Hybrid ZnO–CuO nanoparticle-enhanced waste cooking oil biodiesel for improved diesel engine performance and emission reduction

Abstract

Abstract The well-known trade-off between engine emissions and performance is one of the primary obstacles to using waste cooking oil (WCO) biodiesel. WCO biodiesel frequently results in incomplete combustion and decreased efficiency because to its relatively high viscosity, poor cold flow, and improper atomization characteristics. The goal of this work was to boost the thermophysical characteristics and combustion behavior of WCO methyl ester by using metallic oxide nanoparticles as fuel additives. Methyl ester was converted from WCO via transesterification and blended with diesel oil at 20% volumetric ratio (B20). Zinc oxide (ZnO), copper oxide (CuO), and hybrid ZnO–CuO formulation were incorporated at concentration of 25 ppm. Physicochemical properties of produced biodiesel and prepared nano-blends were evaluated prior to engine testing. Experimental investigations were conducted using diesel engine operating at 1500 rpm rated speed under load variation. Hybrid nano-blend increased brake thermal efficiency at peak load by 4% as related to pure diesel (D100) and by 21% in comparison to B20. Compared to B20, brake-specific fuel consumption was dropped by 22%. In comparison to D100, emission studies showed declines in carbon monoxide (7%), unburned hydrocarbons (16%), and smoke opacity (6%). In contrast with B20, hybrid nano-enhanced blend showed slight rise in exhaust gas temperature (4%) and nitrogen oxide concentrations (9%). Addition of 25 ppm hybrid ZnO–CuO nanoparticles improves engine performance and emissions parameters in a balanced way. Potential of nano-improved WCO biodiesel as a technically and financially feasible renewable fuel for compression ignition engines is supported by these findings.