A small-volume supercooled liquid methane rapid cooling system and method

Abstract

The present invention relates to a cooling system and method for a liquid rocket engine propellant, and particularly to a small-volume subcooled liquid methane rapid cooling system and method, which solves the technical problems of the existing technology that uses liquid nitrogen as a cooling medium and cools liquid methane to a certain temperature through a corresponding heat exchanger, which is prone to excessive heat exchange, resulting in the solidification of liquid methane and blocking the heat exchanger, and has low efficiency and cannot quickly obtain subcooled liquid methane. The small-volume subcooled liquid methane rapid cooling system includes a liquid nitrogen supply container, a liquid methane subcooling container and a liquid nitrogen vaporizer; a flow meter, a throttle, a liquid nitrogen cooling isolation valve V<subgt;4 and a liquid nitrogen injection pipe are arranged on the connecting pipeline between the liquid nitrogen supply container and the liquid methane subcooling container; a saturated liquid methane supply valve V<subgt;1 and a subcooled liquid methane discharge valve V<subgt;2 are arranged at the inlet and outlet of the liquid methane subcooling container; the saturated liquid methane supply valve V<subgt;1 fills the liquid methane subcooling container with saturated liquid methane, and the subcooled liquid methane discharge valve V<subgt;2 discharges the subcooled liquid methane.

Description

Technical Field

[0001] The present invention relates to a cooling system and method for a liquid rocket engine propellant, and more particularly to a small-volume subcooled liquid methane rapid cooling system and method. Background Art

[0002] LNG (Liquefied Natural Gas, hereinafter referred to as LNG, that is, liquid methane) is a cryogenic propellant that has the advantages of low engineering difficulty, excellent performance indicators, environmental protection and no pollution in the field of liquid rocket engines. With the development of the space industry, liquid methane has become a widely used propellant in the space field. How to achieve efficient transportation and storage of liquid methane has also become an important topic for civil space to reduce launch costs and achieve technological leapfrogs. In the prior art, liquid methane is subcooled and densified to alleviate the inconvenience of storage caused by temperature stratification, thereby improving the storage and utilization quality of cryogenic propellants, which is of great significance for the test and rocket body launch of liquid oxygen-methane liquid rocket engines.

[0003] In the research and development test of liquid oxygen-methane liquid rocket engines, the propellant supply system is required to provide the temperature of the propellant required at the inlet of the whole engine or the test piece. To meet the supply temperature of the propellant required at the inlet of the whole engine or the test piece, a large amount of saturated liquid methane needs to be vaporized at the cost. The vaporization loss of saturated liquid methane and the long-time precooling of pipelines not only increase the research and development cost of the research and development test of liquid oxygen-methane liquid rocket engines, but also affect the research and development efficiency of the research and development test of liquid oxygen-methane liquid rocket engines.

[0004] Currently, the method of subcooling LNG used in engineering is mainly through heat exchange. Generally, liquid nitrogen is used as the cooling medium, and liquid methane is cooled to a certain temperature through a corresponding heat exchanger. In terms of technology, since the temperature of normal pressure liquid nitrogen is less than or equal to the solidification temperature of methane under normal pressure, it is easy to cause excessive heat exchange, resulting in the solidification of liquid methane and blocking the heat exchanger, and the efficiency is low, and subcooled liquid methane cannot be obtained quickly. Summary of the Invention

[0005] The object of the present invention is to provide a small-volume subcooled liquid methane rapid cooling system and method for the technical problem that the existing technology of using liquid nitrogen as a cooling medium to cool liquid methane to a certain temperature through a corresponding heat exchanger is prone to excessive heat exchange, resulting in the solidification of liquid methane and blocking the heat exchanger, and the efficiency is low, and subcooled liquid methane cannot be obtained quickly.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A small-volume subcooled liquid methane rapid cooling system, characterized in that it includes a liquid nitrogen supply container, a liquid methane subcooling container and a liquid nitrogen vaporizer;

[0008] The outlets at the bottom of the liquid nitrogen supply container are respectively connected to the liquid nitrogen inlets at the bottom of the liquid methane subcooling container and the liquid nitrogen inlet of the liquid nitrogen vaporizer; the nitrogen outlet of the liquid nitrogen vaporizer is connected to the air inlet at the top of the liquid nitrogen supply container for pressurizing or depressurizing the liquid nitrogen supply container.

[0009] A flow meter, a throttle, a liquid nitrogen cooling isolation valve V4, and a liquid nitrogen injection pipe are provided on the connecting pipeline between the outlet at the bottom of the liquid nitrogen supply container and the liquid nitrogen inlet at the bottom of the liquid methane subcooling container; the liquid nitrogen injection pipe is located at the liquid nitrogen inlet of the liquid methane subcooling container and is coaxially arranged with the liquid nitrogen inlet of the liquid methane subcooling container.

[0010] A vaporizer isolation valve V5 is provided on the connecting pipeline between the outlet at the bottom of the liquid nitrogen supply container and the liquid nitrogen inlet of the liquid nitrogen vaporizer.

[0011] The nitrogen outlet of the liquid nitrogen vaporizer is connected to the air inlet of the liquid nitrogen supply container.

[0012] A pressure relay is provided at the top air outlet of the liquid methane subcooling container; the pressure relay is used to monitor the internal pressure of the liquid nitrogen supply container; a methane subcooler gas release valve V3 and a pressure gauge are provided on the air outlet pipeline of the liquid methane subcooling container; the output end and the input end of the pressure relay are respectively connected to the methane subcooler gas release valve V3 and the pressure gauge.

[0013] A saturated liquid methane supply valve V1 and a subcooled liquid methane discharge valve V2 are provided at the inlet and outlet at the bottom of the liquid methane subcooling container; saturated liquid methane is filled into the liquid methane subcooling container through the saturated liquid methane supply valve V1, and subcooled liquid methane is discharged through the subcooled liquid methane discharge valve V2.

[0014] Further, a liquid nitrogen supply container gas release valve V7 and a safety valve are provided at the air inlet of the liquid nitrogen supply container; the liquid nitrogen supply container gas release valve V7 is used to control the internal pressure of the liquid nitrogen supply container, and a heat insulation layer is provided outside the liquid nitrogen supply container.

[0015] Further, an anti-vortex plate is provided at the position of the inlet and outlet at the bottom inside the liquid methane subcooling container.

[0016] A pressure safety valve is provided on the air outlet pipeline of the liquid methane subcooling container.

[0017] A heat insulation layer is provided outside the liquid methane subcooling container.

[0018] Further, a gas pressurization isolation valve V6 is provided on the connecting pipeline between the nitrogen outlet of the liquid nitrogen vaporizer and the air inlet of the liquid nitrogen supply container.

[0019] Further, the liquid nitrogen injection pipe is a blind pipe, the blind end of which passes through the anti-vortex plate and extends into the liquid methane subcooling container, and the blind end is higher than the height of the bottom head of the liquid methane subcooling container;

[0020] n injection ports are circumferentially arranged on the side wall of the blind end of the liquid nitrogen injection pipe, where n = 0.2 - 0.3A / A0, A is the cross-sectional area of the liquid nitrogen injection pipe, and A0 is the cross-sectional area of the injection port.

[0021] Further, the maximum consumed liquid nitrogen volume V of the liquid nitrogen supply container is (0.1 - 0.15)V 甲烷 , V 甲烷 is the internal liquid methane volume of the liquid methane subcooling container;

[0022] The ratio of the liquid phase volume Vl to the gas phase volume Vg inside the liquid methane subcooling container is 4 - 6.

[0023] Further, the liquid nitrogen supply container is an extrusion type small flow liquid nitrogen supply container with a flow rate of 0.5 - 3 kg / s;

[0024] The liquid methane subcooling container is a vacuum adiabatic container or a heat preservation container, and the volume of the heat preservation container is not more than 40 m 3 ;

[0025] The liquid nitrogen vaporizer is an air-cooled vaporizer;

[0026] The methane subcooler vent valve V3 is a pneumatic valve;

[0027] The diameter Dp of the liquid nitrogen injection pipe is 15 - 20 mm, and the height h of the blind end of the liquid nitrogen injection pipe above the bottom head of the liquid methane subcooling container satisfies h ≤ 0.1D, where D is the inner diameter of the liquid methane subcooling container;

[0028] The high value of the pressure relay is 0.8 MPa, and the low value is 0.5 MPa;

[0029] The value of n is 8 - 16;

[0030] The diameter φd of the injection port is 2 - 4 mm, and the injection inclination angle α of the injection port is 50° - 70°; the injection inclination angle α is the angle between the central axis of the injection port and the radial plane of the liquid nitrogen injection pipe.

[0031] Further, the throttler is a throttle orifice plate or a Venturi nozzle or a Venturi tube.

[0032] Meanwhile, the present invention also provides a method for rapidly cooling small-volume subcooled liquid methane. Based on the above-mentioned small-volume subcooled liquid methane rapid cooling system, the special feature lies in including the following steps:

[0033] Step 1: Open the saturated liquid methane supply valve V1 to fill the liquid methane subcooling container with saturated liquid methane;

[0034] Step 2: Close the saturated liquid methane supply valve V1, open the liquid nitrogen cooling isolation valve V4, fill the liquid methane subcooling container with liquid nitrogen through the liquid nitrogen supply container, and control the opening or closing of the methane subcooler vent valve V3 by using a pressure relay to adjust the internal pressure of the liquid methane subcooling container;

[0035] Step 3: Close the liquid nitrogen cooling isolation valve V4, open the subcooled liquid methane discharge valve V2, and discharge the subcooled liquid methane in the liquid methane subcooling container to complete the rapid cooling of the subcooled liquid methane.

[0036] Furthermore, step 2 further includes:

[0037] Open the vaporizer isolation valve V5 to fill the liquid nitrogen supply container (1) with nitrogen to ensure the pressure when the liquid nitrogen supply container (1) fills the liquid methane subcooling container (2) with liquid nitrogen;

[0038] The specific operation of using the pressure relay to control the opening or closing of the methane subcooler vent valve V3 to adjust the internal pressure of the liquid methane subcooling container in step 2 is as follows:

[0039] When the pressure in the liquid methane subcooling container is less than or equal to 0.5 MPa, close the methane subcooler vent valve V3; when the pressure in the liquid methane subcooling container is greater than 0.8 MPa, open the methane subcooler vent valve V3 to exhaust gas.

[0040] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0041] (1) The small-volume subcooled liquid methane rapid cooling system of the present invention uses a liquid methane subcooling container and a liquid nitrogen vaporizer to form a squeezed small-flow liquid nitrogen, and sprays the liquid nitrogen from the bottom of the liquid methane subcooling container through a liquid nitrogen injection pipe to rapidly subcool the saturated liquid methane in the liquid methane subcooling container.

[0042] (2) The small-volume subcooled liquid methane rapid cooling system of the present invention can rapidly cool and subcool the liquid methane in a liquid methane subcooling container with good heat preservation performance and a volume less than 40 m 3 to obtain subcooled liquid methane with a certain back pressure.

[0043] (3) The small-volume subcooled liquid methane rapid cooling system of the present invention can not only achieve the densification of the liquid methane propellant through the liquid nitrogen vaporizer, but also improve the development efficiency of the liquid oxygen-methane engine and reduce the technical difficulty of cooling the cryogenic propellant supply system.

[0044] (4) A rapid cooling method for small - volume sub - cooled liquid methane in the present invention, which adopts the technology of injecting liquid nitrogen into saturated liquid methane, can quickly obtain small - volume liquid methane with a certain back pressure. The system is simple and highly feasible, and can quickly and efficiently obtain liquid methane with back pressure, which can meet the demand for sub - cooled liquid methane required for the relevant experimental research and development of liquid methane engines. Description of the Drawings

[0045] Figure 1 It is a schematic structural diagram of a rapid cooling system for small - volume sub - cooled liquid methane in the present invention.

[0046] Figure 2 In an embodiment of a rapid cooling system for small - volume sub - cooled liquid methane in the present invention, it is a schematic structural diagram of a liquid nitrogen injection pipe and an anti - vortex plate arranged in a liquid methane sub - cooling container. Where D is the inner diameter of the liquid methane sub - cooling container, h is the height of the blind end of the liquid nitrogen injection pipe above the bottom head of the liquid methane sub - cooling container, α is the injection angle of the injection port, and Dp is the diameter of the liquid nitrogen injection pipe.

[0047] Figure 3 is Figure 2 an enlarged structural diagram at position A in, d is the diameter of the injection port, and L is the distance between the center of the injection port and the end face of the blind end of the liquid nitrogen injection pipe.

[0048] The reference numerals in the figure are:

[0049] 1 - liquid nitrogen supply container, 2 - liquid methane sub - cooling container, 3 - liquid nitrogen vaporizer, 4 - flowmeter, 5 - throttle, 6 - liquid nitrogen injection pipe, 7 - pressure relay, 8 - safety valve, 9 - anti - vortex plate, 10 - pressure safety valve, 11 - bottom head, 12 - injection port, 13 - insulation layer. Detailed Embodiment

[0050] Next, the technical solutions of the present invention will be described clearly and completely in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the technical solutions in the present invention without creative efforts belong to the scope of protection of the present invention.

[0051] As Figure 1 shown, a rapid cooling system for small - volume sub - cooled liquid methane includes a liquid nitrogen supply container 1, a liquid methane sub - cooling container 2 and a liquid nitrogen vaporizer 3;

[0052] The outlets at the bottom of the liquid nitrogen supply container 1 are respectively connected to the liquid nitrogen inlets at the bottom of the liquid methane subcooling container 2 and the liquid nitrogen inlet of the liquid nitrogen vaporizer 3; the nitrogen outlet of the liquid nitrogen vaporizer 3 is connected to the air inlet at the top of the liquid nitrogen supply container 1 for pressurizing or depressurizing the liquid nitrogen supply container 1; a liquid nitrogen supply container vent valve V7 and a safety valve 8 are provided at the air inlet of the liquid nitrogen supply container 1; the liquid nitrogen supply container vent valve V7 is used to control the pressure inside the liquid nitrogen supply container 1.

[0053] A flowmeter 4, a throttler 5, a liquid nitrogen cooling isolation valve V4, and a liquid nitrogen injection pipe 6 are provided on the connecting pipeline between the outlet at the bottom of the liquid nitrogen supply container 1 and the liquid nitrogen inlet at the bottom of the liquid methane subcooling container 2; the liquid nitrogen injection pipe 6 is located at the liquid nitrogen inlet of the liquid methane subcooling container 2 and is coaxially arranged with the liquid nitrogen inlet of the liquid methane subcooling container 2; the liquid nitrogen injection pipe 6 is a blind pipe, and its blind end passes through the anti-vortex plate 9 and extends into the liquid methane subcooling container 2, and the blind end is higher than the height of the bottom head 11 of the liquid methane subcooling container 2; n injection ports 12 are circumferentially arranged on the side wall of the blind end of the liquid nitrogen injection pipe 6, where n = 0.2 - 0.3A / A0, A is the cross-sectional area of the liquid nitrogen injection pipe 6, and A0 is the cross-sectional area of the injection port 12; the diameter φd of the injection port 12 is 2 - 4 mm, and the injection inclination angle α of the injection port 12 is 50° - 70°. A vaporizer isolation valve V5 is provided on the connecting pipeline between the outlet at the bottom of the liquid nitrogen supply container 1 and the liquid nitrogen inlet of the liquid nitrogen vaporizer 3.

[0054] The nitrogen outlet of the liquid nitrogen vaporizer 3 is connected to the air inlet of the liquid nitrogen supply container 1; a gas pressurization isolation valve V6 is provided on the connecting pipeline between the nitrogen outlet of the liquid nitrogen vaporizer 3 and the air inlet of the liquid nitrogen supply container 1.

[0055] An anti-vortex plate 9 is provided at the bottom inlet and outlet position inside the liquid methane subcooling container 2; a pressure safety valve 10 is provided on the gas outlet pipeline of the liquid methane subcooling container 2; an insulating layer is provided outside the liquid methane subcooling container 2. A pressure relay 7 is provided at the gas outlet at the top of the liquid methane subcooling container 2; the pressure relay 7 is used to monitor the internal pressure of the liquid nitrogen supply container 1; a methane subcooler vent valve V3 and a pressure gauge are provided on the gas outlet pipeline of the liquid methane subcooling container 2; the output end and the input end of the pressure relay 7 are respectively connected to the methane subcooler vent valve V3 and the pressure gauge;

[0056] A saturated liquid methane supply valve V1 and a subcooled liquid methane discharge valve V2 are provided at the inlet and outlet at the bottom of the liquid methane subcooling container 2; saturated liquid methane is filled into the liquid methane subcooling container 2 through the saturated liquid methane supply valve V1, and subcooled liquid methane is discharged through the subcooled liquid methane discharge valve V2.

[0057] In this embodiment, the maximum consumed liquid nitrogen volume V of the liquid nitrogen supply container 1 is (0.1 - 0.15)V 甲烷 , V 甲烷is the internal liquid methane volume of the liquid methane subcooling container 2; the lower limit of the liquid nitrogen supply container 1 is 0.1Vmethane, corresponding to the upper limit of the final subcooling temperature of the liquid methane of 100K, and the upper limit corresponds to the final subcooling temperature of the liquid methane of 93K; the liquid nitrogen supply container 1 is an extrusion-type small-flow liquid nitrogen supply container 1.

[0058] The adopted liquid methane subcooling container 2 is a vacuum-insulated container (a heat-insulating container with a volume not greater than 40m 3 can also be used), and the ratio of the liquid phase volume Vl to the gas phase volume Vg inside the liquid methane subcooling container 2 is 4 to 6; the saturated liquid methane supply valve V1 fills the liquid methane subcooling container 2 with saturated liquid methane to generate pressurized subcooled liquid methane, and the temperature of the subcooled liquid methane is 93 to 105K, and the pressure is 0.1 to 0.8MPa; the liquid nitrogen vaporizer 3 is an air-cooled vaporizer; the throttler 5 is a throttle orifice plate.

[0059] Preferably, the internal pressure of the liquid methane subcooling container 2 is realized by controlling the methane subcooler gas release valve V3 through the pressure relay 7, where the methane subcooler gas release valve V3 is a pneumatic valve, and the diameter D of the connecting pipeline of the methane subcooler gas release valve V3 f is 10 to 15dp; the high value of the pressure relay 7 is 0.8MPa, and the low value is 0.5MPa; when the pressure inside the liquid methane subcooling container 2 is less than or equal to 0.5MPa, the methane subcooler gas release valve V3 is closed; when the pressure inside the liquid methane subcooling container 2 is greater than 0.8MPa, the methane subcooler gas release valve V3 is opened for exhaust. <{

[0060] The nitrogen supply container 1 of the present invention is an extrusion-type small-flow liquid nitrogen supply container, with a flow rate of 0.5 - 3kg / s. The extrusion-type small-flow liquid nitrogen is injected from the bottom of the liquid methane subcooling container 2 to quickly subcool the saturated liquid methane inside the liquid methane subcooling container 2. Among them, the small-flow liquid nitrogen flow rate Q = 0.5 - 1kg / s, the extrusion-type liquid nitrogen pressure is 0.6 - 1.0MPa, and a throttle orifice plate is used to control the liquid nitrogen flow rate, and the flow area of the throttle orifice plate is calculated

[0061] A = C[ρN(P1 - P2 + Δp)] 0.5 / Q

[0062] where C is the liquid nitrogen flow coefficient, P1 is the tank pressure of the liquid nitrogen supply container 1, P2 is the pressure after the throttle orifice plate, Δp is the pressure gρNΔh generated by the liquid level difference Δh of the liquid nitrogen supply container 1, g is the acceleration of gravity, ρN is the liquid nitrogen density (kg / m3), and the calculation of the flow area of the throttle orifice plate should comply with the relevant regulations of GB / 2426 - 2006.

[0063] The liquid nitrogen in the liquid nitrogen supply container 1 is pressurized by an air-temperature vaporizer. The pressure is regulated when the liquid nitrogen supply container 1 is filled with liquid methane supercooling container 2 through the vaporizer isolation valve V5 at the liquid nitrogen inlet of the air-temperature vaporizer and the opening and closing of the liquid nitrogen supply container vent valve V7.

[0064] like Figure 2 As shown, a small flow rate liquid nitrogen injection pipe 6 is inserted from the inlet and outlet at the bottom of the liquid methane supercooling container 2, the diameter of the liquid nitrogen injection pipe 6 is Dp=15~20mm, the liquid nitrogen injection pipe 6 is a blind pipe, the liquid nitrogen injection pipe 6 passes through the center of the anti-vortex plate 9, and is coaxially arranged with the liquid methane supercooling container 2, the blind end of the liquid nitrogen injection pipe 6 is higher than the bottom head 11 of the liquid methane supercooling container 2 by a height h≤0.1D, D is the inner diameter of the liquid methane supercooling container 2, and 8 (or 8~16) inclined injection ports 12 with a diameter of φd=4mm are distributed circumferentially along the liquid nitrogen injection pipe 6 with a blind end, the angle between the central axis of the injection port 12 and the radial plane of the liquid nitrogen injection pipe (6) is the injection inclination angle, and the injection inclination angle α is 70°.

[0065] In this embodiment, in addition to using pressure relay 7 to vent the liquid methane subcooling vessel 2, a high-flow, low-set pressure safety valve 10 can also be used for venting. The set pressure of pressure safety valve 10 is determined based on process requirements and is less than or equal to the required pressure of the liquid methane subcooling vessel 2, which is 0.05-0.1 MPa. The minimum flow rate is 3 kg / s. In actual implementation, the trip pressure of pressure safety valve 10 is 0.8 MPa, and the reseating pressure can be determined based on the actual reseating pressure of pressure safety valve 10, which has little impact on the overall subcooling process.

[0066] At the same time, the present invention also provides a small volume supercooled liquid methane rapid cooling method, based on the above-mentioned small volume supercooled liquid methane rapid cooling system, which is special in that it includes the following steps:

[0067] Step 1: Open the saturated liquid methane supply valve V1 and add saturated liquid methane to the liquid methane supercooling container 2;

[0068] Step 2: Close the saturated liquid methane supply valve V1, open the liquid nitrogen cooling isolation valve V4, and add liquid nitrogen to the liquid methane subcooling container 2 through the liquid nitrogen supply container 1; and use the pressure relay 7 to control the methane subcooler vent valve V3 to adjust the internal pressure of the liquid methane subcooling container 2; when the pressure in the liquid methane subcooling container 2 is less than or equal to 0.5 MPa, close the methane subcooler vent valve V3; when the pressure in the liquid methane subcooling container 2 is greater than 0.8 MPa, open the methane subcooler vent valve V3 to vent;

[0069] Open the vaporizer isolation valve V5 and the gas boost isolation valve V6 to fill the liquid nitrogen supply container 1 with nitrogen to ensure the pressure when the liquid nitrogen supply container 1 adds liquid nitrogen to the liquid methane supercooling container 2.

[0070] Step 3: Close the liquid nitrogen cooling isolation valve V4, open the subcooled liquid methane discharge valve V2, and discharge the subcooled liquid methane in the subcooled liquid methane container 2 to complete the rapid cooling of the subcooled liquid methane.

[0071] Example 2

[0072] The difference between Example 2 and Example 1 is that the throttle 5 uses a Venturi tube (in other embodiments, a Venturi nozzle can also be used) to throttle and control the liquid nitrogen flow rate, and the calculation of the Venturi nozzle should comply with the relevant regulations of GB / T2624-2006. The calculation of the throat flow area of the Venturi tube

[0073] A' = C’[ρ’N’Δp] 0.5 / Q

[0074] In the formula: C’ is the liquid nitrogen flow coefficient, Δp is the pressure difference between the inlet pressure and the throat pressure of the Venturi tube, ρ’N’ is the liquid nitrogen density (kg / m3), and Q is the required injection-type liquid nitrogen supply flow rate, generally taken as 0.5 - 3 kg / s.

Claims

1. A rapid cooling system for small-volume subcooled liquid methane, characterized in that: It includes a liquid nitrogen supply container (1), a liquid methane subcooling container (2) and a liquid nitrogen vaporizer (3); The outlet at the bottom of the liquid nitrogen supply container (1) is respectively connected to the liquid nitrogen inlet at the bottom of the liquid methane subcooling container (2) and the liquid nitrogen inlet of the liquid nitrogen vaporizer (3); the nitrogen outlet of the liquid nitrogen vaporizer (3) is connected to the air inlet at the top of the liquid nitrogen supply container (1) for pressurizing or depressurizing the liquid nitrogen supply container (1); A flow meter (4), a throttle (5), a liquid nitrogen cooling isolation valve V4 and a liquid nitrogen injection pipe (6) are arranged on the connecting pipeline between the outlet at the bottom of the liquid nitrogen supply container (1) and the liquid nitrogen inlet at the bottom of the liquid methane subcooling container (2); the liquid nitrogen injection pipe (6) is located at the liquid nitrogen inlet of the liquid methane subcooling container (2) and is coaxially arranged with the liquid nitrogen inlet of the liquid methane subcooling container (2); A vaporizer isolation valve V5 is arranged on the connecting pipeline between the outlet at the bottom of the liquid nitrogen supply container (1) and the liquid nitrogen inlet of the liquid nitrogen vaporizer (3); The nitrogen outlet of the liquid nitrogen vaporizer (3) is connected to the air inlet of the liquid nitrogen supply container (1); A pressure relay (7) is arranged at the air outlet at the top of the liquid methane subcooling container (2); the pressure relay (7) is used to monitor the internal pressure of the liquid nitrogen supply container (1); a methane subcooler vent valve V3 and a pressure gauge are arranged on the air outlet pipeline of the liquid methane subcooling container (2); the output end and the input end of the pressure relay (7) are respectively connected to the methane subcooler vent valve V3 and the pressure gauge; A saturated liquid methane supply valve V1 and a subcooled liquid methane discharge valve V2 are arranged at the inlet and outlet at the bottom of the liquid methane subcooling container (2); saturated liquid methane is filled into the liquid methane subcooling container (2) through the saturated liquid methane supply valve V1, and subcooled liquid methane is discharged through the subcooled liquid methane discharge valve V2.

2. A small-volume subcooled liquid methane rapid cooling system according to claim 1, characterized in that: A liquid nitrogen supply container vent valve V7 and a safety valve (8) are arranged at the air inlet of the liquid nitrogen supply container (1); the liquid nitrogen supply container vent valve V7 is used to adjust the internal pressure of the liquid nitrogen supply container (1); an insulating layer is arranged outside the liquid nitrogen supply container (1).

3. A small-volume subcooled liquid methane rapid cooling system according to claim 2, characterized in that: An anti-vortex plate (9) is arranged at the position of the inlet and outlet at the bottom inside the liquid methane subcooling container (2); A pressure safety valve (10) is arranged on the air outlet pipeline of the liquid methane subcooling container (2); An insulating layer (13) is arranged outside the liquid methane subcooling container (2).

4. A small-volume subcooled liquid methane rapid cooling system according to claim 3, characterized in that: A gas pressurization isolation valve V6 is arranged on the connecting pipeline between the nitrogen outlet of the liquid nitrogen vaporizer (3) and the air inlet of the liquid nitrogen supply container (1).

5. A small-volume subcooled liquid methane rapid cooling system according to claim 4, characterized in that: The liquid nitrogen injection pipe (6) is a blind pipe, and its blind end passes through the anti-vortex plate (9) and extends into the liquid methane subcooling container (2), and the blind end is higher than the height of the bottom head (11) of the liquid methane subcooling container (2); n injection ports (12) are circumferentially arranged on the side wall of the blind end of the liquid nitrogen injection pipe (6), where n is (0.2 - 0.3)A / A0, A is the cross-sectional area of the liquid nitrogen injection pipe (6), and A0 is the cross-sectional area of the injection port (12).

6. A small-volume subcooled liquid methane rapid cooling system according to any one of claims 1 - 5, characterized in that: The maximum volume V of liquid nitrogen consumed by the liquid nitrogen supply container (1) is (0.1 - 0.15)V 甲烷 , V 甲烷 is the internal liquid methane volume of the liquid methane subcooling container (2); The ratio of the liquid phase volume Vl to the gas phase volume Vg inside the liquid methane subcooling container (2) is 4 - 6.

7. A small-volume subcooled liquid methane rapid cooling system according to claim 6, characterized in that: The liquid nitrogen supply container (1) is an extrusion-type small-flow liquid nitrogen supply container with a flow rate of 0.5 - 3 kg / s; The liquid methane subcooling container (2) is a vacuum-insulated container or a heat-insulated container, and the volume of the heat-insulated container is less than or equal to 40 m 3 ; The liquid nitrogen vaporizer (3) is an air-cooled vaporizer; The methane subcooler vent valve V3 is a pneumatic valve; The diameter Dp of the liquid nitrogen injection pipe (6) is 15 - 20 mm, and the height h of the blind end of the liquid nitrogen injection pipe (6) above the bottom head (11) of the liquid methane subcooling container (2) is h ≤ 0.1D, where D is the inner diameter of the liquid methane subcooling container (2); The high value of the pressure relay (7) is 0.8 MPa, and the low value is 0.5 MPa; The value of n is 8 - 16; The diameter φd of the injection port (12) is 2 - 4 mm, and the injection inclination angle α of the injection port (12) is 50° - 70°; the injection inclination angle α is the angle between the central axis of the injection port (12) and the radial plane of the liquid nitrogen injection pipe (6).

8. A small-volume subcooled liquid methane rapid cooling system according to claim 6, characterized in that: The throttle (5) is a throttle orifice plate or a Venturi nozzle or a Venturi tube.

9. A rapid cooling method for small - volume sub - cooled liquid methane, based on the rapid cooling system for small - volume sub - cooled liquid methane according to any one of claims 1 - 7, characterized in that, It includes the following steps: Step 1: Open the saturated liquid methane supply valve V1 to fill the liquid methane subcooling container (2) with saturated liquid methane; Step 2: Close the saturated liquid methane supply valve V1, open the liquid nitrogen cooling isolation valve V4, fill the liquid methane subcooling container (2) with liquid nitrogen through the liquid nitrogen supply container (1), and use the pressure relay (7) to control the opening or closing of the methane subcooler vent valve V3 to adjust the internal pressure of the liquid methane subcooling container (2); Step 3: Close the liquid nitrogen cooling isolation valve V4, open the subcooled liquid methane discharge valve V2, and discharge the subcooled liquid methane in the liquid methane subcooling container (2) to complete the rapid cooling of the subcooled liquid methane.

10. A method for rapidly cooling small-volume subcooled liquid methane according to claim 9, characterized in that: In step 2, it further includes: opening the vaporizer isolation valve V5 to fill the liquid nitrogen supply container (1) with nitrogen to ensure the pressure when the liquid nitrogen supply container (1) fills the liquid methane subcooling container (2) with liquid nitrogen; In step 2, the use of the pressure relay (7) to control the opening or closing of the methane subcooler vent valve V3 to adjust the internal pressure of the liquid methane subcooling container (2) specifically means: When the pressure in the liquid methane subcooling container (2) is less than or equal to 0.5 MPa, close the methane subcooler vent valve V3; when the pressure in the liquid methane subcooling container (2) is greater than 0.8 MPa, open the methane subcooler vent valve V3 to exhaust gas.

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