Simulation of the Loading Density for Gun Propellants with Arbitrary Shapes Using a Discrete Element Method

The determination of the loading density that can be achieved for a certain propellant geometry is a key factor that determines the energy content and hence the performance of propellants in a gun system. Additive manufacturing on the other hand gives charge designers a new freedom in choosing propellant geometries. Therefore, it is important to have a method that can determine the loading density achievable for a given grain geometry without actually manufacturing each possible solution in sufficient quantities for an experimental determination. For this reason, a discrete element method was adapted, and a simulation was setup with the open source 3D computer graphic software Blender and its bullet physics engine, that enables the charge designer to simulate a propellant bed for arbitrary grain and shell geometries. The method is validated by simulating the loading density of real JA2 double base propellant grains (7 perforated cylinder) and comparing it with experimental measurements. It is shown that a good agreement between the simulated and experimental loading densities can be achieved by our method. Afterwards the dependence of the loading density on the length to diameter ratio for cylindrical gun propellants was investigated with the method. It is shown how the loading density decreases with increasing L/D ratio.