Influence of AP Particle Size on Burning Characteristics of HMX/AP Propellants Supplemented with Fe₂O₃

ABSTRACT Nitramine propellants have attracted considerable attention in the domain of solid rockets and gun propulsion because of their energetic and smokeless features. Ammonium perchlorate (AP) is the widely used oxidizer in propellants owing to the excellent burning characteristics. In this study, the burning rates of cyclotetramethylenetetranitramine (HMX)/AP propellant, prepared with varying mass ratios of AP to whole oxidizer ( ξ ) using Fe 2 O 3 as a catalyst, were investigated. Fine AP (FAP) and coarse AP (CAP) were used as the AP samples. The burning rates of HMX/FAP propellants were higher than those of HMX/CAP propellants. The burning rates increased with increasing ξ and with the Fe 2 O 3 addition. The burning characteristics of the HMX/AP propellant displayed unique dependencies on the AP particle size, ξ , and pressure. The maximum effect of Fe 2 O 3 on the increase in burning rate was obtained when ξ = 0.6 because the increase in the catalytic effect for the AP propellant due to the increase in ξ could not be entirely compensated for by the decrease in ξ for the HMX propellant. When ξ < 0.4, the propellant comprising Fe 2 O 3 displayed a non‐luminous flame below 1 MPa; the length of the non‐luminous flame decreased with increasing pressure and ξ and did not depend on the AP particle size. The flame of the HMX/AP propellants at low ξ would be described as a two‐stage flame comprising two reaction zones: the first‐stage reaction zone and the preparation zone. The combustion processes in the first‐stage reaction zone significantly affected the burning characteristics of HMX/AP propellants.