Effects of center of heat release on combustion and emissions in a PCCI diesel engine fuelled by DMC-diesel blend

Abstract

The experiments were performed in a reformed single cylinder common-rail diesel engine which adopts a low temperature premixed charge compression injection (PCCI) mode by a pilot-pilot-main injection strategy coupled with heavy EGR. The objective of this study was to examine the combustion, performance and emission characteristics of neat diesel and D10 (diesel fuel with 10% dimethyl carbonate (DMC) by volume) in five center of heat release (COHR) modes, since there is rare research considered these parameters together. The results show that the COHR has significant influence on the in-cylinder pressure, average bulk gas temperature and the major peak of heat release. By means of postponing fuel injection coupled with heavy EGR, a larger fraction of premixed combustion is achieved, while the stability of the combustion is not evidently affected. Both HC and CO emissions increase slightly with retarding COHR due to the decreased temperature during combustion, which does not favor a sufficient late oxidation. The additions of DMC can reduce PM more than 40% compared to neat diesel, while D10 fuel generates more NOx than the diesel fuel. With retardation of COHR, a tradeoff between NOx and PM emissions can be well tuned, thanks to a higher fraction of premixed combustion.