Effect of assisted hydrogen on combustion and emission characteristics of a diesel engine fueled with biodiesel

Abstract

In this paper, the effects of hydrogen assisted biodiesel with different fatty acid methyl esters (FAMEs) proportion on cylinder pressure, cylinder temperature, indicated thermal efficiency (ITE), NOx emission, HC emission and CO emission of a marine medium speed diesel engine are studied. The corresponding CFD model is executed by CONVERGE coupled to CHEMKIN, and a chemical kinetic mechanism with 314 reactions and 98 species is developed to accurately simulate the fuel injection and combustion processes. The results show that cylinder pressure, cylinder temperature and ITE increased with increasing HEF. Compared with rapeseed methyl ester (RME) and cottonseed methyl ester (CSME), the cylinder pressures are increased by 16.39% and 16.30% for CSME-6%H2 and RME-6%H2 at 100% load, respectively. The cylinder temperatures are increased by 7.42% and 7.14%, and ITE increased by 3.73% and 3.9%, respectively. In addition, the HC and CO emissions decreased significantly with the increase in HEF, while NOx emission increased. Compared with pure CSME and RME, HC emissions are reduced by 70.97% and 72.22% for CSME-6%H2 and RME-6% H2, and CO emissions are reduced by 41.89% and 38.12% for CSME-6%H2 and RME-6% H2 at 100% load, respectively. Overall, the strategy of using CSME-6% H2 mixed fuel for engine is not only economical and practical, but also can prevent performance loss and reduce emissions.