Research on ammonium dinitramide (ADN) ignition with two-phase subsurface reactions

A numerical calculation model with two-phase subsurface reactions was developed to study the physical and chemical processes involved in ADN ignition. The model is based on the conservation equations of mass, species concentration and energy for both condensed phase and gas phase, and takes into account finite-rate chemical kinetics and real thermophysical properties. At last, the equation of state for a multicomponent system was employed to close the equations. A chemical kinetics scheme, containing totally 35 species, 2 global ADN decomposition reaction in condensed phase and 166 detailed reactions in gas phase, was established and employed in the model. The ignition model was employed to predict ADN monopropellant ignition delay time at various initial temperatures at 0.1 MPa. The agreements between calculation results and experimental data are satisfying, which indicates that the model can predict ADN ignition process accurately. The calculation results show that ADN ignition delay time decreased rapidly with the increasing of initial temperature. And if the initial temperature exceeds 600 K, there will be a significant temperature decreasing within a short time. It also shows that the complete combustion products of ADN are H₂O(0.393), N₂(0.394), O₂(0193) and bit NO(0.009), which indicates that ADN is a 'green', environmental friendly and low signature propellant.