Potential Utilization of Higher Alcohols in Unmodified Diesel Engine

Abstract

India does not have large reserves of crude petroleum and spends a huge amount of foreign exchange for importing crude petroleum. The environmental degradation caused by burning of petroleum derived fuels is also causing an ecological imbalance. Research is carried world over on renewable fuels which could either be used as an extender or substitute to petroleum origin fuels and in this context alcohols such as ethanol and butanol have an immense potential. The earlier work on use of alcohols as a blend with diesel in the compression ignition engine has suggested reduction in emissions, however, problems such as phase separation and increase in fuel consumption has also been encountered while utilizing ethanol in diesel engines. To alleviate this problem, isobutanol has the potential to be used along with ethanol to make a homogenous blend without any phase separation and simultaneous advantage of alcohol being an oxygenated fuel which shall improve the combustion and reduce emission. The present study was carried out to explore the potential utilization of ethanol-isobutanol-diesel blends (containing up to 20% ethanol-isobutanol mixture in equal proportions) in compression ignition engine. Three blends were prepared having 5%, 10%, 20% ethanol-isobutanol mixtures respectively and calorific value, kinematic viscosity; specific gravity and density of blends were found to decrease with increase in ethanol-isobutanol percentage. The engine trial was conducted on an unmodified diesel engine to evaluate the performance and emission characteristics on ethanol-isobutanol-diesel blends and results were compared with baseline data of diesel. The results obtained from the engine trial suggested that brake thermal efficiency (BTE) increased and brake specific energy consumption (BSEC) decreased for the blends and considerable reduction in carbon monoxide (CO) and carbon dioxide (CO2) was observed with blends with a small increase in unburnt hydrocarbon (UBHC). The nitrogen oxide (NOx) and smoke emissions were also found to reduce for the ethanol-isobutanol-diesel blends.