Fuel delivery system with 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 defining a liquid fuel supply path, a stripping gas supply path, a liquid fuel outlet path, and a stripping gas return path configured to be in fluid communication with an air source separate from a fuel source, selectively in fluid communication with the fuel source of the aircraft, and selectively in fluid communication with the stripping gas return path. Or both.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of U.S. application No. 16 / 179,077, filed on November 2, 2018, which is hereby incorporated by reference in its entirety. Technical Field

[0002] The present subject matter generally relates to a fuel oxygen reduction unit for a fuel delivery system of a vehicle. Background Art

[0003] A typical aircraft propulsion system includes one or more gas turbine engines. A gas turbine engine generally comprises a turbine, which includes a compressor section, a combustion section, a turbine section, and an exhaust section arranged in series. In operation, air is supplied to the 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 combusted within the combustion section to provide combustion gases. From the combustion section, the combustion gases are transferred to the turbine section. The combustion airflow through the turbine section drives the turbine section and is then transferred through the exhaust section, for example, to the atmosphere.

[0004] Certain operations and systems of gas turbine engines and aircraft may generate relatively large amounts of heat. Fuel has been identified as an effective heat sink for receiving at least some of this heat during operation, at least in part due to its heat capacity and the increased efficiency of combustion operations that can result from burning high-temperature fuel. However, heating the fuel without properly regulating the fuel can cause the fuel to "coke," or form solid particles that can clog certain components of the fuel system (such as fuel nozzles). Reducing the amount of oxygen in the fuel can effectively reduce the likelihood of fuel coking exceeding an unacceptable amount. Fuel oxygen reduction systems have been proposed for this purpose. These fuel oxygen reduction systems are generally located at the engine to reduce the oxygen content of the fuel provided to the engine.

[0005] Additionally, some fuel delivery systems for aircraft including gas turbine engines generally also include systems for removing the oxygen content of air within the plenum of a fuel tank (e.g., a fuel tank from which fuel is supplied 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 plenum air / gas generally operate differently than fuel oxygen reduction systems (used to reduce the oxygen content of liquid fuel).

[0006] The inventors of the present disclosure have discovered that operating each of these various systems can be inefficient. Therefore, a system for reducing the oxygen content of the liquid fuel supplied to each individual aircraft engine and the oxygen content of the gas within the idle space of the fuel tank would be useful. Summary of the Invention

[0007] Aspects and advantages of the application will be set forth in the following description, can be obvious from the description, or can be learned through practice of the application.

[0008] In one example embodiment of the disclosure, a fuel system for an aircraft is provided. The fuel system includes a fuel source; and 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 in fluid communication with the fuel source and optionally in selective fluid communication with the fuel source.

[0009] Technical Solution 1. A fuel system for an aircraft having a fuel source, the system comprising: 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 separate from the fuel source, in selective fluid communication with the fuel source of the aircraft, or both.

[0010] Technical Solution 2. The fuel system of any preceding technical solution, 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.

[0011] Technical Solution 3. The fuel system of any preceding technical solution, 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 an ambient air flow.

[0012] Technical Solution 4. The fuel system of any preceding technical solution, wherein the air flow from the air source is a first air flow, wherein the stripping gas supply path is further in air flow communication with the fuel source for receiving a second air flow from the air source.

[0013] Technical Solution 5. The fuel system of any preceding technical solution, 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.

[0014] Technical Solution 6. The fuel system of any preceding technical solution, 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.

[0015] Technical solution 7. The fuel system according to any of the preceding technical solutions, wherein the fuel oxygen reduction unit comprises: A gaseous oxygen reduction unit is positioned in the stripping gas supply path or the stripping gas return path, and wherein fuel content within the second gas stream from the fuel source assists operation of the gaseous oxygen reduction unit.

[0016] Technical Solution 8. The fuel system according to any of the preceding technical solutions, wherein the fuel system further comprises: a control valve, the control valve being in airflow communication with the stripping gas supply path, for controlling a first flow rate of the first airflow, a second flow rate of the second airflow, or both; and A controller operably coupled to the control valve is configured to receive data indicative of an operating parameter of the fuel oxygen reduction unit and to vary 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.

[0017] Technical Solution 9. The fuel system according to any of the preceding technical solutions, wherein the fuel source comprises a fuel tank, wherein the fuel oxygen reduction unit further comprises: A neutral pump is in gas flow communication with the stripping gas supply path.

[0018] Technical Solution 10. A fuel system according to any of the preceding technical solutions, wherein the fuel source comprises a fuel storage tank, and wherein the stripping gas return path is connected to the idle air flow of the fuel storage tank.

[0019] Technical Solution 11. A fuel system according to any of the preceding technical solutions, wherein the fuel source comprises a fuel tank, and wherein the idle portion of the fuel tank is configured to provide excess airflow to a location separate from the fuel oxygen reduction unit.

[0020] Technical Solution 12. A fuel system according to any of the preceding 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.

[0021] Technical solution 13. The fuel system according to any of the preceding technical solutions, wherein the fuel oxygen reduction unit comprises: a gaseous oxygen reduction unit positioned in the stripping gas supply path or the stripping gas return path; and A fuel oxygen reduction assembly is in fluid communication with the liquid fuel supply path and the liquid fuel return path and is further in gas flow communication with the stripping gas supply path and the stripping gas return path.

[0022] Technical Solution 14. A 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 also includes a second gas oxygen reduction unit in the stripping gas return path.

[0023] Technical solution 15. The fuel system according to any of the preceding technical solutions, wherein the fuel oxygen reduction component comprises: a contactor fluidly connected to the liquid fuel supply path and the stripping gas supply path for mixing a liquid fuel flow from the liquid fuel supply path with a stripping gas flow 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 back into the stripping gas stream and the liquid fuel stream, the separator 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.

[0024] Technical Solution 16. An aircraft, comprising: fuel source; and 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 separate from the fuel source, in selective fluid communication with a fuel source of the aircraft, or both.

[0025] Technical Solution 17. A method of operating an aircraft fuel system, the aircraft fuel system comprising a fuel source, the method comprising: Using a fuel oxygen reduction unit, wherein using the fuel oxygen reduction unit comprises reducing the oxygen content of liquid fuel from the fuel source; and A gas stream having a reduced oxygen content is provided to the fuel source.

[0026] Technical Solution 18. A method according to any of the foregoing technical solutions, wherein using the fuel oxygen reduction unit also includes receiving a gas flow from the stripping gas supply path of the fuel oxygen reduction unit, wherein receiving the gas flow from the stripping gas supply path of the fuel oxygen reduction unit includes: receiving data indicating operating parameters of the fuel oxygen reduction unit; and in response to the received data indicating operating parameters of the fuel oxygen reduction unit, changing the first flow rate of the gas from the air source, changing the second flow rate of the gas from the fuel source, or both.

[0027] Technical Solution 19. A method according to any of the preceding technical solutions, wherein the operating parameters of the fuel oxygen reduction unit are the temperature of the air flow to the stripping gas supply path, the pressure of the air flow to the stripping gas supply path, the fuel content of the air flow to the stripping gas supply path, or a combination thereof.

[0028] Technical Solution 20. A method according to any of the preceding technical solutions, wherein providing the airflow with reduced oxygen content to the fuel source comprises providing the airflow with reduced oxygen content to a neutral position of the fuel system.

[0029] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims.The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] A complete and open disclosure of the present invention including its best mode to those skilled in the art is set forth in the specification with reference to the accompanying drawings, in which: Figure 1 is a top view of an aircraft according to various exemplary embodiments of the present disclosure.

[0031] Figure 2 is a schematic diagram of a fuel delivery system according to an exemplary embodiment of the present disclosure.

[0032] Figure 3 is a partially enlarged schematic diagram of a portion of a fuel delivery system according to an exemplary embodiment of the present disclosure.

[0033] Figure 4 According to an exemplary embodiment of the present disclosure Figure 3 Schematic enlarged fragmentary cross-sectional view of a fuel gas separator of an exemplary fuel oxygen reduction unit of a fuel delivery system.

[0034] Figure 5 is a partially enlarged schematic diagram of a portion of a fuel delivery system according to an exemplary embodiment of the present disclosure.

[0035] Figure 6 is a partially enlarged schematic diagram of a portion of a fuel delivery system according to another exemplary embodiment of the present disclosure.

[0036] Figure 7 is a partially enlarged schematic diagram of a portion of a fuel delivery system according to yet another exemplary embodiment of the present disclosure.

[0037] Figure 8 is a partially enlarged schematic diagram of a portion of a fuel delivery system according to yet another exemplary embodiment of the present disclosure.

[0038] Figure 9 is a partially enlarged schematic diagram of a portion of a fuel delivery system according to yet another exemplary embodiment of the present disclosure.

[0039] Figure 10 is a flow chart of a method for operating a fuel system of an aircraft according to an exemplary aspect of the present disclosure. DETAILED DESCRIPTION

[0040] 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. This detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and the specification are used to refer to like or similar parts of the present invention.

[0041] As used herein, the terms “first,” “second,” and “third” are used interchangeably to distinguish one component from another and are not intended to denote the position or importance of the individual components.

[0042] The terms "upstream" and "downstream" refer to relative directions with respect to fluid flow in a fluid pathway. For example, "upstream" refers to the direction from which the fluid flows, and "downstream" refers to the direction to which the fluid flows.

[0043] The terms “coupled,” “fixed,” and “attached to” refer to both direct coupling, fixing, or attachment, as well as indirect coupling, fixing, or attachment through one or more intermediate members or features, unless otherwise specified herein.

[0044] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0045] As used herein throughout the specification and claims, approximating language is used to modify any quantitative expression that is permissible to vary without resulting in a change in the basic function to which it relates. Thus, a value modified by one or more terms such as "about," "approximately," and "substantially" is not limited to the exact value specified. In at least some cases, approximating language may correspond to the precision of an instrument for measuring a value, or the precision of a method or machine for constructing or manufacturing a component and / or system. For example, approximating language may refer to within a 10 percent margin.

[0046] Here and throughout the specification and claims, range limitations are combined and interchangeable, and such ranges are identified and include all subranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.

[0047] Referring now to the drawings, in which like numerals refer to like elements throughout the figures, Figure 1 A top view of an exemplary aircraft 10, as may be incorporated with various embodiments of the present invention, is provided. 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. Furthermore, aircraft 10 includes a fuselage 12 extending longitudinally from the front end 16 of aircraft 10 toward the rear end 18 of aircraft 10, and a pair of wings 20. A first wing 20A of such wings 20 extends laterally outward from a port side 22 of fuselage 12 about longitudinal centerline 14, and a second wing 20B of such wings 20 extends laterally outward from a right chord 24 of fuselage 12 about longitudinal centerline 14. For the exemplary embodiment depicted, each wing 20 includes one or more leading edge flaps 26 and one or more trailing edge flaps 28. Aircraft 10 also includes vertical stabilizers 30 having rudder flaps 32 for yaw control, and a pair of horizontal stabilizers 34 each having an elevator flap 36 for pitch control. Fuselage 12 further includes an exterior surface or skin 38. However, it should be appreciated that in other exemplary embodiments of the present disclosure, the aircraft 10 may additionally or alternatively include any other suitable configuration of stabilizing wings that may or may not extend directly in the vertical direction or the horizontal / lateral direction L. Furthermore, the aircraft 10 may include any other suitable configuration of wings 20 , fuselage 12 , etc. (e.g., a canard configuration, a blended wing configuration, etc.).

[0048] Figure 1The exemplary aircraft 10 includes a propulsion system 50, referred to herein as "system 50." The exemplary system 50 includes one or more aircraft engines 52. For example, the depicted embodiment includes a plurality of 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 engines 52 are configured as gas turbine engines, such as turbofan jet engines, attached to and suspended below the wings 20 in an underwing configuration (it will be appreciated that in other embodiments, the aircraft engines 52 may be any other suitable, at least partially combustion engines). For example, the aircraft engines 52 include a first aircraft engine 52A and a second aircraft engine 52B. The first aircraft engine 52A is configured to be mounted to a first wing 20A of the aircraft 10, while the second aircraft engine 52 is configured to be mounted to a second wing 20B of the aircraft 10 (i.e., on the opposite side of the aircraft 10). It will be appreciated that although Figure 1 Only two aircraft engines 52 are depicted in the figure, and in other embodiments, the propulsion system 50 of the aircraft 10 may have any other suitable number and type of aircraft engines 52 mounted in any other suitable location (e.g., mounted on a wing, mounted on the fuselage at the tail end of the aircraft 10, mounted on one or more stabilizing fins, etc.).

[0049] As in Figure 1 As further depicted in FIG, the aircraft 10 includes a fuel delivery system 100. More particularly, the fuel delivery system 100 is generally configured to deliver fuel to the aircraft engines 52 (i.e., Figure 1 , a first aircraft engine 52A and a second aircraft engine 52B of the embodiment are supplied with a certain amount of fuel. 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 during operation, as will be explained in more detail below. In this manner, it will be appreciated 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. Furthermore, as will be described below with reference to Figure 2 and 3 As explained in more detail, the fuel oxygen reduction system 104 is further configured to reduce the oxygen content of the air within the idle portion 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, and the like.

[0050] However, it will be appreciated that in other exemplary embodiments, aircraft 10 and / or engine 52 may have any other suitable configuration. For example, in other embodiments, aircraft 10 may have other wing and / or fuselage designs, engine numbers and / or configurations or positioning, etc. Furthermore, in other embodiments, aircraft 10 may be, for example, a vertical takeoff and landing aircraft, such as a helicopter. Other embodiments are also contemplated.

[0051] More particularly, reference will now be made briefly to Figure 2 , providing such as can be combined with Figure 1 Schematic diagram of a fuel delivery system 100 in an aircraft 10 of FIG. 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. The stripping gas supply path 108 and the stripping gas return path 112 are both in fluid communication with the fuel source 102 and, optionally, in selective fluid communication with the fuel source to receive a gas flow 114 (which is stripping gas, as will be explained below) from the fuel source 102 and provide the gas flow 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 flow 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 containing the vapor / air / gas (e.g., within the tank and above the fuel) may generally be referred to as an idle space 118. During operation, it will be appreciated that the fuel oxygen reduction unit 104 is generally configured to receive an air / gas stream 114 from the idle space 118 of the fuel source 102 and a liquid fuel stream 116 from the fuel source 102, reduce the oxygen content of each, provide a relatively low-oxygen content stream of gas 114 back to the idle space 118, and provide a relatively low-oxygen content stream of liquid fuel 116 to the aircraft engine 52. By reducing the oxygen content of the vapor / air / gas in the idle space 118, the risk of ignition or fire within the tank in the event of a spark may be reduced. Furthermore, by reducing the oxygen content of the liquid fuel 116 provided to the engine 52 , more heat can be added thereto with a reduced risk of coking (allowing for increased efficiency of the combustion process and providing an effective heat sink).

[0052] In particular, for the illustrated embodiment, the fuel delivery system 100 is configured to provide fuel 116 having a relatively low oxygen content from the fuel oxygen reduction unit 104 to each of the plurality of aircraft engines 52, which, for the illustrated embodiment, includes the first aircraft engine 52A, the second aircraft engine 52B, through the "Nth" aircraft engine 52N (e.g., the third, fourth, fifth, sixth, 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 therefore configured to provide the liquid fuel 116 having a relatively low oxygen content to each such engine 52.

[0053] As will be discussed in greater detail below, a fuel delivery system 100 according to such exemplary embodiments is capable of maintaining lower oxygen content air within the neutral position 118 while also providing lower oxygen content fuel to the plurality of aircraft engines 52 .

[0054] Notably, for the illustrated embodiment, the fuel delivery system 100 also includes a return valve 120 and a return line 122 for returning a quantity of relatively low-oxygen liquid fuel to the fuel source 102 in the event that such fuel is not required by the aircraft engines 52. However, in other embodiments, the system 100 may be configured without the return valve 120 and the return line 122 and instead regulate the liquid fuel flow 116 in other suitable manners.

[0055] Now refer to Figure 3 , provides a more detailed schematic diagram 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 FIG. 1 may be incorporated into, for example, the fuel delivery system 100 described above with reference to FIG. Figure 1 The exemplary aircraft 10 described herein may be, and / or may be, operated in conjunction with Figure 21. The exemplary fuel delivery system 100 of FIG. 1 is configured in a similar manner to the exemplary fuel delivery system 100 of FIG. 1. 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 that 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. The stripping gas return path 112 and the stripping gas supply path 108 are both in gaseous communication with the fuel source 102. Furthermore, for the depicted embodiment, the liquid fuel supply path 106 of the fuel oxygen reduction unit 104 is in fluidic 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 flow 116 from the fuel source 102, and is also configured to receive a gas flow 114 (referred to herein as "stripping gas") also from the fuel source 102. In addition, 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 embodiments, for Figure 3 In the embodiment of the present invention, the fuel source 102 generally includes a volume of liquid fuel 116 and defines a void 118 above the liquid fuel 116. Gas received through the stripping gas supply path 108 is received from the void 118, and gas provided to the fuel source 102 through the stripping gas return path 112 is provided to the void 118.

[0056] To assist in the flow of the stripping gas 114 from the fuel source 102, or rather, from the idle space 118 of the fuel source 102, the fuel delivery system 100 includes an idle space pump 124 in flow communication with the idle space 118 of the fuel source 102 and the stripping gas supply path 108 of the fuel oxygen reduction unit 104. Similarly, to assist in the flow of the liquid fuel 116 from the fuel source 102, the fuel delivery system 100 includes a fuel pump 126 in fluid communication with the fuel source 102 and the liquid fuel supply path 106.

[0057] Furthermore, for the depicted embodiment, the fuel oxygen reduction unit 104 generally includes a contactor 128 and a fuel gas separator 130. Furthermore, 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 a stripping gas supply path 108 and a 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, and the like, as well as configurations of components within the stripping gas flow path 132.

[0058] It will be appreciated that the term "stripping gas" is used herein as a convenient term to refer to a gas generally capable of performing the functions described herein. In particular, for the depicted embodiment, the stripping gas 114 consists essentially of gas from the slack 118 of the fuel source 102. Thus, the stripping gas 114 may be primarily composed of atmospheric air. Additionally or alternatively, the stripping gas 114 may be any other suitable gas, such as an inert gas or a substantially inert gas.

[0059] Still referring to the depicted embodiment, 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. Figure 3 In the embodiment of the present invention, the power source 134 for driving 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 for driving the fuel gas separator 130 may be configured in any other suitable manner.

[0060] As will be explained in more detail below, Figure 3 In the embodiment of the present invention, the contactor 128 generally defines a gas inlet 136, a liquid fuel inlet 138, and a fuel / gas mixture outlet 140. In addition, 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 gaseous 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. In addition, the gas outlet 142 of the separator 130 is in gaseous 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.

[0061] In addition, for Figure 3, the fuel oxygen reduction unit 104 further 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 within the stripping gas flow path 132 upstream of the contactor 128 (and downstream of the neutral 118), and the second catalyst 150 is positioned at a location within the stripping gas flow path 132 downstream of the separator 130 (and upstream of the neutral 118). However, it will be appreciated that in other embodiments, the listed components may be provided in any suitable flow order and may not include all of the listed components (e.g., see Figure 5 ), or may include additional components not listed.

[0062] also, Figure 3 The exemplary fuel oxygen reduction unit 104 depicted in FIG. 1 further 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, and more specifically, in gaseous communication with the stripping gas flow path, at a location downstream of the second catalyst 150 and upstream of the idle 118. Furthermore, for the illustrated embodiment, the heat exchanger 152 is in thermal communication, or more specifically, in gaseous communication with the liquid fuel supply path 106, such that the liquid fuel supply path 106, or the liquid fuel 116 passing therethrough, can receive heat from the stripping gas flow 114 passing through the stripping gas return path 112 downstream of the second catalyst 150. This can thereby reduce the temperature of the gas flowing into the idle 118 of the fuel source 102.

[0063] During typical operation, the stripping gas 114 is pushed by the idler pump 124 through the stripping gas supply flow path 108 and through the upstream flame arrester 154. In short, the upstream flame arrester 154 can be configured to prevent flames from the stripping gas supply path 108 from entering the fuel source 102, and vice versa. For the illustrated embodiment, the stripping gas 114 flows from the idler pump 124 through the preheater 125 and into the first catalyst 148. The preheater 125 can be an electric resistance heater, a heat exchanger thermally coupled to another system (not shown), or any other suitable heat source for increasing the temperature of the stripping gas 114. The preheater 125 can be configured to increase the temperature of the stripping gas 114 to or above the activation temperature of the first catalyst 148 (e.g., the minimum light-off temperature of the first catalyst 148, which allows the first catalyst 148 to operate properly). While the exemplary preheater 125 is depicted as a separate component from the first catalyst 148 , in other embodiments, the preheater 125 may be integrated into the first catalyst 148 .

[0064] Furthermore, within the first catalyst 148, the oxygen content of the stripping gas 114 is reduced. More specifically, within the first catalyst 148, the stripping gas 114, which may be relatively oxygen-rich, may react to reduce its oxygen content. However, it will be appreciated that the first catalyst 148 may be configured in any suitable manner to reduce the oxygen content of the stripping gas 114. For example, in certain embodiments, the first catalyst 148 may be configured to react the fuel vapor-rich stripping gas 114 with elements within the first catalyst 148 to provide a relatively oxygen-free stripping gas 114 upon exit. For example, the first catalyst 148 may include a geometry of a catalytic component through which the relatively oxygen-rich stripping gas 114 flows to reduce its oxygen content. Since the stripping gas 114 originates from (i.e., is in contact with) the fuel source 102, such reactions may at least partially utilize the fuel content of the stripping gas 114. In one or more of these configurations, byproducts such as water may be produced. If produced, the water may be in vapor form and may continue to be part of the stripping gas 114. Alternatively, water or other byproducts, if produced, may be directed from the first catalyst 148 (at Figure 3 1 ). In one or more of these embodiments, the first catalyst 148 (or other gas oxygen reduction unit discussed below) can be configured to reduce the oxygen content of the stripping gas 114 to less than about three percent (3%) oxygen (O2) by mass, such as less than one percent (1%) oxygen (O2) by mass.

[0065] Stripping gas 114 is provided from the first catalyst 148 to the gas inlet 136 of the contactor 128. Simultaneously, liquid fuel 116 is pushed from the fuel source 102 by the fuel pump 126 toward and through the liquid fuel supply path 106. The liquid fuel 116 flows from the fuel pump 126 through the heat exchanger 152, where it can receive heat from the stripping gas stream 114 via the stripping gas return path 112. From the heat exchanger 152, the liquid fuel 116 flows, still 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 stripping 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.

[0066] In general, 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 mixes 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).

[0067] Now also briefly refer to Figure 4 , which provides Figure 3 15. The fuel gas separator 130 is a partially enlarged schematic cross-sectional view of an exemplary fuel gas separator 130. It will be appreciated that, in the fuel gas separator 130, the stripping gas 114, which has a relatively low oxygen content, is generally separated from the fuel 116, which has a relatively high oxygen content. Specifically, 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. Furthermore, the fuel gas separator 130 is configured as a mechanically driven fuel gas separator 130, or more particularly, as a rotating / centrifugal fuel gas separator 130. Accordingly, the fuel gas separator 130 includes an input shaft 160 mechanically coupled to the separation assembly 162, and a separation assembly 162, the two components being rotatable together about the central axis 158. Furthermore, the input shaft 160 can be mechanically coupled to and driven by, for example, a suitable power source 134.

[0068] Additionally, the depicted exemplary separation assembly 162 generally includes an inner filter 164 arranged along the central axis 158, and a plurality of paddles 166 positioned radially outwardly 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 paddles 166 about the central axis 158 (i.e., in the circumferential direction C), generally forces the heavier liquid fuel 116 outwardly through the inner filter 164 and the lighter stripping gas 114 inwardly through the inner filter 240. In this manner, as indicated, the liquid fuel 116 may exit through the liquid fuel outlet 144 of the fuel-gas separator 130, and the stripping gas 114 may exit through the stripping gas outlet 142 of the fuel-gas separator 130.

[0069] Thus, it will be appreciated that the liquid fuel 116 provided to the liquid fuel outlet 142, having interacted with the stripping gas 114, can have a relatively low oxygen content, allowing for the addition of a relatively large amount of heat thereto, reducing the risk of the fuel coking (i.e., chemically reacting 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.

[0070] Furthermore, it will be appreciated that the Figure 4 . In other embodiments, the separator 130 may 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 centrifugal separator, a gravity-assisted separator, or any other passive separator or power separator, or a combination thereof.

[0071] Now refer back Figure 3 Schematic diagram of the fuel delivery system 100 in FIG, liquid fuel 116 from the liquid fuel outlet 144 of the separator 130 is provided through 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 a relatively low oxygen content fuel to one or more engines 56 (e.g., see Figure 2 ).as Figure 2 In the embodiment of the present invention, the fuel delivery system 100 further includes a return valve 120 and a return line 122. Depending on the one or more engines 56 (see Figure 2 ), at least a portion of the fuel 116 passing through the liquid fuel outlet path 110 may be returned to the fuel source 102 .

[0072] like Figure 3As also depicted in FIG, it will be appreciated that the exemplary fuel oxygen reduction unit 104 returns utilized stripping gas 114 to the idle portion 118 of the fuel source 102. As noted, the stripping gas 114 to be returned to the idle portion 118 (i.e., downstream of the separator 130 and through the stripping gas return path 112) can have a relatively high oxygen content. Therefore, as also noted above, the fuel oxygen reduction unit 104 also includes a second catalyst 150. The stripping gas 114 from the gas outlet 142 of the separator 130 is provided to the second catalyst 150, wherein the oxygen content of the gas 114 is reduced. The second catalyst 150 is positioned in gas flow 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 the stripping gas 114 to the idle portion 118 of the fuel source 102. It will be appreciated that in certain exemplary embodiments, the second catalyst 150 can operate in a manner similar to that described above with respect to the first catalyst 148. For example, in certain embodiments, the second catalyst 150 can be configured in substantially the same manner as the first catalyst 148, or alternatively, can be configured in any other suitable manner. For example, the second catalyst 150 can react the fuel vapor-rich stripping gas 114 with elements within the second catalyst 150 to provide a relatively oxygen-free stripping gas 114 upon exit. Including the second catalyst 150 can ensure that the stripping gas 114 returning to the neutral position 118 has a desired relatively low oxygen content.

[0073] Still refer to Figure 3 In the embodiment shown, the stripping gas 114 passing through the stripping gas return path 112 is further cooled downstream of the second catalyst 150 by a heat exchanger 152 (this is necessary in the presence of the preheater 125). For the embodiment shown, the heat exchanger 152 is a gas-to-liquid heat exchanger that is configured to transfer heat from the stripping gas 114 passing through the stripping gas return path 112 to a heat exchange fluid, and more specifically, 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.

[0074] The resulting cooled and relatively low oxygen content stripping gas 114 is then provided back to the empty space 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 empty space 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 that includes 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 provided to each of the plurality of aircraft engines 52 or combustion aircraft engines 52, as well as to reduce the oxygen content of the air within the idle space 118 of the fuel source 102, an overall more efficient fuel delivery system 100 may be provided.

[0075] However, it will be appreciated that in other exemplary embodiments, fuel delivery system 100 may be configured in any other suitable manner. For example, fuel delivery system 100 may not provide low-oxygen fuel to every, or even multiple, aircraft engines. Furthermore, it will be appreciated that, for the illustrated embodiment, idle 118, whose air oxygen content is reduced, is idle 118 of fuel source 102, which provides liquid fuel 116 via liquid fuel supply path 106 of fuel oxygen reduction unit 104. However, in other embodiments, idle 118 may be any other suitable fuel source, such that fuel oxygen reduction unit 104 may operate with more than one fuel source. For example, in certain embodiments, fuel oxygen reduction unit 104 may operate with a primary fuel tank and a separate secondary fuel tank.

[0076] Additionally, for the illustrated embodiment, the fuel delivery system 100 also includes a second flame arrester 170 immediately upstream of the neutral 118 in the stripping gas return path 112. The second flame arrester 170 may operate in a similar manner as the first flame arrester 154.

[0077] Although not depicted, it will be appreciated that, in at least certain exemplary embodiments, the fuel oxygen reduction unit 104 may further include a supplemental gas source in gaseous communication with, for example, the stripping gas recycle flow path 132. For example, the supplemental gas source may be an ambient air source, a bleed air source, a stripping gas storage tank, etc., in gaseous communication with the flow path 132 to provide additional air / stripping gas 114 to the recycle gas flow path as needed.

[0078] However, it will be appreciated that in other exemplary embodiments, the fuel delivery system 100 may instead be configured in any other suitable manner. For example, referring now 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 may be configured with Figure 31. The exemplary fuel delivery system 100 is configured in substantially the same manner as the exemplary fuel delivery system 100 of FIG. For example, the fuel delivery system 100 generally includes a fuel source 102 and a fuel oxygen reduction unit 104, wherein 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. The stripping gas supply path 108 and the stripping gas return path 110 are both in gaseous communication with the fuel source 102, and more particularly, with a vacancy 118 of the fuel source 102, and the liquid fuel supply path 106 is in fluidic communication with the fuel source 102. Furthermore, 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 flow 114 through a stripping gas inlet 136 in gaseous communication with the stripping gas supply path 108 and a liquid fuel flow 116 through a liquid fuel inlet 138 in fluidic 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 the inlet 146 of the separator 130. The separator 130 is configured to separate the fuel / gas mixture 156 back into the stripping gas stream 114, which is provided back to the fuel source 102 via the stripping gas return path 112, and the liquid fuel stream 116, which is provided to, for example, one or more aircraft engines 52 via the liquid fuel 116 return path.

[0079] However, with Figure 3 Compared with the embodiment, Figure 5 The exemplary fuel delivery system 100 may not include both the first catalyst 148 and the second catalyst 150. Alternatively, for Figure 5 In the exemplary fuel delivery system 100 of FIG. 1 , the fuel oxygen reduction unit 104 includes a single catalyst 172 positioned upstream of the contactor 128 and downstream of the empty space 118 of the fuel source 102. In this 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 empty space 118 of the fuel source 102. For example, the catalyst 172 can reduce the oxygen content of the stripping gas stream 114 (received from the empty space 118 via the stripping gas supply path 108) to less than approximately three percent (3%) oxygen (O2) by mass, such as less than one percent (1%) oxygen (O2) by mass. Although the stripping gas 114 may be increased 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 empty space 118 of the fuel storage tank, the resulting oxygen content of the air within the empty space 118 of the fuel storage tank may still be lower or significantly lower than it would otherwise be (i.e., the oxygen content of the empty space gas may still be below an acceptable oxygen level for the empty space gas).

[0080] Notably, however, as depicted in phantom, in other embodiments, the single catalyst 172 of the fuel oxygen reduction unit 104 may instead be positioned downstream of the separator 130 and upstream of the vacant space 118 of the fuel source 102. With such a configuration, the fuel delivery system 100, or rather, the fuel oxygen reduction unit 104, may still reduce the oxygen content of the air in the vacant space 118 of the fuel source 102 and the liquid fuel 116 provided to one or more aircraft engines 52. For example, with such a configuration, the fuel oxygen reduction unit 104 may maintain the oxygen content of the air in the vacant space 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.

[0081] Still refer to Figure 5 The embodiment, also with Figure 3 Compared to the embodiment of FIG. 1 , 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 Figure 5 In an exemplary embodiment, the heat exchanger 152 is not in fluid communication with the liquid fuel supply path 106. Alternatively, 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 passing through 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.

[0082] Furthermore, in other embodiments, any other suitable configuration may be provided for the fuel delivery system 100. For example, referring now to Figure 6 , a fuel delivery system 100 according to yet another exemplary embodiment of the present disclosure is provided. Figure 6 The exemplary fuel delivery system 100 may be configured with Figure 3 The exemplary fuel delivery system 100 is configured in substantially the same manner as that of 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, wherein 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. The stripping gas supply path 108 and the stripping gas return path 110 are both in gas flow communication with the fuel source 102, and more particularly, with a vacancy 118 of the fuel source 102, and further, the liquid fuel supply path 106 is in fluid communication with the fuel source 102. Furthermore, the exemplary fuel oxygen reduction unit 104 generally includes a contactor 128 and a separator 130.

[0083] as Figure 3 In the embodiment of the present invention, the fuel delivery system 100 includes a first gas oxygen reduction unit and a second gas oxygen reduction unit. Figure 3 Compared with the embodiment of Figure 6 In the exemplary fuel delivery system 100 of FIG. 1 , the first gas oxygen reduction unit and the second gas oxygen reduction unit are not configured as catalysts (i.e., the first catalyst 148 and the second catalyst 150), but are instead 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 booster pump 124 (for the illustrated embodiment) and upstream of the fuel oxygen reduction assembly, or contactor 128 and 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., the contactor 128 and separator 130 for the illustrated embodiment, and upstream of the idle 118 of the fuel source 102.

[0084] 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 respective portions 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 include 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.

[0085] It will be appreciated that with such a configuration, a preheater (e.g., Figure 3 preheater 125), so that a heat exchanger (e.g., heat exchanger 152) may not be required.

[0086] It will be further 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 may be related to Figures 3 to 5For example, in other embodiments, one or more features of the exemplary fuel delivery system 100 may be combined. 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 instead configured as a catalyst. 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, above with reference to Figure 5 described embodiments).

[0087] Furthermore, it will be appreciated that in other exemplary embodiments, other configurations are also contemplated. For example, referring now to Figure 7 , a fuel delivery system 100 according to yet another exemplary embodiment of the present disclosure is provided. Figure 7 The exemplary fuel delivery system 100 may be configured with Figure 3 The exemplary fuel delivery system 100 is configured in substantially the same manner as that of FIG. For example, the fuel delivery system 100 generally includes a fuel source 102 and a fuel oxygen reduction unit 104, wherein 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. Furthermore, the fuel oxygen reduction unit 104 includes a first gas oxygen reduction unit 186 and a second gas oxygen reduction unit 188 positioned within the stripping gas supply path 108 and the return path 110, respectively, upstream and downstream of the fuel oxygen reduction assembly.

[0088] However, for the depicted embodiment, the fuel oxygen reduction assembly is not configured as a contactor and separator, but rather as a membrane fuel oxygen reduction unit 190. The membrane fuel oxygen reduction unit 190 defines a stripping gas chamber 192, which defines a gas inlet 194 and a gas outlet 196, and a fuel chamber 198, which defines a fuel inlet 200 and a fuel outlet 202. The membrane fuel oxygen reduction unit 190 also includes a membrane 204 positioned between the stripping gas chamber 192 and the fuel chamber 198. The membrane 204 can 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 can be any suitable oxygen-permeable membrane.

[0089] Such a configuration may allow for a simultaneous reduction in the neutral 118 and oxygen in the liquid fuel 116 provided to the engine 50 while utilizing less mechanical work.

[0090] It will be further appreciated that in other exemplary embodiments, other configurations are also contemplated. For example, referring now to Figure 8 , a fuel delivery system 100 according to yet another exemplary embodiment of the present disclosure is provided. Figure 8The exemplary fuel delivery system 100 may be configured with Figure 3 The exemplary fuel delivery system 100 is configured in substantially the same manner as that of FIG. For example, the fuel delivery system 100 generally includes a fuel source 102 and a fuel oxygen reduction unit 104, wherein 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. Furthermore, the fuel oxygen reduction unit 104 includes a first gas oxygen reduction unit 186 and a second gas oxygen reduction unit 188 positioned within the stripping gas supply path 108 and the return path 110, respectively, upstream and downstream of the fuel oxygen reduction assembly.

[0091] However, for the depicted embodiment, the gas flow 114 provided to the stripping gas supply path 108 is not only received from the vacancy 118 of the fuel storage tank 102, but is also or alternatively provided from the air source 200. As depicted, the air source 200 is separate from the fuel source (i.e., for the illustrated embodiment, the storage tank 102), and the stripping gas supply path 108 is in gas flow communication with the air source 200 for receiving at least a portion of the gas flow 114 provided to the stripping gas supply path 108 from the air source 200.

[0092] In at least some exemplary embodiments, air source 200 is at least one of an air cycle machine, a gas turbine engine of an aircraft in conjunction with fuel delivery system 100, or a device for collecting ambient airflow. For example, air source 200 may be a compressor section of a gas turbine engine, such that the provided airflow is bleed air from the compressor section. Additionally or alternatively, air source 200 may be an air cavitation cavity, a ram air turbine, or other opening configured to receive ambient airflow above the aircraft.

[0093] However, it is noted that in other embodiments, the air source 200 may be a combination of two or more of the above-described air sources 200 , or any other suitable combination of air sources 200 external to the fuel supply / tank 102 .

[0094] In this way, it will be recognized that Figure 8 In the embodiment, the gas flow from the air source 200 is the first gas flow 114A, and the stripping gas supply path is further connected to the fuel source (or the empty space 118 of the fuel tank 102) to receive the second gas flow 114B.

[0095] It will be further appreciated that, for the depicted embodiment, the fuel delivery system 100 also includes a control valve 202 in gaseous communication with the stripping gas supply path for controlling a first flow rate of the first gas stream 114A, a second flow rate of the second gas stream 114B, or both. More specifically, for the illustrated embodiment, the stripping gas supply path 108 includes a first portion extending from the air source 200, a second portion extending from the fuel source, and a junction where the first and second portions intersect. For the illustrated embodiment, the control valve 202 is positioned at the junction and is configured as a variable-throughput 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 (as well as various ratios therebetween, such as 10:90, 25:75, 50:50, 75:25, 90:10, etc.).

[0096] Thus, the control valve 202 can effectively control the amount of air in the stripping gas flow path 132 from the air source 200 and from the fuel source.

[0097] Briefly, it will be appreciated that the exemplary fuel oxygen reduction unit 104 is still configured to provide a gas flow 114 in the stripping gas return path 112 to the fuel source, or more specifically, to the empty space 118 of the fuel storage tank 102, such that the oxygen content of the gas within the empty space 118 is reduced. However, due to the introduction of the gas flow from the air source 200, the fuel oxygen reduction unit 104 can generally operate as an at least partially open-loop system due to its relationship with the stripping gas flow path 108. Thus, the empty space 118 of the fuel storage tank is configured to provide an excess gas flow 204 to a location separate from the fuel oxygen reduction unit and, more specifically, separate from the stripping gas flow path 108. For example, in certain exemplary embodiments, the location providing the excess gas flow 204 from the empty space 118 of the fuel storage tank can be an ambient location (e.g., an outboard location), or it can be one or more separate systems of the aircraft (e.g., an aircraft engine, a separate fuel oxygen reduction unit, etc.).

[0098] It is worth noting that reference is still made to Figure 8For the illustrated embodiment, a first gas stream 114A from an air source 200 may be provided at a first temperature and a first pressure, while a second gas 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, both the first temperature and the first pressure may be greater than the second temperature and the second pressure, respectively, depending on which stage of the compressor section the first gas stream 114A is provided from. The higher temperature and pressure gas stream may facilitate certain operations of the fuel oxygen reduction unit 104, such as a desired stripping gas volume flow rate and / or other stripping gas operating parameters (e.g., temperature, pressure, etc.).

[0099] However, it will be further appreciated that the fuel content in the second gas stream 114B from the fuel source can be greater than the fuel content in the first gas stream 114A from the air source 200. It will also be appreciated that the fuel oxygen reduction unit 104 can 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 gas stream 114B from the fuel source can assist in the operation of the gas oxygen reduction unit. For example, the gas oxygen reduction unit can be a catalyst 148 or 150 or a burner, and the fuel content in the second gas stream 114B from the fuel source can assist in the operation of the catalyst 148 or 150 or the burner.

[0100] In this manner, fuel delivery system 100 also includes a sensor 206 and a controller 208 operably coupled to control valve 202 and sensor 206. Controller 208 is configured to receive data indicative of an operating parameter of the fuel oxygen reduction unit (e.g., from sensor 206) and to vary 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.

[0101] In certain exemplary embodiments, the operating parameter may be the temperature of the airflow 114, the pressure of the airflow 114, the flow rate of the airflow 114, the volume of the airflow 114, etc. Additionally or alternatively, the operating parameter may be the fuel content of the airflow 114. The sensor 206 may be configured to sense data indicative of one or more of these operating parameters.

[0102] Briefly, it will be further recognized that Figure 8 Controller 208 , depicted in FIG, is configured to receive sensed data from one or more sensors (including sensor 206 , for the illustrated embodiment), and may make control decisions for fuel delivery system 100 , for example, based on the received data.

[0103] In one or more exemplary embodiments, Figure 2The controller 208 depicted in FIG may be a stand-alone controller 208 for the fuel delivery system 100 , or alternatively, may be integrated into one or more of a controller for an aircraft into which the fuel delivery system 100 is integrated, a controller for a gas turbine engine receiving fuel from the fuel delivery system 100 , or the like.

[0104] With particular reference to the operation of controller 208, in at least some embodiments, controller 208 may include one or more computing devices 210. Computing device 210 may include one or more processors 210A and one or more memory devices 210B. The one or more processors 210A may 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 may include one or more computer-readable media, including, but not limited to, non-transitory computer-readable media, RAM, ROM, a hard drive, a flash drive, and / or other memory devices.

[0105] One or more memory devices 210B may store information accessible by one or more processors 210A, including computer-readable instructions 210C executable by one or more processors 210A. Instructions 210C may be any set of instructions that, when executed by one or more processors 210A, cause one or more processors 210A to perform operations. In some embodiments, instructions 210C may be executed by one or more processors 210A to cause one or more processors 210A to perform operations, such as any operations and functions for which controller 208 and / or computing device 210 are configured, such as the operations described herein for operating fuel delivery system 100 (e.g., method 300), and / or any other operations or functions of one or more computing devices 210. Instructions 210C may be software written in any suitable programming language or may be implemented in hardware. Additionally and / or alternatively, instructions 210C may be executed in a separate, logical and / or virtual thread on processor 210A. Memory device 210B may also store data 210D accessible by processor 210A. For example, data 210D may include data indicative of power flow, data indicative of engine / aircraft operating status, and / or any other data and / or information described herein.

[0106] The computing device 210 can also include a network interface 210E for communicating, for example, with other components of the fuel delivery system 100, with a gas turbine engine in conjunction with the fuel delivery system 100, with an aircraft in conjunction with 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 for sensing data indicative of one or more parameters of the fuel delivery system 100. The controller 208 is operably coupled to the one or more sensors, for example, via 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. Further, for the illustrated embodiment, the controller 208 is operably coupled to, for example, the control valve 202. In this manner, the controller 208 can be configured to actuate the control valve 202 (in response to, for example, data sensed by the one or more sensors).

[0107] The network interface 210E can include any suitable components for interfacing with one or more networks, including for example, transmitters, receivers, ports, controllers, antennas, and / or other suitable components.

[0108] It will be further appreciated that in other example embodiments, other configurations can also be contemplated. For example, referring now to Figure 9 , a fuel delivery system 100 is provided in accordance with yet another example embodiment of the present disclosure. Figure 9 The example fuel delivery system 100 of Figure 8 may be configured in substantially the same manner as the example fuel delivery system 100 of . For example, the fuel delivery system 100 generally includes a fuel source 102, an air source 200, and a fuel oxygen reduction unit 104, wherein 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 112. Further, the stripping gas supply path 108 is in airflow communication with the air source 200, and the stripping gas return path 112 is in airflow communication with the fuel source.

[0109] However, for the depicted embodiment, the airflow 114 provided to the stripping gas supply path 108 is provided solely by the air source 200, and the stripping gas supply path 108 is not configured to receive an airflow from the fuel source.

[0110] Figure 10 Referring now to Figures 1 to 9 , a method of operating a fuel system of an aircraft is provided. The fuel system can be configured in accordance with one or more of the example fuel delivery systems discussed above with respect to

[0111] Method 300 generally includes using a fuel oxygen reduction unit at (301). For the depicted example aspect, using the fuel oxygen reduction unit at (301) includes reducing an oxygen content in a liquid fuel from a fuel source. More particularly, for the depicted example aspect, using the fuel oxygen reduction unit at (301) includes receiving a gas stream from a stripping gas supply path of the fuel oxygen reduction unit at (302), and receiving a liquid fuel stream from a liquid fuel supply path of the fuel oxygen reduction unit at (304). Method 300 further includes reducing an oxygen content of the gas stream and the liquid fuel stream within the fuel oxygen reduction unit at (306), and providing the oxygen content reduced gas stream to the fuel source at (308). In certain example embodiments, reducing the oxygen content of the gas stream and the liquid fuel stream within the fuel oxygen reduction unit at (306) can include mixing the liquid fuel stream and the gas stream together in a contactor to form a fuel / gas mixture, and separating the fuel / gas mixture back into the liquid fuel stream and the gas stream. Alternatively, however, reducing the oxygen content of the gas stream and the liquid fuel stream within the fuel oxygen reduction unit at (306) can include using a membrane-based fuel oxygen reduction unit to reduce the oxygen content of the liquid fuel stream and the gas stream.

[0112] Still referring to Figure 10 For the depicted example aspect, receiving the gas stream from the stripping gas supply path of the fuel oxygen reduction unit at (302) includes receiving data indicative of an operating parameter of the fuel oxygen reduction unit at (310), and changing a first flow rate of the gas from the air source, changing a second flow rate of the gas from the 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 example aspects, at (312), changing the first flow rate of the gas from the air source, changing the second flow rate of the gas from the fuel source, or both, can include adjusting a control valve, such as an example three-way valve of Figure 8 .

[0113] In certain example aspects, the operating parameter of the fuel oxygen reduction unit can be a temperature of the gas stream to the stripping gas supply path, a pressure of the gas stream to the stripping gas supply path, a fuel content of the gas stream to the stripping gas supply path, or a combination thereof.

[0114] Such example aspects can allow the fuel oxygen reduction unit to be operated at a desired flow rate, pressure, and / or temperature to provide a desired oxygen reduction level for the fuel stream and the fuel source.

[0115] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems, and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. If such other embodiments include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims, then such other examples are intended to be within the scope of the claims.

[0116] Further aspects of the invention are provided by the subject matter of the following clauses: A fuel system for an aircraft having a fuel source, the system comprising: 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 for fluid communication with the aircraft's fuel source and optionally for fluid communication with the aircraft's fuel source.

[0117] The fuel system of one or more of these clauses, further comprising: an air source separate from the fuel source, wherein the stripping gas supply path is in gas flow communication with the air source for receiving the gas flow from the air source.

[0118] 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 an aircraft, or a device for collecting an ambient air flow.

[0119] The fuel system of one or more of these clauses, wherein the gas flow from the air source is a first gas flow, wherein the stripping gas supply path is further in communication with the fuel source gas flow for receiving a second gas flow from the air source.

[0120] The fuel system of one or more of these clauses, wherein the stripping gas supply path comprises a first stripping gas flow path extending from the fuel source, and wherein the fuel system comprises a check valve in the first stripping gas flow path.

[0121] The fuel system of one or more of these clauses, wherein a first air flow from an air source is provided at a first temperature and a first pressure, wherein a second air flow from a 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.

[0122] The fuel system of one or more of these clauses, wherein the fuel oxygen reduction unit comprises: a gaseous oxygen reduction unit positioned in the stripping gas supply path or the stripping gas return path, and wherein the fuel content within the second gas stream from the fuel source assists operation of the gaseous oxygen reduction unit.

[0123] The fuel system of one or more of these clauses further includes: a control valve in communication with the stripping gas supply path airflow for controlling a first flow rate of the first airflow, a second flow rate of the second airflow, or both; and a controller operably coupled to the control valve, the controller 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.

[0124] The fuel system of one or more of these clauses, wherein the fuel source comprises a fuel storage tank, wherein the fuel oxygen reduction unit further comprises: an idler pump in gas flow communication with the stripping gas supply path.

[0125] The fuel system of one or more of these clauses, wherein the fuel source comprises a fuel storage tank, and wherein the stripping gas return path is in communication with an idle gas stream of the fuel storage tank.

[0126] The fuel system of one or more of these clauses, wherein the fuel source comprises a fuel storage tank, and wherein the vacancy of the fuel storage tank is configured to provide excess gas flow to a location separate from the fuel oxygen reduction unit.

[0127] The fuel system of one or more of these clauses, wherein the liquid fuel supply path is fluidly connected to a fuel source, and wherein the fuel oxygen reduction unit is configured to receive a flow of liquid fuel from the fuel source.

[0128] The fuel system of one or more of these clauses, wherein the fuel oxygen reduction unit comprises: a gaseous 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 gaseous communication with the stripping gas supply path and the stripping gas return path.

[0129] The 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 comprises a second gas oxygen reduction unit in the stripping gas return path.

[0130] A fuel system of one or more of these clauses, wherein the fuel oxygen reduction component includes: a contactor fluidly connected to a liquid fuel supply path and a stripping gas supply path for mixing a liquid fuel flow from the liquid fuel supply path with a stripping gas flow 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 flow and a liquid fuel flow, the separator fluidly connected to a liquid fuel outlet path and a stripping gas return path for providing the liquid fuel flow to the liquid fuel outlet path and providing the stripping gas flow to the stripping gas return path.

[0131] The fuel system of one or more of these clauses, wherein the gaseous oxygen reduction unit is a membrane gaseous oxygen reduction unit.

[0132] The fuel system of one or more of these clauses, wherein the gaseous oxygen reduction unit is a catalyst.

[0133] A fuel system according to one or more of these clauses, incorporated into an aircraft according to one or more of these clauses.

[0134] A fuel system according to one or more of these clauses, incorporating into a method according to one or more of these clauses.

[0135] 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 comprising: receiving a gas 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 gas stream and the liquid fuel stream within the fuel oxygen reduction unit; and providing the gas stream with a reduced oxygen content to the fuel source.

[0136] A method of operating an aircraft fuel system including a fuel source, the method comprising: using a fuel oxygen reduction unit, wherein using the fuel oxygen reduction unit comprises reducing the oxygen content of liquid fuel from the fuel source; and providing a gas flow with reduced oxygen content to the fuel source.

[0137] The method of one or more of these clauses, wherein receiving a gas flow from a stripping gas supply path of a fuel oxygen reduction unit comprises: 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 gas from an air source, changing a second flow rate of gas from a fuel source, or both.

[0138] The method of one or more of these clauses, wherein the operating parameter of the fuel oxygen reduction unit is a temperature of the gas stream to the stripping gas supply path, a pressure of the gas stream to the stripping gas supply path, a fuel content of the gas stream to the stripping gas supply path, or a combination thereof.

[0139] The method of one or more of these clauses, wherein providing the oxygen content reduced gas stream to the fuel source includes providing the oxygen content reduced gas stream to a ullage of the fuel system.

[0140] The method of one or more of these clauses, utilizing the fuel system of one or more of these clauses.

[0141] The method of one or more of these clauses, utilizing the fuel oxygen reduction unit of one or more of these clauses.

[0142] The method of one or more of these clauses, utilizing the aircraft of one or more of these clauses.

[0143] An aircraft, comprising: a fuel source; and 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 in gas flow communication with the fuel source of the aircraft.

[0144] The aircraft of one or more of these clauses, utilizing the fuel oxygen reduction unit of one or more of these clauses.

[0145] A fuel system for an aircraft, the system comprising: a fuel source; and 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 and the stripping gas supply path are each in gas flow communication with the fuel source.

[0146] The fuel system of one or more of these clauses, wherein the fuel source includes a fuel tank, and wherein the stripping gas supply path and the stripping gas return path are each in gas flow communication with an ullage of the fuel tank.

[0147] The 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.

[0148] The fuel system of one or more of these clauses, wherein the fuel oxygen reduction unit is configured to receive a gas stream 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 an oxygen content of the gas stream and the liquid fuel stream.

[0149] The 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 in fluid communication with the liquid fuel supply path and the liquid fuel return path, and further in airflow communication with the stripping gas supply path and the stripping gas return path.

[0150] The 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.

[0151] The 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 liquid fuel flow from the liquid fuel supply path with stripping gas flow 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 the stripping gas flow and the liquid fuel flow, the separator fluidly connected to the liquid fuel outlet path and the stripping gas return path for providing the liquid fuel flow to the liquid fuel outlet path and the stripping gas flow to the stripping gas return path.

[0152] The 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 airflow 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.

[0153] The fuel system of one or more of these clauses, wherein the gaseous oxygen reduction unit is a membrane gaseous oxygen reduction unit.

[0154] The fuel system of one or more of these clauses, wherein the gaseous oxygen reduction unit is a catalytic converter.

[0155] The 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; and a heat exchanger thermally coupled to the stripping gas return path.

[0156] The fuel system of one or more of these clauses, wherein the fuel oxygen reduction unit further includes: a neutral position pump in airflow communication with the stripping gas supply path.

[0157] A propulsion system for an aircraft includes an aircraft engine; and a fuel system including a fuel source; and a fuel oxygen reduction unit, the 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 and the stripping gas supply path are both in fluid communication with the fuel source gas flow, and wherein the liquid fuel outlet path is in fluid communication with the aircraft engine to provide liquid fuel to the aircraft engine.

[0158] The propulsion system of 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 fluidly connected to both the first aircraft engine and the second aircraft engine for providing liquid fuel to both the first aircraft engine and the second aircraft engine.

[0159] The propulsion system of one or more of these clauses, wherein the fuel oxygen reduction unit comprises: a gaseous 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 gaseous communication with the stripping gas supply path and the stripping gas return path.

[0160] The propulsion 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 comprises a second gas oxygen reduction unit in the stripping gas return path.

[0161] A propulsion system of one or more of these clauses, wherein the fuel oxygen reduction assembly comprises: a contactor fluidly connected to a liquid fuel supply path and a stripping gas supply path for mixing a liquid fuel flow from the liquid fuel supply path with a stripping gas flow 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 flow and a liquid fuel flow, the separator fluidly connected to a liquid fuel outlet path and a stripping gas return path for providing the liquid fuel flow to the liquid fuel outlet path and providing the stripping gas flow to the stripping gas return path.

[0162] The propulsion system of 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 a stripping gas supply path and a stripping gas return path, and a fuel chamber in fluid communication with a liquid fuel supply path and a liquid fuel outlet path, the membrane fuel oxygen reduction unit including a membrane separating the stripping gas chamber from the fuel chamber.

[0163] The propulsion system of one or more of these clauses, wherein the gaseous oxygen reduction unit is a membrane gaseous oxygen reduction unit or a catalyst.

[0164] The propulsion system of one or more of these clauses, wherein the liquid fuel supply path is fluidly connected to the fuel source to receive the liquid fuel flow from the fuel source.

[0165] A propulsion system of one or more of these clauses, utilizing a fuel system of one or more of these clauses, utilizing a fuel oxygen reduction unit of one or more of these clauses, incorporated into an aircraft of one or more of these clauses, or used within a method of one or more of these clauses.

Claims

1. A fuel system for an aircraft, the system comprising: fuel source; 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 supply path and the stripping gas return path are both communicated with the idle air flow of the fuel source.

2. 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 flow of liquid fuel from the fuel source.

3. The fuel system according to claim 2, wherein: The liquid fuel supply path is fluidly connected to the fuel source, and wherein the liquid fuel outlet path is in fluid communication with at least one engine.

4. The fuel system according to claim 1, wherein: The fuel oxygen reduction unit is configured to receive a gas flow through the stripping gas supply path and a liquid fuel flow through the liquid fuel supply path, and wherein the fuel oxygen reduction unit is configured to reduce oxygen content of the gas flow and the liquid fuel flow.

5. The fuel system according to claim 1, wherein: The fuel oxygen reduction unit comprises: a gaseous oxygen reduction unit positioned in the stripping gas supply path or the stripping gas return path; and A fuel oxygen reduction assembly is in fluid communication with the liquid fuel supply path and the liquid fuel return path, and is further in gas flow communication with the stripping gas supply path and the stripping gas return path.

6. The fuel system according to claim 5, wherein: The gas oxygen reduction unit is configured to reduce the oxygen content of the stripping gas flowing through the gas oxygen reduction unit to less than about three percent (3%) oxygen (O2) by mass.

7. The fuel system of claim 5, further comprising: A flame arrester is positioned in the stripping gas supply path upstream of the gaseous oxygen reduction unit.

8. The fuel system of claim 5, further comprising: A flame arrester is positioned in the stripping gas supply path upstream of the fuel source.

9. The fuel system according to claim 5, wherein: The gaseous oxygen reduction unit is a membrane gaseous oxygen reduction unit.

10. The fuel system according to claim 5, wherein: The gaseous oxygen reduction unit is a catalyst.

Images