This study investigates the influence of fuel injection pressure and nanoparticle additives on the combustion, performance, and emissions of a CI diesel engine fuelled with diesel–waste cooking oil biodiesel blends. Injection pressure was varied between 180 and 240 bar, and graphene Nano platelets (GNPs) and carbon nanotubes (CNTs) were added at 50 ppm. Increasing the injection pressure to 240 bar improved combustion quality and raised brake thermal efficiency (BTE) by 2.1%, while reducing brake-specific fuel consumption relative to lower pressures. The graphene-based blend (W20G3) exhibited the most significant emission benefits, achieving a 68% reduction in HC, 4.6% reduction in CO, and 2.5% reduction in NOx compared to baseline biodiesel at the same injection pressure. Meanwhile, the CNT-modified blend (W20C3) produced the largest improvement in smoke opacity, achieving a 44.6% reduction due to enhanced soot oxidation associated with its tubular morphology. The results confirm that graphene is more effective in reducing gaseous pollutants, whereas CNTs excel in reducing smoke, and that an injection pressure of 240 bar optimizes nanoparticle-assisted combustion. These findings provide quantitative evidence for improving biodiesel formulations and fuel injection strategies to achieve cleaner and more efficient diesel engine operation.
Raj et al. (Sun,) studied this question.