US3650476A

US3650476A - Liquid fuel burner

Info

Publication number: US3650476A
Application number: US698332A
Authority: US
Inventors: John M Rackley; Ralph H Merryman
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1968-01-16
Filing date: 1968-01-16
Publication date: 1972-03-21
Anticipated expiration: 1989-03-21
Also published as: BR6905379D0; FR2000280A1

Abstract

A liquid fuel burner equipped with an improved atomizer head wherein the liquid fuel is mixed with an atomizing fluid to be discharged as a finely atomized spray. Improvements to the atomizer head include a mixing portion, a flow-diverting portion and a spraying portion serially arranged to provide three stages of atomization. The first stage occurs as the fuel stream is sheared by high velocity steam in the mixing portion, the second stage is the impingement and re-directing of the mixture discharging from the mixing portion into the flow-diverting portion and the third stage takes place as the fluid mixture is expanded through the discharge ports of the spraying portion.

Description

United States Patent Rackley et al.

[4 1 Mar. 21, 1972 [54] LIQUID FUEL BURNER [72] Inventors: John M. Rackley; Ralph H. Merryman,

21 Appl. No: 698,332

[56] References Cited UNITED STATES PATENTS 2,393,887 1/1946 Clements ..239/431X 714,394 11/1902 Pfeiffer et al. .,...239/431 X 982,655 1/1911 Albee ..239/431 1,462,395 7/1923 Thompson... 239/431 X 1,516,408 11/1924 Schumann... .....239/431 1,653,297 12/1927 Labelle .239/431 X 2,348,839 5/1944 Oldham ..239/431 i s l I F I I I 20A 1 f I 2,613,737 10/1952 Schwietert ..239/43l X 2,879,948 3/1959 Seibel ..239/43l X FOREIGN PATENTS OR APPLICATIONS 776,783 6/1957 Great Britain ..239/431 Primary Examiner-Robert B. Reeves Assistant Examiner-11 S. Lane Attorney--J. Maguire [57] ABSTRACT A liquid fuel burner equipped with an improved atomizer head wherein the liquid fuel is mixed with an atomizing fluid to be discharged as a finely atomized spray. Improvements to the atomizer head include a mixing portion, a flow-diverting portion and a spraying portion serially arranged to provide three stages of atomization. The first stage occurs as the fuel stream is sheared by high velocity steam in the mixing portion, the second stage is the impingement and re-directing of the mixture discharging from the mixing portion into the flow-diverting portion and the third stage takes place as the fluid mixture is expanded through the discharge ports of the spraying portion.,

2 Claims, 9 Drawing Figures PAIEIIIEIIIIARZI I972 3,550,47

' sum 2 OF 2 FIG.3A FIG. 3

LIQUID FUEL BURNER The invention relates to fuel burners, and more particularly to a liquid fuel burner equipped with an improved atomizer head wherein the liquid fuel is mixed with an atomizing fluid to be discharged as a finely atomized spray. The burner is adapted for use with hydrocarbon fuels in combination with atomizing fluid such as steam, air or other gaseous medium.

Fluid assist atomizers have been successfully used for some time. For example, US. Pat. No. 2,414,459 issued on Jan. 2 l 1947, in the name of .I. Fletcher, discloses a fluid assist atomizer having good operating characteristics up to an oil flow output capacity of about 5,000 lb./hr. However, during recent years shop assembled industrial. boilers have increased in size and they nowadvantageou'sly require burner capacities of up to 10,000 'lb./hr. oil flows. Initial efforts at raising the output capacity of the type atomizer disclosed in the aforementioned patent were unacceptable, the lack of success generally being characterized by incomplete fuel combustion due to poor internal atomization characteristics. In order to achieve acceptable operation with these burners above their originally rated capacities, fuel atomization was completed externally by raising combustion air velocities. However, these higher air velocities had to be obtained at the expense of higher burner draft losses thus adding both to the capital and operational costs of an installation through the requirements of larger fans and increased power consumption.

The atomizer disclosed in US. Pat. No. 2,414,459atori1izes the fuel in two stages over a distance of approximately 54-inch linear travel. Both stages of atomization takes place in the proximity of the sprayer plate discharge ports. The first stage occurs at the intersection of the fuel and atomizing fluid passageways, the ensuing mixture is then further atomized in a second stage as a result of expansion through the discharge ports. An exhaustive research program directed to studying the performance of this atomizer at fuel flows in excess of 5,000 lb./hr. disclosed that there was incomplete atomization of fuel within the atomizer head, as evidenced by visual observation of the discharge of relatively unatomized slugs of fuel from the burner assembly.

To overcome this problem, the present invention provides an atomizer having three stages of atomization taking place over a linear distance of more than 2 inches and including a fuel atomizing-steam mixing portion adjacent the discharge end of the burner barrel, followed in sequence by a flowdiverting portion and a mixture spraying portion. The first stage of atomization occurs in the mixing portion as the fuel stream is sheared by high velocity atomizing steam, the resultant fluid mixture is discharged into the flow-diverting portion, there impinging on the frustoconically formed surface and there being subsequently directed to a chamber formed in the center of the spraying portion. Thus, the second stage includes the impingement and redirection of the fluid mixture and the further mixing which occurs in the spraying portion chamber. The third stage of atomization takes place as the fluid mixture is expanded through the discharge ports associated with the spraying portion.

A main object of the invention is to provide a burner capable of complete internal atomization of fuel over a wide capacity range extending up to 10,000 lb./hr. fuel flow.

Another object of the invention is to eliminate the requirement of high air velocities in order to provide satisfactory atomization without at the same time leading to poor flame characteristics, such as wall coking, long flames and excessive combustible loss.

A further object of the invention is to provide a burner embodying an operational advantage of ease of cleanability as well as greater convenience and economy of manufacture, by drilling the connecting fuel ports through to the outside of the mixing portion.

In the drawings:

FIG. 1 is a fragmentary sectional side view of the liquid fuel burner according to the present invention.

FIG. 2 is a sectional side view of the atomizer mixing por' tion.

FIG. 3 is a sectional side view of the atomizer flow-diverting portion.

FIG. 4 is a part sectional and part side view of the barrel extension sleeve.

FIG. 5 is a part sectional and part side view of the atomizer spraying portion.

FIG. 2A is an end view of FIG. 2

FIG. 3A is an end view of FIG. 3

FIG. 4A is an end view of FIG. 4

FIG. 5A is an end view of FIG. 5

Referring to FIG. 1 there is shown a liquid fuel burner comprising a barrel assembly 11 joined at one end to a body portion 12 and at the other end to an atomizing head 13. The barrel assembly 11 includes an outer tube 14 coaxially arranged with respect to an inner tube 15. The body portion I2 contains two separate passageways l6 and 17 including

inlet openings

18 and 19 provided for admission of fluid to the respective passageways, and

outlet openings

20A and 21A arranged to threadably engage the inlet ends of inner tube and outer tube 14 respectively. An oil seal ring 22 is welded on the end of the threaded section of inner tube 15. For the specific embodiment illustrated, passage 16 will be described as intendedfor fuel oil and passage 17 for atomizing medium such as steam. Passageway 16 communicates with central passage of inner tube 15 and passageway 17 communicates with annular passage 21 formed between outer tube 14 and inner tube 15. The atomizer assembly 13 consists of a mixing portion 23, a frustoconical flow diverting portion 24, a barrel extension sleeve 25 and a spraying portion 26, all arranged in their proper operative relation to form the burner barrel assembly 11 of liquid fuel burner 10 as shown in FIG. 1. Inner tube 15 at its discharge end accommodates tubular discharge end section 27 which is machined to slidingly fit into center bore 28 of the mixing portion 23. The discharge end 29 of outer tube 14 is threaded to engage with sleeve 25.

FIGS. 2 and 2A show the mixing portion 23 as a cylindrical block of metal consisting of concentrically arranged peripheral section 30 and central section 31. The peripheral section has a recessed inlet and contains a plurality of annular uniformly spaced cylindrical conduits 32 with each conduit having a narrow inlet segment 33 discharging through a uniformly divergent opening 35 into a large diameter outlet segment 34 which serves as a mixing chamber. The center bore 28 is also made up of two segments, a large diameter segment 36 which discharges through a uniformly convergent opening 39 into a smaller diameter segment 37. Conduits 32 extend through the entire length of peripheral section 30 while center bore 28 penetrates through only part of the mixing portion 23. Each of the conduits 32 is connected by a radial port 38 to the center bore 28 for discharge into mixing chambers 34 immediately adjacent openings 35. The peripheral section 30 is formed with circumferentially spaced openings '40 each being aligned with corresponding radial. ports 38.

FIGS. 3 and 3A show the frustoconical flow diverting portion 24 which is in the form of an annular plate having a passage 41 therethrough of frustoconical shape with a large inlet end 42 and a small outlet end 44, the passage 41 thus formed terminating in cylindrical outlet 44.

FIGS. 4 and 4A show the sleeve 25 which has a threaded inlet 45 for attachment to the discharge end 29 of outer tube 14 and a threaded outlet 46 for connection with the threaded section 48 of sprayer portion 26.

FIGS. 5 and FIG. 5A show the sprayer portion 26 consisting of a generally cylindrical cap forming a central chamber 43 having an inner face 47 made up of a threaded section 48, a shoulder section 49 and a bored section 50 including conical wall portions 51 and a central imperforate area substantially normal to the burner axis. The discharge face 52 of sprayer portion 26 being beveled as at 53 to provide a conical surface area for the location of the openings 54, the surface 53 being of substantially of the same inclination as the inner surface at 51.

In the operation of the burner, the pressurized liquid fuel to be atomized is supplied continuously to the opening 18 from which it flows through passage 16 of body portion 12 and discharges through outlet opening 20A into central passage 20 of inner tube 15 to be conveyed to the center bore 28 of the mixing portion 23 and discharged through radial ports 38 into mixing chambers 34 of conduits 32. At the same time, the pressurized atomizing fluid is supplied continuously to the opening 19 from which it flows through passage 17 of body portion 12 and discharges through outlet opening 21A into annular passage 21 formed between inner tube 15 and outer tube 14 to be conveyed to conduits 32 of mixing portion 23. The jets of steam entering the mixing chambers or outlet segments 34 shear the oil stream being discharged from radial ports 38, and an emulsified oil-steam mixture results. This mixture, which is still above atmospheric pressure, is discharged through inlet end 42 of the conical flow diverting portion 24, impinging against the frustoconical sides of passage 41 and thereby being prevented from passing directly to the discharge openings 54 of spraying portion 26. Instead, the emulsified oilsteam mixture discharging from each of the conduits 32 is diverted toward central mixing chamber 43 of the spraying portion 26 where further mixing takes place. From the spraying portion central chamber 43, the mixture passes into and through discharge openings 54 of the sprayer portion 26 where pressure energy is further converted to velocity energy. The resultant expansion of steam causes still further breakup of the liquid fuel into small particles with intimate of the fuel and steam with the result that a substantially homogeneous mixture of finely atomized fuel and steam is produced for subsequent introduction into the combustion air stream.

What is claimed is:

1. A liquid fuel burner assembly comprising,

a tubular barrel,

an inner tube disposed within said barrel to form .therebetween an annular flow passage, means for supplying liquid fuel to be atomized to the inner tube, means for V supplying atomizing fluid to the annular passage, an atomizing head connected to the discharge ends of the inner tube and annular passage, said atomizing head including,

a mixing portion having a center bore communicating with the discharge end of the inner tube, a plurality of conduits communicating with said annular passage, a plurality of ports connecting the center bore to the conduits and extending normal to the axis of the burner barrel, said ports directing all of the liquid fuel into mixing relation with the atomizing fluid to atomize the fuel, and a plurality of peripheral openings each being axially aligned with the corresponding port, flow-diverting portion associated with and receiving outflow from the mixing portion and arranged for converging the flow of atomized flow therethrough, said diverting portion having a passage of frustoconical form with its large and small ends defining the inlet and outlet of said passage respectively, a spraying portion associated with and receiving outflow from the diverting portion and having a discharge face formed with openings arranged for discharge of atomized fuel in diverging paths, said openings extending at an acute angle relative to the axis of the burner barrel, and a sleeve means adapted to engage with the discharge end of the barrel and supportingly enclose the mixing and diverting portions, said sleeve means defining a seal for the peripheral openings and being adapted at its forward end to engage with the spraying portion. 2. A liquid fuel burner assembly comprising, a tubular barrel, an inner tube disposed within said barrel to fonn therebetween an annularflow passage, means for supplying liquid fuel to be atomized to the inner tube, means for supplying atomizing fluid to the annular passage, an atomizing head connected to the discharge ends of the inner tube and annular passage, said atomizing head ineluding, a mixing portion having a center bore communicating with the discharge end of the inner tube, a plurality of conduits communicating with said annular passage, a plurality of ports connecting the center bore to the conduits and extending normal to the axis of the burner barrel, said ports directing all of the liquid fuel into mixing relation with the atomizing fluid to atomize the fuel, and a plurality of peripheral openings each being axially aligned with the corresponding port, each of said conduits including an inlet and an outlet segment, each outlet segment communicating with the discharge ofone ofsaid ports and having a greater cross-sectional area than the inlet segment, each of said conduits including a divergent transition section connecting the inlet and outlet segments and each of said ports communicating with its corresponding outlet segment at the junction thereof with said transition section,

a flow-diverting portion associated with and receiving outflow from the mixing portion and arranged for converging the flow of atomized flow therethrough, said diverting portion having a passage of frustoconical form with its large and small ends defining the inlet and outlet of said passage respectively,

a spraying portion associated with and receiving outflow from the diverting portion and having a discharge face formed with openings arranged for discharge of atomized fuel in diverging paths, said openings extending at an acute angle relative to the axis of the burner barrel.

Claims

1. A liquid fuel burner assembly comprising, a tubular barrel, an inner tube disposed within said barrel to form therebetween an annular flow passage, means for supplying liquid fuel to be atomized to the inner tube, means for supplying atomizing fluid to the annular passage, an atomizing head connected to the discharge ends of the inner tube and annular passage, said atomizing head inclUding, a mixing portion having a center bore communicating with the discharge end of the inner tube, a plurality of conduits communicating with said annular passage, a plurality of ports connecting the center bore to the conduits and extending normal to the axis of the burner barrel, said ports directing all of the liquid fuel into mixing relation with the atomizing fluid to atomize the fuel, and a plurality of peripheral openings each being axially aligned with the corresponding port, a flow-diverting portion associated with and receiving outflow from the mixing portion and arranged for converging the flow of atomized flow therethrough, said diverting portion having a passage of frustoconical form with its large and small ends defining the inlet and outlet of said passage respectively, a spraying portion associated with and receiving outflow from the diverting portion and having a discharge face formed with openings arranged for discharge of atomized fuel in diverging paths, said openings extending at an acute angle relative to the axis of the burner barrel, and a sleeve means adapted to engage with the discharge end of the barrel and supportingly enclose the mixing and diverting portions, said sleeve means defining a seal for the peripheral openings and being adapted at its forward end to engage with the spraying portion.

2. A liquid fuel burner assembly comprising, a tubular barrel, an inner tube disposed within said barrel to form therebetween an annular flow passage, means for supplying liquid fuel to be atomized to the inner tube, means for supplying atomizing fluid to the annular passage, an atomizing head connected to the discharge ends of the inner tube and annular passage, said atomizing head including, a mixing portion having a center bore communicating with the discharge end of the inner tube, a plurality of conduits communicating with said annular passage, a plurality of ports connecting the center bore to the conduits and extending normal to the axis of the burner barrel, said ports directing all of the liquid fuel into mixing relation with the atomizing fluid to atomize the fuel, and a plurality of peripheral openings each being axially aligned with the corresponding port, each of said conduits including an inlet and an outlet segment, each outlet segment communicating with the discharge of one of said ports and having a greater cross-sectional area than the inlet segment, each of said conduits including a divergent transition section connecting the inlet and outlet segments and each of said ports communicating with its corresponding outlet segment at the junction thereof with said transition section, a flow-diverting portion associated with and receiving outflow from the mixing portion and arranged for converging the flow of atomized flow therethrough, said diverting portion having a passage of frustoconical form with its large and small ends defining the inlet and outlet of said passage respectively, a spraying portion associated with and receiving outflow from the diverting portion and having a discharge face formed with openings arranged for discharge of atomized fuel in diverging paths, said openings extending at an acute angle relative to the axis of the burner barrel.