A dynamic modeling method of nuclear power lifting valve in liquid medium based on CFD

Abstract

The present invention discloses a dynamic modeling method of a nuclear power lift valve under liquid medium based on CFD, comprising the following steps: establishing a three-dimensional model of the nuclear power lift valve; extracting and simplifying the calculation flow domain of the nuclear power lift valve; meshing the calculation flow domain; performing valve core dynamics modeling on the nuclear power lift valve; controlling the movement of the valve core of the nuclear power lift valve to realize the fluid-solid coupling of the valve core movement and obtain the dynamic characteristics of the nuclear power lift valve; importing the mesh data into the fluid simulation software for calculation to verify whether the dynamic characteristics of the nuclear power lift valve meet the requirements, and if so, ending the simulation, and if not, changing the structure of the nuclear power lift valve, and performing targeted optimization according to the simulation results. The present invention provides a new scheme and theoretical basis for the design and optimization of the nuclear power lift valve, reduces the cost of the nuclear power lift valve in design optimization, and is the application of simulation calculation methods in the field of valve design and optimization, with the advantages of intuitive results, low cost, and fast time.

Description

Technical Field

[0001] The present invention relates to the field of numerical calculation in the design and optimization of nuclear power valves, and in particular to a dynamic modeling method of a nuclear power lifting valve in a liquid medium based on CFD, which belongs to the intersection of computational fluid dynamics and valve design and optimization. Background Art

[0002] The nuclear power lifting valve is an important part of the nuclear power pipeline system. It is a valve that opens and closes the valve by linear motion of the valve core under the action of driving force. In the pipeline system, it often plays the role of controlling flow, regulating pressure, preventing backflow, and protecting the safety of the entire pipe and valve system. Therefore, the dynamic performance of the nuclear power lifting valve is particularly important for the safety of the entire pipe and valve system.

[0003] At present, the design of nuclear power lifting valves is still mainly based on experience, and the research on the performance of nuclear power lifting valves is mainly based on experiments, which is specifically manifested as: designing the basic structure of the nuclear power lifting valve according to performance indicators and industry standards, processing and manufacturing, and then determining whether the performance of the nuclear power lifting valve meets the standards through experimental methods. The advantage of this method is that it can directly and accurately obtain the performance and corresponding parameters of the valve, but the disadvantage is that this method consumes a lot of manpower and material resources, increases the cost of valve design and manufacturing, and prolongs the valve design and manufacturing cycle.

[0004] With the gradual development of computer technology, economical and efficient simulation calculation methods are gradually applied to various design and analysis fields. CFD (Computational Fluid Dynamics) is the application of computer technology in fluid dynamics. CFD can simulate different flows, has a series of real physical models, and also has a full-featured post-processing tool that can display the characteristics of fluid flow. It is widely used in fluid analysis and calculation. In addition, fluid simulation software can calculate complex fluid-solid coupling problems through UDF program control, and has strong capabilities and advantages in solving multi-physics field problems.

[0005] However, the existing technology lacks a CFD-based modeling technology for the dynamic characteristics of nuclear power lifting valves in liquid media that has intuitive results, low cost, and fast time. Summary of the invention

[0006] In response to the above technical problems, the present invention proposes a CFD-based modeling method for the dynamic characteristics of nuclear power lift valves in liquid media. The modeling method simulates and analyzes the dynamic characteristics of nuclear power lift valves working in liquid media based on CFD, and optimizes the structure of the nuclear power lift valves through the simulation results. The present invention provides a new solution and theoretical basis for the design and optimization of nuclear power lift valves, greatly reducing the cost of design optimization of nuclear power lift valves. It is an application of simulation calculation methods in the field of nuclear power lift valve design and optimization, and has the advantages of intuitive results, low cost, and fast time.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] A dynamic modeling method of a nuclear power lifting valve in a liquid medium based on CFD includes the following steps:

[0009] Step S1, establishing a three-dimensional structure of a nuclear power lifting valve by using three-dimensional modeling software to obtain a three-dimensional model of the nuclear power lifting valve;

[0010] Step S2, extracting the calculation flow domain of the nuclear power lifting valve from the three-dimensional model of the nuclear power lifting valve in step S1 and simplifying it;

[0011] Step S3, using grid division software to grid the calculation flow domain of step S2;

[0012] Step S4: According to Newton's laws of motion, a valve core dynamics model is performed on the nuclear power poppet valve;

[0013] Step S5, writing a UDF program to control the movement of the nuclear power poppet valve core, updating the flow domain in real time through the dynamic mesh technology, realizing the fluid-solid coupling of the valve core movement, and obtaining the dynamic characteristics of the nuclear power poppet valve;

[0014] Step S6: Import the grid data into the fluid simulation software Fluent, load the UDF, set the parameters, and perform simulation calculations.

[0015] Step S7, verify whether the dynamic characteristics of the nuclear power lifting valve meet the requirements. If so, end the simulation; if not, change the structure of the nuclear power lifting valve and return to step S1 to recalculate.

[0016] In the above scheme, the 3D modeling software in step S1 is SolidWorks, Catia or UG, etc. When establishing the 3D structure of the nuclear power lifting valve, the preliminary structural design parameters of the nuclear power lifting valve can be given according to the experience of practitioners and the valve design manual, and on this basis, the dynamic characteristics of the nuclear power lifting valve are analyzed and optimized.

[0017] In the above scheme, the step S2 is specifically:

[0018] The flow channel of the nuclear power lift valve is filled with model processing software, and the calculation flow domain of the nuclear power lift valve, that is, the area where the fluid flows, is extracted from the three-dimensional model of the nuclear power lift valve. Then some unnecessary chamfers and gaps are removed to form a flow area that reflects the performance of the valve system; a pipeline flow domain is added at the inlet of the main water supply check valve, and a pipeline flow domain is also added at the outlet to ensure the full development of the fluid.

[0019] Preferably, the model processing software is SpaceClaim or Designmodeler, etc.

[0020] Preferably, a pipeline flow area is added at the valve inlet, and its length is 5 times the diameter of the inlet. A pipeline flow area is also added at the valve outlet, and its length is 10 times the diameter of the outlet.

[0021] In the above scheme, step S3 specifically includes the following steps:

[0022] The quality of the grid is closely related to the accuracy of simulation calculation. Before dividing the specific grid, the basin is first divided into multiple small blocks according to the fluid movement, and the grid is divided for each small block;

[0023] In the dynamic grid area, the one-way flow characteristics are obvious, and the watershed is regular, the structured grid with faster calculation speed is adopted, and in the irregular watershed part, the unstructured grid that can better reflect the micro characteristics of the watershed is adopted;

[0024] Preferably, a structured grid is adopted at the inlet and outlet pipes of the nuclear power lifting valve, and an unstructured grid is adopted at the connecting part of the inlet and outlet of the nuclear power lifting valve; in the division of the structured grid, a line-surface-body grid division mode is adopted, and a fine surface grid is first drawn by determining the size of the corresponding edge, and then a regular hexahedral grid is formed by scanning; in the division of the unstructured grid, a tetrahedral grid is formed by setting the volume grid size;

[0025] Set the topological relationship between small watersheds. Set the common node topology structure in the watershed grid part without relative motion so that the nodes are shared between the grids. Set the separated topology structure in the watershed grid part with relative motion. Set the interface between two watersheds without common nodes.

[0026] Set dynamic mesh area and parameters: divide the mesh area above and below the nuclear power poppet valve core into the movable body area, and set the surface in contact with the valve body as the static surface area.

[0027] Preferably, the software used for meshing includes ICEM, Fluent meshing or Hypermesh.

[0028] In the above scheme, the dynamic modeling of the nuclear power lifting valve in step S4 is specifically as follows:

[0029] During numerical calculation, the simulation software performs multiple iterations to reduce errors and achieve accurate calculations. In transient calculations, multiple iterations are performed in each time step to obtain stable values ​​before performing numerical calculations in the next time step.

[0030] The dynamic modeling of the nuclear power lifting valve core is that the movement of the nuclear power lifting valve core is a fluid-solid coupling movement under the combined action of fluid force, spring force, and gravity. It is difficult to simulate this movement by theoretical calculation, but the movement of the valve core as a whole still satisfies Newton's laws of motion. The movement of the valve core is discretized into a small time step and follows the following formula:

[0031] F(t0)=F FLUID (t0)+F SPRING (t0)+G(t0)·sinθ

[0032] F(t0)=m·a(t0)

[0033]

[0034] x(t1)=x(t0)+v average (t1) dt

[0035] Where, F is the resultant force on the valve core, F FLUID is the fluid force acting on the valve core, F SPRING is the spring force associated with the valve core, G is the gravity of the valve core and the moving parts that move with it, θ is the angle between the valve installation direction and the horizontal direction; v(t0), a(t0), x(t0) are the instantaneous velocity, acceleration, and displacement of the valve core at time t0, v(t1), a(t1), x(t1) are the instantaneous velocity, acceleration, and displacement of the valve core at time t1, m is the mass of the valve core and the piston, and dt is the discrete time step; v average (t1) is an intermediate variable, which refers to the average velocity of the valve core at time t1 and is used to calculate the actual displacement of the valve core at time t1;

[0036] By calculating the instantaneous velocity v(t0) and acceleration a(t0) at time t0, we can obtain the instantaneous velocity v(t1) and displacement x(t1) at time t1. In this way, the dynamic modeling of the valve core movement can be completed by discrete calculation within a sufficiently small time step.

[0037] In the above scheme, in step S5, a UDF (User-defined Function) is written based on C language to control the movement of the valve core, and the flow domain is updated in real time through the dynamic mesh technology to realize the fluid-solid coupling of the valve core movement;

[0038] Write a UDF that performs the following operations at each time step:

[0039] Initialize variables and set the instantaneous speed v and average speed v of the valve core movement average , acceleration a, displacement x, initial values ​​of variables, set valve core mass m, set time step dt to be the same as transient simulation of fluid simulation software;

[0040] Among the above variables, the valve core mass and time step are fixed quantities that do not change with time, and the given initial values ​​do not change;

[0041] Use the built-in macro command DEFINE_PROFILE in UDF to set the export boundary conditions to simulate the actual working conditions;

[0042] The variables are calculated and updated through the built-in macro command DEFINE_ADJUST in UDF. First, the surface ID of the valve core in contact with the fluid is obtained in the fluid simulation software. According to different IDs, functions are written in UDF to obtain pressure P and area A respectively, thereby calculating the fluid force acting on the valve core.

[0043] In order to solve the problem that the liquid medium is difficult to converge in the numerical calculation process due to the liquid characteristics, multiple intermediate variables are established based on the idea of ​​the mean algorithm. The corresponding instantaneous velocity, acceleration, and average velocity are calculated in each time step, and the results are stored in the solver. The mean operation is performed on the stored multiple data, and this mean is used as the initial condition for the next step of calculation.

[0044] The movement of the dynamic mesh area is controlled by the UDF built-in macro command DEFINE_CG_MOTION. The moving speed of the dynamic mesh is the same as the average speed of the current time step, that is, v average As the actual velocity of the fluid area of ​​the moving grid, the regeneration and collapse of the grid, the real-time update of the flow domain and the fluid-solid coupling of the valve core movement are realized through the fluid simulation software;

[0045] Through the UDF built-in macro command DEFINE_EXECUTE_AT_END, the time, instantaneous speed, average speed, acceleration, driving force, fluid force and various fluid forces in the calculation process are stored and output to the file, so as to realize real-time monitoring of the valve core movement and obtain the dynamic characteristics of the valve opening and closing.

[0046] Furthermore, the mean value calculation in step S5 is performed according to the following formula:

[0047] a=(a m-n+1 +a m-n+2 +…+a m ) / n

[0048] v=(vm-n+1 +v m-n+2 +…+v m ) / n

[0049] v average =(v averagem-n+1 +v averagem-n+2 +…+v averagem ) / n

[0050] Where n is the characteristic value of the mean algorithm, that is, the data in the current time step and the previous time step, a total of n time steps, are averaged as the corresponding parameter of the valve core movement in the current time step; m 、v m 、v averagem are the acceleration, instantaneous velocity and average velocity of the valve core motion calculated by Newton's laws of motion in the mth time step; a, v, v average They are respectively the acceleration, instantaneous speed and average speed of the valve core motion obtained by the mean algorithm in the mth time step.

[0051] In the above scheme, step S6 specifically includes the following steps:

[0052] Mesh import: Import the mesh into the fluid simulation software solver, check the mesh quality, and ensure that the minimum orthogonal quality (Minimum Orthogonal Quality) is greater than 0.2. If the minimum orthogonal quality does not meet the requirements, improve the mesh quality by adaptive meshing or redrawing the mesh;

[0053] Set the solver type: Select a pressure-based solver and set the gravity direction according to the working state of the nuclear power lift valve. Before the simulation starts, select a steady-state solver to simulate the normal working state of the nuclear power lift valve.

[0054] Material setting: Select the corresponding material from the material library of the fluid simulation software according to the actual working conditions. If there is no material that meets the requirements, manually set the material properties, including density and viscosity parameters;

[0055] Select turbulence model: select turbulence model according to materials and working conditions; preferably, the turbulence model includes Standard k-ε model with fast calculation speed and stable calculation results and SST k-ω model with more accurate prediction of fluid force;

[0056] Loading UDF: loading the UDF written in the step S5, and after loading, calculating simultaneously in the fluid simulation calculation process; specifically, the UDF written in C language is compiled, and the EXECUTE_AT_END and ADJUST macro commands in the step S5 need to be manually loaded, and the remaining macro commands are automatically loaded, and after loading, calculating simultaneously in the fluid simulation calculation process;

[0057] Dynamic mesh setting: The methods of mesh updating in fluid simulation software include: Smoothing, Layering, and Remeshing. Preferably, Layering is used for structured meshes; Smoothing and Remeshing are used for unstructured meshes;

[0058] According to the meshing method of step S3, the movable fluid mesh area is set to Rigid Body. If it is a movable surface, the layer height needs to be set, and the speed is specified by the UDF in step S5; the stationary fluid mesh area is set to Stationary. If it is a stationary surface, the layer height needs to be set; the mesh area associated with the movable area is set to Deforming, allowing its mesh to deform following the movable fluid domain;

[0059] Setting boundary conditions: setting the boundary type of the position in contact with the solid to Wall, setting the interface of the flow domains that are in contact with the flow domains and do not have a common node topological relationship to Interface, setting the inlet of the nuclear power lift valve to pressure-inlet, and setting the outlet of the nuclear power lift valve to pressure-outlet, wherein the specific parameters of pressure-inlet and pressure-outlet are set in the fluid simulation software according to actual conditions, or specified by the UDF of step S5;

[0060] Set the solution method: For the simulation analysis of the dynamic performance of nuclear power lifting valves, the solution methods include: SIMPLE and Coupled methods of pressure-velocity coupling. Preferably, SIMPLE method of pressure-velocity coupling is selected, which has faster calculation speed and better convergence.

[0061] Adjust the relaxation factor: While improving the convergence of the calculation, it will prolong the calculation time and increase the calculation cost. It is necessary to comprehensively consider the convergence and convergence speed to determine the appropriate convergence factor. Preferably, the default relaxation factor is used;

[0062] Flow field initialization: For steady-state simulation, hybrid initialization is used to obtain the initial value of calculation according to the actual working condition of the nuclear power lifting valve. For transient simulation, steady-state working condition simulation is performed first, and the result of steady-state simulation is saved as the initialization parameter of transient simulation.

[0063] Transient simulation settings: Set the simulation time step, number of iterations, and convergence residual standard consistent with UDF. Preferably, if the convergence residual standard of 1e-4 can be reached after 200 iterations, the calculation is considered to have converged at this time step.

[0064] For transient simulation, set the simulation termination conditions in UDF, and the simulation will stop automatically after the calculation reaches the termination requirements;

[0065] Set monitoring parameters: including pressure cloud map and speed cloud map, etc. to monitor changes in real time.

[0066] In the above scheme, the step S7 is specifically as follows:

[0067] After completing the simulation calculation, the dynamic characteristics of the nuclear power lifting valve including the opening and closing time and the opening and closing speed are obtained according to the file output by the UDF in step S5, and the dynamic characteristics are analyzed to see whether they meet the working requirements. If not, the structure is optimized;

[0068] According to the simulation results, the real-time pressure cloud map, velocity cloud map, streamline map and other characteristics during the closing process of the nuclear power lifting valve are obtained, the throttling position in the nuclear power lifting valve is determined, and the object is provided for structural optimization.

[0069] According to the above steps, the dynamic characteristics of the nuclear power lifting valve are finally simulated and analyzed, and the structure is optimized on this basis, so that the dynamic characteristics of the nuclear power lifting valve meet the design and use requirements.

[0070] The present invention also provides a computer device, including a memory and a processor, wherein a computer program is stored in the memory. When the processor runs the computer program stored in the memory, the processor executes the dynamic modeling method of the CFD-based nuclear power lifting valve in liquid medium.

[0071] The present invention also provides a computer-readable storage medium, wherein the computer-readable storage medium is used to store a computer program, and the computer program executes the CFD-based dynamic modeling method of a nuclear power lifting valve in a liquid medium.

[0072] Compared with the prior art, the present invention has the following beneficial effects:

[0073] The present invention simulates and analyzes the dynamic characteristics of nuclear power lifting valves working in liquid media based on CFD, and optimizes the structure of nuclear power lifting valves through simulation results. The present invention provides a new solution and theoretical basis for the design and optimization of nuclear power lifting valves, greatly reduces the cost of design optimization of nuclear power lifting valves, and is an application of simulation calculation methods in the field of nuclear power lifting valve design and optimization, with advantages such as intuitive results, low cost, and fast time. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 A flow chart of a dynamic modeling method of a nuclear power lifting valve in liquid medium based on CFD proposed by the present invention;

[0075] Figure 2 This is a simplified structural diagram of a main water supply check valve in one embodiment of the present invention, wherein 1-piston, 2-damping plate, 3-valve disc, 4-valve body;

[0076] Figure 3 A closing curve diagram of an initial structure in one embodiment of the present invention;

[0077] Figure 4 A closing speed curve diagram of an initial structure in one embodiment of the present invention;

[0078] Figure 5 A pressure cloud diagram of an initial structure in one embodiment of the present invention;

[0079] Figure 6 A velocity cloud diagram of an initial structure in one embodiment of the present invention;

[0080] Figure 7 It is a closing curve diagram after structural optimization in one embodiment of the present invention;

[0081] Figure 8 This is a speed curve diagram of closing after structural optimization in one embodiment of the present invention. DETAILED DESCRIPTION

[0082] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0083] like Figure 2 As shown, the main feedwater check valve is a special nuclear power lifting valve, which includes a piston 1, a damping plate 2, a valve disc 3 and a valve body 4. The main feedwater check valve is installed on the main feedwater pipeline of the nuclear power plant. When the pipe and valve system is working normally, the main feedwater is allowed to flow. When abnormal conditions such as upstream pipeline rupture occur, the main feedwater check valve is required to be able to close quickly to prevent the main feedwater and steam from flowing back. The dynamic performance of the main feedwater check valve mainly refers to its closing time under abnormal conditions. If the closing time is too short, it may cause water hammer, cause pressure fluctuations, and damage the pipeline; if the closing time is too long, a large amount of medium will flow back, causing medium leakage, impacting the pipeline, and affecting the normal operation of the water pump.

[0084] like Figure 1 As shown, according to a CFD-based dynamic modeling method for a nuclear power lifting valve in a liquid medium proposed by the present invention, in this embodiment, a certain type of nuclear power main feed water check valve is dynamically modeled, and the specific operations are as follows:

[0085] Step (1) Based on the experience of practitioners and the valve design manual, the preliminary structural design parameters of the main water supply check valve are given, and a three-dimensional model of the main water supply check valve is established using SolidWorks, as shown in the figure. Figure 2 shown.

[0086] Step (2) using the model processing software SpaceClaim and Designmodeler, by filling the flow channel of the main water supply check valve, extracting the calculation flow domain of the main water supply check valve from the three-dimensional model of the main water supply check valve, removing some unnecessary chamfers, gaps, etc., to form a flow area that is easy to calculate and can reflect the performance of the valve system;

[0087] Add a pipe flow area at the inlet of the main water supply check valve, the length of which is 5 times the diameter of the inlet, and add a pipe flow area at the outlet, the length of which is 10 times the diameter of the outlet;

[0088] In the model processing software, the watershed is divided into multiple small blocks through the division and combination commands, and each small block is gridded.

[0089] Step (3) using grid partitioning software to partition the computational watershed grid;

[0090] The inlet and outlet pipes use structured grids, and the connection between the inlet and outlet uses unstructured grids;

[0091] In the valve core movement area, the one-way flow characteristics are obvious, and the regular flow area, the structured grid with faster calculation speed is used, and in the rest of the irregular flow area, the unstructured grid that can reflect the small characteristics is used.

[0092] In the division of structured grids, the line-surface-volume grid division mode is adopted. First, a fine surface grid is drawn, and then a regular hexahedral grid is formed by scanning. In the division of unstructured grids, a relatively fine tetrahedral grid is formed by setting the volume grid size.

[0093] The boundary layer of the grid part is resized, and a reasonable grid size gradient is set between the flow domains with large grid size differences to make the calculation more stable.

[0094] Set the topological relationship between small watersheds. Set the common node topology structure in the watershed grid part without relative motion so that the nodes are shared between the grids. Set the separated topology structure in the watershed grid part with relative motion. Set the interface between two watersheds without common nodes.

[0095] Set the dynamic mesh area and parameters: divide the mesh areas above and below the valve core of the main water supply check valve into the movable body area, and set the surface in contact with the valve body as the static surface area.

[0096] Step (4) according to Newton's law of motion, dynamic modeling of the main water supply check valve is performed;

[0097] During numerical calculation, the simulation software performs multiple iterations to reduce errors and achieve accurate calculations. In transient calculations, multiple iterations are performed in each time step to obtain stable values ​​before performing numerical calculations in the next time step.

[0098] The movement of the main water supply check valve core is a complex fluid-solid coupling movement under the action of multiple forces such as fluid force and gravity. It is difficult to simulate this movement by theoretical calculation, but the movement of the valve core as a whole still satisfies Newton's law of motion. When discretized into a small time step, it follows the following formula:

[0099] F(t0)=F FLUID (t0)+F SPRING (t0)+G(t0)·sinθ

[0100] F(t0)=m·a(t0)

[0101]

[0102] x(t1)=x(t0)+v average (t1) dt

[0103] Where, F is the resultant force on the valve core, F FLUID The fluid force acting on the valve core, there is no spring in the main water supply check valve, so F SPRING is 0, G is the gravity of the valve core and the moving parts moving together with it, θ is the angle between the valve installation direction and the horizontal direction, and in this embodiment, θ=45°;

[0104] v(t0), a(t0), x(t0) are the instantaneous velocity, acceleration, and displacement of the valve core at time t0, respectively; v(t1), a(t1), x(t1) are the instantaneous velocity, acceleration, and displacement of the valve core at time t1, m is the mass of the valve core and the piston, and dt is the discrete time step;

[0105] v average (t1) is an intermediate variable, which refers to the average velocity of the valve core at time t1 and is used to calculate the actual displacement of the valve core at time t1;

[0106] By calculating the instantaneous velocity v(t0) and acceleration a(t0) at time t0, the instantaneous velocity v(t1) and displacement x(t1) at time t1 are obtained. In this way, the dynamic modeling of the valve core movement is completed by discrete calculation within a sufficiently small time step.

[0107] Step (5) writing a UDF (User-defined Function) based on C language to control the movement of the valve core, and updating the flow domain in real time through dynamic mesh technology to achieve fluid-solid coupling of the valve core movement;

[0108] Write a UDF that performs the following operations at each time step:

[0109] Initialize variables and set the instantaneous speed v and average speed v of the valve core movement average , acceleration a, displacement x, initial values ​​of variables, set the mass m of the valve core and piston, and set the same time step dt as the transient simulation of the fluid simulation software;

[0110] The mass of the valve core and the piston and the time step are fixed quantities that do not change with time, and the given initial values ​​do not change. In this embodiment, the mass of the valve core and the piston is set to m = 312.25 kg, and the time step dt = 0.0005 s;

[0111] The outlet boundary condition is set through the UDF built-in macro command DEFINE_PROFILE to simulate the actual working condition. In order to simulate the actual working condition, the outlet boundary of the check valve is set to decay the outlet pressure from 8.3Mpa to 0 within 0.01s.

[0112] The variables are calculated and updated through the built-in macro command DEFINE_ADJUST of UDF. In this embodiment, six surfaces of the piston, valve disc and fluid in contact are obtained in the fluid simulation software, and their IDs are obtained for the six surfaces. Functions are written in UDF to obtain the pressure P and area A respectively, thereby calculating the fluid force acting on the valve disc and the piston;

[0113] In order to solve the problem that incompressible media are difficult to converge in numerical calculation due to liquid characteristics, multiple intermediate variables are established based on the idea of ​​the mean algorithm. The corresponding instantaneous velocity, acceleration, and average velocity are calculated in each time step, and the results are stored in the solver. The mean operation is performed on the stored multiple data, and this mean is used as the initial condition for the next step of calculation. The following formula is used:

[0114] a=(a m-n+1 +a m-n+2 +…+a m ) / n

[0115] v=(v m-n+1 +v m-n+2 +…+v m ) / n

[0116] v average =(v averagem-n+1 +v averagem-n+2 +…+v averagem ) / n

[0117] Wherein, n is the characteristic value of the mean algorithm, that is, the data in the current time step and the previous time step, a total of n time steps, are averaged as the corresponding parameter of the valve core movement in the current time step to reduce the error caused by the incompressible medium in the calculation. Here, the value of n is adjusted according to the demand. In this embodiment, n=10;

[0118] In the formula, a m 、v m 、v averagem are the acceleration, instantaneous velocity and average velocity of the valve core motion calculated by Newton's laws of motion in the mth time step, a, v, v average are respectively the acceleration, instantaneous speed and average speed of the valve core motion obtained by the mean value algorithm in the mth time step;

[0119] The movement of the dynamic mesh area is controlled by the UDF built-in macro command DEFINE_CG_MOTION. The moving speed of the dynamic mesh is the same as the average speed of the current time step, that is, v average As the actual velocity of the fluid area of ​​the moving grid, the regeneration and collapse of the grid, the real-time update of the flow domain and the fluid-solid coupling of the valve core movement are realized through the fluid simulation software;

[0120] Through the UDF built-in macro command DEFINE_EXECUTE_AT_END, the time, instantaneous speed, average speed, acceleration, driving force, fluid force and various fluid forces in the above calculation process are stored and output to the file, so as to realize real-time monitoring of the valve core movement and obtain the dynamic characteristics of the main water supply check valve when it is closed.

[0121] Step (6) importing the grid data into the fluid simulation software, loading the UDF, setting the parameters, and performing simulation calculations;

[0122] Import the mesh into the fluid simulation solver and check the mesh quality first. The minimum orthogonal quality is 0.20104, which meets the minimum orthogonal quality requirement and the mesh quality is good.

[0123] Set the solver type and select the pressure-based solver. According to the working status of the main water supply check valve, set the gravity direction. The gravity acceleration in the x direction is 6.93m / s. 2 , the gravitational acceleration in the y direction is -6.93m / s 2 ;

[0124] Before the simulation starts, select the steady-state solver to simulate the normal working state of the main water supply check valve;

[0125] Material setting: the working medium of the main water supply check valve is liquid water, and the corresponding material is directly selected from the material library of the fluid simulation software;

[0126] According to the working conditions of the main water supply check valve, the Standard k-ε turbulence model with fast calculation speed and stable calculation results is selected for calculation;

[0127] Load UDF. The UDF written in C language in the above step (5) is compiled. The EXECUTE_AT_END and ADJUST macro commands in the above step (4) need to be loaded manually. The remaining macro commands are loaded automatically. After loading, they are calculated simultaneously during the fluid simulation calculation process.

[0128] Setting the dynamic grid. In this embodiment, the motion flow domain is divided in the form of a structural grid, so the dynamic grid strategy selects the scale-based Layering method;

[0129] According to the meshing method described in step (3), the movable fluid mesh area is set as Rigid Body, the movable surface area is set as Rigid Body, the layer height is set to 5 mm according to the meshing method, and the speed of the Rigid Body is specified by the UDF in the above step (5);

[0130] Set the stationary surface area to Stationary, and set the layer height to 5mm, 2mm, 1mm and 0.5mm according to different grids;

[0131] Set boundary conditions, set the boundary type of the location in contact with the solid to Wall, set the interface of the watersheds that are in contact with the watersheds and do not have a common node topological relationship to Interface, set the inlet of the main water supply check valve to pressure-inlet, set the outlet of the main water supply check valve to pressure-outlet, where pressure-inlet is 8.2 MPa, and the parameters of pressure-outlet are specified by the UDF described in the above step (5);

[0132] Set the solution method: Use the SIMPLE method of pressure-velocity coupling, which has faster calculation speed and better convergence;

[0133] The appropriate convergence factor is determined by comprehensively considering the convergence and convergence speed. In this embodiment, the default relaxation factor is selected;

[0134] Flow field initialization. In this embodiment, a steady-state calculation is first performed, and the pressure-inlet is set to 8.2MPa and the pressure-outlet is set to 8.3MPa to simulate the normal working condition of the main water supply check valve and obtain the initial calculation value.

[0135] Save the steady-state simulation results, set pressure-inlet to 8.2MPa, and set pressure-outlet to decay from 8.3MPa to 0 within 0.01s to simulate the rupture condition of the upstream pipeline of the main water supply check valve;

[0136] Set the simulation time step to 0.0005s, the number of iterations to 200, and the convergence residual standard to 1e-4;

[0137] For transient simulation, the valve opening is set in the UDF. When the valve opening is 0, the calculation stops.

[0138] Set up real-time monitoring of pressure and velocity cloud maps, and update them every 10 time steps;

[0139] Step (7) After the calculation is completed, the closing curve of the main water supply check valve is obtained according to the file output by the UDF in the above step (5). Figure 3 As shown, Figure 4 This is the speed curve during the closing process of the main water supply check valve. From the results, it can be seen that the closing time of the main water supply check valve is 1.6s, which is relatively long;

[0140] According to the fluid simulation results, the real-time pressure cloud diagram of the main water supply check valve during closing is obtained ( Figure 5 As shown), speed cloud diagram ( Figure 6 As shown in the figure, determine the throttling position in the main water supply check valve, reduce the throttling size, optimize the structure, and then simulate according to the above steps. The valve closing curve is as follows Figure 7 As shown, Figure 8 After adjusting the structure, the closing speed curve of the main water supply check valve is increased overall compared with the previous structure, so the closing time is shortened. The closing time is 1.3s, and the dynamic characteristics are better.

[0141] According to the above operations, the simulation analysis of the dynamic characteristics of the main water supply check valve is finally completed, and the structure is optimized on this basis so that the dynamic characteristics of the main water supply check valve meet the design and use requirements.

[0142] The method of the present invention provides a new solution and theoretical basis for the design and optimization of nuclear power lifting valves, greatly reducing the cost of design optimization of nuclear power lifting valves. It is the application of simulation calculation methods in the field of valve design and optimization, and has the advantages of intuitive results, low cost, and fast time.

[0143] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0144] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A dynamic modeling method of a nuclear power lifting valve in liquid medium based on CFD, characterized in that: The steps include: Step S1, establishing a three-dimensional structure of a nuclear power lifting valve by using three-dimensional modeling software to obtain a three-dimensional model of the nuclear power lifting valve, wherein the nuclear power lifting valve is a main water supply check valve, and the main water supply check valve comprises a piston (1), a damping plate (2), a valve disc (3) and a valve body (4); Step S2, extracting the calculation flow domain of the nuclear power lifting valve from the three-dimensional model of the nuclear power lifting valve in step S1 and simplifying it; Step S3, using grid division software to grid the calculation flow domain of step S2; Step S4: According to Newton's laws of motion, a valve core dynamics model is performed on the nuclear power poppet valve; Step S5, writing a UDF program to control the movement of the nuclear power poppet valve core, updating the flow domain in real time through the dynamic mesh technology, realizing the fluid-solid coupling of the valve core movement, and obtaining the dynamic characteristics of the nuclear power poppet valve; In step S5, a UDF is written to perform the following operations in each time step: Initialize variables and set the instantaneous speed v and average speed v of the valve core movement average , acceleration a, displacement x, initial value of variable, valve core mass m, time step dt; Use the built-in macro command DEFINE_PROFILE in UDF to set the export boundary conditions to simulate the actual working conditions; The variables are calculated and updated through the built-in macro command DEFINE_ADJUST in UDF. First, the surface ID of the valve core in contact with the fluid is obtained in the fluid simulation software. According to different IDs, functions are written in UDF to obtain pressure P and area A respectively, thereby calculating the fluid force acting on the valve core. Calculate the corresponding instantaneous velocity, acceleration, and average velocity in each time step, store the results in the solver, perform average calculation on the stored multiple data, and use this average as the initial condition for the next step of calculation; The movement of the dynamic mesh area is controlled by the UDF built-in macro command DEFINE_CG_MOTION. The moving speed of the dynamic mesh is the same as the average speed of the current time step, that is, v average As the actual velocity of the fluid area of ​​the moving grid, the regeneration and collapse of the grid, the real-time update of the flow domain and the fluid-solid coupling of the valve core movement are realized through the fluid simulation software; Through the built-in macro command DEFINE_EXECUTE_AT_END in UDF, the time, instantaneous speed, average speed, acceleration, driving force, fluid force and various fluid forces in the calculation process are stored and output to the file, so as to realize the real-time monitoring of the valve core movement and obtain the dynamic characteristics of the valve opening and closing; The mean value calculation in step S5 is performed according to the following formula: a=(a m-n+1 +a m-n+2 +…+a m ) / n v=(v m-n+1 +v m-n+2 +…+v m ) / n v average =(v averagem-n+1 +v averagem-n+2 +…+v averagem ) / n Where n is the characteristic value of the mean algorithm, that is, the data in the current time step and the previous time step, a total of n time steps, are averaged as the corresponding parameter of the valve core movement in the current time step; m 、v m 、v averagem are the acceleration, instantaneous velocity and average velocity of the valve core motion calculated by Newton's laws of motion in the mth time step; a, v, v average are respectively the acceleration, instantaneous speed and average speed of the valve core motion obtained by the mean value algorithm in the mth time step; Step S6: Import the grid data into the fluid simulation software Fluent, load the UDF, set the parameters, and perform simulation calculations. Step S7, verify whether the dynamic characteristics of the nuclear power lifting valve meet the requirements. If so, end the simulation; if not, change the structure of the nuclear power lifting valve and return to step S1 to recalculate.

2. The dynamic modeling method of a nuclear power lifting valve based on CFD in liquid medium according to claim 1 is characterized in that: The step S2 is specifically as follows: The flow channel of the nuclear power lift valve is filled with model processing software, and the calculation flow domain of the nuclear power lift valve, that is, the area where the fluid flows, is extracted from the three-dimensional model of the nuclear power lift valve. Then some unnecessary chamfers and gaps are removed to form a flow area that reflects the performance of the valve system; a pipeline flow domain is added at the inlet of the main water supply check valve, and a pipeline flow domain is also added at the outlet.

3. The dynamic modeling method of a nuclear power lifting valve based on CFD in liquid medium according to claim 1 is characterized in that: The step S3 specifically comprises the following steps: Before dividing the specific grid, the basin is first divided into multiple small blocks according to the fluid movement, and the grid is divided for each small block; Structural grids are used at the inlet and outlet pipes of the nuclear power lifting valve, and unstructured grids are used at the connection between the inlet and outlet of the nuclear power lifting valve; in the division of structural grids, the line-surface-body grid division mode is adopted, and the fine surface grid is first drawn according to the size of the corresponding edge, and then scanned to form a regular hexahedral grid; in the division of unstructured grids, a tetrahedral grid is formed by setting the volume grid size; Set the topological relationship between small watersheds. Set the common node topology structure in the watershed grid part without relative motion so that the nodes are shared between the grids. Set the separated topology structure in the watershed grid part with relative motion. Set the interface between two watersheds without common nodes. Set dynamic mesh area and parameters: divide the mesh area above and below the nuclear power poppet valve core into the movable body area, and set the surface in contact with the valve body as the static surface area.

4. The dynamic modeling method of a nuclear power lifting valve based on CFD in a liquid medium according to claim 1 is characterized in that: The dynamic modeling of the nuclear power lifting valve in step S4 is specifically as follows: The dynamic modeling of the nuclear power lifting valve core is based on the fluid-solid coupling motion of the valve core under the combined action of fluid force, spring force and gravity. The motion of the valve core is discretized into a small time step and follows the following formula: F(t0)=F FLUID (t0)+F SPRING (t0)+G(t0)·sinθ F(t0)=m·a(t0) x(t1)=x(t0)+v average (t1)·dt Where, F is the resultant force on the valve core, F FLUID is the fluid force acting on the valve core, F SPRING is the spring force associated with the valve core, G is the gravity of the valve core and the moving parts that move with it, θ is the angle between the valve installation direction and the horizontal direction; v(t0), a(t0), x(t0) are the instantaneous velocity, acceleration, and displacement of the valve core at time t0, v(t1), a(t1), x(t1) are the instantaneous velocity, acceleration, and displacement of the valve core at time t1, m is the mass of the valve core and the piston, and dt is the discrete time step; v average (t1) is an intermediate variable, which refers to the average velocity of the valve core at time t1 and is used to calculate the actual displacement of the valve core at time t1; By calculating the instantaneous velocity v(t0) and acceleration a(t0) at time t0, the instantaneous velocity v(t1) and displacement x(t1) at time t1 are obtained. The dynamic modeling of the valve core movement is completed by discrete calculation within the time step.

5. The dynamic modeling method of a nuclear power lifting valve based on CFD in a liquid medium according to claim 1 is characterized in that: The step S6 specifically comprises the following steps: Mesh import: import the mesh into the fluid simulation software solver and check the mesh quality; Set the solver type: Select a pressure-based solver and set the gravity direction according to the working state of the nuclear power lift valve. Before the simulation starts, select a steady-state solver to simulate the normal working state of the nuclear power lift valve. Material setting: According to the actual working conditions, select the corresponding material from the material library of the fluid simulation software, or manually set the material properties, including density and viscosity parameters; Select turbulence model: Select turbulence model according to materials and working conditions; Loading UDF: loading the UDF written in step S5, and after loading, calculating simultaneously during the fluid simulation calculation process; Dynamic mesh setting: according to the meshing method in step S3, the movable fluid mesh area is set to RigidBody. If it is a movable surface, the layer height needs to be set, and the speed is specified by the UDF in step S5; the stationary fluid mesh area is set to Stationary. If it is a stationary surface, the layer height needs to be set; the mesh area associated with the movable area is set to Deforming, allowing its mesh to deform along with the movable fluid domain; Setting boundary conditions: setting the boundary type of the position in contact with the solid to Wall, setting the interface of the flow domains that are in contact with the flow domains and do not have a common node topological relationship to Interface, setting the inlet of the nuclear power lift valve to pressure-inlet, and setting the outlet of the nuclear power lift valve to pressure-outlet, wherein the specific parameters of pressure-inlet and pressure-outlet are set in the fluid simulation software according to actual conditions, or specified by the UDF of step S5; Set the solution method: For the simulation analysis of the dynamic performance of nuclear power lifting valves, the SIMPLE method of pressure-velocity coupling is selected; Adjust the relaxation factor: Select the default relaxation factor; Flow field initialization: For steady-state simulation, hybrid initialization is used to obtain the initial value of calculation according to the actual working condition of the nuclear power lifting valve. For transient simulation, steady-state working condition simulation is performed first, and the result of steady-state simulation is saved as the initialization parameter of transient simulation. Transient simulation settings: Set the simulation time step, number of iterations, and convergence residual standard consistent with UDF. For transient simulation, set the simulation termination conditions in UDF, and the simulation will stop automatically after the calculation reaches the termination requirements. Set monitoring parameters: including pressure cloud map and velocity cloud map.

6. The dynamic modeling method of a nuclear power lifting valve based on CFD in a liquid medium according to claim 1 is characterized in that: The step S7 is specifically as follows: After completing the simulation calculation, the dynamic characteristics of the nuclear power lifting valve including the opening and closing time and the opening and closing speed are obtained according to the file output by the UDF in step S5, and the dynamic characteristics are analyzed to see whether they meet the working requirements. If not, the structure is optimized; According to the simulation results, the real-time pressure cloud map, velocity cloud map and streamline map are obtained during the closing process of the nuclear power lifting valve, and the throttling position in the nuclear power lifting valve is determined to provide an object for structural optimization.

7. A computer device, characterized in that: It includes a memory and a processor, wherein a computer program is stored in the memory. When the processor runs the computer program stored in the memory, the processor executes the dynamic modeling method of a nuclear power lifting valve based on CFD in a liquid medium according to any one of claims 1 to 6.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium is used to store a computer program, and the computer program executes the CFD-based dynamic modeling method of a nuclear power lifting valve in a liquid medium as described in any one of claims 1-6.

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