Optimization Of The Structure And Internal Ballistic Performance Of Spherical Flat Shape Variable Burning Rate Propellant

In order to improve the initial velocity of the projectile without increasing the maximum bore pressure of the gun,and thus improve the power of the gun,the combustion law and internal ballistic performance of the spherical flat variable burning rate propellant are studied.Firstly,the structural characteristics of the spherical flat variable burning rate propellant are introduced,and its combustion process is divided into three stages.The first stage is the co-combustion of the outer and inner retarding layers,which ends when the inner retarding layer burns out;The second stage is the co-combustion of the outer remaining slow burning layer and the middle fast burning layer.When the outer remaining slow burning layer burns out,this stage ends;The third stage is the combustion of the remaining rapid-burning layer,which is the combustion of a single rapid-burning propellant.Then,the relationship between the relative combustion percentage/relative combustion surface area and the burning thickness of propellant is deduced through the change law of propellant volume and surface area,and the combustion model is established.Based on Matlab software,the combustion model of propellant under the influence of different burning rate ratio of slow burning layer to fast burning layer,ratio of height to semi-major axis,ratio of height to semi-minor axis and ratio of semi-major axis to semi-minor axis is simulated and calculated,and the influence of various factors on the combustion law of propellant is analyzed.Then,according to the internal ballistic characteristics of the mortar and the shape and structure of the variable burning rate spherical flat propellant,the mortar internal ballistic model is established,and the fourth order Runge-Kutta algorithm is selected to solve the internal ballistic equations.Based on Matlab software,the internal ballistic process of the mortar under the influence of different burning rate ratio of the retarding layer,the shape and size of the propellant,the force of the retarding layer,the force of the retarding layer,the clearance area,and the charge quantity is simulated and calculated,and the optimal result is selected,It is also compared with conventional disc propellant.It is concluded from the analysis that the spherical flat variable burning rate propellant has the characteristics of increasing combustion,and it performs better with the increase of the slow burning rate ratio,the ratio of high to half axle and the size of the inner half axle;The internal ballistic performance of mortar is good,with obvious pressure platform;With the increase of the burning rate ratio,the pressure platform period becomes longer,the maximum bore pressure and the initial velocity of the projectile also increase;With the increase of the ratio of height to half axis and the ratio of length to half axis,the combustion reduction of the propellant becomes weaker,thus increasing the maximum bore pressure of the interior ballistics and the muzzle velocity of the projectile;On the premise of ensuring safety and the projectile can slide down and launch smoothly,improving the propellant force,charge quantity or reducing the clearance area of the slow burning layer and the fast burning layer can improve the interior ballistic performance of the mortar;When the outer half major axis of the spherical flat variable burning rate propellant is 2.8 mm,the inner half major axis is 1.1mm,the ratio of the high half major axis is 4,the ratio of the long half major axis to the short half major axis is 1.5,the retarding layer propellant force is 980 k J/kg,1210 k J/kg,the charge weight is 0.5 kg,and the clearance area is 0.02 dm2,compared with the conventional disc propellant,it has a relatively obvious pressure plateau period,and can improve the initial velocity of the projectile without increasing the maximum bore pressure.