Numerical Simulation to Study the Effect of Oxygenated Fuels on the Combustion and Emission Characteristics of...

Oxygenated fuels, as a potential alternative energy source, are of great significance in promoting the sustainable transition of the energy structure. Through an in-depth analysis of the combustion characteristics of n-butanol and its derivatives, this study not only reveals the potential of these fuels in improving combustion efficiency and reducing pollutant emissions but also provides a scientific basis for promoting the sustainable development of clean energy. n-Butanol is a clean alternative fuel because of its good impermissibility with diesel, volatility, and oxygenation. In this paper, the effects of different blending ratios of n-butanol/diesel fuel on engine combustion and emission were investigated using chemical reaction kinetics combined with three-dimensional simulation, and the chemical mechanism of fuel oxygen in the combustion system on combustion and pollutant generation was revealed. The results show that the addition of n-butanol fuel has a significant effect on both combustion and emission. Since n-butanol has good volatility and low cetane number (CN), the ignition delay time (ID) is gradually prolonged with the increase in the n-butanol blending ratio. The mixture is more homogeneous, the proportion of premixed combustion increases, and the soot emission decreases, while the NO _x emission is not much different. From the chemical kinetics point of view, the ignition of the blended fuel is mainly triggered by the low-temperature active diesel component n-heptane. During the low-temperature reaction before ignition, the OH group produced by n-heptane is occupied by n-butanol, which inhibits the low-temperature dehydrogenation reaction of n-heptane itself. Thus, the ignition of the blended fuel is delayed. At the same time, the addition of n-butanol provided more OH, HO₂, and other oxidizing radicals for the combustion system, which enhanced the in-cylinder oxidation activity and promoted the oxidation of carbon smoke precursors and soot. Moreover, the O atoms in n-butanol combined with C to form a more stable CO, which reduced the amount of C atoms that could form carbon smoke precursors and led to a reduction in soot generation.