US2334314A - Fuel burner - Google Patents

Description

Nov. 16, 1943. ,0. F. CAMPBELL FUEL BURNER Filed April 21, 1941 2 Slpeets-Sheet 1 M m Y N Wm WM E w v T mr T w W k 0mm Nov. 16, 1943.

o. F. CAMPBELL 2,334,314

' FUEL BURNER Filed April 21, 1941 2 Sheets-Sheet 2 INVENTOR Oliver E (m 05622 BY M ,Mn'flm PEA/munch ATTORNEYS burners has been the velocities are ity of such burners, a lower capacity operation.

Patented Nov. 16, 1943 umrsp STATES PATENT OFFICE.

FUEL BURNER 'Oliver F. Campbell, Whiting, Ind., assignor to Sinclair Refining Company,

corporation of Maine Application April 21, 1941, $erial No. 389,518 4 Claims. (Cl. 158-15) This invention relates to fuel burners and more particularly relates to an improved burner capable of operating eihciently over an unusually broad range of capacities. The invention is apment of the burner. For efficient operation it is essential that the relative proportions of fuel and air be kept at an optimum value and that the fuel and air be intimately admixed upon entering the combustion zone,

Some of these fuel burners are adapted to operate only at a given capacity or at a capacity which cannot be changed while the operation. The capacity of other conventional be changed at will over a limited range by varying the amount of fuel and comustion air one. In the latter type of burner, when it becomes desirable to increase the rate of heating of a boiler, for instance, the rate at which fuel is supplied to the combustion zone by the burner, is increased and, when a lower rate of heat ng is desired, the-rate at which the fuel is supplied is decreased.'

If eflicient operation is to be maintained over a range of heating rates, these variations in the rate of fuel supply must be accompaniedby an appropriate change in the amount of air supplied by the burner. However, it is not alone suflicient that the optimum proportions of fuel and air be maintained. It is also essential to efllcient combustion that the fuel and air be properly mixed, that the fuel be highly dispersed in the combustion all.

One of the major defects of conventional their failure to accomplish proper mixing of the fuel and air except when operating within a rather narrow range of capacities. Usually such burners depend to a considerable extent upon turbulence caused by the velocity of the incoming air to effect proper mixing of the air and fuel. In conventional burners the ducts through which the air passes to the combustion zone are usually size and, while effective mixing may be obtained within fixed limits, when the burner is operating at lower capacity too low to accomplish adequate mixing, and poor combustion results, If an attempt is made still further to decrease the capaclimit is soon reached beyond which ignition cannot be maintained.

Burners having air ducts of fixed cross-sectional area 'may, of. course, be designed for low However,

which are usually to some extent controllable by regulation or a'dJustinjected thereby into the combustionif one attempts to providing a spect to the fuel come the capacity range New York, N. Y., a

operate such low capacity burners at considerably higher capacities either sufiicient air cannot be supplied for efficient combustion or the velocity of the air stream is apt to be so great as to extinguish the flame.

Numerous attempts have been 'made to overdeficiency of conventional fuel burners. For instance, it has been proposed to increase the flexibility of the burners with respect to capacity range by providing mechanical means for varying the cross-sectional area of the air duct at the point where it enters the mixing zone. Thus when decreased volumes of air are required, the cross-sectional area of the air duct exit would be decreased so as to maintain velocity and turbulence of the air stream at the point where it meets with the fuel stream. One of the primary viously' proposed arrangements has been the necessity of having moving parts located within the zone of high temperature where they soon cease to function and another has been their in- "ability to sufliciently extend the range of efficient operating capacities.

In accordance with my invention, the difliculties heretofore experienced are eliminated by plurality of air ducts of annular cross-section concentrically positioned with reinjection means and with respect to each other and means without the high temperature zone for causing. air to pass through a greater or less number of these ducts as the firing rate is increased or decreased, respectively,

The air-injection means consists in general of a plurality of concentric converging ducts surrounding the fuel inlet conduit and so positioned with respect to the burner as to direct the stream or streams of air emerging therefrom in, paths converging toward the stream of fuel entering the combustion zone, thus effecting thorough mixing of the air and fuel.

In operation, air may be passed through one or more of these ducts, depending upon the rate at which fuel is being supplied and consequentlyv upon the amount burner is operating at maximum capacity all of the ducts may be employed and, when operating at reduced capacity, a proportionately less number of ducts may be used. At minimum capacity for example, the innermost air duct.

By thus varying the number of air ducts employed in accordance with the operating capacity and consequently with the amount of air being supplied, the velocity of the entering air may be maintained at the optimum value for producing:

the amount of turbulence to give most satisfactory mixing and highest burner efficiency.

Furthermore, in accordance with my invention,

the regulation of the amounts and velocities off difficulties with preof my improved burner of air required. When the commensurate "of either gas, liquid amount of air and degree of turbulence best suited to the burning of a particular fuel under particular operating conditions may readily be obtained over a wide range of capacities wholly independently of the regulation of the fuel stream.

The mixing my invention by providing these air duets with suitable vanes so as to impart to the air a whirling motion as it leaves the respective ducts. Advantageously, the innermost duct is used when mum whirling from so as to motion to the air passing thereobtain the maximum turbulence with the reduced volume of air being supplied.

My invention will be further described with reference to the accompanyin drawings which illustrate a specific embodiment of my invention in a combination burner adapted to the burning or pulverized solid fuel or mixtures thereof. In these drawings, Figure 1 represents conventionally and partly in section a side view of the burner and Figure 2 is an end view thereof.

In these drawings the burner housing I- is shown attached to the wall 2 at the firing 'port 3 of a firebox by means of the brackets 4. Within the burner housing and supported thereby 'isthe conduit 5 through which pulverized solid fuel, when used, is passed to the combustion zone 6. The pulverized solid fuel is delivered to conduit 5 through the inlet 1 from any convenient source in suspension in a gaseous medium such as air by conventional propulsion means not shown. When not in use this duitmay be closed off so as to prevent th pen;- sage of air therethrough into the combustion chamber or may be used for the introduction of a portion of the air for combustion of the liquid or gaseous fuel.

Extending through the conduit 5 isthe annur lar conduit 8 and coaxially arranged within conrduit 8 is a'pipe 9 l0. Where a liquid fuel such as fuel oil is being burned, it is supplied through pipe 9 from any convenient source, not shown, pressure to insure proper atomization in' passing through nozzle I0 into the combustion zone 6.

When a gaseous fuel is being burned, it is supplied from any conventional source and under suitable pressure through the gas inlet II to the annular space within conduit 8 surrounding pipe 9 and it issues therefrom through the gas ports I2. These gas ports are shown in the drawing as openings in the shoulder l3 at the inner end of conduit 8. These gas ports may, if desired, be slotted instead of round holes, as shown in the drawings.

Coaxially positioned with respect to the fuel supply conduits 5, 8 and 9 are a plurality of stationary coaxially arranged truncated cones I4, I5, I6, I 1 and I8 so positioned with respect to each other as to provide annular air ducts I9, 20, 2| and 22 between the surface of one cone and the next adjacent cone. The innermost cone I4 also forms the outer wall of the air duct 23 of the air and fuel may with ad vantage be further promoted in accordance with pulverized solid fuel mm which terminates at the nozzle under sufficient I lying between said cone and the outer wall of conduit 5. These cones are supported at their outer perimeter by 24 adapted to permit the free passage of air air ducts I9 to 22, inclusive. is moved toward the furnace, access first to air duct I9 to air ducts 20, 2| and 22 as the damper 25 is moved further to the right. B regulating this damper 25, for instance, according to the amount burner, a greater or less number of the air ducts are put into service and the quantity and velocity of the air passing to the combustion zone thus controlled.

The arrangement shown is a simple and effec- As this damper air is permitted and then successively tive means for controlling the passage of air a through the respective ducts. be understood that the passage of air through the several ducts may be separately controlled by individual dampers.

When the burner is operating at minimum capacity, the air ducts I9 to 22, inclusive, will normally be closed and the reduced air requirements supplied solely through air duct 23, which is However, it will The converging air thereof. This arrangement also for instance. responsive dampers for opening and closing bustion zone by the burner may angle or pitch of these vanes may vary over a considerable range depending upon the desired degree of whirling to be imparted to the incoming air I have found it advantageous to place these vanes at different angles in the respective air ducts so as to provide greater the center of the fire than at the outer portion has the advantage of providing the maximum only the innermost air duct is being used.

For example, the vanes 21 and 28 in the two innermost ducts I9 and 23 may be laced at an angle of- 45 degrees and vanes 29, 30 and M in ducts 20, 2! and 22 may 35 degrees, 25 degrees and 15 degrees, respectively.

The cylindrical damper 25 may be manually operated or it may be automatically controlled. to fluctuations in the fuel supply. Automatic control devlces'suitable for this purpose are well understood in the art and need not be here described.

In the attached drawings, one means for manually operating the cylindrical damper '25 is shown. This means consists of a shaft 32 sup ported by the burner housing by means of bearings 33 and adapted to be rotated b means of a hand-wheel 3t. Rigidly fastened on shaft 32 near opposite ends thereof are bevelled ears 35 desi ned to cooperate with bevelled gears turbulence at v 36 rigidly I closed to the open position and vanes turbulence when be placed at an angle of I claim:

1. In a fuel burner having means for injecting a stream of fuel into a combustion zone, the improvement comprising a plurality of air ducts of annular cross-section each coaxially arranged with respect to and converging toward the fuel stream in the direction of the combustion zone, a damper removed from the combustion zone for controlling the passage of air through the several ducts said damper being adapted to permit the inward passage of air first to the innermost duct only and progressively to additional successive outer ducts as the damper is moved from the within said ducts adapted to impart a whirling motion to the air emerging therefrom, the pitch of the vanes in the respective ducts being such as to impart more vigorous whirling motion to the air emerging from the inner ducts than that emerging from the outer ducts.

2. An improved fuel burner adapted to the burning of gas, liquid or pulverized solid fuels comprising coaxially arranged conduits adapted respectively for the passage of liquid, gaseous and pulverized solid fuel suspended in a gaseous carrying medium to a combustion zone, a plurality of air ducts of annular cross-section, each coaxially arranged with respect to said conduits and converging toward the common axis of said conduits of the combustion zone, and a damper removed from the combustion zone for controlling the passage of air through the several ducts.

3. An improved fuel burner adapted to the air ducts of annular cross-section, each coaxially' arranged with respect to said conduits and converging toward the common axis of said conduits attached to shafts 31, also supported by the burner housing by means of bearings 38. Rigidly attached to shafts 3T! are pinion gears 39 adapted to coo erate with the racks 40 attached to opposite sides of the cylindrical damper 2 Thus. by'rotating the hand-wheel, the damper 25 may be moved to the desired position so as to open or close off a greater or less number of the air ducts. Instead of the particular type of damper specifically illustrated. independent the entrance to the several air ducts may be used.

The rate at which fuel is supplied to the combe controlled in for instance, by reguwhich the fuel is supthe conventional manner; lating the pressure under plied to the burner.

While I have shown in the drawings only five annular air ducts, it will be understood that a greater or less number may be used, dependin upon the desired flexibility of the burner. It will also be understood that the invention is applicable to-burners designed to burn only one type. of fuel as well as to the type illustrated which is adapted to the burning of different fuels. The invention is likewise applicable to burners of any size including not only large-capacity burners but also domestic burners such as the cone-type, rotary-cup-typ and pressure-atomizing-type burners.

in the direction of the combustion zone and a damper removed from the combustion zone for controlling the passage of air through the several ducts, said damper being adapted to permit the inward passage of air first to the innermost duct only and progressively to additional successive outer ducts as the damper is moved from. the closed to the open position.

4. In a fuel burner having means for injecting a stream of fuel into a combustion zone, the g comprising a plurality of truncated cones coaxlally arranged with respect to the fuel injection means'and spaced apart so as to form a plurality of ducts of annular cross-section converging toward the fuel stream in the direction of the combustion zone, means for passing air through said damper removed from the combustion zone controlling the passage of air through the several ducts, said damper being adapted to permit the inward passage of air first to the innermost duct only and progressively to additional successive outer ducts as the damper is moved from the closed to the open position and vanes within said ducts adapted to impart a whirling motion to the air emerging therefrom, the pitch of the vanes in the respective ducts being such as to impart more vigorous whirling motion to the air emerging from the innermost duct than that emerging from the outer ducts.

P OLIVER F. CAMPBEIL.

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