Impact of Metal Oxide Nanoparticles in Waste Plastic Oil on Diesel Engine Performance, Combustion, Emissions, and Tribology

Abstract The study explores the potential of waste plastic oil (WPO) as a sustainable alternative fuel, aiming to enhance engine performance and emission characteristics by incorporating zinc oxide (ZnO) nanoparticles. The ZnO nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray analysis. Using an ultrasonicator, they were dispersed in WPO20 blends at 30, 60, 90, and 120 ppm concentrations. Engine experiments conducted at 1500 rpm revealed that the WPO20 blend with 120 ppm ZnO exhibited a 23.53% increase in cylinder pressure and a 12.5% enhancement in heat release rate compared to WPO20. The brake thermal efficiency (BTE) of WPO20 + 120 ppm ZnO improved by 6.54%, while brake-specific fuel consumption (BSFC) decreased by 16.02%. Emission analysis showed reductions in carbon monoxide (CO), hydrocarbons (HCs), and smoke opacity by 14.86%, 35.71%, and 12.5%, respectively, with a slight 2.65% rise in nitrogen oxide (NOx) emissions compared to WPO20 at peak load. Tribological evaluations using a four-ball tribometer demonstrated significant improvements, including a 20.79% reduction in the coefficient of friction (COF), a 28.09% decrease in wear scar diameter (WSD), and a 58.65% enhancement in the flash temperature parameter (FTP) compared to WPO20. SEM analysis of worn surfaces confirmed reduced wear and surface damage in blends containing ZnO nanoparticles, with WPO20 + 120 ppm ZnO exhibiting superior overall performance in both engine and tribological tests.