A method for measuring the critical flow velocity of a plate type fuel assembly flow-induced vibration

Abstract

The application discloses a kind of plate fuel assembly flow-induced vibration critical flow velocity measurement methods, belong to nuclear power field.The method includes the following steps: providing test assembly, test assembly simulates real plate fuel assembly, including multiple parallel simulation fuel plates, the surface of multiple simulation fuel plates is provided with strain sensor;Test assembly is placed into flow field, and flow velocity is increased from static until Miller critical flow velocity;The change state of the strain signal of strain sensor with flow velocity is measured, and the flow velocity when nonlinear change occurs is used as the critical flow velocity of real plate fuel assembly.The method can avoid the interference of test process to flow-induced vibration behavior, accurately and efficiently determine the critical flow velocity of plate fuel assembly flow-induced vibration, improve reactor safety.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power, and specifically relates to a method for measuring the critical flow velocity of flow-induced vibration in plate fuel assemblies. Background Technology

[0002] Plate fuel assemblies are widely used in various reactors, including research reactors. Due to their flat plate structure, plate fuel assemblies are significantly affected by flow-induced vibration during service. Severe flow-induced vibration can lead to instability and even irreversible deformation of plate fuel assemblies, resulting in serious safety accidents. The coolant flow rate that causes flow-induced vibration in plate fuel assemblies is called the "critical velocity." Determining the critical velocity of plate fuel assemblies is of great significance for improving the safety of their structural design. Currently, methods for detecting flow-induced vibration in plate fuel assemblies easily damage the structural integrity of the fuel plates, thus affecting the flow-induced vibration characteristics and the accuracy of test results; while non-destructive measurement methods typically only provide relatively accurate results under static conditions. Therefore, providing a method that can accurately measure the critical velocity of flow-induced vibration in plate fuel assemblies is of positive significance for improving their safety. Summary of the Invention

[0003] The purpose of this invention is to provide a method for measuring the critical flow velocity of flow-induced vibration in plate fuel assemblies, thereby improving the accuracy of critical flow velocity measurement.

[0004] According to an embodiment of the present invention, a method for measuring the critical flow velocity of flow-induced vibration in a plate fuel assembly is provided, comprising the following steps:

[0005] Step a): Provide a test assembly, which simulates a real plate fuel assembly and includes a simulated fuel plate. Multiple simulated fuel plates are arranged in parallel at a preset interval. One or more strain sensors are provided on the surface of the multiple simulated fuel plates. The strain sensors are arranged on the central axis of the simulated fuel plate in the horizontal direction and are spaced apart along the height direction.

[0006] Step b): Place the test component in the test flow field. The test flow field is initially in a static state. After the test component is placed in, the flow velocity gradually increases in a direction parallel to the simulated fuel plate to the Miller critical flow velocity.

[0007] Step c): Read the strain signal of the strain sensor as a function of flow velocity, and take the moment when the strain signal changes nonlinearly as the instability moment of the simulated fuel plate, and take the flow velocity at the instability moment as the critical flow velocity of the real plate fuel assembly corresponding to the test component.

[0008] This method ensures the structural integrity of the simulated fuel plate during measurement, guaranteeing that the flow-induced vibration behavior of the simulated fuel plate is consistent with that of a plate fuel assembly under real-world conditions. Furthermore, the measurement process is unaffected by changes in the physical and chemical properties of the fluid, making it suitable for long-term testing. The experimental equipment used in this method is simple, and the testing cost is low, demonstrating good economic efficiency.

[0009] Furthermore, in some embodiments, the space between the two simulated fuel plates equipped with the strain sensors is up to three simulated fuel plates.

[0010] Furthermore, in some embodiments, in step a), at least 10 simulated fuel plates are provided.

[0011] Furthermore, in some embodiments, in step a), the strain sensor is configured as a strain gauge, and the strain gauge is coated with a waterproof coating.

[0012] Furthermore, in some embodiments, on the same simulated fuel plate, the spacing between the strain sensors near the test flow field inlet is smaller than the spacing between the strain sensors away from the test flow field inlet.

[0013] Furthermore, in some embodiments, the spacing between the strain sensors is 0.05-0.2 times the distance between adjacent simulated fuel plates.

[0014] Furthermore, in some embodiments, each of the simulated fuel plates equipped with the strain sensors is provided with 7-8 strain sensors.

[0015] Furthermore, in some embodiments, the thickness of the strain sensor does not exceed 0.3 mm.

[0016] Furthermore, in some embodiments, in step b), the flow velocity of the test flow field is increased in steps of 0.5 m / s to 1 m / s.

[0017] Furthermore, in some embodiments, in step c), when the strain signal does not undergo nonlinear changes, the distance between adjacent simulated fuel plate surfaces is calculated based on the strain signal, and the flow field velocity at the moment when the distance between adjacent simulated fuel plate surfaces is less than 1 / 2 of the initial spacing is taken as the critical flow velocity of the corresponding real plate fuel assembly. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the cross-sectional structure of the test component in one embodiment;

[0019] Figure 2This is a schematic diagram of the installation position of strain gauges on the simulated fuel plate 11 in one embodiment;

[0020] Figure 3 This is a schematic diagram of the installation position of strain gauges on simulated fuel plates 12-14 in one embodiment;

[0021] Figure 4 This is a schematic diagram of a flow-induced vibration critical velocity measurement method for a plate fuel assembly in one embodiment.

[0022] Meaning of reference numerals in the attached figures: 1-Test component; 11-Simulated fuel plate; 12-Simulated fuel plate; 13-Simulated fuel plate; 14-Simulated fuel plate; 2-Side plate; 3-Strain gauge; 4-Flow channel wall; 5-Waterproof coating.

[0023] 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

[0024] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0025] 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.

[0026] In this description, unless otherwise explicitly specified and limited, the technical terms "installation," "connection," "joining," etc., should be interpreted broadly, for example, referring to movable connections, fixed connections, or integration. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0027] 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.

[0028] 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.

[0029] Plate fuel assemblies consist of several flat fuel assemblies arranged in parallel between side plates. They are compact in structure and widely used in research reactors and other novel reactor types. Due to the large area of ​​the fuel plates, the flow channels are divided into relatively independent spaces by the fuel plates and side plates, making it difficult for the coolant in the gaps between adjacent fuel plates to mix sufficiently. Simultaneously, in the service environment of plate fuel assemblies, the coolant inlet structure exhibits a disturbance and diversion effect, resulting in uneven coolant flow distribution in each gap. This leads to a pressure difference across the fuel plate, inducing flow-induced vibration. An increase in coolant velocity leads to a greater pressure difference across the fuel plate, increasing the intensity of the flow-induced vibration. When the flow-induced vibration of the plate fuel assembly exceeds a certain limit, it can cause the fuel plate to become unstable or even undergo irreversible deformation, posing a safety risk. Therefore, for plate fuel assemblies with a specific structure, it is necessary to determine the critical flow velocity that induces fuel plate instability before service and ensure that the operating conditions of the plate fuel assembly are always below the critical flow velocity during actual operation to ensure reactor safety.

[0030] Currently, the technical solution for measuring flow-induced vibration behavior using eddy current sensors will damage the structural integrity of the fuel plate, resulting in a significant deviation between the test conditions and the actual operating conditions. On the other hand, the technical solution for measuring flow-induced vibration behavior using the resistance method is significantly affected by the fluid conductivity, and its accuracy is insufficient under test conditions.

[0031] To address the aforementioned problems, embodiments of the present invention provide a method for measuring the critical flow velocity of flow-induced vibration in plate fuel assemblies, which can accurately determine the critical flow velocity of plate fuel assemblies with specific structures.

[0032] Specifically, the method includes the following steps:

[0033] Step a): Provide a test assembly. The test assembly is used to simulate several components of a real plate fuel assembly. The test assembly includes multiple simulated fuel plates, which have the same geometric dimensions and physical properties such as elastic modulus as real fuel plates. The multiple simulated fuel plates are arranged in parallel, with the spacing between them being the same as the spacing between the fuel plates in the simulated plate fuel assembly. Strain sensors are provided on at least a portion of the surface of the simulated fuel plates. The strain sensors are positioned on the horizontal central axis of the simulated fuel plates, and multiple strain sensors are arranged at intervals along the height direction on the same fuel plate. In a preferred embodiment, there are at most three simulated fuel plates without strain sensors between two simulated fuel plates equipped with strain sensors.

[0034] In a preferred embodiment, the strain sensor is configured as a strain gauge with a waterproof coating. The spacing between strain gauges near the inlet is smaller than the spacing between strain gauges away from the inlet. Seven to eight strain gauges are arranged on the same simulated fuel plate. To prevent interference with the flow field, the thickness of the strain gauges does not exceed 0.3 mm.

[0035] In a preferred embodiment, a test assembly includes at least 10 simulated fuel plates, the number of which should be the same as the number of real plate fuel assemblies being simulated, for example, 20.

[0036] Step b): Place the test component in the test flow field. The test flow field is initially static. After placing the test component, gradually increase the flow field velocity to the Miller critical velocity.

[0037] Specifically, in a preferred embodiment, the rate of increase in flow velocity is 0.5 m / s. 2 -1m / s 2 .

[0038] Step c): Read the strain signal data of the strain sensor as a function of time, and take the moment when the strain signal changes nonlinearly as the moment of instability of the simulated fuel plate, and take the flow velocity of the flow field at the moment of instability as the critical flow velocity of the simulated real plate fuel assembly.

[0039] In some embodiments, when the strain signals of all strain sensors remain linear, the deformation of the simulated fuel plate is calculated based on the strain signals. When the distance between the fuel plate surfaces at any strain sensor location is less than 1 / 2 of the initial distance, the flow velocity at that moment is taken as the critical velocity of the simulated real plate fuel assembly.

[0040] In a preferred embodiment, the measurement process for the critical flow velocity of the flow-induced vibration of the plate fuel assembly is as follows: Figure 4 As shown, the specific steps include:

[0041] First, provide such Figure 1 The test assembly 1 shown includes 20 simulated fuel plates, which are arranged parallel to each other between the measuring side plates 2. Strain gauges 3 are installed on the surfaces of simulated fuel plates 11, 12, 13, and 14 at their horizontal central axes. The initial spacing between adjacent simulated fuel plates is L.

[0042] The arrangement of strain gauges 3 on the simulated fuel plate 11 is as follows: Figure 2As shown in the diagram, the flow field direction is as indicated by arrow A, flowing from top to bottom. Strain gauges 3 are sequentially attached at installation points P1-P8 along the flow direction. The attachment areas of strain gauges 3 are coated with a waterproof coating 5 to prevent fluid intrusion into the strain gauges during the test. Specifically, the distance between P1 and the end of the simulated fuel plate is 0.1L; the distances between P1 and P2, and P2 and P3 are 0.05L; the distances between P3 and P4, P6 and P7, and P7 and P8 are 0.1L; and the distances between P4 and P5, and P5 and P6 are 0.2L.

[0043] The strain gauges on simulated fuel plates 12, 13, and 14 are arranged as follows: Figure 3 As shown in the diagram, the flow field direction is as indicated by arrow A, flowing from top to bottom. Strain gauges 3 are sequentially attached at installation points P1-P7 along the flow direction. The attachment areas of strain gauges 3 are coated with a waterproof coating 5 to prevent fluid intrusion into the strain gauges during the test. Specifically, the distance between P1 and the end of the simulated fuel plate is 0.1L, the distance between P1 and P2, and between P2 and P3 is 0.05L, the distance between P3 and P4 is 0.1L, and the distances between P4 and P5, P5 and P6, and P6 and P7 are 0.2L.

[0044] The strain gauge 3 has a thickness of 0.3 mm, the data transmission line connected to the strain gauge 3 has a wire diameter of no more than 0.3 mm, and the waterproof coating 5 has a thickness of no more than 0.5 mm.

[0045] Because the flow field disturbance effect at the inlet end is relatively significant, the strain gauges 3 in the upstream region of the simulated fuel plate are arranged relatively densely. The selected fuel plates with strain gauges 3 are located in the outer, sub-outer, and middle regions of the test assembly, and their distribution is relatively uniform, which can better reflect the flow-induced vibration characteristics of different regions of the test assembly.

[0046] Next, test component 1 is placed into the test flow channel, which contains cooling water. Initially, the cooling water is stationary. Based on the dimensional parameters of test component 1, the test flow rate range is calculated and determined. Specifically, the Miller critical flow rate corresponding to test component 1 is calculated:

[0047]

[0048] Among them, V c Let V be the Miller critical velocity, ρ be the density of water, b be the channel length, E be the elastic modulus of the simulated fuel plate, a be the thickness of the simulated fuel plate, v be the Poisson's ratio of the simulated fuel plate, and h be the width of the coolant channel. The calculated V... c This represents the upper limit of the cooling water flow rate during the test.

[0049] After placing test component 1, the cooling water flow was driven by a pump set, and the flow rate of the cooling water was gradually increased. The cooling water flow rate in the gap between the simulated fuel plates was increased from 0 to 10 m / s in steps of 1 m / s, and then increased to V in steps of 0.5 m / s. c Under each flow rate condition, the flow rate is increased to the next condition only after the structural displacement and vibration of test component 1 have stabilized.

[0050] Due to the different cooling water flow distribution between the simulated fuel plates in test assembly 1 and between the fuel plates and the flow channel wall 4, test assembly 1 experiences flow-induced vibration, and strain gauges 3 can detect strain signals. The strain signals of each strain gauge 3 are read, and the strain-flow velocity curve of each strain gauge 3 is plotted. Before instability occurs, the strain-flow velocity curve increases linearly. When any strain-flow velocity curve undergoes a nonlinear change, it is determined that the simulated fuel plate has become unstable. The flow velocity at the moment of instability is taken as the critical flow velocity of test assembly 1, which is also the critical flow velocity of the real plate fuel assembly simulated by test assembly 1.

[0051] In some embodiments, as the flow rate increases to V c During the process, the strain-flow velocity curve maintains a linear increase. The normal deformation of the simulated fuel plate is calculated based on the strain signal, and the change in the gap between each simulated fuel plate is calculated. When the gap between the surfaces of the simulated fuel plates at any position decreases to 0.5L, the corresponding flow velocity is determined to be the critical flow velocity, which is also the critical flow velocity of the real plate fuel assembly simulated by test component 1.

[0052] The purpose of the above embodiments is to provide a 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, optimizations or equivalent substitutions of the method steps involved, as well as combinations of implementation methods in different embodiments without causing a conflict of principles, all fall within the protection scope of the present invention.

Claims

1. A method for measuring the critical flow velocity of flow-induced vibration in a plate fuel assembly, characterized in that, Includes the following steps: Step a): Provide a test assembly, which simulates a real plate fuel assembly and includes a simulated fuel plate. Multiple simulated fuel plates are arranged in parallel at a preset interval. One or more strain sensors are provided on the surface of the multiple simulated fuel plates. The strain sensors are arranged on the central axis of the simulated fuel plate in the horizontal direction and at intervals along the height direction. Step b): Place the test component in the test flow field. The test flow field is initially in a static state. After the test component is placed, the flow velocity gradually increases in a direction parallel to the simulated fuel plate to the Miller critical flow velocity. On the same simulated fuel plate, the spacing between the strain sensors near the inlet of the test flow field is smaller than the spacing between the strain sensors away from the inlet of the test flow field. Step c): Read the strain signal of the strain sensor as a function of flow velocity, and take the moment when the strain signal changes nonlinearly as the instability moment of the simulated fuel plate, and take the flow velocity at the instability moment as the critical flow velocity of the real plate fuel assembly corresponding to the test component; when the strain signal does not change nonlinearly, calculate the distance between adjacent simulated fuel plate surfaces based on the strain signal, and take the flow velocity at the moment when the distance between adjacent simulated fuel plate surfaces is less than 1 / 2 of the initial spacing as the critical flow velocity of the corresponding real plate fuel assembly.

2. The method for measuring the critical flow velocity of flow-induced vibration in a plate fuel assembly according to claim 1, characterized in that, The space between the two simulated fuel plates equipped with the strain sensors is at most three simulated fuel plates.

3. The method for measuring the critical flow velocity of flow-induced vibration of a plate fuel assembly according to claim 1 or 2, characterized in that, In step a), at least 10 simulated fuel plates are provided.

4. The method for measuring the critical flow velocity of flow-induced vibration of a plate fuel assembly according to claim 1 or 2, characterized in that, In step a), the strain sensor is configured as a strain gauge, and the strain gauge is coated with a waterproof coating.

5. The method for measuring the critical flow velocity of flow-induced vibration in a plate fuel assembly according to claim 1, characterized in that, The spacing between the strain sensors is 0.05-0.2 times the distance between adjacent simulated fuel plates.

6. The method for measuring the critical flow velocity of flow-induced vibration of a plate fuel assembly according to claim 1 or 2, characterized in that, Each of the simulated fuel plates equipped with the strain sensors has 7-8 strain sensors.

7. The method for measuring the critical flow velocity of flow-induced vibration of a plate fuel assembly according to claim 1 or 2, characterized in that, The thickness of the strain sensor does not exceed 0.3 mm.

8. The method for measuring the critical flow velocity of flow-induced vibration of a plate fuel assembly according to claim 1 or 2, characterized in that, In step b), the flow velocity of the test flow field is increased in steps of 0.5 m / s to 1 m / s.

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