be opposite a fluidic flow, that is, at the end of the enclosure 182 forming part of the first face 121 of the core 12 in contact with the entry layer 14 of the panel for acoustic treatment 10.

[0082] The resonating patch 20 for acoustic treatment comprises a resonant plate 21 with a high Young's module, a transducer 22 and an electrical circuit 23 electrically connected to the transducer 22.

[0083] As is illustrated more clearly in FIG. 4 which shows the resonant plate 21 according to a first embodiment, the resonant plate 21 comprises a peripheral strip 210 extending along the perimeter of the plate, as well as rectilinear cutouts 211 together defining deformable lamellae 212.

[0084] In the first embodiment illustrated in FIG. 4, the deformable lamellae 212 comprise a first end 2120 and a second end 2125, both attached to the peripheral strip 210.

[0085] In the first embodiment, with a general circular form, the resonant plate 21 comprises rectilinear cutouts 211 parallel to each other and separated by the same space with the adjacent cutouts to have lamellae 212 all having the same width to easily allow lamellae of different lengths and also have a frequency range for acoustic treatment greater than with lamellae all of the same length, as would be the case for a resonant plate having a general rectangular form with lamellae all of the same width.

[0086] FIG. 7 illustrates a resonant plate 21 according to a second embodiment. The second embodiment illustrated in FIG. 7 differs from the first embodiment illustrated in FIG. 4 in that only the first end 2120 of the deformable lamellae 212 is connected to the peripheral strip 210, the second end 2125 being free.

[0087] The behaviour of the resonant plate 21 in the face of an aerodynamic flow varies according to the angle of incidence of the flow and the direction.

[0088] In the example illustrated in FIG. 1, in which the panels for acoustic treatment 10 comprising the cells for acoustic treatment 18 are mounted on the walls of a turbomachine 1, the fluidic flow F flows mainly according to the axial direction D.sub.A of the turbomachine 1.

[0089] The orientation of the resonant plate 21 inside a cell for acoustic treatment 18 is defined by an angle formed between the direction of the lamellae 212 and the direction of the fluidic flow F, in other words between the direction of the lamellae 212 and the axial direction D.sub.A of the turbomachine 1.

[0090] The resonant plate 21 according to the first embodiment illustrated in FIG. 4 can function operationally with an orientation defined by an angle between −30° and 30° relative to the axial direction D.sub.A as shown in FIGS. 5 and 6 which show respectively a resonant plate 21 according to the first embodiment with an orientation at 0° and an orientation at −30° relative to the direction of a fluidic flow F, that is, relative to the axial direction D.sub.A of the turbomachine 1.

[0091] The resonant plate 21 according to the second embodiment illustrated in FIG. 7 can function operationally with an orientation defined by an angle between −45° and 45° relative to the axial direction D.sub.A, as shown in FIGS. 8 and 9 which show respectively a resonant plate 21 according to the second embodiment with an orientation at 0° and an orientation at −45° relative to the direction of the fluidic flow F, that is, relative to the axial direction D.sub.A of the turbomachine 1.

[0092] The first embodiment can function in both flow directions (reversible), as opposed to the second embodiment which functions better in the direction presented in FIGS. 8 and 9, that is, with the flow arriving from the first end 2120, the one connected to the peripheral strip 210.

[0093] According to the embodiments, the transducer 21 can have different forms.

[0094] According to a first example, the transducer 21 can be an electrodynamic transducer comprising a thin layer 220 of electrically conductive material on the lamellae 212 and a magnet 225, such as for example an annular magnet, on which is arranged the resonant plate 21, as is illustrated in FIG. 10. The layer 220 of conductive material can be made via deposit of copper at sites having maximum articulation to form a copper coil.

[0095] According to a second example, the transducer 21 can be a piezoelectric transducer comprising a thin layer 220 on the zones of maximal constraints of the lamellae 212, such as at the ends of the lamellae attached to the peripheral strip for maximising the effect according to phases, that is, at the first end 2120 and optionally at the second end 2125 for the second embodiment illustrated in FIGS. 7 to 9.

[0096] FIGS. 11 to 13 schematically illustrate a third, a fourth and a fifth embodiments of the resonant plate 21.

[0097] The third embodiment illustrated in FIG. 8 differs from the first embodiment illustrated in FIG. 7 in that the general form of the resonant plate 21 is a hexagon.

[0098] This hexagonal form easily adapts to cells for hexagonal acoustic treatments 18 such as those presented in FIG. 2, for example.

[0099] The fourth embodiment illustrated in FIG. 9 differs from the first embodiment illustrated in FIG. 7 in that the general form of the resonant plate 21 is any form whatsoever, and the fifth embodiment illustrated in FIG. 10 differs from the fourth embodiment illustrated in FIG. 9 in that the cutouts 21 are not parallel, which produces lamellae of non-constant width having a second action lever on the frequencies of resonance of the lamellae and therefore of the possible range of attenuation frequency.

[0100] In all the embodiments illustrated, the resonant plate 21 can have a form entered in a circle C whereof the diameter is between 5 and 50 mm, and the lamellae 212 can have a length of between 1 and 50 mm, a width of between 0.5 and 20 mm, and a thickness between 20 μm and 2 mm.

[0101] The cutouts 211 between the lamellae 212 can be formed by slots having a width of between 10 μm and 1 mm.

[0102] The panel for acoustic treatment 10 therefore comprises a plurality of cells for acoustic treatments 18 fitted with resonating patches 20 which can all be attuned to the same frequency to have a very fine performance acoustically but narrower bandwidth, or else tuned to different frequencies so as to have less efficiency on frequencies but over a much wider frequency band.

[0103] The panel for acoustic treatment according to the invention accordingly provides a solution for optimised acoustic treatment for attenuations at low frequencies and whereof the attenuation range is greater in reduced bulk so it can be integrated into propulsive architectures with high dilution rate.