US2973032A

US2973032A - Gas or oil burner

Info

Publication number: US2973032A
Application number: US640194A
Authority: US
Inventors: Bertram B Reilly; John J Mehler; Edward L Kells
Original assignee: Dravo Corp
Current assignee: Dravo Corp
Priority date: 1957-02-14
Filing date: 1957-02-14
Publication date: 1961-02-28
Anticipated expiration: 1978-02-28

Description

Feb. 28, 1961 B. B. REILLY Eri-AL 2,973,032

GAS 0R on. BURNER Filed Feb. 14, 1957 5 Sheets-Sheet 2 l; gl.

47 l: 1E. E

INVENTOR. BERTRAM BfRElL-LY- JOHN J. MEHLER. BY EDWARD L. KELLS.

ATTORNEYS.

Feb. 28, 1,961 B. B. REILLY ETAL 2,973,032

GAS 0R on. BURNER Filed Feb. 14, 195'? 3 Sheets-Sheet 3 INVENTOR.

BERTRAM B.RE|LLY. JOHN J. MEHLER. BY EDWARD L. KELLS.

ATTORNEYS.

oAs on onJ BURNER Bertram B. Reilly and .lohn J. Mehler, Pittsburgh, Pa., and Edward L. Kelis, Batavia, Ill., assiguors to Bravo Corporation, Pittsburgh, Pa., a corporation of Pennsyl- Vania Filed Feb. 14, 1957, Ser. No. 640,194

12 Claims. (Cl. 158-11) This invention pertains to a gas or oil burner.

Our invention has special utility in space heaters designed for use in industrial and commercial establishments. An example of such a heater is disclosed in United States Patent No. 2,529,574, granted November 14, 1950, on the application of Ralph M. Rush. The present invention will be hereinafter specifically described with reference to that patent, but it is to be understood that this is only by way of illustration and that the invenion is applicable to other heaters.

In a heater of the type disclosed in said Patent No. 2,529,574, fluid fuel, oil or gas, is burned in a thin metal combustion chamber and discharged through flue passages to a ilue. Air is moved at high velocity by one or more fans around the outside of the combustion chamber and around the tlue passages and discharged into the space to be heated through one or more hoods which discharge the heated air in the desired direction.

It is or" course desirable that these heaters be as compact as possible, and since they are usually required for the warming of large areas and are designed to rapidly diffuse heat, high rates of combustion and high velocities of combustion air are required, with a high rate of removal of the combustion gases. Pressures in the exhaust system must be high enough to overcome stack resistance. rl`hese requirements cumulatively develop pressure conditions or pressure drops across the burner that affect combustion conditions, and forced drafted apparatus suitable for the burning of gas is not equally suitable for the burning of oil. Selection of forced, mixed or induced draft and the method of applying the blowers becomes critical and can have a maior effect on the performance of the heater.

On the other hand, the heaters can not be individually designed for the fuel condition of a particular locality, but are desirably universal. Heaters, to meet fuel conditions in various markets, should effectively burn either gas or oil, and if oil is used, to burn different grades of oil. in some instances, where gas is a primary fuel, it is required that oil be used when the prevailing outside'temperature in the area drops below a given temperature. To provide a heaterr having a burner which can use either oil or gas and any of the commercial grades of oil has long been recognized as desirable, but the flame and burning characteristics of the two types of fuel are'such that attempts to have a single burner that can selectively use gas and various grades of oil have not been satisfactory. A major ditiiculty has been the noiseY and explosivepor uneven burningv character of the ame when developing theV high energy release required in a compact heater. Oil burners for high combustionrat'es generally perform best Awith-a forced draft atthe'burner', and withouty substantial forced draft the combustion is' slow and dirty. AGas,"on the other hand, is usually supplied under' such pressuretliat it'niay be discharged into a combustion zone and" adequately mixed with air without the aid of any blower. Any good combustion burner for high energy releaseA rates then necessarily has a'high pressure drop tarea @arent 2,9%@32 Patented heb. 28, 196i liti@ 2 through it to properly burn oil, so, n burning gas it must burn quietly in the same high velocity air stream.

Present practice generally provides a forced draft blower at the burner and au exhaust fan in the ilue for the burned gases. An attempt is made to balance the eect of the two fans so the combustion chamber is at atmospheric pressure, although theoretically there4 is a condition of positive pressure in one part of the combustion space and a negative pressure in another. However, With two fans it is diicult to maintain a proper balance even where a burner is especially designed for the particular fuel being burned. Y

Another condition which is encountered in air heaters is that the warm airis expelled into a room usually occupied by people, and in heaters of the class specifically mentioned above, the metal walls of the combustion chamber form a thin diaphragm separating the burning gases from the heated air. Should a leak develop in the combustion gas system, any positive pressure Within forces unburned gases into the air stream and thus into the room Where their effects may be either unpleasant or noxious, Such a positive pressure canbe continuous (which could result fromrimproper balance between the forced and induced draft fans), or instantaneous (which can result from minor combustion explosions and momentarily raise the combustion gas pressure above atmospheric pressure even in a system whose pressure averages sub-atmospheric). Because of the diiculty of balancing forced and induced draft blowers concurrently Working on the combustion gases, and in order to insure combustion gas pressure sutliciently below atmospheric so as to make even momentary leaks into the room air impossible under normal operation, We have developed a burner which will satisfactorily burn any of the fuels discussed, using only induced draft. A

The present invention has for its object to provide a burner adapted to selectively burn any of the usual fuel gases or oils which will operate entirely on an induced draft principle so that anegative pressure may be main# tained in the combustion chamber with which the burner is associated, and a further object is to provide a burner which will use either gas or oil and burn quietly and smoothly without positive pressure of either gas or air. Further objects of the invention are to provide a compact burner of unique construction which is simple to manufacture, and which can be readily opened for repair, inspection or replacement of parts. I

These and other objects and advantages are secured by our invention which is illustrated in the accompanying drawings, and in which:

Fig. 1 is a longitudinal section through the burner;

Fig. 2 is an end elevation of the burner from the outer end;

Fig. 3 is an elevation of the swirler plate comprising a part of the invention;

Fig. 4 is a detail front elevational view of the outer end plate or burner face plate of the burner;

Fig. 5 is a vertical section through the plate shown in Fig. 4 with the oil burner nozzle and the electric igniter therefor mounted in the plate; y

Fig. 6 is a rear elevation of the burner plate assembly with the gas pilot assembly and its accessory equipment applied thereto; l v

Fig. 7 is a transverse section through the burner plate showing the gas pilot burner, pilot igniter and llame rod on the plate; and

Fig. 8 is a fragmentary sectional view similar to Fig. 7 but rotated with respect thereto. n

in the consideration of the drawings hereinafter de# scribed in detail, it is` to be understood that the burner opens into a combustion chamber in which a negative pressure, say of the order of l to 2 inches Vofv water is maintained so that fuel gas, when gas is employed, and all of the combustion air is drawn into the burner by suction, as a negative pressure at the terminal of the burner is important to the desired functioning of the burner under all conditions.

Referring to the drawings, particularly Fig. 1, S represents the front end wall of the heater casing, and 15 is the front end wall of the combustion chamber. The plates and 15 as shown in Fig. 1 are spaced some distance apart. With the present invention there is provided a cylindrical metal sleeve 16 having its inner end welded to the plate 15 and having a supporting flange 17 at its outer end that is secured to the front end wall 5 of the casing, the casing having a hole therethrough at the proper` location to receive the burner. A preformed refractory body 18 of a size to be slidably but tightly received in the cylindrical shell 16 is shoved into the shell from the outside before the other parts hereinafter described are put into place, the inner end of the refractory body abutting against a lip 19 formed by reason of the burner hole in plate 15 of the combustion chamber being of less diameter than the metal sleeve 16. This refractory body 18 is of cylindrical form exteriorly, and it has a cylindrical passageway formed therein at its outer end and extending part way therethrough, this cylindrical portion of the passageway being designated 20. inwardly from the part 2i) the walls 20a of the refractory decrease in thickness toward the inner end of the refractory body, thereby forming an opening or passageway through the body of truncated conical contour with the largest diameter at the discharge or innermost end of the refractory body. There is an annular packing ring 18 around the outer end of the refractory body, said body being of slightly less length than the sleeve 16 in which it is received. This packing prevents air leakage around the refractory block.

The flange 17 provides rigidity to the front wall S of the casing which has an opening therethrough coextensive with the interior diameter of the sleeve 16, so as to permit insertion or replacement of the refractory body 1S. Threaded studs 21 project from the flange 17 through the plate 5 around this opening and a metal plate 22 is fitted over these studs and secured tightly in place by nuts 21a on the studs. The studs and nut thus serve to hold both the sleeve 16 and the plate 22 in place.

This plate has a central opening 23 therethrough (Fig. l) and has one or more, preferably two, sheet metal air inlet ducts 24 projecting from the face outwardly from the central opening. These ducts, which are shown as being of rectangular section, are provided with dampers 25 to control the air flow inwardly therethrough. Because of the refractory body 1S being shorter than the sleeve 16, there is an air chamber or plenum 26 between the plate 22 and the end of the refractory body so that air entering past the dampers may flow freely and without noticeable channeling into the open end of the part 20 of the refractory body. The plate has one or more projecting pieces, such as U-shaped straps welded to the inner face thereof that abut against the refractory body to hold it against endwise movement when the plate is in position. This is shown in Fig. 1 and designated 22a.

Bolted to the outer face of plate 22 around the central opening 23 therein is a hollow annulus 27 having a central passage 28 therethrough smaller than the opening 23, this annulus having an inner face 29. From surface 2.9 there projects a plurality of burner tubes 30 arranged in an annular series with their free ends converging toward but not to the center line of the refractory body but projecting into the part 20 of this body. There are several of these tubes 3@ equally spaced from one another, six or eight, and on larger sizes up to twelve being used, so that at their free ends they form an annular pattern in which the ends of the tubes are spaced from one another a distance not greatly exceeding the diameter of a singletube. The annulus is bolted to the plate 22 by bolts passing through pads or feet 27a (Fig. 2) on the annulus so that it may be put in place or removed without disturbing plate 22. For higher rates of combustion, or to secure a more even distribution of gas, other tubes 30a may be provided outside the tubes 30 and parallel with the axis of the burner, as many as twenty-four being used on large burners.

Gas is supplied to the plenum chamber 27b formed within the hollow annulus through a pipe 31 and a metering valve (not shown). The tubes 30 have no restriction or nozzle therein, and low pressure gas is used so as to avoid any Bunsen burner effect through the aspiration of air. The flow of air is induced by the negative pressure maintained in the combustion chamber into which the burner opens through an exhaust fan in the flue, as will be hereinafter more fully described.

Set into portion 2t? of the passage in the refractory and held there by friction is a burner head having a sleeve 33 and a forwardly-proiecting tapered end 34 with a central opening 35 therein. Inside this head, just back of the tapered end, is a swirler plate having a central ring 36 (see Fig. 3), closely spaced radial vanes 37, there being a central opening 38. The gas burner tubes 3) and also the tubes 30a terminate close to but spaced outwardly from this plate.

A burner face plate having a flange 39 and a thicker central area 40 is removably secured by bolts to the outer face of the annulus 27 and closes the outer end of the central passage through the annulus. As shown in Fig. 5' it supports at the axis of the assembly the oil supply tube 41 and oil burner spray tip 42, this tip, as shown in Fig. l, being located at the center of opening 38 in the swirler plate in a plane just outwardly or rearwardly from the plane of the ring 38.

This burner plate also carries the accessory equipment, which for oil includes the two electrodes` 41a and 41h for igniting the oil, as shown in Fig. 5. If the burner operates always on oil, no other accessory equipment is used, except that there may be 4a photo-electric cel-l at position 46 (see Fig. 4) to provide a safety control inV event of ame failure, this being `a conventional control for oil burners. For gas fuel the accessory equipment is shown in Figs. 6 and 7. This comprises a pilot burner 43 having a grounding iin 44 at its inner end. There is a spark rod 45 that terminates close to the fin. As a further safety control there is a ame rod 47 to shut off the `gas supply if the pilot is extinguished. Fig. 9 shows the disposition of the gas accessories under the oil accessories, and of course, should the burner` be sold only for use with gas, the oil accessories could be omitted. In Fig. 4 the accessories themselves are omitted but the reference numerals show the location of the accessories.

Associated with the pilot burner and its controls is a zero regulator 47 at the outside of the burner plate and other conventional iiow control equipment forming no part of this invention. The pressure regulators are of a known type and maintain the gas pressure in the plenum at such a low level that its flow through the tubes 30-30a is primarily induced by the pressure drop across the burner, and not by its own pressure.

In operation, when the burner is working on gas, with a negative pressure at the combustion end of the burner `air will flow uniformly from the air plenum through the burner head, part of the air flowing through the swirler plate and part through the center opening in this plate. The entire air flow described labove is induced by the induced draft fan. The volume and pressure of gas supplied is such that it does not spray out from the tubes with sufcient velocity to produce any Bunsen flame effect or aspirate air into the burner. v When the burner is operating under induced draft the gas is practically drawn by the induced draft from the pipes 30, striking the vanes and mingling with the air ilow passing through the vanes. The vanes impart a swirling motion and turbulence to the gas and airand effect ya mixing of the gas and air. When the fuel mixspaanse d ture is ignited, the base' of the flamewill be just forwardly of the 'swirler plate 37, i.e., to the right as viewed in Fig. 1; operates to first form a combustible mixture on the furnace side of the swirler, and that this mixture forms uniformly so that a steady, quiet, stable fiarne front develops immediately off the diffuser. Since the swirler and burner, therefore, remain cool, the oil burning equipment can stay in place during gas firing.

In burning oil, the gas supply is merely turned off and the oil turned on. The entire flow of air, as when burning gas, is induced by the induced draft fan `and a. negative pressure of the order named is maintained as with the burning of gas. The oil -is sprayed under pressure from the nozzle, the spray being in the form of an inwardly-expanding cone of app-roximately the contour iudicated by the dot-and-dash lines X-.Y on Fig. l. Since the spray tip is positioned outwardly or back of the swirler plate, and in the cylindrical throat of the refractory block, it passes as an expanding cone through the center of the swirler plate fand burner head commingling with the -air downstream of swirler plate. The lines X-Y converge toward the walls 20a of the conical opening -in the refractory at a gradual angle such as not to impinge against the refractory,rat least only at the very inner end. The oil burns with la flame that is of the same general contour, it being generally cylindrical at its inner end, which condition the cylindrical opening in the refractory tends to develop and maintain. The cylindrical portion terminates so that the spray pattern from the nozzle as indicated by lines X--Y docs not impinge against the interior of the cylindrical throat, `and is spaced well inwardly from the refractory where the walls of the refractory start to flare. This is of importance for two reasons: first, it prevents the oil from contacting the refractory and not properly burning, and second, a body of hot gases will be retained between the refractory wall and the outer boundaries of the fiame to prevent undue cooling. Of course, when the burner is operating on oil, the gas burner can remain in place.

It may be pointed out that the gas pilot burner is so positioned that with either fuel, it projects its flame into` the region of the mixing of the oil or gas and air. When used with volatile oils, ignition of the burner is 'accomplished directly from the spark electrodes 41a and 41b. When used with heavy non-volatile oils or gas, the pilot burner assembly 43 is used for ignition. Changeover from one fuel to the other can be accomplished in an instant without requiring anything but the operation of the proper fuel valves. The -arrangement of the parts of the burner is such that the burner may be used as a straight oil burner, or a straight gas burner.

The burner and all parts are readily accessible for assembly, inspection, replacement or repair. For example, by removing the burner face plate, the entire drawer-assembly may be serviced. By removing the annulus or burner ring 37, the gas tubes and combustion heads are available, and by removing theft-ont plate the refractory block is accessible. The burner is thus of simple construction and easy to service and replace parts as necessary. Because the burner operates always under induced draft, combustion gases can not escape into the warm air stream. High velocities and high rates of combustion are secured with quiet, even combustion. Relief doors provided for safety purposes in the heater may be of light construction since the negative pressure in the combustion chamber keeps any such door closed.

While we have shown and specifically described one preferred embodiment of our invention, it will be understood that ch-anges and modifications may be made within the contemplation of our invention.

We claim:

l. A burner for selectively burning liquid or gaseous fuel comprising a cylindrical sleeve, an enclosure providing an air plenum into which one end of the sleeve opens,

It will be seen, then, that this gas-air 'system' a gas plenum concentrically located with respect to the air plenum and the axis of the sleeve and forming part ofv the enclosure for the air plenum, the gas plenum being in the form of an annulus, a burner plate mounted on lthe said annulus and forming a closure for the central passageway through the annulus, a burner tube for liquid fuel separate from the gas plenum on said plate projecting from the plate axially through the center of the gas plenum and the air plenum into the sleeve and terminating -in a spray nozzle, a refractory body in the sleeve between the air plenum and the opposite end of the sleeve having a passageway extending axially therethrough, a fixed swirler plate in the passageway with a central opening adjacent which the spray nozzle of the burner tube is located, the spray nozzle being directed toward the opening in the swirler plate, and an annular series of gas supply tubes yaround said burner tube leading from said gas plenum across the air plenum into the sleeve and which converge toward the axis of the Sleeve and termin-ate in fixed spaced relation to the swirler plate.

2. A burner for selectively burning liquid or gaseous fuel as defined in claim l in which the swirler plate is positioned in a burner head in the opening in the refractory body and has a continuous band of metal around a central opening therethrough with the vanes extending radially from the band to the interior wall of the burner head, the terminals of the gas supply tubes being directed toward said swirler plate so that some of the gas from the tubes is deflected into the central opening and some of it passes through the vanes.

3. A burner for selectively burning liquid or gaseous fuel as defined in claim 1 having damper controlled means for controlling the air flow to the air plenum.

4. A burner for selectively burning liquid or gaseous fuel as defined in claim l in which the passageway through the refractory body is cylindrical at the end adjacent the air plenum with the swirler being located intermediate the ends of the cylindrical portion of the passageway, the passageway flaring in diameter away from the cylindri cal portion toward the opposite end of the body.

5. A burner for selectively burning liquid or gaseous fuel as defined in claim l in which the passageway through the refractory body is substantially cylindrical at the plenum-confronting end of the body with the swirler plate being located in said portion, the passageway being of outwardly-flaring cone form beyond said cylindrical portion, the spray nozzle being designed to project an oil spray through the passageway in a cone-like pattern, thesides of which pattern extend angularly toward the walls of the conical passageway in therefractory body, but being spaced from the refractory body between the said cylindrical portion of the passageway and that end of the refractory body most remote from the nozzle.

6. A burner for selectively burning liquid or gaseous fuel for gas and oil comprising a burner plate, a hollow annulus to the outer surface of which the burner plate is removably mounted with the burner plate closing the passageway through the annulus, a supporting plate having an opening therethrough which is concentric with the annulus, said annulus being removably mounted on said supporting plate and closing the opening in the supporting plate, a metal sleeve at the outer end of which the supporting plate Vis removably secured and for which the supporting plate constitutes an end closure, a cylindrical refractory body in the sleeve having one end confronting the supporting plate but spaced therefrom to form an air plenum, the refractory body having a central passageway therethrough concentric with the opening through the annulus and the opening through the supporting plate, said passageway in the refractory being flared at the end remote from the supporting plate, a swirler plate in the passageway in the refractory body near that end which confronts the supporting plate, an oil burner tube on the burner plate projecting axially through the annulus, the air plenum and into the passageway and terminating in a asraosa nozzle substantially at the center of the swirler plate, an annular series of gas tubes projecting from the hollow annulus and converging toward the axis of the passage through the refractory and terminating in the passageway in the refractory upstream of the swirler plate, means for supplying gas to the hollow annulus for delivery through said tubes, and means on the supporting plate for admitting air to the air plenum.

7. A burner for selectively burning liquid or gaseous fuel for gas and oil comprising a burner plate, a hollow annulus to the outer surface of which the burner plate is removably mounted with the burner plate closing the passageway through the annulus, a supporting plate having an opening therethrough which is concentric with the annulus, said annulus being removably mounted on said supporting plate and closing the opening in the supporting plate, a metal sleeve at the outer end of which the supporting plate is removably secured and for which the supporting plate constitutes an end closure, a cylindrical refractory body in the sleeve having one end confronting the supporting plate but spaced therefrom to form an air plenum, the refractory body having a central passageway therethrough concentric with the opening through the annulus and the opening through the supporting plate, said passageway in the refractory being flared at the end remote from the supporting plate, a swirler plate in the passageway in the refractory body near that end which confronts the supporting plate, an oil burner tube on the burner plate projecting axially through the annulus, the air plenum and into the passageway and terminating in a nozzle substantially at the center of the swirler plate, an annular series of gas tubes projecting from the hollow annulus and converging toward the axis of the passage through the refractory and terminating in the passageway in the refractory upstream of the swirler plate, means for supplying gas to the hollow annulus for delivery through said tubes, means on the supporting plate bearing against one end of the refractory to maintain the spacing between the refractory body and the supporting plate, and an abutment on the sleeve against which the opposite end of the refractory body engages to prevent movement of said body away from the supporting plate.

8. A burner for selectively burning liquid or gaseous fuel for gas and oil comprising a burner plate, a hollow annulus to the outer surface of which the burner plate is removably mounted with the burner plate closing the passageway through the annulus, a supporting plate having an opening therethrough which is concentric with the annulus, said annulus being removably mounted on said supporting plate and closing the opening in the supporting plate, a metal sleeve at the outer end of which the supporting plate is removably secured and for which the supporting plate constitutes an end closure, a cylindrical refractory body in the sleeve having one end confronting the supporting plate but spaced therefrom to form an air plenum, the refractory body having a central passageway therethrough concentric with the opening through the annulus and the opening through the supporting plate, said passageway in the refractory being flared at the end remote from the supporting plate, a swirler plate in the passageway in the refractory body near that end which confronts the supporting plate, an oil burner tube on the burner plate projecting axially through the annulus, the air plenum and into the passageway and terminating in a nozzle substantially at the center of the swirler plate, an annular series of gas tubes projecting from the hollow annulus and converging toward the axis of the passage through the refractory and terminating in the passageway in the refractory up stream of the swirler plate, means for supplying gas to the hollow annulus for delivery through said tubes, means on the supporting plate for admitting air to the air plenum, the burner plate also having accessory elements thereon comprising a gas pilot light and lighter therefor, and oil igniting electrodes, all of said accesseries also extending in an axial direction through the center of the annulus and removable as a unit with the oil burner tube and nozzle by removal of the burner plate from the annulus.

9. A burner for selectively burning liquid or gaseous fuel comprising a refractory shape having a central opening therethrough which is substantially cylindrical at one end and which is flared outwardly from the inner end of the cylindrical portion to the opposite end, a swirler plate in lthe cylindrical portion of the passage, an enclosure providing an air plenum into which the cylindrical end of the passage opens, a gas plenum on the enclosure concentric with the passage, and a plurality of gas tubes extending from the gas plenum into the passage toward the swirler but terminating in spaced relation to the swirler, said tubes being substantially uniformly positioned around the swirler, the relation of the gas tubes to the swirler being such that under induced draft gas is discharged from the tubes adjacent the swirler and mixed with air owing through the passage and combustion takes place at the opposite side of the swirler.

10. A burner for selectively burning liquid or gaseous fuel as defined in claim 9 in which some of the gas tubes converge inwardly toward the axis of the burner and others are parallel with said axis.

11. A burner for selectively burning liquid or gaseous fuel as defined in claim 9 in which there is a gas supply to the plenum with controls that reduce the gas pressure to a level where its flow from the plenum is primarily induced by draft across the burner.

12.V A burner for selectively burning liquid or gaseous fuel as defined in claim 9 in which the gas plenum is a hollow annulus, and there is a plate closing the center of the annulus, the plate having igniting and control accessories thereon comprising a pilot light, a sparking electrode and a arme rod, which accessories extend through the gas plenum into the area surrounded by the tubes.

References Cited in the tile of this patent UNITED STATES PATENTS 1,868,051 Doherty July 19, 1932 1,938,335 Hubbardet al. Dec. 5, 1933 2,172,667 Nelson Sept. 12, 1939 2,263,098 Muller Nov. 18, 1941 2,274,818 Zink Mar. 3, 1942 2,369,236 Jaros Feb. 13, 1945 2,376,140 Henderson et al May 15, 1945 2,458,542 Urquhart Ian. 11, 1949 2,529,574 Rush Nov. 14, 2,635,813 Schlenz Apr. 2l, 1953 2,647,568 Sloan Aug. 4, 1953