A method and apparatus for measuring flow-induced vibrations of a plate

Abstract

A method for measuring flow-induced vibration of plate fuel includes the following steps: arranging an electrode matrix on the fuel assembly to be measured; providing a flow field environment and energizing the electrode matrix; calculating the fluid layer thickness between opposing pairs of electrodes based on the excitation signal received by the electrodes, obtaining a thickness-time function; and calculating the overall flow-induced vibration state of the plate fuel assembly based on the thickness-time function of each pair of electrodes. This method enables accurate measurement of multi-point flow-induced vibration behavior even in situations with narrow gaps between plate fuel assemblies, improving the accuracy and reliability of flow-induced vibration measurement and contributing to enhanced safety design and management of reactors using plate fuel. This invention also provides a plate fuel flow-induced vibration measurement device.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power, specifically relating to a method and apparatus for measuring plate-shaped fuel flow-induced vibration. Background Technology

[0002] Compared to conventional nuclear fuel rods, plate fuel assemblies offer advantages such as compact structure, large heat exchange area, low fuel core temperature, deep burnup, and good safety. Therefore, plate fuels are widely used in various power reactors, neutron reactors, materials reactors, and experimental reactors. However, due to the structural characteristics of plate fuels, flow-induced vibrations caused by coolant impacts during actual operation can lead to damage such as impact failure, fuel plate damage, stress fatigue, cladding plate failure, or material defect propagation, potentially resulting in plate fuel failure. Especially during operation, the presence of critical flow velocities with fluid elastic instability can cause severe vibrations in the plate fuels. These phenomena threaten the safety and stability of reactor operation. Therefore, accurately measuring the flow-induced vibration characteristics of plate fuels is crucial for reactor safety design and management. Because plate fuels are metallic and densely packed, conventional optical or non-invasive electrical measurement methods for measuring flow-induced vibrations are ineffective. Invasive sensors can only reflect single-point flow-induced vibration behavior and cannot measure the relative vibration displacement of the plate fuel in three-dimensional space. Therefore, providing a method for accurately measuring the vibration induced by plate fuel flow is of positive significance for improving the safety and reliability of reactors using plate fuel. Summary of the Invention

[0003] The purpose of this invention is to provide a method for measuring the flow-induced vibration of plate-shaped fuel, accurately measuring the vibration state of compactly arranged plate-shaped fuel. This invention also provides a device for measuring the flow-induced vibration of plate-shaped fuel.

[0004] According to an embodiment of the present invention and one aspect, a method for measuring plate-shaped fuel flow-induced vibration is provided, the method comprising the following steps:

[0005] Step a): Provide a fuel assembly to be measured, the fuel assembly to be measured includes multiple adjacent plate-shaped fuels, and an electrode matrix is ​​arranged on the surface of the plate-shaped fuels. The electrode matrix includes excitation electrodes and receiving electrodes. The excitation electrodes and the receiving electrodes are respectively arranged in an array on the opposite surfaces of adjacent plate-shaped fuels, and the excitation electrodes and the receiving electrodes are aligned one-to-one with each other.

[0006] Step b): Provide a flow field environment for the fuel assembly to be measured, and energize the electrode matrix to cause the excitation electrode to emit an excitation signal, and the receiving electrode to receive the excitation signal;

[0007] Step c): Calculate the thickness of the fluid layer between the excitation electrode and the receiving electrode based on the intensity of the excitation signal received by the receiving electrode, and obtain the thickness-time function;

[0008] Step d): Based on the spatial distribution of each excitation electrode and the receiving electrode and the corresponding thickness-time function, calculate the vibration state of each plate fuel in the fuel assembly.

[0009] The aforementioned method is based on the change in fluid layer thickness between plate-shaped fuels during flow-induced vibration. By utilizing the change in dielectric conductivity between the excitation and receiving electrodes, mechanical vibration is converted into an electrical signal. The distribution of the fluid layer thickness in space is obtained using an electrode matrix, thus yielding the overall vibration information of the plate-shaped fuel. This method enables multi-point measurements on the surface of the plate-shaped fuel, achieving high measurement accuracy, and can accurately measure plate-shaped fuels with narrow gaps. The measurement results are unaffected by fluid transparency, effectively improving the refinement of the analysis of flow-induced vibration behavior in plate-shaped fuels.

[0010] Furthermore, in some embodiments, step a) further includes the step of providing a shielding electrode between at least a portion of the excitation electrodes and between at least a portion of the receiving electrodes, the shielding electrode being grounded. The shielding electrode is used to prevent signal crosstalk and reduce noise.

[0011] Furthermore, in some embodiments, on one surface of the plate-shaped fuel in step a), the excitation electrode or receiving electrode is arranged in a matrix of not less than 4×4.

[0012] Furthermore, in some embodiments, step b) further includes a step of normalizing the excitation signal received by the receiving electrode:

[0013] I*=I / I s ,

[0014] Where I* is the normalized signal strength, I is the original signal strength received by the receiving electrode, and I... s This represents the signal intensity received by the receiving electrode when the flow velocity in the described flow field is 0. Normalization can eliminate interference from environmental factors and improve the accuracy of the analysis results.

[0015] Furthermore, in some embodiments, in step c), the relationship between the fluid layer thickness and the intensity of the excitation signal received by the receiving electrode is obtained by measuring and fitting the plate-shaped fuel with different spacings under the condition that the flow field environment velocity is 0.

[0016] Furthermore, in some embodiments, the relationship between the thickness of the fluid layer and the intensity of the excitation signal received by the receiving electrode is a polynomial function.

[0017] Furthermore, in some embodiments, in step d), the vibration state of the plate-shaped fuel is calculated by establishing a matrix including the spatial distribution of the electrode matrix, the thickness of the fluid layer, and time.

[0018] According to another aspect of the present invention, a plate-shaped fuel flow-induced vibration measuring device is provided. The device is used for the plate-shaped fuel flow-induced vibration measuring method provided in any of the foregoing embodiments, and includes: an electrode matrix, the electrode matrix including an excitation electrode matrix and a receiving electrode matrix; an excitation circuit connected to the electrode matrix and outputting an excitation current; and a data acquisition module connected to the electrode matrix to acquire the excitation signal received by the receiving electrode matrix.

[0019] Furthermore, in some embodiments, the diameter of the electrodes in the electrode matrix is ​​no greater than 2 mm, the thickness is no greater than 0.3 mm, and the diameter of the wires connecting the electrode matrix is ​​no greater than 0.1 mm.

[0020] Furthermore, in some embodiments, the excitation circuit and the data acquisition module are configured as a multiple time-multiplexed scanning circuit. The excitation circuit includes an excitation circuit scanning module, and the data acquisition module includes a receiving scanning circuit module, a data transmission bus, a sample / hold circuit, and an operational amplifier. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a plate-shaped fuel flow-induced vibration measuring device in one embodiment;

[0022] Figure 2 This is a schematic diagram of the electrode distribution on the plate-shaped fuel surface in one embodiment.

[0023] Meaning of reference numerals in the attached diagram: 1-Excitation scanning circuit module; 2-Excitation electrode; 3-Receiver electrode; 4-Receiver scanning circuit module; 5-Data transmission bus; 6-Sampling / holding circuit; 7-Operational amplifier; 8-Shielding electrode; 9-Fuel plate; 10-Wire.

[0024] The purpose of the above-described drawings is to provide a detailed description of the present invention so that those skilled in the art can understand the technical concept of the invention, and is not intended to limit the invention. For the sake of brevity, the above-described drawings only schematically depict the structures related to the technical features of the present invention, and do not depict the complete structure and all details strictly according to actual scale. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0026] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment herein. The phrase appearing in various places in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive, independent, or alternative embodiments. Those skilled in the art will understand that the embodiments herein can be combined with other embodiments without causing structural conflicts.

[0027] In this description, unless otherwise explicitly specified and limited, the technical terms "installation," "connection," "linking," etc., should be interpreted broadly. For example, they can refer to the connection of mechanical structures or the relationship of signal connection; they can refer to movable connections, fixed connections, or integral connections. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0028] In this description, terms such as "upper," "lower," "left," "right," "lateral," "longitudinal," "height," "length," and "width," which indicate orientation or positional relationships, are intended to accurately describe the embodiments and simplify the description, rather than limiting the parts or structures involved to have a specific orientation, or to be installed or operated in a specific orientation, and should not be construed as limiting the embodiments in this document.

[0029] In this description, terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating relative importance or limiting the number, specific order, or primary / secondary relationship of the described technical features. In this description, "multiple" means at least two.

[0030] Plate fuel assemblies are characterized by their compact structure, large heat exchange area, low fuel core temperature, deep fuel burnup, and good safety. They are currently widely used in various power reactors, material reactors, neutron reactors, and experimental reactors, and are applied in both water-cooled and lead-bismuth reactor types. Because plate fuel assemblies are rectangular thin plates with limited rigidity in the thickness direction, and are tightly arranged in the reactor, flow-induced vibrations caused by cooling medium impacts can significantly affect them. This can lead to sideplate impact damage, fuel rod damage, stress fatigue, cladding plate failure, and material defect propagation, and in severe cases, fuel assembly failure. In particular, the critical flow velocity at which fluid elastic instability can occur during operation, potentially causing severe vibrations in the plate fuel, poses a challenge to the safety and stability of reactor operation.

[0031] Therefore, understanding the vibration behavior of plate fuel assemblies under different flow field conditions is crucial for the safe design and management of reactors using plate fuel. Conventional methods for measuring flow-induced vibration include electrical, optical, and acoustic methods. Electrical methods can utilize inductive displacement sensors, eddy current displacement sensors, resistance strain gauges, piezoelectric accelerometers, and microelectromechanical systems (MEMS). Optical methods can employ high-speed cameras, laser vibrometers, laser Doppler vibrometers, and fiber Bragg grating sensors. However, plate fuel assemblies are opaque metal structures, and the spacing between the plates is small (less than 2.5 mm in some designs). This makes it difficult to arrange the sensors used in the above-mentioned measurement methods, and even more difficult to accurately measure the overall vibration state of the plate fuel, making it impossible to determine the relative vibration displacement of two fuel plates in three-dimensional space. This restricts the improvement of safety design and management in reactors using plate fuel.

[0032] To address the aforementioned problems, embodiments of the present invention provide a method for measuring the flow-induced vibration of plate-shaped fuel, capable of accurately capturing the refined three-dimensional flow-induced vibration behavior of plate-shaped fuel. The method includes the following steps:

[0033] Step a): Provide a fuel assembly to be measured. The fuel assembly includes multiple adjacent fuel plates. An electrode matrix is ​​arranged on the surface of these fuel plates. The electrode matrix includes excitation electrodes and receiving electrodes. The excitation electrodes and receiving electrodes are arranged in an array and are respectively set on the surface of two opposite fuel plates. The excitation electrodes and receiving electrodes correspond one-to-one and are centered with each other. The mutual centering means that along the thickness direction of the fuel plate, the centers (usually the geometric centers) of the electrodes on the opposite surfaces of two adjacent fuel plates overlap so that the signal emitted by the excitation electrode can be received by the corresponding receiving electrode.

[0034] Step b): Immerse the fuel assembly to be measured in the flow field environment and energize the electrode matrix to generate an excitation signal from the excitation electrode, which is received by the receiving electrode. In the flow field environment, the fuel assembly undergoes flow-induced vibration, which causes a change in the distance between the excitation electrode and the receiving electrode on the opposite plate-like fuel surface. This, in turn, leads to a change in the conductivity between the electrodes, causing a change in the intensity of the excitation signal received by the receiving electrode. Thus, the mechanical vibration data of the plate-like fuel is converted into signal intensity data of the receiving electrode.

[0035] Step c): Based on the signal intensity received by the receiving electrode, calculate the thickness of the fluid layer between the excitation electrode and the receiving electrode, and obtain the thickness-time function, i.e., the correspondence between thickness and time. The correspondence between signal intensity and fluid layer thickness can be obtained experimentally in a static flow field (the fluid velocity in the flow field environment is 0, i.e., the cooling medium is stationary). By setting up several sets of excitation and receiving electrodes with different spacings, measuring the signal intensity received by the receiving electrode, and fitting the functional relationship between the fluid layer thickness and the excitation signal intensity received by the receiving electrode (thickness-time function δ(t)).

[0036] Step d): Based on the spatial distribution of the excitation electrode and the receiving electrode and the corresponding δ(t) data, the spatial position change of each position of the plate fuel in the fuel assembly over time is calculated, thereby obtaining the flow-induced vibration state of the plate fuel. In a preferred embodiment, a flow-induced vibration state matrix (X, d(t)) of the fuel assembly can be established to calculate the flow-induced vibration state, where X is the coordinate matrix composed of the spatial positions of each excitation electrode-receiving electrode pair, d(t) is the thickness vector composed of the fluid layer thickness of each excitation electrode-receiving electrode pair, and t is time.

[0037] In a preferred embodiment, the signals in the above steps are all normalized based on the static flow field to eliminate interference from environmental factors and improve accuracy.

[0038] Another embodiment of the present invention provides a plate-shaped fuel flow-induced vibration measuring device, the structure of which is as follows: Figure 1 As shown.

[0039] In a preferred embodiment, using as Figure 1 The process of measuring the flow-induced vibration of plate fuel using the plate fuel flow-induced vibration measuring device shown is as follows:

[0040] First, a fuel assembly to be measured is provided, comprising two adjacent fuel plates 9. An electrode matrix is ​​arranged on the surface of the fuel plates 9, the electrode matrix including excitation electrodes 2 and receiving electrodes 3, wherein the excitation electrodes 2 and receiving electrodes 3 are respectively arranged on the surfaces of the two opposing fuel plates 9. Figure 2As shown, the electrode matrix is ​​arranged in an 8×4 matrix. Each electrode is a copper electrode with a diameter of 2 mm and a thickness of 0.3 mm, and is mounted on the surface of the fuel plate 9 using a flexible printed circuit board based on an insulating substrate film. They are connected using flexible enameled wires with a diameter of 0.1 mm. The thickness of the insulating substrate film does not exceed 0.3 mm. By using flexible electrodes and controlling their geometry, the electrodes can prevent them from affecting the vibration of the fuel plate 9 and avoid influencing the mass distribution of the fuel plate 9. The excitation electrodes 2 and receiving electrodes 3 on opposite surfaces of adjacent fuel plates 9 correspond one-to-one, with their centers aligned. To shield signal noise and avoid crosstalk, a shielding electrode 8 is provided between each row of excitation electrodes 2 and receiving electrodes 3. The shielding electrode 8 is grounded.

[0041] The electrode matrix is ​​connected to the excitation circuit and the data acquisition module via wire 10. The excitation circuit and the data acquisition module are designed based on a multiple time-multiplexed scanning circuit. Specifically, the excitation circuit includes an excitation scanning circuit module 1, and the data acquisition module includes a receiving scanning circuit module 4, a data transmission bus 5, a sample / hold circuit 6, and an operational amplifier 7.

[0042] Before starting the flow field test, the relationship between the excitation signal received by receiving electrode 3 and the distance between excitation electrode 2 and receiving electrode 3 is first calibrated. Multiple given spacings are manually set between the electrodes; for example, a set of fuel plates with gradient spacing can be arranged. The fuel plates are immersed in static water and energized, and data is collected using a data acquisition module.

[0043] Next, a flow environment is provided for the test plate fuel assembly, and the signal I measured by each receiving electrode 3 is measured. When water flows between adjacent fuel plates 9, the fuel plates 9 will undergo flow-induced vibration under the excitation of the water flow. The flow-induced vibration causes a change in the gap between two adjacent fuel plates 9, which in turn causes a change in the water layer thickness. The signal strength transmitted from the excitation electrode 2 to the receiving electrode 3 through the water layer also changes with the change in water layer thickness; the greater the water layer thickness, the weaker the signal, and the smaller the water layer thickness, the stronger the signal. In this way, the mechanical signal under the flow-induced vibration of the fuel plates 9 is converted into an electrical signal received by the receiving electrode 3.

[0044] To improve the accuracy of the measurement results and eliminate interference from environmental factors, the signal I measured by each receiving electrode 3 in static water was used as the basis. s Normalize I:

[0045] I*=I / I s .

[0046] Where I* represents the result of normalized processing of the signals measured by each receiving electrode 3.

[0047] Based on the static water measurement results in the calibration test, the relationship between the signal I received by the receiving electrode 3 and the water layer thickness δ between the fuel plate 9 is calculated as I*=F(δ), where F is a fitted function. In the preferred embodiment, F is a fifth-order polynomial, and the polynomial coefficients are obtained through fitting. Using I*=F(δ), the water layer thickness δ between each excitation electrode 2 and the receiving electrode 3 of the test plate fuel assembly can be solved, as well as the function δ(t) of δ changing with time t in flowing water at different times.

[0048] All data collected by the data acquisition module are summarized into a flow-induced vibration state matrix (x, y, d(t)), where x is the vector composed of the abscissas of each electrode pair consisting of excitation electrode 2 and receiving electrode 3, y is the vector composed of the ordinates of each electrode pair, and d(t) is the vector composed of δ(t). The dimension of each vector is 32. The data of each electrode pair reflects the relative vibration relationship between the two fuel plates 9 at its location. Using the flow-induced vibration state matrix, the vibration state at the location of each electrode pair can be determined, and then the overall flow-induced vibration behavior of the fuel plate 9 can be calculated.

[0049] The above method enables accurate measurement of the flow-induced vibration behavior at different locations of the plate-shaped fuel without affecting its overall flow-induced vibration behavior, thus obtaining refined three-dimensional flow-induced vibration behavior measurement results. The use of a multi-time-multiplexed scanning circuit design avoids the measurement data delay effect between electrode matrices, further improving the spatiotemporal resolution of the measurement results. Furthermore, the measurement method used in the above embodiments is non-destructive, protecting the fuel assembly and reducing experimental costs. The normalization processing of the measurement data avoids measurement errors introduced by changes in fluid conductivity and environmental factors.

[0050] In other embodiments, the electrode matrix can be increased according to the actual size of the plate fuel and experimental requirements, and the cooling medium can be adjusted as needed, such as replacing it with heavy water or boron-containing light water. Depending on the actual conditions, the fitting function F can also be in a non-quintic polynomial form or a non-polynomial function form.

[0051] The purpose of the above embodiments is to provide a further detailed description of the present invention in conjunction with the accompanying drawings, so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, optimization or equivalent substitution of the involved part structures or method steps, as well as combination of implementation methods in different embodiments without causing structural and principle conflicts, all fall within the protection scope of the present invention.

Claims

1. A method for measuring plate-shaped fuel flow-induced vibration, characterized in that, Includes the following steps: Step a): Provide a fuel assembly to be measured, the fuel assembly to be measured includes multiple adjacent plate-shaped fuels, and an electrode matrix is ​​arranged on the surface of the plate-shaped fuels. The electrode matrix includes excitation electrodes and receiving electrodes. The excitation electrodes and the receiving electrodes are respectively arranged in an array on the opposite surfaces of adjacent plate-shaped fuels, and the excitation electrodes and the receiving electrodes are aligned one-to-one with each other. Step b): Provide a flow field environment for the fuel assembly to be measured, and energize the electrode matrix to cause the excitation electrode to emit an excitation signal, and the receiving electrode to receive the excitation signal; Step c): Calculate the fluid layer thickness between the excitation electrode and the receiving electrode based on the excitation signal intensity received by the receiving electrode, and obtain the thickness-time function; the relationship between the fluid layer thickness and the excitation signal intensity received by the receiving electrode is obtained by measuring and fitting the plate-shaped fuel with different spacings in the flow field environment when the flow velocity is 0. Step d): Based on the spatial distribution of each excitation electrode and the receiving electrode and the corresponding thickness-time function, the vibration state of each plate fuel in the fuel assembly is calculated; the vibration state of the plate fuel is calculated by establishing a matrix including the spatial distribution of the electrode matrix, the thickness of the fluid layer, and time.

2. The method for measuring plate-shaped fuel flow-induced vibration according to claim 1, characterized in that, Step a) further includes the step of setting a shielding electrode between at least a portion of the excitation electrodes and between at least a portion of the receiving electrodes, wherein the shielding electrode is grounded.

3. The method for measuring plate-shaped fuel flow-induced vibration according to claim 1 or 2, characterized in that, On one surface of the plate-shaped fuel in step a), the excitation electrode and the receiving electrode are arranged in a matrix of not less than 4×4.

4. The method for measuring plate-shaped fuel flow-induced vibration according to claim 1 or 2, characterized in that, Step b) further includes a step of normalizing the excitation signal received by the receiving electrode: I*=I / I s , Where I* is the normalized signal strength, I is the original signal strength received by the receiving electrode, and I... s The signal strength received by the receiving electrode when the flow velocity in the flow field environment is 0.

5. The method for measuring plate-shaped fuel flow-induced vibration according to claim 1 or 2, characterized in that, The relationship between the thickness of the fluid layer and the intensity of the excitation signal received by the receiving electrode is a polynomial function.

6. A plate-shaped fuel flow-induced vibration measuring device, characterized in that, The method for measuring plate-shaped fuel flow-induced vibration as described in any one of claims 1 to 5 The plate-shaped fuel flow-induced vibration measuring device includes: An electrode matrix, comprising an excitation electrode matrix and a receiving electrode matrix; An excitation circuit is connected to the electrode matrix and outputs an excitation current. A data acquisition module is connected to the electrode matrix signal to acquire the excitation signal received by the receiving electrode matrix.

7. The plate-shaped fuel flow-induced vibration measuring device according to claim 6, characterized in that, The diameter of the electrodes in the electrode matrix is ​​no greater than 2 mm, the thickness is no greater than 0.3 mm, and the diameter of the wires connecting the electrode matrix is ​​no greater than 0.1 mm.

8. The plate-shaped fuel flow-induced vibration measuring device according to claim 6 or 7, characterized in that, The excitation circuit and the data acquisition module are configured as a multiple time-multiplexed scanning circuit. The excitation circuit includes an excitation circuit scanning module, and the data acquisition module includes a receiving scanning circuit module, a data transmission bus, a sample / hold circuit, and an operational amplifier.

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