WO2024090076A1 - Conduit d'air équipé d'un silencieux - Google Patents

Conduit d'air équipé d'un silencieux Download PDF

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Publication number
WO2024090076A1
WO2024090076A1 PCT/JP2023/033932 JP2023033932W WO2024090076A1 WO 2024090076 A1 WO2024090076 A1 WO 2024090076A1 JP 2023033932 W JP2023033932 W JP 2023033932W WO 2024090076 A1 WO2024090076 A1 WO 2024090076A1
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WO
WIPO (PCT)
Prior art keywords
silencer
air duct
air passage
air
sound
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PCT/JP2023/033932
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English (en)
Japanese (ja)
Inventor
美博 菅原
昇吾 山添
真也 白田
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富士フイルム株式会社
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Publication of WO2024090076A1 publication Critical patent/WO2024090076A1/fr

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    • 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
    • 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
    • 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 an air duct with a silencer, which is configured by placing a silencer midway through the air duct.
  • a radial fan assembly is provided in the outdoor unit, which takes in outside air and sends it to the indoor unit.
  • the air sent to the indoor unit passes through an air supply and exhaust duct, and a silencer (specifically, a muffler) provided in the air supply and exhaust duct reduces the sound that travels through the duct.
  • a silencer specifically, a muffler
  • the size of the silencer is restricted depending on the size of the device such as the air conditioner or blower, and the smaller the size of the silencer, the lower the sound silencing performance for low frequency sounds (e.g., below 1000 Hz). For this reason, there is a demand for improved sound silencing performance for low frequency sounds in such silencers, particularly sound at the first resonant frequency, which has a high transmittance, and sound in a frequency band lower than the first resonant frequency. Note that "sound at the first resonant frequency” refers to the lowest frequency sound that resonates within the silencer.
  • the sound-absorbing materials typically used in silencers are inferior in silencing low-frequency sounds compared to their ability to silencing high-frequency sounds, and one way to improve silencing performance for low-frequency sounds is to increase the volume of the sound-absorbing material.
  • the objective of the present invention is to provide an air duct with a silencer that can solve the problems of the conventional technology described above, suppress the size increase, and improve the sound silencing performance for low frequency sounds.
  • the present invention has the following configuration.
  • a silencer is disposed in the middle of the air duct,
  • the silencer has a silencer body and a conversion mechanism that converts sound energy into thermal energy and is accommodated in the silencer body.
  • the air passage has a first air passage portion formed inside the silencer main body, a second air passage portion located upstream of the first air passage portion, and a third air passage portion located downstream of the first air passage portion;
  • the acoustic impedance density of the internal space of the silencer body is smaller than the acoustic impedance density of each of the internal spaces of the second air passage portion and the third air passage portion;
  • the effective propagation length determined based on the characteristics of the propagation space of the sound wave in the silencer body is defined as ⁇ E , Determined based on the length of the first air passage portion, assuming that the wavelength of the sound at the frequency at which the silencer body resonates is ⁇ , An air duct with a silencer that satisfies ⁇ 1.97 ⁇ log 10 ( ⁇ E / ⁇ ) ⁇ 0.76.
  • the silencer body is a housing, The cross-sectional area of the housing is larger than the cross-sectional area of each of the second air duct portion and the third air duct portion, The silencer-equipped air passage according to [1], wherein a rear space is provided inside the housing, the rear space being in communication with the air passage space in the first air passage section.
  • the first air passage portion has an air passage wall that divides the air passage space, The silencer-equipped air passage according to [1] or [2], wherein the air passage wall is provided with one or more openings that connect the air passage space and the rear space.
  • the silencer-equipped air duct according to any one of [1] to [ 3] , wherein the total area of all the opening areas of one or more openings is A1 , and the total area of the air duct wall in contact with the air duct space is A2 , the ratio of A1 to the sum of A1 and A2 is more than 10% and less than 85%.
  • the sound absorbing material is positioned in the rear space so as to cover at least a portion of the opening, The opening is located at the center of the first air passage portion in the first direction in which the first air passage portion extends.
  • the air passage with a silencer according to any one of [1] to [8].
  • the present invention provides an air duct with a silencer that can improve the sound silencing performance for low-frequency sounds while preventing the device from becoming too large.
  • FIG. 1 is a diagram showing an air blowing system in which an air duct with a silencer according to one embodiment of the present invention is used; 2 is a cross-sectional view showing the AA cross section of the silencer-equipped air duct shown in FIG. 1.
  • 3 is a cross-sectional view showing the cross section BB of the silencer-equipped air passage shown in FIG. 2.
  • 3 is a cross-sectional view showing the CC cross section of the silencer-equipped air passage shown in FIG. 2.
  • FIG. 13 is a diagram showing a first modified example of a silencer.
  • FIG. 11 is a diagram showing a second modified example of the silencer.
  • FIG. 13 is a diagram showing a third modified example of the silencer.
  • FIG. 13 is a diagram showing a fourth modified example of the silencer.
  • FIG. 13 is a diagram showing a fifth modified example of the silencer.
  • FIG. 13 is a diagram showing a sixth modified example of the silencer.
  • FIG. 13 is a diagram showing a seventh modified example of the silencer.
  • FIG. 13 is a diagram showing the relationship between frequency, log 10 ( ⁇ E / ⁇ ), and sound transmission loss through a silencer.
  • FIG. 13 is a diagram showing the relationship between log 10 ( ⁇ E / ⁇ ) and transmission loss for a sound of a first resonant frequency.
  • FIG. 1 is a diagram showing the relationship between frequency and transmission loss in each of Comparative Example 1, Comparative Example 2, and Example 1.
  • FIG. 13 is a diagram showing the relationship between aperture ratio and transmittance.
  • FIG. 13 is a diagram showing the relationship between frequency and transmittance according to the aperture position.
  • FIG. 13 is a diagram showing the relationship between the aperture position and the transmittance at the first resonance frequency.
  • 11 is a diagram showing the relationship between frequency and transmission loss determined depending on the position of
  • the material and shape of each component used to implement the present invention may be set arbitrarily depending on the application of the present invention and the state of the art at the time of implementing the present invention.
  • the present invention includes its equivalents.
  • a numerical range expressed using “to” means a range that includes the numerical values before and after “to” as the lower and upper limits.
  • “orthogonal” and “parallel” include the range of error permitted in the technical field to which the present invention belongs.
  • “orthogonal” and “parallel” in this specification mean being within a range of less than ⁇ 10° from strictly orthogonal or parallel.
  • the error from strictly orthogonal or parallel is preferably 5° or less, and more preferably 3° or less.
  • the meanings of "same,””identical,””match,” and “equal” may include a generally acceptable range of error in the technical field to which the present invention belongs.
  • any,””allareas,” and “all” include not only 100% but also a generally acceptable range of error in the technical field to which the present invention pertains, and may include, for example, 99% or more, 95% or more, or 90% or more.
  • sound deadening means reducing sound, and is a concept that includes the meanings of both sound insulation and sound absorption.
  • Sound insulation means blocking sound, in other words, not allowing sound to pass through. Sound insulation also includes the reflection of sound (acoustics) and the cancellation of sound (acoustics). Sound absorption means reducing reflected sound, in other words, absorbing sound (acoustics).
  • the upstream side refers to the inlet side of the air passage 30 (i.e., the side where the air source 10 (see FIG. 1) described below is arranged), and the downstream side refers to the outlet side of the air passage 30.
  • the silencer-equipped air duct according to this embodiment (hereinafter, silencer-equipped air duct 100) is used in an air blowing system S.
  • the air blowing system S is used, for example, to transport (blow) air to a specified space (e.g., a room, etc.) within a building for the purpose of air conditioning or ventilation.
  • Buildings include detached houses, individual units in collective housing such as condominiums, stores such as restaurants and shops, and facilities such as hospitals, department stores, movie theaters, etc.
  • wind refers to an artificial flow of air or gas (air current).
  • air current air current
  • the air blowing system S is composed of an air blowing source 10 (blower) and an air duct with silencer 100.
  • the air duct with silencer 100 is composed of a silencer 20 disposed midway along the air duct 30. The detailed configuration of the air duct with silencer 100 will be described in a later section.
  • the air source 10 is a device that has an electric motor such as a motor, and operates when the electric motor is started to blow air. Specifically, it is a blower fan that constitutes an air conditioner, or a ventilation fan. As the fan, well-known fans such as an axial fan (propeller fan), a centrifugal fan, a line flow fan, and the like can be used.
  • the silencer-equipped air passage 100 includes an air passage 30 and a silencer 20 that reduces sound (noise) propagating within the air passage 30 when air is blown.
  • the air passage 30 is a flow path through which the air sent from the air source 10 flows.
  • the upstream end of the air passage 30 (more specifically, the second air passage section 32) is connected to the exhaust port of the air source 10 arranged outside the room via a cylindrical upstream air passage 12 (e.g., a duct, a pipe, a hose, etc.) as shown in FIG. 1.
  • the downstream end of the air passage 30 (more specifically, the third air passage section 33) is connected to the indoor space (room) inside the exterior wall W via a cylindrical downstream air passage 14 (e.g., a duct, a pipe, a hose, etc.).
  • the downstream air passage 14 penetrates the exterior wall W of the building that separates the indoor space and the outdoor space and enters the room to which the air is to be sent.
  • the air blower source 10 is not limited to being placed outdoors, but may be placed, for example, indoors (in a room), and the placement location is not important.
  • the air passage 30 may be disposed at any position between the air source 10 and the exterior wall W, and may be attached, for example, to the housing of the air source 10.
  • the air passage 30 may be disposed in either the indoor space or the outdoor space.
  • the material and structure of the upstream air passage 12 and the downstream air passage 14 are not particularly limited, and for example, flexible hoses such as vinyl hoses, flexible hoses, and tie duct hoses may be used.
  • the air passage 30 has a first air passage section 31 formed inside the silencer 20, a second air passage section 32 located upstream of the first air passage section 31, and a third air passage section 33 located downstream of the first air passage section 31.
  • the first air duct section 31 is formed inside the housing 21 (corresponding to the silencer body). In other words, the first air duct section 31 constitutes a part of the silencer 20. As shown in FIG. 3, the first air duct section 31 has an air duct space 41 surrounded by four imaginary sides that define the outer edge of the first air duct section 31, and an air duct wall 42 that separates the air duct space 41.
  • the air passage wall 42 has a pair of walls 42a, 42b arranged along two imaginary faces that face each other in the Y direction out of the four imaginary faces that surround the air passage space 41, and a wall 42c arranged along one imaginary face (the lower face in FIG. 3) located at one end in the Z direction.
  • wall 42a is composed of two wall pieces arranged in the X direction with an opening 43a (described later) in between
  • wall 42b is composed of two wall pieces arranged in the X direction with an opening 43b (described later) in between.
  • Wall 42c forms part of the end of housing 21 (the lower wall of housing 21 in FIG. 3) which will be described later.
  • Walls 42a, 42b, and 42c are flat walls that extend along the X direction and have rigidity.
  • the virtual face (the upper face in FIG. 3) located opposite the wall 42c in the Z direction does not have an air passage wall 42 arranged thereon.
  • one of the four virtual faces surrounding the air passage space 41 is open, forming an opening 43c.
  • the air passage wall 42 is provided with a plurality of openings 43a, 43b, 43c (three in this embodiment) that connect the air passage space 41 with the rear space 23 described below.
  • the openings 43a, 43b, 43c are located on three sides of the first air passage section 31, more specifically, on the outer edge of the first air passage section 31, at one end in the Z direction (more specifically, the end opposite the wall 42c) and at both ends in the Y direction.
  • each of the pair of walls 42a, 42b has an opening. More specifically, opening 43a is provided in the center of wall 42a in the X direction, and opening 43b is provided in the center of wall 42b in the X direction.
  • the openings 43a, 43b are preferably located within L/4 from the center of the first air passage portion 31 in the X direction.
  • the "length L" of the first air passage portion 31 is equal to the distance from one end of the inner wall surface of the housing 21 in the X direction to the other end in the X direction.
  • Each of the openings 43a, 43b is provided such that the distance between a center line (median line) parallel to the Z direction that bisects the opening in the X direction and a center line (median line) of the first air path portion 31 parallel to the Z direction that bisects the first air path portion 31 in the X direction is within L/4 in the X direction.
  • the center lines of the openings 43a, 43b and the center line of the first air path portion 31 coincide in the X direction.
  • the openings 43a and 43b are located within L/4.5 from the center of the first air passage section 31 in the X direction, and even more preferable that they are located within L/5.
  • the opening 43c is formed along one imaginary surface (the upper surface in FIG. 3) located at the other end in the Z direction (the end opposite the wall 42c) of the four imaginary surfaces surrounding the air passage space 41, and is formed from one end to the other end of the first air passage section 31 in the X direction.
  • the entire area of the one imaginary surface located at the other end in the Z direction is open to the rear space 23.
  • the ratio of A1 to the sum of A1 and A2 is preferably more than 10% and less than 85%.
  • the ratio of A1 to the sum of A1 and A2 is called the "opening ratio.”
  • the opening ratio is 10% or less, the degree to which the sound in the first air passage portion 31 can penetrate into the sound-absorbing material 22 in the rear space 23 decreases, so that the sound-absorbing material 22 cannot be used effectively.
  • the opening ratio is preferably greater than 13% and less than 75%, and more preferably greater than 16% and less than 65%.
  • the second air duct section 32 and the third air duct section 33 are cylindrical sections that surround the internal space through which air flows. As shown in FIG. 1, the second air duct section 32 is a section that protrudes upstream from the upstream end of the silencer 20 in the X direction and is connected to the end of the upstream air duct 12.
  • the third air duct section 33 is a section that protrudes downstream from the downstream end of the silencer 20 in the X direction and is connected to the end of the downstream air duct 14.
  • the second air duct section 32 and the third air duct section 33 are part of the air duct 30 and also function as joints (joints) for connecting the silencer-equipped air duct 100 to the upstream air duct 12 and the downstream air duct 14.
  • the first air duct section 31 and the second air duct section 32 are arranged side by side in the X direction, sandwiching the upstream wall (hereinafter also referred to as the upstream wall) of a pair of walls that face each other in the X direction and constitute the housing 21. More specifically, the upstream end of the first air duct section 31 is connected to the inner surface of the upstream wall of the housing 21, and the downstream end of the second air duct section 32 is connected to the outer surface of the upstream wall of the housing 21.
  • the first air duct section 31 and the second air duct section 32 are in communication with each other through a through hole provided in the upstream wall of the housing 21.
  • the first air duct section 31 and the third air duct section 33 are arranged side by side in the X direction, sandwiching the downstream wall (hereinafter also referred to as the downstream wall) of a pair of walls that face each other in the X direction and constitute the housing 21. More specifically, the downstream end of the first air duct section 31 is connected to the inner surface of the downstream wall of the housing 21, and the upstream end of the third air duct section 33 is connected to the outer surface of the downstream wall of the housing 21.
  • the first air duct section 31 and the third air duct section 33 are in communication with each other through a through hole provided in the downstream wall of the housing 21.
  • each of the first air duct section 31, the second air duct section 32, and the third air duct section 33 is a linear air duct section extending in the X direction, and the central axis of each air duct section extends in the X direction and is located on the same imaginary line.
  • the cross-sectional shape of the air passage 30 (first air passage section 31, second air passage section 32, and third air passage section 33) is, for example, a square (rectangle).
  • the cross section of the air passage 30 means a cross section perpendicular to the extension direction of the air passage 30.
  • the extension direction of the air passage 30 is the X direction
  • the cross section of the air passage 30 means a plane extending in the Y direction and the Z direction.
  • the cross-sectional shape of the air passage 30 is not particularly limited, and may be, for example, a circle, a square, a quadrangle other than a square, a polygon other than a quadrangle, or an indeterminate shape.
  • cross-sectional area refers to the size of the cross section, and means the area of the range enclosed by the outer edge of the cross section.
  • first air duct section 31 it means the area of the air duct space 41
  • second air duct section 32 and the third air duct section 33 it means the area of the internal space enclosed by the respective outer edges.
  • the first air duct section 31, the second air duct section 32, and the third air duct section 33 may have the same cross-sectional shape and cross-sectional area, or either or both of the shape and the cross-sectional area may be different.
  • the material constituting the air passage 30 is not particularly limited, and may be a metal material, a resin material, a paper material, a reinforced plastic material, a carbon fiber, etc. However, from the viewpoint of ensuring moldability and freedom of design, a resin material is preferable.
  • the resin material examples include acrylic resin, polymethylmethacrylate, polycarbonate, polyamide, polyarylate, polyetherimide, polyacetal, polyetheretherketone, polyphenylene sulfide, polysulfone, polyethylene terephthalate, polybutylene terephthalate, polyimide, ABS resin (acrylonitrile, flame-retardant ABS resin, butadiene, styrene copolymer synthetic resin), polypropylene, triacetylcellulose (TAC), polypropylene (PP), polyethylene (PE), polystyrene (PS), ASA (Acrylate Sthrene Acrylonitrile) resin, polyvinyl chloride (PVC) resin, and PLA (Polylactic Acid) resin.
  • reinforced plastic materials include carbon fiber reinforced plastics (CFRP) and glass fiber reinforced plastics (GFRP).
  • Silencer 20 reduces sound propagating within air passage 30, and more specifically, silences sound generated due to the operation of air blower source 10 blowing air into air passage 30, more specifically, sound generated due to the rotational operation of a drive motor (not shown) of air blower source 10.
  • Silencer 20 is provided with respect to air passage 30, and is provided at a midpoint of air passage 30 as shown in FIG.
  • the silencer 20 has a housing 21 (corresponding to the silencer body), the aforementioned first air duct section 31 formed inside the housing 21, a rear space 23 that communicates with the air duct space 41 inside the first air duct section 31, and a conversion mechanism housed inside the housing 21 (more specifically, the rear space 23).
  • the conversion mechanism is a mechanism that converts sound energy into thermal energy, and in this embodiment is a sound absorbing material 22.
  • the housing 21 defines the outer edge of the silencer 20 and is a hollow rectangular parallelepiped (hexahedron) extending in the X direction.
  • a pair of walls that face each other in the X direction each have a through hole as described above, and the ends of the first air duct section 31 and the second air duct section 32 are connected to the through hole on the upstream side, and the ends of the first air duct section 31 and the third air duct section 33 are connected to the through hole on the downstream side wall.
  • the cross section of the housing 21 perpendicular to the X direction is rectangular, and the cross-sectional shape is constant in the X direction.
  • the cross-sectional shape of the housing 21 may be, for example, circular, a quadrangle other than a square, a polygon other than a quadrangle, or an indefinite shape, and may change in the X direction.
  • the cross-sectional area of the housing 21, more specifically, the cross-sectional area of the internal space surrounded by the housing 21, is larger than the cross-sectional area of the internal space of each of the second air duct section 32 and the third air duct section 33. That is, in this embodiment, the silencer 20 is an extension section that is more extended than the second air duct section 32 and the third air duct section 33, and the silencer-equipped air duct 100 can be said to be an air duct equipped with an extended silencer.
  • the first air duct section 31 is in contact with one end of the housing 21 in the Z direction (the bottom wall of the housing 21 in FIG. 3) at the center of the housing 21 in the Y direction. Strictly speaking, as described above, the end of the first air duct section 31 in the Z direction (wall 42c) forms part of the end of the housing 21 in the Z direction.
  • the material that constitutes the housing 21 is not particularly limited, and metal materials, resin materials, paper materials, reinforced plastic materials, carbon fiber, etc. can be used.
  • the detailed types of materials are the same as those of the air passage 30, so a description is omitted.
  • a rear space 23 is provided inside the housing 21, which communicates with the air passage space 41 in the first air passage section 31.
  • the rear space 23 is the internal space surrounded by the housing 21 excluding the first air passage section 31, and as shown in FIG. 3, it surrounds the first air passage section 31 on three sides.
  • the rear space 23 is separated from the air passage space 41 by walls 42a and 42b, and communicates with the air passage space 41 via openings 43a, 43b, and 43c.
  • a sound absorbing material 22 is arranged in the rear space 23. As shown in FIG. 3, the sound absorbing material 22 surrounds the first air passage section 31 on three sides and is arranged in the rear space 23 so as to cover at least a portion of each of the openings 43a, 43b, and 43c. In this embodiment, the sound absorbing material 22 covers the entire area of each of the openings 43a, 43b, and 43c, and fills the entire area of the rear space 23.
  • a material that absorbs sound by converting sound energy into thermal energy can be used as the sound absorbing material 22.
  • materials constituting the sound absorbing material 22 include porous materials such as foams, foam materials, and nonwoven fabric sound absorbing materials.
  • foams and foam materials include expanded urethane foams such as Calmflex F manufactured by Inoac Corporation and urethane foam manufactured by Hikari Co., Ltd., soft urethane foams, ceramic particle sintered materials, phenol foams, melamine foams, insulation boards, and polyamide foams.
  • nonwoven fabric sound-absorbing materials include microfiber nonwoven fabrics such as Thinsulate from 3M, polyester nonwoven fabrics (including those with a two-layer structure having a thin, high-density nonwoven fabric on the front side and a low-density nonwoven fabric on the back side) such as White Qeon from Tokyo Bouon Co., Ltd. and QonPET from Bridgestone KBG Co., Ltd., plastic nonwoven fabrics such as acrylic fiber nonwoven fabrics, natural fiber nonwoven fabrics such as wool and felt, meltblown nonwoven fabrics, metal nonwoven fabrics, glass nonwoven fabrics, floor mats, and carpets.
  • microfiber nonwoven fabrics such as Thinsulate from 3M
  • polyester nonwoven fabrics including those with a two-layer structure having a thin, high-density nonwoven fabric on the front side and a low-density nonwoven fabric on the back side
  • plastic nonwoven fabrics such as acrylic fiber nonwoven fabrics, natural fiber nonwoven fabrics such as wool and felt, meltblown nonwoven fabrics, metal nonwoven fabrics, glass nonwoven fabrics, floor mats,
  • various sound absorbing materials can be used, such as sound absorbing materials made of materials containing minute air particles, for example, glass wool, rock wool, gypsum board, wood wool cement board, and sound absorbing materials made of nanofiber fibers, etc.
  • sound absorbing materials made of materials containing minute air particles, for example, glass wool, rock wool, gypsum board, wood wool cement board, and sound absorbing materials made of nanofiber fibers, etc.
  • nanofiber fibers include silica nanofibers and acrylic nanofibers such as XAI manufactured by Mitsubishi Chemical Corporation.
  • the silencer 20 configured as described above may be formed integrally with the air passage 30, or may be assembled to the air passage 30 as a separate part.
  • the unit of acoustic impedance density Z is rayl/ m2 .
  • the acoustic impedance density of the internal space of the housing 21 is smaller than the acoustic impedance density of each of the internal spaces of the second air path portion 32 and the third air path portion 33.
  • the acoustic impedance density of the internal space of the housing 21 is defined as Zs
  • the acoustic impedance density of the internal space of the second air path portion 32 is defined as Zin
  • the acoustic impedance density of the internal space of the third air path portion 33 is defined as Zout
  • the cross-sectional area A of the housing 21 means the cross-sectional area of the internal space surrounded by the housing 21, and the cross-sectional area A of each of the second air duct section 32 and the third air duct section 33 means the cross-sectional area of the internal space surrounded by the outer edge.
  • the same air flows through the silencer-equipped air duct 100, so the same values are applied for the density ⁇ and the sound speed c used in calculating Zs , Zin , and Zout . Therefore, in this embodiment, the acoustic impedance density Z is a value determined only by the cross-sectional area A and is inversely proportional to the cross-sectional area A.
  • the cross-sectional area A of the housing 21 is the largest, so the acoustic impedance density Zs of the housing 21 is the smallest, and Zs ⁇ Zin and Zs ⁇ Zout are satisfied.
  • Silencer-equipped air duct 100 satisfies -1.97 ⁇ log 10 ( ⁇ E / ⁇ ) ⁇ 0.76, where ⁇ E is the effective propagation length and ⁇ is the wavelength of the air sound at the frequency at which housing 21 resonates (specifically, the first resonant frequency).
  • ⁇ is a propagation constant determined by the characteristics of the medium, and is defined in the Journal of the Acoustical Society of Japan, Vol. 68, No. 9 (2012). Re[ ⁇ ] is the real part of the propagation constant ⁇ .
  • the "sound of the first resonant frequency" refers to the lowest frequency sound among the length-induced resonances occurring in the first air passage portion 31 when the medium is air.
  • the effective propagation length ⁇ E is an effective propagation length determined based on the sound-absorbing material 22 in the housing 21, and the wavelength ⁇ is the wavelength of sound at a frequency (specifically, the first resonant frequency) at which the housing 21 resonates when it does not contain the sound-absorbing material 22.
  • the propagation constant ⁇ can be obtained by measuring using the transfer function method with an acoustic tube and two microphones. This method complies with the standards of JIS A1405-2, ISO 10534-2, and ASTM E 1050.
  • the acoustic tube used can be one that uses the same measurement principle as WinZac manufactured by Nittobo Acoustic Engineering Co., Ltd. This method makes it possible to measure the propagation constant over a wide spectral range.
  • the effective propagation length ⁇ E coincides with the propagation length ⁇ because Vs / Vb is 1.
  • log10 ( ⁇ E / ⁇ ) is inversely proportional to the acoustic resistance, and specifically, as log10 ( ⁇ E / ⁇ ) increases, the acoustic resistance decreases, and as log10 ( ⁇ E / ⁇ ) decreases, the acoustic resistance increases.
  • the silencer 20 by configuring the silencer 20 so as to satisfy the above numerical conditions, it is no longer necessary to increase the volume of the sound-absorbing material contained within the silencer more than necessary, thereby preventing the silencer (air duct with silencer) from becoming too large.
  • the silencer-equipped air duct 100 it is possible to improve the noise reduction performance for low-frequency sounds (specifically, 1000 Hz or less) while suppressing an increase in size.
  • silencer-equipped air duct 100 satisfies -1.80 ⁇ log 10 ( ⁇ E / ⁇ ) ⁇ 0.48, in which case a sound silencing effect with a transmission loss of 5 dB or more can be achieved for the sound of the first resonant frequency.
  • silencer-equipped air duct 100 satisfies -1.69 ⁇ log 10 ( ⁇ E / ⁇ ) ⁇ 0.27, in which case a sound silencing effect with a transmission loss of 7 dB or more can be achieved for the sound of the first resonant frequency.
  • the cross-sectional area of the housing 21 is larger than the cross-sectional area of each of the second air duct portion 32 and the third air duct portion 33, i.e., the silencer 20 forms an extension portion. This realizes a silencer that satisfies the relationships Zs ⁇ Zin and Zs ⁇ Zout in acoustic impedance density Z.
  • the air duct wall 42 is provided with openings 43a, 43b, and 43c, as shown in FIG. 1. This allows the air duct space 41 to communicate with the rear space 23, and allows sound in the air duct space 41 to enter the sound-absorbing material 22 in the rear space 23, allowing the silencer 20 to exert its silencing effect appropriately.
  • the ratio of A1 to the sum of A1 and A2 is more than 10% and less than 85%. This allows the silencer 20 to exhibit an appropriate silencing effect for sounds with frequencies lower than the first resonant frequency (355 Hz in FIG. 15), as shown in FIG.
  • the openings 43a, 43b are located at the center of the first air duct section 31 in the X direction.
  • the openings 43a, 43b are provided at a position where the particle speed of the air (wind) flowing through the first air duct section 31 is fast, and the sound-absorbing material 22 is disposed at this position, so that sound of the first resonant frequency can be more effectively silenced.
  • the openings 43a, 43b are located within L/4 from the center of the first air duct section 31 in the X direction. This more effectively utilizes the effect of providing the openings 43a, 43b at a position where the particle speed of the air (wind) flowing through the first air duct section 31 is faster, thereby more effectively silencing the sound of the first resonant frequency.
  • the wall 42c located at the end of the first air duct section 31 in the Z direction constitutes part of the end of the housing 21 in the Z direction (the lower end in FIG. 3). This ensures a sufficient gap between the end of the first air duct section 31 opposite the wall 42c in the Z direction (i.e., the opening 43c) and the end of the housing 21 opposite the wall 42c in the Z direction (the upper end in FIG. 3). As a result, the peak frequency of silencing in the silencer 20 can be shifted to a lower frequency side compared to when the first air duct section 31 is located in the center of the housing 21 in the Z direction as shown in FIG. 5 (see FIG. 18).
  • the air duct wall 42 has a pair of walls 42a, 42b that face each other in the Y direction, sandwiching the air duct space 41. This allows the position of the air duct space 41 in the Y direction to be determined by the pair of walls 42a, 42b, and allows the air sent from the air source 10 to be appropriately sent inside the housing 21, i.e., in the first air duct section 31.
  • the pair of walls 42a, 42b each have an opening 43a, 43b. This allows sound in the air passage space 41 to enter the area of the sound-absorbing material 22 adjacent to each of the pair of walls 42a, 42b, so that the sound-absorbing effect of the silencer 20 is properly exerted.
  • the silencer-equipped air duct 100 silences the sound generated due to the operation of the air source 10 that sends air into the air duct 30.
  • the silencer-equipped air duct 100 can provide a noise-reduction effect in an air blowing system that blows air into a specified space (e.g., a room) within a building for the purpose of air conditioning, ventilation, etc.
  • the conversion mechanism that converts sound energy into heat energy is the sound-absorbing material 22.
  • the conversion mechanism may not use the sound-absorbing material 22, but may use, for example, wall friction.
  • sound energy may be converted into heat energy based on the surface roughness imparted to the wall surfaces that define the rear space 23 (i.e., the inner wall surfaces of the housing 21 and the outer wall surfaces of the air passage wall 42 shown in FIG. 3).
  • the wall 42c forming the end of the first air passage section 31 in the Z direction constitutes part of the end of the housing 21 in the Z direction (the bottom wall of the housing 21 in FIG. 3).
  • the wall 42c may be disposed at a distance from the end of the housing 21 in the Z direction (the bottom wall of the housing 21 in FIG. 5), as in the silencer 20A shown in FIG. 5.
  • sound absorbing material 22A may be disposed in the space between the wall 42c and the housing 21 (rear space), as shown in FIG. 5.
  • each of the pair of walls 42a, 42b is provided with one opening 43a, 43b.
  • each of the pair of walls 42a, 42b may be provided with multiple openings.
  • each of the walls 42a, 42b may be made of a punched metal with multiple through holes (openings), a wire mesh, or the like.
  • the sound absorbing material 22 fills the entire rear space 23.
  • the sound absorbing material 22B may be disposed in only a part of the rear space 23, as in the silencer 20B shown in Fig. 6.
  • sound absorbing material 22B that is sufficiently thinner in the Y direction than the regions may be disposed along the openings 43a, 43b.
  • one or more communication holes 24C that connect the air passage space 41 and the rear space 23 and penetrate the sound absorbing material 22C may be provided in the sound absorbing material 22C.
  • the air passage wall 42 is provided with a plurality of openings 43a, 43b, and 43c, as shown in FIG. 1.
  • the openings 43a, 43b, and 43c are located on three sides of the first air passage section 31, and more specifically, as shown in FIG. 3, the openings 43a, 43b, and 43c are located on the outer edge of the first air passage section 31, at one end in the Z direction (opposite the wall 42c) and at both ends in the Y direction.
  • this is not limited to this, and for example, as in the silencer 20D shown in FIG. 8, only the opening 43c may be provided in the air passage wall 42.
  • the sound absorbing material 22 may not be arranged in the area of the back space 23 located outside the air passage wall 42 in the Y direction.
  • the pair of walls 42a, 42b are flat walls that extend along the X direction and have rigidity, as shown in FIG. 4.
  • the walls 42a, 42b may be rigid walls that extend along a direction inclined with respect to the X direction, as in the silencer 20E shown in FIG. 9. More specifically, as shown in FIG. 9, the pair of walls 42a, 42b arranged upstream of the openings 43a, 43b in the X direction may extend at an incline toward the outside in the Y direction (toward the rear space 23) as they move downstream.
  • the pair of walls 42a, 42b arranged downstream of the openings 43a, 43b in the X direction may extend at an incline toward the inside in the Y direction (toward the air passage space 41) as they move downstream.
  • the cross section of the housing 21 perpendicular to the X direction is rectangular as shown in FIG. 1, and the cross-sectional shape is maintained as a constant shape in the X direction.
  • the cross section of the housing may be circular, a quadrangle other than a square, a polygon other than a quadrangle, or an indefinite shape, and may change in the X direction.
  • the cross section of the housing 21F perpendicular to the X direction is polygonal, and the cross-sectional area may decrease toward the outside in the X direction (i.e., the direction toward the second air path section 32 and the third air path section 33).
  • the first air path section 31, the second air path section 32, and the third air path section 33 are each a linear air path section extending in the X direction, and the central axis of each air path section extends in the X direction and is located on the same imaginary line.
  • the direction in which the first air path section 31G extends may extend at an angle to the direction in which the second air path section 32G and the third air path section 33G extend, as in the silencer 20G shown in FIG.
  • the configuration of the housing 21G that houses the first air path section 31G may be changed depending on the direction in which the first air path section 31G extends (X direction). For example, as shown in FIG. 11, the direction in which the housing 21G extends may be inclined with respect to the direction in which the second air path section 32G and the third air path section 33G extend.
  • Simulations 1 to 4 were carried out to examine the effects of an air duct with a silencer according to the present invention.
  • the simulations were carried out using the acoustic module of the finite element method calculation software COMSOL version 6.0 (COMSOL, Inc.).
  • Comparative Example 1 a calculation model of an air passage with a silencer was generated.
  • the calculation model had the same configuration as that shown in Figs. 1 to 4 in the above embodiment.
  • the dimensions of the first air passage section were set to a length of 200 mm (the dimension of length L in Fig. 4), a width of 21 mm (length in the Y direction), and a height of 21 mm (length in the Z direction).
  • An opening (corresponding to openings 43a and 43b in Fig. 1) provided on each of a pair of walls (corresponding to walls 42a and 42b in Fig. 1) facing each other in the Y direction was placed at the center of the first air passage section in the X direction, and the dimensions were set to a length of 140 mm (X direction) and a height of 21 mm (Z direction).
  • the entire back space was filled with sound absorbing material, and the flow resistance of the sound absorbing material was set to 18 Pa ⁇ s/ m2 .
  • the density ⁇ of the air flowing through the air passage was set to 1.29 kg/ m3
  • the sound speed c of the sound propagating through the air was set to 340 m/s.
  • the cross-sectional area of the housing was set to 0.004 m2
  • the cross-sectional areas of the second air passage section and the third air passage section were each set to 0.000441 m2 .
  • the acoustic impedance density Zs of the internal space of the housing was 109650 rayl/ m2
  • the acoustic impedance density Zin of the second air passage section and the acoustic impedance density Zout of the third air passage section were 994558 rayl/ m2 .
  • Comparative Example 2 In Comparative Example 2, the flow resistance of the sound absorbing material was set to 1,800,000 Pa ⁇ s/m 2. This resulted in log 10 ( ⁇ E / ⁇ ) being ⁇ 2.07. The other conditions were the same as those in Comparative Example 1.
  • Example 1 In Example 1, the flow resistance of the sound absorbing material was set to 14,384 Pa ⁇ s/m 2. This resulted in log 10 ( ⁇ E / ⁇ ) being ⁇ 0.76. The other conditions were the same as those in Comparative Example 1.
  • the sound (sound waves) emitted by the air source was incident on the entrance of the air duct with silencer (more specifically, the upstream end of the second air duct section), and the amplitude per unit area of the sound reaching the exit of the air duct with silencer (more specifically, the downstream end of the third air duct section) was calculated (see Figure 1 for the calculation model).
  • the amplitude per unit area of the sound emitted by the air source was set to 1.
  • the transmission loss was calculated from the ratio of the amplitude of the sound emitted by the air source to the amplitude of the sound reaching the exit of the air duct with silencer.
  • Fig. 12 is a diagram showing the relationship between frequency, log 10 ( ⁇ E / ⁇ ), and transmission loss.
  • Fig. 13 is a diagram showing the relationship between log 10 ( ⁇ E / ⁇ ) and transmission loss for a sound with a first resonant frequency of 850 Hz, and is a cross section at a frequency of 850 Hz in Fig. 12.
  • Fig. 14 is a diagram showing the relationship between frequency and transmission loss in each of Comparative Example 1, Comparative Example 2, and Example 1.
  • Example 1 exhibited a large transmission loss compared to both Comparative Examples 1 and 2 for low-frequency sounds below 1000 Hz, including the first resonant frequency of 850 Hz, and it was found that the sound-dampening effect of the muffler was adequately demonstrated.
  • FIG. 2 A calculation model with a different aperture ratio was generated based on the calculation model of Example 1. Specifically, the aperture ratio was changed by changing the width dimension in the X direction of a pair of openings (corresponding to openings 43a and 43b in FIG. 1) formed in a pair of air passage walls sandwiching the first air passage section. Note that, in each of the aperture ratios, each of the pair of openings was disposed in the center of the first air passage section in the X direction.
  • the first air passage portion is disposed at the center of the housing in the Z direction as shown in Fig. 5.
  • the space between the outer edge (four faces) of the first air passage portion and the housing i.e., the rear space, is filled with sound absorbing material over the entire rear space.
  • FIG. 15 is a diagram showing the relationship between the aperture ratio and the transmittance, with the horizontal axis representing the aperture ratio and the vertical axis representing the transmittance. As shown in FIG. 15, when the opening ratio is in the range of more than 10% and less than 85%, it was found that the transmittance is reduced for low-frequency sounds, particularly for sounds of 355 Hz, which is lower than the first resonant frequency of 850 Hz.
  • FIG. 16 is a diagram showing the relationship between frequency and transmittance for each opening position, with the horizontal axis showing frequency and the vertical axis showing transmittance.
  • Figure 17 is a diagram showing the relationship between opening position and transmittance for the sound of the first resonance frequency, with the horizontal axis showing the distance in the X direction from the center line of the first air duct section to the center line of the opening (hereinafter referred to as distance D), and the vertical axis showing the transmittance at the first resonance frequency of 850 Hz.
  • the transmittance is high in the frequency band including the first resonant frequency of 850 Hz, with the first resonant frequency at its peak.
  • the transmittance of the frequency band centered on the first resonant frequency of 850 Hz decreases as the distance D is shortened, and when the distance D is 0 mm, the transmittance becomes the same as that of the low-frequency band other than the first resonant frequency. This is presumably because the opening is disposed at a position where the particle speed of the air flowing through the first air passage portion is high, and therefore the transmittance of the frequency band centered on the first resonant frequency of 850 Hz is reduced.
  • the transmittance becomes high in the frequency band including the first resonant frequency of 850 Hz and in the frequency bands including other resonant frequencies, as shown by the dashed dotted line in Figure 16.
  • Fig. 18 is a diagram showing the relationship between frequency and transmission loss determined according to the position of the first air duct section in the Z direction, with the horizontal axis representing frequency and the vertical axis representing transmission loss.
  • the "bottom surface" indicated by a thick solid line means the case where the end of the first air passage portion in the Z direction is at the position of the first pattern.
  • the "center” indicated by a thin solid line means that the end of the first air passage portion in the Z direction is at the position of the second pattern.
  • the "middle” indicated by the dashed line means that the end of the first air passage portion in the Z direction is at the position of the third pattern.
  • Air source (blower) 12 upstream air passage 14: downstream air passage 20, 20A, 20B, 20C, 20D, 20E, 20F, 20G: silencer 21, 21F, 21G: housing (silencer body) 22, 22A, 22B, 22C Sound absorbing material 23 Back space 24C Communication hole 30 Air passage 31, 31G First air passage section 32, 32G Second air passage section 33, 33G Third air passage section 41 Air passage space 42 Air passage wall 42a, 42b, 42c Wall 43a, 43b, 43c Opening 100 Air passage with silencer D Distance L Length S Air blowing system W Outer wall

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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)
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Abstract

L'invention concerne un conduit d'air équipé d'un silencieux qui permet d'améliorer les performances d'atténuation des sons à basse fréquence tout en réduisant les dimensions.　Ce conduit d'air équipé d'un silencieux est configuré en disposant un silencieux dans une position intermédiaire du conduit d'air : le silencieux comprend un corps principal de silencieux et un mécanisme de conversion logé dans le corps principal de silencieux qui transforme l'énergie sonore en énergie thermique ; le conduit d'air comprend une première partie de conduit d'air formée dans le corps principal de silencieux, une deuxième partie de conduit d'air située en amont de la première partie de conduit d'air, et une troisième partie de conduit d'air située en aval de la première partie de conduit d'air ; la densité d'impédance acoustique de l'espace interne du corps principal du silencieux est inférieure aux densités d'impédance acoustique des espaces internes respectifs de la deuxième partie de conduit d'air et de la troisième partie de conduit d'air ; et -1,97 < log10(αE/λ) < 0,76, αE correspondant à une longueur de propagation effective déterminée sur la base de la caractéristique d'un espace de propagation des ondes sonores à l'intérieur du corps principal du silencieux, λ correspondant à la longueur d'onde du son d'une fréquence qui est déterminée sur la base de la longueur de la première partie de conduit d'air et à laquelle le corps principal du silencieux résonne.
PCT/JP2023/033932 2022-10-26 2023-09-19 Conduit d'air équipé d'un silencieux WO2024090076A1 (fr)

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JP2022171441 2022-10-26

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2020024354A (ja) * 2017-12-06 2020-02-13 富士フイルム株式会社 防音システム
WO2020036029A1 (fr) * 2018-08-14 2020-02-20 富士フイルム株式会社 Système de silencieux
WO2022202975A1 (fr) * 2021-03-25 2022-09-29 富士フイルム株式会社 Structure de changement d'impédance acoustique et silencieux de type ventilation

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2020024354A (ja) * 2017-12-06 2020-02-13 富士フイルム株式会社 防音システム
WO2020036029A1 (fr) * 2018-08-14 2020-02-20 富士フイルム株式会社 Système de silencieux
WO2022202975A1 (fr) * 2021-03-25 2022-09-29 富士フイルム株式会社 Structure de changement d'impédance acoustique et silencieux de type ventilation

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