US3529917A - Air-mixing device for fuel burner - Google Patents

Description

p 1970 A. w. HINDENLANG 3,529,917

AIR-MIXING DEVICE FOR FUEL BURNER Filed July 25, 1968 .INVENTOR. ARTHUR .W. HINDENLANG ATTORNEY United States Patent 3,529,917 AIR-MIXING DEVICE FOR FUEL BURNER Arthur W. Hindenlang, Cherry Hill, N.J., assignor to The Engineer Company, South Plainfield, N.J., a corporation of New Jersey Filed July 23, 1968, Ser. No. 746,785 Int. Cl. F23d 15/00 US. Cl. 431-351 2 Claims ABSTRACT OF THE DISCLOSURE An air-mixing device disposed adjacent the periphery of the throat of a fuel burner through which the combustion air passes under pressure and shaped to compress and direct a major portion of the air toward the axis of the throat to form an initial central solid portion of the flame front while an appreciable portion of the combustion air is diverted and directed toward the periphery of the throat of the burner and moves forwardly toward the flame front in a manner to create turbulence and blend with the central portion of the flame to increase the useful diameter of the resulting flame which is of a solid type produced by intimate, thorough and rapid mixing of fuel and air caused by said turbulence and thereby effects maximum efliciency in the combustion of the fuel.

BACKGROUND OF THE INVENTION Fuel burners, and particularly industrial type fuel burners having substantial rates of fuel consumption, have very frequently been incapable heretofore of effecting maximum efiiciency in the consumption of the fuel delivered to the burners. This is due to the fact that burners of the type referred to usually have substantially cylindrical throats. The actual burner is generally concentric with the axis of the throat, regardless of whether it is a ring-type gas burner or a central gun-type utilizing fuel oil or gas as a fuel. Combustion air which is discharged under pressure in an axial direction through the throat tends to combine with the fuel, regardless of which type is used, in such manner that a somewhat hollow or annular type of flame is produced, as distinguished from a solid, compact and massive type of flame which substantially fills the entire cross-section of the throat where maximum combustion occurs.

As a result of the propagation of the flame in a somewhat annular pattern adjacent the walls of the throat, due to the conditions described above, special designs and compositions of refractory throat tile normally are required. Further, an annular type of flame such as is commonly produced by existing burners results in combustion which is not of the highest efficiency, whereby fuel waste occurs.

SUMMARY OF THE INVENTION It is the principal object of the present invention to provide an air-mixing and directing device for use in particular with fuel burners employing a throat which is substantially circular in cross-section and having a fuel burner concentric with the axis of the throat, whether of the annular gas-ring type or axial gun-type for gas or fuel oil, said air-mixing and directing means being positioned adjacent the periphery of the throat and directed toward the axis of the throat, immediately downstream from the burner, to form an initial concentrated flame front axially within the throat. Said mixing and deflecting means also is provided with means to deflect and by-pass another appreciable portion of the combustion air toward the periphery of the throat of the burner in a manner to cause turbulence in the throat adjacent the burner which effects thorough mixing of the fuel and combustion air and thus propagates a flame which is solid, intense, and relatively short and stubby, preferably filling the entire cross-sectional area of the throat of the burner while consuming a minimum amount of excess air and requiring less furnace volume in the combustion zones than in present furnaces.

Another object of the invention is to provide an airmixing and directing means of the type referred to above which is substantially annular and of frusto-conical shape to effect the aforementioned direction of the combustion air toward the axis of the throat but also having intermediate passage means therein to divert portions of the combustion air to pass therethrough in a manner to cause turbulent movement adjacent the periphery of the throat and combine with the central portion of the flame front to increase the cross-sectional area thereof due to thorough mixing of the fuel with the combustion air.

A further object of the invention is to utilize the passage of combustion air through said aforementioned frusto-conical air-mixing and directing means to promote cooling of said means in addition to the air-directing functions thereof to promote turbulence, thereby permitting the use of relatively inexpensive material to form said air-mixing and directing means due to said means being air-cooled.

Details of the invention and foregoing objects thereof, as well as other objects of the invention, are set forth in the following specification and illustrated in the accompanying drawings comprising a part thereof.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary, vertical sectional view illustrating an exemplary combination furnace burner capable of utilizing either gas or fuel oil, selectively, and producing a conventional substantially annular type of flame.

FIG. 2 is a fragmentary illustration of a portion of a fuel burner and a relatively short, stubby type of flame capable of being produced by the structure of the present invention.

FIG. 3 is a fragmentary, somewhat diagrammatic vertical sectional view illustrating one embodiment of airmixing and directing means installed in the throat of an oil-fired burner system.

FIG. 4 is a view similar to FIG. 3 but illustrating the same embodiment of the invention installed in the throat of a burner utilizing gaseous fuel.

FIG. 5 is a view similar to FIG. 3 but showing, in vertical section, another embodiment of air-mixing and directing means of a special type capable of being used with high capacity type burners.

FIG. 6 is a view similar to FIG. 5 but showing the additional embodiment of air-mixing and directing means employed in the throat of a furnace employing a ring-type gas burner adjacent the periphery of the throat of the burner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS There is illustrated in FIG. 1, primarily in vertical section, an exemplary illustration of a conventional furnace burner of the type to which the present invention is applicable and over which structure the various embodiments of the present invention comprise improvements. In the structure shown in FIG. 1, a fragmentary illustration of the wall of a furnace 10 is provided with a suitable burner opening 12 within which an exemplary circular throat member 14 is mounted which, in normal standard types of installations usually is of a ceramic nature.

Extending outwardly from the outer face 16 of the furnace wall 10 and coaxial with the inner throat surface 18 is a sleeve or collar 20' of predetermined length and formed from suitable material such as iron or steel. Circular flanges preferably are provided on the opposite ends thereof respectively to connect the same appropriately to the outer face 16 of the furnace and also to attach thereto an appropriate industrial type of inlet control 22 by which the delivery of combustion air to the sleeve 20 and throat member 14 is regulated.

The sleeve 20 and inlet control 22 for combustion air preferably is contained within a housing 24 with which a suitable blower or fan, not shown, is connected for purposes of delivering air under pressure to the air inlet control means, said means being adjustable by appropriate commercial type mechanism contained within jacket 26. Said jacket also serves to support an appropriate mount 28 for the gun-type burner 30 which, in many current types of installations, includes coaxial conduits respectively arranged to furnish either gas or fuel oil to the burner nozzle which, as will be seen from FIG. 1, is surrounded by a somewhat conical and outwardly flared terminal end 32 disposed within the cylindrical throat opening 18. Gas and/ or fuel oil is delivered to the nozzle 50 at the outer end of the gun-type burner 30 by appropriate conduit means 34, only one of which is shown in FIG. 1 due to the second one being disposed rearwardly therefrom in the view. Said conduit means respectively are connected to supplies of fuel oil and gas.

The burner system shown in FIG. 1 also includes a gas pilot burner 36, the outer end 38 of which also is supported by mount 28 and is connected by conduit 40 to a suitable source of gas.

In addition to the combination gas and/ or oil gun-type burner 30 shown in FIG. 1, it is not uncommon for furnaces of the type shown alsoto be supplied with a ringtype gas burner 42 which, for example, is provided on the inner surface thereof with a plurality of preferably evenly spaced gas burner jets 44. It is to be understood that it is only under the most unusual conditions that both the gun-type burner 30 and the gas ring-type burner 44 will be used simultaneously. Normally, they are used selectively and the principal purpose of providing the same is to enable the user to take advantage of the less expensive fuel, depending upon the season. The ring-type gas burner may be supplied by an inlet conduit 46 which is appropriately connected to the burner 42. A master control valve, not shown, is connected in the conduit 46 at an appropriate location.

Regardless of which type of burner is used at any given time in the furnace illustrated in FIG. 1, the normal difficulty and deficiency resulting from the same is that a somewhat hollow flarne usually is produced, as distinguished from a concentrated, intense solid type of flame. An attempt has been made to illustrate the hollow type of flame somewhat diagrammatically, in vertical section, in FIG. 1. To overcome this, it has been found that by the use of the present invention, a very intense and concentrated, stubby and solid type of flame 48 may be produced as illustrated in exemplary manner, in side elevation, in FIG. 2, said flame being partially propagated from an exemplary burner nozzle 50. A flame of this type results from utilizing either one of several embodiments of air-mixing and directing means, which embodiments are illustrated respectively in FIGS. 3 and 4 and in FIGS. 5 and 6, details of which are as follows.

In FIG. 3, an exemplary throat member 52 is shown which, preferably, is formed from suitable ceramic material similar to that from which industrial firebrick is formed, for example. Throat member 52 preferably is circular in cross-section. Extending rearwardly therefrom is a throat sleeve or tube 54 which preferably is coaxial with the inner circular wall 56 of throat member 52 and comprises a suitable extension of the throat opening to accommodate the exemplary gun-type burner 58 shown in FIG. 3 which, for example, may be similar to the gun-type burner 30 shown in FIG. 1 in that it may be either gas or oil-fired, or the same may embody coaxial tubes respectively to supply and support gas and oil-bur i g nozzles which usually are arranged to be used independently of each other and not simultaneously.

To avoid the formation of the type of so-called hollow flame produced by the conventional burner and throat arrangement shown in FIG. 1, the embodiment of the invention shown in FIG. 3 includes a frusto-conical airmixing and directing member 60. The member 60 may be formed of a number of appropriate materials but, fortunately, because of the nature of the operation thereof, as explained hereinafter, it may be formed relatively inexpensively from sheet metal such as iron or steel. One end of the member 60 is provided with a mounting collar '62 which is aifixed to the interior of the sleeve 54 by any suitable means such as bolts or the like. The frusto-conical portion thereof is provided with a plurality of air passage holes 64 which may be formed therein by simple drilling or punching operations so as to constitute air diverting means, the function of which is as follows.

In the preferred construction of the air-mixing and di recting member 60, the total area of the holes 64 normally is appreciably less than the remaining solid area of the member 60. Accordingly, the major portion of the inner surface of the member 60, the smaller end of which is downstream, functions to converge and compress a substantial part of the combustion air, which is represented by arrows 66, toward the central axis of the circular throat wall 56. Further, as will be seen from FIG. 3, inasmuch as the member 60 is preferably at least slightly downstream from the burner nozzle 50, an intense and solid type of flame will be propagated centrally of the throat wall 56 and coaxial therewith.

The function of the air-diverting opening 64 is to bypass or divert an appreciable portion of the combustion air 6'6 through the walls of the member 60 and thereby direct the same into the region of the periphery of the throat opening, adjacent the inner circular wall surface 56 of the throat. Such action of the diverted and substantial plurality of jets or streams of combustion air in said region functions to create substantial turbulence within the throat opening 56, which turbulence is diagrammatically illustrated by swirling lines. This turbulence causes thorough mixing of the fuel and combustion air and reacts upon what otherwise would be a substantially solid central flame front, which extends forwardly from the downstream end of the member 60, and thereby functions to greatly broaden or increase the cross-sectional area of the flame so as to substantially fill the entire cross-sectional area of the throat opening 56 with a solid, intense flame caused by rapid, intense and substantially complete combustion of the fuel. The foregoing results in maximum production of B.t.u.s in a given period of time and predetermined cross-sectional area of the burner throat, which is much more efficient and effective than the type of flame conventionally produced by more or less standard types of burners and throat constructions such as illustrated in exemplary manner in FIG. 1, wherein a far less solid and intense type of flame is produced.

In addition to the diverting function of the diverting passages 64 which is described above, such diversion of the combustion air serves to maintain the member 60 relatively cool in contrast to the temperatures which would be generated therein if no such passage openings were included, whereby relatively inexpensive steel and the like may be used to manufacture the member, rather than ceramic materials.

In FIG. 4, the same embodiment of the invention as in FIG. 3, is illustrated with respect to the air-mixing and directing member 60. However, such member is shown in association with a ring-type gas burner 68 which, for example, is positioned so as to surround the exterior frusto-conical surface of the member 60. Any suitable supporting means such as appropriate straps 70 may be employed. Also, the ring-type gas burner 68 is provided with a circular ring of gas burner nozzles 72. Appropriate pilot means, not shown, may be utilized to ignite the gas discharging from said nozzles. Particularly in view of the nozzles 72 preferably being disposed around the inner periphery of the ring-type gas burner 68, the member 60 serves to shield the same against the flames from said burners being blown out, especially when the operation of the burner is being initiated or when the burner is being operated at quite low firing rates. In addition, the passages of combustion air through the openings 64 in the member 60 serves to cool said member and thereby offers the same advantage in this regard as explained above with respect to the arrangement shown in FIG. 3.

Notwithstanding the employment of a ring-type gas burner 68 in the arrangement shown in FIG. 4, the directing of the combustion air is represented by the arrows 66 through the member 60 results in concentration of a substantial portion of the air centrally within the throat opening 56 where it meets and mixes with the gas from the ring-type burner 68 and ignition occurs at a location axially between the nozzles 72 and the discharge end of the member 60. Due to the passage of a portion of the combustion air through the openings 64, appreciable turbulence results which effects a highly intimate, thorough and rapid mixing of the fuel and combustion air which promotes rapid, intense and complete combustion of the fuel due to the propagation of a substantially solid and broad flame front which, depending upon the control of the supply of fuel and combustion air, preferably will result in a relatively short, stubby flame such as the typical shape of flame 48 shown in FIGS. 24.

It should also be understood that, if desired, the two types of burners respectively shown in FIGS. 3 and 4 may be combined within the throat means of a single burner system or furnace, somewhat in the manner in which the conventional arrangement in FIG. 1 includes both a gun-type and gas ring-type burner which preferably are used selectively and alternatively, as desired, depending upon the least expensive fuel in any particular season. However, for purposes of simplifying the illustration and the benefits of the respective types of burners when associated with the embodiment of combustion air-mixing and directing means 60 shown in FIGS. 3 and 4, the gun-type burner 58 has been shown independently in FIG. 3 and the ring-type gas burner 68 has been shown independently in FIG. 4.

Particularly in heating systems which require high capacity and substantial rates of heat development, it is preferred that a different embodiment of combustion airmixing and directing means be employed from that shown in FIGS. 3 and 4. One preferred type of additional embodiment of such means is illustrated in FIGS. 5 and 6, respectively in association with a gun-type burner and a ring-type gas burner. In illustrating this additional embodiment it will be seen in FIGS. 5 and 6 that the same numerals have been employed to represent similar elements and means as illustrated correspondingly in FIGS. 3 and 4.

Referring to FIG. 5, it will be seen that the additional embodiment of combustion air-mixing and directing means is a compound unit 74 consisting preferably of a pair of airfoil sections or members 76 and 78 which preferably are circular and coaxial. The member 78 is of smaller diameter than the member 76 and is positioned slightly downstream therefrom. These members may be held in operative position with respect to each other and the throat opening 56 by any suitable bracket means, not shown. Also, as in regard to the preceding embodiment, due to the passage of air therethrough, they are sufliciently cooled by the passing air that they may be formed from relatively inexpensive material, such as iron or steel, as distinguished from more expensive materials having greater resistance to high temperatures.

The annular air passage 80 between the airfoil members 76 and 78 comprises what is termed an aerodynamic slot which, particularly since it is of an annular nature,

and because of the smaller member 78 having a greater angle with respect to the axis of the throat than the larger member 76, results in a greater lift being afforded the portion of the combustion air being diverted through the annular aerodynamic slot 80. As a result, the desired amount of intense turbulence is provided within the throat portion defined by the inner surface 56, thereby producing the desired intimate, thorough and rapid mixing of fuel and combustion air so as to promote the aforementioned desired rapid, intense and complete combustion of the fuel.

As in regard to the precedingembodiment, the embodiment shown in FIGS. 5 and 6 causes the major portion of the combustion air to be compressed and constricted as a result of passing successively through the airfoil members 76 and 78 and especially the latter. This concentrates a major portion of the flame, at least initially, centrally of the throat 56 and such concentrated flame is immediately affected by the turbulence caused by the diverted combustion air passing through the aerodynamic slot 80. The end result is an intense, solid and preferably stubby type of flame 48 shown in exemplary manner in FIG. 5.

The embodiment shown in FIG. 6 is similar to that shown in FIG. 5, as indicated above, except that a ringtype gas burner 68, having a circular row of gas, burner nozzles arranged around the inner periphery thereof, and disposed opposite the outer surface of the larger airfoil member 76, is employed instead of the gun-type burner shown in FIG. 5. Nevertheless, for the reasons explained above particularly in regard to the embodiment shown in FIG. 4, the resulting flame 48 is intense, solid, and preferably of a somewhat stubby nature due to the turbulence created by that portion of the combustion air which is diverted through the annular, aerodynamic slot 80 shown in FIG. 6.

In the exemplary burner system shown in the conventional furnace illustrated in FIG. 1, as well as the guntype burner 58 shown in the embodiments of FIGS. 3 and 5, it is to be understood that especially of the burner is intended solely to consume fuel oil or is a combination gas and fuel oil type burner, the oil may be atomized either by high pressure steam or high pressure air, as desired. Either of these types of atomizing fluid may be supplied appropriately through conduits connected to sources thereof and not shown specifically in the drawing.

In summary, the several embodiments of the present invention, in addition to propagating a substantially solid, intense flame, do so while consuming a minimum amount of excess air and, of equal importance, require less furnace volume or space in the combustion zone than in furnaces using only conventional type burners, whether axial gun-type or gas-ring type burners.

I claim:

1. A fuel burner having throat means substantially circular in cross-section, burner means coaxial relative to the axis of said throat means, and supply means respectively operable to deliver fuel to said burner and blow combustion air under pressure axially through said throat means and past said burner to burn the fuel discharged therefrom in the combustion zone of said throat, in combination with air-mixing and directing means mounted coaxially within said throat means at least partially adjacent the periphery thereof and having converging air-directing means forwardly of said burner shaped and operable to converge and concentrate a substantial part of said combustion air toward the axis of said throat to form an intense concentrated flame front substantially centrally of said throat, said air-mixing and directing means also having means positioned im mediately adjacent the periphery of said converging means operable to direct part of said combustion air moving through said throat partially toward the periphery thereof to produce turbulence in the combustion zone in said throat and immediately surrounding said intense concentrated flame, thereby expanding said intense concentrated flame to form a broad and substantially solid flame in said throat which is relatively short and stubby relative to the diameter thereof and elfects intense and complete combustion of said fuel at various firing rates, said air-mixing and directing means comprising a pair of at least partially concentric airfoil ring members fixedly positioned with respect to each other and separated to provide a narrow aerodynamic circular space therebetween, said ring members being generally frusto- 1O conical and one of the same having a smaller diameter than the other, the surface of said ring having a smaller diameter being substantially at a greater angle with the axis of the throat than the larger diameter ring and tapering forwardly of said burner and inwardly toward the axis of said throat means.

2. The fuel burner according to claim 1 in which the burner means is a gun-type positioned substantially 8, axially within said throat and having a nozzle on the downstream discharge end thereof.

References Cited UNITED STATES PATENTS 1,436,823 11/1922 Purnell 431183 1,951,379 3/1934 Voorheis 431176 2,219,696 10/1940 Mueller et al 239424.5 2,502,210 3/1950 Demuth 239424 X FOREIGN PATENTS 1,296,031 5/1962 France.

642,976 6/1962 Canada.

CARROLL B. DORITY, JR., Primary Examiner US. Cl. X.R. 431-174, 188; 239424.5

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