Diagnostic system and method for fuel cell assembly

Abstract

A fuel cell assembly is provided including a fuel cell stack having a fuel cell having a cathode and an anode; and a multi-gas sensor configured to sense gas composition data of an output product stream from the cathode, gas composition data of an output product stream from the anode, gas composition data of a fluid surrounding the fuel cell, or a combination thereof, to determine fuel cell leak diagnostic information.

Description

Technical Field

[0001] The present disclosure relates to a system and method for operating a fuel cell assembly, such as a fuel cell assembly integrated into a gas turbine engine. Background Art

[0002] A fuel cell stack includes a group of individual fuel cells, each of which includes an anode, a cathode, and an electrolyte in the form of a matrix disposed therebetween. The fuel cell stack also includes passages to and from the anode and cathode to allow fuel and oxidant to flow into the anode and cathode, respectively, and to allow any excess fuel and oxidant and byproducts such as water to flow out.

[0003] The operation of a fuel cell stack to generate electricity involves introducing a fuel, such as hydrogen, into the anode path. Simultaneously, an oxidant, such as air, is introduced into the cathode path. Hydrogen is oxidized at the anode, producing hydrogen ions and free electrons. These electrons flow through an external load, thereby generating electricity, while the hydrogen ions migrate through the matrix to the cathode. At the cathode, the hydrogen ions and free electrons react with oxygen to form water.

[0004] The pathways that direct the fuel to the anode and the oxidant to the cathode are separate and distinct. Since mixing of the fuel and oxidant is undesirable, it may be important to keep these substances separated. Therefore, it may be important to detect leaks that may allow direct contact between these substances, whether outward leakage or cross leakage. Outward leakage refers to leakage outside the cell from the pathway that occurs when the fuel and oxidant are directed to the anode and cathode. Cross leakage refers to leakage between the anode and cathode through the matrix within the cell, which occurs when holes are formed in the matrix. Heating and cooling, especially heating and cooling of high temperature fuel cell assemblies, can produce load stresses that lead to cross and outward leakage. Cross leakage cross-contaminates reactants, reducing efficiency or damaging the fuel cell. Outward leakage also reduces efficiency due to the loss of reactants. Leaks may occur at any fluid interface in the fuel cell assembly, such as the fuel cell, port, and end plate.

[0005] Therefore, the inventors of the present disclosure have discovered that a fuel cell leak diagnostic system and method would be welcome in the art. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] A full and enabling disclosure of the present disclosure, including the best mode thereof, to one of ordinary skill in the art is set forth in the specification with reference to the accompanying drawings, in which:

[0007] Figure 1 is a cross-sectional view of a gas turbine engine according to an exemplary aspect of the present disclosure.

[0008] Figure 2 is a perspective view of an integrated fuel cell and combustor assembly according to the present disclosure.

[0009] Figure 3 yes Figure 2 Schematic axial view of an exemplary integrated fuel cell and combustor assembly.

[0010] Figure 4 is a schematic diagram of a fuel cell of a fuel cell assembly according to an exemplary aspect of the present disclosure, which fuel cell may be incorporated into Figure 2 An exemplary integrated fuel cell and combustor assembly is provided.

[0011] Figure 5 is a schematic diagram of a gas turbine engine including an integrated fuel cell and combustor assembly according to an exemplary aspect of the present disclosure.

[0012] Figure 6 is a schematic diagram of a fuel cell assembly according to an exemplary embodiment of the present disclosure.

[0013] Figure 7 is a schematic diagram of a fuel cell assembly according to another exemplary embodiment of the present disclosure.

[0014] Figure 8 is a schematic diagram of a fuel cell assembly according to yet another exemplary embodiment of the present disclosure.

[0015] Fig. 9 is a schematic diagram of a fuel cell assembly according to yet another exemplary embodiment of the present disclosure.

[0016] Fig.10 is a schematic diagram of a fuel cell assembly according to yet another exemplary embodiment of the present disclosure.

[0017] Fig.11 is a schematic diagram of a fuel cell assembly according to yet another exemplary embodiment of the present disclosure.

[0018] Fig.12 is a schematic diagram of a fuel cell assembly according to yet another exemplary embodiment of the present disclosure.

[0019] Fig.13 is a schematic diagram of a fuel cell assembly according to yet another exemplary embodiment of the present disclosure.

[0020] Fig.14 is a flow chart of a method for determining fuel cell leak diagnostic information according to an exemplary aspect of the present disclosure.

[0021] Fig.15 It is used to determine the fuel cell leak diagnostic information related to the external leakage Fig.13 Flowchart of exemplary aspects of a method.

[0022] Fig.16It is used to determine fuel cell leak diagnostic information related to cross leaks Fig.13 Flowchart of exemplary aspects of a method.

[0023] Fig.17 One embodiment of a multi-gas sensing system according to one embodiment is shown.

[0024] Fig.18 Shows Fig.17 The sensing circuit of the multi-gas sensing system is shown.

[0025] Fig.19 A system layout of a multi-gas sensing system according to one embodiment is shown.

[0026] Fig. 20 A flow chart of one embodiment of a method of sensing a plurality of different gas analytes using a multi-gas sensing system according to one embodiment is shown.

[0027] Fig.21 A graphical representation of the electrical responses of various sensing elements of a multi-gas sensing system is shown according to one embodiment.

[0028] Fig. 22 Shows Fig.21 A graphical representation of the electrical responses of the analytical electrical responses of the individual sensing elements of the multi-gas sensing system is shown.

[0029] Fig.23 A graphical representation of the response of a metal oxide sensing element to a gas of interest is shown according to one embodiment.

[0030] Fig.24 A graphical representation of gas concentration quantification using dielectric excitation gas detection is shown according to one embodiment.

[0031] Fig.25 The effect of water vapor on the resistance and dielectric excitation response over a range of relative humidity is shown.

[0032] Fig.26 A diagram illustrating the operation of a multi-gas monitor under dynamic wind conditions according to one embodiment.

[0033] Fig. 27 is a schematic diagram of the response of a sensing element to hydrogen and methane according to one embodiment.

[0034] Fig.28 A graphical representation of gas concentration quantification using dielectric excitation gas detection is shown according to one embodiment. DETAILED DESCRIPTION

[0035] Reference will now be made in detail to the present embodiments of the present disclosure, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter references to refer to features in the drawings. Like or similar reference numbers in the drawings and description have been used to refer to like or similar parts of the present disclosure.

[0036] The word "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 preferred or advantageous over other implementations. In addition, all embodiments described herein should be considered exemplary unless expressly stated otherwise.

[0037] For the purposes of the description hereinafter, the terms "upper", "lower", "right", "left", "vertical", "horizontal", "top", "bottom", "lateral", "longitudinal" and their derivatives shall relate to the embodiments as they are oriented in the accompanying drawings. However, it should be understood that the embodiments may assume various alternative variations unless expressly indicated to the contrary. It should also be understood that the specific devices shown in the drawings and described in the following specification are merely exemplary embodiments of the present disclosure. Therefore, specific dimensions and other physical characteristics related to the embodiments disclosed herein should not be considered limiting.

[0038] As used herein, the terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another, and are not intended to indicate the position or importance of each component.

[0039] The terms "front" and "rear" refer to relative positions within a gas turbine engine or vehicle and refer to the normal operating attitude of the gas turbine engine or vehicle. For example, for a gas turbine engine, front refers to a position closer to the engine inlet, while rear refers to a position closer to the engine nozzle or exhaust.

[0040] The terms "upstream" and "downstream" refer to relative directions relative to the flow of a fluid in a fluid path. For example, "upstream" refers to the direction from which the fluid is flowing, and "downstream" refers to the direction toward which the fluid is flowing.

[0041] Unless otherwise specified herein, the terms "coupled," "fixed," "attached to," and the like refer to both direct coupling, fixing, or attachment as well as indirect coupling, fixing, or attachment via one or more intermediate components or features.

[0042] The singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0043] The term “at least one” in a context such as “at least one of A, B, and C” or “at least one of A, B, or C” means only A, only B, only C, or any combination of A, B, and C.

[0044] Approximate language as used in the entire specification and claims herein is applied to modify any quantitative representation that can allow variation without causing the basic function associated therewith to change. Therefore, the value modified by terms such as "about", "approximately" and "substantially" is not limited to the specified exact value. In at least some cases, approximate language can correspond to the accuracy of the instrument used to measure the value, or the accuracy of the method or machine used to construct or manufacture parts and / or systems. For example, approximate language can refer to within a margin of 1%, 2%, 4%, 10%, 15% or 20%. These approximate margins can be applied to a single value, any endpoint or two endpoints that limit the range of values, and / or the margin of the range between the endpoints.

[0045] Here and throughout the specification and claims, range limitations are combined and interchanged, and unless context or language indicates otherwise, such ranges are identified and include all sub-ranges contained therein. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.

[0046] As used herein, "tertiary flow" refers to a non-primary flow that can increase fluid energy to produce a small amount of total propulsion system thrust. The pressure ratio of the tertiary flow can be higher than the pressure ratio of the primary propulsion flow (e.g., bypass or propeller-driven propulsion flow). Thrust can be generated through a dedicated nozzle or by mixing the airflow through the tertiary flow with the primary propulsion flow or core flow (e.g., mixing into a common nozzle).

[0047] In certain exemplary embodiments, the operating temperature of the airflow through the third stream can be below the maximum compressor discharge temperature of the engine, and more specifically, can be below 350 degrees Fahrenheit (such as below 300 degrees Fahrenheit, such as below 250 degrees Fahrenheit, such as below 200 degrees Fahrenheit, and at least as high as the ambient temperature). In certain exemplary embodiments, these operating temperatures can promote heat transfer to or from the airflow through the third stream and the separate fluid stream. In addition, in certain exemplary embodiments, under takeoff conditions, or more specifically, when operating at sea level rated takeoff power, static flight speed, 86 degrees Fahrenheit ambient temperature operating conditions, the airflow through the third stream can contribute less than 50% of the total engine thrust (and at least, for example, 2% of the total engine thrust).

[0048] Moreover, in certain exemplary embodiments, aspects of the airflow through the third stream (e.g., airflow, mixing, or exhaust properties), and thereby the above-described exemplary percentage contributions to total thrust, can be passively adjusted during engine operation or purposefully modified through the use of engine control features (such as fuel flow, motor power, variable stators, variable inlet guide vanes, valves, variable exhaust geometry, or flow characteristics) to adjust or optimize overall system performance over a wide range of potential operating conditions.

[0049] The terms “turbomachine” or “turbomachine” refer to a machine that includes one or more compressors, a heat generating section (eg, a combustion section), and one or more turbines that together generate a torque output.

[0050] The term "gas turbine engine" refers to an engine having a turbine as all or part of its power source. Example gas turbine engines include turbofan engines, turboprop engines, turbojets, turboshaft engines, etc., as well as hybrid-electric versions of one or more of these engines.

[0051] When used with reference to compressors, turbines, shaft or spool components, etc., the terms "low" and "high", or their respective comparatives (e.g., "lower" and "higher", where applicable), refer to relative speeds within the engine unless otherwise specified. For example, a "low turbine" or "low-speed turbine" defines a component that is configured to operate at a lower rotational speed (such as the maximum allowable rotational speed) than a "high turbine" or "high-speed turbine" at the engine.

[0052] As will be discussed in more detail below, a fuel cell is an electrochemical device that can convert the chemical energy of a fuel into electrical energy by an electrochemical reaction of a fuel (e.g., hydrogen) with an oxidant (e.g., oxygen contained in the atmosphere). A fuel cell system can be advantageously used as an energy supply system because it can be considered environmentally superior and efficient compared to at least some existing systems. In order to improve system efficiency and fuel utilization and reduce external water consumption, a fuel cell system can include an anode recirculation loop. Since a single fuel cell can only produce a voltage of about 1V, multiple fuel cells can be stacked together (can be referred to as a fuel cell stack) to produce the required voltage. A fuel cell can include a solid oxide fuel cell (SOFC), a molten carbonate fuel cell (MCFC), a phosphoric acid fuel cell (PAFC), and a proton exchange membrane fuel cell (PEMFC), which are generally named after their respective electrolytes. Each of these fuel cells can have specific benefits in the form of preferred operating temperature ranges, power generation capabilities, efficiency, etc.

[0053] The present disclosure generally relates to a propulsion system having a propeller and a fuel cell assembly operable with the propeller. The propeller may be a gas turbine engine, such as a turbofan engine, and the fuel cell assembly may be integrated into the gas turbine engine.

[0054] The fuel cell assembly includes a fuel cell stack and a gas sensor. The fuel cell stack includes a fuel cell, and the fuel cell includes a cathode and an anode. The gas sensor is configured to sense gas composition data of an output product stream from the cathode, gas composition data of an output product stream from the anode, gas composition data of a fluid surrounding the fuel cell, or a combination thereof to determine fuel cell leak diagnostic information. As used herein, the term "gas composition data" refers to data indicating the percentage of one or more gas components in a fluid stream.

[0055] For example, the gas sensor may be configured to sense gas composition data of an output product stream from the cathode and determine anode-to-cathode cross leakage in response to gas composition data indicating an increase in CO2, H2O, cathode exhaust flow rate, or a combination thereof.

[0056] Furthermore, for example, the gas sensor may be configured to sense gas composition data of an output product stream from the anode and determine cathode to anode cross leakage in response to the gas composition data indicating an increase in N2, anode exhaust flow rate, or a combination thereof.

[0057] In addition, for example, the gas sensor may be configured to sense gas composition data of a fluid surrounding the fuel cell and, in response to the gas composition data indicating a reduction in O2 in the fluid, determine an outward leakage from the anode if the O2% is less than the O2% at the cathode exhaust, or determine an outward leakage from the cathode if the O2% is greater than the O2% at the cathode exhaust.

[0058] The gas sensor may be a multi-gas sensor for sensing the above data in line with the above flow.

[0059] A system including one or more of these exemplary aspects can provide an improved fuel cell assembly because the fuel cell assembly can be configured to sense the data required to accurately and quickly determine any leakage information to minimize damage and increase the life of the fuel cell assembly. In addition, the method including the present disclosure can provide timely feedback on the status of the fuel cell for any automatic / autonomous remedial control, which may be particularly important for aircraft usage scenarios. It can also provide service / repair data and root cause analysis to trace back which specific part in the fuel cell failed, which makes it possible to provide quality feedback to the fuel cell production line.

[0060] Referring now to the drawings, wherein like numerals refer to like elements throughout the several views, 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 incorporated into a vehicle. For example, the engine can be an aero engine incorporated into an aircraft. However, alternatively, the engine can be any other suitable type of engine for any other suitable vehicle.

[0061] For the depicted embodiment, the engine is configured as a high bypass turbofan engine 100. Figure 1 As shown, the turbofan engine 100 defines an axial direction A (extending parallel to a centerline axis 101 for reference), a radial direction R, and a circumferential direction (extending around the axial direction A; not shown in FIG. Figure 1 ). Generally, the turbofan engine 100 includes a fan section 102 and a turbine 104 disposed downstream of the fan section 102 .

[0062] The depicted exemplary turbine 104 generally includes a substantially tubular casing 106 defining an annular inlet 108. The casing 106 encloses in serial flow relationship: a compressor section, which includes a boost or low pressure (LP) compressor 110 and a high pressure (HP) compressor 112; a combustion section 114; a turbine section, which includes a high pressure (HP) turbine 116 and a low pressure (LP) turbine 118; and an ejection exhaust nozzle section 120. The compressor section, the combustion section 114, and the turbine section together at least partially define a core air flow path 121 extending from the annular inlet 108 to the ejection 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.

[0063] For the depicted embodiment, the fan section 102 includes a fan 126 having a plurality of fan blades 128 coupled to a disk 130 in a spaced-apart manner. The plurality of fan blades 128 and the disk 130 are rotatable together about the centerline axis 101 via the LP shaft 124. The disk 130 is covered by a rotatable front hub 132 that is aerodynamically shaped to facilitate airflow through the plurality of fan blades 128. In addition, an annular fan case or outer nacelle 134 is disposed circumferentially around the fan 126 and / or at least a portion of the turbine 104. The nacelle 134 is supported relative to the turbine 104 by a plurality of circumferentially spaced-apart outlet guide vanes 136. A downstream section 138 of the nacelle 134 extends over an outer portion of the turbine 104 so as to define a bypass airflow passage 140 therebetween.

[0064] In this manner, it will be appreciated that the turbofan engine 100 generally includes a first flow (e.g., core air flow path 121) and a second flow (e.g., bypass airflow passage 140) extending parallel to the first flow. In certain exemplary embodiments, the turbofan engine 100 may further define a third flow extending, for example, 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 and a downstream compressor stage configured as a ducted mid-fan. The inlet of the third flow may be positioned between the first compressor stage and the downstream compressor stage.

[0065] Still reference Figure 1 , turbofan engine 100 additionally includes an accessory gearbox 142 and a fuel delivery system 146. Fuel delivery system 146 may be an aircraft fuel supply, such as an aircraft fuel supply for a propulsion system of an aircraft. For the illustrated embodiment, accessory gearbox 142 is located within casing / housing 106 of turbine 104. Furthermore, it will be appreciated that for Figure 1 , the accessory gearbox 142 is mechanically coupled to one or more shafts or spools of the turbine 104 and is capable of rotating with the one or more shafts or spools of the turbine 104. For example, in the exemplary embodiment depicted, the accessory gearbox 142 is mechanically coupled to the HP shaft 122 through a suitable gear train 144 and is capable of rotating with the HP shaft 122. The accessory gearbox 142 can provide power to one or more suitable accessory systems of the turbofan engine 100 during at least certain operations, and can further provide power back to the turbofan engine 100 during other operations. For example, for the illustrated embodiment, the accessory gearbox 142 is coupled to a starter motor / generator 152. The starter motor / generator can be configured to extract power from the accessory gearbox 142 and the turbofan engine 100 during certain operations to generate electricity, and can provide power back to the accessory gearbox 142 and the turbofan engine 100 (e.g., to the HP shaft 122) during other operations to add mechanical work back to the turbofan engine 100 (e.g., for starting the turbofan engine 100).

[0066] In addition, the fuel delivery system 146 generally includes a fuel source 148 (such as a fuel tank) and one or more fuel delivery lines 150. The one or more fuel delivery lines 150 provide a 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. For the described embodiment, the one or more fuel delivery lines 150 provide a fuel flow to the integrated fuel cell and combustor assembly 200.

[0067] However, it will be understood that Figure 1 The exemplary turbofan engine 100 depicted in FIG. 1 is provided as an example only. In other exemplary embodiments, any other suitable gas turbine engine may be used with aspects of the present disclosure. For example, in other embodiments, the turbofan engine may be any other suitable gas turbine engine, such as a turboshaft engine, a turboprop engine, a turbojet engine, etc. In this manner, it will be further understood that in other embodiments, the gas turbine engine may have any other suitable configuration, such as any other suitable number or arrangement of shafts, compressors, turbines, fans, etc. In addition, although Figure 1 The exemplary gas turbine engine depicted in is schematically shown as a direct drive fixed pitch turbofan engine, but in other embodiments, the gas turbine engine of the present disclosure may be a geared gas turbine engine (i.e., including a gearbox between the fan 126 and a shaft driving the fan (such as the LP shaft 124)), may be a variable pitch gas turbine engine (i.e., including a fan 126 having a plurality of fan blades 128 that are rotatable about their respective pitch axes), etc. In addition, 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. In addition, 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.

[0068] Reference now Figure 2 , schematically illustrating a portion of the combustion section 114 according to an embodiment of the present disclosure, which includes Figure 1 The gas turbine engine 100 (described above with respect to Figure 1 A portion of an integrated fuel cell and combustor assembly 200 for use in a turbofan engine 100 is depicted.

[0069] It will be appreciated that the combustion section 114 includes a compressor diffuser nozzle 202 and generally extends between upstream and downstream ends in an axial direction A. The combustion section 114 is fluidly coupled to the compressor section at the upstream end via the compressor diffuser nozzle 202 and to the turbine section at the downstream end.

[0070] The integrated fuel cell and combustor assembly 200 generally includes a fuel cell assembly 204 ( Figure 2 only partially described in ; see also Figures 3 to 5) and a combustor 206. 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 an outer shell 220 outside the combustor 206 in a radial direction R to surround the combustor 206, and an inner shell 222 inside the combustor 206 in a radial direction R. The inner shell 222 and the inner liner 208 define an inner passage 224 therebetween, while the outer shell 220 and the outer liner 210 define an outer passage 226 therebetween. The inner shell 222, the outer shell 220, and the dome assembly 212 together at least partially define a combustion chamber 228 of the combustor 206.

[0071] The dome assembly 212 is disposed proximate 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 a swirler assembly 216. The swirler assembly 216 also includes an opening for receiving and retaining a fuel flow line 218. The fuel flow line 218 is further coupled to a fuel source 148 disposed outside of the housing 220 in the radial direction R (see FIG. Figure 1 ), and is configured to receive fuel from fuel source 148. In this manner, fuel flow line 218 can be fluidly coupled to the fuel source 148 described above with reference to Figure 1 One or more fuel delivery lines 150 are depicted.

[0072] The swirler assembly 216 may include a plurality of swirlers (not shown) configured to swirl the compressed fluid prior to injecting the compressed fluid into the combustion chamber 228 to generate combustion gases. In the illustrated embodiment, the hood assembly 214 is configured to hold the liner 208, the outer liner 210, the swirler assembly 216, and the dome assembly 212 together.

[0073] 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 swirler assembly 216 and combust within the combustion chamber 228 to generate combustion gases. The combustion gases are provided to the turbine section to drive one or more turbines (e.g., the high pressure turbine 116 and the low pressure turbine 118) of the turbine section.

[0074] During operation of the gas turbine engine 100 including the integrated fuel cell and combustor assembly 200, a 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 startup of the gas turbine engine 100, the integrated fuel cell and combustor assembly 200 further includes an igniter 231. The igniter 231 may provide a spark or initial flame to ignite the fuel and air mixture within the combustion chamber 228. In certain exemplary embodiments, the integrated fuel cell and combustor assembly 200 may additionally include a dedicated fuel cell igniter 233 (depicted in dashed lines). In particular, for Figure 2 In an embodiment of the invention, the dedicated fuel cell igniter 233 is positioned downstream of at least a portion of the fuel cell, and in particular the fuel cell stack (described below). In this way, the dedicated fuel cell igniter 233 can more efficiently burn the output products of the fuel cell.

[0075] As mentioned above and Figure 2 Schematically depicted in FIG, the integrated fuel cell and combustor assembly 200 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 with an outer liner 210, and the second fuel cell stack 234 is constructed with an inner liner 208. Still 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.

[0076] For the described embodiment, the fuel cell assembly 204 is configured as a solid oxide fuel cell ("SOFC") assembly, wherein the first fuel cell stack 232 is configured as a first SOFC fuel cell stack and the second fuel cell stack 234 is configured as a second SOFC fuel cell stack (each having multiple SOFCs). It will be understood that a SOFC is generally an electrochemical conversion device that produces electricity directly by oxidizing a fuel. In general, fuel cell assemblies, and fuel cells in particular, are characterized by the electrolyte materials used. The SOFC of the present disclosure can generally include solid oxide or ceramic electrolytes. Such fuel cells generally exhibit high overall thermoelectric efficiency, long-term stability, fuel flexibility, and low emissions.

[0077] In addition, 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 in electrical communication with the first power converter 236 via a first plurality of power cables (not labeled), and the second fuel cell stack 234 is in electrical communication with the second power converter 238 via a second plurality of power cables (not labeled).

[0078] The first power converter 236 controls the current drawn from the corresponding first fuel cell stack 232 and can convert power from direct current (“DC”) power to DC power at another voltage level or alternating current (“AC”) power. Similarly, the second power converter 238 controls the current drawn from the second fuel cell stack 234 and can convert power from DC power to DC power at another voltage level or AC power. The first power converter 236, the second power converter 238, or both can be electrically coupled to an electrical bus (such as the electrical bus 326 described below).

[0079] The integrated fuel cell and combustor assembly 200 further includes a fuel cell controller 240 that is in operative communication with the first power converter 236 and the second power converter 238 to, for example, send and receive communications and signals therebetween. For example, the fuel cell controller 240 may send current or power set point signals to the first power converter 236 and the second power converter 238 and may receive, for example, voltage or current feedback signals from the first power converter 236 and the second power converter 238. The fuel cell controller 240 may be configured to communicate with the first power converter 236 and the second power converter 238 in a manner similar to that described below with reference to Figure 5 The controller 240 is constructed in the same manner as described.

[0080] It will be appreciated 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., a direction extending about the centerline axis 101 of the gas turbine engine 100). For example, referring now to Figure 3 , depicts a simplified cross-sectional view of an integrated fuel cell and burner assembly 200, according to an exemplary embodiment of the present disclosure. Although for simplicity, Figure 3 Only the first fuel cell stack 232 is depicted in FIG. 1 , but the second fuel cell stack 234 may be constructed in a similar manner.

[0081] As shown, 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 centerline axis 101. More specifically, the first fuel cell stack 232 includes a plurality of fuel cells 242 arranged along the circumferential direction C. Figure 3The fuel cells 242 visible in FIG. 2 may be a single ring of fuel cells 242, wherein the fuel cells 242 are stacked together in the axial direction A (see FIG. 2A ). Figure 2 ) to form the first fuel cell stack 232. In another example, multiple additional rings of fuel cells 242 can be placed on top of each other to form the first fuel cell stack 232 elongated along the centerline axis 101.

[0082] As will be explained in more detail below, reference Figure 5 , the fuel cells 242 in the first fuel cell stack 232 are positioned to receive exhaust air 244 from, for example, the compressor section and fuel 246 from the fuel delivery system 146. The fuel cells 242 use the air 244 and at least some of the fuel 246 to generate electricity, and direct the partially oxidized fuel 246 and the unused portion of the air 248 radially toward the centerline axis 101 into the combustion chamber 228. The integrated fuel cell and combustor assembly 200 combusts the partially oxidized fuel 246 and the air 248 in the combustion chamber 228 into combustion gases, which are directed downstream into the turbine section to drive or assist in driving one or more turbines therein.

[0083] In addition, now refer to Figure 4 , provided as Figure 2 Schematic diagram of a perspective view of a first fuel cell stack 232 of an integrated fuel cell and combustor assembly 200. A second fuel cell stack 234 may be formed in a similar manner.

[0084] The depicted first fuel cell stack 232 includes a housing 250 having a combustion outlet side 252 and a side 254 opposite the combustion outlet side 252, a fuel and air inlet side 256 and a side 258 opposite the fuel and air inlet side 256, and sides 260, 262. Side 260, side 258, and side 254 are Figure 4 Not visible in the stereogram.

[0085] It will be appreciated that the first fuel cell stack 232 may include, for example, a plurality of fuel cells "stacked" side by side from one end of the first fuel cell stack 232 (e.g., the fuel and air inlet side 256) to the other end of the first fuel cell stack 232 (e.g., the side 258). Thus, it will be further appreciated that the combustion outlet side 252 includes a plurality of combustion outlets 264, each from a fuel cell in the first fuel cell stack 232. During operation, combustion gases 266 (also referred to herein as "output products") are directed out of the housing 250 from the combustion outlets 264. As described herein, the combustion gases 266 are generated using fuel and air that are not consumed by the fuel cells within the housing 250 of the first fuel cell stack 232. The combustion gases 266 are provided to the combustion chamber 228 and are combusted during operation to generate combustion gases, which are used to generate thrust for the gas turbine engine 100 (and a vehicle / aircraft incorporating the gas turbine engine 100).

[0086] 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 can be on the other side of the housing 250. Each of the one or more fuel inlets 268 is fluidly connected to a fuel source for the first fuel cell stack 232 (such as one or more pressurized containers of hydrogen-containing gas or a fuel processing unit further described below). Each of the one or more air inlets 270 is fluidly connected to a source of air for the fuel cell (such as air exhausted from a compressor section and / or an air processing unit also further described below). One or more inlets 268, 270 receive fuel and air from an external fuel and air source separately and direct the fuel and air separately into the fuel cell.

[0087] In certain 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 in, for example, U.S. Patent Application Publication No. 2020 / 0194799A1 filed on 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 may be configured in a similar manner as the first fuel cell stack 232 , or alternatively, may be configured in any other suitable manner.

[0088] Reference now Figure 5 , the operation of the integrated fuel cell and burner assembly 200 according to an exemplary embodiment of the present disclosure will be described. More specifically, Figure 5A schematic diagram of a gas turbine engine 100 and an integrated fuel cell and combustor assembly 200 according to an embodiment of the present disclosure is provided. In certain exemplary embodiments, the gas turbine engine 100 and the integrated fuel cell and combustor assembly 200 may be configured in a manner similar to that of FIG. Figures 1 to 4 One or more exemplary embodiments in are constructed in a similar manner.

[0089] Thus, it will be appreciated that gas turbine engine 100 generally includes fan section 102 having fan 126, LP compressor 110, HP compressor 112, combustion section 114, HP turbine 116, and LP turbine 118. Combustion section 114 generally includes integrated fuel cell and combustor assembly 200 having combustor 206 and fuel cell assembly 204.

[0090] 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 of fuel (e.g., hydrocarbon fuel, including, for example, carbon neutral fuel or synthetic hydrocarbons) for the gas turbine engine 100. In addition, it will be understood that the fuel delivery system 146 also includes a fuel pump 272 and a flow divider 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 150C. The flow divider 274 divides the fuel flow from the fuel source 148 and the fuel pump 272 into a first fuel flow to the fuel cell assembly 204 through the first fuel delivery line 150A, a second fuel flow to the fuel cell assembly 204 (and in particular to the air handling unit described below) through the second fuel delivery line 150B, and a third fuel flow to the burner 206 through the third fuel delivery line 150C. The flow divider 274 may include a series of valves (not shown) to facilitate such diversion of the fuel flow from the fuel source 148, or alternatively, may have a fixed geometry. In addition, for the illustrated embodiment, the 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).

[0091] Gas turbine engine 100 further includes a compressor discharge system and an air flow delivery system. More specifically, the compressor discharge 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 .

[0092] The gas turbine engine 100 further includes an air flow supply conduit 288 (in air flow communication with an air flow supply 290) and an associated air valve 292, which is also in air flow communication with the air flow delivery system, for providing a compressed air flow to the fuel cell assembly 204 of the integrated fuel cell and combustor assembly 200. The air flow supply 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), etc. The air flow supply may be a supplement to the compressor bleed system if a compressor air source is insufficient or unavailable.

[0093] The compressor discharge system (and gas flow supply conduit 288) is in gas flow communication with the gas flow delivery system for providing a compressed gas flow to the fuel cell assembly 204, as will be explained in greater detail below.

[0094] Still reference Figure 5 The fuel cell assembly 204 of the integrated fuel cell and burner assembly 200 includes a fuel cell stack 294, which can be constructed in a similar manner 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 as an electrolyte layer) positioned therebetween. It will be generally understood that the electrolyte 300 can conduct negative oxygen ions from the cathode side 296 to the anode side 298 during operation to generate electrical current and electricity.

[0095] In short, it will be understood that the fuel cell assembly 204 also includes a fuel cell sensor 302, which is configured to sense data indicating fuel cell assembly operating parameters such as the temperature of the fuel cell stack 294 (e.g., the temperature of the cathode side 296 or anode side 298 of the fuel cell), the pressure within the fuel cell stack 294 (e.g., the pressure 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.

[0096] The anode side 298 can support an electrochemical reaction that generates electricity. The fuel can be oxidized in the anode side 298 using oxygen ions received from the cathode side 296 via diffusion through the electrolyte 300. The reaction can produce heat, steam, and electricity in the form of free electrons in the anode side 298, which can be used to power energy consumption devices (such as one or more additional electrical devices 328 described below). Oxygen ions can be produced via oxygen reduction of the cathode oxidant using electrons returned from the energy consumption device to the cathode side 296.

[0097] 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 the fuel cell system uses when generating electricity. The cathode side 296 can be permeable to oxygen ions received from the cathode oxidant.

[0098] The electrolyte 300 may be in communication with the anode side 298 and the cathode side 296. The electrolyte 300 may allow oxygen ions to pass from the cathode side 296 to the anode side 298, and may have little or no conductivity to prevent free electrons from passing from the cathode side 296 to the anode side 298.

[0099] The anode side of a solid oxide fuel cell such as the fuel cell stack 294 may be composed of a nickel / yttria-stabilized zirconia (Ni / YSZ) cermet. The nickel in the anode side serves as a catalyst and current conductor for fuel oxidation. During normal operation of the fuel cell stack 294, the operating temperature may be greater than or equal to about 700° C., and the nickel (Ni) in the anode remains in its reduced form due to the continuous supply of primarily hydrogen fuel gas.

[0100] The fuel cell stack 294 is disposed downstream of the LP compressor 110, the HP compressor 112, or both. Figure 2 It will be understood from the description that the fuel cell stack 294 can be coupled to or otherwise integrated with a liner (e.g., inner liner 208 or outer liner 210) of the combustor 206. In this manner, the fuel cell stack 294 can also be arranged upstream of the combustion chamber 228 of the integrated fuel cell and combustor assembly 200, and further arranged upstream of the HP turbine 116 and the LP turbine 118.

[0101] like Figure 5As 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 can include a fuel reformer or a catalytic partial oxidation converter (CPOx) for generating a hydrogen-rich fuel stream for the fuel cell stack 294. The air processing unit 306 can be any suitable structure for raising the temperature of the air provided thereto to a temperature high enough to achieve fuel cell temperature control (e.g., about 600° C. to about 800° C.). For example, in the described embodiment, the air processing unit includes a pre-combustor system that operates based on a fuel stream through the second fuel delivery line 150B and is configured to, for example, increase the temperature of the air by combustion during transient conditions (such as startup, shutdown, and abnormal conditions).

[0102] In the exemplary embodiment depicted, fuel processing unit 304 and air processing unit 306 are manifolded together within housing 308 to provide conditioned air and fuel to fuel cell stack 294 .

[0103] 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, autothermal reformers, and steam reformers, which may require an additional steam inlet flow with a higher hydrogen content at the reformer outlet flow. 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 5 The air handling unit 306 may alternatively be a heat exchanger or another device for raising the temperature of the air provided thereto to a temperature high enough to achieve fuel cell temperature control (eg, about 600° C. to about 800° C.).

[0104] As described above, the compressor discharge system (and the airflow supply conduit 288) is in airflow communication with the airflow delivery system for providing a compressed airflow to the fuel cell assembly 204. The airflow delivery system includes an anode airflow conduit 310 and an associated anode airflow valve 312 for providing airflow to the fuel processing unit 304, a cathode airflow conduit 314 and an associated cathode airflow valve 316 for providing airflow to the air handling unit 306, and a cathode bypass air conduit 318 and an associated cathode bypass air valve 320 for providing airflow directly to the fuel cell stack 294 (or more specifically, 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 to provide a second fuel flow (e.g., if provided, as a fuel for a pre-combustor system) to the air handling unit 306 via a second fuel delivery line 150B.

[0105] Fuel cell stack 294 outputs generated electricity as fuel cell power output 322. In addition, fuel cell stack 294 directs a cathode air exhaust and an anode fuel exhaust (neither labeled for clarity) into combustion chamber 228 of combustor 206.

[0106] In operation, the air handling unit 306 is configured to heat / cool a portion of the compressed air entering through the cathode air flow conduit 314 to generate processed air to be directed into the fuel cell stack 294, thereby facilitating the functioning of the fuel cell stack 294. The air handling unit 306 receives a second fuel stream from the second fuel delivery line 150B, and may, for example, combust such a second fuel stream to heat the received air to a desired temperature (e.g., about 600° C. to about 800° C.), thereby facilitating the functioning of the fuel cell stack 294. The air processed by the air handling unit 306 is directed into the fuel cell stack 294. In an embodiment of the present disclosure, as shown, the cathode bypass air conduit 318 and the air processed by the air handling unit 306 may be combined into a combined air stream to be fed into the cathode of the fuel cell stack 294.

[0107] In addition, if Figure 5 , the first fuel flow through the first fuel delivery line 150A is directed to the fuel processing unit 304 for use in producing a hydrogen-rich fuel flow (e.g., optimizing the hydrogen content of the fuel flow) to also be fed into the fuel cell stack 294. It will be appreciated, and as discussed below, that the flow of air (process air and bypass air) 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.

[0108] Since the inlet air to the fuel cell stack 294 may come only from the upstream compressor section, without any other separately controlled air source, it will be appreciated that the inlet air to the fuel cell stack 294 exhausted from the compressor section may be affected by variations in air temperature that occur during different phases of flight. As an illustrative example only, the air within a particular location in the compressor section of the gas turbine engine 100 may operate at 200° C. during idle, 600° C. during takeoff, 268° C. during cruise, etc. This type of temperature variation of the inlet air directed to the fuel cell stack 294 may cause significant thermal transient issues (or even thermal shock) to the ceramic materials of the fuel cell stack 294, which may range from cracking to failure.

[0109] Thus, by fluidly connecting the air handling unit 306 between the compressor section and the fuel cell stack 294, the air handling unit 306 can be used 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., plus or minus 100°C, or preferably plus or minus 50°C, or plus or minus 20°C). In operation, the temperature of the air provided to the fuel cell stack 294 (relative to the temperature of the air exhausted from the compressor section) can be controlled by controlling the fuel flow to the air handling unit 306. By increasing the fuel flow to the air handling unit 306, the temperature of the air flow to the fuel cell stack 294 can be increased. By reducing the fuel flow to the air handling unit 306, the temperature of the air flow to the fuel cell stack 294 can be reduced. Optionally, fuel cannot be delivered to the air handling unit 306 to prevent the air handling unit 306 from increasing and / or reducing the temperature of the air exhausted from the compressor section and directed into the air handling unit 306.

[0110] In addition, as depicted in dashed lines, the fuel cell assembly 204 further includes an air flow bypass conduit 321 extending around the fuel cell to allow a portion or all of the air flow conditioned by the air handling unit 306 (and combined with any bypass air passing through the conduit 318) to bypass the cathode side 296 of the fuel cell and enter the combustion chamber 228 directly. The air flow bypass conduit 321 can be in thermal communication with the fuel cell. The fuel cell assembly further includes a fuel bypass conduit 323 extending around the fuel cell to allow a portion or all of the reformed fuel from the fuel processing unit 304 to bypass the anode side 298 of the fuel cell and enter the combustion chamber 228 directly.

[0111] As briefly mentioned above, the fuel cell stack 294 converts the anode fuel flow from the fuel processing unit 304 and the air processed by the air processing unit 306 sent to the fuel cell stack 294 into electrical energy in the form of DC current, i.e., the fuel cell power output 322. The fuel cell power output 322 is directed to the power converter 324 so as to change the DC current into a DC current or AC current that can be effectively utilized by one or more subsystems. In particular, for the depicted embodiment, the power is provided from the power converter to the electrical bus 326. The electrical bus 326 can be an electrical bus dedicated to the gas turbine engine 100, an electrical bus of an aircraft incorporating the gas turbine engine 100, or a combination thereof. The electrical bus 326 is electrically connected to one or more additional electrical devices 328, which can be a power source, a power sink, or both. For example, the additional electrical device 328 can be a power storage device (such as one or more batteries), an electric motor (generator, motor, or both), an electric propulsion device, etc. For example, one or more additional electrical devices 328 can include a starter motor / generator of the gas turbine engine 100.

[0112] Still reference 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 indicative of a flame within the combustion section 114 of the gas turbine engine 100, or some other parameter indicative of an operating condition of the gas turbine engine. For example, the sensor 330 may be a temperature sensor configured to sense data indicative of an outlet temperature of the combustion section 114, an inlet temperature of the turbine section, an 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 indicative of a flame within the combustion section 114 of the gas turbine engine 100.

[0113] In addition, if Figure 5 As further schematically depicted in , the propulsion system, the aircraft including the propulsion system, or both include a controller 240. For example, the controller 240 may be an independent controller, a gas turbine engine controller (e.g., a full authority digital engine controller or FADEC controller), an aircraft controller, a supervisory controller for the propulsion system, combinations thereof, and the like.

[0114] The controller 240 is operably 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 aspect depicted, the controller 240 is operably connected to valves of the compressor discharge system (valves 278, 282, 286), valves of the gas flow delivery system (valves 312, 316, 320), and valves of the fuel delivery system 146 (diverter 274, valves 151A, 151B, 151C), as well as sensors 330 and fuel cell sensors 302 of the gas turbine engine 100. It will be understood from the following description that the controller 240 may communicate with these components by wire or wirelessly. In this way, the controller 240 can receive data from various inputs (including the gas turbine engine sensors 330 and the fuel cell sensors 302), can make control decisions, and can provide data (e.g., instructions) to various outputs (including valves of a compressor discharge system that controls the discharge of airflow from the compressor section, valves of an airflow delivery system that directs airflow discharged from the compressor section, and valves of a fuel delivery system 146 that directs fuel flow within the gas turbine engine 100).

[0115] With particular reference to the operation of the controller 240, in at least some embodiments, the controller 240 may include one or more computing devices 332. The computing devices 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 device, such as a microprocessor, a microcontroller, an integrated circuit, a logic device, and / or other suitable processing device. The one or more memory devices 332B may include one or more computer-readable media, including but not limited to non-transitory computer-readable media, RAM, ROM, a hard drive, a flash drive, and / or other memory devices.

[0116] One or more memory devices 332B may store information that can be accessed by one or more processors 332A, including computer-readable instructions 332C that can be executed 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 perform operations. In some embodiments, instructions 332C may be executed by one or more processors 332A to cause one or more processors 332A to perform operations such as any operations and functions that the controller 240 and / or computing device 332 are configured for, operations for operating a propulsion system as described herein (e.g., method 500), 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 separate threads on processor 332A. Memory device 332B may further store data 332D that may be accessed by processor 332A. For example, data 332D may include data indicative of power flow, data indicative of gas turbine engine 100 / aircraft operating conditions, and / or any other data and / or information described herein.

[0117] The computing device 332 also includes a network interface 332E, which is configured to communicate with other components of the gas turbine engine 100, such as valves of the compressor discharge system (valves 278, 282, 286), valves of the air flow delivery system (valves 312, 316, 320), and valves of the fuel delivery system 146 (diverter 274, valves 151A, 151B, 151C), as well as sensors 330 and fuel cell sensors 302 of the gas turbine engine 100, an aircraft incorporating the gas turbine engine 100, etc. The network interface 332E may include any suitable components for interfacing with one or more networks, including, for example, transmitters, receivers, ports, controllers, antennas, and / or other suitable components. In this manner, it will be understood that the network interface 332E may utilize any suitable combination of wired and wireless communication networks.

[0118] The technology discussed herein refers to computer-based systems, actions taken by computer-based systems, and information sent to and from computer-based systems. It will be appreciated that the inherent flexibility of computer-based systems allows for multiple possible configurations, combinations, and divisions of tasks and functionality between and within components. For example, the processing discussed herein can be implemented using a single computing device or multiple computing devices working in combination. Databases, memories, instructions, and applications can be implemented on a single system, or distributed on multiple systems. Distributed components can operate sequentially or in parallel.

[0119] It will be appreciated 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 only as examples. In other embodiments, the integrated fuel cell and combustor assembly 200 and the fuel cell assembly 204 may have any other suitable configurations. 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 provide hydrogen fuel to the integrated fuel cell and combustor assembly 200, particularly to the fuel cell assembly 206, the fuel cell assembly 204 may not require a fuel processing unit 304.

[0120] Reference now Figure 6 , a schematic diagram of a fuel cell assembly 400 having a fuel cell 402 according to an exemplary embodiment of the present disclosure is provided. More specifically, the fuel cell assembly 400 may include a fuel cell stack having the fuel cell 402, and the fuel cell assembly 400 and the fuel cell stack may be similar to those described above with reference to Figures 1 to 5 One or more of the depicted exemplary fuel cell assemblies 204 and fuel cell stacks 294 are constructed in a similar manner.

[0121] In this way, it can be understood that the fuel cell assembly 400 can operate with a propeller of a propulsion system. For example, the fuel cell assembly 400 can be configured to provide power to the propeller, can be configured to provide output products to one or more parts of the propeller, and so on. More specifically, in at least one exemplary embodiment, the propeller can be configured as a gas turbine engine having a combustion section with a burner, and the fuel cell assembly 400 can be configured to provide output products to the burner.

[0122] Alternatively, Figure 6 The exemplary fuel cell assembly 400 may be operated with any other suitable propulsion device, such as an electric propulsion device.

[0123] The exemplary fuel cell 402 includes an anode 404, a cathode 406, and an electrolyte layer 408 located between the anode 404 and the cathode 406. The anode 404 defines an anode inlet 410 and an anode outlet 412, and similarly, the cathode 406 defines a cathode inlet 414 and a cathode outlet 416. During operation, a fuel flow 418 can be provided to the anode inlet 410, and a gas flow 420 can be provided to the cathode inlet 414 to allow the fuel cell 402 to generate the reactions required for electricity. Also during operation, an output product flow 422 from the cathode 406 can flow through the cathode outlet 416, and an output product flow 424 from the anode 404 can flow through the anode outlet 412.

[0124] from Figure 6 It will also be understood that in the exemplary embodiment of the fuel cell assembly 400, the exemplary fuel cell assembly 400 also includes a control system 426 having a controller 428 and a gas sensor 430. The controller 428 can be used in the same manner as described above with reference to Figure 5 The exemplary controller 240 described above is constructed in a similar manner. The gas sensor 430 is operably connected to the controller 428, so that the controller 428 can be configured to receive data from the gas sensor 430 (e.g., via a wired or wireless communication network). The gas sensor 430 is configured to sense gas composition data of the output product stream 422 from the cathode 406, gas composition data of the output product stream 424 from the anode 404, gas composition data of the fluid surrounding the fuel cell 402, or a combination thereof to determine fuel cell leak diagnostic information.

[0125] More specifically, for Figure 6 In an exemplary embodiment of the present invention, the gas sensor 430 is configured to sense the gas composition of the output product stream 424 from the anode 404. The gas sensor 430 is configured to sense the gas composition data in alignment with the output product stream 424 from the anode 404, that is, the gas sensor 430 is configured to sense the gas composition data without requiring any gas to be siphoned off or diverted from the pipe carrying the output product stream 424. In particular, the gas sensor 430 includes a node 431 exposed to the output product stream 424 from the anode 404.

[0126] The gas composition data may include the percentage of nitrogen (or more specifically, nitrogen gas, N2) in the output product 424 from the anode 404. Notably, for the illustrated embodiment, the fuel cell assembly 400 is also configured to sense data indicative of the flow rate of the output product 424 from the anode 404. More specifically, for the illustrated embodiment, the gas sensor 430 is configured to sense data indicative of the flow rate of the output product 424 in the anode 404.

[0127] Sensed data regarding the percentage of nitrogen in the output product 424 from the anode 404 and the flow rate of the output product 424 from the anode 404 may be provided to the controller 428, and the controller 428 may be configured to determine fuel cell leak diagnostic information in response to such sensed data. For example, for an anode fuel composition that does not have any nitrogen (e.g., when the fuel processing unit is configured as a steam reformer rather than a partial oxidizer), the presence of nitrogen in the output product 424 from the anode 404 may indicate a crossover leak 432A from the cathode 406 to the anode 404 (e.g., Figure 6 404; the term "cross leakage" is synonymous with "cross leakage"), because the fuel flow 418 provided to the anode 404 may not include any nitrogen. Similarly, an increase in the flow rate of the output product 424 from the anode 404 without a corresponding increase in the fuel flow 418 to the anode 404 can also indicate a cross leakage 432A from the cathode 406 to the anode 404.

[0128] For example, when the percentage of nitrogen in the output product 424 from the anode 404 is greater than 0, e.g., greater than 0 and up to about 1%, this may indicate a crossover leak 432A from the cathode 406 to the anode 404. An alternative approach to diagnosing a crossover leak 432A may be based on the trends of these detected gas components rather than their absolute values. If the nitrogen concentration or the anode exhaust flow rate increases, the controller may determine a crossover leak 432A from the cathode 406 to the anode 404 and, for example, provide an alarm indicating the crossover leak.

[0129] As described in more detail below, for Figure 8 In embodiments where the gas sensor 430 is configured to sense data indicative of nitrogen content, the gas sensor 430 may use Raman spectroscopy, an optical analysis technique that relies on the measurement of vibrational and rotational properties of molecules.

[0130] Reference now Figure 7 , a fuel cell assembly 400 according to another exemplary embodiment of the present disclosure is provided. Figure 7 The exemplary fuel cell assembly 400 may be similar to that described above with reference to Figure 6 The exemplary fuel cell assembly 400 described is constructed in substantially the same manner. Accordingly, the same or similar numbers may refer to the same or similar components.

[0131] For example, Figure 7 An exemplary fuel cell assembly 400 of illustrative embodiments may generally include a fuel cell 402 having an anode 404 , a cathode 406 , and an electrolyte layer 408 , and a control system 426 having a controller 428 and a gas sensor 430 .

[0132] However, for Figure 7In an exemplary embodiment of the present invention, the gas sensor 430 is configured to sense gas composition data of the output product stream 422 from the cathode 406, aligned with the output product stream 422 from the cathode 406. In particular, the gas sensor 430 includes a node 431 exposed to the output product stream 422 from the cathode 406.

[0133] In certain exemplary aspects, the gas composition data may include a percentage of carbon dioxide (CO2) in the output product 422 from the cathode 406, a percentage of H2O in the output product 422 from the cathode 406, or both. Notably, for the illustrated embodiment, the fuel cell assembly 400 is also configured to sense data indicative of a flow rate of the output product 422 from the cathode 406. More specifically, for the illustrated embodiment, the gas sensor 430 is configured to sense data indicative of a flow rate of the output product in the cathode 406.

[0134] The sensed data related to the percentage of CO2 and H2O in the output product 422 from the cathode 406 and the flow rate of the output product 422 from the cathode 406 can be provided to the controller 428, and the controller 428 can be configured to determine fuel cell leak diagnostic information in response to such sensed data. For example, as will be explained in more detail below, the presence of carbon dioxide, H2O, or both in the output product 422 from the cathode 406 may indicate a crossover leak 432B ( Figure 7 406), because the gas stream 420 provided to the cathode 406 may not include any carbon dioxide or H2O, and these are components present in the anode 404 during operation. Similarly, an increase in the flow rate of the output product 422 from the cathode 406 without an increase in the flow rate of the gas stream 420 provided to the cathode 406 may indicate a cross-leak 432B from the anode 404 to the cathode 406.

[0135] For example, when the percentage of carbon dioxide in the output product 422 from the cathode 406 is greater than 0, such as greater than 0 and up to about 1%, this may indicate a crossover leak 432B from the anode 404 to the cathode 406. Similarly, when the percentage of H2O in the output product 422 from the cathode 406 is greater than 0, such as greater than 0 and up to about 5%, such as up to about 3%, this may also indicate a crossover leak 432B from the anode 404 to the cathode 406. An alternative approach to diagnosing a crossover leak 432B from the anode 404 to the cathode 406 may be based on the trends of these detected gas components rather than their absolute values. For example, if any increase in the percentage of CO2, the percentage of H2O, or the flow rate of the output product 422 from the cathode 406, the controller may determine a crossover leak 432B from the anode 404 to the cathode 406, and, for example, provide an alarm indicating the crossover leak.

[0136] Reference now Figure 8 , a fuel cell assembly 400 according to another exemplary embodiment of the present disclosure is provided. Figure 8 The exemplary fuel cell assembly 400 may be similar to that described above with reference to Figure 7 The exemplary fuel cell assembly 400 described is constructed in substantially the same manner. Accordingly, the same or similar numbers may refer to the same or similar components.

[0137] For example, Figure 8 An exemplary fuel cell assembly 400 of can generally include a fuel cell 402 having an anode 404, a cathode 406, and an electrolyte layer 408, and a control system 426 having a controller 428 and a gas sensor 430, the gas sensor 430 being configured to sense gas composition data of an output product stream 422 from the cathode 406, aligned with the output product stream 422 from the cathode 406. In particular, the gas sensor 430 includes a first node 431A exposed to the output product stream 422 from the cathode 406.

[0138] However, for Figure 8 In the embodiment of the present invention, it should be understood that the fuel cell assembly 400 also includes an outer cover 434 that at least partially surrounds the fuel cell 402, and although not shown, also includes an outer cover 434 that at least partially surrounds the fuel cell stack including the fuel cell 402. The outer cover 434 can be formed by one or more walls positioned around the fuel cell 402 (and the fuel cell stack). For example, when Figure 8 The exemplary fuel cell 402 is incorporated into Figure 2 When in the fuel cell assembly 400 shown and described above, the outer cover 434 can be positioned between the outer liner 210 and the outer shell 222 to protect the fuel cell stack 232 from being exposed to the outer passage 226 (see FIG. Figure 2) The cover 434 can further help maintain the temperature of the fuel cell 402 (and the fuel cell stack) at a desired operating temperature.

[0139] In addition, for Figure 8 In an embodiment of the present invention, the gas sensor 430 is configured to sense gas composition data of a fluid 436 (e.g., gas) surrounding the fuel cell 402, and more specifically, gas composition data of the fluid 436 surrounding the fuel cell 402 within the housing 434. For example, the gas composition data sensed by the gas sensor 430 may further include a percentage of oxygen (O2) in the fluid 436 surrounding the fuel cell 402. In particular, the gas sensor 430 also includes a second node 431B exposed to the fluid 436 surrounding the fuel cell 402. In this manner, it will be appreciated that the concentrations of CO2 and H2O within the output product 422 from the cathode 406 and the concentration of O2 in the fluid 436 surrounding the fuel cell 402 within the housing 434 are measured by a single sensor having more than one electrical output and detecting CO2, H2O, O2 based on a multivariate sensor response. Such a configuration will be further described below.

[0140] Sensed data regarding the percentage of oxygen in the fluid 436 surrounding the fuel cell 402 may also be provided to the controller 428, and the controller 428 may be configured to further determine fuel cell leak diagnostic information in response to such sensed data. For example, if the percentage of oxygen in the fluid 436 surrounding the fuel cell 402 is increasing, and further, if the percentage of oxygen in the fluid 436 surrounding the fuel cell 402 is greater than the percentage of oxygen in the output product 422 from the cathode 406, this may indicate an outward leak 432C from the cathode 406, such as an upstream outward leak near the cathode inlet 414 or a downstream outward leak near the cathode outlet 416. Further, for example, if the percentage of oxygen in the fluid 436 surrounding the fuel cell 402 is decreasing, and further, if the percentage of oxygen in the fluid 436 surrounding the fuel cell 402 is less than the percentage of oxygen in the output product 422 from the cathode 406, this may indicate an outward leakage 432D from the anode 404, such as an upstream outward leakage near the anode inlet 410 or a downstream outward leakage near the anode outlet 412.

[0141] It is worth noting that for Figure 8 In an embodiment, the sensor 430 may be used in the same manner as described above with reference to Figure 7 The crossover leakage 432B from the anode 404 to the cathode 406 is determined in a similar manner as described above.

[0142] Reference now Fig. 9 , a fuel cell assembly 400 according to another exemplary embodiment of the present disclosure is provided. Fig. 9 The exemplary fuel cell assembly 400 may be similar to that described above with reference to Figure 8 The exemplary fuel cell assembly 400 described is constructed in substantially the same manner. Accordingly, the same or similar numbers may refer to the same or similar components.

[0143] For example, Fig. 9 The exemplary fuel cell assembly 400 may generally include a fuel cell 402 having an anode 404 , a cathode 406 , and an electrolyte layer 408 ; a control system 426 having a controller 428 and a gas sensor 430 ; and an enclosure 434 at least partially surrounding the fuel cell 402 .

[0144] However, for Fig. 9 In an embodiment of the present invention, the gas sensor 430 is located outside of the housing 434, such that the gas sensor 430 is configured to sense gas composition data of the output product stream 422 from the cathode 406 from a location outside of the housing 434. In this manner, the gas sensor 430 can be exposed to a less harsh environment, such as an environment having a lower temperature, pressure, or both, relative to a location within the housing 434 during operation.

[0145] It is worth noting that for Fig. 9 In the configuration of FIG. 4 , the control system 426 may include a dedicated sensor for sensing gas composition data within the housing 434. More specifically, for Fig. 9 In an embodiment of the present invention, the control system 426 includes a dedicated oxygen sensor 438 located within the housing 434 for sensing gas composition data within the fluid 436 surrounding the fuel cell 402, and more specifically, sensing the percentage of oxygen within the liquid 436 surrounding the fuel cell 402. The dedicated oxygen sensor 438 is in operative communication with the controller 428 to provide the controller 428 with gas composition data of the fluid 436 surrounding the fuel cell 402, thereby allowing the controller 428 to determine fuel cell leak diagnostic information.

[0146] Reference now Fig.10 , a fuel cell assembly 400 according to another exemplary embodiment of the present invention is provided. Fig.10 The exemplary fuel cell assembly 400 may be similar to that described above with reference to Fig. 9 The exemplary fuel cell assembly 400 described is constructed in substantially the same manner. Accordingly, the same or similar numbers may refer to the same or similar components.

[0147] For example, Figure 7An exemplary fuel cell assembly 400 of the embodiment of the present invention may generally include a fuel cell 402 having a cathode 406 and an anode 404; a control system 426 having a controller 428, a gas sensor 430 configured to sense gas composition data of an output product stream 422 from the cathode 406, and a dedicated oxygen sensor 438; and an enclosure 434. The gas sensor 430 is positioned outside the enclosure 434, while the dedicated oxygen sensor 438 is positioned inside the enclosure 434.

[0148] However, for Fig.10 In the exemplary embodiment, the gas sensor 430 is further configured to sense gas composition data of the output product stream 424 from the anode 404. More specifically, for the depicted exemplary embodiment, the gas sensor 430 includes a first gas sensor 430A having a first node 431A configured to sense gas composition data of the output product stream 422 from the cathode 406 and a second gas sensor 430B having a second node 431B configured to sense gas composition data of the output product stream 424 from the anode 404.

[0149] It is worth noting that the gas composition data from the first gas sensor 430A can be compared with the above reference Figure 7 The gas composition data from the second gas sensor 430B may be the same as or similar to the gas composition data described above. Figure 6 In this manner, the control system 426 can be configured to sense fuel cell leak diagnostic information associated with a crossover gas leak 432B from the anode 404 to the cathode 406 in the fuel cell 402 (based on data sensed from the first gas sensor 430A); a crossover gas leak 432A from the cathode 406 to the anode 404 in the fuel cell 402 (based on data sensed from the second gas sensor 430B); an outward gas leak 432D from the anode 404 in the fuel cell 402; an outward gas leak 432C from the cathode 406; or any combination thereof.

[0150] It should be understood that Fig.10 In the exemplary embodiment of the present invention, the first gas sensor 430A and the second gas sensor 430B are each positioned outside the housing 434 of the fuel cell assembly 400. However, in other exemplary embodiments, one or both of the first gas sensor 430A and the second gas sensor 430B may alternatively be positioned within the housing 434. For example, referring briefly to Fig.11 An embodiment, which can be Fig.10Otherwise constructed in substantially the same manner as the exemplary embodiment of the present invention, the first gas sensor 430A and the second gas sensor 430B are positioned within the housing 434 of the fuel cell assembly 400 .

[0151] Furthermore, it should be understood that although Fig.10 and 11 In the exemplary embodiment of the present invention, the fuel cell assembly 400, and more specifically the control system 426, includes a first gas sensor 430A, a second gas sensor 430B, and a dedicated oxygen sensor 438, but in other embodiments, two or more of these sensors may be integrally formed into a single sensor.

[0152] For example, briefly refer to Fig.12 , Fig.12 Can be used with Fig.11 In a similar manner to the exemplary embodiment of the present invention, the fuel cell assembly 400 includes a control system 426 having a gas sensor 430 configured to sense gas composition data of the output product stream 424 from the anode 404, configured to sense gas composition data of the output product stream 422 from the cathode 406, and configured to sense gas composition data of the fluid 436 surrounding the fuel cell 402. In particular, for Fig.12 In an embodiment, the fuel cell assembly 400 includes a gas sensor 430, which is configured to sense gas composition data of an output product flow 422 from a cathode 406 through a first node 431A, is configured to sense gas composition data of an output product flow 424 from an anode 404 through a second node 431B, and is configured to sense gas composition data of a fluid 436 surrounding the fuel cell 402 through a third node 431C.

[0153] In addition, for Fig.12 In the embodiment of the present invention, the gas sensor 430 is located within the outer cover 434.

[0154] Also as an example, briefly refer to Fig.13 , Fig.13 Can be used with Fig.10 In a similar manner to the exemplary embodiment of the present invention, the fuel cell assembly 400 includes a control system 426 having a gas sensor 430 configured to sense gas composition data of the output product stream 424 from the anode 404 and configured to sense gas composition data of the output product stream 422 from the cathode 406. In addition, for Fig.13 In an embodiment of the present invention, the gas sensor 430 is positioned outside the housing 434 , and the control system 426 also includes a dedicated oxygen sensor 438 located inside the housing 434 .

[0155] Reference now Fig.14 , a flowchart of a method 500 for determining fuel cell leak diagnostic information according to an exemplary aspect of the present disclosure is provided. The method 500 may be used in the above reference Figures 1 to 13 Thus, the method 500 can be used with a fuel cell assembly having a control system having a gas sensor configured to sense gas composition data of an output product stream from a cathode of a fuel cell (of a fuel cell stack), gas composition data of an output product stream from an anode of a fuel cell, gas composition data of a fluid surrounding the fuel cell, or a combination thereof.

[0156] Method 500 generally entails receiving gas composition data of an output product stream from a cathode, gas composition data of an output product stream from an anode, gas composition data of a fluid surrounding a fuel cell, or a combination thereof from a gas sensor; and determining fuel cell leak diagnostic information in response to the received gas composition data.

[0157] More specifically, for the exemplary aspects of the described method 500, the method 500 includes detecting a trigger at (502). Detecting a trigger at (502) may include detecting an anomaly of a fuel cell assembly, such as detecting an uncommanded change in voltage from a fuel cell and / or fuel cell stack, resistance from a fuel cell and / or fuel cell stack, temperature of a fuel cell and / or fuel cell stack, pressure to or from a fuel cell and / or fuel cell stack or one or more flows within a fuel cell and / or fuel cell stack, and the like.

[0158] The method 500 further includes collecting gas composition data at (504). In particular, for the depicted aspects, collecting gas composition data at (504) may be responsive to a trigger detected at (502). Collecting gas composition data at (504) may include collecting gas composition data using one or more sensors, such as a gas sensor (e.g., a multi-gas sensor), a dedicated oxygen sensor, etc.

[0159] The method 500 further includes initiating an outward leak diagnostic at (508), and initiating a cross leak diagnostic at (510). Fig.15 Various aspects of the outbound leak diagnostic initiated at (508) are described in more detail and will be referenced below. Fig.16 Various aspects of the cross-leak diagnostic initiated at ( 510 ) are described in greater detail.

[0160] Notably, as indicated by the dashed line, the method 500 may include determining at (506) whether the percentage of oxygen within the enclosure at least partially surrounding the fuel cell and the fuel cell stack is increasing based on the collected gas composition data. If it is determined at (506) that the percentage of oxygen within the enclosure is increasing, the method 500 may initiate an outward leak diagnostic at (508), and if not, the method 500 may exclude the outward leak and perform a cross leak diagnostic at (510). Notably, the method may proceed to the cross leak diagnostic at (510) even if it is determined at (506) that the percentage of oxygen within the enclosure is increasing.

[0161] refer to Fig.15 In response to initiating the external leakage diagnostic at (508), method 500 also includes determining (512) whether the percentage of oxygen within the housing is greater than the percentage of oxygen within the output product stream from the cathode based on the collected gas composition data. If it is determined at (512) that the percentage of oxygen within the housing is less than the percentage of oxygen within the output product stream from the cathode, method 500 determines at (514) that the fuel cell is experiencing an anode external leakage. Conversely, if it is determined at (512) that the percentage of oxygen within the housing is greater than the percentage of oxygen within the output product stream from the cathode, method 500 determines at (516) that the fuel cell is experiencing a cathode external leakage.

[0162] Reference now Fig.16 In response to initiating a cross leak diagnostic at (510), the method includes determining at (518) whether a percentage of nitrogen within an output product stream from an anode of the fuel cell is increasing or exceeding a threshold. If it is determined at (518) that the percentage of nitrogen within the output product stream from the anode is increasing or exceeding a threshold, the method 500 also includes determining at (520) whether a percentage of carbon dioxide within the output product stream from the cathode is increasing or exceeding a threshold, whether a percentage of H2O within the output product stream from the cathode is increasing or exceeding a threshold, or both. If it is determined at (520) that one or both of the percentages of carbon dioxide or H2O within the output product stream from the cathode are increasing or exceeding a threshold, the method 500 includes determining at (522) that the fuel cell is experiencing anode-to-cathode cross leak and cathode-to-anode cross leak.

[0163] In particular, an increase in the percentage of nitrogen within the output product stream from the anode, or the presence of nitrogen within the output product stream from the anode exceeding a certain threshold, may indicate a cathode to anode cross-leakage because during operation of the fuel cell assembly, nitrogen will not be part of the fuel provided to the anode of the fuel cell. Similarly, an increase in the percentage of carbon dioxide or H2O within the output product stream from the cathode, or the presence of carbon dioxide or H2O within the output product stream from the cathode exceeding a certain threshold, may indicate an anode to cathode cross-leakage because during operation of the fuel cell assembly, neither carbon dioxide nor H2O will be part of the gas stream provided to the cathode of the fuel cell.

[0164] Still reference Fig.16 In the exemplary aspects of method 500 shown in , it should be understood that if it is determined that neither the percentage of carbon dioxide nor the percentage of H2O within the output product stream from the cathode is increasing or exceeding the respective thresholds, as determined at (520), then method 500 can determine at (524) that the fuel cell is only experiencing cathode to anode cross leakage (due to the percentage of nitrogen within the output product stream from the anode determined at (518)).

[0165] Additionally, if it is determined at (518) that the percentage of nitrogen within the output product stream from the anode is not increasing or is not above a threshold, method 500 may still check for cathode to anode leakage by determining if the flow rate of the output product from the anode is increasing at (526). If the flow rate of the output product from the anode is increasing, as determined at (526), ​​method 500 may again determine at (524) that the fuel cell is experiencing cathode to anode cross leakage.

[0166] After the determination at (526), ​​whether the determination is "yes" or "no", the method includes determining whether the flow rate of the output product from the cathode is increasing at (528). If it is determined at (528) that the flow rate of the output product from the cathode is increasing, the method includes determining at (530) that the fuel cell is experiencing anode-to-cathode cross leakage.

[0167] If it is determined at (528) that the flow rate of the output product from the cathode is not increasing, the method 500 includes determining at (532) whether the percentage of HO, carbon dioxide, or both within the output product stream from the cathode is increasing (similar to the determination at (520)). If it is determined at (532) that the percentage of HO, carbon dioxide, or both is increasing, the method again includes determining at (530) that the fuel cell is experiencing anode-to-cathode cross leakage.

[0168] However, if it is determined at (532) that the percentage of H2O, carbon dioxide, or both within the output product stream from the cathode is not increasing, the method determines at (534) that the fuel cell is not experiencing cross leak.

[0169] It should be understood that the above reference Figures 14 to 16 The described exemplary method 500 is provided as an example only. In other exemplary aspects of the present disclosure, method 500 may not include each of the above steps, and may also include the above queries in any other suitable order. For example, in other exemplary aspects where method 500 may operate with a fuel cell assembly without the ability to sense gas composition data of an output product stream from a cathode, method 500 may not include one or more of (520), (528), (532), etc. Similarly, in other exemplary aspects where method 500 may operate with a fuel cell assembly without the ability to sense gas composition data of an output product stream from an anode, method 500 may not include one or more of (518), (526). Furthermore, in other exemplary aspects where method 500 may operate with a fuel cell assembly without the ability to sense gas composition data of a fluid surrounding the fuel cell, the method may not include (508) or Fig.15 Other aspects of the method 500 are shown in .

[0170] Similarly, as described above, in other exemplary aspects, method 500 can include the above queries in any other suitable order. For example, in other exemplary aspects, one or more of (518), (520), and (532), (526), ​​and (528) can be performed in parallel.

[0171] In addition, it can be further understood from the following description that method 500 can occur in real time. For example, in certain exemplary aspects, receiving gas composition data (or collecting gas composition data at (504)) can include receiving data at a resolution of 1 minute or less. For example, in certain exemplary aspects, receiving gas composition data (or collecting gas composition data at (504)) can more specifically include receiving data at a resolution of 30 seconds or less, such as 15 seconds or less or 5 seconds or less. In this way, the gas sensor used at (504) can be configured to sense gas composition data in real time. In addition, it should be understood that when the gas sensor is used at a resolution similar to, for example, Figures 6 to 13 When constructed in one or more similar manners, collecting gas composition data at (504) can be performed in situ.

[0172] In this way, the method may be able to make control decisions based on data collected 1 minute in advance or faster.

[0173] It should be understood that the gas sensor described above can be any suitable gas sensor for detecting gas composition data of the output product from the cathode of the fuel cell, gas composition data of the output product flow from the anode of the fuel cell, gas composition data of the fluid surrounding the fuel cell, or a combination thereof.

[0174] In particular, in certain exemplary embodiments, the gas sensor may be configured to sense gas composition data of a single component of the fluid (e.g., the percentage of nitrogen within the output product stream from the anode; see, e.g., Figure 6 ). This can allow for a simpler and cost effective leak detection system while still providing valuable fuel cell leak and diagnostic information.

[0175] Alternatively, the gas sensor may be configured to sense gas composition data for multiple components of a single fluid (e.g., the percentage of CO2 and the percentage of H2O within the output product stream from the cathode; see, e.g., Figure 7 ). Such a configuration can provide a more versatile fuel cell leak detection system, providing valuable fuel cell leak and diagnostic information.

[0176] Alternatively, the gas sensor may also be configured to sense gas composition data of one or more components of a plurality of fluids (e.g., the percentage of CO2 and / or the percentage of H2O in the output product stream from the cathode, the percentage of nitrogen in the output product stream from the anode, and / or the percentage of oxygen in the fluid surrounding the fuel cell; see, for example, Figure 8 , 12 and 13). Such a configuration may provide an even more versatile fuel cell leak detection system, providing valuable fuel cell leak and diagnostic information.

[0177] In this manner, it may be appreciated that the gas sensor may be a multi-gas sensor having multiple sensing nodes configured to sense multiple unique responses (eg, multiple unique electrical responses, vibration responses, etc.), or the like.

[0178] For example, in one exemplary embodiment, the gas sensor may use Raman spectroscopy, an optical analysis technique that relies on the measurement of the vibrational and rotational properties of molecules. Raman spectroscopy produces a unique spectral fingerprint that can identify the chemical composition and molecular structure data fluid. Raman spectroscopy can utilize a laser pointed at a fluid. A spectrometer collects and measures the Raman scattered photons, forming a unique spectral fingerprint. Raman measurements are non-destructive and can be collected in seconds (e.g., less than 10 seconds, less than 5 seconds, or less than 3 seconds, depending on the laser power and the desired detection resolution). Raman signals are easily interpreted: the distribution of spectral peaks describes the composition of the molecules, and the signal intensity is linearly related to the concentration. Overlapping Raman peaks can be resolved using known data analysis techniques.

[0179] In certain exemplary aspects, a gas sensor (either a multi-gas sensor or a single-gas sensor) configured to sense a percentage of nitrogen may utilize Raman spectroscopy, as such a technique may be well suited for determining nitrogen concentrations at the relatively low levels disclosed herein.

[0180] Additionally or alternatively, in other exemplary embodiments, the gas sensor may use any other suitable technology. Fig.17 , a gas sensor according to another exemplary aspect of the present disclosure is provided. Fig.17 The gas sensor can be incorporated into the above reference Figures 11 to 16 In one or more exemplary systems and methods described.

[0181] In particular, Fig.17 One embodiment of a gas sensor configured as a multi-gas sensing system 1100 (i.e., a multi-gas sensor) is shown. The multi-gas sensing system 1100 examines a fluid in contact with the system 1100. The fluid may be a gas, liquid, a gas-liquid mixture, a solid, a granular or particulate matter, etc., containing one or more analyte gases to determine gas composition data.

[0182] The multi-gas sensing system 1100 may represent one or more different versions of the sensing systems described herein. The system 1100 includes a sensing circuit 1200, a modifier component 1122, and a management circuit 1110, which can control the operation of the modifier component 1122 and the sensing circuit 1200. In one or more embodiments, the sensing circuit 1200 may be a resistor-capacitor RC circuit that includes one or more resistor R and capacitor C components that may be changed by the presence of one or more analyte gases of interest. For example, the management circuit 1110 may change the resistance and / or capacitance of the sensing circuit 1200. In one or more embodiments, the circuitry of the sensing system 1100 is capable of performing impedance measurements of the sensing system 1100 to determine the impedance response to the one or more analyte gases of interest. The impedance measurements may be performed at one or more different frequencies or one or more different RC configurations of the sensing circuit 1200. For example, the sensing circuit 1200 of the sensing system 1100 may measure the impedance response of the sensing system 1100 at different frequencies, at different resistances of the RC circuit, at different capacitances of the RC circuit, or at any combination of two or more thereof.

[0183] The term impedance as used herein may be a non-limiting term for any electrical response of a sensing system to an alternating current applied to the sensing system. Such responses may be measured as different electrical properties. Non-limiting examples of these commonly measured different electrical responses of a sensing system to an alternating current include impedance, admittance, reactance, susceptance, etc. In this specification, examples of responses are given as impedance, however, other electrical responses of a sensing system to an alternating current may equally be produced.

[0184] In one embodiment, the electrical response of the sensing system may be monitored at the gas modulated leading shoulder of the dielectric relaxation peak of the sensing material.

[0185] The measurement of the impedance of the sensing system 1100 may be performed at a single frequency, at discrete frequencies, or at multiple sweeping frequencies by an impedance analyzer or impedance analyzer circuit, which may be part of or coupled to the management circuit 1110 and / or the system controller 1120, and is conductively coupled to the sensing circuit 1200. Optionally, the management circuit 1110 of the multi-gas sensing system 1100 may also or alternatively be referred to as a spectrum analyzer, an analyzer, an AC current response analyzer, etc.

[0186] In one or more embodiments, an impedance analyzer can be part of the management circuit 1110 and can measure the electrical response of at least two sensing elements of a multi-gas sensing system, where the two sensing elements are based on different detection principles. A non-limiting example of a first sensing element can be an electrode pair coated with a sensing material and positioned on a substrate. The impedance analyzer can measure the gas response of the first sensing element at multiple frequencies or a single frequency near a dielectric relaxation peak of the sensing material. A non-limiting example of a second sensing element can be a mechanical resonator coated with a sensing material, such as a tuning fork resonator, a thickness shear mode resonator, or a surface acoustic wave resonator. The impedance analyzer can measure the resonant peak frequency position of the resonant second sensing element.

[0187] The multi-gas sensing system 1100 may include a system controller 1120. The system controller 1120 may include one or more devices, such as, but not limited to, a power supply 1130, a data analysis unit 1132, an output device 1134 (e.g., such as a security alarm), and a communication system 1136. One or more components of the system controller 1120 may include one or more processors, including one or more microprocessors, field programmable gate arrays, and / or integrated circuits. In one or more embodiments, the sensing system 1100 may be a battery operated device and / or may be powered using energy available from a host control system or by using energy harvested from an environmental source (e.g., light, vibration, heat, electromagnetic energy, etc.). In one or more embodiments, the management circuit 1110 and / or the modifier component 1122 may be part of the system controller 1120. For example, one or more processors of the system controller 1120 may operate in a similar manner to the management circuit 1110 and / or the modifier component 1122.

[0188] The data analysis unit 1132 may be in the form of an integrated circuit controller that is located on the same board as the sensing elements. As an example, the system 1100 may operate with a power requirement of approximately 30 milliamp hours per hour or less for substantially continuous operation. The data analysis unit 1132 may receive data from one or more sensing elements 1102A-C directly or via the management circuit 1110, from other sensing elements located on the same board (such as temperature and / or ambient humidity sensing elements). The data analysis unit 1132 may receive data wirelessly from one or more sensing elements 1102A-C directly, or from one or more sensing elements 1102A-C wirelessly via the management circuit 1110, or from other sensing elements located at different locations in or around the system 1100, etc.

[0189] The data may be stored in short-term and / or long-term memory storage devices (such as archival communication systems), which may be located within or remote from the system 1100, and / or reconstructed and displayed for an operator, such as at an operator workstation, displayed via an output device of the system 1100, etc. The data analysis unit 1132 may include one or more processors for analyzing data received from the management circuit 1110. For example, the one or more processors may be one or more computer processors, controllers (e.g., microcontrollers), or other logic-based devices that operate based on one or more sets of instructions (e.g., software). The instructions for the operation of the one or more processors may be stored on a tangible and non-transitory computer-readable storage medium (such as a memory device). The memory device may include a hard drive, a flash drive, a RAM, a ROM, an EEPROM, etc. Alternatively, the one or more sets of instructions that direct the operation of the one or more processors may be hardwired into the logic of the one or more processors, such as by being hardwired logic formed and / or stored in the hardware of the one or more processors.

[0190] Fig.18 Shows Figure 1 An embodiment of a sensing circuit 1200 of a multi-gas sensing system 1100 of the present invention. The sensing circuit 1200 includes one or more sensing elements 1102A-C. Each of the sensing elements 1102A-C is operable to contact a fluid in which one or more analyte gases may be contained. The sensing elements 1102A-C include a common substrate 1202, such as a dielectric material. Suitable materials for the substrate 1202 may include aluminum oxide, ceramics, and the like. Each sensing element 1102A-C also includes a sensing film or sensing material 1208 coupled to the substrate 1202, and sensing electrodes 1210, 1212. Suitable examples of sensing materials or sensing films include metal oxide materials, composite materials, semiconductor materials, n-type semiconductor materials, p-type semiconductor materials, combinations of n-type and p-type semiconductor materials, nanocomposites, inorganic materials, any known sensing materials capable of operating at up to 900°C, and the like. Non-limiting examples of sensing materials operating at around 900°C include gallium oxide and silicon carbide. Suitable electrodes can be formed using metal etching, screen printing, inkjet printing, and mask-based metal deposition techniques. The thickness of the electrodes fabricated on the substrate can range from about 10 nanometers to about 1000 micrometers. Materials for the interdigitated electrode structure, substrate, sensing layer, and electrode formation methods can be selected based at least in part on application-specific parameters.

[0191] The sensing material 1208 is exposed to, in contact with, indirectly in contact with, etc., at least one analyte gas. One or more heating elements 1204 (such as a high resistor) are coupled to different sides of the substrate 1202 relative to the sensing material 1208. The heating element 1204 receives current from a heater controller 1206, which represents a hardware circuit that conducts a heater current or voltage to the heating element 1204 to heat the substrate 1202 and heat the sensing film or sensing material 1208 coupled to the other side of the substrate 1202. For example, in one or more embodiments of the subject matter described herein, the sensing material 1208 uses a metal oxide sensing film. The management circuit 1110 can control each heating element 1204 by controlling the operation of the heater controller 1206 to manage the temperature of each sensing element 1102A-C. The sensing material 1208 may include one or more materials deposited on the substrate 1202 to perform a function of predictably and repeatably affecting the impedance sensor response when interacting with the environment. For example, metal oxides (such as gallium oxide and silicon carbide) or any other material may be deposited as the sensing material 1208 .

[0192] In one or more embodiments, one or more filters may be disposed above one or more sensing elements 1102A-C. For example, one or more filters may be a barrier or alternative protective mechanism or device that may prevent or reduce the amount of gaseous, liquid and / or solid particles that may come into contact with the sensing material 1208, sensing electrodes 1210, 1212, etc. As an example, a single filter may be disposed above one or more elements, or alternatively, each sensing element may include individual filters disposed on top of each sensing element. One or more filters may be gas permeable membrane filters such that the filter enables the gas of interest to pass through the filter from one side to the other, and may prevent or reduce the amount of interfering gas or solid particles that may pass through the filter from one side to the other. In one or more embodiments, the gas permeable membrane filter may include a fluoropolymer or a fluoropolymer coating. Optionally, the filter may include an alternative coating, such as a flame retardant.

[0193] In the illustrated embodiment, the sensing electrodes 1210, 1212 of each sensing element 1102A-C are coupled to and / or disposed in the sensing material 1208 and connected to the substrate 1202. The sensing electrodes 1210, 1212 are electrical conductors that are conductively coupled to one or more of the modifier assembly 1122, the transducers 1224A-C, and the management circuit 1110. In one or more embodiments, the transducers 1224A-C are electrode structures that are coupled to an impedance detector system, and the sensors are transducers coated with a sensing material. The management circuit 1110 may include an impedance detector system or a resistance detector system. Each of the modifier assembly 1122, the transducers 1224A-C, and the management circuit 1110 may have one or more processors including one or more microprocessors, field programmable gate arrays, and / or integrated circuits.

[0194] exist Fig.18 In the illustrated embodiment, each sensing element 1102A-C is operably coupled to a transducer 1224A-C, respectively. Alternatively, the sensing circuit 1200 may include a single transducer conductively coupled to each sensing element 1102A-C, which may receive an electrical response from each sensing element 1102A-C and convert a change in the electrical response into a physical quantity.

[0195] In one or more embodiments, the sensing electrodes 1210, 1212 may be coated with a sensing material responsive to one or more analyte gases of interest. One or more processors of the management circuit 1110 may direct the sensing electrodes 1210, 1212 to apply electrical stimulation at a frequency, such as an electrical excitation frequency or a single excitation frequency. For example, the management circuit 1110 may excite the sensing elements 1102A-C with an alternating current at at least one predetermined frequency, at a predetermined frequency range, etc.

[0196] The one or more processors of the management circuit 1110 may receive electrical signals from the sensing electrodes 1210, 1212 of each sensing element 1102A-C, the electrical signals representing the electrical impedance or impedance response of the sensing element 1102A-C during exposure of the sensing material 1208 to the fluid sample. For example, the one or more processors of the management circuit 1110 may measure one or more electrical responses of the sensing elements 1102A-C in response to stimulating the sensing electrodes 1210, 1212 with an alternating current at at least one frequency or frequency range.

[0197] The management circuit 1110 may determine one or more characteristics of the sensing circuit 1200 based on the electrical response from each different sensing element 1102. The characteristics of the sensing circuit 1200 may include the temperature of one or more sensing elements, the temperature variation between two or more sensing elements, the state of the sensing circuit 1200 based on the configuration of the sensing element 1102, one or more environmental conditions (e.g., ambient temperature, humidity, etc.) within a predetermined area adjacent to the sensing circuit 1200, and the like. In one or more embodiments, the management circuit 1110 may manage the configuration of each of the one or more sensing elements, such that the management circuit 1110 may manage the resistor-capacitor configuration of at least one sensing element. The management circuit 1110 may determine the state of the sensing circuit 1200 based on the resistor-capacitor configuration of each sensing element of the sensing circuit. Alternatively, the state of the sensing circuit 1200 may be based on another configuration of the sensing circuit.

[0198] In one or more embodiments, the management circuit 1110 may be referred to as a frequency impedance source and detector system. The management circuit 1110 examines the electrical impedance of the sensing elements 1102A-C to determine the presence and / or amount (e.g., concentration) of one or more analyte gases in the environment to which the sensing material 1208 of each sensing element 1102A-C is exposed, as described herein. The management circuit 1110 may provide a scanning capability to measure the sensor impedance response at a single or multiple discrete frequencies. Alternatively, the system controller 1120 may provide the ability to measure the sensor impedance response across a range of frequencies.

[0199] The sensing circuit 1200 can be operably coupled to a modifier component 1122, which can include a multiplexer. The multiplexer can be a single multi-frequency sweep signal analyzer that can operate with a power requirement that is less than 10 milliwatts (mW), less than 5 mW, or in a more preferred embodiment, less than 1 mW. In one or more embodiments, each sensing element 1102A-C can be conductively coupled to the modifier component 1122. The system controller 1120 and / or the management circuit 1110 can direct one or more sensing elements 1102A-C to change the impedance of an electrical stimulus applied to a corresponding sensing material 1208 without changing the excitation frequency. As an example, the modifier component 1122 can include a circuit group having a plurality of circuits (not shown) to change the impedance of each sensing element 1102A-C based on which circuits are electrically coupled or electrically disconnected from the management circuit. Alternatively, the modifier component 1122 may include a single circuit, which may be a variable circuit or a variable device, that may change the impedance of each sensing element 1102. In alternative embodiments, the modifier component may include a multiplexer having any alternative configuration, one or more circuits, or any combination thereof.

[0200] The management circuit 1110 and / or the system controller 1120 can control the modifier component 1122 to apply electrical stimulation to each sensing element 1102A-C at a single or discrete impedance, or at a predetermined range of varying impedances, for interrogating the sensing material 1208 of each respective sensing element 1102A-C, and at what interrogation time, so as to measure the sensor response at each frequency. For example, the multiplexer of the modifier component can electrically connect and / or disconnect one or more different sensing elements 1102A-C from the management circuit 1110 and the corresponding sensing electrodes 1210, 1212 to change which sensing elements 1102A-C of the sensing circuit 1200 are electrically coupled and disconnected from the modifier component 1122 and the management circuit 1110. For example, the modifier component 1122 can change the impedance of each sensing element 1102A-C without changing the electrical excitation frequency of the electrical stimulation applied to the sensing electrodes 1210, 1212.

[0201] The multiplexer of the modifier component 1122 can combine multiple electrical response signals received from each sensing element 1102A-C into a single output that is directed to the management circuit 1110. The management circuit 1110 receives the electrical response signals in response to stimulating the sensing electrodes 1210, 1212 with an alternating current at at least one predetermined frequency, and determines one or more characteristics of the sensing circuit 1200. The management circuit 1110 can transmit or otherwise communicate the electrical response signals and the determined characteristics of the sensing circuit 1200 to one or more processors of the system controller 1120. The concentration of at least one gaseous analyte can be determined based on the electrical responses of the sensing elements 1102A-C and the characteristics of the sensing circuit 1200. For example, the data analysis unit 1132 of the system controller 1120 can convert the sensor responses into analytically useful gas composition data, such as the concentration of the detected gas. Additionally, the data analysis unit 1132 can determine the concentration of at least one gas analyte based on one or more temperatures of each sensing element, environmental conditions close to the sensing circuit 1200 (e.g., within a predetermined close distance or area of ​​the sensing circuit, e.g., within 1 meter, 5 meters, 10 meters, 100 meters, etc.), etc.

[0202] As an example, the system controller 1120 can determine the concentration of at least one analyte gas based on electrical responses from two or more different sensing elements (e.g., sensing elements 1102A, 1102B). The first sensing element 1102A can operate at a first substantially constant temperature, and the second sensing element 1102B can operate at a different second substantially constant temperature. For example, the management circuit 1110 can control the heating element 1204 so that the first sensing element 1102A can operate at a first temperature, and the second sensing element 1102B can operate at a different temperature that can be greater than or less than the first temperature.

[0203] As another example, the system controller 1120 can determine the concentration of one or more gaseous analytes based on electrical responses from two or more different sensing elements (such as sensing elements 1102A and 1102B). The management circuit 1110 can control the operation of the heating element 1204 so as to operate the first sensing element 1102A at a periodically varying temperature, and can operate the second sensing element 1102B at a different periodically varying temperature. For example, the heating element 1204 can change the temperature of the first sensing element 1102A (e.g., such as within a temperature range), which increases and / or decreases the temperature to a predetermined value at a predetermined time, within a predetermined duration, or any combination thereof. Additionally, the heating element 1204 can change the temperature of the second sensing element 1102B (e.g., within a different or the same temperature range), which increases and / or decreases the temperature to a different predetermined value at a different predetermined time, within a different predetermined duration, or any combination thereof. Alternatively, the first sensing element 1102A and the second sensing element 1102B may operate at similar temperature ranges for different durations, may operate at similar durations but at different temperature ranges, may operate at similar temperatures and durations but at different times, and so forth.

[0204] The sensing elements 1102A-C, including the sensing material 1208 and the substrate 1202, the heating element 1204, the heater controller 1206, the modifier assembly 1122, and the transducers 1224A-C are disposed within a common housing 1214. The common housing 1214 can be connected to the substrate or circuit board 1104 (see FIG. 12A ) of the system 1100. Fig.18 ) can be operably coupled to the common housing 1214. Optionally, one or more sensing elements 1102A-C can be disposed in respective housings to separate each sensing element from each other sensing element. Optionally, one or more of the modifier assembly 1122, the heater controller 1206, the one or more transducers 1224, or the management circuit 1110 can be operably coupled to the circuit board 1104 of the system 1100 and can be disposed outside of or separate from the common housing 1214. Optionally, one or more components of the system 1100 can be disposed or contained within a housing together with any other component of the system 1100, or can be disposed or contained within a housing separately from any other component of the system 1100.

[0205] Fig.19The system layout of a multi-gas sensing system 1300 according to one embodiment is shown. The components and devices of the system 1300 are disposed on a substrate or circuit board 1104. In one or more embodiments, one or more components or devices of the system 1300 may be disposed on one or both sides of the circuit board 1104. The system 1300 may include one or more power devices or components such as a power supply 1130 or a power switch, a power regulator, a non-volatile memory or other memory or storage device 1306, a charging source 1308 such as a micro USB, or a charger or charging device 1310. In one or more embodiments, the power supply 1130 may be a battery source or any alternative untethered power source, or include a battery source or any alternative untethered power source. The system 1300 may include processing components such as a management circuit 1110, a system controller 1120, and a modifier component 1122. The management circuit 1110 may include one or more processors including one or more microprocessors, field programmable gate arrays, and / or integrated circuits that may operate or function as an impedance analyzer, a resistor detector system, or the like. The system controller 1120 may include one or more processors that may operate as a data analysis unit, a memory system (e.g., memory 1306), etc. The modifier component 1122 is shown as being separate from the system controller 1120 and the management circuit 1110, but may alternatively be included with one or both of the management circuit 1110 or the system controller 1120.

[0206] System 1300 includes two different sensing elements 1102A, 1102B. In one or more embodiments, sensing elements 1102A, 1102B can each be designed to sense or otherwise detect the presence of one or more of nitrogen (N2), oxygen (O2), carbon dioxide (CO2), water (H2O), methane (CH4), carbon monoxide (CO), etc. Optionally, different sensing elements can be designed to sense or otherwise detect different gases. System 1300 includes sensing element 1302, which can be designed to sense or otherwise detect environmental conditions, such as ambient temperature, ambient humidity, ambient pressure, etc. For example, sensing elements 1102A, 1102B can transmit electrical responses to management circuit 1110 in response to management circuit stimulating sensing elements 1102A, 1102B with an alternating current at at least one predetermined frequency. Management circuit 1110 can measure the electrical responses from sensing elements 1102A, 1102B to determine one or more characteristics of the sensing circuit. Additionally, the sensing element 1302 may detect environmental conditions of an area proximate to the system 1100, and the management circuit 1110 may determine a characteristic of the system 1100 based on the environmental conditions detected by the sensing element 1302. One or more processors of the system controller 1120 may receive the electrical response and the characteristic of the sensing circuit and determine a concentration of at least one gas analyte, such as a gas analyte of interest, based on the electrical response and the characteristic of the sensing circuit.

[0207] In one or more embodiments, the system 1300 may include an output device 1304. As one example, the output device 1304 may be shown as an LED light. For example, the LED light may illuminate based on an electrical response of the sensing element, based on a characteristic of the sensing circuit, etc. Alternatively, the output device 1304 may be any alternative safety device that may illuminate, sound an alarm, vibrate, or otherwise communicate to an operator of the system 1100 if the system controller 1120 determines that the gas of interest exceeds a predetermined threshold.

[0208] Fig. 20 A flowchart 1400 of one embodiment of a method for sensing multiple different gas analytes using a multi-gas sensing system according to one embodiment is shown. The multi-gas sensing system may be Fig.17. At 1402A-C, each of the sensing elements 1102A-C can be operated. For example, the management circuit can excite each sensing element with an alternating current at at least one predetermined frequency. The management circuit can excite sensing element 1102A at a first predetermined frequency, and can excite sensing elements 1102B, 1102C at different, unique, or common frequencies relative to each other and sensing element 1102A. Optionally, one or more of the sensing elements 1102A-C can be excited at a predetermined frequency range. At Fig.17 and Fig.18 In the illustrated embodiment of , the system includes three sensing elements. Alternatively, the system may include less than three or more than three sensing elements. Alternatively, the system may include only one sensing element.

[0209] In one or more embodiments, the management circuit can manage the temperature of one or more sensing elements by controlling a heating element. For example, the management circuit can control the operation of the heating element so that one or more sensing elements operate at a predetermined temperature, operate at a predetermined temperature range, so that different sensing elements operate at different temperatures or at different temperature ranges, etc. In one embodiment, the management circuit can control the heating element to periodically change the temperature of the first sensing element 1102A and substantially maintain the temperature of the second sensing element 1102B and the third sensing element 1102C. For example, the management circuit can control the heating element so that the first sensing element 1102A operates at a first constant or first variable temperature, and the second sensing element 1102B operates at a different second constant temperature or second variable temperature. As another example, the management circuit can control the heating element so that the first sensing element 1102A operates at a periodic variable temperature, and the second sensing element 1102B operates at a different periodic variable temperature. The different periodic temperatures of the second sensing element can be substantially the same temperature, but heated at a different periodic time than the first sensing element. Alternatively, the first sensing element and the second sensing element may be heated at substantially the same or common cycle time, but the first sensing element may be heated to a temperature that is different than the temperature of the second sensing element.

[0210] The management circuit can synchronize the temperature of one or more sensing elements with the excitation of one or more sensing elements. For example, the management circuit can synchronously control a heating element to control the temperature of one or more sensing elements to a predetermined value at substantially the same time or within a predetermined time window when the one or more sensing elements are excited with an alternating current of a predetermined frequency. For example, the management circuit can control a heating element and excite one or more sensing elements at substantially the same time, within a time window, etc. Optionally, the management circuit can synchronize the temperature change of one or more sensing elements with the duration of the excitation of the sensing elements. Optionally, the management circuit can substantially synchronously maintain a temperature range of one or more sensing elements while variably exciting the sensing elements at a predetermined frequency or frequency range. Optionally, the management circuit can synchronize the temperature of the sensing elements with the excitation of the sensing elements in any alternative configuration or in other ways based on one or more predetermined rules.

[0211] At 1404, one or more processors and / or a system controller of the management circuit may analyze an electrical response from the sensing element in response to the excitation of the sensing electrode of the sensing element. The electrical response may be represented as a signal output from each of the one or more sensing elements. An alternating current may be applied to each of the one or more sensing elements at one or more different frequencies or at one or more different resistor-capacitor configurations of each sensing element. For example, a first sensing element may have a first resistor-capacitor configuration, and a first frequency may be applied to the sensing electrode of the first sensing element to excite the first sensing element. Alternatively, a second sensing element may have a second different resistor-capacitor configuration, and a different second frequency may be applied to the sensing electrode of the second sensing element. Alternatively, one or more sensing elements may have a common resistor-capacitor configuration, or a common frequency may be applied to excite one or more sensing elements.

[0212] Fig.21 Graphs of electrical responses of various sensing elements of a multi-gas sensing system according to one embodiment are shown. Graph A represents the electrical response from a first sensing element, which may be designed to detect the presence of methane (CH4). Graph B represents the electrical response from a second sensing element, which may be designed to detect the presence of carbon monoxide (CO). Alternatively, the electrical response may be received from a single sensing element, which may be configured to operate to detect the presence of CH4, CO, and any other gas. Graphs A and B are illustrated with a common horizontal axis 1502 representing time and vertical axes 1504, 1506 representing the impedance of the sensing circuit 1200, respectively.

[0213] Measurements of one or more real parts Z' or imaginary parts Z" of the impedance of the sensing circuit 1200 can be performed within the dielectric relaxation region of the sensing circuit 1200. The dielectric relaxation region of the sensing system 1100 can be a frequency range within a specified threshold of the measured impedance of the sensing circuit 1200 when a relaxation peak occurs, and / or a relaxation point frequency or inflection frequency range of the imaginary part Z" of the impedance. For example, a relaxation peak (also known as a relaxation frequency) can be identified as a location along the imaginary part of the impedance spectrum at which the impedance response changes from concave to convex, or from convex to concave. The inflection frequency is the frequency or frequency range where the inflection point occurs. Alternatively, the inflection point can be determined by examining the real part of the measured impedance of the sensing material 1208 to locate the location where the curvature of the real part of the impedance changes from concave to convex, or from convex to concave. In one or more embodiments, the electrical response of the sensing system is monitored at the gas modulated leading shoulder of the dielectric relaxation peak of the semiconductor sensing material. For n-type semiconductor sensing materials, the leading shoulder can be the high frequency region of the relaxation peak. For p-type semiconductor sensing materials, the leading edge shoulder may be the low frequency region of the relaxation peak.

[0214] As an example, the sensing circuit may be exposed to approximately 11.36% by volume CH4 and 1090 parts per million (ppm) CO. As shown in graphs A and B, the second sensing element (e.g., CO sensor) detects an increase in impedance in the presence of CO as shown in the first segment 1510, but the first sensing element (e.g., CH4 sensor) indicates only a minimal increase in impedance in the presence of CO. Similarly, the second sensing element detects an increase in the presence of CO as shown in the third segment 1514, but the first sensing element has only a minimal increase. Alternatively, the first sensing element detects an increase in impedance in the presence of CH4 as shown in the second segment 1512, but the second sensing element has only a minimal increase. Graphs A and B illustrate the differentiation between CH4 and CO by the first and second sensing elements of the sensing circuit.

[0215] Return to Fig. 20At 1406, the electrical responses received from the one or more sensing elements at the plurality of frequencies are converted into analytically useful concentrations for detecting the analyte gas, and at 1408, one or more electrical characteristics are determined based on the electrical responses. For example, the management circuitry and / or data analysis unit of the system 1100 may analyze the electrical responses received from the sensing elements to determine one or more concentrations of the one or more sensed analyte gases. The analysis may be based on one or more electrical responses of the sensing elements; characteristics of the sensing circuit, such as, but not limited to, the temperature of the sensing elements, the state of the sensing circuit based on the construction of the sensing elements, environmental conditions proximate to the sensing circuit, and the like; or any combination of two or more thereof. In one or more embodiments, the analysis may be based on one or more sensing elements operating at a periodically variable temperature, one or more sensing elements operating at a common or unique substantially constant temperature, different discrete frequencies or frequency ranges for exciting the sensing elements, and the like.

[0216] For example, Fig. 22 Shows Fig.21 is a graphical representation of the results of analysis data of the electrical responses of two sensing elements of the multi-gas sensing system shown in .

[0217] The electrical response may be evaluated using one or more different statistical analysis tools, such as, for example, by performing a principal component analysis (PCA) on the electrical response and other characteristics obtained by the system controller. Alternatively, the concentration of one or more gases may be calculated from a multivariate transfer function, which may be constructed based on the electrical response to the alternating current of the management system, the temperature of the sensing element, the state of the resistor-capacitor configuration of the sensing element, information from the sensing circuit or other sensors regarding environmental conditions surrounding the multi-gas sensing system, etc. Alternatively, an alternative statistical analysis may be used to evaluate the data obtained by the system controller.

[0218] Graph A represents the results of analyzing the data of the combined electrical response using PCA and expressed as the fraction of principal component #1 as a function of experimental time.

[0219] Graph B shows the results of analyzing the data using PCA and expressed as the fraction of principal component #2 as a function of experimental time for the combined electrical response.

[0220] Graphs A and B are shown with a common horizontal axis 1602 representing experimental time and respective linearly scaled vertical axes 1604, 1606 representing principal component #1 and principal component #2, respectively, of the developed PCA classification.

[0221] As shown in Graph A, the first segment 1610 and the third segment 1614 indicate an increased CO concentration, and the second segment 1612 indicates an increased CH4 concentration. Fig.21The PCA principal component #1 response of the CO gas (e.g., segments 1510, 1514 of Figure B), and the second segment indicates the PCA principal component #2 response of the CO gas (e.g., segments 1510, 1514 of Figure B), and the second segment indicates the PCA principal component #1 response of the CO gas (e.g., segments 1510, 1514 of Figure B), and the second segment indicates the PCA principal component #2 response of the Fig.21 PCA principal component #1 response of CH4 gas (e.g., segment 1512 of graph A).

[0222] As shown in Graph B, the first segment 1610 and the third segment 1614 indicate an increased CO concentration, and the second segment 1612 indicates an increased CH4 concentration. Fig.21 The PCA principal component #2 response of the CO gas (e.g., segments 1510, 1514 of Figure B), and the second segment indicates the ... Fig.21 PCA principal component #2 response of CH4 gas (e.g., segment 1512 of graph A).

[0223] In one or more embodiments, one or more processors of the system controller may provide for baseline correction of the sensing element. The baseline correction may be performed periodically, at scheduled intervals (e.g., after so many minutes, hours, days, years, etc. of operation), etc. The baseline correction may also be referred to as calibration of the sensing element. The amount of correction or the method of correcting or verifying the baseline may be based on an electrical response received from the sensing element, a temperature of the sensing element, a state of a resistor-capacitor configuration of the sensing element, information about environmental conditions surrounding or proximate the multi-gas sensing system (e.g., ambient temperature, humidity, pressure, etc.), based on information received from other sensors or sensing devices, based on information wirelessly transmitted to the multi-gas sensing system (e.g., such as from a workstation separate from the multi-gas sensing system), based on information or protocols stored within the multi-gas sensing system, etc.

[0224] Optionally, one or more processors may change the selectivity, sensitivity, or linearity of the electrical response of the multi-gas sensing system 1100 to allow the system to be more responsive to one analyte gas than another analyte gas at different times or under different operating conditions. In one or more embodiments, one or more processors may dynamically change the selectivity, sensitivity, or linearity, so that one or more processors may change one or more of the selectivity, sensitivity, or linearity while the sensing system is operating. Optionally, one or more processors may change one or more of the selectivity, sensitivity, or linearity of the electrical response of the sensing system when the system is not sensing. For example, one or more processors may determine the relaxation region of the impedance response of the sensing circuit. Both the real part of the impedance and the imaginary part of the impedance have relaxation regions. As an example, the relaxation region may be determined by examining the real part of the measured impedance of the sensing material 1208 according to frequency to locate the position where the real part of the impedance changes from a high impedance value with a substantially zero slope at low frequencies to a reduced impedance value with a relatively high slope at higher frequencies and a reduced impedance value with a relatively low slope at even higher frequencies, and the position where the impedance value approaches zero at the highest frequency.

[0225] The one or more processors may determine the location of the relaxation peak of the relaxation region of the imaginary portion of the sensor impedance by identifying the inflection frequency of the sensing circuit 1200. The inflection frequency may be determined as the frequency of the current associated with the inflection point.

[0226] The one or more processors may determine a frequency range for sensor operation that is below and above a relaxation peak of the imaginary portion of the sensor impedance and at or near the relaxation peak of the imaginary portion of the sensor impedance (e.g., within 11%, within 3%, within 5%, or within 110% in various embodiments). Current may be applied to the sensing material 1208 via the electrodes 1210, 1212 of the one or more sensing elements only at frequencies greater than the inflection frequency and / or frequencies within a frequency range greater than the inflection frequency. Operating the sensing circuit 1200 at these frequencies may improve the selective sensing of the sensing circuit 1200 (e.g., the sensitivity of the sensing circuit 1200) to one or more analytes of interest in the second sample relative to one or more other analytes (and relative to operating the sensing circuit 1200 at one or more frequencies at or below the inflection frequency). The sensitivity of the sensing circuit 1200 includes a measured sensor response signal per unit of analyte concentration.

[0227] As another example, one or more processors can selectively sense at least one analyte of interest with improved interference rejection. The resistance and capacitance properties of the sensing circuit 1200 are measured during exposure of the sensing circuit 1200 to a first gas sample and during exposure of the sensing circuit 1200 to a second gas sample. The one or more processors determine a capacitance value or a range of capacitance values ​​of one or more passive electrical components (e.g., capacitive elements) to change the capacitance of one or more sensing elements of the sensing circuit 1200 to match a frequency range or discrete frequency response of the system controller within a dielectric relaxation region of the sensing circuit 1200. Changing the capacitance of the sensing circuit 1200 coupled to the system controller allows the system controller to selectively sense the analyte of interest (e.g., methane, ethane, another hydrocarbon, hydrogen, carbon monoxide, etc.) with interference rejection.

[0228] Selective sensing of one or more analytes of interest is performed using the sensing circuit 1200 operating within the dielectric relaxation region of the sensing circuit to match a discrete frequency response or frequency response range of the system controller 1120. For example, the sensing material 1208 of each sensing element of the sensing circuit 1200 can be exposed to a gas sample potentially having one or more analytes of interest therein. The system controller 1120 can transmit a control signal to the management circuit 1110 to direct the management circuit 1110 to apply an alternating current to the sensing material 1208 via the sensing electrodes 1210, 1212 within the dielectric relaxation region of the sensing circuit 1200 at a specified frequency response range or specified discrete frequencies of the system controller 1120. Operating the sensing circuit 1200 at these frequencies can increase the selective sensing of the multi-gas sensing system 1100 to one or more analytes of interest in the sample relative to one or more other analytes (and relative to operating the sensing circuit 1200 at a different frequency or a different frequency range of the system controller 1120) (e.g., the sensing sensitivity of the sensing system 1100). The sensitivity of the sensing circuit 1200 includes the measured sensor response signal per unit of analyte concentration.

[0229] Return to Fig. 20 , determining whether the resistor-capacitor configuration of one of the sensing elements needs to be changed. If the configuration does need to be changed, the flow of the method proceeds to 1412, where the management circuit changes the resistor-capacitor configuration of one or more sensing elements. The flow of the method then returns to 1402A-C, where the method begins again. Alternatively, if no resistor-capacitor configuration of the sensing element needs to be changed, the flow of the method moves to 1414.

[0230] At 1414, it is determined whether the amount of at least one gas exceeds a predetermined threshold. For example, the system controller may determine, based on the analysis performed in steps 1404 to 1408, that an amount of gas exceeding a predetermined threshold is present and that the concentration of the gas may be dangerous to an operator or user of the multi-gas sensing system. Optionally, the concentration of the gas may be dangerous for an operator to perform a specific task, such as, but not limited to, driving or operating motorized equipment, using inflammatory equipment, remaining in the environment without wearing appropriate safety equipment, etc. In one or more embodiments, it may be determined whether any amount of a specific gas is present. For example, any trace or minimal amount of a specific gas may be dangerous for an operator to continue to operate or remain in the environment.

[0231] In one or more embodiments, one or more processors of the system controller may determine a response action of the asset based on the electrical response through the multi-gas sensing system.For example, the system controller may determine at 1414 whether the concentration of at least one gas analyte exceeds a predetermined threshold.

[0232] If the amount or concentration of the gas analyte does not exceed the predetermined threshold, flow of the method returns to 1402A-C and the method repeats for a predetermined amount of time while the operator is in the environment, until the operator disables the multi-gas sensing system, etc. Alternatively, if the amount or concentration of the gas exceeds the predetermined threshold, flow of the method proceeds to 1416. At 1416, a notification is transmitted to at least a controller or other system incorporating the multi-gas sensing system.

[0233] Fig.23 A graphical representation of the response of a metal oxide sensing element to a gas of interest, such as methane, according to one experiment is shown. In this experiment, the sensing element is a structure that uses micro-electromechanical systems (MEMS) technology to form an integrated heater on a silicon substrate and a metal oxide semiconductor material layer on a sensing chip as a surface mounted ceramic package. The sensing element requires only about 15 mW of heater power consumption. In this experiment, methane was presented to the sensing element at concentrations of 1087 parts per million (ppm), 2174 ppm, 3261 ppm, 4348 ppm, 5435 ppm, 6522 ppm, 7609 ppm, and 8696 ppm.

[0234] Graphs A, B and C are shown with a common horizontal axis 1702 representing experimental time. Graph A is shown with a vertical axis 1704 representing resistance, and graphs B and C are shown with vertical axes 1706, 1708, respectively, representing impedance. Fig.23Graph A of FIG. 1 depicts the electrical response of the sensing element measured by a conventional resistor. The resistance response of the sensing element to methane concentration has a nonlinear response. Additionally, the sensitivity decreases as the methane gas concentration increases. Graphs B and C show the electrical response of the sensing element measured by the dielectric excitation method. The results shown in Graph B were obtained using a benchtop impedance analyzer. The results shown in Graph C were obtained using an integrated circuit impedance analyzer. The very similar response linearity and noise levels in Graphs B and C indicate that the quality of methane sensed using the integrated circuit impedance analyzer is approximately the same as that sensed using the benchtop impedance analyzer.

[0235] The developed sensor system can measure the electrical response of the sensing element in response to an alternating current applied to the sensing element at one or more different frequencies and / or one or more different resistor-capacitor configurations of the sensing element. In order to quantify the gas of interest over its wide concentration range with a linear sensor response and its desired resolution, a dielectric excitation method can be applied at several frequencies. Fig.24 Graphs (graphs A, B and C) of three measured sensor responses at three frequencies ranging from relatively high to medium and to relatively low frequencies are shown. Graphs A, B and C are shown with a common horizontal axis 1802 representing experimental time and vertical axes 1804, 1806, 1808 representing impedance.

[0236] Although responses can be measured at all three frequencies of the measurement system, to determine gas concentration, the calibration curve can start at the highest frequency. If the sensor response is above the approximate bottom 20% of the sensor response at that frequency (e.g., sensor response #1), a linear calibration curve at that frequency can be noted and can be correlated to gas concentration (Graph A). If the sensor response is below the bottom 20% of the sensor response at that frequency (e.g., sensor responses #2 and #3), detection can be switched to ten times lower gas concentrations by using a linear calibration curve at a lower frequency and correlating the sensor response to gas concentration (e.g., sensor response #2, as shown in Graph B). If sensor response 3 is below approximately 10% of the sensor response at that frequency, detection can be further switched to ten times lower gas concentrations and a corresponding calibration curve can be used (e.g., Graph C). Thus, these sensor responses at different frequencies can allow for high resolution determination of gas concentrations over a wide range of gas concentrations using linear responses.

[0237] Another experiment showed that variable air humidity affects the response of conventional chemiresistor sensors based on metal oxide sensing materials by changing their baseline and gas sensitivity. Fig.25The effect of water vapor over a relative humidity (RH) range of 0-80% on the resistance and impedance (dielectric response) response of 4, 8, 12, 16, and 20 ppm concentrations of ethanol (as a model vapor) is shown. Graphs A and B are shown with a common horizontal axis 1002 representing experimental time. Graph A is shown with a vertical axis 1904 representing resistance, and Graph B is shown with a vertical axis 1906 representing impedance.

[0238] The resistive response has a known significant baseline drop and gas sensitivity drop with increasing RH (Figure A). At the same time, dielectric excitation and impedance measurement can provide three improvements over resistive measurement (shown in Figure B). First, the response baseline can be less affected by humidity changes. Second, sensor sensitivity can increase with increasing RH. Third, response linearity can be improved in the presence of water vapor.

[0239] In another experiment, the response of the multi-gas monitor to methane gas was measured outdoors under dynamic field conditions. Fig.26 A graphical result of monitoring a dynamic methane plume outdoors using the developed multi-gas monitor is shown. Time is on the x-axis 2002 and impedance is on the y-axis 2004. Uncontrolled wind conditions may produce a response pattern of the monitor that may be affected by variable wind direction and variable wind speed. Therefore, the detected gas concentration may be a convolution result between the variable wind direction and wind speed. Therefore, such results may provide knowledge about the maximum gas concentration reaching the detector at a certain time.

[0240] In another experiment, measurements of the response of a multi-gas sensor were performed to monitor the responses of H2 and CH4. Fig. 27 The graphical results of these measurements are shown. In particular, Fig. 27 Depicted are response speeds for H2 and CH4 detection using a multi-gas sensor according to one or more exemplary aspects of the present disclosure. In the top graph (Graph A), H2 sensor data is collected every 15 seconds, and one or two data points are required to achieve a 90% sensor equilibrium response to H2. In the bottom graph (Graph B), CH4 sensor data is collected every 5 seconds, and one data point is required to achieve a 90% sensor equilibrium response to CH4.

[0241] In the tests with H2, sensor data was collected every 15 seconds (Graph A), and it was observed that the multi-gas sensor only needed one or two data points to achieve a 90% equilibrium response to increasing H2 concentrations. However, the response to CH4 was even faster. Sensor data for CH4 was collected every 5 seconds (Graph B), and it was observed that the multi-gas sensor only needed one data point to achieve a 90% equilibrium response to increasing CH4 concentrations.

[0242] Fig.28 The detection results of three gases relevant to SOFC monitoring, H2, CH4 and CO, at their relevant high concentrations are depicted in . In particular, Ref. Fig.28 , identifying excitation parameters (also called variable control parameters) from a multi-gas sensor to detect and quantify H2, CO, and CH4 gases using a single multi-gas sensor. Fig.28 Quantification results of H2, CO and CH4 gases using a single multi-gas sensor are shown. Fig.28 Graphs A, B, and C in FIG depict three steady-state responses of a single multi-gas sensor to three gases recorded at different excitation frequencies (also called variable control parameters), respectively. The dashed horizontal lines highlight the different response patterns to the three gases at the three frequencies. In addition, machine learning tools, such as support vector machines (SVM), are applied to cross-validate the quantification of H2, CO, and CH4 gases using this multi-gas sensor, as shown in Graphs D, E, and F.

[0243] In one or more embodiments of the subject matter described herein, a multi-gas sensing system includes a sensing circuit that includes one or more sensing elements. Each of the one or more sensing elements includes a sensing material that is configured to detect at least one gas analyte. A management circuit is configured to excite the one or more sensing elements with an alternating current at at least one predetermined frequency. The management circuit measures one or more electrical responses of the one or more sensing elements in response to exciting the one or more sensing elements with an alternating current at at least one predetermined frequency. The management circuit determines one or more characteristics of the sensing circuit. One or more processors receive the one or more electrical responses of the one or more sensing elements and the one or more characteristics of the sensing circuit. The one or more processors determine the concentration of at least one gas analyte based on the one or more electrical responses of the one or more sensing elements and the one or more characteristics of the sensing circuit.

[0244] Further aspects are provided by the subject matter of the following clauses:

[0245] A fuel cell assembly comprises: a fuel cell stack, the fuel cell stack comprising a fuel cell, the fuel cell comprising a cathode and an anode; and a multi-gas sensor, the multi-gas sensor being configured to sense gas composition data of an output product flow from the cathode, gas composition data of an output product flow from the anode, gas composition data of a fluid surrounding the fuel cell, or a combination thereof, to determine fuel cell leakage diagnostic information.

[0246] The fuel cell assembly of one or more of these clauses, wherein the multi-gas sensor provides real-time in-situ sensing data having more than one electrical output, and wherein the gas composition data includes gas composition data for more than one gas.

[0247] The fuel cell assembly of one or more of these clauses, wherein the gas sensor is configured to detect a cross leak by sensing gas composition data of the output product stream from the anode.

[0248] A fuel cell assembly according to one or more of these clauses, wherein the gas composition data includes a percentage of N2 in the output product stream from the anode, and wherein the fuel cell assembly is further configured to sense data indicative of a flow rate of the output product from the anode.

[0249] A fuel cell assembly according to one or more of these clauses, wherein the fuel cell leak diagnostic information indicates a cathode to anode crossover leak determined in response to an increase in a percentage of N2 in the output product stream from the anode, an increase in a flow rate of the output product stream from the anode, or both.

[0250] The fuel cell assembly of one or more of these clauses, wherein the gas sensor is configured to sense gas composition data of the output product stream from the cathode.

[0251] A fuel cell assembly according to one or more of these clauses, wherein the gas composition data includes a percentage of CO2 in the output product stream from the cathode and a percentage of H2O in the output product from the cathode, and wherein the fuel cell assembly is further configured to sense data indicating a flow rate of the output product stream from the cathode.

[0252] A fuel cell assembly according to one or more of these clauses, wherein the fuel cell leak diagnostic information indicates an anode to cathode cross leakage determined in response to an increase in the percentage of CO2 in the output product stream from the cathode, an increase in the percentage of H2O in the output product stream from the cathode, an increase in the flow rate of the output product stream from the cathode, or a combination thereof.

[0253] The fuel cell assembly of one or more of these clauses, wherein the gas sensor is further configured to sense gas composition data of the fluid surrounding the fuel cell.

[0254] The fuel cell assembly of one or more of these clauses, wherein the gas composition data includes a percentage of O2 in the fluid surrounding the fuel cell.

[0255] A fuel cell assembly according to one or more of these clauses, wherein the fuel cell leak diagnostic information indicates an anode external leakage determined in response to a decrease in the percentage of O2 in the fluid surrounding the fuel cell and the percentage of O2 in the fluid surrounding the fuel cell is less than the percentage of O2 in the output product stream from the cathode.

[0256] A fuel cell assembly according to one or more of these clauses, wherein the fuel cell leak diagnostic information indicates an external leakage of the cathode determined in response to a decrease in the percentage of O2 in the fluid surrounding the fuel cell and the percentage of O2 in the fluid surrounding the fuel cell being greater than the percentage of O2 in the output product stream from the cathode.

[0257] The fuel cell assembly of one or more of these clauses, wherein the gas sensor is further configured to sense gas composition data of the output product stream from the anode.

[0258] A fuel cell assembly according to one or more of these clauses, wherein the gas sensor is a single gas sensor.

[0259] A fuel cell assembly according to one or more of these clauses, wherein the gas sensor includes a first gas sensor and a second gas sensor, wherein the first gas sensor is configured to sense gas composition data of the output product flow from the cathode, and the second gas sensor is configured to sense gas composition data of the output product flow from the anode.

[0260] The fuel cell assembly of one or more of these clauses, wherein the fuel cell assembly further comprises an enclosure at least partially surrounding the fuel cell stack, and wherein the gas sensor is positioned outside the enclosure.

[0261] A fuel cell assembly according to one or more of these clauses, wherein the fuel cell assembly is part of a propulsion system for an aircraft, wherein the propulsion system further includes a gas turbine engine, the gas turbine engine including a combustion section having a burner, and wherein the fuel cell is configured to provide the output product flow from the anode and from the cathode to the burner.

[0262] A method for detecting a leak in a fuel cell of a fuel cell assembly of a propulsion system, the fuel cell comprising a cathode and an anode, the method comprising: receiving gas composition data of an output product stream from the cathode, gas composition data of an output product stream from the anode, gas composition data of a fluid surrounding the fuel cell, or a combination thereof from a gas sensor; and determining fuel cell leak diagnostic information in response to the received gas composition data.

[0263] The method of one or more of these clauses, wherein receiving the gas composition data comprises receiving data at a resolution of 1 minute or less.

[0264] A propulsion system comprises: a thruster; and a fuel cell assembly capable of operating with the thruster, the fuel cell assembly comprising: a fuel cell stack, the fuel cell stack comprising a fuel cell, the fuel cell comprising a cathode and an anode; and a gas sensor, the gas sensor being constructed to sense gas composition data of an output product flow from the cathode, gas composition data of an output product flow from the anode, gas composition data of a fluid surrounding the fuel cell, or a combination thereof, to determine fuel cell leak diagnostic information.

[0265] A fuel cell assembly according to one or more of these clauses, wherein the gas sensor is a vibration and rotational spectroscopy monitor.

[0266] A fuel cell assembly according to one or more of these clauses, wherein the gas sensor is a Raman spectroscopy monitor.

[0267] A method according to one or more of these clauses, wherein receiving the gas composition data includes receiving data indicating an increase in the percentage of N2 in the output product stream from the anode, and wherein determining the fuel cell leak diagnostic information includes determining a cross gas leak from the cathode to the anode in the fuel cell.

[0268] A method according to one or more of these clauses, wherein receiving the gas composition data includes receiving data indicating an increase in the percentage of CO2, H2O, or both in the output product stream from the cathode, and wherein determining the fuel cell leak diagnostic information includes determining a cross gas leak from the anode to the cathode in the fuel cell.

[0269] A method according to one or more of these clauses, wherein receiving the gas composition data includes receiving data indicating a decrease in the percentage of O2 in the fluid surrounding the fuel cell, and wherein determining the fuel cell leak diagnostic information includes determining an outward gas leakage in the fuel cell from the anode.

[0270] A method according to one or more of these clauses, wherein receiving the gas composition data includes receiving data indicating an increase in a percentage of O2 in the fluid surrounding the fuel cell, and wherein determining the fuel cell leak diagnostic information includes determining an outward gas leak in the fuel cell from the cathode.

[0271] This written description uses examples to disclose the present disclosure, including the best mode, and also enables any person skilled in the art to practice the present disclosure, including making and using any device or system and performing any combined methods. The patent scope of the present disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. If these other examples include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not differ substantially from the literal language of the claims, these other examples are intended to fall within the scope of the claims.

Claims

1. A fuel cell assembly, characterized in that: include: A fuel cell stack, the fuel cell stack comprising a fuel cell, the fuel cell comprising a cathode and an anode; and A multi-gas sensor configured to sense gas composition data of an output product stream from the cathode, gas composition data of an output product stream from the anode, gas composition data of a fluid surrounding the fuel cell, or a combination thereof to determine fuel cell leak diagnostic information.

2. The fuel cell assembly according to claim 1, characterized in that: in, The multi-gas sensor provides real-time in-situ sensing data having more than one electrical output, and wherein the gas composition data includes gas composition data for more than one gas.

3. The fuel cell assembly according to claim 1, characterized in that: in, The gas sensor is configured to detect a cross leak by sensing gas composition data of the output product stream from the anode.

4. The fuel cell assembly according to claim 3, characterized in that: in, The gas composition data includes a percentage of N2 in the output product stream from the anode, and wherein the fuel cell assembly is further configured to sense data indicative of a flow rate of the output product from the anode.

5. The fuel cell assembly according to claim 4, characterized in that: in, The fuel cell leak diagnostic information indicates cathode to anode crossover leakage determined in response to an increase in a percentage of N2 in the output product stream from the anode, an increase in a flow rate of the output product stream from the anode, or both.

6. The fuel cell assembly according to claim 1, characterized in that in, The gas sensor is configured to sense gas composition data of the output product stream from the cathode.

7. The fuel cell assembly according to claim 6, characterized in that: in, The gas composition data includes a percentage of CO2 in the output product stream from the cathode and a percentage of H2O in the output product from the cathode, and wherein the fuel cell assembly is further configured to sense data indicative of a flow rate of the output product stream from the cathode.

8. The fuel cell assembly according to claim 7, characterized in that: in, The fuel cell leak diagnostic information indicates an anode-to-cathode crossover leak determined in response to an increase in a percentage of CO2 in the output product stream from the cathode, an increase in a percentage of H2O in the output product stream from the cathode, an increase in a flow rate of the output product stream from the cathode, or a combination thereof.

9. The fuel cell assembly according to claim 8, characterized in that in, The gas sensor is further configured to sense gas composition data of the fluid surrounding the fuel cell.

10. The fuel cell assembly according to claim 9, characterized in that in, The gas composition data includes a percentage of O2 in the fluid surrounding the fuel cell.

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