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The present study aims to bridge the gap on hydrogen assisted biodiesel combustion, and to investigate its impacts on the engine performance, combustion and emission characteristics. Simulations were conducted on a diesel engine fueled by biodiesel with supplementary hydrogen inductions of 0.5%, 1%, 2% and 3% vol of H2 in air. A skeletal reaction mechanism was developed to include the reaction kinetics of biodiesel and hydrogen, with the CO, NOx and soot formation mechanisms embedded. The developed reaction mechanism was validated by performing the ignition delay calculations against the detailed biodiesel reaction mechanism, as well as the 3D numerical simulations against the experimental results. Good agreements in terms of ignition delay, cylinder pressure and heat release rate predictions were obtained. Key simulation results review that with the increase of hydrogen induction, a substantial increase in the peak cylinder pressure and heat release rate can be obtained under 50% and 100% load conditions, indicating an improved performance. But a reduced performance is observed at light load (10% loads) conditions due to the poor ignition and combustion processes. In terms of emissions, a general decreased trend is observed for both CO and soot emissions at all the engine speeds and loads, and a more remarkable reduction is found at 100% engine load conditions. Furthermore, due to the enhanced combustion, NOx emissions are increased slightly at 50% and 100% engine loads.

A blend of 20% (v/v) ethanol/methyl soyate was prepared and added to diesel fuel as an oxygenated additive at volume percent levels of 15 and 20% (denoted as BE15 and BE20). We also prepared a blend containing 20% methyl soyate in diesel fuel (denoted as B20). The fuel blends that did not have any other additive were stable for up to 3 months. Engine performance and emission characteristics of the three different fuels in a diesel engine were investigated and compared with the base diesel fuel. Observations showed that particulate matter (PM) emission decreased with increasing oxygenate content in the fuels but nitrogen oxides (NOx) emissions increased. The diesel engine fueled by BE20 emitted significantly less PM and a lower Bosch smoke number but the highest NOx among the fuel blends tested. All the oxygenate fuels produced moderately lower CO emissions relative to diesel fuel. The B20 blend emitted less total hydrocarbon (THC) emissions compared with base diesel fuel. This was opposite to the fuel blends containing ethanol (BE15, BE20), which produced much higher THC emission.