Effect of iso-butanol addition to diesel fuel on performance and emissions of a DI diesel engine with exhaust gas recirculation

Iso-butanol is a second generation biofuel that has the potential to improve energy security and mitigate harmful pollutants in reciprocating engines. The present study investigates the effect of iso-butanol addition to diesel fuel on performance and emissions of a single cylinder direct-injection diesel engine with exhaust gas recirculation (EGR). For this objective, four iso-butanol/diesel blends containing 10%, 20%, 30%, and 40% were prepared by volume basis and tested in the engine under three EGR rates: 10% to 30% (at increments of 10%) with the combination of two injection timings: 23° and 21° crank angle (CA) before top dead center (bTDC). Experimental results showed that the combination of 30% EGR rate, 40% iso-butanol addition (ISB40) and retarded injection timing by 2° CA bTDC simultaneously reduced NOx emissions from 1284 to 749 ppm and smoke opacity from 20.7% to 1.9% with a slight drop in performance. It was found that higher iso-butanol/diesel blends require higher EGR levels to attain optimum levels of smoke and NOx emissions. Both hydrocarbon (HC) and carbon-monoxide (CO) emissions presented an increasing trend at escalating EGR rates. At retarded injection timing, ISB40 blend presented decreased HC emissions, increased CO emissions with a slight drop in performance compared to its injection at original timing.