Performance and exhaust emission characteristics of direct-injection diesel engine fueled with enriched biodiesel

Biodiesel is a renewable alternative diesel fuel derived from different feedstocks that may have significantly different fatty acid profiles and physiochemical properties. This study aimed to gain further insight into the use of biodiesel in a single-cylinder direct-injection diesel engine. The influences of the properties and compound structure of neat and enriched components of biodiesel on engine performance and exhaust emissions were compared with that of petrodiesel under full load conditions. The enriched blends for testing were prepared by adding methyl oleate (MO) to palm oil methyl ester (PME) at specified volumetric ratios (vol/vol%): PME80:MO20, PME70:MO30, PME60:MO40, and PME50:MO50. Furthermore, various physiochemical properties of neat and enriched blends were evaluated against the ASTM D6751 standard. The impact of key fuel properties of neat and enriched blends associated with the performance of engine and exhaust emissions was discussed. The experimental results exhibited that enriched blends yielded a lower brake torque with higher brake specific fuel consumption (BSFC) than the petroleum diesel because of lower calorific value. Intrinsic reductions in the carbon monoxide (CO) and hydrocarbon (HC) emissions, and exhaust gas temperature (EGT) were also observed, as well as a slight increase in nitrogen oxide (NOx) emission. In addition, enriched blends showed a noticeable improvement in BSFC, with a slight increase in CO emission, HC emission, EGT, and NOx emission over individual PME as a result of lower ignition quality and lower oxygen content. Consequently, biodiesel that possesses more saturated components, and higher oxygen content yields lower EGT, as well as decreased CO, HC, and NOx emissions. However, as a consequence, BSFC is increased.