CN109297804B - Liquid hydrogen temperature area material mechanics test platform based on low-temperature refrigerator and refrigerant circulation - Google Patents
Liquid hydrogen temperature area material mechanics test platform based on low-temperature refrigerator and refrigerant circulation Download PDFInfo
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- CN109297804B CN109297804B CN201811276846.2A CN201811276846A CN109297804B CN 109297804 B CN109297804 B CN 109297804B CN 201811276846 A CN201811276846 A CN 201811276846A CN 109297804 B CN109297804 B CN 109297804B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D17/00—Arrangements for circulating cooling fluids; Arrangements for circulating gas, e.g. air, within refrigerated spaces
- F25D17/02—Arrangements for circulating cooling fluids; Arrangements for circulating gas, e.g. air, within refrigerated spaces for circulating liquids, e.g. brine
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D3/00—Devices using other cold materials; Devices using cold-storage bodies
- F25D3/10—Devices using other cold materials; Devices using cold-storage bodies using liquefied gases, e.g. liquid air
Abstract
The invention relates to the technical field of material mechanics tests, and aims to provide a liquid hydrogen temperature region material mechanics test platform based on a low-temperature refrigerator and refrigerant circulation. The device comprises a universal testing machine, a vacuum heat insulation Dewar cavity, a refrigerant circulating system and a low-temperature refrigerating system; the refrigerant circulating system comprises a nozzle, a second-stage cold end heat exchanger, a second-stage convection type heat exchanger, a first-stage cold end heat exchanger, a first-stage convection type heat exchanger, a high-pressure gas storage tank, a circulating pump, a low-pressure gas storage tank and a helium tank which are arranged outside the universal testing machine, a closed circulating loop is formed through pipelines, and helium is used as a refrigerant. The invention can realize the test of various mechanical properties of isothermal stretching, compression, bending, shearing, fatigue, fracture toughness and the like of the material in a large temperature range from the liquid hydrogen temperature to the room temperature, expand the temperature range of the mechanical test of the material, improve the temperature control precision and stability, simultaneously avoid the great waste of helium gas, greatly reduce the test cost and put an end to the use of liquid hydrogen so as to improve the safety of the system.
Description
Technical Field
The invention relates to the technical field of material mechanics tests, in particular to a liquid hydrogen temperature area material mechanics test platform based on a low-temperature refrigerator and refrigerant circulation. The platform can be used for testing quasi-static mechanical properties of the structural material such as stretching, fatigue, bending, fracture toughness and the like in an environment with liquid hydrogen temperature (-253 ℃) to normal temperature (20 ℃).
Background
Hydrogen energy is one of the important long-term solutions to the current energy problem as an efficient and clean energy source. How to safely and efficiently store and transport hydrogen energy is a key technical challenge for large-scale application of hydrogen energy. With the increasing maturity of cryogenic cooling, heat insulation and vacuum technologies, the storage and transportation mode of low-temperature liquid hydrogen has higher storage density and lower operation pressure, reduces the energy consumption and space cost of unit mass transportation, and is expected to become an effective mode for long-distance transportation and large-scale storage of hydrogen.
The special working temperature of liquid hydrogen storage and transportation undoubtedly puts special requirements on the selection and design of pressure vessels and pipelines required by the liquid hydrogen storage and transportation. In order to realize the light weight of liquid hydrogen storage and transportation equipment and ensure the safety and the service life of products, sufficient and reliable mechanical property data of a material liquid hydrogen temperature area are required to be used as supports. A liquid hydrogen temperature zone mechanical test platform is basic experimental equipment for testing the low-temperature mechanical property of a material.
The traditional low-temperature mechanical property testing device adopts low-temperature freezing liquid such as liquid helium, liquid nitrogen and the like as a cold source and a refrigerant to cool a sample. And to realize the test of the liquid hydrogen temperature zone, the liquid helium and the liquid hydrogen can be selected only from the cryogenic liquid. However, liquid helium is expensive (about 150 yuan/L), at least one hundred liters of liquid helium is required to cool a sample in each test, and the test cost is very high because the helium cannot be recycled after being used for a user without a liquid helium circulating preparation system; the liquid hydrogen has low latent heat of vaporization per unit volume (only 3.18 multiplied by 10)4kJ/m3About 1/7 for lng) and thus is very easily vaporized to cause a rapid rise in system pressure, low ignition energy (0.017mJ) and large flammable range (4-75%) and large detonation range (18.3-59%), and thus is very easily ignited and exploded, small molecular size and low density of hydrogen, and is very easily leaked and diffused, and hydrogen is also easily hydrogen-embrittled by the material, thus requiring very expensive safety equipment and strict operating procedures for using liquid hydrogen. In addition, the sample is soaked by liquid helium or liquid hydrogen, and relatively accurate and stable temperature control at the corresponding boiling point temperature (the boiling point of the liquid helium is-269 ℃ C.; the boiling point of the liquid hydrogen is-253 ℃ C.) can be obtained by means of boiling heat exchange; however, if the test of the boiling point temperature of liquid helium or liquid hydrogen is to be realized, the sample needs to be suspended above the liquid level of liquid helium or liquid hydrogen, and the sample is cooled by utilizing the flash-evaporated helium (or liquid hydrogen) vapor through a natural convection heat exchange mode, so that the heat exchange coefficient of the heat exchange mode is limited, the realization of smaller heat exchange temperature difference and higher temperature control precision and stability is difficult, namely, effective isothermal cannot be performedAnd (5) testing mechanical properties.
Therefore, in order to realize the temperature test of the liquid hydrogen, the existing material mechanical property test system must adopt the liquid helium or the liquid hydrogen as a cold source and a refrigerant, so that the technical problems of high test operation cost, complex operation and poor safety exist, and the isothermal mechanical property test of a temperature region above the temperature of the liquid helium or the liquid hydrogen is difficult to perform.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects of the prior art and provides a liquid hydrogen temperature area material mechanical test platform based on a low-temperature refrigerator and refrigerant circulation.
In order to solve the technical problems, the invention adopts the technical scheme that:
the mechanical testing platform for the liquid hydrogen temperature zone material based on the cryogenic refrigerator and refrigerant circulation comprises a universal testing machine consisting of a base, a frame, an actuator, an upper main shaft, a lower main shaft and a sample clamp; wherein, the frame is arranged on the base, and the actuator is arranged on a beam of the frame; the upper end of the upper main shaft is connected with the actuator through a mechanical sensor, and the lower end of the upper main shaft is fixedly provided with the upper half part of the sample clamp; the lower end of the lower main shaft is fixed on the base, and the upper end of the lower main shaft is fixedly provided with the lower half part of the sample clamp; the test platform also comprises a vacuum heat insulation Dewar cavity, a refrigerant circulating system and a low-temperature refrigerating system;
the vacuum heat insulation Dewar cavity is arranged on the base and is a hollow cavity body consisting of a lower flange, a cylinder body and an upper flange; a hollow radiation cavity consisting of a plurality of layers of external heat insulating materials and an internal radiation screen is sleeved in the hollow radiation cavity, and a test cavity is sleeved in the hollow radiation cavity; the upper main shaft and the lower main shaft sequentially penetrate through the upper flange, the lower flange, the hollow radiation cavity and the test cavity from the upper direction to the lower direction respectively, and the end parts of the upper main shaft and the lower main shaft and the sample clamp are positioned in the test cavity;
the refrigerant circulating system comprises a nozzle arranged in the test cavity, a secondary cold end heat exchanger, a secondary convection type heat exchanger and a primary cold end heat exchanger which are arranged in the hollow radiation cavity, a primary convection type heat exchanger arranged in the Dewar cavity, and a high-pressure gas storage tank, a circulating pump, a low-pressure gas storage tank and a helium tank which are arranged outside the universal testing machine, a closed circulating loop is formed through a pipeline, and helium is used as a refrigerant;
the low-temperature refrigerating system comprises a low-temperature refrigerator, wherein a cold head of the low-temperature refrigerator is arranged on a lower flange of the vacuum heat insulation Dewar cavity and extends upwards into the vacuum heat insulation Dewar cavity and the hollow radiation cavity; the middle part of the cold head is provided with a primary cold head, and the top part of the cold head is provided with a secondary cold head; the first-stage cold head and the second-stage cold head are both located in the hollow radiation cavity, the first-stage cold head is in thermal coupling connection with the first-stage cold-end heat exchanger, and the second-stage cold head is in thermal coupling connection with the second-stage cold-end heat exchanger.
The invention also comprises a vacuum pump which is respectively connected with the vacuum heat insulation Dewar cavity and the refrigerant circulating system through pipelines.
In the invention, the upper part of the test cavity is provided with a connecting pipe which is sleeved outside the upper main shaft; the lower part of the test cavity is sleeved outside the lower main shaft through a corrugated pipe seal.
In the invention, the upper part of the hollow radiation cavity is provided with an upper opening hole for penetrating through the upper main shaft, and the edge of the upper opening hole is hermetically connected to the outer side of the connecting pipe; the lower part of the hollow radiation cavity is provided with a lower opening used for penetrating through the lower main shaft, and the edge of the lower opening surrounds the lower main shaft in a dynamic sealing mode.
In the invention, a lower flange of the vacuum heat insulation Dewar cavity is arranged on a base through a supporting frame, and the lower end part of a lower main shaft is arranged on the base through a centering adjusting ring; an outer corrugated pipe seal is arranged between the lower main shaft and the lower flange, and an axial dynamic seal is arranged between the upper main shaft and the upper flange.
In the invention, side doors are respectively arranged on the walls of the vacuum heat insulation Dewar cavity, the hollow radiation cavity and the test cavity in the same direction.
In the present invention, the refrigerant circulation path of the refrigerant circulation system specifically includes: the circulating pump outlet, the high-pressure gas storage tank, the flow control meter, the high-pressure side of the first-stage convection type heat exchanger, the refrigerant side of the first-stage cold end heat exchanger, the high-pressure side of the second-stage convection type heat exchanger, the refrigerant side of the second-stage cold end heat exchanger and the nozzle are connected through pipelines to realize refrigerant supply; the test cavity, the low-pressure side of the secondary convection type heat exchanger, the low-pressure side of the primary convection type heat exchanger, the low-pressure gas storage tank and the circulating pump inlet are connected through pipelines to realize refrigerant recovery; the helium bottle is connected to the low-pressure side of the circulation loop through a pipeline and used for supplementing a refrigerant.
In the invention, a pressure sensor and a stop valve are arranged in the refrigerant circulating system, a safety valve is arranged on a high-pressure gas storage tank, and a pressure reducing valve is arranged at the outlet of a helium tank.
In the invention, the test cavity is also provided with an electric control heater and a thermometer.
In the invention, the low-temperature refrigerator is a G-M refrigerator, a Stirling refrigerator, a pulse tube refrigerator or a J-T refrigerator; a plurality of layers of heat insulating materials are wrapped outside the low-temperature refrigerator and the hollow radiation cavity; a heat conduction bridge made of heat conduction metal or heat pipes is arranged in the middle of a cold head of the low-temperature refrigerator and is bridged to the middle of the upper main shaft and the lower main shaft.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a liquid hydrogen temperature area material mechanics testing platform based on a cryogenic refrigerator and refrigerant circulation, which takes the cryogenic refrigerator as a cold source and helium as a refrigerant, and utilizes the refrigerant circulation to efficiently and uniformly transmit cold energy generated by the cryogenic refrigerator to a sample to be tested, thereby realizing the testing of various mechanical properties such as isothermal stretching, compression, bending, shearing, fatigue, fracture toughness and the like of the material in a large temperature range from the liquid hydrogen temperature to room temperature (-253 ℃ to 20 ℃), expanding the temperature range of material mechanics testing, improving the temperature control precision and stability, avoiding the great waste of helium at the same time, greatly reducing the testing cost, and fundamentally improving the safety of the system by stopping the use of liquid hydrogen.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention;
the reference numbers in the figures are: 1-1 is a universal testing machine; 44 is a cryogenic refrigerator; 23 is a sample to be measured.
Fig. 2 is a schematic structural diagram of a liquid hydrogen temperature zone material mechanics testing platform according to an embodiment of the present invention.
The reference numbers in the figures are: 1, a base; 2, a flow control meter; 3, a stop valve; 4, a high-pressure gas storage tank; 5, a stop valve; 6 circulating pump; 7 a stop valve; 8, a low-pressure gas storage tank; 9 a helium tank; 10 a pressure reducing valve; 11 a stop valve; 12a pressure sensor; 13, four-way; 14 a stop valve; 15a stop valve; 16 a pressure sensor; 17 a safety valve; 18, sealing the inner corrugated pipe; 19 a vacuum heat insulation cavity cylinder; 20 layers of thermal insulation material; 21 side door of vacuum heat insulation Dewar cavity; 22 an electric heater; 23, testing a sample to be tested; 24 an extensometer; 25 side-opening door of hollow radiation cavity; 26 side-opening doors of the test chamber; 27 a test chamber; 28 a radiation screen; 29 a nozzle; 30 connecting pipes; 31, axially and dynamically sealing the upper main shaft; 32 vacuum barrier valves; 33, a tee joint; 34 a vacuum pump; 35 a cross beam; 36 an actuator; 37 support rods; 38 a mechanical sensor; 39 an upper main shaft; 40 an upper flange; 41 a sample holder; 42 thermometer; 43 a secondary cold side heat exchanger; 44 a compressor; 45, secondary cold head; 46 two-stage convection heat exchanger; 47 primary cold head; 48 heat conducting thermal bridges; 49 primary cold end heat exchangers; 50, cooling the head; 51 a lower flange; 52 centering the adjusting ring; 53 lower main shaft; 54 outer bellows seal; 55 primary convection heat exchanger; 56 support the frame.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the embodiments of the present invention are described in further detail below with reference to the accompanying drawings of the embodiments of the present invention, but the described embodiments are some, not all, embodiments of the present invention. Other embodiments based on the embodiments of the invention, which are not inventive by the person skilled in the art, are within the scope of protection of the invention.
As shown in fig. 2, the liquid hydrogen temperature region material mechanical testing platform based on the cryogenic refrigerator and the refrigerant circulation comprises a refrigerant circulation system, a cryogenic refrigerator 44, a vacuum insulation dewar cavity and a universal testing machine 1-1, wherein the refrigerant circulation system is used for efficiently and uniformly transmitting cold generated by the cryogenic refrigerator 44 to a sample 23 to be tested, the cryogenic refrigerator 44 is used for providing cold at low temperature, the vacuum insulation dewar cavity is used for providing an insulation environment for the refrigerant circulation system, the cryogenic refrigerator 44 and the sample 23 to be tested and reducing environmental heat leakage, and the universal testing machine 1-1 is used for providing mechanical load required by mechanical performance testing.
The refrigerant circulating system comprises a circulating pump 6, a high-pressure gas storage tank 4, a primary convection type heat exchanger 55, a primary cold end heat exchanger 49, a secondary convection type heat exchanger 46, a secondary cold end heat exchanger 43, a nozzle 29, a test cavity 27, a four-way joint 13, a low-pressure gas storage tank 8, a helium bottle 9 and stop valves 5, 3, 15, 14, 11 and 7 arranged at each node; an outlet of the circulating pump 6, a high-pressure gas storage tank 4, a stop valve 3, a flow control meter 2, a high-pressure side of a primary convection type heat exchanger 55, a refrigerant side of a primary cold end heat exchanger 49, a high-pressure side of a secondary convection type heat exchanger 46, a refrigerant side of a secondary cold end heat exchanger 43, a nozzle 29, a test cavity 27, a low-pressure side of the secondary convection type heat exchanger 46, a low-pressure side of the primary convection type heat exchanger 55, a stop valve 15, a four-way joint 13, a low-pressure gas storage tank 8, a stop valve 7 and an inlet of the circulating pump; the refrigerant is helium and flows in the closed circulation loop; the circulating pump 6 is an oil-free pump, so that the refrigerant helium is prevented from being polluted, and the function of the circulating pump is to drive the refrigerant to circulate; the high-pressure gas storage tank 4 is used for stabilizing the pressure of helium circulation within the range of 3-5 bar and storing helium in a helium circulation pipeline when a sample is replaced; the low-pressure gas storage tank 8 is used for stabilizing the pressure of helium gas circulation within the range of 1-3 bar; the high-pressure gas storage tank 4 is provided with a pressure sensor 16 and a safety valve 17, the low-pressure gas storage tank 8 is provided with a pressure sensor 12, the pressure sensor 16 and the pressure sensor 12 are respectively used for monitoring the pressure of the high-pressure side and the low-pressure side of the refrigerant cycle, and the safety valve 17 is used for providing safe discharge when the refrigerant cycle is in overpressure; the flow controller 2 is used for monitoring and controlling the flow and pressure of refrigerant circulation; a pressure reducing valve 10 is arranged at the mouth of the helium bottle 9, and then the pressure reducing valve 11 is connected with a refrigerant circulating four-way 13 through a pipeline, so that the helium can be provided for refrigerant circulation, and helium can be provided for a refrigerant circulating pipeline for purging and replacement when a sample is replaced; the four-way joint 13 is also connected with a three-way joint 33 through a stop valve 14, so that a vacuum pump 34 can be used for vacuumizing and replacing a refrigerant circulating pipeline; the primary convection heat exchanger 55 and the secondary convection heat exchanger 46 have the function of pre-cooling hot helium pumped out by the helium circulating pump by using cold helium circulated and refluxed by a refrigerant, so that the utilization rate of refrigerating capacity of the refrigerating machine is improved; the primary cold end heat exchanger 49 is thermally coupled with the primary cold head 47, the secondary cold end heat exchanger 43 is thermally coupled with the secondary cold head 45, and the functions of the primary cold end heat exchanger and the secondary cold end heat exchanger are that the cold energy generated by the cryogenic refrigerator is transmitted to a refrigerant; the nozzle 29 is positioned in the test cavity 27 and points at the sample 23 to be tested, and is used for spraying a refrigerant onto the sample to be tested, transferring cold carried by the refrigerant to the sample 23 to be tested in a forced convection heat exchange mode, and balancing heat dissipation and various heat leakage of the sample 23 to be tested converted from mechanical work in the test process; the wall of the test cavity 27 is made of stainless steel material, and the upper part of the test cavity is connected with an upper flange 40 of the vacuum heat insulation Dewar cavity through a connecting pipe 30, so that a closed heat insulation space is provided for forced convection heat exchange between a refrigerant and the sample 23 to be tested; the inner corrugated pipe seal 18 is connected with a through hole at the bottom of the test cavity 27 and is used for providing axial seal for the lower main shaft 53, preventing refrigerant helium in the test cavity 19 from entering the vacuum heat insulation Dewar cavity and ensuring that the horizontal position and the axial angle of the lower main shaft 53 are finely adjusted by the centering adjusting ring 52, so that effective seal can be provided while the centering degree of the upper main shaft 39 and the lower main shaft 53 is realized; three thermometers 41 are respectively arranged at the upper end, the middle part and the lower end of the test section of the sample 23 to be tested and used for monitoring the temperature of the test section of the sample 23 to be tested; the upper end and the lower end of the test section of the sample 23 to be tested are respectively provided with two electric heating devices 22 which are used for heating the sample 23 to be tested so as to control the temperature of the test section of the sample 23 to be tested; the test section of the sample to be tested is also arranged with an extensometer 24 for measuring strain.
The low-temperature refrigerator is a two-stage G-M refrigerator and comprises a refrigeration compressor 44 and a cold head 50, wherein the cold head 50 comprises a first-stage cold head 47 and a second-stage cold head 45; the cold head is connected with a lower flange of the vacuum heat insulation cavity through a flange and extends into the vacuum heat insulation cavity; a machine cold head 47 and a secondary cold head 45 are respectively at two temperatures Tc,1And Tc,2Providing cold.
The vacuum heat insulation cavity comprises a supporting frame 56, a lower flange 51, a cylinder 27 and an upper flange 40, and is used for providing a heat insulation environment for a refrigerant circulating system, a low-temperature refrigerator and a sample to be tested; the cavity at the bottom of the vacuum heat insulation cavity is formed by sequentially connecting a lower flange 51, a cylinder 27 and an upper flange 40, and the bottom of the cavity is provided with a supporting frame 56 which is arranged on a base 1 of the universal testing machine; the vacuum heat insulation cavity is connected with a vacuum pump through a vacuum pipeline, a vacuum partition plate valve 32 and a tee joint 33; in order to further reduce heat leakage, a radiation screen 28 and a heat conduction and heat bridge 48 are also arranged in the vacuum heat insulation cavity; the radiation screen 28 is positioned between the vacuum heat insulation cavity and the test cavity, the outer surface of the radiation screen is wrapped with a plurality of layers of heat insulation materials 20, and the radiation screen is in thermal coupling connection with the primary cold head 47 of the low-temperature refrigerator; the heat conduction and heat bridge 48 is made of heat conduction metal or a heat pipe and provides heat coupling connection for the primary cold head 47 of the low-temperature refrigerator and the middle positions of the upper main shaft 39 and the lower main shaft 53; the same side of the testing cavity 27, the radiation screen 28 and the vacuum heat-insulating cavity cylinder 19 is provided with a door (a testing cavity side door 26, a radiation screen side door 25 and a vacuum heat-insulating cavity side door 21) which is used for providing a channel for replacing a sample after being opened in sequence; the upper main shaft axial dynamic seal 31 is connected with the connecting pipe 30 and the vacuum heat insulation cavity upper flange 39 and is used for providing axial dynamic seal for the upper main shaft 39, preventing helium in the test cavity 27 from leaking into the atmosphere and ensuring that the upper main shaft 39 can provide effective seal in the process of freely moving up and down; an outer bellows seal 54 is associated with the through hole in the lower flange 51 of the vacuum insulation chamber and functions to provide an axial seal for the lower spindle 53, to prevent air from the atmosphere from leaking into the vacuum insulation chamber, and to ensure that the alignment of the upper spindle 39 and the lower spindle 53 is achieved while still ensuring effective sealing by fine adjustment of the horizontal position and axial angle of the lower spindle 53 by the centering adjustment ring 52.
The universal testing machine comprises a base 1, a support rod 37, a cross beam 35, an actuator 36, a mechanical sensor 38, an upper main shaft 39, a lower main shaft 53 and a sample clamp 41; the supporting rod 37 is vertically arranged on the base 1; the cross beam 35 is arranged between two support rods 37 and is parallel to the base 1. The beam 35 can move up and down along the support rod 37, and is used for adjusting the distance between the upper spindle 39 and the lower spindle 53 according to different samples 23 to be tested and sample clamps 41 and providing a support platform for the actuator 36; the actuator 36 is arranged in the middle of the cross beam and is used for transmitting the up-down displacement and the load force to the upper main shaft 39; the upper end of the upper main shaft 39 is connected with the actuator 36 through the mechanical sensor 38, and the upper main shaft has the function of transmitting the up-and-down displacement and the load force to the upper end of the sample 23 to be tested through the sample clamp 41 connected with the lower end of the upper main shaft; the mechanical sensor 38 is used for measuring the magnitude of the load force; the lower end of the lower main shaft 53 is vertically arranged on the base 1 through a centering adjusting ring 52, the upper end is connected with the sample clamp 41, and the lower end of the sample 23 to be tested is fixed through the sample clamp 41 at the upper end of the lower main shaft; centering adjustment ring 52 functions to adjust the centering of upper spindle 39 and lower spindle 53; the sample clamp 41 is connected with the lower end of the upper main shaft 39 and the upper end of the lower main shaft 53 and is used for clamping the sample 23 to be tested; the specimen holder 41 may be of different holder types to mount, for example, tensile, compressive, flexural, shear, fatigue or fracture toughness test specimens, depending on different test requirements.
The working process of the liquid hydrogen temperature region material mechanics testing platform based on the low-temperature refrigerator and the refrigerant circulation provided by the invention is specifically described below by combining the attached drawings:
a mounting or replacing the sample to be tested 23:
a1 turning off cryocooler 44, circulation pump 6 and vacuum pump 34;
a2 closes shut-off valves 3, 5, 7, 11 and 14, closes vacuum barrier valve 32, opens shut-off valve 15;
a3, opening a vacuum heat insulation cavity cylinder side door 21, a radiation screen side door 25 and a test cavity side door 26 in sequence, and taking down a to-be-tested sample 23 originally arranged on a sample clamp 41;
a4, adjusting the upper and lower positions of the upper main shaft 39, installing a new sample 23 to be tested on the sample clamp 41, and installing the extensometer 24;
a5 closing the side door 26 of the test chamber, the side door 25 of the radiation screen and the side door 21 of the cylinder body of the vacuum heat insulation chamber in sequence;
b, vacuumizing/purging/replacing a refrigerant circulating pipeline:
b1, opening the stop valve 14, opening the vacuum pump 34, vacuumizing the refrigerant circulation pipeline until the vacuum degree reaches below 1E-2Pa, and closing the stop valve 14;
b2 adjusting the pressure reducing valve 10 to make the outlet pressure about 15atm, then opening the stop valve 11 to make the pure helium enter the refrigerant circulation pipeline, when the reading of the pressure sensor 12 reaches about 12atm, closing the stop valve 11, and letting the system stand for 3-5 minutes;
b3, slowly opening the stop valve 14, and vacuumizing the refrigerant circulation pipeline again;
b4 repeating the above procedure twice;
b5, closing the stop valve 14, opening the stop valves 3, 5 and 7, and diffusing helium stored in the high-pressure gas storage tank 4 into the whole refrigerant circulation pipeline;
c, cooling:
c1 opening the vacuum partition valve and vacuumizing the vacuum heat insulation cavity by the vacuum pump 34;
c2 when the vacuum degree reaches below 1E-2Pa, the low-temperature refrigerator and the circulating pump 6 are opened;
at this time, the primary cold head 47 of the cryogenic refrigerator 44 precools the middle parts of the upper main shaft 39 and the lower main shaft 53 through a heat conduction and heat bridge, and cools the radiation screen 28 and the multilayer heat-insulating material 20 wrapped on the outer surface of the radiation screen; the refrigerant helium is circulated in the refrigerant circulation pipeline under the pumping of the circulating pump 6: helium compressed to high pressure firstly enters a high-pressure gas storage tank 4, then enters a primary convection type heat exchanger 55 through a stop valve 3 and a flow control meter 2 to be pre-cooled by returned cold helium, then enters a primary cold end heat exchanger 49 to be continuously cooled by a primary cold head 47, then enters a secondary convection type heat exchanger 46 to be pre-cooled again by returned cold helium with lower temperature, then enters a secondary cold end heat exchanger to be cooled by a secondary cold head 45, finally fully cooled helium is sprayed into a test cavity 27 through a nozzle 29, and then returns to a circulating pump 6 through two convection type heat exchangers and a low-pressure gas storage 8; along with the continuous reduction of the temperature of the cold head of the refrigerating machine, the helium gas circulates and effectively transmits cold quantity to the test cavity and the sample to be tested, so that the temperature of the test cavity and the sample to be tested is reduced rapidly.
c3 when the temperature of the sample 23 is lower than the temperature to be measured, the heater 22 on the sample can be controlled to heat the sample by PID control, so as to stabilize the temperature of the sample at the temperature to be measured;
c4 waiting for the system until the temperature of the sample 23 and the power of the heater 22 are stable for more than 5 minutes;
d, testing mechanical properties:
d1 starting universal tester to make corresponding mechanical property test
e, rewarming:
e1, after the mechanical property test is finished, closing the low-temperature refrigerator, keeping the circulating pump 6 and the vacuum pump 34 running continuously, and starting the heaters to accelerate rewarming until the temperature meters on the components show room temperature;
f, recycling helium in refrigerant circulation:
f1 closing the stop valve 3, keeping the circulating pump 6 running continuously until the absolute pressure reading of the pressure gauge 12 is about 1E-1Pa, and closing the stop valves 5 and 7;
at this time, the circulating pump 6 pumps most of helium in the refrigerant circulating pipeline into the high-pressure gas storage tank 4, and only a small amount of residual helium remains in the residual pipeline, so that only a small amount of helium is lost when the test chamber side opening door 26 is opened in the subsequent sample replacement, and the helium in the high-pressure gas storage tank 4 can still be continuously used in the next test.
Therefore, the invention adopts the low-temperature refrigerator as a cold source and the circulating helium as a material mechanics test platform of the liquid hydrogen temperature region of the refrigerant, and realizes the material mechanics tests (the quasi-static mechanics performance tests of stretching, compressing, bending, shearing, fatigue, fracture toughness and the like) under the condition of any temperature within a large temperature range from the liquid hydrogen temperature (253 ℃) to the room temperature (20 ℃). Therefore, the invention is mainly used for performing material mechanics test on a sample to be tested in a liquid hydrogen temperature region, and the invention adopts a low-temperature refrigerator and a refrigeration mode of circulating helium gas, thereby greatly expanding the temperature range of the material mechanics test, improving the temperature control precision and stability and greatly reducing the test cost.
In summary, the invention provides a liquid hydrogen temperature region material mechanics testing platform based on a cryogenic refrigerator and refrigerant circulation, helium gas is circulated, waste of helium gas resources is reduced, a helium gas circulating pump is used for intensively recycling the helium gas to a gas reservoir, and vacuum is formed in a vacuum heat insulation Dewar cavity, so that heat exchange with the external environment is reduced, and the temperature requirement of a sample is met.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; the technical scheme of the embodiment can be modified, or part of technical features can be equivalently replaced; modifications and substitutions may be made thereto without departing from the spirit and scope of the embodiments of the invention.
Claims (7)
1. A liquid hydrogen temperature area material mechanics testing platform based on a cryogenic refrigerator and refrigerant circulation comprises a universal testing machine consisting of a base, a frame, an actuator, an upper main shaft, a lower main shaft and a sample clamp; wherein, the frame is arranged on the base, and the actuator is arranged on a beam of the frame; the upper end of the upper main shaft is connected with the actuator through a mechanical sensor, and the lower end of the upper main shaft is fixedly provided with the upper half part of the sample clamp; the lower end of the lower main shaft is fixed on the base, and the upper end of the lower main shaft is fixedly provided with the lower half part of the sample clamp; the test platform is characterized by also comprising a vacuum heat insulation Dewar cavity, a refrigerant circulating system and a low-temperature refrigerating system;
the vacuum heat insulation Dewar cavity is arranged on the base and is a hollow cavity body consisting of a lower flange, a cylinder body and an upper flange; a hollow radiation cavity consisting of a plurality of layers of external heat insulating materials and an internal radiation screen is sleeved in the hollow radiation cavity, and a test cavity is sleeved in the hollow radiation cavity; the upper main shaft and the lower main shaft sequentially penetrate through the upper flange, the lower flange, the hollow radiation cavity and the test cavity from the upper direction to the lower direction respectively, and the end parts of the upper main shaft and the lower main shaft and the sample clamp are positioned in the test cavity;
the refrigerant circulating system comprises a nozzle arranged in the test cavity, a secondary cold end heat exchanger, a secondary convection type heat exchanger and a primary cold end heat exchanger which are arranged in the hollow radiation cavity, a primary convection type heat exchanger arranged in the Dewar cavity, and a high-pressure gas storage tank, a circulating pump, a low-pressure gas storage tank and a helium tank which are arranged outside the universal testing machine, a closed circulating loop is formed through a pipeline, and helium is used as a refrigerant;
the nozzle is positioned in the test cavity and points to a sample to be tested; three thermometers are respectively arranged at the upper end, the middle part and the lower end of the test section of the sample to be tested and used for monitoring the temperature of the test section of the sample to be tested; the upper end and the lower end of the test section of the sample to be tested are respectively provided with two electric heating devices which are used for heating the sample to be tested so as to control the temperature of the test section of the sample to be tested;
the low-temperature refrigerating system comprises a low-temperature refrigerator, wherein a cold head of the low-temperature refrigerator is arranged on a lower flange of the vacuum heat insulation Dewar cavity and extends upwards into the vacuum heat insulation Dewar cavity and the hollow radiation cavity; the middle part of the cold head is provided with a primary cold head, and the top part of the cold head is provided with a secondary cold head; the first-stage cold head and the second-stage cold head are both positioned in the hollow radiation cavity, the first-stage cold head is in thermal coupling connection with the first-stage cold end heat exchanger, and the second-stage cold head is in thermal coupling connection with the second-stage cold end heat exchanger;
the upper part of the test cavity is provided with a connecting pipe which is sleeved outside the upper main shaft; the lower part of the test cavity is sleeved outside the lower main shaft through a corrugated pipe in a sealing manner; the upper part of the hollow radiation cavity is provided with an upper opening hole for penetrating through the upper main shaft, and the edge of the upper opening hole is hermetically connected to the outer side of the connecting pipe; the lower part of the hollow radiation cavity is provided with a lower opening hole for penetrating through the lower main shaft, and the edge of the lower opening hole surrounds the lower main shaft in a dynamic sealing mode; the lower flange of the vacuum heat insulation Dewar cavity is arranged on the base through a supporting frame, and the lower end part of the lower main shaft is arranged on the base through a centering adjusting ring; an outer corrugated pipe seal is arranged between the lower main shaft and the lower flange, and an axial dynamic seal is arranged between the upper main shaft and the upper flange.
2. The mechanical test platform of claim 1, further comprising a vacuum pump connected to the vacuum insulation dewar chamber and the coolant circulation system through pipes.
3. The mechanical testing platform of claim 1, wherein side-opening doors are respectively disposed on the same-direction walls of the vacuum insulation dewar chamber, the hollow radiation chamber and the testing chamber.
4. The mechanical test platform of claim 1, wherein the refrigerant circulation path of the refrigerant circulation system is specifically: the circulating pump outlet, the high-pressure gas storage tank, the flow control meter, the high-pressure side of the first-stage convection type heat exchanger, the refrigerant side of the first-stage cold end heat exchanger, the high-pressure side of the second-stage convection type heat exchanger, the refrigerant side of the second-stage cold end heat exchanger and the nozzle are connected through pipelines to realize refrigerant supply; the test cavity, the low-pressure side of the secondary convection type heat exchanger, the low-pressure side of the primary convection type heat exchanger, the low-pressure gas storage tank and the circulating pump inlet are connected through pipelines to realize refrigerant recovery; the helium bottle is connected to the low-pressure side of the circulation loop through a pipeline and used for supplementing a refrigerant.
5. The mechanical test platform of claim 1, wherein the refrigerant circulation system is provided with a pressure sensor and a stop valve, the high pressure gas tank is provided with a safety valve, and the outlet of the helium tank is provided with a pressure reducing valve.
6. The mechanical test platform of claim 1, wherein the test chamber is further provided with an electrically controlled heater and a thermometer.
7. The mechanical test platform of claim 1, wherein the cryocooler is a G-M cooler, a stirling cooler, a pulse tube cooler, or a J-T cooler; a plurality of layers of heat insulating materials are wrapped outside the low-temperature refrigerator and the hollow radiation cavity; a heat conduction bridge made of heat conduction metal or heat pipes is arranged in the middle of a cold head of the low-temperature refrigerator and is bridged to the middle of the upper main shaft and the lower main shaft.
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