EP0861576B1 - Plasma stream generator with a closed-configuration arc - Google Patents

Description

The present invention relates to a flow generator closed configuration arc plasma.

Plasma technology and especially devices allowing the creation of a configuration flow closed may be used in the processing of surfaces (sterilization, cleaning, pickling, modification, coating and film deposition) of monolithic materials and dispersed, as well as for obtaining and processing chemicals, electronics, automotive, metallurgy, chemicals, industry food, medicine and many other areas again.

We know such a device for creating a flow of closed configuration arc plasma with a zone central, uniform or lowered temperature. This device is illustrated in the document "Bases of the realization of the dynamic plasma treatment method for surfaces solids ", Koulik P. P. and others," Plasmokhimia 1987 ", Moscow 1987, part 2, pp. 58 to 96, as well as in patent application FR 2 678 467.

The documents cited above describe a device which contains two pairs of electrode chambers (cathodes and anodes), connected in pairs to current sources continued. Parameters of the plasma channels of the chambers electrodes (cathodes and anodes) correspond to the data of published in the document "The two-jet plasmatron", Genbaïev G. G. and Enguelsht V. S., Frounze, 1983.

When the electrode chambers are energized two arcs light up and form four plasma jets crossed by the current. Orientation in the space of the jets of plasma is carried out using external magnetic fields directed relative to the electrode chambers in such a way that the plasma jets from the electrode chambers converge and form a common flow of symmetrical plasma axially traversed by currents (plasma funnel) whose section, perpendicular to the axis of symmetry of the flux, has a uniform or lowered temperature zone relative to the peripheral part of the flow.

It is in this zone that, axially, are injected, by a concentric axial channel or channels, the one or more components, gaseous, dispersed, or in monolithic form, for their transformation in the plasma funnel, before their usage.

The interest of this known plasma generator is due to the specific configuration of the plasma flow. Indeed, this one has the shape of a plasma funnel, which allows introduction and processing (processing) by the plasma of different products in different forms (gaseous, liquid or solid) and allows you to use this generator with high efficiency for sterilization of surfaces, their cleaning, stripping, modification and also the film recovery deposit.

The disadvantage of the generator according to the prior art is that the plasma flow always has a reduced dimension, determined by the diameter of the resulting plasma flow. But he is many applications for which a stream of larger plasma would be useful, provided of course the closed configuration of the flow is kept because it allows to have a central temperature zone uniform or lowered.

The purpose of the present invention is to provide a closed configuration arc flow generator according to the preamble of claim 1, the section, perpendicular to the direction of flow, has a elongated shape (plasma curtain) with a central area of uniform or lowered temperature.

To this end, the invention relates to a flow generator arc plasma, closed configuration, comprising electrode chambers working in pairs and generating plasma jets, and a magnetic device for orienting jets arranged outside the electrode chambers, each pair of chambers having an anode and a cathode and being connected to a direct current source, the plasma jets generated being traversed by the current and oriented in space using an external magnetic field generated by said magnetic orientation device and directed so that the plasma jets from the chambers converge and form a common plasma flow with a central area of uniform or lowered temperature, said generator having at least three pairs of electrode chambers as above and said chambers being arranged the relative to each other so that the whole presents symmetry without all the rooms being placed on the same circle, the generator generating a flow of common plasma of closed configuration, having a shape elongated with a central zone of uniform temperature or lowered in relation to the peripheral zone resulting from the convergence of at least six plasma jets.

The magnetic device determining the orientation of plasma jets can be composed, for each pair of electrode chambers, three sections of conductor magnetic, two of which are arranged perpendicularly to the plasma jets and the third between the plasma jets.

The electrode chambers can be arranged in two groups, the two groups of chambers can be arranged in parallel rows, and the rows can be rectilinear.

According to a variant, the electrodes of the same group, respectively of the same row, of chambers are all of the same polarity, the electrode chambers of the same group, respectively of the same row, which can be made of a single block, in one piece.

According to another variant, the same group, respectively the same row of chambers contains electrodes of opposite polarities, the electrodes of the same group or of a same row can be arranged so as to respect, at less partially, an alternation of polarities.

The solution proposed by the present invention consists basically to provide the generator with at least one pair of chambers with electrodes (anodes and cathodes) in addition to the two pairs of electrode chambers (anodes and cathodes) of the known generator according to the document "Koulik", cited above.

• la figure 1 illustre le générateur selon l'invention, réalisé de manière que les chambres à électrodes sont disposées en deux rangées parallèles et rectilignes; les repères relatifs à la figure 1 sont les suivants:
• 1. Chambres à électrodes
• 2. Jets de plasma
• 3. Flux résultant de plasma
• 4. Zone du flux de plasma de température surbaissée
• 5. Conducteurs magnétiques avec bobines d'enroulement
• la figure 2 montre une chambre à électrode en forme de parallélépipède de faible largeur du générateur selon l'invention; et plus particulièrement les détails suivants, 2a. vue générale; 2b. à 2d. sections; les repères relatifs à la figure 2 sont les suivants:
• 2. Jet de plasma
• 7. Electrode
• 8. Diaphragme
• 9. Joint diélectrique d'étanchéité
• 10. Canal de courant
• 11. Canaux de refroidissement à eau
• 12. Câble électrique d'alimentation
• la figure 3 est une vue schématique illustrant l'orientation du dispositif de contrôle magnétique des jets de plasma, dans le plan des jets, selon l'invention; les repères relatifs à la figure 3 sont les suivants:
• 1. Chambre à électrode (anode, cathode)
• 2. Jets de plasma
• 5. Conducteur magnétique
• 6. Bobines d'enroulement
• 13. Lignes magnétiques

The generator according to the invention is described below, based on the drawing or:

• FIG. 1 illustrates the generator according to the invention, produced so that the electrode chambers are arranged in two parallel and rectilinear rows; the references relating to FIG. 1 are as follows:
• 1. Electrode chambers
• 2. Plasma jets
• 3. Flux resulting from plasma
• 4. Low temperature plasma flow area
• 5. Magnetic conductors with winding coils
• FIG. 2 shows a chamber with an electrode in the shape of a parallelepiped of small width of the generator according to the invention; and more particularly the following details, 2a. general view; 2b. at 2d. sections; the references relating to FIG. 2 are as follows:
• 2. Plasma spray
• 7. Electrode
• 8. Diaphragm
• 9. Dielectric seal
• 10. Current channel
• 11. Water cooling channels
• 12. Power supply cable
• Figure 3 is a schematic view illustrating the orientation of the magnetic control device of the plasma jets, in the plane of the jets, according to the invention; the references relating to FIG. 3 are as follows:
• 1. Electrode chamber (anode, cathode)
• 2. Plasma jets
• 5. Magnetic conductor
• 6. Winding coils
• 13. Magnetic lines

With reference to FIG. 1, it can be seen that the electrode chambers are connected, in pairs (formed of an anode with a cathode) to current sources. The proposed plasma generator consists of at least six electrode chambers generating six plasma jets through which the current flows.
The orientation of the electrode chambers aims to create a plasma curtain and not, as according to the prior art, to form only a plasma funnel. As in the document "Koulik" cited above, on the one hand the orientation of the resulting plasma flow and on the other hand the determination of the shape of the flow, are done using external magnetic fields. These magnetic fields are directed relative to the electrode chambers in such a way that the plasma jets, coming from the electrode chambers, form a common plasma flow symmetrical with respect to a given surface, and crossed by the currents coming from the electrode chambers (plasma curtain).

Different arrangements of the electrode chambers are possible along surfaces of different symmetry: cone of circular or elliptical section, parallel planes, single plane, etc. Depending on this arrangement, various configurations of the plasma flow will be obtained, adaptable to different practical solutions, so different applications.

The provision that seems to deserve the most attention is the one in which the electrode chambers are placed in two parallel rows, located in two planes which are cut. In this case, a unique plasma flow is formed which results from the convergence of the initial zones of the jets of plasma from electrode chambers, whose temperature is high and the resulting plasma flow has the form of a flat curtain with a uniform temperature zone or lowered in its middle part.

The arrangement of the electrode chambers in two rows can be done either so that, in each row, the anode and cathode chambers follow one another, that is to say the electrodes of the same row are all of the same type, that is to say all of the anodes or all of the cathodes.

The channels of the electrode chambers, crossed by the current are formed by copper diaphragms with seals sealing dielectrics. The electrodes themselves (anode copper, tungsten cathode) are arranged at the entrance of current channels. All parts of the electrode chambers are cooled with water. Current channels are traversed by the gas forming the plasma. The diameter of the electrodes and diaphragms, as well as their thickness and number are optimized to obtain high stability plasma jets.

The spatial orientation of the plasma jets is controlled by magnetic field. This orientation check aims to force the plasma jets to keep the given direction through the current channel.

Under the action of their own magnetic fields, plasma jets repel each other when they are opposite polarities, and they attract each other in the opposite case.

When the electrode chambers have the same polarity in a row, the mutual attraction of the jets (in the absence magnetic fields) causes the plasma jets at the ends of the row are substantially inclined towards the middle of the row. The external magnetic field, i.e. the control mentioned above, must, in such a case, act to compensate for this attraction and to restore the direction given to the plasma jets by the channel at current.

In the case where the polarities of the jets of the same rank are alternating, the plasma jets repel, causing a change in the distances between the different downstream jets electrode chambers, or slight differences in flow unavoidable gas and current between the different jets of plasma.

The application of external magnetic fields allows restore orientation characteristics to plasma jets desirable and largely corrects effects due to their neighborhood. In all cases, the magnetic force must be oriented in the plane of the plasma jets, perpendicular to their direction of flow.

With regard to FIG. 3, the device is observed magnetic jet control which contains, in the plane of jets, three sections of magnetic conductors with winding coils. The direction of the current in the coils is given in accordance with the direction of action on plasma jets.

The size of the field can be chosen individually for each plasma jet, by variation of the current in the coils. The magnetic device is installed separately for each pair of electrode chambers (anode and cathode). The magnetic conductor, located between the plasma jets, can coincide with the chemical introduction system or the product treated in the plasma curtain.

The arrangement in rows of the rooms, alternating polarity in the row, simplifies magnetic control because the jets crossed by the current partially compensate the own magnetic field (except for jets ends).

However, given the risk of a short circuit between the chambers of different polarity, the distance between them must be such that this short circuit is excluded. Is equivalent to increase the distance between the plasma jets and away the place of their convergence towards lower areas temperature.

The arrangement in rows of the rooms, with the same polarity for the whole row, requires more intense action on the jets from external magnetic fields (especially on end jets). However, this arrangement has the advantage that the electrode chambers can be placed against each other, which decreases the distance between the jets and allows their junction in the area high plasma temperature. In addition, it is possible in this case of making the electrode chambers in a single block and the diaphragms of a single body. This also allows decrease the distance between the jets.

In a more specific practical example, the electrode chambers have a width of 2 cm and are placed one after the other. They are thus arranged in two parallel straight rows of constant polarity. The generator has 50 pairs of electrode chambers. The current flowing through each pair of chambers is 50 A, the voltage is 100 V, the power of each jet being 5 kW, and the gas heating efficiency of 50%.

The plasma curtain, after joining the jets has a length of 1 m, width of 1 cm and total power from 125 kW.

Claims (9)

1. Arc plasma stream generator, of closed configuration, comprising electrode chambers (1) working in pairs and generating plasma jets (2), and a magnetic orientation device (5, 6) for orientation of the jets arranged outside of the electrode chambers, each pair of chambers (1) having an anode and a cathode and being connected to a DC power source, the generated plasma jets having current passing through them, with spatial orientation by means of an external magnetic field generated by said magnetic orientation device (5, 6) and directed such that the plasma jets from the chambers converge and form a common plasma stream (3) with a central zone of uniform or lowered temperature, characterised in that the generator comprises at least three pairs of electrode chambers (1) as above, and in that the said chambers are arranged in relation to each other such that the assembly is symmetrical without all the chambers being positioned in the same circle, the generator creating a common plasma stream of closed configuration being elongated in shape with a central zone (4) of uniform or lowered temperature in relation to the peripheral zone resulting from the convergence of at least six plasma jets.
2. Generator according to claim 1, characterised in that the magnetic device dictating the orientation of the plasma jets consist, for each pair of electrode chambers (1), of three sections of magnetic conductor (5), two of which being positioned perpendicular to the plasma jets and the third between the plasma jets.
3. Generator according to claim 1, characterised in that the electrode chambers are arranged in two groups.
4. Generator according to claim 3, characterised in that the two groups of chambers are arranged in parallel rows.
5. Generator according to claim 4, characterised in that the rows are straight.
6. Generator according to any one of claims 3 to 5, characterised in that the electrodes in one and the same group or the same row of chambers respectively are all of the same polarity.
7. Generator according to any one of claims 3 to 5, characterised in that one and the same group or same row of chambers respectively contains electrodes of opposite polarities.
8. Generator according to claim 7, characterised in that the electrodes in the same group or same row are arranged such that the polarities are alternated, at least partially.
9. Generator according to any one of claims 3 to 5, characterised in that the electrode chambers in the same group, or same row respectively, are constructed in a single, continuous block.

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