Double-wall storage tank

Abstract

The invention relates to a double-wall storage tank. The double-wall storage tank comprises an inner container surrounded by an outer sheath. More specifically, the present invention relates to a double-walled storage tank comprising an arrangement for coupling an inner container relative to an outer jacket.

Description

Technical Field

[0001] The present invention belongs to the field of fluid storage systems. In particular, the present invention relates to a double-walled tank comprising an inner container surrounded by an outer jacket. More specifically, the present invention relates to a double-walled tank comprising an arrangement for coupling the inner container relative to the outer jacket. Background Art

[0002] For environmental reasons, the challenge of reducing the use of fossil fuels must be increasingly faced. In this context, green hydrogen produced based on renewable energy sources is a logical candidate for efficient energy supply. The high energy density of hydrogen makes it an emerging alternative fuel for aircraft applications.

[0003] In particular, hydrogen is an attractive fuel for high-altitude-short-range aircraft because it contains about 3 times more energy per kilogram than traditional hydrocarbon fuels. Therefore, in aircraft applications, the high specific energy of the hydrogen may be a key contributing factor. However, practical considerations have largely hindered its use. Although the specific energy of hydrogen is very high, the energy per unit volume is relatively low. Liquid hydrogen (LH2) improves its energy density relative to the gaseous form, while allowing the mass of the tank required to confine hydrogen therein to be reduced due to the low pressure in the liquid state. Compared with 40 g / l of gaseous hydrogen at 88K and 700 bar, liquid hydrogen at 20K and 1 bar pressure has a density of 70 g / l. Only cryogenically compressed hydrogen has a higher density, with a value of 80 g / l at 38K and 300 bar. According to these parameters, the liquefied cryogenic form allows effective storage at low pressure.

[0004] In this regard, LH2 cryogenic tanks (i.e., tanks configured to contain liquid hydrogen and to maintain the necessary conditions to keep hydrogen in a liquid state) are one of the key components of the structures of future generations of heavy lift launch vehicles, space exploration structures, and new green aircraft. In aircraft, the biggest challenge is to develop systems to store hydrogen due to the need to reduce weight and have the longest dormancy time requirements to obtain good insulation and permeability. Some of the key challenges are geometry, temperature, pressure, permeation, insulation, hydrogen embrittlement, vacuum tightness, system integration inside the tank, and tank integration in the aircraft structure.

[0005] Considering the above conditions, one of the main solutions used in the industry is to use double-walled tanks, especially in the case of storing fuel under cryogenic conditions requiring thermal insulation from the environment and preventing any potential leakage that could compromise operational safety. These double-walled tanks comprise an outer jacket and an inner pressure vessel coupled to each other using rigid elements as spacers, such as struts or annular walls attached to both the outer jacket and the inner vessel by means of fixed connections.

[0006] In this regard, one of the main challenges associated with the design, production and operation of such double-walled tanks is the operational behavior under inertial loads caused by the operation of the aircraft in service and the movement of the fluid stored inside the tank itself, which may lead to failure of the attachment between the outer jacket and the inner container and, in turn, to a loss of structural integrity causing hydrogen leakage or loss of thermal insulation and, therefore, endangering the operational safety of the aircraft. Summary of the invention

[0007] The invention provides a double-wall storage tank and an aircraft.

[0008] In a first aspect of the invention, the present invention provides a double-walled storage tank, the double-walled storage tank comprising:

[0009] an inner container defining an inner chamber configured to contain a fluid,

[0010] an outer sheath defining an outer chamber for housing the inner container, and

[0011] a flexible joint assembly disposed between the inner container and the outer sheath;

[0012] wherein the inner container and the outer sheath extend in a longitudinal direction;

[0013] Wherein, the movable joint assembly includes a polar mounting member and at least three roller supports;

[0014] wherein the polar mounting member and the roller bearing member are disposed between an outer surface of the inner vessel and an inner surface of the outer jacket;

[0015] wherein the polarity mountings are arranged at longitudinal ends of the inner container according to the longitudinal direction, and

[0016] Wherein, each roller support comprises a coupling portion and a rolling portion, and each roller support is arranged as follows:

[0017] wherein the coupling portion is fixed to the outer surface of the inner container and the rolling portion contacts the inner surface of the outer sheath, or

[0018] Therein, the coupling portion is fixed to the inner surface of the outer jacket and the rolling portion contacts the outer surface of the inner container.

[0019] The double-walled storage tank according to the present invention comprises an inner container and an outer jacket. The inner container defines an inner chamber configured to contain a fluid such as a fuel, preferably liquid hydrogen. The outer jacket defines an outer chamber for containing the inner container. Both the inner container and the outer jacket extend in a longitudinal direction so that two corresponding longitudinal ends according to the longitudinal direction can be defined for each of the inner container and the outer jacket. Both the inner container and the outer jacket comprise an inner surface and an outer surface so that the inner surface of the outer jacket faces the outer surface of the inner container.

[0020] The present invention provides a solution for the combination between the inner container and the outer jacket of a double-walled tank. Advantageously, the flexible joint assembly improves the dynamic behavior of the double-walled tank, provides a uniform distribution of the load, and thus minimizes stress concentration. In this regard, when the double-walled tank is subjected to acceleration forces, the flexible joint assembly allows the double-walled tank to withstand dynamic loads in an effective manner, which otherwise may cause failure of the attachment point between the inner container and the outer jacket (especially in the case of using a rigid element attached to both the outer jacket and the inner container by means of a fixed connection, which may cause failure of the attachment point between the inner container and the outer jacket), and in turn cause loss of structural integrity causing fluid leakage or loss of insulation, and thus endangering operational safety. For example, when the double-walled tank is installed in an aircraft, the loads that the double-walled tank and more specifically the inner container must withstand are caused by takeoff, acceleration, turbulence and landing of the aircraft.

[0021] In this regard, sloshing is a known undesirable phenomenon which affects fluids stored inside containers or tanks and which is caused by the jostling to which the container may be subjected, particularly when the container is mounted on a vehicle. Due to such jostling, forces are exerted on the liquid propellant which tend to cause an uneven flow of the fluid along the longitudinal extent of the container wall and an associated uneven distribution of the fluid over the width of the container.

[0022] The sloshing motion of the fluid can cause significant structural loads and rigid body disturbances, which may affect the operation of the control system.

[0023] In addition, thermal effects on the double-walled tank have an impact on the relative displacement between the outer jacket and the inner container, mainly in the longitudinal direction, and therefore on the dynamic behavior and load distribution of the double-walled tank. In this sense, different temperatures of the outer jacket and the inner container can lead to different deformations of the two elements, i.e. thermal expansion / contraction, when the inner container stores fluid in its interior under cryogenic conditions, for example. These different deformations of the outer jacket and the inner container lead to the said relative displacement between the two elements.

[0024] Advantageously, the presence of a union assembly mounted within the inner volume between the outer jacket and the inner container allows for relative displacement and aids in the transfer of structural loads generated between the outer jacket and the inner container.

[0025] In this regard, the union assembly allows the double-walled tank to withstand dynamic loads in an efficient manner when the double-walled tank is subjected to acceleration forces.

[0026] For this purpose, the union assembly comprises a polar mounting piece, which is arranged between a longitudinal end of the inner container according to the longitudinal direction and a corresponding longitudinal end of the outer jacket according to the longitudinal direction, so that the inner container and the outer jacket are kept separated by a predetermined distance. The polar mounting piece serves as a support to withstand loads and moments in any direction at the longitudinal end of the double-walled tank, to which the polar mounting piece is coupled. By virtue of the connection provided by the polar mounting piece between the corresponding longitudinal end of the inner container and the corresponding longitudinal end of the outer jacket, longitudinal relative deformation of the inner container and the outer jacket along the longitudinal direction occurs only between the opposite longitudinal ends of the inner container and the outer jacket, wherein the connection provided by the mounting piece keeps the two ends at a constant separation distance.

[0027] The union assembly also includes at least three roller supports disposed between an exterior surface of the inner container and an interior surface of the outer jacket.

[0028] A roller bearing is an element for providing a bushing or a bearing block with low friction movement through a contact surface. Due to the condition of rolling movement established between the roller bearing and the surface on which the roller bearing rolls, the size of the contact surface of the roller bearing is smaller than the overall size of the roller bearing. Due to the relationship of the size, heat transfer is also minimized, which allows a limited amount of heat to be transferred by conduction. Each of the roller bearings includes a coupling portion and a rolling portion, and each of the roller bearings is arranged to bear radial loads. In particular, each roller bearing is arranged so that the coupling portion is fixed to the outer surface of the inner container and the rolling portion contacts the inner surface of the outer jacket, or the coupling portion is fixed to the inner surface of the outer jacket and the rolling portion contacts the outer surface of the inner container.

[0029] The roller bearing supports the loads to which the double-walled tank is subjected, while minimizing heat transfer and friction between the outer surface of the inner container and the inner surface of the outer jacket through the rolling portion of the roller bearing. Additionally, the roller bearing has sufficient elasticity to be able to absorb relatively small displacements between the inner container and the outer jacket in the radial direction (i.e., in a direction perpendicular to the longitudinal direction), while allowing significantly large displacements along the longitudinal direction by virtue of its rolling ability.

[0030] The union assembly maintains separation between the inner container and the outer jacket of the double-walled tank while helping to minimize the heat transfer path between the inner container and the outer jacket of the double-walled tank by utilizing discrete support elements (e.g., roller supports) that typically provide a smaller heat transfer area than continuous support elements such as walls.

[0031] In an embodiment, the coupling portion of the at least one roller bearing is fixed to the outer surface of the inner container and the rolling portion contacts the inner surface of the outer jacket.

[0032] In an embodiment, the coupling portion of the at least one roller bearing is fixed to the inner surface of the outer jacket and the rolling portion contacts the outer surface of the inner container.

[0033] In an embodiment, at least one roller bearing is a ball bearing, wherein the rolling parts are balls. In a particular embodiment, all roller bearings are ball bearings, wherein the rolling parts are balls.

[0034] Advantageously, the ball bearings provide a low friction contact surface that allows relative movement between the inner container and the outer jacket through the points of contact between the balls and the respective surfaces with which they contact.

[0035] In an embodiment, the double-walled tank comprises a fluid channel system configured to conduct fluid to / from the interior of the double-walled tank, the fluid channel system being arranged at one longitudinal end of the double-walled tank and comprising at least one conduit passing through the outer jacket and the inner container and entering the inner chamber. At least one conduit passes through the inner container and the outer jacket through each respective longitudinal end. According to this embodiment, the polar mounting is arranged between the longitudinal end of the inner container and the longitudinal end of the outer jacket, wherein at least one conduit passes through the inner container and the outer jacket through the longitudinal end. Advantageously, the relative displacement between the inner container and the outer jacket caused by the different thermal expansion is reduced. More specifically, by virtue of the connection provided by the polar mounting between the respective longitudinal ends of the inner container and the respective longitudinal ends of the outer jacket, the longitudinal deformation at the connection joint between the fluid channel system and the double-walled tank is prevented, so that the longitudinal relative deformation of the inner container and the outer jacket along the longitudinal direction occurs only at the longitudinal end opposite to the connection joint, wherein the connection provided by the polar mounting keeps the two ends at a constant separation distance.

[0036] In an embodiment, the coupling part of the roller support comprises GFRP ("Glass Fiber Reinforced Polymer") or CFRP ("Carbon Fiber Reinforced Polymer").

[0037] In an embodiment, the rolling portion of the roller support comprises an elastomer. Advantageously, the rolling portion is less prone to damage or compromise any surface with which the rolling portion contacts.

[0038] In an embodiment, the inner volume between the outer jacket and the inner container is maintained under vacuum conditions.

[0039] The inner vessel, when containing a cryogenic compressed fluid such as hydrogen, will be exposed to extremely low temperatures. Advantageously, maintaining vacuum conditions in the inner volume provides thermal insulation between the inner vessel and the outer jacket, virtually eliminating conductive and convective heat transfer.

[0040] In certain embodiments, the inner volume between the inner container and the outer jacket is under ultra-high vacuum (UHV) conditions. According to the vacuum state, the operating pressure is less than about 100 nPa (1.0×10 -7 Pa; 1.0×10 –9 mbar; 7.5×10 -10 Torr).

[0041] In an embodiment, each of the outer jacket and the inner container comprises a central portion extending along the longitudinal direction.

[0042] In an embodiment, the central portion of the outer sheath is generally cylindrical or generally frusto-conical.

[0043] In an embodiment, the central portion of the inner container is generally cylindrical or generally frusto-conical.

[0044] In an embodiment, one or more of the roller supports are arranged between a central portion of the outer jacket and a central portion of the inner container.

[0045] In an embodiment, all roller supports are arranged between a central portion of the outer jacket and a central portion of the inner container.

[0046] In an embodiment, the outer jacket and the inner container have the same shape, the outer jacket having the larger size and accommodating the inner container. According to an embodiment, the outer surface of the inner container and the inner surface of the outer jacket are arranged parallel to each other, i.e. are evenly separated from each other at all points. In this embodiment, the roller bearing is arranged between the inner surface of the outer jacket and the outer surface of the inner container, thereby maintaining this even separation between the inner surface of the outer jacket and the outer surface of the inner container in a stationary state and contributing to damping relative displacements between the inner surface of the outer jacket and the outer surface of the inner container, i.e. displacements in a radial direction or in a direction perpendicular to the longitudinal direction.

[0047] In an embodiment, the roller supports arranged between the central portion of the outer jacket and the central portion of the inner container are spaced apart from each adjacent roller support by an arc of approximately 360 / n degrees according to a circumferential direction about the longitudinal direction, wherein n is the number of roller supports arranged between the central portion of the outer jacket and the central portion of the inner container. In other words, the projection of the positions of the roller supports on a plane perpendicular to the longitudinal direction, along which the inner container and the outer jacket and the corresponding central portions extend, are evenly spaced. According to this embodiment, the roller supports are evenly spaced around the circumference of the inner container.

[0048] In an embodiment, the roller bearings are arranged closer to the longitudinal end of the inner container opposite to the longitudinal end at which the polar mountings are arranged than to the longitudinal end at which the polar mountings are arranged. Such a distribution of the roller bearings allows an improved balance of the loads and thus an improved dynamic behavior during operation.

[0049] In an embodiment, the roller bearing is arranged at a position relative to the polar mounting, which position is arranged at a distance of at least 75% of the maximum length of the double-walled tank in the longitudinal direction.

[0050] The number of roller supports is related to the size and weight of the double wall tank, which determines the level of load supported and transmitted by the roller supports. The number of roller supports also depends on the thermal characteristics expected to be experienced during operation and the insulation properties of the roller supports.

[0051] In an embodiment, the number of roller supports is greater than or equal to three.

[0052] In an embodiment, the number of roller supports is between three and twenty.

[0053] In an embodiment, the number of roller supports is between three and ten.

[0054] In an embodiment, the number of roller supports is between 3 and 6. Advantageously, a number of roller supports between 3 and 6 allows for relative displacement and helps transfer structural loads originating between the inner vessel and the outer jacket and limits the weight increase associated with a higher number of roller supports and the heat transfer between the inner vessel and the outer jacket due to the presence of such roller supports.

[0055] Based on the above-mentioned design factors, three embodiments with different numbers of supports are described below.

[0056] In an embodiment, the number of roller supports present in the double-walled tank is 3. In an embodiment, the roller supports are arranged so that the projections of their positions on a plane perpendicular to the longitudinal direction are approximately evenly spaced, i.e., there is a spacing of approximately 120 degrees between adjacent projections according to the circumferential direction.

[0057] In an embodiment, the number of roller supports present in the double wall tank is 4. In an embodiment, the roller supports are arranged so that the projection of their positions on a plane perpendicular to the longitudinal direction is approximately evenly spaced, i.e., with a spacing of approximately 90 degrees between adjacent projections according to the circumferential direction.

[0058] From the point of view of dynamic behavior, this embodiment shows improved performance, since the greater symmetrical distribution of the supports around the longitudinal direction of the tank provides a better response to the inertial loads experienced during operation. In particular, the configuration according to this embodiment is also symmetrical with respect to any of the bisecting planes defined between two different roller supports, so as to provide a higher stability of the connection between the inner container and the outer jacket under dynamic loads in any direction.

[0059] In an embodiment, the number of roller supports present in the double wall tank is 10. In an embodiment, the roller supports are arranged so that the projection of their positions onto a plane perpendicular to the longitudinal axis are substantially evenly spaced, ie with a spacing of substantially 36 degrees.

[0060] From a dynamic behavior point of view, this embodiment shows improved performance, in particular for embodiments of larger and heavier double-walled tanks and / or embodiments in which the expected loads experienced during operation are higher.

[0061] In an embodiment, the double-walled tank comprises at least one shell disposed in an outer surface of the inner container and / or an inner surface of the outer jacket, and wherein:

[0062] A coupling portion of one of the roller supports is fixed in the housing; and / or

[0063] A rolling portion of one of the roller bearings is arranged in the housing.

[0064] Embedding the roller bearings within such a housing helps prevent axial and circumferential displacement of the roller bearings.

[0065] According to an embodiment of the invention, the shell is arranged during the manufacturing process of the corresponding inner container or outer jacket, for example in the case of parts made of thermoplastic plastics, it is arranged by means of a co-curing, bonding or welding process, or in the case of parts made of CFRP thermosetting plastics, it is arranged by means of a co-bonding process.

[0066] According to a particular embodiment, the casing is made of a thermoplastic material and is welded to at least one thermoplastic portion or laminate provided at a corresponding portion of the inner container or of the outer jacket.

[0067] In an embodiment where the rolling portion of the roller bearing is arranged in the housing, the housing receives the roller bearing and can limit the movement of the roller bearing. In particular, when the rolling portion of the roller bearing is arranged in the housing, the sliding of the rolling portion is limited by the size of the housing. In this aspect, the housing can be a circumferential groove provided on the inner surface of the outer jacket where the roller bearing is located.

[0068] In an embodiment, the number of housings is equal to the number of roller bearings, and for each roller bearing, the coupling part is fixed in the housing or the rolling part is arranged in the housing.

[0069] In an embodiment, the double-walled tank comprises a damping device arranged to absorb a displacement of one of the roller supports in a direction perpendicular to the surface to which the support is fixed.

[0070] In an embodiment, the double-walled tank comprises a plurality of damping devices, each damping device being arranged to absorb displacements of the roller support in a direction perpendicular to the surface to which the roller support is fixed. More specifically, the damping devices are arranged to damp displacements of the roller support along a radial direction.

[0071] Advantageously, by virtue of the implementation of the damping device, radial disturbances caused by different sources can be absorbed, such as pressure (for example, the pressure difference between the outside and the inner volume of a double-walled tank, in particular the pressure difference between the outside and the inner volume of a double-walled tank when the inner volume is subjected to vacuum conditions, the inner volume being between the inner container and the outer jacket), temperature differences, inertial loads, landing loads, etc.

[0072] In an embodiment, the damping means comprises a spring.

[0073] In an embodiment, the at least one damping device is realized as part of a coupling portion of the at least one roller bearing.

[0074] In an embodiment in which the coupling part of the roller bearing is fixed in the housing, the damping device is fixed between the housing and the coupling part of the roller bearing.

[0075] In an embodiment, the outer surface of the inner container and / or the inner surface of the outer jacket comprises a structural reinforcement provided on:

[0076] at least one region to which the coupling portion of the roller support is fixed, and / or

[0077] At least one area contacted by the rolling portion of a roller support.

[0078] The structural reinforcement used in this embodiment is intended to reinforce the area of ​​the inner vessel and / or outer jacket where the roller bearings are located.

[0079] In an embodiment, the structural reinforcement is arranged at any of the following positions:

[0080] on the outer surface of the inner container, in a portion of the inner container where the rolling portion of the roller support contacts the inner container, to protect and / or enhance this area where the rolling portion of the roller support may roll,

[0081] on the inner surface of the outer jacket, between the coupling portion of the roller support and the region of the inner surface of the outer jacket to which the roller support is fixed, or

[0082] Both on the exterior surface of the inner container and on the interior surface of the outer jacket.

[0083] In an embodiment, the structural reinforcement is arranged at any of the following positions:

[0084] on the inner surface of the outer jacket, in the portion of the outer jacket where the rolling portion of the roller support contacts the outer jacket, to protect and / or reinforce this area where the rolling portion of the roller support may roll,

[0085] on the outer surface of the inner container, between the coupling portion of the roller support and the area of ​​the outer surface of the inner container to which the roller support is fixed, or

[0086] Both on the interior surface of the outer sheath and on the exterior surface of the inner container.

[0087] Therefore, the provision of the structural reinforcement strengthens the critical areas of the inner container and / or the outer jacket that are in contact with the roller bearings, thereby improving the safety and durability of the double-walled storage tank.

[0088] In an embodiment, at least one structural reinforcement comprises insulating material.

[0089] Advantageously, in this embodiment, heat transfer from the outer jacket through the roller bearing to the inner vessel is reduced.

[0090] In an embodiment, at least one structural reinforcement comprises GFRP ("Glass Fiber Reinforced Polymer").

[0091] In an embodiment, at least one structural reinforcement is coated with a thermal barrier coating (TBC) material.

[0092] In an embodiment, the outer sheath comprises at least one dome-shaped portion provided in at least one longitudinal end of the outer sheath.

[0093] In an embodiment, the inner container comprises at least one dome-shaped portion arranged in at least one longitudinal end of the inner container.

[0094] From an architectural and geometric point of view, a dome-shaped structure in the sense of the present invention may be understood as any section of a sphere cut by a plane. The dome-shaped structure may also have a slightly different concave-convex shape, such as, for example, a parabolic shape.

[0095] In an embodiment, the outer jacket comprises a first flange extending outwardly from an exterior surface of the outer jacket.

[0096] Advantageously, the first flange acts as a reinforcement member, facilitating the transfer of loads between the inner vessel and the outer jacket through the roller bearing.

[0097] In an embodiment, the first flange comprises a thickness extending along a portion of the outer jacket according to a longitudinal direction, and at least one roller bearing is arranged between said portion of the outer jacket and the outer surface of the inner container.

[0098] In an embodiment, the first flange extends along at least a portion of a periphery of the outer jacket in a cross section according to a plane perpendicular to the longitudinal direction.

[0099] In an embodiment, the first flange extends along the entire circumference of the outer jacket in a cross section according to a plane perpendicular to the longitudinal direction.

[0100] In an embodiment, the first flange is produced by the joining of two parts attached to each other to form the outer jacket, each part comprising a flange portion abutting and attached to a corresponding flange portion of the other part. In an embodiment, one of the parts forms a dome-shaped end portion of the outer jacket and the other part forms a cylindrical portion of the outer jacket.

[0101] In an embodiment, a dome-shaped portion provided at one longitudinal end of the outer jacket extends from a central portion of said outer jacket, and the first flange is arranged on the central portion adjacent to the dome-shaped portion.

[0102] In an embodiment, the outer jacket comprises a reinforced portion adjacent to the first flange, and at least one roller bearing is arranged between said reinforced portion of the outer jacket and the outer surface of the inner container.

[0103] The reinforced portion is provided with reinforcing features. In an embodiment, the reinforcing features are reinforcing material and / or an increase in thickness of the outer jacket provided during the manufacturing process of the reinforced portion of the outer jacket.

[0104] In an embodiment, the outer jacket includes a second flange extending outwardly from the outer surface, the second flange is disposed on the dome-shaped portion adjacent to the first flange, and the second flange is fixed to the first flange.

[0105] In one aspect, the second flange disposed on the edge of the dome-shaped portion helps to make the assembly process of the double-walled tank more efficient by allowing the coupling of the dome-shaped portion and the central portion by securing the second flange to the first flange.

[0106] In this aspect, the attachment between said second flange of the dome-shaped portion and the first flange of the central portion allows for simultaneous curing of the dome-shaped portion and the central portion providing a pre-cured composite part for the dome-shaped portion and the central portion.

[0107] In another aspect, the second flange further reinforces the area of ​​the outer surface adjacent to the area where the coupling portion of the roller support is secured, the second flange acting as a reinforcement to facilitate the transfer of loads between the inner vessel and the outer jacket through the roller support.

[0108] In an embodiment, the second flange is fixed to the first flange by means of a bolt connection or a riveted connection.

[0109] In an embodiment, the second flange is fixed to the first flange by means of staggered bolt connections.

[0110] In an embodiment, the second flange is fixed to the first flange by means of a band clamp.

[0111] In an embodiment, the coupling joint between the first flange and the second flange comprises sealing means.

[0112] In an embodiment, the sealing means comprises at least one selected from a sealant, an O-ring and a gasket, preferably a cryogenic gasket.

[0113] In an embodiment, the second flange extends along at least a portion of a periphery of the dome-shaped portion in a cross section according to a plane perpendicular to the longitudinal direction.

[0114] In an embodiment, the second flange extends along the entire circumference of the dome-shaped portion in a cross section according to a plane perpendicular to the longitudinal direction.

[0115] In an embodiment, all roller supports are positioned substantially in the same plane perpendicular to the longitudinal direction.

[0116] In an embodiment, at least one of the roller supports is positioned in a plane perpendicular to the longitudinal direction, which plane is different from the plane in which the other roller support is positioned.

[0117] In an embodiment, the inner container and / or the outer jacket comprises a composite material. In a more specific embodiment, at least one of the inner container or the outer jacket comprises a fiber reinforced polymer (FRP) material.

[0118] Advantageously, the use of composite materials for the manufacture of the inner container and / or the outer jacket offers the advantages of composite materials in terms of material properties, weight reduction, material costs, production and industrialization characteristics.

[0119] The use of composite materials for the inner vessel and / or outer jacket produces a double wall tank that is much lighter than tanks using metal portions.

[0120] In a more specific embodiment, at least one of the inner vessel or the outer jacket comprises a CFRP material.

[0121] In an embodiment, the inner container and / or the outer jacket comprises a metallic material.

[0122] In a second invention aspect, the present invention provides an aircraft, which includes a double-walled tank as described above.

[0123] All features described in this specification (including claims, description and drawings) and / or all steps of the methods described may be combined in any combination, except combinations of mutually exclusive features and / or steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0124] These and other features and advantages of the present invention will be clearly understood in view of the detailed description of the present invention which will become apparent from the preferred embodiments of the present invention, which are given by way of example only and not limited thereto, with reference to the accompanying drawings.

[0125] Figure 1 : The figure shows a schematic diagram of a double-walled storage tank according to an embodiment of the present invention.

[0126] Figure 2 : The figure shows a schematic diagram of a lateral cross-section of a double-walled storage tank according to an embodiment of the present invention.

[0127] Figure 3 : The figure shows a cross-section through a plane perpendicular to the longitudinal direction along which the outer sheath and the inner container extend according to an embodiment of the invention.

[0128] Figure 4 : This figure shows a schematic diagram of the arrangement structure of roller supports between the outer jacket and the inner container of a double-walled storage tank according to an embodiment of the present invention.

[0129] Figure 5: This figure shows a schematic diagram of the arrangement structure of roller supports between the outer jacket and the inner container of a double-walled storage tank according to an embodiment of the present invention.

[0130] Figure 6 : The figure shows a schematic diagram of an aircraft including a double-walled tank according to an embodiment of the present invention. DETAILED DESCRIPTION

[0131] Having outlined the objects of the present invention, specific non-limiting embodiments will be described below.

[0132] Figure 1 A schematic diagram of a double-walled storage tank 1 according to an embodiment of the present invention is shown. In particular, Figure 1 There is shown a double-walled tank 1 comprising an inner container 3 defining an inner chamber configured to contain a fluid and an outer jacket 2 defining an outer chamber containing the inner container 3 therein.

[0133] As can be seen, each of the outer jacket 2 and the inner container 3 extends along the longitudinal direction X and comprises a respective central portion which is arranged in the present embodiment in a substantially cylindrical shape. In addition, in this embodiment, the outer jacket 2 and the inner container 3 comprise two respective dome-shaped portions which are arranged at opposite longitudinal ends of the substantially cylindrical central portion. For illustration purposes, Figure 1 In the figure, the outer jacket 2 is shown separated into two halves separated by a vertical mid-plane. More specifically, it can be seen that the disconnected half of the outer jacket 2 is separated from the assembly, which, apart from the separated half of the outer jacket, constitutes the double-walled tank 1. On the other hand, it can be seen that the half of the outer jacket 2 arranged in the service position around the inner container 3 has a striped pattern with bold curves to highlight the contrast between the half of the outer jacket and the inner container 3.

[0134] The double-walled tank 1 further comprises a union assembly arranged between the inner container 3 and the outer jacket 2. The union assembly allows dynamic loads to be accommodated in a more effective manner when compared to a rigid element used as a spacer, attached to both the outer jacket 2 and the inner container 3 by means of a fixed connection. Since this element is part of the union assembly, as described below with respect to Figure 1 As described, there is thus a continuous and uniform load distribution around the double-walled tank 1 , thereby minimizing stress concentrations.

[0135] On the one hand, the union assembly comprises a polar mounting (not shown) arranged between the longitudinal ends of the inner container 3 according to the longitudinal direction X and the corresponding longitudinal ends of the outer sheath 2 according to the longitudinal direction X (i.e., between the outer surface of the dome-shaped portion of the inner container 3 and the inner surface of the corresponding dome-shaped portion of the outer sheath 2). The polar mounting acts as a clamping support to withstand inertial loads and moments in any direction.

[0136] On the other hand, the articulation assembly comprises at least three roller supports (not shown) arranged between the outer surface 3a of the inner container 3 and the inner surface 2a of the outer jacket 2. For illustrative purposes, the position of said supports is shown with the aid of white blocks 5 arranged on the outer surface 3a of the inner container 3, occupying the volume or gap defined between said outer surface 3a of the inner container 3 and the inner surface 2a of the outer jacket 2.

[0137] exist Figure 1 In the particular embodiment shown, the inner volume between the outer jacket 2 and the inner container 3, in which the roller bearings are arranged, is maintained under vacuum conditions which provide thermal insulation between the inner container 3 and the outer jacket 2 and virtually eliminate conductive and convective heat transfer.

[0138] A roller bearing is an element used to provide a bushing or a bearing block with low friction movement through a contact surface. Due to the conditions of rolling movement established between the roller bearing and the surface on which the roller bearing rolls, the contact surface of the roller bearing has dimensions that are smaller than the overall dimensions of the roller bearing. Figure 1 Although not explicitly depicted in the figure, each of the roller supports 5 includes a coupling portion and a rolling portion, and each of the roller supports 5 is arranged to bear a radial load. In particular, each roller support 5 is arranged such that the coupling portion 5a is fixed to the outer surface 3a of the inner container 3 and the rolling portion 5b contacts the inner surface 2a of the outer jacket 2, or the coupling portion 5a is fixed to the inner surface 2a of the outer jacket 2 and the rolling portion 5b contacts the outer surface 3a of the inner container 3.

[0139] about Figure 1 The specific distribution of the roller supports in the illustrated embodiment, with the white blocks 5 representing the positions of the roller supports being distributed in two different planes perpendicular to the longitudinal direction X, between the substantially cylindrical central portion of the outer jacket 2 and the corresponding substantially cylindrical central portion of the inner container 3 .

[0140] More specifically, in Figure 1 In the embodiment shown, there are four roller supports in each of the vertical planes (two of the four roller supports are arranged in each section as shown in FIG. Figure 1The lower section of the double-walled tank 1 is shown hidden), and each roller support is spaced apart from each adjacent roller support by an arc of approximately 90 degrees about the longitudinal direction X.

[0141] In another embodiment, all roller bearings lie substantially in a plane perpendicular to the longitudinal direction X, said plane being located closer to the longitudinal end of the inner container 3 opposite to the longitudinal end where the polar mountings are arranged than to the longitudinal end where the polar mountings are arranged.

[0142] Preferably, the roller bearing is arranged at a position relative to the polar mounting, which position is arranged at a distance of at least 75% of the maximum length of the double-walled tank 1 in the longitudinal direction.

[0143] Figure 2 A schematic diagram of a lateral cross section of a double-walled tank 1 according to one embodiment of the present invention is shown, the lateral cross section being by means of a plane parallel to the longitudinal direction X of the double-walled tank 1 .

[0144] for Figure 2 The union assembly of the double-walled tank 1 is shown with the polarity mounting member 4 attached to the Figure 2 The longitudinal end of the outer jacket 2 on the left and the longitudinal end of the inner container 3 are located between the outer surface 3a of the inner container 3 and the inner surface 2a of the outer jacket 2. On the other hand, three roller supports 5 are arranged between the outer surface 3a of the inner container 3 and the inner surface 2a of the outer jacket 2. One roller support 5 is hidden behind the inner container 3 in the figure.

[0145] Regarding the roller bearing 5 , schematically shown as a dark square block, it is coupled to the outer jacket 2 and the inner container 3 in a manner allowing absorption of relative displacements in radial direction between the outer jacket 2 and the inner container 3 due to pressure and temperature changes during operation of the double-walled tank 1 .

[0146] In this regard, Figure 2 An embodiment is shown in which the damping means 7 is arranged to absorb displacements of the roller supports 5 in a direction perpendicular to the surface 2a, 3a to which each roller support 5 is fixed. In the particular embodiment shown, in which both the central portion of the outer jacket 2 and the central portion of the inner container 3 are substantially cylindrical, the damping means 7 is arranged to absorb displacements of the roller supports 5 in a radial direction perpendicular to a tangent plane to the surface 2a, 3a to which each roller support 5 is fixed.

[0147] The damping means 7 are schematically shown as three springs, one end of which is coupled to a respective roller support 5 and the other end to the inner surface 2a of the outer jacket 2. For illustration purposes, the representation of the damping means 7 and the separation between the inner container 3 and the outer jacket 2 are exaggerated.

[0148] Figure 3 A cross-sectional view through a plane perpendicular to the longitudinal direction, along which the outer jacket 2 and the inner container 3 extend, is shown according to an embodiment of the invention.

[0149] In particular, Figure 3 A schematic diagram of a double-walled storage tank 1 is shown, which includes an inner container 3 and an outer jacket 2, wherein the inner container 3 defines an inner chamber configured to contain a fluid, and the outer jacket 2 defines an outer chamber that contains the inner container 3. It can be seen that the cross-sections of both the outer jacket 2 and the inner container 3 are circular. In addition, Figure 1 Similar to the illustrated embodiment, the inner volume between the outer jacket 2 and the inner container 3 is maintained under vacuum conditions, which provide thermal insulation between the inner container 3 and the outer jacket 2 .

[0150] As can be seen, in this embodiment, three roller supports 5 are arranged between the outer surface 3a of the inner container 3 and the inner surface 2a of the outer jacket 2. The roller supports 5 are spaced apart from each adjacent roller support 5 by an arc of approximately 120 degrees around the longitudinal direction.

[0151] More specifically, Figure 3 An axis system is shown, wherein the Y axis is shown as a horizontal axis with a positive direction to the right, the Z axis is shown as a vertical axis with a positive direction upwards, and the X axis (not explicitly shown) corresponds to the longitudinal direction of the outer jacket 2 and the inner container 3, and the X axis is perpendicular to the plane defined by the Y axis and the Z axis.

[0152] In addition, as can be seen, two of the three supports 5 are located in the lower half of the cross section shown according to the horizontal Y axis and are symmetrically distributed relative to the vertical Z axis. According to this embodiment, in the case of operation of the double-walled tank 1, in which the Z axis roughly corresponds to the direction of gravity, the presence of two symmetrically distributed supports 5 in the lower half of the double-walled tank 1 provides better support for the weight of the inner container 3 and the weight of the contents of the inner container 3 as well as the inertial loads generated during the operation of the double-walled tank 1, thereby providing better static and dynamic behavior. More specifically, according to an embodiment in which the double-walled tank 1 is installed in an aircraft, the loads that the double-walled tank 1 and more specifically the inner container 3 must withstand are caused by take-off, acceleration, turbulence and landing of the aircraft.

[0153] exist Figure 3 In the embodiment of the double-walled storage tank 1, the double-walled storage tank 1 further comprises a structural reinforcement 8 provided in the outer surface 3a of the inner container 3. More specifically, the structural reinforcement is provided in such an area of ​​the outer surface 3a to which the coupling portion of the roller support 5 is fixed or the rolling portion of the roller support 5 contacts.

[0154] Since the structural reinforcement 8 is arranged on the outer surface 3a of the inner container 3, in the case where the inner container 3 is used to store fluid under low temperature conditions, the structural reinforcement 8 is preferably made of a heat insulating material, thereby reducing the heat transfer from the outer jacket 2 through the corresponding roller bearing 5 to the inner container 3. According to a specific embodiment of the present invention, the structural reinforcement 8 includes GFRP. In addition, at least one structural reinforcement 8 can be coated with a thermal barrier coating (TBC) material.

[0155] Figure 4 A schematic diagram showing an arrangement structure of a roller bearing 5 between an outer jacket 2 and an inner container 3 of a double-walled tank 1 according to an embodiment of the present invention is shown.

[0156] In this embodiment, the inner surface 2a of the outer jacket 2 is provided with a shell 6, so that, as can be seen, the coupling portion 5a of the roller bearing 5 is fixed in the shell 6, wherein the rolling portion 5b contacts the surface 2a, 3a opposite to the surface to which the coupling portion 5a is fixed, that is, contacts the outer surface 3a of the inner container 3.

[0157] According to an embodiment of the invention, the shell 6 can be provided during the manufacturing process of the corresponding inner container 3 or outer jacket 2 by means of a co-curing, bonding or welding process in the case of components made of thermoplastics, or by means of a co-bonding process for components made of CFRP thermosetting plastics. According to a more specific embodiment, the shell 6 is made of thermoplastic material and is welded to at least one thermoplastic part or laminate provided at the corresponding part of the inner container 3 or outer jacket 2.

[0158] Embedding the roller support 5 inside such a housing 6 helps prevent axial and circumferential displacement of the roller support 5 .

[0159] exist Figure 4 In an embodiment of the double-walled tank 1, the double-walled tank 1 comprises a damping device 7 arranged to absorb displacements (i.e. expansions / contractions) of the roller support 5 in a direction perpendicular to the inner surface 2a of the outer jacket 2 to which the roller support 5 is fixed, caused by pressure and temperature variations during operation of the double-walled tank 1. As can be seen, said damping device 7 is realized as a part of the coupling portion 5a of the roller support 5. In the particular embodiment shown, in which both the central portion of the outer jacket 2 and the central portion of the inner container 3 are substantially cylindrical, the damping device 7 is arranged to absorb displacements of the roller support 5 in a radial direction perpendicular to the tangent plane of the surfaces 2a, 3a to which the roller support 5 is fixed.

[0160] Furthermore, in this embodiment, a structural reinforcement 8 is provided in the outer surface 3a of the inner container 3. More specifically, the structural reinforcement 8 is provided in the following portion of the outer surface 3a: the portion is arranged as the area contacted by the rolling portion of the roller support 5. Since the structural reinforcement 8 is arranged on the outer surface 3a of the inner container 3, the structural reinforcement 8 is preferably made of a heat-insulating material in the case where the inner container 3 is intended to store fluid under low temperature conditions. According to a specific embodiment of the present invention, the structural reinforcement 8 includes a GFRP material. In addition, at least one structural reinforcement 8 may be coated with a thermal barrier coating (TBC) material.

[0161] In this embodiment, an additional structural reinforcement 8 is provided in the inner surface 2a of the outer jacket 2. More specifically, the structural reinforcement 8 is provided in the portion of the inner surface 2a that is arranged as the area to which the coupling portion 5a of the roller support 5 is fixed. In order to prevent damage to the outer jacket 2, the structural reinforcement 8 provided in the inner surface 2a is implemented as a pad.

[0162] at last, Figure 4 The outer jacket 2 shown comprises an outer surface 2b and a first flange 9 extending outwardly from the outer surface 2b and along a portion of the periphery of the outer surface 2b, the periphery of the outer surface 2b being shown according to a plane perpendicular to the longitudinal direction. As can be seen, the first flange 9 is shaped as a rectangular protrusion and has a thickness extending along a portion 2c of the outer jacket 2 according to the longitudinal direction. According to an embodiment of the present invention, the first flange 9 can be provided during the manufacturing process of the outer jacket 2 by means of a co-curing or co-bonding process.

[0163] The roller support 5 is arranged between the portion 2 c of the outer jacket 2 and the outer surface 3 a of the inner container 3 , along which the first flange 9 extends.

[0164] The first flange 9 acts as a reinforcement to facilitate the transmission of loads between the inner container 3 and the outer jacket 2 via the roller bearing 5 .

[0165] Figure 5 A schematic diagram showing an arrangement structure of roller bearings between an outer jacket 2 and an inner container 3 of a double-walled tank 1 according to an embodiment of the present invention is shown.

[0166] Figure 5 Shown with Figure 4 A part of an embodiment of a double-walled tank 1 similar to the embodiment shown, wherein the double-walled tank has a first flange 9 of a different configuration and further comprises a second flange 10 which is arranged on a dome-shaped portion arranged at a longitudinal end of the outer jacket 2 .

[0167] In particular, Figure 5 The first flange 9 shown comprises a reinforcement portion adjacent to a rectangular portion protruding perpendicularly to the outer jacket 2. The reinforcement portion is shaped to be overly thick relative to the outer jacket 2.

[0168] The roller support 5 is arranged between the portion of the outer jacket 2 along which the reinforced portion of the first flange 9 extends (ie along the portion of the outer jacket 2 having increased thickness) and the outer surface 3a of the inner container 3.

[0169] The dome-shaped portions provided at the longitudinal ends of the outer jacket 2 shown extend from a substantially cylindrical central portion of said outer jacket 2. As can be seen, a first flange 9 is arranged at a position of said substantially cylindrical central portion adjacent to the dome-shaped portion.

[0170] The dome-shaped portion of the outer jacket 2 in turn comprises a second flange 10 extending outwardly from the outer surface 2b, said second flange 10 being arranged adjacent to the first flange 9. The second flange 10 is fixed to the first flange 9.

[0171] Figure 5 The second flange 10 shown comprises a reinforcement portion adjacent to a rectangular portion which protrudes perpendicularly to the outer jacket 2 and more specifically from a dome-shaped portion of the outer jacket 2. The reinforcement portion is shaped so as to be overthick relative to the outer jacket 2.

[0172] Regarding the fixation between the first flange 9 and the second flange 10, Figure 5 Two dashed lines intersecting both the first flange 9 and the second flange 10 and perpendicular to the respective wall portions of the first flange 9 and the second flange 10 are shown, both of which represent bolted or riveted connections. In addition, a black line can be seen between the two wall portions corresponding to each of the first flange 9 and the second flange 10. The black line represents a sealing device provided at the coupling joint between the first flange 9 and the second flange 10. Other embodiments of the sealing device include at least one selected from a sealant, an O-ring, and a gasket, preferably a low-temperature gasket.

[0173] Figure 6 A schematic diagram of an aircraft 20 including a double wall tank according to an embodiment of the present invention is shown.

Claims

1. A double-walled storage tank (1), comprising: an inner container (3), the inner container (3) defining an inner chamber configured to contain a fluid, an outer sheath (2), the outer sheath (2) defining an outer chamber for accommodating the inner container (3), and A flexible joint assembly, the flexible joint assembly being arranged between the inner container (3) and the outer sheath (2); wherein the inner container (3) and the outer sheath (2) extend along a longitudinal direction (X); The movable joint assembly comprises a polar mounting member (4) and at least three roller supports (5); wherein the polar mounting member (4) and the roller supports (5) are arranged between the outer surface (3a) of the inner container (3) and the inner surface (2a) of the outer sheath (2); wherein the polarity mounting member (4) is arranged at a longitudinal end of the inner container (3) according to the longitudinal direction (X), and Each roller support (5) comprises a coupling portion (5a) and a rolling portion (5b), and each roller support (5) is arranged as follows: The coupling portion (5a) is fixed to the outer surface (3a) of the inner container (3) and the rolling portion (5b) contacts the inner surface (2a) of the outer jacket (2), or The coupling portion (5a) is fixed to the inner surface (2a) of the outer jacket (2), and the rolling portion (5b) contacts the outer surface (3a) of the inner container (3).

2. The double-walled storage tank (1) according to claim 1, wherein: Each of the outer jacket (2) and the inner container (3) comprises a central portion extending along the longitudinal direction (X), and wherein the central portion of each of the outer jacket (2) and the inner container (3) is preferably substantially cylindrical or substantially frustoconical.

3. The double-walled storage tank (1) according to claim 2, wherein: One or more of the roller supports (5) are arranged between the central portion of the outer jacket (2) and the central portion of the inner container (3).

4. The double-walled storage tank (1) according to claim 3, wherein: The roller support (5) arranged between the central portion of the outer jacket (2) and the central portion of the inner container (3) is spaced apart from each adjacent roller support by an arc of approximately 360 / n degrees according to a circumferential direction around the longitudinal direction (X), where n is the number of the roller support (5) arranged between the central portion of the outer jacket (2) and the central portion of the inner container (3).

5. The double-walled storage tank (1) according to any one of the preceding claims, further comprising at least one shell (6) arranged in the outer surface (3a) of the inner container (3) and / or the inner surface (2a) of the outer jacket (2), and wherein: The coupling portion (5a) of one of the roller supports (5) is fixed in the housing (6); and / or The rolling portion (5b) of one of the roller supports (5) is arranged in the housing (6).

6. The double-walled tank (1) according to any one of the preceding claims, further comprising a damping device (7), which is arranged to absorb the displacement of one of the roller supports (5) along a direction perpendicular to the surface (2a, 3a) to which the roller support (5) is fixed.

7. Double-walled storage tank (1) according to any one of the preceding claims, wherein: The outer surface (3a) of the inner container (3) and / or the inner surface (2a) of the outer jacket (2) comprises a structural reinforcement (8), wherein the structural reinforcement (8) is arranged on: In at least one region of the roller bearing (5) to which the coupling portion (5a) is fixed, and / or In at least one area where the rolling portion (5b) of the roller bearing (5) contacts.

8. The double-walled storage tank (1) according to claim 7, wherein: At least one of the structural reinforcements (8) comprises a thermally insulating material.

9. Double-walled storage tank (1) according to any one of the preceding claims, wherein: The outer jacket (2) comprises a dome-shaped portion arranged in at least one longitudinal end of the outer jacket (2) according to the longitudinal direction (X), and / or the inner container (3) comprises a dome-shaped portion arranged in at least one longitudinal end of the inner container (3) according to the longitudinal direction (X).

10. Double-walled storage tank (1) according to any one of the preceding claims, wherein: The outer jacket (2) comprises an outer surface (2b) and a first flange (9) extending outwardly from the outer surface (2b).

11. The double-walled storage tank (1) according to claims 10, 9 and 2, wherein: The first flange (9) is arranged on the central portion of the outer jacket (2), wherein the outer jacket (2) comprises a second flange (10) extending outwardly from the outer surface (2b), wherein the second flange (10) is arranged on the dome-shaped portion and adjacent to the first flange (9), and wherein the second flange (10) is fixed to the first flange (9).

12. The double-walled storage tank (1) according to claim 11, wherein: The connecting joint between the first flange (9) and the second flange (10) comprises sealing means.

13. Double-walled storage tank (1) according to any one of the preceding claims, wherein: At least one of the roller supports (5) is positioned in a plane perpendicular to the longitudinal direction (X) and different from the plane in which the other roller support (5) is positioned.

14. Double-walled storage tank (1) according to any one of the preceding claims, wherein: The inner container (3) and / or the outer sheath (2) comprise a composite material or a metal material.

15. An aircraft (20) comprising a double-walled tank (1) according to any one of the preceding claims.

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