Study On The Dynamics Method Of Two-phase Flow Interior Ballistic Accompanying With Propellant Grains Fracture

High muzzle velocity is one of the main features of modern artillery.Generally,the muzzle velocity of projectiles is improved by increasing the loading density and using high energy propellants.Therefore,the loading conditions in the gun bore are becoming more and more complex,the mechanical environment in the chamber is getting worse and worse,and the problem of launch safety is tending to more and more serious.The interior ballistic two-phase flow dynamics theory is a powerful tool for modem interior ballistics calculation.However,when solving the problem of launch safety of propellant depending on the degree of fragmentation of the propellant charge,this theory cannot study and describe the "fracture" of the grain and propellant bed,because of the innate defects of the assumption of "continuous medium".The fracture of propellant charge is an unavoidable "discrete,mechanical phenomenon in the research of launch safety.So the interior ballistic two-phase flow dynamics theory is unable to settle such problem.This paper is a part of the main achievement of China,s national defense innovation plan—fire and explosive special.The process of the force,fracture and the abnormal change of pressure of the propellant during the ignition proeess is described in this paper from theory,ealculation and test.The dynamie method of interior ballistic two-phase flow with the fracture of the propellant is established,which provides theoretical and technical support for the quantitative evaluation of the launch safety of the propellant charge.The major innovations are as follows:(1)Based on discrete element method,a dynamic simulation system of crush and fracture of propellant was established.Therefore,the dynamic calculation of crush and fracture of bulk particles was realized.Through dynamic mechanical properties test,the mechanical properties of the propellant in the neechanical environment in the chamber were obtained.The dynamics tests of the crush and fracture of propellant were carried out,and simulation results had been verified by experiments.The relationship between the extrusion stress and the fracture degree of the propellant charge were determined.(2)The influences of the law of the crush and fracture of the propellant were analyzed,including:the temperature of the propellant,the diameter of the propellant bed and the random accumulation of the grains.The test parameters of the crush and fracture of the propellant were optimized,and the rationality of the dynamic crush and fracture test was proved.(3)The expression of the equivalent shape function of the fractured propellant was derived,and the dynamic simulation method of interior ballistic two-phase flow considering the fracture of propellant charge was established.The relationship between the fracture degree and the maximum bore pressure of a tank gun was determined.(4)The dynamic calculation method of interior ballistic two-phase flow accompanied with the crash and fracture of the propellant was established.The interior ballistic process of a tank gun with the crush and fracture of the propellant was simulated at low temperature,and verified by the tests.The interior ballistic process of breech-blow was simulated successfully by changing the ignition structure of the center igniter.