US3601578A

US3601578A - High-pressure plasma burner

Info

Publication number: US3601578A
Application number: US887578A
Authority: US
Inventors: Rudolf Gebel; Helmut Forster
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1969-07-01
Filing date: 1969-12-23
Publication date: 1971-08-24
Anticipated expiration: 1988-08-24
Also published as: DE1933306A1; BE752676A; ZA704321B; ES381278A1; NL7008865A; AT299403B; DE1933306B2; FR2050422A1; SE351766B; GB1304957A; CH509721A; FR2050422B1

Abstract

High-pressure plasma burner of the gas heater type includes a pressuretight arc chamber containing electrodes adapted to form an arc therein, flow discharge nozzle means for discharging from the arc chamber working gas heated and ionized therein by the arc, coolant channels located in parts of the arc chamber thermally stressed by the arc, the coolant channels being connected in a closed coolant loop, and a pressure transmitter and pressure line pressure transmittingly interconnecting the pressure tight arc chamber and the closed coolant loop.

Description

{72] inventors RudolfGebel Tennenlohe; Helmut Forster, Neunkirchen, both of, Germany [2]] Appl. No. 887,578

221' Filed Dec. 23, 1969 [45 Patented Aug. 24, 1971 [73] Assignee Siemens Aktieugesellschaft 7 Berlin and Munich, Germany [32] Priority July 1, 1969 [33] Germany [54] HIGH-PRESSURE PLASMA BURNER 6 Claims, 2 Drawing Figs.

[52] U.S.Cl 219/121P, 219/75 [51] lnt.Cl 823k 9/00 {50] Field ofSearch 2l9/l21,

[56] References Cited UNITED STATES PATENTS 3,360,682 12/1967 Moore 219/121 X Primary Examiner-Clarence L. Albritton Assistant Examiner-Joseph V. Truhe I Attorneys-Curt M. Avery, Arthur E. Wilfond, Herbert L.

Lerner and Daniel J. Tick ABSTRACT: High-pressure plasma burner of the gas heater type includes a pressuretight are chamber containing electrodes adapted to form an arc therein, flow discharge nozzle means for discharging from the arc chamber working gas heated and ionized therein by the arc, coolant channels located in parts of the arc chamber thermally stressed by the arc, the coolant channels being connected in a closed coolant loop, and a pressure transmitter and pressure line pressure transmittingly interconnecting the pressure tight arc chamber and the closed coolant loop.

HIGH-PRESSURE PLASMA BURNER Our invention relates to a plasma burner of the gas heater typeand more particularly to such plasma burner having an arc chamber containing electrodes adapted-to form an arc therein, a flow discharge nozzle for discharging from the arc chamber working gas heated and ionized therein by the arc,

and coolant channels located in parts of the arc chamber thermally stressed by the arc, the coolant channels being connected in a closed coolant loop.

Through special measures, plasma burners of the gas heater type can be constructed as high-pressure plasma burners. Such plasma burners which operate at high pressure are suitable for supplying wind tunnels in experiments of tests relating to space flight engineering, especially for simulating reentry of missiles into the atmosphere of the earth. Furthermore, such plasma burners can be employed in chemical technology.

In high-pressure plasma burners, it has been conventional heretofore to raise the coolant pressure by means of pumps.

The invention of the instant application derives from the realization that when there is a coolant pressure below the operating pressure in the arc chamber becauseof leaks in the thermally stressed parts thereof, ionized working gas or plasma can penetrate into the leaking or defective part and can cause even greater damage. On the other hand, in order to adjust the coolant pressure to a value above the operating pressure in the arc chamber for high-pressure plasma burners,

considerable pumping expenditure is required and manifold difficulties must be overcome. In addition, further problems must be coped with when starting up and stopping the operation of the plasma burner.

It is accordingly an object of our invention to provide highpressure plasma burner which avoids the aforementioned disadvantages of the heretofore known plasma burners of this general type and which increases the efficiency and the relia- ,bility thereof. More specifically, it is an object of our invention -to provide such plasma burner wherein at startup, during regular operation and at shutdown thereof, the coolant pressure is synchronized with the operating pressure in the arc chamber, and the pressure at each cooling location is maintained at least slightly above the operating pressure within the arc chamber.

With the foregoing and other objects in view, we provide, in accordance with our invention, high-pressure plasma burner of the gas heater type comprising a pressuretight are chamber containing electrodes adapted to form an arc therein, flow 'discharge nozzle means for discharging from the arc chamber working gas heated and ionized therein by the arc, coolant channels formed in parts of the arc chamber thermally stressed by the arc, the coolant channels being connected in a closed coolant loop, and a pressure transmitter pressure line pressure transmittingly interconnecting the pressuretight arc chamber and the closed coolant loophThe coolant is thereby additionally continuously pressurized by the operating pressure in the arc chamber. The pressure to be applied by the circulating pump, and which reduces up to the return flow into the pump, can be kept relatively low.

Advantages of the plasma burner according to our invention is that because the pressure difference between coolant and operating pressure in he arc chamber can be kept very small, the walls between the coolant channels and the inner sides of the operating chambers are able to be of thin-walled construction, which assures good cooling in addition to a saving of material. Also, in accordance with ,thexinvention', coolant hoses are installable inthe plasma burnercutside the range of the arc radiation, because compression of the hoses need not be feared. There is furthermore assured that only coolant can escape at the leakage locations in the thermally stressed arc chamber parts. Also, the coolant pump has to produce only the circulation work.

In accordance with another feature of our invention, we displaceably mount at least one of the two electrodes so as to be able thereby to vary the spacing between the electrodes, the

displaceable electrode being axially displaceable'for a given distance and serving as a closure plate for closing an adjustment chamber having a length correspondingto the given distance along which the displaceable electrode is adjustable, the adjustment chamber and the arc chamber communicating in pressure equilibrium with one another, motor driven adjusting means in the adjusting chamber for adjustably displacing the displaceable electrode, and supply lines passing rigidly through an adjustment chamber wall.

Through such an adjustment chamber, according to the invention, which is kept at the same pressure as that of the operating space in the arc chamber, a pressure-relieved electrode displacement is attained, and sealing problems relating to mounting of the electrodes are avoided. Also, a seal for the adjusting device is obviated by the fact that the motor therefor is located inside the adjustment chamber. The concept of the adjustment chamber together with the fact that the coolant is subjected to the operating pressure in the arc combustion chamber result in the further advantages, that the supply lines for coolant and electric supply current to the displaceable electrode need not have a rigid wall construction nor be displaceably passed through the adjustment chamber wall, but rather, flexible hoses can be employed with rigid lead-ins or fittings in the wall, and together they avoid the use of any displaceable sealing against high pressure.

In accordance with further features of our invention, the electrodes are constructed as substantially cylindrical rings disposed in axial alignment opposite one another and containing magnetic coils, respectively, which rotate the arc during operation of the plasma burner. The magnetic field produced by the magnetic coils is brought in the region of high inductance t0 the lowpoints of the arc.

In accordance with an additional feature of our invention, a supply main or manifold for working gas is provided leading to a location between the electrodes. Depending upon requirements, the supply manifold can extend tangentially, radially or axially to the flow discharge nozzle and opposite the direction of flow discharge through the nozzle.

According to other features of our invention, the pressure transmitter is a pressure-equalizing or balancing vessel to which the pressure line is connected from above and a coolant line from below. Instead of a pressure-equalizing vessel, the pressure transmitter can be in the form of a piston in the pressure line.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in high-pressure plasma burner, it is nevertheless not intended to be limited to the details shown, since various modification and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

- The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a longitudinal sectional view of a high-pressure plasma burner constructed in accordance with our invention;

FIG. 2 is a schematic view of a flow system including a pressure transmitter, coolant circuit and pressure lines from the plasma burner of the invention to the pressure transmitter.

Referring now to the drawings and first, particularly to FIG. 1 thereof, there is shown the burner proper of the high-pressure plasma burner of our invention, formed of an arc chamber 1, an adjustment chamber 2, a burner head 3 and a nozzle member 4, carrying a flow discharge nozzle 5 which, as shown, is in the form of a Laval nozzle. The are chamber 1 has an inner operating space 6 connected through a pressure line 7 and a pressure transmitter 8, in the form of a piston located in the line 7, with coolant in a tube 9 of a coolant circuit. A fixed electrode 10 and a displaceable electrode 11 are contained, at least partly in the operating space 6 of the arc chamber 1. Both electrodes 10 and 11 are in the form of substantially cylindrical rings and are axially aligned opposite one another.-The-electrodes l and 11 contain respective magnetic coils 12 which are excited during operation so that a cusp-field is formed permitting the electric arc, which forms between the faces 13 of the electrodes and 11 to rotate. To supply electric current to the electrode 10, a terminal 14 is provided, and to the electrode 11, a supply tubelS through which coolant is simultaneously supplied, is provided. A profile ring 16 of insulating material, for example epoxide resin reinforced with glass fibers separates the potential of the fixed electrode 10 from that of the displaceable electrode 11. Thus, the walls of the arc chamber 1 and the adjustment chamber 2 are insulated from one another at the flanged junction 70 thereof. It should be noted that the flange bolts 71 are provided with insulating bushings 72 and washers 73 so as to supplement the insulating effect of the ring 16.

The adjustment chamber 2 is in pressure equilibrium with the arc chamber 1 through peripherally distributed intercommunicating bores 17, formed in a support plate 20, located between the chambers 1 and 2. For the self-same purpose, hose connections can be provided at the outer walls of both chambers 1 and 2 so as to interconnect therein. The adjustment chamber 2 is formed in essence by a peripheral chamber wall 18, a baseplate l9 and the support plate 20 which acts as a closure plate. The electrode 11 is displaceably mounted in the support plate 20. A remotely controlled motor 21 located within the adjustment chamber 2 and provided with a gear transmission 74 drives an adjusting device for displacing the electrode 11. The motor 21 thus rotates a spindle 22 suitably mounted in bearings, provided in the baseplate 19 and the supp'ort plate 20 of the adjustment chamber '2 so as to be disposed parallel to the axis of the chamber2, and thereby reciprocates a nutlike adjusting head 23 along the spindle 22. Since the adjusting head 23 is fixed to the electrode 11, the

latter is displaced therewith. The current supply tube and 4 an additional nonillustrated connecting tube for discharging coolant extend rigidly through the baseplate 19 The supply tube 15 passes through a flush fitting 24 rigidly secured in an opening formed in the baseplate 19. An observation window 25 is also provided inthe baseplate 19 for observing the arc formed during operation of the plasma burner of our inven-- tion, and for this purpose, the displaceable electrode 11, is constructed so that it is open at both ends thereof, whereby a viewer at the window 25 can see through the electrode 11 in the axialdirection thereof. The supply tube 15 is connected to an end of a flexible hose 27, which is connected at its other end to the electrode 11 and communicates with the interior of the casing 33 thereof for supplying coolant thereto. A brush or current collector 26 carried by the electrode 11 is in sliding engagement with the rigid supply tube 15 so as to draw current therefrom as the electrode 11 is displaced in the axial direction of the adjustment chamber 2.

The are chamber 1 is formed of axially aligned cascade rings 28, suitable bolted together, as shown at 75, the support plate and the casing 33 for the fixed electrode 10 which forms a closure plate 29. The closure plate 29 provides the electrical connection between the electrode 10 and the terminal 14.

The burner head 3 is formed primarily of an assembly casing 30, spacer walls 31 and a faceplate 32. The nozzle member 4 is mounted on the faceplate 32.

The pressure-stressed outer parts, such as the cascade rings 28, the chamber casing 18 and the assembly casing 30, can be formed of rust-free stainless steel. The parts that should be electrically conductive, as well as the especially heat-stressed and cooled parts such as the electrodes 10 and 11 and the electrode casings 33, are advantageously formed of copper.

At the burner head 3, coolant is introduced through the bore 34 and traverses the space between the closure plate 29 and a spacer wall 31, as well as the space between the electrode casing 33 and the magnetic coil 12 and then flows through the space between the faceplate 32 and a spacer wall 31 and discharges therefrom through a bore 35. Additional coolant channels can be constructed in the cascade rings 28 of the arc chamber 1. Coolant connectors 36, shown broken away, areprovided for the magnetic coil 12 proper of the dismagnetic coil 12 proper of the fixed electrode 10. The nozzle 5 is supplied with coolant through connectors 38.

Working gas is introduced in the illustrated embodiment of FIG. 1, through a supply main or manifold 39 as well as through subsidiary lines 40.

In the schematic flow system of FIG. 2, a pressure line 7 leads from a plasma burner 41, having the construction, for example, of the plasma'burner of FIG. 1, to an elevated equilibrium or balancing vessel 8 and is connected thereto from above.'The pressure-equalizing vessel 8 serves as pressure transmitter and subjects the coolant in the coolant loop 9 to the operating pressure in the inner space 6 of the arc chamber 1, the coolant loop 9 being connected to the pressure-equalizing vessel 8 at the bottom thereof. As illustrated in FIG. 2, the equilibrium vessel 8 is provided with a conventional overpressure safety valve 42 and a conventional liquid level control 43. The liquid level control 43 shuts off the supply of coolant when the proper level thereof is attained in the vessel 8 as it is filled for operating state, and the instant during operation, that the liquid level'drops below a minimum liquid level in the pressure-equalizing vessel 8, as can occur due to loss of coolant from leakage, it shuts off the entire system. v i

The coolant loop 9 includes connecting lines 44 for the circulating pump 45, a distributor line or manifold 46, individual coolant branch lines 48 to 53, a collecting main or'manifold 47 and a return flow line 62. The branch line 48, for example is connected to the displaceable electrode 11, the branch line 49 to the fixed electrode 10, the branch line 50 to the magnetic coil 12 of the displaceable electrode 11, the branch line 51 to the magnetic coil 12 of the fixed electrode 10, the branch line 52 to the cascade rings 28 of the arc chamber 1, and the branch line 53 to the flow discharge nozzle 5. v

As shown diagrammatically in FIG, 2, various control valves 54,"flow rate meters 55 and temperature measuring devices 56, such as thermocouple devices for example, are provided in the branch lines 48 to 53. They serve for determining the power delivered to the coolant and which is a function of the flow through-put rate and temperature different between inlet andoutlet of the respective branch cooling lines 48 to 53.

From the difference to the expended electrical power, the power given up to the working medium or the eff ciency is determinable. i i I In order to recool the coolant, in the illustrated embodiment of FIG. 2, a heat exchanger 57 having a circulatory loop 58,'as well as a heat exchange 59 having a fresh water supply line 60 are suitably provided for the coolant flow loop 9. The freshwater supply through the line 60 is controlled by a valve located in the line 60 in accordance with the return flow temperature of the coolant in the line 62 of the coolant loop 9, as measured by a thermocouple temperature-measuring device 61. i

' At an operating pressure of 50 atmospheres excess pressure in the arc chamber 1 and a discharge flow nozzle 5 of 3mm. diameter at its narrowest location, the pump power in the coolant loop 9 can be 10 atmospheres excess pressure. The coolant water pressure upstream of the circulating pump is then 60 atmospheres excess pressure and, downstream of the circulating pump, it necessarily drops to about 50 atmospheres excess pressure due to flow friction. For such an embodiment of our invention, the plasma burner power can be 500 kw and the throughput or flow-through 'rate of working gas can be 50 grams per second.

We claim:

1. High-pressure plasma burner of the gas heater type comprising a pressuretight arc chamber, first electrode means mounted in said are chamber, second electrode means located adjacent said first electrode means, means for energizing said first and said second electrode means so as to form an electric arc therebetween in said are chamber, flow discharge nozzle placeable electrode being axially displaceable for a given distance and serving as closure plate for closing an adjustment chamber having a length corresponding to the given distance over which said displaceable electrode is adjustable, said adjustment chamber and said arc chamber being in equal pressure communication with one another, motor-driven adjusting means in said adjusting chamber for adjustably displacing said displaceable electrode, and supply line means passing rigidly through a wall of said adjustment chamber.

3. High-pressure plasma burner according to claim 1,

wherein said electrodes are constructed as substantially cylindrical rings disposed in axial alignment opposite one another and containing magnetic coils, respectively.

4. High-pressure plasma burner according to claim 1, including a supply manifold for working gas leading to a location between said electrodes.

5. High-pressure plasma burner according to claim 1, wherein said pressure transmitter comprises a pressure- I equalizing vessel, said pressure line being connected to said pressure-equalizing vessel from above, and said coolant loop being connected to said pressure-equalizing vessel from below.

6. High-pressure plasma burner according to claim 1, wherein said pressure line connects said are chamber and said coolant loop and said pressure transmitter comprises a piston located in said pressure line.

Claims

1. High-pressure plasma burner of the gas heater type comprising a pressuretight arc chamber, first electrode means mounted in said arc chamber, second electrode means located adjacent said first electrode means, means for energizing said first and said second electrode means so as to form an electric arc therebetween in said arc chamber, flow discharge nozzle means for discharging from said arc chamber working gas heated and ionized therein by said arc, coolant channels formed in parts on said arc chamber thermally stressed by said arc, said coolant channels being connected in a closed coolant loop, and a pressure transmitter with a pressure line pressure transmittingly interconnecting said pressuretight arc chamber and said closed coolant loop.

2. High-pressure plasma burner according to claim 1, wherein at least one of said electrodes is displaceably mounted for varying the spacing between said electrodes, said displaceable electrode being axially displaceable for a given distance and serving as closure plate for closing an adjustment chamber having a length corresponding to the given distance over which said displaceable electrode is adjustable, said adjustment chamber and said arc chamber being in equal pressure communication with one another, motor-driven adjusting means in said adjusting chamber for adjustably displacing said displaceable electrode, and supply line means passing rigidly through a wall of said adjustment chamber.

3. High-pressure plasma burner according to claim 1, wherein said electrodes are constructed as substantially cylindrical rings disposed in axial alignment opposite one another and containing magnetic coils, respectively.

5. High-pressure plasma burner according to claim 1, wherein said pressure transmitter comprises a pressure-equalizing vessel, said pressure line being connected to said pressure-equalizing vessel from above, and said coolant loop being connected to said pressure-equalizing vessel from below.

6. High-pressure plasma burner according to claim 1, wherein said pressure line connects said arc chamber and said coolant loop and said pressure transmitter comprises a piston located in said pressure line.