Embodiment disclosed herein relate to combustion systems, combustion burners, and/or methods regarding the same. More particularly, embodiments disclosed herein relate to apparatus and methods for combusting multiple fuels, even more particularly multiple fuels, including biomass fuels, in a vortex-flow, forced air, recuperative burner that will allow for high-temperature, high stay time heat absorption, and even heat distribution within the combustion burner.

External combustion engines such as Stirling engines require combustion burners. With the varied availability and/or unavailability of a single source of fuel, particularly in developing and Third world countries, there is a continued need for combustion burners that are capable of burning multiple fuels.

In one embodiment, a combustion burner comprises: a housing forming a combustion chamber comprised of low density, high temperature resistant material; a structure within the housing that directs forced an air/fuel mixture or combustion gas in a circular fluid path within the chamber; a conduit connected to the combustion chamber; a nozzle connected to the conduit upstream of the combustion chamber and disposed in an air fluid path within the conduit; a fuel inlet connected to the conduit upstream of the combustion chamber and immediately downstream and adjacent to the nozzle; and a blower connected to the conduit for forcing air through the nozzle to cause a back pressure within the conduit sufficient to draw fuel into the conduit; wherein air and fuel mix within the conduit to form an air/fuel mixture and are forced into the chamber; wherein the air/fuel mixture engage the structure creating a circular fluid path within the chamber.

In another embodiment, a combustion system comprises: a combustion burner comprising: a housing forming a combustion chamber comprised of low density, high temperature resistant material, a structure within the housing that directs forced an air/fuel mixture or combustion gas in a circular fluid path within the chamber, a conduit connected to the combustion chamber, a nozzle connected to the conduit upstream of the combustion chamber and disposed in an air fluid path within the conduit, a fuel inlet connected to the conduit upstream of the combustion chamber and immediately downstream and adjacent to the nozzle, and a blower connected to the conduit for forcing air through the nozzle to cause a back pressure within the conduit sufficient to draw fuel into the conduit, wherein air and fuel mix within the conduit to form an air/fuel mixture and are forced into the chamber, wherein the air/fuel mixture engage the structure creating a circular fluid path within the chamber; and a work producing device having a heat exchanger, wherein the heat exchanger is disposed within the chamber and thermally coupled to the burner.

In another embodiment, a method of combusting multiple fuels includes providing an ignition source within a combustion chamber formed from low density, high temperature resistant material; forcing ambient air through a heat recuperator; forcing air from the heat recuperator through a nozzle; creating a back pressure in order to draw fuel into and mix with the ambient air to form an air/fuel mixture; forcing the air/fuel mixture into the combustion chamber; igniting the air/fuel mixture to form high temperature combustion gas; forcing the high temperature combustion gas in a vortex fluid flow path within the chamber; and forcing the high temperature combustion gas through a gap between the heat recuperator and a heat exchanger of a work producing device.

While the specification concludes with claims particularly pointing out and distinctly claiming the invention, it is believed the same will be better understood from the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic representation of a combustion system according to one embodiment;

FIG. 2 is a schematic representation of a combustion system according to one embodiment; FIG. 3 is a schematic representation of an air/fuel connector connected to a multiple fuel input device taken at Detail A of FIG. 1 according to one embodiment; and

FIG. 4 is a schematic representation of an inlet air nozzle according to one embodiment.

The embodiments set forth in the drawings are illustrative in nature and not intended to be limiting of the invention defined by the claims. Moreover, individual features of the drawings and the invention will be more fully apparent and understood in view of the detailed description.

The following text sets forth a broad description of numerous different embodiments of a combustion burner, a combustion system having the combustion burner, and/or methods providing and using the same. The description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment would be impractical, if not impossible, and it will be understood -A-

that any feature, characteristic, component, composition, ingredient, product, step or methodology described herein can be deleted, combined with or substituted for, in whole or part, any other feature, characteristic, component, composition, ingredient, product, step or methodology described herein. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims. All publications and patents cited herein are incorporated herein by reference.

It should also be understood that, unless a term is expressly defined in this patent using the sentence "As used herein, the term ' ' is hereby defined to mean..." or a similar sentence, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). No term is intended to be essential to the present invention unless so stated. To the extent that any term recited in the claims at the end of this patent is referred to in this patent in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such a claim term be limited, by implication or otherwise, to that single meaning. Finally, unless a claim element is defined by reciting the word "means" and a function without the recital of any structure, it is not intended that the scope of any claim element be interpreted based on the application of 35 U.S. C. § 112, sixth paragraph.

Not to be limited by theory, it has been discovered that in order to increase and/or maximize efficiency of combustion burners and/or external combustion engines thermally coupled to such combustion burners, high internal working temperatures (i.e., combustion gas temperatures) on the order of greater than about 400 ⁰ C, in certain embodiments greater than about 500 ⁰ C, in certain other embodiments greater than about 900 ⁰ C, in certain other embodiments greater than about 1,000 ⁰ C, in certain other embodiments from about 950 ⁰ C to about 1,500 ⁰ C, in certain other embodiments from about 1,000 ⁰ C to about 1,200 ⁰ C, and/or in certain other embodiments from about 1,000 ⁰ C to about 1,100 ⁰ C). However, achieving such high internal working temperatures is very difficult, let alone, in a cost effective, consistent, and evenly distributed manner within the combustion burner. Also, not to be limited by theory, it has been discovered that in addition to requiring these high combustion temperatures in order to increase and/or maximize efficiency, external combustion engines such as, for example, Stirling engines, steam engines, etc., further require consistent and even heat distribution along the length and around the circumference of the engine's heat exchanger (see, e.g., heat absorbing heater head 62 of FIGS. 1 and 2) of the external combustion engine (e.g., Stirling engine 60 of FIGS. 1 and 2). Attempting to design a combustion burner and/or combustion system capable of achieving both high-temperatures and consistent and even heat distribution is very difficult. Moreover, not to be limited by theory, it has been further discovered that these challenges are further compounded when combusting biomass fuel, particularly multiple types of biomass fuels, due to the inconsistent and varied nature of biomass fuels. One or more of the embodiments of the combustion system and/or burner described herein may overcome at least one or more of the following difficulties in achieving high temperature combustion: achieving uniform heat distribution and long heat stay times of the high temperature combustion gas (superheated gas) around the heat exchanger; containing such high temperature heat in a long-life, low cost burner; capturing and reusing the exhaust heat from the exhaust combustion gas to increase burner efficiency and extend the life of the burner; designing a single fuel inlet to accommodate multiple fuels; and designing a simple geared blower linked to the fuel feed system for ease of manufacture and enhanced burner performance using a variety of fuels.

In general, the combustion system shown and described herein may comprise a combustion burner and a heat exchanger of a work producing device that is connected to the combustion burner such that the heat exchanger transfers the heat from the combustion burner to the work producing device to produce work. As such, the work producing device may be said to be thermally coupled to the combustion burner. Examples of work producing devices that may be thermally coupled to the combustion burner may include, but not be limited to, external combustion engines (e.g., Stirling engines), water heaters, water boilers, electrical generators, pumps, or any other device that may convert a portion and/or all of the heat energy of the combustion burner to another form of energy to produce work such as mechanical, electrical, usable heat energy, or any combination thereof.

Referring generally to FIGS. 1 - 4, one or more embodiments of a combustion system 10 is shown for illustration purposes only, and not limitation as generally comprising a combustion burner 20, an external combustion engine 60 disposed adjacent to and thermally coupled to burner 20, and a blower 80 in fluid communication with combustion burner 20. Optionally, combustion system 10 is show in FIG. 2 as also include an ash pit 90 disposed below burner 20 for receiving the hot, waste ash from burner 20 and capitalizing on and transferring at least a portion of the remaining heat left in the hot, waste ash back into the burner. Because waste ash pit 90 is positioned below combustion burner 20, heat releasing from the hot, waste ash disposed within the ash pit rises to and transfers to back into the burner, thus assisting in raising and maintaining the high temperatures required within burner 20.

As shown in FIG. 1 combustion burner 20 may include a housing 22 having a first end 21, a second end 23, and a housing sidewall 24 forming a combustion chamber 25 therein. First end 21 may comprise a first end wall that includes an opening 27, wherein both may be sized and shaped such that a heat exchanger of a work producing device (e.g., a heater head 62 of external combustion engine 60) may fit within opening 27. Although not shown, heater head 62 and external engine 60 are sealed within opening 27 and thus to housing 22 such that combustion gases and/or heat cannot escape from combustion burner 20. Any variety of high temperature seals and/or sealing devices such as, for example, high temperature rope seals, may be used to seal engine 60 to housing 22. As shown in this embodiment, a heat recuperator 26 comprises or forms the first end wall of housing 22. As such, heat recuperator 26 encircles and encompasses heater head 62 of engine 60. Heat recuperator 26 may comprise a heat exchanger and thus may be fabricated, at least on the side that is exposed to chamber 25, from a material that will enable efficient heat transfer from the high temperature, exhaust combustion gas as indicated by arrow (C) to inlet ambient air as indicated by arrow (a) prior to exhaust combustion gas C being exhausted from burner 20 into ash pit 90 and inlet ambient air (a) being forced into chamber 22 as will be described in greater detail below herein.

It is understood that in an alternative embodiment the first end wall may comprise a combination of the heat recuperator and a wall fabricated from the same materials as the other housing walls (e.g., sidewall 24) as will be described below herein. Moreover, in other alternative embodiments, the first end wall may comprise a wall fabricated from the same materials as the other housing walls (e.g., sidewall 24) as will be described below herein and then the heat recuperator may be positioned along an inner surface of the first end wall. Second end 23 may comprise a second end wall 28. In one embodiment, second end wall 28 may include a door (not shown) that opens to permit access to within chamber 25 in order to load fuel such as wood and to ignite the fuel to begin the combustion within chamber 25. It is understood that the door may be positioned anywhere along housing 22 of burner 20. At temperatures such as those found within combustion burner 20 of the present embodiment(s) (e.g., from about 1,000 ⁰ C to about 1,200 ⁰ C), most materials (e.g., steel) are not capable of withstanding such high temperatures and thus will warp, melt, corrode, flake, etc. As such, in the present embodiment(s), housing 22, particularly its walls (e.g., second end wall 24, and sidewall 24), may be fabricated from or lined and/or coated with one or more materials having thermal properties that enable the housing to withstand or be resistant to high temperatures (e.g., temperatures greater than about 400 ⁰ C, in certain embodiments greater than about 500 ⁰ C, in certain other embodiments greater than about 900 ⁰ C, in certain other embodiments greater than about 1,000 ⁰ C, in certain other embodiments from about 950 ⁰ C to about 1,500 ⁰ C, in certain other embodiments from about 1,000 ⁰ C to about 1,200 ⁰ C, and/or in certain other embodiments from about 1,000 ⁰ C to about 1,100 ⁰ C). This high temperature resistant material(s) may also comprise a low density. As such, in certain embodiments the housing walls may comprise low density, high temperature resistant material or materials such as clays, fire bricks, composites, ceramics, and/or combinations thereof. More particularly, the low density, high temperature resistant material may comprise, in one embodiment, a commercially available low density, high temperature insulating fire brick or any other low density, high temperature insulating fire material.

As an example, housing 22 may comprise a conventional steel drum (e.g., a conventional 55 gallon steel drum) that is lined with a low density, high temperature resistant, insulating fire brick that is then coated with a thin layer of high temperature ceramic material or paste to form inner surfaces 29 of second end wall inner 28 and side wall 24.

In addition, housing 22 may include a gap 30 formed between inner surfaces 29 and heater head 62 of engine 60 (and/or heat exchange fins 64 of engine 60) that is designed to maximize mass heat flow to heater head 62 in order to optimize the engine's performance (e.g., Q = Mass flow x Cp [Heat Capacity] x ΔT [Change in Temperature]). In order to obtain a more complete combustion of the fuel (i.e., combustion efficiency) and to a more efficient heat transfer from the combusted gas as indicated by arrow (B) in FIG. 1 to heater engine 62 in certain embodiments, the combusted gas temperature of the combusted fuel, i.e., the internal working temperature of combustion burner 20, may be from about 1000 ⁰ C to about 1100 ⁰ C. Spiral fins may be added to burner 20 to further increase the efficiency of this heat transfer between from the exhausted air to the ambient inlet air. To allow burner 20 to reach such high temperatures quickly and retain these high temperatures in order to combust inputted fuel, in many cases almost instantly, ambient air (a) is drawn in from the atmosphere using a blower 80, mixed with one or more fuels at an air/fuel connector 50, and then an air/fuel mixture as indicated by arrow (A) is forced into chamber 25 of burner 20 at second end 23 in a direction tangential to inside surface 29 of the substantially circular cross section housing 22, creating a vortex flow of high temperature combustion gas as indicated by arrows (B). In the one embodiment shown in FIG. 1 , geared blower 80 is in fluid communication with a first inlet air conduit 40 that is connected to and in fluid communication with heat recuperator 26. Heat recuperator 26 is connected to and in fluid communication with a second inlet air conduit 42, which is also connected to and in fluid communication with air/fuel connector 50. Air/fuel connector 50 is connected to and in fluid communication with an air/fuel inlet 44 which enters through housing 22, through sidewall 24, and into chamber 25 in a direction tangential to inside surface 29 as described above and introduces an air/fuel mixture into chamber 25. It is understood that either air/fuel connector 50 or air/fuel inlet 44 may be connected to housing 22 or a third conduit introduced between air/fuel connector 50 and housing 22 as desired and/or necessary. Blower 80 may comprise any number of conventional and/or yet-to-be developed blowers, including but not limited to geared blowers, pulley driven blowers, geared pulleys having a hand crank, and/or other known blowers. In the embodiment shown in FIG. 1, blower 80 is a geared blower having a hand crank device 82 with a handle 84. In addition, blower 80 is mechanically coupled to engine 60 via pulleys, gears, or some combination thereof. In this embodiment, a user may initially hand crank via handle 84 of hand crank device 82 to operate blower 80 until the internal working temperature of chamber 25 is high enough to operate engine 60, at which point, engine 60 will operate blower 80 via pulleys, gears, or some combination thereof in order to force ambient air through the inlet air conduit, heat recuperator, air/fuel connector, and air/fuel inlet, and thus into chamber 25. Blower 80 may comprise conventional dual, spring-biased pulley systems or multiple gear drives that enable the blower speed and thus air flow to be adjusted while the engine is operating at a constant speed.

Still referring to FIG. 1, heat recuperator 26, in this embodiment, is a tube heat exchanger configured to extract heat from exhaust combustion gas as indicated by arrows (C) that has engaged at least one surface of heat recuperator 26 and transfer this heat to inlet ambient air (a) to form pre-heated inlet air as indicated by arrow (a _ph ) exiting the heat recuperator and flowing through second inlet air conduit 42. Heat recuperator 26 may be of any size, shape, and/or configuration. As one example, heat recuperator 26 may comprise a thin metal, tube heat exchanger that is curved such that it encompasses engine heater head 62 at first end 21 of housing 22. It is understood that heat recuperator 26 may be any conventional or yet-to-be developed heat recuperator and/or heat exchanger capable of extracting heat from exhaust combustion gas and transferring it to inlet ambient air. The operation of heat recuperator 26 will be described below herein.

At an end of second inlet air conduit 42 opposite heat recuperator 26, second inlet air conduit 42 may be connected to and in fluid communication with air/fuel connector 50. In this embodiment, air/fuel connector 50 may comprise a air/fuel T-connector 51 having an air inlet 53, a nozzle 52, a fuel inlet 54, and an air/fuel mixture outlet 55. Nozzle 52 is disposed at or just downstream of air inlet 53, yet upstream of fuel inlet 54. Also, nozzle 52 may comprise any size, shape, and/or configuration in order to achieve enough air flow to create sufficient back pressure to entrain and/or draw the fuel into fuel inlet 54 (e.g., venturi effect) and then through air/fuel mixture outlet 55 and out of air/fuel inlet 44. In one embodiment, nozzle 52 comprises a wall 56 transverse to the fluid flow and an aperture 57 disposed within wall 56, wherein the aperture 57 has a diameter that is smaller than the inside diameter of the second inlet air conduit 26 as shown in FIG. 2. In another embodiment shown in FIG. 4, nozzle 52 comprises a wall 56 transverse to the fluid flow, an aperture 57 disposed within wall 56, and an annular side wall 58 surrounding aperture 57 and having an annular inside surface 59, wherein inside surface is angled radially inwardly, creating a narrowing effect.

Referring to back to FIG. 3, burner 20 may comprise a fuel input device 70 that is connected to air/fuel connector 50 via fuel inlet 54. Fuel input device 70 may be as simple as a conduit connected to air/fuel connector 50 that is operable to receive and direct fuel into fuel inlet 54 of air/fuel connector 50. In another embodiment, fuel input device 70 may comprise a hopper connected directly connected to fuel inlet 54 of air/fuel connector 50, wherein the hopper is operable to receive fuel and direct the fuel into air/fuel connector 50. In the embodiment shown, fuel input device 70 comprises a fuel T- connector 71 having a fuel outlet 72, a fuel input device first inlet 73, and a fuel input device second inlet 74. Fuel outlet 72 is connected to and in fluid communication with fuel inlet 54 of air/fuel connector 50, while second inlet 74 may be open to the atmosphere, operable to receive one or more fuels, and/or connected to a fuel source. Fuel input device first inlet 73 of fuel T-connector 71 may be connected to a fuel transporting device 75 for transporting fuel, gaseous, liquid, solid, and/or any combination thereof to fuel input device first inlet 73, and ultimately to air/fuel connector 50. Fuel transporting device 75 may comprise as one example, a fuel conduit 76 and an auger 77 positioned within conduit 76 for moving fuel, liquid or solid, within the conduit. As shown, conduit 76 may comprise a standard pipe with an upper portion of the pipe removed to form an opening 78 for receiving the solid fuel from a lower end 102 of a fuel hopper 100 as shown in FIG. 2. Hopper 100 may include a loading opening 104 for loading fuel, particularly solid fuel (e.g., saw dust, rice husks, corn husks, etc.) into the hopper.

As shown in FIGS. 1 and 3, fuel input device 70 may intersect and connect to air/fuel connector 50 via fuel inlet 54 adjacent to and downstream of nozzle 52 within the air fluid path. Specifically, fuel input device 70 is operable to receive and transport to air/fuel connector 50 multiple fuels, including but not limited to gaseous, liquid, solid fuels, including but not limited to biomass fuels, oils, natural gas, petroleum, trash, waste products, etc., to the air/fuel connector 50. As set forth above, burner 20 may utilize any number of fuels in any number of physical states such as gaseous, liquid, solid, or any combination thereof. The fuel used with burner 20, i.e., combusted, may comprise any number of fuels, including but not limited to biomass fuels (e.g., rice husks, corn husks, sawdust, wood, wood byproducts, vegetation, weeds, grass, etc.), oils, gasoline, natural gas, propane, waste products, industrial and commercial process byproducts (e.g., waste oils), any fuel, or any combination thereof.

Combustion burner 20 may comprise an ignition source 32 to begin to raise the internal working temperature of chamber 25 to a temperature sufficient to ignite the air/fuel mixture (A) being introduced into the chamber at second end 23. Ignition source 32 may comprise any variety of potential fuel ignition sources that may generate enough heat to ignite the air/fuel mixture (A), including but not limited to electrical heating elements, fossil fuel combustion, chemical heating elements, etc. In one embodiment, ignition source 32 comprises a fire fueled by wood. Such a fire may also be fueled by coal, trash, tires, waste materials, or other fossil fuels. Housing 22 may include a door (not shown) disposed within one of the walls, such as second end wall 28 in order to facilitate maintenance of ignition source 32 such as loading fuel (e.g., wood) into the chamber, igniting the fuel, and maintaining the fire 32.

The low thermal mass of housing walls' material such as, for example, the low density, high temperature resistant fire brick allows for the temperature within chamber 22 created by the ignition source 32 to rise very quickly and for the chamber to maintain a consistent temperature throughout the chamber. As an example, to almost instantaneously ignite the air/fuel mixture (A) if a biomass fuel is being used, the ignition source 32 may be generating heat at a minimum temperature of about 500 ⁰ C. In order to achieve increased and/or maximum efficiency of burner 20 and/or combustion system 10 of one embodiment, internal working temperatures will be generated from about 1,000 ⁰ C to about 1,200 ⁰ C.

The present embodiments of the combustion burner permits one to adjust the stay times for heat absorption by the engine heater head 62 by simply adjusting the size, (e.g., length and diameter) of burner housing 22. Also, the stay times and heat absorption of heater head 62 may also be increased through adjustment of the size of gap 30. As set forth above, engine 60 may generally comprise a heat exchanger (i.e., heater head 62), a working fluid (e.g., air, gas, water, steam, other liquids, etc.) within a closed system, and one or more pistons, cylinders, and/or cams that are driven by the expansion and contraction of the working fluid. The heat provided by combustion burner 20 to heater head 62 may cause the working fluid to expand, thus moving the one or more pistons, cylinders, and/or cams in order to perform some desired work as known to one of ordinary skill in the art. As the working fluid is cooled, the working fluid contracts and thus moves the one or more pistons, cylinders, and/or cams in the opposite direction and performs some desired work. In addition, once burner 20 reaches a certain temperature sufficient to cause engine 60 to begin operating, engine 60 will also begin driving blower 80 through a drive system such as a pulley or gear system as known to one of ordinary skill in the art. Also, once engine 60 begins operating, it may also drive fuel transporting device 70 such as the auger drive system via a pulley (e.g., spring-biased, dual pulley system) or gear system as known to one of ordinary skill in the art.

The one or more embodiments of burner 20 shown and described above herein allow for complete combustion of fuels, at high temperatures, and can be applied to any type of applications requiring this type of heat absorption, but specifically external combustion engines. External combustion engine 60 may comprise a variety of engines such as Stirling engines, steam engines, and/or any other external combustion engine known or yet-to-be developed. Examples of Stirling engines that external combustion engine 60 may comprise includes, but is not limited to, alpha Stirling engines, beta Stirling engines, gamma Stirling engines, rotary Stirling engines, Fluidyne engines, Ringbom engines, or "free pistion" Stirling engines. The external combustion engine shown in FIGS. 1 and 2 comprises a Stirling engine. Generally, such conventional Stirling engines comprise heater head 62. One example of Stirling engines that may be used with the burner described herein is Stirling engines manufactured by Stirling Technologies, Inc. of Athens, OH., such as, for example, engine model number ST-5.

For illustration purposes only, and not limitation, the combustion burner and combustion system will be described in operation below herein with reference to the exemplary embodiments shown in FIGS. 1-3. In operation, a fire will be started within chamber 22. A user will begin hand cranking blower 80 via turning handle 84, which begins to draw ambient air (a) into the system 10 and force ambient air (a) through first inlet air conduit 40, through heat recuperator 26, through second inlet air conduit 42, and through nozzle 52. As the air is forced through nozzle 52 just prior to fuel inlet 54, it causes a back pressure (i.e., venturi effect) that draws or sucks the fuel from fuel input device 70 into air/fuel connector 50 where it mixes with the air. The air/fuel mixture (A) is then forced into chamber 25 through air/fuel inlet 44. Chamber 25 comprises a raised pressure atmosphere that the air/fuel mixture (A) would have difficulty entering without the forced air pressure from the blower and/or the nozzle design.

As the air/fuel mixture (A) is forced into the chamber, ignition source 32 ignites, if not instantaneously, the air/fuel mixture (A), creating high temperature combustion gas (e.g., superheated combustion gas) as indicated by arrows (B). In addition, due to the air/fuel mixture (A) being forced into chamber 25 along curved inner surface 29, the air/fuel mixture (A) and/or high temperature combustion gas (B) begin to move in a circular pattern along inner surface 29, thus creating a vortex flow within chamber 25 as indicated by arrows (B). The combustion gas (B) may also be a high velocity flow in this vortex flow pattern within chamber 25, which is then forced into gap 30 around heater head 62, causing the high temperature combustion gas to evenly distribute around heater head 62 and to have a long stay time at the heater head 62. Such uniform distribution and long stay time of the combustion gas (B) at heater head 62 creates a more uniform and efficient heat absorption at heater head 62, and thus more efficient combustion system 10.

In addition, as set forth above, as the combustion gas exits gap 30 as indicated by arrows (C) prior to being exhausted into ash pit 90, the gas (C) is caused to engage heat recuperator 26 such that heat recuperator 26 may extract and transfer heat from exhaust gas (C) and transfer it to ambient air (a) to form pre-heated air (a _Ph ). This heat recuperator also assists in increasing the efficiency of burner 20 and/or system 10. In addition, this transfer of heat from the exhaust gas (C) to the inlet ambient air (a), lowers the temperature (e.g., less than about 700 ⁰ C) of the exhaust gas (C) such that less expensive materials (e.g., steel rather than high temperature resistant materials, i.e., capable of withstanding temperatures at or above 900 ⁰ C) may be used in ash pit 90, and exhaust gas systems (not shown) such as a chimney.

Once the combustion burner 20 gets to a sufficient temperature to cause engine 60 to begin operating as described above, then both blower 80 and fuel transporting device 70 may be operated via pulley and/or gear systems by engine 60, thus making combustion system 10 self-operating. Through a series of belts, pulleys, and/or gears, one may be able to adjust the speed of the blower and/or the fuel transporting device 70 (e.g., the auger) in order to adjust the flow rate of the ambient air and/or the flow rate of the fuel into burner 20 while maintaining a constant engine speed and/or operation.

It is understood that one or more of first and second air inlet conduits 40, and 42, air/fuel connector 50, air/fuel inlet 44, and/or fuel transporting device 70 may be separate components that are connected together by conventional methods or fabricated as one or more integrated component, or some combination thereof.

As set forth above herein, the intersection of combustion air and fuel, which in this embodiment is disposed at air/fuel connector 50, may be fabricated such that a very wide variety of biomass and gasified fuels can be used with very minor changes to the design and still obtain the proper fuel/air mixture for combustion. As an example, if one plans on using a biomass fuel that requires a higher feed rate to obtain the necessary heat levels within the burner, one only needs to change the pulley ratio of the pulley system driving the fuel transporting device 70 and/or block off or increase air flow from blower 80.

The embodiment of this invention allows for the construction of a simple, cost effective, high temperature, long stay time, multiple fuel, and long lasting biomass burner. The target application for such a design is for use with Stirling engines manufactured by

Stirling Technologies, Inc., but can be used for any application which might require such temperature gases.

One or more of the embodiments of the combustion burner shown and described herein provide for an increased combustion efficiency of greater than about 90%, in certain embodiment of greater than about 95%, in certain embodiments from about 90 to 95%, and/or in certain embodiments from about 90% to about 100%. 'Combustion efficient', as used herein, is a measure of how much of the energy available in a fuel (e.g., B TU' s available in fuel prior to combustion) prior to combustion is left in the fuel after combustion (e.g., BTU's available in fuel after combustion). One or more embodiments of the combustion system shown and described herein provide for an increased burner system efficiency of greater than about 90% and/or in certain embodiments of greater than about 95%. 'Burner system efficiency', as used herein, is a measure of the energy inputted into the system (e.g., BTU's of fuel inputted into system) compared to the output energy available to be used by the work producing device (e.g., energy available to be transferred to the heat exchanger 62 of engine 60).

All documents cited in the Detailed Description of the Invention are, in relevant part, incorporated herein by reference; the citation of any document is not to be construed as an admission that it is prior art with respect to the present invention. To the extent that any meaning or definition of a term in this written document conflicts with any meaning or definition of the term in a document incorporated by reference, the meaning or definition assigned to the term in this document shall govern. While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.