EP1319156B1 - Schallabsorptionsvorrichtung - Google Patents

Schallabsorptionsvorrichtung Download PDF

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Publication number
EP1319156B1
EP1319156B1 EP01967894A EP01967894A EP1319156B1 EP 1319156 B1 EP1319156 B1 EP 1319156B1 EP 01967894 A EP01967894 A EP 01967894A EP 01967894 A EP01967894 A EP 01967894A EP 1319156 B1 EP1319156 B1 EP 1319156B1
Authority
EP
European Patent Office
Prior art keywords
absorbent
sound
flow resistance
mat
single layer
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.)
Expired - Lifetime
Application number
EP01967894A
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English (en)
French (fr)
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EP1319156A1 (de
Inventor
Mats Abom
Claes-Göran Johansson
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.)
Flaekt Woods AB
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Flaekt Woods AB
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Publication date
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Publication of EP1319156A1 publication Critical patent/EP1319156A1/de
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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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N1/00—Silencing apparatus characterised by method of silencing
    • F01N1/24—Silencing apparatus characterised by method of silencing by using sound-absorbing materials
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F13/00—Details common to, or for air-conditioning, air-humidification, ventilation or use of air currents for screening
    • F24F13/02—Ducting arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F13/00—Details common to, or for air-conditioning, air-humidification, ventilation or use of air currents for screening
    • F24F13/24—Means for preventing or suppressing noise
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2310/00—Selection of sound absorbing or insulating material

Definitions

  • the present invention relates to an absorbent for a dissipative absorption of sound.
  • the invention relates to a sound attenuator incorporating the absorbent and to a method for sound reduction in a system for transport of a gaseous medium.
  • a transport system comprises a ventilation system.
  • the gas transport system comprises an exhaust gas system and in particular an exhaust gas system for an internal-combustion engine, for example in a ship.
  • the device and the method relate to a channel, from the wall or outlet of which noise is generated, which may be subjected to acoustic requirements.
  • the invention is also advantageously applicable to other elongated gas transport systems, such as in exhaust gas plants in, for example, vehicles with internal-combustion engines or in flue-gas cleaning devices for plants for, for example, production of electric power.
  • sound By sound is meant a physical phenomenon which gives rise to hearing sensations.
  • sound is regarded as a wave motion in a gaseous medium. Sound may, however, also be transported in other media, such as fluids and solid materials.
  • the sound propagates as a longitudinal wave motion at a velocity of about 340 m/s. However, the velocity is dependent on the temperature of the medium.
  • the audible sound comprises frequencies from about 20 Hz to about 20,000 Hz.
  • the wavelength of the audible sound in air with a normal temperature thus varies from the order of magnitude of 3 m at low frequencies (-100 Hz), 30 cm for sound at intermediate frequencies (-1000 Hz), and 3 cm for sound at high frequencies (-10,000 Hz).
  • the sound may vary greatly with both amplitude (sound intensity) and time.
  • Well-known materials for the manufacture of a resistive absorbent are mineral wool and glass wool.
  • the wool is retained by an adhesive which causes a homogeneous structure in the absorbent.
  • these absorbents are less suited since bacteria may develop in the absorbent or fibres may loosen.
  • a common requirement in such hygienic environments is that an absorbent shall be capable of being flushed.
  • the known absorbent has proved to be less resistant and may retain moisture for a long period of time. After repeated flushing, the absorbent is gradually dissolved.
  • the known wool is built up of brittle fibres, in which case a less good mechanical strength is obtained in the absorbent. In case of heavy vibrations, the structure is decomposed in course of time.
  • porous absorbents are available on the market and their sound-absorbing properties are known by measurements.
  • the porous absorbents are characterized by thickness and density.
  • One problem in the manufacture of circular attenuators for, for example, ventilation systems is that the absorbent, which is usually made flat, must be bent to fit into the attenuator. Depending on the original thickness of the absorbent, it will have a varying density in the circular design. On the inside of the sound attenuator, the density will be high and tendencies to folding will arise. On the outside, cracks will sometimes arise as a result of the hard bending.
  • sound attenuator means a device which is capable of consuming sound energy. This may occur by transforming the sound energy into some other form of energy, such as, for example, heat.
  • the designation resistive attenuator refers to a device which is capable of absorbing sound in a gas channel, that is, to transform the sound energy into another form of energy.
  • the designation attenuator in the following text, means a device which is capable of reducing sound, and attenuation means the property of reducing sound.
  • a resistive attenuator is a circular or square tube, the sides of which, exposed to the gas flow, are coated with an absorbent or a porous medium of small coupled cavities.
  • a common such sound attenuator intended for a ventilation system is described in the patent document GB 2,122,256. From the patent document US 2,826,261, another resistive attenuator intended for an exhaust system is previously known.
  • absorbent there is used a resistive absorbent of the type described above.
  • the absorbent may also be protected by an air-permeable surface layer, for example a perforated sheet, to attain a longer service life and better mechanical stability at high gas speeds.
  • Such a resistive attenuator will have a sound-attenuating property which covers a wide frequency range.
  • the attenuation is also dependent on the thickness and flow resistance of the absorbent, the exposed absorbent surface, any surface protection such as, for example, a perforated sheet and the dimensions of the attenuator, such as the length and the diameter thereof.
  • the sound-attenuating properties are also dependent on where in the system the sound attenuator is placed. It often turns out that the properties which are achieved in a laboratory, especially at low frequencies, and which are described in pamphlets, are seldom achieved in practice. This often leads to oversizing in order to attain a desired sound attenuation with sufficient certainty.
  • Another known way of reducing the sound emission from a gas transport system is to prevent the sound from propagating in the channel. This may be achieved by arranging a reflecting obstacle in the gas channel. Such an obstacle is obtained by creating a sound which is in opposition to the sound in the channel, thus achieving extinction.
  • One such technique is active sound attenuation. In connection with active sound attenuation, a sound is added which is directed in a direction opposite to the sound progressing in a channel. This oppositely directed sound is then created by a loudspeaker placed in the channel.
  • controllable conditions are required for an active system to function well.
  • a reactive attenuator substantially operates according to two principles.
  • the first type is a reflection attenuator .
  • This comprises an increase of the cross-section area, whereby the area increase gives rise to a reflection wave which propagates in a direction opposite to the propagation of the sound.
  • the function is a broadband function.
  • the second type is a resonance attenuator .
  • the function is a narrow-band function and may almost be regarded as a filter which eliminates pure tones from the sound.
  • the orifice of a resonance attenuator must be placed in a pressure maximum of the sound field in the channel. The resonance attenuator is thus very sensitive to the position in the channel.
  • Sound attenuator devices in transport systems for gas implies further complications since the wavelength of the sound is changed with the temperature. If, for example, the temperature of the gas is increased from 20°C to 900°C, the sound velocity and hence the wavelength increase twofold.
  • An attenuator which operates well at normal temperature therefore suffers deteriorated properties, especially at low frequencies when the gas is heated. This usually results in sound attenuating devices in transport systems with hot gases becoming very bulky.
  • the transport system shall be simpler, less space-demanding, have a small cross-section area and be less expensive to manufacture than corresponding systems designed according to the prior art.
  • the system shall have a smaller weight and exhibit a smaller pressure drop and less generation of aerodynamic sound than conventional systems. In particular, these properties should be maintained also at high transport speeds of the gas and at different temperatures of the gas.
  • the system shall involve no environmental effect or health hazard, such as emission of torn-off fibres and the like.
  • the absorbent included in the system shall be bendable and rotatable and hence be able to be arranged as a guide vane.
  • the system shall also be simple to maintain and comprise replaceable parts.
  • a sound source When a sound source is brought to sound in a room, a sound field arises, which is caused by the acoustic boundary conditions which characterize the room. These are, for example, the geometry of the room and the absorption properties of the surfaces. It may be said that the room gives a response to the sound source.
  • the sound field is built up of vibrating gas particles which in certain positions move very vigorously whereas in other positions they move very little, or are even stationary.
  • a decisive property of a sound absorbent is the flow resistance through the absorbent. Usually, this is determined by the specific flow resistance which is the pressure difference across the absorbent divided by the product of the speed of the penetrating gas and the thickness of the absorbent. Determining the static flow resistance is simple. At a dynamic state, the absorbent is also subjected to an oscillating movement of the gas particles. Besides resulting in the purely resistive resistance, this superimposed movement also results in a reactive resistance, which increases with the frequency. This is due to the fact that small gas inclusions, mass plugs, are formed and are brought to oscillate in the absorbent. The dynamic flow resistance is thus dependent on one resistive part and one reactive part.
  • the resistive flow resistance may be represented by a curve which substantially has the same flow resistance across the whole frequency range whereas the reactive flow resistance is represented by a curve which increases with the frequency. At a certain frequency, the reactive curve intersects the resistive curve. Below this frequency, the flow resistance is constant and above this frequency, the reactive flow resistance dominates and thus increases with the frequency.
  • a normalized flow resistance is obtained.
  • the normalized flow resistance for a good absorbent should lie between 1 and 2. If the flow resistance is greater than 2, part of the sound is reflected, which part is thus not subjected to any absorption. If the flow resistance is smaller than 1, the greater part of the sound passes through the absorbent, whereby only a minor part of the sound is subjected to absorption. It is thus an overriding object of the invention to manufacture an absorbent which, over a wide frequency range, has a normalized flow resistance of between one half and two. It is especially suitable for the flow resistance to be between one and two.
  • the absorbent is manufactured from a polyester wool, which is first compressed into a thin mat and is then secured into the compressed shape. This is suitably performed by heating, whereby the treads in the wool are welded together.
  • it is suitable to shape the thin mat in accordance with the application into which it is to be inserted.
  • the mat is suitably shaped plane, curved, bent or twisted.
  • the absorbent is arranged with a thin, covering film, which prevents particles or bacteria from penetrating into the absorbent.
  • the film is fixed to the absorbent by welding.
  • the film is then fixed to the absorbent in a line or diamond pattern.
  • the present task is solved by a channel for transport of a gas, in which channel a thin absorbent is inserted, the normalized flow resistance of which is greater than one and smaller than two.
  • the absorbent comprises a thin mat of long threads of a material which is resistant to deformation, such as plastic.
  • the inventive concept also comprises threads formed of other solid materials, such as, for example, metal.
  • the thickness of the absorbent should be smaller than about 5 % of the cross-section area of the channel. Such a small limitation of the channel area only entails a minor pressure increase.
  • the mat is reinforced with a net of, for example, metal.
  • the absorbent is arranged elongated and penetrates through a greater part of the channel system.
  • the absorbent is shaped as a guide vane, for example at bends and descents in the channel system.
  • the absorbent according to the invention is also adapted to be placed in a resistive attenuator.
  • such an attenuator is arranged in combination with one or more reactive attenuators.
  • the sound field in the channel may be locally controlled and optimized attenuating properties be obtained.
  • Figure 1 shows the specific flow resistance versus the frequency of a porous absorbent.
  • the resistive flow resistance is designated z res and the reactive flow resistance is designated z mass .
  • the resistive flow resistance predominates.
  • the reactive flow resistance predominates. This implies that it is very difficult to correctly balance an absorbent which has good absorption properties within a wide frequency range.
  • the transition from a resistive to a reactive flow resistance normally takes place below or within the frequency range f intr where a good absorption is desired.
  • a porous absorbent may be regarded as a large number of interconnected channels with a characteristic length and a characteristic diameter. These channels run in all directions in the absorbent and their characteristic is influenced by the density, thickness and fibrous structure of the absorbent.
  • the resistive flow resistance is proportional to the viscosity of the gas and inversely proportional to the characteristic diameter squared.
  • the reactive flow resistance is instead proportional to the frequency, the characteristic length and the density of the gas.
  • an absorbent which, at normal temperature, has less good absorption properties will thus receive much better properties at higher temperatures.
  • One absorbent which has this property is perforated sheet.
  • Such an absorbent is suitably manufactured from a sheet with a thickness of 1 mm or less, with a degree of perforation which is less than 10 % and with holes which are about 1 mm or less. For a normal temperature, the holes would need to be smaller than one-tenth of a millimetre. Such a perforated sheet is difficult and costly to manufacture.
  • Figure 2 shows a typical absorbent according to the invention. It consists of a thin mat 1 of long elastic fibres, which cross each other in all directions in an irregular pattern.
  • the threads are manufactured of a plastic such as, for example, polyester.
  • An advantage of this material is that, in case of fire, it is decomposed into water and carbon dioxide.
  • other materials of elongated bendable threads or fibres are also possible.
  • the figure also shows an advantageous embodiment of the absorbent in which a thin foil 2 is attached as protection in front of the thin mat. In the shown example, the foil is fused to the mat in a line pattern 3.
  • the foil primarily consists of a polyethylene film but may also be another plastic material or a metal foil.
  • Figure 3 shows the influence of a covering foil on the absorbent. Depending on the thickness or weight of the foil, an absorption - decreasing with the frequency - is obtained at high frequencies.
  • the figure shows a typical basic absorption a of a porous absorbent and the effect of three different thicknesses, 5, 10 and 20 ⁇ m, of such a foil.
  • the foil across the greater part of the absorbent surface, should lie loosely adjacent to the mat. In the shown case, this problem is solved in that the foil is fixed to the mat in lines only. In the case of direct contact, such as by gluing or if the foil is pressed against the absorbent of, for example, perforated sheet, the absorption is deteriorated at high frequencies.
  • a foil prevents particles from penetrating into the absorbent. It is thus suitable for use in environments involving environmental requirements.
  • the foil-clad absorbent will also have better long-term properties since particles do not penetrate into and stop up the porous channels.
  • the absorbent according to the invention is exceedingly suited to be arranged as a resistive attenuator together with a reflection or reaction attenuator in a channel system.
  • a very efficient attenuation may be obtained over a frequency interval such as, for example, a third octave band.
  • the channel system is not limited to comprise a channel system with a circular-cylindrical cross section.
  • the invention may, with an equivalent result, be applied to systems with a multi-edge cross section as well as to systems with longitudinally bent sections.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Absorbent Articles And Supports Therefor (AREA)
  • Saccharide Compounds (AREA)
  • Medicines Containing Plant Substances (AREA)
  • Exhaust Silencers (AREA)
  • Gloves (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)
  • External Artificial Organs (AREA)

Claims (18)

  1. Schallabsorptionsmaterial für Hygieneräume mit einer einschichtigen porösen Matte, dadurch gekennzeichnet, daß der normierte Strömungswiderstand der Matte im Bereich von 0,5 bis 2 liegt.
  2. Schallabsorptionsmaterial nach Anspruch 1, dadurch gekennzeichnet, daß die Matte mehrere lange Fäden aufweist, die zu einer dünnen Bahn verdichtet sind.
  3. Schallabsorptionsmaterial nach Anspruch 2, dadurch gekennzeichnet, daß die Fäden aus einem Kunststoffmaterial hergestellt sind.
  4. Schallabsorptionsmaterial nach Anspruch 3, dadurch gekennzeichnet, daß das Kunststoffmaterial ein Polyester ist.
  5. Schallabsorptionsmaterial nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, daß die Bahn durch ein Netz aus einem formbeständigen Material verstärkt ist.
  6. Schallabsorptionsmaterial nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, daß das Absorptionsmaterial eine Folie aufweist, die freien Kontakt mit der Matte herstellt.
  7. Schallabsorptionsmaterial nach Anspruch 1, dadurch gekennzeichnet, daß das Absorptionsmaterial eine perforierte Bahn aufweist, wenn es bei hohen Gastemperaturen verwendet wird.
  8. Transportsystem für ein gasförmiges Medium mit mehreren Kanalteilstücken, wobei mindestens ein erstes Kanalteilstück ein Absorptionsmaterial mit einer einschichtigen porösen Matte aufweist, dadurch gekennzeichnet, daß die Matte dünn ist und ihr normierter Strömungswiderstand im Bereich von 0,5 bis 2 liegt.
  9. Transportsystem nach Anspruch 8, dadurch gekennzeichnet, daß die Querschnittfläche des Absorptionsmaterials unter 5 % der Querschnittfläche des Kanalteilstücks liegt.
  10. Transportsystem nach Anspruch 8, dadurch gekennzeichnet, daß das Absorptionsmaterial eine Matte aus verdichteten langen Polyesterfäden aufweist.
  11. Transportsystem nach einem der Ansprüche 8 bis 10, dadurch gekennzeichnet, daß das Absorptionsmaterial durch ein Netz aus einem formbeständigen Material verstärkt ist.
  12. Transportsystem nach einem der Ansprüche 8 bis 11, dadurch gekennzeichnet, daß das Absorptionsmaterial in einem Abstand entlang den Wänden des Kanals plaziert ist.
  13. Transportsystem nach einem der Ansprüche 8 bis 12, dadurch gekennzeichnet, daß das Absorptionsmaterial Leitschaufeln im Kanalteilstück bildet.
  14. Verfahren zur Herstellung eines Absorptionsmaterials für Hygieneräume mit einer einschichtigen porösen Matte, gekennzeichnet durch Einstellen des normierten Strömungswiderstands der Matte im Bereich von 1 bis 2.
  15. Verfahren nach Anspruch 14, gekennzeichnet durch Ausbilden der einschichtigen Matte aus mehreren langen Fäden, die zu einer dünnen Bahn verdichtet werden.
  16. Verfahren zur Herstellung eines einschichtigen Absorptionsmaterials mit mehreren Kanälen mit einem charakteristischen Durchmesser, der einen resistiven Teil des normierten Strömungswiderstands beeinflußt, und einer charakteristischen Länge, die einen reaktiven Teil des normierten Strömungswiderstands beeinflußt, gekennzeichnet durch Verdichten mehrerer langer Fäden zu einer einschichtigen dünnen Bahn, bei der der resistive Teil des normierten Strömungswiderstands im Bereich von 0,5 bis 2 liegt und der reaktive Teil des normierten Strömungswiderstands durch den resistiven Teil begrenzt ist.
  17. Verwendung eines Absorptionsmaterials nach Anspruch 1 mit einer einschichtigen porösen Matte, die einen normierten Strömungswiderstand der Matte im Bereich von 0,5 bis 2 hat, in einer Lüftungsanlage.
  18. Verwendung eines Transportsystems nach Anspruch 8 mit mehreren Kanalteilstücken, wobei mindestens ein erstes Kanalteilstück ein einschichtiges dünnes Absorptionsmaterial mit einem normierten Strömungswiderstand im Bereich von 0,5 bis 2 aufweist, in einer Lüftungsanlage.
EP01967894A 2000-09-18 2001-09-17 Schallabsorptionsvorrichtung Expired - Lifetime EP1319156B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE0003349 2000-09-18
SE0003349A SE0003349D0 (sv) 2000-09-18 2000-09-18 Ljudabsorbent
PCT/SE2001/001982 WO2002023099A1 (en) 2000-09-18 2001-09-17 Sound absorbent

Publications (2)

Publication Number Publication Date
EP1319156A1 EP1319156A1 (de) 2003-06-18
EP1319156B1 true EP1319156B1 (de) 2006-03-22

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EP01967894A Expired - Lifetime EP1319156B1 (de) 2000-09-18 2001-09-17 Schallabsorptionsvorrichtung

Country Status (8)

Country Link
US (1) US20040099477A1 (de)
EP (1) EP1319156B1 (de)
AT (1) ATE321248T1 (de)
AU (1) AU2001288177A1 (de)
DE (1) DE60118221T2 (de)
NO (1) NO321542B1 (de)
SE (1) SE0003349D0 (de)
WO (1) WO2002023099A1 (de)

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AU2002232725A1 (en) * 2000-12-20 2002-07-01 Quiet Storm, Llc Method and apparatus for improved noise attenuation in a dissipative internal combustion engine exhaust muffler
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US6698543B2 (en) * 2001-07-03 2004-03-02 Golterman & Sabo, Inc. Acoustical wall panels

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CN101636594B (zh) * 2006-10-27 2013-03-06 空中客车德国运营有限责任公司 用于飞行器的空气管道的吸声装置

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WO2002023099A1 (en) 2002-03-21
AU2001288177A1 (en) 2002-03-26
SE0003349D0 (sv) 2000-09-18
DE60118221D1 (de) 2006-05-11
US20040099477A1 (en) 2004-05-27
NO20031212L (no) 2003-05-16
EP1319156A1 (de) 2003-06-18
DE60118221T2 (de) 2007-04-12
ATE321248T1 (de) 2006-04-15
NO321542B1 (no) 2006-05-22
NO20031212D0 (no) 2003-03-17

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