Auto-ignition of a carbon-free aqueous ammonia/ammonium nitrate monofuel: A thermal and barometric analysis

A carbon-free aqueous solution of ammonium hydroxide and ammonium nitrate (AAN) was studied using differential thermal and barometric analyses under initial N2 pressure of up to 4.6 MPa. The suggested nitrogen-based monofuel exhibited three distinct exothermic processes during heating. Their onset temperatures increased as the initial nitrogen pressure was raised. In addition, a higher extent of reaction was observed at high nitrogen pressures. This result was attributed to the effect of mass diffusion in the system, which decreased at higher pressures. Using a modified mechanism for the combustion of nitrogen-based fuels, the thermal ignition process was simulated. The resulting auto-ignition temperature values were shown to be in good agreement with experiments at initial nitrogen pressures of up to 2.3 MPa. Above this pressure, the agreement between experimental and model results was hampered by mass diffusion effects. Using the modified mechanism, the main chemical pathways prior to auto-ignition of AAN were identified and the reactions leading to ignition were discussed. This paper presents for the first time the auto-ignition of AAN and explores the combustion chemistry of this carbon-free monofuel.