US2044720A - Liquid fuel burner - Google Patents

Description

June 16, 1936. 1 FLETCHER 2,044,720

LIQUID FUEL BURNER F11ed Jan. 17, 1933 2 sheets-sheet 1 June 16, 1936. J. FLETCHER 2,044,720

` LQUID FUEL BURNER Filed Jan. 17, 1953 2 sheets-sheet 2 Patented June 16, 1936 LIQUID FUEL BURNER James Fletcher. Akron. Ohio, assigner to The Babcock & Wilcox Company. Newark. N. J., a corporation of New Jersey Application January 17, 1933, Serial No. 652.132

19 Claims. (Cl. 2Min-120)v My present invention relates to the construction and operation of liquid fuel burners, and particularly to liquid fuel burners of the mechanical-atomizing type adapted for use over a wide range of capacities without change of parts.

Liquid fuel burners of the type stated have been heretofore proposed in which a supply ofv liquid fuel from a common source is divided into two or more independent controllable streams discharging through a common whirling chamber and nozzle opening into a furnace. In such constructions the passages to the whirling chamber are usually divided into two or more separate groups connected to separate feeds of liquid fuel. In the intended mode of operation of such burners, the liquid fuel supply connections are so arranged and controlled that the groups of passages may be used either simultaneously or separately. It has also been proposed to make the several groups of passages of different maximum carrying capacities whereby separate operation of the groups will provide different rates of discharge from the burner. Burner constructions of this type have beenfound to be inherently disadvantageous in that the burner parts surrounding thedischarge passages not in use are continuously exposed to high furnace temperatures, causing solid deposits from the liquid fuel therein and consequently rapid clogging of these passages. Variable-capacity liquid fuel burners heretofore in use in which the fuel flow is through the same discharge passages into a common whirling chamber at all loads have the inherent disadvantage that the angle andneness of spray' will vary substantially over their range of operation, due to the consequent changes in the rotational and yaxial velocity components of the fuel particles discharged.

The general object of my invention is the provision of a variable capacity mechanical-atomizing liquid fuel burner capable of eecting complete atomization of the fuel and maintaining its eifectiveness over a wide capacity range. A more specic object is the provision of a mechanicallyatomizing liquid fuel burner capable of delivering a fuel spray within the desirable 4ranges of spray angle and iineness over a wide capacity range. A further object is the provision of a liquid fuel sprayer plate having an improved construction and` arrangement of primary and secondary liquid fuel discharge passages. A further object is the provision of a liquid fuel burner nozzle in conjunction with a sprayer plate of the character stated and having a whirling chamber and orice constructed and arranged to provide efilcient atomization over a wide fuel range with a minimum pressure drop through the whirling chamber.' A further object is the provision of" fuel supply control means arranged to prevent operation of the burner other than in the most desirable manner.

I'he various features of novelty which char-` acterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specic objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which-1 have illustrated and described a preferred embodiment of my invention.

Of the drawings:

Fig. 1 is a sectional elevation of a liquid fuel burner constructed in accordance with my invention, the burner supporting means and combustion air supply and control meansl being omitted. for purposes of clarity;

Fig. 2 is a sectional view on an enlarged scale of the nozzle shown in Fig. 1;

Fig. 3 is an end view on an enlarged scale of the sprayer plate shown in Fig. 1;

Fig. 4 is a section on the line 4-4 of Fig. 3;

Fig. 5 is a somewhat diagrammatic view illustrating the arrangement of the liquid fuel supply connections and supply control provisions;vand

Fig. 6 is a somewhat diagrammatic view of the liquid fuel burner in an operating position.

The liquid fuel burner unit illustrated comprises a tubular outer casing or distance piece I0 adapted to be slidably mounted in operative relationship to an opening 1 through a furnace wall 8, as shown in'Fig. 6. The inner end of the casing is threaded, as indicate'dat II, for engagement with a suitable impeller 9 for directing a flow of combustion-supporting air around the discharge end of the burner, the impeller being advantageously constructed and arranged and the burner' mounted substantially as shown in U. S. Patent No. 1,602,180 of T. B. Stillman, granted Oct. 5, 1926.

The fuel conduit and spraying parts of the burner are slidably mounted in the casing IIl,

described.` Within and extending axially beyond the ends ofl the barrel I2 is a pipe I1 having its outer end extending across the passage I Ii and epenlngintoaseparatepassageilintheboib member which. preferably connected tothe same soume of liquid fuel. as hereinafter described. Where operating conditions make it desirable. separate sources of the same fuel. or of different fuels may be used. The inner or dischargeend of the burner is formed by a spray discharge head including a sprayer head Il having its inner portion' closely fitting around the inner end portion of the pipe I'I and an outer portion abutting and threaded on the inner end of the barrel If. The inner end of the sprayer head has an annular recess 2| connected to the annular liquid fuel passage surrounding the pipe I1 by a series of parallel passages 22 symmetrically arranged about the axis of the sprayer head.

The supply of liquid fuel passing through the annular passage between the pipe I1 and barrel I2 is hereinafter designated the primary"'fuel supply, while the supply passing directly through the pipe l1 is hereinafter ldesignated the "secondary" fuel supply.

'Ihe discharge head also includes a sprayerv plate Il connected with the recess 2| ofthe sprayer head by an outer series o f symmetrically arranged ports or passages 21 extending parallel to the axis of the sprayer plate and preferably registering with corresponding ports 22. The central portion of the inner face of the sprayer plate is eounterbored to form a circular whirling chamber 2|, to which the primary fuel supply is delivered through a series of discharge nozzle-forming slots 30, preferably of rectangular cross-section, connecting corresponding ports 21 to the whirling chamber. The slots 3l are symmetrically arranged in a transverse plane normal to the axis of the whirling chamber and substantially tangentially to the whirling chamber, the outer walls of each slot being directly tangential to the chamber circumference. The number and' effective cross-sectional area of the fuel passages and slots 30 used will vary with the desired fuel capacity range of the burner. With all such arrangements, a plurality of liquid fuel streams will enter the whirling chamber at circumferentially spaced points at a relatively high velocity and rotate about the periphery thereof in the same direction.

'Ihe sprayer plate is also formed with an inner series of ports or passages -29 symmetrically spaced about and extending parallel to the axis of the plate and connecting the secondary fuel supply Pipe I'l to the whirling chamber. The secondary fuel ports Il advantageously correspond in number to the primary fuel ports I1 and have their inner ends opening to the corresponding discharge slots lll at points intermediate the length thereof, as shown in Figs. 1. 3 and 4. The cross-sectional area of theportion of'the discharge slots between the secondary fueiports and the whirling chamber is substantially increased in width and depth to permit greater fuel iiows therethrough when both the primary and secondary ports are in use, without causing any substantial change in the rotational velocity of the primary fuel streams discharging into the whirling chamber.

The discharge head also includes a nozzle member'l! of substantially the same diameter as the sprayer 'head 2l and having a plane outer surface abutting the inner side of the sprayer plate and thus defining the inner side of the nozzleforming slots 30. By this formation the machining operations required to form the slots are entirely confined to the sprayer plate. The nozzle is formed with an axial discharge passage Il.

lformed as hereinafter deliti'ibetl.A The delilli 0f pendent upon the form of the nozzle passage. Por l0 example, ii the periphery of the nozzle passage throughout its length isin alignment with the periphery ofthe whirling chamber, the whirling effect obtained'wili cause only partial atomization of the liquid fuel. Buch a nozzle passage produces 15 substantially a flat sheet spray. the spray having a number of heavy lines therein corresponding to the number of slots used, indicating that a large portion of the fuel is not atomized. I have found that the character of the spray is substantially 20 improved by forming the nozzle passage with a restricted oridce I4 of a predetermined area, whereby the several streams approaching the orifice will be intimately mixed before their discharge into the furnace.-

Ihe speciiic form of the portion $5 ofthe nozzle passage forming a continuation of the whirling chamber was also found important. With a concave section preceding the orifice, the angle of spray was found tol vary substantially with 30 different rates of fuel discharge. Conditions are substantially improved by the use of a uniformly converging wall formation of the whirling chamber section Il from its inlet to the orifice. as inaimed m 1111.2. 'rem show that the angle of 35 spray increases with increases in the included angle A of the whirling chamber section 3l, and that the fuel capacity decreases with increases in the included angle of the nozzle, and vice versa, although the differences inl capacity range for 40 included angles of from 45 to 90 is not substantial. I have found that the most desirable value for the angle A to be that value giving the least overall pressure drop in the nozzle with both satisfactory atomimuon and at the most 45- satisfactory angle of spray with reference to the air stream.

The portion 38 of the nozzle at the inner end of the orifice is also of conical form uniformly increasing in diameter and having an included 5 angle B of sufficient size to avoid any dragging effect on the outer strata of the spray which would tend to unite the liquid particles in the outerstrata. A set of such nozzle plates, each having the same degree of variation in capacity but with different orifice areas to provide different desirable maximum and minimum capacities, maybe supplied to each user. 'Ihe manufacture and interchangeability of the plate set is facilitated when all of the plates are of the same external size and shape. This is effected while maintaining the included angle A and maximum diameter of the section 3l constant, by making the angle B approximately 120. With this construction, while the size and position of the orince will change, no change in plate thickness will result.

The circumferential inner end portion of the Anozzle 3! is cut away to form a seat for a cap inner portion of the sprayer head.

tion `carrying therewith jthe nipples 45.

burner parts within the casing, Iii may then be retracted without disturbing the `position of the` amano tractable without `disturbing the position ofthe latter. Por thispurpose, vthe lprimary and secthereofacarrying pivot pins 42 Vfor *upper and lower clamp Jarmsf and, respectively.` `The f portions of thegbody member il .at vthe outer endslof the passages `Il and il are beveled as `indl`:ai: ed in 1 `to receive the yrounded vends of ball joint nipples 4l carried inthe `clamp "arms "flexible primaryfand secondary liquid fuel ,supply lines `46 and 41. respectively. The free lend `of the clamp arm ,44 carries a pivot pin 4I on a which aclamp `bolt 49 is mounted. The upper A end ofthe clamp ,bolt` isadapted to be'received in the forked free end of theclamparm and N is ordinarily held in 'that position by a washer 6l and clamp `nut Si.

With the supply connectionsin their-operating position, as shown in Eig. l, inspection and/or cleaning of the burner parts is easilyeifected i after the supplies of liquid fuel have-,been cut olf by closing cut-off valves 5I of any suitable type inthe supply lines, by loosening the clampl` nut 5I and swingingthe clamp boltfout of en- ,gagement with the clamp arm 43. The `clamp arms 43 and44` may then'be swung out of posilatter.

with a liquid fuel burner constructed as de'- scribed, changes in fuel capacity from minimum to maximum ratings with a given sprayer plate and nozzle while maintaining the spray angle and neness within desirable limits are prefer-V ably secured by first operating with primary fuel alone at a pressure suilicient to secure satis- "factory atomization. 'I'he capacity may be increased to apredetermined amount by increases in the primary fuel pressure. Further capacity increases are then secured by opening the secondary fuel -supply line and supplying secondary fuel at the minimum secondary pressure effective to overcome the backpressure existing in the a whirling chamber. Further increases in capacity are obtained byy progressivelyincreasing the .ef-p

fective secondary pressure to its maximum value.

To change the burnerccapacityfrom` maximum to minimum rating, the procedure isjthe re* verse. I have found that a'four-to-one capacity range with a spray of a desirable character is` easily obtained in `operation with a burner .con-v structed as described. i

In Fig. 5 is shown' a liquid fuel supply system and control provisions arranged. to insure the use of my preferred mode of `-operation. 'I'he liquid fuel is delivered under `a high pressure from a common source to a supply main 55 connected to the primary and secondary branch supplyf lines 46 and 41, respectively. Controlvalves 58 and 51 are arranged in the supply main 55 and secondary supply line 41, respectively, and may mits `each streamv of secondary'fuel to enter the fstreams.' minimizing changes `in velocity of the The' `statutes I have illustrated and described herein 5 `being alone in operation.` A further control effeet maybe had yby varying the pressure of the fueidelivered` to thsmain Il.

a 'The `particular sprayer plate formation de- 5. ondary fuelfsupplyconnections tothe body mem- 1i ber `Il.arealdvaiitageously n exlble and readily detachable therefrom." As shown in Figs. i and 5, Y, 'the oliterfiidof `the casing It is externally threaded for'fengsgementfby an adjustable col-` larll'havlngpairs of wings 4i von oppositesldes l l streams. distributed about the circumference of fthewhirling chamber. The high rotational vescribed` is especiallyadvantageous in a" wide rangefuel burner of this type.A When the primarysupply alone is used the supply is substantially` uniformly divided between all of the ports 21 and enterethe 'whirling chamber. substantially tangentially in `several high velocity loclty of the streamsin the whirling chamber is maintained throughout its length. the individual streams being A,gradually combined and united at `theorifice. atomized by the centrifugal force acquired in the whirling chamber and enter the furnacein a hollow conical spray of substantial- .capacitiescf The described arrangement of the `discharge slots and secondary fuel ports perwhirling fichamber with no harmful Ainfluence on the',correspondingstream ofprimary fuel. The secondary streamswill mainly flow through the slots `below and at oneside of the primary primary streams andUthereby changes in the character of the .spray developedb The primary andsecondary streams from each slot enter the whirlingchamber side-by-side.' The arrangement of `the discharge `slots for the primary and secondary fuel feeds in `a transverse plane normal to the whirling chamber axis greatly con- 'tributes to the maintenance of desirable spray conditions. Any fuel in the secondary ports whenfthe primary portsalone are in operation is protected from the furnace heat by continuous passage of the primary streams across the ends fof thesecondary ports. Solid deposits from the liquid fuel in the secondaryports are thus minimized. A continuous cleaning of the portions of the discharge slots utilized by the secondary fuel will be eifectedwhen the primary feed alone is in use. Y

While in accordance with the provisions of the the bestform of my invention now known to l me, those skilledinthe art will understand that 'changes may be made inthe form of the appaa use of other features.

I claim: H

1. mechanical-stemming liquid fuel burner 65 comprising a secondary liquid fuel supply conduit connected to a source` of fuel supply, a discharge head at the discharge end of said conduit and including Va. substantially circular chamber, a series of secondary fuel ports connected to said fuel 70 conduit i and having their discharge ends arranged aboutthe circumference of said chamber,

a series of primary fuel ports arranged outside said secondaryl fuelports, a separate liquid fuel supply conduit connected to a source of fuel sup- 75 plyandopeningtosaidprimaryfuelportaa series of nozzle-forming slots, each connecting a pair of corresponding primary and secondary fuel ports to said chamber, and a restricted outlet from said chamber. i v

2. A mechanical-atomislng liquid fuel burner comprising an axially arranged secondary liquid fuel supply conduit, a discharge head at the discharge end of said conduit and including-a circul a series of nozzle-forming slots connecting said primary and secondary fuel ports to said whirling chamber. each of said slots extending substantially tangentially to said whirling chamber and having corresponding primary and secondary fuel ports opening thereto at spaced points along its length, and a restricted outlet from said whirling chamber.

3. A mechanical-atomizing liquid fuel burner.

comprising an axially arranged secondary liquid fuel supply conduit, a discharge head at the discharge end of said conduit and including a circular whirling chamber, a series of secondary fuel ports connected to said fuel conduit and having their discharge ends symmetrically arranged outside the circumference of said whirling chamber, a series of primary fuel ports symmetrically arranged about said whirling chamber and outside said secondary fuel ports, a separate liquid fuel supply connection opening to said primary fuel ports, a series of symmetrically arranged nozzle-forming slots connecting said primary and secondary fuel ports kto said whirling chamber and extending substantially tangentially to the circumference of said whirling chamber, the slot for each primary port registering with the discharge end of the slot of a corresponding secondary port, and a restricted outlet from said whirling chamber.

4. A mechanical-atomizing liquid fuel burner comprising a secondary liquid fuel supply conduit extending axially of said burner, a primaryyliquid fuel supply conduit surrounding said secondary fuel conduit, a sprayer plate at the discharge end of said conduits and having an outer series of ports opening into said primary fuel conduit, a central circular whirling chamber, an inner series of ports opening into said secondary fuel conduit, a series of nozzle-forming slots symmetrically arranged in a plane normal to the axis of said whirling chamber, each slot connecting corresponding inner and outer ports to said whirling chamber and extending substantially tangentially to said whirling chamber, and a nozzle contacting with the inner face of said sprayer plate and having a restricted axial discharge passage. l

5. A mechanical-atomizing liquid fuel burner comprising a` secondary liquid fuel supply conduit extending axially of said burner, a primary liquid fuel supply conduit surrounding said secondary fuel'conduit, a sprayer plate at the dischargeend of said conduits and having an outer series of ports opening into said primary fuel conduit, a central circular whirling chamber, an inner series of ports opening into said secondary fuel conduit and having their centers symmetrically spaced outside and relative to the circumference of said whirling chamber, a series of aosavco nomic-forming slots each connecting a pair of corresponding inner and outer ports to said whirling chamber and extending substantially tangentially to said whirling clnmber. and a nosslecontactingwiththeinnerfaceofsaid 5 sprayerplateandhavingaportionformima continuation of said whirling chambervwlnlsively decreasing in cross-sectional area and an gziiiceatthereducedendofsaidwhirlingcham- 6, A mechanical-stunning liquid fuel burner comprising a dischargev head having a whirling chamber, a series of discharge nozzle-forming slots extending substantially tangentially to said whirling chamber. primary liquid fuel supply Il connections to the outer ends of said slots, a secondary liquid fuel supply connection to said slots at points intermediate their length, a restricted outlet from said whirling chamber, a common source of liquid fuel, and control means arranged to provide a secondary liquid fuel supply from said common source only when said primary liquid fuel supply connection is open.

7. A mechanical-atomizing liquid fuel burner comprising a liquid fuel supply pipe, a second liquid fuel supply pipe concentric with said nrst named fuel pipe, means forming a fuel whirling chamber, a series of passages connecting one of said fuel pipes to said whirling chamber extendmg substsnuauy tangentiauy to the eircumzerence of said whirling chamber, passages separately connecting the other fuel pipe to said first named passages, and an outlet from said whirling chamber.

s. A mechanical-atomizinguquid fuel burner comprising a liquid fuel supply pipe, a second liquid fuel supply pipe within and concentric with said first named fuel pipe, means forming a fuel whirling chamben'a series of passages connecting said first named fuel pipe to said whirling 40 chamber extending substantially tangentially to the circumference of said whirling chamber, passages separately connecting said second fuel pipe to said first named passages at points intermediate their length, and an outlet from said whirling chamber.

9. A mechanical-atomizlng liquid fuel burner comprising a primary liquid fuel supply pipe, a secondary liquid fuel supply pipe within and concentric with said primary fuel pipe, a discharge head having a fuel whirling chamber, a series of nozzle-forming slots opening into said whirling chamber substantially tangential to the circumference thereof, passages connecting said primary fuel pipe to the outer ends of said slots, passages separately connecting said secondary fuel pipe to the same slots at points intermediate their length, and an outlet from said whirling chamber axially spaced from said norzle-forming slot openings thereto.

10. A mechanical-atcmizing liquid fuel burner comprising a primary liquid fuel supply pipe, a secondaryv liquid fue1 supply pipe within and concentric with said primary fuel pipe, a discharge head having a fuel whirling chamber, a series of 6 nozzle-forming slots symmetrically arranged in a plane normal to the axis of said whirling chamber and extending substantially tangentially to the circumference of said whirling chamber, passages connecting said primary fuel pipe to the outer ends of said slots, passages separately connecting said secondary fuel pipe to the same slots at points intermediate their length, and a restricted. outlet from said whirling chamber axially spaced from said nozzle-forming slot openings thereto.

11. A wide range mechanical-atomizing liquid fuel burner comprising a discharge head having a substantially circular whirling chamber, a series Aof nozzle-forming slots having their inner ends discharging into said whirling chamber at an oblique angle to the circumference thereof, a liquid fuel supply connection opening to the outer end of each of said slots, and a separate 'liquid fuel supply connection opening to each of said slots at a point intermediate its length.

12. A wide range mechanical-atomizing liquid fuel burner comprising a discharge head having a substantially circular whirling chamber, a series of nozzle-forming slots having their inner ends opening substantially tangentially into said whirling chamber, a liquid fuel supply connection opening to the outer end of each of said slots, and a `separate liquid fuel supply connection opening to each of said slots at a point intermediate its length.

13. A wide range mechanical-atomizing liquid fuel burner comprising a discharge head having a central substantially circular whirling chamber, a series of nozzle-forming slots having their inner ends opening substantially tangentially into said whirling chamber, a liquid fuel supply connection opening to the outer end of each of said slots, a separate liquid fuel supply connection v opening to each of said slots at a point intermediate its length, and a restricted outlet from said whirling chamber.

14. A wide range mechanical-atomizing liquid fuel burner comprising a discharge head having a substantially circular whirling chamber, a series of nozzle-forming slots symmetrically arranged in a plane normal to the axis of said whirling chamber and having their inner ends opening substantially tangentially into said whirling chamber, a liquid fuel supply connection connected to the outer end of each of said slots, and a separate liquid fuel supply connection opening to each of said slots at a point intermediate its length.

l5. A sprayer plate for a liquid fuel burner having a central circular whirling chamber formed in one face thereof, a nozzle-forming slot formed in said face and having its inner end opening substantially tangentially into said chamber, a liquid fuel supply connected yto the outer end of said slot. and a separate liquid fuel supply passage opening through the bottom of said slot at an intermediate point therein.

16. A sprayer plate for a' liquid fuel burner having a central circular whirling chamber formed in one face thereof, a nozzle-forming 5 slot formed in said face and having its inner end opening substantially tangentially into said chamber, a liquid fuel supply passage connected to the outer endof said slot, and a separate liquid fuel passage extending through said plate 1o transversely of said face and opening through the bottom of said slot at an intermediate point therein.

17. A sprayer plate for a liquid fuel burner having a central substantially circular whirling 15 chamber formed in one face thereof, a nozzle-- forming slot formed in said face substantially tangentially to the circumference of said chamber and having its inner end opening to said chamber, an outer liquid fuel port extending 20 through said plate and opening into the outer end of said slot, and a separate inner liquid fuel port extending through said plate and opening through the bottom of said slot atan intermediate point therein.

18. A sprayer plate for a liquid fuel burner having a central substantially circular whirling chamber formed in one face thereof, a series of nozzle-forming slots formed in said face substantially tangentially to the circumference of 30 said chamber and having their inner en'ds opening to said chamber, a liquid fuel supply connec tion opening into the outer end of each of said slots, and a separate inner series of liquid fuel ports, each extending through said plate and 35 opening through the bottom of one of said slots at an intermediate point therein. i i

19. A sprayer plate for a liquid fuel burner having a central substantially circular whirling chamber formed in one face thereof, a series40 of symmetrically arranged nozzle-forming slots formed insaid fac'e substantially tangentially to the circumference of said chamber and having their inner ends opening tosaid chamber, an outer Vseries of symmetrically arranged liquid fuel ports, each extending through said plate and opening into the outer end of a corresponding slot, and a separate inner series of symmetrically arranged liquid fuel ports, each extending through said plate and opening through the bottom of one of said slots at an intermediate point therein.

JAMIE FIETCHER.

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