Laser Absorption Measurement of Key Species During Ammonia Oxidation in a Shock Tube

Current ammonia chemical kinetics models require improvements prior to the integration of ammonia into aeronautical and aerospace applications. Current chemical speciation data are limited to stable species such as NH3, N2O, and H2O. Even with the current literature available, models show continued deficiencies in satisfactorily modeling stable and intermediate species. Therefore, a tunable diode laser diagnostic has been implemented at Texas A&M University to measure NH2 concentrations for ammonia model calibration. The tunable laser diode for NH2 was centered at 597.375 nm and was paired with a 10.44-µm quantum cascade laser diagnostic to verify initial ammonia concentrations. Both systems were used to measure ammonia oxidation at fuel-lean conditions at 1915 and 2256 K. This paper presents the latest NH2 experimental results and comparisons between the species time histories and recent ammonia chemical kinetics models. Lastly, NH2 + HO2 ⇄ NH3 + O2 was identified as a key reaction in ammonia oxidation.