Pressure vessel liner, pressure vessel, and method

Abstract

A segmented lining for a pressure vessel, the pressure vessel including the segmented lining and an outer layer disposed around the segmented lining, the segmented lining including: at least two lining segments, wherein each lining segment includes an internal network structure; and at least two cap segments, wherein the at least two cap segments and the at least two lining segments are adapted to be assembled into the segmented lining.

Description

Technical Field

[0001] The present invention relates to a liner for a pressure vessel, a pressure vessel including the liner, and a method of manufacturing a pressure vessel liner and a conformal pressure vessel. Background Art

[0002] As a renewable energy source, hydrogen has become a promising candidate energy source in recent years. Compared with battery technology, due to its inherent advantages, its application in the transportation industry has received particular attention. For example, compared with battery technology, the hydrogen refueling time of a hydrogen storage system is faster and the weight is lighter.

[0003] Hydrogen can be stored in three states: solid-state storage by means of adsorption or absorption materials; cryogenic liquid storage; and high-pressure gaseous storage. In the field of automotive applications, among other requirements, high volumetric energy density and gravimetric energy density are also required. In solid-state storage devices and liquid storage devices, temperature management and control systems often need to be provided. Such systems increase the complexity and weight of the storage system and reduce its effective energy density. Therefore, compressed hydrogen systems have become the first choice in this industry.

[0004] The storage pressure of compressed hydrogen systems is extremely high. For example, the gauge pressure required by the ISO14687-2 and ISO12619-1:2014 standards is 700 bar. The pressures required by other standards are 300 bar, 350 bar, and 500 bar. Undoubtedly, high pressure can increase the volumetric energy density and gravimetric energy density of compressed gases. However, at high pressures, pressure vessels containing compressed gases must be additionally reinforced to ensure their mechanical strength. Such reinforcement often results in an increase in the thickness of the container, which in turn leads to an increase in weight and overall volume, and may thus cause a decrease in the overall energy density of the pressure vessel.

[0005] In addition to the extremely high flammability of hydrogen, high pressure generally also poses significant safety risks. In the transportation field, this risk is further complicated by the proximity of the pressure vessel to passengers. In addition, conventional pressure vessels are based on cylindrical or spherical designs, which are not only difficult to operate but also prone to rolling. Therefore, pressure vessels of such shapes often need to be fixed in place by a support structure.

[0006] Figure 1A Shown is a conventional pressure vessel 100 in the prior art. The pressure vessel 100 includes a liner 102 (shown in dashed lines) surrounded by an outer covering 104. The pressure vessel defines a volume 106 for containing a gas. Figure 1BCross-sectional view along AA', showing the double-wall structure of a conventional pressure vessel 100. The inner liner 102 is a non-structural member that serves as a barrier for containing gas. The outer covering 104 is a structural member that withstands the forces of the pressurized gas. The two ends of the conventional pressure vessel 100 are generally covered with hemispherical end caps, which are not shown in the figure. In the development of composite column tanks, Figure 1A and Figure 1B the configurations shown are referred to as "Type III" or "Type IV". The inner liner 102 of a Type III column tank is a metal-like inner liner, such as aluminum or aluminum alloy, and the outer covering 104 is generally a diagonally wrapped fiber-reinforced composite material. The inner liner 102 of a Type IV column tank is a thermoplastic inner liner, and the outer covering 104 is a fiber-reinforced composite material. Due to the anisotropic properties of the fibers, the filament winding process is complex and highly dependent on the wrapping angle and winding pattern. This manufacturing method necessarily limits Type III and Type IV composite pressure vessels to simple shapes such as cylindrical or spherical.

[0007] US-A-2016061381 discloses a pressure vessel having an internal support structure for reducing the pressure applied to the outer covering of the pressure vessel. The internal connectors of the support structure are mainly connected to a central support member. US-A-2016061381 discloses a compartmentalized or honeycomb design. In this design, the openings connecting each opening to the central support member can limit the overcurrent capacity, thereby reducing the explosion risk caused by external damage to the container.

[0008] US2006 / 0261073 discloses a pressure vessel inner liner that includes a tubular main body and end plates that enclose opposite ends of the main body. Reinforcing walls are provided in the inner liner to improve the resistance to longitudinal forces. Summary of the Invention

[0009] According to a first aspect of the present invention, there is provided a segmented inner liner for a pressure vessel, the pressure vessel including the segmented inner liner and an outer layer disposed around the segmented inner liner, the segmented inner liner including: at least two inner liner segments, wherein each inner liner segment includes an internal network structure; and at least two cap segments, wherein the at least two cap segments and the at least two inner liner segments are adapted to be assembled into the segmented inner liner.

[0010] The at least two inner liner segments may include interlocking portions provided at opposite open ends, and these interlocking portions may be the same or complementary in shape. The at least two cap segments may include interlocking portions that are the same or complementary in shape to the interlocking portions of the at least two inner liner segments. Thus, the cap segments and the inner liner segments can be used for assembly through the interlocking portions. The interlocking portions can be fixed in place by adhesive bonding and / or welding.

[0011] Each inner lining section and the cap section can each be a single molded part.

[0012] The cross-sectional shape of the segmented inner lining defined by the outer surface of the inner lining section is one of a square or a rounded square. Additionally, it can also be other shapes.

[0013] The internal network structure of the segmented inner lining can include: a first set of support members including a plurality of first support members, wherein each of the first support members extends across the internal corners of the inner lining section. Optionally, it further includes: a second set of support members including a plurality of second support members, wherein each of the second support members extends between two of the first support members that extend across adjacent corners of the inner lining section. Optionally, it further includes: a third set of support members including a plurality of third support members, wherein each of the third support members extends between two adjacent second support members to form a square or rounded square cross-section. Optionally, it further includes: a fourth set of support members including a plurality of fourth support members, wherein each of the fourth support members extends radially between the surface defined by the inner surface of the inner lining section and the vertices of the square or rounded square formed by the third set of support members. Optionally, each of the support members in the fourth set bisects one or more of the second support members. Optionally, it further includes: a fifth set of support members including a plurality of fifth support members, wherein each of the fifth support members extends radially between the internal corners of the inner lining section and one or more of the first support members. Optionally, each of the support members in the fifth set bisects one or more of the first support members.

[0014] The internal network structure of the segmented inner lining can be integrally formed within the wall thickness of the inner lining section, and optionally, wherein the wall thickness of the inner lining section is the largest along its corner edges and the smallest at the center of each of its faces. The variation in the wall thickness of the inner lining section can define a volume whose cross-sectional shape is substantially similar to the outer surface of the inner lining section wall. The internal network structure can include one or more openings located on each corner edge of the inner lining section. Optionally, the one or more openings are partial circumferential holes.

[0015] According to a first aspect of the present invention, there is provided a pressure vessel, comprising: the above-mentioned segmented inner lining; and an outer layer provided around the segmented inner lining.

[0016] The outer layer can include a woven carbon fiber cloth impregnated with resin or a carbon fiber wound covering.

[0017] According to a first aspect of the present invention, there is provided a method of manufacturing the above-mentioned segmented inner lining, comprising: injection molding or casting the at least two inner lining sections and the at least two cap sections; and assembling the sections together.

[0018] Assembling the respective segments together may include adhesive bonding or welding.

[0019] The segmented liner can be manufactured, for example, by an additive manufacturing method. The segmented liner can be electronically represented in the form of a design file. A design file or a computer-aided design (CAD) file is a configuration file that encodes one or more of the surface or volume constructs of the product shape. That is, the design file represents the geometric arrangement or shape of the product.

[0020] Once the design file is obtained, the design file can be converted into a set of computer-executable instructions that, when executed by a processor, cause the processor to control an additive manufacturing device to manufacture a product according to the geometric arrangement specified in the design file. The conversion operation can convert the design file into slices or layers to be sequentially formed by the additive manufacturing device. The instructions (also referred to as geometric codes or "G-codes") can be calibrated for a specific additive manufacturing device and can precisely specify the material positions and material amounts to be formed at each stage of the manufacturing process.

[0021] The additive manufacturing device can be controlled according to the computer-executable instructions to instruct the additive manufacturing device to print out one or more parts of the liner. These parts can be printed either in an assembled form or in an unassembled form. For example, the respective segments of the liner can be printed separately (as a set of unassembled components) and then assembled together. Alternatively, different parts can also be printed in an assembled form. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Some embodiments of the present invention will be described below in conjunction with the drawings by way of example only. In the drawings:

[0023] FIG. 1 shows an exemplary pressure vessel known in the prior art;

[0024] Figure 2A is a perspective schematic view of an exemplary liner;

[0025] Figure 2B is a schematic view of an exemplary internal network structure;

[0026] Figure 3A is a perspective schematic view of an exemplary pressure vessel;

[0027] Figure 3B is Figure 3A a plan schematic view of the pressure vessel;

[0028] Figure 4 shows an exemplary simulation result of a pressure vessel;

[0029] Figure 5 shows an exemplary internal network structure;

[0030] Figures 6A to 6D Shown is an exemplary central portion of an internal network structure;

[0031] Figure 7 Shown is an exemplary conforming pressure vessel;

[0032] Figure 8 Shown is an exemplary internal network structure;

[0033] Figure 9 Shown is an exemplary internal network structure;

[0034] Figure 10 Shown is an exemplary internal network structure;

[0035] Figure 11 Shown is an exemplary internal network structure;

[0036] Figure 12 Shown is an exemplary internal network structure;

[0037] Figure 13A and Figure 13B Shown is a segmented lining;

[0038] Figure 14A and Figure 14B Shown are the simulation results of a pressure vessel;

[0039] Figures 15A to 15D Shown is an exemplary internal network structure;

[0040] Figure 16 Shown is an exemplary internal network structure;

[0041] Figures 17A to 17C Shown is an interlocking mating device between the lining segments. DETAILED DESCRIPTION

[0042] The present invention provides a lining and a pressure vessel that solve one or more of the above problems of the prior art. The present invention also provides a segmented lining and a segmented pressure vessel.

[0043] Figure 2A Shown is an exemplary lining 200 of a cylindrical pressure vessel of the present invention. The lining includes an outer surface 202 that surrounds an internal network 204 composed of interconnected support members, hereinafter referred to as the "internal network" 204. For clarity, the ends of the outer surface 202 of the cylindrical pressure vessel are not shown in the illustrated embodiment.

[0044] The inner lining 200 of the present invention has multiple functions. The function of the outer surface 202 of the inner lining 200 is to substantially prevent the gas contained in the pressure vessel from permeating through, while the function of the internal network structure 204 of the inner lining 200 is to provide support to the pressure vessel walls 202, 302. Thus, compared with conventional designs such as the inner lining shown in FIG. 1, the inner lining 200 of the present invention can reduce the stress on the pressure vessel walls 202, 302 while containing pressurized gas. This result has been verified by a feasibility model, which will be described in detail below.

[0045] The internal network 204 and the outer surface 202 of the inner lining 200 define a volume 206 for containing fluid. Preferably, the volume 206 is internally interconnected. Those skilled in the art should understand that in some embodiments, the fluid includes pressurized gases such as hydrogen, nitrogen, oxygen, biogas, natural gas, ammonia, or any other gas. Those skilled in the art should understand that in other embodiments, the fluid includes pressurized liquids such as liquid hydrogen, liquid nitrogen, liquid oxygen, liquid biogas, liquid ammonia, liquid natural gas, or any other pressurized liquid. For the latter case, it goes without saying that a gas stored in a liquid state can be formed at any pressure and temperature defined by the corresponding pressure / temperature phase diagram.

[0046] The outer surface 202 of the inner lining 200 includes a material for containing the contained fluid with only a negligible amount of leakage. That is to say, this material hardly allows the contained fluid to permeate through. For example, if the fluid is pressurized hydrogen, the inner lining does not allow hydrogen to permeate through. Therefore, the function of the outer surface is similar to, but not exactly the same as, the inner lining 102 of a conventional pressure vessel.

[0047] Preferably, the internal network 204 and the outer surface 202 are integrally formed. That is to say, the internal network 204 and the outer surface 202 are formed as a single component. In other embodiments, the internal network 204 and the outer surface 202 can be formed separately and then combined together through a connection step.

[0048] Figure 2B For Figure 2A A partially enlarged view of the internal network shown as being composed of interconnected support members 204. As shown in FIG. 2, the internal network 204 is a tetrahedral or diamond cubic lattice structure. Referring to Figure 2A and Figure 2B , this internal network includes, for example, the following features:

[0049] · A first group of members composed of one or more members 208 that are bonded to or otherwise permanently mechanically contacted with the outer surface 202 at a first set of contact points;

[0050] · A second group of members composed of one or more members 208 that are bonded to or otherwise permanently mechanically contacted with the outer surface 202 at a second set of contact points;

[0051] · wherein, a first and a second set of components each composed of one or more components 208 are bonded or otherwise permanently mechanically contacted with a third set of components composed of one or more components 208, and there is a continuous path between a first set of contact points on the outer surface 202 and a second set of contact points on the outer surface 202; and

[0052] · wherein, the first, second, and third sets of components each composed of one or more components 208 form a periodic or quasi-periodic lattice structure.

[0053] Figure 2B The illustrated internal network structure 204 is a three-dimensional periodic structure based on a tetrahedral (diamond cubic) structure. The form of this periodic structure is not limited to this. According to the inventor's conception, the specific lattice structure of the internal network 204 can vary according to the operating requirements. The internal network structure 204 can be extended to any form of Bravais lattice, such as any one of triclinic lattice, monoclinic lattice, orthorhombic lattice, tetragonal lattice, cubic lattice, trigonal lattice, and hexagonal lattice. Among them, in applicable cases, the base-centered, body-centered, and face-centered forms of these structures are also within the scope of conception. Thus, the first type of internal network structure 204 mimics the known physical atomic structures in nature.

[0054] The support member 208 can be a support rod, a support sheet, a support plate, a support panel, etc., and can include one or more openings. These openings can be through holes that define openings within the support member 208, or can be openings on the edge of the support member. In the latter case, the openings change the proportion of the outer part of the support member 208. The length and width of the support member 208 depend on the size and geometry of the internal network structure 204, the geometry of the outer surface 202 of the inner lining 200, the internal pressure, and the unit cell size. In the illustrated embodiment, the size of the support member 208 is 1 mm and 40 mm.

[0055] Figure 3A Shown is an exemplary pressure vessel 300. The pressure vessel 300 includes an inner lining 200 housed within an outer covering 302. The exemplary pressure vessel 300 is used for operation under high pressure, such as above 300 bar or above 350 bar, for example above 500 bar or above 700 bar. The exemplary dimensions of the pressure vessel 300 are as follows: radius 50 - 250 mm; length 250 - 2000 mm.

[0056] The internal network 204 composed of interconnected support members provides structural reinforcement for the pressure vessel 300, thereby while achieving a way to increase the gauge pressure of the pressure vessel, it is also possible to improve the weight energy density and / or volume energy density of the pressure vessel, especially the hydrogen storage container in automotive applications.

[0057] During operation, or when the pressure vessel 300 is at least partially filled with pressurized gas, the pressurized gas exerts a hydrostatic pressure on the walls 202, 302 of the pressure vessel. In general, this hydrostatic pressure is greater than the external pressure (the pressure outside the pressure vessel), and thus an outward pushing force is generated on the pressure vessel. According to Newton's third law, in the equilibrium state, in order to counteract the internal hydrostatic pressure, the pressure vessel must exert a force equal in magnitude and opposite in direction to this hydrostatic pressure. This restoring force is generated by elastic strain, and this elastic strain in turn causes internal stress in the walls 202, 302 of the pressure vessel. When the gauge pressure is greater than zero, the elastic strain is a tensile strain. As the internal pressure increases, the tensile stress in the walls 202, 302 of the pressure vessel increases until the material forming the walls 202, 302 plastically fails or fails in some other way. In the technical field of pressure vessels, especially those for containing highly flammable gases such as hydrogen, plastic formation or plastic failure is not allowed. For this reason, the pressure vessel operates only within the elastic range, and for the following context of this application, this means that the cladding 302 must operate within the elastic range.

[0058] As described above, the internal network 204 includes: a first and a second set of members each consisting of one or more members 208 bonded or otherwise permanently mechanically contacted with the outer surface 202 at first and second sets of contact points; and a continuous path defined between the first and second sets of contact points by mechanical connection with a third set of members 208. In this case, the hydrostatic pressure exerted by the pressurized gas is also applied to the internal network 104. For regions of the internal network 204 that are far from the outer surface 202 of the liner 200 (i.e., regions where edge effects can be ignored), the internal pressure exerts a hydrostatic compressive stress on the members 208 forming the internal network 204. However, at the same time, the internal pressure exerts a force on the walls 202, 302 of the pressure vessel to cause it to expand, and the internal structure 204 must also expand accordingly by elastic strain. Depending on the magnitude of the internal pressure and the structure of the internal network 204, the sum of the stress tensor components can be tensile, thereby increasing the effective stiffness of the walls 202, 302 of the pressure vessel. Correspondingly, since part of the elastic strain is "absorbed" by the internal network structure 204, the elastic strain of the walls 202, 302 of the pressure vessel is reduced. Further, since it can be assumed that the stiffness of the walls 202, 302 of the pressure vessel remains constant (within the elastic range), at a given internal pressure, the stress in the walls 202, 302 of the pressure vessel is reduced. Thus, the internal pressure of the pressure vessel 300 can be increased without increasing the thickness of the cladding 302.

[0059] It should be emphasized that, in order to cause elastic strain and stress in the member 208 of the internal network structure 204, the member 208 is subject to certain constraints as compared to the cladding 302 of the pressure vessel. That is to say, there is a continuous path 304 between at least one point among the first set of contact points on the outer surface 202 of the inner liner 200 and at least one point among the second set of contact points. Such a path 304 is shown in Figure 3B (schematic diagram, not drawn to scale). In this way, the member 208 can cause the stress in the cladding 302 of the pressure vessel 300 to decrease in the required manner by dissipating the strain (and thus the stress), rather than moving freely with the cladding 302.

[0060] Figure 3A The shown pressure vessel 300 is used for a feasibility study to demonstrate the above stress reduction principle.

[0061] This feasibility study is a simulation carried out in the ANSYS software package, in which the following assumptions are made:

[0062] · The stiffness remains constant;

[0063] · Linear elastic material model;

[0064] · Transient or inertial effects are not considered;

[0065] · The contact points between the internal network structure 204, the outer surface 202, and the cladding 302 transfer the load force; and

[0066] · There is an internal pressure inside the pressure vessel (the external pressure is set to zero, i.e., the pressure is gauge pressure).

[0067] In the feasibility study, the following parameters are set as constants:

[0068] · The radius of the cylindrical pressure vessel is 0.1 m;

[0069] · The length of the cylindrical pressure vessel is 5 "lattice pattern" units;

[0070] · The Young's modulus, Poisson's ratio, and density of the internal network structure 204 and the outer surface 202 are 3.5 GPa, 0.35, and 1150 kg / m -3 (consistent with thermoplastics);

[0071] · The Young's modulus, Poisson's ratio, and density of the cladding 302 are 90 GPa, 0.05, and 1900 kg / m -3 (consistent with carbon fiber with uniform and isotropic properties);

[0072] · The width of the member 208; and

[0073] · The internal network structure 204 adopts a periodic diamond cubic structure model, and each repeating unit of the diamond cubic structure constitutes a "lattice pattern" unit.

[0074] In the feasibility study, by varying the following parameters, pressure vessels 300 with different configurations are formed:

[0075] · The length of the component 208;

[0076] · The thickness of the carbon fiber cladding 302;

[0077] · The thickness of the outer surface 202 of the inner liner 200; and

[0078] · The internal pressure of the cylindrical pressure vessel 300.

[0079] The parameter values of each configuration are shown in Table 1.

[0080]

[0081] Figure 4 Shown are the stress / strain reduction percentage (y-axis) results for each configuration relative to X7. X7 is a conventional "Type IV" pressure vessel. The main results are summarized as follows.

[0082] · As can be seen from X1 to X3 and X4 to X6, increasing the internal network structure can reduce the hoop stress of the cladding 302 and the outer surface 202 of the inner liner 200, and reduce the radial deformation of these components 202, 302.

[0083] · As can be seen from the comparison between X1 and X2, increasing the length of the component 208 can reduce the stress / strain reduction.

[0084] · As can be seen from the comparison between X1 and X3, increasing the thickness of the cladding 302 can reduce the reduction of the hoop stress of the cladding 302 and the outer surface 202 of the inner liner 200, but will increase the reduction of the radial deformation.

[0085] · As can be seen from the comparison between X3 and X5, increasing the thickness of the outer surface 202 of the inner liner 200 can increase the reduction of the hoop stress of the cladding 302, but reduce the reduction of the hoop stress of the outer surface 202 of the inner liner 200. That is, increasing the thickness of the outer surface 202 can reduce the hoop stress of the cladding 302, but increase the hoop stress of the outer surface 202.

[0086] · As can be seen from the comparison between X3 and X5 (70 MPa), within the elastic range, increasing the pressure does not significantly affect the stress / strain reduction.

[0087] Table 2 and Table 3 show the contribution amounts of the mass and volume of the components in each pressure vessel configuration model.

[0088] Table 4 shows the calculation results of the maximum radial deformation and the average circumferential stress of the outer surface 202 of the inner liner 200 and the overwrap 302 under a gauge pressure of 35 MPa.

[0089]

[0090]

[0091]

[0092]

[0093] By comparing the results of X1 and X0 and the results of X3 and X7 in Tables 2 to 4, the influence of the internal network structure 204 on the weight energy density and the volume energy density can be estimated. For clarity, X0 and X7 represent conventional "Type IV" composite pressure vessels, and X1 and X3 have respectively equivalent physical properties. The difference is that X1 and X3 also include Figure 2B the shown diamond lattice structure as the support structure of the internal network 204.

[0094] Comparison result between X1 and X0

[0095] X1 is approximately 70 percentage points heavier than X0. The gas storage volume 206 of X1 is approximately 9 percentage points smaller than that of X0. The radial deformation, the circumferential stress of the outer surface 202, and the circumferential stress of the overwrap 302 of X1 are reduced by 2.4, 2.3, and 1.8 percentage points respectively.

[0096] Comparison result between X3 and X7

[0097] X3 is approximately 70 percentage points heavier than X7. The gas storage volume of X3 is only 91% of that of X7. Compared with X7, the radial deformation, the circumferential stress of the outer surface 202, and the circumferential stress of the overwrap 302 of X3 are reduced by approximately 3%, 8.5%, and 6.8% respectively.

[0098] Therefore, the results of the feasibility study confirm that the inner liner 200 reduces the stress and strain generated in the pressure vessel walls 202, 302. However, the results of this preliminary study indicate that Figure 2B the stress reduction amount of the exemplified internal network structure 204 does not exceed the loss amount of the mass and the total gas storage volume 206. However, it should be emphasized that the above experimental data are for feasibility studies and do not represent an optimized design structure. In any case, the comparison results of X3 and X7 show that there is a great possibility that the stress reduction amount exceeds the volume reduction amount (9% compared to 8.5%).

[0099] Figure 5Shown is a portion of the aperiodic internal network structure 500. The aperiodic internal network structure is inspired by fractal or "treelike" structures in nature in terms of bionics, but still includes a hierarchical or graded structure based on Figure 2A the internal network structure 204 shown. In some embodiments, the aperiodic internal network structure 500 replaces the periodic internal network structure 204 in the pressure vessel 300. When replacing the Figure 2A periodic internal structure 204 therein, the shape of the outer surface 202 of the liner 200 does not necessarily have to be (but can be) cylindrical or spherical. In embodiments where the shape of the outer surface 202 of the liner 200 is not cylindrical or spherical, other shapes can be adopted, such as an oblate spheroid, an ellipsoid, a rounded cube, or a rounded rectangular cube. Generally, the aperiodic internal network structure 500 includes the following features:

[0100] · A first set of members composed of one or more members 502 bonded or otherwise permanently mechanically contacted with the outer surface 202 at a first set of contact points;

[0101] · A second set of members composed of one or more members 502 bonded or otherwise permanently mechanically contacted with the outer surface 202 at a second set of contact points;

[0102] · Wherein, there is a continuous path between the first set of contact points on the outer surface 202 and the second set of contact points on the outer surface 202, and the continuous path includes one or more nodes 512; and

[0103] · Wherein, the number density of the local support members varies along the continuous path. The number density of the local support members is defined as the number of support members within a given local volume. The local volume is defined as a spherical volume with a radius between one and five times the length of the support member, where the length of the support member is the maximum dimension of the support member.

[0104] The internal network structure 500 includes a plurality of radially extending support members 502. In some embodiments, the number of the radially extending support members 502 increases with the distance from the center point 504 of the pressure vessel. This is the purpose of setting the nodes 512 in the internal network structure 500. In some embodiments, the center point 504 of the pressure vessel is the center 504 of the volume of the pressure vessel. In some embodiments, the center point 504 is the centroid of the pressure vessel. Depending on the overall geometry of the pressure vessel, the centroid and the center of volume may coincide with each other.

[0105] In Figure 5In the illustrated internal network structure 500, the number of radially extending support members 502 increases stepwise at each node 512 in the internal network structure 500. Each step is shown alongside the illustrated internal network structure 500. The number of support members 502 increases at each node 512 by a multiplication factor. For example, Figure 5 the multiplication factor in Figure 5 is equal to three. This description does not limit the magnitude of the multiplication factor. The spacing length between each node is equal to the length of the support member 502.

[0106] The support members “born” at each node 512 by the multiplication factor are spaced apart by a certain angle from each other. In some embodiments, the support members are equally angularly spaced. In one embodiment, when the multiplication factor is four, the angle between each support member can be 109.5 degrees.

[0107] As Figure 5 shown, the nodes 512 define discrete volumes 506, 508, 510. In each discrete volume 506, 508, 510, the number density of the members is substantially constant. In the illustrated embodiment, the discrete volumes 506, 508, 510 are circular / spherical. More generally, the discrete volumes 506, 508, 510 may not be circular. This is especially the case when the shape of the pressure vessel contains at least one circular axis of symmetry. More generally, the regions defined by the discrete volumes 506, 508, 510 depend on the overall shape of the pressure vessel, where the shape of the pressure vessel may not contain a circular axis of symmetry. In such cases, the shape of the pressure vessel causes a stress / strain distribution in the “virtually” periodic internal network structure 204. Thus, this non-periodic structure defines corresponding volumes 506, 508, 510 that “demarcate” regions of increased stress / strain. Thus, more generally, the shapes of these discrete volumes 506, 508, 510 are similar to those that can produce the “virtually” stress / strain distribution of the periodic internal network structure 204. Therefore, these volumes 506, 508, 510 define the hierarchical levels in the hierarchical structure of the internal network structure 500. In one embodiment, the number of discrete volumes 506, 508, 510 can be three, and the multiplication factors for each volume can be 1, 100, and 1000 respectively. However, the present invention places no limitation on the number of hierarchical levels or the multiplication factors.

[0108] In some embodiments, each volume 506, 508, 510 may include a periodic structure internal network structure 204 substantially as shown in FIG. 2. At the junctions (506, 508), (508, 510) between each volume, the internal network structure can be a quasi-periodic structure. In these embodiments, the support member 502 can have a different cross-section in each volume 506, 508, 510.

[0109] The motivation for constructing this internal network structure 500 is that the inventors realized that the stress and strain occurring in the outermost support members 208 of the periodic internal network structure 204 are greater than those occurring in the more inner members 208. This is at least partly due to the local stress concentration generated at the contact points of the support members 208, 502 with the outer surface 202 of the inner liner 200. Therefore, in Figure 5 the structure shown, the number of contact points on the outer layer 202 of the inner liner 200 is increased by using nodes 512 with a multiplication factor greater than one. By increasing the number of contact points on the outer surface 202 of the inner liner 200, the total distribution area of the load can be increased, thereby reducing the stress concentration. In addition, in Figure 5 the internal network structure 500 shown, by increasing the number of surrounding adjacent support members 502, the more local stress and strain at the high stress / strain contact points can be dissipated, thereby flattening the "de facto" stress concentration distribution of the non-periodic internal network structure 500 shown in Figure 5 .

[0110] As can be seen, increasing the number density of the support members 502 in the adjacent area of the outer surface 202 of the inner liner 200 is a way to reduce the stress concentration in such areas, and adopting a graded or layered structure is a way to achieve this. In a graded structure, the number density of the support members in the internal network structure can vary continuously. In a layered structure, the number density of the support members in the internal network structure can vary stepwise. Generally speaking, the stress in the high stress areas most likely to fail can be dissipated by varying the number density of the support members. The number density can vary in many different ways to produce a graded or layered structure.

[0111] As described above, an alternative way to increase the number density of the support members is to use nodes with a multiplication factor greater than one. In this way, by increasing the multiplication factor as the distance from the center point 504 increases, a gradual change in the number density of the support members can be produced, thereby obtaining a "tree-like" structure in which the support members 502 (branches) become more and more complex and are distributed more and more densely. Another alternative is to shorten the length of the support members 502 to reduce the distance between adjacent nodes, thereby increasing the local node density. By making the support members closer to the outer surface 202 of the inner liner 200 have shorter lengths, a gradual change in the number density of the support members can be produced. In other words, by shortening the length of the support members 502, the number of nodes between the center point 504 and the outer surface 202 of the inner liner 200 can be increased, thereby increasing the number of branch points. Another alternative is to increase the node density. Another alternative is to increase the angle between adjacent support members 502 branching out from a given node 512. By changing this angle, the continuous path defined by the support members 502 can be made longer and more tortuous, thereby increasing the number of nodes between the center point 506 and the outer surface 202 of the inner liner 200.

[0112] The above (as described in the previous paragraph) optional approach can also increase the local support member density. Additionally, the local support member density can be gradually changed by varying the cross-section (width and / or height) of the support member 502. This optional approach can create a graded structure in the periodic internal network structure 204. In some embodiments, the local support member density can be gradually changed by reducing the cross-section of the support member 502 on the side towards the outer surface 202 of the inner liner 200. Any of the above optional approaches for increasing the number and / or local density of the support members can be combined in any manner. For example, when reducing the cross-section of the support member 502 on the side close to the outer surface 202 of the inner liner 200, the node density close to this surface 202 can be correspondingly increased.

[0113] As described above, there is a stress concentration distribution at the contact points between the support members 208 and the outer surface 202 of the inner liner 200 in the internal network structures 204, 500. Therefore, in the periodic internal network structure 204, these stress concentration sites (the contact points of the outer surface 202 of the inner liner 200) are most prone to failure, while the overall stress in the internal region of the internal network is relatively small and less likely to fail. Thus, at least part of the internal region of the internal network structure is a redundant region structurally. By adopting a graded or layered structure, this structural redundancy can be partially eliminated, thereby potentially increasing both the volumetric energy density and the gravimetric energy density of the pressure vessel 300 simultaneously. Improving the volumetric energy density and the gravimetric energy density of stored gases such as compressed hydrogen is the goal pursued in automotive applications such as hydrogen-powered vehicles. The above-mentioned graded or layered structure may be particularly effective in improving such energy densities.

[0114] Generally, the stress / strain distribution can vary at least with the following factors: the way the number density or volume density (local density) of the support members changes; the lengths of the support members 208, 502; the cross-sections (width and height) of the support members 208, 502; and the geometries of the support members 208, 502 with respect to the shape of the outer surface 202.

[0115] In summary, compared with Figure 2A the periodic structures such as shown, the following potential advantages may exist in adopting a layered or graded structure:

[0116] · Reducing the stress concentration at the contact points of the outer surface 202 of the inner liner 200 (by distributing the load over a larger area of the outer surface 202 and having a larger proportion of the support members 502 located near such high-stress regions);

[0117] · Potentially reducing the total mass of the internal structure 500 (by eliminating the structural support members 202 in the innermost volumes 506, 508);

[0118] · It is possible to increase the total volume of gas that can be stored at a given pressure (by eliminating or reducing the structural support members 202 in the innermost volumes 506, 508).

[0119] In other embodiments, the "virtual" stress / strain distribution at the outer edge of the internal network structure 204, 500 of the liner 200 can be further "flattened" by spatially varying the stiffness or other mechanical properties of the materials that make up the internal network structure 204, 500. Similar to Figure 5 the principle of increasing the effective stiffness of the internal structure 500 near such regions by increasing the number of support members 502 in the direction towards the outer surface 202 of the liner 200, the stiffness of the internal structure 500 can also be controlled by spatially varying the materials that make up the network 500. That is, each core volume 506, 508, 510 can contain a material with a given compliance. The compliance of different core volumes 506, 508, 510 can be different - increasing in the direction towards the outer surface 202. It is contemplated that such a gradual change in compliance can be used in combination with a periodic or non-periodic gradient or layered internal structure 204, 500 configuration. Such a change in the material stiffness in the internal network structure 204, 500 can further increase the volumetric energy density and gravimetric energy density of the stored gas.

[0120] Figures 6A to 6D Shown is an exemplary structure at the center point 504 of a pressure vessel for implementing Figure 5 one or more of the non-periodic structures 500 shown. Similarly, each resulting periodic structure 500 is contemplated to replace the periodic structure 204 of the liner shown in FIG. 2.

[0121] In Figure 6A , the central portion 601 of the non-periodic internal network structure 500 includes a connection surface 605 located between the root 602 of the first non-periodic structure 500 and the root 603 of the second non-periodic structure 500. Generally, the root of the non-periodic structure 500 is a point or a support member 502 that can provide all the connection paths formed by the support members 502. In some embodiments, the connection surface 605 is formed by a mechanical structure that abuts the root 602 of the first non-periodic structure against another root 603 and defines a bonding interface. In other embodiments, the first and second non-periodic structures include integrally formed components, and the connection surface 605 constitutes the intersecting surface of the roots 602, 603. In these configurations, if the first and second non-periodic structures are the same, the connection surface can constitute a plane of symmetry. In other embodiments, the non-periodic structures containing the roots 602, 603 can be different.

[0122] In Figure 6BIn [the structure], the central portion 610 of the non-periodic internal network structure 500 includes a disk or plate body 611 against which one or more roots 612 of the non-periodic network structure 500 are mechanically connected or abutted. In some embodiments, the root 612 and the disk body 611 form an integrally molded component. In other embodiments, the root 612 forming the non-periodic structure 500 and the disk body 611 are separately manufactured and connected together by a mechanical connection process. In some embodiments, the disk body 611 further includes one or more openings 613. These openings reduce the total mass of the central portion 610 and increase the total volume for accommodating gas.

[0123] In Figure 6C [the structure], the central portion 620 of the internal network structure 500 includes a sphere 621, a cylinder, or an oblate spheroid against which one or more roots 622 are mechanically connected or abutted. In some embodiments, the root 622 and the sphere 621 form an integrally molded component. In other embodiments, the root 622 forming the non-periodic structure 500 and the sphere 621 are separately manufactured and connected together by a mechanical connection process. In some embodiments, the sphere 621 further includes one or more openings 623. These openings reduce the total mass of the central portion 620 and increase the total volume for accommodating gas.

[0124] Other shapes of the central portions 610, 620, such as ellipsoids or deformed cylinders, are also contemplated. All such common deformation forms of the shapes of the central portions 610, 620 are within the knowledge of those skilled in the art.

[0125] In Figure 6D [the structure], the central portion 630 of the internal network structure 500 includes an annular body or an annular central support member 631 against which one or more roots 632 are mechanically connected or abutted against each other. In some embodiments, the root 632 and the central support member 631 form an integrally molded component. In other embodiments, the root 632 forming the non-periodic structure 500 and the central support member 631 are separately manufactured and connected together by a mechanical connection process. As shown, the annular central support member 631 defines an annular hole 633. This hole reduces the total mass of the central portion and increases the surface area / volume ratio for the root 632 to be mechanically bonded or abutted against the central portion 630.

[0126] Figure 7Illustrated is a conformable pressure vessel 700. The conformable pressure vessel 700 may have a general shape designed to match a desired space. That is, while the shape of a conventional pressure vessel is fixed as a cylinder or a sphere, for the conformable pressure vessel 700, the shape is a parameter that can be controlled and is envisioned to be fixed by the space in which the pressure vessel is to be placed during operation. For example, in the field of automotive applications technology, the conformable pressure vessel can be designed to match any space within a vehicle. In some embodiments, depending on the available space in the operating environment, the conformable pressure vessel 700 can be a cylindrical or spherical container.

[0127] The pressure vessel 700 includes an outer cover 302 and an inner liner 200. The inner liner 200 includes a non-periodic internal network structure 500 having any one of the Figures 6A to 6D illustrated central portions 601, 610, 620, 630. In such embodiments, the shape of the outer surface 202 of the inner liner 200 substantially corresponds to the shape of the outer cover 302. As described above, the inner liner 200 contains pressurized gas through a layer of the outer surface 202 that substantially does not allow the pressurized gas to permeate through, and reduces the stress on the outer cover 302 of the pressure vessel 300 through the structural design of the internal network structure 500. This illustrated conformable pressure vessel is for operation at high pressures, such as 300 bar, 350 bar, 500 bar, or 700 bar. An illustrated size of the conformable pressure vessel 700 is a width, length, and height in the range of 50 - 2000 mm. The overall width, length, and height of the conformable pressure vessel 700 can be defined by a specific use, such as the available space within a vehicle. In some cases, the overall size of the pressure vessels 300, 700 may also be limited by the manufacturing method. For example, in some additive manufacturing methods, the physical size of the part may be limited by the physical size of the equipment or the physical size of the working area. For example, in stereolithography methods such as vat photopolymerization, conventional systems are volumetrically limited by the size of the resin container or vat. For this reason, large pressure vessels 300, 700 with dimensions greater than 500 mm may need to be manufactured by conventional methods such as injection molding.

[0128] Since the non-periodic internal network structure can dissipate stress concentration, a pressure vessel 700 with an unconventional shape can be adopted. Since the pressure vessel 700 with an unconventional shape can be customized according to the requirements of the operating environment, the pressure vessel 700 can be made into a conformal pressure vessel. According to the existing knowledge of those skilled in the art, the structural feature 702 in the shape of a "corner" should not be adopted. This is because these features will introduce unacceptable stress concentration, which may lead to catastrophic accidents. However, the above non-periodic internal network structure can dissipate such stress concentration and allows for the production of conformal pressure vessels including irregular shapes, for example, to match the internal space of a vehicle. As described above, by increasing the number density of the support members 502 near the high-stress regions, such stress concentration can be dissipated. Generally speaking, such stress concentration occurs around the regions with the minimum effective curvature radius. Therefore, increasing the number density of the support members 502 near the regions with a smaller effective curvature radius seems to be a reasonable way to reduce the influence of stress concentration. However, for example, as shown in Figure 14B below, stress concentration can also occur in other parts of the inner lining surface (these parts may not have a smaller effective curvature radius), such as the central regions of each face. The maximum value of the stress results from the stress and strain patterns of the non-circular cross-section inner lining (for example, caused by the concentration of bending stress, hoop stress, and tensile stress). For such regions with higher stress, the internal network structure can be made to provide greater support force to them. The exact positions of such high-stress / strain regions depend on the cross-sectional shape of the inner lining. The above support structure is used to relieve the stress in such stress concentration regions by dispersing part of the stress / strain within the internal network structure (for example, by controlling the local stiffness near such high-stress regions, or increasing the number density of the members within the support structure, or by any other means described herein). In this way, by redistributing the stress within the internal network structure, the maximum stress and strain in such regions can be reduced.

[0129] By definition, a cube that can enclose a cylindrical pressure vessel must have a larger volume. Therefore, the cubic conformal pressure vessel 700 has an additional volume for containing pressurized gas. In actual use, although there will be a certain loss in the volume increase effect, the corner parts of the pressure vessel 700 can be rounded to reduce stress concentration. In this case, the volume increase effect achieved by the cubic conformal pressure vessel is still not negligible. For example, for a rectangular cube with a nominal cross-sectional area of 1×1 and a nominal length of 3, compared with the largest cylindrical pressure vessel that can be enclosed within the cube and has hemispherical end caps at both ends, the volume of the rectangular cube increases by 38%. Therefore, such conformal pressure vessels provide a feasible way to increase the weight energy density and volume energy density of pressure vessels in the field of energy storage technology.

[0130] The internal network structures 204, 500 can also enhance safety in the event of a catastrophic accident such as a vehicle collision. In the case of a conventional pressure vessel 100, once the outer covering 104 is damaged, the pressurized gas will rapidly escape from the vessel due to an explosion. This rapid release exerts a very large force on the pressure vessel, often causing the pressure vessel to acquire kinetic energy and ultimately effectively become a projectile. In contrast, in the case of a pressure vessel having internal network structures 204, 500, since the volumes within the internal network structure communicate with each other and form a tortuous and winding path, the release rate of the pressurized gas is reduced. In this way, when the pressure vessel is damaged, the gas will be released at a slower speed. By extending the total time required for gas release, the total force generated during this process can be reduced, and the probability of the pressure vessel causing damage can be decreased. Additionally, in a catastrophic accident, the rupture mechanism of a conventional cylindrical pressure vessel is different from that of the pressure vessels 300, 700 described in the present application. In the case of a conventional cylindrical pressure vessel, the rupture surface of the outer covering 104 typically extends directly along the longitudinal axis of the vessel and spreads relatively quickly, resulting in a single explosion. In contrast, in the case of a pressure vessel whose inner lining 200 contains internal network structures 204, 500, the failure occurs in a more controllable manner - the gas is released in multiple sequential stages. Consistent with the way an automotive crash buffer dissipates energy through plastic deformation, in the initial stage of rupture, the internal network structures 204, 500 can dissipate some of the elastic / plastic energy stored in the outer covering 302, thereby slowing down the spread rate of the rupture (additionally, due to the release of the pressure inside the vessel, this process may even proceed in a stable manner), and causing the energy to be released at a slower rate through sequential rupture stages compared to the conventional case. Thus, the safety of the inner lining of the present invention is further enhanced.

[0131] Compared with conventional cylindrical or spherical pressure vessels, a conformal pressure vessel has at least the following advantages:

[0132] · Less prone to rolling over;

[0133] · No additional support structure or outer covering is required to prevent such rolling over;

[0134] · There is a possibility of increasing the weight energy density (considering its support structure);

[0135] · There is a possibility of increasing the volume energy density (considering its support structure);

[0136] · Can be stacked, thus saving space;

[0137] · Can be custom-designed to "fit" the requirements of a restricted space; and

[0138] · In the event of a catastrophic accident (such as a collision accident), there is a possibility of achieving higher safety.

[0139] In general, the internal network structure of the conformal pressure vessel 700 is a gradient structure. In other embodiments, the gradient can be a stepped gradient, thereby forming a layered structure. The number density, angle, width, length, and geometric shape of the support members 502 in the region 703 near the "corner-like" structural feature 702 are different from those in the region 704 far from such a structural feature 702. It is contemplated that, if necessary, a third region can be provided between such regions 702, 703 to ensure the mutual "matching" of such regions 702, 703. Such regions can define different hierarchical levels of the layered system. In some embodiments, the above characteristics can vary continuously within the regions 702, 703. In other embodiments, the above characteristics remain constant within the regions 702, 703, and a connecting region connecting the two is provided between these two regions 702, 703, and the above characteristics vary continuously within this connecting region.

[0140] In some embodiments, the roots 612, 622 are located on the disks / spheres 611, 621 in the central part to direct the layered aperiodic structure to the region 702 with locally higher stress / strain.

[0141] It is contemplated that such regions 703, 704 are defined by a stress threshold. That is, for a given gauge pressure, the stress distribution within the "de facto" periodic structure 202 can be obtained by calculation. The part of the "de facto" periodic structure where the stress is greater than the given threshold constitutes the region 703. In some embodiments, the stress can be the von Mises stress or the Tresca stress, and the above threshold is the yield stress of the material constituting the "de facto" periodic structure 202. In addition, if the stress is lower than a second threshold (such as a part of the pre-determined yield stress), then it defines another region. In some embodiments, the stress in the region 704 is less than the first threshold. In other embodiments, the stress in the region 704 is less than the first and second thresholds. According to such regions defined by stress, the structure of the aperiodic structure 500 can be adjusted so as to be able to better dissipate higher stress. For example, according to the inventor's contemplation, the aperiodic structure 500 can be used to achieve this effect. The exact form and structure of the aperiodic structure 500 can be optimized by iteratively calculating the above stress regions 703, 704 and making corresponding modifications to the structure. It is contemplated that such optimization can minimize the mass or volume for a given external shape and gauge pressure.

[0142] Reference Figure 7, the non-circular cross-section of the conformal pressure vessel defines another region 705, which is an additional volume that can be filled with pressurized gas compared to a conventional circular cross-section pressure vessel. In a conventional design, region 705 should correspond to a support structure that is not used for containing gas. In this way, it is possible for the conformal pressure vessel 700 to achieve an increase in volumetric energy density.

[0143] It will be apparent to those skilled in the art that there may be countless internal network structures 204, and which "actual" design to adopt is a complex matter that depends on operating conditions, the environment, the manufacturing route, and the commercial costs of such routes. Due to the inevitable variability of these designs, it is impossible to cover them all in writing. The general uses and functions of the internal network structure 204 have been described in detail above, and those skilled in the art should understand from the description herein that the above specific designs do not constitute limitations.

[0144] Figures 8 to 12 Some other exemplary internal network structures 800, 900, 1000, 1100, 1200 are shown. In some embodiments, the exemplary internal network structures 800, 900, 1000, 1100, 1200 shown in these figures represent only a part of the internal network structure. Generally, by expanding the corresponding patterns of the internal network structures 800, 900, 1000, 1100, 1200, the radial dimensions of the internal network structures 800, 900, 1000, 1100, 1200 can be increased.

[0145] The internal network structures 800, 900 are improved forms of the internal network structure 500. In these non-periodic structures, the region near the outer surface 202 of the inner liner 200 has a greater density of support members. In the internal network structures 800, 900, by adjusting the length of the support members 502, the density of the support members is increased. In this way, a tortuous and interconnected structure can be obtained. The internal network structure 900 particularly shows the effect of shortening the length of the support members 502 on the local support member density. As shown in such structures 800, 900, the closer to the outer surface 202 of the inner liner 200, the greater the local support member density. In other words, the farther the distance from the center point 504 of the inner liner, the greater the local support member density.

[0146] In the exemplary internal network structure 1000, the support member 502 is reinforced at each node 512. The motivation for the reinforcement at each node 512 is to prevent premature failure at such nodes 512. Obviously, since each node is used to connect one support member 502 in a given stress state to another support member 502, the stress state (von Mises stress) at the node 512 can be more complex and generally greater. By reinforcing the support member 502 within the internal network structure 1000, such nodes 512 can withstand greater stresses. A portion of the nodes 512 may be in contact with the outer surface 202 of the liner 200. In some embodiments, the reinforcement may include changing the thickness and / or width of the support member, and the same applies to any other internal network structures 204, 500, 800, 900. In other embodiments, the material forming the reinforced node region may have a greater stiffness and / or a greater yield stress than the other portion of the support member 502. Accordingly, the reinforced node region may be made of a different material or may contain different proportions of reinforcing fillers.

[0147] The internal network structure 1100 is another embodiment of the network structures 204, 502, 800, 900, 1000, 1200. In this embodiment, the intercommunicating volume 206 is not defined by the support member 502, but rather by a series of "bubbles" 1101 or interconnected openings within the internal body 1102. The bubbles 1101 are formed within the internal body 1102. The internal body 1102 may replace the internal network structure 204 in FIG. 2. Such "bubbles" 1101 may form a lattice arrangement structure, such as any of the Bravais lattice structures described above. That is, the bubbles 1101 are periodically arranged and are actually at the lattice points of the Bravais lattice. In some embodiments, the bubbles are interconnected by additional bubble channels (not shown in the figure). In other embodiments, for a pressurized gas, the internal body 1102 may be substantially a porous structure. For example, as the gas with the smallest molecules, hydrogen can diffuse through the porous internal body 1102 relatively unhindered. Alternatively, the "bubbles" 1101 may form an aperiodic or graded structure that can be incorporated within the conformal pressure vessel 700. In these embodiments, near the outer covering 302 of the conformal pressure vessel 700 (such as Figure 7 the region 703 therein) may have a smaller local bubble volume density to dissipate the stress concentration in that region. More generally, from the center point 1103 of the internal body to the region near the outer covering 302, the local volume density may vary continuously or stepwise within the internal body 1102. In still further other embodiments, the local bubble density may be substantially uniformly distributed or pseudo-randomly distributed.

[0148] The bubble internal network structure 1100 has one or more of the following characteristics:

[0149] · The internal body 1102 includes one or more openings 1101;

[0150] · The one or more openings 1101 define a volume;

[0151] · The volume is for containing a pressurized gas, which can pass through the internal body by diffusion or through a diffusion process in one or more interconnecting channels between the one or more openings 1101,

[0152] from one bubble to another.

[0153] In some embodiments, the internal network structure 1100 may include a foamed structure. The foamed structure may preferably be an open-cell structure. That is, each of the one or more bubbles 1101 in the internal network structure 1100 is interconnected.

[0154] The internal network structure 1200 is another example of a support structure design. The internal network structure 1200 includes one or more radially extending support members 502, and the support members 502 include one or more openings 1201. Such openings 1201 ensure that the volumes for containing gas between the support members 502 are interconnected. In some embodiments, the radially extending support members 502 may be support sheets, support plates, support rods, or support panels. Any central support structure in FIG. 6 can be combined with this type of internal network structure.

[0155] For any of the above internal network structures 204, 500, 800, 900, 1000, its optimized structure can be determined through at least one or more of the following process steps. The optimized structure can maximize the weight energy density, volume energy density, or mass of the pressure vessel for a given gauge pressure. In the following embodiments, an iterative method is used to minimize the mass of the optimized internal network structure. 1) Determine the operating conditions and environment including the gauge pressure of the pressure vessel work sheet and the overall shape and dimensions.

[0156] 2) Determine the shape of the support member 208. In some embodiments, the support member 208 may be a support rod, a support sheet, a support plate, a support panel, etc., and may include one or more openings.

[0157] 3) Determine the dimensions of the support member 208, determine the thickness of the pressure vessel outer covering 302, and the thickness of the outer surface of the inner lining 200. The thickness can be preset according to the comparison result of the costs of these components and the cost of the internal network structure 204. These thicknesses should be less than the corresponding thicknesses of the corresponding conventional pressure vessels 100 under the same gauge pressure.

[0158] 4) Calculate the mass and volume of the periodic internal network structure 204 according to any Bravais lattice type. The choice of Bravais lattice is expected to have an impact on the overall comparison results of the optimized structure with other structures. Among them, comparative studies can be carried out on different Bravais lattice types.

[0159] 5) In one embodiment, generate a model within the elastic range in a finite element model simulation package.

[0160] 6) Mesh the model and apply any relevant boundary conditions.

[0161] 7) Calculate the stresses and strains of all components of the pressure vessel, including the pressure vessel walls 202, 302 and the support member 208.

[0162] 8) Determine whether the cladding 302 of the pressure vessel yields (the stress is higher than the yield stress). If no yielding occurs, after reducing the thickness, repeat step 4).

[0163] 9) Calculate the "effective" volume where the stresses and strains are within the elastic range and the stress is less than the yield stress multiplied by "f", where "f" is less than 1.

[0164] 10) Calculate the "effective volume" where the stresses and strains are greater than the yield stress. If there is no volume where any stress is greater than the yield stress, increase the size of the support member 208 (to reduce the support member density) and then repeat the above step 3).

[0165] 11) In the case of the "effective volume" where the stresses and strains are greater than the yield stress, increase the support member density by a "k1" factor, where "k1" is greater than 1. Among them, the support member density can be increased by increasing the multiplier factor to the nearest integer at each applicable node of the internal network structure 204. As described above, the support member density can also be increased by other means. Any of the above methods can be used for the iterative calculation of the internal network structure.

[0166] 12) In the case of the "effective volume" where the stresses and strains are greater than the yield stress, reduce the support member density by a "k2" factor, where "k2" is greater than 1. Among them, the support member density can be reduced by reducing the multiplier factor to the nearest integer greater than zero at each applicable node of the internal network structure 204. As described above, the support member density can also be reduced by other means. Any of the above methods can be used for the iterative calculation of the internal network structure.

[0167] 13) After replacing the Bravais structure with the modified structure, starting from step 5), repeat until the support member 208 and the pressure vessel cladding 302 no longer yield and the mass and / or volume are reduced to the greatest extent. To avoid ambiguity, step 12) is used to increase the mass and decrease the volume, while step 13) is used to decrease the mass and increase the volume. Thus, it can be seen that each iteration can increase or decrease the mass and volume.

[0168] The present invention can be summarized as the following numbered clauses:

[0169] 1. A liner for a pressure vessel, the pressure vessel including the liner and an outer layer disposed around the liner, the liner including: a surface defining a closed volume; and an internal network structure disposed within the closed volume, wherein the internal network structure includes a plurality of connecting support members defining a continuous path. The liner can reduce the hoop stress transmitted into the outer layer of the pressure vessel and form a barrier that does not allow the gas contained within the pressure vessel to permeate therethrough. By incorporating the liner into the pressure vessel, the weight energy density and volume energy density of the pressure vessel can be increased. The internal network structure can be based on a periodic structure or an aperiodic structure.

[0170] 2. The liner of clause 1, wherein the liner surface and the internal network structure define an interconnected volume for containing a fluid.

[0171] 3. The liner of any one of clauses 1 to 2, wherein the continuous path includes one or more nodes, the nodes defining points at which one support member is connected to at least one other support member, such that the number of the at least one other support member defines a multiplication factor. A plurality of contact points can be in contact with the liner surfaces on opposite sides of the liner, and such contact points are mechanically connected to each other through one or more of the continuous paths.

[0172] 4. The liner of clause 3, wherein the multiplication factor is a constant. Additionally, the multiplication factor can also vary.

[0173] 5. The liner of any one of clauses 1 to 4, wherein the effective stiffness of the internal network varies along the continuous path.

[0174] 6. The liner of clause 5, wherein the change in the effective stiffness of the internal network is controlled by changing the local support member number density along the continuous path.

[0175] 7. The liner of clause 6, wherein the change in the local support member number density is controlled by changing any one or any combination of the following:

[0176] i) The distance between adjacent nodes in the continuous path;

[0177] ii) the multiplication factor of the one or more nodes; and / or

[0178] iii) the angle between the at least one support member at each node.

[0179] Since the number density of the local support members can be controlled, the number of contact points on the inner lining surface can be controlled. The number of contact points can determine the magnitude of the stress concentration formed at such contact points under a given gauge pressure.

[0180] 8. The inner lining according to item 5, wherein the change in the effective stiffness of the internal network is controlled by changing the material composition and / or material of the support member.

[0181] 9. The inner lining according to item 5, wherein the change in the effective stiffness of the internal network is controlled by changing the cross-sectional area of the support member.

[0182] 10. The inner lining according to any one of items 5 to 9, wherein the closer to the inner lining surface, the greater the effective stiffness of the internal network along the continuous path. From the center of the internal network structure to the contact point on the inner lining surface, the effective thickness can increase in a stepped, pseudo-continuous or continuous manner.

[0183] 11. The inner lining according to any one of items 5 to 10, wherein the closer to the inner lining surface area, the smaller the effective radius of curvature, and the greater the effective stiffness of the internal network along the continuous path.

[0184] 12. The inner lining according to item 10 or 11, wherein increasing the effective stiffness of the internal network along the continuous path includes one or more of the following:

[0185] i) reducing the distance between adjacent nodes in the continuous path;

[0186] ii) increasing the multiplication factor of the one or more nodes;

[0187] iii) increasing the angle between the at least one support member at each node;

[0188] iv) increasing the proportion of the material with higher rigidity in the composition;

[0189] v) increasing the cross-sectional area of the support member.

[0190] 13. The inner lining according to any one of items 1 to 12, wherein the inner lining comprises a polymer, ceramic, metal or a composite thereof. The inner lining can be a single component or an integrally formed component.

[0191] 14. The liner according to any one of items 1 to 13, wherein the internal network structure includes graphene as a filling material. The filling material can be used as a toughening filler component.

[0192] 15. The liner according to any one of items 1 to 14, wherein the shape of the surface is one of a cylinder, a sphere, an oblate spheroid, an ellipsoid, a rounded cube, or a rounded rectangular cube. The shape of the liner can be designed to be optimal in terms of the trade-off between reducing the extra mass of the liner; reducing the stress on the outer layer of the pressure vessel; and reducing the stress concentration formed on the surface of the liner. Among them, optimization for this purpose can be achieved by a computer-implemented method. This method can be an iterative method. The shape of the liner can be designed to match a specific space in the operating environment.

[0193] 16. A pressure vessel, comprising: the liner according to any one of items 1 to 15; and an outer layer provided around the liner.

[0194] 17. The pressure vessel according to item 16, wherein the volume of the liner is used to contain a fluid, and the fluid includes a compressed gas or a liquid. The gauge pressure of the pressure vessel can be greater than 300 bar, 350 bar, 500 bar, or 700 bar.

[0195] 18. The pressure vessel according to item 17, wherein the fluid includes one of hydrogen, nitrogen, oxygen, natural gas, methane, ammonia, biogas, liquid hydrogen, liquid nitrogen, liquid nitrogen, liquefied natural gas, liquid ammonia, liquid methane, or liquid biogas.

[0196] 19. The pressure vessel according to any one of items 16 to 18, wherein the outer layer includes a woven carbon fiber cloth impregnated with resin. The fiber can be a carbon fiber.

[0197] 20. A method for additive manufacturing of the liner of the pressure vessel according to any one of items 1 to 15, including any of the following methods: vat photopolymerization; material spraying; binder spraying; direct metal laser sintering; selective laser sintering; selective laser sintering; multi-jet fusion; fused deposition modeling; injection molding; or investment casting.

[0198] 21. A method for manufacturing the pressure vessel according to any one of items 16 to 19 having the liner by applying an outer layer around the liner including an internal network structure by any of the following methods: resin infusion; cryomolding; filament winding; or vacuum-assisted resin transfer molding.

[0199] 22. A computer program, including computer-executable instructions, which when executed by a processor, cause the processor to control an additive manufacturing device to manufacture the liner according to any one of items 1 to 15.

[0200] 23. An additive manufacturing method according to item 22, the method comprising: obtaining an electronic file representing the geometry of a product, wherein the product is a lining according to item 1; and controlling an additive manufacturing apparatus to manufacture the product according to the geometry specified in the electronic file in one or more additive manufacturing steps.

[0201] The present invention also relates to a segmented lining and a segmented pressure vessel including the segmented lining.

[0202] The overall dimensions and shape of the segmented pressure vessel 100 can vary according to the operating requirements. Generally speaking, the dimensions of the segmented pressure vessel 100 can be in the range of 50 to 2000 mm, and the shape of the segmented pressure vessel 100 can be configured, for example, to match any space within a vehicle or to be stackable in shape. Therefore, the segmented pressure vessel 100 can be referred to as a "conformal pressure vessel".

[0203] The segmented pressure vessel 1300 includes an outer covering 102 and a plurality of interlocking lining segments 1302, 1304, 1306 which, when joined together, form an outer surface 202 of the segmented lining 1300 disposed within the outer covering 102. The lining segments are divided into three types as follows: a central segment 1302; a cap segment 1306; and an intermediate segment 1304.

[0204] Each such lining segment 1302, 1304, 1306 includes at least one interlocking portion 1308, 1310 for engaging with complementary interlocking portions 1308, 1310 of adjacent lining segments 1302, 1304, 1306 such that the lining segments 1302, 1304, 1306 can be mated with each other. In one embodiment, the complementary interlocking portions 1308, 1310 respectively include complementary bushing / flange portions that can be interlocked together. Those skilled in the art should understand that other examples include a mortise and tenon structure, a toothed structure or any other latching mechanism. More generally, the interlocking portions 1308, 1310 can be referred to as "male" type or "female" type.

[0205] The central section and the intermediate sections 1302, 1304 include two opposite open ends, while the cap section 1306 includes one open end and one closed end. The closed end defines one of the segmented liner end faces 1312 therein. The central liner section 1302 may include the same type of interlocking portions 1308, 1310 (i.e., male / male or female / female) respectively located at its respective open ends. The intermediate liner section 1304 includes opposite (or complementary) types of interlocking portions 1308, 1310 (i.e., female / male or male / female) respectively located at its respective open ends. The cap section 1306 includes a single interlocking portion 1308, 1310 (i.e., male or female) located at its open end. Thus, the segmented liner 1300 may be composed of the central inner section 1302, two cap sections 1306, and optionally one or more intermediate liner sections 1304.

[0206] Each liner section 1302, 1304, 1306 includes an internal network structure, and this internal network structure can be any structure shown in FIG. 2, FIG. 3, Figures 8 to 12 or FIG. 15 to Figure 16 However, it should be understood that such internal network structures are not intended to constitute any limitation, but are only illustrative examples. The specific internal network structure used in the segmented liner can be determined by optimization based on operating requirements (such as the dimensions and shapes required to conform to a "conformal" pressure vessel). The outer surface 202 of the segmented liner defines a volume for storing fluids. The segmented liner is envisioned for storing hydrogen, but other fluids such as nitrogen, oxygen, natural gas, ammonia, biogas, methane gas, liquid hydrogen, liquid nitrogen, liquid nitrogen, liquefied natural gas, liquid ammonia, liquid methane, or liquid biogas can also be stored. The segmented pressure vessel 1300 is used for storing fluids at high pressures such as 300 bar, 350 bar, 500 bar, or 700 bar.

[0207] In another embodiment (not shown), the segmented liner 1300 includes two end sections 1306 and does not include any intermediate or central liner sections 1302, 1304. In this structure, the segmented liner 1300 is similar to a split "clam shell". The dividing line between the respective end sections 1306 can be either parallel or orthogonal to the longitudinal axis of the liner. Optionally, each end section 1306 includes an internal network structure described in further detail in conjunction with FIG. 15 and Figure 16 In the "split clam shell" embodiment, the interlocking ends 1308, 1310 of the respective end sections 1306 are complementary to each other so that they can be mated with each other.

[0208] In Figure 13A the central and intermediate liner sections 1302, 1304 are in close contact with each other in a plane perpendicular to the longitudinal direction of the pressure vessel. In another exemplary segmented liner 1320, as Figure 13BAs shown, the central and intermediate lining segments 1302, 1304 are in close contact with each other in a plane containing the longitudinal direction of the pressure vessel. In this alternative embodiment, the pressure vessel further includes two other cap segments 1314 in close contact with the adjacent intermediate lining segment 1304, and these two cap segments and the cap segment 1306 form a closed segmented lining 1320.

[0209] Compared with the conventional cylindrical or spherical pressure vessel designs, a non-circular cross-section (such as Figure 13A the rounded square cross-section shown) can store a larger volume of fluid. Therefore, as long as the efficiency increase effect is not offset by any strength decrease effect brought by the non-circular shape, it is possible to achieve an improvement in the volumetric energy density and / or the weight energy density efficiency. The internal network structures provided in each of the lining segments 1302, 1304 serve as structural supports for this purpose.

[0210] Now refer to Figure 14A , which shows the radial deformation of the hexagonal lining segment 1400 when the internal fluid is over-pressurized. Figure 14A The shown lining segment 1400 does not include an internal network structure. For clarity, the original shape of the outer surface 1402 of the lining segment 1400 is also shown in the figure. This result is the calculation result of a known commercial software package based on finite element analysis simulation. The result shows that each edge 1408 of the lining segment has a tendency to move towards the axial center of the lining segment 1400 (i.e., corresponding to negative radial deformation), while the center of each face of the lining segment 1400 has a tendency to move outwards away from the axial center of the lining segment 1400 (i.e., outward bending, corresponding to positive radial deformation). The radial deformation away from the center of the lining segment 1400 reaches the maximum at the center of each face of the outer surface 1402 of the lining segment. The radial deformation towards the center of the lining segment reaches the maximum along each edge 1408 of the lining segment. The radial deformation continuously changes between these two types of positions and is symmetric in the circumferential direction of the entire lining segment 1400. Thus, it can be seen that when over-pressurized internally, the lining segment including the "sharp" edges 1408 has a tendency to return to a circular shape.

[0211] Figure 14B Shown is Figure 14A the corresponding von Mises stress of the radial deformation. This stress is calculated by a known commercial software package. The result shows that the von Mises stress is the maximum along each edge 1408 of the lining segment and at the center of each face of the lining. Such maximum values correspond to Figure 14A the maximum positive and negative radial deformations shown. The von Mises stress continuously changes between such maximum values and is symmetric in the circumferential direction of the entire lining segment 1400. Preliminary research results show that failure occurs at each edge 1408 of the lining segment. This result also applies to lining segments with square or any other non-circular cross-sections.

[0212] Refer to Figure 15A andFigure 15B , these two figures are cross-sectional views of the liner segments 1302, 1304 including the internal network structures 1500, 1510. In Figure 15A , the internal network structure 1500 includes a first set of support members 1514, and this set of support members 1514 includes a plurality of first support members 1504. Each support member 1504 extends across one of the internal corners 1508 of the liner surface 202. The internal corner 1508 corresponds to the corner edge in three dimensions, and the "corner" mentioned in other parts of this article is interpreted in this way. Thus, the first set of support members 1514 exerts restrictions on the surfaces 1502 of the liner segments 1302, 1304 to reduce their tendency to bend outward (as shown in Figure 14A and Figure 14B ). Therefore, the first set of support members 1514 has the effect of reducing stress and strain or distributing the stress and strain from the liner surfaces 1502 (especially from the centers of the surfaces 1502) to the internal network structure. In this way, the stress and strain can be distributed over a larger area, thereby reducing stress concentration and premature failure, and enabling a higher storage pressure to be adopted within the pressure vessel.

[0213] In Figure 15A the illustrated embodiment, the cross-section of the liner is square, and the support members 1504 extending across the corners are arranged at a 45-degree angle to the surfaces. More generally, the setting angle of the support members 1504 extending across the corners relative to the surfaces 1502 can be equal to half of the interior angle of the liner surface 202.

[0214] In Figure 15B , the internal network structure 1510 includes:

[0215] As Figure 15A shown, the first set of support members 1514; and

[0216] a second set of support members 1516 including a plurality of second support members 1506. Each support member 1506 extends between two first support members 1504 that extend across two adjacent corners 1508 of the liner.

[0217] Thus, the second set of support members 1516 exerts restrictions on the first support members 1504, thereby reducing their tendency to bend outward (bending outward in a similar manner as shown in Figure 14A and Figure 14B ), and the first set of support members in turn exerts restrictions on the liner surfaces 1502. In this way, the stress and strain can be effectively distributed from the liner surfaces 1502 to a larger area of the internal network structure 1510. In this way, stress concentration can be further reduced to achieve a higher storage pressure and the possibility of improving the weight storage efficiency.

[0218] On the other hand, when more support members are added to the internal network structure, the total volume available for fluid pressurized storage will be reduced. The number of support members can be optimized to maximize the weight efficiency of the segmented pressure vessel.

[0219] Figure 15C Shown is a longitudinal cross-section of the internal structure of the optimized liner section. The liner section includes interlocking portions 1308, 1310 and an internal network structure 1520. As shown, the cross-section of the internal network structure 1520 remains constant along the longitudinal axis of the liner section. That is, the internal network structure 1520 can be easily formed by die extrusion or by injection molding with split dies.

[0220] Figure 15D Shown is a cross-section of the internal network structure 1520 of the optimized liner section. The optimized internal network structure 1520 includes:

[0221] A first set of support members 1514 including a plurality of first support members 1504, wherein each support member 1504 extends across one of the internal corners 1508 of the liner surface 202;

[0222] A second set of support members 1516 including a plurality of second support members 1506a, 1506b, wherein each support member 1506a, 1506b extends between two first support members 1504 that extend across adjacent corners 1508 of the liner;

[0223] A third set of support members 1518 including a plurality of third support members 1528, wherein each support member 1528 extends between two adjacent second support members 1506b and forms a square;

[0224] A fourth set of support members 1522 including a plurality of fourth support members 1512, wherein each support member 1512 extends radially between the center of the corresponding face 1502 of the liner section and the vertices of the square formed by the third set of support members 1518. Optionally, the support member 1512 may bisect one or more of the second support members 1506a, 1506b; and

[0225] A fifth set of support members 1524 including a plurality of fifth support members 1526, wherein each support member 1526 extends radially between the internal corner 1508 of the liner and one or more of the first support members 1504. Optionally, the support member 1526 may bisect one or more of the first support members 1504.

[0226] In Figure 15DIn the illustrated embodiment, the third set of support members 1518 forms a square, and each vertex 1530 of the square points to the center of each face 1502 of the liner section. More generally, when the shape of the outer surface 202 of the liner section is an axisymmetric shape, the shape formed by the third set of support members 1518 is substantially similar to the shape defined by the outer surface 202 of the liner section.

[0227] The fourth and fifth sets of support members 1522, 1524 respectively provide radial support to the second and first sets of support members. As described above, the first support member 1504 and the second support members 1506a, 1506b have a tendency to bend outward (although this tendency is reduced by the second and third sets of support members respectively). When bending the first and second support members 1504, 1506a, 1506b outward, pressure must be applied to the radially extending support members 1512, 1514. Therefore, the fourth and fifth sets of support members 1522, 1524 respectively impose restrictions on the second and first sets of support members to reduce the maximum stress of the first and second sets of support members 1514, 1516. In this way, the stress and strain can be more evenly distributed over a larger area.

[0228] Now refer to Figure 16 , which shows another internal network structure 1600. The internal network structure 1600 is not disposed within the volume defined by the outer surface 202 of the liner, but is integrally formed within a certain thickness of the liner wall 1602. The thickness of the liner wall 1602 formed by the internal network structure is not uniform. More specifically, the thickness of the liner wall 1602 is the thickest at the corner ridges 1608, the thinnest at the center of each face of the liner section, and varies monotonically between the two. Preferably, the cross-sectional shape of the internal volume defined by the thickness variation is substantially the same as the outer surface 202 of the liner section wall. The internal network structure 1600 includes one or more openings 1606 located at each corner ridge of the liner section. The one or more holes 1606 can be partial circumferential holes.

[0229] Figure 17A An exemplary flange joint 1700 including complementary and interlocking portions 1308, 1310 of liner sections 1302, 1304, 1306 is shown. The interlocking portions 1308, 1310 define a sealing surface 1702 in the mated state (i.e., the flange between adjacent liner sections 1302, 1304, 1306 that is partially marked as a slanted area in Figure 17A and for which the above connection method can be used). Accordingly, Figure 5 the intermediate or central liner sections 1302, 1304 in

[0230] Figure 17B Shown is another flange joint 1710 between the liner segments 1302, 1304, 1306. The flange joint 1710 is equivalent to that shown in Figure 17A but differs in that the intermediate or central liner segments 1302, 1304 include an outer sleeve 1708. Accordingly, the interlocking portion 1310 of the cap liner segment 1306 defines a liner sleeve 1706 when mating with the interlocking portion 1308 of the adjacent liner segment, thereby forming a sealing surface 1702.

[0231] Figure 17C Shown is yet another flange joint 1720 between the liner segments 1302, 1304, 1306. In the flange joint 1720, the intermediate or central liner segments 1302, 1304 include both a liner sleeve 1706 and an outer sleeve 1708, thereby defining a groove. The interlocking portion 1310 of the cap liner segment 1306 defines a "ridge" 1722 when mating with the interlocking portions 208 of the adjacent liner segments 1302, 1304, thereby forming a sealing surface 1702.

[0232] In Figures 17A to 17C the sealing surface 1702 includes a step 1704. However, in some embodiments, multiple steps may also be provided. In such a case, the interlocking portions 1308, 1310 of the liner segments 1302, 1304, 1306 may include multiple complementary steps. The stepped-profile sealing surface 1702 forms a tortuous flow path when fluid escapes from the segmented pressure vessel 1300, thereby reducing the tendency to leak. And the sealing strength is improved by increasing the total surface area at the seal. In one embodiment, the sleeve length may be 25 mm.

[0233] Material

[0234] (Segmented) liners 200, 1300 may include a thermoplastic or thermosetting polymer such as high density polyethylene (HDPE), polyaryletherketone (PAEK), polyetheretherketone (PEEK), nylon (such as PA6, PA12), epoxy resin or a mixture thereof.

[0235] In some embodiments, the internal network structures 204, 500, 800, 900, 1000, 1100, 1200, 1500, 1510, 1520 of the (segmented) liners 200, 1300 may include additives. Such additives or fillers may be functional and / or structural additives or fillers. In one embodiment, the stiffness and yield stress of the internal structures 204, 500, 800, 900, 1000, 1100, 1200, 1500, 1510, 1520 are increased by adding nano-fillers such as graphene, carbon fibers (e.g., carbon fibers in the form of short "cut" fibers), and / or carbon nanotubes. In some embodiments, the internal network structure may include light metal additives such as aluminum or aluminum alloys, titanium or titanium alloys, or ceramics such as alumina. In this way, the internal network structure can include polymer / metal composites or polymer / ceramic composites. As described above, in some embodiments, a gradual change in stiffness can be achieved by varying the stiffness of the support members 208, 502. An alternative way to produce this stiffness change is to vary the volume or mass fraction of the structural additive.

[0236] In other embodiments, the internal network structures 204, 500, 1500, 1510, 1520 may be light metals or ceramics. Metals that may be used include, but are not limited to, aluminum and aluminum alloys. Ceramics that may be used include, but are not limited to, alumina.

[0237] In other embodiments, additives that absorb or adsorb hydrogen may be added to the internal network structures 204, 500, 800, 900, 1000, 1100, 1200, 1500, 1510, 1520. In this way, the effective volume 206 for containing the pressurized gas can be increased. Such additives that absorb or adsorb hydrogen are used to release hydrogen in a controlled manner when the pressure drops.

[0238] In some embodiments, the outer surface 202 of the (segmented) liners 200, 1300 also includes structural additives. It is contemplated that since the outer surface 202 of the liner 200 is relatively thin, the additives preferably do not affect the permeability of the outer surface 202 of the liner 200 to the gas contained therein.

[0239] In embodiments where the pressurized gas is hydrogen, the material forming the (segmented) liners 200, 1300 is not prone to hydrogen embrittlement. More generally, the choice of material may depend on a series of other factors such as the cost, density, stiffness, and yield stress of the material. Using an Ashby chart to select a material by optimizing the specific stiffness or its equivalent parameter is a known practice for those skilled in the art.

[0240] In the internal network structure 1100 within a bubble or foam, the internal body 1102 may include a foamed thermosetting material, a metal foam, or a ceramic foam. The thermosetting material may be an epoxy resin. The metal may be a lightweight alloy of aluminum or titanium. The ceramic may be alumina, zirconia, or other lightweight ceramics. In the above embodiments, the foaming process may be facilitated by adding a supplementary foaming agent of various materials.

[0241] The cladding 302 of the pressure vessels 300, 700 may include a thermosetting fiber-reinforced composite (FRC) wound in filaments or bands, a compression-molded FRC, a resin-infused carbon fiber, or a thermosetting plastic vacuum-assisted resin transfer molding (VARTM) carbon fiber. The composite filaments or bands may include carbon fibers (such as pitch-based carbon fibers or T1000), aramid fibers, or boron fibers. The resin may include any one of epoxy resins, cyanate esters, polyurethanes, polyesters, vinyl esters, phenolic resins, furans, or polyamides.

[0242] Manufacturing method

[0243] The pressure vessels 200, 700 are manufactured in four main steps. The segmented pressure vessel 1300 may further include a joining step as described below.

[0244] i) Structural optimization

[0245] The first step is to optimize the internal network structure through simulation to minimize the mass under a given shape and internal working sheet pressure. This optimization may be based on iterative techniques. Other forms of optimization may also be employed, such as the optimization of weight energy density and volume energy density. Consistent with the above, through the structural optimization of the internal network structure, the redistribution of stress from the "high" stress regions within the internal network structure to the "low" stress regions can be improved, thereby homogenizing each lining element to prevent premature failure at stress concentration points. Thus, the stress applied to the cladding and the lining surface can be reduced.

[0246] ii) Manufacturing the lining 200 or lining segments 1302, 1304, 1306

[0247] In the second step, the optimized lining 200 (with internal network structures 204, 500, 800, 900, 1000, 1100, 1200) may be manufactured by an additive manufacturing method. In other embodiments, the manufacturing method may also employ conventional processes such as mesh forming. In other embodiments, the manufacturing method may also employ a subtractive manufacturing method. In some such embodiments, the manufacturing method may include a foaming agent.

[0248] The inner lining segments 1302, 1304, 1306 can be manufactured by additive manufacturing, injection molding, or die casting. One or more valve ports can be added to each of the inner lining end segments 1306 using manufacturing techniques known to those skilled in the art.

[0249] Additive manufacturing

[0250] The exact choice of additive manufacturing depends at least in part on the material selection of the inner lining 200. Additive manufacturing includes, but is not limited to, stereolithography (vat photopolymerization), material jetting, binder jetting, powder bed fusion (direct metal laser sintering (DMLS), selective laser sintering (SLS), selective laser melting (SLM), multi-jet fusion (MJF), electron beam melting (EBM)), and filament extrusion processes (fused deposition modeling (FDM)). Net shape manufacturing methods include, but are not limited to, injection molding, investment casting, or lost wax casting.

[0251] Injection molding

[0252] In some embodiments, the internal network structure can be manufactured by injection molding. This manufacturing method is particularly advantageous for manufacturing large internal network structures 204, 500, 800, 900, 1000, 1200 that cannot be implemented or are time-consuming by additive manufacturing routes. Large internal network structures 204, 500, 800, 900, 1000, 1200 are internal network structures with dimensions greater than 500 mm. For example, in the FDM method, the part size is limited by the working range of the raster device and the size of the heating table (generally less than 500 mm). The segmented inner lining segments 1302, 1304, 1306 can also be manufactured by injection molding, especially by split mold forming techniques.

[0253] Extrusion molding

[0254] In some embodiments, the intermediate and / or central inner lining segments can be manufactured by extrusion molding. Subsequently, the interlocking portions 1308, 1310 can be manufactured by any subtractive manufacturing technique known to those skilled in the art.

[0255] Subtractive manufacturing

[0256] The internal network structure 1200 can be manufactured by selectively removing material rather than by an additive manufacturing route. In some embodiments, the internal network structure 1200 can be manufactured by drilling holes in a plate 502 manufactured by an injection molding process. Such subtractive manufacturing methods include CNC (computer numerical control) of drills, lathes, etc.

[0257] Foaming process

[0258] In some embodiments, the internal network structure 1100 may form a foam. Such foam may be manufactured by a foaming process that produces an open-cell structure. The foaming process may include a foaming agent. For polymeric materials, the foaming agent may be a chemical reagent. The chemical reagent may be used to synthesize polymers and generate gases as reaction byproducts. In other embodiments, the foaming agent may include an inert gas such as argon. In the latter case, regions of different bubble densities may be formed by spatially controlling the local flow of the gas, so that the bubble diameter at the center is larger or the density is lower, and the foam density gradually decreases toward the outer surface 202 of the liner 200, so that the bubbles gradually become smaller in this direction. The foaming agent may be used in combination with any applicable additive manufacturing approach. In addition, the foam may also be produced in a molding process and thus may form a preparatory step in a subtractive manufacturing method.

[0259] iii) Forming a segmented lining by connecting lining segments

[0260] In the case of a segmented liner, after the liner segments 1302, 1304, 1306 are manufactured, the complementary interlocking portions 1308, 1310 are mated and the sealing surfaces 1702 are sealed by adhesive bonding or welding to connect the liner segments together. Adhesive bonding is applicable to both polymeric and metallic liner segments 202, 204, 206, 400. Welding is applicable to metallic liner segments 202, 204, 206, 400. In addition, other connection methods known to those skilled in the art may also be used.

[0261] iv) Manufacturing outer covering (outer envelope) 302

[0262] In the third step, the outer covering 302 of the liner 200 or the segmented liner is made of a carbon fiber reinforced resin composite material or other reinforcing fibers. In some embodiments, the carbon fiber reinforced resin is applied by a winding method. Among them, a suitable machine known to those skilled in the art can be used to control the winding angle and tension. Alternatively, the outer covering 302 can also be formed by curing the filament braid under vacuum after resin infusion. In addition, the outer covering can also be formed by automatic fiber placement. Optional methods include: a wound dry fiber / strip preform for resin impregnation, or a pre-impregnated fiber / strip prepreg.

[0263] In other embodiments, a pre-prepared woven carbon fiber cloth may be applied and bonded to the outer surface 202 of the (segmented) liner 200, 1300 by a resin infusion process or a low temperature compression molding process. In the latter process, two pre-prepared woven carbon fiber cloths are pre-impregnated and then bonded together using an autoclave during the curing process. In some embodiments, the carbon fiber cloth may be replaced by any of the filamentary or ribbon materials described above.

[0264] The advantage of the segmented liner is that the length of the segmented liner 1300 can be adjusted according to the operating requirements and is not (like a conventional liner) limited by the physical dimensions of the manufacturing equipment. In addition, in the case of die casting and injection molding, only a limited number of molds are required to manufacture liners 1300 of any length.

[0265] v) Valve integration

[0266] During the manufacturing of the liner by injection molding or additive manufacturing, the metal valve ports, such as the pole bosses used as gas inlets / outlets, can be manufactured by overmolding or insert molding.

[0267] One or more valves can be integrated into the end section 1306 of the pressure vessels 300, 700, 1300. In the segmented case, optionally, one or more valves are molded into the end section 1306 during the injection molding process. Alternatively, one or more valves can be installed using methods known to those skilled in the art, either before or after the overmolding step.

[0268] The fluid contained in the pressure vessel can be hydrogen, nitrogen, oxygen, methane, natural gas, ammonia, biogas, liquid hydrogen, liquid nitrogen, liquid nitrogen, liquid natural gas, liquid ammonia, liquid methane or liquid biogas.

[0269] The present invention has been described in detail in connection with the exemplary embodiments. Modifications can be made without departing from the scope of the invention defined by the claims. Each technical feature disclosed or elucidated in this specification can be incorporated into the present invention individually or in any suitable combination with any other technical feature disclosed or elucidated herein.

Claims

1. A segmented inner lining for a pressure vessel, characterized in that, The segmented liner includes: At least two liner segments and at least two cap segments assembled together, wherein each of the liner segments includes an internal network structure, and the internal network structure includes: A first set of support members including a plurality of first support members, wherein each of the first support members extends across an internal corner of the liner segment or extends between adjacent faces of the liner segment; and A second set of support members including a plurality of second support members, wherein each of the second support members extends between two adjacent first support members to reduce the tendency of the first support members to bend outward.

2. The segmented inner lining according to claim 1, wherein Each of the liner segments and the cap segments is a single molded part.

3. The segmented inner lining according to claim 1, wherein The cross-sectional shape defined by the outer surface of the liner segment is one of a square or a rounded square.

4. The segmented lining according to claim 3, wherein The internal network structure further includes: A third set of support members including a plurality of third support members, wherein each of the third support members extends between two adjacent second support members to form a square or rounded square cross-section.

5. The segmented inner liner according to claim 4, wherein The internal network structure further includes: A fourth set of support members including a plurality of fourth support members, wherein each of the fourth support members extends radially between the face defined by the inner surface of the liner segment and the vertices of the square or rounded square formed by the third set of support members.

6. The segmented inner lining according to claim 5, characterized in that, Each of the fourth support members in the fourth set of support members bisects one or more of the second support members.

7. The segmented inner lining according to any one of claims 3-6, characterized in that, The internal network structure further includes: A fifth set of support members including a plurality of fifth support members, wherein each of the fifth support members extends radially between the internal corner of the liner segment and one or more of the first support members.

8. The segmented lining according to claim 7, wherein Each of the fifth support members in the fifth set of support members bisects one or more of the first support members.

9. A pressure vessel, characterized in that, Comprising: The segmented liner according to any one of claims 1-8; And An outer layer disposed around the segmented liner.

10. The pressure vessel according to claim 9, wherein The outer layer includes a woven carbon fiber cloth impregnated with resin or a carbon fiber-wound covering.

11. A method of manufacturing a segmented lining according to claim 1, characterized in that, Comprising: Additive manufacturing, injection molding or die casting the at least two liner segments and the at least two cap segments; And Assembling the segments together.

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