US2242797A - Method of and apparatus for burning fluid fuel - Google Patents

Description

May 20, 1941. c. ,5. LUCKE 2,242,797

METHOb OF AND APPARATUS FOR BURNING FLUID FUEL Filed Feb. 26, 1938 IN VENTOR.

Char/es E l uc/re Patented May 20, 1941 METHOD or AND APPARATUS FOR BURNING FLUID FUEL Charles E. Lucke. New York, N. Y., assignor to The Babcock & Wilcox Company, Newark, N. J.,a corporation of New Jersey The present invention relates to the construction of fluid fuel burners, and more particularly, to fluid fuel burners arranged to discharge a Application February 26, 1938, Serial No. 192,699

1 2 Claims.

stream of fluid fuel of substantial cross-sectional dimensions from a burner port and a stream of air for combustion around the periphery o f ..the fuel stream.

' In fluid fuel burners of the character described the rate of combustion largely depends upon the rapidity of mixing of the fuel and air streams. With concentric fuel and air streams, for example, the air scrubs the outer peripheral surface of the fuel stream causing the fuel particles in that portion of the fuel stream to be contacted by the air and burn on reaching ignition temperature. In burning, the air envelope tends to be replaced by an envelope of products of combustion and combustion of the particles progresses depending upon the rate at which the enveloping products of combustion are replaced by air. As either the air or the fuel stream or both together are introduced with a substantial axial velocity component, a substantial length of flame travel will necessarily be required in the furnace chamber before the fuel particles in the inner portion of the fuel stream are ignited and completely burned. Modern furnace design is based upon the eco nomic desirability of burning the maximum amoimt of fuel with the least possible amount of air in excess of the theoretical amount required be had to the accompanying tive matter.

Of the drawing: I v Fig. 1' is a partly diagrammatic sectional elevation of a preferred form offuel burner construction for carrying out the methodof my invention; Fig. 2 is afurnace end view of the apparatus shown in Fig. 1;.and

Fig. 3 is a view similar to Fig. 1 illustrating a modified burner construction. In accordance with my method of burning fluid fuel in suspension a stream of fluid fuel, such as sprayed oil, gas, or a mixture of pulverizedfuel ably circular or annular.

and primary air, is introduced through a fuel burner port of a furnace chamber in a stream of substantialperimeter of cross-section and prefer- Combustion air approximating in amount the theoretical air requirements of the amount of fluid fuel .to b burned is introduced through the burner port in two parts, The major portion of the combustion for complete combustion of the fuel in the smallest furnace capable of withstanding the operating conditions without excessive maintenance.

, The main object of my invention is to provide an improved method of and apparatus for burn- I ing fluid fuel in suspension which'are character-- quirement for complete combustion of the fuel in such a manner that substantially all portions of the fuel stream receive air for combustion during the initial portion of the flame path to effect rapid combustion of the fueland a consequent shortening of the length of flame travel and furized by the introduction of the combustion air in an amount approximating the theoretical air reair is introduced in a stream surrounding the fuel stream. As the fuel and this air stream enter the furnace chamber with the air flowing in con tact with the peripheral portions of the fuel stream a scrubbing of .thefuel stream takes place at a rate depending upon the relative linear and angular velocities of the two streams. Mixing or diffusion of the fuel-and air streams will occur, and on ignition combustion will proceed at, a relatively rapid.rate.- 1 v With the combustion air'introduced'as a stream around the periphery .of the fuel stream, the fuel particles inside the periphery would ordinarily be the last to be scrubbed or mixed with the air stream. In accordance with my invention combustion of this portion ofjthe fuel stream is expedited by the introduction of the remaining portion of the combustion air in a series of adequate velocity jets directed in converging' paths across theperipheral air stream and impinging on the peripheral surface of the fuel stream. ,The effect of the impinging air jets on the fuel stream will depend primarily on their velocity relative'to that of the peripheral air stream and fuel stream. It

. is' preferred that air pressure conditions be maintained such that the jets will penetrate the air terize my invention are pointed outwith particularity in the claims annexed to and forming a part of this specification. For a better understanding I ditions in comparison to fuel burners without such of the invention, its operating advantages and spe cific objects attained by its use, reference should.

stream and the peripheral surface of the fuel stream and mix with the fuel particles in the ire-- .terior thereof. I consider it less advantageous,

although resulting in improved combustion conair jets, to maintain on the one hand higher air jet velocities causing the air jets to also penetrate 'With the air jets penetrating the fuel stream,

combustion will proceed simultaneously on the peripheral and in the central portions ofthe fuel stream, whereby substantially all portions of the fuel stream will receive their air requirements for combustion'in a relatively short time, causing combustion to progress at a rapid rate and substantially shortening the length of the flame path required in the furnace chamber or alternatively, more fuel can be burned in the same furnace chamber. The required volume ofthe furnace chamber for a given burning capacity will be thus reduced, with consequent advantages in the reduction of the cost and floor space requirements of the associated furnace.

In the drawing I have illustrated two forms of fluid fuel burning apparatus for carrying out the described method. In the construction shown in Figs. 1 and 2 an inwardly flaring burner port ID of frusto-conical shape extends'through a furnace' chamber wall H. rel ll!v is arranged axially of the burner port l and provided with a spray nozzle [3 at its inner end for discharging a hollow substantially conical spray stream of liquid fuel through the burn er port I0 into the furnace chamber. An air supply casing I5 extends along the furnace wall II for delivering combustion air 'to the burner I port. An air register I 6 ofcylindrical shape is arranged coaxially with the fuel burner barrel l2 and provided with a series of curved pivoted doors or dampers I! for controlling the passage .of air from the air casing l5 to the burner port M. The air register dampers are externally operable simultaneously to move them into and out of their closing position. The air register and damper-construction described is well known in this art, and a more detailed-description is unnecessary.

An. annular air casing or manifold of heat resistant material surrounds the burner port In at its outer side. The inner peripheral surface of the air chamber 20 is defined by an inwardly converging outer section 2| and an adjoining inwardly flaring inner section 22. The outer cas- A liquid fuel burner bar--' verging jets of suiiicient velocity to cross the annular stream of air flowing through the burner port and penetrate into the interior of the hollow conical fuel stream discharged by the nozzle l3.

To secure a higher air pressure in the air casing 20 I have provided a booster fan or blower having its inlet 3| connected to the air casing I5 at a point therein at the inlet side of the air register I6 and its outlet 32' connected to the air 1o chamber 20. With the fan '30 in operation the pressure of the air in the chamber 20 can be readily maintained substantially higher than the air I pressure within the air register 16. With this construction an adequate supply of combustion air can beintroduced into the interior of the liquid fuel stream and combustion will take place therein simultaneously with the combustion along its peripheral surface.

In the modified construction illustrated in Fig. 3, the booster fan 30 and connecting parts are eliminated and the chamber 20 provided with a. series of relatively large air inlet openings 35 in its outer wall and an annular shut-ofi damper 36 having openings 31 therein adapted to register with the openings 35. In operation the air register dampers Il may be partly closed to create an air pressure within the air register substaning section 2| registers with the discharge end of the air register I6 so that air entering through the register openings will flow inwardly through the air casing 20 around the discharge end of the burner barrel l2. The burner-barrel carries an impeller or deflector plate 24 on its inner end with the impeller blades arranged to direct part of the air inwardly toward the fuel stream and the remaining portion around the impeller; The

' outer section 2| of the air casing inner peripheral wall is provided with a series of inwardly.

tially lower ,than the air pressure in the casing-- l5 and chamber 20. The operation is otherwise similar to that previously described.

It will be understood that the air chamber 20 alone may be supplied with forced draftair and the flow of the peripheral air 'stream caused by natural draft,-and that in any case control of one or both of the two supplies of air will permit of regulation of the fraction of the total air that enters as jets through the orifices 26.

- While in accordance with the provisions of the.

statutes I have illustrated and described herein various embodiments of my invention now known to me, those skilled in the art will understand that changes may be made without departing from the spirit of the invention covered by my claims, and that certain features of my invention maysometimes be used to advantage without a corresponding use of other features.

I claim: I

1. The method of burning fluid fuel in suspension'in a furnace chamber which comprises introducing the fuel through a burner part into the furnace chamber in afstream of relatively large cross-sectional -area, andv introducing air for combustion partly in a stream of air through the burner port surrounding the fuel stream and partly in a series 'of jets at a higher velocity than and directed across the surrounding air stream and impinging on-said fuel,stream.-- Y

2. The method ofburning fluid fuel in suspen- 'sion in a. furnace chamber whichcomprises introducing the fuel through a burnerport into the furnace chamber in a stream of circular crossextending blades or vanes'23 which are set at similar angles to) the axis of the burner port so that a whirling motionwill be given to the inc0m-' ing air as it passes into the'burner port.

In accordance with my invention the inner section 22 of the air casing inner peripheral wall is flared inwardly and provided with a circular series of symmetricallyarranged orifices 26 -having their section, and introducing air for combustion -partly in an annular stream of air through the bu'rner port around the fuel stream and partly. in a series of converging jets at a higheryelocity than and directed across the annularairstreamand penetrating into the interior of'said fuel stream. a 3. The method of burning fluidg f uel Tin suspension-in a furnace chamber which comprises introducing the fuel through a b 1 ,1r nerport into I the furnace chamber in a hollow stream er cirdischarge axes defining aninwardly-tapering cone I coaxial with the burner port, as diagrammatically illustrated in Fig. L The orifices 26 arearranged to discharge a symmetrical circular series of concular crossesection, and introducing air for combustion partly in an, annular whirling stream of around the fuel air through the burner stream and partly in a circularseri of converging jets at a higher velocity than .and directed across the annular airstream into the interior of said fuel stream.

4. The method of burning fluid fuel in suspension in a furnace chamber which comprises introducing the fuel through a burner port into the furnace chamber in a hollow conical stream, and introducing air for combustion in an air-fuel ratio approximating the theoretical air require ments for complete combustion partly in an annular whirling stream of air under pressure through the burner port around the fuel stream and partly in a circular series of converging high velocity jets under substantially higher pressure than and directed across the annular air stream into the interior of said fuel stream. d

5. In combination with a furnace wall having a fuel burner port therein, a fluid fuel burner comprising nozzle means constructed to discharge a stream of fluid fuel of relatively large cross-sectional area through said burner port, means causing a stream of combustion air to flow through said burner 'por-t surrounding said fuel stream, and means for discharging a series of air jets at a higher velocity than and through said surrounding air stream and impinging on said fuel stream.

6. In combination with a furnace wall having a fuel burner port therein, a fluid fuel burner comprising nozzle means constructed to discharge fluid fuel in a stream of circular crosssection through said burner port, means for discharging a stream of combustion air through said burner port around said fuel stream, and means for discharging a plurality of air jets at a higher velocity than and through said annular air stream and impinging on said fuel stream.

'7. In combination with a furnace wall having a fuel burner port therein, a fluid fuel burner comprising nozzle means constructed to discharge fluid fuel in a stream of circular cross-section through said burner port, means causing an annular stream of combustion air to flow through said burner port around said fuel stream, and means for discharging a. series of converging air jets at a higher velocity than and through said annular air stream and penetrating into the interior of said fuel stream.

8. In combination with a furnace wall having a circular fuel burner port therein, a fluid fuel burner compris' discharge a hollow conical stream of fluid fuel through said burner port, an air casing for. discharging an annular whirling stream of combustion air through said burner port around said fuel stream, and means for discharging a symmetrically arranged circular series of converging air jets at a higher velocity than and across said annular air stream and into the interior of said conical fuel stream.

9. In combination with a furnace wall having a fuel burner port therein; a fluid fuel burner comprising nozzle means co to discharge a stream of fluid fuel of circular cross-section throughsaidburnerport,anaircasingfordisnozzle means constructed to I charging an annular stream of combustion air through said burner pprt around said fuel stream, and means for discharging a series of converging air jets at a higher velocity than and across said annular, air stream and into the interior of said fuel stream, said last mentioned means including an annular air chamber surrounding said nozzle means and provided with a circular series a of air discharge orifices directed towards said fuel stream.

10. In combination with a furnace wall having a fuel burner port therein, a fluid fuel burner comprising nozzle means constructed to discharge a. stream of fluid fuel of circular cross-section discharge orifices directed towards said fuel stream, and means for creating an air pressure in said chamber higher than in said air casing.

11. In combination with a furnace wall having a fuel burner port therein; a fluid fuel burner comprising nozzle means constructed to 'discharge a stream of fluid fuel of circular. crosssection through said burner port, an air casing for discharging an annular stream of combustion airthrough said burner port around said fuel stream, and'means for discharging a series of converging air jets at a higher velocity than and across said annular air stream and into the interior of said fuel stream; said last "mentioned means including an annular air chamber surrounding said nozzle means and provided with a circular series of air discharge orifices directed towards said fuel stream, and fan means arranged to withdraw air from said casing and;

deliver said air at a higher pressure to said air chamber.

12. In combination with a furnace wall having a fuel burner port therein, a fluid fuel 'bumer' comprising nozzle means constructed to discharge a stream of fluid fuel of; circular crosssectionthroughsaid burner port, an air casing, an air register in said casing for dischargingau annular stream of combustion air through said burner port around said fuel stream, and means for discharging a series of converging air jets at a higher velocity than and across said annular air stream and into the interior of said fuel stream, said last mentioned means including an.

said air chamber.

CHARLES E. LUCKE.

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