抄録
Technologies that modify the combustion of the propellant components are crucial for developing novel high-energy propellants. Amide compounds function as fuels and also act as melting point depressants for ammonium dinitramide (ADN)-based energetic ionic liquids (EILs). A formulation comprising ADN, monomethylamine nitrate (MMAN), and urea in a 40/40/20 weight ratio (AMU442) has demonstrated potential as a hydrazine substitute. However, AMU442 faces limitations in terms of its ignitability and reactivity. In this study, the flame structure of acetamide (AA), which exhibits superior reactivity with ADN compared with urea in the liquid phase, was investigated. AA was combined with ADN/MMAN to function both as a fuel and melting point depressant. The influence of amide compounds on the combustion process was systematically explored. Burning rates and combustion temperatures of two mixtures with varying oxygen balances (ADN/MMAN/AA, denoted as AMA) were assessed using strand burners. The results indicated that AMA992 and AMA442 exhibited significantly higher burning rates at 68 mm･s -1 and 5.5 mm･s -1 , respectively, compared to 2.7 mm･s -1 for AMU442. The combustion temperature profiles revealed six stages: liquid phase, gas-liquid phase, 1 st flame region, two constant temperature plateaus (primary and secondary), and 2 nd flame region. Both AMU442 and AMA992 exhibited the secondary plateau during the 2 nd flame stage. The maximum flame temperature of AMA992 exceeded 1800°C, surpassing 1684°C of AMU442, while AMA442 reached a lower maximum of approximately 900°C. In AMA442, ADN and AA predominantly reacted in the liquid phase, and the primary plateau was attributed to the endothermic decomposition of MMAN. In AMA992, ADN decomposed in the gas phase and reacted with MMAN to generate a high-temperature flame. The liquid-phase reaction between ADN and AA contributed to a higher burning rate than that observed in AMU442. Furthermore, the heat released in the AMA992 flame enhanced the burn rate. These findings suggest that selecting a fuel that both lowers the melting point and reacts effectively with ADN in the liquid phase, such as AA, offers a promising approach to overcome the low reactivity limitations of AMU.
