Laminar flame speed of ethanol/ammonia blends–An experimental and kinetic study

Abstract

Blending bio-ethanol with ammonia is an interesting approach to reach carbon-neutrally combustion systems. As a fundamental parameter, laminar flame speed for different blends of ethanol/ammonia is explored using the spherical expanding flame technique under constant pressure conditions. A comparison to the few recent literature experimental results is proposed. An empirical correlation is developed to estimate the laminar flame speed of any ammonia/ethanol mixture as a function of the equivalence ratio at 1 bar and 423 K. Some simulation results are also provided to compare kinetics mechanisms accuracy to experimental data and identify the most relevant sensitive reactions. Two mechanisms are compared, one from the literature and another from the fusion of two mechanisms originally developed for pure ethanol and pure ammonia respectively. One major conclusion is that none of these mechanisms allows sufficient agreement with experimental data and more in-depth studies are still needed to provide high accurate kinetics mechanisms for ethanol/ammonia mixture. Sensitivity analysis highlights an important difference between the sensitive reactions with pure ammonia and ethanol blends. The key role of carbon reactions HCO(+M)<=>H+CO(+M) and CO+OH<=>CO₂+H on the laminar flame speed is shown for blends containing more than 50% of ethanol.