CN107967012B - Active control system and control method for zero-evaporation storage of low-temperature propellant - Google Patents
Active control system and control method for zero-evaporation storage of low-temperature propellant Download PDFInfo
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- CN107967012B CN107967012B CN201711036253.4A CN201711036253A CN107967012B CN 107967012 B CN107967012 B CN 107967012B CN 201711036253 A CN201711036253 A CN 201711036253A CN 107967012 B CN107967012 B CN 107967012B
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Abstract
The invention relates to an active control system and a control method for zero evaporation storage of a low-temperature propellant, which break through the technical problem of zero evaporation storage of the low-temperature propellant, combine an active refrigeration technology with a passive heat-proof technology, and provide and verify a method for realizing zero evaporation storage of liquid nitrogen working media; meanwhile, the invention realizes the zero evaporation storage of the liquid nitrogen by adopting the design of the cold head high-efficiency heat exchanger, the power and layout design of the heater, the optimization design of an orthogonal test and the like, and ensures the normal operation of the system by adopting the necessary low-temperature refrigeration system high-efficiency heat dissipation technology with lower cost.
Description
Technical Field
The invention relates to an active control system and a control method for zero-evaporation storage of a low-temperature propellant, and belongs to the field of long-term on-orbit storage and management of the low-temperature propellant.
Background
The low-temperature propellant has the characteristics of high specific flushing rate, no toxicity and no pollution. The low-temperature propellant represented by liquid hydrogen/liquid oxygen is considered as the most economical and most efficient chemical propellant for entering space and orbit transfer, is widely applied to domestic and foreign carrier rockets and upper-level vehicles, and is the first choice propellant for carrying out moon exploration, Mars exploration and farther-distance deep space exploration in the future. However, the low-temperature propellant has a low boiling point and is easy to evaporate when heated, and in future deep space exploration projects, a low-temperature storage tank can run on track for several days or even several years, so how to effectively control the evaporation of the low-temperature propellant becomes a core technical problem of on-track application of the low-temperature propellant. In order to ensure the on-track safe operation of the low-temperature storage tank, the evaporation capacity of the low-temperature storage tank needs to be controlled below a reasonable index. The introduction of active refrigeration technology is an important way to realize 'zero evaporation' on-track storage of low-temperature propellant.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides an active control system for the zero-evaporation storage of a low-temperature propellant, combines an active refrigeration technology with a passive heat-proof and insulation technology, realizes the zero-evaporation storage of liquid nitrogen, and solves the technical problem that the existing low-temperature propellant inevitably loses part of quality due to evaporation.
It is another object of the present invention to provide an active control method for "zero-boil-off" storage of cryogenic propellants.
The above purpose of the invention is mainly realized by the following technical scheme:
the active control system for the zero evaporation storage of the low-temperature propellant comprises a liquid nitrogen storage and transportation system, a data acquisition system, a refrigeration system and a liquid nitrogen evaporation amount control platform, wherein:
the liquid nitrogen storage and transportation system is used for storing liquid nitrogen and transporting the liquid nitrogen to the liquid nitrogen evaporation capacity control test platform; the data acquisition system is used for monitoring pressure, temperature, liquid level and flow data in the liquid nitrogen evaporation capacity control platform; the refrigerating system is used for generating cold energy, transmitting the cold energy to the liquid nitrogen evaporation capacity control test platform and carrying out refrigeration control on the liquid nitrogen evaporation capacity control test platform; the liquid nitrogen evaporation capacity control platform is used for receiving the liquid nitrogen conveyed by the liquid nitrogen storage and conveying system and the cold quantity conveyed by the refrigerating system, and actively controlling the liquid nitrogen evaporation capacity to realize the zero evaporation storage of the liquid nitrogen.
In the active control system, the liquid nitrogen storage and transportation system comprises a liquid nitrogen storage pressure tank, a liquid nitrogen vaporization pressurization valve and a liquid nitrogen transportation valve, wherein the liquid nitrogen storage pressure tank is used for storing liquid nitrogen; one end of the liquid nitrogen vaporization pressurization valve is communicated with the liquid part of the liquid nitrogen storage pressure tank, and the other end of the liquid nitrogen vaporization pressurization valve is communicated with the gas part of the liquid nitrogen storage pressure tank and is used for pressurizing the liquid nitrogen storage pressure tank; and the liquid nitrogen transportation valve is used for communicating the liquid nitrogen storage and transportation system with the liquid nitrogen evaporation amount control platform.
In the active control system, the refrigerating system comprises a refrigerator, a heat dissipation system and a cold head heat exchanger, wherein the refrigerator generates cold quantity and transmits the cold quantity to the cold head heat exchanger, and waste heat generated by the refrigerator is transmitted to the heat dissipation system; the heat dissipation system dissipates the waste heat generated by the refrigerator to the external environment; the cold head heat exchanger conveys cold energy generated by the refrigerator to the liquid nitrogen evaporation capacity control platform.
In the active control system, the heat dissipation system comprises a water-cooling unit and a cooling water storage tank, and an external circulating pump is used for pumping cooling water in the cooling water storage tank and conveying the cooling water into the water-cooling unit; and the water cooling unit cools the cooling water and then conveys the cooled cooling water to the refrigerator, the refrigerator transmits the generated waste heat to the cooled cooling water, and the cooling water returns to the cooling water storage tank to complete a cycle and continuously repeat the cycle.
In the active control system, the cold head heat exchanger is of a length-adjustable structure and comprises a heat exchanger, a heat conducting rod and a cold head, and when the cold head heat exchanger inputs cold energy to a gas phase region in the liquid nitrogen evaporation amount control platform, the cold head is directly connected with the heat exchanger; when the cold head heat exchanger inputs cold energy to the liquid phase region in the liquid nitrogen evaporation capacity control platform, the cold head is connected with one end of the heat conducting rod, and the other end of the heat conducting rod is connected with the heat exchanger.
In the above active control system, the surface area of the heat exchanger is not less than 0.1 square meter; the heat exchanger comprises a bottom plate and fins vertical to the bottom plate; the heat exchanger is made of metal copper.
In the active control system, the liquid nitrogen evaporation capacity control platform comprises a liquid nitrogen storage pressure container, a steam cooling device, a temperature measuring and heating device, a liquid level meter, a gas mass flow meter, a pressure transmitter, an upper cover, an exhaust valve and an exhaust valve of the steam cooling device, wherein the steam cooling device is used for cooling the liquid nitrogen storage pressure container, and the temperature measuring and heating device is used for heating or measuring the temperature of liquid nitrogen in the liquid nitrogen storage pressure container; the liquid level meter is used for measuring the liquid level of liquid nitrogen in the liquid nitrogen storage pressure container; one end of the exhaust valve is communicated with the liquid nitrogen storage pressure container, the other end of the exhaust valve is communicated with the gas mass flowmeter, and the exhaust valve is used for exhausting nitrogen; the gas mass flow meter is used for measuring the flow of the nitrogen; the pressure transmitter is used for measuring the pressure in the liquid nitrogen storage pressure container; the upper cover is positioned at the upper part of the liquid nitrogen storage pressure container and used for sealing the liquid nitrogen storage pressure container, and the exhaust valve of the steam cooling device is communicated with the steam cooling device and used for exhausting nitrogen in the steam cooling device.
In the active control system, the liquid nitrogen evaporation capacity control platform further comprises a liquid inlet valve, one end of the liquid inlet valve is communicated with the measurement liquid nitrogen storage pressure container, the other end of the liquid inlet valve is communicated with a liquid nitrogen transport valve in the liquid nitrogen storage and transport system, and the liquid nitrogen is controlled to enter the measurement liquid nitrogen storage pressure container.
In the active control system, the liquid nitrogen storage pressure container is of a sandwich structure, the steam cooling device is arranged inside the sandwich structure and is a spiral cooling pipe surrounding the outer surface of the inner wall of the sandwich structure of the liquid nitrogen storage pressure container, and nitrogen is filled in the spiral cooling pipe.
In the active control system, the liquid nitrogen evaporation capacity control platform further comprises an inner tank safety valve and a vacuum pumping port, wherein the inner tank safety valve is communicated with the liquid nitrogen storage pressure container, and when the pressure in the liquid nitrogen storage pressure container exceeds the upper limit of the safety pressure, the inner tank safety valve is automatically opened to exhaust; the vacuumizing port is arranged on the outer wall of the sandwich structure of the liquid nitrogen storage pressure container and is used for vacuumizing the sandwich structure.
In the active control system, the refrigerating capacity of the refrigerating system is greater than the total heat leakage quantity of the liquid nitrogen evaporation capacity control platform.
The control method of the active control system for the zero-evaporation storage of the low-temperature propellant comprises the following steps:
opening a liquid nitrogen vaporization pressurization valve in a liquid nitrogen storage and transportation system, discharging part of liquid nitrogen and vaporizing the part of liquid nitrogen to increase the pressure in a liquid nitrogen storage pressure tank, and opening the liquid nitrogen transportation valve and a liquid inlet valve to transport the liquid nitrogen to a liquid nitrogen storage pressure container when the pressure in the liquid nitrogen storage pressure tank rises to a set value;
closing an exhaust valve of the steam cooling device, opening the exhaust valve, transmitting a liquid level signal to a data acquisition system through a liquid level meter, and sequentially closing a liquid inlet valve, the exhaust valve, a liquid nitrogen transport valve and a liquid nitrogen vaporization pressurization valve when the data acquisition system displays that the liquid level in the liquid nitrogen storage pressure container reaches a set value V;
and step three, starting a heater in the temperature measurement and heater to accelerate vaporization and evaporation of liquid nitrogen in the liquid nitrogen storage pressure container, transmitting a pressure signal to a data acquisition system through a pressure transmitter, and displaying that the pressure in the liquid nitrogen storage pressure container rises to a set value P by the data acquisition systemmaxTurning off a heater of the temperature measuring and heating devices;
step four, starting a refrigerator and a heat dissipation system in the refrigeration system;
monitoring by a data acquisition system, and when the pressure in the liquid nitrogen storage pressure container is reduced to a set value PminWhen the pressure in the liquid nitrogen storage pressure container rises again, the refrigerating machine and the heat dissipation system are closed, and when the pressure reaches the set value P againmaxAnd (5) returning to the step (four).
In the control method of the active control system, the pressure set value in the step (I) is 0.6-0.8 MPa.
In the control method of the active control system, the liquid level set value V in the step (ii) indicates that the liquid level in the liquid nitrogen storage pressure vessel reaches 70% to 80% of the volume of the liquid nitrogen storage pressure vessel.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention breaks through the technical problem of zero evaporation storage of low-temperature propellant, combines the active refrigeration technology with the passive heat-proof technology, and provides and verifies a method for realizing zero evaporation storage of liquid nitrogen working medium, and the method provides a system and a method for realizing rapid depressurization and zero evaporation control of low-temperature working medium based on a refrigerator on the basis of the original low-temperature propellant storage tank, thereby realizing zero evaporation storage of liquid nitrogen and solving the technical problem that the existing low-temperature propellant storage inevitably loses partial quality due to evaporation;
(2) the invention realizes the zero evaporation storage of the liquid nitrogen by adopting the design of the cold head high-efficiency heat exchanger, the power and layout design of the heater, the optimization design of the orthogonal test and the like, and ensures the normal operation of the system by adopting the necessary low-temperature refrigeration system high-efficiency heat dissipation technology with lower cost;
(3) the invention carries out innovative design on the cold head heat exchanger in the refrigeration system, the cold head heat exchanger is of a length-adjustable structure, can carry out position adjustment according to the requirement, and has simple and reliable structure and easy operation; the configuration design can be used for verifying that the cold input in a gas phase area and the cold input in a liquid phase area of the low-temperature propellant are at the different and same points for realizing the zero evaporation storage of the liquid nitrogen;
(4) the heat dissipation system adopted by the invention has simple and reliable structure, lower cost and obvious effect, fully utilizes the large heat capacity of large-volume cooling water, utilizes a water-cooling unit with smaller power to realize the heat dissipation task of the high-power refrigerator, and can stably work for more than 12 hours under the condition of not replacing the cooling water;
(5) the scheme design of the invention not only can realize the zero evaporation storage of the liquid nitrogen and reduce the storage loss of the propellant, but also can complete various liquid nitrogen evaporation rate control tests such as an experiment for reducing the evaporation rate of the liquid nitrogen through a steam cooling device, an experiment for regulating and controlling the system pressure through periodic exhaust and the like, can still effectively reduce the evaporation capacity of the liquid nitrogen under the condition of not starting a refrigerator, has more flexible and various realization modes and meets different scene requirements.
Drawings
FIG. 1 is a schematic diagram of the active control system for "zero-boil-off" storage of the cryogenic propellant of the present invention;
FIG. 2 is a schematic diagram of a cold head heat exchanger according to the present invention;
fig. 3 is a schematic view of the heat dissipation system of the present invention.
Detailed Description
The invention is described in further detail below with reference to the following figures and specific examples:
fig. 1 is a schematic diagram of the composition of an active control system for zero-evaporation storage of the low-temperature propellant, and it can be seen that the active control system of the invention comprises a liquid nitrogen storage and transportation system I, a data acquisition system II, a refrigeration system III and a liquid nitrogen evaporation amount control platform IV, wherein: the liquid nitrogen storage and transportation system I is used for storing liquid nitrogen and transporting the liquid nitrogen to a liquid nitrogen evaporation capacity control test platform IV; the data acquisition system II is used for monitoring pressure, temperature, liquid level and flow data in the liquid nitrogen evaporation capacity control platform IV; the refrigerating system III is used for generating cold energy, conveying the cold energy to the liquid nitrogen evaporation capacity control test platform IV and performing refrigeration control on the liquid nitrogen evaporation capacity control test platform IV; and the liquid nitrogen evaporation capacity control platform IV is used for receiving the liquid nitrogen conveyed by the liquid nitrogen storage and conveying system I and the cold quantity conveyed by the refrigerating system, and actively controlling the liquid nitrogen evaporation capacity to realize zero evaporation storage of the liquid nitrogen.
As shown in fig. 1, the liquid nitrogen storage and transportation system I comprises a liquid nitrogen storage pressure tank 1, a liquid nitrogen vaporization pressurization valve V4, a liquid nitrogen transportation valve V0 and a pipeline, wherein the liquid nitrogen storage pressure tank 1 is used for storing liquid nitrogen; one end of the liquid nitrogen vaporization pressurization valve V4 is communicated with the liquid part of the liquid nitrogen storage pressure tank 1, the other end of the liquid nitrogen vaporization pressurization valve V4 is communicated with the gas part of the liquid nitrogen storage pressure tank 1 after being connected with a vaporization chamber, and the vaporization chamber vaporizes part of liquid nitrogen discharged by the liquid nitrogen vaporization pressurization valve V4 to realize pressurization of the liquid nitrogen storage pressure tank 1; and a liquid nitrogen conveying valve V0 is used for communicating the liquid nitrogen storage and conveying system I with the liquid nitrogen evaporation amount control platform IV.
The refrigerating system III comprises a refrigerator 3, a heat dissipation system 4 and a cold head heat exchanger 5, wherein the refrigerator 3 generates cold quantity and transmits the cold quantity to the cold head heat exchanger 5, and waste heat generated by the refrigerator 3 is transmitted to the heat dissipation system 4; the heat dissipation system 4 is used for dissipating waste heat generated by the refrigerator 3 outwards; the cold head heat exchanger 5 conveys the cold energy generated by the refrigerator 3 to the liquid nitrogen evaporation capacity control platform IV. In the embodiment of the invention, the refrigerant 3 adopts a G-M refrigerator.
As shown in fig. 3, which is a schematic diagram of the heat dissipation system of the present invention, it can be seen that the heat dissipation system 4 includes a water chiller 13 and a cooling water storage tank 14, and an external circulating pump pumps the cooling water in the cooling water storage tank 14 and delivers the cooling water into the water chiller 13; the water chiller unit 13 cools the cooling water and then delivers the cooled cooling water to the refrigerator 3, the refrigerator 3 transmits the generated waste heat to the cooled cooling water, and the cooling water returns to the cooling water storage tank 14 to complete a cycle, and the cycle is repeated continuously. The high-capacity cooling water in the cooling water storage tank 14 can dilute high-temperature return water, so that the temperature of the recirculated cooling water is raised very low, and the workload of the water cooling unit 13 is reduced.
As shown in fig. 2, which is a schematic structural diagram of the cold head heat exchanger of the present invention, it can be seen that the cold head heat exchanger 5 is in a length-adjustable configuration, and includes a heat exchanger 15, a heat conducting rod 16 and a cold head 17, and when the cold head heat exchanger 5 inputs cold energy to a gas phase region in a liquid nitrogen evaporation amount control platform IV, the cold head 17 is directly connected with the heat exchanger 15. When the cold head heat exchanger 5 inputs cold energy to the liquid phase region in the liquid nitrogen evaporation capacity control platform IV, the cold head 17 is connected with one end of the heat conducting rod 16, and the other end of the heat conducting rod 16 is connected with the heat exchanger 15. The heat conductive rod 16 of the present invention is made of aluminum metal or copper metal.
The surface area of the heat exchanger 15 in the invention is not less than 0.1 square meter, as shown in fig. 2, the heat exchanger 15 comprises a bottom plate and a plurality of fins vertical to the bottom plate, the fins are uniformly or non-uniformly distributed on the bottom plate, and the material of the heat exchanger 15 is copper.
As shown in fig. 1, the liquid nitrogen evaporation capacity control platform IV includes a liquid nitrogen storage pressure vessel 6, a vapor cooling device 7, a temperature measuring and heating device 8, a liquid level meter 9, a gas mass flow meter 10, a pressure transmitter 11, an upper cover 12, a liquid inlet valve V1, an exhaust valve V2, a vapor cooling device exhaust valve V3, an inner tank safety valve S, and a vacuum pumping port Z4.
The liquid nitrogen storage pressure container 6 is of a sandwich structure, the steam cooling device 7 is arranged inside the sandwich structure, the steam cooling device 7 is a spiral ascending cooling pipe and surrounds the outer surface of the inner wall of the sandwich structure of the liquid nitrogen storage pressure container 6, and nitrogen is filled in the spiral cooling pipe. The vapor cooling device 7 is used for cooling the liquid nitrogen storage pressure vessel 6.
The temperature measuring and heating device 8 is arranged inside the liquid nitrogen storage pressure container 6 and used for heating or measuring the temperature of the liquid nitrogen inside the liquid nitrogen storage pressure container 6 and transmitting the temperature data to the data acquisition system II.
The liquid level meter 9 is used for measuring the liquid level of liquid nitrogen in the liquid nitrogen storage pressure container 6 and transmitting liquid level data to the data acquisition system II. One end of an exhaust valve V2 is communicated with the liquid nitrogen storage pressure container 6, the other end of the exhaust valve V2 is communicated with the gas mass flowmeter 10, and an exhaust valve V2 is used for exhausting nitrogen; the gas mass flow meter 10 is used for measuring the flow rate of nitrogen and transmitting the flow rate data to the data acquisition system II. The pressure transmitter 11 is communicated with the liquid nitrogen storage pressure vessel 6 and is used for measuring the pressure in the liquid nitrogen storage pressure vessel 6 and transmitting the pressure data to the data acquisition system II. The upper cover 12 is an upper flange cover, is located at the upper part of the liquid nitrogen storage pressure container 6, seals the liquid nitrogen storage pressure container 6, and is used as a bearing for instrument installation. The exhaust valve V3 of the steam cooling device is communicated with the steam cooling device 7 to exhaust nitrogen in the steam cooling device 7. One end of the liquid inlet valve V1 is communicated with the measurement liquid nitrogen storage pressure container 6, and the other end is communicated with a liquid nitrogen transportation valve V0 in the liquid nitrogen storage and transportation system I, so that liquid nitrogen is controlled to enter the measurement liquid nitrogen storage pressure container 6.
The inner tank safety valve S is communicated with the liquid nitrogen storage pressure container 6, and when the pressure in the liquid nitrogen storage pressure container 6 exceeds the upper limit of the safety pressure, the inner tank safety valve S is automatically opened to exhaust. And a vacuumizing port Z4 is arranged on the outer wall of the sandwich structure of the liquid nitrogen storage pressure container 6 and is used for vacuumizing the sandwich structure.
The data acquisition system II comprises a multi-channel data acquisition instrument, a computer, automatic data acquisition software and a direct current stabilized power supply. And the data acquisition system II is mainly used for acquiring and monitoring pressure, temperature, liquid level and flow data in the liquid nitrogen evaporation capacity control platform IV.
The refrigerating capacity (namely the refrigerating capacity of the refrigerating machine) of the refrigerating system III is larger than the total heat leakage quantity of the liquid nitrogen evaporation quantity control platform IV.
The invention relates to a control method of an active control system for zero evaporation storage of a low-temperature propellant, which specifically comprises the following steps:
opening a liquid nitrogen vaporization pressurization valve V4 in a liquid nitrogen storage and transportation system I, discharging part of liquid nitrogen and vaporizing the liquid nitrogen, increasing the pressure in a liquid nitrogen storage pressure tank 1 to enable the pressure in the liquid nitrogen storage pressure tank 1 to rise to a set value, opening a liquid nitrogen transportation valve V0 and a liquid inlet valve V1, and transporting the liquid nitrogen to a liquid nitrogen storage pressure container 6. The mass of part of liquid nitrogen discharged in the embodiment of the invention is less than 0.01 percent of the total mass of the liquid nitrogen. In the embodiment of the invention, the pressure setting value is 0.6-0.8 MPa.
Step (II), closing an exhaust valve V3 of the steam cooling device, opening an exhaust valve V2, transmitting a liquid level signal to a data acquisition system II through a liquid level meter 9, and when the data acquisition system II displays that the liquid level in the liquid nitrogen storage pressure container 6 reaches a set value V, closing a liquid inlet valve V1, an exhaust valve V2, a liquid nitrogen transport valve V0 and a liquid nitrogen vaporization pressurization valve V4 in sequence; in the embodiment of the invention, the liquid level set value V is that the liquid level of the liquid nitrogen storage pressure container 6 reaches 70-80% of the volume of the liquid nitrogen storage pressure container 6.
And step (III) starting a heater in the temperature measurement and heater 8 to accelerate vaporization and evaporation of the liquid nitrogen in the liquid nitrogen storage pressure container 6, transmitting a pressure signal to the data acquisition system II through the pressure transmitter 11, and displaying that the pressure in the liquid nitrogen storage pressure container 6 rises to a set value P by the data acquisition system IImaxWhile, the heater of the temperature measurement and heater 8 is turned off; setting value P in the embodiment of the inventionmaxIs 0.4 MPa.
And step (IV), starting the G-M refrigerator 3 and the heat dissipation system 4 in the refrigeration system III.
Step five, the data acquisition system II monitors, when the pressure in the liquid nitrogen storage pressure container 6 is reduced to a set value PminWhen the refrigerating machine 3 and the heat dissipation system 4 are closed, the pressure in the liquid nitrogen storage pressure container 6 gradually rises, and when the pressure reaches the set value P againmaxAnd (5) repeating the step (IV). Setting value P in the embodiment of the inventionminIs 0.2 MPa. In the method, the liquid nitrogen stored in the liquid nitrogen storage pressure container 6 realizes that the system pressure does not exceed a set range, the air is not exhausted, the liquid nitrogen is stored without damage, and the storage target of the liquid nitrogen is realized by 'zero evaporation'.
The invention can realize the zero evaporation storage of the liquid nitrogen, reduce the storage loss of the propellant, and simultaneously can complete various liquid nitrogen evaporation rate control tests such as an experiment for reducing the evaporation rate of the liquid nitrogen by a steam cooling device, an experiment for regulating and controlling the system pressure by periodic exhaust and the like, can still effectively reduce the evaporation capacity of the liquid nitrogen under the condition of not starting a refrigerating machine, has more flexible and various realization modes, and meets the requirements of different scenes.
The heat dissipation system adopted by the invention has simple and reliable structure, lower cost and obvious effect, and the structure fully utilizes the large volume (1 m)3) The large heat capacity of the cooling water realizes the heat dissipation task of the high-power (7500W) G-M refrigerator by using a water-cooling unit with smaller power (2000W). The system can stably work for more than 12 hours under the condition of not replacing cooling water.
The invention aims at the heat leakage design steps of the system as follows:
the liquid nitrogen storage pressure container 6 has the volume of 0.5m3The design pressure is 0.6MPa, the used medium is liquid nitrogen, the working temperature is 77K, the main body adopts a vacuum multilayer heat insulation tank body, and the top of the main body adopts an internal and external foaming heat insulation flange form, so that the low-temperature container has certain heat leakage loss. The low temperature container main part adopts the adiabatic jar body of vacuum multilayer, the top is the adiabatic flange form of foaming, consequently, its heat leakage mainly includes two parts: the first part is the heat leakage of the main vacuum multi-layer tank body; the second part is the heat leakage of the foaming flange cover. The calculation formula of the total heat leakage quantity of the system is as follows:
Qgeneral assembly＝QTank body+QFlange
Wherein; qTank bodyHeat leakage of the vacuum multi-layer tank body; qFlangeHeat leakage of the foaming flange cover.
The internal vacuum degree of the vacuum multi-layer tank body is far less than 103Pa, the gas convection heat transfer can be ignored, the heat leakage mainly comprises four parts of residual gas heat conduction, conduit heat conduction on the inner wall and the outer wall, radiant heat, flange heat conduction on the inner tank body and the like, and the heat transfer quantity is calculated and expressed as the following calculation formula:
Qtank body＝Qg+Qr+Qc+Qf
Wherein QgHeat leakage heat of residual gas in the vacuum interlayer; qrHeat leakage for tank wall radiation; qcHeat is leaked for heat conduction of the connecting pipe; qfHeat is leaked for the heat conduction of the upper flange.
The gas heat conduction of the gas cavity of the liquid nitrogen storage pressure container 6 can be calculated according to the heat conduction of gas molecules in a free molecular state, and the heat transfer quantity can be calculated according to the following formula:
wherein α is adaptive coefficient dependent on the gas type, wall temperature and the ratio of inner and outer wall area, K is gas adiabatic index, R is universal gas constant, P is vacuum interlayer gas pressure, M is gas molecular weight, and T ismIs the average temperature between layers; a is the heat transfer surface area; t iso，TiThe surface temperatures of the outer wall and the inner wall, respectively; n is the number of adiabatic layers.
A liquid inlet pipe, a direct exhaust pipe and a cold shield exhaust pipe are arranged on the vertical liquid nitrogen storage pressure container 6 and respectively and directly penetrate through the inner wall and the outer wall of the tank body, so that heat is transferred from the outer wall to the inner wall through the guide pipes, and the heat transfer quantity is calculated as shown in the following formula.
In the formula: lambda is the heat conductivity coefficient of the conduit; l is the thermal bridge length; t iso，TiThe surface temperatures of the outer wall and the inner wall, respectively; and A is the cross-sectional area of the supporting thermal bridge.
Considering the radiant heat between the inner wall and the outer wall, in order to simplify the calculation, the inner wall and the outer wall are simplified into two layers of cold shields for calculation, and the radiant heat transfer quantity QrCalculated from the following equation
In the formula: sigma is Stefan-Boltzmann constant; epsilon-the emission coefficient of the reflecting screen; n is the number of heat insulation layers; t iso，TiThe surface temperatures of the outer wall and the inner wall, respectively; a. theiIs the internal surface area.
The main tank body of the low-temperature container is of a vacuum multilayer structure, the inner tank body of the low-temperature container is connected with the outer tank body through an upper flange, and the flange is exposed in the environment, so that part of heat is transmitted to the interior of the container through the flange and the inner tank body. The heat quantity is calculated as shown in the following formula
In the formula: lambda is the heat conductivity coefficient of the conduit; l is the thermal bridge length; t iso，TiThe surface temperatures of the outer wall and the inner wall, respectively; and A is the cross-sectional area of the supporting thermal bridge.
The refrigerating machine interface tube, the capacitance liquid level meter interface tube and the temperature measuring rod interface tube are arranged on the upper flange cover, so that certain heat leakage exists. In order to reduce heat leakage loss, an epoxy glass fiber reinforced plastic gasket with a certain thickness is arranged between the lower part of the upper flange cover and the inner container, so that direct contact between each equipment interface guide pipe and the flange is avoided, foaming heat insulation is carried out on the periphery of the upper flange, foaming heat insulation is also carried out on the partial structure of the upper surface, and only the installation position of the refrigerator is reserved without foaming heat insulation. The heat transfer capacity is as follows:
Qflange＝Qz+Ql+Qt+Qp
Wherein QzHeat conduction and heat leakage of a refrigerating machine connecting pipe are realized; qlHeat conduction and heat leakage are carried out on a liquid level meter connecting pipe; qtHeat conduction and heat leakage of the temperature measuring rod connecting pipe are realized; qpThe heat is conducted and leaked by the upper flange cover.
One end of the refrigerating machine connecting pipe is fixed on the lower plate of the foaming heat insulation sleeve in the upper flange cover, and the other end of the refrigerating machine connecting pipe is connected with the epoxy glass fiber reinforced plastic, so that heat leakage loss is reduced. The outer side of the flange at the installation position of the refrigerator is not foamed and is directly exposed in the external environment. The heat calculation is shown below:
in the formula: lambda is conduit guideThermal coefficient; l is the length of the heat bridge of the catheter; t iso，TiThe external environment and the internal temperature of the container are respectively; and A is the cross-sectional area of the catheter.
One end of a connecting pipe of the capacitance liquid level meter is fixed on the lower plate of the foaming heat-insulating sleeve in the upper flange cover, and the other end of the connecting pipe is connected with the epoxy glass fiber reinforced plastic, so that heat leakage loss is reduced. The heat calculation is shown below:
in the formula: lambda is the heat conductivity coefficient of the conduit; l is the thermal bridge length; t iso，TiThe surface temperatures of the outer wall and the inner wall, respectively; and A is the cross-sectional area of the supporting thermal bridge.
One end of the temperature measuring rod connecting pipe is fixed on the lower plate of the foaming heat-insulating sleeve in the upper flange cover, and the other end of the temperature measuring rod connecting pipe is connected with the epoxy glass fiber reinforced plastic, so that heat leakage loss is reduced. The heat calculation is shown below:
in the formula: lambda is the heat conductivity coefficient of the conduit; l is the thermal bridge length; t iso，TiThe surface temperatures of the outer wall and the inner wall, respectively; and A is the cross-sectional area of the supporting thermal bridge.
In order to reduce heat leakage loss, the upper flange cover is subjected to internal and external foaming heat insulation, and the outer side of the flange is not foamed at the installation position of the refrigerator. Therefore, the heat conduction quantity of the upper flange cover is calculated and divided into two parts, namely foaming outside the upper flange cover and non-foaming outside the upper flange cover.
For the foamed part outside the upper flange cover, the heat conduction path is as follows: the heat respectively enters the interior of the container through the outer side foaming layer, the upper flange cover, the epoxy glass fiber reinforced plastic liner and the inner side foaming layer.
According to the heat conduction calculation formula, there are:
in the formula: λ is the heat conductivity of the conduit, λ1、λ2、λ3The thermal conductivity coefficients of the polyurethane foaming layer, the stainless steel flange and the epoxy glass fiber reinforced plastic gasket are respectively; l is the length of the heat bridge of the catheter, l1、l2、l3、l4The thicknesses of the outer polyurethane foaming layer, the stainless steel flange cover, the epoxy glass fiber reinforced plastic liner and the inner polyurethane foaming layer are respectively set; t iso，TiRespectively the external ambient and internal temperature, T, of the container12、T23、T34Respectively calculating the temperature between each layer; and A is the area of the unfoamed part on the outer side of the upper flange cover.
For the non-foamed part on the outer side of the upper flange cover, the external environment directly transfers heat with the flange, and the heat respectively enters the interior of the container through the upper flange cover, the epoxy glass fiber reinforced plastic liner and the inner side foaming layer. According to the heat conduction calculation formula, there are:
in the formula: λ is the heat conductivity of the conduit, λ1、λ2、λ3The thermal conductivity coefficients of the polyurethane foaming layer, the stainless steel flange and the epoxy glass fiber reinforced plastic gasket are respectively; l is the length of the heat bridge of the catheter, l1、l2、l3、l4The thicknesses of the stainless steel flange cover, the epoxy glass fiber reinforced plastic gasket and the polyurethane foaming layer at the inner side are respectively set; t iso，TiRespectively the external ambient and internal temperature, T, of the container12、T23Respectively calculating the temperature between each layer; and A is the area of the unfoamed part on the outer side of the upper flange cover.
The total heat leak from the cryogen vessel was calculated to be about 40.41W, as shown in table 1. The total refrigerating capacity of the G-M refrigerating machine selected in the invention is not less than 130W at 77K, and the refrigerating capacity is greater than the total heat leakage quantity of the container, thereby meeting the design and use requirements.
TABLE 1 heat leakage of cryogenic vessel
The above description is only for the best mode of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention disclosed herein should be covered within the scope of the present invention.
Those skilled in the art will appreciate that the invention may be practiced without these specific details.
Claims (12)
1. The active control system for the zero evaporation storage of the low-temperature propellant is characterized in that: including liquid nitrogen storage transport system (I), data acquisition system (II), refrigerating system (III) and liquid nitrogen evaporation capacity control platform (IV), wherein:
the liquid nitrogen storage and transportation system (I) is used for storing liquid nitrogen and transporting the liquid nitrogen to a liquid nitrogen evaporation capacity control test platform (IV); the data acquisition system (II) is used for monitoring pressure, temperature, liquid level and flow data in the liquid nitrogen evaporation capacity control platform (IV); the refrigerating system (III) is used for generating cold energy, conveying the cold energy to the liquid nitrogen evaporation capacity control test platform (IV) and performing refrigeration control on the liquid nitrogen evaporation capacity control test platform (IV); the liquid nitrogen evaporation capacity control platform (IV) is used for receiving the liquid nitrogen conveyed by the liquid nitrogen storage and conveying system (I) and the cold quantity conveyed by the refrigerating system (III), and actively controlling the liquid nitrogen evaporation capacity to realize 'zero evaporation' storage of the liquid nitrogen;
the refrigerating system (III) comprises a refrigerator (3), a heat dissipation system (4) and a cold head heat exchanger (5), wherein the refrigerator (3) generates cold quantity and transmits the cold quantity to the cold head heat exchanger (5), and waste heat generated by the refrigerator (3) is transmitted to the heat dissipation system (4); the heat dissipation system (4) dissipates the waste heat generated by the refrigerator (3) to the external environment; the cold head heat exchanger (5) conveys the cold energy generated by the refrigerator (3) to the liquid nitrogen evaporation capacity control platform (IV);
the cold head heat exchanger (5) is of a length-adjustable structure and comprises a heat exchanger (15), a heat conducting rod (16) and a cold head (17), and when the cold head heat exchanger (5) inputs cold energy to a gas phase region in the liquid nitrogen evaporation capacity control platform (IV), the cold head (17) is directly connected with the heat exchanger (15); when the cold head heat exchanger (5) inputs cold energy to the liquid phase region in the liquid nitrogen evaporation capacity control platform (IV), the cold head (17) is connected with one end of the heat conducting rod (16), and the other end of the heat conducting rod (16) is connected with the heat exchanger (15).
2. The active control system of claim 1, wherein: the liquid nitrogen storage and transportation system (I) comprises a liquid nitrogen storage pressure tank (1), a liquid nitrogen vaporization pressurization valve (V4) and a liquid nitrogen transportation valve (V0), wherein the liquid nitrogen storage pressure tank (1) is used for storing liquid nitrogen; one end of a liquid nitrogen vaporization pressurization valve (V4) is communicated with the liquid part of the liquid nitrogen storage pressure tank (1), and the other end is communicated with the gas part of the liquid nitrogen storage pressure tank (1) and is used for pressurizing the liquid nitrogen storage pressure tank (1); and a liquid nitrogen delivery valve (V0) is used for communicating the liquid nitrogen storage and delivery system (I) with the liquid nitrogen evaporation amount control platform (IV).
3. The active control system of claim 1, wherein: the heat dissipation system (4) comprises a water cooling unit (13) and a cooling water storage tank (14), and an external circulating pump is used for pumping cooling water in the cooling water storage tank (14) and conveying the cooling water into the water cooling unit (13); the water cooling unit (13) is right the cooling water is cooled and then is conveyed to the refrigerating machine (3), the refrigerating machine (3) transmits the generated waste heat to the cooling water after being cooled, the cooling water returns to the cooling water storage tank (14), a cycle is completed, and the cycle is repeated continuously.
4. The active control system of claim 1, wherein: the surface area of the heat exchanger (15) is not less than 0.1 square meter; the heat exchanger (15) comprises a bottom plate and fins vertical to the bottom plate; the heat exchanger (15) is made of metal copper.
5. The active control system of claim 1, wherein: the liquid nitrogen evaporation capacity control platform (IV) comprises a liquid nitrogen storage pressure container (6), a steam cooling device (7), a temperature measuring and heating device (8), a liquid level meter (9), a gas mass flow meter (10), a pressure transmitter (11), an upper cover (12), an exhaust valve (V2) and an exhaust valve (V3) of the steam cooling device, wherein the steam cooling device (7) is used for cooling the liquid nitrogen storage pressure container (6), and the temperature measuring and heating device (8) is used for heating or measuring the temperature of liquid nitrogen in the liquid nitrogen storage pressure container (6); the liquid level meter (9) is used for measuring the liquid level of liquid nitrogen in the liquid nitrogen storage pressure container (6); one end of an exhaust valve (V2) is communicated with the liquid nitrogen storage pressure container (6), the other end of the exhaust valve is communicated with the gas mass flowmeter (10), and the exhaust valve (V2) is used for exhausting nitrogen; the gas mass flow meter (10) is used for measuring the flow of the nitrogen; the pressure transmitter (11) is used for measuring the pressure in the liquid nitrogen storage pressure container (6); the upper cover (12) is positioned at the upper part of the liquid nitrogen storage pressure container (6) and seals the liquid nitrogen storage pressure container (6), and the exhaust valve (V3) of the steam cooling device is communicated with the steam cooling device (7) to exhaust nitrogen in the steam cooling device (7).
6. The active control system of claim 5, wherein: the liquid nitrogen evaporation amount control platform (IV) further comprises a liquid inlet valve (V1), one end of the liquid inlet valve (V1) is communicated with the liquid nitrogen storage pressure container (6) for measurement, the other end of the liquid inlet valve is communicated with a liquid nitrogen transportation valve (V0) in the liquid nitrogen storage and transportation system (I), and liquid nitrogen is controlled to enter the liquid nitrogen storage pressure container (6) for measurement.
7. The active control system of claim 5, wherein: the liquid nitrogen storage pressure container (6) is of a sandwich structure, the steam cooling device (7) is arranged inside the sandwich structure, the steam cooling device (7) is a spiral cooling pipe and surrounds the outer surface of the inner wall of the sandwich structure of the liquid nitrogen storage pressure container (6), and nitrogen is filled in the spiral cooling pipe.
8. The active control system of claim 5, wherein: the liquid nitrogen evaporation capacity control platform (IV) further comprises an inner tank safety valve (S) and a vacuumizing port (Z4), wherein the inner tank safety valve (S) is communicated with the liquid nitrogen storage pressure container (6), and when the pressure in the liquid nitrogen storage pressure container (6) exceeds the upper limit of the safety pressure, the inner tank safety valve is automatically opened to exhaust; the vacuumizing port (Z4) is arranged on the outer wall of the sandwich structure of the liquid nitrogen storage pressure container (6) and is used for vacuumizing the sandwich structure.
9. The active control system according to any one of claims 1 to 8, wherein: the refrigerating capacity of the refrigerating system (III) is larger than the total heat leakage quantity of the liquid nitrogen evaporation quantity control platform (IV).
10. The method of controlling an active control system for the "zero evaporation" storage of cryogenic propellants according to one of claims 1 to 8, characterized in that: the method comprises the following steps:
step one, opening a liquid nitrogen vaporization pressurization valve (V4) in a liquid nitrogen storage and transportation system (I), discharging part of liquid nitrogen and vaporizing the part of liquid nitrogen, increasing the pressure in a liquid nitrogen storage pressure tank (1), and when the pressure in the liquid nitrogen storage pressure tank (1) rises to a set value, opening a liquid nitrogen transportation valve (V0) and a liquid inlet valve (V1) to transport the liquid nitrogen to a liquid nitrogen storage pressure container (6);
step (II), closing an exhaust valve (V3) of the steam cooling device, opening the exhaust valve (V2), transmitting a liquid level signal to a data acquisition system (II) through a liquid level meter (9), and closing a liquid inlet valve (V1), the exhaust valve (V2), a liquid nitrogen transport valve (V0) and a liquid nitrogen vaporization pressurization valve (V4) in sequence when the data acquisition system (II) displays that the liquid level in the liquid nitrogen storage pressure container (6) reaches a set value V;
and step three, starting a heater in the temperature measurement and heater (8) to accelerate vaporization and evaporation of liquid nitrogen in the liquid nitrogen storage pressure container (6), transmitting a pressure signal to the data acquisition system (II) through the pressure transmitter (11), and when the data acquisition system (II) displays that the pressure in the liquid nitrogen storage pressure container (6) rises to a set value PmaxWhen the temperature is higher than the set temperature, the heater in the temperature measuring and heating device (8) is turned off;
step four, starting a refrigerator (3) and a heat dissipation system (4) in the refrigeration system (III);
monitoring by a data acquisition system (II) when the pressure in the liquid nitrogen storage pressure container (6) is reduced to a set value PminWhen the refrigerator (3) and the heat dissipation system (4) are closed, the pressure in the liquid nitrogen storage pressure container (6) rises again, and when the pressure rises, the liquid nitrogen storage pressure container is openedThe pressure again reaches the set value PmaxAnd (5) returning to the step (four).
11. The control method of the active control system according to claim 10, characterized in that: the pressure set value in the step (I) is 0.6-0.8 MPa.
12. The control method of the active control system according to claim 10, characterized in that: and (3) the liquid level set value V in the step (II) represents that the liquid level in the liquid nitrogen storage pressure container (6) reaches 70-80% of the volume of the liquid nitrogen storage pressure container (6).
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| CN110553969B (en) * | 2019-08-22 | 2020-08-04 | 西安交通大学 | Experimental device for measuring porous medium low temperature wicking characteristic with adjustable superheat degree |
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