EP2071561A2 - Schallabsorptionsstruktur zum Dämpfen von Geräuschen, die hauptsächlich durch einen Rotor erzeugt werden, und eine solche Struktur umfassende Verkleidung - Google Patents

Schallabsorptionsstruktur zum Dämpfen von Geräuschen, die hauptsächlich durch einen Rotor erzeugt werden, und eine solche Struktur umfassende Verkleidung Download PDF

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Publication number
EP2071561A2
EP2071561A2 EP08020965A EP08020965A EP2071561A2 EP 2071561 A2 EP2071561 A2 EP 2071561A2 EP 08020965 A EP08020965 A EP 08020965A EP 08020965 A EP08020965 A EP 08020965A EP 2071561 A2 EP2071561 A2 EP 2071561A2
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EP
European Patent Office
Prior art keywords
absorbent structure
height
structure according
cavities
porous wall
Prior art date
Legal status (The legal status 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 status listed.)
Granted
Application number
EP08020965A
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English (en)
French (fr)
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EP2071561A3 (de
EP2071561B1 (de
Inventor
Henri-James Marze
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Airbus Helicopters SAS
Original Assignee
Eurocopter France SA
Eurocopter SA
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Publication date
Application filed by Eurocopter France SA, Eurocopter SA filed Critical Eurocopter France SA
Publication of EP2071561A2 publication Critical patent/EP2071561A2/de
Publication of EP2071561A3 publication Critical patent/EP2071561A3/de
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Publication of EP2071561B1 publication Critical patent/EP2071561B1/de
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    • 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 technical field of acoustic treatment to reduce noise pollution emitted by rotors, motors or other.
  • acoustic treatment is often essential in the aeronautical field and in particular on helicopters.
  • the present invention relates more particularly to an acoustic treatment of an anti-torque streamlined rotor vein also called "fenestron".
  • Any rotating rotor in a vein, fed by a more or less turbulent air, will generate acoustic waves that can be organized or random.
  • the organized waves constitute what is commonly called the rotational noise, which is characterized in the noise spectrum by discrete frequencies (lines) corresponding to the rotation frequencies of the blades, the transmission shaft, their subharmonic and harmonics or at frequencies modulated by an angular phase shift of the blades or the rotation regime.
  • Random waves are characterized in the noise spectrum by a high spectral density over a very wide band of frequencies. These random waves generate so-called "broadband" noises.
  • absorbent structures to reduce the propagation of acoustic waves emitted by noisy devices such as rotors or motors, comprising a rigid partition, a porous wall and separation means for disposing the porous wall at a determined distance of the rigid partition, delimiting cavities between said porous wall and said rigid partition, the height of which is determined to obtain a maximum absorption of a given frequency of the transmitted acoustic waves.
  • the audible acoustic waves emitted are most often composed of random and organized waves distributed over a wide band of frequencies, making the known materials insufficiently effective to effectively mitigate, in any field of flight, the acoustic waves thus composed. It is necessary for example to treat pure sounds and their harmonics but also noise sources operating over a wide range of speed variation as is the case for aircraft and operating over a temperature range of -40 ° VS at + 40 ° C. The sources of parasitic noise that must be treated are many and very diverse.
  • the document US 6,114,652 describes for example a method for producing acoustic attenuation chambers using a honeycomb structure.
  • the cells comprise at least two absorbent and porous layers in which perforations are provided by means of a laser.
  • the constituent material of the layers is based on polymers and is chosen for its energy absorption properties according to a given radiation frequency of the laser.
  • the layers thus have perforations of different diameter, distributed differently, to optimize the sound absorption properties.
  • This document describes an absorbent structure for reducing the propagation of acoustic waves comprising a rigid partition, at least one porous wall and separation means for disposing the porous wall at a determined distance from the rigid partition, delimiting cavities of a given height between said porous wall and said rigid partition.
  • the objects of the present invention therefore aim to provide a new absorbent structure for attenuating pure sounds as well as having a high absorption efficiency of acoustic waves in a wide frequency band.
  • the absorbent structure according to the invention thus makes it possible to treat groups of pure sounds and / or so-called "broadband" noises. This produces a substantial and audible reduction of the spurious noise generated.
  • Another object of the present invention is to provide an absorbent structure providing an acoustic coating on the one hand and constituting a rigid structural element on the other. So, in the application pertaining to rotors helical anticouples of helicopters, the absorbent structure constitutes the air flow vein of said anti-torque rotors.
  • Another object of the present invention is to propose an absorbent structure not significantly increasing the weight and / or the bulk of the elements on which or in which it is used as a replacement for metal elements made of simple sheet metal or walls. simple composite materials.
  • an absorbent structure for reducing the propagation of acoustic waves emitted by noisy devices of the rotor or motor type, comprising a rigid partition, at least one porous wall and means separation device for arranging the porous wall at a determined distance from the rigid partition, delimiting cavities of a height h1 between said porous wall and said rigid partition, said height h1 being determined to obtain a maximum absorption of a base frequency F1 given transmitted acoustic waves, said structure comprising complementary absorption means to obtain a maximum absorption of the acoustic waves transmitted to at least one additional base frequency Fi, of the acoustic wave spectrum emitted, i being an integer greater than or equal to at 2, characterized in that the porous wall (4,5) comprises at least a first layer (4a, 5a) in fine mesh and at least a second layer (4b, 5b) of fiber felt. The combination of these two layers provides on the one hand an optimal porosity and on the other hand a sufficient
  • the complementary absorption means in combination with the porous wall and the cavities allow therefore to obtain a maximum absorption coefficient of 100% for at least one basic frequency F1 and Fi and an absorption coefficient of substantially 80% around these basic frequencies F1 and Fi, and this over a wide frequency band ranging for example from 0.7.Fi to 1.3.Fi.
  • the absorbent structure according to the invention also has the advantage of presenting, in addition to a maximum attenuation for each basic frequency F1 or Fi, a maximum attenuation for multiples of the basic frequencies corresponding to (2n + 1) .Fi, where n is an integer greater than or equal to 1.
  • the total attenuation of a line at 1000 Hz is therefore accompanied by an attenuation of about 80% of the other lines of the noise spectrum, representative of the noise at frequencies between 667 Hz and 1333 Hz and preferably between 700 Hz and 1300 Hz and to those between 1400 Hz and 2600 Hz.
  • the complementary absorption means comprise a complementary porous wall, disposed in the cavities, at an intermediate height h2.
  • the heights h1 and h2 therefore correspond respectively to the attenuation of the respective frequencies F1 and F2.
  • the cavities of height h1 and h2 are thus arranged in parallel, thereby reducing the overall thickness of the absorbent structure by relative to a series arrangement of two successive cavities of height h1 and h2.
  • the complementary absorption means are materialized by an inclination of the rigid partition relative to the porous wall so as to continuously modify, in at least one direction, the height h 1 d one cavity to another.
  • Such a design makes it possible to promote the processing of noise over a wide frequency band. It is therefore advantageous according to another exemplary embodiment according to the invention, to associate these complementary absorption means with complementary absorption means favoring the processing of noise at one or more basic frequencies Fi.
  • the complementary absorption means comprise, alternately with the cavities of height h1, additional cavities of height h3, said height h3 being smaller than the height h1.
  • These additional cavities of height h3 are for example made with a deposit of an absorbent material on the rigid partition in certain cavities of height h1, for example in every other cavity.
  • the mesh and / or the felt are preferably made of metallic or composite materials.
  • the first layer and the second layer are assembled by gluing or welding. These operations, as well as the assembly of a porous wall and the rigid partition defining the cavities, are easily automated during the manufacture of the absorbent structure.
  • the rigid partition is preferably made of glass fibers. It is the same, preferably for the rising partitions. This provides rigidity, strength and lightness, required especially in the field of helicopters.
  • the objects assigned to the present invention are also achieved by means of a helicopter anti-torque rotor vein constituted at least in part by an absorbent structure as shown.
  • the objects assigned to the present invention are also achieved by means of a ducted rotorcraft rotor for helicopters having a fairing consisting at least in part of an absorbent structure as shown.
  • the absorbent structure according to the invention a part of which is illustrated in FIG. figure 1 , comprises a rigid partition 1, for example made of glass fibers, as well as rising partitions 2 extending substantially orthogonally from the rigid partition 1 to delimit cavities 3.
  • the rising partitions 2, for example made of glass fibers, extend to a porous wall 4 and constitute separation means between the rigid partition 1 and the porous wall 4.
  • the cavities 3 have a height h1 whose value, with a good approximation, is proportional to the inverse of the base frequency F that must be absorbed, and this at a given temperature T.
  • h vs . T 1 / 2 .1 / F
  • c is a constant, F being the frequency to be absorbed, is known as such.
  • the value h corresponds substantially to a quarter or to a multiple of a quarter of the wavelength of the frequency F which should be absorbed.
  • the porous wall 4 comprises a first layer 4a of fine or very fine mesh metal mesh and a second layer 4b of metal fiber felt.
  • the mesh and the felt can also be made of composite materials.
  • the layers 4a and 4b are for example assembled by gluing or welding.
  • the figure 2 illustrates an embodiment of the absorbent structure according to the invention.
  • the latter comprises a second porous wall 5 disposed between the rigid partition 1 and the porous wall 4.
  • Each of the cavities 3 is thus divided in two by means of the second porous wall 5.
  • the porous wall 5 is spaced apart from the rigid partition 1, extending at a height h2 less than h1.
  • the height h2 is determined by the same relationship as that determining h1 and specified above.
  • the porous wall 5 is preferably identical to or similar to the porous wall 4 and comprises a first layer 5a of fine mesh metal mesh and a second 5b of metal fiber felt.
  • This absorbent structure makes it possible to absorb two basic frequencies F1 and F2, corresponding to two distinct lines of the noise spectrum which should be attenuated.
  • the figure 3 illustrates another embodiment of the absorbent structure according to the invention.
  • the complementary absorption means comprise additional cavities 7 having a height h3, alternating with cavities of height h1.
  • the height h3 is also determined by the relationship specified above.
  • the additional cavities 7 are obtained thanks to a deposit of an absorbent material 7a on the rigid partition 1, in certain cavities 3.
  • a cavity 3 on two can thus be transformed into additional cavity 7 having a height h3 .
  • the cavities 3 and the additional cavities 7 thus make it possible respectively to absorb acoustic waves of distinct frequencies F1 and F3 from the spectrum of the noise emitted.
  • the figure 4 represents another embodiment of the absorbent structure according to the invention, wherein the additional absorption means are obtained by an inclination of the rigid partition 1 relative to the porous wall 4. This results in rising partitions 2 having a different height h1 (n) passing from one rising wall 2 to the next.
  • the figure 5 schematizes in section an exemplary embodiment of a helicopter anti-torque rotor rotor.
  • the anti-torque rotor comprises a hub 10 driving blades 11.
  • Retaining plates 12 are provided to firstly maintain the hub 10 in position in a vein 13 of air circulation and secondly ensure a rectification of the air expelled by said rotor. This rectification is obtained by a particular orientation of the holding plates 12, for example a radial orientation 12a for the one 12a and an orientation quasi-radial for the other 12b holding plates 12, represented for example at the figure 6 .
  • the air sucked by the anti-torque rotor is shown by the arrows A.
  • the sucked air enters the air circulation stream 13 through an inlet 13a of the vein 13, and is expelled via an outlet 13b of the vein 13.
  • the inlet 13a and the outlet 13b of the vein 13 are delimited by a fairing 15 of the rotor.
  • This fairing 15 is made by means of absorbent structure elements according to the invention or by elements coated with an absorbent structure according to the invention.
  • the air circulation duct 13 also comprises a constriction 16 positioned around the trajectory of the ends of the blades 11.
  • the holding plates 12a, 12b are for example provided on each of their faces with an absorbent structure according to the invention.
  • all the parts of the fairing 15 delimiting the stream 13 of air circulation comprises a coating of an absorbent structure according to the invention.
  • these parts can also be made directly with absorbent structure elements.
  • absorbent structure elements thus constitute rigid structural elements of the anti-torque rotor.
  • the figure 7 illustrates a cross-sectional view of a helicopter modeled anti-torque rotor, in which the hub 10 transmits to the blades 11 a rotational movement through a transmission shaft 17.
  • the hub 10 comprises a housing 10a and a covering element 10b coated or made of an absorbent structure according to the invention.
  • the stream 13 of air circulation is defined in particular by air inlet lips 18 and by a diffusion cone 19 coated with or constituted by an absorbent structure according to the invention.
  • the whole of the stream 13 of air circulation is preferably treated, namely coated or constituted, with the absorbent structure according to the invention.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Building Environments (AREA)
  • Motor Or Generator Frames (AREA)
EP08020965.3A 2007-12-14 2008-12-03 Schallabsorptionsstruktur zum Dämpfen von Geräuschen, die hauptsächlich durch einen Rotor erzeugt werden, und eine solche Struktur umfassende Verkleidung Active EP2071561B1 (de)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR0708699A FR2925208B1 (fr) 2007-12-14 2007-12-14 Structure absorbante pour l'attenuation de bruits generes notamment par un rotor et carenage comportant une telle structure

Publications (3)

Publication Number Publication Date
EP2071561A2 true EP2071561A2 (de) 2009-06-17
EP2071561A3 EP2071561A3 (de) 2017-05-17
EP2071561B1 EP2071561B1 (de) 2021-02-03

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EP08020965.3A Active EP2071561B1 (de) 2007-12-14 2008-12-03 Schallabsorptionsstruktur zum Dämpfen von Geräuschen, die hauptsächlich durch einen Rotor erzeugt werden, und eine solche Struktur umfassende Verkleidung

Country Status (6)

Country Link
US (1) US7779965B2 (de)
EP (1) EP2071561B1 (de)
JP (1) JP2009145891A (de)
CN (1) CN101458926B (de)
CA (1) CA2646933C (de)
FR (1) FR2925208B1 (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2706009A1 (de) 2012-09-07 2014-03-12 Eurocopter Deutschland GmbH Leitwerk eines Helikopters
WO2015023389A1 (en) * 2013-08-12 2015-02-19 Hexcel Corporation Sound wave guide for use in acoustic structures
EP2913271A1 (de) * 2014-02-28 2015-09-02 AIRBUS HELICOPTERS DEUTSCHLAND GmbH Drehflügler mit mindestens einem Hauptrotor und mindestens einem rotor zum Drehmomentausgleich
EP2913269A1 (de) * 2014-02-28 2015-09-02 AIRBUS HELICOPTERS DEUTSCHLAND GmbH Drehflügler mit mindestens einem Hauptrotor und mindestens einem Rotor zum Drehmomentausgleich
EP2913270A1 (de) * 2014-02-28 2015-09-02 AIRBUS HELICOPTERS DEUTSCHLAND GmbH Drehflügler mit mindestens einem Hauptrotor und mindestens einem Rotor zum Drehmomentausgleich

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US7913813B1 (en) * 2009-10-21 2011-03-29 The Boeing Company Noise shield for a launch vehicle
US8770343B2 (en) * 2011-11-23 2014-07-08 The Boeing Company Noise reduction system for composite structures
GB201209658D0 (en) * 2012-05-31 2012-07-11 Rolls Royce Plc Acoustic panel
JP5787947B2 (ja) * 2013-08-09 2015-09-30 三菱電機株式会社 防音装置、エレベータ用巻上機及びエレベータ
EP2878433B1 (de) 2013-11-29 2016-04-20 AIRBUS HELICOPTERS DEUTSCHLAND GmbH Ummantelte Drehanordnung aus segmentiertem Verbundwerkstoff für Flugzeuge sowie verfahren zu deren Herstellung
AU2016267963B2 (en) * 2015-05-25 2020-08-13 Dotterel Technologies Limited A shroud for an aircraft
CN105620716A (zh) * 2016-03-07 2016-06-01 刘海涛 载人多旋翼飞行器隔音方法
FR3054608B1 (fr) * 2016-07-29 2020-06-26 Safran Panneau acoustique pour une turbomachine et son procede de fabrication
JP7006083B2 (ja) * 2017-09-26 2022-01-24 富士フイルムビジネスイノベーション株式会社 騒音低減構造及び画像形成装置
CN108791868A (zh) * 2018-07-31 2018-11-13 刘浩然 一种安全稳定的新型运输无人机
JP7398742B2 (ja) 2020-06-09 2023-12-15 戸田建設株式会社 伝搬音抑制構造及び管内伝搬音抑制構造
CN113674727A (zh) * 2021-08-05 2021-11-19 北京市劳动保护科学研究所 深亚波长低频吸声结构及吸声单元

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2706009A1 (de) 2012-09-07 2014-03-12 Eurocopter Deutschland GmbH Leitwerk eines Helikopters
US9266602B2 (en) 2012-09-07 2016-02-23 Airbus Helicopters Deutschland Empennage of a helicopter
WO2015023389A1 (en) * 2013-08-12 2015-02-19 Hexcel Corporation Sound wave guide for use in acoustic structures
EP2913271A1 (de) * 2014-02-28 2015-09-02 AIRBUS HELICOPTERS DEUTSCHLAND GmbH Drehflügler mit mindestens einem Hauptrotor und mindestens einem rotor zum Drehmomentausgleich
EP2913269A1 (de) * 2014-02-28 2015-09-02 AIRBUS HELICOPTERS DEUTSCHLAND GmbH Drehflügler mit mindestens einem Hauptrotor und mindestens einem Rotor zum Drehmomentausgleich
EP2913270A1 (de) * 2014-02-28 2015-09-02 AIRBUS HELICOPTERS DEUTSCHLAND GmbH Drehflügler mit mindestens einem Hauptrotor und mindestens einem Rotor zum Drehmomentausgleich

Also Published As

Publication number Publication date
FR2925208B1 (fr) 2016-07-01
EP2071561A3 (de) 2017-05-17
CN101458926B (zh) 2012-07-04
EP2071561B1 (de) 2021-02-03
CA2646933C (fr) 2013-05-21
JP2009145891A (ja) 2009-07-02
FR2925208A1 (fr) 2009-06-19
CN101458926A (zh) 2009-06-17
CA2646933A1 (fr) 2009-06-14
US20090152395A1 (en) 2009-06-18
US7779965B2 (en) 2010-08-24

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