Analysis of Projectile Motion in Bore and Transfer Efficiency for Electromagnetic Railgun
Electromagnetic railgun (EMG) use a high-current, high-energy electrical pulse to accelerate projectiles to hypersonic velocities. A pulsed power supply (PPS) that employ capacitors as the energy store are typically used to shape the required electrical pulse. In this paper, the differential equations of projectile moving in the bore has been given and solved. The general pattern of projectile moving in the bore has been studied. Considering the influence of current fluctuation on velocity, the stability of armature has been discussed. In order to improving system performance, the efficiency of main energy transfer process has been calculated. The influence of current shape consists of several electrical pulse on muzzle velocity and efficiency has been studied. And some important conclusions have been reached, which provide theoretical references for guiding railgun design and choosing waveform of discharging current.
Dynamic Response of Electromagnetic Rail Launcher Due to Projectile Motion
The dynamic response in the dynamic launching process of electromagnetic rail launcher (EMRL) is very important for the design of launchers and armatures. With the Bernoulli–Euler beam located on an elastic support as an object of the study, the analytical model of EMRL dynamic characteristics under the influence of EM repulsive force and contact force between the armature and the rail is obtained, and the corresponding 3-D finite-element simulation model [moving load–rail model (MR model)] is established. On this basis, the 3-D finite-element simulation model [projectile–rail model (PR model)] considering the projection vibration is established to obtain the dynamic response of EMRL due to projectile vibration. Studies show that the calculation results of the analytical model agree well with that of the MR model. When the moving load works at a critical speed and reaches the point of action, the rail will have an increased deformation and then a harmonic vibration, whose amplitude is five or six times than that under the noncritical operating condition. The analysis of the impact of projectile vibration on the rail deformation makes it known that the vibration amplitude of the PR model is four or five times than that of the MR model because of projectile vibration. The greater the gap between the rail and the armature is, the more violent is the projectile vibration and the greater is the vertical deformation of the rail, and the greater the density of the payload with the same volume is, the more intense is the projectile vibration and the greater is the vertical deformation of the rail. When launching reaches the critical speed, the rail deformation of the PR model is less than that of the MR model, which is mainly caused by the vibration of the projectile, but the vibration periods of those two models are the same.
Liquid state 1H high field NMR in food analysis.
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