THERMAL MANAGEMENT OF A FUEL CELL ASSEMBLY

A fuel cell assembly includes a plurality of fuel cells. The fuel cell includes a bipolar separator plate disposed between each fuel cell of the plurality of fuel cells. The bipolar separator plate includes one or more fuel cell sub-units each comprising a plurality of unit-cells. Each unit-cell in the plurality of unit-cells has an outer surface and defines an internal volume that extends in multiple directions between a plurality of openings defined on the outer surface. Each unit-cell in the plurality of unit-cells is disposed adjacent to a neighboring unit-cell in the plurality of unit-cells such that the plurality of unit-cells collectively define one or more channels.

FIELD

The present disclosure relates to the thermal management of a fuel cell assembly.

BACKGROUND

A gas turbine engine generally includes a turbomachine and a rotor assembly. Gas turbine engines, such as turbofan engines, may be used for aircraft propulsion. In the case of a turbofan engine, the turbomachine includes a compressor section, a combustion section, and a turbine section in serial flow order, and the rotor assembly is configured as a fan assembly.

During operation, air is compressed in the compressor and mixed with fuel and ignited in the combustion section for generating combustion gases which flow downstream through the turbine section. The turbine section extracts energy therefrom for rotating the compressor section and fan assembly to power the gas turbine engine and propel an aircraft incorporating such a gas turbine engine in flight.

At least certain gas turbine engines include a fuel cell assembly operable therewith.

DETAILED DESCRIPTION

As used herein, the term “line” may include a hose, pipe, or other fluid conduit that carries a fluid.

The term “at least one of” in the context of, e.g., “at least one of A, B, and C” or “at least one of A, B, or C” refers to only A, only B, only C, or any combination of A, B, and C.

As used herein “unit-cell” is a singular cell, which may be positioned adjacent to other unit-cells to collectively define a cell sub-unit. For example, a “cell sub-unit” may be a collection of unit-cells in contact, and in fluid communication, with one another.

A fuel cell assembly and a propulsion system are provided. The fuel cell assembly includes a plurality of fuel cells each having an anode, a cathode, and a solid electrolyte disposed between the anode and the cathode. The fuel cell assembly includes a bipolar separator plate that is disposed between each fuel cell of the plurality of fuel cells. The bipolar separator plate includes one or more fuel cell sub-units that each comprise a plurality of unit-cells. The plurality of unit-cells each define an interior volume and are be disposed adjacent to one another, such that the interior volume of the plurality of unit-cells collectively define one or more channels. The one or more channels may each receive a fluid for use in, or for the thermal management of, the fuel cell. For example, the one or more channels may include an oxidant channel for the cathode, a fuel channel for the anode, and a coolant channel disposed between the oxidant channel and the fuel channel for collection of heat from the fuel cell.

The fuel cell assembly of the present disclosure advantageously includes single-fluid (i.e., fluidly isolated) fuel cell sub-units that define the fuel, coolant, and oxygen channels in the bipolar separator plate and end plate. Each of the fuel cell sub-units include a plurality of single-fluid unit-cells that enable multidirectional flow at each channel to achieve better thermal distribution. To control the temperature of the fuel cell assembly, the coolant channel may be disposed in fluid communication on a dedicated coolant loop, which may use a coolant (e.g. supercritical CO2, water, and air) as the working fluid. The bipolar separator plate may be integrally formed, e.g., manufactured as a single-material component to further reduces thermal stress across the fuel cell assembly.

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 vehicle.

For the embodiment depicted, the engine is configured as a high bypass gas turbine engine100. As shown inFIG.1, the gas turbine engine100defines an axial direction A (extending parallel to a centerline axis101provided for reference), a radial direction R, and a circumferential direction (extending about the axial direction A; not depicted inFIG.1). In general, the gas turbine engine100includes 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 nozzle exhaust 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 fan blades128and disk130are together rotatable about the centerline axis101by the LP shaft124. The disk130is covered by a 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 nacelle134is supported relative to the turbomachine104by a plurality of circumferentially-spaced outlet guide vanes136. A downstream section138of the nacelle134extends over an outer portion of the turbomachine104so as to define a bypass airflow passage140therebetween.

In such a manner, it will be appreciated that gas turbine engine100generally includes a first stream (e.g., core air flowpath121) and a second stream (e.g., bypass airflow passage140) extending parallel to the first stream. In certain exemplary embodiments, the gas turbine engine100may further define a third stream extending, e.g., from the LP compressor110to the bypass airflow passage140or to ambient. With such a configuration, the LP compressor110may generally include a first compressor stage configured as a ducted mid-fan and downstream compressor stages. An inlet to the third stream may be positioned between the first compressor stage and the downstream compressor stages.

Referring still toFIG.1, the gas turbine engine100additionally includes an accessory gearbox142and 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 for the embodiment depicted schematically inFIG.1, the accessory gearbox142is mechanically coupled to, and rotatable with, one or more shafts or spools of the turbomachine104. For example, in the exemplary embodiment depicted, the accessory gearbox142is mechanically coupled to, and rotatable with, the HP shaft122through a suitable geartrain144. The accessory gearbox142may provide power to one or more suitable accessory systems of the gas turbine engine100during at least certain operations, and may further provide power back to the gas turbine engine100during other operations. For example, the accessory gearbox142is, for the embodiment depicted, coupled to a starter motor/generator152. The starter motor/generator may be configured to extract power from the accessory gearbox142and gas turbine engine100during certain operation to generate electrical power, and may provide power back to the accessory gearbox142and gas turbine engine100(e.g., to the HP shaft122) during other operations to add mechanical work back to the gas turbine engine100(e.g., for starting the gas turbine engine100).

Moreover, the fuel delivery system146generally includes a fuel source148, such as a fuel tank, and one or more fuel delivery lines150. The one or more fuel delivery lines150provide a fuel flow through the fuel delivery system146to the combustion section114of the turbomachine104of the gas turbine engine100. As will be discussed in more detail below, the combustion section114includes an integrated fuel cell and combustor assembly200. The one or more fuel delivery lines150, for the embodiment depicted, provide a flow of fuel to the integrated fuel cell and combustor assembly200.

It will be appreciated, however, that the exemplary gas turbine engine100depicted inFIG.1is provided by way of example only. In other exemplary embodiments, any other suitable gas turbine engine may be utilized with aspects of the present disclosure. For example, in other embodiments, the turbofan 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 engine, 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 a shaft driving the fan, such as the LP shaft124), may be a variable pitch gas turbine engine (i.e., including a fan126having a plurality of fan blades128rotatable about their respective pitch axes), etc. Moreover, although the exemplary gas turbine engine100includes a ducted fan126, in other exemplary aspects, the gas turbine engine100may include an unducted fan126(or open rotor fan), without the nacelle134. Further, although not depicted herein, in other embodiments the gas turbine engine may be any other suitable type of gas turbine engine, such as a nautical gas turbine engine.

Referring now toFIG.2, illustrated schematically is a portion of the combustion section114including a portion of the integrated fuel cell and combustor assembly200used in the gas turbine engine100ofFIG.1, according to an embodiment of the present disclosure.

As will be appreciated, the combustion section114includes a compressor diffuser nozzle202and extends between an upstream end and a downstream end generally along the axial direction A. The combustion section114is fluidly coupled to the compressor section at the upstream end via the compressor diffuser nozzle202and to the turbine section at the downstream end.

The integrated fuel cell and combustor assembly200generally includes a fuel cell assembly204(only partially depicted inFIG.2; see alsoFIGS.3through5) and a combustor206. The combustor206includes an inner liner208, an outer liner210, a dome assembly212, a cowl assembly214, a swirler assembly216, and a fuel flowline218. The combustion section114generally includes an outer casing220outward of the combustor206along the radial direction R to enclose the combustor206and an inner casing222inward of the combustor206along the radial direction R. The inner casing222and inner liner208define an inner passageway224therebetween, and the outer casing220and outer liner210define an outer passageway226therebetween. The inner casing222, the outer casing220, and the dome assembly212together define at least in part a combustion chamber228of the combustor206.

The dome assembly212is disposed proximate the upstream end of the combustion section114(i.e., closer to the upstream end than the downstream end) and includes an opening (not labeled) for receiving and holding the swirler assembly216. The swirler assembly216also includes an opening for receiving and holding the fuel flowline218. The fuel flowline218is further coupled to the fuel source148(seeFIG.1) disposed outside the outer casing220along the radial direction R and configured to receive the fuel from the fuel source148. In such a manner, the fuel flowline218may be fluidly coupled to the one or more fuel delivery lines150described above with reference toFIG.1.

The swirler assembly216can include a plurality of swirlers (not shown) configured to swirl the compressed fluid before injecting it into the combustion chamber228to generate combustion gas. The cowl assembly214, in the embodiment depicted, is configured to hold the inner liner208, the outer liner210, the swirler assembly216, and the dome assembly212together.

During operation, the compressor diffuser nozzle202is configured to direct a compressed fluid230from the compressor section to the combustor206, where the compressed fluid230is configured to be mixed with fuel within the swirler assembly216and combusted within the combustion chamber228to generate combustion gasses. The combustion gasses are provided to the turbine section to drive one or more turbines of the turbine section (e.g., the high pressure turbine116and low pressure turbine118).

During operation of the gas turbine engine100including the integrated fuel cell and combustor assembly200, a flame within the combustion chamber228is maintained by a continuous flow of fuel and air. In order to provide for an ignition of the fuel and air, e.g., during a startup of the gas turbine engine100, the integrated fuel cell and combustor assembly200further includes an ignitor231. The ignitor231may provide a spark or initial flame to ignite a fuel and air mixture within the combustion chamber228. In certain exemplary embodiments, the integrated fuel cell and combustor assembly200may additionally include a dedicated fuel cell ignitor233(depicted in phantom). In particular, for the embodiment ofFIG.2, the dedicated fuel cell ignitor233is positioned downstream of at least a portion of a fuel cell, and in particular of a fuel cell stack (described below). In such a manner, the dedicated fuel cell ignitor233may more effectively combust output products of the fuel cell.

As mentioned above and depicted schematically inFIG.2, the integrated fuel cell and combustor assembly200further includes the fuel cell assembly204. The exemplary fuel cell assembly204depicted includes a first fuel cell stack232and a second fuel cell stack234. More specifically, the first fuel cell stack232is configured with the outer liner210and the second fuel cell stack234is configured with the inner liner208. More specifically, still, the first fuel cell stack232is integrated with the outer liner210and the second fuel cell stack234is integrated with the inner liner208. Operation of the fuel cell assembly204, and more specifically of a fuel cell stack (e.g., first fuel cell stack232or second fuel cell stack234) of the fuel cell assembly204will be described in more detail below.

For the embodiment depicted, the fuel cell assembly204is configured as a solid oxide fuel cell (“SOFC”) assembly, with the first fuel cell stack232configured as a first SOFC fuel cell stack and the second fuel cell stack234configured as a second SOFC fuel cell stack (each having a plurality of SOFC's). As will be appreciated, a SOFC is generally an electrochemical conversion device that produces electricity directly from oxidizing a fuel. In generally, fuel cell assemblies, and in particular fuel cells, are characterized by an electrolyte material utilized. The SOFC's of the present disclosure may generally include a solid oxide or ceramic electrolyte. This class of fuel cells generally exhibit high combined heat and power efficiency, long-term stability, fuel flexibility, and low emissions.

Moreover, the exemplary fuel cell assembly204further includes a first power converter236and a second power converter238. The first fuel cell stack232is in electrical communication with the first power converter236by a first plurality of power supply cables (not labeled), and the second fuel cell stack234is in electrical communication with the second power converter238by a second plurality of power supply cables (not labeled).

The first power converter236controls the electrical current drawn from the corresponding first fuel cell stack232and may convert the electrical power from a direct current (“DC”) power to either DC power at another voltage level or alternating current (“AC”) power. Similarly, the second power converter238controls the electrical current drawn from the second fuel cell stack234and may convert the electrical power from a DC power to either DC power at another voltage level or AC power. The first power converter236, the second power converter238, or both may be electrically coupled to an electric bus (such as the electric bus326described below).

The integrated fuel cell and combustor assembly200further includes a fuel cell controller240that is in operable communication with both of the first power converter236and second power converter238to, e.g., send and receive communications and signals therebetween. For example, the fuel cell controller240may send current or power setpoint signals to the first power converter236and second power converter238, and may receive, e.g., a voltage or current feedback signal from the first power converter236and second power converter238. The fuel cell controller240may be configured in the same manner as the controller240described below with reference toFIG.4.

It will be appreciated that in at least certain exemplary embodiments the first fuel cell stack232, the second fuel cell stack234, or both may extend substantially 360 degrees in a circumferential direction C of the gas turbine engine (i.e., a direction extending about the centerline axis101of the gas turbine engine100). For example, referring now toFIG.3, a simplified cross-sectional view of the integrated fuel cell and combustor assembly200is depicted according to an exemplary embodiment of the present disclosure. Although only the first fuel cell stack232is depicted inFIG.3for simplicity, the second fuel cell stack234may be configured in a similar manner.

As shown, the first fuel cell stack232extends around the combustion chamber228in the circumferential direction C, completely encircling the combustion chamber228around the centerline axis101in the embodiment shown. More specifically, the first fuel cell stack232includes a plurality of fuel cells242arranged along the circumferential direction C. The fuel cells242that are visible inFIG.3can be a single ring of fuel cells242, with fuel cells242stacked together along the axial direction A (seeFIG.2) to form the first fuel cell stack232. In another instance, a plurality of additional rings of fuel cells242can be placed on top of each other to form the first fuel cell stack232that is elongated along the centerline axis101.

As will be explained in more detail, below, with reference toFIG.4, the fuel cells242in the first fuel cell stack232are positioned to receive discharged air244from, e.g., the compressor section and fuel246from the fuel delivery system146. The fuel cells242generate electrical current using this air244and at least some of this fuel246, and radially direct partially oxidized fuel246and unused portion of air248into the combustion chamber228toward the centerline axis101. The integrated fuel cell and combustor assembly200combusts the partially oxidized fuel246and air248in the combustion chamber228into combustion gasses that are directed downstream into the turbine section to drive or assist with driving the one or more turbines therein.

Referring now toFIG.4, operation of an integrated fuel cell and combustor assembly200in accordance with an exemplary embodiment of the present disclosure will be described. More specifically,FIG.4provides a schematic illustration of a gas turbine engine100and an integrated fuel cell and combustor assembly200according to an embodiment of the present disclosure. The gas turbine engine100and integrated fuel cell and combustor assembly200may, in certain exemplary embodiments, be configured in a similar manner as one or more of the exemplary embodiments ofFIGS.1through4.

Accordingly, it will be appreciated that the gas turbine engine100generally includes a fan section102having a fan126, an LP compressor110, an HP compressor112, a combustion section114, an HP turbine116, and an LP turbine118. The combustion section114generally includes the integrated fuel cell and combustor assembly200having a combustor206and a fuel cell assembly204.

A propulsion system including the gas turbine engine100further includes a fuel delivery system146. The fuel delivery system146generally includes a fuel source148and one or more fuel delivery lines150. The fuel source148may include a supply of fuel (e.g., a hydrocarbon fuel, including, e.g., a carbon-neutral fuel or synthetic hydrocarbons) for the gas turbine engine100. In addition, it will be appreciated that the fuel delivery system146also includes a fuel pump272and a flow divider274, and the one or more fuel delivery lines150include a first fuel delivery line150A, a second fuel delivery line150B, and a third fuel delivery line150C. The flow divider274divides the fuel flow from the fuel source148and fuel pump272into a first fuel flow through the first fuel delivery line150A to the fuel cell assembly204, a second fuel flow through the second fuel delivery line150B also to the fuel cell assembly204(and in particular to an air processing unit, described below), and a third fuel flow through a third fuel delivery line150C to the combustor206. The flow divider274may include a series of valves (not shown) to facilitate such dividing of the fuel flow from the fuel source148, or alternatively may be of a fixed geometry. Additionally, for the embodiment shown, the fuel delivery system146includes a first fuel valve151A associated with the first fuel delivery line150A (e.g., for controlling the first fuel flow), a second fuel valve151B associated with the second fuel delivery line150B (e.g., for controlling the second fuel flow), and a third fuel valve151C associated with the third fuel delivery line150C (e.g., for controlling the third fuel flow).

The gas turbine engine100further includes a compressor bleed system and an airflow delivery system. More specifically, the compressor bleed system includes an LP bleed air duct276and an associated LP bleed air valve278, an HP bleed air duct280and an associated HP bleed air valve282, an HP exit air duct284and an associated HP exit air valve286.

The gas turbine engine100further includes an air stream supply duct288(in airflow communication with an airflow supply290) and an associated air valve292, which is also in airflow communication with the airflow delivery system for providing compressed airflow to the fuel cell assembly204of the integrated fuel cell and combustor assembly200. The airflow supply may be, e.g., a second gas turbine engine configured to provide a cross-bleed air, an auxiliary power unit (APU) configured to provide a bleed air, a ram air turbine (RAT), etc. The airflow supply may be complimentary to the compressor bleed system if the compressor air source is inadequate or unavailable.

The compressor bleed system (and air stream supply duct288) is in airflow communication with airflow delivery system for providing compressed airflow to the fuel cell assembly204, as will be explained in more detail below.

Referring still toFIG.4, the fuel cell assembly204of the integrated fuel cell and combustor assembly200includes a fuel cell stack294. The fuel cell stack294is depicted schematically as a single fuel cell having a cathode side296, an anode side298, and an electrolyte300positioned therebetween. As will generally be appreciated, the electrolyte300may, during operation, conduct negative oxygen ions from the cathode side296to the anode side298to generate an electric current and electric power.

Briefly, it will be appreciated that the fuel cell assembly204further includes a fuel cell sensor302configured to sense data indicative of a fuel cell assembly operating parameter, such as a temperature of the fuel cell stack294(e.g., of the cathode side296or anode side298of the fuel cell), a pressure within the fuel cell stack294(e.g., of within the cathode side296or anode side298of the fuel cell).

The fuel cell stack294is disposed downstream of the LP compressor110, the HP compressor112, or both. Further, as will be appreciated from the description above with respect toFIG.2, the fuel cell stack294may be coupled to or otherwise integrated with a liner of the combustor206(e.g., an inner liner208or an outer liner210). In such a manner, the fuel cell stack294may also be arranged upstream of a combustion chamber228of the integrated fuel cell and combustor assembly200, and further upstream of the HP turbine116and LP turbine118.

As shown inFIG.4, the fuel cell assembly204also includes a fuel processing unit304and an air processing unit306. The fuel processing unit304may be any suitable structure for generating a hydrogen rich fuel stream. For example, the fuel processing unit304may include a fuel reformer or a catalytic partial oxidation convertor (CPOx) for developing the hydrogen rich fuel stream for the fuel cell stack294. The air processing unit306may be any suitable structure for raising the temperature of air that is provided thereto to a temperature high enough to enable fuel cell temperature control (e.g., about 600° C. to about 800° C.). For example, in the embodiment depicted, the air processing unit includes a preburner system, operating based on a fuel flow through the second fuel delivery line150B, configured for raising the temperature of the air through combustion, e.g., during transient conditions such as startup, shutdown and abnormal situations.

In the exemplary embodiment depicted, the fuel processing unit304and air processing unit306are within a housing308to provide conditioned air and fuel to the fuel cell stack294.

It should be appreciated, however, that the fuel processing unit304may additionally or alternatively include any suitable type of fuel reformer, such as an autothermal reformer and steam reformer that may need an additional stream of steam inlet with higher hydrogen composition at the reformer outlet stream. Additionally, or alternatively, still, the fuel processing unit304may include a reformer integrated with the fuel cell stack294. Similarly, it should be appreciated that the air processing unit306ofFIG.4could alternatively be a heat exchanger or another device for raising the temperature of the air provided thereto to a temperature high enough to enable fuel cell temperature control (e.g., about 600° C. to about 800° C.).

As mentioned above, the compressor bleed system (and air stream supply duct288) is in airflow communication with airflow delivery system for providing compressed airflow to the fuel cell assembly204. The airflow delivery system includes an anode airflow duct310and an associated anode airflow valve312for providing an airflow to the fuel processing unit304, a cathode airflow duct314and associated cathode airflow valve316for providing an airflow to the air processing unit306, and a cathode bypass air duct318and an associated cathode bypass air valve320for providing an airflow directly to the fuel cell stack294(or rather to the cathode side296of the fuel cell(s)). The fuel delivery system146is configured to provide the first flow of fuel through the first fuel delivery line150A to the fuel processing unit304, and the second flow of fuel through the second fuel delivery line150B to the air processing unit306(e.g., as fuel for a preburner system, if provided).

The fuel cell stack294outputs the power produced as a fuel cell power output322. Further, the fuel cell stack294directs a cathode air discharge and an anode fuel discharge (neither labeled for clarity purposes) into the combustion chamber228of the combustor206.

In operation, the air processing unit306is configured to heat/cool a portion of the compressed air, incoming through the cathode airflow duct314, to generate a processed air to be directed into the fuel cell stack294to facilitate the functioning of the fuel cell stack294. The air processing unit306receives the second flow of fuel from the second fuel delivery line150B and may, e.g., combust such second flow of fuel to heat the air received to a desired temperature (e.g., about 600° C. to about 800° C.) to facilitate the functioning of the fuel cell stack294. The air processed by the air processing unit306is directed into the fuel cell stack294. In an embodiment of the disclosure, as is depicted, the cathode bypass air duct318and the air processed by the air processing unit306may combine into a combined air stream to be fed into a cathode of the fuel cell stack294.

Further, as shown in the embodiment ofFIG.4, the first flow of fuel through the first fuel delivery line150A is directed to the fuel processing unit304for developing a hydrogen rich fuel stream (e.g., optimizing a hydrogen content of a fuel stream), to also be fed into the fuel cell stack294. As will be appreciated, and as discussed below, the flow of air (processed air and bypass air) to the fuel cell stack294(e.g., the cathode side296) and fuel from the fuel processing unit304to the fuel cell stack294(e.g., the anode side298) may facilitate electrical power generation.

Because the inlet air for the fuel cell stack294may come solely from the upstream compressor section without any other separately controlled air source, it will be appreciated that the inlet air for the fuel cell stack294discharged from the compressor section is subject to the air temperature changes that occur at different flight stages. By way of illustrative example only, the air within a particular location in the compressor section of the gas turbine engine100may work at 200° C. during idle, 600° C. during take-off, 268° C. during cruise, etc. This type of temperature change to the inlet air directed to the fuel cell stack294may lead to significant thermal transient issues (or even thermal shock) to the ceramic materials of the fuel cell stack294, which could range from cracking to failure.

Thus, by fluidly connecting the air processing unit306between the compressor section and the fuel cell stack294, the air processing unit306may serve as a control device or system to maintain the air processed by the air processing unit306and directed into the fuel cell stack294within a desired operating temperature range (e.g., plus or minus 100° C., or preferably plus or minus 50° C., or plus or minus 20° C.). In operation, the temperature of the air that is provided to the fuel cell stack294can be controlled (relative to a temperature of the air discharged from the compressor section) by controlling the flow of fuel to the air processing unit306. By increasing a fuel flow to the air processing unit306, a temperature of the airflow to the fuel cell stack294may be increased. By decreasing the fuel flow to the air processing unit306, a temperature of the airflow to the fuel cell stack294may be decreased. Optionally, no fuel can be delivered to the air processing unit306to prevent the air processing unit306from increasing and/or decreasing the temperature of the air that is discharged from the compressor section and directed into the air processing unit306.

Moreover, as is depicted in phantom, the fuel cell assembly204further includes an airflow bypass duct321extending around the fuel cell stack294to allow a portion or all of an airflow conditioned by the air processing unit306(and combined with any bypass air through duct318) to bypass the cathode side296of the fuel cell stack294and go directly to the combustion chamber228. The bypass duct321may be in thermal communication with the fuel cell stack294. The fuel cell assembly further includes a fuel bypass duct323extending around the fuel cell stack294to allow a portion or all of a reformed fuel from the fuel processing unit304to bypass the anode side298of the fuel cell stack294and go directly to the combustion chamber228.

As briefly mentioned above, the fuel cell stack294converts the anode fuel stream from the fuel processing unit304and air processed by the air processing unit306sent into the fuel cell stack294into electrical energy, the fuel cell power output322, in the form of DC current. This fuel cell power output322is directed to a power convertor324in order to change the DC current into DC current or AC current that can be effectively utilized by one or more subsystems. In particular, for the embodiment depicted, the electrical power is provided from the power converter to an electric bus326. The electric bus326may be an electric bus dedicated to the gas turbine engine100, an electric bus of an aircraft incorporating the gas turbine engine100, or a combination thereof. The electric bus326is in electric communication with one or more additional electrical devices328, which may be a power source, a power sink, or both. For example, the additional electrical devices328may be a power storage device (such as one or more batteries), an electric machine (an electric generator, an electric motor, or both), an electric propulsion device, etc. For example, the one or more additional electrical devices328may include the starter motor/generator of the gas turbine engine100.

Moreover, as is further depicted schematically inFIG.4, the propulsion system, an aircraft including the propulsion system, or both, includes a controller240. For example, the controller240may be a standalone controller, a gas turbine engine controller (e.g., a full authority digital engine control, or FADEC), an aircraft controller, supervisory controller for a propulsion system, a combination thereof, etc.

The controller240is operably connected to various the sensors, valves, etc. within at least one of the gas turbine engine100and the fuel delivery system146. More specifically, for the exemplary aspect depicted, the controller240is operably connected to the valves of the compressor bleed system (valves278,282,286), the airflow delivery system (valves312,316,320), and the fuel delivery system146(flow divider274, valves151A,151B,151C) of the gas turbine engine100and the fuel cell sensor302. As will be appreciated from the description below, the controller240may be in wired or wireless communication with these components. In this manner, the controller240may receive data from a variety of inputs (including the fuel cell sensor302), may make control decisions, and may provide data (e.g., instructions) to a variety of output (including the valves of the compressor bleed system to control an airflow bleed from the compressor section, the airflow delivery system to direct the airflow bled from the compressor section, and the fuel delivery system146to direct the fuel flow within the gas turbine engine100).

Referring particularly to the operation of the controller240, in at least certain embodiments, the controller240can include one or more computing device(s)332. The computing device(s)332can include one or more processor(s)332A and one or more memory device(s)332B. The one or more processor(s)332A can include any suitable processing device, such as a microprocessor, microcontroller, integrated circuit, logic device, and/or other suitable processing device. The one or more memory device(s)332B can include one or more computer-readable media, including, but not limited to, non-transitory computer-readable media, RAM, ROM, hard drives, flash drives, and/or other memory devices.

The one or more memory device(s)332B can store information accessible by the one or more processor(s)332A, including computer-readable instructions332C that can be executed by the one or more processor(s)332A. The instructions332C can be any set of instructions that when executed by the one or more processor(s)332A, cause the one or more processor(s)332A to perform operations. In some embodiments, the instructions332C can be executed by the one or more processor(s)332A to cause the one or more processor(s)332A to perform operations, such as any of the operations and functions for which the controller240and/or the computing device(s)332are configured, the operations for operating a propulsion system, as described herein, and/or any other operations or functions of the one or more computing device(s)332. The instructions332C can be software written in any suitable programming language or can be implemented in hardware. Additionally, and/or alternatively, the instructions332C can be executed in logically and/or virtually separate threads on processor(s)332A. The memory device(s)332B can further store data332D that can be accessed by the processor(s)332A. For example, the data332D can include data indicative of power flows, data indicative of gas turbine engine100/aircraft operating conditions, and/or any other data and/or information described herein.

The computing device(s)332also includes a network interface332E configured to communicate, for example, with the other components of the gas turbine engine100(such as the valves of the compressor bleed system (valves278,282,286), the airflow delivery system (valves312,316,320), and the fuel delivery system146(flow divider274, valves151A,151B,151C) of the gas turbine engine100and the fuel cell sensor302), the aircraft incorporating the gas turbine engine100, etc. The network interface332E can include any suitable components for interfacing with one or more network(s), including for example, transmitters, receivers, ports, controllers, antennas, and/or other suitable components. In such a manner, it will be appreciated that the network interface332E may utilize any suitable combination of wired and wireless communications network(s).

The technology discussed herein makes reference to computer-based systems and actions taken by and information sent to and from computer-based systems. It will be appreciated that the inherent flexibility of computer-based systems allows for a great variety of possible configurations, combinations, and divisions of tasks and functionality between and among components. For instance, processes discussed herein can be implemented using a single computing device or a plurality of computing devices working in combination. Databases, memory, instructions, and applications can be implemented on a single system or distributed across a plurality of systems. Distributed components can operate sequentially or in parallel.

It will be appreciated that the gas turbine engine100, the exemplary fuel delivery system146, the exemplary integrated fuel cell and combustor assembly200, and the exemplary fuel cell assembly204are provided by way of example only. In other embodiments, the integrated fuel cell and combustor assembly200and fuel cell assembly204may have any other suitable configuration. For example, in other exemplary embodiments, the fuel cell assembly204may include any other suitable fuel processing unit304. Additionally, or alternatively, the fuel cell assembly204may not require a fuel processing unit304, e.g., when the combustor of the gas turbine engine100is configured to burn hydrogen fuel and the fuel delivery system146is configured to provide hydrogen fuel to the integrated fuel cell and combustor assembly200, and in particular to the fuel cell assembly204.

Referring now toFIG.5, a schematic view of a thermal management system500is illustrated in accordance with exemplary aspects of the present disclosure. For example, the thermal management system500may be incorporated in the propulsion system described above with reference toFIGS.1through4. As shown, the thermal management system500may include a fuel cell assembly502(which may be the same as the fuel cell assembly204described above or a different fuel cell assembly). As shown inFIG.5, the fuel cell assembly502may include a plurality of fuel cells504each having an anode506, a cathode508, and a solid electrolyte510disposed between the anode506and the cathode508. For example, the fuel cell assembly502may include a first fuel cell501and a second fuel cell503. In many embodiments, the fuel cell assembly502may include a bipolar separator plate512disposed between the first fuel cell501and the second fuel cell503of the plurality of fuel cells504. Particularly, the bipolar separator plate512may include a cathode cell sub-unit514, a coolant cell sub-unit516, and an anode cell sub-unit518. The cathode cell sub-unit514may be disposed adjacent (i.e., in contact) to the cathode508of the first fuel cell501, and the anode cell sub-unit518may be disposed adjacent (i.e., in contact) to the anode506of the second fuel cell503. The coolant cell sub-unit516may be disposed between the anode cell sub-unit518and the cathode cell sub-unit514.

In various embodiments, the cathode cell sub-unit514may defines an oxidant channel515fluidly coupled to the compressor section. For example, the oxidant channel515may be in fluid communication with one or more stages of the compressor section, such that the oxidant channel515may receive a flow of air (e.g., bleed air) from a stage in the compressor section, utilize the flow of air for transferring heat from the plurality of fuel cells504, and return the flow of air to the compressor section (e.g., to another of the one or more stages in the compressor section). Particularly, the oxidant channel515may include an oxidant inlet520and an oxidant outlet522. The oxidant inlet520may be fluidly coupled to a low pressure compressor stage524of the compressor section via a bleed air line526. The oxidant outlet522may be fluidly coupled to a high pressure compressor stage528of the compressor section via a cathode exhaust line530. For example, the low pressure compressor stage524may be a stage in the LP compressor110described above with reference toFIG.1, such that the oxidant channel515may receive a flow of low pressure air from the LP compressor110. Similarly, the high pressure compressor stage528may be a stage in the HP compressor112, such that air from the oxidant channel515may be returned to the HP compressor112. Additionally, or alternatively, the oxidant outlet522may be fluidly coupled to the combustion chamber228such that the exhaust air from the oxidant channel515is directly sent to the combustion chamber228.

In some embodiments, an air-to-air heat exchanger532(e.g., a first recuperator heat exchanger) may thermally couple the bleed air line526and the cathode exhaust line530. For example, the air-to-air heat exchanger532may exchange heat between the air in the bleed air line526and the air in the cathode exhaust line530. The air-to-air heat exchanger532may be disposed in fluid communication on the bleed air line526upstream of the oxidant channel515with respect to a flow of air through the bleed air line526. Further, the air-to-air heat exchanger532may be disposed in fluid communication on the cathode exhaust line530downstream of the oxidant channel515with respect to a flow of air through the cathode exhaust line530.

In exemplary embodiment, the anode cell sub-unit518may define a fuel channel534that is fluidly coupled to the combustion section. For example, the fuel channel534may receive a flow of fuel (e.g., liquid hydrogen or other suitable fuel) from a fuel tank536via a fuel supply line538. In particular, the fuel channel534may include a fuel inlet540and one or more outlets (e.g., a first outlet542and a second outlet544). In many embodiments, the fuel inlet540may be fluidly coupled to the fuel supply line538. The one or more outlets542,544may be fluidly coupled to the combustion chamber228. Particularly, the first outlet542of the fuel channel534may exhaust water546from the anode506(e.g., anode water). The water546may be provided to one or both of the combustion chamber228to reduce nitrogen oxide (NOx) emission and/or the turbine section for turbine cooling548. The water546may be provided to one or more stages in the turbine section. For example, turbine cooling548may include cooling of one or more turbine section components (e.g., one or more turbine rotor blades, stator vanes, or other components in the turbine section). The second outlet544of the fuel channel534may exhaust excess fuel not utilized by the anode506in the fuel channel534via an excess fuel line550.

In many embodiments, a fuel-to-fuel heat exchanger552(e.g., second recuperator heat exchanger) may thermally couple the fuel supply line538and the excess fuel line550from the fuel outlet544. Particularly, the fuel-to-fuel heat exchanger552may be disposed in fluid communication on the fuel supply line538upstream of the fuel channel534with respect to the flow of fuel through the fuel supply line538. Additionally, the fuel-to-fuel heat exchanger552may be disposed in fluid communication on the excess fuel line550downstream of the fuel channel534with respect to the flow of fuel through the excess fuel line550.

In various embodiments, the thermal management system500may further include a series of heat exchangers554fluidly and thermally coupled to the fuel supply line538upstream of the fuel-to-fuel heat exchanger552. The series of heat exchangers554may include an hydrogen-to-oil heat exchanger, a hydrogen-to-air heat exchanger, and/or a hydrogen-to-coolant (e.g., coolant from the fuel cell assembly dedicated coolant loop). The series of heat exchangers554may receive liquid hydrogen (H2) from the fuel tank536and transfer heat to (or away from) the liquid hydrogen, such that the hydrogen provided to the fuel cell assembly502and/or the combustion chamber228has a desired temperature. Particularly, the hydrogen may leave the fuel tank536in a liquid state, and the hydrogen may be provided to the fuel cell assembly502and/or the combustion chamber228in a gaseous state.

In exemplary embodiments, the bipolar separator plate512may further include a coolant cell sub-unit516that defines a coolant channel556. The coolant channel556may function to remove heat from the fuel cell assembly502as part of a thermal transport bus where the coolant acts as the working fluid being recirculated between the heat source (the fuel cell assembly502, and more particularly the coolant channel556) and the heat-sink heat exchanger558in a closed cycle loop.

For example, in many embodiments, the coolant channel556may be in fluid communication with a heat-sink heat exchanger558, which may remove heat from the coolant. Particularly, the coolant channel may be disposed in fluid communication on a dedicated coolant loop or closed cycle loop560. The dedicated coolant loop560may circulate coolant fluid (e.g., with a pump562) through the coolant channel556and the heat-sink heat exchanger558. The coolant fluid may be supercritical CO2, air, water, or other suitable coolant fluid. The heat-sink heat exchanger558may thermally couple the coolant fluid within the dedicated coolant loop560with a sink fluid564, such that the sink fluid564may remove heat from the coolant fluid via the heat-sink heat exchanger558. The sink fluid564may be liquid hydrogen (e.g., from the fuel supply line538), air, or other suitable fluids.

In many embodiments, each of the channels515,534,556defined in the bipolar separator plate512may be fluidly isolated from one another. For example, the oxidant channel515defined in the cathode cell sub-unit514of the bipolar separator plate512, the fuel channel534defined in the anode cell sub-unit518of the bipolar separator plate512, and the coolant channel556defined in the coolant cell sub-unit516may each be fluidly isolated from one another. Additionally, the oxidant channel515may be at least partially defined by the cathode508of the first fuel cell501in the plurality of fuel cells504, such that the oxidant channel515is defined collectively by the cathode508and the cathode cell sub-unit514. Similarly, the fuel channel534may be at least partially defined by the anode506of the second fuel cell503in the plurality of fuel cells504, such that the fuel channel534is collectively defined by the anode506and the anode cell sub-unit518.

In various embodiments, the thermal management system500may further include a three-fluid heat exchanger566in fluid communication with the oxidant channel515and the fuel channel534to preheat the fuel and air (prior to being sent to the fuel cell assembly) during transient conditions such as startup. For example, the three-fluid heat exchanger566may be fluidly coupled to the bleed air line526via an air supply line568. The air supply line568may extend from the bleed air line526, upstream of the air-to-air heat exchanger532, to the three-fluid heat exchanger566. An air return line570may extend from the three-fluid heat exchanger566to the bleed air line526downstream of the air-to-air heat exchanger532. Additionally, the three-fluid heat exchanger566may be one of the series of heat exchangers554, or may be a separate heat exchanger in addition to the series of heat exchangers554. The three-fluid heat exchanger566may be fluidly coupled to the series of heat exchangers554(and/or the fuel supply line538) via a fuel input line572. A fuel output line574may extend from the three-fluid heat exchanger566to the fuel supply line538downstream of the fuel-to-fuel heat exchanger552. Furthermore, the three-fluid heat exchanger566may receive a flow of exhaust gases576(e.g. from one or more nozzles or elsewhere), and the three-fluid heat exchanger566may exhaust the exhaust gases576to the atmosphere. In this way, the three-fluid heat exchanger566may exchange heat between air (prior to the air being sent to the fuel cell assembly502), fuel (prior to the fuel being sent to the fuel cell assembly502), and exhaust gases576.

Referring now toFIG.6, a fuel cell assembly502is illustrated in accordance with embodiments of the present disclosure. As shown, the fuel cell assembly502may include a plurality of fuel cells504each having an anode506, a cathode508, and a solid electrolyte510disposed between the anode506and the cathode508. For example, the fuel cell assembly502may include a first fuel cell582, one or more intermediary fuel cells584, and a last fuel cell586. During operation of the fuel cell assembly502, electrical current may flow from the anode506of the first fuel cell582to the cathode508of the last fuel cell586.

In many embodiments, the fuel cell assembly502may include one or more bipolar separator plates512disposed between the plurality of fuel cells504. Particularly, the bipolar separator plate512may include one or more fuel cell sub-units514,516,518each comprising a plurality of unit-cells590,591,593. In exemplary embodiments, the one or more fuel cell sub-units514,516,518may include a cathode cell sub-unit514, a coolant cell sub-unit516, and an anode cell sub-unit518. The cathode cell sub-unit514may be disposed adjacent (i.e., in contact) to the cathode508of the first fuel cell582(or one of the intermediary fuel cells584), and the anode cell sub-unit518may be disposed adjacent (i.e., in contact) to the anode506of the last fuel cell586(or one of the intermediary fuel cells584). The coolant cell sub-unit516may be disposed between the anode cell sub-unit518and the cathode cell sub-unit514. Additionally, in many embodiments, the fuel cell assembly502may include end plates (e.g., a first end plate578and a second end plate580) disposed on opposite sides of the fuel cell assembly502. The first end plate578may be in contact with the anode506of the first fuel cell582, and the second end plate580may be in contact with the cathode508of the last fuel cell586.

In exemplary embodiments, the coolant cell sub-unit516may be collectively formed by the plurality of unit-cells590, the cathode cell sub-unit514may be collectively formed by the plurality of unit-cells591, and the anode cell sub-unit518may be collectively formed by the plurality of unit-cells593. In many embodiments, the anode cell sub-unit518and the cathode cell sub-unit514may be formed from the same type of unit-cell, such that the anode cell sub-unit518and the cathode cell sub-unit514are substantially the same component disposed on opposite sides of the coolant cell sub-unit516. In exemplary embodiments, each unit-cell in the plurality of unit-cells590,591,593may include an outer surface630(e.g., an exterior surface) and may define an internal volume636,638,640that extends in a plurality of directions (e.g., the vertical direction V, the longitudinal direction L, and the transverse direction T described below) between a plurality of openings642,644,646defined on the respective outer surface630. Additionally, each unit-cell in the plurality of unit-cells590,591,593may be disposed adjacent to (and in contact with) a neighboring unit-cell in the plurality of unit-cells590,591,593such that the plurality of unit-cells590,591,593collectively define the one or more channels515,534,556.

For example, each unit-cell590in the plurality of unit-cells590of the coolant cell sub-unit516may be disposed adjacent to (e.g., in contact with and fixedly coupled to) a neighboring unit-cell590in the plurality of unit-cells590of the coolant cell sub-unit516, such that the plurality of unit-cells590of the coolant cell sub-unit516collectively define the coolant channel556. Similarly, each unit-cell591in the plurality of unit-cells591of the cathode cell sub-unit514may be disposed adjacent to (e.g., in contact with and fixedly coupled to) a neighboring unit-cell591in the plurality of unit-cells591of the cathode cell sub-unit514, such that the plurality of unit-cells591of the cathode cell sub-unit514collectively define the oxidant channel515. Likewise, each unit-cell593in the plurality of unit-cells593of the anode cell sub-unit518may be disposed adjacent to (e.g., in contact with and fixedly coupled to) a neighboring unit-cell593in the plurality of unit-cells593of the anode cell sub-unit518, such that the plurality of unit-cells593of the anode cell sub-unit518collectively define the fuel channel534.

In exemplary embodiments, at least one opening of the plurality of openings642,644,646of each unit-cell in the plurality of unit-cells590,591,593may align with a neighboring opening of the plurality of openings642,644,646in the neighboring unit-cell of the plurality of unit-cells590,591,593such that the internal volume636,638,640of each unit-cell of the plurality of unit-cells590,591,593collectively define the one or more channels515,534,556. For example, at least one opening642of the plurality of openings642of each unit-cell590in the coolant cell sub-unit516may align with a neighboring opening642in a neighboring unit-cell590in the coolant cell sub-unit516, such that the internal volumes636of the plurality of unit-cells590in the coolant cell sub-unit516collectively define the coolant channel556. Similarly, at least one opening644of the plurality of openings644of each unit-cell591in the cathode cell sub-unit514may align with a neighboring opening644in a neighboring unit-cell591in the cathode cell sub-unit514, such that the internal volumes638of the plurality of unit-cells591in the cathode cell sub-unit514collectively define the oxidant channel515. Likewise, at least one opening646of the plurality of openings646of each unit-cell593in the anode cell sub-unit518may align with a neighboring opening646in a neighboring unit-cell593in the anode cell sub-unit518, such that the internal volumes640of the plurality of unit-cells593in the anode cell sub-unit518collectively define the fuel channel534.

The multidirectional internal volumes636,638,640of each unit-cell590,591,593advantageously increases the thermal distribution and heat transfer efficiency of the entire bipolar separator plate512, thereby extending the hardware life of the bipolar separator plate512and increasing the efficiency of the fuel cell assembly502.

In many embodiments, the bipolar separator plate512described herein may be integrally formed as a single component. That is, each of the subcomponents, e.g., the cathode cell sub-unit514, the coolant cell sub-unit516, and the anode cell sub-unit518, and any other subcomponent of the bipolar separator plate512(such as the plurality of unit-cells590,591,593), may be manufactured together as a single body or object. In exemplary implementations, this may be done by utilizing an additive manufacturing system and method, such as direct metal laser sintering (DMLS), direct metal laser melting (DMLM), or other suitable additive manufacturing techniques. In other embodiments, other manufacturing techniques, such as casting or other suitable techniques, may be used. In this regard, by utilizing additive manufacturing methods, the bipolar separator plate512may be integrally formed as a single piece of continuous metal and may thus include fewer sub-components and/or joints compared to prior designs. The integral formation of the bipolar separator plate512through additive manufacturing may advantageously improve the overall assembly process. For example, the integral formation reduces the number of separate parts that are assembled, thus reducing associated time and overall assembly costs. Additionally, existing issues with, for example, leakage, joint quality between separate parts, and overall performance may advantageously be reduced.

Referring now toFIG.7, a fuel cell assembly502having one or more fluid connections is illustrated in accordance with embodiments of the present disclosure. In exemplary embodiments, the one or more channels515,534,556may include an oxidant channel515defined in a cathode cell sub-unit514of the one or more fuel cell sub-units, a coolant channel556defined in a coolant cell sub-unit516of the one or more fuel cell sub-units, and a fuel channel556defined in an anode cell sub-unit518of the one or more fuel cell sub-units. In various embodiments, the oxidant channel515, the coolant channel556, and the fuel channel534are fluidly isolated from one another. For example, the cathode cell sub-unit514and the anode cell sub-unit518may each include a solid wall portion598that contacts the coolant cell sub-unit516to fluidly isolate the one or more channels515,534,556. Particularly, the coolant cell sub-unit516may be disposed between the solid wall portion598of the cathode cell sub-unit514and the solid wall portion598of the anode cell sub-unit518. The oxidant channel515may be at least partially defined by a cathode508in the plurality of fuel cells504, such that the oxidant channel515is defined collectively by the cathode508and the cathode cell sub-unit514. Similarly, the fuel channel534may be at least partially defined by an anode506in the plurality of fuel cells504, such that the fuel channel534is collectively defined by the anode506and the anode cell sub-unit518.

As shown inFIG.7, each oxidant channel515may be fluidly coupled to an oxidant circuit600. The oxidant circuit600may include an oxidant inlet602having an oxidant inlet manifold604that distributes an oxidant to a respective oxidant channel515in the fuel cell assembly502. Additionally, the oxidant circuit600may include an oxidant outlet606having an outlet manifold608. Similarly, the fuel channel534may be fluidly coupled to a fuel circuit610. The fuel circuit610may include a fuel inlet612having a fuel inlet manifold614that distributes a fuel to a respective fuel channel534in the fuel cell assembly502. Additionally, the fuel circuit610may include a fuel outlet616having an outlet manifold618. Furthermore, each coolant channel556may be fluidly coupled to a coolant circuit620. The coolant circuit620may include a coolant inlet622having a coolant inlet manifold624that distributes an oxidant to a respective coolant channel556in the fuel cell assembly502. Additionally, the coolant circuit620may include a coolant outlet626having an outlet manifold628. The fuel and air stream are in similar flow direction to ensure effective operation of the fuel cell. For example, the fuel and air stream may flow in a first flow direction. The coolant flow can either be in counterflow (opposite) direction, co-flow (same) direction, or in cross flow (perpendicular) direction with the fuel and air flow direction. In this way, the coolant flow may flow in a second flow direction that is either the same as the first flow direction or different than the first flow direction. When the coolant flow is in crossflow direction with the fuel and air flows (i.e. coolant flows into/out of the page inFIG.7), the coolant inlet and outlet manifolds would be perpendicular to the inlet and outlet manifold of the fuel and air stream (not illustrated). The different flow configurations may be used based on requirements for the fuel cell assembly cooling load, compactness, allowable coolant pressure-drop, etc.

As shown by the arrows inFIG.7(which indicate flow direction of the fluids in each circuit), oxidants (such as air or other oxidants) may flow through the oxidant channel515in a first flow direction. Fuel may flow through the fuel channel534in the first flow direction, such that the fuel in the fuel channel534and the oxidants in the oxidant channel515flow in the same direction (e.g., co-flow). In various embodiments, coolant may flow through the coolant channel556in a second flow direction. The second flow direction may be the same or different than the first flow direction. For example, the second flow direction may be one of a countercurrent flow direction (e.g., 180° different than the first flow direction), a co-flow direction (e.g., the same direction as the first flow direction), or cross-flow direction (e.g., 90° different than the first flow direction).

Referring now toFIGS.8and9, various aspects of a bipolar separator plate512are illustrated in accordance with an embodiment of the present disclosure. For example,FIG.8illustrates a perspective view of the bipolar separator plate512.FIG.9illustrates a perspective partially exploded view of the bipolar separator plate512, in which the coolant cell sub-unit516is separated from an electrode cell sub-unit517. The electrode cell sub-unit517may be representative of either (or both) of the anode or cathode cell sub-units514or518described above.

As shown inFIG.8, the bipolar separator plate512may define a cartesian coordinate system having a vertical direction V, a longitudinal direction L, and a transverse direction T mutually perpendicular to one another. The bipolar separator plate512may be stacked with unit-cells vertically, longitudinally, and transversely. For example, the coolant cell sub-unit516may include a plurality of rows of unit-cells stacked together along each of the vertical direction V, the longitudinal direction L, and the transverse direction T. In some embodiment, as shown, the cathode cell sub-unit514and the anode cell sub-unit518may each include a plurality of rows of unit-cells stacked together along each of the vertical direction V and the transverse direction T, but the cathode cell sub-unit514and the anode cell sub-unit518may each only include a singular row of unit-cells stacked along the longitudinal direction L. In many embodiments, the cathode cell sub-unit514and the anode cell sub-unit518may each include a solid wall portion598that contacts the coolant cell sub-unit516to fluidly isolate the one or more channels515,534,556. Particularly, the coolant cell sub-unit516may be disposed between the solid wall portion598of the cathode cell sub-unit514and the solid wall portion598of the anode cell sub-unit518.

As shown inFIG.9, the electrode cell sub-unit517may partially define a channel688(which may be either the oxidant channel515or the fuel channel534described above depending on the electrode that the electrode cell sub-unit517is placed in contact with). For example, if the electrode cell sub-unit517is positioned in contact with the anode506, then the anode506and the electrode cell sub-unit517may collectively define the fuel channel534. Likewise, if the electrode cell sub-unit517is positioned in contact with a cathode508, then the cathode508and the electrode cell sub-unit517may collectively define the oxidant channel515. As shown inFIG.9, the channel688may include vertically extending portions690and transversely extending portions692. For example, each of the vertically extending portions690of the channel688may extend along a vertical axis691without interruption (i.e., no blockages or other impediments) from a top of the electrode cell sub-unit517to a bottom of the electrode cell sub-unit517. Similarly, each of the transversely extending portions692may extend along a transverse axis693without interruption from a first end to a second end of the electrode cell sub-unit517.

FIG.10illustrates a perspective view of a unit-cell590(e.g., a single-fluid unit-cell) in the plurality of unit-cells590that collectively make up the coolant cell sub-unit516of the bipolar separator plate512.FIG.11illustrates a cross-sectional perspective view of the unit-cell590from along the line11-11shown inFIG.10. As shown inFIGS.10and11, the unit-cell590may be shaped as a polyhedron having a plurality of side surfaces652and a plurality of corners654(or vertices) defined at junctions between the plurality of side surfaces652. In exemplary embodiments, as shown, the unit-cell590may be shaped as a cuboid, rectangular prism, or a cube, such that the unit-cell590has six side surfaces652and eight corners654. Each side surface652may be perpendicular to four other side surfaces652and parallel to one other side surface652. The plurality of side surfaces652may include a top side surface656and a bottom side surface658spaced apart from one another in the vertical direction V. The plurality of side surfaces652may further include a first side surface660and a second side surface662spaced apart from one another in the longitudinal direction L. The plurality of side surfaces652may further include a third side surface664and a fourth side surface666spaced apart from one another in the transverse direction T.

In exemplary embodiments, the unit-cell590may define a plurality of openings642and an internal volume636extending along the longitudinal direction L, the vertical direction V, and the transverse direction T between each of the openings642on two opposite side surfaces652. For example, each opening642of the plurality of openings642may be defined on a respective side surface652. Each of the openings642may be shaped as a circle; however, in other embodiments, the openings642may be shaped as an oval, square, rectangle, or other shapes. Particularly, the openings642may each be defined on the center of a respective side surface652(e.g., the side surface652may be shaped as a square and the opening642may be centered on the square).

As shown inFIGS.10and11, each unit-cell590may defines a longitudinal centerline668, a transverse centerline670, and a vertical centerline672each extending through a centroid673(e.g., where all the centerlines intersect) of the unit-cell590and mutually orthogonal to one another. For example, the longitudinal centerline668may extend in the longitudinal direction L through the centroid673(i.e., geometric center) of the unit-cell590, the transverse centerline670may extend in the transverse direction T through the centroid673of the unit-cell590, and the vertical centerline672may extend in the vertical direction V through the centroid673of the unit-cell590. In exemplary embodiments, as shown, the internal volume636may extend along the longitudinal centerline668, the transverse centerline670, and the vertical centerline672between respective openings642of the plurality of openings642. Particularly, the internal volume636may include a cylindrically shaped portion extending along each of the centerlines668,670,672. For example, the internal volume636may include a first cylindrically shaped portion that extends along the longitudinal centerline668between two openings642on opposite side surfaces652. Further, the internal volume636may include a second cylindrically shaped portion that extends along the transverse centerline670between two openings642on opposite side surfaces652. Furthermore, the internal volume636may include a third cylindrically shaped portion that extends along the vertical centerline672between two openings642on opposite side surfaces652.

The unit-cell590may define three cylindrically shaped passages that each extend through the centroid673of the cell, extend mutually perpendicularly to one another, and collectively define the internal volume636. For example, as shown inFIGS.10and11, the internal volume636may extend along the longitudinal centerline668from a first opening defined on the first side surface660, through a centroid673of the unit-cell590, to a second opening defined on the second side surface662. Additionally, the internal volume636may extend along the transverse centerline670from a third opening defined on the third side surface664, through the centroid673of the unit-cell590, to a fourth opening defined on the fourth side surface666. Furthermore, the internal volume636may extend along the vertical centerline672from a fifth opening defined on a bottom side surface656, through the centroid673of the unit-cell, to a sixth opening defined on a top side surface658.

As shown inFIG.11, the unit-cell590may include a plurality of edge portions674each extending between two corners654of the plurality of corners654. As shown inFIG.11, the edge portions674may each have a generally rectangular shaped cross-sectional shape.

FIG.12illustrates a unit-cell650(e.g., a single-fluid unit cell) from the electrode cell sub-unit517. The unit-cell650may be representative of either or both of the unit-cell591or the unit-cell593described above, such that the unit-cell650may be included in the cathode cell sub-unit514and/or the anode cell sub-unit518. The unit-cell650may include a solid side676and a plurality of side surfaces678each extending perpendicularly from the solid side676. When implemented in a fuel cell sub-unit, such as the electrode cell sub-unit517, the solid sides676of the unit-cells650may collectively define the solid wall portion598. As used herein “solid side” may include a wall or surface that does not include any openings, voids, or cavities (i.e., the surface is impermeable). When assembled, the solid side676of the unit-cell650may contact one or more unit-cells590in the coolant cell sub-unit516to partially define the coolant channel556. The unit-cell650may include four edge portions680each extending from the solid side676to a free end682. The free end682may have a generally rectangular or square cross-sectional shape. When assembled, each of the free ends682may contact (directly contact) an electrode (e.g., the anode506or the cathode508), such that the electrode and the plurality of unit-cells650define a channel (i.e., either the fuel channel or the oxidant channel).

Generally, as shown inFIG.12, the unit-cell650may generally be shaped as a rectangular prism and may define an internal volume684that includes two semi-cylindrical portions686,687. The first semi-cylindrical portion686may extend generally vertically from a first semi-circular opening to a second semi-circular opening, and the second semi-cylindrical portion687may extend generally transversely from a third semi-circular opening to a fourth semi-circular opening.

Referring now toFIGS.13and14, various aspects of a bipolar separator plate512are illustrated in accordance with another embodiment of the present disclosure. For example,FIG.13illustrates a perspective view of the bipolar separator plate512.FIG.14illustrates a perspective partially exploded view of the bipolar separator plate512, in which the coolant cell sub-unit516is separated from an electrode cell sub-unit517. The electrode cell sub-unit517may be representative of either (or both) of the anode or cathode cell sub-units514or518described above.

As shown inFIG.14, the electrode cell sub-unit517may partially define a channel688(which may be either the oxidant channel515or the fuel channel534described above depending on the electrode that the electrode cell sub-unit517is placed in contact with). For example, if the electrode cell sub-unit517is positioned in contact with the anode506, then the anode506and the electrode cell sub-unit517may collectively define the fuel channel534. Likewise, if the electrode cell sub-unit517is positioned in contact with a cathode508, then the cathode508and the electrode cell sub-unit517may collectively define the oxidant channel515. As shown inFIG.14, the channel688may include a plurality of oblique extending portions694. Each of the oblique extending portions694may extend generally oblique to both the vertical direction V and the transverse direction T. For example, each of the oblique extending portions694of the channel688of the electrode cell sub-unit517may extend without interruption along an oblique axis695.

FIG.15illustrates a perspective view of a unit-cell590(e.g., a single-fluid unit-cell) in the plurality of unit-cells590that collectively make up the coolant cell sub-unit516of the bipolar separator plate512.FIG.16illustrates a cross-sectional perspective view of the unit-cell590fromFIG.15along the line16-16. As shown inFIGS.15and16, the unit-cell590may be shaped as a polyhedron having a plurality of side surfaces652and a plurality of corners654(or vertices) defined at junctions between the plurality of side surfaces652. In exemplary embodiments, as shown, the unit-cell590may be shaped as a cuboid, rectangular prism, or a cube, such that the unit-cell590has six side surfaces652and eight corners654. Each side surface652may be perpendicular to four other side surfaces652and parallel to one other side surface652. The plurality of side surfaces652may include a top side surface656and a bottom side surface658spaced apart from one another in the vertical direction V. The plurality of side surfaces652may further include a first side surface660and a second side surface662spaced apart from one another in the longitudinal direction L. The plurality of side surfaces652may further include a third side surface664and a fourth side surface666spaced apart from one another in the transverse direction T.

In exemplary embodiments, the unit-cell590may define a plurality of openings642and an internal volume636extending in a plurality of directions between each of the openings642on two adjacent side surfaces652. For example, each opening642of the plurality of openings642may be defined on a respective side surface652. Each of the openings642may be shaped as a circle; however, in other embodiments, the openings642may be shaped as an oval, square, rectangle, or other shapes. Particularly, the openings642may each be defined on the center of a respective side surface652(e.g., the side surface652may be shaped as a square and the opening642may be centered on the square).

As shown inFIGS.15and16, each unit-cell590may defines a longitudinal centerline668, a transverse centerline670, and a vertical centerline672each extending through a centroid673(e.g., where all the centerlines intersect) of the unit-cell590and mutually orthogonal to one another. For example, the longitudinal centerline668may extend in the longitudinal direction L through the centroid673(i.e., geometric center) of the unit-cell590, the transverse centerline670may extend in the transverse direction T through the centroid673of the unit-cell590, and the vertical centerline672may extend in the vertical direction V through the centroid673of the unit-cell590. In exemplary embodiments, as shown, the internal volume636may extend at least partially along the longitudinal centerline668, the transverse centerline670, and the vertical centerline672between respective openings642of the plurality of openings642without extending through the centroid673of the unit-cell590.

As shown inFIG.16, the unit-cell590may include a plurality of edge portions675each extending between two corners654of the plurality of corners654. As shown inFIG.16, the edge portions675may each have a triangular shaped cross-sectional shape.

Additionally, as shown inFIG.16the centroid673of the unit-cell590may be solid and partially define the internal volume636. For example, the centroid673of the unit-cell590may be disposed on a solid center portion696. The solid center portion696may have a generally rectangular or square shaped cross-section. In many embodiments, as shown inFIG.16, the internal volume636may further include a plurality of cylindrically shaped portions698. Each of the cylindrically shaped portions698may extend generally oblique to each of the vertical direction V, the longitudinal direction L, and the transverse direction T of the unit-cell590. For example, each of the cylindrically shaped portions698may extend between the solid center portion696and the edge portion675. Particularly, as shown inFIG.16, each of the cylindrically shaped portions698may extend between a straight edge of the solid center portion696and a hypotenuse of the edge portion675.

FIG.17illustrates a unit-cell650(e.g., a single-fluid unit-cell) from the electrode cell sub-unit517. The unit-cell650may be representative of either or both of the unit-cell591or the unit-cell593described above, such that the unit-cell650may be included in the cathode cell sub-unit514and/or the anode cell sub-unit518. The unit-cell650may include a solid side676and a plurality of side surfaces678each extending perpendicularly from the solid side676. As used herein “solid side” may include a wall or surface that does not include any openings, voids, or cavities (i.e., the surface is impermeable). When assembled, the solid side676of the unit-cell650may contact one or more unit-cells590in the coolant cell sub-unit516to partially define the coolant channel556. The unit-cell650may include four edge portions681each extending from the solid side676to a free end683. The free end683may have a generally triangular cross-sectional shape. When assembled, each of the free ends683may contact (directly contact) an electrode (e.g., the anode506or the cathode508), such that the electrode and the plurality of unit-cells650define a channel (i.e., either the fuel channel or the oxidant channel).

As shown inFIG.17, the unit-cell650may generally be shaped as a rectangular prism and may define an internal volume685that includes four semi-cylindrical portions700each extending between opening portions702. The unit-cell may include a solid center portion685shaped as a rectangular prism (e.g., a square) having four sides and four corners. Each of the opening portions702may be defined between two edge portions681and a corner of the solid center portion685, and each of the semi-cylindrical portions700may extend between two opening portions702oblique to each of the vertical direction V and the longitudinal direction L. For example, each of the semi-cylindrical portions700may be defined by a side of the solid center portion685and a hypotenuse side of an edge portion681.

Referring now toFIGS.18through20, various aspects of a bipolar separator plate512is illustrated in accordance with another embodiment of the present disclosure. For example,FIG.18illustrates a perspective view of a coolant cell sub-unit516of a bipolar separator plate512.FIG.19illustrates a perspective view of a unit-cell590(e.g., a single-fluid unit-cell) in the plurality of unit-cells590that collectively make up the coolant cell sub-unit516of the bipolar separator plate512.FIG.20illustrates a cross-sectional perspective view of the unit-cell590fromFIG.19from along the diagonal section line20-20shown inFIG.19.

As shown inFIGS.18through20, the unit-cell590may be shaped as a polyhedron having a plurality of side surfaces652and a plurality of corners654(or vertices) defined at junctions between the plurality of side surfaces652. In exemplary embodiments, as shown, the unit-cell590may be shaped as a cuboid, rectangular prism, or a cube, such that the unit-cell590has six side surfaces652and eight corners654. Each side surface652may be perpendicular to four other side surfaces652and parallel to one other side surface652. The plurality of side surfaces652may include a top side surface656and a bottom side surface658spaced apart from one another in the vertical direction V. The plurality of side surfaces652may further include a first side surface660and a second side surface662spaced apart from one another in the longitudinal direction L. The plurality of side surfaces652may further include a third side surface664and a fourth side surface666spaced apart from one another in the transverse direction T.

In exemplary embodiments, the unit-cell590may define a plurality of openings643and an internal volume636extending in a plurality of directions between each of the openings643. For example, each opening643of the plurality of openings643may be defined on a respective corner654. Each of the openings643may be shaped as a circle; however, in other embodiments, the openings642may be shaped as an oval, square, rectangle, or other shapes. In exemplary embodiments, as shown, the at least one corner654of the plurality of corners654may define a chamfered end704that forms part of a sphere. In such embodiments, as shown, each of the openings643may be disposed on a respective chamfered end704(e.g., centered on the chamfered end). The chamfered end may form ⅛thof sphere, such that when eight unit-cells are disposed adjacent to one another, the eight chamfered ends may collectively define an entire sphere. Alternatively stated, when four unit-cells are disposed adjacent to one another (as shown inFIG.18), the four chamfered ends may collectively define a half sphere.

As shown inFIG.20, the internal volume636may include a plurality of cylindrically shaped portions706each extending between diagonally opposite corners654(e.g., diametrically opposed corners654). of the plurality of corners654. For example, each of the cylindrically shaped portions706may extend diagonally (or oblique) to the vertical direction V, the longitudinal direction L, and the transverse direction between a first corner and a second corner opposite the first corner. Each of the cylindrically shaped portions706may extend through the centroid of the unit-cell590. Particularly, the internal volume636may further include a spherical center708, and each of the cylindrically shaped portions706may extend from a respective corner654to the spherical center708of the internal volume636.

A fuel cell assembly comprising: a plurality of fuel cells; and a bipolar separator plate disposed between each fuel cell of the plurality of fuel cells, the bipolar separator plate comprising: one or more fuel cell sub-units each comprising a plurality of unit-cells, each unit-cell in the plurality of unit-cells having an outer surface and defining an internal volume that extends in multiple directions between a plurality of openings defined on the outer surface, and wherein each unit-cell in the plurality of unit-cells is disposed adjacent to a neighboring unit-cell in the plurality of unit-cells such that the plurality of unit-cells collectively define one or more channels.

The fuel cell assembly as in one or more of these clauses, wherein at least one opening of the plurality of openings of each unit-cell in the plurality of unit-cells aligns with a neighboring opening of the plurality of openings in the neighboring unit-cell of the plurality of unit-cells such that the internal volume of each unit-cell of the plurality of unit-cells collectively define the one or more channels.

The fuel cell assembly as in one or more of these clauses, wherein the one or more channels comprises an oxidant channel defined in a cathode cell sub-unit of the one or more fuel cell sub-units, a coolant channel defined in a coolant cell sub-unit of the one or more fuel cell sub-units, and a fuel channel defined in an anode cell sub-unit of the one or more fuel cell sub-units, and wherein the oxidant channel, the coolant channel, and the fuel channel are fluidly isolated from one another.

The fuel cell assembly as in one or more of these clauses, wherein each fuel cell of the plurality of fuel cells comprises an anode, a cathode, and a solid electrolyte disposed between the anode and the cathode, wherein the oxidant channel is at least partially defined by the cathode of a first fuel cell in the plurality of fuel cells, and wherein the fuel channel is at least partially defined by the anode of a second fuel cell in the plurality of fuel cells.

The fuel cell assembly as in one or more of these clauses, wherein each unit-cell of the plurality of unit-cells is shaped as a polyhedron having a plurality of side surfaces and a plurality of corners defined at junctions between the plurality of side surfaces.

The fuel cell assembly as in one or more of these clauses, wherein each opening of the plurality of openings is defined on a respective side surface.

The fuel cell assembly as in one or more of these clauses, wherein each unit-cell of the plurality of unit-cells defines a longitudinal centerline, a transverse centerline, and a vertical centerline each extending through a centroid of the unit-cell and mutually orthogonal to one another, and wherein the internal volume extends along the longitudinal centerline, the transverse centerline, and the vertical centerline between each of the openings on two opposite side surfaces.

The fuel cell assembly as in one or more of these clauses, wherein the internal volume extends between each of the openings on adjacent side surfaces.

The fuel cell assembly as in one or more of these clauses, wherein each opening of the plurality of openings is defined on a corner of the plurality of corners and wherein the internal volume includes a plurality of cylindrically shaped portions each extending between diagonally opposite corners of the plurality of corners and wherein at least one corner of the plurality of corners defines a chamfered end forming part of a sphere.

The fuel cell assembly as in one or more of these clauses, wherein the oxidant channel is fluidly coupled to an oxidant inlet manifold and an oxidant outlet manifold, the fuel channel is fluidly coupled to a fuel inlet manifold and a fuel outlet manifold, and the coolant channel is fluidly coupled to a coolant inlet manifold and a coolant outlet manifold.

The fuel cell assembly as in one or more of these clauses, wherein oxidants flow through the oxidant channel in a first flow direction, wherein fuel flows through the fuel channel in the first flow direction, and wherein coolant flows through the coolant channel in a second flow direction, and wherein the second flow direction is one of the same or different than the first flow direction.

The fuel cell assembly as in one or more of these clauses, wherein a centroid of each unit-cell of the plurality of unit-cells is solid and partially defines the internal volume and wherein the internal volume comprises a plurality of cylindrically shaped portions.

A propulsion system comprising: a turbomachine comprising a compressor section and a combustion section; and a fuel cell assembly comprising: a plurality of fuel cells; and a bipolar separator plate disposed between each fuel cell of the plurality of fuel cells, the bipolar separator plate including a cathode cell sub-unit that defines an oxidant channel fluidly coupled to the compressor section, a coolant cell sub-unit that defines a coolant channel, and an anode cell sub-unit that defines a fuel channel fluidly coupled to the combustion section, wherein the oxidant channel, the coolant channel, and the fuel channel are fluidly isolated from one another.

The propulsion system as in one or more of these clauses, wherein the oxidant channel is at least partially defined by the cathode of a first fuel cell in the plurality of fuel cells, and wherein the fuel channel is at least partially defined by the anode of a second fuel cell in the plurality of fuel cells.

The propulsion system as in one or more of these clauses, wherein the oxidant channel comprises an oxidant inlet and an oxidant outlet, wherein the oxidant inlet is fluidly coupled to a low pressure compressor stage of the compressor section via a bleed air line, and wherein the oxidant outlet is fluidly coupled to one of a high pressure compressor stage of the compressor section via a cathode exhaust line or the combustion section.

The propulsion system as in one or more of these clauses, wherein the fuel channel comprises a fuel inlet and one or more outlets, wherein the fuel inlet fluidly is fluidly coupled a fuel supply line, and wherein the one or more outlets of the fuel channel is fluidly coupled to one of the combustion section or one or more turbine stage in the turbine section.

The propulsion system as in one or more of these clauses, wherein an air-to-air heat exchanger thermally couples the bleed air line and the cathode exhaust line, and wherein a fuel-to-fuel heat exchanger thermally couples the fuel supply line and the one or more fuel channel outlets.

The propulsion system as in one or more of these clauses, wherein the coolant channel is in fluid communication with a heat-sink heat exchanger in a closed cycle loop.

The propulsion system as in one or more of these clauses, wherein each fuel cell of the plurality of fuel cells comprises an anode, a cathode, and a solid electrolyte disposed between the anode and the cathode, wherein the oxidant channel is at least partially defined by the cathode of a first fuel cell in the plurality of fuel cells, and wherein the fuel channel is at least partially defined by the anode of a second fuel cell in the plurality of fuel cells.

The propulsion system as in one or more of these clauses, wherein the bipolar separator plate further comprises a plurality of unit-cells each having an outer surface, each unit-cell of the plurality of unit-cells defining an internal volume that extends in multiple directions between a plurality of openings defined on the outer surface, wherein each unit-cell in the plurality of unit-cells is disposed adjacent to a neighboring unit-cell in the plurality of unit-cells such that the plurality of unit-cells collectively define one or more channels, and wherein the one or more channels comprises the oxidant channel, the coolant channel, and the fuel channel.