US3038409A - Eddy current magnetic liquid metal pump - Google Patents

Description

SR 33 REFEREEQCE SvUSBaQO? G. E. EDGERLY ETAL EDDY CURRENT MAGNETIC LIQUID METAL PUMP June 12, 1962 2 Sheets-Sheet 1 Filed April 15, 1960 R u E S D RENN .Y. oeH N TDAL W R NEHw o a T W 6 I Y A NYE W W .Em 6H5 June 12, 1962 e. E. EDGERLY ETAL 3,038,409

EDDY CURRENT MAGNETIC LIQUID METAL PUMP Filed April 15, 1960 2 Sheets-Sheet 2 F IG- 2 2g 15 44 a0 54 50 P l (3.3 Q

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INVENTORS GLENN E- EDGERLY HENRY R- HAHN SIDNEY AUSLENDER ATTORNEY United States Patent 3,038,409 EDDY CURRENT MAGNETIC LIQUID METAL PUMP Glenn E. Edgerly, Meriden, and Henry R. Hahn, Portland, Conn., and Sidney Auslender, Baltimore, Md., assignors to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed Apr. 15, 1960, Ser. No. 22,436 11 Claims. (Cl. 103-1) This invention relates to apparatus for pumping electrically conductive fluid and has as one of its objects to provide apparatus of this sort which is more eflicient and which is much lighter in weight than prior devices.

Another object of this invention is to provide a pump of this type utilizing a tube cell rectangular in cross section and of high electrical resistance.

A further object of the invention is to provide a much lighter magnetic circuit weight than has been possible hitherto in liquid metal pumps.

A further object of this invention is to provide a pump which is adapted for production in large sizes.

A further object is to provide elongated rectangular pole faces having their length arranged perpendicular to the flow direction in a tube cell of rectangular cross section.

A still further object of the invention is to provide a liquid metal pump with a minimum number of rotating parts presenting a minimum of rotating weight.

A further object is to provide a rotating pole unit which acts as a centrifugal blower to reduce convection heating of the magnetic circuit.

A yet further object is generally to improve the construction and operation of liquid metal pumps.

These and other objects and advantages of the pump of this invention will be pointed out in connection with the following detailed description of a preferred embodiment shown in the accompanying drawings. In the drawings:

FIG. 1 is a plan view of the pump in ope-rating position, with parts broken away;

FIG. 2 is a sectional view taken on line 22 of FIG. 1;

FIG. 3 is a sectional view taken on line 3-3 of FIG. 1;

FIG. 4 is a sectional view through the flow divider of the tube cell taken on line 4-4 of FIG. 2;

FIG. 5 is a section on line 5-5 of FIG. 1 showing the shape of the pole tips;

FIG. 6 is a section on line 6-6 of FIG. 3; and

FIG. 7 is a radial sectional view through a tube cell of modified contruction.

Referring particularly to FIGS. 1 through 3, the improved pump of this invention includes an annular frame 10 in which an axial shaft 12 is mounted for rotation on bearings 14 and :16. It will be understood that the pump is adapted to be operated with the shaft in a vertical position, although it is not required.

The frame 10 includes a mounting ring 18 at the bottom end and a similar ring 20 at the top end. The mounting rings include inwardly directed flanges 22 and 24 with tubular mounting sleeves 26 and 2-8 welded thereto which are spaced from shaft 12. The rings 18 and 20 also have outwardly oblique stringers 30 and 32 at spaced points about the periphery of the frame which support the tube cell mounting ring assembly 36 which is generally parallel with the shaft. Tubular mounting sleeves 26 and 28 have rings 38 and 40 welded to their adjacent ends (FIG. 2). These rings are connected to the tube cell ring mounting assembly by struts 42 and 44, webs 46 and 48 being provided between struts 42, 44 and the adjacent frame members, as shown in FIG. 3. These webs are provided with suitable lighter holes 50 in a usual manner.

Shaft 12 comprises end portions 52 and 54 which are "ice formed of good magnetic material and an intermediate portion 56 which is of nonmagnetic material. The adjacent ends of shaft portions 52 and 54 have integral flanges 58 and 60 provided with beveled shoulders 62 and 64. Intermediate shafit portion 56 has radial flanges 66 and 68, which are connected to similar radial faces of flanges 58 and 60 by bolts 70, as shown in FIG. 2. The bolts 70 also secure two pole pieces 72 against beveled shoulders 62 and 64. Each pole piece 72, as shown most clearly in FIG. 1, comprises a circular disc having six radial arms extended outwardly from the disc. Each arm is provided with an integral right angle pole tip 74, the pole tips of like arms of the two pole pieces being tapered and inwardly directed toward each other and terminating in spaced rectangular pole faces 75, as shown in FIG. 5, between which an annular tube cell 76, rectangular in cross section, is closely received (FIGS. 2 and 3).

The annular tube cell 76 is made in two complemental parts, each having an inner ring 78 and an outer ring 80 connected by a narrow web 82 so located that, when the two-ringed members are located side-by-side, a long narrow annular cell passage 84, rectangular in section, is provided for the flow of the liquid metal to be pumped.

As shown most clearly in FIG. 3, the tube cell ring mount assembly 36 includes radial flanges 86 and 88, which are spaced apart a suitable distance to receive the tube cell therebetween. Radial flanges 8'6 and 88 have annular tube cell mounting plates 90 and 92 secured thereto by screws 94. These plates have radial slots 96 in which the heads of screws 98 and the shanks of screws 98 are free to move radially. An annular row of screws 98 is extended through the slots in each tube cell mounting plate and is threaded into the outer rings 80 of the tube cell, thus providing a floating connection for the tube cell on the frame-carried mounting ring. The outer periphery of the tube cell is surrounded by a ring 100 which is secured between the cell mounting plates 90 and 92 in fixed position by a plurality of spaced longitudinal ribs 102 (FIG. 6). Between each pair of ribs 102 is provided a longitudinal row of balls 1104 located in radial passages in ring 100. The balls are constantly biased by springs 106 against the outer peripheral ring 80 of tube cell 76, the springs 106 being enclosed by caps 108 which are threaded to sleeves 110 secured to ring 100 over the ballreceiving passages. The two-part cell 76 is welded together about the periphery of the inner and outer rings 78 and 80 to provide a unitary structure. The liquid metal is introduced into the tube cell by means of a flow divider shown in FIG. 4, which as shown, provides an inlet passage 112 and an outlet passage 114 with an integral divider 116 forming a barrier in the annular cell passage 84 between the inlet and outlet passages. A slot is milled at a suitable place in the annular cell to receive the flow divider which is then made an integral part of the cell by welding.

The magnetic shaft portion 52 is surrounded by a sleeve 120 of good magnetic material which occupies the annular space between the shaft and the mounting sleeve 26. Sleeve 120 is axially positioned between ring 38 and the flange of a ring 122 screw-fastened to tubular mounting sleeve 26. The magnetic shaft portion 54 is provided with a similar sleeve 124 of magnetic material.

Two radial sets of electromagnets 125 are provided, one about each shaft portion 52 and 54. As herein shown there are six electromagnets in each set, and each has a radial core 126 of good magnetic material having its inner end adjacent the shaft threaded into one of the sleeves 120, 124 in equally spaced relation about the periphery of the sleeve. It will be noted that these cores 126 of the electromagnets extend through openings in the mounting sleeves 26, 28, thus positioning them rigidly on the frame and preventing their rotation. The mag- 3 netic circuit is completed by six bars 128 of good magnetic material, one of which is provided between the outer end of corresponding cores 126 of the two sets of electromagnets. These bars are secured in good fluxconducting relation to the cores by cap screws 130, which extend through the bars and are threaded axially into the outer ends of the cores.

The shaft is provided at its upper end with a shoulder 132 against which the bearing 14 abuts. A reduced threaded portion 134 is provided to receive a nut 136 on the other side of the hearing. A closure member 138 is provided between the annular member 122 and the shaft, suitable sealing means being provided between this member and the shaft.

At the lower end of the pump an annular flange member 140 is provided which is similar to member 122 at the upper end of the pump. Flange member 140 is screwfastened to tubular mounting sleeve 28 of mounting ring 20. The bearing 16 is seated against suitable shoulders on flange member 140 and shaft portion 54, and is held in place by a nut 142 which is threaded on a portion of reduced diameter on the shaft at 144. A cap 146 threaded to member 140 provides a closure for the shaft at the lower end of the pump.

In FIG. 7, a tube cell 26a is shown, which differs from the tube cell described above in connection with FIGS. 1 through 6, by having an annular recess 147 provided in the outer ring 80a and a similar recess 148 provided in the inner ring 78a. The recesses 147 and 148 are adapted to contain silver. Suitable closures 150 and 152 are provided for the recesses which may be welded to the tube cell after the introduction of the silver.

In the operation of the pump, the coils are energized by a suitable D.-C. current, not shown. Magnetic flux generated in cores 126 by the coils of electromagnets 125 of the right-hand set of coils (FIG. 2) is fed into the sleeve 124 surrounding the shaft portion 54. The flux jumps the gap between sleeve 124 and shaft portion 54, this gap being maintained as small as possible, and enters the shaft. It travels along the shaft and, since it cannot flow through the nonmagnetic section 56, it flows outwardly through the pole piece 72 attached to shaft portion 54. The flux then jumps the gap between the pole faces 75 and in so doing passes through the liquid metal in the tube cell. The flux then flows along the shaft portion 52, jumps the gap into sleeve 120, flows through the cores 126 of the left-hand set of electromagnets, and then flows through bars 128 to the cores 126 of the right-hand set of coils, thus completing the circuit. The pole unit is smoothly faired and rounded to reduce magnetic loss, and is entirely chrome plated to reduce heat transfer by radiation from the tube cell to the poles.

Tube cell 76 is rectangular in shape and can be made entirely of a poor conductor, such as stainless steel, as shown in FIGS. 1 through 6. In either form it will be noted that large bosses are provided on the fuel cell to carry the current. The rectangular cross section is advantageous because of the fact that field strength varies inversely as the square of the distance separating the poles. The rectangular section allows a much greater flow area with a small air gap as compared with previous configurations.

The relative motion of a pole piece and therefore of a flux concentration past a section of the tube cell induces eddy currents in that section. Their amplitude is directly proportional to the rate of change of flux and inversely proportional to the electrical resistivity of the materials in that section. The eddy currents are so oriented that the magnetic flux caused by these currents interacts with the primary flux field in such a manner as to produce a force which opposes, or tends to reduce, the relative motion between the tube cell and the pole piece. Induced currents flowing through the cell also by interaction with the primary field tend to move the fluid along the tube passage 84. Since the wall of the tube cell is stationary, the interaction with the wall should be kept to a minimum. This is accomplished by making it of a material with as large an electrical resistivity as is practical. The energy absorbed by the tube wall is equal to the resistance heating of the wall multiplied by the eddy current flowing in the wall. Although the tube cell is stationary, the liquid metal inside the cell can move, and the force of interaction between the two magnetic fields and the induced currents will cause the liquid metal to flow around the loop. There will, of course, be some resistance heating in the liquid metal being pumped.

From the above description of one embodiment of the invention, it will be evident that a liquid metal pump has been provided which is light in weight and in which there is a minimum of rotating Weight due to the stationary coils.

It will also be evident that because of the fact that there are no rotating parts except the shaft and the two pole pieces, the pump is adapted to be built in large sizes without becoming cumbersome.

As a result of the novel tube cell and pole piece design, it has been possible to greatly increase the efficiency of the pump. The gain which has been made in pumping action is a result of making the longest length of the rectangular pole faces perpendicular to the flow direction and in making the cell rectangular to increase the flow path area with an actual decrease in the flux air gap length. The narrow pole gap also increases the peripheral length of changing flux with respect to the length of constant flux.

While only one embodiment of the invention has been illustrated and described, it will be understood that various changes may be made in the construction and arrangement of the various parts without exceeding the scope of the accompanying claims.

We claim: 7,

1. Apparatus for pumping electrically conductive fiuid comprising a stationary frame, a shaft journalled for rotation in said frame, an annular tube cell for the fluid to be pumped carried by said frame, said cell having a flow passage of rectangular cross section, said section having its greatest dimension perpendicular to the axis of said shaft, two pole members fixed on said shaft including like radially extending pole pieces having confronting rectangular pole faces on opposite sides of said tube cell, said pole faces having their greatest length perpendicular to the flow path through said cell, a set of stationary electromagnets adjacent each pole member, each of said magnets having a radially extended core, and means including said shaft for completing the electromagnetic circuits through said radial cores and said radial pole pieces.

2. Apparatus for pumping conductive fluid comprising a frame of nonmagnetic material, a shaft journalled for rotation in said frame having end portions of magnetic material and an intermediate portion of nonmagnetic material, a pole member mounted on each end portion of said shaft and rotatable therewith, each including a plurality of radially projecting pole pieces terminating in inwardly directed tips, said pole tips having confronting rectangular faces having their longest dimension disposed radially of said shaft axis, an annular tube cell carried by said frame and disposed between said pole faces, said cell being rectangular in cross section with its longest cross-sectional dimension located radially of said shaft axis, a sleeve of good magnetic material on each of said shaft portions, a series of electromagnets surrounding each of said sleeves, each electrom-agnet having a radial core threaded into its sleeve, and a plurality of longitudinal bars of good magnetic material connecting the outer ends of cores of corresponding magnets in said series.

3. In a liquid metal pump, a frame, a shaft rotatable in said frame, said shaft comprising three axially aligned connected sections, the end sections being formed of good magnetic material and the intermediate section being formed of nonmagnetic material, a series of radially disposed stationary coils surrounding each end section, each coil having a core the inner end of which terminates closely adjacent its shaft end, longitudinal bars of magnetic material connecting the outer ends of the cores of corresponding coils of the two series, a pole member cartried by each shaft end section and rotatable with said shaft, each of said pole members having a plurality of radially projecting pole pieces terminating in rectangular end faces, the faces of adjacent pole pieces of the two series being inwardly directed toward each other into spaced confronting relationship, an annular nonmagnetic tube cell located between said confronting pole faces, and means including a cell mounting ring carried by said frame and surrounding said cell for supporting said tube cell.

4. In a liquid metal pump, a frame of nonmagnetic material, a shaft journalled on bearings in said frame, said shaft having end portions of good magnetic material and an intermediate connecting portion of nonmagnetic material, a sleeve of good magnetic material on each end por-, tion, a series of stationary electromagnets arranged about each of said sleeves, each magnet having a radially disposed core threaded into its sleeve, said frame having a coil mounting sleeve surrounding each of said first-mentioned sleeves, said coil mounting sleeves having apertures therein through which said cores extend, pole members carried by the adjacent ends of said shaft end portions, said pole members having radially extended pole pieces, the pole pieces of said pole members terminating in inwardly directed pole tips having confronting rectangular faces, said rectangular faces having their longitudinal dimensions disposed radially of said shaft axis, an annular tube cell of rectangular cross section located between the confronting end faces of said pole pieces, means for sup: porting the periphery of said tube cell resiliently on said frame for limited radial movement, means carried by said frame for guiding said tube cell accurately during said radial movements, and a plurality of bars of magnetic material parallel with said shaft for connecting the outer ends of corresponding cores of said series of magnets to complete the magnetic circuits through said cores and said pole pieces.

5. In a liquid metal pump, a frame, a shaft journalled in said frame, said shaft having two portions of magnetic material and an intermediate portion of nonmagnetic ma terial, a pole member carried by each magnetic shaft portion having radially extended pole pieces, corresponding pole pieces of said pole members having mutually inwardly directed pole tips terminating in spaced confronting pole faces, means for establishing a magnetic field in the space between pairs of confronting pole faces including stationary electromagnets carried by said frame, said electromagnets having cores arranged radially about said magnetic shaft portions, the inner ends of each core terminating closely adjacent its associated magnetic shaft portion, an annular tube cell rectangular in cross section located between said pole faces through which liquid metal is to be pumped, and a flow divider in said cell providing inlet and outlet connections to said cell, said cell having its greater cross-sectional dimension radially disposed with respect to the axis of said shaft.

6. In a liquid metal pump, a frame, a shaft journalled in said frame, said shaft having two portions of magnetic material and an intermediate portion of nonmagnetic material, a pole member carried by each magnetic shaft portion having radially extended pole pieces, corresponding pole pieces of said pole members having mutually inwardly directed pole tip terminating in spaced confronting pole faces which are rectangula and which have their greatest cross-sectional dimension disposed radially of the axis of said shaft, means for establishing a magnetic field in the space between each pair of confronting pole faces including a set of electromagnets carried by said frame, each set having a magnet associated with each of said magnetic shaft portions, each electromagnet having a radial core, the inner end of which terminates closely adjacent its associated magnetic shaft portion, and an annular tube cell having its periphery supported on said frame and in the space located between said pole faces, said cell having a flow passage rectangular in cross section and having the direction of liquid metal flow therein perpendicular to the greater cross-sectional dimension of said pole faces.

7. In a liquid metal pump, a frame, a shaft journalled in said frame, said shaft having two portions of magnetic material and an intermediate portion of nonmagnetic material, a pole member carried by each magnetic portion having radially extended pole pieces, said pole pieces having spaced confronting rectangular pole faces, means for establishing a magnetic field in the space between each pair of confronting pole faces including a set of electromagnets carried by said frame, each set having a magnet associated with each of said magnetic shaft portions, each electromagnet having a radial core, the inner end of which terminates closely adjacent its associated magnetic shaft portion, an annular tube cell supported at its periphery on said frame and having a rectangula passage for the flow of liquid metal located in the field between said pole faces, said rectangular pole faces having their greater cross-sectional dimension perpendicular to the direction of liquid metal flow in said tube cell, and means for completing the magnetic circuit through said pole members.

8. In a liquid metal pump, a frame, a shaft journalled for rotation in said frame, said shaft having two portions of magnetic material connected by a portion of nonmagnetic material, a pole member carried by each magnetic portion having radially extended pole pieces, the corresponding pole pieces of said pole members having mutually inwardly directed pole tips terminating in spaced confronting pole faces rectangular in cross section, and means for establishing a magnetic field in the space between each pair of confronting pole faces including a pair of electromagnets carried by said frame, each electromagnet having a radial core the inner end of which terminates closely adjacent a dilferent one of said magnetic shaft portions, and an annular tube cell supported at its periphery on said frame having a liquid metal flow passage rectangular in cross section, said rectangular Pole faces having their greater cross-sectional dimension perpendicular to the direction of flow of said liquid metal in said flow passage, said tube cell having inner and outer annular bosses which overlie said inwardly directed pole tips.

9. In a liquid metal pump, a frame of nonmagnetic material, a shaft journalled for rotation in said frame having two magnetic portions and a connecting nonmagnetic portion, pole members carried by each magnetic portion and rotatable with said shaft, each member having a plurality of radially extended pole pieces, the corresponding pole pieces of said pole members having mutually inwardly directed pole tips terminating in spaced rectangular pole faces, and means for establishing a magnetic field in the space between said pair of confronting pole faces including a pair of electromagnets carried by said frame, each electromagnet having a radial core the inner end of each terminates closely adjacent a different one of said magnetic shaft portions, an annular tube cell having -a liquid metal flow passage which is rectangular in cross section, and means for supporting said tube on said frame with its rectangular flow passage in the space between said pole faces including an annular frame member surrounding said tube cell having radial passages spaced about its periphery, and spring-biased means projecting through said passages and engaging the periphery of said annular cell.

10. Apparatus for pumping electrically conductive fluids comprising a stationary frame, a shaft journalled for rotation in said frame, said shaft having end portions of magnetic material and a connecting intermediate portion of nonmagnetic material, two pole members mounted in spaced relation, one on each shaft end portion for rotation therewith, each -pole member including a plurality of radially extending pole pieces, the corresponding pole pieces on each shaft end portion having mutually inwardly directed free ends terminating in rectangular confronting pole faces, a stationary annular tube cell for the fluid to be pumped rectangular in cross section located between said pole faces, and two sets of stationary electromagnetic members, each set having a plurality of radially extended cores terminating at their inner ends close to a different one of said shaft end portions, and means comprised of good magnetic material connecting the outer ends of corresponding radial cores of said two electromagnetic sets.

11. Apparatus for pumping electrically conductive fluids comprising a stationary frame, a shaft journalled for rotation in said frame having end portions of magnetic material and an intermediate portion of nonmagnetic material, two pole members carried by said shaft end portions respectively and rotatable with said shaft, each including a plurality of radially extended pole pieces having confronting pole faces, :an annular tube cell rectangular in cross section located between said pole faces, a plurality of stationary electromagnets carried by said frame having cores, and means for completing the magnetic circuits through said cores and said pole pieces including sleeves of good magnetic material surrounding said shaft end portions into which the inner ends of the cores of said electromagnets are threaded and bars of magnetic material connecting the outer ends of the cores of corresponding electromagnets.

References Cited in the file of this patent UNITED STATES PATENTS 2,847,936 Richter Aug. 19, 1958 2,915,973 Findlay Dec. 8, 1959 2,928,349 Findlay Mar. 15, 1960 2,940,393 Baker June 14, 1960

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