US3843309A

US3843309A - Liquid fuel grid burner for vitiated air using auxiliary combustion air

Info

Publication number: US3843309A
Application number: US00338993A
Authority: US
Inventors: S Lambiris
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1973-03-07
Filing date: 1973-03-07
Publication date: 1974-10-22
Anticipated expiration: 1991-10-22
Also published as: FR2220750A1; GB1458123A; JPS5244650B2; DE2410356A1; DE2410356C2; NL7402966A; NL177938C; FR2220750B3; NL177938B; JPS5024826A

Abstract

A grid burner suitable for combustion of liquid fuel in vitiated air with auxiliary combustion air. Rows of auxiliary combustion air supply pipes support spaced fuel nozzles supplied by inner fuel pipes. Burner wings supported by the auxiliary air pipes include openings to direct vitiated air and auxiliary air into the combustion zone to provide the proper combustion and cooling patterns.

Description

[ Oct. 22, 1974 United States Patent [191 Lambiris 3,051,464 8/1962 Yeo et al. 432/222 3,178,161 4/1965 Yeo et a1. 432/222 431/351 LIQUID FUEL GRID BURNER FOR VITIATED AIR USING AUXILIARY COMBUSTION AIR Inventor:

3,632,286 1/1972 Kegan.... 3.64921 1 [75] Sortiris Lambiris, Andover, Mass.

Primary Examiner-John J. Camby Assistant Examiner-Henry C. Yuen Attorney, Agent, or Firm-John F. Ahern; James W. Mitchell Appl. No.: 338,993

[57] ABSTRACT A grid burner suitable for combustion of liquid fuel in vitiated air with auxiliary combustion air. Rows of auxiliary combustion air supply pipes support spaced fuel nozzles supplied by inner fuel pipes. Burner wings supported by the auxiliary air pipes include openings vto direct vitiated air and auxiliary air into the combustion zone to provide the proper combustion and cooling patterns.

431/285 Int. F23q 9/00, F23m 9/02 [58] Field of Search................ 432/222; 60/39.?2 R; 431/350, 285, 351, 284; 110/8 A [56] References Cited UNITED STATES PATENTS 2,796,118 6/1957 Parker et a1. 431/353 5 Cl 4 D F. 2.799991 7/1957 Conrad 60/39.72 R aims, lawlng lgures Pmminum 19M 3.843.309 sum 10; 2

LIQUID FUEL GRID BURNER FOR VITIATED AIR USING AUXILIARY COMBUSTION AIR BACKGROUND OF-THE INVENTION This invention relates generally to a grid burner suitable for burning liquid fuel to raise the temperature of vitiated air. More particularly, the invention relates to an improved design of a liquid fuel burner employing auxiliary combustion air.

A grid burner employs a grid of fuel nozzles disposed transversely across a duct in order to raise the temperature of vitiated air or waste heat gases'passing through the duct. A common use of a grid burner is to raise the temperature of gas turbine exhaust gases in order to generate steam in a heat recovery steam generator. The gas turbine exhaust contains sufficient oxygen-to support combustion, but improved burning will result from proper introduction of v auxiliary combustionsupporting air. I

An example of a grid burner is shown in US. Pat. No. 3,632,286 issued Jan. 4, 1972 to R. E. Kegan and F. A. Underwood and assigned to the present assignee. That burner, adapted for burning both gas and liquid fuel, employed a fuel pipewithin another pipe, theoutside pipe supporting spaced fuel nozzles along its length and also supporting burner wingswith appropriately spaced holes to direct the flow of the vitiated air. That patent suggested introduction of pressurized air into the outer pipe for atomization of liquid fuel. The present construction concerns an arrangement which is more suitable for introduction of auxiliary combustion air at a relatively low pressure difference above the vitiated air pressure for support of combustion rather than for fuel atomization. Also the foregoing Kegan et al, burner required the removal of the entire assembly in order to correct anyproblem with the liquid fuel nozzles.

In a grid burner for burning vitiated air, the design should be such as to provide a low velocity sheltered region within the wings of the burner which is supplied with recirculating gases having enough residence time to ignite all of the liquid droplets and fragments injected from the nozzle. Fuel pressure and geometry at the injection point should be such that, at the recirculating regions, the injected fuel can ignite, partially combust, and interact with the recirculating gases replenishing their thermal capacity. Also portions of the fuel penetrate into the unsheltered gas stream to complete its combustion in as uniform a manner as possible. For this reason, the arrangement of ports for admission of air to the sheltered region within the wings is extremely critical.

Accordingly, one object of the present invention is to provide a grid burner with an improved arrangement for admitting vitiated and auxiliary combustion air to provide uniform combustion.

Another object of the invention is to providean improved liquid fuel nozzle assembly fora grid burner which can be easily removed for servicing.

Still another object of the invention is to provide an improved wing support and hole geometry for a liquid fuel grid burner.

DRAWING The invention both as toorganization and method of practice, together with further objects and advantages thereof, will best be understood by reference to the fol- FIG. 4 is a cross section through the burner element taken along lines IVIV of FIG. 3.

SUMMARY OF THE INVENTION Briefly stated, the invention is practiced by providing a number of auxiliary air pipes extending across a duct, wing members supported on and spaced from the auxiliary air pipes, a number of liquid fuel nozzles spaced on a liquid fuel supply pipe supported within the air pipe and removable therefrom, a plurality of fuel injection openings through the wing and air pipe, and a plurality of vitiated air and auxiliary air admission openings through the wing members.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 of the drawing, the grid burner comprises a rectangular open frame 1 having spaced cross members 2. Individual burner elements 3 are spaced across the short dimension of frame 1. Each burner element 3 includes gutter-type flame holder wings 4 with fuel injection openings 5 arranged in a grid of suitable spacing over the entire duct. Liquid fuel supply pipes 6 and auxiliary combustion air pipes 7 are connected to each burner element. 3 on one side of the duct. A pilot ignition tube 8 extends lengthwise along the duct. The entire base of frame 1 is covered by grid of stainless steel wire mesh 9 to distribute the flow.

In one intended application of the present invention, frame 1 is interposed in a duct carrying combustionsupporting exhaust gas from a gas turbine and is used to heat the gas in a process known as supplementary firing as the gas travels toward aheat recovery steam generator. These details are not shown, but a typical system may be seen by reference to US. Pat. No. 3,443,550 issued to H. F. May and J. M. Kovacik on May'l3, 1969 and assigned to the present assignee.

Referring now to FIG. 2 of the drawing, each burner element 3 is supported in both side walls of frame 1 indicated at 10 and 10a. At side wall 10a each burner elements auxiliary air pipe 13 rests and is free to slide there on a cantilevered support Ila rigidly attached to wall 10a. At side wall 10 each burner element 3 is supported at 10 within a cantilevered support chamber 11 extending through wall 10. A first removable plate 12 is connected to an auxiliary air combustion pipe 13 for removal of the entire burner element 3. A second flanged connection at 14 permits removal of the liquid fuel supply pipe 6 and fuel nozzle assemblies. The wing members 4 are supported on spacer elements 15 welded to the top of auxiliary air pipe 13. Wings 4 are in sections, one end of each being welded to a spacer member 15 and the other being free to slide thereon for thermal expansion and contraction.

Positioned'within auxiliary air pipe 13 is an assembly of short pipe segments 6a connected between fuel manifold support blocks 16. Each support block 16 carries afuel nozzle 17 and a pair of locater pins 18. Each fuel nozzle 17 is positioned below an admission port 19 in the wing, thus forming a fuel injection point 5. The tops of fuel nozzles 17 are short enough so that the entire fuel supply assembly of manifolds l6, connecting segments 6a can be withdrawin longitudinally from the auxiliary air pipe 13, by breaking the flanged connection 14.

Referring now together to the plan view of FIG. 3 and the crosssection of FIG. 4, the arrangement of elements will be describedin more detail. It is seen'that the cross section of each wing member 4 is roughly W- shaped, except that the central portion 20 of the W rests on spacer member and spaced above the auxiliary air pipe 13. The cross section of the wing member shows that the flat central portion bends down toward the pipe 13 to form ashort inner leg portion 21, and then reverse curvature to form diverging outer leg portions 22. The latter form an included angle on the order of 90 degrees, although this will vary somewhat with the design. Inner legs 21, together with the sides of pipe 13, form an elongated air supply passage 23 collecting vitiated air' on either side of the pipe.

Vitiated air is admitted to a recirculating zone 24 between outer legs 22 through a number of different types of passages. A first group of elongated slots 25 are arranged along the inner leg portions 21 of the wings. A second group of spaced ports 26 are disposed approximately midway along the outer leg portions 22. A third group of passages 27 are spaced alongthe central portion 20 between the fuel injection points.

At the location of each fuel nozzle 17, and aligned with openings 19 in the auxiliary air pipe, the wings are provided with enlarged openings 28. Openings 28 are of a greater diameter than openings 19, and are proportioned with respect thereto so that a generally conical spaced is left surrounding the spray conical angle 17a of fuel from the nozzle to admit both vitiated air and auxiliary combustion air. Although the type of nozzle 17 is not material to the present invention, suitable results have been obtained using a Delavan simplex spray nozzle providing a solid conical spray with an included angle on the order of 90. Primarycombustion takes place in a zone29 within the fuel spray angle. t

- It remains to note that the fuel manifold blocks 16 are beveled along their lower edges at 30. By this means, together with locating pins 18, the fuel manifold is properly positioned inside the pipe so that nozzle 17 is at the correct position and so that the fuel assembly can he slid out for servicing. If desired, a small leaf spring may be attached to the underside of each manifold to maintain correct location and to permit easy withdrawal of the assembly.

OPERATION Operation of the invention will be understoodby reference to FIG. 4 of the drawing. Primary combustion of the fuel is enhanced by auxiliary air supplied at a slight pressure, on the order of 5 psi for example, above the vitiated air pressure in the duct. This auxiliary air flows in annular sheaths through holes 19 surrounding the fuel spray conical angle 17A as indicated by arrow 31, commencing penetration into the fuel envelope with oxygen-rich air. This air flow is supplemented by annular sheaths of vitiated air flowing from passages 23 around the fuel spray cone, as indicated by flow arrow 32. This comprises the air supply-at each of the fuel injection points 5 in the grid.

Additional vitiated air is supplied alongthe wings to provide cooling and a recirculating air flow. vitiated air from entry passages 23 enters through the elongated slots 25 and sweeps along the outer legs 22. Air also enters from ports 26 in the outer legs and creates a recirculation of vitiated air and burning fuel in zone 24. Zone 24, it is understood, extends longitudinally along the burner, whereas'zones 29 are discrete or spaced along the burner above the fuel injection points.

The improved W-shape of the burner wing serves to provide a very useful and simple means of providing the vitiated air supply passages 23. This enables the introduction of vitiated air through the space between the wing and the auxiliary combustion air pipe 13. At the fuel injection points, the arrangement provides for an inner sheath of auxiliary combustion air surrounding and penetrating the fuel spray cone and an outer sheath of vitiated air at a greater distance from the nozzle.

Since the fuel nozzle assembly is completely disposed within the auxiliary pipe, it can be removed in the event that nozzles 17 become plugged or require routine cleaning without thenecessity of removing the entire burner assembly. This can be done while the remaining burners in the grid are in operation.

While there has been disclosed what is considered herein to be the preferred embodimentof the invention, other modifications will occur to those skilled in the art,.and it is desired to include in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is: 1. In a grid burner having a plurality of spaced burner elements and adapted for flow of vitiated air past said burner elements to be heated thereby, the combination of:

an auxiliary air pipe connected to a source of auxiliary combustionair at a pressure slightly above that of said vitiated air,

a fuel supply and nozzle assembly adapted to be withdrawn from said auxiliary air pipe and comprising a plurality of spaced fuelnozzles interconnected by fuel supply pipe sections, the fuel nozzles disposed entirely within the auxiliary air pipe,

at least one elongated wing member supported by and spaced from said auxiliary air pipe, said wing member being formed with inner leg portions to provide elongated vitiated airsupply passages on either side adjacent said auxiliary pipe and also having outwardly diverging outer leg portions providing a shielded circulation zone,

said pipe and said wing member each having openings concentric with and downstream from each of said fuel nozzles to admit annular sheaths of auxiliary and vitiated air-respectively around the fuel from said nozzle.

2..The combination according to claim 1, wherein said wing member is substantially W-shaped and wherein the inner legs of said W are provided with a first group of longitudinally spaced vitiated air admission openings, whereby vitiated air can flow from said elongated viatiated air supply passages through said first openings along the outer legs of the wing member.

3. The combination according to claim 2, wherein said wing members include a second group of vitiated air admission .openings spaced substantially midway along the outer legs of said wing member.

mission openings disposed substatially midway on said outer legs.

5. The combination according to claim 1, wherein said fuel nozzle assembly includes a plurality of fuel manifolds furnished with locating means to position the manifolds within the auxiliary air pipe, said locating means permitting withdrawal of the assembly longitudinally through said pipe.

UNITED STATES PATENT orwcs CERTEHQATE @i QQRREQ'HQN Patent No, 3,843,309 Dat d October 22, 197

In t Sotiris Lambiris It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The inv nt r's name should read:

-- Sotiria Lambiris gmd and gmaed this Twenty-seventh E December I 977 [SEAL] Arrest:

RUTH C. MASON LUTRELLE F. PARKER Arresting Officer Acting Commissioner of Patents and Trademarks

Claims

1. In a grid burner having a plurality of spaced burner elements and adapted for flow of vitiated air past said burner elements to be heated thereby, the combination of: an auxiliary air pipe connected to a source of auxiliary combustion air at a pressure slightly above that of said vitiated air, a fuel supply and nozzle assembly adapted to be withdrawn from said auxiliary air pipe and comprising a plurality of spaced fuel nozzles interconnected by fuel supply pipe sections, the fuel nozzles disposed entirely within the auxiliary air pipe, at least one elongated wing member supported by and spaced from said auxiliary air pipe, said wing member being formed with inner leg portions to provide elongated vitiated air supply passages on either side adjacent said auxiliary pipe and also having outwardly diverging outer leg portions providing a shielded circulation zone, said pipe and said wing member each having openings concentric with and downstream from each of said fuel nozzles to admit annular sheaths of auxiliary and vitiated air respectively around the fuel from said nozzle.

2. The combination according to claim 1, wherein said wing member is substantially W-shaped and wherein the inner legs of said W are provided with a first group of longitudinally spaced vitiated air admission openings, whereby vitiated air can flow from said elongated viatiated air supply passages through said first openings along the outer legs of the wing member.

3. The combination according to claim 2, wherein said wing members include a second group of vitiated air admission openings spaced substantially midway along the outer legs of said wing member.

4. The combination according to claim 1, wherein said wing member is substantially W-shaped, the inner legs of said W being provided with a first group of longitudinally spaced vitiated air admission openings, whereby vitiated air can flow from said elongated vitiated air supply passages through said first openings along the outer legs of the wing member, and wherein said outer legs of said wing member are provided with a second group of longitudinally spaced vitiated air admission openings disposed substatially midway on said outer legs.