Cryogenic tank and its manufacturing method

Abstract

To provide a cryogenic tank which can store cryogenic fluid therein and reduce stress generated by a difference between linear expansion coefficients and a pressure to a permissible value or lower in a temperature range from a normal temperature to a cryogenic temperature and a predetermined pressure range, and to provide a manufacturing method of the cryogenic tank.SOLUTION: A cryogenic tank includes: a hollow liner for storing cryogenic fluid L therein; a mouth piece integrated with the liner and having a passage for loading or discharging the cryogenic fluid; an outer shell which restricts expansion of the liner; and a mold release processing material which is provided on an outer surface of the liner or an inner surface of the outer shell and prevents adhesion between the outer surface and the inner surface. The liner is formed of a resin which does not break by the time when the liner contacts with the outer shell in a pressure loading state when the cryogenic fluid is stored therein. The mouth piece is formed of a resin, a fiber-reinforced plastic, or a metal which has corrosion resistance to the cryogenic fluid and withstands a heat load during liner molding. The outer shell is formed of a fiber-reinforced plastic whose molding temperature is lower than a melting start temperature of the liner.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cryogenic tank for storing cryogenic fluids at extremely low temperatures and a method for manufacturing the same.

Background Art

[0002] [[ID=—11]] Conventionally, in the aerospace field, metal tanks (cryogenic tanks) for storing cryogenic fluids such as liquid oxygen have been used. However, such metal tanks are heavy, and there is a demand for weight reduction.

[0003] To meet this demand, for example, Patent Document 1 has been proposed. In addition, a flame-retardant material related to the present invention has been proposed in Patent Document 2.

[0004] The cryogenic composite pressure vessel of Patent Document 1 includes a pressure-resistant layer having an inner shell and an outer shell, and an airtight resin layer formed on the inner surface of the inner shell. The inner shell is formed of a fiber-reinforced resin composite material that can withstand heating above the melting point of the airtight resin layer, and the airtight resin layer is formed by fusing a thermoplastic airtight resin film to the inner surface of the inner shell. The outer shell is formed of a fiber-reinforced resin composite material that is molded at a temperature below the melting point of the airtight resin layer.

[0005] The flame-retardant material of Patent Document 2 contains carbon fibers having a tensile modulus of elasticity of 700 GPa or more and a flame-retardant material such as polycarbonate.

Prior Art Documents

Patent Documents

[0006] [[ID=3 — 8]]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The cryogenic composite pressure vessel described in Patent Document 1 above had the following problems. (1) An airtight resin layer is formed by fusing a thermoplastic airtight resin film to the inner surface of the inner shell, so the resin film is fused to the inner shell. Therefore, at room temperature, the resin film is fused to the inner shell, and when a cryogenic fluid (for example, liquid oxygen) is filled in, the inner shell and the resin film are cooled to the temperature of the cryogenic fluid (for example, approximately -180°C in the case of liquid oxygen). In this case, because the difference in the coefficient of thermal expansion between the inner shell and the resin film is large, tensile stress acts on the resin film, which may cause the resin film to peel off from the inner shell.

[0008] (2) The specific shaped film used to form the airtight resin layer has a long, roughly trapezoidal planar shape with a wide side, a narrow side, and two gently curved long sides connecting them. When fusing a thermoplastic airtight resin film to the inner surface of the inner shell, specific shaped films are overlapped and joined together to form a film that conforms to the shape of the inner surface of the upper shell member and the inner surface of the lower shell member. Therefore, the airtight resin layer is made up of numerous films of specific shapes joined together, and when tensile stress is applied to the resin film due to the aforementioned temperature changes, there is a possibility that a portion of the films of specific shapes may peel off from the inner shell at the joints.

[0009] (3) The mouthpiece is attached with adhesive to the area around the mounting hole of the upper shell member that makes up the inner shell. Therefore, the aforementioned temperature changes can cause stress in the adhesive exceeding its strength, potentially leading to leakage of cryogenic fluid around the nozzle.

[0010] The present invention was devised to solve the above-mentioned problems. In other words, the object of the present invention is to provide a cryogenic tank and a method for manufacturing the same that can store cryogenic fluid inside in a temperature range from room temperature to cryogenic temperatures and in a predetermined pressure range, and that can suppress the difference in the coefficient of linear expansion and the stress generated due to pressure to below an acceptable value. [Means for solving the problem]

[0011] According to the present invention, a hollow liner for storing an extremely cold cryogenic fluid inside, A nozzle integrated with the liner and having a channel for filling or discharging the cryogenic fluid, An outer shell that restricts the expansion of the liner, The liner is provided on the outer surface or the inner surface of the outer shell and includes a release agent to prevent adhesion between the two, The cryogenic fluid is liquid oxygen, liquid hydrogen, or liquid natural gas. The liner is made of a resin that has corrosion resistance and liquid tightness to the cryogenic fluid in a temperature range from room temperature to the cryogenic fluid, and that does not rupture before the cryogenic fluid comes into contact with the outer shell under the pressure load conditions during storage. The outer shell is made of fiber-reinforced plastic having a tensile strength exceeding the in-plane stress generated when the liner expands, and having a molding temperature lower than the melting start temperature of the liner. In a state in which the cryogenic fluid is filled inside the liner, a part of the liner is located away from the outer shell. Cryogenic tanks will be provided.

[0012] Furthermore, according to the present invention, The above A method for manufacturing a cryogenic tank, The liner integrated with the nozzle is manufactured, The release agent is applied to the entire outer surface of the liner. A method for manufacturing a cryogenic tank is provided, in which the liner is rotated around the axis of the nozzle, and the outer shell made of fiber-reinforced plastic is formed on the outer surface of the liner, excluding the nozzle. [Effects of the Invention]

[0013] According to the present invention, since the liner is hollow and the outer shell restricts the expansion of the hollow liner, cryogenic fluid can be stored inside the liner within a predetermined pressure range.

[0014] Furthermore, since it is provided with a mold release treatment material that is provided on the outer surface of the liner or the inner surface of the outer shell to prevent adhesion between the two, when the liner and the outer shell are cooled to extremely low temperatures by an extremely low temperature fluid, the liner and the outer shell contract independently with their respective coefficients of linear expansion. Therefore, the stress generated due to the difference in the coefficients of linear expansion between the liner and the outer shell and the pressure can be suppressed below the allowable value.

Brief Description of the Drawings

[0015] [Figure 1] It is an overall cross-sectional view of the cryogenic tank according to the present invention. [Figure 2] It is an enlarged view of part A in FIG. 1. [Figure 3] It is a comparison diagram of when the inside of the liner is empty at normal temperature (A) and when it is filled with an extremely low temperature fluid at extremely low temperature (B). [Figure 4] It is a comparison diagram of when the pressure of the extremely low temperature fluid starts to increase (A), during the pressure increase (B), and when the pressure increase is completed (C) after the inside of the liner is filled with the extremely low temperature fluid. [Figure 5] It is an explanatory diagram of a method for manufacturing a capped liner by cutting out from a resin block. [Figure 6] It is an explanatory diagram of a method for manufacturing a capped liner by compression molding. [Figure 7] It is an explanatory diagram of the second step of a method for manufacturing a cryogenic tank.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings. In the drawings, the same reference numerals are given to common parts, and redundant descriptions are omitted.

[0017] FIG. 1 is an overall cross-sectional view of a cryogenic tank 100 according to the present invention. In this figure, the cryogenic tank 100 includes a hollow liner 10, a base 20, and an outer shell 30.

[0018] The liner 10 is a hollow container for storing cryogenic fluid L inside. The liner 10 is preferably a single molded product, but it may also be manufactured in sections and then integrated. The cryogenic fluid L is either liquid oxygen (LOX), liquid hydrogen (LH2), or liquid natural gas (LNG). The temperature of liquid oxygen is approximately -180°C, and the temperature of liquid hydrogen is approximately -253°C. The liner 10 is made of a resin that has corrosion resistance and liquid tightness to cryogenic fluid L in a temperature range from room temperature to cryogenic temperatures. Furthermore, the liner 10 is made of a resin that does not rupture before the cryogenic fluid L comes into contact with the outer shell 30 under the pressure load conditions during storage. In other words, this resin needs to have a greater elongation at cryogenic temperatures than the amount of thermal shrinkage of the cryogenic fluid L from room temperature to cryogenic temperatures. The resin is preferably polycarbonate (PC), but is not limited thereto. In the case of liquid hydrogen, it may also be polyether ether ketone (PEEK) or liquid crystal polymer (LCP).

[0019] The nozzle 20 is integrated with the liner 10 and has a flow path 22 for filling or discharging cryogenic fluid L. The nozzle 20 is made of a resin, fiber-reinforced plastic, or metal that is corrosion-resistant to cryogenic fluid L and can withstand the thermal load during liner molding (e.g., blow molding). The resin should be the same resin used for the liner 10. The fiber-reinforced plastic should be the same as that used for the outer shell 30. The metal should preferably be titanium, a titanium alloy, or stainless steel. Furthermore, if the nozzle 20 is made of the same resin as the liner 10, it is preferable to mold it integrally or machine it integrally from a resin block.

[0020] The outer shell 30 restricts the expansion of the liner 10. Preferably, the outer shell 30 is located along the outer surface of the liner 10. The outer shell 30 is made of fiber-reinforced plastic (FRP) that has a tensile strength exceeding the in-plane stress generated when the liner 10 expands, and whose molding temperature is lower than the melting start temperature of the liner 10. The fiber-reinforced plastic (FRP) is preferably carbon fiber reinforced plastic (CFRP). Furthermore, the carbon fiber reinforced plastic (CFRP) is preferably room-temperature curing, but it may also be thermosetting or thermoplastic. Furthermore, the fiber-reinforced plastic may be glass fiber-reinforced plastic, aramid fiber-reinforced plastic, etc. In this example, the outer shell 30 is a hollow rotating body centered on axis ZZ.

[0021] In Figure 1, the cryogenic tank 100 further includes a release agent 40 provided on the outer surface of the liner 10 or the inner surface of the outer shell 30 to prevent adhesion between the two (liner 10 and outer shell 30). The release agent 40 is a release film or a liquid release agent. Teflon® tape or polyimide tape is preferred as the release film material, and a fluorine-based release agent is preferred as the liquid release agent.

[0022] In Figure 1, the cryogenic tank 100 has a support structure 50, an expansion joint 52, and fixed piping 54. The support structure 50 is fixed to the outer shell 30 and secures the outer shell 30 to the outside (for example, a fixed frame inside a rocket or satellite). The expansion joint 52 connects one end (the upper end in the diagram) of the fitting 20 to the external piping (for example, the propulsion system of a rocket or satellite). In this example, the expansion joint 52 is a bellows pipe that can expand and contract in the axial direction. The fixed piping 54 is fixed between the other fitting 20 (at the bottom in the diagram) and the external piping (for example, the propulsion system of a rocket or satellite), and is a pipe that does not expand or contract in the axial direction.

[0023] Note that in Figure 1 (and Figures 2-4 described later), the gap between the outer shell 30 and the liner 10 is only at the top. This is because the fixed piping 54 does not expand or contract in the axial direction, and the figure is drawn this way due to the influence of gravity. Furthermore, in Figure 1, bellows piping (expansion piping 52) may also be placed on the lower side.

[0024] Figure 2 is an enlarged view of section A in Figure 1, with the expansion joint 52 omitted. In this figure, the nozzle 20 is a hollow circular disc centered on the axis ZZ, and has an outer surface 20a, an inner surface 20b, an inner circumferential surface 20c, and an outer circumferential surface 20d.

[0025] The outer surface 20a is located on the axial outer side (upper side in the figure) of the liner 10, and the inner surface 20b is located on the axial inner side (lower side in the figure) of the liner 10. In this example, the outer surface 20a and the inner surface 20b are planes perpendicular to the axis ZZ, but are not limited to this; they may also be inclined at an angle to the axis ZZ or be curved surfaces.

[0026] The inner circumferential surface 20c surrounds the flow path 22 and, in this example, is a cylindrical surface, but it may also be a prefix conical surface. The outer circumferential surface 20d is located radially outward from the inner circumferential surface 20c and extends axially from the outer surface 20a towards the inner surface 20b. In this example, the outer end of the outer circumferential surface 20d is a prefix cone surface.

[0027] In this figure, the liner 10 has a clamping portion 12 that sandwiches the outer surface 20d and the inner surface 20b of the nozzle 20 (hollow disc) between them. The clamping portion 12 is in close contact with the outer surface 20d and the inner surface 20b.

[0028] Figure 3 is a comparison of the liner 10 at room temperature with an empty interior (A) and at cryogenic temperatures with the interior filled with cryogenic fluid L (B). In this figure, FL1 is the axial fixed position of the support structure 50, and FL2 is the axial fixed position of the expansion joint 52. Fixed positions FL1 and FL2 are the same in (A) and (B).

[0029] In Figure 3(A), the inside of the liner 10 is filled with low-pressure gas (e.g., air at atmospheric pressure), and the temperature of the liner 10 and the outer shell 30 is at room temperature (e.g., 20-30°C). In this state, the outer surface of the liner 10 and the inner surface of the outer shell 30 are in close contact with the release agent 40 sandwiched between them. Furthermore, the in-plane stress generated in the liner 10 and the outer shell 30 is negligible (effectively zero). Furthermore, the expansion joint 52 is located at the midpoint of its expansion range. In the figure, AL represents the axial displacement position of the outer surface 20a of the fitting 20.

[0030] In Figure 3(B), when the inside of the liner 10 is filled with cryogenic fluid L, the liner 10 is cooled to the temperature of the cryogenic fluid L (for example, in the case of liquid oxygen, a cryogenic temperature of approximately -180°C), and the outer shell 30 is also cooled to near the temperature of the cryogenic fluid L. Due to this cooling, the outer surface of the liner 10 and the inner surface of the outer shell 30 contract according to their respective coefficients of linear expansion, as the release agent 40 is sandwiched between them. The coefficient of linear thermal expansion is greater for the resin (e.g., polycarbonate) that makes up the liner 10 than for the carbon fiber reinforced plastic that makes up the outer shell 30. For example, the coefficient of linear thermal expansion of polycarbonate is approximately 5.6 × 10⁻⁶. -5 The coefficient of thermal expansion of CFRP is approximately 0.2 to 0.4 × 10⁻⁶. -5 It is / K. Therefore, as shown in this figure, the displacement position AL of the outer surface 20a of the nozzle 20 is displaced axially inward (downward in the figure) compared to when it is at room temperature, and the expansion joint 52 is in a more elongated state than when it is at room temperature. In this case, the outer shell 30 also displaces due to cooling, but because the coefficient of linear expansion of CFRP is small, the amount of displacement of the outer shell 30 is smaller than that of the liner 10, and the liner 10 is located at a distance from the outer shell 30.

[0031] Figure 4 is a comparison diagram showing the state of the cryogenic fluid L after filling the inside of the liner 10 with cryogenic fluid L at the start of pressurization (A), during pressurization (B), and after pressurization is complete (C). In this figure, the fixed positions FL1 and FL2 are the same in (A), (B), and (C). The pressure can be increased, for example, by introducing helium gas through piping 52. In this case, the helium gas may be supplied to the thruster together with the cryogenic fluid L. Furthermore, as the cryogenic fluid L is used, gaps will appear, so it is also possible to increase the pressure while monitoring the internal pressure.

[0032] In Figure 4(A), when the cryogenic fluid L is pressurized, the pressure of the cryogenic fluid L acts on the liner 10, causing the resin (e.g., polycarbonate) that makes up the liner 10 to stretch and the liner 10 to expand radially and axially. As a result, the outer surface of the liner 10 comes into contact with the inner surface of the outer shell 30 via the release agent 40 (Figure 4(B)). In Figure 4(B), the outer shell 30 restricts the expansion of the liner 10, but the internal pressure acting on the outer shell 30 is small, and the in-plane stress generated in the outer shell 30 is negligible (essentially zero).

[0033] In Figure 4(B), as the pressure of the cryogenic fluid L increases further, the liner 10 and the outer shell 30 expand together as a single unit, while the liner 10 remains in contact with the outer shell 30 via the release agent 40. In this case, the pressure of the cryogenic fluid L is supported by the outer shell 30, and a large in-plane stress is generated in the outer shell 30. However, since the carbon fiber reinforced plastic that makes up the outer shell 30 has a tensile strength that exceeds the in-plane stress, damage to the outer shell 30 can be prevented.

[0034] For example, the Young's modulus (tensile modulus) of polycarbonate is approximately 2-18 GPa, while that of carbon fiber reinforced plastic (CFRP) is approximately 60-250 GPa. In other words, since the resin (e.g., polycarbonate) that makes up the liner 10 has a Young's modulus that is more than an order of magnitude smaller than that of carbon fiber reinforced plastic, even if the liner 10 expands to follow the inner surface of the outer shell 30 which expands under pressure, damage to the liner 10 can be prevented.

[0035] In Figure 4(C), when the cryogenic fluid L is pressurized to completion, the liner 10 and the outer shell 30 expand further as a single unit from the state in Figure 4(B). In this case, the liner 10 and the outer shell 30 stretch together in the radial and axial directions. However, similar to the state in Figure 4(B), the carbon fiber reinforced plastic constituting the outer shell 30 has a tensile strength that exceeds the in-plane stress, so damage to the outer shell 30 can be prevented, and damage to the liner 10 can also be prevented.

[0036] The method for manufacturing a cryogenic tank according to the present invention consists of a first step and a second step. In the first step, a liner with a nozzle 15 is manufactured, in which the liner 10 and the nozzle 20 are integrated.

[0037] Figure 5 is an explanatory diagram of the manufacturing method of the liner 15 with a nozzle by machining from a resin block, and consists of steps S1 to S4. In this method, a resin block is prepared in step S1, and in step S2, two dome sections with nozzles 10a are manufactured by machining, with the nozzle 20 and the dome section of the liner 10 integrated into one unit. In addition, a ring-shaped body section 10b of the liner 10 is manufactured according to the length of the cryogenic tank 100. In step S3, the dome sections with nozzles 10a and the body section 10b are bonded together to complete the liner with nozzles 15 (S4). Adhesive bonding can be achieved using methods such as welding, heat welding, friction stir welding, and adhesive bonding.

[0038] Figure 6 is an explanatory diagram of the manufacturing method for a die-type liner 15 by compression molding, and consists of steps T1 to T7. In this method, in step T1, molds 1a and 1b are prepared to fit the dome portion 10a with a nozzle, and in step T2, the liner material 2 (resin) of the liner 10 is placed between the molds 1a and 1b. Next, in step T3, the upper mold 1a is pressed against the lower mold 1b, and the liner material 2 is compressed (heated and pressurized) between the molds 1a and 1b. Furthermore, in step T4, the molds 1a and 1b are cooled to below the glass dislocation temperature of the resin, and in step T5, they are demolded to complete the liner 15 with a nozzle.

[0039] Next, similar to Figure 5, the body portion 10b of the liner 10 is manufactured, and in step T6, the dome portion 10a with a nozzle and the body portion 10b are bonded together to complete the liner with a nozzle 15 (T7).

[0040] The liner 15 with a nozzle will be tested for its dimensions, thickness, pressure resistance, and airtightness.

[0041] Figure 7 is an explanatory diagram of the second step in the manufacturing method of the cryogenic tank 100. In the second step, an outer shell 30 made of fiber-reinforced plastic is molded around the liner 15 with a nozzle. In this diagram, (A) is the release process, (B-1) and (B-2) are the filament winding processes, and (C) is the testing process. Furthermore, the second step is not limited to filament winding. For example, if a thermoplastic resin is applied to the matrix, molding may be performed by AFP (Automated Fiber Placement).

[0042] In Figure 7(A), a release agent 40 is applied to the entire outer surface of the liner 10. The release agent 40 is preferably a release film (Teflon® tape or polyimide tape). Alternatively, a liquid release agent may be applied instead of the release agent 40.

[0043] In Figures 7(B-1) and (B-2), the liner 10 is rotated around the axis ZZ of the nozzle 20, and an outer shell 30 made of fiber-reinforced plastic is formed on the outer surface of the liner 10, excluding the nozzle 20, by filament winding. Furthermore, the matrix resin applied to the outer shell 30 is not limited to room-temperature curing resins, but can be either thermosetting resins or thermoplastic resins. Figure 7(B-1) shows the case of the Wet FW method using room-temperature curing resins and thermosetting resins, while (B-2) shows the case where a thermosetting or thermoplastic resin prepreg is used.

[0044] Furthermore, when forming the outer shell 30 by filament winding, a pressurized fluid may be sealed inside the liner 10. The pressurized fluid can be a gas or a liquid. The pressure of the pressurized fluid is set so that the liner 10 can maintain its shape during filament winding.

[0045] In Figure 7(C), the dimensions, thickness, pressure resistance, airtightness, and low-temperature pressure resistance of the molded cryogenic tank 100 are tested, and the cryogenic tank 100 is completed.

[0046] According to the embodiments of the present invention described above, the liner 10 is hollow and made of a resin that has corrosion resistance and liquid tightness to the cryogenic fluid L in a temperature range from room temperature to cryogenic temperatures, so that the cryogenic fluid L can be stored inside the liner 10 in a temperature range from room temperature to cryogenic temperatures.

[0047] Furthermore, the outer shell 30 is made of fiber-reinforced plastic (preferably carbon fiber-reinforced plastic) having a tensile strength that exceeds the in-plane stress generated when the hollow liner 10 expands, and is positioned along the outer surface of the liner 10 to restrict the expansion of the liner 10. This allows the cryogenic fluid L to be stored inside the liner 10 within a predetermined pressure range.

[0048] Furthermore, since a release agent 40 is provided on the outer surface of the liner 10 or the inner surface of the outer shell 30 to prevent adhesion between the two, when the liner 10 and the outer shell 30 are cooled to extremely low temperatures by the cryogenic fluid L, the liner 10 and the outer shell 30 contract independently according to their respective coefficients of thermal expansion. Therefore, the difference in the coefficients of thermal expansion between the liner 10 and the outer shell 30 and the stress generated by the pressure can be kept below the allowable value.

[0049] It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. [Explanation of Symbols]

[0050] AL: Displacement position, FL1, FL2: Fixed position, L: Cryogenic fluid, ZZ axis, 1a, 1b mold, 2 liner material, 10 liner, 10a Dome section with mouthpiece, 10b Body section, 12 Clamping section, 15 Liner with nozzle, 20 nozzle, 20a outer surface, 20b inner surface, 20c Inner surface, 20d Outer surface, 22 Flow channel, 30 Outer shell, 40. Release agents (release films, liquid release solutions), 50 Support structure, 52 Expansion piping, 54 Fixed piping, 100 Cryogenic tank

Claims

1. A hollow liner for storing extremely cold cryogenic fluid inside, A nozzle integrated with the liner and having a channel for filling or discharging the cryogenic fluid, An outer shell that restricts the expansion of the liner, The liner is provided on the outer surface or the inner surface of the outer shell and includes a release agent to prevent adhesion between the two, The cryogenic fluid is liquid oxygen, liquid hydrogen, or liquid natural gas. The liner is made of a resin that has corrosion resistance and liquid tightness to the cryogenic fluid in a temperature range from room temperature to the cryogenic fluid, and that does not rupture before the cryogenic fluid comes into contact with the outer shell under the pressure load conditions during storage. The outer shell is made of fiber-reinforced plastic having a tensile strength exceeding the in-plane stress generated when the liner expands, and having a molding temperature lower than the melting start temperature of the liner. A cryogenic tank in which, when the cryogenic fluid is filled inside the liner, a portion of the liner is located away from the outer shell.

2. The cryogenic tank according to Claim 1, wherein, when the inside of the liner is filled with low-pressure gas at room temperature, the outer surface of the liner and the inner surface of the outer shell are in close contact with the release agent sandwiched between them.

3. A support structure fixed to the outer shell and for fixing the outer shell to the outside, The cryogenic tank according to claim 1, further comprising an expandable and retractable pipe connecting the nozzle and the external piping.

4. The aforementioned outer shell is a hollow rotating body centered on its axis. The aforementioned nozzle is a hollow circular disc centered on the axis, The cryogenic tank according to claim 1, wherein the nozzle is made of a resin, fiber-reinforced plastic, or metal that has corrosion resistance to the cryogenic fluid and can withstand the thermal load during liner molding.

5. A method for manufacturing a cryogenic tank according to Claim 1, The liner integrated with the nozzle is manufactured, The release agent is applied to the entire outer surface of the liner. A method for manufacturing a cryogenic tank, comprising rotating the liner around the axis of the nozzle and forming the outer shell made of fiber-reinforced plastic on the outer surface of the liner, excluding the nozzle.

6. The outer shell is formed by filament winding, The method for manufacturing a cryogenic tank according to claim 5, wherein pressurized fluid is sealed inside the liner during the filament winding process.

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