US3351022A

US3351022A - Fluid pump

Info

Publication number: US3351022A
Application number: US407342A
Authority: US
Inventors: Harvey G Allen
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1964-10-29
Filing date: 1964-10-29
Publication date: 1967-11-07
Anticipated expiration: 1984-11-07

Description

Nov. 7, 1967 H. G. ALLEN 3,351,022

FLUID PUMP 2 sheets sheet 1 Filed Oct. 29, 1964 FIG. I. fa

44 4e 50 46: so i H 52 48 H 42 so 55 a4 64 62 e: 14 28 as Isa INVENTOR WITNEISSESI g, W Harvey G. A len I ATTORNEY Nov. 7, 1967 H. G ALLEN 3,351,022

FLUID P Filed Oct. 29, 1964 United States Patent 3,351,022 FLUID PUMP Harvey G. Allen, Franklin Township, Murrysville, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 29, 1964, Ser. No. 407,342 9 Claims. (Cl. 103--89) The invention is directed to fluid pumping apparatus and more particularly to a new and improved induced flow pump capable of permitting a large natural circu1ation flow therethrough when the pump is not in operation.

In the field of liquid cooled heterogeneous, nuclear reactors, for example, canned motor pumps have become widely used as the referred main coolant pumps for the primary systems thereof. Canned motor pumps permit zero leakage which is deemed essential when radioactive or other hazardous fluids are being circulated. It has been determined that the assurance of having the zero leakage is well worth the added cost necessitated by canned motor pumps over the more conventional packing gland type pump. Canned motor pumps provide a complete hermetic barrier between the rotor and the stator of the pump motor with the rotor chamber being exposed to the relatively high pressure of the reactor primary system. A can or relatively thin enclosure provides such isolation between the rotor and the stator.

Main coolant pumps for nuclear reactor primary systems have conventionally been constructed with centrifugal type impellers. Such impellers are disposed within the primary system How circuit thereby preventing a substantial degree of natural circulation of the primary system coolant when the pump is not in operation. Such reactors having centrifugal pumps in the primary system normally rely upon forced circulation of the coolant through the primary system.

Reactor constructions have been developed, however, wherein natural circulation or convection flow of the coolant through the primary system is utilized. In such natural circulation reactor systems, it has been determined that it is desirable to provide a forced circulation capability. In furtherance of this purpose, a backup bumping means for emergency conditions is provided to supply forced circulation. It is desirable that such backup pumping means fulfill the reqiurement of zero leakage that have been achieved with canned motor pumps. In addition it is desirable that the backup pumping means he formed to permit the normal natural circulation flow of the reactor coolant through the pumping means under normal operating conditions.

Accordingly, it is an object of this invention to provide a new and improved fluid pump arrangement which provides a substantial natural circulation flow path therethrough.

Another object of this invention is to provide a propeller type fluid pumping apparatus having a large by-pass flow circuit formed therein.

A further object of this invention is to provide a new and improved canned motor pump arrangement having substantial natural circulation flow path formed in the pumping portion thereof.

Briefly, the present invention accomplishes the abovecited objects by providing a fluid pump having generally L-shaped tubular pump casing. A propeller type pump is disposed within the tubular casing and is positioned centrally in spaced relationship therewith to provide an annular natural circulation flow path, in bypassing relationship with the propeller. The canned motor pump is offset from one of the legs of the L-shaped pump casing with the shaft of the motor pump extending coaxially with the last-mentioned leg.

More specifically, the pump casing is provided with a flow passageway therein extending between the suction nozzle and the discharge nozzle. A flow splitting means is formed in the casing passageway adjacent the suction nozzle to divide the suction flow to pass into a pair of suction volutes which are disposed in mirror image relationship in the pump casing. The suction volutes provide a pair of streamlined flow paths of decreasing cross sectional area between the suction nozzle and the pump energizer or propeller. The pump energizing section of the motor pump is disposed concentrically of the adjacent portion of the pump casing in spaced relationship therewith to provide a casing throat in parallel with the energizer, both communicating with the suction volute. Positioned between the energizer section of the pump and the casing throat and the pump casing discharge nozzle is a diffuser section. The pump energizer desirably is formed to promote axial flow or liquid injection into the diffuser region. More particularly the pump energizer desirably is of the propeller type with the impeller being disposed within an annular housing. Desirably, radial guide vanes are provided on the suction side of the propeller and curved diffusion vanes are provided at the discharge side.

With the aforedescribed arrangement, a substantial natural circulation flow path is formed within the pump casing and forced circulation may be achieved by the liquid injection type pump.

Another important feature of induced flow pump of this invention is that the pump construction has an extremely high specific speed. This permits the use of a much smaller, higher rotative speed motor drive. For example, for a natural circulation reactor system with hydraulic condi tions of 2000 g.p.m. and a 2 foot head, a 1750 rpm. motor can be used with the instant pump construction. Calculating the specific of this induced fiow pump:

where N '=specific speed. r.p.m.=speed of rotation. g.p.m.:flow.

H =head.

r.p.m.=750

The motor drive of 750 r.p.m. or less for a centrifugal pump design requires a much larger motor, and which is necessarily non-standard.

Further objects and advantages of this invention will become apparent as the following description proceeds and features of novelty which characterize the invention will be pointed out in particularity in the claims connected to and forming a part of this specification.

For a better understanding of this invention reference may be had to the accompanying drawings, in which:

FIGURE 1 is a sectional view through a motor pump unit constructed in accordance with the principles of this invention and having the motor portion thereof illustrated in elevation.

FIG. 2 is a sectional view through the pump casing of FIG. 1 and taken substantially along the lines II-II thereof; and

FIG. 3 is a fragmentary sectional view through the pump energizer and taken substantially along the lines IIIIII of FIG. 1.

In accordance with the invention and referring to the drawings, there is provided a generally L-shaped tubular pump casing forming a flow passageway therethrough. The casing 10 includes a horizontally extending portion 12 open at one end to form a suction port 14 and a vertically extending portion 16 open at the lower end forming a discharge nozzle 18. The pump casing 10 desirably is fabricated of a material having a thickness sufficient to withstand pressure on the order of 2,500 psi. and from a suitable corrosion resistant material, such as stainless steel. The pump casing 10 is formed so that it may be conveniently connected into the piping of a flow circuit, for example, in the primary system piping of a heterogeneous nuclear reactor. Such connections desirably are made by a pair of circumferential Welds between casing 10 and the flow system piping positioned respectively

adjacent ends

14 and 18 of casing 10.

The casing 10 is provided with an opening 20 positioned in alignment with the vertical portion 16 of casing 10 to receive a motor pump unit 24 therein. The pump portion or energizer 22 of the motor pump unit 24 extends through opening 20 into the vertical casing section 16 with the pump portion 22 being disposed centrally of section 16 and in spaced relationship with the inner wall thereof. Casing section 16 desirably is enlarged adjacent energizer 22 to form an annular passageway 34 in parallel with the flow passageway formed within energizer 22.

Adjacent suction port 14, there is provided a flow splitter 26 of generally streamlined configuration and extending vertically to divide casing portion 12 in half and providing equalized flow on opposite sides thereof. The flow splitter 26 provides communication between inlet 14 and the entrances to a pair of suction volutes 28 formed on opposite sides of the horizontal casing portion 12 and forming a streamlined flow path in the pump casing on the suction side of the energizer 22 of decreasing cross sectional area, as illustrated by the dotted lines on FIG. 1 and in FIG. 2. Each suction volute 28 has its largest cross sectional area adjacent flow splitter 26 and its smallest cross sectional area on the remote end of horizontal section 12. The suction volutes 28 are positioned in mirror image relationship on opposite sides of the horizontal casing portion 12 with the volutes 28 serving to direct inlet flow toward the energizer 22 of the motor pump unit 24.

As seen in FIG. 2, while the suction volute provides a flow path of decreasing cross sectional area along the length thereof, the suction volutes 28 surround the energizer section 22. To accommodate both the energizer 22 and the suction volutes 28, the horizontal section 12 of the pump casing 10 is enlarged in cross sectional configuration adjacent the energizer section 22. Each suction volute 28 communicates both with the suction side of energizer 22 and with the annular region or casing throat 34. The vertical section of the casing flow passageway becomes narrowed below the energizer 22 with narrowed portion 36 being venturi-shaped to form a diffuser. As is conventional the diffuser 36 is enlarged in cross section at the outlet side thereof by outwardly tapered wall portion 38. The energizer 22 is formed in part by a stationary housing 40 and by a propeller type impeller 42 which is rotated by the motor of unit 24. The energizer housing 40 includes an upper shroud 44 of generally annular configuration which is contoured downwardly from diffuser 28 in a concave shape to form a relatively streamlined flow path. A lower annular shroud 46 is disposed below the upper shroud 44 and is connected thereto by a plurality of radial guide vanes 48 which extend laterally between the upper and lower shrouds 44 and 46. The radial guide vanes 48 are formed to be straight vanes so as to extend linearly parallel to the direction of fluid flow between the shrouds 44 and 46. The upper shroud 44 is provided with a central opening 50 therein through which the shaft 52 of the motor pump 24 extends with the lower end of shaft 52 having the propeller 42 mounted thereon. The lower shroud 46 is provided with an extension 54 thereon which is re ferred to herein as the casing barrel, and the propeller 42 is disposed for rotative movement within the casing barrel 54. The propeller 42 desirably is constructed to operate at a relatively high speed with the propeller 42 having a plurality of blades 56 which are desirably doubly curved or Francis type blades which serve to impart a tangential velocity to the fluid flowing therepast. The lower end of the shaft 50 desirably is threaded to receive an impeller retaining nut 58 thereon with the retaining nut 58 being disposed in an opening 60 formed in a hub 62 disposed below the propeller 42. The hub 62 is secured to the casing barrel 54 by a plurality of transversely extending diffuser vanes 64 which desirably are doubly curved or Francis type vanes.

Considering now the pump hydraulics, flow fluid enters the pump casing 10 through the suction port 14 and is divided in half by the flow splitter 26 whereby substantial equal portions of the fluid flow passes through the two suction volutes 28. From the suction volutes 28, the fluid moves either to the casing throat 34 or into the energizer 22 through the opening 66. Fluid entering the opening 66 is flowing therein with a generally radial flow vector imported thereto by the volutes 28 and such flow is straightened to generally axial flow by the straight guide vanes 48. The rotation of the impeller 46 imparts both energy to the flow and a tangential velocity thereto. The tangential velocity imparted in the flow by the impeller blades 56 is changed to a static head by the doubly curved diffuser vanes and into axially directed flow. The diffuser vanes 64 act to impart energy to the energizer flow in the axial direction and such kinetic energy appears at the energizer discharge opening 68. The kinetic energy at 68 causes a lower pressure area at positions adjacent the flow discharge 68, thereby inducing additional flow in the casing throat 34. Fluid flow from the energizer 22 is then mixed with the lower energy fluid flow from the bypass or throat area 34 in the casing diffuser section 36.

It will be seen that, when the propeller 42 is not operating, the pressure drops .across the casing 10' between suction port 14 and discharge 18 is minimal because of the relatively large cross sectional area of the natural circulation flow passageway at all points along casing 10. Natural circulation flow through the pump casing 10 passes from suction port 14 to volutes 28 and therefrom through the angular bypass region 34 to diffuser 36 to discharge nozzle 18. Thus, the foregoing construction not only acts to provide forced circulation capability to a system with which it is utilized but also serves to permit substantially unobstructed natural circulation flow therethrough.

As is known by those skilled in the art, a propeller type pump normally is most advantageous in systems wherein there is required a relatively high flow at a low head. A normal centrifugal pump cannot achieve the specific speed required for certain operations without constructing a pump impeller having an extremely large radial dimen-- sion. Since a propeller type pump achieves substantially higher specific speeds than a centrifugal pump, its use in a high flow, low-head system is extremely desirable.

Referring now to the constructional details of the motor pump unit 24, it will be appreciated that the motor portion of the unit may be constructed pursuant to the teachings of such constructions illustrated in my Patents 3,077,- 161 or 2,799,227. A propeller type energizer 22 is mounted on the shaft of such motor constructions such that rotation of the shaft causes suction at the opening 66 and discharge at the opening 68. 'In this manner a zero-leakage canned motor unit is employed to insure the fulfillment of safety requirements for nuclear applications. In this regard, the motor pump 24 is provided with a relatively large flanged retaining member 70 which is adapted to fixedly position the motor pump 24 on casing adjacent opening 20. A plurality of mounting bolts 72 pass through flange 70 and are threa-dedly secured to casing 10. The lower end of the motor frame, depicted by the reference character 74, is sized to rest upon the upper surface 76 of casing 10. To provide a hermetic seal between the motor pump unit 24 of casing 10, an annular canopy weld 78 is formed across the junction between surfaces 74 and 76. The pump casing and thermal barrier portion of the motor pump unit 24 extend downwardly through the opening with the thermal barrier region being shown partially in section and identified by the reference character 80. The shaft 52 of the motor pump unit extends through a central opening in the thermal barrier 80 and a labyrinthine type seal 82 is formed to surround the shaft 52 to minimize the leakage flow along the shaft 52 to the motor section of the motor pump 24. The lower end of the thermal barrier portion 80 forms the upper shroud 44 of the energizer 22 and the casing barrel -40 of energizer 22 is fixedly secured to shroud 46 by suitable means such as by bolts 84. Thus, the entire energizer portion 22 is secured to the motor pump unit 24 and is positioned within casing 10 as a unit.

By use of a hermetically sealed canned motor for the unit 24 and the hermetically sealed canopy weld between casing 10 and motor pump 24 there is provided a hermetically sealed motor-pump construction pursuant to this invention.

It will be appreciated that many modifications may be made to the preferred embodiment of this invention described herein without departing from the broad spirit and scope of the invention. Accordingly, it is specifically intended that the detailed description contained herein be interpreted as illustrative of this invention rather than limitative thereof.

I claim as my invention:

1. A fluid pump comprising a pump casing having a flow passageway formed therein, said casing having a suction port and a discharge nozzle at opposite ends of said flow passageway, a fluid energizer having an annular housing means disposed in said casing and extending into said passageway, said energizer having impeller means disposed in said housing means for imparting energy to fluid flowing through said passageway, said housing means being mounted in spaced relationship with the walls of said casing to form a bypass fluid flow path in parallel with said housing means, a flow splitter mounted in said pump casing adjacent said suction port for splitting the flow passing through said suction port, said casing forming a pair of suction volutes of decreasing cross sectional area disposed between said suction port and said energizer housing means, and said flow splitter being positioned to direct fluid entering said suction port to each of said suction volutes.

2. A fluid pump comprising a pump casing having a flow passageway formed therein, said casing having a suction port and a discharge nozzle at opposite ends of said flow passageway, a fluid energizer having an annular housing disposed in said casing and extending into said passageway, said energizer including an impeller means positioned in said housing for imparting energy to fluid flowing through said passageway, said housing being mounted in spaced relationship with the walls of said casing to form a bypass fluid flow path in parallel with said housing, a flow splitter mounted in said pump casing adjacent said suction port for splitting the flow passing through said suction port, said casing forming a pair of suction volutes of decreasing cross sectional area disposed between said suction port and said energizer portion, said flow splitter being positioned to supply fluid entering said suction port to each of said suction volutes, and said casing forming a diffuser region in said passageway and positioned intermediate said energizer and said discharge nozzle.

3. A fluid pump comprising a pump casing having a fluid flow passageway formed therein, a fluid energizer having an annular housing disposed in said casing in spaced relationship with the walls of said passageway to form a bypass fluid flow path in parallel therewith, said housing having a fluid flow path formed therein, a rotatable propeller disposed in said housing for imparting energy to fluid flowing through said flluid flow path, and said casing having a pair of spaced means formed therein for transporting fluid into said housing flow path with a radial flow vector and a flow splitter positioned in said casing for directing fluid into each of said transporting means.

4. A fluid pump comprising a pump casing having a fluid flow passageway formed therein, a fluid energizer having an annular housing disposed in said casing in spaced relationship with the walls of said passageway to form a bypass fluid flow path in parallel therewith, said housing having a fluid flow path formed therein, a rotatable propeller disposed in said housing for imparting energy to fluid flowing through said fluid flow path, said casing having a pair of spaced means formed therein for transporting fluid into said housing flow path with a radial flow vector, a flow splitter positioned in said casing for directing fluid into each of said transporting means, a plurality of axially extending radial guide vanes positioned in said housing flow path intermediate the inlet thereof and said propeller for converting the .radial flow vector of fluid flowing into said housing flow path to an axial flow vector, said propeller having doubly curved blades formed thereon for imparting a tangential velocity to such flow, and a plurality of doubly curved diffuser vanes disposed intermediate said impeller and the outlet of said Energizer flow path for converting said flow into a static ead.

5. A fluid pump comprising an L-shaped pump casing having an L-shaped flow passageway formed therein, said casing having a suction port in one of the legs thereof and a discharge nozzle in the other of the legs thereof at opposite ends of said passageway, said casing having an opening in said one leg positioned opposite said discharge nozzle, a canned motor-pump mounted on said pump casing and having a fluid energizer extending through said opening into said other leg of said pump casing, said one casing leg forming a pair of suction volutes of decreasing cross sectional area and positioned in mirror image relationship with one another, said flow passageway providing communication between said suction nozzle and each of said suction volutes, said pump energizer having an annular housing mounted in said casing in spaced relationship with the walls of said passageway, said housing f0rming a flow path in parallel with said casing flow passageway, said suction volutes being formed to direct fluid flow into said flow path with a radial flow vector, a plurality of axially extending radial guide vanes positioned adjacent the inlet of said flow path for converting said radial flow to generally axial flow, a propeller disposed in said housing flow path and rotated by said motor pump, said propeller having a plurality of doubly curved blades thereon for imparting a tangential velocity to the flow through said flow path, a plurality of doubly curved diffuser vanes disposed in said flow path and positioned intermediate said propeller blades and the outlet of said fiow path for converting said flow to static head, whereby said energizer imparts energy to the fluid flowing through said energizer flow path which induces additional flow of fluid in the region between said housing and said passageway walls, and said pump casing having a diffuser formed in said other leg thereof and positioned intermediate said energizer and said discharge nozzle.

6. A fluid pump comprising a pump casing having a flow passageway formed therein, said casing having a suction port and a discharge nozzle at opposite ends of :said ,flow passageway, a fluid energizer having impeller means disposed in said casing for imparting energy to fluid flowing through said passageway, flow splitting means mounted in said pump casing adjacent said suction port and said impeller means, said casing defining a pair of opposed suction volute passages located upstream of said impeller means for directing opposed streams of fluid into said impeller means, and said flow splitting means being positioned to direct fluid entering said suction port to each of said suction volute passages.

7. A fluid pump comprising a pump casing having a flow passageway formed therein, said casing having a suction port and a discharge nozzle at opposite ends of said flow passageway, a fluid energizer having impeller means disposed in said casing for imparting energy to fluid flowing through said passageway, flow splitting means mounted in said pump casing adjacent said suction port, said casing defining a pair of opposed suction volute passages located upstream of said impeller means for directing opposed streams of fluid into said impeller means, said flow splitting means being positioned to diregt fluid entering said suction port to each of said suction volute passages, and said casing forming a diffuser region in said passageway and positioned intermediate said impeller means and said discharge nozzle.

8. A fluid pump comprising a pump casing having a fluid flow passageway formed therein, a fluid energizer having a rotatable propeller disposed in said casing for imparting energy to fluid flowing therethrough, said casing having a pair of spaced opposed volute means formed therein upstream of said propeller for transporting fluid into said propeller with a radial flow vector, and a flow splitter positioned in said casing upstream of said volute means for directing fluid into each of said volute means.

9. A fluid pump comprising a pump casing having a fluid flow passageway formed therein, a fluid energizer having a .rotatable propeller disposed in said casing for imparting energy to fluid flowing therethrough, said casing having a pair of spaced opposed volute means formed therein upstream of said propeller for transporting fluid into said propeller with a radial flow vector, a flow splitter positioned in said casing upstream of said volute means for directing fluid into each of said volute means, a plurality of axially extending radial guide vanes positioned in said casing intermediate said transporting means and said propeller for converting the radial flow vector of the flowing fluid to an axial flow vector, said propeller having doubly curved blades formed thereon for imparting a tangential velocity to such flow, and a plurality of doubly curved diffuser vanes disposed intermediate said impeller and the outlet of said casing for converting said flow into a static head.

References Cited UNITED STATES PATENTS 1,502,865 7/1924 Moody 10389 1,625,893 4/1927 Hollander 103-89 1,683,949 9/1928 Bergdoll 10389 1,720,333 7/1929 Ketchum 103-89 1,959,817 5/1934 Denk 103--89 2,799,227 7/1957 Allen 10387 FOREIGN PATENTS 866,053 3/1941 France.

OTHER REFERENCES German printed application, 1,013,986, August 1957.

DONLEY J. STOCKING, Primary Examiner.

HENRY F. RADUAZO, Examiner.

MARK NEWMAN, Assistant Examiner.

Claims

1. A FLUID PUMP COMPRISING A PUMP CASING HAVING A FLOW PASSAGEWAY FORMED THEREIN, SAID CASING HAVING A SUCTION PORT AND A DISCHARGE NOZZLE AT OPPOSITE ENDS OF SAID FLOW PASSAGEWAY, A FLUID ENERGIZER HAVING AN ANNULAR HOUSING MEANS DISPOSED IN SAID CASING AND EXTENDING INTO SAID PASSAGEWAY, SAID ENERGIZER HAVING IMPELLER MEANS DISPOSED IN SAID HOUSING MEANS FOR IMPARTING ENERGY TO FLUID FLOWING THROUGH SAID PASSAGEWAY, SAID HOUSING MEANS BEING MOUNTED IN SPACED RELATIONSHIP WITH THE WALLS OF SAID CASING TO FORM A BYPASS FLUID PATH IN PARALLEL WITH SAID HOUSING MEANS, A FLOW SPLITTER MOUNTED IN SAID PUMP CASING ADJACENT SAID SUCTION PORT FOR SPLITTING THE FLOW PASSING THROUGH SAID SUCTION PORT, SAID CASING FORMING A PAIR OF SUCTION VOLUTES OF DECREASING CROSS SECTIONAL AREA DISPOSED BETWEEN SAID SUCTION PORT AND SAID ENERGIZER HOUSING MEANS, SAID FLOW SPLITTER BEING POSITIONED TO DIRECT FLUID ENTERING SAID SUCTION PORT TO EACH OF SAID SUCTION VOLUTES.