Multi-physical field testing method for layering and rolling process of low-temperature multi-component fluid

Abstract

The invention discloses a multi-physical field testing method for a low-temperature multi-component fluid layering and rolling process. The multi-physical field testing method comprises the following steps: S1, completing assembly and construction of a testing device; s2, starting a vacuum pump; s3, liquid nitrogen is introduced into the liquid nitrogen cold screen; s4, adding tracer particles mixed with the alcohol into the test chamber, blowing off the alcohol with nitrogen, pre-cooling the test chamber, and then adding a fluorescent dye suitable for a test temperature zone; s5, introducing a low-temperature fluid a into the test chamber; s6, introducing another low-temperature fluid b into the test cabin according to a preset initial volume ratio or mass ratio; s7, starting a control host; s8, collecting pressure data, velocity field data, temperature field data and density field data of the vacuum low-temperature container; and S9, stopping the test after the planned test time is up. According to the invention, high-precision visual testing of low-temperature multi-component fluid can be realized, and tiny flow state changes such as tiny layers and flowing vortexes can be accurately captured; and a low-temperature heat and mass transfer coupling mechanism is comprehensively disclosed.

Description

Technical Field

[0001] This invention belongs to the field of low-temperature multi-component fluid testing technology, specifically relating to a multi-physics field testing method for the stratification and tumbling process of low-temperature multi-component fluids. Background Technology

[0002] Cryogenic multicomponent fluids (such as liquefied natural gas, liquid air, cryogenic refrigerants, and aerospace cryogenic propellants) have become core working media in strategic fields such as energy storage and transportation, cryogenic refrigeration, and aerospace due to their high energy density and unique physicochemical properties. Because different components have different evaporation rates, multicomponent fluids can experience tumbling during storage due to thermodynamic imbalances. In-depth research into their stratification and tumbling process characteristics is crucial for the technological development of related fields.

[0003] Existing technologies face three major challenges in this research: First, traditional ambient temperature fluid visualization techniques (such as high-speed photography) cannot adapt to low-temperature environments, have insufficient resolution, and the viewing window is prone to interference, making it difficult to quickly capture subtle flow regime changes (such as stratified diffusion and micro vortices) in low-temperature multi-component fluids. Second, heat and mass transfer processes are the result of dynamic coupling of multiple parameters such as temperature, pressure, flow rate, and concentration, but traditional experimental methods often use a single-parameter independent measurement mode, resulting in spatial deviations in the measurement areas of each parameter and inconsistent data acquisition frequencies, making it impossible to establish real-time correlations among multiple parameters and comprehensively reveal the coupling mechanism. Third, the physical properties of low-temperature fluids change rapidly, and traditional data acquisition methods are unable to record transient phenomena in real time. Furthermore, tracer particles and fluorescent dyes in low-temperature fluids are prone to uneven dispersal and agglomeration, limiting the depth of mechanism research.

[0004] Therefore, there is an urgent need for a testing method and process that is adapted to low-temperature environments, can realize simultaneous measurement of multiple physical fields, and can solve the problem of tracer particle distribution, so as to provide key technical support for the mechanism research and engineering application of low-temperature multi-component fluids. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a multi-physics field testing method for the stratification and tumbling process of low-temperature multi-component fluids, which can accurately capture subtle flow regime changes in multi-component fluids under low-temperature conditions, achieve synchronous correlation measurement of temperature, pressure, flow rate, and concentration, and reveal the heat and mass transfer coupling mechanism.

[0006] The technical solution adopted in this invention is: A multi-physics field testing method for the stratification and tumbling process of low-temperature multi-component fluids is provided, which is implemented using a multi-physics field testing device for the stratification and tumbling process of low-temperature multi-component fluids. The multi-physics field testing device for the stratification and tumbling process of low-temperature multi-component fluids includes a vacuum cryogenic container, a schlieren background plate, a vacuum pump, a data acquisition device, a camera system, a lens group, a control host, a laser system, a heating system, and a BOS light source. The vacuum cryogenic container includes a vacuum chamber, a liquid nitrogen cooling screen, and a test chamber, which are coaxially arranged and do not directly contact each other. The liquid nitrogen cooling screen is located inside the vacuum chamber. The test chamber is located inside the liquid nitrogen cooling screen and is fixed to the top end cap of the vacuum chamber. The heating system includes a heating film attached to the outer wall of the test chamber and a power supply. The heating film is electrically connected to the power supply, and the heating power is independently adjustable. The vacuum cryogenic container, schlieren background plate, vacuum pump, camera system, lens group, laser system, and BOS light source are all placed on the floor in the light-shielding chamber, with the schlieren background plate positioned between the BOS light source and the vacuum cryogenic container. The vacuum pump is used to evacuate the vacuum cryogenic container. The data acquisition device, camera system, laser system, heating system, and BOS light source are all connected to the control host. The data acquisition device is connected to the test chamber and is used to measure the pressure, temperature, and fluid composition inside the vacuum cryogenic container. The laser system, BOS light source, and camera system are respectively positioned facing different vacuum glass windows on the side of the vacuum chamber. The camera system includes three cameras, which are used to acquire BOS, PIV, and LIF images respectively. A schlieren background plate is provided between the BOS light source and the vacuum glass window it faces. The lens group is placed between the camera system and the vacuum cryogenic container. The lens group includes a bandpass beam splitter and several reflecting mirrors, which are used to transmit the light source signals to the corresponding cameras. Includes the following steps: S1. Complete the assembly and construction of the multi-physics field testing device for the stratification and tumbling process of low-temperature multi-component fluids; S2. Start the vacuum pump until the pressure inside the cryogenic vacuum container is ≤5E-3Pa; S3. Pour liquid nitrogen into the liquid nitrogen cooling screen until its temperature reaches below -180℃ and stabilizes; S4. Add tracer particles mixed with alcohol into the test chamber, purge the alcohol with nitrogen and pre-cool the test chamber, then add fluorescent dye suitable for the test temperature range. S5. Introduce a cryogenic fluid a into the test chamber until the liquid level reaches the design position. S6. Introduce another cryogenic fluid b into the test chamber at a preset initial volume ratio or mass ratio, so that it is fully mixed with cryogenic fluid a. S7. Start the control host and set the wall heat flow conditions; the mixed fluid in the test chamber gradually forms thermal stratification and density stratification under the action of wall heating. After the initial stratification conditions of the mixed fluid are formed, start the camera system, laser system, BOS light source and acquisition program. S8. Continuously collect pressure data of the vacuum cryogenic container; the camera system collects PIV, LIF and BOS images every 1 to 10 minutes, and simultaneously collects velocity field, temperature field and density field data. S9. After the planned test time is reached, stop the camera system, laser system and BOS light source; wait until there is no residual liquid in the test chamber and the temperature returns to normal, then stop the heating system and vacuum pump.

[0007] Furthermore, steps S1-S9 are repeated multiple times, with each step S7 setting different wall heat flow conditions. By changing the wall heat flow conditions, the effects of different wall heating conditions on the thermal stratification, natural convection, evaporation, and stratification tumbling characteristics of low-temperature multi-component fluids are studied.

[0008] Furthermore, S1-S9 were repeated multiple times, with the initial volume ratio or mass ratio preset in step S6 being different for each step, to study the influence of the initial components on its thermal stratification, natural convection, evaporation, and stratification tumbling characteristics.

[0009] Furthermore, S1-S9 were repeated multiple times, with the pressure inside the vacuum cryogenic container in step S2 being different for each step. By changing the pressure inside the test chamber, the influence of the chamber pressure on the thermal stratification, natural convection, evaporation, and stratification tumbling characteristics of cryogenic multi-component fluids was studied.

[0010] Furthermore, the vacuum chamber includes a vacuum chamber body made of stainless steel. The side of the vacuum chamber body is provided with three vacuum glass windows at the same height. Two of the three vacuum glass windows are coaxial, and the axis of the third vacuum glass window is perpendicular to the axes of the two coaxial vacuum glass windows. The vacuum glass window is made of quartz. The top end cover is installed on the top of the vacuum chamber. The top end cover is equipped with a temperature measuring Dewar tube, a top heat sink inlet / outlet Dewar tube, cable connector a, and a test chamber inlet / outlet Dewar tube. The side of the vacuum chamber is equipped with a side heat sink inlet / outlet Dewar tube, a vacuum pump interface, and cable connector b.

[0011] Furthermore, the liquid nitrogen cooling screen is made of copper and includes a cylindrical sidewall and a circular base plate. The circular base plate is fixed to the inner wall of the vacuum chamber by multiple support rods. Copper tubes are coiled on the sidewall of the liquid nitrogen cooling screen, and the copper tubes are connected to the external liquid nitrogen supply equipment through the top heat sink liquid inlet / outlet Dewar tube and the side heat sink liquid inlet / outlet Dewar tube.

[0012] Furthermore, the test chamber is a square container made of stainless steel. The side of the test chamber is provided with three test glass windows at the same height. The test glass windows are made of high borosilicate material and correspond one-to-one with the three vacuum glass windows of the vacuum chamber. The side of the test chamber is also provided with an exhaust pipe and a liquid inlet / outlet pipe assembly. The exhaust pipe and the liquid inlet / outlet pipe assembly extend to the outside of the vacuum chamber through the liquid inlet / outlet Dewar pipe of the test chamber.

[0013] Furthermore, heating films are attached to the outer walls of all six sides of the test chamber. The heating films are made of polyacetamide.

[0014] Furthermore, the data acquisition device includes a pressure sensor, a temperature sensor, a multi-component analyzer, a vacuum gauge, and a flow meter; the pressure sensor and temperature sensor are respectively connected to cable connector a and cable connector b; the multi-component analyzer and flow meter are connected to the exhaust pipe of the test chamber through pipes; the vacuum gauge is fixed to the side of the vacuum chamber body through a flange; cable connector a, cable connector b, multi-component analyzer, vacuum gauge, and flow meter are respectively electrically connected to the control host.

[0015] Furthermore, the vacuum pump interface is connected to a vacuum pump via a pipe, and the vacuum pump is a vacuum pump assembly consisting of a mechanical pump and a molecular pump.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention enables high-precision visual testing of multi-component fluids at low temperatures ranging from -196°C to room temperature, accurately capturing subtle flow regime changes such as minute stratification and flow vortices. Its multi-physics simultaneous measurement capability acquires real-time correlated data of temperature, velocity, and density, comprehensively revealing the heat and mass transfer coupling mechanism. The use of uniformly distributed tracer particles ensures the accuracy and reliability of the test data. This invention provides precise experimental data for engineering design in fields such as liquefied natural gas storage and transportation, cryogenic refrigeration systems, and aerospace cryogenic propellants, reducing wasted R&D costs and safety hazards caused by unreasonable design. Attached Figure Description

[0017] Figure 1 This is a flowchart of the present invention.

[0018] Figure 2 This is a structural diagram of the multi-physics field testing device for the low-temperature multi-component fluid stratification and tumbling process used in this invention.

[0019] Figure 3 This is a top view of the vacuum cryogenic container of the present invention.

[0020] Figure 4 This is a side cross-sectional view of the vacuum cryogenic container of the present invention.

[0021] Figure 5 This is a side view of the vacuum cryogenic container of the present invention. Detailed Implementation

[0022] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] like Figure 2-5As shown, the multiphysics field testing device for the low-temperature multi-component fluid stratification and tumbling process used in this invention includes a vacuum cryogenic container 1, a schlieren background plate 2, a vacuum pump 3, a data acquisition device 4, a camera system 5, a lens group 6, a control host 7, a laser system 8, a heating system 9, and a BOS light source 10. The vacuum cryogenic container 1, the schlieren background plate 2, the vacuum pump 3, the camera system 5, the lens group 6, the laser system 8, and the BOS light source 10 are all placed on the floor of a light-shielding chamber.

[0024] The vacuum cryogenic container 1 includes a vacuum chamber 101, a liquid nitrogen cooling screen 102, and a test chamber 103. The liquid nitrogen cooling screen 102 is located inside the vacuum chamber 101 and is fixedly supported to the inner wall of the vacuum chamber by a support rod 1021. The test chamber 103 is located inside the liquid nitrogen cooling screen 102 and is fixed to the top end cap 1015 by welding. The vacuum chamber 101, the liquid nitrogen cooling screen 102, and the test chamber 103 are placed coaxially and do not directly contact each other.

[0025] The vacuum chamber 101 includes a vacuum chamber body 1011, which is a vertical container made of stainless steel. Three vacuum glass windows are provided on the side of the vacuum chamber body 1011. The three vacuum glass windows are: vacuum glass window a1012, vacuum glass window b1013, and vacuum glass window c1014. Vacuum glass windows a1012, b1013, and c1014 are circular structures made of quartz and are fixed to the side of the vacuum chamber body 1011 by flanges. Vacuum glass windows a1012 and c1014 are coaxial, and the axis of vacuum glass window b1013 is perpendicular to the axis of vacuum glass window a1012.

[0026] A top end cap 1015 is fixedly installed on the top of the vacuum chamber 1011. The top end cap 1015 is equipped with a top heat sink inlet / outlet Dewar tube 1016, cable connector a 1017, a pressure gauge 1018, a temperature measuring Dewar tube 1019, and a test chamber inlet / outlet Dewar tube 10110. A vacuum pump interface 10111, a side heat sink inlet / outlet Dewar tube 10112, and cable connector b 10114 are located on the side of the vacuum chamber 1011. A vacuum pump 3 is connected to the vacuum pump interface 10111 on the side of the vacuum chamber 1011 via a pipe and is fixedly installed via a flange. The vacuum pump 3 is a vacuum pump assembly consisting of a mechanical pump and a molecular pump.

[0027] Temperature measuring Dewar tube 1019, top heat sink inlet / outlet Dewar tube 1016, and test chamber inlet / outlet Dewar tube 10110 are welded and fixed to the top end cap 1015. Side heat sink inlet / outlet Dewar tube 10112 and vacuum pump interface 10111 are welded and fixed to the side of the vacuum chamber 1011. Cable connector a 1017 and pressure gauge 1018 are fixed to the top end cap 1015 via flanges, and cable connector b 10114 is fixed to the side of the vacuum chamber 1011 via flanges.

[0028] The liquid nitrogen cooling screen 102 is made of copper and includes a cylindrical sidewall and a circular base plate. The circular base plate is fixed to the inner wall of the vacuum chamber 101 by multiple support rods 1021. Copper tubes are coiled on the sidewall of the liquid nitrogen cooling screen 102, and the copper tubes are connected to the external liquid nitrogen supply equipment through the top heat sink liquid inlet / outlet Dewar tube 1016 and the side heat sink liquid inlet / outlet Dewar tube 10112.

[0029] The test chamber 103 includes a test chamber body 1031. Three test glass windows, all at the same height, are located on the side of the test chamber 1031. These test glass windows are made of high borosilicate material. The three test glass windows are designated as test glass window a1032, test glass window b1033, and test glass window c1034. The test chamber body 1031 is a square container made of stainless steel. A heating system 9 is installed on the outer wall of the test chamber 103. The heating system 9 includes heating films 1038 attached to the outer walls of the six sides of the test chamber 103 using low-temperature adhesive, and a power supply. The heating films 1038 are connected to the power supply and are made of polyacetamide. The heating power of the heating films 1038 is independently adjustable; the heating amount can be controlled by changing the voltage and current. The control host 7 controls the heating power of the heating films 1038. Test glass windows a1032, b1033, and c1034 are circular structures made of high borosilicate material and are fixed to three adjacent sides of the test chamber 1031 via flanges. The three test glass windows are at the same height and correspond one-to-one with the three vacuum glass windows of the vacuum chamber.

[0030] The exhaust pipe 1036 and the liquid inlet / outlet pipe assembly 1037 are welded to the side of the test chamber 1031. The exhaust pipe 1036 and the liquid inlet / outlet pipe assembly 1037 are led out to the outside of the vacuum chamber 1011 through the liquid inlet / outlet Dewar pipe 10110 of the test chamber. The exhaust pipe 1036 and the liquid inlet / outlet pipe assembly 1037 do not contact the vacuum chamber 1011.

[0031] Camera system 5, laser system 8, and BOS light source 10 are respectively positioned opposite three vacuum glass windows on the side of the vacuum chamber. Camera system 5 is used to acquire laser signals from laser system 8 and light source signals from BOS light source 10. A schlieren background plate 2 is positioned between BOS light source 10 and its opposite vacuum glass window c1014, illuminating BOS light source 10. Laser system 8 is positioned opposite vacuum glass window b1013 at the same height as its center. Camera system 5 is positioned opposite vacuum glass window a1012 at the same height as its center. Camera system 5 includes three CCD cameras, used to acquire BOS, PIV, and LIF images respectively. Lens group 6 is positioned between camera system 5 and vacuum glass window a1012. Lens group includes a bandpass beam splitter and several reflecting mirrors, used to transmit light source signals to the corresponding cameras. Data acquisition device 4, camera system 5, laser system 8, and heating system 9 are electrically connected to control host 7 to achieve coupled control and real-time acquisition.

[0032] The data acquisition device 4 includes measurement and analysis equipment such as a pressure sensor, a temperature sensor, a multi-component analyzer, a vacuum gauge 10113, and a flow meter. The pressure sensor and temperature sensor are connected via cable connectors a1017 and b10114, respectively. The multi-component analyzer and flow meter are connected to the exhaust pipe 1036 via pipes. Cable connectors a1017 and b10114, the multi-component analyzer, the vacuum gauge 10113, and the flow meter are electrically connected to the control host. The vacuum gauge 10113 is fixed to the side of the vacuum chamber 1011 via a flange.

[0033] The temperature sensor employs a thermocouple or a PT100 temperature sensing element. A temperature sensing rod 1035, made of stainless steel, is installed inside the test chamber 103, around which the thermocouple or PT100 temperature sensing element is wound. The lower part of the temperature sensing rod extends to the bottom of the test chamber 1031 without contacting the lower surface of the test chamber, while the upper part extends to the outside of the vacuum chamber 1011 through the temperature sensing Dewar tube 1019. The cable for the thermocouple or PT100 temperature sensing element is connected to a cable connector a1017.

[0034] Example 1

[0035] When studying the effects of wall heating on the thermal stratification, natural convection, and evaporation characteristics of low-temperature multicomponent fluids, multiple sets of comparative tests were conducted, such as... Figure 1 As shown, each test group is performed according to the following steps: S1. Complete the assembly and construction of the multi-physics field testing device for the stratification and tumbling process of low-temperature multi-component fluids; S2. Start vacuum pump 3 until the pressure inside the vacuum cryogenic container 1 is ≤5E-3Pa; S3. Pour liquid nitrogen into the liquid nitrogen cooling screen 102 until its temperature reaches below -180℃ and stabilizes; S4. Add tracer particles mixed with alcohol into test chamber 103, purge the alcohol with nitrogen and pre-cool the test chamber, then add fluorescent dye suitable for the test temperature range. S5. Introduce a cryogenic fluid a into the test chamber 103 until the liquid level reaches the design position. S6. Introduce another cryogenic fluid b into the test chamber at a preset initial volume ratio or mass ratio, so that it is fully mixed with cryogenic fluid a. S7. Start the control host 7 and set the wall heat flow conditions; the mixed fluid in the test chamber 103 gradually forms thermal and density stratification under the wall heating effect, serving as the initial stratification conditions for subsequent tests. The intensity of this stratification can be controlled by adjusting the ratio of cryogenic fluid a and cryogenic fluid b in S6, the heating power, and the heating time. After the initial stratification conditions of the mixed fluid are formed, start the camera system 5, laser system 8, BOS light source 10, and acquisition program; S8. Continuously acquire pressure data of the vacuum cryogenic container; the camera system acquires PIV, LIF and BOS images once every 1 minute, and simultaneously acquires velocity field, temperature field and density field data; S9. After the planned test time is reached, stop the camera system 5, laser system 8 and BOS light source 10; wait until there is no residual liquid in the test chamber 103 and the temperature returns to normal, then stop the heating system 9 and vacuum pump 3.

[0036] In the tests of different groups, different wall heat flux conditions were set in step S7. By controlling the initial composition and chamber pressure to be the same, and changing the wall heat flux conditions (wall heating location and wall heat flux density), the thermal stratification, natural convection, evaporation, and stratification tumbling characteristics of low-temperature multi-component fluids under different wall heating conditions were studied.

[0037] Example 2

[0038] When studying the effects of initial components on thermal stratification, natural convection, evaporation, and stratification tumbling of low-temperature multicomponent fluids, multiple sets of comparative tests were conducted, and each set of tests was performed according to the following steps: S1. Complete the assembly and construction of the multi-physics field testing device for the stratification and tumbling process of low-temperature multi-component fluids; S2. Start vacuum pump 3 until the pressure inside the vacuum cryogenic container 1 is ≤5E-3Pa; S3. Pour liquid nitrogen into the liquid nitrogen cooling screen 102 until its temperature reaches below -180℃ and stabilizes; S4. Add tracer particles mixed with alcohol into test chamber 103, purge the alcohol with nitrogen and pre-cool the test chamber, then add fluorescent dye suitable for the test temperature range. S5. Introduce a cryogenic fluid a into the test chamber 103 until the liquid level reaches the design position. S6. Introduce another cryogenic fluid b into the test chamber at a preset initial volume ratio or mass ratio, so that it is fully mixed with cryogenic fluid a. S7. Start the control host 7 and set the wall heat flow conditions; the mixed fluid in the test chamber gradually forms thermal and density stratification under the wall heating effect, serving as the initial stratification conditions for subsequent tests. The intensity of this stratification can be controlled by adjusting the ratio of cryogenic fluid a and cryogenic fluid b in S6, the heating power, and the heating time. After the initial stratification conditions of the mixed fluid are formed, start the camera system 5, laser system 8, BOS light source 10, and acquisition program; S8. Continuously acquire pressure data of the vacuum cryogenic container; every 5 minutes, camera system 5 acquires PIV, LIF and BOS images, and simultaneously acquires velocity field, temperature field and density field data; S9. After the planned test time is reached, stop the camera system 5, laser system 8 and BOS light source 10; wait until there is no residual liquid in the test chamber 103 and the temperature returns to normal, then stop the heating system and vacuum pump.

[0039] In the tests of different groups, different initial volume ratios or mass ratios were set in step S6. By controlling the wall heating conditions and the pressure inside the test chamber 103 to be the same, the initial component ratios of cryogenic fluid b and cryogenic fluid a were changed to study the thermal stratification, natural convection, evaporation, and stratification tumbling characteristics of cryogenic multi-component fluids under different initial components.

[0040] Example 3

[0041] When studying the effect of chamber pressure on the thermal stratification, natural convection, evaporation, and stratification tumbling characteristics of cryogenic multicomponent fluids, multiple sets of comparative tests were conducted, and each set of tests was performed according to the following steps: S1. Complete the assembly and construction of the multi-physics field testing device for the stratification and tumbling process of low-temperature multi-component fluids; S2. Start vacuum pump 3 until the pressure inside the vacuum cryogenic container 1 is ≤5E-3Pa; S3. Pour liquid nitrogen into the liquid nitrogen cooling screen 102 until its temperature reaches below -180℃ and stabilizes; S4. Add tracer particles mixed with alcohol into test chamber 103, purge the alcohol with nitrogen and pre-cool the test chamber, then add fluorescent dye suitable for the test temperature range. S5. Introduce a cryogenic fluid a into the test chamber 103 until the liquid level reaches the design position. S6. Introduce another cryogenic fluid b into the test chamber at a preset initial volume ratio or mass ratio, so that it is fully mixed with cryogenic fluid a. S7. Start the control host 7 and set the wall heat flow conditions; the mixed fluid in the test chamber gradually forms thermal and density stratification under the wall heating effect, serving as the initial stratification conditions for subsequent tests. The intensity of this stratification can be controlled by adjusting the ratio of cryogenic fluid a and cryogenic fluid b in S6, the heating power, and the heating time. After the initial stratification conditions of the mixed fluid are formed, start the camera system 5, laser system 8, BOS light source 10, and acquisition program; S8. Continuously collect pressure data of the vacuum cryogenic container; every 10 minutes, camera system 5 collects PIV, LIF and BOS images, and simultaneously collects velocity field, temperature field and density field data. S9. After the planned test time is reached, stop the camera system 5, laser system 8 and BOS light source 10; wait until there is no residual liquid in the test chamber 103 and the temperature returns to normal, then stop the heating system 9 and vacuum pump 3.

[0042] In the tests of different groups, different pressures were set inside the vacuum cryogenic container in step S2. By controlling the wall heat flow conditions and the initial composition, the pressure inside the test chamber 103 was changed to study the thermal stratification, natural convection, evaporation, and stratification tumbling characteristics of the cryogenic multi-component fluid under different pressures inside the test chamber 103.

Claims

1. A multi-physics field testing method for the stratification and tumbling process of low-temperature multi-component fluids, which is implemented using a multi-physics field testing device for the stratification and tumbling process of low-temperature multi-component fluids. The multi-physics field testing device for the stratification and tumbling process of low-temperature multi-component fluids includes a vacuum cryogenic container, a schlieren background plate, a vacuum pump, a data acquisition device, a camera system, a lens group, a control host, a laser system, a heating system, and a BOS light source. The vacuum cryogenic container includes a vacuum chamber, a liquid nitrogen cooling screen, and a test chamber, which are coaxially arranged and do not directly contact each other. The liquid nitrogen cooling screen is located inside the vacuum chamber. The test chamber is located inside the liquid nitrogen cooling screen and is fixed to the top end cap of the vacuum chamber. The heating system includes a heating film attached to the outer wall of the test chamber and a power supply. The heating film is electrically connected to the power supply, and the heating power is independently adjustable. The vacuum cryogenic container, schlieren background plate, vacuum pump, camera system, lens group, laser system, and BOS light source are all placed on the floor in the light-shielding chamber, with the schlieren background plate positioned between the BOS light source and the vacuum cryogenic container. The vacuum pump is used to evacuate the vacuum cryogenic container. The data acquisition device, camera system, laser system, heating system, and BOS light source are all connected to the control host. The data acquisition device is connected to the test chamber and is used to measure the pressure, temperature, and fluid composition inside the vacuum cryogenic container. The laser system, BOS light source, and camera system are respectively positioned facing different vacuum glass windows on the side of the vacuum chamber. The camera system includes three cameras, which are used to acquire BOS, PIV, and LIF images respectively. A schlieren background plate is provided between the BOS light source and the vacuum glass window it faces. The lens group is placed between the camera system and the vacuum cryogenic container. The lens group includes a bandpass beam splitter and several reflecting mirrors, which are used to transmit the light source signals to the corresponding cameras. Its features are, Includes the following steps: S1. Complete the assembly and construction of the multi-physics field testing device for the stratification and tumbling process of low-temperature multi-component fluids; S2. Start the vacuum pump until the pressure inside the cryogenic vacuum container is ≤5E-3Pa; S3. Pour liquid nitrogen into the liquid nitrogen cooling screen until its temperature reaches below -180℃ and stabilizes; S4. Add tracer particles mixed with alcohol into the test chamber, purge the alcohol with nitrogen and pre-cool the test chamber, then add fluorescent dye suitable for the test temperature range. S5. Introduce a cryogenic fluid a into the test chamber until the liquid level reaches the design position. S6. Introduce another cryogenic fluid b into the test chamber at a preset initial volume ratio or mass ratio, so that it is fully mixed with cryogenic fluid a. S7. Start the control host and set the wall heat flow conditions; the mixed fluid in the test chamber gradually forms thermal stratification and density stratification under the action of wall heating. After the initial stratification conditions of the mixed fluid are formed, start the camera system, laser system, BOS light source and acquisition program. S8. Continuously acquire pressure data of the vacuum cryogenic container; the camera system acquires PIV, LIF and BOS images every 1 to 10 minutes, and simultaneously acquires velocity field, temperature field and density field data; S9. After the planned test time is reached, stop the camera system, laser system and BOS light source; wait until there is no residual liquid in the test chamber and the temperature returns to normal, then stop the heating system and vacuum pump.

2. The multiphysics field testing method for the stratification and tumbling process of low-temperature multi-component fluids according to claim 1, characterized in that, Steps S1 to S9 were repeated multiple times, with each step S7 setting different wall heat flow conditions. By changing the wall heat flow conditions, the effects of different wall heating conditions on the thermal stratification, natural convection, evaporation, and stratification tumbling characteristics of low-temperature multi-component fluids were studied.

3. The multiphysics field testing method for the stratification and tumbling process of low-temperature multi-component fluids according to claim 1, characterized in that, Repeat steps S1 to S9 multiple times, with each step S6 having a different initial volume ratio or mass ratio, to study the effects of the initial components on thermal stratification, natural convection, evaporation, and stratification tumbling characteristics.

4. The multiphysics field testing method for the stratification and tumbling process of low-temperature multi-component fluids according to claim 1, characterized in that, S1~S9 were repeated multiple times, with the pressure inside the vacuum cryogenic container in step S2 being different for each step. By changing the pressure inside the test chamber, the influence of the chamber pressure on the thermal stratification, natural convection, evaporation, and stratification tumbling characteristics of cryogenic multi-component fluids was studied.

5. The multiphysics field testing method for the stratification and tumbling process of low-temperature multi-component fluids according to claim 1, characterized in that: The vacuum chamber includes a vacuum chamber body made of stainless steel. Three vacuum glass windows at the same height are provided on the side of the vacuum chamber body. Two of the three vacuum glass windows are coaxial, and the axis of the third vacuum glass window is perpendicular to the axes of the two coaxial vacuum glass windows. The vacuum glass window is made of quartz. The top end cover is installed on the top of the vacuum chamber. The top end cover is equipped with a temperature measuring Dewar tube, a top heat sink inlet / outlet Dewar tube, cable connector a, and a test chamber inlet / outlet Dewar tube. The side of the vacuum chamber is equipped with a side heat sink inlet / outlet Dewar tube, a vacuum pump interface, and cable connector b.

6. The multiphysics field testing method for the stratification and tumbling process of low-temperature multi-component fluids according to claim 1, characterized in that: The liquid nitrogen cooling screen is made of copper and includes a cylindrical sidewall and a circular base plate. The circular base plate is fixed to the inner wall of the vacuum chamber by multiple support rods. Copper tubes are coiled on the sidewall of the liquid nitrogen cooling screen, and the copper tubes are connected to the external liquid nitrogen supply equipment through the top heat sink liquid inlet / outlet Dewar tube and the side heat sink liquid inlet / outlet Dewar tube.

7. The multiphysics field testing method for the stratification and tumbling process of low-temperature multi-component fluids according to claim 5, characterized in that: The test chamber is a square container made of stainless steel. The side of the test chamber has three test glass windows at the same height. The test glass windows are made of high borosilicate material and correspond one-to-one with the three vacuum glass windows of the vacuum chamber. The side of the test chamber is also equipped with an exhaust pipe and a liquid inlet / outlet pipe assembly. The exhaust pipe and the liquid inlet / outlet pipe assembly extend to the outside of the vacuum chamber through the liquid inlet / outlet Dewar tube of the test chamber.

8. The multiphysics field testing method for the stratification and tumbling process of low-temperature multi-component fluids according to claim 1, characterized in that: Heating films, made of polyacetamide, are attached to the outer walls of all six sides of the test chamber.

9. The multiphysics field testing method for the stratification and tumbling process of low-temperature multi-component fluids according to claim 5, characterized in that: The data acquisition device includes a pressure sensor, a temperature sensor, a multi-component analyzer, a vacuum gauge, and a flow meter. The pressure sensor and temperature sensor are connected to cable connector a and cable connector b, respectively. The multi-component analyzer and flow meter are connected to the exhaust pipe of the test chamber through pipes. The vacuum gauge is fixed to the side of the vacuum chamber body through a flange. Cable connector a, cable connector b, multi-component analyzer, vacuum gauge, and flow meter are electrically connected to the control host.

10. The multiphysics field testing method for the stratification and tumbling process of low-temperature multi-component fluids according to claim 5, characterized in that: The vacuum pump interface is connected to the vacuum pump via a pipe. The vacuum pump is a vacuum pump assembly consisting of a mechanical pump and a molecular pump.

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