Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
  • F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
  • F02C7/24—Heat or noise insulation
• • 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

Definitions

• the present invention relates to the field of sound absorption for nacelles of aircraft turbojets.
• the noise emissions generated by the jet engines of an aircraft are particularly intense at takeoff, whereas the aircraft is generally close to populated areas.
• these panels operate according to the principle of Helmholtz resonators, and include for this purpose a set of cavities sandwiched between a solid structuring skin on the one hand, and a perforated skin on the other.
• the perforated skin is arranged facing the noise emitting zone, so that the acoustic waves penetrate through these perforations inside the cavities and attenuate inside them.
• the cavities are defined by cells of substantially hexagonal cross-section, so that these acoustic absorption panels are commonly referred to as "honeycombs".
• the present invention is thus particularly intended to provide acoustic absorption means having a smaller footprint, substantially comparable efficiency.
• this object of the invention is achieved with a thin acoustic wave absorption panel emitted by an aircraft nacelle turbojet engine, this panel comprising at least one plate able to vibrate so as to render said waves evanescent.
• This evanescence which refers to well-known notions of the theory of vibro-acoustic coupling between a wall and a fluid in which waves propagate, allows optimal absorption of acoustic wave energy by the plate that vibrates.
• noise reduction means are obtained which, while being very efficient, are particularly compact.
• this thin panel comprises at least one structuring skin on which said plate is fixed, studs being interposed between this skin and this plate: the structuring skin makes it possible to maintain the desired profile for the plate, and the pads allow the vibratory movements of this plate.
• the present invention also relates to a nacelle for aircraft turbojet, comprising at least one thin panel according to the above.
• said thin sound absorption panel is fixed between sound absorption sandwich panels: this arrangement makes it possible to mix different acoustic absorption means within one and the same nacelle;
• said nacelle comprises such thin acoustic absorption panels in the zones chosen from the group comprising: the air inlet, the cold air vein, the hot air vein.
• FIG. 1 is a schematic view in longitudinal section of a nacelle of the prior art, surrounding an aircraft turbojet engine, FIGS. 2, 3, 4, 5, 6, 7 are diagrammatic views similar to those of FIG. 1, of nacelles according to the present invention,
• FIG. 2a is a detail view of the nacelle of FIG. 2,
• FIGS. 3a, 3b, 3c, 3d are detailed views of four possible variants of the nacelle of FIG. 3,
• FIG. 7a is a cross-sectional view taken along line A-A of the nacelle of FIG. 7, and
• FIGS. 7b and 7c are cross-sectional views taken along the line B-B of Fig ure 7, two variants of this nacelle.
• Figure 1 shows a conventional nacelle dual flow, defining an air inlet vein 1, a cold flow vein 3 and a hot flow stream 4.
• this nacelle has a symmetry of revolution about its longitudinal axis A.
• the air intake duct 1 is surrounded by an acoustic absorption shell 9 formed by the assembly of acoustic absorption sandwich panels.
• the cold flow duct 3 is in turn delimited by radially outer and inner walls also at least partially coated with acoustic absorption sandwich panels January 1 and 13, respectively.
• the hot flow stream 4 is delimited by a primary nozzle and an ej ect io n of g az, coated ivem ent resp u e and partially m u n of sound absorption sandwich panels 15, 17.
• the locations of the acoustic absorption sandwich panels 9, 1 1, 13, 15, 17 correspond to the areas of the acoustic emissions of the nacelle.
• the presence of these acoustic absorption sandwich panels makes it possible to substantially reduce the perceived sound level in the vicinity of the aircraft, especially during take-off or landing.
• FIG. 2a on which a nacelle according to the invention can be seen, in which the acoustic absorption sandwich panels 9, 11, 13, 15, 17 are all replaced by thin absorption panels. acoustic according to the invention.
• these thin panels comprise plates 19 and structuring skins 21, pads being interposed between these plates 19 and these skins 21.
• the studs 23 fixed on the structuring skin 21 are in simple contact with the plate 19, thus allowing the vibrations thereof.
• the plates 19 and the skins 21 are fixed to one another.
• the plate 19 may for example be formed of aluminum-based alloy, and have a thickness of the order of one millimeter.
• the structuring skin 21 may itself be formed either of a metal alloy base or of a composite material, as may the pads 23.
• the characteristics of the plate 19 are chosen so as to make evanescent the acoustic waves circulating in the air veins delimited by these plates.
• the continuous bold lines designate conventional acoustic absorption sandwich panels
• the discontinuous bold lines designate thin sound absorption panels according to the invention.
• the sound absorption assembly 13 situated on the radially inner wall of the cold flow duct 3 is formed of a substantially annular thin panel 13a sandwiched between two acoustic absorption sandwich panels 13b and 13c.
• this thin panel 13a may have the structure shown in Figure 2a, fixed at its ends to acoustic panels respectively having beveled ends (Figure 3a) or straight (Figure 3d).
• this thin panel 13a may be formed of a simple metal alloy plate 19, fixed at its ends on sandwich panels 13b, 13c respectively presenting beveled or straight ends. .
• Figures 5 and 6 show other variants of such axial alternations.
• FIG. 7a it can be seen that it is possible, for example, to have four thin panels interposed with three sandwich panels to form the sound absorption assembly 9 of at least a portion of the inlet vein. of air 1.
• FIGS. 7b and 7c it can be seen that in the cold flow duct 3, it is possible to provide that the magnetic panels and the acoustic absorption sandwich panels are circumferentially alternated, and respectively spoiled externally. 1 and inside 13 of the cold flow vein, are arranged vis-à-vis (Figure 7b) or opposed two by two ( Figure 7).
• the invention provides noise reduction means which are very compact radially and extremely simple in design.
• the thin acoustic absorption panels of the present invention are particularly suitable for nacelles with a high dilution rate, and more generally for nacelles whose aim is to reduce the thickness of the aerodynamic lines.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Multimedia (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Soundproofing, Sound Blocking, And Sound Damping (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)
• Other Liquid Machine Or Engine Such As Wave Power Use (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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• 2012
  • 2012-04-20 FR FR1253633A patent/FR2989814B1/fr not_active Expired - Fee Related
• 2013
  • 2013-04-18 WO PCT/FR2013/050858 patent/WO2013156739A1/fr active Application Filing
  • 2013-04-18 EP EP13722502.5A patent/EP2839458A1/de not_active Withdrawn
  • 2013-04-18 RU RU2014145641A patent/RU2014145641A/ru not_active Application Discontinuation
  • 2013-04-18 BR BR112014023607A patent/BR112014023607A8/pt not_active IP Right Cessation
  • 2013-04-18 CA CA2869623A patent/CA2869623A1/fr not_active Abandoned
  • 2013-04-18 CN CN201380020793.7A patent/CN104246868A/zh active Pending
• 2014
  • 2014-10-20 US US14/518,496 patent/US20150068837A1/en not_active Abandoned

Non-Patent Citations (1)

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