Solid oxide fuel cell assembly

Abstract

A propulsion system for an aircraft, the aircraft including an aircraft fuel supply, the propulsion system comprising: a turbomachine including, in serial flow order, a compressor section, a combustion section, and a turbine section, the combustion section configured to receive a flow of aviation fuel from the aircraft fuel supply; and a fuel cell assembly including a fuel cell stack having solid oxide fuel cells, the solid oxide fuel cells defining an outlet positioned to remove an output product from the solid oxide fuel cells and provide the output product to the combustion section, the solid oxide fuel cells including a cathode; an electrolyte layer; and an anode positioned opposite the cathode from the electrolyte layer, the anode including a metal ceramic including less than 25 vol% nickel.

Description

Technical Field

[0001] This disclosure relates to fuel cell components, and more specifically, to solid oxide fuel cell components that can be incorporated into aerospace propulsion systems. Background Technology

[0002] A gas turbine engine generally consists of a turbine and a rotor assembly. Gas turbine engines (such as turbofan engines) can be used for aircraft propulsion. In the case of a turbofan engine, the turbine includes a compressor section, a combustion section, and a turbine section in a sequential flow sequence, and the rotor assembly is configured as a fan assembly.

[0003] During operation, air is compressed in the compressor and mixed with fuel in the combustion section and ignited to produce combustion gases, which flow downwards through the turbine section. The turbine section extracts energy from the combustion gases to rotate the compressor section and fan assembly, thereby powering the gas turbine engine and propelling the aircraft containing this gas turbine engine during flight.

[0004] At least some gas turbine engines include fuel cell components that can operate in conjunction with them. Attached Figure Description

[0005] The complete and feasible disclosure of this disclosure, including its best mode, is set forth in the specification with reference to the accompanying drawings, for those skilled in the art, wherein:

[0006] Figure 1 This is a cross-sectional view of a gas turbine engine according to an exemplary aspect of this disclosure.

[0007] Figure 2 This is a perspective view of the integrated fuel cell and burner assembly according to this disclosure.

[0008] Figure 3 yes Figure 2 A schematic axial view of an exemplary integrated fuel cell and burner assembly.

[0009] Figure 4 This is a schematic diagram of a fuel cell assembly according to an exemplary aspect of the present disclosure, the fuel cell assembly being incorporated into... Figure 2 An exemplary integrated fuel cell and burner assembly.

[0010] Figure 5 This is a schematic diagram of a gas turbine engine including an integrated fuel cell and burner assembly, according to an exemplary aspect of this disclosure.

[0011] Figure 6 This is a flowchart of a method for starting a gas turbine engine according to an exemplary aspect of this disclosure.

[0012] Figure 7 This is a flowchart of a method for starting a fuel cell assembly according to an exemplary aspect of this disclosure.

[0013] Figure 8 This is a flowchart of a method for starting a fuel cell assembly according to another exemplary aspect of this disclosure.

[0014] Figure 9 This is a flowchart of a method for starting a fuel cell assembly according to yet another exemplary aspect of this disclosure.

[0015] Figure 10 This is a flowchart of a method for starting a fuel cell assembly according to yet another exemplary aspect of this disclosure.

[0016] Figure 11 This is a schematic diagram of a gas turbine engine including an integrated fuel cell and burner assembly, according to another exemplary aspect of this disclosure.

[0017] Figure 12 This is a schematic diagram of a gas turbine engine including an integrated fuel cell and burner assembly, according to yet another exemplary aspect of this disclosure.

[0018] Figure 13 This is a schematic diagram of a gas turbine engine including an integrated fuel cell and burner assembly, according to another exemplary aspect of this disclosure.

[0019] Figure 14 This is a flowchart of a method for performing a hot start-up of a fuel cell assembly, according to another exemplary aspect of this disclosure.

[0020] Figure 15 This is a schematic diagram of a gas turbine engine including an integrated fuel cell and burner assembly, according to another exemplary aspect of this disclosure.

[0021] Figure 16 yes Figure 15 A close-up schematic diagram of a fuel cell assembly that integrates an exemplary fuel cell and a burner assembly.

[0022] Figure 17 This is a graph showing the percentage of open-circuit operating voltage (OCV) of a fuel cell stack with a nickel / yttrium-stabilized zirconium oxide anode during redox cycles.

[0023] Figure 18 This is a graph showing the OCV percentage of a fuel cell stack with a nickel / yttrium-stabilized zirconium oxide anode during redox cycles.

[0024] Figure 19This is a graph showing the percentage of hydrogen stack output of a fuel cell stack with a lanthanum strontium titanate / gadolinium oxide-doped cerium dioxide anode during redox cycles.

[0025] Figure 20 This is a flowchart of a method for starting a fuel cell assembly according to another exemplary aspect of this disclosure.

[0026] Figure 21 This is a flowchart of a method for operating a gas turbine engine and a fuel cell assembly according to another exemplary aspect of this disclosure.

[0027] Figure 22 This is a flowchart of a method for shutting down a gas turbine engine and cooling a fuel cell assembly according to an exemplary aspect of this disclosure.

[0028] Figure 23 This is a schematic diagram of the control system according to this disclosure. Detailed Implementation

[0029] Reference will now be made in detail to the present embodiments of this disclosure, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerals and letter reference numerals to denote features in the drawings. Similar or analogous reference numerals in the drawings and description have been used to denote similar or analogous portions of this disclosure.

[0030] The term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as superior or better than other implementations. Furthermore, unless explicitly stated otherwise, all embodiments described herein should be considered exemplary.

[0031] For the purposes described below, the terms “upper,” “lower,” “right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” “lateral,” “longitudinal,” and their derivatives should be associated with the embodiments in which they are oriented in the accompanying drawings. However, it should be understood that various alternative variations may be assumed in the embodiments unless explicitly stated otherwise. It should also be understood that the specific devices shown in the drawings and described in the following description are merely exemplary embodiments of this disclosure. Therefore, the specific dimensions and other physical characteristics associated with the embodiments disclosed herein should not be considered limiting.

[0032] As used herein, the terms “first,” “second,” and “third” are used interchangeably to distinguish one component from another and are not intended to indicate the location or importance of the individual components.

[0033] The terms "front" and "rear" refer to relative positions within a gas turbine engine or vehicle, and specifically to the normal operating posture of the gas turbine engine or vehicle. For example, in the case of a gas turbine engine, "front" refers to the position closer to the engine inlet, while "rear" refers to the position closer to the engine nozzle or exhaust port.

[0034] The terms "upstream" and "downstream" refer to the relative directions of fluid flow within a fluid path. For example, "upstream" refers to the direction from which the fluid flows, and "downstream" refers to the direction from which the fluid flows.

[0035] Unless otherwise specified herein, the terms “connection,” “fixed,” “attached to,” etc., refer to both direct connection, fixation, or attachment, and indirect connection, fixation, or attachment via one or more intermediate components or features.

[0036] Unless the context clearly indicates otherwise, the singular forms “a,” “a,” and “the” include plural references.

[0037] In the context of, for example, “at least one of A, B and C” or “at least one of A, B or C”, the term “at least one” means only A, only B, only C, or any combination of A, B and C.

[0038] As used throughout the specification and claims, approximate language is applied to modify any quantitative expression that allows for variation without altering its underlying function. Therefore, values ​​modified by terms such as “about,” “approximate,” and “substantially” are not limited to specified exact values. In at least some cases, approximate language may correspond to the precision of the instrument used to measure the value, or the precision of the method or machine used to construct or manufacture the component and / or system. For example, approximate language may refer to margins of 1%, 2%, 4%, 10%, 15%, or 20%. These approximate margins may apply to a single value, to either end of a range defining a numerical value, or to margins between two ends, and / or between the ends.

[0039] Throughout this specification and claims, scope limitations are combined and interchanged, and unless the context or language otherwise indicates otherwise, such scopes are identified and include all subscopes contained herein. For example, all scopes disclosed herein include endpoints, and endpoints may be combined independently of each other.

[0040] As used herein, "third stream" refers to a non-mainstream flow that can increase fluid energy to generate a small amount of total propulsion thrust. The pressure ratio of the third stream can be higher than that of the main propulsion flow (e.g., bypass or propeller-driven propulsion flow). Thrust can be generated through dedicated nozzles or by mixing the airflow through the third stream with the main propulsion flow or core flow (e.g., mixing it into a common nozzle).

[0041] In some exemplary embodiments, the operating temperature of the airflow through the third flow can be below the engine's maximum compressor discharge temperature, and more specifically, below 350 degrees Fahrenheit (e.g., below 300 degrees Fahrenheit, below 250 degrees Fahrenheit, below 200 degrees Fahrenheit, and at least as high as ambient temperature). In some exemplary embodiments, these operating temperatures can facilitate heat transfer to or from the airflow through the third flow and the separate fluid flow. Furthermore, in some exemplary embodiments, under takeoff conditions, or more specifically, under operating conditions of sea-level rated takeoff power, static flight speed, and an ambient temperature of 86 degrees Fahrenheit, the airflow through the third flow can contribute less than 50% (and at least, for example, 2%) of the total engine thrust.

[0042] Furthermore, in some exemplary embodiments, the aforementioned exemplary percentage contribution of the third flow's airflow aspects (e.g., airflow, mixing, or exhaust properties) to the total thrust can be passively adjusted during engine operation or purposefully modified by using engine control features (such as fuel flow, motor power, variable stator, variable inlet guide vanes, valves, variable exhaust geometry, or fluid characteristics) to adjust or optimize overall system performance under a wide range of potential operating conditions.

[0043] The term “turbine” or “turbomachinery” refers to a machine that includes one or more compressors, a heating section (e.g., a combustion section), and one or more turbines that together generate torque output.

[0044] The term "gas turbine engine" refers to an engine that has a turbine as its power source, in whole or in part. Examples of gas turbine engines include turbofan engines, turboprop engines, turbojet engines, turboshaft engines, and hybrid electric versions of one or more of these engines.

[0045] When used with compressors, turbines, shafts, or spool components, unless otherwise specified, the terms “low” and “high,” or their respective comparatives (e.g., “lower” and “higher,” where applicable), refer to relative speeds within the engine. For example, “low-speed turbine” or “low-turbine” defines a component constructed to operate at a rotational speed (such as the maximum permissible rotational speed) lower than that of a “high-speed turbine” or “high-turbine” at the engine.

[0046] As will be discussed in more detail below, a fuel cell is an electrochemical device that converts the chemical energy from a fuel (such as hydrogen) into electrical energy through an electrochemical reaction between the fuel and an oxidant (such as oxygen contained in the atmosphere). Fuel cell systems can be advantageously used as energy supply systems because they can be considered environmentally superior and highly efficient compared to at least some existing systems. To improve system efficiency and fuel utilization and reduce external water consumption, fuel cell systems may include an anode recirculation loop. Since a single fuel cell can only generate about 1V of voltage, multiple fuel cells can be stacked together (which may be called a fuel cell stack) to generate a desired voltage. Fuel cells can include solid oxide fuel cells (SOFC), molten carbonate fuel cells (MCFC), phosphoric acid fuel cells (PAFC), and proton exchange membrane fuel cells (PEMFC), which are generally named after their respective electrolytes. Each of these fuel cells may have specific benefits in the form of a preferred operating temperature range, power generation capacity, efficiency, etc.

[0047] (i) Figure 1 Implementation examples

[0048] Referring now to the accompanying drawings, where the same numbers indicate the same elements throughout all the drawings. Figure 1 A schematic cross-sectional view of an engine according to an exemplary embodiment of the present disclosure is provided. The engine can be integrated into a vehicle. For example, the engine can be an aircraft engine integrated into an aircraft. However, alternatively, the engine can be any other suitable type of engine for any other suitable vehicle.

[0049] In the depicted embodiment, the engine is configured as a high-bypass turbofan engine 100. As... Figure 1 As shown, the turbofan engine 100 defines an axial direction A (extending parallel to the centerline axis 101 provided for reference), a radial direction R, and a circumferential direction (extending around the axial direction A; not shown in the diagram). Figure 1 (As shown in the figure). Typically, the turbofan engine 100 includes a fan section 102 and a turbine 104 disposed downstream of the fan section 102.

[0050] The depicted exemplary turbine 104 generally includes a substantially tubular housing 106 defining an annular inlet 108. The housing 106 surrounds, in a series flow relationship: a compressor section including a boost or low-pressure (LP) compressor 110 and a high-pressure (HP) compressor 112; a combustion section 114; a turbine section including a high-pressure (HP) turbine 116 and a low-pressure (LP) turbine 118; and an exhaust nozzle section 120. The compressor section, combustion section 114, and turbine section together at least partially define a core airflow path 121 extending from the annular inlet 108 to the exhaust nozzle section 120. The turbofan engine further includes one or more drive shafts. More specifically, the turbofan engine includes a high-pressure (HP) shaft or spool 122 drivingly connecting the HP turbine 116 to the HP compressor 112, and a low-pressure (LP) shaft or spool 124 drivingly connecting the LP turbine 118 to the LP compressor 110.

[0051] In the depicted embodiment, fan section 102 includes a fan 126 having a plurality of fan blades 128 spaced apart and coupled to disk 130. The plurality of fan blades 128 and disk 130 are rotatable together about a centerline axis 101 via LP shaft 124. Disk 130 is covered by a rotatable front hub 132, which is aerodynamically shaped to facilitate airflow through the plurality of fan blades 128. Furthermore, an annular fan housing or outer nacelle 134 is configured to circumferentially surround at least a portion of fan 126 and / or turbine 104. Nacelle 134 is supported relative to turbine 104 by a plurality of circumferentially spaced outlet guide vanes 136. A downstream section 138 of nacelle 134 extends over the outer portion of turbine 104 to define a bypass airflow passage 140 therebetween.

[0052] In this way, it will be understood that the turbofan engine 100 generally includes a first flow (e.g., a core airflow path 121) and a second flow extending parallel to the first flow (e.g., a bypass airflow passage 140). In some exemplary embodiments, the turbofan engine 100 may further define a third flow, for example, extending from the LP compressor 110 to the bypass airflow passage 140 or to the environment. With this configuration, the LP compressor 110 may generally include a first compressor stage configured as a ducted intermediate fan and a downstream compressor stage. The inlet of the third flow may be located between the first compressor stage and the downstream compressor stage.

[0053] Still referencing Figure 1The turbofan engine 100 additionally includes an accessory gearbox 142 and a fuel delivery system 146. The fuel delivery system 146 may be an aircraft fuel supply unit, such as an aircraft fuel supply unit for an aircraft propulsion system. In the illustrated embodiment, the accessory gearbox 142 is located within the shroud / casing 106 of the turbine 104. Additionally, it will be understood that for... Figure 1 In the schematically depicted embodiment, accessory gearbox 142 is mechanically coupled to one or more shafts or spools of turbine 104 and is rotatable with one or more shafts or spools of turbine 104. For example, in the depicted exemplary embodiment, accessory gearbox 142 is mechanically coupled to HP shaft 122 via a suitable gear train 144 and is rotatable with HP shaft 122. Accessory gearbox 142 can provide power to one or more suitable accessory systems of turbofan engine 100 during at least some operations and can further provide power back to turbofan engine 100 during other operations. For example, in the illustrated embodiment, accessory gearbox 142 is coupled to starter motor / generator 152. Starter motor / generator can be configured to draw power from accessory gearbox 142 and turbofan engine 100 to generate electricity during some operations and can provide power back to accessory gearbox 142 and turbofan engine 100 (e.g., to HP shaft 122) during other operations to add mechanical work back to turbofan engine 100 (e.g., for starting turbofan engine 100).

[0054] Furthermore, the fuel delivery system 146 generally includes a fuel source 148 (such as a fuel tank) and one or more fuel delivery lines 150. One or more fuel delivery lines 150 supply fuel flow through the fuel delivery system 146 to the combustion section 114 of the turbine 104 of the turbofan engine 100. As will be discussed in more detail below, the combustion section 114 includes an integrated fuel cell and combustor assembly 200. In the described embodiment, one or more fuel delivery lines 150 supply fuel flow to the integrated fuel cell and combustor assembly 200.

[0055] However, it will be understood that, Figure 1 The exemplary turbofan engine 100 depicted is provided by way of example only. In other exemplary embodiments, any other suitable gas turbine engine may be used in conjunction with aspects of this disclosure. For example, in other embodiments, the turbofan engine may be any other suitable gas turbine engine, such as a turboshaft engine, a turboprop engine, a turbojet engine, etc. In this way, it will be further understood that in other embodiments, the gas turbine engine may have any other suitable construction, such as any other suitable number or arrangement of shafts, compressors, turbines, fans, etc. Furthermore, although Figure 1The exemplary gas turbine engine depicted herein is schematically shown as a direct-drive fixed-pitch turbofan engine, but in other embodiments, the gas turbine engine of this disclosure may be a geared gas turbine engine (i.e., including a gearbox between a fan 126 and a shaft (such as LP shaft 124) driving the fan), a variable-pitch gas turbine engine (i.e., including a fan 126 having a plurality of fan blades 128 capable of rotating about their respective pitch axes), etc. Furthermore, although the exemplary turbofan engine 100 includes a ducted fan 126, in other exemplary aspects, the turbofan engine 100 may include a non-ducted fan 126 (or an open rotor fan) without a nacelle 134. Moreover, although not depicted herein, in other embodiments, the gas turbine engine may be any other suitable type of gas turbine engine, such as a marine gas turbine engine.

[0056] (ii) Figure 2 Implementation examples

[0057] Now for reference Figure 2 The illustration schematically shows a portion of a combustion section 114 according to an embodiment of the present disclosure, which includes... Figure 1 Gas turbine engine 100 (above about Figure 1 Described as part of the integrated fuel cell and burner assembly 200 used in the turbofan engine 100.

[0058] It will be understood that the combustion section 114 includes a compressor diffuser nozzle 202 and extends generally along the axial direction A between an upstream end and a downstream end. The combustion section 114 is fluidly connected via the compressor diffuser nozzle 202 to the compressor section at the upstream end and to the turbine section at the downstream end.

[0059] The integrated fuel cell and burner assembly 200 generally includes fuel cell assembly 204. Figure 2 Only a partial description is provided; see also Figures 3 to 5 The combustor 206 includes an inner liner 208, an outer liner 210, a dome assembly 212, a shroud assembly 214, a swirler assembly 216, and a fuel flow line 218. The combustion section 114 generally includes a housing 220 radially outward of the combustor 206 to surround it, and an inner housing 222 radially inward of the combustor 206. The inner housing 222 and the inner liner 208 define an inner passage 224 therebetween, while the outer housing 220 and the outer liner 210 define an outer passage 226 therebetween. The inner housing 222, the outer housing 220, and the dome assembly 212 together at least partially define the combustion chamber 228 of the combustor 206.

[0060] The dome assembly 212 is positioned near the upstream end of the combustion section 114 (i.e., closer to the upstream end than the downstream end) and includes an opening (not labeled) for receiving and retaining the swirler assembly 216. The swirler assembly 216 also includes an opening for receiving and retaining the fuel flow line 218. The fuel flow line 218 is further coupled to a fuel source 148 disposed radially R outside the housing 220 (see [link to fuel source 148]). Figure 1 It is configured to receive fuel from fuel source 148. In this way, fuel flow line 218 can be fluidly connected to the reference above. Figure 1 Describes one or more fuel delivery pipelines 150.

[0061] The swirler assembly 216 may include a plurality of swirlers (not shown) configured to swirl the compressed fluid before it is injected into the combustion chamber 228 to generate combustion gases. In the illustrated embodiment, the shroud assembly 214 is configured to hold the inner liner 208, the outer liner 210, the swirler assembly 216, and the dome assembly 212 together.

[0062] During operation, the compressor diffuser nozzle 202 is configured to direct compressed fluid 230 from the compressor section to the combustor 206, wherein the compressed fluid 230 is configured to mix with fuel within the cyclone assembly 216 and burn within the combustion chamber 228 to generate combustion gases. The combustion gases are supplied to the turbine section to drive one or more turbines of the turbine section (e.g., high-pressure turbine 116 and low-pressure turbine 118).

[0063] During operation of the gas turbine engine 100, which includes an integrated fuel cell and combustor assembly 200, the flame within the combustion chamber 228 is maintained by a continuous flow of fuel and air. To provide ignition of the fuel and air, for example during start-up of the gas turbine engine 100, the integrated fuel cell and combustor assembly 200 further includes an igniter 231. The igniter 231 can provide a spark or initial flame to ignite the fuel and air mixture within the combustion chamber 228. In some exemplary embodiments, the integrated fuel cell and combustor assembly 200 may additionally include a dedicated fuel cell igniter 233 (depicted in dashed lines). Specifically, for Figure 2 In one embodiment, a dedicated fuel cell igniter 233 is positioned downstream of at least a portion of the fuel cell, and particularly downstream of at least a portion of the fuel cell stack (described below). In this way, the dedicated fuel cell igniter 233 can more efficiently combust the fuel cell's output products.

[0064] As mentioned above and Figure 2The diagram schematically depicts an integrated fuel cell and burner assembly 200, which further includes a fuel cell assembly 204. The depicted exemplary fuel cell assembly 204 includes a first fuel cell stack 232 and a second fuel cell stack 234. More specifically, the first fuel cell stack 232 is constructed together with an outer liner 210, and the second fuel cell stack 234 is constructed together with an inner liner 208. Even more specifically, the first fuel cell stack 232 is integrated with the outer liner 210, and the second fuel cell stack 234 is integrated with the inner liner 208. The operation of the fuel cell assembly 204, and more specifically, the operation of the fuel cell stacks (e.g., the first fuel cell stack 232 or the second fuel cell stack 234) of the fuel cell assembly 204, will be described in more detail below.

[0065] In the described embodiments, fuel cell assembly 204 is configured as a solid oxide fuel cell (“SOFC”) assembly, wherein a first fuel cell stack 232 is configured as a first SOFC fuel cell stack, and a second fuel cell stack 234 is configured as a second SOFC fuel cell stack (each having multiple SOFCs). It will be understood that an SOFC is generally an electrochemical conversion device that generates electricity directly by oxidizing fuel. Generally, fuel cell assemblies, and especially fuel cells, are characterized by the electrolyte material used. The SOFCs of this disclosure generally may include solid oxide or ceramic electrolytes. Such fuel cells generally exhibit high overall thermoelectric efficiency, long-term stability, fuel flexibility, and low emissions.

[0066] Furthermore, the exemplary fuel cell assembly 204 further includes a first power converter 236 and a second power converter 238. The first fuel cell stack 232 is electrically connected to the first power converter 236 via a first plurality of power cables (unlabeled), and the second fuel cell stack 234 is electrically connected to the second power converter 238 via a second plurality of power cables (unlabeled).

[0067] The first power converter 236 controls the current drawn from the corresponding first fuel cell stack 232 and can convert direct current (“DC”) power to DC power or alternating current (“AC”) power at another voltage level. Similarly, the second power converter 238 controls the current drawn from the second fuel cell stack 234 and can convert DC power to DC power or AC power at another voltage level. The first power converter 236, the second power converter 238, or both can be electrically connected to an electrical bus (such as electrical bus 326 described below).

[0068] The integrated fuel cell and burner assembly 200 further includes a fuel cell controller 240, which is operatively communicable with a first power converter 236 and a second power converter 238 to send and receive communications and signals, for example, between the two. For example, the fuel cell controller 240 can send current or power setpoint signals to the first power converter 236 and the second power converter 238, and can receive voltage or current feedback signals, for example, from the first power converter 236 and the second power converter 238. The fuel cell controller 240 can be configured in accordance with the following references. Figure 5 The fuel cell controller 240 described is constructed in the same manner.

[0069] (iii) Figure 3 and 4 Examples of implementations.

[0070] It will be understood that, in at least some exemplary embodiments, the first fuel cell stack 232, the second fuel cell stack 234, or both may extend substantially 360 degrees in the circumferential direction C of the gas turbine engine (i.e., the direction in which it extends about the centerline axis 101 of the gas turbine engine 100). For example, now referring to Figure 3 A simplified cross-sectional view of an integrated fuel cell and burner assembly 200 is depicted according to an exemplary embodiment of this disclosure. Although for simplicity... Figure 3 Only the first fuel cell stack 232 is depicted, but the second fuel cell stack 234 can be constructed in a similar manner.

[0071] As shown in the figure, the first fuel cell stack 232 extends around the combustion chamber 228 in the circumferential direction C, and in the illustrated embodiment, completely surrounds the combustion chamber 228 around the central axis 101. More specifically, the first fuel cell stack 232 includes a plurality of fuel cells 242 arranged in the circumferential direction C. Figure 3 The fuel cell 242 visible in the image can be a single ring of fuel cell 242, wherein fuel cells 242 are stacked together along the axial direction A (see [link]). Figure 2 In another example, multiple additional rings of fuel cells 242 may be placed on top of each other to form a first fuel cell stack 232 extending along the centerline axis 101.

[0072] The following will explain this in more detail; please refer to [reference needed]. Figure 5In the first fuel cell stack 232, fuel cell 242 is positioned to receive exhaust air 244 from, for example, a compressor section and fuel 246 from a fuel delivery system 146. Fuel cell 242 uses the air 244 and at least some of the fuel 246 to generate an electric current and guides partially oxidized fuel 246 and unused portion of air 248 radially toward the centerline axis 101 into combustion chamber 228. Integrated fuel cell and combustor assembly 200 combusts the partially oxidized fuel 246 and air 248 in combustion chamber 228 into combustion gases, which are then guided downstream into a turbine section to drive or assist in driving one or more turbines therein.

[0073] In addition, now refer to Figure 4 Provided as Figure 2 A schematic perspective view of the first fuel cell stack 232 of the integrated fuel cell and burner assembly 200. The second fuel cell stack 234 can be formed in a similar manner.

[0074] The depicted first fuel cell stack 232 includes a casing 250 having a combustion outlet side 252 and a side 254 opposite to the combustion outlet side 252, a fuel and air inlet side 256 and a side 588 opposite to the fuel and air inlet side 256, and sides 260 and 262. Sides 260, 258, and 254 are... Figure 4 It is not visible in the 3D image.

[0075] It will be understood that the first fuel cell stack 232 may include, for example, multiple fuel cells “stacked” side-by-side from one end of the first fuel cell stack 232 (e.g., fuel and air inlet side 256) to the other end of the first fuel cell stack 232 (e.g., side 258). Therefore, it will be further understood that the combustion outlet side 252 includes multiple combustion outlets 264, each combustion outlet originating from a fuel cell within the first fuel cell stack 232. During operation, combustion gases 266 (also referred to herein as “output products”) are directed from the combustion outlets 264 out of the housing 250. As described herein, the combustion gases 266 are generated using fuel and air not consumed by the fuel cells within the housing 250 of the first fuel cell stack 232. The combustion gases 266 are supplied to the combustion chamber 228 and combusted during operation to generate combustion gases used to generate thrust for the gas turbine engine 100 (and vehicles / aircraft in conjunction with the gas turbine engine 100).

[0076] The fuel and air inlet side 256 includes one or more fuel inlets 268 and one or more air inlets 270. Optionally, one or more of the inlets 268, 270 may be located on the other side of the housing 250. Each of the one or more fuel inlets 268 is fluidly connected to a fuel source (such as hydrogen gas or one or more pressurized containers of a fuel processing unit further described below) for the first fuel cell stack 232. Each of the one or more air inlets 270 is fluidly connected to an air source (such as air discharged from the compressor section and / or the air processing unit also further described below) for the fuel cell. The one or more inlets 268, 270 separately receive fuel and air from external fuel and air sources and separately direct the fuel and air into the fuel cell.

[0077] In some exemplary embodiments, Figures 2 to 4 The first fuel cell stack 232 may be constructed in a manner similar to one or more of the exemplary fuel cell systems (labeled 100) described, for example, in U.S. Patent Application Publication No. 2020 / 0194799A1, filed December 17, 2018, the entire contents of which are incorporated herein by reference. It will be further understood that... Figure 2 The second fuel cell stack 234 can be constructed in a similar manner to the first fuel cell stack 232, or alternatively, it can be constructed in any other suitable manner.

[0078] (iv) Figure 5 Implementation examples

[0079] Now for reference Figure 5 The operation of the integrated fuel cell and burner assembly 200 according to exemplary embodiments of the present disclosure will be described. More specifically, Figure 5 A schematic diagram of a gas turbine engine 100 and an integrated fuel cell and combustor assembly 200 according to embodiments of the present disclosure is provided. In some exemplary embodiments, the gas turbine engine 100 and the integrated fuel cell and combustor assembly 200 can be coupled with… Figures 1 to 4 One or more exemplary embodiments are constructed in a similar manner to those described above.

[0080] Therefore, it will be understood that the gas turbine engine 100 generally includes a fan section 102 with a fan 126, an LP compressor 110, an HP compressor 112, a combustion section 114, an HP turbine 116, and an LP turbine 118. The combustion section 114 generally includes an integrated fuel cell and combustor assembly 200 with a combustor 206 and a fuel cell assembly 204.

[0081] The propulsion system including the gas turbine engine 100 further includes a fuel delivery system 146. The fuel delivery system 146 generally includes a fuel source 148 and one or more fuel delivery lines 150. The fuel source 148 may include a supply section for fuel (e.g., hydrocarbon fuel, including, for example, carbon-neutral fuel or synthetic hydrocarbons) for the gas turbine engine 100. Furthermore, it will be understood that the fuel delivery system 146 also includes a fuel pump 272 and a distributor 274, and the one or more fuel delivery lines 150 include a first fuel delivery line 150A, a second fuel delivery line 150B, and a third fuel delivery line 15C. Diverter 274 divides the fuel flow from fuel source 148 and fuel pump 272 into a first fuel flow through a first fuel delivery line 150A to fuel cell assembly 204, a second fuel flow through a second fuel delivery line 150B also to fuel cell assembly 204 (and particularly to the air handling unit described below), and a third fuel flow through a third fuel delivery line 150C to burner 206. Diverter 274 may include a series of valves (not shown) to facilitate this diversion of the fuel flow from fuel source 148, or alternatively, may have a fixed geometry. Additionally, for the illustrated embodiment, fuel delivery system 146 includes a first fuel valve 151A associated with the first fuel delivery line 150A (e.g., for controlling the first fuel flow), a second fuel valve 151B associated with the second fuel delivery line 150B (e.g., for controlling the second fuel flow), and a third fuel valve 151C associated with the third fuel delivery line 150C (e.g., for controlling the third fuel flow).

[0082] The gas turbine engine 100 further includes a compressor exhaust system and an air delivery system. More specifically, the compressor exhaust system includes an LP bleed air duct 276 and an associated LP bleed air valve 278, an HP bleed air duct 280 and an associated HP bleed air valve 282, and an HP outlet air duct 284 and an associated HP outlet air valve 286.

[0083] The gas turbine engine 100 further includes an air supply duct 288 (in airflow communication with the air supply unit 290) and an associated air valve 292, which is also in airflow communication with the air delivery system, for providing compressed airflow to the fuel cell assembly 204 of the integrated fuel cell and combustor assembly 200. The air supply unit may be, for example, a second gas turbine engine configured to provide cross-bleed air, an auxiliary power unit (APU) configured to provide bleed air, a ram air turbine (RAT), an ambient location (e.g., free-flowing air), etc. If the compressor air source is insufficient or unavailable, the air supply unit may supplement the compressor exhaust system.

[0084] The compressor discharge system (and air supply duct 288) is in airflow communication with the airflow delivery system for supplying compressed airflow to the fuel cell assembly 204, as will be explained in more detail below.

[0085] Still referencing Figure 5 The fuel cell assembly 204, which integrates the fuel cell and burner assembly 200, includes a fuel cell stack 294, which can be constructed in a manner similar to, for example, the first fuel cell stack 232 described above. The fuel cell stack 294 is schematically depicted as a single fuel cell having a cathode side 296 (also referred to herein as "cathode 296"), an anode side 298 (also referred to herein as "anode 298"), and an electrolyte 300 (also referred to herein as an electrolyte layer) positioned between them. Generally, it will be understood that the electrolyte 300 can conduct negative oxygen ions from the cathode side 296 to the anode side 298 during operation to generate current and electricity.

[0086] In simple terms, it will be understood that the fuel cell assembly 204 further includes a fuel cell sensor 302 configured to sense data indicating operating parameters of the fuel cell assembly, such as the temperature of the fuel cell stack 294 (e.g., the cathode side 296 or anode side 298 of the fuel cell), the pressure within the fuel cell stack 294 (e.g., within the cathode side 296 or anode side 298 of the fuel cell), and / or the composition (e.g., chemical composition) of the output products from the fuel cell assembly 204.

[0087] The anode side 298 can support an electrochemical reaction that generates electricity. Fuel can be oxidized in the anode side 298 via diffusion through the electrolyte 300, utilizing oxygen ions received from the cathode side 296. This reaction can generate heat, vapor, and electricity in the form of free electrons in the anode side 298, which can be used to power energy-consuming devices (such as one or more additional electrical devices 328 described below). Oxygen ions can be generated using electrons returning from the energy-consuming device to the cathode side 296 via oxygen reduction of the cathode oxidant.

[0088] The cathode side 296 can be coupled to a cathode oxidant source, such as atmospheric oxygen. The cathode oxidant is defined as the oxidant supplied to the cathode side 296, which is used by the fuel cell system to generate electricity. The cathode side 296 can be permeable to oxygen ions received from the cathode oxidant.

[0089] Electrolyte 300 can be connected to both the anode side 298 and the cathode side 296. Electrolyte 300 allows oxygen ions to pass from the cathode side 296 to the anode side 298, and can have very low conductivity or no conductivity to prevent free electrons from passing from the cathode side 296 to the anode side 298.

[0090] The anode side of a solid oxide fuel cell (such as fuel cell stack 294) can be made of nickel / yttrium oxide-stabilized zirconium oxide (Ni / YSZ) cermet. Nickel in the anode side serves as a catalyst for fuel oxidation and a current conductor. During normal operation of fuel cell stack 294, the operating temperature can be greater than or equal to approximately 700°C, and the nickel (Ni) in the anode retains its reduced form due to the continuous supply of primarily hydrogen fuel gas.

[0091] The fuel cell stack 294 is located downstream of the LP compressor 110, the HP compressor 112, or both. Furthermore, from the above regarding... Figure 2 As will be understood from the description, fuel cell stack 294 may be coupled to or otherwise integrated with the bushings (e.g., inner liner 208 or outer liner 210) of burner 206. In this way, fuel cell stack 294 may also be arranged upstream of combustion chamber 228, which integrates fuel cell and burner assembly 200, and further upstream of HP turbine 116 and LP turbine 118.

[0092] like Figure 5 As shown, the fuel cell assembly 204 also includes a fuel processing unit 304 and an air processing unit 306. The fuel processing unit 304 can be any suitable structure for generating a hydrogen-rich fuel stream. For example, the fuel processing unit 304 may include a fuel reformer or a catalytic partial oxidation converter (CPO). x An air handling unit 306 is used to generate a hydrogen-rich fuel stream for the fuel cell stack 294. The air handling unit 306 can be any suitable structure for raising the temperature of the air supplied to it to a temperature sufficiently high to achieve fuel cell temperature control (e.g., about 600°C to about 800°C). For example, in the depicted embodiment, the air handling unit includes a pre-burner system that operates based on the fuel stream via a second fuel delivery line 150B and is configured to raise the air temperature by combustion, for example, during transient conditions such as start-up, shutdown, and abnormal situations.

[0093] In the exemplary embodiment depicted, the fuel processing unit 304 and the air processing unit 306 are manifolded together within the housing 308 to provide conditioned air and fuel to the fuel cell stack 294.

[0094] However, it should be understood that the fuel processing unit 304 may additionally or alternatively include any suitable type of fuel reformer, including but not limited to catalytic partial oxidizers, automatic thermal reformers, or steam reformers, which may require an additional steam inlet stream with a higher hydrogen composition at the reformer outlet stream. Additionally or alternatively, the fuel processing unit 304 may also include a reformer integrated with the fuel cell stack 294. Similarly, it should be understood that... Figure 5The air handling unit 306 may alternatively be a heat exchanger or another device for raising the temperature of the air supplied thereto to a temperature high enough to achieve fuel cell temperature control (e.g., about 600°C to about 800°C).

[0095] As described above, the compressor discharge system (and air supply duct 288) is in airflow communication with the airflow delivery system for providing compressed airflow to the fuel cell assembly 204. The airflow delivery system includes an anode airflow duct 310 and associated anode airflow valve 312 for providing airflow to the fuel processing unit 304, a cathode airflow duct 314 and associated cathode airflow valve 316 for providing airflow to the air processing unit 306, and a cathode bypass air duct 318 and associated cathode bypass air valve 320 for providing airflow directly to the fuel cell stack 294 (or more precisely, to the cathode side 296 of the fuel cell). The fuel delivery system 146 is configured to provide a first fuel flow to the fuel processing unit 304 via a first fuel delivery line 150A and a second fuel flow to the air processing unit 306 via a second fuel delivery line 150B (e.g., as fuel for the pre-combustor system, if provided).

[0096] The fuel cell stack 294 outputs electricity as generated by the fuel cell power output 322. In addition, the fuel cell stack 294 directs cathode air emissions and anode fuel emissions (not labeled for clarity) into the combustion chamber 228 of the burner 206.

[0097] In operation, the air treatment unit 306 is configured to heat / cool a portion of the compressed air entering through the cathode airflow duct 314 to generate treated air to be guided into the fuel cell stack 294, thereby facilitating the operation of the fuel cell stack 294. The air treatment unit 306 receives a second fuel flow from the second fuel delivery line 150B and can, for example, combust this second fuel flow to heat the received air to a desired temperature (e.g., about 600°C to about 800°C), thereby facilitating the operation of the fuel cell stack 294. The air treated by the air treatment unit 306 is guided into the fuel cell stack 294. In embodiments of this disclosure, as shown, the cathode bypass air duct 318 and the air treated by the air treatment unit 306 can be combined into a combined airflow to be fed into the cathode 296 of the fuel cell stack 294.

[0098] In addition, such as Figure 5As shown in the embodiment, a first fuel flow via a first fuel delivery line 150A is directed to a fuel processing unit 304 for generating a hydrogen-rich fuel flow (e.g., optimizing the hydrogen content of the fuel flow), which is also fed into the fuel cell stack 294. It will be understood, and discussed below, that the air (processing air and bypass air) flow to the fuel cell stack 294 (e.g., cathode side 296) and the fuel from the fuel processing unit 304 to the fuel cell stack 294 (e.g., anode side 298) can facilitate power generation.

[0099] Since the inlet air to the fuel cell stack 294 may originate solely from the upstream compressor section without any other separately controlled air source, it will be understood that the inlet air to the fuel cell stack 294 discharged from the compressor section will be affected by air temperature variations occurring at different stages of flight. As an illustrative example only, the air in a specific location within the compressor section of the gas turbine engine 100 may operate at 200°C during idling, 600°C during takeoff, 268°C during cruise, and so on. This type of temperature variation in the inlet air directed to the fuel cell stack 294 can cause significant thermal transient problems (or even thermal shock) to the ceramic material of the fuel cell stack 294, potentially ranging from cracking to failure.

[0100] Therefore, by fluidly connecting the air handling unit 306 between the compressor section and the fuel cell stack 294, the air handling unit 306 can serve as a control device or system to maintain the air processed by the air handling unit 306 and directed into the fuel cell stack 294 within a desired operating temperature range (e.g., ±100°C, or preferably ±50°C, or ±20°C). During operation, the temperature of the air supplied to the fuel cell stack 294 (relative to the temperature of the air discharged from the compressor section) can be controlled by controlling the fuel flow to the air handling unit 306. Increasing the fuel flow to the air handling unit 306 can raise the temperature of the airflow to the fuel cell stack 294. Decreasing the fuel flow to the air handling unit 306 can lower the temperature of the airflow to the fuel cell stack 294. Optionally, fuel cannot be supplied to the air handling unit 306 to prevent the air handling unit 306 from raising and / or lowering the temperature of the air discharged from the compressor section and directed into the air handling unit 306.

[0101] Furthermore, as depicted in dashed lines, the fuel cell assembly 204 further includes an airflow bypass duct 321 extending around the fuel cell to allow part or all of the airflow regulated by the air handling unit 306 (and combined with any bypass air passing through duct 318) to bypass the cathode side 296 of the fuel cell and enter directly into the combustion chamber 228. The airflow bypass duct 321 may be in thermal communication with the fuel cell. The fuel cell assembly further includes a fuel bypass duct 323 extending around the fuel cell to allow part or all of the reformed fuel from the fuel handling unit 304 to bypass the anode side 298 of the fuel cell and enter directly into the combustion chamber 228.

[0102] As briefly mentioned above, fuel cell stack 294 converts the anode fuel stream from fuel processing unit 304 and the air processed by air processing unit 306 into electrical energy in the form of DC current, i.e., fuel cell power output 322. This fuel cell power output 322 is directed to power converter 324 to convert the DC current into DC or AC current that can be efficiently utilized by one or more subsystems. Specifically, in the depicted embodiment, power is supplied from the power converter to electrical bus 326. Electrical bus 326 may be an electrical bus dedicated to gas turbine engine 100, an electrical bus of an aircraft in conjunction with gas turbine engine 100, or a combination thereof. Electrical bus 326 is electrically connected to one or more auxiliary electrical devices 328, which may be a power source, a power sink, or both. For example, auxiliary electrical devices 328 may be energy storage devices (such as one or more batteries), motors (generators, electric motors, or both), electric propulsion devices, etc. For example, one or more auxiliary electrical devices 328 may include a starter motor / generator of gas turbine engine 100.

[0103] Still referencing Figure 5 The gas turbine engine 100 further includes a sensor 330. In the illustrated embodiment, the sensor 330 may be configured to sense data indicating the flame within the combustion section 114 of the gas turbine engine 100, or some other parameter indicating the operating conditions of the gas turbine engine. The sensor 330 may be, for example, a temperature sensor configured to sense data indicating the outlet temperature of the combustion section 114, the inlet temperature of the turbine section, the exhaust temperature, or a combination thereof. Additionally or alternatively, the sensor 330 may be any other suitable sensor, or any suitable combination of sensors, configured to sense one or more gas turbine engine operating conditions or parameters, including data indicating the flame within the combustion section 114 of the gas turbine engine 100.

[0104] In addition, such as Figure 5Further schematically depicted, the propulsion system, the aircraft including the propulsion system, or both include controller 240. For example, controller 240 may be a standalone controller, a gas turbine engine controller (e.g., a full authority digital engine controller or a FADEC controller), an aircraft controller, a supervisory controller for the propulsion system, or combinations thereof.

[0105] The controller 240 is operatively connected to various sensors, valves, etc., within at least one of the gas turbine engine 100 and the fuel delivery system 146. More specifically, for the exemplary aspects depicted, the controller 240 is operatively connected to valves (valve 278, 282, 286) of the compressor discharge system, valves (valve 312, 316, 320) of the gas flow delivery system, and valves (splitter 274, valves 151A, 151B, 151C) of the fuel delivery system 146, as well as sensors 330 of the gas turbine engine 100 and fuel cell sensor 302. It will be understood from the following description that the controller 240 can communicate wirelessly with these components, either wired or wirelessly. In this way, the controller 240 can receive data from various inputs (including gas turbine engine sensor 330 and fuel cell sensor 302), make control decisions, and provide data (e.g., instructions) to various outputs (including valves of the compressor discharge system that control the airflow discharge from the compressor section, valves of the airflow delivery system that guide the airflow discharge from the compressor section, and valves of the fuel delivery system 146 that guide the fuel flow within the gas turbine engine 100).

[0106] Referring specifically to the operation of controller 240, in at least some embodiments, controller 240 may include one or more computing devices 332. Computing device 332 may include one or more processors 332A and one or more memory devices 332B. The one or more processors 332A may include any suitable processing means, such as a microprocessor, microcontroller, integrated circuit, logic device, and / or other suitable processing means. The one or more memory devices 332B may include one or more computer-readable media, including but not limited to non-transitory computer-readable media, RAM, ROM, hard disk drives, flash drives, and / or other memory devices.

[0107] One or more memory devices 332B may store information accessible by one or more processors 332A, including computer-readable instructions 332C executable by one or more processors 332A. Instructions 332C may be any set of instructions that, when executed by one or more processors 332A, cause one or more processors 332A to operate. In some embodiments, instructions 332C may be executed by one or more processors 332A to cause one or more processors 332A to operate, such as any operations and functions configured for the controller 240 and / or computing device 332, operations for operating the propulsion system as described herein (e.g., method 600), and / or any other operations or functions of one or more computing devices 332. Instructions 332C may be software written in any suitable programming language or may be implemented in hardware. Additionally and / or alternatively, instructions 332C may be executed in logically and / or virtually decoupled threads on the processor 332A. Memory device 332B may further store data 332D accessible by processor 332A. For example, data 332D may include data indicating power flow, data indicating operating conditions of the gas turbine engine 100 / aircraft, and / or any other data and / or information described herein.

[0108] The computing device 332 also includes a network interface 332E, which is configured to communicate, for example, with other components of the gas turbine engine 100 (such as valves of the compressor exhaust system (valve 278, 282, 286), valves of the airflow delivery system (valve 312, 316, 320), and valves of the fuel delivery system 146 (splitter 274, valves 151A, 151B, 151C), as well as sensors 330 and fuel cell sensors 302 of the gas turbine engine 100), and with an aircraft associated with the gas turbine engine 100. The network interface 332E may include any suitable components for communication with one or more network interfaces, including, for example, transmitters, receivers, ports, controllers, antennas, and / or other suitable components. In this way, it will be understood that the network interface 332E can utilize any suitable combination of wired and wireless communication networks.

[0109] The techniques discussed in this paper refer to computer-based systems, actions taken by computer-based systems, and information sent to and from computer-based systems. It will be understood that the inherent flexibility of computer-based systems allows for a wide variety of possible configurations, combinations, and divisions of tasks and functionalities between and within components. For example, the processes discussed herein can be implemented using a single computing device or multiple computing devices working in combination. Databases, memory, instructions, and applications can be implemented on a single system or distributed across multiple systems. Distributed components can operate sequentially or in parallel.

[0110] It will be understood that the gas turbine engine 100, the exemplary fuel delivery system 146, the exemplary integrated fuel cell and combustor assembly 200, and the exemplary fuel cell assembly 204 are provided as examples only. In other embodiments, the integrated fuel cell and combustor assembly 200 and the fuel cell assembly 204 may have any other suitable configuration. For example, in other exemplary embodiments, the fuel cell assembly 204 may include any other suitable fuel processing unit 304. Additionally or alternatively, for example when the combustor of the gas turbine engine 100 is configured to burn hydrogen fuel, and the fuel delivery assembly 146 is configured to supply hydrogen fuel to the integrated fuel cell and combustor assembly 200, particularly to the fuel cell assembly 204, the fuel cell assembly 204 may not require the fuel processing unit 304.

[0111] (v) Introduction to ground startup

[0112] As will be understood from the description herein, this includes integrated fuel cells and burner assemblies (such as those referenced above). Figures 1 to 5 Ground start-up of a gas turbine engine (one or more exemplary integrated fuel cell and combustor assemblies 200) described herein may require coordinated execution to address various issues associated with start-up time, environmental and safety standards. As used herein, the term “ground start-up” relative to a gas turbine engine refers to accelerating a gas turbine engine from a shut-off position (or a slow-rotating position, e.g., less than about 50 revolutions per minute) to at least ground idle operation.

[0113] For example, as briefly mentioned above, in at least some exemplary embodiments, the anode of a solid oxide fuel cell (SOFC) can be made of a porous cermet comprising nickel and yttrium-stabilized zirconium oxide. The nickel component provides electrical conductivity, electrochemical capability, and fuel handling capability. The nickel component can also enhance certain mechanical properties of the fuel cell. However, nickel is a relatively unstable metal at high temperatures, and particularly unstable in the presence of free oxygen at temperatures above approximately 350°C to 400°C. At normal operating temperatures of fuel cell components, such as 600°C to 1000°C, the anode may need to be subjected to a reducing atmosphere with an oxygen partial pressure below the nickel-nickel oxide equilibrium level. This allows nickel to remain in a reduced metallic state without oxidation. The tendency of nickel to oxidize during SOFC start-up and shutdown can cause structural and operational problems. If the nickel anode is oxidized to form nickel oxide, an increase in volume and weight may occur, introducing undesirable stresses into the anode structure. This can lead to physical failures of the anode, the fuel cell electrolyte, or both. Furthermore, after conversion to nickel oxide, the fuel cell may fail to efficiently convert chemical energy into electrical energy and may be considered a faulty component. Therefore, for fuel cells with a nickel anode, when the anode temperature is above approximately 350°C-400°C, a reducing gas needs to be maintained in the anode.

[0114] Additionally, if nickel (or nickel oxide) comes into contact with carbon monoxide at a temperature below about 150°C to about 230°C, nickel carbonyl may form. The chemical reaction is: Ni + 4CO → Ni(CO)₄. This reaction is undesirable for environmental and safety reasons.

[0115] Therefore, during the startup and shutdown of fuel cell components, it may be necessary to protect the nickel-containing anode from oxidation and prevent carbon monoxide-containing gases from contacting the anode at temperatures below approximately 230°C to ensure that nickel carbonyl is not formed.

[0116] (vi) Example Figure 6 Gas turbine engine start-up process

[0117] As mentioned above, it is desirable to coordinate the startup of the fuel cell assembly with the startup of the gas turbine engine that can operate in conjunction with the fuel cell assembly. This coordination will be described in more detail below with reference to the accompanying drawings.

[0118] However, first refer to Figure 6A method 400 for starting a gas turbine engine is provided. Specifically, method 400 describes a ground start sequence for the gas turbine engine, which can be executed to accelerate the gas turbine engine from shut-off conditions (e.g., rotating at zero RPM, or less than about 50 RPM) to ground idle operating conditions. Method 400 is compatible with any suitable gas turbine engine (such as those mentioned above, for example, referenced in [reference]). Figure 1 and Figure 5 Used together with one or more exemplary gas turbine engines 100 as described.

[0119] Method 400 includes activating the starter of the gas turbine engine (e.g., turning on the starter switch) at (402). The starter activated at (402) can be used in conjunction with... Figure 1 The exemplary starter motor generator 152 of the exemplary gas turbine engine 100 is constructed in a similar manner. The starter activated at (402) can generate the initial rotation of the gas turbine engine.

[0120] Method 400 further includes, at (404), initiating a fuel flow once the gas turbine engine reaches a first threshold speed. In the exemplary embodiment shown, the first threshold speed may refer to a core speed between approximately 15% and 20% of the rated core speed. The core speed may generally refer to the speed of the gas turbine engine, for example, capable of operating with a high-pressure compressor and a high-pressure turbine (see, for example...). Figure 1 The high-voltage spool rotates together with the HP compressor 112 and HP turbine 116.

[0121] Subsequently, method 400 includes igniting the gas turbine engine at (406). The gas turbine engine may include detecting a flame within the combustion zone of the gas turbine engine at (408) via one or more sensors, such as a flame detector. Method 400 may use data from the flame detector at (408) to determine at (410) whether a flame is present within the combustion zone of the gas turbine engine, and more specifically, whether a flame is present within the combustion chamber of the gas turbine engine (see, for example...). Figure 2 The exemplary gas turbine engine 100 has a combustion chamber 228. If no flame is detected, the method may continue to accelerate the gas turbine engine to a higher speed at (412) using a starter and re-ignite at (406). However, in contrast, if a flame is detected at (410), the method 400 includes continuing to accelerate the gas turbine engine at (414). Accelerating the gas turbine engine at (414) may include providing a combination of electricity from a starter motor generator and utilizing energy input through fuel combustion.

[0122] It will be understood that, in response to the detection of a flame at (410), the gas turbine engine can be considered to be in a "flame-on condition".

[0123] Method 400 includes closing the starter at (416). Closing the starter at (416) may include closing the starter in response to determining that the gas turbine engine is rotating at a predetermined self-sustaining speed. Once the starter is closed at (416) and the gas turbine engine is rotating at a sufficient speed to sustain combustion within the combustion zone (e.g., the predetermined self-sustaining speed), the gas turbine engine may be considered to be in a “sustained flame-on condition”.

[0124] Method 400 further includes, at (418), accelerating the gas turbine engine to a desired idle speed, such as ground idle speed. Once at idle speed, the gas turbine engine can be considered to be in “idling conditions.” It will be understood that the term “idling speed” in relation to the gas turbine engine speed refers to the rotational speed at which the gas turbine engine is sufficient to operate continuously and, for example, to power the gas turbine engine and desired accessory systems of, for example, an aircraft equipped with the gas turbine engine.

[0125] It will be understood that the exemplary method 400 for starting a gas turbine engine is provided by way of example only, and in other exemplary embodiments, any other suitable method for starting a gas turbine engine may be provided.

[0126] (vii) Figure 7 Example: Ground start-up of fuel cell assembly without air handling unit

[0127] Now for special reference Figure 7 The document provides a method 500 for operating a propulsion system of an aircraft, and more specifically, a method 500 for starting a fuel cell assembly and a gas turbine engine according to exemplary aspects of this disclosure. The fuel cell assembly can be configured with one or more exemplary fuel cell assemblies described herein (e.g., [missing information]). Figures 2 to 5 , Figures 11 to 13 , Figures 15 to 16 The fuel cell assembly 204, etc., is constructed in a similar manner, and the gas turbine engine can be constructed according to one or more exemplary gas turbine engines described herein (e.g., Figure 1 , Figure 2 , Figure 5 It can be constructed using a gas turbine engine 100, etc. Therefore, a fuel cell assembly can generally include a fuel cell stack with a fuel cell, the fuel cell defining an outlet that is positioned to remove the output products from the fuel cell during operation.

[0128] Method 500 can be broadly referred to as the startup sequence of fuel cell components. From Figure 7The lieutenant general understands that method 500 can be used in method 400 for starting a gas turbine engine (see...). Figure 6 ) to be executed simultaneously with or after. More specifically, it will be understood that for Figure 7 In an exemplary aspect, method 500 can be used to start the gas turbine engine in a specific sequence (such as starting...) Figure 6 The method 400 (e.g., opening the launcher at (402)) is executed simultaneously with or after the method 400. The benefits of this timing will be described in more detail below.

[0129] In short, as will be described in more detail below and in other exemplary aspects of this disclosure, more specifically, method 500 can be performed simultaneously with or after the gas turbine engine achieves flame-opening conditions; simultaneously with or after achieving continuous flame-opening conditions for the gas turbine engine; or simultaneously with or after achieving idling conditions for the gas turbine engine. The benefits of these timings will also be described in more detail below.

[0130] Still referencing Figure 7 Method 500 generally includes operating in a purge state at (502) after the start-up sequence of the fuel cell assembly begins; operating in a first heating state at (504) before the temperature of the fuel cell stack reaches a first fuel cell temperature threshold; operating in a second heating state at (506) after the temperature of the fuel cell stack reaches the first fuel cell temperature threshold and before the temperature of the fuel cell stack reaches a second fuel cell temperature threshold; and operating in a power generation mode at (508) after the temperature of the fuel cell stack reaches the second fuel cell temperature threshold.

[0131] More specifically, referring first to operation in a purging state at (502), method 500 includes operating in a purging state at (510) to provide an airflow from the compressor section of the gas turbine engine to purge the fuel cell, and more specifically, to purge the anode and cathode of the fuel cell. The airflow from the compressor section can be at a temperature of at least about 150°C and up to about 225°C. Purging the fuel cell during the purging state at (502) can also serve as initial heating of the fuel cell. It is noteworthy that performing the start-up sequence of the fuel cell assembly simultaneously with or after performing the start-up sequence of the gas turbine engine at (400) allows pressurized air from the compressor of the gas turbine engine to perform this operation.

[0132] Method 500 further includes, at (516), determining whether the temperature of the fuel cell assembly, such as the temperature of the fuel cell stack of the fuel cell assembly, has reached a first fuel cell temperature threshold. For example, method 500 may include receiving data indicating that the temperature of the fuel cell stack is greater than or equal to the first fuel cell temperature threshold, and in response, initiating operation in a second heating state at (506).

[0133] As can be understood from the above description, the first fuel cell temperature threshold can be a temperature threshold that eliminates the risk of unwanted gas formation. When the temperature of the fuel cell stack is within a certain temperature range, unwanted gases may form within the anode of the fuel cell upon exposure to certain gases (such as carbon monoxide). The first fuel cell temperature threshold can be between approximately 150°C and 400°C, such as between approximately 200°C and 300°C, such as approximately 230°C, to avoid the formation of such unwanted gases.

[0134] For example, nickel carbonyl can form when nickel (or nickel oxide) in the fuel cell anode comes into contact with carbon monoxide at a temperature below the first fuel cell temperature threshold. The chemical reaction is: Ni + 4CO → Ni(CO)₄. For various reasons, the formation of nickel carbonyl is undesirable. Therefore, during SOFC system startup and shutdown, it may be necessary to protect the nickel-containing anode from oxidation and prevent carbon monoxide-containing gases from contacting the anode at temperatures below the first fuel cell temperature threshold to ensure that nickel carbonyl does not form. Based on this design consideration, step (504) in method 500 prevents fuel treatment unit exhaust gas (or reforming gas) from passing through the fuel cell anode containing nickel material.

[0135] Still referencing Figure 7 As mentioned, method 500 further includes, at (504), operating in a first heated state before the temperature of the fuel cell stack reaches a first fuel cell temperature threshold. Operating in the first heated state at (504) includes, at (512), initiating operation of the fuel processing unit and providing a heated gas flow from the fuel processing unit to the cathode of the fuel cell. Specifically, for the exemplary aspects depicted, providing a heated gas flow from the fuel processing unit to the cathode of the fuel cell may include providing exhaust gas from the fuel processing unit along with an additional gas flow to the cathode of the fuel cell. The fuel processing unit may be configured with one or more fuel processing units as described herein (see, for example...). Figure 5 The fuel processing unit (304) is constructed in a similar manner to, but is not limited to, a catalytic partial oxidizer, an autothermal reformer, and a steam reformer. The exhaust gas from the fuel processing unit may include reformed fuel from the fuel processing unit.

[0136] Operating in a first heated state at (504) further includes continuing to heat the fuel cell at (514), for example, using a fuel processing unit. It will be understood that continuing to heat the fuel cell at (514) may further include using an additional heat source, such as a resistance heater. Furthermore, continuing to heat the fuel cell at (514) may include supplying heated air from the fuel processing unit, hydrogen from the fuel processing unit, or both to the anode of the fuel cell. The flow from the fuel processing unit to the anode at (514) may be free of carbon monoxide or substantially completely free of carbon monoxide (e.g., less than 1% carbon monoxide by volume).

[0137] It is worth noting that, in at least some exemplary aspects of this disclosure, operation at (504) in a first heating state may further include a burner to the combustion section (see, for example...). Figure 2 The combustor 206 provides output products from the fuel cell while the gas turbine engine operates at flame-opening conditions or faster (i.e., faster than when flame-opening conditions are met), and more specifically, to the combustion chamber (e.g., Figure 2 The combustion chamber 228 provides output products from the fuel cell. The output products may be, for example, exhaust gas from the fuel treatment unit passing through the cathode of the fuel cell. Additionally or alternatively, in one or more exemplary aspects of this disclosure, operating at (504) in a first heated state may include supplying exhaust gas from the fuel treatment unit to the combustor of the combustion section of the gas turbine engine around (i.e., bypassing) the anode of the fuel cell, and particularly may include supplying exhaust gas from the fuel treatment unit to the combustor of the combustion section around the anode of the fuel cell while the gas turbine engine operates more rapidly in flame-open conditions. In this way, the exhaust gas may bypass the anode of the fuel cell. In one or more of these exemplary aspects, the output products and / or exhaust gas may include hydrogen. When a flame is present within the gas turbine engine in these exemplary aspects, hydrogen can be used to help stabilize combustion in the gas turbine engine and improve combustion efficiency.

[0138] As mentioned above, method 500 further includes, at (516), determining whether the temperature of the fuel cell assembly (such as the temperature of the fuel cell stack of the fuel cell assembly) has reached a first fuel cell temperature threshold.

[0139] As mentioned, once the temperature of the fuel cell assembly, more specifically, the temperature of the fuel cell stack, has reached the first fuel cell temperature threshold, as determined at (516), method 500 begins operation in a second heated state at (506). The anode of a solid oxide fuel cell (SOFC) is typically made of porous cermet, which is composed of nickel and yttrium-stabilized zirconium oxide. The nickel component provides electrical conductivity, electrochemical capability, and fuel handling capability. The nickel component also enhances the mechanical properties of the cell. Nickel is a relatively unstable metal at high temperatures, and in particular, it is unstable in the presence of free oxygen at temperatures above approximately 350-400°C (the high end of the first temperature threshold). At normal SOFC operating temperatures of 600°C to 1000°C, the anode must be subjected to a reducing atmosphere with an oxygen partial pressure below the nickel-nickel oxide equilibrium level. This allows nickel to remain in a reduced metallic state. The tendency of nickel to oxidize during SOFC start-up and shutdown can cause structural and operational problems. If nickel is anolyzed to form nickel oxide, an increase in volume and weight will occur, introducing significant stress into the anode structure. This can lead to physical failure of the anode, electrolyte, or both. Furthermore, after conversion to nickel oxide, the battery cannot efficiently convert chemical energy into electrical energy and is considered a faulty component. Therefore, when the fuel cell anode temperature exceeds a first temperature threshold as shown later in step (506), a reducing gas needs to be maintained in the fuel cell anode.

[0140] When operating in a second heated state at (506), the method may include, at (518), supplying exhaust gas (reduced or reduced gas) exiting the fuel processing unit to the anode of the fuel cell. This process may be in response to receiving data indicating that the temperature of the fuel cell stack is greater than or equal to a first fuel cell temperature threshold. Supplying exhaust gas from the fuel processing unit to the anode of the fuel cell can help protect the anode from anodic oxidation, since the reduced gas from the fuel processing unit may be oxygen-free or substantially oxygen-free.

[0141] Furthermore, it will be understood that, for Figure 7 An exemplary aspect of the method 500 described herein, providing exhaust gas from the fuel processing unit to the anode of the fuel cell at (518) may further include, for example, providing exhaust gas from the fuel processing unit to the cathode of the fuel cell in response to receiving data indicating that the temperature of the fuel cell stack is greater than or equal to a first fuel cell temperature threshold. In this way, method 500 can simultaneously heat both the anode and cathode of the fuel cell while operating in a second heating state at (506).

[0142] It will be further understood that, in certain exemplary aspects of this disclosure, operating in a second heated state at (506) may further include setting the pressure within the anode to be higher than the pressure within the cathode to prevent gases (e.g., oxygen-containing gases) from the cathode from permeating into the anode through the electrolyte layer located therebetween.

[0143] Still referencing Figure 7 Method 500 includes, at (520), determining whether the temperature of the fuel cell assembly has exceeded a second fuel cell temperature threshold, or more specifically, determining whether the temperature of the fuel cell stack of the fuel cell assembly has exceeded the second fuel cell temperature threshold. In at least some exemplary aspects, the determination at (520) may include receiving data indicating that the temperature of the fuel cell stack is greater than or equal to the second fuel cell temperature threshold. In response, method 500 may switch to power generation mode operation at (508). For example, method 500 may include, at (522), for example, in response to determining that the temperature of the fuel cell assembly has exceeded the second fuel cell temperature threshold, or more specifically, in response to the temperature of the fuel cell stack of the fuel cell assembly exceeding the second fuel cell temperature threshold, initiating operation of the fuel cell assembly in power generation mode.

[0144] The second fuel cell temperature threshold can be a temperature threshold under which the fuel cell assembly can operate to generate electricity with a desired efficiency. In some exemplary aspects, the second fuel cell temperature threshold can be greater than the first fuel cell temperature threshold and is between about 400°C and 800°C, such as at least about 500°C, such as at least about 600°C, such as at least about 700°C, such as up to 750°C. The second fuel cell temperature threshold can be driven by various seals and other structures within the fuel cell assembly, such as within the fuel cell stack.

[0145] After the start-up sequence of the fuel cell assembly is executed, the fuel cell can operate in fuel cell power generation mode at (524). As will be understood, operating the fuel cell assembly in power generation mode at (508) may include operating the fuel cell assembly at (526) to provide output products to the combustion section of the gas turbine engine.

[0146] As described above, the exemplary method 500 generally includes initiating a startup sequence of the fuel cell assembly simultaneously with or after the startup sequence of the gas turbine engine at (400). One or more exemplary aspects of the exemplary method 500 may facilitate certain efficiencies, such as allowing airflow from the compressor of the gas turbine engine to be used for startup operations (e.g., providing purge airflow during (502), providing airflow to the fuel processing unit during (504) and / or during (506), etc.). Furthermore, the exhaust gas from the fuel processing unit containing hydrogen may improve combustion within the combustion chamber of the gas turbine engine. Further efficiencies can be achieved because heating the fuel cell assembly may require less fuel combustion, as preheated air from the engine is available for startup operations of the fuel cell assembly, and radiant heat from the burner may also help heat the fuel cell stack during the startup sequence of the fuel cell assembly. This benefit is relevant to the construction of the integrated burner and fuel cell assembly disclosed herein (see, for example...). Figure 2 The integrated burner and fuel cell components can be unique.

[0147] Furthermore, while the start-up sequence of the fuel cell assembly can be initiated simultaneously with or after the start-up sequence of the gas turbine engine, additional benefits can be achieved by initiating the start-up sequence of the fuel cell assembly simultaneously with or after achieving the flame-opening conditions of the gas turbine engine, the sustained flame-opening conditions of the gas turbine engine, or the idling conditions of the gas turbine engine. In particular, the higher the rotational speed of the gas turbine engine and the hotter the flame, the more one or more efficiency benefits described above can be achieved, and the combustion within the combustion chamber can utilize any hydrogen in the output products and / or the exhaust gas supplied thereto, for example, at (504), (506). Another benefit from exemplary method 500 is enhanced reliability and reduced weight when applied to systems without a pre-burner, or enhanced flexibility and availability when the pre-burner has partial or complete failure for fuel cell systems constructed with a pre-burner.

[0148] (i) Figure 8 Example: Ground startup of fuel cell assembly using air handling unit.

[0149] If it is understood that, Figure 7 Example method 500 with air handling units (such as those mentioned above, for example) Figure 5 The exemplary air handling unit 306 described herein operates independently. However, reference is now made to... Figure 8A flowchart of a method 600 for operating a propulsion system of an aircraft according to another exemplary aspect of this disclosure is provided. More specifically, a flowchart of an exemplary method 600 for starting a fuel cell assembly including an air handling unit and a gas turbine engine is depicted. The fuel cell assembly may be coupled with one or more exemplary fuel cell assemblies described herein (e.g., Figures 2 to 5 , Figures 11 to 13 , Figures 15 to 16 The fuel cell assembly 204, etc., is constructed in a similar manner, and the gas turbine engine can be constructed according to one or more exemplary gas turbine engines described herein (e.g., Figure 1 , Figure 2 , Figure 5 It is constructed using a gas turbine engine (100) as described above.

[0150] Exemplary method 600 can generally be compared with Figure 7 The exemplary method 500 operates in a similar manner, and similar reference figures can refer to similar processes (e.g., Figure 8 (602) and Figure 7 (502) corresponds, unless otherwise stated herein).

[0151] Therefore, it will be understood that the exemplary method 600 generally includes, at (602), operating in a purge state after the start-up sequence of the fuel cell assembly begins; at (604), operating in a first heating state before the temperature of the fuel cell stack reaches a first fuel cell temperature threshold; at (606), operating in a second heating state after the temperature of the fuel cell stack reaches the first fuel cell temperature threshold and before the temperature of the fuel cell stack reaches a second fuel cell temperature threshold; and at (608), operating in a power generation state after the temperature of the fuel cell stack reaches the second fuel cell temperature threshold.

[0152] However, as mentioned, exemplary method 600 can be used with a fuel cell assembly including an air treatment unit, or specifically, with a fuel cell assembly including a pre-burner that generates fully oxidized gas (without H2 and CO). In this way, method 600 may include additional or alternative steps when operating, for example, in a first heating state and / or a second heating state. In particular, for the exemplary embodiments depicted, when operating in the first heating state at (604), method 600 generally includes operating the air treatment unit at (612) to provide oxidized exhaust gas to the anode, cathode, or both of the fuel cell. In particular, in at least some exemplary aspects, the air treatment unit may be operated at (612) to provide oxidized exhaust gas to both the anode and cathode of the fuel cell. Similarly, operating in the first heating state at (604) may further include, at (614), using the air treatment unit, continuing to heat the fuel cell, such as the cathode and anode, according to a temperature control arrangement.

[0153] In addition, still refer to Figure 8 For the exemplary aspect described, operating in a second heated state at (606) includes using both an air handling unit and a fuel handling unit to heat the fuel cell stack to a second fuel cell temperature threshold. More specifically, method 600 includes, at (618), supplying exhaust gas from the fuel handling unit to the anode of the fuel cell and exhaust gas from the air handling unit to the cathode of the fuel cell to simultaneously heat the anode and cathode. Figure 8 Similar to the exemplary method 500, providing exhaust gas from the fuel treatment unit to the anode at (618) and providing exhaust gas from the air treatment unit to the cathode may include setting the pressure within the anode to be higher than the pressure within the cathode to prevent oxygen-containing gas within the cathode from permeating through the electrolyte layer to the anode.

[0154] This article references Figure 8 Other aspects of method 600, which are not described, may be similar to those mentioned above. Figure 7 The corresponding aspect of method 500 is described.

[0155] Although not in Figure 8 The exemplary flowcharts are reflected, but it will be understood that, in at least some exemplary aspects, aspects of method 600 may be combined with aspects of method 500. For example, in some exemplary aspects, operating in a first heated state at (604) may additionally include operating the fuel processing unit to supply exhaust gas to the cathode to aid in heating the fuel cell, and / or to supply exhaust gas to the combustor of the gas turbine engine to aid in the combustion operation of the gas turbine engine.

[0156] Exemplary method 600 has similar benefits to exemplary method 500. An additional benefit of exemplary method 600 is a potentially faster start-up process. This is because simultaneously heating the cathode and anode using a pre-burner before reaching the first temperature threshold enhances heat transfer from the heated gas to the fuel cell solids.

[0157] (ii) Figure 9 and Figure 10 Example: Ground startup of fuel cell assembly prior to gas turbine engine startup.

[0158] Now for reference Figure 9 and Figure 10 The flowcharts for two additional methods and systems of the aircraft are depicted. Specifically, Figure 9 This is a flowchart of a method 700 for starting a fuel cell assembly according to a first additional exemplary embodiment of the present disclosure, and Figure 10 This is a flowchart of a method 800 for starting a fuel cell assembly according to a second additional exemplary embodiment of the present disclosure.

[0159] Figure 9 The exemplary method 700 can be used with Figure 7 The exemplary method 500 is constructed in essentially the same manner, and similar reference figures can refer to similar processes (e.g., Figure 9 (702) and Figure 7 (502) corresponds to, unless otherwise stated herein. Therefore, it will be understood that, Figure 9 The exemplary method 700 can be used with fuel cell assemblies that do not have an air treatment unit (e.g., no pre-burner).

[0160] Similarly, Figure 10 The exemplary method 800 can be used with Figure 8 The exemplary method 600 is constructed in essentially the same manner, and similar reference numerals can also refer to similar processes (e.g., Figure 10 (802) and Figure 8 (602) corresponds to, unless otherwise stated herein. Therefore, it will be understood that, Figure 10 The exemplary method 800 can be used with fuel cell assemblies that include an air handling unit (e.g., a pre-combustion unit) and a fuel handling unit.

[0161] However, with Figure 7 and Figure 8 Compared to exemplary methods 500 and 600, Figure 9 and Figure 10 Exemplary methods 700, 800 define the start of the start sequence 400 of the gas turbine engine (see [link]). Figure 6 Different temporal relationships. In particular, Figure 9 and Figure 10 The first boot sequence 400A, the second boot sequence 400B, and the third boot sequence 400C are described.

[0162] Specifically, methods 700 and 800 each include initiating the start-up sequence of the fuel cell assembly (generally 700 and 800), and further include, at (402A), (402B), and (402C), initiating the start-up sequence of the gas turbine engine after initiating the start-up sequence of the fuel cell assembly. As a result, methods 700 and 800 can vary relative to methods 500 and 600 discussed above. For example, when operating in purge mode (702) and (802), the method can receive purge airflow from an external air source (e.g., a ground-based air supply vehicle, auxiliary power unit, etc.) of the gas turbine engine. Similarly, the airflow used in the operation of the air handling unit (if included) and the fuel handling unit can also originate from an external air source of the gas turbine engine, at least until the engine start-up procedure / sequence 400A, 400B, and 400C begins.

[0163] (1) Program 1

[0164] First, referring to the first engine start sequence 400A, using this configuration, at (402A), after the start sequence of the fuel cell assembly is started, the start sequence of the gas turbine engine is started, including after the temperature of the fuel cell stack has reached the second fuel cell temperature threshold (as determined at (720), (820)). Specifically, for Figure 9 In the exemplary aspect depicted, the first engine start sequence 400A is started simultaneously or after the operation of the fuel cell assembly in power generation mode is started at (722) and (822).

[0165] It will be understood that using the first engine start sequence 400A can result in a more efficient gas turbine engine start-up. With this configuration, the fuel cell, more specifically, the fuel cell stack, will heat one or more bushings of the gas turbine engine's combustor, resulting in higher combustion efficiency. Furthermore, with this configuration, the fuel cell's output products can be used to help achieve combustion stability more quickly due to the relatively high hydrogen content within the output products. Even further, with this configuration, the electricity generated by the fuel cell assembly can be used to help start the gas turbine engine.

[0166] (2) Program 2

[0167] Referring now to the second engine start sequence 400B, with this configuration, the start sequence of the gas turbine engine can be started after the start sequence of the fuel cell assembly. This can include starting the gas turbine engine after the temperature of the fuel cell stack has reached the first fuel cell temperature threshold (as determined at (716), (816)) and before the temperature of the fuel cell stack has reached the second fuel cell temperature threshold (as determined at (720), (820)).

[0168] It will be understood that, similar to using the first engine start sequence 400A, using the second engine start sequence 400B can result in a more efficient gas turbine engine start-up, as the fuel cell stack will heat one or more bushings of the gas turbine engine's combustor, resulting in higher combustion efficiency during startup. Furthermore, the fuel cell's output products can again help achieve combustion stability more quickly due to the relatively high hydrogen content within the output products. However, it is worth noting that, compared to the first engine start sequence 400A, using the second engine start sequence 400B requires less fuel and air to start the fuel cell assembly, as heat from the gas turbine engine helps heat the fuel cell during the second heating states (706), (806), and air can be extracted from, for example, the gas turbine engine's compressor.

[0169] (3) Program 3

[0170] Furthermore, referring now to the third engine start-up sequence 400C, this configuration allows the gas turbine engine start-up sequence to begin after the start-up sequence of the fuel cell assembly has begun, but before the temperature of the fuel cell stack reaches the first fuel cell temperature threshold. In the illustrated embodiment, for the third engine start-up sequence 400C, the start-up sequence of the gas turbine engine begins before the fuel cell assembly (704), (804) is operated in a first heated state, or more specifically, before the operation of the air handling unit of the fuel cell assembly, the operation of the fuel handling unit of the fuel cell assembly, or both.

[0171] However, it is worth noting that in other exemplary embodiments of this disclosure, for the third engine start sequence 400C, the start sequence of the gas turbine engine can occur simultaneously with or after the operation of the fuel cell assembly (704), (804) in the first heated state, and more specifically, simultaneously with or after the operation of the air handling unit of the fuel cell assembly, the operation of the fuel handling unit of the fuel cell assembly, or both.

[0172] It will be understood that, similar to using the first engine start sequence 400A and the second engine start sequence 400B, using the third engine start sequence 400C can result in a more efficient gas turbine engine start-up, because the fuel cell stack will heat one or more bushings of the gas turbine engine's combustor, resulting in higher combustion efficiency during startup. Furthermore, similar to using the second engine start sequence 400B, by using the third engine start sequence 400C, less fuel and air can be required to start the fuel cell assembly, because heat from the gas turbine engine can help heat the fuel cell during the second heating state (706), (806), and air can be drawn from, for example, the gas turbine engine's compressor. Furthermore, with the third engine start sequence 400C, any combustible gas supplied from the fuel cell assembly to the gas turbine engine's combustor during the startup of the fuel cell assembly can be combusted by the flame within the combustion zone.

[0173] (iii) Figures 11 to 13 Implementation examples; recycling

[0174] As will be understood, based on the references above in this article, for example Figure 9 and Figure 10 In one or more exemplary aspects described, when the fuel cell assembly and the gas turbine engine are started, the output products of the fuel cell in the fuel cell assembly can be provided to the combustion chamber of the gas turbine engine's combustor before the gas turbine engine reaches flame-on conditions, continuous flame-on conditions, or idling conditions. The output products may include, for example, hydrogen, and it may be undesirable for hydrogen to accumulate in the combustion chamber and / or flow through the unburned gas turbine engine.

[0175] Therefore, a brief reference is now available. Figures 11 to 13 Simplified schematic diagrams of fuel cell assembly and gas turbine engine according to various exemplary embodiments of the present disclosure are provided, and more specifically, simplified schematic diagrams of gas turbine engine having an integrated fuel cell and combustor assembly that can solve the above problems. Figures 11 to 13 The exemplary gas turbine engine and the integrated fuel cell and combustor assembly can be used in conjunction with the above reference. Figure 5 The exemplary gas turbine engine 100 and the integrated fuel cell and combustor assembly 200 described are constructed in substantially the same manner. Therefore, the same or similar reference numerals may refer to the same or similar parts. For example, Figures 11 to 13 The fuel cell controller 240 of the embodiment depicted can be coupled with... Figure 5 The exemplary fuel cell controller 240 is constructed in a similar manner.

[0176] For example, utilizing each of these configurations, the integrated fuel cell and burner assembly 200 generally comprises a fuel cell assembly 204 having an air handling unit 306, a fuel handling unit 304, and a fuel cell stack 294, the fuel cell stack 294 including a fuel cell (and depicted as a single fuel cell) having a cathode 296, an anode 298, and an electrolyte layer 300 positioned between the cathode 296 and the anode 298. Figures 11 to 13 As schematically depicted herein, air treatment unit 306 may provide a first flow (not labeled for clarity) to cathode 296, and fuel treatment unit 304 may provide a second flow (not labeled for clarity) to anode 298. As will be understood from the description herein, in certain exemplary aspects of fuel cell assembly 204, air treatment unit 306 may be configured to additionally or alternatively provide a first flow to anode 298, and fuel treatment unit 304 may be configured to additionally or alternatively provide a second flow to cathode 296. The first flow may generally be an airflow heated by air treatment unit 306. The second flow may generally be a reformed fuel flow containing hydrogen.

[0177] Furthermore, for each of these configurations, the fuel cell is configured to provide output products to the combustor 206, or more specifically, to the combustion chamber 228 of the combustor 206. In particular, for the illustrated embodiment, the fuel cell assembly 204 includes a cathode path 350 and an anode path 354. The cathode path 350 provides fluid communication between the cathode 296 and the combustion chamber 228, and the anode path 354 provides fluid communication between the anode 298 and the combustion chamber 228.

[0178] As mentioned, during certain exemplary aspects of this disclosure, during the start-up of fuel cell assembly 204, the output products from the fuel cell may include hydrogen, and it may be undesirable to supply hydrogen to combustion chamber 206 before certain operating conditions of the gas turbine engine have been achieved. Similarly, it may be desirable to supply one or more streams to, for example, anode 298 during certain operating periods to avoid undesirable results. For example, it may be desirable to supply a gas stream containing a small amount of oxygen or no oxygen to anode 298 during start-up operation of fuel cell assembly 204 to, for example, prevent oxidation of anode 298.

[0179] (1) Example A, Figure 11

[0180] Therefore, special reference Figure 11In an exemplary embodiment, for the depicted exemplary fuel cell assembly 204, the fuel cell assembly 204 further defines a cathode recirculation path 352 and a first anode recirculation path 356. The cathode recirculation path 352 fluidly connects the cathode path 350 back to the air handling unit 306, and the first anode recirculation path 356 similarly fluidly connects the anode path 354 back to the air handling unit 306. In this way, the air handling unit 306 can be configured to further utilize any fuel (e.g., hydrogen) from the fuel cell's output products, causing combustion of the fuel cell's output products. This prevents the supply of fuel from the anode 298 and / or cathode 296's output products to the combustion chamber 228 before, for example, sufficient airflow has been achieved through the combustion chamber 228 and / or the gas turbine engine 100 has achieved flame-opening conditions (such as stable flame conditions). Further, the airflow further combusted by the air handling unit 306 can then be supplied to the cathode 296 for heating the cathode 296, and to the anode 298 for heating the anode 298, or both. This flow is indicated by the dashed line 358. Additionally or alternatively, the flow provided back to the air treatment unit 306 to the recirculation paths 352, 356 can be completely converted from unused fuel into carbon dioxide and steam through the air treatment unit 306. This can mitigate or eliminate the emission impact of unused fuel on downstream equipment when the SOFC is started before the burner is started.

[0181] (2) Example B Figure 12

[0182] Now for specific reference Figure 12 In an exemplary embodiment, the fuel cell assembly 204 again includes a cathode path 350 and an anode path 354. However, for Figure 12 In an exemplary aspect, the fuel cell assembly 204 further includes a second anode recirculation path 360, which fluidly connects the anode path 354 back to the fuel processing unit 304. Figure 11 Similar embodiments include a second anode recirculation path 360 that allows all or part of the output products from anode 298 to be transferred back to fuel treatment unit 304 during one or more start-up operations to prevent or minimize the amount of fuel (e.g., hydrogen) supplied to combustion chamber 228 of the gas turbine engine. The fuel within the output products recirculated back via the second anode recirculation path 360 can be used for fuel treatment, which can reduce overall fuel consumption during the sequential execution of the start-up sequence of fuel cell assembly 204, while also reducing any emission impact from unused fuel supplied to combustor 206 of gas turbine engine 100. When there is no air treatment unit (e.g., pre-combustion unit) in the system or when the air treatment unit (e.g., pre-combustion unit) fails, Figure 12This embodiment B provides a valuable alternative.

[0183] (3) Example C Figure 13

[0184] Now for special reference Figure 13 In an exemplary aspect, the exemplary fuel cell assembly 204 includes Figure 11 and Figure 12 Two exemplary aspects of fuel cell assembly 204. In particular, Figure 13 An exemplary fuel cell assembly 204 includes a cathode recirculation path 352, a first anode recirculation path 356, and a second anode recirculation path 360. (See above reference...) Figure 11 and Figure 12 The functions of these corresponding paths are described.

[0185] In this way, it will be understood that, according to one or more exemplary aspects of this disclosure (e.g., Figure 9 Method 700 Figure 10 In method 800), during the execution of the start-up sequence of fuel cell assembly 204, fuel cell assembly 204 can be configured to use one or more of these recirculation paths. In one example, the system may include a cathode exhaust gas recirculation path 352 to air handling unit 306 (e.g., a pre-combustor) and a fuel handling unit 304 (e.g., a CPO). x The anode exhaust gas recirculation path 360. In another example, the system may include a cathode exhaust gas recirculation path 352 to an air treatment unit 306 (e.g., a pre-combustor), while the anode exhaust gas is recirculated to a fuel treatment unit (e.g., CPO) via a flow path 360. x And it is recirculated to the air treatment unit (e.g., pre-combustion unit) via the first anode recirculation path 356. An active actuation control valve, together with the system controller (referred to herein as fuel cell controller 240), can be used to achieve the desired recirculation flow distribution between flow paths 356 and 360.

[0186] (4) The impact of recirculation on startup sequence

[0187] Brief reference Figure 9 and Figure 10 In some exemplary aspects, prior to completing the startup sequence of the fuel cell assembly, methods 700, 800 may include directing one or more streams of output products from the fuel cell to an air handling unit via one or more recirculation paths. For example, one or more streams may include a cathode stream, such that methods 700, 800 include directing the output products from the fuel cell to an air handling unit via a recirculation path (such as cathode recirculation path 352); Figure 11 , 13Directing the output products from the cathode to the air handling unit may include an anode flow, such that methods 700 and 800 include via a recirculation path (such as a first anode recirculation path 356). Figure 11 , 13 The output products from the anode are directed to the air handling unit, or both.

[0188] Still a brief reference Figure 9 and Figure 10 In some exemplary aspects, prior to completing the startup sequence of the fuel cell assembly, methods 700, 800 may further include directing one or more streams of output products from the fuel cell to a fuel processing unit via one or more recirculation paths. For example, the one or more streams may include cathode streams, such that methods 700, 800 include directing the output products from the fuel cell to a fuel processing unit via one or more recirculation paths (…). Figures 11 to 13 (not depicted in the text) Directing the output products from the cathode to the fuel processing unit may include an anode stream, such that methods 700, 800 include via a recirculation path (such as a second anode recirculation path 360). Figure 12 , 13 The output products from the anode are directed to the fuel processing unit, or both.

[0189] (iv) Figure 14 Implementation example; Warm standby mode

[0190] In some exemplary aspects, the fuel cell assembly can be maintained in a warm state to facilitate, for example, faster start-up of the fuel cell assembly and power generation from the fuel cell assembly. Now refer to Figure 14 A flowchart of method 900 is provided, illustrating warm-ground start-up operation of a gas turbine engine and fuel cell assembly according to one or more exemplary aspects of this disclosure. The fuel cell assembly can be configured in conjunction with one or more exemplary fuel cell assemblies described herein (e.g., Figures 2 to 5 , Figures 11 to 13 , Figures 15 to 16 The fuel cell assembly 204, etc., is constructed in a similar manner, and the gas turbine engine can be constructed according to one or more exemplary gas turbine engines described herein (e.g., Figure 1 , Figure 2 , Figure 5 It is constructed using a gas turbine engine (100, etc.).

[0191] The exemplary method 900 may be similar to one or more other methods described herein for starting a fuel cell assembly.

[0192] However, compared to the previously described method, Figure 14An exemplary method 900 includes, at (912), maintaining the fuel cell stack of the fuel cell assembly in a warm standby state (or warm standby mode). Maintaining the fuel cell stack of the fuel cell assembly in a warm standby state at (912) can include, for example, during aircraft steering, aircraft refueling, engine shutdown (e.g., where the gas turbine engine is in a shutdown mode), maintaining the fuel cell stack in a warm standby state. During the warm standby state, there may be no power output drawn from the fuel cell stack, or alternatively, there may be a relatively small amount of power output drawn from the fuel cell stack (e.g., less than about 10% of the maximum power output, such as less than about 5% of the maximum power output) for thermal self-sustainability. It will be understood that when the gas turbine engine is not in flame-on operating conditions, the gas turbine engine may not be able to efficiently process the hydrogen in the fuel cell output products from the fuel cell stack, therefore not operating the fuel cell assembly to draw power can prevent hydrogen from flowing into, for example, the combustion section of the gas turbine engine.

[0193] As used herein, the term "warm standby state" can refer to a condition in which the fuel cell assembly, or more precisely the fuel cell stack, is at a temperature equal to at least about 40% of the maximum operating temperature (i.e., the maximum design temperature for expected operation). This includes conditions such as at least about 60% of the maximum operating temperature, at least about 70% of the maximum operating temperature, and up to about 90% of the maximum operating temperature. In this way, when maintained in the warm standby state, the fuel cell assembly can transition to power generation mode in about five minutes or less. If no power is extracted, the fuel cell stack can be maintained in the warm standby mode using, for example, a heated air source external to the gas turbine engine, a resistance heater, a gas turbine engine hot bus, etc.

[0194] Although optional, for an exemplary aspect of the depicted method 900, the method further includes, at (914), switching the fuel cell assembly to a ground idling power output mode (also referred to as a "ground idling power generation mode") to provide power to, for example, an aircraft. Operating in ground power output mode at (914) includes, at (915), operating the fuel cell assembly to achieve the highest level of fuel utilization and fuel efficiency. For example, the fuel cell assembly can operate within 10% of the maximum fuel utilization for a given power output level. This can minimize the amount of hydrogen supplied to the combustion chamber of the gas turbine engine and can further reduce fuel use and load on, for example, the air handling unit, fuel handling unit, or both.

[0195] Additionally, for aspects of the depicted method 900, operation in ground-based power output mode at (914) includes, at (916), operating the fuel cell assembly to recycle the fuel cell output products of the fuel cell stack, thereby minimizing the amount of hydrogen supplied to the combustion chamber of the gas turbine engine. In this way, unused fuel in the fuel cell output products of the fuel cell stack produced at (914) (and, for example, (912)) can be recycled to, for example, a fuel processing unit, eliminating the need for an additional afterburner to burn unused fuel from the anode of the fuel cell. Output products from the cathode of the fuel cell can similarly be recycled to an air processing unit, potentially reducing the air flow required for the fuel cell assembly. This can reduce the auxiliary power usage of a separate air supply unit, potentially reducing the size and weight of such an air supply unit.

[0196] Method 900 further includes, at (918), receiving an engine start command to start the gas turbine engine. Receiving the engine start command at (918) can trigger an engine start process (as described above in the reference). Figure 6 The execution of method 400 (or any other suitable engine start-up procedure) described herein. It is worth noting that by operating the fuel cell assembly in a warm standby mode at (912) and using method 900 described herein, the start-up of the gas turbine engine can be aided by maintaining the temperature of one or more bushings of the combustor of, for example, a gas turbine engine at an elevated temperature, which can lead to faster sustainable combustion therein.

[0197] For the exemplary aspect described, once the engine start-up sequence (e.g., method 400) is completed, method 900 includes, at (920), switching to the normal power generation mode of the fuel cell assembly. Switching to the normal power generation mode of the fuel cell assembly may be in response to the completion of the engine start-up sequence, or alternatively, may be in response to determining that the temperature of the fuel cell stack has reached a second fuel cell assembly reference temperature (not shown).

[0198] (v) Figures 15 to 16 Examples; Redox Stabilized Anode System

[0199] As discussed above, a solid oxide fuel cell assembly can generally include a fuel cell stack 294 having a solid oxide fuel cell (or more precisely, for example, multiple solid oxide fuel cells 294 arranged in series). The solid oxide fuel cell generally includes a cathode 296 and an electrolyte layer 300, and an anode 298 positioned on the electrolyte layer 300 opposite the cathode 296. With certain configurations, the anode 298 comprises a cermet with a relatively high nickel concentration. For example, the cermet can be a nickel / yttrium oxide-stabilized zirconium oxide (Ni / YSZ) cermet. While this configuration provides certain benefits to the solid oxide fuel cell in terms of, for example, electrical conductivity, certain operational limitations exist when the solid oxide fuel cell is used in, for example, aviation operations. To address one or more of these operational limitations, the inventors of this disclosure propose an aviation assembly having a more stable solid oxide fuel cell that can address one or more operational limitations.

[0200] For example, now refer to Figure 15 The present disclosure depicts a gas turbine engine and a fuel cell assembly according to another exemplary embodiment of the present disclosure. Figure 15 The exemplary gas turbine engine and fuel cell assembly depicted in the above reference can be used in conjunction with the above reference. Figure 5 The exemplary gas turbine engine and fuel cell assembly described are constructed in essentially the same way. The same numbers can refer to the same parts.

[0201] For example, a fuel cell assembly generally includes an air delivery assembly, an air handling unit 306, and a fuel cell stack 294 with the fuel cell. In the illustrated embodiment, the fuel cell is a solid oxide fuel cell. The air delivery assembly is configured to receive airflow from the compressor section and / or additional airflow supply unit 290 of a gas turbine engine. The air delivery assembly is further configured to provide this airflow directly to the cathode 296, or optionally to the air handling unit 306, which can then supply, for example, heated air to the cathode 296.

[0202] However, the anode 298 of the fuel cell is configured as an operationally stable anode 298, as will be referred to below for example. Figure 16Described in more detail. Specifically, the anode 298 may be capable of internal fuel reforming operations and may be further configured to accommodate oxygen-containing gas across a wider temperature range. Therefore, it will be understood that, for the illustrated embodiment, the fuel cell assembly does not include a separate fuel processing unit configured to convert hydrocarbon-based fuel into hydrogen fuel. Specifically, the fuel supply unit of the aircraft including the depicted system may be a hydrocarbon fuel supply unit, and the fuel cell assembly may be configured to supply hydrocarbon fuel from the hydrocarbon fuel supply unit to the anode 298. The hydrocarbon fuel supply unit may be a fuel supply unit without a fuel reformer (supplying hydrocarbon fuel that has not yet passed through, for example, an onboard fuel reformer). More specifically, for the illustrated embodiment, the fuel cell assembly includes a fuel line in fluid communication with a first fuel delivery line 150A of the fuel supply unit for receiving hydrocarbon fuel and supplying hydrocarbon fuel to the anode 298 of the fuel cell.

[0203] Furthermore, it will be understood that the air delivery assembly is further configured to provide an oxygen-containing gas flow to the anode 298. Specifically, for Figure 15 In one embodiment, the cathode gas flow channel of the fuel cell assembly is instead configured as a cathode and anode gas flow channel 314', which is configured to further supply an oxygen-containing gas flow to the anode 298 via an anode supply channel 319. In the illustrated embodiment, a heat exchanger 317 is thermally coupled to an air handling unit 306 to increase the temperature of the gas flow through the anode supply channel 319. In this way, it will be understood that the fuel cell assembly is configured to supply both a hydrocarbon fuel flow and an oxygen-containing gas flow to the anode 298 to facilitate, for example, internal fuel reforming operations within the anode 298 during operation of the fuel cell assembly.

[0204] As will be further understood from the description herein, internal fuel reforming operations can generate relatively high levels of heat within the fuel cell. In this way, the fuel cell assembly can be configured to control the flow of oxygen-containing gas to anode 298, the flow of hydrocarbon fuel to anode 298, or both. This control can be responsive to one or more heat demands on or for the fuel cell assembly (e.g., the temperature of the fuel cell stack 294), one or more heat demands on or for the gas turbine engine (e.g., the heat demand within the combustor of the combustion section of the gas turbine engine, the combustion dynamics within the combustor of the combustion section of the gas turbine engine), etc.

[0205] therefore, Figure 15 The exemplary gas turbine engine and fuel cell assembly depicted include one or more features for controlling oxygen-containing gas to the anode 298 of the fuel cell and hydrocarbon fuel to the anode 298 of the fuel cell, as well as further features for sensing data to facilitate certain control decisions by the controller 240, as described in more detail below.

[0206] Specifically, in the illustrated embodiment, the fuel cell assembly includes an anode flow valve 312 in flow communication with the anode flow channel 318 for controlling the flow of gas through the anode flow channel 318. The anode flow valve 312 is depicted as being wirelessly operable to communicate with the controller 240. Similarly, the fuel cell assembly includes a hydrocarbon fuel flow valve 151A in fluid communication with the fuel line 150A of the fuel cell assembly for controlling the fuel flow through the fuel line 150A to the anode 298. The hydrocarbon fuel flow valve 151A is depicted as being wirelessly operable to communicate with the controller 240.

[0207] Furthermore, the fuel cell assembly, gas turbine engine, or both include one or more sensors configured to sense data indicating one or more operating conditions of the gas turbine engine or both. For example, the fuel cell assembly includes a fuel cell sensor 302 configured to sense data indicating operating parameters of the fuel cell assembly, such as the temperature of the fuel cell stack 294 (e.g., the cathode side 296 or anode side 298 of the fuel cell), the pressure within the fuel cell stack 294 (e.g., within the cathode side 296 or anode side 298 of the fuel cell), and / or the composition (e.g., chemical composition) of the output products from the fuel cell assembly 204. Also by way of example, the depicted exemplary gas turbine engine includes a sensor 330. Sensor 330 may be, for example, a temperature sensor configured to sense data indicating the outlet temperature of the combustion section 114, the inlet temperature of the turbine section, the exhaust temperature, or a combination thereof. Additionally or alternatively, sensor 330 may be any other suitable sensor or any suitable combination of sensors configured to sense one or more operating conditions or parameters of the gas turbine engine. Sensors 302 and 330 are depicted as being operatively communicating wirelessly with a controller.

[0208] What will be understood is that, despite Figure 15 The exemplary fuel cell assembly does not include a separate fuel processing unit (see, for example...). Figure 5 The fuel processing unit 304 may be used, but in other exemplary embodiments, an exemplary fuel cell assembly having both an operationally stable anode 298 and a fuel processing unit may be provided.

[0209] See now Figure 16 It describes one or more fuel cell components (such as...) that can be incorporated into this disclosure. Figure 15 A fuel cell stack 294 having an operationally stable solid oxide fuel cell in an exemplary fuel cell assembly (fuel cell stack 294 in Figure 16 A close-up schematic diagram (illustrated as having a single solid oxide fuel cell).

[0210] Figure 16 A stable fuel cell assembly generally includes a cathode 296 and an electrolyte layer 300, as well as an anode 298 located in the electron layer opposite to the cathode 296.

[0211] Cathode 296 defines inlet 362, which is configured to receive a first airflow 364 from the air delivery assembly of the fuel cell assembly. Anode 298 defines a second inlet 366 for receiving a second airflow 368 from the air delivery assembly and a third inlet 370 for receiving hydrocarbon fuel 372. In this way, the fuel cell can be incorporated into a fuel cell assembly without a fuel processing unit.

[0212] However, as depicted by the dashed lines, the anode 298 of the fuel cell can further define a fourth inlet 374, which is configured to receive reformed fuel 376 from the fuel processing unit 304. In this way, the fuel cell can be further incorporated into a fuel cell assembly having a fuel processing unit.

[0213] As will be understood, the anode 298 generally comprises a composite material comprising an operationally stable ceramic phase and a metallic phase (i.e., cermet). The metallic phase may be finely dispersed within a ceramic matrix of the ceramic phase. As used herein, the term "operationally stable" means that the presence of an oxidizing gas (e.g., oxygen) at the anode 298 at a normal operating temperature of a fuel cell assembly, such as 600°C to 1000°C, does not cause significant oxidation of the metallic phase of the cermet in the anode 298. For example, the oxygen content of the oxidizing gas at the anode 298 may be greater than about 0.1% by mass, such as greater than about 2% by mass, such as greater than about 5% by mass (and, for example, up to 100% oxygen). In embodiments, the anode 298 of an operationally stable fuel cell may be substantially nickel-free. In another embodiment, the nickel content of the anode 298 of the operationally stable fuel cell may be less than or equal to about 25% by volume (nickel volume divided by total volume, or vol / vol), such as less than or equal to about 10% vol / vol, such as less than or equal to about 5% vol / vol, such as less than or equal to about 1% vol / vol, or such as less than or equal to about 0.5% vol / vol.

[0214] The ceramic phase of anode 298 may include any suitable ion-conducting ceramic material, such as doped cerium dioxide and / or doped zirconium oxide. For example, the ceramic phase may include, but is not limited to, yttrium oxide-stabilized zirconium oxide (YSZ), gadolinium oxide-doped cerium dioxide (GDC), samarium oxide-doped cerium dioxide (SDC), ytterbium oxide-doped cerium dioxide (YDC), scandium oxide-stabilized zirconium oxide (SSZ), ytterbium oxide-cerium dioxide-scandium oxide-stabilized zirconium oxide (YCSSZ), etc.

[0215] The metallic phase of anode 298 can contain a perovskite-based catalyst and a p- or n-type semiconductor. The perovskite-based catalyst has a crustal structure similar to that of perovskite minerals composed of perovskite oxides (CaTiO3). The general chemical formula of the perovskite-based catalyst is ABX3. A and B are two distinct cations. X is an anion, typically an oxide. The anion bonds the two cations. The perovskite-based catalyst can also have a bis-perovskite structure (i.e., A2B2O6).

[0216] Examples of suitable perovskite-based catalysts include titanate-based materials such as lanthanum-strontium titanate (LaSrTiO3), strontium titanate (SrTiO3), niobium titanate (niobium-doped SrTiO3), calcium titanate (CaTiO3), lead titanate (PbTiO3), etc. Other examples of suitable perovskite-based catalysts include lanthanum-strontium-iron-molybdenum oxide (LaSrFeMoO6), bismuth ferrite (BiFeO3), lanthanum-ytterbium oxide (LaYbO3), silicate perovskite (MsSiO3), lanthanum manganeseite (LaMnO3), yttrium aluminum perovskite (YAlO3), etc. Examples of suitable p-type or n-type semiconductors include boron-doped silicon, aluminum-doped silicon, boron-doped germanium, arsenic-doped silicon, phosphorus-doped silicon, arsenic-doped germanium, phosphorus-doped germanium, etc. Alternatively or additionally, the metallic phase of anode 298 may contain any suitable metal catalyst that operates as an electronic conductor, such as nickel (Ni), cobalt (Co), copper (Cu), and their alloys.

[0217] In embodiments, the operationally stable fuel cell may also have internal fuel reforming capability, i.e., the fuel cell may be capable of catalytic partial oxidation (CPOx) fuel reforming. Therefore, in embodiments, separate fuel processing units (see, for example...) Figure 5 The fuel processing unit 304 may be optional. However, even in embodiments with internal fuel reforming capabilities, operationally stable fuel cell assemblies can be efficiently operated using reformers (e.g., using separate fuel processing units).

[0218] In this embodiment, the internal fuel reforming capability is provided by the cermet material of the anode 298. In this embodiment, the internal fuel reforming capability can be enhanced and / or provided by introducing noble metals (e.g., platinum, ruthenium, palladium, etc.) or other ceramic materials (such as doped cerium oxide, including gadolinium-doped cerium dioxide (GDC), samarium-doped cerium dioxide (SDC), etc.) onto the surface of the anode or on any surface of the fuel upstream of the contact anode 298 within the fuel cell assembly.

[0219] The operational stability of the solid oxide fuel cell 294 provides advantages over existing solid oxide fuel cells 294. The anode 298 is less susceptible to oxidation due to conditions where oxidizing gases are present at the operating temperature or otherwise elevated temperatures (e.g., above 230°F). Examples of such conditions include abnormal shutdowns or oxidizing gases escaping from the combustion chamber before the fuel cell cools. Therefore, the anode 298 exhibits increased volumetric stability during redox and / or thermal cycling, and is thus less susceptible to structural damage associated with volume changes in the anode 298. Furthermore, in embodiments of the fuel cell 294 that are operationally stable with an anode 298 that is substantially devoid of nickel content or has an anode 298 with a nickel content less than or equal to about 25% vol / vol (e.g., less than or equal to about 10% vol / vol, such as less than or equal to about 5% vol / vol, such as less than or equal to about 1% vol / vol, or such as less than or equal to about 0.5% vol / vol), this can eliminate or reduce the threat of toxic nickel carbonyl gas generated due to the oxidation of nickel in the anode 298.

[0220] The operational stability of the fuel cell assembly discussed in this article offers advantages that can result in savings in aircraft manufacturing and operation. The operational stability of the fuel cell assembly allows for reduced shutdown and start-up times, greater flexibility in shutdown and start-up procedures, and a reduced need for external controls to ensure safety and reliability. Furthermore, internal fuel reforming capabilities provide flexibility and redundancy in the operation of the fuel cell assembly, and when excluding separate fuel handling units (see, for example...), Figure 5 When the fuel processing unit (304) is used, weight and system complexity can be reduced. Furthermore, the internal fuel reforming process generates relatively high heat, which can help heat the fuel cell stack during the start-up sequence of the fuel cell assembly.

[0221] Further explanation and benefits will be understood from the following examples:

[0222] Example 1, Redox Stress Test: Comparison of Ni / YSZ Stabilized Zirconia (Ni / YSZ) Ceramic Anode Fuel Cell Stacks

[0223] Two 100cm cells with nickel / yttrium-stabilized zirconium oxide anodes 2 The fuel cell stack underwent a redox stress test as described below. The fuel cell stack was placed at operating temperature (approximately 800°C), and fuel and air flow were initiated. The open-circuit operating voltage was measured to obtain a baseline (cycle 0). The fuel cell stack was then shut down under normal conditions and cooled (i.e., cooled using a protective hydrogen flow).

[0224] The fuel cell stack is brought to operating temperature, and fuel and air flow are initiated a second time. The open-circuit operating voltage is measured and compared to a baseline to determine if damage occurred during the previous shutdown (cycle 1). The fuel cell stack is then shut down under normal conditions, and a second cooling operation is performed (i.e., cooling using a protective hydrogen flow).

[0225] The fuel cell stack is brought to operating temperature, and fuel and air flow are initiated for the third time. The open-circuit operating voltage is measured and compared to a baseline to determine if damage has occurred during the previous shutdown (cycle 2). Under redox stress conditions (e.g., conditions that allow anodic oxidation), the fuel cell stack is shut down. Specifically, fuel and air flow are stopped at operating temperature. For safety, the anode gas lines are purged with nitrogen for five minutes. The fuel cell stack is allowed to cool while air is allowed to diffuse into the fuel lines. Cooling is carried out at approximately 1.5°C / min over a total of 12 hours (some stacks are only cooled to 90-100°C).

[0226] The fuel cell stack is brought to operating temperature, and fuel and air flow are initiated for the last time. The open-circuit operating voltage is measured and compared to a baseline to determine if damage occurred during the previous shutdown (cycle 3).

[0227] Figure 17 The results are shown in the figure, where the x-axis represents the cycle number and the y-axis represents the open-circuit voltage (“OCV”) of the cycle relative to the baseline OCV. A point on the y-axis represents the baseline OCV (cycle 0). The first two vertical lines (i.e., the vertical lines immediately to the right of the y-axis) represent thermal cooling using a protective hydrogen flow. The third vertical line represents thermal cooling under redox stress conditions. When cooled using a protective hydrogen flow, the subsequent OCV is 100% of the baseline (cycles 1 and 2). However, cooling under redox stress conditions causes irreversible damage to the fuel cell stack, as shown by the OCV of cycle 3, which is approximately 75% of the baseline OCV. Furthermore, no hydrogen was detected at the OCV at the stack outlet after the redox stress cooling cycle, indicating that the volume changes associated with nickel oxidation caused irreversible structural damage to the electrolyte layer and led to the combustion of almost all the hydrogen in the stack.

[0228] Example 2: Operationally stable lanthanum strontium titanate / gadolinium oxide-doped cerium dioxide (LST / GDC) cerium-ceramic anode fuel cell stack

[0229] Two two-cell fuel cell stacks, fabricated using standard or modified surfaces and doped with lanthanum strontium titanate / gadolinium oxide anodes, were subjected to redox stress testing as described below under hydrogen plasma conditions. The fuel cell stacks were placed at operating temperature (approximately 800°C) and fuel and air flow were initiated. The open-circuit operating voltage was measured to obtain a baseline (cycle 1). The fuel cell stacks were then shut down under normal conditions and cooled (i.e., cooled using a protective hydrogen flow).

[0230] The fuel cell stack is brought to operating temperature, and fuel and air flow are initiated for the second time. The open-circuit operating voltage and stack outlet hydrogen percentage are measured and compared to a baseline to determine if damage has occurred during the previous shutdown (cycle 2).

[0231] When used under redox stress conditions (e.g., conditions that allow for anodic oxidation), the fuel cell stack is repeatedly shut down. Specifically, fuel and air flows are stopped at the operating temperature. For safety, the anode gas lines are purged with nitrogen for five minutes. The fuel cell stack is allowed to cool while air is allowed to diffuse into the fuel lines. Cooling is performed at approximately 1.5°C / min over a total of 12 hours (some stacks are cooled only to 90-100°C). After each shutdown, the open-circuit operating voltage is measured and compared to a baseline to determine if any damage has occurred during the previous shutdown (cycles 3-5). In cycles 3 and 4, the stack outlet hydrogen percentage is measured and compared to a baseline to determine if any damage has occurred during the previous shutdown.

[0232] Figure 18 and 19 The results are displayed, where the x-axis represents the number of cycles and the y-axis represents the open-circuit voltage of the cycle relative to the baseline OCV. Figure 18 ) or the amount of hydrogen at the outlet ( Figure 19 The first vertical line to the right of the y-axis represents thermal cooling using a protective hydrogen flow. Subsequent vertical lines represent thermal cooling under redox stress conditions. Special Reference Figure 18 When cooled using a protective hydrogen stream, the subsequent OCV is 100% of the baseline (cycle 1). Under redox stress cooling, the subsequent OCV is approximately 100% of the baseline. Furthermore, specific references are made. Figure 19 The reactor outlet showed that the percentage of hydrogen at the OCV after the redox stress cooling cycle did not decrease compared to the percentage of hydrogen at the OCV after thermal cooling using a protective hydrogen flow.

[0233] In this way, it will be understood that these examples demonstrate the benefit of an operationally stable fuel cell (e.g., an operationally stable fuel cell stack) that can withstand redox stress conditions without experiencing failure or a significant decrease in the OCV of the hydrogen content at the fuel cell outlet. As discussed herein, further benefits can be realized based on this operational stability when fuel cells (as well as fuel cell stacks and fuel cell assemblies) are incorporated into aircraft engines.

[0234] (vi) Figure 20 Example; Start-up of a redox stabilized anode system

[0235] As will be understood from the description herein, fuel cells including those with operationally stable anodes can further facilitate changes to certain operations of fuel cell assemblies having such fuel cells.

[0236] For example, now refer to Figure 20 A flowchart of a method 1100 for starting a gas turbine engine and a fuel cell assembly according to another exemplary embodiment of the present disclosure is provided. Exemplary method 1100 can be used with one or more exemplary gas turbine engines of the present disclosure (e.g., Figure 1 , Figure 2 , Figure 5 Gas turbine engine 100, etc., and one or more exemplary fuel cell assemblies of the present disclosure having a fuel cell with an operationally stable anode (e.g., gas turbine engine 100, etc.). Figures 15 to 18 (Fuel cell assembly 204). Alternatively, method 1100 can be used for any other suitable gas turbine engine and fuel cell assembly.

[0237] Exemplary method 1100 includes performing a startup sequence of a fuel cell assembly. Specifically, performing a startup sequence of a fuel cell assembly includes, at (1102), purging the anode and cathode of the fuel cell within an air source.

[0238] Further, method 1100 includes heating the fuel cell assembly at (1104), and more particularly, heating the fuel cell stack comprising the fuel cell assembly. Heating the fuel cell assembly at (1104) can generally include heating the fuel cell assembly from a cold start temperature to a second fuel cell reference temperature at (1105). The cold start temperature may be less than 100°C, such as less than about 80°C, and at least approximately equal to the ambient temperature.

[0239] Furthermore, for Figure 20An exemplary aspect of the method 1100 described herein includes, at (1104), heating the fuel cell assembly, further comprising, at (1106), using an air treatment unit to heat the fuel cell assembly. Heating the fuel cell assembly using the air treatment unit at (1106) includes, at (1108) activating the pre-combustion unit of the air treatment unit, and at (1110) supplying exhaust gas from the pre-combustion unit to the anode and cathode of the fuel cell to simultaneously heat both the anode and cathode. In this manner, heating the fuel cell assembly using the air treatment unit at (1106) generally includes, by arranging the air treatment unit at a heating rate, heating the fuel cell assembly to a desired temperature, such as a second fuel cell reference temperature.

[0240] However, for the exemplary aspect described, heating the fuel cell assembly at (1104) further includes heating the fuel cell at (1112) using a fuel processing unit. Specifically, for Figure 20 An exemplary aspect of the method 1100 described herein includes heating the fuel cell using a fuel treatment unit at (1112) and further including starting operation of the fuel treatment unit at (1114) and supplying exhaust gas from the fuel treatment unit to the anode of the fuel cell at (1116).

[0241] Generally speaking, it will be understood that including an operationally stable anode in a fuel cell can provide greater flexibility in ground-start operations by heating the fuel cell stack.

[0242] Specifically, still refer to Figure 20 It will be understood that the startup sequence of the fuel cell assembly, and more specifically, heating the fuel cell assembly at (1104) generally includes, at (1118) providing a flow containing oxygen to the anode of the fuel cell when the temperature of the fuel cell stack is less than or equal to a first fuel cell temperature threshold. The oxygen content can be greater than about 0.1% by mass, such as greater than about 2% by mass, such as greater than about 5% by mass. The first fuel cell temperature threshold can be between about 230°C and about 400°C. The oxygen-containing gas (i.e., the flow containing oxygen) provided to the anode of the fuel cell at (1114) can be a heated gas flow from an air handling unit, or any other suitable heated gas flow source. With this configuration, an operationally stable fuel cell can include an anode that is substantially nickel-free.

[0243] Furthermore, for Figure 20An exemplary aspect of method 1100 described herein is performing a startup sequence of a fuel cell assembly, and more specifically, heating the fuel cell assembly at (1104) further includes, at (1120) providing a flow having an oxygen content to the anode of the fuel cell when the temperature of the fuel cell stack is less than or equal to a second fuel cell temperature threshold (e.g., before the temperature of the fuel cell stack is greater than or equal to the second fuel cell temperature threshold during the startup sequence). For example, providing a flow to the anode of the fuel cell at (1120) may include providing a flow having an oxygen content to the anode of the fuel cell when the temperature of the fuel cell stack is between a first fuel cell temperature threshold and a second fuel cell temperature threshold. The oxygen content may be greater than about 0.1% by mass, such as greater than about 2% by mass, such as greater than about 5% by mass. The second fuel cell temperature threshold may be greater than the first fuel cell temperature threshold, for example, between about 400°C and about 750°C. Using this configuration, an operationally stable fuel cell may include an anode having a nickel content of less than or equal to about 25%, such as less than or equal to about 10%.

[0244] Furthermore, fuel cells, including those with operationally stable anodes and precious metal or ceramic materials for catalytic partial oxidation of, for example, aviation fuels, can allow for internal fuel reforming at the anode of the fuel cell assembly. This internal fuel reforming can generate relatively high levels of heat, which can help heat the fuel cell stack during the start-up sequence of the fuel cell assembly.

[0245] In particular, for Figure 20 An exemplary aspect of method 1100 described herein is the execution of a startup sequence for the fuel cell assembly, and more specifically, heating the fuel cell assembly (1104) further includes performing a fuel reforming operation at the anode of the fuel cell in the fuel cell assembly at (1122). For the described exemplary aspect, performing the fuel reforming operation at the anode of the fuel cell at (1122) includes supplying a hydrocarbon fuel stream to the anode of the fuel cell at (1124) and supplying an oxygen-containing gas stream to the anode of the fuel cell at (1126). In this way, method 1100 can heat the fuel cell stack more quickly, resulting in a faster startup time for the fuel cell assembly. It is noteworthy that the fuel reforming operation at the anode of the fuel cell at (1122) may include providing a limited or controlled amount of oxygen to prevent complete combustion with the supplied hydrocarbon fuel. As will be understood, since the anode is an operationally stable anode, the oxygen content of the fuel will not cause oxidation of the anode.

[0246] Still referencing Figure 20The exemplary method 1100 described herein further includes, at (1128), determining that the fuel cell stack temperature is greater than or equal to a second fuel cell temperature threshold, and at (1130), switching to the power generation mode of the fuel cell assembly.

[0247] Furthermore, as will be understood, Figure 20 The exemplary start-up sequence depicted can be combined with the gas turbine engine start-up sequence (such as according to the reference above). Figure 6 The exemplary gas turbine engine start-up sequence of method 400 is described. According to the exemplary gas turbine engine start-up sequence of method 400, the fuel cell assembly can be started before the start-up sequence of the fuel cell assembly is executed (e.g., before (1102)), or alternatively, it can be started at any other suitable time during the heating of the fuel cell stack at (1104). Alternatively, the gas turbine engine start-up sequence may not be started until the fuel cell stack temperature is determined to be greater than or equal to a second fuel cell temperature threshold at (1128) and the fuel cell assembly is switched to power generation mode (1130).

[0248] (vii) Figure 21 Examples; Thermal management of fuel cell modules with redox-stabilized anodes.

[0249] Now for reference Figure 21 It will be further understood that, in certain exemplary aspects of this disclosure, including a fuel cell with an operationally stable anode in the fuel cell stack of a fuel cell assembly may allow thermal management of the fuel cell, thermal management of a gas turbine engine including the fuel cell assembly, or both.

[0250] In particular, Figure 21 A flowchart of a method 1200 for operating a fuel cell assembly according to an exemplary aspect of this disclosure is provided. The exemplary method 1200 can be used with one or more exemplary fuel cell assemblies described herein (e.g., referenced above). Figures 15 to 19 One or more fuel cell components 204 described herein, and one or more exemplary gas turbine engines described herein (e.g., referenced above). Figure 1 and Figure 5 The gas turbine engine 100 described herein (or both). In this way, it will be understood that method 1200 can be used in a fuel cell assembly having a fuel cell stack with a solid oxide fuel cell. The solid oxide fuel cell may include an anode, a cathode, and an electrolyte layer positioned therebetween. The anode and cathode may be configured to provide output products through the fuel cell outlet during operation of the fuel cell assembly.

[0251] Method 1200 includes determining a temperature setpoint at (1202) for the fuel cell stack, the output products of the fuel cell stack, or both, and at (1204) controlling the volume of oxidant supplied to the anode in response to the temperature setpoint determined at (1202) to control the temperature of the fuel cell stack, the temperature of the output products of the fuel cell stack, or both.

[0252] In particular, for Figure 21 An exemplary aspect of the method 1200 depicted includes performing a fuel reforming operation at the anode at (1206). Performing the fuel reforming operation at the anode includes receiving hydrocarbon-based fuel at the anode at (1208) and receiving oxygen-containing gas at the anode at (1210). Using this configuration, controlling the oxidant volume supplied to the anode of the fuel cell at (1204) may include controlling the oxidant volume supplied to the anode of the fuel cell simultaneously with performing the fuel reforming operation at (1206) at (1211).

[0253] As described in detail above, fuel reforming at the anode can generate relatively large amounts of heat, which can allow the fuel cell stack to reach (or reach more quickly) the temperature setpoint, allow the fuel cell output products to reach the setpoint, or both.

[0254] In addition, as mentioned above, the oxygen-containing gas can be ambient airflow, or alternatively, the oxygen-containing gas can be airflow from the compressor section of a gas turbine engine.

[0255] Still referencing Figure 21 An exemplary aspect of method 1200 described herein further includes performing a start-up operation of the fuel cell assembly at (1212). The start-up operation of the fuel cell assembly can be one or more of the exemplary start-up operations described above. Utilizing this exemplary aspect, determining a temperature setpoint at (1202) more specifically includes determining the temperature setpoint at (1214) while performing the start-up operation of the fuel cell assembly, and controlling the volume of oxidant supplied to the anode at (1204) further includes controlling the volume of oxidant supplied to the anode at (1216) while performing the start-up operation of the fuel cell assembly at (1212). More specifically, controlling the volume of oxidant supplied to the anode at (1216) can include controlling the volume of oxidant supplied to the anode in response to the temperature setpoint determined at (1214). The start-up operation can be one or more of the exemplary start-up operations described herein.

[0256] Furthermore, utilizing this exemplary aspect, controlling the volume of oxidant supplied to the anode at (1204) further includes, at (1218), supplying oxygen-containing gas to the anode before the temperature of the fuel cell stack exceeds a first fuel cell temperature threshold. This is likely at least in part due to the inclusion of an operationally stable anode.

[0257] In this way, method 1200 can be used to achieve the desired operating temperature of the fuel cell assembly, or to achieve the desired operating temperature of the fuel cell assembly more quickly.

[0258] Furthermore, for Figure 21 An exemplary aspect of method 1200 described herein includes operating the fuel cell assembly in a power generation mode at (1220). Operating the fuel cell assembly in a power generation mode generally includes supplying power from the fuel cell stack to a power bus, one or more accessory systems, or both. Using this configuration, determining a temperature setpoint at (1202) may include determining a temperature setpoint at (1221) in response to gas turbine engine operating conditions. Gas turbine engine operating conditions may generally be gas turbine engine operating conditions indicating emission parameters, combustion kinetic parameters, power output parameters, or combinations thereof. As will be understood from the description herein, adding heat to the combustion chamber of the gas turbine engine's combustor generally affects the gas turbine engine's emissions (e.g., NOx and CO emissions), combustion kinetics within the gas turbine engine's combustor, the amount of power that can be extracted through the turbine section of the gas turbine engine, etc. In this way, it will be understood that the temperature setpoint determined by (1202) and (1221) can be determined, for example, to reduce gas turbine engine emissions, reduce combustion dynamics in the combustor of the gas turbine engine, increase the amount of power that can be extracted to the turbine section of the gas turbine engine, etc.

[0259] Still referencing Figure 21 It will be further understood that controlling the volume of oxidant supplied to the anode at (1204) can more specifically include, at (1222), while operating the fuel cell assembly in power generation mode at (1220), and more specifically, controlling the volume of oxidant supplied to the anode in response to temperature setpoints determined at (1220) and (1221).

[0260] (viii) Figure 22 Examples; Cooling procedure for redox stabilized anode systems

[0261] Now for reference Figure 22 It will be further understood that, in certain exemplary aspects of this disclosure, including a fuel cell with an operationally stable anode in the fuel cell stack of a fuel cell assembly can allow for improvements in the cooling and shutdown procedures of the fuel cell assembly.

[0262] In particular, Figure 22 A propulsion system for operating an aircraft is provided, and in particular, a method 1300 for coordinating the cooling or shutdown of a fuel cell assembly in conjunction with the shutdown of a gas turbine engine incorporating the fuel cell assembly. The fuel cell assembly and the gas turbine engine can be constructed in a manner similar to one or more exemplary fuel cell assemblies and gas turbine engines described herein. For example, the fuel cell assembly may generally comprise a fuel cell stack of a solid oxide fuel cell with a defined outlet positioned to remove output products from the solid oxide fuel cell during operation.

[0263] Method 1300 includes, at (1302), operating the fuel cell assembly to provide output products to the combustor (e.g., the combustion chamber of the combustor) in the combustion section of the gas turbine engine. Operating the fuel cell assembly at (1302) to provide output products may include, at (1303), operating the fuel cell assembly, the gas turbine engine, or both, in steady-state flight operation (e.g., cruise operating conditions and / or power generation mode).

[0264] Method 1300 further includes, at (1315), operating the fuel cell assembly, the gas turbine engine, or both, such that while operating the gas turbine engine, the pressure within the anode of the solid oxide fuel cell is less than the pressure within the cathode of the solid oxide fuel cell, less than the pressure within the combustion chamber of the gas turbine engine, or both.

[0265] For example, as will be understood from the description herein, operating the fuel cell assembly, gas turbine engine, or both at (1315) may generally include operating the fuel cell assembly at (1316) such that, while operating the gas turbine engine, the pressure within the anode of the solid oxide fuel cell is less than the pressure within the cathode of the solid oxide fuel cell. This may, for example, occur while the fuel cell assembly is shut down. Utilizing this exemplary aspect, operating the fuel cell assembly at (1316) such that, while operating the gas turbine engine, the pressure within the anode of the solid oxide fuel cell is less than the pressure within the cathode of the solid oxide fuel cell includes, at (1318), reducing the fuel flow to the anode of the solid oxide fuel cell.

[0266] Furthermore, in certain exemplary aspects, such as in Figure 22In the exemplary aspect described, the fuel cell assembly is operated at (1316) such that, while operating the gas turbine engine, the pressure within the anode of the solid oxide fuel cell is less than the pressure within the cathode of the solid oxide fuel cell. This further includes, at (1320), allowing oxidant to flow into the anode when the temperature of the solid oxide fuel cell is between approximately 230 degrees Celsius and 700 degrees Celsius. As described, this can be adapted by including an operationally stable fuel cell.

[0267] See still Figure 22 Operating the fuel cell assembly, gas turbine engine, or both at (1315) may additionally or alternatively include operating the fuel cell assembly, gas turbine engine, or both such that, while operating the gas turbine engine, the pressure within the anode of the solid oxide fuel cell is less than the pressure within the combustion chamber of the gas turbine engine, or both. More specifically, for Figure 20 An exemplary aspect is that operating the fuel cell assembly, gas turbine engine, or both at (1315) includes performing a shutdown sequence of the gas turbine engine at (1304) and performing a cooling sequence of the fuel cell assembly at (1306) while performing the shutdown sequence of the gas turbine engine at (1304).

[0268] In this context, "cooling" refers to any reduction in temperature, such as that of a fuel cell stack, and does not necessarily require shutting down the fuel cell assembly. In some exemplary aspects, a cooling sequence may refer to allowing the fuel cell assembly to cool down without any active cooling of the fuel cell assembly. For example, performing a cooling sequence may include allowing the fuel cell assembly, or more precisely, the fuel cell stack, to cool at a rate of less than 0.75°C per minute, such as less than about 0.70°C per minute, such as less than about 0.65°C per minute, such as less than about 0.60°C per minute, such as less than about 0.50°C per minute.

[0269] More specifically, for the exemplary aspects depicted, performing the gas turbine engine shutdown sequence at (1304) may include performing the gas turbine engine shutdown sequence at (1305) after operating the fuel cell assembly at (1302). Further, for the illustrated embodiment, performing the gas turbine engine shutdown sequence at (1304) includes decelerating the gas turbine engine to a shutdown condition at (1308), and even more specifically, includes decelerating the gas turbine engine from at least a ground idling operating condition to a shutdown condition.

[0270] Furthermore, still referencing Figure 22In the exemplary aspect described, performing the shutdown sequence of the gas turbine engine at (1306) while simultaneously performing the cooling sequence of the fuel cell assembly more specifically includes (1310) operating the fuel cell assembly to limit the pressure in the anode of the solid oxide fuel cell to be less than the pressure in the combustion chamber of the combustor of the gas turbine engine. (See references herein) Figure 22 In the exemplary aspects of method 1300 described herein, the term "pressure" may refer to static pressure.

[0271] It is noteworthy that, when performing the cooling sequence of the gas turbine engine at (1306), method 1300 includes, at (1312), reducing the pressure of the fuel flow to the anode of the solid oxide fuel cell, reducing the pressure of the gas flow to the cathode of the solid oxide fuel cell, or both. Specifically, for the illustrated embodiment, performing the cooling sequence of the fuel cell assembly at (1306) more specifically includes reducing the pressure of the fuel flow to the anode of the solid oxide fuel cell as part of (1312).

[0272] More specifically, for an exemplary aspect of the depicted method 1300, performing the cooling sequence of the fuel cell assembly at (1306) includes cutting off the fuel flow to the anode of the solid oxide fuel cell, the gas flow to the cathode of the solid oxide fuel cell, or both, at (1313). In particular, for the illustrated embodiment, performing the cooling sequence of the fuel cell assembly at (1306) more specifically includes cutting off the fuel flow to the anode of the solid oxide fuel cell. In some exemplary aspects, cutting off the fuel flow to the anode of the solid oxide fuel cell may occur when the temperature of the fuel cell stack is between about 230°C and about 700°C, and when the gas turbine engine is operating at a speed of at least 100 revolutions per minute.

[0273] In this way, it will be understood that while performing the shutdown sequence of the gas turbine engine at (1306), the gas in the combustion chamber of the gas turbine engine can travel to the anode of the solid oxide fuel cell (e.g., through the outlet of the solid oxide fuel cell). More specifically, it will be understood that, for the exemplary aspects described, performing the cooling sequence of the fuel cell assembly at (1306) includes, at (1314), providing an airflow from the combustion chamber to the anode of the solid oxide fuel cell. The airflow may include oxygen-containing gas and may be at a temperature between about 230°C and about 700°C.

[0274] It will be understood that, in some exemplary aspects, performing the cooling sequence of the fuel cell assembly at (1306) may further include transitioning to a warm standby state, as referenced above. Figure 14The warm standby state described in method 900 (e.g., may be included at (912) to maintain the fuel cell stack of the fuel cell assembly in a warm standby state).

[0275] In this way, it will be understood that operating a fuel cell assembly according to one or more exemplary aspects of this disclosure can allow for more efficient operation of both the fuel cell assembly and the gas turbine engine incorporating the fuel cell assembly. For example, during shutdown operation of the gas turbine engine, operating a fuel cell assembly, gas turbine engine, or both of which have an operationally stable fuel cell according to this disclosure can allow the fuel flow to the fuel cell assembly to terminate before the flame in the combustion chamber of the gas turbine engine is extinguished, allowing all hydrogen in the output products to be combusted. Furthermore, this exemplary aspect can allow for more efficient operation by allowing the pressure within the cathode of the fuel cell to exceed the pressure within the anode of the fuel cell, without concern for anode oxidation, thereby saving fuel and airflow.

[0276] Furthermore, the operation of a fuel cell assembly, gas turbine engine, or both of which have an operationally stable fuel cell according to this disclosure can allow the fuel cell to be maintained at a lower baseline pressure due to its tolerance to surge conditions within the combustor, thereby allowing gas in the combustion chamber to flow into the anode of the fuel cell.

[0277] (ix) Figure 23 Implementation examples; control system diagram

[0278] Now for reference Figure 23 , Figure 23 A schematic diagram of a control system 1400 is shown, which can be used in one or more exemplary systems and methods described herein, such as one or more exemplary fuel cell assemblies 204 described above; ground start-up methods 500, 600, 700, 800, 1100, 1200; exemplary warm standby method 900; and exemplary cooling method 1300.

[0279] See Figure 23 The control system 1400 includes a hybrid power controller 1410 (which can be referenced above). Figure 5 The exemplary fuel cell controller 240 described herein is constructed in a similar manner to the human-machine interface (HMI) 1412, a memory device 1414, and a processor 1416. The HMI 1412 can be used to input data and interact with the hybrid power controller 1410. The processor 1416 can be configured similarly to the one described above. Figure 5 The processor 332A described is constructed in a similar manner, and the memory device 1414 can be referenced above. Figure 5 The memory device 332B described is constructed in a similar manner.

[0280] The control system 1400 includes a fuel cell subsystem 1420, which controls parameters and conditions related to the fuel cell stack of the fuel cell assembly during, for example, ground start-up, warm standby, or cooling processes. The control system 1400 further includes an engine subsystem 1430, which controls parameters and conditions related to a gas turbine engine system (such as a gas turbine engine system incorporating a fuel cell assembly) during, for example, ground start-up, warm standby, or cooling processes.

[0281] The fuel cell subsystem 1420 includes a fuel cell temperature sensor 1422 and a fuel cell pressure sensor 1424. The fuel cell temperature sensor 1422 senses data indicating the temperature of the high-temperature fuel cell stack, and the fuel cell pressure sensor 1424 senses data indicating the pressure of the high-temperature fuel cell stack. The fuel cell subsystem 1420 also includes a fuel cell fuel flow sensor 1426 and a fuel cell air flow sensor 1428. The fuel cell fuel flow sensor 1426 senses data indicating the fuel flow associated with the high-temperature fuel cell stack, and the fuel cell air flow sensor 1428 senses data indicating the air-fuel flow associated with the high-temperature fuel cell stack. The fuel cell subsystem 1420 further includes a fuel cell fuel flow valve 1442 and a fuel cell air flow valve 1444. The fuel cell fuel flow valve 1442 controls the fuel flow to the high-temperature fuel cell stack, and the fuel cell air flow valve 1444 controls the airflow to the high-temperature fuel cell stack. The fuel cell subsystem 1420 also includes a fuel cell stack exhaust igniter 1446, which ignites the fuel cell effluent within the burner. In this way, it will be understood that the fuel cell subsystem 1420 includes both data inputs (e.g., sensors) and control outputs (e.g., controls for valves, igniters, etc., used to control the operation of the fuel cell assembly).

[0282] Engine subsystem 1430 includes an engine speed sensor 1432, an engine fuel flow sensor 1434, and an engine temperature sensor 1436. Engine speed sensor 1432 senses data indicating the operating speed of the gas turbine engine, engine fuel flow sensor 1434 senses data indicating the fuel flow of the gas turbine engine, and engine temperature sensor 1436 senses data indicating the temperature of the gas turbine engine. Engine subsystem 1430 also includes an engine starter 1452 and a combustor igniter 1454. Engine starter 1452 starts the gas turbine engine, and combustor igniter 1454 ignites the fuel-air combustion mixture within the combustor. Engine subsystem 1430 also includes an engine fuel flow valve 1456, which controls the fuel flow to the combustor. In this way, it will be understood that engine subsystem 1430 includes both data inputs (e.g., sensors) and control outputs (e.g., control of valves, igniters, etc., for controlling the operation of the gas turbine engine) for the fuel cell assembly.

[0283] As described above, gas turbine engines with fuel cell components (such as SOFC fuel cell components) can be used in hybrid-electric aircraft systems. Certain operations of a hybrid-electric aircraft may require coordination of the gas turbine engine, fuel cell, fuel processing unit, and other components. For example, the startup sequence of these components needs to be coordinated during the ground startup of the hybrid-electric aircraft. Using some exemplary embodiments, the fuel cell heating process may take the longest, for example, about twenty to thirty minutes. The startup process of a CPOx fuel processing unit, for example, may take about one to two minutes. The engine needs about one to two minutes to reach a predetermined idle speed from the start-up speed.

[0284] Furthermore, environmental and safety standards during ground startup must comply with emission limits related to H2 / CO emissions from human / airport personnel, and keep fuel cell materials within integrity chemical, thermal, and mechanical limits. The control system 1400, including this disclosure, can more effectively allow coordination between the fuel cell assembly and the gas turbine engine, for example, by directly receiving data instructing the fuel cell assembly via the fuel cell subsystem 1420, directly receiving data instructing the gas turbine engine via the engine subsystem 1430, and making control decisions directly on the gas turbine engine and fuel cell assembly via the engine subsystem 1430 and fuel cell subsystem 1420, respectively. In this way, control of the gas turbine engine and fuel cell assembly can be implemented more effectively, including performing one or more exemplary methods disclosed herein.

[0285] This written description uses examples to disclose this disclosure, including best practices, and also enables any person skilled in the art to practice this disclosure, including making and using any device or system and methods of making any combination. The patent scope of this disclosure is defined by the claims, but may include other examples that would occur to a person skilled in the art. Such other examples are intended to fall within the scope of the claims if they include structural elements that are not indistinguishable from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims.

[0286] Further aspects are provided by the subject matter of the following clauses:

[0287] A method for operating a propulsion system for an aircraft, the propulsion system including a gas turbine engine and a fuel cell assembly, the fuel cell assembly including a fuel cell stack having a fuel cell with a defined outlet positioned to remove output products from the fuel cell during operation, the method comprising: executing a start-up sequence of the gas turbine engine, wherein executing the start-up sequence includes initiating the start-up sequence of the gas turbine engine; executing a start-up sequence of the fuel cell assembly concurrently with or after initiating the start-up sequence of the gas turbine engine; and operating the fuel cell assembly to provide output products to a combustion section of the gas turbine engine.

[0288] According to one or more of these provisions, the method of performing the start-up sequence of the gas turbine engine includes: achieving the flame-opening condition of the gas turbine engine, and the method of performing the start-up sequence of the fuel cell assembly includes: performing the start-up sequence of the fuel cell assembly simultaneously with or after achieving the flame-opening condition of the gas turbine engine.

[0289] According to one or more of these provisions, the method of performing the start-up sequence of the fuel cell assembly includes operating in a purge state after starting the start-up sequence of the fuel cell assembly; operating in a first heating state before the temperature of the fuel cell stack reaches a first fuel cell temperature threshold; operating in a second heating state after the temperature of the fuel cell stack reaches the first fuel cell temperature threshold and before the temperature of the fuel cell stack reaches a second fuel cell temperature threshold; and operating in a power generation state after the temperature of the fuel cell stack reaches the second fuel cell temperature threshold.

[0290] According to one or more of these provisions, the method wherein performing the startup sequence of the fuel cell assembly includes: operating in a purging state to provide airflow from the compressor section of the gas turbine engine to purge the anode and cathode of the fuel cell.

[0291] According to one or more of these provisions, the airflow from the compressor section is at a temperature of at least about 200 degrees Celsius.

[0292] According to one or more of these provisions, the method of performing the start-up sequence of the fuel cell assembly further includes: while the gas turbine engine is operating under flame-on conditions or faster, supplying the output products from the fuel cell to the combustor of the combustion section, wherein the output products include hydrogen.

[0293] According to one or more of these provisions, the method of performing the start-up sequence of the fuel cell assembly includes: initiating operation of the fuel processing unit and supplying exhaust gas from the fuel processing unit to the combustor of the combustion section of the gas turbine engine around the anode of the fuel cell.

[0294] According to one or more of these provisions, the method of performing the start-up sequence of the fuel cell assembly further includes: providing a heated gas flow from the fuel processing unit to the cathode of the fuel cell.

[0295] According to one or more of these provisions, the method of performing the start-up sequence of the fuel cell assembly further includes receiving data indicating that the temperature of the fuel cell stack is greater than or equal to a first fuel cell temperature threshold; and in response to receiving the data indicating that the temperature of the fuel cell stack is greater than or equal to the first fuel cell temperature threshold, supplying the exhaust gas of the fuel processing unit to the anode of the fuel cell.

[0296] According to one or more of these provisions, the method of performing the start-up sequence of the fuel cell assembly further includes, in response to receiving data indicating that the temperature of the fuel cell stack is greater than or equal to a first fuel cell temperature threshold, supplying the exhaust gas of the fuel processing unit to the cathode of the fuel cell.

[0297] According to one or more of these provisions, the method of supplying the exhaust gas of the fuel processing unit to the cathode of the fuel cell comprises: supplying the exhaust gas of the fuel processing unit to the cathode of the fuel cell at a pressure lower than that of the exhaust gas of the fuel processing unit supplied to the anode of the fuel cell.

[0298] According to one or more of these provisions, the method of performing the startup sequence of the fuel cell assembly further includes: receiving data indicating that the temperature of the fuel cell stack is greater than or equal to a second fuel cell temperature threshold; and starting the operation of the fuel cell assembly in power generation mode.

[0299] According to one or more of these provisions, the second fuel cell temperature threshold is at least about 400 degrees Celsius.

[0300] According to one or more of these provisions, the startup sequence of the fuel cell assembly includes: operating the air handling unit; and supplying exhaust gas from the air handling unit to the cathode, anode, or both of the fuel cell.

[0301] According to one or more of these provisions, the method of performing the startup sequence of the fuel cell assembly further includes receiving data indicating that the temperature of the fuel cell stack is greater than or equal to a first fuel cell temperature threshold; operating a fuel processing unit; in response to receiving data indicating that the temperature of the fuel cell stack is greater than or equal to the first fuel cell temperature threshold, providing exhaust gas from the fuel processing unit to the anode of the fuel cell; and in response to receiving data indicating that the temperature of the fuel cell stack is greater than or equal to the first fuel cell temperature threshold, providing exhaust gas from the air processing unit to the cathode of the fuel cell.

[0302] According to one or more of these provisions, the method wherein performing the startup sequence of the fuel cell assembly includes: supplying an oxygen-containing flow to the anode of the fuel cell before the temperature of the fuel cell stack is greater than or equal to a first fuel cell temperature threshold.

[0303] According to one or more of these provisions, the method of performing the startup sequence of the fuel cell assembly includes: supplying an oxygen-containing flow to the anode of the fuel cell before the temperature of the fuel cell stack is greater than or equal to a second fuel cell temperature threshold.

[0304] According to one or more of these provisions, the startup sequence of the fuel cell assembly includes performing a fuel reforming operation at the anode of the fuel cell.

[0305] According to one or more of these provisions, the fuel reforming action at the anode of the fuel cell assembly includes: providing a hydrocarbon fuel stream to the anode and providing an oxygen-containing gas stream to the anode.

[0306] A propulsion system for an aircraft having a gas turbine engine, the aircraft including an aircraft fuel supply unit, the propulsion system comprising: a fuel cell assembly including a fuel cell stack having fuel cells defining an outlet positioned to remove output products from the fuel cells; a turbine including a compressor section, a combustion section, and a turbine section arranged in a serial flow sequence, the combustion section being configured to receive an aviation fuel flow from the aircraft fuel supply unit and further configured to receive the output products from the fuel cells; and a controller including a memory and one or more processors, the memory storing instructions that, when executed by the one or more processors, cause the propulsion system to operate, the operation including executing a start-up sequence of the gas turbine engine, wherein executing the start-up sequence includes initiating the start-up sequence of the gas turbine engine; executing a start-up sequence of the fuel cell assembly concurrently with or after initiating the start-up sequence of the gas turbine engine; and operating the fuel cell assembly to provide output products to the combustion section of the gas turbine engine.

[0307] A method for operating a propulsion system for an aircraft, the propulsion system including a gas turbine engine and a fuel cell assembly, the fuel cell assembly including a fuel cell stack having a fuel cell with a defined outlet positioned to remove output products from the fuel cell during operation, the method comprising: performing a start-up sequence of the fuel cell assembly, wherein performing the start-up sequence of the fuel cell assembly includes initiating the start-up sequence of the fuel cell assembly; performing a start-up sequence of the gas turbine engine, wherein performing the start-up sequence of the gas turbine engine includes initiating the start-up sequence of the gas turbine engine after initiating the start-up sequence of the fuel cell assembly; and operating the fuel cell assembly to provide output products to a combustion section of the gas turbine engine.

[0308] According to one or more of these provisions, the method of performing the start-up sequence of the fuel cell assembly includes: operating in a purge state after starting the start-up sequence of the fuel cell assembly; operating in a first heating state before the temperature of the fuel cell stack reaches a first fuel cell temperature threshold; operating in a second heating state after the temperature of the fuel cell stack reaches the first fuel cell temperature threshold and before the temperature of the fuel cell stack reaches a second fuel cell temperature threshold; and operating in a power generation state after the temperature of the fuel cell stack reaches the second fuel cell temperature threshold.

[0309] According to one or more of these provisions, the method of starting the gas turbine engine after starting the start-up sequence of the fuel cell assembly includes: starting the start-up sequence of the gas turbine engine before the temperature of the fuel cell stack reaches a first fuel cell temperature threshold.

[0310] According to one or more of the methods described in these terms, the first fuel cell temperature threshold is at least about 230 degrees Celsius.

[0311] According to one or more of these provisions, the method of starting the gas turbine engine after starting the start-up sequence of the fuel cell assembly includes: starting the start-up sequence of the gas turbine engine after the temperature of the fuel cell stack has reached a first fuel cell temperature threshold and before the temperature of the fuel cell stack reaches a second fuel cell temperature threshold.

[0312] According to one or more of these provisions, the first fuel cell temperature threshold is between about 230 degrees Celsius and about 400 degrees Celsius, the second fuel cell temperature threshold is between about 400 degrees Celsius and about 750 degrees Celsius, and the second fuel cell temperature threshold is greater than the first fuel cell temperature threshold.

[0313] According to one or more of these provisions, the method of starting the gas turbine engine after starting the start-up sequence of the fuel cell assembly includes: starting the start-up sequence of the gas turbine engine after the temperature of the fuel cell stack has reached a second fuel cell temperature threshold.

[0314] According to one or more of these provisions, the second fuel cell temperature threshold is between approximately 400 degrees Celsius and approximately 750 degrees Celsius.

[0315] According to one or more of these provisions, the method wherein the fuel cell assembly includes an air handling unit, and wherein performing the startup sequence of the fuel cell assembly further includes: completing the startup sequence of the fuel cell assembly, and before completing the startup sequence of the fuel cell assembly, directing one or more streams of the output products from the fuel cell to the air handling unit.

[0316] According to one or more of these provisions, the one or more streams of the output products from the fuel cell include an anode stream, a cathode stream, or both.

[0317] According to one or more of these provisions, the method wherein the fuel cell assembly includes a fuel processing unit, and wherein performing the start-up sequence of the fuel cell assembly further includes: completing the start-up sequence of the fuel cell assembly, and before completing the start-up sequence of the fuel cell assembly, directing one or more streams of the output products from the fuel cell to the fuel processing unit.

[0318] According to one or more of these provisions, the one or more streams of the output products from the fuel cell include an anode stream, a cathode stream, or both.

[0319] According to one or more of these provisions, the startup sequence of the fuel cell assembly includes: operating the fuel cell assembly in a warm standby state; operating the fuel cell assembly in a ground idling power generation mode; and operating the fuel cell assembly in a normal power generation mode.

[0320] The method according to one or more of these provisions, wherein operating the fuel cell assembly in the ground idling power generation mode includes operating the fuel cell assembly at a fuel utilization rate of approximately 10% of the maximum fuel utilization rate.

[0321] According to one or more of these provisions, the method of performing the start-up sequence of the fuel cell assembly includes: initiating operation of the fuel treatment unit and supplying exhaust gas from the fuel treatment unit to the combustor of the combustion section of the gas turbine engine, the air treatment unit of the fuel cell assembly, or both, around the anode of the fuel cell.

[0322] According to one or more of these provisions, the method wherein the fuel cell assembly includes an air handling unit and a fuel handling unit, wherein performing the startup sequence of the fuel cell assembly includes: supplying exhaust gas from the air handling unit to the cathode of the fuel cell and supplying exhaust gas from the fuel handling unit to the anode of the fuel cell.

[0323] According to one or more of these provisions, the method wherein performing the startup sequence of the fuel cell assembly includes: supplying an oxygen-containing flow to the anode of the fuel cell before the temperature of the fuel cell stack is greater than or equal to a first fuel cell temperature threshold.

[0324] According to one or more of these provisions, the method of performing the startup sequence of the fuel cell assembly includes: supplying an oxygen-containing flow to the anode of the fuel cell before the temperature of the fuel cell stack is greater than or equal to a second fuel cell temperature threshold.

[0325] According to one or more of these provisions, the method for performing the startup sequence of the fuel cell assembly includes: performing a fuel reforming operation at the anode of the fuel cell assembly.

[0326] The method according to one or more of these provisions, wherein performing fuel reforming at the anode of the fuel cell assembly includes supplying a hydrocarbon fuel stream to the anode and supplying an oxygen-containing gas stream to the anode.

[0327] A propulsion system for an aircraft having a gas turbine engine, the aircraft including an aircraft fuel supply unit, the propulsion system comprising: a fuel cell assembly including a fuel cell stack having fuel cells, the fuel cells defining an outlet positioned to remove output products from the fuel cells; a turbine including a compressor section, a combustion section, and a turbine section arranged in a serial flow sequence, the combustion section being configured to receive an aviation fuel flow from the aircraft fuel supply unit and further configured to receive the output products from the fuel cells; and a controller including a memory and one or more processors, the memory storing instructions that, when executed by the one or more processors, cause the propulsion system to operate, the operation including: executing a start-up sequence of the fuel cell assembly, wherein executing the start-up sequence of the fuel cell assembly includes initiating the start-up sequence of the fuel cell assembly; executing a start-up sequence of the gas turbine engine, wherein executing the start-up sequence of the gas turbine engine includes initiating the start-up sequence of the gas turbine engine after initiating the start-up sequence of the fuel cell assembly; and operating the fuel cell assembly to provide output products to the combustion section of the gas turbine engine.

[0328] A propulsion system for an aircraft, the aircraft including an aircraft fuel supply unit, the propulsion system comprising: a turbine including a compressor section, a combustion section, and a turbine section arranged in a serial flow sequence, the combustion section being configured to receive an aviation fuel flow from the aircraft fuel supply unit; and a fuel cell assembly including a fuel cell stack having a solid oxide fuel cell, the solid oxide fuel cell defining an outlet positioned to remove output products from the solid oxide fuel cell and to supply the output products to the combustion section, the solid oxide fuel cell including a cathode; an electrolyte layer; and an anode positioned on the electrolyte layer opposite the cathode, the anode comprising a cermet comprising less than 25% by volume nickel.

[0329] The propulsion system according to one or more of these provisions, wherein the cermet comprises less than 10% by volume of nickel.

[0330] The propulsion system according to one or more of these terms, wherein the cermet comprises less than 0.01% by volume of nickel.

[0331] The propulsion system according to one or more of these provisions, wherein the aircraft fuel supply unit is a hydrocarbon fuel supply unit, and wherein the fuel cell assembly is configured to supply hydrocarbon fuel from the hydrocarbon fuel supply unit to the anode.

[0332] The propulsion system according to one or more of these provisions, wherein the fuel cell assembly includes a gas delivery system in communication with the anode gas flow for supplying oxygen-containing gas to the anode.

[0333] The propulsion system according to one or more of these provisions, wherein the airflow delivery system is configured to receive oxygen-containing gas from the compressor section of the turbine, from an ambient location, or both.

[0334] The propulsion system according to one or more of these provisions, wherein the metal-ceramic catalyst catalyzes the partial oxidation of aviation fuel.

[0335] According to one or more of these provisions, the propulsion system wherein the anode comprises a noble metal or ceramic material that catalytically oxidizes aviation fuel.

[0336] According to one or more of these provisions, the propulsion system wherein the metal-ceramic catalyst catalyzes the catalytic partial oxidation of aviation fuel, and wherein the anode further comprises a noble metal or ceramic material that catalyzes the catalytic partial oxidation of aviation fuel.

[0337] According to one or more of these provisions, in a propulsion system, a precious metal or ceramic material that catalytically oxidizes aviation fuel adheres to at least a portion of the surface of the fuel cell assembly upstream of the anode.

[0338] The propulsion system according to one or more of these provisions, wherein the fuel cell assembly includes an air handling unit configured to provide airflow to the cathode.

[0339] According to one or more of these provisions, the propulsion system wherein the fuel cell stack defines the fuel cell stack temperature, and the fuel cell assembly is configured to supply oxygen-containing gas to the anode when the fuel cell stack temperature is less than 450 degrees Celsius.

[0340] According to one or more of these provisions, the propulsion system wherein the fuel cell stack defines the fuel cell stack temperature, and the fuel cell assembly is configured to supply oxygen-containing gas to the anode when the fuel cell stack temperature is greater than 80 degrees Celsius and less than 250 degrees Celsius.

[0341] According to one or more of these provisions, the propulsion system wherein the fuel cell stack defines the fuel cell stack temperature, and the fuel cell assembly is configured to supply oxygen-containing gas to the anode when the fuel cell stack temperature is greater than 450 degrees Celsius and less than 750 degrees Celsius.

[0342] According to one or more of these provisions, the propulsion system wherein the aircraft fuel supply unit is a hydrocarbon fuel supply unit, wherein the fuel cell assembly includes a fuel processing unit, and wherein the fuel cell assembly is configured to selectively supply hydrocarbon fuel from the hydrocarbon fuel supply unit to the anode and hydrogen fuel from the fuel processing unit to the anode.

[0343] A fuel cell assembly for a propulsion system of an aircraft, the propulsion system including a gas turbine engine having a combustion section, the fuel cell assembly including: a fuel cell stack having a solid oxide fuel cell defining an outlet positioned to remove output products from the solid oxide fuel cell and supply the output products to the combustion section when the fuel cell assembly is mounted with the gas turbine engine, the solid oxide fuel cell including a cathode; an electrolyte layer; and an anode positioned on the electrolyte layer opposite the cathode, the anode comprising a cermet comprising less than 25% by volume nickel.

[0344] The fuel cell assembly according to one or more of these terms, wherein the metal ceramic comprises less than 10% by volume of nickel.

[0345] The fuel cell assembly according to one or more of these terms, wherein the metal ceramic comprises less than 0.01% by volume of nickel.

[0346] According to one or more of these provisions, the fuel cell assembly wherein the anode comprises a metal-ceramic that catalytically oxidizes aviation fuel.

[0347] According to one or more of these provisions, the fuel cell assembly, wherein the anode comprises a noble metal or ceramic material that catalytically oxidizes aviation fuel.

[0348] A method for operating a fuel cell assembly, the fuel cell assembly including a fuel cell stack having a solid oxide fuel cell having an anode, a cathode and an electrolyte, the method comprising: determining a temperature setpoint of the fuel cell stack, the output products of the fuel cell stack, or both; and, in response to the determined temperature setpoint, controlling the volume of oxidant supplied to the anode to control the temperature of the fuel cell stack, the temperature of the output products of the fuel cell stack, or both.

[0349] The method described according to one or more of these provisions further includes: performing a fuel reforming operation at the anode.

[0350] According to one or more of these provisions, the fuel reforming operation at the anode includes: receiving hydrocarbon-based fuel at the anode; and receiving oxygen-containing gas at the anode.

[0351] The oxygen-containing gas described in one or more of these provisions is ambient air.

[0352] According to one or more of these provisions, the fuel cell assembly is integrated into a gas turbine engine, and the oxygen-containing gas is compressed air from the compressor section of the gas turbine engine.

[0353] According to one or more of these provisions, the anode comprises less than 25% by volume nickel.

[0354] According to one or more of these provisions, the anode is substantially nickel-free.

[0355] According to one or more of these provisions, the method wherein the fuel cell assembly is integrated into a gas turbine engine, wherein the gas turbine engine includes a combustion section having a burner, wherein the solid oxide fuel cell defines an outlet positioned to remove output products from the solid oxide fuel cell, and wherein the method further includes: supplying the output products from the solid oxide fuel cell to the burner.

[0356] The method according to one or more of these provisions further includes: performing a start-up operation of the fuel cell assembly, and wherein controlling the volume of oxidant supplied to the anode includes: controlling the volume of oxidant supplied to the anode while performing the start-up operation of the fuel cell assembly.

[0357] The method according to one or more of these provisions further includes: performing a start-up operation of the fuel cell assembly, and wherein determining the temperature setpoint includes: determining the temperature setpoint while performing the start-up operation of the fuel cell assembly.

[0358] According to one or more of these provisions, the method wherein controlling the volume of oxidant supplied to the anode includes: providing an oxygen-containing gas flow at the anode before the temperature of the fuel cell stack exceeds a first fuel cell temperature threshold.

[0359] The method according to one or more of these provisions further includes: operating the fuel cell assembly in a power generation mode, and wherein controlling the volume of oxidant supplied to the anode includes: controlling the volume of oxidant supplied to the anode while operating the fuel cell assembly in the power generation mode.

[0360] According to one or more of these provisions, the method wherein the fuel cell assembly is integrated into a gas turbine engine, the gas turbine engine defining gas turbine engine operating conditions, and wherein determining the temperature setpoint comprises: determining the temperature setpoint in response to the gas turbine engine operating conditions.

[0361] The method according to one or more of these provisions, wherein the gas turbine engine operating conditions indicate emission parameters, combustion dynamics parameters, power output parameters, or a combination thereof.

[0362] A propulsion system for an aircraft, the aircraft including an aircraft fuel supply unit, the propulsion system comprising: a fuel cell assembly including a fuel cell stack having fuel cells, the fuel cells defining an outlet positioned to remove output products from the fuel cells; a turbine including a compressor section, a combustion section, and a turbine section arranged in a serial flow sequence, the combustion section being configured to receive an aviation fuel flow from the aircraft fuel supply unit and further configured to receive the output products from the fuel cells; and a controller including a memory and one or more processors, the memory storing instructions that, when executed by the one or more processors, cause the propulsion system to perform operations including determining a temperature setpoint for the fuel cell stack, the output products of the fuel cell stack, or both; and, in response to the determined temperature setpoint, controlling the volume of oxidant supplied to the anode to control the temperature of the fuel cell stack, the temperature of the output products of the fuel cell stack, or both.

[0363] According to one or more of these provisions, the propulsion system wherein the aircraft fuel supply unit is a hydrocarbon fuel supply unit, wherein the fuel cell assembly includes a fuel processing unit, and wherein the fuel cell assembly is configured to selectively supply hydrocarbon fuel from the hydrocarbon fuel supply unit to the anode and hydrogen fuel from the fuel processing unit to the anode.

[0364] According to one or more of these provisions, the propulsion system further includes: performing fuel reforming at the anode.

[0365] According to one or more of these provisions, the fuel reforming operation at the anode includes: receiving hydrocarbon-based fuel at the anode; and receiving oxygen-containing gas at the anode.

[0366] According to one or more of these provisions, the propulsion system wherein the fuel cell assembly is integrated into a gas turbine engine, and wherein the oxygen-containing gas is compressed air from the compressor section of the gas turbine engine.

[0367] According to one or more of these provisions, the propulsion system wherein the anode comprises less than 25% by volume nickel.

[0368] A method for operating a propulsion system for an aircraft, the propulsion system including a gas turbine engine and a fuel cell assembly, the fuel cell assembly including a fuel cell stack having a solid oxide fuel cell, the solid oxide fuel cell defining an outlet positioned to remove output products from the solid oxide fuel cell during operation, the method comprising:

[0369] Operate the fuel cell assembly to provide output products to the combustor in the combustion section of the gas turbine engine; and

[0370] The fuel cell assembly, the gas turbine engine, or both are operated such that, while the gas turbine engine is being operated, the pressure within the anode of the solid oxide fuel cell is less than the pressure within the cathode of the solid oxide fuel cell, less than the pressure within the combustion chamber of the gas turbine engine, or both.

[0371] The method according to one or more of these provisions, wherein operating the fuel cell assembly, the gas turbine engine, or both comprises:

[0372] Execute the shutdown sequence of the gas turbine engine, wherein executing the shutdown sequence includes decelerating the gas turbine engine to a shutdown condition; and

[0373] While performing the shutdown sequence of the gas turbine engine, a cooling sequence of the fuel cell assembly is performed, wherein performing the cooling sequence of the fuel cell assembly includes operating the fuel cell assembly to limit the pressure in the anode of the solid oxide fuel cell to be less than the pressure in the combustion chamber of the combustor of the gas turbine engine.

[0374] According to one or more of these provisions, performing the shutdown sequence includes: decelerating the gas turbine engine from ground idling operating conditions to the shutdown conditions.

[0375] According to one or more of these provisions, the method wherein performing the cooling sequence of the fuel cell assembly while performing the shutdown sequence of the gas turbine engine includes: providing airflow from the combustion chamber to the anode of the solid oxide fuel cell.

[0376] According to one or more of these provisions, the method of supplying gas flow from the combustion chamber to the anode of the solid oxide fuel cell includes: supplying gas flow from the combustion chamber to the anode of the solid oxide fuel cell when the temperature of the solid oxide fuel cell is between about 230 degrees Celsius and 700 degrees Celsius.

[0377] The method according to one or more of these provisions, wherein the gas flow supplied from the combustion chamber to the anode of the solid oxide fuel cell is an oxygen-containing flow.

[0378] According to one or more of these provisions, the method wherein performing the cooling sequence of the fuel cell assembly includes reducing the pressure of the fuel flow to the anode of the solid oxide fuel cell, the pressure of the gas flow to the cathode of the solid oxide fuel cell, or both.

[0379] According to one or more of these provisions, the method wherein performing the cooling sequence of the fuel cell assembly includes: cutting off the fuel flow to the anode of the solid oxide fuel cell, the gas flow to the cathode of the solid oxide fuel cell, or both.

[0380] According to one or more of these provisions, performing the cooling sequence includes maintaining the fuel cell assembly in a warm standby state.

[0381] According to one or more of these provisions, maintaining the fuel cell assembly in the warm standby state includes: drawing less than about 10% of the maximum power output of the fuel cell assembly from the fuel cell assembly.

[0382] According to one or more of these provisions, performing the cooling sequence includes operating the fuel cell assembly in a ground idling power output mode.

[0383] The method according to one or more of these provisions, wherein operating the fuel cell assembly in the ground idling power output mode includes: recirculating the output products from the solid oxide fuel cell to a location upstream of the fuel cell.

[0384] According to one or more of these provisions, performing the cooling sequence includes: maintaining the fuel cell assembly in a warm standby state, operating in a ground idling power output mode, or both, while the gas turbine engine is in the shut-off condition.

[0385] According to one or more of these provisions, the anode comprises less than 25% by volume nickel.

[0386] According to one or more of these provisions, the anode is substantially nickel-free.

[0387] The method according to one or more of these provisions, wherein operating the fuel cell assembly, the gas turbine engine, or both comprises: operating the fuel cell assembly such that, while operating the gas turbine engine, the pressure within the anode of the solid oxide fuel cell is less than the pressure within the cathode of the solid oxide fuel cell.

[0388] According to one or more of these provisions, operating the fuel cell assembly such that, while operating the gas turbine engine, the pressure within the anode of the solid oxide fuel cell is less than the pressure within the cathode of the solid oxide fuel cell comprises: allowing an oxidant to flow into the anode when the temperature of the solid oxide fuel cell is between about 230 degrees Celsius and 700 degrees Celsius.

[0389] According to one or more of these provisions, operating the fuel cell assembly such that, while operating the gas turbine engine, the pressure within the anode of the solid oxide fuel cell is less than the pressure within the cathode of the solid oxide fuel cell comprises: reducing the fuel flow to the anode of the solid oxide fuel cell.

[0390] A propulsion system for an aircraft having a gas turbine engine, the aircraft including an aircraft fuel supply unit, the propulsion system comprising: a fuel cell assembly including a fuel cell stack having a solid oxide fuel cell, the solid oxide fuel cell defining an outlet positioned to remove output products from the solid oxide fuel cell; a turbine including a compressor section, a combustion section and a turbine section arranged in a serial flow sequence, the combustion section being configured to receive an aviation fuel flow from the aircraft fuel supply unit and further configured to receive the output products from the solid oxide fuel cell; and a controller including a memory and one or more processors, the memory storing instructions that, when executed by the one or more processors, cause the propulsion system to perform operations, the operations including: operating the fuel cell assembly, the gas turbine engine, or both, such that, while operating the gas turbine engine, the pressure within the anode of the solid oxide fuel cell is less than the pressure within the cathode of the solid oxide fuel cell, less than the pressure within the combustion chamber of the gas turbine engine, or both.

[0391] According to one or more of these provisions, the propulsion system wherein operating the fuel cell assembly, the gas turbine engine, or both comprises: performing a shutdown sequence of the gas turbine engine, wherein performing the shutdown sequence comprises decelerating the gas turbine engine to a shutdown condition; and simultaneously performing a cooling sequence of the fuel cell assembly, wherein performing the cooling sequence of the fuel cell assembly comprises: operating the fuel cell assembly to limit the pressure in the anode of the solid oxide fuel cell to be less than the pressure in the combustion chamber of the combustion section of the turbine.

Claims

1. A propulsion system for an aircraft, the aircraft including an aircraft fuel supply unit, characterized in that, The propulsion system includes: A turbine comprising a compressor section, a combustion section, and a turbine section arranged in a serial flow sequence, the combustion section being configured to receive an aviation fuel flow from the aircraft fuel supply unit, wherein the combustion section includes a swirler assembly, an inner liner, and an outer liner, wherein the inner liner and the outer liner define a combustion chamber, and wherein the swirler assembly is disposed upstream of the combustion chamber; and A fuel cell assembly comprising a plurality of fuel cell stacks arranged circumferentially along the outer or inner liner, each of the plurality of fuel cell stacks having a solid oxide fuel cell, the solid oxide fuel cell defining an outlet positioned to remove output products from the solid oxide fuel cell and to supply the output products to the combustion section via the outer or inner liner downstream of the cyclone assembly, the solid oxide fuel cell comprising: cathode; Electrolyte layer; and The anode is positioned on the electrolyte layer opposite the cathode, and the anode comprises a cermet comprising less than 25% by volume nickel.

2. The propulsion system according to claim 1, characterized in that, The cermet contains less than 10% by volume of nickel.

3. The propulsion system according to claim 1, characterized in that, The cermet contains less than 0.01% by volume of nickel.

4. The propulsion system according to claim 1, characterized in that, The aircraft fuel supply unit is a hydrocarbon fuel supply unit, and the fuel cell assembly is configured to supply hydrocarbon fuel from the hydrocarbon fuel supply unit to the anode.

5. The propulsion system according to claim 1, characterized in that, The fuel cell assembly includes a gas delivery system in communication with the anode gas flow for supplying oxygen-containing gas to the anode.

6. The propulsion system according to claim 5, characterized in that, The airflow delivery system is configured to receive oxygen-containing gas from the compressor section of the turbine, from an ambient location, or both.

7. The propulsion system according to claim 1, characterized in that, The aforementioned metal-ceramic catalyst catalyzes the partial oxidation of aviation fuel.

8. The propulsion system according to claim 1, characterized in that, The anode comprises a noble metal or ceramic material that catalyzes the partial oxidation of aviation fuel.

9. The propulsion system according to claim 1, characterized in that, The cermet catalyst catalyzes the partial oxidation of aviation fuel, and the anode further comprises a noble metal or ceramic material that catalyzes the partial oxidation of aviation fuel.

10. The propulsion system according to claim 1, characterized in that, The precious metal or ceramic material that catalytically oxidizes aviation fuel adheres to at least a portion of the surface of the fuel cell assembly upstream of the anode.

11. The propulsion system according to claim 1, characterized in that, The fuel cell assembly includes an air handling unit configured to provide airflow to the cathode.

12. The propulsion system according to claim 1, characterized in that, The fuel cell stack defines the fuel cell stack temperature, and the fuel cell assembly is configured to supply oxygen-containing gas to the anode when the fuel cell stack temperature is less than 450 degrees Celsius.

13. The propulsion system according to claim 1, characterized in that, The fuel cell stack defines the fuel cell stack temperature, and the fuel cell assembly is configured to supply oxygen-containing gas to the anode when the fuel cell stack temperature is greater than 80 degrees Celsius and less than 250 degrees Celsius.

14. The propulsion system according to claim 1, characterized in that, The fuel cell stack defines the fuel cell stack temperature, and the fuel cell assembly is configured to supply oxygen-containing gas to the anode when the fuel cell stack temperature is greater than 450 degrees Celsius and less than 750 degrees Celsius.

15. The propulsion system according to claim 1, characterized in that, The aircraft fuel supply unit is a hydrocarbon fuel supply unit, the fuel cell assembly includes a fuel processing unit, and the fuel cell assembly is configured to selectively supply hydrocarbon fuel from the hydrocarbon fuel supply unit to the anode and hydrogen fuel from the fuel processing unit to the anode.

16. A fuel cell assembly for a propulsion system of an aircraft, the propulsion system comprising a gas turbine engine having a combustion section, characterized in that, The combustion section includes a swirler assembly, an inner liner, and an outer liner, wherein the inner liner and the outer liner define a combustion chamber, and wherein the swirler assembly is disposed upstream of the combustion chamber; The fuel cell assembly includes: A plurality of fuel cell stacks arranged circumferentially along the outer liner or the inner liner, each of the plurality of fuel cell stacks having a solid oxide fuel cell, the solid oxide fuel cell defining an outlet positioned to remove output products from the solid oxide fuel cell when the fuel cell assembly is installed with the gas turbine engine, and to supply the output products to the combustion section via the outer liner or the inner liner downstream of the cyclone assembly, the solid oxide fuel cell comprising: cathode; Electrolyte layer; and The anode is positioned on the electrolyte layer opposite the cathode, and the anode comprises a cermet comprising less than 25% by volume nickel.

17. The fuel cell assembly according to claim 16, characterized in that, The cermet contains less than 10% by volume of nickel.

18. The fuel cell assembly according to claim 16, characterized in that, The cermet contains less than 0.01% by volume of nickel.

19. The fuel cell assembly according to claim 16, characterized in that, The anode comprises a metal-ceramic material that catalyzes the partial oxidation of aviation fuel.

20. The fuel cell assembly according to claim 16, characterized in that, The anode comprises a noble metal or ceramic material that catalyzes the partial oxidation of aviation fuel.

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