Theoretical And Experimental Research On The Containment Eddy-current In Electromagnetic Railgun

The Electromagnetic(EM)railgun is a research focus for its all-electric mode and hypervelocity.As an important part of EM railgun,the containment is used to support the barrel and offset the rails repulsion.But the containment eddy-current will influence the launching performance.In this paper,the containment eddy-current of EM railgun were investigated in combination with theoretical calculation and experimental measurement.a?The generating mechanism of containment eddy-current and its influences on launching efficiency and barrel stress.In this paper,the difference between proximity effect and skin effect was expounded,the influence of proximity effect on inductance gradient and resistance gradient was analyzed,and the effect factors of proximity effect were researched.Containment nearby the rails will be induced huge eddy-current by proximity effect.The distribution and change characteristics of containment eddy-current were investigated based on the finite element method A-?.And the eddy-current loss was calculated.A current model of EM railgun with Synchronous discharge was built for researching the influences of containment eddy-current on launching efficiency and barrel stress.Results show that,the eddy-current on the stainless steel containment makes a 3.65%decreases in launching efficiency,and the laminated structure or high permeability silicon steel instead of stainless steel can significantly improve the efficiency.Eddy-current impairs the magnetic field surrounding of the armature,makes a 27%decreases and 29%decreases in the axial force and radial force of armature respectively,and ultimately affect the launching efficiency.b?The influence of containment eddy-current on energy consumption of EM railgun system.The measurement methods of EM railgun experimental parameters were described in details.Based on the experiment,a theory model of series augmented electromagnetic railgun with sequential discharge was built in this paper.In this theory model,the lumped parameter of PPS,the actual factors like contact resistance and frictional force,and the containment eddy-current induced by proximity effect are considered.Through solving the current equation and kinematic equation by high order Runge-kutta method,several important parameters can be obtained.For verify the rationality and correctness of the theoretical model,the calculational results and experimental results were compared.Based on this model,the energy consumption distribution of EM railgun system was calculated.Results show that,the muzzle energy accounts for 30%of total energy,the rail consumption accounts for 44.7%of total energy,much higher than other energy consumption,and the eddy-current loss in containment is about 7.2%.The total resistance loss of pulse power source and coaxial cables are less than 10%.The energy consumption of EM rail gun with and without containment was compared.Researches show that,containment eddy-current makes the muzzle energy decrease 3.6%,makes the rail consumption increase 5.7%,and makes the PPS consumption increase 1%.c?The influence of containment eddy-current on the magnetic field outside the barrel.For measuring the magnetic field outside the barrel,a 3D B-dot was made in the experiment.Meanwhile,a line current model of series augmented electromagnetic railgun was built,whose containment was not considered.The calculational results were compared and verified by the experimental results.Results show that,the change law of three directions magnetic induction intensity is in good agreement,and the moment of armature moving to the probe location is the same basically.The 30%decline of magnetic induction of experimental result and calculation result is due to containment eddy-current,which can be verified through comparing with the calculational results by Maxwell.d?The containment was optimization analyzed from size and material in order to enhance the muzzle velocity.The containment eddy-current influence both inductance gradient and resistance gradient which can be calculated by the finite element method.Substituting the inductance gradient and resistance gradient into the EM railgun system theory model,the muzzle velocity can be obtained.Results show that,the farther the distance between containment and rails,the higher the inductance gradient,and the lower the resistance gradient,and the higher the muzzle velocity.For the impact extent of muzzle velocity by containment size,the thickness is the largest,and the longitudinal distance is the minimum.With the increase of containment conductivity,the inductance gradient decreases,and the resistance gradient increases rapidly first,then drops fast,finally decreases slowly,forming a peak.The muzzle velocity will be improved significantly if using minuscule conductivity or non-conductive containment.If using metal containment in order to ensure the stiffness,the containment conductivity should be more than 1×106S/m,to avoid the peak area of the resistance gradient.At this point,the muzzle velocity increases with containment conductivity.With the increase of containment relative permeability,the inductance gradient increases rapidly first,then remain unchanged basicly,and the resistance gradient also increases.If using non-conductive containment,the muzzle velocity will increase with the increase of relative permeability,but if using magnetic and conductive containment,the resistance gradient and inductance gradient will increase with the increase of relative permeability,and the muzzle velocity will decrease.