Research On Modeling And Efficiency Improvement Of Distributed Energy Storage Electromagnetic Rail Launch System

Electromagnetic railgun is an electric power-driven weapon that accelerates macroscopic objects to hypervelocity through electromagnetic force.Its launching efficiency can be described as the conversion efficiency from electrical energy to kinetic energy.The launch efficiency improvement has always been the research hotspot and development bottleneck in electromagnetic launch technology.A set of pulse power supply design schemes,including the trigger time and feed-in point,is an effective way to improve the launch efficiency of the electromagnetic rail launch system.Considering the high capital investment and long development cycle,simulation calculation is an inevitable choice for performance assessment and efficiency analysis of the distributed energy storage(DES)electromagnetic railgun.Firstly,the simulation model of the DES electromagnetic rail launch system is established,which is divided into three components,including the pulse forming unit(PFU),the impedance component on the rail/armature,and the dynamics component of the armature,to carry out mechanism research and modular model.(1)The PFU: Two types of the PFU circuit topology are introduced,and their advantages and disadvantages are analyzed and compared.Considering the operating mode of distributed energy storage and time-sharing trigger,a better topology is selected.In the case of linear load,the analytical expressions of the electrical characteristics of the PFU are derived.(2)The impedance component on the rail/armature: The current skin effect,the velocity skin effect and the conducting rail under the DES mode are analyzed,and the corresponding mathematical model is given.(3)The dynamics component of the armature: The electromagnetic force,sliding friction and air resistance of the armature are combined to construct the governing motion equations of the armature.In MATLAB/Simulink,through the measurement module and controlled voltage source module to realize the mutual conversion of mathematical signals and circuit signals.The three components are linked to form the complete Simulink model of the DES electromagnetic rail launch system.Next,the output characteristics are discussed in detail based on the above DES electromagnetic rail launch system.Compared with the breech-feed configurations,it turns out that the DES ones can effectively avoid the generation of unnecessary magnetic field or ohmic loss on the launcher,and more electric energy can be converted into kinetic energy,and ultimately achieving a significant launch efficiency improvement.The controllable factors,that can affect the output characteristics and launch efficiency of the DES electromagnetic railgun,are thoroughly investigated,such as feed-in points,the number of discharge stages,rails' length,the voltage and capacitance of the capacitor,the mass of the armature,the inductance gradient and resistance gradient of rails.The results suggest that increasing the rail inductance gradient or decreasing the rail resistance gradient can effectively improve the launch efficiency without the huge cost of high-power devices,especially energy storage capacitors and switches.Then,the rail structure is designed to improve the launch efficiency of the railgun.Based on Maxwell platform,the electromagnetic field distribution features on and around the rail are analyzed,as well as the influential factors like the amplitude and frequency of excitation current,and the structure of the rail.The calculation formulas for the resistance and inductance gradients of the rail are deduced,and the gradient values under different cross-sectional structures and geometric parameters are calculated.The results illustrate that material selection and structure design of rails are valid ways to increase the inductance gradient or decrease the resistance gradient,while enlarging the separation between parallel rails can both improve the inductance gradient and reduce the resistance gradient.Three kinds of rail structures are designed,and the calculated gradient values are substituted into the simulation model of the DES electromagnetic railgun for performance comparison.The results indicate that the launch efficiency can be dramatically improved with the designed concave-section rail.Finally,the multi-parameter optimization with the genetic algorithm is applied to the Simulink model of the DES electromagnetic railgun.Adopt the launch efficiency as the objective function along with constraints described by the peak current,the muzzle velocity of the armature and a certain range of parameters to optimize parameters like the capacitor voltage,the capacitor capacitance and the armature mass.This thesis eventually developed a DES electromagnetic railgun with 0.3545 MJ capacitive energy,which can accelerate the armature weighted 43 g to 3000 m/s on the designed concave rail measured 5 m in length,and the launching efficiency reaches 54.58%,which is 31.88% higher than that before optimization.