Patent Application
20100083883
The present invention relates to a solid fuel downdraft combustion boiler assembly including a primary combustion chamber and a secondary combustion chamber, each arranged to receive a controlled amount of combustion air.
Various designs of boilers are known in the prior art in which fuel is consumed for heating a fluid which is in turn used to transfer heat to a target area to be heated. Prior art examples are described in U.S. Pat. No. 6,718,819 by Brazier et al, U.S. Pat. No. 4,479,481 by Ingersoll et al., and U.S. Pat. No. 1,501,847 by Howell and European patent application 0 084 852 by Giovanni. None of the prior art configurations however are suited for providing heat only during requested intervals while being arranged to be fully shutdown quickly when no heat is desired for maximum efficiency.
According to one aspect of the invention there is provided a boiler assembly comprising:
a primary combustion chamber enclosed by surrounding walls and being arranged to receive a solid fuel for combustion therein;
a primary blower;
a primary combustion air passage arranged to deliver primary combustion air to the primary combustion chamber from the primary blower;
a primary air control arranged to control air flow through the primary combustion air passage from the primary blower to the primary combustion chamber;
a secondary combustion chamber enclosed by surrounding walls below the primary combustion chamber;
a combustion passage communicating between a bottom end of the primary combustion chamber and a top end of the secondary combustion chamber therebelow;
a secondary blower;
a secondary combustion air passage arranged to deliver secondary combustion air to the secondary combustion chamber from the secondary blower;
a secondary air control arranged to control air flow through the secondary combustion air passage from the secondary blower to the secondary combustion chamber;
a boiler chamber arranged to receive fluid to be heated therein;
a heat exchanger passage communicating through the boiler chamber so as to be arranged to exchange heat with fluid in the boiler chamber; and
an exhaust passage communicating from the secondary combustion chamber to the heat exchanger passage;
the primary and secondary air controls each being operable between an open position arranged to communicate combustion air through the respective combustion air passage and a closed position in which the respective combustion air passage is fully sealed and air flow to the combustions chambers is prevented.
By providing a boiler assembly including both first and second combustion chambers with respective air controls operable between an open position and a fully sealed closed position, the combustion chambers can be fully sealed for accurately halting combustion until heat is required. Accordingly the fuel in the boiler is combusted in the most efficient manner only as required without wasting heat. In the preferred embodiment, suitable high temperature sealing material is used to optimally seal the air controls in the closed position in which the sealing member is protected on an exterior side of the seating surface against which the sealing material is seated. Similarly any linkage or operating components for opening and closing the air controls is protected at an exterior side of the seating surface about the air passage controlled by the air controls.
Furthermore in the preferred embodiment, all of the components related to the actuation and control of the air controls and the blowers which deliver the air being controlled to the first and second combustion chambers, are mounted in a modular fashion so as to be readily separated and replaceable within a control housing which is mounted externally from the housing of the boiler assembly locating the combustion chambers and the boiler chamber therein. In the preferred embodiment, communication between each blower and the respective combustion chamber is controlled by both a hinged gate and a slidable damper which can be set independently of one another at various positions between respective open and closed positions to readily control both the volume of air communicated through the respective combustion air passages as well as readily controlling opening and closing of the air passages with the operating components being protected in the optimal manner from creosote and other residuals from the combustion process within the combustion chambers.
By further locating communication of the secondary combustion air at one end of an elongate secondary combustion chamber which in turn communicates with the primary combustion chamber at a central location therein, it ensures that the secondary combustion air is introduced at a location which is prevented from reaching the high temperatures of the combustion area by the incoming lower temperature combustion air. Accordingly a perforated diffuser member formed of metal may be placed at the location of secondary combustion air introduction into the secondary combustion chamber to optimize mixing of the secondary combustion air into the exhaust from the primary combustion chamber entering the secondary combustion chamber. Furthermore, because the diffuser is kept from becoming too hot by relatively cool incoming secondary air, the diffuser member can be made of low cost metals that do not require any costly alloys or coating to protect the diffuser member from the high temperatures normally encountered at the introduction of secondary combustion air into the secondary combustion chamber.
There may be provided a combustion air actuator arranged to proportionally control each of the air controls through a range of positions between the open position and the closed position thereof.
When each air control comprises a peripheral seating surface surrounding the respective combustion air passage, a gate may be supported for pivotal movement between the open position in which the gate is positioned externally between the seating surface and the respective blower and the closed position in which gate is sealed against the seating surface.
There may be provided an actuator mechanism arranged for displacing each gate between the open and closed positions in which the gate being supported on the actuator mechanism so as to be readily releasable therefrom.
Each gate may be supported on the respective actuator mechanism by a slidably releasable mounting pin.
An inner surface of each gate may comprise a rigid plate arranged to span partway across the respective air passage and a resilient sealing member may span outwardly beyond a periphery of the rigid plate so as to be arranged to engage the respective seating surface about a full periphery thereof in the closed position of the gate.
There may be provided an adjustable damper supported between each blower and the respective air control arranged to adjustably control maximum available air flow from the blower to the respective air control. There may further be provided a damper actuator arranged to proportionally control each of the dampers through a range of positions between a fully open position and a closed position thereof.
When the primary combustion chamber, the secondary combustion chamber and the boiler chamber are supported in a common main housing, the primary and secondary air controls may each comprise a respective control housing supported externally on the main housing and coupled to the respective combustion air passages such that the control housings are readily releasable from the main housing and the respective combustion air passages.
The surrounding walls of the primary combustion chamber may comprise four upright side walls in which each of the four side walls is inclined downwardly and outwardly away from an opposing one of the side walls.
The combustion passage may be in communication with the secondary combustion chamber at a location partway in between communication of the secondary combustion chamber with the secondary combustion air passage and with the exhaust passage.
One of the surrounding walls of the secondary combustion chamber may comprise an upright diffuser wall comprising a plurality of openings communicating therethrough in which the secondary combustion air passage communicates with the secondary combustion chamber through the openings in the diffuser wall.
The diffuser wall may comprise a perforated metallic plate member.
When the secondary combustion chamber is elongate in a longitudinal direction between two opposed ends of the chamber, the diffuser wall may be supported at one of the two opposed ends.
The exhaust passage may communicate with the secondary combustion chamber at the end of the secondary combustion chamber opposite the diffuser wall.
When there is provided a combustion actuator associated with each air control and a boiler control arranged to determine a heating condition and a standby condition, the combustion actuators may be arranged to displace each air control into the open position so as to initiate combustion responsive to determination of the heating condition by the boiler control and being arranged to displace each air control into the closed position so as to interrupt combustion responsive to determination of the standby condition by the boiler control.
The boiler control may also be arranged to increase or decrease the volume of combustion air being supplied by proportionally controlling the gate members, the damper members and/or the blowers responsive to data collected from one or more gas sampling sensors arranged to sense gas content in the furnace exhaust and/or an exhaust temperature sensor to optimize combustion which helps control combustion efficiency and exhaust emissions.
According to a second aspect of the present invention there is provided a boiler assembly comprising:
a primary combustion chamber enclosed by surrounding walls and being arranged to receive a solid fuel for combustion therein;
a primary blower;
a primary combustion air passage arranged to deliver primary combustion air to the primary combustion chamber from the primary blower;
a primary air control arranged to control air flow through the primary combustion air passage from the primary blower to the primary combustion chamber;
a secondary combustion chamber enclosed by surrounding walls below the primary combustion chamber;
a combustion passage communicating between a bottom end of the primary combustion chamber and a top end of the secondary combustion chamber therebelow;
a secondary blower;
a secondary combustion air passage arranged to deliver secondary combustion air to the secondary combustion chamber from the secondary blower;
a secondary air control arranged to control air flow through the secondary combustion air passage from the secondary blower to the secondary combustion chamber;
a boiler chamber arranged to receive fluid to be heated therein;
a heat exchanger passage communicating through the boiler chamber so as to be arranged to exchange heat with fluid in the boiler chamber; and
an exhaust passage communicating from the secondary combustion chamber to the heat exchanger passage;
the primary combustion chamber, the secondary combustion chamber and the boiler chamber being supported in a common main housing; and
the primary and secondary air controls each comprising a respective control housing supported externally on the main housing and being coupled to the respective combustion air passages such that the control housings are readily releasable from the main housing and the respective combustion air passages.
Furthermore, each air control may be coupled to the respective air passage by a tubular member formed of resilient material to ensure an air tight connection while remaining easily releasable.
According to another aspect of the present invention there is provided a boiler assembly comprising:
a primary combustion chamber enclosed by surrounding walls and being arranged to receive a solid fuel for combustion therein;
a primary blower;
a primary combustion air passage arranged to deliver primary combustion air to the primary combustion chamber from the primary blower;
a primary air control arranged to control air flow through the primary combustion air passage from the primary blower to the primary combustion chamber;
a secondary combustion chamber enclosed by surrounding walls below the primary combustion chamber;
a combustion passage communicating between a bottom end of the primary combustion chamber and a top end of the secondary combustion chamber therebelow;
a secondary blower;
a secondary combustion air passage arranged to deliver secondary combustion air to the secondary combustion chamber from the secondary blower;
a secondary air control arranged to control air flow through the secondary combustion air passage from the secondary blower to the secondary combustion chamber;
a boiler chamber arranged to receive fluid to be heated therein;
a heat exchanger passage communicating through the boiler chamber so as to be arranged to exchange heat with fluid in the boiler chamber; and
an exhaust passage communicating from the secondary combustion chamber to the heat exchanger passage;
the combustion passage being in communication with the secondary combustion chamber at a location partway in between communication of the secondary combustion chamber with the secondary combustion air passage and with the exhaust passage.
One embodiment of the invention will now be described in conjunction with the accompanying drawings in which:
In the drawings like characters of reference indicate corresponding parts in the different figures.
Referring to the accompanying figures there is illustrated a solid fuel down draft combustion boiler assembly generally indicated by reference numeral 10. The boiler assembly 10 is particularly suited for combusting a solid fuel, for example wood in a two stage combustion in which primary and secondary combustion air is provided in a controlled manner for efficient on demand combustion of the fuel being consumed to maintain the fluid being heated at an optimal set point temperature. The boiler is also well suited for use as an outdoor wood boiler in which a main housing 12 of the boiler can be insulated and appropriately clad to be set up as a stand alone unit outdoors.
The main housing 12 of the boiler has a front wall 14, a rear wall 16 and two side walls 18 spanning in an upright orientation from the front wall to the rear wall. The main housing further comprises a top wall 20 enclosing the top end of the main housing and a bottom wall 22 enclosing the bottom side of the main housing. The bottom side 22 is supported on four legs 24 adjacent the four corners of the rectangular main housing to support the bottom wall 22 spaced upwardly above the ground.
The main housing 12 commonly locates a primary combustion chamber 26, a secondary combustion chamber 28 and a boiler chamber 30 therein. The primary combustion chamber 26 serves to receive a solid fuel therein for initial combustion. The secondary combustion chamber located below the primary combustion chamber receives products of combustion from the primary combustion chamber for further combustion when mixed with secondary combustion air therein. The boiler chamber 30 is arranged to contain a fluid to be heated therein and is arranged in communication for exchanging heat with the primary and secondary combustion chambers and the exhaust therefrom.
The primary combustion chamber 26 comprises two side walls extending alongside the side walls 18 of the main housing at a location spaced inwardly therefrom. A front wall 34 and a rear wall 36 extend between the two side walls so that the two side walls, the front wall and the rear wall are in a generally rectangular configuration when viewed from above. The top of the primary chamber is enclosed by a top wall 38. The two side walls, the front wall and the rear wall extend downwardly from the top wall to a bottom end 40 of the primary combustion chamber such that the walls are inclined downwardly and outwardly away from one another in all four directions. In this manner the cross sectional dimension of the combustion chamber increases in all directions from the top end to the bottom end of the primary combustion chamber to prevent bridging of the solid fuels contained therein. An inclination of greater than one or two degrees is generally sufficient to prevent bridging of the solid fuel therein. In the preferred embodiment the side walls are sloped downwardly and outwardly by approximately 1.51 degrees from vertical, while the front wall is sloped outwardly by 2.5 degrees from vertical and the rear wall is sloped approximately six degrees from vertical.
The walls of the primary chamber surround the chamber such that the interior chamber comprises an enclosed spaced where the solid fuel is initially combusted. All of the upright walls about the chamber and the top wall are spaced inwardly from corresponding walls of the main housing to define a surrounding gap or space where water can be received to form an insulating water jacket about the primary combustion chamber.
A front access door 42 is supported in the front wall of the main housing by a hinge along one side thereof and a latch on the other side to selectively retain the gate in the closed position. The front door 42 communicates with an access channel spanning across the gap between the front wall of the primary combustion chamber and the front wall of the main housing so that opening the front door 42 provides access to the interior of the primary combustion chamber.
A primary combustion air passage 44 delivers the primary combustion air to the top side of the primary combustion chamber. The air passage 44 communicates through one of the side walls 18 of the main housing and the corresponding side wall 32 of the primary combustion chamber adjacent the top rear side thereof. The air passage 44 communicates the combustion air from the exterior of the housing to an interior deflector 46 supported in the top end of the combustion chamber for directing the primary combustion air downwardly in an outwardly spread configuration.
The down draft of combustion air is directed from the top end of the combustion chamber to the bottom end 40 of the primary chamber which comprises a layer of refractory material 48 in brick form including a central opening in the form of an elongate slot which defines a combustion passage 50. The combustion passage 50 is for communicating products of combustion from the primary combustion chamber to the secondary combustion chamber 28 therebelow. The layer of refractory material 48 also forms the top wall of the secondary combustion chamber. The combustion passage 50 comprises an elongate slot which is elongate in a longitudinal direction extending from the front end to the rear end of the boiler assembly.
The secondary chamber is similarly elongate in the longitudinal direction, however the secondary combustion chamber is many times wider than the lateral dimension of the combustion passage 50. The elongate configuration of the secondary combustion chamber is defined by two side walls 52 extending the longitudinal direction along opposing sides of the chamber, the layer of refractory material 48 thereabove and a second layer of refractory material 54 spanning the bottom of the secondary combustion chamber. The secondary combustion chamber spans in the longitudinal direction from a rear end 56 locating a diffuser wall 58 where the secondary combustion air is introduced into the secondary combustion chamber to an opposing front end 60 where products of combustion exit the secondary combustion chamber.
The diffuser wall 58 comprises an upright steel plate arranged to span a substantial portion of the height and the full lateral width of the secondary combustion chamber at the rear end 56 thereof. The upright steel plate is perforated to define a plurality of spaced apart apertures in a grid pattern therethrough for communication between the secondary combustion chamber and an inlet chamber 62 on the opposing side of the plate which is surrounded by bricks of refractory material enclosed about the inlet chamber 62. The diffuser wall further comprises an upper flange and a lower flange projecting perpendicularly from the steel plate in a common direction to form a generally U-shaped member with the perforated plate. The upper and lower flanges serve to lie adjacent top and bottom walls of the inlet chamber to locate the diffuser wall relative to the secondary combustion chamber and maintain the perforated portion in a vertical orientation.
A tubular member 64 communicates through the side wall of the main housing into the inlet chamber 62 to define the secondary combustion air passage 66 which introduces the secondary combustion air from an exterior of the housing through the tubular member 64 and inlet chamber 62 to be subsequently directed through the openings in the diffuser wall 58 for mixing with the products of combustion of the primary combustion chamber in the secondary combustion chamber. The grid pattern of openings in the diffuser wall ensure that the air is directed into the secondary combustion chamber for thorough mixing with the products of combustion entering from the combustion passage 50 at a location which is central and spaced from both the diffuser wall 58 at one end and the opposing outlet at the front end 60.
The front end of the secondary combustions chamber is open to a manifold spaced 68 spanning substantially a full width of the primary combustion chamber thereabove so that the secondary combustion chamber outlet communicates with two ducts 70 extending the longitudinal direction along opposing sides of the secondary combustion chamber from the manifold 68 at the front end rearwardly to a location below a rear end of the primary combustion chamber at opposing sides of the diffuser wall 58 at the rear end 56 of the secondary combustion chamber.
The walls surrounding the sides, top and bottom of the secondary combustion chamber and the two ducts 70 alongside the secondary combustion chamber are all formed of similar refractory material so that the layer of material 54 forming the bottom side of the secondary combustion chamber is continuous across the bottom of the ducts 70. The two ducts 70 collectively define an exhaust passage where any non-combusted products of combustion in the exhaust stream can be further combusted before reaching the rear of the boiler assembly where the exhaust exchanges heat with the fluid in the boiler chamber.
An access door 76 is provided on the front wall of the main housing adjacent the bottom end for alignment with the secondary combustion chamber and the two ducts of the exhaust passage. Accordingly the front end of the secondary exhaust chamber and the exhaust passage at the manifold 68 are all open through a suitable channel communicating across the gap between the front wall of the primary combustion chamber and the front wall of the main housing for access to the secondary combustion chamber and exhaust passage for cleaning out when the access door 76 is open. The access door is supported by a hinge along one side and suitable latching on the opposing side to selectively retain the door closed similarly to the front door 42 spaced thereabove.
The boiler chamber is centrally located at the rear side of the boiler assembly to define an inlet manifold chamber 72 spanning a full width of the main housing below the boiler chamber and an exhaust manifold chamber 74 spanning the full width of the main housing directly above the boiler chamber.
The inlet manifold chamber 72 and the exhaust manifold chamber 74 communicate with one another through the boiler chamber by a suitable heat exchange passage comprising a plurality of flue tubes 80. Each of the flue tubes communicates from an opening in the bottom wall of the boiler chamber forming the top wall of the inlet manifold chamber 72 and a respective opening in the top wall of the boiler chamber defining the bottom wall of the exhaust manifold chamber thereabove.
The top wall of the boiler chamber comprises a horizontal portion 82 extending the full longitudinal depth of the chamber adjacent one side of the boiler assembly and an inclined portion 84 along side the horizontal portion 82 which similarly extends the full longitudinal dimension of the boiler chamber. The inclined portion 84 is sloped from the horizontal portion 82 defining a low profile area of the exhaust manifold chamber thereabove downwardly and outwardly to the opposing side of the boiler assembly. Accordingly the overall height of the exhaust manifold chamber 74 increases towards one of the side walls of the chamber which locates a suitable side access door 86 therein. Both the inlet and exhaust manifold chambers span the full width between the two outer side walls of the main housing so that the access door 86 provided in the side wall at the inclined portion 84 of the top wall of the boiler chamber provides direct access to the exhaust manifold chamber 74.
A rear exhaust port 88 is provided in the rear wall of the main housing communicating from the exhaust manifold chamber 74 to the exterior of the main housing. An auxiliary outlet 90 is provided in direct communication between the rear wall of the primary combustion chamber adjacent the top end thereof to the exhaust manifold chamber 74 immediately rearward of the primary combustion chamber adjacent the top end thereof. The auxiliary outlet 90 permits products of combustion from the primary combustion chamber to be communicated directly to the exhaust manifold chamber 74 when the auxiliary outlet 90 is open.
A suitable gate member 92 is mounted in the auxiliary outlet 90 to be operable between an open position in which the auxiliary outlet 90 is unobstructed and a closed position in which the auxiliary outlet is fully sealed in a closed position. Under normal operating conditions the gate 92 is fully closed so that the primary combustion chamber is operated in a down draft configuration through the secondary combustion chamber and subsequently through the inlet and exhaust manifold chambers and the flue tubes 80 therebetween for heating the fluid in the boiler chamber prior to being exhausted from the boiler assembly through the rear exhaust port 88. A suitable linkage 94 is coupled between the gate member 92 and a suitable handle adjacent the front end of the boiler assembly for manually controlling the gate member between the open and closed positions thereof. When it is desirable to manually bypass the secondary combustion chamber, the exhaust passage and the heat exchanger passage, the gate member 92 is opened.
The flue tubes 80 communicating between the inlet manifold chamber 72 and the exhaust manifold chamber 74 collectively define the heat exchanger passage which communicates through the boiler chamber so as to be arranged to exchange heat between the exhaust passing therethrough and the fluid in the boiler chamber. The flue tubes 80 communicate with respective openings in the bottom wall of the boiler chamber at the bottom end thereof at locations which are evenly spaced across substantially the full width and depth of the chamber so as to be evenly distributed in the horizontal direction both laterally and longitudinally. The flue tubes extend at an upward and laterally outward incline in one direction towards one side of the boiler assembly corresponding to the location of the inclined portion 84 of the top wall and the side access door 86.
All of the openings in the top wall of the boiler chamber communicating with the top ends of the flue tubes are accordingly located offset to one side in the lateral direction in the inclined portion 84 where the height of the exhaust manifold chamber 74 is increased for greater access to the interior of the flue tubes for cleaning as may be desired. For further cleaning access an auxiliary cleanout door 96 is provided in the side wall of the main housing of the boiler assembly opposite the access door 76 at the bottom rear end thereof for alignment with the inlet manifold chamber 72. The cleanout door 96 is similarly supported on hinges for pivotal movement between open and closed positions and includes a suitable latch for retaining the door in the closed position.
The boiler chamber 30 surrounds the flue tubes defining the heat exchanger passage extending therethrough and may communicate with the gap between the combustion chambers and the surrounding housing which defines the water jacket about the combustion chambers so that fluid can be circulated through both the boiler chamber and the water jacket area for heating when fuel is combusted.
In addition to the refractory material surrounding the secondary combustion chamber and exhaust passages, suitable sheet metal surrounds the refractory material so as to be substantially continuous with the walls of the primary combustion chamber thereabove to maintain a water tight seal between the combustion chambers and the surrounding water jacket.
A suitable inlet pipe 98 communicates from the exterior of the boiler assembly through the side wall into the boiler chamber at a location adjacent the top end thereof to be nearest the exhaust manifold chamber 74. Water introduced into the boiler chamber thus passes over the heat exchanger passage from the exhaust manifold chamber 74 towards the inlet manifold chamber 72 therebelow and through the gap defining the water jacket surrounding the combustion chambers. A suitable outlet 100 is coupled through the side wall of the housing adjacent the top end of the primary combustion chamber for communicating the water in the water jacket gap to the exterior of the boiler assembly for use in heating a target area to be heated.
The primary and secondary air passages receive combustion air from a primary blower 102 and a secondary blower 104 respectively. Each of the blowers is mounted externally on the exterior side wall of the housing by suitable fasteners to permit ready separation and replacement of the blowers as may be desired. Air is controlled from the blowers to the respective primary and secondary air passages through a primary air control 106 and a secondary air control 108 respectively.
Each of the air controls is operable between an open position in which air is communicated therethrough in a substantially unobstructed manner and a closed position in which the respective combustion air passage can be fully sealed to prevent any airflow therethrough and accordingly prevent airflow to the respective combustion chambers for halting the combustion therein.
Each of the air controls 106 and 108 comprises a control housing 110 which is assembled from modular components using suitable fasteners which permit ready separation and release of the various components from one another and from the main housing of the boiler assembly upon which the control housing 110 is mounted for ready separation and replacement as required. Each air control includes a first portion 112 locating a hinged gate member 114 therein and a second portion 116 including a sliding damper plate 118 therein. A tubular outlet 120 is provided at the outlet end of the control housing 110 for connection in series with the respective combustion air passage communicating through the side wall of the boiler assembly to the respective combustion chamber.
The first portion of the control housing is generally rectangular in shape including a top wall 122, a bottom wall 124, and two side walls 126 extending in the flow direction therethrough between an inlet end wall 128 and an outlet end wall 130 which supports the tubular outlet 120 to communicate therethrough.
The second portion 116 is similarly rectangular in shape including a top wall 132, a bottom wall 134 and two side walls 136 extending in the flow direction between the respective blower and the inlet end wall 128 of the first portion.
The gate member 114 is arranged for sealing engagement upon a peripheral seating surface 138 defined by the inner end of the tubular outlet 120 so as to extend circumferentially about the combustion air passage extending therethrough. The gate member 114 is supported in the first portion of the control housing 110 so as to be positioned in both the open and closed positions on the exterior side of the seating surface 138 between the seating surface and the blower.
The gate member 114 is formed by a circular metallic inner plate 140 defining the inner surface of the gate member and a circular metal outer plate 142 defining the outer surface of the gate member. The inner and outer plates clamp a circular resilient sealing member 143 therebetween by a central bolt extending axially through both plates and the sealing member.
The inner plate 140 has a diameter which closely fits within the interior diameter of the tubular outlet 120 for substantially spanning across the combustion air passage in the closed position of the gate member by being received within the periphery of the seating surface 138. The resilient sealing member is formed of a high temperature sealing material and is larger in dimension so as to extend radially outward beyond the periphery of the inner plate about the full periphery thereof such that the diameter of the sealing member is greater than the diameter of the peripheral seating surface 138 about the air passage. The sealing material thus serves to overlap the exterior of the seating surface about the full periphery thereof for providing a fully sealed connection in the closed position of the gate member. The gate member is supported by a suitable actuator mechanism in the form of a linkage 144 so as to be pivotal from the closed position spanning the combustion air passage to an open position about an axis which is offset radially in relation to the opening of the tubular outlet 120 so as to not obstruct the airflow therethrough.
A pair of mounting flanges 146 are supported on the outer plate 142 of the gate member with apertures formed therein in alignment with one another for connection to the linkage 144. The linkage generally comprises a link arm 148 which is pivotally coupled about a vertical hinge axis on the outer end wall of the first portion of the control housing. A suitable pivot shaft is coupled to the link arm 148 at the hinge axis for pivotal movement therewith about the hinge axis in which the pivot shaft 150 extends to the exterior of the control housing for connection to a suitable actuator.
The other end of the link arm 148 includes cooperating apertures formed therein for alignment with apertures in the two flanges 146 on the gate member. Accordingly a mounting pin 152 can be coupled to be received through the cooperating apertures in the link arm and in the two flanges for coupling the gate member to the link arm of the linkage. The mounting pin is arranged to be slidable in a longitudinal direction of the pin through the cooperating apertures. Suitable spring mounted retainers are provided at opposing ends of the mounting pin to selectively retain the mounting pin in a mounted position coupling the gate member to the linkage. The mounting pin can be quickly removed by deflecting the sprung retainers at the opposing ends of the mounting pin for quickly removing the gate member from the linkage for replacement if the sealing material becomes worn out. By permitting the gate member to be readily separable and replaceable relative to the linkage defining the actuator mechanism of the gate member, a minimum number of parts is required to maintain the boiler assembly in optimum operating condition.
To further provide access to the gate member and for convenience of changing the gate member, one of the side walls 126 of the first portion of the control housing along with the adjacent bottom wall 124 coupled thereto are arranged to be readily separated from the remainder of the housing by suitable fasteners for easy access to the gate member for replacement as may be desired.
The second portion of the control housing 110 of each air control includes a bottom slot 154 in the bottom wall 34 thereof for slidably receiving the damper plate 118 therethrough in a vertical direction between an open position in which the respective air passage communicating through the housing is unobstructed and a closed position in which the damper plate fully spans across the cross sectional opening of the second portion of the control housing to interrupt the air flow therethrough. The damper plate is oriented by the slot receiving the plate therethrough to be generally perpendicular to the direction of airflow through the control housing. A suitable guide rail 156 is mounted externally on the second portion of the housing for guiding the sliding movement of the damper plate between the open and closed positions thereof.
In a preferred embodiment a combustion air actuator 158 is coupled to the pivot shaft 150 of the actuator mechanism for controllably opening and closing the gate member against the peripheral seating surface 138. Accordingly there is provided a primary combustion air actuator 158 associated with the primary air control 106 and a secondary combustion air actuator 158 in association with the secondary air control 108. The actuator 158 may comprise a rotary actuator or a linear actuator coupled to a crank arm fixed on the pivot shaft for rotation therewith. In either instance the actuator 158 is arranged to be supported externally on the housing by suitable fasteners to permits ready release and separation of the actuator for replacement and interchangeability as may be desired.
In some embodiments the damper plate can also be controlled by a damper actuator 160 comprising a linear actuator which is arranged to position the damper plate at any one of numerous positions between the open and closed positions thereof.
A suitable boiler control 162 is provided for controlling operation of the various aspects of the boiler assembly. A suitable temperature sensor 164 monitors the temperature of the fluid in the boiler chamber as it exits the boiler assembly for comparison of the temperature of the fluid being heated to a prescribed set point temperature.
The boiler control is arranged to determine that there is a demand for heat when the temperature of the fluid being heated falls below the set point temperature of the boiler control. When demand for heat is determined, the boiler control 162 actuates the blowers and actuates the combustion air actuators 158 to operate the air controls and open the respective gate members. In this manner combustion air is provided to the first and second combustion chambers for combusting the fuel therein and for heating the fluid in the boiler chamber.
When the temperature of fluid in the boiler chamber reaches the set point temperature and no further heat is required, the boiler control 162 then communicates with the blowers and the combustion air actuators to seal the gate members of the air controls in the closed position for sealing the combustion chambers and preventing further combustion. The primary and secondary blowers in turn shut down when the gate members are closed.
The damper plates are typically set at a prescribed opening and left at the prescribed opening setting corresponding to a maximum available airflow desired when the gate members are in the fully open position for optimal combustion of the fuel in the combustion chambers. If a greater volume of combustion air is desired when the gate members are in the open position, the damper plates can be positioned closer to the fully open position thereof. Alternatively if less airflow is desired when the gate members are in the fully open position, the damper plates can be positioned at a setting which is closer to the closed position thereof. Accordingly the damper plates can typically be manually set at a prescribed position without considerable ongoing adjustment being required.
In some embodiments, the boiler control is arranged to automatically increase or decrease the volume of combustion air being supplied by proportionally controlling the gate members, the damper plates and/or the blowers responsive to data collected from one or more gas sampling sensors or analysers 166 arranged to sense gas content in the furnace exhaust and/or an exhaust temperature sensor 168 to optimize combustion which helps control combustion efficiency and exhaust emissions.
In a preferred embodiment, the amount of air delivered through each of the air controls in the open position of the gate members can be provided by providing a proportional control actuator for operating the gate members to position the gate members at any one of plural intermediate open positions between the closed position and the fully open position thereof. Each of the intermediate open positions corresponds to a different amount of airflow passing through in the open position.
The boiler assembly according to the present invention is advantageous in that the primary and secondary air control permit 100% sealing of combustion air passages delivering combustion air to the primary and secondary combustion chambers. There are no holes in which combustion gases can escape during the off cycle of the heating process. This provides better combustion control and protects all of the dampers and fans from being damages or contaminated with creosote and or heat. The design of the boiler assembly is also completely flexible from an airflow control standpoint. That is the design is easily adaptable to both a linear or rotary actuator that can be controlled to simply open and close the respective combustion air passages or the actuators can be proportional for total combustion control.
The boiler assembly is also very easy to maintain. All of the pivotal connections of the gate member, the mounting connections for replacing the gate member and the like, the actuator components, the linkage components and blower fans are situated on an exterior side of the rubber sealing member, opposite the side of the sealing member that is exposed to the combustion chamber conditions. Accordingly, all of the working components are protected from the combustion chamber and the high temperature rubber sealing member is the only item that is exposed to the harsh environment in the combustion chambers during the off cycle. The sealing member is easily replaced as the design gives fast and easy access to the gate member to remove the sealing gate simply by pulling a single pin. Furthermore the entire assembly can be quickly and easily removed. All that is required is the power supply of the assembly being unplugged, a single clamp is loosened and/or a set screw is removed to permit removal of the entire air control and blower assembly. The design permits mounting of the air control assembly in many different orientations which results in many combustion air delivery options in the boiler or furnace design. The air control assembly including the control gates and dampers as well as the blower can be easily attached to and removed from the housing of the boiler assembly. Access to the interior of the control housing can be achieved quickly by removal of a single suitable fastener to permit one of the side walls and the bottom wall to be readily separated for access to the interior for cleaning or replacement of components as may be desired.
The present invention is also advantageous in that secondary combustion air is introduced into the secondary combustion chamber from a rear end of the chamber opposite from the front exit of the chamber when the products of combustion from the primary chamber enter at an intermediate location between introduction of secondary combustion air and the outlet of the secondary combustion chamber. In this manner no complex passageways of funnelling secondary air to multiple entry ports in the secondary burn area are required so that the configuration of the refractory material is simplified. Furthermore, a diffusion member can be used which is prevented from reaching the high combustion temperatures of the secondary combustion chamber by the lower temperature incoming secondary combustion air so that the diffusion member is away from the intense heat area of secondary combustion to increase the surface time span of the diffusion member without the diffusion member being formed of exotic or expensive materials. In the event that any of the secondary supply components including the diffuser member or the supply tube forming the secondary air passage burn out, the components are easy to remove and replace.
A further advantage of the boiler assembly described herein is that all four sides of the primary combustion chamber are tapered downwardly and outwardly from the top end to the bottom end thereof to reduce the amount of bridging that occurs as the furnace consumes wood or other solid fuel material. This is especially important for a down draft burning boiler of this type in which wood is consumed at the bottom of the pile first and the wood has to steadily settle downwards.
The design of the air control and blower to be modular permits the entire air control assembly to be readily broken down into five assemblies including, the blower, the first and second portions of the air control housing, the damper plate, the sealing member, and the linkage operating the sealing member. If any cleaning is required beyond the rubber seal, this can easily be done when the removable side wall of the air control housing as all surfaces that may require cleaning are readily accessible. The only component that requires regular maintenance is the high temperature sealing member as this is the only component in contact with the harsh environment in the combustion chambers when closed.
A single mounting brace can be added to stabilise the air control assembly for attachment between the control housing and the main housing of the boiler assembly at any point on the first and second portions of the control housing. Quick connection between the tubular outlet of the control housing and the respective air passage to which it is connected is accomplished by providing a high temperature silicone rubber hose or tubing at the outlet for securement by a circular clamp which holds the silicone rubber hose onto the exit tubing of the air supply assembly. A second circular clamp attaches the silicone hose to the tubular member which in turn delivers the combustion air to the respective combustion chambers. This allows the removal of the entire assembly for maintenance and repairs.
Use of a high temperature resistant silicone or rubber tubular member 110 for connecting each air control to the respective combustion air passage through the main housing permits better sealing due to the resilient nature of the tubular member, while still permitting the tubular member to be readily releasable. Use of rubber or silicone hose instead of a flanged bolt on method or steel sleeve type connector has the advantage in that the method of the present invention is inherently air tight while the other methods allow some leakage. The resilient material prevents any air leaks to ensure a faster and complete interruption of combustion air when the gate members of the air controls are closed.
Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.
