Performance and emission evaluation of a marine diesel engine fueled with natural gas ignited by biodiesel-diesel blended fuel

Abstract

In this paper, a marine dual fuel diesel engine fueled with the natural gas (NG: 60%, 70% and 80%) ignited by the biodiesel-diesel blended fuel (25%, 50% and 75% biodiesel by volume) was studied under different conditions. Based on the experiment, a computational fluid dynamics (CFD) model was established, and an improved chemical kinetic mechanism was developed to simulate the fuel spray process and combustion process. The ignition, combustion and emission characteristics of diesel engine fueled with different blended fuels were investigated under different load conditions. In addition, the temperature sensitivity of methane mole fraction with different NG energy fractions was analyzed at the 800 K and 1000 K. The results showed that the additions of NG and biodiesel in the blended fuel had a significant effect on the combustion and emission characteristics of the diesel engine. The starting of combustion (SOC) of the dual fuel engine lagged with the increases of NG and biodiesel content. The maximum enhancement of SOC reached 0.72°CA. The biggest influence on temperature was R122, which was the main reason for the shorter ignition delay during the combustion process. In all cases, NOx, CO and soot emissions decreased with increasing NG energy fraction. The maximum values of NOx, CO and soot emissions reached 1590 ppm, 461 ppm and 1.42 E−07 kg. Considering the combustion and emission characteristics of the engine, the best fuel blending ratio was EF80-B25.