US3355604A - Continuous electrodes for magnetohydrodynamic generators - Google Patents

Description

FI P85 32 Nov. 28, 1967 KLElN ETAL 3,355,604

CONTINUOUS ELECTRODES FOR MAGNETOHYDRODYNAMIC GENERATORS Filed May 16. 19 63 3 Sheets-Sheet l JITOEIUE Y /NVA!7'0RS Geo/ac es KLEIN 9 2/0196 0148013 BY W 777 FIG. 2

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NOV. 28, 1967 KLElN ETAL 3,

CONTINUOUS ELECTRODES FOR MAGNETOHYDRODYNAHIC GENERATORS 3 Sheets-Sheet 2 Filed May 16, 1963 FIG. 6

Ill/(160177723 Geo/ages mm; flluae DuBv/s av Q; 77 0 NOV. 28, 1967 KLElN ETAL 3,355,604

CONTINUOUS ELECTRODES FOR MAGNETOHYDRODYNAMIC GENERATORS 3 Sheets-Sheet 5 Filed May 16, 1963 FIG/IO FIG .12

FIG/I1 /UVE/IITdFS mm new M045 Oman/s BY 2- a y. 4/ Y United States Patent Ofifice Fatented Nov. 28, 1967 France Filed May 16, 1963, Ser. No. 280,803 Claims priority, application France, May 18, 1962, 898.041 7 Claims. (Cl. 31011) The present invention relates to electric generators of type known as magnetohydrodynamic, and more particularly, to the electrodes used in such generators.

It is an object of the invention to provide an electrode, known as a continuous or consumable electrode, that is to say one that is regenerated as and when it is consumed or becomes worn in the generator.

These continuous or consumable electrodes are used for several purposes, particularly in some electric ovens, where such an electrode comprises a tube filled with a paste constituting the electrode itself. As a rule, these tubes are arranged vertically, and the paste is inserted at the upper end, whereas the electric oven is situated underneath.

The heat of the oven hardens the paste in the lower part of the tube and in this way a solid electrode is formed, which goes down in a slow and regular movement as it becomes worn or consumed in the oven.

The present invention has for its object an electrode based on a similar principle, specially designed for magnetohydrodynamic electric generators.

It is already known to make use of crushed coal to provide an arrangement of continuous electrodes for magnetohydrodynamic generators. The coal advances between two fiat and parallel walls, usually set vertically. In this way there is one single electrode extending to the full height of the generator, whose vein for the gaseous flow is also set vertically. This arrangement has the disadvantage of making it only possible to use a limited number of electrodes, whereas in some cases it is useful to have several multiples of ten. Furthermore, considerable force must be used to make the crushed coal advance. Besides, the coal contains silica, which is not consumed in the generator at the same time as the coal and which remains on the refractory walls of the generator. As and when the coal is consumed, the silica accumulates. Even with coal of low silica content, in time,

the quantity of silica becomes sufficient to destroy the refractory walls of the generator. In fact, it is known that gasses inside the generator must be at a very high temperature, in the region of from 2,000 to 3,000 0., and that for resistance at such temperatures pure alumina is the refractory material usually employed. Now silica and alumina form eutectoid compounds which melt at l,500 and at 1,800" C. Coal also contains other impurities such as iron oxide Fe O which with alumina forms an eutectoid melting at 1,300 C.

Other eutectoids also exist which may be formed with the impurities to be found in carbon, for example the CaO, FeO eutectoid, which melts at 1,280 C.

It is certain that with slow evolution these various different compounds may form in time, resulting sooner or later in the destruction of the refractory walls of the generator. Now it is essential to work at a high temperature for satisfactory results. Indeed, at a fairly low temperature, the plasma is impoverished in relation to the seed, which can deposit, for example, between 1,500" and 1,600 C. (boiling temperature of potash).

The present invention has for its object an electrode which eliminates these various diiferent drawbacks.

According to the present invention, the electrode is made of a paste, composed of graphite and oil; latter acting as a binding and lubricating agent. It has been noted that for a minimum oil content the paste is not an electrical conductor and offers little resistance to movement in the guide tubes of the electrodes. In the part next to the vein, the high prevailing temperature makes the paste harden, and the mass gradually becomes harder and conducts electricity. The current engendered can be taken by means of the metal covering using any appropriate method, or else by means of a rod set suitably in the electrode.

A characteristic of the present invention is that the paste should contain at least 30% of oil, and preferably between 40 and 50%. It has in fact been noted that the electric conductivity of the paste, varying according to the oil content, falls sharply at round about those amounts. It has also been recorded that for the same amounts of oil content, there was a sharp drop in the effort required to move the paste in the pipes leading to the electrodes and in the casings or tubes of the electrodes.

The use of electrodes in graphite yields the same advantages as those which have already been obtained by using combustible electrodes, such as electrodes made of coal; indeed, the combustion of the graphite in the magnetohydrodynamic tewel produces additional calories, which heat up the gaseous vein especially near the walls where the electrodes are situated; this is important in view of the less hot border layers on the walls of such generators.

The graphite used to make up the paste costs more than coal, but it is free from the impurities contained in coal, which, as described above, destroy the refractory walls of the generator very quickly. Nevertheless, it has been noted that graphite also had an effect on the refractory walls, but that it attacked them less quickly than in the case of coal. Hence, in accordance with the present invention, steps have been taken to control the position of the graphite in the magnetohydrodynamic chamber in such a way that it cannot attack the refractory walls of that chamber.

According to the present invention, then, a control device is used which determines the position of the graphite electrode in the generator. This position is especially important, because, if it penetrates into the generator too far, Wear on the refractory Walls Will occur,

as explained above. On the other hand, if it does not penetrate far enough into th generator, there is insuflicient contact between the graphite and the plasma, which causes resistance, thereby reducing the efficiency of the appliance considerably. Furthermore, it is essential that the end of the electrode should be hot enough, for example between 1,500 and 2,000 C., below which temperature there would be considerable loss. Now if the electrode is too far away from the magnetohydrodynamic chamber, it will cool down and fall to temperatures which are too low for satisfactory working.

The oxygen required for combustion of the electrode, for the purpose of raising the temperature of its end, can be found in the gaseous flow owing to the fact of partial decomposition of burnt gasses, the carbonic gas having become disassociated into oxygen and carbon monoxide. However, in some cases it my prove advantageous to supply oxygen to the gaseous flow, if it is desired to increase the number of calories given oil.

It is also possible to provide for oxygen jets around the electrode, so as to make sure of having a very hot and very hard layer all around it.

The present invention is designed more especially for generators comprising a certain number of electrodes,

3 as, for example, generators with segmented electrodes and generators of the Hall type. In fact, it is a question of placing together from 20 to 50 pairs of electrodes per metre of conversion-tewel in such generators. As is well known, the electrodes are aligned in the vein according to the direction of the flow of gasses, so as to provide a very hot zone all along the passage of the thin thread of gas which follows a series of aligned electrodes.

Another characteristic of the present invention is that the walls of the electrodes are cooled. This makes it possible to achieve less solidification of the outer part of the electrode, thus making it easier to move the latter in its casing. On the other hand, the central part of the electrode can be very hot and very hard, and brought to the temperature required for working.

The electrodes according to the invention, thas is to say the casings which canalise the pastry substance, may just be round, but they can also be, for example, rectangular with rounded corners, so as to be able to place as many electrodes as possible together in a given volume.

The movement of the paste substance in the casings can be brought about by several known methods. It can be carried out by means of pistons and clack-valves suitably arranged. It can also be carried out in a continuous manner, for example by means of an Archimedes screw as in extrusion machines used in the plastic industry. It is also possible to use an Archimedes screw of diminishing diameter so as to obtain longitudinal equalisation of the pressure of the paste.

Owing to the fact that the paste has an insulating capacity, it is possible to provide central distribution for the various different electrodes with a central pressure system. The casings, in cases where they are made of metal, then provide the appropriate insulating joints.

But each individual electrode can also be connected to a bank of distinct matter.

According to another feature of the present invention the propagation of the matter in several tubes or casings is ensured by an organ in common, which is insulated electrically from the substance and the various different tubes.

According to yet another feature of the present invention, the control device detects the position of the electrode in the chamber by measurin the resistance of the electrode itself between two points situated in the immediate region of the reaction chamber. Indeed, as and when the paste becomes solid, under the effect of the heat, its conductivity changes from practically nothing to that of the solid electrode, which conducts electricity. For the purpose of making this measurement, a sounding-rod can be inserted into the mass of the electrode at a place where the paste is in the process of hardening,

According to another method of carrying out the present invention, the position of the electrode in the gaseous vein is recorded by the measurement of the contact-resistance of the electrode with the plasma. This measurement can advantageously be obtained by comparing this resistance with the resistance measured between two fixed electrodes inserted into the vein.

In accordance with yet another feature of this present invention, for the purpose of regulating the outflow of the paste, a tightening organ constituting a strangler is used. It is controlled according to indications supplied by one of the above-mentioned arrangements. This strangler device can also usefully take the form of a ring, made partly at least of rubber, which can be tightened up to strangle the vein through the application of variable pressure. Furthermore, this rubber ring has the added advantage of constituting an insulating joint inside the casing, so as to separate and uncouple electrically the various different electrodes from each other.

Other characteristics and advantages of the present invention will be apparent in the following description.

On the joined drawings;

FIGURE 1 represents a sectional view perpendicular to the direction of the threads in the gaseous vein, of a generator made on the lines of the present invention;

FIGURE 2 represents a frontal view of one of the component parts of the generator illustrated in FIGURE 1;

FIGURE 3 illustrates a possible arrangement of several electrodes on a generator of the type of this invention;

FIGURE 4 shows another arrangement of electrodes;

FIGURE 5 is a sectional view of the working of a rod for measuring the resistance of the paste of the electrode with a view to detecting the position of the electrode in the generator for controlling the movement of the paste in the casing;

FIGURE 6 shows a variant of a rod for detecting the position of the electrode;

FIGURE 7 shows the temperature curve for the electrode according to its position in relation to the gen erator chamber;

FIGURE 8 shows another variant of a rod for detecting the position of the electrode.

FIGURE 9 is an axial sectional diagram inside an electrode casing of a device for controlling the movement of the paste;

FIGURES 10, 11 and 12 represent different views or diagrams of systems for supplying graphite paste to the electrodes.

In the form of generator shown in FIGURE 1, the installation comprises a pair of electrodes protruding into an enclosure 1. Each electrode is composed of a tube 2, 2 and is filled with conductor paste 3 (3) coming from a tank 4. The paste is pushed into the tube by a piston 5. A series of clack-valves, 6 and 7, makes certain that this injection device works according to a cycle like that of suction and force pumps.

In FIGURE 5 a sounding-rod is shown which can be used as an electric plug or/ and for use with sensitive organs in the control mechanism, about which we shall speak later. This sounding-rod, 8, can be fixed in any appropriate manner, for example to a grating, 10, like the one shown in FIGURE 2.

With reference to FIGURE 1, cooling of the outer wall of the electrode is ensured by means of a helical coil, 12, through which, for example, water runs. This has the effect of keeping inside the casing of the electrode a border layer of viscous matter, represented by shading in 13, 13'.

FIGURE 3, which shows a sectional diagram 111.3 of FIGURE 1, represents a possible lay-out and form for electrodes 15, 16, 17. The electrodes are placed roughly in the same plane parallel to the axis of the vein. Their ends are aligned so as to favour the creation of a hot zone in the central part of the electrodes, in order to enable the generator to function efiiciently.

FIGURE 4 shows an analogous arrangement, but one in which the electrodes 25, 26, 27 are roughly rectangular in section, the angles being rounded off so as to facilitate the movement of the viscous mass inside the casings.

FIGURE 5 shows, as an example, a diagram of a possible structure of a sounding-rod for purposes of control. The rod, 8, comprises peripherical electric contacts, 31, 32, 33, connected by conductors, 31,, 32 33,, to an appropriate appliance of any well-known type working the control system according, for example, to measured electric resistances.

FIGURE 6 shows a diagram of another method of observing the position of the electrode by means of two rods, 35 and 36. With this type, the rods only measure the temperature of the graphite. The graph in FIGURE 7 shows the temperature measured by the rod, according to the position of the front side of the electrode in the casing near the inside wall of the magnetohydrodynamic reactor.

With respect to FIGURE 7, A represents the point corresponding to the best position of the electrode in the casing near the magnetohydrodynamic vein. The horizontal axis represents the position of the front side of the mass of graphite in the casing: if the electrode protrudes beyond the end of the casing and penetrates into the inside of the vein, the point approaches its original place on the horizontal axis. It has been noted that when the electrode penetrates into the vein, it heats up quickly up to a maximum temperature represented by stage B, which the curve shows near the temperature axis. The further back the front side of the electrode is situated in the casing, the greater the fall in temperature recorded by rod 35, as the front side of the electrode is further away from the hot zone. But beyond a certain position, the temperature recorded rises quickly, for example as from point C, as there is no longer any layer of graphite to protect the rod, which is then exposed directly to rays coming from the vein. The working of the control mechanism is placed around point A; the slope of the curve is used to indicate the incorrect D position.

36 in FIGURE 6, represents a second thermocouple, slightly to the back of thermocouple 35, so as to correct the information given by the first thermocouple resulting from a change in the combustion rate. When the speed of the plasma or its temperature decreases in the vein, the quantity of heat received by the electrode, decreases very quickly. Now the position of the electrode, as defined by the temperature registered by rod 35, must be determined independently of the temperature of the plasma and of the mined intensity of the circulation in the vein. These influences can be corrected by means of the information supplied by rod 36. The two rods can, for example, be mounted on a Wheatstones bridge.

FIGURE 8 represents another method of detecting the position of the electrode for the purpose of working the control system. With this type, the contact-resistance of the electrode and the plasma is measured, and then this resistance is compared to the tension taken from between the two electrodes immersed in the gaseous flow. To do this, a measurement is taken of the resistance between the electrode constituted by the paste 3, by means of the measurement rod, 9, and an electrode, 41, fixed in a wall of the magnetohydrodynamic vein, immersed in the gaseous flow, that is to say extending beyond the border layer represented by the interrupted line, 42. Furthermore, a measurement is taken of the resistance between the 41 electrode and an analogous electrode, 43. To do this, tension is applied between rod 9 and the electrode 41 by means of a transformer, 45, fed with alternating current applied between terminals 46, 47. Furthermore, by means of another transformer, 48, an alternating current is applied between electrodes 41 and 43. On the graphite electrode circuit a transformer of intensity, 49, is fitted and another transformer of intensity, 50, is provided on the circuit connecting the two electrodes 41 and 43. Appropriate attenuation factors are also considered on the two circuits, so that the two currents collected by transformers 49 and 50 should be in opposition, re sulting in the proper working of the magnetohydrodynamic generator. A sensitive appliance, for example a narrow-band alternating amplifier is also fitted; this is sensitive to the phase for working the control system.

FIGURE 9 represents, as an example, a practical set up for a control system based on the principle of the present invention. The arrangement illustrated acts both as a strangler to limit the amount of graphite paste passing through and also as an electric insulating joint separating the part of the casing situated near the electrode itself from the rest of the circuit through which the graphite paste circulates. This insulation is of particular interest in the case of multiple electrodes, which must naturally be insulated from each other.

In the figure, the casing is composed of two sections, 55 and 56, in metal tubing, for example, separated by a ring-Washer, 57, preferably made of an insulating material, such as, for example, polytetrafiuorethylene. A hollow ring in some flexible substance, say rubber, comprises a base, 59, and two Wings, 60 and 61. The two wings, 60 and 61, are tightened in a suitable manner between the ring-washer, 57, and the two other parts, 55 and 56, so as to make sure they are water-tight.

A pipe, 62, make it possible to send compressed air to the inside of the hollow part in rubber, between this latter part and the ring-washer, 57, which makes it possible, varying with the pressure applied, to make the rubber part swell up to a lesser or greater degree, thus strangling the passage and limiting the flow of graphite paste. The dimensions of the different parts and the airpressure are, of course, regulated according to the pressure of the paste above the joint.

A compressed-air arrangement of this kind is easy to make and takes up little room, and this is an important factor in a magneto'hydrodynamic generator, where the space available for accessories is very limited. This arrangement solves two problems at once: regulation and electric uncoupling of the electrodes. It therefore makes a centralised distribution system possible for the graphite paste. The above-mentioned centralised distribution system is placed outside the interferric space at some distance from the apparatus, thus giving more room in the immediate neighbourhood of the latter.

FIGURES 10, 11 and 12 represent, as examples, three possible methods of assembling distribution circuits. The parts common to the three different methods are shown on the three figures with the same reference numbers, that is the generator, 70, the electrodes, 71, the pump, 72, and the control valves, 73. In FIGURE 10, the electrodes are arranged in a straight line, starting from the pump. This arrangement is inconvenient in that all the pressures upstream from each electrode are different and that control devices must be regulated independently for each electrode.

The arrangement in FIGURE 11 comprises individual supply to each electrode. It therefore makes it possible to apply the same amount of pressure to each electrode, by selecting pipes of identical length for carrying the graphite paste.

' Finally, FIGURE 12 represents an arrangement supplying the electrodes in a double line. With this arrangement, if the consumption of graphite in the electrodes decreases, the unused graphite goes back through the return-pipe to the pumps supply tank. The pump can therefore work at a practically constant rate without being influenced by variations in the graphite consumption rate, which greatly simplifies the installation.

It is also possible to construct the control system so that it acts directly on the pump, without strangling the flow through the pipes. In this latter case, the pipes merely have insulating joints for electric uncoupling, as they have no function as flow regulating agents. However, each pipe can still be fitted with a fixed regulating contraption, so as to compensate for the different lengths of the supply pipes.

Of course the invention is by no means limited to the methods of use described and illustrated here, which have merely been given as examples.

We claim:

1. In a magnetohydrodynamic generator having a combustion chamber and a continuous electrode element comprising a casing operative to receive an electrode composition composed of graphite and an oil binding and lubrieating agent, said electrode composition being introduced into said casing as said electrode element is consumed, the improvement essentially consisting of, means to regulate the introduction of said electrode composition into said casing such that as said electrode is consumed the position of the consumed portion is fixed relative to the entrance of the magnetohydrodynamic combustion cham-

Claims (1)

1. IN A MAGNETOHYDRODYNAMIC GENERATOR HAVING A COMBUSTION CHAMBER AND A CONTINUOUS ELECTRODE ELEMENT COMPRISING A CASING OPERATIVE TO A RECEIVE AN ELECTRODE COMPOSITION COMPOSED OF GRAPHITE AND AN OIL BINDING AND LUBRICATING AGENT, SAID ELECTRODE COMPOSITION BEING INTRODUCED INTO SAID CASING AS SAID ELECTRODE ELEMENT IS CONSUMED, THE IMPROVEMENT ESSENTIALLY CONSISTING OF, MEANS TO REGULATE THE INTRODUCTION OF SAID ELECTRODE COMPOSITION INTO SAID CASING SUCH THAT AS SAID ELECTRODE IS CONSUMED THE POSITION OF THE CONSUMED PORTION IS FIXED RELATIVE TO THE ENTRANCE OF THE MAGNETOHYDRODYNAMIC COMBUSTION CHAMBER, SAID MEANS ALSO SERVING TO INSULATE SAID ELECTRODE COMPOSITION FROM SAID CASING, AND MEANS TO DETECT AND MONITOR THE POSITION OF THE CONSUMABLE PORTION OF SAID ELECTRODE COMPOSITION IN THE MAGNETOHYDRODYNAMIC CHAMBER BY MEASURING THE ELECTRICAL RESISTANCE OF SAID ELECTRODE COMPOSITION.

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