COMBUSTION SYSTEM WITH AUTOMATED CONTROL OF PRIMARY AND SECONDARY AIRFLOWS

Abstract

A combustion system includes sensor, an exhaust sensor, a primary actuator associated with primary airflow, a secondary actuator associated with secondary airflow, and a processor. When the combustion system is in at least one of an initiation phase or an initiation transition phase, the processor is configured to control primary actuator and the secondary actuator based on an initiation configuration. The processor is further configured to determine a transition of the combustion system to an equilibrium phase based at least in part on: a comparison of a chamber temperature measurement received from the chamber sensor with a chamber endothermic setpoint; and a comparison of an exhaust temperature measurement received from the exhaust sensor with an exhaust ignition setpoint. When the combustion system is in the equilibrium phase, the processor is configured to control the primary actuator and the secondary actuator based on an equilibrium configuration.

Claims

1. A method for controlling a combustion system comprising a chamber sensor, an exhaust sensor, a primary actuator associated with primary airflow, a secondary actuator associated with secondary airflow, and at least one processor in communication with the chamber sensor, the exhaust sensor, the primary actuator and the secondary actuator, the method comprising: when the combustion system is in at least one of an initiation phase or an initiation transition phase, controlling, with the at least one processor, the primary actuator and the secondary actuator based on an initiation configuration; determining, with the at least one processor, a transition of the combustion system to an equilibrium phase based at least in part on: a comparison of at least one chamber temperature measurement received from the chamber sensor with a chamber endothermic setpoint; and a comparison of at least one exhaust temperature measurement received from the exhaust sensor with an exhaust ignition setpoint; and when the combustion system is in the equilibrium phase, controlling, with the at least one processor, the primary actuator and the secondary actuator based on an equilibrium configuration.

2. The method of claim 1, wherein determining the transition to the equilibrium phase further comprises determining that the transition to the equilibrium phase has occurred when the at least one chamber temperature measurement is greater than the chamber endothermic setpoint.

3. The method of claim 1, wherein controlling the primary actuator and the secondary actuator based on the initiation configuration comprises: controlling the primary actuator based at least in part on a primary comparison of the at least one chamber temperature measurement with the chamber endothermic setpoint; and controlling the secondary actuator based at least in part on a secondary comparison of the at least one exhaust temperature measurement with an exhaust upper setpoint and an exhaust lower setpoint.

4. The method of claim 1, wherein controlling the primary actuator and the secondary actuator based on the equilibrium configuration comprises: controlling the primary actuator based on a primary comparison of at least one chamber temperature measurement received from the chamber sensor with the chamber endothermic setpoint; and controlling the secondary actuator based on an equilibrium secondary comparison of at least one exhaust temperature measurement received from the exhaust sensor with an exhaust upper setpoint and an exhaust lower setpoint.

5. The method of claim 1, further comprising setting, with the at least one processor, a termination event flag during the equilibrium phase based at least in part on the at least one chamber temperature measurement is greater than a sum of the chamber endothermic setpoint and a chamber termination value.

6. The method of claim 5, further comprising at least one of: determining, with the at least one processor, a transition from the equilibrium phase to a termination transition phase; or determining, with the at least one processor, a transition from the termination transition phase to a termination phase.

7. The method of claim 6, wherein determining the transition from the equilibrium phase to the termination transition phase comprises: determining, with the at least one processor, whether the termination event flag has been set; comparing, with the at least one processor, at least one current chamber temperature measurement received from the chamber sensor with, at least, at least one previous chamber temperature measurement received from the chamber sensor; comparing, with the at least one processor, at least one current exhaust temperature measurement received from the exhaust sensor with, at least, at least one previous exhaust temperature measurement received from the exhaust sensor; and determining, with the at least one processor, that the transition to the termination transition phase has occurred based at least in part on the termination event flag being set, the at least one current chamber temperature measurement being less than the at least one previous chamber temperature measurement, and the at least one current exhaust temperature measurement being less than the at least one previous exhaust temperature measurement.

8. The method of claim 7, further comprising, when the combustion system is in the termination transition phase, controlling, with the at least one processor, the primary actuator and the secondary actuator based on a termination initiation configuration.

9. The method of claim 8, wherein controlling the primary actuator and the secondary actuator based on the termination initiation configuration comprises controlling, with the at least one processor, the secondary actuator and the primary actuator based at least in part on a comparison of at least one chamber temperature measurement received from the chamber sensor with the chamber endothermic setpoint.

10. The method of claim 7, further comprising, when the combustion system is in the termination phase, controlling, with the at least one processor, the secondary actuator and the primary actuator based on a termination configuration.

11. The method of claim 10, wherein controlling the secondary actuator and the primary actuator based on the termination configuration comprises controlling the secondary actuator and the primary actuator based at least in part on a comparison of at least one chamber temperature measurement received from the chamber sensor with a chamber under-zone setpoint.

12. The method of claim 1, further comprising at least one of: determining, with the at least one processor, a transition into the initiation phase; and determining, with the at least one processor, a transition from the initiation phase to the initiation transition phase.

13. The method of claim 12, wherein determining the transition into the initiation phase comprises determining whether an ignition event has occurred.

14. The method of claim 11, wherein determining the transition from the initiation phase to the initiation transition phase comprises: comparing, with the at least one processor, at least one chamber temperature measurement received from the chamber sensor with at least a chamber ignition setpoint; comparing, with the at least one processor, the at least one exhaust temperature measurement received from the exhaust sensor with at least the exhaust ignition setpoint; and determining, with the at least one processor, that the transition to the initiation transition phase has occurred when the at least one chamber temperature measurement is greater than the chamber ignition setpoint and the at least one exhaust temperature measurement is greater than the exhaust ignition setpoint.

15. A method for reducing emissions of a combustion system comprising a chamber and an exhaust coupled to the chamber, the method comprising: directing a first portion of airflow within the chamber to pass through a catalyst coupled to a top wall of the chamber before entering an opening of the exhaust, wherein the catalyst covers a catalyst portion of the opening and wherein the catalyst is coupled to the top wall at an angle relative to a plane of the opening; and directing a second portion of the airflow entering the opening without passing through the catalyst, wherein the catalyst does not cover a bypass portion of the opening.

16. The method of claim 15, wherein the catalyst portion of the opening is at least 60% of a total area of the opening.

17. A combustion system comprising: a chamber; an exhaust coupled to the chamber, the exhaust having a catalyst portion of an opening of the exhaust and a bypass portion of the opening of the exhaust; and a catalyst coupled to a top wall of the chamber proximate to the opening of the exhaust, wherein the catalyst covers the catalyst portion of the opening to permit a first portion of air exiting the chamber to pass through the catalyst before entering an opening of the exhaust while a second portion of airflow enters the opening by the bypass portion without passing through the catalyst.

18. The combustion system of claim 17, wherein the bypass portion of the opening is at least 35% of a total area of the opening.

19. The combustion system of claim 17, wherein the catalyst is coupled to the top wall at an angle relative to a plane of the opening.

20. The combustion system of claim 19, wherein the angle is 12.5.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0049] In drawings which illustrate embodiments:

[0050] FIG. 1 is a front view of a combustion system in accordance with one embodiment.

[0051] FIG. 2 is a cross-sectional side view of the combustion system of FIG. 1 in accordance with one embodiment.

[0052] FIG. 3 is a cross sectional top view of the combustion system of FIG. 1 in accordance with one embodiment.

[0053] FIG. 4 is a schematic of a controller of the combustion system of FIG. 1 in accordance with one embodiment.

[0054] FIG. 5 is a chart illustrating combustion phases and temperatures of a combustion cycle of solid fuel within the combustion system of FIG. 1 in accordance with one embodiment.

[0055] FIGS. 6A and 6B are flow charts illustrating a determine phase process executed by the controller of FIG. 4 in accordance with one embodiment.

[0056] FIG. 7 is a flow chart illustrating a controller airflow process executed by the controller of FIG. 4 in accordance with one embodiment.

[0057] FIG. 8 is a schematic of a catalyst component of the combustion system of FIG. 1 in accordance with one embodiment.

[0058] FIG. 9 is a schematic of the catalyst component of FIG. 9 covering a portion of an opening of an outlet of the combustion system of FIG. 1 in accordance with one embodiment.

DETAILED DESCRIPTION

[0059] FIGS. 1 and 2, illustrate a front view and a side cross-sectional view of a combustion system 100 in accordance with one embodiment. The combustion system 100 includes a chamber 102 in which solid fuel may placed, and which contains a combustion (e.g., fire) generated from the solid fuel. The chamber 102 may also be referred to as a combustion chamber or a firebox. The chamber 102 can be made from concrete, brick, stone, iron, ceramic, or any other materials suitable for withstanding high temperatures of the combustion of the solid fuel contained within. The chamber 102 is defined by chamber walls 104 that include a top wall 400, a bottom wall 401, a rear wall 404, a first sidewall 402, a second sidewall 403, and by a door 106. The door 106 is configured to be openable (e.g., by a user, via a hinge or alternative opening mechanism) to load the solid fuel into the chamber 102 and closed to allow combustion of the solid fuel within the chamber 102. In some embodiments, the door 106 may instead be a front wall, and the top wall 400 may instead include a top door that is opened to load the solid fuel into the chamber 102 and closed to allow combustion of the solid fuel in the chamber 102.

Primary Air System 110

[0060] Referring to FIGS. 2 and 3, the combustion system 100 includes a primary air system 110. In the embodiment shown, the primary air system 110 includes at least one upper primary inlet 112 and associated upper primary damper 113 and at least one lower primary inlet 114 and associated lower primary damper 115. Both the primary inlets 112 and 114 are located proximate the door 106. In other embodiments, the primary air system 110 may include only the upper primary inlets 112 and damper 113 or may include only the lower primary inlets 114 and damper 115 or may include alternatively positioned primary inlets and dampers (not shown) or may include additional primary inlets and dampers (also not shown).

[0061] The upper and lower primary inlets 112 and 114 and the upper and lower primary dampers 113 and 115 generally allow primary airflow 170 to flow from an ambient environment into the chamber 102. The primary airflow 170 is typically drawn into the chamber 102 proximate the bottom wall 401 to supply oxygen to a primary combustion of the solid fuel. For example, at least one of the upper and lower primary inlets 112 and 114 may be associated with primary airflow conduits which direct the primary airflow 170 from the at least one of the upper and lower primary inlets 112 and 114 proximate the door 106, through the upper and lower primary dampers 113 and 115, and towards the solid fuel contained in the chamber 102.

[0062] The upper and lower primary inlets 112 and 114 and/or the upper and lower dampers 113 and 115 are associated with at least one primary actuator 140 configured to move between a plurality of positions for controlling an amount of the primary airflow 170 allowed into the chamber 102 at any particular time. For example, the primary actuator 140 may be directly coupled with the upper and lower primary dampers 113 and 115 and may include motors controlled by signals from a controller 150 of the combustion system 100 (described below) to open and close the upper and lower primary dampers 113 and 115 to according to certain primary airflow percentage values determined by the controller 150. In some embodiments, the primary actuator 140 may be operable to position the primary inlets 112 and 114 and/or the primary dampers 113 and 115 in specific and discrete open configurations to generate specific and discrete amounts of the primary airflow 170, such as fully 100% open, 75% open, 50% open, 25% open, 0% open (e.g., closed), etc. In other embodiments, the primary actuator 140 may be operable to position the primary inlets 112 and 114 and/or the primary dampers 113 and 115 in any configuration between a fully 100% open and 0% open (e.g., closed) to generate any primary airflow percentage value between 100% primary airflow 170 and 0% primary airflow 170.

[0063] Further, in the embodiment shown in FIG. 2, the primary airflow 170 through upper and lower primary inlets 112 and 114 may be individually controlled by the primary actuator 140 independent of each other. For example, the upper primary damper 113 and the lower primary damper 115 may be individually and independently controlled by the primary actuator 140 and may be operable to be positioned in different and individual configurations similar to those described above. Further, in embodiments where the upper and lower primary inlets 112 and 114 include more than one respective primary inlet, each primary inlet may also be individually controlled by the primary actuator 140 independent of each other. For example, referring briefly to FIG. 3, in the embodiment shown, the at least one upper primary inlet 114 includes a first upper primary inlet 114A associated with a first upper primary damper 115A and a second upper primary inlet 114B associated with a second upper primary damper 115B. The first and second upper primary dampers 115A and 115B may be individually and independently controlled by the primary actuator 140 and may be operable to be positioned in different and individual configurations similar to those described above.

Secondary Air System 120

[0064] Still referring to FIGS. 2 and 3, the combustion system 100 further includes a secondary air system 120. In the embodiment shown, the secondary air system 120 includes at least one first secondary inlet 122 located proximate the top wall 400 and the first sidewall 402 and at least one second secondary inlet 124 located proximate the top wall 400 and the second sidewall 403. The first secondary inlets 122 may be associated with a first secondary damper 123 and the second secondary inlets 124 may be associated with a second secondary damper 125 (shown in FIG. 3). In other embodiments, the secondary air system 120 may include only the first secondary inlets 122 and the first secondary damper 123, may only include the second secondary inlets 124 and the second secondary damper 125, may include alternatively positioned secondary inlets and dampers (not shown) or may include additional secondary inlets and dampers (also not shown).

[0065] The first and second secondary inlets 122 and 124 and the first and second secondary dampers 123 and 125 generally allow secondary airflow 172 to flow from the ambient environment into the chamber 102. The secondary airflow 172 is typically drawn into the chamber 102 proximate the top wall 400 to supply oxygen to a secondary combustion of gases produced by the primary combustion of the solid fuel. For example, at least one of the first and second secondary inlets 122 and 124 may be associated with secondary airflow conduits which direct the secondary airflow 172 from the ambient environment, through at least one of the first and second secondary dampers 123 and 125, and then through at least one of the first and second secondary inlets 122 and 124 proximate the top wall 400.

[0066] The first and second secondary inlets 122 and 124 and/or the first and second secondary dampers 123 and 125 are associated with at least one secondary actuator 142 configured to move between a plurality of positions for controlling an amount of the secondary airflow 172 allowed into the chamber 102 at any particular time. For example, the secondary actuator 142 may directly coupled to the first and second secondary dampers 123 and 125 and may include motors controlled by signals from the controller 150 to open and close the first and second secondary dampers 123 and 125 according to certain secondary airflow percentage values determined by the controller 150. In some embodiments, the secondary actuator 142 may be operable to position the first and second secondary inlets 122 and 124 and/or the first and second secondary dampers 123 and 125 in specific and discrete open configurations to generate specific discrete amounts of the secondary airflow 170 similar to the primary actuator 140 as described above; in other embodiments, the secondary actuator 142 may be operable to position the first and second secondary inlets 122 and 124 and/or the first and second secondary dampers 123 and 125 in any configuration between a fully 100% open and 0% open (e.g., closed) to generate any secondary airflow percentage value between hundred percent secondary airflow 172 and 0% secondary airflow 172.

[0067] The secondary airflow 170 through the first secondary inlets 122 may be individually controlled by the secondary actuator 142 independent of the secondary airflow 172 through the second secondary inlets 124. For example, the first secondary damper 123 and the second secondary damper 125 may be individually and independently controlled by the secondary actuator 142. Further, in embodiments where the first and second secondary inlets 122 and 124 include more than one respective secondary inlet, each secondary inlet may also be individually controlled by the secondary actuator 142 independent of another secondary inlet.

Exhaust 116

[0068] The combustion system 100 further includes an exhaust 116, also referred to as a flue. Referring briefly to FIGS. 8 and 9, the exhaust 116 is coupled to the chamber 102 via an outlet 117 defining an opening 742. The primary airflow 170 received in the chamber 102 from the upper and lower primary inlets 112 and 114, as well as the secondary airflow 172 received in the chamber 102 from the first and second secondary inlets 122 and 124 may then exit the chamber 102 via the exhaust 116 as exhaust airflow 174. Accordingly, the at least one upper primary inlet 112, the at least one lower primary inlet 114, the at least one first secondary inlet 122, the at least one second secondary inlet 124 and the exhaust 116 are each in fluid communication with the chamber 102.

Sensor System 118

[0069] The combustion system 100 further includes a sensor system 118 which measures different conditions of the combustion system 100 and/or different conditions of the solid fuel loaded into the combustion system 100.

[0070] The sensor system 118 includes a chamber sensor 130 configured to monitor the condition of the chamber 102 and an exhaust sensor 132 that configured to monitor the condition of the exhaust airflow 174 exiting via the exhaust 116. In the embodiment shown, the chamber and exhaust sensors 130 and 132 both comprise temperature sensors, with the chamber sensor 130 generally configured to sense a chamber temperature T.sub.c within the chamber 102 and the exhaust sensor 132 generally configured to sense an exhaust temperature T.sub.e of the exhaust airflow 174 exiting the exhaust 116. However, in other embodiments, the chamber and exhaust sensors 130 and 132 may further comprise pressure sensors (e.g., configured to sense a pressure within the chamber 102 and/or a pressure of the exhaust airflow 174) or flow sensors.

[0071] In other embodiments, the sensor system 118 may also include a fuel sensor (not shown) that monitors conditions of the solid fuel within the chamber 102. For example, the fuel sensor may comprise a weight sensor positioned below the bottom wall 401 which is configured to provide weight information indicative of when the solid fuel has been loaded into the chamber 102 (e.g., a heavy weight as measured by the fuel sensor) and/or when a previously loaded solid fuel has been consumed (e.g., a progressively decreasing weight as measured by the fuel sensor). In further embodiments, the sensor system 118 may include additional or alternative sensors, including a movement sensor associated with the door 106 (e.g., such as with a handle or hinges of the door 106) to detect whether the door 106 has been opened or a motion sensor configured to detect whether a user is in the ambient environment proximate the combustion system 100.

Controller 150

[0072] The chamber and exhaust sensors 130 and 132 and the primary and secondary actuators 140 and 144 are connected to, and controlled by, a control system or controller 150. Referring to FIG. 4, in one embodiment, the controller 150 includes at least one local processor 151 and a storage memory 152, a program memory 154 and a I/O interface 156, all in communication with the local processor 151. Other embodiments of the controller 150 may include fewer, additional or alternative components. Additionally, although only a single local processor 151, single storage memory 152, single program memory 154 and single I/O interface 156 is shown in FIG. 4, other embodiments of the controller 150 may include more than one of each of these components.

[0073] The I/O interface 156 includes an interface for the processor 151 to communicate commands to, and receive information from, different components of the combustion system 100, including the chamber and exhaust sensors 130 and 132 and the primary and secondary actuators 140 and 144 for example. In the embodiment shown, the local processor 151 may communicate with these components via a wired connection; in other embodiments, the local processor 151 may also communicate with these components over a wireless network (e.g., a wireless network such as a wifi or a cellular network). In some embodiments, the I/O interface 156 may further include a communication module which generally enables the local processor 151 to (a) communicate with a remote processor of a remote server over the wireless network and (b) a user device associated with a user of the combustion system 100 over the wireless network. The I/O interface 156 may also include other features, such switches, and a power connection. The I/O interface 156 may be any communication interface which enables the local processor 151 to communicate with the chamber and exhaust sensors 130 and 132 and the primary and secondary actuators 140 and 144 as described below, including specialized or standard I/O interface technologies such as channel, port-mapped, asynchronous for example.

[0074] The storage memory 152 stores information received or generated by the local processor 151 and may generally function as an information or data store. In the embodiment shown, the storage memory 152 may include a setpoint data store 180 and temperature data store 182; in other embodiments, the storage memory 152 may include fewer, additional or alternative data stores.

[0075] The program memory 154 stores various blocks of code (alternatively called processor-executable instructions and/or computer-executable instructions), for directing the processor 151 to perform various processes, such as a determine phase process 500, a control airflow process 600 and a method 800 as described below. The various processes stored in the program memory 154 generally directs the processor 151 to respond to a current combustion phase of the solid fuel by controlling at least one of primary and secondary actuators 140 and 142 based on measurements received from at least one of the chamber and exhaust sensors 130 and 132. The program memory 154 may also store database management system computer-executable instructions for managing the data stores in the storage memory 152. In other embodiments, the program memory 154 may store fewer, additional or alternative computer-executable instructions directing the local processor 151 to execute additional or alternative processes.

[0076] The storage memory 152 and the program memory 154 may each be implemented as one or a combination of a non-transitory computer-readable medium and/or non-transitory machine-readable medium such as a hard disk drive, a flash memory, a read-only memory, a compact disk, a digital versatile disk, a cache, a random-access memory and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching thereof). The expression non-transitory computer-readable medium or non-transitory machine-readable medium as used herein is defined to include any type of computer-readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media.

Combustion Cycle 300

[0077] A typical combustion cycle 300 of the solid fuel by the combustion system 100 is shown in FIG. 5. The typical combustion cycle 300 can be divided into different phases based on the exhaust temperature within the exhaust 116 (shown by an exhaust temperature curve 302, e.g., generated using exhaust temperatures sensed by the exhaust sensor 132) and the chamber temperature within the chamber 102 (shown by a chamber temperature curve 304, e.g., generated using chamber temperature sensed by the chamber sensor 130). The combustion cycle 300 typically includes (A) an initiation phase 310 and an initiation transition phase 320 in certain embodiments), in which the solid fuel is loaded into the chamber 102 (e.g., a reload event 311) and an initial ignition of the solid fuel occurs (e.g., an ignition event 313); (B) an equilibrium phase 330, in which the solid fuel is combusting in the primary combustion until the solid fuel has been depleted (e.g., a termination event 315); (C) a termination transition phase 340 also referred to as a charcoal transition phase, in which the solid fuel has been substantially depleted; and (C) a termination phase 350 also referred to as a charcoal phase, in which the solid fuel has been substantially depleted and the combustion system 100 has also had a time to cool down. The combustion cycle 300 may then revert to the initiation phase 310 after additional reload and ignition events 311 and 313.

[0078] A length of, and even existence of, each phase in a particular instance of a combustion cycle 300 varies greatly depending on how often a user of the combustion system 100 reloads the solid fuel (e.g., initiates the reload event 311). For example, if the user reloads additional solid fuel during the equilibrium phase 330 (e.g., initiates an additional reload event 311), the combustion cycle 300 of the solid fuel in combustion system 100 may revert back to the initiation phase 310 due to loss of temperature in the chamber 102 and subsequent ignition of the additional solid fuel in an additional ignition event 313. This may continue with further reloads of additional solid fuel (e.g., further reload events 311) such that the solid fuel and the combustion system 100 may not reach the termination transition phase 340 or the termination phase 350 until all reloaded solid fuel is depleted. As an alternative example, if the user reloads additional solid fuel during the termination transition phase 340, the combustion cycle 300 solid fuel may revert back to the initiation phase 310, and the combustion system 100 may not reach the termination phase 350 again until all reloaded solid fuel is depleted.

[0079] Additionally, a length of each phase in a particular instance of a combustion cycle 300 varies greatly also varies greatly depending on a quality and an amount of the solid fuel which is loaded into the chamber 102 and conditions of the ambient environment. For example, a larger amount of solid fuel or solid fuel including more moisture content may require a longer time to ignite. Additionally, a colder and wetter ambient environment may also result in a longer time to ignite a standard amount of solid fuel.

[0080] To lower emissions resulting from the combustion of the solid fuel, as well as to optimize combustion during the combustion cycle 300, airflow within the chamber 102 (e.g., an amount of the primary airflow 170 and an amount of the secondary airflow 172) may need to be modified during different phases of the typical combustion cycle 300. For example, during the initiation phase 310 in the initiation transition phase 320, a significant amount of primary air 170 may be required; in contrast, during the equilibrium phase 330, the amount of primary air 170 may be reduced while the amount of secondary air 172 may be increased to optimize equilibrium combustion and to reduce emissions resulting from the secondary combustion; in contrast again, during the termination transition phase 340 and the termination phase 350, the amount of both primary air 170 and 172 may be reduced after the solid fuel is depleted. However, a typical user of the combustion system 100 may not have expertise in how to control the airflow in the chamber 102 in order to lower emissions and optimize combustion the solid fuel, and it may be onerous or time-consuming for the typical user of the combustion system 100 to manually control the primary airflow 170 and/or the secondary airflow 172 by manually adjusting dampers of the combustion system 100. Accordingly, the processor 151 is generally configured to periodically or continuously execute the determine phase process 500 in order to determine a current phase of the combustion cycle 300 and to periodically or continuously execute the control airflow process 600 to control the primary and secondary airflows 170 and 172 within the chamber 102 based on the current phase determined using the determine phase process 500 as described below.

Combustion Zones

[0081] Still referring to FIG. 5, a particular combustion system 100 may also be associated with different combustion zones corresponding to different temperature ranges. Generally, the combustion zones comprise: (A) a temperature range corresponding to zone A 360 also referred to as a under-fire zone, where the solid fuel in the chamber 102 is not currently undergoing combustion; (B) a temperature range corresponding to zone B 362 also referred to as a working zone, where the solid fuel in the chamber is combusting and/or decaying; and (B) a temperature range corresponding to zone C 364 also referred to as an over-fire zone, which may represent an over-heating of the combustion system 100. These temperature ranges may include at least one of (a) ranges of the chamber temperature as measured by the chamber sensor 130, or (b) ranges of the exhaust temperature as measured by the exhaust sensor 132.

[0082] Precise values of the temperature ranges which define the different combustion zones of a particular combustion system 100 may vary depending on a variety of factors associated with the combustion system 100, as well as factors associated an ambient environment around the particular combustion system 100, including without limitation size and material of the chamber 102, configuration of a baffle in the chamber 102, size and material of the exhaust 116 and the outlet 117, distance of the particular combustion system 100 relative to a wall in the ambient environment, the conditions of the ambient environment, etc. For example, in the embodiment shown in FIG. 5, the combustion system 100 has a zone A 360 corresponding to a chamber temperature of below approximately 200 C., a zone B 362 corresponding to a chamber temperature of between approximately 200 C. and approximately 350 C., and a zone C 364 corresponding to a chamber temperature above 350 C. In other embodiments, a zone A 360 may correspond to a chamber temperature below anywhere between 100 C. and 300 C., a zone C 364 may correspond to a chamber temperature above anywhere between 200 C. and 600 C., and a zone B 362 may be corresponding temperature ranges therebetween.

[0083] Initial determination of the temperature ranges which define the different combustion zones of a particular combustion system 100 may be determined by a manufacturer of the particular combustion system 100 using methods known to those skilled in the art. For example, the manufacturer may perform combustion tests using a standard amount of solid fuel in the particular combustion system 100 at a standard ambient temperature and ambient humidity during the manufacture process. The manufacturer may also provide recommendations and requirements for distance between the combustion system 100 and walls in the ambient environment to ensure safety and consistency in the temperature ranges which define the different combustion zones. The determined temperature ranges which define the different combustion zones of a particular combustion system 100 may be stored in the setpoint data store 180 of that particular combustion system 100.

[0084] To define the different combustion zones associated with a particular combustion system 100, and in particular to define the optimal working zone B 362, a particular combustion system 100 may be associated with an under-zone setpoint (corresponding to a temperature marking a transition between the zone A 360 and the zone B 362 for that particular combustion system 100) and an over-zone setpoint (corresponding to a temperature a transition between the zone B 362 and the zone C 368. Similar to the temperature ranges described above, these setpoints may also correspond to at least one of (A) a chamber temperature as measured by the chamber sensor 130, namely a chamber zone setpoint or (B) an exhaust temperature as measured by the exhaust sensor 132, namely an exhaust zone setpoint In the embodiment shown in FIG. 5, the combustion system 100 has a chamber under-zone setpoint C.sub.za (corresponding to the chamber temperature as measured by the chamber sensor 130) of approximately 200 C. and a chamber over-zone setpoint C.sub.zc of approximately 350 C. In other embodiments, the under-zone chamber setpoint C.sub.za may range between approximately 100 C. and approximately 300 C., while the over-zone chamber setpoint C.sub.zc may range between approximately 200 C. and 450 C. Precise values of the zone setpoints may also vary depending on the variety of factors associated with the combustion system 100 and the ambient environment around the particular combustion system 100. The precise values of the zone setpoints may be determined by a manufacturer of the particular combustion system 100 using methods known to those skilled in the art (e.g., combustion tests as described above), and the determined zone setpoints may be stored in the setpoint data store 180 for that particular combustion system 100.

[0085] The determined temperature ranges and the determined setpoints, in particular the under-zone chamber setpoint C.sub.za and the over-zone chamber setpoint C.sub.zc, may be used by the processor 151 in the determine phase process 500 to determine the current phase of the combustion cycle 300 as described below and/or in the control airflow process 600 to modulate control of the primary and secondary airflows 170 and 172 as also described below.

Temperature Setpoints

[0086] A particular combustion system 100 may also be associated with a variety of different temperature setpoints indicative of certain events occurring in the chamber 102 and/or transition of the combustion system 100 through the different phases of the combustion cycle 300.

[0087] For example, a particular combustion system 100 may be associated with endothermic setpoints representing an upper limit of a temperature during an endothermic phase of the primary combustion of the solid fuel (before an exothermic phase where the solid fuel releases heat). Generally, during the endothermic phase of the primary combustion, the chamber and exhaust temperatures decrease as the solid fuel absorbs energy from the combustion system 100 until enough energy is absorbed to initiate the exothermic phase of the primary combustion (e.g., ignition of the solid fuel at the ignition event 313). The endothermic setpoints may correspond to at least one of (A) a chamber temperature as measured by the chamber sensor 130, namely a chamber endothermic setpoint C.sub.endo, or (B) an exhaust temperature as measured by the exhaust sensor 132, namely an exhaust endothermic setpoint E.sub.endo.

[0088] In the embodiment shown in FIG. 5, the combustion system 100 has a chamber endothermic setpoint C.sub.endo of approximately 320 C. and an exhaust endothermic setpoint E.sub.endo of approximately 480 C. In other embodiments and in other combustion systems 100, the chamber endothermic setpoint C.sub.endo may range between approximately 200 C. and 450 C., while the exhaust endothermic setpoint E.sub.endo may range between approximately 300 C. and 600 C. Precise values of the endothermic setpoints may vary depending on the variety of factors associated with a particular combustion system 100 and the ambient environment around the particular combustion system 100. The precise values of the endothermic setpoints may be determined by a manufacturer of the particular combustion system 100 using methods known to those skilled in the art (e.g., combustion tests as described above), and the determined endothermic setpoints may be stored in the setpoint data store 180 of the particular combustion system 100.

[0089] A particular combustion system 100 may also be associated with initiation transition value, which may represent a weighted temperature change required for a particular combustion system 100 to transition to the initiation transition phase 320. The initiation transition values may be combined with a temperature of the combustion system 100 when the solid fuel is ignited (i.e., when the ignition event 313 has occurred) to determine whether the combustion system 100 has transitioned to the initiation transition phase 320. The initiation transition values may also reflect a change in at least one of (A) a chamber temperature as measured by the chamber sensor 130, namely a chamber initiation transition value C.sub.inital_trans, or (B) an exhaust temperature as measured by the exhaust sensor 132, namely an exhaust initiation transition value E.sub.inital_trans. Precise values of the initiation transition values may vary depending on the variety of factors associated with the combustion system 100 and the ambient environment around the particular combustion system 100. The precise values of the initiation transition setpoints may be determined by a manufacturer of the particular combustion system 100 using methods known to those skilled in the art (e.g., combustion tests as described above), and the determined initiation transition values may be stored in the setpoint data store 180 of the particular combustion system 100.

[0090] Additionally, a particular combustion system 100 may also be associated with equilibrium value, which may represent a weighted temperature change required for a particular combustion system 100 to transition to the equilibrium phase 330. The equilibrium values may be combined with a temperature of the combustion system 100 when the solid fuel is ignited (i.e., when the ignition event 313 has occurred) to determine whether the combustion system 100 has transitioned to the equilibrium phase 330. The equilibrium value may also reflect a change in at least one of: (A) a chamber temperature as measured by the chamber sensor 130, namely a chamber equilibrium value C.sub.equil, or (B) an exhaust temperature as measured by the exhaust sensor 132, namely an exhaust equilibrium value E.sub.equil. Precise values of the equilibrium values may also vary depending on the variety of factors associated with the combustion system 100 and the ambient environment around the particular combustion system 100. The precise values of the equilibrium values may be determined by a manufacturer of the particular combustion system 100 using methods known to those skilled in the art (e.g., combustion tests as described above), and the determined equilibrium values may be stored in the setpoint data store 180 of the particular combustion system 100.

[0091] Additionally, a particular combustion system 100 may also be associated with termination transition value, which may represent a weighted temperature change required for a particular combustion system 100 to transition from the equilibrium phase 330 to the termination transition phase 340. The termination transition values may be combined with the endothermic setpoints of the combustion system 100 to determine whether the combustion system 100 has transitioned to the equilibrium phase 330 to the termination transition phase 340, and is typically only utilized after the controller 150 determines that the termination event 315 has occurred for a particular combustion cycle 300. The termination transition value may also reflect a change in at least one of: (A) a chamber temperature as measured by the chamber sensor 130, namely a chamber termination transition value C.sub.term_tans, or (B) an exhaust temperature as measured by the exhaust sensor 132, namely an exhaust termination transition value E.sub.term_trans. Precise values of the termination transition values may also vary depending on the variety of factors associated with the combustion system 100 and the ambient environment around the particular combustion system 100. The precise values of the termination transition values may be determined by a manufacturer of the particular combustion system 100 using methods known to those skilled in the art (e.g., combustion tests as described above), and the determined termination transition values may be stored in the setpoint data store 180 of the particular combustion system 100.

[0092] Additionally, a particular combustion system 100 may also be associated with termination value, which may represent a weighted temperature change required for a particular combustion system 100 to transition from to the termination phase 350. The termination transition values may be combined with a temperature of the combustion system 100 when the solid fuel is ignited (i.e., when the ignition event 313 has occurred) to determine whether the combustion system 100 has transitioned to the termination phase 350, and is also typically only utilized after the controller 150 determines that the termination event 315 has occurred for a particular combustion cycle 300. The termination value may also reflect a change in at least one of: (A) a chamber temperature as measured by the chamber sensor 130, namely a chamber termination value C.sub.term, or (B) an exhaust temperature as measured by the exhaust sensor 132, namely an exhaust termination value E.sub.term. Precise values of the termination values may also vary depending on the variety of factors associated with the combustion system 100 and the ambient environment around the particular combustion system 100. The precise values of the termination values may be determined by a manufacturer of the particular combustion system 100 using methods known to those skilled in the art (e.g., combustion tests as described above), and the determined termination transition values may be stored in the setpoint data store 180 of the particular combustion system 100.

[0093] Additionally, a particular combustion system 100 may also be associated with upper setpoints which may represent an upper limit of temperature during a typical combustion cycle 300 and corresponding lower setpoints which may represent a lower limit of temperature during a typical combustion cycle 300. The upper and lower setpoints may be used by the processor 151 to modulate primary and secondary airflow percentage value generated by the processor 151 during the control airflow process 600. The upper and lower setpoints may correspond to at least one of: (A) a chamber temperature as measured by the chamber sensor 130, namely a chamber upper setpoint C.sub.upper and a chamber lower setpoint C.sub.lower, or (B) an exhaust temperature as measured by the exhaust sensor 132, namely an exhaust upper setpoint E.sub.upper and an exhaust lower setpoint E.sub.lower.

[0094] In the embodiment shown in FIG. 5, the combustion system 100 has an exhaust upper setpoint E.sub.tower of approximately 100 C. and an exhaust upper setpoint E.sub.upper of approximately 500 C. In other embodiments and in other combustion systems 100, the exhaust upper and lower setpoints E.sub.upper and E.sub.lower may, respectively, range between approximately 400 C. and 700 C. and between approximately 0 C. and 200 C. Precise values of upper and lower setpoints may vary depending on the variety of factors associated with a particular combustion system 100 and the ambient environment around the particular combustion system 100. The precise values of the upper and lower setpoints may be determined by a manufacturer of the particular combustion system 100 using methods known to those skilled in the art (e.g., combustion tests as described above), and the determined upper and lower setpoints may be stored in the setpoint data store 180 of the particular combustion system 100.

[0095] Precise values of the termination values may also vary depending on the variety of factors associated with the combustion system 100 and the ambient environment around the particular combustion system 100. The precise values of the termination values may be determined by a manufacturer of the particular combustion system 100 using methods known to those skilled in the art (e.g., combustion tests as described above), and the determined termination transition values may be stored in the setpoint data store 180 of the particular combustion system 100.

[0096] The determined setpoints and values may be used by the processor 151 in the determine phase process 500 to determine the current phase of the combustion cycle 300 as described below and/or in the control airflow process 600 to modulate control of the primary and secondary airflows 170 and 172 as also described below.

Determine Phase Process 500 and Control Airflow Process 600

[0097] As briefly described above, to lower emissions resulting from the combustion of the solid fuel, as well as to optimize combustion during the combustion cycle 300, the amount of the primary airflow 170 and the amount of the secondary airflow 172 may need to be modified during different phases of the typical combustion cycle 300. The processor 151 is thus generally configured to periodically or continuously execute the determine phase process 500 to determine a current phase of the combustion cycle 300 of the combustion within a particular combustion system 100, and then to execute the control airflow process 600 to control the primary and secondary airflows 170 and 172 within the chamber 102 based on the current phase of the combustion cycle 300.

[0098] Referring to FIGS. 6A ad 6B, the determine phase process 500 generally includes codes which direct the processor 151 to determine whether the combustion system 100 is in one of the different phases of the typical combustion cycle 300, based at least in part on the chamber temperatures retrieved from the chamber sensor 130 and the exhaust temperatures retrieved from the exhaust sensor 132. Referring to FIG. 7, the control airflow process 600 generally include codes which direct the processor 151 to generate signals to control the primary airflow 170 and the secondary airflow 172 (e.g., activate the primary actuator 140 and the secondary actuator 142 differently) based on the phase determined using the determine phase process 500. In the embodiment shown in FIGS. 6A, 6B and 7, the determine phase process 500 and the control airflow process 600 comprises machine, processor and/or computer readable/executable instructions stored in the program memory 154 for execution by the processor 151; in other embodiments, the determine phase process 500 and the control airflow process 600 may comprise machine, processor and/or computer readable instructions alternatively stored on other non-transitory computer readable storage medium such as a CD-ROM, a floppy disk, a hard drive, a DVD, a Blu-ray disk or another component associated with the controller 150; in yet other embodiments, the determine phase process 500, the control airflow process 600 and/or parts thereof could alternatively be executed by a device other than the processor 151 and/or embodied in firmware or dedicated hardware.

[0099] Referring now to FIG. 6A, the determine phase process 500 begins at block 502, which may include codes directing the processor 151 to retrieve a current chamber temperature T.sub.cc (e.g., by retrieving a chamber temperature measured by the chamber sensor 130) and a current exhaust temperature T.sub.ec (e.g., by retrieving an exhaust temperature measured by the exhaust sensor 132). In the embodiment shown, block 502 directs the processor 151 to retrieve the current chamber and exhaust temperatures T.sub.cc and the T.sub.ec every 1 minute; however, in other embodiments, the processor 151 may be directed to retrieve the current chamber and exhaust temperatures T.sub.cc and the T.sub.ec at different intervals, including without limitation every second, 5 seconds, 30 seconds, five minutes, 10 minutes, 15 minutes, etc. Block 502 may also direct the processor 151 to store the retrieved current chamber and exhaust temperatures T.sub.cc and T.sub.ec in the temperature data store 182 associated with a current time of execution of block 502.

Initiation Phase 310

[0100] The determine phase process 500 then continues to block 504, which may include codes directing the processor 151 to determine whether the combustion system 100 is in the initiation phase 310. Broadly, block 504 directs the processor 151 to determine whether the reload event 311 and/or the ignition event 313 in order to determine whether the combustion system 100 is in the initiation phase 310. One embodiment of block 504 is described below; however, one skilled in the art will recognize that alternative methods for determining whether the combustion system 100 is in the initiation phase 310 based on the current chamber and exhaust temperatures T.sub.cc and T.sub.ec retrieved at a current time, alone or in combination with previous chamber and exhaust temperatures T.sub.cn and T.sub.en retrieved at previous times, are possible.

[0101] In accordance with the embodiment shown in FIG. 6A, block 504 begins at subblock 550, which may include codes for directing the processor 151 to determine whether the current chamber temperature T.sub.cc retrieved at block 502 indicates that the combustion system 100 is currently in the zone A 360, the zone B 362 or the zone C 364 for that particular combustion system 100. For example, subblock 550 may direct the processor 151 to determine whether the current chamber temperature T.sub.cc is (A) below the under-zone chamber setpoint C.sub.za; (B) is between the under-zone chamber setpoint C.sub.za and the over-zone chamber setpoint C.sub.zc; or (C) is above the over-zone chamber setpoint C.sub.zc. The under-zone and over-zone chamber setpoints C.sub.za and C.sub.zc may be retrieved by the processor 151 from the setpoint data store 180 and may be generated by the manufacturer of the particular combustion system 100 as described above.

[0102] If at subblock 550, the processor 151 determines that the combustion system 100 is currently in the zone A 360 (e.g., the current chamber temperature T.sub.cc is below the under-zone chamber setpoint C.sub.za) or is currently in the zone B 362 (e.g., the current chamber temperature T.sub.cc is between the under-zone chamber setpoint C.sub.za and the over-zone chamber setpoint C.sub.zc), block 504 continues to subblock 552. Subblock 552 may include codes directing the processor 151 to perform a reload event detection to determine whether the reload event 311 has occurred. As described above, the reload event 311 may corresponding to a user adding the solid fuel into the chamber 102. However, in some cases, the reload event 311 may also correspond to the user manually actuating one or more air dampers associated with the combustion system 100 (e.g., the dampers 113, 115, 123 and 125 shown in FIGS. 2 and 3) based on personal preference, the user manually activating one or more convection fans associated with the chamber 102 or the exhaust 116, or due to the solid fuel shifting in the chamber 102 (e.g., a piece of unignited wood falls over).

[0103] The reload event detection performed at subblock 552 may be based on the chamber and exhaust temperatures measured by the chamber and exhaust sensors 130 and 132. For example, subblock 552 may direct the processor 151 to determine whether the current exhaust temperature T.sub.ec (e.g., retrieved at block 502) is different (either increased or decreased) relative to at least one previous exhaust temperature T.sub.en, such as by using equation (1) below. The reload event 311 may correspond to any change between the current and previous exhaust temperatures T.sub.ec and T.sub.en. In this regard, any change between the current and previous exhaust temperatures T.sub.ec and T.sub.en indicates a change in temperature of the combustion system 100, such as that caused by opening of the door 106, which is in turn required to reload the solid fuel (e.g., required when the reload event 311 occurs).

[00001]$\begin{array}{cc}{T}_{\mathrm{en}}-T_{\mathrm{ec}}=T_{\mathrm{en}-\mathrm{ec}}0& \left(1\right)\end{array}$ [0104] wherein the current chamber temperature T.sub.cc may be retrieved from a current block 502 executed at a current time; and the previous exhaust temperature T.sub.en may be retrieved from the temperature data store 182 after being generated by a previous block 502 executed at a previous time earlier than the current time. The previous time may be an immediate previous block 502. For example, when the current time is 12:00 and when block 502 is executed every 1 minute: subblock 552 may retrieve a T.sub.en corresponding to the previous time of 11:59. The previous time may additionally or alternatively be a non-immediate previous block 502, and may correspond to a previous time which was a certain period of time in the past relative to the current time. For example, when the current time is 12:00, in embodiments where block 502 is executed every 1 minute and the period of time is 5 minutes: subblock 552 may retrieve a T.sub.en corresponding to the previous time of 11:55. The previous time may be a previous block 502 or otherwise associated with an indicator or a flag.

[0105] The reload event detection may also be performed using alternative sensors associated with the combustion system 100. In some embodiments, subblock 552 may direct the processor 151 to determine whether the door 106 has been opened with the movement sensor associated with the door 106. The reload event 311 may correspond to an indication that the door 106 has been opened, as would be required to reload the solid fuel. In other embodiments, subblock 552 may direct the processor 151 to determine whether the weight sensor below the bottom wall 401 indicates that matter has been added to the chamber 102. The reload event 311 may correspond to an indication that there is additional mass in the chamber 102, as would be required when the solid fuel is reloaded.

[0106] If the reload event 311 is not detected, block 504 may end and the determine phase process 500 may return to block 502 and continue therefrom as described above and below.

[0107] If the reload event 311 is detected, block 504 may continue to subblock 554, which may includes code directing the processor 151 to set flags, setpoints and timers to assist in further determinations of the initiation phase 310, the initiation transition phase 320, the equilibrium phase 330, the termination transition phase 340 and the termination phase 350.

[0108] For example, subblock 554 may direct the processor 151 to associate the current chamber and exhaust temperatures T.sub.cc and T.sub.ec with a reload event flag. For example, the processor 151 may store the reload event flag in association with the current chamber and exhaust temperatures T.sub.cc and T.sub.ec and the current time in the temperature data store 180. Subblock 554 may also direct the processor 151 to: (A) set the current chamber temperature T.sub.cc as a chamber reload setpoint C.sub.reload representing the chamber temperature at the reload event 311; and (B) set the current exhaust temperature T.sub.ec as a exhaust reload setpoint E.sub.reload representing the exhaust temperature at the reload event. For example, the processor 151 may store the current chamber and exhaust temperatures T.sub.cc and T.sub.ec as, respectively, the current chamber and exhaust reload setpoints C.sub.reload and E.sub.reload in the setpoint data store 182.

[0109] In some embodiments, subblock 554 may direct the processor 151 to mark the current time of block 502 as a time of the reload event 311 t.sub.reload and initiate an ignition event detection timer which begins counting from t.sub.reload (i.e., t.sub.reload=t.sub.0). Subblock 554 may also direct the processor 151 to use the chamber reload setpoint C.sub.reload and the chamber endothermic setpoint C.sub.endo, in combination with the t.sub.reload, to determine a maximum allowed time t.sub.allowed for assessing whether the ignition event 313 has occurred, such as by using equation (2) below. Generating the maximum allowed time t.sub.allowed generally allows the processor 151 to distinguish between a true reload event 311 which will result in ignition of the solid fuel and a false reload event 311 (e.g., when a user manually adjusts the air dampers or the convection fans as described above).

[00002]$\begin{array}{cc}{t}_{\mathrm{allowed}}=\frac{\left[\left(C_{\mathrm{reload}}-C_{\mathrm{za}}\right)\left(0-t_{\max }\right)\right]}{\left[\left(C_{\mathrm{endo}}-C_{\mathrm{za}}\right)\right]}+t_{\max }& \left(2\right)\end{array}$ [0110] wherein the chamber reload setpoint C.sub.reload, the chamber endothermic setpoint C.sub.endo and the under-zone chamber setpoint C.sub.za and t.sub.max may all be retrieved from the setpoint data store 182. t.sub.max may represent a maximum amount of time possible for the ignition event detection timer of a particular combustion system 100 and may be approximately 30 minutes. In other embodiments, t.sub.max may range anywhere between 1 minute and 60 minutes and may primarily depend on a size of the chamber 102 for example. The precise values of t.sub.max may be determined by a manufacturer of the particular combustion system 100 using methods known to those skilled in the art (e.g., combustion tests as described above), and the determined t.sub.max may be stored in the setpoint data store 180 of the particular combustion system 100.

[0111] Equation (2) means that t.sub.allowed decreases as the chamber reload setpoint C.sub.reload increases and approaches the chamber endothermic setpoint C.sub.endo. For example, when C.sub.endo iS approximately 320 C., C.sub.za is approximately 200 C. and t.sub.max is 30 minutes (1800 seconds): (A) if C.sub.reload is 280 C., t.sub.allowed would be approximately 10 minutes (600 seconds); however (B) if C.sub.reload is 210 C., t.sub.allowed would be approximately 27.5 minutes (1650 seconds)

[0112] Block 504 then continues to subblock 555, which may include codes directing the processor 151 to retrieve current chamber and exhaust temperatures T.sub.cc and T.sub.ec (e.g., from the chamber and exhaust sensors 130 and 132) for the duration of the t.sub.allowed determined at subblock 554. Similar to block 502 described above, subblock 555 may direct the processor 151 to retrieve the current chamber and exhaust temperatures T.sub.cc and the T.sub.ec every 1 minute; in other embodiments, the current chamber and exhaust temperatures T.sub.cc and T.sub.ec may be retrieved at different intervals. Subblock 555 may also direct the processor 151 to store the retrieved current chamber and exhaust temperatures T.sub.cc and T.sub.ec in the temperature data store 182 associated with a current time of execution of subblock 555.

[0113] Block 504 then continues to subblock 556, which may include codes directing the processor 151 to perform an ignition event detection to determine whether the ignition event 313 (corresponding to an ignition of the solid fuel) has occurred during the t.sub.allowed determine using subblock 554.

[0114] The ignition event detection performed at subblock 556 may be based on the chamber and exhaust temperatures measured by the chamber and exhaust sensors 130 and 132. Additionally, the ignition event detection performed at subblock 556 may also be based on whether at subblock 550, the processor 151 determined that the combustion system 100 is in the zone A 360 or the zone B 362.

[0115] For example, subblock 556 may direct the processor 151 to determine an ignition event chamber temperature change f(T.sub.c) needed for the ignition event 313 to occur given a particular current chamber temperature T.sub.cc measured at the current subblock 555, such as according to equation (3) below.

[00003]$\begin{array}{cc}f\left(T_c\right)=\frac{\left(C_{\mathrm{endo}}-C_{\mathrm{za}}\right)}{\left(C_{\mathrm{endo}}-T_{\mathrm{cc}}\right)}*\mathrm{kfit}& \left(3\right)\end{array}$ [0116] wherein the chamber endothermic setpoint C.sub.endo, the under-zone chamber setpoint C.sub.za, and the kfit may all be retrieved from the setpoint data store 182; and the current chamber temperature T.sub.cc may be retrieved from a currently executed subblock 555. kfit may represent to value or algorithm based on an amount of energy required to heat and/or dry the solid fuel prior to the exothermic phase of the primary combustion. kfit may primary depend on a size of the chamber 102 for example. The precise values of kfit may be determined by a manufacturer of the particular combustion system 100 using methods known to those skilled in the art (e.g., combustion tests as described above), and the determined kfit may be stored in the setpoint data store 180 of the particular combustion system 100.

[0117] Equation (3) generally means that the ignition event chamber temperature change f(T.sub.c) needed for to indicate that the ignition event 313 has occurred increases as the current chamber temperature T.sub.cc approaches the chamber endothermic setpoint C.sub.endo. Using the example described above, when C.sub.endo is approximately 320 C. and C.sub.za is approximately 200 C.: (A) if T.sub.cc is approximately 280 C., f(T.sub.c) would be approximately 3 C.; but, (B) if T.sub.cc is approximately 300 C., f(T.sub.c) would be approximately 6 C.; but (C) if T.sub.cc is approximately 250 C., f(T.sub.c) would be approximately 1.7 C. This generally means that the chamber temperature change f(T.sub.c) required to indicate that the ignition event 313 has occurred increases as the current chamber temperature T.sub.cc approaches the chamber endothermic setpoint C.sub.endo. Equation (3) may allow the processor 151 to more stringently detect the ignition event 313, which may be useful when the combustion system 100 is in the zones A and B 360 and 362 when other events (e.g., the reload event 311 and the termination event 315) may be occurring. Equation (3) also generally requires the current chamber temperature T.sub.cc to be higher than the under-zone chamber setpoint C.sub.za for the ignition event 313 to occur.

[0118] If at subblock 550, the processor 151 determined that the combustion system 100 is in the zone A 360, subblock 556 may direct the processor 151 to determine whether the ignition event 313 occurred by determining if a difference between the current chamber temperature T.sub.cc and at least one previous chamber temperature T.sub.cn is greater than the ignition event chamber temperature change f(T.sub.c), such as by using equation (4) below.

[00004]$\begin{array}{cc}{T}_{\mathrm{cn}}-T_{\mathrm{cc}}=T_{\mathrm{cn}-\mathrm{cc}}f\left(T_c\right)& \left(4\right)\end{array}$ [0119] wherein the current chamber temperature T.sub.cc may be retrieved from a current subblock executed 555 at a current time; and the previous chamber temperature T.sub.cn may be retrieved from the temperature data store 182 after being generated by a previous subblock 555 (or block 502) at a previous time earlier than the current time. The previous time may be an immediate previous subblock 555 (or block 502), may be a non-immediate previous subblock 555 (or block 502), or may be a previous subblock 555 (or block 502) otherwise associated with an indicator or a flag.

[0120] If T.sub.cn-cc<f(T.sub.c), then the chamber temperature has not decreased sufficiently to indicate the ignition event 313 has occurred. Subblock 556 may direct the processor 151 to return to subblock 555 and continue therefrom as described above when the t.sub.allowed determined at subblock 554 has not yet expired. Subblock 556 may instead direct the processor to return to block 502 (or to optionally to subblock 550 to perform a further combustion zone determination) and continue therefrom as described above when the t.sub.allowed determined at subblock 554 has expired.

[0121] If T.sub.cn-ccf(T.sub.c), then the chamber temperature has decreased sufficiently to indicate the ignition event 313. Subblock 556 may then direct the processor 151 to determine that the combustion system 100 has entered the initiation phase 310 and to execute block 602 of the control airflow process 600 to control the primary and secondary actuators 140 and 142 in an initiation configuration to optimize the initiation phase 310 as described below. Block 504 may also continue to subblock 558, which may include codes directing the processor 151 to set flags, setpoints and timers to assist in further determinations of the initiation transition phase 320, the equilibrium phase 330, the termination transition phase 340 and the termination phase 350 as described above.

[0122] For example, subblock 558 may direct the processor 151 to associate the current chamber and exhaust temperatures T.sub.cc and T.sub.ec with an ignition event flag. For example, the processor 151 may store the ignition event flag in association with the current chamber and exhaust temperatures T.sub.cc and T.sub.ec in the temperature data store 180. Subblock 558 may also direct the processor 151 to: (A) set the current chamber temperature T.sub.cc as a chamber ignition setpoint C.sub.ignition representing a chamber temperature at the ignition event 313; and (B) set the current exhaust temperature T.sub.ec as an exhaust ignition setpoint E.sub.ignition representing an exhaust temperature at the ignition event 313. For example, the processor 151 may store the current chamber and exhaust temperatures T.sub.cc and T.sub.ec as, respectively, the chamber and exhaust ignition setpoints C.sub.ignition and E.sub.ignition in the setpoint data store 182.

[0123] In some embodiments, subblock 558 may also direct the processor 151 to mark the current time of the current subblock 555 as a time of the ignition event 313 t.sub.ignition and initiate a cycle timer which begins counting from t.sub.ignition (i.e., t.sub.ignition=t.sub.0). The cycle timer may be used by the determine airflow process 600 to modulate different primary airflow percentage values and secondary airflow percentage values as described below.

[0124] However, if at subblock 550, the processor 151 determined that the combustion system 100 is in the zone B 362, subblock 556 may direct the processor 151 to determine whether the ignition event 313 occurred by: (A) determining if a difference between at least one previous chamber temperature T.sub.cn and the current chamber temperature T.sub.cc is greater than the ignition event chamber temperature change f(T.sub.c), such as by using equation (4) above, and reproduced again below; and/or (B) determining if the current exhaust temperature T.sub.ec is greater than the exhaust reload setpoint E.sub.reload, such as by using equation (5) below. Active combustion (e.g., an active fire, necessary after the ignition event 313 has occurred) of the solid fuel in the chamber 102 may be indicated by an increase in the current exhaust temperature T.sub.ec relative to the reload exhaust setpoint E.sub.reload.

[00005]$\begin{array}{cc}{T}_{\mathrm{cn}}-T_{\mathrm{cc}}=T_{\mathrm{cn}-\mathrm{cc}}f\left(T_c\right)& \left(4\right)\end{array}$$\begin{array}{cc}{T}_{\mathrm{ec}}{E}_{\mathrm{reload}}& \left(5\right)\end{array}$ [0125] wherein the current exhaust temperature T.sub.ec may be retrieved from a current block 555 at a current time; and the reload exhaust setpoint E.sub.reload may be retrieved from the setpoint data store 182.

[0126] If T.sub.ec<E.sub.reload or T.sub.cn-cc<f(T.sub.c), then the exhaust temperature is not hot enough or and the chamber temperature has not decreased sufficiently to indicate that the ignition event 313 has occurred. Subblock 556 may direct the processor 151 to return to subblock 555 and continue therefrom as described above when the t.sub.allowed determined at subblock 554 has not yet expired. Subblock 556 may instead direct the processor to return to block 502 (or to optionally to subblock 550 to perform a further combustion zone determination) and continue therefrom as described above when the t.sub.allowed determined at subblock 554 has expired.

[0127] If T.sub.ecE.sub.reload and T.sub.cn-ccf(T.sub.c), then the exhaust temperature is hot enough and the chamber temperature has decreased sufficiently to indicate that the ignition event 313 has occurred. Subblock 556 may direct the processor 151 to determine that the combustion system 100 has entered the initiation phase 310, to execute block 602 of the control airflow process 600 and to continue from subblock 558 as described above.

[0128] If at subblock 550, the processor 151 determines that the combustion system 100 is currently in the zone C 364 (e.g., e.g., the current chamber temperature T.sub.cc is above the over-zone chamber setpoint C.sub.zc), subblock 550 may direct the processor 151 to return to block 502 and continue therefrom as described above. Generally, the combustion system 100 cannot be in the initiation phase 310 when the current chamber temperature T.sub.cc is above the over-zone chamber set point C.sub.zc.

Initiation Transition Phase 320

[0129] Still referring to FIG. 6A, in the embodiment shown, after block 504 ends, the determine phase process 500 continues to block 506, which may include codes directing the processor 151 to determine whether the combustion system 100 is in the initiation transition phase 320. In other embodiments, the determine phase process 500 may execute blocks 504 and 506 substantially simultaneously, such that the processor 151 determines whether the combustion system is in the initiation phase 310 or is in the initiation transition phase 320 substantially simultaneously. Broadly, block 506 includes codes directing the processor 151 to: (A) compare a current chamber temperature T.sub.cc retrieved from the chamber sensor 130 with certain chamber setpoints; and/or (B) compare a current exhaust temperature T.sub.ec received from the exhaust sensor 132 with certain exhaust setpoints, in order to determine whether the combustion system 100 is in the initiation transition phase 320. One embodiment of block 506 is described below; however, one skilled in the art will recognize that alternative methods of determining whether the combustion system 100 is in the initiation transition phase 320 based on the current chamber and exhaust temperatures T.sub.cc and T.sub.ec retrieved at a current time (e.g., from a current block 502 or subblock 555 or subblock 570), alone or in combination with previous chamber and exhaust temperatures T.sub.cn and T.sub.en retrieved at previous times (e.g., from previous blocks 502 or subblocks 555 or subblocks 570), are possible.

[0130] In accordance with the embodiment shown in FIG. 6A, block 506 begins at subblock 570, which may include codes directing the processor 151 to retrieve current chamber and exhaust temperatures T.sub.cc and T.sub.ec. Similar to block 502 and subblock 555 described above, subblock 570 may direct the processor 151 to retrieve the current chamber and exhaust temperatures T.sub.cc and the T.sub.ec every 1 minute; however, in other embodiments, the current chamber and exhaust temperatures T.sub.cc and the T.sub.ec may be retrieved at different intervals. Subblock 570 may also direct the processor 151 to store the retrieved current chamber and exhaust temperatures T.sub.cc and T.sub.ec in the temperature data store 182 associated with a current time of execution of subblock 570.

[0131] Block 506 may then continue to subblock 572, which may include codes directing the processor 151 to perform an initiation transition phase detection to determine whether the combustion system 100 has transitioned into the initiation transition phase 320. The initiation transition phase detection performed at subblock 572 may be based on the chamber and exhaust temperatures measured by the chamber and exhaust sensors 130 and 132.

[0132] For example, subblock 572 may direct the processor 151 to determine whether the current exhaust temperature T.sub.ec is above a sum of the exhaust ignition setpoint E.sub.ignition (e.g., set after a most recent subblock 558) and the exhaust initiation transition value E.sub.inital_trans, such as by using equation (6) below. The current exhaust temperature T.sub.ec increasing from the exhaust ignition setpoint E.sub.ignition (after the ignition event 313 has occurred) by the initiation transition setpoint E.sub.inital_trans may indicate that the combustion system 100 has an active fire and is consistently combusting the solid fuel to generate heat.

[00006]$\begin{array}{cc}{T}_{\mathrm{ec}}>E_{\mathrm{ignition}}+E_{\mathrm{inital\_trans}}& \left(6\right)\end{array}$ [0133] wherein the current exhaust temperature T.sub.ec may be retrieved from a current subblock 570 executed at a current time; and the exhaust ignition setpoint E.sub.ignition and the initiation transition value E.sub.inital_trans may both be retrieved from the setpoint data store 180.

[0134] Additionally or alternatively, subblock 572 may also direct the processor 151 to determine (A) whether the current chamber temperature T.sub.cc retrieved at a currently executed subblock 570 is above the chamber ignition setpoint C.sub.ignition (e.g., set after a most recent subblock 558), such as by using equation (7) below; and/or (B) whether a difference between at least one prior chamber temperature measurement T.sub.cn and the current chamber temperature T.sub.cc is below 0, such as by using equation (8) below. The current chamber temperature T.sub.cc being higher than the chamber ignition setpoint C.sub.ignition (set after the ignition event 313 has occurred) may indicate that the combustion system 100 has an active fire and is consistently combusting the solid fuel to generate heat. The current chamber temperature T.sub.cc being higher than previous chamber temperatures T.sub.cn may indicate that the chamber temperature is consistently increasing.

[00007]$\begin{array}{cc}{T}_{\mathrm{cc}}>C_{\mathrm{ignition}}& \left(7\right)\end{array}$$\begin{array}{cc}{T}_{\mathrm{cn}}-T_{\mathrm{cc}}=T_{\mathrm{cn}-\mathrm{cc}}<0& \left(8\right)\end{array}$ [0135] wherein the current chamber temperature T.sub.cc may be retrieved from a current subblock 570 at a current time; the chamber ignition setpoint C.sub.ignition may be retrieved from the setpoint data store 180; and the previous chamber temperature T.sub.cn may be retrieved from the temperature data store 182 after being generated by a previously executed subblock 570 (or block 502 or subblock 555) at a previous time earlier than the current time. As described above, the previous time may be an immediate previous subblock 570 (or block 502 or subblock 555), may be a non-immediate previous block subblock 570 (or block 502 or subblock 555) or may be a previous subblock 570 (or block 502 or subblock 55) otherwise associated with an indicator or a flag.

[0136] If T.sub.ecE.sub.ignition+E.sub.initial_trans or T.sub.ccC.sub.ignition or T.sub.cn-cc0, then the exhaust temperature is not high enough, the chamber temperature is not high enough and/or the chamber temperature is not increasing, which may indicate that a transition into the initiation transition phase 320 has not yet occurred. Subblock 572 may direct the processor 151 to return to subblock 570 and continue therefrom as described above.

[0137] If T.sub.ec>E.sub.ignition+E.sub.initial_trans and T.sub.cc>C.sub.ignition and T.sub.cc-cn<0, then the exhaust temperature is high enough, the chamber temperature is high enough and/or the chamber temperature is increasing to indicate a transition into the initiation transition phase 320 has occurred. Subblock 572 may direct the processor 151 to determine that the combustion system 100 has entered the initiation transition phase 320 and to execute block 602 of the control airflow process 600 as described above.

Block 602: Initiation Configuration

[0138] Referring now to FIG. 7, after the processor 151 determines that the combustion system 100 has entered the initiation phase 310 or the initiation transition phase 320 (e.g., after subblock 556 or 572 of the determine phase process 500 described above), the processor 151 may execute block 602 of the control airflow process 600 to control the primary and secondary actuators 140 and 142 based on an initiation configuration. Broadly, the initiation configuration directs the processor 151 to: (A) control the primary actuator 140 based on the current chamber temperature T.sub.cc (e.g., received from the chamber sensor 130 at subblocks 555 or 570) as compared to certain chamber setpoints; and (B) control the secondary actuator 142 based on the current exhaust temperature T.sub.ec (e.g., received from the exhaust sensor 132 at subblocks 555 or 570) as compared to certain exhaust setpoints. One embodiment of block 602 is described below; however, one skilled in the art will recognize that alternative methods of controlling the primary and secondary actuators 140 and 142 to optimize the primary and secondary airflows 170 and 172 during the the initiation phase 310 and the initiation transition phase 320 based on the current chamber and exhaust temperatures T.sub.cc and T.sub.ec, alone or in combination with previous chamber and exhaust temperatures T.sub.cn and T.sub.en, are possible.

[0139] In accordance with the embodiment shown in FIG. 7, block 602 may implement the initiation configuration by executing subblock 650, which may include codes directing the processor 151 to control the primary actuator 140 to determine the primary airflow percentage value for the primary airflow 170 based at least in part on: (A) a comparison of current chamber temperature T.sub.cc and the chamber endothermic setpoint C.sub.endo and/or (B) a comparison of the current exhaust temperature T.sub.ec and the exhaust upper setpoint E.sub.upper.

[0140] For example, if T.sub.cc>C.sub.endo, subblock 650 may direct the processor 151 to control the primary actuator 140 to generate 0% primary airflow 170. This can reduce the primary airflow 170 when the chamber 102 is too hot while the combustion system 100 is still in the initiation phase 310 or the initiation transition phase 320.

[0141] However, if T.sub.ccC.sub.endo, subblock 650 may direct the processor 151 to control the primary actuator 140 to default to 0% primary airflow 170, but proportionally increase the primary airflow percentage value as the current chamber temperature T.sub.cc diverges from the chamber endothermic setpoint C.sub.endo. For example, where the chamber endothermic setpoint C.sub.endo is approximately 320 C.: (A) if T.sub.cc is 300 C. (e.g., slightly<C.sub.endo), subblock 650 may direct the processor 151 to generate 10% primary airflow 170; but (B) if T.sub.cc is 100 C. (e.g., significantly<C.sub.endo), subblock 650 may direct the processor 151 to generate 90% primary airflow 170. This may result in increased primary airflow 170 when the current chamber temperature T.sub.cc is low.

[0142] In some embodiments, if T.sub.ccC.sub.endo and T.sub.ecE.sub.upper, subblock 650 may also direct the processor 151 to modulate the primary airflow percentage value by proportionally decreasing the primary airflow percentage value as the current exhaust temperature T.sub.ec diverges from the exhaust upper limit endothermic setpoint C.sub.endo. In the example described above, when the exhaust upper setpoint E.sub.upper is approximately 500 C., the chamber endothermic setpoint C.sub.endo is approximately 320 C. and the current chamber temperature T.sub.cc is approximately 100 C.: (A) if T.sub.ec is approximately 400 C. (e.g., <E.sub.upper), subblock 650 may direct the processor 151 to actuate the primary actuator 140 to generate the same 90% primary airflow 170; however (B) if T.sub.ec is approximately 550 C. (e.g., >E.sub.upper), subblock 650 may direct the processor 151 to actuate the primary actuator 140 to reduce the primary airflow percentage value to 60% primary airflow 170 instead. This modulation decreases the primary airflow 170 when the current exhaust temperature T.sub.ec is high, and may account for increased secondary airflow 172 as described below.

[0143] Additionally, block 602 may implement the initiation configuration by executing subblock 652, which may include codes directing the processor 151 to control the secondary actuator 142 to determine the secondary airflow percentage value for the primary airflow 172 based at least in part on: (A) a comparison of the current exhaust temperature T.sub.ec to the exhaust upper setpoint E.sub.upper and the exhaust lower setpoint E.sub.tower; and/or (B) a comparison of current chamber temperature T.sub.cc and the chamber endothermic setpoint C.sub.endo. In the embodiment shown in FIG. 7, subblocks 650 and 652 are executed substantially simultaneously, such that the processor 151 may generate signals for controlling both the primary and secondary actuators 140 and 142 substantially simultaneously; in other embodiments, subblocks 650 and 652 may be executed sequentially.

[0144] For example, if T.sub.ecE.sub.upper, subblock 652 may direct the processor 151 to control the secondary actuator 142 to default to between 50% and 100% secondary airflow 172, and to proportionally decrease the secondary airflow percentage value as the current exhaust temperature T.sub.ec diverges from the exhaust upper setpoint E.sub.upper. In the example described above, when the exhaust upper setpoint E.sub.upper is approximately 500 C.: (A) if T.sub.ec is 500 C. (e.g., =E.sub.upper), subblock 652 may direct the processor 151 to generate 50% secondary airflow 172; however (B) if T.sub.ec is 550 C. (e.g., >E.sub.upper), subblock 652 may instead direct the processor 151 to generate 30% secondary airflow 172. This decrease of the secondary airflow 172 when the current exhaust temperature T.sub.ec is high allows the chamber 102 to heat up during the initiation and the initiation transition phases 310 and 320.

[0145] In some embodiments, if T.sub.ecE.sub.upper and T.sub.ccC.sub.endo, subblock 652 may direct the processor 151 to control the secondary actuator 142 to default to between 50% to 100% secondary airflow 172, to proportionally decrease the secondary airflow percentage value as the current exhaust temperature T.sub.ec diverges from the exhaust upper setpoint E.sub.upper, but to add the primary airflow percentage value determined at subblock 650 to the secondary airflow percentage value. In the example described above, when the exhaust upper setpoint E.sub.upper is approximately 500 C., the chamber endothermic setpoint C.sub.endo is approximately 320 C. and the current exhaust temperature T.sub.ec is approximately 550 C. (e.g., >E.sub.upper): (A) if T.sub.cc is 400 C. (e.g., >C.sub.endo), subblock 652 may direct the processor 151 to generate the same 30% secondary airflow 172; however (B) if T.sub.cc is 300 C. (e.g., <C.sub.endo), subblock 652 may direct the processor 151 to instead generate a higher 60% secondary airflow 172. This allows the exhaust temperature to increase past the exhaust upper setpoint E.sub.upper when the chamber temperature is low, which can allow the chamber 102 to heat up during the initiation and the initiation transition phases 310 and 320.

[0146] If E.sub.upper<T.sub.ec>E.sub.lower, subblock 652 may direct the processor 151 to control the secondary actuator 142 to default to 50% secondary airflow 172, but to proportionally increase the secondary airflow percentage value as the current exhaust temperature T.sub.ec approaches the exhaust upper setpoint E.sub.upper and to proportionally decrease the secondary airflow percentage value as the current exhaust temperature T.sub.ec approaches E.sub.lower. In the previously described example where the exhaust upper setpoint E.sub.upper is approximately 500 C. and the exhaust lower setpoint E.sub.tower is approximately 100 C.: (A) if T.sub.ec is 450 C., subblock 652 may direct the processor 151 to actuate the secondary actuator 142 to generate 90% secondary airflow 172; however, (B) if T.sub.ec is approximately 200 C., subblock 652 may instead direct the processor 151 to generate 20% secondary airflow 172.

[0147] However, if T.sub.ecE.sub.lower, subblock 652 may direct the processor 151 to control the secondary actuator 142 to default to between 50% and 100% secondary airflow 172, and to proportionally decrease the secondary airflow percentage value as the current exhaust temperature T.sub.ec diverges from the exhaust lower setpoint E.sub.lower. In the previously described example where the exhaust lower setpoint E.sub.tower is approximately 100 C. and where the default is 50% secondary airflow 172: (A) if T.sub.ec is 90 C. (e.g., slightly<E.sub.lower), subblock 662 may direct the processor 151 to generate 50% secondary airflow 172; but (B) if T.sub.ec is 40 C. (e.g., significantly<E.sub.tower), subblock 662 may instead direct the processor 151 to generate 10% secondary airflow 172.

[0148] In other embodiments, subblocks 650 and 652 may generally direct the processor 151 to control the primary and secondary actuators 140 and 142 during the initiation and initiation transition phases 310 and 320 to generally achieve increases in the current chamber temperature T.sub.cc and the current exhaust temperature T.sub.ec relative to, respectively, at least one previous chamber temperature T.sub.cn and at least one previous exhaust temperature T.sub.en. In such embodiments, block 602 may generally include codes that direct the processor 151 to intermittently adjust the primary airflow percentage value (and corresponding signals to control the primary actuator 140) and the secondary percentage airflow value (and corresponding signals to control the secondary actuator 142) based on comparisons between the current chamber and exhaust temperatures T.sub.cc and T.sub.ec and the previous chamber and exhaust temperatures T.sub.cn and T.sub.en to achieve such increases.

Equilibrium Phase 330

[0149] Referring back to FIG. 6A, in the embodiment shown, after block 506 ends, the determine phase process 500 continues to block 508, which may include codes directing the processor 151 to determine whether the combustion system 100 is in the equilibrium phase 330. In other embodiments, the determine phase process 500 may execute block 508 after block 504, such that the processor 151 determines whether the combustion system 100 is in the equilibrium phase 330 directly after determining whether in the combustion system 100 has entered the initiation phase 310. Broadly, block 508 includes codes directing the processor 151 to: (A) compare a current chamber temperature T.sub.cc received from the chamber sensor 130 with certain chamber setpoints, and/or (B) to compare a current exhaust temperature T.sub.ec received from the exhaust sensor 132 with certain exhaust setpoints, in order to determine whether the combustion system 100 is in the equilibrium phase 330. One embodiment of block 508 is described below; however, one skilled in the art will recognize that alternative methods of determining whether the combustion system 100 is in the equilibrium phase 330 based on the current chamber and exhaust temperatures T.sub.cc and T.sub.ec retrieved at a current time (e.g., from a current block 502 or subblock 555 or subblock 570 or subblock 580), alone or in combination with previous chamber and exhaust temperatures T.sub.cn and T.sub.en retrieved at previous times (e.g., from previous blocks 502 or subblocks 555 or subblocks 570 or subblocks 580), are possible.

[0150] In accordance with the embodiment shown in FIG. 6A, block 508 begins at subblock 580, which may include codes directing the processor 151 to retrieve current chamber and exhaust temperatures T.sub.cc and T.sub.ec. Subblock 580 may direct the processor 151 to retrieve the current chamber and exhaust temperatures T.sub.cc and the T.sub.ec every 1 minute; however, in other embodiments, the current chamber and exhaust temperatures T.sub.cc and the T.sub.ec may be retrieved at different intervals. Subblock 580 may also direct the processor 151 to store the retrieved current chamber and exhaust temperatures T.sub.cc and T.sub.ec in the temperature data store 182 associated with a current time of execution of subblock 580.

[0151] Block 508 may then continue to subblock 582, which may include codes directing the processor 151 to perform an equilibrium phase detection to determine whether the combustion system 100 has transitioned into the equilibrium phase 330. The equilibrium phase detection performed at subblock 582 may use the chamber and exhaust temperatures measured by the chamber and exhaust sensors 130 and 132.

[0152] For example, subblock 582 may direct the processor 151 to determine whether the current exhaust temperature T.sub.ec is above the sum of the exhaust ignition setpoint E.sub.ignition and the exhaust initiation transition value E.sub.inital_trans (in a manner similar to subblock 572 described above), such as by using equation (6) above, reproduced again below. The current exhaust temperature T.sub.ec increasing from the exhaust ignition setpoint E.sub.ignition by the initiation transition value E.sub.inital_trans may again indicate that the combustion system 100 has an active fire and is consistently combusting the solid fuel to generate heat.

[00008]$\begin{array}{cc}{T}_{\mathrm{ec}}>E_{\mathrm{ignition}}+E_{\mathrm{inital\_trans}}& \left(6\right)\end{array}$ [0153] wherein the current exhaust temperature T.sub.ec may be retrieved from a current subblock 580 executed at a current time; and the exhaust ignition setpoint E.sub.ignition and the exhaust initiation transition value E.sub.inital_trans may both be retrieved from the setpoint data store 180.

[0154] Additionally or alternatively, subblock 582 may also direct the processor 151 to determine: (A) whether the current chamber temperature T.sub.cc is above the chamber endothermic setpoint C.sub.endo, such as by using equation (9) below; and/or (B) whether the current chamber temperature T.sub.cc is above a sum of the chamber ignition setpoint C.sub.ignition (e.g., set after a most recent subblock 558) and the chamber equilibrium value C.sub.equil, such as by using equation (10) below. The current chamber temperature T.sub.cc being above the chamber endothermic setpoint C.sub.endo may indicate that the combustion system 100 has an active fire. Similarly, the current chamber temperature T.sub.cc increasing from the chamber ignition setpoint C.sub.ignition by the chamber equilibrium value C.sub.equil may again indicate that the combustion system 100 indicate that the combustion system 100 has an active fire and has not cooled down from the combustion sufficiently to enter the termination transition phase 340.

[00009]$\begin{array}{cc}{T}_{\mathrm{cc}}>C_{\mathrm{endo}}& \left(9\right)\end{array}$$\begin{array}{cc}{T}_{\mathrm{cc}}>C_{\mathrm{ignition}}+C_{\mathrm{equil}}& \left(10\right)\end{array}$ [0155] wherein the current chamber temperature T.sub.cc may be retrieved from a current subblock 580 executed at a current time; and the chamber ignition setpoint C.sub.ignition, the chamber equilibrium value C.sub.equil and the endothermic chamber setpoint C.sub.endo may all be retrieved from the setpoint data store 180.

[0156] If T.sub.ecE.sub.ignition+E.sub.initial_trans Or (T.sub.ccC.sub.endo and T.sub.ecC.sub.ignition+C.sub.equil), then the exhaust temperature is not high enough and the chamber temperature is not high enough, which may indicate that a transition into the equilibrium phase 330 has not yet occurred. Subblock 582 may direct the processor 151 to return to subblock 580 and continue therefrom as described above.

[0157] If T.sub.ecE.sub.ignition+E.sub.initial_trans and (T.sub.cc>C.sub.endo Or T.sub.cc>C.sub.ignition+C.sub.equil), then the exhaust temperature is high enough and/or the chamber temperature is high enough to indicate that a transition into the equilibrium phase 330 has occurred. Subblock 582 may direct the processor 151 to determine that the combustion system 100 has entered the equilibrium phase 330 and to execute block 604 of the control airflow process 600 to control the primary and secondary actuators 140 and 142 in an equilibrium configuration to optimize the equilibrium phase 330 as described below.

Block 604: Equilibrium Configuration

[0158] Referring back to FIG. 7, after the processor 151 determines that the combustion system 100 has entered the equilibrium phase 330 (e.g., after subblock 582 of the determine phase process 500 described above), the processor 151 may execute block 604 to control the primary and secondary actuators 140 and 142 based on the equilibrium configuration. Broadly, the equilibrium configuration directs the processor 151 to: (A) control the primary actuator 140 based on the current chamber temperature T.sub.cc (e.g., received from the chamber sensor 130 at subblock 580) as compared to certain chamber setpoints; and (B) control the secondary actuator 142 based on the current exhaust temperature T.sub.ec (e.g., received from the exhaust sensor 132 at subblock 580) as compared to certain exhaust setpoints. One embodiment of block 604 is described below; however, one skilled in the art will recognize that alternative methods of controlling the primary and secondary actuators 140 and 142 to optimize the primary and secondary airflows 170 and 172 during the equilibrium phase 330 based on the current chamber and exhaust temperatures T.sub.cc and T.sub.ec, alone or in combination with previous chamber and exhaust temperatures T.sub.cn and T.sub.en, are possible.

[0159] In accordance with the embodiment shown in FIG. 7, block 604 may implement the equilibrium configuration by executing subblock 660, which may includes codes directing the processor 151 to determine the primary airflow percentage value for the primary airflow 170 by comparing the current chamber temperature T.sub.cc to the chamber endothermic setpoint C.sub.endo.

[0160] For example, if T.sub.cc>C.sub.endo, subblock 660 may direct the processor 151 to control the primary actuator 140 to default to 0% primary airflow 170. This can reduce the primary airflow 170 when the chamber 102 is too hot.

[0161] However, if T.sub.ccC.sub.endo, subblock 660 may direct the processor 151 to control the primary actuator 140 to default to 0% primary airflow 170, but will proportionally increase the primary airflow percentage value as the current chamber temperature T.sub.cc diverges from the chamber endothermic setpoint C.sub.endo. In the example described above, where the chamber endothermic setpoint C.sub.endo is approximately 320 C.: (A) if T.sub.cc is 300 C. (e.g., slightly<C.sub.endo), subblock 650 may direct the processor 151 to generate 10% primary airflow 170; but (B) if T.sub.cc IS 100 C. (e.g., significantly<C.sub.endo), subblock 650 may direct the processor 151 to generate 90% primary airflow 170. This may result in increased primary airflow 170 when the current chamber temperature T.sub.cc is low.

[0162] Subblock 660 may also direct the processor 151 to initiate block 506 or block 510 to determine whether the combustion system 100 has transition back into the initiation transition phase 320 if the termination event 315 has not yet occurred (e.g., determined using subblock 592 described below) or transitioned forward into the termination transition phase 340 if the termination event 315 has occurred.

[0163] Additionally, block 604 may implement the equilibrium configuration by executing subblock 662, which may include codes directing the processor 151 to determine a secondary airflow percentage value for the secondary airflow 172 by: (A) comparing the current exhaust temperature T.sub.ec to the exhaust upper setpoint E.sub.upper and the exhaust lower setpoint E.sub.tower; and/or (B) a comparison of current chamber temperature T.sub.cc and the chamber endothermic setpoint C.sub.endo. In the embodiment shown in FIG. 7, subblocks 660 and 662 are executed substantially simultaneously, such that the processor 151 may generate signals for controlling both the primary and secondary actuators 140 and 142 substantially simultaneously; in other embodiments, subblocks 660 and 662 may be executed sequentially.

[0164] For example, if T.sub.ecE.sub.upper, subblock 662 may direct the processor 151 to control the secondary actuator 142 to default to 100% secondary airflow 172, and to proportionally decrease the secondary airflow percentage value as the current exhaust temperature T.sub.ec diverges from the exhaust upper setpoint E.sub.upper. In the previously described example where the exhaust upper setpoint E.sub.upper is approximately 500 C.: (A) if T.sub.ec is 550 C. (e.g., slightly>E.sub.upper), subblock 652 may direct the processor 151 to generate 90% secondary airflow 172; however, (B) if T.sub.ec IS 600 C. (e.g., significantly>E.sub.upper), subblock 652 may instead direct the processor 151 to generate 10% secondary airflow 172.

[0165] Additionally, in some embodiments, if T.sub.ecE.sub.upper and T.sub.ccC.sub.endo, Subblock 662 may also direct the processor 151 to default to 100% secondary airflow 172, to proportionally decrease the secondary airflow percentage value as the current exhaust temperature T.sub.ec diverges from the exhaust upper setpoint E.sub.upper, but to add the primary airflow percentage value determined at subblock 660 to the secondary airflow percentage value. In the previously described example where the exhaust upper setpoint E.sub.upper is approximately 500 C., the chamber endothermic setpoint C.sub.endo is approximately 320 C., and the current exhaust temperature T.sub.ec is approximately 600 C. (e.g., >E.sub.upper): (A) if T.sub.cc is 400 C. (e.g., >C.sub.endo), subblock 662 may direct the processor 151 to generate the same 10% secondary airflow 172 as described above; however (B) if T.sub.cc is 300 C. (e.g., <C.sub.endo), subblock 662 may direct the processor 151 to instead generate a higher modulated 20% secondary airflow 172 instead. This can allow the exhaust temperature to increase past the exhaust upper setpoint E.sub.upper when the chamber temperature is low.

[0166] If E.sub.upper<T.sub.ec>E.sub.lower, subblock 662 may direct the processor 151 to control the secondary actuator 142 to default to 100% secondary airflow 172. This increases the secondary airflow 172 for any secondary combustion occurring during the equilibrium phase 330.

[0167] If T.sub.ecE.sub.lower, subblock 662 may direct the processor 151 to default to between 50% and 100% secondary airflow 172, and to proportionally decrease the secondary airflow percentage value as the current exhaust temperature T.sub.ec diverges from the exhaust lower setpoint E.sub.lower. In the previously described example where the exhaust lower setpoint E.sub.lower is approximately 100 C. and the default is 50% secondary airflow 172: (A) if T.sub.ec is 90 C. (e.g., slightly<E.sub.lower), subblock 662 may direct the processor 151 to generate 50% secondary airflow 172; but (B) if T.sub.ec is 40 C. (e.g., significantly<E.sub.lower), subblock 662 may instead direct the processor 151 to generate 10% secondary airflow 172.

[0168] In other embodiments, subblocks 660 and 662 may generally direct the processor 151 to control the primary and secondary actuators 140 and 142 during the equilibrium phase 330 to generally achieve a relatively consistent or a relatively small delta as between current chamber and exhaust temperatures T.sub.cc and T.sub.ec relative to, respectively, at least one previous chamber and exhaust temperatures T.sub.cn and T.sub.en. In such embodiments, block 604 may include codes that direct the processor 151 to intermittently adjust the primary airflow percentage value (and corresponding signals to control the primary actuator 140) and the secondary percentage airflow value (and corresponding signals to control the secondary actuator 142) based on comparisons between the current chamber and exhaust temperatures T.sub.cc and T.sub.ec and the previous chamber and exhaust temperatures T.sub.cn and T.sub.en to achieve this relatively consistency.

Termination Transition Phase 340

[0169] Referring now to FIGS. 6A and 6B, after block 508 ends, the determine phase process 500 continues to block 510, which may include codes directing the processor 151 to determine whether the combustion system 100 is in the termination transition phase 340. Broadly, block 510 directs the processor 151 to: (A) determine whether the termination event 315 has occurred; (B) compare a current chamber temperature T.sub.cc received from the chamber sensor 130 with certain chamber setpoints; and (C) compare a current exhaust temperature T.sub.ec received from the exhaust sensor 132 with certain exhaust setpoints, in order to determine whether the combustion system 100 is in the termination transition phase 340. One embodiment of block 510 is described below; however, one skilled in the art will recognize that alternative methods of determining whether the combustion system 100 is in the termination transition phase 340 based on the current chamber and exhaust temperatures T.sub.cc and T.sub.ec retrieved at a current time (e.g., from a current block 502 or subblock 555 or subblock 570 or subblock 580 or subblock 590 or subblock 595), alone or in combination with previous chamber and exhaust temperatures T.sub.en and T.sub.en retrieved at previous times (e.g., retrieved from previous blocks 502 or subblocks 555 or subblocks 570 or subblocks 580 or subblocks 590 or subblocks 595), are possible.

[0170] In accordance with the embodiment shown in FIG. 6B, block 510 begins at subblock 590, which may include codes directing the processor 151 to retrieve current chamber and exhaust temperatures T.sub.cc and T.sub.ec. Subblock 590 may direct the processor 151 to retrieve the current chamber and exhaust temperatures T.sub.cc and the T.sub.ec every 1 minute; however, in other embodiments, the current chamber and exhaust temperatures T.sub.cc and the T.sub.ec may be retrieved at different intervals. Subblock 590 may also direct the processor 151 to store the retrieved current chamber and exhaust temperatures T.sub.cc and T.sub.ec in the temperature data store 182 associated with a current time of execution of subblock 590.

[0171] Block 510 may then continue to subblock 592, which may include code directing the processor 151 to perform a termination event detection to determine whether the termination event 315 has occurred. The termination event detection performed at subblock 592 may use the chamber and exhaust temperatures measured by the chamber and exhaust sensors 130 and 132.

[0172] For example, subblock 592 may direct the processor 151 to determine whether the current chamber temperature T.sub.cc is above or equal to a sum of the chamber endothermic setpoint C.sub.endo and the chamber termination transition value C.sub.term_trans, such as by using equation (11) below for example. The current chamber temperature T.sub.cc increasing above the chamber endothermic setpoint C.sub.endo by the chamber termination transition value C.sub.term_trans may indicate that the combustion system 100 has reached a maximum chamber temperature possible for the combustion system 100 and is ready to enter the termination transition phase 340.

[00010]$\begin{array}{cc}{T}_{\mathrm{cc}}{C}_{\mathrm{endo}}+C_{t\mathrm{erm\_trans}}& \left(11\right)\end{array}$ [0173] wherein the current chamber temperature T.sub.cc may be retrieved from a current subblock 590 executed at a current time; and the chamber endothermic setpoint C.sub.endo and the chamber initiation transition value C.sub.term_trans may both be retrieved from the setpoint data store 180.

[0174] If T.sub.cc<C.sub.endo+C.sub.term_trans, then the chamber temperature has not reached a maximum chamber temperature, which may indicate that the termination event 315 has not occurred. Subblock 592 may direct the processor 151 to return to subblock 590 and continue therefrom as described above. Subblock 592 may optionally also direct the processor 151 to return to subblock 580 and continue therefrom, to determine whether the combustion system 100 has reverted back into the initiation transition phase 320 rather than forward into the termination transition phase 340. The combustion system 100 cannot proceed to the termination transition phase 340 or the termination phase 350 until the termination event 315 has occurred.

[0175] If T.sub.ccC.sub.endo+C.sub.term_trans, then the chamber temperature has reached the maximum chamber temperature, which may indicate that the termination event 315 has occurred. Block 510 may then continue to subblock 594, which may include codes directing the processor 151 to set flags to assist in further determinations of the termination transition phase 340 and the termination phase 350. For example, subblock 594 may direct the processor 151 to associate the current chamber and exhaust temperatures T.sub.cc and T.sub.ec with a termination event flag. For example, the processor 151 may store the termination event flag in association with the current chamber and exhaust temperatures T.sub.cc and T.sub.ec and the current time in the temperature data store 180.

[0176] Block 510 may then continue to subblock 595, which may include code directing the processor 151 to retrieve another current chamber and exhaust temperatures T.sub.cc and T.sub.ec (e.g., from the chamber and exhaust sensors 130 and 132). Subblock 595 may direct the processor 151 to retrieve the current chamber and exhaust temperatures T.sub.cc and the T.sub.ec every 1 minute; in other embodiments, the current chamber and exhaust temperatures T.sub.cc and T.sub.ec may be retrieved at different intervals. Subblock 595 may also direct the processor 151 to store the retrieved current chamber and exhaust temperatures T.sub.cc and T.sub.ec in the temperature data store 182 associated with a current time of execution of subblock 595. B

[0177] Block 510 may then continue to subblock 596, which may includes codes directing the processor 151 to perform a termination transition phase detection to determine whether the combustion system 100 has transitioned into the termination transition phase 340. Subblock 596 is only performed after the processor 151 determines at subblock 595 that the termination event 315 has occurred; as described above, the combustion system 100 cannot proceed to the termination transition phase 340 or the termination phase 350 until the termination event 315 has occurred. The termination transition phase detection performed at subblock 596 may be based on the chamber and exhaust temperatures measured by the chamber and exhaust sensors 130 and 132.

[0178] For example, subblock 570 may direct the processor 151 to determine: (A) whether the current exhaust temperature T.sub.ec is less than the sum of the exhaust ignition setpoint E.sub.ignition and the exhaust initiation transition setpoint E.sub.inital_trans, in a manner similar to subblocks 571 and 582 described above, such as by using equation (6.1) below, and/or (B) whether a difference between at least one prior exhaust temperature T.sub.en retrieved at a previously executed subblock 595 and the current exhaust temperature T.sub.ec is above 0, such as by using equation (12) below. The current exhaust temperature T.sub.ec decreasing from the exhaust ignition setpoint E.sub.ignition by the initiation transition value E.sub.inital_trans and decreasing relative to previous exhaust temperatures may indicate that the exhaust 116 is cooling and that there is no longer an active fire in the combustion system 100 generating heat.

[00011]$\begin{array}{cc}{T}_{\mathrm{ec}}<E_{\mathrm{ignition}}+E_{\mathrm{inital\_trans}}& \left(6.1\right)\end{array}$$\begin{array}{cc}{T}_{\mathrm{en}}-T_{\mathrm{ec}}=T_{\mathrm{en}-\mathrm{ec}}>0& \left(12\right)\end{array}$ [0179] wherein the current exhaust temperature T.sub.ec may be retrieved from a current subblock 595 executed at a current time; the exhaust ignition setpoint E.sub.ignition and the exhaust initiation transition value E.sub.inital_trans may be retrieved from the setpoint data store 180; and the previous exhaust temperature T.sub.en may be retrieved from the temperature data store 182 after being generated by a previous subblock 595 (or previous block 502 or subblock 555 or subblock 570 or subblock 580 or subblock 590) at a previous time earlier than the current time.

[0180] Additionally or alternatively, subblock 596 may also direct the processor 151 to determine: (A) whether the current chamber temperature T.sub.cc retrieved at a currently executed subblock 570 is less than the sum of the chamber endothermic setpoint C.sub.endo and the chamber termination transition value C.sub.term_trans, in a manner similar to subblock 592 above, such as by using equation (11.1) below for example; and (B) whether a difference between at least one previous chamber temperature T.sub.en retrieved at a previous subblock 595 (or previous block 502 or subblock 555 or subblock 570 or subblock 580 or subblock 590) and the current chamber temperature T.sub.cc is above 0, in a manner similar to subblock 572 above, such as by using equation (8.1) below. The current chamber temperature T.sub.cc decreasing to below the sum of the chamber endothermic setpoint C.sub.endo and the chamber termination transition value C.sub.term_trans from the termination transition sum (e.g., the maximum chamber temperature) and decreasing relative to previous chamber temperatures may generally indicate that the chamber 102 is cooling and that there is no longer an active fire in the combustion system 100 generating heat.

[00012]$\begin{array}{cc}{T}_{\mathrm{cc}}<C_{\mathrm{endo}}+C_{t\mathrm{erm\_trans}}& \left(11.1\right)\end{array}$$\begin{array}{cc}{T}_{\mathrm{cn}}-T_{\mathrm{cc}}=T_{\mathrm{cn}-\mathrm{cc}}>0& \left(8.1\right)\end{array}$ [0181] wherein the current chamber temperature T.sub.cc may be retrieved from a currently executed subblock 595 at a current time; the chamber endothermic setpoint C.sub.endo and the chamber initiation transition value C.sub.term_trans may be retrieved from the setpoint data store 180; and the previous chamber temperature T.sub.cn may be retrieved from the temperature data store 182 after being generated by a previous subblock 595 (or previous block 502 or subblock 555 or subblock 570 or subblock 580 or subblock 590) at a previous time earlier than the current time.

[0182] If T.sub.ecE.sub.ignition+E.sub.initial_trans or T.sub.en-ec<0 or T.sub.ecC.sub.endo+C.sub.term_trans or T.sub.cn-cc<0, then the exhaust temperature is not low enough, the exhaust temperature is not decreasing, the chamber temperature is not low enough, or the chamber temperature is not decreasing, all of which may indicate that a transition into the termination transition phase 340 has not yet occurred. Subblock 596 may direct the processor 151 to return to subblock 595 and continue therefrom as described above.

[0183] If T.sub.ec<E.sub.ignition+E.sub.initial_trans and T.sub.en-ec0 and T.sub.cc<C.sub.endo+C.sub.term_trans and T.sub.cn-cc0, then the exhaust temperature may be low enough, the exhaust temperature may be decreasing, the chamber temperature may be low enough, or the chamber temperature may be decreasing, all of which may indicate that a transition into the termination transition phase 340 has occurred. Subblock 596 may direct the processor 151 to determine that the combustion system 100 has entered the termination transition phase 340 and to execute block 606 of the control airflow process 600 to control the primary and secondary actuators 140 and 142 in the termination transition configuration to optimize the termination transition phase 340 as described below.

Block 606: Termination Transition Configuration

[0184] Referring back to FIG. 7, after the processor 151 determines that the combustion system 100 has entered the termination transition phase 340 (e.g., after subblock 596 of the determine phase process 500 described above), the processor 151 may execute block 606 to control the primary and secondary actuators 140 and 142 based on the termination transition configuration. Broadly, the termination transition configuration directs the processor 151 to control both the primary and secondary actuators 140 and 142 based on the current chamber temperature T.sub.cc as compared to certain chamber setpoints. One embodiment of block 606 is described below; however, one skilled in the art will recognize that alternative methods of controlling the primary and secondary actuators 140 and 142 to optimize the primary and secondary airflows 170 and 172 during the termination transition phase 340 based on the current chamber and exhaust temperatures T.sub.cc and T.sub.ec, alone or in combination with previous chamber and exhaust temperatures T.sub.cn and T.sub.en, are possible.

[0185] In accordance with the embodiment shown in FIG. 7, block 606 may implement the termination transition configuration by executing subblock 672, which may include codes directing the processor 151 to control the secondary actuator 142 to determine a secondary airflow percentage value for the secondary airflow 172 by comparing the current chamber temperature T.sub.cc to the chamber endothermic setpoint C.sub.endo.

[0186] For example, if T.sub.ccC.sub.endo, subblock 672 may direct the processor 151 to control the secondary actuator 142 to default to 100% secondary airflow 172, and when proportionally decrease the secondary airflow percentage value as the current chamber temperature T.sub.cc diverges from the chamber endothermic setpoint C.sub.endo. In the previously described example where the chamber endothermic setpoint C.sub.endo is approximately 320 C.: (A) if T.sub.cc is approximately 330 C. (e.g., slightly>C.sub.endo), subblock 672 may direct the processor 151 to generate 90% secondary airflow 172; and (B) if T.sub.cc is approximately 400 C. (e.g., significantly>C.sub.endo), subblock 662 may direct the processor 151 to generate 10% secondary airflow 172 instead.

[0187] If T.sub.cc<C.sub.endo, subblock 672 may direct the processor 151 to control the secondary actuator 142 to default to 100% secondary airflow 172, and proportionally decrease the secondary airflow percentage value as the current chamber temperature T.sub.cc diverges from the chamber endothermic setpoint C.sub.endo. In the previously described example where the chamber endothermic setpoint C.sub.endo is approximately 320 C.: (A) if T.sub.cc is 300 C. (e.g., slightly<C.sub.endo), subblock 672 may direct the processor 151 to generate 90% secondary airflow 172; and (B) if T.sub.cc is 100 C. (e.g., significantly<C.sub.endo), subblock 662 may direct the processor 151 to generate 10% secondary airflow 172 instead. As a result, as the current chamber temperature T.sub.cc decreases away from the chamber endothermic setpoint C.sub.endo, the secondary airflow 170 decreases.

[0188] Additionally, block 606 may implement the termination transition configuration by executing subblock 670, which may include codes directing the processor 151 to determine a primary airflow percentage value for the primary airflow 170 by comparing the current chamber temperature T.sub.cc to the chamber endothermic setpoint C.sub.endo.

[0189] For example, if T.sub.ccC.sub.endo, subblock 670 may direct the processor 151 to control the primary actuator 140 to default to 0% primary airflow 170, but will increase the primary airflow percentage value based on a multiple of the secondary airflow percentage value determined at subblock 672. In the previously described example where the chamber endothermic setpoint C.sub.endo is approximately 320 C.: (A) if T.sub.cc is 300 C. and if subblock 672 directs the processor 151 to generate 90% secondary airflow 172, subblock 670 may direct the processor 151 to generate 45% primary airflow 170; and (B) if T.sub.cc is 100 C. and subblock 672 directs the processor 151 to generate 10% secondary airflow 172, subblock 670 may direct the processor 151 to generate 5% primary airflow 170.

[0190] If T.sub.cc<C.sub.endo, subblock 670 may again direct the processor 151 to control the primary actuator 140 to default to 0% primary airflow 170, but will increase the primary airflow percentage value proportional to an amount that the current chamber temperature T.sub.cc diverges from the chamber endothermic setpoint C.sub.endo. In the previously described example where the chamber endothermic setpoint C.sub.endo is approximately 320 C.: (A) if T.sub.cc is 300 C. (e.g., slightly<C.sub.endo), subblock 672 may direct the processor 151 to generate 10% primary airflow 170; and (B) if T.sub.cc is 100 C. (e.g., significantly<C.sub.endo), subblock 672 may direct the processor 151 to generate 100% primary airflow 170. As a result, as the current chamber temperature T.sub.cc decreases away from the chamber endothermic setpoint C.sub.endo, the primary airflow 170 increases.

[0191] In other embodiments, subblocks 670 and 672 may generally direct the processor 151 to control the primary and secondary actuators 140 and 142 during the termination transition phase 340 to generally achieve decreases in the current chamber temperature T.sub.cc and the current exhaust temperature T.sub.ec relative to, respectively, at least one previous chamber temperature T.sub.cn and at least one previous exhaust temperature T.sub.en. In such embodiments, block 606 may include codes that direct the processor 151 to intermittently adjust the primary airflow percentage value (and corresponding signals to control the primary actuator 140) and the secondary percentage airflow value (and corresponding signals to control the secondary actuator 142) based on comparisons between the current chamber and exhaust temperatures T.sub.cc and T.sub.ec and the previous chamber and exhaust temperatures T.sub.cn and T.sub.en to achieve this decrease.

Termination Phase 350

[0192] Referring now to FIG. 6B, after block 510 ends, the determine phase process 500 continues to block 512, which may include codes directing the processor 151 to determine whether the combustion system 100 is in the termination phase 350. In some embodiments, the determine phase process 500 may not include block 512 and may involve not determining the termination phase 350 separate from determining the termination transition phase 340. Broadly, block 512 includes codes directing the processor 151 to: (A) compare a current chamber temperature T.sub.cc received from the chamber sensor 130 with certain chamber setpoints; and (B) to compare a current exhaust temperature T.sub.ec received from the exhaust sensor 132 with certain exhaust setpoints, in order to determine whether the combustion system 100 is in the termination phase 350. One embodiment of block 512 is described below; one skilled in the art will recognize that alternative methods of determining whether the combustion system 100 is in the termination phase 350 based on the current chamber and exhaust temperatures T.sub.cc and T.sub.ec retrieved at a current time (e.g., from a current block 502 or subblock 555 or subblock 570 or subblock 580 or subblock 590 or subblock 595 or subblock 560), alone or in combination with previous chamber and exhaust temperatures T.sub.cn and T.sub.en at previous times (e.g., retrieved from previous blocks 502 or subblocks 555 or subblocks 570 or subblocks 580 or subblocks 590 or subblocks 595 or subblocks 560), are possible.

[0193] In accordance with one embodiment, block 512 begins at subblock 560, which may include codes directing the processor 151 to retrieve current chamber and exhaust temperatures T.sub.cc and T.sub.ec. Subblock 560 may direct the processor 151 to retrieve the current chamber and exhaust temperatures T.sub.cc and the T.sub.ec every 1 minute; however, in other embodiments, the current chamber and exhaust temperatures T.sub.cc and the T.sub.ec may be retrieved at different intervals. Subblock 560 may also direct the processor 151 to store the retrieved current chamber and exhaust temperatures T.sub.cc and T.sub.ec in the temperature data store 182 associated with a current time of execution of subblock 560.

[0194] Block 512 may then continue to subblock 562, which may include codes directing the processor 151 to perform a termination phase detection to determine whether the combustion system 100 has transitioned into the termination phase 350. The termination phase detection performed at subblock 562 may use the chamber and exhaust temperatures measured by the chamber and exhaust sensors 130 and 132.

[0195] For example, subblock 562 may direct the processor 151 to determine whether the current exhaust temperature T.sub.ec is equal to or below the exhaust reload setpoint E.sub.reload, in a manner similar to subblock 550 above, such as by using equation (5.5) below. The current exhaust temperature T.sub.ec being below the exhaust reload setpoint E.sub.reload may indicate that the exhaust 116 has cooled significantly.

[00013]$\begin{array}{cc}{T}_{\mathrm{ec}}{E}_{\mathrm{reload}}& \left(5.5\right)\end{array}$ [0196] wherein the current exhaust temperature T.sub.ec may be retrieved from a current subblock 560 executed at a current time; and the exhaust reload setpoint E.sub.reload may be retrieved from the setpoint data store 180.

[0197] Additionally or alternatively, subblock 562 may also direct the processor 151 to determine (A) whether the current chamber temperature T.sub.cc is less than the chamber endothermic setpoint C.sub.endo, in a manner similar to subblock 582 above, such as by using equation (9.1) below and/or (b) whether the current chamber temperature T.sub.cc is less a sum of the chamber ignition setpoint C.sub.ignition (e.g., set after a most recent subblock 558) and the chamber termination value C.sub.term, such as by using equation (13) below. The current chamber temperature T.sub.cc being below the chamber endothermic setpoint C.sub.endo and the sum of the chamber ignition setpoint C.sub.ignition and the chamber termination value C.sub.term may similarly indicate that may that the chamber 102 has cooled significantly.

[00014]$\begin{array}{cc}{T}_{\mathrm{cc}}{C}_{\mathrm{endo}}& \left(9.1\right)\end{array}$$\begin{array}{cc}{T}_{\mathrm{cc}}{C}_{\mathrm{ignition}}+C_{\mathrm{term}}& \left(13\right)\end{array}$ [0198] wherein the current chamber temperature T.sub.cc may be retrieved from a current subblock 580 executed at a current time; and the chamber ignition setpoint C.sub.ignition, the chamber termination value C.sub.term and the endothermic chamber setpoint C.sub.endo may all be retrieved from the setpoint data store 180.

[0199] If T.sub.ec>E.sub.reload Or (T.sub.cc>C.sub.endo and T.sub.cc>C.sub.ignition+C.sub.term), the exhaust temperature may not be low enough and the chamber temperature may not be low enough, which may indicate that a transition in the termination phase 350 has not yet occurred. Subblock 562 may direct the processor 151 to return to subblock 560 and continue therefrom as described above.

[0200] If T.sub.ecE.sub.reload and (T.sub.ccC.sub.endo Or T.sub.ccC.sub.ignition+C.sub.term), the exhaust temperature may be low enough and the chamber temperature may be low enough to indicate that a transition in the termination phase 350 has occurred. Subblock 562 may direct the processor 151 to determine that the combustion system 100 has entered the termination phase 350 and to execute block 608 of the control airflow process 600 to control the primary and secondary actuators 140 and 142 in a termination configuration to optimize the termination phase 350 as described below.

Block 608: Termination Configuration

[0201] Referring back to FIG. 7, after the processor 151 determines that the combustion system 100 has entered the termination phase 350 (e.g., after subblock 562 of the determine phase process 500 described above), the processor 151 may execute block 608 to control the primary and secondary actuators 140 and 142 based on the termination configuration. Broadly, the termination configuration directs the processor 151 to: (A) control the primary actuator 140 based on the current chamber temperature T.sub.cc as compared to certain chamber setpoints; and (B) control the secondary actuator 142 based on both the current chamber and exhaust temperatures T.sub.cc and T.sub.ec as compared to certain chamber and exhaust setpoints. One embodiment of block 608 is described below; however, one skilled in the art will recognize that alternative methods of controlling the primary and secondary actuators 140 and 142 to optimize the primary and secondary airflows 170 and 172 during the termination phase 350 based on the current chamber and exhaust temperatures T.sub.cc and T.sub.ec, alone or in combination with previous chamber and exhaust temperatures T.sub.cn and T.sub.en, are possible.

[0202] In accordance with one embodiment, block 608 may implement the termination configuration by executing subblock 680, which may include codes directing the processor 151 to determine a primary airflow percentage value for the primary airflow 170 by comparing the current chamber temperature T.sub.cc to the chamber under-zone setpoint C.sub.za, the chamber termination value C.sub.term and the chamber endothermic setpoint C.sub.endo.

[0203] For example, if T.sub.cc<C.sub.zaC.sub.term, subblock 680 may direct the processor 151 to control the primary actuator 140 to generate 0% primary airflow 170.

[0204] However, if T.sub.ccC.sub.zaC.sub.term and T.sub.cc<C.sub.endo, subblock 680 may direct the processor 151 to control the primary actuator 140 to default to 0% primary airflow 170, but proportionally increase the primary airflow percentage value as the current chamber temperature T.sub.cc approaches the chamber endothermic setpoint C.sub.endo. In the previously described example where the chamber endothermic setpoint C.sub.endo is approximately 320 C.: (A) if T.sub.cc is 200 C., subblock 680 may direct the processor 151 to generate 10% primary airflow 170; however (B) if T.sub.cc is 300 C., subblock 680 may direct the processor 151 to generate 90% primary airflow 170 instead.

[0205] Additionally, block 686 may implement the termination configuration by executing subblock 682, which may include codes directing the processor 151 to determine a secondary airflow percentage value for the primary airflow 170 by: (A) comparing the current chamber temperature T.sub.cc to the chamber under-zone setpoint C.sub.za and the chamber termination value C.sub.term and (B) comparing the current exhaust temperature T.sub.ec to the exhaust upper setpoint E.sub.upper and the exhaust lower setpoint E.sub.lower.

[0206] For example, if T.sub.cc<C.sub.zaC.sub.term, subblock 682 may direct the processor 151 to control the secondary actuator 142 to generate 0% secondary airflow 172.

[0207] However, if T.sub.ccC.sub.zaC.sub.term, subblock 682 may direct the processor 151 to control the secondary actuator 142 by comparing the current exhaust temperature T.sub.ec to the exhaust upper setpoint E.sub.upper and the exhaust lower setpoint E.sub.tower. If E.sub.upper<T.sub.ec>E.sub.lower, subblock 682 may direct the processor 151 to control the secondary actuator to generate 100% secondary airflow 172. If T.sub.ecE.sub.tower, subblock 682 may direct the processor 151 to control the secondary actuator to generate 100% secondary airflow 172, but proportionally decrease the secondary airflow percentage value as the current exhaust temperature T.sub.ec diverges away from the exhaust lower setpoint E.sub.tower. In the previously described example where the exhaust lower setpoint E.sub.tower is 100 C.: (A) if T.sub.ec is 90 C. (e.g., slightly<E.sub.lower), subblock 682 may direct the processor 151 to generate 90% secondary airflow 172; and (B) if T.sub.ec is 40 C. (e.g., significantly<E.sub.lower), subblock 682 may instead direct the processor 151 to generate 10% secondary airflow 172. Similarly, if T.sub.ecE.sub.upper, subblock 682 may direct the processor 151 to control the secondary actuator to generate 100% secondary airflow 172, but proportionally decrease the secondary airflow percentage value as the current exhaust temperature T.sub.ec diverges away from the exhaust lower setpoint E.sub.upper. In the previously described example where the exhaust upper setpoint E.sub.upper is 500 C.: (A) if T.sub.ec is 550 C. (e.g., slightly>E.sub.upper), subblock 682 may direct the processor 151 to generate 90% secondary airflow 172; and (B) if T.sub.ec is 600 C. (e.g., significantly>E.sub.upper), subblock 652 may instead direct the processor 151 to generate 10% secondary airflow 172.

[0208] In other embodiments, subblocks 680 and 682 may generally direct the processor 151 to control the primary and secondary actuators 140 and 142 during the termination phase 350 to generally achieve consistent decreases in the current chamber temperature T.sub.cc and the current exhaust temperature T.sub.ec relative to, respectively, at least one previous chamber temperature T.sub.cn and at least one previous exhaust temperature T.sub.en. In such embodiments, block 608 may include codes that direct the processor 151 to intermittently adjust the primary airflow percentage value (and corresponding signals to control the primary actuator 140) and the secondary percentage airflow value (and corresponding signals to control the secondary actuator 142) based on comparisons between the current chamber and exhaust temperatures T.sub.cc and T.sub.ec and the previous chamber and exhaust temperatures T.sub.cn and T.sub.en to achieve these consistent decreases.

Catalyst Component 160

[0209] Referring to FIGS. 2, 8 and 9, the combustion system 100 includes a catalyst component 160 (e.g., a component with a catalyst-coated media) positioned proximate the outlet 117 fluidly coupling the exhaust 116 with the chamber 102. The catalyst component 160 may generally function to reduce emissions associated with combustion (e.g., both the primary combustion and the secondary combustion) of the solid fuel when contacted with the exhaust airflow 174.

[0210] In the embodiment shown in FIGS. 2, 8 and 9, the catalyst component 160 is generally configured to cover a portion (e.g., covers a catalyst portion 740) but not all (e.g., does not cover a bypass portion 744) of an opening 742 of the outlet 117. For example, the catalyst portion 740 may have an area that covers at least 60% of a total area of the opening 742, or may have a width which covers at least 60% of a total length or diameter of the opening 742; in other embodiments, the catalyst portion 740 may range between approximately 60% to 90% of the total area or the total length or diameter of the opening 742. The bypass portion 744 may have a corresponding area that covers at most 40% of the total area of the opening 742 or may have a width which covers at most 40% of the total length or diameter of the opening 742; in other embodiments, the bypass portion 744 may range between approximately 10% to 40% of the total area or the total length or diameter of the opening 742. In some specific embodiments, the bypass portion 744 may an area that covers at most 35% of the total area of the opening 742 or may have a width which covers at most 35% of the total length or diameter of the opening 742. For example, in certain embodiments, the catalyst component 160 may have a width of approximately 6 inches, a depth of approximately 2 inches, and a thickness of approximately 1 inch. However, precise dimensions of the catalyst component 160 may be varied based on dimensions of the outlet 117 and/or the exhaust 116 to achieve the proportional catalyst and bypass portions 740 and 744 as described above.

[0211] In the embodiment shown in FIGS. 2, 8 and 9, the catalyst component 160 is coupled to the top wall 400 of the chamber 102 at an angle 746 relative to a plane 730 of the outlet 117. The angle 746 may be approximately 12.5. However, in other embodiments, the angle 746 may range between 5 and 75.

[0212] In operation, a first portion of the exhaust airflow 174 (e.g., resulting from primary and secondary airflows 170 and 172) exiting the chamber 102 via the exhaust 116 may pass through the catalyst component 160 and then through the catalyst portion 740 of the opening 742 of the outlet 117. This first portion of the exhaust airflow 174 may benefit from a catalytic conversion in the catalyst component 160 to reduce emissions from the primary combustion and/or the secondary combustion of the solid fuel. A second portion of the exhaust airflow 174 exits the chamber 102 via the bypass portion 744 of the opening 742 of the outlet 117 without passing through the catalyst component 160.

[0213] Further, as the exhaust airflow 174 exiting the chamber 102 is heated during a majority of the combustion cycle 300 of the solid fuel, the exhaust airflow 174 may corresponding raise a temperature of the catalyst component 160. As a result, a temperature of the catalyst portion 740 may be higher than a temperature of the bypass portion 744, which may in turn promote addition exhaust airflow 174 through the catalyst portion 740 versus the bypass portion 744. As a result, the first portion of the exhaust airflow 174 passing through the catalyst component 160 in the catalyst portion 740 may be greater than the second portion of the exhaust airflow 174 passing through the bypass portion 744. For example, the first portion of the exhaust airflow 174 may approximately 1 to 4 times greater than the second portion of the exhaust airflow 174.

CONCLUSION

[0214] While specific embodiments have been described and illustrated, such embodiments should be considered illustrative of the subject matter described herein and not as limiting the claims as construed in accordance with the relevant jurisprudence.

[0215] Note that the expression at least one of A or B, as used herein, is interchangeable with the expression A and/or B. It refers to a list in which you may select A or B or both A and B. Similarly, at least one of A, B, or C, as used herein, is interchangeable with A and/or B and/or C or A, B, and/or C. It refers to a list in which you may select: A or B or C, or both A and B, or both A and C, or both B and C, or all of A, B and C. The same principle applies for longer lists having a same format.

[0216] The scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

[0217] Any module, component, or device exemplified herein that executes instructions may include or otherwise have access to a non-transitory computer/processor readable storage medium or media for storage of information, such as computer/processor readable instructions, data structures, program modules, and/or other data. A non-exhaustive list of examples of non-transitory computer/processor readable storage media includes magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, optical disks such as compact disc read-only memory (CD-ROM), digital video discs or digital versatile disc (DVDs), Blu-ray Disc, or other optical storage, volatile and non-volatile, removable and non-removable media implemented in any method or technology, random-access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology. Any such non-transitory computer/processor storage media may be part of a device or accessible or connectable thereto. Any application or module herein described may be implemented using computer/processor readable/executable instructions that may be stored or otherwise held by such non-transitory computer/processor readable storage media.

[0218] Memory, as used herein, may refer to memory that is persistent (e.g., read-only-memory (ROM) or a disk), or memory that is volatile (e.g., random access memory (RAM)). The memory may be distributed, e.g., a same memory may be distributed over one or more servers or locations.