Finite-Element Electromagnetic Simulations Of Reconnection Electromagnetic Launch Systems

Electromagnetic launchers represent multiple advantages of launch promptness,long flight-shot,favourable controllability and concealment so as to become the prospective technology for future launching schemes.Reconnection electromagnetic launcher averts abrasive wear between the projectile armature with rail-track of the electromagnetic rail-gun and can achieve appreciably higher axis electromagnetic acceleration force and launch efficiency than of electromagnetic coil catapult,while being restricted by the shape of projectile armature.In the present study,the fundamental characteristics of reconnection electromagnetic launchers are theoretically investigated by means of analytical models based on electromagnetic theory and circuit principle.In particular,the dynamic processes and launching performances of the single plate,multi-wing and multi-pole reconnection electromagnetic launch systems are comprehensively simulated and analyzed with the three-dimensional transient models of electromagnetic fields by the finiteelement method,according to which the optimized design schemes are put forward.Electromagnetic forces and projectile armature motions in single-plate reconnection electromagnetic launch systems are investigated by transient simulations of electromagnetic fields to elucidate the correlative mechanisms of the projectile position,pulse voltage and capacity,drive coil,and armature structure affecting on the launching performances.Electromagnetic-force symmetry on projectile armature should be broken by slightly shifting projectile armature along the launching direction to shorten the initial time and significantly promote launch speed.Launch speed can be improved by elevating the voltage and capacity of pulse power,while the maximum launch efficiency will appear with the increase of pulse power supply.The increment in the number of drive coils leads to the delay of arising electric-current peak in drive coils and the reduction of launch speed.Furthermore,it is noteworthy of making the center-hollow structure in aluminum projectile armature to improve the launch speed and efficiency.Based on the simulation results of single-plate reconnection electromagnetic launchers,three-dimensional dynamic model of multi-wing and multi-pole reconnection electromagnetic launch systems are established to simulate transient electromagnetic fields in launching process.It is indicated for the multi-wing structures that: launch efficiency of applying positive current in drive coils is evidently higher than that of negative drive current;it is preferable by abating the number of drive coils to improve launch speed and efficiency;with the increased number of projectile wings,both the coupling coefficient and negatively induced electromotive potential in drive coils will increase,possibly resulting in the reduction of launch efficiency;The launching performances of six-wing structure is higher than that of four-wing and eight-wing structures.Even though a higher voltage and capacity of pulse power supply could be applied to achieve a higher launch speed,the energy conversion efficiency of the whole launching system will accordingly decrease,implying that the pulse power supply should be modified to acquire optimal launch efficiency.The quadrupole,hexapole,octapole and cylindrical projectile-armatures are individually modeled for simulating the dynamic launching processes of multi-pole reconnection electromagnetic launch systems.The highest launch speed has been acquired by quadrupole armature than the other projectile structures.Although the cylindrical armature could rotate under the electromagnetic forces along the circumferential tangential direction,the projectile armature maintains a high stability after starting launch.Being attributed to the characteristic configuration of multi-pole reconnection electromagnetic launch system,the launch speed and efficiency could be prominently improved by enlarging the external drive coils.