US3198119A

US3198119A - Electro-magnetic pump

Info

Publication number: US3198119A
Application number: US306519A
Authority: US
Inventors: George N J Mead
Original assignee: Individual
Current assignee: Individual
Priority date: 1963-09-04
Filing date: 1963-09-04
Publication date: 1965-08-03
Anticipated expiration: 1982-08-03
Also published as: GB1052098A

Description

WE Pu L [.8 E g S U DH C Aug. 3, 1965 G. N. J. MEAD ELECTRO-MAGNETIC PUMP 4 Sheets-Sheet 1 Filed Sept. 4, 1965 w mE M md V WN E G R O E 6 Wow M ATTORNEYS Aug. 3, 1965 c. N. J. MEAD ELECTED-MAGNETIC PUMP 4 Sheets-Sheet 2 Filed Sept. 4 1963 INVENTOR GEORGE N.J. MEAD ATTORNEYS 3, 1965 G. N. J. MEAD 3,198,119

ELECTRO-MAGNETIC PUMP Filed Sept. 4, 1963 4 Sheets-Sheet 3 ATTORNEYS Aug. 3, 1965 s. N. J. MEAD ELECTRO-MAGNETIC PUMP 4 Sheets-Sheet 4 Filed Sept. 4, 1963 I NVENTOR.

GEORGE N. J MEAD MWWW ATTORNEYS United States Patent 3,198,119 ELECTRD-MAGNETIC PUMP George N. J. Mead, 5 Robin Lane, Exeter, NH. Filed Sept. 4, 1963, Ser. No. 306,519 Claims. (Cl. 1031) This invention relates generally to electro-magnetic pumps and more particularly is directed towards a new and improved electro-magnetic pump in which an electrically conductive fluid is moved axially along a conduit by the interaction of at least a pair of overlapping magnetic fields, one of which is fixed to the conduit and the other of which is formed by an electrical current passed spirally through the fluid between the walls of the conduit and its center axis.

In general, electro-magnetic pumps operate on the principle that a force is exerted upon a conductor (the fluid) carrying a current in a magnetic field. The high electrical conductivity of liquid metals makes it possible to pump by electro-magnetic means. For use in nuclear reactors, where a minimum amount of maintenance is desirable, electro-magnetic pumps are often preferable to conventional mechanical pumps because they have no moving parts, bearings, or seals. It has been found, for example, that highly corrosive liquid sodium, which is used as the primary coolant and moderator in some reactors, is diflicult to pump by mechanical means because of the rapid deterioration of the various parts of the pump.

To avoid this problem, electro-magnetic pumps are employed since they have no moving parts and they can be fabricated from materials which are substantially inert to the corrosive liquid. In addition to reactor systems, electro-magnetic pumps are also employed in transferring liquid or powdered metals, moving columns of mercury to operate actuators, mixing of molten metals in furnaces, pumping of liquid metals to die casting equipment and various other applications.

Heretofore direct current conduction pumps embodied applications of Flemings right-hand rule which states that a current passing at right angles to a magnetic field will produce a force at right angles to both. Pump performance depends upon the magnitude of the current, magnetic field intensity and the geometry of the pump duct. In its simplest form a pump of this type consists of a rectangular tube with electrodes attached to the short sides of the rectangular section and with the long axis of the section placed between the poles of a magnet. Thus current flowing through the fluid along the axis is cut by the magnetic field and produces a longitudinal thrust on the fluid in the tube. Corrections must be made for the magnetic field produced by the flow of current through the duct walls and provision must be made to minimize end losses (flow of current through the fluid but outside the magnetic field). The disadvantage of this type of pump is the very high current (thousands of amperes at low voltages typically 1 to 3 volts) required.

Heretofore, electro-magnetic pumps have been characterized by low operating efliciency as the result of high pumping losses and by armature reaction or eddy current losses. Also, the pressure output attainable by existing electro-magnetic fluid pumps generally has been substantially below that of a mechanical pump. Pumps of this type have also been bulky and heavy by reason of iron jackets which form part of the electro-magnetic circuit and by auxiliary cooling systems sometimes provided for the coil windings which may function in the range of 1000 F. or more. A further disadvantage of existing electro-magnetic pumps is their requirement for operating on high current and low voltage levels necessitating specialized and expensive power supplies. The losses for such systems have proven to be quite high so that the equipment and its operation are substantially higher than comparable positive displacement pumps.

Accordingly, is is an object of the present invention to provide improvements in electro-magnetic conductive fluid pumps.

Another object of this invention is to reduce the pumping losses and otherwise improve the eflficiency in electromagnetic conductive fluid pumps.

Still another object of this invention is to provide an electro-magnetic conductive fluid pump capable of highpressure operation and of simple, low-cost construction.

A further object of this invention is to provide an electro-magnetic conductive fluid pump adapted to func tion at high voltages to reduce the heat loss for a given power input and to eliminate the specialized power generating equipment required for high current, low voltage pumps.

More particularly this invention features a direct current electro-magnetic conductive fluid pump comprising a conduit for the conductive fluid with a plurality of fixed magnetic elements disposed along the conduit and oriented with their axes parallel to the axis of the conduit. The magnets are disopsed in end-to-end relation with the fields of adjacent magnets opposing one another. In one embodiment one electrode extends along the conduit axis and other electrode extends along the inner surface of the conduit. A spiral non-conducting baffle disposed within the conduit provides a spiral fluid connection between the electrodes. In the practice of the invention, a series of batfles are disposed lengthwise within the conduit with adjacent baflies having reversely wound spirals and with each baflle terminating midway between the poles of a fixed magnet. Current applied to the electrodes will flow spirally towards the center of the conduit to produce a magnetic field which will react with the field of the magnets to produce a flow of fluid. Each spiral of conducting fluid thus constitutes a fluid electromagnet with the fields of adjacent baflle sections opposing one another.

The interaction between the fields of the fixed magnets and the fields of the fluid electro-magnets produces a resultant axial force on the fluid electromagnets. Since the conductive fluid carries the electric current that establishes the field of the fluid electro-magnet, the conductive fluid is propelled axially along the conduit.

This invention also features an electro-magnetic conductive fluid pump comprising a pair of coaxial conduits each having alternating spiral battles to form fluid electromagnets and interacting in such a fashion that conductive fluid within the inner conduit is pumped in one direction while fluid in the outer conduit is pumped in the opposite direction.

This invention also features a novel arrangement for switching the electrodes so as to reverse the magnetic fields of adjacent spiral baflies.

But these and other features of the invention, along with further objects and advantages thereof, will become more fully apparent from the following detailed description of the preferred embodiments of the invention, with reference being made to the accompanying drawings, in which:

FIG. 1 is a partially exploded perspective view, somewhat schematic, of an electro-magnetic fluid conductive pump made according to the invention,

FIG. 2 is a sectional view in side elevation of the pump shown in FIG. 1,

FIG. 3 is a cross-sectional View taken along the line 3-3 of FIG. 2,

FIG. 4 is a cross-sectional view taken along the line 44 of FIG. 2,

FIG. 5 is a schematic diagram showing the polar relationship of the pump sections,

FIG. 6 is a sectional view in side elevation showing a modification of the invention,

FIG. 7 is a cross-sectional view taken along the line 7-7 of FIG. 6,

FIG. 8 is a sectional view in side elevation of another modification of the invention,

FIG. 9 is a cross-sectional view taken along the line 9-9 of FIG. 8,

FIG. 10 is a cross-sectional view taken along the line 10-10 of FIG. 8, and

FIG. 11 is a sectional View taken along the line 1111 of FIG. 9.

Referring now to the drawings, the reference character 10 generally indicates an electro-magnetic pump, comprising a tubular conduit 12, typically fabricated from stainless steel or other suitable material coated on its inner surface with a refractory material, such as zirconia or the like, to electrically insulate the conduit from an electrically conductive fluid medium passing through the conduit. Disposed along the outer cylindrical surface of the conduit 12, is a series of electromagnets 16 each comprising a winding 18 and an iron jacket 20 for reducing the reluctance of the magnetic circuit. The electro-magnets 16 are disopsed coaxially with the conduit 12, and each electro-magnet is oriented with its magnetic field opposing that of its adjacent electro-rnagnet. In practice this may be done by means of a continuous conductor with the direction of winding 18 of the coil for one electro-magnet being reversed from the adjacent electro-magnet as suggested in FIG. 1.

Extending lengthwise along the inner wall of the conduit 12 is an electrically conductive strip 22 which forms the negative electrode of a DC. circuit to be described herein. Extending along the center axis of the conduit 12 is the positive electrode of the circuit in the form of an elongated conductive rod 24. Mounted in end to end relation within the conduit 12 is a series of axially straight baflles 26 which wind spirally from the rod 24 to the inner wall of the conduit 12 adjacent the electrode 22. The baflles are open-ended to define axial passages for the flow of an electrically conductive fluid medium which is to be pumped while at the same time forming a spiral path for the flow of current between the positive and

negative electrodes

22 and 24. In practice the baffles 26 may be fabricated from the same material as the conduit 12, that is stainless steel, with the exposed surfaces coated with a refractory material to provide electrical insulation. The

electrodes

22 and 24 may be formed from any suitable material such as nickel, iron or copper, depending upon the fluid medium which is to be pumped. If, for example, mercury is to be pumped through the device, a copper electrode would have to be coated with an inert material such as rhodium to prevent amalgamation.

It will be noted in the drawings that the spiral baflles 26 alternate in their direction of winding (left-hand, right-hand, etc.) from one baflle to the next. Also it will be noted that each baflie has substantially the same axial length as an electro-magnet 16, but the baflies and electro-magnets are arranged so that each spiral bafile overlaps an electro-magnet by half a length.

It will be understood that a DC current applied to the

electrodes

22 and 24 will flow in a spiral path through the conductive fluid medium from one electrode to the other. This spiral current flow will produce a flux pattern similar to an electromagnet 16. Thus, each spiral of conducting fluid acts as a fluid electro-magnet having its own flux which may co-act with that of the electro-magnet 16 fixed to the conduit. By reason of the fact the direction of spiral reverses from one baffle to an adjacent bafile, the fields developed by the fluid electro-magnets will oppose one another. In FIG. the polarity of the fields of the fluid electro-magnets are shown in relation to the polarity of the fields of the fixed electro-magnets with the several fields being arranged to produce a component of force axially along the conduit. In FIG. 5,

it will be seen that the right hand or north pole end of a fluid electro-magnet A is located mid-way between the poles of a fixed electro-magnet 16. This will produce a magnetic repulsion to the right between the north pole or" the fluid electro-magnet A and the north pole of the first fixed electro-magnet 16. At the same time there will be an attraction between the south pole of the fluid electro-magnet A and the north pole of the fixed electromagnet 16. The result will be that the conductive fluid which is free to flow axially will be pumped to the right along the conduit 12, as viewed in FIG. 5.

This action will be repeated in stages along the length of the pump. For example, as the fluid enters the second baflle, the direction of the spiral will be reversed so that the polarity of the fluid electro-magnet B will be opposing that of the fluid electro-magnet A. Thus the north pole of the fluid electro-magnet B will be attracted to the south pole common to the first two fixed electromagnets 16, and there will be a repulsion between the south pole of the second fluid electro-magnet B and the south pole common to the first two fixed electro-magnets 16. Since the conductive fluid carries the electric current that establishes the field of the electro-magnet, the conductive fluid is propelled axially along the conduit.

Insofar as the magnetic poles of the fixed electro-magnets and the fluid electro-magnets maintain their position relative to one another because the spiral baffles and the electro-magnets 16 are fixed relative to one another only the fluid can move and the propulsive force remains constant.

By employing a spiral path to produce a fluid electromagnet, the pumping action is increased substantially over a one pass flow of electricity. In addition, the arrangement requires a higher voltage than other electromagnetic pumps thus eliminating ineflicient high-current, low-voltage power supplies. Commutation occurs within each given fluid particle which undergoes a reversal of current as it flows between a right-hand and a lefthand spiral baflle. There is no problem of short circuiting or sparking. The flow of the fluid medium may be improved by forming a gap between adjacent baflles and insulating the

electrodes

22 and 24 over the span of the gap to prevent short circuiting.

The use of iron jackets 20 reduces the reluctance of the flux and thereby intensifies the pumping action. The thickness of the iron jacket 20 may be reduced between like poles in view of the fact that the lines of the flux between like poles cancel each other whereas between unlike poles the lines of flux combine. As best shown in FIG. 2, the jackets 20 will be seen to be reduced in thickness at zones 28 lying between like poles of adjacent electro-magnets. To improve the flow of flux into and out of the conduit 12, an iron spacer 30 is located around the conduit between adjacent sets of electro-magnets.

If the fluid medium which is being pumped through the conduit is at a low temperature, the coil windings 18 may be located close to or in direct contact to the surface of the conduit for conductive cooling by the fluid medium. Alternatively, where high-temperature fluids are being pumped, the windings 18 may be displaced outwardly from the conduit and an auxiliary cooling system added if required.

In FIGS. 6 and 7 there is shown a modification of the invention, and in this embodiment a double flow electromagnetic pump is provided. As shown, the modification includes a pair of

concentric conduits

30 and 32 with the 1111161 conduit 32 extending in spaced parallel relation within the outer conduit 30. The inner conduit 32 is of a construction similar to that of the principal embodiment with the exception that there are no electro-magnets fixed to the outer surface of the conduit 32. In place of the fixed electro-magnets, a series of fluid electro-magnets 34 are employed. As before the inner conduit 32 includes a series of spiral bafiies 36 with the direction of each spiral alternating from one baflle to the next.

Extending axially along the center of the conduit 32 is an elongated rod 38 of conductive material forming the positive electrode of the pump circuit. In this instance, the negative electrode is in the form of a strip disposed lengthwise along the wall of the outer conduit 30. A con ductive strip 40 is disposed lengthwise along the inner conduit 32 to provide series connection between the inner fluid electro-magnets and the outer fluid electro-magnets.

The outer fluid electro-magnets 34 comprise a seres of spiral bafiles with adjacent baffles wound in opposite directions and with the bafiles 42 of the outer conduit overlapping the baffles 36 of the inner conduit.

It will be understood that a current applied to the electrodes 38 and 40 will flow in a spiral clockwise path in the annular space formed between the outer and inner conduits in the case of the section of FIG. 7. The current will then pass through the connecting strip 40 to flow in the annular space between the inner conduit 32 and the rod 38 in a counter-clockwise direction. The opposing fields set up by the spiral currents will cause the conductive fluid within the inner conduit to flow to the right, as viewed in FIG. 6, and the fluid in the outer conduit to flow to the left. It will be understood that the outer fluid electro-magnets 34 replace the conventional electro-magnets 16 of the principal embodiment. The spiral baffles are arranged in such a fashion that the polarity arrangement corresponds with that of the principal embodiment as indicated in FIG. 5.

A pump of this construction may be employed in instances where the conductive fluid medium is too hot for conventional copper windings. This arrangement avoids the necessity of adding a special cooling system for the copper conductors. As an added advantage, the fluid windings may be connected in series and thereby increase the voltage requirements of the power supply. As in the first embodiment the reluctance of the flux may be reduced by employing an iron jacket about the outer conduit 30.

Referring now more particularly to FIGS. 8, 9 and 10, there is illustrated another modification of the invention in which a conduit 44 is provided with a series of electromagnets 46 and baflles 48 in an arrangement similar to the pump of FIGS. 1-5. However, in this embodiment a pair of

electrodes

50 and 52 are both located along the wall of the conduit 44. The two electrodes, one being the positive terminal and the other being the negative terminal of a DC circuit, are in strip form and extend lengthwise along the conduit. A single non-conductive spiral, wound in one direction only, extends the full length of the pump with a conductive tube or rod 54 connected along the center.

The two

electrodes

50 and 52 are disposed along the line where the balfle meets the inner surface of the conduit, one electrode being disposed on the left-hand side of the joint between the baflle and the conduit, and the other electrode being disposed on the right-hand side there of as viewed in FIGS. 9 and 10. As appears in FIG. 9, the left-hand electrode which may be connected to the positive terminal of the power supply, is exposed to the fluid medium within the conduit while the right-hand electrode 52, which may be connected to the negative side of the power supply, is covered by a strata of electrically insulating material 56. In the adjacent bafile section, as shown in FIG. 10, the positive electrode 50 is covered with insulation 58, while the negative electrode 52 is exposed. This arrangement is continued throughout all sections of the pump with alternate fluid electrode magnets having first the negative and then the positive electrode insulated.

In operation, with the positive electrode of FIG. 9 exposed, a current flows spirally and counterclockwise to the conductive rod 54, and then axially along the rod to the adjacent spiral section where the current flows clockwise from the conductive rod to the exposed negative electrode 52 and so on along the pump. Short circuiting between exposed electrodes is avoided by causing the current to make a complete circuit around the conduit. Magnetic fields with incorrect polarity are prevented by an insulator 59 which blocks the electric current from flowing counterclockwise in the section of FIG. 10 and in all other clockwise fluid electro-magnets. The system may be optimized by increasing the resistance of the outer fluid winding and decreasing the resistance of the inner fluid winding. This condition may be obtained by adjusting the spacing of the spiral convolutions. It will be appreciated that the current is forced to make two spiral traversals of the fluid between the two electrodes which will cause a higher voltage to be required of the power supply.

The present invention has a number of distinct advantages. For example, by causing the fluid to move axially along the lines of action of the applied forces, pumping loses are minimized and efficiency is increased. In addition there is no armature reaction which would tend to reduce efficiency. The pumping action may be increased by merely increasing the number of fixed and fluid magnets and arranging their fields in the proper relation. Thus a high pressure head may be obtained.

The present pump offers both high flow and high pressure capabilities at an efliciency superior to pumps of this type heretofore available. As another advantage the pump is characterized by a very high rate of energy conversion within a restricted volume. The inherently small frontal area per unit of flow area permits high.

Volume pumping and also makes the pump suitable as a propulsion tube in sea water, for example. Obviously the pump may be employed for driving auxiliary equipment, such as a turbine or other device as desired.

While the invention has been described with particular reference to the illustrated embodiments, it will be understood that numerous modifications thereto will ap pear to those skilled in the art. Accordingly, the above description and accompanying drawings should be taken as illustrative of the invention and not in a limiting sense.

Having thus described the invention, what I claim and desire to obtain by Letters Patent of the United States 1s:

1. A device for pumping an electrically conductive fluid medium, comprising a conduit for said medium, magnetic means fixed to said conduit for producing a first magnetic field lengthwise thereof, a first electrode adjacent the inner surface of said conduit, a second electrode spaced from said first electrode and within said conduit, an electrically insulating wall extending in a spiral path from said first electrode to said second electrode and defining an axial passage for the flow of said medium, and means for applying a DC. current to said electrodes whereby said current will flow through said medium in a spiral path between said electrodes defining a fluid electro-magnet to produce a second magnetic field extending lengthwise of said first magnetic field for interaction with said first field, the interaction of said fields being operative to pump said medium in an axial direction.

2. A device according to claim 1 wherein said magnetic means includes conductive windings disposed about said conduit.

3. A device according to claim 1 wherein said second electrode is disposed along the center longtudinal axis of said conduit.

4. A device according to claim 1 wherein said magnetic means axially overlaps said fluid electro-magnets.

5. A device for pumping an electrically conductive fluid medium, comprising a conduit for said medium, magnetic means fixed to said conduit for producing a first magnetic field lengthwise thereof, a first electrode extending lengthwise adjacent the inner surface of said conduit, a second electrode parallel to said first and disposed inwardly thereof, an electrically insulating wall extending in a spiral path from said first electrode to said second electrode and efining an axial passage for the flow of said medium, said Wall and said magnetic means being disposed in overlapping relation and means for applying a DC. current to said electrodes whereby said current will flow through said medium in a spiral path between said electrodes to produce a second magnetic field extending lengthwise of said first magnetic field for interaction with said first field, the interaction of said fields being operative to pump said medium in an axial direction.

6. A device according to claim wherein said magnetic means includes an iron annulus to reduce the reluctance of said first magnetic field.

7. A device for pumping an electrically conductive fluid medium, comprising a conduit for said medium, a plurality of magnetic means in alternating polar relation fixed to said conduit for producing first magnetic fields lengthwise of said conduit, first and second electrodes extending in spaced parallel relation lengthwise adjacent the inner surface of said conduit, a conductor parallel to said electrodes and disposed inwardly thereof, an electrically insulating wall extending in a spiral path from said first electrode to said second electrode and defining an axial passage for the flow of said medium, each of said electrodes having sections that are alternately insulated and exposed to the fluid medium with each section extending in overlapping relation to adjacent magnetic means, the insulated and exposed sections of one electrode being staggered with respect to the other electrode and means for applying a DC. current to said electrodes whereby said current will flow through said medium inwardly in a spiral path from one electrode to said conductor, axially along said conductor, and outwardly in a spiral path to another electrode, the current flow being clockwise in one section and counterclockwise in an adjacent section to produce second magnetic fields in alternating polar relation extending lengthwise of said first magnetic fields for interaction with said first fields, the interaction of said fields being operative to pump said medium in an axial direction.

8. A device for pumping an electrically conductive fluid medium, comprising a conduit for said medium, a plurality of magnetic means in alternating polar relation fixed to said conduit for producing first magnetic fields lengthwise of said conduit, a first electrode extending lengthwise adjacent the inner surface of said conduit, a second electrode parallel to said first and disposed inwardly thereof and a plurality of axially adjacent electrically insulating walls extending in spiral paths from said first electrode to said second electrode and defining an axial passage for the flow of said medium, the direction of spiral of one wall being opposite to that of an adjacent wall, said walls and said magnetic means being disposed in overlapping relation and means for applying a DC. current to said electrodes whereby said current will flow through said medium in spiral paths of alternating directions between said electrodes to produce second magnetic fields extending lengthwise of said first magnetic fields for interaction with said first fields, the interaction of said fields being operative to pump said medium in an axial direction.

9. A device according to claim 8 wherein said magnetic means comprises a second conduit concentric with the first mentioned conduit and defining an annular fluid passage therewith, a plurality of spiral walls extending between said conduits, the direction of spiral of one wall being opposite to that of an adjacent wall and means for applying a DC. current between said conduits to form said first magnetic fields.

10. A device for pumping continuously an electrically conductive fluid medium, comprising a conduit open at both ends for said medium, means fixed to said conduit for producing a first magnetic field lengthwise of said conduit, a pair of spaced electrodes within said conduit and extending lengthwise thereof, curved Walls extending between said electrodes to define a curved passage for said medium, said passage being in free communication throughout with said conduit for the free flow of said medium from said conduit through said passage, and means for applying a current to said electrodes whereby said current will flow through said medium in a curved path between said electrodes to define a fluid electro-magnet operative to produce a second magnetic field extending lengthwise of said conduit for interaction with said first magnetic field, the interaction of said fields being operative to pump said medium under pressure lengthwise of said conduit.

References Cited by the Examiner UNITED STATES PATENTS 2,807,212 9/57 Lindenblad 103-1 2,982,214 5/61 Cochran et a1 1031 3,084,629 4/63 Yevick 103-1 LAURENCE V. EFNER, Primary Examiner.

Claims

1. A DEVICE FOR PUMPING AN ELECTRICALLY CONDUCTIVE FLUID MEDIUM, COMPRISING AN CONDUIT FOR SAID MEDIUM, MAGNETIC MEANS FIXED TO SAID CONDUIT FOR PRODUCING A FIRST MAGNETIC FIELD LENGTHWISE THEREOF, A FIRST ELECTRODE ADJACENT THE INNER SURFACE OF SAID CONDUIT, A SECOND ELECTRODE SPACED FROM SAID FIRST ELECTRODE AND WITHIN SAID CONDUIT, AN ELECTRICALLY INSULATING WALL EXTENDING IN A SPIRAL PATH FROM SAID FIRST ELECTRODE TO SAID SECOND ELECTRODE AND DEFINING AN AXIAL PASSAGE FOR THE FLOW OF SAID MEDIUM, AND MEANS FOR APPLYING A D.C. CURRENT TO SAID ELECTRODES WHEREBY SAID CURRENT WILL FLOW THROUGH SAID