US2959215A

US2959215A - Apparatus for opposing flare back in fluid fuel burners

Info

Publication number: US2959215A
Application number: US372652A
Authority: US
Inventors: Robert I Warnecke
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-06-19
Filing date: 1953-08-06
Publication date: 1960-11-08
Anticipated expiration: 1977-11-08

Description

Nov. 8, 1960 Q R, WARNECKE 2,959,215

APPARATUS FOR OPPOSING FLARE BACK IN FLUID FUEL BURNERS Original Filed June 19, 1948 s Sheets-Sheet 1' IN VHV TOR.

Nov. 8, 1960 R. 1. WARNECKE 2,959,215

APPARATUS FOR OPPOSING FLARE BACK IN FLUID FUEL BURNERS Original Filed June 19, 1948 I5 Sheets-Sheet 2 Gfiforrreys.

APPARATUS FOR OPPOSING FLARE BACK IN FLUID FUEL BURNERS Original Filed June 19, 1948 Nov. 8, 1960 R. WARNECKE 3 Sheets-Sheet 3 VENTOR. 75W! fi/ Qfc orne ys.

United States Patent APPARATUS FOR OPPOSING FLARE BACK IN FLUID FUEL BURNERS Robert I. Warnecke, 31 Eastvale Court, Cheektowago, N.Y.

Original application June 19, 1948, Ser. No. 33,983. Divided and this application Aug. 6, 1953, Ser. No. 372,652

3 Claims. (Cl. 158-99) This invention relates to improvements in fluid fuel burners and particularly to method and means for opposing the flare back of flame, burned or unburned gases into the air passage of the burner during lighting of the same. This application is a division of my co-pending application Serial No. 33,983, filed June 19, 1948, now abandoned.

When a fluid or solid fuel is discharged into and ignited in a comparatively cool combustion chamber of a furnace the rapid expansion of the burning within creates a pressure within the chamber resisted by the mass of still air within the furnace, due to the fact that a draft in the furnace has not as yet been established. To overcome this inertia, the fuel and air can be discharged into the combustion chamber at pressures in excess of atmospheric pressure or an induced draft might be employed. There are, however, devices which must operate at or near atmospheric pressure and where no induced draft and little, if any, natural draft is practical. When this condition exists, the burner passages, and any other openingsinto the combustion chamber may offer less resistance to the flow of burned and unburned gases than the passages provided in the furnace for the discharge of burned gases. The result is flaring out of the gases and flame through the burner passages,-which may constitute a fire hazard and in some cases, an objectionable noise and overheating the burner. The use of screens in the burner passages to prevent flare back has been suggested, but screens are objectionable, since they obstruct the natural flow of air through the burner, particularly when they become partly clogged with dust or other foreign material.

One of the objects of this invention is to provide a method and device by means of which flare back may be eliminated or greatly reduced by utilizing hte pressure developed in the combustion chamber during ignition to divert or oppose the flow of gases into a burner passage. A further object is to provide a device in this kind which is reliable in its action to reduce flare back, and which in no way interferes with the free passage of fuel and air through the burner passages during normal operation of the burner.

Other objects and advantages of this invention will appear from the following description and claims.

In the accompanying drawings:

Fig. l is a fragmentary sectional elevation showing a fluid fuel burner arranged in a combustion chamber and having applied thereto means embodying this invention for obstructing flare back.

Fig. 2. is a sectional plan view thereof, on line 22, Fig. 1.

Fig. 3 is a transverse sectional elevation thereof, on line 33, Fig. 1.

Fig. 4 is a fragmentary sectional elevation of a fuel burner arranged in a furnace and provided with means of modified form for obstructing flare back.

Fig. '5 is anelevation showing the inner face of the burner construction illustrated in Fig. 4, and looking in the direction indicated by the line 5-5, Fig. 4.

ice

Fig. 6 is a top plan view of a vertical burner provided with the improvements embodying this invention.

Fig. 7 is an elevation thereof, partly in section.

Referring to the construction shown in Figs. 1 to 3, represents a portion of the bottom wall of a furnace or heating device and 8 represents a portion of a front wall thereof provided with an opening 9 through which a burner may project, the furnace having a combustion chamber 10. A furnace or combustion chamber of any other suitable or desired construction may be employed, if desired.

My improvements may operate in connection with fluid fuel burners of various types, and consequently, the burner is only partly shown in the accompanying drawings and includes a fuel nozzle or fuel supply pipe 11 arranged within an air inlet duct 12. When the burner is of the type adapted for use in connection with gaseous fuel, the fuel nozzle 11 conducts either gas alone or a primary mixture of air and gas to the combustion chamber and the tube 12 conducst the air required for combustion of the gas or primary mixture into the combustion chamber. The burner may be mounted on a closure member 14 for the furnace, which extends about the opening 9 in the front wall 8 of the furnace to exclude from the combustion chamber all air except that which passes through the burner. i

The fuel nozzle extends through the opening 9 into the combustion chamber of the furnace. usually employed within the combustion chamber in connection with burners of this type against which the fuel and air discharged from the nozzle 11 are directed, and which assists in the intimate mixing of the fuel with the air for combustion of the fuel. any suitable construction, an upright wall of fire brick (not shown) being commonly employed. In the construction illustrated, I have shown a metal deflector 17,

the path of fuel projected into the combustion chamber 10.

During the normal operation of a furnace of this type, i

the products of combustion pass from the combustion chamber into flueways of the furnace to a draft regulating device and then to'a flue or chimney (not shown), and because of the heat in the products of combustion, a natural draft is obtained in the usual manner which draws outside air through the air passage 12 into the combustion chamber to support combustion. However, when the draft through the furnace and flue passages has been interrupted or reduced and the burner is started by projecting fuel into the combustion chamber and lighting the same, the gases expand rapidly in the combustion chamber, thus developing a pressure which is in excess of the atmospheric pressure. Consequently, on igniting the fuel in the combustion chamber, this pressure causes what is generally known as a flare back, which consists of flow of burned and unburned gases and possibly flame through the air passage 12 in a direction opposite to that in which the air normally flows in this passage. While this flare back lasts only for a very short time interval, until the draft through the furnace is established, yet this flare back does create a fire hazard, and if the same is sufliciently severe, it may also in the case of gas burners ignite the gas at the orifice or orifices, causing the gas to burn within the mixer in which gas and primary air are mixed or discharged through the fuel duct 11.

I have found that this flare back can be in many instances entirely eliminated, and in other cases, reduced to such an extent as to avoid the objectionable ignition providing means for guiding or deflecting a portion of the burned or unburned gases from the combustion chamber" into the air inlet passage in such a manner as to form A deflector is This deflector may be of a transversely flowing stream or curtain of burned or unburned gas or flame within the air passage, which obstructs the flow of gases and flame outwardly from the furnace through the air passages. The terms gas or gases is herein used to include non-burning gas or gases as well as flame.

The gas guiding or deflecting member may be of any suitable or desired construction. In the construction shown in Figs. 1 to 3, for the purpose of illustrating an embodiment of my invention, I have provided about the fuel duct and in spaced relation thereto a tube 19 which forms substantially an extension of the air duct 12 and which has an opening or a plurality of openings 20, which in the construction shown in Figs. 1 to 3, are in the form of perforations or slots extending lengthwise of the tube 19. It will be understood, however, that the opening or-openings may be of any desired form and may extend in any direction. This tube may be formed integral with the air duct 12, or it may be secured to the air duct 12 in any suitable manner to form substantially an extension thereof opening into the combustion chamber of the furnace and about the discharge end of thefuel duct 11. In the construction shown for this purpose, I provide the tube 19 with an outwardly extending flange 21 which may be secured to the closure member 14.. The outer end of the tube 19 as shown telescopes into the end of the air conduit 12.

The openings 20 in the tube 19 receive burned or unburned gases or flame when the products of combustion first become ignited so that these gases will flow in the direction indicated by the arrows in Fig. 1, thus causing these gases to flow into the air passage in an angular direction to or crosswise of the same. This angular or crosswise flow of gases and/or flame produces a curtain in the air passage which has been found to effectively retard the flow of gases lengthwise of the air passage in the reverse direction, i.e., out of the combustion chamber. While this curtain does not form a positive stop of the reverse flow of gases in the air passage, it does obstruct this flow to such an extent that the danger of having flame discharged through the air receiving end of the air passage is eliminated. Furthermore, these apertures or slots in the tube '19 in no way interfere with the normal operation of the burner after ignition and during normal combustion of the fuel.

The gas guiding or deflecting device described may be further augmented by providing about the tube 19 an outer imperforate sleeve 22 arranged in spaced relation to the perforate tube 19. This sleeve is open at the inner end thereof and the space between the tube 19 and the sleeve 22 is closed at the end thereof away from the combustion chamber, for example, by means of an inwardly extending flange 23 of the sleeve 22, which may be secured to the flange 21 for securing the sleeve to the burner assembly. This sleeve 22, consequently, forms a pocket about the air tube 19 into which gases may enter during ignition of the fuel. During the ignition period, gases entering the open end of this sleeve 22, as indicated by the arrows in Fig. 1, will create a pressure within the tube 22, and thus force the gases to flow through the openings 20. The outer tube 22, therefore, acts as a guide for the gases from the combustion chamber into the openings and, under some conditions increases the effectiveness of the curtain of gas formed within the air passage.

In the particular construction shown, the curved metal deflector 17 is secured to the tube 19, but this deflector may be otherwise mounted on the burner or in the combustion chamber.

The. tube 19 and sleeve 22, in the construction shown, are square in cross section, but it will be obvious that tubes and sleeves of any other desired shape may be provided. It is also not necessary with all types of burners that'the perforations in the tube 19 or the sleeve 22 extend, completely about the gas supply tube 11. When a deflector such as shown in Figs. 1 to 3 is employed, the gases upon ignition will be deflected toward the upper portion of the burner, so that perforations in the tube 19 and sleeve 22 are not always required at the lower portion of the furnace. It is also not necessary that the fuel supply tube 11, the tube 19 and the sleeve 20 extend into the furnace as shown, since equally good results are obtained when these tubes and sleeve are arranged on the exterior of the furnace and terminate at or near the opening 9 of the combustion chamber, so that the interior of the sleeve 22 constitutes an extension of the combustion chamber of the furnace.

In the modified construction shown in Figs. 4 and 5, I have provided another type of gas guiding or deflecting device which comprises an air inlet tube 25 defining an air inlet passage about a fuel duct 26. This tube 25 also extends into the combustion chamber 10 of the furnace and has the portion thereof within the combustion chamber and about the fuel duct 26 provided with a series of open-ended slots 27 extending inwardly from the inner edge of the tube 25. These slots 27 serve the same purpose as the holes 20 shown in Figs. 1 to 3, in that they permit gas within the combustion chamber to flow as indicated by the arrows in Fig. 4 more or less radially into the slots or openings 27, and thus form a curtain across the air inlet passage which retards or obstructs the flow of gases and flame in a reverse direction through the air inlet passage, and thus prevents or materially reduces flare back.

The air inlet tube 25 may be made of cast metal and may be suitably secured to the front wall 28 of the furnace in any desired manner, for example, by means of annular outwardly extending

flanges

29 and 30 preferably formed integral with the tube and which may be bolted or otherwise secured to portions of the front wall 28 of the furnace or heater. This air inlet tube may also be provided with inwardly extending

lugs

32 and 33 which maybe used in any desired manner. For-example, the lug 32 may have secured thereto a strap 32a which is secured to the fuel duct 26 for supporting the same in operative relation to the gas deflecting memher, and the lug 33 may be utilized as a support for one end of a deflector 34 which is arranged within the combustion chamber.

The method of operation of the device shown in Figs. 4 and S is similar to that shown in Figs. 1 to 3. In some types of combustion chambers, the gases upon ignition of the flame take paths approximately such as indicated by the arrows in Fig. 4, and the whirling motion of the gases causes them to enter readily into the slots 27, and thus form a curtain in the air inlet passage which obstructs the outward or reverse flow of such gases in this passage. If desired in the case of some types of combustion chambers, a sleeve similar to the sleeve 22 shown in Figs. 1 to 3 may be provided about the discharge end of the air inlet tube 25. I

It is not necessary that the fuel supply tube enter the furnace horizontally and in the construction shown in Figs. 6 and 7, the invention herein described is illustrated as applied to a vertical burner. It will be understood that the burner may be arranged at any desired angle with reference to the furnace. In Figs. 6 and 7, 50 represents the fuel inlet nozzle which is supplied with fuel from a fuel supply duct 51. This nozzle, which constitutes an extension of the supply duct 51 may be mounted or supported on the bottom wall of the furnace by means of a base 52 and an upright rod or pillar 53, the lower portion of which may have a screw-threaded engagement with the nozzle 50 to facilitate adjustment of the nozzle to the desired height in the furnace.

The lower part of the furnace or heating device may be separated or divided from the combustion chamber thereof by means of a horizontal wall or partition 55. The lower part of the furnace or heating device below the partitio 55 constitutes a part of the airinlet passage for the burner, to which air may be admitted in any suitable manner, for example, through an air inlet duct 56. The partition 55 is provided with a hole or opening 58 through which the burner nozzle 50 may extend, the hole 58 being larger than the nozzle so that the space between the nozzle and the periphery of the hole constitutes the air inlet to the combustion chamber.

The standard 53 may extend substantially axially through the nozzle 50 and above the same and may be provided at the upper portion thereof with a flame deflector, that shown being in the form of a disk 59 suitably secured to the upper portion of the standard.

In order to obstruct or prevent a flare back of gases from the combustion chamber during ignition of the fuel into the air space below the partition 55 and through the air duct 56, a gas guide member or deflector is provided which comprises an apertured tubular member 60 which extends about the upper portion of the burner nozzle 50. This tubular member may conveniently be secured to the upper face of the partition 55 and has openings 61 therein of any suitable or desired form. Consequently, when pressure is suddenly developed in the combustion chamber during ignition of the fuel, the gases will take courses generally as indicated by the arrows in Fig. 7, and will pass through the openings 61 to form a curtain or screen of gas in the air passage between the tubular member 60 and the burner nozzle, thus resisting flare back as described in connection with the perceding figures.

In all of the constructions described in which my improved method is carried out, the flaring out which results from the ignition of fuel in a relatively cool combustion chamber is muffled to a large extent because a portion of the flaring gas is directed into the air inlet passage in such a manner as to form a flowing stream or curtain of burned or unburned gas or flame within the air passage, which obstructs the flow of gases and flame outwardly from the furnace through the air passages, and the fire hazard resulting from such ignition is eliminated. In the case of gas burners, by preventing flare back of flame on ignition through the secondary air duct, ignition of fuel at the fuel orifice before the mixer is also prevented. It will be noted that in both of the constructions illustrated, no interference whatever with the normal operation of the burner after draft has been established results from the anti-flare back method and from the constructions shown.

While I have shown tubular members with openings or perforations therein to deflect gases in a direction generally crosswise of the direction of the flow of air for combustion into the combustion chamber, it will be obvious that gas deflectors or guide members of other types may be employed, if desired.

It will be understood that various changes in the details, materials, and arrangements of parts which have been herein described and illustrated in order to explain 6 the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention, as expressed in the appended claims.

The term crosswise is herein used to designate the direction of flow of gases at any angle to the flow of air in the air duct.

I claim as my invention:

1. A fuel burner construction for opposing flare back of gases and for use with a furnace having a combustion chamber, comprising an air duct for mounting in an opening in said combustion chamber, having one end for opening into said combustion chamber and the other end for opening to atmospheric air outside said combustion chamber, said air duct having openings in the wall thereof adjacent to said one end thereof, a fuel duct encircled by said air duct and in spaced relation thereto and having an open end portion for discharging into said combustion chamber, the axes of said openings of said air duct being normal to the axis of said fuel ducts open end portion, said fuel ducts open end being located forward of said openings in said air duct, whereby when said burner is mounted in said combustion chamber, combustion gases flowing toward said burner are directed through the openings in said air duct and through said one end of said air duct so that those gases directed through said openings intersect those gases directed through said end of said air duct so as to obstruct reverse flow of said gases in said air duct.

2. A fuel burner construction as in claim 1 and having a sleeve encircling said air duct in spaced relation thereto and having a rear wall connected to said air duct, the forward end of said sleeve being substantially aligned with and substantially as long as said one end of said air duct.

3. A fuel burner construction as in claim 1 and wherein said openings in said one end of said air duct are slots.

References Cited in the file of this patent UNITED STATES PATENTS 633,859 Lewis Sept. 26, 1899 657,228 Trapp Sept. 4, 1900 1,305,436 Blanchard June 3, 1919 1,346,952 Goreau July 20, 1920 1,574,547 Bell Feb. 23, 1926 1,614,359 Gaston Jan. 11, 1927 2,050,577 Littleton Aug. 11, 1936 2,177,225 Ohlsson Oct. 24, 1939 2,247,977 Ushold et a1. July 1, 1941 2,368,179 Turpin Jan. 30, 1945 2,532,740 Speer Dec. 5, 1950 2,540,308 Weyenbert Feb. 6, 1951 FOREIGN PATENTS 4,113 Sweden Feb. 15, 1893 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No. 2 959315 November 8 1960 Robert I; Warnecke It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected belowa In the grant lines 1, 2 and 3 for "Robert Ia Warnecke of (Zheektowaoyo New York, read Robert L Warneckeof Cheektowago New York assignor to Roberts-Gordon Appliance Corporation, of Buffalo New York line 12 for Robert Ia Warnecke his heirs" read Roberts-=Gordon Appliance Corporation its successors in the heading to the printed specification lines 4 and 5 for "Robert 18 Warnecke 31 Eastvale Court Cheektowago Na Y, read Robert Io Warnecke Cheektowago Ne Ya assignor to Roberts=Gordon Appliance Corporation Buffalo N, Ya

Signed and sealed this 18th day of April 1961a (SEAL) Attest:

ERNEST W, SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents