Liquid hydrogen storage device and method

Abstract

The invention discloses a liquid hydrogen storage device and method, and relates to the technical field of liquid hydrogen. The device comprises a helium circulating pipeline, a liquid hydrogen storage tank and a cold screen, the helium circulation pipeline is sequentially connected with the helium compressor unit, the cooler, a high-temperature channel of the heat regenerator, the helium expansion machine, the cold shield and a low-temperature channel of the heat regenerator and returns to the helium compressor unit. The cold shield is located in the liquid hydrogen storage tank and comprises a plurality of variable-density sub cold shields which are connected through valves from top to bottom, and the variable-density sub cold shields are further connected with an inlet and an outlet of the cold shield through valves respectively, so that the variable-density sub cold shields with the required number and position can operate according to needs; the bottom of the liquid hydrogen storage tank is connected with a filling pipeline with a filling valve, and the top of the liquid hydrogen storage tank is connected with an exhaust pipeline with an exhaust valve. Aiming at the coupling link of the active refrigerating machine and the liquid hydrogen storage tank, a novel cold shield structure is designed based on the temperature distribution of the liquid hydrogen storage tank, the efficiency of the reverse Brayton refrigerating machine is maximized, the evaporation loss of liquid hydrogen is reduced, and the storage period is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid hydrogen, and in particular to a liquid hydrogen storage device and method. Background Art

[0002] Cryogenic propellants, due to their high specific impulse and lack of pollution, have become the propellant of choice for deep space exploration missions such as lunar and Mars exploration. The United States has conducted research on on-orbit refueling modes for both its lunar return program and its manned Mars exploration mission. Before on-orbit refueling, the engine can be briefly ignited to generate gravity, achieving the initial state of gas-liquid phase separation before refueling with cryogenic propellant. Due to the temperature difference from ambient temperature propellants, on-orbit refueling of cryogenic propellants includes two functions: storage and refueling. The former mainly weakens or offsets the adverse effects of external heat sources, while the latter mainly enables the efficient transfer of propellant from the refueling station to the spacecraft. The combination of the two constitutes the on-orbit refueling capability of cryogenic propellants. Therefore, it is crucial to achieve long-term storage by reducing the evaporation of cryogenic propellants.

[0003] The saturation temperature of liquid hydrogen propellant at atmospheric pressure is approximately 20.28K, which is much lower than that of liquid xenon, liquid methane, and liquid oxygen. It is also suitable for both chemical and nuclear thermal propulsion, and has become a typical representative of on-orbit research on cryogenic propellants. Liquid hydrogen on-orbit storage technologies can be divided into two categories: passive and active. Among them, active technologies mainly include thermodynamic exhaust technology and cryogenic refrigerator technology, which are suitable for medium- and long-term storage needs. The reverse Brayton refrigerator has the advantages of a wide temperature range, few moving parts, long life, and low vibration. It has great potential in the field of on-orbit storage of liquid hydrogen propellant. However, how to achieve efficient coupling of the reverse Brayton refrigerator and the liquid hydrogen storage tank is still a blank. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the prior art and provide a liquid hydrogen storage device and method. This invention addresses the coupling between an active refrigerator and a liquid hydrogen storage tank, designing a novel cold shield structure based on the temperature distribution of the liquid hydrogen storage tank. This maximizes the efficiency of the reverse Brayton refrigerator, reduces liquid hydrogen evaporation losses, and increases the storage cycle.

[0005] The specific technical solutions adopted in the present invention are as follows:

[0006] In a first aspect, the present invention provides a liquid hydrogen storage device comprising a helium circulation pipeline, a liquid hydrogen storage tank, and a cold shield;

[0007] The helium circulation pipeline is connected in sequence to the helium compressor unit, the cooler, the high-temperature channel of the regenerator, the helium expander, the cold screen, the low-temperature channel of the regenerator and returns to the helium compressor unit to form a closed thermal cycle loop; a branch is provided on the helium circulation pipeline between the low-temperature channel of the regenerator and the helium compressor unit, and the branch enters the helium buffer tank after passing through a helium shut-off valve; the helium circulation pipeline enters the cold screen from an inlet located in the high-temperature gas phase zone of the liquid hydrogen storage tank and flows out of the cold screen from an outlet located in the low-temperature liquid phase zone of the liquid hydrogen storage tank; the cold screen is located inside the liquid hydrogen storage tank and includes several variable-density quantum cold screens connected from top to bottom by valves, and each variable-density quantum cold screen is also connected to the inlet and outlet of the cold screen by a valve, so that the required number and position of variable-density quantum cold screens can operate as needed; the bottom of the liquid hydrogen storage tank is connected to a filling pipeline provided with a filling valve, and the top is connected to an exhaust pipeline provided with an exhaust valve.

[0008] Preferably, the helium compressor unit comprises at least three helium compressors connected in series.

[0009] Preferably, in the variable density quantum cold shield, the density of the cold shield pipelines is greater where the liquid hydrogen temperature is higher.

[0010] Preferably, the inlet of the cold screen is located at the upper part, and the outlet is located at the lower part.

[0011] Preferably, the variable density sub-cold screen is provided with two, namely a variable density upper cold screen and a variable density lower cold screen; the helium circulation pipeline located in the cold screen is divided into two branches, the first branch is connected in sequence to the first stop valve, the variable density upper cold screen inlet, the variable density upper cold screen, the variable density upper cold screen outlet and the fourth stop valve, the second branch is connected in sequence to the second stop valve, the variable density lower cold screen inlet, the variable density lower cold screen and the variable density lower cold screen outlet, and then the two branches merge and flow out of the cold screen; the variable density upper cold screen outlet and the variable density lower cold screen inlet are connected by a pipeline provided with a third stop valve.

[0012] Preferably, the exhaust line is connected to an external exhaust pipe.

[0013] Preferably, the cooler adopts a water cooling cycle.

[0014] Preferably, the helium circulation pipeline, the filling pipeline and the exhaust pipeline are all provided with an insulation layer on the outside.

[0015] In a second aspect, the present invention provides a liquid hydrogen storage method using the liquid hydrogen storage device described in the first aspect, as follows:

[0016] Open the filling valve and exhaust valve, and external liquid hydrogen enters the liquid hydrogen storage tank through the filling valve via the filling pipeline; first pre-cool the liquid hydrogen storage tank, and then carry out the filling process. The vaporized hydrogen generated during the pre-cooling and filling process is discharged through the exhaust valve via the exhaust pipeline; after the liquid hydrogen is filled to the specified liquid level height of the liquid hydrogen storage tank, close the filling valve to complete the filling; when the helium circulating working medium cools the liquid hydrogen storage tank through the helium circulating pipeline, close the exhaust valve to reduce hydrogen loss and prevent air backflow;

[0017] During the cooling process, one of the operating modes S1 to S3 is selected according to the different temperature distributions inside the liquid hydrogen storage tank, as follows:

[0018] S1: Open the first stop valve, the third stop valve and the helium stop valve; the helium buffer tank replenishes helium to the helium circulation pipeline through the helium stop valve, and then closes the helium stop valve; start the helium compressor unit and the helium expander in sequence, the helium circulating working medium is first compressed by the helium compressor unit, and the helium circulating working medium after pressure increase and temperature increase is initially cooled by the cooler, and then enters the high-temperature channel of the regenerator to continue heat exchange and cooling, and transfers heat to the helium circulating working medium in the low-temperature channel of the regenerator. After the secondary cooling, the helium circulating working medium enters the helium expander for expansion, pressure reduction and temperature reduction, and enters the cold screen after reaching the set temperature; in the cold screen, the helium circulating working medium first enters the variable density upper cold screen through the first stop valve to cool the upper half of the inner cavity of the liquid hydrogen storage tank, and then the initially heated helium circulating working medium enters the variable density lower cold screen through the third stop valve to cool the lower half of the inner cavity of the liquid hydrogen storage tank, and the secondary heated helium circulating working medium flows out of the cold screen, enters the low-temperature channel of the regenerator through the helium circulation pipeline, absorbs heat and enters the helium compressor unit again for compression;

[0019] S2: Open the first stop valve, the fourth stop valve and the helium stop valve; the helium buffer tank replenishes helium to the helium circulation pipeline through the helium stop valve, and then closes the helium stop valve; start the helium compressor unit and the helium expander in sequence, the helium circulating working medium is first compressed by the helium compressor unit, and the helium circulating working medium after pressure increase and temperature increase is initially cooled by the cooler, and then enters the high-temperature channel of the regenerator to continue heat exchange and cooling, and transfers heat to the helium circulating working medium in the low-temperature channel of the regenerator. After the secondary cooling, the helium circulating working medium enters the helium expander for expansion, pressure reduction and temperature reduction, and enters the cold screen after reaching the set temperature; in the cold screen, the helium circulating working medium first enters the variable density upper cold screen through the first stop valve to cool the upper half of the inner cavity of the liquid hydrogen storage tank, and then the initially heated helium circulating working medium flows out of the cold screen through the fourth stop valve, enters the low-temperature channel of the regenerator through the helium circulation pipeline, absorbs heat and enters the helium compressor unit again for compression;

[0020] S3: Open the second stop valve and the helium stop valve; the helium buffer tank replenishes helium to the helium circulation pipeline through the helium stop valve, and then closes the helium stop valve; start the helium compressor unit and the helium expander in sequence, the helium circulating working fluid is first compressed by the helium compressor unit, and the helium circulating working fluid after pressure increase and temperature increase is initially cooled by the cooler, and then enters the high-temperature channel of the regenerator to continue heat exchange and cooling, and transfers heat to the helium circulating working fluid in the low-temperature channel of the regenerator. After the secondary cooling, the helium circulating working fluid enters the helium expander for expansion, pressure reduction and temperature reduction, and enters the cold screen after reaching the set temperature; in the cold screen, the helium circulating working fluid first enters the variable density lower cold screen through the second stop valve to cool the lower half of the inner cavity of the liquid hydrogen storage tank, and then the initially heated helium circulating working fluid flows out of the cold screen, enters the low-temperature channel of the regenerator through the helium circulation pipeline, absorbs heat and enters the helium compressor unit again for compression;

[0021] By selecting one of the helium circulating working fluids to circulate back and forth along the helium circulating pipeline in accordance with the S1 to S3 operating modes, the evaporation rate of liquid hydrogen inside the liquid hydrogen storage tank can be greatly reduced or zero evaporation can be achieved.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The helium circulating fluid of the reverse Brayton refrigeration system is directly cooled by a novel cold screen structure, avoiding intermediate heat exchange and offering the advantages of compact structure and high heat exchange efficiency. The cold screen, designed in parallel with the inner and outer walls of the liquid hydrogen storage tank, has multiple operating modes, which can enhance the cooling freedom of the reverse Brayton refrigerator and achieve specific cooling of the "high-temperature area" of the liquid hydrogen storage tank. At the same time, the cold screen coil is designed as a variable-density cold screen with a positive correlation between the density value and the liquid hydrogen temperature value, comprehensively improving the cooling effect. Furthermore, the inlet of the helium circulating fluid at the cold screen is located in the high-temperature gas phase area of the liquid hydrogen storage tank, and the outlet is located in the low-temperature liquid phase area of the liquid hydrogen storage tank, improving the overall heat exchange efficiency between the liquid hydrogen storage tank and the helium circulating fluid.

[0024] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of a liquid hydrogen storage device of the present invention.

[0026] In the figure: helium circulation pipeline 1, helium compressor unit 2, cooler 3, regenerator 4, helium expander 5, liquid hydrogen storage tank 6, cold screen 7, first stop valve 8, variable density upper cold screen inlet 9, variable density upper cold screen 10, variable density upper cold screen outlet 11, second stop valve 12, third stop valve 13, variable density lower cold screen inlet 14, variable density lower cold screen 15, variable density lower cold screen outlet 16, fourth stop valve 17, helium buffer tank 18, helium stop valve 19, filling pipeline 20, filling valve 21, exhaust pipeline 22, exhaust valve 23. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in the various embodiments of the present invention can be combined accordingly without conflicting with each other.

[0028] In the description of the present invention, it should be understood that when an element is considered to be "connected" to another element, it can be directly connected to the other element or indirectly connected, that is, there are intermediate elements. On the contrary, when an element is said to be "directly" connected to another element, there are no intermediate elements.

[0029] In the description of the present invention, it should be understood that the terms "first," "second," "third," and "fourth" are used solely for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being described. Therefore, a feature identified as "first," "second," "third," or "fourth" may explicitly or implicitly include at least one of such features.

[0030] like Figure 1 As shown, it is a schematic diagram of the connection structure of a liquid hydrogen storage device provided by a preferred embodiment of the present invention. The device mainly includes a helium circulation pipeline 1, a helium compressor unit 2, a cooler 3, a regenerator 4, a helium expander 5, a liquid hydrogen storage tank 6, a cold shield 7, a first stop valve 8, a variable density upper cold shield inlet 9, a variable density upper cold shield 10, a variable density upper cold shield outlet 11, a second stop valve 12, a third stop valve 13, a variable density lower cold shield inlet 14, a variable density lower cold shield 15, a variable density lower cold shield outlet 16, a fourth stop valve 17, a helium buffer tank 18, a helium stop valve 19, a filling pipeline 20, a filling valve 21, an exhaust pipeline 22, and an exhaust valve 23.

[0031] It should be noted that the regenerator 4 is provided with two low-temperature channels and a high-temperature channel that can form heat exchange with each other.

[0032] The structure and connection method of each component will be described in detail below.

[0033] In the device of the present invention, the helium circulation pipeline 1 sequentially connects the helium compressor unit 2, the cooler 3, the high-temperature passage of the regenerator 4, the helium expander 5, the cold screen 7, the low-temperature passage of the regenerator 4, and returns to the helium compressor unit 2, forming a closed thermal cycle. The helium circulation pipeline 1 also includes a branch. One end of the branch connects to the helium circulation pipeline 1 between the low-temperature passage of the regenerator 4 and the helium compressor unit 2, and the other end connects to the helium buffer tank 18 through a helium shut-off valve 19. This branch allows for the filling and storage of helium during the helium circulation process.

[0034] As a preferred embodiment of the present invention, the helium compressor unit 2 includes at least three helium compressors, which are connected in series.

[0035] As a preferred embodiment of the present invention, the cooler 3 may adopt a water cooling cycle to improve the temperature stability of the helium circulating working medium.

[0036] In the device of the present invention, the helium circulation pipeline 1 enters from the inlet of the cold screen 7 and then flows out from the outlet of the cold screen 7, wherein the inlet of the cold screen 7 is set in the gas phase high temperature area of the liquid hydrogen storage tank 6, and the outlet of the cold screen 7 is set in the liquid phase low temperature area of the liquid hydrogen storage tank 6, so as to improve the overall cold utilization efficiency.

[0037] As a preferred embodiment of the present invention, the cold shield 7 is arranged vertically, with its inlet located at the upper part and its outlet located at the lower part.

[0038] In the device of the present invention, the cold shield 7 is located inside the liquid hydrogen storage tank 6 and comprises a plurality of variable-density quantum cold shields arranged from top to bottom. Each variable-density quantum cold shield is sequentially connected end-to-end via valves. Each variable-density quantum cold shield is also connected to the inlet and outlet of the cold shield 7 via valves. This ensures that when the cold shield 7 is in operation, the required number and position of variable-density quantum cold shields can be coordinated and operated as needed.

[0039] As a preferred embodiment of the present invention, Figure 1As shown, two variable-density sub-cold shields are provided: an upper variable-density cold shield 10 and a lower variable-density cold shield 15. Components such as a first shut-off valve 8, a second shut-off valve 12, a third shut-off valve 13, and a fourth shut-off valve 17 are also provided in conjunction with this structure. These components are connected via a helium circulation pipeline 1. The upper variable-density cold shield 10 has an upper variable-density cold shield inlet 9 at its top and an upper variable-density cold shield outlet 11 at its bottom. The lower variable-density cold shield 15 has a lower variable-density cold shield inlet 14 at its top and an lower variable-density cold shield outlet 16 at its bottom. The helium circulation pipeline 1 within the cold shield 7 is divided into two branches. The first branch sequentially connects the first shut-off valve 8, the variable density upper cold shield inlet 9, the variable density upper cold shield 10, the variable density upper cold shield outlet 11, and the fourth shut-off valve 17, thereby cooling the area inside the liquid hydrogen storage tank 6 corresponding to the variable density upper cold shield 10. The second branch sequentially connects the second shut-off valve 12, the variable density lower cold shield inlet 14, the variable density lower cold shield 15, and the variable density lower cold shield outlet 16, thereby cooling the area inside the liquid hydrogen storage tank 6 corresponding to the variable density lower cold shield 15. The two branches then merge and flow out of the cold shield 7. In addition, the variable density upper cold shield outlet 11 and the variable density lower cold shield inlet 14 are connected by a pipeline equipped with a third shut-off valve 13. In other words, the variable density upper cold shield outlet 11 of the first branch and the variable density lower cold shield inlet 14 of the second branch are connected by a pipeline equipped with the third shut-off valve 13, thereby enabling the helium circulating medium to flow from the variable density upper cold shield 10 to the variable density lower cold shield 15.

[0040] Of course, in addition to the two-stage parallel setting of the variable density upper cold screen and the variable density lower cold screen provided in this embodiment, the cold screen area can also be changed to a multi-stage parallel setting to improve the control flexibility of the reverse Brayton refrigeration system.

[0041] During actual use, the low-temperature helium circulating medium flows in the cold shield 7 , thereby realizing the cooling function of the liquid hydrogen inside the liquid hydrogen storage tank 6 .

[0042] As a preferred embodiment of the present invention, the density of the variable-density quantum cold screen is positively correlated with the liquid hydrogen temperature value, that is, the higher the liquid hydrogen temperature in the liquid hydrogen storage tank, the greater the density of the cold screen pipelines, thereby improving the cooling response speed.

[0043] In the device of the present invention, a filling line 20 is provided at the bottom of the liquid hydrogen storage tank 6, connecting the inner cavity of the liquid hydrogen storage tank 6 with the filling line 20. A filling valve 21 is provided on the filling line 20 to control the filling operation of the liquid hydrogen. An exhaust line 22 is provided at the top of the liquid hydrogen storage tank 6, connecting the inner cavity of the liquid hydrogen storage tank 6 with the exhaust line 22. An exhaust valve 23 is provided on the exhaust line 22 to control the exhaust operation of the hydrogen.

[0044] As a preferred embodiment of the present invention, the exhaust line 22 is connected to an external exhaust pipe.

[0045] As a preferred embodiment of the present invention, the helium circulation pipeline 1, the filling pipeline 20 and the exhaust pipeline 22 are all provided with an insulation layer on the outside to prevent heat leakage.

[0046] The present invention also provides a liquid hydrogen storage method using the above liquid hydrogen storage device. Figure 1 A liquid hydrogen storage device structure of a preferred embodiment is shown (i.e., two variable density quantum cold screens are provided, namely, a variable density upper cold screen 10 and a variable density lower cold screen 15), to illustrate the liquid hydrogen storage method of the present invention (i.e., the operating principle).

[0047] Assume that the system has been replaced and all valves are closed.

[0048] Liquid hydrogen filling stage:

[0049] Open filling valve 21 and exhaust valve 23, and external liquid hydrogen enters liquid hydrogen storage tank 6 through filling valve 21 via filling line 20. Liquid hydrogen storage tank 6 is first precooled, followed by the filling process. The vaporized hydrogen generated during the precooling and filling process is discharged through exhaust line 22 and exhaust valve 23. Once the liquid hydrogen reaches the specified level in liquid hydrogen storage tank 6, fill valve 21 is closed, completing the filling process. While the helium circulating medium cools liquid hydrogen storage tank 6 through helium circulating line 1, exhaust valve 23 is closed to minimize hydrogen loss and prevent air backflow.

[0050] Because the temperature field within the liquid hydrogen storage tank 6 fluctuates significantly during filling, storage, and transfer, conventional overall cooling will reduce response time and energy efficiency. Therefore, the cold shield 7 can operate in different modes depending on different operating conditions. Under the device structure provided in this embodiment, the operating modes include: 1) Mode 1: The variable density upper cold shield 10 and the variable density lower cold shield 15 operate together to achieve uniform cooling across the entire area of the liquid hydrogen storage tank 6; 2) Mode 2: The variable density upper cold shield 10 operates alone to achieve rapid cooling of the high-temperature gas phase region in the upper half of the liquid hydrogen storage tank 6; 2) Mode 3: The variable density lower cold shield 15 operates alone to achieve rapid cooling of the low-temperature liquid phase region in the lower half of the liquid hydrogen storage tank 6.

[0051] When reducing the evaporation rate of the liquid hydrogen storage tank 6 during the filling, storage, and transfer processes, the operating mode is selected according to the different temperature distributions. That is, during the cooling process, the cold shield can select one of the three operating modes according to the different temperature distributions inside the liquid hydrogen storage tank 6, as follows:

[0052] Mode 1: The variable density upper cooling screen 10 and the variable density lower cooling screen 15 operate together:

[0053] Open the first shut-off valve 8, the third shut-off valve 13, and the helium shut-off valve 19. The helium buffer tank 18 replenishes helium into the helium circulation pipeline 1 through the helium shut-off valve 19, and then closes the helium shut-off valve 19. The helium compressor unit 2 and the helium expander 5 are sequentially started. The helium circulating medium is first compressed by the helium compressor unit 2. After being pressurized and heated, the helium circulating medium is initially cooled by the cooler 3. It then enters the high-temperature channel of the regenerator 4 for further heat exchange and cooling, transferring heat to the helium circulating medium in the low-temperature channel of the regenerator 4. After the secondary cooling, the helium circulating medium enters the helium expander 5 for expansion, pressure reduction, and temperature reduction. After reaching the set temperature, it enters the cold screen 7. In the cold shield 7, the helium circulating medium first enters the variable density upper cold shield 10 through the first stop valve 8 to cool the upper half of the inner cavity of the liquid hydrogen storage tank 6. Then, the helium circulating medium that has been initially heated enters the variable density lower cold shield 15 through the third stop valve 13 to cool the lower half of the inner cavity of the liquid hydrogen storage tank 6. The helium circulating medium that has been heated for the second time flows out of the cold shield 7, enters the low-temperature channel of the regenerator 4 through the helium circulation pipeline 1, absorbs heat, and enters the helium compressor unit 2 for compression again.

[0054] Mode 2: variable density upper cold screen 10 runs alone:

[0055] Open the first shut-off valve 8, the fourth shut-off valve 17, and the helium shut-off valve 19. Helium is replenished from the helium buffer tank 18 to the helium circulation pipeline 1 through the helium shut-off valve 19, and then the helium shut-off valve 19 is closed. The helium compressor unit 2 and the helium expander 5 are sequentially started. The helium circulating fluid is first compressed by the helium compressor unit 2. After being pressurized and heated, the helium circulating fluid passes through the cooler 3 for initial cooling. It then enters the high-temperature channel of the regenerator 4 for further heat exchange and cooling, transferring heat to the helium circulating fluid in the low-temperature channel of the regenerator 4. After this secondary cooling, the helium circulating fluid enters the helium expander 5 for expansion, pressure reduction, and temperature reduction. Once it reaches the set temperature, it enters the cold screen 7. Within the cold screen 7, the helium circulating fluid first passes through the first shut-off valve 8 and enters the variable-density upper cold screen 10, cooling the upper half of the interior of the liquid hydrogen storage tank 6. The initially heated helium circulating fluid then flows out of the cold screen 7 through the fourth shut-off valve 17, passes through the helium circulation pipeline 1, enters the low-temperature channel of the regenerator 4, absorbs heat, and then enters the helium compressor unit 2 for compression again.

[0056] Mode 3: Cold screen 15 operates independently under variable density:

[0057] Open the second shut-off valve 12 and the helium shut-off valve 19. Helium buffer tank 18 replenishes helium to helium circulation pipeline 1 through helium shut-off valve 19, and then closes helium shut-off valve 19. The helium compressor unit 2 and helium expander 5 are sequentially started. The helium circulating fluid is first compressed by the helium compressor unit 2. After being pressurized and heated, the helium circulating fluid passes through cooler 3 for initial cooling. It then enters the high-temperature channel of the regenerator 4 for further heat exchange and cooling, transferring heat to the helium circulating fluid in the low-temperature channel of the regenerator 4. After this secondary cooling, the helium circulating fluid enters the helium expander 5 for expansion, pressure reduction, and temperature reduction. Once it reaches the set temperature, it enters the cold screen 7. Within the cold screen 7, the helium circulating fluid first passes through the second shut-off valve 12 and enters the variable-density lower cold screen 15, cooling the lower half of the interior of the liquid hydrogen storage tank 6. The initially heated helium circulating fluid then flows out of the cold screen 7, passes through the helium circulation pipeline 1, enters the low-temperature channel of the regenerator 4, absorbs heat, and then enters the helium compressor unit 2 for compression again.

[0058] By the helium circulating medium reciprocating along the helium circulating pipeline 1 according to one of the above-mentioned operating modes, the evaporation rate of the liquid hydrogen inside the liquid hydrogen storage tank 6 can be greatly reduced or zero evaporation can be achieved.

[0059] Of course, if other liquid hydrogen storage methods using variable density quantum cold screens are used, the same principle applies. The variable density quantum cold screens in each area can be operated individually or in combination as needed. Those skilled in the art will understand the operation method based on the method provided in this embodiment, and will not be described in detail here.

[0060] The embodiment described above is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent substitution or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A liquid hydrogen storage device, characterized in that: It comprises a helium circulation pipeline (1), a liquid hydrogen storage tank (6) and a cold shield (7); The helium circulation pipeline (1) is connected in sequence to the helium compressor unit (2), the cooler (3), the high-temperature channel of the regenerator (4), the helium expander (5), the cold screen (7), the low-temperature channel of the regenerator (4) and returns to the helium compressor unit (2), forming a closed thermal cycle loop; a branch is provided on the helium circulation pipeline (1) located between the low-temperature channel of the regenerator (4) and the helium compressor unit (2), and the branch enters the helium buffer tank (18) after passing through the helium stop valve (19); the helium circulation pipeline (1) enters the liquid hydrogen storage tank (6) from the inlet located in the gas phase high-temperature zone A cold screen (7) is provided, and the cold screen (7) flows out of the cold screen (7) from an outlet located in a liquid phase low temperature zone of the liquid hydrogen storage tank (6); the cold screen (7) is located inside the liquid hydrogen storage tank (6), and includes a plurality of variable density quantum cold screens connected from top to bottom through valves, each variable density quantum cold screen is also connected to the inlet and outlet of the cold screen (7) through a valve, so that the variable density quantum cold screens of the required number and position can be operated as required; the bottom of the liquid hydrogen storage tank (6) is connected to a filling pipeline (20) provided with a filling valve (21), and the top is connected to an exhaust pipeline (22) provided with an exhaust valve (23).

2. A liquid hydrogen storage device according to claim 1, characterized in that: The helium compressor unit (2) comprises at least three helium compressors connected in series.

3. A liquid hydrogen storage device according to claim 1, characterized in that: In the variable density quantum cold shield, the density of the cold shield pipelines is greater where the liquid hydrogen temperature is higher.

4. A liquid hydrogen storage device according to claim 1, characterized in that: The inlet of the cold screen (7) is located at the upper part, and the outlet is located at the lower part.

5. The liquid hydrogen storage device according to claim 1, characterized in that: The variable density sub-cold screen is provided with two, namely a variable density upper cold screen (10) and a variable density lower cold screen (15); the helium circulation pipeline (1) located in the cold screen (7) is divided into two branches, the first branch is connected in sequence to the first stop valve (8), the variable density upper cold screen inlet (9), the variable density upper cold screen (10), the variable density upper cold screen outlet (11) and the fourth stop valve (17); the second branch is connected in sequence to the second stop valve (12), the variable density lower cold screen inlet (14), the variable density lower cold screen (15) and the variable density lower cold screen outlet (16), and then the two branches are merged and flow out of the cold screen (7); the variable density upper cold screen outlet (11) and the variable density lower cold screen inlet (14) are connected through a pipeline provided with a third stop valve (13).

6. The liquid hydrogen storage device according to claim 1, characterized in that: The exhaust line (22) is connected to an external exhaust pipe.

7. The liquid hydrogen storage device according to claim 1, characterized in that: The cooler (3) adopts a water cooling cycle.

8. The liquid hydrogen storage device according to claim 1, characterized in that: The helium circulation pipeline (1), the filling pipeline (20) and the exhaust pipeline (22) are all provided with a heat insulation layer on the outside.

9. A method for storing liquid hydrogen using the liquid hydrogen storage device according to claim 5, characterized in that: The details are as follows: The filling valve (21) and the exhaust valve (23) are opened, and external liquid hydrogen enters the liquid hydrogen storage tank (6) through the filling valve (21) via the filling pipeline (20); first, the liquid hydrogen storage tank (6) is precooled, and then the filling process is carried out, and the vaporized hydrogen generated during the precooling and filling process is discharged through the exhaust pipeline (22) and the exhaust valve (23); after the liquid hydrogen is filled to a specified liquid level height of the liquid hydrogen storage tank (6), the filling valve (21) is closed to complete the filling; when the helium circulating working medium cools the liquid hydrogen storage tank (6) through the helium circulating pipeline (1), the exhaust valve (23) is closed to reduce hydrogen loss and prevent air backflow; During the cooling process, one of the operation modes S1 to S3 is selected according to the different temperature distributions inside the liquid hydrogen storage tank (6), as follows: S1: Open the first stop valve (8), the third stop valve (13) and the helium stop valve (19); the helium buffer tank (18) replenishes helium to the helium circulation pipeline (1) through the helium stop valve (19), and then closes the helium stop valve (19); the helium compressor unit (2) and the helium expander (5) are started in sequence, and the helium circulation working medium is first compressed by the helium compressor unit (2), and the helium circulation working medium after the pressure and temperature are increased is initially cooled by the cooler (3), and then enters the high-temperature channel of the regenerator (4) to continue heat exchange and cooling, and transfers heat to the helium circulation working medium in the low-temperature channel of the regenerator (4). After the secondary cooling, the helium circulation working medium is cooled. The working medium enters the helium expander (5) for expansion, decompression and temperature reduction, and enters the cold screen (7) after reaching the set temperature; in the cold screen (7), the helium circulating working medium first enters the variable density upper cold screen (10) through the first stop valve (8) to cool the upper half of the inner cavity of the liquid hydrogen storage tank (6); then the helium circulating working medium with initial temperature increase enters the variable density lower cold screen (15) through the third stop valve (13) to cool the lower half of the inner cavity of the liquid hydrogen storage tank (6); the helium circulating working medium with secondary temperature increase flows out of the cold screen (7), enters the low-temperature channel of the regenerator (4) through the helium circulation pipeline (1), absorbs heat and enters the helium compressor unit (2) again for compression; S2: Open the first stop valve (8), the fourth stop valve (17) and the helium stop valve (19); the helium buffer tank (18) replenishes helium to the helium circulation pipeline (1) through the helium stop valve (19), and then closes the helium stop valve (19); start the helium compressor unit (2) and the helium expander (5) in sequence, and the helium circulation working medium is first compressed by the helium compressor unit (2). The helium circulation working medium after pressure increase and temperature increase passes through the cooler (3) for preliminary cooling, and then enters the high-temperature channel of the regenerator (4) to continue heat exchange and cooling, and transfers heat to the regenerator (4). The helium circulating working medium in the low-temperature channel, after being cooled twice, enters the helium expander (5) for expansion, pressure reduction and temperature reduction, and enters the cold screen (7) after reaching the set temperature; in the cold screen (7), the helium circulating working medium first enters the variable density upper cold screen (10) through the first stop valve (8) to cool the upper half of the inner cavity of the liquid hydrogen storage tank (6); then, the helium circulating working medium with initial temperature increase flows out of the cold screen (7) through the fourth stop valve (17), enters the low-temperature channel of the regenerator (4) through the helium circulation pipeline (1), absorbs heat and enters the helium compressor unit (2) again for compression; S3: Open the second stop valve (12) and the helium stop valve (19); the helium buffer tank (18) replenishes helium to the helium circulation pipeline (1) through the helium stop valve (19), and then closes the helium stop valve (19); the helium compressor unit (2) and the helium expander (5) are started in sequence, and the helium circulation working medium is first compressed by the helium compressor unit (2), and the helium circulation working medium after the pressure and temperature are increased is initially cooled by the cooler (3), and then enters the high-temperature channel of the regenerator (4) to continue heat exchange and cooling, and transfers heat to the regenerator (4). The helium circulating working medium in the low-temperature channel, after being cooled twice, enters the helium expander (5) for expansion, pressure reduction and temperature reduction, and enters the cold screen (7) after reaching the set temperature; in the cold screen (7), the helium circulating working medium first enters the variable density lower cold screen (15) through the second stop valve (12) to cool the lower half of the inner cavity of the liquid hydrogen storage tank (6), and then the helium circulating working medium with initial temperature increase flows out of the cold screen (7), enters the low-temperature channel of the regenerator (4) through the helium circulation pipeline (1), absorbs heat and enters the helium compressor unit (2) again for compression; By selecting one of the helium circulating working fluids to circulate back and forth along the helium circulating pipeline (1) in accordance with the S1 to S3 operating modes, the evaporation rate of liquid hydrogen inside the liquid hydrogen storage tank (6) is greatly reduced or zero evaporation is achieved.

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