A comparative analysis of n-butanol/diesel and 1-pentanol/diesel blends in a compression ignition engine

Abstract

The use of alcohols in diesel engines is an alternative way of reducing dependence on diesel fuel. Specifically, higher alcohols such as n-butanol (nB) and 1-pentanol (Pn), which consist of high carbons and can be produced from mainly non-edible sources, can directly be mixed with diesel fuel which in return provides significant promise from economic and environmental stand points. For this reason, the examination of the use of such high-carbon alcohols in diesel engines has become significantly important in recent years. In this work, six different binary (D-nB and D-Pn) fuel mixtures were obtained by mixing the diesel fuel with n-butanol and 1-pentanol at low and high mixing ratios (5%, 25% and 35% alcohol by volume) and basic fuel properties were examined. The test fuels were tested at four different loads (0, 3, 6 and 9 kW) at a constant engine speed (1800 rpm) in a direct injection diesel engine with diesel as the reference fuel. Fuel properties of the binary fuels were in compliance with the European Norm (EN590) and all of the fuels exhibit a steady phase without any indication of phase separation. Compared to diesel fuel’s engine characteristics, brake specific fuel consumption (BSFC) increased by 14.02% in binary blends, resulting in a 7.36% reduction in brake thermal efficiency (BTE). However, exhaust gas temperature (EGT) increased by an average of 47.55%. The addition of 1-pentanol to diesel had a significant impact on the decrease of oxides of nitrogen (NOx) emissions as an average decrease of 14.27% was observed. On the other hand, the higher latent heat of evaporation (LHE) of n-butanol and 1-pentanol had multiple disadvantageous outcomes such as a cooling effect in-cylinder, lower combustion efficiency and slightly higher carbon monoxide (CO) and hydrocarbon (HC) emissions as compared to diesel. The results indicated that the binary blends with 35% alcohol content happened to be a promising alternative for lower NOx emissions at the expense of increasing CO and HC emissions. Overall, it is concluded that n-butanol and 1-pentanol blends can be safely used in diesel engines without any engine modification or any additive.