Fuel delivery system with a fuel oxygen reduction unit

Abstract

A fuel system for an aircraft having a fuel source is provided. The system includes a fuel oxygen reduction unit that defines a liquid fuel supply path, a stripping gas supply path, a liquid fuel outlet path, and a stripping gas return path, wherein the stripping gas return path is configured to be in fluid communication with an air source separated from the fuel source, selectively in fluid communication with the fuel source of the aircraft, or both.

Description

[0001] Cross - Reference to Related Applications

[0002] This application is a partial continuation of U.S. Application No. 16 / 179,077, filed on November 2, 2018, which is hereby incorporated by reference in its entirety. Technical Field

[0003] The present subject matter generally relates to a fuel oxygen reduction unit for a fuel delivery system of a vehicle. Background Art

[0004] Typical aircraft propulsion systems include 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 an inlet of the compressor section, where one or more axial compressors gradually compress the air until it reaches the combustion section. Fuel is mixed with the compressed air and burned within the combustion section to provide combustion gases. The combustion gases are transferred from the combustion section to the turbine section. The combustion airflow through the turbine section drives the turbine section and then is transferred through the exhaust section, e.g., to the atmosphere.

[0005] Certain operations and systems of gas turbine engines and aircraft can generate a relatively large amount of heat. Fuel has been determined to be an effective heat sink for receiving at least a portion of such heat during operation, at least in part due to its heat capacity and the improvement in combustion operation efficiency that can result from burning high - temperature fuel. However, heating fuel without properly conditioning it can cause fuel "coking", or the formation of solid particles that can clog certain components of the fuel system, such as fuel nozzles. Reducing the oxygen content in the fuel can effectively reduce the likelihood of fuel coking beyond an unacceptable amount. For this purpose, fuel oxygen reduction systems have been proposed. These fuel oxygen reduction systems are generally located at the engine to reduce the oxygen content of the fuel provided to the engine.

[0006] In addition, certain fuel delivery systems for aircraft including gas turbine engines generally also include a system for removing the oxygen content of the air in the ullage of a fuel tank (e.g., a fuel tank from which fuel is provided to the gas turbine engine). Reducing the oxygen content of such gases can reduce the risk of fire within the fuel tank. Systems for removing the oxygen content of the air / gas in the ullage generally operate differently from fuel oxygen reduction systems (for reducing the oxygen content of liquid fuel).

[0007] The inventors of the present disclosure have found that operating each of these various systems can be inefficient. Thus, a system for reducing the oxygen content of liquid fuel provided to each individual aircraft engine and the oxygen content of the gas in the ullage of a fuel tank would be useful. Summary of the Invention

[0008] Aspects and advantages of the present invention will be set forth in the following description, or will be apparent from the description, or may be understood by practicing the present invention.

[0009] In one exemplary embodiment of the present disclosure, a fuel system for an aircraft is provided. The fuel system includes a fuel source; and a fuel oxygen reduction unit that defines a liquid fuel supply path, a stripping gas supply path, a liquid fuel outlet path, and a stripping gas return path, wherein the stripping gas return path is in fluid communication with the fuel source and optionally selectively in fluid communication with the fuel source.

[0010] Technical Solution 1. A fuel system for an aircraft having a fuel source, the system comprising:

[0011] A fuel oxygen reduction unit that defines a liquid fuel supply path, a stripping gas supply path, a liquid fuel outlet path, and a stripping gas return path, wherein the stripping gas return path is configured to be in fluid communication with an air source separated from the fuel source, selectively in fluid communication with the fuel source of the aircraft, or both.

[0012] Technical Solution 2. The fuel system according to any of the preceding technical solutions, wherein the stripping gas return path is configured to be in fluid communication with an air source for receiving an air flow from the air source.

[0013] Technical Solution 3. The fuel system according to any of the preceding technical solutions, wherein the air source is at least one of an air cycle machine, a gas turbine engine of the aircraft, or a device for collecting ambient air flow.

[0014] Technical Solution 4. The fuel system according to any of the preceding technical solutions, wherein the air flow from the air source is a first air flow, and wherein the stripping gas supply path is further in fluid communication with the fuel source air flow for receiving a second air flow from the air source.

[0015] Technical Solution 5. The fuel system according to any of the preceding technical solutions, wherein the stripping gas supply path includes a first stripping gas flow path extending from the fuel source, and wherein the fuel system includes a check valve in the first stripping gas flow path.

[0016] Technical Solution 6. The fuel system according to any of the preceding technical solutions, wherein the first air flow from the air source is provided at a first temperature and a first pressure, wherein the second air flow from the fuel source is provided at a second temperature and a second pressure, and wherein the first temperature is greater than the second temperature, the first pressure is greater than the second pressure, or both.

[0017] Technical solution 7. The fuel system according to any of the foregoing technical solutions, wherein the fuel oxygen reduction unit comprises:

[0018] A gas oxygen reduction unit, the gas oxygen reduction unit being located in the stripping gas supply path or the stripping gas return path, and wherein the fuel content in the second gas stream from the fuel source assists the operation of the gas oxygen reduction unit.

[0019] Technical solution 8. The fuel system according to any of the foregoing technical solutions, wherein the fuel system further comprises:

[0020] A control valve, the control valve being in fluid communication with the stripping gas supply path for controlling the first flow rate of the first gas stream, the second flow rate of the second gas stream, or both; and

[0021] A controller, the controller being operably coupled to the control valve, the controller being configured to receive data indicative of an operating parameter of the fuel oxygen reduction unit and to change the first flow rate, the second flow rate, or both in response to the received data indicative of the operating parameter of the fuel oxygen reduction unit.

[0022] Technical solution 9. The fuel system according to any of the foregoing technical solutions, wherein the fuel source comprises a fuel tank, and wherein the fuel oxygen reduction unit further comprises:

[0023] A vent pump, the vent pump being in fluid communication with the stripping gas supply path.

[0024] Technical solution 10. The fuel system according to any of the foregoing technical solutions, wherein the fuel source comprises a fuel tank, and wherein the stripping gas return path is in fluid communication with the vent of the fuel tank.

[0025] Technical solution 11. The fuel system according to any of the foregoing technical solutions, wherein the fuel source comprises a fuel tank, and wherein the vent of the fuel tank is configured to provide an excess gas flow to a location separated from the fuel oxygen reduction unit.

[0026] Technical solution 12. The fuel system according to any of the foregoing technical solutions, wherein the liquid fuel supply path is fluidly connected to the fuel source, and wherein the fuel oxygen reduction unit is configured to receive a liquid fuel flow from the fuel source.

[0027] Technical solution 13. The fuel system according to any of the foregoing technical solutions, wherein the fuel oxygen reduction unit comprises:

[0028] A gas oxygen reduction unit positioned in the stripping gas supply path or the stripping gas return path; and

[0029] A fuel oxygen reduction assembly fluidly connected to the liquid fuel supply path and the liquid fuel return path and further in gas flow communication with the stripping gas supply path and the stripping gas return path.

[0030] Technical solution 14. The fuel system according to any of the foregoing technical solutions, wherein the gas oxygen reduction unit is a first gas oxygen reduction unit positioned in the stripping gas supply path, and wherein the fuel oxygen reduction unit further includes a second gas oxygen reduction unit in the stripping gas return path.

[0031] Technical solution 15. The fuel system according to any of the foregoing technical solutions, wherein the fuel oxygen reduction assembly includes:

[0032] A contactor fluidly connected to the liquid fuel supply path and the stripping gas supply path for mixing a liquid fuel stream from the liquid fuel supply path with a stripping gas stream from the stripping gas supply path to form a fuel / gas mixture; and

[0033] A separator fluidly connected to the contactor for receiving the fuel / gas mixture and separating the fuel / gas mixture back into the stripping gas stream and the liquid fuel stream, the separator being fluidly connected to the liquid fuel outlet path and the stripping gas return path for providing the liquid fuel stream to the liquid fuel outlet path and the stripping gas stream to the stripping gas return path.

[0034] Technical solution 16. An aircraft comprising:

[0035] A fuel source; and

[0036] A fuel system including a fuel oxygen reduction unit defining a liquid fuel supply path, a stripping gas supply path, a liquid fuel outlet path, and a stripping gas return path, wherein the stripping gas return path is configured to be in fluid communication with an air source separated from the fuel source, selectively in fluid communication with the fuel source of the aircraft, or both.

[0037] Technical solution 17. A method of operating an aircraft fuel system, the aircraft fuel system including a fuel source, the method comprising:

[0038] Using a fuel oxygen reduction unit, wherein using the fuel oxygen reduction unit includes

[0039] Reduce the oxygen content in the liquid fuel from the fuel source; and

[0040] Provide an oxygen-reduced gas stream to the fuel source.

[0041] Aspect 18. The method according to any of the preceding aspects, wherein using the fuel oxygen reduction unit further comprises receiving a gas stream from the stripping gas supply path of the fuel oxygen reduction unit, and receiving the gas stream from the stripping gas supply path of the fuel oxygen reduction unit comprises: receiving data indicating an operating parameter of the fuel oxygen reduction unit; and in response to the received data indicating the operating parameter of the fuel oxygen reduction unit, changing a first flow rate of the gas from an air source, changing a second flow rate of the gas from the fuel source, or both.

[0042] Aspect 19. The method according to any of the preceding aspects, wherein the operating parameter of the fuel oxygen reduction unit is the temperature of the gas stream to the stripping gas supply path, the pressure of the gas stream to the stripping gas supply path, the fuel content of the gas stream to the stripping gas supply path, or a combination thereof.

[0043] Aspect 20. The method according to any of the preceding aspects, wherein providing the oxygen-reduced gas stream to the fuel source comprises providing the oxygen-reduced gas stream to the ullage of the fuel system.

[0044] These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and the appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] A complete and open disclosure of the present invention, including the best mode thereof for those skilled in the art, is set forth in the specification with reference to the accompanying drawings, in which:

[0046] Figure 1 is a top view of an aircraft according to various exemplary embodiments of the present disclosure.

[0047] Figure 2 is a schematic diagram of a fuel delivery system according to an exemplary embodiment of the present disclosure.

[0048] Figure 3 is a partially enlarged schematic diagram of a part of a fuel delivery system according to an exemplary embodiment of the present disclosure.

[0049] Figure 4 is according to an exemplary embodiment of the present disclosure Figure 3Schematic partial enlarged cross-sectional view of the fuel gas separator of an exemplary fuel oxygen reduction unit of a fuel delivery system.

[0050] Figure 5 Is a partial enlarged schematic view of a part of a fuel delivery system according to an exemplary embodiment of the present disclosure.

[0051] Figure 6 Is a partial enlarged schematic view of a part of a fuel delivery system according to another exemplary embodiment of the present disclosure.

[0052] Figure 7 Is a partial enlarged schematic view of a part of a fuel delivery system according to yet another exemplary embodiment of the present disclosure.

[0053] Figure 8 Is a partial enlarged schematic view of a part of a fuel delivery system according to yet another exemplary embodiment of the present disclosure.

[0054] Figure 9 Is a partial enlarged schematic view of a part of a fuel delivery system according to yet another exemplary embodiment of the present disclosure.

[0055] Figure 10 Is a flowchart of a method for operating a fuel system of an aircraft according to an exemplary aspect of the present disclosure. Detailed Description

[0056] Reference will now be made in detail to embodiments of the present invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and alphabetical labels to refer to features in the drawings. Like or similar labels in the drawings and the description are used to refer to like or similar parts of the present invention.

[0057] As used herein, the terms "first", "second", and "third" may be used interchangeably to distinguish one component from another and are not intended to denote the position or importance of the individual components.

[0058] The terms "upstream" and "downstream" refer to the relative direction with respect to the fluid flow in a fluid passage. For example, "upstream" refers to the direction from which the fluid flows, and "downstream" refers to the direction to which the fluid flows.

[0059] The terms "coupled", "fixed", "attached to" refer to direct coupling, fixing, or attachment, as well as indirect coupling, fixing, or attachment through one or more intermediate components or features, unless otherwise specified herein.

[0060] The singular forms "a", "an", and "the" include plural objects unless the context clearly indicates otherwise.

[0061] As used throughout the specification and claims herein, approximate language is used to modify any quantitative representation that may vary without resulting in a change in the basic function to which it is related. Thus, a value modified by a term such as "about," "approximately," or "substantially" is not limited to the exact value specified. In at least some instances, the approximate language may correspond to the precision of the instrument used to measure the value, or the precision of the method or machine used to fabricate or construct the component and / or system. For example, the approximate language may refer to within a margin of 10 percent.

[0062] Here and throughout the specification and claims, ranges are limited and combined and interchanged, and this range is recognized and includes all subranges subsumed therein, unless the context or language indicates otherwise. For example, all ranges disclosed herein include endpoints, and the endpoints can be combined independently of each other.

[0063] Now referring to the figures, where like numerals indicate like elements throughout the figures, Figure 1 A top view of an exemplary aircraft 10 is provided that may be combined with various embodiments of the present invention. The aircraft 10 defines a longitudinal centerline 14 extending therethrough, a vertical direction (not shown), a lateral direction L, a front end 16, and a rear end 18. Additionally, the aircraft 10 includes a fuselage 12 extending longitudinally from the front end 16 of the aircraft 10 toward the rear end 18 of the aircraft 10, and a pair of wings 20. A first wing 20A of such wings 20 extends laterally outward from the port side 22 of the fuselage 12 with respect to the longitudinal centerline 14, and a second wing 20B of such wings 20 extends laterally outward from the starboard side 24 of the fuselage 12 with respect to the longitudinal centerline 14. For the depicted exemplary embodiment, each wing 20 includes one or more leading-edge flaps 26 and one or more trailing-edge flaps 28. The aircraft 10 further includes a vertical stabilizer 30 having a rudder flap 32 for yaw control, and a pair of horizontal stabilizers 34 each having an elevator flap 36 for pitch control. The fuselage 12 additionally includes an outer surface or skin 38. However, it should be recognized that in other exemplary embodiments of the present disclosure, additionally or alternatively, the aircraft 10 may include any other suitable configuration of stabilizers that may or may not extend directly along the vertical direction or the horizontal / lateral direction L. Additionally, the aircraft 10 may include any other suitable configuration of the wings 20, fuselage 12, etc. (e.g., canard configuration, blended wing configuration, etc.).

[0064] Figure 1Exemplary aircraft 10 includes a propulsion system 50, referred to herein as "system 50". Exemplary system 50 includes one or more aircraft engines 52. For example, the depicted embodiment includes multiple aircraft engines 52, each aircraft engine configured to be mounted to the aircraft 10, such as to one of a pair of wings 20. More particularly, for the depicted embodiment, the aircraft engine 52 is configured as a gas turbine engine, such as a turbofan engine, and is attached and suspended below the wing 20 in an under-wing configuration (it should be appreciated that in other embodiments, the aircraft engine 52 can be any other suitable engine that is at least partially a combustion engine). For example, the aircraft engine 52 includes a first aircraft engine 52A and a second aircraft engine 52B. The first aircraft engine 52A is configured to be mounted to the first wing 20A of the aircraft 10, while the second aircraft engine 52 is configured to be mounted to the second wing 20B of the aircraft 10 (i.e., on opposite sides of the aircraft 10). It will be recognized that although Figure 1 only two aircraft engines 52 are depicted, in other embodiments, the propulsion system 50 of the aircraft 10 can have any other suitable number and type of aircraft engines 52 mounted in any other appropriate location (e.g., on the wing, on the fuselage at the tail end of the aircraft 10, on one or more stabilizer wings, etc.).

[0065] As further depicted in Figure 1 , the aircraft 10 includes a fuel delivery system 100. More particularly, the fuel delivery system 100 is generally configured to supply a quantity of fuel to the aircraft engines 52 (i.e., Figure 1 the first aircraft engine 52A and the second aircraft engine 52B of the depicted embodiment) during operation. More particularly, for the illustrated embodiment, the fuel delivery system 100 is configured to provide fuel with a relatively low oxygen content to the aircraft engines 52, as will be explained in more detail below. In such a manner, it will be recognized that the fuel delivery system 100 generally includes a fuel source 102 (e.g., a fuel tank) and a fuel oxygen reduction unit 104. The fuel oxygen reduction unit 104 is configured to receive fuel from the fuel source 102, reduce the oxygen content of such fuel, and provide such fuel to the aircraft engines 52. Additionally, as will be explained in more detail with reference to Figure 2 and 3 , the fuel oxygen reduction system 104 is further configured to reduce the oxygen content of the air in the ullage of the fuel source 102. Notably, as used herein, the term "fuel oxygen reduction unit" generally refers to a device capable of reducing the free oxygen content of fuel, such as a fuel oxygen conversion unit, a fuel oxygen extraction unit, etc.

[0066] However, it will be recognized that in other exemplary embodiments, the aircraft 10 and / or the engine 52 may have any other suitable configuration. For example, in other embodiments, the aircraft 10 may have other wing and / or fuselage designs, number and / or configuration or positioning of engines, etc. Additionally, in other embodiments, the aircraft 10 may be, for example, a vertical takeoff and landing aircraft, such as a helicopter. Other embodiments are also contemplated.

[0067] More particularly, now briefly referring to Figure 2 , there is provided a schematic view of a fuel delivery system 100 that may be incorporated into an aircraft 10 such as Figure 1 . As depicted, the fuel delivery system 100 generally includes a fuel source 102 and a fuel oxygen reduction unit 104, and defines a plurality of flow paths. In particular, for the illustrated embodiment, the fuel delivery system 100 and the fuel oxygen reduction unit 104 generally define a liquid fuel supply path 106, a stripping gas supply path 108, a liquid fuel outlet path 110, and a stripping gas return path 112. Both the stripping gas supply path 108 and the stripping gas return path 112 are in fluid communication with the fuel source 102, and optionally in selective fluid communication with the fuel source, to receive an air stream 114 (which is a stripping gas, as will be explained below) from the fuel source 102, and to provide the air stream 114 back to the fuel source 102. Similarly, for the illustrated embodiment, the liquid fuel supply path 106 is in fluid communication with the fuel source 102 to receive a liquid fuel stream 116 therefrom. Notably, for the illustrated embodiment, the fuel source 102 is configured as a fuel tank. Within the fuel tank, the fuel source 102 includes a quantity of liquid fuel and a quantity of vapor / air / gas. The space within the tank that contains the vapor / air / gas (e.g., within the tank and above the fuel) may generally be referred to as ullage 118. During operation, it will be recognized that the fuel oxygen reduction unit 104 is generally configured to: receive an air / air stream 114 from the ullage 118 of the fuel source 102 and a liquid fuel stream 116 from the fuel source 102, to reduce the oxygen content of each, to provide a gas 114 stream of relatively low oxygen content back to the ullage 118, and to provide a stream of relatively low oxygen content of the liquid fuel 116 to the aircraft engine 52. By reducing the oxygen content of the vapor / air / gas in the ullage 118, the risk of fire or conflagration occurring within the tank in the event of a spark can be reduced. Additionally, by reducing the oxygen content of the liquid fuel 116 provided to the engine 52, more heat can be added thereto, where the risk of coking is reduced (allowing for increased efficiency of the combustion process and providing an effective heat sink).

[0068] In particular, for the illustrated embodiment, the fuel delivery system 100 is configured to supply fuel 116 having a relatively low oxygen content from the fuel oxygen reduction unit 104 to each of a plurality of aircraft engines 52, which for the illustrated embodiment includes a first aircraft engine 52A, a second aircraft engine 52B, up to an "Nth" aircraft engine 52N (e.g., three, four, five, six, etc. aircraft engines 52). In this manner, it will be appreciated that the fuel deoxygenation unit 104 is fluidly coupled to each of the plurality of aircraft engines 52 via the liquid fuel outlet path 110 and is thus configured to supply liquid fuel 116 having a relatively low oxygen content to each such engine 52.

[0069] As will be discussed in more detail below, the fuel delivery system 100 according to such an exemplary embodiment is capable of maintaining air having a lower oxygen content within the plenum 118 while also supplying fuel having a lower oxygen content to the plurality of aircraft engines 52.

[0070] Notably, for the illustrated embodiment, the fuel delivery system 100 further includes a return valve 120 and a return line 122 for returning a quantity of the relatively low oxygen content liquid fuel to the fuel source 102 in the event that the aircraft engines 52 do not require such fuel. However, in other embodiments, the system 100 may be configured without the return valve 120 and the return line 122 and instead may regulate the liquid fuel flow 116 in other suitable ways.

[0071] Now referring to Figure 3 , there is provided a more detailed schematic view of a fuel delivery system 100 for an aircraft 10 according to an exemplary embodiment of the present disclosure. In at least some exemplary embodiments, Figure 3 the exemplary fuel delivery system 100 depicted in Figure 1 may be incorporated into, for example, the exemplary aircraft 10 described above with reference to Figure 2The exemplary fuel delivery system 100 is configured in a similar manner. Thus, it will be appreciated that the fuel delivery system 100 generally includes a fuel source 102 and a fuel oxygen reduction unit 104, and the fuel delivery system 100 and the fuel oxygen reduction unit 104 generally define a liquid fuel supply path 106, a stripping gas supply path 108, a liquid fuel outlet path 110, and a stripping gas return path 112. Both the stripping gas return path 112 and the stripping gas supply path 108 are in gas flow communication with the fuel source 102. Additionally, for the depicted embodiment, the liquid fuel supply path 106 of the fuel oxygen reduction unit 104 is in fluid communication with the fuel source 102. In this manner, it will be appreciated that the fuel oxygen reduction unit 104 is generally configured to receive a liquid fuel stream 116 from the fuel source 102 and is also configured to receive an air stream 114 (referred to herein as "stripping gas") that also originates from the fuel source 102. Additionally, as will be described in detail below, the fuel oxygen reduction unit 104 is configured to return the stripping gas 114 to the fuel source 102. As noted with reference to the above embodiment, for Figure 3 the embodiment, the fuel source 102 generally includes a quantity of liquid fuel 116 and defines a ullage 118 above the liquid fuel 116. The gas received through the stripping gas supply path 108 is received from the ullage 118, and the gas provided to the fuel source 102 through the stripping gas return path 112 is provided to the ullage 118.

[0072] To assist the flow of the stripping gas 114 from the fuel source 102 or, more specifically, from the ullage 118 of the fuel source 102, the fuel delivery system 100 includes a ullage pump 124 that is in gas flow communication with the ullage 118 of the fuel source 102 and the stripping gas supply path 108 of the fuel oxygen reduction unit 104. Similarly, to assist the flow of the liquid fuel 116 from the fuel source 102, the fuel delivery system 100 includes a fuel pump 126 that is in fluid communication with the fuel source 102 and the liquid fuel supply path 106.

[0073] Additionally, for the depicted embodiment, the fuel oxygen reduction unit 104 generally includes a contactor 128 and a fuel gas separator 130. Additionally, the exemplary fuel oxygen reduction unit 104 defines a stripping gas flow path 132. For the illustrated embodiment, the stripping gas flow path 132 includes the stripping gas supply path 108 and the stripping gas return path 112. Thus, the stripping gas flow path 132 generally extends from a location upstream of the contactor 128 through the contactor 128 and the separator 130 to a location downstream of the separator 130. In certain exemplary embodiments, the stripping gas flow path 132 may be formed by any combination of one or more conduits, tubes, pipes, etc., and the structure of the components within the stripping gas flow path 132.

[0074] 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. In particular, for the depicted embodiments, the stripping gas 114 consists essentially of the gas from the void 118 of the fuel source 102. Thus, the stripping gas 114 may consist primarily of air. Additionally or alternatively, the stripping gas 114 may be any other suitable gas, such as an inert gas or a substantially inert gas.

[0075] Still referring to the depicted embodiments, the fuel gas separator 130 is a mechanically driven fuel gas separator 130 that is mechanically coupled to and driven by a power source 134. For Figure 3 the embodiments, the power source 134 that drives the fuel gas separator 130 may be any suitable power source, such as an electric motor, a hydraulic motor, a pneumatic motor, a combustion engine, a power source shared with other components, etc. However, in other embodiments, the fuel gas separator 130 and the power source 134 that drives the fuel gas separator 130 may be configured in any other suitable manner.

[0076] As will be explained in more detail below, for Figure 3 the embodiments, the contactor 128 generally defines a gas inlet 136, a liquid fuel inlet 138, and a fuel / gas mixture outlet 140. Additionally, the fuel gas separator 130 generally defines a gas outlet 142, a liquid fuel outlet 144, and a fuel / gas mixture inlet 146. The gas inlet 136 of the contactor 128 is in fluid communication with the stripping gas supply path 108, the liquid fuel inlet 138 of the contactor 128 is fluidly connected to the liquid fuel supply path 106, and the fuel / gas mixture outlet 140 of the contactor 128 is fluidly coupled to the inlet 146 of the fuel gas separator 130. Additionally, the gas outlet 142 of the separator 130 is in fluid communication with the stripping gas return path 112 of the stripping gas flow path 132, and the liquid fuel outlet 144 of the separator 130 is fluidly connected to the liquid fuel outlet path 110.

[0077] Furthermore, for Figure 3The exemplary fuel oxygen reduction unit 104 depicted in Figure 5 also includes a first catalyst 148 and a second catalyst 150. For the illustrated embodiment, the first catalyst 148 and the second catalyst 150 are each arranged in series along the stripping gas flow path 132. More particularly, for the illustrated embodiment, the first catalyst 148 is positioned at a location in the stripping gas flow path 132 upstream of the contactor 128 (and downstream of the dead space 118), and the second catalyst 150 is positioned at a location in the stripping gas flow path 132 downstream of the separator 130 (and upstream of the dead space 118). However, it will be appreciated that in other embodiments, the listed components may be provided in any suitable flow order, may not include all of the listed components (e.g., see Figure 5 ), or may include additional components not listed.

[0078] In addition, Figure 3 the exemplary fuel oxygen reduction unit 104 depicted in

[0079] also includes a heat exchanger 152. For the illustrated embodiment, the heat exchanger 152 is positioned in thermal communication with the stripping gas flow path 132 at a location downstream of the second catalyst 150 and upstream of the dead space 118, and more particularly, in fluid communication with the stripping gas flow path. In addition, for the illustrated embodiment, the heat exchanger 152 is in thermal communication with the liquid fuel supply path 106, or more particularly, in fluid communication with the liquid fuel flowing through the liquid fuel supply path 106, such that the liquid fuel supply path 106, or the liquid fuel 116 flowing therethrough, can receive heat from the stripping gas stream 114 returning through the stripping gas return path 112 downstream of the second catalyst 150. This can thus reduce the temperature of the gas flowing into the dead space 118 of the fuel source 102.

[0080] In addition, within the first catalytic converter 148, the oxygen content of the stripping gas 114 is reduced. More particularly, within the first catalytic converter 148, the potentially relatively oxygen-rich stripping gas 114 may react to reduce its oxygen content. However, it will be appreciated that the first catalytic converter 148 may be configured in any suitable manner to reduce the oxygen content of the stripping gas 114. For example, in some embodiments, the first catalytic converter 148 may be configured to cause the stripping gas 114 rich in fuel vapor to react with elements within the first catalytic converter 148 to provide a relatively oxygen-free stripping gas 114 upon exit. For example, the first catalytic converter 148 may include a geometry of catalytic components through which the relatively oxygen-rich stripping gas 114 flows to reduce its oxygen content. Due to the stripping gas 114 originating from the fuel source 102 (i.e., coming into contact with the fuel therein), such reactions may at least partially utilize the fuel content of the stripping gas 114. In one or more of these configurations, by-products may be produced, such as water. If produced, the water may be in vapor form and may continue to be part of the stripping gas 114. Alternatively, if produced, the water or other by-products may be withdrawn from the first catalytic converter 148 (in a conduit not depicted in the Figure 3 embodiments). In one or more of these embodiments, the first catalytic converter 148 (or other gas oxygen reduction units discussed below) may be configured to reduce the oxygen content of the stripping gas 114 by mass to less than about three percent (3%) oxygen (O2), such as less than one percent (1%) oxygen (O2) by mass.

[0081] The stripping gas 114 is provided from the first catalytic converter 148 to the gas inlet 136 of the contactor 128. At the same time, the liquid fuel 116 is pushed by the fuel pump 126 from the fuel source 102 and through the liquid fuel supply path 106. The liquid fuel 116 flows from the fuel pump 126 through the heat exchanger 152, where the liquid fuel 116 may receive heat from the stripping gas stream 114 through the stripping gas return path 112. The liquid fuel 116 still flows from the heat exchanger 152 through the liquid fuel supply path 106 to the liquid fuel inlet 138 of the contactor 128. Within the contactor 128, the stripping gas 114 received through the gas inlet 136 is mixed with the liquid fuel stream 116 received through the liquid fuel inlet 138 to produce a fuel / gas mixture 156. The fuel gas mixture 156 produced within the contactor 128 is provided to the inlet 146 of the fuel gas separator 130.

[0082] Generally, it will be appreciated that during operation of the fuel oxygen reduction unit 104, the liquid fuel 116 provided to the contactor 128 via the liquid fuel supply path 106 may have a relatively high oxygen content. In contrast, the stripping gas 114 provided to the contactor 128 may have a relatively low oxygen content or other specific chemical structure. Within the contactor 128, the liquid fuel 116 is mixed with the stripping gas 114 to produce a fuel / gas mixture 156. As a result of such mixing, physical exchange may occur, whereby at least a portion of the oxygen within the fuel 116 is transferred to the stripping gas 114 such that the fuel component of the mixture 156 has a relatively low oxygen content (compared to the fuel 116 provided via the liquid fuel supply path 106), and the stripping gas 114 component of the mixture 146 has a relatively high oxygen content (compared to the stripping gas 114 provided to the contactor 128 via the stripping gas supply path 108).

[0083] Reference is now also briefly made to Figure 4 which provides Figure 3 a partially enlarged schematic cross-sectional view of an exemplary fuel gas separator 130, it will be appreciated that within the fuel gas separator 130, the stripping gas 114 having a relatively low oxygen content is generally separated from the fuel 116 having a relatively high oxygen content. In particular, for the illustrated embodiment, the fuel gas separator 130 defines a central axis 158 and a circumferential direction C extending about the central axis 158. Additionally, the fuel gas separator 130 is configured as a mechanically driven fuel gas separator 130, or more particularly, as a rotary / centrifugal fuel gas separator 130. Accordingly, the fuel gas separator 130 includes an input shaft 160 and a separation assembly 162, the input shaft 160 being mechanically coupled to the separation assembly 162, and the two components together being rotatable about the central axis 158. Further, the input shaft 160 may be mechanically coupled to and driven by a suitable power source 134, for example.

[0084] Additionally, the depicted exemplary separation assembly 162 generally includes an inner filter 164 disposed along the central axis 158, and a plurality of vanes 166 positioned radially outward of the inner filter 164. During operation, rotation of the separation assembly 162 about the central axis 158, and more particularly, rotation of the plurality of vanes 166 about the central axis 158 (i.e., in the circumferential direction C), generally forces the heavier liquid fuel 116 outward through the inner filter 164, and the lighter stripping gas 114 inward through the inner filter 240. In this manner, as indicated, the liquid fuel 116 may exit via the liquid fuel outlet 144 of the fuel gas separator 130, and the stripping gas 114 may exit via the stripping gas outlet 142 of the fuel gas separator 130.

[0085] Accordingly, it will be appreciated that the liquid fuel 116 provided to the liquid fuel outlet 142 that has interacted with the stripping gas 114 can have a relatively low oxygen content, such that a relatively large amount of heat can be added thereto, reducing the risk of fuel coking (i.e., a chemical reaction occurs to form solid particles that can clog or damage components within the fuel flow path). For example, in at least some exemplary aspects, the fuel 116 provided to the liquid fuel outlet 144 can have an oxygen content of less than 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.

[0086] In addition, it will be appreciated that the exemplary fuel gas separator 130 depicted in Figure 4 is provided by way of example only. In other embodiments, the separator 130 can have any other suitable configuration for separating the liquid fuel 116 from the stripping gas 114. For example, in other embodiments, the separator 130 is instead configured as a centrifuge separator, a gravity-assisted separator, or any other passive separator or power separator or a combination thereof in another form.

[0087] Now referring back to Figure 3 the schematic diagram of the fuel delivery system 100 in Figure 2 , the liquid fuel 116 from the liquid fuel outlet 144 of the separator 130 is provided via the liquid fuel outlet path 110. The liquid fuel outlet path 110 is fluidly coupled to a liquid fuel source line 168, which can provide fuel with a relatively low oxygen content to one or more engines 56 (e.g., see Figure 2 )). As in the Figure 2 embodiment, the fuel delivery system 100 also includes a reflux valve 120 and a reflux line 122. Depending on the fuel requirements of one or more engines 56 (see Figure 2 ), at least a portion of the fuel 116 passing through the liquid fuel outlet path 110 can be returned to the fuel source 102.

[0088] As Figure 3Also depicted in, it will be appreciated that the exemplary fuel oxygen reduction unit 104 returns the utilized stripping gas 114 to the ullage 118 of the fuel source 102. As noted, the stripping gas 114 to be returned to the ullage 118 (i.e., downstream of the separator 130 and via the stripping gas return path 112) can have a relatively high oxygen content. Thus, as also noted above, the fuel oxygen reduction unit 104 further includes a second catalytic converter 150. The stripping gas 114 from the gas outlet 142 of the separator 130 is provided to the second catalytic converter 150, where the oxygen content of the gas 114 is reduced. The second catalytic converter 150 is positioned in fluid communication with the stripping gas return path 112 to reduce the oxygen content of the stripping gas 114 flowing through the stripping gas return path 112 before returning this stripping gas 114 to the ullage 118 of the fuel source 102. It will be appreciated that in some exemplary embodiments, the second catalytic converter 150 can operate in a manner similar to the operation described above with reference to the first catalytic converter 148. For example, in some embodiments, the second catalytic converter 150 can be configured in substantially the same manner as the first catalytic converter 148, or alternatively, can be configured in any other suitable manner. For example, the second catalytic converter 150 can react the fuel vapor-rich stripping gas 114 with elements within the second catalytic converter 150 to provide a relatively oxygen-free stripping gas 114 upon exit. Including the second catalytic converter 150 can ensure that the stripping gas 114 returned to the ullage 118 has a desired relatively low oxygen content.

[0089] Still referring to Figure 3 the embodiment, the stripping gas 114 passing through the stripping gas return path 112 is further cooled by a heat exchanger 152 downstream of the second catalytic converter 150 (which is necessary in the presence of the preheater 125). For the illustrated embodiment, the heat exchanger 152 is a gas-liquid heat exchanger configured to transfer heat from the stripping gas 114 passing through the stripping gas return path 112 to a heat exchange fluid, and more particularly to the liquid fuel 116 flowing through the liquid fuel supply path 106. In this manner, the heat exchanger 152 can reduce the temperature of the stripping gas 114 passing through the stripping gas return path 112 and can increase the temperature of the liquid fuel 116 passing through the liquid fuel supply path 106.

[0090] Then, the resulting cooled and relatively low-oxygen-content stripping gas 114 is provided back to the ullage 118 of the fuel source 102 via the remainder of the stripping gas flow path 132 or the stripping gas return path 112. In this manner, the fuel oxygen reduction unit 104 can be configured to simultaneously reduce the oxygen content of the gas within the ullage 118 of the fuel source 102 and reduce the oxygen content of the liquid fuel 116 provided to one or more aircraft engines 52 of the propulsion system 50 of the aircraft 10 including the fuel delivery system 100 (e.g., see Figure 1and Figure 2 )。By including a single fuel oxygen reduction system 104 to reduce the oxygen content of the fuel that will be provided to each of a plurality of aircraft engines 52 or rather a plurality of combusting aircraft engines 52, and reducing the oxygen content of the air within the ullage 118 of the fuel source 102, a more efficient overall fuel delivery system 100 can be provided.

[0091] However, it will be recognized that in other exemplary embodiments, the fuel delivery system 100 can be configured in any other suitable manner. For example, the fuel delivery system 100 may not provide fuel with a low oxygen content to each or even a plurality of aircraft engines. Additionally, it will be recognized that for the illustrated embodiment, the ullage 118 with a reduced oxygen content in the air is the ullage 118 of the fuel source 102, which provides liquid fuel 116 through the liquid fuel supply path 106 of the fuel oxygen reduction unit 104. However, in other embodiments, the ullage 118 can be any other suitable fuel source such that the fuel oxygen reduction unit 104 can operate with more than one fuel source. For example, in certain embodiments, the fuel oxygen reduction unit 104 can operate with a main fuel tank and a separate auxiliary fuel tank.

[0092] In addition, for the illustrated embodiment, the fuel delivery system 100 further includes a second flame arrester 170 immediately upstream of the ullage 118 in the stripping gas return path 112. The second flame arrester 170 can operate in a manner similar to the first flame arrester 154.

[0093] Although not depicted, it will be recognized that in at least some exemplary embodiments, the fuel oxygen reduction unit 104 may further include a supplementary gas source in gas flow communication with, for example, the stripping gas circulation flow path 132. For example, the supplementary gas source can be a source of ambient air, bleed air, stripping gas tank, etc. in gas flow communication with the flow path 132 to provide additional air / stripping gas 114 to the circulating gas flow path as needed / on demand.

[0094] However, it will be recognized that in other exemplary embodiments, the fuel delivery system 100 can instead be configured in any other suitable manner. For example, now referring to Figure 5 , a fuel delivery system 100 according to another exemplary embodiment of the present disclosure is provided. Figure 5 The exemplary fuel delivery system 100 can be in a manner similar to Figure 3configured in substantially the same manner as the exemplary fuel delivery system 100. For example, the fuel delivery system 100 generally includes a fuel source 102 and a fuel oxygen reduction unit 104, where the fuel oxygen reduction unit 104 generally defines a liquid fuel supply path 106 and a liquid fuel outlet path 110, as well as a stripping gas supply path 108 and a stripping gas return path 110. Both the stripping gas supply path 108 and the stripping gas return path 110 are in gas flow communication with the fuel source 102, and more particularly, the ullage 118 of the fuel source 102, and the liquid fuel supply path 106 is in fluid communication with the fuel source 102. Additionally, the exemplary fuel oxygen reduction unit 104 generally includes a contactor 128 and a separator 130. The contactor 128 is configured to receive a stripping gas stream 114 through a stripping gas inlet 136 that is in gas flow communication with the stripping gas supply path 108 and a liquid fuel stream 116 through a liquid fuel inlet 138 that is in fluid communication with the liquid fuel supply path 106. The contactor 128 is further configured to mix the stripping gas stream 114 with the liquid fuel stream 116 to form a fuel / gas mixture 156 and provide such fuel / gas mixture 156 to an inlet 146 of the separator 130. The separator 130 is configured to separate the fuel / gas mixture 156 back into a stripping gas stream 114 and a liquid fuel stream 116, with the stripping gas stream being provided back to the fuel source 102 through the stripping gas return path 112 and the liquid fuel stream being provided to, for example, one or more aircraft engines 52 through the liquid fuel 116 return path.

[0095] However, compared to Figure 3 the embodiment of Figure 5 the exemplary fuel delivery system 100 may not include both a first catalyst 148 and a second catalyst 150 simultaneously. Instead, for Figure 5 the exemplary fuel delivery system 100, the fuel oxygen reduction unit 104 includes a single catalyst 172 that is positioned upstream of the contactor 128 and downstream of the ullage 118 of the fuel source 102. In such a manner, the fuel delivery system 100, or rather the fuel oxygen reduction unit 104, can still reduce the oxygen content of the air within the ullage 118 of the fuel source 102. For example, the catalyst 172 can reduce the oxygen content in the stripping gas stream 114 (received from the ullage 118 through the stripping gas supply path 108) to less than about three percent (3%) by mass of oxygen (O2), such as less than one percent (1%) by mass of oxygen (O2). Although the stripping gas 114 may increase in oxygen content by mixing with the liquid fuel 116 within the contactor 128 before being separated back into the stripping gas stream 114 in the separator 130 and returned to the ullage 118 of the fuel tank, the resulting oxygen content in the air within the fuel tank ullage 118 may still be lower or much lower than otherwise (i.e., the oxygen content of the ullage gas is still below the acceptable oxygen level of the ullage gas).

[0096] However, it is noted that, as depicted by the phantom lines, in other embodiments, a single catalytic converter 172 of the fuel oxygen reduction unit 104 may instead be positioned downstream of the separator 130 and upstream of the ullage 118 of the fuel source 102. With such a configuration, the fuel delivery system 100 or, more particularly, the fuel oxygen reduction unit 104 can still reduce the oxygen content in the air in the ullage 118 of the fuel source 102 and in the liquid fuel 116 provided to one or more aircraft engines 52. For example, with such a configuration, the fuel oxygen reduction unit 104 can maintain the oxygen content in the air within the ullage 118 of the fuel source 102 at a relatively low level such that, after such air is provided to the contactor 128 via the stripping gas supply path 108 and mixed with the liquid fuel 116, it may still be able to reduce the oxygen content of the fuel to an acceptable or desired level.

[0097] Still referring to Figure 5 the embodiment of Figure 3 and also compared to the embodiment of Figure 5 the exemplary fuel delivery system 100 includes a heat exchanger 152 downstream of the separator 130 and upstream of the fuel source 102. However, for the embodiment of

[0098] the heat exchanger 152 is not in fluid communication with the liquid fuel supply path 106. Instead, the exemplary fuel delivery system 100 includes a separate heat transfer system 174, and the heat exchanger 152 is thermally coupled to such heat transfer system 174. The heat transfer system 174 can be configured to receive heat from the stripping gas 114 via the stripping gas supply path 108 to reduce the temperature of such stripping gas 114. The heat transfer system 174 can be any suitable heat transfer system, such as a bypass air system, a lubrication system, etc.

[0098] In addition, in other embodiments, any other suitable configuration may be provided for the fuel delivery system 100. For example, now referring to Figure 6 a fuel delivery system 100 is provided in accordance with yet another exemplary embodiment of the present disclosure. Figure 6 The exemplary fuel delivery system 100 of Figure 3 can be configured in substantially the same manner as the exemplary fuel delivery system 100 of Figure 3 For example, the fuel delivery system 100 generally includes a fuel source 102 and a fuel oxygen reduction unit 104, where the fuel oxygen reduction unit 104 generally defines a liquid fuel supply path 106 and a liquid fuel outlet path 110, as well as a stripping gas supply path 108 and a stripping gas return path 110. Both the stripping gas supply path 108 and the stripping gas return path 110 are in gas flow communication with the fuel source 102, and more particularly, the ullage 118 of the fuel source 102, and further, the liquid fuel supply path 106 is in fluid communication with the fuel source 102. In addition, the exemplary fuel oxygen reduction unit 104 generally includes a contactor 128 and a separator 130.

[0099] As in Figure 3 the embodiment of, the fuel delivery system 100 includes a first gas oxygen reduction unit and a second gas oxygen reduction unit. However, compared with Figure 3 the embodiment of, for Figure 6 the exemplary fuel delivery system 100, the first gas oxygen reduction unit and the second gas oxygen reduction unit are not configured as catalytic converters (i.e., the first catalytic converter 148 and the second catalytic converter 150), and instead are configured as a first membrane gas oxygen reduction unit 176 and a second membrane gas oxygen reduction unit 178, respectively. The first membrane gas oxygen reduction unit 176 is positioned in the stripping gas supply path 108 / stripping gas flow path 132, downstream of the boost pump 124 (for the illustrated embodiment) and upstream of the fuel oxygen reduction assembly, or upstream of the contactor 128 and the separator 130. The second membrane gas oxygen reduction unit 178 is positioned in the stripping gas return path 112 / stripping gas flow path 132, downstream of the fuel oxygen reduction assembly - i.e., for the illustrated embodiment, the contactor 128 and the separator 130 - and upstream of the ullage 118 of the fuel source 102.

[0100] Each of the first membrane gas oxygen reduction unit 176 and the second membrane gas oxygen reduction unit 178 can be configured in any suitable manner to reduce the oxygen content of the stripping gas 114 flowing through the corresponding portion of the stripping gas flow path 132. For the illustrated embodiment, the first membrane gas oxygen reduction unit 176 and the second membrane gas oxygen reduction unit 178 each generally define a gas flow chamber 180 and an oxygen reduction chamber 182 through which the stripping gas 114 flows and includes a membrane 184. The oxygen reduction chamber 182 and the membrane 184 can have any suitable configuration for extracting oxygen from the stripping gas 114 flowing through the gas flow chamber 180. For example, the oxygen reduction chamber 182 can be a relatively low pressure chamber (e.g., a vacuum), and the membrane 184 can be an oxygen permeable membrane that allows oxygen within the stripping gas 114 within the gas flow chamber 180 to migrate therethrough and into the oxygen reduction chamber 182. However, other configurations are also contemplated, including various other chamber and membrane geometries.

[0101] It will be appreciated that with such a configuration, a preheater (e.g., Figure 3 the preheater 125 of) may not be required, and thus a heat exchanger (e.g., the heat exchanger 152) may also not be required.

[0102] It will further be appreciated that while the exemplary fuel oxygen reduction unit includes the first membrane gas oxygen reduction unit 176 and the second membrane gas oxygen reduction unit 178 as the first gas oxygen reduction unit and the second gas oxygen reduction unit, in other embodiments, Figure 6 the features of the fuel delivery system 100 of may be the same as Figures 3 to 5One or more feature combinations of the exemplary fuel delivery system 100. For example, in other embodiments, one of the first membrane gas oxygen reduction unit 176 or the second membrane gas oxygen reduction unit 178 is configured as a catalytic converter. Alternatively, in other embodiments, the fuel delivery system 100 may include only one of the first membrane gas oxygen reduction unit 176 or the second membrane gas oxygen reduction unit 178 (i.e., a single membrane gas oxygen reduction unit for the fuel oxygen reduction unit 104; see, for example, the embodiments described above with reference to Figure 5 ).

[0103] In addition, it will be appreciated that in other exemplary embodiments, other configurations may also be contemplated. For example, now referring to Figure 7 , a fuel delivery system 100 according to another exemplary embodiment of the present disclosure is provided. Figure 7 The exemplary fuel delivery system 100 may be configured in substantially the same manner as the Figure 3 exemplary fuel delivery system 100. For example, the fuel delivery system 100 generally includes a fuel source 102 and a fuel oxygen reduction unit 104, where the fuel oxygen reduction unit 104 generally defines a liquid fuel supply path 106 and a liquid fuel outlet path 110, as well as a stripping gas supply path 108 and a stripping gas return path 110. In addition, the fuel oxygen reduction unit 104 includes a first gas oxygen reduction unit 186 and a second gas oxygen reduction unit 188 located in the stripping gas supply path 108 and the return path 110 upstream and downstream of the fuel oxygen reduction assembly, respectively.

[0104] However, for the depicted embodiment, the fuel oxygen reduction assembly is not configured as a contactor and separator, but is instead configured as a membrane fuel oxygen reduction unit 190. The membrane fuel oxygen reduction unit 190 defines a stripping gas chamber 192 and a fuel chamber 198, the stripping gas chamber defines a gas inlet 194 and a gas outlet 196, and the fuel chamber defines a fuel inlet 200 and a fuel outlet 202. The membrane fuel oxygen reduction unit 190 also includes a membrane 204 located between the stripping gas chamber 192 and the fuel chamber 198. The membrane 204 may be any suitable membrane for allowing oxygen in the liquid fuel 116 flowing through the fuel chamber 198 to migrate to the stripping gas 114 flowing through the stripping gas chamber 192. For example, the membrane 204 may be any suitable oxygen-permeable membrane.

[0105] Such a configuration may allow for simultaneous reduction of the dead space 118 and oxygen in the liquid fuel 116 provided to the engine 50 while using less mechanical work.

[0106] It will further be appreciated that in other exemplary embodiments, other configurations may also be contemplated. For example, now referring to Figure 8 , a fuel delivery system 100 according to another exemplary embodiment of the present disclosure is provided. Figure 8Exemplary fuel delivery system 100 can be configured in substantially the same manner as Figure 3 Exemplary fuel delivery system 100. For example, fuel delivery system 100 generally includes a fuel source 102 and a fuel oxygen reduction unit 104, where the fuel oxygen reduction unit 104 generally defines a liquid fuel supply path 106 and a liquid fuel outlet path 110, as well as a stripping gas supply path 108 and a stripping gas return path 110. In addition, the fuel oxygen reduction unit 104 includes a first gas oxygen reduction unit 186 and a second gas oxygen reduction unit 188 located in the stripping gas supply path 108 and the return path 110 upstream and downstream of the fuel oxygen reduction assembly, respectively.

[0107] However, for the depicted embodiment, the air stream 114 provided to the stripping gas supply path 108 is received not only from the ullage 118 of the fuel tank 102, but additionally or alternatively from an air source 200. As depicted, the air source 200 is separate from the fuel source (i.e., the tank 102 for the illustrated embodiment), and the stripping gas supply path 108 is in fluid communication with the air source 200 to receive at least a portion of the air stream 114 provided from the air source 200 to the stripping gas supply path 108.

[0108] In at least some exemplary embodiments, the air source 200 is at least one of an air cycle machine, a gas turbine engine of an aircraft incorporating the fuel delivery system 100, or a device for collecting ambient air flow. For example, the air source 200 can be a compressor section of a gas turbine engine such that the provided air stream is bleed air from the compressor section. Additionally or alternatively, the air source 200 can be an air flow orifice, a ram air turbine, or other opening configured to receive ambient air flow above the aircraft.

[0109] However, it is noteworthy that in other embodiments, the air source 200 can be a combination of two or more of the above air sources 200, or any other suitable combination of air sources 200 external to the fuel supply / fuel tank 102.

[0110] In this manner, it will be appreciated that for Figure 8 the embodiment, the air stream from the air source 200 is a first air stream 114A, and the stripping gas supply path is further in fluid communication with the fuel source (or the ullage 118 of the fuel tank 102) to receive a second air stream 114B.

[0111] It will be further appreciated that for the depicted embodiments, the fuel delivery system 100 further includes a control valve 202 that is in fluid communication with the stripping gas supply path for controlling the first flow rate of the first air stream 114A, the second flow rate of the second air stream 114B, or both. More particularly, for the illustrated embodiments, the stripping gas supply path 108 includes a first portion extending from an air source 200, a second portion extending from a fuel source, and a junction where the first and second portions intersect. For the illustrated embodiments, the control valve 202 is positioned at the junction and configured as a variable flux three-way valve. In certain example embodiments, the control valve 202 can be configured to vary the ratio of the flow rate of air 114A from the air source 200 to the flow rate of air 114B from the fuel source between 100:0 and 0:100 (and various ratios therebetween such as 10:90, 25:75, 50:50, 75:25, 90:10, etc.).

[0112] Thus, the control valve 202 can effectively control the amount of air from the air source 200 and from the fuel source in the stripping gas flow path 132.

[0113] Briefly, it will be appreciated that the exemplary fuel oxygen reduction unit 104 is still configured to provide an air stream 114 in the stripping gas return path 112 to the fuel source or more particularly to the ullage 118 of the fuel tank 102 such that the oxygen content of the gas within the ullage 118 is reduced. However, considering the introduction of the air stream from the air source 200, the fuel oxygen reduction unit 104 can generally operate as at least a partially open-loop system due to its association with the stripping gas flow path 108. Accordingly, the ullage 118 of the fuel tank is configured to provide an excess air stream 204 to a location that is separate from the fuel oxygen reduction unit and more particularly separate from the stripping gas flow path 108. For example, in certain exemplary embodiments, the location providing the excess air stream 204 from the ullage 118 of the fuel tank can be an ambient location (e.g., an outboard location), or it can be one or more individual systems of the aircraft (e.g., an aircraft engine, a separate fuel oxygen reduction unit, etc.).

[0114] Notably, still referring to Figure 8, for the illustrated embodiment, a first air stream 114A from an air source 200 may be provided at a first temperature and a first pressure, while a second air stream 114B from a fuel source may be provided at a second temperature and a second pressure. The first temperature may be greater than the second temperature and / or the first pressure may be greater than the second pressure. For example, when the air source 200 is a compressor section of a gas turbine engine, depending on which stage of the compressor section the first air stream 114A is provided from, both the first temperature and the first pressure may be greater than the second temperature and the second pressure, respectively. The higher temperature and pressure air stream may facilitate certain operations of the fuel oxygen reduction unit 104, such as a desired stripping gas volumetric flow rate and / or other stripping gas operating parameters (e.g., temperature, pressure, etc.).

[0115] However, it will be further appreciated that the fuel content in the second air stream 114B from the fuel source may be greater than the fuel content in the first air stream 114A from the air source 200. It should also be appreciated that the fuel oxygen reduction unit 104 may include a gas oxygen reduction unit positioned in the stripping gas flow path 132 (e.g., within the stripping gas supply path 108 or the stripping gas return path 112). The fuel content of the second air stream 114B from the fuel source may assist in the operation of the gas oxygen reduction unit. For example, the gas oxygen reduction unit may be a catalyst 148 or 150 or a burner, and the fuel content in the second air stream 114B from the fuel source may assist in the operation of the catalyst 148 or 150 or the burner.

[0116] In this manner, the fuel delivery system 100 further includes a sensor 206 and a controller 208 operably coupled to the control valve 202 and the sensor 206. The controller 208 is configured to receive data indicative of the operating parameters of the fuel oxygen reduction unit (e.g., from the sensor 206) and to change the first flow rate, the second flow rate, or both in response to the received data indicative of the operating parameters of the fuel oxygen reduction unit.

[0117] In certain exemplary embodiments, the operating parameters may be the temperature of the air stream 114, the pressure of the air stream 114, the flow rate of the air stream 114, the volume of the air stream 114, etc. Additionally or alternatively, the operating parameter may be the fuel content in the air stream 114. The sensor 206 may be configured to sense data indicative of one or more of these operating parameters.

[0118] Briefly, it will be further appreciated that Figure 8 the controller 208 depicted in is configured to receive data sensed from one or more sensors (including the sensor 206 for the illustrated embodiment) and may make control decisions for the fuel delivery system 100 based on the received data, for example.

[0119] In one or more exemplary embodiments, Figure 2The controller 208 depicted in [description] can be a stand-alone controller 208 for the fuel delivery system 100, or alternatively, can be integrated into one or more of a controller for an aircraft that integrates the fuel delivery system 100, a controller for a gas turbine engine that receives fuel from the fuel delivery system 100, etc.

[0120] With particular reference to the operation of the controller 208, in at least some embodiments, the controller 208 can include one or more computing devices 210. The computing device 210 can include one or more processors 210A and one or more memory devices 210B. The one or more processors 210A can include any suitable processing device, such as a microprocessor, a microcontroller, an integrated circuit, a logic device, and / or other suitable processing device. The one or more memory devices 210B can include one or more computer-readable media, including but not limited to non-transitory computer-readable media, RAM, ROM, hard disk drives, flash drives, and / or other memory devices.

[0121] The one or more memory devices 210B can store information accessible by the one or more processors 210A, including computer-readable instructions 210C executable by the one or more processors 210A. The instructions 210C can be any set of instructions that, when executed by the one or more processors 210A, cause the one or more processors 210A to perform operations. In some embodiments, the instructions 210C can be executed by the one or more processors 210A to cause the one or more processors 210A to perform operations, such as any operations and functions for which the controller 208 and / or the computing device 210 are configured, such as the operations (e.g., method 300) for operating the fuel delivery system 100 described herein, and / or any other operations or functions of the one or more computing devices 210. The instructions 210C can be software written in any suitable programming language, or can be implemented in hardware. Additionally and / or alternatively, the instructions 210C can be executed in separate logical and / or virtual threads on the processor 210A. The memory device 210B can also store data 210D accessible by the processor 210A. For example, the data 210D can include data indicating power flow, data indicating engine / aircraft operating status, and / or any other data and / or information described herein.

[0122] The computing device 210 may also include a network interface 210E that is configured to communicate, for example, with other components of the fuel delivery system 100, a gas turbine engine incorporating the fuel delivery system 100, an aircraft incorporating the fuel delivery system 100, and the like. For example, in the depicted embodiment, as noted above, the fuel delivery system 100 includes one or more sensors that sense data indicative of one or more parameters of the fuel delivery system 100. The controller 208 is operatively coupled to the one or more sensors via, for example, the network interface 210E such that the controller 208 can receive data indicative of various operating parameters sensed by the one or more sensors during operation. Additionally, for the illustrated embodiment, the controller 208 is operatively coupled to, for example, the control valve 202. In this manner, the controller 208 can be configured to actuate the control valve 202 (responsive to, for example, data sensed by the one or more sensors).

[0123] The network interface 210E may include any suitable components for interfacing with one or more networks, such as including a transmitter, a receiver, ports, a controller, an antenna, and / or other suitable components.

[0124] It will be further appreciated that in other exemplary embodiments, other configurations may also be contemplated. For example, now referring to Figure 9 , there is provided a fuel delivery system 100 in accordance with another exemplary embodiment of the present disclosure. Figure 9 The exemplary fuel delivery system 100 of Figure 8 may be configured in substantially the same manner as the exemplary fuel delivery system 100 of

[0125] For example, the fuel delivery system 100 generally includes a fuel source 102, an air source 200, and a fuel oxygen reduction unit 104, where the fuel oxygen reduction unit 104 generally defines a liquid fuel supply path 106 and a liquid fuel outlet path 110, as well as a stripping gas supply path 108 and a stripping gas return path 110. Additionally, the stripping gas supply path 108 is in fluid communication with the air source 200, and the stripping gas return path 112 is in fluid communication with the fuel source.

[0126] Now referring to Figure 10 , there is provided a method of operating a fuel system of an aircraft. The fuel system may be configured in accordance with one or more of the exemplary fuel delivery systems discussed above with respect to Figures 1 to 9 Accordingly, the fuel system may generally include a fuel source and a fuel oxygen reduction unit.

[0127] Method 300 generally includes using a fuel oxygen reduction unit at (301). For the illustrated exemplary aspect, using a fuel oxygen reduction unit at (301) includes reducing the oxygen content in the liquid fuel from a fuel source. More particularly, for the illustrated exemplary aspect, using a fuel oxygen reduction unit at (301) includes receiving an air stream at (302) from a stripping gas supply path of the fuel oxygen reduction unit, and receiving a liquid fuel stream at (304) from a liquid fuel supply path of the fuel oxygen reduction unit. Method 300 further includes reducing the oxygen content of the air stream and the liquid fuel stream within the fuel oxygen reduction unit at (306), and providing an air stream with reduced oxygen content to the fuel source at (308). In certain exemplary embodiments, reducing the oxygen content of the air stream and the liquid fuel stream within the fuel oxygen reduction unit at (306) may include mixing the liquid fuel stream and the air stream together in a contactor to form a fuel / gas mixture, and separating the fuel / gas mixture back into a liquid fuel stream and an air stream. However, alternatively, reducing the oxygen content of the air stream and the liquid fuel stream within the fuel oxygen reduction unit at (306) may include using a membrane-based fuel oxygen reduction unit to reduce the oxygen content of the liquid fuel stream and the air stream.

[0128] Still referring to Figure 10 , for the depicted exemplary aspect, receiving an air stream at (302) from a stripping gas supply path of the fuel oxygen reduction unit includes receiving data indicative of an operating parameter of the fuel oxygen reduction unit at (310), and changing a first flow rate of a gas from an air source, changing a second flow rate of a gas from a fuel source, or both, in response to the received data indicative of the operating parameter of the fuel oxygen reduction unit at (312). In certain exemplary aspects, at (312), changing a first flow rate of a gas from an air source, changing a second flow rate of a gas from a fuel source, or both may include adjusting a control valve, such as Figure 8 the exemplary three-way valve of

[0129] In certain exemplary aspects, the operating parameter of the fuel oxygen reduction unit may be the temperature of the air stream to the stripping gas supply path, the pressure of the air stream to the stripping gas supply path, the fuel content of the air stream to the stripping gas supply path, or a combination thereof.

[0130] Such exemplary aspects may allow the fuel oxygen reduction unit to operate at a desired flow rate, pressure, and / or temperature to provide a desired level of oxygen reduction for the fuel stream and the fuel source.

[0131] This written description uses examples to disclose the invention, including the best mode, and also enables any person skilled in the art to practice the invention, including making and using any device or system, and performing any combination of methods. The patent scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. If such other embodiments include structural elements that are not different from the written language of the claims, or if they include equivalent structural elements that do not materially differ from the written language of the claims, then it is intended that such other examples be within the scope of the claims.

[0132] Other aspects of the invention are provided by the subject matter of the following clauses:

[0133] A fuel system for an aircraft having a fuel source, the system comprising: a fuel oxygen reduction unit that defines a liquid fuel supply path, a stripping gas supply path, a liquid fuel outlet path, and a stripping gas return path, wherein the stripping gas return path is configured to be in fluid communication with the fuel source of the aircraft and optionally in fluid communication with the fuel source of the aircraft.

[0134] The fuel system of one or more of these clauses further comprises: an air source separated from the fuel source, wherein the stripping gas supply path is in fluid communication with the air source airflow for receiving an airflow from the air source.

[0135] The fuel system of one or more of these clauses, wherein the air source is at least one of an air cycle machine, a gas turbine engine of the aircraft, or a device for collecting ambient airflow.

[0136] The fuel system of one or more of these clauses, wherein the airflow from the air source is a first airflow, and wherein the stripping gas supply path is further in fluid communication with the fuel source airflow for receiving a second airflow from the air source.

[0137] The fuel system of one or more of these clauses, wherein the stripping gas supply path includes a first stripping gas flow path extending from the fuel source, and wherein the fuel system includes a check valve in the first stripping gas flow path.

[0138] The fuel system of one or more of these clauses, wherein the first airflow from the air source is provided at a first temperature and a first pressure, wherein the second airflow from the fuel source is provided at a second temperature and a second pressure, and wherein the first temperature is greater than the second temperature, the first pressure is greater than the second pressure, or both.

[0139] The fuel system of one or more of these clauses, wherein the fuel oxygen reduction unit comprises: a gas oxygen reduction unit that is positioned in the stripping gas supply path or the stripping gas return path, and wherein the fuel content in the second airflow from the fuel source aids in the operation of the gas oxygen reduction unit.

[0140] A fuel system of one or more of these clauses further includes: a control valve that is in fluid communication with the stripping gas supply path airflow and configured to control a first flow rate of a first airflow, a second flow rate of a second airflow, or both; and a controller operably coupled to the control valve, the controller being configured to receive data indicating operating parameters of the fuel oxygen reduction unit and to change the first flow rate, the second flow rate, or both in response to the received data indicating the operating parameters of the fuel oxygen reduction unit.

[0141] A fuel system of one or more of these clauses, wherein the fuel source includes a fuel tank, and wherein the fuel oxygen reduction unit further includes: a neutral pump that is in fluid communication with the stripping gas supply path airflow.

[0142] A fuel system of one or more of these clauses, wherein the fuel source includes a fuel tank, and wherein the stripping gas return path is in fluid communication with the neutral airflow of the fuel tank.

[0143] A fuel system of one or more of these clauses, wherein the fuel source includes a fuel tank, and wherein the neutral of the fuel tank is configured to provide an excessive airflow to a location separated from the fuel oxygen reduction unit.

[0144] A fuel system of one or more of these clauses, wherein the liquid fuel supply path is fluidly connected to the fuel source, and wherein the fuel oxygen reduction unit is configured to receive a liquid fuel flow from the fuel source.

[0145] A fuel system of one or more of these clauses, wherein the fuel oxygen reduction unit includes: a gas oxygen reduction unit that is positioned in the stripping gas supply path or the stripping gas return path; and a fuel oxygen reduction assembly that is in fluid communication with the liquid fuel supply path and the liquid fuel return path and further in fluid communication with the stripping gas supply path and the stripping gas return path airflow.

[0146] A fuel system of one or more of these clauses, wherein the gas oxygen reduction unit is a first gas oxygen reduction unit positioned in the stripping gas supply path, and wherein the fuel oxygen reduction unit further includes a second gas oxygen reduction unit in the stripping gas return path.

[0147] A fuel system of one or more of these clauses, wherein the fuel oxygen reduction assembly includes: a contactor fluidly connected to a liquid fuel supply path and a stripping gas supply path for mixing a liquid fuel stream from the liquid fuel supply path with a stripping gas stream from the stripping gas supply path into a fuel / gas mixture; and a separator fluidly connected to the contactor for receiving the fuel / gas mixture and separating the fuel / gas mixture into a stripping gas stream and a liquid fuel stream, the separator being fluidly connected to a liquid fuel outlet path and a stripping gas return path for providing the liquid fuel stream to the liquid fuel outlet path and the stripping gas stream to the stripping gas return path.

[0148] A fuel system of one or more of these clauses, wherein the gas oxygen reduction unit is a membrane gas oxygen reduction unit.

[0149] A fuel system of one or more of these clauses, wherein the gas oxygen reduction unit is a catalytic converter.

[0150] A fuel system of one or more of these clauses, incorporated into an aircraft of one or more of these clauses.

[0151] A fuel system of one or more of these clauses, incorporated into a method of one or more of these clauses.

[0152] A method of operating a fuel system for an aircraft, the fuel system including a fuel source and a fuel oxygen reduction unit, the method including: receiving an air stream from a stripping gas supply path of the fuel oxygen reduction unit; receiving a liquid fuel stream from a liquid fuel supply path of the fuel oxygen reduction unit; reducing the oxygen content of the air stream and the liquid fuel stream within the fuel oxygen reduction unit; and providing an air stream with a reduced oxygen content to the fuel source.

[0153] A method of operating an aircraft fuel system, the aircraft fuel system including a fuel source, the method including: using a fuel oxygen reduction unit, wherein using the fuel oxygen reduction unit includes reducing the oxygen content of a liquid fuel from the fuel source; and providing an air stream with a reduced oxygen content to the fuel source.

[0154] A method of one or more of these clauses, wherein receiving an air stream from a stripping gas supply path of the fuel oxygen reduction unit includes: receiving data indicative of an operating parameter of the fuel oxygen reduction unit; and in response to the received data indicative of the operating parameter of the fuel oxygen reduction unit, changing a first flow rate of a gas from an air source, changing a second flow rate of a gas from the fuel source, or both.

[0155] A method of one or more of these clauses, wherein the operating parameter of the fuel oxygen reduction unit is the temperature of the airflow to the stripping gas supply path, the pressure of the airflow to the stripping gas supply path, the fuel content of the airflow to the stripping gas supply path, or a combination thereof.

[0156] A method of one or more of these clauses, wherein providing the airflow with reduced oxygen content to the fuel source includes providing the airflow with reduced oxygen content to the ullage of the fuel system.

[0157] A method of one or more of these clauses, using a fuel system of one or more of these clauses.

[0158] A method of one or more of these clauses, using a fuel oxygen reduction unit of one or more of these clauses.

[0159] A method of one or more of these clauses, using an aircraft of one or more of these clauses.

[0160] An aircraft, comprising: a fuel source; and a fuel system including a fuel oxygen reduction unit that defines a liquid fuel supply path, a stripping gas supply path, a liquid fuel outlet path, and a stripping gas return path, wherein the stripping gas return path is in fluid communication with the fuel source airflow of the aircraft.

[0161] An aircraft of one or more of these clauses, using a fuel oxygen reduction unit of one or more of these clauses.

[0162] A fuel system for an aircraft, the system comprising: a fuel source; and a fuel oxygen reduction unit that defines a liquid fuel supply path, a stripping gas supply path, a liquid fuel outlet path, and a stripping gas return path, wherein both the stripping gas return path and the stripping gas supply path are in fluid communication with the fuel source airflow.

[0163] A fuel system of one or more of these clauses, wherein the fuel source includes a fuel tank, and wherein both the stripping gas supply path and the stripping gas return path are in fluid communication with the ullage airflow of the fuel tank.

[0164] A fuel system of one or more of these clauses, wherein the liquid fuel supply path is fluidly connected to the fuel source, and wherein the fuel oxygen reduction unit is configured to receive a liquid fuel stream from the fuel source.

[0165] A fuel system of one or more of these clauses, wherein the fuel oxygen reduction unit is configured to receive an airflow through the stripping gas supply path and a liquid fuel stream through the liquid fuel supply path, and wherein the fuel oxygen reduction unit is configured to reduce the oxygen content of the airflow and the liquid fuel stream.

[0166] A fuel system of one or more of these clauses, wherein the fuel oxygen reduction unit includes: a gaseous oxygen reduction unit positioned in the stripping gas supply path or the stripping gas return path; and a fuel oxygen reduction assembly fluidly connected to the liquid fuel supply path and the liquid fuel return path, and further in gas flow communication with the stripping gas supply path and the stripping gas return path.

[0167] A fuel system of one or more of these clauses, wherein the gaseous oxygen reduction unit is a first gaseous oxygen reduction unit positioned in the stripping gas supply path, and wherein the fuel oxygen reduction unit further includes a second gaseous oxygen reduction unit in the stripping gas return path.

[0168] A fuel system of one or more of these clauses, wherein the fuel oxygen reduction assembly includes: a contactor fluidly connected to the liquid fuel supply path and the stripping gas supply path for mixing a liquid fuel stream from the liquid fuel supply path with a stripping gas stream from the stripping gas supply path to form a fuel / gas mixture; and a separator fluidly connected to the contactor for receiving the fuel / gas mixture and separating the fuel / gas mixture into a stripping gas stream and a liquid fuel stream, the separator being fluidly connected to the liquid fuel outlet path and the stripping gas return path for providing the liquid fuel stream to the liquid fuel outlet path and the stripping gas stream to the stripping gas return path.

[0169] A fuel system of one or more of these clauses, wherein the fuel oxygen reduction assembly includes: a membrane fuel oxygen reduction unit defining a stripping gas chamber in gas flow communication with the stripping gas supply path and the stripping gas return path, and a fuel chamber fluidly connected to the liquid fuel supply path and the liquid fuel outlet path, the membrane fuel oxygen reduction unit including a membrane separating the stripping gas chamber from the fuel chamber.

[0170] A fuel system of one or more of these clauses, wherein the gaseous oxygen reduction unit is a membrane gaseous oxygen reduction unit.

[0171] A fuel system of one or more of these clauses, wherein the gaseous oxygen reduction unit is a catalytic converter.

[0172] A fuel system of one or more of these clauses, wherein the fuel oxygen reduction unit further includes: a preheater thermally coupled to the stripping gas supply path; a heat exchanger thermally coupled to the stripping gas return path.

[0173] A fuel system of one or more of these clauses, wherein the fuel oxygen reduction unit further includes: a vent pump in gas flow communication with the stripping gas supply path.

[0174] A propulsion system for an aircraft, comprising an aircraft engine; and a fuel system including a fuel source; and a fuel oxygen reduction unit that defines a liquid fuel supply path, a stripping gas supply path, a liquid fuel outlet path, and a stripping gas return path, wherein the stripping gas return path and the stripping gas supply path are both in gas flow communication with the fuel source gas stream, and wherein the liquid fuel outlet path is in fluid communication with the aircraft engine to supply liquid fuel to the aircraft engine.

[0175] A propulsion system according to one or more of these clauses, wherein the aircraft engine is a first aircraft engine, and wherein the propulsion system further comprises: a second aircraft engine, wherein the liquid fuel outlet path is in fluid communication with both the first aircraft engine and the second aircraft engine for supplying liquid fuel to both the first aircraft engine and the second aircraft engine.

[0176] A propulsion system according to one or more of these clauses, wherein the fuel oxygen reduction unit comprises: a gas oxygen reduction unit positioned in the stripping gas supply path or the stripping gas return path; and a fuel oxygen reduction assembly in fluid communication with the liquid fuel supply path and the liquid fuel return path, and further in gas flow communication with the stripping gas supply path and the stripping gas return path.

[0177] A propulsion system according to one or more of these clauses, wherein the gas oxygen reduction unit is a first gas oxygen reduction unit positioned in the stripping gas supply path, and wherein the fuel oxygen reduction unit further comprises a second gas oxygen reduction unit in the stripping gas return path.

[0178] A propulsion system according to one or more of these clauses, wherein the fuel oxygen reduction assembly comprises: a contactor fluidly connected to the liquid fuel supply path and the stripping gas supply path for mixing a liquid fuel stream from the liquid fuel supply path with a stripping gas stream from the stripping gas supply path to form a fuel / gas mixture; and a separator fluidly connected to the contactor for receiving the fuel / gas mixture and separating the fuel / gas mixture into a stripping gas stream and a liquid fuel stream, the separator being fluidly connected to the liquid fuel outlet path and the stripping gas return path for supplying the liquid fuel stream to the liquid fuel outlet path and supplying the stripping gas stream to the stripping gas return path.

[0179] A propulsion system according to one or more of these clauses, wherein the fuel oxygen reduction assembly comprises: a membrane fuel oxygen reduction unit defining a stripping gas chamber in gas flow communication with the stripping gas supply path and the stripping gas return path, and a fuel chamber in fluid communication with the liquid fuel supply path and the liquid fuel outlet path, the membrane fuel oxygen reduction unit including a membrane separating the stripping gas chamber from the fuel chamber.

[0180] A propulsion system of one or more of these clauses, wherein the gaseous oxygen reduction unit is a membrane gaseous oxygen reduction unit or a catalytic converter.

[0181] A propulsion system of one or more of these clauses, wherein the liquid fuel supply path is fluidly connected to a fuel source to receive a liquid fuel stream from the fuel source.

[0182] A propulsion system of one or more of these clauses, using a fuel system of one or more of these clauses, using a fuel oxygen reduction unit of one or more of these clauses, incorporated into an aircraft of one or more of these clauses, or within a method of one or more of these clauses.

Claims

1. A fuel system for an aircraft having a fuel source, the system comprising: A fuel oxygen reduction unit that defines a liquid fuel supply path, a stripping gas supply path, a liquid fuel outlet path, and a stripping gas return path, wherein the stripping gas return path is configured to be in fluid communication with the fuel source of the aircraft; Wherein the fuel oxygen reduction unit comprises: A gas oxygen reduction unit positioned in the stripping gas supply path or the stripping gas return path, the gas oxygen reduction unit being configured to reduce the oxygen content in the stripping gas from the ullage of the fuel source; and A fuel oxygen reduction assembly in fluid communication with the liquid fuel supply path and the liquid fuel outlet path, and further in gas flow communication with the stripping gas supply path and the stripping gas return path; Wherein the fuel oxygen reduction assembly is configured to mix the liquid fuel with the stripping gas processed by the gas oxygen reduction unit to form a mixture and effect a physical exchange therebetween, whereby at least a portion of the oxygen in the fuel is transferred to the stripping gas processed by the gas oxygen reduction unit, such that the fuel component of the mixture has a relatively lower oxygen content compared to the fuel provided through the liquid fuel supply path, while the stripping gas component of the mixture has a relatively higher oxygen content compared to the stripping gas provided through the stripping gas supply path.

2. The fuel system according to claim 1, characterized in that, The stripping gas return path is configured to be in fluid communication with an air source for receiving an air stream from the air source.

3. The fuel system according to claim 2, characterized in that, The air source is at least one of an air cycle machine, a gas turbine engine of the aircraft, or a device for collecting ambient air flow.

4. The fuel system according to claim 2, wherein, The air stream from the air source is a first air stream, wherein the stripping gas supply path is further in fluid communication with the fuel source to receive a second air stream from the air source.

5. The fuel system according to claim 4, characterized in that, The stripping gas supply path includes a first stripping gas flow path extending from the fuel source, and wherein the fuel system includes a check valve in the first stripping gas flow path.

6. The fuel system according to claim 4, characterized in that, The first air stream from the air source is provided at a first temperature and a first pressure, wherein the second air stream from the fuel source is provided at a second temperature and a second pressure, and wherein the first temperature is greater than the second temperature, the first pressure is greater than the second pressure, or both.

7. The fuel system according to claim 4, characterized in that, The fuel oxygen reduction unit comprises: A gas oxygen reduction unit positioned in the stripping gas supply path or the stripping gas return path, and wherein the fuel content in the second air stream from the fuel source aids in the operation of the gas oxygen reduction unit.

8. The fuel system according to claim 4, characterized in that, The fuel system further comprises: A control valve in gas flow communication with the stripping gas supply path for controlling a first flow rate of the first air stream, a second flow rate of the second air stream, or both; and A controller operably coupled to the control valve, the controller configured to receive data indicative of operating parameters of the fuel oxygen reduction unit and to change the first flow rate, the second flow rate, or both in response to the received data indicative of the operating parameters of the fuel oxygen reduction unit.

9. The fuel system according to claim 1, characterized in that, The fuel source includes a fuel tank, and wherein the fuel oxygen reduction unit further includes: A purge pump, the purge pump being in fluid communication with the purge gas supply path air flow.

10. The fuel system according to claim 1, wherein, The fuel source includes a fuel tank, and wherein the purge gas return path is in fluid communication with the ullage air flow of the fuel tank.

11. The fuel system according to claim 1, wherein The fuel source includes a fuel tank, and wherein the ullage of the fuel tank is configured to provide an excessive air flow to a location separated from the fuel oxygen reduction unit.

12. The fuel system according to claim 1, wherein, The liquid fuel supply path is fluidly connected to the fuel source, and wherein the fuel oxygen reduction unit is configured to receive a liquid fuel flow from the fuel source.

13. The fuel system according to claim 1, wherein The gas oxygen reduction unit is a first gas oxygen reduction unit positioned in the purge gas supply path, and wherein the fuel oxygen reduction unit further includes a second gas oxygen reduction unit in the purge gas return path.

14. The fuel system according to claim 1, characterized in that, The fuel oxygen reduction assembly includes: A contactor, the contactor being fluidly connected to the liquid fuel supply path and the purge gas supply path for mixing a liquid fuel flow from the liquid fuel supply path with a purge gas flow from the purge gas supply path to form a fuel / gas mixture; and A separator, the separator being fluidly connected to the contactor for receiving the fuel / gas mixture and separating the fuel / gas mixture back into the purge gas flow and the liquid fuel flow, the separator being fluidly connected to the liquid fuel outlet path and the purge gas return path for providing the liquid fuel flow to the liquid fuel outlet path and providing the purge gas flow to the purge gas return path.

15. An aircraft, the aircraft including: A fuel source; And A fuel system, the fuel system including a fuel oxygen reduction unit that defines a liquid fuel supply path, a purge gas supply path, a liquid fuel outlet path, and a purge gas return path, wherein the purge gas return path is configured to be in fluid communication with the fuel source of the aircraft; Wherein, the fuel oxygen reduction unit includes: A gas oxygen reduction unit, the gas oxygen reduction unit being positioned in the purge gas supply path or the purge gas return path, the gas oxygen reduction unit being configured to reduce the oxygen content in the purge gas from the ullage of the fuel source; and A fuel oxygen reduction assembly, the fuel oxygen reduction assembly being in fluid communication with the liquid fuel supply path and the liquid fuel outlet path, and further in air flow communication with the purge gas supply path and the purge gas return path; Wherein, the fuel oxygen reduction assembly is configured to mix the liquid fuel with the purge gas processed by the gas oxygen reduction unit into a mixture and cause a physical exchange therebetween, whereby at least a portion of the oxygen in the fuel is transferred to the purge gas processed by the gas oxygen reduction unit, such that the fuel component of the mixture has a relatively lower oxygen content compared to the fuel provided through the liquid fuel supply path, while the purge gas component of the mixture has a relatively higher oxygen content compared to the purge gas provided through the purge gas supply path.

16. A method of operating an aircraft fuel system according to any one of claims 1 - 14, the aircraft fuel system including a fuel source, the method comprising: using a fuel oxygen reduction unit, wherein using the fuel oxygen reduction unit includes reducing the oxygen content in the liquid fuel from the fuel source; and providing an oxygen-reduced gas stream to the fuel source.

17. The method according to claim 16, wherein Using the fuel oxygen reduction unit further includes receiving a gas stream from a stripping gas supply path of the fuel oxygen reduction unit, wherein receiving the gas stream from the stripping gas supply path of the fuel oxygen reduction unit includes: receiving data indicative of an operating parameter of the fuel oxygen reduction unit; and in response to the received data indicative of the operating parameter of the fuel oxygen reduction unit, changing a first flow rate of a gas from an air source, changing a second flow rate of a gas from the fuel source, or both.

18. The method according to claim 17, wherein The operating parameter of the fuel oxygen reduction unit is the temperature of the gas stream to the stripping gas supply path, the pressure of the gas stream to the stripping gas supply path, the fuel content of the gas stream to the stripping gas supply path, or a combination thereof.

19. The method according to claim 16, wherein Providing the oxygen-reduced gas stream to the fuel source includes providing the oxygen-reduced gas stream to a ullage of the fuel system.

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