Note: Descriptions are shown in the official language in which they were submitted.
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PI10T BURNER APPARATUS
_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
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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
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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
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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.
