US2839128A - Burner - Google Patents

Description

June 17, 1958 E, J. SCHWEITZER ETAL 2,839,128

BURNER Filed March 25, 1953 2 Sheets-Sheet l I lm/enfor Edw/n J Schwe/fzer l l a/mce E Sam/0g y A genfs n 1958 E. J. SCHWEITZER ETAL 2,839,128

BURNER Filed March 25. 1953 I 2 Sheets- Sheet 2 hive/#0! Edwin J Sc/rweifzsr Wallace E. Son/flay United BURNER Edwin J. Schweitzer, Plymouth Township, Norristown County, and Wallace E. Sonntag, Drexel Hill, Pa., assignors to Thermal Research and Engineering Corporation, Conshohociten, Pa., a corporation of Delaware Application March 25, 1953, Serial No. 344,512

2 Claims. (Cl. 1S87) Burner,;now Patent No. 2,701,608, granted Feb. 8, 1955' there is disclosed a burner in which fuel and air are mixed and preheated in a mixing section and burned in a combustion section. An abrupt enlargement of the burner at the entrance of the mixing section into the combustion section provides a peripheral shoulder which protects a portion of the fuel-air m'mture within the combustion section against turbulence caused by the rapid movement of the mixture into the combustion section. This shoulder provides an open flame holder where the flame is continuously maintained within the combustion chamber and from which area combustion progressesinwardly toward the center of the stream of fuel-air mixture to cause combustion of the entire fuel-air stream within the combustion chamber.

An important feature of the invention disclosed in this copending patent application is the fact that it makes possible rapid combustion with high heat release in a combustion chamber of minimum size. Iowever, when burning large quantities of fuel and with fuel-air mixture velocities of great magnitude the progress of ignition inwardly from the flame holder may require such time that an unduly long combustion chamber becomes necessary if combustion is to be completed within the combustion chamber.

We have now found that it is possible to increase the tats atent O tages of the open peripheral flame holder of the aforesaid contemplates addition to the apparatus of an ignition chamber disposed between the fuel-air mixture supply section and the combustion chamber, together with means in the ignition chamber having a surface facing downstrearnof the burner centrally of the stream of fuel-air mixture which protects a portion of the fuel-air mixture adjacent said downstream surface against turbulence caused by the rapid movement of the mixture into the combustion chamber and provides, as in the case of the peripheral shoulder, a flame holding surface facing downstream of the burner for continuously maintaining an open flame adjacent to said surface for igniting substan tially centrally the column of fuel-air mixture passing therethrough. Such central ignition of the fuel-air mixture stream caused by the above-mentioned flame holding surface, added to the peripheral ignition effected by the peripheral flame holding shoulder within the combustion 2,839,128 Patented June 17, 1958 Fig. 3 is a cross-section taken on the line IHIII of Fig. 2;

Fig. 4 is a broken cross-section taken on the line IVIV of Fig. 1;

Fig. 5 is a perspective view of an igniter block or central flame holder generally similar to that shown in Fig. 1;

Fig. 6 is a perspective view of another type of central flame holder;

Fig. 7 is a view similar to that shown in Fig. 4 illustrating an alternative arrangement of central flame holders within the ignition chamber shown in Fig. 1;

Fig. 8 is a" longitudinal mid-section, similar to that illustrated in Fig. 1, illustrating a different initial ignition arrangement and a different position of central flame holder; and

Fig. 9 is a side elevational view partially in section of the apparatus of the present invention.

In the embodiment of the invention illustrated in Figs. 1 to 4, there is shown a burner 16 comprising in sequence a fuel-air mixture supply section 11, an ignition chamber 12 and a combustion chamber 13. Thus a combustible mixture of the fuel and air enters the burner 10 through its supply section 11, passes thence through its ignition chamber 12 where it is initially ignited, and thence enters the combustion section 13 of the burner where its combustion is completed.

The supply section 11 is formed as a flanged tube, here a cylindrical tube having an anterior flange 14 for connection with a fuel-air mixture delivery conduit and a larger posterior flange 15 for connection with the ignition chamber 12. Air is supplied to the supply section at a high velocity, for example, by means of a blower 14a as illustrated in Fig. 9 which is interconnected with the entrance to the supply section through a duct'14b. The fuel may be supplied in any desired manner; for example, the fuel may be injected into the air supply to form the fuel-air mixture by means of an injection nozzle 14c supplied by a pipe 14d through which the fuel passes under pressure.

The ignition chamber 12 is of generally cylindrical shape and comprises an outer flanged member 16 having a forward outwardly turned flange 17 which is connected to the posterior flange 15 of the supply section 11, as by bolts 18. At the opposite end of the member 16', there is formed a rear outwardly turned flange 19 by which the entire burner 10 may be fixed in operative position, as to a furnace wall (not shown). Beyond the rear outwardly turned flange 19 a cylindrical rear extension 20 v of the outer flanged member 16 extends co-axially'with the member 16 for supporting, the combustion chamber 13, to which it is joined, as by welding, cementing or other fixing means.

Within the outer flanged member 16 a ring 21 is closely positioned in order to provide a proper fit between the member and certain parts within the ignition chamber, and also to insulate and strengthen the construction. Inside of the ring 21 a container ring 22' is fitted for a purpose which will presently appear. The container ring has a conical central opening 23 therein, the base of which is of the same diameter as the internal diameter of the supply section 11. The container ring is radially slotted, as at 24, from its periphery, through the conical portion of the fuel-air mixture adjacent thereto and creates adjacent the downstream surface of the central flame holder a generally quiescent zone of burning fuel-air mixture. See Figs. 1 and 4. The central flame holder may take different forms, depending upon the nature and condition of the fuel-air mixture which enters the burner 10 through the supply section 11. In the embodiment illustrated in Figs. 1 and 4 the'central flame holder is formed of refractory material, for example a ceramic material, and is of solid construction. Fig. 5 shows, in perspective, a mod iied form of such central flame holder, indicating further'its'general construction. The central flame holder 25 has a length equal to the distance between the periphery of the container ring 22 and the bottom of the slot 24 in which it is held in position; and

its breadth is such that it fits snugly within the slot. The remaining dimension of the central flameholder is such that its front end bears against the inner flange of the supply section 11 where the central flame holder fits into the bottom of the slot 24, and the opposite base,

I spark plug 29 projects through the inner flange 15 of the supply section into the initial ignition space 28 in'order to ignite the fuel-air mixture in the ignition chamber when operation of the burner is started. It will be recognized, however, that the initial ignition space 28 is relatively protected and that the force of the on-rushing combustible mixture will not blow out the flame therein.

4 r combustion chamber immediately surrounding the o'pening in the terminal ring 26. Accordingly, the shoulder 30 provides a peripheral pocket of ignited mixture which is protected from the turbulence caused by entrance of the fuel-air mixture into the combustion chamber..

.From the foregoing, operation of the apparatus will be easily understood. A combustible mixture of fuel and air is projected into the supply section 11 of the burner at high velocity. The fuel-air mixture passes thence into the ignition chamber which it fills, including the relatively protected initial ignition space 28. Thence the fuel-air mixture, passing through the conical open- The fuel-air mixture passing from the supply section 11 into the ignition chamber 12 is thus ignited when the burner '10 is put into operation.

The terminal ring 26 is a somewhat flat ring which is positioned rearwardly in the ignition chamber 12,'being the inner surface of the ring 21. Upon the forward face L 7 held in place by friction between its peripheral surface and of the terminal ring 26 the rear surface of the'central flame holder 25 and the rear surface of the container ring 22 bear in frictional contact. 7 terminal ring'26 is in frictional contact with the forward surface of the combustion chamber wall, as'will later. 7 be explained. The central opening through the terminal.

ring 26 is cylindrical in form and coincides in diameter 22 when the two rings are in position. See Fig. .1. will be evident that the central opening through the terminal ring 26 forms a connecting passage between the ignition chamber 12 and the combustion chamber 13.

The combustion chamber 13 is held firmly in place against the ignition chamber 12 by the-cylindrical rear making a tight joint between the ignition chamber and It isto benoted that the Y the combustion chamber. interior cross-section of the combustion chamber 13 is greater than the opening throughthe terminal ring 26' thereby providing a flame holding shoulder 30 within the The rear face of the t with that of the conical opening 23 of the container ring; It

mg 23 in the'container ring 22 and through the'opening in the terminal ring 26', enters the combustion chamber 13. To start operation of the burner the spark plug 29 I first ignites the combustible fuel-air mixture inthe initial ignition space 28, whence ignition passes to the downstream end of the'supply section 11 and thence through the conical opening 23 past the central flame holder 25. As the ignited fuel-air mixture passes the central flame holder 25 some of thisburning mixture'remains behind thetrailing face of the central flame holder 25 where continues to burnand continues to ignite transversely and centrally the column of fuel-airmixture passing the central flame holder. Thereupon, the spark plug need no longer be used,

' It has been found that a very thin trailing face of central flame holder will afford sufiicient protection toz a ribbon of burning fuel-air mixture to maintain the latter in a semiquiescent state at that point. This burn ing ribbon of .fuel-air mixture continuously augmented I by increments from the fuel-air mixture passing on either side of the central flame holder, acts to provide central ignition of the stream of fuel air mixture during thl' the downstream side. of the peripheral flame holding surface which operates to continually ignitethe fuel-air. mixture peripherally as it enters the combustion chain Thus the fuel-air mixture is transversely and cen-i V trally ignited in the ignition chamber 12 and is peripherber.

ally ignited in the combustion chamber 13, forwhich reason the fuel-air mixture burns rapidly and completely;

in a combustion chamber, the size and length of which 1 may beheld to a minimum. a V I;

In order to secure more thoroughignition acrossthe fuel-air mixture passing through the ignition chamber, 3

a pair of central flame holders 25, 25 may be employed;

One arrangement of such pair of central flame holder s V is illustrated in- Fig. 7 of the drawings. In the embodi ment' illustrated in Fig. 7, the pair of flame holders 25,

25 are formed as a unitary structure, being connected by is illustrated in Fig. 5. This form of central flame holder is provided with side grooves 31, 31 which extend for-f wardly and downwardly along the sides of the'centi'al; f flame holder 25a from the cut-away portion 27 to the for- 1 flame holder 25 shown in Fig.1, the grooves 31, 31 con- If in cases where the fuel-air mixture is not preheated. The

igniter 25b is positioned in the slot 24 exactly as is the central flame holder 25, but does not extend at its top to the ring 21, thereby leaving an initial ignition space which extends completely along its top.

The igniter 25b is horse-shoe shaped in longitudinal cross-section, the base of the horse-shoe providing its leading face. A series of orifices 32 are formed in this leading face for admission into the interior of the igniter of a portion of the un-ignited fuel-air mixture from the supply section 11. A plate 33 extends transversely across the interior of the igniter 25b near its trailing face and a series of orifices 34 are formed in the plate 33 for outward passage of the ignited mixture. Within the igniter 25b there is therefore provided a comparatively sheltered chamber which oflers protection from the force of the on-rushing fuel-air mixture in the supply section 11. The mixture within the igniter 25b is initially ignited following ignition of the mixture above the igniter by the spark plug 29; and the sheltered ignited mixture continues to burn in the igniter, flame issuing through the orifices 34 to ignite centrally the mixture passing through the opening in the terminal ring 26. Thus the action of the igniter 25b is substantially the equivalent of the action of the central flame holder 25 heretofore described.

In the embodiment of the invention which is illustrated in Fig. 8, a substantially completely rectangular central flame holder 25c is positioned horizontally across the opening in the terminal ring 26a. The spark plug 29 extends through the wall of the supply section 11a in a position wherein its electrodes are cooled by the on-rushing unignited combustible mixture. Immediately behind the spark plug 29 the container ring 22a and the terminal ring 26a are cut-away to form a chamber 35 behind a shoulder 36 which protects a continuing flame, such flame being carried through the chamber 35 to the opening in the terminal ring 26a behind the central flame holder 250.

From the foregoing it will be evident that the invention provides means for continuously igniting the high-velocity column of fuel-air mixture both centrally and peripherally, with the result that extremely rapid combustion occurs in the combustion chamber of the burner. The burner may therefore be given a minimum size, and will provide an exceedingly high rate of heat release.

Burners constructed in accordance with the invention may be employed with a variety of such fluid fuels as may be mixed with and carried along by a column of air moving at high velocity. Such fuels may be gases, vapors, dispersed liquids, or finely divided solids. In all cases ignition of the hight velocity stream of fuel-air mixture entering the combustion chamber is maintained transversely and substantially centrally and is simultaneously maintained circumferentially of the stream of fuel-air mixture. The length of the flame required for substantially complete combustion is thus shortened and the time required for combustion is reduced to a minimum. Com pact burners of small size and high capacity are thereby made possible.

The forms of the invention here described and illustrated are presented merely as examples of how the invention may be applied. Other forms and embodiments of the invention coming within the proper scope of the appended claims Will, of course, suggest themselves to those skilled in the combustion art.

We claim:

1. A burner for a fuel-air mixture comprising a sup- 6 ply chamber, a combustion chamber in which combustion is substantially completed, and an ignition chamber intermediate said supply and combustion chambers, means to supply the fuel-air mixture at a high velocity to said supply chamber and cause said fuel-air mixture to pass at a high velocity in a stream through the ignition chamber and into the combustion chamber, an igniter positioned in said ignition chamber out of the path of travel of the stream of fuel-air mixture operable to initially ignite the fuel-air mixture at the start of operation of the burner, a terminal ring adjacent the inlet end of the combustion chamber having a central opening through which the stream of fuel-air mixture is discharged into said combustion chamber, said central opening in the terminal ring being of smaller diameter than the combustion chamber and supply chamber and defining an annular flame retaining wall at the entrance to v the combustion chamber operable to maintain a substantially quiescent zone of burning fuel-air mixture at the downstream side of said flame retaining wall and circumferentially of the high velocity stream of fuel-air mixture entering the combustion chamber, a container ring positioned about said ignition chamber intermediate said supply chamber and said terminal ring and having a central opening therein through which the stream of fuel-air mixture passes, said container ring central opening converging inwardly from said supply chamber to the central opening of said terminal ring, a central flame holder in the ignition chamber carried within the container ring and positioned adjacent the upstream side of the terminal ring, said container ring having alined slots extending radially of said container ring central opening, one of which slots is located adjacent said igniter, said central flame holder being positioned within said slots and extending diametrically across said container ring central opening and being cut away at said one of said slots adjacent said igniter to provide communication between said igniter and said container ring central opening, said central flame holder having at the downstream side thereof a flame holding surface extending diametrically at least partially across the stream of fuel-air mixture passing through said terminal ring and creating at the downstream side of said central flame holder and within the central opening of said terminal ring a substantially quiescent zone of burning fuel-air mixture substantially removed from the path of high velocity fuel-air mixture passing thereby, and said quiescent zones of burning fuel-air mixture downstream of the central flame holder and the annular flame retaining wall operating to ignite the high velocity stream of fuel-air mixture entering the combustion chamber through the central opening in said terminal ring.

2. A burner for a fuel-air mixture comprising a supply chamber, a combustion chamber in which combustion is substantially completed, and an ignition chamber intermediate said supply and combustion chambers, means to supply the fuel-air mixture at a high velocity to said supply chamber and cause said fuel-air mixture to pass at a high velocity in a stream through the ignition chamber and into the combustion chamber, an igniter positioned in said ignition chamber out of the path of travel of the stream of fuel-air mixture operable to initially ignite the fuel-air mixture at the start of operation of the burner, a terminal ring adjacent the inlet end of the combustion chamber having a central opening through which the stream of fuel-air mixture is discharged into said combustion chamber, said central opening in the terpositioned about said ignition chamber intermediate said supply chamber and said terminal ring and having a central openingtherein through which the stream of fuelair mixture passes, said container ring central'opening converging inwardly fromsaid supply chamber to the central opening of said terminal ring, said container ring having a pair of slots equally spaced at oppositesides of a radial line of said container ring, and a slot in said container ring located diametrically opposite said pair of slots, said last mentioned slot being located adjacent said container ring positioned within said slots and ex- ,tending'across said container ring central opening, said central flame holders having at the downstream; side thereof a flame holding surface extending diametrically at least partially a'crossthe stream of fuel-air mixture passing through said terminal ring and creating atthe downstream'side of said central flameholders and within thecentral opening of saidterminalring .a substantially quiescent-Zone of'burning ,fnel-airmixture' substantially removedtfrom the path of highgvelocityfuel-air mixture t downstream of the central flame holders 'and the annular flame retaining wall operating to ignite the high velocity V stream of fuel-air mixture entering the combustion cham- 107f I said igniter, a pair of centralfiame holders carried by her through the central opening said terminal ring. 1. 1 References Cited in the file ofthis patent UNITEDTSTATES PATENTS I

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