Simulation method for arc ablation resistance of insulating material surface with pyrolysis effect

Abstract

The application provides a simulation method for arc ablation resistance of insulating material surface with pyrolysis effect, and belongs to the field of insulating material performance detection. The method comprises the following steps: establishing a simulation model; setting a model boundary condition; introducing a pyrolysis theory on the basis of MHD control equations on the fluid side to couple and simulate actual ablation conditions; and judging the arc ablation resistance of the insulating material through comparison with a TGA curve and a DTG curve of the insulating material. The application takes a dynamic power frequency alternating current arc and a non-ideal insulating material as simulation objects, is more in line with engineering practice, can simulate the surface arc ablation resistance process of any insulating material by changing the physical property parameters of the insulating material, and can introduce the TGA curve of the material to judge the arc ablation resistance performance of the insulating material, so as to accurately determine the arc ablation resistance limit and comprehensive performance of the epoxy / alumina composite material.

Description

Technical Field

[0001] This invention relates to the field of insulation material performance testing, and specifically to a simulation method for simulating the arc ablation resistance of insulation material surfaces by introducing pyrolysis effects. Background Technology

[0002] In the field of electrical equipment manufacturing, insulating powder is widely used in the fabrication of various components, such as busbars, supports, bus trunking, and some busbars. It can be applied using simple spraying or electrostatic deposition to effectively improve the dielectric strength of electrical equipment and its environmental resistance under complex operating conditions, and has been widely used in the field of insulation protection.

[0003] The stable and reliable operation of high-voltage switchgear is closely related to the safety of the power system, and the arc resistance of insulating materials is an important indicator for evaluating switchgear. In the event of a partial fault (such as an emergency tripping fault due to a short circuit in a high-voltage circuit breaker), a high-energy arc of tens of thousands of degrees Celsius will be generated, causing destructive thermal ablation of the insulating material surface. This structural damage can lead to a sharp drop in insulation strength and may trigger a transient flashover fault. Therefore, designing a simulation method for arc ablation resistance of insulating material surfaces with pyrolysis effects is necessary to comprehensively simulate the complete arc ablation process, accurately describe the ablation impact of arcs on the insulating material surface, and improve the performance evaluation system for insulating materials.

[0004] The paper titled "Magnetic Hydrodynamic Modeling, Simulation and Experimental Study of Vacuum Arc Combustion Process" (Yu Ruijie. Magnetohydrodynamic Modeling, Simulation and Experimental Study of Vacuum Arc Combustion Process [D]. Shenyang University of Technology. 2025) constructs a three-dimensional transient simulation model of the vacuum arc plasma arc column region based on the three conservation equations of fluid mechanics to solve the vacuum arc combustion process, focusing on analyzing the arc characteristics and its mechanism. However, it does not analyze the influence of arc ablation on insulating materials, only studying the arc's own combustion process. In the experiment, the performance of the insulating material is the core issue of the arc resistance test.

[0005] In summary, the existing technology has the following problems: (1) Existing models mostly focus on studying the characteristics of the electric arc itself, neglecting the characterization of the insulation material under test and the mechanism of the electric arc on the insulation material in the overall arc resistance test, which makes it difficult to guide practical engineering problems; (2) Existing models mostly focus on the temperature distribution under the direct action of electric arc, while ignoring the pyrolysis of the epoxy itself under the high temperature of electric arc. Therefore, existing models can only basically reflect the partial temperature trend distribution of insulating materials under the action of electric arc, but cannot reflect the actual mechanism of electric arc resistance test on the surface of insulating materials. (3) The existing model does not dynamically describe the material parameters of the insulating material to be ablated under temperature and decomposition conditions, and cannot realize the actual parameters such as damage accumulation under the action of real electric arc. At the same time, it cannot determine the surface morphology characteristics of the ablated material, and cannot guide the actual engineering needs. Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the deficiencies of the prior art. Specifically, this invention provides a simulation method for simulating the arc ablation resistance of insulating material surfaces by introducing a pyrolysis effect. The method involves calculating the arc ablation resistance model of the insulating material surface using COMSOL finite element simulation software, and determining the degree of arc ablation resistance of the insulating material by combining the TGA curve of the insulating material. This simulation test method verifies the arc ablation resistance performance of the insulating material.

[0007] The technical solution of the present invention is as follows: A simulation method for arc ablation resistance of insulating material surfaces incorporating pyrolysis effects includes the following steps: Step 1: Establish a three-dimensional multi-domain coupled simulation model that includes an insulating platform, an insulating material target plate, a V-shaped needle electrode, a columnar arc, and the surrounding air domain, and import it into the COMSOL finite element simulation software; Step 2: Given the material properties of each component in the three-dimensional multi-domain coupled simulation model, set the constraints of the three-dimensional multi-domain coupled simulation model; Step 3: Construct the MHD governing equations of the three-dimensional multi-domain coupled simulation model, and... Arrhenius The equations tracking the pyrolysis reaction rate are coupled with the interpolation function of the degree of pyrolysis and the thermal damage equation into a three-dimensional multi-domain coupled simulation model; the set of all equations and interpolation functions is denoted as the governing equations; Step 4: Define the parameters involved in the governing equations in the global definition module of the COMSOL finite element simulation software; configure the circuit module, magnetic field and electric field module, laminar flow module, heat transfer module, deformable mesh module, and coefficient form partial differential equation module for the three-dimensional multi-domain coupled simulation model, and set the required boundaries in these modules; Step 5: Configure the user-defined mesh in the COMSOL finite element simulation software; Step 6: Perform continuous arc ablation simulation on the three-dimensional multi-domain coupled simulation model in COMSOL finite element simulation software, and iteratively calculate the MHD flow field evolution and material pyrolysis process using steady-state solver and transient solver. Step 7: Based on the data from the arc ablation simulation, obtain the evolution curves of the proportion of each phase with temperature, ablation morphology diagram, surface temperature distribution diagram, and cross-sectional temperature distribution diagram.

[0008] Preferably, in step 1, the insulating platform is at the bottom of the three-dimensional multi-domain coupled simulation model, the insulating material target plate is located at the center of the upper surface of the insulating platform, two needle-shaped electrodes are placed in a V-shape above the insulating material target plate, and the columnar arc is located between the two needle electrodes. The space above the insulating platform, the insulating material target plate, the columnar arc, and the needle electrodes is an air domain for fluid and heat exchange. The columnar arc is the columnar arc plasma generated in the discharge channel after the V-shaped needle electrode is pressurized in the actual arc ablation test.

[0009] Preferably, the material properties of each component in step 2 include: the V-shaped needle electrode is tungsten, the insulating platform is an insulating material, the air domain is air, the upper part of the insulating material target plate is epoxy resin, and the lower part of the insulating material target plate is copper. The constraints of the three-dimensional multi-domain coupled simulation model described in step 2 are as follows: Assuming that the columnar arc plasma in the discharge channel is in laminar flow mode and is completely ionized, its internal energy exchange satisfies the local thermodynamic equilibrium condition; Ignore the ablation process of the electrode by the electric arc; Ignore the effects of gravity and the inertial components of electrons; Assume that the plasma density, specific heat capacity at constant pressure, electrical conductivity, and net radiative dissipation coefficient of total volume are univariate functions that depend only on the local temperature; Secondary interference of various gases generated by the melting of the needle electrode on the flow field is ignored.

[0010] Preferably, the MHD governing equations in step 3 include the magnetofluid mass conservation equation, the magnetofluidity conservation equation, the energy conservation equation, and the electromagnetic field equation; the magnetofluid mass conservation equation, the magnetofluidity conservation equation, the energy conservation equation, and the electromagnetic field equation... Arrhenius The equations, interpolation functions, and thermal damage equations are as follows: The magnetic flux mass conservation equation is: ; in, ρ For fluid density, t For time, U The velocity vector of the fluid motion. For curl operator; The energy conservation equation for the magnetohydrodynamic fluid is: ; in, T For temperature, C For specific heat capacity, q The heat flux density vector, Q For the heat source term, its expression is: ; In the formula,J For current density, k B Boltz constant, e For electron charge, E For electric field strength, Q rad For total volumetric heat dissipation, , ε rad Net radiation coefficient; The equation for the conservation of magnetic flux is: ; ; ; In the formula, u, v, w They are respectively x, y, z Gas flow velocity in the direction; η The viscosity coefficient of the fluid; S u 、S v 、S w They are respectively x、 y, z The source component of the direction is expressed as follows: ; ; ; In the formula, F x , F y , F z They are respectively volume forces in x, y, z Components in direction; The electric and magnetic field equations are expressed using Maxwell's equations, as follows: ; In the formula, ρ e For charge density, D It is the electric displacement vector. B Magnetic flux density H Let be the magnetic field strength, where is the magnetic field strength. H and electric displacement vector D The expressions are as follows: ; ; In the formula, μ Permeability, ε0 The vacuum permittivity, ε r The relative permittivity of the medium; The Arrhenius The equation is used to describe the pyrolysis reaction rate at any given time. V Specifically, assume that the densities of the epoxy phase, residual carbon phase, and gaseous phase are all constants in the pyrolysis reaction. Arrhenius The equation is: ; In the formula, e This represents the real-time volume fraction of the epoxy phase. E a The activation energy for the pyrolysis reaction. V 0 is the pyrolysis reaction constant. R The gas constant is... For temperature T Over time t Changes; The interpolation function is used to characterize the degree of pyrolysis. Specifically, the real-time volume fractions of the epoxy phase, residual carbon phase, and gas phase are used as core variables to control the density of the solid phase. ρ ( T ) specific heat C ( T ) and thermal conductivity k ( T The solid phase is a combination of epoxy and residual carbon phases, and the expression for the interpolation function is: ; In the formula, e ( T ), c ( T ), g ( T The figures represent the real-time volume fractions of the epoxy phase, residual carbon phase, and gaseous phase, respectively. ρ e , ρ c , ρ g The densities of the epoxy phase, residual carbon phase, and gas phase are respectively. C e , C c , C g The specific heats are those of the epoxy phase, residual carbon phase, and gas phase, respectively. k e , k c ,k g Let be the thermal conductivity of the epoxy phase, residual carbon phase, and gas phase, respectively, and satisfy the following: ; ; In the formula, ρ e The density of the epoxy phase. ρ c Γ is the density of the residual carbon, and Γ is the gasification coefficient of the epoxy resin; The thermal damage equation is: ; In the formula, Q e Thermal damage caused by the vaporization of epoxy groups. L e It is the latent heat of vaporization of epoxy groups.

[0011] Preferably, the boundary settings for the circuit module, magnetic field and electric field module, laminar flow module, heat transfer module, deformable mesh module, and coefficient form partial differential equation module described in step 4 are as follows: For the circuit module, a two-end circuit network is set up. The open-circuit voltage of the circuit network is set to AC high voltage, one end is set to ground, and the other end is coupled to the magnetic field and electric field module. For the magnetic field and electric field modules, one of the needle electrodes is grounded at its tail end, and the other needle electrode is coupled to the circuit module at its tail end. The remaining boundaries of the two needle electrodes are set to be electrically insulated. For the laminar flow module, the outer boundary of the air domain is set as an open boundary, and the remaining boundaries of the air domain are wall boundaries without slippage. For the heat transfer module, the outer boundary of the air domain is set as an open boundary, and the boundary around the insulating platform is set as a natural convection heat transfer boundary. For the deformable mesh module, select the fixed mesh region and the free deformable region in the mesh, and set the specified normal mesh velocity boundary; For the coefficient form of partial differential equations module, through Arrhenius The equations track the interpolation function of the degree of pyrolysis generated by the pyrolysis reaction rate and the thermal damage equation. The interpolation function is used to set the epoxy phase and residual carbon phase to characterize the degree of pyrolysis of the material under test, and the solid phase is set to be epoxy phase at the beginning of the simulation; the gas phase is set using measurement parameters.

[0012] Preferably, the mesh described in step 5 is a tetrahedral mesh, and the mesh size is determined by a partitioning method, specifically: The arc generation area is designated as region 1, and its settings are: grid size of 0.03mm to 1.93mm and curvature factor of 0.2; The V-shaped electrode area is designated as region 2, and its settings are: grid size of 0.3mm to 7mm and curvature factor of 0.3; The area outside the arc generation zone on the insulating material target plate is designated as region 3, and its settings are: grid size of 0.22mm to 3.4mm and curvature factor of 0.3; The area outside the above three areas is designated as Area 4, and its settings are: grid size of 3.6mm to 20mm and curvature factor of 0.6.

[0013] Preferably, step 6 is implemented as follows: In COMSOL finite element simulation software, continuous arc ablation simulation was performed on a three-dimensional multi-domain coupled simulation model. During the simulation, a steady-state solver was used to solve for the electric and magnetic field distributions, and a transient solver was used to solve for the thermal field, pyrolysis degree, and multiphysics coupling results. The MHD governing equations and... Arrhenius The parameters describing the electro-magnetic-thermal-pyrolysis behavior are solved by coupled iterative equations to simulate the continuous arc ablation process on the surface of insulating materials with pyrolysis effects.

[0014] Preferably, step 7 is implemented as follows: Step 7.1, the simulation process of step 6 continues until the arc ablation stage on the surface of the insulating material is completely finished. Based on the data collected during the simulation, we obtain the evolution curves of the proportion of each phase with temperature, the surface temperature distribution map, the cross-sectional temperature distribution map, and the ablation morphology map. We analyze the phase evolution characteristics and damage mechanism to find out the reason why the arc resistance test causes the insulation layer of the insulating material target plate to fail. Step 7.2 involves comparing and cross-validating the causes obtained in Step 7.1 with the different heating rates obtained from TGA thermogravimetric analysis to determine the material's pyrolysis process, thereby accurately determining the material's ablation resistance limit and overall performance.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention focuses on characterizing the properties of the tested insulating material and analyzes the mechanism of electric arc on the tested insulating material. It abandons the traditional static parameters and uses real-time calculated epoxy phase, residual carbon phase and gas phase as core variables to control the density, specific heat and thermal conductivity of the solid phase. It analyzes the electro-magnetic-thermal-pyrolysis process of each part of the overall three-dimensional multi-domain coupled simulation model.

[0016] (2) This invention proposes a simulation method for simulating the arc-resistant ablation characteristics of insulating material surfaces by introducing pyrolysis effects, constructing the MHD governing equations of a three-dimensional multi-domain coupled simulation model, and integrating them with the simulation results. ArrheniusThe interpolation function of the degree of pyrolysis generated by the equation tracking the pyrolysis reaction rate and the thermal damage equation are coupled into a three-dimensional multi-domain coupled simulation model. A steady-state solver is used to solve for the electric and magnetic field distributions, while a transient solver solves for the thermal field, degree of pyrolysis, and multi-physics coupling results. The overall simulation is achieved through the MHD governing equations and... Arrhenius The parameters describing the electro-magnetic-thermal-pyrolysis behavior are solved by coupled iterative equations to simulate the continuous arc ablation process on the surface of the insulating material with pyrolysis effect. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the three-dimensional multi-domain coupled simulation model in this invention.

[0018] Figure 2 For volumetric radiation dissipation in this invention The value is a nonlinear function graph of temperature T.

[0019] Figure 3 This is a schematic diagram of mesh partitioning in an embodiment of the present invention.

[0020] Figure 4 This is a true image of the surface morphology of epoxy decomposition.

[0021] Figure 5 This is a simulated epoxy decomposition morphology diagram obtained through simulation in an embodiment of the present invention.

[0022] Figure 6 This is a simulated temperature distribution map of the damaged area obtained through simulation in an embodiment of the present invention.

[0023] Figure 7 This is a simulation curve showing the evolution of phase ratio as a function of temperature in an embodiment of the present invention.

[0024] Figure 8 This is a surface temperature distribution diagram obtained through simulation in an embodiment of the present invention.

[0025] Figure 9 This is a cross-sectional temperature distribution diagram obtained through simulation in an embodiment of the present invention.

[0026] Figure 10 The TGA thermogravimetric analysis curve is shown in the embodiment of the present invention.

[0027] Figure 11 The DTG thermogravimetric analysis curve is shown in the embodiment of the present invention. Detailed Implementation

[0028] To enable those skilled in the art to understand the technical solution of the present invention more clearly, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0029] This invention provides a simulation method for simulating the arc ablation resistance of insulating material surfaces by introducing pyrolysis effects, comprising the following steps: Step 1: Establish a three-dimensional multi-domain coupled simulation model that includes an insulating platform, an insulating material target plate, a V-shaped needle electrode, a columnar arc, and the surrounding air domain, and import it into the COMSOL finite element simulation software.

[0030] Figure 1 This is a schematic diagram of the three-dimensional multi-domain coupled simulation model in this invention. Figure 1 As can be seen, in this embodiment, the insulating platform is at the bottom of the three-dimensional multi-domain coupling simulation model, the insulating material target plate is located at the center of the upper surface of the insulating platform, the two needle-shaped electrodes are placed in a V-shape above the insulating material target plate, and the columnar electric arc is located between the two needle electrodes. The space above the insulating platform, the insulating material target plate, the columnar electric arc, and the needle electrodes is an air domain for fluid and heat exchange.

[0031] The columnar arc refers to the columnar arc plasma generated in the discharge channel after the V-shaped needle electrode is pressurized in the actual arc ablation test.

[0032] In this embodiment, the specific dimensions of this three-dimensional model are as follows: the insulating stage is 200mm long, 200mm wide, and 10mm high. The insulating target plate is composed of an epoxy resin with a height of 1mm and a copper plate with a height of 3mm, and is 100mm long and 100mm wide. Two needle-shaped electrodes are positioned at 45°, with their needle tips placed on the surface of the insulating material, spaced 6.35mm apart. The electrode material is tungsten. A columnar arc is formed between the tips of the two needle-shaped electrodes, with a length of 6.35mm and a diameter of 0.2mm. The air domain is a rectangular space with a length of 200mm, a width of 200mm, and a height of 100mm.

[0033] Step 2: Given the material properties of each component in the three-dimensional multi-domain coupled simulation model, set the constraints of the three-dimensional multi-domain coupled simulation model.

[0034] In this embodiment, the material properties of each component include: the V-shaped needle electrode is tungsten, the insulating platform is an insulating material, and the air domain is air; the upper part of the insulating material target plate is epoxy resin material, and the lower part of the insulating material target plate is copper material.

[0035] In this embodiment, the constraints of the three-dimensional multi-domain coupled simulation model are: Assuming that the columnar arc plasma in the discharge channel is in laminar flow mode and is completely ionized, its internal energy exchange satisfies the local thermodynamic equilibrium condition; Ignore the ablation process of the electrode by the electric arc; Ignore the effects of gravity and the inertial components of electrons; Assume that the plasma density, specific heat capacity at constant pressure, electrical conductivity, and net radiative dissipation coefficient of total volume are univariate functions that depend only on the local temperature; Secondary interference of various gases generated by the melting of the needle electrode on the flow field is ignored.

[0036] In this embodiment, the material parameters of each part are shown in Table 1 and Table 2.

[0037] Table 1

[0038] Table 2

[0039] Step 3: Construct the MHD governing equations of the three-dimensional multi-domain coupled simulation model, and... Arrhenius The equations tracking the pyrolysis reaction rate are coupled with the interpolation function of the degree of pyrolysis and the thermal damage equation into a three-dimensional multi-domain coupled simulation model; the set of all equations and interpolation functions is denoted as the governing equations; In this embodiment, the MHD governing equations include the magnetofluid mass conservation equation, the magnetofluidity conservation equation, the energy conservation equation, and the electromagnetic field equation.

[0040] The aforementioned magnetic flux mass conservation equation, magnetic flux conservation equation, energy conservation equation, and electromagnetic field equation Arrhenius The equations, interpolation functions, and thermal damage equations are as follows: The magnetic flux mass conservation equation is: ; in, ρ For fluid density, t For time, U The velocity vector of the fluid motion. For curl operator.

[0041] The energy conservation equation for the magnetohydrodynamic fluid is: ; in, T For temperature, C For specific heat capacity, q The heat flux density vector, Q For the heat source term, its expression is: ; In the formula, J For current density, k B Boltz constant, e For electron charge, E For electric field strength, Q rad For total volumetric heat dissipation, , ε rad This is the net radiation coefficient.

[0042] Total volumetric radiation dissipation The value is temperature. T The nonlinear function, the specific curve is as follows Figure 2 As shown.

[0043] The equation for the conservation of magnetic flux is: ; ; ; In the formula, u, v, w They are respectively x, y, z Gas flow velocity in the direction; η The viscosity coefficient of the fluid; S u 、S v 、S w They are respectively x、 y, z The source component of the direction is expressed as follows: ; ; ; In the formula, F x , F y , F z They are respectively volume forces in x, y, z Components in direction.

[0044] The electric and magnetic field equations are expressed using Maxwell's equations, as follows: ; In the formula, ρ e For charge density, D It is the electric displacement vector. B Magnetic flux density H Let be the magnetic field strength, where is the magnetic field strength. H and electric displacement vector D The expressions are as follows: ; ; In the formula, μ Permeability, ε0 The vacuum permittivity, ε r is the relative permittivity of the medium.

[0045] The Arrhenius The equation is used to describe the pyrolysis reaction rate at any given time. V Specifically, assume that the densities of the epoxy phase, residual carbon phase, and gaseous phase are all constants in the pyrolysis reaction. Arrhenius The equation is: ; In the formula, e This represents the real-time volume fraction of the epoxy phase. E a The activation energy for the pyrolysis reaction. V 0 is the pyrolysis reaction constant. R The gas constant is For temperature T Over time t The changes.

[0046] The interpolation function is used to characterize the degree of pyrolysis. Specifically, the real-time volume fractions of the epoxy phase, residual carbon phase, and gas phase are used as core variables to control the density of the solid phase. ρ ( T ) specific heat C ( T ) and thermal conductivity k ( T The solid phase is a combination of epoxy and residual carbon phases, and the expression for the interpolation function is: ; In the formula, e ( T ), c ( T ), g ( T The figures represent the real-time volume fractions of the epoxy phase, residual carbon phase, and gaseous phase, respectively. ρ e , ρ c , ρ g The densities of the epoxy phase, residual carbon phase, and gas phase are respectively. C e , C c , C g The specific heats are those of the epoxy phase, residual carbon phase, and gas phase, respectively. k e ,k c , k g Let be the thermal conductivity of the epoxy phase, residual carbon phase, and gas phase, respectively, and satisfy the following: ; ; In the formula, ρ e The density of the epoxy phase. ρ c Γ represents the density of the residual carbon, and Γ represents the vaporization coefficient of the epoxy resin.

[0047] The thermal damage equation is: ; In the formula, Q e Thermal damage caused by the vaporization of epoxy groups. L e It is the latent heat of vaporization of epoxy groups.

[0048] Step 4: Define the parameters involved in the governing equations in the global definition module of the COMSOL finite element simulation software; configure the three-dimensional multi-domain coupled simulation model with circuit module, magnetic field and electric field module, laminar flow module, heat transfer module, deformable mesh module and coefficient form partial differential equation module, and set the required boundaries in these modules.

[0049] In this embodiment, the boundary settings of the circuit module, magnetic field and electric field module, laminar flow module, heat transfer module, deformable mesh module, and coefficient form partial differential equation module are as follows: For the circuit module, a two-end circuit network is set up. The open-circuit voltage of the circuit network is set to AC high voltage, one end is set to ground, and the other end is coupled to the magnetic field and electric field module. For the magnetic field and electric field modules, one of the needle electrodes is grounded at its tail end, and the other needle electrode is coupled to the circuit module at its tail end. The remaining boundaries of the two needle electrodes are set to be electrically insulated. For the laminar flow module, the outer boundary of the air domain is set as an open boundary, and the remaining boundaries of the air domain are wall boundaries without slippage. For the heat transfer module, the outer boundary of the air domain is set as an open boundary, and the boundary around the insulating platform is set as a natural convection heat transfer boundary. For the deformable mesh module, select the fixed mesh region and the free deformable region in the mesh, and set the specified normal mesh velocity boundary; For the coefficient form of partial differential equations module, through ArrheniusThe equations track the interpolation function of the degree of pyrolysis generated by the pyrolysis reaction rate and the thermal damage equation. The interpolation function is used to set the epoxy phase and residual carbon phase to characterize the degree of pyrolysis of the material under test, and the solid phase is set to be epoxy phase at the beginning of the simulation; the gas phase is set using the measured parameters.

[0050] In this embodiment, the initial voltage at the tail end of the needle electrode coupled to the circuit module in the magnetic field and electric field module is 0 / V. The AC high voltage in the circuit module is a 50Hz AC high voltage. In the laminar flow module, the normal stress at the open boundary is 0 N / m. 2 In the heat transfer module, the outer boundary temperature of the air domain, the surface temperature around the insulating platform, and the bottom surface are all 293.15 K. In the deformable mesh module, the ablation region is set as the free deformation region, and the remaining area of ​​the insulating material target plate is set as the fixed mesh region. The geometric function in the coordinate system settings is set to 2. In the coefficient form partial differential equation module, the unit for the source term physical quantity is set to kg / (m²). 3 ×s).

[0051] Step 5: Configure the user-defined mesh in the COMSOL finite element simulation software.

[0052] Figure 3 This is a schematic diagram of mesh generation in an embodiment of the present invention. Figure 3 As can be seen, in this embodiment, the mesh is a tetrahedral mesh, and the mesh size is determined by a partitioning method, specifically: The arc generation area is designated as region 1, and its settings are: grid size of 0.03mm to 1.93mm and curvature factor of 0.2; The V-shaped electrode area is designated as region 2, and its settings are: grid size of 0.3mm to 7mm and curvature factor of 0.3; The area outside the arc generation zone on the insulating material target plate is designated as region 3, and its settings are: grid size of 0.22mm to 3.4mm and curvature factor of 0.3; The area outside the above three areas is designated as Area 4, and its settings are: grid size of 3.6mm to 20mm and curvature factor of 0.6.

[0053] Step 6: Perform continuous arc ablation simulation on the three-dimensional multi-domain coupled simulation model in COMSOL finite element simulation software. Iteratively calculate the MHD flow field evolution and material pyrolysis process using steady-state and transient solvers.

[0054] In this embodiment, step 6 is implemented as follows: In COMSOL finite element simulation software, continuous arc ablation simulation was performed on a three-dimensional multi-domain coupled simulation model. During the simulation, a steady-state solver was used to solve for the electric and magnetic field distributions, and a transient solver was used to solve for the thermal field, pyrolysis degree, and multiphysics coupling results. The MHD governing equations and... Arrhenius The parameters describing the electro-magnetic-thermal-pyrolysis behavior are solved by coupled iterative equations to simulate the continuous arc ablation process on the surface of the insulating material with pyrolysis effect.

[0055] Step 7: Based on the data from the arc ablation simulation, obtain the evolution curves of the proportion of each phase with temperature, ablation morphology diagram, surface temperature distribution diagram, and cross-sectional temperature distribution diagram. Compare and cross-verify the above results with the actual arc ablation experimental results and TGA / DTG simulation data to accurately determine the ablation resistance limit and comprehensive performance of the material.

[0056] In this embodiment, step 7 is implemented as follows: Step 7.1 and Step 6 continue the simulation process until the arc ablation stage on the surface of the insulating material is completely finished. Based on the data collected during the simulation, we obtain the evolution curves of the proportion of each phase with temperature, the surface temperature distribution map, the cross-sectional temperature distribution map, and the ablation morphology map. We analyze the phase evolution characteristics and damage mechanism to find out the reason why the arc resistance test causes the insulation layer of the insulating material target plate to fail.

[0057] Step 7.2 involves comparing and cross-validating the causes obtained in Step 7.1 with the different heating rates obtained from TGA thermogravimetric analysis to determine the material's pyrolysis process, thereby accurately determining the material's ablation resistance limit and overall performance.

[0058] Figures 5-9 Some of the figures obtained from the simulation are shown. Figure 5 To simulate the morphology of epoxy decomposition. Figure 6 A simulated temperature distribution map of the damaged area. Figure 7 This is a curve showing the evolution of phase ratio as a function of temperature. Figure 8 This is a surface temperature distribution diagram. Figure 9 This is a cross-sectional temperature distribution diagram.

[0059] Figure 4 These are actual surface morphology images of epoxy decomposition. The left image shows the morphology after 26 s of arc ablation, and the right image shows the morphology after 182 s of arc ablation. These images are used to compare with... Figure 5 The simulated epoxy decomposition morphology images were compared.

[0060] Figure 10 , Figure 11The thermogravimetric analysis (TGA) and thermogravimetric differential (DTG) curves of the samples under nitrogen atmosphere at different heating rates are shown. In an oxygen-free environment, the epoxy powder coating exhibits only one thermogravimetric process within the temperature range of 25–800 °C, and the trends of the TGA curves of the samples at different heating rates are basically consistent. With the increase of the reaction rate, key characteristic parameters such as the reaction initiation temperature, the maximum weight loss rate temperature, and the termination temperature all shift towards higher temperatures. TGA was used to quantitatively analyze the pyrolysis process of the material at different heating rates, and comparative cross-validation was performed to accurately determine the ablation resistance limit and overall performance of the epoxy / alumina composite material.

Claims

1. A simulation method for arc ablation resistance of insulating material surfaces incorporating pyrolysis effects, characterized in that, Includes the following steps: Step 1: Establish a three-dimensional multi-domain coupled simulation model that includes an insulating platform, an insulating material target plate, a V-shaped needle electrode, a columnar arc, and the surrounding air domain, and import it into the COMSOL finite element simulation software; Step 2: Given the material properties of each component in the three-dimensional multi-domain coupled simulation model, set the constraints of the three-dimensional multi-domain coupled simulation model; Step 3: Construct the MHD governing equations of the three-dimensional multi-domain coupled simulation model, and... Arrhenius The equations tracking the pyrolysis reaction rate are coupled with the interpolation function of the degree of pyrolysis and the thermal damage equation into a three-dimensional multi-domain coupled simulation model; the set of all equations and interpolation functions is denoted as the governing equations; Step 4: Define the parameters involved in the governing equations in the global definition module of the COMSOL finite element simulation software; configure the circuit module, magnetic field and electric field module, laminar flow module, heat transfer module, deformable mesh module, and coefficient form partial differential equation module for the three-dimensional multi-domain coupled simulation model, and set the required boundaries in these modules; Step 5: Configure the user-defined mesh in the COMSOL finite element simulation software; Step 6: Perform continuous arc ablation simulation on the three-dimensional multi-domain coupled simulation model in COMSOL finite element simulation software, and iteratively calculate the MHD flow field evolution and material pyrolysis process using steady-state solver and transient solver. Step 7: Based on the data from the arc ablation simulation, obtain the evolution curves of the proportion of each phase with temperature, ablation morphology diagram, surface temperature distribution diagram, and cross-sectional temperature distribution diagram.

2. The simulation method for arc ablation resistance of insulating material surface by introducing pyrolysis effect according to claim 1, characterized in that, In step 1, the insulating platform is located at the bottom of the three-dimensional multi-domain coupled simulation model, the insulating material target plate is located at the center of the upper surface of the insulating platform, two needle-shaped electrodes are placed in a V-shape above the insulating material target plate, and the columnar arc is located between the two needle electrodes. The space above the insulating platform, the insulating material target plate, the columnar arc, and the needle electrodes is an air domain for fluid and heat exchange. The columnar arc is the columnar arc plasma generated in the discharge channel after the V-shaped needle electrode is pressurized in the actual arc ablation test.

3. The simulation method for arc ablation resistance of insulating material surface by introducing pyrolysis effect according to claim 2, characterized in that, The material properties of each component mentioned in step 2 include: the V-shaped needle electrode is tungsten, the insulating platform is an insulating material, the air domain is all air, the upper part of the insulating material target plate is epoxy resin material, and the lower part of the insulating material target plate is copper material; The constraints of the three-dimensional multi-domain coupled simulation model described in step 2 are as follows: Assuming that the columnar arc plasma in the discharge channel is in laminar flow mode and is fully ionized, its internal energy exchange satisfies the local thermodynamic equilibrium condition. Ignore the ablation process of the electrode by the electric arc; Ignore the effects of gravity and the inertial components of electrons; Assume that the plasma density, specific heat capacity at constant pressure, electrical conductivity, and net radiative dissipation coefficient of total volume are univariate functions that depend only on the local temperature; Secondary interference of various gases generated by the melting of the needle electrode on the flow field is ignored.

4. The simulation method for arc ablation resistance of insulating material surface by introducing pyrolysis effect according to claim 3, characterized in that, Step 3 describes the MHD governing equations, which include the magnetofluid mass conservation equation, the magnetofluidity conservation equation, the energy conservation equation, and the electromagnetic field equation. Arrhenius The equations, interpolation functions, and thermal damage equations are as follows: The magnetic flux mass conservation equation is: in, ρ For fluid density, t For time, U The velocity vector of the fluid motion. For curl operator; The energy conservation equation for the magnetohydrodynamic fluid is: in, T For temperature, C For specific heat capacity, q The heat flux density vector, Q For the heat source term, its expression is: In the formula, J For current density, k B Boltz constant, e For electron charge, E For electric field strength, Q rad For total volumetric heat dissipation, , ε rad Net radiation coefficient; The equation for the conservation of magnetic flux is: In the formula, u, v, w They are respectively x, y, z Gas flow velocity in the direction; η The viscosity coefficient of the fluid; S u 、S v 、S w They are respectively x, y, z The source component of the direction is expressed as follows: In the formula, F x , F y , F z They are respectively volume forces in x, y, z Components in direction; The electric and magnetic field equations are expressed using Maxwell's equations, as follows: In the formula, ρ e For charge density, D It is the electric displacement vector. B It represents the magnetic flux density. H Let be the magnetic field strength, where is the magnetic field strength. H and electric displacement vector D The expressions are as follows: In the formula, μ Permeability, ε 0 The vacuum permittivity, ε r The relative permittivity of the medium; The Arrhenius The equation is used to describe the pyrolysis reaction rate at any given time. V Specifically, assume that the densities of the epoxy phase, residual carbon phase, and gaseous phase are all constants in the pyrolysis reaction. Arrhenius The equation is: In the formula, e This represents the real-time volume fraction of the epoxy phase. E a The activation energy for the pyrolysis reaction. V 0 is the pyrolysis reaction constant. R The gas constant is For temperature T Over time t Changes; The interpolation function is used to characterize the degree of pyrolysis. Specifically, the real-time volume fractions of the epoxy phase, residual carbon phase, and gas phase are used as core variables to control the density of the solid phase. ρ ( T ) specific heat C ( T ) and thermal conductivity k ( T The solid phase is a combination of epoxy and residual carbon phases, and the expression for the interpolation function is: In the formula, e ( T ), c ( T ), g ( T The figures represent the real-time volume fractions of the epoxy phase, residual carbon phase, and gaseous phase, respectively. ρ e , ρ c , ρ g The densities of the epoxy phase, residual carbon phase, and gas phase are respectively. C e , C c , C g The specific heats are those of the epoxy phase, residual carbon phase, and gas phase, respectively. k e , k c , k g Let be the thermal conductivity of the epoxy phase, residual carbon phase, and gas phase, respectively, and satisfy the following: In the formula, ρ e The density of the epoxy phase. ρ c Γ is the density of the residual carbon, and Γ is the gasification coefficient of the epoxy resin; The thermal damage equation is: In the formula, Q e Thermal damage caused by the vaporization of epoxy groups. L e It is the latent heat of vaporization of epoxy groups.

5. The simulation method for arc ablation resistance of insulating material surface by introducing pyrolysis effect according to claim 4, characterized in that, The boundary settings for the circuit module, magnetic field and electric field module, laminar flow module, heat transfer module, deformable mesh module, and coefficient form partial differential equation module mentioned in step 4 are as follows: For the circuit module, a two-end circuit network is set up. The open-circuit voltage of the circuit network is set to AC high voltage, one end is set to ground, and the other end is coupled to the magnetic field and electric field module. For the magnetic field and electric field modules, one of the needle electrodes is grounded at its tail end, and the other needle electrode is coupled to the circuit module at its tail end. The remaining boundaries of the two needle electrodes are set to be electrically insulated. For the laminar flow module, the outer boundary of the air domain is set as an open boundary, and the remaining boundaries of the air domain are wall boundaries without slippage. For the heat transfer module, the outer boundary of the air domain is set as an open boundary, and the boundary around the insulating platform is set as a natural convection heat transfer boundary. For the deformable mesh module, select the fixed mesh region and the free deformable region in the mesh, and set the specified normal mesh velocity boundary; For the coefficient form of partial differential equations module, through Arrhenius The equations track the interpolation function of the degree of pyrolysis generated by the pyrolysis reaction rate and the thermal damage equation. The interpolation function is used to set the epoxy phase and residual carbon phase to characterize the degree of pyrolysis of the material under test, and the solid phase is set to be epoxy phase at the beginning of the simulation; the gas phase is set using measurement parameters.

6. The simulation method for arc ablation resistance of insulating material surface by introducing pyrolysis effect according to claim 5, characterized in that, The mesh described in step 5 is a tetrahedral mesh, and the mesh size is determined by a partitioning method, specifically: The arc generation area is designated as region 1, and its settings are: grid size of 0.03mm to 1.93mm and curvature factor of 0.2; The V-shaped electrode area is designated as region 2, and its settings are: grid size of 0.3mm to 7mm and curvature factor of 0.3; The area outside the arc generation zone on the insulating material target plate is designated as region 3, and its settings are: grid size of 0.22mm to 3.4mm and curvature factor of 0.3; The area outside the above three areas is designated as Area 4, and its settings are: grid size of 3.6mm to 20mm and curvature factor of 0.

6.

7. The simulation method for arc ablation resistance of insulating material surface by introducing pyrolysis effect according to claim 6, characterized in that, The implementation process of step 6 is as follows: In COMSOL finite element simulation software, continuous arc ablation simulation was performed on a three-dimensional multi-domain coupled simulation model. During the simulation, a steady-state solver was used to solve for the electric and magnetic field distributions, and a transient solver was used to solve for the thermal field, pyrolysis degree, and multiphysics coupling results. The MHD governing equations and... Arrhenius The parameters describing the electro-magnetic-thermal-pyrolysis behavior are solved by coupled iterative equations to simulate the continuous arc ablation process on the surface of insulating materials with pyrolysis effects.

8. The simulation method for arc ablation resistance of insulating material surface by introducing pyrolysis effect according to claim 7, characterized in that, The implementation process of step 7 is as follows: Step 7.1, the simulation process of step 6 continues until the arc ablation stage on the surface of the insulating material is completely finished. Based on the data collected during the simulation, we obtain the evolution curves of the proportion of each phase with temperature, the surface temperature distribution map, the cross-sectional temperature distribution map, and the ablation morphology map. We analyze the phase evolution characteristics and damage mechanism to find out the reason why the arc resistance test causes the insulation layer of the insulating material target plate to fail. Step 7.2 involves comparing and cross-validating the causes obtained in Step 7.1 with the different heating rates obtained from TGA thermogravimetric analysis to determine the material's pyrolysis process, thereby accurately determining the material's ablation resistance limit and overall performance.

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