EP0017201B1 - Chalumeau à plasma à courant continu - Google Patents

Chalumeau à plasma à courant continu Download PDF

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Publication number
EP0017201B1
EP0017201B1 EP80101692A EP80101692A EP0017201B1 EP 0017201 B1 EP0017201 B1 EP 0017201B1 EP 80101692 A EP80101692 A EP 80101692A EP 80101692 A EP80101692 A EP 80101692A EP 0017201 B1 EP0017201 B1 EP 0017201B1
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EP
European Patent Office
Prior art keywords
cathode
plasma torch
torch according
gas
plasma
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP80101692A
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German (de)
English (en)
Other versions
EP0017201A1 (fr
Inventor
Erwin Gehringer
Werner Hennig
Helmut Dr.-Ing. Hügel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Deutsches Zentrum fuer Luft und Raumfahrt eV
Original Assignee
Deutsche Forschungs und Versuchsanstalt fuer Luft und Raumfahrt eV DFVLR
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Publication of EP0017201A1 publication Critical patent/EP0017201A1/fr
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Publication of EP0017201B1 publication Critical patent/EP0017201B1/fr
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • H05H1/40—Details, e.g. electrodes, nozzles using applied magnetic fields, e.g. for focusing or rotating the arc
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • H05H1/3436—Hollow cathodes with internal coolant flow

Definitions

  • the invention relates to a direct current plasma torch with a rod-shaped cathode and a concentrically arranged, rotationally symmetrical anode and an annular gap between the cathode and the anode for supplying the gas to be heated, the cathode having an annular edge at its free end and the free end the cathode is located in an axially parallel, temporally constant magnetic field, while in the region located downstream of the free end of the cathode there is a temporally constant magnetic field which diverges in the direction of flow, such that the plasma arc which forms between the cathode and the anode is set in rotation.
  • gases can be heated in a direct or alternating current arc discharge.
  • the main technological problems lie in the control or reduction of the electrode erosion through the arc attachments, directly related to the guarantee of a sufficient service life of the electrodes and the cleanliness of the arc plasma as well as in the realization of the properties of the highly heated medium required for the application. In certain applications, for example, spatial homogeneity and constant temperature can be required.
  • the aim is still to operate the discharge at the highest possible voltage. Since the electrophysical electrode losses are proportional to the current strength, the constant the current intensity, the lower the power loss at the electrodes, the higher the arc voltage.
  • the electrode erosion can be reduced by shortening the dwell time of the arc attachment on a specific surface element of the electrode.
  • Devices which, for the purpose of moving the arc attachments, introduce the medium to be heated in its entirety or only partially tangentially into the space between the electrodes (German patents 1,564,333 and 2,236,487).
  • the arc attachment is driven in the circumferential direction, but because of the axial velocity component of the gas, which is caused by the flow through the hollow cylindrical electrodes, a longitudinal movement is also forced on it.
  • the arc oscillates between different foot spots, causing its column length and thus voltage to take on temporally variable values.
  • a constant in time and spatially homogeneous hot gas or plasma cannot be achieved in this way.
  • the cathode can also be produced from tungsten or thoriated tungsten in apparatus operated with direct current (DE-OS 2027626, DE-PS 2 033 072).
  • direct current DE-OS 2027626, DE-PS 2 033 072
  • the thermal load at the tip of a conical cathode becomes so high that the material melts in the arch approach and gets into the plasma as an impurity.
  • This effect is avoided in the technical design according to DE-PS 2 033 072, in that a certain amount of the arc gas flows into a hollow cathode and leads there to the arc attachment.
  • the bow does not find a preferred starting point, experience has shown it to perform an erratic movement, which in turn causes fluctuations in tension and ultimately temperature fluctuations.
  • an outlet channel for the plasma gases is surrounded by a number of individual electrodes in the shape of a cone (British Patent 1 112 935).
  • the entire arrangement is to be rotated so that the plasma arc begins successively on different individual electrodes.
  • the plasma arc begins at one of the many rod-shaped electrodes surrounding the gas outlet openings, it will maintain this starting point even during rotation, since the field distribution at the tip of this electrode is particularly favorable.
  • the mechanical rotation thus swirls the plasma arc, which will only tear off after considerable swirling and will jump over to another electrode. This results in an extremely unstable plasma arc.
  • severe erosion occurs at the tips of the individual electrodes, since the plasma arc emanates for a long time continuously from the same electrode tip.
  • the invention has for its object to improve a direct current plasma torch in such a way that it can be used to heat gases and gas mixtures at pressures of up to 20 bar to temperatures in the range from a few 100 degrees to approximately 20,000 K, with long service lives of the electrodes , Cleanliness of the plasma, high efficiency and stationarity and spatially uniform distribution of the gas properties are to be achieved.
  • This object is achieved according to the invention in a plasma torch of the type described in the introduction in that the cathode has a continuous inner bore through which part of the gas to be heated can be introduced into the plasma torch at such a flow rate that the cathode-side plasma arc attachment on the annular edge of the cathode is localized.
  • the advantages achieved by the invention are that the design of the cathode with an annular edge of the cathode approach and due to the axial gas flow and the anode approach of the arc are each fixed in a certain axial position, which results in a temporally constant arc length and arc voltage and finally Temperature results.
  • the arc as such is set in rotation by electromagnetic forces, as a result of which its electrode attachments move rapidly in the circumferential direction, which leads to an extremely short dwell time on a specific surface element. As a result, the electrode material does not melt, and long service lives and clean plasmas can be achieved.
  • the cathode consists of thorium tungsten.
  • the annular edge has a cutting shape.
  • the anode can have the shape of a circular cylinder and have an internal width which is larger than the outside diameter of the cathode.
  • the outside diameter of the cathode is preferably considerably smaller than the inside diameter of the anode, so that there is a relatively wide annular gap between the two.
  • the formation of a negative pressure on the inside of the cathode is avoided, so that the plasma arc also has no tendency to migrate away from the edge into the inside of the cathode.
  • the formation of a negative pressure on the inside of the cathode is also counteracted by the gas flowing through the inner bore.
  • a magnetic coil or a permanent magnet are arranged concentrically to the cathode axis in order to generate the magnetic field in such a way that their plane of symmetry in a region between the annular edge of the cathode and a maximum of five diameters of the annular edge in Countercurrent direction shifted level.
  • the cathode and / or the element generating the magnetic field are preferably adjustable in the axial direction.
  • the arc approach is in an essentially axially parallel magnetic field.
  • an equalization chamber with an outer housing and a jacket arranged therein connects to the combustion chamber and that an annular space extending essentially over the entire height of the equalization chamber is arranged between the housing and the jacket with a gas supply line and on the other hand via holes in the jacket with the interior of the compensation chamber in connection.
  • the jacket is preferably made of a refractory material. It is also favorable if the housing is machined on the side facing the annular space in a mirror-like manner.
  • This configuration enables a gas to be introduced into the space between the jacket and the housing by a gas supply, which gas extracts heat from the jacket before it enters the compensation chamber through inlet openings in the jacket.
  • the energy flow from the jacket to the cooled wall of the housing is reduced to 30% of the value that occurs in known devices in which the energy flow from the hot gas to the cooled wall takes place through convective heat transfer, since the energy flow from the jacket to the cooled wall the compensation chamber according to the invention can only be carried out by radiation transport.
  • the drawing shows a preferred embodiment of a plasma torch in longitudinal section.
  • a cylindrical housing 1 has a central longitudinal bore 2 which is lined in its upper area by means of an insulating sleeve 3 and in its lower area by means of a circular cylindrical anode 4.
  • a rod-shaped cathode 5 with a central longitudinal bore 6 projects into the longitudinal bore 2 from the open upper side.
  • the cathode 5 is tapered in the region of its free end, so that a cutting-shaped ring edge 7 results at the outlet of the longitudinal bore 6.
  • the outer diameter of the rod-shaped cathode 5 is smaller than the inside width of the insulating sleeve 3 and the anode 4, so that an annular gap 8 is formed between them and the cathode 5.
  • the cylindrical housing 1 is surrounded by a magnetic coil 9, which can be excited by a current source, not shown in the drawing.
  • the magnet coil 9 is displaceable in the direction of the longitudinal axis of the housing.
  • the rod-shaped cathode 5 can also be displaceable in the direction of the longitudinal axis of the housing.
  • an equalizing chamber 10 Downstream of the housing 1 there is an equalizing chamber 10 with a likewise cylindrical housing 11 and a cavity 12 connected to the longitudinal bore 2.
  • a circular cylindrical jacket 13 is inserted into the cavity 12 in such a way that in its end regions 14 and 15 it lies tightly against ring webs 16 and 17 at the upper and lower ends of the housing 11, while in the remaining region between the jacket 13 and the housing 11 an annular chamber 18 is formed.
  • This annular space 18 is connected via a channel-shaped line 19 to a gas source (not shown in the drawing) and via openings 20 in the jacket 13 to the interior 21 of the compensation chamber 10.
  • the side walls 22 of the annular space 18 on the housing side are machined in a mirror-like manner.
  • the jacket 13 is preferably made of a refractory material.
  • the working gas flows on the one hand through the annular gap 8 and on the other hand through the longitudinal bore 6 into the interior of the housing 1 and thereby flows essentially axially parallel to it.
  • An arc burns between the anode 4 and the cathode 5, the cathode-side arc attachment being located on the cutting-shaped ring edge 7.
  • the magnet coil 9 is excited and thereby generates a magnetic field which runs essentially axially parallel in the region of the ring edge 7, while diverging in a region located downstream. This magnetic field causes the arc to rotate around the longitudinal axis of the housing, so that the starting point of the arc on the cathode side travels along the cutting-shaped ring edge 7.
  • the starting point runs in a radial plane, so that the length of the arc does not change, so that the voltage and temperature of the arc remain constant during this migration. It is essential that the magnetic field in the area of the ring edge runs essentially axially parallel.
  • the magnet coil 9 is moved into a corresponding axial position, according to the invention it is arranged such that its plane of symmetry lies in a region between the annular edge 7 of the cathode 5 and a plane displaced in the countercurrent direction by a maximum of five diameters of the annular edge 7.
  • the length of the arc and thus its temperature can be influenced by changing the axial position of the magnetic coil 9 and / or the rod-shaped cathode.
  • the starting point on the anode side is also defined by the diverging magnetic field in the area of the anode in the axial direction, while a migration of the starting point is ensured in the circumferential direction.
  • cathodes made of conventional materials can be used even at high powers, but it is expedient to produce the cathode additionally from highly heat-resistant material, for example from thorium tungsten.
  • magnet coil 7 can be replaced by an appropriately magnetized permanent magnet.
  • the jacket 14 which preferably consists of a refractory material, together with the annular space 18 ensures good thermal insulation of the gases. Since the jacket 14 is only in direct thermal contact with the cooled housing 11 in a small area, heat can be transferred from the jacket 14 to the housing 11 essentially only by radiation. Radiation losses are additionally reduced by the reflective processing of the side walls 22 of the annular space 18 on the housing side. Overall, the jacket 14 thus acts as a heat shield.
  • a further gas or a gas mixture can be admixed to the heated gas in the interior 21 of the compensation chamber via the line 19, the annular space 18 and the openings 20.
  • This gas entering through the annular space 18 is preheated in the latter, so that part of the heat losses can be compensated for in this way.
  • the desired final temperature of the gas mixture emerging from the compensation chamber can be set by adding further gases. It is also favorable that gas components can be added to the superheated gas which cannot be heated to the high temperatures prevailing in the plasma torch itself, be it that they are decomposed at these temperatures or that they can cause harmful reactions at these temperatures with the components of the plasma torch.
  • the temperature control can be carried out in two ways, namely by moving the solenoid 9 and / or the cathode 5 and by admixing a gas in the compensation chamber. You get an extremely variable and simple combination.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Plasma Technology (AREA)

Claims (12)

1. Chalumeau à plasma à courant continu, comprenant une cathode en forme de barre, une anode à symétrie de révolution disposée concentriquement à la cathode et un passage annulaire entre la cathode et l'anode pour l'amenée du gaz à chauffer, la cathode présentant à son extrémité libre un bord annulaire et l'extrémité libre de la cathode se trouvant dans un champ magnétique constant dans le temps et parallèle à l'axe, tandis qu'un champ magnétique constant dans le temps mais divergent dans la direction d'écoulement existe dans la zone située en aval de l'extrémité libre de la cathode, de sorte que l'arc-plasma qui se forme entre la cathode et l'anode est mis en rotation, caractérisé en ce que la cathode (5) présente un alésage intérieur traversant (6), par lequel une partie du gaz à chauffer peut être introduite dans le chalumeau à plasma à une telle vitesse d'écoulement que l'extrémité cathodique de l'arc-plasma est localisée sur le bord annulaire (7) de la cathode (5).
2. Chalumeau à plasma selon la revendication 1, caractérisé en ce que la cathode (5) est en tungstène-thorium.
3. Chalumeau à plasma selon la revendication 1 ou 2, caractérisé en ce que le bord annulaire (7) est en forme de tranchant.
4. Chalumeau à plasma selon l'une des revendications précédentes, caractérisé en ce que l'anode (4) possède une forme cylindrique circulaire et possède une largeur interne qui est plus grande que le diamètre extérieur de la cathode (5).
5. Chalumeau à plasma selon l'une des revendications précédentes, caractérisé en ce que, pour produire le champ magnétique, on dispose un bobine d'électro-aimant (9) ou un aimant permanent concentriquement à l'axe de la cathode, de telle manière que le plan de symétrie de la bobine ou de l'aimant est situé dans une région comprise entre le bord annulaire (7) de la cathode (5) et un plan déporté, à partir de ce bord, dans le sens contraire à la direction d'écoulement du gaz, d'une distance correspondant tout au plus à cinq fois le diamètre du bord annulaire (7).
6. Chalumeau à plasma selon l'une des revendications précédentes, caractérisé en ce que la cathode et/ou l'élément (9) engendrant le champ magnétique est ou sont réglable(s) en direction axiale.
7. Chalumeau à plasma selon l'une des revendications précédentes, caractérisé en ce que le gaz est amené parallèlement à l'axe.
8. Chalumeau à plasma selon l'une des revendications précédentes, caractérisé en ce que l'espace de combustion est suivi par une chambre d'égalisation (10) définie par un corps extérieur (11) dans lequel est disposée une chemise (14) et en ce qu'un espace annulaire (18) s'étendant sensiblement sur toute la hauteur de la chambre d'égalisation (10) est formé entre le corps (11) et la chemise (14), cet espace annulaire (18) communicant d'une part avec un conduit d'amenée de gaz (19) et d'autre part, à travers des orifices (20) de la chemise (14), avec l'espace intérieur (21) de la chambre d'égalisation (10).
9. Chalumeau à plasma selon la revendication 8, caractérisé en ce que la chemise (14) est faite d'un matériau réfractaire.
10. Chalumeau à plasma selon la revendication 8 ou 9, caractérisé en ce que le corps (11) possède un fini spéculaire du côté tourné vers l'espace annulaire (18).
11. Chalumeau à plasma selon l'une des revendications 8, 9 et 10, caractérisé en ce que la chambre de compensation (10) possède une forme cylindrique, semi-cylindrique, prismatique ou sphérique.
12. Chalumeau à plasma selon l'une des revendications 8 à 11, caractérisé en ce que l'axe principal de la chambre de compensation (10) est parallèle ou perpendiculaire à celui du chalumeau à plasma.
EP80101692A 1979-04-04 1980-03-29 Chalumeau à plasma à courant continu Expired EP0017201B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2913464A DE2913464C3 (de) 1979-04-04 1979-04-04 Gleichstrom-Plasmabrenner
DE2913464 1979-04-04

Publications (2)

Publication Number Publication Date
EP0017201A1 EP0017201A1 (fr) 1980-10-15
EP0017201B1 true EP0017201B1 (fr) 1982-10-27

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EP80101692A Expired EP0017201B1 (fr) 1979-04-04 1980-03-29 Chalumeau à plasma à courant continu

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DE (2) DE2913464C3 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9532440B2 (en) 2013-08-27 2016-12-27 Fronius International Gmbh Method and device for generating a plasma jet

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FR2514223A1 (fr) * 1981-10-01 1983-04-08 Anvar Dispositif pour produire un plasma, notamment pour la fusion des ceramiques et pour la metallurgie extractive
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US4862032A (en) * 1986-10-20 1989-08-29 Kaufman Harold R End-Hall ion source
DE3642375A1 (de) * 1986-12-11 1988-06-23 Castolin Sa Verfahren zur aufbringung einer innenbeschichtung in rohre od. dgl. hohlraeume engen querschnittes sowie plasmaspritzbrenner dafuer
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NO176300C (no) * 1991-12-12 1995-03-08 Kvaerner Eng Anordning ved plasmabrenner for kjemiske prosesser
DE19518208C2 (de) * 1994-05-20 2000-05-25 Steinbeis Transferzentrum Raum Anlage zum thermischen Behandeln von Stoffen
AU4274196A (en) * 1995-11-27 1997-06-19 Volgogradskoe Otkrytoe Aktsionernoe Obschestvo "Khimprom" Process for obtaining titanium dioxide and a plasmo-chemical reactor for carrying out said process
DE19930925B4 (de) * 1998-07-06 2011-05-05 Laure, Stefan, Dr. Plasmagenerator
DE19953928B4 (de) * 1999-11-10 2004-01-29 Steinbeis-Transferzentrum Raumfahrtsysteme-Reutlingen Plasmaerzeugungseinrichtung zur Erzeugung von thermischen Lichtbogenplasmen
US7079370B2 (en) 2003-04-28 2006-07-18 Air Products And Chemicals, Inc. Apparatus and method for removal of surface oxides via fluxless technique electron attachment and remote ion generation
TWI274622B (en) * 2003-04-28 2007-03-01 Air Prod & Chem Apparatus and method for removal of surface oxides via fluxless technique involving electron attachment and remote ion generation
DE102004006636B4 (de) * 2004-02-10 2013-10-17 Dr. Laure Plasmatechnologie Gmbh Plasmagenerator und Verfahren zur Reduktion und Reinigung von oxidhaltigen Metallverbindungen
BR102012023179A2 (pt) * 2012-09-14 2014-11-11 Roberto Nunes Szente Processo termo mecânico para perfuração
CN110519903A (zh) * 2019-08-14 2019-11-29 成都金创立科技有限责任公司 空气筒状等离子发生器间隙结构

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9532440B2 (en) 2013-08-27 2016-12-27 Fronius International Gmbh Method and device for generating a plasma jet

Also Published As

Publication number Publication date
DE2913464A1 (de) 1980-10-16
EP0017201A1 (fr) 1980-10-15
DE2913464B2 (de) 1981-04-02
DE3060990D1 (en) 1982-12-02
DE2913464C3 (de) 1983-11-10

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