Modeling and Simulation of Multi‐Material and Complex‐Shaped Gun Propellant Combustion in Closed Vessels

The geometric shape and material structure of gun propellant grains control the pressure evolution during combustion and, consequently, the performance of the ammunition. Due to the large number of degrees of freedom, additive manufacturing offers novel opportunities for grain shape and structure design. However, this new freedom necessitates the development of new algorithms for modeling and simulation of surface regression. In traditional combustion models, it is assumed that the propellant′s burn rate is a global quantity on its surface, which enables separate simulation of the surface regression and pressure evolution. To exploit the full potential of additive manufacturing and optimize designs for different applications, it is necessary to simulate grain structures with locally different burn rates on the surface. This work presents a model to simulate quantitatively the combustion of multi‐material and complex‐shaped solid propellant grains in a closed vessel for the first time. A lumped parameter pressure model is coupled with a surface regression simulation based on the level set method. The model is validated by comparison to analytical surface regression. Then, for the first time, a combustion simulation of a multi‐material ball propellant grain consisting of two hemispheres in a closed vessel is presented. Compared to a combustion simulation using global and weighted mean burn rate values, the pressure and vivacity curve shows significant differences. This demonstrates impressively that for predicting the performance potential of multi‐material and complex‐shaped solid gun propellant grains, a quantitative and accurate combustion simulation is indispensable.