Thermal management system and / or method

Abstract

The system can include: a fuel cell, a set of fluid loops, a set of propulsion motors, and / or any other suitable components. The set of fluid loops can include: a set of super-ambient cooling loops, a hydrogen loop, a fluid cooling loop, and / or any other suitable fluid loops. The system can optionally include or be used with a waste heat recapture system (e.g., turbocharger). The system functions to facilitate fuel cell operation(s) and / or thermal management for a hydrogen-electric propulsion aircraft. However, the system (100) can additionally or alternatively include any other suitable set of components.

Description

THERMAL MANAGEMENT SYSTEM AND / OR METHODCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of US Provisional Application number 63 / 708,905, filed 18-OCT-2O24, and US Provisional Application number 63 / 639,514, filed 26-APR-2024, each of which is incorporated in its entirety by this reference.TECHNICAL FIELD

[0002] This invention relates generally to the aviation field, and more specifically to a new and useful thermal management system and / or method in the aviation field.BRIEF DESCRIPTION OF THE FIGURES

[0003] FIGURE 1 is a schematic representation of a variant of the system.

[0004] FIGURE 2 is a schematic representation of a variant of the system.

[0005] FIGURE 3 is a schematic representation of a variant of the system.

[0006] FIGURE 4 is a schematic representation of a variant of the system.

[0007] FIGURE 5 is a schematic representation of a variant of the system.

[0008] FIGURE 6 is an example schematic arrangement with multiple heat exchangers in series along the air manifold in one of a variant of the system.

[0009] FIGURE 7A is an example schematic illustrating a turbocharger in one or more variants of the system.

[0010] FIGURE 7B is an example of a hydrogen loop in one or more variants of the system.

[0011] FIGURE 7C is a schematic representation of a variant of a fluid loop in one or more variants of the system.

[0012] FIGURE 8 is a schematic representation of a variant of the system.

[0013] FIGURE 9 is an example schematic representation, illustrating flow temperature and pressure for a variant of the system.

[0014] FIGURE 10 is an example schematic representation, illustrating flow temperature and pressure for a variant of the system.DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The following description of the preferred embodiments of the invention is not intended to limit the invention to these preferred embodiments, but rather to enable any person skilled in the art to make and use this invention.1. Overview.

[0016] The system 100, an example of which is shown in FIGURE 1, can include: a fuel cell no, a set of propulsion motors 120, a set of fluid loops 200, and / or any other suitable components. The set of fluid loops 200 can include: a set of super-ambient cooling loops 210, a hydrogen loop 220, a fluid coolant loop 230, and / or any othersuitable fluid loops. The system can optionally include or be used with a waste heat recapture system (e.g., turbocharger). The system too functions to facilitate fuel cell operation(s) and / or thermal management for a hydrogen-electric propulsion aircraft. However, the system too can additionally or alternatively include any other suitable set of components.

[0017] The term “intercooler” as utilized herein preferably refers to a heat exchanger which can facilitate heat transfer between a pressurized gas and a working fluid coolant. For example, intercoolers may typically be utilized to cool a gas after compression, transferring heat from the gas into the working fluid coolant (e.g., which may improve system efficiency in a turbo-compression system). However, it is understood that when the reverse temperature gradient exists (e.g., coolant at higher temperature than pressurized gas), an intercooler would instead heat the gas after compression (e.g., which maybe advantageous for net efficiency improvements and / or heat recovery in fuel cell systems). Thus, the term “intercooler” as utilized herein maybe used interchangeably with “interheater,” and / or can be otherwise suitably used / referenced herein. Furthermore, it is understood that the physical structure of such systems and terminology use is not intended to limit the system to a specific temperature gradient or direction of heat flow. Additionally or alternatively it is understood that, in some variants, the term “intercooler” maybe interpreted as a “heat exchanger” (e.g., such as a liquid-gas type heat exchanger, fluid heat exchanger, phase change heat exchanger), and / or maybe otherwise used / referenced herein. However, the term intercooler and / or heat exchanger can be otherwise suitably referenced herein.

[0018] The term “radiator” as utilized herein preferably refers to a component which rejects heat predominantly by forced convection (or facilitate heat exchange to a fluid such as air), and may thus be equivalently referenced as a “heat exchanger” and / or a “convective heat exchangers.” Additionally or alternatively, the term radiator can be otherwise suitably used / referenced, and / or may otherwise refer to any other suitable radiation-based heat rejection system(s) (e.g., which can reject heat from a working fluid at least partially by radiation).

[0019] Additionally, it is understood that the term “heat exchanger” as utilized herein may refer to a radiator, intercooler, inter-heater, evaporator, condenser, and / or other term in various contexts.1.1 Variants.

[0020] In a first set of variants (e.g., an example is shown in FIGURE 8), a system for a hydrogen-electric aircraft, comprises: a High Temperature Proton Exchange Membrane (HTPEM) fuel cell defining a first inlet, a second inlet, and an exhaust outlet; a first heat exchanger fluidly coupling the first inlet to a first source flow; a turbocompression system comprising: a turbine fluidly coupled to an exhaust flow from the exhaust outlet of the HTPEM fuel cell; a compressor mechanically coupled to the turbine; and a second heat exchanger fluidly coupling the compressor to the second outlet and configured to receive a second source flow from the compressor; and a fluid loop comprising a coolant, the fluid loop fluidly coupling the HTPEM fuel cell to the first heat exchanger and the second heat exchanger in series, wherein the second heat exchangerthermally couples the second source flow to the coolant, wherein the first heat exchanger thermally couples the first source flow to the coolant.

[0021] In one or more variants, the second source flow comprises turbocompressed ram air from a ram air intake which is further pressurized via the compressor, wherein the second heat exchanger is configured to precondition the second source flow using heat from the coolant within the coolant loop. In an example, the first heat exchanger is configured to precondition the first source flow with heat from the coolant within the coolant loop.

[0022] In one or more variants, the HTPEM fuel cell is configured to operate above 160 degrees Celsius, wherein the first source flow and the second source flow are each preconditioned to a temperature above 160 degrees Celsius at the first and second inlets, respectively.

[0023] In one or more variants, the coolant loop further comprises an electric heater and a radiator arranged in series between the first heat exchanger and the HTPEM fuel cell. In one example, the system further comprises a DC-DC converter electrically coupling the HTPEM fuel cell to the electric heater.

[0024] In one or more variants, prior to aircraft operation, an electric heater is powered to pre-condition the system (e.g., fuel cell temperature, coolant temperature, source gas temperature[s], etc.).

[0025] In one or more variants, during aircraft operation, an electric heater is selectively powered to continuously maintain at least a base load of the HTPEM fuel cell (e.g., 20% nominal load; which may avoid degradation of the fuel cell).

[0026] In one or more variants, the system comprises: a diffuser coupled to an ambient air intake; and a variable-geometry nozzle, a radiator arranged in series between the diffused and the variable geometry nozzle.

[0027] In one or more variants, the exhaust flow is fluidly coupled to the variablegeometry nozzle downstream of the turbine. As an example, the exhaust flow comprises water vapor (e.g., or an air / vapor mixture).

[0028] In one or more variants, downstream of the turbine, the exhaust flow is above 100 degrees Celsius. As an example, the exhaust flow gas may remain above the vapor dome upon exiting the turbine to avoid condensation (e.g., avoid contrails and / or negative impacts resulting from liquid water degrading the turbine or other elements of the system, etc.).

[0029] In one or more variants, the HTPEM fuel cell further defines a coolant inlet and a coolant outlet within the coolant loop, wherein a first temperature difference between the coolant outlet and the first inlet is less than 20 degrees Celsius, wherein a second temperature difference between the coolant outlet and the second inlet is less than 20 degrees Celsius.

[0030] In one or more variants, the turbo-compression system spans the HTPEM fuel cell and is configured to harvest waste heat from the HTPEM fuel cell.

[0031] In one or more variants, the first source flow comprises hydrogen, wherein the first heat exchanger comprises an evaporative heat exchanger which is configured to provide the hydrogen gas to the HTPEM fuel cell.

[0032] In one or more variants, the coolant loop is configured to facilitate phase change cooling across the HTPEM fuel cell.

[0033] In one or more variants, the system further comprises: a first pump configured to circulate the coolant through the coolant loop; and a second pump configured to circulate the first source flow through the fuel cell.

[0034] In one or more variants, the HTPEM fuel cell is electrically coupled to a propulsion motor and a turbo-compression motor of the turbo-compression system which is mechanically coupled to the compressor.

[0035] In one or more variants, the system further comprises a water reservoir, wherein the coolant comprises water, wherein, in a peak thermal load configuration, the coolant loop is configured to reject heat by venting water vapor from the coolant loop.2. Benefits.

[0036] Variations of the technology can afford several benefits and / or advantages.

[0037] First, variations of this technology can reduce parasitic losses from thermal management in hydrogen-electric propulsion aircraft, which can be particularly advantageous because of the compounding nonlinear effects of inefficiencies in such systems. Similarly, variants can reduce the weight and / or cost of thermal management in hydrogen-electric propulsion aircraft architectures to improve unit economics of commercial aircraft in terms of cost per available seat kilometer (CASK), as a function of fuel and capital costs. For example, variations of this technology can reduce fuel costs inaviation by utilizing hydrogen fuel cells and / or liquid hydrogen (LH2) as the primary energy source. However, variants can otherwise reduce parasitic losses.

[0038] Second, variations of this technology can leverage a higher operating temperature range in a hydrogen fuel cell (e.g., HTPEM) to facilitate waste heat recapture, such as via a turbocharger, and reduce parasitic loss in the thermal management system. For example, HTPEM fuel cells may operate above 160 degrees Celsius, thus enabling waste heat to be harvested from fluid loops (e.g., at high, super-ambient temperatures) and transferred back into the fuel cell reactants (e.g., reusing waste energy to heat LH2or O2) and / or harvested via a turbine (e.g., captured via electric motor regeneration and / or powering the turbo-compressor. In particular, where the turbo-compression system can span the fuel cell, leveraging waste heat from the fuel cell and / or exhaust flow to precondition and / or turbo compress a fuel cell source flow[s]). However, variants can be otherwise configured.

[0039] Third, variations of this technology can facilitate turbo-regeneration and / or energy recapture while exhaust gases remain above the vapor dome (e.g., above 100C), which may avoid condensation of water vapor within the exhaust stream (e.g., which may otherwise directly result in contrail formation and / or excess parasitic losses from the exhaust). However, variants can be otherwise configured.

[0040] Fourth, variants of the thermal management architecture can reduce temperature differentials across the fuel cell and / or maintain temperature differentials within a nominal range (e.g., 20 degrees C; 10 degrees C; etc.), which may improve the cycle life of the fuel cell and / or avoid degradation of the fuel cell membrane(s). Forexample, the temperature difference between the coolant outlet and the source flow(s) can be less than 20 degrees C (e.g., during peak load; during minimum load; during all periods of operation and / or aircraft flight). Additionally, variants can utilize electrical energy sinks within the thermal management architecture (e.g., turbo-compressor; heater; etc.) to maintain at least a minimum fuel cell load (e.g., about 20% of capacity; where membrane degradation may occur below the minimum fuel cell load threshold).

[0041] However, variations of the technology can additionally or alternately provide any other suitable benefits and / or advantages.3. System.

[0042] The system 100, an example of which is shown in FIGURE 1, can include: a fuel cell no, a set of propulsion motors 120, a set of fluid loops 200, and / or any other suitable components. The system can optionally include a waste heat recapture system and / or a compressor (e.g., turbo-compressor; within a turbocharger). The set of fluid loops can include: a set of super-ambient cooling loops, a hydrogen loop, a fluid cooling loop, and / or any other suitable fluid loops. The system can optionally include or operate in conjunction with an air manifold 240. However, the system 100 can additionally or alternatively include any other suitable set of components. The system 100 functions to facilitate fuel cell operation(s) and / or thermal management for a hydrogen-electric propulsion aircraft. Examples of the system 100 are shown in FIGURES 2, 7A-7C, 9, and10.

[0043] In variants, a single instance of the system can be integrated on an aircraft and / or propulsion system thereof (e.g., for a multi-prop aircraft). Alternatively, the system can be redundant, and / or can include duplicative, parallel instances of any combinations of element(s). For example, the system can include redundant instances of the fuel cell and fluid cooling loops on the left and right sides of the aircraft (e.g., an example of which is shown in FIGURE 10).3.1 Hydrogen-electric Powertrain.

[0044] The system can include or be used in conjunction with a set of propulsion motors 120. The set of propulsion motors functions to provide aircraft propulsion via propellers / rotors, powered by a fuel cell. For example, the fuel cell may supply about 220 kW of power at 800VDC to the set of propulsion motors for aircraft propulsion (e.g., at peak load, nominal, etc.). Additionally or alternatively, it is understood that the system can include or operate in conjunction with any suitable set of electrical energy sinks, such as power electronics (e.g., DC / DC converter), batteries, aircraft avionics / electronics (e.g., control systems, sensors, control surface actuators, etc.), electric heaters (e.g., resistive heating elements), and / or any other suitable components.

[0045] The system and / or the set of propulsion motors thereof can be integrated into any suitable aircraft architecture. Variants of the system are preferably integrated into a fixed wing aircraft architecture, but can additionally or alternatively be integrated into rotary wing, VTOL, and / or any other suitable aircraft architecture(s). For example, the set of propulsion motors can be integrated into a single prop aircraft or multi-propaircraft (e.g., driven by a corresponding set of motors). The system can include 1, 2, 3, 4, 5, 6, more than 6, and / or any other suitable number of propulsion motors (and corresponding rotors / propellers). In variants, the set of propulsion motors can include an integrated motor controller and / or can be used with a separate motor controller(s).

[0046] Propulsion motors can include any other suitable types of motor(s), such as in-runner motors, outrunner motors, brushless DC motors, permanent magnet synchronous motors, induction motors, axial flux motors, radial flux motors, switched reluctance motors, and / or any suitable motor type(s). The set of propulsion motors can have any suitable power characteristics and / or operating range. For example, the power output range can be 10 kW to 500 kW per motor, depending on aircraft size and application.

[0047] However, the system can include any other suitable motor(s) and / or electric energy sinks, and / or can be otherwise configured.

[0048] The fuel cell no functions to generate electricity to power the set of propulsion motors and thermal management of the system (e.g., via a DC / DC and / or battery). The fuel cell can receive an H2source flow and an O2(or O2gas mixture) source flow from the hydrogen loop and the air manifold, respectively. The fuel cell can output vapor (e.g., water vapor) and / or gas vapor mixture (e.g., air gasses with water vapor) byproducts at an exhaust flow, which may be exhausted to the aircraft exterior (e.g., via the air manifold, downstream of the source flow). Additionally, in variants the H2source flow and / or fuel cell exhaust gasses may be fully enclosed (and / or contained within anenvelope of a secondary fluid loop), such that any (high temperature) H2gas leaks from the fuel cell are cooled prior to being vented to the exterior and are fluidly isolated from a remainder of the aircraft, which may mitigate potential combustion risks. For example, fuel cell byproducts and reactants may be cooled by within or more of the fluid loops (e.g., turbine; LH2) prior to being released into the aircraft environment. This may be particularly advantageous for high temperature fuel cells, since H2combustion risk (within oxygenated air) may otherwise increase at higher gas temperatures and / or concentrations.

[0049] In one variant, the fuel cell can include a first (inlet) port coupled to the first source flow 112, a second (inlet) port coupled to the second source flow 114, and a third (exhaust / outlet) port which is coupled to the first and second ports and which exhausts the byproducts (e.g., water vapor) resulting from the fuel cell reaction via exhaust flow 116. Additionally, the fuel cell can include a fourth (inlet) port which is fluidly coupled to the fifth (outlet) port coupled, each fluidly coupled to fluid coolant loop (e.g., allowing fluid loop to circulate the coolant through the interior of the fuel cell). The fuel cell can optionally include a sixth (outlet) port, which allows the first (hydrogen) source flow to be recirculated through the

[0050] The fuel cell is preferably a High Temperature Proton Exchange Membrane (HTPEM) fuel cell. The HTPEM fuel cell can be a high temperature fuel cell which operates at about i8o°C. However, system can additionally or alternatively use any other type(s) of hydrogen fuel cells, such as Polymer Electrolyte Membrane (PEM) fuel cells, Alkaline Fuel Cells (AFC), Phosphoric Acid Fuel Cells (PAFC), Molten Carbonate FuelCells (MCFC), Solid Oxide Fuel Cells (SOFC), and / or any other suitable type of hydrogen fuel cell. However, the fuel cell can be otherwise configured. Additionally, the fuel cell can be configured to operate within any suitable temperature range(s), such as below ambient temperature, below 50C, 50C, 100C, 150C, 160C, 170C, 180C, 190C, 200C, 220C, above 220C, any open or closed range(s) bounded by the aforementioned values, and / or at any other suitable temperature(s) or temperature ranges.

[0051] The fuel cell can be thermally managed by fluid control of the input source flows by operation and working fluid temperature regulation within the fluid loop(s) (e.g., such as by a first and second heat exchanger). The fluid loops are preferably configured to receive (and manage / recapture) the heat load generated by the fuel cell (e.g., within the hydrogen loop and / or exhaust to the air manifold). For example, the fuel cell can have a nominal heat load of about 260 kW. Alternatively, the fuel cell can generate a heat load of less than 10 kW, 5okW, 100 kW, 150 kW, 200 kW, 220 kW, 240 kW, 280 kW, 300 kW, 350 kW, 500 kW, 1 MW, 5 MW, greater than 5 MW, and / or any other suitable heat load.

[0052] In some variants (e.g., particularly high temperature fuel cells, such as HTPEM), the fuel cell reactants may be preheated during startup to avoid excessive temperature differences across the fuel cell membrane, which may accelerate degradation. For example, the fuel cell may preheat reactants with a heated coolant and / or electric heater (e.g., preheat H2via a first heat exchanger thermally coupling the hydrogen source flow to a fluid loop with a heater). Alternatively, the HTPEM fuel cell can be bootstrapped during startup, and / or can be otherwise configured.

[0053] Additionally, since fuel cells (e.g., high temperature fuel cell, such as HTPEM) may not perform well at idle power (e.g., below 20%, below 10%, etc.), the fuel cell maybe continuously operated above an idle power threshold, dumping excess energy into an energy sink (e.g., battery, electric heater in the fluid loop). However, the fuel cell can be otherwise operated in various power scenarios.

[0054] However, the fuel cell can be otherwise configured and / or operated.3.2 Thermal Management.

[0055] A set of fluid loops functions to supply the fuel cell no with source fluids (e.g., first source flow 112 and second source flow 114) and facilitate thermal management of the system.

[0056] The set of fluid loops can include a set of super-ambient loops 210 (e.g., water-glycol cooling loops), a hydrogen loop 220, a fluid coolant loop 230 (e.g., oil loop, water loop, etc.), an air manifold 240, and / or any other suitable fluid loops. In one example, the hydrogen loop can function to supply (and / or recirculate) pre-conditioned hydrogen to the fuel cell; the set of super-ambient cooling loops can function to manage temperature of the electrical energy sinks (e.g., motor / inverter cooling) within a design operating range; the fluid loop can function to circulate a liquid coolant (e.g., phasechange liquid such as water; coolant) for thermal management to facilitate heat transfer between fluid loops; and the air manifold can function to supply 02to the fuel cell system while rejecting heat and fuel cell byproducts to the ambient exterior. However, the set of fluid loops can be otherwise configured.

[0057] Additionally, the set of fluid loops can include and / or operate with a set of heat exchangers, which function to facilitate heat exchange and / or heat transfer between fluid loops. The heat exchangers are preferably fluid-fluid type heat exchangers, each thermally coupling a pair of respective pair of fluid loops, but can additionally or alternatively include: liquid-liquid type heat exchangers, liquid-gas type heat exchangers, plate-fin type heat exchangers, shell-and-tube heat exchangers, fluid intercoolers, radiators, double-pipe heat exchangers, brazed plate heat exchangers, finned tube heat exchangers, gasketed plate heat exchangers, phase-change heat exchangers (e.g., evaporator; condenser; etc.) and / or any other suitable type(s) of heat exchanger(s). The heat exchangers can include inlet and outlet ports, heat exchange surfaces, flow channels, and / or any other suitable components / features. However, the heat exchangers can be otherwise configured.

[0058] In one set of variants, examples of which are shown in FIGURE 2 and FIGURE 8, the system can include a first heat exchanger 232 and a second heat exchanger 234-

[0059] The first HEX 232 functions to precondition the hydrogen source flow to the fuel cell. Additionally, the first heat exchanger can function to cool the coolant within the fluid coolant loop (e.g., transferring heat from the coolant into the hydrogen loop; cooled by cryogenic hydrogen). The first HEX and / or a first interior thereof (e.g., extending between a first and second fluid port) is preferably fluidly coupled to the hydrogen loop and / or H2source flow (e.g., from cryogenic storage). Additionally or alternatively, the first interior of the first HEX can be within the hydrogen loop and / orpartially define a fluid envelope of the hydrogen loop. Additionally, the first HEX and / or a second interior thereof (e.g., extending between a third and fourth fluid port) is preferably fluidly coupled to the fluid coolant loop and / or working fluid thereof. Additionally or alternatively, the second interior of the first HEX can be within the fluid coolant loop and / or partially define a fluid envelope of the fluid coolant loop.

[0060] In variants, the first heat exchanger can be an evaporative heat exchanger and / or can operate in conjunction with an evaporator (e.g., an example is shown in FIGURE 10). For example, an evaporator can be integrated with the first heat exchanger and / or the first heat exchanger may facilitate the evaporative phase change from LH2to GH2(e.g., using ambient heat and / or heat from the coolant flow). Alternatively, an evaporator can be upstream of the first heat exchanger (e.g., separate from the first HEX and fluidly coupled to the first HEX; using glycol or a glycol mixture to avoid freezing), and / or can be otherwise suitably configured.

[0061] However, the first heat exchanger can be otherwise configured.

[0062] The second HEX functions 234 to precondition the second (O2) source flow (or air gas mixture from the air manifold) to the fuel cell. Additionally or alternatively, the second heat exchanger can optionally function to facilitate intercooling and waste heat regeneration of a (turbo-)compressed source flow. Additionally, the second heat exchanger can function to transfer heat between the coolant into the hydrogen and the air manifold (e.g., compressed, oxygenated source flow to the fuel cell). The second HEX and / or a first interior thereof (e.g., extending between a first and second fluid port) is preferably fluidly coupled to the air manifold and / or oxygen source flow (e.g., frompressurized ram air). Additionally or alternatively, the first interior of the first HEX can be within the air manifold and / or partially define a fluid envelope of the air manifold (e.g., heat exchanger within a turbo-compressor). Additionally, the second HEX and / or a second interior thereof (e.g., extending between a third and fourth fluid port) is preferably fluidly coupled to the fluid coolant loop and / or working fluid thereof. Additionally or alternatively, the second interior of the second HEX can be within the fluid coolant loop and / or partially define a fluid envelope of the fluid coolant loop. However, the second heat exchanger can be otherwise configured.

[0063] However, first and second heat exchangers can be otherwise configured. Additionally, the system can include any suitable set of radiators, which function to facilitate heat transfer into the air manifold from another fluid loop. For instance, each super-ambient (e.g., water-glycol loop) can include a radiator, which functions to reject heat from the super-ambient loop to the air manifold (i.e., cooling with ambient air and / or ram air within the air manifold). As a second example, the fluid coolant loop can include and / or may be selectively coupled to a radiator to regulate temperature in the fluid coolant loop. The heat exchangers and / or radiators can be arranged in any suitable combination of series / parallel along the air manifold, can be integrated within a single component, can be separate components, and / or can be otherwise arranged within the air manifold and / or channels thereof. An example is shown in FIGURE 6.

[0064] However, the system can include or operate in conjunction with any other suitable heat exchangers.

[0065] The system can include a hydrogen loop which functions to facilitate operation of the fuel cell. For instance, a hydrogen loop can circulate hydrogen through the system, supply hydrogen to the fuel cell, remove excess hydrogen from the fuel cell, and / or recirculate unused / heated hydrogen back to the fuel cell. The hydrogen loop (e.g., an example is shown in FIGURE 7B) can include: a hydrogen source, a first heat exchanger, a pump, and / or any other suitable components.

[0066] The hydrogen loop and / or pump thereof can be configured to maintain a desired pressure and flow rate of hydrogen within the system. The hydrogen loop can be controlled to operate at various temperatures and pressures, depending on the specific requirements of the fuel cell and overall system. For instance, the hydrogen loop can be controlled to supply hydrogen at about 1.5 bar and 180 degrees C for a high temperature, hydrogen fuel cell.

[0067] The hydrogen source stores and supplies hydrogen to the system. The hydrogen source can be, for example, a high-pressure tank (e.g., CcH2tank), a doublewalled vessel (e.g., dewar), a liquid storage vessel, a cryogenic storage vessel, and / or any other suitable hydrogen source. For example, the source can store liquid hydrogen, cryocompressed hydrogen, and / or any other suitable form(s) of hydrogen. However, the hydrogen source can be otherwise configured, and / or the system can utilize any other suitable hydrogen source(s). As an example, the hydrogen source can store hydrogen at or below 28K and at pressures between 1.5 bar and 10 bar. Similarly, the hydrogen loop can be pressure regulated (e.g., at 1.5 bar) to meet fuel cell requirements.[oo68] In variants, the hydrogen loop can include or operate in conjunction with the first heat exchanger. For example, the source flow from the source can pass through the first heat exchanger before being circulated through the fuel cell and / or hydrogen loop. As a second example, the first HEX can be within the hydrogen loop.

[0069] The hydrogen pump in the hydrogen loop functions to circulate hydrogen through the hydrogen loop. For example, the pump can be controlled to a desired flow rate and / or pressure requirement for the fuel cell. Alternatively, the hydrogen source flow can be driven by gas pressure (e.g., resulting from hydrogen evaporation at a phasechange heat exchanger, a.k.a. evaporator), driven by a compressor, and / or otherwise configured.

[0070] In a first variant, a hydrogen pump can circulate the hydrogen source flow through the fuel cell and / or drive the hydrogen source flow pressure to the fuel cell. In a second variant, phase change conversion at an evaporator can drive the hydrogen source flow pressure and / or (mass) flow rate (e.g., where the flow rate can be pressure regulated by a set of valves, etc.). In a third variant, the hydrogen source flow can be directed unidirectionally into the fuel cell, where excess (unconverted / unreacted) hydrogen may be evacuated through the exhaust flow (e.g., through air manifold and / or turbine).

[0071] However, a hydrogen loop can be otherwise configured.

[0072] The set of super-ambient cooling loops 210 functions to facilitate thermal management of the power electronics by transferring excess heat into the gas within the air manifold and / or rejecting heat into the ambient environment. For example, the set ofsuper-ambient cooling loops can transfer heat from electrical sinks (e.g., power electronics, propulsion motors, etc.) to a radiator and / or at least a partial volume of air within the air manifold.

[0073] The set of super-ambient cooling loops can be configured to cool power electronics individually or collectively. For example, in a first example, the set of superambient cooling loops can have a i:n relationship with power electronics (e.g., multiple heat generating components cooled by a single loop and / or radiator). In a second example, the set of super-ambient cooling loops can have a 1:1 relationship with power electronics (e.g., each cooled by a respective loop and / or radiator; an example is shown in FIGURE 6). The set of super-ambient cooling loops can be configured in various ways. For example, the set of super-ambient cooling loops can include parallel loops, series loops, or a combination of parallel and series loops. The set of super-ambient cooling loops can be designed to operate at different temperature ranges, flow rates, or pressures to accommodate specific cooling requirements of different power electronics components. Additionally, the set of super-ambient cooling loops can incorporate heat exchangers, expansion tanks, or flow control valves to optimize thermal management. For instance, the set of super-ambient cooling loops can be designed to handle multiple heat sources with varying thermal characteristics, such as motors, motor controllers, DC-DC converters, and high-power pumps (e.g., hydrogen pump; compressor, etc.).

[0074] Each super-ambient cooling loop can include a pump, working fluid, and radiator. The pump can function to circulate the working fluid through the cooling loops.The working fluid can transfer heat from the power electronics to a radiator. The radiatorcan dissipate heat from the working fluid to the gas / air within the air manifold and / or ambient environment. However, the set of super-ambient cooling loops can be otherwise configured.

[0075] The pump functions to circulate working fluid through the loop. The pump can have a size, flow rate, and pressure suited to the application. For example, the pump can circulate about 30 LPM to facilitate super-ambient cooling of the propulsion motor (e.g., with a heat load of about 2okW at peak). Any suitable types of pumps can be used, such as: centrifugal, positive displacement, dynamic, reciprocating, axial-flow, ram, turbine, and / or any other suitable types of pump(s).

[0076] The working fluid functions to transfer heat within the thermal control system. For example, the working fluid can function to absorb heat from one (heat generating) component and transfer it to another component (e.g., radiator) within the loop. The working fluid can be, for example, a water glycol mixture (e.g., 50 / 50, and / or any suitable mixture ratio), oil, ethylene glycol, propylene glycol, dielectric fluids, nanofluids, phase change fluids, and / or any suitable heat transfer fluid(s) can be used.

[0077] Each super-ambient loop can include a radiator, which functions to reject heat from the power electronics and / or super-ambient cooling loop to ambient. For example, the radiator can function to reject heat via air manifold exhaust gasses. The radiator can be fluidly coupled to an air manifold (e.g., by a set of extended surfaces / fins fluidly coupled to the air manifold). However, the super-ambient loops can include or be coupled to any other suitable heat exchangers and / or radiators, and / or can be otherwise suitably configured.

[0078] The fluid coolant loop(s) 230 functions to facilitate thermal management and / or heat transfer between fluid loops by circulating a coolant. The fluid coolant loop is preferably fluidly coupled to the fuel cell and configured to facilitate cooling and / or thermal management of the fuel cell. The fluid coolant loop can include a pump, coolant (e.g., distilled / pure water, water glycol mixture, etc.), an intercooler, a heater, a radiator, a radiator bypass, and / or any other suitable components. In one variant, the fluid coolant loop can be a super-ambient cooling loop which is thermally coupled to the fuel cell and / or other fluid loops (e.g., an example is shown in FIGURE 7C).

[0079] The fluid coolant loop can provide liquid cooling to the fuel cell (e.g., where the coolant remains in a liquid state through an interior of the fuel cell). Additionally or alternatively, the fluid coolant loop can provide phase change cooling to the fuel cell (e.g., where the coolant evaporates through an interior of the fuel cell; where the fuel cell functions as an evaporator). For example, the coolant may be atomized and circulated through the interior of the fuel cell, which may allow the coolant loop to operate at a lower (mass) flow rate through the fuel cell (e.g., to achieve equivalent heat rejection). In variants which leverage phase-change water cooling, the coolant loop can optionally be configured to reject heat by venting water vapor from the coolant loop (e.g., leveraging an excess water reservoir to accommodate peak / excess cooling load, such as during an initial climb), such as selectively venting water vapor into the exhaust flow. As an example, additional water within the loop can be stored in a reservoir to provide additional thermal mass to smooth cooling performance during nominal operation and / or facilitate ventingto reject excess heat in a peak load configuration (e.g., between 500ml to 5L of excess liquid water maybe stored in a reservoir of the cooling loop prior to operation, which may be evaporated and vented into the exhaust steam to exceed the nominal heat rejection capacity during peak load, such as an initial climb). However, the coolant loop may alternatively leverage liquid cooling exclusively, maintain a fixed coolant mass during operation, and / or can be otherwise configured.

[0080] The pump functions to circulate coolant through the loop. The pump can have a size, flow rate, and pressure suited to the application. For example, the pump can circulate coolant through the fuel cell at about 12 bar. Any suitable type(s) of pump(s) can be used, such as: centrifugal, positive displacement, dynamic, reciprocating, axial-flow, ram, turbine, and / or any other suitable types of pump(s). The coolant is preferably water, but can additionally or alternatively be, for example, a water-glycol mixture (e.g., 50 / 50, and / or any suitable mixture ratio), oil, ethylene glycol, propylene glycol, dielectric fluids, nanofluids, phase change fluids, and / or any suitable coolant(s) can be used.

[0081] The fluid coolant loop can include an intercooler (i.e., second heat exchanger), which functions to precondition the compressed oxygen source flow (e.g., ram air; turbo-compressed; etc.) and / or other gasses before they enter the fuel cell. Additionally, the intercooler can harvest waste heat leaving the fuel cell and use it to precondition the oxygen source flow. Additionally or alternatively, the fluid cooling loop can include the first and second heat exchangers, and / or can otherwise operate without an intercooler and / or waste heat recapture system(s).

[0082] The fluid coolant loop can optionally include a heater, which functions to (electrically) heat the coolant. In a first variant, the heater can heat the coolant to facilitate reactant preconditioning during startup (e.g., in conjunction with a radiator bypass). In a second variant, the heater can heat the coolant as a dynamic electrical sink (i.e., to avoid idling the fuel cell when propulsion is not necessary). The heater is preferably an electric heater which can be powered by a battery and / or the fuel cell (e.g., via DC / DC). However, the heater can alternatively be excluded (e.g., where the fuel cell is bootstrapped during startup) and / or the system can be otherwise configured.

[0083] The fluid loop can optionally include an atomizer, which can be integrated with the fuel cell and / or separate, which may facilitate phase-change (evaporative) cooling through the interior of the fuel cell. Alternatively, the fluid loop can exclude an atomizer; or can otherwise facilitate phase-change and / or liquid cooling of the fuel cell.

[0084] The fluid coolant loop can include or be used in conjunction with a radiator, which functions to dissipate excess heat from the coolant to the gasses within the air manifold and / or reject heat to the aircraft exterior. As an example, the radiator can be configured to reject about 26okW of heat during peak operation.

[0085] The fluid coolant loop can optionally include or be used with a radiator bypass (e.g., an example is shown in FIGURE 3). The radiator bypass functions to allow the coolant routing to ‘bypass’ the radiator when ambient cooling is not required and / or not desirable for control of the coolant temperature. As an example, the radiator bypass can include a set of electronically controlled valves, which can be controlled by the thermal control system to selectively decouple the fluid coolant loop from the radiator(and / or partially restrict flow through the radiator). drafFor instance, the radiator bypass maybe used when the coolant is used to warm / precondition the fuel cell during startup (e.g., using batteries or an external, offboard power source on the ground). However, the fluid coolant loop can alternatively exclude a radiator bypass and / or can be otherwise configured.

[0086] Additionally or alternatively, variants can leverage external fluid flows and / or electricity from ground infrastructure to precondition the system and / or any components thereof prior to aircraft operation (e.g., stationary on the runway; while physically coupled to a ground infrastructure).

[0087] However, the fluid coolant loop can be otherwise configured.

[0088] The air manifold 240 functions to provide oxygen to the fuel cell and reject heat from the radiator(s). The air manifold can use ram air from aircraft movement. The air manifold can have air that flows through ducting and radiators. The air manifold can include a variable geometry nozzle to modulate airflow (e.g., allowing the exhaust to be accelerated to reduce parasitic drag). The ducting of the air manifold can provide structural support for other components (e.g., for example, motor mounting). As an example, the air manifold can include various ducting and gas routing components which can be rigid, semi-rigid, flexible, structural, non-structural, and / or have any other suitable material properties / composition (e.g., composite, alloyed metal, plastic, etc.). In a first variant, the air manifold can optionally include or be used with a turbo-compressor system. In a second variant, nonexclusive with the first, the air manifold can utilizecompressed ram air to supply compressed reactant (oxygen gas) to the fuel cell and evacuate exhaust heat and byproducts.

[0089] In variants, the air manifold preferably includes a diffuser, a nozzle (e.g., outlet), a fuel cell source channel, and / or any other suitable subcomponents. Additionally or alternatively, the air manifold can include any suitable ducting, baffles, valves, vents, plenums, insulation, fittings, filters, and / or other suitable components.

[0090] The air manifold preferably routes (pressurized / ram) air through a subset of the heat exchangers, such as the radiators and / or second HEX, which can be arranged in any combination of series and / or parallel flow. For example, the second HEX can include a (turbo-compressed) source flow to the fuel cell substantially in parallel with a primary airflow path (e.g., with the radiators in series). Additionally or alternatively, the air manifold can include any suitable number of inlet(s) and outlet(s). For example, the air manifold can include a single inlet and a single outlet (e.g., with all external air passing between the inlet and the outlet) or multiple inlets / outlets (e.g., parallel flow paths, split flows, joining flow paths, etc.). However, the air manifold can be configured to achieve any suitable air routing and / or external air cooling between the inlet(s) and outlet(s).

[0091] The diffuser functions to decelerate ram air at the air manifold intake. For instance, the intake can be adjacent to a front propeller and / or arranged at a leading end of the aircraft. However, any ram air intake(s) can be used for any suitable aircraft configuration(s), and / or a diffuser(s) maybe otherwise configured.

[0092] The nozzle functions to accelerate the gas at the air manifold outlet. For example, the nozzle functions to reduce pressure drag loss. The nozzle is preferablyadjustable and / or controllable, allowing for variable gas flow rates and pressures. This adjustability can be achieved through mechanical means, such as movable flaps or segments, or through electronic control systems. Additionally or alternatively, the nozzle orifice geometry(ies) can be static, fixed, and / or invariant during continuous operation, and / or the system can be otherwise configured.

[0093] In a first variant, the nozzle can include or be used with energy harvesting mechanisms to recapture waste heat from the high temperature and / or pressurized exhaust gasses. For example, variants can include turbine-regeneration to harvest energy from the exhaust gasses (e.g., powering turbofan compressor in the air manifold) and / or any suitable cooling techniques. In a second variant, the nozzle is preferably designed and / or controlled to improve efficiency and reduce energy losses, but can additionally or alternatively be configured to prioritize other factors such as noise reduction or compact design.

[0094] However, the air manifold nozzle(s) can be otherwise configured.

[0095] The fuel cell source channel functions to supply source gas to the fuel cell. For example, the fuel cell source channel functions to supply O2or O2gas mixture (e.g., ambient air) to the fuel cell. The fuel cell source channel can be configured to receive source gas from the ram air intake and can be fluidly coupled to the fuel cell. The fuel cell source channel can include or route gas through an optional filter, a heat exchanger (e.g., the second heat exchanger), and / or any other suitable components. The source channel can route source gas through the second heat exchanger (i.e., an intercooler).

[0096] The air manifold can optionally include or be used with a filter along the fuel cell source channel, which can function to remove contaminants from the source gas. For instance, a filter can be positioned upstream of the heat exchanger (and fuel cell) in the fuel cell source channel along the O2source flow. The filter can be a desiccant filter, a particulate filter, a chemical filter, or a combination thereof. As an example, the filter can be a HEPA filter. However, a filter maybe otherwise configured and / or can be altogether excluded in some variants.

[0097] However, the fuel cell source channel may be otherwise configured.

[0098] However, the air manifold can be otherwise configured.3.3 Thermal Management.

[0099] An optional waste heat recapture system can function to recover waste heat generated by the system and / or fuel cell thereof. Additionally or alternatively, variants of the waste heat recapture system can recover waste heat from exhaust gasses, for example, prior to venting from the air manifold. In a first variant, the waste heat recapture system can include a turbocharger. The turbocharger can function to recover waste heat from exhaust gasses and convert it into mechanical energy. In a second variant, the waste heat recapture system can extract thermal energy from the exhaust gasses and convert it into usable forms of energy, such as electrical or mechanical energy. In a third variant, the waste heat recapture system can include a component for heating a working fluid within a multi-stage thermal system. This component can function to utilize waste heat toincrease the temperature of a working fluid, which can then be used in various thermal processes or for energy generation.

[0100] However, the waste heat recapture system may be otherwise configured. Additionally or alternatively, the exhaust gas can be accelerated through a nozzle at the exhaust to improve the overall system efficiency by reducing decrease drag-losses at the outlet (e.g., thus reducing the propulsive energy demand and corresponding thermal requirements for the remainder of the system) and / or advantageously generating additional thrust, contributing to aircraft propulsion.

[0101] In the first variant, the waste heat recapture system may include a turbocharger system, which can include or be used with a compressor, an intercooler, and / or any other suitable components. The turbocharger can be configured to utilize waste heat from the fuel cell to drive a turbine. This turbine can be mechanically coupled to the compressor, which compresses the intake air and / or O2source flow to the fuel cell. The compressed air can then be directed to the fuel cell for improved performance. The intercooler can function to heat the compressed air before it enters the fuel cell. For example, the intercooler can precondi tion / pre-heat the compressed source flow using waste heat from the fuel cell (e.g., intercooling within the second HEX; within the coolant loop), which can further increase the overall system efficiency. Additionally, heat within the source flow may be subsequently recycled / regenerated via exhaust gasses (e.g., through the turbine). An example is shown in FIGURE 7A.

[0102] The turbocharger can optionally include or be used with a compressor motor. The compressor motor can function to supply additional power to theturbocompressor (e.g., during low exhaust flow conditions). For example, the compressor motor can be an electric motor that can be activated to supplement the turbine-driven compression, which may allow the turbocharger to operate across a larger range of system conditions. For example, the turbocharger can adjust its operation based on factors such as system load, ambient temperature, and / or fuel cell output. Additionally or alternatively, where the compressor is mechanically coupled to a turbine, the compressor motor may facilitate turbine regeneration (e.g., via turbine regeneration).

[0103] However, the turbocharger can be otherwise integrated to facilitate waste heat recapture and / or efficiency benefits.

[0104] In the second variant, nonexclusive with the first, harvesting energy from exhaust gas functions to capture and utilize thermal energy from the exhaust gasses produced by the system. For example, harvesting energy from exhaust gas can improve overall system efficiency by converting waste heat into usable energy. Energy can be harvested / recaptured at the outlet of an air manifold (e.g., via a turbine), between fluid loops (e.g., at the second heat exchanger), at a turbine (e.g., via turbine regeneration), and / or at any other suitable elements within the system.

[0105] In the second variant, turbine regeneration may be used to recover energy from exhaust gasses. The internal energy in the exhaust gasses can be converted into usable mechanical energy (e.g., at a turbine shaft) and / or electrical energy (e.g., by motor generation). For example, a turbine at the outlet can be coupled to a compressor motor. Alternatively, the turbine can purely function as a generator (e.g., transforming exhaustgas energy into usable electricity; an example is shown in FIGURE 5). However, turbine regeneration maybe otherwise configured.

[0106] However, waste heat within exhaust gas can be otherwise utilized. Additionally or alternatively, waste heat and / or excess internal energy within the exhaust gas can be utilized to reduce parasitic losses resulting from system operation (e.g., reducing pressure drag, reducing thermal requirements, etc.).

[0107] In a third variant, waste heat can be recovered by multi-stage thermal integration with other subsystems, such intercooling via the first or second heat exchangers, to advantageously heat a working fluid within one or more of the fluid loops. For example, waste heat can be recovered to preheat a reactant(s) for the fuel cell, to supply energy to auxiliary systems, and / or to contribute to cabin heating in vehicle applications (e.g., HVAC heating). However, multi-stage thermal architectures may be otherwise configured to recover and / or utilize waste heat.

[0108] However, the system can include any other suitable waste heat recovery system(s) and / or can be otherwise configured to utilize waste heat, or the system may altogether exclude such systems in some variants.

[0109] The system can include or operate in conjunction with a thermal control system which functions to regulate and manage the temperature of various components within the system by controlling the fluid loop(s) (e.g., via pump and / or valve control, etc.). For example, the thermal control system functions to maintain operating temperatures within design ranges for the fuel cell, propulsion motors, and other heatgenerating elements. The thermal control system can include various flow controlarchitectures and control schemes. For example, the thermal control system can operate with any suitable control schemes, such as feedback controls (e.g., linear, non-linear, etc.), feedforward controls, open-loop control elements, optimal control techniques (e.g., MPC, LQG, etc.), robust control techniques (e.g., H-infinity loop shaping), stochastic control techniques, adaptive control, hierarchical control techniques, intelligent control (e.g., ANNs, fuzzy logic, ML, Bayesian probability, evolutionary computation and genetic algorithms, and / or a combination thereof, etc.), and / or any suitable combination thereof.

[0110] The thermal control system can control fluid flow through any suitable set(s) of fluid loops (e.g., using the pumps, compressors, valves therein) based on the sensor measurements. For example, fluid flow controls can be automated, controlled by electronic or pneumatic actuators that respond to signals from the thermal control system (e.g., dynamically, based on sensor measurements, etc.). However, the thermal control system maybe otherwise configured / regulated.

[0111] However, the system can include any other suitable components.

[0112] Embodiments of the system and / or method can include every combination and permutation of the various system components and the various method processes, wherein one or more instances of the method and / or processes described herein can be performed asynchronously (e.g., sequentially), contemporaneously (e.g., concurrently, in parallel, etc.), or in any other suitable order by and / or using one or more instances of the systems, elements, and / or entities described herein. Components and / or processes of the following system and / or method can be used with, in addition to, in lieu of, or otherwiseintegrated with all or a portion of the systems and / or methods disclosed in the applications mentioned above, each of which are incorporated in their entirety by this reference.

[0113] As a person skilled in the art will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of this invention defined in the following claims.

Claims

CLAIMSWe claim:

1. A system for a hydrogen-electric aircraft, comprising:• a High Temperature Proton Exchange Membrane (HTPEM) fuel cell defining a first inlet, a second inlet, and an exhaust outlet;• a first heat exchanger fluidly coupling the first inlet to a first source flow;• a turbo-compression system comprising:• a turbine fluidly coupled to an exhaust flow from the exhaust outlet of the HTPEM fuel cell;• a compressor mechanically coupled to the turbine; and• a second heat exchanger fluidly coupling the compressor to the second outlet and configured to receive a second source flow from the compressor; and• a fluid loop comprising a coolant, the fluid loop fluidly coupling the HTPEM fuel cell to the first heat exchanger and the second heat exchanger in series, wherein the second heat exchanger thermally couples the second source flow to the coolant, wherein the first heat exchanger thermally couples the first source flow to the coolant.

2. The system of claim 1, wherein the second source flow comprises turbocompressed ram air from a ram air intake which is further pressurized via the compressor,wherein the second heat exchanger is configured to precondition the second source flow using heat from the coolant within the coolant loop.

3. The system of claim 2, wherein the first heat exchanger is configured to precondition the first source flow with heat from the coolant within the coolant loop.

4. The system of claim 3, wherein the HTPEM fuel cell is configured to operate above 160 degrees Celsius, wherein the first source flow and the second source flow are each preconditioned to a temperature above 160 degrees Celsius at the first and second inlets, respectively.

5. The system of claim 1, wherein the coolant loop further comprises an electric heater and a radiator arranged in series between the first heat exchanger and the HTPEM fuel cell.

6. The system of claim 5, further comprising a DC-DC converter electrically coupling the HTPEM fuel cell to the electric heater.

7. The system of claim 6, wherein, prior to aircraft operation, the electric heater is powered to pre-condition the system.

8. The system of claim 6, wherein, during aircraft operation, the electric heater is selectively powered to continuously maintain at least a base load of the HTPEM fuel cell.

9. The system of claim 5, further comprising a diffuser coupled to an ambient air intake; and a variable-geometry nozzle, the radiator arranged in series between the diffused and the variable geometry nozzle.

10. The system of claim 9, wherein the exhaust flow is fluidly coupled to the variablegeometry nozzle downstream of the turbine.

11. The system of claim 10, wherein the exhaust flow comprises water vapor.

12. The system of claim 1, wherein, downstream of the turbine, the exhaust flow is above 100 degrees Celsius.

13. The system of claim 1, wherein the HTPEM fuel cell further defines a coolant inlet and a coolant outlet within the coolant loop, wherein a first temperature difference between the coolant outlet and the first inlet is less than 20 degrees Celsius, wherein a second temperature difference between the coolant outlet and the second inlet is less than 20 degrees Celsius.14- The system of claim 1, wherein the turbo-compression system spans the HTPEM fuel cell and is configured to harvest waste heat from the HTPEM fuel cell.

15. The system of claim 1, wherein the first source flow comprises hydrogen, wherein the first heat exchanger comprises an evaporative heat exchanger which is configured to provide the hydrogen gas to the HTPEM fuel cell.

17. The system of claim 1, wherein the coolant loop is configured to facilitate phase change cooling across the HTPEM fuel cell.

18. The system of claim 1, further comprising: a first pump configured to circulate the coolant through the coolant loop; and a second pump configured to circulate the first source flow through the fuel cell.

19. The system of claim 1, wherein the HTPEM fuel cell is electrically coupled to a propulsion motor and a turbo-compression motor of the turbo-compression system which is mechanically coupled to the compressor.

20. The system of claim 1, further comprising a coolant reservoir, wherein the coolant comprises water, wherein, in a peak thermal load configuration, the coolant loop is configured to reject heat by venting water vapor from the coolant loop.

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