US3450905A - Wall structures of magnetohydrodynamic conversion ducts and method of fabrication of said structures - Google Patents

Wall structures of magnetohydrodynamic conversion ducts and method of fabrication of said structures Download PDF

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Publication number
US3450905A
US3450905A US617198A US3450905DA US3450905A US 3450905 A US3450905 A US 3450905A US 617198 A US617198 A US 617198A US 3450905D A US3450905D A US 3450905DA US 3450905 A US3450905 A US 3450905A
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United States
Prior art keywords
structures
electrodes
ducts
fabrication
duct
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Expired - Lifetime
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US617198A
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English (en)
Inventor
David Yerouchalmi
Pierre Zettwoog
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K44/00—Machines in which the dynamo-electric interaction between a plasma or flow of conductive liquid or of fluid-borne conductive or magnetic particles and a coil system or magnetic field converts energy of mass flow into electrical energy or vice versa
    • H02K44/08—Magnetohydrodynamic [MHD] generators
    • H02K44/12—Constructional details of fluid channels

Definitions

  • a wall structure for magnetohydrodynamic conversion ducts is constituted by an alternate arrangement of thin segments of refractory metals which form conducting electrodes and segments of refractory materials which form thermal and electric insulators, said electrodes being adapted to project inwardly from the internal surface of the duct wall.
  • the present invention relates to wall structures of magnetohydrodynamic (MHD) conversion ducts of the closed-loop type.
  • MHD magnetohydrodynamic
  • the resistance of a material to chemical attack and its properties of non-contamination of the plasma are greater as the temperature of the material is lower, which runs counter to the need for minimized thermal losses and good thermionic emission.
  • the distribution of electric potentials as defined by the series of electrodes and insulators can be impaired by short-circuits which take place behind the electrodes, in particular across ceramic materials which have been rendered conductive either by deposition or by migration of cesium vapors, or even by condensed liquid cesium.
  • the Wall structures of MHD conversion ducts in accordance with the invention are characterized in that they are constituted by an alternate arrangement of thin segments of refractory metals forming the electrodes and segments of refractory materials which serve as thermal Patented June 17, 1969 and electric insulating material, said electrodes being adapted to project inwardly from the internal wall of the duct.
  • the electrode segments attain their working temperature at a fast rate.
  • the process of heat transfer by convection at high velocity from the hot plasma to the insulating walls takes place either by conduction through the segments which is negligible owing to the small thickness of said segments or by convection at low velocity or conduction within the spaces filled with gases which are trapped between each segment, this heat transfer process being also of low efficiency if the segments are set fairly close together.
  • the main temperature difference between ambient temperature and the plasma is therefore within the layer which is immediately adjacent to the insulating refractories, the thermal flux being of a low order and the ceramic elements being at low temperatures.
  • FIG. 1 shows diagrammatically a portion of a MHD duct in accordance with the invention
  • FIG. 2 is a longitudinal sectional view of a MHD conversion duct
  • FIGS. 3 and 4 are two transverse sectional views of a MHD conversion duct, the view of FIG. 3 being taken in cross-section along the line I-I of FIG. 1;
  • FIGS. 5, 6 and 7 illustrate the assembly of the different elements of a duct in accordance with the invention.
  • the MHD conversion duct is fabricated of a refractory material such as alumina, beryllium oxide or boron nitride and the electrodes are fabricated of a refractory material such as tantalum, nickel or of a noble metal such as platinum.
  • the duct may have any desired cross-sectional profile without thereby affecting the properties claimed.
  • reference will more especially be made to a duct of circular cross-sectional configuration, although it will be understood that the invention also applies to ducts having other cross-sectional shapes.
  • the invention is also concerned with a method of fabrication of these ducts and comprises two modes of execution.
  • a tube fabricated for example, of alumina is cut lengthwise along a chord of the circular cross-section which projects by approximately 10% beyond the diameter-line of said cross-section as shown in FIGS. 3 and 4.
  • the same operation is repeated in the case of a second tube having the same length and the same circular cross-section.
  • a suitable scarf joint as shown in FIG. 7
  • Such pairs of elements can be joined lengthwise in interfitting relation with pairs of elements having the same dimensions so as to constitute ducts of the required length. As is thus shown in FIG. 5, two pairs of elements 1, 2 and 1, 2 can accordingly be fitted one inside the other and FIG. 6
  • the complete structural assembly thus formed is housed within a concentric tube fabricated, for example, of aluminum oxide, thereby centering the MHD conversion duct and ensuring leak-tightness.
  • the semi-cylindrical tubes are provided internally with equidistant grooves 3 of small width and depth for the purpose of accommodating annular metal segments 4 which constitute the electrodes.
  • the grooves referred to are formed, for example, by means of a diamond-tipped saw.
  • the annular segments had a thickness varying between 0.25 mm. and 0.5 mm. and a depth of the order of 0.5 mm. and were separated by 0.5 mm. of ceramic material.
  • the second mode of execution of the invention is more especially applicable to the case in which the thermal masses of the electrodes are very small with respect to the ceramic insulators which surround these latter.
  • a ceramic tube is employed as a starting element and cut with a diamond-tipped saw. The tube is then re-assembled by placing thin annular segments 4 of refractory metal between the ceramic rings 5, as shown in FIG, 2.
  • ceramic rings have a thickness, for example, of 0.25 to l being lower than that of the ceramic material constituting the tube, then sintered at a temperature of the order of 1600 C.
  • the completed assembly is fitted within a concentric tube of refractory material which ensures leak-tightness and centering of the MHD conversion duct while at the same time preventing any short-circuits within the duct support structure.
  • Wall structures for magnetohydrodynamic conversion ducts comprising an alternate arrangement of thin segments of refractory metals forming the electrodes and segments of refractory thermal and electric insulation material, said electrodes projecting inwardly from the internal wall of the duct, the ratio of the internal projection of said electrode to the distance between adjacent ones of said electrodes being approximately 1:5.

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Measuring Volume Flow (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
US617198A 1966-03-09 1967-02-20 Wall structures of magnetohydrodynamic conversion ducts and method of fabrication of said structures Expired - Lifetime US3450905A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR52619A FR1478505A (fr) 1966-03-09 1966-03-09 Structures de parois de tuyères de conversion par magnétohydrodynamique et leur procédé de fabrication

Publications (1)

Publication Number Publication Date
US3450905A true US3450905A (en) 1969-06-17

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Family Applications (1)

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US617198A Expired - Lifetime US3450905A (en) 1966-03-09 1967-02-20 Wall structures of magnetohydrodynamic conversion ducts and method of fabrication of said structures

Country Status (9)

Country Link
US (1) US3450905A (en。)
BE (1) BE694113A (en。)
CH (1) CH470809A (en。)
ES (1) ES337745A1 (en。)
FR (1) FR1478505A (en。)
GB (1) GB1139375A (en。)
IL (1) IL27451A (en。)
LU (1) LU53145A1 (en。)
NL (1) NL6702268A (en。)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4230959A (en) * 1979-03-06 1980-10-28 The United States Of America As Represented By The United States Department Of Energy Magnetohydrodynamic (MHD) channel corner seal

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3154702A (en) * 1960-01-25 1964-10-27 Avco Corp Electrode arrangement in mhd equipment
US3397331A (en) * 1965-07-20 1968-08-13 Avco Corp Electrode structure for a magnetohydrodynamic device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3154702A (en) * 1960-01-25 1964-10-27 Avco Corp Electrode arrangement in mhd equipment
US3397331A (en) * 1965-07-20 1968-08-13 Avco Corp Electrode structure for a magnetohydrodynamic device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4230959A (en) * 1979-03-06 1980-10-28 The United States Of America As Represented By The United States Department Of Energy Magnetohydrodynamic (MHD) channel corner seal

Also Published As

Publication number Publication date
LU53145A1 (en。) 1967-05-08
GB1139375A (en) 1969-01-08
ES337745A1 (es) 1969-05-16
NL6702268A (en。) 1967-09-11
FR1478505A (fr) 1967-04-28
IL27451A (en) 1970-11-30
BE694113A (en。) 1967-07-17
CH470809A (fr) 1969-03-31

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