Effects of hybrid metal oxide nanoparticles on the tribological and emission attributes of algae‐derived biofuel in compression ignition engines

Abstract

The growing demand for sustainable fuels has accelerated the development of algae‐derived biodiesel for compression‐ignition engines. In this study, Chlorella vulgaris methyl ester (AME) exhibited physicochemical properties comparable to diesel and satisfied ASTM D6751 fuel quality requirements, making it suitable for blending. The effects of hybrid nanoparticles on the combustion, performance, and emission characteristics of an AME20 blend were experimentally investigated in a single‐cylinder diesel engine operating at 1500 rpm under different loads. Four test fuels, namely diesel, AME20, AME20 + 50 ppm (TiO 2  + SiO 2 ), and AME20 + 100 ppm (TiO 2  + SiO 2 ), were evaluated. Compared with AME20, the AME20 + 100 ppm (TiO 2  + SiO 2 ) blend increased peak cylinder pressure and heat release rate by 5.1% and 21.48%, respectively. Brake thermal efficiency (BTE) improved by 3.64%, while brake‐specific fuel consumption (BSFC) decreased by 12.64%. Carbon monoxide (CO), unburned hydrocarbon (HC), and smoke emissions were reduced by 21.3%, 23.6%, and 6.31%, respectively, whereas NO X showed a slight increase due to higher combustion temperatures. Tribological analysis demonstrated reductions of 14.88% in wear scar diameter (WSD) and 12.35% in coefficient of friction (COF), with SEM observations confirming the formation of a protective tribo‐film. Overall, AME20 + 100 ppm (TiO 2  + SiO 2 ) effectively enhanced the combustion, emission, and lubrication performance of AME20, demonstrating its potential as a sustainable diesel fuel.