Independently modulated fuel cell compressors

Abstract

An integrated hydrogen-electric engine includes an air compressor system 60, a hydrogen fuel source, a fuel cell 26, an elongated shaft 10 configured to drive the air compressor system and a propulsor

Description

[0001] The present disclosure relates to integrated hydrogen fuel cell electric engine systems. The disclosure has particular utility to hydrogen fuel cell electric engines for use with transport vehicles including aircraft and will be described in connection with such utility, although other utilities including terrestrial transport vehicles and water craft are contemplated.

[0002] Exhaust emissions from transport vehicles are a significant contributor to climate change. Conventional fossil fuel powered aircraft engines release CO2 emissions. Also fossil fuel powered aircraft emissions include non-CO2 effects due to nitrogen oxide (NOx), vapor trails and cloud formation triggered by the altitude at which aircraft operate. These non-CO2 effects are believed to contribute twice as much to global warming as aircraft CO2 and were estimated to be responsible for two thirds of aviation’s climate impact. Additionally, the high-speed exhaust gasses of conventional fossil fuel powered aircraft engines contribute significantly to the extremely large noise footprint of commercial and military aircraft, particularly in densely populated areas.

[0003] Moreover, in surveillance and defense applications, the high engine noise and exhaust temperatures of conventional fossil fuel burning engines significantly hamper the ability of aircraft to avoid detection and therefore reduce the mission capabilities of the aircraft.

[0004] Rechargeable battery powered terrestrial vehicles, i.e., “EVs” are slowly replacing conventional fossil fuel powered terrestrial vehicles. However, the weight of batteries and limited energy storage of batteries makes rechargeable battery powered aircraft generally impractical.

[0005] Hydrogen fuel cells offer an attractive alternative to fossil fuel burning engines. Hydrogen fuel cell tanks may be quickly filled and store significant energy, and other than the relatively small amount of unreacted hydrogen gas, the exhaust from hydrogen fuel cells comprises essentially only water.

[0006] In our co-pending US Application Serial No. 16 / 950,735 filed November 17, 2020, the contents of which are incorporated herein by reference, we disclose an integrated hydrogen-electric engine that reduces aircraft noise and heat signatures of conventional fossil fuel burning engines, improves component reliability, increases the useful life of the engine, limits environmental pollution, and decreases the probability of failure per hour of operation. In particular, we disclose an integrated turboshaft engine 1 with a multi-stage compressor similar to current turboshaft engines in the front, but with the remaining components replaced with a fuel cell system that utilizes compressed air and compressed hydrogen to produce electricity that powers electric motors on an elongated shaft to deliver useful mechanical power to a propulsor (e.g., a fan or propeller). Part of the generated power can be utilized to drive the multi-stage compressor. This architecture delivers very high-power density and is able to deliver similar power density to modem jet engines (e.g., 6-8 kW / kg) at a pre-compression ratio of 30+ (common in today’s turbofan engines).

[0007] While the integrated hydrogen-electric engine described in our aforesaid US Application Serial No. 16 / 950,735 provides a technically and commercially viable solution to the aforesaid and other disadvantages of conventional fossil fuel burning engines, driving the compressor by the same motor and shaft that drives the prime mover propulsor as described in our aforesaid US Application Serial No. 16 / 950,735 is less than ideal since optimal compressor RPM generally is much higher than propulsor RPM. Even if compressor RPM is increased through gearing, the compressor is stuck at one RPM which may not be optimal for the compressor given different fuel cell demands at ambient pressures, e.g., sea level versus altitude, for example 10,000 feet above mean sea level (MSL).

[0008] In order to overcome the aforesaid and other problems of the prior art, we provide a system i.e., a method and apparatus, for selectively driving the compressor from the same motor and shaft that drives the prime mover propulsor, but through an engagement mechanism such as a clutch and gears.

[0009] In one aspect of the disclosure we provide an integrated hydrogen-electric engine comprising an air compressor system, a hydrogen fuel source, a fuel cell, an elongated shaft connected to the propulsor and a motor assembly disposed in electrical communication with the fuel cell, wherein the air compressor system is connected to the shaft through an engagement mechanism such as a clutch and gear box. The engagement mechanism may be a magnetic clutch, an hydraulic or pneumatic clutch, or a mechanical or electromechanical clutch.

[0010] In another aspect of the disclosure, the hydrogen-electric engine comprises a multi-stage or multi-spool engine comprising a first turbo cell and at least a second turbo cell, wherein each turbo cell stage comprises an air compressor system configured to be selectively driven by the shaft through an engagement mechanism and gears. As before, 2 the engagement mechanism may be a magnetic clutch, a hydraulic or pneumatic clutch or a mechanical or electromechanical clutch.

[0011] In yet another aspect of the disclosure, the compressor or compressors are driven in response to air consumption needs of the fuel cell by engaging or disengaging the engagement mechanism or clutch under the following conditions: • Low Power, High Ambient P (e.g. Sea level) —► clutch free • High Power, High Ambient P (e.g. >10,000 ft MSL) —► clutch engaged, low gear speed • Low Power, Low Ambient P —► clutch engaged, low gear speed • High Power, Low Ambient P —► clutch engaged, high gear speed

[0012] In still yet another embodiment of the disclosure, the compressor may be driven by a controller in response to aircraft and / or fuel cell states comprising one or more of: • Throttle position • Oxygen depletion • Hydrogen depletion • Hydrogen demand • Phase of flight

[0013] In another embodiment of the disclosure, the hydraulic-electric engine comprises a multi-spool compressor system including a low pressure compressor having a first inlet and an outlet, and a high pressure compressor downstream of the low pressure compressor, having an inlet in fluid communication with the outlet of the low pressure compressor and an outlet connected to the fuel cell, wherein the low pressure compressor and the high pressure compressor are each connected to the shaft through engagement mechanisms. Alternatively, the hydraulic-electric engine may comprise a two-stage turbocell with first and second coaxial shafts connected via an engagement mechanism to first and second stage compressors. In such embodiment the first and second coaxial shafts are configured to run independently of one another, i.e., at different speeds. This permits us to provide essentially constant pressure to a fuel cell while varying flow rate or outside ambient air pressure independently operating the compressors as follows: • Low altitude: inner compressor • High altitude: pre-compressor; which at low altitude / ground operations may include: • A bypass gate • Blades designed to produce little air resistance • Variable guide vanes to reduce air resistance.

[0014] In still yet another aspect of the disclosure, two or more compressors are provided which may be engaged or disengaged to provide oxygen flow depending on hydrogen flow needs.

[0015] In still yet another embodiment, the compressor is driven selectively by the shaft or by a battery powered auxiliary electric motor, with an engagement mechanism configured to switch between the shaft and the electric motor. This allows us to start the compressor without spinning the propeller, or to power the compressor from the main motor and / or wind milling the propeller.

[0016] The compressors may comprise axial or centrifugal compressors.

[0017] The present disclosure also provides a method for driving an air-compressor system of an integrated hydrogen-electric engine comprising: a compressor system; a hydrogen fuel course; a fuel cell; an elongated shaft configured to drive the air compressor system and a propulsor; and a motor assembly disposed in electrical communication with the fuel cell, comprising selectively mechanically, connecting the air compressor system to the elongated shaft through an engagement mechanism.

[0018] In one embodiment of the method of engagement comprises a magnetic clutch, a hydraulic or pneumatic clutch, or a mechanical or electromechanical clutch, and including the step of engaging or disengaging the clutch.

[0019] In another aspect of the method, the clutch is engaged or disengaged under the following conditions: • Low Power, High Ambient Pressure —► clutch free • High Power, High Ambient Pressure —► clutch engaged, low gear speed • Low Power, Low Ambient Pressure —► clutch engaged, low gear speed • High Power, Low Ambient Pressure —► clutch engaged, high gear speed.

[0020] In still yet another aspect of the method, the clutch is engaged or disengaged in response to aircraft or fuel cell states comprising one or more of: • Throttle position • Oxygen depletion • Hydrogen depletion • Hydrogen demand • Phase of flight.

[0021] In yet another aspect of the method the integrated hydrogen-electric engine further comprises an auxiliary electrically driven motor configured to power the air compressor system, and including the step of selectively engaging / disengaging the auxiliary electrically driven motor or the elongated shaft.

[0022] In yet another aspect of the method the clutch is configured to act as a brake to prevent rotation of one or more of the motor shaft, propeller shaft, and compressor for ground operation without spinning the propulsor, or a proulsor brake to reduce aerodynamic drag when desired, or to reduce drag in case of a motor or proulsor failure.

[0023] In a further aspect of the method the auxiliary electrically driven motor is battery powered.

[0024] According to aspect “A” of the present invention there is provided an integrated hydrogen-electric engine comprising: an air compressor system; a hydrogen fuel source; a fuel cell; an elongated shaft configured to drive the air compressor system and / or a propulsor; and a motor assembly disposed in electrical communication with the fuel cell, wherein the air compressor system is connected to the elongated shaft through an engagement mechanism.

[0025] Preferably the engagement mechanism includes a gear box.

[0026] Preferably the engagement mechanism comprises a magnetic clutch, a hydraulic or pneumatic clutch or a mechanical or electromechanical clutch.

[0027] Preferably the integrated hydrogen electric engine further includes a controller configured to control operation of the engagement mechanism.

[0028] Preferably the controller is configured to control operation of the engagement mechanism to activate the air compressor in response to air consumption requirements of the fuel cell.

[0029] Preferably the controller is configured to control operation of the engagement mechanism to engage the air compressor in response to air consumption needs of the fuel cell under the following conditions: • Low Power, High Ambient Pressure —► clutch free • High Power, High Ambient Pressure —► clutch engaged, low gear speed • Low Power, Low Ambient Pressure —► clutch engaged, low gear speed • High Power, Low Ambient Pressure —► clutch engaged, high gear speed.

[0030] Preferably the controller is configured to control operation of the engagement mechanism to engage the air compressor in response to aircraft and / or fuel cell states comprising one or more of: •  Throttle position •  Oxygen depletion •  Hydrogen depletion •  Hydrogen demand •   Phase of flight.

[0031] Preferably the integrated hydrogen-electric engine further comprises a plurality of compressors configured to be driven by the shaft through a plurality of engagement mechanisms.

[0032] Preferably the air compressor system comprises a multi-spool compressor system including a low pressure compressor having a first inlet and an outlet, and a high pressure compressor downstream of the low pressure compressor, having an inlet in fluid communication with the outlet of the low pressure compressor and an outlet connected to the fuel cell, wherein the low pressure compressor and the high pressure compressor are each connected to the shaft through engagement mechanisms.

[0033] Preferably the engagement mechanisms include gear boxes.

[0034] Preferably the integrated hydrogen-electric engine further comprises an auxiliary electrically driven motor configured to power the air compressor system, wherein the engagement mechanism is configured to switch between the elongated shaft and the auxiliary electrically driven motor.

[0035] Preferably the auxiliary electrically driven motor is battery powered.

[0036] Preferably the integrated hydrogen-electric engine is configured to power an aircraft.

[0037] According to aspect “B” of the present invention there is provided a method for driving an air compressor system of an integrated hydrogen-electric engine according to aspect “A” of the present invention.

[0038] According to aspect “C” of the present invention there is provided a method for driving an air compressor system of an integrated hydrogen-electric engine comprising: an air compressor system; a hydrogen fuel source; a fuel cell; an elongated shaft configured to drive the air compressor system and propulsor; and a motor assembly disposed in electrical communication with the fuel cell comprising selectively connecting the air compressor system to the elongated shaft through an engagement mechanism.

[0039] Preferably the engagement mechanism comprises a gear box and a magnetic clutch, a hydraulic or pneumatic clutch, or a mechanical or electromechanical clutch, and including the step of controlling the clutch and optionally adjusting the gear box.

[0040] Preferably the clutch and / or gear box are controlled under the following conditions: • Low Power, High Ambient Pressure —► clutch free • High Power, High Ambient Pressure —► clutch engaged, low gear speed • Low Power, Low Ambient Pressure —► clutch engaged, low gear speed • High Power, Low Ambient Pressure —► clutch engaged, high gear speed.

[0041] Preferably the clutch and / or gear box are controlled in response to aircraft or fuel cell states comprising one or more of: • Throttle position • Oxygen depletion • Hydrogen depletion • Hydrogen demand • Phase of flight.

[0042] Preferably the integrated hydrogen-electric engine further comprises an auxiliary electrically driven motor configured to power the air compressor system, and including the step of selectively engaging / disengaging the auxiliary electrically driven motor or the elongated shaft.

[0043] Preferably the clutch is configured to act as a brake to prevent rotation of one or more of the motor shaft, propeller shaft, and compressor for ground operation without spinning the propulsor, or a propulsor brake to reduce aerodynamic drag when desired, or to reduce drag in case of a motor or propulsor failure.

[0044] Preferably the auxiliary electrically driven motor is battery powered.

[0045] According to aspect “D” of the present invention there is provided a fuel cell powered airplane comprising at least one electric motor, and an integrated hydrogenelectric engine according to aspect “A” of the present invention.

[0046] Further features and advantages of the present disclosure will be seen from the following detailed description of taken in conjunction with the following drawings, wherein like numerals depict like parts, and wherein: Fig. 1 is a schematic view of an integrated hydrogen fuel cell-electric engine system in accordance with our prior US Application Serial No. 16 / 950,735; Fig. 2 is a schematic view of an integrated hydrogen-electric engine system in accordance with a first embodiment of the disclosure; Figs. 3-5 are views similar to Fig. 2 of second, third and fourth embodiment of the disclosure; and Fig. 6 is a schematic view of an integrated hydrogen-electric engine system installed on an airplane in accordance with the present disclosure.

[0047] Fig. 1 illustrates an integrated hydrogen-electric engine system 1 that can be utilized, for example, in a turboprop or turbofan system, to provide a streamlined, lightweight, power-dense and efficient system, in accordance with our aforesaid US Application Serial No. 16 / 950,735. In general, integrated hydrogen-electric engine system 1 includes an elongated shaft 10 that defines a longitudinal axis “L” and extends through the entire powertrain of integrated hydrogen-electric engine system 1 to function as a common shaft for the various components of the powertrain. Elongated shaft 10 supports propulsor 14 (e.g., a fan or propeller) and a multi-stage air compressor system 12, a pump 22 in fluid communication with a fuel source (e.g., liquid hydrogen), a heat exchanger 24 in fluid communication with air compressor system 12, a fuel cell 26 (e.g., a fuel cell stack) in fluid communication with heat exchanger 24, and a motor assembly 30 disposed in electrical communication with inverters 28. Alternatively, one or more components e.g., pump 22A shown in phantom may be electrically driven by output from fuel cell 26.

[0048] Propulsor 14 includes an air inlet portion 12a at a front end thereof and a compressor portion 12b that is disposed proximally of air inlet portion 12a for uninterrupted, axial delivery of air flow in the proximal direction. Compressor portion 12b supports a plurality of longitudinally spaced-apart rotatable bladed compressor wheels 16 (e.g., multi-stage) that rotate in response to rotation of elongated shaft 10 for compressing air received through air inlet portion 12a for pushing the compressed air to a fuel cell 26 for conversion to electrical energy. As can be appreciated, the number of compressor wheels / stages 16 and / or diameter, longitudinal spacing, and / or configuration thereof can be modified as desired to change the amount of air supply, and the higher the power, the bigger the propulsor 14. These compressor wheels 16 can be implemented as axial or centrifugal compressor stages. Further, the compressor can have one or more bypass valves and / or wastegates 17 to regulate the pressure and flow of the air that enters the downstream fuel cell, as well as to manage the cold air supply to any auxiliary heat exchangers in the system.

[0049] Compressor 12 optionally can be mechanically coupled to elongated shaft 10 via a gearbox 18 to change (increase and / or decrease) propulsor rotations per minute (RPM).

[0050] Integrated hydrogen-electric engine system 1 further includes a gas management system such as a heat exchanger 24 disposed concentrically about elongated shaft 24 and configured to control thermal and / or humidity characteristics of the compressed air from air compressor system 12 for conditioning the compressed air before entering fuel cell 26. Integrated hydrogen-electric engine system 1 further also includes a fuel source 20 of cryogenic fuel (e.g., liquid hydrogen - LH2, or cold hydrogen gas) that is operatively coupled to heat exchanger 24 via a pump 22 configured to pump the fuel from fuel source 20 to heat exchanger 24 for conditioning compressed air. In particular, the fuel, while in the heat exchanger 24, becomes gasified because of heating (e.g., liquid hydrogen converts to gas) removes heat from the system. The hydrogen gas is then heated in the heat exchanger 24 to a working temperature of the fuel cell 26, which results in a control of flow through the heat exchanger 24. In embodiments, an electric heater 19 can be coupled to or included with heat exchanger 24 to increase heat as necessary, for instance, when running under a low power regime or under cold ambient conditions. Additionally, and / or alternatively, one or more fuel cells 28, inverters 29 and motor assemblies 30 can be coupled to heat exchanger 24 for fluid communication with the cooling / heating loops and respective components as necessary. Such heating / cooling control can be managed, for instance, via controller 200 of integrated hydrogen-electric engine system 1. In embodiments, fuel source 20 can be disposed in fluid communication with one or more of fuel cells 26, inverters 28, motor assembly 30, or any other suitable component to facilitate cooling of such components.

[0051] Pump 22 also can be coaxially supported on elongated shaft 10 for actuation thereof in response to rotation of elongated shaft 10. Heat exchanger 24 is configured to cool the compressed air received from air compressor system 12 with the assistance of the pumped cryogenic fluid.

[0052] The integrated hydrogen-electric engine system 1 further includes an energy core in the form of a fuel cell 26, which may be circular, and is also coaxially supported on elongated shaft 10 (e.g., concentric) such that air channels through fuel cell 26 may be oriented in parallel relation with elongated shaft 10 (e.g., horizontally or left-to-right). Fuel cell 26 may be in the form of a proton-exchange membrane fuel cell (PEMFC). The fuel cells of the fuel cell 26 are configured to convert chemical energy liberated during the electrochemical reaction of hydrogen and oxygen to electrical energy. Depleted air and water vapor are exhausted from fuel cell 26. The electrical energy generated from fuel cell 26 is then transmitted to inverters 28 and then motor assembly 30, which are also coaxially / concentrically supported around elongated shaft 10. In aspects, integrated hydrogen-electric engine system 1 may include any number of external radiators 19 for facilitating air flow and adding, for instance, additional cooling. Notably, fuel cell 26 can include liquid cooled and / or air cooled cell types so that additional cooling may be performed by external radiators or other devices.

[0053] One or more inverters 28 is configured to convert the direct current to alternating current for actuating one or more of a plurality of motors 30 in electrical communication with the inverters 28. The motor assembly 30 is configured to drive (e.g., rotate) the elongated shaft 10 in response to the electrical energy received from fuel cell 26 for operating the components on the elongated shaft 10 as elongated shaft 10 rotates.

[0054] In aspects, one or more of the inverters 28 may be disposed between motors 30 (e.g., a pair of motors) to form a motor subassembly, although any suitable arrangement of motors 30 and inverters 28 may be provided. The motor assembly 30 can include any number of motor subassemblies supported on elongated shaft 10 for redundancy and / or safety. Motor assembly 30 can include any number of fuel cell modules 26 configured to match the power of the motors 30 and the inverters 28 of the subassemblies. In this regard, for example, during service, the fuel cell modules 26 can be swapped in / out. Each fuel cell module 26 can provide any power, such as 400kW or any other suitable amount of power, such that when stacked together (e.g., 4 or 5 modules), total power can be about 2 megawatts on the elongated shaft 10. In embodiments, motors 30 and inverters 28 can be coupled together and positioned to share the same thermal interface so a motor casing of the motors 30 is also an inverter heat sink so only a single cooling loop goes through motor assembly 30 for cooling the inverters 28 and the motors 30 at the same time. This reduces the number of cooling loops and therefore the complexity of the system.

[0055] Up to this point, the integrated hydrogen cell-electric engine is essentially identical to the integrated hydrogen fuel cell-electric engine described in our aforesaid co-pending US Application Serial No. 16 / 950,735, filed November 17, 2020, the contents of which are incorporated herein by reference.

[0056] Referring to Fig. 2, in accordance with one aspect of the present disclosure, we provide an integrated fuel cell-electric engine in which the compressor 12b is connected via gear box 18 which preferably comprises a multi speed gear box through an engagement mechanism such as a clutch 50 to the propulsor shaft 10. Clutch 50 which may be a magnetic clutch, a hydraulic clutch or pneumatic clutch or a mechanical or electromechanical clutch, is controlled via controller 200 so that the compressor 12b is driven in response to air consumption needs of the fuel cell. Thus the gear box may be disengaged, i.e., the clutch freed under low- power high ambient air pressure conditions, for example sea level, taxiing and descent and / or the clutch engaged to engage the gear box selected to low gear speed for low compressor speed operation, and the clutch engaged with the gear box selected to high gear speed for high power demands and / or low ambient pressure conditions, i.e., climbing and cruising above 10,000 MSL.

[0057] In use, the clutch 50 is engaged / disengaged to drive the compressor 12b by a controller 200 in response to aircraft and fuel cell states comprising criteria including one or more of: • Throttle position • Oxygen depletion • Hydrogen depletion • Hydrogen demand • Phase of flight

[0058] Referring to Fig. 3, in yet another embodiment, multiple clutches 52, 54 and multiple gear boxes 56, 58 may be arranged on the same shaft 10. This permits us to employ fixed gear ratios in the different gear boxes 56, 58, simplifying the gear boxes which are connected to the common propulsor shaft 10. In such embodiment the compressors comprise two compressors 60 and 62, connected in series to the fuel cell 26.

[0059] More particularly, in this embodiment we include a first clutch 52 connected via a first gear box 56 for driving a first compressor 60 and a second clutch 54 connected to a second gear box 58 for driving a second compressor 62. As before, the clutches 52, 54 are engaged / disengaged to drive the compressors 60, 62 in response to aircraft and fuel cell needs.

[0060] Referring to Fig. 4, in yet another embodiment, the integrated hydrogen-electric engine system comprises a multi-spool engine 100, including a low pressure compressor 102, and medium pressure compressor 104, situated downstream from the low pressure compressor, and a high pressure compressor 106 situated downstream from the medium pressure compressor 104. The medium pressure compressor 104 and the high pressure compressors 106 are connected to a common shaft 10 through clutches 110, 112, respectively which include dogs and spines which intermesh when the effective clutches are in engaged conditions. As before, the clutches 110, 112 are engaged under controller 200 in response to aircraft and fuel cell needs.

[0061] A feature of multi spool engines is that it permits us to provide constant pressure to a fuel cell while varying flow rate or outside ambient air pressure with improved efficiency relative to fixed-ratio compressors. • Low altitude: inner compressor, and • High altitude: pre-compressor; which at low altitude / ground operations: i. Bypassed with a gate ii. Design blades so not much air resistance iii. Variable guide vanes to reduce air resistance

[0062] Referring also to Fig. 5, in yet another embodiment the integrated hydrogenelectric engine system comprises first and second coaxial shafts 302, 304 connected via engagement mechanisms 306, 308 and gear boxes 310, 312 to first and second stage compressors 314, 316, respectively. First and second coaxial shafts 302, 304 are configured to run independently from one another, i.e., at different speeds. Thus the second stage compressor 316, for example, may be stationary or run more slowly than the first stage compressor 314 on the ground and at low altitude, and driven by fuel cell exhaust gasses at higher altitudes where more compression is required. Also by engaging / disengaging the engagement mechanisms 306, 308 and selecting gears via gear box 310, 312 we can better tailor air flow to fuel cell demands.

[0063] As before, controller 200 is provided configured to receive among data, aircraft location, i.e., altitude, ambient air pressure, temperature and relative humidity, air stream speed and direction, etc., from various sensors (not shown), and includes a memory device including operating instructions.

[0064] Features and advantages of the present disclosure include: • Reliability • Operation over wide ambient pressure range • More power to propulsor at sea level where the compressor has less work to do as a result of the higher ambient air pressure.

[0065] Fig. 6 illustrates a pair of integrated hydrogen-electric engines 82A, 82B having air compressors in accordance with the present disclosure installed on an airplane 80.

[0066] Various changes may be made in the foregoing disclosure without departing from the spirit and scope thereof.

Claims

04 07 24What is Claimed:

1. An integrated hydrogen-electric engine comprising:an air compressor system comprising a plurality of air compressors;a hydrogen fuel source;a fuel cell;a propulsor;an elongated shaft configured to drive the air compressor system and the propulsor; anda motor assembly disposed in electrical communication with the fuel cell, wherein the plurality of air compressors are configured to be driven by the elongated shaft through a plurality of engagement mechanisms.

2. The integrated hydrogen-electric engine of claim 1, wherein the engagement mechanisms include gear boxes.

3. The integrated hydrogen-electric engine of claim 1 or claim 2, wherein the engagement mechanisms comprise a magnetic clutch, a hydraulic or pneumatic clutch or a mechanical or electromechanical clutch.

4. The integrated hydrogen-electric engine of any preceding claim, further including a controller configured to control operation of the engagement mechanisms.

5. The integrated hydrogen-electric engine of claim 4, wherein the controller is configured to control operation of the engagement mechanisms to activate the air compressors in response to air consumption requirements of the fuel cell.

6. The integrated hydrogen-electric engine of claim 4 or claim 5, wherein the controller is configured to control operation of the engagement mechanisms to engage the air compressors in response to air consumption needs of the fuel cell under the following conditions:• Low Power, High Ambient Pressure —> clutch free• High Power, High Ambient Pressure —> clutch engaged, low gear speed• Low Power, Low Ambient Pressure —> clutch engaged, low gear speed• High Power, Low Ambient Pressure —> clutch engaged, high gear speed.

7. The integrated hydrogen-electric engine of any of claims 4 to 6, wherein the controller is configured to control operation of the engagement mechanisms to engage the air compressors in response to aircraft and / or fuel cell states comprising one or more of:04 07 24• Throttle position• Oxygen depletion• Hydrogen depletion• Hydrogen demand• Phase of flight.

8. The integrated hydrogen-electric engine of any preceding claim, wherein the air compressor system comprises a multi-spool compressor system including a low pressure compressor having a first inlet and an outlet, and a high pressure compressor downstream of the low pressure compressor, having an inlet in fluid communication with the outlet of the low pressure compressor and an outlet connected to the fuel cell, wherein the low pressure compressor and the high pressure compressor are each connected to the shaft through engagement mechanisms.

9. The integrated hydrogen-electric engine of any preceding claim, further comprising an auxiliary electrically driven motor configured to power one of the air compressors without driving the propulsor.

10. The integrated hydrogen-electric engine of claim 9, wherein the auxiliary electrically driven motor is battery powered.

11. The integrated hydrogen-electric engine of any preceding claim, configured to power an aircraft.

12. A method for driving an air compressor system of an integrated hydrogen-electric engine, said integrated hydrogen-electric engine comprising:an air compressor system comprising a plurality of air compressors;a hydrogen fuel source;a fuel cell;a propulsor;an elongated shaft configured to drive the air compressor system and propulsor; anda motor assembly disposed in electrical communication with the fuel cell, wherein the plurality of air compressors are configured to be driven by the elongated shaft through a plurality of engagement mechanisms, comprising:selectively connecting the plurality of air compressors to the elongated shaft through the plurality of engagement mechanisms.04 07 2413. The method of claim 12, wherein the engagement mechanism comprises a gear box and a magnetic clutch, a hydraulic or pneumatic clutch, or a mechanical or electromechanical clutch, and including the step of controlling the clutch and optionally adjusting the gear box.

14. The method of claim 13, wherein the integrated hydrogen-electric engine is configured to power an aircraft, wherein the clutch and / or gear box are controlled under the following conditions:• Low Power, High Ambient Pressure —> clutch free• High Power, High Ambient Pressure —> clutch engaged, low gear speed• Low Power, Low Ambient Pressure —> clutch engaged, low gear speed• High Power, Low Ambient Pressure —> clutch engaged, high gear speed.

15. The method of claim 13 or claim 14, wherein the integrated hydrogen-electric engine is configured to power an aircraft, wherein the clutch and / or gear box are controlled in response to aircraft or fuel cell states comprising one or more of:• Throttle position• Oxygen depletion• Hydrogen depletion• Hydrogen demand• Phase of flight.

16. The method of any of claims 12 to 15, wherein the integrated hydrogen-electric engine further comprises an auxiliary electrically driven motor configured to power one of the air compressors without driving the propulsor.

17. The method of any of claims 12 to 16, wherein the integrated hydrogen-electric engine is configured to power an aircraft, and wherein the clutch is configured to act as a brake to prevent rotation of one or more of the motor shaft, propeller shaft, and compressors for ground operation without spinning the propulsor, or a propulsor brake to reduce aerodynamic drag when desired, or to reduce drag in case of a motor or propulsor failure.

18. The method of claim 16 or claim 17, wherein the auxiliary electrically driven motor is battery powered.

19. A fuel cell powered airplane comprising at least one electric motor, and an integrated hydrogen-electric engine as claimed in any of claims 1 to 11.

20. An integrated hydrogen-electric engine comprising:04 07 24an air compressor system comprising a plurality of air compressors;a hydrogen fuel source;a fuel cell;a propulsor;an elongated shaft configured to drive the air compressor system and the propulsor;a motor assembly disposed in electrical communication with the fuel cell, wherein the plurality of air compressors are configured to be driven by the elongated shaft through a plurality of engagement mechanisms, which include a clutch, anda controller configured to control operation of the engagement mechanisms, wherein the controller is configured to control operation of the engagement mechanisms to engage the air compressors in response ambient pressure and to air consumption needs of the fuel cell under the following conditions:• Low Power, High Ambient Pressure —> clutch free• High Power, High Ambient Pressure —> clutch engaged, low gear speed• Low Power, Low Ambient Pressure —> clutch engaged, low gear speed• High Power, Low Ambient Pressure —> clutch engaged, high gear speed.

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