Method for burning a fuel in a wood stove, a wood stove with a controller; and an air regulator for a wood stove

Abstract

A method for burning a fuel in a wood stove having a door to a combustion chamber with a base, which combustion chamber is isolated from the air by an exhaust and an intake at which intake there is provided an air regulator having at least primary, secondary and tertiary air intake ducts. The stove is controlled by a burn controller configured to operate between the different operating, i.e. different combustion states.

Claims

1. A method for burning a fuel in a wood stove having a door to a combustion chamber with a base, which combustion chamber is isolated from the air by an exhaust and an intake at which intake there is an air regulator having at least three valves, a primary valve connected via a primary air duct to regulate supply of primary combustion air to the combustion chamber through the base, a secondary valve connected via a secondary air duct to regulate supply of secondary combustion air to the combustion chamber between the base and the exhaust, and a tertiary valve connected via a tertiary air duct to supply tertiary combustion air to the combustion chamber at its upper end, wherein at least two of said three valves each are controlled by a burn controller configured to operate between the following states: 0.sup.th state; which is a cold start state of a burn of a fuel; 1.sup.st state; which is a warm start state of a burn of a fuel; 2.sup.nd state; which is a combustion state of a burn of a fuel; 3.sup.rd state; which is a glow state of a burn of a fuel; and 4.sup.th state; which is an off state; wherein a shift from said each state, 0.sup.th, 1.sup.st 2.sup.nd 3.sup.rd, 4.sup.th to any other said state, 0.sup.th, 1.sup.st 2.sup.nd 3.sup.rd, 4.sup.th is provided according to a logic in the burn controller.

2. A method for burning a fuel in a wood stove having a door to a combustion chamber with a base, which combustion chamber is isolated from the air by an exhaust and an intake at which intake there is an air regulator having at least three valves, a primary valve connected via a primary air duct to regulate supply of primary combustion air to the combustion chamber through the base, a secondary valve connected via a secondary air duct to regulate supply of secondary combustion air to the combustion chamber between the base and the exhaust, and a tertiary valve connected via a tertiary air duct to supply tertiary combustion air to the combustion chamber at its upper end, wherein at least two of said three valves each are controlled by a burn controller configured to operate between the following states: 0.sup.th state; which is a cold start state of a burn of a fuel; 1.sup.st state; which is a warm start state of a burn of a fuel; 2.sup.nd state; which is a combustion state of a burn of a fuel; 3.sup.rd state; which is a glow state of a burn of a fuel; and 4.sup.th state; which is an off state); wherein a state or a shift between each state is controlled according to exhaust measures provided by exhaust measure means or in inputs provided from a user interface means.

3. A method for burning a fuel in a wood stove having a door to a combustion chamber with a base, which combustion chamber is isolated from the air by an exhaust and an intake at which intake there is an air regulator having at least three valves, a primary valve connected via a primary air duct to regulate supply of primary combustion air to the combustion chamber through the base, a secondary valve connected via a secondary air duct to regulate supply of secondary combustion air to the combustion chamber between the base and the exhaust, and a tertiary valve connected via a tertiary air duct to supply tertiary combustion air to the combustion chamber at its upper end, wherein at least two of said three valves each are controlled by a burn controller configured to operate between the following states: 0.sup.th state; which is a cold start state of a burn of a fuel; 1.sup.st state; which is a warm start state of a burn of a fuel; 2.sup.nd state; which is a combustion state of a burn of a fuel; 3.sup.rd state; which is a glow state of a burn of a fuel; and 4.sup.th state; which is an off state; wherein a state and/or a shift between each state are controlled according to an output from a door status means.

4. A method for burning a fuel in a wood stove having a door to a combustion chamber with a base, which combustion chamber is isolated from the air by an exhaust and an intake at which intake there is an air regulator having at least three valves, a primary valve connected via a primary air duct to regulate supply of primary combustion air to the combustion chamber through the base, a secondary valve connected via a secondary air duct to regulate supply of secondary combustion air to the combustion chamber between the base and the exhaust, and a tertiary valve connected via a tertiary air duct to supply tertiary combustion air to the combustion chamber at its upper end, wherein at least two of said three valves each are controlled by a burn controller configured to operate between the following states: 0.sup.th state; which is a cold start state of a burn of a fuel; 1.sup.st state; which is a warm start state of a burn of a fuel; 2.sup.nd state; which is a combustion state of a burn of a fuel; 3.sup.rd state; which is a glow state of a burn of a fuel; and 4.sup.th state; which is an off state; wherein a state and/or a shift between each state are controlled according to an output from a door status means; and wherein the shift from one state to another state is activated from the 4.sup.th state to the 0.sup.th state: when a start instruction is given; at which time a timer is reset and started to give a time t; from the 0.sup.th state to the 0.sup.th state: when a door open status is detected by the door status means; from the 0.sup.th state to the 1.sup.st state: when a level of O.sub.2 concentration in the exhaust decreases to below between 20% to 14%, and preferably about 15%; from the 1.sup.st state to the 1.sup.st state: when a door open status is detected by the door status means; from the 1.sup.st state to the 2.sup.nd state: when the T-measurement is above a Tset plus a T-offset, where the T-offset is between 0-50° C., and preferably about 5° C.; or when the primary valve is between 0 to 10%, and preferably about 0%; from the 1.sup.st state to the 3.sup.rd state: when the time t is larger than between 5 to 20 min, and preferably about 15 min and the secondary valve is between 0 to 10%, and preferably about 0%; from the 2.sup.nd state to the 1.sup.st state: when a door open status is detected by the door status means, or when the T-measurement is below T.sub.set minus a T-offset, where the T-offset is between 0-50° C., and preferably about 15° C.; from the 2.sup.nd state to the 3.sup.rd state: when the time t is larger than between 5 to 20 min; and preferably about 15 min, and the secondary valve is between 0 to 10%, and preferably about 0%; from the 3.sup.rd state to the 1.sup.st state: when a door open status is detected by the door status means; from the 3.sup.rd state to the 4.sup.th state: when the level of O.sub.2 concentration in the exhaust increases to above between 14% and 20%, and preferably about 17.5%.

5. A wood stove having a door to a combustion chamber with a base, which combustion chamber is isolated from the air by an exhaust and an intake at which intake there is an air regulator having at least three valves, a primary valve connected via a primary air duct to regulate supply of primary combustion air to the combustion chamber through the base, a secondary valve connected via a secondary air duct to regulate supply of tertiary combustion air to the combustion chamber between the base and the exhaust, and a tertiary valve connected via a tertiary air duct to supply tertiary combustion air to the combustion chamber at its upper end, wherein at least two of said three valves each are controlled via an intake control by a burn controller that is configured to manage at least five burn states of the wood stove.

6. The wood stove according to claim 5 wherein the burn controller is connected to exhaust measure means comprising is at least a thermometer and/or a O.sub.2-measuring device such as a λ-probe.

7. A method for producing a wood stove comprising the steps: a wood stove is provided and prepared for installing: an air regulator having at least one valve and preferably three valves and with a housing configured for fitting into a wood stove and configured for receiving control signals from a burn controller, which air regulator is fitted into the wood stove; a burn controller comprising means for receiving inputs from exhaust measure means and/or a user interface and means for sending outputs to an air regulator, which outputs are generated by a burn control algorithm comprising a state machine with five burn states: 0.sup.th state; which is a cold start state of a burn of a fuel; 1.sup.st state; which is a warm start state of a burn of a fuel; 2.sup.nd state; which is a combustion state of a burn of a fuel; 3.sup.rd state; which is a glow state of a burn of a fuel; 4.sup.th state; which is an off state, which burn controller is fitted into the wood stove; exhaust measure means are fitted to the wood stove or the chimney to the wood stove; the air regulator is connected to the burn controller; the exhaust measure means are connected to the burn controller; and providing a user interface and connecting the user interface to the burn controller.

Description

DESCRIPTION OF THE DRAWINGS

(1) The invention is described with reference to the drawings, wherein

(2) FIG. 1 shows a stove with a controller for controlling the burning in the stove;

(3) FIG. 2 shows a wood burning stove with a combustion chamber whereto combustion air is fed from a air regulator;

(4) FIG. 3 shows an example of a state diagram for controlling the burning in a stove;

(5) FIG. 4 shows an example of a cold start phase or phase 0 state of the controller in an embodiment of the invention, in which all three valves are controllable;

(6) FIG. 5 shows an example of a warm start phase or phase 1 of the controller in an embodiment of the invention, in which all three valves are controllable;

(7) FIG. 6 shows an example of a combustion phase or phase 2 of the controller in an embodiment of the invention, in which all three valves are controllable;

(8) FIG. 7 shows an example of a glow phase or phase 3 of the controller in an embodiment of the invention, in which all three valves are controllable;

(9) FIG. 8 shows and example of an OFF-phase or phase 4 of the controller in an embodiment of the invention, in which all three valves are controllable;

(10) FIG. 9 shows an example of a cold start phase or phase 0 state of the controller in an embodiment of the invention, in which only valves are controlled, and in which the tertiary valve is maintained at a constant position;

(11) FIG. 10 shows an example of a warm start phase or phase 1 of the controller in an embodiment of the invention, in which only valves are controlled, and in which the tertiary valve is maintained at a constant position;

(12) FIG. 11 shows an example of a first combustion phase or phase 2 of the controller in an embodiment of the invention, in which only valves are controlled, and in which the tertiary valve is maintained at a constant position;

(13) FIG. 11a shows an example of a second combustion phase or phase 2 of the controller in an embodiment of the invention, in which only valves are controlled, and in which the tertiary valve is maintained at a constant position;

(14) FIG. 12 shows an example of a glow phase or phase 3 of the controller in an embodiment of the invention, in which only valves are controlled, and in which the tertiary valve is maintained at a constant position;

(15) FIG. 13 shows and example of an OFF-phase or phase 4 of the controller in an embodiment of the invention, in which only valves are controlled, and in which the tertiary valve is maintained at a constant position;

(16) FIG. 14 shows an embodiment of an air regulating box with three valves: a primary, a secondary, and a tertiary valve;

(17) FIG. 15 shows and embodiment of a valve, a cylinder valve

(18) FIG. 16 shows sectional view of an air box with and two cylinder valves, one of which is seen in a cross sectional view;

(19) FIG. 17 shows a cross sectional view of a cylinder valve, and

(20) FIG. 18 shows the temperature of exhaust and the CO2 in the exhaust for a wood stove without the burn controller and air regulator and for a wood stove with the burn controller.

(21) TABLE-US-00001 Detailed Description of the Invention No Part  1 Wood stove  2 Burn Controller  3 Exhaust  4 Exhaust measure means  4′ Thermometer, T-measurement  4″ λ-probe, O.sub.2 measurement  5 Intake  6 Intake control  6′ Primary valve control  6″ Secondary valve control  6′″ Tertiary valve control  7 Burn Control Algorithm  8 Valve controllers  9 Door status means  10 Thermostatic controller  11 User interface  12 User interface communication means  13 Door  14 Combustion chamber  15 Base  16 Combustion air  17 Air regulator  18 Flue gas Exhaust  19 Valves  19′ Primary valve  19″ Secondary valve  19′″ Tertiary valve  20 Air duct  20′ Primary air duct  20″ Secondary air duct  20′″ Tertiary air duct  21 Chimney 100 Start instruction 101 4.sup.th State or Off State 102 0th State or Cold Start State 103 1.sup.st State or Warm Start state 104 2.sup.nd State or Combustion State 105 3.sup.rd State or Glow State 110 Initialisation 111 4-1 shift or Start to Cold shift 112 0-0 shift or Cold to Warm shift 113 0-1 shift or Cold to Warm Shift 114 1-1 shift or Warm to Warm Shift 115 1-2 shift or Warm to Combustion shift 116 1-3 shift or Warm to Glow shift 117 2-1 shift or Combustion to Warm Shift 118 2-3 shift or Combustion to Glow Shift 119 3-1 shift or Glow to Warm shift 120 3-4 shift or Glow to off shift 130 Cold start control 131 Warm start control 132 Combustion control 133 Glow control 134 Off control 150 Cold start valve control scheme 151 Initial value 151′ Primary Initial Value 151″ Secondary Initial value 151′″ Tertiary Initial value 152 Controller input 152′ Primary controller input 152″ Secondary controller input 152′″ Tertiary controller input 153 Set Point Value 153′ Primary Set Point Value 153″ Secondary Set Point Value 153′″ Tertiary Set Point Value 160 Cold to Warm Valve control scheme 161 Combustion to Warm Valve control scheme 162 Glow to Warm Valve control scheme 170 First Warm to Combustion Valve control Scheme 171 Subsequent Warm to Combustion Valve control scheme 180 Warm Start to Glow Valve control Scheme 181 Combustion to Glow Valve Control Scheme 190 OFF valve control scheme 200 Housing 201 Intake connection means 202 Air duct connection means 210 Cylindrical valve 211 Valve housing 212 Valve piston 213 Actuator Connector 214 Actuator Means 215 Valve port 216 Valve port frame

(22) FIG. 1 shows a schematic of wood stove 1 with a burn controller 2 for controlling a burn in the wood stove 1. The wood stove 1 has an exhaust 3 that is equipped with exhaust measure means 4 such as a thermometer 4″ and such as a O.sub.2 measuring means 4″ like a λ-probe. The exhaust 3 is located at the upper end of the wood stove 1.

(23) The measuring means 4 are connected to the burn controller 2.

(24) The wood stove 1 has an intake 5 configured to supply air to the wood stove 1. The intake is located at the lower end of the wood stove 1. The intake 5 is controlled by an intake control 6 from the burn controller 2. The intake control in this embodiment has a primary valve control 6′, a secondary valve control 6″, and a tertiary valve control 6′″.

(25) The burn controller 2 has means for storing and executing a burn control algorithm 7 which controls valve controllers 8.

(26) In this embodiment the burn controller 2 has a wood stove door status means 9 configured to receive input about weather a door 13 is open or closed.

(27) The burn controller 2 has a thermostatic controller 10 configured to receive input from the thermometer 4′ and from a user interface 11 via some user interface communication means 12.

(28) The burn controller 2 and the user interface 11 are configured to send and receive signals.

(29) A first signal 12′ is a desired temperature or burn level entered via the user interface 11.

(30) A second signal 12″ is a start or stop signal entered via the user interface 11.

(31) A third signal 12′″ is a refill signal send from the burn controller 2 to the user interface 11, which refill signal informs that more fuel is needed to maintain the desired temperature or burn cleanliness.

(32) The wood stove 1 in this embodiment has a door 13 which in this case is a window in front of a combustion chamber 14.

(33) FIG. 2 shows a wood stove 1 with a combustion chamber 14 with a base 15 and whereto combustion air 16 is fed from a air regulator 17 and wherefrom a flue gas exhaust 18 guided away.

(34) The wood stove 1 has the air regulator 17 positioned at the lower part of the wood stove below the base 15 of the combustion chamber 14.

(35) The air regulator 17 has a number of valves 19 each connected via an air duct 20 to conduct combustion air 16 from the outside of the combustion chamber 14 to inside the combustion chamber 14.

(36) In particular the air regulator 17 has a primary valve 19′ that controls the flow of combustion air 16′ through a primary air duct 20′ from the intake 5 to the lower part of the combustion chamber 14. In this embodiment the primary air duct 20′ is adapted to guide combustion air 16′ through the base 15.

(37) In particular the air regulator 17 has a secondary valve 19″ that controls the flow of combustion air 16″ through a secondary air duct 20″ from the intake 5 to the middle part of the combustion chamber 14.

(38) In this embodiment the secondary air duct 20″ is adapted to guide combustion air 16″ to the rear side of the combustion chamber 14, which rear sided is opposite the window or door 13.

(39) In particular the air regulator 17 has a tertiary valve 19′″ that controls the flow of combustion air 16′″ through a tertiary air duct 20′″ from the intake 5 to the upper part of the combustion chamber 14.

(40) In this embodiment the tertiary air duct 20″ is adapted to guide combustion air 16′″ to the front side of the combustion chamber 14, which front side is the same side as the door or window 13.

(41) The wood stove 1 has connection means for connecting the exhaust 3 or connection to a chimney 21. In this embodiment the exhaust measure means 4 are positioned inside the chimney 21. The exhaust measure means 4 includes a thermometer 4′ and a λ-probe as the O.sub.2-measurement means 4″.

(42) FIG. 3 shows an example of a state diagram for controlling the burn in a wood stove 1. The state diagram is embedded in the burn controller 2 as a software programme and in particular as burn control algorithm 7.

(43) The state diagram or state controller has a set of start instructions 100 followed by five states during operation. The five states include a 4.sup.th state 101, 0.sup.th state 102, a 1.sup.st state 103, a 2.sup.nd state 104, and a 3.sup.rd state 105.

(44) The 0.sup.th state is a cold start state 102 where the wood stove 1 is cold meaning.

(45) The 1.sup.st state is a warm start state 103 where the wood stove 1 has been operated and is still warm.

(46) The 2.sup.nd state is a combustion state 104 where the fuel burns in the wood stove 1.

(47) This allows for the burn controller 2 to maintain the burn in the wood stove 1 as long as there is fuel and settings and measures require combustion.

(48) The 3.sup.rd state is a glow state 105 where the fuel glows in the wood stove 1.

(49) The 4.sup.th state is an off state 101 where the wood stove 1 is closed down and the fuel burn is terminated.

(50) During each state 101, 102, 103, 104, 105 the burn controller 2 controls valves 19 in the air regulator 19.

(51) The burn controller 2 is configured to receive input from exhaust measures 4 and in this case from a user interface 11 which measures and inputs are used to determine when the state controller shall make a shift or a transition from one state to the same, “a reset”, or another state.

(52) In the show embodiment of the state controller there are transitions or shifts from one state to another state as follows.

(53) 4-1 shift 111 is a shift or transition from the 4th state 101 to the 0th state 102 or from the start state to the OFF-state.

(54) 0-0 shift 112 is a shift or transition from the 0.sup.th state 102 to the 0.sup.th state 102 or from the cold start state to the cold start state. Such shift or transition from and to the same state is performed if the procedure in the state is not finished or need to be restarted.

(55) 0-1 shift 113 is a shift or transition from the 0.sup.th state 102 to the 1.sup.st state 103 or from the cold start state to the warm state.

(56) 1-1 shift 114 is a shift or transition from the 1st state 103 to the 1st state 103 or from the warm state to the warm state.

(57) 1-2 shift 115 is a shift or transition from the 1st state 103 to the 2nd state 104 or from the warm state to the combustion state.

(58) 1-3 shift 116 is a shift or transition from the 1st state 103 to the 3rd state 105 or from the warm state to the glow state.

(59) 2-1 shift 117 is a shift or transition from the 2nd state 104 to the 1st state 103 or from the combustion state to the warm state.

(60) 2-3 shift 118 is a shift or transition from the 2nd state 104 to the 3rd state 105 or from the combustion state to the glow state.

(61) 3-1 shift 119 is a shift or transition from the 3rd state 105 to the 1st state 103 or from the glow state to the warm state.

(62) 3-4 shift 120 is a shift or transition from the 3rd state 105 to the 4th state 101 or from the glow state to the off state.

(63) As is apparent other possible shifts such as 0-0, 2-1, . . . etc. are not shown in this embodiment, but they are implementable in a similar way.

(64) FIGS. 4 through 13 illustrate valve control schemes for each of the states 0.sup.th 101, 1.sup.st 102, 2.sup.nd 103, 3.sup.rd 104, and 4.sup.th 105 states. Each state is controlled at least one valve control scheme depending on the previous state. The control schemes shown in FIGS. 4 to 8 relate to an embodiment of the invention, in which the primary, secondary and tertiary air ducts are controllable by means of respective valves 19, 19′, 19″, 19′″, and FIGS. 8 to 13 relate to an embodiment of the invention, in which only the primary and secondary air ducts are controlled by means of respective valves, while the tertiary air duct is kept at a constant position.

(65) Each scheme has an initial value, a PD controller input and a set point value for each of the primary, secondary, and, where applicable, tertiary valves.

(66) FIGS. 4 and 9 show an example of a cold start phase 102, the 0.sup.th state, with a cold start control 130 that includes a cold start valve control scheme 150. The cold start valve control scheme 150 has initial values 151, PD controller input values 152, and set point values 153 for each of the primary, secondary, and tertiary valves.

(67) There is a primary initial value 151′ which in this instance is 100% resulting in that the primary valve 19′ is 100% opened for a maximum intake of primary combustion air 16′ to the combustion chamber 14.

(68) There is a secondary initial value 151″ which in this instance is 0% resulting in that the secondary valve 19″ is 0% opened, i.e. 100% closed, for a minimum or zero intake of secondary combustion air 16′″ to the combustion chamber 14.

(69) There is a tertiary initial value 151′″ which in the instance of FIG. 4 is 100% resulting in that the tertiary valve 19′″ is 100% opened for a maximum intake of tertiary combustion air 16″ to the combustion chamber 14. In the instance of FIG. 9, the tertiary initial value is fixed at 50% opened.

(70) There is a primary controller input 152′ that is unregulated or floating. Likewise the secondary controller input 152″ and the tertiary controller input 152′″ are unregulated or floating.

(71) There is a primary set point value 153′ that is empty or null. Likewise the secondary set point value 153″ and the tertiary set point values are empty or null.

(72) FIGS. 5 and 10 show an example of a warm start phase 103, the 1.sup.st state or phase, with a warm start control 131 that includes a cold to warm start valve control scheme 160, a combustion to warm valve control scheme 161, and a glow to warm valve control scheme 162.

(73) Following the numeration from FIG. 4, the cold to warm start valve control scheme 160 has:

(74) A primary initial value of 100% resulting in that the primary valve 19′ is fully opened for delivering a maximum of primary combustion air 16′ to the combustion chamber 14.

(75) There is a primary controller input that regulates the temperature. The regulator is based on a primary set point value Tset according to for example a user input via the user interface or a preset standard desirable temperature.

(76) There is a secondary initial value of 0% resulting in that the secondary valve 19″ is fully closed for initially delivering no secondary combustion air 16″ to the combustion chamber.

(77) There is a secondary controller input that regulates the oxygen, O.sub.2, level in the exhaust 3 towards a secondary set point value of 13% O.sub.2.

(78) In FIG. 5, a tertiary initial value of 100% results in that the tertiary valve 19′″ is fully opened for delivering a maximum of tertiary combustion air 16′″ to the combustion chamber 14. In FIG. 10, the tertiary initial value is fixed at 50% opened.

(79) In the embodiment of FIGS. 4-8, there is provided a tertiary controller input that is left unregulated or floating and with a null nor irrelevant set point value.

(80) The combustion to warm start valve control scheme 161 has:

(81) A primary initial value of 20% (FIG. 5) resulting in that the primary valve 19′ is 20% open for delivering some primary combustion air 16′ to the combustion chamber 14. In FIG. 10, the primary initial value is between 0% (i.e. closed) and 50%.

(82) There is a primary controller input that regulates the temperature in the exhaust 3 towards a primary set point value that is determined by Tset.

(83) There is a secondary initial value that is unchanged (FIGS. 5 and 10 alike).

(84) There is a secondary controller input that, in the embodiment of FIG. 5, regulates the Oxygen level towards a tertiary set point value of 11.5% O.sub.2. (8.5% O.sub.2 in FIG. 10).

(85) There is a tertiary initial value of 100% resulting in that the tertiary valve 19′″ is fully open for delivering a maximum of secondary combustion air 16′″ to the combustion chamber 14.

(86) There is a tertiary controller input that is left unregulated or floating and with a null nor irrelevant set point value resulting in that the tertiary valve 19′″ is left at the initial value (FIG. 5). At 161, the tertiary initial value is fixed at 50% in FIG. 10.

(87) The glow to warm start valve control scheme 162 has:

(88) A primary initial value of 20% resulting in that the primary valve 19′ is 20% open for delivering some primary combustion air 16′ to the combustion chamber 14. In FIG. 10, the primary initial value is between 25 and 50%.

(89) There is a primary controller input that regulates the temperature in the exhaust 3 towards a primary set point value that is determined by Tset.

(90) In FIG. 5, there is a secondary initial value of 50% resulting in that the secondary valve 19″ is half open for delivering half maximum of tertiary combustion air 16″ to the combustion chamber. In FIG. 10, the secondary initial value is unchanged at 162.

(91) There is a secondary controller input that regulates the Oxygen level towards a secondary set point value of 11.5% O.sub.2. In FIG. 10, the secondary oxygen set point value is 8.5% O.sub.2.

(92) There is a tertiary initial value of 100% (FIG. 5) resulting in that the tertiary valve 19′ is fully open for delivering a maximum of secondary combustion air 16′ to the combustion chamber 14. In FIG. 5, the tertiary initial value remains fixed at 50%.

(93) In FIG. 5, there is a tertiary controller input that is left unregulated or floating and with a null nor irrelevant set point value resulting in that the tertiary valve 19′ is left at the initial value.

(94) The warm start control 131 is further configured for determining the previous state thereby enabling the desired selection of the valve control scheme 160, 161, 162.

(95) FIGS. 6 and 11 show examples of a combustion state 104, the 2.sup.nd state, and a combustion control 132 controlling a first warm to combustion valve control scheme 170 and a subsequent warm to combustion valve control scheme 171. The combustion state of FIG. 11 is a first combustion state, whereas a second combustion state is described below with reference to FIG. 11a.

(96) The first warm to combustion valve control scheme 170 has:

(97) A primary initial value of 0% resulting in that the primary valve 19′ is fully closed for delivering zero primary combustion air 16′ to the combustion chamber 14.

(98) There is a primary controller is left unregulated and the primary set point value is null.

(99) There is a secondary initial value that is left unchanged.

(100) There is a secondary controller input that regulates the oxygen, O.sub.2, level in the exhaust 3 towards a tertiary set point value of 13% O.sub.2 (FIG. 6) and 8.5% O.sub.2 (FIG. 11), respectively.

(101) In the embodiment of FIG. 6, a tertiary initial value of 100% results in that the tertiary valve 19′ is fully opened for delivering a maximum of tertiary combustion air 16′ to the combustion chamber 14. In FIG. 11, the tertiary initial value remains fixed at 50%.

(102) In the embodiment of FIG. 6, there is provided a tertiary controller input that regulates temperature towards a temperature determined by a tertiary set point value Tset, whereas no controller input is provided in the embodiment of FIG. 11.

(103) The subsequent warm to combustion valve control scheme 171 has:

(104) A primary initial value of 0% resulting in that the primary valve 19′ is fully closed for delivering zero primary combustion air 16′ to the combustion chamber 14 (FIGS. 6 and 11 alike).

(105) There is a primary controller is left unregulated and the primary set point value is null.

(106) There is a secondary initial value that is left unchanged in the embodiment of FIG. 6, whereas the secondary initial value at 171 is set to 20% open for the secondary valve 19″ in the embodiment of FIG. 11.

(107) There is a secondary controller input that regulates the oxygen, O.sub.2, level in the exhaust 3 towards a secondary set point value of 11.5% O.sub.2 (FIG. 6) and 8.5% O.sub.2 (FIG. 11), respectively.

(108) In FIG. 6, a tertiary initial value of 100% results in that the tertiary valve 19′″ is fully opened for delivering a maximum of secondary combustion air 16′″ to the combustion chamber 14. In FIG. 11, the tertiary initial value remains fixed at 50%.

(109) In the embodiment of FIG. 6, a tertiary controller input is provided for regulating temperature towards a temperature determined by a tertiary set point value Tset.

(110) FIGS. 7 and 12 show examples of a glow state 105, the 3.sup.rd state, and a glow state control 133 that controls a warm start to glow valve control scheme 180 and a combustion to glow valve control scheme 181.

(111) Before describing the glow state 105 of FIGS. 7 and 12, reference is initially made to FIG. 11a, which shows second combustion phase, i.e. phase 3a.

(112) The warm start to glow valve control scheme 180 of FIG. 11a includes the following:

(113) A primary initial value that is left unchanged and with a maximum of 50% resulting in that the primary valve 19′ is at maximum half opened for delivering half primary combustion air 16′ to the combustion chamber 14 as a maximum.

(114) There is a primary controller regulates temperature towards a primary set point value determined by Tset.

(115) There is a secondary initial value of 0%, i.e. closing the secondary valve 19″.

(116) There is a secondary controller input that regulates oxygen level towards an oxygen level at 8.5% O.sub.2.

(117) The combustion I state to glow valve control scheme 181 of FIG. 11a includes the following:

(118) A primary initial value that is 0% resulting in that the primary valve 19′ is closed for delivering no primary combustion air 16′ to the combustion chamber 14.

(119) There is a primary controller regulates temperature towards a primary set point value determined by Tset.

(120) There is a secondary initial value at 0%, i.e. closing the secondary valve 19″.

(121) There is a secondary controller input that regulates oxygen level towards an oxygen level at 8.5% O.sub.2.

(122) In FIGS. 7 and 12, the warm start to glow valve control scheme 180 includes the following:

(123) A primary initial value that is left unchanged and with a maximum of 50% resulting in that the primary valve 19′ is at maximum half opened for delivering half primary combustion air 16′ to the combustion chamber 14 as a maximum.

(124) There is a primary controller regulates temperature towards a primary set point value determined by Tset (FIG. 7) and that regulates oxygen towards an O.sub.2 level of 8.5% (FIG. 12).

(125) There is a secondary initial value of 0% resulting in that the secondary valve 19′″ is closed.

(126) There is a secondary controller input that is left unregulated with no set point value (FIG. 7). In FIG. 12, the secondary controller input regulates O.sub.2 to a maximum level of about 8.5%.

(127) In FIG. 7, there is provided a tertiary initial value of that is left unchanged with a minimum of 10% resulting in that the tertiary valve 19′″ is opened for delivering small amounts of tertiary combustion air 16′″ to the combustion chamber 14. In FIG. 12, the tertiary value remains fixed at 50%.

(128) There is a tertiary controller input that regulates oxygen level towards an oxygen level at 13% O.sub.2.

(129) The combustion state to glow valve control scheme 181 (FIG. 7 embodiment only) includes the following:

(130) A primary initial value that is 0% resulting in that the primary valve 19′ is closed for delivering no primary combustion air 16′ to the combustion chamber 14.

(131) There is a primary controller regulates temperature towards a primary set point value determined by Tset.

(132) There is a secondary initial value of 0% resulting in that the secondary valve 19′″ is closed.

(133) There is a secondary controller input that is left unregulated with no set point value.

(134) There is a tertiary initial value of that is left unchanged with a minimum of 10% resulting in that the tertiary valve 19′″ is slightly opened for delivering small amounts of tertiary combustion air 16″ to the combustion chamber 14.

(135) There is a tertiary controller input that regulates oxygen level towards an oxygen level at 11.5% O.sub.2.

(136) FIGS. 8 and 13 show examples of an OFF-state 105, the 4.sup.th state, and a OFF state control 134 that controls a combustion to glow valve control scheme 190.

(137) There is primary initial value of 0% resulting in that the primary valve 19′ is closed for zero delivery of primary combustion air 16′ to the combustion chamber 14.

(138) There is a primary controller input that is left unregulated with a null set point value.

(139) There is a secondary initial value of 0% resulting in that the secondary valve 19″ is closed for zero delivery of tertiary combustion air 16″ to the combustion chamber 14. There is a tertiary control input that is left unregulated with a null set point value.

(140) In FIG. 8, there is a tertiary initial value of 10% resulting in that the tertiary valve 19′″ is a slightly open for a delivery of small amounts of tertiary combustion air 16′″ to the combustion chamber 14. In the embodiment of FIG. 13, the tertiary initial value remains fixed at 50%. However, in order to avoid heat from the surrounding room to dissipate into the cooled-down stove through the tertiary air duct, it may be closed to 0% in the off state.

(141) In the embodiment of FIG. 8, there is a tertiary controller input regulating temperature if the temperature is below 50 degrees Celsius. Thereby remaining fuel is slowly extinguished. The tertiary set point value is null.

(142) FIG. 9 shows an embodiment of an air regulator 17 with three valves 19: a primary valve 19′, a secondary valve 19″, and a tertiary valve 19′″. The air regulating box 17 has a housing 200 with a intake connection means 201 and is formed to fit into a wood stove 1 so that the intake connection means 201 gets combustion air 16 from the intake 5.

(143) The air regulator 17 has air duct connection means 202 for each valve 19.

(144) There is a primary air duct connection means 202′ for connecting the air box 17 to a primary air duct 20′ allowing combustion air 16 from the intake 5 to be fed the combustion chamber 14 as primary combustion air 16′ controlled by the primary valve 19′.

(145) Likewise for the separate secondary and tertiary channels.

(146) FIG. 10 shows and embodiment of a valve 19 which is a cylinder valve 210 with a valve housing 211 and a valve piston 212. The valve piston 212 is in extended to a position furthest out of the valve housing 211.

(147) FIG. 11 shows sectional view of an air box 17 with and two cylinder valves 210, one of which is seen in a cross sectional view. In both cases the valve piston 212 is withdrawn into the valve housing 211.

(148) The movement of the valve piston 212 is done via an actuator connector 213 connected to a actuator means 214. In this case the actuator connector 213 and actuator means combination is a shredded linear line that is rotated by a motor thereby linearly moving and positioning the valve piston 212 within the housing 200 to form a valve port 215 due to interaction or relative positioning against a valve port frame 216.

(149) FIG. 12 shows a cross sectional view of a cylinder valve 210 with the valve housing 211, the valve piston 212 linearly movable in and out of the valve housing 211. The movement of the valve piston 212 is done along the actuator connector 213, which in this case is a screw that can be rotated by a motor as the actuator means 214.

(150) The actuator means 214 is controlled by the valve control 6 and the arrangement with the calibrated, in particular the relative positioning of the valve port frame 216, the valve housing 211 and the valve piston 212 so that a signal of 100% open to the valve control 6 results in a withdrawal of the valve piston 212 into the valve housing 211 thereby making a maximum valve port 215 opening.

(151) Likewise a signal of 0% open (close) to the valve control 6 results in a valve piston 212 out of the valve housing 211 and closing towards the valve port frame 216.

(152) In this embodiment it is seen that the valve port frame 216 has a V-shaped opening so that the size of the valve port 15 opening can be controlled more precisely allowing for a finer control of smaller vale port 15 openings.

(153) FIG. 13 shows the temperature of exhaust and the CO.sub.2%-level in the exhaust for a wood stove without the burn controller and air regulator, A, and for a wood stove with the burn controller, B.

(154) Each diagram shows the timely development of the temperature of the exhaust Texhaust on a scale from 0-700° C. and the percentage CO.sub.2 level in the exhaust on a scale from 0-20%.

(155) The test has carried out as a standard test according to EN13240 to be able to compare the a burn of a fuel in a standard wood stove with an embodiment of wood stove as disclosed in the case where standard wood stove is fitted with a air regulator, a burn controller and exhaust measures (albeit the O2 sensor being replaced with an equivalent CO2 sensor).

(156) According to the standard test, there are three conditions or test circumstances: The best user is a laborant, best compromise for the chimney and installation, and best possible fuel load (in moist and weight distribution).

(157) Each spike in the figures represents a refueling of the wood stove. It is clearly observed that the controlled or regulated burn is more constant. Although there are spikes present, these are narrow. The T.sub.exhaust is very stable at about 380° C.

(158) The standard test shows that the controlled wood stove according to an embodiment of the invention results in a reduction in fuel consumption of about 15-30%.

(159) The controlled wood stove gives an ease of use with a more stable (i.e. less modulation) room temperature with less refills of wood. No or reduced chances of overheating and consequently a reduced risk of damage to the wood stove and therefore a longer life expectancy of the wood stove.

(160) The controlled wood stove furthermore results in less build-up of soot in the wood stove and the chimney.

(161) As for the environmental impact the controlled wood stove from a cold to a cold state showed emission reductions of about 60-80% again according to the norm EN 13240.

(162) Besides the standard test circumstances (Laboratory Conditions) other normal and abnormal tests have been conducted. These other conditions include: “best user”, “worst user”, “bad chimney”, “moist wood”, and “wrong amount of wood”. These conditions have been tested for different burn scenarios.

(163) For comparison the un-controlled wood stove in the cases of a best user, worst user and bad chimney for nominal burn condition had efficiencies of 77.6%, 73.4%, and 61.3%, respectively.

(164) For the controlled wood stove according to the invention, these efficiencies were 84.6%, 84.6%, and 80.1%, respectively.