A method, system, and computer readable storage medium for identification and localization of a fluid excitation source within a primary loop

Abstract

This invention discloses a method, system, and computer-readable storage medium for identifying and locating fluid excitation sources within a main loop. The method detects the main loop flow path subdomain where the problematic component, which exhibits abnormal vibration due to fluid excitation, is located. It then establishes a structural dynamics model of the problematic component to obtain its dynamic parameters, identifies large-scale eddies in typical geometric structures, selects analysis paths that include these large-scale eddies, analyzes the correlation and spatiotemporal evolution of the flow field in different regions within the main loop, and finally accurately identifies the location of the fluid excitation source causing the abnormal vibration of the component. This provides a foundation for subsequent optimization of the flow channel structure in the fluid excitation source region.

Description

Technical Field

[0001] This invention relates to the field of engineering technology, and in particular to a method, system, and computer-readable storage medium for identifying and locating fluid excitation sources in a main circuit. Background Technology

[0002] The main circuit is a crucial component of a nuclear power plant, operating under extreme high-temperature and high-pressure conditions for extended periods. Its operational status directly impacts the plant's safety and reliability. The fluid flow characteristics within the main circuit are complex, involving various flow-induced vibration phenomena such as turbulent excitation, bouncy instability, vortex shedding, and acoustic resonance. These fluid-induced component vibrations can lead to component fatigue and wear, potentially causing safety hazards and affecting the normal operation of the reactor.

[0003] In recent years, some large nuclear power plants at home and abroad have experienced problems such as large fluctuations in nuclear power, low-frequency vibration of fuel assemblies, and even fuel assembly damage during reactor power operation. Research on these problems still has some limitations when dealing with complex main loop fluid flow issues, such as: 1) Research methods using scaled-down separation effect tests or computational fluid dynamics simulations of local areas (such as the reactor area) only study the fluid flow patterns in a limited area of ​​the vibrating component, obtaining the excitation load on the component, ignoring the fluid within the main loop as a whole, the spatiotemporal correlation between upstream and downstream fluids, and failing to fully consider the influence of far-field fluid flow outside the local area; 2) In research methods using prototype tests under actual nuclear power plant operating conditions (such as flow-induced vibration of in-reactor components), due to limitations in installation location or inaccessible measurement locations, only the excitation load (pressure pulsation) or vibration response at a few measurement points near the component can be obtained, and the source of the fluid excitation load causing component vibration is not comprehensively traced throughout the flow region of the entire loop. These problems result in insufficient ability to identify and locate fluid excitation sources that cause abnormal vibrations in components within the main circuit, making it difficult to achieve efficient control of abnormal vibrations in the main circuit components of nuclear power plants. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address at least one defect of the related technologies mentioned in the background: the related technologies only study the fluid flow law in a limited area of ​​the vibrating component, and do not conduct a comprehensive tracing of the source of the fluid excitation load that causes the component vibration in the entire circuit, thus making it impossible to accurately locate the fluid excitation source that causes the abnormal vibration of the component.

[0005] The technical solution adopted by this invention to solve its technical problem is: to construct a method for identifying and locating fluid excitation sources in the main circuit, including the following steps: The main loop flow path subdomain of the problematic component that is experiencing abnormal vibration due to fluid excitation is detected, and a structural dynamics model of the problematic component is established to obtain its dynamic parameters. In the main loop flow path subdomain, identify typical geometric structures that are prone to inducing large-scale separation vortices or vortex shedding, and identify large-scale vortices in typical geometric structures. Based on the main loop flow path subdomain where the problematic component is located, an analysis path including large-scale vortices is selected. The vortex evolution law of the analysis path is calculated, and the correlation analysis of the signals of nearby points or adjacent cross sections of the analysis path is performed to obtain the correlation analysis results. By analyzing the dynamic parameters and correlation results of the problematic component, the energy transfer relationship from the large-scale vortex to the problematic component in the analysis path is determined, and the fluid excitation source of the problematic component is located.

[0006] In some embodiments, before detecting the main loop flow path subdomain where the problematic component experiencing abnormal vibration due to fluid excitation is located, the method further includes: Import the 3D models of the main loop components into the modeling software and connect them to obtain the main loop fluid domain; Based on the structural and operational characteristics of the main loop components, the main loop fluid domain is divided into several main loop flow path subdomains. For different main loop flow path subdomains, set up corresponding physical models, provide operating condition data, set the calculation time step and the total physical calculation time, and then perform simulation calculations to obtain the unsteady flow parameters of the main loop.

[0007] In some embodiments, establishing a structural dynamics model of the problematic component to obtain its dynamic parameters includes: Based on the main loop flow path subdomain where the problem component is located and the unsteady flow parameters of the main loop, a numerical model of the region where the problem component is located is established, and the excitation load of the problem component is calculated. A structural dynamic model of the problem component is established, and the dynamic parameters of the problem component are obtained by using the excitation load of the problem component as input.

[0008] In some embodiments, the main loop components are imported into modeling software and connected to obtain the main loop fluid domain, including: Determine the minimum modeling range for the main loop components, establish a 3D model of the main loop components based on the structural parameters of the minimum modeling range, import the main loop components into the modeling software respectively, and connect the 3D models of the main loop components according to the main loop topology to obtain the main loop fluid domain; The minimum modeling scope includes the reactor, steam generator, main pump, and the piping connecting the reactor, steam generator, and main pump.

[0009] In some embodiments, the main loop fluid domain is divided into several main loop flow path subdomains based on the structural and operational characteristics of the main loop components, including: Based on the structural and operational characteristics of the main loop components, the key links that truncate the continuous evolution path of large-scale eddies are determined. The key links are the eddy-free subdomains of the main loop flow path, and the main loop fluid domain is divided into other main loop flow path subdomains using the key links as nodes.

[0010] In some embodiments, the main loop flow path subdomain includes at least one main loop component within the minimum modeling range; Set up corresponding physical models for different main loop flow path subdomains, including: A porous medium model was used for the reactor core and the heat transfer tube region of the steam generator; For other main loop flow path subdomains, use a real geometric model or an equivalent model.

[0011] In some embodiments, corresponding physical models are set for different main loop flow path subdomains, including: The main loop fluid domain is spatially discretized into a grid to obtain the main loop numerical model. Based on the main loop numerical model, corresponding physical models are set for different main loop flow path subdomains.

[0012] In some embodiments, given operating condition data and after setting the calculation time step and total physical calculation time, simulation calculations are performed to obtain unsteady flow parameters in the main loop, including: Given operating condition data, the simulation calculation is started when the calculation time step is less than or equal to the first preset threshold and the total physical calculation time is greater than the second preset threshold. Data acquisition is performed after the calculation time is greater than or equal to the third preset threshold, and the unsteady flow parameters of the main loop are stored. The unsteady flow parameters in the main loop include global velocity and global pressure.

[0013] In some embodiments, after obtaining the dynamic parameters of the problematic component, the method further includes: adjusting the time step for calculating the unsteady flow parameters of the main loop and the total physical calculation time based on the dynamic parameters.

[0014] In some embodiments, the time step for calculating the unsteady flow parameters of the main loop and the total physical calculation time are adjusted according to the dynamic parameters, including: Adjust the time step and total physical duration of the calculation of the unsteady flow parameters of the main loop so that the frequency range of the unsteady flow parameters of the main loop covers the characteristic frequencies of the dynamic parameters of the problem component. The time step is S, the total physical duration is T, and the characteristic frequency of the dynamic parameter of the problem component is f, which satisfies 1 / (2×S)≥f≥1 / T.

[0015] In some embodiments, after obtaining the dynamic parameters of the problematic component, the method further includes: The accuracy of the excitation load on the problematic component is verified by comparing its dynamic parameters with the measured values, and then it is determined whether the calculation model of the unsteady flow parameters of the main loop needs to be adjusted. The computational model includes: a numerical model of the main loop and corresponding physical models for different main loop flow path subdomains.

[0016] In some embodiments, the unsteady flow parameters of the main loop include the unsteady flow parameters at the inlet of the region where the problem component is located. Based on the main loop flow path subdomain where the problem component is located and the unsteady flow parameters of the main loop, a numerical model of the region where the problem component is located is established, and the excitation load of the problem component is calculated, including: If the problematic component is located in the reactor core or the heat transfer tube area of ​​the steam generator, or in other areas using an equivalent model, a real geometric model needs to be further established in the area where the problematic component is located. Unsteady flow calculations in the area where the problematic component is located are carried out using the unsteady flow parameters at the inlet of the area where the problematic component is located as boundary conditions to obtain the excitation load of the problematic component. Otherwise, the unsteady flow calculations in the region where the problem component is located are carried out directly based on the unsteady flow parameters of the main loop to obtain the excitation load of the problem component.

[0017] In some embodiments, an analysis path including large-scale eddies is selected based on the main loop flow path subdomain where the problematic component is located, including: If the problematic component is located in the vortex-free region of the main loop flow path, then select an analysis path for each of its adjacent main loop flow path sub-regions. Alternatively, if the problematic component is located in another main loop flow path subdomain, then select an analysis path within the main loop flow path subdomain where the problematic component is located.

[0018] In some embodiments, the vortex evolution law of the analysis path is calculated and correlation analysis is performed on the signals of nearby points or adjacent cross sections of the analysis path to obtain the correlation analysis results, including: Based on the distance of the analysis path and the characteristics of the flow channel, extract a number of points or sections. Calculate the self-power spectral density of the point or section signal according to the flow direction of the fluid. Then, calculate the cross-power spectral density of the signals at two adjacent points or sections in sequence. Calculate the coherence coefficient of the two signals in the frequency domain and extract the phase spectrum contained in the cross-power spectral density.

[0019] In some embodiments, the dynamic parameters of the problematic component include characteristic frequencies, coherence coefficients and phase spectra from correlation analysis results. By combining the dynamic parameters of the problematic component with the correlation analysis results, the energy transfer relationship from large-scale eddies to the problematic component in the analysis path is determined, and the fluid excitation source of the problematic component is located, including: If, within a preset frequency range controlled by the characteristic frequency of the dynamic parameters of the problematic component, the coherence coefficient is within a preset value range and the phase spectrum changes stably, then it is determined that there is significant energy transfer from the large-scale vortex to the component in the selected analysis path, and the region that generates the vortex is identified as the location of the main excitation source; otherwise, the analysis path including other large-scale vortices is selected again, and correlation analysis of the signals of nearby points or adjacent cross sections of the analysis path is performed to obtain the corresponding correlation analysis results. The above analysis is repeated until the location is successfully determined.

[0020] In some embodiments, the characteristic frequency of the dynamic parameter of the problematic component is f, and the preset frequency range controlled by the characteristic frequency of the dynamic parameter of the problematic component is 0.8f~1.2f, and the preset numerical range is 0.8~1.

[0021] In some embodiments, the method further includes: Visualize the evolution of the fluid excitation source, analyze the causes of large-scale eddies, and optimize the geometry of the location of the fluid excitation source until the vibration behavior of the problematic component reaches the design target.

[0022] In some embodiments, visualization of the evolution of the fluid excitation source and analysis of the origin of large-scale eddies are performed, including: By combining the unsteady flow parameters of the main loop, the eddy spatial distribution of large-scale eddies is analyzed using the eddy identification criterion. Large-scale eddies are reconstructed in three dimensions, and eddy structure parameters are obtained for the genesis of large-scale eddies.

[0023] This invention constructs a system for identifying and locating fluid excitation sources within a main circuit, comprising: The detection and calculation module is used to detect the main loop flow path subdomain where the problematic component, which is experiencing abnormal vibration due to fluid excitation, is located, and to establish a structural dynamics model of the problematic component to obtain its dynamic parameters. The identification module is used to determine typical geometric structures in the main loop flow path subdomain that are prone to inducing large-scale separation vortices or vortex shedding, and to identify large-scale vortices in typical geometric structures. The analysis module is used to select an analysis path including large-scale eddies based on the main loop flow path subdomain where the problematic component is located, calculate the eddy evolution law of the analysis path, and perform correlation analysis on signals from nearby points or adjacent cross-sections of the analysis path to obtain the correlation analysis results; and, The localization module is used to determine the energy transfer relationship from the large-scale vortex to the problem component in the analysis path by using the dynamic parameters of the problem component and the correlation analysis results, and to locate the fluid excitation source of the problem component.

[0024] The present invention constructs a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements a method for identifying and locating fluid excitation sources in the main circuit as described in any of the above embodiments.

[0025] By implementing this invention, the following beneficial effects are achieved: This invention establishes a structural dynamics model of the problematic component by detecting the main loop flow path subdomain where the component exhibits abnormal vibration due to fluid excitation, thereby obtaining the component's dynamic parameters. It also identifies large-scale eddies in typical geometric structures, selects analysis paths that include these large-scale eddies, analyzes the correlation and spatiotemporal evolution of the flow field in different regions within the main loop, and ultimately accurately identifies the location of the fluid excitation source causing the component's abnormal vibration. This provides a foundation for subsequent optimization of the flow channel structure in the fluid excitation source region. Attached Figure Description

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 A schematic diagram of the fluid flow path within the main loop is shown (typical megawatt-class three-loop pressurized water reactor). Figure 1 The reference numerals in the attached diagram are as follows: 1-Steam generator (SG); 2-Heat transfer tube; 3-Outlet chamber; 4-Inlet chamber; 5-Reactor pressure vessel; 6-Top cover chamber; 7-Guide tube; 8-Nozzle; 9-Upper chamber; 10-Core; 11-Descent annulus; 12-Flow distribution device; 13-Bottom chamber; 14-Heat pipe section; 15-Cold pipe section; 16-Main pump; 17-Transition section; Figure 2 The flowchart illustrates an embodiment of a method for identifying and locating fluid excitation sources within a main circuit according to the present invention. Figure 3 This invention illustrates a block diagram of the main loop flow path subdomain partitioning. Figure 4 A schematic diagram showing the principle of component vibration induced by the fluid excitation source in the main circuit is shown; Figure 5 The diagram shows an embodiment of a system for identifying and locating fluid excitation sources within a main circuit according to the present invention. Detailed Implementation

[0027] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0028] It should be noted that the flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0029] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0030] It should be noted that "the following refers to at least two, which can be two, three, or any number. At least one can be one, two, or any number."

[0031] Nuclear power plant main loops typically employ a design of multiple loops in parallel (usually 2 to 4 loops). Each independent loop generally includes a steam generator (SG), main pumps, and main piping connecting them (including cold pipe sections, hot pipe sections, and transition sections). These parallel loops share a single reactor (including pressure vessel, reactor core, in-core components, etc.).

[0032] Taking a typical megawatt-class three-loop pressurized water reactor as an example, the main flow path of the fluid in the main loop is as follows: Figure 1 As shown, fluid flows out from the outlet of the main pump 16 and enters the reactor descending annulus 11 via the cold pipe section 15. Within the descending annulus 11, the majority of the fluid flows downwards into the bottom chamber 13; a small portion flows upwards into the top cover chamber 6 via nozzles 8. In the bottom chamber 13, the fluid flows through the flow distribution device 12 and then upwards into the reactor core 10. While flowing through the fuel assemblies within the reactor core 10, the fluid absorbs heat from nuclear fission, increasing its temperature. The heated fluid flows out of the reactor core 10 and into the reactor upper chamber 9, where it mixes with the fluid flowing downwards from the top cover chamber 6 via the control rod guide tube 7. The mixed fluid flows out of the reactor pressure vessel 5 and into the heat pipe section 14. Afterwards, the fluid flows through the heat pipe section 14 into the inlet chamber 4 at the bottom of the steam generator 1 and upwards through the U-shaped heat transfer tube 2. During this process, the fluid transfers heat to the cooling water on the secondary loop side (causing it to generate steam) and is itself cooled. The cooled fluid gathers in the outlet chamber 3 at the bottom of the steam generator 1, and then flows back to the main pump 16 area through the transition section 17, completing the entire flow cycle.

[0033] The fluid flowing through the aforementioned different regions within the main loop exhibits highly complex and non-uniform flow patterns. These patterns primarily include: shear turbulence with rotational effects at the main pump outlet; wall turbulence and fully developed turbulence within the pipes; wall-attached jets and strong shear flow at the reactor pressure vessel inlet; complex separated and secondary flows within the pressure vessel and steam generator bottom head; and turbulence and flow around cylinders within the complex structures of the reactor core. High-intensity turbulent fluctuations, periodic vortex shedding, and large-scale vortex separation are prevalent phenomena in these complex flow fields.

[0034] like Figure 2 As shown, some embodiments of the present invention disclose a method for identifying and locating fluid excitation sources within a main circuit, comprising the following steps: The main loop flow path subdomain of the problematic component that is experiencing abnormal vibration due to fluid excitation is detected, and a structural dynamics model of the problematic component is established to obtain its dynamic parameters. In the main loop flow path subdomain, identify typical geometric structures that are prone to inducing large-scale separation vortices or vortex shedding, and identify large-scale vortices in typical geometric structures. Based on the main loop flow path subdomain where the problematic component is located, an analysis path including large-scale vortices is selected. The vortex evolution law of the analysis path is calculated, and the correlation analysis of the signals of nearby points or adjacent cross sections of the analysis path is performed to obtain the correlation analysis results. By analyzing the dynamic parameters and correlation results of the problematic component, the energy transfer relationship from the large-scale vortex to the problematic component in the analysis path is determined, and the fluid excitation source of the problematic component is located.

[0035] This embodiment detects the main loop flow path subdomain of the problematic component that experiences abnormal vibration due to fluid excitation, establishes a structural dynamics model of the problematic component to obtain its dynamic parameters, identifies large-scale eddies in typical geometric structures, selects analysis paths that include large-scale eddies, analyzes the correlation and spatiotemporal evolution of the flow field in different regions within the main loop, and finally accurately identifies the location of the fluid excitation source causing the abnormal vibration of the component, thus providing a foundation for subsequent optimization of the flow channel structure in the fluid excitation source region.

[0036] Specifically, based on statistical data of abnormal equipment vibration during actual operation of in-service nuclear power plants (i.e., vibration amplitude measured during actual power plant operation exceeding design values), the main loop flow path subdomain of the problematic component experiencing abnormal vibration due to fluid excitation is detected. Establishing the structural dynamics model of the problematic component requires knowledge of its geometric model, materials, and mechanical properties. Since the geometric model, materials, and mechanical properties are all known data, establishing the structural dynamics model of the component is common knowledge in mechanical analysis and will not be elaborated upon here. The dynamic parameters of the problematic component include: its characteristic frequency, mode shape, and response displacement.

[0037] In some embodiments, before detecting the main loop flow path subdomain where the problematic component experiencing abnormal vibration due to fluid excitation is located, the method further includes: Import the 3D models of the main loop components into the modeling software and connect them to obtain the main loop fluid domain; Based on the structural and operational characteristics of the main loop components, the main loop fluid domain is divided into several main loop flow path subdomains. For different main loop flow path subdomains, set up corresponding physical models, provide operating condition data, set the calculation time step and the total physical calculation time, and then perform simulation calculations to obtain the unsteady flow parameters of the main loop.

[0038] In some embodiments, establishing a structural dynamics model of the problematic component to obtain its dynamic parameters includes: establishing a numerical model of the region where the problematic component is located based on the main loop flow path subdomain where the problematic component is located and the unsteady flow parameters of the main loop, and calculating the excitation load of the problematic component; establishing a structural dynamics model of the problematic component and using the excitation load of the problematic component as input to obtain its dynamic parameters.

[0039] In some embodiments, the main loop components are imported into modeling software and connected to obtain the main loop fluid domain. This includes: determining the minimum modeling range for the main loop components; establishing a 3D model of the main loop components based on the structural parameters of each minimum modeling range; importing the main loop components into the modeling software and connecting the 3D models of the main loop components according to the main loop topology to obtain the main loop fluid domain. Specifically, after connecting the components, the modeling software (e.g., Solidworks, AutoCAD, CATIA, etc.) performs Boolean operations (e.g., merge, cut, intersection, wrap, etc.) on the geometry to obtain the main loop fluid domain.

[0040] In some embodiments, the minimum modeling scope is the reactor, steam generator, main pump, and piping connecting the reactor, steam generator, and main pump.

[0041] Determining the minimum modeling range for the main loop components, including the reactor, steam generator, main pump, or the pipelines connecting the reactor, steam generator, and main pump, and establishing a 3D model of the main loop components based on the structural parameters of each minimum modeling range, is a prerequisite for establishing a high-fidelity 3D numerical model of the main loop fluid domain, solving for unsteady flow parameters, and obtaining physical field data such as transient velocity and pressure across the entire domain.

[0042] In some embodiments, if a branch pipe and a voltage regulator are connected to the main pipe, the modeling of the corresponding branch pipe and voltage regulator is increased or decreased within the minimum modeling range based on the abnormal vibration of the problematic component.

[0043] Typically, the main pipeline is connected to multiple branch pipes and a pressure regulator (usually connected to a hot pipe section of a loop) to maintain pressure stability in the main loop. Depending on the abnormal vibration of the problematic component, the modeling of relevant branch pipes can be added or removed within the minimum modeling range of the main loop provided in this invention. Adding or removing the modeling of corresponding branch pipes and pressure regulators is beneficial for the accuracy of excitation source location and the simplification of the calculation of unsteady flow parameters in the main loop.

[0044] In some embodiments, the main loop fluid domain is divided into several main loop flow path subdomains based on the structural and operational characteristics of the main loop components. This includes: determining the key links that cut off the continuous evolution path of large-scale eddies based on the structural and operational characteristics of the main loop components. The key links are the eddy-free subdomains of the main loop flow path, and the main loop fluid domain is divided into other main loop flow path subdomains using the key links as nodes.

[0045] It should be noted that the absence of vortices in the vortex-free domain of the main loop flow path specifically refers to the absence of large-scale vortices. That is, the vortex-free domain of the main loop flow path may include smaller-scale vortices. Large-scale vortices are relative to the characteristic frequency f of the problem component. If the characteristic frequency of the problem component of interest is f, then large-scale vortices refer to vortices with a characteristic frequency ≤ 0.8f, where the size of the vortex is inversely proportional to the characteristic frequency.

[0046] Specifically, the porous media structure of the reactor core and steam generator heat transfer tubes has the effect of actively trimming the turbulent kinetic energy spectrum (i.e., transferring large-scale eddy energy to small-scale and accelerating its dissipation), which can be regarded as a key link in cutting off the eddy evolution path; the main pump impeller is the main loop energy input source and turbulence generator, and its working characteristics will fundamentally change the structure and energy distribution of its downstream flow field, which can also be regarded as a key link in cutting off the continuous evolution path of eddies.

[0047] In general, porous media refer to solid materials containing a large number of interconnected or closed pores (cavities). In computational fluid dynamics analysis, it is a numerical modeling method that simplifies complex geometries. It does not precisely characterize every pore, but uses macroscopic physical effects to represent the influence of fluid flowing through the region, in order to balance computational cost and simulation accuracy in the simulation.

[0048] like Figure 3As shown, the main loop fluid domain is divided into six main loop flow path subdomains based on key nodes: ① Main pump impeller outlet to reactor core inlet; ② Core inlet to core outlet; ③ Core outlet to steam generator heat transfer tube inlet; ④ Steam generator heat transfer tube inlet to heat transfer tube outlet; ⑤ Steam generator heat transfer tube outlet to main pump impeller inlet; ⑥ Main pump impeller inlet to impeller outlet. Among these, ②, ④, and ⑥ are key nodes, which are vortex-free subdomains of the main loop flow path. ①, ③, and ⑤ are the other main loop flow path subdomains. By establishing a comprehensive flow path division system, a feasible solution is proposed to address the problem that existing technologies cannot fully trace the source of vibration anomalies in main loop components with complex structures, enabling more precise and efficient monitoring of fluid flow within the main loop.

[0049] In some embodiments, the main loop flow path subdomain includes at least one main loop component within the minimum modeling range. Examples include the reactor core, the heat transfer tubes of the steam generator, and the main pump impeller.

[0050] Set up corresponding physical models for different main loop flow path subdomains, including: A porous medium model was used for the reactor core and the heat transfer tube region of the steam generator; For other main loop flow path subdomains, use a real geometric model or an equivalent model.

[0051] The use of a porous media model for the reactor core and steam generator heat transfer tube regions is due to the complexity of these regions within the main loop. Existing computer resources cannot perform modeling and calculations of the true structure; therefore, a porous media model is typically used to represent these two parts as equivalents. The main pump impeller can be modeled using a momentum source term model (this method does not require establishing a true geometric model of the rotating components of the main pump; it achieves this by adding source terms to the momentum equation of the corresponding region, resulting in low computational cost; these source terms include parameters such as pressure and velocity), or a true impeller geometric model can be established (this method uses multiple reference frames or sliding meshes to realize the relative motion of the pump's moving and stationary components, resulting in high computational cost but more accurate simulation of the rotating flow effect generated by the pump). For other main loop flow path subdomains (such as main loop flow path subdomains ①, ③, and ⑤), a true geometric model can be selected based on the required computational accuracy, or an equivalent model can be selected based on the required computational efficiency.

[0052] In some embodiments, corresponding physical models are set for different main loop flow path subdomains, including: spatially discretizing the main loop fluid domain into partitions to obtain a main loop numerical model, and setting corresponding physical models for different main loop flow path subdomains based on the main loop numerical model.

[0053] The spatial discretization of the main loop fluid domain into subdomains aims to obtain higher-quality, more realistic discrete grids based on the geometric characteristics of each main loop flow path subdomain, thus ensuring high efficiency and accuracy for subsequent numerical calculations. Grid discretization breaks down the main loop fluid domain into tens of millions of grid nodes, which form the basis for obtaining unsteady flow parameters.

[0054] In some embodiments, given operating condition data, including: the heat flux density per unit volume corresponding to the operating conditions of the heat source and cold source in the given main loop fluid domain.

[0055] In some embodiments, given operating condition data and after setting the calculation time step and the total physical calculation time, simulation calculation is performed to obtain the unsteady flow parameters of the main loop. This includes: given operating condition data, setting the calculation time step to be less than or equal to a first preset threshold, starting the simulation calculation when the total physical calculation time is greater than a second preset threshold, and collecting data after the calculation time is greater than or equal to a third preset threshold, and storing the unsteady flow parameters of the main loop; wherein, the unsteady flow parameters of the main loop include global velocity and global pressure.

[0056] Specifically, for the heat source (core) and cold source (steam generator heat transfer tubes) in the main loop fluid domain, the unit volume heat flux density (total power / volume, positive for heat source, negative for cold source) corresponding to the nuclear power plant operating conditions is given. The calculation time step is set to ≤0.01s, and the total calculation time is >5s. Transient unsteady flow parameters such as velocity and pressure changing over time are acquired. Data acquisition begins after the calculation time is ≥1s, and snapshots of the unsteady flow parameters such as velocity and pressure are stored at uniform time intervals (≤0.05s). It should be noted that the above parameters are only examples and can be set to other values ​​as needed.

[0057] In some embodiments, after obtaining the dynamic parameters of the problematic component, the method further includes: adjusting the time step for calculating the unsteady flow parameters of the main loop and the total physical calculation time based on the dynamic parameters.

[0058] In some embodiments, adjusting the time step and total physical duration for calculating the unsteady flow parameters of the main loop according to the dynamic parameters includes: adjusting the time step and total physical duration for calculating the unsteady flow parameters of the main loop so that the frequency range of the unsteady flow parameters of the main loop covers the characteristic frequency of the dynamic parameters of the problem component; wherein the time step is S, the total physical duration is T, and the characteristic frequency of the dynamic parameters of the problem component is f, i.e., satisfying 1 / (2×S)≥f≥1 / T.

[0059] Specifically, total physical duration = time step × number of time steps. The frequency range from which unsteady flow parameters can be resolved in the frequency domain is: highest frequency = 1 / (2 × time step), lowest frequency = 1 / total physical duration. It should be ensured that the highest frequency ≥ the characteristic frequency of the problematic component ≥ the lowest frequency; only under these conditions can the unsteady flow parameters reflect the flow characteristics related to the characteristic frequency of the problematic component.

[0060] In some embodiments, after obtaining the dynamic parameters of the problematic component, the method further includes: The accuracy of the excitation load on the problematic component is verified by comparing its dynamic parameters with the measured values, thereby determining whether the calculation model of the unsteady flow parameters in the main loop needs to be adjusted. The calculation model includes the numerical model of the main loop and the corresponding physical model for different sub-control bodies.

[0061] Specifically, a structural dynamics model of the problematic component is established to obtain its dynamic parameters (the excitation load acts on the problematic component, causing deformation and stress; these deformation displacements and stresses are the dynamic parameters of the problematic component, which can be obtained through simulation calculations). These parameters are then compared with measured values ​​to indirectly confirm the correctness of the excitation load, thereby confirming the correctness of the flow field calculation (the excitation load is the result of the flow field calculation), and finally determining whether it is necessary to adjust the calculation model of the unsteady flow parameters of the main loop.

[0062] In some embodiments, the accuracy of the excitation load of the problematic component is verified by comparing the dynamic parameters of the problematic component with the measured values, and then it is determined whether the calculation model of the unsteady flow parameters of the main loop needs to be adjusted. This includes: if the absolute difference between the dynamic parameters of the problematic component and the measured values ​​is less than or equal to a preset error range threshold, it indicates that the excitation load of the problematic component is accurate and no adjustment of the calculation model is required; if the absolute difference between the dynamic parameters of the problematic component and the measured values ​​is greater than the preset error range threshold, it indicates that the excitation load of the problematic component is inaccurate and the calculation model needs to be adjusted.

[0063] Determining whether the calculation model for unsteady flow parameters in the main loop needs adjustment by comparing the absolute difference between the dynamic parameters of the problematic component and the measured values ​​ensures the accuracy of the flow field data for subsequent correlation analysis.

[0064] In some embodiments, the unsteady flow parameters of the main loop include the unsteady flow parameters at the inlet of the region where the problem component is located. A numerical model of the region where the problem component is located is established based on the main loop flow path subdomain and the unsteady flow parameters of the main loop, and the excitation load of the problem component is calculated. This includes: if the problem component is located in the heat transfer tube region of the reactor core or steam generator, or in other regions using an equivalent model, a real geometric model needs to be further established in the region where the problem component is located, and the unsteady flow calculation of the region where the problem component is located is carried out using the unsteady flow parameters at the inlet of the region where the problem component is located as boundary conditions to obtain the excitation load of the problem component; otherwise, the unsteady flow calculation of the region where the problem component is located is directly carried out based on the unsteady flow parameters of the main loop to obtain the excitation load of the problem component.

[0065] Specifically, if the abnormal vibration component is located in one of the following regions: ② from the core inlet to the core outlet, ④ from the steam generator heat transfer tube inlet to the heat transfer tube outlet, or ⑥ from the main pump impeller inlet to the impeller outlet (where ⑥ only applies to the case where the equivalent momentum source term model is used for the main loop modeling), it is also necessary to establish a true geometric model of ② / ④ / ⑥. The flow parameters at the inlets of regions ② / ④ / ⑥ are used as boundary conditions to conduct computational fluid dynamics analysis of the main loop flow path subdomains of ② / ④ / ⑥ to obtain the excitation load of the problematic component. If the abnormal vibration component is located in one of the following regions: ① from the main pump impeller outlet to the reactor core inlet, ③ from the core outlet to the steam generator heat transfer tube inlet, or ⑤ from the steam generator heat transfer tube outlet to the main pump impeller inlet, the excitation load of the problematic component can be obtained directly from the calculation results of the unsteady flow parameters.

[0066] In some embodiments, the key element is the vortex-free domain of the main loop flow path, and the main loop fluid domain is divided into other main loop flow path subdomains using the key element as a node. These subdomains include: a first other main loop flow path subdomain located between the main pump impeller and the reactor core, a second other main loop flow path subdomain located between the reactor core and the steam generator, and a third other main loop flow path subdomain located between the steam generator and the main pump impeller.

[0067] In some embodiments, typical geometries that easily induce large-scale separation vortices or vortex shedding include: the main pump casing, cold pipe section elbow, pressure vessel inlet pipe, pressure vessel descending annular cavity, and lower end cap located in the first other main loop flow path subdomain; the upper chamber cylindrical structure, outlet nozzle, heat pipe section elbow, and steam generator bottom inlet end cap located in the second other main loop flow path subdomain; and the steam generator bottom outlet end cap, transition section elbow, and main pump guide vanes located in the third other main loop flow path subdomain. Specifically, the first other main loop flow path subdomain is ① from the main pump impeller outlet to the reactor core inlet, the second other main loop flow path subdomain is ③ from the core outlet to the steam generator heat transfer tube inlet, and the third other main loop flow path subdomain is ⑤ from the steam generator heat transfer tube outlet to the main pump impeller inlet.

[0068] In some embodiments, identifying large-scale eddies in typical geometries includes: performing data processing on unsteady flow parameters to extract high-energy, low-frequency components at the location of large-scale eddies, thereby identifying large-scale eddies in typical geometries.

[0069] Specifically, data processing is performed based on the obtained unsteady flow parameters. The data processing methods include using the power spectral density method for frequency domain decomposition to identify the characteristic frequency range and the low-frequency bands with significant energy (usually a few hertz to tens of hertz), and quantifying their energy proportion by frequency band integration; using intrinsic orthogonal decomposition or spectral intrinsic orthogonal decomposition to determine the flow principal mode of the location of large-scale eddies, extracting the high-energy low-frequency components at the location of large-scale eddies, thereby identifying large-scale eddies in typical geometric structures.

[0070] Vortex structures are the primary source of pressure pulsations in a flow field. During transport, their morphology and intensity continuously evolve due to interactions with the mean flow, interactions with other vortices, and fluid viscous dissipation. The presence of vortex structures in the main loop causes fluctuations (pressure pulsations) in the internal pressure field of the fluid. Different vortex structures correspond to different frequency domain characteristics of pressure pulsations: small-scale vortices tend to generate high-frequency pressure pulsations, which are usually dissipated rapidly, while large-scale vortices tend to generate low-frequency pressure pulsations, which dissipate slowly with the flow energy and can propagate to distant regions.

[0071] The process by which a fluid excitation source in the main circuit induces component vibration, such as... Figure 4As shown, specific structural regions in the main loop are more prone to inducing large-scale vortices (fluid excitation sources), such as the bottom head of pressure vessels, the bottom head of steam generators, and bends in main pipelines. Pressure pulsations generated in these regions can be transmitted to component surfaces at considerable distances, potentially causing component vibrations and affecting equipment operational safety. Therefore, identifying typical geometries that easily induce large-scale separation vortices or vortex shedding, and recognizing large-scale vortices within these typical geometries, is a crucial preparatory step for achieving accurate simulation and analysis of complex flow processes within the main loop, and for clearly describing the energy transfer path from fluid excitation sources within the main loop to components in specific regions.

[0072] Power spectral density is a statistical measure describing the power distribution of a random signal in the frequency domain. Its unit is power / frequency, which represents the distribution of a signal's power (or energy) in the frequency domain. It tells us how much power each frequency component of the signal contributes.

[0073] Cross-spectral density: The distribution of the joint power between two signals in the frequency domain. It reflects not only the amplitude relationship between the two signals at the same frequency, but also their phase relationship.

[0074] Intrinsic orthogonal decomposition method: A mathematical method for extracting feature information from discrete data. It decomposes the flow field into different modes based on differences in energy levels. Each mode is the product of orthogonal basis functions and a time function, and can be viewed as a time-varying flow structure with a specific energy amplitude.

[0075] Spectral eigenorthogonal decomposition method: A mathematical method for extracting single-frequency dominant spatiotemporal modes from unsteady flow field data. It can be understood as a method of frequency domain decomposition (Fourier transform) + eigenorthogonal decomposition. By performing eigenorthogonal decomposition on transient flow field data in the frequency domain, spatial orthogonal modes that are separated by frequency and have optimal energy are obtained.

[0076] In some embodiments, an analysis path including large-scale eddies is selected based on the main loop flow path subdomain where the problematic component is located, including: If the problematic component is located in a vortex-free subdomain of the main loop flow path, then an analysis path is selected for each of its adjacent main loop flow path subdomains. That is, if the problematic component is located in one of the main loop flow path subdomains in ② / ④ / ⑥, and large-scale vortices exist in ① / ③ / ⑤, then upstream and downstream analyses are required. For example, if the problematic component is located in ②, then an analysis path is selected in ① (upstream) and another in ③ (downstream).

[0077] Alternatively, if the problematic component is located in another main loop flow path subdomain, then an analysis path is selected within that subdomain. That is, if the problematic component is located on a path within one of the main loop flow path subdomains in ① / ③ / ⑤, and its upstream and downstream are already included in that path, any component exceeding that path will be truncated by ② / ④ / ⑥. Therefore, an analysis path is directly selected within the main loop flow path subdomain where the problematic component is located.

[0078] Furthermore, the starting point of the analysis path is a typical geometric structure region that is prone to inducing large-scale separation vortices or vortex shedding, and the ending point is the location of the problematic component.

[0079] In some embodiments, the vortex evolution law of the analysis path is calculated, and correlation analysis is performed on the signals of nearby points or adjacent cross sections of the analysis path to obtain the correlation analysis results. This includes: extracting a number of points or cross sections based on the distance and flow channel characteristics of the path; calculating the self-power spectral density of the point or cross section signals according to the fluid flow direction; then calculating the cross-power spectral density of the signals of two nearby points or adjacent cross sections; calculating the coherence coefficient of the two signals in the frequency domain; and extracting the phase spectrum contained in the cross-power spectral density. The distance and flow channel characteristics of the path are obtained during modeling. A point refers to a point on the flow path; a cross section is a plane perpendicular to the flow path.

[0080] The formulas for calculating the coherence coefficient and phase spectrum correlation are shown below: in For cross-power spectral density, These are the autopower spectral densities of the two signals, respectively. and These are the imaginary and real parts of the cross-spectral density, respectively.

[0081] In some embodiments, a number of points or sections are extracted based on the distance of the path and the flow channel features, including: if the distance of the path is L, and the distance between two adjacent points or two adjacent sections is ≤L / 10, the number of points or sections extracted is ≥10, wherein the flow channel features refer to the basic shape and geometric dimensions of the section.

[0082] It should be noted that a point refers to a point on the flow path; a cross section refers to a plane perpendicular to the flow path.

[0083] In some embodiments, the dynamic parameters of the problematic component include characteristic frequencies, coherence coefficients and phase spectra from correlation analysis results. By using the dynamic parameters of the problematic component and the correlation analysis results, the energy transfer relationship from large-scale vortices in the analysis path to the problematic component is determined, and the fluid excitation source of the problematic component is located. This includes: obtaining the characteristic frequencies of the dynamic parameters of the problematic component and the coherence coefficients and phase spectra from the correlation analysis results; if the frequency corresponding to the correlation analysis results is within a preset frequency range controlled by the characteristic frequencies of the dynamic parameters of the problematic component, the coherence coefficient is within a preset numerical range, and the phase spectrum changes stably, then it is determined that there is significant energy transfer from the large-scale vortex in the selected analysis path to the component, and the region generating the vortex is identified as the location of the main excitation source; otherwise, the analysis path including other large-scale vortices is selected again, and correlation analysis of signals from nearby points or adjacent cross-sections of the analysis path is performed to obtain the corresponding correlation analysis results. The above analysis is repeated until the location is successfully determined.

[0084] Furthermore, the characteristic frequency of the dynamic parameter of the problematic component is f, and the preset frequency range controlled by the characteristic frequency of the dynamic parameter of the problematic component is 0.8f~1.2f, and the preset numerical range is 0.8~1.

[0085] For example, if the characteristic frequency of the dynamic parameters of the problematic component is f, and the correlation analysis results show that the corresponding frequency falls within the preset frequency range of 0.8f to 1.2f, with a coherence coefficient between 0.8 and 1 and a stable phase spectrum, then it is determined that there is significant energy transfer from the large-scale vortex to the component in the selected analysis path, and the region generating this vortex is identified as the main excitation source location. It should be noted that the above values ​​are merely examples, and other values ​​may also apply.

[0086] In some embodiments, the method further includes: visualizing the evolution of the fluid excitation source, analyzing the causes of large-scale eddies, and optimizing the geometry at the location of the fluid excitation source until the vibration behavior of the problematic component reaches the design target.

[0087] Specifically, the unsteady flow parameters of the main loop flow path subdomain where the problem component is located are calculated. Post-processing methods such as streamlines, contour maps, and eddy spatial distribution of parameters such as pressure / velocity / turbulent kinetic energy are used to visualize the evolution of the fluid excitation source. The causes of large-scale eddies are analyzed, and the geometry of the location of the fluid excitation source is optimized until the vibration behavior of the problem component reaches the design target.

[0088] In some embodiments, the evolution of the fluid excitation source is visualized and the formation of large-scale eddies is analyzed, including: combining the unsteady flow parameters of the main loop to apply the eddy spatial distribution of large-scale eddies with the eddy identification criterion, reconstructing the large-scale eddies in three dimensions, and obtaining eddy structure parameters for the formation of large-scale eddies.

[0089] Among them, the vortex identification criteria include: Q criterion, Criteria, Δ criterion, Ω criterion. Vortex structure parameters include: vortex structure morphology, vortex structure scale, and vortex structure evolution frequency. The causes of large-scale vortices include: abrupt changes in cross-section, tortuous channels, surface protrusions, surface depressions, branching, confluence, and complex disturbance structures. Large-scale vortices are reconstructed in three dimensions, and their spatiotemporal evolution process is dynamically displayed.

[0090] Specifically, vortex structure criteria are a series of mathematical definitions based on flow field variables (mainly velocity gradients) used to objectively and automatically identify the location, shape and core region of vortex structures in complex flow fields. Q-criterion: compares local rotation rate and strain rate. The Lambda-Criterion criterion identifies the pressure minimum region. In inviscid, steady flow, the vortex core center is the local pressure minimum point. The Delta-Criterion criterion distinguishes local flow regimes based on the discriminant of the velocity gradient tensor. The Omega-Criterion criterion normalizes rotational and strain intensities, improving the accuracy of identification in low vorticity boundary regions.

[0091] In some embodiments, the vortex evolution law and correlation analysis results are verified based on the visualization results of the fluid excitation source evolution. Specifically, based on the visualization results of the fluid excitation source evolution, the vortex evolution process along the analysis path from the determined main excitation source location to the abnormal vibration component is observed to verify the vortex evolution law and correlation analysis results.

[0092] like Figure 5 As shown, some embodiments of the present invention disclose a system for identifying and locating fluid excitation sources within a main circuit, comprising: The detection and calculation module is used to detect the main loop flow path subdomain where the problematic component, which is experiencing abnormal vibration due to fluid excitation, is located, and to establish a structural dynamics model of the problematic component to obtain its dynamic parameters. The identification module is used to determine typical geometric structures in the main loop flow path subdomain that are prone to inducing large-scale separation vortices or vortex shedding, and to identify large-scale vortices in typical geometric structures. The analysis module is used to select an analysis path including large-scale eddies based on the main loop flow path subdomain where the problematic component is located, calculate the eddy evolution law of the analysis path, and perform correlation analysis on signals from nearby points or adjacent cross-sections of the analysis path to obtain the correlation analysis results; and, The localization module is used to determine the energy transfer relationship from the large-scale vortex to the problem component in the analysis path by using the dynamic parameters of the problem component and the correlation analysis results, and to locate the fluid excitation source of the problem component.

[0093] This embodiment detects the main loop flow path subdomain of the problematic component that experiences abnormal vibration due to fluid excitation, establishes a structural dynamics model of the problematic component to obtain its dynamic parameters, identifies large-scale eddies in typical geometric structures, selects analysis paths that include large-scale eddies, analyzes the correlation and spatiotemporal evolution of the flow field in different regions within the main loop, and finally accurately identifies the location of the fluid excitation source causing the abnormal vibration of the component, thus providing a foundation for subsequent optimization of the flow channel structure in the fluid excitation source region.

[0094] Specifically, based on statistical data of abnormal equipment vibration during actual operation of in-service nuclear power plants (i.e., vibration amplitude measured during actual power plant operation exceeding design values), the main loop flow path subdomain of the problematic component experiencing abnormal vibration due to fluid excitation is detected. Establishing the structural dynamics model of the problematic component requires knowledge of its geometric model, materials, and mechanical properties. Since the geometric model, materials, and mechanical properties are all known data, establishing the structural dynamics model of the component is common knowledge in mechanical analysis and will not be elaborated upon here. The dynamic parameters of the problematic component include: its characteristic frequency, mode shape, and response displacement.

[0095] In some embodiments, the system further includes: a modeling module, a partitioning module, and a simulation module; before detecting the main loop flow path subdomain where the problematic component with abnormal vibration due to fluid excitation is located, the modeling module is used to import the three-dimensional models of the main loop components into modeling software and connect them to obtain the main loop fluid domain; the partitioning module is used to divide the main loop fluid domain into several main loop flow path subdomains according to the structural and operational characteristics of the main loop components; the simulation module is used to set corresponding physical models for different main loop flow path subdomains, and after providing operating condition data and setting the calculation time step and total physical calculation time, perform simulation calculations to obtain the unsteady flow parameters of the main loop.

[0096] In some embodiments, establishing a structural dynamics model of the problematic component to obtain its dynamic parameters includes: establishing a numerical model of the region where the problematic component is located based on the main loop flow path subdomain where the problematic component is located and the unsteady flow parameters of the main loop, and calculating the excitation load of the problematic component; establishing a structural dynamics model of the problematic component and using the excitation load of the problematic component as input to obtain its dynamic parameters.

[0097] In some embodiments, the main loop components are imported into modeling software and connected to obtain the main loop fluid domain. This includes: determining the minimum modeling range for the main loop components; establishing a 3D model of the main loop components based on the structural parameters of each minimum modeling range; importing the main loop components into the modeling software and connecting the 3D models of the main loop components according to the main loop topology to obtain the main loop fluid domain. Specifically, after connecting the components, the modeling software (e.g., Solidworks, AutoCAD, CATIA, etc.) performs Boolean operations (e.g., merge, cut, intersection, wrap, etc.) on the geometry to obtain the main loop fluid domain.

[0098] In some embodiments, the minimum modeling scope is the reactor, steam generator, main pump, and piping connecting the reactor, steam generator, and main pump.

[0099] Determining the minimum modeling range for the main loop components, including the reactor, steam generator, main pump, or the pipelines connecting the reactor, steam generator, and main pump, and establishing a 3D model of the main loop components based on the structural parameters of each minimum modeling range, is a prerequisite for establishing a high-fidelity 3D numerical model of the main loop fluid domain, solving for unsteady flow parameters, and obtaining physical field data such as transient velocity and pressure across the entire domain.

[0100] In some embodiments, if a branch pipe and a voltage regulator are connected to the main pipe, the modeling of the corresponding branch pipe and voltage regulator is increased or decreased within the minimum modeling range based on the abnormal vibration of the problematic component.

[0101] Typically, the main pipeline is connected to multiple branch pipes and a pressure regulator (usually connected to a hot pipe section of a loop) to maintain pressure stability in the main loop. Depending on the abnormal vibration of the problematic component, the modeling of relevant branch pipes can be added or removed within the minimum modeling range of the main loop provided in this invention. Adding or removing the modeling of corresponding branch pipes and pressure regulators is beneficial for the accuracy of excitation source location and the simplification of the calculation of unsteady flow parameters in the main loop.

[0102] In some embodiments, the main loop fluid domain is divided into several main loop flow path subdomains based on the structural and operational characteristics of the main loop components. This includes: determining the key links that cut off the continuous evolution path of large-scale eddies based on the structural and operational characteristics of the main loop components. The key links are the eddy-free subdomains of the main loop flow path, and the main loop fluid domain is divided into other main loop flow path subdomains using the key links as nodes.

[0103] It should be noted that the absence of vortices in the vortex-free domain of the main loop flow path specifically refers to the absence of large-scale vortices. That is, the vortex-free domain of the main loop flow path may include smaller-scale vortices. Large-scale vortices are relative to the characteristic frequency f of the problem component. If the characteristic frequency of the problem component of interest is f, then large-scale vortices refer to vortices with a characteristic frequency ≤ 0.8f, where the size of the vortex is inversely proportional to the characteristic frequency.

[0104] Specifically, the porous media structure of the reactor core and steam generator heat transfer tubes has the effect of actively trimming the turbulent kinetic energy spectrum (i.e., transferring large-scale eddy energy to small-scale and accelerating its dissipation), which can be regarded as a key link in cutting off the eddy evolution path; the main pump impeller is the main loop energy input source and turbulence generator, and its working characteristics will fundamentally change the structure and energy distribution of its downstream flow field, which can also be regarded as a key link in cutting off the continuous evolution path of eddies.

[0105] In general, porous media refer to solid materials containing a large number of interconnected or closed pores (cavities). In computational fluid dynamics analysis, it is a numerical modeling method that simplifies complex geometries. It does not precisely characterize every pore, but uses macroscopic physical effects to represent the influence of fluid flowing through the region, in order to balance computational cost and simulation accuracy in the simulation.

[0106] like Figure 3 As shown, the main loop fluid domain is divided into six main loop flow path subdomains based on key nodes: ① Main pump impeller outlet to reactor core inlet; ② Core inlet to core outlet; ③ Core outlet to steam generator heat transfer tube inlet; ④ Steam generator heat transfer tube inlet to heat transfer tube outlet; ⑤ Steam generator heat transfer tube outlet to main pump impeller inlet; ⑥ Main pump impeller inlet to impeller outlet. Among these, ②, ④, and ⑥ are key nodes, which are vortex-free subdomains of the main loop flow path. ①, ③, and ⑤ are the other main loop flow path subdomains. By establishing a comprehensive flow path division system, a feasible solution is proposed to address the problem that existing technologies cannot fully trace the source of vibration anomalies in main loop components with complex structures, enabling more precise and efficient monitoring of fluid flow within the main loop.

[0107] In some embodiments, the main loop flow path subdomain includes at least one main loop component within the minimum modeling range. Examples include the reactor core, the heat transfer tubes of the steam generator, and the main pump impeller.

[0108] Set up corresponding physical models for different main loop flow path subdomains, including: A porous medium model was used for the reactor core and the heat transfer tube region of the steam generator; For other main loop flow path subdomains, use a real geometric model or an equivalent model.

[0109] The use of a porous media model for the reactor core and steam generator heat transfer tube regions is due to the complexity of these regions within the main loop. Existing computer resources cannot perform modeling and calculations of the true structure; therefore, a porous media model is typically used to represent these two parts as equivalents. The main pump impeller can be modeled using a momentum source term model (this method does not require establishing a true geometric model of the rotating components of the main pump; it achieves this by adding source terms to the momentum equation of the corresponding region, resulting in low computational cost; these source terms include parameters such as pressure and velocity), or a true impeller geometric model can be established (this method uses multiple reference frames or sliding meshes to realize the relative motion of the pump's moving and stationary components, resulting in high computational cost but more accurate simulation of the rotating flow effect generated by the pump). For other main loop flow path subdomains (such as main loop flow path subdomains ①, ③, and ⑤), a true geometric model can be selected based on the required computational accuracy, or an equivalent model can be selected based on the required computational efficiency.

[0110] In some embodiments, corresponding physical models are set for different main loop flow path subdomains, including: spatially discretizing the main loop fluid domain into partitions to obtain a main loop numerical model, and setting corresponding physical models for different main loop flow path subdomains based on the main loop numerical model.

[0111] The spatial discretization of the main loop fluid domain into subdomains aims to obtain higher-quality, more realistic discrete grids based on the geometric characteristics of each main loop flow path subdomain, thus ensuring high efficiency and accuracy for subsequent numerical calculations. Grid discretization breaks down the main loop fluid domain into tens of millions of grid nodes, which form the basis for obtaining unsteady flow parameters.

[0112] In some embodiments, given operating condition data, including: the heat flux density per unit volume corresponding to the operating conditions of the heat source and cold source in the given main loop fluid domain.

[0113] In some embodiments, given operating condition data and after setting the calculation time step and the total physical calculation time, simulation calculation is performed to obtain the unsteady flow parameters of the main loop. This includes: given operating condition data, setting the calculation time step to be less than or equal to a first preset threshold, starting the simulation calculation when the total physical calculation time is greater than a second preset threshold, and collecting data after the calculation time is greater than or equal to a third preset threshold, and storing the unsteady flow parameters of the main loop; wherein, the unsteady flow parameters of the main loop include global velocity and global pressure.

[0114] Specifically, for the heat source (core) and cold source (steam generator heat transfer tubes) in the main loop fluid domain, the unit volume heat flux density (total power / volume, positive for heat source, negative for cold source) corresponding to the nuclear power plant operating conditions is given. The calculation time step is set to ≤0.01s, and the total calculation time is >5s. Transient unsteady flow parameters such as velocity and pressure changing over time are acquired. Data acquisition begins after the calculation time is ≥1s, and snapshots of the unsteady flow parameters such as velocity and pressure are stored at uniform time intervals (≤0.05s). It should be noted that the above parameters are only examples and can be set to other values ​​as needed.

[0115] In some embodiments, after obtaining the dynamic parameters of the problematic component, the detection calculation module is also used to adjust the time step and the total physical calculation time of the unsteady flow parameters of the main loop according to the dynamic parameters.

[0116] In some embodiments, adjusting the time step and total physical duration for calculating the unsteady flow parameters of the main loop according to the dynamic parameters includes: adjusting the time step and total physical duration for calculating the unsteady flow parameters of the main loop so that the frequency range of the unsteady flow parameters of the main loop covers the characteristic frequency of the dynamic parameters of the problem component; wherein the time step is S, the total physical duration is T, and the characteristic frequency of the dynamic parameters of the problem component is f, i.e., satisfying 1 / (2×S)≥f≥1 / T.

[0117] Specifically, total physical duration = time step × number of time steps. The frequency range from which unsteady flow parameters can be resolved in the frequency domain is: highest frequency = 1 / (2 × time step), lowest frequency = 1 / total physical duration. It should be ensured that the highest frequency ≥ the characteristic frequency of the problematic component ≥ the lowest frequency; only under these conditions can the unsteady flow parameters reflect the flow characteristics related to the characteristic frequency of the problematic component.

[0118] In some embodiments, after obtaining the dynamic parameters of the problematic component, the method further includes: The accuracy of the excitation load on the problematic component is verified by comparing its dynamic parameters with the measured values, thereby determining whether the calculation model of the unsteady flow parameters in the main loop needs to be adjusted. The calculation model includes the numerical model of the main loop and the corresponding physical model for different sub-control bodies.

[0119] Specifically, the dynamic parameters of the problematic component are obtained (the excitation load acts on the problematic component, and the component will produce deformation and stress. The deformation displacement and stress of these problematic components are the dynamic parameters of the problematic component, which can be obtained through simulation calculation), and compared with the measured values ​​to indirectly confirm the correctness of the excitation load, and then confirm the correctness of the flow field calculation (the excitation load is the result of the flow field calculation), and then determine whether it is necessary to adjust the calculation model of the unsteady flow parameters of the main loop.

[0120] In some embodiments, the accuracy of the excitation load of the problematic component is verified by comparing the dynamic parameters of the problematic component with the measured values, and then it is determined whether the calculation model of the unsteady flow parameters of the main loop needs to be adjusted. This includes: if the absolute difference between the dynamic parameters of the problematic component and the measured values ​​is less than or equal to a preset error range threshold, it indicates that the excitation load of the problematic component is accurate and no adjustment of the calculation model is required; if the absolute difference between the dynamic parameters of the problematic component and the measured values ​​is greater than the preset error range threshold, it indicates that the excitation load of the problematic component is inaccurate and the calculation model needs to be adjusted.

[0121] Determining whether the calculation model for unsteady flow parameters in the main loop needs adjustment by comparing the absolute difference between the dynamic parameters of the problematic component and the measured values ​​ensures the accuracy of the flow field data for subsequent correlation analysis.

[0122] In some embodiments, the unsteady flow parameters of the main loop include the unsteady flow parameters at the inlet of the region where the problem component is located. Based on the main loop flow path subdomain where the problem component is located and the unsteady flow parameters of the main loop, a numerical model of the region where the problem component is located is established, and the excitation load of the problem component is calculated. This includes: if the problem component is located in the heat transfer tube region of the reactor core or steam generator, or in the main pump region and is equivalent to a momentum source term model, a real geometric model needs to be further established in the region where the problem component is located, and the unsteady flow calculation of the region where the problem component is located is carried out using the unsteady flow parameters at the inlet of the region where the problem component is located as boundary conditions to obtain the excitation load of the problem component; otherwise, the unsteady flow calculation of the region where the problem component is located is carried out directly based on the unsteady flow parameters of the main loop to obtain the excitation load of the problem component.

[0123] Specifically, if the abnormal vibration component is located in one of the following regions: ② from the core inlet to the core outlet, ④ from the steam generator heat transfer tube inlet to the heat transfer tube outlet, or ⑥ from the main pump impeller inlet to the impeller outlet (where ⑥ only applies to the case where the equivalent momentum source term model is used for the main loop modeling), it is also necessary to establish a true geometric model of ② / ④ / ⑥. The flow parameters at the inlets of regions ② / ④ / ⑥ are used as boundary conditions to conduct computational fluid dynamics analysis of the main loop flow path subdomains of ② / ④ / ⑥ to obtain the excitation load of the problematic component. If the abnormal vibration component is located in one of the following regions: ① from the main pump impeller outlet to the reactor core inlet, ③ from the core outlet to the steam generator heat transfer tube inlet, or ⑤ from the steam generator heat transfer tube outlet to the main pump impeller inlet, the excitation load of the problematic component can be obtained directly from the calculation results of the unsteady flow parameters.

[0124] In some embodiments, the key element is the vortex-free domain of the main loop flow path, and the main loop fluid domain is divided into other main loop flow path subdomains using the key element as a node. These subdomains include: a first other main loop flow path subdomain located between the main pump impeller and the reactor core, a second other main loop flow path subdomain located between the reactor core and the steam generator, and a third other main loop flow path subdomain located between the steam generator and the main pump impeller.

[0125] In some embodiments, typical geometries that easily induce large-scale separation vortices or vortex shedding include: the main pump casing, cold pipe section elbow, pressure vessel inlet pipe, pressure vessel descending annular cavity, and lower end cap located in the first other main loop flow path subdomain; the upper chamber cylindrical structure, outlet nozzle, heat pipe section elbow, and steam generator bottom inlet end cap located in the second other main loop flow path subdomain; and the steam generator bottom outlet end cap, transition section elbow, and main pump guide vanes located in the third other main loop flow path subdomain. Specifically, the first other main loop flow path subdomain is ① from the main pump impeller outlet to the reactor core inlet, the second other main loop flow path subdomain is ③ from the core outlet to the steam generator heat transfer tube inlet, and the third other main loop flow path subdomain is ⑤ from the steam generator heat transfer tube outlet to the main pump impeller inlet.

[0126] In some embodiments, identifying large-scale eddies in typical geometries includes: performing data processing on unsteady flow parameters to extract high-energy, low-frequency components at the location of large-scale eddies, thereby identifying large-scale eddies in typical geometries.

[0127] Specifically, data processing is performed based on the obtained unsteady flow parameters. The data processing methods include using the power spectral density method for frequency domain decomposition to identify the characteristic frequency range and the low-frequency bands with significant energy (usually a few hertz to tens of hertz), and quantifying their energy proportion by frequency band integration; using intrinsic orthogonal decomposition or spectral intrinsic orthogonal decomposition to determine the flow principal mode of the location of large-scale eddies, extracting the high-energy low-frequency components at the location of large-scale eddies, thereby identifying large-scale eddies in typical geometric structures.

[0128] Vortex structures are the primary source of pressure pulsations in a flow field. During transport, their morphology and intensity continuously evolve due to interactions with the mean flow, interactions with other vortices, and fluid viscous dissipation. The presence of vortex structures in the main loop causes fluctuations (pressure pulsations) in the internal pressure field of the fluid. Different vortex structures correspond to different frequency domain characteristics of pressure pulsations: small-scale vortices tend to generate high-frequency pressure pulsations, which are usually dissipated rapidly, while large-scale vortices tend to generate low-frequency pressure pulsations, which dissipate slowly with the flow energy and can propagate to distant regions.

[0129] The process by which a fluid excitation source in the main circuit induces component vibration, such as... Figure 4As shown, specific structural regions in the main loop are more prone to inducing large-scale vortices (fluid excitation sources), such as the bottom head of pressure vessels, the bottom head of steam generators, and bends in main pipelines. Pressure pulsations generated in these regions can be transmitted to component surfaces at considerable distances, potentially causing component vibrations and affecting equipment operational safety. Therefore, identifying typical geometries that easily induce large-scale separation vortices or vortex shedding, and recognizing large-scale vortices within these typical geometries, is a crucial preparatory step for achieving accurate simulation and analysis of complex flow processes within the main loop, and for clearly describing the energy transfer path from fluid excitation sources within the main loop to components in specific regions.

[0130] Power spectral density is a statistical measure describing the power distribution of a random signal in the frequency domain. Its unit is power / frequency, which represents the distribution of a signal's power (or energy) in the frequency domain. It tells us how much power each frequency component of the signal contributes.

[0131] Cross-spectral density: The distribution of the joint power between two signals in the frequency domain. It reflects not only the amplitude relationship between the two signals at the same frequency, but also their phase relationship.

[0132] Intrinsic orthogonal decomposition method: A mathematical method for extracting feature information from discrete data. It decomposes the flow field into different modes based on differences in energy levels. Each mode is the product of orthogonal basis functions and a time function, and can be viewed as a time-varying flow structure with a specific energy amplitude.

[0133] Spectral eigenorthogonal decomposition method: A mathematical method for extracting single-frequency dominant spatiotemporal modes from unsteady flow field data. It can be understood as a method of frequency domain decomposition (Fourier transform) + eigenorthogonal decomposition. By performing eigenorthogonal decomposition on transient flow field data in the frequency domain, spatial orthogonal modes that are separated by frequency and have optimal energy are obtained.

[0134] In some embodiments, an analysis path including large-scale eddies is selected based on the main loop flow path subdomain where the problematic component is located, including: If the problematic component is located in a vortex-free subdomain of the main loop flow path, then an analysis path is selected for each of its adjacent main loop flow path subdomains. That is, if the problematic component is located in one of the main loop flow path subdomains in ② / ④ / ⑥, and large-scale vortices exist in ① / ③ / ⑤, then upstream and downstream analyses are required. For example, if the problematic component is located in ②, then an analysis path is selected in ① (upstream) and another in ③ (downstream).

[0135] Alternatively, if the problematic component is located in another main loop flow path subdomain, then an analysis path is selected within that subdomain. That is, if the problematic component is located on a path within one of the main loop flow path subdomains in ① / ③ / ⑤, and its upstream and downstream are already included in that path, any component exceeding that path will be truncated by ② / ④ / ⑥. Therefore, an analysis path is directly selected within the main loop flow path subdomain where the problematic component is located.

[0136] Furthermore, the starting point of the analysis path is a typical geometric structure region that is prone to inducing large-scale separation vortices or vortex shedding, and the ending point is the location of the problematic component.

[0137] In some embodiments, the vortex evolution law of the analysis path is calculated, and correlation analysis is performed on the signals of nearby points or adjacent cross sections of the analysis path to obtain the correlation analysis results. This includes: extracting a number of points or cross sections based on the distance and flow channel characteristics of the path; calculating the self-power spectral density of the point or cross section signals according to the fluid flow direction; then calculating the cross-power spectral density of the signals of two nearby points or adjacent cross sections; calculating the coherence coefficient of the two signals in the frequency domain; and extracting the phase spectrum contained in the cross-power spectral density. The distance and flow channel characteristics of the path are obtained during modeling. A point refers to a point on the flow path; a cross section is a plane perpendicular to the flow path.

[0138] The formulas for calculating the coherence coefficient and phase spectrum correlation are shown below: in For cross-power spectral density, These are the autopower spectral densities of the two signals, respectively. and These are the imaginary and real parts of the cross-spectral density, respectively.

[0139] In some embodiments, a number of points or sections are extracted based on the distance of the path and the flow channel features, including: if the distance of the path is L, and the distance between two adjacent points or two adjacent sections is ≤L / 10, the number of points or sections extracted is ≥10, wherein the flow channel features refer to the basic shape and geometric dimensions of the section.

[0140] It should be noted that a point refers to a point on the flow path; a cross section refers to a plane perpendicular to the flow path.

[0141] In some embodiments, the dynamic parameters of the problematic component include characteristic frequencies, coherence coefficients and phase spectra from correlation analysis results. By using the dynamic parameters of the problematic component and the correlation analysis results, the energy transfer relationship from large-scale vortices in the analysis path to the problematic component is determined, and the fluid excitation source of the problematic component is located. This includes: obtaining the characteristic frequencies of the dynamic parameters of the problematic component and the coherence coefficients and phase spectra from the correlation analysis results; if the frequency corresponding to the correlation analysis results is within a preset frequency range controlled by the characteristic frequencies of the dynamic parameters of the problematic component, the coherence coefficient is within a preset numerical range, and the phase spectrum changes stably, then it is determined that there is significant energy transfer from the large-scale vortex in the selected analysis path to the component, and the region generating the vortex is identified as the location of the main excitation source; otherwise, the analysis path including other large-scale vortices is selected again, and correlation analysis of signals from nearby points or adjacent cross-sections of the analysis path is performed to obtain the corresponding correlation analysis results. The above analysis is repeated until the location is successfully determined.

[0142] Furthermore, the characteristic frequency of the dynamic parameter of the problematic component is f, and the preset frequency range controlled by the characteristic frequency of the dynamic parameter of the problematic component is 0.8f~1.2f, and the preset numerical range is 0.8~1.

[0143] For example, if the characteristic frequency of the dynamic parameters of the problematic component is f, and the correlation analysis results show that the corresponding frequency falls within the preset frequency range of 0.8f to 1.2f, with a coherence coefficient between 0.8 and 1 and a stable phase spectrum, then it is determined that there is significant energy transfer from the large-scale vortex to the component in the selected analysis path, and the region generating this vortex is identified as the main excitation source location. It should be noted that the above values ​​are merely examples, and other values ​​may also apply.

[0144] In some embodiments, the system further includes a visualization and causal analysis module. This module is used to visualize the evolution of the fluid excitation source, analyze the causes of large-scale eddies, and optimize the geometry at the location of the fluid excitation source until the vibration behavior of the problematic component reaches the design target.

[0145] Specifically, the unsteady flow parameters of the main loop flow path subdomain where the problem component is located are calculated. Post-processing methods such as streamlines, contour maps, and eddy spatial distribution of parameters such as pressure / velocity / turbulent kinetic energy are used to visualize the evolution of the fluid excitation source. The causes of large-scale eddies are analyzed, and the geometry of the location of the fluid excitation source is optimized until the vibration behavior of the problem component reaches the design target.

[0146] In some embodiments, the evolution of the fluid excitation source is visualized and the formation of large-scale eddies is analyzed, including: combining the unsteady flow parameters of the main loop to apply the eddy spatial distribution of large-scale eddies with the eddy identification criterion, reconstructing the large-scale eddies in three dimensions, and obtaining eddy structure parameters for the formation of large-scale eddies.

[0147] Among them, the vortex identification criteria include: Q criterion, Criteria, Δ criterion, Ω criterion. Vortex structure parameters include: vortex structure morphology, vortex structure scale, and vortex structure evolution frequency. The causes of large-scale vortices include: abrupt changes in cross-section, tortuous channels, surface protrusions, surface depressions, branching, confluence, and complex disturbance structures. Large-scale vortices are reconstructed in three dimensions, and their spatiotemporal evolution process is dynamically displayed.

[0148] Specifically, vortex structure criteria are a series of mathematical definitions based on flow field variables (mainly velocity gradients) used to objectively and automatically identify the location, shape and core region of vortex structures in complex flow fields. Q-criterion: compares local rotation rate and strain rate. The Lambda-Criterion criterion identifies the pressure minimum region. In inviscid, steady flow, the vortex core center is the local pressure minimum point. The Delta-Criterion criterion distinguishes local flow regimes based on the discriminant of the velocity gradient tensor. The Omega-Criterion criterion normalizes rotational and strain intensities, improving the accuracy of identification in low vorticity boundary regions.

[0149] In some embodiments, the visualization and causal analysis module is also used to verify the vortex evolution law and correlation analysis results based on the visualized display results of the fluid excitation source evolution. Specifically, based on the visualized display results of the fluid excitation source evolution, the vortex evolution process along the analysis path from the determined main excitation source location to the abnormal vibration component is observed to verify the vortex evolution law and correlation analysis results.

[0150] Some embodiments of the present invention also disclose a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method for identifying and locating fluid excitation sources in the main circuit as described in any of the above embodiments.

[0151] By implementing this invention, the following beneficial effects are achieved: 1) This invention proposes a method for establishing a high-fidelity three-dimensional numerical model of the main loop (determining the minimum modeling range for the reactor, steam generator, main pump, or pipelines connecting the reactor, steam generator, and main pump as the main loop components, and establishing a three-dimensional model of the main loop components based on the structural parameters of each minimum modeling range). The reactor core and steam generator heat transfer tube regions adopt a porous medium model, while the main pump region adopts an equivalent model (adding a source term to the momentum equation) or establishing a real impeller geometry model. This enables accurate analysis of complex flow processes within the main loop, establishes a high-fidelity three-dimensional numerical model of the main loop fluid domain, solves unsteady flow parameters, obtains physical field data such as transient velocity and pressure across the entire domain, and improves the understanding of fluid flow characteristics within the main loop.

[0152] 2) Based on the turbulent shearing characteristics of porous media and the turbulence generator characteristics of the main pump impeller, this invention proposes a method to divide the main loop fluid domain into six main loop flow path subdomains: ① Main pump impeller outlet to reactor core inlet; ② Core inlet to core outlet; ③ Core outlet to steam generator heat transfer tube inlet; ④ Steam generator heat transfer tube inlet to heat transfer tube outlet; ⑤ Steam generator heat transfer tube outlet to main pump impeller inlet; ⑥ Main pump impeller inlet to impeller outlet. By establishing a comprehensive flow path division system, this invention proposes a feasible solution to the problem that existing technologies cannot fully trace the source of vibration anomalies in main loop components with complex structures, and achieves efficient monitoring of fluid flow within the main loop.

[0153] 3) This invention employs various mathematical analysis methods to identify large-scale eddies and extract their features, accurately locating the energy generation region of low-frequency pressure pulsations. Combined with the structural dynamic parameters of the abnormally vibrating components, it comprehensively analyzes the correlation and spatiotemporal evolution of the flow field in different regions within the main loop of a nuclear power plant. It proposes a method for identifying significant energy transfer paths from selected eddies to components, achieving accurate location of the fluid excitation source causing abnormal component vibration. Combining the structural dynamic parameters of the abnormally vibrating components, it uses methods such as large-scale eddy source identification, eddy evolution correlation analysis, and turbulence evolution visualization to clearly describe the energy transfer path from the fluid excitation source in the main loop to components in specific regions.

[0154] 4) This invention establishes an iterative optimization closed-loop process of "main loop modeling and analysis - propagation path division - extraction of dynamic parameters of vibrating component structure - vortex identification and feature extraction - energy transfer path discrimination - fluid excitation source location - cause analysis - structural optimization - effect verification," providing a systematic analytical means for main loop flow channel optimization and component structure design, and proposing a complete solution from problem diagnosis to suppression. It realizes a closed-loop technical means from vortex source identification to flow channel structure optimization verification, enabling targeted flow channel structure improvements based on the characteristics of the fluid excitation source. This method can also be applied to flow-induced vibration control in nuclear power plants and other large-scale hydraulic systems, solving the problem of difficulty in systematically and comprehensively analyzing the causes of vibration in existing technologies, and improving the operational safety and reliability of nuclear power plants.

[0155] It is understood that the above embodiments only illustrate some implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above embodiments or technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. That is, the embodiments described "in some embodiments" can be freely combined with any of the preceding and following embodiments. Therefore, all equivalent transformations and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.

Claims

1. A method for identifying and locating fluid excitation sources within a main circuit, characterized in that, Includes the following steps: The main loop flow path subdomain where the problematic component that is vibrating abnormally due to fluid excitation is located is detected, and a structural dynamics model of the problematic component is established to obtain the dynamic parameters of the problematic component; In the main loop flow path subdomain, determine the typical geometric structures that are prone to inducing large-scale separation vortices or vortex shedding, and identify the large-scale vortices in the typical geometric structures. Based on the main loop flow path subdomain where the problematic component is located, an analysis path including the large-scale vortex is selected, the vortex evolution law of the analysis path is calculated, and correlation analysis is performed on the signals of nearby points or adjacent cross sections of the analysis path to obtain the correlation analysis results. By comparing the dynamic parameters of the problematic component with the correlation analysis results, the energy transfer relationship from the large-scale eddy to the problematic component in the analysis path is determined, and the fluid excitation source of the problematic component is located.

2. The method for identifying and locating the fluid excitation source in the main circuit according to claim 1, characterized in that, Before detecting the main loop flow path subdomain of the problematic component experiencing abnormal vibration due to fluid excitation, the process also includes: Import the 3D models of the main loop components into the modeling software and connect them to obtain the main loop fluid domain; Based on the structural and operational characteristics of the main loop components, the main loop fluid domain is divided into several main loop flow path subdomains. For different main loop flow path subdomains, set corresponding physical models, provide operating condition data, set the calculation time step and total physical calculation time, and then perform simulation calculations to obtain the unsteady flow parameters of the main loop.

3. The method for identifying and locating the fluid excitation source in the main circuit according to claim 2, characterized in that, The process of establishing a structural dynamics model of the problematic component to obtain its dynamic parameters includes: Based on the main loop flow path subdomain where the problematic component is located and the unsteady flow parameters of the main loop, a numerical model of the region where the problematic component is located is established, and the excitation load of the problematic component is calculated. A structural dynamics model of the problematic component is established, and the dynamic parameters of the problematic component are obtained by using the excitation load of the problematic component as input.

4. The method for identifying and locating the fluid excitation source in the main circuit according to claim 3, characterized in that, The process of importing the main loop components into the modeling software and connecting them to obtain the main loop fluid domain includes: Determine the minimum modeling range for the main loop components, establish a three-dimensional model of the main loop components based on the structural parameters of the minimum modeling range, import the main loop components into the modeling software respectively, and connect the three-dimensional models of the main loop components according to the main loop topology to obtain the main loop fluid domain; The minimum modeling scope includes the reactor, steam generator, main pump, and the piping connecting the reactor, steam generator, and main pump.

5. The method for identifying and locating the fluid excitation source in the main circuit according to claim 2, characterized in that, The process of dividing the main loop fluid domain into several main loop flow path subdomains based on the structural and operational characteristics of the main loop components includes: Based on the structural and operational characteristics of the main loop components, the key link that cuts off the continuous evolution path of large-scale eddies is determined. The key link is the eddy-free subdomain of the main loop flow path, and the main loop fluid domain is divided into other main loop flow path subdomains using the key link as a node.

6. The method for identifying and locating the fluid excitation source in the main circuit according to claim 4, characterized in that, The main loop flow path subdomain includes at least one main loop component within the minimum modeling range; Setting corresponding physical models for different main loop flow path subdomains includes: A porous media model is used for the reactor core and the heat transfer tube region of the steam generator; For other main loop flow path subdomains, use a real geometric model or an equivalent model.

7. The method for identifying and locating the fluid excitation source in the main circuit according to claim 3, characterized in that, Setting corresponding physical models for different main loop flow path subdomains includes: The main loop fluid domain is spatially discretized into a grid to obtain a main loop numerical model. Based on the main loop numerical model, corresponding physical models are set for different main loop flow path subdomains.

8. The method for identifying and locating the fluid excitation source in the main circuit according to claim 2, characterized in that, After providing the given operating condition data and setting the calculation time step and total physical calculation time, simulation calculations are performed to obtain the unsteady flow parameters of the main loop, including: Given operating condition data, the calculation time step is set to be less than or equal to a first preset threshold, and the simulation calculation begins when the total physical calculation time is greater than a second preset threshold. Data acquisition is performed after the calculation time is greater than or equal to a third preset threshold, and the unsteady flow parameters of the main loop are stored. The unsteady flow parameters of the main loop include global velocity and global pressure.

9. The method for identifying and locating the fluid excitation source in the main circuit according to claim 1, characterized in that, After obtaining the dynamic parameters of the problematic component, the method further includes: adjusting the time step and the total physical calculation time for calculating the unsteady flow parameters of the main loop based on the dynamic parameters.

10. The method for identifying and locating the fluid excitation source in the main circuit according to claim 9, characterized in that, The adjustment of the time step and total physical duration for calculating the unsteady flow parameters of the main loop based on the dynamic parameters includes: Adjust the time step and total physical duration for calculating the unsteady flow parameters of the main loop so that the frequency range of the unsteady flow parameters of the main loop covers the characteristic frequencies of the dynamic parameters of the problem component. Wherein, the time step is S, the total physical duration is T, and the characteristic frequency of the dynamic parameter of the problem component is f, that is, 1 / (2×S)≥f≥1 / T.

11. The method for identifying and locating the fluid excitation source in the main circuit according to claim 7, characterized in that, After obtaining the dynamic parameters of the problematic component, the process further includes: The accuracy of the excitation load on the problematic component is verified by comparing its dynamic parameters with the measured values, and then it is determined whether the calculation model of the unsteady flow parameters of the main loop needs to be adjusted. The computational model includes: the main loop numerical model and the corresponding physical model set for different main loop flow path subdomains.

12. The method for identifying and locating the fluid excitation source in the main circuit according to claim 6, characterized in that, The unsteady flow parameters of the main loop include the unsteady flow parameters at the inlet of the region where the problem component is located. The step of establishing a numerical model of the region where the problem component is located based on the main loop flow path subdomain where the problem component is situated and the unsteady flow parameters of the main loop, and then calculating the excitation load on the problem component, includes: If the problematic component is located in the reactor core or the heat transfer tube region of the steam generator, or in other regions using an equivalent model, a real geometric model needs to be further established in the region where the problematic component is located. Unsteady flow calculations are then performed in the region where the problematic component is located, using the unsteady flow parameters at the inlet of the region where the problematic component is located as boundary conditions, to obtain the excitation load of the problematic component. Otherwise, the unsteady flow calculation of the region where the problem component is located is carried out directly based on the unsteady flow parameters of the main loop to obtain the excitation load of the problem component.

13. The method for identifying and locating the fluid excitation source in the main circuit according to claim 5, characterized in that, The step of selecting an analysis path that includes the large-scale eddy based on the main loop flow path subdomain where the problematic component is located includes: If the problematic component is located in the vortex-free region of the main loop flow path, then an analysis path is selected for each of its adjacent main loop flow path sub-regions. Alternatively, if the problematic component is located in another main loop flow path subdomain, an analysis path is selected from the main loop flow path subdomain where the problematic component is located.

14. The method for identifying and locating the fluid excitation source in the main circuit according to claim 1, characterized in that, The calculation yields the vortex evolution law of the analysis path, and correlation analysis is performed on the signals of nearby points or adjacent cross sections of the analysis path to obtain the correlation analysis results, including: Based on the distance of the analysis path and the characteristics of the flow channel, a number of points or sections are extracted. According to the flow direction of the fluid, the self-power spectral density of the point or section signal is calculated respectively. Then, the cross-power spectral density of the signals of two adjacent points or adjacent sections is calculated in turn. The coherence coefficient of the two signals in the frequency domain is calculated and the phase spectrum contained in the cross-power spectral density is extracted.

15. The method for identifying and locating the fluid excitation source in the main circuit according to claim 14, characterized in that, The dynamic parameters of the problematic component include characteristic frequencies, coherence coefficients and phase spectra in the correlation analysis results. By comparing the dynamic parameters of the problematic component with the correlation analysis results, the energy transfer relationship from large-scale eddies to the problematic component in the analysis path is determined, and the fluid excitation source of the problematic component is located, including: If, within a preset frequency range controlled by the characteristic frequency of the dynamic parameters of the problematic component, the coherence coefficient is within a preset value range and the phase spectrum changes stably, then it is determined that there is significant energy transfer to the large-scale vortex-to-component along the selected analysis path, and the region that generates the vortex is identified as the main excitation source location; otherwise, the analysis path including other large-scale vortices is selected, and correlation analysis of the signals of nearby points or adjacent cross sections of the analysis path is performed to obtain the corresponding correlation analysis results. The above analysis is then repeated until the location is successfully determined.

16. The method for identifying and locating the fluid excitation source in the main circuit according to claim 15, characterized in that, The characteristic frequency of the dynamic parameter of the problematic component is f, and the preset frequency range controlled by the characteristic frequency of the dynamic parameter of the problematic component is 0.8f~1.2f, and the preset numerical range is 0.8~1.

17. The method for identifying and locating the fluid excitation source in the main circuit according to claim 2, characterized in that, The method also includes: The evolution of the fluid excitation source is visualized, the formation of the large-scale eddies is analyzed, and the geometry of the location of the fluid excitation source is optimized until the vibration behavior of the problematic component reaches the design target.

18. The method for identifying and locating the fluid excitation source in the main circuit according to claim 17, characterized in that, The visualization of the evolution of the fluid excitation source and the analysis of the origin of the large-scale eddies include: By combining the unsteady flow parameters of the main loop, the vortex spatial distribution of the large-scale vortex is analyzed using the vortex identification criterion. The large-scale vortex is then reconstructed in three dimensions, and the vortex structure parameters are obtained for the formation of the large-scale vortex.

19. A system for identifying and locating fluid excitation sources within a main circuit, characterized in that, include: The detection and calculation module is used to detect the main loop flow path subdomain where the problematic component that is vibrating abnormally due to fluid excitation is located, and to establish a structural dynamics model of the problematic component to obtain the dynamic parameters of the problematic component; The identification module is used to determine typical geometric structures in the main loop flow path subdomain that are prone to inducing large-scale separation vortices or vortex shedding, and to identify large-scale vortices in the typical geometric structures. The analysis module is used to select an analysis path including the large-scale vortex based on the main loop flow path subdomain where the problem component is located, calculate the vortex evolution law of the analysis path, and perform correlation analysis on the signals of nearby points or adjacent cross sections of the analysis path to obtain the correlation analysis results. as well as, The positioning module is used to determine the energy transfer relationship from the large-scale vortex to the problem component in the analysis path by using the dynamic parameters of the problem component and the correlation analysis results, and to locate the fluid excitation source of the problem component.

20. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the method for identifying and locating fluid excitation sources in the main circuit as described in any one of claims 1-18.

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