Combustion and emission characteristics of diesel engine fueled with diesel/cyclohexanol blend fuels under different exhaust gas recirculation ratios and injection timings

Abstract

Cyclohexanol is obtained from abundant lignocellulosic biomass sources at low cost, and it is a promising alternative fuel for diesel engines. In this study, cyclohexanol was blended with diesel at various volume ratios and the mixtures were denoted as D100 (100 % diesel + 0 % cyclohexanol), D90CH10 (90 % diesel + 10 % cyclohexanol), and D80CH20 (80 % diesel + 20 % cyclohexanol), respectively. Subsequently, the effects of exhaust gas recirculation and pilot plus main injections at various pilot injection timings on the combustion and emissions of the diesel engine fueled with various mixtures were evaluated. The results demonstrated that diesel/cyclohexanol blends had a longer ignition delay, but shorter combustion duration. D80CH20 had the highest oxygen content, peak combustion temperature (PCT), and peak heat release rate (PHRR) at medium and high loads. Cyclohexanol blending with diesel significantly decreased the particulate number (PN) and volume concentrations at the expense of higher NOx emissions. Advancing the pilot injection timing prolonged the ignition delay and combustion duration, and increased the PCT and PHRR. Therefore, it emitted higher NOx emissions, but lower PN emissions. D80CH20 with 8 % EGR can simultaneously reduce the PN and NOx emissions at medium and high loads.