Injection system modification and optimization for performance enhancement and emission reduction in a light-duty diesel engine fuelled by biodiesel-water emulsion

In conventional diesel engines, adding water to carbon–neutral biodiesel simultaneously reduces nitrogen oxides (NOx) and smoke emissions whilst improving engine performance. However, such investigations reported in the literature are conducted with engines equipped with a mechanically actuated fuel supply system lacking flexibility in the injection schedule. The present investigation aims at modifying and optimizing an existing mechanical fuel injection system to an electronic common rail injection (CRDi) system for utilizing biodiesel-water emulsion. A light-duty diesel engine's performance and emission characteristics with the modified CRDi system operated with biodiesel-water emulsion is compared with the mechanical injection system. The formulated Karanja biodiesel and water emulsion contained 18 % water, and 2 % of the raw oil was utilized as the stabilizer for the emulsion. The results show that the CRDi system results in lower peak cylinder pressure, higher heat release rates, and retarded combustion phasing for all the tested fuels compared to the mechanical injection counterpart. Compared to diesel with the mechanical injection system, biodiesel-water emulsion with CRDi system reduced fuel consumption and increased thermal efficiency by 30 % and 14 %, respectively, at 5.08 bar brake mean effective pressure (BMEP). The NOx emissions for the emulsion were similar to diesel with the mechanical injection system, whereas a decrease of 29, 30 and 10 % was observed for emissions of smoke, unburned hydrocarbon (HC) and carbon monoxide (CO), respectively. The current investigation reveals that utilizing biodiesel-water emulsion with a flexible injection system reduces engine exhaust emissions while simultaneously improving the performance characteristics.