US3680999A

US3680999A - Burner unit

Info

Publication number: US3680999A
Application number: US19365A
Authority: US
Inventors: Friedrich W Hill
Original assignee: AGA AB
Current assignee: AGA AB
Priority date: 1969-03-14
Filing date: 1970-03-13
Publication date: 1972-08-01
Anticipated expiration: 1989-08-01
Also published as: DE1913014C3; DE1913014B2; DE1913014A1

Abstract

A burner unit for the production of a high energy flame of oxygen gas or air and a fuel gas, preferably acetylene. The burner comprises two separate inlets for the oxygen or air and for the fuel gas. A non-return valve is built into each inlet. The oxygen or air inlet is in communication with a central bore of a nozzle pressure plug mounted inside a nozzle cap. The central bore develops into a cone giving the oxygen or air a high velocity. Inside the nozzle cap and downstream of said nozzle pressure plug, a nozzle slot-piece is inserted. On the outer perimeter of the nozzle slot-piece a number of mixing ducts are arranged. The mixing ducts are in longitudinal alignment with fuel gas supply openings surrounding the central bore of the nozzle pressure plug and are provided with a small twist. Inside the central bore a safety device is attached to the wall of the bore. The safety device is made as a substance which separates or melts at a predetermined temperature and which is carried away by the gas stream to close the conical ending of the central bore.

Description

United States Patent Hill 51 Aug. 1, 1972 [54] BURNER UNIT Primary Examiner-Carroll B. Dority, Jr. [72] Inventor: Friedrich W. Hill, Hamburg, Ger- Taylor and Hmds many 57 ABSTRACT [73] Assignee: AGA Aktlebolag, Lidingo, Sweden A burner unit for the production of a high energy Flledi March 1970 flame of oxygen gas or air and a fuel gas, preferably 2'1 1 19,3 5 acetylene. The burner comprises two separate inlets for the oxygen or air and for the fuel gas. A nonreturn valve is built into each inlet. The oxygen or air I30] Fomgn Apphcaflon Pnomy Data inlet is in communication with a central bore of a noz- March 14, 1969 Germany ..P l9 13 014.4 zle pressure plug mounted inside a nozzle cap. The central bore develops into a cone giving the oxygen or [52] US. Cl. ..431/21, 239/399, 239/4l6.4, air a high velocity. Inside the nozzle cap and 2 /4 1 downstream of said nozzle pressure plug, a nozzle slot- [51] Int. Cl ..F23ll 5/02 piece is inserted on the outer perimeter of the nozzle Field Search 416-5, slot-piece a number of mixing ducts are arranged. The 239/430, 431, 399 mixing ducts are in longitudinal alignment with fuel gas supply openings surrounding the central bore of References and the nozzle pressure plug and are provided with a small twist. Inside the central bore a safety device is at- UNITED STATES PATENTS tached to the wall of the bore. The safety device is Falls-Ck eta] made as a ubstance separates or melts at a Ma-l'hn X predetermined temperature and is carried away ggg g $9 3 by the gas stream to close the conical ending of the 1g on central bow 2,659,426 11/1953 Rowell ..431/21 X 20 Claims, 13 Drawing Figures PATENIEDAus 1 m2 SHLU 1 OF 3 FIG. 1

IN VENTOR FRIEDRICH-WILHELM HILL BURNER UNIT BACKGROUND OF THE INVENTION The invention relates to a burner unit for the production of a high energy flame of oxygen gas or air and a fuel gas, e.g. propane, hydrogen, benzene vapor, coal gas or methane, but preferably acetylene. There are two general types of gas burners: uniform pressure burners; and injector burners. Acetylene gas must be used at low pressures. Thus uniform pressure burners which operate at highpressures must be excluded from consideration when using acetylene gas. Equipment designed to operate with high pressure acetylene gas is, accordingly, rejected in oxyacetylene engineering, for the triple unsaturated alkyne, which has a heat of formation of 61 Kcal/Mol, is far more likely to explode and to disintegrate when compressed in the presence of a suitable source of ignition than when the gas is under a low pressure of not more than about 1.5 atmospheres.

Injector burners, which operate on the principle of the injector pump, require the presence of mixed gases in the, burner. For oxyacetylene equipment of high gas consumption, e.g., for jet flame burners used to clean concrete, the injector type burner requires a large volume of mixed gas. This large volume of mixed oxygen and acetylene is always liable to detonate and presents a serious hazard. When this gas mixture is ignited in the burner, explosion or back-firing occurs inside the equipment. The opinion, sometimes even expressed by experts, that explosion is relatively harmless whereas back-firing is dangerous as it is often accompanied by setting fire to the hose, is false, for explosion and back-firing have the same root cause, i.e. the detonation of the gas mixture. The vector sign of the reaction process is reversed in these situations but the direction of the event is purely accidental.

The present invention relates particularly to a burner for the production of a flame of high energy of oxygen gas and acetylene. The invention can, however, generally also be used with advantage for all fuel gases, e.g. propane, hydrogen gas, benzene vapor, coal gas and methane. The burner unit design of the invention is particularly useful as a flame jet. Concrete flame jet burners are used to clean concrete surfaces by the application of heat to remove dirt deposits of all kinds, e.g. oil, rubber tire abrasion, thawing salt, etc., and to remove the carbonated sludges. Such a cleaning process is always necessary if the concrete is to be preserved by means of modern plastic materials and the process is becomming more widely used. The thermal cleaning process depends entirely on the availibility of a suitable burner. A burner can be considered as suitable if it meets the following minimum requirements:

a. The burner must be supplied separately with acetylene and oxygen gas. The use of mixed gas, except of mixed gas in extremely small spaces immediately before delivery from the nozzle, is not allowed. The acetylene pressure must not exceed about 1 atmosphere whereas the oxygen pressure is optional.

b. The injector type burner is ruled out, because it operates with mixed gas.

c. Completely reliable operation, even if wrongly manipulated.

d. Economy of operation, i.e. treatment of a larger area per unit of time than was possible hitherto, which means increased feed.

The foregoing requirements can be met only partially with conventional burners. In particular, there is no complete reliability of operation, which must be guaranteed under all circumstances, as the burners used at present are always variations of the well-known injector welding torch. The burner head, which is of considerable size for flame jet burners, is supplied with highly explosive acetylene-oxygen mixed gas from the injector tube. In spite of fitted safety devices, (e.g. a long nozzle, in order to keep the burner head as far away as possible from the flame; guard plates protecting against sooting, etc.) the conventional burners are far from fool proof. A sudden stoppage of the gas stream will naturally cause a pressure deop. A sudden clogging of the nozzles reduces the discharge velocity to zero. Both conditions cause detonation of the gas in the burner head, because the ignition velocity is greater than the gas delivery velocity under these conditions. The detonation itself becomes manifest as an explosion or as back-firing.

To give an indication of the size of a conventional burner unit, the following data is given. A burner unit is 250 mm long with a cross-section of about 50 X50 mm, it has 21 simple nozzles, each of which has a bore of 1 mm diameter. The length of one single nozzle is 50 mm. The standard burner is 750 mm long and consists of three main parts. The gas consumption of this burner is approximately 8,000 liters of acetylene and 8,500 liters of oxygen per hour. The economy of a bunner of such a design is also insufficient, because of the limited amounts of energy available for attacking the concrete surface. The advance on standard concrete is about 1 meter/min.

It is, therefore, an object of the present invention to provide a burner without the aforementioned defects.

The gas-dynamic design of all conventional injection-type burners implies that the burners are neither explosion proof nor back-fire proof.

Uniform pressure burners had to be excluded from the start for the solution of the problem because acetylene can be used without risk of detonation only under low pressure.

BRIEF SUMMARY OF THE INVENTION The invention provides a completely new approach to the solution of the problems described above. The characteristic feature of the present invention is that an oxygen or an air jet is sent through a nozzle with high velocity into a reaction chamber, into which the fuel gas flows at a slow rate through at least one fuel gas supply bore and that several mixing ducts with an opening to the atmosphere are connected to the reaction chamber at a point outside the axis of the oxygen or air jet. It will be clear to those having ordinary skill in the art that a completely different system of gas supply has thus been devised.

It is a known fact of fluid dynamics and gas dynamics, that vectorial parallel and highly accelerated gas jets (Mach number 1 and more), which are passed through a stationary or only lightly agitated gas medium, transfer their impulses (momentum: m v at their boundary surface via the boundary molecules to the stationary molecules of the medium passed through. This produces a laminar flow of both gas types side by side. The expression m v shows that the impulse is the product of the mass of the highly accelerated gas molecule and its velocity. With time, the static gas assumes the velocity of the highly accelerated gas. The gas flowing with high velocity (gas jet) thus forms the core, and the surrounding gas, which has now also been accelerated by the transfer of the impulse, forms the outer shield of the newly createdlaminar two-phase gas jet. In this form, both gases cannot be used as carriers of thermal energy. According to the invention, both gases in laminar flow are now forced through a system of twisted slots. The twisting thus produced mixes both gases into a gas mixture of high potential thermal energy, Which burns evenly without the possibility of decomposition or detonation.

It will be clearly evident, therefore, that the device provided according to the present invention isv completely new for oxyacetylene design. According to the invention a burner unit comprises a burner body, a reaction chamber is said body, conduit means to convey a fuel gas at low velocity to said chamber, a plurality of elongate mixing ducts extending from said chamber and open to the atmosphere at the other end, and conduit means to introduce an oxygen containing gas at high velocity into said elongate mixing ducts for mixing said fuel gas and said oxygen containing gas. In one embodiment, the oxygen containing gas is fed to the reaction chamber and in another embodiment the oxygen-containinggas is fed to said elongate mixing ducts. The mixing ducts are preferably provided as thin slots in a nozzle slot piece peripherally closed with a nozzle cap.

DETAILED DESCRIPTION OF THE INVENTION There follows a detailed description of a preferred embodiment of the invention, together with accompanying drawings. However, it is to be understood that the detailed description and accompanying drawings are provided solely for the purpose of illustrating a preferred embodiment and that the invention is capable of numerous modifications and variations apparent to those skilled in the art without departing from the spirit and scope of the invention.

FIG. 1 is an elevation, partly in section of a burner assembly;

FIG. 2a is a sectional view through a burner element cap of FIG. 1;

FIG. 2b is a bottom view of the cap of FIG. 2a;

FIG. 3a is a section view through the nozzle block of FIG. 1;

FIG. 3b is a section view through the nozzle block of FIG. 1 in a plane at right angles to the sectional plane of FIG. 3a;

FIGS. 3c and 3d are top and bottom views, respectively, of the nozzle block of FIG. 3a;

FIG. 4 is an enlarged sectional view through the pressure nozzle for the assembly in FIG. 1;

FIG. 5a is a section through the nozzle slot-piece of FIG. v1 along the line A-B of FIG. 5b;

FIG. 5b is a top view of the nozzle slot-piece of FIG. 1 as seen from the mixing nozzle opening;

FIG. 56 is a top view of the nozzle slot-piece of FIG. 1 as seen from the reaction chamber;

FIG. 51! is a side elevation of the nozzle slot-piece of FIG. 5a; and

FIG. 6 is an elevation view, partly in section, of an alternative burner unit according to the invention.

In a burner unit according to the invention, the two gases, oxygen and acetylene, are supplied separately from two self-contained tanks place closely together to one or several burner units of the invention. The acetylene tank is a vessel preferably provided with a corresponding number of nozzle connections for the gas supply. The oxygen tank is located very close to the acetylene tank and preferably connected with it by heat transfer ribs. The expanding oxygen thus regeneratively cools the acetylene through the ribbed heat transfer connection. The burner assembly shown in FIG. 1 contains a nozzle block 1, which has two threaded connections 19, 20 (see FIGS. 3a and 3b for the gas connections. Oxygen gas enters under pressure through the connection 19, whereas the connection 20 is used for the supply of the fuel gas, e.g. acetylene (low pressure) in the example described. Each of the two threaded connections is used for attaching a valve body 4 (see FIG. 1) which includes nozzle connection 4a for connecting the corresponding pipe line 4b. A non-return valve 3 is built into the valve body 4.

A nozzle pressure plug 6 inside the nozzle assembly 1 forms on the side a reaction chamber 17 and on the other side a fuel gas distribution chamber 18. The pressure nozzle plug 6 is centered by a round collar 24 in the bore 2 of the nozzle assembly, which is in communication with the connection for the oxygen gas. The fuel gas distribution chamber 18 is connected with the fuel gas connection by bores 22 in the nozzle body 1.

The reaction chamber 17, partly formed by the nozzle pressure plug 6, is sealed by the front face 9 of a nozzle slot-piece 8, which is enclosed by a nozzle cap 7. The nozzle cap 7 also serves to secure the nozzle pressure plug 6 and the nozzle slot-piece 8 to the nozzle block 1. The nozzle pressure plug 6 also contains a safety device 5, which will be described in greater detail later on.

The single parts of the assembly are now described with reference to FIGS. 2a-5d.

The nozzle cap shown in FIGS. 2a-2b has an internal thread 27, which is screwed on to the corresponding external thread 28 (see FIG. 3) of the nozzle body 1. It serves to fasten the pressure nozzle 6 and the nozzle slot-piece 8 to the nozzle body, as shown in FIG. 1. The nozzle cap 7 has also a cylindrical bore 29, to which is joined a conical bore 30. The nozzle slot-piece 8 of FIGS. 5a-5d is inserted into the cylindrical bore 29 and the conical bore 30, and a 'collar 31 of the nozzle slotpiece 8 than is seated on the area 32 of the counterbore of the nozzle cap 7.

The nozzle block shown in FIGS. 3a3d is in communication with the supply of fuel gas by the threaded bore 20, into which a valve body 4 is screwed. The outer cylindrical space 33 is thus in communication with the fuel gas, e.g. acetylene. This circular space 33 is connected with the inner face 35 of the nozzle block by bores 22. In a specific device according to the invention, four bores 22 with 1 mm diameter each have been provided which means that a cross-sectional area of 3.2 mm is available for the passage of the fuel gas.

From the facing 35 of the nozzle block an oxygen gas supply bore 2 is drilled into the nozzle block, the internal end of which is connected with the oxygen connection 19 by a duct 23. The central collar 24 of the pressure nozzle 6 shown in FIG. 4 is fitted tightly into the end of this bore 2. The collar 24 includes a flange 25 which rests on the facing 35 of the nozzle block after assembly. The pressure nozzle plug 6 has, furthermore, a circular set of holes 26 which is surrounded by a continuous ring wall 14 on the outside away from the collar 24. The distance between the facing 15 of the ring wall and the bottom facing 34 is an essential feature of the invention and is about 1 mm in this particular example. The bore 21 of the pressure nozzle, through which the oxygen under pressure is delivered, develops into a cone 36, to which the oxygen jet nozzle 37 is attached, which has a diameter of about 0.8 mm in this example. The space formed by the internal surface 38 of the ring wall and the bottom facing area 34, into which the centered oxygen jet nozzle 37 discharges, is defined as reaction chamber 17 (see FIG. 1). The bores 39 with about 1.5 mm diameter are evenly distributed on a central diameter of about 7 mm. These bores 39 are described in the following description also as gas supply bores. The ratio between the cross-sectional area of the oxygen jet nozzle 37 and the cross-sectional area of the eight fuel gas supply nozzles 39 is critical and is approximately 1:28 for the embodiment of the invention as described. It may, however, vary between 1:15 and 1:50.

Between the face of flange 25 of the pressure nozzle plug 6 and the circular set of holes 26 lies the cylindri cal portion 16, the length of which determines the size of the fuel gas distribution chamber after the assembly of the pressure nozzle plug (see FIG. 1). The fuel gas enters into this distribution chamber through the bores 22 and flows from here through the gas supply bores 39 of the circular set of holes 26 into the reaction chamber 17. The previously mentioned safetly device shaped as a brass sphere 5 is soldered to the wall of the bore 21. The solder is selected to melt at a given temperature, in this embodiment a temperature of approximately 300 C. The solder melts at an undue increase of the temperature of the pressure nozzle plug, and, in that event, the brass ball 5 is carried away with the gas flow and deposited as a ball value in front of the oxygen jet nozzle 37, where it fuses with the metal seating and firmly seals the opening.

Apart form the pressure plug 6, the nozzle slot-piece 8, shown in FIGS. 5a-5d is of particular importance. It is fitted into the bore of the nozzle cap 7 as already mentioned. The nozzle slot-piece 8 has a conical body 13 with approximately 2 taper, with the large diameter at the end 9 facing the reaction chamber 17 and the small diameter at the opposite end 10. There are a total of 12 slots 1 1 each with a twist of 10 angle minutes.

All slot areas are tangential to a circle 12 located concentrically of body 13 as shown in FIG. 50. The width of each single slot is 0.25 mm at the base of the slot and increases outward with the wedge shape of 1 slope. The depth of the single slots at end 10 is about 1 mm.

The nozzle slot-piece 8 is pushed into the nozzle cap 7, as shown in FIG. 1. After the pressure nozzle plug 6 has been pushed tightly with its collar 24 into the bore 2 of the nozzle body 1, nozzle cap 7 is screwed with its thread 27 on to the external thread 28. The facing of the ring wall 14 is thereby closely seated on surface 9 of collar 31 of the nozzle slot-piece 8.

During operation, oxygen gas and acetylene flow into the nozzle assembly, through the non-retum valves 3. 1f

the pressure of the oxygen gas or the fuel gas increases for any reasons whatsoever inside the nozzle body, the valves close automatically. The gases cannot re-enter the tanks. The oxygen flows from an ante-chamber of very small dimensions, which is formed mainly by the bore 2 in the nozzle body 1 through the oxygen jet nozzle 37 into the reaction chamber 17. The oxygen enters this chamber 17 approximately at the speed of sound.

A similar process takes place at the acetylene nonretum valve 3, but under low pressure conditions. The flow velocity of the acetylene is, therefore, relatively small. Although only a low pressure of about 0.1 at mospheres exists in the four ducts 22 in the nozzle body 1, the acetylene is forced at an initial pressure of about 0.6 atmospheres and a final pressure of about 0.4 atmospheres through the fuel gas supply lines 39 against the periphery of the compact and highly accelerated oxygen jet which has a diameter of about 1 mm. The acetylene (or other fuel gas) diffuses into the oxygen jet and receives an impulse through the kinetic energy of the oxygen jet. Both gases impinge still fairly unmixed on the enclosed face of the core 13 of the nozzle slot-piece 8, which is coaxial with and opposite the delivery opening of the oxygen jet nozzle 37.

The gases now enter the slightly twisted slots 11 of the nozzle slot-piece 8. Mixing of the gases takes place inside these twisted slots, which can, therefore, also be described as mixing ducts. The nozzle slot-piece 8 is encased by the nozzle cap 7. The laminar gas flow as well as the gas flow which has been made turbulent by the impingement on the face 9 of the nozzle slot-piece 8 receive a strong monentum of rotation through the small angle of twist of the slots 11, because of the high gas velocity. The rotation releases a completely mixed gas body after a calculated distance of travel in slot 11 (distance, angle of twist and gas velocity are intendependent functions). The gas emitted burn with a powerful but calm flame.

The volume of one slot 11 and the volume of the reaction chamber 17 is preferably very small, so that in case of ignition only a slight hissing sound can be heard. If a combustion should actually develop inside the reaction chamber 17 which could happen only under most unfavorable conditions -the non-retum valves 3 to the acetylene tank as well as to the oxygen tank are closed by the excess pressure developed. The gas streams cease and the flame is deprived of its fuel. Should the valves leak, the safety device 5 in the oxygen supply bore 21 of the pressure nozzle plug 6 is activated. This event occurred during laboratory tests only when the nozzle cap and the slotted piece were fused together in a liquid magma. The temperature of the nozzle block had risen to approximately 300 C. (the temperature was measured with thermochrome plugs). It has already been mentioned that a brass ball is attached by soft soldering as safety device inside the oxygen supply bore 21 of the nozzle pressure plug 6. The brass ball has a slightly larger diameter than the delivery opening of the oxygen jet nozzle 37. If the temperature of the pressure nozzle plug rises about 300C, the solder melts and the ball is deposited in front of the delivery opening and is soldered in place by the adhering soft solder. The oxygen supply is completely cut off by these events and only the cold sooty flame of the acetylene is still burning. The situation can, therefore,

never become dangerous, even if the non-return valves fail. The mechanical design of the nozzle assembly is thus doubly safeguarded. The principal safety measure remains, however, the design of the separate gas supply.

The cooling of nozzle body 1 is by regeneration with oxygen escaping from the pressure gas block at high velocity preferably approximately the velocity of sound. The expansion cools the nozzle so effectively that the temperature of the nozzle block 1 under thermal load for one hour does not rise to more than 70 C. in an experiment where the vertical distance between the nozzle opening 10 and a concrete surface is 30 mm and the angle of inclination of the flame jet is 50The result is the more remarkable as it is obtained with a long time test. The concrete, having only a poor heat transfer capacity, is changed into a light liquid glassy lava. This substance solidifies during cooling to a dark glass.

The balance of heat dissipation is a little less fovorable if several assemblies are grouped together to one burner. Contrary to the heating circuit of a single nozzle with constant temperature decrease along the radial length (s f (t) a multiple nozzle burner develops an ellipse with isothermal curves, the slope (ds/dt) of which is considerably less steep. The heat radiation is obviously also reducedby this arrangement. However, despite this reduction, oxygen cooling by regeneration for sufficient r safe handling of the burner.

The assembly employs the principle of diffusion and twist for mixing. This eliminates uniform pressure operation as in an acetylene burner. Furthermore, there are no large mixing spaces, as is the case with injector burners. Detonations (explosion and back-firing) are impossible with the present design principle. As there is not acetylene-oxygen mixture contained in the burner head, many possible dangers are avoided. Even a sudden pressure drop is not dangerous, because the non-return valves stop any kind of combustion inside the burner assembly. Even a reduction-of the flow velocity below the rate of ignition will not harm this design, because back-firing of the ignition flame into a mixing room is not possible. Any flame which may possibly blow back through one or the other slot 11 reaches only the almost completely unmixed gas in the reaction chamber 17 below the pressure nozzle 37. In case of a combustion of the very small gas volume the pressure would increase, which would cause the nonreturn valves to close.

To safeguard the burner unit, the oxygen valve should be opened first, and the acetylene valve should be opened afterwards. This sequence is important in order to achieve firstly a marked diffusion effect and secondly to avoid any soot formation. For this reason, the handwheels of both valves are preferably suitably arranged in a conventional manner for the operator to prevent any wrong operation.

The design of the burner unit follows exact mathematical laws. The pressure limits of the gas supply during operation are, therefore, very narrow. The unit as described and illustrated here can operate at constant oxygen pressure of 4.5 atmospheres most effectively only if the related acetylene pressure is in the range from 0.6 to 0.55 atmospheres. The table below illustrates this condition for a wider range.

Oxygen pressure Acetylene pressure: Acetylene pres- (atmospheres) for optimum sure: flame operating flame breaks away (atmospheres) (atmospheres) The best operation range lies between 4.5 and 5.0 atmospheres oxygen. Optimum conditions then prevail for flame intensity and gas consumption. The exemplified embodiment of the invention refers to an oxyacetylene burner. When using air or when using other fuel gases, the explosion proof or back-firing proof design of the burner may noW be, under cettain conditions, of decisive importance. However, for all fuel gases, the large energy output, the possibility of a large increase of the burner feed, and the small number of component parts are particular advantages of the invention.

FIG. 6 shows a modification of the burner assembly having a pressure nozzle 40 the end of which faces the slotted member 8' is provided with a stepped extension 41 of graduated diameter, which adjoins a circumferential flange 14 whose diameter is essentially equal to the core diameter of the inner thread 27 of the nozzle cap v7 and through which pass a large number of small borings 39 which are uniformly distributed over a circle concentrically situated in relation to the axis of the pressure nozzle 37'. The flange 14' is followed, on the side opposite to the stepped extension 41 by a stepped cylindrical section 6 of graduated diameter, the part having the larger diameter being supported by a shoulder 25 which clears the ducts 22 at the front surface 35' of the nozzle body, 1, whereas the section having the smaller diameter makes a gastight seal with the blank boring 2 of the nozzle body 1 The extension 41 of the graduated diameter forms a shoulder supported by the front surface 9' of the slotted member 8' of the part having the smaller diameter, making a gastight connection with an axial blank bore 8a of the slotted member 8. The flange 14 and the adjoining stepped sections on both sides of the pressure nozzle, 6 form annular spaces 17' and 18 which communicate via the borings, 39' of the flange 14' but which are sealed off from the oxygen-carrying part of the assembly.

Milled into the shell surface of the slotted member 8, in equal angle divisions, are twelve slots 1 1' having a width of 0.25 mm, extending in the lengthwise direction at a twist angle of 2 which slots form a tangent with an imaginary circle concentrically situated in relation to the longitudinal axis and which enclose, form the tapering end to the other end, an angle of 2 in relation to the longitudinal axis. As already pointed out, an axial blank bore 8a extends from the collar end into the slotted member and intersects the slots at the angle of 2 so that passages are created from this point of intersection to the bottom of the blank bore 8a for the gaseous oxygen introduced at sonic velocity into the blank bore. This area of transition from the blank bore 8a to the slots 11' forms the diffusion chamber in this embodiment.

In the burner assembly according to the invention, the fuel gaseous oxygen, supplied at a pressure of about 0.4 atmospheres, and the gaseous oxygen, supplied at a pressure of about 6 atmospheres, remain separate as far as the point of intersection of the blank bore 8a and the slots 11' of the slotted member 8. Diffusion between fuel gas and oxygen occurs between this point of intersection and the bottom of the blank bore, the gases being intimately mixed over the remaining slot length covered by the nozzle cap 7'. Over the free slot length, i.e. the length over which the slotted member 8' projects from the nozzle cap 7', the centrifugal force developed by the twist angle of the slots 11, eg 2is of such magnitude that the gas mixture firmly adheres to the slot wall so that optimum flame distribution is achieved. In this embodiment, the slots are twisted from about 2 to about 6 along their length. As has already been mentioned, this provides a burner assembly which is completely foolproof and accident-proof and which will not assume unduly high temperatures even in long term operation.

While the invention has been described in detail in relation to preferred embodiment, it will be understood that numerous modifications can be made within the spirit and scope of the invention. For example, in order to ensure a uniform fuel gas supply, the number of fuel gas supply, bores of equal size and uniformity may be located around the central oxygen or air jet nozzle can be varied widely. According to the invention, the mixing ducts or slots are arranged centrically around the axis of the oxygen or air jet nozzle and preferably coincide with the axial elongations of the fuel gas supply openings.

Excellent operation is achieved according to the invention if the axial length of the reaction chamber in the direction of the oxygen or air jet is not less than the diameter of the jet nozzle. Furthermore, it has proved to be advantageous to provide a distance, equal to at least the diameter of the fuel gas supply bores, between each fuel gas supply bore and the opening of the jet nozzle. It is also preferred if the length of the mixing ducts equals at least 10 times, preferably 25 to 75 times, the length of the reaction chamber.

In order to achieve intensive mixing of the gas components with laminar flow, the invention utilizes twisted mixing ducts, the angle of twist of the mixing ducts being less than 1, and preferably in the order of 10 angle minutes. It is preferred that the mixing ducts are arranged on the outer perimeter of a nozzle slotpiece the periphery of which iS closed to atmosphere by a nozzle cap perimeter which fits closely around the outer perimeter of the nozzle slot-piece.

In the illustrated embodiment it is provided that the mixing ducts shall be in the shape of slots for example 12 in number, which are 0.25 mm wide at the bottom of the slot and which broaden radially outward wedgeshaped at the slot angle of 1The total cross-sectional area of the mixing ducts adjacent the reaction chamber is preferably about two thirds of the cross-sectional area of the fuel gas supply bores and decreases gradually towards the gas delivery end until the sectional area of the mixing ducts at the gas delivery end equals approximately half the cross-section of these ducts adjacent the reaction chamber.

For the formation of the base of the mixing ducts, the nozzle slot-piece is suitable designed as a truncated cone, the smaller area of which is situated at the gas delivery end. It has been arranged that the area of the mixing ducts on the nozzle slot-piece tangentially touches a circle the diameter of which is approximately half the outside diameter of the nozzle slot-piece.

The geometrical design of the mixing ducts in the noule slot-piece, which by means of their twist create the rotation and thereby the mixing of the gases, is such that the individual flames contain only one cold core, which, as space element tends towards zero (the sum of the space elements is represented by a triple integral fff x, y, 2 (dx, dy, dz) The cooling of the flame by the core which always occurs in a single flame, is thus eliminated according to the invention and the energy supply by the flame thus sub-divided is now considerably higher, a fact which correspondingly affects the temperature.

In the embodiment of FIG. 6, the pressure nozzle is provided with a jet extension which tightly engages an axial blank bore of the slotted member, which bore intersects the slots at a point between the free end of the pressure nozzle extension and the end of the blank bore at an acute angle in order to form passages from the part of the assembly carrying oxygen or air to the part carrying fuel gas, for mixing the gases. Furthermore, the outlet end of the slotted member projects axially from the nozzle cap. In this embodiment, the gaseous oxygen or air is forced a highly accelerated jet into the blank boring of the slotted member regeneratively from the inner wall. At the end of the blank boring, the get of oxygen or air is divided into as many partial jets as there are slots in the slotted member. The partial jets diffusely absorb the fuel gas n the slots which is practically static and flow, together with the fuel gas, under considerable rotation due to the twist of the slots, through the length of the slotted path covered by the nozzle cap to the outlet. Rotation of the two gases produces an intimate gas mixture. Further, the gas mixture is forced against the slot wall by rotation resulting from the centrifugal force generated, so that it does not escape to atmosphere in the area of free path length, i.e., at the point where the nozzle cap is recessed in relation to the slotted member. With pressures at their optimum setting, the flame burns perfectly at a distance of about 0.05 mm form the mouth of the slotted member, i.e., the flame is practically established in the air, deriving only its geometrical shape from the slotted member. After two hours of operation of the burner assembly, at an oxygen pressure of 6 atmospheres, and an acetylene pressure of 0.45 atmospheres, the temperature of the end of the nozzle cap adjacent the outlet is only about 25C. When a steel disc is forced against the burner assembly in an attempt to close the nozzle mouth completely, the flames escape to the side. The outlet flow velocity of the gas is in no way affected by this procedure. The same phenomenon is observed when a piece of wood is forced against the burner. But if the piece of timber is applied to the flame for about 30 seconds, the nozzle mouthpiece simply melts into a shapeless metallic mass, without any sensational consequences.

What is claimed is:

1. A burner for the production of a flame from a fuel gas comprising: a burner body; a reaction chamber in said body; conduit means to convey a fuel gas at low velocity to said chamber; a plurality of elongate mixing ducts extending from said chamber and open to the atmosphere at the other end; conduit means to introduce an oxygen containing gas at high velocity into said reaction chamber for mixing said fuel gas and said oxygen containing gas; said oxygen containing gas conduit means comprising a nozzle positioned to introduce said gas into said reaction chamber; and said fuel gas conduit means comprising a plurality of bores arranged peripherally about said nozzle.

2. A burner for the production of a flame from a fuel gas comprising: a burner body; a reaction chamber in said body; conduit means to convey a fuel gas at low velocity to said chamber; a plurality of elongate mixing ducts extending from said chamber, and open to the atmosphere at the other end; conduit means to introduce an oxygen containing gas at high velocity into said reaction chamber for mixing said fuel gas and said oxygen containing gas; said mixing ducts being provided on the periphery of a tubular nozzle slot piece member; said burner including a nozzle cap member enclosing said nozzle slot piece member; and said slots being substantially tangential to an imaginary circle on the nozzle slot piece member, the diameter of said circle being about one half the diameter of said nozzle slot piece member.

3. A burner for the production of a flame from a fuel gas comprising: a burner body; a reaction chamber in said body; conduit means to convey a fuel gas at low velocity to said chamber; a plurality of elongate mixing ducts extending from said chamber and open to the atmosphere at the other end; conduit means to introduce an oxygen containing gas at high velocity into said reac tion chamber for mixing said fuel gas and said oxygen containing gas; said mixing ducts being provided on the periphery of .a tubular nozzle slot piece member; said burner including a nozzle cap member enclosing said nozzle slot piece member; the outer end of said nozzle slot piece member projecting axially form said nozzle cap member; and said slots being twisted a total of from 2 to 6 along their length.

4. In a burner for producing a high energy flame of oxygen-containing gas and a fuel gas, wherein the gases are mixed prior to ignition along an elongate mixing portion, the improvement, wherein said burner includes a substantially disk-shaped reaction space having an axial length less than its diameter; nozzle means for introducing a jet of oxygen-containing gas axially into said reaction chamber; including bores for introducing fuel gas into said reaction chamber peripherally of said nozzle means; and a plurality of elongate mixing ducts extending from a face of said reaction chamber remote from said nozzle means to the atmosphere, said elongate mixing ducts being located peripherally of said nozzle means.

5. A burner according to claim 1 wherein said mixing ducts are arranged peripherally about said nozzle and in alignment with said bores.

6. A burner according to claim 1 wherein the axial length of said reaction chamber is not less than the diameter of said nozzle.

7. A burner according to claim 1 wherein the fuel gas bores are located at a distance fromsaid nozzle not less th th diameter of a fuel bore.

g} A burner according t claim 1 wherein the length of the mixing ducts is at least 10 times the axial length of the reaction chamber.

9. A burner according to claim 8 wherein the length of the mixing ducts is from 25 to times the axial length of said reaction chamber.

10. A burner according to claim 4 wherein said mixing ducts are slightly twisted.

1 1. A burner according to claim 10 wherein said mixing ducts are twisted a total of less than 1 along the length thereof.

12. A-bumer according to claim 4 wherein said mixing ducts are provided on the periphery of a tubular nozzle slot piece member, and said burner includes a nozzle cap member enclosing said nozzle slot piece member.

13. A burner according to claim 12 wherein said mixing ducts comprise slots having a width of about 0.25 mm at the bottom and increasing in width radially outwards at an angle of about 1.

14. A burner according to claim 13 wherein the total cross-sectional area of the mixing ducts adjacent the reaction chamber is about two-thirds of the cross sectional area of said fuel gas bores and decreases to about one-half of said fuel gas bores cross sectional area at the end of said nozzle slot piece member remote from said reaction chamber.

15. A burner according to claim 12 wherein the nozzle slot piece member comprises a truncated cone forming the bottom of said mixing ducts, the smaller area of which is at the end of said member remote from said reaction chamber.

16. A burner according to claim 12 wherein the outer end of said nozzle slot piece member projects axially from said nozzle cap member.

17. A burner according to claim 4 including nonreturn valve means in said fuel gas conduit means and in said oxygen-containing gas conduit means.

18. A burner according to claim 1 including a central duct for supplying oxygen containing gas to said nozzle, said duct including a body secured to said duct by a substance which melts at elevated temperature to release said body whereby said body is transported by said oxygen containing gas to close said nozzle.

19. A burner according to claim l8 wherein said body comprises a brass alloy and said substance comprises solder.

20. A burner according to claim 19 wherein said body comprises a ball having diameter larger than the diameter of said nozzle.

Claims

2. A burner for the production of a flame from a fuel gas comprising: a burner body; a reaction chamber in said body; conduit means to convey a fuel gas at low velocity to said chamber; a plurality of elongate mixing ducts extending from said chamber and open to the atmosphere at the other end; conduit means to introduce an oxygen containing gas at high velocity into said reaction chamber for mixing said fuel gas and said oxygen containing gas; said mixing ducts being provided on the periphery of a tubular nozzle slot piece member; said burner including a nozzle cap member enclosing said nozzle slot piece member; and said slots being substantially tangential to an imaginary circle on the nozzle slot piece member, the diameter of said circle being about one half the diameter of said nozzle slot piece member.

3. A burner for the production of a flame from a fuel gas comprising: a burner body; a reaction chamber in said body; conduit means to convey a fuel gas at low velocity to said chamber; a plurality of elongate mixing ducts extending from said chamber and open to the atmosphere at the other end; conduit means to introduce an oxygen containing gas at high velocity into said reaction chamber for mixing said fuel gas and said oxygen containing gas; said mixing ducts being provided on the periphery of a tubular nozzle slot piece member; said burner including a nozzle cap member enclosing said nozzle slot piece member; the outer end of said nozzle slot piece member projecting axially form said nozzle cap member; and said slots being twisted a total of from 2* to 6* along their length.

7. A burner according to claim 1 wherein the fuel gas bores are located at a distance from said nozzle not less than the diameter of a fuel gas bore.

8. A burner according to claim 1 wherein the length of the mixing ducts is at least 10 times the axial length of the reaction chamber.

9. A burner according to claim 8 wherein the length of the mixing ducts is from 25 to 75 times the axial length of said reaction chamber.

11. A burner according to claim 10 wherein said mixing ducts are twisted a total of less than 1* along the length thereof.

12. A burner according to claim 4 wherein said mixing ducts are provided on the periphery of a tubular nozzle slot piece member, and said burner includes a nozzle cap member enclosing said nozzle slot piece member.

13. A burner according to claim 12 wherein said mixing ducts comprise slots having a width of about 0.25 mm at the bottom and increasing in width radially outwards at an angle of about 1*.

17. A burner according to claim 4 including non-return valve means in said fuel gas conduit means and in said oxygen-containing gas conduit means.

19. A burner according to claim 18 wherein said body comprises a brass alloy and said substance comprises solder.