Experimental Investigation on the Evaporation and Combustion Processes of Ammonium-Dinitramide-Based Liquid Propellant

In this work, the evaporation and combustion processes of liquid propellant ammonium dinitramide–methanol aqueous solution were investigated by a thermogravimetric analyzer and a Curie-point pyrolysis unit, respectively, and the gas-phase products were measured by a Fourier transform infrared spectroscopy. The results showed that methanol and water evaporated first, followed by the decomposition of ammonium dinitramide at heating rates of 5–15°C/min. When a catalyst was added, ammonium dinitramide decomposed much faster and released heat that let methanol evaporate immediately as the propellant solution was in contact with the catalyst particles. To explore how the decomposition of ammonium dinitramide is coupled with the oxidation of methanol, the propellant solution was heated by a Curie-point pyrolysis unit at a rate of 3000°C/s to temperatures ranging from 160 to 670°C. Large amounts of nitrous oxide and ammonia were detected at all temperatures, suggesting that most of the decomposition of ammonium dinitramide occurred at the condensed phase. Finally, a detailed gas-phase ammonium dinitramide–methanol reaction model was built to analyze the coupling between the decomposition of ammonium dinitramide and the oxidation of methanol.