Fuel system for supplying an aircraft with hydrogen, method and aircraft

Abstract

The invention relates to a fuel system (1) for supplying an aircraft (2) with hydrogen (3). The fuel system (1) comprises a first inner tank (4) and a separate second inner tank (6), each for storing hydrogen (3), and an outer tank (5) which surrounds the inner tanks (4, 6). The first inner tank (4) and the second inner tank (6) are fluidically connected, separately from one another, to at least one first supply device (7) for supplying the aircraft (2) with hydrogen (3). The invention also relates to an aircraft (2) having a fuel system (1), and to a method.

Description

[0001] Fuel system for supplying an aircraft with hydrogen, as well as process and aircraft

[0002] Description

[0003] The invention relates to a fuel system for supplying an aircraft with hydrogen. The fuel system comprises a first internal tank for storing hydrogen and an external tank. The invention further relates to an aircraft with a fuel system and a related method.

[0004] In modern aviation, hydrogen is becoming increasingly attractive as a fuel for aircraft propulsion in many ways. The hydrogen is carried in tanks whose requirements differ significantly from those of traditional kerosene tanks. Compared to kerosene, the volume of liquid hydrogen is four times greater while weighing 2.8 times less. Consequently, this may mean different requirements for the design of fuel tanks for aviation applications.

[0005] DE 10 2007 025 217 A1 describes a device and method for storing hydrogen for an aircraft, in which the outer tank is connected to the inner tank in such a way that the hydrogen from the outer tank can be supplied to the inner tank in order to increase its efficiency.

[0006] DE 10 2014 107 316 Al shows a tank system for the cryogenic storage of hydrogen, which, due to its structure, can be integrated into the load-bearing primary structure of an aircraft.

[0007] For the use of a hydrogen fuel system in a commercial aviation application, it is important to meet the applicable certification requirements, which are particularly demanding with regard to safety requirements in the event of a failure. In particular, systems must be designed redundantly and have a correspondingly robust design. However, the installation space in the aircraft is limited. Furthermore, unlike a kerosene fuel system, the hydrogen tanks cannot be easily integrated into the wing.

[0008] The invention is based on the object of providing a fuel system for supplying an aircraft with hydrogen, the probability of failure of which is minimized while optimizing the use of installation space.

[0009] The problem is solved by the subject matter of the independent patent claims. Advantageous developments of the invention are described by the dependent patent claims, the following description, and the figures.

[0010] One aspect of the invention provides a fuel system for supplying an aircraft with hydrogen. The fuel system comprises at least a first inner tank for storing hydrogen, and at least one outer tank. The fuel system comprises, in particular, a second inner tank for storing hydrogen, which is fluidically separated from the first inner tank, wherein the first inner tank and the second inner tank are stored inside the outer tank, and wherein the first inner tank and the second inner tank are each fluidly connected, separately from one another, to a first supply device of the fuel system for supplying the aircraft with hydrogen.

[0011] This dual-tank arrangement of the fuel system according to the invention allows for efficient use of the aircraft's installation space. In particular, the integration of the two separate inner tanks into a single outer tank advantageously eliminates the need for an additional outer tank. In addition to saving installation space, the fuel system according to the invention can save material and weight, which can advantageously contribute to the efficiency of the entire aircraft.

[0012] At the same time, the separation of the two inner tanks advantageously ensures a dual-channel fuel supply – if one inner tank fails, the other inner tank guarantees at least half the aircraft's range. This redundant system allows for the safety of the fuel system and thus the aircraft itself to be particularly secure. In particular, if one inner tank is lost or malfunctions, the other inner tank remains fully functional, so that in the event of a failure, only the range is reduced.

[0013] The fuel system may also include other components necessary to supply the aircraft. The aircraft may, for example, be a conventional aircraft, a rotary-wing aircraft, an airship, or the like, which uses the hydrogen, in particular, as fuel to power one or more main, secondary, or auxiliary engines. The propulsion system may, in particular, be a hydrogen combustion engine, a gas turbine, or a fuel cell with a downstream electric motor.

[0014] The first and second inner tanks, hereinafter also referred to simply as inner tanks, are particularly designed and configured to store the hydrogen taking into account its specific physical conditions. In particular, the inner tanks can withstand an overpressure inside the tank depending on the operating conditions. Furthermore, a third or many further inner tanks can be provided, for which the preceding and following descriptions can be applied accordingly. The first inner tank can in particular be identical to or different from the second inner tank. The inner tanks are in particular designed or can be designed separately from one another. In other words, the inner tanks are not directly or indirectly fluidically connected to one another. Furthermore, the inner tanks can be structurally separate from one another.However, the inner tanks can also be fluidically separated from each other and integrated into a common tank module.

[0015] The outer tank encloses or covers, in particular, the inner tanks, preferably completely. The outer tank can preferably be designed to be dent-resistant and pressure-resistant. For example, the inner tanks can be mounted and mechanically supported by struts or another structure, spaced from a shell of the outer tank. The outer tank can, in particular, be provided for mandatory insulation purposes for the inner tanks. The inner tanks are, in particular, fluidically separated from the outer tank. In other words, it is not intended that hydrogen can pass from the inner tanks into the outer tank.

[0016] The first inner tank is fluidically connected, in particular, to the first supply device. Separate from the connection of the first inner tank to the first supply device, the second inner tank is connected, in particular, to the first supply device, so that hydrogen can be transported from the first inner tank or from the second inner tank to the first supply device.

[0017] A fluidic connection is a connection through which a fluid can flow. In particular, hydrogen can flow from an internal tank to a supply device.

[0018] The two inner tanks can, in particular, be designed to be fluidically separable from one another, which can mean that they can be fluidically connected in a specific configuration, for example, by means of a valve of the supply device or the like. The inner tanks can, in particular, be designed to be fluidically connectable to the supply device, which can mean that they can be fluidically separated in a specific configuration, in particular independently of one another.

[0019] The fuel is, in particular, hydrogen, preferably pure hydrogen. However, it can also be understood, although less preferably, as a hydrogen-containing or hydrogen-based fuel, or a fuel that has storage properties comparable to those of hydrogen.

[0020] One embodiment provides that the fuel system comprises a second supply device for supplying the aircraft with hydrogen, wherein the first inner tank and the second inner tank are fluidically connected to the second supply device separately from one another. In other words, the first inner tank is fluidically connected, in particular, to the second supply device. Separate from the connection of the first inner tank to the second supply device, the second inner tank is connected, in particular, to the second supply device, such that hydrogen can be transported from the first inner tank or from the second inner tank to the second supply device. Thus, the failure of one of the two supply devices can also be compensated for by the further supply device in that one supply device is fluidically connected to each of the inner tanks.This redundancy advantageously increases the safe operation of the fuel system or the aircraft.

[0021] The first supply device can preferably be designed separately from the second supply device. The respective supply device, also referred to as a system capsule, balance of plant or cold box, is designed and provided to supply the aircraft with hydrogen. In particular, the supply device is designed and provided to withdraw hydrogen from the first and / or second inner tank. Furthermore, the supply device can be designed and provided to carry out appropriate conditioning of the hydrogen in the first and / or second inner tank. Furthermore, the supply device can be designed and provided to monitor the inner tanks, in particular to control or regulate the physical conditions for storing the hydrogen.

[0022] The supply device can in particular comprise valves, safety valves, heat exchangers, lines, control elements, regulators, circuits and the like, which can preferably be designed redundantly within a supply device.

[0023] One embodiment provides that the first inner tank is connected to the first supply device via a first channel and is fluidically connected to the second supply device via a second channel separate from the first channel. Alternatively or additionally, it is provided that the second inner tank is connected to the first supply device via a third channel and is fluidically connected to the second supply device via a fourth channel separate from the third channel. Thus, the separation of the inner tanks can be advantageously and reliably realized, so that a failure of one inner tank cannot affect the availability of the other inner tank.

[0024] Preferably, the inner tanks can each have a separate connection for the respective channel, which can in particular be arranged displaced from one another. Accordingly, the supply devices can each have a separate connection for the respective channel. This advantageously ensures the fluidic separation of the inner tanks from one another.

[0025] The outer tank may have appropriately sealed passage openings for the ducts between the inner tanks and supply equipment.

[0026] One embodiment provides that the first supply device has a first shut-off valve for fluidically separating or connecting the first channel and / or a second shut-off valve for fluidically separating or connecting the second channel, and / or the second supply device has a third shut-off valve for fluidically separating or connecting the third channel and / or a fourth shut-off valve for fluidically separating or connecting the fourth channel. The respective shut-off valves can be designed separately from the supply device, for example, integrated into the respective channel. The shut-off valves can advantageously seal off a defective inner tank or a defective supply device so that they cannot affect functioning components.

[0027] One embodiment provides for an intermediate space between the outer tank and the first inner tank and the second inner tank to be evacuated. In other words, a technical vacuum, or at least an approximate one, exists in the intermediate space. This advantageously allows the inner tanks to be thermally insulated extremely effectively. The outer tank is particularly designed and can be specifically intended to maintain the vacuum. Accordingly, it can be sealed airtight. The outer tank can thus correspond to a vacuum shell. The vacuum allows the inner tanks to be insulated particularly effectively.

[0028] One embodiment provides that the first inner tank and / or the second inner tank comprises a first insulation layer. The insulation layer is intended in particular to thermally insulate the respective inner tank, so that a temperature and / or pressure of the hydrogen can advantageously be maintained at a certain level. The insulation layer can be designed in various ways, in particular using appropriate insulating material. Preferably, the insulation layer, in conjunction with the enveloping vacuum, can have superinsulation, which is also referred to as multilayer insulation (MLI). This can consist of a few to several dozen layers of metal-deposited plastic films, which are kept apart by suitable perforations or gauze (spacers). MLI films hinder heat transport by thermal radiation. The inner tanks can thus be insulated particularly effectively.

[0029] One embodiment provides that the outer tank comprises a second insulation layer, so that the insulation can be further improved. The second insulation layer can be arranged inside and / or outside the outer tank. The insulation layer is intended, in particular, to thermally insulate the respective inner tank so that a temperature and / or pressure of the hydrogen can advantageously be maintained at a certain level. On the inside, the insulation layer can have an MLI in conjunction with the enclosing vacuum. On the outside, the outer tank can have a corresponding insulating material as a second insulation layer.

[0030] One embodiment provides that the first inner tank and / or the second inner tank is designed and configured to store hydrogen cryogenically, in particular in a liquid state and at a very low temperature, for example, at -253°C. In this state, the hydrogen can be stored particularly safely. In particular, the inner tanks can be configured to withstand a specific hydrogen pressure. This can, for example, be between 1 bar and 10 bar, or even a pressure of up to 350 bar.

[0031] One embodiment provides that the first inner tank and / or the second inner tank is / are of modular design. In other words, the inner tanks are not installed integrally with the outer tank, but can be easily installed and removed. For this purpose, the outer tank can preferably be reversibly opened so that the first inner tank and / or the second inner tank is / are replaceable. For example, the outer tank can have a locking mechanism for opening and closing the outer tank shell. This also advantageously allows the inner tanks to be inspected and maintained or removed. It is also conceivable for an emptied inner tank to be replaced by an inner tank filled with hydrogen.

[0032] One embodiment provides that the first supply device and / or the second supply device is configured to withdraw liquid or cryogenic hydrogen from the first inner tank and / or from the second inner tank. In particular, the supply device can condition the withdrawn hydrogen accordingly to supply the aircraft with the conditioned hydrogen. For example, the supply device can evaporate the liquid hydrogen before it is further conveyed.

[0033] Alternatively or additionally, the supply device can be designed to remove gaseous hydrogen from the inner tanks.

[0034] One embodiment provides that the fuel system comprises a sensor device configured to detect a malfunction of the first inner tank and / or the second inner tank and / or the outer tank. The sensor device is preferably configured to detect a malfunction of the first supply device and / or the second supply device. Thus, the faulty component can advantageously be identified and appropriate countermeasures can be taken, for example, by shutting off valves. This can increase the safety of the system and the aircraft. A further aspect of the invention provides a method for operating a fuel system according to the invention.The method comprises at least the step of supplying the aircraft with hydrogen from the first inner tank in the event of a malfunction of the second inner tank, or supplying the aircraft with hydrogen from the second inner tank in the event of a malfunction of the first inner tank.

[0035] One embodiment provides that the method comprises at least the step of supplying the aircraft with hydrogen via the first supply device in the event of a malfunction of the second supply device, or supplying the aircraft with hydrogen via the second supply device in the event of a malfunction of the first supply device.

[0036] The redundant design of the components ensures particularly safe operation of the fuel system and thus the aircraft. In particular, the aircraft can be advantageously supplied with hydrogen if either an internal tank or a fuel system fails.

[0037] The invention also includes further developments of the method according to the invention that have features already described in connection with the further developments of the fuel system according to the invention. For this reason, the corresponding further developments of the method according to the invention are not described again here. In particular, the fuel system is designed to carry out the method according to the invention.

[0038] A further aspect of the invention provides an aircraft with at least one fuel system according to the invention. The aircraft may, for example, be a conventional aircraft, a rotary-wing aircraft, an airship, or the like, which uses hydrogen, in particular as fuel, to power one or more main, secondary, or auxiliary engines. The aircraft's propulsion system may, in particular, be a hydrogen combustion engine, a gas turbine, or a fuel cell with a downstream electric motor.

[0039] The invention also encompasses combinations of the features of the described embodiments. The invention therefore also encompasses implementations that each comprise a combination of the features of several of the described embodiments, unless the embodiments are described as mutually exclusive.

[0040] Further advantageous developments of the present invention emerge from the dependent claims and the following description of preferred embodiments. These show:

[0041] FIG. 1 shows a schematic representation of an embodiment of a fuel system according to the invention;

[0042] FIG. 2 is a schematic representation of an embodiment of an aircraft according to the invention.

[0043] FIG. 1 shows a schematic representation of an embodiment of a fuel system 1 according to the invention for supplying an aircraft 2 with hydrogen 3. In this embodiment, the hydrogen 3 can be stored cryogenically in a first inner tank 4 and in a second inner tank 6, wherein these can be fluidically separated from one another. The two redundant inner tanks 4, 6 can in particular be surrounded by a common outer tank 5. Between the outer tank 5 and the inner tanks 4, 6, an intermediate space 17 can be formed, which is preferably evacuated. This means that a technical vacuum can prevail in the intermediate space 17. The outer tank 5 can accordingly be dent-resistant and designed to be able to maintain a vacuum.

[0044] The first inner tank 4 can be fluidically connected to a first supply device 7 for supplying the aircraft 2 with hydrogen 3 via a first channel 9 for transporting the hydrogen 3. In addition, the first inner tank 4 can be fluidically connected to a second supply device 8 for supplying the aircraft 2 with hydrogen 3 via a second channel 10 for transporting the hydrogen 3, which is formed separately from the first channel 9.

[0045] The second inner tank 6 can be fluidically connected to the first supply device 7 via a third channel 11 for transporting the hydrogen 3. In addition, the second inner tank 6 can be fluidically connected to one of the second supply devices 8 via a fourth channel 12, formed separately from the third channel 11, for transporting the hydrogen 3.

[0046] The redundant supply devices 7, 8 can, in particular, comprise valves, heat exchangers, safety valves, and / or lines, which can be designed redundantly and can be configured to handle the conditioning of the cryogenic or liquid hydrogen 3 in the inner tanks 4, 6 to the necessary operating conditions. For example, the first supply device 7 can supply the aircraft 2 with gaseous hydrogen 3 via a first supply line 20, and the second supply device 8 can supply it via a second supply line 21.

[0047] The channels 9, 10, 11, 12 can, for example, each have a separate shut-off valve 13, 14, 15, 16, which can fluidically separate or connect the respective associated channel 9, 10, 11, 12. The shut-off valves 13, 14, 15, 16 can also be integrated into the supply devices 7, 8. In one exemplary embodiment, the inner tanks 4, 6 can each have a first insulation layer 18 for thermal insulation. This can, for example, be designed as an MLI. The outer tank 5 can also have a second insulation layer 19 for thermal insulation inside or outside the vacuum-maintaining shell of the outer tank 5.

[0048] FIG. 2 shows a schematic representation of an embodiment of an aircraft 2 according to the invention. The aircraft 2 is shown merely as an example, as a conventional aircraft. Likewise, the placement of the fuel system 1 of the aircraft 2 is arbitrarily chosen and is not limited to this position.

[0049] Overall, the examples demonstrate how a dual-channel design for hydrogen tanks (inner tanks 4, 6) can be constructed. Due to the low temperatures (storage temperature of approximately -253°C) of cryogenic liquid hydrogen (LH2), LH2 tanks 4, 6 require very efficient insulation. In addition to insulation 18 on the surface of tanks 4, 6, a design with a vacuum shell can be implemented. The vacuum tank consists of an inner tank 4, 6 and an outer tank 5 (vacuum in the intermediate space 17) and has a high insulating effect. The cryogenic hydrogen is located in the inner tank 4, 6, which can withstand an overpressure inside the tank depending on the operating conditions. The outer tank 5 is dent-resistant and can maintain the vacuum.For example, to achieve a dual-channel fuel system 1 (redundant fuel supply to minimize the probability of failure) with optimized use of installation space, a dual tank (two separate inner tanks 4, 6 for storing LH2) can be integrated into a common enclosing vacuum envelope 5 (for insulation). The advantage over two separate vacuum tanks (each tank has its own vacuum envelope) is, on the one hand, a reduction in the required installation space and, on the other hand, a reduction in the mass of the necessary vacuum envelope. At the same time, the separation of the two inner tanks 4, 6 guarantees a dual-channel fuel supply - if one inner tank 4, 6 fails, the other inner tank 4, 6 guarantees half the range. The design can exhibit the following behavior in the event of a failure:

[0050] - Outer tank failure (vacuum insulation defective): The second insulation made of multilayer or foam (on the inner tank 4, 6 or outer tank 5) can prevent strong heat input and thus a higher evaporation of the LH2 in tank 5 than is taken from the consumer.

[0051] - Failure of an inner tank (leakage): If one inner tank 4, 6 is lost, the other inner tank 4, 6 may still be fully functional, so that in the event of a failure, only the range is reduced. The leak in the inner tank 4, 6 may result in the LH2 escaping and evaporating; however, the intact insulation of the outer tank 5 can prevent further excessive evaporation of the escaping LH2; the outer tank 5 may be subjected to the internal pressure of the inner tank 4, 6.

[0052] Essentially, in a dual-channel LH2 system, the two LH2 tanks 4, 6 may not communicate with each other, but rather have independent extraction systems. This way, in the event of a failure, half the range can still be guaranteed, and a single inner tank 4, 6 can compensate for any single failure of the other tank 4, 6 and the outer shell 5.

[0053] Analogous to the dual-channel design of the inner tanks 4, 6, a dual-channel design of the supply device 7, 8 is also implemented. This allows the failure of one supply capsule 7, 8 to be compensated for by the other supply device 7, 8. A suitable system architecture can accommodate a large number of possible failures – the failure of one inner tank 4, 6 and one supply device 7, 8 can be compensated for (cross-connections possible), see table:

[0054]

[0055] List of reference symbols:

[0056] 1 fuel system

[0057] 2 aircraft

[0058] 3 Hydrogen

[0059] 4 First inner tank

[0060] 5 External tank

[0061] 6 Second inner tank

[0062] 7 First care facility

[0063] 8 Second care facility

[0064] 9 First Channel

[0065] 10 Second channel

[0066] 11 Third Channel

[0067] 12 Fourth Channel

[0068] 13 First shut-off valve

[0069] 14 Second shut-off valve

[0070] 15 Third shut-off valve

[0071] 16 Fourth shut-off valve

[0072] 17 space

[0073] 18 First insulation layer

[0074] 19 Second insulation layer

[0075] 20 First supply line

[0076] 21 Second supply line

Claims

Patent claims 1. Fuel system (1) for supplying an aircraft (2) with hydrogen (3), comprising - a first inner tank (4) for storing hydrogen (3), and - an external tank (5), characterized by - a second inner tank (6) for storing hydrogen (3), which is fluidically separated from the first inner tank (4), wherein - the first inner tank (4) and the second inner tank (6) are stored in an interior of the outer tank (5), and - the first inner tank (4) and the second inner tank (6) are fluidically connected separately from one another to a first supply device (7) of the fuel system (1) for supplying the aircraft (2) with hydrogen (3).

2. Fuel system (1) according to claim 1, characterized by a second supply device (8) for supplying the aircraft (2) with hydrogen (3), wherein the first inner tank (4) and the second inner tank (6) are fluidically connected separately from one another to the second supply device (8).

3. Fuel system (1) according to claim 2, characterized in that the first inner tank (4) is fluidically connected to the first supply device (7) via a first channel (9) and to the second supply device (8) via a separate, second channel (10), and / or the second inner tank (6) is fluidically connected to the first supply device (7) via a third channel (11) and to the second supply device (8) via a separate, fourth channel (12).

4. Fuel system (1) according to claim 3, characterized in that the first supply device (7) has a first shut-off valve (13) for fluidically separating or connecting the first channel (9) and / or a second shut-off valve (14) for fluidically separating or connecting the second channel (10), and / or the second supply device (8) has a third shut-off valve (15) for fluidically separating or connecting the third channel (11) and / or a fourth shut-off valve (16) for fluidically separating or connecting the fourth channel (12).

5. Fuel system (1) according to one of the preceding claims, characterized in that an intermediate space (17) between the outer tank (5) and the first inner tank (4) and the second inner tank (6) is evacuated.

6. Fuel system (1) according to one of the preceding claims, characterized in that the first inner tank (4) and / or the second inner tank (6) has a first insulation layer (18).

7. Fuel system (1) according to one of the preceding claims, characterized in that the outer tank (6) has a second insulation layer (19).

8. Fuel system (1) according to one of the preceding claims, characterized in that the first inner tank (4) and / or the second inner tank (6) is / are designed to store hydrogen (3) cryogenically.

9. Fuel system (1) according to one of the preceding claims, characterized in that the first inner tank (4) and / or the second inner tank (6) is / are modular and the outer tank (5) is / are reversibly openable, so that the first inner tank and / or the second inner tank is / are interchangeable.

10. Fuel system (1) according to one of the preceding claims, characterized in that the first supply device (7) and / or the second supply device (8) is / are designed to remove liquid hydrogen (3) from the first inner tank (4) and / or from the second inner tank (6).

11. Fuel system (1) according to one of the preceding claims, characterized by a sensor device which is designed to detect a fault in the first inner tank (4) and / or the second inner tank (6) and / or the outer tank (5).

12. Fuel system (1) according to claim 11, characterized in that the sensor device is designed to detect a fault in the first supply device (7) and / or the second supply device (8).

13. A method for operating a fuel system (1) according to any one of the preceding claims, comprising the steps: - supplying the aircraft (2) with hydrogen (3) from the first inner tank (4) in the event of a malfunction of the second inner tank (6), or supplying the aircraft (2) with hydrogen (3) from the second inner tank (6) in the event of a malfunction of the first inner tank (4).

14. The method according to claim 13, comprising the steps: - supplying the aircraft (2) with hydrogen (3) via the first supply device (7) in the event of a malfunction of the second supply device (8), or Supplying the aircraft (2) with hydrogen (3) via the second supply device (8) in the event of a malfunction of the first supply device (7).

15. Aircraft (2) with a fuel system (1) according to one of claims 1 to 12.

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