Effect of liquid film (indium) on thermal and electromagnetic distribution of an electromagnetic launcher with new armature

Abstract

An advanced high-power electromagnetic launcher (EML) improves performance by as much as 30% over a conventional launcher. Electrical energy is the main driving source for the electromagnetic launcher. In existing electromagnetic launchers with solid armature, velocity skin effect (VSE), degradation, and ablation of contact surfaces, generated by friction and nonuniformity of electrical current, causes the armature to melt and deform. To reduce the friction and avoid degradation and ablation, a new armature design is utilized. In addition, liquid film with high electrical conductivity (indium) has been placed between the rail and the new armature. The purpose of this study is to investigate the effect of the new armature as well as a good electric conductance liquid film (indium) on the thermal and magnetic induction distribution of the rail and the armature. In our formulation of governing, nonlinear differential equations, Maxwell equations coupled with energy equation are applied to the rail, the new armature, and the liquid film. Also, the speed of the armature and velocity profile of the liquid film is calculated and is used in the energy equation. To solve the nonlinear governing differential equations, a finite difference code based on alternative directional implicit (ADI) method is utilized. Results obtained for the rails and the armature show that the maximum temperature occurs at the trailing edge of the armature and the corner inside the armature cut. In this region, the temperature reaches up to about 940 K. The new armature shows little effect on this temperature. However, using liquid indium not only improves the electrical conductivity of the rail and the armature contact area, it also reduces the friction and delays the melting of the armature.