FUEL OXYGEN REDUCTION UNIT WITH RECUPERATIVE HEAT EXCHANGER

A fuel oxygen reduction unit is provided that includes an inlet fuel line and an outlet fuel line; an oxygen transfer assembly in fluid communication with the inlet fuel line, the outlet fuel line, and a stripping gas flowpath for reducing an amount of oxygen in an inlet fuel flow through the inlet fuel line using a stripping gas flow through the stripping gas flowpath; a catalyst in communication with the stripping gas flowpath at a location downstream of the oxygen transfer assembly, the catalyst configured to reduce an oxygen content of the stripping gas flow through the stripping gas flowpath; and a recuperative heat exchanger in airflow communication with the stripping gas flowpath at a location downstream of the catalyst and upstream of the catalyst for exchanging heat from the stripping gas flow flowing from the catalyst with the stripping gas flow flowing through the recuperative heat exchanger at the location upstream of the catalyst.

FIELD

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

BACKGROUND

Typical aircraft propulsion systems include one or more gas turbine engines. The gas turbine engines generally include a turbomachine, the turbomachine including, in serial flow order, a compressor section, a combustion section, a turbine section, and an exhaust section. In operation, air is provided to an inlet of the compressor section where one or more axial compressors progressively compress the air until it reaches the combustion section. Fuel is mixed with the compressed air and burned within the combustion section to provide combustion gases. The combustion gases are routed from the combustion section to the turbine section. The flow of combustion gasses through the turbine section drives the turbine section and is then routed through the exhaust section, e.g., to atmosphere.

Certain operations and systems of the gas turbine engines and aircraft may generate a relatively large amount of heat. Fuel has been determined to be an efficient heat sink to receive at least some of such heat during operations due at least in part to its heat capacity and an increased efficiency in combustion operations that may result from combusting higher temperature fuel.

However, heating the fuel up without properly conditioning the fuel may cause the fuel to “coke,” or form solid particles that may clog up certain components of the fuel system, such as the fuel nozzles. Reducing an amount of oxygen in the fuel may effectively reduce the likelihood that the fuel will coke beyond an unacceptable amount.

DETAILED DESCRIPTION

The following description is provided to enable those skilled in the art to make and use the described embodiments contemplated for carrying out the disclosure. Various modifications, equivalents, variations, and alternatives, however, will remain readily apparent to those skilled in the art. Any and all such modifications, variations, equivalents, and alternatives are intended to fall within the scope of the present disclosure.

The term “turbomachine” or “turbomachinery” refers to a machine including one or more compressors, a heat generating section (e.g., a combustion section), and one or more turbines that together generate a torque output.

The term “gas turbine engine” refers to an engine having a turbomachine as all or a portion of its power source. Example gas turbine engines include turbofan engines, turboprop engines, turbojet engines, turboshaft engines, etc., as well as hybrid-electric versions of one or more of these engines.

The term “combustion section” refers to any heat addition system for a turbomachine. For example, the term combustion section may refer to a section including one or more of a deflagrative combustion assembly, a rotating detonation combustion assembly, a pulse detonation combustion assembly, or other appropriate heat addition assembly. In certain example embodiments, the combustion section may include an annular combustor, a can combustor, a cannular combustor, a trapped vortex combustor (TVC), or other appropriate combustion system, or combinations thereof.

In a fuel oxygen reduction unit of the present disclosure, an oxygen transfer assembly reduces an amount of oxygen in an inlet fuel flow through an inlet fuel line using a stripping gas flow through a stripping gas flowpath. In certain embodiments, a pre-heater may be in thermal communication with the stripping gas flowpath at a location downstream of the oxygen transfer assembly. The pre-heater is configured to receive and add heat energy to the stripping gas flow from the oxygen transfer assembly. A catalyst is in airflow communication with the stripping gas flowpath at a location downstream of the oxygen transfer assembly and the pre-heater, if included. The catalyst is configured to reduce an oxygen content of the the stripping gas flow through the stripping gas flowpath. The stripping gas flow from the catalyst may be referred to as a stripping gas stream. A recuperative heat exchanger is in airflow communication with the stripping gas flowpath at a location downstream of the catalyst and upstream of the catalyst. The heat exchanger is configured to take a portion of heat from the stripping gas stream from the catalyst for exchanging heat from the stripping gas flow from the catalyst with the stripping gas flow at the location upstream of the catalyst.

For example, the stripping gas flow may be configured to travel through the stripping gas flowpath from the oxygen transfer assembly, through the recuperative heat exchanger as a heat sink, through the catalyst, through the recuperative heat exchanger as a heat source, and back to the oxygen transfer assembly. It will be appreciated that such a flow arrangement is not exclusive of other intermediate components, such as a pre-heater if provided.

Advantageously, the stripping gas stream that flows from the heat exchanger to the oxygen transfer assembly has a lower temperature because the heat exchanger takes a portion of the heat from the stripping gas stream. Furthermore, the heat exchanger of the present disclosure ensures a lower amount of energy is required from the pre-heater to heat the stripping gas flow that flows from the heat exchanger to the pre-heater and subsequently to the catalyst.

Referring now to the drawings, wherein identical numerals indicate the same elements throughout the figures,FIG.1provides a schematic, cross-sectional view of an engine in accordance with an exemplary embodiment of the present disclosure. The engine may be incorporated into a vehicle. For example, the engine may be an aeronautical engine incorporated into an aircraft. Alternatively, however, the engine may be any other suitable type of engine for any other suitable aircraft.

For the embodiment depicted, the engine is configured as a high bypass turbofan engine100. As shown inFIG.1, the turbofan engine100defines an axial direction A (extending parallel to a longitudinal centerline or axis101provided for reference), a radial direction R, and a circumferential direction (extending about the axial direction A; not depicted inFIG.1). In general, the turbofan100includes a fan section102and a turbomachine104disposed downstream from the fan section102.

The exemplary turbomachine104depicted generally includes a substantially tubular outer casing106that defines an annular inlet108. The outer casing106encases, in serial flow relationship, a compressor section including a booster or low pressure (LP) compressor110and a high pressure (HP) compressor112; a combustion section114; a turbine section including a high pressure (HP) turbine116and a low pressure (LP) turbine118; and a jet exhaust nozzle section120. The compressor section, combustion section114, and turbine section together define at least in part a core air flowpath121extending from the annular inlet108to the jet exhaust nozzle section120. The turbofan engine further includes one or more drive shafts. More specifically, the turbofan engine includes a high pressure (HP) shaft or spool122drivingly connecting the HP turbine116to the HP compressor112, and a low pressure (LP) shaft or spool124drivingly connecting the LP turbine118to the LP compressor110.

For the embodiment depicted, the fan section102includes a fan126having a plurality of fan blades128coupled to a disk130in a spaced apart manner. The plurality of fan blades128and disk130are together rotatable about the longitudinal axis101by the LP shaft124. The disk130is covered by rotatable front hub132aerodynamically contoured to promote an airflow through the plurality of fan blades128. Further, an annular fan casing or outer nacelle134is provided, circumferentially surrounding the fan126and/or at least a portion of the turbomachine104. The outer nacelle134is supported relative to the turbomachine104by a plurality of circumferentially-spaced outlet guide vanes136. A downstream section138of the outer nacelle134extends over an outer portion of the turbomachine104so as to define a bypass airflow passage140therebetween.

Referring still toFIG.1, the turbofan engine100additionally includes an accessory gearbox142, a fuel oxygen reduction unit144, and a fuel delivery system146. For the embodiment shown, the accessory gearbox142is located within the cowling/outer casing106of the turbomachine104. Additionally, it will be appreciated that, although not depicted schematically inFIG.1, the accessory gearbox142may be mechanically coupled to, and rotatable with, one or more shafts or spools of the turbomachine104. For example, in at least certain exemplary embodiments, the accessory gearbox142may be mechanically coupled to, and rotatable with, the HP shaft122. Further, for the embodiment shown, the fuel oxygen reduction unit144is coupled to, or otherwise rotatable with, the accessory gearbox142, although in other embodiments the fuel oxygen reduction unit144may use other, or additional sources, of rotary power such as an electric motor. In such a manner, it will be appreciated that the exemplary fuel oxygen reduction unit144is driven by the accessory gearbox142. Notably, as used herein, the term “fuel oxygen conversion or reduction” generally means a device capable of reducing a free oxygen content of the fuel.

Moreover, the fuel delivery system146generally includes a fuel source148, such as a fuel tank, and one or more fuel lines150. The one or more fuel lines150provide a fuel flow through the fuel delivery system146to the combustion section114of the turbomachine104of the turbofan engine100.

It will be appreciated, however, that the exemplary turbofan engine100depicted inFIG.1is provided by way of example only. In other exemplary embodiments, any other suitable engine may be utilized with aspects of the present disclosure. For example, in other embodiments, the engine may be any other suitable gas turbine engine, such as a turboshaft engine, turboprop engine, turbojet engine, etc. In such a manner, it will further be appreciated that in other embodiments the gas turbine engine may have any other suitable configuration, such as any other suitable number or arrangement of shafts, compressors, turbines, fans, etc. Further, although the exemplary gas turbine engine depicted inFIG.1is shown schematically as a direct drive, fixed-pitch turbofan engine100, in other embodiments, a gas turbine engine of the present disclosure may be a geared gas turbine engine (i.e., including a gearbox between the fan126and shaft driving the fan, such as the LP shaft124), may be a variable pitch gas turbine engine (i.e., including the fan126having the plurality of fan blades128rotatable about their respective pitch axes), etc. Further, although not depicted herein, in other embodiments the gas turbine engine may be any other suitable type of gas turbine engine, such as an industrial gas turbine engine incorporated into a power generation system, a nautical gas turbine engine, etc. Further, still, in alternative embodiments, aspects of the present disclosure may be incorporated into, or otherwise utilized with, any other type of engine, such as reciprocating engines.

Moreover, it will be appreciated that although for the embodiment depicted, the turbofan engine100includes the fuel oxygen reduction unit144positioned within the turbomachine104, i.e., within the outer casing106of the turbomachine104, in other embodiments, the fuel oxygen reduction unit144may be positioned at any other suitable location. For example, in other embodiments, the fuel oxygen reduction unit144may instead be positioned remote from the turbofan engine100. Additionally, in other embodiments, the fuel oxygen reduction unit144may additionally or alternatively be driven by other suitable power sources such as an electric motor, a hydraulic motor, or an independent mechanical coupling to the HP or LP shaft, etc.

Referring now toFIGS.2and3, schematic drawings of a fuel oxygen reduction unit200for a gas turbine engine in accordance with an exemplary aspect of the present disclosure is provided. In at least certain exemplary embodiments, the exemplary fuel oxygen reduction unit200depicted may be incorporated into, e.g., the exemplary engine100described above with reference toFIG.1(e.g., may be the fuel oxygen reduction unit144depicted inFIG.1and described above).

As will be appreciated from the discussion herein, in an exemplary embodiment, the fuel oxygen reduction unit200generally includes an oxygen transfer assembly201. As will be explained in more detail, below, the oxygen transfer assembly201generally includes a contactor202and a separator204. Further, the fuel oxygen reduction unit200additionally includes a catalyst210, and a recuperative heat exchanger211, and for the embodiment depicted, a pre-heater212. In the exemplary embodiment depicted, the separator204is a dual separator pump as described in more detail below and as shown inFIG.3.

It will be appreciated, however, that in other exemplary embodiments, other separators may be utilized with the fuel oxygen reduction unit200of the present disclosure. It will further be appreciated that in other exemplary embodiments, the oxygen transfer assembly201may additionally or alternatively include a membrane meant to filter or suck out the oxygen from the fuel into the stripping gas, or chemically react with the oxygen in the fuel to reduce the oxygen in the fuel. In such embodiments, the oxygen transfer assembly201may not include a contactor and a separator.

The oxygen transfer assembly201reduces an amount of oxygen in an inlet fuel flow226through an inlet fuel line222using a stripping gas flow220through a stripping gas flowpath206as described herein.

The pre-heater212is in thermal communication with the stripping gas flowpath206at a location downstream of the oxygen transfer assembly201, e.g., at a location downstream of the contactor202and the separator204, and upstream of the catalyst210. The pre-heater212is configured to add heat energy to the stripping gas flow220that flows from the oxygen transfer assembly201, e.g., an outlet stripping gas flow221.

The catalyst210is in airflow communication with the stripping gas flowpath206at a location downstream of the oxygen transfer assembly201, e.g., at a location downstream of the contactor202and the separator204, and the pre-heater212. The catalyst210is configured to receive and treat the outlet stripping gas flow221from the pre-heater212. The catalyst210more specifically is configured to reduce an oxygen content of the stripping gas flow220through the stripping gas flowpath206. The stripping gas flow220from the catalyst210may be referred to as a stripping gas stream240.

The recuperative heat exchanger211is in airflow communication with the stripping gas flowpath206at a location downstream of the catalyst210and upstream of the catalyst210. More specifically, in the exemplary embodiment depicted, the recuperative heat exchanger211is in airflow communication with the stripping gas flowpath206at a location downstream of the catalyst210and upstream of the pre-heater212. The recuperative heat exchanger211is configured to take a portion of heat from the stripping gas stream240to heat the outlet stripping gas flow221before entering the pre-heater212and catalyst210.

More specifically, it will be appreciated that the recuperative heat exchanger211is generally configured as an air-to-air heat exchanger defining a heat sink path (or rather a heat sink airflow path) and a heat source path (or rather a heat source airflow path). The recuperative heat exchanger211is configured to transfer heat from an airflow through the heat source path to an airflow through the heat sink path. In the embodiment depicted, the outlet stripping gas flow221from the oxygen transfer assembly201to the catalyst210is provided through the heat sink path as a heat sink, and the stripping gas flow220from the catalyst210to the oxygen transfer assembly201is provided through the heat source path as a heat source. In such a manner, the recuperative heat exchanger211is configured to transfer heat from the stripping gas flow220from the catalyst210to the oxygen transfer assembly201to the stripping gas flow220from the oxygen transfer assembly201to the catalyst210. Such may result in warmer stripping gas flow221provided to the catalyst210and cooler stripping gas flow220provided to the oxygen transfer assembly201.

Advantageously, the stripping gas stream240that flows from the recuperative heat exchanger211to the oxygen transfer assembly201, e.g., the contactor202, has a lower temperature (e.g., lower than it otherwise would be without the recuperative heat exchanger211) because the recuperative heat exchanger211takes a portion of the heat from the stripping gas stream240. Furthermore, the recuperative heat exchanger211of the present disclosure ensures a lower amount of energy is required from the pre-heater212to heat the outlet stripping gas flow221that flows from the recuperative heat exchanger211to the pre-heater212.

In a fuel oxygen reduction unit200of the present disclosure, the catalyst210receives and treats the outlet stripping gas flow221that flows out of the separator204to reduce an oxygen content of the stripping gas flow220in order to reuse the stripping gas flow220.

The exemplary contactor202depicted may be configured in any suitable manner to substantially mix a received stripping gas flow220and an inlet fuel flow226, as will be described below. For example, the contactor202may, in certain embodiments be a mechanically driven contactor (e.g., having paddles for mixing the received flows), or alternatively may be a passive contactor for mixing the received flows220,226using, at least in part, a pressure and/or flowrate of the received flows220,226. For example, a passive contactor may include one or more turbulators, a venturi mixer, etc.

Moreover, the exemplary stripping gas flowpath206of the fuel oxygen reduction unit200includes a stripping gas line205, and more particularly, includes a plurality of stripping gas lines205, which together at least in part define the stripping gas flowpath206extending from the separator204to the contactor202. In certain exemplary embodiments, the stripping gas flowpath206may be formed of any combination of one or more conduits, tubes, pipes, etc. in addition to the plurality stripping gas lines205and structures or components within the stripping gas flowpath206.

As will be explained in greater detail, below, the fuel oxygen reduction unit200generally provides for the stripping gas flow220through the plurality of stripping gas lines205and stripping gas flowpath206during operation. It will be appreciated that the term “stripping gas” is used herein as a term of convenience to refer to a gas generally capable of performing the functions described herein. The stripping gas flow220flowing through the stripping gas flowpath/circulation gas flowpath206may be an actual stripping gas functioning to strip oxygen from the fuel within the contactor, or alternatively may be a sparging gas bubbled through a liquid fuel to reduce an oxygen content of such fuel. For example, as will be discussed in greater detail below, the stripping gas flow220may be an inert gas, such as Nitrogen or Carbon Dioxide (CO2), a gas mixture made up of at least 50% by mass inert gas, or some other gas or gas mixture having a relatively low oxygen content.

Referring specifically toFIG.2, in an exemplary embodiment, the fuel oxygen reduction unit200includes a compressor250that is in airflow communication with the stripping gas flowpath206at a location downstream of the oxygen transfer assembly201, e.g., at a location downstream of the contactor202and the separator204, and upstream of the recuperative heat exchanger211. The compressor is generally configured to increase a pressure of the stripping gas flow220to provide for the flow of the stripping gas flow220through the stripping gas flowpath206. The compressor250may be configured as a pump or the like. It is also contemplated that other pumps, gas boost pumps, or similar components may be used in the fuel oxygen reduction unit200to increase a pressure of the stripping gas flow220.

Referring now toFIG.3, the fuel oxygen reduction unit200ofFIG.2is depicted providing a more detailed schematic view of the separator204. In the exemplary embodiment depicted, the separator204generally includes the stripping gas outlet214, a fuel outlet216, and an inlet218. It will also be appreciated that the exemplary fuel oxygen reduction unit200depicted is operable with a fuel delivery system, such as the fuel delivery system146of the gas turbine engine including the fuel oxygen reduction unit200or an engine fuel system151(see, e.g.,FIGS.1and2). The exemplary fuel delivery system146generally includes a plurality of fuel lines, and in particular, the inlet fuel line222and an outlet fuel line224. The inlet fuel line222is fluidly connected to the contactor202for providing the inlet fuel flow226(the flow of liquid fuel) to the contactor202(e.g., from the fuel source148, such as a fuel tank; seeFIG.1) and the outlet fuel line224is fluidly connected to the fuel outlet216of the separator204for providing a flow of deoxygenated liquid fuel or outlet fuel flow227to the engine fuel system151.

Generally, it will be appreciated that during operation of the fuel oxygen reduction unit200, the inlet fuel flow226provided through the inlet fuel line222to the contactor202may have a relatively high oxygen content. The stripping gas flow220provided to the contactor202may have a relatively low oxygen content or other specific chemical structure. Within the contactor202, the inlet fuel flow226is mixed with the stripping gas flow220, resulting in a fuel/gas mixture228. As a result of such mixing a physical exchange may occur whereby at least a portion of the oxygen within the inlet fuel flow226is transferred to the stripping gas flow220, such that the fuel component of the fuel/gas mixture228has a relatively low oxygen content (as compared to the inlet fuel flow226provided through the inlet fuel line222) and the stripping gas component of the fuel/gas mixture228has a relatively high oxygen content (as compared to the stripping gas flow220provided through the stripping gas flowpath206to the contactor202).

Within the separator204the relatively high oxygen content stripping gas flow220is then separated from the relatively low oxygen content fuel flow226back into respective flows of an outlet stripping gas flow (the stripping gas flow220provided back to the stripping gas flowpath206from the separator204) and outlet fuel227.

As previously stated, in one exemplary embodiment, the separator204is a dual separator pump as shown inFIG.3. For example, the dual separator pump defines a central axis230, radial direction R, and a circumferential direction C extending about the central axis230. Additionally, the dual separator pump is configured as a mechanically-driven dual separator pump, or more specifically as a rotary/centrifugal dual separator pump. Accordingly, the dual separator pump includes an input shaft232and a single-stage separator/pump assembly234. The input shaft232is mechanically coupled to the single-stage separator/pump assembly234, and the two components are together rotatable about the central axis230. Further, the input shaft232may be mechanically coupled to, and driven by, e.g., an accessory gearbox (such as the exemplary accessory gearbox142ofFIG.1). However, in other embodiments, the input shaft232may be mechanically coupled to any other suitable power source, such as an electric motor. As will be appreciated, the single-stage separator/pump assembly234may simultaneously separate the fuel/gas mixture228into flows of the outlet stripping gas flow221and outlet fuel227and increase a pressure of the separated outlet fuel227(as will be discussed in greater detail below).

Additionally, the exemplary single-stage separator/pump assembly234depicted generally includes an inner gas filter236arranged along the central axis230, and a plurality of paddles238positioned outward of the inner gas filter236along the radial direction R. During operation, a rotation of the single-stage separator/pump assembly234about the central axis230, and more specifically, a rotation of the plurality of paddles238about the central axis230(i.e., in the circumferential direction C), may generally force heavier liquid fuel flow226outward along the radial direction R and lighter stripping gas flow220inward along the radial direction R through the inner gas filter236. In such a manner, the outlet fuel227may exit through the fuel outlet216of the dual separator pump and the outlet stripping gas flow221may exit through the stripping gas outlet214of the dual separator pump, as is indicated.

Further, it will be appreciated that with such a configuration, the outlet fuel227exiting the dual separator pump through the fuel outlet216may be at a higher pressure than the inlet fuel flow226provided through the inlet fuel line222, and further higher than the fuel/gas mixture228provided through the inlet218. Such may be due at least in part to the centrifugal force exerted on such liquid fuel flow226and the rotation of the plurality of paddles238. Additionally, it will be appreciated that for the embodiment depicted, the fuel outlet216is positioned outward of the inlet218(i.e., the fuel gas mixture inlet) along the radial direction R. Such may also assist with the increasing of the pressure of the outlet fuel227provided through the fuel outlet216of the separator204.

For example, it will be appreciated that with such an exemplary embodiment, the separator204of the fuel oxygen reduction unit200may generate a pressure rise in the fuel flow during operation. As used herein, the term “pressure rise” refers to a net pressure differential between a pressure of the flow of outlet fuel227provided to the fuel outlet216of the separator204(i.e., a “liquid fuel outlet pressure”) and a pressure of the inlet fuel flow226provided through the inlet fuel line222to the contactor202. In at least certain exemplary embodiments, the pressure rise of the liquid fuel flow226may be at least about sixty (60) pounds per square inch (“psi”), such as at least about ninety (90) psi, such as at least about one hundred (100) psi, such as up to about seven hundred and fifty (750) psi. With such a configuration, it will be appreciated that in at least certain exemplary embodiments of the present disclosure, the liquid fuel outlet pressure may be at least about seventy (70) psi during operation. For example, in at least certain exemplary embodiments, the liquid fuel out of pressure may be at least about one hundred (100) psi during operation, such as at least about one hundred and twenty-five (125) psi during operation, such as up to about eight hundred (800) psi during operation.

Further, it will be appreciated that the outlet fuel227provided to the fuel outlet216, having interacted with the stripping gas flow220, may have a relatively low oxygen content, such that a relatively high amount of heat may be added thereto with a reduced risk of the fuel coking (i.e., chemically reacting to form solid particles which may clog up or otherwise damage components within the fuel flow path). For example, in at least certain exemplary aspects, the outlet fuel227provided to the fuel outlet216may have an oxygen content of less than about five (5) parts per million (“ppm”), such as less than about three (3) ppm, such as less than about two (2) ppm, such as less than about one (1) ppm, such as less than about 0.5 ppm.

Moreover, as will be appreciated, the exemplary fuel oxygen reduction unit200depicted recirculates and reuses the stripping gas flow220(i.e., the stripping gas flow220operates in a substantially closed loop). However, the outlet stripping gas flow221exiting the separator204, having interacted with the liquid fuel flow226, has a relatively high oxygen content. Accordingly, in order to reuse the stripping gas flow220, an oxygen content of the outlet stripping gas flow221from the stripping gas outlet214of the separator204needs to be reduced. For the embodiment depicted, and as noted above, the outlet stripping gas flow221flows through the pre-heater212, through the catalyst210where the oxygen content of the stripping gas flow220is reduced, and through the recuperative heat exchanger211as described in detail above. More specifically, within the catalyst210the relatively oxygen-rich outlet stripping gas flow221is reacted to reduce the oxygen content thereof. It will be appreciated that catalyst210may be configured in any suitable manner to perform such functions. For example, in certain embodiments, the catalyst210may be configured to combust the relatively oxygen-rich outlet stripping gas flow221to reduce an oxygen content thereof. However, in other embodiments, the catalyst210may additionally, or alternatively, include geometries of catalytic components through which the relatively oxygen-rich outlet stripping gas flow221flows to reduce an oxygen content thereof. In one or more of these embodiments, the catalyst210may be configured to reduce an oxygen content of the outlet stripping gas flow221to less than about five percent (5%) oxygen (O2) by mass, such less than about two (2) percent (3%) oxygen (O2) by mass, such less than about one percent (1%) oxygen (O2) by mass.

As described herein, a catalyst210is disposed downstream of the separator204and the pre-heater212, and the catalyst210receives and treats the outlet stripping gas flow221that flows out the pre-heater212and the stripping gas outlet214of the separator204. In an exemplary embodiment, the catalyst210removes oxygen from the outlet stripping gas flow by chemically converting the oxygen in the outlet stripping gas flow into a water vapor and a carbon dioxide in the outlet stripping gas flow221. Next, the outlet stripping gas flow221flows out of the catalyst210and to the recuperative heat exchanger211of the present disclosure as described herein.

The resulting relatively low oxygen content gas, e.g., the stripping gas stream240that flows from the recuperative heat exchanger211to the contactor202of the oxygen transfer assembly201and has a lower temperature because the recuperative heat exchanger211takes a portion of the heat from the stripping gas stream240, is then provided through the remainder of the stripping gas flowpath206and back to the contactor202, such that the cycle may be repeated.

In such a manner, it will be appreciated that the stripping gas flow220may be any suitable gas capable of undergoing the chemical transitions described above. For example, the stripping gas may be air from, e.g., a core air flowpath of a gas turbine engine including the fuel oxygen reduction unit200(e.g., compressed air bled from the HP compressor112; seeFIG.1). However, in other embodiments, the stripping gas may instead be any other suitable gas, such as an inert gas, such as Nitrogen or Carbon Dioxide (CO2), a gas mixture made up of at least 50% by mass

inert gas, or some other gas or gas mixture having a relatively low oxygen content. It will be appreciated, however, that the exemplary fuel oxygen reduction unit200described above is provided by way of example only. In other embodiments, the fuel oxygen reduction unit200may be configured in any other suitable manner.

In other embodiments, the stripping gas flow220may not flow through a stripping gas flowpath206, and instead the fuel oxygen reduction unit200may include an open loop stripping gas flowpath, with such flowpath in flow communication with a suitable stripping gas source, such as a bleed air source, and configured to dump such air to the atmosphere downstream of the separator204.

Referring now toFIG.4, a method400for operating a fuel oxygen reduction unit for a fuel delivery system of a gas turbine engine is provided. In certain exemplary aspects, the method400may be utilized with one or more of the exemplary fuel delivery systems or fuel oxygen reduction units described above.

The method400includes at (402) within an oxygen transfer assembly, reducing an amount of oxygen in an inlet fuel flow using a stripping gas flow through a stripping gas flowpath as described in detail above with reference toFIGS.1through3.

The method400further includes at (404) reducing an oxygen content of the stripping gas flow through the stripping gas flowpath using a catalyst as described in detail above with reference toFIGS.1through3.

For the exemplary aspect depicted, the method400further includes at (406) transferring heat from the stripping gas flow downstream of the catalyst to the stripping gas flow upstream of the catalyst using a recuperative heat exchanger as described in detail above with reference toFIGS.1through3.

A fuel oxygen reduction unit defining a stripping gas flowpath having a stripping gas flow provided therethrough during operation of the fuel oxygen reduction unit, the fuel oxygen reduction unit comprising: an inlet fuel line and an outlet fuel line; an oxygen transfer assembly in fluid communication with the inlet fuel line, the outlet fuel line, and the stripping gas flowpath for reducing an amount of oxygen in an inlet fuel flow through the inlet fuel line using the stripping gas flow through the stripping gas flowpath; a catalyst in airflow communication with the stripping gas flowpath at a location downstream of the oxygen transfer assembly, the catalyst configured to reduce an oxygen content of the stripping gas flow through the stripping gas flowpath; and a recuperative heat exchanger in airflow communication with the stripping gas flowpath at a location downstream of the catalyst and upstream of the catalyst for exchanging heat from the stripping gas flow flowing from the catalyst with the stripping gas flow flowing through the recuperative heat exchanger at the location upstream of the catalyst.

The fuel oxygen reduction unit of any preceding clause, wherein the stripping gas flow is configured to travel through the stripping gas flowpath from the oxygen transfer assembly, through the recuperative heat exchanger as a heat sink, through the catalyst, back through the recuperative heat exchanger as a heat source, and back to the oxygen transfer assembly.

The fuel oxygen reduction unit of any preceding clause, wherein the fuel oxygen reduction unit further comprises a pre-heater in thermal communication with the stripping gas flowpath upstream of the catalyst for heating the stripping gas flow provided to the catalyst.

The fuel oxygen reduction unit of any preceding clause, wherein the location of the recuperative heat exchanger is upstream of the pre-heater.

The fuel oxygen reduction unit of any preceding clause, wherein a temperature of the stripping gas flow traveling to the oxygen transfer assembly is lower than a temperature of the stripping gas flow traveling to the pre-heater.

The fuel oxygen reduction unit of any preceding clause, further comprising a compressor in airflow communication with the stripping gas flowpath at a location downstream of the oxygen transfer assembly and upstream of the heat exchanger.

The fuel oxygen reduction unit of any preceding clause, wherein the oxygen transfer assembly comprises: a contactor including a fuel inlet in fluid communication with the inlet fuel line for receiving the inlet fuel flow and a stripping gas inlet in fluid communication with the stripping gas flowpath for receiving an inlet stripping gas flow from the stripping gas flowpath, the contactor configured to form a fuel/gas mixture; and a separator including an inlet in fluid communication with the contactor that receives the fuel/gas mixture, a fuel outlet, and a stripping gas outlet, wherein the separator is configured to separate the fuel/gas mixture into an outlet stripping gas flow and an outlet fuel flow and provide the outlet stripping gas flow to the stripping gas flowpath through the stripping gas outlet and the outlet fuel flow to the outlet fuel line through the fuel outlet.

The fuel oxygen reduction unit of any preceding clause, wherein the inlet stripping gas flow exits the recuperative heat exchanger and flows to the contactor.

The fuel oxygen reduction unit of any preceding clause, wherein the outlet fuel flow has a lower oxygen content than the inlet fuel flow, and wherein the outlet stripping gas flow has a higher oxygen content than the inlet stripping gas flow.

The fuel oxygen reduction unit of any preceding clause, wherein the catalyst removes oxygen from the stripping gas flow by chemically converting the oxygen in the outlet stripping gas flow into a water vapor and a carbon dioxide.

The fuel oxygen reduction unit of any preceding clause, wherein the fuel oxygen reduction unit recirculates the stripping gas flow.

A method for operating a fuel oxygen reduction unit for a fuel delivery system of a gas turbine engine, the method comprising: within an oxygen transfer assembly, reducing an amount of oxygen in an inlet fuel flow using a stripping gas flow through a stripping gas flowpath; reducing an oxygen content of the stripping gas flow through the stripping gas flowpath using a catalyst; and transferring heat from the stripping gas flow downstream of the catalyst to the stripping gas flow upstream of the catalyst using a recuperative heat exchanger.

The method of any preceding clause, further comprising: providing the stripping gas flow from the oxygen transfer assembly through a heat sink path of the recuperative heat exchanger to the catalyst; and providing the stripping gas flow from the catalyst through a heat source path of the recuperative heat exchanger to the oxygen transfer assembly.

The method of any preceding clause, wherein providing the stripping gas flow from the catalyst through the heat source path of the recuperative heat exchanger to the oxygen transfer assembly comprises reducing a temperature of the stripping gas flow from the catalyst to the oxygen transfer assembly.

The method of any preceding clause, wherein the fuel oxygen reduction unit further comprises a pre-heater in thermal communication with the stripping gas flowpath upstream of the catalyst, and wherein providing the stripping gas flow from the oxygen transfer assembly through the heat sink path of the recuperative heat exchanger to the catalyst further comprises providing the stripping gas from the recuperative heat exchanger to the pre-heater and from the pre-heater to the catalyst.

The method of any preceding clause, wherein reducing the amount of oxygen in the inlet fuel flow using the stripping gas flow through the stripping gas flowpath comprises: mixing the inlet fuel flow with the stripping gas flow from the stripping gas flowpath within a contactor to form a fuel/gas mixture; separating the fuel/gas mixture out within a separator into an outlet fuel flow and the stripping gas flow; providing the outlet fuel flow to an outlet fuel line from the separator; and providing the stripping gas flow back to the stripping gas flowpath from the separator.

The method of any preceding clause, wherein mixing the inlet fuel flow with the stripping gas flow within the contactor comprises receiving the stripping gas flow from the recuperative heat exchanger.

The method of any preceding clause, wherein the outlet fuel flow has a lower oxygen content than the inlet fuel flow, and wherein the stripping gas flow provided back to the stripping gas flowpath from the separator has a higher oxygen content than the stripping gas flow through the stripping gas flowpath immediately upstream of the contactor.

The method of any preceding clause, wherein reducing the oxygen content of the stripping gas flow through the stripping gas flowpath using the catalyst comprises removing oxygen from the stripping gas flow by chemically converting the oxygen in the outlet stripping gas flow into a water vapor and a carbon dioxide.

The method of any preceding clause, further comprising recirculating a stripping gas within the oxygen transfer assembly.