Theoretical Study On The Properties Of The Armature In Railgun

Railgun is one of the new concept weapons which to use accelerate a projectile by using electromagnetic technology. It has a broad application prospect in military field with the advantages of the high-speed, long range, easy control, low cost and so on. As the key components of the railgun, the armature has an important impact on the performance of launch. Considering the complex working process of the armature and the coupling effect between variables, it is difficult to define the electromagnetic properties of the armature, as well as its impact on the railgun performance only by experiment. So the using of numerical simulation technology is necessary.The main contents of the dissertation are mainly divided into the following three aspects:(1) Research on eletromagnetic characteristics and heat conduction of solid armature: Two- and three-dimensional unsteady computational models are applied to investigate the electromagnetic effect and heat conduction in block and U-shaped solid armatures. Coupling calculations are carried out by P-R and Douglas Finite Difference Method, and the magnetic induction, current density and temperature distributions in different sections are evaluated accurately. The results show a local concentration of current and joule heating at the interface because of the velocity skin effect, and significant ablation occurs at the back edges of the armature. Based on these, three-dimensional unsteady computational models about the solid armature with brachial angles are built. The influence factors on electromagnetic properties, such as input current, shape, material and so on, are analyzed and discussed in detail, which contribute to the choice and design of the solid armature;(2) Research on eletromagnetic and fluid characteristics of plasma armature:Possible two- and three-dimensional magnetohydrodynamics (MHD) models are established respectively to investigate the plasma armature. The characteristics and distributions of physical parameters of the plasma have been attained. The results show that extremely high pressure can always be observed ahead of the armature; the temperature distribution is affected by the boundary conditions about the radiative heat flux, with the maximum temperature appearing in the center near the base of the projectile; resulted from the unbalanced force between the Lorentz force and pressure gradient, the circulation patterns of velocity are evident, and the position of the high temperature region and the acceleration curve oscillate in time until a new steady state is achieved; meanwhile, in consideration of the ablation quality of the rail, the pressure ahead of the armature and the internal temperature of the plasma become slightly lower, and the maxmum density becomes much higher.Considering of viscosity, the distribution of the velocity vectors near the wall changes obviously;(3) Research on the application of the space-time conservation element and solution element (CE/SE) method in magnetohydrodynamics:The MHD equations consist of fluid dynamics equations coupled with Maxwell's equations. Taking into account the effect of the magnetic field on the momentum and energy items, numerical solution of MHD equations is much more complex than the traditional equations of aerodynamics. So the choice of methods is essential. In this dissertation, the computing scheme of the CE/SE method is derived first for solving one-and two-dimensional inviscid MHD equations. Several standard MHD cases have been solved to verify the applicability and high-accuracy of this method; then, based on the practical MHD engineering problems, two- and three-dimensional computational schemes of the CE/SE method and Jacobian coefficent matrices are derived for solving the coupling flow field and electromagnetic field of plasma armature.In this dissertation, by coupling calculations of electromagnetism-heat and electromagnetism-fluid properties about the solid and plasma armatures, some results with great significance of the theoretical and engineering application have been obtained. Meanwhile, the research can reduce the cost and shorten the development cycle, castsing some light on the optimization of the railgun system.