A method for equivalent application of electromagnetic force simulation plasma current and halo current of a magnetic confinement nuclear fusion device

Abstract

This invention discloses a method for equivalent application of plasma current and corona current in electromagnetic force simulation of magnetic confinement fusion devices, belonging to the field of electromagnetic numerical calculation technology for fusion devices. Addressing the problem that the complex spatiotemporal evolution of plasma current and corona current under extreme conditions in magnetic confinement fusion devices makes it difficult to balance computational efficiency with accurate reconstruction of spatially non-uniform distribution characteristics in three-dimensional finite element simulations, this invention first achieves time dimension reduction by extracting the physical inflection point of the transient total current. Then, it maps the current density at each moment to a structured square mesh through mesh node interpolation and reconstructs a three-dimensional equivalent plasma envelope flow channel composed of multiple independent solid channels. Next, it automatically imports the datasets of each flow channel in batches using a control script and automatically creates windings and terminals for association and binding. Finally, it calculates the corona current based on a non-uniform circumferential sinusoidal distribution and applies the time-varying load to the surface of the divertor component in a body-fitted equivalent manner. This invention effectively improves the spatial equivalent mapping accuracy and loading efficiency of time-varying current excitation in transient electromagnetic force simulation.

Description

Technical Field

[0001] This invention belongs to the field of numerical calculation and electromagnetic finite element simulation of nuclear fusion devices, and specifically relates to a method for simulating the equivalent application of plasma current and corona current in electromagnetic force simulation of magnetic confinement nuclear fusion devices. Background Technology

[0002] In the structural safety assessment of magnetic confinement fusion devices based on the finite element method, transient processes such as the large plasma burst (MD) and vertical displacement event (VDE) are extremely destructive extreme conditions. During these transient processes, the plasma current decays rapidly and undergoes violent spatial drift. This transient variable magnetic field induces strong eddy currents in vacuum chamber components such as the vacuum chamber and divertor. These eddy currents interact with the device's inherent strong static magnetic field, generating enormous transient electromagnetic forces. To accurately calculate and evaluate the structural strength of these components, accurately reconstructing and loading the time-varying plasma excitation source in the simulation preprocessing stage is a crucial prerequisite.

[0003] However, the raw plasma current density data generated by two-dimensional physics simulation programs (such as DINA) are typically extremely large, constituting high-dimensional spatiotemporally coupled datasets. These datasets exhibit irregular current cross-sectional shapes, non-uniform internal current density distribution, and dynamic displacement of the plasma's geometric center within the vacuum chamber cavity over time. Currently, mainstream electromagnetic force simulation finite element analysis software (such as ANSYS Maxwell) lacks a batch data import interface, making it impossible to directly map such complex spatiotemporally distributed excitations. If a simplified method is used, equating the plasma to a single long straight conductor or a few current lines, it fails to reflect the true non-uniform current density distribution and the impact of positional drift on induced eddy currents in surrounding components, resulting in excessively large local mechanical analysis errors. Manually configuring hundreds of sub-channels and binding them one by one to time-varying datasets in the simulation software is not only extremely cumbersome and inefficient but also prone to introducing human errors such as data mismatch. Furthermore, under extreme conditions, the contact between the plasma and the vessel wall generates asymmetric halo currents flowing into the wall. How to accurately discretize and load these currents onto the surface of the finite element three-dimensional discontinuous flow channel with high precision is also a current technical challenge.

[0004] Therefore, this invention proposes a method for simulating the equivalent application of plasma current and corona current in electromagnetic force simulation of magnetic confinement nuclear fusion devices. Through a sophisticated data reconstruction mechanism and a scripted batch control interface, it achieves efficient and high-precision equivalent reconstruction and application of complex transient excitation sources in three-dimensional finite element space. Summary of the Invention

[0005] The purpose of this invention is to provide a method for simulating the equivalent application of plasma current and corona current in electromagnetic force simulation of a magnetic confinement nuclear fusion device. Based on the idea of ​​spatial equivalent reconstruction and scripted automatic control, it solves the problem that it is difficult to balance computational efficiency and accurate reproduction of spatial distribution characteristics in three-dimensional electromagnetic finite element simulation of complex time-varying current excitation sources.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for simulating the equivalent application of plasma current and corona current in electromagnetic force simulation of a magnetically confined nuclear fusion device includes the following steps:

[0008] S1. Obtain raw plasma transient current data and perform time-series feature dimensionality reduction and preprocessing;

[0009] S2. Construct a multi-channel three-dimensional plasma solid flow channel model and complete the equivalent mapping of the spatial mesh;

[0010] S3. Write automated control scripts to realize the automatic batch loading of transient current excitation sources in electromagnetic finite element software;

[0011] S4. Based on the circumferential peaking factor, the asymmetric corona current is applied to the divertor surface in a body-fit equivalent manner.

[0012] S5. Construct a simulation output verification mechanism to evaluate the equivalent accuracy and numerical consistency of the applied equivalent excitation source.

[0013] Further, step S1 includes the following sub-steps:

[0014] S11. Read the original multidimensional spatiotemporally coupled plasma current density dataset. The dataset contains transient current density values ​​corresponding to two-dimensional RZ coordinate points of the plasma cross-section at different time steps;

[0015] S12. Perform closed-loop spatial integration along the cross-section of the vacuum chamber to calculate the total current variation curve. Integrate the spatially distributed current density value for each time step to obtain the total plasma current I. p Trend curve of change with time t;

[0016] S13. Extract key time points based on transient physical characteristics to achieve time series dimensionality reduction. Based on the total current change trend curve, identify the starting time of rapid current decay, the point of maximum decay rate, and the key physical inflection points of the quenching stage. Extract N feature time points at non-equidistant intervals to reduce the dimensionality of continuous time series data.

[0017] Further, step S2 includes the following sub-steps:

[0018] S21. Construct a structured square mesh for the cross-section. Extract the maximum geometrical envelope boundary of the plasma cross-section, divide it into a structured two-dimensional mesh containing M sub-elements, and determine the center coordinates (r) of each mesh element. i ,z i );

[0019] S22. Perform two-dimensional spatial current density interpolation mapping. Using the bilinear spatial interpolation algorithm, the continuous current density at the N feature times extracted in step S1 is mapped and assigned to the M structured grid cells;

[0020] S23, Three-dimensional multi-physics channel stretching and model construction. Two-dimensional square mesh cells are stretched at a specific angle along the circumferential direction to generate a three-dimensional equivalent solid model composed of M spatially parallel independent stretched channels, and it is given an equivalent conductivity that characterizes the plasma resistance properties.

[0021] Further, step S3 includes the following sub-steps:

[0022] S31. Batch export of time-series excitation datasets. Output the equivalent current time-varying arrays of M channels at each characteristic time point as M independent external time-series dataset text files, categorized by channel index.

[0023] S32. Automatic registration of batch datasets in the background. Using a scripting language to call the finite element analysis software interface, the software iterates through and imports the M text files, and automatically creates the corresponding time-varying design datasets in batches within the software environment.

[0024] S33. Automatic Excitation Winding Creation Module. Using script control, automatically create M coil winding structures in batches, specify the excitation type as a time-varying current source, and bind them to the corresponding design dataset;

[0025] S34. Cross-section identification and automatic coil terminal assignment and binding. The script automatically identifies the end cross-sections of each solid flow channel in the three-dimensional equivalent plasma envelope model, assigns coil terminals to them, and maps them one by one with the corresponding coil windings to form a closed current excitation flow channel.

[0026] Further, step S4 includes the following sub-steps:

[0027] S41. Calculate the corona current fraction and circumferential asymmetric distribution coefficient under extreme operating conditions. Based on the maximum plasma current of the device, calculate the total corona current fraction under specific large rupture conditions. And combined with the circumaxial peaking factor (TPF) to determine the circumaxial asymmetric distribution;

[0028] S42. Discretized configuration of circumferential channels at equal angles and transient numerical calculation of each channel. The circumferential sector is configured into K virtual conductive channels at equal angles, and the time-varying excitation peak value shared by each virtual conductive channel is calculated using a sinusoidal distribution function;

[0029] S43. Modeling and applying corona current to the virtual flow channel of the divertor. A physical guide rail corresponding to the K discrete intervals is created by stretching on the surface of the divertor as the corona current path, and the time-varying load calculated in step S42 is applied to the guide rail as a current excitation.

[0030] Further, step S5 includes the following sub-steps:

[0031] S51. Perform transient magnetic field calculations in three-dimensional electromagnetic finite element software;

[0032] S52. Extract characteristic physical quantities of electromagnetic field response for comparative verification. Extract and compare the physical responses such as magnetic flux density, induced eddy current density, and component force at specific detection points under equivalent multi-channel plasma excitation and original continuous excitation, and verify the accuracy and effectiveness of equivalent application within the set error allowable range.

[0033] Beneficial effects

[0034] The present invention has the following beneficial effects:

[0035] This invention, based on the concepts of spatial equivalent reconstruction and scripted automatic control, and grounded in three-dimensional finite element transient electromagnetic analysis, designs a multi-channel spatial equivalent mapping mechanism for plasma, achieving accurate reconstruction of complex, non-uniform, and dynamically drifting plasma current excitations. Simultaneously, it introduces an automated script interface, solving the problems of extremely low efficiency and high error rate associated with traditional manual configuration of hundreds of sub-channel time-varying datasets, enabling rapid and automatic application of load inputs. Furthermore, this invention combines circumferential peaking factors and sinusoidal discretization algorithms to provide a standardized procedure for the equivalent application of asymmetric corona currents on the surface of discontinuous internal components in a vacuum chamber, significantly improving the application accuracy and efficiency of excitation sources in electromagnetic simulations under extreme operating conditions of nuclear fusion devices. Attached Figure Description

[0036] Figure 1 The overall flowchart of the plasma and corona current equivalent application method based on spatial reconstruction and script-driven method of the present invention;

[0037] Figure 2 Schematic diagram of two-dimensional mesh generation and interpolation mapping of plasma cross section;

[0038] Figure 3 : Curve showing the trend of total plasma current over time;

[0039] Figure 4Distribution map of characteristic time points of total plasma current;

[0040] Figure 5 : A schematic diagram of the equivalent solid model of the M=447 channel three-dimensional plasma obtained by the reconstruction of this invention;

[0041] Figure 6 : Data flow binding program architecture diagram of the automated control script of this invention in finite element analysis software;

[0042] Figure 7 Schematic diagram of the asymmetric corona current-fitted flow channel on the divertor surface and six equal-angle loading regions;

[0043] Figure 8 A comparison curve of the induced electromagnetic force of the vacuum chamber components after finite element analysis, with and without the equivalent application method of this invention. Detailed Implementation

[0044] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] like Figure 1 As shown, the electromagnetic force simulation method for plasma current and corona current equivalent application in this embodiment of the magnetic confinement fusion device is implemented based on a type of tokamak fusion experimental device. The design parameters of this device are: plasma current I... p =2.5MA, circumferential static magnetic field strength B T =2.5T.

[0046] S1. Obtain the raw plasma transient current data and perform time-series feature dimensionality reduction and preprocessing.

[0047] The specific processing includes the following sub-steps:

[0048] S11. Read the original multidimensional spatiotemporal coupled dataset.

[0049] S12. Perform a closed-loop spatial integration along the cross-section of the vacuum chamber to calculate the total current variation curve. Perform a closed-loop spatial integration on the transient current density J(R,Z,t) on the two-dimensional RZ cross-section at each moment to calculate its time-varying total current I. total (t):

[0050]

[0051] S13. Extract key time points based on transient physical characteristics to achieve temporal dimensionality reduction. Figure 3 The figure shows the total current I. pThe trend curve of current change with time t. Within this evolution stage, based on the onset time of rapid current quenching, the point of maximum rate of change, and the transient evolution inflection point, N=28 characteristic time points are extracted at non-equidistant intervals. Their specific extraction distribution is as follows: Figure 4 As shown, this step successfully reduced the time-varying current to 28 transient data points in the time dimension.

[0052] S2. Construct a multi-channel three-dimensional plasma solid flow channel model and complete the equivalent mapping of the spatial mesh.

[0053] Specifically, it includes the following sub-steps:

[0054] S21. Construct a structured square mesh for the plasma cross-section. Extract the maximum geometric envelope boundary of the plasma cross-section and divide it into a two-dimensional square structured mesh, such as... Figure 2 As shown. In this embodiment, the number of grid cells is M=447, and the coordinates of the center point of each cell (r) are calculated. i ,z i );

[0055] S22. Perform two-dimensional spatial current density interpolation mapping. Using a bilinear interpolation algorithm, the non-uniformly distributed current density corresponding to the characteristic time in step S1 is mapped and distributed into 447 square grids. During the mapping process, a quality check is performed on the total mapped current at each characteristic time.

[0056]

[0057] Set the convergence verification threshold ε = 0.001·I total (t). The check is passed if and only if the error E(t) < ε.

[0058] S23, 3D multi-physics channel stretching and model construction. Stretching mesh elements along the circumferential direction generates a 3D equivalent solid model consisting of 447 independent flow channels, such as... Figure 5 As shown, it is imported as a three-dimensional geometric entity into the finite element electromagnetic solver.

[0059] S3. Write automated control scripts to achieve automatic batch loading of transient current excitation sources in electromagnetic finite element software.

[0060] Specifically, it includes the following sub-steps:

[0061] S31. Batch export of time-varying datasets. Export the time-varying equivalent current data of 447 channels at 28 time points after dimensionality reduction as independent external time-series dataset text files according to channel number.

[0062] S32. Batch Data Registration. Write a control script to import the timing files into the electromagnetic simulation software in batches and register them as design datasets with time-driven variables.

[0063] S33. Automatically create excitation winding modules. Batch automatically create 447 coil winding modules.

[0064] S34. Section Recognition and Automatic Coil Terminal Assignment and Binding. The script automatically identifies the planes of each sub-entity in the 3D flow channel model, automatically assigns coil terminals, and establishes binding mappings, such as... Figure 6 As shown, the entire preprocessing for payload source binding can be completed automatically in just a few minutes using script-driven methods.

[0065] S4. Based on the circumferential peaking factor, the asymmetric corona current is applied to the divertor surface in a body-equivalent manner.

[0066] Specifically, it includes the following sub-steps:

[0067] S41. Calculate the corona current fraction and circumferential asymmetric distribution coefficient under extreme operating conditions. Based on calibration specifications, the total fraction of the time-varying corona current under this condition is calculated as 50% of the total plasma current, i.e. Set the circumferential peaking factor (TPF) to 2.0.

[0068] S42. Discretization configuration of circumferential channels at equal angles and transient numerical calculations for each channel. The circumferential 36° divertor sector angle is discretized into K=6 virtual conductive channels, with the angle step size corresponding to a single channel being... =6°. The circumferential angles corresponding to the center positions of each flow channel are configured as follows: 75°, 81°, 87°, 93°, 99°, 105°.

[0069] The peak time-varying corona current allocated to each discrete channel is calculated using the following formula:

[0070]

[0071] The calculated equivalent time-varying corona current input excitation peak values ​​for each flow channel are: 40.95kA, 41.40kA, 41.63kA, 41.63kA, 41.40kA, and 40.95kA.

[0072] S43, Divertor-fitted virtual flow channel modeling and corona current application. For example... Figure 7 As shown, in the finite element divertor model, a solid conductive surface containing 6 circumferential discrete elements is established to fit its outer surface as an equivalent corona current transmission channel. The time-varying load calculated in step S42 is applied to the channel as a current excitation using a control script.

[0073] S5. Construct a simulation output verification mechanism to evaluate the equivalent accuracy and numerical consistency of the applied equivalent excitation source.

[0074] Specifically, it includes the following sub-steps:

[0075] S51. Perform transient magnetic field calculation in three-dimensional electromagnetic finite element software. Set the time step of the electromagnetic transient solution to match the time frequency in step S11, and complete the transient solution.

[0076] S52. Extract characteristic physical quantities of the electromagnetic field response for comparison and verification. Extract the induced eddy current distribution of the component obtained from simulation calculations. For example... Figure 8 As shown, the transient response of the electromagnetic force on the vacuum chamber during plasma abrupt changes is compared between the equivalent multi-channel mapping excitation method of this invention and the simplified method using a single long straight wire. The comparison reveals that the method without multi-channel equivalent reconstruction fails to represent the spatial displacement of the current density, leading to a significant underestimation of the calculated local induced magnetic field strength and peak electromagnetic force, with an underestimation deviation reaching 12.3%. In contrast, the multi-channel equivalent method of this invention effectively restores the physical response under non-uniform spatial distribution, ensuring high accuracy of the simulation analysis results.

[0077] The specific implementation scheme of this invention aims to illustrate the physical and mathematical implementation process of the invention method. Its technical essence belongs to the algorithm innovation of nuclear fusion numerical simulation, and is not the only limitation of the protection boundary of this invention.

Claims

1. A method for applying equivalent plasma current and corona current in electromagnetic force simulation of a magnetic confinement nuclear fusion device, characterized in that, Includes the following steps: S1. Extraction and dimensionality reduction of time-varying plasma current temporal features; S2, Multi-channel three-dimensional plasma equivalent solid flow channel reconstruction; S3. Batch application of plasma current based on control script; S4. Corona current is applied to the body based on a non-uniform circumferential sinusoidal distribution.

2. The method for applying equivalent plasma current and corona current in electromagnetic force simulation of a magnetic confinement nuclear fusion device according to claim 1, characterized in that: In step S1, the original time-varying current distribution data is a five-dimensional array from a two-dimensional physical simulation program, which includes the spatial coordinates of the plasma cross section, the time step, and the transient current density value corresponding to each coordinate. The extraction of the N key time points is achieved by identifying the current instantaneous failure start point, the maximum decay rate point, and the key bending inflection point of the rapid current quenching stage in the total current change trend curve.

3. The method for applying equivalent plasma current and corona current in electromagnetic force simulation of a magnetic confinement nuclear fusion device according to claim 1, characterized in that: In step S2, the mapping grid adopts a two-dimensional square grid. Using bilinear interpolation or nearest neighbor interpolation algorithms, continuous current density values ​​are mapped to discrete square grid nodes to ensure that the equivalent total current characteristics are consistent before and after grid mapping.

4. The method for applying equivalent plasma current and corona current in electromagnetic force simulation of a magnetic confinement nuclear fusion device according to claim 1, characterized in that: In step S2, the cross-sectional shape and number of the M independent solid channels are completely consistent with the two-dimensional square grid cell; each independent solid channel is given an equivalent resistivity property to characterize the conductivity characteristics of the plasma under different electromagnetic transient conditions.

5. The method for applying equivalent plasma current and corona current in electromagnetic force simulation of a magnetic confinement nuclear fusion device according to claim 1, characterized in that: In step S3, the automated control script is written in IronPython and implements the following automated process by calling the background application programming interface of the electromagnetic finite element analysis software: (1) Automatically traverse and read the M time series dataset texts containing channel index identifiers, and call the dataset addition interface to create M design datasets with time variables; (2) Automatically create M coil winding structures in batches and set their excitation type to the time-varying current source mode driven by the design dataset; (3) According to the geometric naming rules, the cross section of the three-dimensional equivalent plasma envelope flow channel model is automatically identified, M coil terminals are assigned, and the coil terminals are automatically assigned to the corresponding coil windings.

6. The method for applying equivalent plasma current and corona current in electromagnetic force simulation of a magnetic confinement nuclear fusion device according to claim 1, characterized in that: In step S4, the angular discretization configuration of the circumferential channels specifically involves configuring K virtual conductive channels within the angular range corresponding to the divertor sector, with each virtual conductive channel carrying an angular span of [missing information]. .

7. The method for applying equivalent plasma current and corona current in electromagnetic force simulation of a magnetic confinement nuclear fusion device according to claim 1, characterized in that: In step S4, each virtual conductive channel carries a time-varying non-uniform excitation value I. i The calculation formula is as follows: 。 8. Among them, θ i Let be the circumferential center angle corresponding to the i-th virtual conductive channel. I represents the circumferential angular span corresponding to a single channel, TPF is the circumferential peaking factor, and I h,max This represents the transient maximum circumferential corona current amplitude.

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