A liquid methane rapid supercooling device and method thereof

Abstract

The application discloses a liquid methane rapid subcooling device and a method thereof. In the device, a spiral tapering methane pipeline is divided into multiple parts through open containers with gradually increasing diameters. When the outlet temperature of the methane is regulated, the liquid level in the open containers is adjusted from top to bottom. Since the volume of the liquid nitrogen medium in the upper open container is small, the response is very fast during temperature regulation. Meanwhile, when the liquid level in the open container is lowered to a certain value, the boiling heat transfer coefficient of the pipeline surface will obviously increase with the decrease of the liquid level, that is, there is a critical liquid level in each open container, which can improve the boiling heat transfer coefficient of the liquid nitrogen medium as a whole. The sparse needle ribs arranged at the front end of the spiral tapering methane pipeline can effectively overcome the gas film heat transfer weakening phenomenon caused by strong boiling due to large subcooling degree, and the dense needle ribs at the rear end can increase the bubble generation rate under small subcooling degree.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cryogenic propellant densification, in particular to a liquid methane rapid subcooling device and method thereof. BACKGROUND

[0002] With the rise of reusable rocket concepts, rocket engines using liquid oxygen / methane propellant combinations have received increasing attention. Compared with kerosene, methane has higher vacuum specific impulse, excellent regenerative cooling and membrane cooling performance, and almost no carbon deposition during combustion. Therefore, under the background of the rapid development of commercial spaceflight in the 20th century, methane is considered to be a promising propellant. By means of deep subcooling and other methods, the density and sensible heat of the methane propellant will be greatly increased, and the saturation pressure will be greatly reduced, so as to effectively reduce the size of the on-board tank and the pressure of the propellant entering the engine, further improving the performance of the methane propellant.

[0003] The deep subcooling method can be divided into helium bubble subcooling, vacuum subcooling and low-temperature medium heat transfer subcooling. The helium bubble subcooling utilizes the endothermic phenomenon when the methane propellant diffuses into the helium bubble to cool down, which has the advantages of simple operation and fast subcooling speed, but a large amount of helium is consumed. The vacuum subcooling reduces the gas-liquid saturation temperature, thereby causing the low-temperature propellant to spontaneously vaporize and absorb heat to cool down, which has the advantages of simple equipment and low investment, but the performance requirements of the vacuum system are relatively high. The low-temperature medium heat transfer subcooling directly subcools the methane by using liquid helium or liquid nitrogen medium. Since the triple point temperature of methane is 90.69K, which is higher than the standard boiling point of liquid nitrogen medium 77K, the low-temperature medium heat transfer subcooling method using liquid nitrogen medium is currently the most promising densification method. However, when using liquid nitrogen medium to cool the methane propellant, the liquid nitrogen medium will produce violent boiling, and the vaporized nitrogen will affect the heat transfer efficiency of the liquid nitrogen and the methane. At the same time, since the boiling point of liquid nitrogen is lower than the triple point temperature of methane, there is a risk of ice blocking of the methane propellant inside the heat exchanger. SUMMARY

[0004] The purpose of the present application is to provide a liquid methane rapid subcooling device to improve the subcooling rate of methane under liquid nitrogen boiling conditions, while precisely controlling the outlet temperature of methane and preventing ice blocking.

[0005] The present application adopts the following technical solutions to achieve the purpose of the present application:

[0006] In a first aspect, the present application provides a liquid methane rapid subcooling device, which comprises an adiabatic tank body, the adiabatic tank body is provided with a liquid nitrogen filling pipeline, a spiral tapered methane pipeline and a stepped container structure, and the top of the adiabatic tank body is provided with a nitrogen discharge pipe for discharging nitrogen in the tank;

[0007] The stepped container structure is formed by vertically arranging a plurality of open containers with open top;

[0008] The inlet end of the liquid nitrogen filling pipeline is connected to an external liquid nitrogen source, and the rear end is located inside the adiabatic tank and is divided into a plurality of liquid nitrogen filling branches. A liquid nitrogen filling valve is arranged on each liquid nitrogen filling branch to control the opening and closing of the pipeline.

[0009] The open containers in the stepped container structure gradually increase in volume from top to bottom. Each open container corresponds to a liquid nitrogen filling branch for filling liquid nitrogen medium into the container. Each open container is provided with a liquid nitrogen emptying valve at the bottom. The liquid nitrogen medium in the upper open container can be discharged into the lower open container by opening the liquid nitrogen emptying valve at the bottom, so as to sequentially regulate the liquid level of the liquid nitrogen medium in each open container from top to bottom.

[0010] The inlet of the spiral tapered methane pipeline is located at the bottom of the adiabatic tank, and the outlet extends out of the top of the adiabatic tank. The main pipeline in the inner cavity of the adiabatic tank includes a plurality of concentric ring pipes arranged vertically in steps. Each ring pipe is horizontally arranged, and adjacent ring pipes are connected by inclined pipes to continuously transport liquid methane. The diameters of all the ring pipes gradually increase from top to bottom. The main pipeline sequentially passes through each open container in the stepped container structure from bottom to top. Each open container has a plurality of ring pipes within the liquid level regulation range of the liquid nitrogen medium. Each ring pipe can form a heat exchange with the liquid nitrogen medium to cool the internal liquid methane.

[0011] The outer surface of the main pipeline is arranged with needle ribs at intervals, and the density of the needle ribs on the main pipeline gradually changes from dense to sparse along the flow direction of the methane.

[0012] As a preferred embodiment of the first aspect, the stepped container structure includes three open containers, namely a first open container, a second open container, and a third open container. The outlet end of the liquid nitrogen filling pipeline is divided into three liquid nitrogen filling branches, and the three liquid nitrogen filling branches are respectively provided with a first liquid nitrogen filling valve, a second liquid nitrogen filling valve, and a third liquid nitrogen filling valve for controlling the filling of liquid nitrogen medium into the first open container, the second open container, and the third open container, respectively.

[0013] As a preferred embodiment of the first aspect, the open containers in the stepped container structure are in the form of open barrels. All the open containers are coaxially arranged and increase in diameter from top to bottom.

[0014] As a preferred embodiment of the first aspect, the adiabatic tank is externally insulated with polyurethane foam material or a double-layer vacuum insulation layer.

[0015] As a preferred embodiment of the first aspect, the open containers in the stepped container structure include four or more.

[0016] As a preferred form of the first aspect, a plurality of spiral-tapered methane pipelines are provided, each of which passes through the stepped container structure in the adiabatic tank body to synchronously perform liquid methane subcooling in parallel.

[0017] As a preferred form of the first aspect, in the main pipeline of the spiral-tapered methane pipeline, the projections of all the annular tubes on the horizontal plane are staggered and do not overlap.

[0018] In a second aspect, the application provides a method for rapidly subcooling liquid methane by using the subcooling device according to any one of the solutions of the first aspect, which comprises the following steps:

[0019] S1, opening the control valve on the spiral-tapered methane pipeline to allow liquid methane from the liquid methane source to fill the spiral-tapered methane pipeline and flow into the storage tank;

[0020] S2, continuing to fill the liquid methane, and sequentially opening the liquid nitrogen filling valves of the open containers in the stepped container structure according to the filling sequence from top to bottom, to fill liquid nitrogen into the open containers, respectively, when the liquid nitrogen medium in each open container reaches the specified liquid level, reducing the opening degree of each liquid nitrogen filling valve to balance the liquid nitrogen filling amount and the vaporization amount of each open container, and the nitrogen gas generated by the heat exchange and boiling of the liquid nitrogen in the open container and the liquid methane in the spiral-tapered methane pipeline is discharged through the nitrogen discharge pipe;

[0021] S3, when the methane outlet temperature of the spiral-tapered methane pipeline enters the methane icing risk temperature zone, the heat exchange area between the spiral-tapered methane pipeline and the liquid nitrogen needs to be adjusted to prevent icing; when adjusting the heat exchange area, first, the liquid nitrogen height in the open containers is gradually reduced in sequence from top to bottom by cooperating the liquid nitrogen filling valves and the liquid nitrogen emptying valves, the spiral-tapered methane pipeline area constituting the heat exchange with the liquid nitrogen in the open containers is reduced by gradually discharging the liquid nitrogen in the upper level, the methane outlet temperature is increased to make it out of the methane icing risk temperature zone, if the methane outlet temperature is still in the methane icing risk temperature zone after the liquid nitrogen in the upper level is completely discharged, the liquid nitrogen height in the next level is continued to be reduced until the methane outlet temperature is out of the methane icing risk temperature zone;

[0022] S4, after the subcooling operation of the liquid methane is completed, the control valve on the spiral-tapered methane pipeline, the liquid nitrogen filling valves, and the liquid nitrogen emptying valves are closed, and after the remaining liquid nitrogen medium in the adiabatic tank body is completely vaporized and discharged, the nitrogen discharge pipe is closed to prevent foreign matters from entering.

[0023] As a preferred form of the second aspect, the methane icing risk temperature zone is 90K-91K.

[0024] As a preferred embodiment of the second aspect, in the S4, the liquid nitrogen filling valves and the liquid nitrogen emptying valves corresponding to all the open containers in the cascade container structure are closed in the order from top to bottom.

[0025] The present application has the following advantages over the prior art: the spiral tapering methane pipeline can greatly improve the heat exchange effect of liquid nitrogen and methane, on the one hand, the methane flow direction is changed from vertical to horizontal, effectively avoiding the problem of heat transfer deterioration caused by the nitrogen film covering the pipeline due to boiling in vertical flow, on the other hand, the spiral diameter of the methane pipeline gradually decreases, effectively avoiding the influence of the rising of nitrogen bubbles on the top pipeline. The spiral tapering methane pipeline is divided into multiple parts by the open containers with gradually increasing diameters, and when adjusting the outlet temperature of methane, the liquid level in the open containers is adjusted from top to bottom. Since the volume of liquid nitrogen medium in the upper open container is small, the response is very rapid when the temperature is adjusted. At the same time, when the liquid level in the open container decreases to a certain value, the boiling heat transfer coefficient of the pipeline surface will obviously increase with the decrease of the liquid level, that is, there is a critical liquid level in each open container, which can improve the boiling heat transfer coefficient of the liquid nitrogen medium as a whole. The sparse needle ribs arranged at the front end of the spiral tapering methane pipeline can effectively overcome the heat transfer weakening phenomenon caused by the gas film of strong boiling under large supercooling degree, and the dense needle ribs at the rear end can increase the bubble generation rate under small supercooling degree.

[0026] The concept, specific structure and technical effects of the present application will be further described below with reference to the accompanying drawings, so as to fully understand the purpose, features and effects of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a structural schematic diagram of a liquid methane rapid supercooling device according to the present application.

[0028] Figure 2 is a structural schematic diagram of a spiral tapering methane pipeline according to the present application.

[0029] In the drawings, the reference signs are as follows: high adiabatic tank body 1, liquid nitrogen filling pipeline 2, first liquid nitrogen filling valve 3, second liquid nitrogen filling valve 4, third liquid nitrogen filling valve 5, spiral tapering methane pipeline 6, liquid methane inlet valve 7, liquid methane outlet valve 8, first open container 9, second open container 10, third open container 11, first liquid nitrogen emptying valve 12, second liquid nitrogen emptying valve 13, third liquid nitrogen emptying valve 14, nitrogen discharge pipe 15, sparse needle ribs 6-1, secondary dense needle ribs 6-2, dense needle ribs 6-3. DETAILED DESCRIPTION

[0030] In order to make the above objectives, characteristics and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below with reference to the drawings. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the concept of the present application, so the present application is not limited to the specific embodiments disclosed below. The technical features in each embodiment of the present application can be combined accordingly without conflict.

[0031] In the description of the present application, 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 to the other element with an intermediate element. In contrast, when an element is referred to as being "directly" connected to another element, there is no intermediate element.

[0032] In the description of the present application, it should be understood that the terms "first", "second" are only used for distinguishing purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features.

[0033] Referring to Figure 1 In a preferred embodiment of the present application, a liquid methane rapid subcooling device is provided, the main body of the device is an adiabatic tank 1, the adiabatic tank 1 is provided with a liquid nitrogen filling pipe 2, a spiral tapered methane pipe 6 and a stepped container structure, and the adiabatic tank 1 is provided at the top with a nitrogen discharge pipe 15 for discharging nitrogen in the tank. Liquid methane propellant can be injected into the tapered methane pipe 6, the intermediate main body portion is filled with liquid nitrogen medium injected through the liquid nitrogen filling pipe 2 in the adiabatic tank 1 to complete the rapid subcooling of the methane propellant, and the methane propellant is stored in the subsequent tank, while the nitrogen gas generated by vaporization is discharged through the nitrogen discharge pipe 15 at the top of the high adiabatic tank 1. The assembly relationship between the components is described in detail below.

[0034] In the embodiment of the present application, the adiabatic tank 1 should be a high adiabatic tank, which needs to have high adiabatic performance, and the outer part of the adiabatic tank 1 can be insulated by polyurethane foaming material or double vacuum insulation layer. The core component for realizing the rapid subcooling of liquid methane in the adiabatic tank 1 is a stepped container structure and a spiral tapered methane pipe 6. The specific structure of the stepped container structure and the spiral tapered methane pipe 6 is described in detail below.

[0035] Continuing to refer to Figure 1The stepped container structure is arranged in vertical steps by three open-top open containers, namely a first open container 9, a second open container 10 and a third open container 11. The inlet end of the liquid nitrogen filling pipeline 2 is connected to an external liquid nitrogen source, and the rear end is located inside the adiabatic tank body 1 and is divided into a plurality of liquid nitrogen filling branches. The number of liquid nitrogen filling branches can be the same as the number of open containers in the stepped container structure. Each liquid nitrogen filling branch is provided with a liquid nitrogen filling valve for controlling the opening and closing of the pipeline. In the embodiment of the present application, since there are three open containers in the stepped container structure, the number of liquid nitrogen filling branches is also three, that is, the outlet end of the liquid nitrogen filling pipeline 2 is divided into three liquid nitrogen filling branches, and the three liquid nitrogen filling branches are respectively provided with a first liquid nitrogen filling valve 3, a second liquid nitrogen filling valve 4 and a third liquid nitrogen filling valve 5, which can respectively control the filling of liquid nitrogen medium to the first open container 9, the second open container 10 and the third open container 11.

[0036] In addition, the open containers in the stepped container structure are arranged in steps, and the adjacent open containers in the three open containers have an up-down spatial relationship and maintain a proper distance between them. The open containers in the stepped container structure gradually increase in volume from top to bottom, and each open container corresponds to a liquid nitrogen filling branch for filling liquid nitrogen medium into the container. Each open container is further provided with a liquid nitrogen emptying valve at the bottom. The open container above can discharge the liquid nitrogen medium in the interior into the open container below by opening the liquid nitrogen emptying valve at the bottom, so that the liquid level of the liquid nitrogen medium in any open container can be controlled by the cooperation of the liquid nitrogen filling valve and the liquid nitrogen emptying valve. In the embodiment of the present application, the liquid nitrogen emptying valves provided at the bottoms of the first open container 9, the second open container 10 and the third open container 11 are respectively a first liquid nitrogen emptying valve 12, a second liquid nitrogen emptying valve 13 and a third liquid nitrogen emptying valve 14. The three liquid nitrogen emptying valves are normally closed, and when the outlet temperature of the methane is too low, the liquid nitrogen emptying valves can be opened to discharge the excess liquid nitrogen medium in the open container, thereby reducing the heat exchange area.

[0037] The regulation sequence of the liquid level of the liquid nitrogen medium in the open containers in the stepped container structure is to regulate the liquid level of the liquid nitrogen medium in each open container from top to bottom, that is, to regulate the liquid level of the liquid nitrogen medium in the uppermost open container first, and then to regulate the liquid level of the liquid nitrogen medium in the next open container, and so on. This regulation sequence is related to the structure and arrangement form of the subsequent spiral tapered methane pipeline 6.

[0038] It should be noted that the cross-sectional dimension of the open container in the stepped container structure is not limited, but considering the processing and liquid level control requirements, the open container in the stepped container structure is in the form of an open barrel in the embodiment of the present application, and the cross section is circular. All open containers are coaxially arranged and have the same height, and the diameter increases from top to bottom, so that the volume gradually increases from top to bottom.

[0039] Continuing to refer to Figure 1 As shown, the above-mentioned spiral tapered methane pipeline 6 is a pipeline for conveying liquid methane in a spiral form. The inlet of the spiral tapered methane pipeline 6 is located at the bottom of the adiabatic tank 1, the outlet extends out of the top of the adiabatic tank 1, and the main pipeline in the inner cavity of the adiabatic tank 1 comprises a plurality of concentric ring pipes arranged in vertical steps, each ring pipe is horizontally arranged, and adjacent ring pipes are connected by inclined pipes to continuously convey liquid methane. The diameter of all ring pipes gradually increases from top to bottom, and the whole presents a stepped structure gradually expanding from top to bottom. The main pipeline sequentially passes through each open container in the stepped container structure from bottom to top, and each open container has a plurality of ring pipes within the liquid level adjustment range of the liquid nitrogen medium, and each ring pipe can form heat exchange with the liquid nitrogen medium to cool the internal liquid methane. Control valves for opening and closing the pipeline are required on the spiral tapered methane pipeline 6, and in this embodiment, the inlet end and the outlet end of the spiral tapered methane pipeline 6 outside the adiabatic tank 1 are respectively provided with a liquid methane inlet valve 7 and a liquid methane outlet valve 8.

[0040] Since the first open container 9, the second open container 10, and the third open container 11 divide the main body of the spiral tapered methane pipeline 6 into three parts from top to bottom, and the volume of the liquid nitrogen medium gradually increases, when the liquid level is adjusted, the small volume of liquid nitrogen in the first open container 9 is adjusted first, the adjustment rate is greatly improved, and then the overall heat exchange effect is accurately controlled, effectively preventing the freezing of methane. If the adjustment range of the first open container 9 is not enough, the second open container 10 is continuously adjusted, and so on. At the same time, since the spiral tapered methane pipeline 6 in the first open container 9, the second open container 10, and the third open container 11 can realize the critical liquid level, the corresponding boiling heat transfer coefficient will be greatly increased.

[0041] In addition, the outer surface of the main pipeline of the above-mentioned spiral tapered methane pipeline 6 located inside the adiabatic tank 1 can be arranged with needle ribs at intervals, and the density of the needle ribs on the main pipeline gradually changes from dense to sparse along the flow direction of the methane. As shown in Figure 2As shown, in the embodiment of the present application, the spiral tapered methane pipeline 6 is sequentially provided with sparse needle ribs 6-1, secondary dense needle ribs 6-2 and dense needle ribs 6-3 on the outer surface in the direction of methane flow. The sparse needle ribs 6-1 at the front end can overcome the heat transfer weakening phenomenon of gas film caused by strong boiling under large supercooling degree, and the dense needle ribs 6-3 at the rear end can increase the bubble generation rate under small supercooling degree. However, it should be noted that the relative density concept of the sparse needle ribs 6-1, the secondary dense needle ribs 6-2 and the dense needle ribs 6-3 is introduced only for the convenience of description, and does not limit the absolute density. In theory, the density of the needle ribs on the main pipeline gradually changes from dense to sparse along the direction of methane flow, and the heat exchange area of the pipeline per unit length gradually increases accordingly.

[0042] In addition, in the embodiment of the present application, the projections of all the annular tubes in the main pipeline of the spiral tapered methane pipeline 6 on the horizontal plane are preferably staggered and do not overlap. In this way, the spiral tapered methane pipeline has a certain spacing in the vertical direction, which reduces the influence of the nitrogen bubbles generated by the bottom pipeline on the upper pipeline.

[0043] It should be noted that the above Figure 1 In the stepped container structure shown, the number of open containers is three, but in fact, the stepped container structure can also be provided with four or more open containers, which is not limited. By dividing the spiral tapered methane pipeline 6 into more parts through more open containers, the number of critical liquid level generation positions can be increased, and the boiling heat exchange capacity can be strengthened.

[0044] In addition, in the embodiment of the present application, the spiral tapered methane pipeline 6 can be provided in multiple, and each spiral tapered methane pipeline 6 passes through the stepped container structure in the adiabatic tank body 1 to perform liquid methane supercooling in parallel. The specific parallel group number of the spiral tapered methane pipeline 6 and its accessories inside the high adiabatic tank body can be set according to the flow size to improve the processing efficiency of the device.

[0045] In another embodiment of the present application, based on the above Figure 1 The supercooling device shown also provides a method for rapidly supercooling liquid methane by using the supercooling device, which includes the following steps:

[0046] S1, methane filling: sequentially open the liquid methane outlet valve 8 and the liquid methane inlet valve 7, so that the liquid methane from the liquid methane source fills the spiral tapered methane pipeline 6 and flows into the storage tank;

[0047] S2, Liquid nitrogen filling and methane subcooling: Continue to fill with liquid methane, and in accordance with the filling sequence of all open containers in the stepped container structure from top to bottom, open the liquid nitrogen filling valves corresponding to each open container in turn, and fill each open container with liquid nitrogen. When the liquid nitrogen medium in each open container reaches the specified liquid level, reduce the opening of each liquid nitrogen filling valve so that the liquid nitrogen filling amount and vaporization amount in each open container reach a balance. The nitrogen generated by the heat exchange and boiling of the liquid nitrogen inside the open container and the liquid methane in the spiral converging methane pipeline 6 is discharged through the nitrogen discharge pipe 15.

[0048] S3. Methane Anti-icing Control: When the methane outlet temperature of the spiral converging methane pipeline 6 enters the methane ice blockage risk zone, icing must be prevented by adjusting the heat exchange area between the spiral converging methane pipeline 6 and liquid nitrogen. When adjusting the heat exchange area, firstly, the liquid nitrogen height in the open container is gradually reduced from top to bottom by coordinating the liquid nitrogen filling valve and the liquid nitrogen emptying valve. By gradually discharging the liquid nitrogen in the previous stage, the area of ​​the spiral converging methane pipeline 6 that exchanges heat with the liquid nitrogen in the open container is reduced, thereby increasing the methane outlet temperature of the spiral converging methane pipeline 6 to move it out of the methane ice blockage risk zone. If the methane outlet temperature still has not moved out of the methane ice blockage risk zone when the liquid nitrogen in the previous stage open container is completely emptied, the liquid nitrogen height in the next stage open container is continued to be reduced until the methane outlet temperature moves out of the methane ice blockage risk zone.

[0049] S4. Unit shutdown: After the subcooling operation of liquid methane is completed, close the liquid methane inlet valve 7, liquid methane outlet valve 8, each liquid nitrogen filling valve, and each liquid nitrogen venting valve in sequence. After all the remaining liquid nitrogen medium inside the insulated tank 1 has been vaporized and vented, close the nitrogen discharge pipe 15 to prevent foreign objects from entering.

[0050] In an embodiment of the present invention, the risk temperature zone for methane ice blockage in the pipeline needs to be determined based on actual tests. Since the triple point temperature of methane is 90.69K, the risk temperature zone for methane ice blockage can be set to 90K to 91K.

[0051] In addition, in step S4 above, the corresponding liquid nitrogen filling valves and liquid nitrogen venting valves must be closed in the order of all open containers in the stepped container structure from top to bottom.

[0052] The rapid subcooling methods for liquid methane shown in S1 to S4 above are applicable to tiered container structures with any number of open containers. For the aforementioned... Figure 1 The specific subcooling process of the embodiment with a tiered container structure having three open containers shown is as follows:

[0053] First, control Figure 1 All valves in the subcooling unit are closed, and then the following process is executed:

[0054] (1)Methane filling: open the liquid methane outlet valve 8, the liquid methane inlet valve 7, the methane from the liquid methane source fills the spiral tapered methane pipeline 6, and enters the tank. The methane can be effectively prevented from being blocked by ice when it is filled before the liquid nitrogen medium is filled. At this time, the liquid methane entering the tank is in a normal state.

[0055] (2) Liquid nitrogen filling and methane subcooling: open the first liquid nitrogen filling valve 3, the second liquid nitrogen filling valve 4, and the third liquid nitrogen filling valve 5 in turn, and fill the liquid nitrogen into the first open container 9, the second open container 10, and the third open container 11 in large quantities. When the liquid nitrogen medium reaches the specified liquid level, the opening of the first liquid nitrogen filling valve 3, the second liquid nitrogen filling valve 4, and the third liquid nitrogen filling valve 5 is gradually reduced to balance the amount of liquid nitrogen filling and vaporization. Due to the special structure of the spiral tapered methane pipeline 6, a large amount of liquid nitrogen in the open container will boil, and the generated nitrogen gas will be discharged through the nitrogen gas discharge pipe 15.

[0056] (3) Methane anti-icing regulation: when the methane outlet temperature of the spiral tapered methane pipeline 6 approaches 90K-91K, the methane in the pipeline is at risk of icing. Due to the large fluctuation of the methane flow regulation, the heat exchange area between methane and liquid nitrogen can be adjusted to prevent icing. For the first open container 9, first close the first liquid nitrogen filling valve 3 and open the first liquid nitrogen emptying valve 12. The liquid nitrogen medium in the first open container 9 enters the second open container 10 under the influence of gravity and overflows to the bottom of the high adiabatic tank body 1. As the liquid level of the liquid nitrogen in the first open container 9 gradually decreases, the heat exchange area between methane and liquid nitrogen decreases, and the outlet temperature of methane gradually increases. If the liquid nitrogen in the first open container 9 is completely emptied, and the outlet temperature of methane is still too low, the same steps can be taken for the second open container 10 and the third open container 11 until the outlet temperature of methane reaches the set value.

[0057] (4) Device stop: close the liquid methane inlet valve 7, the liquid methane outlet valve 8, the first liquid nitrogen filling valve 3, the second liquid nitrogen filling valve 4, the third liquid nitrogen filling valve 5, the first liquid nitrogen emptying valve 12, the second liquid nitrogen emptying valve 13, and the third liquid nitrogen emptying valve 14 in turn. After the remaining liquid nitrogen medium in the high adiabatic tank body 1 is completely vaporized and emptied, close the nitrogen gas discharge pipe 15 to prevent foreign matter from entering.

[0058] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A device for rapid subcooling of liquid methane, characterized in that, The application relates to a liquid nitrogen and methane storage tank. The open containers in the cascade container structure are in the form of open barrels, all the open containers are coaxially arranged and the diameters of the open containers increase from top to bottom. The inlet end of the liquid nitrogen filling pipeline (2) is connected with an external liquid nitrogen source, the rear end is located in the interior of the heat-insulating tank body (1) and is divided into a plurality of liquid nitrogen filling branches, a liquid nitrogen filling valve for controlling the opening and closing of the pipeline is arranged on each liquid nitrogen filling branch. The open containers in the cascade container structure are in the form of open barrels, all the open containers are coaxially arranged and the diameters of the open containers increase from top to bottom. The inlet of the spiral tapering methane pipeline (6) is located at the bottom of the heat-insulating tank body (1), the outlet extends out of the top of the heat-insulating tank body (1), the main pipeline in the internal cavity of the heat-insulating tank body (1) comprises a plurality of concentric ring pipes arranged in vertical cascade, each ring pipe is horizontally arranged, adjacent ring pipes are connected through inclined pipes to continuously transport liquid methane, and the diameters of all the ring pipes gradually increase from top to bottom; the main pipeline sequentially passes through each open container in the cascade container structure from bottom to top, each open container has a plurality of ring pipes in the liquid level adjustment range of the liquid nitrogen medium, and each ring pipe can form heat exchange with the liquid nitrogen medium to cool the internal liquid methane. The outer surface of the main pipeline is arranged with needle ribs at intervals, and the density of the needle ribs on the main pipeline gradually changes from dense to sparse along the methane flow direction. The open containers in the cascade container structure are in the form of open barrels, all the open containers are coaxially arranged and the diameters of the open containers increase from top to bottom. The spiral tapering methane pipeline (6) is provided with a plurality of pipelines, each of which passes through the cascade container structure in the heat-insulating tank body (1) to synchronously perform liquid methane supercooling in a parallel form. In the main pipeline of the spiral tapering methane pipeline (6), the projections of all the ring pipes on the horizontal plane are staggered and do not overlap.

2. The apparatus for rapid subcooling of liquid methane according to claim 1, wherein The cascade container structure comprises three open containers, namely a first open container (9), a second open container (10) and a third open container (11), the outlet end of the liquid nitrogen filling pipeline (2) is divided into three liquid nitrogen filling branches, and the three liquid nitrogen filling branches are respectively provided with a first liquid nitrogen filling valve (3), a second liquid nitrogen filling valve (4) and a third liquid nitrogen filling valve (5) for respectively controlling the liquid nitrogen medium filling of the first open container (9), the second open container (10) and the third open container (11).

3. The apparatus for rapid subcooling of liquid methane according to claim 1, wherein The heat-insulating tank body (1) is externally insulated by using polyurethane foaming material or double vacuum insulation.

4. The apparatus for rapid subcooling of liquid methane of claim 1, wherein, The open containers in the cascade container structure comprise four or more.

5. A method for rapidly supercooling liquid methane using the supercooling device according to any one of claims 1 to 4, characterized by, The application further discloses a liquid nitrogen and methane storage tank liquid level adjustment method. S1, open the control valve on the spiral tapered methane pipeline (6) to allow liquid methane from the liquid methane source to fill the spiral tapered methane pipeline (6) and flow into the tank; S2, continue to fill the liquid methane, and according to the filling order of all open containers in the stepped container structure from top to bottom, open the liquid nitrogen filling valves of the open containers in turn, and fill liquid nitrogen into each open container. When the liquid nitrogen medium in each open container reaches the specified liquid level, reduce the opening of each liquid nitrogen filling valve to balance the liquid nitrogen filling amount and the vaporization amount of each open container. The nitrogen gas generated by the heat exchange and boiling of liquid nitrogen in the open container and liquid methane in the spiral tapered methane pipeline (6) is discharged through the nitrogen discharge pipe (15); S3, when the methane outlet temperature of the spiral tapered methane pipeline (6) enters the methane icing risk temperature zone, the heat exchange area between the spiral tapered methane pipeline (6) and the liquid nitrogen needs to be adjusted to prevent icing. When adjusting the heat exchange area, first reduce the liquid nitrogen height in the open container in order from top to bottom through the cooperation of the liquid nitrogen filling valve and the liquid nitrogen emptying valve. By gradually discharging the liquid nitrogen in the upper stage, the area of the spiral tapered methane pipeline (6) that exchanges heat with the liquid nitrogen in the open container is reduced, and the methane outlet temperature of the spiral tapered methane pipeline (6) is increased to escape the methane icing risk temperature zone. If the methane outlet temperature has not escaped the methane icing risk temperature zone after the liquid nitrogen in the upper stage open container is completely discharged, the liquid nitrogen height of the next stage open container will be adjusted until the methane outlet temperature escapes the methane icing risk temperature zone. S4, after the supercooling of the liquid methane is completed, close the control valve on the spiral tapered methane pipeline (6), the liquid nitrogen filling valve and the liquid nitrogen emptying valve. After the remaining liquid nitrogen medium in the adiabatic tank body (1) is completely vaporized and discharged, close the nitrogen discharge pipe (15) to prevent foreign matter from entering.

6. The method of rapid supercooling of liquid methane according to claim 5, wherein, The methane icing risk temperature zone is 90 K ~ 91 K.

7. The method of rapid supercooling of liquid methane according to claim 5, wherein In S4, according to the order of all open containers in the stepped container structure from top to bottom, close the corresponding liquid nitrogen filling valve and liquid nitrogen emptying valve.

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