Energy, Emissions and Exergy Analyses of Ethanol-Biodiesel-Coconut Oil Ternary Fuel Blends and Comparative Assessment of Their Performance in Compression Ignition Engines

Abstract

The demands on future energy conversion technologies are becoming increasingly stringent. Biofuels, which are considered to have a critical role in meeting growing energy needs, must find increasing avenues for compliance. Accordingly, ternary fuel blends have received significant attention because their physiochemical properties can be very similar to diesel, while overcoming some challenges associated with traditional biofuel use. Consequently, this work assesses the use of alcohol-biodiesel-vegetable oil blends in Compression Ignition (CI) engines. Three ethanol-biodiesel-vegetable oil blends were developed using 10%, 20% and 30% alcohol and their performances were compared to diesel and neat coconut oil. These blends were tested in a single cylinder diesel engine and their performances assessed using energy, emissions and exergy analyses. The results indicated that the blends had better brake thermal efficiency (BTE) values than diesel at high to medium loads, with the E30 blend having the highest BTE value of 31% at full load conditions as compared to 28.9% for diesel. The blends were also found to be comparable to diesel based on a First Law energy analysis. Additionally, it was found that the blends had better nitric oxides (NO) emission levels than diesel; at full load conditions, the E30 blend had the lowest value of 281 ppm as compared to diesel having a value of 299 ppm. However, they were found to have comparable levels for the other emissions characteristics that were examined. Further, the Second Law analyses indicated that the blends made better use of their fuel energy potential and thus, can be considered as a more suitable fuel for CI engine combustion. Collectively, the results suggest that the ternary blends are a viable candidate for future energy conversion via CI engines. Keywords: Ternary blends; ethanol; coconut oil; CI engines; exergy analysis; alternative fuels