US20200200184A1 - Centrifugal rotating machine - Google Patents

Centrifugal rotating machine Download PDF

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Publication number
US20200200184A1
US20200200184A1 US16/717,134 US201916717134A US2020200184A1 US 20200200184 A1 US20200200184 A1 US 20200200184A1 US 201916717134 A US201916717134 A US 201916717134A US 2020200184 A1 US2020200184 A1 US 2020200184A1
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United States
Prior art keywords
flow path
peripheral surface
impeller
protrusion portion
casing
Prior art date
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Abandoned
Application number
US16/717,134
Other languages
English (en)
Inventor
Makoto Iwasaki
Rimpei Kawashita
Yasunori TOKIMASA
Shuichi Yamashita
Jo Masutani
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Heavy Industries Ltd
Original Assignee
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: IWASAKI, MAKOTO, KAWASHITA, RIMPEI, MASUTANI, JO, TOKIMASA, Yasunori, YAMASHITA, SHUICHI
Publication of US20200200184A1 publication Critical patent/US20200200184A1/en
Abandoned legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/26—Rotors specially for elastic fluids
    • F04D29/28—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps
    • F04D29/284—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps for compressors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D17/00—Radial-flow pumps, e.g. centrifugal pumps; Helico-centrifugal pumps
    • F04D17/08—Centrifugal pumps
    • F04D17/10—Centrifugal pumps for compressing or evacuating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/40—Casings; Connections of working fluid
    • F04D29/42—Casings; Connections of working fluid for radial or helico-centrifugal pumps
    • F04D29/4206—Casings; Connections of working fluid for radial or helico-centrifugal pumps especially adapted for elastic fluid pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D17/00—Radial-flow pumps, e.g. centrifugal pumps; Helico-centrifugal pumps
    • F04D17/08—Centrifugal pumps
    • F04D17/10—Centrifugal pumps for compressing or evacuating
    • F04D17/12—Multi-stage pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D17/00—Radial-flow pumps, e.g. centrifugal pumps; Helico-centrifugal pumps
    • F04D17/08—Centrifugal pumps
    • F04D17/10—Centrifugal pumps for compressing or evacuating
    • F04D17/12—Multi-stage pumps
    • F04D17/122—Multi-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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/05—Shafts or bearings, or assemblies thereof, specially adapted for elastic fluid pumps
    • F04D29/053—Shafts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/08—Sealings
    • F04D29/16—Sealings between pressure and suction sides
    • F04D29/161—Sealings between pressure and suction sides especially adapted for elastic fluid pumps
    • F04D29/162—Sealings between pressure and suction sides especially adapted for elastic fluid pumps of a centrifugal flow wheel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/40—Casings; Connections of working fluid
    • F04D29/42—Casings; Connections of working fluid for radial or helico-centrifugal pumps
    • F04D29/44—Fluid-guiding means, e.g. diffusers
    • F04D29/441—Fluid-guiding means, e.g. diffusers especially adapted for elastic fluid pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
    • F04D29/661—Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps
    • F04D29/667—Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps by influencing the flow pattern, e.g. suppression of turbulence
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
    • F04D29/661—Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps
    • F04D29/668—Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps damping or preventing mechanical vibrations

Definitions

  • the present invention relates to a centrifugal rotating machine.
  • a centrifugal compressor has a rotating shaft which extends along an axis, an impeller which is provided on the rotating shaft, and a casing which covers the impeller from an outside.
  • an impeller referred to as a closed impeller.
  • the closed impeller has a disk-shaped disk centered on an axis, a plurality of blades which are provided on one surface of the disk, and a conical cover which covers the plurality of blades from one side.
  • a clearance (outer flow path) is provided between an outer peripheral surface of the cover and an inner peripheral surface of the casing.
  • a fluid flows through a flow path defined by the blades.
  • the fluid is compressed and brought into a high pressure state while flowing through the flow path from an inlet side toward an outlet side of the flow path.
  • the fluid having a pressure higher than that of the inlet side flows through the outlet side of the flow path, and thus, the fluid flows into the above-described outer flow path. Accordingly, in a case where lot of fluid flows into the outer flow path, compression efficiency of the centrifugal compressor decreases. Therefore, a technology is known in which a seal portion for preventing the flow of the fluid is provided on the inner peripheral surface of the casing.
  • WO 2016/043090 discloses a configuration in which a seal fin is provided on the inlet side of the impeller in the inner peripheral surface of the casing as a specific example of the seal portion. By providing the seal fin, the fluid which flows into the outer flow path is reduced.
  • the present invention is made to solve the above-described problems, and an object thereof is to provide a centrifugal rotating machine in which a vibration is further reduced.
  • a centrifugal rotating machine including: a rotating shaft which extends along an axis; an impeller which is configured to pump a fluid flowing in from one side in an axial direction to an outside in a radial direction, the impeller including a disk fixed to the rotating shaft and a cover covering a blade provided on the disk; and a casing which accommodates the impeller, in which an impeller flow path through which the fluid is pumped is formed by an upstream surface of the disk in the axial direction and an inner peripheral surface of the cover, an outer flow path is formed by an outer peripheral surface of the cover and an inner peripheral surface of the casing facing the outer peripheral surface of the cover, the outer flow path is connected to the impeller flow path at an outlet of the impeller flow path, and a protrusion portion protruding from the inner peripheral surface of the casing is provided in the outer flow path.
  • the fluid which has flowed into the outer flow path is guided by the protrusion portion provided on the inner peripheral surface of the casing. Therefore, even in a case where the fluid includes a swirl component (swirling flow component), the fluid is guided by the protrusion portion, and thus, the swirl component can be reduced.
  • an excitation force (seal excitation force) in a direction orthogonal to a displacement direction acts on the impeller. This seal excitation force is continuously added, and thus, a swing-rotation vibration is generated in the rotating shaft and the impeller.
  • the possibility of the above-described problems can be reduced.
  • a plurality of the protrusion portions may be formed at intervals in a circumferential direction.
  • the plurality of protrusion portions are formed at intervals in the circumferential direction. Therefore, the swirl component can be uniformly reduced over the entire area of the outer flow path in the circumferential direction. Thereby, the pressure distribution of the fluid in the outer flow path becomes uniform, and thus, vibrations generated in the impeller can be further effectively suppressed.
  • the protrusion portion may be provided at a predetermined region on the inner peripheral surface of the casing.
  • the protrusion portion may be provided at a position overlapping the outlet of the impeller flow path in a radial direction with respect to the axis.
  • the protrusion portion is provided at the position overlapping the outlet of the impeller flow path in the radial direction. Therefore, the swirl component included in the fluid which has flowed into the outer flow path can be reduced immediately after the inflow.
  • the present inventors performed a CFD analysis on the excitation force by the swirl component. As a result, it was found that the excitation force generated in the impeller cover was large. The excitation force generated in this cover is caused by the fluid flowing into the outer flow path. Accordingly, as described in the configuration, the protrusion portion is provided at the position overlapping the inlet of the outer flow path, that is, the outlet of the impeller flow path. Therefore, the swirl component is reduced, and the excitation force generated in the cover can be more positively reduced.
  • the swirl component increases as it gets closer to the outlet of the impeller flow path. Therefore, the swirl component can be more effectively reduced. As a result, it is possible to further reduce a possibility of the impeller being displaced or excited due the influence of the swirl component. Further, as compared to a configuration in which the protrusion portion extends over the entire area of the outer flow path, only a necessary and sufficient amount of the swirl component is removed. Accordingly, it is also possible to avoid an increase in a frictional resistance between the cover outer peripheral surface of the impeller and the fluid due to an excessive reduction of the swirl component.
  • the centrifugal rotating machine may further include a step which is provided on the outer peripheral surface of the cover and is an annual step centered on the axis in the outer flow path, in which the step may be provided radially outside the protrusion portion.
  • the step is provided on the outer peripheral surface of the cover. Therefore, the fluid flowing out from the outlet of the impeller passes through a radially outer portion of the outer flow path. That is, more fluid flows along the inner peripheral surface of the casing where the protrusion portion is provided. As a result, more fluid is guided toward the protrusion portion provided on the inner peripheral surface of the casing. Thereby, the swirl component of the fluid which flows into the outer flow path can be more positively reduced.
  • the protrusion portion may be provided over the entire area of the casing inner peripheral surface in the outer flow path.
  • the protrusion portion is provided over the entire area of the outer flow path, the swirl component of the fluid which has flowed into the outer flow path can be further reduced.
  • the protrusion portion is curved from one side toward the other side in a circumferential direction with respect to the axis as the protrusion portion goes outward in the radial direction.
  • the swirl component which turns from the other side toward the one side in the circumferential direction (that is, toward front side in rotation direction of the impeller) is added to the fluid flowing into the outer flow path.
  • the protrusion portion is curved from the one side toward the other side in the circumferential direction as the protrusion goes radially outward from the inlet side. That is, the protrusion portion is curved in a direction opposite to a turning direction of the swirl component. Therefore, the swirl component can be rectified in the opposite direction by the protrusion portion. As a result, it is possible to further reduce the possibility of the rotating shaft and the impeller being excited due to the influence of the swirl component.
  • the protrusion portion may be twisted from one side toward the other side in a circumferential direction with respect to the axis with reference to the inner peripheral surface of the casing as the protrusion portion goes from the outlet side toward the inlet side.
  • the protrusion portion since the twist of the protrusion portion is small on the outlet side, the protrusion portion has a large angle with respect to the inner peripheral surface of the casing. Therefore, the flow of the fluid including the swirl component which has flowed into the outer flow path from the outlet side (that is, upstream side of outer flow path of the impeller can be captured more efficiently. Thereby, the swirl component can be further reduced.
  • the centrifugal rotating machine may further include a seal portion which is provided on a radially inner end portion of the outer flow path and seals leakage of the fluid between the inner peripheral surface of the casing and the outer peripheral surface of the cover.
  • the protrusion portion since the twist of the protrusion portion is large on the inlet side (that is, downstream side of outer flow path) of the impeller, the protrusion portion has a small angle with respect to the inner peripheral surface of the casing. Therefore, the fluid guided by the protrusion portion flows around the inner peripheral surface of the casing. As a result, for example, in a case where the seal portion is provided on the upstream side of the casing inner peripheral surface, the fluid can flow more positively toward the seal portion itself rather than toward the clearance between the seal portion and the cover outer peripheral surface of the impeller.
  • the flow into the seal portion on the inlet side of the impeller becomes a radially inward flow state (down flow) from the casing inner peripheral surface to the cover outer peripheral surface, and thus, a contraction effect in the seal portion increases. Thereby, a leak flow which passes through the seal portion can be further reduced.
  • the protrusion portion may be twisted from a front side toward a rear side in a rotation direction of the impeller with reference to the inner peripheral surface of the casing as the protrusion portion goes inward in the radial direction.
  • the protrusion portion is twisted toward a rear side (that is, side opposite to turning direction of swirl component included in flow in outer flow path) in a rotation direction of the impeller. Accordingly, it is possible to more effectively capture and reduce the swirl component.
  • a circumferential dimension of the protrusion portion with respect to the axis gradually decreases as the protrusion portion is separated from the inner peripheral surface of the casing.
  • the protrusion portion has a tapered shape such that a dimension thereof in a circumferential direction gradually decreases. Accordingly, for example, even in a case where the outer peripheral surface of the impeller comes into contact with the protrusion portion, a contact area between the protrusion portion and the outer peripheral surface can be suppressed to be small. As a result, it is possible to prevent the impeller from being damaged or from being vibrated.
  • a centrifugal rotating machine including: a rotating shaft which extends along an axis; an impeller which is configured to pump a fluid flowing in from one side in an axial direction to an outside in a radial direction, the impeller including a disk fixed to the rotating shaft and a cover covering a blade provided on the disk; and a casing which accommodates the impeller, in which an impeller flow path through which the fluid is pumped is formed by an upstream surface of the disk in the axial direction and an inner peripheral surface of the cover, an outer flow path is formed by an outer peripheral surface of the cover and an inner peripheral surface of the casing facing the outer peripheral surface of the cover, the outer flow path is connected to the impeller flow path at an outlet of the impeller flow path, and a step which is an annual step centered on the axis is provided on the outer peripheral surface of the cover in the outer flow path.
  • the step is provided on the outer peripheral surface of the cover, the gap between the outer peripheral surface of the cover and the inner peripheral surface of the casing can be reduced. That is, the amount of fluid flowing into the outer flow path can be limited. As a result, it is possible to reduce the excitation force to the impeller generated when a large amount of fluid flows into the outer flow path.
  • the centrifugal rotating machine that is capable of further reducing vibrations.
  • FIG. 1 is a cross-sectional view of a centrifugal compressor according to a first embodiment of the present invention.
  • FIG. 2 is an enlarged cross-sectional view of a main portion of the centrifugal compressor according to the first embodiment of the present invention.
  • FIG. 3 is an enlarged cross-sectional view of a main portion of a centrifugal compressor according to a second embodiment of the present invention.
  • FIG. 4 is a perspective view of an impeller according to the second embodiment of the present invention.
  • FIG. 5 is an enlarged cross-sectional view of a main portion of a centrifugal compressor according to a third embodiment of the present invention.
  • FIG. 6 is a view when an impeller according to a third embodiment of the present invention is viewed in an axial direction.
  • FIG. 7 is an enlarged sectional view of a main portion of a centrifugal compressor according to a fourth embodiment of the present invention.
  • FIG. 8 is a view when an impeller according to a fourth embodiment of the present invention is viewed in the axial direction.
  • FIG. 9 is an explanatory view showing a flow of a fluid in a seal portion according to the fourth embodiment of the present invention.
  • FIG. 10 is a cross-sectional view showing a modified example of a protrusion portion according to each embodiment of the present invention.
  • centrifugal compressor 100 (centrifugal rotating machine) according to a first embodiment of the present invention will be described with reference to the drawings.
  • the centrifugal compressor 100 includes a rotating shaft 1 which rotates around an axis O, a casing 3 which covers a periphery of the rotating shaft 1 to form a flow path 2 , a plurality of stages of impeller 4 which are provided on the rotating shaft 1 , and protrusion portions 9 which are provided in the casing 3 .
  • the casing 3 is formed in a cylindrical shape extending along the axis O.
  • the rotating shaft 1 extends to penetrate an inside of the casing 3 along the axis O.
  • a journal bearing 5 and a thrust bearing 6 are respectively provided on both end portions of the casing 3 in a direction of the axis O.
  • the rotating shaft 1 is rotatably supported around the axis O by the journal bearing 5 and the thrust bearing 6 .
  • An intake port 7 through which air serving as a working fluid G is taken in from the outside is provided on a first side (one side) of the rotating shaft 1 of the casing 3 in the direction of the axis O.
  • an exhaust port 8 through the working fluid G compressed inside the casing 3 is exhausted is provided on a second side (other side) of the rotating shaft 1 of the casing 3 in the direction of the axis O.
  • An internal space which communicates with the intake port 7 and the exhaust port 8 is formed inside the casing 3 .
  • An inner diameter of the internal space repeatedly increases and decreases.
  • the internal spaces accommodate a plurality of impellers 4 and form a portion of the flow path 2 .
  • a side on which the intake port 7 is located in the flow path 2 is referred to as an upstream side
  • a side on which the exhaust port 8 is located is referred to as a downstream side.
  • a return vane 50 is provided on the downstream side of each impeller 4 on the flow path 2 .
  • each impeller 4 includes a disk-shaped disk 41 centered on the axis O, a plurality of blades 42 which are provided on an upstream surface of the disk 41 , and a cover 43 which covers the plurality of blades 42 from the upstream side.
  • an outer dimension of the disk in the radial direction is formed so as to gradually expand from the first side to the second side in the direction of the axis O, and thus, the disk 41 is formed in an approximately conical shape.
  • a plurality of blades 42 are radially arranged radially outward about the axis O on a surface (disk upstream surface 41 A) facing the upstream side of both surfaces of the disk 41 in the direction of the axis O. More specifically, each blade is formed by a thin plate erected from the disk upstream surface 41 A toward the upstream side.
  • the plurality of blades 42 is curved to be directed from one side from the other side in a circumferential direction with respect to the axis O.
  • the disk back surface 41 B and the casing 3 (casing facing surface 3 B) are disposed with a gap in the direction of the axis O. This gap is formed along a direction perpendicular to the direction of the axis O.
  • An upstream end edge of the blade 42 is covered with the cover 43 .
  • the plurality of blades 42 are interposed between the cover 43 and the disk 41 in the direction of the axis O. Accordingly, a space is formed by the cover 43 , the disk 41 , and a pair of blades 42 adjacent to each other. This space forms an impeller flow path 21 which is a portion of the above-described flow path 2 .
  • a radially inner end portion of the impeller flow path 21 is referred to as an inlet 21 A, and a radially outer end portion thereof is referred to as an outlet 21 B.
  • An outer peripheral surface (cover outer peripheral surface 43 A) of the cover 43 extends radially outward toward the second side in the direction of the axis O, and thus, is formed in an approximately conical shape.
  • the cover outer peripheral surface 43 A faces an inner peripheral surface (casing inner peripheral surface 3 A) of the casing 3 with a gap.
  • the casing inner peripheral surface 3 A extends radially outward from the first side toward the second side in the direction of the axis O, following a shape of the cover outer peripheral surface 43 A.
  • An outer flow path F is defined between the casing inner peripheral surface 3 A and the cover outer peripheral surface 43 A.
  • An annular space centered on the axis O is formed radially inside the casing inner peripheral surface 3 A. This space is referred to as a cavity C.
  • a seal portion S is provided on a first side (upstream side) of the cavity C in the direction of the axis O.
  • the seal portion S is provided to seal leakage of a fluid between the casing 3 and the cover outer peripheral surface 43 A.
  • the seal portion S has a plurality of seal fins S 1 and a base portion S 2 which supports the seal fins S 1 .
  • a plurality of protrusion portions 9 for guiding the fluid flowing into the outer flow path F are provided in the outer flow path F.
  • Each protrusion portion 9 protrudes from the casing inner peripheral surface 3 A toward the second side in the direction of the axis O and extends from the outlet side toward the inlet side.
  • the plurality of protrusion portions 9 are arranged at intervals in a circumferential direction with respect to the axis O in the outer flow path F.
  • Each protrusion portion 9 is formed in a plate shape which extends from the outlet side toward the inlet side.
  • the protrusion portion 9 is provided at a position overlapping the outlet 21 B of the impeller 4 in the radial direction with respect to the axis O.
  • the protrusion portion 9 when viewed in the direction of the axis O, the protrusion portion 9 is provided at a position overlapping the outlet 21 B of the impeller 4 . Moreover, in a cross-sectional view including the axis O, the protrusion portion 9 is formed in a rectangular shape.
  • the centrifugal compressor 100 When the centrifugal compressor 100 is operated, first, the rotating shaft 1 is rotationally driven by a drive source such as an electric motor. As the rotating shaft 1 rotates, the impellers 4 rotate, and the working fluid G is introduced from the intake port 7 into the flow path 2 . The working fluid G introduced into the flow path 2 is sequentially compressed while passing through the impeller flow path 21 in each impeller 4 . The working fluid G that has been compressed and brought into a high pressure state is pumped to the outside via the exhaust port 8 .
  • a drive source such as an electric motor
  • the high pressure working fluid G may flow in from the outlet 21 B side of the impeller flow path 21 .
  • a swirl component (swirling flow component) accompanying rotation of the impeller 4 is added to the fluid flowing through the outer flow path F.
  • the swirl component turns in the same direction as a rotation direction of the impeller 4 . Due to an influence of this swirl component, an excitation force directed in a direction orthogonal to a displacement direction acts on impeller 4 .
  • a swing-rotation vibration may occur in the rotating shaft 1 and the impeller 4 by continuously adding this excitation force.
  • the working fluid G which has flowed into the outer flow path F is guided by the protrusion portion 9 provided on the inner peripheral surface (casing inner peripheral surface 3 A) of the casing 3 .
  • the protrusion portion 9 extends from the outlet 21 B side of the impeller 4 toward the inlet 21 A side thereof in the outer flow path F. Therefore, even in a case where the working fluid G includes the swirl component, the working fluid G is guided by the protrusion portion 9 , and thus, the swirl component can be reduced. As a result, the possibility of the swing-rotation vibration occurring in the rotating shaft 1 and the impeller 4 can be reduced.
  • the protrusion portion 9 is provided at the position overlapping the outlet 21 B of the impeller 4 in the radial direction. Accordingly, the swirl component included in the working fluid G which has flowed into the outer flow path F can be reduced immediately after the inflow. In particular, in the outer flow path F, the closer the outlet 21 B of the impeller flow path 21 is, the more the swirl component is. Therefore, the swirl component can be more effectively reduced by the above configuration. As a result, it is possible to further reduce the possibility of the impeller 4 being displaced or excited due to the influence of the swirl component.
  • the plurality of protrusion portions 9 are formed at intervals in the circumferential direction. Accordingly, the swirl component can be uniformly reduced over the entire area of the outer flow path F in the circumferential direction. Thereby, a pressure distribution of the fluid in the outer flow path F becomes uniform, and thus, vibrations generated in the rotating shaft 1 and the impeller 4 can be further effectively suppressed.
  • FIGS. 3 and 4 a second embodiment of the present invention will be described with reference to FIGS. 3 and 4 .
  • the same reference numerals are assigned to the same configurations as those of the first embodiment, and detail descriptions thereof are omitted.
  • a position of a protrusion portion 9 B is different from that in the first embodiment, and a step 10 is provided on the cover outer peripheral surface 43 A closer to the outlet 21 B side than the protrusion portion 9 B.
  • FIG. 4 is a view showing a state where only the impeller 4 is extracted.
  • a casing 3 is attached so as to cover an outside of the impeller 4 , and the outer flow path F is formed between the impeller 4 and the casing 3 .
  • the rotating shaft 1 is attached to the impeller 4 so as to penetrate a center hole of the impeller 4 , and the impeller 4 rotates together with the rotating shaft 1 .
  • the casing 3 is a case which covers the whole and is a member that does not rotate (stationary member). It is naturally necessary to form a gap between the casing 3 and the impeller 4 , and thus, the outer flow path F is necessarily formed.
  • the step 10 protrudes from the cover outer peripheral surface 43 A toward the first side in the direction of the axis O.
  • the step 10 has an annular shape centered on the axis O.
  • the step 10 is arranged closer to the outlet 21 B side than the protrusion portion 9 B when viewed in a cross section perpendicular to the axis O.
  • the protrusion portion 9 B and the step 10 are arranged with an interval. More specifically, when viewed from the direction in which the outer flow path F extends, the protrusion portion 9 B and step 10 overlap each other.
  • a cross section of step 10 is rectangular.
  • a cross-sectional shape of step 10 may be a triangle or a trapezoid in addition to a rectangle.
  • the step 10 is provided on the cover outer peripheral surface 43 A of the impeller 4 . Therefore, the working fluid G (broken line in FIG. 3 ) flowing out from the outlet 21 B of the impeller flow path 21 is obstructed by the step 10 , and thus, the working fluid G passes through a radially outer portion of the outer flow path F. That is, more fluid flows along the casing inner peripheral surface 3 A where the protrusion portion 9 B is provided. As a result, more fluid is guided toward the protrusion portion 9 B. Thereby, the swirl component of the working fluid G which flows into the outer flow path F can be more positively reduced. Therefore, the possibility of vibrations occurring in the rotating shaft 1 and the impeller 4 can be further reduced.
  • the second embodiment of the present invention is described.
  • various changes and modifications can be made to the configuration without departing from the gist of the present invention.
  • the configuration in which the protrusion portion 9 B and the step 10 are provided is described.
  • the protrusion portion 9 B may not necessarily be provided, and a configuration in which only the step 10 is provided on the cover outer peripheral surface 43 A of the impeller 4 may be adopted.
  • the gap between the cover outer peripheral surface 43 A and the casing inner peripheral surface 3 A can be reduced. That is, the amount of working fluid G flowing into the outer flow path F can be limited. As a result, it is possible to reduce the excitation force to the impeller 4 generated when a large amount of working fluid G flows into the outer flow path F.
  • a shape of a protrusion portion 9 C is different from those of the embodiments.
  • the protrusion portion 9 C extends over the entire area from the outlet 21 B to the inlet 21 A of the impeller flow path 21 in the outer flow path F. More specifically, the protrusion portion 9 C extends from the outlet 21 B of the impeller flow path 21 to an end portion on the second side of the cavity C in the direction of the axis O.
  • the protrusion height (protrusion dimension from the casing inner peripheral surface 3 A) of the protrusion portion 9 C is constant over the entire area in the extension direction of the protrusion portion 9 C. Furthermore, as shown in FIG. 6 , the protrusion portion 9 C is curved from a first side toward a second side in a circumferential direction with respect to the axis O as the protrusion portion 9 C goes from the inlet 21 A side toward the outlet 21 B side. In other words, the protrusion portion 9 C is curved in a curved shape which is convex toward a front side in the rotation direction of the impeller 4 . Further, the protrusion portion 9 C extends in a direction intersecting a radial direction with respect to the axis O (broken line in FIG. 6 ).
  • the protrusion portion 9 C is provided over the entire area of the outer flow path F, the swirl component of the working fluid G which has flowed into the outer flow path F can be further reduced. As a result, the possibility that vibrations occur in the rotating shaft 1 and the impeller 4 can be further reduced.
  • a swirl component which turns from the second side toward the first side in the circumferential direction (that is, toward front side in rotation direction of the impeller) is added to the fluid flowing into the outer flow path F.
  • the protrusion portion 9 C is curved from the first side toward the second side in the circumferential direction as the protrusion portion 9 C goes from the inlet side toward the outlet 21 B. That is, the protrusion portion 9 C is curved in a direction opposite to a turning direction of the swirl component. Therefore, the swirl component can be rectified in the opposite direction by the protrusion portion 9 C. As a result, it is possible to further reduce the possibility of the impeller 4 being displaced or excited due to the influence of the swirl component.
  • a shape of a protrusion portion 9 D is different from that of each of the embodiments.
  • the protrusion portion 9 D is twisted from a first side toward a second side in a circumferential direction with respect to axis O with reference to an end edge 91 on the casing inner peripheral surface 3 A side as the protrusion portion 9 D goes from the outlet 21 B side to the inlet 21 A side.
  • an end edge 92 on a side opposite to the end edge 91 is curved from the first side toward the second side along an arc centered on the end edge 91 as the end edge 92 goes from the outlet 21 B side toward the inlet 21 A side.
  • the end edge 92 is twisted from a front side toward a rear side (that is, side opposite to turning direction of swirl component included in flow in outer flow path) in a rotation direction R of the impeller 4 as the end edge 92 goes from the outlet 21 B side toward the inlet 21 A side. Therefore, the angle formed between the protrusion portion 9 D and the casing inner peripheral surface 3 A is larger as the angle is closer to the outlet 21 B side, and is smaller as the angle is closer to the inlet 21 A side.
  • the protrusion portion 9 D since the twist of the protrusion portion 9 D is small on the outlet 21 B side, the protrusion portion 9 D has a large angle with respect to the casing inner peripheral surface 3 A. Therefore, the flow of the working fluid G including the swirl component which has flowed into the outer flow path F from the outlet 21 B side (that is, upstream side of outer flow path F) can be captured more efficiently. Thereby, the swirl component can be further reduced. Further, since the twist of the protrusion portion 9 D is large on the inlet 21 A side (that is, downstream side of outer flow path F), the protrusion portion 9 D has a small angle with respect to the casing inner peripheral surface 3 A.
  • the fluid guided by the protrusion portion 9 D flows in a region biased in the vicinity of the casing inner peripheral surface 3 A.
  • the flow into the seal fin S 1 on the inlet 21 A side of the impeller 4 becomes a radially inward flow state (down flow) from the casing inner peripheral surface 3 A to the cover outer peripheral surface 43 A, and thus, a contraction effect in the seal fin S 1 increases. Therefore, the working fluid G can flow more positively toward the seal fin S 1 itself rather than toward a clearance V 1 between the seal fin S 1 provided on the upstream side of the casing inner peripheral surface 3 A and the impeller 4 (cover outer peripheral surface 43 A) (refer to FIG. 9 ).
  • an apparent clearance V 2 of the seal fin S 1 can be made smaller than the actual clearance V 1 . Thereby, a leak flow which passes through the seal fin S 1 can be further reduced.
  • the fourth embodiment of the present invention is described.
  • various changes and modifications can be made to the configuration without departing from the gist of the present invention.
  • a configuration as shown in FIG. 10 can be adopted.
  • the protrusion portion 9 ( 9 B, 9 C, 9 D) has a tapered shape such that a dimension thereof in a circumferential direction gradually decreases as the protrusion portion is separated radially inward from the casing inner peripheral surface 3 A.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
US16/717,134 2018-12-25 2019-12-17 Centrifugal rotating machine Abandoned US20200200184A1 (en)

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JP2018-241697 2018-12-25
JP2018241697A JP7168441B2 (ja) 2018-12-25 2018-12-25 遠心回転機械

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US20200200184A1 true US20200200184A1 (en) 2020-06-25

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CN111379744A (zh) 2020-07-07
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JP2020101169A (ja) 2020-07-02

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