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.

Issues such as rising fuel prices, fuel costs, and lowering reserves highlight the importance of research into sustainable fuels derived from biological sources. This study is focused on experiments on a CI engine using ethanol and propanol-based ternary blends. Palm biodiesel is kept constant at 40% volumetric concentration, while diesel and ethanol/propanol are varied in different batches. The results obtained with ternary blends were compared with reference fuel diesel, pure palm biodiesel, and a palm biodiesel–diesel binary blend. The ternary blends exhibit lower brake thermal efficiency and higher brake specific energy consumption than diesel and binary blends due to their lower calorific value. Despite in-fuel oxygen presence, lower brake specific oxides of nitrogen and smoke opacity were observed for engine operation with a ternary blend due to the predominant role of higher latent heat of vaporization and volatility of alcohols, but unburned hydrocarbon and carbon monoxide emissions increased due to the interactive effect of a lower cetane number, higher latent heat of vaporization, and lower kinematic viscosity of alcohols when compared to reference fuels. Among the tested fuels, in-cylinder pressure was observed to decrease with ternary blends due to their lower calorific value, but a raised heat release rate was attributed to lower viscosity and faster burning of alcohols.

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