Multispecies combustion diagnostics using tunable diode laser absorption spectroscopy

摘要

Multi-species measurements of N_2O, CO, NO within an ammonium dinitramide (AND) based thruster arepresented using quantum cascade lasers ， while gas temperature are obtained using near-infrared H_2O two-linethermometry. AND monopropellant represents a new generation of green propellant for spacecraft propulsion.Measurements using the developed mid-infrared diagnostic system provide an access to characterize the combustionprocess inside the AND based thruster, while theoretical study of AND monopropellant combustion is still under study.Both steady-state firing and pulse-mode firing for AND based thruster operation are measured in the present experiments.Results of multispecies concentration agree well with the mechanism of the combustion process and divide the wholeprocess into decomposition stage and combustion stage. Reaction (R1,NH_4N(NO_2 )_2→NH_3+N_2O+HNO_3 ) is theprimary reaction branch as N_2O generation is much higher and faster than NO generation in decomposition stage at themeasured position. To the author's knowledge, this work represents the first multispecies simultaneous measurements inan actual AND based thruster using mid-infrared laser absorption spectroscopy. The time-resolved multispecies resultsaid in an improved understanding of the AND monopropellant combustion and demonstrate mid infrared diagnostictechnique's practicality for small-sized AND based thruster.