Lightweight structure of liquid hydrogen storage cylinder shell and manufacturing method thereof

Abstract

The present application relates to a kind of liquid hydrogen storage hydrogen bottle shell light weight structure and manufacturing method, including inner bag, the outer surface of the inner bag is provided with heat barrier layer, the heat barrier layer is equipped with barrier layer, the barrier layer is the shell structure matched with the outer shape of the inner bag, first vacuum zone is formed between the barrier layer and inner bag, the barrier layer is the non-metallic material of gas permeation prevention;The barrier layer outer layer is provided with heat insulation layer, the outer shell is equipped with outer shell, the outer shell is non-metallic material, second vacuum zone is formed between the outer shell and the barrier layer;The vacuum degree of the second vacuum zone is higher than the vacuum degree of the first vacuum zone, to optimize container shell structure based on vacuum insulation mode, realize the lightweight design and manufacture of liquid hydrogen storage container.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field, in particular to a light-weight structure of a liquid hydrogen storage bottle shell and a manufacturing method. BACKGROUND

[0002] Liquid hydrogen storage (and nitrogen storage) needs to adopt a double-layer or multi-layer structure, and a heat insulation layer formed by a vacuum or heat insulation filler is arranged in the middle part between an innermost layer inner container and an outermost layer shell. Since the temperature range of the saturated vapor curve of hydrogen is from-259 DEG C to-240 DEG C, when the liquid hydrogen is at about-253 DEG C, the pressure required to maintain the hydrogen in a liquid state or a gas-liquid two-phase saturated state is one atmosphere; when the temperature of hydrogen rises to-240 DEG C due to the inflow of external heat, the saturated atmospheric pressure of hydrogen is about 12.8 atmospheres, and the pressure in the container will be increased to 12.8 atmospheres accordingly; when the temperature in the container continues to rise and exceeds-240 DEG C, even if the pressure is increased, the hydrogen will completely change into a gaseous state or a supercritical state. The normal temperature working range of the liquid hydrogen is from-253 DEG C to-240 DEG C, and the corresponding pressure range is 1 to 12.8 atmospheres.

[0003] The structure of the liquid hydrogen storage container needs to have good heat insulation performance and also needs to have structural strength and rigidity meeting the requirements of the industry or the national standard in specific application scenarios. The shell structure design and the vacuum heat insulation mode of the hydrogen storage container are main technical means to ensure the safety of the hydrogen storage container. At present, the liquid hydrogen has been widely applied, but the tank body structure is mainly made of austenitic alloy steel or aluminum alloy material, and the container is heavy. In recent years, with the gradual application of high-pressure gaseous hydrogen storage and ultralow-temperature liquid hydrogen storage containers in the vehicle field, how to design and manufacture the light-weight liquid hydrogen storage container has become a key technology to be broken through. SUMMARY

[0004] In view of the defects in the above-mentioned existing production technology, the application provides a light-weight structure of a liquid hydrogen storage bottle shell and a manufacturing method, so as to optimize the container shell structure on the basis of the vacuum heat insulation mode and realize the light-weight design and manufacturing of the liquid hydrogen storage container.

[0005] The technical scheme adopted by the application is as follows:

[0006] A light-weight structure of a liquid hydrogen storage bottle shell, comprising an inner container, a heat resistance layer is arranged on the outer surface of the inner container, a barrier layer is arranged outside the heat resistance layer, the barrier layer is a shell structure matched with the outer shape of the inner container, a first vacuum zone is formed between the barrier layer and the inner container, and the barrier layer is made of a non-metal material capable of preventing gas permeation;

[0007] The outer layer of the barrier layer is provided with a heat insulation layer, and the heat insulation layer is provided with an outer shell body made of non-metallic material, and a second vacuum area is formed between the outer shell body and the barrier layer.

[0008] The vacuum degree of the second vacuum area is higher than that of the first vacuum area.

[0009] Further technical solutions are as follows.

[0010] The material of the inner container is aluminum alloy, and the structure of the inner container comprises a cylindrical shell and arc-shaped heads arranged at both ends of the cylindrical shell, a plurality of annular reinforcing ribs are arranged on the outer surface of the cylindrical shell in the axial direction, and the arc-shaped heads are rotary shells, and the rotary curved surface line type of the arc-shaped heads is an isostatic curve.

[0011] A plurality of fixing members for supporting the barrier layer are arranged between the inner container and the barrier layer, and the structure of a single fixing member comprises a block-shaped ring, the material of the ring is metal, the ring is welded to the outer surface of the inner container, and the inner portion of the ring is provided with a plug hole, and the structure further comprises a block-shaped plug, the outer surface of the plug is a tapered surface, and the tapered surface is in linear contact with the opening end of the plug hole.

[0012] One end of the plug penetrates through the opening on the barrier layer and is matched with the ring, and the other end of the plug is located at the opening, the outer surface of the barrier layer at the opening is fixed with a closing plate, and the closing plate is matched with the end of the plug to fix the position of the plug.

[0013] The plug is a quadrangular pyramid, the plug hole is a square hole, and the four tapered surfaces of the plug are respectively in linear contact with the four edges of the opening end of the plug hole.

[0014] The heat resistance layer is a foamed plastic filler wrapped with a polyester film, and the foamed plastic material is polymethacrylimide rigid foamed plastic or polyurethane foamed plastic.

[0015] The barrier layer is divided into an upper shell, a middle shell and a lower shell arranged in the axial direction of the inner container outside the heat resistance layer in sequence, the upper shell, the middle shell and the lower shell are connected by welding, the material of the upper shell, the middle shell and the lower shell is ultra-high molecular weight polyethylene, and the upper shell, the middle shell and the lower shell are formed by rolling or injection molding.

[0016] The heat insulation layer is formed by laying a plurality of layers of heat insulation materials on the surface of the barrier layer.

[0017] The structure of the outer shell comprises an inner shell for preventing gas leakage, the structure of the inner shell comprises upper, middle and lower inner shells arranged in sequence along the axial direction of the inner container outside the heat insulation layer, the upper, middle and lower inner shells are connected by welding, the space between the heat insulation layer and the inner shell is the second vacuum area, the inner wall of the inner shell is provided with a plurality of stiffeners in contact with the heat insulation layer, and the upper, middle and lower inner shells are formed by rolling or injection molding;

[0018] The outer part of the inner shell is a composite material shell prepared by laying and pasting a prepreg tape or a prepreg cloth made of carbon fiber and resin.

[0019] The barrier layer and the outer shell body are respectively provided with first and second pipe interfaces, the first and second pipe interfaces correspond to the functional pipe on the inner container, and the structures of the first and second pipe interfaces are the same;

[0020] The structure of the second pipe interface comprises an inner joint with a cap structure, a first hexagonal boss is arranged on the edge of the opening end of the inner joint, the first hexagonal boss is matched with the inner surface of the outer shell body, and is used for limiting the rotation of the inner joint relative to the outer shell body, an inner interface is arranged on the bottom of the inner joint, and the structure of the second pipe interface further comprises an outer joint with a tubular structure, the inner part of the outer joint is a channel, one end of the outer joint penetrates through the outer shell body and is threadedly connected with the inner joint, the channel is communicated with the inner interface, the other end of the outer joint is located outside the outer shell body and is provided with a second hexagonal boss, and the first and second hexagonal bosses are sealingly matched with the outer shell body through gaskets;

[0021] The end of the functional pipe is connected with the inner interface of the first pipe interface, and the channel of the first pipe interface is connected with the inner interface of the second pipe interface through an intermediate pipe.

[0022] A manufacturing method of a liquid hydrogen storage bottle shell light weight structure, comprising the following steps:

[0023] Step one, making a metal inner container;

[0024] Step two, welding a ring between the outer surface of the inner container and the adjacent two annular reinforcing ribs, and making a plurality of rings at the same position along the axial direction of the inner container distributed at equal intervals on the outer wall of the inner container;

[0025] Step three, according to the position of the ring and the size of the inner container, laying and pasting a polyacrylimide rigid foam plastic or polyurethane foam plastic filler on the outer surface of the inner container, and then wrapping a polyester film to form a heat insulation layer;

[0026] Step four, use ultra-high molecular weight polyethylene to form the plastic shell of the three-section convolute by rotational molding or injection molding, which are the upper shell, the middle shell and the lower shell, and the upper shell and the lower shell correspond to the arc-shaped end cover;

[0027] Step five, open the hole corresponding to the plug-in ring on the barrier layer, open the through hole corresponding to the functional pipeline on the inner container on the barrier layer, and install the first pipeline interface at the through hole;

[0028] Step six, put the upper shell, the middle shell and the lower shell outside the heat insulation layer, connect the functional pipeline on the inner container with the first pipeline interface, align the hole with the plug-in ring, insert the plug into the hole of the plug-in ring through the hole on the barrier layer, and seal the hole by bonding or welding with the same sealing plate as the barrier layer material, at this time the position of the plug is fixed, the upper shell, the middle shell and the lower shell are attached outside the heat insulation layer, and then the first vacuum area is formed between the barrier layer and the inner container by welding;

[0029] Step seven, lay the heat insulation layer on the outer surface of the barrier layer;

[0030] Step eight, use high-density polyethylene or nylon to make the inner lining shell inside the outer shell, adopt rotational molding or injection molding to form the three-section shell, which are the upper inner lining, the middle inner lining and the lower inner lining, and the upper inner lining and the lower inner lining correspond to the arc-shaped end cover, and form the reinforcing member on the middle inner lining;

[0031] Step nine, open the hole on the inner lining shell and install the second pipeline interface, put the upper inner lining, the middle inner lining and the lower inner lining outside the heat insulation layer, connect the first pipeline interface and the second pipeline interface with the intermediate pipe, and then weld the upper inner lining, the middle inner lining and the lower inner lining to form a sealed shell, and form the second vacuum area between the inner lining shell and the barrier layer;

[0032] Step ten, lay the prepreg or prepreg tape made of carbon fiber and resin on the outer surface of the inner lining shell to form a composite shell, and then put it into an oven for curing and forming;

[0033] Step eleven, vacuumize the first vacuum area and the second vacuum area, the pressure of the first vacuum area is in the order of 10 - 3 torr, and the pressure of the second vacuum area is in the order of 10 -4 torr and below 10 -4 torr.

[0034] The beneficial effects of the present application are as follows:

[0035] This invention features a compact and rational structure, and is easy to operate. By sequentially setting a non-metallic barrier layer and an outer shell around the metal inner liner, and isolating two independent and heat-insulated vacuum zones, the weight of the hydrogen storage tank shell is reduced while improving the safety of the liquid hydrogen storage tank. Even if one vacuum zone fails, a large amount of heat will not flow into the hydrogen storage tank, causing the stored liquid hydrogen to suddenly heat up and vaporize. The two independent vacuum zones have different vacuum levels, which can also reduce the cost of vacuum treatment. Thus, the container shell structure is optimized based on vacuum insulation, achieving a lightweight design for liquid hydrogen storage containers.

[0036] Furthermore, the present invention also has the following advantages:

[0037] (1) The design of the fixed component adopts the "minimum contact surface" method, which can effectively reduce the effect of heat conduction.

[0038] (2) In this embodiment, when selecting the materials for the barrier layer and inner liner shell constituting the two vacuum zones, ultra-high molecular weight polyethylene (UHMWPE) and general high-density polyethylene (HDPE) or nylon (PA6 or PA66) polymer barrier materials were used, based on the temperature distribution and the lower limit of the material's operation under low-temperature conditions. These polymer materials have excellent gas permeability resistance, which can effectively maintain the vacuum state of the enclosed space. At the same time, their density is significantly lower than that of metal materials, reducing the weight of the hydrogen storage tank shell.

[0039] (3) The outer layer of the hydrogen storage tank shell, that is, the heat-insulating structure adjacent to the outer shell, consists of a high-vacuum second vacuum zone and a multi-layered heat-insulating layer made of a plastic sheet (MLI) with a metal (aluminum) coating on the surface. Due to the presence of the vacuum space, the heat transfer of this heat-insulating structure is mainly thermal radiation plus thermal conduction through the reinforcing members (i.e., the supporting structure). This "high vacuum + MLI material" approach can effectively reduce the heat input from the outside.

[0040] (4) By installing a pipe interface with two-sided interfaces at the opening on the non-metallic shell, the shell at the pipe interface is sealed, and pipes can be connected on the inner and outer sides of the shell. This effectively prevents gas from penetrating at the connection between the metal pipe and the non-metallic shell, thus maintaining the vacuum level in the corresponding range and facilitating the installation of the pipe system. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of the present invention.

[0042] Figure 2 This is a schematic diagram of the structure of the shell wall of the present invention.

[0043] Figure 3 This is a schematic diagram of the inner liner of the present invention.

[0044] Figure 4 Structure diagram of the barrier layer of the present application.

[0045] Figure 5 Structure diagram of the fixing member of the present application.

[0046] Figure 6 Structure diagram of the fixing member of the present application.

[0047] Figure 7 Structure diagram of the second pipe interface of the present application.

[0048] Figure 8 Structure diagram of the second pipe interface of the present application (perspective view).

[0049] Figure 9 Thermodynamic phase diagram of hydrogen.

[0050] Figure 10 Elongation curve shape of the top of the arc-shaped head.

[0051] Figure 11 Perspective view of the arc-shaped head.

[0052] Wherein: 1, inner container; 11, arc-shaped head; 12, cylindrical shell; 13, ring-shaped reinforcing rib;

[0053] 2, fixing member; 21, insertion ring; 211, insertion hole; 22, plug; 23, closure plate;

[0054] 3, heat-insulating layer; 4, barrier layer; 41, upper shell; 42, middle shell; 43, lower shell; 44, opening; 5, thermal insulation layer; 6, second vacuum area;

[0055] 7, outer shell; 71, inner lining shell; 711, reinforcing member; 72, composite material outer shell;

[0056] 8, second pipe interface; 81, external connector; 811, passage; 812, second hexagonal boss; 82, gasket; 83, internal connector; 831, internal interface; 832, first hexagonal boss. DETAILED DESCRIPTION

[0057] The specific embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0058] Example 1:

[0059] As Figures 1-2As shown, the liquid hydrogen storage bottle shell lightweight structure of the embodiment includes an inner container 1, the outer surface of the inner container 1 is provided with a heat insulation layer 3, the heat insulation layer 3 is provided with a barrier layer 4, the barrier layer 4 is a shell structure matched with the shape of the inner container 1, a first vacuum area is formed between the barrier layer 4 and the inner container 1, and the barrier layer 4 is a non-metal material capable of preventing gas permeation;

[0060] The barrier layer 4 is provided with an insulating layer 5 on the outer layer, the insulating layer 5 is provided with an outer shell 7, the outer shell 7 is a non-metal material, and a second vacuum area 6 is formed between the outer shell 7 and the barrier layer 4;

[0061] The vacuum degree of the second vacuum area 6 is higher than that of the first vacuum area.

[0062] The barrier layer 4 and the outer shell 7 of the non-metal material are sequentially arranged outside the metal inner container 1, and two independent and heat-insulated vacuum areas are isolated, thereby reducing the weight of the hydrogen storage bottle shell and improving the safety of the liquid hydrogen storage bottle. Even if one of the vacuum areas fails, a large amount of heat flow will not be transmitted into the hydrogen storage bottle to cause the liquid hydrogen stored therein to suddenly heat and vaporize. The vacuum degrees of the two independent vacuum areas are different, and such distribution can also reduce the cost of vacuum treatment, thereby optimizing the container shell structure based on the vacuum heat insulation mode and realizing the lightweight design of the liquid hydrogen storage container.

[0063] The first vacuum area is a "soft" vacuum (pressure is in the order of 10 -3 torr); and the second vacuum area is a high vacuum (pressure is in the order of 10 -4 torr and below 10 -4 torr).

[0064] In specific implementation, the first vacuum area can be controlled at 0.5x10 -3 to 1.0x10 -3 torr; and the pressure of the second vacuum area 6 can be considered as 0.5x10 -4 torr or below.

[0065] Further, as shown in Figure 1 , Figure 3 , the material of the inner container 1 is aluminum alloy, and the structure of the inner container 1 includes a cylindrical shell 12 and arc-shaped heads 11 arranged at both ends of the cylindrical shell 12. The cylindrical shell 12 is provided with a plurality of annular reinforcing ribs 13 arranged at intervals along the axial direction on the outer surface, and the arc-shaped heads 11 are rotary shells. The rotary curved surface line type of the arc-shaped heads 11 is an isotensoid curve.

[0066] Specifically, the innermost metal aluminum alloy inner container 1 plays a role in preventing hydrogen leakage and bearing, and resists the load of the pressure of the liquid hydrogen in the saturated state applied to the inner wall surface of the inner container, as shown in Figure 9As shown: liquid hydrogen at -253℃ contains vapor pressure of about one atmosphere, at the critical temperature -240℃, its critical saturation vapor pressure is about 12.8 atmospheres, when the temperature of the liner 1 is higher than its critical temperature, liquid hydrogen will no longer exist, become gaseous or supercritical state; the choice of alloy aluminum is because it has good hydrogen embrittlement resistance as austenitic alloy steel, but it is lighter than the latter; the design of the liner 1 is further detailed as follows:

[0067] i) The preliminary design of the wall thickness of the liner 1 can be first estimated according to the following formula (a):

[0068]

[0069] In formula (a), the radius of the liner 1 is R0, the thickness is t, is the highest saturated vapor pressure on the hydrogen saturation curve (about 1.28 MPa), σ S is the tensile or yield strength of the metal of the liner 1;

[0070] The thickness of the liner 1 given in formula (a) is the minimum reference thickness, and the actual thickness also needs to consider the safety factor and local stress concentration;

[0071] ii) The curved surface design of the arc-shaped part of the liner 1: the most ideal case is to design the arc shape as a convolute formed by an isochoric curve (as shown in Figure 10 ), which can be calculated according to the following formula (b) (for details, see: L. Zu, S. Koussios, and A. Beukers. 2010. Composites: Part A. 41: 1312-1320):

[0072]

[0073] Formula (b) is applicable to anisotropic composite shells, in formula (b), ρ is the dimensionless radius of the convolute, ζ is the dimensionless height of the convolute, k is the anisotropy index, and α is the deflection angle; for details, see the above cited literature.

[0074] For isotropic metals, k = 1, so formula (b) becomes:

[0075]

[0076] The isochoric curve of the arc-shaped head 11 of the liner 1 can be calculated according to formula (c) (as shown in Figure 10 ).

[0077] When the above calculated arc-shaped surface is suitable for being adopted due to process forming technology or cost control, the end face member can be prepared by simply giving the R-angle forming mode, but the corresponding wall thickness needs to be thickened in the transition area of the arc top.

[0078] iii) The inner container 1 has a ring-shaped reinforcing structure on its outer surface, which further increases the load-bearing capacity of the inner container 1. The load-bearing capacity of the reinforced inner container 1 is further strengthened, and precise strength analysis results can be obtained through CAE finite element software simulation.

[0079] Further, as shown in Figures 1-6 , a plurality of fixing members 2 for supporting the barrier layer 4 are arranged between the inner container 1 and the barrier layer 4. The structure of a single fixing member 2 is as follows: a ring-shaped insert 21 with a block structure, the insert 21 being made of metal and welded to the outer surface of the inner container 1, and the insert 21 having an insert hole 211 inside; and a block-shaped plug 22, the outer surface of the plug 22 being a tapered surface, and the tapered surface being in linear contact with the opening end of the insert hole 211.

[0080] One end of the plug 22 is in cooperation with the insert 21 after passing through the opening 44 on the barrier layer 4, and the other end of the plug 22 is located at the opening 44. The outer surface of the barrier layer 4 at the opening 44 is fixed with a closing plate 23, and the closing plate 23 cooperates with the end of the plug 22 to fix the position of the plug 22.

[0081] Specifically, the insert 21 is a metal structure or other light metal with the same material as the inner container 1. The plurality of fixing members 2 are evenly distributed along the outer wall of the inner container in a ring shape. The fixing member 2 is designed in a "minimum contact surface" manner, which can effectively reduce the effect of heat conduction.

[0082] The opening 44 is processed on the barrier layer 4 made of ultra-high molecular weight polyethylene (UHMWPE), which is used to place the plug 22 in the insert hole 211 of the insert 21. After the plug 22 is placed, the opening 44 is sealed by the closing plate 23 at the opening 44 to prevent gas transmission in the gap between the fixing member 2 and the barrier layer 4. The assembled fixing member 2 plays a role in fixing the barrier layer 4.

[0083] Further, as shown in Figure 5 , the plug 22 is a four-pyramid, and the insert hole 211 is a square hole. The four tapered surfaces of the plug 22 are in linear contact with the four edges of the opening end of the insert hole 211, respectively. This structure is convenient to process and saves materials.

[0084] Embodiment Two:

[0085] This embodiment further reasonably configures the material selection and structure of the two vacuum zones based on the structure of Embodiment One.

[0086] The heat-resistant layer 3 is a foam plastic filler wrapped with a polyester film. The foam plastic material is polymethacrylimide rigid foam plastic or polyurethane foam plastic.

[0087] Specifically, a distributed PMI foam or PU foam filler is laid on the outer surface of the inner container 1 to form a heat barrier layer body; the foam filler can be applied in a "soft" vacuum environment (pressure in the order of 10 -3 torr); theoretically, the heat transfer index k-value of the foam filler under this condition is in the order of 1 (mW / m-K).

[0088] As shown in Figure 4 , the barrier layer 4 is divided into an upper shell 41, a middle shell 42 and a lower shell 43 arranged in turn along the inner container axis 1 outside the heat barrier layer 3, and the upper shell 41, the middle shell 42 and the lower shell 43 are connected by welding, and the material of the upper shell 41, the middle shell 42 and the lower shell 43 is ultra-high molecular weight polyethylene, which is formed by roto-molding or injection molding.

[0089] Specifically, the barrier layer is established by using ultra-high molecular weight polyethylene (UHMWPE), which can work at very low temperatures such as -200°C, and does not reach the low temperature requirement of -253°C of the inner container 1 wall surface, but due to the effect of the heat barrier layer 3 of PMI or PU mentioned above and the heat flow introduced from the outside, the temperature here is generally not lower than -200°C.

[0090] As shown in Figures 1-2 , the heat insulation layer 5 is formed by laying multiple layers of heat insulation material on the surface of the barrier layer 4.

[0091] Specifically, the heat insulation material is MLI (multi-layer insulation), which is composed of multiple layers of thin polymeric materials such as polyimide (PI) or polyester (PLI), and the surface of the thin sheet is coated with a metal (such as aluminum) coating for reflecting heat from the outside radiation; the heat insulation layer 5 formed by MLI should be applied in a high vacuum environment (pressure in the order of 10 -4 torr and below 10 -4 torr); the k-value of MLI under high vacuum conditions can reach the order of 0.1 or less; the outside of the heat insulation layer 5 is a high vacuum space, and the outer boundary of the high vacuum space is the outer shell 7.

[0092] As shown in Figures 1-2As shown, the structure of the outer shell 7 includes an inner liner 71 for preventing gas leakage, the structure of the inner liner 71 includes an upper inner liner, a middle inner liner and a lower inner liner which are sequentially arranged axially outside the thermal insulation layer 5, the upper inner liner, the middle inner liner and the lower inner liner are connected by welding, the space between the thermal insulation layer 5 and the inner liner 71 is the second vacuum area 6, and the inner wall of the inner liner 71 is provided with a plurality of stiffeners 711 in contact with the thermal insulation layer 5, and the upper inner liner, the middle inner liner and the lower inner liner are formed by rolling or injection molding.

[0093] The outer part of the inner liner 71 is a composite material shell 72 which is prepared by laying a prepreg tape or prepreg cloth made of carbon fiber and resin.

[0094] Specifically, the inner liner 71 is used to prevent external gas from penetrating, and the material of the inner liner is high-density polyethylene (HDPE) or nylon (such as PA6 or PA66); the stiffeners 711 can increase the rigidity and strength of the shell 71, and can also support the outer shell 7;

[0095] The composite material shell 72 is prepared by laying a prepreg tape made of carbon fiber and resin by a tape laying machine, or manually laying a prepreg cloth on the outer surface of the above-mentioned high polymer inner liner 71 to obtain the composite material shell 72; for a container with a smaller size, a fiber winding forming process can also be used to complete the forming, and the composite material shell 72 is cured and formed in an oven; the composite material shell 72 bears external pressure and ensures that the shell does not have a local instability phenomenon under the required external force; the thickness of the inner liner 71 and the support effect of the stiffeners 711 on the inner surface of the inner liner 71 are analyzed in advance by using industrialized CAE finite element analysis software (such as abaqus, ansys and nastran) to obtain an optimized configuration that meets the requirements of industry standards and achieves the purpose of lightweight; the total thickness of the composite material shell 72 and the fiber angle of each layer can be optimized by mechanical simulation calculation according to the requirements of structural strength and rigidity.

[0096] In this embodiment, when selecting the materials of the barrier layer 4 and the inner liner 71 constituting the two vacuum areas, according to the distribution of temperature and the lower limit of the material under low temperature conditions, ultra-high molecular weight polyethylene (UHMWPE) and general high-density polyethylene (HDPE) or nylon (PA6 or PA66) high polymer barrier materials are used respectively. These high polymer materials have good gas permeation resistance and can effectively maintain the vacuum state of the enclosed space, and their density is significantly lower than that of metal materials, thereby reducing the weight of the hydrogen storage bottle shell.

[0097] The outer layer of the hydrogen storage bottle shell, i.e. the heat insulation structure next to the outer shell 7, is composed of a second vacuum area 6 with high vacuum degree and a heat insulation layer 5 composed of a multi-layer structure of plastic sheets (MLI) with metal (aluminum) sprayed on the surface. Due to the existence of the vacuum space, the heat transfer is mainly thermal radiation plus heat conduction through the stiffeners 711 (i.e. the support structure), and such a "high vacuum + MLI material" mode can effectively reduce the heat conduction from the outside.

[0098] The barrier layer 4 and the inner liner shell 71 are formed separately by injection molding or rotational molding, and after the parts are placed in the corresponding positions, they are welded together by laser or heat welding to realize the forming and assembly of the sealed shell.

[0099] Example Three:

[0100] The liquid hydrogen storage container also usually has complex internal and external systems, including support suspension, hydrogen charging and discharging pipeline, pressure reducing and pressurizing valve, vacuum control system, cooling system and temperature and pressure monitoring system, etc. These can be referred to the design of existing metal liquid hydrogen bottles, and will not be described in detail here.

[0101] Unlike the metal liquid hydrogen storage container, the non-metal barrier layer 4 and the outer shell 7 are used in the above-mentioned examples, which involves the sealing and assembly problems between the special-shaped materials of the metal pipeline passing through the non-metal shell.

[0102] This embodiment gives a configuration design scheme of an interface sealing element based on the above-mentioned examples, and the scheme is as follows:

[0103] As shown in Figures 7-8 , the barrier layer 4 and the outer shell 7 are respectively provided with a first pipeline interface and a second pipeline interface 8, which correspond to the functional pipelines on the inner container 1, and the structures of the first pipeline interface and the second pipeline interface 8 are the same.

[0104] The structure of the second pipeline interface 8 is as follows: an inner joint 83 with a cap-shaped structure, a first hexagonal boss 832 is arranged on the edge of the opening end of the inner joint 83, which cooperates with the inner surface of the outer shell 7 to limit the rotation of the inner joint 83 relative to the outer shell 7, and an inner interface 831 is arranged at the bottom of the inner joint 83; an outer joint 81 with a tubular structure, the inside of the outer joint 81 is a channel 811, one end of the outer joint 81 is threadedly connected with the inner joint 83 after penetrating through the outer shell 7, the channel 811 is in communication with the inner interface 831, and the other end of the outer joint 81 is located outside the outer shell 7 and is provided with a second hexagonal boss 812, and the first hexagonal boss 832 and the second hexagonal boss 812 are both sealed and cooperated with the outer shell 7 through a gasket 82;

[0105] The end of the functional pipeline is connected with the inner interface 831 of the first pipeline interface, and the channel 811 of the first pipeline interface is connected with the inner interface 831 of the second pipeline interface 8 through an intermediate pipe.

[0106] Specifically, the functional pipeline is not shown in Figure 1 ; a hexagonal recess matching the first hexagonal boss 832 is arranged on the inner surface of the outer shell 7, the inner interface 831 is internally threaded, and the outer joint 81 is internally threaded at the connection with the pipeline, as shown in Figure 7 .

[0107] By installing a pipeline interface with two interfaces at the hole of the non-metal shell, the shell sealing at the pipeline interface is realized, and the pipeline can be connected on both sides of the shell, effectively preventing gas penetration at the connection structure of the metal pipeline and the non-metal shell, achieving the purpose of maintaining the vacuum degree of the corresponding interval, and facilitating the installation of the pipeline system.

[0108] Embodiment Four:

[0109] As shown in Figures 1-11 , this embodiment introduces a manufacturing method of a lightweight structure of a liquid hydrogen storage hydrogen bottle shell based on the above embodiments:

[0110] including the following steps:

[0111] Step one, make the metal liner 1;

[0112] Step one includes:

[0113] Material selection of the liner 1: Since hydrogen can cause hydrogen embrittlement with most metals, the material can be 6061 alloy aluminum or austenitic alloy steel. Considering that the density of steel is much higher than that of the former, the embodiment adopts 6061 alloy aluminum;

[0114] Structure of the liner 1: Determine the shape and thickness of the metal liner:

[0115] Liner shape: this invention takes the shape shown in Figure 3 as an example; including a cylindrical shell 12 and an arc-shaped head 11 at both ends, wherein:

[0116] The shape of the arc-shaped head 11 adopts an isotropic tension curve, and the curve shape can be obtained from formula (c), as shown in Figure 11 . If limited to forming process and cost, a simple geometric shape can also be used, but abrupt angle changes in the transition area should be avoided;

[0117] The thickness t of the inner container 1: The inner container 1 has two functions, one is to prevent hydrogen leakage, and the other is to bear the internal pressure load, so when designing the thickness of the inner container 1, it should be calculated according to the working pressure of the liquid hydrogen storage cylinder; if 6061 alloy aluminum is selected as the metal inner container material, its yield strength is about 276 MPa, and the tensile fracture strength is about 310 MPa (for the sake of safety, the yield strength can be used for calculation),

[0118] Assuming the radius R0 of the container is 0.6 m, the height H0 is 1.5 m, and the σ S = 276 MPa, Then the minimum inner container thickness t min according to formula (a) is:

[0119] t min ≈ 2.8 mm

[0120] The wall thickness of the metal inner container obtained above is the theoretical minimum value, and the actual structural design needs to consider the safety factor according to the industry standard. When there is no clear industry standard, some relevant high-pressure cylinder design standards can be used for estimation, for example, set the safety factor to 2.3 (national standard GB / T 42612-2023), according to the recommended value in the literature (B.W. Tew, 1995. Transactions of the ASME. 117: pp390-394), the thermal attenuation factor is 0.8, and the stress concentration factor is 0.75, so the metal design thickness can be preliminarily selected as:

[0121]

[0122] Determine the position of the pipe opening on the inner container 1 in order to install the corresponding various pipelines and valve systems, and set multiple ring stiffeners 13 on the outer surface of the cylindrical shell 12, the ring stiffeners 13 and the inner container 1 are made of the same material, which is 6061 alloy aluminum, and the ring stiffeners 13 and the inner container 1 with local openings are analyzed more accurately for stress and strength by using finite element CAE software (such as ansys, abaqus, nastran or other industrialized CAE software), and the corresponding fatigue life prediction is carried out.

[0123] Use common metal processing techniques (such as forging heat treatment, machining forgings, spinning forming, integral heat treatment, etc.) to prepare the cylindrical shell 12 and the arc-shaped head 11; after the cylindrical shell 12 and the arc-shaped head 11 are formed, the ring stiffeners 13 are installed on the outer surface of the cylindrical shell 12 of the inner container 1 by welding, and the functional pipelines are installed at the pipe opening position of the inner container 1.

[0124] Step two, welding the insert ring 21 on the outer surface of the inner container 1 between two adjacent ring stiffeners 13, and making the multiple insert rings 21 at the same axial position of the inner container 1 equidistantly distributed on the outer wall of the inner container 1.

[0125] Step three, after laying the polymethacrylimide rigid foam or polyurethane foam filler on the outer surface of the inner container 1 according to the position of the insert ring 21 and the size of the inner container 1, wrapping the outer surface with Mylar film to form the thermal barrier layer 3.

[0126] In step three, the polyester film Mylar-wrapped polymethacrylimide rigid foam or polyurethane foam plastic is adhered to the outer surface of the inner container 1 using an epoxy propane (Epon)-polyamide resin (Versamid)-based adhesive that can withstand ultra-low temperature (or NHJ-44 adhesive, polyurethane modified epoxy adhesive, DWJ-46 adhesive that matches the expansion coefficient of polyimide and aluminum tank, etc. for bonding the common bottom and thermal insulation layer of the liquid hydrogen and liquid oxygen storage tank of the launch vehicle, which are all domestic products).

[0127] Step four, using ultra-high molecular weight polyethylene to form the plastic thin shells of the three-section convolute by rotational molding or injection molding, which are the upper shell 41, the middle shell 42, and the lower shell 43, and the upper shell 41 and the lower shell 43 correspond to the arc-shaped head 11.

[0128] Step five, opening the hole 44 corresponding to the insert ring 21 on the barrier layer 4, opening the through hole corresponding to the functional pipeline on the inner container 1 on the barrier layer 4, and installing the first pipeline interface at the through hole.

[0129] Step six, fitting the upper shell 41, the middle shell 42, and the lower shell 43 outside the thermal barrier layer 3, connecting the functional pipeline on the inner container 1 with the first pipeline interface, aligning the hole 44 with the insert ring 21, inserting the plug 22 into the socket 211 of the insert ring 21 through the hole 44 on the barrier layer 4, and then sealing the hole 44 with the same sealing plate 23 as the material of the barrier layer 4 by adhesion or welding, at this time the position of the plug 22 is fixed, the upper shell 41, the middle shell 42, and the lower shell 43 are attached outside the thermal barrier layer 3, and then the barrier layer 4 and the inner container 1 are connected by welding to form a sealed first vacuum area.

[0130] Step seven, laying the thermal insulation layer 5 on the outer surface of the barrier layer 4.

[0131] In step seven, the thermal insulation layer 5 is made of multi-layer insulation (MLI), which is composed of multiple layers of polymer materials such as polyimide (PI) or polyester (PLI), and the surface of the sheet is coated with a metal (such as aluminum) coating, which can be purchased or self-prepared.

[0132] Step eight, the inner liner 71 is made of high-density polyethylene or nylon and is located inside the outer shell 7. The three-section liner is formed by rotational molding or injection molding, including the upper section, the middle section, and the lower section. The upper section and the lower section correspond to the arc-shaped end cover 11, and the reinforcing member 711 is formed on the middle section.

[0133] Step nine, the second pipe interface 8 is installed on the inner liner 71. After the upper section, the middle section, and the lower section are sleeved outside the thermal insulation layer 5, the first pipe interface and the second pipe interface 8 are connected by an intermediate pipe, and then the upper section, the middle section, and the lower section are welded to form a sealed shell, thereby forming the second vacuum area 6 between the inner liner 71 and the barrier layer 4.

[0134] Step ten, the outer shell 72 is formed by laying carbon fiber reinforced resin prepreg or prepreg tape on the outer surface of the inner liner 71, and then curing and forming in an oven.

[0135] The thickness and fiber placement angle of the composite outer shell 72 are designed according to the shape of the container and the working condition of the internal and external pressure difference (one atmosphere) by using CAE finite element software to ensure that the composite outer shell 72 meets the use requirements.

[0136] Step eleven, the first vacuum area and the second vacuum area 6 are subjected to vacuum treatment. The pressure of the first vacuum area is on the order of 10 - 3 torr, and the pressure of the second vacuum area 6 is on the order of 10 -4 torr and below 10 -4 torr. In specific implementation, the first vacuum area can be controlled at 0.5x10 -3 to 1.0x10 -3 torr; and the pressure of the second vacuum area 6 can be considered 0.5x10 -4 torr or below.

[0137] The above method not only realizes the assembly of the metal inner liner 1 and the two non-metal vacuum shells, but also realizes the sealing installation of the functional pipe of the inner liner 1 through different materials. The manufacturing method and assembly method are simple, and the weight of the hydrogen storage bottle shell is reduced.

[0138] The technical points of the above embodiment are:

[0139] The materials are selected according to the minimum working temperature, heat resistance, density, and mechanical properties of the non-metallic materials (including thermal insulation materials, gas barrier layers, support elements, and adhesives, etc.), and the thermal insulation materials are reasonably arranged according to the temperature distribution in the liquid hydrogen storage container shell, the setting of the vacuum area, and the requirements of structural strength and stiffness to prevent the materials from failing in a low-temperature environment outside their working temperature range.

[0140] The inner container 1 is externally provided with two barrier layers (the inner liner 71 and the barrier layer 4) made of polymer, which are used to maintain the vacuum degree of the corresponding vacuum zones, and form two independent vacuum zones, and the heat insulation materials in the two vacuum zones are adapted to the vacuum degrees of the two vacuum zones.

[0141] The liquid hydrogen storage bottle shell design and manufacturing scheme are improved and optimized in terms of the design of corresponding components, the selection of materials and corresponding process forming technologies, so as to realize the lightweight design and manufacturing of the liquid hydrogen storage container.

[0142] The above description is an explanation of the application, not a limitation of the application, the scope of the application is defined in the claims, within the protection scope of the application, any form of modification can be made.

Claims

1. A method for manufacturing a lightweight structure for a liquid hydrogen storage cylinder shell, characterized in that: Includes the following steps: Step 1: Make a metal inner liner (1). The inner liner (1) includes a cylindrical shell (12) and arc-shaped end caps (11) at both ends of the cylindrical shell (12). The outer surface of the cylindrical shell (12) is provided with multiple circumferential reinforcing ribs (13) at intervals along the axial direction. Step 2: Weld the insert rings (21) to the outer surface of the inner liner (1) between two adjacent circumferential reinforcing ribs (13), and distribute multiple insert rings (21) at the same position along the axial direction of the inner liner (1) at equal intervals on the outer wall of the inner liner (1); Step 3: Based on the position of the insert ring (21) and the size of the inner liner (1), lay polymethyl methacrylate rigid foam or polyurethane foam filler on the outer surface of the inner liner (1) and then wrap it with a polyester film to form a heat-insulating layer (3). Step 4: Use ultra-high molecular weight polyethylene to form a three-section spiral plastic shell by rotational molding or injection molding, namely the upper shell (41), the middle shell (42) and the lower shell (43), with the upper shell (41) and the lower shell (43) corresponding to the arc-shaped end cap (11). Step 5: The barrier layer (4) is divided into an upper shell (41), a middle shell (42) and a lower shell (43). An opening (44) corresponding to the insert ring (21) is made on the barrier layer (4). A through hole corresponding to the functional pipeline on the inner liner (1) is made on the barrier layer (4), and the first pipeline interface is installed at the through hole. Step 6: Place the upper shell (41), middle shell (42) and lower shell (43) on the outside of the heat-insulating layer (3) and connect the functional pipeline on the inner liner (1) to the first pipeline interface. Align the opening (44) with the plug ring (21), insert the plug (22) through the opening (44) on the barrier layer (4) into the plug hole (211) of the plug ring (21), and seal the opening (44) with a sealing plate (23) of the same material as the barrier layer (4) by bonding or welding. At this time, the position of the plug (22) is fixed. The upper shell (41), middle shell (42) and lower shell (43) are attached to the outside of the heat-insulating layer (3) and then connected by welding to form a sealed first vacuum zone between the barrier layer (4) and the inner liner (1). Step 7: Lay a heat insulation layer (5) on the outer surface of the barrier layer (4); Step 8: Use high-density polyethylene or nylon to make an inner liner shell (71) located inside the outer shell (7). Use rotational molding or injection molding to form three sections of shell, namely the upper inner liner, the middle inner liner and the lower inner liner. The upper inner liner and the lower inner liner correspond to the arc-shaped end cap (11), and a reinforcing member (711) is formed on the middle inner liner. Step 9: Make a hole in the inner liner shell (71) and install the second pipeline interface (8). After the upper, middle and lower inner liners are put over the insulation layer (5), the first pipeline interface and the second pipeline interface (8) are connected with an intermediate pipe. The insulation layer (5) is in contact with the reinforcing member (711). Then the upper, middle and lower inner liners are welded to form a sealed shell, forming a second vacuum zone (6) between the inner liner shell (71) and the barrier layer (4). Step 10: Lay a prepreg or prepreg tape made of carbon fiber and resin on the outer surface of the inner liner shell (71) to form a composite material shell (72), and then put it into an oven to cure and shape. Step 11: Perform vacuum treatment on the first vacuum zone and the second vacuum zone (6). The pressure in the first vacuum zone is 10. - 3 The pressure in the second vacuum region (6) is on the order of torr, and the pressure is on the order of 10. -4 The magnitude of torr and 10 -4 The order of magnitude below torr.

2. The method for manufacturing the lightweight structure of the liquid hydrogen storage tank shell as described in claim 1, characterized in that: The inner liner (1) is made of aluminum alloy, the arc-shaped end cap (11) is a rotating shell, and the rotating surface of the arc-shaped end cap (11) is an isotension curve.

3. The method for manufacturing the lightweight structure of the liquid hydrogen storage tank shell as described in claim 1, characterized in that: Multiple fixing components (2) for supporting the barrier layer (4) are provided between the inner liner (1) and the barrier layer (4). The structure of a single fixing component (2) is as follows: it includes a block-shaped insert ring (21) made of metal, and the insert ring (21) has a socket (211) inside. It also includes a block-shaped plug (22) with a conical outer surface and the conical surface in line contact with the opening end of the socket (211).

4. The method for manufacturing the lightweight structure of the liquid hydrogen storage tank shell as described in claim 3, characterized in that: The plug (22) is a square pyramid, the socket (211) is a square hole, and the four conical surfaces of the plug (22) respectively contact the four side lines of the opening end of the socket (211).

5. The method for manufacturing the lightweight structure of the liquid hydrogen storage tank shell as described in claim 1, characterized in that: The insulation layer (5) is formed by laying multiple layers of insulation material on the surface of the barrier layer (4).

6. The method for manufacturing the lightweight structure of the liquid hydrogen storage tank shell as described in claim 1, characterized in that: The first pipe interface and the second pipe interface (8) have the same structure; The structure of the second pipeline interface (8) is as follows: it includes an inner connector (83) with a cap-like structure, a first hexagonal boss (832) provided on the edge of the opening end of the inner connector (83), the first hexagonal boss (832) cooperating with the inner surface of the outer shell (7) to restrict the rotation of the inner connector (83) relative to the outer shell (7), an inner interface (831) provided at the bottom of the inner connector (83), and also includes an outer connector (81) with a tubular structure. The interior of the outer connector (811) is a channel (811). One end of the outer connector (81) passes through the outer shell (7) and is threadedly connected to the inner connector (83). The channel (811) communicates with the inner interface (831). The other end of the outer connector (81) is located on the outside of the outer shell (7) and is provided with a second hexagonal boss (812). The first hexagonal boss (832) and the second hexagonal boss (812) are both sealed to the outer shell (7) through a gasket (82). The end of the functional pipeline is connected to the inner interface (831) of the first pipeline interface, and the channel (811) of the first pipeline interface is connected to the inner interface (831) of the second pipeline interface (8) through an intermediate connecting pipe.

Images