WO2011089512A2 - Centrifugal pump - Google Patents

Centrifugal pump Download PDF

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Publication number
WO2011089512A2
WO2011089512A2 PCT/IB2011/000088 IB2011000088W WO2011089512A2 WO 2011089512 A2 WO2011089512 A2 WO 2011089512A2 IB 2011000088 W IB2011000088 W IB 2011000088W WO 2011089512 A2 WO2011089512 A2 WO 2011089512A2
Authority
WO
WIPO (PCT)
Prior art keywords
supporting shaft
rear plate
outside diameter
longitudinal axis
hub
Prior art date
Application number
PCT/IB2011/000088
Other languages
French (fr)
Other versions
WO2011089512A3 (en
WO2011089512A8 (en
Inventor
Matteo Cipelli
Paolo Costa
Egidio Salin
Amedeo Valente
Original Assignee
Itt Manufacturing Enterprises, Inc.
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Itt Manufacturing Enterprises, Inc. filed Critical Itt Manufacturing Enterprises, Inc.
Publication of WO2011089512A2 publication Critical patent/WO2011089512A2/en
Publication of WO2011089512A3 publication Critical patent/WO2011089512A3/en
Publication of WO2011089512A8 publication Critical patent/WO2011089512A8/en

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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
    • F04D29/18—Rotors
    • F04D29/22—Rotors specially for centrifugal pumps
    • F04D29/2205—Conventional flow pattern
    • F04D29/2216—Shape, geometry
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D1/00—Radial-flow pumps, e.g. centrifugal pumps; Helico-centrifugal pumps
    • F04D1/06—Multi-stage pumps
    • F04D1/063—Multi-stage pumps of the vertically split casing type
    • 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
    • F04D29/18—Rotors
    • F04D29/22—Rotors specially for centrifugal pumps
    • F04D29/2261—Rotors specially for centrifugal pumps with special measures

Definitions

  • the present invention relates to a centrifugal pum .
  • the present invention relates to an electric vertical-axis multistage centrifugal pump for pumping large masses of water, to which the following description refers purely by way of example.
  • electric multistage centrifugal pumps comprise a pumping assembly fitted inside with a number of cascade-connected centrifugal impellers fitted rigidly, a given distance apart, to a central supporting shaft; and a single- or three-phase electric motor fitted to the pumping assembly casing to rotate the supporting shaft.
  • the impeller shaft is housed to rotate axially inside the pumping assembly casing, which, inside, has a number of disk-shaped cavities arranged successively along the impeller shaft, and each sized to house a respective centrifugal impeller.
  • the disk-shaped cavities are connected to one another by a succession of central, circular-section, through conduits coaxial with and larger in diameter than the impeller shaft, so that the impeller shaft fits through and rotates axially inside them, while allowing water to flow from one disk-shaped cavity to another.
  • the electric motor is fixed to and projects from the pumping assembly casing, coaxially with the impeller shaft; and the electric motor shaft is connected rigidly by a mechanical joint to the end of the impeller shaft projecting from the pumping assembly casing.
  • Each centrifugal impeller comprises a central tubular hub designed to fit rigidly to the impeller shaft; a circular rear plate fixed rigidly to the body of the central tubular hub and perfectly coaxial with the longitudinal axis of the hub; and a circular front plate coaxial with and a given distance from the circular rear plate, and also perfectly coaxial with the longitudinal axis of the hub.
  • the two plates have the same outside diameter, and so form a disk-shaped gap; and the centrifugal impeller has a number of flat radial blades or ribs, which extend from one plate to the other to connect them rigidly, are spaced angularly about the longitudinal axis of the hub, and in the meantime project spirally from the periphery of the gap towards the central tubular hub.
  • the circular front plate has a circular central through hole larger in diameter than the central tubular hub and the impeller shaft, and roughly the same diameter as the central conduits connecting the disk- shaped cavities in the casing; and a cylindrical tubular sleeve, which surrounds and bounds the circular through hole, and projects from the face of the plate, coaxially with the longitudinal axis of the hub.
  • the cylindrical tubular sleeve and the central tubular hub thus form an annular opening, which completely surrounds the impeller shaft when the impeller is fitted to the shaft, allows water to flow to the centre of the impeller, and forms the intake of the impeller.
  • Each centrifugal impeller is positioned inside the respective disk-shaped cavity with the cylindrical tubular sleeve of the front plate fitted inside the mouth of the central through conduit connecting the disk-shaped cavity to the preceding disk-shaped cavity, so the impeller intake draws all the outflow from the preceding disk-shaped cavity.
  • each disk-shaped cavity is fitted with an outflow manifold/baffle, known as a diffuser, which surrounds the periphery of the centrifugal impeller and is designed to receive the radial outflow from the periphery of the centrifugal impeller and convert it into axial flow to the mouth of the central through conduit to the next disk-shaped cavity.
  • a diffuser which surrounds the periphery of the centrifugal impeller and is designed to receive the radial outflow from the periphery of the centrifugal impeller and convert it into axial flow to the mouth of the central through conduit to the next disk-shaped cavity.
  • the main drawback of electric multistage centrifugal pumps of this sort lies in the design of the centrifugal impellers generating axial thrust, which is discharged onto the impeller shaft and increases in proportion to the number of impellers fitted to the shaft, at times to such an extent as to force manufacturers to adopt complicated, high-cost countermeasures .
  • some manufacturers reduce the axial thrust of the centrifugal impellers by forming through holes in the rear plate of each impeller to reduce the water pressure on the outer face of the rear plate, or form labyrinth seals on the outer face of the rear plate to prevent the outflow from the periphery of the impeller from striking part of the outer face of the rear plate.
  • Electric motors 'specially designed' for this purpose (commercial electric motors are not normally fitted with thrust bearings for continually withstanding such severe axial thrust) obviously greatly increase the manufacturing cost of the pump, and pose serious problems in terms of spare part management.
  • centrifugal pump as defined in Claim 1 and preferably, though not necessarily, in any one of the dependent Claims .
  • centrifugal impeller as defined in Claim 11 and preferably, though not necessarily, in any one of the dependent Claims .
  • FIG. 1 shows a section of an electric multistage centrifugal pump in accordance with the teachings of the present invention
  • Figure 2 shows a larger-scale detail, with parts removed for clarity, of the multistage centrifugal pump in Figure 1 ;
  • Figure 3 shows a view in perspective of a centrifugal impeller of the electric multistage centrifugal pump in Figures 1 and 2 ;
  • Figure 4 shows a section of the Figure 3 centrifugal impeller.
  • number 1 indicates as a whole an electric multistage centrifugal pump, particularly suitable for pumping large masses of water or other liquid, with a head of several hundred metres .
  • Pump 1 substantially comprises a pumping assembly 2 , in turn having an intake 2a and an outlet 2b, through which water flows in and out of pumping assembly 2, and a number of internal centrifugal impellers 3 fitted rigidly, a given distance apart, to a rotary supporting shaft 4 and designed to impart a rotating movement to the water flowing through them, to increase the speed and pressure of the liquid; and an electric motor 5, preferably, though not necessarily, a single- or three- phase asynchronous motor, fitted to pumping assembly 2 to rotate supporting shaft 4.
  • pumping assembly 2 has a preferably, though not necessarily, cylindrical rigid metal outer casing 6; and supporting shaft 4 extends partly inside rigid casing 6, coaxially with the longitudinal axis L of the casing, and rotates freely about its own longitudinal axis, which coincides locally with longitudinal axis L of the casing.
  • Impeller supporting shaft 4 is fitted with one or more annular seals 7 to prevent water leakage from the shaft exit hole, and is preferably, though not necessarily, also fitted with one or more self- lubricating bushings 8 or other rolling bearings, interposed between supporting shaft 4 and rigid casing 6 to keep supporting shaft 4 perfectly coaxial with the longitudinal axis L of the casing, and prevent direct contact between supporting shaft 4 and rigid casing 6.
  • Electric motor 5 is fixed to and projects from rigid casing 6 of pumping assembly 2, is coaxial with impeller supporting shaft 4, and faces the far end of supporting shaft 4 projecting from rigid casing 6; and the rotary shaft 5a of electric motor 5 is connected to the far end of supporting shaft 4, in angularly rigid and stable, but easily releasable manner, by a removable mechanical joint 9 between electric motor 5 and pumping assembly 2.
  • electric motor 5 is fixed to and projects from a preferably, though not necessarily, cylindrical tubular spacer 10, which projects from the cover 6a of rigid casing 6, is coaxial with the end portion 4a of impeller supporting shaft 4 projecting from rigid casing 6, and is designed to house both end portion 4a of supporting - shaft 4, and mechanical joint 9.
  • rigid casing 6 has a number of disk-shaped cavities 11 aligned successively along impeller supporting shaft 4, coaxial with the shaft axis and longitudinal axis L of rigid casing 6, ' and each sized to house a respective impeller 3; and a succession of substantially circular-section central connecting conduits 12, which extend inside rigid casing 6, are locally coaxial with impeller supporting shaft 4 to connect disk-shaped cavities 11 successively to one another, and are larger in diameter than impeller supporting shaft 4, so supporting shaft 4 fits through and rotates axially inside them, while allowing water to flow from one disk-shaped cavity 11 to another .
  • each disk-shaped cavity 11 is fitted with an outflow manifold/baffle 13, known as a diffuser, which surrounds the periphery of centrifugal impeller 3 and is designed to receive the substantially radial outflow f from the periphery of the centrifugal impeller, direct it towards the mouth of central conduit 12 leading to the next disk-shaped cavity 11, and convert it into axial flow f' parallel to impeller supporting shaft 4.
  • a diffuser which surrounds the periphery of centrifugal impeller 3 and is designed to receive the substantially radial outflow f from the periphery of the centrifugal impeller, direct it towards the mouth of central conduit 12 leading to the next disk-shaped cavity 11, and convert it into axial flow f' parallel to impeller supporting shaft 4.
  • rigid casing 6 has an intake conduit 14, which connects the inlet of the first central connecting conduit 12 to the outside, and terminates in a flanged union forming intake 2a of pumping assembly 2; and a delivery conduit 15, which connects the outlet of the last central connecting conduit 12 to the outside, and terminates in a flanged union forming outlet 2b of pumping assembly 2.
  • the flanged unions on the end of intake conduit 14 and delivery conduit 15 project from the opposite end of rigid casing 6 from electric motor 5, and are both coaxial with a reference axis A locally perpendicular to longitudinal axis L of the casing.
  • centrifugal impellers 3 of pumping assembly 2 are preferably, though not necessarily, made of metal, and each comprise a central tubular hub 16 designed to fit angularly rigidly to impeller supporting shaft 4, so the longitudinal axis B of the hub 16 coincides with the longitudinal axis of the shaft; a circular rear plate 17 fixed rigidly to the body of hub 16 and perfectly coaxial with longitudinal axis B; and a circular front plate 18, which is coaxial with and positioned a given distance from rear plate 17, is also coaxial with longitudinal axis B of the hub, and forms a substantially disk-shaped gap with rear plate 17.
  • Front plate 18 has a central circular through hole larger in diameter than hub 16 and impeller supporting shaft 4, and roughly the same diameter as central conduit 12 connecting disk-shaped cavities 11 of the casing; and a cylindrical tubular sleeve 18a, which surrounds and bounds the circular through hole, projects from the face of front plate 18 on the opposite side to rear plate 17, and is locally coaxial with longitudinal axis B of hub 16, so as to form with hub 16 an annular opening 3a, which completely surrounds impeller supporting shaft 4 when impeller 3 is fitted to the shaft, allows water flow to the centre of impeller 3, and forms the intake of impeller 3.
  • centrifugal impeller 3 comprises a number of substantially flat oblong radial blades 19, which extend from one plate to the other to connect them rigidly, are spaced angularly about longitudinal axis B of the hub, and project from the periphery of the gap towards central tubular hub 16 along a known curved, substantially spiral trajectory.
  • radial blades 19 are inscribed in a cylindrical reference surface locally coaxial with longitudinal axis B of hub 16, and project towards hub 16 along a curved, substantially spiral trajectory.
  • radial blades 19 comprise a number of elongated rectangular metal straps 19 bent into an arc and welded on-edge to rear plate 17 and front plate 18 to form a rigid one-piece structure that can be fitted in angularly rigid manner to impeller supporting shaft 4.
  • each centrifugal impeller 3 is fitted to supporting shaft 4, inside respective disk-shaped cavity 11 of rigid casing 6, so that cylindrical tubular sleeve 18a of front plate 18 fits inside the mouth of central conduit 12 connecting disk-shaped cavity 11 to the preceding disk-shaped cavity 11, to feed the outflow from the preceding disk- shaped cavity 11 into impeller 3; and so that rear plate 17 directly faces outflow manifold/baffle 13 in disk- shaped cavity 11.
  • the outside diameter di of front plate 18 is greater than the outside diameter d 2 of rear plate 17; and the diameter d 3 of the cylindrical surface enclosing radial blades 19 is less than or equal to outside diameter di of front plate 18 and preferably, though not necessarily, greater than outside diameter d 2 of rear plate 17, so radial blades 19 project from the peripheral edge of rear plate 17.
  • outside diameter di of front plate 18 and outside diameter d 2 of rear plate 17 ranges between 2 and 20 percent of outside diameter d 2 of rear plate 17, and the difference between outside diameter d 2 of rear plate 17 and diameter d 3 of the cylindrical reference surface enclosing radial blades 19 is preferably, though not necessarily, less than 18 percent of outside diameter d 2 of rear plate 17.
  • diameter d 3 of the cylindrical reference surface enclosing radial blades 19 is always less than or equal to outside diameter di of front plate 18.
  • centrifugal impellers 3 therefore has major advantages. Firstly, by drastically reducing the axial thrust produced by the impellers, the thrust bearings along the impeller supporting shaft may all be eliminated (the slight axial thrust transmitted by the impellers can be effectively counteracted by the normal rolling bearings fitted to the impeller supporting shaft and/or electric motor shaft), thus greatly simplifying the design of the pumping assembly, with all the manufacturing advantages this affords. Secondly, by drastically reducing the axial thrust produced by the impellers, commercial electric motors can be used, even when working with large numbers of centrifugal impellers, with all the economic advantages this affords.
  • multistage centrifugal pump 1 as described herein without, however, departing from the scope of the present invention.
  • electric motor 5 may be replaced with a hydraulic motor or combustion engine.
  • pumping assembly 2 may comprise only one centrifugal impeller 3 fitted to supporting shaft 4.

Abstract

A centrifugal pump (1) having a pumping assembly (2) provided internally with a rotary supporting shaft (4) and with at least one centrifugal impeller (3) fitted to the supporting shaft (4); the centrifugal impeller (3) having a central hub (16), front (18) and rear plates (17) rigidly to the central hub (16) coaxial with the longitudinal axis (B) of the hub, and a number of angularly spaced radial blades (19) which extend from one plate (17, 18) to the other, and project from the periphery of the gap towards the central hub (16) along a predetermined trajectory; the outside diameter (d1) of the front plate (18) being greater than the outside diameter (d2) of the rear plate (17), and the diameter (d3) of the cylindrical surface enclosing the radial blades (19) being less than or equal to the outside diameter (d1) of the front plate (18).

Description

CENTRIFUGAL PUMP
TECHNICAL FIELD
The present invention relates to a centrifugal pum .
More specifically, the present invention relates to an electric vertical-axis multistage centrifugal pump for pumping large masses of water, to which the following description refers purely by way of example. BACKGROUND ART
As is known, electric multistage centrifugal pumps comprise a pumping assembly fitted inside with a number of cascade-connected centrifugal impellers fitted rigidly, a given distance apart, to a central supporting shaft; and a single- or three-phase electric motor fitted to the pumping assembly casing to rotate the supporting shaft.
More specifically, the impeller shaft is housed to rotate axially inside the pumping assembly casing, which, inside, has a number of disk-shaped cavities arranged successively along the impeller shaft, and each sized to house a respective centrifugal impeller. The disk-shaped cavities are connected to one another by a succession of central, circular-section, through conduits coaxial with and larger in diameter than the impeller shaft, so that the impeller shaft fits through and rotates axially inside them, while allowing water to flow from one disk-shaped cavity to another. The electric motor is fixed to and projects from the pumping assembly casing, coaxially with the impeller shaft; and the electric motor shaft is connected rigidly by a mechanical joint to the end of the impeller shaft projecting from the pumping assembly casing.
Each centrifugal impeller comprises a central tubular hub designed to fit rigidly to the impeller shaft; a circular rear plate fixed rigidly to the body of the central tubular hub and perfectly coaxial with the longitudinal axis of the hub; and a circular front plate coaxial with and a given distance from the circular rear plate, and also perfectly coaxial with the longitudinal axis of the hub.
The two plates have the same outside diameter, and so form a disk-shaped gap; and the centrifugal impeller has a number of flat radial blades or ribs, which extend from one plate to the other to connect them rigidly, are spaced angularly about the longitudinal axis of the hub, and in the meantime project spirally from the periphery of the gap towards the central tubular hub.
The circular front plate has a circular central through hole larger in diameter than the central tubular hub and the impeller shaft, and roughly the same diameter as the central conduits connecting the disk- shaped cavities in the casing; and a cylindrical tubular sleeve, which surrounds and bounds the circular through hole, and projects from the face of the plate, coaxially with the longitudinal axis of the hub. The cylindrical tubular sleeve and the central tubular hub thus form an annular opening, which completely surrounds the impeller shaft when the impeller is fitted to the shaft, allows water to flow to the centre of the impeller, and forms the intake of the impeller.
Each centrifugal impeller is positioned inside the respective disk-shaped cavity with the cylindrical tubular sleeve of the front plate fitted inside the mouth of the central through conduit connecting the disk-shaped cavity to the preceding disk-shaped cavity, so the impeller intake draws all the outflow from the preceding disk-shaped cavity.
The rear of each disk-shaped cavity is fitted with an outflow manifold/baffle, known as a diffuser, which surrounds the periphery of the centrifugal impeller and is designed to receive the radial outflow from the periphery of the centrifugal impeller and convert it into axial flow to the mouth of the central through conduit to the next disk-shaped cavity.
The main drawback of electric multistage centrifugal pumps of this sort lies in the design of the centrifugal impellers generating axial thrust, which is discharged onto the impeller shaft and increases in proportion to the number of impellers fitted to the shaft, at times to such an extent as to force manufacturers to adopt complicated, high-cost countermeasures .
For example, some manufacturers reduce the axial thrust of the centrifugal impellers by forming through holes in the rear plate of each impeller to reduce the water pressure on the outer face of the rear plate, or form labyrinth seals on the outer face of the rear plate to prevent the outflow from the periphery of the impeller from striking part of the outer face of the rear plate.
These solutions, however, reduce the overall efficiency of the centrifugal impellers and, hence, performance of the pump for a given electric motor.
To avoid impairing pump performance, some manufacturers prefer to fit the impeller shaft with massive thrust bearings, in addition to the annular seals and self-lubricating bushings normally supporting the shaft.
Having to continually withstand severe axial forces, however, the additional thrust bearings are subject to much faster wear than the annular seals and self-lubricating bushings, thus resulting in more frequent routine maintenance of the pump.
When working with a large number of impellers, manufacturers are also forced to fit the electric motor shaft with a special thrust bearing to discharge part of the axial thrust transmitted by the centrifugal impellers to the impeller shaft onto the electric motor casing too.
Electric motors 'specially designed' for this purpose (commercial electric motors are not normally fitted with thrust bearings for continually withstanding such severe axial thrust) obviously greatly increase the manufacturing cost of the pump, and pose serious problems in terms of spare part management.
'Specially designed' electric motors are much more expensive than commercial types of the same power, and because the two are not interchangeable in the event of breakdowns, manufacturers are forced to stock, at considerable expense in terms of invested capital, a suitable number of 'specially designed' electric motors to satisfy customer demand for spare parts within a reasonable time frame.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide an electric multistage centrifugal pump designed to eliminate the above drawbacks, and which is also cheaper to produce.
According to the present invention, there is provided a centrifugal pump as defined in Claim 1 and preferably, though not necessarily, in any one of the dependent Claims .
According to the present invention, there is also provided a centrifugal impeller as defined in Claim 11 and preferably, though not necessarily, in any one of the dependent Claims .
BRIEF DESCRIPTION OF THE DRAWINGS
A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which :
Figure 1 shows a section of an electric multistage centrifugal pump in accordance with the teachings of the present invention;
Figure 2 shows a larger-scale detail, with parts removed for clarity, of the multistage centrifugal pump in Figure 1 ;
Figure 3 shows a view in perspective of a centrifugal impeller of the electric multistage centrifugal pump in Figures 1 and 2 ;
Figure 4 shows a section of the Figure 3 centrifugal impeller.
BEST MODE FOR CARRYING OUT THE INVENTION
With reference to Figures 1 and 2, number 1 indicates as a whole an electric multistage centrifugal pump, particularly suitable for pumping large masses of water or other liquid, with a head of several hundred metres .
Pump 1 substantially comprises a pumping assembly 2 , in turn having an intake 2a and an outlet 2b, through which water flows in and out of pumping assembly 2, and a number of internal centrifugal impellers 3 fitted rigidly, a given distance apart, to a rotary supporting shaft 4 and designed to impart a rotating movement to the water flowing through them, to increase the speed and pressure of the liquid; and an electric motor 5, preferably, though not necessarily, a single- or three- phase asynchronous motor, fitted to pumping assembly 2 to rotate supporting shaft 4.
More specifically, pumping assembly 2 has a preferably, though not necessarily, cylindrical rigid metal outer casing 6; and supporting shaft 4 extends partly inside rigid casing 6, coaxially with the longitudinal axis L of the casing, and rotates freely about its own longitudinal axis, which coincides locally with longitudinal axis L of the casing.
Impeller supporting shaft 4 is fitted with one or more annular seals 7 to prevent water leakage from the shaft exit hole, and is preferably, though not necessarily, also fitted with one or more self- lubricating bushings 8 or other rolling bearings, interposed between supporting shaft 4 and rigid casing 6 to keep supporting shaft 4 perfectly coaxial with the longitudinal axis L of the casing, and prevent direct contact between supporting shaft 4 and rigid casing 6.
Electric motor 5 is fixed to and projects from rigid casing 6 of pumping assembly 2, is coaxial with impeller supporting shaft 4, and faces the far end of supporting shaft 4 projecting from rigid casing 6; and the rotary shaft 5a of electric motor 5 is connected to the far end of supporting shaft 4, in angularly rigid and stable, but easily releasable manner, by a removable mechanical joint 9 between electric motor 5 and pumping assembly 2.
In the example shown, electric motor 5 is fixed to and projects from a preferably, though not necessarily, cylindrical tubular spacer 10, which projects from the cover 6a of rigid casing 6, is coaxial with the end portion 4a of impeller supporting shaft 4 projecting from rigid casing 6, and is designed to house both end portion 4a of supporting - shaft 4, and mechanical joint 9.
As shown in Figures 1 and 2, inside, rigid casing 6 has a number of disk-shaped cavities 11 aligned successively along impeller supporting shaft 4, coaxial with the shaft axis and longitudinal axis L of rigid casing 6,' and each sized to house a respective impeller 3; and a succession of substantially circular-section central connecting conduits 12, which extend inside rigid casing 6, are locally coaxial with impeller supporting shaft 4 to connect disk-shaped cavities 11 successively to one another, and are larger in diameter than impeller supporting shaft 4, so supporting shaft 4 fits through and rotates axially inside them, while allowing water to flow from one disk-shaped cavity 11 to another .
The rear of each disk-shaped cavity 11 is fitted with an outflow manifold/baffle 13, known as a diffuser, which surrounds the periphery of centrifugal impeller 3 and is designed to receive the substantially radial outflow f from the periphery of the centrifugal impeller, direct it towards the mouth of central conduit 12 leading to the next disk-shaped cavity 11, and convert it into axial flow f' parallel to impeller supporting shaft 4.
Inside, rigid casing 6 has an intake conduit 14, which connects the inlet of the first central connecting conduit 12 to the outside, and terminates in a flanged union forming intake 2a of pumping assembly 2; and a delivery conduit 15, which connects the outlet of the last central connecting conduit 12 to the outside, and terminates in a flanged union forming outlet 2b of pumping assembly 2.
In the example shown in Figure 1, the flanged unions on the end of intake conduit 14 and delivery conduit 15 project from the opposite end of rigid casing 6 from electric motor 5, and are both coaxial with a reference axis A locally perpendicular to longitudinal axis L of the casing.
With reference to Figures 2, 3 and 4, centrifugal impellers 3 of pumping assembly 2 are preferably, though not necessarily, made of metal, and each comprise a central tubular hub 16 designed to fit angularly rigidly to impeller supporting shaft 4, so the longitudinal axis B of the hub 16 coincides with the longitudinal axis of the shaft; a circular rear plate 17 fixed rigidly to the body of hub 16 and perfectly coaxial with longitudinal axis B; and a circular front plate 18, which is coaxial with and positioned a given distance from rear plate 17, is also coaxial with longitudinal axis B of the hub, and forms a substantially disk-shaped gap with rear plate 17. Front plate 18 has a central circular through hole larger in diameter than hub 16 and impeller supporting shaft 4, and roughly the same diameter as central conduit 12 connecting disk-shaped cavities 11 of the casing; and a cylindrical tubular sleeve 18a, which surrounds and bounds the circular through hole, projects from the face of front plate 18 on the opposite side to rear plate 17, and is locally coaxial with longitudinal axis B of hub 16, so as to form with hub 16 an annular opening 3a, which completely surrounds impeller supporting shaft 4 when impeller 3 is fitted to the shaft, allows water flow to the centre of impeller 3, and forms the intake of impeller 3.
In the gap formed by rear plate 17 and front plate 18, centrifugal impeller 3 comprises a number of substantially flat oblong radial blades 19, which extend from one plate to the other to connect them rigidly, are spaced angularly about longitudinal axis B of the hub, and project from the periphery of the gap towards central tubular hub 16 along a known curved, substantially spiral trajectory.
In other words, radial blades 19 are inscribed in a cylindrical reference surface locally coaxial with longitudinal axis B of hub 16, and project towards hub 16 along a curved, substantially spiral trajectory.
In the example shown, radial blades 19 comprise a number of elongated rectangular metal straps 19 bent into an arc and welded on-edge to rear plate 17 and front plate 18 to form a rigid one-piece structure that can be fitted in angularly rigid manner to impeller supporting shaft 4.
With reference to Figure 2, each centrifugal impeller 3 is fitted to supporting shaft 4, inside respective disk-shaped cavity 11 of rigid casing 6, so that cylindrical tubular sleeve 18a of front plate 18 fits inside the mouth of central conduit 12 connecting disk-shaped cavity 11 to the preceding disk-shaped cavity 11, to feed the outflow from the preceding disk- shaped cavity 11 into impeller 3; and so that rear plate 17 directly faces outflow manifold/baffle 13 in disk- shaped cavity 11.
As shown in Figures 3 and 4, unlike currently marketed electric multistage centrifugal pumps, the outside diameter di of front plate 18 is greater than the outside diameter d2 of rear plate 17; and the diameter d3 of the cylindrical surface enclosing radial blades 19 is less than or equal to outside diameter di of front plate 18 and preferably, though not necessarily, greater than outside diameter d2 of rear plate 17, so radial blades 19 project from the peripheral edge of rear plate 17.
More specifically, the difference between outside diameter di of front plate 18 and outside diameter d2 of rear plate 17 ranges between 2 and 20 percent of outside diameter d2 of rear plate 17, and the difference between outside diameter d2 of rear plate 17 and diameter d3 of the cylindrical reference surface enclosing radial blades 19 is preferably, though not necessarily, less than 18 percent of outside diameter d2 of rear plate 17.
Obviously, diameter d3 of the cylindrical reference surface enclosing radial blades 19 is always less than or equal to outside diameter di of front plate 18.
Operation of multistage centrifugal pump 1 is clear from the above description, with no further explanation required.
As regards operation of centrifugal impellers 3, on the other hand, tests have shown that, when the outside diameter di of front plate 18 is greater than outside diameter d2 of rear plate 17, and radial blades 19 project from the peripheral edge of rear plate 17, the axial thrust produced by impeller 3 is drastically reduced, practically eliminated, with no significant impairment in the fluid-dynamic efficiency of the impeller .
The design of centrifugal impellers 3 therefore has major advantages. Firstly, by drastically reducing the axial thrust produced by the impellers, the thrust bearings along the impeller supporting shaft may all be eliminated (the slight axial thrust transmitted by the impellers can be effectively counteracted by the normal rolling bearings fitted to the impeller supporting shaft and/or electric motor shaft), thus greatly simplifying the design of the pumping assembly, with all the manufacturing advantages this affords. Secondly, by drastically reducing the axial thrust produced by the impellers, commercial electric motors can be used, even when working with large numbers of centrifugal impellers, with all the economic advantages this affords.
Clearly, changes may be made to multistage centrifugal pump 1 as described herein without, however, departing from the scope of the present invention.
For example, in a different embodiment, electric motor 5 may be replaced with a hydraulic motor or combustion engine.
In a simplified embodiment, pumping assembly 2 may comprise only one centrifugal impeller 3 fitted to supporting shaft 4.

Claims

1) A centrifugal pump (1) comprising a pumping assembly (2) internally provided with a rotary supporting shaft (4) and with at least one centrifugal impeller (3) fitted to said supporting shaft (4) ; and a motor (5) fitted to said pumping assembly (2) to rotate the supporting shaft (4) about its longitudinal axis (L) ; the centrifugal impeller (3) comprising :
- a central hub (16) designed to fit onto the supporting shaft (4) so that the longitudinal axis (B) of the hub coincides with the longitudinal axis (L) of the shaft;
- a rear plate (17) fixed rigidly to the central hub (16) and coaxially with the longitudinal axis (B) of the hub;
- a front plate (18) , which is coaxial with, and at a given distance from, the rear plate (17), so as to be also coaxial with the longitudinal axis (B) of the hub, and so as to form a disk-shaped gap with the rear plate (17); and
- a number of radial blades (19), which, inside the gap, extend from one plate (17, 18) to the other, connect them rigidly, are angularly spaced about the longitudinal axis (B) of the hub, and project from the periphery of said gap towards the central hub (16) along a predetermined trajectory;
the front plate (18) also having a central through holelarger in diameter than the central hub (16) and said supporting shaft (4); and the centrifugal pump (1) being characterized in that the outside diameter (di) of the front plate (18) is greater than the outside diameter (d2) of the rear plate (17), and the diameter (d3) of the cylindrical surface enclosing the radial blades (19) is less than or equal to the outside diameter (di) of the front plate (18) .
2) A centrifugal pump as claimed in Claim 1, characterized in that the diameter (d3) of the cylindrical surface enclosing the radial blades (19) is greater than the outside diameter (d2) of the rear plate (17), so that the radial blades (19) project from the peripheral edge of the rear plate (17) .
3) A centrifugal pump as claimed in Claim 1 or 2 , characterized in that the difference between the outside diameter (di) of the front plate (18) and the outside diameter (d2) of the rear plate (17) ranges between 2 and 20 percent of the outside diameter (d2) of the rear plate (17) .
4) A centrifugal pump as claimed in Claim 1, 2 or 3, characterized in that the difference between the outside diameter (d2) of the rear plate (17) and the diameter (d3) of the cylindrical surface enclosing the radial blades (19) is less than 18 percent of the outside diameter (d2) of the rear plate 17.
5) A centrifugal pump as claimed in any one of the foregoing Claims, characterized in that the front plate (18) is provided with a cylindrical tubular sleeve (18a) , which surrounds and bounds the central through hole, projects from the face of the front plate (18) on the opposite side to the rear plate (17), and is locally coaxial with the longitudinal axis (B) of the hub, so as to form with the central hub (16) an annular opening (3a) , which completely surrounds the supporting shaft (4) of the pumping assembly (2) when the impeller (3) is fitted to the shaft.
6) A centrifugal pump as claimed in any one of the foregoing Claims, characterized in that the pumping assembly (2) is provided with an outer casing (6), and the supporting shaft (4) extends partly inside the outer casing (6) and rotates freely about its own longitudinal axis (L) ; and in that the motor ( 5 ) is fixed to and projects from the outer casing (6) of the pumping assembly (2), so as to be coaxial with the supporting shaft (4) and as to face the far end of the supporting shaft (4) projecting from the outer casing (6); the far end of the supporting shaft (4) being connected rigidly and stably, but in easily releasable manner, to the rotary shaft (5a) of said motor (5) by a mechanical joint (9) .
7) A centrifugal pump as claimed in any one of the foregoing Claims, characterized in that the pumping assembly (2) comprises a plurality of centrifugal impellers (3) fitted, a given distance apart, to said supporting shaft (4) . 8) A centrifugal pump as claimed in Claims 6 and 7, characterized in that, inside, the outer casing (6) has a number of disk-shaped cavities (11) aligned successively along said supporting shaft (4) , coaxial with the longitudinal axis (L) of the shaft, and each sized to house a respective centrifugal impeller (3); and a succession of central connecting conduits (12), which extend inside the outer casing (6), are locally coaxial with the supporting shaft (4) to connect the disk-shaped cavities (11) successively to one another, and are larger in diameter than the supporting shaft (4), so that the supporting shaft (4) fits through and rotates axially inside them, while allowing fluid to flow from one disk-shaped cavity (11) to another.
9) A centrifugal pump as claimed in Claims 5 and 8, characterized in that each centrifugal impeller (3) is fitted to the supporting shaft (4), inside the corresponding disk-shaped cavity (11) , so that the cylindrical tubular sleeve (18a) of the front plate (18) fits inside the mouth of the central conduit (12) connecting the disk-shaped cavity (11) to the preceding disk-shaped cavity (11) .
10) A centrifugal pump as claimed in any one of the foregoing Claims, characterized in that the motor (5) is an electric motor (5) .
11) A centrifugal impeller (3) for a centrifugal pump (1), which comprises a pumping assembly (2) provided internally with a rotary supporting shaft (4) and with at least one centrifugal impeller (3) fitted to said supporting shaft (4) ; and a motor (5) fitted to said pumping assembly (2) to rotate the supporting shaft (4) about its longitudinal axis (L) ; the centrifugal impeller (3) comprising :
- a central hub (16) designed to fit to the supporting shaft (4) so that the longitudinal axis (B) of the hub coincides with the longitudinal axis (L) of the shaft;
- a rear plate (17) fixed rigidly to the central hub (16) and coaxially with the longitudinal axis (B) of the hub;
- a front plate (18) , which is coaxial with, and at a given distance from, the rear plate (17), so as to be also coaxial with the longitudinal axis (B) of the central hub and as to form a disk-shaped gap with the rear plate (17); and
- a number of radial blades (19) which, inside the gap, extend from one plate (17, 18) to the other to connect them rigidly, are angularly spaced about the longitudinal axis (B) of the hub, and project from the periphery of said gap towards the central hub (16) along a predetermined trajectory;
the front plate (18) also having a central through hole larger in diameter than the central hub (16) and said supporting shaft (4); the centrifugal impeller (3) being characterized in that the outside diameter (di) of the front plate (18) is greater than the outside diameter (d2) of the rear plate (17) , and the diameter (d3) of the cylindrical surface enclosing the radial blades (19) is less than or equal to the outside diameter (di) of the front plate (18) .
12) A centrifugal impeller as claimed in Claim 11, characterized in that the diameter (d3) of the cylindrical surface enclosing the radial blades (19) is greater than the outside diameter (d2) of the rear plate (17) , so that the radial blades (19) project from the peripheral edge of the rear plate (17) .
13) A centrifugal impeller as claimed in Claim 11 or 12, characterized in that the difference between the outside diameter (di) of the front plate (18) and the outside diameter (d2) of the rear plate (17) ranges between 2 and 20 percent of the outside diameter (d2) of the rear plate (17) .
14) A centrifugal impeller as claimed in Claim 11, 12 or 13, characterized in that the difference between the outside diameter (d2) of the rear plate (17) and the diameter (d3) of the cylindrical surface enclosing the radial blades (19) is less than 18 percent of the outside diameter (d2) of the rear plate 17.
15) A centrifugal impeller as claimed in any one of Claims 11 to 14, characterized in that the front plate (18) is provided with a cylindrical tubular sleeve (18a) , which surrounds and bounds the central through hole, projects from the face of the front plate (18) on the opposite side to the rear plate (17), and is locally coaxial with the longitudinal axis (B) of the central hub, so as to form with the central hub (16) an annular opening (3a) , which completely surrounds the supporting shaft (4) of the pumping assembly (2) when the impeller (3) is fitted to the supporting shaft.
PCT/IB2011/000088 2010-01-22 2011-01-21 Centrifugal pump WO2011089512A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT000041A ITTO20100041A1 (en) 2010-01-22 2010-01-22 CENTRIFUGAL PUMP
ITTO2010A000041 2010-01-22

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WO2011089512A2 true WO2011089512A2 (en) 2011-07-28
WO2011089512A3 WO2011089512A3 (en) 2011-12-01
WO2011089512A8 WO2011089512A8 (en) 2012-02-16

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Cited By (2)

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EP2503156A1 (en) * 2011-03-20 2012-09-26 Hydro-Vacuum S.A. Impeller for centrifugal pump
CN113883063A (en) * 2021-08-30 2022-01-04 安徽凯特泵业有限公司 Centrifugal pump with vibration damping base

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US3612716A (en) * 1970-06-15 1971-10-12 Red Jacket Mfg Co Multistage centrifugal pump
US4886417A (en) * 1988-12-06 1989-12-12 Sundstrand Corporation Fuel pump and radial-flow impeller therefor
US6481961B1 (en) * 2001-07-02 2002-11-19 Sea Chung Electric Co., Ltd. Stage for a centrifugal submersible pump
US6979174B2 (en) * 2003-10-01 2005-12-27 Schlumberger Technology Corporation Stage pump having composite components

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2503156A1 (en) * 2011-03-20 2012-09-26 Hydro-Vacuum S.A. Impeller for centrifugal pump
CN113883063A (en) * 2021-08-30 2022-01-04 安徽凯特泵业有限公司 Centrifugal pump with vibration damping base
CN113883063B (en) * 2021-08-30 2024-02-13 安徽凯特泵业有限公司 Centrifugal pump with damping base

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WO2011089512A3 (en) 2011-12-01
WO2011089512A8 (en) 2012-02-16

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