A simulation method and system for arc discharge under pivot-rail contact and complete loss of contact conditions.

Abstract

This invention discloses a simulation method and system for arc discharge under pivot-rail contact and complete loss of contact conditions, relating to the field of electromagnetic orbital launch device technology. The method includes: constructing a multi-field coupled magnetohydrodynamic simulation model; analyzing the electrothermal field coupling distribution at the pivot-rail contact interface under different pivot-rail contact state development stages; analyzing the variation laws of pivot-rail contact interface parameters and arc discharge parameters under different metal liquefaction layer thicknesses and armature tail fin roughness under the coexistence of three contact states; obtaining the arc morphology and the variation laws of arc temperature and arc energy flux density in the plasma gap with launch time under the complete loss of pivot-rail contact state, as well as the variation laws of pivot-rail contact interface parameters and arc discharge parameters under different pivot-rail micro-contact point numbers, pivot-rail gap widths, and track surface roughness. The multi-physics field coupling distribution characteristics of the contact interface under different pivot-rail contact state development stages are simulated and analyzed.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic orbital launch device technology, and in particular to a method and system for simulating arc discharge under pivot-rail contact and complete loss of contact conditions. Background Technology

[0002] During electromagnetic orbit launch, the pivot-rail contact surface undergoes physicochemical changes such as material melting, vaporization, and plasma generation, leading to deterioration in electrical conductivity and mechanical properties. These changes can disrupt the stability of the sliding electrical contact, causing orbital transitions and resulting in severe ablation, shortening orbital life, reducing launch stability, and hindering the development of electromagnetic orbit launch technology.

[0003] Current research on the transition arc initiation mechanism is mostly limited to the thermal perspective caused by melting waves or the electromagnetic perspective caused by pulsed currents. However, the relative motion between the armature and the track is a high-current, high-speed sliding electrical contact process, and the armature-track transition occurs under the combined effects of ultimate impact electromagnetic-thermal-mechanical loads. It is necessary to establish an arc discharge model between the contact interfaces to study the coupling characteristics of electromagnetics, thermodynamics, and fluid kinematics. Furthermore, equivalent simulation methods for the characteristics of the armature-track contact interface and the transition arc initiation between the armature and track have not been fully established from the initial launch to the transition arc initiation process. Further simulation of the entire development process of the armature-track contact state is needed to determine the specific development stage corresponding to the occurrence of transition arc initiation and clarify the transition arc initiation mechanism based on the contact interface characteristics. During this process, changes in the armature-track contact state will affect its multi-field coupling distribution characteristics, necessitating a detailed analysis of the interface electrothermal characteristics and arc discharge parameters.

[0004] Secondly, the cumulative number of launches increases the surface roughness of the orbit, leading to plasma gaps between the armature and the rail due to insufficient contact, which in turn triggers electric arcs. This not only affects the armature's motion behavior and launch quality but also causes severe ablation damage to the rail surface, resulting in a sharp decline in various orbital performance characteristics and a significant reduction in service life and reusability.

[0005] Studies have shown that the destructive changes in the pivot-rail interface properties caused by arc generation are the primary cause of pivot-rail metal ablation. However, current research on the spatiotemporal evolution mechanism of the pivot-rail arc and its resulting metal ablation is insufficient, failing to consider changes in key parameters such as arc discharge morphology, energy flux density, and internal temperature during electromagnetic emission. The dynamic development of arc morphology and parameters within the plasma gap, as well as the mechanisms by which pivot-rail contact interface properties and arc discharge parameters are influenced by factors such as the number of micro-contact points, gap width, and track surface roughness, remain to be clarified. Summary of the Invention

[0006] To address the aforementioned issues, this invention proposes a simulation method and system for arc discharge under pivot-rail contact and complete loss of contact conditions. It establishes a pivot-rail contact interface model considering damage roughness and a magnetohydrodynamic model for the development of arc discharge between the interfaces, and performs simulation analysis on the multi-physics coupling distribution characteristics of the contact interface under different pivot-rail contact states.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for simulating arc discharge under pivot-rail contact and complete loss of contact conditions, comprising:

[0009] By synthesizing randomly distributed track rough surface data, track surface curves under different roughness are constructed, and then geometric models are constructed when the pivot-rail contact interface undergoes transition under different roughness. Based on the geometric model, a magnetohydrodynamic simulation model of arc discharge between the pivot-rail contact interface is constructed, which simultaneously considers the multi-field coupling of electric field, magnetic field, thermal field and fluid field.

[0010] Based on the magnetohydrodynamic simulation model, the electrothermal field distribution at the pivot-rail contact interface is analyzed in three stages: dry sliding contact, mixed lubrication contact (with dry sliding and liquefied metal layer), and transitional contact (with liquefied metal layer and plasma gap). The maximum current density, highest temperature, and their respective positions at the pivot-rail contact interface are observed as the contact state stages change. Furthermore, based on the constructed arc discharge model between the pivot-rail contact interfaces under the three coexisting contact states, the variation of pivot-rail contact interface parameters and arc discharge parameters under different liquefied metal layer thicknesses and armature tail roughness is analyzed.

[0011] Based on the magnetohydrodynamic simulation model, arc ablation simulation was performed under the condition of complete loss of contact between the pivot and the rail. The changes in arc morphology, temperature and energy flux density in the plasma gap with the emission time were obtained, as well as the changes in the pivot-rail contact interface parameters and arc discharge parameters under different numbers of pivot-rail micro-contact points, pivot-rail gap width and track surface roughness.

[0012] Secondly, the present invention provides an arc discharge simulation system under pivot-rail contact and complete loss of contact conditions, comprising:

[0013] The model building module is configured to construct track surface curves under different roughnesses by synthesizing randomly distributed track roughness surface data, and then construct geometric models when the pivot-rail contact interface undergoes transition under different roughnesses. Based on the geometric model, a magnetohydrodynamic simulation model of arc discharge between the pivot-rail contact interface is constructed, which simultaneously considers the multi-field coupling of electric field, magnetic field, thermal field and fluid field.

[0014] The simulation module for the pivot-rail contact state is configured to analyze the electrothermal field distribution at the pivot-rail contact interface based on a magnetohydrodynamic simulation model. This analysis is conducted in three stages: the dry sliding contact state, the mixed lubrication contact state where dry sliding and a metal liquefaction layer coexist, and the transitional contact state where a metal liquefaction layer and a plasma gap coexist. The module obtains the variation patterns of the maximum current density, the highest temperature, and their respective positions at the pivot-rail contact interface as the contact state stages change. Furthermore, based on the constructed arc discharge model between the pivot-rail contact interfaces with the three coexisting contact states, the module analyzes the variation patterns of the pivot-rail contact interface parameters and arc discharge parameters under different metal liquefaction layer thicknesses and armature tail fin roughnesses.

[0015] The simulation module for complete loss of contact is configured to perform arc ablation simulation under the complete loss of contact state of the pivot rail according to the magnetohydrodynamic simulation model. It obtains the variation law of arc morphology, temperature and energy flux density in the plasma gap with the emission time, as well as the variation law of pivot rail contact interface parameters and arc discharge parameters under different numbers of pivot rail micro-contact points, pivot rail gap width and track surface roughness.

[0016] Thirdly, the present invention provides an electronic device including a memory and a processor, and computer instructions stored in the memory and running on the processor, wherein the computer instructions, when executed by the processor, perform the method described in the first aspect.

[0017] Fourthly, the present invention provides a computer-readable storage medium for storing computer instructions, which, when executed by a processor, perform the method described in the first aspect.

[0018] Fifthly, the present invention provides a computer program product, including a computer program that, when executed by a processor, implements the method described in the first aspect.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] The track surface damage results from electromagnetic orbital launch experiments show that increased launch frequency and usage frequency lead to frequent cumulative damage from various types of ablation. Among these, transition ablation accompanied by electric arc is the most destructive, causing significant changes in the physical state of the pivot-rail contact. The generation of the discharge arc at the pivot-rail contact interface is closely related to the characteristics of the contact interface at various stages of the pivot-rail contact state development. However, currently, there is a lack of suitable experimental instruments and methods for effective on-site detection of the generation principle of the arc at the pivot-rail contact interface and the development law of transition ablation. Furthermore, the equivalent simulation of the pivot-rail contact interface characteristics and the transition arc initiation between the pivot and rail is also incomplete. To simulate and inversely deduce the damage law, this invention establishes a pivot-rail contact interface model considering damage roughness and a magnetohydrodynamic model of the arc discharge development between the interfaces. It analyzes the multi-physics coupling distribution characteristics of the contact interface at different stages of the pivot-rail contact state development, exploring the generation mechanism and dynamic evolution characteristics of the arc initiation discharge when the pivot-rail contact interface develops to the transition contact state. Considering the actual situation where multiple pivot-rail contact states coexist, this study investigates the influence of two pivot-rail contact conditions—the thickness of the liquefied metal layer and the surface roughness of the armature tail fin—on the contact interface and the parameters of the transition arc discharge.

[0021] This invention addresses the scenario of the strongest arc discharge and most severe arc ablation between the armature and rail, where complete loss of contact between the armature and rail has resulted in the complete depletion of the liquefied metal layer, with conduction maintained only by the plasma gap. This transitional ablation transforms into the most destructive arc ablation. Based on a magnetohydrodynamic model, this invention designates the inner contact surface of the rail as the arc discharge anode and the armature contact surface as the cathode, investigating the dynamic development of the arc morphology and parameters within the plasma gap over time. Attached Figure Description

[0022] Figure 1 This is a flowchart of the arc discharge simulation method under pivot contact and complete loss of contact provided in Embodiment 1 of the present invention;

[0023] Figure 2 This is a schematic diagram of the magnetohydrodynamic simulation model of arc discharge between the pivot and rail contact interfaces provided in Embodiment 1 of the present invention;

[0024] Figure 3 A graph showing the variation trends of pulse current, dry friction heat power, and maximum temperature of the pivot-rail contact interface during the launch process, provided in Embodiment 1 of the present invention.

[0025] Figure 4 This is a spatial distribution diagram of the current density at the pivot-rail contact interface under the pivot-rail dry sliding contact state provided in Embodiment 1 of the present invention;

[0026] Figure 5This is a time distribution diagram of the current density at the pivot-rail contact interface under the pivot-rail dry sliding contact state provided in Embodiment 1 of the present invention;

[0027] Figure 6 This is a spatial distribution diagram of the temperature at the pivot-rail contact interface under dry sliding contact state provided in Embodiment 1 of the present invention.

[0028] Figure 7 This is a time distribution diagram of the temperature at the pivot-rail contact interface under dry sliding contact state provided in Embodiment 1 of the present invention;

[0029] Figure 8 The variation of the highest temperature, maximum current density, and maximum energy flux density of the electromagnetic orbital launcher provided in Embodiment 1 of the present invention with the gap length is shown.

[0030] Figure 9 A schematic diagram of a pivot rail contact interface model where three contact states coexist, as provided in Embodiment 1 of the present invention.

[0031] Figure 10 This is a graph showing the change of arc energy flow density with increasing horizontal axis under different metal liquefaction layer thicknesses provided in Embodiment 1 of the present invention.

[0032] Figure 11 This is a graph showing the change of arc energy flow density with increasing vertical axis under different metal liquefaction layer thicknesses provided in Embodiment 1 of the present invention.

[0033] Figure 12 This is a graph showing the variation of armature-rail contact interface parameters and arc discharge parameters under different armature tail fin roughnesses provided in Embodiment 1 of the present invention.

[0034] Figure 13 This is a diagram illustrating the dynamic development of arc discharge temperature within the gap of 0.5ms emission time provided in Embodiment 1 of the present invention.

[0035] Figure 14 The diagram shows the dynamic development of arc discharge temperature during the 1.5ms emission interval provided in Embodiment 1 of the present invention.

[0036] Figure 15 The diagram shows the dynamic development of arc discharge temperature during the 2.5ms emission interval provided in Embodiment 1 of the present invention.

[0037] Figure 16 The diagram shows the dynamic development of arc discharge temperature during the 3.5ms emission time interval provided in Embodiment 1 of the present invention.

[0038] Figure 17 The diagram shows the dynamic development of arc energy flow density during the 0.5ms emission interval provided in Embodiment 1 of the present invention.

[0039] Figure 18 The diagram shows the dynamic development of arc energy flow density during the 1.5ms emission time interval provided in Embodiment 1 of the present invention.

[0040] Figure 19 The diagram shows the dynamic development of arc energy flow density during the 2.5ms emission interval provided in Embodiment 1 of the present invention.

[0041] Figure 20 The diagram shows the dynamic development of arc energy flow density during the 3.5ms launch interval provided in Embodiment 1 of the present invention. Detailed Implementation

[0042] Example 1

[0043] This embodiment provides a simulation method for arc discharge under pivot-rail contact and complete loss of contact conditions, such as Figure 1 As shown, it includes:

[0044] By synthesizing randomly distributed track rough surface data, track surface curves under different roughness are constructed, and then geometric models are constructed when the pivot-rail contact interface undergoes transition under different roughness. Based on the geometric model, a magnetohydrodynamic simulation model of arc discharge between the pivot-rail contact interface is constructed, which simultaneously considers the multi-field coupling of electric field, magnetic field, thermal field and fluid field.

[0045] Based on the magnetohydrodynamic simulation model, the electrothermal field distribution at the pivot-rail contact interface is analyzed in three stages: dry sliding contact, mixed lubrication contact (with dry sliding and liquefied metal layer), and transitional contact (with liquefied metal layer and plasma gap). The maximum current density, highest temperature, and their respective positions at the pivot-rail contact interface are observed as the contact state stages change. Furthermore, based on the constructed arc discharge model between the pivot-rail contact interfaces under the three coexisting contact states, the variation of pivot-rail contact interface parameters and arc discharge parameters under different liquefied metal layer thicknesses and armature tail roughness is analyzed.

[0046] Based on the magnetohydrodynamic simulation model, arc ablation simulation was performed under the condition of complete loss of contact between the pivot and the rail. The changes in arc morphology, temperature and energy flux density in the plasma gap with the emission time were obtained, as well as the changes in the pivot-rail contact interface parameters and arc discharge parameters under different numbers of pivot-rail micro-contact points, pivot-rail gap width and track surface roughness.

[0047] The following section first describes the construction of geometric models for the transition of the pivot-rail contact interface under different roughness conditions.

[0048] After multiple electromagnetic orbital launch experiments, under extreme conditions such as frequent high-energy pulsed current flow and high-speed armature friction, various irreversible damages occur on the orbital surface, such as groove ablation, gouging ablation, transition ablation, and arc ablation, severely affecting the service life, launch quality, and efficiency of the launch device. Among these, arc ablation causes the most severe damage to the orbital, but transition ablation is the main inducing factor. Transition refers to the damage to the armature and orbital surfaces causing loose armature-rail contact and the formation of gaps, which in turn generates a high-temperature, high-energy plasma arc, exacerbating arc ablation and leading to material melting, sputtering, adhesion, and even sublimation. Since this process is difficult to observe directly through experimental means, it is necessary to establish an arc discharge plasma model between the armature and rail contact interface for numerical simulation studies.

[0049] During electromagnetic orbit launch, due to the microscopic roughness of the metal surface, actual contact between the pivot and the rail occurs only at a few raised micro-contact points. As current flows through these discrete micro-contact points, path contraction occurs, concentrating the flow from the micro-contact points into the next conductor. Surface roughness can be used to measure the degree of damage and geometric micromorphology of the orbital surface. Common roughness indices include mean roughness. Ra Maximum height Rz and root mean square roughness Rq .

[0050] (1);

[0051] (2);

[0052] (3);

[0053] in, Ra The average of the absolute values ​​of the profile's deviation from the baseline. L The total length of the measured track. y ( x ) represents the offset value of the track surface profile; Rz This refers to the maximum height difference between the peak and the trough within the measurement interval; Rq is the root mean square value of the deviation of each point on the contour line from the average line; x is the abscissa value of the contour of the track surface.

[0054] When constructing the geometric model of the rough surface, based on spatial frequency and elementary wave theory, the sum of trigonometric functions extended by Fourier series is used to synthesize completely randomly distributed real rough surface data, including one-dimensional curves of the rough surface. for:

[0055] (4);

[0056] In the formula, φ ( υ () represents the phase angle, ± V Spatial frequency υ Maximum and minimum cutoff values, P The proportionality coefficient of the amplitude; For each spatial frequency υ The amplitude corresponding to the elementary wave; g ( υ Let be a random function with a Gaussian distribution; a ( υ () represents the amplitude of each element wave. Multiply by a random function with a Gaussian distribution g ( υ The generated amplitude; w ( υ ) is a uniform random function, and the phase angle is from the uniform random function. w ( υ Sampling in ) so that it is between –π / 2 and π The interval between / 2 conforms to a uniform random distribution, let φ ( υ )= w ( υ ); The spectral index represents the decay rate of the amplitude of a higher frequency elementary wave.

[0057] The calculation and generation of the corresponding roughness curve can be completed by programming the built-in functions of the finite element simulation software. Based on equation (4), the variables are... V and β The values ​​are set to 20 and 1 respectively, and the scaling factor is changed accordingly. P Various track surface curves with different roughnesses were obtained, and a geometric model of the pivot-rail contact interface transition under different track damage roughnesses was constructed. The average roughness of different track surface roughnesses was calculated using equations (1)-(3). Ra Maximum height Rz and root mean square roughness Rq It was found that with the amplitude proportionality coefficient P As the diameter increases, the surface roughness of the track also increases accordingly.

[0058] The following describes the construction of a magnetohydrodynamic simulation model for arc discharge between the pivot and rail contact interfaces.

[0059] First, electromagnetic-thermal multi-field coupling is introduced into the equivalent circuit model of the electromagnetic orbit launch device to obtain an electromagnetic-thermal multi-field coupling model of the entire electromagnetic orbit launch process. Then, the equivalent equations of magnetohydrodynamics (MHD) of plasma discharge are introduced. A two-dimensional symmetrical magnetohydrodynamic simulation model is established, symmetrical about the launch direction centerline, comprising the track, armature and its contact interface, and the air domain within the launch chamber, perpendicular to the xy-plane. Figure 2 As shown. It mainly consists of copper rails, an aluminum armature, and an air zone, with a length of 40mm. The contact interfaces between the armature and rail are not tightly fitted, leaving an air gap of approximately 0.25mm to simulate the arc discharge space during transition due to poor contact between the armature and rail. The surface roughness of the inner contact surface of the copper rail is set to... Ra =541.2μm, representing the surface damage caused by multiple electromagnetic launches on the track. The magnetohydrodynamic simulation model of the arc discharge between the pivot and track contact interfaces involves multi-field coupling of electric, magnetic, thermal, and fluid fields. At the electromagnetic field level, since the electromagnetic track launch device model is transformed from three-dimensional space to a two-dimensional xy plane, the value of the pulse current terminal boundary condition should also be divided by the track height of 23mm, becoming 1 / 23 of the original pulse current value.

[0060] At the thermal level, the boundary conditions between the copper orbital and the air domain and the external environment are both in the form of convective heat flux. Based on the inherent properties of the material, its heat transfer coefficient... h Set to 400W / (m) 2 ·K) and 15W / (m 2 ·K); while the aluminum armature's connection module with the outside world is still its other half, so its heat flux boundary condition is an inward heat flux, with a value of approximately 237W / m. 2 The air domain is configured for fluid heat transfer, while the copper rails and aluminum armatures are configured for solid heat transfer.

[0061] At the fluid field level, if the armature is considered relatively stationary during firing, the air inside the barrel continuously accelerates from the front to the rear of the armature at a relative velocity, forming laminar flow. In this model, the normal inflow velocity of the air in front of the armature is approximately equal to the actual firing velocity of the armature. According to the Navier-Stokes equations (NS equations) and the continuity equation, the equations for the airflow motion are:

[0062] (5);

[0063] (6);

[0064] In the formula, ρ It is the density of a fluid or solid, expressed in kg / m³. 3 ;p It is fluid pressure. η It is the dynamic viscosity of the fluid; u is the fluid velocity, in m / s; It is a vector differential operator; T Let I be temperature; let I be current. The Navier-Stokes equation (5) represents the conservation of momentum, and the continuity equation (6) represents the conservation of mass.

[0065] Finally, after coupling the electromagnetic, thermal, and fluid fields, a multiphysics coupled model of magnetohydrodynamics for arc discharge in an air gap was constructed to simulate the interaction between the magnetic field and the conductive fluid. This model is achieved by coupling the magnetic field interface and the laminar flow interface. Its core bidirectional coupling mechanism is as follows:

[0066] (7);

[0067] (8);

[0068] In the formula, J For current density, B , is the magnetic flux density F For Lorentz force, E For induced electromotive force. Equation (7) represents the Lorentz force F The electromotive force (induced electric field) is coupled from the magnetic field level to the laminar flow level; Equation (8) indicates that the electromotive force (induced electric field) is coupled from the laminar flow level to the magnetic field level.

[0069] For the coupling of electromagnetic and thermal fields, the contact surface of the track is set as the anode of the equilibrium discharge boundary heat source, and the contact surface of the armature is set as the cathode. The equilibrium discharge heat source is a total heat source composed of multi-physics field coupling. Q for:

[0070] (9);

[0071] Q Including resistance Joule heating Q ohm Net radiation loss per unit volume Q rad and electron transport enthalpy Q enthalpy .in, Q ohm , Q enthalpy The equations are as follows:

[0072] (10);

[0073] (11);

[0074] In the formula, k BBoltzmann's constant, T For temperature, q It represents the amount of charge; k It is the thermal conductivity of the fluid, with units of W / (m·K); C p It is the heat capacity of a fluid or solid under constant pressure, and the unit is J / (kg·K).

[0075] The following describes the multi-field coupling distribution characteristics of the contact interface during the development stage of the pivot-rail contact state.

[0076] 1. Pivot rail dry sliding contact state.

[0077] At the beginning of electromagnetic launch, the amplitude of the pulse current in the circuit is very small, the armature speed in the barrel is very low, and the temperature of the armature-rail interface is far below the melting point of the aluminum armature. At this time, the armature-rail contact interface is completely in a dry sliding contact state. The heat source of the armature-rail contact interface mainly includes two components: contact resistance Joule heating effect and dry friction heat generation.

[0078] Among them, the Joule heat power generated by contact resistance P J for: ; i The pulse current flowing through the contact resistance, R c Contact resistance. Contact resistance Joule heat power. P J The magnitude depends primarily on the pulse current and contact resistance. Because the electromagnetic launching device remains in ideal, tight contact without transition during the dry contact state between the pivot and rail, the contact points between the pivot and rail are dense, and the contact area is large. A c The contact resistance is very high. R c The value is very small, on the order of nanoohms.

[0079] Dry frictional heat power of another heat source at the pivot-rail contact interface P f1 : Due to the dry sliding friction coefficient of solid-solid friction μ 1 is relatively large, so the value is taken as 0.2. Dry friction heat power. P f1 Inductance gradient of track and armature materials Under the premise of keeping it unchanged, with pulse current i Square, initial preload F n0 It shows a positive correlation with armature speed. v They are in a direct proportional relationship.

[0080] Due to contact resistance R cThe value is extremely small, contact resistance, Joule heat power P J The value is much smaller than the dry friction heat power. P f1 ,Right now P J ≪ P f1 Therefore, when the pivot-rail interface is in a dry sliding contact state of solid-solid close contact, dry frictional heat power is the most important heat source and the most significant factor causing its temperature rise. To investigate the pulse current under dry sliding contact conditions... i Dry friction heat power P f1 and the highest temperature at the pivot rail contact interface T c Based on the electromagnetic orbit launch field-circuit coupling model, the interaction and variation patterns among the three factors were investigated using six time points: 0.5 ms, 1.13 ms, 2 ms, 4 ms, 6 ms, and 8 ms (when the pulse current reaches its peak). The study explored the trend of these factors' variation with launch time. Figure 3 As shown, the electromagnetic track launch field-circuit coupling model is obtained by performing launch simulation on the equivalent circuit model to obtain the armature circuit pulse current, armature mechanical parameters and armature kinematic parameters, and then importing them into the electromagnetic-thermal multiphysics field coupling model to obtain the field-circuit coupling model of the electromagnetic track launch device.

[0081] like Figure 3 It can be seen that the amplitude of the pulse current has been increasing since 0.5ms, reaching a peak of 67148A at 1.13ms, and then begins to decrease as the energy of the pulse capacitor is released. The dry friction heat power and the highest temperature of the pivot-rail contact interface change with the emission time in the same way, both increasing continuously from 0.5ms to 2ms, and reaching their maximum value at 2ms. At this time, the maximum value of the dry friction heat power is 8194.2W and the highest temperature of the pivot-rail interface is 57.2℃. Then, starting from 2ms, it decreases continuously with the rapid decay of the pulse current.

[0082] In summary, pulse current i The peak value is not reached at the same time as the dry friction heat power. P f1 Highest temperature at the contact interface with the pivot rail T c Synchronous P f1 and T c The time when the maximum value is reached is always delayed by i This is because of the heat power generated by dry friction. P f1 The magnitude is not only related to the pulse current iIt is related to the square of the current and is also directly proportional to the armature's velocity, especially in pulse currents. i When the peak value is reached at 1.13 ms, the armature velocity is only 31.73 m / s. At 2 ms, although the pulse current amplitude decreases slightly to 52898 A, the armature firing velocity increases to 71.57 m / s. Therefore, calculations show that the dry friction heat power is at its maximum at 2 ms. Furthermore, since the maximum temperature rise at the armature-rail interface mainly depends on the dry friction heat power, T c The moment when the maximum value is generated during the launch process is also P f1 The maximum value corresponds to 2ms.

[0083] To analyze the multi-field coupling distribution characteristics of the electromagnetic rail launcher under the influence of track surface damage and roughness in the dry sliding contact state, a two-dimensional electrothermal field coupling model of the rail interface and the air domain inside the gun barrel was obtained based on the improved three-dimensional finite element model of the electromagnetic rail launcher. Due to the limitations of the simulation software, there are differences between the simulation results of the two-dimensional model and the three-dimensional model; this embodiment uses the two-dimensional model as the standard. By analyzing the current density and temperature distribution under the dry sliding contact state at the maximum dry frictional heat power moment of 2 ms, it can be seen that the current density in the track is mainly concentrated in the section before the pulse current flows into the armature through the track, and the current density distribution is uniform, approximately 4.6 × 10⁻⁶. 5 A / m 2 In the track section before the armature head along the launch direction, the current density in areas not forming a current path with the armature and the opposite track is 0. The main areas of concentrated current density in the armature are the armature recess and the beginning and end of the armature-rail contact side; these two locations represent the highest current density in the entire launch device at that moment. At the armature-rail interface, due to the skin effect and velocity skin effect, the current density is even more concentrated at the high-curvature bends at both ends of the interface. Specifically, a portion of the current first enters from the rear corner of the armature tail fin, and the remaining current flows into the armature through the head corner on the armature side. Therefore, these two corners are the areas with the highest concentration of current density and Joule heat. Regarding the temperature distribution at 2ms, under the combined effects of Joule heating and frictional heating, the high-temperature region of the track is mainly located in the section about 40mm behind the hub-track interface. The track temperature decreases from the highest point towards both sides of the track, with the highest temperature point being at the rear corner of the armature tail fin, reaching 57.2℃. The high-temperature region of the armature is also concentrated at the rear of the armature tail fin, gradually decreasing from near the corner end towards the armature head. The high-temperature region in the air domain adheres to the surface of the high-temperature regions of the track and armature, and rapidly decreases towards the surrounding low-temperature air.

[0084] While the above analysis reflects the current density and temperature distribution of the entire device under the dry sliding contact state between the armature and rail, the spatiotemporal characteristics of the electrothermal field coupling distribution at the armature-rail contact interface still require further analysis. Therefore, taking the end corner of the armature tail fin as the origin and the launch direction as the positive axis, the variation characteristics of current density and temperature at the armature-rail contact interface over time were investigated.

[0085] Figures 4-5 The figures show the spatial and temporal distribution of the current density at the pivot-rail contact interface under dry sliding contact conditions. At each launch moment corresponding to different pulse current amplitudes, the 28mm long contact interface exhibits a "two-segment high, middle low" distribution. The current density at the very front (28mm) of the pivot-rail contact interface is higher than that at the very back (0mm), representing the highest current density across the entire pivot-rail interface. At the same moment, the current density rapidly decreases from the very back, gradually leveling off around 2mm from the very back, then rapidly increases again from approximately 26mm from the very back, finally reaching its maximum value at the very front of the pivot-rail interface. As the launch process progresses, the current density at the pivot-rail interface increases rapidly with the pulse current (from 0ms to 1.13ms), reaching its maximum value at 1.13ms, and then gradually decreases from 2ms onwards as the current decays.

[0086] Figures 6-7 The figures show the spatial and temporal distribution of the temperature at the pivot-rail contact interface under dry sliding contact conditions. During launch, along the positive direction of the contact interface, the highest temperature points at each moment are located between 2.5 mm and 4.7 mm from the outermost edge of the contact interface, exhibiting a spatial characteristic of "local increase followed by overall decrease." The pivot-rail contact interface temperature reaches its peak of 57.2℃ at 2 ms, while the peak temperature of the non-pulse current occurs at 1.13 ms. The temperature then gradually decreases, consistent with... Figure 3 The revealed pattern is as follows: During the heating phase (0.5ms, 1.13ms, 2ms), the location of the highest temperature point continuously moves forward along the positive direction of the pivot-rail contact interface as the temperature increases. At 2ms, the highest temperature point is located approximately 4.7mm from the end of the contact interface, closer to the front end. During the cooling phase (4ms, 6ms, 8ms), the location of the highest temperature point gradually shifts back. Therefore, under dry sliding contact conditions, the higher the temperature of the pivot-rail contact interface, the closer its temperature peak point is to the front end, and the more concentrated the high-temperature region is at the end of the interface.

[0087] 2. A mixed lubrication contact state in which dry sliding of the pivot rail and a metal liquefaction layer coexist.

[0088] During electromagnetic orbit launch, when the temperature at the armature-rail contact interface exceeds the melting point of the aluminum alloy armature, the solid aluminum on the armature contact surface melts into liquid aluminum, forming a liquefied metal layer (LMF). The contact state gradually transitions from the initial dry sliding phase to a stage where the LMF fully covers the surface, and the physical state of the armature-rail contact changes from "solid-solid" to "solid-liquid-solid." However, in the dry sliding contact model, the highest contact interface temperature is only 57.2℃, far below the melting point of the 6061 aluminum alloy armature material (582℃). Therefore, a LMF cannot form, and the contact remains in a dry sliding state. The main reason for this is the pulsed current. i The value is small, resulting in dry friction heat power. P f1 The current is too low, resulting in insufficient heat generation. Therefore, to achieve a higher temperature rise, it is necessary to increase the pulse current value, that is, increase the charging voltage of the pulse capacitor module in the equivalent circuit model co-programmed with the field model. By increasing the charging voltage of the pulse capacitor in the equivalent circuit model from 7kV to 13.5kV, simulations show that the pulse current amplitude at 2ms exceeds 100kA, increasing to 102.024kA, and the driving force on the armature... F e Increased to 2094.86 N, armature speed v A The speed reached 266.38 m / s. After re-importing the updated parameters into the multi-field coupling model, the temperature at the pivot-rail contact interface reached a maximum of 681°C, which exceeded the melting point of the 6061 aluminum alloy armature. The pivot-rail interface entered a mixed lubrication contact stage where dry sliding and a liquefied metal layer coexisted.

[0089] To describe the sliding friction coefficient of the pivot-rail contact interface μ The relationship between the changes in contact state and the overall situation was analyzed, and Stribeck lubrication curves were plotted using dimensionless lubrication parameters. ηv / p Lubricating viscosity η Speed ​​of movement v and normal load pThe x-axis represents the transition process under different lubrication states. It can be seen that during the initial operation phase of the armature, the armature-rail contact is dry sliding contact, with small pulse currents, low armature speed, and limited temperature rise at the armature-rail interface. This is a boundary lubrication zone of solid-solid contact, with a high sliding friction coefficient of approximately 0.2. As the armature speed increases and the pulse current rises, the armature-rail contact interface begins to generate significant heat exceeding the armature's melting point, causing the solid aluminum surface of the armature to continuously melt. Liquid aluminum forms and expands, and the lubrication state between the armature and rail enters a mixed lubrication region where solid-solid and solid-liquid-solid coexist. The friction coefficient gradually decreases due to lubrication. Finally, under the sustained high temperature generated by frictional heat, a liquefied metal layer covers the entire armature-rail contact interface, and the lubrication state between the armature and rail enters a fluid lubrication region, with the friction coefficient finally stabilizing at approximately 0.04. Therefore, during launch, the current-carrying sliding friction coefficient between the armature and rail continuously decreases from the dry sliding friction stage, eventually stabilizing at a saturation minimum.

[0090] Based on the sliding friction coefficient revealed by the Stribek lubrication curve μ The changing pattern of the friction coefficient between the liquefied metal layer of the armature and the copper rails. μ 2. The value is set to 0.04, which is the frictional heat source of the liquefied metal layer. P f2 The dry frictional heat from solid-solid contact is converted into viscous frictional heat of the fluid. To simplify the analysis of the lubrication behavior of the liquefied metal layer formed at the armature contact interface under multi-field coupling and sliding friction conditions in the model, it is assumed that the thickness of the liquefied metal layer remains constant at 20 μm throughout the entire launch process, only undergoing lateral expansion along the x-axis of the launch direction, and exhibiting no slippage on the armature surface, moving forward at the same velocity as the armature as a whole. Under this assumption, the Reynolds equation, representing the hydrodynamic lubrication behavior of the liquefied metal layer between relatively moving surfaces, is introduced into the model, as shown in equation [equation missing]. In the formula, h For liquid film thickness, p For the pressure inside the liquid film, η For the dynamic viscosity of liquid metal, v r The velocity vector of the relatively moving surface. t The temperature distribution at the armature-rail contact interface during dry sliding contact shows that the highest temperature of the armature during launch is located at the rear of the armature tail fin, and the temperature gradually decreases from near the tail fin corner towards the armature head. Therefore, the liquefied metal layer first forms at the rear of the armature tail fin and gradually develops towards the armature head as launch progresses, until it covers the entire contact interface.

[0091] To investigate the distribution of the electrothermal coupling field at the armature-rail contact interface caused by the extension of the liquefied metal layer towards the armature head during the mixed lubrication contact state, the development length of the liquefied metal layer was measured.L LMF The armature contact interface lengths were selected as 3.5 mm, 7 mm, 10.5 mm, 14 mm, 17.5 mm, 21 mm, 24.5 mm, and 28 mm, and the spatial distribution characteristics of current density and temperature at different lengths were analyzed at 0.2 ms. It can be seen that, under the mixed lubrication contact state, although the development length of the liquefied metal layer varies considerably, the overall distribution trend of current density at the armature contact interface remains basically consistent. Due to the velocity skin effect, the current density reaches its maximum peak value of 1.8 × 10⁻⁶ at the corner of the armature tail fin. 6 A / m 2 The conductivity of liquid aluminum decreases rapidly within a 2mm range, then stabilizes, and finally rises slightly near the very edge of the contact interface. This is due to the low conductivity of liquid aluminum (3.97 × 10⁻⁶). 6 The S / m ratio is much lower than that of solid aluminum (3.03×10). 7 The current density (S / m) tends to flow from the contact interface in the dry sliding contact state where the conductivity is high, resulting in a higher current density in the dry sliding contact region than in the metal liquefaction layer region.

[0092] However, within the overall distribution described above, the current density experiences a jump at the point where the liquefied metal layer intersects with the dry sliding contact. Just before transitioning from the solid-liquid-solid contact form containing the liquefied metal layer to the solid-solid contact form, the current density concentrates and flows into the armature. This flow increases with the length of the liquefied metal layer. L LMF As the thickness increased from 3.5 mm to 14 mm, the current density increased from 664,173 A / m. 2 Gradually reduced to 502128 A / m 2 The presence of a liquefied metal layer alters the current density distribution at the pivot-rail contact interface. L LMF As the thickness gradually increases to 14 mm, the current flowing into the liquefied metal layer increases, while the current flowing into the dry sliding contact interface decreases, indicating that the current gradually tends to reach equilibrium between the two regions; and when L LMF When the diameter continues to increase to 24.5 mm, the current density actually rises to its maximum value of 713549 A / m. 2 This is because with L LMF As development continues, the low-conductivity liquefied metal lubrication zone expands while the high-conductivity dry sliding zone compresses. Current is forced to concentrate in the shorter contact interface within the dry sliding zone, causing the current density at the junction of the two contact states to increase again. Ultimately, at... L LMFWhen the thickness is 28 mm, the contact interface is completely covered by a liquefied metal layer, resulting in an overall decrease in conductivity. Combined with the skin effect and tip effect, the current density is concentrated at both ends of the pivot-rail contact interface, while the distribution of the liquefied metal layer is sparser in the middle. In summary, the continuously advancing liquefied metal layer, due to its decreasing conductivity, significantly alters the current density distribution pattern at the pivot-rail contact interface.

[0093] As the LMF (Liquefied Metal Layer) length increases from 3.5 mm to 24.5 mm, the temperature distribution at the contact interface is affected by the development of the liquefied metal layer. The location of the highest temperature point continuously shifts towards the front end of the contact interface as the LMF length increases. Compared to the dry sliding contact state where the highest temperature occurs at the end corner of the armature tail fin, in the mixed lubrication state, the highest temperature occurs in front of the junction between the LMF lubrication zone and the dry sliding zone, and remains within the dry sliding contact zone. Regardless of the LMF length, the highest temperature is higher than the 681℃ in the dry sliding contact state. In terms of temperature distribution, in the mixed lubrication contact state, the temperature rises slowly from the end of the contact interface, with a significant jump at the junction of the two contact states, reaching its highest point with a steeper slope, and then rapidly decreasing from the highest temperature point towards the front end of the contact interface. This is because the thermal conductivity of liquid aluminum (90 W / (m·K)) is lower than that of solid aluminum (201 W / (m·K)), causing heat to accumulate in the LMF and making it difficult to dissipate, resulting in a gradual increase in temperature at the contact interface during the lubricated contact state. However, during the transition to the dry sliding contact state, the higher thermal conductivity of solid aluminum and solid copper facilitates heat dissipation, causing the temperature to decrease rapidly along the x-axis of the emission direction. As the length of the LMF increases from 3.5 mm to 24.5 mm, the temperature at the junction of the lubricated and dry sliding contact states in the liquefied metal layer exhibits a pattern of first decreasing and then increasing. L LMF As the thickness increased to 17.5mm, the temperature at the connection point decreased, and the temperature at the contact interface became more uniform. L LMF When the length was further increased to 24.5 mm, the temperature at the contact interface tip rose. This indicates that the development of the LMF alters the temperature distribution characteristics of the armature-rail contact interface, pushing the highest temperature point forward, thereby intensifying the melting of the aluminum alloy on the armature surface under dry-sliding contact conditions and promoting further LMF expansion. As the length of the low-thermal-conductivity LMF continues to increase, while the length of the high-thermal-conductivity dry-sliding contact interface continues to shorten, the high-temperature region tends to concentrate at the tip of the armature-rail contact interface, making the temperature rise trend more pronounced. L LMF When the diameter is 28mm, the fully fluid-lubricated contact stage is achieved, and the contact interface temperature drops sharply, with the highest temperature starting from [missing value]. L LMFThe temperature drops from approximately 760℃ at a thickness of 24.5mm to approximately 180℃. This is because the isobaric heat capacity of liquid aluminum increases from 900 J / (kg·K) to 1176.73 J / (kg·K), an increase of approximately 30%, which enhances the temperature inertia of the LMF and reduces the rate of temperature rise. In summary, with the development of LMF, its lower thermal conductivity and higher isobaric heat capacity have significantly altered the temperature distribution at the pivot-rail contact interface.

[0094] 3. The transitional contact state in which the metal liquefaction layer and the plasma gap coexist.

[0095] When the armature-rail contact interface is in a fully fluid-lubricated contact state, the armature is still accelerating within the barrel. Due to inertia, the liquefied metal layer adhering to the end surface of the armature tail fin lags behind the armature, causing it to splash backward in the direction of armature movement. Simultaneously, the viscous force between the liquid aluminum and solid copper rails also leaves some liquefied metal layer on the rail surface, resulting in continuous loss of the liquefied metal layer. As the liquefied layer gradually decreases, a local gap appears at the contact interface. This gap extends from the armature tail fin towards the front of the contact interface, eventually leading to a transition phenomenon due to the armature-rail contact interface not being tightly fitted.

[0096] During the transition, the discharge gas in the gap rapidly fills the contact interface gap. Due to the extremely low conductivity of the gas, the contact resistance increases sharply, and an anode and cathode are formed at the upper and lower interfaces of the pivot rail. The induced electromotive force between the two electrodes rises sharply, forming an arc discharge in the gap. This transforms the contact interface into a "solid-plasma-solid" contact form. The strong energy and extreme high temperature accompanying the plasma arc discharge cause severe transition ablation damage to the pivot rail contact interface.

[0097] When the pivot-rail contact interface is in a transitional contact state where a liquefied metal layer and a plasma gap coexist, to investigate the influence of the plasma gap length on the multiphysics coupling distribution of the contact interface, based on the equivalent equation of magnetohydrodynamics of plasma discharge, different gap lengths at 2 ms were established in finite element simulation software. L plm ( L plm A coupled electromagnetic, thermal, and fluid field model (with diameters of 4mm, 8mm, 12mm, 16mm, 20mm, and 24mm) is presented. In the model, the average roughness of the armature contact surface within the plasma gap is... Ra All layers were set to 62 μm thick to simulate the surface condition after the loss of the metal liquefaction layer, while the non-transition region was interspersed with a 20 μm thick metal liquefaction layer. Subsequently, a preliminary analysis was conducted on the temperature, current density, and energy flux density distribution of the entire pivot-rail contact interface.

[0098] by L plmTaking a 20mm diameter as an example, analysis of the temperature, current density, and energy flux density distribution in the plasma gap at the pivot-rail contact interface at 2ms reveals that the highest armature temperature is mainly concentrated at the transition point from the transition gap to the liquefied metal layer lubrication contact state. The temperature gradually decreases from this position towards the surrounding area, with the cooling rate towards the armature head being greater than that towards the armature tail. The high-temperature region of the rail is concentrated in the contact area with the armature liquefied metal layer. At the liquefied metal layer lubrication contact interface, the temperature decreases from the highest value at the very end of the LMF to the very front end, while the high temperature generated by the arc discharge at the plasma gap contact interface gradually decreases from the very front end of the gap towards the inflection point at the end of the armature tail. Therefore, the highest temperature at the pivot-rail contact interface is located at the junction of the transition gap and the LMF, with the temperature continuously decreasing in the forward and backward directions. The current density distribution is affected by the high resistivity of the gas gap, causing the pulse current to be unable to flow smoothly and instead concentrate its flow from the end of the liquefied metal layer, with its maximum value occurring at the transition point from the transition gap to the liquefied metal layer. The energy flux density distribution is mainly concentrated at the peak height of the rough surface of the armature tail fin at the end of the gap and at the peak height of the rough surface where the distance between the armature and rail contact interfaces is narrow.

[0099] To study the gap length L plm The influence of multi-physics coupling distribution on the pivot-rail contact interface Figure 8 The study demonstrates the variation of the maximum temperature, maximum current density, and maximum arc discharge energy flux density of the armature, orbital, liquefied metal layer, and plasma gap at 2 ms. This variation is influenced by the gap length. L plm As the length increases, the liquefied metal layer shortens, causing the maximum temperature in the four regions to gradually decrease, from... L plm The temperature dropped from approximately 780°C at 4mm to... L plm The temperature is approximately 730℃ at a gap length of 24mm. This is because the liquefied metal layer, as the main heat source at the armature-rail contact interface, reduces frictional heat as it shrinks, thereby lowering the temperature rise in the armature, rail, LMF, and plasma gap. The highest temperatures among these four components are, in descending order: LMF, armature, rail, and plasma gap, but the temperature differences between them are small, within 5℃, indicating that the high temperature generated by the LMF as the main heat source diffuses to the surrounding area through heat conduction and convection. The maximum current density increases with gap length. L plm As the gap length increases, the current density increases. Due to the extremely low conductivity of the air gap, the current density flows almost entirely from the liquefied metal layer into the armature. Therefore, as the liquefied metal layer shrinks, the current density flows more concentratedly through this region, causing its maximum value to continuously increase. The maximum energy flux density increases significantly with increasing gap length, from... L plm 7.86×10 when =4mm4 W / m 2 Increase to L plm =24mm, 2.24×10 5 W / m 2 The length of the plasma gap increases by nearly three times. This indicates that when the armature contact interface is in a transitional contact state where the plasma gap and the liquefied metal layer coexist, the expansion of the plasma gap length will increase the discharge area of ​​the armature contact surface as the cathode. According to equation (9), which characterizes the heat source of the arc discharge, arc discharge occurs everywhere in a longer transitional gap. L plm The increase in the arc discharge gap causes the arc discharge region to extend from the end of the interface to the front, thereby increasing the arc discharge intensity and energy flux density. Therefore, the longer the plasma discharge gap, the more intense the arc discharge intensity and energy will be.

[0100] In the transitional contact state where the metal liquefaction layer and the plasma gap coexist, to investigate the distribution law of the electrothermal coupling field when the plasma gap continuously replaces the metal liquefaction layer and extends towards the armature head, the gap length is selected. L plm The spatial distribution characteristics of current density and temperature along the pivot-rail contact interface at 0.2 ms were analyzed for gap lengths of 4 mm, 8 mm, 12 mm, 16 mm, 20 mm, and 24 mm. Analysis revealed that under transition contact conditions, the current density at the contact interface exhibits two peaks for different gap lengths: one at the interface between the plasma gap and the liquefied metal layer, and the other at the very front of the contact interface, with the first peak being larger. The current density distribution is uniform at the transition gap, with values ​​approximately 4.5 × 10⁻⁶ at all locations. 5 A / m 2 In the surface track, some pulse currents accumulate on the upper and lower contact surfaces of the gap, forming an arc through the transition gap, and providing sufficient charge for the continuous burning of the arc; while the current density distribution in the metal liquefaction layer region is similar to the fully fluid lubrication contact state when the metal liquefaction layer development length is equal to 28 mm, concentrated at both ends of the liquefaction layer. L plm The increase in the maximum current density at the pivot-rail contact interface reflects the continuous exposure of the plasma discharge gap between the interfaces as the liquefied metal layer is continuously ejected and viscous losses occur. This forces the pulsed current to concentrate more within the shrinking, highly conductive liquefied layer, leading to a further increase in current density. In summary, the existence and development of the plasma gap significantly alters the spatial distribution of current density at the pivot-rail contact interface.

[0101] Under transitional contact conditions, the spatial temperature distribution at the pivot-rail contact interface exhibits a trend of "increasing first and then decreasing": the temperature gradually rises within the plasma gap, accelerating near the junction of the plasma gap and the liquefied metal layer, reaching a peak at the end of the LMF, and then gradually decreasing along the beginning of the LMF. This is because, under transitional contact conditions, the main heat source at the pivot-rail contact interface is the viscous frictional heat generated by the LMF, and due to the effects of velocity trend and current skin effect, the highest temperature is located at the end of the LMF, and the temperature decreases from there to both sides. In the plasma gap, although the arc temperature remains lower than the LMF temperature, the arc energy is highly concentrated at the protrusions on the rough metal surface, forming an extremely high energy flux density. Simultaneously, the electromagnetic force damage caused by the arc discharge and its oxidation significantly disrupt the microstructure of the contact surface, ultimately leading to a higher degree of damage to the pivot-rail contact interface than LMF frictional heat. Furthermore, the arc discharge generates even more heat at the junction of the plasma gap and the LMF, approaching the LMF peak value. This is because the current converges at the junction of the plasma gap and the LMF under the combined influence of the current skin effect and the velocity skin effect, resulting in higher thermal power, with heat diffusing into adjacent plasma gap regions. As the length of the plasma gap increases... L plm As the temperature increased, the overall temperature distribution at the pivot-rail contact interface decreased, with the highest temperature dropping from 778.1℃ to 729.19℃. The main reason for this is... Figure 8 The viscous frictional heat in the LMF shown continuously decreases. In summary, the changes in the length of the plasma gap and the transition arc discharge behavior are similar to those of the LMF, both significantly affecting its spatial temperature distribution.

[0102] In summary, the development of the pivot-rail contact state will affect the electrothermal field coupling distribution at the pivot-rail contact interface, change the distribution characteristics of current density and temperature along the contact interface, and eventually lead to transitional ablation accompanied by arc initiation.

[0103] The following section describes the influence of pivot-rail contact conditions on the characteristics of the contact interface and the parameters of arc discharge.

[0104] In the actual operation of electromagnetic orbital launchers, the wear and ablation of the pivot-rail contact interface are dynamic and random, and three contact states may coexist: dry sliding, a liquefied metal layer, and a plasma gap. Therefore, based on the pivot-rail contact state development model, with the end corner of the armature tail fin as the origin and the armature launch direction as positive, an arc discharge model between the pivot-rail contact interface with the three contact states coexisting is established, as follows: Figure 9 As shown. The length of the terminal plasma gap is 4 mm, the length of the middle metal liquefaction layer is 12 mm, the length of the front dry sliding contact interface is 12 mm, and the average exposed roughness of the armature tail fin is... Ra AThe thickness was set at 62 μm. Considering practical considerations, the thickness of the metal liquefaction layer was analyzed in detail. h LMF and the roughness of the armature tail fin exposed in the gap Ra A The influence of the contact interface and arc discharge parameters.

[0105] 1. Thickness of the liquefied metal layer.

[0106] The above only discussed the development length of the metal liquefaction layer. L LMF The influence of the coupling distribution of the electrothermal and electrical fields at the pivot-rail contact interface is considered, but in reality, the solid aluminum alloy continuously melts under high temperature, resulting in a thicker liquefied metal layer. h LMF Add, Select h LMF The spatial distribution of current density and temperature at the pivot-rail contact interface with three contact states coexisting were studied, with contact sizes of 20μm, 40μm, 60μm, 80μm, and 100μm.

[0107] Analysis revealed that the current density at the pivot-rail contact interface peaked at two points (4 mm and 16 mm) where the three contact states transitioned. The first peak (4.1 mm) occurred at the junction of the plasma gap and the liquefied metal layer, exceeding 1.5 × 10⁻⁶. 6 A / m 2 This is significantly higher than the 5.5 × 10⁻⁶ at the junction of the lubricated contact state and the dry sliding contact state of the liquefied metal layer at 16.1 mm. 5 A / m 2 Under the condition of three contact states coexisting, the overall distribution law of current density along the pivot-rail contact interface is as follows: it first remains stable along the contact interface, then rises sharply to the first peak, then slowly decreases to the second peak, and finally slowly decreases in the dry sliding zone and rises slightly at the very front. Corresponding to the current density distribution when only two contact states coexist, the current density distribution when three contact states coexist is equivalent to a continuous splicing of two contact states.

[0108] With the thickness of the metal liquefaction layer h LMF As the current density increases, the amplitude of the internal current density does not change significantly in the three states, but the peak current density at the junction of the two contact states is affected. h LMF The effect. Specifically, the peak current density at 4 mm varies with... h LMF The current density at 16mm increases and decreases, but the peak current density at 16mm decreases instead. h LMFThe current density increases as the thickness of the liquefied layer increases. This is because an increase in the thickness of the liquefied layer leads to a larger volume, and since the conductivity of liquid aluminum is much lower than that of solid aluminum, the resistance of the liquefied metal layer accumulates and increases. Current tends to flow more through the dry sliding contact area, where the conductivity is higher. Therefore, the current density in the transition region from the liquefied metal layer to the dry sliding contact area is higher, while the current density at the very tip of the liquefied metal layer is lower. Thus, the thickness of the liquefied metal layer significantly affects the current density distribution at the junction of the pivot-rail contact state.

[0109] Analysis revealed that when the plasma gap, liquefied metal layer, and dry sliding contact state coexist, the spatial temperature distribution exhibits a trend of first increasing and then decreasing. Within the plasma gap, the temperature continuously rises towards the front end of the gap, reaching a peak (exceeding 950°C) at the junction of the plasma gap and the liquefied metal layer. Subsequently, as the temperature enters the liquefied metal layer region, it gradually decreases, but experiences a slight rebound at the transition between the liquefied metal layer and the dry sliding contact state. Finally, the temperature rapidly decreases at the contact interface front end, reaching a minimum of approximately 650°C.

[0110] With the thickness of the metal liquefaction layer h LMF As the temperature increases, the overall temperature distribution at the pivot-rail contact interface will decrease slightly. h LMF =20μm and h LMF The difference in the highest temperature corresponding to a thickness of 100 μm is 22.98 °C. Since the constant-pressure heat capacity of liquid aluminum is higher than that of solid aluminum, increasing the thickness increases its heat capacity, resulting in a decrease in temperature rise under the same heat source, thus the overall temperature decreases slightly. Furthermore, due to the splashing, adhesion, vaporization, and sublimation of the liquefied metal layer during launch, the rough surface at the end of the armature tail fin is gradually exposed, forming a plasma discharge gap at the rear of the armature-rail contact interface. Therefore, the distribution law of arc discharge in the plasma gap was studied under the condition of three states coexisting, and energy flux density was used as an indicator to measure the intensity of arc discharge. When arc discharge occurs between the armature and rail, 10 typical coordinate points (peak height of the convex point and valley depth of the concave point) on the rough surface of the armature were selected in the plasma gap, and the energy flux density eroded by the arc was measured. The coordinates of the selected points are shown in Table 1.

[0111] Table 1. Abscissa and ordinate of 10 points on the rough surface of the armature tail fin;

[0112] .

[0113] Based on 10 typical points and their coordinates on the rough surface of the armature tail fin, points 2 and 10, due to their negative ordinates, are below the contour baseline of the rough surface and belong to the deep valleys of the rough surface, while the rest are convex peaks. This study aims to investigate the distribution of arc discharge energy flux density in the plasma gap on the rough surface and the thickness of the liquefied metal layer. h LMF The influence of 5 different h LMF The values ​​were used to plot the changes in arc energy flow density as the horizontal and vertical coordinates of typical points increased, as shown in the figure. Figures 10-11 As shown, the points with higher arc energy flow density along the horizontal axis are 1, 3, 4, and 5, with point 4 having the highest density. h LMF It reaches 109960 W / m at 20μm. 2 The first point has coordinates (1.376, 0.14). Next are point 1 (0, 0.035) at the inflection point of the armature tail fin, and points 3 (0.935, 0.081) and 5 (1.620, 0.073) which are close to point 4. After point 6 (2.056, 0.017), the arc energy flux density gradually decreases at points 7 (2.497, 0.048), 8 (2.815, 0.085), 9 (3.421, 0.046), and 10 (3.937, -0.151). The most unusual point is 2 (0.604, -0.149), which has a small abscissa but the smallest ordinate and the largest vertical distance from the track surface, resulting in the smallest energy flux density, close to that of point 10. This demonstrates that the arc energy flux density does not change monotonically with the abscissa.

[0114] As the ordinate increases, the arc energy flux density does not show a continuous increasing trend. The point with the highest arc energy flux density remains point 4, followed by points 5, 1, and 3. Point 4 is the highest peak of the armature rough surface convexity and is closest to the inner side of the track. Points 10 and 2, with the lowest arc energy flux density, are located in the depths of the rough surface depressions, both with negative values. The ordinates of points 7 and 8 are similar to those of points 3 and 5, but their energy flux densities are lower. Considering the distribution of both the ordinate and axle, the arc energy flux density is mainly concentrated at the convex peaks with smaller axle coordinates and larger ordinate coordinates. This is because the convex peaks are closest to the inner surface of the track, have the lowest gas gap resistance, and are prone to arc discharge. Conversely, the energy flux density decreases significantly further away from the armature tail fin tip or in the depths of the rough surface depressions. Therefore, the convex peak at the tail fin tip is the area with the most severe arc discharge and ablation. (Metal liquefaction layer thickness) h LMF The effect on the distribution of energy flux density is weak, as... h LMF As the arc energy flux density increases, the values ​​at various points are approximately several thousand W / m². 2The growth of, but in actual movement, h LMF The maximum size is within about 100μm, so it does not significantly change the distribution pattern of the electric arc energy flow density.

[0115] 2. Armature tail fin surface roughness.

[0116] The raised peaks on the rough surface at the end of the armature tail fin cause the accumulation of arc energy flux density, while the average roughness of the surface curve... Ra The increase in height results in a higher peak height, and the maximum peak height is closer to the orbital discharge surface. Therefore, in addition to the thickness of the liquefied metal layer, the surface roughness of the armature tail fin also plays a role. Ra A As another pivot-rail contact condition, it also affects the contact interface and arc discharge parameters. According to equation (1), select... Ra A The values ​​were 6.1 μm, 32 μm, 62 μm, 100.8 μm, and 148 μm, respectively, to study different... Ra A The variation patterns of the parameters at the lower pivot rail contact interface and the arc discharge parameters, such as... Figure 12 As shown. It can be seen that, with... Ra A With the increase of [value], the maximum temperatures of the armature, rail, liquefied metal layer, and plasma gap did not change significantly, indicating that the roughness of the armature tail fin has no effect on the overall temperature, and the temperature distribution characteristics are mainly determined by the armature-rail contact state. Regarding current density, the maximum current density at the junction of the plasma gap and the liquefied metal layer increases with [value]. Ra A The increase gradually decreased, from 2.92 × 10 6 A / m 2 ( Ra A =6.1μm) decreased to 2.72×10 6 A / m 2 ( Ra A =148μm). The maximum arc energy flow density increases with... Ra A It increased rapidly, from 4.19 × 10 4 A / m 2 ( Ra A =6.1μm) increased to 2.9 ×10 5 A / m 2 ( Ra A =148μm). This is because, Ra AThe increase in plasma density raises the maximum peak height of the armature surface profile, shortens the inter-electrode distance between the armature surface discharge cathode and the track surface discharge anode, reduces the gas gap impedance between the two electrodes, and promotes arc discharge. The arc energy flux density concentrated at the peak height then increases. As the arc discharge intensifies, more current and charge flow through the plasma gap to form a high-energy arc discharge channel, thus reducing the residual current and charge flowing through the contact interface and consequently lowering the current density at the armature-track contact interface.

[0117] In this embodiment, based on a magnetohydrodynamic (MHD) inter-interface arc discharge model, the distribution of current density and temperature along the contact interface during the development stage of the armature-rail contact state is studied. When considering the coexistence of multiple contact states during actual launch, the influence of two armature-rail contact conditions—the thickness of the liquefied metal layer and the surface roughness of the armature tail fin—on the contact interface and arc discharge parameters is investigated. The main conclusions are as follows:

[0118] 1. Based on spatial frequency and elementary wave theory, the sum of trigonometric functions extended by Fourier series was used to synthesize real track rough surface data with a completely random distribution, and a geometric model of the pivot-rail contact interface considering damage roughness was constructed. Based on this model, combined with the coupling equivalent equations of electric field, magnetic field, thermal field and fluid field, a magnetohydrodynamic multiphysics coupling model of the development of arc discharge between pivot and rail was finally constructed.

[0119] 2. During electromagnetic orbit launch, the pivot-rail contact state sequentially progressed through three stages: a dry sliding contact stage, a mixed lubrication contact stage with both dry sliding and a liquefied metal layer, and a transitional contact stage with both a liquefied metal layer and a plasma gap. In the final transitional contact stage, arc discharge and transitional ablation occurred between the pivot and rail due to the splashing and adhesion of the liquefied metal layer. The coupling distribution of the electrothermal field at the pivot-rail contact interface during these three stages is as follows:

[0120] (1) During the dry sliding contact stage of the pivot rail, the maximum current density is located at the front end of the pivot rail contact interface, while the highest temperature is located at the end of the contact interface.

[0121] (2) In the mixed lubrication contact state where dry sliding of the pivot rail and metal liquefaction layer coexist, the highest temperature of the pivot rail interface increases significantly due to the decrease in thermal conductivity of the metal liquefaction layer and the increase in constant pressure heat capacity. As the length of the metal liquefaction layer increases, the temperature first decreases and then increases. The maximum current density increases slightly. The highest temperature position is at the end of the pivot rail contact interface, while the position of the maximum current density moves from the front end to the back end of the contact interface. When the metal liquefaction layer is fully covered (complete fluid lubrication state), the maximum current density and position are stable, but the highest temperature drops significantly and the position returns to about 6 mm from the end.

[0122] (3) During the transitional contact stage where the metal liquefaction layer and the plasma gap coexist, the highest temperature and the maximum current density increase again; and the maximum current density increases with the length of the plasma gap. L plm The temperature increases continuously, while the maximum temperature decreases continuously; both positions stabilize at the junction of the plasma gap and the liquefied metal layer. The increase in gap length significantly increases the energy flux density, prompting transition arc initiation discharge and transition ablation to occur in the plasma gap.

[0123] In summary, the evolution and changes in the pivot-rail contact state affect the electrothermal field coupling distribution at the pivot-rail contact interface, altering the current density and temperature distribution characteristics along the contact interface. When a plasma gap forms at the end of the pivot-rail contact interface, resulting in a transitional contact state, transitional arc initiation discharge and transitional ablation begin to occur and develop within the gap.

[0124] 3. Considering the arc discharge model at the pivot-rail contact interface where three contact states coexist during actual launch, the effects of the thickness of the liquefied metal layer and the surface roughness of the armature tail fin on the contact interface and arc discharge parameters were analyzed. Increasing the thickness of the liquefied metal layer reduces the current density at the junction of the plasma gap and the liquefied metal layer; the peak current density in the transition zone between the liquefied metal layer and the dry sliding contact state increases, while the overall temperature decreases slightly. The thickness of the liquefied metal layer has no significant effect on the arc energy flow density distribution in the gap; the raised peaks on the rough surface at the end of the armature tail fin remain areas of severe arc discharge and ablation. The roughness of the armature tail fin has no effect on the overall temperature of the device, but it suppresses the maximum current density at the pivot-rail contact interface and promotes the maximum arc energy flow density.

[0125] The results of the track surface damage experiment show that with the increase in usage frequency and firing frequency, track surface wear and ablation intensify, the aluminum deposition layer thickens, and the track surface roughness further increases. This exacerbates the wear and ablation of the armature surface, affecting its movement behavior and firing quality within the gun barrel, and may even lead to longer-lasting and more severe arc ablation. For the scenario of complete loss of contact between the armature and rail, complete depletion of the metal liquefaction layer, and the most severe arc ablation under transition conditions, based on the established magnetohydrodynamic model, the inner side of the track is designated as the arc discharge anode, and the armature contact surface as the arc discharge cathode. The dynamic development of arc morphology and parameters with firing time, as well as the influence mechanisms of the number of armature-rail micro-contact points, gap width, and track roughness on the armature-rail contact interface and arc discharge, were investigated.

[0126] The dynamic development of arc morphology and parameters is described below.

[0127] In the multi-physics coupled electrohydrodynamic model of arc discharge, the width of the pivot-rail gap is taken as... d The average surface roughness of the track is 0.5 mm. Ra R The diameter was 278.7 μm. The study investigated the changes in arc morphology, arc temperature, and arc energy flux density within the plasma gap as the launch time progressed.

[0128] Figures 13-16 The figures show the dynamic development of arc discharge temperature within the gap at emission times of 0.5ms, 1.5ms, 2.5ms, and 3.5ms, respectively. It can be seen that when the pivot-rail contact interface is completely in a transitional contact state due to loss of contact, the arc temperature within the plasma gap is much higher than when multiple contact states coexist, reaching a maximum temperature of 1.74 × 10⁻⁶. 7 The arc temperature reached ℃, far exceeding the levels of the dry sliding contact state and the lubricated contact state of the liquefied metal layer, indicating stronger arc ablation energy. This is due to the rapid increase in arc energy caused by the expansion of the electrode area. The arc temperature distribution shows a pattern of highest temperature in the middle arc column and lowest temperature at the arc roots on both sides. As the launch time increases, the arc temperature first decreases and then increases, and the severity of ablation also changes accordingly, consistent with the trend of track damage increasing and then decreasing from the rear to the front in the experiment. Moreover, the highest arc temperature occurs at 1.5 ms, lagging behind the peak value of the pulse current by 1.2 ms. The air velocity direction in the fluid field is opposite to the armature launch velocity. When the airflow passes through the narrow gap, its velocity increases, causing a significant change in the arc shape. At 0.5 ms, the arc is evenly distributed throughout the gap; from 1.5 ms to 3.5 ms, the arc shape is gradually blown towards the rear of the gap and is stretched and overflows to the rear at the inflection point of the armature tail fin. The change in arc temperature with launch time is also related to the change in arc shape. At the beginning, the arc temperature is evenly distributed in the gap and concentrated at the convex peak of the rough surface of the track. The high temperature region of the arc is concentrated at the rear end of the gap as the airflow blows and increases from the front end to the rear end along the gap. The highest temperature is always located at the tail end of the gap that overflows from the pivot rail.

[0129] Depend on Figures 17-20 The figures show the dynamic development of arc energy flux density within the gap at launch times of 0.5ms, 1.5ms, 2.5ms, and 3.5ms. The development pattern of energy flux density is completely consistent with the temporal distribution characteristics of the arc morphology and arc temperature, gradually concentrating from an initial uniform distribution to the rear and rear regions of the gap. In the direction perpendicular to the pivot-rail contact surface, the arc energy flux density decreases from the center of the arc column towards the arc roots on both sides. The energy flux density in the fully pivot-rail transition contact state is much higher than when multiple contact states coexist, with the maximum value also appearing at 1.5ms, reaching 2.27 × 10⁻⁶. 12 W / m 2Located at the tail end of the arc overflow gap. Combining the arc temperature and energy flux density, it can be seen that when the transition covers the entire pivot-rail contact interface, the contact resistance of the pivot-rail gap increases significantly, the induced electromotive force between the anode and cathode increases substantially, and the electrode discharge area expands. This leads to the extreme accumulation and splitting of plasma arc energy under the combined effect of higher potential and larger discharge area, resulting in extremely severe ablation damage to the track and armature. It may even cause incalculable and serious safety hazards such as explosion, impact, and irreversible damage to key components of the entire device.

[0130] In this embodiment, based on the magnetohydrodynamic model of arc discharge development at the pivot-rail contact interface, considering the pivot-rail transitional contact state due to loss of contact, the dynamic development characteristics of the arc morphology and parameters in the pivot-rail gap were analyzed, as well as the influence mechanism of three variables—the number of pivot-rail micro-contact points, the pivot-rail gap width, and the track surface roughness—on the pivot-rail contact interface and arc discharge parameters. The main conclusions are as follows: When the entire pivot-rail contact interface is in a state of complete loss of contact, the ablation damage type changes from transitional ablation to the most severe arc ablation. The arc temperature in the plasma gap is much higher than in the mixed contact state, and the arc temperature and energy flux density are highest at the middle arc column and lowest at the arc root on the track and armature surfaces, increasing first and then decreasing over time. The arc morphology is initially uniformly distributed, but is later blown to the rear of the gap by the moving airflow and extends outwards.

[0131] Example 2

[0132] This embodiment provides an arc discharge simulation system under pivot-rail contact and complete loss of contact conditions, including:

[0133] The model building module is configured to construct track surface curves under different roughnesses by synthesizing randomly distributed track roughness surface data, and then construct geometric models when the pivot-rail contact interface undergoes transition under different roughnesses. Based on the geometric model, a magnetohydrodynamic simulation model of arc discharge between the pivot-rail contact interface is constructed, which simultaneously considers the multi-field coupling of electric field, magnetic field, thermal field and fluid field.

[0134] The simulation module for the pivot-rail contact state is configured to analyze the electrothermal field distribution at the pivot-rail contact interface based on a magnetohydrodynamic simulation model. This analysis is conducted in three stages: the dry sliding contact state, the mixed lubrication contact state where dry sliding and a metal liquefaction layer coexist, and the transitional contact state where a metal liquefaction layer and a plasma gap coexist. The module obtains the variation patterns of the maximum current density, the highest temperature, and their respective positions at the pivot-rail contact interface as the contact state stages change. Furthermore, based on the constructed arc discharge model between the pivot-rail contact interfaces with the three coexisting contact states, the module analyzes the variation patterns of the pivot-rail contact interface parameters and arc discharge parameters under different metal liquefaction layer thicknesses and armature tail fin roughnesses.

[0135] The simulation module for complete loss of contact is configured to perform arc ablation simulation under the complete loss of contact state of the pivot rail according to the magnetohydrodynamic simulation model. It obtains the variation law of arc morphology, temperature and energy flux density in the plasma gap with the emission time, as well as the variation law of pivot rail contact interface parameters and arc discharge parameters under different numbers of pivot rail micro-contact points, pivot rail gap width and track surface roughness.

[0136] In further embodiments, the following is also provided:

[0137] An electronic device includes a memory and a processor, as well as computer instructions stored in the memory and running on the processor, wherein the computer instructions, when executed by the processor, perform the method described in Embodiment 1.

[0138] A computer-readable storage medium for storing computer instructions, which, when executed by a processor, perform the method described in Embodiment 1.

[0139] A computer program product includes a computer program that, when executed by a processor, implements the method described in Embodiment 1.

[0140] For the sake of brevity, the specific implementation methods of the above embodiments will not be described in detail here.

[0141] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A simulation method for arc discharge under pivot-rail contact and complete loss of contact conditions, characterized in that, include: By synthesizing randomly distributed track rough surface data, track surface curves under different roughness are constructed, and then geometric models are constructed when the pivot-rail contact interface undergoes transition under different roughness. Based on the geometric model, a magnetohydrodynamic simulation model of arc discharge between the pivot-rail contact interface is constructed, which simultaneously considers the multi-field coupling of electric field, magnetic field, thermal field and fluid field. Based on the magnetohydrodynamic simulation model, the electrothermal field distribution at the pivot-rail contact interface is analyzed in three stages: dry sliding contact, mixed lubrication contact (with dry sliding and liquefied metal layer), and transitional contact (with liquefied metal layer and plasma gap). The maximum current density, highest temperature, and their respective positions at the pivot-rail contact interface are observed as the contact state stages change. Furthermore, based on the constructed arc discharge model between the pivot-rail contact interfaces under the three coexisting contact states, the variation of pivot-rail contact interface parameters and arc discharge parameters under different liquefied metal layer thicknesses and armature tail roughness is analyzed. Based on the magnetohydrodynamic simulation model, arc ablation simulation was performed under the condition of complete loss of contact between the pivot and the rail. The changes in arc morphology, temperature and energy flux density in the plasma gap with the emission time were obtained, as well as the changes in the pivot-rail contact interface parameters and arc discharge parameters under different numbers of pivot-rail micro-contact points, pivot-rail gap width and track surface roughness.

2. The method for simulating arc discharge under pivot-rail contact and complete loss of contact as described in claim 1, characterized in that, Real track roughness surface data with a completely random distribution is synthesized using the sum of trigonometric functions extended by Fourier series, thereby constructing a geometric model of the transition at the pivot-rail contact interface under different roughnesses; among which, the track surface curves for: ； in, P Amplitude The proportionality coefficient; υ For spatial frequency, a ( υ () represents the amplitude Multiply by a random function with a Gaussian distribution g ( υ The generated amplitude, φ ( υ () represents the phase angle, ± V These are the maximum and minimum cutoff values ​​for spatial frequency. w ( υ ) is a uniform random function. For spectral index.

3. The method for simulating arc discharge under pivot-rail contact and complete loss of contact as described in claim 1, characterized in that, During the dry sliding contact stage of the pivot rail, at the same time, the spatial distribution of current density along the pivot rail contact interface shows a trend of first decreasing and then increasing. The maximum current density is located at the foremost end of the pivot rail contact interface, and the highest temperature is located at the end of the pivot rail contact interface. In the mixed lubrication contact state stage where dry sliding of the pivot rail and the metal liquefaction layer coexist, the metal liquefaction layer begins to appear at the rear of the armature tail fin where the temperature is highest, and gradually develops towards the armature head as the launch progresses, until it covers the entire pivot rail contact interface. The highest temperature of the pivot rail contact interface changes according to the length of the metal liquefaction layer, first decreasing and then increasing, with the highest temperature located at the end of the pivot rail contact interface. The location of the maximum current density shifts from the front end to the back end of the pivot rail contact interface. When the metal liquefaction layer develops to cover the entire pivot rail contact interface, the pivot rail contact state is a fully fluid lubrication contact state. In this contact state, the maximum current density and its location remain unchanged, the maximum temperature decreases, and the highest temperature is located at the end of the pivot rail contact interface. During the transitional contact phase where the liquefied metal layer and the plasma gap coexist, the maximum temperature recovers and the maximum current density increases. As the length of the plasma gap increases, the maximum current density continues to rise while the maximum temperature continuously decreases. The locations of the maximum temperature and maximum current density are always at the junction of the plasma gap and the liquefied metal layer. Transitional arc initiation discharge and transitional ablation occur in the plasma gap, and the increase in gap length leads to an increase in arc discharge energy flow density.

4. The method for simulating arc discharge under pivot-rail contact and complete loss of contact as described in claim 1, characterized in that, When the three contact states coexist, the parameters of the pivot-rail contact interface include the highest armature temperature, the highest rail temperature, the highest temperature of the liquefied metal layer, and the highest temperature of the plasma gap; the parameters of the arc discharge include the maximum current density of the pivot-rail contact interface and the maximum energy flux density of the arc discharge. As the thickness of the liquefied metal layer gradually increases, the maximum current density amplitude decreases at the position where the plasma gap connects with the liquefied metal layer, and the peak value of the maximum current density increases at the position where the liquefied metal layer transitions to the dry sliding contact state. The change in the thickness of the liquefied metal layer has no effect on the parameters of the pivot-rail contact interface and the maximum energy flux density of the arc discharge. The roughness of the armature tail fin has no effect on the parameters of the armature-rail contact interface, but it has a weakening effect on the maximum current density and a promoting effect on the maximum energy flux density.

5. The method for simulating arc discharge under pivot-rail contact and complete loss of contact as described in claim 1, characterized in that, When the armature and rail are completely out of contact, the spatial distribution of arc temperature and arc energy flow density is characterized by the highest temperature and energy flow density in the central arc column, and the lowest temperature and energy flow density at the arc root on both sides of the rail and the armature surface. The temporal distribution is characterized by the arc temperature and arc energy flow density first increasing and then decreasing. The arc shape is initially uniformly distributed in the gap, and then the arc shape is gradually blown to the rear of the gap by the moving airflow, and is elongated at the inflection point at the end of the armature tail fin and overflows to the rear of the armature-rail gap.

6. The method for simulating arc discharge under pivot-rail contact and complete loss of contact as described in claim 1, characterized in that, In the state of complete loss of contact between the armature and the rail, the parameters of the armature-rail contact interface include the highest armature temperature, the highest rail temperature, and the highest plasma gap temperature; the parameters of the arc discharge include the maximum current density at the armature-rail contact interface and the maximum energy flux density of the arc discharge. The increase in the number of micro-contact points on the pivot rail leads to a decrease in the gap contact resistance, which in turn weakens the parameters of the pivot rail contact interface and the arc discharge parameters. Under the combined influence of the armature gap width and the track surface roughness, for the maximum armature temperature, only the increase in the armature gap width leads to an increase in the maximum armature temperature; for the maximum track temperature, both the increase in the armature gap width and the increase in track surface roughness lead to an increase in the maximum track temperature; for the maximum plasma gap temperature, only the increase in the armature gap width leads to an increase in the maximum plasma gap temperature; for the maximum current density, both the decrease in the armature gap width and the increase in track surface roughness lead to an increase in the maximum current density; for the maximum energy flux density, both the increase in the armature gap width and the increase in track surface roughness lead to an increase in the maximum energy flux density.

7. A simulation system for arc discharge under pivot-rail contact and complete loss of contact conditions, characterized in that, include: The model building module is configured to construct track surface curves under different roughnesses by synthesizing randomly distributed track roughness surface data, and then construct geometric models when the pivot-rail contact interface undergoes transition under different roughnesses. Based on the geometric model, a magnetohydrodynamic simulation model of arc discharge between the pivot-rail contact interface is constructed, which simultaneously considers the multi-field coupling of electric field, magnetic field, thermal field and fluid field. The simulation module for the pivot-rail contact state is configured to analyze the electrothermal field distribution at the pivot-rail contact interface based on a magnetohydrodynamic simulation model. This analysis is conducted in three stages: the dry sliding contact state, the mixed lubrication contact state where dry sliding and a metal liquefaction layer coexist, and the transitional contact state where a metal liquefaction layer and a plasma gap coexist. The module obtains the variation patterns of the maximum current density, the highest temperature, and their respective positions at the pivot-rail contact interface as the contact state stages change. Furthermore, based on the constructed arc discharge model between the pivot-rail contact interfaces with the three coexisting contact states, the module analyzes the variation patterns of the pivot-rail contact interface parameters and arc discharge parameters under different metal liquefaction layer thicknesses and armature tail fin roughnesses. The simulation module for complete loss of contact is configured to perform arc ablation simulation under the complete loss of contact state of the pivot rail according to the magnetohydrodynamic simulation model. It obtains the variation law of arc morphology, temperature and energy flux density in the plasma gap with the emission time, as well as the variation law of pivot rail contact interface parameters and arc discharge parameters under different numbers of pivot rail micro-contact points, pivot rail gap width and track surface roughness.

8. An electronic device, characterized in that, It includes a memory and a processor, as well as computer instructions stored in the memory and running on the processor, which, when executed by the processor, perform the method according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, Used to store computer instructions, which, when executed by a processor, perform the method described in any one of claims 1-6.

10. A computer program product, characterized in that, Includes a computer program, which, when executed by a processor, implements the method described in any one of claims 1-6.

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