Protection device for an aircraft's hydrogen tank

Abstract

The invention relates to a protective device for a hydrogen tank (4, 5), particularly for an aircraft, the protective device (1) comprising an outer casing delimiting an internal volume, and an extinguishing agent, preferably in gaseous phase, within said internal volume, the outer casing being provided with at least one pressure relief valve (14) for releasing said at least one extinguishing agent when the pressure within the internal volume exceeds a threshold value, and the outer casing being shaped for installation in the fuselage (3) of an aircraft (2). Abstract figure: Figure 2

Description

Title of the invention: Device for protecting an aircraft hydrogen tank. Technical field

[0001] The present invention relates to a protection device for a hydrogen tank, in particular for an aircraft. Previous technique

[0002] In an effort to reduce the climate impact of aviation, the Holder has developed aircraft projects whose engines operate with hydrogen propulsion. This type of propulsion requires specific equipment, including one or more tanks containing hydrogen, preferably in liquid form and at cryogenic temperature, in order to increase its density and reduce the volume required for its storage.

[0003] However, due to the presence of hydrogen in the aircraft, additional considerations must be taken into account. Thus, efforts are made to reduce hydrogen leaks.

[0004] The object of the invention is to remedy at least partially these drawbacks. Summary

[0005] To this end, a protection device for a hydrogen tank, in particular for an aircraft, is proposed, the device comprising an outer casing delimiting an internal volume, and an extinguishing agent, preferably in gaseous phase in said internal volume, the outer casing being provided with at least one pressure relief valve, to release said at least one extinguishing agent when a pressure prevailing in the internal volume is greater than a threshold value, and the outer casing being shaped to be installed in an aircraft fuselage.

[0006] Thus, thanks to the device according to the present invention, it is possible to considerably reduce risks since, in the event of an accident, the extinguishing agent is released by the pressure relief valve and reduces the concentrations of oxygen and hydrogen. Furthermore, the extinguishing agent also acts against other sources of ignition, such as an electrical fire, for example. And, the shape of the outer casing, specifically tailored to an aircraft, makes the device according to the present invention perfectly suited to protecting hydrogen tanks in the event of an impact by preventing the tank from striking structural parts of the aircraft and absorbing some of the energy due to the impact.

[0007] According to another aspect, the outer casing includes a curved part intended to be placed against a lower part of the aircraft fuselage and to follow its contour.

[0008] According to another aspect, the outer casing includes a flat part intended to be in contact with a floor of the aircraft fuselage.

[0009] According to another aspect, the outer casing has, in the installed position in the aircraft, a thickness equal to a center distance between two consecutive frames between which the protective device is intended to be installed.

[0010] According to another aspect, the outer casing includes at least one orifice for filling with extinguishing agent.

[0011] Advantageously, said at least one filling orifice is disposed on the outer casing so as to be accessible in the installed position in the aircraft.

[0012] Advantageously, said at least one overpressure valve is disposed on the outer casing so as to be accessible in the installed position in the aircraft.

[0013] According to another aspect, the threshold pressure is between 2.5*105 Pa and 5*105 Pa, preferably 3*105 Pa.

[0014] According to another aspect, said extinguishing agent has a pressure between 105 Pa and 2*105 Pa, preferably 1.5* 105 Pa.

[0015] According to another aspect, the outer casing is made of flexible and / or deformable material, so that the internal volume is variable and depends on the pressure of the gases contained in the casing.

[0016] The invention also relates to an aircraft, comprising a fuselage having a structure equipped with a set of annular frames, the aircraft also comprising at least one hydrogen tank and at least one protection device as described above arranged under said at least one hydrogen tank, in a horizontal position of the fuselage.

[0017] According to another aspect, the aircraft includes at least one protective device as described above, the curved part of which rests on at least one of the annular frames of the fuselage part.

[0018] According to another aspect, the outer casing has a thickness equal to a center distance between two consecutive frames between which the protective device is installed.

[0019] According to another aspect, the aircraft comprises at least a first and a second protective device, each disposed below said at least one hydrogen tank, in a horizontal position on the fuselage, the extinguishing agent of the first protective device being different from the extinguishing agent of the second protective device. Brief description of the drawings

[0020] Other features, details and advantages will become apparent from reading the detailed description below and from analyzing the accompanying drawings, in which: Fig. 1

[0021] [Fig-1] is a schematic perspective view of a protective device for a hydrogen tank of a hydrogen-powered aircraft, according to the present invention. Fig. 2

[0022] [Fig.2] is a schematic perspective view of a part of an aircraft fuselage, comprising two hydrogen tanks and a plurality of protection devices for the [Fig.1]. Fig. 3

[0023] [Fig.3] is a schematic cross-sectional view of the fuselage part of [Fig.2], Fig. 4

[0024] [Fig.4] is a schematic view of a cross-section of the fuselage part of [Fig.3], after collision against a surface (ground, water). Description of the implementation methods

[0025] The examples and associated conditions detailed herein are primarily intended to assist the reader in understanding the principles of the present invention and not to limit its scope to these specific examples and conditions. It will be understood that a person skilled in the art can conceive of various arrangements which, although not explicitly described or illustrated herein, nevertheless embody the principles of the present invention and are included in its spirit and scope.

[0026] Furthermore, to facilitate understanding, the following description may describe relatively simplified implementations of the present invention. As a person skilled in the art will understand, other implementations of the present invention may be of greater complexity.

[0027] In some cases, examples of modifications to the present invention may also be shown. This is done simply to aid understanding and, again, not to define the scope or establish the limits of the present invention. These modifications are not an exhaustive list, and a person skilled in the art may make other modifications while remaining within the scope of the present invention.

[0028] Furthermore, all the following statements relating to the principles, aspects and implementations of the present invention, as well as specific examples thereof, are intended to encompass both the structural and functional equivalents thereof, whether currently known or developed in the future.

[0029] As can be seen from the figures, the invention relates to a protective device 1 for at least one hydrogen tank. The invention also relates to an aircraft 2 in which a fuselage 3 is equipped with at least one protective device 1.

[0030] A hydrogen tank is defined as a container for storing dihydrogen fluid, H2, in gaseous phase, and / or, preferably, liquid, in order to increase its density and reduce the volume required for its storage. A cryogenic storage temperature is preferred.

[0031] In the figures, in a non-limiting manner, a first hydrogen tank, referenced 4, and a second hydrogen tank, referenced 5, are shown. In the figures, each of the tanks 4, 5, has an elongated cylindrical shape, with axis A4, A5. The axes A4, A5 are preferably arranged parallel to the longitudinal axis A of the aircraft fuselage.

[0032] The protection device 1 is now described in detail, more particularly with reference to [Fig.1].

[0033] As can be seen in this figure, the protective device 1 comprises an outer envelope 6 delimiting an internal volume V. Preferably, the outer envelope is made of a flexible material, such as latex or canvas, or polyethylene.

[0034] The flexible envelope is almost flat when not filled and pressurized with the gas that will be used for extinguishing, which allows for easy transport and easy installation in the aircraft, inflation being carried out after installation in the aircraft.

[0035] The envelope 6 is shaped to be housed in the fuselage 3 of the aircraft 2. In other words, the shape of the envelope 1 is adjusted for the aircraft 2, as will be detailed later.

[0036] The shape of the envelope 6 is now described once installed in the fuselage 3 and filled with the extinguishing agent.

[0037] The envelope 6 has a general shape of a flat and truncated cylinder comprising a curved part 7 and a flat part 8.

[0038] The curved portion 7 is delimited by two panels 9, 10, preferably identical, spaced apart and facing each other. Each panel 9, 10 comprises a straight edge 9-1, 10-1, and an edge 9-2, 10-2, with a circular arc-shaped contour C. The curved portion 7 is also delimited by a base 11 joining the panels 9, 10 and joined by two opposite straight edges, 11-1, 11-2, of the flat portion 8.

[0039] The flat part 8 is a rectangle whose edges coincide with the edges 9-1, 10-1 of the panels 9 and 10 and the edges 11-1, 11-2 of the base 11. We denote E the thickness of the device 1, which corresponds to the length of the edges 11-1, 11-2.

[0040] The device 1 also includes at least one filling orifice 12 drilled in the casing 6. Preferably, each orifice 12 is located on the casing 6 in such a way that it is accessible in the installed position in the aircraft, as will be explained in more detail later. In [Fig. 1], the device 1 includes an orifice 12, located substantially in the center of the flat portion 8.

[0041] Device 1 also includes at least one safety valve, or pressure relief valve. Preferably, each valve is located on the housing 1 in such a way that it is accessible in the installed position in the aircraft, as will be explained in more detail later. In [Fig. 1], device 1 includes two pressure relief valves, referenced 13 and 14, located respectively near the midpoint of opposite edges 11-1, 11-2.

[0042] It should be noted that the pressure relief valves are the outlets through which the extinguishing gas will be released, as explained later. Their number and positions are defined to ensure optimal release of the extinguishing gas and optimal filling of the area around the tanks.

[0043] The internal volume V is filled with an extinguishing agent, in powder form, or preferably in gaseous phase. The extinguishing agent is chosen from the following non-exhaustive list: the halon family, or an inert gas, such as, for example, helium, nitrogen, or intergen IG-541.

[0044] The extinguishing agent is stored in the internal volume V at an absolute pressure between 1 BarA (105 Pa) and 2 BarA, preferably 1.5 BarA.

[0045] Each pressure relief valve 13, 14 is configured to open at a pressure greater than or equal to a threshold value, between 2.5 and 5 BarA, preferably 3 BarA.

[0046] Thus, under normal operating conditions, the valve is closed, while when an impact occurs, the device 1 is compressed, which increases its internal pressure up to the threshold value; then, the valve opens and the extinguishing agent is released.

[0047] The presence of the extinguishing agent acts by displacing the oxygen and replacing it with the extinguishing gas. If, despite the presence of the protective devices 1, the tank is nevertheless damaged and a hydrogen leak occurs, then the oxygen concentration is drastically reduced, which decreases not only the risks due to hydrogen, but also the risks of other fires starting, such as an electrical fire.

[0048] Aircraft 2 equipped with protective devices 1 is now described in detail in relation to Figures 2 to 4. In these figures, a part of the fuselage 3, for example the rear part, forming for example an unpressurized compartment, of aircraft 2, at the rear of a cabin part, from which it is separated by a partition Cl (visible on [Fig.2]).

[0049] As can be seen in these figures, the fuselage 3 comprises a set of frames 21. The frames 21 are annular elements, preferably concentric, with axis A corresponding to the longitudinal axis of the aircraft. The frames 21 are regularly spaced at a distance denoted D.

[0050] As already indicated, in the illustrated embodiment, the fuselage 2 comprises the first and second cylindrical hydrogen tanks, 4, 5. The tanks are arranged so that their longitudinal axes A4, A5 are parallel to axis A. L denotes a transverse distance consisting of the sum of the two diameters Di of the tanks 4, 5 and the shortest distance between them d (lengths illustrated in Figures 3 and 4).

[0051] As illustrated in [Fig.2], the fuselage 2 includes a plurality of protective devices 1 (five devices in [Fig.2]), arranged under the hydrogen tanks 4, 5 in a position in which the aircraft is placed on the ground of the aircraft 2. This position corresponds to a horizontal position of the fuselage 3.

[0052] In [Fig. 2], each device 1 is housed between two consecutive frames 21, the thickness E of each device 1 corresponding to the distance D between the two frames in which the device 1 is located. The length of the edges 9-1, 10-1 is preferably greater than the distance L, which allows each device 1 to act on both hydrogen tanks 4, 5 in the event of a collision. Alternatively, the length of the edges 9-1, 10-1 is equal to the diameter Di of one of the tanks, so that each device 1 is dedicated to only one of the tanks 4, 5.

[0053] The flat portion 8 of each device 1 is located under and near the tanks 4, 5, while the curved portion 7 rests on the annular contour of the frames 21. Thus, the shape of each device 1 is perfectly adapted to the profile of the aircraft 2, the curved portion 7 conforming to the annular shape of the frames 21 (the curvature of the device 1 is the same as that of the frames 21) and the thickness E corresponding to the center distance D between the frames 21. The flat portion 8 ensures that the device 1 does not obstruct the installation of the tanks 4, 5.

[0054] In [Fig.2], the protective devices 1 are regularly installed, leaving a space S between two frames 21 free of any device 1. The fact that the devices 1 are regularly spaced ensures homogeneous protection of the tanks 3, 4, in case of impact.

[0055] The spacing of the arrangement of the devices 1 is of course not limited to this configuration. They can also be arranged in each space S, or on the contrary spaced further apart, depending on the geometry of the fuselage, and of the tanks, in particular.

[0056] In [Fig.2], the devices 1 cover only part of the length of the tanks 4, 5. However, the invention is not limited to this configuration, and the devices 1 can cover the entire length of the tanks 4, 5, in order to maximize the protection of the tanks.

[0057] As can be seen more particularly in Figures 3 and 4, each filling orifice 12 is located between the two reservoirs 4, 5, which makes it accessible in case maintenance, to fill device 1, by an operator for example, even when tanks 4, 5, remain installed in aircraft 2.

[0058] As also visible in figures 3 and 4, the safety valves 13, 14 are arranged close to the frames 21, which makes them accessible in case of maintenance, for opening or closing by an operator for example, even when the tanks 4, 5, remain installed in the aircraft 2.

[0059] It is noted that, depending on whether one seeks to concentrate on a specific type of fire outbreak or to protect the aircraft from several types of fire, one can choose that the extinguishing agents of the devices 1 are all identical, or that some differ, or that the extinguishing agent of each device 1 is different.

[0060] The action of devices 1 in aircraft 2 is now described in the event of an impact against a hard surface, referenced Su on [Fig.4], such as ground or water.

[0061] When the aircraft collides with the surface Su, the tanks 4, 5, lower against the devices 1 whose casing 6 deforms to envelop the lower part of the tanks 4, 5. Thus, part of the energy due to the impact is absorbed by the devices 1 and, simultaneously, the risk of contact with hard points is reduced, since the tanks are less likely to hit structural elements of the aircraft 2.

[0062] When the tanks strike the devices 1, the internal pressure in the devices 1 increases until it exceeds the threshold value of the safety valves 13, 14, and the extinguishing agents are released into the compartment around the tanks 4, 5. The flow of the extinguishing agent is represented by dashed arrows in [Fig. 4]. As already explained, the extinguishing agents then drastically reduce the risks (during the chemical reaction of water formation from the dihydrogen in the tanks, in the event of a leak, and from the dioxygen in the air) and / or combustion.

[0063] If the aircraft falls into the water, then the devices 1 increase the buoyancy of the aircraft as long as they have not been completely emptied.

[0064] As is already apparent from the preceding description, the devices 1 are installed, empty, in the fuselage 3, and then filled with extinguishing agent. Next, the tanks 4, 5 are placed in the fuselage 3, above the protective devices 1. Thus, the devices 1 have the advantage of occupying space which, due to the presence of the tanks, cannot be occupied by aircraft systems.

[0065] As is already apparent from the preceding description, the present invention offers numerous combined advantages. The devices 1 provide enhanced protection for the tanks 4, 5 by absorbing the energy of an impact, reducing the risk of damage to the tanks and thus decreasing the risk of hydrogen leaks. The flow of extinguishing agents released by the safety valves further reduces the risk fire suppression is achieved by expelling oxygen from around the tanks. Furthermore, the bag-shaped devices 1 are simple, inexpensive, and effective, and can be installed under the tanks, which would otherwise be wasted space. Thus, the devices 1 according to the present invention constitute multifunctional safety bags.

[0066] Modifications and improvements to the above-described implementations of the present invention may be apparent to a person skilled in the art. The above description is illustrative by way of examples rather than exhaustive. The scope of the present invention is therefore limited only by the scope of the claims below.

Claims

Demands

1. Protective device for a hydrogen tank (4, 5), in particular for an aircraft, the protective device (1) comprising an outer casing (6) delimiting an internal volume (V), and an extinguishing agent, preferably in gaseous phase in said internal volume (V), the outer casing being provided with at least one pressure relief valve (13, 14), for releasing said at least one extinguishing agent when a pressure prevailing in the internal volume (V) is greater than a threshold value, and the outer casing being shaped to be installed in a fuselage (3) of an aircraft (2).

2. Protective device according to the preceding claim, wherein the outer casing (6) includes a curved portion intended to be placed against a lower part of the fuselage (3) of the aircraft (2) and follow its contour.

3. Protective device according to any one of claims 1 or 2, wherein the outer casing (6) has, in the installed position in the aircraft, a thickness (E) equal to a center distance between two consecutive frames (21) between which the protective device (1) is intended to be installed.

4. Protective device according to any one of the preceding claims, wherein the outer casing (6) includes at least one orifice for filling with extinguishing agent (12).

5. Protective device according to any one of the preceding claims, wherein the threshold pressure is between 2.5*105 Pa and 5*105 Pa, preferably 3*105 Pa.

6. Protective device according to any one of the preceding claims, wherein said extinguishing agent has a pressure between 105 Pa and 2*105 Pa, preferably 1.5*105 Pa.

7. Protective device according to any one of the preceding claims, wherein the outer casing (6) is made of deformable material.

8. Aircraft, comprising a fuselage (3) having a structure provided with a set of annular frames (21), the aircraft also comprising at least one hydrogen tank (4, 5) and at least one protective device (1) according to any one of the preceding claims disposed under said at least one hydrogen tank (4, 5), in a horizontal position of the fuselage (3).

9. Aircraft according to the preceding claim, comprising at least one protective device according to claim 3, the curved part of which (7) rests on at least one of the annular frames of the fuselage part.

10. Aircraft according to the preceding claim, comprising at least a first and a second protective device each disposed under said at least one hydrogen tank, in a horizontal position of the fuselage, the extinguishing agent of the first protective device being different from the extinguishing agent of the second protective device.

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