A comprehensive CFD study of the spray combustion, soot formation and emissions of ternary mixtures of diesel, biodiesel and gasoline under compression ignition engine-relevant conditions

In this research, the spray combustion, soot formation and exhaust emissions of diesel, biodiesel, gasoline fuels and their mixtures are analysed in a constant volume chamber. A multicomponent kinetic mechanism (CDBG) suitable for diesel-biodiesel-gasoline mixtures developed by our research group is utilised, and the associated physicochemical properties are thoroughly calculated. Adaptive mesh refinement scheme with appropriate mesh independency analysis are applied. Liquid penetration length, lift-off length, ignition delay and soot formation have been benchmarked against experimental data in the literature. A hybrid RANS-LES model, known as DES model, is used to simulate the turbulent condition. The effects of different ambient temperature/oxygen levels on the flame structure, soot formation and emissions of different ternary mixtures of D75 vertical bar BD20 vertical bar G5, D70 vertical bar BD20 vertical bar G10 and D65 vertical bar BD20 vertical bar G15 were analysed. D65 vertical bar BD20 vertical bar G15 resulted in a lower soot mass yield than that of BD100 (pure biodiesel) and D100 (pure diesel) for about 35% and 27%, respectively, at T = 900 K vertical bar O-2 = 15%. Greater soot mass reductions for the tested fuels were captured by the decrease in ambient temperature from 900 K to 800 K by a factor of similar to 1/3 (same ambient O-2 concentration). Lower nitrogen oxides (NOx) emissions were obtained for D100 by factors of similar to 1/2 at T = 900 K vertical bar O-2 = 15% compared to BD100. Gasoline-added mixtures revealed lower NOx compared to BD100 (similar to 20%) yet still higher than D100. Lower carbon dioxide (CO2) and carbon monoxide (CO) emissions were captured for D65 vertical bar BD20 vertical bar G15 compared to BD100 and D100.

Automated summary

This research analyzes the combustion, soot formation, and exhaust emissions of diesel, biodiesel, gasoline fuels, and their mixtures in a constant volume chamber. The study focuses on the effects of different ambient temperature and oxygen levels on flame structure and emissions. The results show that the mixture D65 | BD20 | G15 has lower soot formation and nitrogen oxide emissions. Lowering the ambient temperature and increasing the oxygen concentration further reduce the emissions.