Effects of higher ratios of n-butanol addition to diesel-vegetable oil blends on performance and exhaust emissions of a diesel engine
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n-Butanol is a promising next generation alternative fuel for stabilizing diesel fuel-vegetable oil blends at low temperatures. In this study, the effects of higher n-butanol contents in diesel fuel-vegetable oil blends in a diesel engine were investigated. Ternary blends of diesel fuel (D)-cotton oil (CtO)-n-butanol (nB) as percentages (vol.%) of 60%D-10%CtO-30%nB (TB1), 50%D-30%CtO-20%nB (TB2), 30%D-30%CtO -40%nB (TB3), 30%D-10%CtO-60%nB (TB4) and 20%D-20%CtO-60%nB (TB5) were selected in the soluble area of the ternary phase diagram for low temperature (-15 degrees C) operability. The tests were conducted employing each of the above ternary blends and diesel fuel, with the engine operating at full load and eight different engine speeds between 1800 and 4400 rpm. Increasing presence of n-butanol in the blends improved density, kinematic viscosity and cold filter plugging point (CFPP), while deteriorated cetane number (CN) and heating value of the ternary blends. Experimental test results of ternary blends showed that average brake torque, brake power, brake thermal efficiency (BTE) and exhaust gas temperature decreased, while brake specific fuel consumption (BSFC) increased with increasing presence of n-butanol in the blends. Addition of n-butanol to diesel fuel vegetable oil blends increased oxides of nitrogen (NO and NO2) formations, while drastically decreasing formation of carbon monoxide (CO) and hydrocarbon (HC) emissions. TB4 and TB5, which have the highest ratio of n-butanol, are promising candidate for decreasing CO and HC emissions at the expense of increasing BSFC.