The spray ignition characteristics of ethanol blended with hydro-processed renewable diesel in a constant volume combustion chamber

In this study, the ignition characteristics of ethanol blended with hydro-processed renewable diesel (HRD) in a constant volume combustion chamber were conducted in both experiments and zero-dimensional (0-D) chemical kinetic simulations. The experimental results revealed that ignition delay (ID) increased with increasing ethanol concentration. The emissions of carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbon (HC) under lean and stoichiometric conditions were studied at a chamber pressure (P-chamb) of 7 bar. It was found that CO2 emissions reduced with increasing ethanol concentration. However, opposite trend was observed for NOx emissions. Since ethanol has a lower heating value than HRD fuel, the combustion temperature was reduced with the use of the HRD-ethanol blend, which subsequently resulted in lower NOx formation. The addition of ethanol also increased the oxygen concentration which aided in promoting further oxidization of CO to form CO2, thereby reducing the amount of CO produced. Besides, the effect of the addition of ethanol in HRD on HC emission was also observed whereby increasing its ratio increased the oxygen concentration in fuel which had the advantage of reducing HC emission. A kinetic model of 144 species and 600 reactions for the ethanol blended with HRD was also formulated. The kinetic model reasonably reproduced the measured ID periods at initial pressures of 10-20 bar, temperatures of 600-818 K and equivalence ratios of 0.13-0.354, despite quantitative disagreement with the experiment at the lower temperatures. Additionally, the measured trend where the ID periods elongated with respect to the increase in the ethanol concentration was replicated by the kinetic model.

Automated summary

This study investigated the ignition characteristics and emissions of ethanol blended with hydro-processed renewable diesel (HRD) through experiments and simulations. The results showed that increasing the ethanol concentration delayed ignition, reduced CO2 emissions but increased NOx emissions. The addition of ethanol lowered the combustion temperature, resulting in lower NOx formation, and increased oxygen concentration, aiding in the oxidation of CO to form CO2 and reducing CO emissions. The addition of ethanol also helped reduce hydrocarbon emissions. A kinetic model was developed and reasonably reproduced the experimental results, capturing the trend of elongated ignition delay with increasing ethanol concentration.