An experimental and kinetic modeling study on the auto-ignition of ammonia/butan-1-ol mixtures

Ignition delay times (IDTs) of ammonia(NH3)/butan-1-ol mixtures with NH3/butan-1-ol mole ratios of 100/0, 95/5, 90/10 and 70/30 were measured behind reflected shock waves in a shock tube over a range of experimental conditions: temperature range of 1100 - 2000 K, pressures of 0.14 and 0.5 MPa, equivalence ratios of 0.5, 1.0 and 2.0. A new NH3/butan-1-ol reaction mechanism, capable of predicting the experimental results reliably, was developed. Chemical kinetic analyses were performed with the model. It is demonstrated that increasing the content of butan-1-ol in the reaction system results in a non-linear trend of shortening on the IDTs of mixtures, adding 5 % molar fraction of butan-1-ol results in shortening rates of over 70 %. As the butan-1-ol blending ratio increases from 5 % to 30 %, the discrepancy in IDT of the mixture between equivalence ratios of 0.5 and 1.0 diminishes while it remains more pronounced between equivalence ratios of 1.0 and 2.0. The presence of butan-1-ol does not change the oxidation pathways of the NH3 mixture. R72(NH3 + M = NH2 + H + M) and R75(NH2 + HO2 = NH3 + O-2) are key reactions to activate chain reactions of the NH3 mixture during the initial reaction stage, for a temperature of 1500 K, a pressure of 0.14 MPa, and an equivalence ratio of 1.0. Reactive radicals produced through the process of butan-1-ol oxidation result in a significant increase in the initial dehydrogenation consumption rate of NH3, by a factor of 5 similar to 6 powers of ten, accelerating chain reactions.