Modeling simulation and multi-field coupling analysis method and system for electromagnetic railgun system

A method for modeling-simulation and multi-field coupling analysis of an electromagnetic railgun system before launching process to ensure the reliability and safety of the electromagnetic railgun system, comprising the following steps:

• building, respectively, a mathematical model of pulse shaping unit, a mathematical model of armature impedance, a mathematical model of rail and a dynamic model of armature of an electromagnetic railgun system;
• forming, by using a modularization method, a simulation model of the electromagnetic railgun based on each of the built models;
• carrying out a three-dimensional coupling simulation on a current density and a magnetic induction intensity distribution of the simulation model of the electromagnetic railgun, and analyzing a coupling action and distribution characteristics of an electromagnetic field in a launching process of the electromagnetic railgun and an influence of the electromagnetic field on a temperature field distribution;
• and, determining, based on the analysis result, positions where a severe ablation appeared and/or where an electric contact arcing to be generated on the electromagnetic railgun and taking corresponding actions to prevent and mitigate the occurrence of the severe ablation and/or the electric contact arcing;
• wherein:
• a specific process of building the mathematical model of pulse shaping unit of the electromagnetic railgun system comprises:
• building a model of topological structure according to a topological structure of the pulse shaping unit;
• dividing a discharge process into a discharge stage and a freewheeling stage according to whether a freewheeling diode is turned on or not when the model of topological structure is provided with a linear load;
• and, building circuit equations of the two stages respectively to form the mathematical model of pulse shaping unit;
• a specific process of building the mathematical model of armature impedance of the electromagnetic railgun system comprises:
• expressing a resistance caused by a skin effect of current on an armature, dividing a contact resistance caused by a skin effect of velocity into two parts, comprising a contact resistance under skin effect of velocity on rails and a contact resistance under skin effect of velocity on the armature, and respectively expressing each part to form the mathematical model of armature impedance;
• a specific process of building the mathematical model of rail of the electromagnetic railgun system comprises:
• constructing an expression of resistance of the rails, calculating a resistance gradient of the rails, expressing a skin depth of the rails in combination with the calculated resistance gradient, and constructing a loop current expression of the rails based on a circuit structure of the rails;
• and
• a specific process of building the dynamic model of armature of the electromagnetic railgun system comprises:
• calculating an electromagnetic force on the armature based on magnetic field energy of a launching system, expressing a friction force between the rails and the armature based on a sliding friction coefficient;
• expressing a dynamic normal pressure on the armature under assumptions that a force acting on the armature is linearly distributed and that a transformation from an axial stress to a radial stress is described by a linear function;
• expressing an air resistance under assumptions that a density of an air being uncompressed in the rails before electromagnetic launch is of a standard atmospheric state, that a time taken for the air to be compressed is ignored when a shock wave is generated immediately after an armature acceleration, that the density and pressure of the air being compressed are uniform and a specific heat rate is constant, and that the speed of the air being compressed in the rails is consistent with that of the armature;
• and
• expressing, in a form of differential equation, a motion equation of the armature based on the friction force between the rails and the armature, the dynamic normal pressure on the armature and the air resistance.