Analysis and Calculation of Rail Transient Temperature During Electromagnetic Launch

The thermal characteristics of the interface between armatures and rails of electromagnetic railguns (EMRGs) have an impact on the state of armature-rail contact and the launching performance of its system. In the launching process of EMRGs, the temperature rise of rails is mainly caused by the Joule heat generated by the rail resistance and armature-rail contact resistance and the friction heat generated by high-velocity movement of armatures. According to the theories of electromagnetic field, conservation of energy, Joule’s law, and generation of heat by friction, this paper analyzes the property of the contact resistance of the interface between armatures and rails of railguns and the friction factor of the interface, and develops a formula to calculate the transient temperature of rails resulting from the Joule heat and friction heat. Through a launch experiment, such dynamic data as muzzle voltage, rail current, armature displacement, and velocity during the actual launching process are obtained to calculate relevant parameters such as contact resistance, rail resistance under velocity skin effect, and armature-rail contact pressure. Such parameters are substituted into the temperature calculation formula for calculation of the Joule heat generated by the rail resistance and armature-rail contact resistance and the friction heat generated by high-velocity movement of armatures. The calculation produces a curve of change of rail maximum temperature over time under the joint effect of the three factors, thus allowing for the calculation of the transient temperature of rails during the launching process.