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
  • G10K11/162—Selection of materials
• • 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

Definitions

• the present invention relates to the general field of acoustic treatments for absorbing noise, and more particularly acoustic treatments comprising porous materials for absorbing noise.
• porous materials are used.
• the low frequency noise absorption limit of these porous materials is related to their thickness. This becomes quite constraining when low frequencies have to be absorbed.
• significant noise absorption is only possible above the visco-inertial transition frequency of the porous material which will then work in the inertial regime. This transition frequency depends on the microstructure of the porous material.
• BPF “Blade Passing Frequency”
• the minimum frequency of perfect absorption is usually reached when the thickness of the porous material is approximately equal to a quarter of the acoustic wavelength. This has the direct consequence of requiring acoustic treatments based on porous materials that are much too bulky and therefore incompatible with the space available in the thin nacelles of the new generations of aircraft engines.
• the invention relates to an acoustic treatment coating comprising a metamaterial, characterized in that the metamaterial comprises a solid structure comprising at least one free space forming a folded cavity and at least one porous material placed in said free space of the solid structure.
• the folded cavity is delimited by a helicoid.
• the metamaterial is produced by additive manufacturing.
• the advantage of using additive manufacturing to form the metamaterial, in particular the solid structure is to be able to precisely adapt the geometry of the structure solid (number of free spaces, number of folded cavities, etc.) at the frequencies that one wishes to attenuate.
• the solid structure is made of:
• thermoplastic materials PEEK (Poly Ether Ether Keton), or the thermoplastic polyimides PEI (Poly Ether Imide, which offer the advantage of extruding well and having increased properties (mechanical resistance, resistance fire resistance, temperature resistance, etc.); or
• thermoplastic material such as nylon, ABS or PLA polymer, which may or may not be reinforced with fibers (carbon fibers, glass fibers or Kevlar fibers for example) or with powders in order to increase structural strength;
• thermosetting material consisting of a polymer base and a crosslinking agent possibly including glass beads or even silica to improve the abradability and erosion properties; or more widely in
• titanium alloy metallic material such as Ti6A4IAV
• Nickel-chromium alloy Inco718, nickel-chromium-iron-molybdenum alloy (Hastelloy X) or else based on nickel alloy (René 77);
• the solid structure can be made of any material that can be printed in three dimensions by the various known additive manufacturing processes.
• each porous material comprises layers of filaments superimposed on each other.
• the advantage of using such a porous material is to be able to precisely adapt the geometry of the porous material (diameter of the filaments, thickness between each layer, size of the pores, etc.) to the frequencies to be attenuated and thus to optimize the treatment. acoustic.
• the effective thickness of the porous material governs the frequencies of the absorption peaks while the pore geometry influences these frequencies and governs the corresponding absorption levels.
• the smaller the diameter of the filaments the larger the absorption peaks and the smaller the pores, the higher the losses.
• Additive manufacturing also makes it possible to produce the solid structure and the porous material simultaneously, which facilitates the placement of the porous material within the free spaces of the solid structure.
• each porous material is made from foams or felts, or from stochastic materials or any porous material whose microstructure is controllable.
• the solid structure comprises between 2 and 6 free spaces, each free space forming a folded cavity.
• the folded cavity is for example delimited by at least one helicoid.
• a section of the solid structure is of circular, triangular, hexagonal or rectangular shape.
• a thickness of the metamaterial is between 5 mm and 500 mm. It is, for example, between 15 mm and 150 mm.
• the folded cavities formed by the empty spaces of the solid structure are identical.
• At least one folded cavity of the solid structure has a different length from the other cavities.
• an internal detuning This can, for example, be achieved by external detuning by assembling several solid structures having a different number of revolutions of the helicoids between the solid structures if the folded cavities are bounded by helicoids. They can also be produced by internal detuning by assembling the same solid structure several times, but whose folded cavities are interrupted before reaching the bottom of the treatment.
• Another object of the invention is a turbomachine fan comprising an acoustic treatment coating according to the invention.
• FIG. 1 shows, schematically and partially, a turbine engine section comprising an acoustic coating according to one embodiment of the invention.
• FIG. 2A represents, schematically and partially, a perspective view of a metamaterial of the acoustic treatment coating according to one embodiment of the invention.
• FIG. 2B represents, schematically and partially, a perspective view of a metamaterial of the acoustic treatment coating according to another embodiment of the invention.
• FIG. 2C represents, schematically and partially, a perspective view of a metamaterial of the acoustic treatment coating according to another embodiment of the invention.
• Figure 3 shows, schematically and partially, porous materials of the acoustic treatment coating according to several embodiments.
• FIG. 4 represents the absorption as a function of the acoustic frequency of an acoustic treatment coating comprising a metamaterial according to one embodiment of the invention and of an acoustic treatment coating comprising only a straight porous material (not folded).
• FIG. 5 represents the absorption as a function of the acoustic frequency of acoustic treatment coatings according to several embodiments of the invention.
• Figure 6 shows, schematically and partially, a porous material of the acoustic treatment coating according to one embodiment, as well as its absorption as a function of the acoustic frequency.
• FIG. 1 schematically and partially represents a section of a turbomachine 100.
• the turbomachine 100 comprises a fan 120 and a thin nacelle 130.
• An acoustic treatment coating 110 according to one embodiment of the invention is present on one part of the 130 nacelle.
• the coating 110 makes it possible to absorb low frequencies, for example between 1000 Hz and 2000 Hz, while having a relatively small thickness, the thickness of the metamaterial included in the coating being between 5 mm and 500 mm, and more particularly between 15mm and 150mm.
• FIGS. 2A, 2B and 2C show, schematically and partially, a perspective view of a metamaterial of the acoustic coating according to several embodiments of the invention.
• the metamaterial 201 comprises a solid structure 210 and three free spaces 211, 212 and 213. Each free space 211, 212 and 213 is formed by 0.75 revolution helicoids 241, 242 and 243.
• the metamaterial 201 has a hexagonal section, and the free spaces 211, 212 and 213 are identical.
• metamaterial 202 includes a solid structure 220 and six free spaces 221, 222, 223, 224, 225 and 226. Each free space 221-226 is formed by one revolution helicoids.
• the metamaterial 202 has a hexagonal shape section, and the free spaces 221 to 226 formed by the helicoids are identical.
• the metamaterial 203 comprises a solid structure 230 and four free spaces 231, 232, 233 and 234. Each free space 231, 232, 233 and 234 is formed by helicoids at 0.75 revolutions.
• the metamaterial 203 has a square-shaped section, and the free spaces 231 to 234 are identical.
• the number of revolutions of the helicoids forming the free spaces of the solid structure can vary between 0.1 and 100.
• Each metamaterial 201, 202 and 203 also includes a porous material placed in each free space 211 to 213, 221 to 226 and 231 to 234 of the metamaterials 201 to 203.
• the solid structure can be made of: a polymer material, such as PEEK (Poly Ether Ether Keton) thermoplastic materials, or PEI (Poly Ether Imide) thermoplastic polyimides, which offer the advantage of to extrude well and to dispose of increased properties (mechanical resistance, fire resistance, temperature resistance, etc.); Where
• thermoplastic material such as nylon, ABS or PLA polymer, which may or may not be reinforced with fibers (carbon fibers, glass fibers or Kevlar fibers for example) or with powders in order to increase structural strength;
• thermosetting material consisting of a polymer base and a crosslinking agent possibly including glass beads or even silica to improve the abradability and erosion properties; or more widely in
• titanium alloy metallic material such as Ti6A4IAV
• Nickel-chromium alloy Inco718, nickel-chromium-iron-molybdenum alloy (Hastelloy X) or else based on nickel alloy (René 77);
• the material forming the solid structure can also be an abradable or porous material.
• the solid structure can be produced by additive manufacturing. This makes it possible to easily adapt the dimensions of the solid structure, such as for example the shape of the section of the structure and of the free spaces, the number of free spaces, or even the number of folded cavities, to the desired performance of the acoustic treatment.
• the porous material comprised in the metamaterials can comprise layers of filaments superimposed on each other.
• the porous material can also be a foam or a felt, or a stochastic (cellular) material or any other porous material whose microstructure is controllable.
• it can be a porous material made up of micro-channels, or a fibrous porous material, or a cellular porous material, such as a foam with connected pores, or even a granular porous material, such as a powder.
• FIG. 3 represents examples of porous materials 301, 302, 303 and 304 comprising layers of filaments according to several embodiments of the invention.
• the porous material 301 comprises filaments 311 to 317 forming two layers superimposed one on the other. Filaments 311 to 317 have a circular section. The angle formed between two filaments of two adjacent layers, for example between filaments 311 and 317, is 90°.
• the porous material 302 comprises filaments 321 to 327 forming two layers superimposed one on the other. Filaments 321 to 327 have a square section.
• the angle formed between two filaments of two adjacent layers, for example between filaments 321 and 327, is 90°.
• the porous material 303 comprises filaments 331 to 337 forming two layers superimposed one on the other.
• Filaments 331 to 337 have a triangular section.
• the angle a formed between two filaments of two adjacent layers, for example between filaments 333 and 337, is greater than 90°.
• the porous material 304 comprises filaments 341 to 352 forming three layers superimposed on each other.
• the filaments 341 to 352 are arranged in pairs and have a circular section.
• the angle a formed between two pairs of filaments of two adjacent layers, for example between the pair of filaments 341, 342 and the pair of filaments 343, 344 is 90°.
• the filaments forming the superimposed layers of the porous material can have a section of triangular, hexagonal, rectangular, square, circular, star shape or any shape.
• the diameter or a characteristic length of the filaments can vary between 1 ⁇ m and 2000 ⁇ m.
• a spacing L between the filaments can vary between 1 ⁇ m and 10 mm.
• the height of the porous material that is to say the superposition of the layers of filaments, can vary between 5 mm and 50 cm. Typically, the height between the layers of filaments forming the porous material can vary between 0.1 and 100 times the diameter of the filament.
• the angle a formed between two filaments of two adjacent layers can vary between 0° and 180°.
• the layers of filaments can be produced by additive manufacturing. This makes it possible in particular to precisely adapt the dimensions of the filaments and of the layers of the porous material to the frequency ranges which it is desired to absorb and to the desired performance of the acoustic treatment. Furthermore, the layers of filaments of the porous material and the solid structure can be produced simultaneously thanks to additive manufacturing.
• FIG. 4 represents the absorption A at normal incidence as a function of the acoustic frequency f of an acoustic treatment covering comprising a metamaterial according to one embodiment of the invention and of an acoustic treatment covering comprising only a porous material .
• the metamaterial according to the invention is composed of a single type of folded porous material, there is no detuning.
• the acoustic frequency f is expressed in Hertz and varies between 0 and 6000 Hz.
• Curve 401 represents the absorption A of a coating comprising only a homogeneous straight porous material. There is therefore no folded cavity.
• This porous material comprises layers of filaments superimposed on each other.
• the diameter D of the filaments is 200 ⁇ m.
• the spacing L between the center of the filaments is 670 ⁇ m.
• the coating thickness is 30 mm.
• Curve 402 represents the absorption A of the coating according to one embodiment of the invention.
• the metamaterial of the invention comprises a porous material comprising layers of filaments superimposed on each other.
• the diameter D of the filaments is 200 ⁇ m and the spacing L between the center of the filaments is 400 ⁇ m.
• the helicoids forming the free spaces of the solid structure have a number of revolutions of 1.
• the metamaterial has a thickness of 30 mm.
• curves 401 and 402 make it possible to show that the coating according to the invention indeed makes it possible to absorb lower frequencies than with a conventional coating comprising only a homogeneous straight porous material. This comparison also makes it possible to show that the coating according to the invention generates a refinement of the absorption peaks.
• FIG. 5 represents the absorption A as a function of the acoustic frequency f of two acoustic treatment coatings according to embodiments of the invention.
• the acoustic frequency f is expressed in Hertz and varies between 0 and 6000 Hz.
• Curve 501 represents the absorption A of a coating of the invention in which the porous material comprises layers of filaments superimposed on each other, the filaments having a diameter of 400 ⁇ m.
• the free spaces of the coating metamaterial are formed by helicoids having 1 revolution.
• the spacing between the filaments is 670 ⁇ m.
• Curve 502 represents the absorption A of a coating of the invention in which the porous material comprises layers of filaments superimposed on each other, the filaments having a diameter of 200 ⁇ m.
• the free spaces of the coating metamaterial are formed by helicoids having 1 revolution.
• the spacing between the filaments is 1000 ⁇ m.
• the coating has a thickness of 30 mm.
• the comparison of the two curves 501 and 502 shows that by decreasing the diameter of the filaments while keeping the number of revolutions of the helicoids constant, it is possible to widen the absorption peaks around the local maxima.
• the free spaces of the metamaterial according to the invention can also have different dimensions. For this, it is possible, for example, to vary the length of the helicoids forming the free spaces. By combining several lengths of folded cavities, the absorption peaks at neighboring frequencies are combined and a coating capable of absorbing noise effectively (absorption A close to 1) is thus obtained over a wide frequency range.
• the porous material included in each of these free spaces is also suitable for adjusting its losses and being able to attenuate the targeted frequencies.
• the coating therefore comprises free spaces each tuned to a particular frequency.
• FIG. 6 represents an example of this type of coating (FIG. 6A) as well as the absorption A of this coating as a function of the acoustic frequency f (curve 601, FIG. 6B).
• the metamaterial 600 of the coating comprises 4 solid structures 610, 620, 630 and 640. Each of the solid structures 610, 620, 630 and 640 comprises folded cavities having a different number of revolution. The filaments forming the porous materials present in the folded cavities have a thickness of 200 ⁇ m.
• the absorption A of this covering 600 (curve 601) is compared with the absorption A of a covering comprising only one solid structure (602). Both coatings are 30 mm thick. In the coating comprising only one solid structure, the spacing between the filaments is 670 ⁇ m and their thickness is 200 ⁇ m. The folded cavity of this liner has a revolution of 1.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Multimedia (AREA)
• Soundproofing, Sound Blocking, And Sound Damping (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)
• Exhaust Silencers (AREA)

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• 2020
  • 2020-11-13 CA CA3099284A patent/CA3099284A1/fr active Pending
• 2021
  • 2021-11-09 EP EP21823961.4A patent/EP4244844A1/de active Pending
  • 2021-11-09 US US18/252,808 patent/US20230419937A1/en active Pending
  • 2021-11-09 WO PCT/FR2021/051986 patent/WO2022101579A1/fr active Application Filing
  • 2021-11-09 CN CN202180076157.0A patent/CN116529811A/zh active Pending

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