Fuel oxygen reduction unit for specifying operating conditions

Abstract

The invention relates to a fuel oxygen reduction unit for specifying operating conditions. A fuel oxygen reduction unit for an engine is provided. The fuel oxygen reduction unit includes: an inlet fuel line; a stripping gas source; a contactor in selective fluid communication with the stripping gas source, the inlet fuel line, or both to form a fuel / gas mixture; a separator receiving the fuel / gas mixture, the separator configured to separate the fuel / gas mixture into an outlet stripping gas stream and an outlet fuel stream; wherein the stripping gas stream passes through the fuel oxygen reduction unit at a single time.

Description

Technical Field

[0001] The present subject matter generally relates to a fuel oxygen reduction unit for an engine and a method of operating the same. Background Art

[0002] A typical aircraft propulsion system includes one or more gas turbine engines. A gas turbine engine generally includes a turbine that includes a compressor section, a combustion section, a turbine section, and an exhaust section in a serial flow order. In operation, air is provided to the inlet of the compressor section, where one or more axial compressors progressively compress the air until the air reaches the combustion section. Fuel is mixed with the compressed air and burned in the combustion section to provide combustion gases. The combustion gases are directed from the combustion section to the turbine section. The flow of combustion gases through the turbine section drives the turbine section, and is then directed to, for example, the atmosphere through the exhaust section.

[0003] Certain operations and systems of gas turbine engines and aircraft can generate relatively large amounts of heat. Fuel has been identified as an efficient heat sink to receive at least some of such heat during operation, due at least in part to the thermal capacity of the fuel and the increased combustion operating efficiency that can result from burning higher temperature fuels.

[0004] However, heating the fuel without properly conditioning the fuel can cause the fuel to "coke," or form solid particles that can clog certain components of the fuel system, such as fuel nozzles. Reducing the amount of oxygen in the fuel can effectively reduce the likelihood that the fuel will coke beyond an unacceptable amount. Summary of the invention

[0005] Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

[0006] In an exemplary embodiment of the present disclosure, a fuel oxygen reduction unit for an engine is provided. The fuel oxygen reduction unit includes: an inlet fuel line; a stripping gas source; a contactor selectively in fluid communication with the stripping gas source, the inlet fuel line, or both to form a fuel / gas mixture; and a separator receiving the fuel / gas mixture, the separator being configured to separate the fuel / gas mixture into an outlet stripping gas stream and an outlet fuel stream; wherein the stripping gas stream passes through the fuel oxygen reduction unit a single time.

[0007] In certain exemplary embodiments, the fuel oxygen reduction unit includes a valve downstream of a stripping gas source and upstream of a contactor, wherein the valve is capable of switching between a closed position, in which the stripping gas source is not in fluid communication with the contactor, and an open position, in which the stripping gas flows to the contactor.

[0008] In certain exemplary embodiments, the valve switches to an open position under specified operating conditions.

[0009] In certain exemplary embodiments, the prescribed operating condition is a weight-on-wheels condition.

[0010] In certain exemplary embodiments, the prescribed operating condition is an engine speed condition.

[0011] In certain exemplary embodiments, the prescribed operating condition is a wind down condition of the engine.

[0012] In certain exemplary embodiments, the fuel oxygen reduction unit defines a maximum continuous operation time of one hour or less.

[0013] In certain exemplary embodiments, the separator includes an inlet in fluid communication with the contactor, a fuel outlet, and a stripping gas outlet, the inlet receiving a fuel / gas mixture, wherein the separator is configured to separate the fuel / gas mixture into an outlet stripping gas flow and an outlet fuel flow, and provide the outlet stripping gas flow to the stripping gas outlet, and provide the outlet fuel flow to the fuel outlet.

[0014] In certain exemplary embodiments, the outlet stripping gas stream is vented to the atmosphere downstream of the separator.

[0015] In certain exemplary embodiments, the stripping gas source comprises a refillable inert gas bottle.

[0016] In certain exemplary embodiments, the stripping gas source comprises an inert gas generator.

[0017] In certain exemplary embodiments, the outlet fuel stream has a lower oxygen content than the inlet fuel stream, and wherein the outlet stripping gas stream has a higher oxygen content than the inlet stripping gas stream.

[0018] In another exemplary embodiment of the present disclosure, a fuel oxygen reduction system for an engine is provided. The fuel oxygen reduction system includes: an inlet fuel line; a stripping gas source; a contactor selectively in fluid communication with the stripping gas source, the inlet fuel line, or both to form a fuel / gas mixture; a separator receiving the fuel / gas mixture, the separator being configured to separate the fuel / gas mixture into an outlet stripping gas stream and an outlet fuel stream; and a storage tank receiving the outlet fuel stream.

[0019] In certain exemplary embodiments, the stripping gas source comprises an inert gas generator.

[0020] In certain exemplary embodiments, the fuel oxygen reduction system includes: a main tank containing a main fuel flow; and a valve downstream of the storage tank and the main tank, wherein the valve is capable of switching between a first position and a second position, in which the main tank is in fluid communication with the engine and in which the storage tank is in fluid communication with the engine.

[0021] In certain exemplary embodiments, the valve switches to the second position under specified operating conditions.

[0022] In certain exemplary embodiments, the prescribed operating condition is a weight-on-wheels condition.

[0023] In certain exemplary embodiments, the prescribed operating condition is an engine speed condition.

[0024] In certain exemplary embodiments, the main tank defines a first volume, wherein the storage tank defines a second volume, and wherein the second volume is less than 20% of the first volume.

[0025] In certain exemplary embodiments, the separator includes an inlet in fluid communication with the contactor, a fuel outlet, and a stripping gas outlet, the inlet receiving the fuel / gas mixture, wherein the separator is configured to provide an outlet stripping gas flow to the stripping gas outlet and to provide an outlet fuel flow to a storage tank via the fuel outlet.

[0026] In an exemplary aspect of the present disclosure, a method for operating a fuel delivery system for a gas turbine engine is provided. The method includes: receiving an inlet fuel flow in a fuel oxygen reduction unit for reducing the amount of oxygen in the inlet fuel flow using a stripping gas flow through a stripping gas flow path; and passing the stripping gas flow through the fuel oxygen reduction unit a single time.

[0027] Technical Solution 1. A fuel oxygen reduction unit for an engine, comprising: inlet fuel line; a stripping gas source; a contactor in selective fluid communication with the stripping gas source, the inlet fuel line, or both to form a fuel / gas mixture; and a separator receiving the fuel / gas mixture, the separator being configured to separate the fuel / gas mixture into an outlet stripping gas stream and an outlet fuel stream; The stripping gas stream passes through the fuel oxygen reduction unit a single time.

[0028] Technical solution 2. The fuel oxygen reduction unit according to any of the above technical solutions, characterized in that the fuel oxygen reduction unit further comprises: a valve downstream of the stripping gas source and upstream of the contactor, The valve is switchable between a closed position in which the stripping gas source is not in fluid communication with the contactor and an open position in which the stripping gas flows to the contactor.

[0029] Technical Solution 3. A fuel oxygen reduction unit according to any of the preceding technical solutions, characterized in that the valve is switched to the open position under specified operating conditions.

[0030] Technical Solution 4. A fuel oxygen reduction unit according to any of the foregoing technical solutions, characterized in that the prescribed operating condition is a wheel weight condition.

[0031] Technical Solution 5. The fuel oxygen reduction unit according to any of the foregoing technical solutions is characterized in that the prescribed operating condition is an engine speed condition.

[0032] Technical Solution 6. The fuel oxygen reduction unit according to any of the foregoing technical solutions is characterized in that the prescribed operating condition is a relaxed condition of the engine.

[0033] Technical Solution 7. A fuel oxygen reduction unit according to any of the preceding technical solutions, characterized in that the fuel oxygen reduction unit is limited to a maximum continuous operation time of one hour or less.

[0034] Technical Solution 8. A fuel oxygen reduction unit according to any of the preceding technical solutions, characterized in that a desired fuel flow is defined when the engine is operating under cruising conditions, and wherein the outlet fuel flow is less than the desired fuel flow.

[0035] Technical Solution 9. A fuel oxygen reduction unit according to any of the foregoing technical solutions, characterized in that the separator includes an inlet, a fuel outlet, and a stripping gas outlet which are fluidly connected to the contactor, the inlet receiving the fuel / gas mixture, wherein the separator is configured to separate the fuel / gas mixture into an outlet stripping gas flow and an outlet fuel flow, and provide the outlet stripping gas flow to the stripping gas outlet, and provide the outlet fuel flow to the fuel outlet, and wherein the outlet stripping gas flow is released to the atmosphere downstream of the separator.

[0036] Technical Solution 10. A fuel oxygen reduction unit according to any of the preceding technical solutions, characterized in that the stripping gas source comprises a refillable inert gas bottle.

[0037] Technical Solution 11. A fuel oxygen reduction unit according to any of the preceding technical solutions, characterized in that the stripping gas source comprises an inert gas generator.

[0038] Technical Solution 12. A fuel oxygen reduction unit according to any of the preceding technical solutions, characterized in that the outlet fuel flow has a lower oxygen content than the inlet fuel flow, and wherein the outlet stripping gas flow has a higher oxygen content than the inlet stripping gas flow.

[0039] Technical Solution 13. A fuel oxygen reduction system for an engine, comprising: inlet fuel line; a stripping gas source; a contactor in selective fluid communication with the stripping gas source, the inlet fuel line, or both to form a fuel / gas mixture; a separator receiving the fuel / gas mixture, the separator being configured to separate the fuel / gas mixture into an outlet stripping gas stream and an outlet fuel stream; and A storage tank receives the outlet fuel flow.

[0040] Technical solution 14. The fuel oxygen reduction system according to any of the above technical solutions, characterized in that the fuel oxygen reduction system further comprises: a main tank containing a main fuel flow; and a valve, downstream of the storage tank and the main tank, The valve is switchable between a first position in which the main tank is in fluid communication with the engine and a second position in which the storage tank is in fluid communication with the engine.

[0041] Technical Solution 15. A fuel oxygen reduction system according to any of the preceding technical solutions, characterized in that the main tank defines a first volume, wherein the storage tank defines a second volume, and wherein the second volume is less than 20% of the first volume.

[0042] Technical Solution 16. A fuel oxygen reduction system according to any of the preceding technical solutions, characterized in that the valve is switched to the second position under specified operating conditions.

[0043] Technical Solution 17. A fuel oxygen reduction system according to any of the foregoing technical solutions, characterized in that the prescribed operating condition is a wheel weight condition.

[0044] Technical Solution 18. A fuel oxygen reduction system according to any of the foregoing technical solutions, characterized in that the prescribed operating condition is an engine speed condition.

[0045] Technical Solution 19. A fuel oxygen reduction system according to any of the preceding technical solutions, characterized in that the stripping gas source comprises an inert gas generator.

[0046] Technical Solution 20. A fuel oxygen reduction system according to any of the preceding technical solutions, characterized in that the separator comprises an inlet, a fuel outlet and a stripping gas outlet which are fluidly connected to the contactor, the inlet receiving the fuel / gas mixture, wherein the separator is configured to provide the outlet stripping gas flow to the stripping gas outlet, and to provide the outlet fuel flow to the storage tank via the fuel outlet.

[0047] Technical Solution 21. A method for operating a fuel delivery system for a gas turbine engine, comprising: receiving an inlet fuel flow in a fuel oxygen reduction unit for reducing the amount of oxygen in the inlet fuel flow using a stripping gas flow through a stripping gas flow path; and The stripping gas stream is passed a single time through the fuel oxygen reduction unit.

[0048] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims.The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] A complete and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art is set forth in the specification with reference to the accompanying drawings, in which: Figure 1 is a schematic cross-sectional view of a gas turbine engine according to an exemplary embodiment of the present disclosure.

[0050] Figure 2 is a schematic diagram of a fuel oxygen reduction unit according to an exemplary embodiment of the present disclosure.

[0051] Figure 3A is a schematic diagram of a fuel oxygen reduction unit according to another exemplary embodiment of the present disclosure.

[0052] Figure 3B is a schematic diagram of an inert gas generator according to an exemplary embodiment of the present disclosure.

[0053] Figure 3C is a schematic diagram of an inert gas generator according to another exemplary embodiment of the present disclosure.

[0054] Figure 4 is a schematic diagram of a fuel oxygen reduction system according to an exemplary embodiment of the present disclosure.

[0055] Figure 5 is a schematic diagram of a fuel oxygen reduction system according to another exemplary embodiment of the present disclosure.

[0056] Figure 6 A flow chart of a method of operating a fuel system for an aviation gas turbine engine according to aspects of the present disclosure.

[0057] Figure 7 A flow chart of a method of operating a fuel system for an aviation gas turbine engine according to another aspect of the present disclosure.

[0058] Corresponding reference characters indicate corresponding parts throughout the several views.The illustrations set forth herein illustrate exemplary embodiments of the present disclosure, and such illustrations are not to be construed as limiting the scope of the present disclosure in any way. DETAILED DESCRIPTION

[0059] Reference will now be made in detail to the present embodiments of the present invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. The same or similar designations in the drawings and description have been used to refer to the same or similar parts of the present invention.

[0060] The following description is provided to enable those skilled in the art to make and use embodiments contemplated for implementing the description of the present invention. However, multiple modifications, equivalents, variations, and alternatives will still be readily apparent to those skilled in the art. Any and all such modifications, variations, equivalents, and alternatives are intended to fall within the spirit and scope of the present invention.

[0061] For the purpose of the description hereinafter, the terms "upper", "lower", "right", "left", "vertical", "horizontal", "top", "bottom", "lateral", "longitudinal" and their derivatives shall refer to the present invention as it is oriented in the accompanying drawings. However, it will be understood that the present invention may take a variety of alternative variations, except where expressly specified to the contrary. It will also be understood that the specific devices illustrated in the drawings and described in the following specification are merely exemplary embodiments of the present invention. Therefore, specific dimensions and other physical characteristics related to the embodiments disclosed herein are not to be considered limiting.

[0062] As used herein, the terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another, and are not intended to indicate the position or importance of individual components.

[0063] The terms "upstream" and "downstream" refer to relative directions with respect to the flow of a fluid in a fluid pathway. For example, "upstream" refers to the direction from which the fluid is flowing, and "downstream" refers to the direction to which the fluid is flowing.

[0064] Unless otherwise specified herein, the terms "coupled," "fixed," "attached to," and the like refer to both direct coupling, fixing, or attachment as well as indirect coupling, fixing, or attachment through one or more intermediate members or features.

[0065] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0066] Approximate language, as used throughout the specification and claims herein, is applicable to modify any quantitative representation that may vary without causing a change in the basic function to which it is associated. Therefore, a value modified by one or more terms such as "approximately," "approximately," and "substantially" will not be limited to the exact value specified. In at least some instances, the approximate language may correspond to the accuracy of an instrument used to measure the value, or the accuracy of a method or machine used to construct or manufacture a component and / or system. For example, approximate language may refer to being within a 10 percent margin.

[0067] Here and throughout the specification and claims, range limitations are combined and interchanged, and unless context or language indicates otherwise, such ranges are identified and include all sub-ranges contained therein. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.

[0068] In the fuel oxygen reduction unit of the present disclosure, the fuel oxygen reduction unit is a static system that is constructed and sized to operate (e.g., deoxygenate the fuel) under specified operating conditions. In addition, the fuel oxygen reduction unit of the present disclosure can be retrofitted on existing engine systems and / or incorporated into new engine systems.

[0069] In the fuel oxygen reduction system of the present disclosure, the fuel oxygen reduction system provides a system that continuously deoxygenates fuel and then stores the deoxygenated fuel in a storage tank. The deoxygenated fuel stored in the storage tank is then provided to the engine under specified operating conditions.

[0070] Referring now to the drawings, wherein like numerals refer to like elements throughout, Figure 1 A schematic cross-sectional view of an engine according to an exemplary embodiment of the present disclosure is provided. The engine may be incorporated into a vehicle. For example, the engine may be an aerospace engine incorporated into an aircraft. However, alternatively, the engine may be any other suitable type of engine for any other suitable aircraft.

[0071] For the depicted embodiment, the engine is configured as a high bypass turbofan engine 100. Figure 1 As shown in FIG. 1 , turbofan engine 100 defines an axial direction A (extending parallel to a longitudinal centerline or axis 101 provided for reference), a radial direction R, and a circumferential direction (extending about axial direction A; not shown in FIG. 1 ). Figure 1). Generally, the turbofan engine 100 includes a fan section 102 and a turbine 104 disposed downstream of the fan section 102 .

[0072] The depicted exemplary turbine 104 generally includes a substantially tubular casing 106 that defines an annular inlet 108. The casing 106 encloses, in a serial flow relationship: a compressor section including a boost or low pressure (LP) compressor 110 and a high pressure (HP) compressor 112; a combustion section 114; a turbine section including a high pressure (HP) turbine 116 and a low pressure (LP) turbine 118; and a jet exhaust nozzle section 120. The compressor section, the combustion section 114, and the turbine section together at least partially define a core air flow path 121 extending from the annular inlet 108 to the jet nozzle exhaust section 120. The turbofan engine further includes one or more drive shafts. More specifically, the turbofan engine includes a high pressure (HP) shaft or spool 122 drivingly connecting the HP turbine 116 to the HP compressor 112, and a low pressure (LP) shaft or spool 124 drivingly connecting the LP turbine 118 to the LP compressor 110.

[0073] For the depicted embodiment, the fan section 102 includes a fan 126 having a plurality of fan blades 128 coupled to a disk 130 in a spaced-apart manner. The fan blades 128 and the disk 130 are rotatable together about the longitudinal axis 101 by the LP shaft 124. The disk 130 is covered by a rotatable forward hub 132, the profile of which is aerodynamically set to facilitate air flow through the plurality of fan blades 128. In addition, an annular fan case or outer nacelle 134 is provided, which circumferentially surrounds at least a portion of the fan 126 and / or the turbine 104. The nacelle 134 is supported relative to the turbine 104 by a plurality of circumferentially spaced outlet guide vanes 136. A downstream section 138 of the nacelle 134 extends over an outer portion of the turbine 104 so as to define a bypass airflow path 140 therebetween.

[0074] Still refer to Figure 1 , the turbofan engine 100 further includes an accessory gearbox 142, a fuel oxygen reduction unit or system 144, and a fuel delivery system 146. For the illustrated embodiment, the accessory gearbox 142 is positioned within the cowling / casing 106 of the turbine 104. In addition, it will be appreciated that although in Figure 1104, but the accessory gearbox 142 may be mechanically coupled to one or more shafts or shafts of the turbine 104 and may be capable of rotating with the one or more shafts or shafts of the turbine 104. For example, in at least some exemplary embodiments, the accessory gearbox 142 may be mechanically coupled to the HP shaft 122 and may be capable of rotating with the HP shaft 122. Additionally, for the illustrated embodiment, a fuel oxygen reduction unit 144 may be coupled to the accessory gearbox 142 or may otherwise be capable of rotating with the accessory gearbox 142. In this manner, it will be appreciated that the exemplary fuel oxygen reduction unit 144 may be driven by the accessory gearbox 142. In other exemplary embodiments, the exemplary fuel oxygen reduction unit 144 may be driven by other sources. Notably, as used herein, the term "fuel oxygen conversion" generally means a device capable of reducing the free oxygen content of a fuel.

[0075] In addition, the fuel delivery system 146 generally includes a fuel source 148 (such as a fuel tank) and one or more fuel lines 150. The one or more fuel lines 150 provide a fuel flow through the fuel delivery system 146 to the combustion section 114 of the turbine 104 of the turbofan engine 100. In the exemplary engine configuration, the combustion section 114 includes a plurality of fuel nozzles circumferentially around the centerline axis 101. The fuel nozzles define a plurality of fuel flow passages that define a volume such that when the flow of fuel to the nozzles is stopped, a certain volume of fuel remains within the nozzles.

[0076] During typical operation in such a configuration, the main fuel oxygen reduction unit 144 is operable to reduce the oxygen content of the fuel flow to the combustion section 114 (and more particularly, to such fuel nozzles). However, during relaxed conditions, it may be necessary to further reduce the oxygen content of the fuel. For example, depending on, for example, the thermal mass of the core of the engine 100 and the turbine inlet temperature during idle conditions of the engine, heat from the core of the engine 100 may be "sucked back" to these fuel nozzles, thereby heating a certain volume of fuel retained in the fuel nozzles to the point that a certain volume of fuel retained in the fuel nozzles will coke unless the oxygen content of such volume of fuel is reduced to below the level provided by the exemplary fuel oxygen reduction unit 144 of the present disclosure.

[0077] Thus, the exemplary fuel oxygen reduction unit 144 of the present disclosure may operate during relaxation conditions to ensure that the volume of fuel remaining within the fuel nozzles after the engine has been shut down is sufficiently low to prevent the fuel flow from coking or otherwise deteriorating beyond undesirable levels when heat from the core of the engine 100 is sucked back into such fuel nozzles.

[0078] However, it will be recognized that Figure 1The exemplary turbofan engine 100 depicted in FIG. 1 is provided by way of example only. In other exemplary embodiments, any other suitable engine may be utilized with aspects of the present disclosure. For example, in other embodiments, the engine may be any other suitable gas turbine engine, such as a turboshaft engine, a turboprop engine, a turbojet engine, etc. In this manner, it will be further appreciated that in other embodiments, the gas turbine engine may have any other suitable configuration, such as any other suitable number or arrangement of shafts, compressors, turbines, fans, etc. In addition, although Figure 1 The exemplary gas turbine engine depicted in FIG is schematically shown as a fixed pitch direct drive turbofan engine 100, but in other embodiments, the gas turbine engine of the present disclosure may be a geared gas turbine engine (i.e., including a gearbox between the fan 126 and a shaft driving the fan (such as the LP shaft 124)), may be a variable pitch gas turbine engine (i.e., including a fan 126 having a plurality of fan blades 128 that can rotate about their respective pitch axes), etc. In addition, although not depicted herein, in other embodiments, the gas turbine engine may be any other suitable type of gas turbine engine, such as an industrial gas turbine engine incorporated into a power generation system, a marine gas turbine engine, etc. Moreover, in alternative embodiments, aspects of the present disclosure may be incorporated into or otherwise utilized with any other type of engine (such as a reciprocating engine).

[0079] Furthermore, it will be appreciated that while for the depicted embodiment, the turbofan engine 100 includes a fuel oxygen reduction unit 144 positioned within the turbine 104 (i.e., within the casing 106 of the turbine 104), in other embodiments, the fuel oxygen reduction unit 144 may be positioned at any other suitable location. For example, in other embodiments, the fuel oxygen reduction unit 144 may instead be positioned away from the turbofan engine 100, such as proximate to a tank of the fuel delivery system 146, or within a tank of the fuel delivery system 146. Additionally, in other embodiments, the fuel oxygen reduction unit 144 may additionally or alternatively be driven by other suitable power sources, such as an electric motor, a hydraulic motor, or an independent mechanical coupling to the HP or LP shaft, etc.

[0080] Reference now Figure 2 , provides a schematic diagram of a fuel oxygen reduction unit 200 for a gas turbine engine according to an exemplary embodiment of the present disclosure. In at least some exemplary embodiments, the exemplary fuel oxygen reduction unit 200 depicted may be incorporated into, for example, the above reference Figure 1 The exemplary engine 100 described herein (eg, may be Figure 11 and described above). The fuel oxygen reduction unit 200 of the present disclosure may be a static system that is constructed and sized to operate under specified operating conditions. Additionally, the fuel oxygen reduction unit 200 of the present disclosure may be retrofitted on existing engine systems and / or incorporated into new engine systems.

[0081] As will be appreciated from the discussion herein, in an exemplary embodiment, Figure 2 The exemplary fuel oxygen reduction unit 200 generally includes a contactor 202, a separator 204, a stripping gas source 210, and a valve 212. In the exemplary embodiment, the exemplary fuel oxygen reduction unit 200 generally defines a one-way gas flow path or a one-way system 206 from the stripping gas source 210 to the contactor 202 and out of the separator 204, as described herein. In particular, for the illustrated embodiment, the fuel oxygen reduction unit 200 is configured to pass the stripping gas flow through the fuel oxygen reduction unit 200 a single time. For example, the stripping gas flow passes through the fuel oxygen reduction unit 200 a single time and may then exit from the system to the atmosphere.

[0082] In this manner, it will be appreciated that the term "single shot" as used with respect to the stripping gas flow passing through the fuel oxygen reduction unit refers to the stripping gas flow not being recycled in a continuous manner throughout all flight periods / operating modes of the engine and / or aircraft incorporating the fuel oxygen reduction unit 200. In this manner, it will be appreciated that the term "single shot" as used with respect to the stripping gas flow passing through the fuel oxygen reduction unit may refer to the stripping gas not being recycled through the fuel oxygen reduction unit 200 during operation (i.e., the outlet stripping gas flow 229 is not provided back to the contactor 202 as the inlet flow of stripping gas 220). It will also be appreciated that the term "single shot" as used with respect to the stripping gas flow passing through the fuel oxygen reduction unit refers to passing the stripping gas flow through a fuel oxygen reduction unit that lacks a gas oxygen reduction feature (such as a catalyst, preheater, membrane, or the like). Additionally or alternatively, it will be appreciated that the term "single" as used with respect to the flow of stripping gas through the fuel oxygen reduction unit may refer to a particular volume of stripping gas being used only for one particular flight period or mission of an aircraft incorporating the fuel oxygen reduction unit. For example, a flight period or mission may be a relaxed condition of an engine capable of operating with / incorporating the fuel oxygen reduction unit. This may ensure that relatively low oxygen content fuel remains in the engine at shutdown, minimizing the risk of damage to certain components of the engine (such as fuel nozzles) due to heat back absorption at shutdown. Additionally or alternatively, furthermore, it will be appreciated that the term "single" as used with respect to the flow of stripping gas through the fuel oxygen reduction unit may refer to a particular volume of stripping gas being used only for a single period of time, such as one (1) hour or less, or thirty (30) minutes or less. Thus, it will be appreciated that in at least one exemplary embodiment, the fuel oxygen reduction unit 200 limits a maximum continuous operating time of one hour or less.

[0083] In an exemplary embodiment, the contactor 202 can be configured in any suitable manner to significantly mix the received gas and liquid streams. For example, in certain embodiments, the contactor 202 can be a mechanically driven contactor (e.g., having paddles for mixing the received streams), or alternatively, can be a passive contactor for mixing the received streams at least in part using the pressure and / or flow rate of the received streams. For example, the passive contactor can include one or more turbulators, venturi mixers, etc.

[0084] It will be appreciated that the fuel oxygen reduction unit 200 generally provides a flow of stripping gas 220 to the contactor 202 for mixing with the fuel flow during operation. It will be appreciated that the term "stripping gas" is used herein as a convenient term to refer to a gas that is generally capable of performing the functions described herein. The stripping gas 220 can be an actual stripping gas that acts to strip oxygen from the fuel within the contactor, or alternatively, can be a bubbling gas that is bubbled through a liquid fuel to reduce the oxygen content of such fuel. For example, as will be discussed in more detail below, the stripping gas 220 can be an inert gas such as nitrogen or carbon dioxide (CO2), a gas mixture composed of at least 50% by mass of an inert gas, or some other gas or gas mixture having a relatively low oxygen content.

[0085] refer to Figure 2 In the exemplary embodiment, separator 204 generally includes a stripping gas outlet 214, a fuel outlet 216, and an inlet 218. It will also be appreciated that the depicted exemplary fuel oxygen reduction unit 200 can be integrated with a fuel delivery system 146 (such as a fuel delivery system 146 of a gas turbine engine including the fuel oxygen reduction unit 200 (see, e.g., Figure 1 )) operate together. The exemplary fuel delivery system 146 generally includes a plurality of fuel lines, and more particularly, includes an inlet fuel line 222 and an outlet fuel line 224. The inlet fuel line 222 is fluidly connected to the contactor 202 for providing a liquid fuel stream or inlet fuel stream 226 (e.g., from a fuel source such as a fuel tank) to the contactor 202, and the outlet fuel line 224 is fluidly connected to the fuel outlet 216 of the separator 204 for receiving a deoxygenated liquid fuel stream or outlet fuel stream 227.

[0086] Additionally, during typical operation, a stream of stripping gas 220 flows to the contactor 202, wherein the stripping gas 220 mixes with a stream of inlet fuel 226 from an inlet fuel line 222 to generate a fuel gas mixture 228. The fuel gas mixture 228 generated within the contactor 202 is provided to the inlet 218 of the separator 204. The stripping gas source 210 is selectively in fluid communication with the stripping gas inlet of the contactor 202 for selectively introducing the stripping gas into the contactor 202.

[0087] For the depicted embodiment, the stripping gas source 210 is in fluid communication with the contactor 202 via a valve 212, which can be actuated to supply a stripping gas stream 220 to the contactor 202 under specified operating conditions. Figure 2, valve 212 is downstream of the stripping gas source 210 and upstream of the contactor 202. The valve 212 is capable of switching between a closed position, in which the stripping gas source 210 is not in fluid communication with the contactor 202, and an open position, in which the stripping gas 220 flows to the contactor 202. As described herein, the valve 212 switches to the open position under specified operating conditions. In this way, the fuel oxygen reduction unit 200 of the present disclosure operates only during desired engine parameters (e.g., parameters indicating the engine at the end of a cycle). This enables the fuel oxygen reduction unit 200 of the present disclosure to be a static, smaller and lighter unit to deoxygenate the fuel at the end of an engine cycle, for example, to prevent coking of the fuel. In other words, the fuel oxygen reduction unit 200 of the present disclosure reduces the oxygen content of the fuel so that a relatively large amount of heat can be added to the fuel with a reduced risk of fuel coking (i.e., chemically reacting to form solid particles that can block or otherwise damage components within the fuel flow path).

[0088] The prescribed operating condition may be any desired engine parameter. For example, the prescribed operating condition may be a weight-on-wheel condition indicating the end of an engine cycle. Also, the prescribed operating condition may be an engine speed condition, an engine slack condition, a time condition, or other engine parameter conditions.

[0089] In general, it will be appreciated that during operation of the fuel oxygen reduction unit 200, the inlet fuel 226 provided to the contactor 202 via the inlet fuel line 222 may have a relatively high oxygen content. The stripping gas 220 provided to the contactor 202 may have a relatively low oxygen content or other specific chemical structure. Within the contactor 202, the inlet fuel 226 mixes with the stripping gas 220, thereby resulting in a fuel gas mixture 228. As a result of such mixing, a physical exchange may occur, whereby at least a portion of the oxygen within the inlet fuel 226 is transferred to the stripping gas 220, such that the fuel component of the mixture 228 has a relatively low oxygen content (compared to the inlet fuel 226 provided via the inlet fuel line 222), and the stripping gas component of the mixture 228 has a relatively high oxygen content (compared to the inlet stripping gas 220 provided to the contactor 202).

[0090] Within separator 204, the relatively high oxygen content stripping gas 220 is then separated from the relatively low oxygen content fuel 226 back into respective streams of outlet stripping gas 229 and outlet fuel 227. Separator 204 is configured to separate the fuel / gas mixture 228 into an outlet stripping gas stream 229 and an outlet fuel stream 227, and to provide the outlet stripping gas stream 229 to stripping gas outlet 214 and the outlet fuel stream 227 to fuel outlet 216. In the exemplary embodiment, the outlet stripping gas stream 229 is vented to the atmosphere downstream of separator 204.

[0091] Furthermore, it will be appreciated that the outlet fuel 227 provided to the fuel outlet 216 that has interacted with the stripping gas 220 can have a relatively low oxygen content, such that a relatively large amount of heat can be added to the outlet fuel 227 with a reduced risk of the fuel coking (i.e., chemically reacting to form solid particles that can clog or otherwise damage components within the fuel flow path). For example, in at least certain exemplary aspects, the outlet fuel 227 provided to the fuel outlet 216 can have an oxygen content of less than about five (5) parts per million ("ppm"), such as less than about three (3) ppm, such as less than about two (2) ppm, such as less than about one (1) ppm, such as less than about 0.5 ppm.

[0092] refer to Figure 2 In an exemplary embodiment, stripping gas source 210 is a refillable inert gas bottle 232. Inert gas bottle 232 may be located somewhere on engine 100 or aircraft. Bottle 232 stores a quantity of an oxygen-free inert gas, such as CO2 or N2 gas. Bottle 232 may be refilled at standard intervals.

[0093] refer to Figure 3A In the exemplary embodiment, the stripping gas source 210 is an inert gas generator 234. The inert gas generator 234 is capable of taking air from a source (e.g., air from the atmosphere, air from a pump, air from a compressor bleed) and generating a continuous supply of inert gas. In the exemplary embodiment, the inert gas generator 234 is used to continuously replenish the supply of inert gas to the inert gas bottle 232 described above.

[0094] For example, refer to Figure 3B In the first exemplary embodiment, the inert gas generator 234 is a membrane 236. For example, the membrane 236 separates oxygen from nitrogen. In this way, oxygen-free stripping gas is continuously provided to the system.

[0095] refer to Figure 3CIn a second exemplary embodiment, the inert gas generator 234 is a pressure swing adsorption (PSA) system 238. The PSA system 238 is used to separate a first gas species from a gas mixture under pressure based on the species' molecular characteristics and affinity for an adsorbent material. The PSA system 238 of the present disclosure separates a gas, such as nitrogen, from oxygen, for example. In this manner, oxygen-free stripping gas is continuously provided to the system.

[0096] Reference now Figure 4 , provides a schematic diagram of a fuel oxygen reduction system 400 for a gas turbine engine according to an exemplary embodiment of the present disclosure. In at least some exemplary embodiments, the depicted exemplary fuel oxygen reduction system 400 may be incorporated into, for example, the above referenced Figure 1 The exemplary engine 100 described herein (eg, may be Figure 1 1 and described above). The fuel oxygen reduction system 400 of the present disclosure may be a static system that is constructed and sized to operate under specified operating conditions.

[0097] Figure 4 The embodiment illustrated in the figure includes Figure 2-3A For the sake of brevity, these similar components will not be all included together. Figure 4 The embodiments illustrated in FIG.

[0098] As will be appreciated from the discussion herein, in an exemplary embodiment, Figure 4 The exemplary fuel oxygen reduction system 400 generally includes a contactor 402, a separator 404, a stripping gas source 410, a storage tank 411, a first valve 412, a main tank 413, and a second valve 415. In the exemplary embodiment, the exemplary fuel oxygen reduction system 400 generally defines a one-way gas flow path or system 406 from the stripping gas source 410 to the contactor 402 and out of the separator 404, as described herein. In the exemplary embodiment of the present disclosure, the main tank 413 defines a first volume, the storage tank 411 defines a second volume, and the second volume is less than 20% of the first volume. However, it is contemplated that the second volume can have other sizes relative to the first volume.

[0099] In an exemplary embodiment, contactor 402 can be configured in any suitable manner to significantly mix the received gas and liquid streams. For example, in certain embodiments, contactor 402 can be a mechanically driven contactor (e.g., having paddles for mixing the received streams), or alternatively, can be a passive contactor for mixing the received streams at least in part using the pressure and / or flow rate of the received streams. For example, a passive contactor can include one or more turbulators, venturi mixers, and the like.

[0100] The fuel oxygen reduction system 400 of the present disclosure provides a system that continuously deoxygenates fuel and then stores the deoxygenated fuel in a storage tank 411. The deoxygenated fuel stored in the storage tank 411 may then be provided to the engine under specified operating conditions.

[0101] It will be appreciated that the fuel oxygen reduction system 400 generally provides a flow of stripping gas 420 to the contactor 402 for mixing with the fuel flow during operation to continuously provide deoxygenated fuel that can be stored in the storage tank 411 .

[0102] refer to Figure 4 In the exemplary embodiment, the stripping gas source 410 is an inert gas generator 434. As described above, the inert gas generator 434 can take air from a source (e.g., air from the atmosphere, air from a pump, air from a compressor bleed) and generate a continuous supply of inert gas.

[0103] During typical operation, a stream of stripping gas 420 flows to the contactor 402, wherein the stripping gas 420 mixes with a stream of inlet fuel 426 from an inlet fuel line 422 to generate a fuel gas mixture 428. The fuel gas mixture 428 generated within the contactor 402 is provided to the inlet 418 of the separator 404. The stripping gas source 410 is selectively in fluid communication with the stripping gas inlet of the contactor 402 for selectively introducing the stripping gas into the contactor 402.

[0104] As described above, the stripping gas source 410 is in fluid communication with the contactor 402 via the first valve 412, which can be actuated to supply the stripping gas stream 420 to the contactor 402. Figure 4 , the first valve 412 is downstream of the stripping gas source 410 and upstream of the contactor 402. The first valve 412 is switchable between a closed position, in which the stripping gas source 410 is not in fluid communication with the contactor 402, and an open position, in which the stripping gas 420 flows to the contactor 420.

[0105] In general, it will be appreciated that during operation of the fuel oxygen reduction system 400, the inlet fuel 426 provided to the contactor 402 via the inlet fuel line 422 may have a relatively high oxygen content. The stripping gas 420 provided to the contactor 402 may have a relatively low oxygen content or other specific chemical structure. Within the contactor 402, the inlet fuel 426 mixes with the stripping gas 420, thereby resulting in a fuel gas mixture 428. As a result of such mixing, a physical exchange may occur, whereby at least a portion of the oxygen within the inlet fuel 426 is transferred to the stripping gas 420, such that the fuel component of the mixture 428 has a relatively low oxygen content (compared to the inlet fuel 426 provided via the inlet fuel line 422), and the stripping gas component of the mixture 428 has a relatively high oxygen content (compared to the inlet stripping gas 420 provided to the contactor 402).

[0106] Within separator 404, the relatively high oxygen content stripping gas 420 is then separated from the relatively low oxygen content fuel 426 back into respective streams of outlet stripping gas 429 and outlet fuel 427. Separator 404 is configured to separate fuel / gas mixture 428 into outlet stripping gas stream 429 and outlet fuel stream 427, and provide outlet stripping gas stream 429 to stripping gas outlet 414, and provide outlet fuel stream 427 to fuel outlet 416. In the exemplary embodiment, outlet stripping gas stream 429 is vented to the atmosphere downstream of separator 404.

[0107] In addition, it will be appreciated that the outlet fuel 427 provided to the fuel outlet 416 that has interacted with the stripping gas 420 can have a relatively low oxygen content so that a relatively large amount of heat can be added to the fuel with a reduced risk of coking (i.e., chemically reacting to form solid particles that can clog or otherwise damage components within the fuel flow path) .

[0108] This deoxygenated fuel 427 is then provided and stored in storage tank 411 and may be provided to the engine under specified operating conditions.

[0109] refer to Figure 4 In the exemplary embodiment, fuel oxygen reduction system 400 includes a main tank 413 containing a main fuel flow 440, and a second valve 415 downstream of storage tank 411 and downstream of main tank 413. Main fuel flow 440 has a higher oxygen content than deoxygenated fuel 427.

[0110] The second valve 415 is switchable between a first position, in which the main tank 413 is in fluid communication with the engine 100, and a second position, in which the storage tank 411 is in fluid communication with the engine 100. With the second valve 415 in the first position, the main fuel flow 440 from the main tank 413 is provided to the engine 100. With the second valve 415 in the second position, the deoxygenated fuel 427 from the storage tank 411 is provided to the engine 100. In this way, the fuel oxygen reduction system 400 of the present disclosure allows switching that can switch from providing the main fuel flow 440 to the engine 100 or providing the deoxygenated fuel 427 to the engine 100.

[0111] The fuel oxygen reduction system 400 includes a second valve 415 that switches to a second position under a specified operating condition. In this manner, the deoxygenated fuel 427 from the storage tank 411 is provided to the engine 100 only during a desired engine parameter (e.g., a parameter indicating that the engine 100 is at the end of a cycle). The specified operating condition may be any desired engine parameter. For example, the specified operating condition may be a weight on wheels condition indicating the end of an engine cycle. Also, the specified operating condition may be an engine speed condition, a time condition, or other engine parameter condition.

[0112] Reference now Figure 5 , a schematic diagram of a fuel oxygen reduction system 500 for a gas turbine engine according to another exemplary embodiment of the present disclosure is provided. In at least some exemplary embodiments, the depicted exemplary fuel oxygen reduction system 500 may be incorporated into, for example, the above referenced Figure 1 The exemplary engine 100 described herein (eg, may be Figure 1 The fuel oxygen reduction unit 144 depicted in and described above).

[0113] Figure 5 The embodiment illustrated in the figure includes Figure 4 For the sake of brevity, these similar components will not be all included together. Figure 5 The embodiments illustrated in FIG.

[0114] refer to Figure 5 The fuel oxygen reduction system 500 for a gas turbine engine includes a fuel tank 502, such as Figure 4 The fuel oxygen reduction system 400, a booster pump 504, a set of valves 510, and a set of pumps 520 are shown in FIG. The fuel oxygen reduction system 500 can be used with Figure 4 Utilized together with the fuel oxygen reduction system 400 shown in FIG. 1 and providing a set of valves 510, a set of pumps 520, and a fuel system 500 that can use its own pressure to exhaust its oxygen-rich fuel and then pump in the deoxygenated fuel 427 ( Figure 4 ) to supplement the fuel system. In other words, the system 500 can be directed to the deoxygenated fuel 427 ( Figure 4 ) flow and quickly and efficiently switch to oxygen-rich fuel.

[0115] In an embodiment of the present disclosure, the fuel oxygen reduction system 400 may be positioned before or after the boost pump 504 .

[0116] Reference now Figure 6 , a flow chart of a method 300 of operating a fuel system for an aviation gas turbine engine is provided. The method 300 may be utilized with one or more of the exemplary fuel systems, gas turbine engines, etc. described above, or alternatively, may be utilized with any other suitable fuel system.

[0117] Method 300 includes operating an aircraft gas turbine engine during a cruise condition. More specifically, method 300 includes providing a fuel flow to a fuel nozzle of the aircraft gas turbine engine during a cruise condition of the aircraft gas turbine engine at (301). Method 300 further includes operating the aircraft gas turbine engine in a relaxed condition. More specifically, method 300 includes providing a fuel flow to a fuel nozzle of the aircraft gas turbine engine during a relaxed condition at (302). As noted above, a relaxed condition may be an engine operating condition or sequence of operating conditions that occurs when the engine transitions to a fully shut down condition (i.e., when fuel is no longer provided to the fuel nozzle(s) and the engine's shaft(s) are not rotating or are rotating at a low speed). The relaxed condition may include a landing idle condition of the engine (when the engine taxis to its door or pylon at the end of a flight mission (e.g., for a commercial aircraft)), and / or a shutdown sequence of the engine in which the engine transitions from a landing idle condition to a fully shut down condition. In this manner, it will be appreciated that providing a flow of fuel to the fuel nozzle at (302) includes providing fuel to the fuel nozzle at a first flow rate at (304) to facilitate operation of the engine at a desired operating speed (eg, idle).

[0118] Exemplary method 300 further includes operating a fuel oxygen reduction unit during the relaxed condition to reduce the oxygen content of a fuel flow provided to a fuel nozzle of the aircraft gas turbine engine at (306). The fuel oxygen reduction unit may be configured as described above with reference to Figures 1 to 5 One or more of the described exemplary auxiliary fuel oxygen reduction units may be similarly configured, or alternatively, may be any other suitable fuel oxygen reduction unit.

[0119] In this manner, it will be appreciated that, in at least some exemplary aspects, operating the fuel oxygen reduction unit at (306) includes operating the fuel oxygen reduction unit substantially exclusively during a relaxed condition at (308). In the context of this step, "substantially exclusively" refers to at least 90% of the total operating time within a particular flight mission of an aircraft incorporating the fuel oxygen reduction unit.

[0120] In this manner, it will be appreciated that the fuel oxygen reduction unit may be limited to a maximum operating time of one hour per mission or less, such as 30 minutes per mission or less.

[0121] Additionally or alternatively, it will be appreciated that an aircraft incorporating an aviation gas turbine engine may define a maximum fuel capacity (e.g., a maximum amount of fuel that may be loaded in a fuel tank of the aircraft during typical operation). The fuel oxygen reduction unit may define a maximum fuel throughput volume per flight mission, wherein the maximum fuel throughput volume of the fuel oxygen reduction unit is less than 10 percent of the maximum fuel capacity of the aircraft.

[0122] Additionally or alternatively, furthermore, the fuel oxygen reduction unit may define a maximum fuel flow rate capacity. The maximum fuel flow rate capacity of the fuel oxygen reduction unit may refer to the maximum flow rate that the fuel oxygen reduction unit can effectively handle (i.e., can handle an oxygen reduction level of at least 50% of its maximum oxygen reduction level). Further, as noted above, method 300 includes operating an aviation gas turbine engine during cruise conditions. Operating an aviation gas turbine engine during cruise conditions may include providing a fuel flow to a combustion section of the aviation gas turbine engine at a cruise condition flow rate. The maximum fuel flow rate capacity of the fuel oxygen reduction unit is less than the cruise condition flow rate. In this manner, it will be appreciated that the fuel oxygen reduction unit is not a steady-state fuel oxygen reduction unit, but is instead a dedicated fuel oxygen reduction unit.

[0123] In this way, it will be appreciated that in other exemplary aspects, the fuel oxygen reduction unit is configured to operate substantially continuously. In such a configuration, the fuel oxygen reduction unit may still define a maximum fuel flow rate capacity. The maximum fuel flow rate capacity may still be less than the cruise condition flow rate, and the fuel provided to the gas turbine engine may not be effectively regulated at all. However, it is worth noting that it will be appreciated that, depending on the operating temperature of the gas turbine engine, the fuel flow rate, the resonance time of the fuel within the combustion section of the gas turbine engine, etc., the fuel may not need to be effectively regulated by the fuel oxygen reduction unit during, for example, cruise operation. The fuel oxygen reduction unit may still effectively handle substantially all fuel flows to the gas turbine engine during a relaxed condition.

[0124] Still refer to Figure 6In an exemplary aspect of the method 300, the method 300 further includes stopping providing a flow of fuel to a fuel nozzle of the aircraft gas turbine engine at (310), the fuel nozzle including a volume of fuel after stopping providing a flow of fuel to the fuel nozzle. In this manner, it will be appreciated that in the exemplary aspect shown, stopping providing a flow of fuel to the fuel nozzle of the aircraft gas turbine engine at (310) includes maintaining a volume of fuel in the fuel nozzle after a relaxed condition at (312). Notably, the volume of fuel remaining in the fuel nozzle may be at least approximately 10 milliliters, and stopping providing a flow of fuel to the fuel nozzle of the aircraft gas turbine engine at (310) may be immediately after a relaxed condition of the engine. In an exemplary embodiment, the volume of fuel may be at least 10 milliliters of fuel, such as at least 20 milliliters of fuel, such as at least 50 milliliters of fuel, such as at least 100 milliliters of fuel, and up to three (3) liters of fuel.

[0125] The exemplary method 300 may facilitate preventing the fuel within the fuel nozzle from coking or otherwise deteriorating beyond a threshold amount following a relaxed condition of the engine, despite the fact that the fuel may reach a potentially relatively high temperature due to heat back-absorption. For example, in the exemplary aspect depicted, it will be appreciated that operating the fuel oxygen reduction unit at (306) includes operating the fuel oxygen reduction unit at (314) to reduce the oxygen content of the fuel volume in the fuel nozzle to less than 20 parts per million, and more specifically, includes operating the fuel oxygen reduction unit at step (316) to reduce the oxygen content of the fuel volume in the fuel nozzle to less than 15 parts per million.

[0126] Notably, method 300 further includes operating the aircraft gas turbine engine during an idle condition at (315). When the aircraft gas turbine engine is operated during an idle condition at (315), the gas turbine engine defines a turbine inlet temperature greater than 1000 degrees Fahrenheit. In certain exemplary embodiments, the turbine inlet temperature T3 (which may be indicative of an overall temperature of the core) may be at least 1000 degrees Fahrenheit, such as at least 1100 degrees Fahrenheit, such as at least 1250 degrees Fahrenheit, such as at least 1400 degrees Fahrenheit, such as at least 1500 degrees Fahrenheit, such as at least 1550 degrees Fahrenheit, and up to 3500 degrees Fahrenheit during idle standard day conditions (e.g., sea level and 70 degrees Fahrenheit ambient).

[0127] Furthermore, it will be appreciated that, in accordance with the above Figures 1 to 6 As discussed above, the core of the engine may define a relatively high thermal mass. In this way, it will be appreciated that the combination of relatively high turbine inlet temperatures and relatively high thermal mass during idling, back-sucking may be relatively important, such that a reduction in the oxygen content of the fuel volume retained in the fuel nozzle is necessary to reduce the risk of fuel coking above a certain threshold.

[0128] This may allow the volume of fuel remaining in the fuel nozzle to withstand relatively high temperatures without coking beyond a threshold level.

[0129] It will be further appreciated that in certain exemplary aspects, the oxygen level of the fuel flow to the fuel nozzle can be monitored and / or reduced during other operating conditions of the engine. Figure 7 , a flow chart of a method 300 for operating a fuel system for an aviation gas turbine engine according to another exemplary aspect of the present disclosure is provided. The method 300 may be utilized with one or more of the exemplary fuel systems, gas turbine engines, etc. described above, or alternatively, may be utilized with any other suitable fuel system.

[0130] Figure 7 Method 300 is similar to Figure 6 Method 300. For example, Figure 7 The method 300 generally includes: providing a fuel flow to a fuel nozzle of an aircraft gas turbine engine during a relaxed condition at (302); operating a fuel oxygen reduction unit during a relaxed condition at (306) to reduce the oxygen content of the fuel flow provided to the fuel nozzle of the aircraft gas turbine engine; and ceasing to provide the fuel flow to the fuel nozzle of the aircraft gas turbine engine at (310).

[0131] However, for Figure 7 In exemplary aspects of the present invention, the oxygen level of the fuel flow to the fuel nozzle may be further monitored and / or reduced during other operating conditions of the engine.

[0132] For example, for Figure 7 For exemplary aspects of the invention, method 300 includes providing a fuel flow to a fuel nozzle of an aircraft gas turbine engine during a second condition separate from a relaxed condition at (320). For exemplary aspects depicted, an oxygen content of the fuel flow to the fuel nozzle of the aircraft gas turbine engine during the second condition is greater than an oxygen content of a volume of fuel in the fuel nozzle after providing the fuel flow to the fuel nozzle is stopped. For example, in certain exemplary aspects, an oxygen content of the fuel flow to the fuel nozzle of the aircraft gas turbine engine during a flight condition is at least 1.5 times the oxygen content of the volume of fuel in the fuel nozzle after providing the fuel flow to the fuel nozzle is stopped.

[0133] More specifically, for the illustrated embodiment, providing the fuel flow to the fuel nozzle during the second condition at (320) includes providing the second fuel flow to the fuel nozzle of the aircraft gas turbine engine at (322). The oxygen content of the fuel volume in the fuel nozzle after stopping providing the fuel flow to the fuel nozzle at (310) is a first value, and the oxygen content of the second fuel flow provided to the fuel nozzle during the second condition at (322) is a second value. The second value is equal to at least 1.5 times the first value. More specifically, in at least some exemplary aspects, the second value is equal to at least three times the first value, such as at least five times the first value, such as up to 100 times the first value.

[0134] In some exemplary aspects, the second condition is a flight condition of the engine. For example, in some exemplary aspects, the second condition is a take-off flight condition, a climbing flight condition, or both.

[0135] Still refer to Figure 7 In an exemplary aspect of the invention, the method further includes providing a fuel flow to a fuel nozzle of an aviation gas turbine engine during a third condition separated from a relaxed condition and a second condition at (324). Providing a fuel flow to a fuel nozzle during the third condition at step (324) includes providing a third fuel flow to a fuel nozzle of an aviation gas turbine engine during the third condition at step (326). Similar to the exemplary aspects above, the oxygen content of the third fuel flow provided to the fuel nozzle during the third condition is a third value. The third value is less than the second value and greater than the first value. With respect to such exemplary aspects, it will be appreciated that the second condition is a relatively high-power flight condition and the third condition is a relatively low-power flight condition. For example, the second condition may be a takeoff flight condition, a climb flight condition, or both, and the third condition may be a cruise flight condition.

[0136] In certain exemplary aspects, the main fuel oxygen reduction unit may be operated during the second condition and the third condition (and optionally, during the first condition) (see Figure 1 ).

[0137] In this way, it will be appreciated that the fuel flow to the fuel nozzle is higher during the second and third conditions than during the relaxed condition. In this way, the fuel is not exposed to high temperatures for a long time, and the volume of fuel passing through the fuel nozzle is greater, so that there is less risk of coking of the fuel within the nozzle.

[0138] In an exemplary aspect of the present disclosure, a method for operating a fuel delivery system for a gas turbine engine is provided. The method includes: receiving an inlet fuel flow in a fuel oxygen reduction unit for reducing the amount of oxygen in the inlet fuel flow using a stripping gas flow through a stripping gas flow path; and passing the stripping gas flow through the fuel oxygen reduction unit a single time.

[0139] Further aspects of the invention are provided by the subject matter of the following clauses: 1. A fuel oxygen reduction unit for an engine, comprising: an inlet fuel line; a stripping gas source; a contactor, the contactor being selectively fluidly connected to the stripping gas source, the inlet fuel line, or both to form a fuel / gas mixture; and a separator, the separator receiving the fuel / gas mixture, the separator being configured to separate the fuel / gas mixture into an outlet stripping gas flow and an outlet fuel flow; wherein the stripping gas flow passes through the fuel oxygen reduction unit a single time.

[0140] 2. A fuel oxygen reduction unit according to any of the preceding clauses, further comprising a valve downstream of the stripping gas source and upstream of the contactor, wherein the valve is capable of switching between a closed position and an open position, in which the stripping gas source is not in fluid communication with the contactor and in which the stripping gas flows to the contactor.

[0141] 3. A fuel oxygen reduction unit according to any preceding clause, wherein the valve switches to an open position under specified operating conditions.

[0142] 4. A fuel oxygen reduction unit according to any preceding clause, wherein the specified operating condition is a weight-on-wheels condition.

[0143] 5. A fuel oxygen reduction unit according to any preceding clause, wherein the prescribed operating condition is an engine speed condition.

[0144] 6. A fuel oxygen reduction unit according to any preceding clause, wherein the prescribed operating condition is a relaxed condition of the engine.

[0145] 7. A fuel oxygen reduction unit according to any preceding clause, wherein the fuel oxygen reduction unit defines a maximum continuous operation time of one hour or less.

[0146] 8. A fuel oxygen reduction unit according to any preceding clause, wherein the separator comprises an inlet in fluid communication with the contactor, a fuel outlet and a stripping gas outlet, the inlet receiving the fuel / gas mixture, wherein the separator is configured to separate the fuel / gas mixture into an outlet stripping gas flow and an outlet fuel flow, and to provide the outlet stripping gas flow to the stripping gas outlet and the outlet fuel flow to the fuel outlet.

[0147] 9. A fuel oxygen reduction unit according to any preceding clause, wherein the outlet stripping gas stream is vented to the atmosphere downstream of the separator.

[0148] 10. A fuel oxygen reduction unit according to any preceding clause, wherein the stripping gas source comprises a refillable inert gas bottle.

[0149] 11. A fuel oxygen reduction unit according to any preceding clause, wherein the stripping gas source comprises an inert gas generator.

[0150] 12. A fuel oxygen reduction unit according to any preceding clause, wherein the outlet fuel stream has a lower oxygen content than the inlet fuel stream, and wherein the outlet stripping gas stream has a higher oxygen content than the inlet stripping gas stream.

[0151] 13. A fuel oxygen reduction system for an engine, comprising: an inlet fuel line; a stripping gas source; a contactor, the contactor being selectively fluidly connected to the stripping gas source, the inlet fuel line, or both to form a fuel / gas mixture; a separator, the separator receiving the fuel / gas mixture, the separator being configured to separate the fuel / gas mixture into an outlet stripping gas flow and an outlet fuel flow; and a storage tank, the storage tank receiving the outlet fuel flow.

[0152] 14. A fuel oxygen reduction system according to any preceding clause, wherein the stripping gas source comprises an inert gas generator.

[0153] 15. A fuel oxygen reduction system according to any of the preceding clauses, further comprising: a main tank containing a main fuel flow; and a valve downstream of the storage tank and the main tank, wherein the valve is capable of switching between a first position and a second position, in which the main tank is in fluid communication with the engine and in which the storage tank is in fluid communication with the engine.

[0154] 16. A fuel oxygen reduction system according to any preceding clause, wherein the second valve switches to the second position under specified operating conditions.

[0155] 17. A fuel oxygen reduction system according to any preceding clause wherein the specified operating condition is a weight-on-wheels condition.

[0156] 18. A fuel oxygen reduction system according to any preceding clause, wherein the prescribed operating condition is an engine speed condition.

[0157] 19. The fuel oxygen reduction system according to any preceding clause, wherein the main tank defines a first volume, wherein the storage tank defines a second volume, and wherein the second volume is less than 20% of the first volume.

[0158] 20. A fuel oxygen reduction system according to any preceding clause, wherein the separator comprises an inlet in fluid communication with the contactor, a fuel outlet, and a stripping gas outlet, the inlet receiving the fuel / gas mixture, wherein the separator is configured to provide an outlet stripping gas flow to the stripping gas outlet, and to provide an outlet fuel flow to a storage tank via the fuel outlet.

[0159] 21. A method of operating a fuel system for an aviation gas turbine engine, the method comprising: providing a fuel flow to a fuel nozzle of the aviation gas turbine engine during a relaxed condition; operating a fuel oxygen reduction unit during the relaxed condition to reduce the oxygen content of the fuel flow provided to the fuel nozzle of the aviation gas turbine engine; and ceasing to provide the fuel flow to the fuel nozzle of the aviation gas turbine engine, the fuel nozzle including a fuel volume after ceasing to provide the fuel flow to the fuel nozzle; wherein operating the fuel oxygen reduction unit comprises operating the fuel oxygen reduction unit to reduce the oxygen content of the fuel volume in the fuel nozzle to less than 20 parts per million.

[0160] 22. The method according to one or more of these clauses, wherein operating the fuel oxygen reduction unit comprises operating the fuel oxygen reduction unit to reduce the oxygen content of the fuel volume in the fuel nozzle to less than 15 parts per million.

[0161] 23. The method according to one or more of these clauses, further comprising: operating the aircraft gas turbine engine during an idle condition, wherein the gas turbine engine defines a turbine inlet temperature greater than 1000 degrees Fahrenheit when the aircraft gas turbine engine is operated during the idle condition.

[0162] 24. Method according to one or more of these clauses, wherein the aviation gas turbine engine comprises a core defining a thermal mass.

[0163] 25. The method according to one or more of these clauses, wherein operating the fuel oxygen reduction unit comprises operating the fuel oxygen reduction unit substantially exclusively during relaxed conditions.

[0164] 26. A method according to one or more of these clauses, wherein the fuel oxygen reduction unit is limited to a maximum operating time of one hour or less per flight mission.

[0165] 27. A method according to one or more of these clauses, wherein the aviation gas turbine engine is incorporated into an aircraft, wherein the aircraft defines a maximum fuel capacity, wherein the fuel oxygen reduction unit defines a maximum fuel throughput volume per flight mission, and wherein the maximum fuel throughput volume is less than 10 percent of the maximum fuel capacity of the aircraft.

[0166] 28. A method according to one or more of these clauses, further comprising: operating an aviation gas turbine engine during cruise conditions, wherein operating the aviation gas turbine engine during cruise conditions comprises providing a fuel flow to a combustion section of the aviation gas turbine engine at a cruise condition flow rate, wherein a fuel oxygen reduction unit limits a maximum fuel flow rate capacity, and wherein the maximum fuel flow rate capacity of the fuel oxygen reduction unit is less than the cruise condition flow rate.

[0167] 29. A method according to one or more of these clauses, further comprising: providing a fuel flow to a fuel nozzle of an aircraft gas turbine engine during a second condition separated from the relaxation condition, wherein the oxygen content of the fuel flow to the fuel nozzle of the aircraft gas turbine engine during the second condition is greater than the oxygen content of the fuel volume in the fuel nozzle after stopping providing the fuel flow to the fuel nozzle.

[0168] 30. A method according to one or more of these clauses, wherein the oxygen content of the fuel flow to a fuel nozzle of an aviation gas turbine engine during flight conditions is at least 1.5 times the oxygen content of the fuel volume in the fuel nozzle after the fuel flow to the fuel nozzle is stopped.

[0169] 31. A method according to one or more of these clauses, further comprising: providing a second fuel flow to a fuel nozzle of an aviation gas turbine engine during a second condition separated from the relaxation condition, wherein the oxygen content of the fuel volume in the fuel nozzle after stopping providing the fuel flow to the fuel nozzle is a first value, wherein the oxygen content of the second fuel flow provided to the fuel nozzle during the second condition is a second value, and wherein the second value is equal to at least 1.5 times the first value.

[0170] 32. The method according to one or more of these clauses, wherein the second value is equal to at least 3 times the first value.

[0171] 33. A method according to one or more of these clauses, wherein the second condition is a flight condition.

[0172] 34. A method according to one or more of these clauses, wherein the second condition is a take-off flight condition, a climb flight condition, or both.

[0173] 35. A method according to one or more of these clauses, further comprising: providing a third fuel flow to a fuel nozzle of an aviation gas turbine engine during a third condition separated from the relaxation condition, wherein the oxygen content of the third fuel flow provided to the fuel nozzle during the third condition is a third value, wherein the third value is less than the first value, wherein the second condition is a relatively high power flight condition, and wherein the third condition is a relatively low power flight condition.

[0174] 36. A method according to one or more of these clauses, wherein the fuel volume in the fuel nozzle is at least 10 ml of fuel.

[0175] 37. The method according to one or more of these clauses, wherein ceasing to provide fuel flow to a fuel nozzle of an aviation gas turbine engine comprises: maintaining a fuel volume in the fuel nozzle during and after a slack condition.

[0176] 38. A method for operating a fuel delivery system for a gas turbine engine is provided. The method comprises: receiving an inlet fuel flow in a fuel oxygen reduction unit for reducing the amount of oxygen in the inlet fuel flow using a stripping gas flow through a stripping gas flow path; and passing the stripping gas flow through the fuel oxygen reduction unit a single time.

[0177] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems, and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not differ substantially from the literal language of the claims.

[0178] Although the present disclosure has been described as having an exemplary design, the present disclosure may be further modified within the spirit and scope of the present disclosure. The application is therefore intended to cover any variation, use or transformation of the present disclosure using the general principles of the present disclosure. In addition, the application is intended to cover such deviations from the present disclosure as falling within known or customary practices in the field to which the present disclosure belongs and falling within the limitations of the appended claims.

Claims

1. A method for operating a fuel delivery system for a gas turbine engine, comprising: receiving an inlet fuel stream in a fuel oxygen reduction unit for reducing an amount of oxygen in the inlet fuel stream using a stripping gas flow through a stripping gas flow path; as well as The stripping gas stream is passed through the fuel oxygen reduction unit a single time.

2. The method according to claim 1, characterized in that Further including: The gas turbine engine is operated during an idle condition, wherein the gas turbine engine defines a turbine inlet temperature greater than 1000 degrees Fahrenheit when the gas turbine engine is operated during the idle condition.

3. The method according to claim 1, characterized in that Operating the fuel oxygen reduction unit includes operating the fuel oxygen reduction unit to reduce an oxygen content of a fuel volume in a fuel nozzle of the gas turbine engine to less than 15 parts per million.

4. The method according to claim 1, characterized in that: Operating the fuel oxygen reduction unit includes operating the fuel oxygen reduction unit substantially exclusively during relaxation conditions.

5. The method according to claim 4, characterized in that Further includes A first fuel flow is provided to a fuel nozzle of the gas turbine engine during a second condition separate from the relaxed condition, wherein a first oxygen content of the first fuel flow to the fuel nozzle of the gas turbine engine during the second condition is greater than a second oxygen content of the fuel volume in the fuel nozzle after supply of the first fuel flow to the fuel nozzle is stopped.

6. The method according to claim 5, characterized in that A first oxygen content of a first fuel flow to a fuel nozzle of the gas turbine engine during the second condition is at least 1.5 times a second oxygen content of a fuel volume in the fuel nozzle after provision of the first fuel flow to the fuel nozzle is stopped.

7. The method according to claim 5, characterized in that The second condition is a flight condition.

8. The method according to claim 5, characterized in that The second condition is a take-off flight condition, a climb flight condition, or both.

9. The method according to claim 5, characterized in that Ceasing to provide the first flow of fuel to a fuel nozzle of the gas turbine engine includes maintaining a fuel volume in the fuel nozzle during and after the relaxed condition.

10. The method according to claim 4, characterized in that Further including: A second fuel flow is provided to a fuel nozzle of the gas turbine engine during a second condition separate from the relaxed condition, wherein a first oxygen content of a fuel volume in the fuel nozzle is a first value after providing the second fuel flow to the fuel nozzle is stopped, wherein a second oxygen content of the second fuel flow provided to the fuel nozzle during the second condition is a second value, and wherein the second value is equal to at least 1.5 times the first value.

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