Liquefied hydrogen tank and method of designing the same

Abstract

A liquefied hydrogen tank mounted on a ship has an inner tank that stores liquefied hydrogen and an outer tank that surrounds the inner tank, at least one of the inner tank and the outer tank being a leakproof tank, the leakproof tank having a wall thickness that does not propagate an initial defect to more than half of the thickness of the wall during the service life of the tank.

Description

Technical Field

[0001] This disclosure relates to the structure of liquefied hydrogen tanks mounted on ships transporting liquid hydrogen (hereinafter referred to as liquefied hydrogen carriers) and the design method of liquefied hydrogen tanks. Background Technology

[0002] As cargo tanks for liquefied hydrogen transport ships, cargo tanks are known to have an inner tank for containing liquefied hydrogen, an outer tank surrounding the inner tank, and an insulation layer between the inner and outer tanks. Patent Document 1 discloses an example of a cargo tank for a liquefied hydrogen transport ship.

[0003] The design and manufacture of ships transporting liquefied gases must comply with the international code IGC (non-patent document 1). The currently used IGC code is for ships transporting liquefied gases such as LPG and LNG. Liquefied hydrogen transport ships are not subject to the application of the IGC code, and there are no requirements for the transportation of liquid hydrogen.

[0004] It is known that the primary cause of crack propagation in cargo tanks mounted on ships is the dynamic stress generated by the repeated loads exerted on the tanks due to the ship's rolling motion. According to the design approach for Type C tanks based on the IGC code, considering safety margins, the design vapor pressure Po is set sufficiently high, thus increasing the minimum design pressure. To achieve the strength corresponding to this minimum design pressure, the tank wall thickness is designed to be sufficiently large. As a result, the dynamic stress variation in the tank is sufficiently small, and the anticipated propagation of the initial defect becomes relatively small relative to the wall thickness. Therefore, leakage of the liquid cargo is not considered, and there is no obligation to install a secondary protective wall.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication WO2014 / 174820

[0008] Non-patent literature

[0009] Non-patent document 1: International Maritime Organization, International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code), Chapter 4 Cargo Containment, adopted on May 22, 2014. Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] For volumes exceeding 20,000 m³ 3 Large, freestanding cargo tanks for liquefied gas transportation have traditionally been designed using methods other than Type C tanks (i.e., Type A or Type B tanks) as defined by the IGC code. The Type C tank design based on the IGC code is primarily applicable only to tanks with a volume of 20,000 m³. 3The following refers to small tanks. The reason is that if the design method of C-type tanks based on IGC codes is applied to large tanks, the wall thickness of the tank corresponding to the minimum design pressure will exceed the achievable range.

[0012] This disclosure was made in view of the above circumstances, and its purpose is to provide a structure and design method for preventing leakage of liquid or gaseous hydrogen in a liquefied hydrogen tank mounted on a ship, regardless of the size of the liquefied hydrogen tank, when realizing the large-scale transportation of cryogenic liquefied hydrogen.

[0013] Methods for solving problems

[0014] The liquefied hydrogen tank of the present invention is a liquefied hydrogen tank mounted on a ship, characterized in that it has an inner tank for containing liquefied hydrogen and an outer tank surrounding the inner tank, at least one of the inner tank and the outer tank being a leak-proof tank, the leak-proof tank having a wall thickness that prevents initial defects from propagating to more than half the wall thickness during the tank's lifespan.

[0015] Furthermore, the design method for the liquefied hydrogen tank disclosed herein is a design method for a liquefied hydrogen tank mounted on a ship, the liquefied hydrogen tank having an inner tank for storing liquefied hydrogen and an outer tank surrounding the inner tank, the design method of the aforementioned liquefied hydrogen tank being characterized in that...

[0016] At least one of the aforementioned inner tank and the aforementioned outer tank shall be designated as a leak-proof tank.

[0017] The first processor obtains the lifespan of the leak-proof tank, the size of the initial defect of the leak-proof tank, the temperature of the leak-proof tank, the stress propagation coefficient of the leak-proof tank, and the stress generated in the leak-proof tank. Then, through fatigue crack propagation analysis, the crack propagation amount of the initial defect caused by the stress, corresponding to the number of repetitions of the tank life, is calculated.

[0018] The second processor obtains the calculated crack propagation amount and the design wall thickness of the leak-proof tank. If the crack propagation amount does not exceed half of the design wall thickness, the design wall thickness is determined to be appropriate; if the crack propagation amount exceeds half of the design wall thickness, the design wall thickness is determined to be inappropriate.

[0019] The wall thickness of the aforementioned leak-proof tank is determined such that it is above the aforementioned design wall thickness, which is deemed appropriate.

[0020] The effects of the invention

[0021] According to this disclosure, a structure and design method can be provided to prevent leakage of liquid or gaseous hydrogen in a liquefied hydrogen tank mounted on a ship, regardless of the size of the liquefied hydrogen tank. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a ship equipped with a liquefied hydrogen tank according to one embodiment of the present invention.

[0023] Figure 2 This is a cross-sectional view of a liquefied hydrogen transport ship.

[0024] Figure 3 This is a diagram showing the configuration of a leak-proof tank design.

[0025] Figure 4 This is a functional block diagram of the design device for the leak-proof tank. Detailed Implementation

[0026] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

[0027] Figure 1 This is a schematic diagram of the configuration of a ship 1 equipped with a liquefied hydrogen tank 3 according to one embodiment of the present disclosure. Figure 1 The vessel 1 shown has a hull 2 ​​and four liquefied hydrogen tanks 3 mounted on the hull 2. In this embodiment, the liquefied hydrogen tanks 3 are cargo tanks for transporting liquefied hydrogen, and the vessel 1 is a liquefied hydrogen transport ship. In this embodiment, the liquefied hydrogen tanks 3 are arranged along the length of the vessel, but if the vessel is wide, they can also be arranged along the width of the vessel. In addition, the number of liquefied hydrogen tanks 3 mounted on the hull 2 ​​can be one or more than two.

[0028] In this embodiment, the four liquefied hydrogen tanks 3 have substantially the same structure. In this embodiment, the liquefied hydrogen tanks 3 are configured as multi-layer tanks. However, when the ship 1 is equipped with a plurality of liquefied hydrogen tanks 3, the plurality of liquefied hydrogen tanks 3 may each have different structures.

[0029] Figure 2 This is a cross-sectional view of ship 1. (For example...) Figure 1 and Figure 2 As shown, the liquefied hydrogen tank 3 comprises an inner tank 4 for storing liquefied hydrogen and an outer tank 5 surrounding the inner tank 4. The volume of the inner tank 4 exceeds 20,000 m³. 3 And it is 50,000m 3 Below, liquefied hydrogen tank 3 is classified as a relatively large tank.

[0030] The inner tank 4 has a generally spherical inner tank body 41. An inner tank top may also be provided on the inner tank 4, protruding upwards from the inner tank body 41. The outer tank 5 has a generally spherical outer tank body 51. An outer tank top may also be provided on the outer tank 5, protruding upwards from the outer tank body 51. However, the inner tank body 41 and the outer tank body 51 do not necessarily have to be spherical; they can also be cylindrical shapes that are elongated horizontally or vertically. Alternatively, the inner tank body 41 and the outer tank body 51 can also be cubic or cuboid.

[0031] The inner tank 4 and the outer tank 5 are separated in the thickness direction of the tanks. The area between the inner tank 4 and the outer tank 5 is referred to as the "first region 31". A first insulation layer is formed in the first region 31. The first insulation layer is composed of a first gas filled in the first region 31 and an insulation material.

[0032] The first region 31, filled with a first gas, is essentially at atmospheric pressure or a low vacuum. The first gas is either hydrogen or helium. Atmospheric pressure represents approximately 10... 5 Pa, but the pressure in the first region 31 sometimes fluctuates due to temperature, hull 2 ​​rolling, etc. Therefore, in this specification and claims, "substantially atmospheric pressure" can include about 10 Pa. 5 Pa, and above approximately 10 Pa within the range of pressure variations. 5 The pressure is Pa. Additionally, a low vacuum state refers to a pressure lower than atmospheric pressure and 10 Pa. 5 Pa to 10 2 The gas pressure is between Pa. When the first gas is hydrogen, the gas phase portion of the inner tank 4 can also be connected to the first region 31, so that the vaporized gas generated in the inner tank 4 flows into the first region 31. It should be noted that, as described above, the liquefied hydrogen tank 3 of this embodiment is not a vacuum insulation method, but an insulation layer can be provided in the first region 31 and the first region 31 can be made a vacuum, thereby providing a vacuum insulation layer between the inner tank 4 and the outer tank 5.

[0033] The hull 2 ​​has a plurality of upward-opening cargo holds 21. The plurality of cargo holds 21 are arranged along the length of the ship and are separated from each other by walls 22. Furthermore, the lower parts of the inner tank 4 and the outer tank 5 are housed inside the cargo holds 21. The upper part of the outer tank 5 is covered by a tank cover 6. The outer tank 5 is surrounded by the walls 22 and the tank cover 6, which are components of the hull 2 ​​and form the cargo holds 21. The area between the outer tank 5, the tank cover 6, and the walls 22 of the cargo holds 21 is referred to as the "second region 32". A second insulation layer is formed in the second region 32. The second insulation layer consists of insulation material disposed around the outer wall of the outer tank 5 and a second gas filled in the second region 32.

[0034] The second region 32, filled with the second gas, is substantially at atmospheric pressure. While not specifically limited, the pressure in the second region 32 can be higher than that in the first region 31. The second gas comprises at least one of an inert gas such as nitrogen and dry air. For example, dry air can be filled in the second region 32, while the inert gas is held in the second insulation layer.

[0035] Inside each cargo hold 21, a pair of skirts 25, separated from each other along the length of the ship, are provided. The skirts 25 support the outer tank 5. In addition, a pair of support members 35 supporting the inner tank body 41 are provided between the inner tank 4 and the outer tank 5. In this embodiment, the skirts 25 are arranged along the extension line of the support members 35, but the arrangement of the support members 35 and the skirts 25 is not limited to this embodiment.

[0036] [Tank type of liquefied hydrogen tank 3]

[0037] Here, the tank type of liquefied hydrogen tank 3 will be described in detail.

[0038] The outer tank 5 is an independent tank separate from the hull 2, and the liquefied hydrogen tank 3 is also an independent tank. An independent tank refers to a self-supporting tank that does not form part of the hull structure and is not indispensable for the strength of the hull.

[0039] At least one of the inner tank 4 and the outer tank 5 is a leak-proof tank. The leak-proof tank has a wall thickness such that an initial defect will not propagate to more than half the wall thickness during the tank's lifespan. Because the assumed propagation of the initial defect is sufficiently small relative to the wall thickness, leakage of the liquid or gas contained within the leak-proof tank is not contingent upon. From the viewpoint that leakage of the contained liquid or gas is not contingent upon, such a leak-proof tank is equivalent to a Type C tank as defined by the IGC code.

[0040] In this embodiment, both the inner tank 4 and the outer tank 5 are leak-proof tanks. In the liquefied hydrogen tank 3 of this embodiment, liquefied hydrogen is contained in the inner tank 4, and hydrogen gas is filled in the first region 31 of the inner tank 4 and the outer tank 5. Therefore, it is difficult to distinguish whether the hydrogen in the first region 31 comes from a leak in the inner tank 4 or is gas pre-filled in the first region 31. Thus, since it is difficult to detect a leak of liquefied hydrogen from the inner tank 4, a structure that prevents liquid hydrogen leakage from the inner tank 4 is particularly required. Therefore, it is desirable for at least the inner tank 4 to be a leak-proof tank. When the inner tank 4 is a leak-proof tank and the outer tank 5 is not a leak-proof tank, the required level of fracture strength for the outer tank 5 decreases, allowing for a thinner outer tank 5 plate, thereby reducing material costs. In addition, in this embodiment, in order to prevent flammable hydrogen gas in the first region 31 from leaking from the outer tank 5, it is desirable for the outer tank 5 to be a leak-proof tank. In addition, if the outer tank 5 is a leak-proof tank and the first region 31 is filled with a first gas other than hydrogen or the first region 31 is a vacuum, the inner tank 4 may not be a leak-proof tank.

[0041] [Design method for leak-proof tank of liquefied hydrogen tank 3]

[0042] Here, the design method of the leak-proof tanks in the inner tank 4 and outer tank 5 that constitute the liquefied hydrogen tank 3 is described in detail.

[0043] Figure 3This is a schematic diagram of the design apparatus 8 for a leak-proof tank. The design method for the leak-proof tank is implemented using the design apparatus 8. The design apparatus 8 consists of at least one computer 80. Each computer 80 includes a processor 81 and a memory 82 storing programs, information, etc., executed by the processor 81. The memory 82 is connected to the processor 81 in a manner capable of reading and writing information. Additionally, the processor 81 may be connected to input devices, output devices, auxiliary storage devices, and communication interfaces, etc. The functions of the design apparatus 8 disclosed in this specification can be performed as follows: using a general-purpose processor, special-purpose processor, integrated circuit, ASIC (Application Specific Integrated Circuits), existing circuit, and / or a circuit or processing circuit comprising a combination thereof configured or programmed to perform the disclosed functions. The processor contains transistors or other circuits and is therefore considered a processing circuit or circuit. In this disclosure, a circuit, component, or unit is hardware that performs the listed functions. The hardware may be the hardware disclosed herein, or it may be other known hardware programmed or configured to perform the listed functions. In the case of a processor where hardware is considered as a type of circuit, the circuit, unit, or component is a combination of hardware and software, with the software used to construct the hardware and / or processor.

[0044] Figure 4 This is a functional block diagram of the design device 8. The design device 8 includes a stress analysis unit 84, a fatigue crack propagation analysis unit 85 for determining crack propagation amount, a stress propagation coefficient analysis unit 86 for determining stress propagation coefficient, a determination unit 87, and a wall thickness determination unit 88. The plurality of functional units can be configured into a single computer 80, or the plurality of functional units can be configured to be distributed among multiple computers 80.

[0045] When implementing the design method for the leak-proof tank, the design wall thickness is set by the design device 8. The design wall thickness is arbitrary, but it is set within the range of values ​​that can be implemented for the wall plate of the leak-proof tank. For example, if the wall plate of the leak-proof tank is steel plate, the design wall thickness is set to a range of 60 mm or less; if the wall plate of the leak-proof tank is non-ferrous steel plate, the design wall thickness can be set to a range of 80 mm or less.

[0046] The design method for leak-proof tanks includes: (1) stress analysis step, (2) stress expansion coefficient analysis step, (3) crack propagation analysis step, (4) judgment step, and (5) wall thickness determination step. Among them, the wall thickness determination step can also be performed by the designer instead of the wall thickness determination unit 88.

[0047] (1) Stress analysis steps

[0048] Ship 1 navigates in ocean waves, resulting in varying pressures on the surface of hull 2 ​​caused by the waves. Hull 2 ​​rolls due to these varying pressures, and due to the acceleration of this rolling, varying loads caused by the inertial force of the liquid hydrogen carried as cargo act on the leak-proof tank. These varying loads generate varying stresses, i.e., dynamic stresses, within the leak-proof tank. The stress analysis unit 84 calculates the stresses generated in the leak-proof tank, particularly at the welded sections, due to the rolling of hull 2.

[0049] The stress analysis method of the stress analysis unit 84 is not particularly limited. Besides numerical analysis methods such as the finite element method, simulation can also be used. For example, the stress analysis unit 84 can obtain the swaying of the hull 2 ​​caused by waves during navigation, and the variable loads caused by waves on the hull 2. This variable load is then applied to a numerical analysis model of the entire ship 1, including the hull structure, the leak-proof tank structure, and the tank support structure, to calculate the generated stress (stress distribution in the leak-proof tank) estimated through numerical analysis. A predetermined wall thickness is incorporated into the leak-proof tank structure as a parameter. The variable load and the numerical analysis model can be provided to the stress analysis unit 84 in advance. The variable load can be calculated through simulation based on the conditions of the ship 1's route, or experimentally.

[0050] (2) Steps for analyzing the stress amplification factor

[0051] The stress expansion coefficient analysis unit 86 calculates the stress expansion coefficient of the crack (stress expansion coefficient distribution of the leak-proof tank). Various methods for analyzing stress expansion coefficients are well-known. The stress expansion coefficient analysis method of the stress expansion coefficient analysis unit 86 is not particularly limited; numerical analysis methods such as the finite element method can be cited as examples. The stress expansion coefficient analysis unit 86 uses, for example, a numerical analysis model including the stress generation, leak-proof tank structure including the weld shape, the size of the initial defect in the leak-proof tank, and the crack shape, obtained by the stress analysis unit 84, to calculate the stress expansion coefficient of the crack through elastic stress analysis based on the finite element method. The stress expansion coefficient analysis unit 86 can also change the analysis method depending on the analysis location of the leak-proof tank.

[0052] (3) Crack propagation analysis steps

[0053] The fatigue crack propagation analysis unit 85 determines the crack propagation amount of the initial defect in the leak-proof tank through fatigue crack propagation analysis. The method used by the fatigue crack propagation analysis unit 85 for fatigue crack propagation analysis is not particularly limited; in addition to numerical analysis methods such as the finite element method, simulation can also be used. For example, the fatigue crack propagation analysis unit 85 obtains the tank life of the leak-proof tank, the fracture toughness of the leak-proof tank material, the stress expansion coefficient of the analysis area, and the stress generated at the analysis area, and applies these to the fatigue crack propagation analysis model for numerical analysis, thereby determining the crack propagation amount of the initial defect during the tank life. Information related to the tank structure, such as tank life, the size of the initial defect, the temperature of the leak-proof tank, and the fracture toughness of the leak-proof tank material, is provided in advance to the fatigue crack propagation analysis unit 85. The size of the initial defect can be any value comparable to the size of an actual possible initial defect. The tank life can be any value comparable to the life of the ship 1. Based on the tank life, the number of stress repetitions during the tank life can be estimated. The temperature of the leak-proof tank is the temperature of the leak-proof tank when liquefied hydrogen is contained in the inner tank 4. The fracture toughness can be determined using the fracture toughness of the material at the temperature of the leak-proof tank when liquefied hydrogen is contained in the inner tank 4. The stress expansion factor of the analytical section can be the value calculated by the stress expansion factor analysis unit 86. The stress generated in the analytical section can be the stress calculated by the stress analysis unit 84.

[0054] (4) Judgment Steps

[0055] The determination unit 87 determines the design wall thickness as "appropriate" if it meets the requirement that "the initial defect does not propagate to a wall thickness exceeding half the wall thickness during the tank's lifespan," and otherwise determines it as "inappropriate." Specifically, the determination unit 87 obtains the crack propagation amount of the initial defect during the tank's lifespan, calculated by the fatigue crack propagation analysis unit 85. If the crack propagation amount does not exceed half the design wall thickness (i.e., if the crack propagation amount is less than half the design wall thickness), the design wall thickness is determined to be appropriate; if the crack propagation amount exceeds half the design wall thickness, the design wall thickness is determined to be inappropriate.

[0056] (5) Steps for determining wall thickness

[0057] The wall thickness determination unit 88 determines the wall thickness of the leak-proof tank, such that the wall thickness is above or equal to the appropriate design wall thickness determined by the judgment unit 87. A leak-proof tank with such determined wall thickness is designed.

[0058] In the leak-proof tank design method described above, the appropriateness of the design wall thickness is determined based on the crack propagation amount. However, in addition to this, the appropriateness of the design wall thickness can also be determined based on whether unstable fracture occurs. In this case, the stress propagation factor analysis unit 86 calculates the stress propagation factor of the crack (i.e., the crack during the tank's life) whose initial defect only propagates beyond the crack propagation amount calculated by the fatigue crack propagation analysis unit 85, as a criterion for determining unstable fracture. If this criterion is above the fracture toughness value, unstable fracture is expected to occur during the tank's life. Therefore, the determination unit 87 obtains the determination criterion and the fracture toughness value of the leak-proof tank material. If the determination criterion is above the fracture toughness value, the design wall thickness is determined to be inappropriate; if the determination criterion is below the fracture toughness value, the design wall thickness is determined to be appropriate.

[0059] [Summarize]

[0060] The liquefied hydrogen tank 3 of the present disclosure is mounted on a ship 1, characterized in that it has an inner tank 4 for containing liquefied hydrogen and an outer tank 5 surrounding the inner tank 4, at least one of the inner tank 4 and the outer tank 5 is a leak-proof tank, the leak-proof tank having a wall thickness that prevents initial defects from propagating to more than half the thickness of the wall during the life of the tank.

[0061] In the aforementioned liquefied hydrogen tank 3, both the inner tank 4 and the outer tank 5 can be leak-proof tanks.

[0062] In the aforementioned liquefied hydrogen tank 3, hydrogen gas is filled between the inner tank 4 and the outer tank 5, and the inner tank 4 can be a leak-proof tank.

[0063] In the aforementioned liquefied hydrogen tank 3, hydrogen gas is filled between the inner tank 4 and the outer tank 5, and the outer tank 5 can be a leak-proof tank.

[0064] According to the liquefied hydrogen tank 3 constructed as described above, even if an initial defect exists in the leak-proof tank of the liquefied hydrogen tank 3, the expansion of the initial defect during the tank's lifespan is sufficiently small relative to the wall thickness, therefore leakage of the liquid or gas contained in the leak-proof tank is not anticipated. From the viewpoint that leakage of the contained liquid or gas is not anticipated, such a leak-proof tank is equivalent to a Type C tank as defined by the IGC code. Therefore, the leak-proof tank and the liquefied hydrogen tank 3 equipped with such a leak-proof tank can omit the secondary protective wall.

[0065] In the aforementioned liquefied hydrogen tank 3, the volume of the inner tank 4 can exceed 20,000 m³. 3 And it is 50,000m 3 the following.

[0066] In this way, even if the liquefied hydrogen tank 3 is a relatively large tank as described above, it can still have the required leak-proof function and become a wall thickness that can be practically constructed.

[0067] Furthermore, the design method of the liquefied hydrogen tank 3 in this embodiment is characterized by the following:

[0068] The first processor (fatigue crack propagation analysis unit 85) obtains the tank life, the size of the initial defect of the leak-proof tank, the temperature of the leak-proof tank, the stress propagation coefficient of the leak-proof tank, and the stress generated in the leak-proof tank. Through fatigue crack propagation analysis, the amount of crack propagation of the initial defect caused by the stress corresponding to the tank life is calculated.

[0069] The second processor (determination unit 87) obtains the calculated crack propagation amount and the design wall thickness of the leak-proof tank. If the crack propagation amount does not exceed half of the design wall thickness, the design wall thickness is determined to be appropriate; if the crack propagation amount exceeds half of the design wall thickness, the design wall thickness is determined to be inappropriate.

[0070] Determine the wall thickness of the leak-proof tank so that it is above the design wall thickness that is deemed appropriate.

[0071] It should be noted that the first processor and the second processor can be physically the same processor or they can be independent processors.

[0072] Based on the design method of the liquefied hydrogen tank 3 described above, it is possible to design a tank that does not leak the contained gas or liquid within the range of realistic wall thickness.

[0073] The design method for the aforementioned liquefied hydrogen tank 3 may further include:

[0074] The stress propagation factor of the crack that propagates from the initial defect during the life of the tank is calculated by the third processor (stress propagation factor analysis unit 86) and used as a criterion.

[0075] The fourth processor (wall thickness determination unit 88) obtains the fracture toughness value of the leak-proof tank material. If the determination index is above the fracture toughness value, it is expected that an unstable fracture will occur during the tank's lifespan. Therefore, the design wall thickness is determined to be inappropriate.

[0076] It should be noted that the stress expansion factor can be calculated based on the final crack shape after the tank's lifespan, or sequentially based on the crack shapes that expand during the tank's lifespan. Furthermore, the first to fourth processors can be physically identical processors or independent processors.

[0077] Based on the above design method, the appropriateness of the designed wall thickness can be further determined by whether instability and fracture occur, thus enabling the design of tanks that more reliably prevent leakage.

[0078] In the above embodiments, the inner tank 4 is generally classified as a large tank, but the inner tank 4 can also be 20,000 m³. 3 The following are classified as small tanks, and the inner tank 4 can also be a leak-proof tank. That is, the structure and design method of the liquefied hydrogen tank 3 disclosed herein are not limited by the size of the tank and can be applied to small tanks or tanks exceeding 50,000 m³. 3 Large tanks.

[0079] In the above embodiments, the liquefied hydrogen tank 3 is a cargo tank, but the structure and design method of the liquefied hydrogen tank 3 disclosed herein can also be applied to fuel tanks mounted on the ship 1. In this case, the ship 1 is not limited to a liquefied hydrogen transport ship.

[0080] The foregoing discussion in this disclosure is for illustrative and explanatory purposes only and is not intended to limit this disclosure to the manner disclosed in this specification. For example, in the detailed description above, various features of this disclosure are summarized into one implementation for the purpose of rationalizing this disclosure. However, the plurality of features included in this disclosure can be combined with alternative implementations, configurations, or methods beyond those discussed above.

Claims

1. A design method for a liquefied hydrogen tank, the liquefied hydrogen tank comprising an inner tank for storing liquefied hydrogen and an outer tank surrounding the inner tank, the liquefied hydrogen tank being mounted on a ship, wherein, At least one of the inner tank and the outer tank shall be used as a leak-proof tank. The first processor obtains the tank life, the size of the initial defect, the temperature, the stress propagation factor, and the stress generated in the leak-proof tank. Then, through fatigue crack propagation analysis, the crack propagation amount of the initial defect caused by the stress, corresponding to the tank life, is calculated for a number of repetitions. The second processor obtains the calculated crack propagation amount and the design wall thickness of the leak-proof tank. If the crack propagation amount does not exceed half of the design wall thickness, the design wall thickness is determined to be appropriate; if the crack propagation amount exceeds half of the design wall thickness, the design wall thickness is determined to be inappropriate. The wall thickness of the leak-proof tank is determined such that it is above the design wall thickness that is deemed appropriate.

2. The design method for a liquefied hydrogen tank according to claim 1, wherein, The stress propagation factor of the crack that propagates from the initial defect during the life of the tank is determined by a third processor and used as a criterion. The fracture toughness value of the material of the leak-proof tank is obtained by the fourth processor. If the determination index is above the fracture toughness value, it is expected that an unstable fracture will occur during the life of the tank. Therefore, the design wall thickness is determined to be inappropriate.

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