CA1250801A

CA1250801A - Pilot burner apparatus

Info

Publication number: CA1250801A
Application number: CA000448839A
Authority: CA
Inventors: Samuel O. Napier
Original assignee: John Zink Co
Current assignee: Zinklahoma Inc
Priority date: 1984-01-24
Filing date: 1984-03-05
Publication date: 1989-03-07
Also published as: JPS60216110A; EP0159421A2; EP0159421A3

Abstract

Abstract of the Disclosure Pilot burner apparatus is provided which has improved flame stability and other characteristics. The pilot burner is com-prised of a hollow body member having a combustible gas inlet nozzle portion at one end connected to a sleeve portion which forms an outlet at the other end. A heat retaining member is disposed within the sleeve portion adjacent the outlet end thereof. Upon short duration combustion disturbances, flame sta-bility is maintained by the burner.

Description

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_c g ound of the Invention l. Field of the_Inven _on The present invention relates generally to pilot burner appa-ratus, and more particularly, but not by way of limitation, to pilot burner apparatus of the type used to ignite combustible materials emitted from one or more other burners in flares, heaters and other similar apparatus.

2 Descrio-tion of the Prior Art ___ A great variety of pilot burner designs and apparatus have been developed and used over the years. Generally, a pilot burner functions to provide a continuous pilot flame adjacent one or more main burners for igniting combustible materials periodi-cally emitted from the main burners. Examples of applications oE
pilot burners in association with main burners are domestic and industrial heaters, boilers, dryers, etc. In addition, a variety of emergency and/or waste disposal flare apparatus for burning combustible materials are utilized in industry which include pilot burners.
In the above mentioned and other applications for pilot bur-ners, it is desirable that the pilot burners have maximum flame stability in a variety of environmental conditions, i.e., that the burners be capable of maintaining a pilot flame in various forms and quantities of draft, at varying inlet combustible gas pressures, when exposed to draft or winds from various directions and other similar conditions. In addition, it is desirab:le that a pilot burner have the ability to maintain flame stability upon short duration combustion disturbances. The ~erm "combustion disturbance" is used herein to mean any of a number of circum-stances causing flame instability and a possible flame outage such as a combustible gas flow interrup-tion, the flame being blown away from the pilot by wind, snuEfed by wind or a momentary increase in external pressure, pulled away from the burner by momentary decreases in external pres-sure, etc.
By the present invention, pilot burner apparatus is provided having improved operational stability and other characteristics including the ability to maintain flame stability during and after short term combustion disturbances.
Summary of the Invention The present inventio~ provides a pilot burner comprised of a hollow body member having a combustible gas inlet nozzle por-tion at one end connected to a sleeve por-tion which forms an ou-tlet at the other end. A heat retain-ing member is disposed within the sleeve portion of the body member adjacent the ou-tlet end thereof whereby during the combustion of a combustible gas at the burner, the heat retaining member is heated and upon short duration combus-tio~ disturbances, flame stabili-ty is maintained by the burner. The nozzle portion of the body member includes a radially inwardly extending in-ternal wall which forms a central discharge orifice therein and including a plurality of discharge apertures disposed therethrough positioned around said central discharge orifice.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodi- .....

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ments which follows when taken in conjuncti.on with the accom-panying drawings.
Brief Description of the _rawings FIGURE 1 is a schematic illustration of a typical pilot burner assembly associated with a main burner.
FIGURE 2 is a side view of the pilot burner of the present invention.
FIGURE 3 is a partially sectional side view of the pilot burner of FIGURE 2.
FIGURE 4 is a cross-sectional view taken along line 4-4 of FIGURE 3.
FIGURE 5 is a cross-sectional view taken along line 5-5 of FIGURE 3.
FIGURE 6 is a cross-sectional view taken along line 6-6 of FIGURE 3.
FIGURE 7 is a side view of an al-ternate Eorm of the pilot burner of the present inventi.on.
FIGURE 8 is a partially sectional side view of the pilot burner of FIGURE 7.
FIGURE 9 is a cross-sectional view taken along line 9-9 of FIGURE 8.
FIGURE 10 is a cross-sectional vi.ew taken along line 10-10 of FIGURE 8.
FIGURE 11 is an end view taken along line 11-11 of FIGURE 8.
FIGURE 12 is a partially sectional side view of yet another form of the pilot burner of the present invention.
FIGURE 13 is a cross-sectional view taken along line 13-13 of FIGURE 12.

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Descript_o_ of Pr f_ red Em _ d _ nts Referring now to the drawings, and particularly to FIGURE 1, a typical pilot burner assembly, generally designated by the numeral 10, and a main burner 12 are illustrated schematically.
The pilot burner assembly 10 is posi-tioned with respect to the main burner 12 such that a pilot Elame is continuously maintained in a position whereby upon ~he emission of combustible materials from the main burner 12, the ignition thereof is e~fected by the pilot burner flame.
The pilot burner assembly 10 is comprised of a pilot burner of the present invention 14 which is positioned adjacent the main burner 12. The pilot burner 14 is connected by a conduit 15 to a conventional fuel-air mixer appara-tus 17. While various fuel-air mixer apparatus have been developed, the most commonly used are oE the Venturi type which inspirate air into the fuel as a result of fuel flow through the mixer. A conduit 19 connects the fuel-air mixer 17 to a source of pressurized fuel. When desired, the assembly 10 also includes a shut-off valve 21 disposed in the conduit 19 which is maintained in the open position only so long as a flame exists at the pilot burner 14 as determined by a con-ventional flame sensing device 23 operably connected to the valve 21.
In operation of the pilot burner assembly lO, a constant Elow of pressurized fuel from a source thereof passes through the shut-off valve 21 and the conduit 19 into and through the fuel-air mixer 170 While flowing through the fuel-air mixer 17~ air is inspirated into the fuel stream and mixed therewith and the resulting fuel-air mixture flows by way of the conduit 15 through the pilot burner 14 where it is combusted. As a result of the combustion, a pilot ~lame is produced at the pilot burner 14 adjacent the main burner 12.

The flame sensing device 23 maintains the shut-off valve 21 in the open position only so long as a pilot flame exists at the burner 14. In the event ~ombustion is terminatad and the flame is extinguished, the flame sensing device 23 shuts off the flow of fuel and air to the pilot burner by causing the shut-off valve 21 to close. In addition, the control signal from the flame sensing device 23 can be used to actuate a main burner combustible material shut-off. As long as the pilot burner assembly 10 produces a flame at the pilot burner 14, combustible material such as a fuel or a combustible waste emitted from the main burner 12 is ignited by the pilot flame and combusted.
The pilot burner 14, flame sensing device 23 and main burner or burners 12 may be disposed within a heat-er or other similar structure wherein the draft (inta~e of atmospheric air) is induced naturally or wherein one or more blowers are used for inducing the draft (forced draft). In a flare application, the pilot burner assem bly 10 and one or more main burners 12 can be disposed within an enclosure such as in a stack or they can be disposed in the open, either at ground level or at an elevated level.
Referri.ng now to FIGURES 2-6, a presently preferred form of the pilot burner 14 is illustrated. The pilot burner 14 is comprised of a hollow body member 16 having a combustible gas inlet nozzle portion 18 at one end connected to a sleeve portion 20 which forms an outlet 22 at the other end. The combustible gas inlet nozzle portion 18 of the body member 16 can take various forms, but in a preferred form the portion 18 includes a centrally disposed threaded bore 24 and a hexagonal shaped exterior whereby it can be conveniently threaded to a conduit. The nozzle portion 18 also includes an internal wall 26 which~

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forms a central discharge orifice 28 positioned within and concentrically to the sleeve portion 20 of khe body member 16. In the form of the pilot burner illustrated in FIGVRES 2-6, with respect to the longitudinal ~xis of the body member 16, the wall 26 extends radially inward-ly a short distance, then longitudinally towards the discharge end 22 of the member 16 a short distance and then radi~lly inwardly again whereby a cylindrical nozzle, generally designated by the numeral 25, is formed interiorly of the sleeve portion 20. The nozzle 25 and the interior of the sleeve portion 20 forms an annular space 27 therebetween.
A first plurality of spaced apart discharge aper-tures 30 are disposed in the first radially inwardly extending portion of the nozzle 25. The apertures 30 extend from khe interior of the no~zle 25 to the annulus 27. A second plurality of spaced apart discharge aper-tures 32 are disposed in the longitudinal portion of the wall 26 and extend from the interior thereof to the annulus 27. As best shown in FIGURES 3 and 4, the aper-tures 30 and 32 are positioned around the interior of the nozzle 25 in spaced relationship to each other. In addition, the axes of the apertures 30 and 32 converge.
Finally, a plurality of spaced apart sloks 34 are formed in the second radially inwardly extending portion of the wall 26. The slots 34 extend ~rom the centrally disposed discharge orifice 28 radially outwardly to the discharge apertures 32.
The sleeve portion 20 of the body me-mber 16 in-cludes a plurality of spaced apart ports 36 positionedaround the sleeve portion 20 in a plane perpendicular to khe longitudinal axis thereof.
Positioned within the sleeve por-tion 20 and termin-ating adjacent the outlet 22 thereof is a heat retaining member 38. In the Eorm illustrated in FIGURES 3 and 6, the heat retaining member 38........................ ~

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is a helical coil formed of an elongated metallic material, the ends of which are rigidly attached, such as by welding, to the sides of the sleeve 20. In this form, the heat retaining member 38 is preferably a heat resistant metal alloy capable of with~
standing prolonged heating such as an alloy of nickel and chro-mium. However, other suitable metals or ceramlc materials can also be used.
Operati of the Pilot Burner 14_ In operation of the pilot burner 14, a fuel-air mixture enters the interior of the nozzle portion 18 from a conduit threadedly connected thereto. The fuel-air mixture is driven by pressure differential through the discharge apertures 30 and 32, the discharge slots 34 and the discharge orifice 2~, all in the nozzle 25. The portion of the fuel~air mixture flowing through the discharge orifice 28 forms a jet which flows longitudinally through the sleeve portion 20 and out of the sleeve portion 20 by way of the outlet 22 as the fuel-air mixture burns. The fuel-air mixture flowing through the discharge apertures 30 and 32 form jets which collide with each other and with the interior wall of the sleeve portion 20 within the annulus 27 as the fuel-air mix-ture begins to burn. The collisions bring about a reduction in the velocity of the jets and improve the stability of the flame produced by the pilot burner 14. The discharge slots 34 act to transfer the burning to the main jet produced by the discharge orifice 28. Also, portions of the fuel-air mixture adjacent the internal walls of the sleeve portion 20 may flow through the ports 36 therein and be combusted outside the sleeve portion 20.
The ports 36 act to help equalize pressure between the interior of the sleeve 20 and the external environmental surrounding the sleeve 20.

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As indicated above, the fuel-air mixture flowing through the body member 16 of the pilot burner 14 is partially combusted within the sleeve portion 20 and partially combusted outside the sleeve portion 20 whereby an elongated flame extends from within the sleeve portion 20 a distance beyond the outlet 22 thereof. The combustion that takes place within the sleeve portion 20 of the pilot burner 14 continuously heats the member 38 disposed therein. In the event of short duration combustion disturbances, the heat retain-ing member 38 remains hot and re-ignites or otherwise stabilizes the flame produced from the fuel-air mixture.
Referring now to FIGURES 7~ an alternate form of the pilot burner of the present invention is illustrated and generally designated by the numeral 40. The struc-ture and operation of the pilot burner 40 is similar to the structure and operation of the pilot burner 14 except that the heat retaining member of the pilot burner 40 is removable. Also, the pilot burner 40 is illustrated with an alternate nozzle discharge orifice and aperture arrangement. ~ore specifically, the pilot burner 40 includes a hollow body member 42 havin~ a combustible gas inlet nozzle portion 44 at one end connected to a sleeve portion 46 which forms an outlet 48 at the other end~ The nozzle portion 44 of the body memher 42 can, and in most cases preferably does, include a radially inwardly extending internal wall forming an internal nozzle with a central discharye ori-fice and two sets of discharge apertures identical to the nozzle 25 of the pilot burner 14 described above.
However, for purposes of this disclosure, the nozzle portion 44 of the pilot burner 40 is illustrated with an optional nozzle arrangement which can be utili2ed in applications where the operating environment and/or requir~merlts for the pilot burner are different.

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The nozzle portion 44 of the pilot burner 40 includes a radially inwardly extending wall 50 which forms a central discharge orifice 52. A single plural-ity of spaced apart discharge apertures 54 is provided, the apertures being spaced around the interior of the wall 50 and extending therethrough.
The sleeve portion ~6 of the body member 42 includes a plurality of ports 56 formed therein, which function in the same manner as the ports 36 described above, and positioned within the slsave portion 46 is a removable heat retaining member 60. The heat retaining member 60 is similar to the heat retaining member 38 described above in connection with the pilot burner 14 in that it includes a helical coil 62 formed of heat resistant metal such as a metal alloy. However, instead of being direct-ly attached to the sleeve portion 46 of the body member 42, the coil 62 is attached to three elongated spacing members 64 which are in turn slidably disposed within the interior of the sleeve portion 46. Enlarged portions are provided on the members 64 to prevent the heat retaining member S0 from being moved inwardly within the sleeve portion 46 too far and for facilikating the removal thereof.
Referring now to FIGURES 12 and 13, yet another form of the pilot burner of the present invention is illus~
trated and generally designated by the numeral 70. The pilot burner 70 is similar in structure and operation to the pilot burners 1~ and 40 described above. More speci-fically, the pilot burner 70 is comprised of a hollow body member 72 having a combustible gas inlet nozzle portion 74 at one end connected to a sleeve portion 76 which forms an outlet 78 at the other end. The inlet nozzle portion 74 is illustrated in the same arrangement as the pilot burner 40, i.e., it includes a radially inwardly extending internal wall 75 which forms a , ~,, central discharge orifice 77 and discharye apertures 79. The sleeve portion 76 of the body mernber 72 includes a heat retaining member 82 which is removably disposed within the sleeve portion 76. However, instead of a helical coil Eormed oE elongated heat resistant material, the heat retaininy member 82 is of an alter-nate design which includes three elongated longitudinally posi-tioned heat resistant heat retaining plates 8~ formed of a suitable material. The plates 84 are connected together at the inner sides thereof and the outer sides are in slidable contact with the interior of the sleeve portion 76 so that the member 82 is removable. Each of the plates 84 forming the heat retaining rnember 82 can include a plurality of openings 86 formed therein for promoting mixing, etc.
As will be understood by those skilled in the art, the heat retaining member utilized with the pilot burner of the present invention can take various forms other than those which are pre-sently preferred and specifically disclosed herein. Further, the heat retaining rnember can be formed from a variety oE rmaterials with those having the properties of long life and high heat retention beiny preferred.
The pilot burner of the present invention has improved flame stability properties over a variety oE conditions including over a broad range of fuel gas pressures, under back pressures, over a broad range of draft conditions, both natural and forced, and under various air supply and wind conditions including those at directions transverse to the axis of the pilot burner. For example, while the times vary with a variety of factors, under simulated low natural draft conditions (0.08 inches of water column) and a fuel pressure of 15 psig, a pilot burner of the present invention (as illustrated in FIG~RES 2-6) with a heat ~{~

retaining member 38 formed oE a heat resistant alloy o-E nickel and chromium re-ignites the fuel mixture after fuel mixture Elow interruptions of up to six seconds. Under simultated forced draft conditions of 0.2 inches water column positive pressure and 15 psig fuel pressure, re-ignition is achieved after a fuel mix-ture flow interruption of four seconds. Under a positive pres-sure oE 0.7 inches water column, the maximum time the Euel mixture flow can be interrupted with re-iynition taking place is two seconds with full heat retaining member reheating between interruptions. Under 0.7 inches water column positive pressure and only a four second reheat time, the maximum pilot burner fuel mixture Elow interruption time is one second.
Thus, the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned as well as those inherent therein. While presently preferred embodiments of the invention have been described herein for purposes oE disclo-sure, numerous changes in the construction and arrangement of parts can be rnade by those skilled in the art, which changes are encompassed within the spirit of this invention as defined by the appended claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A pilot burner comprising:
a hollow body member having a combustible gas inlet nozzle portion at one end connected to a sleeve portion which forms an outlet at the other end;
said nozzle portion of said body member including a radially inwardly extending internal wall which forms a central discharge orifice therein and including a plurality of discharge apertures disposed therethrough positioned around said central discharge orifice; and a heat retaining member disposed within said sleeve portion of said body member adjacent the outlet end thereof whereby during the combustion of a combustible gas at said burner said heat retaining member is heated and upon short duration combustion disturbances, flame stabil-ity is maintained by said burner.

2. The apparatus of Claim 1, wherein said heat retaining member is removably disposed within said sleeve portion of said body member.

3. The apparatus of Claim 1, wherein said heat retaining member is at least partially formed in the shape of a helical coil.

4. The apparatus of Claim 1, wherein said sleeve portion of said body member includes at least one port formed in a side thereof.

5. The apparatus of Claim 4, wherein said nozzle portion of said body member further includes a plurality of spaced slots disposed in said internal wall and extending radially outwardly from said central discharge orifice to said discharge apertures therein.

6. The apparatus of Claim 1, wherein said heat retaining member is formed of metal.

7. The apparatus of Claim 1, wherein said heat retaining member is formed of ceramic material.

8. A pilot fuel gas burner assembly comprising:
means for mixing air with pressurized fuel having a fuel inlet, an air inlet and a fuel-air mixture outlet;
first conduit means connected between a source of pressurized fuel and said fuel inlet of said fuel-air mixing means;
second conduit means connected to the fuel-air mixture outlet of said fuel-air mixing means; and a fuel-air mixture burner connected to said second conduit means, said burner being comprised of a hollow body member having a fuel-air mixture nozzle portion at one end connected to a sleeve portion which forms an outlet at the other end, the nozzle portion of the body member being con-nected to said second conduit means and including a radi-ally inwardly extending internal wall which forms a central discharge orifice therein positioned concentrically to said sleeve portion and said internal wall including a plurality of discharge apertures disposed therethrough and positioned around said central discharge orifice; and a heat retaining member disposed within said sleeve portion of said body member adjacent the outlet end thereof whereby during the combustion of said fuel-air mixture at said burner said heat retaining member is heated and upon short duration combustion disturbances, flame stability is maintained by said burner.

9. The apparatus of Claim 8, wherein said heat retaining member is removably disposed within said sleeve portion of said burner.

10. The apparatus of Claim 8, wherein said heat retaining member is at least partially formed in the shape of a helical coil.

11. The apparatus of Claim 8, wherein said sleeve portion of said burner includes at least one fuel-air mix-ture discharge port formed in a side thereof.

12. The apparatus of Claim 11, wherein said nozzle portion of said burner further includes a plurality of spaced slots disposed in said internal wall and extending radially outwardly from said central discharge orifice to said dis-charge apertures therein.

13. The apparatus of Claim 8, wherein said heat retaining member is formed of metal.

14. The apparatus of Claim 8, wherein said heat retaining member is formed of ceramic material.

15. A pilot burner comprising:
a hollow body member having a combustible gas in-let nozzle portion at one end connected to a sleeve portion which forms an outlet at the other end;
said nozzle portion of said body member including an internal wall which extends radially inwardly a short distance, then longitudinally towards the discharge end of said body member a short distance and then radially inwardly again whereby a cylindrical nozzle is formed interiorly of said sleeve portion having a central discharge orifice therein and forming an annular space between the interior of said sleeve portion and said cylindrical nozzle, said internal wall including first and second pluralities of spaced apart discharge apertures disposed therein positioned around said central discharge orifice, extending from the interior of said cylindrical nozzle to said annular space and having axes, respectively, which converge and inter-sect the interior of said sleeve portion; and a heat retaining member disposed within said sleeve portion of said body member adjacent the outlet end thereof whereby during the combustion of a combustible gas at said burner said heat retaining member is heated and upon short duration combustion disturbances, flame stability is main-tained by said burner.

16. The pilot burner of Claim 15, wherein said heat retaining member is at least partially formed in the shape of a helical coil.

17. The pilot burner of Claim 16, wherein said sleeve portion of said body member includes at least one combustible gas discharge port formed in a side thereof.

18. The pilot burner of Claim 17, wherein said nozzle portion of said body member further includes a plu-rality of spaced slots disposed in said internal wall and extending radially outwardly from said central discharge orifice to said second plurality of discharge apertures therein.

19. The pilot burner of Claim 18, wherein said heat retaining member is removably disposed within said sleeve portion of said body member.