Note: Descriptions are shown in the official language in which they were submitted.
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Back~round of the Invention `
This invention relates to a flame-producing burner for
- firing a tube. Such a tube may, for example, be a ceramic or alloy
; tube of the type used to heat a kiln, a heat treating furnace, a lehr or
the like. In such an instance, one end portion of the tube may be
disposed in an opening in a heat-insulating wall. Alternatively, the
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tube may be an immersion tube which is submerged within a tank of
liquid in order to heat the liquid. The latter tube may have a return
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~- portion for exhausting the products of combustion from the liquid or
10 the products of combustion may be exhausted through the liquid itself.
In some respects, the burner of the present invention ~
is similar to that disclosed in Spielman et al United States Patent p
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3, 418, 060, issued December 24, 1968. Such a burner includes a
tubular burner body which houses a fuel supply pipe that extends
through the closed end of a cup adapted to form combustion air into a -`
tubular stream prior to p~imary mixing of the air with the fuel. -
In other respects, the present burner is similar to the
burner disclosed in Moore United States Patent 4, 003, 692, issued - -
- January 18, 1977.
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That burner is of the dual fuel type and is adapted to burn either fuel
oil or gas.
Summar~ of the Invention
The primary aim of the present invention is to provide a
new and improved tube firing burner, preferably of the dual fuel type, ;
which extends its flame well i-nto the tube so as to avoid excessive
heating and burn-out of that end portion of the tube which is adjacent the
burner and which sometimes is surrounded by a heat-insulating wall. -
A further object of the invention is to provide a burner
10 which is capable of firing initially cold tubes such as liquid-surrounded
tubes without generating any significant amount of smoke or carbon xl ~ .
within the tube.
Still another object i~s to provide a dual fuel tube firing ,
burner which has the ability to operate with low excess combustion air
without smoking or sooting, which maintains better flame stability over
a wide range of air/fuel ratios, which has greater turn-down capability
than conventional dual fuel burners. and which produces betb~r ~ ;
temperature profiles within the tube.
The burner of the invention is particularly characterized .~ ,
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20 by the provision of a unique combustion sleeve which is located within
the tube to extend the flame well into the end portion of the tube, the
combustion sleeve being kept cool by the tubular stream of combustion `-
air and serving to cre~tte turbulence in the air/fuel mixture so as to
retard smoking and promote better flame retention. -
In summary, the invention comprises the combination of
a heat-insulating wall having inner and outer sides and having an opening
extending between said sides. a radiant tube projecting inwardly from
~: the inner side of said wall and having an outer portion disposed within
the full length of said opening, and a burner for firing said tube and
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having a tubular body secured to the outer side of said wall and located
in substantially coaxial relation with said tube, a fuel delivery pipe
extending into said body from the outer end portion thereof, means for
supplying a flow of fuel through said pipe, means for supplying a flow
of combustion air into said body from the outer end portion thereof,
means for shaping said air into a tubular stream adjacent the discharge
end of said delivery pipe, a metallic combustion sleeve coaxial with
said delivery pipe and positioned to receive the flow of fuel and the .,.
tubular stream of air, said combustion sleeve exte~ding through the full
10 length of said opening and being telescoped within and spaced radially
inwardly from the outer end portion of said tube, said combustion
sleeve having an inner end extending inwardly beyond the inner side of
said wall so as to discharge the fuel/air mixture into said tube beyond
said wall, and an abrupt restriction within said sleeve adjacent the
inner end thereof and beyond the inner side of said wall to create turbulence
within the fuel/air mixture discharged from said sleeve.
These and other objects and advantages of the invention
will become more apparent from the following detailed description when
taken in conjunction with the accompanying drawings.
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Brief Description of the Drawin~s
FIGURE l is a side elevation of a tube firing burner
incorporating the novel features of the present invention and shows
the burner in conjunction with an exemplary tube, portions of the view
being broken away and shown in section. ~-
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FIG. 2 is an enlarged cross-section taken substantially
along the line 2-2 of FIG. 1.
Detailed Description of the Preferred Embodiment
As shown in the drawings for purposes of illustrationJ
10 the invention is embodied in a burner 10 for firing a tube 11 which,
in the disclosed embodimentJ is a cylindrical ceramic tube of the type
used in a kiln or other heat treating furnace. One wall 13 of the furnace ~ -
is shown in FIG. 1 and is made of brick or other refractory material `
capable of withstanding high temperatures and insulating the heating .rr. ~ '
chamber of the furnace. One end portion of the tube is telescoped
into an opening 14 formed in the wall and extending between the inner ~- -
and outer sides lS and 16 thereofJ the tube having a flange 17 located
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adjacent the outer side of the wall. Combustion of an air/fuel mixture
within the tube raises the temperature thereof so that heat is transferred
by radiation and/or convection to the work being processed in the furnace. -
The burner 10 comprises a tubular body 19 made of cast -
iron and fastened at its inner end to the outer side 16 of the wall 13 by
screws 20 extending thro,ugh a mounting nange 21 on the inner end of the
body and also extending through the nange 17. Gaseous fuel may be
supplied to the burner through a line 23 and is delivered into a housing
24 which is attached to the outer end of the body 19. The gas flows
out of the housing and into a gas supply pipe 25 whose outer end is
fastened to the outer end of the body and whose inner discharge end is
open and is formed with a series of angularly spaced holes or ports 26.
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As an alternative to gas operation, the burner 10 may
be selectively operated on fuel oil. For this purpose, oil is adapted
to be delivered to the burner by way of a line 27 and an adjustable
control valve 29 and flows through the housing 24 through a small
diameter tube 30. The tube is located within the gas supply pipe 25
and is connected at its inner end to an oil nozzle 31 which is formed
with angularly spaced holes 33 (FIG. 2).
In order to break the oil up into small droplets, atomizing
air is delivered into the housing 24 through a line 34 (FIG. 1) and flows
10 through a tube 35 which is telescoped into the gas pipe 25 and over the
oil tube 30. Just prior to leaving the tube 35, the atomizing air
encounters and is spun by helically extending and circumferentially
spaced vanes 36 formed around the outside of the oil nozzle 31. The
spinning atomizing air is discharged adjacent the holes 33 in the oil
nozzle and causes the oil to be transformed into a fine mist. The oil -
nozzle is located well short of the inner end of the gas supply pipe 25
and thus the oil mist passes within and ultimately is discharged out of
the pipe.
Air for supporting combustion of the fuel is supplied by
20 a blower (not shown) and is delivered into the burner body 19 through
a radially extending pipe 37. Such air flows inwardly along the exterior
of the fuel supply pipe 25 and then encounters a cylindrical cup 39 which
forms the air into a tubu~ar stream. As shown, the cup is located
with its open end adjacent the outer end of the opening 14 in the wall
13 and with its closed end 40 disposed outwardly of the discharge end
of the fuel pipe 25. Axially spaced rows of circumferentially spaced
holes 41 are formed through the cylindrical wall of the cup 39 while
holes 43 arranged in a circumferentially extending row are formed
through the closed end 40 of the cup. The cup is centered within the
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burner body 19 and is somewhat smaller in diameter than the body ~-
so that an annular gap 44 is left between the body and the cup to allow
a tubular stream of combustion air to flow past the cup. A tubular
extension 45 is formed integrally with the closed end of the cup and
is telescoped over and fastened to the fuel pipe 25 to support the cup ---~
within the body 19. Also, a spark plug 46 is supported by the body 19
and is located with its electrodes positioned within the cup so as to
provide a spark for initially igniting the air/fuel mixture in the cup.
In accordance with the present invention, a combustion .~ ~,
10 sleeve 50 is located adjacent the open end of the cup 39 and serves to
extend the name of the burner 10 well into the radiant tube 11 so that
the flame will not directly contact and damage that end portion of the
tube which is disposed within the opening 14 and which is insulated by ;
the refractory wall 13. Moreover, the combustion sleeve serves to ~
create turbulence in the air/fuel mixture being discharged from the --
cup 39 and into the tube 11 so as to maintain good flame retention and ~- -
to promote clean burning even if the mixture contains little or no excess -~
air.
More specifically, the combustion sleeve S0 is generally
20 cylindrical and is made of stainless steel or other material capable of
withstanding high temperatures. The sleeve is telescoped into the inner
end portion of the tube 11 and includes an outer ilange 51 which i8
sandwiched between the ~langes 17 anu 21, the sleeve being held in
place by the screws 20. Importantly, the sleeve 50 is spaced radially
inwardly from the tube 11 and thus is not in conductive contact with the
tube. Also, the sleeve is at least sufficiently long to project the flame
front beyond the inner side 15 of the wall 13. To accomplish this, the
sleeve of the preferred embodiment projects inwardly a substantial
distance beyond the inner side of the wall as shown in FIG 1. In
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keeping with the invention, the sleeve is of substantially uniform
diameter throughout its length except at the extreme inner end of
the sleeve. There the sleeve is bent inwardly to form an abrupt or
sharp-edged annular restriction 53 so that a reduced diameter discharge
opening 54 is defmed at the end of the sleeve. -
With the foregoing arrangement, most of the combustion
- air supplied through the pipe 37 passes over the cup 39 and through the
gap 44 and thus is formed into a tubular stream which flows along the
interior wall of the sleeve 50 and keeps the sleeve relatively cool.
10 Some of the combustion air, however, passes into the cup 39 through
the holes 41 and 43 and mixes with a small amount of fuel which escapes
into the cup through the holes 26 in the fuel pipe 25. This air/fuel
mixture is ignited by the spark plug 46 to create a pilot flame. At
all airflow rates within the range of the burner 10, the air/fuel ratio
of the mixture in the cup 39 is within combustible limits and thus the '
pilot flame is maintained continuously during operation of the burner.
When the burner 10 is being operated on gas, most of
the gas is discharged out of the extreme inner end of the fuel pipe 25
and passes out of the open end of the cup 39 to mix with the tubular air
20 stream flowing past the cup and into the sleeve 50. Accordingly, the
most intense flame is produced adjacent and beyond the inner end of
the sleeve 50 and thus the sleeve extends the flame inwardly beyond
the inner end portion of Ithe tube 11. As pointed out above, the tubular
air stream scrubs the interior wall of the sleeve to keep the latter
relatively cool and this, together with the fact that the sleeve is spaced ;
radially inwardly from the tube 11, helps avoid the application of - -
extremely high temperatures to the inner end portion of the tube. ~ ~`
Thus, the inner end portion of the tube is not likely to burn out even
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though it is insulated by the refractory wall 13 and i8 not capable of
readily losing heat.
When the burner 10 is being operated on oil, the spinning
atomizing air passing by the vanes 36 creates a vortex which acts on
hot gases from the pilot flame in the cup 39 and pulls such gases ~
reversely into the fuel pipe 25. These recirculated hot gases cause ~ -
vaporization of part of the oil being sprayed from the nozzle 31 and `~
provide retention for the flame which starts buring within the pipe 25.
The air/fuel mixture be~ng discharged from the sleeve
10 50 encounters the abrupt restriction 53 at the inner end of the sleeve
and thus i8 rapidly contracted and formed into a turbulent flow. This ,;
turbulence causes recirculation of hot gases within the radiant tube 11 ~ ~
and such recirculation assists in vaporizing the oil so as to provide for ~ - -
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clean burning of the oil even though only little excess air is present in
the mixture. Accordingly, combustion of a mixture containing little
or no excess air may occur without creating any significant amount -
of carbon or smoke within the tube 11.
From the foregoing, it will be apparent that the present
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invention brings to the art a new and improved burner 10 having a unique ~
20 combustion sleeve 50 which serves a twofold purpose. First, the ;,
81eeve extends the flame inwardly beyond the wall 13 so as to prevent .
burn-out of the end portion of the tube 11 and to produce a better
temperature profile alor~g the tube. &condly, the turbulence imparted i' ~;
to the fuel/air mixture by the restriction 53 promotes cleaner and ~;~
more efficient burning of the fuel within the tube. It has been found `
that the present burner can start liquid-surrounded tubes without ~-,
creating significant amounts of smoke or carbon and that the burner
possesses better flame stability and greater turndown ability than the
- dual fuel burners which are presently available.
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