US2414459A - Fluid fuel burner apparatus - Google Patents

Description

m- 1947- J. FLETCHER 2,414,459

nmb m1. aumma APPARATUS Filed Jan. "28. 1944 ml I IN V EN TOR.

- James Fletcher BY A TTORNE Y Patented Jan. 21, 1947 UNITED STATES PATENT OFFICE FLUID FUEL BURNER APPARATUS James Fletcher, Akron, Ohio, assignor to The Babcock & Wilcox Company, Rockleigh, N. J a corporation of New Jersey Application January 28, 1944, Serial 'No. 520,012

12 Claims. 1

The invention herein disclosed relates to burner apparatus adapted for the utilization of fluid fuels of liquid or semi-liquid character including especially hydrocarbon oils of various densities andviseosities.

The invention contemplates the discharge of the fuel in a relatively thin-walled spray readily permeable by the stream or streams of air generally supplied to produce a combustible mixture, thespray being desirably of hollow frustoconical formation to afford a maximum amount of surface exposure to a surrounding envelope of combustion air.

For the successful burning of a fuel oil, regardless of its grade, it is essential that the oil be completely atomized to a very fine mist, and further that the atomized oil be thoroughly mixed with suflicient air to assure complete combustion.

In order to provide the necessary high degree of atomization, it is proposed by this invention to utilize a fiuid such as steam, air, or other gaseous medium to effect atomization of the fuel, with bothfiuids under suitable pressures, and preferably to divide the total fuel and steam, for example, into relatively small unit quantities so that a predetermined portion of the atomizing medium may be mingled with a predetermined portion of the fuel and the separately mingled unit portions discharged individually from the burner.

It is also an object to direct divisional quantities of the fuel through a series of separate passages and to direct divisional quantities of the atomizing medium through a second series of separate passages intersecting with the first named passages, the resulting unit mixtures being discharged through a series of outlet passages in a spray of the desired formation.

An additional object contemplates a series of outlet passages diverging in the direction of discharge from a common central axis to provide a spray of hollow truncated form.

Another object is to provide a circular series of passages for the fuel and atomizing medium respectively, each passage of one series converging with a passage of the other series at an acute anle to effect atomization of the fuel at minimum pressure requirements.

A further object is to provide an atomizer having a circular series of inlet passages for each of two different fluids, one fluid being oil for example and the other a fluid atomizing medium such as steam, the passages of one series converging toward a common central axis and intersecting passages, of the other series; the passages of one series being extended to form a series of outlet passages for the resulting mixture.

More specific objects relate to a form of atomizer in which the series of intersecting inlet passages together with the outlet passages are formed within a single member, thereby simplifying manufacture and assembly and assuring a fixed relative disposition of passages throughout service; also, to a form of atomizer adapted for operation over a wide range of capacities under control of the applied fluid pressure or pressures.

Other objects relate to directing air in suitable relation to the discharging stream of atomized fuel to provide a fuel-air mixture of optimum combustion characteristics.

A more complete understanding of the invention will be had from the description to follow, whereby the foregoing objects and others are made more apparent, and various features of the invention more fully explained, particularly with respect to a selected embodiment of the invention as illustrated by the accompanying drawing, in which:

Fig. 1 is a longitudinal assembly view, mainly in section, of a fluid fuel burner constructed in accordance with my invention;

Fig. 2,is an enlarged longitudinal section showing details of the atomizer assembly included in Fig. 1; V

Fig. 3 is an end view of Fig. 2, taken along line member constituting a part of the atomizer as- Figs. 4, 5 and 6 are vertical sections along lines 4-4, 5-5' and 6-4 respectively of Fig. 2, viewed in the directions indicated by the arrows which bear corresponding numbers; the lines 4-4 and 5'5 being in a common transverse plane; and,

Fig. 7 is a longitudinal section of the sprayer formed with a series of circumferentially spaced outlet openings l5 through'which atomized fuel is discharged in an outwardly expanding hollow conical spray.

Air is admitted to the burner from a duct l6 and is directed into the combustion zone through atomizer and burner opening may be adjusted,

the impeller plate being formed with circumferentially spaced openings 28 through which a central portion; of the combustion air is admitted to. the spray of atomized fuel upon dishaving an inwardly charge from the atomizer, the air passing through the impeller plate openings 28 being circumferentially deflected by blades 30 bent inwardly from the metal of the cone in forming the openings 28. The supply of air to the burner is under control of a series of louvre plates 32 pivoted at their outer edges as at 30 adjacent the outer end of the ring structure I8 and at their inner edges as at 38 in a ring member 38 constituting a part of the operating mechanism by which the pivotal positions of the plates 32 may be adjusted. Reference. may be had to U. S. Patent 2,260,062, T. B. Stillman, issued October 21, 1941, for a more detailed disclosure of the air directing elements above identified.

The atomizer I4 includes a body portion 40 at its outer extremity formed with fluid chambers or passages 42 and 44 communicating with corresponding passages in a coupling member 48 wherein inlet connections 48 and, 50 are provided for the admission of fluids to the respective passages. For the specific embodiment, illustrated, the passage 42 will be described as intended for fuel oil and the passage 44 for a gaseous atomizing medium such as steam, the passage 42 communicating with an annular passage 52 formed between the outer tube or barrel 54 of the atomizer and a central inner tube 58, and the passage 44 communicating with the central passage 58 constituting the bore of tube 58.

A sprayer head or'nozzle 80 is removably secured at one end to the inner end of tube 58 as by threads 82 and at its opposite end is formed witha flange 84 seated within the counterbore 88 at the inner, end of the atomizer barrel 54; the nozzle having flattened areas 81 at opposite sides for engagement by a wrench.

The face of the nozzle is formed with an annular groove 88 which is connected with the annular space I0 surrounding the nozzle and thereby with the annular fuel snace52 by means of a series of circumferentially spaced holes 12 extending through the flange 84. Fuel thus delivered to the groove 88 is admitted through diametrically positioned holes I4 to an annular groove I8 in the face of an intermediate annular plate 18 assembled adjacent the base of the sprayer plate 80. The nozzle is formed with a receiving chamber 82 of circular cross section for the atomizing fluid, the chamber'being in open communication with the ,c'entral atomizer passage 88 and being connected by means of circumferentlally spaced holes 84 with the centrally disposed space 88 interiorlyof the annular plate I8 and adjacent the base of the sprayer plate 80.

- thereby maintain the sprayer plate 80, the intermediate plate I8 and the nozzle 80 in their proper throughout with its longitudinal axis a straight assembled relation adjacent the counterbored end of the atomizer barrel-80.

The sprayer plate 80 is machined from a solid block of metal, the base of the plate being recessed to provide'successive conical wall portions 98 and 90 of difierent' angula'rity and the outer face being beveled as at I00 to provide a conical surface area for the location of the outlet opentively and thus being inclined outwardly from the central axis in the direction of flow, the passages I08 extending partially through the plate 80 and being inclined inwardly toward the central axis to intersect and form junctures with the passages I04. Each passage or port I04 or I08 is preferably of cylindrical formation line in a plane with the central axis of the sprayer plate, thelongitudinal axes of each port I04 and its intersecting or connecting port I08 lying in a common plane.

The inner end sections I08 of passages I04 serve as inlet passages for fluid entering from the central space 88 while the passages I08 serve as inlet passages for fluid entering from the annu'- lar groove 18 with which their inner ends are in register. If preferred, the groove I8 may be formed in the base of the sprayer plate instead of in the plate I8, in which case the plate I8 may be made somewhat thinner since only the holes I4 need be formed therein. In certain instances, the plate 18 may be omitted entirely and the sprayer plate 80 placed in contact with the nozzle 80, the passages I08 then receiving fluid di-,

sages I 08 together with fluid admitted from the annular groove 18 through the inlet passages I08, the outlet section IIO of each passage I04 thus constituting an individual mixing chamber for divisional unit quantities of the fuel and atomizing medium. Each passage I08 Joins a passage I04 adjacent the base of the outlet section H0 and thus at a suflicient distance in advance of the outlet Opening I5 to afford a positive directional influence on the issuing mixture.

Where the passages I08 are used for oil, and

the passages I04 for steam, the oil pressure at.

the juncture of the streams need only be sufllcient to keep the oil in contact and converged with the steam at this point, any excess oicil pressure tending to be more detrimental than beneficial to satisfactoryatomization. Since it is desirable to maintain a relatively high pressure in the oil supply line for control purposes, the plate I8 is inserted as described, with asmall number of holes I4 of small total flow area, to serve as a restrictor for reducing the oil pressure to the value required at the mixing zone.

The machining of the holes or passages I04 and I06 may be completed in a minimum number of operations due to each having a straight line central axis throughout its length, and since the holes are cylindrical and have intersecting axes, it is convenient to machine all holes to a predetermined uniform size for any given series, and to form juncture openings of uniform size and shape at the intersections between holes of different series, to provide uniformity of fluid flow in all groups of passages. The machining of the passages I06 is further facilitated by leaving an excess of metal on the original blank, as indicated by the broken lines in Fig. '7, for example, to provide a beveled drilling surface II2 normal to the central axis of each such passage, the excilitates the accurate drilling of these holes besides enabling their inlet ends to be kept separate and providing substantially circular edges at both ends for uniform distribution of fluid to such holes and for symmetrical discharge of fluid from each and throughout the group.

The specific sizes of holes I 04 and I06, their number and disposition relative to the central axis are governed principally by the conditions to be met including for example. the kinds of fluids to be handled, their density or viscosity values, the capacity or range of capacities under which the atomizer is to be operated, and the ultimate character and angularity of spray desired. When the fluids involved are oil and steam, it is customary to utilize the outer series of holes I06 for the oil, and the inner series of holes I04 for the steam, the two fluids being thoroughly mingled in the enlarged section IIO of passage I04 and the resultant mixture including the atomized fuel being discharged through the circular series of outlet openings I5 in the form of a thin walled conical spray. Under certain conditions, and with due regard .for their relative sizes, the fuel may be directed into the i her series of holes I04 and the atomizing fluid into the outer series I 06. The atomizer may also be employed for mixing and spraying other fluids including for example a condition wherein'both fluids are of a combustible character or, if desired, wherein neither fluid is combustible.

Under conditions wherein oil is admitted to the outer series of holes I06 and steam as the atomizing agent is admitted to the inner series I04, it is desirable to make the oil inlet passages I06 of greater cross section than the steam inlet sections I08 of the passages I04, the mixing and outlet section IIO of the passage I04 having a cross section larger than the cross section of either of the passages I06or I08 to provide a flow of divergence A of the inner series of passages I 04, including steam inlet and common outlet sections, is approximately seventy degrees, and the included angle of convergence B of the outer series of passages I08, for oil, about forty-five degrees.

The embodiment of such an atomizer in a burner as shown provides a combination whereby ings I5 at a diameter of about one inch, for an.

overall barrel diameter of about one and threequarter inches.

The angle of spray is substantially the same for -all capacities due to the directional effect afforded by the outlet ends of the diverging passages I04, and thus the spray cuts across each column or layer of combustion air at constant angle. Moreover, the oil is atomized close to its exit through openings I5 and is therefore in a state of complete atomization upon. discharge when it is immediately contacted by a whirling current of air directed through the impeller plate openings 28 to initiate combustion close to the atomizer tip; in practice, the normal adjustment of atomizer being to place the tip end flush with the furnace face of the impeller cone 24. forward of the position indicated in Fig. 1.

The small size of sprayer plate required results in a minimum area of the atomizer tip being exposed to direct heat of combustion, this bein the central imperforate area I02 which is flat and subjected to the cooling effect of the atomizing steam in the closely adjacent chamber 86; the conical recess in the base of the plate serving to shorten the heat conducting path by reducing the thickness of metal between the exposed outer surface I02 and the inner wall surface 98; the introduction of fluid to the chamber 86 through circumferentially spaced holes 84 adjacent its maximum diameter tending to maintain an active steam flow condition over the entire wall area of the recess for maximum absorption of heat from the metal of the plate; the introduction of steam to the chamber 86 through a circle of holes 84 as shown also tending to maintain a condition of uniform steam pressure at the entrances to the passages I04. for uniform distribution of steam to suchpassages.

The burner may be operated over a considerable range of capacities, in general, for a steamatomizing oil burner of this description, the capacity being varied by regulating both the oil and steam supply pressures up to a predetermined capacity value, and above that value by regulating oil pressure alone. Over the range where both oil and steam pressures are varied, it is customary to maintain a steam pressure at about 15 or 20 p. s. i. in excess of the oil pressure until the oil pressure' reaches approximately 1.25 p. s. i. For higher capacities, as the oilpres'sures are increased, there is ordinarily no further increase required in steam pressure. It will be understood that the variations in oil or steam pressures or both for various capacities are to be accompanied by suitable adjustments of the combustion air supply. When a steady pressure of oil is available, the burner may be operated at extremely low capacity requiring for example an oil pres sure of approximately only 2 p. s. i. As an alternative to the above method of operation the steam pressure may be held constant at about 1.25 p. s. 1., a nominal value for maximum capacity operation, and the capacity varied by varying the oil an mus 7 pressure only; While this simplifies the method of control to a certain extent it is somewhat less economical of steam than the method first mentioned, particularly when operating at the lower capacities. 7

32 claim:

1. A combination atomizing and spraying member of one-piece construction adapted to atomize liquid received therein and to discharge said liquid in an atomized state in a series of annularly arranged jets, said member having oppositely disposed transversely arranged inner and outer surfaces and having a series of circumferentially spaced ports extending therethrough from one of said surfaces to the other, each of said ports being of circular cross section throughout and having its axis of flow extending in a straight line normal to at least the inner of said surfaces, said 1 member .having a series of circumferentially spaced ports extending partially therethrough from the inner of said surfaces and terminating at locations intermediate said surfaces in junctures with ports of said first named series, at least one of said series of ports being tapered to effect said junctures and the ports of said first named series terminating in said outer surface in a series of discharge openings arranged in a circle about a central imperforate area. i

2. A sprayer plate of one-piece construction for atomizing a liquid and for spraying said liquid in an atomized state in jets angularly spaced about a central axis, said plate having axially displaced transversely arranged inner and outer surfaces and having a tapering series of circumferentially spaced ports extending therethrough from one of said surfaces to the other, said plate having a tapering series of circumferentially spaced ports extending partially therethrough from the inner of said surfaces and terminating at locations intermediate said surfaces in junctures with ports of said first named series, each of said port's being of circular cross section throughout and having its axis of flow in a straight line substantially coplanar with said axis, the ports of said first named seriesdiverging in 8 forward surface centrally of said outlet circle being imperforate.

.' 4. A sprayer plate having an annular portionto said inner and outer conically formed surface portions, said ports having their inlets in a circle in the conical wall portion of said recess and their outlets in a circle in the conical annular portion of said forward surface, a series of cylindrical ports extending into said plate from the annular portion of said rearward surface and terminating in junctures with said first named ports within the body of said plate, each port of a series having its longitudinal axis in a straight line and the longitudinal axes of ports forming each juncture intersecting in a plane with said central axis.

5. In a liquid fuel burner for wide range operation adapted for mounting in a furnace wall opening of substantially circular formation about a central axis, an atomizer arranged to extend axially of said opening having a sprayer plate constructed to discharge atomized fuel into said opening at varying fuel flow capacities in a series of circumferentially spaced outlet passages diverging toward their discharge openings in r the forward surface of said plate, said sprayer the directionof said outer surface and forming a circle of "outlet openings in said outersurface marginal of a central imperforate area.

3. A member of one-piece construction for effecting mixture of two fluids' delivered thereto and for spraying the resulting mixture in the form of a hollow cone, said member being symmetrically formed about a central axis and having axially displaced forward and rearward surfaces, said 'member having concentric groups of circularly arranged inlet openings formed in its rearward surface, a series of inlet ports extending into-"said member from the outer circleof'said inlet openings and converging toward said forward surface, a series of inlet ports extending into said member from the inner circle of said inlet openings and diverging toward said forward surface, each of said inlet ports being of circular cross-section throughout and v having itscentral axis formed as a straight line plate having separate sets of inlet passage for liquid fuel and for a fuel atomizing fluid respectively joined to said outlet. passages within the body of said plate, each of said outlet and inlet passages having its axis of flow substantially straight and coplanar with said central axis, means for delivering combustion air through said opening in a stream surrounding said atomizer sprayer plate, angi a-diffuser cone coaxial with said sprayer plate for imparting rotational movement t5 an inner layer of said air and for directing said rotating layer into intimate contact with the peripheral surface of each of said jets adjacent their origin at said plate.

6. A sprayer plate. having concentric inner and outer circles of inlet openings formed in a surface thereof for the separate admission of liquid fuel and a, fuel atomizing medium, together with separate groups of inlet passages extending into said plate from said openings. and forming junctures between individual passages of one group and individual pasages of the other, and a series of outlet passages extending from said junctures to an opposite outlet surface of said plate for dischargingatomized fuel in a series of circumferentially spaced jets diverging in generally frusto-conical arrangement from said outlet surface, said outlet ly coplanar with-the axes of flow of the associated inlet passages, said outlet passages terminating at said outlet surface in discharge openings 76 circumferentially spaced at distances greater opening of said inner circle with one of said outlet openings, each of said passages being of circular cross section throughout and having its axis of flow extending in a straight line from one of said surfaces to the other in normal relation to at least one of said surfaces, and a 'series of passages individualy connecting each inlet opening of said outer circle with one of said first named passages to form a series of circumferentially spaced junctures within the body of said plate.

8. In a liquid fuel atomizer, a sprayer plate constructed and arranged to discharge atom ized fuel therefrom in a series of circumferentiaily spaced jets diverging from a common central axis, said sprayer plate having inner and outer sets of inlet pasages extending into said plate from rearward transverse surface portions thereof and adapted to separately receive a liquid fuel and a fuel atomizing fluid, each of said fluids under pressure, each passage of one set Joining with a passage of the second set to form a series of internal fuel atomizing zones from which said atomized fuel is discharged, and a restrictor plate removably joined to said sprayer plate for reducing the pressure at which one of said fluids is supplied to one of said sets of inlet passages, said restrictor plate having a central opening therethrough communicating with said inner set of inlet passages and having at least one other opening therein of considerably smaller flow area than the combined flow area of said outer set of inlet passages, and a circular recess formed at the Joint between said plates for distributing fluid from said last named opening to saidouter set of inlet passages.

9. A sprayer member for effecting mixture of two fluids delivered thereto and for discharging the resulting mixture in a series of jets angularly spaced about a common axis, said member having axially displaced forward and rearward surfaces and having a series of angularly spaced ports extending therethrough from one of said surfaces to the other; said member having a series of angularly spaced ports extending partially therethrough from said rearward surface and terminating at locations-intermediate said surfaces in junctures with ports of said first named series, said rearward surface including a centrally disposed recessed portion having its wall formed as a surface of revolution about said axis, each port of said first named series having its axis of flow extending in a straight line substantially coplanar with said common axis and diverging obliquely therefrom in a direction normal to the wall of said-recessed surface portion.

10, A combination atomizing and spraying member of one-piece construction adapted to atomize liquid received therein and to discharge said liquid in an atomized state in lets angular-1y spaced about a common axis, said member having axially displaced forward and rearward surfaces and having an inner and an outer group of inlet passages extending from angularly spaced openings in said rearward surface and forming junctures within said member between individual ports'of the respective groups, said member having a group of outlet passages connecting said junctures with-angularly spaced outlet openings in said forward surface, each of said outlet passages being of circular cross section and providing a constant flow area throughout greater than the flow area of any one of said inlet passages, said outlet openings having spaces therebetween greater than the diameter of any one of said outlet passages, each of said inlet and outlet passages having its axis of flow extending in a straight line substantially coplanar with said common axis. I

11. A sprayer member of one-piece construction for effecting mixture of two fluids delivered thereto and for discharging the resulting mixture in a series of diverging jets, said member having forward and rearward surfaces of symmetrical formation about a common central axis and having a first series of spaced ports extending therethrough from one of said surfaces to the other, said member having a second series of spaced ports extending partially therethrough from said rearward surface and terminating at locations intermediate said surfaces in junctures with ports of said first series, said rearward surface including a centrally disposed recessed portion together with an annular surface portion surrounding said recessed portion, each port of said first series having its inlet in said recessed portion and having its axis of flow in a straightline substantially coplanar with said common axis and diverging obliquely from the corresponding axis of flow of the next adjacent port, each port of said second series having its inlet in said annular surface portion.

12. A sprayer member of one-piece construction for effecting mixture of two fluids delivered thereto and for discharging the resulting mixture in a series of diverging jets, said member having forward and rearward surfaces of symmetrical formation about a common central axis and having a first series of spaced ports extending therethrough from one of said surfaces to the other, said member having a second series of spaced ports extending partially therethrough from said rearward surface and terminating at locations intermediate said surfaces in junctures with ports of said first series, each port of said first series having its inlet for one of said fluids in a centrally disposed portion of said rearward surface and having its axis of flow in a straight line substantially coplanar with said common axis and diverging obliquely from the corresponding axis of flow of the next adjacent port. each port of said second series having its inlet for the other of said fluids in a portion of said rearward surface surrounding said centrally disposed portion, the ports of one of said series including ports each having its axis of flow substantially normal to one of said portions of said rearward surface.

JAMES FLETCHER.

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