| Electromagnetic railgun is developed into a new type of weapon launcher by using the characteristics of force effect of electric conductor in magnetic field.It can push the projectile to high speed or ultra-high speed in a short distance and break the launch speed limit for traditional artillery.It is called ’ one of the five weapons that can change the future war ’and became an object of research in the world because it has the advantages of high initial speed,large distance and good concealment.The rail and armature constitute a closed circuit,and the armature slides along the rail at high speed during the launching process of electromagnetic railgun.The rail was vibrated and deformed by time-varying load during the launch,which affects the firing accuracy and reliability of the electromagnetic railgun.Using the same excitation current intensity,the higher the emission energy conversion efficiency,the greater the armature outlet speed and the farther the shooting distance.Therefore,it is of great significance to carry out the research on the vibration characteristics of the rail of the electromagnetic railgun and the analysis of the emission energy conversion efficiency.The main contents of this paper are as follows:(1)The force of armature and rail of electromagnetic railgun is analyzed theoretically and the calculation formula of the force is deduced.The armature motion equation is established under considering sliding friction,and the motion law of the armature in the launching process is obtained.(2)The inductance gradient of electromagnetic railgun is simulated by Maxwell software.The variation trend of inductance gradient with different rail width,rail height,rail spacing,excitation current frequency and rail material is analyzed.Compared with the existing theoretical calculation formula,the main influencing factor of inductance gradient is the geometric parameters of rail,which is negatively correlated with rail width and rail height,and positively correlated with rail spacing.(3)According to the theory of elastic foundation beam,the rail in the electromagnetic railgun is simplified as Euler-Bernoulli beam under various time-varying loads.The vibration differential equation of rail is established and solved.The critical velocity of rail vibration is calculated and the influence of basic elastic coefficient,rail width and rail height on the vibration characteristics of rail is analyzed.The results show that the maximum deflection of the rail is effectively reduced when the large basic elastic coefficient,rail width and height,and the small excitation current parameter.(4)The calculation formula of emission energy conversion efficiency under pulse current mode(zero outlet current mode)is derived by the theory of emission energy conversion efficiency of electromagnetic railgun under constant inductance gradient.The influence of the size of the rail and the material of the rail on the emission energy conversion efficiency is analyzed.The results show that the emission energy conversion efficiency reaches the maximum when the armature runs to the maximum speed(i.e.,the outlet speed),and with the decrease of the rail width,the rail height and the increase of the rail spacing,the emission energy conversion efficiency increases. |
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