Green nanofuel strategy on performance, emission, and combustion characteristics of graphene-integrated tamanu biodiesel blends

This study experimentally investigated the performance, combustion, and emission characteristics of a compression ignition engine (CI) fueled with tamanu methyl ester biodiesel blended at 20% with diesel (TMB20) and enhanced with graphene oxide (GPO) nanoadditives. The tested fuel variants included TMB20, TMB20 + GPO15 ppm, TMB20 + GPO30 ppm, TMB20 + GPO45 ppm, and TMB20 + GPO60 ppm, which were evaluated against diesel. The results revealed that GPO integration significantly improved engine performance, with the TMB20 + GPO60 ppm blend exhibiting the highest brake thermal efficiency and lowest brake-specific fuel consumption. Enhanced atomization, a higher calorific value, and a shorter ignition delay contribute to improved combustion efficiency. Emission analysis indicated notable reductions in carbon monoxide (29.68%), unburned hydrocarbons (50.54%), and smoke opacity (44.92%) compared to diesel. While most blends showed an increase in nitrogen oxide (NOx) emissions, the TMB20 + GPO60 ppm blend achieved a 9.75% reduction in NOx emissions compared to diesel. Moreover, the peak cylinder pressure and heat release rate increased with increasing GPO concentrations, confirming the superior combustion characteristics of GPO. In general, the integration of GPO nanoadditives with tamanu biodiesel substantially enhanced engine performance and emission behavior, underscoring its potential as a sustainable and efficient alternative fuel for CIs used in automobile and marine applications.