Liquid metal two-phase flow experiment platform and method for realizing flow calibration thereof

Abstract

The invention provides a liquid metal two-phase flow experiment platform and a method for realizing flow calibration. The experiment platform comprises a liquid metal storage tank, a test section, a mixing chamber, a gas injection device, a gas-liquid separation device, a descending section and a main circulation driving unit, the gas injection device is located in the mixing chamber and connected with the liquid metal storage tank, and the mixing chamber is connected with the bottom of the test section and used for inputting mixed gas to the test section; the gas-liquid separation device is connected with the top of the test section and the top of the descending section; the channel of the test section is a cylindrical channel or a rectangular channel, and is connected with the gas-liquid separation device and the gas injection device through circular interfaces; the rectangular channel is connected with the gas-liquid separation device and the gas injection device through transition pieces. According to the experimental device, a modularized replaceable structure is adopted, the defect that a traditional device is single in geometric form is overcome, and the application range of two-phase flow and heat exchange research is expanded.

Description

Technical Field

[0001] This invention relates to the field of nuclear energy engineering technology, and in particular to an experimental platform for liquid metal two-phase flow and a method for achieving flow rate calibration. Background Technology

[0002] In nuclear energy systems, gas-liquid two-phase flow and heat transfer phenomena are crucial to the safety of system operation. Therefore, it is necessary to develop a liquid metal two-phase flow experimental platform to provide basic conditions for the study of gas-liquid two-phase flow through experimental devices.

[0003] However, existing experimental devices have fixed layouts and simple forms between components, making it impossible to switch them flexibly or adjust control and measurement parameters. Therefore, a single experimental device cannot simultaneously meet the needs of simulation, flow pattern evolution analysis, and numerical model verification for various experimental conditions and different accident scenarios.

[0004] Therefore, the existing technology needs further improvement. Summary of the Invention

[0005] The purpose of this invention is to provide an experimental platform for liquid metal two-phase flow and a method for flow rate calibration. Through modular design, it overcomes the shortcomings of existing experimental devices with fixed layout and poor flexibility in adjusting parameters.

[0006] The technical solution adopted by this invention to solve the technical problem is as follows: In a first aspect, this application provides a liquid metal two-phase flow experimental platform, which includes: a main loop; the main loop includes: a liquid metal storage tank, a test section, a mixing chamber, a gas injection device, a gas-liquid separation device, a descent section, and a main circulation drive unit; The gas injection device is located in the mixing chamber and connected to the liquid metal storage tank. The mixing chamber is connected to the bottom of the test section and is used to input mixed gas into the test section. The gas-liquid separation device is connected to the top of the test section and the top of the descending section, and is used to separate the gas phase and liquid phase in the mixed flow input to the test section; the descending section is connected to the main circulation drive unit, which drives the liquid metal to circulate between the descending section and the test section; the channel shape of the test section is a cylindrical channel or a rectangular channel, and the cylindrical channel is connected to the gas-liquid separation device and the gas injection device through a circular interface; the rectangular channel is connected to the gas-liquid separation device and the gas injection device using a transition piece; one end of the transition piece is adapted to the shape of both ends of the rectangular channel, and the other end is adapted to the gas-liquid separation device and the gas injection device through a circular interface.

[0007] Optionally, a differential pressure measurement system for measuring the two-phase flow parameters of the test section is provided along the pipe axis direction of the test section. The differential pressure measurement system includes: multiple pressure taps and sensor slots. The pressure taps are used for pressure measurement, and the sensor slots are used to arrange multiple conductivity probes.

[0008] Optionally, the gas injection device includes a detachable nozzle module, which includes a detachable air chamber and a nozzle plate; the orifice size, number, and arrangement spacing of each nozzle plate connected to the detachable air chamber are all custom-configured.

[0009] Optionally, the main circulation drive unit is a mechanical pump.

[0010] Optionally, it also includes a calibration branch connected to the main circuit; the calibration branch is a liquid flow control system connected to the mechanical pump; the liquid flow control system includes: a liquid flow meter and a flow calibration device; The flow calibration device is connected to the liquid flow meter and the mechanical pump and is used to obtain the fitting relationship between the volumetric flow rate of liquid metal and the output signal in the liquid flow meter, so as to realize the monitoring and control of liquid flow rate based on the fitting relationship.

[0011] Optionally, the flow calibration device includes a calibration tank and a baffle plate disposed on the inner wall of the calibration tank, a level gauge disposed on the top cover of the calibration tank, and a flow stabilizer plate disposed inside the calibration tank and located at the bottom.

[0012] Optionally, it also includes a heating and temperature control device; the heating and temperature control device is respectively installed on the side of the liquid metal storage tank, the test section, the mixing chamber, the gas injection device, the gas-liquid separation device, the descending section, the main circulation drive unit and the calibration tank, and is used to maintain the temperature value in the experimental conditions.

[0013] Optionally, the top and lowering sections of the gas-liquid separation device are respectively provided with fine mesh and coarse mesh filters, and a demisting device is installed at the bottom of the coarse mesh filter.

[0014] Secondly, this application discloses a method for flow calibration of the liquid metal two-phase flow experimental platform, wherein the liquid metal two-phase flow experimental platform is provided with a flow calibration device, the flow calibration device comprising: a calibration tank and a baffle plate disposed on the inner wall of the calibration tank, a level gauge disposed on the top cover of the calibration tank and a flow stabilizer disposed inside the calibration tank and located at the bottom end; a first valve and a fourth valve are disposed between the descending section and the flow calibration device; a second valve and a third valve are disposed between the test section and the flow calibration device; wherein, one end of the first valve is connected to the descending section and the other end is connected to the fourth valve and the mechanical pump; one end of the second valve is connected to the test section and the other end is connected to the flow meter and the third valve; one end of the third valve is connected to the second valve and the other end is connected to the flow calibration device; one end of the fourth valve is connected to the mechanical pump and the first valve and the other end is connected to the flow calibration device. The flow rate calibration method includes: When calibrating the flow meter, keep the first and third valves open, close the second valve, and record the change in the liquid level in the calibration tank over time to determine the actual flow rate of the liquid metal. A calibration function is established based on the actual flow rate and the liquid flow meter signal, and the flow rate is calibrated using the calibration function. After calibration, open the second and fourth valves and close the third valve to allow all the liquid metal in the calibration tank to be discharged into the main circuit. Then close the fourth valve and keep the circuit running.

[0015] Beneficial effects: This invention provides an experimental platform for two-phase flow of liquid metal and a method for flow rate calibration. The experimental device includes: a liquid metal storage tank, a test section, a mixing chamber, a gas injection device, a gas-liquid separation device, a descending section, and a main circulation drive unit. The gas injection device is located in the mixing chamber and connected to the liquid metal storage tank. The mixing chamber is connected to the bottom of the test section and is used to input mixed gas into the test section. The gas-liquid separation device is connected to the top of the test section and the top of the descending section, and is used to separate the gas and liquid phases in the mixed flow input to the test section. The descending section is connected to the main circulation drive unit, which drives the liquid metal to circulate between the descending section and the test section. The main circulation drive unit is a mechanical pump. The experimental device disclosed in this invention adopts a modular and replaceable structure, enabling rapid interchange between cylindrical and rectangular channels in the test section. It allows for cross-geometric comparative studies under the same external conditions, overcoming the limitations of traditional devices with their single geometric form and expanding the applicability of two-phase flow and heat transfer research. Attached Figure Description

[0016] Figure 1 A schematic diagram of the structure of the liquid metal two-phase flow experimental platform provided by the present invention; Figure 2 This is a schematic diagram of the flow calibration device provided by the present invention; Figure 3 A top view of the calibration tank provided by this invention; Figure 4 A flowchart illustrating the steps of the experimental method for liquid metal two-phase flow provided by the present invention; Figure 5 A flowchart illustrating the steps of the method for flow calibration of the liquid metal two-phase flow experimental platform provided by this invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0018] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein.

[0019] Liquid metal cooling technology is a crucial development direction for fourth-generation advanced nuclear energy systems. Liquid metal coolants, represented by lead-bismuth eutectic (LBE) alloys, possess high thermal conductivity, high boiling point, low neutron capture cross-section, and excellent chemical and radiation stability, thus being widely used in liquid metal-cooled fast reactors (LFRs), accelerator-driven subcritical systems (ADS), and high-temperature materials test loops. In these devices, gas-liquid two-phase flow and heat transfer phenomena are critical to system operational safety. Typical accident scenarios, such as steam generator tube rupture (SGTR) or heat exchanger leakage, can lead to high-pressure gas or water entering the primary loop, forming a complex gas-liquid two-phase flow structure. The generation, coalescence, breakup, and migration of bubbles significantly alter local flow fields and heat transfer conditions, even triggering coupled effects such as thermo-mechanical-corrosion. Therefore, in-depth research into the mechanisms of liquid metal two-phase flow and heat transfer is of great significance.

[0020] To meet research needs, a number of experimental platforms for liquid metal two-phase flow have been developed both domestically and internationally. These experimental devices typically employ a vertically arranged circular tube test section, with gas injected at the bottom through a multi-hole nozzle or partial opening. Experimental data are then acquired using conductivity probes, differential pressure gauges, and flow meters. While these devices provide fundamental conditions for gas-liquid two-phase flow research, a series of shortcomings have still been revealed during their application: First, the geometry of the test sections is too simplistic. Existing devices almost exclusively use fixed circular tube test sections, lacking comparative studies of rectangular channels or other geometric structures. This limits the experimental results to reflecting only the patterns under circular tube conditions, failing to reveal the influence of geometric factors on two-phase flow patterns, bubble distribution, and pressure drop characteristics, thus restricting the ability to extrapolate to complex engineering geometries.

[0021] Second, the gas injection device lacks flexibility. Traditional experimental platforms mostly use fixed nozzle plates or needle valves for gas injection, with fixed nozzle diameters and numbers, making it difficult to adjust flexibly as needed. This results in uncontrollable bubble generation frequency and scale, limiting the scope of experimental conditions. For example, when the total gas volume is constant, if the number of nozzles cannot be adjusted, it is impossible to actively control the bubble frequency and collective behavior, which is not conducive to systematically conducting flow pattern evolution research.

[0022] Third, the measurement methods are limited in scope. Most existing experimental setups rely on conductivity probes or differential pressure measurements, which often only provide local or single-point data, lacking multi-point, three-dimensional measurement arrangements. In high-temperature LBE environments, the sealing and structural stability of the probes are even more challenging, making it difficult to simultaneously obtain key parameters such as bubble frequency distribution, local cavitation rate, and transient interface velocity, thus reducing the comprehensiveness and reliability of the experimental results.

[0023] Fourth, flow calibration struggles to meet high-precision requirements. Liquid metals have high density and high temperature, demanding extremely high stability from flow meters. While vortex flow meters are commonly used, they are prone to zero-point drift and signal attenuation during long-term operation, leading to accumulated measurement errors. Traditional calibration methods, such as the level method or cold injection method, not only require interrupting the loop but are also difficult to implement under high-temperature conditions, making hot online calibration impossible. This directly affects the accuracy of flow data and consequently impacts the inversion of secondary parameters such as cavitation rate and volume fraction.

[0024] Fifth, existing liquid metal two-phase flow experimental platforms generally use electromagnetic pumps to regulate flow. However, electromagnetic pump flow regulation is not only limited in its regulation method (mainly relying on changing the input current or magnetic field strength), but also has a slow dynamic response (the magnetic field needs a certain amount of time to establish, which is difficult to meet the needs of rapidly changing flow switching). Under low flow conditions, the magnetic field force weakens. Therefore, electromagnetic pumps have certain limitations in terms of the flexibility of flow regulation and the continuity of operation.

[0025] In summary, existing experimental platforms for liquid metal two-phase flow have significant limitations in areas such as the geometric diversity of the test section, the controllability of the gas injection method, the completeness of measurement dimensions, and the reliability of flow calibration. These shortcomings restrict the systematic study of the gas-liquid two-phase flow mechanism and also affect the accuracy and repeatability of experimental data.

[0026] To address the problems of existing technologies, such as the single geometry of the test section, fixed gas injection method, limited measurement dimensions, and poor reliability of flow calibration, this invention provides a novel experimental platform for liquid metal two-phase flow. By modularly designing the geometry of the test section, setting up replaceable nozzle modules and hot online flow calibration functions, it can not only achieve stable operation under high-temperature hot conditions, but also achieve experimental conditions with comparable test section geometry, adjustable bubble frequency, and more comprehensive data acquisition, thus meeting the needs of accident condition simulation, flow pattern evolution analysis, and numerical model verification.

[0027] The following description, in conjunction with the accompanying drawings, further illustrates the experimental platform for liquid metal two-phase flow provided by the present invention and the method for achieving flow rate calibration.

[0028] This invention discloses an experimental platform for liquid metal two-phase flow, such as... Figure 1 As shown, it includes: a main circuit; the main circuit includes: a liquid metal storage tank 8, a test section 1, a mixing chamber 5, a gas injection device 4, a gas-liquid separation device 15, a descending section 14, and a main circulation drive unit 11.

[0029] The gas injection device 4 is located inside the mixing chamber 5 and is connected to the liquid metal storage tank 8. The mixing chamber 5 is connected to the bottom of the test section 1 and is used to input mixed gas into the test section 1.

[0030] The gas-liquid separation device 15 is connected to the top of the test section 1 and the top of the descending section 14, and is used to separate the gas phase and liquid phase in the mixed flow input to the test section 1. The descending section 14 is connected to the main circulation drive unit 11, which drives the liquid metal to circulate between the descending section 14 and the test section 1. The channel shape of the test section 1 is a cylindrical channel or a rectangular channel. The cylindrical channel is connected to the gas-liquid separation device 15 and the gas injection device 4 through a circular interface. The rectangular channel is connected to the gas-liquid separation device 15 and the gas injection device 4 through a transition piece. One end of the transition piece is adapted to the shape of both ends of the rectangular channel, and the other end is adapted to the gas-liquid separation device 15 and the gas injection device 4 through a circular interface.

[0031] In the experimental setup of this embodiment, the channel shape of the test section adopts a modular and replaceable design, meaning that it can switch between cylindrical and rectangular channels. Both ends of the cylindrical channel are connected to a uniform circular flange interface, so the two ends of the cylindrical channel can be directly connected to the circular flange interface. The rectangular channel can be connected to the circular flange interface through a rectangular-circular transition piece.

[0032] Furthermore, in practice, the inner wall of the test section is kept in a natural passivation film state to truly reproduce the wetting characteristics of liquid metal and structural materials.

[0033] Furthermore, such as Figure 1 As shown, a differential pressure measurement system 3 for measuring two-phase flow parameters of the test section is arranged along the pipe axis. The differential pressure measurement system 3 includes multiple pressure taps and sensor slots. The pressure taps are used for pressure measurement, and the sensor slots are used to arrange multi-point conductivity probes. By arranging multiple pressure taps and sensor slots along the pipe axis of the test section for differential pressure measurement and the arrangement of multi-point conductivity probes, two-phase flow parameters such as pressure distribution along the pipe, bubble frequency, and cavitation rate can be obtained.

[0034] Furthermore, to achieve adjustable gas injection mode, the gas injection device in this embodiment includes a detachable nozzle module, which comprises a detachable gas chamber and nozzle plates. The orifice size, number, and arrangement spacing of each nozzle plate connected to the detachable gas chamber are customizable. During experiments, the orifice size, number, and array pattern of the nozzle plates can be quickly changed according to experimental requirements. By adjusting the number of nozzle plates and the flow rate per orifice, the bubble generation frequency and individual bubble size can be controlled while keeping the total gas volume constant. Specifically, when the number of nozzles increases, the flow rate per orifice decreases, the bubble frequency increases, and the size decreases; conversely, the frequency decreases and the size increases, thereby achieving controllable adjustment of the evolution rhythm and distribution law of bubble groups in the two-phase flow.

[0035] In detail, such as Figure 1 As shown, the gas injection device 4 is connected to a gas flow meter 6, which is connected to a high-pressure gas cylinder 7. The high-pressure gas cylinder stores a chemically inert gas, such as nitrogen, carbon dioxide, or argon. The inert gas (such as nitrogen or argon) output from the high-pressure gas cylinder enters the pressure stabilizing chamber and the rectifying chamber after being controlled by the gas flow meter 6, and is then uniformly released into the liquid lead-bismuth in the test section through a nozzle, forming a stable gas-liquid two-phase flow, supporting the evolution study of various flow patterns such as bubbly flow and slug flow.

[0036] Furthermore, in this embodiment, the main circulation drive unit is a mechanical pump, that is, a mechanical pump is used as the main driving force to drive the high-temperature liquid metal to continuously circulate in a closed loop. Because a mechanical pump is used as the main circulation drive unit for the liquid metal, it has excellent high-temperature pressure resistance and stable output capability, overcoming the limitations of traditional electromagnetic pumps in terms of flow regulation flexibility and operational continuity, making it more suitable for experimental needs in high-temperature, high-density liquid metal environments.

[0037] Furthermore, the experimental apparatus also includes heating and temperature control devices; these devices are respectively installed on the sides of the liquid metal storage tank, the test section, the mixing chamber, the gas injection device, the gas-liquid separation device, the descent section, the main circulation drive unit, and the calibration tank, and are used to maintain the temperature value during the experimental operation.

[0038] The gas-liquid separator 15 is located at the upper end of the test section and connected to its top. Its function is to separate the gas phase and liquid phase in the mixed flow. The gas portion is discharged to the waste gas recovery system 16, while the liquid metal returns to the main circuit through the descending section 14. To prevent oxide particles in the liquid metal from being discharged with the gas, fine mesh and coarse mesh filters are respectively installed at the top and in the descending section of the gas-liquid separator, and a demister is installed at the bottom of the coarse mesh filter.

[0039] The liquid metal storage tank 8 is located at the bottom of the entire experimental setup and is connected to the main circuit via a bottom pipeline. It is responsible for the initial filling and replenishment of lead and bismuth. Multiple level gauges and thermocouples are installed inside the tank to monitor its operating status. To prevent oxidation of the liquid metal (e.g., liquid lead and bismuth), an argon-hydrogen mixture 10 is introduced into the upper part of the tank to establish an inert atmosphere, while simultaneously providing pressure to drive the liquid metal into the circuit. A vacuum pump 9 is used to vent air from the pressure vessel and the main circuit, and then accumulate nitrogen in the pressure vessel and the main circuit.

[0040] To achieve accurate monitoring and control of the liquid metal flow rate, the experimental apparatus also includes a calibration branch connected to the main circuit; the calibration branch is a liquid flow control system connected to the mechanical pump; the liquid flow control system includes a liquid flow meter and a flow calibration device.

[0041] Combination Figure 1 and Figure 2 As shown, the flow calibration device 13 is connected to the liquid flow meter 12 and the mechanical pump, and is used to obtain the fitting relationship between the volumetric flow rate of liquid metal and the output signal in the liquid flow meter, so as to realize the monitoring and control of liquid flow rate based on the fitting relationship.

[0042] like Figure 2 and Figure 3 As shown, the flow calibration device includes a calibration tank 24, a baffle 21 disposed on the inner wall of the calibration tank, a level gauge 22 disposed on the top cover 23 of the calibration tank, and a flow stabilizer 25 disposed inside the calibration tank and located at the bottom.

[0043] The experimental apparatus disclosed in this application uses a mechanical pump as the main circulation drive unit for liquid metal, which has good high-temperature pressure resistance and stable output capability. It solves the limitations of traditional electromagnetic pumps in terms of flow regulation flexibility and continuous operation, and is more suitable for experimental needs in high-temperature and high-density liquid lead-bismuth environments.

[0044] The experimental apparatus disclosed in this invention is modularly integrated, with a clear structure and well-defined functional zones for the main circulation, gas injection, measurement, separation, and safety recovery units, providing excellent scalability and maintainability. Each subsystem can be flexibly replaced or upgraded according to research needs, thus adapting to studies of various two-phase flow structures and gas injection methods.

[0045] Secondly, this application provides a parameter measurement method for a liquid metal two-phase flow experimental platform, such as... Figure 4 As shown, the parameter measurement method applied to the experimental apparatus includes: Step S1: Use a mechanical pump to provide the main circulation driving force to drive the liquid metal to circulate in the main circuit; Step S2: Measure the two-phase flow parameters of the test section using a differential pressure measurement system set along the pipe axis of the test section.

[0046] In this step, during parameter measurement, the entire circuit is first heated to the required experimental temperature. Then, inert gas is introduced into the circuit to remove air and moisture. Next, the mechanical pump is turned on to introduce liquid metal from the liquid metal storage tank into the circuit. While the liquid metal is flowing in the circuit, data is collected and recorded using a differential pressure measurement system, a conductivity probe information acquisition system, and thermocouples. After data collection is complete, the mechanical pump is turned off, and the liquid metal is discharged from the main circuit through the valve on the control channel, flowing back to the liquid metal storage tank. The valve and the electric heating system are then closed, ending the experiment.

[0047] The following is combined Figure 1 The specific experimental methods of this experimental setup will be explained in more detail.

[0048] In practical application implementation, the following steps are included: 1) Preheating circuit: Start the heating and temperature control device (in specific implementation, the heating and temperature control device can be electric heat tracing insulation cotton) to heat the entire experimental circuit to the temperature required for the experiment.

[0049] 2) Open valves a and j to introduce nitrogen gas and fill the circuit to remove air and moisture from the circuit.

[0050] 3) Gas settings for each section: To prevent backflow of liquid metal, the gas is pressurized, and nitrogen is flowed at a very low rate to the pressure measuring port provided in the testing section. Similarly, pressures from high to low are applied to the four different pressure measuring ports from bottom to top.

[0051] 4) Differential pressure gauge offset correction: Since the differential pressure measurement system requires an offset voltage to measure the porosity when the test section is empty and filled with liquid, the average value of the differential pressure signal is recorded for 20 seconds in both states.

[0052] 5) Introducing liquid metal into the circuit: Connect the drain pipe from the bottom of the liquid metal storage tank to the circuit, open valves e, k, and c, pressurize the liquid metal storage tank with argon and hydrogen gas to introduce liquid metal into the circuit, filling it to about half the height of the gas-liquid separator, and then close valves e, k, and c to introduce liquid metal into the circuit.

[0053] 6) Circuit trial operation: Open valves f and i, and start the mechanical pump to circulate the liquid metal. The output of the mechanical pump will fluctuate at the beginning of the operation, so a trial operation of about 1 hour is required. Figure 1 The solid black arrow in the middle indicates the flow direction of the liquid metal during circuit trial and operation.

[0054] The experimental method provided in this embodiment combines functions such as high-temperature liquid metal circulation, replaceable test sections, adjustable inert gas injection, and bypass hot flow calibration. It can accurately reproduce typical flow patterns in accident conditions and provide high-quality experimental data for multiphase flow model development, flow heat transfer mechanism research, and CFD verification.

[0055] The method provided in this embodiment utilizes a mechanical pump as the main circulation drive unit and sets the gas injection device as a detachable and replaceable nozzle module to adjust the liquid metal flow rate and the frequency and scale of bubble generation during the experiment. This improvement aims to flexibly change a single variable to obtain more comprehensive observation results. Since the flow rate adjustment accuracy of the mechanical pump depends on the adjustment accuracy of the calibration branch, the method and apparatus provided in this application can achieve more comprehensive measurement data while also obtaining more accurate measurement results.

[0056] Thirdly, this application discloses a method for flow calibration on a liquid metal two-phase flow experimental platform, applied to a flow calibration device. The flow calibration device includes: a calibration tank and a baffle plate disposed on the inner wall of the calibration tank, a level gauge disposed on the top cover of the calibration tank, and a flow stabilizer disposed inside the calibration tank and located at the bottom. A first valve and a fourth valve are disposed between the descending section and the flow calibration device. A second valve and a third valve are disposed between the test section and the flow calibration device. The first valve is connected at one end to the descending section and at the other end to the fourth valve and a mechanical pump. The second valve is connected at one end to the test section and at the other end to the flow meter and the third valve. The third valve is connected at one end to the second valve and at the other end to the flow calibration device. The fourth valve is connected at one end to the mechanical pump and the first valve and at the other end to the flow calibration device.

[0057] like Figure 5 As shown, the flow rate calibration method includes: H1. When calibrating the flow meter, keep the first and third valves open, close the second valve, and record the change in the liquid level in the calibration tank over time to determine the actual flow rate of the liquid metal.

[0058] H2. Establish a calibration function based on the actual flow rate and the liquid flow meter signal, and use the calibration function to calibrate the flow rate.

[0059] H3. After calibration, open the second and fourth valves and close the third valve to allow all the liquid metal in the calibration tank to be discharged into the main circuit. Then close the fourth valve and keep the circuit running.

[0060] In practical implementation, taking lead-bismuth as an example of liquid metal, the calibration method disclosed in this embodiment includes: First, stop the mechanical pump and adjust the zero point of the liquid flow meter to ensure that the displayed value is zero.

[0061] Next, close the second valve i, open the third valve h, start the mechanical pump, and send lead and bismuth into the calibration tank. Measure the time it takes for the liquid level to change in the level gauge on the calibration tank. And the voltage value U of the liquid flow meter at that time. Then open the second valve i and the fourth valve g, close the third valve h, so that all the lead and bismuth in the calibration tank are discharged into the main circuit, close the fourth valve g, and keep the circuit running.

[0062] Secondly, during flow calibration, the liquid metal in the calibration tank gradually rises, and the moment when the liquid metal contacts each level gauge is recorded. And the voltage value U of the liquid flow meter at the corresponding moment, and then based on the vertical distance between two adjacent liquid level gauge probes. And the bottom area A of the inner wall of the calibration tank can be calculated. Volumetric flow rate at time (The formula is shown in formula (1) below). Then the liquid metal volumetric flow rate can be calculated. The relationship between the liquid flow meter output signal U and the liquid flow meter output signal U is fitted. Based on the current liquid flow meter output signal U, the corresponding liquid metal volume flow rate is obtained through the established relationship, and then multiplied by the liquid metal density under the current operating conditions to obtain the liquid metal mass flow rate under the current operating conditions.

[0063] (1) Readjustment of differential pressure gauge offset: In order to measure the porosity via the differential pressure measurement system, the offset of each differential pressure gauge is measured again when filling with liquid.

[0064] Finally, data acquisition and recording were performed, and the experiment was terminated: During loop operation, data was acquired and recorded using a differential pressure measurement system, a conductivity probe signal acquisition system, and thermocouples. After data recording was completed, the mechanical pump was turned off, valves k and c were opened, and the lead and bismuth were allowed to drain completely from the main loop into the storage tank. All valves were then closed, the electric heating was turned off, and the experiment was terminated.

[0065] This embodiment not only proposes an independent flow calibration branch but also a volume-time method for online flow calibration suitable for high-temperature liquid metal environments. By bypassing a portion of the liquid metal into the calibration tank, the liquid level change over time is recorded, and the actual flow rate is calculated using the effective volume of the calibration tank. A calibration function is then established with the liquid flow meter signal to achieve periodic calibration under hot operating conditions. This method is independent of cold-state or level-based methods and can be performed without interrupting the main circuit, significantly improving the accuracy of flow measurement and the reliability of experimental data.

[0066] This invention provides an experimental platform for two-phase flow of liquid metal and a method for flow rate calibration. The experimental device includes: a liquid metal storage tank, a test section, a mixing chamber, a gas injection device, a gas-liquid separation device, a descending section, and a main circulation drive unit. The gas injection device is located in the mixing chamber and connected to the liquid metal storage tank. The mixing chamber is connected to the bottom of the test section and is used to input mixed gas into the test section. The gas-liquid separation device is connected to the top of the test section and the top of the descending section, and is used to separate the gas and liquid phases in the mixed flow input to the test section. The descending section is connected to the main circulation drive unit, which drives the liquid metal to circulate between the descending section and the test section. The experimental device disclosed in this invention adopts a modular and replaceable structure, enabling rapid interchange between cylindrical and rectangular channels in the test section. It allows for cross-geometric comparative studies under the same external conditions, overcoming the limitations of traditional devices with their single geometric form and expanding the applicability of two-phase flow and heat transfer research.

[0067] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0068] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A liquid metal two-phase flow experimental platform, characterized in that, The utility model relates to a two-phase flow test loop, comprising: a main loop; the main loop comprises: a liquid metal storage tank, a test section, a mixing chamber, a gas injection device, a gas-liquid separation device, a descending section and a main circulation driving unit; the gas injection device is located in the mixing chamber and is connected to the liquid metal storage tank, the mixing chamber is connected to the bottom of the test section, and the mixing chamber is used for inputting mixed gas into the test section; the gas-liquid separation device is connected to the top of the test section and the top of the descending section, and is used for separating the gas phase and the liquid phase in the mixed flow input by the test section; the descending section is connected to the main circulation driving unit, and the main circulation driving unit drives the circulation of the liquid metal between the descending section and the test section; the channel shape of the test section is a cylindrical channel or a rectangular channel, the cylindrical channel is connected to the gas-liquid separation device and the gas injection device through a circular interface, the rectangular channel is connected to the gas-liquid separation device and the gas injection device by using a transition piece, one end of the transition piece is matched with the shape of the two ends of the rectangular channel, and the other end is matched with the circular interface between the gas-liquid separation device and the gas injection device.

2. The liquid metal two-phase flow experimental platform according to claim 1, wherein, A differential pressure measurement system for measuring the two-phase flow parameters of the test section is arranged along the pipe axis direction of the test section, the differential pressure measurement system comprises: a plurality of pressure tapping holes and sensor insertion slots, the pressure tapping holes are used for pressure measurement, and the sensor insertion slots are used for arranging multipoint conductivity probes.

3. The liquid metal two-phase flow experimental platform of claim 1, wherein, The gas injection device comprises a detachable nozzle module, the detachable nozzle module comprises a detachable gas cavity and a nozzle plate, and the aperture size, number and arrangement pitch of each nozzle plate connected to the detachable gas cavity are all self-defined configurations.

4. The liquid metal two-phase flow experimental platform of claim 1, wherein, The main circulation driving unit is a mechanical pump.

5. The liquid metal two-phase flow experimental platform according to claim 4, characterized in that, Further comprising a calibration branch connected to the main loop; the calibration branch is a liquid flow control system connected to the mechanical pump; the liquid flow control system comprises: a liquid flow meter and a flow calibration device; the flow calibration device is in communication with the liquid flow meter and the mechanical pump, is used for obtaining the fitting relationship between the liquid metal volume flow and the output signal in the liquid flow meter, and realizes monitoring and control of the liquid flow based on the fitting relationship.

6. The liquid metal two-phase flow experimental platform according to claim 5, wherein, The flow calibration device comprises a calibration tank, a baffle arranged on the inner wall of the calibration tank, a liquid level meter arranged on the top cover of the calibration tank and a steady flow plate arranged in the interior of the calibration tank and located at the bottom end.

7. The liquid metal two-phase flow experimental platform according to claim 6, wherein, Further comprising a heating and temperature control device; the heating and temperature control device is arranged at the side of the liquid metal storage tank, the test section, the mixing chamber, the gas injection device, the gas-liquid separation device, the descending section, the main circulation driving unit and the calibration tank respectively, and is used for maintaining the temperature value in the experimental working condition.

8. The liquid metal two-phase flow experimental platform according to claim 6, wherein, Fine mesh filters and coarse mesh filters are respectively arranged in the top of the gas-liquid separation device and the descending section, and a demisting device is installed at the bottom of the coarse mesh filter.

9. A method for flow calibration of a liquid metal two-phase flow experimental platform according to any one of claims 1-8, characterized in that, The liquid metal two-phase flow experimental platform is provided with a flow calibration device, the flow calibration device comprises a calibration tank, baffles arranged on the inner wall of the calibration tank, a liquid level meter arranged on the top cover of the calibration tank, and a steady flow plate arranged inside the calibration tank and located at the bottom end; a first valve and a fourth valve are arranged between the descending section and the flow calibration device; a second valve and a third valve are arranged between the test section and the flow calibration device; one end of the first valve is connected with the descending section, the other end is connected with the fourth valve and a mechanical pump, one end of the second valve is connected with the test section, the other end is connected with a flow meter and the third valve, one end of the third valve is connected with the second valve, the other end is connected with the flow calibration device, one end of the fourth valve is connected with the mechanical pump and the first valve, the other end is connected with the flow calibration device; The flow calibration method comprises: When calibrating the flow meter, keep the first valve and the third valve open, close the second valve, and record the change of the liquid level in the calibration tank with time to determine the actual flow of the liquid metal; A calibration function is established according to the actual flow and the liquid flow meter signal, and the flow calibration is performed by using the calibration function; After the calibration is completed, open the second valve and the fourth valve, close the third valve, make the liquid metal in the calibration tank all flow into the main loop, close the fourth valve, and keep the loop running.

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