US3692431A

US3692431A - Apparatus for generating a gas jet

Info

Publication number: US3692431A
Application number: US83520A
Authority: US
Inventors: Rudolf Gebel
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1969-10-31
Filing date: 1970-10-23
Publication date: 1972-09-19
Anticipated expiration: 1989-09-19
Also published as: DE1954851B2; DE1954851A1; FR2065621A1; JPS5628229B1; GB1326429A; FR2065621B1; SU437320A3

Abstract

An apparatus for generating a gas jet of high velocity along a jet axis has a nozzle assembly coaxial with the axis and having a gas inlet thereon. Also provided, is an arcing chamber structure disposed adjacent to the nozzle assembly for transmitting the gas along the axis to the gas inlet. The nozzle assembly has two nozzle members one of which has a first nozzle passage coaxial with the axis and communicating with the gas inlet. The nozzle passage terminates in a nozzle opening. The two nozzle members can jointly form a second nozzle passage communicating with the gas inlet and have a nozzle outlet arrangement laterally of the jet axis.

Description

waited Etates tent Gehel [54] APPARATUS FOR GENERATING A GAS .EET

Inventor: Rudolf Gebel, Tcnnelohe, near fiel ewsa eifi [30] Foreign Application Priority Data Oct. 31, 1969 Germany ..P 19 54 851.7

11.8. C1 ..417/183, 60/203 int. Cl ..F04E 5/48, 621d Field of Search... ..417/48, 77, 187, 197, 198,

[56] Reierences Cited UNITED STATES PATENTS 7/1964 Spongberg ..60/203 X 3/1967 Ferrie et al. ..60/203 12/1967 Ferric et al. ..60/203 Assignee: Siemens Aktiengesellschatft, Berli n 1 Sept. w, 1972 Friedmann et al.....4l7/l83 X 11/1966 Nielsen ..417/183 X Primary Examiner-Robert M. Walker 571 sc'r An apparatus for generating a gas jet of high velocity along a jet axis has a nozzle assembly coaxial with the axis and having a gas inlet thereon. Also provided, is an arcing chamber structure disposed adjacent to the nozzle assembly for transmitting the gas along the axis to the gas inlet. The nozzle assembly has two nozzle members one of which has a first nozzle passage coaxial with the axis and communicating with the gas inlet. The nozzle passage terminates in a nozzle opening. The two nozzle members can jointly form a second nozzle passage communicating with the gas inlet and have a nozzle outlet arrangement laterally of the jet axis.

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APPARATUS FOR GENERATING A GAS JET My invention relates to an apparatus for generating a gas jet of high velocity which passes over a discharge nozzle after exiting from an arcing chamber structure.

In several areas of modern technology plasma flows having velocities faster than the speed of sound are required. Such flows are required for example for synthesizing the flow relationships associated with the flight of rockets and with other flying vehicles capable of flying at high Mach numbers, for example, with Mach numbers of and larger in the so-called hypersonic wind tunnels as well as with the jet power plants of rockets. In German Pat. No. 1,080,324 there is taught an apparatus for generating an ionized gas flow of supersonic velocity; this apparatus comprises a pressure tight housing, a so-called pressure chamber, a light arcing arrangements arranged within the pressure chamber, and a Laval nozzle, the latter serving as an ejector nozzle.

One of the electrodes for generating the light arc can be configured as a cup electrode, from which the light are burns into a cylinder electrode during operation with gas being supplied tangentially. Such plasma burners are known from the publication "IEEE TRANSACTIONS ON NUCLEAR SCINECE, January 1964, pages 41 to 46. In the axial region of the plasma burner there is formed a through-passing flow column that extends up to and into the cylinder electrode. By means of this flow relationship, the light are is gas stabilized. The light are can be rotated by means of magnetic coils arranged around the electrode.

German published patent application No. 1,271,852 teaches a light are chamber whose cup electrode is adjustable in the axial direction of the chamber, this axial direction being at the same time the axis of the gas jet. The cup electrode can be provided with a central gas inlet channel. A high velocity of the gas jet is obtained when there is a large difference between the heat content of the gases in front of the nozzle compared to their heat content behind the nozzle, that is, after the gas expands.

Good operating conditions with average air temperatures of up to 6,000K and electrode operating life up to about 25 hours are obtainable with known plasma burners for heating air with eddy stabilized light arcs at volumetric flows of air between and 100 g per second. With smaller amounts of air flow of between I to 10 g per second it is in contrast difficult to convey a corresponding high electric energy of the air because the dimensions of the electrode become too small compared to the diameter of the light are and the proportion of surface to volume of the burning chamber becomes too great. In such instances, a corresponding low efficiency is obtained. The small electrical energy and a low efiiciency give rise to low air temperatures and a corresponding low gas velocity.

German Pat. No. 685,455 teaches how to direct a hot flow of gas to a workpiece, the peripheral outer portion of the gas stream being pared oh by deflecting screens. These deflection screens are positioned at a certain distance in front of the nozzle outside of the light arc chamber. With this paring apparatus, the velocity of the gas jet cannot be affected, in contrast, the velocity is reduced and the gas flow is disturbed by eddy formations behind the deflection screens.

According to Austrian Pat. No. 128,301, an ancillary portion of the gas flow can be diverted or pared from the gas flow within the light are chamber. This ancillary gas portion is directed through bores that are arranged at a given spacing from the mouth of the nozzle. The pared portion of the gas flow is again directed toward the primary flow of gas by means of appropriate plates after exiting from the nozzle. This pared-off portion of the gas flow serves to protect the nozzle.

In addition, the arrangement of a double nozzle is known, for example, from the British Pat. No. 958,3 75. These double nozzles are arranged in the direction of the gas flow and behind one another. Between the tow nozzle portions there are provided means for adding carrier gas with a powder. The carrier gas with the powder can if necessary, be supplied through a bore in the forward nozzle, that is, the so-called secondary nozzle.

German published patent application No. 1,085,353 illustrates a plasma accelerator for generating flows having velocities greater than the speed of sound with which an additional medium is admitted to the light are chamber for the purpose of raising the density of the plasma and to restrict the plasma to a thin jet. A portion of the medium not used can be passed off through lead-off slits that are arranged in the region of the nozzle. This apparatus requires an additional medium that to someextent must be again directed away through the slits.

Form U.S. Pat. No. 3,226,592 a double nozzle in coaxial arrangement is also known. This double nozzle is provided for drawing in an ionized medium. The polarity of the potentials of both coaxial nozzle portions is changed with higher frequency. In this way the ions and electrons are respectively admitted to the light are chamber at different times.

It is an object of my invention to provide large electric arc energies. Subsidiary to this object, it is an object of my invention to provide an apparatus for generating a gas jet of high velocity which operates at good efficiency of the arcing chamber structure of the apparatus with large amounts of air.

It is still another object of my invention to provide a gas jet producing apparatus equipped'with a new and improved nozzle assembly.

According to a feature of the invention, a concentric double nozzle is provided to serve as the ejection nozzle of the first mentioned apparatus for generating a gas jet of high temperature, the gas jet exiting from the double nozzle at its inner nozzle opening. The necessary volume of air is selected from the hot core of the eddy flow and accelerated by the inner nozzle throat. The required volume of air amounts to only a portion of the total volume of the gas jet, for example approximately one-third to one-tenth of this total. The outermost, for the most part cold layers of the eddy flow are directed to the outside by means of the larger, ringshape configured nozzle and subsequently by one or more preferably liquid-cooled tubes. This lead-off tube can be disposed preferably somewhat tangentially to the flow of gas.

The removed gas can be cooled to a low temperature by means of a cooler and flow out through a valve to the ambient atmosphere. The valve can advantageously be used to control or regulate the pared-off portion of the gas flow. The air ejecting from the outer nozzle can, in addition, be directed away by being mixed with a cool flow of air that flows around the light are chamber in a direction corresponding to the axis of the chamber. The cold air stream surrounding the light arc chamber functions on the pared-off portion of the gas flow like a jet-type pump. In addition, a regulation of the pared-off portion of the gas flow or ancillary portion is possible by means of an axial movement of the two nozzle portions. By means of an axial movement of both nozzle portions, the outer ring-like nozzle slit is enlarged or reduced in size.

With the apparatus according to the invention, large amounts of electric are energy are obtainable because the arc roots extend far into the electrodes. By means of a small proportion of surface to volume of the burner space and the high light arc energy, a good efiiciency of the burner with a large quantity of air is obtained. For generating a gas jet of small airquantity, a relatively larger burner can be used and a high air temperature is obtained with the large burner because the core with the highest temperature is removed from the heated gas jet. The total efficiency is given by the following equation:

N k mot ew;

This total efficiency is obtained from the burning efficiency N and from the ratio of the energy N, of the pared-off core to the total energy transferred to the air in the burner N N This total efiiciency can at least be in the same order of magnitude or higher as with a burner equipped with small electrodes. in this connection N is the energy of the air streaming through the outer nozzle. Since a large surface is available in a larger electrode for the light arc, the life of the electrodes are correspondingly increased. Copper or copper oxide burnt off or worn off at the roots of the light are is directed away to the outer nozzle by means of the eddy flow. These removed metal parts are therefore not contained in the useful flow which passes through the inner nozzle. The inner nozzle is therefore not clogged and a model located in a following wind tunnel is not influenced by these metal parts. The gas particles in the outer portions of the gas jet have the greatest impulse moment because the greatest azimuthal velocity component and the largest density occur in the outer portion of the eddy flow. Since this portion of the gas jet is pared-off by the outer nozzle, the gas particles exiting from the inner nozzle contain only a negligibly small impulse moment and this exiting gas jet has thereby an essentiall uniform axial flow.

With the burning through of the cold electrode, the primary portion of the cooling water and above all, the water droplets not vaporized, are directed away via the outer nozzle with the gas moment. A primary or useful flow of gas can be regulated by regulating the paredoff portion when the total flow of gas remains constant. The control in contrast to the regulation of large quantitles with small burners is not associated with a change of the electric energy.

The invention will now be described with reference to the drawing wherein:

FIG. 1 illustrates a gas jet generating apparatus equipped with a double nozzle as required by the invention.

FIG. 2 illustrates a valve for volume controlling the pared-off portion of the gas, and

FIG. 3 illustrates the carrying away of the pared-off gas portions by means of a wind tunnel in accordance with the principle of a jet-type pump.

Referring to FIG. 1, a light arc chamber 2 is closed off by a cylinder type chamber wall 3 and a base plate 4 as well as a cover 5. A drive mechanism 8 of a cup electrode 10 extends through the base plate 4. The electrode 10 is preferably adjustable in the direction of the axis of the light are chamber, the adjusting apparatus not being illustrated in the drawing. The bottom of the electrode 10 can be provided with a central bore for accommodating a flow of gas. Opposite the opening of the cup electrode in axial direction of the light are chamber, there is provided a cylinder electrode 12. The light are chamber 2 can be equipped in a known manner. The individual parts are not illustrated in the figure. The gas entering the cup electrode 10 is heated by means of the light are 14 that burns between electrodes l0 and 12. An ejection nozzle or exiting nozzle is arranged in front of the chamber opening in the direction of the flow of the gas jet. The exit nozzle is, according to the invention, configured as a double nozzle, preferably with the position

adjustable parts

16 and 18 positioned in the axial direction of the gas jet. The inner nozzle portion 16 is provided with outside cooling preferably liquid cooling, especially water cooling. The cooling liquid is supplied via a water connection 20 and via a corresponding connection 21 is again carried away. in a similar manner, the outer nozzle portion is provided with a liquid supply 23 and a carry-off means 24. The cross-section of the inner exit opening 26 has the form of a Laval nozzle. The outer, ring-shaped exit opening 28 can be in the form of a Laval nozzle for advantageous flow. For exhausting the pared-off or ancillary portion of the gas flow, one or more exit channels can be provided, these channels preferably running tangential to the How of gas.

Depending upon circumstances it can be advantageous to select the shape of the outer nozzle opening so that no essential change of the gas velocity results when the gas jet exits.

The inner and outer nozzle portions should be movable relative to each other along the axis of the light are chamber and thereby along the gas jet. This movability is indicated in FIG. 1 by the fact that a portion of the outer wall of the outer nozzle portion 18 is enclosed by the outer wall 32 of the inner nozzle portion 16. This portion of the outer wall 32 should enclose the outer wall 31 of the nozzle portion 18 in a gas tight manner. The required sealing means are not illustrated.

The illustrated arrangement of the movable nozzle portions are to be viewed simply as illustrative, because different configurations of such nozzle portions of like practicability are reasonable and thinkable. The two

nozzle portions

16 and 18 can for example be provided with a common cylindrical outer wall and at least one of the two nozzle portions can be adjustable on this outer wall in axial direction or arranged so that it is displaceable on this wall.

The arrangement according to FIG. 1 is simply a schematic illustration in which the details, for example, the electric insulation of the flow directing parts are not contained in the figures.

According to FIG. 2, at least on of the exit channels for paring-off the ancillary portion of the gas flow can be provided with an adjustable cross-section. The exit channel can be bounded by two wall portions 32' and 36 from which the one part 36 is configured as a slider member. By moving this slider 36 transverse to the direction of flow of the outflowing gases, that is, the axial direction of the exit channel 30, the cross-section of the channel 30 is correspondingly changed and thereby the pared-off portion or ancillary portion of the gas flow is adjusted. The slider member 36 can preferably be provided with water cooling means having a supply and exhaust pipe represented by arrows in the drawing. The cooling liquid flows through the cooling channel 38 of the slider member 36. In a similar manner, the

walls

32 and 33 and 34 of the outlet channels can be provided with subsidiary cooling. The slider 36 is sealed by means of special seals 39 and 40 against the

channel walls

32 and 34. To protect these seals 39 and 40, cold air can be supplied in the region of the seal via a supply opening 42 in the channel 30.

According to FIG. 3, a wind tunnel is configured from an essentially cylindrical outer wall 50 so as to surround the light are chamber containing the electrodes and 12, as well as the

nozzle arrangement

16 and 18. The ancillary portion of the gas flows streams with a high velocity from the light are chamber and out the outer nozzle 28. The air in the flow channel is torn along in accordance with the jet-type pump principle of operation by the ancillary portion of the gas flow and cools the latter. The cooled gas mixture is directed away via a pipe stud 52. For this purpose the two

nozzle portions

16 and 18 and especially the outer nozzle portion 18 can be configured so that a good flow action results. The core of the gas jet exiting from the inner nozzle opening 26 remains essentially without axial eddy forces so that a flow is substantially axial direction results in the gas path 54 of a following wind tunnel.

With a relatively small pressure in the light arc chamber 2 and a correspondingly small velocity of the gas portion exiting from the nozzle 28, the cool air flow can also be added by means of a blower not illustrated in the figure.

To those skilled in the art it will be obvious upon a study of this disclosure that my invention permits of various modifications and may be given embodiments other than particularly illustrated herein, without departing from the essential features of the invention and within the scope of the claims annexed hereto.

Iclaim:

)1. Apparatus for generating a gas jet of high velocity along a jet axis comprising a nozzle assembly coaxial with said axis and having a gas inlet thereon, and an arcing chamber structure disposed adjacent said nozzle assembly for transmitting said gas along said axis to said gas inlet, said nozzle assembly comprising two nozzle members, one of said nozzle members having a first nozzle passage coaxial with said axis and communicating with said gas inlet, said nozzle passage terminating in a nozzle opening, said two nozzle members conjointly forming a second nozzle passage communicating with said gas inlet, and having nozzle outlet means laterally of said jet axis.

2. In apparatus according to claim 1, said nozzle outlet means forming a chamber ar und said axis and ereby the gas lSSU- around said first nozzle passage, w ing from said outlet means acts as a jet-type pump upon the axial gas flow through said arcing chamber structure.

3. Apparatus according to claim 2, said outlet means comprising at least one exit port disposed radially of said gas jet.

4. Apparatus according to claim 3, said outlet means comprising a plurality of exit ports disposal radially of said gas jet, and valve means for adjusting the width of at least one of said exit ports.

5. Apparatus according to claim 4, said valve means including a slidable member, cool air supply means connected to at least one of said exit ports for supplying cool air for protecting the sealing capability of said slidable member.

6. Apparatus for generating a gas jet of high velocity comprising a nozzle member, and an arcing chamber for transmitting the gas to the inlet of said nozzle member, the latter comprising two nozzle portions concentric with each other and defining an inner opening through which said gas jet exits.

7. Apparatus according to claim 6, said inner opening being adapted to have the form of a Laval nozzle.

8. Apparatus according to claim 6, said two nozzle portions defining a ring-like outer opening having a section corresponding to that of a Laval nozzle.

9. Apparatus according to claim 8, said apparatus comprising outlet means communicating with said outer opening for venting at least a portion of the gas of said jet.

10. Apparatus according to claim 6, at least one of said two nozzle portions being movable along the axis of said gas jet.

* a a a a

Claims

1. Apparatus for generating a gas jet of high velocity along a jet axis comprising a nozzle assembly coaxial with said axis and having a gas inlet thereon, and an arcing chamber structure disposed adjacent said nozzle assembly for transmitting said gas along said axis to said gas inlet, said nozzle assembly comprising two nozzle members, one of said nozzle members having a first nozzle passage coaxial with said axis and communicating with said gas inlet, said nozzle passage terminating in a nozzle opening, said two nozzle members conjointly forming a second nozzle passage communicating with said gas inlet, and having nozzle outlet means laterally of said jet axis.

2. In apparatus according to claim 1, said nozzle outlet means forming a chamber around said axis and around said first nozzle passage, whereby the gas issuing from said outlet means acts as a jet-type pump upon the axial gas flow through said arcing chamber structure.