Study On Interior Ballistics Performances Of Variable-Burning Rate Propellant For Mortar

In order to enable the variable-burning rate propellant to be applied to related weapons,the geometric combustion model of the variable-burning propellant was established,and the characteristics of the combustion process were analyzed,and the shape function in the combustion process was deduced.Based on the classical internal ballistic theory,the program of internal ballistic is compiled,and the internal ballistic performance of the variable-burning rate propellant in mortars was studied.Providing a theoretical guidance for the application of the variable-burning rate propellant.According to the special structure and combustion characteristics of the variable-burning rate propellant,and based on the geometrical combustion law,the combustion process of the variable-burning rate propellant is divided into two stages:the first stage is the simultaneous combustion process of the inner layer of fast-burning layer and the outer layer of slow-burning layer.Since the slow-burning layer is thin,when the slow-burning layer is burned out,the first phase ended.The second stage is the separate combustion process of the remaining fast-burning layer,similar to the combustion of the traditional tubular propellant,the remaining slow-burning layer is burned out,the second combustion stage is over,and the burning of tubular variable-burning rate propellant is completed.Through the analysis and calculation of the internal ballistic calculation results of the variable-burning rate propellant for mortar,the results show that:(1)The variable-burning rate propellant showed good combustion graduality.By adjusting the content ratio of fast-burning layer and slow-burning layer,the length to diameter ratio,and the inner diameter,thecombustion gradation can be further improved by controlling the burning surface.(2)The internal ballistic simulation curve p-t of the variable-burning propellant in the mortar showed a relatively obvious pressure platform effect,indicating that the variable-burning rate propellant showed combustion advantage in the mortar.(3)Properly increasing the propellant force constant of the slow-burning layer and the fast-burning layer of the variable-burning rate propellant can increase the energy of the propellant and improve the initial velocity of the projectile.(4)With the increase of the slow-burning layer ratio,the maximum gun pressure and the initial velocity of the projectile are correspondingly increased.(5)In the case of maintaining the same coefficient of other propellant types,the arc thickness of the slow-burning layer is set as 0.15 mm,which can better express the advantages of the burning progressively of the variable-burning rate propellant.(6)With the increase of the diameter of bore,the maximum pressure inside the crucible changes little,and the initial velocity of the projectile is continuously increased accordingly.Considering the condition that the inner diameter of the variable burning rate propellant is 1.0 mm,the condition of not increasing the maximum internal pressure can be achieved.Under,effectively improve the initial kinetic energy of the projectile.(7)When the length-to-diameter is greater than 2.5,the length-to-diameter has a small beneficial effect on the initial velocity of the projectile and the maximum internal pressure of the burning,but the packing density of the propellant is limited;considering of combustion performance and internal ballistic performance,the length-to-diameter is selected between 2.0~2.5.