Measurement of oxy-ammonia laminar burning velocity at normal and elevated temperatures

Ammonia is considered as a carbon-free alternative fuel and hydrogen carrier to realize green and renewable energy conversion, but the oxidation mechanism of NH3 still needs to be improved and validated by more experimental data. In this study, the laminar burning velocity (LBV) was measured in a constant volume vessel at various equivalence ratios, initial temperatures, and oxygen fractions up to undiluted condition. Thirteen latest NH3 kinetics mechanisms were collected and compared with each other and the experiments. Results showed that large discrepancies of predictions presented between different mechanisms. The maximum LBV of undiluted NH3/O-2 mixtures could reach 125.05 cm/s. The maximum predicted LBV of NH3/O-2 is nearly two times higher than the minimum one for NH3/O-2 mixtures. The reduced Okafor (2019) and Zhang (2017) mechanism gave the best agreement with experiments for lean and rich mixtures, respectively. Sensitivity analysis of rate constant, species thermal, and transport parameters were adopted to identify the critical reactions and species in the premixed flame. It was found that because of the coupled nature of the properties mentioned above in the premixed flame, the species involved in the essential reactions also exhibit substantial thermal and transport sensitivities.