CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to Provisional Application No. 61/503,422, filed Jun. 30, 2011, which is herein incorporated by reference in its entirety.
BACKGROUND Various pellet furnace, or pellet stove technologies have been employed to burn pelletized biomass or non-pelletized biomass (e.g., compressed wood pellets or kernals of corn). Various challenges face pellet stove manufacturers and users, including effective biomass fuel delivery of and efficient burning thereof.
SUMMARY Some embodiments relate to a pellet furnace that includes a pellet feed assembly, a conveyor assembly, a combustion blower assembly, a baffle assembly, and a control system. The pellet feed assembly includes a distribution tray having a plurality of distribution pins for spreading a mass of pellets over a desired area. The conveyor assembly includes an air distribution plenum and a plurality of grate plates for maintaining a deposited mass of pellets and receiving air from air distribution plenum to facilitate primary combustion of the mass of pellets. The baffle assembly is configured to facilitate secondary combustion of the exhaust air from primary combustion at the conveyor assembly and defines a lower secondary combustion chamber including a plurality of flow deflectors and secondary air injectors, the lower secondary combustion chamber being connected to an upper secondary combustion chamber including a plurality of flow deflectors. The baffle assembly is formed of a ceramic material, such as fused silicate material, for example. The control system is optionally pre-programmed and/or programmable with heat/temperature settings on a day by day heat demand for a complete livestock growth cycle (e.g., a chick growth cycle), or for other heating cycles as desired.
While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a pellet furnace, according to some embodiments.
FIG. 2 is a front view of the pellet furnace of FIG. 1, according to some embodiments.
FIG. 3 is a back view of the pellet furnace of FIG. 1, according to some embodiments.
FIG. 4 is a side view of the pellet furnace of FIG. 1, according to some embodiments.
FIG. 5 is a back view of an engine assembly of the pellet furnace of FIG. 1, according to some embodiments.
FIG. 6 is a side view of the engine assembly of FIG. 4, according to some embodiments.
FIG. 7 is a top view of the engine assembly of FIG. 4 with a baffle assembly removed, according to some embodiments.
FIG. 8 is a sectional view along line 8-8 of FIG. 6, according to some embodiments.
FIG. 9 is a schematic view of a distribution tray pin pattern of the engine assembly of FIG. 4, according to some embodiments.
FIG. 10 is a perspective view of a baffle assembly of the pellet furnace of FIG. 1, according to some embodiments.
FIG. 11 is a disassembled view of components of the baffle assembly of FIG. 10, according to some embodiments.
FIG. 12 is a top view of the baffle assembly of FIG. 10, according to some embodiments.
FIG. 13 is a side view of the baffle assembly of FIG. 10, according to some embodiments.
FIG. 14 is a sectional view of the baffle assembly taken along line 14-14 of FIG. 12, according to some embodiments.
FIG. 15 is a perspective view of an air baffle of the baffle assembly of FIG. 9, according to some embodiments.
FIG. 16 is a back view of the air baffle of FIG. 15, according to some embodiments.
FIG. 17 is a side view of the air baffle of FIG. 15, according to some embodiments.
FIG. 18 is a top view of the air baffle of FIG. 15, according to some embodiments.
FIG. 19 is a bottom view of the air baffle of FIG. 15, according to some embodiments.
FIG. 20 is a left side view of a blower assembly of the pellet furnace of FIG. 1, according to some embodiments.
FIG. 21 is a front view of the blower assembly of FIG. 20, according to some embodiments.
FIG. 22 is a right side view of the blower assembly of FIG. 20, according to some embodiments.
FIG. 23 is a medial sectional view of the pellet furnace of FIG. 1, according to some embodiments.
DETAILED DESCRIPTION Various embodiments relate to pellet furnaces that burn pelletized or other biomass materials, and more particular, to a high energy output pellet furnace of a relatively compact size and high efficiency. In some embodiments, the pellet furnace is employed to heat confined animal feeding operations and green houses, such as chicken growing farms. Use of the pellet furnace in livestock applications is intended to improve animal health and livability, improve animal growth rate, and reduce ammonia levels by reducing air moisture levels, for example. While various embodiments are described in association with pelletized biomass, it should be understood that use of non-pelletized biomass, such as corn, is contemplated.
FIGS. 1, 2, 3, and 4 are perspective, front, back, and side views, respectively, of a pellet furnace 10, according to some embodiments. As shown, the pellet furnace 10 includes an engine assembly 20, a blower assembly 22, and a control system 24. The engine assembly 20 generally receives pellets (not shown) or other biomass (e.g., corn), ignites and maintains primary biomass combustion, or primary combustion, and also generates secondary biomass combustion, or secondary combustion. The blower assembly 22 receives heated exhaust products, or exhaust air Ae, from the engine assembly 20 and, through use of heat exchange, delivers heat from the heated exhaust products into convection air being circulated through the blower assembly 22. The convection air is delivered into portions of a structure that are to be heated, or is otherwise dispensed as desired through use of a convection air distribution system (not shown) that includes ductwork, blowers, evaporators, humidifiers, UV treatment, and/or other air treatment devices as desired.
FIG. 5 is a back view and FIG. 6 is a side view of the engine assembly 20 of the pellet furnace 10, according to some embodiments. FIG. 7 is a top view and FIG. 8 is a sectional view of the engine assembly 20 taken along line 8-8 in FIG. 6, according to some embodiments. As shown in one or more of FIGS. 5-8, the engine assembly 20 includes a housing 30 maintaining a primary combustion air inlet assembly 32, an ash pan assembly 34, a temperature probe 36, a secondary combustion air inlet assembly 38, a pellet feed assembly 40, an igniter assembly 42, a conveyor assembly 44, an access door assembly 46, and a baffle assembly 48 (FIG. 10).
In some embodiments, the housing 30 is formed of sheet metal materials and includes legs, armatures, brackets, and/or other features as desired for supporting the various components of the engine assembly 20 and defines an interior burn chamber 58, or firebox (FIG. 8).
In some embodiments, the primary combustion air inlet assembly 32 includes an inlet cover 60 having one or more slots 62 or openings in fluid communication with the conveyor assembly 44. The inlet cover 60 is optionally replaced with another inlet cover having a larger or smaller slot to control the flow of combustion air into the engine assembly 20. In some embodiments, the inlet cover 60 further includes means for adjusting a size of the opening in the inlet cover 60, such as a sliding door (not shown). In some embodiments, a second air inlet assembly (not shown) is provided on an opposite side of the housing 30 as an additional inlet for combustion air.
In some embodiments, the ash pan assembly 34 includes a sliding tray 70 that is trapezoidal in transverse cross-section and is positioned underneath the conveyor assembly 44. The ash pan assembly 34 is able to be slid out from under the conveyor assembly 44 so that the ash trapped in the sliding tray 70 may be more easily cleaned on a periodic basis. In other embodiments, the engine assembly 20 includes an automatic ash disposal system (not shown), such as a motorized conveyor and/or auger for transporting waste ash from the engine assembly 20 as desired.
In some embodiments, the temperature probe 36 is adapted to provide feedback to the control system 24 relating to temperature of the burn chamber 58.
In some embodiments, the secondary combustion air inlet assembly 38 includes first and second inlet tubes 90, 92 extending into the housing 30. The first inlet tube 90 has a first outer vent cover 94 and the second inlet tube 92 has a second outer vent cover 96. The secondary combustion air inlet assembly 38 feeds into the baffle assembly 48 (FIG. 10) to provide air for secondary combustion in the pellet furnace 10.
In some embodiments, the pellet feed assembly 40 includes a distribution tray 100 and a feed tube 102. The distribution tray 100 is connected to the feed tube 102. Motorized loading systems, such as ones known to those of ordinary skill in the art, are able to be connected to the feed tube 102 to deliver pellets (not shown) into the feed tube 102 and through the distribution tray 100 onto the conveyor assembly 44. The distribution tray 100 includes a slide housing 104 and a plurality of distribution pins 106 secured within the slide housing 104 in a desired pattern, such as a trapezoidal pattern as shown in FIG. 9 (which is a schematic view of the pin patter), a rectangular pattern, or a triangular pattern, for example. Generally, the distribution pins 106 act to spread pellets (not shown) across the distribution tray 100 as they travel in the direction of the arrow in FIG. 9. In this manner, the distribution tray 100 helps to spread pellets out across the conveyor assembly 44 as the pellets pass through a delivery port 106 (FIG. 8) of the distribution tray 100.
In some embodiments, the igniter assembly 42 includes an igniter element 108, such as a coil igniter or ceramic hot surface igniter. The igniter assembly 42 is adapted to ignite pellets that have been delivered through the pellet feed assembly 40 onto the conveyor assembly 44. As shown in FIG. 8, the tip of the igniter assembly 42 is located proximate the conveyor assembly 44, as well as the delivery port 106 of the distribution tray 100.
In some embodiments, a first pair of wheels 112 that are substantially similar and coaxial with one another (only one of the pair is shown in FIG. 8, the other being hidden from view), a second pair of wheels 114 that are substantially similar and coaxial with one another (only one of the pair is shown in FIG. 8, the other being hidden from view), an air distribution plenum 116, a plurality of grate plates 118, and a drive motor 120 (FIG. 7).
As shown in one or both of FIGS. 7 and 8, each of the plurality of grate plates 118 has an elongate, rectangular profile and a substantially rectangular transverse cross-section with a hollow interior 130, an open bottom 132, and a closed top 134 perforated by a plurality of slots 136. Each of the grate plates 118 extends parallel to an adjacent grate plate 118 and each grate plate 118 has a longitudinal axis oriented perpendicular to the direction of travel of the grate plate 118. The slots 136 extend into the hollow interiors 130 of the grate plates 118 and are generally configured to allow air to pass up through the grate plates 118 without allowing the biomass fuel being burned (e.g., pellets or corn) to pass through the grate plates 118.
In some embodiments, each one of the grate plates 118 includes a drive link 110 that are interlinked with one another, connecting the grate plates 118 in a continuous chain. The drive links 110 are configured to be driven by the first and second pairs of wheels 112, 114. The first and second pairs of wheels 112, 114 are rotatably connected to the housing 30, for example each of the pairs 112, 114 being disposed on axels maintained by the housing 30. As shown, the drive links 110 form part of the grate plates 118 such that the drive motor 120 rotates the first pair of wheels 112 to move the grate plates 118 along a continuous, oval-shaped, or elongate path.
As shown in FIG. 8, the air distribution plenum 116 is located between the pairs of wheels 112, 114. The air distribution plenum 116 optionally has a trapezoidal cross-section as shown, or other shape as desired. The air distribution plenum 116 is in fluid communication with the primary combustion air inlet assembly 32 (FIG. 5) such that primary combustion air Ap (FIG. 8) flowing into the primary air inlet assembly 32 passes into the air distribution plenum 116 and out of the top of the air distribution plenum 116 to the plurality of grate plates 118 located above the air distribution plenum 116. As shown, the air distribution plenum 116 is positioned such that primary combustion air Ap flows up into the hollow interiors 130 and through the slots 136 of the grate plates 118 that are positioned over the air distribution plenum 116. For example, during an ignition sequence (described in greater detail below), the air distribution plenum 116 provides primary combustion air Ap to a grate plate 118A positioned proximate the igniter element 108 and the delivery port 106, as well as any other grate plates 118 positioned over the distribution plenum 116.
In some embodiments, the conveyor assembly 44 optionally achieves a variety of advantages. For example, the slotted design of the grate plates 118 and perpendicular orientation of the grate plates 118 relative to the direction of travel provides means for reducing the overall diameter of the pairs of wheels 112, 114, and thus the overall height of conveyor assembly 44, helping allow for a relatively compact design.
In some embodiments, the access door assembly 46 is connected to the housing 30 and provides means for viewing and/or accessing the components in the interior burn chamber 58 of the housing 30.
FIG. 10 is a perspective view of the baffle assembly 48 and FIG. 11 is a view of the baffle assembly 48 in an unassembled state. As shown, the baffle assembly 48 includes a pair of refractor legs 140, a lower refractor ring 142, an air baffle 144, an air baffle cap 146, a middle ring 148, a top baffle 150, and a top ring 152. The baffle assembly 48 generally provides means for secondary combustion of exhaust products from primary combustion of the biomass fuel. Moreover, while stainless steel can potentially be employed as a baffle assembly material, ceramic materials, and particular, fused silica ceramic material, has been found to work particularly well for forming the aforementioned components, providing a highly efficient secondary combustion means.
In some embodiments, the refractor legs 140 are each substantially U-shaped, or C-shaped, each of the refractor legs 140 defining a first recess 160 and a second recess 162. FIG. 12 is a top view of the baffle assembly 48, FIG. 13 is a side view of the baffle assembly 48, and FIG. 14 is a sectional view of the baffle assembly 48 along line 14-14 of FIG. 13. As shown in one or more of FIGS. 12-14, when assembled the refractor legs 140 are positioned at a bottom portion of the baffle assembly and define an open bottom 163 and a first lower side opening 164 and a second lower side opening 166 into the baffle assembly 48. As shown in FIG. 14, each of the refractor legs 140 has a receiving channel 168 formed about the perimeter of the top of each of the legs 140.
As shown in FIG. 11, the lower refractor ring 142 is substantially ring shaped with a rectangular top profile. The lower refractor ring 142 has an open bottom 169, a front secondary combustion air opening 170, a back secondary combustion air opening 172, and a probe opening 174 and forms a lower assembly rail 175 (FIG. 14), an inner ledge 176, and a receiving channel 178 formed about the perimeter of the top of the lower refractor ring 142. The lower refractor ring 142 also forms a pair of assembly stops 179 used to guide assembly of the air baffle 144 into the lower refractor ring 142. While the lower assembly rails of the various components are shown as semi-circular in cross-section, a variety of shapes (e.g., rectangular or triangular) are contemplated.
FIGS. 15-19 are perspective, back, side, top and bottom views, respectively, of the air baffle 144, according to some embodiments. As shown, the air baffle 144 is substantially ring shaped with a rectangular top profile. The air baffle 144 is adapted to be received within the lower refractor ring 142 and has a front secondary combustion air opening 180 that aligns with the front secondary combustion air opening 170 following assembly, a back secondary combustion air opening 182 that aligns with the back secondary combustion air opening 172 following assembly, and a receiving channel 188 formed about the perimeter of the top of the air baffle 144. The air baffle 144 has a plurality of lower air injection ports 192 through the bottom of the air baffle 144 and a plurality of side air injection ports 194 through the side of the air baffle 144. The air baffle 144 has a closed bottom 196, with a bottom face of the air baffle 144 forming a plurality of raised flow deflectors 198 substantially parallel to one another and extending across the bottom 196 of the air baffle 144. Each of the plurality of lower air injection ports 192 is angled as it extends through the bottom 196 of the air baffle 144 (e.g., about 45 degrees). The flow deflectors have substantially rounded, semicircular transverse cross-sections.
As shown, the lower air injection ports 194 originate at the top face of the bottom 196 and extend down through the bottom 196 and out of one of the plurality of raised flow deflectors 198 formed by the lower face of the bottom 196. The angled, lower air injection ports 192, as well as the raised profiles of the air baffles 144 help mix secondary combustion air As with exhaust air Ae passing through baffle assembly 48 as indicated in FIG. 14. The lower air injection ports 192 include three rows of holes, as well as three flow deflectors 198, one for each row, which operates in a desirable manner for many applications, though a variety of configurations and numbers of ports 192 and deflectors 198 are contemplated. The side air injection ports 194 pass through a side wall 200 of the air baffle 144 and are positioned to direct flow of secondary combustion air As with exhaust air Ae passing by the air baffle 144 up through the baffle assembly 48 as indicated in FIG. 14.
As shown in FIG. 11, the air baffle cap 146 has a substantially rectangular top profile and includes a lower assembly rail 210 (FIG. 14) extending around the perimeter of the air baffle cap 146. The lower assembly rail 210 is adapted to form a complementary fit with the receiving channel 188 of the air baffle 144.
As shown in FIG. 11, the middle ring 148 is ring-shaped with a substantially rectangular top profile and defines a recessed portion 220 and an enlarged portion 222 having a greater height than the recessed portion 220. The bottom of the middle ring 148 forms a lower assembly rail 224 (FIG. 14) adapted to form a complementary fit with the receiving channel 178 of the lower refractor ring 142. The recessed portion 220 defines a receiving channel 226 and the enlarged portion 222 defines a receiving channel 228.
In some embodiments, the top baffle 150 is adapted to form a complementary fit in the recessed portion 220 of the middle ring 148. The top baffle 150 defines a raised, textured bottom surface that forms a plurality of flow deflectors 240, such as the saw tooth pattern, or triangular transverse cross-section, shown in FIG. 14. The top baffle 150 has a lower assembly rail 242 (FIG. 14) adapted to form a complementary fit with the receiving channel 226. The top surface of the top baffle 150 also defines a receiving channel 244 which, when the top baffle 150 is received on the recessed portion 220, extends continuously with the receiving channel 228 of the enlarged portion 222 of the middle ring 148.
In some embodiments, the top ring 152 is ring shaped having a substantially rectangular top profile. The bottom perimeter of the top ring 152 forms a lower assembly rail 250 (FIG. 14) adapted to form a complementary fit with the receiving channels 244, 228 of the top baffle 150 and the middle ring 148, respectively. The upper perimeter of the top ring 152 optionally forms a receiving channel 252. The top ring 152 also has an auxiliary port 254 for inspecting and/or cleaning purposes, allowing access into the baffle assembly 48.
As shown in FIGS. 10 and 14, upon assembly, the baffle assembly 48 tapers from a narrower bottom portion to a relatively wider upper portion. Assembly of the baffle assembly 48 includes fitting the refractor legs 140 to the lower refractor ring 142 with the lower assembly rail 175 received in the receiving channels 168 of the refractor legs 140. The air baffle 144 is fit inside the lower refractor ring 142 so that the air baffle 144 rests on the inner ledge 176 and forms an air gap 260 with the lower refractor ring 142. The air baffle cap 146 is fit onto the air baffle 144 and the middle ring 148 is fit onto the lower refractor ring 142. The top baffle 150 is fit into the recessed portion 220 leaving an air gap 262 with the middle ring 148. The top ring 152 is assembled onto the middle ring 148 completing the baffle assembly 48. As shown in FIG. 14, the baffle assembly 48 defines a lower inlet 268, a lower secondary combustion chamber 270 including the plurality of flow deflectors 198 and lower air injection ports 192, an upper secondary combustion chamber 272 including the plurality of flow deflectors 240, a first vertical pathway 276 between the lower and upper secondary combustion chambers 272, 274 including the plurality of side air injection ports 194, and a second vertical pathway 278 to an upper stack 280 and upper outlet 282. The baffle assembly 48 is generally configured to generate turbulent flow (as indicated generally by arced flow arrows) of the exhaust air Ae as it passes up through the baffle assembly 48 and are injected with secondary combustion air As through the injection ports 192, 194.
FIGS. 20-22 show left side, front, and right side views, respectively, of the blower assembly 22, according to some embodiments. As shown, the blower assembly 22 includes a housing 300, a convection blower assembly 302, a combustion blower assembly 304, and a heat exchanger assembly 306. The convection blower assembly 302 delivers air to be heated (e.g., room air from a return duct in a building) to the heat exchanger assembly 306 to be heated by exhaust air Ae from the engine assembly 20 that is also being delivered to the heat exchanger assembly 306.
In some embodiments, the housing 300 is formed of sheet metal materials and includes legs, armatures, brackets, and/or other features as desired for supporting the various components of the blower assembly 22.
In some embodiments, the convection blower assembly 302 is represented generally by a box having an “X” in the middle in FIG. 21 and is shown in cross-section in FIG. 23. The convection blower assembly 302 includes a blower and is optionally of a type known to those of skill in the art. The convection blower assembly 302 directs convection air Ac (FIG. 23) from a source location, such as a building structure, through a convection air port 320 in the housing 300 so that the convection air passes through the heat exchanger assembly 306. In some embodiments, the convection blower assembly 302 pushes air through the heat exchanger assembly 306 and out from the convection air port 320. In other embodiments, the convection blower assembly 302 pulls air through the heat exchanger assembly 306 in through the convection air port 320. The convection blower assembly 302 and the air port 320 are optionally connected to ductwork such that air can be delivered to the pellet furnace 10 from a remote location and/or from the pellet furnace 10 to a remote location, such as another room in the building in which the pellet furnace 10 is housed or to location(s) remote from the pellet furnace 10.
In some embodiments, the combustion blower assembly 304 includes a blower that is optionally of a type known to those of skill in the art. The blower is connected to the heat exchanger assembly 306 as indicated by broken lines in FIGS. 20 and 22 and provides a negative pressure on the heat exchanger assembly 306. The negative pressure draws hot exhaust air Ae up from the engine assembly 20, and more particularly baffle assembly 48, through the heat exchanger assembly 306, and then pushes exhaust air Ae which has been cooled as it passes through the heat exchanger out away from the pellet furnace 10 (e.g., through an exhaust chimney).
In some embodiments, the heat exchanger assembly 306 has one or more convection air flow chambers 340 and one or more exhaust air flow chambers 342, where the chambers 340, 342 cross paths to exchange heat from exhaust air Ae flow passing through the one or more exhaust air flow chambers 342 into the convection air passing through the one or more convection air flow chambers 340. As shown in FIGS. 20 and 21, there is a single convection air flow chamber 340 with an inlet 344 and an outlet 346, the inlet 344 having convection air fed into it by the convection blower assembly 302. The exhaust air flow chambers 342 include a plurality of tubes 348 that pass upward through convection air flow chamber 340 to a common outlet 350 that feeds into the combustion blower assembly 304.
The control system 24 is shown in FIG. 1 with a covered housing over a user interface including one or more display screens, LEDs, controls, and/or other features for allowing control of the pellet furnace 10 known to those of skill in the art that are otherwise hidden from view. In some embodiments, the control system 24 is connected to various blowers, thermocouples, motors, and other equipment for operating the pellet furnace 10. The control system 24 includes one or more microprocessors, software, memory, power sources and/or other hardware as desired for controlling operation of the pellet furnace 10.
In some embodiments, the control system 24 is configured to automatically operate one or more of the following outputs based upon user input (where user input optionally includes changing thermal energy between a low, medium, and high settings): a motor of the convection blower assembly 302; a motor of the combustion blower assembly 304; a motor of the conveyor assembly 44; a motor of the pellet feed assembly 40; an automatic ash control system (not shown), for example including auger and vacuum systems; powering of the igniter assembly 44, including an ignition air pump used during an ignition sequence; and/or other outputs. The control system 24 is optionally connected to various inputs, including temperature probes (e.g., temperature probe 36) and motor feedbacks to monitor operation of the pellet furnace 10 and, for example, provide warnings or alarms in case of improper or otherwise undesired performance. In some embodiments, the control system 24 is programmed to control heating levels of the pellet furnace 10 for a desired growth cycle of a particular livestock (e.g., 50 days), allowing an operator of the pellet furnace 10 to set a desired heat/temperature on a day by day heat demand for the complete growth cycle.
In some embodiments, the control system 24 includes a PLC (programmable logic controller) configured to operate the pellet furnace 10 through an ignition sequence, ignition check, and heating sequence. The ignition sequence includes turning on the combustion blower assembly 304 for a desired time and rate, turning on the pellet feed assembly 40 for a desired time and rate, turning on the igniter assembly 42 for a desired time and power, and receiving temperature information from the one or more temperature probes regarding combustion chamber temperature. The ignition check includes evaluating whether a temperature difference in the combustion chamber 270 (e.g., at a location prior to where exhaust air enters the baffle assembly 48) before and after the ignition sequence is greater than a predetermined value. If the combustion chamber temperature difference is greater than the predetermined value the control system 24 begins the heating sequence. If not, the control system 24 restarts the ignition sequence until a predetermined number of attempts have been initiated, at which point a visual fault error and/or audible alarm are initiated. In some embodiments, the heating sequence operates at a desired setting (e.g., low, medium, or high settings) and includes alternatively operating the pellet feed assembly 40 and the conveyor assembly 44 at a desired rate and frequency, as well as operating the combustion blower assembly 304 for a desired time and rate. The convection blower assembly 302 is also operated for a desired time and rate depending upon, for example, room temperature readings fed back to the control system 24.
FIG. 23 is a medial sectional view of the pellet furnace 10 with flow arrows indicating various air flow paths through the pellet furnace 10. As shown in FIG. 23, during operation, the combustion blower assembly 304 (FIG. 20) draws primary combustion air Ap (FIG. 8) through the into the air distribution plenum 116 and up through the grate plates 118. Pellets (not shown) on the grate plates 118 are ignited, for example as described above, to create a smoldering mass of pellets. During steady state operation, exhaust air Ae from the burning pellets is drawn up into the baffle assembly 48 by the negative air pressure and secondary combustion air As is also drawn into the baffle assembly 48. As the exhaust air Ae is drawn through the baffle assembly 48 and secondary combustion air As is injected into the exhaust air flow Ae as it passes through the baffle assembly 48. The tortuous flow path of the baffle assembly 48 (with a plurality of 180 degree flow turns), the angle and position of the injection ports 192, 194 (FIG. 14), and the flow deflectors 198, 240 (FIG. 14) help generate turbulent flow in the baffle assembly 48, encouraging secondary combustion of the exhaust air Ae within the baffle assembly 48. As the exhaust air Ae passes through the heat exchanger assembly 306, heat is pulled off the exhaust air and delivered into convection air Ac passing through the heat exchanger assembly 306. Thus, the baffle assembly 48 helps deliver a highly efficient and relatively dry (e.g., in comparison to LP furnaces) heating mechanism.
Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the above described features.
