US2618325A

US2618325A - Method of controlling a burner flame

Info

Publication number: US2618325A
Application number: US29753A
Authority: US
Inventors: Rudolph O Seitz
Original assignee: Air Reduction Co Inc
Current assignee: Airco Inc
Priority date: 1948-05-28
Filing date: 1948-05-28
Publication date: 1952-11-18
Anticipated expiration: 1969-11-18

Description

Nov. 18, 1952 R. o. SEITZ METHOD OF CONTROLLING A BURNER FLAME 2 SHEETS-SHEET 1 Filed Ilay 28, 1948 PIC-3.2

FIG.|

FlG.-3

m 3m Fm Rm M Q 7 G F Patented Nov. 18, 1952 2,618,325 Marnon or CONTROLLING A BURNER FLAME Rudolph 0. Seitz, East Orange, N. J assignor to Air Reduction Company, Incorporated, a corporation of New York Application May 28, 1948, Serial No. 29,753

3 Claims. (Cl. 158-1175) which a. fuel-gas, and some combustion-supporting gas such as air or oxygen, are mixed at some point prior to their issuance from the orifice or orifices at which they burn.

One of the problems that have always confronted manufacturers and users of gas burners is backfire. A backfire occurs when the rate of flame propagation exceeds the velocity ofthe combustible gas mixture issuing from the burner. An oxyacetylene flame is particularly unstable and a backfire in an oxyacetylene torch can be very destructive and costly if it results in a flashback, i. e., a continued burning of the gases within the torch. Another problem is so-called flame blow-away. When the velocity of the stream of combustible gas mixture issuing from the burner exceeds the rate of burning of the gas mixture, in whatever state of dilution has been caused by the surrounding air, the flame recedes or blows away from the burner orifice and is usually extinguished altogether. The burner flame remains stationary or seated at the discharge orifice of the burner, or a very small distance from it, only when the velocity of the stream of combustible as mixture issuing from the orifice is substantially equal to the rate of burning of the gas in the stream.

One object of this invention is to provide a method of controlling a burner flame fed by premixed gases so that it is very stable and the possibility of backfire is substantially eliminated.

The invention is based on the discovery that if a stream of combustible gas mixture is deliberately caused to issue from' a burner orifice at a velocity which exceeds the flame blow-away velocity of the gas for that Particular orifice so that the flame will recede from or blow away from the orifice, and a protuberance or pin of the proper length is positioned in the center of and parallel to the gas stream, the gas stream is slowed down sufliciently by friction effects along the pin and by turbulence at the end of the pin to cause the velocity of the gas stream to become substantially equal to the rate of burning of. the gas in the stream at or just on the end of the pinand therefore the gas will burn with a flame that remains seated at or close to the end of the pin instead of at the discharge orifice. The flame is therefore stable and there is little or no possibility of backfire because at'all points along the.

pin, up to its end, the velocity of the gas is higher than the flame blow-away velocity, and the gas issuing from the orifice is constantly attempting to blow the flame away from the orifice to the end of the pin. It has also been found that the flame at the end of the pin has a form or pattern quite different from that of the standard type of burner fiame in that the inner cone is inverted so that the base or large-area portion of the cone is toward the tip of the flame, whereas in e. standard burner flame the pointed end of the inner cone is toward the tip of the flame. In fact, the inner zone of the flame has somewhat of a mushroom shape instead of a true inverted-cone shape. Other shapes can be given to the inner zone of the flame by giving the pin or its end portion different configurations. Certain advantages of causing the inner zone of the flame to have an inverted cone or mushroom shape will be pointed out later. I r

The method according to the invention in its broad aspect therefore comprises discharging a combustible gas mixture from an apertured member at a velocity which exceeds the flame blowaway velocity of the gas stream, and at a region which is a predetermined distance from the apertured member producing a retarding effect on the velocity of the gas stream that will cause the flame to remain spaced substantially said predetermined distance from the apertured member.

The accompanying drawings illustrate" a number of different kinds of gas burners that are adapted for use in carrying out the method. In the drawings? Figure 1 is an enlarged side elevation, partly in vertical section, of one form of gas burner embodying the invention;

Fig. 2 is an end view of the burner of Fig. 1;

Fig. 3 is an enlarged side elevation, partly in vertical section, of a different form of a gas bumer embodying the invention:

Fig. 4 is an end view of the burner of Fig. 3;

Fig. 5 is an enlarged side elevation, partly in vertical section, of another different form of gas Fig. 11 is an enlarged side elevation showing the type of flame produced by the burners of'the invention; and

Fig. 12 is an enlarged side elevation showing the type of flame produced by a conventional gas burner.

Referring first to Figs. 1 and2, the gas burner closes the end of the tube ID. A pin or wire I2 I is fitted into a suitable hole ln'the face p ate" ll so that it projects a. short distance from the face plate, as shown in Fig. 1. The face plate ll is drilled to provide a circular series of .small jet shown in Figs. 1 and 2. In addition to the simpassages 13 which surround the' base of the pin, the series of passages being in concentric rela-f tion with the pin. The gas mixture flows from the tube out of the jet passages-l3 in the face plate. Theface plate therefore constitutes an apertured gas-discharging member. The gas jets issuing from the passages 13 blend so that there is formed in effect a single streamof gas which is directedlongitudinally along the pin l2 toward its distal end and in the center of which the pinis located. The pressure under which the combustible gas mixture is delivered to the tube l and the-size and number ofthe jet passages I; are such that the gas mixture issues from thejet passages at a velocity above the flame blow-away velocity of the gas stream. The pin l2 isof such a length that by the time the stream of gas mixture reachesthe end-of it, the velocity 01' the gas stream will have been retarded sufflciently by friction effects alongthe pin and bi'f'turbulenceat its end to, cause theyelocity of the. gas stream at the'end of the'pin tobe' substantially equal to the burning, rate of .the gas'mixture'at the end of thepin in whatever state of dilution exists at this point byreason of contact of thegas stream with the surrounding air as the gas stream blows along the pin. Cone sequently, when the gas vmixture issuing from the jet passages 13 is ignited, the gas surrounding the pin will burn with a flame which re,- I'nains stationary at or just off the end of the pin} The general form of the flame produced. is I illustrated in Fig. 11. For sake of comparison a conventional burner flame is shown in Fig. 12. It will be noted that whereas the pointed end o'f'the inner cone .l 4 ofthe conventional burner flame is toward the tip of the flame; in the flame pt oducedin accordancewith the invention,- the inner cone I5 is linverted so that the base of the. cone is toward the tip of the flame. Actually the inner zone of the flame takes on somewhat of a. mushroom shape the headof which is toward the fiames tip as depicted in Fig. 11. The outer envelope l6 of the flame produced in accordance with the invention is very little different from the outer envelope ll of the conventional burner flame.

The hottest part of the conventional oxyacety j lene flame is a relatively small zone just beyond the tip of the inner cone. In the flame produced by th s invention the hottest part of the flame is also just beyond the inner zone, vbut the hot.

zone is much more extensive due to the mushroom shape of .the inner zone. Fig. 11 alsoshows how theflanie produced in accordance with theinven .directed' toward its distal end.

beyond the end of the pin and this, combined with the fact that the gas flowing along the length of the pin has a cooling effect on the pin, makes it possible for the burner to function for a long period of time without becoming excessively hot Figs. 3 and 4 illustrate a. gas burner operating on thesame principle as that shown in Figs. 1 and 2, but in this case a face plate l8, or apertured gas-discharging member, has a single central opening IS in which is force-fitted a length of pinion wire 20, i. e. a pin or wire that is fluted longitudinally to provide radially projecting ribs or teeth -2l. The flutes in the pin 20 and the inner wall of the central opening in the face plate l8 form jet passages for the gas mixture corresponding to the jet passages l3 of the burner plicity 'of this type of burner it has the functional advantage of having the gas ports or passages close to the pin.

Instead of providing a circular series of jet passages around the pin, through 'which the combustible gas-mixture is discharged, a single annular jet passage may be provided immediately adjacent the pin. One way of accomplishing this is illustrated in Figs. 5 and 6. The burner illustrated in these figures includes an insert or plug 22 fitted into the closed end 23 of a burner tube 24 far enough so that it projects into the interior of the burner tube, as shown. This insert corresponds to the faceplate or apertured gas-discharging member of the burners of Figs. 1-4. A pin 25 is fitted into a hole 26 drilled in the insert 22 so that it projects outwardly a short distancebeyond the end of the insert. This hole is enlarged at its forward end to form an annular space 26} around. the pin 25. A series of gas ports flare drilled radially through the insert 22 to place the annular space 26' around the pin in communication. with an annular space 28 formed between the external wall of the insert 22 and the interior wall of the burner tube 24. The; combustible gas mixture fed to the burner tube 24, under pressure, issues through the annular jet passage 26 and forms an annular stream of gas surrounding the pin and which is This type of burner functions in the same manner as those previouslydescribed.

ll'Thespin projecting outwardly beyond the apertured gas-discharging member need not be a pin in the strict-sense of the word. In case it is desired to produce an elongated flame of the ribbon type the pin may be more in the nature of a flattened protuberance having a rectangular cross-section, and slot-type jet passages may be employed for discharging the gas mixture. One a way in which a burner of this type can be.con-. structed is illustrated in Figs. 7 and 8. It has a burner tube l0 similar to the tube of the burners illustrated in Figs. 1-4, having a face plate or apertured member 29,. the apertures of which comprise a. pair of slot-type jet passages 30 at opposite sides of a plate-like protuberance 3| which projects outwardly a short distance beyond the apertured member. A convenient way of making the face plate and protuberance assembly is to cut a single rectangular opening in the face pla'te of, greater width than the thickness of the flat protuberance, then center the latter in the rectangular opening, and secure it'in-that position in any suitable way as by making the inner end pf the flat protuberance somewhat wider than the rectangular opening-is long to provide shoulder portions 32 (Fig. 8) which can be silver soldered to the inner face of the face plate.

As already made clear, the gas mixture must issue from all of the burners above described at a velocity which is above the flame blow-away velocity of the gas stream. It so happens that a flame, fed by an oxyacetylene gas mixture of the kind usually utilized in gas torches, could be blown away from the burner orifice only by utilizing excessively high gas pressures if it were not for the fact that the boundary layer of the gas stream is diluted somewhat by the surrounding air as it leaves the burner oriflce which has the effect of lowering the velocity level of the gas stream at which the flame will blow away from the orifice. Therefore, if the boundary layer of the gas stream is protected from the diluting effect of the atmosphere in any way, it is extremely difllcult to blow the flame away at the pressure of the gas mixture that is usually permissible. If several burner units of the type heretofore described are grouped together to form a mat-type burner, it is evident that the group of flames surrounding the stream of combustible gas mixture issuing from any given burner unit would tend to exclude the atmospheric air from that gas stream and prevent the desired diluting effect of the gas stream above referred to. Therefore, when a number of burner units of the kind above described are grouped together, some provision must be made to allow each stream of combustible gas mixture to come in contact with suflicient air in order to make it possible to cause the gas stream to issue from its burner unit at a velocity above the flame blow-away velocity of the gas stream at a reasonable pressure of the gas mixture. A suitable construction for a multiflame burner in which provision of this kind is made is illustrated in Figs. 9 and 10. In this type of burner the combustible gas mixture is fed from a manifold 33 to a number of burner units 34 each of which may be similar in construction to any one of the burners previously described, or each burner unit may have a pin 35 which is similar to the pin 2! of the burner shown in Figs. 3 and 4 except that it is made from hexagonal stock instead of being fluted longitudinally, the pin being fitted into the central opening of a short tube 36 so that it projects outwardly a short distance beyond the end of the tube. Each tube 36 communicates at its inner endvwith the manifold 33. The combustible gas mixture passes out from the manifold 33 through the spaces between the flat faces on the hexagonal pins and the inner walls of the tubes 38. Surround-= ing all of the tubes 38 is a second manifold chamber 31 to which compressed air is supplied by means of a tube 38. The manifold chamber 37 has a front wall 39 provided with a series of openings to receive the outer ends of the tubes 34, these openings being slightly larger in diameter than the external diameter of the tubes. This forms an annular port 60 around each of the tubes 34 from which an annular stream of air issues that surrounds the corresponding stream of combustible gas mixture issuing from the interior of the sleeve around the pin. Thus the boundary layer of each stream of combustible gas mixture is diluted with air and this makes it possible to blow away the flames to the ends of the pins in accordance with the invention without the use of an excessively high pressure for the gas mixture. Gases other than air, such as nitrogen or carbon dioxide, or a fuel gas such as city gas, will have a similar diluting effect on the streams or combustible gas mixture issuing from the burner units and such a gas may be fed to the manifold chamber 31 instead'of air if sov desired.

Because of the fact that the velocity of the gas stream at which the flame will blow away from the burner oriflcedepends in part upon the state of dilution of the combustible gas mix- In all the burners herein described the size I of the jet passages through which the combustible gas mixture is discharged, and the distance the pin or other protuberance projects beyond the gas-discharging member, and the pressure of the gas mixture fed to the burner tube, may all vary somewhat and yet the burners will operate in accordance with the invention. By way of example, the pin I2 of the burner shown in Figs. 1 and 2 might be 1% in diameter and may project about A from the outer face of the gas-discharging member ii. The ports i3 may be eight in number and may be made by a No. '71 drill. The pressure of the gas mixture fed to the burner tube should be around 6 p. s. i. In general, the pin or other protuberance may project from the gas-discharging member anywhere from to /2" for pressures of the gas mixture ranging from about 4.5 p. 5.1.170 about 20 p. s. i.

It will be understood that in all cases the constituent gases for the combustible gas mixture are supplied from suitable sources, such as oxygen and acetylene cylinders, and are mixed in any suitable way and then fed to the burner tube or tubes, the supply of gases and their delivery pressures being controlled by valves and gas pressure regulators of the usual type. Such valves and pressure regulators make it possible to deliver to the burner tube a gas mixture under the desired pressure and in which the gases are mixed in the desired proportions.

I claim:

1. A flame control method which comprises feeding pro-mixed gases including a fuel gas and a combustion supporting gas to a series of discharge orifices arranged in a small circle, discharging the gas mixture from the discharge orifices to form a plurality of separate jets of the gas mixture which surround a. central axis with which said circle is concentric and with which the jet axes are in parallel relation, the gas mixture being discharged from said dis charge orifices at a velocity which exceeds the flame blow-away velocity of the gas mixture in each jet, and producing a retarding effect on the velocity of the jets of gas mixture solely along said central axis while the jet axes are in parallel relation to the central axis so that at a predetermined point along such axis the velocity of the jets of gas mixture and the dilution of the gas mixture in the jets by the surrounding air will be such that the rate of buming of the diluted gas mixture when ignited will substantially equal the velocity of the jets of gas mixture and the gas mixture in the jets will burn to produce a single flame the base of which remains substantially at said predetermined point along said central axis and thelongitudinal axis of which is substantially in alignment with said central axis and is a straight-line prolongation thereof throughout the length of the fi ame.

2. A flame control method which comprises feeding pre-mixed gases including a fuel gas and a combustion supporting gas to each of a number of closely positioned discharge orifices, discharging a diluent gas around the stream of mixed gases issuin from each discharge orifice, discharging the mixture of pre-mixed gases from each discharge orifice about a, central axis and at a velocity which exceeds the flame blow-away velocity of the mixture, and producing a retarding effect on the velocity of each of the streams of mixed gases after it leaves its discharge crifice and solely along its central axis so that at a distance from such orifice the velocity of the gas stream and the dilution of the gas mixture by said diluent gas will be such that the rate of burning of the diluted gas mixture when ignited will substantially equal the velocity of the gas stream and the gas mixture in the stream will burn to produce a single flame which will remain seated at said distance from the orifice and the longitudinal axis of which is substan- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 622,482 Jackson Apr. 4, 1899 701,347 Johnson June 3, 1902 1,146,724 Lucke July 13, 1915 1,423,750 Brombacher July 25, 1922 1,536,176 Aldrich May 5, 1925 1,604,525 Lysnkey Oct. 26, 1926 1,661,929 Deemar Mar. 6, 1928 1,913,170 McCutcheon et al. June 6, 1933 2,310,116 Ratclifl Feb. 2, 1943 2,345,247 7 Erickson Mar. 28, 1944 2,475,240 Hassmer et a1. July 5, 1949 FOREIGN PATENTS Number Country Date 227,566 Great Britain Jan. 22, 1925