Numerical Study On Interior Ballistics Of Partially Cut Multiperforation Stick Propellant In Large Caliber Gun

To improve the large caliber gun muzzle velocity,high energy and loading density propellant and progressive burning charge systems are employed.Compared with the conventional random packed grains charge,a partly cut multi-perforation stick propellant charge system has advantages in higher loading density,better flame-spreading and high progressive property.Meanwhile,the improper cutting parameters,such as the over long propellant may lead the overlarge internal perforation pressure and erosive burning phenomenon.The dissertation aims to provide theoretical guidelines for the partly cut multiperforation TEGDN propellant charge system and getting the proper cutting parameter,and contains following contents:a)To study the characteristics of erosive burning and gas flow in internal perforation of a tubular propellant,an interior ballistic model of a closed bomb is established considering the gas phase region inside the tube,gas phase region outside the tube and solid propellant region.The accuracy of the interior ballistic model and calculation method of the closed bomb are verified through comparing the numerical simulation results with the experimental data in the literature.On this basis,the effects of different length,internal diameter and loading density of propellant on the erosive burning of internal perforation are discussed respectivelyb)Tube propellant is good for both flame spreading and the high loading density,and the tube propellant interior ballistics model is established to study the erosive burning phenomenon.The tube propellant interior ballistics model consists of three regions: the internal perforation gas region,the external gas region behind the projectile and solid propellant region.The twodimensional axisymmetric flow field model considering the erosive burning is established for the internal perforation region,and the dynamic grid technique is used for the propellant back burning motion.According to the numerical simulations,the model shows the ability to describe the stick propellant combustion process,as well as to reveal the internal perforation field.Different factors with respect to the stick propellant,including propellant length,internal perforation diameter and loading density are analyzed in detail.Stick propellant length and the internal perforation diameter have a significant influence on the ballistic performance,longer or smaller internal propellant has a greater erosive burning effect to the ballistic performance.Loading density has very weak influence on the ballistic.c)Partially cut multi-perforated propellants are used in gun charges because of its good flame spreading,high progressivity and loading density.However,the specific internal perforation flow fields within the propellant appears to be impossible for experimental measurement,because the propellant combustion is uninterruptible and the small size of the propellant also increases the complexity of the experiments.To investigate the complex flow field in the partially cut multi-perforation stick propellant,a steady three-dimensional model for compressible viscid internal perforation and the vent gas region flow field is established and simulated by ANSYS Fluent,and the standard k-epsilon turbulence model is employed.The influences of different cutting parameters,such as cutting width,the same side cutting length,the reserve side cutting length and the perforation diameter,are analyzed in detail.d)The main ingredient of double base propellant are nitrocotton(NC)and nitroglycerin(NG).And the TEGDN propellant is one kind of double base propellant,in which the TEGDN is added.To investigate the combustion characteristics of the TEGDN propellant gas region,a gas combustion model based on global kinetics is established.The accuracy of the combustion model and calculation method are verified through comparing the numerical simulation results with the data in the literature.On this basic,the propellant combustion characters of different NG and TEGDN mass fraction and in different pressure are discussed,respectively.e)The one-dimensional multi-perforation grain propellant two-phase gun model considering the one-dimensional two-phase ignition tube is created,and the MacCormack scheme method is used to simulate the two-phase field.For the partly cut multi-perforation long stick propellant two phase model,the Euler and Lagrange methods are used to describe the gas and stick propellant motion,and the MacCormack scheme method is used.The gas and propellant grain velocity distributions,pressure wave,propellant bundle velocity and locations are studied,and comparisons of the interior ballistic performance in two kind charges are studied,which will give the guidelines for the use of the new propellant charge.