An optical study on spray and combustion characteristics of ethanol/ hydrogenated catalytic biodiesel blends in a constant volume combustion chamber

Ethanol fuel holds significant potential for emissions reduction, but its poor ignition capability poses challenges in achieving stable compression ignition within internal combustion engines. To enhance the ignition properties of ethanol fuel, this study blended with another highly reactive and renewable fuel, hydrogenated catalytic biodiesel, conducted an investigation on spray and combustion characteristics of two different blending ratios of ethanol/hydrogenated catalytic biodiesel/n-octanol (co-solvent) blends in a constant volume combustion chamber. The results show that the influence mechanism of cetane number and latent heat of evaporation on ignition delay varies depending on ambient temperature and oxygen concentration. At low temperatures and low oxygen conditions, E15 has a longer ignition delay than D100 due to its higher latent heat of evaporation. However, its larger cetane number makes its ignition delay less than D100 under high temperature and high oxygen conditions. When the ambient temperature exceeds 825 K and the oxygen concentration is 21 %, E15 has better ignition and combustion characteristics compared to diesel on ignition delay and lift-off length, whereas E30 exhibits inferior performance under various conditions. To further explore the quantitative effects of ambient variables on the ignition of E15, when the ambient temperature increases from 750 K to 900 K, the ignition delay decreases by 81.5 %. When the oxygen concentration increases from 15 % to 21 %, the ignition delay decreases by 50.6 %. Therefore, the research findings demonstrate the better potential of E15 under high temperature and high oxygen conditions, offering theoretical guidance for the practical engineering application of ethanol fuel.