Laminar burning velocity of NH3 at elevated preheating temperatures and with N2 dilution: Measurements and evaluation of kinetic models

Ammonia is a promising hydrogen carrier and carbon-free fuel. In this work, new laminar burning velocity data of ammonia under intensified preheating (773K-848K) and N2 diluted condition is provided. Temperature coefficient that reflects the exponentially positive effect of preheating is reevaluated and compared with literature data at lower preheating temperatures, which is in the range of 2.08-2.30 with an improved accuracy. In contrast, dilution is of a linearly negative effect. The laminar burning velocity decreases by more than 20% as the O2 content drops from 21% to 19%. Besides, 11 recently published kinetic models are evaluated based on the experimental data. The Otomo18 model makes the best prediction with a small relative difference (<=+/- 5%). Accordingly, the effects of radiation heat loss and dilution are analyzed in detail. The former is found insignificant, and the latter is mainly attributed to the adiabatic flame temperature drop.