Performance, Emissions, Combustion and Vibration Analysis of a CI Engine Fueled with Coconut and Used Palm Cooking Oil Methyl Ester

Biodiesels from coconut and palm cooking oil are viable alternatives to diesel fuel due to their environmental sustainability and similar physicochemical properties compared to diesel. In the present study, these fuels were tested separately in a diesel engine by blending with fossil diesel in proportions of 10%, 20%, 30% and 40% by volume. Experiments were conducted under a constant brake mean effective pressure (BMEP) of 400 kPa and at 2000 rpm. The results revealed similarities in engine performance, emissions, combustion and engine block vibration for used palm cooking oil methyl ester (UPME) fuel blends and coconut methyl ester (CME) fuel blends. Most blends resulted in slight improvements in brake specific energy consumption (BSEC) and brake thermal efficiency (BTE). A maximum reduction of 54%, 89% and 16.8% in pollutant emissions of brake specific hydrocarbons (BSHC), brake specific carbon monoxide (BSCO) and brake specific nitrogen oxides (BSNOx), respectively, was observed with UPME and CME in the blends. The cylinder pressure profiles when UPME-diesel and CME-diesel blends were used were comparable to a standard diesel pressure trace, however, some deviations in peak pressure were also noticed. It was also apparent from the results that engine vibration was influenced by the type of methyl ester used and its blend composition. Notably, the rate of pressure increase was maintained within an acceptable limit when the engine was fueled with both of the methyl ester blends.