Method of controlling pressure in hydrogen fuel tank, hydrogen fuel control system, hydrogen fuel system, aircraft and non-transitory computer readable storage medium

Abstract

A method of controlling pressure in a hydrogen fuel tank of an aircraft hydrogen fuel system, a hydrogen fuel control system, a hydrogen fuel system, an aircraft, and a non-transitory computer-readable storage medium are disclosed. The hydrogen fuel tank stores hydrogen fuel. The method includes receiving leakage information indicative of a leakage of hydrogen fuel from the hydrogen fuel system. The method further includes causing control of pressure in the hydrogen fuel tank based on the received leak information.

Description

Technical Field

[0001] The present invention relates to methods for controlling pressure in a hydrogen fuel tank, particularly computer-implemented methods, to hydrogen fuel system controllers including processors configured to perform such methods, to hydrogen fuel systems including such hydrogen fuel system controllers, and to aircraft including hydrogen fuel system controllers and / or hydrogen fuel systems. Background Technology

[0002] A hydrogen fueling system for an aircraft typically includes a hydrogen fuel tank that stores hydrogen fuel at cryogenic conditions. Such a system is configured to distribute the stored hydrogen fuel to the aircraft's consumption units (e.g., the aircraft's engines and / or generators) to power such engines and / or generators. Summary of the Invention

[0003] A first aspect of the present invention provides a method for controlling the pressure in a hydrogen fuel tank of an aircraft hydrogen fuel system, the hydrogen fuel tank storing hydrogen fuel, the method comprising: receiving leakage information indicating that hydrogen fuel is leaking from the hydrogen fuel system; and inducing control of the pressure in the hydrogen fuel tank based on the received leakage information.

[0004] As hydrogen fuel leaks from the hydrogen fuel tank, the pressure inside the tank may drop. In the event of a leak, controlling the pressure inside the hydrogen fuel tank can provide improved flexibility compared to an uncontrolled pressure drop. For example, controlling the pressure inside the hydrogen fuel tank during a leak allows for control over the amount of hydrogen fuel in the tank, which in turn enables measures to be taken to provide the desired amount of fuel in the tank in the event of a leak.

[0005] Optionally, controlling the pressure in the hydrogen fuel tank includes controlling the pressure of the hydrogen fuel in the hydrogen fuel tank. This, in turn, provides control over the hydrogen fuel pressure at the point where hydrogen fuel leaks from the hydrogen fuel system into the atmosphere outside the hydrogen fuel system. This allows measures to be taken during a leak to control the amount of hydrogen fuel entering the atmosphere from the hydrogen fuel system, and thus control the amount of hydrogen fuel in the hydrogen fuel tank. This can provide a flexible hydrogen fuel tank and / or hydrogen fuel system capable of better responding to hydrogen fuel leaks from the hydrogen fuel system.

[0006] Optionally, the hydrogen fuel is stored in a hydrogen fuel tank under cryogenic conditions. Optionally, the hydrogen fuel tank includes liquid hydrogen fuel stored therein. Optionally, the hydrogen fuel tank includes gaseous hydrogen fuel stored therein. Optionally, control over the pressure of the hydrogen fuel in the hydrogen fuel tank includes control over the pressure of the liquid and / or gaseous hydrogen fuel stored in the hydrogen fuel tank.

[0007] Optionally, controlling the pressure in the hydrogen fuel tank includes making the pressure in the hydrogen fuel tank exceed the external pressure of the atmosphere into which the hydrogen fuel leaks.

[0008] By providing pressure within the hydrogen fuel tank that exceeds external pressure, the ability of the atmosphere to enter the hydrogen fuel tank can be limited. This reduces the likelihood of hydrogen fuel mixing with the atmosphere within the tank.

[0009] Optionally, pressurizing the hydrogen fuel tank above the external pressure includes pressurizing the hydrogen fuel in the tank above the external pressure. This can cause the hydrogen fuel to leak from the tank into the atmosphere at the leak source, and prevent the atmosphere from entering the hydrogen fuel tank (or reduce the likelihood of the atmosphere entering the hydrogen fuel tank).

[0010] Optionally, the method includes: while the amount of hydrogen fuel in the hydrogen fuel tank is still above a threshold amount, causing the pressure in the hydrogen fuel tank to exceed the external pressure of the atmosphere into which the hydrogen fuel leaks.

[0011] Maintaining the pressure in the hydrogen fuel tank (and / or the pressure of the hydrogen fuel in the tank) above the external pressure ensures that atmospheric air cannot enter the hydrogen fuel tank until the amount of hydrogen fuel in the tank reaches or falls below a threshold amount. In this way, the method can provide the amount of hydrogen fuel in the tank that is at or below the threshold amount when atmospheric air could enter the hydrogen fuel tank and react with the hydrogen fuel. The ability to provide the desired amount of hydrogen fuel in the hydrogen fuel tank allows for control of the energy released during the reaction of the hydrogen fuel tank with the atmosphere in the event of such intrusion, thereby improving the lifespan of the hydrogen fuel tank.

[0012] Specifically, the threshold amount can be less than the amount that would normally be present in the hydrogen fuel tank when the pressure in the tank reaches or falls below the external pressure, without inducing pressure control in the hydrogen fuel tank. In this way, less hydrogen may be present in the tank during the time the atmosphere can enter, compared to the case where no pressure control is required. This, in turn, reduces the amount of energy released in the reaction between the hydrogen fuel in the tank and the atmosphere when the atmosphere enters the tank. This can improve the lifespan of the hydrogen fuel system and / or the hydrogen fuel tank.

[0013] The amount of hydrogen fuel in the hydrogen fuel tank includes the mass and / or number of moles of hydrogen fuel in the hydrogen fuel tank.

[0014] Optionally, inducing pressure control in the hydrogen fuel tank includes inducing heating of the hydrogen fuel in the tank. The pressure of the hydrogen fuel in the tank can be increased proportionally to the temperature of the hydrogen fuel in the tank. Since hydrogen fuel is typically stored in the tank at low temperatures, the required temperature of the heat source used to heat the hydrogen fuel can be correspondingly low. For example, the hydrogen fuel can be heated by the temperature of the atmosphere outside the hydrogen fuel tank (e.g., ambient air outside the aircraft) or even below that temperature, even when the aircraft is at cruising altitude. In this way, inducing heating of the hydrogen fuel provides a convenient and energy-efficient way to induce pressure control in the hydrogen fuel tank.

[0015] Optionally, the hydrogen fuel includes gaseous hydrogen fuel, and heating the hydrogen fuel in the hydrogen fuel tank includes heating the gaseous hydrogen fuel. An increase in the temperature of the gaseous hydrogen fuel can increase the pressure of the gaseous hydrogen fuel in the hydrogen fuel tank.

[0016] Optionally, the hydrogen fuel includes liquid hydrogen fuel, and heating the hydrogen fuel in the hydrogen fuel tank involves evaporating some or all of the liquid hydrogen fuel. This can increase the amount of gaseous hydrogen fuel in the hydrogen fuel tank, thereby increasing the pressure of the gaseous hydrogen fuel in the hydrogen fuel tank.

[0017] Optionally, inducing heating of the hydrogen fuel in the hydrogen fuel tank includes passing the hydrogen fuel from the hydrogen fuel tank through a heat exchanger and returning it to the hydrogen fuel tank.

[0018] In this way, the amount of hydrogen fuel flowing through the heat exchanger and / or the heat supplied to the hydrogen fuel in the heat exchanger can be controlled. This, in turn, allows for predictable and / or precise control of the temperature of the hydrogen fuel in the hydrogen fuel tank, and therefore also allows for predictable and / or precise control of the pressure in the hydrogen fuel tank. Furthermore, allowing hydrogen fuel to pass from the hydrogen fuel tank through the heat exchanger and back into the hydrogen fuel tank allows the liquid hydrogen fuel from the hydrogen fuel tank to be heated in the heat exchanger and returned to the hydrogen fuel tank as gaseous hydrogen fuel. Since gaseous hydrogen fuel is more compressible than liquid hydrogen fuel, returning gaseous hydrogen fuel to the hydrogen fuel tank allows for higher pressures to be achieved in the hydrogen fuel tank than if only liquid hydrogen were returned to the hydrogen fuel tank.

[0019] Optionally, inducing heating of the hydrogen fuel includes flowing a heat exchange medium through a heat exchanger to transfer heat between the hydrogen fuel and the heat exchange medium within the heat exchanger. This can provide efficient heating of the hydrogen fuel. For example, the heat exchange medium may include a fluid from another system of an aircraft that includes a hydrogen fuel system (e.g., a cooling system for the aircraft's engine). For example, the heat exchange medium may be heated by using it to cool components of the aircraft (e.g., a portion of the aircraft's engine or a component of the hydrogen fuel system) before it passes through the heat exchanger. Optionally, inducing heating of the hydrogen fuel includes passing the heat exchange medium through another heat exchanger to induce heating of the heat exchange medium. For example, inducing heating of the hydrogen fuel system may include exchanging heat in another heat exchanger between the heat exchange medium and another fluid (e.g., the atmosphere outside the hydrogen fuel tank, such as ambient air). Alternatively, the heat exchange medium may include heated hydrogen fuel that has already been heated during delivery through the hydrogen fuel system (e.g., toward the aircraft's engine). In any case, the heat already present in this heat exchange medium can be used to heat the hydrogen fuel in the heat exchanger, thus providing an efficient use of existing thermal energy.

[0020] Optionally, allowing hydrogen fuel to pass from the hydrogen fuel tank through a heat exchanger and return to the hydrogen fuel tank includes: operating a pump to pump hydrogen fuel through the heat exchanger and return it to the hydrogen fuel tank. Optionally, allowing hydrogen fuel to pass from the hydrogen fuel tank through a heat exchanger and return to the hydrogen fuel tank includes: operating one or more valves to allow hydrogen fuel to flow from the hydrogen fuel tank through the heat exchanger and return to the hydrogen fuel tank. Optionally, inducing heating of the hydrogen fuel in the hydrogen fuel tank includes supplying heated hydrogen fuel from the aircraft's engine to the hydrogen fuel tank. The engine may include a hydrogen combustion engine and / or a hydrogen fuel cell. The hydrogen fuel may include excess and / or unused hydrogen fuel from the engine.

[0021] Optionally, the method includes inducing heating of the heat exchanger heating elements (e.g., electric heating elements of the heat exchanger) of the heat exchanger. This can provide a light, hot hydrogen fuel system, such as a hydrogen fuel system without pipes for passing the heat exchange medium through the heat exchanger. Alternatively, inducing heating of the heat exchanger heating elements can supplement the heat provided by the heat exchange medium, thereby providing increased heat transfer to the hydrogen fuel in the heat exchanger.

[0022] Heating the hydrogen fuel can include operating a fuel tank heating element located in the hydrogen fuel tank to directly heat the hydrogen fuel in the tank. This can provide a light hydrogen fuel system, such as a hydrogen fuel system without pipes, valves, and / or other components for passing the hydrogen fuel through a heat exchanger. Alternatively, heating the hydrogen fuel tank heating element can supplement the heat provided by the heat exchanger, either to provide additional heating of the hydrogen fuel or to provide backup heating when heating via the heat exchanger is unavailable.

[0023] Optionally, heating the hydrogen fuel in the hydrogen fuel tank includes increasing the thermal conductivity of the hydrogen fuel tank. This can increase the rate of heat transfer between the hydrogen fuel in the hydrogen fuel tank and the atmosphere outside the hydrogen fuel tank (which may be the atmosphere into which the hydrogen fuel has leaked). The atmosphere may be at a higher temperature than the hydrogen fuel in the hydrogen fuel tank. For example, the hydrogen fuel may be stored in the hydrogen fuel tank as cryogenic liquid hydrogen, and the atmosphere may be atmospheric air at a temperature greater than or equal to the temperature outside the aircraft including the hydrogen fuel tank.

[0024] By increasing the thermal conductivity of the hydrogen fuel tank, the fuel within can be passively heated. For example, by increasing the thermal conductivity of the hydrogen fuel tank, the hydrogen fuel can be heated without the need for pump operation, as described above, to pump hydrogen (or the heat exchange medium) through a heat exchanger, and / or without the need to supply energy to the electric heater in the hydrogen fuel tank. Therefore, this provides an energy-efficient method for heating the hydrogen fuel in the tank.

[0025] Alternatively, increasing the thermal conductivity of the hydrogen fuel tank can provide redundancy in cases where the aforementioned heat exchanger, the components for allowing hydrogen fuel to flow through the heat exchanger, and / or the hydrogen fuel tank heating element are unavailable.

[0026] Optionally, the hydrogen fuel tank includes an inner wall, an outer wall, and a vacuum in the space between the inner and outer walls, and the increased thermal conductivity of the hydrogen fuel tank includes the vacuum in the release space.

[0027] A vacuum typically insulates hydrogen fuel from the atmosphere outside the fuel tank, which helps maintain the hydrogen fuel in a cryogenic liquid state within the tank. Therefore, by releasing the vacuum, the thermal conductivity of the hydrogen fuel tank can increase, thereby increasing the rate of heat transfer between the hydrogen fuel inside the tank and the outside atmosphere.

[0028] Optionally, releasing the vacuum in the space includes actuating a vacuum vent valve to allow atmospheric air from outside the hydrogen fuel tank to enter the space via the valve. In this way, the atmosphere can come into direct contact with the inner and outer walls, thereby increasing the rate of heat transfer between the atmosphere and the hydrogen fuel in the tank across the inner and outer walls. This can provide a reliable way to heat the hydrogen fuel, for example, when alternative heaters (such as the heat exchanger and / or heating element described above) are unavailable.

[0029] Optionally, releasing the vacuum in the space includes injecting a heat-conducting fluid, such as a heat-conducting liquid or gas, into the space. Optionally, the heat-conducting liquid or gas is inert. This can, for example, reduce the likelihood of a reaction between the heat-conducting fluid in the gap and the hydrogen in the fuel tank in the event of hydrogen fuel leakage into the gap.

[0030] Optionally, the received leak information indicates any one or more of the following: the flow rate of hydrogen fuel from the hydrogen fuel tank; the pressure of hydrogen fuel in the hydrogen fuel tank; and the hydrogen concentration outside the hydrogen fuel system.

[0031] For example, a non-zero flow rate of hydrogen fuel from the hydrogen fuel tank through the exhaust line can indicate a leak in the exhaust line, especially if the pressure in the hydrogen fuel tank is lower than the pressure required for hydrogen to flow through the exhaust line under normal conditions. The presence of hydrogen outside the hydrogen fuel system and / or an increase in the hydrogen concentration outside the hydrogen fuel system can also indicate a leak. Receiving leak information indicating the flow rate of hydrogen fuel from the hydrogen fuel tank and / or the concentration of hydrogen outside the hydrogen fuel system provides a convenient and / or reliable way to identify hydrogen fuel leaks from the hydrogen fuel system.

[0032] Furthermore, when the leak information indicates a flow rate of hydrogen fuel from the hydrogen fuel tank, the method may include: inducing pressure control within the hydrogen fuel tank to maintain a positive flow rate of hydrogen fuel from the tank. This can reduce the likelihood of external atmospheric entry into the hydrogen fuel tank, at least until the amount of hydrogen fuel in the tank falls below the aforementioned threshold amount.

[0033] Optionally, leakage information includes the aircraft's fuel consumption, such as the calculated and / or actual consumption of hydrogen fuel. A mismatch between calculated and actual consumption can indicate a leak of hydrogen fuel from the aircraft. Leakage information may include the aircraft's center of gravity, such as the calculated and / or actual center of gravity. Changes in the aircraft's center of gravity and / or the difference between the calculated and actual center of gravity can indicate that there is less fuel in the hydrogen fuel tank than expected, which can similarly indicate a leak of hydrogen fuel from the hydrogen fuel tank. Leakage information may include any other aircraft-related values ​​that also indicate a leak of fuel from the hydrogen fueling system.

[0034] Optionally, leakage information is received from one or more leakage detection sensors, such as a flow sensor in a pipeline fluidly connected to the hydrogen fuel tank, a pressure sensor in the hydrogen fuel tank, and / or a hydrogen concentration sensor in the external atmosphere outside the hydrogen fuel tank. Optionally, receiving leakage information includes sensing leakage information using a flow sensor, a pressure sensor, and / or a hydrogen concentration sensor.

[0035] Optionally, the method includes determining, based on leakage information, that there is a leak of hydrogen fuel from the hydrogen fuel system, such as from the hydrogen fuel tank and / or from a pipe or component fluidly connected to the hydrogen fuel tank. Optionally, the method includes increasing the pressure in the hydrogen fuel tank in response to a positive determination of a leak of hydrogen fuel from the hydrogen fuel system.

[0036] Optionally, the determination of the presence of a hydrogen fuel leak is performed by the leak detection system, and information indicating a leak is received from the leak detection system.

[0037] Optionally, the method includes receiving status information representing the operational status of a hydrogen fuel tank, a hydrogen fuel system, and / or an aircraft including an aircraft hydrogen fuel system; and initiating control of the pressure in the hydrogen fuel tank based on the received status information.

[0038] In this way, the pressure in the hydrogen fuel tank can be controlled in different ways based on the received status information. This provides a flexible and varied approach to inducing pressure control in the hydrogen fuel tank.

[0039] Optionally, the status information indicates any one or more of the following: the pressure outside the hydrogen fuel tank; the amount of liquid and / or gaseous hydrogen fuel in the hydrogen fuel tank; the consumption rate of hydrogen fuel in the hydrogen fuel tank by the aircraft's consumption unit; the temperature in the hydrogen fuel tank; the flight status of the aircraft; and the movement or expected movement of the aircraft.

[0040] Optionally, when the leak information indicates the flow rate of hydrogen fuel from the hydrogen fuel tank, and when the status information indicates the amount of gaseous and liquid hydrogen fuel in the hydrogen fuel tank and the flight status of the aircraft (e.g., distance to the nearest runway), the method includes inducing pressure control in the hydrogen fuel tank to provide a desired flow rate of hydrogen fuel from the hydrogen fuel tank such that the amount of hydrogen fuel in the hydrogen fuel tank is sufficient for the aircraft to reach the nearest runway. Optionally, the method includes inducing pressure control in the hydrogen fuel tank to provide a desired flow rate of hydrogen fuel from the hydrogen fuel tank such that the amount of hydrogen fuel in the hydrogen fuel tank is sufficient for passengers to disembark the aircraft before the pressure in the hydrogen fuel tank reaches a point where external atmosphere might be able to enter the fuel tank.

[0041] The method may include, based on received status information, controlling the amount and / or flow rate of hydrogen fuel moving from the hydrogen fuel tank caused by the hydrogen fuel system, such as controlling the amount of fuel transferred from the hydrogen fuel tank to the aircraft's engines. For example, when leakage information indicates a high leakage rate of fuel from the hydrogen fuel tank, and / or when status information indicates a low amount of fuel in the hydrogen fuel tank and / or a long distance to the nearest runway, the method may include reducing the rate at which fuel moves from the hydrogen fuel tank. This can save a certain amount of hydrogen fuel in the hydrogen fuel tank.

[0042] Optionally, when the status information indicates the temperature in the hydrogen fuel tank, the method includes inducing heating of the hydrogen fuel in the hydrogen fuel tank to provide a desired temperature in the hydrogen fuel tank. This allows the temperature to be maintained within a desired range and ensures that the pressure in the hydrogen fuel tank remains higher than the pressure of the external atmosphere, while not exceeding necessary limits.

[0043] Liquid hydrogen in the hydrogen fuel tank can act as a radiator to lower the temperature of gaseous hydrogen in the empty space of the hydrogen fuel tank, which can lead to some condensation of gaseous hydrogen. This may result in a decrease in pressure in the gaseous hydrogen. Therefore, when the state information indicates the ratio of liquid hydrogen fuel to gaseous hydrogen fuel in the hydrogen fuel tank, the method may include: the more liquid hydrogen present in the hydrogen fuel tank relative to the gaseous hydrogen, the greater the degree of heating of the hydrogen fuel in the hydrogen fuel tank. This can provide greater pressure in the hydrogen fuel tank, greater evaporation of liquid hydrogen in the hydrogen fuel tank, and / or reduced condensation of gaseous hydrogen in the hydrogen fuel tank. This ensures that the pressure in the hydrogen fuel tank remains higher than the external atmospheric pressure without exceeding necessary limits.

[0044] Optionally, when the state information indicates movement of the aircraft, the method includes inducing heating of the hydrogen fuel in the hydrogen fuel tank based on the aircraft's movement. Movement of the aircraft, particularly movement causing a change in the aircraft's attitude, can cause movement of the liquid hydrogen fuel in the hydrogen fuel tank. This can further lead to increased mixing of the liquid and gaseous hydrogen fuel in the hydrogen fuel tank, thereby increasing the cooling of the gaseous hydrogen fuel and / or causing increased condensation of the gaseous hydrogen fuel. The method may include heating the hydrogen fuel in the hydrogen fuel tank to a greater or lesser degree accordingly when the state information indicates a larger or smaller movement of the aircraft. This ensures that the pressure in the hydrogen fuel tank remains higher than the external atmospheric pressure without exceeding necessary limits.

[0045] Optionally, the flight status of the aircraft includes the aircraft's altitude. Optionally, when the status information indicates the flight status of the aircraft, the method may include: causing an increase in pressure in the hydrogen fuel tank, and / or causing heating of the hydrogen fuel in the hydrogen fuel tank such that the pressure is greater than the atmospheric pressure at that altitude. It should be recognized that atmospheric pressure will increase as the aircraft descends, therefore, as the aircraft descends, the pressure in the hydrogen fuel tank will need to be correspondingly higher to reduce the likelihood of external atmospheric entry into the hydrogen fuel tank. Optionally, the method includes receiving information indicating the ambient atmosphere at the runway the aircraft is approaching. Optionally, the method includes controlling the pressure in the hydrogen fuel tank to provide a desired flow rate of hydrogen fuel from the hydrogen fuel tank to ensure that when the aircraft lands on the runway, there is sufficient fuel remaining in the fuel tank to provide a pressure higher than the external atmospheric pressure at the runway.

[0046] Optionally, when the status information indicates the flight status of the aircraft and indicates that the aircraft has landed and / or taken off, the method may include causing the pressure in the hydrogen fuel tank to increase as much as possible, and / or causing the hydrogen fuel in the hydrogen fuel tank to be heated as much as possible.

[0047] Optionally, status information is received from one or more status sensors of the hydrogen fuel system and / or the aircraft, such as: a pressure sensor outside the hydrogen fuel tank; a fuel level gauge in the hydrogen fuel tank; a fuel consumption sensor of the aircraft; a temperature sensor in the hydrogen fuel tank; and / or attitude, altitude, movement and / or sensors of the aircraft.

[0048] Optionally, the method is a computer-implemented method, wherein: receiving leakage information includes the control system receiving leakage information, and inducing control of pressure in the hydrogen fuel tank includes the control system inducing control of pressure in the hydrogen fuel tank.

[0049] Optionally, to induce pressure control in the hydrogen fuel tank, the computer-implemented method includes controlling the system to induce heating of the hydrogen fuel in the hydrogen fuel tank. Optionally, the control system inducing heating of the hydrogen fuel in the hydrogen fuel tank includes: the control system causing the hydrogen fuel to flow from the hydrogen fuel tank through a heat exchanger (if provided) and back to the hydrogen fuel tank. Optionally, the control system inducing heating of the hydrogen fuel in the hydrogen fuel tank includes: the control system commanding a pump to pump the hydrogen fuel through the heat exchanger and back to the hydrogen fuel tank. Optionally, the computer-implemented method includes the control system sending commands to one or more valves to control the opening of one or more valves, for example, to control the flow of hydrogen fuel from the hydrogen fuel tank through the heat exchanger and back to the hydrogen fuel tank.

[0050] Optionally, the method includes heating the hydrogen fuel in the hydrogen fuel tank by increasing the thermal conductivity of the hydrogen fuel tank, which is achieved by a command from the control system to a vacuum vent valve to open the vacuum vent valve. In this way, increasing the thermal conductivity of the hydrogen fuel tank includes releasing the vacuum in the space between the inner and outer walls of the fuel tank. Optionally, the method includes spraying the hydrogen fuel in the tank with a cryogenic inert gas (e.g., liquid nitrogen). This can lower the temperature of the gaseous hydrogen fuel in the fuel tank and boil the liquid nitrogen, thereby further increasing the pressure in the hydrogen fuel tank. This can provide a positive pressure differential for a longer period of time compared to not providing an inert gas, for example, to allow the aircraft to land and / or disembark passengers before the outside atmosphere can enter the hydrogen fuel tank. This can also, or alternatively, increase the flow rate of hydrogen fuel out of the tank, thereby further reducing the mass of hydrogen fuel remaining in the tank. For example, spraying the hydrogen fuel in the tank with a cryogenic inert gas can be performed when it is no longer possible to control the pressure in the hydrogen fuel tank by heating the hydrogen fuel to the desired level. This could mean that only (or most) of the hydrogen in the fuel tank remains as gaseous hydrogen. This can improve the lifespan of the hydrogen fuel tank and / or the hydrogen fueling system.

[0051] Optionally, receiving status information includes the control system receiving status information. Optionally, inducing pressure control in the hydrogen fuel tank based on the received status information includes: the control system inducing pressure control in the hydrogen fuel tank based on the received status information. Inducing pressure control in the hydrogen fuel tank can be in any of the ways described above.

[0052] Optionally, the control system includes one or more controllers, each configured to perform one or more corresponding actions of the method. For example, the control system may include a single controller configured to receive leakage information and, based on the leakage information, induce pressure control in the hydrogen fuel tank. Alternatively, the control system may include a first controller and a second controller, the first controller configured to receive leakage information, and the second controller configured to, for example, induce pressure control in the hydrogen fuel tank in response to leakage information received from the first controller, or in response to a leak-information-based instruction from the first controller.

[0053] It should be recognized that any action described above with respect to the first aspect of the method can be performed by a control system. Furthermore, any optional features and / or advantages attributable to the method can be similarly applied when the method is a computer-implemented method.

[0054] A second aspect of the invention provides a non-transitory computer-readable storage medium comprising instructions that, when executed by a processor, cause the processor to perform the method of the first aspect.

[0055] A third aspect of the invention provides a hydrogen fuel control system including one or more processors configured to perform the methods of the first aspect. Optionally, the hydrogen fuel control system is communicatively coupled to a non-transitory computer-readable storage medium of the second aspect, and the processors are configured to execute instructions. Optionally, the hydrogen fuel control system includes a control system for the methods of the first aspect.

[0056] The control system may include and / or benefit from any optional features and / or advantages of the method of the first aspect or the non-transitory computer-readable storage medium of the second aspect.

[0057] A fourth aspect of the invention provides a hydrogen fuel system comprising a hydrogen fuel control system and a hydrogen fuel tank as described in the third aspect. The hydrogen fuel system may include and / or benefit from any optional features and / or advantages of the data processing method of the first aspect, the non-transitory computer-readable storage medium of the second aspect, or the hydrogen fuel control system of the third aspect.

[0058] Specifically, a hydrogen fuel system may include any or more of the components described above. For example, a hydrogen fuel system may include a heat exchanger. A hydrogen fuel system may include a loop comprising a hydrogen fuel tank, a heat exchanger, and a pump for pumping hydrogen fuel from the hydrogen fuel tank to the heat exchanger and back to the hydrogen fuel tank. Optionally, the hydrogen fuel system may include one or more valves for controlling the flow in the loop.

[0059] Optionally, the hydrogen fueling system includes an exhaust system arranged to transfer hydrogen fuel from the hydrogen fuel tank to the atmosphere outside the tank, such as the atmosphere outside an aircraft. Optionally, the exhaust system includes a first exhaust line comprising a pressure relief valve capable of being operated, for example by a hydrogen fuel control system and / or passively operated in response to pressure detected in the hydrogen fuel tank, to allow or prevent hydrogen fuel from flowing through the first exhaust line. Optionally, the exhaust system includes a second exhaust line comprising a ruptureable valve capable of rupturing to allow hydrogen fuel to flow from the hydrogen fuel tank through the second exhaust line.

[0060] Optionally, the hydrogen fuel system includes any of the aforementioned status sensors and / or leak detection sensors.

[0061] Optionally, the information indicating a leak received by the data processing unit includes the mass flow rate through the exhaust system. This can indicate that hydrogen fuel is leaking through the exhaust system, for example, due to a failure of the pressure reducing valve and / or a ruptured valve. In this way, the method and / or the data processing unit can provide a means of controlling the pressure and / or quantity of hydrogen fuel in the hydrogen fuel tank in the event of such a failure or rupture.

[0062] It should be recognized that leaks can occur in any part of the hydrogen fuel system, such as in the fluid loop, heat exchanger, valves and / or pumps used to control the flow of fuel through the fluid loop. In practice, the present invention is particularly advantageous when leaks occur in parts of the hydrogen fuel system that cannot be isolated from the hydrogen fuel tank (e.g., components immediately downstream of the hydrogen fuel tank and / or the hydrogen fuel tank itself). In such cases, the pressure and / or quantity of fuel in the hydrogen fuel tank can be controlled in a manner that prolongs the integrity of the hydrogen fuel tank and ensures sufficient fuel is present in the tank to complete the aircraft's current mission (e.g., the current flight, for example until the point where passengers have disembarked), thereby improving the reliability of the hydrogen fuel system compared to a hydrogen fuel system without such control.

[0063] The fifth aspect of the invention provides an aircraft comprising a non-transitory computer-readable storage medium of the second aspect, a hydrogen fuel control system of the third aspect, and / or a hydrogen fuel system of the fourth aspect.

[0064] Optionally, the aircraft includes an engine and / or a generator, and the hydrogen fueling system is configured to supply fuel from a hydrogen fuel tank to the engine to power the engine and / or the generator.

[0065] The aircraft may include and / or benefit from any optional features and / or advantages attributable to the method of the first aspect, the non-transitory computer-readable storage medium of the second aspect, the hydrogen fuel control system of the third aspect, and / or the hydrogen fuel system of the fourth aspect. Attached Figure Description

[0066] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, wherein:

[0067] Figure 1 An example aircraft is shown;

[0068] Figure 2 Shown Figure 1 A schematic diagram of an example hydrogen fuel system for the aircraft shown; and

[0069] Figure 3 Controls are shown Figure 2 The flowchart illustrates an example method for controlling pressure in a hydrogen fuel system. Detailed Implementation

[0070] Figure 1An aircraft 1 is shown, comprising an engine 3 and a hydrogen fuel system 2 for supplying hydrogen fuel to the engine 3. The engine 3 is a combustion engine configured to burn hydrogen fuel. It should be recognized that, in other examples, the engine 3 may include a hydrogen fuel cell. Such a hydrogen fuel cell may be configured to convert hydrogen and oxygen into water to generate electricity. The electricity may be used to power an electric motor to provide propulsion for the aircraft, or to power other (non-propulsion) electronic components of the aircraft.

[0071] like Figure 2 As shown, the hydrogen fuel system 2 includes a hydrogen fuel tank 10, which is a double-walled pressure vessel comprising an inner wall 11, an outer wall 12, and a vacuum in a gap 13 between the inner and outer walls 11 and 12. The inner wall 11 defines a chamber 14 in which hydrogen fuel 15 is stored in a cryogenic form. Specifically, the hydrogen fuel 15 comprises a liquid component defining a fuel level 15a in the chamber 14 and a gaseous component occupying a volume space 15b above the fuel level 15a. The vacuum in the gap 13 insulates the hydrogen fuel tank 10 to limit heat transfer between the hydrogen fuel 15 in the hydrogen fuel tank 10 and the external atmosphere 4 outside the hydrogen fuel tank 10 (and outside the hydrogen fuel system 2). The hydrogen fuel tank 10 also includes a vacuum vent valve 16 fluidly connected between the gap 13 and the external atmosphere 4 outside the hydrogen fuel tank 10.

[0072] The hydrogen fueling system 2 includes a fuel line 20, which includes a pump 21 and a fuel line valve 22 fluidly connected between the pump 21 and the hydrogen fuel tank 10. The hydrogen fueling system 2 also includes a heat exchange line 30 fluidly connected between the hydrogen fuel tank 10 and the fuel line 20 downstream of the pump 21. The hydrogen fueling system 2 includes a metering valve 23 upstream of the engine 3 and downstream of the junction 24 between the fuel line 20 and the heat exchange line 30, and an engine flow sensor 25 downstream of the metering valve 23.

[0073] The hydrogen fuel system 2 also includes: a heat exchanger 31, comprising a fuel side 32 fluidly connected to a heat exchange line 30; and a heat exchange valve 34 fluidly connected to the heat exchange line 30 between the fuel side 32 and the hydrogen fuel tank 10. The heat exchanger 31 also includes a heat exchange side 33 fluidly connected to a heat exchange system 40 of the aircraft 1. The heat exchange system 40 includes another heat exchanger 41 configured to exchange heat between a heat exchange medium (specifically a water-glycol mixture) in the other heat exchanger 41 and the aircraft atmosphere 5 outside the hydrogen fuel system 2. The heat exchange system 40 also includes a heat exchange pump 42 fluidly connected between the other heat exchanger 41 and the heat exchange side 33 of the heat exchanger 31.

[0074] The hydrogen fueling system 2 also includes an exhaust system 50 that fluidly connects the chamber 14 of the hydrogen fuel tank 10 to an exhaust system outlet 53, which opens to the ambient atmosphere 6 outside the aircraft 1. The exhaust system 50 includes an exhaust valve 51 configured to open in response to the pressure of the hydrogen fuel 15 in the chamber 14 exceeding a threshold pressure to release pressure in the chamber 14. The exhaust system 50 also includes a rupture valve 52 fluidly connected in parallel with the exhaust valve 51 between the chamber 14 and the exhaust system outlet 53. The rupture valve 52 is configured to irreversibly rupture if the pressure of the hydrogen fuel 15 in the chamber 14 exceeds another threshold pressure above the threshold pressure.

[0075] The hydrogen fuel system 2 also includes a flow sensor 60 fluidly connected to detect the flow rate of hydrogen fuel from the hydrogen fuel tank 10 through the exhaust system 50. The hydrogen fuel system 2 also includes a first temperature sensor 61a, a second temperature sensor 61b, a first pressure sensor 62a, a second pressure sensor 62b, and level sensors 65a, 65b in the chamber 14 of the hydrogen fuel tank 10 to detect the fuel level 15a of the hydrogen fuel 15 in the hydrogen fuel tank 10, as well as a first temperature and a second temperature, a first pressure, and a second pressure, respectively. The first temperature sensor 61a and the first pressure sensor 62a are positioned toward the ends of the hydrogen fuel tank 10 opposite to the second temperature sensor 61b and the second pressure sensor 62b. Providing the first temperature sensor 61a and the second temperature sensor 61b and the first pressure sensor 62a, the second pressure sensor 62b in this arrangement enables the sensing of both the temperature and pressure of the liquid and gaseous hydrogen fuel. For example, when the orientation of the hydrogen fuel tank 10 and the fuel level 15a in the hydrogen fuel tank 10 are as follows... Figure 2 As shown, the first temperature sensor 61a and the first pressure sensor 62a are immersed in liquid hydrogen fuel to detect the temperature of the liquid hydrogen fuel. In contrast, in Figure 2 In this configuration, the second temperature sensor 61b and the second pressure sensor 62b are located in the deficient space 15b above the fuel level 15a, and thus detect the temperature of the gaseous hydrogen fuel in the deficient space 15b. Furthermore, by providing more than one level sensor 65a, 65b, the fuel level 15a can be detected even in irregularly shaped hydrogen fuel tanks 10 under different orientations. The aircraft 1 includes an external pressure sensor 63 and a hydrogen sensor 64 in the external atmosphere 4 for detecting the pressure and hydrogen concentration in the external atmosphere 4, respectively.

[0076] The hydrogen fuel system 2 also includes a controller 200 which is communicatively connected to each of the following: pump 21, fuel valve 22, heat exchange valve 34, heat exchange pump 42, flow sensor 60, first temperature sensor 61a and second temperature sensor 61b, first pressure sensor 62a and second pressure sensor 62b, level sensors 65a and 65b, external pressure sensor 63 and hydrogen sensor 64.

[0077] The controller 200 is configured to operate the pump 21 to pump hydrogen fuel from the hydrogen fuel tank 10 to the engine 3 via the fuel line 20. The controller 200 is also configured to operate the metering valve 23 to control the flow rate of fuel toward the engine based on a signal received from the engine flow sensor 25. Specifically, the controller 200 is configured to operate the metering valve 23 to provide a mass flow rate of hydrogen fuel through the fuel line 20 that is greater than the sum of the mass flow rate of hydrogen fuel through the heat exchange line 30 and the mass flow rate of hydrogen fuel toward the engine 3 via the metering valve 23. The controller 200 is also configured to operate the fuel valve 22 to isolate the hydrogen fuel tank 10 from the pump 21 (and thus also isolate downstream components of the pump 21, including the engine 3 and the heat exchanger 31, relative to the hydrogen fuel tank 10).

[0078] As now relative to Figure 3 As described in the exemplary method 300 shown, the controller 200 is also configured to cause various components of the fuel system 2 to which it is communicatively connected to to operate in order to control the pressure of the hydrogen fuel 15 in the hydrogen fuel system.

[0079] Example method 300 includes a controller 300 receiving pressure and flow information 310 from a flow sensor 60 and a first pressure sensor 62a and / or a second pressure sensor 62b. The flow information includes the flow rate of fuel from chamber 14 through exhaust system 50 to the surrounding atmosphere 6, and the pressure information includes the pressure of hydrogen fuel 15 in the hydrogen fuel tank. The controller 200 is configured to determine 320 that there is a leak of hydrogen fuel 15 from hydrogen fuel system 2 when the flow rate of fluid through exhaust system 50 is non-zero and the pressure sensed by pressure sensor 61 is below a threshold pressure of exhaust valve 51. This indicates that fuel is flowing through exhaust system 50 when the pressure in hydrogen fuel tank 10 is insufficient to allow exhaust valve 51 to open properly. Furthermore, this can indicate, for example, that exhaust valve 51 is stuck in the "open" position, and / or burstable valve 52 has ruptured, and therefore hydrogen fuel is "leaking" through exhaust valve 51 and / or burstable valve 52.

[0080] The controller 200 is configured to, based on the determination of a leak of hydrogen fuel 15 from the hydrogen fuel system 2, induce operation 330 of the fuel line valve 22, pump 21, heat exchange pump 42, and heat exchange valve 34. Specifically, the controller 200 commands the fuel line valve 22 and heat exchange valve 34 to open, commands the metering valve 23 to restrict the flow of hydrogen fuel toward the engine 3, and commands the pump 21 to pump hydrogen fuel from the hydrogen fuel tank 10 through the fuel side 32 of the heat exchanger 31 and back to the hydrogen fuel tank 10. The controller 200 also commands the heat exchange pump 42 to pump the heat exchange medium in the heat exchange system 40 through the heat exchange side 33 of the heat exchanger 31. This causes heat to be transferred from the heat exchange medium to the hydrogen fuel flowing through the heat exchanger 31, thereby heating the hydrogen fuel. Specifically, the hydrogen fuel 15 is stored in the hydrogen fuel tank 10 at cryogenic conditions, and the heat exchange medium is at a temperature closer to that of the aircraft atmosphere 5 due to heat exchange between the heat exchange medium and the aircraft atmosphere 5 in another heat exchanger 41. The temperature of the aircraft atmosphere 5 is equal to or higher than the temperature of the ambient atmosphere 6 outside the aircraft 1. During the flight of the aircraft 1, this temperature can be greater than -70°C, while the cryogenic hydrogen fuel 15 in the hydrogen fuel tank 10 is at a cryogenic temperature of liquid or gaseous hydrogen. Therefore, the hydrogen fuel passing through the fuel side 32 is at a lower temperature than the heat exchange medium passing through the heat exchange side 33. As a result, the hydrogen fuel in the heat exchanger 31 is heated.

[0081] The heated hydrogen fuel is then transferred back to the hydrogen fuel tank 10 to heat the hydrogen fuel 15 within the tank. This heating of the hydrogen fuel 10 causes an increase in the pressure of the hydrogen fuel 15 within the tank. Specifically, the heating of the hydrogen fuel 15 causes some liquid hydrogen fuel to evaporate, which increases the amount of gaseous hydrogen fuel in the shortage space 15b (and thus increases the pressure). The heating of the gaseous hydrogen fuel also causes an increase in its pressure.

[0082] Then, the controller 200 receives signals from the first temperature sensor 61a and the second temperature sensor 61b, the first pressure sensor 62a and the second pressure sensor 62b, the external pressure sensor 63, and the fuel level sensors 65a and 65b, respectively. These signals represent the first temperature and the second temperature of the hydrogen fuel 15 in the hydrogen fuel tank 10, the first pressure and the second pressure of the hydrogen fuel 15 in the hydrogen fuel tank 10, the pressure of the external atmosphere 4 outside the hydrogen fuel system 2, and the fuel level 15a of the liquid component of the hydrogen fuel in the hydrogen fuel tank 10.

[0083] Then, the controller 200 operates the heat exchange valve 34 downstream of the heat exchanger 31 350, specifically by controlling the opening degree of the heat exchange valve 34, to control the flow rate of hydrogen fuel through the heat exchanger 31. In this way, the controller controls the amount of heating of the hydrogen fuel flowing through the heat exchanger 31 and returning to the hydrogen fuel tank 10. Specifically, the controller 200 controls the amount of heating of the hydrogen fuel to provide a desired pressure differential between the pressure of the hydrogen fuel 15 in the hydrogen fuel tank 10 and the pressure of the external atmosphere 4 into which the hydrogen fuel 15 leaks. More specifically, the controller controls the operation of the heat exchange valve 34 to heat the hydrogen fuel 15 in the hydrogen fuel tank 10 such that the pressure of the hydrogen fuel 15 in the hydrogen fuel tank 10 is sufficiently higher than the pressure of the external atmosphere 4 into which the hydrogen fuel 15 leaks, to prevent the external atmosphere 4 from entering the hydrogen fuel tank 10.

[0084] The controller 200 is configured to operate the heat exchange valve 34 to provide a positive pressure differential until the amount of hydrogen fuel 15 in the hydrogen fuel tank 10 drops below a threshold fuel amount. The controller 200 is configured to determine the amount of fuel in the hydrogen fuel tank 10 based on signals from temperature sensors 61a, 61b, pressure sensors 62a, 62b, and fuel level sensors 65a, 65b. Specifically, the controller 200 is configured to determine the amount of fuel based on the amount of liquid hydrogen fuel remaining in the tank, as well as the temperature and pressure of the remaining liquid hydrogen fuel (using fuel level sensors 65a, 65b, the first temperature sensor 61a, and the first pressure sensor 62a), and to determine the amount of gaseous hydrogen fuel in the tank based on the temperature and pressure of gaseous hydrogen fuel in the hydrogen fuel tank 10 (sensed using the second temperature sensor 61b and the second pressure sensor 62b) in conjunction with the ideal gas law. More specifically, knowing the liquid hydrogen fuel level 15 in the hydrogen fuel tank 10 allows the deduction of the volumes of liquid and gaseous hydrogen fuel in the tank. This volume can be combined with the pressure and temperature of the gaseous and liquid hydrogen fuel, as well as the ideal gas law for the gaseous hydrogen fuel, to determine the number of moles of hydrogen fuel in the tank 10. In other examples, additional sensors, such as additional fuel level sensors, temperature sensors, and / or pressure sensors, and / or other types of sensors, such as density and / or dielectric constant sensors, can be provided in the hydrogen fuel tank 10. Increasing the number of sensors and / or providing different types of sensors in the hydrogen fuel tank 10 can improve the accuracy of determining the amount of liquid and / or gaseous hydrogen fuel in the tank 10.

[0085] Then, when the fuel quantity drops below a threshold fuel quantity, the controller 200 is configured to reduce the heating rate of the 370 hydrogen fuel, specifically by commanding at least the heat exchange valve 34 to close or partially close. By controlling the heating (and pressure) of the hydrogen fuel 15 in this way, less hydrogen fuel may be present in the hydrogen fuel tank when the atmosphere is able to enter the hydrogen fuel, compared to the case where heating (and pressure) is not controlled. Such entry may occur, for example, when the pressure difference between the external atmospheric pressure 4 and the pressure of the hydrogen fuel 15 in the hydrogen fuel tank 10 approaches, reaches, or drops below zero. Furthermore, due to the reduced amount of hydrogen fuel 15 in the hydrogen fuel tank 10, the amount of energy released in the reaction between the hydrogen fuel in the hydrogen fuel tank and the atmosphere is similarly reduced when a portion of the atmosphere 4 enters the hydrogen fuel tank 10. In this way, the threshold fuel quantity is the maximum permissible fuel quantity for successful reaction decay. In other words, the threshold fuel quantity is a fuel quantity based on the structural limitations of the hydrogen fuel tank 10, below which the energy released in the reaction between the external atmospheric pressure 4 and the hydrogen fuel in the hydrogen fuel tank 10 is within acceptable limits.

[0086] In this example, if the amount of fuel in the hydrogen fuel tank 10 is not yet below a threshold amount, the controller 200 is also configured to determine whether the hydrogen fuel 15 in the hydrogen fuel tank 10 has been heated as expected. Specifically, the controller 200 determines whether the temperature sensed by the temperature sensor 61 is within the expected temperature range after heating, and whether the pressure difference is within the expected pressure difference range after heating. If the temperature and / or pressure are not within the corresponding expected range, the controller 200 is configured to operate the vacuum vent valve 16, specifically by commanding the vacuum vent valve 16 to open, allowing outside atmosphere 4 to enter the gap 13 in the fuel tank 10. This reduces the vacuum in the gap 13, thereby increasing the rate of heat transfer from outside atmosphere 4 through the gap 13 to the hydrogen fuel 15 in the hydrogen fuel tank 10. This results in an increased heating rate of the hydrogen fuel 15 in the hydrogen fuel tank. In this way, the vacuum vent valve 16 can be operated by the controller 200 to supplement the heating provided by the heat exchanger 31, or as a backup if the heat exchanger 31 does not heat the hydrogen fuel 15 as expected.

[0087] Alternatively, if the controller 200 determines that the temperature is within the desired temperature range and the pressure difference is within the desired pressure range, the process loops back to the action of receiving the signal from the sensor 340. This enables closed-loop control of the heating (and pressure) of the hydrogen fuel 15 in the hydrogen fuel tank 10, wherein the controller 200 adjusts the heating as the fuel level 15a decreases and the pressure in the hydrogen fuel tank 10 decreases over time.

[0088] It should be recognized that controller 200 can control the pressure in hydrogen fuel tank 10 in other ways. For example, controller 200 can determine the amount of energy (“reaction energy”) that will be released in the reaction between the external atmosphere and the hydrogen fuel in the hydrogen fuel tank based on the amount of hydrogen fuel in the hydrogen fuel tank. The controller can control the pressure in the hydrogen fuel tank until the reaction energy is below a reaction energy threshold of fuel tank 10. In some examples, controller 200 is configured to determine the time until the reaction energy drops below the reaction energy threshold. This determination can be achieved using a reaction energy model that includes the determined amount of fuel, the leakage rate of hydrogen fuel from the hydrogen fuel tank (e.g., as sensed by flow sensor 60), and the reaction energy as a function of the amount of hydrogen fuel in the hydrogen fuel tank.

[0089] As described above, controller 200 controls the amount of hydrogen fuel heated to provide a desired pressure differential between the pressure of the hydrogen fuel 15 in the hydrogen fuel tank 10 and the pressure of the external atmosphere 4 into which the hydrogen fuel 15 leaks. In some examples, the controller is configured to control the heating of the hydrogen fuel such that a positive pressure differential is maintained until the mission is over, and specifically until the aircraft has landed and all passengers have disembarked. For example, the controller may control the pressure differential to provide a flow rate of hydrogen fuel from the hydrogen fuel tank that ensures sufficient hydrogen fuel is present in the hydrogen fuel tank so that the positive pressure differential can be maintained until the mission is over.

[0090] In some examples, controller 200 is configured to receive signals from motion sensors of aircraft 1. Movement of the aircraft can cause a corresponding movement of hydrogen fuel 15 in hydrogen fuel tank 10. This movement of the hydrogen fuel can lead to an increase in the mixing of the liquid and gaseous components of the hydrogen fuel 15 within hydrogen fuel tank 10. The liquid hydrogen fuel can act as a radiator, particularly when there is more liquid hydrogen fuel in the hydrogen fuel tank than gaseous hydrogen fuel, causing this mixing to cause some of the gaseous hydrogen in hydrogen fuel tank 10 to condense. This, in turn, may reduce the pressure of the gaseous hydrogen fuel in the shortage space 15b. Therefore, controller 200 can be configured to increase the amount of heating applied to the hydrogen fuel in response to an increase in movement of aircraft 1 detected by the motion sensors.

[0091] In other examples, the hydrogen fuel system 2 includes a heat exchanger heating element configured to cause heating of the hydrogen fuel passing through the heat exchanger 31, and causing heating of the hydrogen fuel 15 includes the controller 200 operating the heat exchanger heating element. In some such examples, the heat exchanger system 20 may be omitted, and heating may be provided solely by the heat exchanger heating element. In other examples, the heat exchanger heating element supplements the heating provided by the heat exchanger system 20. In other examples, the hydrogen fuel system 2 includes a fuel tank heating element located within the hydrogen fuel tank 10 and operable by the controller 200 to cause direct heating of the hydrogen fuel in the hydrogen fuel tank 10. Again, such heating may be a supplement to or alternative to heating the hydrogen fuel 15 using the heat exchanger 31.

[0092] In another example, to control the pressure in the hydrogen fuel tank 10, the hydrogen fuel system 20 may include a pressurized inert gas source fluidly connected to the chamber 14 via a valve. The controller 200 may be configured to operate the valve to allow pressurized inert gas to enter the chamber 14, thereby increasing the pressure in the chamber 14, and in particular increasing the pressure of the hydrogen fuel 15 in the chamber 14.

[0093] The aforementioned heat exchange system 40 includes another heat exchanger 41 configured to exchange heat between the water-glycol mixture within the heat exchanger 41 and the aircraft atmosphere 5 outside the hydrogen fuel system 2. In other examples, the heat exchange medium in the heat exchange system 40 is alternatively hydrogen fuel, such as unconsumed hydrogen fuel received from the engine 3 or fuel cell. Such hydrogen fuel will be at a higher temperature than the fuel in the hydrogen fuel tank, and therefore at a higher temperature than the fuel in the heat exchange side 33 of the heat exchanger 31. In some such examples, the heat exchange pump 42 and / or the other heat exchanger 41 may not be provided.

[0094] It should also be recognized that controller 200 can determine 320 the presence of hydrogen fuel leakage from hydrogen fuel system 2 in any other suitable manner. For example, controller 200 can determine that a leak has occurred based on a signal from hydrogen concentration sensor 63 indicating the presence of hydrogen fuel in the external atmosphere 4. In some examples, the system may include a separate leak detection system comprising, for example, one or more of a flow sensor 60, an external pressure sensor 63, and a hydrogen sensor 64, and a leak detection controller configured to determine that a leak has occurred based on information received from the flow sensor, the external pressure sensor 63, and / or the hydrogen sensor 64. Leakage information received by controller 200 may be received from the leak detection controller. For example, controller 200 can determine that a leak has occurred based on a signal indicating a leak received from the leak detection controller. In some examples, hydrogen fuel system 2 includes a hydrogen fuel control system that includes controller 200 and a leak detection controller.

[0095] In some examples, the aircraft atmosphere 5 includes the external atmosphere 4.

[0096] In some examples, in the event of a leak from any of the fuel line 20, heat exchange line 30, fuel line valve 22, pump 21, heat exchanger 31, or heat exchange valve 34, controller 200 can operate vacuum vent valve 16 to release the vacuum in gap 13, instead of using heat exchanger 31 to induce heating of the hydrogen fuel. This allows the hydrogen fuel 15 in hydrogen fuel tank 10 to be heated without the hydrogen fuel 15 passing through one or more leaking components.

[0097] Other variations and modifications of the aircraft 1, fuel system 2 and / or method 300 will be apparent to those skilled in the art.

[0098] It should be noted that, unless otherwise expressly stated, the term “or” as used herein should be interpreted as meaning “and / or”.

Claims

1. A method for controlling the pressure in a hydrogen fuel tank of an aircraft hydrogen fuel system, the hydrogen fuel tank storing hydrogen fuel, the method comprising: Receive leakage information indicating that hydrogen fuel is leaking from the hydrogen fuel system; as well as Based on the received leakage information, pressure control is initiated in the hydrogen fuel tank.

2. The method according to claim 1, wherein, Controlling the pressure in the hydrogen fuel tank includes making the pressure in the hydrogen fuel tank exceed the external pressure of the atmosphere into which the hydrogen fuel leaks.

3. The method according to claim 2, comprising: When the amount of hydrogen fuel in the hydrogen fuel tank is still above a threshold amount, the pressure in the hydrogen fuel tank is made to exceed the external pressure of the atmosphere into which the hydrogen fuel leaks.

4. The method according to any one of claims 1 to 3, wherein, Controlling the pressure in the hydrogen fuel tank includes inducing heating of the hydrogen fuel in the hydrogen fuel tank.

5. The method according to claim 4, wherein, Heating the hydrogen fuel in the hydrogen fuel tank involves passing the hydrogen fuel from the hydrogen fuel tank through a heat exchanger and returning it to the hydrogen fuel tank.

6. The method according to claim 4 or 5, wherein, Heating the hydrogen fuel in the hydrogen fuel tank includes increasing the thermal conductivity of the hydrogen fuel tank.

7. The method according to claim 6, wherein, The hydrogen fuel tank includes an inner wall, an outer wall, and a vacuum in the space between the inner wall and the outer wall, and increasing the thermal conductivity of the hydrogen fuel tank includes releasing the vacuum in the space.

8. The method according to any one of claims 1 to 7, wherein, The received leaked information indicates any one or more of the following: The flow rate of hydrogen fuel from the hydrogen fuel tank; The pressure of the hydrogen fuel in the hydrogen fuel tank; and The hydrogen concentration outside the hydrogen fuel system.

9. The method according to any one of claims 1 to 8, wherein, The method includes receiving status information indicating the operational status of the hydrogen fuel tank, the hydrogen fuel system, and / or an aircraft including the aircraft's hydrogen fuel system; and Based on the received status information, pressure control is initiated in the hydrogen fuel tank.

10. The method according to claim 9, wherein, The status information indicates any one or more of the following: The pressure outside the hydrogen fuel tank; The amount of liquid hydrogen fuel and / or gaseous hydrogen fuel in the hydrogen fuel tank; The rate at which the aircraft's consumption unit consumes hydrogen fuel in the hydrogen fuel tank; The temperature in the hydrogen fuel tank; The flight status of the aircraft; and The movement or anticipated movement of the aircraft.

11. The method according to any one of claims 1 to 10, wherein, The method is a computer-implemented method, and wherein: Receiving the leakage information includes the control system receiving the leakage information, and Controlling the pressure in the hydrogen fuel tank includes the control system inducing pressure control in the hydrogen fuel tank.

12. A non-transitory computer-readable storage medium comprising instructions that, when executed by a processor, cause the processor to perform the method according to any one of claims 1 to 11.

13. A hydrogen fuel control system comprising one or more processors configured to perform the method according to claim 11.

14. A hydrogen fuel system comprising a hydrogen fuel control system according to claim 13 and the hydrogen fuel tank.

15. An aircraft comprising a non-transitory computer-readable storage medium according to claim 12, a hydrogen fuel control system according to claim 13, and / or a hydrogen fuel system according to claim 14.

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