A high temporal and spatial resolution measurement system for liquid metal two-phase flow in a rod bundle channel and a measurement method thereof

Abstract

The application discloses a kind of liquid metal two-phase flow high space-time resolution measurement systems for rod bundle channel, belong to nuclear reactor thermal hydraulic two-phase flow measurement technical field.The flow channel pipe (1) is vertically placed column, the inside of the flow channel pipe (1) constitutes a closed channel for fluid experiment, the upper core area of the flow channel pipe (1), multiple simulation fuel rod bundles (2) are arranged in matrix along the axial direction, the simulation fuel rod bundle (2) is firmly clamped by positioning grid (10) to maintain flow channel gap, when coolant passes through the grid of channel formed by simulation fuel rod bundle (2), it is subjected to along the way resistance, the probe of each simulation fuel rod bundle (2) leads out a signal lead (13), the signal lead (13) is accessed acquisition module.The application is used to solve the problem of liquid metal liquid film superconducting short circuit and the problem of embedded measuring instrument in complex rod bundle channel flow end measurement ability weakening, realize high space resolution measurement of full field blind area.

Description

Technical Field

[0001] This invention belongs to the field of nuclear reactor thermal-hydraulic two-phase flow measurement technology, specifically relating to a high spatiotemporal resolution measurement system and method for liquid metal two-phase flow oriented towards rod bundle channels. Background Technology

[0002] In the thermal-hydraulic experimental study of reactor core fuel assemblies, the transient phase distribution of the high-temperature liquid metal two-phase flow in the rod bundle channel is key to evaluating heat transfer performance and reactor safety margin.

[0003] However, due to the high inherent electrical conductivity, optical opacity, and high-temperature corrosiveness of liquid metals, experimental measurement of two-phase flow of liquid metals is a recognized challenge in the industry.

[0004] When the measurement channel becomes further complex, consisting of a densely packed bar bundle, the difficulty of measuring two-phase flow increases exponentially. The interior of the bar bundle channel is composed of intricately interwoven sub-channels, with limited physical space and severe spatial geometric obstruction. On the one hand, traditional conductivity probes or measurement circuits typically have relatively large insulating protective sleeves on the outside of their electrodes to ensure mechanical rigidity under high-temperature, heavy-load, high-speed liquid flow. Due to the tight gaps and obstructions between the bars, these large-volume probes are difficult to place in physical space, making it difficult to achieve high-density discrete point placement. If multiple probes are forcibly arranged in a local sub-channel, the macroscopic volume of the large sleeve itself will cause severe cross-sectional mechanical blockage and introduce unpredictable flow resistance and deflection disturbances, disrupting the prototype flow field structure of the reactor assembly.

[0005] On the other hand, traditional wire mesh-air sensors (WMS) heavily rely on a crisscrossing, double-layered, suspended orthogonal metal wire structure. Once introduced into the liquid metal environment of the rod bundle channel, the continuous, highly conductive liquid metal film adhering to the circular outer surface of the dense fuel rod bundle and the wall of the flow channel can cause a global electrical short circuit or a liquid bridging hard short circuit in the sensor, completely losing its phase resolution capability. Furthermore, limited by the suspended wiring path of traditional leads, existing measurement equipment cannot physically reach or be deployed in the clamping and limiting blade area of ​​the positioning grid, the narrow slit dead angles between rods (only a few millimeters apart), or the irregular outer boundary sub-channels. These typical complex and irregular geometric boundary areas have huge thermal measurement blind spots, making it impossible for traditional methods to effectively obtain three-dimensional high spatiotemporal resolution distribution data of the two-phase flow phases within the rod bundle channel. Therefore, how to eliminate geometric obstruction and complex boundary blind spots in the internal space of the rod bundle while maintaining low disturbance of the flow field in the prototype channel of the rod bundle assembly, and realize high-resolution three-dimensional phase state full-field measurement of the rod bundle channel, is a technical problem that urgently needs to be solved in the fields of fluid measurement and nuclear thermal hydraulics.

[0006] Due to the different media, many problems in traditional aqueous phase measurements need to be reconsidered in liquid metal measurements. In particular, liquid metals have strong conductivity; when two-phase flows through the channel, the continuous liquid metal film adhering to the surface and walls of the rod bundle exhibits electrical "superconducting short-circuit" characteristics. Traditional wire mesh sensors used for conventional fluids employ a double-layer suspended orthogonal metal wire structure. Once introduced into a liquid metal flow field, this suspended orthogonal mesh is short-circuited by the "superconducting" liquid film, causing the spatial conductivity signal to lose its local resolution and become ineffective.

[0007] Furthermore, to avoid interference from wiring in the flow field, traditional designs typically confine sensors to specific geometric intersections, which directly disrupts the original geometry of the rod bundle channels within the fuel assembly. More seriously, traditional wiring methods cannot reach the positioning grid clamping area, the narrow gaps between rods, and the peripheral boundary sub-channels near the outer wall of the flow channel. The thermal measurement blind spots existing in these complex boundary areas cannot capture the dynamic evolution parameters of the wall-attached liquid film.

[0008] To overcome the shortcomings of the prior art, the present invention provides a high spatiotemporal resolution measurement system for liquid metal two-phase flow oriented towards a rod bundle channel. Summary of the Invention

[0009] This invention provides a high spatiotemporal resolution measurement system and method for liquid metal two-phase flow in rod bundle channels, which solves the problem of superconducting short circuits in liquid metal films and the weakening of the measurement capability of embedded measurement instruments in complex rod bundle channels, and achieves high spatial resolution measurement without blind zones.

[0010] This invention is achieved through the following technical solution: A high spatiotemporal resolution measurement system for liquid metal two-phase flow oriented towards a rod bundle channel, the system comprising a flow channel 1, a simulated fuel rod bundle 2, an excitation application component located at the axial end, and a signal receiving component attached to the rod wall; The flow channel 1 is a vertically placed column. The interior of the flow channel 1 forms a closed channel for fluid experiments. In the upper core area of ​​the flow channel 1, multiple simulated fuel rod bundles 2 are arranged in a matrix along the axial direction. The simulated fuel rod bundles 2 are firmly clamped by positioning grids 10 to maintain the flow channel gap. When the coolant passes through the grid of the channel formed by the simulated fuel rod bundles 2, it is subjected to friction resistance. Each probe of the simulated fuel rod bundle 2 leads out a signal lead 13, which is connected to the acquisition module.

[0011] Furthermore, there are peripheral boundary sub-channels 11 between the periphery of the simulated fuel rod bundle 2, and corner sub-channels 12 are formed at the corners of the flow channel 1.

[0012] Furthermore, each of the simulated fuel rod bundles 2 includes an outer wall insulating coating 4, an isolation sleeve 9, a receiving electrode metal wire 5, and a high-temperature resistant inorganic insulating layer 6; The outer wall insulating coating 4 has radial through holes 8 through which a high-temperature resistant inorganic insulating layer 6 passes. The isolation sleeve 9 is located at the center of the simulated fuel rod bundle 2. A signal lead 13 is installed inside the isolation sleeve 9. The receiving electrode wire 5 is covered with the high-temperature resistant inorganic insulating layer 6 at both the through hole and the protruding section, except that the sensing section inside the rod bundle is exposed. The bottom end of the isolation sleeve 9 is positioned against the high-temperature resistant inorganic insulating layer 6. After the structure is fixed, the signal lead 13 is electrically connected to the exposed part of the receiving electrode wire 5.

[0013] Furthermore, the micro-exposed measuring points 7 on the walls of each hollow simulated rod are staggered at equal intervals along the geometric length of the channel, so that the full-section measuring points on the entire rod bundle assembly 2 are arranged upwards as the channel width increases. That is, the three sets of receiving electrodes of different lengths set along the length gradient are arranged in equal arithmetic or equal ratios, and the three sets of receiving electrodes of different lengths are evenly arranged along the circumference, outlining a virtual full-coverage measurement grid that adheres to the rod wall inside the flow channel.

[0014] Furthermore, the outermost periphery of the simulated fuel rod bundle 2 includes peripheral rods close to the inner wall of the flow channel tube 1, and receiving electrode wires 5 on the side of the peripheral rods facing the inner wall of the flow channel tube 1 are symmetrically retained in the outer boundary sub-channel 11 and corner sub-channel 12 of the flow field.

[0015] Furthermore, all the signal leads of one of the simulated fuel rod bundles 2 are connected to the signal lead 13 inside the simulated fuel rod bundle 2, and the signal leads 13 of all the rod bundles, i.e. all the measuring points, are gathered at the outlet and connected to the acquisition module.

[0016] Furthermore, on the inner surface of the axial total inlet and total outlet pipe wall of the flow channel pipe 1, an emitter ring 3 is electrically insulatedly attached to the inner surface of the pipe wall. The emitter ring 3 is connected to the signal lead 13. The signal lead 13 is led out from the side wall or top of the flow channel pipe 1, and an insulating gasket 14 is installed at the outlet end to achieve reliable insulation between the internal components and the external DAQ card and excitation signal transmission module, and to prevent short circuit.

[0017] Furthermore, the circumferential position of the micro-exposed measuring point 7 is precisely aligned and limited to the structural clamping and limiting position of the corresponding positioning grid 10, as well as the nearest flow channel narrow slit dead angle position between two adjacent simulated fuel rod bundles 2, in order to capture the extremely thick liquid film that is easily gathered at the narrow slit due to surface tension.

[0018] A high spatiotemporal resolution measurement method for liquid metal two-phase flow oriented towards a rod bundle channel, the method using the aforementioned high spatiotemporal resolution measurement system for liquid metal two-phase flow oriented towards a rod bundle channel, the method comprising the following steps: Step S1 of applying the excitation signal: A high-frequency AC voltage signal is generated by an external signal source and applied to two emitter rings attached to the inner surface of the axial total inlet and total outlet pipe wall of the flow channel; the two emitter rings are electrically insulated from the inner surface of the pipe wall and in full circumference contact with the liquid metal fluid, so that the liquid metal body with high conductivity forms a current-carrying conductor between the two emitters, forming a uniformly distributed current density field in the flow channel; Step S2 of local signal sensing: When liquid metal with bubbles flows through the rod bundle channel, the miniature exposed measuring points on the wall of each rod bundle, i.e. the exposed sensing sections of the receiving electrode wires, directly form electrical contact with the liquid metal after being immersed in it. At this time, the corresponding measuring point captures a high current signal. Conversely, when the measuring point is near or in contact with a bubble, due to the difference of several orders of magnitude in the conductivity between the bubble and the liquid metal, the receiving electrode corresponding to the measuring point can only capture a weak low current signal. The signal leads of each measuring point are connected through the isolation sleeve of the simulated fuel rod bundle cavity, and after being led out through the insulating pad at the exit end, they are connected to the external acquisition module. Step S3 of synchronous demodulation and noise reduction: The same frequency and phase voltage waveform output by the signal source is synchronously sent into the phase-locked demodulation system as a reference. A phase scale is established with this reference. The high-frequency AC current signals of each channel acquired by the acquisition module are amplified by phase-locking and the amplitude and phase information reflecting the phase state distribution of the two-phase flow are extracted, thereby suppressing non-same frequency background noise and thermoelectric potential interference, and obtaining high signal-to-noise ratio time series voltage signals of each measurement point. Step S4 of spatial projective inversion and image reconstruction: The external data acquisition system performs high-frequency inspection scanning of the lead matrix led out of the rod through a high-speed multiplexer. Combined with the precise axial and circumferential spatial geometric coordinate matrices of each micro-exposed measuring point, the time-series electrical signals at each measuring point are mapped into spatial distribution information. Under the premise of eliminating liquid film short-circuit interference and zero lead flow obstruction, the cross-sectional image of the three-dimensional two-phase flow phase state inside the rod bundle channel is measured with high precision. This provides a reliable measurement basis for subsequent processing steps such as bubble interface reconstruction and phase interface concentration calculation.

[0019] A high spatiotemporal resolution measurement system for liquid metal two-phase flow facing a rod bundle channel, as described above, is used for measuring thermal-hydraulic two-phase flow in a nuclear reactor.

[0020] The beneficial effects of this invention are: This invention creates a virtual, fully covered measurement grid inside the flow channel by arranging micro-exposed measurement points at equal intervals and staggered along the axial direction on each simulated fuel rod, and by uniformly arranging receiving electrodes of different lengths in the circumferential direction.

[0021] This invention precisely limits the circumferential position of the measuring point to the clamping point of the positioning grid and the dead corner point of the narrow gap in the flow channel between adjacent rod bundles. It can keenly capture the dynamics of the liquid film in high-risk areas, providing more realistic boundary condition data for reactor thermal-hydraulic analysis and avoiding heat transfer calculation deviations caused by missing liquid film measurements.

[0022] This invention employs a multi-layer composite protection structure, leaving only the sensing section exposed, and the signal leads pass through insulating pads, effectively protecting the internal metal wires and signal lines from corrosion by liquid metal and the risk of short circuits, ensuring the long-term operational stability and electrical reliability of the sensor under extreme conditions. Attached Figure Description

[0023] Figure 1 This is a panoramic schematic diagram of the overall structure of the present invention.

[0024] Figure 2 This is an enlarged view of the external end of the present invention.

[0025] Figure 3 This is a cross-sectional view of the present invention.

[0026] Figure 4 This is an enlarged schematic diagram of the distribution of measuring points in a single rod bundle according to the present invention.

[0027] Figure 5 This is a schematic cross-sectional view (BB) of the present invention.

[0028] Figure 6 yes Figure 5 A magnified schematic diagram of a single rod bundle.

[0029] Figure 7 yes Figure 2 A magnified schematic diagram of the local structure at the micro-observation point.

[0030] Explanation of reference numerals in the attached figures: 1-Flow channel tube; 2-Simulated fuel rod bundle; 3-Emitter ring; 4-Inner wall insulating coating; 5-Receiver metal wire; 6-High temperature resistant inorganic insulation layer; 7-Miniature exposed measuring point; 8-Radial through hole; 9-Isolation sleeve; 10-Positioning grid; 11-Outer boundary sub-channel; 12-Corner sub-channel; 13-Signal lead; 14-Insulating pad. Detailed Implementation

[0031] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of this application with unnecessary detail.

[0032] It should be understood that, when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0033] It should also be understood that the terminology used in this application specification is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this application specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0034] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0035] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0036] Implementation Method 1 This embodiment provides a high spatiotemporal resolution measurement system for liquid metal two-phase flow in rod bundle channels. It utilizes the axial redundant space inside the simulated rod, originally intended for thermal experiments, and transforms it into an electrically protected flow channel for the measurement signal leads. This solves the problem of superconducting short circuits in liquid metal films without introducing any flow channel lead obstruction and maintaining low intrusion influence from the wire mesh sensor, achieving high spatial resolution measurement with no blind spots throughout the entire field.

[0037] A high spatiotemporal resolution measurement system for liquid metal two-phase flow oriented towards a rod bundle channel, the system comprising a flow channel 1, a simulated fuel rod bundle 2, an excitation application component located at the axial end, and a signal receiving component attached to the rod wall; The flow channel 1 is a vertically placed column. The interior of the flow channel 1 forms a closed channel for fluid experiments. In the upper core area of ​​the flow channel 1, multiple simulated fuel rod bundles 2 are arranged in a matrix along the axial direction. The simulated fuel rod bundles 2 are firmly clamped by positioning grids 10 to maintain the flow channel gap. When the coolant passes through the grid of the channel formed by the simulated fuel rod bundles 2, it is subjected to friction resistance. Each probe of the simulated fuel rod bundle 2 leads out a signal lead 13. The number of signal leads in a simulated rod bundle is the same as the number of probes. The signal leads 13 are connected to the acquisition module.

[0038] Furthermore, there are peripheral boundary sub-channels 11 between the periphery of the simulated fuel rod bundle 2, and corner sub-channels 12 are formed at the corners of the flow channel 1.

[0039] Furthermore, each of the simulated fuel rod bundles 2 includes an outer wall insulating coating 4, an isolation sleeve 9, a receiving electrode metal wire 5, and a high-temperature resistant inorganic insulating layer 6; The outer wall insulating coating 4 serves to isolate the conduction of electrical signals within the flow channel; The outer wall insulating coating 4 has radial through holes 8 through which a high-temperature resistant inorganic insulating layer 6 passes. A receiving electrode metal wire 5 is fitted inside the high-temperature resistant inorganic insulating layer 6. The high-temperature resistant inorganic insulating layer 6 is removed to form a miniature exposed measuring point 7. The isolation sleeve 9 is located at the center of the simulated fuel rod bundle 2. A signal lead 13 is installed inside the isolation sleeve 9. The receiving electrode metal wire 5 is covered with the high-temperature resistant inorganic insulating layer 6 in both the through hole and the protruding section, except that the sensing section inside the rod bundle is exposed. The bottom end of the isolation sleeve 9 is positioned against the high-temperature resistant inorganic insulating layer 6. After the structure is fixed, the signal lead 13 is electrically connected to the exposed part of the receiving electrode metal wire 5.

[0040] Furthermore, the micro-exposed measuring points 7 on the walls of each hollow simulated rod are staggered at equal intervals along the geometric length of the channel, so that the full-section measuring points on the entire rod bundle assembly 2 are arranged upwards as the channel width increases. That is, the three sets of receiving electrodes of different lengths, namely 5-A, 5-B and 5-C, set along the length gradient are arranged in an arithmetic or geometrical manner. They can be adjusted according to different channel types and sizes. The three sets of receiving electrodes of different lengths are evenly arranged along the circumference, outlining a virtual full-coverage measurement grid that adheres to the rod wall inside the flow channel.

[0041] Furthermore, the outermost periphery of the simulated fuel rod bundle 2 includes peripheral rods close to the inner wall of the flow channel tube 1, including edge rods and corner rods. In order to overcome the boundary measurement blind zone, for these peripheral rods, the receiving electrode wires 5 on the side of the peripheral rods facing the inner wall of the flow channel tube 1 are symmetrically retained in the outer boundary sub-channels 11 and corner sub-channels 12 of the flow field. The vertical distance from the edge measurement point and the corner measurement point to the inner wall of the flow channel tube 1 is strictly limited to the narrow slit characteristic width of the boundary flow channel.

[0042] Furthermore, all the signal leads of one of the simulated fuel rod bundles 2 are connected to the signal lead 13 inside the simulated fuel rod bundle 2. At the outlet, the signal leads 13 of all the rod bundles, i.e. all the measuring points, are gathered together for protection and fixed inside the sleeve, and then connected to the acquisition module.

[0043] Furthermore, on the inner surface of the axial total inlet and total outlet pipe wall of the flow channel pipe 1, an emitter ring 3 is electrically insulatedly attached to the inner surface of the pipe wall. The emitter ring 3 is connected to the signal lead 13. The signal lead 13 is led out from the side wall or top of the flow channel pipe 1, and an insulating gasket 14 is installed at the outlet end to achieve reliable insulation between the internal components and the external DAQ card and excitation signal transmission module, and to prevent short circuit.

[0044] Furthermore, the micro-exposure measuring point 7 is circumferentially positioned at the clamping limit of the corresponding positioning grid 10 and precisely arranged at the minimum cross-section of the flow channel between two adjacent simulated fuel rod bundles 2, in order to capture the extremely thick liquid film that is easily gathered at the narrow gap due to surface tension.

[0045] The system is illustrated using a common two-section 5×5 fuel rod bundle array and a flat rectangular flow channel as a specific example. However, in practical engineering applications, this system is also applicable to any array size, such as 4×4, 6×6, etc., any channel length, and rod bundle flow channel with different cross-sectional shapes.

[0046] like Figure 1 As shown, the measurement system provided in this embodiment mainly includes a rod bundle channel 1, a simulated fuel rod bundle 2 fixed therein, an excitation application component located at the axial end, and a signal receiving component attached to the rod wall.

[0047] like Figure 1 , Figure 3 and Figure 5 As shown, the interior of the flow channel 1 forms a channel for the axial flow of liquid metal two-phase flow. The rod bundle assembly 2 consists of multiple parallel hollow simulated fuel rod bundles 2, structurally constrained and fixed by a multi-stage positioning grid 10. Emitter rings 3 are flush with and electrically insulatedly embedded on the inner surfaces of the axial total inlet and total outlet walls of the flow channel 1. The emitter rings are in full circumference contact with the fluid and apply an excitation electrical signal to the fluid as a whole, causing the continuous liquid metal fluid itself to act as a moving charged conductor.

[0048] Specifically, such as Figure 2 and Figure 3 As shown, the signal receiving component includes receiving electrode wires 5 laid on the circular outer wall of each hollow simulated fuel rod bundle 2. Each receiving electrode wire 5 is radially stretched and attached to the metal outer wall of the simulated fuel rod bundle 2 in a circumferential direction, and the straight line containing each receiving electrode wire passes through the center of the simulated fuel rod bundle 2 in its cross-sectional projection. In order to achieve mechanical rigidity and electrical insulation between each measuring point in the highly conductive liquid metal, the outer surface of the receiving electrode wire 5 is entirely covered with a high-temperature resistant inorganic insulating layer 6, which is preferably a magnesium oxide coating in this embodiment.

[0049] To prevent electrical signals from being trapped within the measuring channel, an insulating coating 4 is applied to the inner wall of the channel and the outer layer of the fuel rod bundle. Figure 1 and Figure 4 As shown), the measuring channel has insulating gaskets 14 at both ends. Figure 1 (As shown).

[0050] like Figure 4 and Figure 6 As shown, in order to accurately capture local electrical signals at specific spatial coordinate points, this embodiment employs a precision stripping technique to remove the high-temperature resistant inorganic insulation layer 6 at a specific location, thereby forming a miniature exposed measuring point 7. For example... Figure 4 As shown in the magnified view of the micro observation point, the laser ablation depth is equal to the thickness of the high-temperature resistant inorganic insulating layer 6; the window width along the axis of the simulated fuel rod bundle 2 at the ablation point is controlled at 0.20 mm. Through this precision ablation process, the receiving electrode wire 5 forms an extremely small exposed cross-section at the micro-exposed measuring point 7, which is in direct contact with the liquid metal fluid in the flow channel.

[0051] like Figure 7 As shown, the receiving electrode wire 5 extends outward from the corresponding micro-exposed measuring point 7 by an extremely short distance (limited to 0.4 mm in this embodiment) and is immediately introduced into the protective flow channel inside its cavity through the radial through-hole 8 passing through the wall of the fuel rod bundle. Subsequently, the lead wire 13 is vertically straightened and transmitted within the cavity, completely decoupling the long path from the violent scouring of the external fluid and the positioning grid 10 in spatial physical form, and finally safely extends to the blind end outside the flow channel tube for convergence and exit. The high-temperature resistant isolation sleeve 9 provides secondary spatial physical isolation and insulation protection.

[0052] This embodiment breaks with traditional design by reusing the axial redundant space inside each hollow simulated fuel rod bundle, which was originally used for thermal experiments, and transforming it into an internal electrical protection channel for signal leads. For example... Figure 3As shown, all the receiving electrode signal leads are gathered inside a rod bundle. These leads are led upwards along the inner cavity of the rod bundle and finally connected to the information collection module.

[0053] To enable the system to achieve high spatial resolution reconstruction with no blind spots across the entire field, the measurement points were specifically arranged in space (see reference). Figure 4 and Figure 6 ): Overall cross-sectional layout: such as Figure 2 As shown, the miniature exposed measuring points 7 on the wall of each hollow simulated rod are staggered at equal intervals along the geometric length of the channel (in this embodiment, the step size is set to 10 mm), so that the full-section measuring points on the entire rod bundle assembly 2 are arranged upwards as the channel width increases. That is, the three sets of receiving electrodes of different lengths (5-A, 5-B and 5-C) set along the length gradient are evenly arranged along the circumference, outlining a virtual full-coverage measurement grid that adheres to the rod wall inside the flow channel.

[0054] Targeted placement of points inside the cross-section: combined with Figure 4 The cross-sectional view shows that the circumferential position of the micro-exposed measuring point 7 is precisely aligned and limited to the structural clamping and limiting position of the corresponding positioning grid 10, as well as the nearest flow channel narrow slit dead corner position between two adjacent simulated fuel rod bundles 2, in order to capture the extremely thick liquid film that is easily gathered at the narrow slit due to surface tension.

[0055] The design retains the outer boundary and corner sub-channels: such as Figure 4 and Figure 6 As shown in the detailed diagram, the outermost part of the rod bundle assembly 2 includes peripheral rods (including edge rods and corner rods) close to the inner wall of the flow channel 1. To overcome the boundary measurement blind zone, the receiving electrode wires 5 on the side of these peripheral rods facing the inner wall of the flow channel 1 are symmetrically retained in the outer boundary sub-channels 11 and 12 of the flow field. The vertical distance from the edge measuring points and corner measuring points to the inner wall of the flow channel 1 is strictly limited to the narrow slit characteristic width of the boundary flow channel.

[0056] Receiver wiring design: such as Figure 2 and Figure 6 As shown, all signal leads of a rod bundle are connected through the inner cavity of the rod bundle, and at the outlet, the leads of all rod bundles, i.e. all measurement points, are gathered together and connected to the acquisition module.

[0057] When liquid metal with a two-phase flow interface flows through the detection system, the external data acquisition system performs high-frequency inspection and scanning of the lead matrix led out of the rod through a high-speed multiplexer. By using the precise axial and circumferential spatial geometric coordinate matrices of each measuring point to perform spatial projective inversion mapping, a high-definition transient evolution cross-sectional image of the entire three-dimensional two-phase flow phase state inside the entire rod bundle channel can be accurately inverted and reconstructed under the premise of eliminating liquid film short-circuit interference and zero lead flow obstruction.

[0058] Implementation Method 2 This embodiment provides a high spatiotemporal resolution measurement method for liquid metal two-phase flow oriented towards a rod bundle channel. The measurement method uses a high spatiotemporal resolution measurement system for liquid metal two-phase flow oriented towards a rod bundle channel as described in Embodiment 1. The measurement method includes the following steps: Step S1 of applying the excitation signal: A high-frequency AC voltage signal is generated by an external signal source and applied to two emitter rings attached to the inner surface of the axial total inlet and total outlet pipe wall of the flow channel; the two emitter rings are electrically insulated from the inner surface of the pipe wall and in full circumference contact with the liquid metal fluid, so that the liquid metal body with high conductivity forms a current-carrying conductor between the two emitters, forming a uniformly distributed current density field in the flow channel; Step S2 of local signal sensing: When liquid metal with bubbles flows through the rod bundle channel, the miniature exposed measuring points on the wall of each rod bundle, i.e., the exposed sensing sections of the receiving electrode wires, directly form electrical contact with the liquid metal after being immersed in it. At this time, the corresponding measuring point captures a high current signal. Conversely, when the measuring point is near or in contact with a bubble, due to the difference of several orders of magnitude in the conductivity between the bubble and the liquid metal, the receiving electrode corresponding to the measuring point can only capture a weak low current signal. The exposed measuring points have a certain measurement range. When a bubble approaches or covers the measuring point, the electrical signal value of the measuring point will decrease sharply (bubble approaches) and form a significant signal trough (bubble covers the measuring point). The signal leads of each measuring point converge through the isolation sleeve of the simulated fuel rod bundle cavity, and are led out through an insulating gasket at the exit end and connected to the external acquisition module. Step S3 of synchronous demodulation and noise reduction: The same frequency and phase voltage waveform output by the signal source is synchronously sent into the phase-locked demodulation system as a reference. A phase scale is established with this reference. The high-frequency AC current signals of each channel acquired by the acquisition module are amplified by phase-locking and the amplitude and phase information reflecting the phase state distribution of the two-phase flow are extracted, thereby suppressing non-same frequency background noise and thermoelectric potential interference, and obtaining high signal-to-noise ratio time series voltage signals of each measurement point. Step S4 of spatial projective inversion and image reconstruction: The external data acquisition system performs high-frequency inspection scanning of the lead matrix led out of the rod through a high-speed multiplexer. Combined with the precise axial and circumferential spatial geometric coordinate matrices of each micro-exposed measuring point, the time-series electrical signals at each measuring point are mapped into spatial distribution information. Under the premise of eliminating liquid film short-circuit interference and zero lead flow obstruction, the cross-sectional image of the three-dimensional two-phase flow phase state inside the rod bundle channel is measured with high precision. This provides a reliable measurement basis for subsequent processing steps such as bubble interface reconstruction and phase interface concentration calculation.

[0059] Furthermore, during the execution of steps S3 to S4 above, the amplitude of the high-frequency alternating current captured by the micro-exposed measuring point 7 exhibits a regular evolution as the bubble moves. This evolution process can be divided into the following five typical response states, constituting the five-state criteria for bubble pose recognition and liquid film thickness inversion: The first typical response state is the far-field undisturbed state: when the bubble is outside the electric field sensitive area from the micro-exposed measuring point 7, the parallel current density field formed by the liquid metal on the two emitter rings 3 remains undisturbed. The high-frequency alternating current captured at this measuring point maintains its maximum stable amplitude. This state serves as the pure liquid phase reference value. This is used for the relative calibration of subsequent states; The second typical response state is the near-neighbor non-contact state: as the bubble moves upward to the vicinity of the micro-exposed measuring point 7 but has not yet covered the measuring point, since the bubble is an electrical insulator, it pushes the current line flowing to the measuring point away to form a bypass effect, which leads to an increase in the local equivalent resistance of the measuring point. At this time, the amplitude of the probe current shows a predictive decrease with a gradual decline at the leading edge. The attenuation slope in this stage is related to the curvature of the bubble shape and the movement speed. The third typical response state is the edge rubbing / local contact state: the edge of the bubble partially covers the exposed cross-section of the micro-exposed measuring point 7, the local conductive cross-sectional area decreases sharply, and the probe current amplitude shows a steep semi-step-like drop. The duration of this state directly reflects the contact arc length of the bubble rubbing against the rod wall. The fourth typical response state is the fully enclosed state: the center of the bubble passes through the miniature exposed measuring point 7, the exposed section is completely enclosed by the bubble insulator, the local equivalent resistance of the measuring point approaches infinity, and the probe current amplitude drops vertically to near zero level. The dwell time of this state can be used to calculate the axial chord length of the bubble. The fifth typical response state is the wake detachment and liquid film rewetting state: after the bubble tail leaves the micro-exposed measuring point 7, the liquid metal rapidly rewets the exposed cross-section under the drive of surface tension. The probe current amplitude rises rapidly and, after a brief overshoot jitter (reflecting the eddies and secondary liquid film fluctuations in the wake region), recovers to the pure liquid phase reference value. .

[0060] By extracting the temporal characteristics of the five-state current waveforms, the external data acquisition system can accurately determine the spatial relative position, contact mode, and detachment dynamics of the bubble and the wall of each simulated fuel rod bundle 2. Then, in the spatial projection inversion mapping in step S4, the cross-sectional time series electrical signal is converted into a two-dimensional cross-sectional phase distribution and a three-dimensional transient evolution cross-sectional image, realizing high spatiotemporal resolution measurement without blind spots in the entire field.

[0061] Implementation Method 3 This embodiment provides a high spatiotemporal resolution measurement system for liquid metal two-phase flow oriented towards a rod bundle channel as described in Embodiment 1. The measurement system is applied to the measurement of high-temperature, high-density, and highly conductive liquid metal flow field environments.

Claims

1. A high spatiotemporal resolution measurement system for liquid metal two-phase flow oriented towards a rod bundle channel, characterized in that, The system includes a flow channel (1), a simulated fuel rod bundle (2), an excitation application component located at the axial end, and a signal receiving component attached to the rod wall; The flow channel tube (1) is a vertically placed column. The interior of the flow channel tube (1) forms a closed channel for fluid experiments. In the upper core area of ​​the flow channel tube (1), multiple simulated fuel rod bundles (2) are arranged in a matrix along the axial direction. The simulated fuel rod bundles (2) are firmly clamped by positioning grids (10) to maintain the flow channel gap. When the coolant passes through the grid of the channel formed by the simulated fuel rod bundles (2), it is subjected to friction resistance. Each probe of the simulated fuel rod bundle (2) leads out a signal lead (13), and the signal lead (13) is connected to the acquisition module.

2. The system according to claim 1, characterized in that, There are peripheral boundary sub-channels (11) between the periphery of the simulated fuel rod bundle (2) and corner sub-channels (12) are formed at the corners of the flow channel (1).

3. The system according to claim 1, characterized in that, Each of the simulated fuel rod bundles (2) includes an outer wall insulating coating (4), an isolation sleeve (9), a receiving electrode wire (5), and a high-temperature resistant inorganic insulating layer (6). The outer wall insulating coating (4) has a radial through hole (8), through which a high-temperature resistant inorganic insulating layer (6) passes. The isolation sleeve (9) is located at the center of the simulated fuel rod bundle (2). A signal lead (13) is installed inside the isolation sleeve (9). The receiving electrode wire (5) is covered with a high-temperature resistant inorganic insulating layer (6) in both the through hole and the protruding section, except that the sensing section inside the rod bundle is exposed. The bottom end of the isolation sleeve (9) is positioned against the high-temperature resistant inorganic insulating layer (6). After the structure is fixed, the signal lead (13) is electrically connected to the exposed part of the receiving electrode wire (5).

4. The system according to claim 3, characterized in that, The micro-exposed measuring points (7) on the wall of each hollow simulated rod are staggered at equal intervals along the geometric length of the channel, so that the full-section measuring points on the entire rod bundle assembly (2) are arranged upward as the channel width increases. That is, the three sets of receiving electrodes of different lengths set along the length gradient are arranged in equal arithmetic or equal ratio. The three sets of receiving electrodes of different lengths are evenly arranged along the circumference, outlining a virtual full-coverage measuring grid that adheres to the rod wall inside the flow channel.

5. The system according to claim 1, characterized in that, The outermost part of the simulated fuel rod bundle (2) includes the receiving electrode wire (5) on the side of the outer rod facing the inner wall of the flow channel tube (1) and symmetrically retained in the outer boundary sub-channel (11) and corner sub-channel (12) of the flow field.

6. The system according to claim 1, characterized in that, All signal leads of the simulated fuel rod bundle (2) are connected through the internal signal lead (13) of the simulated fuel rod bundle (2), and the signal leads (13) of all rod bundles, i.e. all measuring points, are gathered at the outlet and connected to the acquisition module.

7. The system according to claim 2, characterized in that, On the inner surface of the axial total inlet and total outlet pipe wall of the flow channel pipe (1), an emitter ring (3) is electrically insulatedly attached to the inner surface of the pipe wall. The emitter ring (3) is connected to the signal lead (13). The signal lead (13) is led out from the side wall or top of the flow channel pipe (1) and an insulating gasket (14) is installed at the outlet end to achieve reliable insulation between the internal components and the external DAQ card and excitation signal transmission module, and to prevent short circuit.

8. The system according to claim 3, characterized in that, The micro-exposure measuring point (7) is circumferentially positioned at the clamping limit of the corresponding positioning grid (10) and precisely arranged at the minimum cross section of the flow channel between two adjacent simulated fuel rod bundles (2) to capture the extremely thick liquid film that is easily gathered in the narrow gap due to surface tension.

9. A high spatiotemporal resolution measurement method for liquid metal two-phase flow oriented towards a rod bundle channel, characterized in that, The measurement method uses a high spatiotemporal resolution measurement system for liquid metal two-phase flow oriented towards a rod bundle channel as described in any one of claims 1-8. The measurement method is as follows: Step S1 of applying the excitation signal: A high-frequency AC voltage signal is generated by an external signal source and applied to two emitter rings attached to the inner surface of the axial total inlet and total outlet pipe wall of the flow channel; the two emitter rings are electrically insulated from the inner surface of the pipe wall and in full circumference contact with the liquid metal fluid, so that the liquid metal body with high conductivity forms a current-carrying conductor between the two emitters, forming a uniformly distributed current density field in the flow channel; Step S2 of local signal sensing: When liquid metal with bubbles flows through the rod bundle channel, the miniature exposed measuring points on the wall of each rod bundle, i.e. the exposed sensing sections of the receiving electrode wires, directly form electrical contact with the liquid metal after being immersed in it. At this time, the corresponding measuring point captures a high current signal. Conversely, when the measuring point is near or in contact with a bubble, due to the difference of several orders of magnitude in the conductivity between the bubble and the liquid metal, the receiving electrode corresponding to the measuring point can only capture a weak low current signal. The signal leads of each measuring point are connected through the isolation sleeve of the simulated fuel rod bundle cavity, and after being led out through the insulating pad at the exit end, they are connected to the external acquisition module. Step S3 of synchronous demodulation and noise reduction: The same frequency and phase voltage waveform output by the signal source is synchronously sent into the phase-locked demodulation system as a reference. A phase scale is established with this reference. The high-frequency AC current signals of each channel acquired by the acquisition module are amplified by phase-locking and the amplitude and phase information reflecting the phase state distribution of the two-phase flow are extracted, thereby suppressing non-same frequency background noise and thermoelectric potential interference, and obtaining high signal-to-noise ratio time series voltage signals of each measurement point. Step S4 of spatial projective inversion and image reconstruction: The external data acquisition system performs high-frequency inspection scanning of the lead matrix led out of the rod through a high-speed multiplexer. Combined with the precise axial and circumferential spatial geometric coordinate matrices of each micro-exposed measuring point, the time-series electrical signals at each measuring point are mapped into spatial distribution information. Under the premise of eliminating liquid film short-circuit interference and zero lead flow obstruction, the cross-sectional image of the three-dimensional two-phase flow phase state inside the rod bundle channel is measured with high precision. This provides a reliable measurement basis for subsequent processing steps such as bubble interface reconstruction and phase interface concentration calculation.

10. A high spatiotemporal resolution measurement system for liquid metal two-phase flow oriented towards a rod bundle channel as described in any one of claims 1-8, characterized in that, The measurement system is applied to the measurement of high-temperature, high-density, and highly conductive liquid metal flow field environments.

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