Effect of emulsified biomass-fuel on the film formation behavior of diesel engine lubricating oil

As a kind of petroleum fuel alternatives, emulsified biomass fuel(EBF) can be used in a diesel engine. The problem of lubricating oil dilution by diesel engine fuel can't be prevented. Research on the effect of EBF on the oil film formation behavior of diesel engine lubricating oil was very important. The friction and wear behaviors of engine lubricating oil (CH-4 20W-50) were investigated as diluted by different contents of EBF by using a cylinder-piston ring tribometer. The surface morphology and composition of oil film on the cylinder liners were analyzed by SEM with EDS and XPS. The results showed that the kinematic viscosity of lubricating oil decreased from 24.55mm²/s to 14.55mm²/s when diluted by 10% EBF, leading to the decrease of oil film thickness. Besides, the friction induced the formation of tribofilm containing ZnO, iron oxides, sulfides, phosphates, nitrogen-containing chemicals, which was benefit for the anti-friction and anti-wear properties of engine lubricating oil. The mechanism of EBF influence on the oil film formation of lubricating oil was ascribable to its dilution role and then the composition change of tribofilm.