U.S. patent application number 13/047714 was filed with the patent office on 2011-09-15 for hybrid wood burning fireplace assembly.
Invention is credited to Alan R. Atemboski, Jeremy Halston, Russell A. McBrian, Kurt W.F. Rumens.
Application Number | 20110220090 13/047714 |
Document ID | / |
Family ID | 44558750 |
Filed Date | 2011-09-15 |
United States Patent
Application |
20110220090 |
Kind Code |
A1 |
Atemboski; Alan R. ; et
al. |
September 15, 2011 |
HYBRID WOOD BURNING FIREPLACE ASSEMBLY
Abstract
A hybrid wood-burning fireplace assembly configured for burning
wood-based fuel, wherein the burning generates combustion exhaust.
The assembly comprising a fire box having an interior area, a
baffle in the interior area defining lower and upper combustion
chambers relative to the baffle. The upper combustion chamber has
an upper exhaust passageway between baffle and the top portion of
the firebox. A secondary combustion airway has air outlets in the
firebox that direct the secondary combustion air adjacent to the
baffle to mix with the exhaust for non-catalytic secondary
combustion of the exhaust before the exhaust flows through the
upper exhaust passageway. A catalytic combustion unit is positioned
above the baffle and across the upper exhaust passageway, whereby
the exhaust will pass through the catalytic combustion unit after
the non-catalytic secondary combustion of the exhaust and before
the exhaust exits the upper combustion chamber through the upper
exhaust passageway.
Inventors: |
Atemboski; Alan R.; (Renton,
WA) ; Rumens; Kurt W.F.; (Kirkland, WA) ;
McBrian; Russell A.; (Snohomish, WA) ; Halston;
Jeremy; (Lynnwood, WA) |
Family ID: |
44558750 |
Appl. No.: |
13/047714 |
Filed: |
March 14, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61313678 |
Mar 12, 2010 |
|
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|
Current U.S.
Class: |
126/500 |
Current CPC
Class: |
F24B 1/026 20130101;
F24B 1/006 20130101; F24B 1/19 20130101; F24B 13/00 20130101; F24B
9/006 20130101; F23L 9/00 20130101; F23J 15/02 20130101; F24B
1/1902 20130101; F24B 1/181 20130101; F24B 1/192 20130101 |
Class at
Publication: |
126/500 |
International
Class: |
F24B 1/19 20060101
F24B001/19 |
Claims
1. A hybrid fireplace assembly, comprising: a fire box with an
interior area configured to contain a combustible fuel that will
burn and generate exhaust, the firebox having a front wall, a back
wall, sidewalls, a base plate, a top portion, and an exhaust
outlet; a baffle connected to the firebox and disposed in the
interior area to define a lower combustion chamber below the baffle
and an upper combustion chamber above the baffle, the lower
combustion chamber being sized and shaped to contain at least a
portion of the fire from burning combustible fuel, the upper
combustion chamber having an upper exhaust passageway between
baffle and the top portion of the firebox; a primary combustion air
passageway configured to carry primary combustion air to the lower
combustion chamber, the primary combustion air passageway having an
inlet that receives air therein for primary combustion and having
at least one outlet in the firebox that directs primary combustion
air toward the fire in the lower combustion chamber; a secondary
combustion air passageway configured to carry secondary combustion
air into the firebox, the secondary combustion air passageway
having an inlet that receives air therein for secondary combustion
of at least portions of exhaust from the burning of the combustible
fuel in the lower combustion chamber, the secondary combustion air
passageway having air outlets in the firebox that directs the
secondary combustion air adjacent to the baffle to mix with the
exhaust for non-catalytic secondary combustion of the exhaust
before the exhaust flows through the upper exhaust passageway; and
a catalytic combustion unit positioned above the baffle and across
the upper exhaust passageway whereby the exhaust will pass through
the catalytic combustion unit after the non-catalytic secondary
combustion of the exhaust and before the exhaust exits the upper
combustion chamber through the upper exhaust passageway, the
catalytic combustion unit configured to remove combustion
byproducts from the exhaust when the exhaust passes through the
catalytic combustion unit.
2. The assembly of claim 1 wherein the baffle comprises a support
structure that supports an insulation layer that forms an upper
portion of the baffle.
3. The assembly of claim 2 wherein the insulation layer includes at
least one of firebricks, ceramic fiber and vermiculite board.
4. The assembly of claim 1 wherein the baffle is sloped relative to
the base plate.
5. The assembly of claim 1 wherein the hybrid fireplace assembly is
at least one of a wood-burning fireplace unit, wood-burning stove,
and a wood-burning fireplace insert.
6. The assembly of claim 1 wherein the secondary combustion air
passageway comprises a secondary combustion air tube positioned
below the baffle.
7. The assembly of claim 1 wherein the baffle has a leading edge
spaced apart from the firebox to define a portion of the exhaust
passageway adjacent to the leading edge of the baffle, and the
catalytic combustion unit is spaced away from the leading edge of
the baffle.
8. The assembly of claim 1 wherein the catalytic combustion unit is
a catalytic converter.
9. The assembly of claim 1 wherein the secondary combustion air
passageway is configured to facilitate the combustion of exhaust
particles in a first range of temperatures with a first level of
efficiency, and the catalytic combustion unit being configured to
provide combustion of exhaust particles in the first range of
temperatures with a second level of efficiency less than the first
level of efficiency.
10. The assembly of claim 9 wherein the secondary combustion air
passageway is configured to facilitate the combustion of exhaust
particles in a second range of temperatures greater than with a
third level of efficiency, and the catalytic combustion unit being
configured to provide combustion of exhaust particles in the range
of second temperatures with a fourth level of efficiency greater
than the third level of efficiency.
11. A hybrid wood-burning fireplace assembly configured for burning
wood-based fuel, wherein the burning generates combustion exhaust,
the assembly comprising: a fire box having an interior area, a base
portion, and a top portion with an exhaust outlet; a baffle in the
interior area defining a lower combustion chamber below the baffle
and an upper combustion chamber above the baffle, the upper
combustion chamber having an upper exhaust passageway between
baffle and the top portion of the firebox; a primary combustion
airway having an inlet that receives primary combustion air therein
and having at least one outlet in the firebox that directs the
primary combustion air to the lower combustion chamber for primary
combustion with the burning wood-based fuel; a secondary combustion
airway having an inlet that receives air therein for secondary
combustion of at least portions of exhaust from the burning
wood-based fuel in the lower combustion chamber, the secondary
combustion airway having air outlets in the firebox that directs
the secondary combustion air adjacent to the baffle to mix with the
exhaust for non-catalytic secondary combustion of the exhaust
before the exhaust flows through the upper exhaust passageway; and
a catalytic combustion unit positioned above the baffle and across
the upper exhaust passageway whereby the exhaust will pass through
the catalytic combustion unit after the non-catalytic secondary
combustion of the exhaust and before the exhaust exits the upper
combustion chamber through the upper exhaust passageway.
12. The assembly of claim 11 wherein the baffle is sloped relative
to the base plate.
13. The assembly of claim 11 wherein the baffle comprises a support
structure that supports an insulation layer that forms an upper
portion of the baffle.
14. The assembly of claim 11 wherein the hybrid wood-burning
fireplace assembly is at least one of a wood-burning fireplace
unit, wood-burning stove, and a wood-burning fireplace insert.
15. The assembly of claim 11 wherein the secondary combustion
airway comprises a plurality of secondary combustion air tubes
positioned below the baffle.
16. The assembly of claim 11 wherein the baffle has a leading edge
spaced apart from the firebox to define a portion of the exhaust
passageway adjacent to the leading edge of the baffle, and the
catalytic combustion unit is spaced away from the leading edge of
the baffle.
17. The assembly of claim 11 wherein the secondary combustion
airway is configured to facilitate the combustion of exhaust
particles in a first range of temperatures with a first level of
efficiency, and the catalytic combustion unit is configured to
provide combustion of exhaust particles in the first range of
temperatures with a second level of efficiency less than the first
level of efficiency.
18. The assembly of claim 17 wherein the secondary combustion
airway is configured to facilitate the combustion of exhaust
particles in a second range of temperatures greater than with a
third level of efficiency, and the catalytic combustion unit is
configured to provide combustion of exhaust particles in the range
of second temperatures with a fourth level of efficiency greater
than the third level of efficiency.
19. A method of reducing emissions from a wood-based fuel burning
fireplace assembly, comprising: burning a wood-based fuel in
firebox of the fireplace assembly during primary combustion of the
fuel to generate exhaust with particulates therein, the fireplace
assembly having a baffle in the firebox that divides an interior
area into an upper combustion chamber and a lower combustion
chamber, the upper combustion chamber having an upper exhaust
passageway between baffle and a top portion of the firebox;
directing secondary combustion air into the lower chamber below the
baffle for mixing with the exhaust for secondary combustion of the
exhaust in the firebox; burning particulates in the exhaust in the
secondary combustion adjacent to the baffle; passing the exhaust
after the secondary combustion through a catalytic combustion unit
positioned across an exhaust passageway in the upper combustion
chamber above the baffle, wherein passing the exhaust through the
catalytic combustion unit removed additional particulates from the
exhaust after the secondary combustion; and directing the exhaust
out of the firebox after the exhaust exits the catalytic combustion
unit.
20. The method of claim 19 wherein directing secondary combustion
air into the lower combustion chamber below the baffle includes
passing the secondary combustion air through a secondary combustion
air tube and directing the air through outlets in the secondary
combustion air tube into the lower combustion chamber below the
baffle for mixing with the exhaust for secondary combustion of the
exhaust in the firebox.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a non-provisional patent application
that claims priority to and claims the benefit of U.S. Provisional
Patent Application No. 61/313,678, titled HYBRID WOOD BURNING
FIREPLACE ASSEMBLY and filed Mar. 12, 2010, the disclosure of which
is incorporated by reference in its entirety by reference
thereto.
TECHNICAL FIELD
[0002] The present invention relates to fireplace assemblies, and
more particularly to wood burning fireplace assemblies, including
fireplace units, fireplace inserts and stoves and associated
methods.
BACKGROUND
[0003] Conventional fireplace assemblies are configured to burn a
selected fuel, such as wood, pellets, gas, etc., and this burning
of the fuel results in exhaust that contains combustion
bi-products. As an example, a wood burning fireplace assembly, such
as a stove or insert, is used to burn wood in the firebox, which
creates combustion bi-products (solid and gaseous) that exit the
firebox as exhaust. Technology has been developed to reduce or
otherwise control the emissions from the fireplace assemblies,
including catalytic fireplace assemblies and non-catalytic
fireplace assemblies that provide for secondary combustion of the
exhaust to reduce the emissions.
[0004] Conventional catalytic fireplace assemblies having catalytic
converters are generally effective in achieving low particulate
emissions at low temperatures, but become less effective as
temperatures rise. On the other hand, conventional non-catalytic
fireplace assemblies having secondary combustion tubes are
generally effective in causing secondary combustion of the
combustion bi-products to achieve low particulate emissions at high
temperatures, but become less effective as temperatures fall. In
both cases, a bypass damper may need to be frequently controlled
and/or other manual adjustments may need to be made in order to
regulate the rate of combustion within the fireplace assembly.
SUMMARY
[0005] The present invention provides a fireplace assembly that
overcomes drawbacks experienced in the prior art and that provide
other embodiments. At least one embodiment of the invention
provides a hybrid fireplace assembly, including a fireplace unit, a
stove or an insert, that comprises a fire box with an interior area
configured to contain a combustible fuel that will burn and
generate exhaust. The firebox has a front wall, a back wall,
sidewalls, a base plate, a top portion, and an exhaust outlet. A
baffle is connected to the firebox and disposed in the interior
area to define a lower combustion chamber below the baffle and an
upper combustion chamber above the baffle. The lower combustion
chamber is sized and shaped to contain at least a portion of the
fire from burning combustible fuel. The upper combustion chamber
has an upper exhaust passageway between baffle and the top portion
of the firebox. A primary combustion air passageway configured to
carry primary combustion air to the lower combustion chamber. The
primary combustion air passageway having an inlet that receives air
therein for primary combustion and having at least one outlet in
the firebox that directs primary combustion air toward the fire in
the lower combustion chamber. A secondary combustion air passageway
is configured to carry secondary combustion air into the firebox.
The secondary combustion air passageway has an inlet that receives
air therein for secondary combustion of at least portions of
exhaust from the burning of the combustible fuel in the lower
combustion chamber. The secondary combustion air passageway has air
outlets in the firebox that directs the secondary combustion air
adjacent to the baffle to mix with the exhaust for non-catalytic
secondary combustion of the exhaust before the exhaust flows
through the upper exhaust passageway. A catalytic combustion unit
is positioned above the baffle and across the upper exhaust
passageway whereby the exhaust will pass through the catalytic
combustion unit after the non-catalytic secondary combustion of the
exhaust and before the exhaust exits the upper combustion chamber
through the upper exhaust passageway. The catalytic combustion unit
is configured to remove combustion byproducts from the exhaust when
the exhaust passes through the catalytic combustion unit.
[0006] In one embodiment the secondary combustion air passageway is
configured to facilitate the combustion of exhaust particles in a
first range of temperatures with a first level of efficiency. The
catalytic combustion unit is configured to provide combustion of
exhaust particles in the first range of temperatures with a second
level of efficiency less than the first level of efficiency. The
secondary combustion air passageway facilitates the combustion of
exhaust particles in a second range of temperatures greater than
with a third level of efficiency, and the catalytic combustion unit
is configured to provide combustion of exhaust particles in the
range of second temperatures with a fourth level of efficiency
greater than the third level of efficiency.
[0007] Another aspect of an embodiment provides a hybrid
wood-burning fireplace assembly configured for burning wood-based
fuel, wherein the burning generates combustion exhaust. The
assembly comprising a fire box having an interior area, a base
portion, and a top portion with an exhaust outlet. A baffle is in
the interior area defining a lower combustion chamber below the
baffle and an upper combustion chamber above the baffle. The upper
combustion chamber has an upper exhaust passageway between baffle
and the top portion of the firebox. A primary combustion airway has
an inlet that receives primary combustion air therein and has at
least one outlet in the firebox that directs the primary combustion
air to the lower combustion chamber for primary combustion with the
burning wood-based fuel. A secondary combustion airway has an inlet
that receives air therein for secondary combustion of at least
portions of exhaust from the burning wood-based fuel in the lower
combustion chamber. The secondary combustion airway has air outlets
in the firebox that directs the secondary combustion air adjacent
to the baffle to mix with the exhaust for non-catalytic secondary
combustion of the exhaust before the exhaust flows through the
upper exhaust passageway. A catalytic combustion unit positioned
above the baffle and across the upper exhaust passageway whereby
the exhaust will pass through the catalytic combustion unit after
the non-catalytic secondary combustion of the exhaust and before
the exhaust exits the upper combustion chamber through the upper
exhaust passageway.
[0008] Another aspect provides a method of reducing emissions from
a wood-based fuel burning fireplace assembly. The method comprises
burning a wood-based fuel in firebox of the fireplace assembly
during primary combustion of the fuel to generate exhaust with
particulates therein. The fireplace assembly has a baffle in the
firebox that divides an interior area into an upper combustion
chamber and a lower combustion chamber. The upper combustion
chamber has an upper exhaust passageway between baffle and a top
portion of the firebox. The method includes directing secondary
combustion air into the lower chamber below the baffle for mixing
with the exhaust for secondary combustion of the exhaust in the
firebox, burning particulates in the exhaust in the secondary
combustion adjacent to the baffle, and passing the exhaust after
the secondary combustion through a catalytic combustion unit
positioned across an exhaust passageway in the upper combustion
chamber above the baffle, wherein passing the exhaust through the
catalytic combustion unit removed additional particulates from the
exhaust after the secondary combustion. The method can also include
directing the exhaust out of the firebox after the exhaust exits
the catalytic combustion unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is an isometric view of a hybrid wood burning
fireplace assembly in accordance with an embodiment of the present
invention.
[0010] FIG. 2 is an enlarged front isometric view of the hybrid
fireplace assembly of FIG. 1 showing a hybrid combustion
system.
[0011] FIG. 3 is an enlarged partial front isometric view of the
hybrid fireplace assembly of FIG. 1 showing the secondary
combustion tubes in the firebox of the assembly.
[0012] FIG. 4 is an enlarged, partial isometric view of the
catalytic converter of the hybrid combustion system of FIG. 2.
[0013] FIG. 5 is an enlarged, partial top isometric view of the
fireplace assembly of FIG. 1 showing a portion of the catalytic
converter and a bypass damper visible through an exhaust aperture
when the exhaust flue is removed.
DETAILED DESCRIPTION
[0014] A hybrid fireplace assembly is described in detail herein in
accordance with embodiments and aspects of the present invention.
In one embodiment, a hybrid wood-burning fireplace assembly
includes a hybrid combustion system having both catalytic and
non-catalytic components. A non-catalytic component comprises one
or more secondary combustion tubes that remove particulate
emissions, such as carbon monoxide, from the exhaust gases
generated by a wood burning fire. A catalytic component comprises a
catalytic converter that removes additional particulate emissions
from the exhaust gases before the gases are emitted from the
fireplace assembly. Among other benefits, the hybrid fireplace
assembly described herein improves heating efficiency and achieves
low particulate emissions over a wide range of temperatures.
[0015] The hybrid fireplace assembly described herein employs both
a catalytic converter and secondary combustion tubes. At higher
temperatures, the secondary combustion tubes are more effective at
reducing particulate emissions, and the catalytic converter is used
relatively less. At lower temperatures, the secondary combustion
tubes are less effective at reducing particulate emissions, and the
catalytic converter is used relatively more. The hybrid fireplace
assembly provides a user-friendly, self-regulating system that
accommodates temperature changes, without requiring excessive
control of a bypass damper, opening and closing a door of the
fireplace assembly, and/or making other manual adjustments.
[0016] The fireplace assembly described herein may be used in
combination with wood burning fireplaces, stoves, and fireplace
inserts. In the following description, numerous specific details
are discussed to provide a thorough and enabling description for
embodiments of the disclosure. One skilled in the relevant art,
however, will recognize that the disclosure can be practiced
without one or more of the specific details. In other instances,
well-known structures or operations are not shown, or are not
described in detail, to avoid obscuring aspects of the disclosure.
In general, alternatives and alternate embodiments described herein
are substantially similar to the previously described embodiments,
and common elements are identified by the same reference
numbers.
[0017] FIG. 1 is a front isometric view of a hybrid fireplace
assembly 100 in accordance with an embodiment of the present
invention. The hybrid fireplace assembly 100 includes a firebox 105
for containing a wood burning fire. The firebox 105 comprises a
front wall 110, a back wall 115, a base plate 120, a top plate 125,
and sidewalls 130.
[0018] The front wall 110 of the firebox 105 includes an opening
135 for receiving wood. The opening 135 receives a door 140 mounted
by hinges 145 (identified individually as a first hinge 145a and a
second hinge 145b) coupled to the front wall 110. The door 140 has
a glass window 150 or the like that allows the interior of the
firebox 105 to be observed while the door is closed. A door seal
155 extending about the inside of the door 140 engages with the
front panel 110 to provide an airtight seal when the door is
closed. The door 140 also includes a handle 160 that can be rotated
to latch and unlatch the door.
[0019] In the illustrated embodiment, the hybrid fireplace assembly
100 also includes a flue adapter 165 configured to receive a direct
vent chimney. The flue adapter 165 can be located on the top, back,
or side of the hybrid fireplace assembly 100. In an alternative
embodiment, the hybrid fireplace assembly 100 includes two
separate, non-concentric flues (e.g., an exhaust flue and an air
intake flue) connected to the top, back, or side of the
assembly.
[0020] When the hybrid fireplace assembly 100 is operated, wood is
placed within the firebox 105 adjacent to the base plate 120 and
ignited in a usual manner. As the fire burns, it produces exhaust
gases that contain particulate emissions, such as carbon monoxide,
unburned hydrocarbons, and/or other gases that may be undesirable,
such as for the environment. The exhaust gases are processed by a
hybrid combustion system that includes a series of combustion
stages--primary, secondary, tertiary, and catalytic. At each stage
of combustion, particulate emissions are removed from the exhaust
gases, so that by the time the exhaust gases reach the flue adapter
165, most of the particulate emissions have been eliminated. This
improved combustion of the wood fuel and the particulate emissions
results in more heat produced by the same amount of wood.
[0021] FIG. 2 is an enlarged front isometric view of the hybrid
fireplace assembly 100 of FIG. 1 showing a hybrid combustion
system. The firebox 105 includes a baffle 205 extending between the
sidewalls 130 from the back wall 115 toward the front wall 110, and
terminating in a leading edge 220 before it reaches the front wall
110. The baffle 205 separates the firebox into a lower combustion
chamber 210 between the baffle and the base plate 120, and an upper
combustion chamber 215 between the baffle and the top plate 125. In
the illustrated embodiment, the baffle is configured so the leading
edge 220 is spaced apart from the front wall to provide an
exhaust/air flow path from under the baffle, up and around the
leading edge between the baffle and the front wall 110 to above the
baffle 205. In other embodiments, the baffle can be configured in
another position or arrangement, such as to provide the leading
edge adjacent to and spaced apart from, as an example, the rear
wall or a side wall, so that the exhaust/air flow path is between
the baffle's leading edge and the adjacent, spaced apart rear wall
or side wall.
[0022] The upper combustion chamber 215 includes a catalytic
component of the hybrid combustion system--a catalytic converter
245. The lower combustion chamber 210 includes a non-catalytic
component of the hybrid combustion system--one or more secondary
combustion air passageways, such as secondary combustion air tubes
230 affixed to the underside of the baffle 205.
[0023] In the illustrated embodiment, the baffle 205 comprises a
metal plate having a top insulation layer. The insulation layer can
comprise firebricks, ceramic fiber, vermiculite board, or the like.
In other embodiments, the baffle 205 comprises one or more
firebricks mounted on brackets. The insulated baffle 205 retains
heat in the lower combustion chamber 210 below the baffle, in order
to facilitate combustion at the secondary combustion tubes 230.
[0024] The location and thickness of the baffle 205 are determined
based at least in part on the space needed above the baffle for the
catalytic converter 245. For example, the size of the hybrid
fireplace assembly 100 can affect a minimum size and/or surface
area needed for optimum performance of the catalytic converter 245.
A small hybrid fireplace assembly 100, which generates relatively
fewer particulate emissions, may require a relatively small
catalytic converter 245. Accordingly, the baffle 205 may be
positioned relatively closer to the top plate 125, and/or the
baffle may be relatively thicker. A large hybrid fireplace assembly
100, which generates relatively more particulate emissions, may
require a relatively large catalytic converter 245. Accordingly,
the baffle 205 may be positioned relatively further away from the
top plate 125, and/or the baffle may be relatively thinner.
[0025] In some embodiments, the baffle 205 is substantially
horizontal and parallel with the base plate 120. In other
embodiments, the baffle 205 is sloped, such as upward from the rear
wall 115 toward the front wall 110, such that the leading edge 220
of the baffle is higher than a rear edge of the baffle that
intersects with the rear wall. The degree of slope is determined
based at least in part on the size of the firebox 105. For example,
a relatively large firebox 105 can generally accommodate a sloped
baffle 205, while a relatively small firebox may be better suited
for a horizontal baffle. The slope of the baffle 205 (or lack
thereof) can affect the speed of the flow of a secondary air supply
along the underside of the baffle, described in additional detail
herein. A horizontal baffle 205 (i.e., with zero or approximately
zero degree slope) can cause the secondary air supply to flow at a
relatively slow rate. As the degree of slope of the baffle 205
increases, the secondary air supply is directed increasingly
upward, and thus flows at a relatively faster rate.
[0026] Primary and secondary combustion occur in the lower
combustion chamber 210 of the firebox 105. Primary combustion
occurs adjacent to the base plate 120, as the burning wood comes
into contact with a primary air supply and generates exhaust gases.
The primary air supply can be distributed into the firebox 105 from
a variety of locations, such as a primary air intake aperture 225
(identified individually as first primary air intake aperture 225a
and second primary air intake aperture 225b) located in the base
plate 120. The primary air intake aperture(s) 225 are fluidly
coupled to a base chamber 170 on the underside of the base plate
120 that freely provides the primary air supply to the aperture(s).
The primary air supply mixes with the exhaust gases adjacent to the
base plate 120 and upstream of the secondary combustion tubes 230,
removing particulate emissions from the exhaust gases.
[0027] In some embodiments, the primary air supply is spaced apart
from the firebox 105, such that the primary air supply is not
heated substantially by the firebox prior to entry via the primary
air intake aperture(s) 225. For example, the base chamber 170 may
be located apart from the firebox 105, and/or an insulation layer
between the firebox and the base chamber may reduce the flow of
heat from the firebox to the base chamber. Such an arrangement
enables delivery of a maximum concentration of oxygen (O.sub.2) to
the base plate 120 for primary combustion.
[0028] In some embodiments, a primary air control (not shown) is
provided to allow a user to selectively control the flow of the
primary air supply. The primary air control can extend along the
underside of the firebox 105 through a control opening 250
(identified individually as a first control opening 250a and a
second control opening 250b). The primary air control can be opened
completely to allow for free flow of the primary air supply through
the primary air intake aperture(s) 225, or the primary air control
can be progressively closed to reduce the flow of the primary air
supply through the primary air intake aperture(s).
[0029] Secondary combustion also occurs in the lower combustion
chamber 210. Secondary combustion occurs adjacent to one or more
secondary combustion tubes 230 that carry a secondary air supply.
FIG. 3 is an enlarged front isometric view of the hybrid fireplace
assembly 100 of FIG. 1 showing the secondary combustion tubes 230.
In the illustrated embodiment, the hybrid fireplace assembly 100
includes four secondary combustion tubes 230, 320, 325, and 330.
The number, size, and position of the secondary combustion tubes
230, 320, 325, and 330 can vary based on, as an example, the size
of the firebox 105, the desired oxygen (O.sub.2) level for mixture
with the exhaust gases, and/or a variety of other factors.
[0030] The secondary combustion tubes 230, 320, 325, and 330 are
mounted to common side chambers 305 (only one side chamber shown)
by fasteners 310 (only one fastener shown). The side chambers 305
receive the open ends of the secondary combustion tubes 230, 320,
325, and 330, as illustrated by the broken line 315. The side
chambers 305 are fluidly coupled to a secondary air supply, and
freely provide this secondary air supply to the secondary
combustion tubes 230, 320, 325, and 330. In some embodiments, the
secondary air supply is warmed to within a particular temperature
range in order to facilitate more efficient secondary
combustion.
[0031] Each of the secondary combustion tubes 230 includes a
plurality of air distribution holes 235 along the length of the
tube that distribute the secondary air supply into the firebox 105.
In some embodiments, the air distribution holes 235 are oriented at
a selected angle relative to the baffle, such as substantially
parallel or horizontally. The air distribution holes 235 direct the
secondary air supply into the firebox 105 toward the leading edge
220 of the baffle 205. Such an arrangement of air distribution
holes 235 helps to reduce or avoid turbulence between the secondary
air supply and the burning fire, and allows the secondary air
supply to blend with the flow of exhaust gases passing forwardly
under the baffle 205, while maintaining an active flame in the
firebox 105.
[0032] In the illustrated embodiment, each of the secondary
combustion tubes 230, 320, 325, and 330 has air distribution holes
235 that are similarly spaced, sized, and oriented. In other
embodiments, each of the secondary combustion tubes 230, 320, 325,
and 330 has air distribution holes 235 that are differently spaced,
sized, and/or oriented. The spacing, size, and/or orientation of
the air distribution holes 235 can be based on the size of the
firebox, the desired oxygen (O.sub.2) level for mixture with the
exhaust gases, and/or a variety of other factors. In the
illustrated embodiments, the air distribution holes are shown below
the baffle. In other embodiments, one or more secondary combustion
tube 230 can be positioned, configured, or oriented to that a
plurality of the air distribution holes are positioned above a
portion of the baffle, e.g., above the leading edge area of the
baffle, but still upstream of the catalytic converter discussed
above. This arrangement can provide for an air flow above the
baffle that mixes with the exhaust gases before passing through the
catalytic converter.
[0033] As the secondary air supply is distributed into the firebox
105 by the air distribution holes 235, the secondary air supply
mixes with the exhaust gases downstream of primary combustion and
upstream of the leading edge 220 of the baffle 205, removing
additional particulate emissions from the exhaust gases. The
secondary combustion tubes 230, 320, 325, and 330 are more
effective at reducing particulate emissions at higher temperatures.
Accordingly, fewer particulate emissions remain to be removed
during the tertiary and catalytic combustion stages, described
herein. At lower temperatures, the secondary combustion tubes 230,
320, 325, and 330 are less effective at reducing particulate
emissions. Accordingly, more particulate emissions remain to be
removed during the tertiary and catalytic combustion stages.
[0034] Conventional secondary combustion tubes used by existing
non-catalytic fireplace assemblies are not used in the hybrid wood
burning fireplace assembly 100 described herein. For example, to
obtain a desired level of particulate emissions at high
temperatures, secondary combustion tubes with a conventional size,
orientation, hole distribution, etc., generate a high level of
excess air. If these conventional secondary combustion tubes were
to be combined with a catalytic converter, the conventional tubes
would provide an excessive flow of air (including too much oxygen)
around the baffle and through the catalytic converter, resulting in
ineffective use of the catalytic converter. Accordingly, the
secondary combustion tubes in the hybrid wood burning fireplace
assembly 100 described herein must be configured with a desired
size, spacing, and/or orientation of the air distribution holes of
the tubes, based at least in part upon the configuration of the
firebox, the catalytic converter, and other factors.
[0035] In some embodiments, secondary combustion includes a rear
air supply in addition to the secondary air supply. In the
illustrated embodiment, a back wall chamber 340 mounted to the back
wall 115 is fluidly coupled to a rear air supply. The back wall
chamber 340 includes a plurality of rear air distribution holes
335. Like the air distribution holes 235 of the secondary
combustion tubes 230, the rear air distribution holes 335 in the
illustrated embodiment are spaced substantially horizontally, such
that they direct a rear air supply into the firebox 105 toward the
leading edge of the baffle 205. This arrangement of rear air
distribution holes 335 helps to reduce or avoid turbulence between
the rear air supply and the burning fire, allowing the rear air
supply to blend with the flow of exhaust gases passing forwardly
under the baffle 205, while maintaining an active flame in the
firebox 105.
[0036] Like the air distribution holes 235 of the secondary
combustion tubes 230, the rear air distribution holes 335 can be
evenly spaced across the surface of the back wall chamber 340. In
other embodiments, including the illustrated embodiment, the rear
air distribution holes 335 are variably spaced across the surface
of the back wall chamber 340. Such variations in the placement of
the rear air distribution holes 340 can be based on the size of the
firebox, the desired oxygen (O.sub.2) level for mixture with the
exhaust gases, and/or a variety of other factors. Alternatively or
additionally, variations can be made in the size and orientation of
the rear distribution air holes 340 based on similar factors.
[0037] The presence or absence of a back wall chamber 340 can be
determined based on the size of the firebox, the desired oxygen
(O.sub.2) level for mixture with the exhaust gases, and/or a
variety of other factors. For example, a small hybrid fireplace
assembly 100, which generates relatively fewer particulate
emissions, requires a smaller overall air supply for combustion of
the particulate emissions. Accordingly, the back wall chamber 340
may have relatively fewer rear air distribution holes 355, or the
back wall chamber may be omitted altogether. A large hybrid
fireplace assembly 100, which generates relatively more particulate
emissions, typically requires a larger overall air supply for
combustion of the particulate emissions. Accordingly, the back wall
chamber 340 may have more rear air distribution holes 340 and/or
larger rear air distribution holes 355.
[0038] Returning to FIG. 2, tertiary combustion takes place
downstream of the secondary combustion tubes 230 and upstream of
the catalytic converter 245. The leading edge 220 of the baffle 205
forms an exhaust passageway 240 adjacent to the front wall 110 of
the firebox 105. The exhaust gases from the burning fire are
directed from the lower combustion chamber 210, through the exhaust
passageway 240, and into the upper combustion chamber 215. A
tertiary air supply mixes with the exhaust gases in the exhaust
passageway 240, removing additional particulate emissions.
[0039] The tertiary air supply can be distributed into the firebox
105 from a variety of locations, such as an air wash passageway 255
adjacent to the interior of the front wall 110 and near the top of
the front wall. The tertiary air supply in the illustrated
embodiment is directed downwardly through the exhaust passageway
240 and across the face of the window 150. In addition to removing
particulate emissions from the exhaust gases, the tertiary air
supply can help cool and/or clean the surface of the window
150.
[0040] As previously described, the hybrid combustion system
includes both catalytic and non-catalytic components. Once the
exhaust gases have passed through the primary, secondary, and
tertiary combustion stages, the exhaust gases enter the catalytic
combustion stage. Catalytic combustion takes place in the upper
combustion chamber 215. As previously described, the catalytic
converter 245 is mounted above the baffle 205 so that all of the
exhaust gases will pass through the catalytic converter 245 before
entering the exhaust flue. The catalytic converter 245 is
positioned rearward of the leading edge 220 of the baffle 205, such
that the exhaust gases mix with sufficient air during secondary and
tertiary combustion to achieve desired oxygen (O.sub.2) levels
before entering the catalytic converter. In the illustrated
embodiment, the desired oxygen level is within in the range of
5-6%, while other embodiments, the desired oxygen level falls
within a different range. The desired oxygen level may be based in
part on the size of the hybrid fireplace assembly 100, in addition
to other factors. If the catalytic converter 245 is positioned too
close to the leading edge 220 of the baffle 205, the exhaust gases
may not mix with enough air during secondary and tertiary
combustion, causing the catalytic converter to be used
ineffectively.
[0041] FIG. 4 is a front isometric view of the catalytic converter
245 of FIG. 2. The catalytic converter 245 is a honeycomb 410,
steel wool 405, or other base or matrix structure coated with
selected metals, such as precious metals or the like. The surface
properties of these metals are such that particulate emissions that
are too cool to burn on their own will ignite when they react with
the catalytic converter 245. In other words, the catalytic
converter 245 provides a reaction with the components in the
exhaust gas, such as the carbon monoxide, that causes portions of
the catalytic converter to heat up to a temperature so as to cause
the particulate emissions to burn and be substantially removed from
the exhaust. In the illustrated embodiment, the catalytic converter
245 is serviceable, and may be removed for repair and/or
replacement as necessary.
[0042] The catalytic converter 245 reacts with the exhaust gases
downstream of tertiary combustion and upstream of the flue adapter
165, removing additional particulate emissions from the exhaust
gases before these gases reach the flue adapter 165. As previously
discussed, at higher temperatures, the secondary combustion tubes
230, 320, 325, and 330 are more effective at reducing particulate
emissions, and the catalytic converter 245 is used relatively less.
At lower temperatures, the secondary combustion tubes 230, 320,
325, and 330 are less effective at reducing particulate emissions,
and the catalytic converter 245 is used relatively more. Regardless
of the temperature, the catalytic converter 245 is configured to
allow sufficient air to flow therethrough in order to maintain an
active flame in the firebox 105.
[0043] The catalytic converter 245 can be engaged and disengaged
via a bypass damper. FIG. 5 is a top isometric view of the
fireplace assembly 100 of FIG. 1 showing a bypass damper 505. In
some embodiments, a damper control (not shown) is provided to allow
the user to selectively open and close the bypass damper 505. The
damper control can extend along the top plate 125 through a damper
control opening 510. When the bypass damper 505 is closed, the
exhaust gases generated by the burning fire must flow through the
catalytic converter 245 before reaching the flue adapter 165. When
the bypass damper is open, the exhaust gases may flow around the
catalytic converter 245 and reach the flue adapter 165 without
being processed by the catalytic converter. In the illustrated
embodiment, the bypass damper 505 is downstream of the catalytic
converter 245. However, in other embodiments, the bypass damper 505
is located upstream of the catalytic converter 245.
[0044] The hybrid fireplace assembly 100 described herein allows
for the use of a thinner catalytic converter 245 than those used in
conventional catalytic fireplace assemblies. Conventional catalytic
fireplace assemblies (which do not include non-catalytic secondary
combustion tubes 230, 320, 325, and 330) generally have catalytic
converters that are 2-4'' thick, depending on the size of the
firebox. Because the hybrid fireplace assembly 100 described herein
reduces particulate emissions during primary, secondary, and
tertiary combustion, there are fewer particulate emissions to be
processed by the catalytic converter 245. Accordingly, the hybrid
fireplace assembly 100 allows for use of a thinner catalytic
converter 245. In some embodiments, the catalytic converter 245
employed by the hybrid fireplace assembly 100 is 1-2'' thick,
depending on the size of the firebox 105. That is, in some
embodiments, the reduction in the size of the catalytic converter
245 over those used by conventional catalytic fireplace assemblies
is approximately fifty percent. Among other benefits, the reduction
in the size of the catalytic converter 245 lowers the cost of the
catalytic converter, and thus the cost of the fireplace assembly
100.
[0045] The hybrid fireplace assembly 100 described herein achieves
better particulate emission levels than both conventional catalytic
fireplace assemblies and conventional non-catalytic fireplace
assemblies having secondary combustion tubes. A standard catalytic
fireplace assembly achieves a maximum particulate emission level of
approximately 2.5 grams/hour, while a standard non-catalytic
fireplace assembly having secondary combustion tubes achieves a
maximum particulate emission level of approximately 4.5 grams/hour.
In contrast, the hybrid fireplace assembly 100 described herein
achieves a maximum particulate emission level of approximately 1.0
grams/hour.
[0046] The above description of illustrated embodiments of the
disclosure is not intended to be exhaustive or to limit the
invention to the precise form disclosed. While specific embodiments
of, and examples for, the disclosure are described herein for
illustrative purposes, various equivalent modifications are
possible within the scope of the disclosure, as those skilled in
the relevant art will recognize. The teachings of the disclosure
herein can be applied to other wood burning fireplace assemblies,
not necessarily the assemblies described above.
[0047] While certain aspects of the disclosure are presented below
in certain claim forms, the inventors contemplate the various
aspects of the disclosure in any number of claim forms. In general,
in the following claims, the terms used should not be construed to
limit the disclosure to the specific embodiments disclosed in the
specification and claims, but should be construed to include all
components and methods of manufacturing the components, in
accordance with the claims. Accordingly, the disclosure is not
limited by the description, but instead the scope of the disclosure
is to be determined entirely by the claims.
[0048] From the foregoing, it will be appreciated that specific
embodiments of the invention have been described herein for
purposes of illustration, but that various modifications may be
made without deviating from the spirit and scope of the invention.
Accordingly, the invention is not limited except as by the appended
claims.
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