Note: Descriptions are shown in the official language in which they were submitted.
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MULTI-CONE FUEL BURNER APPARATUS FOR
MULTI-TUBE HEAT EXCHANGER
BACKGROUND OF THE INVENTION
The present invention relates generally to fuel-fired heating appliances, such
as air
heating furnaces, and more particularly provides specially designed combustion
apparatus for
such fuel-fired heating appliances.
In fuel-fired heating appliances such as, for example, air heating furnaces, a
known
firing method is to flow a fuel/air mixture into a burner box structure in
which a burner
structure and an associated igniter structure are disposed and are operative
to combust the
fuel/air mixture and thereby create hot combustion gases used to heat air (or
another fluid as
the case may be) for delivery to a location served by the heating appliance.
The hot
combustion gases are flowed through a series of heat exchanger tubes ,
externally across
which the fluid to be heated is flowed, and then discharged from the heating
appliance into a
suitable flue structure.
Typically, spaced apart open inlet portions of the heat exchanger tubes extend
through
openings in a wall of the burner box that faces the burner structure which, in
a conventional
form thereof, is an elongated flat or curved single mesh burner. FIG. 1
schematically depicts
a conventional fuel-fired heating appliance combustion section 10 comprising,
from left to
right in FIG. 1, a burner box 12, a heat exchange housing i4, and a collector
box 16, joined
together as indicated. The burner box 12 forwardly terminates at a rear wall
18 of the heat
exchange housing 14, and the heat exchange housing 14 forwardly terminates at
a rear wall
20 of the collector box 16.
A spaced plurality of heat exchanger tubes 22 (representatively five in
number)
extend through the interior of the heat exchange housing 14 and have open rear
inlet ends 24
supported in corresponding openings in the rear wall 18 of the heat exchange
housing 14, and
open front outlet ends 26 supported in corresponding openings in the rear wall
20 of the
collector box 16. As can be seen in FIG. 1, the open rear inlet ends 24 of the
heat exchanger
tubes 22 are interdigitated with imperforate sections 28 of the rear heat
exchange housing
wall 18. A draft inducer fan 30 is operatively positioned as shown in the
collector box 16.
Referring now additionally to FIG. 2, a representative conventional elongated
rectangular flat metal mesh burner 32 is positioned within the burner box 12
in a rearwardly
spaced, facing relationship with the open inlet ends 24 of the heat exchanger
tubes 22.
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Burner 32 is carried within a suitable metal frame 34 (sec FIG. 2) secured to
an interior
flange portion 36 of the burner box 12. A conventional igniter 38 is
operatively associated
with the flat burner 32.
During firing of the heating appliance with which the burner 32 is associated,
a flow
40 of pre-mixed fuel and air is forwardly drawn through the burner box 12 to
the burner 32 at
which point the flow 40 is combusted by the igniter 38 to form along an
elongated reaction
flame pattern 42 emanating from the front side of the burner 32. As can be
seen in FIG. 1,
portions of the flame 42 are drawn into the heat exchanger tube inlets 24 and
form therein hot
combustion gases 44, while the balance of the flame 42 is directed against the
imperforate
portions 28 of the rear wall 18 of the heat exchange housing 14.
During firing of the conventional combustion section 10, air 46 (or other
fluid as the
case may be) is suitably flowed externally across the heat exchanger tubes 22
to create heated
air 48 for delivery to a conditioned space served by the heating appliance.
Simultaneously,
the draft inducer fan 30 draws cooled combustion gases 50 from the heat
exchanger tube
outlet ends 26, through the interior of the collector box 16, and then
exhausts the cooled
combustion gases 50 to a suitable flue.
A variety of well known problems, limitations and disadvantages are present in
this
conventional design of a premixed fuel/air combustion system and are primarily
created by
the use of the flat burner 32. For example, in this application, the negative
pressure created
by the draft inducer fan 30 tends to forwardly bow the heated burner 32 to its
dashed line
orientation shown in FIG. 1. This bowing can undesirably change the reacting
flow pattern,
and can also facilitate some undesired fuel/air mixture flow paths around the
burner.
Additionally, the flat burner 32, by virtue of presenting a fairly large
single
combustion zone within the burner box 12, causes a large amount of the created
combustion
products to exist within and heat up the burner box 12 prior to being drawn
through the heat
exchanger tubes 22 by the draft inducer fan 30. IIigh temperatures inside the
heating
appliance cabinet is not desirable because it can cause problems for the other
components and
it also is a form of efficiency reducing heat loss. Moreover, the flat burner
32 has been found
to often be a primary source of an undesirable source of operating noise,
including ignition
noise, structural vibration noise and stcady state high frequency noise.
Replacing the flat
burner 32 with a curved single burner has been found to at least somewhat
alleviate the
bowing problem of the flat burner, but still can create an unacceptably large
level of
operational noise when used in a premixed fuel/air combustion application.
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As can be readily seen from the foregoing, a need exists for improved premixed
fuel/air combustion apparatus for use in fuel-fired heating appliances. It is
to this need that
the present invention is primarily directed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic cross-sectional view through a portion of a conventional
flat
burner-based combustion section of a fuel-fired heating appliance;
FIG. 2 is a cross-sectional view through the combustion section taken along
line 2-2
of FIG. 1;
FIG. 3 is a schematic cross-sectional view through a portion of a specially
designed
fuel-fired heating appliance combustion section embodying principles of the
present
invention;
FIG. 4 is a front side perspective view of a unique multi-cone burner assembly
portion
of the FIG. 3 combustion section;
FIG. 5 is an exploded perspective view of the FIG. 4 multi-cone burner
assembly;
FIG. 6 is a rear side perspective view of the FIG. 4 multi-cone burner
assembly;
FIG. 7 is a schematic cross-sectional view through a heat exchanger tube
portion of
the FIG. 3 combustion section; and
FIG. 8 is a schematic side edge elevational view of an alternate embodiment of
the
FIG. 4 multi-cone burner assembly.
DETAILED DESCRIPTION
Cross-sectionally depicted in schematic form in FIG. 3 is a portion of a fuel-
fired
heating appliance, representatively an air heating furnace 60, that
incorporates therein a
premixed fuellair combustion section 62 embodying principles of the present
invention.
While the heating appliance 60 is representatively an air heating furnace,
principles of the
present invention are not limited to furnaces, and could be employed to
advantage in a variety
of other types of fuel-fired heating appliances including, but not limited to,
water heaters,
boilers and pool heaters.
The combustion section 62 comprises, from left to right in FIG. 3, a mixing
box 64, a
burner box or combustion chamber 66, a hcat Cxchange housing 68, and a
collector box 70
joined together as indicated. At the juncture of the mixing box 64 and the
burner box is a
perforated diffuser plate 72 which may be similar in configuration and
operation to the
perforated diffuser plate 64 illustrated and described in copending U.S.
application no.
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14/084,095 owned by thc assignee of the present application. The burner box 66
forwardly
terminates at a rear wall 74 of the heat exchange housing 68, and the heat
exchange housing
68 forwardly terminates at a rear wall 76 of the collector box 70.
A spaced plurality of heat exchanger tubes 78 (representatively five in
number)
extend through the interior of the heat exchange housing 68 and have open rear
inlet ends 80
supported in corresponding openings in the rear wall 74 of the heat exchange
housing 68, and
open front outlet ends 82 supported in corresponding openings in the rear wall
84 of the
collector box 70. The open rear inlet ends 80 of the heat exchanger tubes 78
are
interdigitated with imperforate sections 86 of the rear heat exchange housing
wall 74. A draft
inducer fan 88 is operatively positioned as shown in the collector box 70.
With reference now to FIGS. 3-6, according to an aspect of the present
invention, a
specially designed burner assembly, illustratively a multi-cone burner
assembly 90, is
supported within the burner box 66 between the perforated diffuser plate 72
and the open
inlet ends 80 of the heat exchanger tubes 78. As best illustrated in FIGS. 4-
6, burner
assembly 90 includes a support structure comprising an elongated rectangular
metal support
plate 92, an elongated rectangular metal mesh backing member 94, and an
elongated
rectangular metal mounting frame 96, the backing member 94 being sandwiched as
shown
between the support plate 92 and the mounting frame 96. The support plate 92
has front and
rear sides 98 and 100, and five longitudinally spaced circular openings 102
extending
therethrough and being joined by slots 104 formed through the support plate
92.
The burner assembly 90 further includes five hollow metal mesh cone-shaped
burners
106 pressed, apexes first, forwardly through the circular openings 102, and
projecting
forwardly beyond the front support plate side 98 along cone axes 108. After
the burners 106
are positioned in the circular support plate openings 102, they are retained
therein by placing
the backing member 94 on the rear side 100 of the support plate 92 and
securing the
mounting frame 96 to a peripheral portion of the support plate 92, as with
suitable fasteners
110. As later described herein, the conical burners 106 are lit by a suitable
igniter 112
illustratively positioned between the bottom two burners 106 as viewed in FIG.
3. A created
flame on either of these two burners is passed to the other four burners via a
metal mesh
flame carryover structure 114 (see FIG. 4) disposed in thc support plate slots
104
interconnecting the circular plate openings 102, and thus interconnecting the
burner cones
106.
Turning now to FIG. 3, the plate-mounted burner cones 106 are operatively
positioned
within the burner box 66 with the burner cones 106 projecting forwardly,
apexes-first, toward
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the heat exchanger tube inlets 80, the burner cone axes 108 aligned with the
tube axes 116,
and the cone burner apexes projecting slightly into the heat exchanger tube
inlet ends 80, by
securing the support plate 92 to an interior burner box flange portion 118
over an opening
120 therein. While this illustrative positioning of the burner assembly 90
within the burner
5 box 66 positions the burner cone apexes slightly within the heat
exchanger tube inlets 80, the
burner assembly could be alternatively positioned somewhat forwardly or
rearwardly of its
indicated FIG. position within the burner box 66 without departing from
principles of the
present invention.
During firing of the furnace 60, an initially pre-mixed flow 122 is forwardly
drawn by
the draft inducer fan 88 through the interior of the mixing box 64 and into
the interior of the
burner box 66 via the plate perforations 124 to form further mixed flows 126
of the fuel/air
mixture that in turn are drawn forwardly into the interiors of the burner
cones 106. The
flows 126 of fuellair mixture entering the burner cones 106 are combusted to
create at the
burner cones 106 a spaced series of individual flames 128 that are
interdigitated with the
imperforate sections 86 of the rear wall 74 of the heat exchanger housing 68
and enter the
heat exchanger tube inlets 80.
Referring now to FIGS. 3 and 7, flames 128 are drawn forwardly through the
heat
exchanger tubes 78 while air 130 (or another type of fluid as the case may be)
is suitably
flowed externally across the heat exchanger tubes 78, receives combustion heat
therefrom,
and is discharged from the heating appliance 60 as heated air. This heat
transfer from the
heat exchanger tubes 78 to the air 130 cools the hot combustion gases created
within the heat
exchanger tubes 78, with the cooled combustion gases 132 entering the interior
of the
collector box 70 for discharge from the collector box 70 to a suitable flue
(not shown) by the
draft inducer fan 88.
The use of the specially designed multi-cone burner assembly 90 provides
several
advantages over the conventional single elongated flat burner 32 shown in FIG.
1, or a
laterally curved version thereof. For example, as can be seen by comparing
FIG. 3 to FIG. 1,
the flame pattern generated by the multi-cone burner assembly 90 of the
present invention is
defined by a spaced series of individual flames 128 that directly enter the
heat exchanger
tubes 78 without appreciably extending across the imperforate portions 86 of
the heat
exchange housing wall 74, as compared to the blanketing of the corresponding
imperforate
wall areas 28 by the single extended flame pattern 42 generated by the
conventional flat
burner 32 shown in FIG. 1. This feature of the present invention reduces the
inefficiency
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caused in the FIG. 1 system by undesirably transferring a substantial portion
of the generated
combustion heat to the burner box 12 instead of to the hcat exchanger tubes
22.
Moreover, the reduction of combustion heat transfer to the burner box 66
diminishes
the potential damage to other components of the heating appliance 60 due to
combustion heat
transferred thereto. Additionally, the cone burners 106 of the present
invention, due to their
hollow, forwardly projecting configurations, are substantially more
dimensionally stable
when being fired than the conventional flat burner 32 shown in FIG. 1 which
may tend to
bow forwardly to its dotted line position during firing, thereby creating
undesirable
operational noise. This operational noise is substantially reduced, if not
entirely eliminated,
in the burner assembly 90 of the present invention.
The forward extension of the hollow burner cones 106 beyond their supporting
structure increases the total active burner surface beyond that of a
corresponding number of
flat circular burners used in place of the cone burners 106. Accordingly the
cone burners 106
may be sized to provide generally the same overall burner area of a
corresponding single flat
burner (such as the flat burner 32 in FIGS. 1 and 2), thereby providing the
cone burners 106
with operational temperatures similar to that of the single flat burner 32.
While the burners 106 shown in FIGS. 3-6 are illustratively of hollow conical
configurations, the present invention is not limited to conical
configurations, and a variety of
other hollow, forwardly projecting burner configurations may be utilized if
desired without
departing from principles of the present invention. By way of non-limiting
example, an
alternate embodiment 90a of the previously described burner assembly 90 is
shown in FIG. 8.
For ease in comparing the two burner assemblies, components in the burner
assembly 90a
similar to those in burner assembly 90 have been given identical reference
numerals to which
the subscripts "a" have been appended.
With reference now to FIG. 8, the burner assembly 90a representatively has
five
spaced apart hollow, generally dome-shaped metal mesh burners 106a extending
through
spaced apart circular openings (not visible in FIG. 8) in the metal support
plate 92a and
projecting forwardly from its front side 98a. The dome-shaped burners 106a are
interconnected by metal mesh flame carryover sections 114a disposed in slots
(not visible in
FIG. 8) in the support plate 92a. The igniter 112a is representatively
disposed between the
two rightmost burners 106a and is operative to create the spaced apart
individual burner
flames 128a from the pre-mixed flows 126a of fuel and air sequentially passing
forwardly
through the mounting frame 96a, the perforate backing member 94a, the circular
support
plate holes (not visible in FIG. 8) and into the interiors of the burners
106a.
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The foregoing detailed description is to be clearly understood as being given
by way
of illustration and example only, the spirit and scope of the present
invention being limited
solely by the appended claims.
