Green-synthesized silver nanoparticle additives from Allium tuncelianum for diesel engine operation with a cottonseed biodiesel-diesel blend

This study investigates, to the best of the authors’ knowledge, the first use of silver nanoparticles synthesized with an aqueous extract of the endemic Allium tuncelianum as additives for a cottonseed oil-derived B20 biodiesel-diesel fuel. Particle formation and phytochemical association were assessed by ultraviolet–visible spectroscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, and thermogravimetric-differential thermal analysis. AgNPs were dispersed in B20 at 50 and 100 mg L − 1 , and the fuels were tested in a single-cylinder, direct-injection diesel engine at full load and 1000, 1500, and 2000 rpm. Density, kinematic viscosity, and lower heating value were measured using ASTM methods. Triplicate testing yielded coefficients of variation below 1.5%, while estimated relative uncertainties did not exceed 2.8%. At 2000 rpm, B20-Ag50 increased brake torque and brake power by 10.3% relative to B20, whereas B20-Ag100 provided only a 3.0% improvement. The torque reduction between 1000 and 2000 rpm was 14.7% for B20-Ag50 compared with 23.1% for B20. These gains were accompanied by substantial emission penalties. At 2000 rpm, carbon monoxide emissions from B20-Ag50 and B20-Ag100 were 111.8% and 71.9% higher than B20, respectively, while nitrogen oxides were 489 and 356 ppm compared with 117 ppm for B20. Exhaust gas temperature increased to 457.1 and 399.4 °C, respectively, versus 335.1 °C for B20. Thus, 50 mg L − 1 offered the best high-speed performance, but neither nanofuel achieved an overall performance-emission advantage. Long-term stability, in-cylinder combustion, particulate emissions, durability, nanoparticle fate, and techno-economic feasibility require further investigation.