An experimental and kinetic modeling study on the ignition characteristics of ammonia/ethanol at high temperatures

The ignition delay times (IDTs) of ammonia/ethanol mixtures with ethanol fractions of 0%, 5%, 10%, and 30% were measured in a shock tube at equivalence ratios of 0.5, 1.0, and 2.0, temperatures of 1250-1980 K, and pressures of 0.14 and 1.0 MPa. A new ammonia/ethanol model (NH3-E) was proposed, and this model was able to predict the experimental results reliably. The chemical reaction kinetics were analyzed based on the proposed model. The experiments revealed that ethanol had a nonlinear and strong ignition-enhancing effect on the IDT of ammonia, e.g., the IDT of the ammonia/ethanol mixture was able to be shortened by more than 65% with the addition of 5% ethanol as compared to neat ammonia. The natural logarithm of the IDT (ln & tau;ign) of the ammonia/ ethanol mixtures and the reciprocal of the ignition temperature (1/T) satisfied the Arrhenius relationship at different stoichiometric ratios and pressures. The rapid consumption of ethanol in the early stages of combustion generated a large number of reactive free radicals, which was a key factor in promoting ammonia combustion. With increasing ethanol content, ethanol consumption became more important through H-abstraction reactions. By adding a higher percentage (30%) of ethanol, the concentration of CH3 in the free radical pool increased, and this CH3 was able to react with NH2 to generate a toxic species of cyanide.

Automated summary

In this study, the ignition delay times (IDTs) of ammonia/ethanol mixtures with different ethanol fractions were measured and analyzed. The results showed that ethanol had a nonlinear and strong ignition-enhancing effect on the IDT of ammonia. A new ammonia/ethanol model was proposed to predict the experimental results reliably.