Numerical Investigation on the Effect of Ammonium Perchlorate Content and Position on the Combustion Characteristics of an Ammonium Perchlorate/Hydroxyl-Terminated Polybutadiene Propellant

A gas–solid-coupled sandwich combustion model was established for ammonium perchlorate (AP)/hydroxyl-terminated polybutadiene (HTPB) composite propellant. Numerical simulations were conducted to investigate the influence of the content of AP and the relative position of the coarse AP on the flame structure and the burning rate of the propellant. The results indicated that the overall AP mass fraction has a significant effect on the gas-phase flame temperature and burning rate, and there exists an optimal oxygen-to-fuel ratio that maximizes the burning rate. As the mass fraction of fine AP increased, the premixed flame above the binder matrix gradually took over the dominance of the diffusion flame, and the intensity of the diffusion flame near the interface of coarse AP and binder matrix also increased, resulting in a significant increase in the burning rate. As the mass fraction of fine AP increases from 0% to 70.0%, the average surface temperature increases from 937 K to 1026 K, and the burning rate rises from 0.9 cm/s to 2.7 cm/s. The location of the coarse AP causes the flame tilts to the side with less binder matrix, but it had little effect on the burn rate of the propellant.