A test method and device for analyzing the dynamic characteristics of a nuclear main pump shaft system

Abstract

This invention relates to the field of nuclear main pump testing, and more particularly to a testing method and apparatus for analyzing the dynamic characteristics of nuclear main pump shaft systems. The method comprises: installing the testing apparatus, setting experimental parameters, and conducting initial operation; collecting vibration acceleration, displacement, fluid pressure, and temperature data using sensor units; processing the collected parameters to extract key characteristic parameters; constructing structural dynamics and fluid dynamics modules to process the fluid-structure interaction boundary; establishing a quantitative relationship model between parameters and vibration indices through parametric analysis and sensitivity quantification; verifying the accuracy of the quantitative relationship model by comparing numerical simulation results with experimentally measured vibration data, thereby forming a complete dynamic model for predicting and optimizing the vibration of nuclear main pump shaft systems; and optimizing parameters using the dynamic model. This invention accurately analyzes the influence of the structural parameters and fluid dynamics parameters of the water-guided bearing on the vibration of the main pump shaft system, providing a scientific basis for the design optimization, fault diagnosis, and safe operation of nuclear main pumps.

Description

Technical Field

[0001] This invention relates to the field of nuclear main pump testing, and more particularly to a testing method and apparatus for analyzing the dynamic characteristics of the shaft system of a nuclear main pump. Background Technology

[0002] The main nuclear pump is a core component of the primary loop system in the nuclear island. Its main function is to drive the continuous circulation of coolant within the reactor coolant system. The safe and stable operation of the main nuclear pump directly affects the safety and stability of the nuclear power generation system. Operating the main nuclear pump continuously for extended periods under high temperature, high pressure, and high radiation conditions presents numerous challenges. Among these, the most complex is the associated abnormal vibration problem, which can lead to equipment damage, decreased system stability, and increased safety risks. Although some progress has been made in the research and mitigation of abnormal vibration in the main nuclear pump, some unresolved issues remain, the most critical of which is the shaft dynamics problem.

[0003] Pressurized water reactor nuclear power plants widely use vertical shaft-sealed nuclear main pumps, most of which employ a three-bearing design: two oil-lubricated radial bearings on the motor side and one water-lubricated radial bearing on the pump side. Extensive research has revealed that the water-lubricated bearing has a significant impact on the vibration characteristics of the nuclear main pump. However, currently, experimental research on the quantitative impact of the structural and hydrodynamic parameters of the water-lubricated bearing on the vibration of the main pump shaft system is lacking, and related technical methods and experimental equipment are insufficient. Existing nuclear main pump testing equipment is complex in structure, difficult to install and disassemble, and inconvenient for rotor core removal and maintenance operations, increasing equipment maintenance costs and time. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a test method and device for analyzing the dynamic characteristics of the shaft system of a nuclear main pump. By accurately analyzing the influence of the structural parameters and fluid dynamic parameters of the water-guided bearing on the vibration of the main pump shaft system, the invention provides a scientific basis for the design optimization, fault diagnosis and safe operation of the nuclear main pump, thereby solving the technical problems existing in the prior art, such as insufficient experimental means, complex devices, limited data acquisition and analysis capabilities and lack of basis for optimization design.

[0005] This invention provides a testing device for analyzing the dynamic characteristics of a nuclear main pump shaft system. It adopts a vertical structure, with each component assembled sequentially in a vertical direction, including:

[0006] The motor is fixed at the top by a support component; the motor's output shaft faces downwards and is directly connected to the coupling.

[0007] The lower end of the coupling is connected to the rotating shaft, the bearing seat is fixed to the inner wall of the cylinder, and the water guide bearing is installed in the bearing seat, forming a clearance fit with the rotating shaft.

[0008] The impeller is installed at the bottom of the shaft, inside the cylinder;

[0009] Vibration sensors collect cylinder vibration data; eddy current displacement sensors collect axial displacement data at the water guide bearing; pressure sensors collect pressure pulsations at the water guide bearing; and temperature sensors collect and measure the fluid temperature at the water guide bearing.

[0010] In one specific embodiment of the present invention, the bearing seat is fixed on the inner wall of the cylinder, and the bushing of the water guide bearing is installed in the bearing seat, with the bushing and the rotating shaft forming a clearance fit; the rotating shaft rotates within the bushing.

[0011] In one specific embodiment of the present invention, the supporting component includes a motor bracket, an experimental component bracket, and an auxiliary bracket.

[0012] The motor bracket has its upper end connected to the lower end of the motor and its lower end connected to the test component bracket.

[0013] The experimental component support is connected to the upper end of the cylinder;

[0014] The auxiliary bracket is connected to the side of the motor at the top and fixed to the bottom surface at the bottom, forming a support for the motor.

[0015] This invention provides a test method for analyzing the dynamic characteristics of a nuclear main pump shaft system, comprising the following steps:

[0016] Step 1: Install the testing equipment, set the experimental parameters, and perform initial operation;

[0017] Step 2: Use the sensor unit to collect vibration acceleration, displacement, fluid pressure, and temperature data;

[0018] Step 3: Process the collected parameters and extract key feature parameters;

[0019] The processing method includes: using signal processing technology to perform bandpass filtering on the acquired high-frequency vibration acceleration and displacement signals, and using a bidirectional IIR filter architecture to achieve zero-phase delay filtering;

[0020] Adaptive variational mode decomposition is applied to the displacement and acceleration signals;

[0021] Detect phase coupling peaks, perform high-order spectral analysis to identify nonlinear coupling frequencies, and accurately locate bearing fluid vortex frequencies;

[0022] A data fusion algorithm is used to dynamically track the displacement of multiple displacement sensor signals by multi-sensor data fusion, construct a three-dimensional dynamic shaft center trajectory, and calculate the normal offset exponent to quantify the rotor motion state.

[0023] Collect pressure data from pressure sensors and generate a high-precision pressure distribution cloud map of the entire area in real time.

[0024] Step 4: Construct structural dynamics and fluid dynamics modules, process fluid-structure interaction boundaries, and establish a quantitative relationship model between parameters and vibration indices through parametric analysis and sensitivity quantification; verify the accuracy of the quantitative relationship model by comparing numerical simulation results with experimentally measured vibration data, and thus form a complete dynamic model for vibration prediction and optimization of the nuclear main pump shaft system.

[0025] Step 5: Optimize the parameters using the aforementioned dynamic model.

[0026] In a specific embodiment of the present invention, in step 2, the sensor unit is used to collect vibration acceleration data of different shaft sections of the rotor, displacement data of both sides of the rotor bearings at each cross section, vibration acceleration data of the motor housing and the cylinder housing, fluid pressure and temperature data of the water-conducting bearing, and flow rate, pressure and temperature parameters of the system pipeline.

[0027] In a specific embodiment of the present invention, step 4, constructing the structural dynamics module, specifically includes:

[0028] 1.1 Discretization of beam element model: The shaft system is discretized into multiple beam elements along the axial direction. Each element contains nodal mass and moment of inertia parameters. The vibration mode of the shaft system is described by the nodal degrees of freedom.

[0029] 1.2 Introduction of Gyro Effect: For high-speed rotating shaft systems, a gyro torque term related to the rotational speed is added to the dynamic equation to quantify the coupling effect of rotational angular velocity on the lateral vibration of the shaft system;

[0030] 1.3 Shear Deformation Correction: The traditional Euler beam model is corrected by adopting beam theory that considers shear deformation and ignoring the limitations of shear stiffness;

[0031] 1.4 Bearing support modeling: The bearing is simplified as an elastic support with cross-coupling characteristics. The cross terms in the stiffness matrix are obtained through experiments or bearing dynamic parameters to characterize the anisotropy of the bearing oil film force.

[0032] The construction of the fluid dynamics module specifically includes:

[0033] 2.1 Reynolds equation solution framework: Based on lubrication theory, an oil film pressure control equation is established. For the high-speed operation of the nuclear main pump, a turbulence correction factor is introduced to adapt to the flow state under high Reynolds number.

[0034] 2.2 Finite Volume Discretization: The flow field in the bearing clearance is divided into grid cells. The laws of mass conservation and momentum conservation are applied to each control volume. The pressure field is solved iteratively using the line-by-line scanning method or the multi-grid method. The convergence stability is ensured by the pressure-velocity coupling algorithm.

[0035] 2.3 Boundary condition settings: The journal surface is set as a rotating wall boundary, the bearing housing is set as a fixed wall, and the oil film inlet and outlet adopt pressure boundary or flow continuity conditions, considering the influence of centrifugal force on the oil film thickness distribution.

[0036] In a specific embodiment of the present invention, the fluid-structure interaction boundary treatment specifically includes:

[0037] 3.1 Definition of coupling interface: The journal surface is taken as the fluid-structure interaction interface. The fluid dynamics module calculates the oil film pressure distribution and converts it into a distributed force acting on the journal. The structural dynamics module solves the journal displacement and feeds it back to the fluid dynamics module to update the oil film thickness.

[0038] 3.2 Iterative solution process: The structural dynamics module initializes the journal position, and the fluid dynamics module calculates the initial oil film force; the structural dynamics module solves for the journal vibration displacement based on the oil film force; the fluid dynamics module updates the oil film clearance based on the new displacement and recalculates the oil film force; the above steps are repeated until the iterative residual between displacement and force is less than the set threshold.

[0039] In a specific embodiment of the present invention, the parametric analysis and sensitivity quantification, establishing a quantitative relationship model between these parameters and vibration indices, specifically includes:

[0040] 4.1 Screening of key variables;

[0041] 4.2 Parameter Space Design: Orthogonal experimental design or Latin hypercube sampling method is adopted to generate multiple sets of sample points within the parameter feasible region, and an input matrix containing various parameter combinations is constructed to cover single-factor and multi-factor coupled scenarios.

[0042] 4.3 Global Sensitivity Analysis: Perform fluid-structure interaction numerical simulations for each set of parameter samples, obtain response data, calculate the first-order Sobol exponent and total order exponent of each parameter, and sort and filter parameters with a contribution of more than 15%;

[0043] 4.4 Establish a quantitative relationship model between the parameters and vibration index.

[0044] In a specific embodiment of the present invention, step 3, which involves adaptive variational mode decomposition of the displacement and acceleration signals, specifically includes: firstly, estimating the number of modes K by the number of significant peaks in the power spectral density, and decomposing the signal into multiple intrinsic mode functions; then, based on the joint criterion of kurtosis and information entropy of each intrinsic mode function, automatically separating the characteristic components, which include bearing fluid noise, rotor imbalance, misalignment, and structural resonance.

[0045] In a specific embodiment of the present invention, the step of collecting pressure data from a pressure sensor and generating a high-precision pressure distribution cloud map of the entire area in real time specifically includes:

[0046] Real-time pressure data at discrete points is collected and preprocessed, with outliers being removed or missing values ​​being filled in.

[0047] Based on the spatial correlation of data, the Kriging interpolation algorithm is used to estimate the pressure value at any location within the region.

[0048] The region is divided into a fine grid, and a dynamic cloud map is generated by mapping the pressure value with color gradients. The latest data is incorporated through a sliding window to achieve real-time updates.

[0049] Compared with the prior art, the test method and apparatus of the present invention for analyzing the dynamic characteristics of the nuclear main pump shaft system have the following advantages:

[0050] (1) Based on the dynamic similarity theory, the rotor shaft system segment size and mass are controlled by the scaling criterion to maintain the equivalence of the dynamic characteristics of the prototype and the experimental device, so that the experimental results can directly guide the setting of the fault diagnosis threshold of the nuclear main pump. The device adopts a modular adjustable structure, with a core-pulling rotor and gap adjustment, to realize the rapid replacement and online adjustment of parameters, solving the problems of cumbersome disassembly and single working conditions of traditional experimental devices.

[0051] (2) Adaptive variational mode decomposition and kurtosis-entropy criterion are used to adaptively separate fault features, and high-order spectral analysis is combined to accurately locate nonlinear coupling frequencies. Real-time high-resolution reconstruction of shaft center trajectory and pressure gradient is achieved through bidirectional IIR zero-phase filtering, Kalman data fusion, and Kriging dynamic cloud map. The beam element model based on gyro effect correction and the Reynolds equation adapted to turbulence are solved, and the vibration response prediction accuracy is improved through strong coupling iteration. A fluid-vibration coupling decoupling analysis method is adopted, and the contribution rate of water film stiffness / damping of the main pump shaft system to vibration is quantified through embedded sensors and a computational model. Response surface-Gaussian process regression joint modeling is adopted to reveal the nonlinear coupling effect of gap, viscosity, and pressure, and the accuracy is significantly improved compared with the traditional regression model.

[0052] (3) By accurately measuring and analyzing the influence of the structural parameters and fluid dynamic parameters of the water-guided bearing on the shaft vibration, the abnormal vibration of the nuclear main pump can be effectively reduced, and the stability and safety of the equipment operation can be improved.

[0053] (4) It provides technical support for the design optimization and fault diagnosis of nuclear main pumps, which helps to extend the service life of equipment and reduce maintenance costs.

[0054] (5) It fills the gap in the quantitative study of the vibration of the main pump shaft system by the structural parameters and fluid dynamic parameters of the water-guided bearing, and provides new experimental methods and devices for research in related fields.

[0055] (6) It solves the vibration problem faced by the nuclear main pump when it is running in high temperature, high pressure and high radiation environment, reduces the safety risks caused by vibration, and ensures the safe operation of the nuclear power generation system. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the overall structure of a test method and apparatus for analyzing the dynamic characteristics of a nuclear main pump shaft system according to the present invention.

[0057] Figure 2 This is a diagram showing the support and external shape of the testing method and apparatus for analyzing the dynamic characteristics of the shaft system of a nuclear main pump according to the present invention.

[0058] Figure 3 This is a schematic diagram of a core-removable rotor for a test method and apparatus for analyzing the dynamic characteristics of a nuclear main pump shaft system according to the present invention.

[0059] In the diagram, 1 is the motor, 2 is the coupling, 3 is the experimental component, 4 is the support component, 5 is the sensor unit, 3-1 is the shaft seal, 3-2 is the rotating shaft, 3-3 is the bushing, 3-4 is the water guide bearing, 3-5 is the bearing housing, 3-6 is the cylinder, 4-1 is the motor bracket, 4-2 is the experimental component bracket, 4-3 is the auxiliary bracket, 5-1 is the eddy current displacement sensor, 5-2 is the vibration sensor, 5-3 is the pressure sensor, and 5-4 is the temperature sensor. Detailed Implementation

[0060] To further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the present invention.

[0061] An embodiment of the present invention discloses a testing device for analyzing the dynamic characteristics of a nuclear main pump shaft system, such as... Figures 1-3 As shown, it adopts a vertical structure, and the components are assembled in sequence in a vertical direction, including:

[0062] The system comprises a motor 1, a coupling 2, an experimental component 3, a support component 4, and a sensor unit 5. The experimental component 3 mainly includes a shaft seal 3-1, a rotating shaft 3-2, a shaft sleeve 3-3, a water-guided bearing 3-4, a bearing housing 3-5, a cylinder 3-6, and other fasteners. The support component 4 includes a motor bracket 4-1, an experimental component bracket 4-2, and an auxiliary bracket 4-3. The sensor unit 5 includes an eddy current displacement sensor 5-1, a vibration sensor 5-2, a pressure sensor 5-3, and a temperature sensor 5-4.

[0063] Motor 1 is fixed to the top of the device by support component 4 to ensure stability. The output shaft of motor 1 faces downward and is directly connected to coupling 2 to transmit power. The upper end of coupling 2 is connected to the motor output shaft, and the lower end is connected to the rotating shaft 3-2 of experimental component 3. Bearing seat 3-5 is fixed on the inner wall of cylinder 3-6. The bushing 3-3 of water guide bearing 3-4 is installed in bearing seat 3-5, and bushing 3-3 and rotating shaft 3-2 form a clearance fit. Rotating shaft 3-2 rotates within bushing 3-3.

[0064] The shaft seal 3-1 is installed near the contact surface where the cylinder 3-6 and the rotating shaft 3-2 move relative to each other; it uses a conventional mechanical seal, which is reliable in structure and easy to maintain.

[0065] The upper end of the cylinder 3-6 is connected to the support component 4, and the lower end is fixed on the experimental platform; the impeller is installed at the bottom of the rotating shaft 3-2 and is located inside the cylinder 3-6.

[0066] Experimental component 3 is designed as a core-removable rotor, and different water-guided bearings 3-4 can be replaced to conduct test experiments.

[0067] The motor bracket 4-1 is connected at its upper end to the lower end of the motor 1 to support the motor 1, and at its lower end to the test component bracket 4-2.

[0068] Experimental component support 4-2 is used to support experimental component 3, specifically, it is connected to the upper end of cylinder 3-6;

[0069] The auxiliary bracket 4-3 is connected to the side of the motor 1 at the top and fixed to the bottom surface at the bottom to form a support for the motor 1;

[0070] Eddy current displacement sensor 5-1 is arranged on the edge of the rotating shaft 3-2 on the upper side of the water guide bearing 3-4. Two identical eddy current displacement sensors 5-1 are arranged on the same horizontal plane with a 90-degree phase difference between them. Vibration sensor 5-2 is arranged on the horizontal plane of the outer wall of the cylinder 3-6, which is located in the middle of the cylinder 3-6. Four identical vibration sensors 5-2 are arranged on this horizontal plane with a 90-degree phase difference between them. Four pressure sensors 5-3 are arranged in the gap formed between the water guide bearing 3-4 and the rotating shaft 3-2. One temperature sensor 5-4 is arranged in the liquid inside the inner cavity of the cylinder 3-6 near the water guide bearing 3-4.

[0071] Motor 1: The rotor system used to drive the nuclear main pump, providing a stable power source with adjustable speed.

[0072] Coupling 2: Connects the motor to the main pump rotor to ensure efficient power transmission.

[0073] Water-guided bearings 3-4: Installed on the pump side, water-lubricated, providing radial support to the rotor. The structural and hydrodynamic parameters of the water-guided bearings are the key variables studied in this invention. The structural parameters include: bearing clearance, bearing structure, and bearing length; the hydrodynamic parameters include fluid viscosity and pressure distribution.

[0074] Cylinder 3-6: Serves as the pressure-bearing outer shell of the entire device, protecting the internal components and providing a mounting base.

[0075] Shaft seal 3-1: Prevents or reduces the leakage of high-temperature, high-pressure water from inside the cylinder.

[0076] Impeller: Designed to simplify the structure and simulate the hydrodynamic and rotor dynamic characteristics of an actual nuclear main pump impeller, while reducing the complexity and cost of the device.

[0077] Support component 4: includes motor bracket, experimental component bracket, auxiliary bracket, etc., to ensure the structural stability of the device.

[0078] Sensor unit 5 includes an eddy current displacement sensor 5-1, a vibration sensor 5-2, a pressure sensor 5-3, and a temperature sensor 5-4, which are used to monitor the rotational speed, vibration characteristics, displacement of the rotor shaft system, fluid pressure distribution of the water-guided bearing, and ambient temperature in real time.

[0079] Vibration sensor 5-2 collects vibration data from cylinder 3-6; eddy current displacement sensor 5-1 collects axial displacement data from water guide bearing 3-4; pressure sensor 5-3 collects pressure pulsation data from water guide bearing 3-4; temperature sensor 5-4 collects and measures fluid temperature at water guide bearing 3-4.

[0080] An embodiment of the present invention discloses a test method for analyzing the dynamic characteristics of a nuclear main pump shaft system, comprising the following steps:

[0081] Step 1: Install the testing equipment, set the experimental parameters, and perform initial operation;

[0082] The experimental parameters specifically include: the motor speed and the lubrication conditions of the water-conducting bearing;

[0083] Start the device at its lowest speed for initial operation, then increase the speed until it reaches the rated maximum value. Record all parameters during the initial operation.

[0084] Step 2: Real-time high-frequency acquisition of vibration acceleration data of different shaft sections of the rotor, displacement data of both sides of the rotor bearings at each cross section; vibration acceleration data of the motor housing and cylinder housing; fluid pressure and temperature data of the water-conducting bearing; flow rate, pressure, and temperature parameters of the system pipeline through various sensors;

[0085] The system piping is used in conjunction with the testing device to allow circulating fluid to circulate within it.

[0086] All sensors use the keyway signal of the rotating shaft as a reference, and phasor measurement unit (PMU) technology is used to align the timestamps of all sensors. A spatial coordinate system is established for displacement and acceleration data according to axial position and circumferential angle. The axial angles are selected as 0°, 90°, 180°, and 270°.

[0087] Step 3: Process the collected parameters and extract key feature parameters;

[0088] The key characteristic parameters include vibration frequency, amplitude, displacement, axis trajectory, and pressure distribution.

[0089] The processing method specifically includes: using signal processing technology to perform bandpass filtering on the acquired high-frequency vibration acceleration and displacement signals, and using a bidirectional IIR filter architecture to achieve zero-phase delay filtering to avoid signal distortion;

[0090] Adaptive variational mode decomposition (AVMD) is used for displacement and acceleration signals: First, the number of modes K is initially estimated by the number of significant peaks in the power spectral density (PSD), and the signal is decomposed into multiple intrinsic mode functions; then, based on the joint criterion of kurtosis and information entropy of each intrinsic mode function, characteristic components such as bearing fluid noise, rotor imbalance, misalignment and structural resonance are automatically separated.

[0091] Detect phase coupling peaks, perform high-order spectral analysis to identify nonlinear coupling frequencies, and accurately locate bearing fluid vortex frequencies;

[0092] Using data fusion algorithms such as Kalman filtering, the displacement of multiple displacement sensor signals is dynamically tracked by multi-sensor data fusion, a three-dimensional dynamic shaft center trajectory is constructed, and the normal offset exponent is calculated to quantify the rotor motion state.

[0093] Collect pressure data from pressure sensors and generate a high-precision pressure distribution cloud map of the entire area in real time; specifically including:

[0094] Real-time pressure data at discrete points is collected and preprocessed, with outliers being removed or missing values ​​being filled in.

[0095] Based on the spatial correlation of data, the Kriging interpolation algorithm is used to estimate the pressure value at any location within the region.

[0096] The region is divided into a fine grid, and a dynamic cloud map is generated by mapping the pressure value with color gradients. The latest data is incorporated through a sliding window to achieve real-time updates.

[0097] Step 4: Based on the key characteristic parameters and combined with shaft dynamics theory, analyze the influence of the structural parameters and fluid dynamics parameters of the water-guided bearing on the vibration of the nuclear main pump shaft.

[0098] Specifically,

[0099] Step 4-1: Construct the structural dynamics module;

[0100] Specifically, it includes:

[0101] 1.1 Discretization of beam element model: The shaft system is discretized into multiple beam elements along the axial direction. Each element contains nodal mass and rotational inertia parameters. The vibration mode of the shaft system is described by the nodal degrees of freedom.

[0102] 1.2 Introduction of Gyro Effect: For high-speed rotating shaft systems, a gyro torque term related to the rotational speed is added to the dynamic equation to quantify the coupling effect of rotational angular velocity on the lateral vibration of the shaft system.

[0103] 1.3 Shear Deformation Correction: The traditional Euler beam model is corrected by adopting beam theory that considers shear deformation, ignoring the limitations of shear stiffness, and improving the accuracy of the model under high-frequency vibration.

[0104] 1.4 Bearing support modeling: The bearing is simplified as an elastic support with cross-coupling characteristics. The cross terms in the stiffness matrix are obtained through experiments or bearing dynamic parameters, that is, the horizontal-vertical stiffness coupling, which characterizes the anisotropy of the bearing oil film force.

[0105] Step 4-2: Construct the fluid dynamics module;

[0106] Specifically, it includes:

[0107] 2.1 Reynolds Equation Solution Framework: Based on lubrication theory, an oil film pressure control equation is established. For the high-speed operation of the nuclear main pump, a turbulence correction factor is introduced to adapt to the flow state at high Reynolds numbers. The turbulence correction factor is obtained by correcting the viscosity coefficient using empirical formulas or by using the Reynolds stress model.

[0108] 2.2 Finite Volume Discretization: The flow field in the bearing gap is divided into grid cells. The laws of mass conservation and momentum conservation are applied to each control volume. The pressure field is solved iteratively using the line-by-line scanning method or the multi-grid method. The convergence stability is ensured by the pressure-velocity coupling algorithm.

[0109] 2.3 Boundary condition settings: The journal surface is set as a rotating wall boundary, the speed is equal to the shaft speed, the bearing housing is set as a fixed wall, and the oil film inlet and outlet adopt pressure boundary or flow continuity conditions, considering the influence of centrifugal force on the oil film thickness distribution.

[0110] Step 4-3: Fluid-structure interaction boundary treatment;

[0111] Specifically, it includes:

[0112] 3.1 Definition of coupling interface: The journal surface is used as the fluid-structure interaction interface. The fluid dynamics module calculates the oil film pressure distribution and converts it into a distributed force acting on the journal. The structural dynamics module solves for the journal displacement and feeds it back to the fluid dynamics module to update the oil film thickness.

[0113] 3.2 Iterative solution process: A two-way strongly coupled iterative strategy is adopted. The steps include: the structural dynamics module initializes the journal position, and the fluid dynamics module calculates the initial oil film force; the structural dynamics module solves the journal vibration displacement based on the oil film force; the fluid dynamics module updates the oil film clearance based on the new displacement and recalculates the oil film force; the above steps are repeated until the iterative residual of displacement and force is less than the set threshold.

[0114] Step 4-4: Parametric analysis and sensitivity quantification, establishing a quantitative relationship model between parameters and vibration indices;

[0115] Specifically, it includes:

[0116] 4.1 Key variable selection: Define shaft vibration response indicators, such as vibration amplitude, dominant frequency, and shaft center trajectory offset; identify physical parameters that affect the response, such as bearing clearance, lubricating oil viscosity, shaft speed, bearing length-to-diameter ratio, and oil film temperature; and establish a parameter list.

[0117] The key variables are derived from the parameters collected in step 2 and the key feature parameters extracted in step 3;

[0118] For example, the flow rate and temperature collected in step 2, and the pressure, vibration frequency, and amplitude extracted in step 3;

[0119] 4.2 Parameter Space Design: Orthogonal experimental design or Latin hypercube sampling method is adopted to generate multiple sets of sample points within the parameter feasible region, and an input matrix containing various parameter combinations is constructed to cover single-factor and multi-factor coupled scenarios.

[0120] 4.3 Global Sensitivity Analysis: Based on the Sobol index method, the contribution of each parameter to the response index is quantified through variance decomposition, distinguishing between main effects and interaction effects. The steps include performing fluid-structure interaction numerical simulations on each parameter sample to obtain response data, calculating the first-order Sobol index and the total-order index of each parameter, and sorting and screening parameters with a contribution exceeding 15%.

[0121] 4.4 Establish a quantitative relationship model between the parameters and vibration indices;

[0122] Steps 4-5: By comparing the numerical simulation results with the experimentally measured vibration data, the accuracy of the model is verified, and a complete dynamic model that can be used for vibration prediction and optimization of the nuclear main pump shaft system is formed.

[0123] Step 5: Change variables such as structural parameters, operating parameters, and system parameters, use dynamic models to predict vibration changes after parameter adjustment, optimize parameters to reduce shaft vibration, and improve the operational stability of the nuclear main pump;

[0124] After optimizing the parameters, the device was run again and data was collected. The vibration data before and after the optimization were compared and the effect was analyzed.

[0125] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0126] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A test method for analyzing the dynamic characteristics of a nuclear main pump shafting, characterized by, Based on the implementation of the testing device, which adopts a vertical structure and whose components are assembled sequentially in a vertical direction, including: The motor is fixed at the top by a support component; the motor's output shaft faces downwards and is directly connected to the coupling. The lower end of the coupling is connected to the rotating shaft, the bearing seat is fixed to the inner wall of the cylinder, and the water guide bearing is installed in the bearing seat, forming a clearance fit with the rotating shaft. The impeller is installed at the bottom of the shaft, inside the cylinder; Vibration sensors collect cylinder vibrations; eddy current displacement sensors collect axial displacements at the water guide bearings; pressure sensors collect pressure pulsations at the water guide bearings; and temperature sensors collect and measure the fluid temperature at the water guide bearings. The sensor unit consists of an eddy current displacement sensor, a vibration sensor, a pressure sensor, and a temperature sensor. Includes the following steps: Step 1: Install the testing equipment, set the experimental parameters, and perform initial operation; Step 2: Use the sensor unit to collect vibration acceleration, displacement, fluid pressure and temperature data in real time; Step 3: Process the collected parameters and extract key feature parameters; The processing method includes: using signal processing technology to perform bandpass filtering on the acquired high-frequency vibration acceleration and displacement signals, and using a bidirectional IIR filter architecture to achieve zero-phase delay filtering; Adaptive variational mode decomposition is applied to the displacement and acceleration signals; Detect phase coupling peaks, perform high-order spectral analysis to identify nonlinear coupling frequencies, and accurately locate bearing fluid vortex frequencies; A data fusion algorithm is used to dynamically track the displacement of multiple eddy current displacement sensor signals, construct a three-dimensional dynamic shaft center trajectory, and calculate the normal offset exponent to quantify the rotor motion state. Collect pressure data from pressure sensors and generate a high-precision pressure distribution cloud map of the entire area in real time. Step 4: Construct structural dynamics and fluid dynamics modules, process fluid-structure interaction boundaries, and establish a quantitative relationship model between parameters and vibration indices through parametric analysis and sensitivity quantification; verify the accuracy of the quantitative relationship model by comparing numerical simulation results with experimentally measured vibration data, and thus form a complete dynamic model for vibration prediction and optimization of the nuclear main pump shaft system. Step 5: Optimize the parameters using the aforementioned dynamic model; The constructed structural dynamics module specifically includes: 1.1 Discretization of beam element model: The shaft system is discretized into multiple beam elements along the axial direction. Each element contains nodal mass and moment of inertia parameters. The vibration mode of the shaft system is described by the nodal degrees of freedom. 1.2 Introduction of Gyro Effect: For high-speed rotating shaft systems, a gyro torque term related to the rotational speed is added to the dynamic equation to quantify the coupling effect of rotational angular velocity on the lateral vibration of the shaft system; 1.3 Shear Deformation Correction: The traditional Euler beam model is corrected by adopting beam theory that considers shear deformation and ignoring the limitations of shear stiffness; 1.4 Bearing support modeling: The bearing is simplified as an elastic support with cross-coupling characteristics. The cross terms in the stiffness matrix are obtained through experiments or bearing dynamic parameters to characterize the anisotropy of the bearing oil film force. The construction of the fluid dynamics module specifically includes: 2.1 Reynolds equation solution framework: Based on lubrication theory, an oil film pressure control equation is established. For the high-speed operation of the nuclear main pump, a turbulence correction factor is introduced to adapt to the flow state under high Reynolds number. 2.2 Finite Volume Discretization: The flow field in the bearing clearance is divided into grid cells. The laws of mass conservation and momentum conservation are applied to each control volume. The pressure field is solved iteratively using the line-by-line scanning method or the multi-grid method. The convergence stability is ensured by the pressure-velocity coupling algorithm. 2.3 Boundary condition settings: The journal surface is set as a rotating wall boundary, the bearing housing is set as a fixed wall, and the oil film inlet and outlet adopt pressure boundary or flow continuity conditions, considering the influence of centrifugal force on the oil film thickness distribution; The fluid-structure interaction boundary treatment specifically includes: 3.1 Definition of coupling interface: The journal surface is taken as the fluid-structure interaction interface. The fluid dynamics module calculates the oil film pressure distribution and converts it into a distributed force acting on the journal. The structural dynamics module solves the journal displacement and feeds it back to the fluid dynamics module to update the oil film thickness. 3.2 Iterative solution process: The structural dynamics module initializes the journal position, and the fluid dynamics module calculates the initial oil film force; the structural dynamics module solves for the journal vibration displacement based on the oil film force; the fluid dynamics module updates the oil film clearance based on the new displacement and recalculates the oil film force; the above steps are repeated until the iterative residual between displacement and force is less than the set threshold. The parametric analysis and sensitivity quantification, which establish a quantitative relationship model between these parameters and vibration indices, specifically includes: 4.1 Screening of key variables; 4.2 Parameter Space Design: Orthogonal experimental design or Latin hypercube sampling method is adopted to generate multiple sets of sample points within the parameter feasible region, and an input matrix containing various parameter combinations is constructed to cover single-factor and multi-factor coupled scenarios. 4.3 Global Sensitivity Analysis: Perform fluid-structure interaction numerical simulations for each set of parameter samples, obtain response data, calculate the first-order Sobol exponent and total order exponent of each parameter, and sort and filter parameters with a contribution of more than 15%; 4.4 Establish a quantitative relationship model between the parameters and vibration index.

2. The test method for analyzing the dynamic characteristics of a core pump shaft system according to claim 1, wherein, In step 2, the sensor unit is used to collect in real time the vibration acceleration of different shaft sections of the rotor, the displacement data of the rotor on both sides of each bearing section, the vibration acceleration data of the motor housing and the cylinder housing, the fluid pressure and temperature data of the water-conducting bearing, and the flow rate, pressure and temperature parameters of the system pipeline.

3. The test method for analyzing the dynamic characteristics of a nuclear pump shafting according to claim 1, characterized in that, In step 3, the adaptive variational mode decomposition of the displacement and acceleration signals specifically includes: firstly, estimating the number of modes K by the number of significant peaks in the power spectral density, and decomposing the signal into multiple intrinsic mode functions; then, based on the joint criterion of kurtosis and information entropy of each intrinsic mode function, automatically separating the characteristic components, which include bearing fluid noise, rotor imbalance, misalignment, and structural resonance.

4. The test method for analyzing the dynamic characteristics of a core pump shaft system according to claim 1, wherein, The process of acquiring pressure data from pressure sensors and generating a high-precision pressure distribution cloud map of the entire area in real time specifically includes: Real-time pressure data at discrete points is collected and preprocessed, with outliers being removed or missing values ​​being filled in. Based on the spatial correlation of data, the Kriging interpolation algorithm is used to estimate the pressure value at any location within the region. The region is divided into a fine grid, and a dynamic cloud map is generated by mapping the pressure value with color gradients. The latest data is incorporated through a sliding window to achieve real-time updates.

5. The test method for analyzing the dynamic characteristics of a nuclear pump shafting according to claim 1, characterized in that, The bearing housing is fixed on the inner wall of the cylinder, and the bushing of the water guide bearing is installed in the bearing housing, with the bushing and the rotating shaft forming a clearance fit; the rotating shaft rotates within the bushing.

6. The test method for analyzing the dynamic characteristics of a nuclear pump shafting according to claim 1, characterized in that, The supporting components include a motor bracket, an experimental component bracket, and an auxiliary bracket. The motor bracket has its upper end connected to the lower end of the motor and its lower end connected to the test component bracket. The experimental component support is connected to the upper end of the cylinder; The auxiliary bracket is connected to the side of the motor at the top and fixed to the bottom surface at the bottom, forming a support for the motor.

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