US20200208655A1 - Centrifugal compressor - Google Patents

Centrifugal compressor Download PDF

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Publication number
US20200208655A1
US20200208655A1 US16/726,358 US201916726358A US2020208655A1 US 20200208655 A1 US20200208655 A1 US 20200208655A1 US 201916726358 A US201916726358 A US 201916726358A US 2020208655 A1 US2020208655 A1 US 2020208655A1
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US
United States
Prior art keywords
silencer
centrifugal compressor
acoustic
casing
compressor according
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.)
Abandoned
Application number
US16/726,358
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English (en)
Inventor
Toshifumi Kudo
Takaya KODA
Yuichiro Sawada
Yoshiko Takei
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Mitsubishi Heavy Industries Ltd
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Mitsubishi Heavy Industries Ltd
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Filing date
Publication date
Application filed by Mitsubishi Heavy Industries Ltd filed Critical Mitsubishi Heavy Industries Ltd
Assigned to MITSUBISHI HEAVY INDUSTRIES, LTD. reassignment MITSUBISHI HEAVY INDUSTRIES, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KODA, Takaya, KUDO, TOSHIFUMI, SAWADA, YUICHIRO, TAKEI, Yoshiko
Publication of US20200208655A1 publication Critical patent/US20200208655A1/en
Abandoned legal-status Critical Current

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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04DNON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00Details, component parts, or accessories
    • F04D29/66Combating cavitation, whirls, noise, vibration or the like; Balancing
    • F04D29/661Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps
    • F04D29/663Sound attenuation
    • F04D29/664Sound attenuation by means of sound absorbing material
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04DNON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00Details, component parts, or accessories
    • F04D29/40Casings; Connections of working fluid
    • F04D29/42Casings; Connections of working fluid for radial or helico-centrifugal pumps
    • F04D29/4206Casings; Connections of working fluid for radial or helico-centrifugal pumps especially adapted for elastic fluid pumps
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04DNON-POSITIVE-DISPLACEMENT PUMPS
    • F04D17/00Radial-flow pumps, e.g. centrifugal pumps; Helico-centrifugal pumps
    • F04D17/08Centrifugal pumps
    • F04D17/10Centrifugal pumps for compressing or evacuating
    • F04D17/12Multi-stage pumps
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04DNON-POSITIVE-DISPLACEMENT PUMPS
    • F04D17/00Radial-flow pumps, e.g. centrifugal pumps; Helico-centrifugal pumps
    • F04D17/08Centrifugal pumps
    • F04D17/10Centrifugal pumps for compressing or evacuating
    • F04D17/12Multi-stage pumps
    • F04D17/122Multi-stage pumps the individual rotor discs being, one for each stage, on a common shaft and axially spaced, e.g. conventional centrifugal multi- stage compressors
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04DNON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00Details, component parts, or accessories
    • F04D29/40Casings; Connections of working fluid
    • F04D29/42Casings; Connections of working fluid for radial or helico-centrifugal pumps
    • F04D29/4206Casings; Connections of working fluid for radial or helico-centrifugal pumps especially adapted for elastic fluid pumps
    • F04D29/4226Fan casings
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04DNON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00Details, component parts, or accessories
    • F04D29/40Casings; Connections of working fluid
    • F04D29/42Casings; Connections of working fluid for radial or helico-centrifugal pumps
    • F04D29/44Fluid-guiding means, e.g. diffusers
    • F04D29/441Fluid-guiding means, e.g. diffusers especially adapted for elastic fluid pumps
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04DNON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00Details, component parts, or accessories
    • F04D29/66Combating cavitation, whirls, noise, vibration or the like; Balancing
    • F04D29/661Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps
    • F04D29/663Sound attenuation
    • F04D29/665Sound attenuation by means of resonance chambers or interference
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05DINDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2260/00Function
    • F05D2260/96Preventing, counteracting or reducing vibration or noise
    • F05D2260/963Preventing, counteracting or reducing vibration or noise by Helmholtz resonators

Definitions

  • a centrifugal compressor including a silencer to reduce noise emitted from a centrifugal compressor is disclosed.
  • the centrifugal compressor of Patent Document 1 includes a plurality of impellers which send gas outward in the radial direction by rotation about an axis, a casing which covers the plurality of impellers, and the above-described silencer.
  • the plurality of impellers are arranged in an axial direction of the impellers.
  • An inlet which introduces gas into the inside, an outlet which discharges the gas, and a passage which guides the gas flowing in from the inlet to the outlet through the plurality of impellers are formed in the casing.
  • the silencer includes a perforated plate and a space forming body.
  • the perforated plate has a first surface and a second surface, and a plurality of acoustic holes which penetrate from the first surface to the second surface opposite to the first surface.
  • the space forming body forms an acoustic space on the second surface side of the perforated plate.
  • the silencer is disposed so that the first surface of the perforated plate forms part of an inner surface of the casing which defines the radial passage.
  • An object of the present invention is to provide a centrifugal compressor which is able to enhance a sound absorption effect.
  • a centrifugal compressor including one or more impellers configured to rotate about an axis and to send a gas to a radially outer side of the axis and to guide the gas from an inlet to an inside to discharge the gas from an outlet, a casing configured to cover the one or more impellers, and a silencer.
  • the casing has an outlet scroll passage which extends in a circumferential direction of the axis and communicates with the outlet.
  • the silencer includes a perforated plate in which a first surface and a second surface opposite to the first surface and a plurality of acoustic holes penetrating from the first surface to the second surface are formed, and a space forming body configured to form an acoustic space connected to the plurality of acoustic holes on a second surface side of the perforated plate.
  • the first surface of the silencer forms part of an inner surface of the casing which defines the outlet scroll passage.
  • the centrifugal compressor of the aspect includes a silencer which uses the principle of a Helmholtz resonator. Tests were performed on a relationship between the sound absorption coefficient of the silencer using the principle of a Helmholtz resonator and the velocity of the gas flowing through the passage. As a result, it was found that the sound absorption coefficient of the silencer which faces a passage portion increases as the velocity of the gas flowing through the passage portion decreases.
  • the first surface of the silencer may form only part of the inner surface of the outlet scroll passage.
  • a first silencer and a second silencer may be provided as the silencers.
  • the casing may have a radial passage which guides the gas flowing out from a final stage impeller of the one or more impellers to the radially outer side and communicates with the outlet scroll passage.
  • the first surface of the first silencer may form part of the inner surface of the outlet scroll passage
  • the first surface of the second silencer may form part of an inner surface of the casing which defines the radial passage.
  • the centrifugal compressor of the aspect includes the first silencer and the second silencer, it is possible to increase a sound absorption amount compared with a case in which only the first silencer is provided.
  • the first surface of the second silencer may not form an inner surface in an inner region including an end radially inward with respect to the axis but may form at least part of the inner surface in an outer region on the radially outer side from the inner region in the radial passage.
  • the velocity of the gas is lower in the outer region than in the inner region.
  • the sound absorption coefficient of the second silencer can be increased.
  • a short distance silencer and a long distance silencer may be provided as the second silencers.
  • the short distance silencer may be disposed at a position closer to the final stage impeller than the long distance silencer is in a radial direction of the axis, and inner diameters of the plurality of acoustic holes of the short distance silencer may be smaller than those of the plurality of acoustic holes of the long distance silencer.
  • the inner diameters of the plurality of acoustic holes of the short distance silencer is smaller than those of the plurality of acoustic holes of the long distance silencer, even when the short distance silencer is disposed in a region in which the velocity of the gas is high, a decrease in the sound absorption coefficient of the short distance silencer can be curbed.
  • a centrifugal compressor including one or more impellers configured to rotate about an axis and to send a gas to a radially outer side of the axis, a casing configured to cover the one or more impellers and to guide the gas from an inlet to an inside to discharge the gas from an outlet, and a short distance silencer and a long distance silencer as silencers.
  • the casing has an outlet passage which guides the gas flowing out from a final stage impeller of the one or more impellers to the outlet.
  • Each of the short distance silencer and the long distance silencer includes a perforated plate in which a first surface and a second surface opposite to the first surface and a plurality of acoustic holes penetrating from the first surface to the second surface are formed, and a space forming body configured to form an acoustic space connected to the plurality of acoustic holes on a second surface side of the perforated plate.
  • Both the first surface of the short distance silencer and the first surface of the long distance silencer form part of an inner surface of the casing which defines the outlet passage.
  • a distance along the outlet passage from the final stage impeller to the short distance silencer is shorter than that along the outlet passage from the final stage impeller to the long distance silencer.
  • Inner diameters of the plurality of acoustic holes of the short distance silencer are smaller than those of the plurality of acoustic holes of the long distance silencer.
  • the inner diameters of the plurality of acoustic holes of the short distance silencer are smaller than those of the plurality of acoustic holes of the long distance silencer, even when the short distance silencer is disposed in a region in which the velocity of the gas is high, a decrease in the sound absorption coefficient of the short distance silencer can be curbed.
  • At least part of the space forming body of the silencer may be formed of the same material as that of the casing and may be integrally formed with the casing.
  • a portion except part of the space forming body formed integrally with the casing can be easily installed in and separated from the casing.
  • the perforated plate may be formed of a material having a linear expansion coefficient larger than that of the casing.
  • a gap is formed between the perforated plate and at least part of the space forming body, and a gap is formed between the perforated plate and the casing according to the situation of the centrifugal compressor.
  • the gas compressed by the centrifugal compressor contains a component which becomes a liquid at room temperature, and the centrifugal compressor is cooled and the centrifugal compressor and the gas therein reach room temperature, some of the gas changes to a liquid.
  • the liquid may remain in the acoustic space of the silencer.
  • all the liquid in the acoustic space may not be vaporized, and some of the liquid may remain as a liquid. In this case, a problem that the silencer cannot absorb sound in a target frequency range may occur.
  • the silencer in this aspect can discharge a liquid from the gap even when a liquid remains in the acoustic space.
  • a problem in that the silencer cannot absorb the sound in the target frequency range can be avoided, and reduction in the sound absorption effect can be curbed.
  • the silencer may have a drain hole which discharges a liquid in the acoustic space outside of the acoustic space.
  • the silencer in this aspect has the drain hole, even when a liquid remains in the acoustic space, the liquid can be discharged outside the acoustic space from the drain hole. Accordingly, in this aspect, the problem that the silencer cannot absorb the sound in the target frequency range can be avoided, and the reduction of the sound absorption effect can be curbed.
  • a centrifugal compressor including one or more impellers configured to rotate about an axis and to send a gas to a radially outer side of the axis, a casing configured to cover the one or more impellers and to guide the gas from an inlet to an inside to discharge the gas from an outlet, and a silencer.
  • the casing has a passage which guides the gas flowing in from the inlet to the outlet through the one or more impellers.
  • the silencer includes a perforated plate in which a first surface and a second surface opposite to the first surface and a plurality of acoustic holes penetrating from the first surface to the second surface are formed, a space forming body configured to form an acoustic space connected to the plurality of acoustic holes on a second surface side of the perforated plate, and a drain hole configured to discharge a liquid in the acoustic space outside of the acoustic space.
  • the first surface of the silencer forms part of an inner surface of the passage.
  • the silencer in this aspect has the drain hole, even when a liquid remains in the acoustic space, the liquid can be discharged from the drain hole to the outside of the acoustic space. Therefore, in this aspect, the problem that the silencer cannot absorb the sound in the target frequency range can be avoided, and the reduction of the sound absorption effect can be curbed.
  • the drain hole may have a first opening which opens in an inner surface of the space forming body which faces the acoustic space, and a second opening which opens in an outer surface of the casing.
  • an opening area of the first opening may be 20% or less of a total opening area of all the acoustic holes in a portion of the perforated plate which defines one acoustic space.
  • the silencer may have a valve capable of partitioning a space in the drain hole from an outer space of the casing.
  • a moisture absorbent may be disposed in the drain hole.
  • the drain hole may have a first opening which opens in the first surface of the perforated plate, and a second opening which opens in the second surface of the perforated plate, and a moisture absorbent may be disposed in the drain hole.
  • the silencer in this aspect since a gap is formed between a plurality of parts constituting the silencer, the liquid can be discharged from the gap even when a liquid remains in the acoustic space. Therefore, also in this aspect, the problem that the silencer cannot absorb the sound in the target frequency range can be avoided, and the reduction of the sound absorption effect can be curbed.
  • inner diameters of the plurality of acoustic holes may be 0.2 mm or more to 1.0 mm or less.
  • FIG. 1 is a cross-sectional view of a centrifugal compressor according to a first embodiment.
  • FIG. 3 is a graph showing a relationship between a sound absorption coefficient of a silencer and a velocity of a gas flowing through a passage.
  • FIG. 5 is a cross-sectional view of a main part of a centrifugal compressor according to a second modified example of the first embodiment.
  • FIG. 6 is a cross-sectional view of a main part of a centrifugal compressor according to a second embodiment.
  • FIG. 10 is a cross-sectional view of a main part of the centrifugal compressor in a state in which the centrifugal compressor according to the fifth embodiment is cooled.
  • FIG. 11 is a cross-sectional view of a main part of a centrifugal compressor according to a sixth embodiment.
  • FIG. 13 is a cross-sectional view around a silencer of the centrifugal compressor according to the seventh embodiment.
  • FIG. 14 is a cross-sectional view around a silencer of a centrifugal compressor according to an eighth embodiment.
  • the centrifugal compressor according to this embodiment is a multistage centrifugal compressor. As shown in FIG. 1 , the centrifugal compressor according to this embodiment includes a rotary shaft 10 , bearings 15 a and 15 b , a plurality of impellers 11 , a casing 20 , and a silencer 30 A.
  • the rotary shaft 10 has a cylindrical shape and rotates around an axis Ar.
  • the bearings 15 a and 15 b rotatably support the rotary shaft 10 .
  • the plurality of impellers 11 are installed on the rotary shaft 10 and rotate around the axis Ar together with the rotary shaft 10 .
  • the casing 20 surrounds the impellers 11 .
  • the silencer 30 A is provided in the casing 20 .
  • a direction in which the axis Ar extends is referred to as an axial direction Da.
  • the bearing 15 a side in the axial direction Da is referred to as the first side Da 1 .
  • the bearing 15 b side is referred to as the second side Da 2 .
  • a radial direction with respect to the axis Ar is referred to as a radial direction Dr.
  • the side closer to the axis Ar in the radial direction Dr is referred to as the radially inner side Dri.
  • the side away from the axis Ar in the radial direction Dr is referred to as the radially outer side Dro.
  • a circumferential direction around the axis Ar is referred to as a circumferential direction Dc.
  • the rotary shaft 10 is provided to pass through the casing 20 in the axial direction Da.
  • the centrifugal compressor according to this embodiment includes a thrust bearing 15 a and a journal bearing 15 b as the bearings 15 a and 15 b .
  • the thrust bearing 15 a is provided at an end of the casing 20 on the first side Da 1 and supports an end of the rotary shaft 10 on the first side Da 1 .
  • the journal bearing 15 b is provided at an end of the casing 20 on the second side Da 2 and supports an end of the rotary shaft 10 on the second side Da 2 .
  • the plurality of impellers 11 are arranged in the axial direction Da to be spaced apart from each other in the axial direction Da.
  • An in-impeller flow path 12 through which a gas flows is formed in each of the impellers 11 .
  • the in-impeller flow path 12 has an impeller inlet 13 and an impeller outlet 14 .
  • the impeller inlet 13 is open from the inside of the in-impeller flow path 12 toward the first side Da 1 in the axial direction Da.
  • the impeller outlet 14 is open from the inside of the in-impeller flow path 12 toward the radially outer side Dro.
  • the casing 20 has an inlet 20 i which guides a gas into the casing 20 , an outlet 20 o which discharges the gas, and a passage 20 p .
  • the inlet 20 i is formed on the first side Da 1 with respect to the plurality of impellers 11 .
  • the outlet 200 o is formed on the second side Da 2 with respect to the plurality of impellers 11 .
  • the passage 20 p guides the gas flowing in from the inlet 20 i to the outlet 20 o via the plurality of impellers 11 .
  • the casing 20 has an inlet casing 21 , an intermediate casing 23 , and an outlet casing 25 .
  • the inlet casing 21 has an inlet 20 i and an inlet passage 21 p .
  • the inlet passage 21 p guides the gas flowing in from the inlet 20 i to the impeller inlet 13 of the initial stage impeller 11 a .
  • the intermediate casing 23 partitions the two impellers 11 adjacent to each other in the axial direction Da.
  • the intermediate casing 23 is disposed between the inlet casing 21 and the outlet casing 25 in the axial direction Da.
  • the intermediate casing 23 has a plurality of intermediate passages 23 p .
  • the intermediate passage 23 p has a diffuser passage 23 pa , a turning passage 23 pb , and a return passage 23 pc .
  • the diffuser passage 23 pa guides the gas flowing out from the impeller outlet 14 of the impeller 11 on the first side Da 1 , among the two impellers 11 adjacent to each other in the axial direction Da, to the radially outer side Dro. That is, the diffuser passage 23 pa is a passage which extends in the radial direction Dr.
  • the turning passage 23 pb is connected to an end of the diffuser passage 23 pa on the radially outer side Dro.
  • the intermediate casing 23 has the intermediate passage 23 p .
  • the intermediate casing 23 forms part of a radial passage 26 as shown in FIG. 2 .
  • the radial passage 26 is a passage which guides the gas flowing out from the impeller outlet 14 of the final stage impeller 11 b to the radially outer side Dro.
  • the outlet scroll passage 27 extends in the circumferential direction Dc and allows communication between a portion of the radial passage 26 on the radially outer side Dro and the outlet 20 o .
  • An inner surface of the outlet scroll passage 27 which extends in the circumferential direction Dc has an external inner surface 27 o , an internal inner surface 27 i , a first side inner surface 27 a , and a second side inner surface 27 b .
  • the external inner surface 270 and the internal inner surface 27 i expand in the circumferential direction Dc and the axial direction Da.
  • the external inner surface 27 o is located closer to the radially outer side Dro than the internal inner surface 27 i .
  • the external inner surface 27 o faces the radially inner side Dri.
  • the internal inner surface 27 i faces the radially outer side Dro.
  • the first side inner surface 27 a and the second side inner surface 27 b expand in the circumferential direction Dc and the radial direction Dr.
  • the second side inner surface 27 b is located closer to the second side Da 2 than the first side inner surface 27 a .
  • the second side inner surface 27 b faces the first side Da 1 .
  • the first side inner surface 27 a faces the second side Da 2 .
  • the silencer 30 A includes a perforated plate 31 and a space forming body 35 .
  • a first surface 32 and a second surface 33 opposite to the first surface 32 , and a plurality of acoustic holes 34 are formed in the perforated plate 31 .
  • the first surface 32 and the second surface 33 constitute both surfaces of the perforated plate 31 .
  • the plurality of acoustic holes 34 penetrate from the first surface 32 to the second surface 33 .
  • Inner diameters of the plurality of acoustic holes 34 are preferably 0.1 mm or more to 3.0 mm or less.
  • the inner diameters of the plurality of acoustic holes 34 are, for example, 1.0 mm.
  • the inventor performed a test regarding a relationship between a sound absorption coefficient of the silencer using the principle of a Helmholtz resonator and a velocity of the gas flowing through the passage. Test results will be described with reference to a graph shown in FIG. 3 .
  • a horizontal axis in the graph shown in FIG. 3 indicates the velocity (Mach number) of the gas flowing through a passage portion which is a portion of the passage through which the gas flows and which faces the perforated plate of the silencer.
  • a vertical axis in the graph shown in FIG. 3 is the sound absorption coefficient of the silencer.
  • Inner diameters of the plurality of acoustic holes in the silencer used in the test are 1.0 mm, similar to the inner diameters of the plurality of acoustic holes 34 in this embodiment.
  • the sound absorption coefficient of the silencer facing the passage portion is about 0.2.
  • the sound absorption coefficient of the silencer facing the passage portion is about 0.4.
  • the sound absorption coefficient of the silencer facing the passage portion is about 0.6. Therefore, as the velocity of the gas flowing through the passage portion becomes lower, the sound absorption coefficient of the silencer facing the passage portion becomes greater.
  • the silencer 30 A faces part of the outlet scroll passage 27 , the sound absorption coefficient is higher than that of the silencer facing part of the radial passage 26 in which a flow rate of the gas is faster than that in the outlet scroll passage 27 . Therefore, the sound absorption coefficient can be enhanced in the silencer 30 A.
  • a pressure loss of the gas occurs due to the presence of the plurality of acoustic holes 34 of the silencer.
  • the pressure loss is proportional to the square of the velocity of the gas. Since the silencer 30 A faces part of the outlet scroll passage 27 , the pressure loss of the gas can be made smaller than that in a silencer which faces part of the radial passage 26 in which the flow rate of the gas is faster than that in the outlet scroll passage 27 .
  • the velocity of the gas at the impeller outlet 14 of the final stage impeller 11 b is, for example, Mach number 0.6 to 0.8.
  • the velocity of the gas at the impeller outlet 14 of the final stage impeller 11 b is the velocity of the gas at the end of the radial passage 26 on the radially inner side Dri.
  • the velocity of the gas flowing through the radial passage 26 gradually decreases as it flows to the radially outer side Dro due to the above-described reason.
  • the velocity of the gas in the outlet scroll passage 27 is Mach number 0.4 or less. Therefore, the sound absorption coefficient of the silencer 30 A which faces part of the outlet scroll passage 27 becomes about 0.4 or more.
  • the inner diameter of the acoustic hole 34 is set to 1.0 mm which is a minimum inner diameter that can be drilled with a drill, or an inner diameter close to the minimum inner diameter.
  • Hole machining can be performed using a laser as well as drilling.
  • the acoustic holes 34 When the acoustic holes 34 are machined with a laser, the acoustic holes 34 having an inner diameter of 1.0 mm or less can be formed. Therefore, considering the case in which the acoustic holes 34 are machined with a laser, the inner diameter of the acoustic hole 34 is preferably 0.2 mm or more to 1.0 mm or less.
  • the first surface 32 of the perforated plate 31 is disposed to form part of the external inner surface 27 o among the inner surfaces defining the outlet scroll passage 27 in the casing 20 .
  • a silencer 30 Aa in a first modified example of the first embodiment has the same configuration as that of the silencer 30 A in the first embodiment.
  • the first surface 32 of the perforated plate 31 is disposed to form part of the second side inner surface 27 b among the inner surfaces defining the outlet scroll passage 27 in the outlet casing 25 .
  • a silencer 30 Ab in a second modified example of the first embodiment has the same configuration as the silencer 30 A in the first embodiment.
  • the silencer 30 Ab is disposed so that the first surface 32 of the perforated plate 31 forms part of the internal inner surface 27 i among the inner surfaces which define the outlet scroll passage 27 in the outlet casing 25 .
  • the silencer 30 Aa of the first modified example and the silencer 30 Ab of the second modified example are also disposed so that the first surface 32 of the perforated plate 31 forms part of the inner surface which defines the outlet scroll passage 27 in the outlet casing 25 . Therefore, as in the first embodiment, the silencer 30 Aa of the first modified example and the silencer 30 Ab of the second modified example can also increase the sound absorption coefficient and can reduce the pressure loss of the gas.
  • the silencer 30 A may be disposed so that the first surface 32 of the perforated plate 31 forms part of one of the inner surfaces which define the outlet scroll passage 27 in the outlet casing 25 . Therefore, the silencer may be disposed so that the first surface 32 of the perforated plate 31 forms part of the first side inner surface 27 a among the inner surfaces which define the outlet scroll passage 27 in the casing 20 .
  • a centrifugal compressor according to a second embodiment will be described with reference to FIG. 6 .
  • the centrifugal compressor according to this embodiment includes a first silencer 30 B 1 and a second silencer 30 B 2 .
  • each of the first silencer 30 B 1 and the second silencer 30 B 2 includes the perforated plate 31 in which the plurality of acoustic holes 34 are formed, and the space forming body 35 which forms a plurality of acoustic spaces S.
  • the first silencer 30 B 1 is disposed so that the first surface 32 of the first silencer 30 B 1 forms part of the external inner surface 27 o of the outlet scroll passage 27 , as in the silencer 30 A in the first embodiment.
  • the first silencer 30 B 1 may be disposed so that the first surface 32 of the perforated plate 31 forms part of one of the inner surfaces which define the outlet scroll passage 27 .
  • the second silencer 30 B 2 is disposed so that the first surface 32 of the second silencer 30 B 2 forms part of the first side inner surface 26 a of the radial passage 26 .
  • the second silencer 30 B 2 only needs to be disposed so that the first surface 32 of the perforated plate 31 forms part of the inner surface of the radial passage 26 .
  • the second silencer 30 B 2 may be disposed to form part of the second side inner surface 26 b of the radial passage 26 .
  • the first surface 32 of the second silencer 30 B 2 does not form the inner surface in an inner region including an end on the radially inner side Dri and forms at least part of the inner surface in an outer region on the radially outer side Dro from the inner region.
  • the velocity of the gas flowing through the radial passage 26 is gradually reduced as it flows to the radially outer side Dro. Therefore, in this embodiment, in order to increase the sound absorption coefficient of the second silencer 30 B 2 , the first surface 32 of the second silencer 30 B 2 is disposed to form at least part of the inner surface in the outer region of the radial passage 26 .
  • the centrifugal compressor according to this embodiment includes the second silencer 30 B 2 disposed so that the first surface 32 forms part of the inner surface of the radial passage 26 in addition to the first silencer 30 B 1 disposed so that the first surface 32 forms part of the inner surface of the outlet scroll passage 27 , as in the silencer 30 A according to the first embodiment. Accordingly, the centrifugal compressor according to this embodiment can further increase a sound absorption amount.
  • a centrifugal compressor according to a third embodiment will be described with reference to FIG. 7 .
  • the centrifugal compressor according to this embodiment also includes a first silencer 30 C 1 and a second silencer 30 C 2 , as in the centrifugal compressor according to the second embodiment.
  • Both the first silencer 30 C 1 and the second silencer 30 C 2 have the same configuration as those of the silencers in the first embodiment and the second embodiment. That is, each of the first silencer 30 C 1 and the second silencer 30 C 2 includes the perforated plate 31 in which the plurality of acoustic holes 34 are formed and the space forming body 35 which forms the plurality of acoustic spaces S.
  • the first silencer 30 C 1 is disposed so that the first surface 32 of the first silencer 30 C 1 forms part of the external inner surface 27 o of the outlet scroll passage 27 , as in the silencer 30 A in the first embodiment.
  • the first silencer 30 C 1 may be disposed so that the first surface 32 of the perforated plate 31 forms part of one of the inner surfaces which define the outlet scroll passage 27 , as described in the modified example of the first embodiment.
  • the second silencer 30 C 2 is disposed so that the first surface 32 of the second silencer 30 C 2 forms part of the first side inner surface 26 a of the radial passage 26 .
  • the second silencer 30 C 2 only needs to be disposed so that the first surface 32 of the perforated plate 31 forms part of the inner surface of the radial passage 26 .
  • the second silencer 30 C 2 may be disposed to form part of the second side inner surface 26 b of the radial passage 26 , for example.
  • Each of the first silencer 30 C 1 and the second silencer 30 C 2 has the plurality of acoustic spaces S.
  • the acoustic spaces S have different volumes, for example, to change a sound absorption frequency range. Therefore, it can be said that both the first silencer 30 C 1 and the second silencer 30 C 2 have a silencer for each of the plurality of acoustic spaces S.
  • the second silencer 30 C 2 has three acoustic spaces S. That is, the second silencer 30 C 2 includes three silencers 30 Ca, 30 Cb, and 30 Cc.
  • the three silencers 30 Ca, 30 Cb, and 30 Cc in the second silencer 30 C 2 are arranged in the radial direction Dr.
  • the silencer 30 Ca which is closest to the final stage impeller 11 b in the radial direction Dr is referred to as a second short distance silencer 30 Ca.
  • the silencer 30 Cb adjacent to the radially outer side Dro of the second short distance silencer 30 Ca is referred to as a second intermediate distance silencer 30 Cb.
  • the silencer 30 Cc adjacent to the radially outer side Dro of the second intermediate distance silencer 30 Cb is referred to as a second long distance silencer 30 Cc. Therefore, the velocity of the gas flowing through the passage portion which faces the second short distance silencer 30 Ca is faster than that of the gas flowing through the passage portion which faces the second intermediate distance silencer 30 Cb.
  • the inner diameters of the acoustic holes 34 of the second long distance silencer 30 Cc and the second intermediate distance silencer 30 Cb are the same.
  • the inner diameter of the acoustic hole 34 of the second short distance silencer 30 Ca is smaller than those of the acoustic holes 34 of the second long distance silencer 30 Cc and the second intermediate distance silencer 30 Cb.
  • the inner diameters of the acoustic holes 34 of the second short distance silencer 30 Ca, the second intermediate distance silencer 30 Cb, and the second long distance silencer 30 Cc are preferably smaller than that of the acoustic hole 34 of the first silencer 30 C 1 . This is because passage distances of the second short distance silencer 30 Ca, the second intermediate distance silencer 30 Cb, and the second long distance silencer 30 Cc are shorter than that of the first silencer 30 C 1 and the velocity of the gas flowing in the passage portion which faces each of the second short distance silencer 30 Ca, the second intermediate distance silencer 30 Cb, and the second long distance silencer 30 Cc is faster than that of the gas flowing through the passage portion which faces the first silencer 30 C 1 .
  • the passage distance is a distance along the outlet passage 25 p from the impeller outlet 14 of the final stage impeller 11 b .
  • the inner diameter of the acoustic hole 34 of the first silencer 30 C 1 is 1.0 mm
  • the inner diameter of the acoustic hole 34 of each of the second long distance silencer 30 Cc and the second intermediate distance silencer 30 Cb is set to 0.8 mm
  • the inner diameter of the acoustic hole 34 of the second short distance silencer 30 Ca is set to 0.6 mm.
  • the inner diameter of the acoustic hole 34 of the second intermediate distance silencer 30 Cb may be smaller than that of the acoustic hole 34 of the second long distance silencer 30 Cc, and the inner diameter of the acoustic hole 34 of the second short distance silencer 30 Ca may be smaller than that of the acoustic hole 34 of the second intermediate distance silencer 30 Cb.
  • the inner diameter of the acoustic hole 34 of the first silencer 30 C 1 is 1.0 mm
  • the inner diameter of the acoustic hole 34 of the second long distance silencer 30 Cc is set to 0.8 mm
  • the inner diameter of the acoustic hole 34 of the second intermediate distance silencer 30 Cb is set to 0.6 mm
  • the inner diameter of the acoustic hole 34 of the second short distance silencer 30 Ca is set to 0.5 mm.
  • a centrifugal compressor according to a fourth embodiment will be described with reference to FIG. 8 .
  • the centrifugal compressor according to each of the above-described embodiments includes a short distance silencer 30 Da and a long distance silencer 30 Db as the silencer.
  • Each of the short distance silencer 30 Da and the long distance silencer 30 Db includes the perforated plate 31 in which the plurality of acoustic holes 34 are formed, and the space forming body 35 which forms the plurality of acoustic spaces S, as in the silencer according to each of the above-described embodiments.
  • the centrifugal compressor according to each of the above-described embodiments includes the silencer disposed so that the first surface 32 of the perforated plate 31 forms part of the inner surface of the outlet scroll passage 27 .
  • the centrifugal compressor according to this embodiment does not include a silencer disposed so that the first surface 32 of the perforated plate 31 forms part of the inner surface of the outlet scroll passage 27 .
  • the centrifugal compressor according to this embodiment includes a short distance silencer 30 Da and a long distance silencer 30 Db disposed so that the first surface 32 of the perforated plate 31 forms part of the first side inner surface 26 a of the radial passage 26 .
  • the short distance silencer 30 Da and the long distance silencer 30 Db may be disposed so that the first surface 32 of the perforated plate 31 forms part of the inner surface of the radial passage 26 .
  • the short distance silencer 30 Da and the long distance silencer 30 Db may be disposed to form part of the second side inner surface 26 b of the radial passage 26 , for example.
  • the short distance silencer 30 Da is disposed on the radially inner side Dri from the long distance silencer 30 Db.
  • the passage distance of the short distance silencer 30 Da is shorter than that of the long distance silencer 30 Db.
  • the inner diameter of the acoustic hole 34 of the short distance silencer 30 Da is smaller than that of the acoustic hole 34 of the long distance silencer 30 Db.
  • the inner diameter of the acoustic hole 34 of the long distance silencer 30 Db is 0.8 mm
  • the inner diameter of the acoustic hole 34 of the short distance silencer 30 Da is 0.5 mm.
  • a centrifugal compressor according to a fifth embodiment will be described with reference to FIGS. 9 and 10 .
  • the centrifugal compressor according to this embodiment is a modified example of the centrifugal compressor according to the first embodiment.
  • the centrifugal compressor according to this embodiment is different from the centrifugal compressor according to the first embodiment only in the configuration of the silencer, and the other configurations are the same as those of the centrifugal compressor according to the first embodiment.
  • a silencer 30 E includes a perforated plate 31 e in which a plurality of acoustic holes 34 are formed, and a space forming body 35 e which forms a plurality of acoustic spaces S, as in the silencer 30 A according to the first embodiment.
  • the silencer 30 E in this embodiment is disposed so that the first surface 32 of the perforated plate 31 e forms part of the inner surface of the outlet scroll passage 27 , as in the silencer 30 A in the first embodiment.
  • the space forming body 35 e of the silencer 30 E in this embodiment includes an outer frame 36 e which forms a space between the outer frame 36 e and the perforated plate 31 e on the second surface 33 side of the perforated plate 31 e , and a partition wall 39 e which partitions the space into a plurality of acoustic spaces S, as in the space forming body 35 of the silencer 30 A in the first embodiment.
  • the outer frame 36 e has a bottom wall 37 and a side peripheral wall 38 .
  • the bottom wall 37 faces the perforated plate 31 e with an interval therebetween.
  • the side peripheral wall 38 is located between the perforated plate 31 e and the bottom wall 37 and defines a side periphery of the above-described space.
  • the partition wall 39 e is integrally formed with the side peripheral wall 38 of the outer frame 36 e .
  • the bottom wall 37 is formed of the same material as that of the outlet casing 25 and is integrally formed with the outlet casing 25 .
  • the bottom wall 37 is formed by part of the outlet casing 25 .
  • a portion excluding the bottom wall 37 , and the perforated plate 31 e are formed of a material having a larger linear expansion coefficient than that of the outlet casing 25 .
  • a recessed portion 28 is formed in the outlet casing 25 . As shown in FIG. 10 , the recessed portion 28 is formed to be recessed from the inner surface of the outlet scroll passage 27 toward the outer side of the outlet casing 25 . A portion of the recessed portion 28 which forms a bottom surface forms the bottom wall 37 of the space forming body 35 e . In this embodiment, a portion of the silencer 30 E excluding the bottom wall 37 is fitted into the recessed portion 28 . However, the portion of the silencer 30 E excluding the bottom wall 37 is not fixed into the recessed portion 28 .
  • the gas compressed by the centrifugal compressor includes a component which becomes liquid at room temperature, and the centrifugal compressor is cooled, and the centrifugal compressor and the gas therein reach room temperature, some of the gas changes to liquid.
  • the liquid may remains in the acoustic space S of the silencer 30 E.
  • all the liquid in the acoustic space S may not be vaporized, and some of the liquid may remain as the liquid. In this case, a problem that the silencer 30 E cannot absorb the sound in a target frequency range occurs.
  • the silencer 30 E of this embodiment when the centrifugal compressor is cooled, the gap is formed between the plurality of parts constituting the silencer 30 E. Therefore, even when the liquid remains in the acoustic space S, the silencer 30 E can discharge the liquid from the gap.
  • the problem that the silencer 30 E cannot absorb the sound in the target frequency range can be avoided, and thus reduction of the sound absorption effect can be curbed.
  • the gap is formed between the plurality of parts constituting the silencer 30 E.
  • those other than the parts integrally formed with the outlet casing 25 can be easily installed in and separated from the outlet casing 25 .
  • a centrifugal compressor according to a sixth embodiment will be described with reference to FIG. 11 .
  • the centrifugal compressor according to this embodiment is a modified example of the centrifugal compressor according to the fifth embodiment.
  • the centrifugal compressor according to this embodiment is different from the centrifugal compressor according to the fifth embodiment only in the configuration of the silencer, and the other configurations are the same as those of the centrifugal compressor according to the fifth embodiment.
  • a silencer 30 F in this embodiment also includes a perforated plate 31 f in which a plurality of acoustic holes 34 are formed, and a space forming body 35 f which forms a plurality of acoustic spaces S, as in the silencers in the first and fifth embodiments.
  • the silencer 30 F in this embodiment is also disposed so that the first surface 32 of the perforated plate 31 f forms part of the inner surface of the outlet scroll passage 27 , as in the silencers in the first embodiment and the fifth embodiment.
  • the space forming body 35 f of the silencer 30 F in this embodiment is formed of the same material as that of the outlet casing 25 and is integrally formed with the outlet casing 25 . In other words, the space forming body 35 f is formed by part of the outlet casing 25 .
  • the perforated plate 31 f of the silencer 30 F is formed of a material having a larger linear expansion coefficient than that of the outlet casing 25 . The perforated plate 31 f is not fixed to the space forming body 35 f.
  • the gap is formed between the plurality of parts constituting the silencer 30 F when the centrifugal compressor is cooled, as in the silencer 30 E in the fifth embodiment.
  • the silencer 30 F can discharge a liquid from the gap even when the liquid remains in the acoustic space S. Therefore, also in this embodiment, the problem that the silencer 30 F cannot absorb the sound in the target frequency range can be avoided, and the reduction of the sound absorption effect can be curbed.
  • the gap is formed between the plurality of parts constituting the silencer 30 F.
  • those excluding the parts integrally formed with the outlet casing 25 can be easily installed in and separated from the outlet casing 25 .
  • the silencers in the fifth embodiment and the sixth embodiment are modified examples of the silencer 30 A in the first embodiment.
  • the silencers in the first modified example and the second modified example of the first embodiment, and the second to fourth embodiments may be modified in the same manner as that in the silencer in the fifth or sixth embodiment.
  • a centrifugal compressor according to a seventh embodiment will be described with reference to FIGS. 12 and 13 .
  • the centrifugal compressor according to this embodiment also includes a silencer 30 G as in each of the above-described embodiments and modified examples.
  • the silencer 30 G according to this embodiment also includes the perforated plate 31 in which the plurality of acoustic holes 34 are formed, and the space forming body 35 which forms the plurality of acoustic spaces S, as in each of the above-described embodiments and modified examples.
  • the silencer 30 G in this embodiment is disposed so that the first surface 32 of the perforated plate 31 forms part of the inner surface of the radial passage 26 .
  • the silencer 30 G in this embodiment further includes a plurality of drain holes 40 , a plurality of drain pipes 43 , and a plurality of valves 44 .
  • the drain hole 40 is provided for each of the plurality of acoustic spaces S.
  • the drain pipe 43 is provided for each of the plurality of drain holes 40 .
  • the valve 44 is provided for each of the plurality of drain pipes 43 .
  • the drain holes 40 include a hole formed in the space forming body 35 and a hole formed in the casing 23 ( 20 ). The hole formed in the space forming body 35 and the hole formed in the casing 23 ( 20 ) are connected to each other.
  • the drain hole 40 has a first opening 41 and a second opening 42 .
  • the first opening 41 is open in an inner surface of the space forming body 35 which faces the acoustic space S.
  • the second opening 42 is open in an outer surface of a lower portion of the casing 23 ( 20 ).
  • the first opening 41 is open at a lower portion of the inner surface of the space forming body 35 which faces the acoustic space S.
  • a position of the lowermost end 41 x of the first opening 41 is a position at a distance d 2 within an inner diameter d 1 of the first opening 41 from the lowermost end Sx of the inner surface of the space forming body 35 which faces the acoustic space S.
  • the drain pipe 43 is connected to the second opening 42 of the drain hole 40 as shown in FIG. 12 .
  • the valve 44 is provided in the drain pipe 43 .
  • a portion of the space forming body 35 which includes the first opening 41 that opens in the inner surface facing the acoustic space S and which maintains the inner diameter of the first opening 41 from the inner surface including the first opening 41 in an extending direction of the drain hole 40 is referred to as a first opening portion 41 a .
  • An inner diameter of the first opening portion 41 a is smaller than that of the other portion of the drain hole 40 .
  • the inner diameter of the drain hole 40 excluding the first opening portion 41 a is larger than that of the first opening portion 41 a .
  • An opening area of the first opening 41 is 20% or less of the total opening area of all the acoustic holes 34 in a portion of the perforated plate 31 which defines the acoustic space S in which the first opening 41 is open, in other words, all the acoustic holes 34 facing the acoustic space S in which the first opening 41 is open.
  • the opening area of the first opening 41 is preferably 10% or less of the total opening area of all the acoustic holes 34 . This is to minimize a decrease in the sound absorption effect due to the acoustic space S even when the acoustic space S and the drain hole 40 communicate with each other.
  • the reason why the inner diameter of the drain hole 40 excluding the first opening 41 is larger than that of the first opening 41 is to allow the liquid which has passed through the first opening 41 to be easily discharged outside the casing 20 .
  • a length t (m) of the first opening portion 41 a in the extending direction of the drain hole 40 is preferably a value represented by the following Equation (1).
  • Equation (1) fmax (Hz) indicates an upper limit of the sound absorption frequency range by the acoustic space S. and c (m/s) indicates the velocity of sound.
  • the silencer 30 G of this embodiment since the silencer 30 G of this embodiment has the drain hole 40 , the liquid remaining in the acoustic space S can be discharged outside the acoustic space S. Thus, in this embodiment, the problem in that the silencer 30 G cannot absorb the sound in the target frequency range can be avoided, and the reduction of the sound absorption effect can be curbed.
  • the valve 44 When the liquid remaining in the acoustic space S is discharged, the valve 44 is opened. However, when the liquid remaining in the acoustic space S is not discharged, the valve 44 is closed to curb the pressure leak of the gas in the passage.
  • the second opening 42 of the drain hole 40 for each of the plurality of acoustic spaces S is open in an outer surface of the casing 20 .
  • the second opening 42 of the drain hole 40 of the first acoustic space S may be open in the outer surface of the casing 20 .
  • the second opening 42 of the drain hole 40 in the second acoustic space S is open in the first acoustic space S
  • the second opening 42 of the drain hole 40 in the third acoustic space S is open in the first acoustic space S or the second acoustic space S.
  • the liquid remaining in the second acoustic space S and the third acoustic space S flows into the first acoustic space S and is then discharged from the first acoustic space S to the outside of the casing 20 through the drain hole 40 .
  • the centrifugal compressor according to this embodiment is a modified example of the centrifugal compressor according to the seventh embodiment.
  • a silencer 30 H in this embodiment also includes the perforated plate 31 , the space forming body 35 , the drain hole 40 , the drain pipe, and the valve, as in the silencer 30 G in the seventh embodiment.
  • the perforated plate 31 has the plurality of acoustic holes 34 formed therein.
  • the space forming body 35 forms the plurality of acoustic spaces S.
  • the drain hole 40 is provided for each of the plurality of acoustic spaces S.
  • the drain pipe is provided for each of the plurality of drain holes 40 .
  • the valve is provided for each of the plurality of drain pipes.
  • FIG. 14 shows only part of the perforated plate 31 , the space forming body 35 , and the drain hole 40 among the parts of the silencer 30 H and does not show other elements to clarify the characteristics of the silencer 30 H of this embodiment.
  • the other elements are the same as the corresponding elements shown in FIG. 12 showing the centrifugal compressor according to the seventh embodiment.
  • the silencer 30 H in this embodiment is also disposed so that the first surface 32 of the perforated plate 31 forms part of the inner surface of the radial passage 26 .
  • the drain hole 40 in this embodiment has a first opening 41 h and a second opening, as in the drain hole 40 in the seventh embodiment.
  • the first opening 41 h is open in the inner surface of the space forming body 35 which faces the acoustic space S.
  • the second opening is open in the outer surface of the lower portion of the casing 20 .
  • the first opening 41 h of the drain hole 40 in this embodiment is basically not limited in the opening area, as in the first opening 41 of the drain hole 40 in the seventh embodiment. Therefore, the opening area of the first opening 41 h of the drain hole 40 in this embodiment may be larger than that of the first opening 41 of the drain hole 40 in the seventh embodiment.
  • the silencer 30 H in this embodiment further includes a moisture absorbing member 45 disposed in the drain hole 40 .
  • the moisture absorbing member 45 includes particles of a plurality of moisture absorbents 46 , and an adhesive which connects the particles of the plurality of moisture absorbents 46 .
  • the moisture absorbent 46 is a solid which absorbs moisture, or a material which can be handled as a solid while moisture is absorbed. Specifically, the moisture absorbent 46 is silica gel, calcium chloride, calcium oxide or the like.
  • An amount of the moisture absorbent 46 in the moisture absorbing member 45 is determined on the basis of an amount of liquid assumed to remain in the acoustic space S, a moisture absorption capacity of the moisture absorbent 46 , an environmental change such as a temperature change and a pressure change in the acoustic space S, and the like.
  • the moisture absorbing member 45 is disposed at a position in the drain hole 40 including the first opening 41 h or a position close to the first opening 41 h .
  • the moisture absorbing member 45 is disposed at a position in the drain hole 40 substantially including the first opening 41 h .
  • the moisture absorbing member 45 is provided so that the drain hole 40 is closed. That is, an area of the drain hole 40 in a direction perpendicular to the extending direction of the drain hole 40 is substantially equal to a cross-sectional area of the moisture absorbing member 45 in the direction perpendicular to the extending direction of the drain hole 40 . Therefore, in this embodiment, even when the acoustic space S and the drain hole 40 communicate with each other, the decrease in the sound absorption effect due to the acoustic space S can be minimized.
  • the liquid remaining in the acoustic space S can be discharged outside the acoustic space S. Therefore, the problem that the silencer 30 H cannot absorb the sound in the target frequency range can be avoided, and the reduction of the sound absorption effect can be curbed. Furthermore, in this embodiment, since the moisture absorbing member 45 is provided in the drain hole 40 to close the drain hole 40 , the reduction of the sound absorption effect due to the communication between the acoustic space S and the drain hole 40 is further curbed.
  • the second opening of the drain hole 40 for each of the plurality of acoustic spaces S in this embodiment is open in the outer surface of the casing 20 , as in the seventh embodiment.
  • the second opening of the drain hole 40 of the first acoustic space S may be open in the outer surface of the casing 20 .
  • the second opening of the drain hole 40 of the second acoustic space S is open in the first acoustic space S
  • the second opening of the drain hole 40 of the third acoustic space S is open in the first acoustic space S or the second acoustic space S.
  • the moisture absorbing member 45 is disposed in each of the drain holes 40 , as in this embodiments. Also in this case, the liquid remaining in the second acoustic space S and the third acoustic space S flows into the first acoustic space S and is then discharged from the first acoustic space S through the drain hole 40 to the outside of the casing 20 .
  • a centrifugal compressor according to a ninth embodiment will be described with reference to FIG. 15 .
  • the centrifugal compressor according to this embodiment is a modified example of the centrifugal compressor according to the eighth embodiment.
  • a silencer 30 I in this embodiment also includes the perforated plate 31 , the space forming body 35 , the drain hole 40 , and the moisture absorbing member 45 , as in the silencer 30 H in the eighth embodiment.
  • a plurality of acoustic holes 34 are formed in the perforated plate 31 .
  • the space forming body 35 forms a plurality of acoustic spaces S.
  • the drain hole 40 is formed for each of the plurality of acoustic spaces S.
  • the moisture absorbing member 45 is provided for each of the plurality of drain holes 40 .
  • the silencer 30 I according to this embodiment does not include the drain pipe 43 provided for each of the plurality of drain holes 40 and the valve 44 provided for each of the plurality of drain pipes 43 in the silencers 30 G and 30 H according to the seventh and eighth embodiments
  • the silencer 30 I in this embodiment is also disposed so that the first surface 32 of the perforated plate 31 forms part of the inner surface of the radial passage 26 .
  • the drain hole 40 i of this embodiment is formed in the perforated plate 31 .
  • the drain hole 40 i has a first opening 41 i and a second opening 42 i .
  • the first opening 41 i is open in the first surface 32 of the perforated plate 31 .
  • the second opening 42 i is open in the second surface 33 of the perforated plate 31 .
  • the second opening 42 is open at a lower portion of the perforated plate 31 .
  • a position of the lowermost end of the second opening 42 is a position at a distance within the inner diameter of the second opening 42 from the lowermost end in the acoustic space S.
  • the moisture absorbing member 45 is the same as the moisture absorbing member 45 of the eighth embodiment.
  • the moisture absorbing member 45 is disposed in the drain hole 40 i to close the drain hole 40 i .
  • the silencer 30 I of this embodiment also has the drain hole 40 i as described above, the liquid remaining in the acoustic space S can be discharged outside the acoustic space S. Specifically, the liquid component in the acoustic space S is adsorbed by the moisture absorbing member 45 in the drain hole 40 i . The liquid component adsorbed by the moisture absorbing member 45 is discharged into the radial passage 26 . Therefore, in this embodiment, the problem that the silencer 30 I cannot absorb the sound in the target frequency range can be avoided, and the reduction of the sound absorption effect can be curbed.
  • the silencer 30 I since the moisture absorbing member 45 is provided in the drain hole 40 i to close the drain hole 40 i , the reduction of the sound absorption effect can be further curbed as compared with the seventh embodiment.
  • the drain pipe 43 and the valve 44 in the silencers 30 G and 30 H in the seventh and eighth embodiments are unnecessary, and the drain hole 40 i only needs to be formed in the perforated plate 31 .
  • the silencer 30 I can be simplified in structure, and manufacturing cost can be reduced.
  • the drain discharge mechanism of any one of the silencers 30 G, 30 H, and 30 I in the above-described seventh to ninth embodiments may be applied to the silencer in each of the first to fourth embodiments and each of the modified examples of the first embodiment.
  • the drain discharge mechanism of any one of the silencers 30 G, 30 H, and 30 I in the above-described seventh to ninth embodiments may be applied to a silencer in which the first surface 32 of the perforated plate 31 is disposed to form part of the inner surface of the intermediate passage 23 p (shown in FIG. 1 ).
  • centrifugal compressors in the above-described embodiments and modified examples are all multistage centrifugal compressors
  • the centrifugal compressor according to the present invention is not limited to the multistage centrifugal compressors. That is, the centrifugal compressor according to the present invention may be a single-stage centrifugal compressor having one impeller.

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US11378096B2 (en) * 2018-04-26 2022-07-05 Mitsubishi Heavy Industries Compressor Corporation Centrifugal compressor
US20230093314A1 (en) * 2021-09-17 2023-03-23 Carrier Corporation Passive flow reversal reduction in compressor assembly

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