Inductance Gradient in Electromagnetic Launcher Under Channel Cooling Condition

Abstract

Avoiding the ablation on the rail surface and obtaining large enough electromagnetic thrust to push the armature forward to high speed are two core contents of the electromagnetic launch technology. Reducing the ablation on the rail surface as much as possible can effectively extend the service life of the electromagnetic launcher (EML). The greater the electromagnetic thrust, the greater the initial velocity of the armature launched by the EML. The ablation on the rail is closely related to the temperature of the rail surface, and the electromagnetic thrust is proportional to the inductance gradient in the rails. The water flowing through cooling channels in rails can take away most of the heat generated by megaampere current flowing through the rails and armature in a few milliseconds. In this way, serious ablation on the rail can be avoided. Although the cooling channels are very helpful to reduce the ablation on rails, if the location distribution of the cooling channels in rails is not appropriate, the inductance gradient in the rails will be affected. This will affect the electromagnetic thrust in the EML. Therefore, the expressions of the inductance gradient in the rails with or without cooling channels are deduced and verified by the FEA in this article. The influence of the position distribution of the cooling channel on the inductance gradient in rails is analyzed. The results show that, with the increase of frequency, the influence of cooling channels on the inductance gradient in the rails diminishes gradually; if the distance between the cooling channels and the surface of the rails is greater than a certain value, the inductance gradient is no longer influenced by the cooling channels. At last, the relationship among <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L} ^{\prime} $ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L} _{\mathbf {1}}$ </tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L} _{\mathbf {2}}$ </tex-math></inline-formula> are fit in this article. It can be used to find the rail parameters that meet both thermal management and electromagnetic driving force requirements.