Abstract:
A pulsed detonation combustor (PDC) is described. The PDC includes an outer casing defining a first hollow chamber configured to receive a flow and an inner liner. The inner liner includes at least one portion positioned within the first hollow chamber and configured to receive the flow from a plenum formed between the outer casing and inner liner. The PDC further includes a flow turning device with geometric features configured to direct the flow from the plenum to a second hollow chamber defined within the inner liner. The PDC also includes at least one fuel injection port located downstream of an inlet to the outer casing and an ignition device located downstream of the at least one fuel injection port and configured to periodically ignite fuel.

Description:
BACKGROUND OF THE INVENTION 
     The present invention generally relates to cyclic pulsed detonation combustors (PDCs) and more particularly to a design that incorporates a “folded” flow path in order to cool the PDC using an oxidizer and/or fuel prior to a combustion process and, which utilizes heat produced in the combustion process to preheat and mix fuel and/or oxidizer and vaporize fuel prior to initiation. 
     A typical pulse detonation combustion system generates a thrust upon igniting a mixture of fuel and air within the system. However, the thrust may not be effectively generated and may be expensive to generate. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, A pulsed detonation combustor (PDC) is described. The PDC includes an outer casing defining a first hollow chamber configured to receive a flow and an inner liner. The inner liner includes at least one portion positioned within the first hollow chamber and configured to receive the flow from a plenum formed between the outer casing and inner liner. The PDC further includes a flow turning device with geometric features configured to direct the flow from the plenum to a second hollow chamber defined within the inner liner. The PDC also includes at least one fuel injection port located downstream of an inlet to the outer casing and an ignition device located downstream of the at least one fuel injection port and configured to periodically ignite fuel. 
     In another aspect, a pulsed detonation combustor system is described. The pulse detonation combustor system includes a fuel supply configured to supply fuel, an oxidizer supply configured to supply an oxidizer, and an outer casing defining a first hollow chamber configured to receive a flow from at least one of the fuel supply and the oxidizer supply. The pulsed detonation combustor system further includes an inner liner comprising at least one portion positioned within the first hollow chamber and configured to receive the flow from a plenum formed between the outer casing and inner liner, a flow turning device with geometric features configured to direct the flow from the plenum to a second hollow chamber defined within the inner liner, and at least one fuel injection port located downstream of an inlet to outer casing. The pulsed detonation combustor system also includes an initiation device located downstream of the at least one fuel injection port and configured to periodically ignite fuel. 
     In yet another aspect, a method for generating thrust in a self-cooling, pre-heating pulsed detonation combustor is described. The method includes receiving a flow in an outer casing defining a first hollow chamber, receiving the flow from a plenum formed between the outer casing and an inner liner located within the first hollow chamber, directing the flow from the plenum to a second hollow chamber within the inner liner, placing at least one fuel injection port downstream of an inlet to the outer casing, and periodically igniting fuel by an initiation device located downstream of the at least one fuel injection port. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an exemplary self-cooling, pre-heating Pulsed Detonation Combustor (PDC) illustrating a folded flow path. 
         FIG. 2  is a cross-sectional view of the system shown in  FIG. 1 . 
         FIG. 3  is a schematic diagram of an alternative embodiment of a self-cooling, pre-heating PDC. 
         FIG. 4  is a schematic diagram of another alternative embodiment of a self-cooling, pre-heating PDC. 
         FIG. 5  is a schematic diagram of yet another alternative embodiment of a self-cooling, pre-heating PDC. 
         FIG. 6  is a schematic diagram of still another embodiment of a self-cooling, pre-heating PDC. 
         FIG. 7  is a schematic diagram of another embodiment of a self-cooling, pre-heating PDC. 
         FIG. 8  is a schematic illustration of an exemplary gas hybrid turbine engine that may be used with the systems shown in  FIGS. 1-7 . 
         FIG. 9  is a zoomed-in view of the gas hybrid turbine engine of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As used herein, a “pulse detonation combustor” (PDC) includes a device or system that produces both a pressure rise and velocity increase from a single, or a series of repeating, detonations or quasi-detonations within the device. A “quasi-detonation” is a supersonic turbulent combustion process that produces a pressure rise and velocity increase higher than a pressure rise and velocity increase produced by a sub-sonic deflagration wave. Embodiments of PDCs include a device that ignites a fuel/oxidizer mixture, such as, for example, a fuel/air mixture, and a detonation chamber, in which pressure wave fronts initiated by an ignition coalesce to produce a detonation wave. Each detonation or quasi-detonation is initiated either by an external ignition, such as spark discharge or laser pulse, or by gas dynamic processes, such as shock focusing, autoignition or by another detonation (cross-fire). A geometry of a detonation chamber is such that the pressure rise of the detonation wave expels combustion products out an exhaust of the PDC to produce a thrust force. Pulse detonation can be accomplished in a number of types of chambers, including detonation chambers, shock tubes, resonating detonation cavities and annular detonation chambers. As used herein, the term “casing” includes tubes having circular or alternatively non-circular cross-sections. Each of the circular and non-circular cross-sections have either a constant or a varying cross sectional area. Exemplary casings include cylindrical tubes and tubes having polygonal cross-sections, such as, for example, hexagonal tubes. Additionally, as used herein, the term “liner” includes tubes having the circular or alternatively the non-circular cross-sections. Exemplary liners include cylindrical tubes and tubes having polygonal cross-sections, such as, for example, hexagonal tubes. As used herein, “downstream” refers to a direction of flow of at least one of fuel or oxidizer. 
       FIGS. 1 and 2  are schematic diagrams of an exemplary self-cooling, pre-heating PDC  100 , with folded flow path, for generating thrust. PDC  100  is referred to as a system  100 . System  100  includes an outer casing  102 , an inner liner  104 , a flow turning device  106 , an ignition device  108 , an outer chamber  109 , a plenum  110  formed between outer casing  102  and inner liner  104 , a chamber  112  formed within inner liner  104 , a protrusion  113  for the re-atomization of coalesced liquid fuel droplets, a plurality of oxidizer supply inlets  118  and  120 , a plurality of gaseous fuel supply inlets  122  and  124 , and a plurality of liquid fuel supply inlets  126  and  128 . Outer chamber  109  is a hollow chamber formed within outer casing  102 . At least a portion of inner liner  104  is placed within outer chamber  109 . In an alternative embodiment, system  100  may include one of inlets  122  and  124 . In another alternative embodiment, system  100  may include one of inlets  126  and  128 . In yet another alternative embodiment, system  100  may includes one of inlets  118  and  120 . Protrusion  113  is made of a material, such as, stainless steel, aluminum, inconel, or carbon steel. Protrusion  113  is integrated with, such as machined, or attached to, such as welded, glued, and/or bolted, an inner surface  151  of outer casing  102 . System  100  is operable with a plurality of different fuels including, but not limited to, gaseous fuels, such as, hydrogen, ethylene, natural gas, or propane, liquid fuels, such as, gasoline, kerosene, or aviation fuels, and a plurality of oxidizers including, but not limited to, air. Ignition device  108  can be, but is not limited to being, a spark plug, a plasma igniter, and/or a laser source. 
     Each of fuel supply inlets  122 ,  124 ,  126 , and  128  may include a valve to allow an active pulsing of fuel into the plenum  110 . Alternatively, a valve may be coupled to a supply line that is coupled to inlet  122  and the valve is pulsed to provide a supply of fuel to plenum  110  via inlet  122 . In another alternative embodiment, a valve may be coupled to a supply line that is coupled to inlet  124  and the valve is pulsed to provide a supply of fuel to plenum  110  via inlet  124 . Optionally, a valve may be coupled to a supply line that is coupled to inlet  126  and the valve is pulsed to provide a supply of fuel to plenum  110  via inlet  126 . In yet another alternative embodiment, a valve may be coupled to a supply line that is coupled to inlet  128  and the valve is pulsed to provide a supply of fuel to plenum  110  via inlet  128 . 
     Each of oxidizer supply inlets  118  and  120  may also include a valve to actively control a flow of oxidizer into plenum  110 . Alternatively, a valve may be coupled to a supply line that is coupled to oxidizer supply inlet  118  and the valve actuated to control a flow of oxidizer to plenum  110  via oxidizer supply inlet  118 . In another alternative embodiment, a valve may be coupled to a supply line that is coupled to oxidizer supply inlet  120  and the valve actuated to control a flow of oxidizer to plenum  110  via oxidizer supply inlet  120 . An example of a valve includes, but is not limited to, a solenoid valve, and the valve is controlled via a controller to open and close at desired intervals. The controller controls an activation of ignition device  108  to ignite fuel and oxidizer mixture. As used herein, the term controller is not limited to just those integrated circuits referred to in the art as a controller, but broadly refers to a processor, a microprocessor, a microcontroller, a programmable logic controller, an application specific integrated circuit, and another programmable circuit. 
     In the exemplary embodiment, inner-liner  104  is a substantially round cylinder, and extends substantially parallel to an x-axis from a y-z plane defined by a point  136  to a y-z plane defined by a point  138 . Moreover, outer casing  102  extends parallel to the x-axis from a y-z plane defined by a point  145  of outer casing  102  to a y-z plane defined by a point  146  of outer casing  102 . A y-z plane is formed by a y-axis and a z-axis as oriented in the  FIG. 1 . Accordingly, in the exemplary embodiment, outer casing  102  is aligned substantially concentrically with respect to inner liner  104 , and each of outer casing  102  and inner liner  104  is a hollow cylinder having a substantially circular cross-section. Alternatively, outer casing  102  and inner liner  104  have non-circular cross-sectional profiles, such as, a polygonal cross-section, a triangular cross-section, a square cross-section, and/or a hexagonal cross-section. In another alternative embodiment, inner liner  104  has a different cross-sectional profile than that of outer casing  102 . Cross-sectional profiles of inner liner  104  and outer casing  102  are formed in a y-z plane. 
     Referring to  FIG. 1 , although each of outer casing  102  and inner liner  104  extend substantially linearly along the x-axis, in an alternative embodiment, outer casing  102  and inner liner  104  extend arcuately, such as spirally, along the x-axis and as such are not parallel to the x-axis. In the exemplary embodiment, inner liner  104  has a diameter ranging from 1.5 inches to 2.5 inches, and outer casing  102  has a diameter ranging from two inches to three inches. Flow turning device  106  is integrated with outer casing  102  or is coupled, such as glued, welded, and/or bolted, to an end  144  between point  145  and a point  147  of outer casing  102 . Furthermore, in an alternative embodiment, flow turning device  106  is curved. For example, flow turning device  106  is an end cap, or has a concave cross-section in an x-y plane formed by an x-axis and the y-axis and an x-z plane formed by the x-axis and the z-axis. In the exemplary embodiment, a plenum  110  is defined between outer casing  102  and inner liner  104  that extends substantially parallel to the x-axis. In the same embodiment, inner liner  104  defines a chamber  112  that extends substantially parallel to the x-axis. Plenum  110  and inner chamber  112  are arranged substantially concentrically. Flow turning device  106  enables a flowing substance, such as fuel and/or an oxidizer, to enter inner chamber  112  from plenum  110 , the flowing substance flows within chamber  112 , and the flowing substance exits at a y-z plane at an end  149  of inner liner  104 . 
     System  100  includes a plurality of support structures  160  and  162 , which reinforce plenum  110  to keep inner liner  104  substantially concentric with outer casing  102 . Any number, such as ranging from and including one to ten, of each of the support structures  160  and  162  can be placed along the length of the plenum  110 . The length of plenum  110  is parallel to the x-axis. Support structures  160  and  162  are integrated with, such as machined, or attached to, such as glued, welded, and/or bolted to, inner surface  151  or alternatively to an outer surface  153  of inner liner  104 . Outer surface  153  and inner surface  151  face plenum  110 . Examples of each of support structures  160  and  160  include, but are not limited to, a bolt, a dowel, and a fin. In alternative embodiment, system  100  does not include support structures  160  and  162  to maintain plenum  110  along a length of outer casing  102 . The length of outer casing  102  is parallel to the x-axis. 
     In exemplary system  100 , an oxidizer, including but not limited to air, flows from a supply or a plurality of supplies including, but not limited to, air compressors, into plenum  110  via inlets  118  and  120 . Gaseous fuel may enter plenum  110  through inlets  122  and  124  via a plurality of orifices around circumference of outer casing  102  or through a mixing element in plenum  110 . Liquid fuel may enter plenum  110  via inlets  126  and  128 , via a plurality of atomizing nozzles or orifices located around circumference of outer casing  102 , and/or via a mixing element in plenum  110 . As liquid or gaseous fuel enters plenum  110 , the fuel mixes with oxidizer supplied through inlets  118  and  120 . This mixture then flows within plenum  110  towards an end of plenum between points  144  and  145 . As the fuel and oxidizer mixture travels along plenum  110 , the mixture is transferred heat from a previous combustion cycle through inner liner  104 . This transfer of heat serves to raise the temperature of the mixture in plenum  110  as well as cool the inner liner  104 . Each of outer casing  102  and inner liner  104  are made of a metal, such as stainless steel, inconel, aluminum, or carbon steel. The metal of inner liner  104  enables a transfer of heat from inner chamber  112  through inner liner  104  into plenum  110 . As the fuel and oxidizer mixture continues to travel through plenum  110 , the mixture encounters a reduction in a cross-sectional area caused by protrusion  113 , which is located along an entire inner circumference of outer casing  102 . The cross-sectional area reduction caused by protrusion  113  accelerates the mixture allowing re-entraining of any liquid fuel coalesced on inner surface  151  or outer surface  153 . Any number of protrusions  113 , such as ranging from and including 1 to 20, may be used, and a profile of protrusion  113  may vary. In another embodiment, there are no cross sectional area reductions or protrusions. In another embodiment, when system  100  heats up via repeated combustion with a gaseous fuel/oxidizer mixture, the gaseous fuel supply is halted, for instance, by preventing the valves controlled to control the supply of fuel to inlets  122  and  124  from actuating. When the gaseous fuel supply is halted, the liquid fuel is supplied through inlets  126  and  128  via the valves that are controlled to control the supply of fuel to inlets  126  and  128  in a timing similar to how the gaseous fuel was supplied. The liquid fuel can be supplied such that liquid fuel impinges on the now hot outer surface  153  of liner  104  and/or gets directly entrained in the oxidizer flowing along the plenum  110 . In this manner, the heat from liner  104  serves to vaporize fuel within plenum  110  directly, or heat the oxidizer and any liquid fuel droplets entrained in plenum  110  allowing the droplets to vaporize as the mixture of fuel and oxidizer flows along plenum  110 . 
     The fuel and oxidizer mixture within plenum  110  continues to flow towards passage  155  and flow turning device  106 , which directs the oxidizer and fuel from passage  155  toward chamber  112 . The mixture continues to flow along chamber  112  towards end  149 . 
     In an exemplary embodiment, upon determining that a sufficient amount of time, t, has passed since opening of the valves actuated to control a flow of fuel via inlets  122 ,  124 ,  126 , and  128  to fill a volume of inner chamber  112 , the controller sends a signal to close the valves. The oxidizer remains flowing, carrying the fuel and oxidizer mixture through a flow path defined by outer plenum  110  and inner chamber  112 . Upon determining that a sufficient amount of time, r, has passed since time t, the controller sends a signal to ignition device  108 . 
     Ignition device  108  ignites fuel within inner combustion chamber  112  upon receiving a signal from the controller. Upon igniting, a flame is formed within chamber  112  and the flame begins to consume the fuel and oxidizer mixture within chamber  112 . The flame propagates and accelerates through chamber  112 , generating an increase in pressure and temperature within system  100  to create a current combustion cycle. This increase in pressure and temperature can be caused by a detonation or “quasi-detonation” during the current combustion cycle. Heat generated by the current combustion cycle heats inner liner  104  including surface  153  and the heat heats oxidizer and/or fuel in plenum  110  prior to a subsequent fill and combustion cycle. The current combustion cycle ends when the combustion gases formed during the current combustion cycle exit through end  149  of inner liner  104 . Upon exit of the combustion gases, remaining combustion products are purged via oxidizer supplied through inlets  118  and  120  until the subsequent fill and combustion cycle is begun. The subsequent fill and combustion cycle begins when the controller sends a signal to the valves actuated to control a flow of fuel via at least one of inlets  122 ,  124 ,  126 , and  128  to open again. Ignition device  108  can be located in any single location or plurality of locations to initiate the fuel and oxidizer mixture within outer plenum  110 , a passage  155 , or chamber  112 . Passage  155  is formed between inner liner  104  and flow turning device  106 . Each of inner liner  104  and outer casing  102  are fabricated from a material, such as, inconel, stainless steel, aluminum, or carbon steel. 
       FIG. 3  is a schematic diagram of an embodiment of a self-cooling pre-heating PDC  300 , referred to as a system  300 . Oxidizer inlets  118  and  120  within system  300  remain in the same location as in  FIG. 1 . In system  300 , liquid or alternatively gaseous fuel is injected directly into chamber  112  via an inlet  302 . Liquid or alternatively gaseous fuel is injected directly into chamber  112  via an inlet  304 . In an alternative embodiment, system  300  includes one of inlets  302  and  304 . A valve is coupled to inlet  302  and is opened by the controller to inject fuel into chamber  112 . Alternatively, a valve is coupled to inlet  304  and is opened by the controller to inject fuel into chamber  112 . Moreover, the valves that are actuated to control a flow of fuel via inlets  122 ,  124 ,  126 , and  128  are closed when the valves coupled to inlets  302  and  304  are open. The oxidizer is heated by the heat transfer through walls of inner liner  104  into plenum  110 , however, fuel is injected via at least one of inlets  302  and  304  into the oxidizer after the oxidizer has traversed plenum  110  and as the oxidizer enters chamber  112 . The fuel injected via at least one of inlets  302  and  304  combines with the oxidizer received from plenum  110  to form the mixture of fuel and oxidizer. The mixture enters from passage  155  into inner chamber  112 . A mixing element may be placed either in chamber  112  and/or in passage  155  to ensure an even distribution of the fuel and oxidizer mixture, which would more readily ignite/detonate. Gaseous or liquid fuel could be injected through a plurality of orifices in the mixing element to ensure even fuel distribution. One can imagine any combination of fueling locations mentioned above, which can be used together and are not limited to just the embodiments mentioned above. The fuel and oxidizer mixture within chamber  112  is ignited using ignition device  108 , which may be located anywhere along a length of chamber  112 . The length of inner chamber  112  is parallel to the x-axis. In an alternative embodiment, fuel is supplied to plenum  110  via at least one of inlets  122 ,  124 ,  126 ,  128 ,  302 , and  306 . 
       FIG. 4  is an alternative embodiment of a self-cooling pre-heating PDC  400 , referred to as a system  400 . System  400  is similar to system  100  except that system  400  includes a plurality of protrusions  190  along an inner surface  402  of inner liner  104  to promote turbulence within chamber  112 , which enhances a transition of the flame to a detonation. System  400  includes any number, such as, ranging from and including one to 2000, protrusions  190 . In an alternative embodiment, as shown in  FIG. 5 , protrusions  190  are integrated with, such as machined, or are attached to, such as glued, welded, and/or bolted to, the outer surface  153  and inner surface  402  of inner liner  104 . In an alternative embodiment, protrusion  190  is integrated with, or attached to one of inner surface  402  and outer surface  153 . 
     In another alternative embodiment, as shown in  FIG. 6 , a self-cooling pre-heating PDC  600  includes a plurality of protrusions  602  that are formed by bending surfaces  153  and  402  of inner liner  104 . Self-cooling pre-heating PDC  600  is also referred to as a system  600 . In another embodiment, protrusion  602  is formed on inner surface  402  in an opposite direction to that of protrusion  602  formed on outer surface  153 . In another alternative embodiment, protrusion  602  formed on outer surface  153  has the same dimensions as that of protrusion  602  formed on inner surface  402 . Any number of protrusions  602 , such as ranging from and including one to 3000, can be formed on surfaces  153  and  402 . Protrusions  602  are integrated with, such as machined/formed, or attached to, such as glued, welded, and/or bolted to, the outer surface  153  and inner surface  402  of inner liner  104 . In an alternative embodiment, protrusion  602  is formed into or attached to one of inner surface  402  and outer surface  153 . 
     Each of protrusion  190  and protrusion  602  enhances turbulence of flow within inner liner  104 , enhances an amount of heat transferred from inner chamber  112  to plenum  110 , and facilitates an atomization of liquid fuel coalesced in plenum  110 . Each of protrusion  190  and  602  can be, but is not limited to, a ridge, or other shapes, spaced along a length and circumference of inner liner  104 . The length of inner liner  104  is parallel to the x-axis. In an alternative embodiment, system  400  does not include protrusions  190  and system  600  does not include protrusions  602 . In another alternative embodiment, protrusions  190  and  602  are replaced by localized recesses or grooves. 
       FIG. 7  is a schematic of an alternative embodiment of a self-cooling pre-heating PDC  700 , referred to as a system  700 . System  700  is similar to system  100  except that ignition device  108  is located within inner chamber  112  and except that system  700  includes a valve element  710  downstream of plenum  110  and prior to an inlet of inner chamber  112 . The inlet of inner liner  104  is located between point  136  and a point  712  of inner liner  104 . Valve element  710  acts as a plunger so that when no flow is desired, the plunger is pressed up against the inlet to inner chamber  112  sealing around the circumference of inner liner  104 . Valve element  710  is located between flow turning device  106  and inner chamber  112 . Alternatively, valve element  710  is located within plenum  110 . For example, valve element  710  acts as a plunger to seal between inner surface  151  and outer surface  153  in plenum  110  formed between outer casing  102  and inner liner  104 . In another alternative embodiment, valve element  710  is integrated within flow turning device  106 . The controller opens valve element  710  and the opening of valve element  710  allows flow from plenum  110  to inner chamber  112 . On the other hand, the controller closes valve element  710  to prevent a flow from plenum  110  to inner chamber  112 . Valve element  710  is operated, such as opened and closed, by the controller in addition to or instead of operating fuel supply inlets  122 ,  124 ,  126 , and  128 . The controller pulses valve element  710  to open and close valve element  710 . Upon determining that a sufficient amount of time, q, has passed since opening of the valve element  710  to fill a volume of inner chamber  112  with the flow of the mixture, the controller sends a signal to close the valve element  710  and seals the inlet of the inner chamber  112 . Ignition device  108  ignites the mixture within chamber  112  to generate a combustion within inner chamber  112 . 
     In an alternative embodiment of any of the above exemplary systems  100 ,  300 ,  400 ,  600 , and  700 , an area reduction device is located at end  149 . Examples of the area reduction device include, but are not limited to, a nozzle and a venturi. A purpose of this area reduction device is to increase the pressure within chamber  112  to enhance initiation and detonation transition. Another purpose of the area reduction device is to reflect shocks within chamber  112 . The area reduction device is integrated with, such as machined, or attached to, such as frictionally fit, bolted, and/or welded, inner liner  104  at end  149 . 
       FIG. 8  is a schematic of an embodiment of a gas turbine engine  800  in which compressors  802  and  804  supply air to at least one of systems  100 ,  300 ,  400 ,  600 , and  700 . Pulsed detonations create the combustion within at least one of systems  100 ,  300 ,  400 ,  600 , and  700  to turn a plurality of turbines  808  and  810  to generate thrust and turn compressors  802  and  804 . A single system  100  or alternatively a plurality of systems  100  can be used within gas turbine engine  800 . Similarly, in an alternative embodiment, at least one system  300  can be used within gas turbine engine  800 . Moreover, in another alternative embodiment, at least one system  400  can be used within gas turbine engine  800 . In another embodiment, at least one system  600  can be used within gas turbine engine  800 . In yet another alternative embodiment, at least one system  700  can be used within gas turbine engine  800 . 
       FIG. 9  shows a zoomed-in view of gas turbine engine  800  of  FIG. 8  and illustrates an exemplary embodiment of system  100 . Chamber  112  and plenum  110  are shown. Initiation occurs within at least one of systems  100 ,  300 ,  400 ,  600 , and  700  creating hot pressurized combustion products which, expand through turbines  808  and  810 . In an alternative embodiment, any combination of systems  100 ,  300 ,  400 ,  600 , and  700  can be used within gas turbine engine  800  or for other applications, such as, propelling a missile, or driving a generator to generate electricity. 
     Technical effects of the herein described systems and methods include cooling of the systems  100 ,  300 ,  400 ,  600 , and  700  using fuel and/or oxidizer prior to combustion as it flows through plenum  110  formed between outer casing  102  and inner liner  104 . Cooling of inner liner  104  performed by oxidizer and/or fuel flowing within plenum  110  reduces a need for a separate source of air or other fluid to cool inner liner  104 , which can become hot enough to possibly cause a mechanical failure. A separate source of air to cool inner liner  104  increases costs. Since oxidizer and/or fuel within plenum  110  is used to cool inner liner  104  and chamber  112 , and also subsequently in combustion within chamber  112 , the oxidizer is efficiently used and not wasted. Technical effects of the herein described systems and methods also include pre-heating fuel and/or oxidizer in the plenum  110  prior to combustion by transmitting heat within inner chamber  112  to plenum  110 . Typically, vaporization of liquid fuel by a separate process/device may take a long time and results in an additional cost/power requirement of the separate device. Other technical effects include the ability to use either liquid or gaseous fuel (Dual Fueled), which is made possible by the flow path that allows for pre-heating of fuel and/or oxidizer. 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.