Double-duct liquid metal magnetohydrodynamic engine

• US 5,637,935 A
• Filed: 05/05/1994
• Issued: 06/10/1997
• Est. Priority Date: 03/24/1994
• Status: Expired due to Fees

• Current Assignee: Martin Marietta Energy Systems, Inc.
• Original Assignee: Martin Marietta Energy Systems, Inc.
• Inventors: Haaland, Carsten M.
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): JONES, JUDSON
• Application Number:
  US08/238,281
• Time in Patent Office: 1,132 Days
• Field of Search: 310/11
• US Class Current: 310/11
• CPC Class Codes: F02G 1/0435 the engine being of the free piston type
• CPC Class Codes: F02G 2243/54 thermo-acoustic
• CPC Class Codes: F02G 2244/50 Double acting piston machines
• CPC Class Codes: H02K 44/085 with conducting liquids
• CPC Class Codes: H02K 44/24 by reversing the direction of fluid
• CPC Class Codes: H02K 7/1884 structurally associated with free piston engines

Abstract

An internal combustion, liquid metal (LM) magnetohydrodynamic (MHD) engine and an alternating current (AC) magnetohydrodynamic generator, are used in combination to provide useful AC electric energy output. The engine design has four pistons and a double duct configuration, with each duct containing sodium potassium liquid metal confined between free pistons located at either end of the duct. The liquid metal is forced to flow back and forth in the duct by the movement of the pistons, which are alternatively driven by an internal combustion process. In the MHD generator, the two LM-MHD ducts pass in close proximity through a Hartmann duct with output transformer. AC power is produced by operating the engine with the liquid metal in the two generator ducts always flowing in counter directions. The amount of liquid metal maintained in the ducts may be varied. This provides a variable stroke length for the pistons. The engine/generator provides variable AC power at variable frequencies that correspond to the power demands of the vehicular propulsion. Also the engine should maintain nearly constant efficiency throughout the range of power usage. Automobiles and trucks could be powered by the invention, with no transmission or power converter devices being required.

Claims

1. A magnetohydrodynamic apparatus comprising:

first sealed duet means for containing a quantity of liquid metal;

second duct means for containing a quantity of liquid metal;

piston means for imparting reciprocating motion in the liquid metal contained in the first and second ducts in opposite directions; and

means for imposing a magnetic field on a portion of the first and second duct means, thereby generating an AC electric potential.

2. A magnetohydrodynamic apparatus according to claim 1, wherein each of the first and second duct means includes a Hartmann duct portion having top and bottom insulating walls and two opposite side conductive walls.

3. A magnetohydrodynamic apparatus according to claim 2, wherein the Hartmann duct portions of the first and second duct means are vertically stacked and assembled to include a common insulating wall therebetween, the side conductive walls of each being vertically aligned.

4. A magnetohydrodynamic apparatus according to claim 1, wherein the means for imposing a magnetic field comprises a permanent magnet having north and south pole pieces separated by a gap.

5. A magnetohydrodynamic apparatus according to claim 4, wherein each of the first and second duct means includes a Hartmann duct portion which converge one over the other in the gap of the permanent magnet.

6. A magnetohydrodynamic apparatus according to claim 5, wherein the Hartmann duct portions of the first and second duct means comprise three spaced apart parallel insulating plates, first and second side wall electrodes disposed between an upper-most one and medial one of the three insulating plates to form the Hartmann portion of the first duct means, and third and fourth side wall electrodes disposed between a lower-most one and the medial one of the three insulating plates to form the Hartmann portion of the second duct means.

7. A magnetohydrodynamic apparatus according to claim 6, further comprising a bus bar electrically connecting the first and third side wall electrodes, and a transformer electrically connected to the second and fourth side wall electrodes.

8. A magnetohydrodynamic apparatus according to claim 1, wherein the each of the first and second duct means includes first and second opposite end portions.

9. A magnetohydrodynamic apparatus according to claim 8, further comprising first and second fluid-moving pistons disposed respectively in the first and second opposite end portions of the first duct means for confining the liquid metal therebetween, and third and fourth fluid-moving pistons disposed respectively in the opposite end portions of the second duct means for confining the liquid metal therebetween.

10. A magnetohydrodynamic apparatus according to claim 9, wherein the means for imparting reciprocating motion comprises an internal combustion engine having first, second, third and fourth reciprocating combustion pistons coupled respectively to the first, second, third and fourth fluid-moving pistons through coupling means.

11. A magnetohydrodynamic apparatus according to claim 10, wherein the coupling means comprise magnetic material imposing a magnetic attraction between the combustion pistons and corresponding fluid-moving pistons.

12. A magnetohydrodynamic apparatus according to claim 11, wherein the first and second opposite end portions of the first and second duct means are made of non-conductive composite material.

13. A magnetohydrodynamic apparatus according to claim 12, wherein each combustion piston includes a hollow shank which slidably engages corresponding end portions of the first and second duct means.

14. A magnetohydrodynamic apparatus according to claim 1, further comprising means for adjusting the amount of liquid metal in each of the first and second duct means.

15. A magnetohydrodynamic apparatus according to claim 10, further comprising means for adjusting the amount of liquid metal in each of the first and second duct means.

16. A magnetohydrodynamic apparatus according to claim 15, wherein the adjusting means comprises first and second liquid metal reservoirs in fluid communication with the first duct means, and second and third liquid metal reservoirs in fluid communication with the second duct means, a stroke length of the combustion pistons varying in accordance with variations in the amount of liquid metal in the first and second duct means.

17. A magnetohydrodynamic apparatus according to claim 16, wherein each combustion piston is disposed in a corresponding combustion cylinder having a side-ported adjustable sleeve, the sleeve being positionally adjustable to correspond to changes in combustion piston stroke length.

18. A magnetohydrodynamic apparatus comprising:

a first duct having first and second closed, opposite axial ends and a Hartmann portion disposed between the opposite axial ends;

a second duct having first and second closed, opposite axial ends and a Hartmann portion disposed between the opposite axial ends;

the Hartmann portions of the first and second ducts being formed by three vertically spaced apart insulating plates, first and second conductive side electrode plates disposed between an upper-most one and a medial one of the three insulating plates, and third and fourth conductive side electrode plates disposed between a lower-most one and the medial one of the three insulating plates;

a permanent magnet having north and south pole pieces and a gap, the Hartmann portions of the first and second ducts being disposed in the gap of the permanent magnet;

first and second fluid-moving pistons disposed in opposite end portions of the first duct and confining a quantity of liquid metal therebetween;

third and fourth fluid-moving pistons disposed in opposite end portions of the second duct and confining a quantity of liquid metal therebetween; and

means for imparting synchronous, reciprocating motion in the first, second, third and fourth fluid-moving pistons to thereby impart reciprocating movement of liquid metal through the first and second ducts in opposite directions.

19. A method of producing AC electric current comprising the steps of:

containing a quantity of liquid metal in first duct means;

containing a quantity of liquid metal in a second duct means;

juxtaposing a portion of the first and second duct means;

imparting reciprocating motion in the liquid metal contained in the first and second duct means in opposite directions; and

imposing a magnetic field on the juxtaposed portions of the first and second duct means, thereby generating an AC electric potential as the liquid metal passes through the magnetic field in opposite directions.

20. A method according to claim 19 wherein the step of imparting reciprocating motion comprises driving fluid-moving pistons disposed in opposite ends of each of the first and second duct means with an internal combustion engine.

21. A magnetohydrodynamic apparatus comprising:

first duct means for containing a quantity of liquid metal;

second duct means for containing a quantity of liquid metal;

internal combustion means, disposed at opposite ends of each of the first and second duct means, for imparting reciprocating motion in the liquid metal contained in the first and second ducts in opposite directions;

starter means, disposed in the first and second duct means, for starting the internal combustion means; and

field means for imposing a magnetic field on a portion of the first and second duct means, thereby generating an AC electric potential.

22. A magnetohydrodynamic apparatus according to claim 21, wherein the starter means comprises first and second Hartmann devices disposed respectively in the first and second duct means.

23. A magnetohydrodynamic apparatus according to claim 22, wherein each of the first and second Hartmann devices includes an AC electromagnetic, and two opposite side electrodes.

24. A magnetohydrodynamic apparatus according to claim 23, further comprising a DC power source having an inverted AC output simultaneously coupled to the field means, and to the electromagnets and two opposite side electrodes of the first and second Hartmann devices.