Evaluation of composition and carbon atoms distribution of the exhaust hydrocarbons by varying post-injection parameters in DI diesel engine

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This study was aimed to explore the effects of different post-injection parameters on the cracking, formation mechanism, composition, and carbon atoms distribution of exhaust hydrocarbon (HC) compounds of the diesel engine. The influence of three post-injection fuel masses (PIM) and six dwell duration with different start of injection (SOI) timings were assessed with an operating speed of 1000 rpm and a basic engine load of 0.5 MPa. Post-injection strategy greatly influenced the composition and carbon atoms distribution of exhaust gases emissions. It was noted that the formation of light HC species was lowered during early post-injection at SOI 20-40° crank angle (CA) due to the high in-cylinder temperature and more oxidation but increased as the SOI delayed due to more cracking of diesel fuel. An increase in the PIM also increased the formation of HC species at all SOI. Peak values of C1 (one carbon), C2 (two carbon), and C3 (three-carbon) compounds were recorded at SOI 60°CA with 15 mg PIM respectively, and the maximum value of 2700 ppm was observed for non-methane hydrocarbon (NMHC) at SOI 80°CA. While higher HC (C8) compounds achieved a peak of 275 ppm at SOI 80°CA with 15 mg PIM. At early SOI 20-40°CA, lighter HCs compounds concentration fractions were accounted for about 50–80% of THC emissions with 5–15 mg PIM. While at later SOI 80-120°CA C8 concentration fractions were dominant over all other HC fractions occupying a concentration fraction of more than 50% with 5, 10, and 15 mg PIM.