| Claims: 1. A fuel-burning stove, comprising a base, wall or walls and a top together defining a chamber, an outlet provided at or near the top of the chamber, one or more air inlets, one or more air vents coupled to one or more of the air inlets via air ducts, for directing air from the air inlet(s) into the chamber, wherein the air vents are arranged in sets and one or more of the sets is arranged at a different height to another in relation to the base of the stove. 2. A stove as claim in claim 1 , wherein there is any one of 1 , 2, 3, 4, 5 or 6 inlets per set. 3. A stove according to Claim 2, wherein the ducts are constructed with a varying cross-section to aid equal and consistent flow through the air vents. 4. A stove according to any preceding claim, further comprising a first baffle panel mounted so as to extend into the chamber spaced from but across the air outlet to provide a path for gases between a centre of the chamber and the outlet that extends around a periphery of the first baffle panel. 5. A stove according to Claim 4, further comprising at least one secondary baffle panel mounted so as to extend into the chamber spaced from and partially overlapping with the first path so as to provide an extension in the path for gases between the centre of the chamber and the outlet. 6. A stove according to Claim 5, wherein the space between the first and secondary baffle panels forms an additional high-temperature combustion chamber. 7. A stove according to Claim 5 or 6, wherein the baffle panels are located at the back or on a side of the stove. 8. A stove according to any one of Claims 5 to 7, wherein the first and secondary baffle panels are mounted to extend into the chamber from opposite, or adjacent walls of the stove. 9. A stove according to any one of Claims 5 to 8, wherein the secondary baffle panel comprises a mesh. 10. A stove according to Claim 9, wherein the secondary baffle panel comprises a fine mesh which reduces the production of pollutants including larger ash particles. 11. A stove according to any one of Claims 5 to 10, wherein the secondary baffle panel comprises a heat-conducting material. 12. A stove according to any one of Claims 5 to 11 , wherein the secondary baffle panel is made from stainless steel or vermiculite board. 13. A stove according to any one of Claims 5 to 12, wherein the secondary baffle panel comprises a catalytic material enhancing combustion in the stove. 14. A stove according to any one of Claims 1 to 13, wherein the air vents are arranged to direct air from the air inlet(s) into the chamber in a direction not substantially radially towards the centre of the chamber, so as to produce rotation of air in the chamber about a substantially vertical axis passing through the centre of the chamber and whilst substantially maintaining the swirl diameter. 15. A stove according to Claim 14, wherein each air vent directs air from an air inlet towards an adjacent air vent in a clockwise or anti-clockwise series. 16. A stove according to Claim 14 or 15, wherein the air vents are arranged in corners of the stove pointing along a wall thereof in a clockwise or anticlockwise series. 17. A stove according to Claim 16, wherein the air vents are arranged tangentially in a round or oval chamber in a clockwise, or anti-clockwise, series. 18. A stove according to any one of Claims 1 to 17, further comprising one or more ducts between the air inlet(s) and the air vent(s), wherein the duct(s) is at least partially constructed from a heat-conducting material which is positioned to conduct heat from the chamber to the inside of the duct(s) so as to raise the temperature of the air within the duct before it reaches the chamber. 19. A stove according to Claim 18, wherein at least one duct is constructed with a high ratio of surface area to volume to aid heat transfer from the chamber to the air within the duct. 20. A fuel-burning stove, comprising a base, wall or walls and a top together defining a chamber, an outlet provided at or near the top of the chamber, one or more air inlets and one or more air vents coupled to one or more of the air inlets for directing air from the air inlet(s) into the chamber in a direction not substantially radially towards a centre of the chamber, so as to produce rotation of air in the chamber about a substantially vertical axis passing through the centre of the chamber. 21. A stove according to Claim 20, comprising a plurality of air vents arranged around a periphery of the chamber at a predetermined height above the base of the stove, wherein each air vent directs air from an air inlet towards an adjacent air vent in a clockwise or anti-clockwise series. 22. A stove according to Claim 21 , wherein the air vents are arranged in corners of the stove pointing along a wall thereof in a clockwise, or anticlockwise, series. 23. A stove according to Claim 21 , wherein the air vents are arranged tangentially in a round or oval chamber in a clockwise, or anti-clockwise, series. 24. A stove according to any of claims 21 to 23, further comprising a first baffle panel mounted so as to extend into the chamber spaced from but across the air outlet to provide a path for gases between a centre of the chamber and the outlet that extends around a periphery of the first baffle panel. 25. A stove according to Claim 24, further comprising at least one secondary baffle panel mounted so as to extend into the chamber spaced from and partially overlapping with the first path so as to provide an extension in the path for gases between the centre of the chamber and the outlet. 26. A stove according to Claim 25, wherein the first and secondary baffle panels provide a path for the gases, such path comprising an additional high-temperature combustion chamber. 27. A stove according to Claim 25 or 26, wherein the baffle panels are located at the back or on a side of the stove. 28. A stove according to any one of Claims 25 to 27, wherein the first and secondary baffle panels are mounted to extend into the chamber from opposite, or adjacent walls of the stove. 29. A stove according to any one of Claims 25 to 28, wherein the at least one secondary baffle panel comprises a mesh. 30. A stove according to Claim 29, wherein the at least one secondary baffle panel comprises a fine mesh which reduces the production of pollutants including larger ash particles. 31. A stove according to any one of Claims 25 to 30, wherein the at least one secondary baffle panel comprises a heat-conducting material. 32. A stove according to any one of Claims 25 to 31 , wherein the at least one secondary baffle panel is made from stainless steel. 33. A stove according to any one of Claims 25 to 31 , wherein the at least one secondary baffle panel comprises a catalytic material enhancing combustion in the stove. 34. A stove according to any of claims 20 to 33, further comprising one or more ducts between the air inlet(s) and the air vent(s), wherein the duct(s) is at least partially constructed from a heat-conducting material which is positioned to conduct heat from the chamber to the inside of the duct(s) so as to raise the temperature of the air within the duct before it reaches the chamber. 35. A stove according to Claim 34, wherein at least one duct is constructed with a high ratio of surface area to volume to aid heat transfer from the chamber to the air within the duct. 36. A fuel-burning stove, comprising a base, wall or walls and a top together defining a chamber, an outlet provided at or near the top of the chamber, one or more air inlets, one or more air vents coupled to one or more of the air inlets for directing air from the air inlet(s) into the chamber, a first baffle panel mounted so as to extend into the chamber spaced from but across the air outlet to provide a path for gases between a centre of the chamber and the outlet that extends around a periphery of the first baffle panel and at least one secondary baffle panel mounted so as to extend into the chamber spaced from and partially overlapping with the first path so as to provide an extension of the path for gases between the centre of the chamber and the outlet. 37. A stove according to Claim 36, wherein the first and secondary baffle panels provide a path for the gases, such path comprising an additional combustion chamber. 38. A stove according to Claim 37, wherein the space between the first and secondary baffle panels forms an additional high-temperature combustion chamber. 39. A stove according to Claim 37 or 38, wherein the baffle panels are located at the back or on a side of the stove. 40. A stove according to any one of Claims 36 to 39, wherein the first and secondary baffle panels are mounted to extend into the chamber from opposite, or adjacent walls of the stove. 41. A stove according to any one of Claims 36 to 40, wherein the at least one secondary baffle panel comprises a mesh. 42. A stove according to Claim 41 , wherein the at least one secondary baffle panel comprises a fine mesh which reduces the production of pollutants including larger ash particles. 43. A stove according to any one of Claims 36 to 42, wherein the secondary baffle panel comprises a heat-conducting or reflecting material. 44. A stove according to any one of Claims 36 to 43, wherein the secondary baffle panel is made from stainless steel. 45. A stove according to any one of Claims 36 to 44, wherein the secondary baffle panel comprises a catalytic material enhancing combustion in the stove. 46. A stove according to any one of Claims 36 to 45, wherein the air vents are arranged to direct air from the air inlet(s) into the chamber in a direction not substantially radially towards the centre of the chamber, so as to produce rotation of air in the chamber about a substantially vertical axis passing through the centre of the chamber. 47. A stove according to Claim 46, comprising a plurality of air vents arranged around a periphery of the chamber at a predetermined height above the base of the stove, wherein each air vent directs air from an air inlet towards an adjacent air vent in a clockwise or anti-clockwise series. 48. A stove according to Claim 47, wherein the air vents are arranged in corners of the stove pointing along a wall thereof in a clockwise or anti- clockwise series. 49. A stove according to Claim 47 or 48 wherein the air vents are arranged tangentially in a round or oval chamber in a clockwise, or anti-clockwise, series. 50. A stove according to any one of Claims 36 to 49, further comprising one or more ducts between the air inlet(s) and the air vent(s), wherein the duct(s) is at least partially constructed from a heat-conducting material which is positioned to conduct heat from the chamber to the inside of the duct(s) so as to raise the temperature of the air within the duct before it reaches the chamber. 51. A stove according to Claim 50, wherein at least one duct is constructed with a high ratio of surface area to volume to aid heat transfer from the chamber to the air within the duct. 52. A fuel-burning stove, comprising a base, wall or walls and a top together defining a chamber, an outlet vent provided at or near the top of the chamber, one or more air inlets, one or more air vents coupled to one or more of the air inlets via one or more ducts for directing air from the air inlet(s) into the chamber, wherein the duct(s) is at least partially constructed from a heat-conducting material which is positioned to conduct heat from the chamber to the inside of the duct(s) so as to raise the temperature of the air within the duct before it reaches the chamber. 53. A stove according to Claim 52, wherein at least one duct is constructed with a high ratio of surface area to volume to aid heat transfer from the chamber to the air within the duct. 54. A stove according to either Claim 52 or Claim 53, further comprising a first baffle panel mounted so as to extend into the chamber spaced from but across the air outlet to provide a path for gases between a centre of the chamber and the outlet that extends around a periphery of the first baffle panel. 55. A stove according to Claim 54, further comprising at least one secondary baffle panel mounted so as to extend into the chamber spaced from and partially overlapping with the first path so as to provide an extension in the path for gases between the centre of the chamber and the outlet. 56. A stove according to Claim 55, wherein the space between the first and secondary baffle panels forms an additional high-temperature combustion chamber. 57. A stove according to Claim 55 or 56, wherein the baffle panels are located at the back or on a side of the stove. 58. A stove according to any one of Claims 55 to 57, wherein the first and secondary baffle panels are mounted to extend into the chamber from opposite, or adjacent walls of the stove. 59. A stove according to any one of Claims 55 to 58, wherein the secondary baffle panel comprises a mesh. 60. A stove according to Claim 59, wherein the secondary baffle panel comprises a fine mesh which reduces the production of pollutants including larger ash particles. 61. A stove according to any one of Claims 55 to 60, wherein the secondary baffle panel comprises a heat-conducting or reflecting material. 62. A stove according to any one of Claims 55 to 61 , wherein the secondary baffle panel is made from stainless steel. 63. A stove according to any one of Claims 55 to 62, wherein the secondary baffle panel comprises a catalytic material enhancing combustion in the stove. 64. A stove according to any one of Claims 55 to 63, wherein the air vents are arranged to direct air from the air inlet(s) into the chamber in a direction not substantially radially towards the centre of the chamber, so as to produce rotation of air in the chamber about a substantially vertical axis passing through the centre of the chamber. 65. A stove according to Claim 64, comprising a plurality of air vents arranged around a periphery of the chamber at a predetermined height above the base of the stove, wherein each air vent directs air from an air inlet towards an adjacent air vent in a clockwise or anti-clockwise series. 66. A stove according to Claim 65, wherein the air vents are arranged in corners of the stove pointing along a wall thereof in a clockwise or anticlockwise series. 67. A stove according to Claim 65 or 66, wherein the air vents are arranged tangentially in a round or oval chamber in a clockwise, or anti-clockwise, series. 68. A stove according to any preceding Claim, further comprising a grill arranged on the base for receiving fuel to be combusted thereon. 69. A stove according to any preceding Claim, further comprising a chimney coupled to the outlet. 70. A stove according to any preceding Claim, wherein the base, wall or walls and top of the stove are formed of an insulating material. 71. A stove according to Claim 70, wherein the insulating material is vermiculite board. 72. A fuel-burning stove substantially as hereinbefore described, with reference to any of Figures 2 to 5 of the drawings. |
The present invention relates to a fuel-burning stove, particularly, though not exclusively, to a natural wood fuel-burning stove having improved fuel-burning efficiency.
Fire and heating systems have been an essential element of human home life for more years than has been recorded. The core process remains the same: that fuel is burned and releases heat, radiating a portion of the heat and transferring a portion of the heat into the surrounding air and waste gases, causing them to rise. While there are no simpler or more-convenient heat sources, the present environmental climate discourages the use of open fires to provide heat. However, there is still commercial demand for stoves to provide heat and, in present changing times the demand has changed for less-polluting and more-efficient stoves.
Most current wood-burning systems rely on the natural draw of the chimney to pull oxygen over the fuel. While electric fans are sometimes used known to pump, or draw, air through a combustion chamber, most conventional stoves rely on convection from the heated air leaving the combustion chamber rising up through the chimney to draw fresh air into the combustion chamber through air vents. The incoming air is directed into the combustion chamber at various levels, forcing the flame to the back or front of the combustion chamber and the heated air escapes out the chimney.
It is known in the art that, to obtain good or near-complete combustion of fuel, three conditions are required:
1. Thorough mixing of oxygen and the fuel.
2. Time for the mixing to continue and the reaction to complete. 3. A high combustion chamber temperature in which the combustion takes place.
Figure 1 is a diagram showing a cross-section of a typical modern stove 100 as is known in the art. A typical modern stove 100 has a base 101 , a top 116, sides (not shown in the cross-sectional view of Figure 1), and a back wall 105, such construction enclosing a chamber 114. The typical modern stove 100 also has an air outlet 102, a chimney 115, a baffle panel 103, and a front wall 117 comprising a lower air inlet 108, a glass door 109, and an upper air inlet 110 which provides an air wash to the glass door 109 and reduces the amount of soot deposited on the glass door 109, and some stoves have an extra rear air inlet 106. Fuel 111 is placed on the base 101 or on a grill 112 and is set alight. The fuel 111 burns with air from the upper air inlet 110, the lower air inlet 108 and the rear air inlet 106. As the fuel 111 burns, the flames 113 rise and hot gases are conveyed by convection upward and out of the chimney 115, drawing unburned air in through the upper air inlet 110, the lower air inlet 108 and the rear air inlet 106. The hot gases above the flames 113 pass over the baffle panel 103 and transfers heat to the baffle panel 103.
The baffle panel 103 is mounted so as to extend into the chamber and is spaced from but across the air outlet 102 in order to provide a path for gases between the centre of the chamber and the outlet 102. The baffle panel 103 therefore extends the path length of the escaping gases in order to increase the combustion time.
Such a typical modern stove 100 has at least the following problems:
1. Combustion is not complete when the gases enter the flue pipe or heat transfer area at the top of the stove. As a result, the interaction of the ongoing combustion with the heat transfer area and/or flue pipe causes soot to be deposited and carbon monoxide to be produced. These lower the efficiency of the stove and contribute to pollution.
2. Within the stove, there are cold spots, corners and uneven temperatures. This variation in temperature slows the speed of the reaction and can cause the reaction to stop before complete burning has occurred. Also, the uneven burning and variation in temperature compromise effective heat transfer from the stove. 3. Some of the air is introduced cold at room temperature; this can chill the flame and impair the reaction.
Examples of three different prior art stoves can be found in US 5,673,682 A (Hannebaum), US 4,332,235 A (Hannebaum) and US 4,181 ,117 A (Hannebaum). In US 5 673, 682 there is disclosed a stove with a truncated conical hood, which has an air directing means aligned with an air inlet means to impart a downward tangential flow through the fire enclosure that keeps the glass fire enclosure cool and clean.
The present invention therefore seeks to provide a fuel-burning stove which overcomes, or at least reduces the above-mentioned problems of the prior art to provide: near complete combustion, low pollution exhaust, and the end result of a clean burning appliance that has an increased efficiency, all without the need for an electric fan.
Accordingly in a first aspect, the invention provides a fuel-burning stove comprising a base, wall or walls and a top together defining a chamber, an outlet provided at or near the top of the chamber, one or more air inlets, one or more air vents coupled to one or more of the air inlets via air ducts, for directing air from the air inlet(s) into the chamber, wherein the air vents are arranged in sets and one or more of the sets is arranged at a different height to another in relation to the base of the stove in order to add oxygen continuously to the burning gases. This allows the diameter of the swirl of air inside the chamber to substantially be maintained, which has the following advantages:
a) increasing the mixing of the fuel and oxygen to help complete combustion; b) increasing the path length and in so doing the time the flame/combusting gases have to burn in the hot combustion chamber before exiting; and
c) gradually adding hot oxygen to the flame/combusting gasses as they rise up the combustion chamber to ensure combustion is completed from CO to CO 2 with minimum excess air. Preferably wherein there may be any one of 1 , 2, 3, 4, 5 or 6 inlets per set, further preferably wherein there may be 4 air inlets per set.
Preferably, wherein the ducts may be constructed with a varying cross-section to aid equal and consistent flow through the air vents.
Further preferably comprising a first baffle panel mounted so as to extend into the chamber spaced from, but across, the air outlet to provide a path for gases between a centre of the chamber and the outlet that extends around a periphery of the first baffle panel.
Further preferably comprising at least one secondary baffle panel mounted so as to extend into the chamber spaced from and partially overlapping with the first path so as to provide an extension in the path for gases between the centre of the chamber and the outlet.
Further preferably, wherein the space between the first and secondary baffle panels may form an additional high-temperature combustion chamber.
Further preferably, wherein the baffle panels may be located at the back or on a side of the stove.
Further preferably, wherein the first and secondary baffle panels may be mounted to extend into the chamber from opposite, or adjacent walls of the stove. Also preferably, wherein the secondary baffle panel may comprise a mesh and/or wherein the secondary baffle panel comprises a fine mesh which reduces the production of pollutants including larger ash particles.
Further preferably, wherein the secondary baffle panel may comprise a heat- conducting material, such as stainless steel or vermiculite board. Also preferably wherein the secondary baffle panel comprises a catalytic material enhancing combustion in the stove. Preferably, wherein the air vents may be arranged to direct air from the air inlet(s) into the chamber in a direction not substantially radially towards the centre of the chamber, so as to produce rotation of air in the chamber about a substantially vertical axis passing through the centre of the chamber and whilst substantially maintaining the swirl diameter.
Further preferably, comprising a plurality of air vents arranged around a periphery of the chamber at a predetermined height above the base of the stove, wherein each air vent directs air from an air inlet towards an adjacent air vent in a clockwise or anti-clockwise series and/or wherein the air vents may be arranged in corners of the stove pointing along a wall thereof in a clockwise or anti-clockwise series. Also preferably, wherein the air vents may be arranged tangentially in a round or oval chamber in a clockwise, or anti-clockwise, series.
Preferably the stove may further comprise one or more ducts between the air inlet(s) and the air vent(s), wherein the duct(s) may be at least partially constructed from a heat-conducting material which may be positioned to conduct heat from the chamber to the inside of the duct(s) so as to raise the temperature of the air within the duct before it reaches the chamber and/or wherein at least one duct may be constructed with a high ratio of surface area to volume to aid heat transfer from the chamber to the air within the duct.
Accordingly, in a second aspect, the invention provides a fuel-burning stove, comprising a base, walls and a top together defining a chamber, an outlet provided at or near the top of the chamber, one or more air inlets and one or more air vents coupled to one or more of the air inlets for directing air from the air inlet(s) into the chamber in a direction not substantially radially towards a centre of the chamber, so as to produce rotation of air in the chamber about a substantially vertical axis passing through the centre of the chamber. Preferably, a plurality of air vents may be arranged around a periphery of the chamber at a predetermined height above the base of the stove, wherein each air vent directs air from an air inlet towards an adjacent air vent in a clockwise or anti-clockwise series. Also preferably, the air vents may be arranged in corners of the stove pointing along a wall thereof in a clockwise, or anti-clockwise, series.
Accordingly, in a third aspect, the invention provides a fuel-burning stove, comprising a base, walls and a top together defining a chamber, an outlet provided at or near the top of the chamber, one or more air inlets, one or more air vents coupled to one or more of the air inlets for directing air from the air inlet(s) into the chamber, a first baffle panel mounted so as to extend into the chamber spaced from but across the air outlet to provide a path for gases between a centre of the chamber and the outlet that extends around a periphery of the first baffle panel and at least one secondary baffle panel mounted so as to extend into the chamber spaced from and partially overlapping with the first path so as to provide an extension of the path for gases to travel between the centre of the chamber and the outlet. Preferably, the first and secondary baffle panels may further comprise an additional high-temperature combustion chamber. Preferably also, the baffle panels may be located at the back or on a side of the stove. Preferably also, the first and secondary baffle panels may be mounted to extend into the chamber from opposite, or adjacent walls of the stove. Further preferably, at least one secondary baffle panel further may comprise a mesh, and may further preferably be a fine mesh which reduces the production of pollutants including larger ash particles. Also preferably, at least one secondary baffle panel may comprise a heat-conducting & reflecting material, such as stainless steel, or may comprise a catalytic material enhancing combustion in the stove.
Accordingly, in a fourth aspect, the invention provides a fuel-burning stove, comprising a base, walls and a top together defining a chamber, an outlet vent provided at or near the top of the chamber, one or more air inlets, one or more air vents coupled to one or more of the air inlets via one or more ducts for directing air from the air inlet(s) into the chamber, wherein the duct(s) is at least partially constructed from a heat-conducting material which is positioned to conduct heat from the chamber to the inside of the duct(s) so as to raise the temperature of the air within the duct before it reaches the chamber. Preferably, at least one duct is constructed with a high ratio of surface area to volume to aid heat transfer from the chamber to the air within the duct.
Further preferable features may be found in the dependent claims.
Four embodiments of the invention will now be more fully described, by way of example, with reference to the drawings, of which:
Figure 1 is a diagram showing a cross sectional view of a typical wood-burning or multi-fuel stove, as known in the art;
Figure 2 is a diagram showing a cross sectional view of stove according to a first embodiment of the present invention;
Figure 3 is a diagram showing a cross sectional view of a stove according to a second embodiment of the present invention;
Figure 4a is a diagram showing a first view of a stove according a third embodiment of the present invention;
Figure 4b is a diagram showing a second view of the stove of Figure 4a; and
Figure 5 is a diagram showing a cross sectional view of a stove according to a fourth embodiment of the present invention.
In a brief overview of the embodiments of the present invention, there is shown in Figure 2 one embodiment of a stove 100 according to the present invention. The same reference numerals are used for features which are the same as those in Figure 1. The stove 100 has a base 101 , top 116, an air outlet 102, a chimney 115, sides (not shown in cross-section of Figure 1), and a back wall 105, such construction enclosing a chamber 114. The stove 100 also has a baffle panel 103, a rear air inlet 106, and a front wall 117 comprising a lower air inlet 108, a glass door 109, an upper air inlet 110, fuel 111 on a grill 112 and flames 113. The chamber 114 is constructed from insulating material in the base 101 , back wall 105 and sides (not shown in cross-section of Figure 1), has ashes on the base 101 , and an insulating double-glazed glass door 109. An insulating material such as vermiculite board may be used in the construction of the base 101 , sides 104, and front wall 117. The baffle panel 103 may be made from reflective stainless steel or vermiculite board. The upper air inlet 110, lower air inlet (108) and rear air inlet 106 may be made from a metal such as stainless steel or other conductive material. It should be clear to someone skilled in the art that a variety of other suitable materials may be used.
The stove 100 further comprises two ducts 216, located between the air inlets 108, 106 and two air vents 120, wherein the ducts 216 is at least partially constructed from a heat-conducting material which is positioned to conduct heat from the chamber to the inside of the ducts 216 so as to raise the temperature of the air within the duct 116 before it reaches the chamber 114, therefore the incoming air is preheated, which aids combustion of its oxygen.
The ducts 216 may additionally have fins or other extrusions which create a high ratio of surface area to volume. This high ratio of surface area to volume aids the ducts 216 to further act as a heat sink within the chamber 114 and also as a heat sink to the incoming air at the air inlets 106, 108. This transfer of energy increases the combustion temperature within the chamber 114, enabling the chamber 114 to heat up faster and maintains for a longer time the high temperatures required for complete combustion.
There is shown in Figure 3 a stove according to a second embodiment of the present invention. In addition to the features of the stove described in Figure 2 above, Figure 3 shows a stove 100 having a secondary baffle panel 315. As explained previously, the first baffle panel 103 is mounted so as to extend into the chamber to provide an extended path for gases between the centre of the chamber and the outlet. The secondary baffle panel 315 is mounted so as to extend into the chamber 114 and is spaced from and partially overlapping with the first baffle panel 103 so as to provide an undulation in the path for escaping gases between the centre of the chamber 114 and the outlet 102. The secondary baffle panel 315 therefore greatly lengthens the distance that combusted gases must travel to exit the chamber 114, thus delaying the path of air exiting from the stove. The additional distance travelled provides the advantages of lengthening the time in which the air may mix with the flames 113 to combust and ensuring that more energy is released from combustion while in the chamber 114 rather than in the chimney 115.
Additionally, the secondary baffle panel 315 may be made of a heat-conducting material, preferably formed with a high ratio of surface area to volume, stainless steel or vermiculite board (among other suitable materials), and may incorporate a fine mesh (not shown in the present figure) made, for example from stainless steel. Where the secondary baffle panel 315 incorporates a fine mesh, the mesh heats up quickly, stops the production of pollutants including larger ash particles and acts like a catalyser to help the reaction. It should be clear to someone skilled in the art that further baffle panels could be included to further delay the air from exiting the chamber.
The baffle panels 103, 315 provide an extension of the path of the gases that flow between the centre of the chamber 114 and the air outlet 102. Further, due to the combination of a first baffle panel 103 made of insulating material and a second baffle panel 315 made of heat conducting material, the space in- between the baffle panels 103, 315 effectively forms an additional combustion chamber inside of which further combustion is able to occur at higher temperatures than in the main chamber of the stove.. The baffle panels 103, 315 and the path defining such a chamber may be located above the flames 113, or at the back or on a side of the stove 100.
In Figures 4a and Figure 4b there is shown a stove, according to a third embodiment of the present invention. The stove 100 having a plurality of air vents 417. In addition to the features described above, Figure 4a shows a horizontal cross section at a fixed height from the base (not shown in this Figure). In Figure 4a, the sides 104, back wall 105 and front wall 107 are coupled to columns 416. The air vents 417 are coupled to the air inlets 106, 108 for directing air from the air inlets 106, 108 into the chamber 114 in a direction not directly towards a centre of the chamber 114, but so as to produce rotation of air in the chamber 114 about a substantially vertical axis passing through the centre of the chamber 114. Wherein the path of the rotation of the air substantially maintains the same diameter as it travels up the height of the stove 100. This is due the addition of further air through each air vent 417 passed, as the air travels in the vertical direction inside the chamber 114.
As a result, the air within the chamber 114 is able to swirl around its centre in a cyclonic motion, wherein the cyclonic air substantially maintains its swirl diameter. Due to this swirling movement of the air, any combustion happening in the air within the chamber 114 travels in the vortex of air and so has a longer distance to travel before exiting the chamber 114 and continually mixes with the fuel (not shown in Figure 4a), burnt and unburned gases, which increases the proportion of the fuel fully burned and lowers the amount of pollutants produced.
The use of air vents 417 through the height of the chamber 114 causes a simple rotation starting at the fire bed (base of the chamber), with small amounts of extra oxygen being introduced as the combustion rises in order to maintain the diameter of the swirl. The purpose of this is threefold, as described following:
a) increasing the mixing of the fuel and oxygen to help complete combustion; b) increasing the path length and in so doing the time the flame/combusting gases have to burn in the hot combustion chamber before exiting; and c) gradually adding hot oxygen to the flame/combusting gasses as they rise up the combustion chamber to ensure combustion is completed from CO to CO 2 with minimum excess air.
These effects are to increase the efficiency by reducing the excess air required, and to aid almost complete combustion to reduce pollution and give cleaner exhaust gases.
In particular, Figure 4a shows a cross-section of a stove 100 having four columns 416 arranged to form a rectangular stove shape. The air vents 417 are placed in the columns 416 because the hollow shape (not shown) of each column 416 is ideal to duct air into the chamber 114. The air vents 417 are not aimed at the centre of the chamber 114 and the four sets of air vents 417 shown in the columns 416 of Figure 4a allow air into the chamber following the direction of annotating arrows 418. This supports the clockwise or anticlockwise rotation of the air in the chamber 114 and as described, maintaining the diameter of the swirl of air as it travels the height of the stove 100.
Figure 4b shows a sample frame having a base 101 , columns 416 and a top structure 419. There are shown air vents 417 in the columns 416, and there are also obscured air vents 417a whose position is not directly visible in Figure 4b due to the obscured air vents being hidden by the columns 416. The air vents 417, 417a are arranged asymmetric to the chamber 114 and introduce air moving into the chamber 114 in a direction around the central axis of the chamber 114. The fuel 111 may sit on a grill 418. Additionally, the base 101 also has air vents 417, 417a again arranged to cause and sustain a swirl or rotation in the air around the flames so as to improve the mixing of the incoming air (not shown) with the combustion flames (not shown). The air vents 417 may also be positioned in a graduated arrangement, evenly spaced throughout the height of the chamber 114, or grouped in varying arrangements.
Figure 5 is a diagram showing a stove according to a fourth embodiment of the present invention. The stove 100 has, in addition to the common features known in the art, air vents 417 arranged to create a swirling movement of the air within the chamber 114, a secondary baffle panel 315, heat-conducting ducts 523 arranged to transfer heat from the stove 100 to unbumed air drawn into the stove 100. The air vents 417 range in height in the chamber 114 and cause an ongoing supply of unburned air which improves the combustion characteristics of the stove 100 and increases the proportion of fuel fully combusted.
The air vents 417 may be each located in columns (not shown) in the corner of the stove 100 and the air vents 417 may be arranged pointing at the next pillar in a clockwise or anti-clockwise sequence defined by the common wall shared by the two columns. Alternatively, the air vents 417 may be arranged to direct air tangentially to the chamber 114, or be arranged so that any plurality of air vents 417 each point along an axis which no two air vents 417 share. The purpose of the arrangement is to improve the mixing of the air inside the chamber 114 and to increase the proportion of fuel combusted, thus the diameter of the air swirl inside the chamber 114 is effectively maintained. The air vents 417 may be connected to air inlets 106, 108, 110 by ducts 216, 523.
It should be clear to someone skilled in the art that a circular or oval stove could be envisaged with the inventive features described above; in this case, the definition of the feature "walls" found in the present application would be the same as the curved surrounding wall of a circular stove. The columns 416 would not be located in the "corners" of the stove per se, but spread at set distances around the inner wall of the stove.
It will be appreciated that although only one particular embodiment of the invention has been described in detail, various modifications and improvements can be made by a person skilled in the art without departing from the scope of the present invention.