Cryogenic fluid storage unit

Abstract

Cryogenic Fluid Storage Unit The storage unit (1) comprises an internal reservoir (3) internally delimiting a cryogenic fluid storage volume (5), an external reservoir (7) in which the internal reservoir (3) is housed, and a suspension (9) fixing the internal reservoir (3) to the external reservoir (7), the suspension (9) comprising a link (23, 25) having: - an external tube (27) having an external proximal end (29) fixed to the internal reservoir (3) and an external distal end (31) located inside the storage volume (5); - a bottom plate (33) closing the external distal end (31); - an internal tube (41) arranged inside the external tube (27), having an internal proximal end (43) linked to the external reservoir (7) and an internal distal end (45) fixed to the internal reservoir (3);- a movement limiter (81), limiting a displacement of the inner tube (41) relative to the inner reservoir (3) in a plane perpendicular to a central axis (C) of the inner tube (41). Figure for the abbreviation: 2;

Description

Title of the invention: Cryogenic fluid storage unit

[0001] The present invention relates generally to a cryogenic fluid storage unit.

[0002] Such a storage unit may comprise an internal tank internally delimiting a cryogenic fluid storage volume, an external tank in which the internal tank is housed and a suspension fixing the internal tank to the external tank.

[0003] In order to limit heat transfer by convection from the external reservoir to the internal reservoir, the space delimited between the internal reservoir and the external reservoir is typically maintained under a high vacuum.

[0004] Radiation transfers are limited by arranging a layer of insulating material on the internal reservoir.

[0005] Heat transfers by conduction from the external reservoir to the internal reservoir mainly pass through the suspension.

[0006] They can be relatively high.

[0007] In this context, the invention aims to propose a storage unit whose suspension is designed to minimize the thermal flow circulating by conduction from the external reservoir to the internal reservoir.

[0008] To this end, the invention relates to a cryogenic fluid storage unit, comprising an internal reservoir internally delimiting a storage volume for the cryogenic fluid, an external reservoir in which the internal reservoir is housed and a suspension fixing the internal reservoir to the external reservoir, the suspension comprising a connection comprising:

[0009] - an outer tube having an outer proximal end attached to the reservoir internal and an external distal end located inside the storage volume;

[0010] - a bottom plate closing the external distal end;

[0011] - an inner tube arranged inside the outer tube, having one end internal proximal end attached to the external reservoir and an internal distal end attached to the internal reservoir;

[0012] - a movement limiter, limiting a movement of the internal tube relative to the internal reservoir in a plane perpendicular to a central axis of the internal tube.

[0013] The inner tube is designed only to withstand the usual mechanical stresses corresponding to normal use of the storage. When the storage unit is on board a motor vehicle, these stresses result, for example, from emergency braking, a hairpin bend, or even vibrations generated by the vehicle rolling on a road in poor condition.

[0014] On the other hand, in the case where the storage unit is subjected to exceptional stress such as an accidental impact, the movement limiter makes it possible to limit the movement of the internal tube in a plane perpendicular to the central axis of the internal tube.

[0015] This makes it possible to limit the deformation of the internal tube, by preventing it from entering the plastic domain and therefore undergoing irreversible deformation.

[0016] In the absence of a movement limiter, the probability that the internal tube would be damaged in the event of exceptional stress would be significant.

[0017] The movement limiter thus makes it possible to choose a reduced wall thickness for the internal tube, just sufficient to withstand the usual mechanical stresses. This helps to limit heat transfer by conduction from the external tank to the internal tank.

[0018] The fluid storage unit may further represent one or more of the following characteristics, considered individually or in all technically possible combinations:

[0019] - the internal reservoir has an orifice through which the internal tube is connected to the external tank, the movement limiter cooperating with the orifice to limit the movement of the internal tube;

[0020] - the movement limiter being rigidly fixed to the internal tube;

[0021] - the storage unit comprises: - * a distributor block fixed to the inner proximal end of the inner tube and having at least one internal passage for the cryogenic fluid; * at least one circulation tube extending inside the inner tube and fluidly connecting the at least one inner passage to the storage volume; the movement limiter being rigidly fixed to the distributor block;

[0022] - the movement limiter has a determined axial length and is engaged in the orifice over a length less than 50% of said determined length

[0023] - the movement limiter is fixed to the internal tank and cooperates with the end internal proximal;

[0024] - the connection comprises a first cup having a first central part ri rigidly fixed directly to the inner proximal end and a first edge rigidly fixed to the outer reservoir;

[0025] - the connection comprises a second cup having a second central portion and a second edge rigidly fixed to the external reservoir, the connection comprising a sliding tube passing through a second orifice of the second central part and rigidly fixed to the second central part, the internal proximal end being slidably engaged in the sliding tube, the sliding tube extending opposite of the movement limiter perpendicular to the central axis.

[0026] Other characteristics and advantages of the invention will emerge from the detailed description given below, for information purposes only and in no way limiting, with reference to the appended figures, among which: - [Fig.l] [Fig.l] is an axial sectional view of the cryogenic fluid storage unit; - [Fig.2] [Fig.2] is an enlarged axial sectional view of part of the suspension of the storage unit of [Fig.l]; - [Fig.3] [Fig.3] is a view similar to that of [Fig.2], illustrating a second embodiment, - [Fig.4] [Fig.4] is a view similar to that of [Fig.2], illustrating a third embodiment for a connection not providing for the passage of cryogenic fluid conduits; and - [Fig.5] [Fig.5] is an enlarged view of a detail V of [Fig.4].

[0027] In Figures 2 to 5, certain welds connecting the parts to each other are not shown.

[0028] The storage unit 1 shown in [Fig.l] is intended to store a cryogenic fluid.

[0029] Cryogenic fluid is understood to mean a fluid at a very low temperature, which may be at least partially in the liquid state inside the storage unit.

[0030] This fluid is typically hydrogen. Alternatively, the fluid is helium, nitrogen, a natural gas such as methane CH4, air, or any other suitable fluid.

[0031] This storage unit is typically intended to be mounted on board a vehicle having an electric propulsion motor, for example a motor vehicle, a train, a boat or any other vehicle.

[0032] The motor vehicle is for example a car, a utility vehicle, a truck, etc.

[0033] The storage unit 1 is intended to power a fuel cell. The fuel cell is configured to produce electricity and electrically power the electric propulsion motor of the vehicle.

[0034] The cryogenic fluid storage unit 1 comprises an internal tank 3 internally delimiting a cryogenic fluid storage volume 5, an external tank 7 inside which the internal tank 3 is housed, and a suspension 9 fixing the internal tank 3 to the external tank 7.

[0035] In the example shown, the internal reservoir 3 has a horizontal central axis C.

[0036] The internal reservoir 3 comprises a shell 11, closed at its two axial ends by bottoms 13.

[0037] The ferrule 11 is cylindrical, centered on the central axis C.

[0038] The external tank 7 also has a horizontal axis.

[0039] It comprises a ferrule 15, closed at its two axial ends by bottoms 17.

[0040] The ferrule 15 is cylindrical, centered on the central axis C.

[0041] The internal tank 3 and the external tank 7 delimit between them an inter space median 19, maintained under a high vacuum.

[0042] This vacuum is typically of the order of 105 mbar, so as to greatly limit the heat transfer by convection from the external reservoir 7 to the internal reservoir 3.

[0043] Thermal insulation 21 is interposed between the internal tank 3 and the external tank 7. The thermal insulation 21 is typically placed on the external surface of the internal tank 3. The thermal insulation 21 comprises, for example, a plurality of metal sheets superimposed on each other, with interposition of layers of fibers.

[0044] The suspension 9 is arranged such that the entire weight of the internal tank 3 is taken up by the external tank 7 via the suspension 9.

[0045] The weight of the internal tank 3 is understood here to include the weight of the cryogenic fluid stored in the internal tank 3.

[0046] The accelerations undergone by the internal tank 3 and the cryogenic fluid contained in the internal tank 3 are also transmitted to the external tank 7 via the suspension 9.

[0047] When the storage unit 1 is mounted in a vehicle, these accelerations result from changes in direction of the vehicle, from braking applied to the vehicle or from acceleration of the vehicle, from roughness or irregularities in the road, or from shocks applied to the vehicle.

[0048] In the example shown, the suspension 9 comprises two links 23, 25.

[0049] The links 23, 25 each suspend one of the two opposite axial ends of the internal reservoir 3 to the external reservoir 7.

[0050] Links 23 and 25 are different from each other.

[0051] The connection 23 is provided to allow the passage of the cryogenic fluid to the storage volume 5, or from the storage volume 5.

[0052] On the contrary, the connection 25 is not provided for the passage of the cryogenic fluid.

[0053] As illustrated in [Fig.2], the link 23 comprises:

[0054] - an external tube 27 having an external proximal end 29 fixed to the reservoir internal 3 and an external distal end 31 located inside the storage volume 5;

[0055] - a bottom plate 33 closing the external distal end 31;

[0056] - an inner tube 41 arranged inside the outer tube 31, having one end internal proximal end 43 connected to the external reservoir 7 and an internal distal end 45 fixed to the internal reservoir 3.

[0057] Link 23 also includes: .

[0058] - an intermediate tube 35 arranged inside the external tube 27, having a intermediate proximal end 37 attached to the internal reservoir 3 and an intermediate distal end 39; and

[0059] - an annular ring 47 connecting the intermediate distal end 39 to the end internal distal 45.

[0060] Thus, the internal distal end 45 is fixed to the internal reservoir 3 by means of the annular ring 47 and the intermediate tube 35.

[0061] The outer tube 27 is substantially cylindrical, and is coaxial with the central axis C.

[0062] It is located inside the storage volume 5, typically entirely inside the storage volume 5.

[0063] An opening 49 is provided in the bottom 13 of the internal tank 3. An internal ring 51 is engaged in the opening 49 and rigidly fixed to the bottom 13. The external peripheral edge of the internal ring 51 is welded in a sealed manner to the edge of the opening 49.

[0064] On a face facing the storage volume 5, the internal ring 51 has an external rib 53 of substantially cylindrical shape.

[0065] The external rib 53 is coaxial with the central axis C, and has substantially the same diameter as the external proximal end 29.

[0066] The outer proximal end 29 is welded in a sealed manner to the outer rib 53.

[0067] In the same way, the internal ring 51 carries on its face facing the storage volume 5 a second rib 55, of substantially cylindrical shape.

[0068] This second rib 55 is coaxial with the central axis C, and has the same diameter as the intermediate proximal end 37.

[0069] The intermediate proximal end 37 is welded in a sealed manner to the second rib 55.

[0070] The bottom plate 33 seals the external distal end 31 in a sealed manner. It has a bottom 57 extended by a raised edge 59 welded in a sealed manner to the external distal end 31.

[0071] The bottom 57 is curved towards the inside of the storage volume 5.

[0072] The annular ring 47 is coaxial with the central axis C.

[0073] It has U-shaped sections in radial planes containing the central axis C. The annular ring 47 thus has an external cylindrical wall 61 and an internal cylindrical wall 63, connected to each other by a bottom 65.

[0074] The outer wall 61 has substantially the same diameter as the distal end. intermediate 39, and is welded to this intermediate distal end 39.

[0075] The inner wall 63 has substantially the same diameter as the inner proximal end 45, and is welded to it.

[0076] The intermediate tube 35 has a wall thickness of between 0.5 mm and 2.5 mm, preferably between 0.5 and 1.5 mm, and for example 1 mm.

[0077] It is made of an austenitic stainless steel having for example an Rp 0.2 of 270 MPa. Typically, it is made of stainless steel of grade 1.4310 or type 304.

[0078] The intermediate proximal end 37 and the intermediate distal end 39 are for example encircled by sleeves 67, so as to increase the rigidity respectively of the connection with the rib 55 and of the connection with the external wall 61.

[0079] In the same way, the internal tube 41 has a wall thickness of between 0.5 mm and 2.5 mm, preferably between 0.5 and 1.5 mm, and for example 1 mm.

[0080] It is made of an austenitic stainless steel having for example an Rp 0.2 of 270 MPa. Typically it is made of stainless steel of grade 1.4310 or type 304.

[0081] The internal proximal end 43 and the internal distal end 45 are for example encircled by sleeves 71, so as to increase the rigidity respectively of the connection with the internal wall 63 and of the connection with a distributor block 73.

[0082] The distributor block 73 is fixed to the inner proximal end 43 of the inner tube 4L

[0083] The distributor block 73 has at least one internal passage 74 for the fluid cryogenic.

[0084] The storage unit 1 further comprises at least one circulation tube 75 extending inside the internal tube 41 and fluidically connecting the at least one internal passage 74 to the storage volume 5.

[0085] Typically, the distributor block 73 comprises four internal passages 74, connected to four circulation tubes 75.

[0086] In this case, one of the passages 74, and the corresponding tube 75, are provided for filling the storage volume 5. Another passage 74, and the corresponding tube 75, are provided for emptying the storage volume 5.

[0087] The two other passages 74, and the two other corresponding tubes 75, are provided to circulate the cryogenic fluid to a heat exchanger, in a loop.

[0088] The distributor block 73 is placed axially in the extension of the internal tube 4L

[0089] It has, towards the internal tube 41, a substantially cylindrical end part 76.

[0090] The end portion 76 is coaxial with the central axis C. It is delimited radially towards the outside by an external surface 77, and axially towards the internal tube 41 by a connection surface 78.

[0091] The external surface 77 is substantially cylindrical. It has a perpendicular section dicularly to the central axis C substantially identical to that of the internal proximal end 43.

[0092] The inner proximal end 43 is connected to the peripheral edge of the connecting surface 78.

[0093] The internal reservoir 3 also has an orifice 79 through which the internal tube 41 is connected to the external reservoir 7.

[0094] The orifice 79 is formed in the internal ring 51. The subassembly constituted by the distributor block 73 and the internal tube 41 passes through the orifice 79.

[0095] Thus, the space delimited inside the external tube 27 is isolated from the storage volume 5 but communicates with the intermediate space 19 through the orifice 79.

[0096] Advantageously, the connection 23 comprises a movement limiter 81, limiting a movement of the internal tube 41 relative to the internal reservoir 3, in a plane perpendicular to the central axis of the internal tube 41, to a maximum of less than 3 mm.

[0097] In the example shown, the central axis of the internal tube 41 corresponds to the central axis C. The movement of the internal tube 41 is taken at the level of the internal proximal end 43. It corresponds to the radial offset of the internal proximal end 43 relative to its rest position.

[0098] The maximum is set, as indicated above, at a value less than 3 mm, typically between 1.5 and 2.5 mm, and for example 2 mm.

[0099] The movement limiter 81 cooperates with the orifice 79 to limit the movement of the internal tube 4L

[0100] The movement limiter 81 is rigidly fixed to the distributor block 73.

[0101] Alternatively, it is attached to the inner tube 41, typically at the inner proximal end 43.

[0102] According to another variant, it is fixed both to the distributor block 73 and to the internal tube 4L

[0103] The movement limiter 81 is a sleeve arranged around the inner proximal end 43. The radial spacing between the movement limiter 81 and the inner surface of the orifice 79 thus corresponds to the maximum travel of the inner tube 4L

[0104] Advantageously, the connection 23 comprises a first cup 83 of which a first central part 84 is placed opposite the bottom 13 of the internal tank 3 and of which the first edge 85 is rigidly fixed to the internal surface of the external tank 7. This cup is for example of the type described in the application filed under number FR2211366.

[0105] The first central part 84 of the cup 83 is oriented substantially perpendicular to the central axis C. It has a first central orifice 86, crossed by the distribution block 73.

[0106] The movement limiter 81 is advantageously a shouldered washer.

[0107] It has a cylindrical part 87, arranged around the distributor block 73 and ri firmly fixed thereto. An outgoing collar 88 is formed at one end of the cylindrical portion 87. The outgoing collar 88 is rigidly fixed to the first cup 83, around the first central orifice 86.

[0108] Only the end 89 of the cylindrical part 87, opposite the outgoing collar 88, is engaged in the orifice 79 of the internal reservoir 3.

[0109] Thus, if the movement limiter 81 has a determined total length axially, this movement limiter 81 is only engaged in the orifice 79 over a length less than 50% of said determined total length.

[0110] This makes it possible to avoid excessive heat transfers by radiation between the movement limiter 81 and the edge of the orifice 79.

[0111] Each internal passage 74 has, at one end, a counterbore 93 formed in the connection surface 78. A connection sleeve 95 is rigidly fixed in this counterbore 93. The corresponding circulation tube 75 is rigidly fixed by one of its ends, in a sealed manner, to the connection sleeve 95.

[0112] Furthermore, each circulation tube 75 is connected to the bottom plate 33 and communicates with the storage volume 5 through the bottom plate 33.

[0113] To do this, the base plate 33 has orifices 97, in which other connection sleeves 99 are engaged. Each circulation tube 75 is rigidly fixed, in a sealed manner, to one of the other connection sleeves 99.

[0114] Each circulation tube 75 has a wall thickness of between 0.1 and 0.6 mm, preferably between 0.2 and 0.4 mm and for example 0.3 mm. These circulation tubes 75 are typically made of a 316 L type stainless steel.

[0115] In order to compensate for the differential expansion between the or each circulation tube 75 and the external tube 27, the or each circulation tube 75 comprises at least one thermal expansion compensator 101.

[0116] Indeed, the or each circulation tube 75 may have a temperature significantly lower than that of the external tube 27, in particular during the first filling of the storage volume 5. During this first filling, the storage volume 5 is at ambient temperature, like the external tube 27. On the other hand, the circulation tubes 75 are substantially at the same temperature as the cryogenic fluid. For a circulation tube 75 of 420 mm, the contraction in length of the circulation tube 75 can then reach 1.6 mm when the cryogenic fluid is liquid hydrogen at 20 K.

[0117] In the example shown, each circulation tube 75 comprises several thermal expansion compensators 101, distributed along its length.

[0118] For example, it comprises three thermal expansion compensators 101, reg- widely spaced along the circulation tube 75.

[0119] The or each thermal expansion compensator 101 is advantageously a corrugated section of the circulation tube 75.

[0120] Each ringed section comprises a plurality of annular zones 103 projecting towards the outside of the circulation tube 75, each delimiting an internal groove open towards the inside of the circulation tube 75. These projecting annular zones 103 are connected to each other by annular zones 105 recessed towards the outside of the circulation tube 75. The recessed annular zones 105 are curved towards the inside of the circulation tube 75, and delimit between the projecting annular zones 103 a groove open towards the outside of the circulation tube 75. Considered in section in a plane containing the axis of the circulation tube 75, the ringed section has a sinuous shape.

[0121] The circulation tubes 75 are rectilinear and parallel to the central axis C.

[0122] The connection 23 also comprises external thermal insulation 107, arranged between the intermediate tube 35 and the external tube 27.

[0123] This external thermal insulation 107 extends from the intermediate distal end 39 over a length less than 75% of the total length of the intermediate tube 35.

[0124] The external thermal insulation 107 is typically of the same type as the thermal insulation 21. It comprises a plurality of metal sheets or plastic sheets (for example PET or polyethylene terephthalate, PA or polyamide, PEEK or aluminized polyetheretherketone) superimposed on each other, with interposition of layers of fibers.

[0125] The external thermal insulation 107 is preferably pressed against the intermediate tube 35. It covers the weld securing the intermediate distal end 39 to the annular ring 47. It also covers the radially external surface of this annular ring 47. The external thermal insulation 107 extends approximately over 50% of the total length of the intermediate tube 35.

[0126] The connection 23 also comprises internal thermal insulation 109, arranged between the intermediate tube 35 and the internal tube 4L.

[0127] This internal thermal insulation 109 extends from the internal proximal end 43 over a length less than 75% of a total length of the internal tube 4L

[0128] The internal thermal insulation 109 is of the same type as the thermal insulation 21. It comprises a plurality of aluminized metal sheets or plastic sheets (for example PET, PA, PEEK) superimposed on each other, with interposition of layers of fibers. It is pressed against the internal tube 4L

[0129] The internal thermal insulation 109 does not cover the weld connecting the internal proximal end 43 to the distribution block 73 nor the movement limiter 81. It begins a short distance from the bond weld. It typically extends about two-thirds of the total length of the inner tube 41.

[0130] It will be noted that there is an axial overlap between the external thermal insulation 107 and the internal thermal insulation 109, as illustrated in [Fig.2].

[0131] As explained above, the usual mechanical stresses such as emergency braking, hairpin turns of the vehicle, vibrations, shocks resulting from a poor state of the road surface, cause displacements of the internal proximal end 43 which are not greater than 1 mm. These stresses therefore do not cause contact between the movement limiter 81 and the edge of the orifice 79.

[0132] On the other hand, in the case where the storage unit 1 is subjected to exceptional stress, such as for example in the event of an accidental impact of the vehicle, the internal proximal end 43 may be subjected to an acceleration of up to 10 G. The movement limiter 81, in this case, comes into contact with the edge of the orifice 79. This will limit the deformation of the internal tube 41 and the intermediate tube 35. These tubes 41, 35 will not undergo irreversible plastic deformation. The movement limiter 81 is sufficiently rigid so as not to be deformed during such an impact.

[0133] It should be noted that the external thermal insulation 107 only covers the area of ​​the intermediate tube 35 where the temperature difference between the intermediate tube 35 and the external tube 27 is the greatest. Indeed, the external tube 27 is at the temperature of the cryogenic fluid, that is to say approximately 20 K in the case where this fluid is liquid hydrogen. The temperature of the intermediate tube 35 varies between 50 K at the intermediate proximal end 37 and 130 K at the intermediate distal end 39. The temperature difference is therefore greater near the intermediate distal end 39. As a result, the radiation from the intermediate tube 35 on the external tube 27 is greater at this level. The installation of thermal insulation on this portion of the intermediate tube 35 therefore makes it possible very effectively to limit heat transfers by radiation, without excessively increasing the cost.

[0134] The internal thermal insulation 109 is also placed in the zone where the temperature difference between the internal tube 41 and the intermediate tube 35 is the greatest.

[0135] It should be noted that the transition from a suspension with two tubes (intermediate tube and internal tube) with low wall thickness instead of a single tube, as described in the application filed under number FR2207054, makes it possible to reduce the thermal inputs from 6.9 W to 4 W for a typical embodiment (hydrogen storage of capacity suitable for a motor vehicle). The fact of using cryogenic fluid circulation tubes with particularly thin walls makes it possible to reduce the thermal transfer from 5 W to 3.5 W for the same embodiment.

[0136] According to a variant not shown of the first embodiment, the end The inner proximal end 43 of the inner tube 41 is extended and passes through the first central orifice 86. The first cup 83 is welded directly onto the inner tube 41. The movement limiter 81 is arranged around the inner proximal end 43 and rigidly fixed thereto.

[0137] A second embodiment will now be described, with reference to [Fig. 3]. Only the points in which the second embodiment differs from the first embodiment will be detailed below. Elements which are identical or provide the same function will be designated by the same references in both embodiments.

[0138] In the second embodiment, the movement limiter 81 is fixed to the internal tank 3.

[0139] It cooperates with the inner proximal end 43 of the inner tube 4L

[0140] Alternatively, it cooperates with the distributor block 73, or it cooperates with both the internal proximal end 43 and the distributor block 73.

[0141] The movement limiter 81 has an annular shape, centered on the central axis C.

[0142] Advantageously, it is continuous.

[0143] Alternatively, it is formed from several distinct segments, separated from each other, arranged in a ring.

[0144] The movement limiter 81 is fixed to the inner ring 51, typically on a face 111 of the inner ring 51 facing the outside of the inner reservoir 3.

[0145] The movement limiter 81 surrounds the orifice 79 and projects radially inward from the orifice 79.

[0146] The inner proximal end 43 covers the outer surface 77 of the distributor block 73. More precisely, it covers the part of the outer surface 77 located towards the inner reservoir 3.

[0147] The internal proximal end 43 is rigidly fixed to the distributor block 73, by any suitable means, for example by welding.

[0148] The end portion 76 of the distributor block 73 is engaged in the internal proximal end 43. It has an external section substantially identical to the internal section of the internal proximal end 43.

[0149] The first central portion 84 of the first cup 83 is rigidly fixed directly to the internal proximal end 43.

[0150] The inner proximal end 43 is engaged through the first central orifice 86 of the first cup 83 and is welded to the edge of said orifice 86.

[0151] The movement limiter 81 has an inner diameter equal to the outer diameter of the inner proximal end 43, typically increased by 4 mm.

[0152] The movement limiter 81 is welded to the inner ring 51 once the intermediate tube 35, the inner tube 41 and the bottom 65 are already welded to the inner ring 51.

[0153] The advantage of this solution lies in the fact that the 2 mm clearance between the movement limiter 81 and the inner tube 41 is adjusted once the suspension is assembled. In other words, the position of the movement limiter 81 is adjusted by knowing the position of the inner proximal end 43 of the inner tube 41 relative to the inner ring 51.

[0154] Furthermore, the inner proximal end 43 of the inner tube 41 is elongated so that the inner tube 41 is welded directly to the first cup 83. This avoids an intermediate weld that the first embodiment required (welding the tube 41 to the distributor block 73 then welding the first cup 83 to the distributor block 73). This also makes it possible to eliminate a connection on the critical path of the transfer of thermal loads.

[0155] A third embodiment will now be described, with reference to Figures 4 and 5. Only the points by which the third embodiment differs from the second will be detailed below. Elements that are identical or provide the same function will be designated by the same references in both embodiments.

[0156] This embodiment is particularly well suited to the connection 25, which is not provided for the passage of the cryogenic fluid. The connection 25 is provided for the suspension of the end of the first tank located opposite the fluid inlet and outlet ports of the storage unit 1.

[0157] Consequently, no distributor block and no cryogenic fluid circulation tube is integrated into the connection 25.

[0158] The connection 25 comprises, on the other hand, a second cup 113 having a second central part 115 and a second edge 117 rigidly fixed to the external reservoir 7 ([Fig.l]).

[0159] The second central part 115 is placed opposite the bottom 13 of the internal tank 3. The second edge 117 is rigidly fixed to the internal surface of the external tank 7. This second cup 113 is for example of the type described in the application filed under number FR2211366.

[0160] The connection 25 comprises a sliding tube 119 passing through a second orifice 120 of the second central part 115.

[0161] The sliding tube 119 is coaxial with the central axis C.

[0162] It is rigidly fixed to the second central part 115, for example by welding.

[0163] The sliding tube 119 extends opposite the movement limiter 81 perpendicular to the central axis C. In other words, the movement limiter 81 is arranged around the sliding tube 119.

[0164] The inner proximal end 43 of the inner tube 41 is slidably engaged in the slide tube 119.

[0165] The internal proximal end 43 is therefore connected to the sliding tube 119 with a degree of freedom, in axial translation.

[0166] As visible in [Fig.5], an internal surface of the sliding tube 119 carries a coating 121 facilitating the sliding of the internal proximal end 43 in contact with the sliding tube 119.

[0167] For example, a radial clearance of 2 mm is provided between the movement limiter 81 and the sliding tube 119.

[0168] In this embodiment, the movement limiter 81 cooperates with the internal tube 41 to limit the movement of this internal tube, indirectly through the sliding tube 119.

[0169] This sliding possibility makes it possible to manage the variation in axial length of the internal tank 3 relative to the external tank 7. When filling the internal tank 3 with cryogenic fluid, this tank 3 will contract under the effect of cooling. Its axial length decreases.

[0170] In the third embodiment, the connection 25 comprises a single layer of thermal insulation 123, replacing the internal 107 and external 109 thermal insulations. It is arranged between the internal tube 41 and the intermediate tube 35, typically against the internal tube 41.

[0171] It covers the internal cylindrical wall 63, and the greater part of the internal tube 41. It stops a short distance from the sliding tube 119.

[0172] According to a variant not shown, the movement limiter 81 is a sleeve fixed to the sliding tube 119.

[0173] It cooperates with the orifice 79 crossed by the internal tube 41.

[0174] The storage unit described above has multiple advantages.

[0175] Providing that the movement limiter cooperates with the orifice of the internal reservoir to limit the movement of the internal tube, allows the use of a particularly simple movement limiter. The movement is controlled by appropriately choosing the gap between the internal surface of the orifice and the movement limiter.

[0176] Providing that the movement limiter is rigidly fixed to the inner tube and / or the distributor block makes it possible to very conveniently arrange the movement limiter in the orifice.

[0177] Providing that the movement limiter is only engaged in the orifice over a length less than 50% of its total length makes it possible to limit transfers by radiation between the movement limiter and the internal reservoir.

[0178] Providing that the movement limiter is fixed to the inner reservoir and cooperates with the inner proximal end also allows for the use of a particularly simple movement limiter. Adjustment of the clearance between the movement limiter and the inner tube is facilitated, since the position of the movement limiter is adjusted a once the suspension is assembled, knowing the position of the internal proximal end.

[0179] When the connection comprises a first cup having a first central portion rigidly fixed directly to the inner proximal end and a first edge rigidly fixed to the outer reservoir, the assembly of the connection is facilitated, as explained above. The number of welds in the path of the thermal loads is reduced.

[0180] When the connection comprises a second cup having a second central portion and a second edge rigidly attached to the external reservoir, the connection comprising a tube passing through an orifice of the second central portion and rigidly attached to the second central portion, the inner proximal end being slidably engaged in the tube, the tube extending opposite the movement limiter perpendicular to the central axis, the connection allows thermal expansion or retraction of the internal reservoir, axially, relative to the external reservoir.

[0181] Providing that the connection comprises an intermediate tube arranged between the outer tube and the inner tube and an annular ring connecting the intermediate distal end to the inner distal end, means that the thermal path leading from the outer reservoir to the inner reservoir by conduction passes first through the inner tube, then through the annular ring and then through the intermediate tube. The heat flow therefore circulates in two tubes arranged one inside the other, such that the heat flow path is particularly long.

[0182] Furthermore, the presence of the movement limiter makes it possible to use an intermediate tube and an internal tube both having a particularly low wall thickness, between 0.5 mm and 2.5 mm, which contributes to reducing the heat flow by conduction.

[0183] Providing that the suspension comprises external thermal insulation, arranged between the intermediate tube and the outer tube, and extending from the intermediate distal end over a length less than 75% of a total length of the intermediate tube, makes it possible to very effectively limit transfers by radiation between the outer tube and the intermediate tube. The external thermal insulation is placed in the area where the temperature difference is the highest between the two tubes.

[0184] Providing that the suspension includes internal thermal insulation, arranged between the intermediate tube and the outer tube, and extending from the inner proximal end over a length less than 75% of a total length of the inner tube, also makes it possible to reduce radiation transfers between the intermediate tube and the inner tube. This internal thermal insulation is placed in the area where the temperature difference is greatest between the intermediate tube and the inner tube.

[0185] When each circulation tube has a wall thickness of between 0.1 and 0.6 mm, it is possible to drastically reduce heat transfer by conduction from the external tank to the internal tank.

[0186] In this case, it is advantageous to provide that the circulation tube comprises at least one thermal expansion compensator, to allow differential expansion between the circulation tube and the external tube.

[0187] Producing the thermal expansion compensator in the form of a section of corrugated tube is particularly convenient and economical.

[0188] The storage unit can have multiple variants.

[0189] The connection may not include an intermediate tube and an annular ring. The internal tube is then directly fixed to the base plate. The connection is, for example, of the type described in the application filed under number FR2207054.

[0190] The movement limiter may not be in the form of a shouldered washer. For example, the movement limiter may be a simple cylindrical sleeve, fixed to the distributor block or to the internal tube.

[0191] According to another variant, reliefs could be formed around the orifice 79, projecting towards the outside of the internal reservoir. The movement limiter can then be a cup fixed to the distributor block 73, with an edge raised towards the surface of the internal reservoir. The raised edge surrounds the reliefs, and limits the movement of the assembly consisting of the internal tube and the distribution block by cooperating with the reliefs.

[0192] The storage unit may have two connections with the circulation tubes 77 and the distributor block 73, or two connections without circulation tubes 77 or distributor block 73.

[0193] The connection without circulation tubes 77 or distributor block 73 may not include a sliding tube. In this case, the inner tube 41 is directly fixed to the second cup 113. The movement limiter 81 is a sleeve mounted directly on the inner proximal end 43 of the inner tube, or is fixed to the inner reservoir 3 as described above.

Claims

Claims

1. Storage unit (1) for cryogenic fluid, comprising an internal reservoir (3) internally delimiting a volume (5) for storing the cryogenic fluid, an external reservoir (7) in which the internal reservoir (3) is housed and a suspension (9) fixing the internal reservoir (3) to the external reservoir (7), the suspension (9) comprising a connection (23, 25) comprising: - an external tube (27) having an external proximal end (29) fixed to the internal reservoir (3) and an external distal end (31) located inside the storage volume (5); - a bottom plate (33) closing the external distal end (31); - an internal tube (41) arranged inside the external tube (27), having an internal proximal end (43) linked to the external reservoir (7) and an internal distal end (45) fixed to the internal reservoir (3);- a movement limiter (81), limiting a movement of the internal tube (41) relative to the internal reservoir (3) in a plane perpendicular to a central axis (C) of the internal tube (41).;

2. A storage unit according to claim 1, wherein the inner reservoir (3) has an orifice (79) through which the inner tube (41) is connected to the outer reservoir (7), the movement limiter (81) cooperating with the orifice (79) to limit the movement of the inner tube (41).

3. A storage unit according to claim 2, wherein the movement limiter (81) is rigidly fixed to the inner tube (41).

4. Storage unit according to claim 2, wherein the storage unit (1) comprises: - a distributor block (73) fixed to the inner proximal end (43) of the inner tube (41) and having at least one internal passage (74) for the cryogenic fluid; - at least one circulation tube (75) extending inside the inner tube (41) and fluidically connecting the at least one internal passage (74) to the storage volume (5); the movement limiter (81) being rigidly fixed to the distributor block (73).

5. Storage unit according to any one of claims 2 to 4, in which the movement limiter (81) has a determined axial length and is engaged in the orifice (79) over a length less than 50% of said determined length.

6. Storage unit according to claim 1, wherein the movement limiter (81) is fixed to the internal reservoir (3) and cooperates with the internal proximal end (43).

7. A storage unit according to claim 6, wherein the connection (23) comprises a first cup (83) having a first central portion (84) rigidly fixed directly to the inner proximal end (43) and a first edge (85) rigidly fixed to the outer reservoir (7).

8. A storage unit according to claim 6 or 7, wherein the connection (25) comprises a second cup (113) having a second central portion (115) and a second edge (117) rigidly fixed to the external reservoir (7), the connection (25) comprising a sliding tube (119) passing through a second orifice (121) of the second central portion (115) and rigidly fixed to the second central portion (115), the inner proximal end (43) being slidably engaged in the sliding tube (119), the sliding tube (119) extending opposite the movement limiter (81) perpendicular to the central axis (C).

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