FR3079172A1 - GAS TANK USED FOR THE PRODUCTION OF ELECTRICITY, IN PARTICULAR IN A MOTOR VEHICLE - Google Patents

Abstract

The invention relates mainly to a gas tank (18) intended to be used for the production of electricity in a motor vehicle comprising: - a casing (20) delimiting at least two storage chambers (22) of spherical shape, each chamber (22) being defined by a center (C), an inner radius (Rint), and an outer radius (Rext), and - a communication zone (24) between the chambers (22), characterized in that distance (E) between the center (C) of the two chambers (22) is smaller than the sum of the internal radii (Rint) of the two chambers (22) so as to define an interference zone (26) in which the communication zone (24) between the two chambers (22).

Description

GAS TANK USED FOR THE PRODUCTION OF ELECTRICITY, PARTICULARLY IN A MOTOR VEHICLE The present invention relates to a gas tank used for the production of electricity, in particular in a motor vehicle.

[0002] Motor vehicles are known on which are mounted fuel cells of the polymer electrolyte type, supplied with hydrogen. Fuel cells can be used as the main energy source intended to propel the vehicle by means of an electric powertrain, or as an auxiliary energy source, for example in addition to a main thermal powertrain. .

The development of this type of vehicle is still very limited or at the experimental stage. One of the major reasons why fuel cells are slow to be used massively, especially on vehicles intended for the general public, undoubtedly lies in the dangers inherent in the confinement and handling of hydrogen.

It is indeed known that hydrogen is an extremely flammable and detonating gas. We know for example that the lower flammability limit of hydrogen is around 4% of hydrogen in ambient air, while the lower detonability limit is around 18% of hydrogen in air ambient.

Thus, it will be understood that a motor vehicle with a fuel cell, provided with a hydrogen storage tank for supplying the cell presents particularly significant risks of ignition and explosion.

The invention aims to limit the risk of using a fuel cell by proposing a gas tank intended to be used for the production of electricity in a motor vehicle comprising:

a casing delimiting at least two storage chambers of spherical shape, each chamber being defined by a center, an internal radius, and an external radius, and

- a communication zone between the chambers, characterized in that a difference between the center of the two chambers is less than the sum of the internal radii of the two chambers so as to define an interference zone in which the communication zone is formed between the two rooms.

The invention thus allows to provide a mechanically rigid tank limiting the risk of leakage and therefore the risk of explosion of the gas it contains. In addition, the invention is of economic interest insofar as the reservoir can easily be produced by molding in particular or rapid prototyping.

In one embodiment, the tank has at least three storage chambers of spherical shape.

In one embodiment, the centers of the three storage chambers are aligned with each other.

According to one embodiment, the storage chambers have identical dimensions.

According to one embodiment, the storage chambers are formed in the same casing.

In one embodiment, the housing is made of a metallic material.

In one embodiment, the housing is made of a plastic material, optionally reinforced with fibers.

In one embodiment, the housing comprises stiffening ribs extending between two adjacent chambers in a longitudinal direction of the tank. This variant is preferably applied for embodiments of metallic material.

In one embodiment, the communication area has a tubular shape which can be axially a straight tube or have an ovoid shape.

The invention also relates to a motor vehicle comprising a gas tank intended to be used for the production of electricity as defined above.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given only by way of illustration but in no way limit the invention.

Figure 1 is a perspective view of a motor vehicle provided with a hydrogen storage assembly according to the invention integrated under the body structure;

Figure 2 is an exploded perspective view of a hydrogen storage tank according to the present invention;

Figure 3 is a schematic representation of a reservoir formed by two hemispheres and a cylinder;

Figures 4a to 4c are schematic representations for assessing the impact of pressure on a cylindrical part of the tank;

Figures 5a to 5c are schematic representations for assessing the impact of pressure on a spherical part of the tank.

Similar or similar identical elements retain the same reference from one figure to another.

Figure 1 shows a body structure 10 of a motor vehicle 11 on which are mounted a front axle 12.1 and a rear axle 12.2. Seats 14 for passengers are arranged on the side of the upper face of the body structure 10. A storage assembly 16 comprises one or more gas tanks 18 intended to be used for the production of electricity in the motor vehicle 11 and described in more detail below. The storage assembly 16 is arranged on the lower side of the body structure 10, between the front axle 12.1 and the rear axle 12.2 of the vehicle 11. As a variant, the tank 18 may be arranged in the upper part of the vehicle 11, in particular on the roof.

This storage assembly 16 is intended to supply a fuel cell housed in a compartment of the vehicle 11 via a supply duct. This assembly 16 ensures storage in the gaseous form of the hydrogen in the reservoir (s) 18.

More specifically, as shown in Figure 2, the reservoir 18 includes a housing 20 defining at least two storage chambers 22 of spherical shape. In this case, the casing 20 has five chambers 22. Of course, the number of chambers 22 can be adapted according to the application and in particular the volume of gas to be stored and the space available in the underbody.

Each chamber 22 is defined by a center C, an internal radius Rint, and an external radius Rext. The centers C of the various storage chambers 22 are aligned with each other. The storage chambers 22 here have identical dimensions but could alternatively have different dimensions.

A difference E between the center C of two consecutive chambers 22 is less than the sum of the internal radii Rint of these two chambers 22 so as to define an interference zone 26 in which is formed a communication zone 24 between two 22 consecutive rooms. This communication zone 24 extends between the chambers 22 to allow communication between the internal volumes of the chambers 22. Advantageously, the communication zone 24 has a tubular shape which can be axially a straight tube or have an ovoid shape, at the image of a barrel.

The casing 20 comprises stiffening ribs 28 extending between two adjacent chambers 22 in a longitudinal direction D of the reservoir 18.

Advantageously, the chambers 22 are formed in the same housing 20. The housing 20 may be made of a metallic material, in particular aluminum. This casing 20 can be obtained by a process known as rapid prototyping according to which a molten metal powder is deposited by a nozzle to obtain the shape of the reservoir 18 desired. As a variant, the casing 20 may be made of a plastic material, if necessary reinforced with fibers, for example carbon fibers. According to an exemplary embodiment, the plastic shape of the casing 20 can be obtained by molding and then be surrounded by stiffening fibers.

In an exemplary embodiment, a chamber 22 has an internal diameter of around 180 mm, an external diameter of around 200 mm, and a communication area 24 having a diameter of around 90 mm. By around, we mean a variation of plus or minus 20% around the target value.

The reservoir 18 illustrated in Figure 2 comprises a single line of spherical chambers 22 communicating with each other. As a variant, the reservoir 18 could of course comprise several rows of chambers 22 arranged one next to the other, so as to form rows and columns of storage chambers 22. The reservoir 18 then defines a matrix of storage chambers 22 A chamber 22 then communicates with at least one adjacent chamber 22 located in the same row and with at least one adjacent chamber 22 located in the same column.

As shown in Figure 3, we can define a reservoir formed by an assembly of two hemispheres 30 and a cylinder 31 by determining the relationship for these two types of geometry and the characteristics that make the resistance of the tank for a given pressure, for example of the order of 700 bars or 70 MPa.

The impact of the pressure on a tube is evaluated below. If it is admitted, as shown in FIG. 4a, that a hollow cylinder of length I has a thickness e much less significant compared to the radius ri of the tube, the actions on a small sector of tube are represented in FIGS. 4b and 4c.

The small surface supporting the pressure is expressed:

Ds p = η · άθ l [0036] [0037]

The surface supporting the Dft effort will be expressed:

Ds _T - el

Knowing that we can express Dft as a function of Dfn:

Dfn = P · Ds _P = P · r _i · άθ · l [0038]

Also :

Dft άθ = Dfii = P Dsp = P r _t l [0039]

So the stress σ in the tube will be expressed:

Ds _T le ri „di

2-e

It can be noted that the maximum stress in a tube is a direct relationship between the radius ri and its thickness e.

ri „di ~ ï ~ e We evaluate below the impact of pressure on a sphere. If we consider a hollow sphere of a thickness e much less important compared to its internal radii ri and external, we can represent in Figure 5a a small sector of sphere in a quarter of spheres.

Representing in FIG. 5b this small sphere sector, we have:

ri · άψ _ν = rx-d (ù _{y If} άψ _ν = άθ _{ζ a | ors} r άψ _ν = r άθ _ζ = rx-dGJ _y [0043] This makes it possible to represent in FIG. 5c the actions on the sector of sphere:

Dfn = dsi · P _{and with} dsi = r-d0-r- COS (θ) · ά0 θ _{η a} Dfn = r ² άθ COS (6 ”) - ddJ P [0044] With the above representation:

7> / l = Df2 _therefore Dfn = 2 · Dft · άθ _a | _ors p, _άθ . _cos (ff). dGJ P = 2 - Dft άθ, r ² COS {fi) dGJ P

So Dft s is expressed --------------- = Dft [0045] We know that for our sector of sphere 7) 51 = Ds2 _with Dsl = r-toP-r COS (f)) · Άω θ | Ds2 = rd0e so it is possible to express the maximum stress σ like this:

r ² COS {0) · àGJ P _σ __ ^D ft ________2_________ _r ^ri -p ^di

Dsl = Ds2 r · COS '(P) · to (û- e 2-e 4 e [0046] Although not surprising, it is the tubular part, the fragile part of the reservoir 18 whose maximum stress is expressed for reminder :

„ ^Ri & tube ~ P 'e In other words, for the same constraint, the smaller the radius of the tube, the thinner the reservoir 18. This expression corresponds to the results obtained for thin envelopes frequently used in boilermaking.

The pre-sizing of the tank can be as follows:

if we admit that a steel, or a composite material can withstand an extension or compression stress at more than 1000 MPa and that we take a safety factor of three knowing that safety lies more in management of spontaneous elimination 5 which without resistance generates not an explosion but a flame front of length ri limited, then one can evaluate a stress for a tube with _tube -P-— and for a sphere e ri ^σ sphere = ^p ' - ^maximum otuhe = a _sphire = maxz = 330 MPa [0049] the height available under the board being about 200 mm while a _tube = 330 = 70 - ^e - for a tube requires a thickness of 18 mm.

e ^σ sphere = 330 = 70 - ^ —- for a sphere, a thickness of 9 mm is required.

2- e For an overall diameter of 200 mm, the smaller the thickness e of the walls, the more hydrogen can be stored. A tank according to the invention 18 composed of spherical chambers 22 will thus be more resistant than a conventional cylindrical tank. In addition, the reservoir 18 makes it possible to store more hydrogen than a conventional reservoir because of the reduction in thickness of its walls.

Claims (10)

1. Gas tank (18) intended to be used for the production of electricity in a motor vehicle (11) comprising: - a casing (20) delimiting at least two storage chambers (22) of spherical shape, each chamber (22) being defined by a center (C), an internal radius (Rint), and an external radius (Rext), and - a communication zone (24) between the chambers (22), characterized in that a gap (E) between the center (C) of the two chambers (22) is less than the sum of the internal radii (Rint) of the two chambers (22) so as to define an interference zone (26) in which the communication zone (24) between the two chambers (22) is provided. 2. Tank according to claim 1, characterized in that it comprises at least TWO storage chambers (22) of spherical shape. 3. Tank according to claim 2, characterized in that the centers (C) of the three storage chambers (22) are aligned with each other. 4. Tank according to any one of claims 1 to 3, characterized in that the storage chambers (22) have identical dimensions. 5. Tank according to any one of claims 1 to 4, characterized in that the storage chambers (22) are formed in the same housing (20). 6. Tank according to any one of claims 1 to 5, characterized in that the casing (20) is made of a metallic material. 7. Tank according to any one of claims 1 to 5, characterized in that the housing (20) is made of a plastic material, optionally reinforced with fibers. 8. Tank according to any one of claims 1 to 7, characterized in that the casing (20) has stiffening ribs (28) extending between two adjacent chambers (22) in a longitudinal direction (D) of the tank (18). 9. Tank according to any one of claims 1 to 8, characterized in that the communication zone (24) has a tubular shape which can be axially a straight tube or have an ovoid shape. 10. Motor vehicle (11) characterized in that it comprises a gas tank (18) 5 intended to be used for the production of electricity as defined in any one of the preceding claims.