Modeling transient combustion and regression behavior of NEPE propellant based on random particle packing

A sophisticated numerical framework has been proposed as a powerful tool to comprehend the thermal behavior of NEPE propellant during rapid pressure decay. This framework consists of two crucial components: a 2D propellant pack generation module based on the sequential algorithm and a refined combustion model code. To track the regression of the propellant surface, we employ a straightforward single-value equation of the Hamilton-Jacobi type. This equation enables us to model the movement and evolution of the propellant surface as it undergoes combustion. To validate the credibility of the simulations, comparisons between the simulated burning rate and predicted average surface temperature are made with experimental studies. Encouragingly, reasonable agreement has been achieved between the numerical predictions and experimental data, further affirming the reliability and effectiveness of the proposed numerical framework. Simulation results suggest that the flame structure transforms from a complex diffusion flame in the initial stage of this transient burning to a premixed flame with a heat core altering with time in the final stage of fast depressurization. The surface cores of coarse AP and HMX particles regress most slowly, while the interface between AP and HMX powders moves most fast. Regarding the regression of the propellant surface, it is observed that the surface core of coarse AP and HMX particles exhibits a slower regression rate, while the interface between AP and HMX powders experiences a faster movement. This discrepancy in regression rates underscores the heterogeneity of NEPE propellant combustion, where different components contribute differently to the overall regression process. Furthermore, the entire surface morphology undergoes significant changes during rapid depressurization and combustion in the atmospheric environment. This suggests that pressure changes alone are not the sole factors influencing the shape of the propellant surface. The presence of oxidizing particles within the propellant pack emerges as an important factor that influences the regression mechanism of the propellant surface. This investigation provides valuable insights into the dynamic behavior of NEPE propellant, shedding light on the underlying physical phenomena at play.