Comparative analyses of diesel–waste oil biodiesel and propanol, n-butanol or 1-pentanol blends in a diesel engine

• Propanol, n-butanol and 1-pentanol were added diesel–biodiesel blends.
• Cold flow properties of the diesel–biodiesel blends were improved by adding higher alcohols.
• Engine characteristics of higher alcohol blends were reported and compared to diesel–biodiesel blend.
• There were different results in terms of HC emissions as a result of higher alcohol addition to diesel–biodiesel.
• All higher alcohol blends increased CO emissions, while they reduced NOx emissions as compared to diesel–biodiesel blend.

Higher alcohols are important alternative fuel resources for use in internal combustion engines promising positive economical and environmental outcomes. Moreover, higher alcohols are advantageous over lower alcohols due to their better blending capabilities, hydrophobic properties, higher cetane numbers and calorific value. The aim of this work is to investigate and compare the basic fuel properties of the ternary blends of diesel (D), waste oil methyl ester (biodiesel (B)) and the higher alcohols of propanol (Pro), n-butanol (nB) and 1-pentanol (Pn), and their effects on engine performance and exhaust emissions of a diesel engine. As test fuels four different blends were prepared by volume: 50%D–50%B (D50B50), 40%D–40%B–20%Pro (D40B40Pro20), 20%nB (D40B40nB20) and 20%Pn (D40B40Pn20). Addition of higher alcohols to diesel–biodiesel blend improved especially the cloud point (CP) and cold filter plugging point (CFPP), while slightly decreased density, lower heating value, kinematic viscosity, cetane number and flash point. In order to determine engine performance and exhaust emissions, tests were performed at four engine loads (1, 3, 6, 9 kW) with a constant engine speed (1800 rpm). Based on the engine performance and exhaust emissions, D40B40Pro20 had higher brake specific fuel consumption (BSFC) values than the ternary blends of D40B40nB20 and D40B40Pn20 at all engine loads. The exhaust gas temperatures (EGT) of D40B40Pro20, D40B40nB20 and D40B40Pn20 were higher than that of the diesel–biodiesel blend. All blends of the higher alcohols reduced oxides of nitrogen (NOx) emissions as 1-pentanol, n-butanol and propanol were the most to least effective alcohols respectively. However, carbon monoxide (CO) emissions were increased with the addition of the alcohols to the blends. When the effects of higher alcohols on hydrocarbon (HC) emissions are compared in terms of emission reduction, the order from best to worst was as follows: D40B40Pn20, D40B40nB20.

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