US3455641A - Burner throat - Google Patents

Description

A. J. POOLE BURNER THROAT July 15, 1969 2 Sheets-Sheet 1 Filed March 26, 1968 ATTORNEY July 15, 1969 A. J. POOLE 3,455,641

' BURNER THROAT Filed March 26, 1968 2 Sheets-Sheet 2 INVENTOR. Arihur J. Poole ATTORNEY United States Patent US. Cl. 431-167 4 Claims ABSTRACT OF THE DISCLOSURE A circular burner throat having an inner periphery formed of axially-oriented surfaces alternately spaced with flared surfaces. The axially-oriented surfaces are selectively arranged to constrain the burner flame and to project it in an axial direction so as to preclude impingeplishes' this ,by providing a burner throatwhose inner periphery consists of alternately spaced axially-oriented and flared surfaces selectively arranged so that, the axially-oriented portions willij act to constrain the flame project ,itin an axial direction, thereby eliminating impingement where burner throat to side wall. clearances areinsufficient or'mar'ginal, while .the flared surfaces positioned where there isample clearance will allow .me fiam'e to expand in aradial direction. Another object of this invention is to combinethe a air pressure drop characteristic'of a flaredeurfacejwith the flame pattern controlcharacteristic '6fithe'axiallyv oriented surface to provide a burner'throat which, while ment on the side walls of the combustion chamber where there is insufficient clearance between the burner throat and the floor, roof and side walls of the combustion chamber. The flared surfaces are disposed where there is ample clearance. The combination of flared and axiallyoriented surfaces maintains the throat pressure drop within acceptable limits. The irregular contour and sharp transitions formed by the alternating flared and axiallyoriented throat surfaces promote turbulence and the mixing of fuel and air.

The invention relates generally relates generally to liqnid fuel burners and more particularly to an improved burner throat for controlling the flame pattern in a furnace combustion chamber.

The modern trend has been toward the shop fabrication of small and medium sized steam generators. Due to the restrictions imposed by transportation facilities these boilers have been limited asto their height and width dimensions, so that capacity increases can only be obtained by lengthening the unit to permit installation .of additional heating surface. These limitations have resulted in the steam generators having long and relatively narrow furnace chambers. These units are usually equipped with fuel burners discharging thro'ugh circular type throats which are flared in the direction of the combustion chamher. The mixing of fuel and air is primarily accomplished by imparting a rotational component of movement to the incoming combustion air through the adjustment of register doors, with consequent short, bushy flame and 'a tendency for the flame to expand in a radial direction.

' With every increase in the steam generating output of these boilers, there has been a corresponding increase in the capacity of the fuel burners and in effect a resultant decrease in the desired lateral'clearances between the burner throat and the roof, floor and sidewalls due to r the aforementioned limitations in height and width dimensions. The combination of higher fuel inputs and reduced burner throat to side wall clearances has aggravated the problem of flame impingement resulting in the formation of heavy coke deposits on the side walls of the which proved fdamaging eliminating flame impingement; .will alsoiretaina com.- mercially acceptable air pressure drop value. i I' i 1" A further object of this nvention is'to'improve the efficiency of the unit by reducing thevexcess air required for complete combustion of the fuel. This is accomplished through increased turbulence and better mixing of fuel and air caused by abrupt flow pattern transitions'resulting from the alternating flaredvand axially-oriented throat surfaces. L i

In the drawings: 7 FIG. 1 is a diagrammatic perspective of the burner and furnace chamber associated with the present invention. A FIG. 2 is a sectional side view of the burner assembly including the burner throat taken along line 22' of FIG. 3.

FIG. 3 is a view looking toward the inside of the burner wall of FIG. 1.

In the illustrated embodiment disclosed in the drawings, the burner assembly is shown as adaptedfor liquid fuel and applied to a furnace having a refractory Wall 'wherein the burner port is provided with a refractory throat of the special configuration which characterizes the invention. It should be understood, however, that the invention is equally applicable for burners usingsolid or gaseous fuel. i 7 Referring to FIG. 1, the boiler setting 9 shown therein is provided with a furnace chamber 10 0f rectangular cross section which includesv burner wall 11, furnace side walls 12 and 14, rear wall 13, floor 15 and roof 16'. Extending alongside furnace'chamber '10 is gas'pass 17.."con- 1 taining convection heat absorbing surface (not shown) which is separated from the furnace and formedby's'ide wall 12 and boiler side wall 20 and cornmunicatesjwith the furnace throughpassage 18 formed'betwejentheend of side wall 12 and rearwall 13. The other endof. gals pass 17 is provided with an outlet passage 19 forrn'ed between the end of boiler sidewall 20 and end wallf Zl, for discharging combustion gasesgenerated in'thefurnaee chamber 10 to a suitable. stack (not-shown) .after they have traversed the length of the gas pass. A-burner"22"is arranged to fire through arefr'actory burner throat23 formed in the part 24 of the burner-wall 11. Alljof the above-mentioned walls with the exception of thebu rne'r wall 11 are lined with steam generating tubes (not shown). The burner walli1 1ispreferably formed of rig. fractory thereby eliminating the need for costly, intricate tube bending "to zacco'm m od'ate the throat" 23, however, this isnot intendedas alimitation 'and 's'hould arise, the invention would be equally applicable being of uniform c'ross 'sectional'area along "at leasta major portion of its axial length. The sides of the frustoconical segments 25 cooperate with the throat 23 to form channels 26 flaring outwardly in the direction of the furnace chamber. In the illustrated embodiment, the burner throat 23 is shown "with four frusto-conical segments 25 alternately spaced with flared channels 26. The four channels extend along radial lines to respective corners formed by the side walls 12 and 14 and burner wall 11, while the four 'radiallyextending frusto-conical segments extendalong radial lines generally normal to "nectar at its inlet end to atomizer'assembly 47 and at the respectively adjacent furnace side walls 12 and 14, the

"floor 15 and roof 16.The flared channel sections 26 perim i t the flame'f towiden at will wherethere isadequate the burner throat within acceptable limits. The sharp irregularity of the burner throat contour resulting from the abrupt transition between a frusto-conical segment and the adjoining channels promotes turbulence: and the better mixing of air and burning fuel. Referring to FIG. 2, the liquid fuel burner 22 is shown in a partially retracted position for the sake of clarity. The burner 22 is mounted centrally of a circular type burner assembly 27 which is in alignment with burner throat 23 and extends into port 24 formed in a portion of burner wall 11. The burner throat 23 is made from a suitable refractory material and includes alternately spaced flared channels 26 and frusto-conical segments the small ends 25A of which form the openings 23A.

Spaced outwardly from the burner wall 11 and extending substantially parallel thereto is the burner outer casing 28 which cooperates with the burner wall to form a windbox 29 to facilitate the flow of combustion air from a forced draft fan (not shown) to the burner port 24. An air entrance means in the form of a hollow truncated cone 30 centrally positioned immediately adjacent to the exterior side of port 24 directs combustion air into the burner throat 23. In the illustrated embodiment, the air directing cone 30 converges toward the entrance of port 24 and a portion of it extends into recess 31 formed at the inlet of throat 23. The combustion air is directed to the cone 30 from an air register 32 having an outer wall 33 and inner wall 34, the inner wall being connected to the directing cone 30. It will be noted that within the confines of the walls 33 and 34, the air register is provided with adjustable air doors 35 suitably controlled by operator means 36 to impart a whirling motion to the air. This effect is further augmented by a plurality of vanes 37 in cone 30 so that the air discharging from the register '32 tends to form a whirling, turbulent stream of air which hugs the inner periphery of the burner throat 23. A circular coverplate 38 closes an access opening 39 in the casing 28 and a cylindrical housing 40 extends inwardly from the circumferential periphery of access opening 39 through the windbox 29 to the outer wall 33 of the air register 32. The circular cover 38 supports a central sleeve member 41 through which there extends a distance piece 42 forming part of the fuel burner assembly 27. The distance piece '42,is axially adjustable along the central axis of burner 22 and can be locked into a selected position with the bolt 43. The inlet end 44 of the distance piecel42 is threaded to receive the yoke assembly 45 which is connected to the liquid fuel and atomizing steam lines .(not 'showm- T-he discharge end 46 of the yoke 45 connects-to theatomizer assembly 47 forthe through passage 'of fuel and atomizing steam. A leak-proof fit between yoke 45 and atomizer 47 is.achieved by introducing a gasket furnace.

the side walls.

its outlet end to sprayer plate 50 and retaining cap 51. Attached to support ring 52 at the distal end of distance piece 42 is an impeller deflector 53 in the shape of a truncated cone, concentrically disposed about the longitudinal axis of the liquid fuel burner 22. An ignition device 57 is provided for lighting the main fuel and includes the electrical junction box 58, fuel intake chamber 53, fuel conduit 60, electric lead 61, insulators 62 and ignition chamber 63. I

Referring to FIG. 3, the portion of burner wall 11 shown therein includes port 24 and burner throat 23, and has flared channels 26 spaced alternately with frustoconical segments25 whose small ends 25A form the opening" 23A. Impeller 53 and directional vanes 37 are concentrically arranged about the axis of the burner throat. The impeller 53 is provided with a series of equally spaced air openings 55 and air deflector vanes 56 and a central port 64 to allow passage of sprayer plate 50 "and cap 51. Ignition chamber 63 is positioned to discharge a lighting flame through the annular space between the impeller 53 and cone 30.

The geometric pattern of alternate frusto-conical segments and flared channels shown in the drawings is not intended as a limitation, but rather represents only one of many possible arrangements with respect to the relative size and location of the contoured portions.

"In operation, combustion air from windbox 29 is admitted to circular burner assembly 27 through air register doors 35 which are adjusted to impart a whirling motion to the air. Cone plate 30 directs the air into the opening 23A and vanes 37 are used to augment the whirling motion of the air. The firing position (not shown) of liquid fuel burner 22 requires that distance piece 42 be inserted in the direction of the furnace chamber 10 thereby positioning impeller 53 with its leading edge in the same plane as the small end of recess 31. Steam or air is used to atomize the fuel prior to its discharge from sprayer plate 50 in the form of a conical-shape mist. The fuel spray mixes with the incoming combustion air and is lighted from a flame produced by ignition device 57.

Theignition device operates only for the short interval required to light the main flame. After light-oft, ignition of the main flame becomes self-sustaining and will generally occur within the dished contour of the impeller. The flame is projected through the burner throat where its shape is regulated to eliminate impingement. The frusto-conical segments 25 will act to constrain the flame andto guide it in an axial direction where throat to side wall clearances are inadequate or marginal. The use of flared channels 26 alternately spaced with frusto-conical segments 25 keeps the burner throat pressure drop within acceptable limits and promotes turbulence and the better mixing of air and burning fuel.

. The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In combination with a furnace chamber having a burner wall, a circular burner throat in the burner wall, a burner in the central portion of the throat, said throat formed with frusto-conical refractory segments projecting radially inward at spaced positions along the periphery of the throat with their small ends forming an opening about and adjacent to the burner of uniform circular cross-section along at least a major portion of its axial length and with theirsides cooperating with the throat to form channels flaring in the direction of the ..2. The combination according to'claim 1 wherein the .furnace :chamber includes side walls connected to the "burner wall, and the throat has at least two segments opposedto each other and extending generally normal to 3. The combination according to claim 1 wherein the furnace chamber is of rectangular cross-section and the .5 6 throat has four channels extending along radial lines to the corners formed by the side and burner walls. FREDERICK L. MATTESON, 111., Primary Examiner 4. The combination according to claim 3 wherein the burner wall is upright.

References Cited 5 UNITED STATES PATENTS 1,532,041 3/1925 Couch 431-83 3,076,498 2/1963 Williams et a1. 431-348,

EDWARD G. FAVORS, Assistant Examiner

Images