EP3875831B1 - Structure for reinforcing a tank for cryogenic fluid, such as liquefied natural gas, for motor vehicles - Google Patents

Description

Field of the invention

The field of the invention is that of cryogenic fluid storage tanks, such as for example Liquefied Natural Gas (LNG) or liquid nitrogen, intended to equip vehicles (such as motor vehicles, such as cars, trucks or even buses, maritime vehicles or even mobile units such as, for example, generators or containers for storage and/or transport of goods. FR3068106A1 discloses such a reservoir.

Prior art

The very rapid development of energy and environmental problems makes it necessary to use the advantages of alternative energies. Thus, road transport is faced with this double challenge: energy diversification and an ecological solution.

In view of these challenges, the motor vehicle market, and in particular heavy goods vehicles, running on liquefied natural gas (LNG) has entered a phase of significant growth.

Liquefied natural gas is natural gas stored in liquid form. This liquid state is reached when the gas is cooled to a temperature of about -161°C at atmospheric pressure.

Liquefaction makes it possible to reduce the gas volume of the natural gas and to store it in one or more tanks installed, for example, on the chassis of the heavy goods vehicle.

In known manner, the liquefied natural gas contained in such a tank is regasified so as to supply the engine of the heavy goods vehicle.

This fuel is less polluting than gasoline and diesel, and the range of heavy goods vehicles using this fuel makes them suitable for long-distance road transport.

The liquefied natural gas tanks of heavy goods vehicles are designed to meet strict safety requirements, in particular pressure and maintenance of a very low temperature, to maintain the gas in its liquid phase.

The tanks usually used have a cylindrical shape and have a double stainless steel wall between which are arranged a multi-layer insulation and vacuum conventionally. Their weight is therefore relatively high and their useful volume is limited. The cylindrical shape of such tanks allows a uniform distribution of the stresses, linked to the pressure of the gas, on the internal wall of the tank.

However, tanks having this shape take up a lot of space and are not suited to the spaces/compartments of various shapes of the vehicle in which they are intended to be installed.

Summary of the invention

• un contenant de stockage de fluide cryogénique, le contenant comprenant une structure de renfort interne, et
• une enveloppe externe de protection disposée autour dudit contenant,

le contenant et ladite enveloppe externe présentant chacun une forme générale sensiblement parallélépipédique.The invention proposes for this purpose a tank for a motor vehicle intended to contain a cryogenic fluid, such as liquefied natural gas, comprising:

• a cryogenic fluid storage container, the container including an internal reinforcing structure, and
• an outer protective envelope placed around said container,

the container and said outer casing each having a substantially parallelepipedic general shape.

• des plaques de renfort d'angle fixées sur la paroi interne dudit contenant et reliant chacune deux faces internes adjacentes dudit contenant,
• des rails de renfort fixés au centre de chacune des quatre parois longitudinales internes du contenant et s'étendant selon l'axe longitudinal dudit réservoir,
• une ossature de renfort disposée le long de l'axe longitudinal dudit réservoir, et
• des moyens de solidarisation de ladite ossature de renfort sur chacun des rails de renfort, lesdits moyens de solidarisation étant disposés à l'intérieur desdits rails de renfort.

According to the invention, said internal reinforcement structure comprises:

• corner reinforcement plates fixed to the internal wall of said container and each connecting two adjacent internal faces of said container,
• reinforcing rails fixed to the center of each of the four internal longitudinal walls of the container and extending along the longitudinal axis of said tank,
• a reinforcing framework arranged along the longitudinal axis of said tank, and
• means for securing said reinforcing framework to each of the reinforcing rails, said securing means being arranged inside said reinforcing rails.

The invention thus proposes a tank for cryogenic fluid (LNG for example) with double walls, of substantially parallelepipedal general shape, comprising a container forming the inner wall and an outer casing arranged around said container forming the outer protective wall.

Between these walls, which are not in contact, is formed an intermediate space containing vacuum and/or an insulating material.

The parallelepipedal shape of the container optimizes its liquefied gas storage capacity and the parallelepipedal shape of the outer casing allows optimal integration of the tank into the architecture of the vehicle.

The reinforcement means arranged in the container comprise longitudinally spaced rings which are mounted on reinforcement rails and which are locked on the latter by means of securing means which are housed in the rails. In addition, corner reinforcement plates are fixed at the four corners of the inner wall of the container.

This particular reinforcement structure allows an optimal distribution of the stresses along the container and optimizes the mechanical resistance of the container to the internal pressure of the liquefied gas.

The internal reinforcement structure can be made of aluminum, stainless steel, or a composite material, for example.

According to a particular embodiment of the invention, the reinforcing framework consists of reinforcing rings spaced apart along the longitudinal axis of said tank and each extending in a plane transverse to said longitudinal axis.

In another embodiment of the invention, the reinforcing framework consists of a cable wound in one piece.

According to a particular aspect of the invention, the reinforcing rails have several spaced apart slots along their length for passage of the reinforcing rings.

According to a particular aspect of the invention, the means for securing the reinforcing rings comprise a locking tube housed in each of the reinforcing rails so as to retain each of the reinforcing rings in said corresponding slots/grooves.

According to a particular aspect of the invention, each of the reinforcing rings has a square or rectangular shape.

According to a particular aspect of the invention, said container is secured to said outer casing by clamping means intended to compensate for the variation in length of the container along the longitudinal axis of the reservoir.

The attachment of the container to said outer casing by clamping means makes it possible to provide a degree of freedom between the two elements, so as to limit the heat transfers by conduction and to compensate for the thermal expansion/retraction due to the cooling of the internal container by limiting the contribution of stresses.

The clamping means also allow mechanical movement of the container relative to said outer casing. More precisely, the degree of freedom makes it possible to compensate for the variation in length of the container when it is cold (from 25° C. to -161° C.).

By way of example, when the container has an initial length of 2 m, these clamping means allow a variation in the length of said container along the longitudinal axis of the tank of the order of 8 mm.

The clamping means thus make it possible to compensate for the retraction of the internal container.

The liquefied gas can be LNG (liquid methane), or liquid nitrogen for refrigerated trucks, for example.

According to a particular aspect of the invention, said container is connected to a first side wall of said outer casing by a first clamping device movable along the longitudinal axis and to a second side wall of said outer casing by a second clamping device fixed.

According to a particular aspect of the invention, the clamping means allow a variation in the length of said container of between 2 and 10 mm.

According to a particular aspect of the invention, the first clamping device comprises at least one movable element secured to the container and mounted to slide along the longitudinal axis on a tube secured to a side wall of the outer casing, a return spring being disposed around the tube between said at least one movable element and said side wall of the outer casing.

According to a particular aspect of the invention, said clamping means are made of a thermally insulating material.

According to a particular aspect of the invention, said clamping means comprise support studs for the outer casing resting on said container.

According to a particular aspect of the invention, the container, the reinforcing framework and the outer casing are made of aluminum.

According to a particular aspect of the invention, the wall of the container and the wall of the outer casing are spaced from each other, the intermediate space between these walls being filled at least partially with insulating means.

The invention also relates to a motor vehicle, such as a heavy goods vehicle, comprising at least one tank as described above.

List of Figures

• [Fig 1] est une vue partielle, en perspective, d'un réservoir conforme à l'invention;
• [Fig 2] est une vue en coupe d'une extrémité latérale d'un réservoir conforme à l'invention;
• [Fig 2A] est une vue de détail d'un dispositif de bridage situé à l'extrémité latérale du réservoir illustrée sur la figure 2;
• [Fig 3] est une vue en coupe longitudinale du réservoir de la figure 2;
• [Fig 3A] est une vue de détail d'un dispositif de bridage situé à l'autre extrémité du réservoir de la figure 2;
• [Fig 4] est une vue de détail de la partie supérieure du réservoir de la figure 3 montrant des plots de support de l'enveloppe externe;
• [Fig 5] est une vue en perspective, en coupe longitudinale, du réservoir de la figure 3.

The proposed technique, as well as the various advantages it presents, will be more easily understood, in the light of the following description of illustrative and non-limiting embodiments thereof, and of the appended drawings, among which:

• [ Fig 1 ] is a partial perspective view of a tank according to the invention;
• [ Fig 2 ] is a sectional view of a side end of a tank according to the invention;
• [ Fig 2A ] is a detail view of a clamping device located at the side end of the tank illustrated in the picture 2 ;
• [ Fig.3 ] is a longitudinal sectional view of the tank of the picture 2 ;
• [ Fig 3A ] is a detail view of a clamping device located at the other end of the tank of the picture 2 ;
• [ Fig 4 ] is a detail view of the upper part of the tank of the picture 3 showing outer casing support studs;
• [ Fig.5 ] is a perspective view, in longitudinal section, of the tank of the picture 3 .

Detailed description of the invention

The invention relates to a tank for a motor vehicle intended to contain a cryogenic fluid, such as liquefied natural gas.

• un contenant de stockage de fluide cryogénique, le contenant comprenant une structure de renfort interne destinée à venir en appui contre les parois longitudinales internes du contenant, et
• une enveloppe externe de protection disposée autour dudit contenant, ledit contenant interne et ladite enveloppe externe présentant chacun une forme générale sensiblement parallélépipédique.

Such a reservoir comprises:

• a cryogenic fluid storage container, the container comprising an internal reinforcing structure intended to bear against the internal longitudinal walls of the container, and
• an outer protective casing disposed around said container, said inner container and said outer casing each having a substantially parallelepipedic general shape.

Partially represented on the figure 1 , in perspective, a motor vehicle tank 1 according to the invention comprising a container 11 which is housed in an outer casing 12 of the tank 1.

This tank 1 is visible on the picture 3 , which is a longitudinal sectional view, but also on the figure 5 which is a perspective and sectional view.

The wall of the container 11 and the wall of the outer casing 12 are spaced from each other, the intermediate space between these walls being filled with insulating means (not shown). It can be a multi-layer insulation, foam and/or vacuum which thus makes it possible to avoid heat exchanges by indirect contact between the container and the external envelope.

A perforated tube 20 extends between the two bottoms of the tank and is welded to the latter. It makes it possible to take up the forces exerted by the pressure on the two flat bottoms. The space between the wall of the container and the wall of the outer casing is, for example, between 5 and 30 mm.

The interior space of the container 11 constitutes a sealed enclosure for the storage of cryogenic fluid, such as liquefied natural gas under pressure (up to 16 bars, for example).

The container 11 and the outer casing 12 each have a substantially parallelepipedic general shape.

In this example, the container 11 is made of aluminum and has a length of two meters. The parallelepipedal shape of the container 11 optimizes its fuel storage capacity and allows optimal integration into the architecture of the vehicle. The container 11 and the outer casing 12 extend longitudinally along the longitudinal axis Ax of the tank 1 and their cross section to the axis Ax is a square whose corners are rounded (the cross section of the container and of the casing external could be a rectangle).

The container 11 comprises a reinforcing structure comprising in particular several reinforcing rings 14 forming a reinforcing framework, arranged inside the container 11 and regularly spaced along the longitudinal axis Ax. The reinforcing rings 14 each extend in a plane transverse to said longitudinal axis Ax.

The container 11 further comprises four reinforcing rails 15 fixed to the center of each of the four internal longitudinal walls of the container 11 and extending along the longitudinal axis Ax of the container 11. These central reinforcing rails 15 are hollow and have a section trapezoid with a rounded top. It is the base of the trapezium which is fixed to an internal wall of the container 11.

The container 11 also comprises means for securing the reinforcing rings 14 to each of the four central reinforcing rails 15 .

Each of the reinforcing rails 15 comprises at its rounded top slots 151 for passage of the reinforcing rings 14 formed at regular intervals along the longitudinal axis Ax.

The reinforcing rings 14 pass through the aligned slots 151 of each of the central reinforcing rails 15 and are thus arranged parallel to each other within the interior volume of the container 11, over at least part of the length of the latter. The central reinforcement rails 15 allow a distribution of the stresses along the container 11 and the maintenance of the internal reinforcement rings 14 .

In this embodiment, planar corner reinforcing plates 16 are attached to the inner wall of container 11 at each of the four inner corners. These corner reinforcement plates 16 are here hollow to allow the circulation of the gas and their relief, and have internal crosspieces connecting the two opposite longitudinal faces.

The corner reinforcement plates 16 extend along the four corners of the internal longitudinal wall of the container 11 along the longitudinal axis Ax. These reinforcement plates are fixed on their lateral edges to two adjacent internal faces of the container 11, of so that a space is provided between each corner reinforcement plate 16 and the corresponding rounded corner of the container 11.

The container 11, the reinforcing rings 14 and the outer casing 12 are made of aluminum, for example, or of another material.

For example, the outer casing 12 can be made of stainless steel (Inox) or aluminum.

The reinforcement rings 14 each consist of an aluminum plate with a section equal to 14×5 mm, for example.

The reinforcing rings 14 could be made of aluminum or stainless steel cables, or of rings made of synthetic or composite material.

Furthermore, the central reinforcing rails 15 and the corner reinforcing plates 16 are, for example, welded to the container 11.

In the illustrated embodiment, the means for securing the reinforcing rings 14 to each of the central reinforcing rails 15 take the form of tubes 17 which are each housed in a central reinforcing rail 15 and extend longitudinally along the surface/internal wall of the container 11, along the longitudinal axis Ax.

These tubes 17 are configured to fix the plurality of square-shaped reinforcement rings 14 at each of their corners on the central reinforcement rails 15 and thus secure the plurality of reinforcement rings 14 together.

The group of reinforcing rings 14 is thus fixed to the central reinforcing rails 15 by sliding the four tubes 17 in the four central reinforcing rails 15 .

It is noted that the reinforcing rings 14 do not come into contact with the inner wall of the container 11 once they are mounted on the central reinforcing rails 15 and locked in position by the tubes 17.

Furthermore, the tank 1 implements means for clamping or holding the container 11 in the outer casing 12.

There picture 2 is a partial view of the inner container 11 when it is expanded and shows in detail the first mobile clamping device connecting the side face 111 of a longitudinal end of the container 11 to a side face 120 of the outer casing 12 located opposite -notice.

There figure 2A shows this first mobile clamping device in more detail.

It comprises a hollow cylinder or hub 121 of "U" section welded to the side face 120 of the outer casing 12 in which is mounted a movable element 114 of "H" section. This mobile element 114 is secured to the side face 111 of the container 11. It is carried by a hollow cylinder 113 fixedly housed in a hub 112 secured to the side face 111 of the container 11.

The hollow cylinder 121 carries a tube 122 extending along the longitudinal axis Ax on which is slidably mounted the movable element 114 along the longitudinal axis Ax. A return spring 123 is placed around the tube 122 between the hollow cylinder 121 and the movable element 114.

This first clamping device makes it possible in particular to compensate for the thermal expansion/retraction of the internal container 11 due to the cooling of the cryogenic liquid that it contains by limiting the contributions of stresses. It is recalled that the LNG is for example stored at a temperature of -130° C. in the tank.

Parts 111, 112, 113 and 114 are fixed relative to each other. Part 114 can move relative to part 121 along the longitudinal axis Ax.

Thus, when the side wall 111 of the container 11 expands or retracts, the movable element 114 moves in the hollow cylinder 121 and compresses the return spring 123 or relaxes the latter.

On the figure 2A , the container 11 is expanded (in the sense that it is not retracted) and the spring is in a configuration of maximum compression, the clearance being zero between the parts 114 and 121.

It is understood that when the container 11 retracts, the movable element 114 slides to the left along the tube 122 under the effect of the return spring 123.

Each of the parts of this first clamping device or else only the cylinder 113 is made of a thermally insulating material to limit heat transfer by conduction. This thus makes it possible to avoid heat exchanges by direct contact between the container 11 and the outer casing 12. It is indeed crucial to prevent the temperature of the liquefied natural gas from increasing and that it remains in liquid form.

For example, all or part of these elements are made of epoxy resin and fiberglass (insulation).

There Figure 3A shows in detail the second clamping device connecting the side face of the other longitudinal end of the container 11 to the side face of the outer casing 12 located opposite.

This second clamping device is fixed and comprises a cylinder 113 connecting the side face 111 of the container 11 to the side face 120 of the outer casing 12. More specifically, the cylinder 113 is fixed on each side in a hub 112, 121 carried by each of the side faces 111 and 120 of the container 11 and of the outer casing 12 respectively.

By way of example, all or part of the elements forming the second clamping device is made of epoxy resin and glass fibers (insulation).

Thus, the clamping means comprise a fixed point on one side face (second clamping device) and a mobile point on the other side face (first clamping device) of the reservoir 1. They make it possible to compensate for the expansion or retraction of the container 11 along the longitudinal axis Ax.

Other clamping elements are implemented on the periphery of tank 1 and are visible on the figures 3 to 5 .

In the embodiment illustrated in these figures, studs or pins 124 and wedges forming internal reinforcement extend between the outer envelope 12 and the container 11, and prevent the outer envelope 12 from being crushed.

These studs and wedges are arranged around the perimeter of the container 11, at regular intervals, along the container 11.

This clamping solution is configured in such a way as to minimize container sloshing, even in the event of a vehicle collision.

The clamping means offer a minimum degree of freedom and allow movement of the container 11 relative to the outer casing 12 on one side of the tank 1 along the longitudinal axis Ax.

More specifically, the clamping means allow mechanical movement of the container relative to said outer casing and in particular make it possible to compensate for the variation in length of the container when cold (from 25° C. to -161° C.) of the latter. .

By way of example, when the container has an initial length of 2 m, these clamping means allow a variation in the length of the container of the order of 8 mm.

• mise en place et soudure, par friction malaxage par exemple, des renforts d'angle 16 dans l'espace intérieur du contenant 11,
• mise en place et soudure, par friction malaxage par exemple, des rails de renforts 15 centraux dans l'espace intérieur du contenant 11,
• mise en place des anneaux de renfort 14 par translation dans l'espace intérieur du contenant 11, puis rotation des anneaux de renfort 14 de sorte à ce que ces derniers traversent les fentes 151 des rails de renfort 15 centraux,
• mise en place des tubes de verrouillage 17 des anneaux de renfort 14 dans les rails de renfort 15 centraux.

The assembly of the reinforcement structure in the container 11 is relatively easy and comprises the following steps:

• installation and welding, by friction mixing for example, of the corner reinforcements 16 in the interior space of the container 11,
• installation and welding, by friction mixing for example, of the central reinforcement rails 15 in the interior space of the container 11,
• placement of the reinforcing rings 14 by translation in the interior space of the container 11, then rotation of the reinforcing rings 14 so that the latter pass through the slots 151 of the central reinforcing rails 15,
• installation of the locking tubes 17 of the reinforcing rings 14 in the central reinforcing rails 15.

Other types of welding can be considered.

Other aspects and variants

In all the embodiments described above, the outer casing of the tank can be made of any material suitable for resisting fire and possibly other safety constraints.

According to a particular implementation, the outer surface of the outer casing can be covered with at least one layer of material suitable for resisting fire.

More generally, a fire-resistant paint or other type of coating can be applied to the exterior and/or interior surface of the outer shell and/or to the exterior surface of the container.

The outer casing can be made of a fire resistant material.

In this case, the outer envelope can be made of stainless steel or composite materials.

• un élément de connexion à un autre réservoir ;
• une soupape de sécurité ;
• un dispositif de remplissage du contenant.

The side faces of the container can each carry one or more support plates for at least one of the following elements (the list being non-exhaustive):

• a connection element to another reservoir;
• a safety valve;
• a device for filling the container.

It will be noted that all or part of these elements can alternatively be carried by at least one of the side and/or longitudinal walls of the outer casing in which the container is intended to be housed.

The tank according to the invention can be installed on other types of motor vehicles, such as buses, trucks, coaches, refrigerated vehicles, maritime vehicles or any other vehicle.

The tank of the invention can be accommodated in vehicle compartments of complex shapes.

In other words, the shape of the tank can be adapted to the volumes available on the chassis of the vehicle.

The tank according to the invention can be installed in mobile units such as, for example, generators or containers for storing and/or transporting goods.

It should be noted that the side faces located at the longitudinal ends of the container can be curved, curved or flat.

Furthermore, the longitudinal faces of the container (defining the body of the container) may have a curve.

Rather than independent reinforcing rings, a one-piece coiled cable forming a reinforcing framework could be used.

The tank of the invention can contain any type of liquefied gas, such as LNG (liquid methane), or even liquid nitrogen for refrigerated trucks or heavy goods vehicles, for example.

Of course, the invention is not limited to the examples which have just been described and many adjustments can be made to these examples without departing from the scope of the invention, defined by the claims.

In particular, the different characteristics, forms, variants and embodiments of the invention may be associated with each other in various combinations insofar as they are not incompatible or exclusive of each other, within the scope of the claims.

In particular, all the variants and embodiments described above can be combined with one another, within the scope of the claims.

Claims (14)

1. A tank (1) for an automobile vehicle intended to contain a cryogenic fluid, such as liquefied natural gas, comprising:

   - a cryogenic fluid storage container (11), the container comprising an inner reinforcing structure, and

   - an outer protective shell (12) disposed around said container (11),

   the container (11) and said outer shell (12) each having generally a substantially parallelepipedal shape,

   said tank (1) being characterised in that said inner reinforcing structure comprises:

   - corner reinforcing plates (16) attached to the inner wall of said container (11) and each connecting two adjacent inner faces of said container (11),

   - reinforcing rails (15) attached in the centre of each of the four inner longitudinal walls of the container (11) and extending along the longitudinal axis (Ax) of said tank (1),

   - a reinforcing framework (14) disposed along the longitudinal axis (Ax) of said tank (1), and

   - means for securing said reinforcing framework (14) to each of the reinforcing rails (15), said securing means being disposed inside said reinforcing rails (15).
2. The tank (1) according to claim 1, characterised in that the reinforcing framework (14) consists of reinforcing rings (14) spaced apart along the longitudinal axis (Ax) of said tank (1) and each extending in a plane transverse to said longitudinal axis (Ax).
3. The tank (1) according to claim 2, characterised in that the reinforcing rails (15) have over their length several spaced apart slots (151) for passing the reinforcing rings (14) therethrough.
4. The tank (1) according to claim 3, characterised in that the securing means of the reinforcing rings (14) comprise a locking tube (17) housed in each of the reinforcing rails (15) so as to retain each of the reinforcing rings (14) in said corresponding slots/grooves (151).
5. The tank (1) according to one of claims 2 to 4, characterised in that each of the reinforcing rings (14) has a square or rectangular shape.
6. The tank (1) according to one of claims 1 to 5, characterised in that said container (11) is secured to said outer shell (12) by clamping means intended to compensate for the variation in length of the container (11) along the longitudinal axis (Ax) of the tank (1).
7. The tank (1) according to claim 6, characterised in that said container (11) is connected to a first side wall of said outer shell (12) through a first clamping device movable along the longitudinal axis (Ax) and to a second side wall of said outer shell (12) through a fixed second clamping device.
8. The tank (1) according to claim 6 or 7, characterised in that the clamping means allow variation in length of said container (11) of between 2 and 10 mm.
9. The tank (1) according to claim 7 or 8, characterised in that the first clamping device comprises at least one movable element integral with the container (11) and slidably mounted along the longitudinal axis (Ax) to a tube integral with a side wall of the outer shell (12), a return spring being disposed about the tube between said at least one movable element and said side wall of the outer shell (12).
10. The tank (1) according to one of claims 6 to 9, characterised in that said clamping means are manufactured from a thermally insulating material.
11. The tank (1) according to one of claims 6 to 10, characterised in that said clamping means comprise studs for supporting the outer shell (12) bearing against said container (11).
12. The tank (1) according to any of the preceding claims, characterised in that the container (11), the reinforcing framework (14) and the outer shell (12) are manufactured from aluminium.
13. The tank (1) according to any of the preceding claims, characterised in that the wall of the container (11) and the wall of the outer shell (12) are remote from each other, the intermediate space between these walls being at least partially filled with insulating means.
14. An automobile vehicle, such as a heavy truck, comprising at least one tank according to one of claims 1 to 13.

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