US2255636A - Gas burner - Google Patents

Description

SCP 9 EMF-o R. A. WITTMANN 2,255,636

. GAS BURNER Filed Sept. 16, 1959 2 Sheets-Sheet 2 al., y

J f, W

Patented Sept. 9, -1941 oAs BURNER Robert* A. Wittmann, Chicago, lll., assignor to Chicago By-Products Corporation, a corporation of Iliinois Application September 16, V1939; Serial No. 295,1486

(Cl. S- 99)` f 2 Claims.

My invention' relates to gas burners. The

present application is a continuation in part of my prior application Serial Number 142,358, filed May 13, 1937. 'I'he present burner is designed to secure a combination of actions which cooperate to produce eillcient combustion over a wide range of rates of combustion and a freedom from flashback. 'I'he speciflciorm hereln shown'and described is constructed from a length of seamless metal tubing which is an ideal medium because of thin walls of high heat conductivity and the facility of securing the desired shapes of the functional parts in a simple efficient manner. However, the method of construction is not herein claimed. 'Ihe present invention is in the structure `which secures a novel interrelation of actions and capabilities which give the burner superior operating. characteristics and large capacity in small space.l

The burner of my invention embodies certain structural features and relations as follows:

The gas (mixed with primary air) is supplied to relatively long narrow ports through a narrow passageway deilned by parallel vertical walls. These walls are spaced apart a distancev which is small enough to act as a flame arresting passageway when the walls are kept relatively cool. The parallel walls extend above a distributing duct i'ar enough to be effectively cooled' by free iiow of secondary air around and in contact with them.

The ports are direct continuations of the nar row ilamel arresting passageway without any constriction, hence the velocity of gas ow is substantially the same in the passageway as out of the ports and a temporary downdraft or back pressure which forces the vflame vdown does not give the ilame a chance to propagate in a region of lower velocity below the port.

The cross-sectionalshape or external outline of the burner tube at the ported portion resembles somewhat an elongated truncated teardrop shape with the gas ports at the truncated end. The secondary air iiows upwardly along the side walls,

lcooling them and arriving at the port and tending to pull the gas air mixture out of the slotcomplete combustion. Nowthe completeness oi combustion of -a fuel gaswith reference to the oxygen of the air depends upon repeated opportunities for a combustible gas-particle to meet an oxygen' particle of the air while these two gases are at ignition temperature. Turbulence is a means for creating these opportunities. It has like port in a thin narrow sheetlike stream in ideal form for intimate mixture and consequent turbulence is very effective in securing complete-- ness of combustion, under the conditions of maintained ignition temperature.

According to my present invention',vI produce the turbulence by means of the eddiesformed at the square stern of a body, the sides of which permit substantially streamline flow to the square stern. In the'present invention, the square stern is the active face of a burner, that is the face containing the gas emitting port. As will appear from a later detailed description, theburner of -my invention provides directing side Walls which permit or induce streamline iiow to occur along the sides of the burner to a square end or square stern relative to the direction of air iio'w. Air tlow's to the square stern on each lateral side, so that when the stream arrives at the square stern eddies are formed at the shoulders of the square stern. 'I 'he wall thickness outside the gas port is s'o selected relative to port thickness and air velocity as to secure the beneiit oi this turbulent etjlect.A The gas port'betweenthese shoulders, is so proportioned in widthv to the thickness of the shoulders and to the velocity of air ow that the air flow produces the desired turbulence and the issuing stream of gas is so thin that there is produced a very high ratio of area to volume of the issuing gas. As the result of these two actions,

that is, the turbulence, and the inherent nearness of any gas particle to the surface of the issuing gas stream, the turbulence at the edges oi' the port sets up a thorough mixing of the issuing gas and the flowing air. with the result that the iiame or eld of combustion hugs the shoulv air to rise and thereby creates the necessary upward ilow to produce the action above described. 'I'he velocity oi air ilow is low but by suitably relating the above factors the desired eiect is readily secured. The flow of the secondary air along the side walls which dene the narrow passageway and slotted port between them 'I'he speciilc mechanical construction herein disclosed and constituting the\ preferred embodivbeen demonstrated in many instances that high ment of the invention involves the use of a tube orsheet of metal of desired thickness and of good heat conductivity which is formed to the desired shape. Numerous methods of forming or shaping as by slotting and bending, or by bending an .7 slotting, or other operations, will at once occurto those skilled in the art, but specifically, there is an advantage in forming the tube out of a single piece of seamless tubing. The tube herein illustrated and describedl as the preferred f orm is mechanically organized lin-to functional parts as follows: First, there is an injection mixer which restricts and proportions the air iiow and gas flow. Second, there is a duct for conducting the gas and primary air along the length of the burner. Third, there is a slot or nar row passageway which serves to equalize the out- A flow along the length of the burner. Fourth, there are the ports opening onto the end faces oi' the side walls or stern of the burner, and, fifth, there are the integral bridges performing the mechanical function of holding the edges of the slot and is immediately involved in an of the slot at the right spacing, and -the fluidV ilow function of sealing off the air iiow along the sections of the burner to equalize the outflow of gas f the corresponding section and to prevent uneven burning and backring.

While I have herein described a speciiic form of burner `tube embodying the full complement of functions above recited, it is to be understood that the invention may be embodied in various forms in which some of these functional parts may be modified or omitted. I I

The burner, whether consisting of a single tube, or a plurality of tubes in parallel, has a low heat content. The metal does not get overheated. 'Ihe burner itself runs cool and stays clean.

In operation, the burner lights easily and starts ofl.' promptly without any noise. It burns very quietly over a wide range of rates of combustion without flashback or lifting of the flame, and

when the gas is shut off, the burner goes outwithout the slightest noise or puff.

The burner produces substantially perfect combustion over a wide range of gas pressures and flows, and operates with substantially uniform flame distribution over its entire portedsurface. The flame will not lift or blow oif the ports but v instead hugs the ports closely and produces complete combustiqn of the gas almost as soon as itbrought about. The gas ports are so proportioned that the gas flow issuing therethrough presents a verylarge ratio of lateral surface to volume. Not only is the ratio of lateral surface to volume large, but the transverse dimension, i. e., thickness of the stream, is so small that every gas particle is only a minute distance from the surface where it can get the necessaryoxygen for combustion. With such small distance to travel lateddy or turbulence which produces a very short squat non-luminous ame. In fact the flame is 'nearly invisible. ThoroughV mixing of the gas with the primary air before delivery of the mixture to the ports is a requirement of an ideal burner. In the present structure, the pull of the secondary air upon the, burner ports during operation pulls air in through the venturi. The

venturi, as above mentioned, restricts the inow of air by its throat. The velocity of the gas and air through the throat produces the desired mixing of gas and the primary air in the interior of the burner tube'.

In' order to acquaint those skilled in the art with the manner of constructing and operating a device embodying my invention, Isha'll now describe, in connection with the accompanying drawings, a specific embodiment of the invention, and the manner of constructing and using the same.

In the drawings:

Figure l is a side elevation of a gas burner tube embodying my invention, shown in connection with its supporting yand gas supplying means;

Figure 21s a top plan view of the burner tube;v Figure 3 is an end view of the burner tube taken from the lef-t of Figure 2, showing the Venturishaped inlet;

Figure 4 is a cross sectional view through the throat of the burner, taken on'the line 4-4 of Figure 1;

5 Figure 5 is a vertical cross sectional view taken greatly enlarged scale of the action of iiuid ow at the square stern of a solid body disposed in a fluid stream;

erally to securecontact 'with the air only a narrow depth of turbulence is needed to secure the desired completeness of combustion. Hence, al-

though the secondary air velocity is low and does not have great energy content, by proportion-` ing the thickness of the issuing gas stream, the width of the shoulders, velocity of the issuing gas and the primary air ratio all to the Velocity Figure 8 is a similar diagrammatic Iview. of a solid body of a shape to produce substantially minimum disturbance in streamline ow in a stream of fluid; l

Figure 9 is a similar diagrammatic view of a body similar to that of Figure 8, buthaving a square stern; H I

Figure 10 illustrates on an enlarged scale the action of gas and air iiow past the square stern of the present burner; y

Figurev ll is a fragmentary cross sectional view on an enlarged scale illustrating a modified form of square stern for the burner in which the face of the burner is concave; l Figure 12 is a cross sectional view illustrating the grouping of a series of burner tubes in parallel and illustrating the thermodynamic action of producing a Avertical current of air which viiows along the sides of the burner tubes;l and the air flow actingV upon a given port, indicating A be described later.

the large area of`gas flow exposed to the secondary air.

I shall iirst 'describe in 'detail a specific and' mary lair throughoutthe `full length of the burn' shaped and is formed of twov like sheet metal parts welded together, there being wings 2|, 2i

er; a distributing slot I for equalizing the pressure along the gas outlets or ports Il-Il and the burner face 5 which provides the gas ports and square stern hereafter described in detail.

Preferably, the burner tube herein shown is constructed of a piece of seamless aluminum tubing, of suitable wall thickness, diameter and length, whichv is suitably slotted and die formed into the shape illustrated. Obviously, the tube need not be a seamless tube. It could be a seamed tube if so desired, or the burner could be shaped out of one or more sections of sheet metal if so desired. However, there is a simplicity and directness in forming the tube out of a piece of tubing of uniform initial diameter. In forming this tube, shown in Figures l and 42, the original tubing is die shaped to produce the conguration illustrated and described. A part of the .walls of the tube are collapsed along the sides of the Venturi portion to produce the tins or webs 6, 6 which are of gusset shape, the lobject being to reduce progressively the diameter of the tubular portion to a throat 1 at the narrowest part and to form gradually expanding tubular portion 9 which merges into 'the tubular duct 3 and into the ilattened .slot denning portion l. The walls of the slot defining portion 4 are approximately parallel at the top of the burner as illustrated in Figure I, thatis, as they reach the burner face 5 which forms the square stern portion. These side wall portions which approach parallelism asillustrated atl III, III in\ l gas may be ignitedlat one end of the row of -which grip the adjacent portions of the webs 5, 8 between them, whereby the C-shaped bracket is rigidly connected to the burnerv tube. The gas nozzle I9 has a suitable bore or opening for discharging a stream or gas into the throat 1 4through the funnel shaped inlet portion 8. This introduces a proportionate volume oi' fair into ,theinside of the burner tube. The ilow of gas and primary air expands and decreases in ve- I locity through the expanding portion 9 and is conveyed to the duct portion l. Gas mixed with primary air ilows throughout the `length of the duct I to the narrow slot in the portion l between the side walls I0, III, and issues at the ports I4, I4 between the bridges' I3. I3. The

ports and itwill quickly be transmitted the full lengthof the tube. The ports I4, Il are separated by the bridges I3, I 3, which bridges perform the dual function, first of mechanical support for the edges of the walls I0', I0, and, second. of sealing the burner portions with air, so that the eliect of the air flow is equalized on the respective ports, particularly if there is a component of air ilow endwise of the tube. The wall thickness and width of the shoulders I2, I2 and the width of the port Il may for example be approximately %4 each.

In operation, the burner produces a very low (i. e., short) intense llame which is almost invisible, but of very high emciency* of combustion, that is, completeness of combustion. The

thin gas stream and the turbulence produced at the issuing point of the stream result inrapid and complete combustion. The llame does not need to reach for' oxygen as the oxygen is churned into it immediately. Combustion in this burner produces substantially no detectable carbon monoxide. The llame is very low and squatty, and

duced by the turbulent burning.

Figures 5 and 10, terminate in square edges I2,

I 2 where the metal'of the original tube wall has been removed or cut away. This removal may be effected by punching or siotting the walls of the tube prior to forming or it may be done by cutting or grinding awaythe metal after the tube is formed in the dies, or `it may be done in any other preferred manner.

The edges I2, I2 of the side walls I0, I0 provide the square stern to streamline ilow. as will A series of integral bridges I3. I3 which are continuations of the side walls when the side walls are folded together, form a series of ties and seals for the ports Il, Il which lie between them, and which are, in effeet, continuations' of the slot between the walls I0, I0, which slot terminates on the face of the square stern portion 5 in the ports Il, Il. The rear end of the burner tube is closed as by collapsing the walls by pressure, as shown at I5, I5. The rear end, which is in the shape oi a vertical fin, may rest in a notched support I6 forming part of a supporting frame. The front end ,A

with a bracket l1 which through a suitable valve under control of the operator or attendant. The bracket I1 is c- I shall now explain the manner in which turbulent combustion is produced in this burner.

Assume, as shown diagrammatically in Figure 7, that a solid body 25, with a square stern 25, is disposed in a stream of fluid flow andthat the fluid assumes a streamline flow along the sides of the body, the streamline ilow will' be broken when the iluid passes the square stern. resulting in a region 21 of generally reduced pressure and of violent turbulence causedby the fluid attempting to ll the space and in doing so resolving itself into eddies. Depending upon the relative velocity between the body and the fluid stream and the density of the iluid stream, the size of the area 21, the reduction inpresvsure and the violence oi' disturbance therein will vary.

It is known that in order to reduce the disturbance of a solid body passing through a iluid, or of a iluid ilow past a solid body, the shape which offers minimum opposition to such iiow is like that of a falling raindrop or what might-be called a tear drop shape in cross section. Such a shape is illustrated in Figure 8. It will not produce eddies at the rear or stern. Obviously the proportions will bev varied for the relative speed between the iluid and the solid and'for the density of the ilu'id, but the general character of the shape is well known.

If, now, the stern portion of the teardrop. or tadpole shape shown in Figure 8 be cut oi, as

3 tures.

is a highly 'usefu1 errent. i keep a surprisingly uniform flame along its l length for any given rate of gas feed.

illustrated in Figure 9, to produce a squarevstern 29, the region of turbulence 21 will attempt to fill outA the shape ofthe ideal form with an eddyl ing mass of the fluid.

If, now, the solid body 28'-be hollowed out according to the dotted line 30, it will be -seen Now in the operation of the vpresent burner,l

the gas is first turned on and flows through the pipe 20 and nozzle 9 into the Venturi portion 6 by Way of the funnel-shaped opening 8, the neck 1, expanding tube 9, to the interior of the duct portion 3 and the slot portion 4. Referring now to Figurey 10, gas issuing through the relatively narrow passageway of the slot portion 4 and issuing out of the port I4 Y tends, lof itself, to issue as a sheet like the old shtail burner, al` though, due to the design of the present burner the velocity of issuance is relatively -low since the pressure of the fuel vgas itself is not applied to -the ports but only through induction by the effect of the nozzle I9 and the Venturi por-` tion 6. As soon as thel gas is ignited the air is expanded by the heat of combustion and in duces afluid flow v'ertically, as will be apparent from the diagram f Figure I2 where a series of burner tubes I, I are placed side by side. The region of'hot expanded air above the burner. in conjunction with the region of colder and denser air below the burner tube induces a Vertical`- draft 'producing an effective vertical streamline flow of the air around each one of the tubes` vertically as illustrated diagrammaticallyin Fig- Iure 9.' This vertical flow of secondary air immediately produces the region of turbulence at 21, with the result that the ame, instead of being a flame of the flshtail type, is a low, squat,` fuzzy looking flame, which is little more than a -bluehaze producing a combustion more complete than any other burner known to me. During combustion at the ports I4 the reduced pres-v sure created in the region 21 (Figure 10) by the flow of secondary air pulls the gasfair 'mixture out' of the ports I4.

'Ihe essential features for securing this result are the thin sheet like issuing stream of gas A and the turbulence so related to it vas to secure almost instant churning together of gas and air. When greater turbulence can be sustained by reason of greater air velocity and hence greater energycontent the thickness of the stream of gas may be greater. Those skilled in the art will readily be able to correlate these two basic fea- The interruption to streamline ow at the face The reduction in pressure 4is not inof pressure. However, th reduction in pressure in conjunction with the expansion of y gas when burning tends to produce an equalization of flame along the length of the burner port. This The'burnertends to Tests of the products of combustion indicate gaseoso -combustion is proceeding, is very short and squat and does not lift off of 'the shoulders I2, I2 but remains close to them. Any heat which is transmitted from the burning gases to the metal of the shoulders I2, I2 is rapidly dissipated by contact with the thin walls of the stream of sec-` ondary air which hugs the surfaces of these walls. Hence, the burner tube, which preferably is vof aluminum, although obviously it may be made of other metals or alloys, always remainscocl and nol part of the burner tube -becomes overheated. The heat which is conducted through the metal and is transferred to the secstood that this is afunctional designation rather than a definition, in that obviously the surfaces I2, I2, do notneed' to lie in the same plane, nor do they need to be parallel. For vexample, in Figure 11 I have shown the edges I2', I2' of the sheet metal sides I0, I0 as being inclined inwardly and towards each other to produce a concave face. noulnced than shown in lFigure 11. The important considerations are that the streamlined flow of fluids follow along the sidewalls III-Io and then be interrupted or interfered with sufficiently to produce a region of high turbulence and that the issuing stream of fuel gas be so thin that the turbulence so produced is able tov penetrate the full thickness of `the issuing stream i and produce a complete churning of gas and airimmedlately. If the turbulence is small the thickness of the gas stream must likewise be small. If the turbulence is more extensive a greater thickness of the issuing gasstream is the respective ports I4, I4 lie insubstantially -a straight line in the specic fo'rm shown. This is desirable where a planar Vzone of combustion is desired, but it will be apparent that the in# vention is notnecessar'ily limited to that specific detail. By having the portsv all at the same height, substantially equal effect is produced upon the respective ports. Instead of being a straight tube, obviously the burner tube might be coiled up into a -coil, or disposed on a curve or otherwise the form thereof may be modified without departing from the invention.

The bridges I3, I3 which constitute the unslotted parts of the original tube wall serve the desirable function, mechanically, of spacing thel side walls I0, I0 so as to maintain the sides of the slots I4 accurately for any variations in tem- A perature or the like. They perform, also, an important function in tending to equalize the effect upon a port, or upon adjacent ports, as-is illustrated diagrammatically in Figure 13. Assume a nozzle 35 made up of a section oi the tube shown in Figures 1 and 2, with the ends thereof sealed except for the opening 36, and assume that adjacent layers or sheets of vertically flowing air S1,

This may be more pro- 31 flow vertically up along the sides of the hollow body 35 and past lthe shoulders I2, I2 on each side of the slots I4. It can be seen that these bridges I3, I3, in effect, tend to ll out the ends of the space in which the turbulence produced by com- 5 bustion of the gas issuing from the port' I4 occurs. Thus, in effect, the ends 'of the longitudinally extending regionl of turbulence 21 are sealed, off because the sheet of air hugs the solid bridges effect upon the specificport Il.y Since each port is thus sealed by the uid ow of the secondary air and the bridges I3, the likelihood of air being drawn down one port I4 in order to make up the complement of gas issuing at another port I4, is greatly reduced. Hence, the Width of the port I4 is not so critical. It may be wider or narrower than the accepted figure of .08" for a tubular duct which will not tend to ash back. The

present burner. willY function satisfactorily with l a port width of .055 .to as low as .040 without danger of clogging up and with no fllash back.

It is, however, essential that the cross sectional outline 'of the burner tube at the ports be such as tov permit the secondary air to flow around the outside walls of the duct 3 and hug the side- Walls III-l0 fori-the dual purpose of keeping the sidewalls IIl-ID cool to serve as a flame arrester and to create the region of turbulence andreduc-` 'tion of pressure at 21, as above explained. Tov 30 fulfill these requirements, the duct 3 is preferablyround and the vertical walls I0-Ill must extend far enough above the duct 3 that the rising stream of secondary air sweeps along their sides in iiowing up to shoulders I2I2 where the 35 ports are located. To do this effectively, the walls Ill-IIJ should extendabove the duct 3' by a vertical distance not less than` the horizontal radius of the duct 3.v Thereby the secondary will freely flow up from below around the duct and along 40 the sidewalls III- IIL I am aware that burners with a large number of round port openings closely disposed along the length of a burner tube are old; also thatburners with a series of elongated openings are old, and

I do not claim such as my invention. No device ofthe prior art of which I amaware has provided for the issuance .of the gas from a narrow slot which maybe of any desired length, wherewith means are provided on each side of the slot to produce eddies of secondary air by the iiow of secondary air which at the same time keeps the Walls defining the slot relatively cool. The width of the slot is so related to 'the eddy producing means that the gas issuing from said slot is immediately involved in a churning operation by the effect' of the eddies with-the result that a perfection of combustion heretofore unattainable is secured. The gasame may be extended horizontally as long as .desired by suitably extending the length of the slot, but the thickness of the issuing stream must be no greater than what ca n be thoroughly churned by the size e of construction may be widely varied to meet particular conditions land that the novel principle and mode of burning may be embodied in a wide varietyof forms. I3 and tends thereby to produce a' more uniform 10 I do not intend to be limited to the precise details shown except and unless the same are made a part of the invention defined by the appended claims. 4

substantially parallel vertical walls terminating in substantially parallel straight edges interrupted at relatively long intervals by relatively short integral upwardly arched portions of the 'side wallsjoining the side walls mechanically and holding them in spaced relation and having between said arched portions relatively long narrow port openings of the same width as the distance between said vertical walls, the lower parts of,said vertical `walls diverging outwardly and constituting integral walls of a tubular distributing duct which duct opens upwardly into said narrow passageway along its length,l the cross sectional outline of the burner tube being approximately that of an elongated and truncated teardrop to permit upward ow of the secondary air to 'wipe the upper margins of said vertical sidewalls with substantially streamline flow, the

said substantially vertical side walls extendingA y above said duct portion a distance not substantially less than the horizontal radius of the said distributing duct and into the region where the upward current of secondary air'induced by the burning of gas at said ports flows in effective heat exchanging' contact with said side walls and cools the same, the narrow pasagewaybetween said side walls comprising the'only comunication between the ports and said distributing duct, said narrow passageway between said cooled side walls being effective as a name arrester to prevent ashback.

2. The burner tube of claim 1 characterized by an integral induction portion forming a forward extension of the walls of the burner tube for the entry of .gas and primary air, said induction portion comprising a double tapered Venturi portion the walls of which merge into triangular gusset shaped flanges of double wall thickness disposed vertically on opposite sides of the Venturi portion, the walls of each iiange being integral e

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