Emission and combustion profile study of unmodified research engine propelled with neat biofuels

The current work focuses on the experimental investigation to analyze the combustion and emission characteristics of a direct injection diesel engine fueled with neat biodiesel (BD100) and different proportions of cyclohexanol blends as a fuel additive in various volume fractions. Cyclohexanol is dispersed into a neat biodiesel in a volume fraction of 10, 20, and 30 vol%. The biodiesel is produced from neem oil by the conventional transesterification process. The experimental results revealed that with the increased cyclohexanol fraction, the combustion was found smooth. The addition of cyclohexanol has a positive influence on various physical and chemical properties of neat biodiesel. The in-cylinder pressure is comparatively low for diesel followed by cyclohexanol and biodiesel blends when compared with neat biodiesel. This is due to shorter ignition delay period. The heat-release rate of neat biodiesel is the highest among all fuels. The overall HC emission of BD70COH30 is 12.19% lower than BD100 and 16.34% lower than diesel. The overall CO₂ emission of BD70COH30 is 13.91% higher than BD100 and 19.5% higher than diesel. The overall NOₓ emission of BD70COH30 is 5.31% lower than BD100 at all load engine operations. The presence of 10, 20, and 30% of cyclohexanol in biodiesel decreased smoke emissions as compared with neat biodiesel and diesel. The overall smoke emission of BD70COH30 is 19.23% lower than BD100 and 25.51% lower than diesel. The overall CO emission of cyclohexanol blended with biodiesel by 30 vol% (BD70COH30) is 17% lower than neat biodiesel and 21.8% lower than diesel. Based on the outcome of this study, neem oil biodiesel and cyclohexanol blends can be employed as a potential alternative fuel for existing unmodified diesel engines owing to its lesser emission characteristics.