Device and method for measuring three-dimensional velocity field of rod cluster channel

Abstract

The invention discloses a device and a method for measuring a three-dimensional velocity field of a rod cluster channel, which are applied to the field of nuclear power reactor core thermal hydraulic power and are used for accurately measuring the three-dimensional velocity field of a coolant in the rod cluster channel. The lower rectifying chamber, the experimental square cavity and the upper rectifying chamber are sequentially communicated from bottom to top to form a fluid channel; a plurality of hollow-core fuel rods which are arranged in an array are arranged in the experimental square cavity, and the hollow-core fuel rods are fixed through a positioning grillwork and a positioning partition plate. The UDV ultrasonic probe system comprises a transverse UDV probe array, an axial UDV probe array and an embedded measuring unit, wherein the lateral surface of the transverse UDV probe array is arranged in a layered manner and corresponds to the rod gap; the axial UDV probe array is arranged at the top of the transverse UDV probe array; the axis of the axial UDV probe array is vertical to the cross section; the embedded measurement unit comprises an embedded UDV probe and a positioning device, the positioning device adjusts the position of the probe through an axial adjusting device, a circumferential adjusting knob and the like, and measurement coverage and accuracy are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of nuclear reactor core thermal-hydraulic technology, and more specifically, to a device and method for measuring the three-dimensional velocity field of a rod bundle channel. Background Technology

[0002] In the study of the thermal-hydraulic characteristics of nuclear reactor cores, flow field measurement in rod bundle channels is a core element in revealing flow and heat transfer mechanisms and optimizing fuel assembly design. While current optical particle image velocimetry (PIV) technology enables non-invasive measurements, its application is typically limited to characterizing the velocity field in small rod bundle channels of 5×5 or smaller. Facing the simulation requirements of full-size fuel assemblies in nuclear power engineering, traditional PIV technology is limited by optical penetration depth and tracer particle concentration gradients, compressing the effective measurement cross-section to below 50 cm², and failing to fully capture key fluid characteristics such as secondary flow and turbulent quasi-sequential structures in large flow areas. Although ultrasonic Doppler velocimetry is unaffected by penetration depth and particle concentration, its emitted signals have poor penetration between fuel rods, limiting its measurement to velocities within finite gaps between fuel rods. Summary of the Invention

[0003] This specification provides a device and method for measuring the three-dimensional velocity field of a rod bundle channel, in order to overcome at least one technical problem existing in related technologies.

[0004] According to a first aspect of the embodiments of this specification, a measuring device for a three-dimensional velocity field of a rod bundle channel is provided, comprising: The system comprises a lower rectifier chamber, an experimental square cavity, and an upper rectifier chamber; wherein the lower rectifier chamber, the experimental square cavity, and the upper rectifier chamber are connected sequentially from bottom to top to form a fluid channel; The experimental cavity contains multiple hollow fuel rods arranged in an array, which are fixed by positioning grids and positioning partitions; the positioning grids include ordinary positioning grids and positioning grids with mixing wings arranged along the fluid flow direction. The measuring device also includes a UDV ultrasonic probe system, which comprises: The transverse probe array consists of multiple transverse UDV probes, which are arranged in layers on the side of the experimental cavity, with each layer of probes corresponding to the gap between the hollow fuel rods. An axial probe array, consisting of multiple axial UDV probes, is arranged at the top of the experimental cavity. The probe axis of the axial UDV probe is perpendicular to the cross-section of the experimental cavity, and each axial probe corresponds to the rod bundle channel between the hollow fuel rods. Multiple embedded measurement units are provided, each unit including an embedded UDV probe disposed inside the hollow fuel rod and an embedded probe positioning device for mounting the probe; wherein, the embedded probe positioning device includes an axial adjustment device, a positioning platform, a drive shaft, a circumferential adjustment knob, and an embedded positioning disk; the positioning platform is horizontally positioned above the hollow fuel rod, and the axial adjustment device is disposed on the positioning platform; one end of the drive shaft is connected to the axial adjustment device and the circumferential adjustment knob, and the other end of the drive shaft is connected to the embedded positioning disk inside the hollow fuel rod, with the middle position of the drive shaft penetrating through the positioning platform; the embedded UDV probe is installed in the central opening of the embedded positioning disk, and the embedded positioning disk is in contact with the inner wall of the hollow fuel rod; a data transmission line is connected to the tail of the embedded UDV probe; The axial adjustment device is driven and connected to the drive shaft.

[0005] In some alternative implementations, the plurality of hollow fuel rods are arranged in a 10×10 square array.

[0006] In some alternative implementations, the lateral UDV probe and the axial UDV probe are supported and their positions adjusted by a positioning bracket.

[0007] In some optional embodiments, the upper part of the embedded positioning disk is provided with a routing slot for arranging the data transmission line, and the diameter of the central opening of the embedded positioning disk is adapted to the outer diameter of the embedded UDV probe.

[0008] In some alternative implementations, each axial UDV probe in the axial probe array is aligned and positioned directly above the center of each rod bundle channel in the array.

[0009] In some alternative embodiments, the embedded UDV probe has a cylindrical structure, and the outer diameter of the embedded UDV probe is adapted to the inner wall of the hollow fuel rod.

[0010] According to a second aspect of the embodiments of this specification, a method for measuring the three-dimensional velocity field of a rod bundle channel is provided, which is applied to the measuring device for the three-dimensional velocity field of a rod bundle channel described above, and includes the following steps: The configuration includes a measuring device with an experimental cavity. Multiple hollow fuel rods are arranged in an array within the cavity. Lateral UDV probes are layered on the sides of the cavity to form a lateral probe array, with each layer corresponding to the gap between the hollow fuel rods. An axial UDV probe array is formed on the top of the cavity, with the probe axes of the axial UDV probes perpendicular to the cross-section of the cavity. Embedded measuring units are arranged inside the hollow fuel rods. Each embedded measuring unit includes an embedded UDV probe and an embedded probe positioning device for adjusting its position and angle. Set the measurement parameters for each UDV probe, divide the detection range of the UDV ultrasonic probe into multiple continuous segments, and set the signal acquisition sequence from near to far. The fluid flows from bottom to top through the fluid channel formed by the lower rectifier chamber, the experimental square cavity, and the upper rectifier chamber, establishing a stable flow field in the rod bundle channel; The transverse probe array, axial probe array, and embedded measurement unit are activated simultaneously. The transverse probe array adopts a dual-channel parallel measurement method to detect the intersection point from two different directions, and the signal acquisition of the two channels is delayed in time. At the same time, the measurement depth and measurement angle of the embedded UDV probe are adjusted by the axial adjustment device and the circumferential adjustment knob in the embedded probe positioning device, respectively, so as to achieve targeted measurement of the measurement blind zone near the surface of the fuel rod. The ultrasonic Doppler velocimetry signals from each UDV probe are acquired, and the acquired signals are filtered, denoised, and enhanced. The velocity signals collected by the transverse probe array and the embedded measurement unit are processed and merged. In the overlapping area of ​​the measurement regions of the transverse probe array and the embedded measurement unit, the data of the two are assigned corresponding weights. The global two-dimensional velocity field of the cross section of the rod bundle channel is reconstructed through the data fusion algorithm. The axial velocity data collected by the axial probe array and the reconstructed two-dimensional velocity field data are registered and fused in a three-dimensional coordinate system with the geometric center of the upper surface of the positioning grid as the origin. A complete three-dimensional velocity field of the rod bundle channel is generated by a three-dimensional interpolation algorithm.

[0011] One embodiment of this specification can achieve at least the following beneficial effects: 1. The technical solution of this application constructs a UDV ultrasonic probe system that coordinates a transverse probe array, an axial probe array, and an embedded measurement unit, thereby overcoming the bottlenecks of insufficient penetration depth in traditional optical measurement techniques and the measurement blind zone inherent in single ultrasonic techniques. This device utilizes an external transverse array to rapidly acquire mainstream field data in the fuel rod bundle gap, while simultaneously using precisely positioned embedded probes to directly acquire velocity information in key areas such as the boundary layer near the fuel rod surface. Ultimately, all data can be fused to generate a complete three-dimensional velocity field.

[0012] 2. The technical solution of this application, through the axial and circumferential adjustment functions of the embedded probe positioning device, enables directional and precise acquisition of flow velocity at specific points within the measurement blind zone, ensuring the authenticity and traceability of the supplementary data. In data processing, a fusion strategy that assigns equal weights to data in overlapping areas effectively improves the signal-to-noise ratio and statistical reliability of the data in those areas. The resulting three-dimensional velocity field not only has complete spatial coverage but also possesses high spatial resolution.

[0013] 3. The main body of the measuring device provided by the technical solution of this application adopts a non-invasive design. The external probe array does not interfere with the flow field, and the embedded probe is built in through a hollow fuel rod, which can realize the true reproduction of the original flow state. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments or related technologies of this specification, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 A schematic diagram of the overall structure of the measuring device for the three-dimensional velocity field of the rod bundle channel provided by the present invention; Figure 2 A design illustration of the embedded probe in the measuring device for the three-dimensional velocity field of the rod bundle channel provided by the present invention; Figure 3 A schematic diagram of the structure of the probe embedded in the measuring device for the three-dimensional velocity field of the rod bundle channel provided by the present invention; Figure 4 A schematic diagram of the positioning disk in the measuring device for the three-dimensional velocity field of the rod bundle channel provided by the present invention; Figure 5 A schematic diagram of the measurement range of the transverse probe of the three-dimensional velocity field measurement device for the rod bundle channel provided by the present invention, showing the measurement area of ​​the transverse UDV probe for the flow field between the rod bundles and the "measurement blind zone" formed by the fuel rods blocking the flow. Figure 6 This is a schematic diagram of the measurement range of the embedded probe in the three-dimensional velocity field measurement device for the rod bundle channel provided by the present invention, showing the range of the embedded UDV probe by rotating to cover the flow field near the fuel rod and supplementing the "measurement blind zone" of the transverse probe; Figure 7 This is a schematic diagram of the measurement range of the axial probe in the three-dimensional velocity field measurement device for the rod bundle channel provided by the present invention, to illustrate the arrangement of the axial UDV probe directly above the center of the rod bundle channel and the measurement direction of the ultrasonic signal beam perpendicular to the cross-section of the experimental cavity.

[0016] Wherein, 1 represents a hollow fuel rod, 2 represents a positioning partition, 3 represents a transverse UDV probe, 4 represents an experimental cavity, 5 represents an axial UDV probe, 6 represents an upper rectifier chamber, 7 represents an embedded probe and positioning disk, 8 represents a positioning grid with mixed wings, 9 represents a standard positioning grid, 10 represents a lower rectifier chamber, 11 represents an axial adjustment device, 12 represents a positioning platform, 13 represents a drive shaft, 14 represents an embedded UDV probe, 15 represents a circumferential adjustment knob, 16 represents a data transmission line, 17 represents an embedded positioning disk, and 18 represents an ultrasonic signal beam. Detailed Implementation

[0017] The technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Figure 1 A schematic diagram of the overall structure of the measuring device for the three-dimensional velocity field of the rod bundle channel provided by the present invention; Figure 2 The design illustration of the embedded probe of the measuring device for the three-dimensional velocity field of the rod bundle channel provided by the present invention shows the connection and assembly logic of the axial adjustment device, positioning platform, transmission shaft, embedded UDV probe, circumferential adjustment knob, data transmission line, and embedded positioning disk. Figure 3 This is a schematic diagram of the structure of the embedded probe in the measuring device for the three-dimensional velocity field of the rod bundle channel provided by the present invention, to show the cylindrical shape of the embedded UDV probe and the connection method between its tail and the data transmission line. Figure 4 This is a schematic diagram of the positioning disk in the measuring device for the three-dimensional velocity field of the rod bundle channel provided by the present invention, to show the opening in the center of the embedded positioning disk for installing the embedded UDV probe and the wiring slot on the upper part for arranging data transmission lines. Figure 5 A schematic diagram of the measurement range of the transverse probe of the three-dimensional velocity field measurement device for the rod bundle channel provided by the present invention, showing the measurement area of ​​the transverse UDV probe for the flow field between the rod bundles and the "measurement blind zone" formed by the fuel rods blocking the flow. Figure 6 This is a schematic diagram of the measurement range of the embedded probe in the three-dimensional velocity field measurement device for the rod bundle channel provided by the present invention, showing the range of the embedded UDV probe by rotating to cover the flow field near the fuel rod and supplementing the "measurement blind zone" of the transverse probe; Figure 7 This is a schematic diagram of the measurement range of the axial probe in the three-dimensional velocity field measurement device for the rod bundle channel provided by the present invention, to illustrate the arrangement of the axial UDV probe directly above the center of the rod bundle channel and the measurement direction of the ultrasonic signal beam perpendicular to the cross-section of the experimental cavity.

[0019] The structure of a three-dimensional velocity field measuring device for a rod bundle channel provided by the present invention will be described below with reference to the accompanying drawings. Figure 1 As shown, the measuring device may include a lower rectifier chamber 10, an experimental cavity 4, and an upper rectifier chamber 6; wherein the lower rectifier chamber 10, the experimental cavity 4, and the upper rectifier chamber 6 are connected sequentially from bottom to top to form a fluid channel. In this device, fluid enters the device from the lower rectifier chamber 10, flows upward through the experimental cavity 4 after rectification, and finally flows out from the upper rectifier chamber 6 into the external circulation pipeline.

[0020] The experimental cavity 4 contains multiple hollow fuel rods 1 arranged in an array (e.g., multiple hollow fuel rods 1 arranged in a 10×10 square array). The hollow fuel rods 1 are fixed by positioning grids and positioning partitions 2. The positioning grids can include ordinary positioning grids 9 set along the fluid flow direction and positioning grids 8 with mixing wings. The ordinary positioning grid 9 is used to basically fix and support the fuel rods, while the positioning grid 8 with mixing wings is set in the fluid flow direction. Its mixing wing structure can intensify the lateral mixing of the fluid to simulate the flow conditions in a real reactor. It should be noted that the "ordinary" in ordinary positioning grid 9 can be understood from the perspective of structure and function, relative to the positioning grid 8 with mixing wings. The former's function is to fix and maintain the relative position between the fuel rods, preventing the fuel rods from vibrating, bending, or colliding under fluid impact. It can be imagined as a honeycomb-like grid skeleton, with a fuel rod passing through the center of each cell. This skeleton can ensure that all fuel rods remain parallel and equidistant throughout the entire assembly. The grid with mixing blades 8 is based on the ordinary grid, with specially designed small blades, namely mixing blades, added to the strips of the grid. In addition to providing support, when the coolant flows through the grid, the mixing blades will deliberately disturb the flow field, destroy the boundary layer, enhance fluid mixing, and allow the coolant to be exchanged between different channels.

[0021] The measuring device may also include a UDV ultrasonic probe system, which consists of three subsystems: a transverse probe array, an axial probe array, and an embedded measuring unit. These probes can work together to achieve comprehensive measurement of the three-dimensional velocity field of the rod bundle channel. The following is a detailed description of each subsystem: The transverse probe array consists of multiple transverse UDV probes 3, which are arranged in layers on the side of the experimental cavity 4, with each layer corresponding to the gap between the hollow fuel rods 1. This arrangement allows the probes to emit ultrasonic waves from the side, covering most of the flow field in the gap region between the rod bundles. Its function is to roughly measure the two-dimensional flow field velocity, i.e., the horizontal component velocity, within the cross-section of the rod bundle channel. Because the ultrasonic signal is blocked by the fuel rods, its effective detection range is limited to the open gaps between the rod bundles, thus creating a measurement blind zone, such as the flow field near the surface of the fuel rods. Figure 5 As shown, Figure 5 This diagram illustrates the measurement range of the lateral probes, showcasing the arrangement and measurement range of the lateral UDV probe array on the experimental cavity 4. Multiple lateral UDV probes 3 are arranged in layers on the side of the experimental cavity 4, with each layer corresponding to the gaps between the hollow fuel rods 1. This arrangement allows the lateral UDV probes 3 to accurately detect the flow field in the gap region between the hollow fuel rods 1. The layered design covers the flow field between the rods at different heights within the experimental cavity 4, providing comprehensive spatial coverage for subsequent flow field data acquisition and analysis, ensuring multi-dimensional and accurate measurement of the flow field in the rod bundle gap region.

[0022] The axial probe array consists of multiple axial UDV probes 5, arranged on top of the experimental cavity 4. The probe axis of each axial UDV probe 5 is perpendicular to the cross-section of the experimental cavity 4, and each axial probe corresponds to the rod bundle channel between the hollow fuel rods 1, enabling it to detect the flow field within the rod bundle channel vertically downwards. The axial UDV probes 5 are also supported by positioning brackets, whose positions can be adjusted. Each axial UDV probe 5 is aligned directly above the center of each rod bundle channel in the array, ensuring accurate detection of the axial flow field in each rod bundle channel. Figure 7 As shown, Figure 7 This diagram illustrates the measurement range of the axial probe, showcasing the detection coverage of the axial UDV probe array. Multiple hollow fuel rods 1 are arranged in an array inside the experimental cavity 4, with gaps between adjacent rods. The axial UDV probe array is positioned at the top of the experimental cavity 4, with its probe axis perpendicular to the cavity's cross-section, enabling the detection of the cross-sectional flow field in the lower rod bundle channel. Figure 7 As can be seen, the detection range of the axial probe covers the array area of ​​the hollow fuel rods 1 and the gaps between them. With this arrangement, the axial UDV probe can collect flow field information in the axial direction of the rod bundle channel, providing axial flow field data support for subsequent data fusion with the transverse probe array and embedded measurement unit to reconstruct the global two-dimensional velocity field of the rod bundle channel cross section, thereby realizing multi-dimensional and comprehensive measurement of the flow field of the rod bundle channel.

[0023] The measuring device provided in this application also includes multiple embedded measuring units, wherein each unit includes an embedded UDV probe 14 disposed inside the hollow fuel rod 1 and an embedded probe positioning device for mounting the probe. For example, Figure 1As shown, the embedded probe positioning device includes an axial adjustment device 11, a positioning platform 12, a drive shaft 13, a circumferential adjustment knob 15, and an embedded positioning disc 17. The positioning platform 12 is horizontally positioned above the hollow fuel rod 1, and the axial adjustment device 11 is fixedly mounted on the upper surface of the positioning platform 12. One end of the drive shaft 13 is connected to the axial adjustment device 11 and the circumferential adjustment knob 15, and the other end is rigidly connected to the embedded positioning disc 17 inside the hollow fuel rod 1 (this connection ensures that the axial movement and circumferential rotation of the drive shaft 13 are accurately transmitted to the embedded positioning disc 17, allowing the embedded positioning disc 17 to move axially and rotate circumferentially synchronously with the drive shaft 13). The middle position of the drive shaft 13 passes through the positioning platform 12, thus forming... The structure forms a complete rotating structure; the embedded UDV probe 14 is installed in the central opening of the embedded positioning disk 17, and the embedded positioning disk 17 is in contact with the inner wall of the hollow fuel rod 1. The axial adjustment device 11 can drive the transmission shaft 13 to make axial (vertical) linear motion along its own axis, thereby driving the embedded positioning disk 17 and the embedded UDV probe 14 connected to it to move axially inside the hollow fuel rod 1, realizing the axial position adjustment of the probe to measure the velocity field at different axial heights inside the fuel rod; the tail of the embedded UDV probe 14 is connected to a data transmission line 16. Figure 6 As shown, Figure 6 This diagram illustrates the measurement range of the embedded probe, showcasing the detection capabilities of the embedded measurement unit inside the hollow fuel rod 1. In the diagram, gaps are formed between the hollow fuel rods 1, and the embedded UDV probe 14 is positioned inside the hollow fuel rod 1, capable of circumferential rotation (as indicated by the arrows in the diagram). This design allows the embedded UDV probe 14 to perform multi-directional detection of the flow field near the inner wall of the hollow fuel rod 1 and in the gap region, accurately capturing the flow field information inside and near the wall of the hollow fuel rod 1. This provides data support for subsequent data fusion with the transverse probe array and reconstruction of the global two-dimensional velocity field of the rod bundle channel cross-section.

[0024] Meanwhile, in this technical solution, the circumferential adjustment knob 15 is connected to the drive shaft 13, meaning that the rotational movement of the circumferential adjustment knob 15 can be directly and effectively transmitted to the drive shaft 13, causing the drive shaft 13 to rotate as well. When the operator manually or drives the knob via a motor, the knob's rotation is converted into the rotational movement of the drive shaft 13 around its own axis through this transmission connection. Simultaneously, the axial adjustment device 11 is connected to the drive shaft 13, acting as a power source to provide a linear driving force along the drive shaft 13's axis. When the axial adjustment device 11 is working, it drives the drive shaft 13 to move vertically. These two connections together form the basis for the precise positioning of the embedded probe. The circumferential adjustment knob 15 controls the probe's measurement angle through the transmission connection, while the axial adjustment device 11 controls the probe's measurement depth through the drive connection. Their coordinated operation ensures that the embedded UDV probe 14 can be accurately positioned at a specific location inside the hollow fuel rod 1, thereby enabling targeted measurement of the flow field in the blind zone near the fuel rod surface.

[0025] Based on the technical solutions described above, this application also provides some more specific technical solutions, which are described below.

[0026] In an optional embodiment, the lateral UDV probe 3 and the axial UDV probe 5 are supported and their positions adjusted by a positioning bracket.

[0027] In this embodiment, the positioning bracket provides a stable mechanical support for the probe, ensuring that it maintains the preset measurement position during the experiment and avoids displacement due to fluid impact or vibration.

[0028] In addition, the positioning bracket can be used to adjust the position of the probes. That is, through the adjustment function of the bracket, the operator can accurately calibrate each transverse probe in the initial stage of the experiment, so that its ultrasonic signal beam 18 can accurately pass through the gap of the target rod bundle. At the same time, each axial probe can also be finely adjusted to ensure that it is strictly aligned with the center line of the rod bundle channel directly below, and to ensure that its probe axis is perpendicular to the cross-section of the experimental cavity.

[0029] In an optional embodiment, the upper part of the embedded positioning disk 17 is provided with a routing slot for arranging the data transmission line 16, and the diameter of the central opening of the embedded positioning disk 17 is adapted to the outer diameter of the embedded UDV probe 14.

[0030] In this embodiment, the upper part of the embedded positioning disk 17 is provided with a routing slot for arranging the data transmission line 16. This slot provides a dedicated routing path for the data transmission line 16, allowing the data transmission line 16 connected to the tail of the embedded UDV probe 14 to be orderly fixed and guided, thereby preventing it from becoming entangled, excessively bent, or interfering with moving parts in the narrow space inside the hollow fuel rod 1. Meanwhile, as... Figure 4 As shown, the diameter of the central opening of the embedded positioning disk 17 is adapted to the outer diameter of the embedded UDV probe 14, combined with Figure 3 The cylindrical probe shape shown in the schematic diagram of the embedded probe structure, specifically the diameter of the central opening, is designed to fit snugly with the outer diameter of the probe. This ensures that the embedded UDV probe 14 is securely mounted in the preset position, preventing loosening or displacement during measurement and ensuring the accuracy of the ultrasonic signal beam 18 emission angle. Simultaneously, this fit may also help maintain a relative seal between the probe and the disk, reducing the adverse effects of fluid on probe fixation and signal transmission.

[0031] In an optional embodiment, each axial UDV probe 5 in the axial probe array is aligned with and arranged directly above the center of each rod bundle channel in the array.

[0032] In this embodiment, each axial UDV probe 5 in the axial probe array is aligned and arranged directly above the center of each rod bundle channel in the array. Specifically, each probe needs to be aligned with the rod bundle channel it is responsible for measuring, and the installation position of the probe is limited to directly above the centerline of the rod bundle channel. This arrangement ensures that the ultrasonic signal beam 18 emitted from the axial UDV probe 5 can propagate downward along the axial centerline of the rod bundle channel, and its probe axis is set perpendicular to the cross-section of the experimental cavity. This alignment and arrangement allows the ultrasonic signal to cover the entire cross-sectional area of ​​the rod bundle channel to the maximum extent, thereby accurately capturing the axial velocity component of the flow field within the channel, providing reliable and representative axial velocity data for the subsequent construction of a complete three-dimensional velocity field.

[0033] In an optional embodiment, the embedded UDV probe 14 is a cylindrical structure, and the outer diameter of the embedded UDV probe 14 is adapted to the inner wall of the hollow fuel rod 1.

[0034] In this embodiment, the embedded UDV probe 14 has a cylindrical structure, and its outer diameter is adapted to the inner wall of the hollow fuel rod 1. Specifically, from... Figure 4As can be seen, the embedded UDV probe 14 is cylindrical and installed in the central opening of the embedded positioning disk 17. The embedded positioning disk 17 is tightly fitted to the inner wall of the hollow fuel rod 1. This design allows the outer wall of the embedded UDV probe 14 to be precisely matched with the inner wall of the hollow fuel rod 1, which can ensure the stability of the probe installation and effectively detect the target flow field area inside the hollow fuel rod 1, without causing loose installation or flow field interference due to size differences.

[0035] In the above technical solution, the embedded UDV probe 14 can achieve 360° circumferential rotation through the transmission cooperation between the circumferential adjustment knob 15 and the transmission shaft 13. During the rotation, the embedded positioning disk 17 is always in close contact with the inner wall of the hollow fuel rod 1 without relative wobbling, thus effectively avoiding measurement errors caused by relative wobbling. The connection and arrangement of the data transmission line 16 adopts an embedded design. After being led out from the tail of the embedded UDV probe 14, it is completely embedded in the wiring slot of the embedded positioning disk 17, and then arranged axially upward along the outer wall of the transmission shaft 13. After passing through the preset wiring hole on the positioning platform 12, it extends to the outside of the measuring device and connects with the external data acquisition system, which can ensure the stability of signal transmission and the non-interference of device movement.

[0036] Based on the measuring device described above, the present invention also provides a method for measuring the three-dimensional velocity field of a rod bundle channel, applied to the measuring device described above, and the method may include the following steps: Step S1: Configure a measuring device including an experimental cavity 4. Arrange multiple hollow fuel rods 1 in an array within the experimental cavity 4. Arrange transverse UDV probes 3 in layers on the side of the experimental cavity 4 to form a transverse probe array, with each layer of probes corresponding to the gaps between the hollow fuel rods 1. Arrange axial UDV probes 5 on the top of the experimental cavity 4 to form an axial probe array, with the probe axis of the axial UDV probes 5 perpendicular to the cross-section of the experimental cavity. Arrange embedded measuring units inside the hollow fuel rods 1. Each embedded measuring unit includes an embedded UDV probe 14 and an embedded probe positioning device for adjusting its position and angle.

[0037] Step S2: Set the measurement parameters for each UDV probe, divide the detection range of the UDV ultrasonic probe into multiple continuous segments, and set the signal acquisition sequence from near to far.

[0038] The detection range of a UDV ultrasonic probe is physically represented as a ray-shaped ultrasonic signal beam emanating outward from the probe's center. In actual measurement, this continuous ray can be divided into several spatially continuous detection segments, which can be called "gates." Gate division discretizes the continuous measurement ray into a series of measurement units with specific depth information. After gate division, the signal acquisition sequence can be further defined. In this step, the sequence is specified as from near to far, starting with the gate closest to the probe and sequentially acquiring signals towards the gates furthest from the probe. This near-to-far acquisition sequence ensures the orderly acquisition of signals over time, thus providing the necessary data structure foundation for subsequent accurate analysis of fluid velocities at different depths.

[0039] Step S3: Allow the fluid to flow from bottom to top through the fluid channel formed by the lower rectifier chamber 10, the experimental square cavity 4, and the upper rectifier chamber 6 to establish a stable rod bundle channel flow field.

[0040] Step S4: Synchronously start the transverse probe array, axial probe array and embedded measurement unit. The transverse probe array adopts a dual-channel parallel measurement method to detect the intersection position from two different directions, and the signal acquisition of the two channels is delayed in time. At the same time, the axial adjustment device 11 and the circumferential adjustment knob 15 in the embedded probe positioning device are used to adjust the measurement depth and measurement angle of the embedded UDV probe 14 respectively, so as to realize the targeted measurement of the measurement blind zone near the surface of the fuel rod.

[0041] In this step, the operation of the transverse probe array, axial probe array, and embedded measurement unit is first started synchronously to ensure that all data acquisition units are consistent in time, providing a unified time reference for subsequent data fusion. The transverse probe array is started and operated using a dual-channel parallel measurement method. This method is specifically implemented by simultaneously probing the intersection points within the rod bundle channel from two different spatial directions. During this process, the detection range of each UDV probe is defined as a ray emanating from the probe center. This ray is divided into several continuous detection segments, or "gates," and signal acquisition follows a sequence from near to far, sequentially performing the acquisition on each "gate."

[0042] In this dual-channel parallel measurement method, the signal acquisition of the two channels has a timing delay to eliminate signal interference. Specifically, when the ultrasonic signals from the two channels converge in space, if the convergence point is located within different "gates" of the two channels, signal isolation can be achieved by relying on the inherent difference in the acquisition order. Even if the convergence point falls within the same "gate," this preset, minute channel switching delay ensures that the two signals are not processed simultaneously, thereby avoiding mutual interference between signals and guaranteeing the independence and accuracy of the measurement data.

[0043] While the transverse and axial probe arrays perform external measurements, the embedded measurement unit is simultaneously activated to address the measurement blind zone issue. By operating the embedded probe positioning device, its axial adjustment device 11 drives the embedded UDV probe 14 to move vertically to control its measurement depth, and its circumferential adjustment knob 15 drives it to rotate horizontally to precisely control its measurement angle. This adjustment mechanism allows the probe to accurately align with flow areas near the fuel rod surface that traditional external probes cannot effectively detect, thereby achieving targeted measurements of the "measurement blind zone" and supplementing key data in the global velocity field.

[0044] Step S5: Acquire ultrasonic Doppler velocimetry signals from each UDV probe, and perform filtering, noise reduction, and signal enhancement processing on the acquired signals.

[0045] Step S6: Process the velocity measurement signals collected by the transverse probe array and the embedded measurement unit, merge the measurement data of the two, assign corresponding weights to the data of the two in the overlapping measurement areas of the transverse probe array and the embedded measurement unit, and reconstruct the global two-dimensional velocity field of the cross section of the rod bundle channel through the data fusion algorithm.

[0046] This step involves merging the data from the lateral probe and the embedded probe to reconstruct a complete two-dimensional velocity field across the cross-section. This process requires processing the velocity signals acquired by both types of probes. In the overlapping areas of the lateral and embedded probe measurement regions, corresponding weights are assigned to the data from both sources. For example, the weights can be the same, i.e., both weights are 0.5. This specific weight allocation method ensures that the two independent data sources contribute information equally in the overlapping area, rather than simply having one source's data cover or dominate the other. This mathematically achieves smooth integration and averaging of the data, effectively improving the reliability of the data in the overlapping area.

[0047] Using the aforementioned equal-weighted data merging method and data fusion algorithm, the ultimate goal of this step is to reconstruct the global two-dimensional velocity field of the rod bundle channel cross-section. Here, "global" means that the final velocity field covers the entire cross-section, filling in the "measurement blind spots" that cannot be avoided by relying solely on external transverse probes—that is, the unmeasured areas near the fuel rod surface formed by the obstruction of ultrasonic signals. The specialized measurement data from the embedded probe is precisely designed to fill these blind spots. Through seamless fusion with the data measured by the transverse probe in the open gap region, a complete and comprehensive two-dimensional velocity distribution map is ultimately formed.

[0048] Step S7: The axial velocity data collected by the axial probe array and the reconstructed two-dimensional velocity field data are registered and fused in a three-dimensional coordinate system with the geometric center of the upper surface of the ordinary positioning grid 9 as the origin. The complete three-dimensional velocity field of the rod bundle channel is generated by a three-dimensional interpolation algorithm.

[0049] In step S7, all velocity data first need to be unified into a defined three-dimensional spatial reference system, namely a three-dimensional coordinate system with the geometric center of the upper surface of the ordinary positioning grid 9 as the origin. The axial velocity component data of the flow field collected by the axial probe array is then coordinate-registered with the two-dimensional velocity field (i.e., the velocity components within the cross-section) data reconstructed in step S6. This coordinate registration process ensures that data points measured from different probes (lateral, embedded, and axial) at different positions and directions can be accurately corresponded and aligned according to their actual spatial positions in the experimental setup, laying a geometric foundation for subsequent data fusion.

[0050] After accurate coordinate registration, the registered discrete data points are processed using a three-dimensional interpolation algorithm. This algorithm can calculate the three-dimensional velocity vectors at all positions within the fluid domain of the entire rod bundle channel, based on the axial and lateral velocity values ​​of surrounding known points, within a defined three-dimensional coordinate system grid. Ultimately, a complete three-dimensional velocity field for the rod bundle channel can be generated, which simultaneously includes the lateral and axial components of the fluid motion, thus achieving a complete and refined characterization of the complex three-dimensional flow structure within a large-area rod bundle channel.

[0051] This application's technical solution constructs a UDV ultrasonic probe system that coordinates a transverse probe array, an axial probe array, and an embedded measurement unit. This system overcomes the limitations of insufficient penetration depth in traditional optical measurement techniques and the blind spots inherent in single ultrasonic technologies. The device utilizes an external transverse array to rapidly acquire mainstream flow field data between the fuel rod bundles. Simultaneously, the precisely positioned embedded probe directly acquires velocity information from key areas such as the boundary layer near the fuel rod surface. All data can then be fused to generate a complete three-dimensional velocity field. Furthermore, the axial and circumferential adjustment functions of the embedded probe positioning device enable directional and precise acquisition of flow velocities at specific points within the measurement blind spot, ensuring the authenticity and traceability of the supplementary data. In data processing, an equal-weighted fusion strategy for overlapping region data effectively improves the signal-to-noise ratio and statistical reliability of the data in these regions. The resulting three-dimensional velocity field not only has complete spatial coverage but also high spatial resolution. Moreover, the main body of the measurement device provided in this application adopts a non-invasive design; the external probe array does not interfere with the flow field, and the embedded probe, housed within the hollow fuel rod, enables a true reproduction of the original flow state.

[0052] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for measuring the three-dimensional velocity field of a rod bundle channel, characterized in that, include: The lower rectifier chamber (10), the experimental square cavity (4), and the upper rectifier chamber (6) are connected sequentially from bottom to top to form a fluid channel. The experimental cavity (4) is provided with a plurality of hollow fuel rods (1) arranged in an array. The hollow fuel rods (1) are fixed by a positioning grid and a positioning partition (2). The positioning grid includes a common positioning grid (9) arranged along the fluid flow direction and a positioning grid with a mixing wing (8). The measuring device also includes a UDV ultrasonic probe system, which comprises: The transverse probe array consists of multiple transverse UDV probes (3), which are arranged in layers on the side of the experimental cavity (4), and each layer of probes corresponds to the gap between the hollow fuel rods (1). An axial probe array, consisting of multiple axial UDV probes (5), is arranged on the top of the experimental cavity (4). The probe axis of the axial UDV probe (5) is perpendicular to the cross-section of the experimental cavity (4), and each axial probe corresponds to the rod bundle channel between the hollow fuel rods (1). Multiple embedded measurement units, each unit including an embedded UDV probe (14) disposed inside the hollow fuel rod (1) and an embedded probe positioning device for mounting the probe; wherein, the embedded probe positioning device includes an axial adjustment device (11), a positioning platform (12), a drive shaft (13), a circumferential adjustment knob (15), and an embedded positioning disk (17); the positioning platform (12) is horizontally disposed above the hollow fuel rod (1), and the axial adjustment device (11) is disposed on the positioning platform (12); the drive shaft (13) of the UDV probe (14) is disposed on the hollow fuel rod (1) and the circumferential adjustment knob (15) is disposed on the hollow fuel rod (1). One end of the drive shaft (13) is connected to the axial adjustment device (11) and the circumferential adjustment knob (15), and the other end of the drive shaft (13) is connected to the embedded positioning disk (17) inside the hollow fuel rod (1). The middle position of the drive shaft (13) passes through the positioning platform (12). The embedded UDV probe (14) is installed in the central opening of the embedded positioning disk (17), and the embedded positioning disk (17) is in contact with the inner wall of the hollow fuel rod (1). The tail of the embedded UDV probe (14) is connected to a data transmission line (16). The axial adjustment device (11) is driven to be connected to the transmission shaft (13).

2. The measuring device for the three-dimensional velocity field of the rod bundle channel according to claim 1, characterized in that, The transverse UDV probe (3) and the axial UDV probe (5) are supported and their positions are adjusted by a positioning bracket.

3. The measuring device for the three-dimensional velocity field of the rod bundle channel according to claim 1, characterized in that, The upper part of the embedded positioning disk (17) is provided with a routing slot for arranging the data transmission line (16), and the diameter of the central opening of the embedded positioning disk (17) is adapted to the outer diameter of the embedded UDV probe (14).

4. The measuring device for the three-dimensional velocity field of the rod bundle channel according to claim 1, characterized in that, Each axial UDV probe (5) in the axial probe array is aligned with and arranged directly above the center of each rod bundle channel in the array.

5. The measuring device for the three-dimensional velocity field of the rod bundle channel according to claim 1, characterized in that, The embedded UDV probe (14) has a cylindrical structure, and the outer diameter of the embedded UDV probe (14) is adapted to the inner wall of the hollow fuel rod (1).

6. A method for measuring the three-dimensional velocity field of a rod bundle channel, applied to the measuring device described in claim 1, characterized in that, The method includes the following steps: The apparatus includes a measuring device with an experimental cavity (4). Multiple hollow fuel rods (1) are arranged in an array inside the experimental cavity (4). Transverse UDV probes (3) are arranged in layers on the side of the experimental cavity (4) to form a transverse probe array, with each layer of probes corresponding to the gap between the hollow fuel rods (1). An axial UDV probe (5) is arranged on the top of the experimental cavity (4) to form an axial probe array, with the probe axis of the axial UDV probe (5) perpendicular to the cross-section of the experimental cavity. An embedded measuring unit is arranged inside the hollow fuel rods (1). Each embedded measuring unit includes an embedded UDV probe (14) and an embedded probe positioning device for adjusting its position and angle. Set the measurement parameters for each UDV probe, divide the detection range of the UDV ultrasonic probe into multiple continuous segments, and set the signal acquisition sequence from near to far. The fluid flows from bottom to top through the fluid channel formed by the lower rectifier chamber (10), the experimental square cavity (4) and the upper rectifier chamber (6) to establish a stable rod bundle channel flow field; The transverse probe array, axial probe array and embedded measurement unit are started simultaneously. The transverse probe array adopts a dual-channel parallel measurement method to detect the intersection position from two different directions, and the signal acquisition of the two channels is delayed in time. At the same time, the measurement depth and measurement angle of the embedded UDV probe (14) are adjusted by the axial adjustment device (11) and the circumferential adjustment knob (15) in the embedded probe positioning device, so as to realize the targeted measurement of the measurement blind area near the surface of the fuel rod. The ultrasonic Doppler velocimetry signals from each UDV probe are acquired, and the acquired signals are filtered, denoised, and enhanced. The velocity signals collected by the transverse probe array and the embedded measurement unit are processed and merged. In the overlapping area of ​​the measurement regions of the transverse probe array and the embedded measurement unit, the data of the two are assigned corresponding weights. The global two-dimensional velocity field of the cross section of the rod bundle channel is reconstructed through the data fusion algorithm. The axial velocity data collected by the axial probe array and the reconstructed two-dimensional velocity field data are registered and fused in a three-dimensional coordinate system with the geometric center of the upper surface of the ordinary positioning grid (9) as the origin. The complete three-dimensional velocity field of the rod bundle channel is generated by a three-dimensional interpolation algorithm.

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