Abstract:
The present invention provides a fuel injector, comprising a housing having a sealable injector seat; a fuel injector pin disposed within the housing proximate to the injector seat such that the injector seat may be sealed and unsealed by displacing the fuel injector pin; a resilient element biasing the fuel injector pin in an unsealed direction; a piezoelectric actuator disposed within the housing proximal to the fuel injector pin configured to actuate to force the injector pin towards the injector seat to seal the injector seat; and a thermal compensating unit disposed within the housing proximal to the actuator and configured to compensate for thermal expansion or contraction of a component of the fuel injector.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority from U.S. Provisional Application Ser. No. 61/081,326 filed Jul. 16, 2008. 

   FIELD OF THE INVENTION 
   The invention broadly relates to fuel injection systems and, more particularly to a piezoelectrically actuated fuel injector having a heated and catalyzed section for engines, specifically, internal combustion engines. 
   BACKGROUND OF THE INVENTION 
   Much of the world&#39;s energy consumption is dedicated to powering internal combustion based vehicles. Most gasoline and diesel car engines are only 20-30% efficient, such that a major portion of the hydrocarbon fuels is wasted, thereby depleting global resources while producing an excessive quantity of pollutants and greenhouse gasses. With hydrocarbon fuels becoming more scare and more expensive it is desirable to obtain more efficient use of those fuels. 
   Typical fuel injectors may have hydraulically, electromagnetically, or piezoelectrically actuated injector pins. A piezoelectric element is a material that changes dimensions when a voltage is applied across the element. When the voltage is removed, the piezoelectric element returns to its original dimensions. When used as actuators, many piezoelectric elements are stacked together to form larger piezoelectric elements or “piezoelectric stacks” to increase the displacement of the actuator. In a piezoelectrically actuated fuel injector, one or more of these piezoelectric elements or piezoelectric stacks are used to actuate a fuel injector pin for fuel metering into an internal combustion engine. 
   SUMMARY OF THE INVENTION 
   Some embodiments of the invention provide a fuel injector having a piezoelectrically actuated injector pin and a temperature compensator unit. In further embodiments, the injector includes both a heated portion and a catalytic portion. The injector pin contacts a seating surface that when closed prevents fuel from entering the combustion chamber of the engine. In this embodiment, a resilient element biases the injector pin in an open position and the piezoelectric actuator displaces to seal the seating surface. The temperature compensating unit is positioned at the opposite end of the injector pin. The temperature compensating unit comprises a fluid chamber that can expand or contract to position the piezoelectric element to allow accurate control of the injector assembly. The temperature compensating unit incorporates a chamber to allow for controlled fluid flow into and out of the chamber. 
   A further embodiment of the fuel injector according to the present invention provides a fuel injector having a piezoelectrically actuated injector pin having a catalytic portion and a temperature compensating unit. In this embodiment, a heater is not required as the fuel is heated prior to delivery to the fuel injection system. 
   The present invention also provides a method of dispensing fuel into a combustion chamber of an internal combustion engine. The method requires pressurizing fuel in a lower fluid chamber inside the fuel injector to a first pressure value and also pressurizing fuel in an upper fluid chamber of the fuel injector to a second pressure value. The first value is greater than the second value and this pressure differential causes the injector pin to move and allow fuel to be dispensed into the combustion chamber of the internal combustion engine. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates an example vehicle in which an embodiment of the invention may be employed. 
       FIG. 2  illustrates an example in which an embodiment of the invention may be employed. 
       FIG. 3  illustrates a schematic diagram of an embodiment of the invention. 
       FIG. 4  illustrates an exterior view of a fuel injector in accordance with the principles of the invention. 
       FIG. 5  illustrates a cut away view of a fuel injector in accordance with the principles of the invention. 
       FIG. 6  is a detailed view of the seal assembly of a fuel injector in accordance with the principles of the invention. 
       FIG. 7  is a detailed view of a portion of the seal assembly of a fuel injector in accordance with the principles of the invention. 
       FIG. 8  is a detailed view of a portion of the fuel injector, including the upper fluid chamber in accordance with the principles of the invention. 
       FIG. 9  is a detailed view of a portion of the piezoelectric assembly of a fuel injector according to an additional embodiment in accordance with the principles of the invention. 
       FIG. 10  is a cut away view of a fuel injector according to an additional embodiment in accordance with the principles of the invention. 
       FIG. 11  is a cut away view of a fuel injector seal assembly according to an additional embodiment in accordance with the principles of the invention. 
       FIG. 12  is a cut away view of a fuel injector according to an additional embodiment accordance with the principles of the invention. 
       FIG. 3  illustrates a schematic section view of a fuel injector in accordance with an embodiment of the invention. 
   

   DETAILED DESCRIPTION 
   In the following paragraphs, the present invention will be described in detail by way of example with reference to the attached drawings. Throughout this description, the preferred embodiment and examples illustrated should be considered as exemplars, rather than as limitations on the present invention. As used herein, the “present invention” refers to any one of the embodiments of the invention described herein, and any equivalents. Furthermore, reference to various feature(s) of the “present invention” throughout this document does not mean that all claimed embodiments or methods must include the referenced feature(s). 
   Before describing the invention in detail, it is useful to describe a few example environments with which the invention can be implemented. One such example is that of a vehicle powered by internal combustion engine.  FIG. 1  illustrates such a vehicle  50 . A fuel supply  51  is disposed within the vehicle and coupled to an engine  52  by a fuel line  53 . Fuel from fuel supply  51  is used to power engine  52  to provide motive power to vehicle  50 . A more particular example is that of an internal combustion engine as illustrated with respect to  FIG. 2 . Engine  52  comprises a plurality of cylinders  54  having pistons  55  disposed therein. A plurality of fuel injectors  56  is configured to supply fuel to engine  52  and is connected  53  to a fuel source  51 . Pistons  55  and cylinders  54  are configured to form combustion chambers into which fuel  58  is metered from fuel injector  56  during a power stroke of the engine. When the fuel  58  is mixed with air and ignited, the piston  55  is displaced, thereby turning crankshaft  57  and providing motive force. 
   From time-to-time, the present invention is described herein in terms of these example environments. Description in terms of these environments is provided to allow the various features and embodiments of the invention to be portrayed in the context of an exemplary application. After reading this description, it will become apparent to one of ordinary skill in the art how the invention can be implemented in different and alternative environments. 
     FIG. 3  illustrates a schematic view of a fuel injector  100  according to an embodiment of the invention. Fuel injector  100  comprises a housing  202  having a fuel injector pin  205  and a piezoelectric element comprising one or more piezoelectric actuator stacks  234  disposed therein. A fuel chamber  216  is formed between housing  202  and the fuel injector pin  205 . Housing  202  further comprises an injection seat  212  configured to receive the injector pin such that the injector may be opened to allow fuel to be metered out or closed to prevent fuel from escaping the injector. Piezoelectric stacks  234  comprise a plurality of piezoelectric elements  230 , as described herein. Piezoelectric stacks  234  are coupled to electrical line  75  to allow a voltage to be applied to stacks  234 , causing them to expand and force injector pin  205  into injector seat  212 , thereby sealing the fuel injector. A temperature compensating  76  comprises a temperature compensator  240  that is disposed to provide a base against which piezoelectric elements  234  expand. Temperature compensating unit  76  further comprises a fluid chamber  506  coupled to a fluid source via inlet duct  241  to allow fluid to enter or exit fluid chamber  506 , thereby causing fluid chamber  506  to be expanded or contracted. This expansion and contraction changes the position of temperature compensator  240 , thereby changing the position of the base of piezoelectric actuator  234 . In some embodiments, changes in the temperature of various components of fuel injector  100  will cause the displacement distance required to properly actuate the fuel injector pin  205  to vary. Accordingly, temperature compensating unit  76  may be configured to vary the position of actuators  234  to compensate for these changes. In further embodiments, a resilient element  509  is disposed within the housing and configured to bias temperature compensator  240  in the direction of fuel injection seat  212 . In still further embodiments, viscous flow or hydraulic pressure is provided by fluid chamber  506  to allow dampened displacement of temperature compensator  240  during actuation of the fuel injector thereby compensating for a lengthening of fuel injector pin  205  caused by increased temperature. 
     FIG. 4  illustrates an exterior view of a fuel injector according to an embodiment. The injector pin includes a heated and catalytic portion. The injector pin contacts a seating surface and when closed prevents fuel from entering the combustion chamber of the engine. The injector pin is directly actuated by the piezoelectric element.  FIG. 5  illustrates a cut-away view of a fuel injector according to an embodiment. 
   The injector pin assembly is contained in an outer housing that is concentric and coaxial with an inner housing. The inner housing surface allows for the sliding movement of the injector pin. A lower pin assembly and the inner surface of the inner housing form a seal to prevent fluid below the lower pin from contacting or mixing with fluid from the upper pin assembly. The lower pin and inner surface may use any appropriate sealing mechanism such as precision ground seals, bellows seals, o-ring seals, diaphragm, elastomers, or energized seals. 
   In one embodiment, a catalytic element can be applied to both the outer surface of the lower pin and the inner surface of the inner housing. However, only one of these surfaces may be coated in further embodiments. 
   The invention further includes an injector element which can be a piezoelectric element. The piezoelectric element is made up of at least one piezoelectric stack that is controlled by a controller. The piezoelectric element is directly attached to the injector pin. The individual piezoelectric stacks are retained inside the outer housing by a support structure. The piezoelectric stack has at least one resilient element biasing the injector pin into an open position. The piezoelectric stacks must be charged to close the fuel injector assembly. 
   A temperature compensating unit is positioned at the opposite end of the piezoelectric element from the injector pin. The temperature compensating unit is a fluid chamber that allows for the expansion and contraction of the piezoelectric element and injector pin and takes into account temperature changes. This allows for accurate control of the injector assembly. The temperature compensating unit has a chamber that allows for controlled flow of liquid fuel in and out of the chamber. 
   An advantage of the current invention is that the catalyst material in the fuel injector allows for oxidation of the fuel or conversion of the fuel, for example through hydrocarbon cracking, for more efficient engine operation. A further advantage of the current invention is that the use of a piezoelectric element allows for a fast acting and responsive fuel injector. 
   Referring to  FIG. 4  a fuel injector  100  of the present invention is illustrated. The fuel injector  100  has a lower housing  104  connected to an upper housing  102 . The lower  104  and upper  102  housings are connected to each other by a bayonet style connection, however, any type of fastening method can be used. The lower housing  104  has an outer housing made of stainless steel, however, any appropriate metal can be used. The outer housing has a lower portion having an injector seat. The injector seat comprises the inner surface of the outer housing, including at least one orifice that allows for fuel to exit the fuel injector  100 . There can be a plurality of orifices leading out of the fuel injector  100 . 
     FIG. 5  illustrates a cut away view of a fuel injector  200  of the present invention. Positioned concentrically inside the outer housing  202  is an inner housing  204  having a hollow inner surface for the passage of injector pin  205 . The inner housing may include an inner diameter of about 4 mm, although any appropriate size may be used. 
   The injector pin  205  includes a lower portion  206  and an upper portion  208 . The lower portion  206  has a pin tip  210  that can have a double angled surface such that when the injector is in a closed position, the pin surface contacts an injector seat  212  formed in the outer housing  202  to create a fluid tight seal. The injector seat  212  can have an included angle of between 180 degrees and 45 degrees, however, in a preferred embodiment the included angle is approximately 90 degrees. The injector seat  212  has a plurality of fuel holes or orifices below the seat surface to allow fuel to pass through when the pin tip is not in contact with the injector seat. The injector seat  212  can be formed of a high impact resistant metal, ceramic material or ceramic metallic matrix. The pin tip  210  that contacts the injector seat can be a ground seal tip or a ball seal type tip. 
   With continued reference to  FIG. 5 , the upper portion  208  includes a seal assembly  214 . In the illustrated embodiment, seal assembly  214  is positioned around the upper portion of the injector pin between the lower and upper portion. Adjacent to the injector seat  212  and formed between the lower portion  206  and the inner housing is a lower fluid chamber  216 . The lower fluid chamber  216  is connected to an input port and allows for pressurized fuel to be delivered to the combustion chamber of the engine. 
   In a preferred embodiment, the inner housing  204  adjacent the lower fluid chamber  216  contains a heating element  218 . Heating element  218  may be an electrical resistance coil or heat pipe or any other suitable means to allow for controlled selective heating of the inner surface of the inner housing. Heating element  218  may have a heat shield material wrapped around the outer surface of the heating element  218  and be positioned between the heating element  218  and the outer housing  202  to insulate the heating element  218 . The heat shield can be a plurality of metallic layers made of steel or other suitable heat resistant material. The heating element  218  allows for the fuel in a first fluid chamber to be heated to a temperature of 400 degrees Fahrenheit to 1400 degrees Fahrenheit, thereby causing the fuel to reach a supercritical temperature and allowing for more efficient combustion. The heating element  218  extends from the injector seat  212  to the top of the lower portion of the injector pin to form a consistent heating of the entire lower fluid chamber. Accordingly, the fuel that is present in the lower fluid chamber is predominantly in a supercritical phase. In an alternative embodiment, the fuel can be heated prior to entering the fuel injector lower fluid chamber and no heating element is necessary. 
   The present invention further includes a catalyst element  220  in the lower fluid chamber  216 . Catalyst element  220  may be a coating, brazing, plating, surface treatment, wire winding or bonding that is attached or formed integrally with the lower portion of the injector pin and/or the inner surface of the inner housing. In the illustrated embodiment, the catalyst element  220  forms part of the outer surface of the lower portion of the injector pin. The catalyst element  220  may also be disposed on a portion of the inner wall of the inner housing  204  adjacent the lower fluid chamber  216 . The fuel contained in the lower fluid chamber  216  reacts with the catalyst  220  to allow for a more efficient burning of the fuel in the combustion chamber. Preferably, the catalyst is nickel with about 5% molybdenum. However, any of the following catalysts can be used: nickel, nickel-molybdenum, alpha alumina, aluminum silicon dioxide, other air electrode oxygen reduction catalysts, and other catalysts used for hydrocarbon cracking. 
   As depicted in  FIG. 5 , the upper portion  208  of the injector pin is inserted through the seal assembly  214 .  FIG. 6  illustrates the detail of the seal assembly  214 . In particular, seal assembly  214  has a body portion  300  that is positioned inside the outer housing  202 . The body portion  300  can be substantially cylindrical in shape and is held a distance from the outer housing wall by a plurality of stand-off supports  302 . Referring to  FIG. 5 , seal assembly  214  has an inner chamber  222 , wherein the upper portion  208  of the injector pin  205  extends through the inner chamber  222  and a main seal  224  is formed between the upper portion  208  of the injector pin and the inner chamber sidewall of the seal body. Main seal  224  can be an o-ring, ground sliding, bellows, lip seal, wiper, labyrinth or any other appropriate sealing mechanism. In addition, a secondary backup seal  226  can be positioned adjacent the main seal  224  to function as a safety device in the event that main seal  224  fails. The secondary backup seal  226  may be made of a metallic or elastomeric material. Additionally, the secondary backup seal  226  may be a diaphragm seal. A Teflon backing ring may be positioned between the injector pin and the inner chamber sidewall adjacent the main seal  224 . The main seal  224  prevents the fuel in the lower fluid chamber  216  from escaping while still allowing the pin to move in a longitudinal direction in relation to the seal assembly body portion. The body portion can have a cooling groove around its peripheral edge to aid in cooling the main seal. 
   Referring to  FIG. 7 , the upper portion  208  of the pin  205  extends through the seal assembly  214  to a flange section  228 . The flange section  228  forms a substantially flat surface that contacts the injector element  234 . In the illustrated embodiment, the flange section  228  includes a cap portion  248  positioned on top of the upper portion  208  of the injector pin  205 . The cap portion  248  is cylindrical in shape and has a curved surface on the upper portion. The curved surface contacts flange section  228 , which in turn contacts the injector element  234 . The curved portion allows for even distribution of pressure from the injector element  234  to the injector pin  205  in the event that the pressure exerted by the injector element  234  on the flat portion is uneven. The flange section  228  and the injector pin  205  are biased in an upward direction away from the injector seat by a plurality of resilient elements  232 . The resilient elements  232  can be belleville springs, coil springs, tube springs, a non-linear spring or any other suitable device. 
   The injector element  234  may comprise one or more piezoelectric elements  234  or stacks aligned in series or parallel configuration. The piezoelectric stacks may be lined up in series to allow for a greater degree of movement of the injector pin. The piezoelectric stacks  234  can be actuated in parallel or individually to allow for more precise control. The lower piezoelectric stack contacts the flange section  228  directly such that when a charge is supplied to the piezoelectric assembly, the lower piezoelectric stack pushes against the flange section  228  to move the injector pin  205  downward toward the fuel injector seat  212 . Piezoelectric stacks  234  are housed in a shuttle  236  which is held in place in the outer housing by one or more guides  402 . The shuttle  236  can be made of a temperature insensitive material, such as invar, in order to minimize load variations in the injector element  234  due to temperature changes. In an alternative embodiment, the shuttle can be cooled by an external device in order to improve the efficiency of the injector element. The upper piezoelectric stack of piezoelectric element  234  contacts a temperature compensator  240 . 
   Referring to  FIG. 8 , the temperature compensator  240  is positioned at the upper end of the fuel injector. In operation, the temperature compensator  240  is used to compensate for thermal expansion of the injector element  234  and injection pin  205 , and also allows for tolerance variations in the construction of the injector element, injector pin and spacers  504 . The temperature compensator  240  has a flange shaped bottom portion  244  proximal to the injector element  234 . The flange portion  244  is positioned inside the upper outer housing  502 . In the illustrated embodiment, one or more circular spacers  504  are placed between the injector element  234  and the flange portion  244  to allow for manufacturing differences and to take up excess space between the injector element  234  and the flange portion  244 . An upper fluid chamber  506  is formed between the flange portion  244  and the outer housing  502 . The upper fluid chamber  506  has an inlet duct  241  that allows a fluid to flow in and out of the upper fluid chamber  506 . The fluid used in the upper fluid chamber  506  can be fuel or any other suitable oil or hydraulic fluid. The inlet duct  241  can have a needle orifice or check valve to control the fluid flow. A resilient element  509 , such as belleville springs, coil springs, tube springs, a non-linear spring or any other suitable device is used to bias the flange portion  244  toward the injector element  234 . A compensator seal  508  such as an o-ring, ground sliding, bellows, lip seal, wiper, labyrinth or any other appropriate sealing mechanism, can be positioned between the outer peripheral edge of the flange portion  244  and the upper outer housing to create the upper fluid chamber  506 . The temperature compensator  240  functions by viscous damping or creating a dynamic pressure differential between the fluid chamber  506  and the inlet duct  241 . 
   Referring to  FIGS. 9-12 , an alternative embodiment of the temperature compensator is illustrated. As illustrated, the flange portion  244  is positioned inside the upper housing  202 . A plurality of circular spacers  504  can be placed between the injector element  234  and the flange portion  244  to allow for manufacturing differences and to take up excess space between the injector element  234  and the flange portion  244 . A piston disk  602  is attached to the flange portion  244  forming a second fluid chamber  604  and a third fluid chamber  606 . A compensator seal  508  such as an o-ring, ground sliding, bellows, lip seal, wiper, labyrinth or any other appropriate sealing mechanism, can be positioned between the outer peripheral edge of the piston disk  602  and the upper housing  202  to create the second fluid chamber  604  and the third fluid chamber  606 . The piston disk  602  has a duct  608  that fluidly connects the second fluid chamber  604  and third fluid chamber  606  so that fluid can freely flow between the chambers to create a damping action. A diaphragm  610  forms an upper wall of the second fluid chamber  602  to form a floor of a fourth fluid chamber  612  in the upper outer housing  502 . The fourth fluid chamber  612  has an inlet duct  614  that allows fuel pressure into the fourth fluid chamber which in turn exerts a downward pressure on the diaphragm  610 . 
   It is envisioned that as the injector pin  205  expands due to an increase in temperature, the flange portion  244  is pushed in an upward direction. As the flange portion  244  is pushed in an upward direction, the piston disk  602  is likewise pushed in an upward direction. The fluid contained in the second fluid chamber  604  is expanded and fluid from the third fluid chamber  606  is drawn into the second fluid chamber  604 . The fuel pressure acts on the opposite side of the diaphragm  610  in the fourth fluid chamber  612  to push against the fluid pressure in the third fluid chamber  606 . The piston disk  602  is allowed to move in an upward direction as the fluid flows from the second fluid chamber  604  to the third fluid chamber  606  to dampen thermal expansion of the injector pin  205 . 
   The manner of operating various embodiments of the invention are now described. Referring to  FIG. 5 , in a first embodiment, the fuel is first pressurized to the correct pressure and allowed to flow into the upper fluid chamber  246  and the lower fluid chamber  216 . The heating element  218  around the lower fluid chamber  216  is heated allowing the fuel to reach a supercritical state. 
   The injector element is slowly charged to operating voltage to close the injector pin against the injector seat  212  to create a fluid tight seal. When the fuel injector is in a closed position, pressurized fuel is pumped in through the input port  242  into the lower fluid chamber  216 . The upper fluid chamber  246  is filled with fuel pressurized at the substantially the same pressure as the fuel in the lower fluid chamber  216 . The fuel is allowed to flow into the upper fluid chamber  246  by way of the inlet duct  241 . The charge to the injector element  234  is then dropped to allow the injector pin  205  to lift off of the injector seat  212 . The fuel is then allowed to flow out of the fuel injector into the combustion chamber. 
   In order to close the injector, the charge supplied to the injector element  234  is increased causing the injector element  234  to push the injector pin  205  against the injector seat  212 , sealing the fuel injector. At the same time, the temperature compensator flange  244  is pushed against by the injector element  234 . The temperature compensator  240  acts as an adjustable reference plane against which to push/pull the injector pin  205 . This motion, in turn, pushes some of the fluid out of the upper fluid chamber  246  through the orifice  250 . The action of the liquid fuel flowing out of the upper fluid chamber  246  acts as both a temperature compensator and damper for the piezoelectric injector. 
   In a second embodiment, the fuel injector is actuated using a pressure differential. The fuel pressure in the lower chamber  246  is different than the fuel pressure provided to the temperature compensator  240 . In this embodiment, the fuel pressure in the lower fluid chamber  216  is higher than the fuel pressure in the upper fluid chamber  246 , which biases the injector pin  205  to an open position. In an alternative configuration, the fuel pressure provided to the lower fluid chamber  216  is lower than the fuel pressure provided to the upper fluid chamber  246  so that the injector pin  205  is biased to a closed position. 
   Referring to  FIGS. 9-12 , in a third embodiment, the fuel injector is actuated using damping fluid at the temperature compensator  240 . In this embodiment, pressurized damping fluid with a higher viscosity than fuel is used in the second fluid chamber  604  and third fluid chamber  606 . Fuel is pumped into the fourth fluid chamber  612 , which causes the injector pin  205  to be biased to a closed position. Fuel or other pressurized gas is pumped into the lower fluid chamber  216  at a pressure substantially equal to the fuel or gas pumped into the fourth fluid chamber  612 , and the pressure of the damping fluid biases the injector pin into an open position. The opposing forces of the fuel in the lower fluid chamber  216  and the fourth fluid chamber  612 , combined with the damping fluid pressure, hold the injector pin  205  in a pressure neutral state. 
   In a fourth embodiment, the fuel injector is actuated with both fuel and a damping fluid. In this embodiment, a pressurized damping fluid with a higher viscosity than fuel is used in the second fluid chamber  604  and third fluid chamber  606 . Fuel or other pressurized gas is pumped into the fourth fluid chamber  612 , which causes the injector pin to be biased to a closed position. Fuel is pumped into the lower fluid chamber  216  at a pressure different than the fuel or gas pumped into the fourth fluid chamber  612 , and the pressure of the damping fluid biases the injector pin into an open position. Depending on the pressure difference between fuel pressure in the lower fluid chamber  216  and the fuel pressure in the fourth fluid chamber  612 , the injector pin can be selectively biased toward an open or closed position. 
   The charging and discharging of the fuel injector element for the second, third, and fourth embodiments, is substantially the same as the first embodiment. 
   In all of the embodiments of the present invention, the fuel can be pressurized by a common pump, separate and distinct pumps, pressure modifying devices, or any combination thereof. 
   In the above embodiments, the use of the piezoelectric element allows accurate and fast control of the fuel injector. In addition, the use of the temperature compensator allows for the compensation of expansion of the injector pin and also allows damping of the piezoelectric element. The heating element associated with the first fluid chamber allows for the heating of the fuel to a supercritical temperature. Furthermore, if the fuel is pressurized to a supercritical pressure, more efficient combustion results, thus saving fuel. Efficiency is further enhanced because the catalyst used in the first fluid chamber allows for the oxidation of the fuel or conversion of the fuel, resulting in more efficient combustion when the fuel is released. 
   One skilled in the art will appreciate that the present invention can be practiced by other than the various embodiments and preferred embodiments, which are presented in this description for purposes of illustration and not of limitation, and the present invention is limited only by the claims that follow. It is noted that equivalents for the particular embodiments discussed in this description may practice the invention as well. 
   While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not of limitation. Likewise, the various diagrams may depict an example architectural or other configuration for the invention, which is done to aid in understanding the features and functionality that may be included in the invention. The invention is not restricted to the illustrated example architectures or configurations, but the desired features may be implemented using a variety of alternative architectures and configurations. Indeed, it will be apparent to one of skill in the art how alternative functional, logical or physical partitioning and configurations may be implemented to implement the desired features of the present invention. Also, a multitude of different constituent module names other than those depicted herein may be applied to the various partitions. Additionally, with regard to flow diagrams, operational descriptions and method claims, the order in which the steps are presented herein shall not mandate that various embodiments be implemented to perform the recited functionality in the same order unless the context dictates otherwise. 
   Although the invention is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead may be applied, alone or in various combinations, to one or more of the other embodiments of the invention, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments. 
   Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; the terms “a” or “an” should be read as meaning “at least one,” “one or more” or the like; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future. 
   The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. The use of the term “module” does not imply that the components or functionality described or claimed as part of the module are all configured in a common package. Indeed, any or all of the various components of a module, whether control logic or other components, may be combined in a single package or separately maintained and may further be distributed across multiple locations. 
   Additionally, the various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other illustrations. As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives may be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular architecture or configuration.