| HAN-based liquid propellants have been pursued as liquid gun and rocket propellants for many years due to low environmental impact and high density. To realize these advantages, however, several crucial operational problems must be solved including combustion instability, material incompatibility, and reliable ignition at low pressure. Therefore, extensive studies are being undertaken to characterize the ignition and combustion behavior of the propellants. The objectives of this study are to identify the gas-phase decomposition products of a HAN-based liquid propellant, XM46, as well as its ingredients, which are formed from rapid condensed-phase reactions, and to determine the reaction rates of a reduced reaction model for HAN by applying an inverse-based fitting technique.; Measurements were made by FTIR spectroscopy in order to determine the thermal decomposition of hydroxylammonium nitrate (HAN), triethanolammonium nitrate (TEAN), as well as XM46, a propellant composed of HAN, TEAN, and water, at atmospheric pressure in a nitrogen environment. The major detected decomposition species of HAN were H2O, N2O, NO, NO2, and HNO3. Solid TEAN produced the IR-active decomposition species, H2O, NO, CO2, CO, N2O, and NO2. In XM46 decomposition, a sequential decomposition of HAN and TEAN was revealed. Evaporation of H2O was followed by HAN dominated decomposition, producing N2O, NO, and HNO3. In the later stage, TEAN reactions became dominant to form CO2 and additional NO.; A numerical analysis was conducted to deduce the Arrhenius-type reaction rates of the reduced reaction model for HAN. The reaction rates were obtained by an inverse-based analysis in a way that minimized an objective function, which consisted of the difference between the calculated concentrations from the numerical model and the experimental data as well as the uncertainties in the experimental data. With the best-fit rate constants of the reaction model, the species evolution profiles of 13M HAN were reasonably recovered. The reaction model was applied to the simulation of the species evolutions for solid HAN and HAN-water solutions including 10.7 and 9M. The simulated gas-phase concentrations coincided well with the experimental data, indicating that the proposed global reaction mechanism captured most of the key reactions of HAN. |
