US3285315A - Oil burner with widely variable operating range - Google Patents

Description

Nov. 15, 1966 T. s. VOORHElS OIL BURNER WITH WIDELY VARIABLE OPERATING RANGE Filed April 15, 1965 INVENTOR. TEMPLE 8. VOORHEIS WWW ATTORNEYS United States Patent 3,285,315 OIL BURNER WITH WIDELY VARIABLE OPERATING RANGE Temple S. Voorheis, Palo Alto, Calif., assignor to Coen Company, Burlingame, Califl, a corporation of California Filed Apr. 15, 1965, Ser. No. 448,303 7 Claims. (Cl. 158-28) This invention relates to a burner for combustion chambers of the type used for firing commercial and marine apparatus, such as, for example, water tube boilers and the like. More particularly, the invention relates to such burner that has an extremely wide load range.

For convenience of description the objects of the present invention will be stated in terms of a burner for firing a marine boiler of the type used for producing steam that is supplied to the turbine that provides motive power for a water-borne vessel. A boiler operating in such environment must be capable of providing steam over widely varying operating ranges. For example, far more steam is needed when a vessel is under way than when it is standing by. In the latter condition, although virtually no steam is required, it is impractical to interrupt the burner operation since start-up is a timeconsuming and dangerous operation. In the prior art steam-producing systems, one or more enginemen were stationed at a plurality of boilers so that one or more boilers could be manually turned down at lower ranges of steam demand. Such mode of operation, in addition to being expensive from the standpoint of required manpower, is slow in that each time that a boiler is turned down and restarted it must be purged of residual fuel and produces much soot and smoke during the light-off procedure. Moreover, it has been found that the majority of explosions and other accidents occur during light-off.

The principal object of the present invention is the provision of a burner having such a wide range of operation that the burner can be turned down to approximately of its full rated capacity. Such object is achieved by providing two or more fuel lines extending through a throat into a combustion chamber and by providing on each such fuel line a burner cap in which are formed fuel passageways so oriented that each fuel line supplies fuel to a discrete sector of the combustion chamber interior. Means are provided for totally arresting or shutting off the fuel supply through one or more of the fuel lines so that at lower ranges, less than all of the fuel lines are supplying fuel to the combustion chamber. At

such low range of operation the heat output of the burners is minimal but is sufficient to sustain combustion and ready the burner for turn-up with the advent of increased demand.

Another object is to provide an improved burner cap having fuel passages formed therein in such pattern and orientation that the combustion chamber is provided with a uniform flame pattern at full and intermediate ranges of operation. In the specific example, described in more detail hereinafter, two burner caps are shown and each has plural fuel passages arranged in a generally semicircular pattern so that the two caps in combination will afford uniform and complete distribution of flame within the combustion chamber. In such specific example, a fantail flame is desired, one that is extensive in one direction and thin in a direction transverse of the first-mentioned direction. Burner caps for developing such flame pattern are provided with individual fuel passages formed at different angles with respect to the central axis of the burner throat to accomplish the necessary flame distribution.

A further object is to provide a cap of the type referred to above in which the amount of fuel emanating from each fuel passageway is uniform. In understanding this object it should be appreciated that atomizers for mixing with fuel oil such gaseous materials as steam, air or combustible gas are employed wherein the oil and/or gaseous material is spun or whirled to enhance the atomization and emulsion thereof. Such atomizing structure is located upstream of the burner cap as a consequence of which the atomized fuel arriving at the burner cap is whirling or spinning with respect to the longitudinal axis of the fuel line. It has been found empirically in respect to caps lacking fuel passageways throughout the entire periphery of the cap that fuel flow through each of the various passages will be different due to the whirling or spinning of the atomized fuel. The present invention includes on the interior of the cap a hemispherical surface on which a dam is formed opposite that portion of the cap in which the fuel passages are formed. Although the theoretical justification for such dam is not fully understood at this time, it is believed that the darn interrupts or deflects the whirling motion of the atomized fuels such that each passageway is provided with a uniform amount of fuel.

Other objects, features and advantages of the present invention will be more apparent after referring to the following specification and accompanying drawing in which:

FIG. 1 is a partially schematic view of a burner of the present invention installed in a burner throat through a wall of the combustion chamber;

FIG. 2 is an elevation view of the burner taken, at an enlarged scale, substantially along line 2-2 of FIG. 1;

FIG. 3 is an elevation view of a burner cap constructed in accordance with the present invention; and

FIG. 4 is a cross-sectional view taken along line 44 of FIG. 3.

Referring more particularly to the drawing, reference numeral 12 indicates the wall of a combustion chamber of a furnace, for example, a boiler furnace, which wall includes refractory lining 14 and a burner throat 16 extending from the interior of the combustion chamber to the exterior of wall 12. In FIG. 1 the interior of the combustion chamber is at the top of the picture. Mounted exteriorly of the combustion chamber on the outer surface of wall 12 is a Windbox 18 for directing and distributing air into throat 16 from a duct 20 that is supplied with air by a conventional blower or fan not shown. Windbox 18 can be provided with known air control and distributing devices such as the type disclosed in detail in my US. Patents 2,838,103 and 2,889,871. Such air flow control systems aiford a uniform air flow through throat 16 without imparting unnecessary spiral or radial components of force to the air as it emanates into the combustion chamber interior.

Extending through Windbox 18 and into throat 16 are first and second fuel lines 22 and 24. Such fuel lines typically include concentric passages for fuel 25F and for an atomizing medium 25S such as steam which are mixed at an atomizer, designated schematically at 26, prior to delivery to the inner ends of the fuel lines. Fuel supplied through lines 22 and 24 is controlled by a throttle valve 28 which is supplied from a conventional source of fuel oil (not shown) through a fuel delivery line 30. Valve 28 is controlled by a conventional controller system 32 in accordance with the demands of the combustion chamber or furnace being fired by the burner which controller also has provisions for controlling the quantity of air delivered through duct 20. Since controller 32 is not part of the present invention and since many controllers for accomplishing the desired mode of operation 3 are known in the art, further detailed description of the controller will not be here necessary.

One of fuel lines 22 and 24, for example, fuel line 22, is provided with a solenoid valve 34 which is operative to totally arrest flow through line 22 when the valve is actuated.

The operation and control of valves 28 and 34 by controller 32 can be understood by first assuming that the burner is firing at a range of between full capacity and about of full capacity. In such range, controller 32 adjusts valve 28 and the amount of air supplied through duct to maintain the proper fuel-air mixture necessary to supply the load within the combustion chamber. At a point typically around 10% of full operating capacity, controller '32 acts to close solenoid valve 34 so that the amount of fuel supplied to the combustion chamber is halved whereas the amount of air supplied to the combustion chamber remains constant. It may be seen therefore that the burner is operating at about 5% rated capacity when solenoid valve 34 is actuated to arrest the fuel flow through line 22. Such level of operation has been found in marine boilers, for example, to be adequate to maintain proper temperatures within the combustion chamber and to generate sufiicient steam to power auxiliary equipment. Such point of operation of the system however provides no steam for operation of the main motivating turbine. Of course, when steam demand increases, controller 32 acts to open solenoid valve 34 and throttle valve 28 thereby increasing heat output of the burner. Since the interior of the combustion chamber is not reduced to a dangerously low temperature level even when valve 34 is closed, the temperatures necessary for the increased load are rapidly reached without any danger that liquid fuel will be admitted into the combustion chamber before it is totally atomized and ignited.

Each fuel line 22, 24 has on the inner end thereof a cap 36 and 38, respectively, that resides in a shield 40 within burner throat 16 (see FIG. 2). In the example here under consideration there are two fuel lines and consequently two caps disposed in an oval or elliptic throat. Such showing is only exemplary, however, because throats of other configurations with other numbers of caps are deemed equivalent.

The internal details of the preferred form of the caps 36 and 38 can be seen in FIGS. 3 and 4. Since both caps are identical, only cap 38 will be described in detail. The cap includes an interiorly-threaded flange 42 for securing the cap to the inner end of fuel line 24. The cap has an end wall 44 formed on the interior thereof with a generaly hemispheric surface 46 of a diameter approximately equal to the inner diameter of fuel line 24. The outer surface of end wall 44 defines a frusto-conioal surface portion 48. Parallel shoulders 50 and 52 are provided on the end cap for defining a wrench grip useful in installing and orienting the cap. Fuel passages are provided in, end wall 44 and extend from hemispheric surface 46 to frustoconical surface 48. The fuel passages are oriented so as to distribute the fuel within the combustion chamber in a desired manner. For this purpose, and as can be seen more clearly in FIG. 3, the holes are limited to a 180 or semi-circular portion of the cap. Such showing is merely exemplary of the required relationship that fuel openings are limited to a sector of the cap that extends (in degrees) around the cap by an amount approximately equal to a fraction having a numerator of 360 and a denominator N equal to the number of fuel caps provided in burner throat. In the exemplary cap here shown there are two caps as a consequence of which all fuel openings are restricted to an approximate 180 portion of end wall 44.

At the center of the 180 portion is formed a passageway 54 that is parallel to a line extending between the centers of caps 36 and 38 which line in the present example is horizontal. The passageway 54 is, however, slanted outwardly at a rather steep angle with respect to the longitudinal axis of fuel line 24 so that fuel is supplied to the lateral or side portions of the combustion chamber. Above and below passageway 54 are second passageways 56, each of which is formed at a lesser angle with respect to the central longitudinal axis of fuel line 24 but slanted slightly away from horizontal. Accordingly, fuel issuing through passageway 56 is spread laterally to a lesser extent but upwardly and downwardly to a greater extent than is the case with fuel issuing from passageway 54. Spaced from passageways 56 are third passageways 58 that are formed at still a smaller lateral angle with respect to the central axis of fuel line 24. The passageways 58 have but a slight component in the lateral direction but distribute the fuel upwardly (or downwardly) within the combustion chamber. It can be seen that the above-described orientation of passageways 54, 56 and 58 effects a uniform distribution of fuel within one-half of the combustion chamber and that installation of fuel cap 36 with identical passageways oppositely disposed will effect uniform fuel distribution within the other half of the combustion chamber.

Allusion has been made hereinabove to atomizer 26, a conventional expedient for intimately intermixing a gaseous medium with the fuel oil so as to promote mixture with combustion air and combustion. Such atomizers typically include a whirl plate 59 or the like that imparts swirl as at arrow 598 to the atomizing medium and the fuel oil to promote the mixture. Fuel arriving in the chamber defined by hemispheric surface 46 within cap 38 is therefore swirling rapidly with respect to the central axis of fuel line 24. In order to obtain uniform fuel delivery to each passageway 54, 56, 58, there is provided a dam -60 affixed to hemispheric surface 46 and located in the portion of cap 38 opposite the'portion in which the fuel passageways are defined. Dam 60 includes a longitudinally-extending wall 62 and a laterally-extending wall 64. Each wall is formed by a fiat plate having an arcuate surface thereon that has a radius of curvature equal to that of hemispheric wall 46. Consequently, the dam can be elfectively secured to the hemispheric wall. As can be seen most clearly in FIG. 3, longitudinally-extending wall 62 is spaced laterally of the central axis and on the side thereof opposite from the fuel passageways. The dam has been found effective in distributing the fuel uni- -formly over the five passageways so as to afford uniform flame distribution within the combustion chamber.

Referring again to FIG. 1, it will be seen that when fuel is supplied through both fuel lines 22 and 24, a generally fantail-shaped flame is developed and the entire boiler furnace interior is supplied with flame. As the operating rate is reduced to a point at or about 10% of capacity, solenoid valve 34 is closed, thereby arresting fuel flow through fuel line 22 and its associated cap 36. It has been found in one installation of a burner of the present invention that a flame pattern of the general form depicted at 66 in FIG. 1 is formed. That is to say, one-half of the boiler is being fired at a reduced rate; the other half is not being fired at all. The uniform movement of air through the throat ismore than suflicient to support combustion of the atomized oil emanating from the cap 38 and to promote heat distribution within the boiler so as to avoid dangerous temperature differentials across the water tubes and combustion chamber walls. However, sufficient heat to light-off fuel oilfrom cap 36 when valve 34 is again opened is maintained in the combustion chamber so that operation from only one fuel line (24) is sufficient to provide safe minimum load operation and to avoid damage to the boiler interior.

. Thus it will be seen that the present invention provides a burner system capable of an extremely wide operating range; in one installation safe operation at 5% of rated capacity was accomplished. The invention additionally provides a burner that is readily adapted to automated operation in that no boiler needbe continuously shut down and re-lit as'the load demands vary. '7

Although one embodiment of the invention has been shown and described, it will be obvious that other adaptations and modifications can be made Without departing from the true spirit and scope of the invention.

I claim:

1. In combination with a combustion chamber having a wall defining a burner throat therein and means for providing combustion air to said chamber through said throat, an improved fuel oil supply system comprising a plurality of fuel lines extending through said throat into said combustion chamber, each said fuel line having on the inner end thereof a cap, each said cap having at least one obliquely oriented fuel passage therein for diver-gently directing fuel into a discrete sector of said combustion chamber, the totality of said caps and said fuel passageways being oriented so that all sectors of the combustion chamber are supplied with fuel when fuel is supplied from all said caps, means for controlling the amount of combustion air and fuel supplied to said combustion chamber over a range in accordance with the load demand of said combustion chamber, and means operable at the low end of the range of fuel flow to arrest fuel flow through at least one of said fuel lines and less than all said fuel lines so that less than all sectors of said combustion chamber are fired at the low end of the range.

2. A variable load burner for a combustion chamber comprising a wall forming a boundary of the combustion chamber and having a burner throat therein, first and second fuel lines extending into the combustion chamber through said throat, first and second nozzle caps mounted on the inner end of respective said fuel lines, each said nozzle cap defining a generally semicircular pattern of fuel openings therein, said nozzle caps being oriented so that fuel openings in one said cap are furthermost from openings in the other said cap, thereby affording a fantail flame symmetrical relative the central axis of the throat, means for throttling the fuel supplied to said fuel lines, and means operable at a low rate of fuel supply for arresting fuel flow to one said nozzle.

3. A burner for a combustion chamber comprising first and second fuel lines for supplying fuel to said combustion chamber, means in each said line for atomizing and swirling fuel therein, a cap mounted on the inner end of each said fuel line, each said cap having a generally hemispheric surface interiorly thereof and a generally frusto-conical surface exten'orly thereof, a plurality of fuel passages extending from said interior surface to said exterior surface, said holes being disposed in one-half of said cap, a dam formed interiorly of said cap on the opposite half from said holes, said dam having a first planar face normal to the axis of its associated fuel line and a second planar face perpendicular to said first face and lying in a plane parallelly spaced from the central axis of said line, and means for totally arresting fuel flow to one said fuel line at a low operating point thereof.

4. An oil fired burner for controllably injecting fuel and air into a combustion chamber of the type having a wall forming one boundary of the combustion chamber, said burner comprising a portion of said wall having a refractory throat opening therethrough, said throat having an oval cross-sectional shape that has its greatest dimension along a major diametral axis, first and second fuel lines mounted in said throat in spaced relation along said major axis, a cap mounted on the inner end of each said fuel line, each said cap including a plurality of orifices formed in a generally semicircular pattern therein, the orifices remote from said diametral axis being formed at a first angle with respect to the central axis of the orifice, the orifices proximate said diametral axis being oriented at a second angle with respect to the central axis of the orifice, said second angle being greater than the first angle so that a generally fan shape flame pattern that is flattened along the plane of said diametral axis is produced, means for supplying fuel to said fuel lines, and means for supplying air through said throat to support combustion of said fuel in said combustion chamber. 1

5. A burner according to claim 4 including controller means for controllably throttling fuel and air delivered to said burner in accordance with the load demand thereon, valve means in said first fuel line for totally arresting fuel flow therethrough; and means operatively connecting said valve means to said controller means for arresting fuel flow through said first fuel line at a preselected low point of operation of said burner, whereby upon arresting fuel flow through said first fuel line, said burner fires only through said second fuel line and its associated cap.

'6. A burner according to claim 4 including means in said fuel lines for atomizing fuel oil therein by intermixing a gaseous medium therewith by swirling, whereby fuel arriving at said caps is moving in a spiral path, and means in said cap for defining a dam, said dam being disposed oppositely of said orifices and having a first wall aligned parallel to the central axis of said fuel and a second wall normal to said first wall and extending therefrom in a direction opposite from said orifices so that spirally moving fuel impinging on said dam is distributed uniformly to said orifices. v

7. The improved oil supply system of claim 1 comprising N fuel lines extending through said throat in substantially symmetrically spaced relation relative the central axis of said throat, the fuel passage in each cap being limited to a sector thereof further-most from the central throat axis, said sector having radial extent limited to 360/N degrees, wherein N is a positive integer.

References Cited by the Examiner UNITED STATES PATENTS 1,229,030 6/1917 Cecil.

1,536,230 5/1925 McCue 158-28 2,315,412 3/1943 Galumbeck 158-28 X 3,180,395 4/1965 Reed 15876 X JAMES W. WESTI-IAVER, Primary Examiner.

Claims (1)

1. IN COMBINATION WITH A COMBUSTION CHAMBER HAVING A WALL DEFINING A BURNER THROAT THEREIN AND MEANS FOR PROVIDING COMBUSTION AIR TO SAID CHAMBER THROUGH SAID THROAT, AN IMPROVED FUEL OIL SUPPLY SYSTEM COMPRISING A PLURALITY OF FUEL LINES EXTENDING THROUGH SAID THROAT INTO SAID COMBUSTION CHAMBER, EACH SAID FUEL LINE HAVING ON THE INNER END THEREOF A CAP, EACH SAID CAP HAVING AT LEAST ONE OBLIQUELY ORIENTED FUEL PASSAGE THEREIN FOR DIVERGENTLY DIRECTING FUEL INTO A DISCRETE SECTOR AND OF SAID COMBUSTION CHAMBER, THE TOTALITY OF SAID CAPS AND SAID FUEL PASSAGEWAYS BEING ORIENTED SO THAT ALL SECTORS OF THE COMBUSTION CHAMBER ARE SUPPLIED WITH FUEL WHEN FUEL IS SUPPLIED FROM

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