A Consistency Research On The Interior Ballistic Performance Parameters Of Ultrahigh Firing Rate Guns

Ultrahigh firing rate guns have the ability to launch a large number of projectiles within an extremely short period;and can form a high firing density of barrage with a concentrated impact point.The Ultrahigh firing rate gun has a significant influence on the development of the short-range defense system,which is required to maintain the functions of anti-attack and regional blockade in the army system.However,the development of ultrahigh firing rate gun has not been developed thoroughly and several technical problems with respect to both the numerical simulation and the practical engineering implementations need to be overcome,in particular,the interior ballistic performance parameters consistency technique in the Ultrahigh firing rate gun.In this work,the influences of the ammunition structure,the different firing order projectile's travel range,the firing frequency and the muzzle flow field,on the interior ballistic performance is studied deeply to provide a theoretical guidance for the development of the ultrahigh firing rate gun.The conclusions and methods are summarized as follows:a)The classical interior ballistic model of the ultrahigh firing rate gun with serial loaded ammunition is established,and the fourth-order Runge-Kutta algorithm is used in the numerical simulations.Based on the verified simulation results,the launch processes of three serials loaded ammunitions are calculated with different launch time intervals and different loading conditions.The influence of launch time interval and loading condition on the interior ballistic performance is obtained;and the interior ballistic performance parameters consistency results of the ultrahigh firing rate gun with serial loaded ammunitions are obtained simply and conveniently via the combination of the interior ballistic calculation code and quantitative correction formulation.b)The classical interior ballistic model of the ultrahigh firing rate gun with whole mounted ammunition is established;and the fourth-order Runge-Kutta algorithm is used in the numerical simulations.Three serials whole mounted ammunitions' launch processes are calculated with different launch time intervals and different loading conditions.The influences of launch time interval and the loading conditions on the interior ballistic performance are obtained.The interior ballistic performance parameters consistency results are obtained simply and conveniently via the similar approach as that used in the traditional mounted systems,which is combining with calculation code and quantitative correction formulation.However,the whole mounted ammunition is not a well-designed ammunition system since its special structure reduces the work efficiency of propellant gas and wastes the propellant energy.c)According to the advantages of the existing projectile positioning structures,the projectile self-locking positioning structure is chosen to enhance the positioning performance in the ultrahigh firing rate gun systems.Based on the static finite element analysis,the feasibility of the selected structure is verified and the influences of the maximum friction coefficients and the structure geometry parameters on the positioning performance are obtained.The size of the ammunition structure is determined to provide reasonable computing initial conditions for the two-phase flow numerical simulations of the ultrahigh firing rate gun.In such way,the difficulties of the numerical modeling and simulations with respect to the two-phase flow are simplified.d)To investigate the specific influence of the propellant gas movement in the launch processes involved with the motions of two projectiles in the body tube at the same time,the two-phase flow interior ballistic model is established and the MacCormark difference scheme is used to undertake the numerical simulations.Based on the verified simulation results,the launch process of three serials loaded ammunitions are used as the illustrations with different launch time intervals and different loading conditions.The influences of the launch time intervals and the loading conditions on the interior ballistic performance are obtained.The main reason for the large difference of the numerical results between two interior ballistic models is that the gas pressure in front of projectile are quite different.When the firing time interval is large,the interior ballistic performance parameters consistency results are obtained simply and conveniently by the combination of with two-phase flow interior ballistic calculation code and quantitative correction formulation;when the firing time interval is small,though the velocity consistency results can be obtained,the pressure is not consistent.Because of the difference of the projectile head pressure,the results of the two models are different;the two-phase flow model has better accuracy in the sense of capturing the physics.e)To investigate the influence of the muzzle flow field on velocity consistency,considering the initial flow field and coupling the classical interior ballistic model,the muzzle flow field computational fluid dynamics model is established via the consideration of the initial flow field and the combination with the classical interior ballistic model.The finite volume method is used to carry on the flow field marching of the serial loaded ammunition,in particular,two projectiles are considered in this case;and it can be observed that the projectile velocity increment is strongly affected by the muzzle pressure which can be treated as the basis of the projectile velocity increment.Via adjusting the muzzle pressure,the inconsistency of the projectile velocity can be corrected to be a consistent value accordingly in the interior ballistic design of the ultrahigh firing rate gun system.Meanwhile,coupling with the accurate projectile head pressure,the classical interior ballistic model can obtain similar interior ballistic performance parameters as that of the two-phase flow interior ballistic model.The evolution of the muzzle flow field of the ultrahigh firing rate gun is different from that of the traditional gun.With shortening of the launch time interval,the influence of muzzle flow field on projectile head pressure increases gradually,the variation range of the projectile head pressure curve increases.However,setting the projectile head pressure to zero rarely has effect on the interior ballistic calculation results,after the second and its subsequent projectiles leave the muzzle.