Liquid oxygen / liquid methane ground test system meeting common base zero boil-off storage requirements

Abstract

The application discloses a liquid oxygen / liquid methane ground test system satisfying the requirement of co-base zero evaporation storage, which comprises an outer cylinder wall, a large-area cold screen hung in the inner part of the outer cylinder wall, a liquid nitrogen cavity, a hot water cavity arranged outside the outer cylinder wall, a liquid methane cavity and a liquid oxygen cavity hung in the large-area cold screen, and the liquid methane cavity and the liquid oxygen cavity jointly form a liquid oxygen / liquid methane co-base storage tank. The application measures the influence of different materials on the storage state of liquid oxygen / liquid methane propellant by changing the co-base interlayer material between the liquid oxygen / liquid methane cavities; the balance of the liquid oxygen / liquid methane state in the zero evaporation storage process is destroyed by controlling the opening and closing of oxygen / methane exhaust valves, and the state change of the liquid oxygen / liquid methane in the balance recovery process is measured; the liquid oxygen and liquid methane are obtained by in-situ liquefaction of oxygen / methane gas by using liquid nitrogen, the purchase and transportation of dangerous liquid oxygen / liquid methane are omitted, and the safety in the test process is improved; the heat flux density entering the storage tank through the refrigeration system and the multilayer thermal insulation material when the refrigeration machine is turned off is measured according to the low-temperature fluid steady evaporation method. By controlling the thermal boundary temperature simulation screen and the vacuum control valve in the system, the liquid oxygen / liquid methane propellant co-base zero evaporation storage state can be tested under different thermal boundary temperatures and different vacuum degrees.

Description

Technical Field

[0001] This invention relates to a technology in the field of aerospace fuels, specifically a liquid oxygen / liquid methane ground testing system that meets the requirements for common-bottom zero-evaporation storage. Background Technology

[0002] With the continuous development of deep space exploration technology, cryogenic propellants need to adapt to the requirements of long-term storage missions in orbit for months or even years in the future. Because cryogenic propellants have extremely low saturation temperatures and low latent heat of vaporization, they are easily evaporated during storage, making them difficult to store for long periods.

[0003] Employing a space cryogenic refrigerator, which consumes a certain amount of externally input electrical energy to cool the propellant in the tank, achieving zero evaporation of the cryogenic propellant, is an ideal solution to the aforementioned problems. Furthermore, current research on in-orbit storage mainly focuses on independent tanks for single propellants, while in reality, propellants are always used in pairs: fuel and oxidizer. Experimental data on co-bottom zero-evaporation storage of paired cryogenic propellants, such as liquid hydrogen / liquid oxygen and liquid oxygen / liquid methane, are extremely scarce. Extensive performance testing and optimization studies are needed before practical application. Therefore, there is an urgent need for a system capable of comprehensively and accurately testing the co-bottom zero-evaporation storage performance of combined cryogenic propellants on the ground. Summary of the Invention

[0004] This invention addresses the aforementioned shortcomings of existing technologies by proposing a ground-based testing system for liquid oxygen / liquid methane that meets the requirements for co-bottom zero-evaporation storage. It measures the impact of different materials on the storage state of the liquid oxygen / liquid methane propellant by changing the co-bottom interlayer material between the liquid oxygen / liquid methane chambers. It also measures the state changes of liquid oxygen / liquid methane during the equilibrium recovery process by controlling the opening and closing of oxygen / methane exhaust valves to disrupt the zero-evaporation storage process. Furthermore, it utilizes liquid nitrogen to liquefy oxygen / methane gas in situ, eliminating the need for hazardous purchase and transportation of liquid oxygen / liquid methane and improving safety during testing. The system measures the heat flux density entering the storage tank through the refrigeration system and multi-layer insulation material when the refrigeration unit is shut down using a cryogenic steady-state evaporation method. By controlling the thermal boundary temperature simulation screen and vacuum control valves in the system, this invention can test the co-bottom zero-evaporation storage state of liquid oxygen / liquid methane propellant under different thermal boundary temperatures and vacuum levels.

[0005] This invention is achieved through the following technical solution:

[0006] This invention relates to a liquid oxygen / liquid methane ground testing system that meets the requirements for co-bottom zero-evaporation storage, comprising: an outer cylinder wall, a large-area cold shield suspended inside it, a liquid nitrogen chamber, a hot water chamber located outside the outer cylinder wall, and a liquid methane chamber and a liquid oxygen chamber suspended inside the large-area cold shield, wherein: the liquid nitrogen chamber and the hot water chamber are respectively connected to the liquid methane chamber and the liquid oxygen chamber, and the liquid methane chamber and the liquid oxygen chamber are respectively connected to an external methane source and an oxygen source, and the liquid methane chamber and the liquid oxygen chamber together form a liquid oxygen / liquid methane co-bottom storage tank.

[0007] The large-area cold screen has a diameter larger than that of the liquid oxygen cavity and the liquid methane cavity, and is nested and surrounds the outside of the liquid oxygen / liquid methane common bottom tank. It has the same shape as the cold screen and the center of the two overlaps. Multiple layers of thermal insulation material are provided between the large-area cold screen and the liquid methane cavity and the liquid oxygen cavity, and between the large-area cold screen and the thermal boundary temperature simulation screen.

[0008] The multilayer insulation material is, but is not limited to, one or more different combinations of equal-density vacuum multilayer, variable-density vacuum multilayer, or polyurethane foam. The position of the large-area cold shield within the insulation material is changed by adjusting the amount of insulation material on the inner and outer sides of the large-area cold shield.

[0009] This invention relates to a test method for a liquid oxygen / liquid methane co-bottom zero-evaporation storage device based on the above system, comprising:

[0010] 1) Preparation Phase: After evacuating the chamber using the molecular pump unit, the heater in the hot water chamber is turned on, and the refrigeration system is activated. A helium circulation pump delivers cooling energy to the cold shield, lowering the temperature of the liquid oxygen and liquid methane chambers to the liquid oxygen temperature to prevent excessive evaporation after oxygen / methane liquefaction. Then, oxygen and methane liquefaction is initiated. Once the liquid oxygen and liquid methane chambers are filled with cryogenic liquid, the temperature controller is activated, and the temperature of the thermal boundary temperature simulation screen is set to the predetermined value.

[0011] 2) Testing phase: Record the thermometer temperature on the large-area cold screen, the thermometer temperature inside the liquid oxygen chamber, the thermometer temperature inside the liquid methane chamber, the helium circulation flow rate, the oxygen exhaust flow rate, and the methane exhaust flow rate; by opening and closing the oxygen / methane exhaust valves or by locally heating the liquid oxygen chamber and the liquid methane chamber, the liquid oxygen / liquid methane is made to deviate from the equilibrium state, and the state change of the liquid oxygen / liquid methane co-bottom storage system when it recovers from the non-equilibrium state to the equilibrium state is measured, and then the performance of the liquid oxygen / liquid methane co-bottom zero evaporation storage device is analyzed.

[0012] Technical effect

[0013] Compared with the prior art, the present invention can realize the isothermal co-bottom zero-evaporation storage test measurement of liquid oxygen / liquid methane. That is, the co-bottom interlayer material is made of stainless steel without heat insulation capacity, so that there is good heat transfer between liquid oxygen and liquid methane, thereby realizing the isothermal non-isobaric coexistence of liquid oxygen / liquid methane, and measuring the state characteristics of liquid oxygen / liquid methane isothermal non-isobaric co-bottom storage.

[0014] This invention employs a regenerative method to connect the liquid oxygen / liquid methane filling and venting pipelines and the helium circulation pipelines. Simultaneously, it utilizes a thermally conductive copper strip to direct the cold energy of the cryogenic liquid in the liquid nitrogen chamber to the connection points of the liquid oxygen / liquid methane filling and venting pipelines and the helium circulation pipelines. This effectively avoids various parasitic heat leakage problems generated in the pipelines, ensuring more accurate measurement results.

[0015] This invention utilizes a refrigeration cycle system, employing liquid nitrogen to simulate a refrigeration unit, to provide cooling capacity for circulating helium. This system removes leaking heat that enters the storage tank through multiple layers of insulation materials and pipelines, thus maintaining the co-bottom zero-evaporation storage of liquid oxygen / liquid methane.

[0016] This invention utilizes an in-situ liquefaction system to liquefy oxygen / methane in situ using liquid nitrogen. This avoids the problem of methane solidification during liquefaction, which may occur because the temperature of liquid nitrogen at room temperature (approximately 77K) is much lower than the freezing temperature of methane (approximately 91K). It also solves the problems of high losses and easy leakage during liquid oxygen / liquid methane filling, while reducing the diameter of the liquid oxygen / liquid methane filling pipeline and reducing pipeline heat leakage.

[0017] This invention enables zero-evaporation storage tests of liquid oxygen and liquid methane using a common-bottom tank. However, this common-bottom tank is not designed for any specific cryogenic fluid combination; it can meet the testing requirements for the common-bottom zero-evaporation storage characteristics of combined propellants such as liquid oxygen / liquid methane and liquid oxygen / liquid hydrogen. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention;

[0019] In the diagram: 1. Circulating air pump; 2. One-way valve; 3. Liquid nitrogen chamber; 4. Outer cylinder wall / thermal boundary temperature simulation screen; 5. External multi-layer insulation material; 6. Large area cold screen; 7. Thermometer; 8. Common bottom jacket; 9. Inner multi-layer insulation material; 10. Liquid oxygen filling pipe; 11. Liquid oxygen chamber end cap; 12. Liquid oxygen chamber wall; 13. Liquid oxygen chamber exhaust pipe; 14. Epoxy resin rod; 15. Thermometer; 16. Liquid methane filling pipe; 17. Liquid methane chamber end cap; 18. Vacuum port; 19. Vacuum control valve; 20. Liquid methane filling port; 21. Oxygen liquefaction pipe; 22. Oxygen exhaust port; 23. Flow meter; 24. Pressure sensor; 25. Hot water chamber; 26. Methane exhaust port; 27. Liquid methane chamber; 28. Liquid oxygen chamber; 29. ​​Flange end cap; 30. Helium cooling pipe; 31. Thermally conductive copper strip; 32. Thermally conductive copper sheet.

[0020] Figure 2This is a schematic diagram illustrating the effects of an example; in the diagram, a represents the change in the state of liquid oxygen; and b represents the change in the state of liquid methane. Detailed Implementation

[0021] like Figure 1 As shown, this embodiment relates to a periodic testing system for a liquid oxygen / liquid methane co-bottom zero-evaporation storage state, comprising: an outer cylinder wall 4, a large-area cold shield 6 suspended inside it, a liquid nitrogen chamber 3, a hot water chamber 25 disposed on a flange end cover 29, and a liquid methane chamber 27 and a liquid oxygen chamber 28 suspended inside the large-area cold shield 6, wherein: the liquid nitrogen chamber 3 and the hot water chamber 25 are respectively connected to the liquid methane chamber 27 and the liquid oxygen chamber 28, and the liquid methane chamber 27 and the liquid oxygen chamber 28 are respectively connected to an external methane source and an oxygen source.

[0022] The large-area cold screen 6 has a diameter larger than that of the liquid oxygen chamber 27 and the liquid methane chamber 28, and is nested and surrounds the outside of the liquid oxygen / liquid methane common-bottom tank. It has the same shape as the tank, and their centers coincide. The inlet and outlet of the large-area cold screen 6 are connected to the helium circulation pipeline via flexible pipes. The cooling capacity from the liquid nitrogen chamber 3 is transferred to the large-area cold screen 6 through the circulation pipeline, ensuring that heat leakage from the external environment does not enter the liquid methane chamber 27 and the liquid oxygen chamber 28. The inlet and outlet of the large-area cold screen 6 have a detachable structure, allowing for the replacement of large-area cold screens with different structures. Insulation materials are provided between the large-area cold screen 6 and the liquid methane chamber 27 and the liquid oxygen chamber 28, and between the large-area cold screen 6 and the thermal boundary temperature simulation screen 4.

[0023] The outer cylinder wall 4 serves as a thermal boundary temperature simulation screen. It is equipped with an electric heating film to provide heat while the electric heating power is adjusted by a temperature controller for thermal compensation temperature control, which can realize continuous change of thermal boundary temperature within a wide temperature range.

[0024] The liquid methane chamber 27, liquid oxygen chamber 28, and large-area cold screen 6 are all suspended inside the outer cylinder wall 4 via end cap flange 29, forming a closed vacuum chamber together with the end cap flange 29 and the outer cylinder wall 4.

[0025] The flange end cover 29 is equipped with three mass flow meters 23, a vacuum port 18, and two pressure sensors 24. The two pressure sensors are respectively located at the oxygen exhaust port and the methane exhaust port to detect the internal pressure of the liquid oxygen chamber and the internal pressure of the liquid methane chamber during the experimental test. The three mass flow meters are respectively used to measure the exhaust flow rate of oxygen and methane and the helium circulation flow rate during the experiment.

[0026] The vacuum port 18 is equipped with a vacuum control valve 19 and a molecular pump unit in sequence. The vacuum level inside the cavity can be continuously controlled by the dynamic vacuuming of the molecular pump unit and the continuous automatic gas replenishment by the vacuum control valve 19.

[0027] The liquid methane chamber 27 and liquid oxygen chamber 28 are respectively equipped with epoxy resin rods 14 to mount thermometers, which are used to test the temperature fluctuations of liquid oxygen and liquid methane and the temperature gradient in the vertical direction during the experiment, and to monitor the liquid level fluctuations inside the test chamber.

[0028] The liquid nitrogen chamber 3 is equipped with an oxygen liquefaction pipe 21, a methane liquefaction pipe 20, and a helium cooling pipe 30. Liquid nitrogen provides cooling for these three parts simultaneously, enabling oxygen liquefaction, methane liquefaction, and reducing helium to a suitable temperature.

[0029] The hot water chamber 25 is equipped with an oxygen exhaust pipe 22, a methane exhaust pipe 26, and a helium heating pipe 30. The hot water chamber can heat the low-temperature oxygen and low-temperature methane to room temperature, so that the flow meter 24 can measure the exhaust flow rate. The hot water chamber can also heat the helium to room temperature, so that the flow meter 24 can measure the flow rate. The circulating air pump 1 pressurizes the helium.

[0030] The cryogenic vapors in the liquid oxygen chamber 28 and liquid methane chamber 27 can be directly discharged outside the vacuum chamber through the oxygen exhaust pipe 22 and the methane exhaust pipe 26. This is used to measure the basic heat leakage when the refrigeration system is not turned on. At the same time, it can be used to test the state changes of liquid oxygen / liquid methane during the process of restoring equilibrium in the liquid oxygen / liquid methane co-bottom storage tank when the liquid oxygen / liquid methane is out of equilibrium.

[0031] This embodiment relates to the testing process of the above-mentioned device, specifically including:

[0032] 1) Connect the inlet and outlet of the large-area cold screen 6 to the helium circulation pipeline. Depending on the needs, different types of insulation materials can be arranged on the inner and outer sides of the large-area cold screen 6. The inner insulation material directly covers the outer surfaces of the liquid methane chamber 27 and the liquid oxygen chamber 28, while the outer insulation material covers the outer surface of the large-area cold screen 6. During the covering process, a batch of thermometers is installed on the surface of the large-area cold screen 6 to measure the temperature distribution on it. Another batch of thermometers is evenly arranged along the thickness direction within the insulation material to measure the temperature gradient within the insulation material. Then, all the above components are installed into the vacuum chamber. A thermal boundary temperature simulation copper screen is installed on the outer cylinder wall.

[0033] 2) The vacuum level inside the cavity is evacuated to 10 using a molecular pump unit. -4After reaching the Pa level, the heater in the hot water chamber is turned on, and the refrigeration system is started. Cold energy is transferred to the cold shield via a helium circulation pump to lower the temperature of the liquid oxygen chamber 28 and the liquid methane chamber 29 to the liquid oxygen temperature, preventing excessive evaporation after oxygen / methane liquefaction. Then, the liquefaction and filling of oxygen and methane begins. Once the liquid oxygen chamber 28 and the liquid methane chamber 29 are filled with cryogenic liquid, the temperature controller is turned on, and the temperature of the thermal boundary temperature simulation screen 4 is set to a predetermined value. The testing phase then begins. During the test, the thermometer temperatures on the large-area cold shield 6, the thermometer temperatures inside the liquid oxygen chamber 28 and the liquid methane chamber 29, the helium circulation flow rate, the oxygen exhaust flow rate, and the methane exhaust flow rate are recorded. By opening and closing the oxygen / methane exhaust valves or by locally heating the liquid oxygen chamber 28 and the liquid methane chamber 29, the liquid oxygen / liquid methane is deviated from its equilibrium state. The state changes of the liquid oxygen / liquid methane co-bottom storage system as it recovers from a non-equilibrium state to an equilibrium state are measured, thereby analyzing the performance of the liquid oxygen / liquid methane co-bottom zero-evaporation storage device.

[0034] Through specific practical experiments, the state changes of liquid oxygen and liquid methane within 120 hours after the start of the zero-evaporation test can be obtained, such as... Figure 2 As shown. The initial experimental parameters were set as follows: initial temperature of liquid oxygen 90.17 K, initial temperature of liquid methane 111.67 K, initial pressure of both at atmospheric pressure, initial filling rate of liquid oxygen and liquid methane chambers 0.8, common bottom material of aluminum, and 45 layers of multilayer insulation material. Because aluminum was used as the common bottom interlayer material between liquid oxygen and liquid methane, the thermal resistance between them was relatively low. Simultaneously, the temperature difference between liquid oxygen and liquid methane was relatively large (approximately 20 K), and the specific heat of liquid oxygen was lower than that of liquid methane, resulting in greater temperature fluctuations. Therefore, in the short period after zero evaporation begins, the average temperature of the liquid oxygen gas phase is mainly determined by the average temperature of the liquid methane liquid phase. As the average temperature of the liquid oxygen phase increases, the temperature difference between the liquid oxygen and liquid methane phases increases. When this difference reaches a certain value, the influence of the average temperature of the liquid oxygen liquid phase on the average temperature of the liquid oxygen phase gradually becomes dominant. Therefore, Figure 2 The average temperature of the oxygen phase in the liquid phase will show a trend of first increasing sharply and then slowly decreasing to a stable value.

[0035] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A liquid oxygen / liquid methane ground test system that meets zero boil-off storage requirements, characterized in that, It comprises: The outer cylinder wall, the large-area cold screen hung in its interior, the liquid nitrogen cavity, the hot water cavity arranged outside the outer cylinder wall, the liquid methane cavity and the liquid oxygen cavity hung in the large-area cold screen, wherein: the liquid nitrogen cavity and the hot water cavity are connected with the liquid methane cavity and the liquid oxygen cavity respectively, the liquid methane cavity and the liquid oxygen cavity are connected with the external methane source and the oxygen source respectively, the liquid methane cavity and the liquid oxygen cavity jointly constitute the liquid oxygen / liquid methane common bottom storage tank, the inlet and outlet of the large-area cold screen are connected with the helium circulation pipeline through the flexible pipeline, and the cold quantity in the liquid nitrogen cavity is transmitted to the large-area cold screen through the helium circulation pipeline; The liquid methane cavity, the liquid oxygen cavity and the large-area cold screen are hung in the outer cylinder wall through the end cover flange, and the end cover flange and the outer cylinder wall jointly constitute a closed vacuum cavity. Three mass flow meters, a vacuum exhaust port and two pressure sensors are arranged on the flange end cover, wherein: the two pressure sensors are arranged at the oxygen exhaust port and the methane exhaust port respectively, and are used for detecting the internal pressure of the liquid oxygen cavity and the internal pressure of the liquid methane cavity in the experimental test process; the three mass flow meters are respectively used for measuring the exhaust flow of oxygen and methane and the circulation flow of helium in the experimental process; The liquid nitrogen cavity is provided with an oxygen liquefaction pipe, a methane liquefaction pipe and a helium cooling pipe, wherein: the liquid nitrogen simultaneously provides cold quantity for the three parts, realizes oxygen liquefaction and methane liquefaction, and simultaneously reduces the helium to a suitable temperature; The hot water cavity is provided with an oxygen exhaust pipe, a methane exhaust pipe and a helium heating pipe, wherein: the hot water cavity can heat the low-temperature oxygen and the low-temperature methane to normal temperature state, so as to facilitate the measurement of the exhaust flow by the flow meter; the hot water cavity heats the helium to normal temperature state, so as to facilitate the measurement of the flow by the flow meter, and the helium is pressurized by the circulation gas pump; The low-temperature vapour in the liquid oxygen cavity and the liquid methane cavity can be directly exhausted outside the vacuum cavity through the oxygen exhaust pipe and the methane exhaust pipe, is used for measuring the basic heat leakage when the refrigeration system is not started, and can make the liquid oxygen / liquid methane in the liquid oxygen / liquid methane common bottom storage tank deviate from the equilibrium state, and is used for testing the state change of the liquid oxygen / liquid methane in the process of the liquid oxygen / liquid methane common bottom storage system recovering the equilibrium. The liquid oxygen / liquid methane common bottom storage tank is made of stainless steel without thermal insulation capacity.

2. The LO / LM ground test system satisfying the zero boil-off storage requirement of claim 1, wherein, The large-area cold screen has a diameter larger than that of the liquid oxygen cavity and the liquid methane cavity, is nested and surrounded outside the liquid oxygen / liquid methane common bottom storage tank, has the same shape as the liquid oxygen / liquid methane common bottom storage tank, and the centers of the two are coincident.

3. The LO / LM ground test system satisfying the zero boil-off storage requirement according to claim 1 or 2, characterized in that, A plurality of layers of thermal insulation materials are arranged between the large-area cold screen and the liquid methane cavity and the liquid oxygen cavity, and between the large-area cold screen and the hot boundary temperature simulation screen.

4. The LO / LM ground test system satisfying the zero boil-off storage requirement of claim 3, wherein, The plurality of layers of thermal insulation materials adopt one or more different combinations of equal-density vacuum multilayer, variable-density vacuum multilayer or polyurethane foam; the change of the position of the large-area cold screen in the thermal insulation material is realized by adjusting the amount of thermal insulation material on the inside and outside of the large-area cold screen.

5. The LO / LM ground test system satisfying the zero boil-off storage requirement of claim 1, wherein, A vacuum control valve and a molecular pump unit are sequentially arranged on the vacuum exhaust port, the vacuum degree in the cavity can be continuously controlled through dynamic vacuumization of the molecular pump unit and continuous automatic air supply of the vacuum control valve.

6. A test method of a liquid oxygen / liquid methane common bottom zero evaporation storage device based on the system of any one of claims 1-5, comprising: 1) Preparation stage: After the cavity is vacuumized by molecular pump unit, the heater of hot water cavity is turned on, the refrigeration system is started, the cold energy is delivered to the cold screen by helium circulating pump, the temperature of liquid oxygen cavity and liquid methane cavity is reduced to the temperature of liquid oxygen, so as to avoid the large evaporation after oxygen / methane liquefaction, then the liquefaction of oxygen and methane is started, after the liquid oxygen cavity and the liquid methane cavity are filled with low-temperature liquid, the temperature control instrument is turned on and the temperature of the hot boundary temperature simulation screen is set to the predetermined value; 2) Test stage: the temperature of the thermometer on the large-area cold screen, the temperature of the thermometer in the liquid oxygen cavity, the temperature of the thermometer in the liquid methane cavity, the circulating flow of helium, the exhaust flow of oxygen and the exhaust flow of methane gas are recorded; By opening and closing the oxygen / methane gas exhaust valve or locally heating the liquid oxygen cavity and the liquid methane cavity, the liquid oxygen / liquid methane deviates from the equilibrium state, the state change of the liquid oxygen / liquid methane common bottom storage system from the non-equilibrium state to the equilibrium state is measured, and then the performance of the liquid oxygen / liquid methane common bottom zero evaporation storage device is analyzed.

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