Abstract
In this study, the combustion and emission characteristics of a diesel/methanol/n-butanol blended fuel engine with different pre-injection timings and pre-injection mass ratios were investigated by a computational fluid dynamics (CFD) model. The CFD model was verified by the measured results and coupled with a simplified chemical kinetics mechanism. Firstly, the corresponding three-dimensional CFD model was established by CONVERGE software and the CHEKMIN program, and a chemical kinetic mechanism containing 359 reactions and 77 species was developed. Secondly, the combustion and emission characteristics of the diesel engine with different diesel/methanol/n-butanol blended fuels were analyzed and discussed. The results showed that increases in the pre-injection timing and the pre-injection mass ratio could increase cylinder pressure and cylinder temperature and decrease soot, HC, and CO emissions. At 100% load, the maximum cylinder pressures at the start of pre-injection timing from −15 °CA to −45 °CA, were 7.71, 9.46, 9.85, 9.912, and 9.95 MPa, respectively. The maximum cylinder pressures at pre-injection fuel mass ratios from 0.1 to 0.9 were 7.98, 9.10, 9.96, 10.52, and 11.16 MPa, respectively. At 50% load, with increases of the pre-injection timing and pre-injection fuel mass ratio, the soot emission decreased by 7.30%, 9.45%, 27.70%, 66.80%, 81.80% and 11.30%, 20.03%, 71.32%, 83.80%, 93.76%, respectively, and CO emissions were reduced by 5.77%, 12.31%, 22.73%, 53.59%, 63.22% and 8.29%, 43.97%, 53.59%, 58.86%, 61.18%, respectively. However, with increases of the pre-injection timing and pre-injection mass ratio, NOx emission increased. In addition, it was found that the optimal pre-injection timing and optimal pre-injection mass ratio should be −30 °CA and 0.5, respectively. Therefore, through this study we can better understand the potential interaction of relevant parameters and propose pre-injection solutions to improve combustion and emission characteristics.
Highlights
Due to its high thermal efficiency, good reliability, and sufficient and stable power, the diesel engine has been favored for a long time by the fields of national defense and the military, and in power plants, transportation, engineering machinery, and agricultural machinery [1]
The results showed that the cylinder pressure, cylinder temperature, and NOx emission decreased with increased methanol content
The results showed that compared with pure diesel, the maximum cylinder pressure of diesel engine fuel with diesel/n-butanol blends increased by 5.3% and the emission characteristics of blends of diesel engine fuel with diesel/n-butanol improved
Summary
Due to its high thermal efficiency, good reliability, and sufficient and stable power, the diesel engine has been favored for a long time by the fields of national defense and the military, and in power plants, transportation, engineering machinery, and agricultural machinery [1]. The development of the diesel engine has faced great challenges with the collection and utilization of oil resources [3]. This is mainly reflected in energy shortages caused by the massive utilization of fossil fuels and the environmental pollution caused by combustion emissions [4]. Facing the global energy crisis and environmental degradation [5], how to find renewable energy, and how to effectively reduce diesel engine emissions are the problems that need to be solved in today’s society [6]. The use of alternative fuels in diesel engines is considered to be an effective measure to reduce their dependence on diesel and reduce pollutant emissions [8]. Research on exploring new renewable alternative fuels has attracted more and more attention [10,11]
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