Dry Tribological Behaviors Of Biofuel Soot Particles

Biomass-fuel, one of potential engine fuels, is one of the most popular and clean renewable energy. It can be applied to diesel engine by mixed with diesel fuel with micro-emulsification process, because the physic-chemical properties of the mixture are closed to those of0diesel fuel. In addition, the soot particles are produced inevitably in the process of diesel engine working, which will increase the engine wear. Because the composition of biomass fuel is very complex, the morphology, structure and composition of biomass-fuel soot particles (BS) are different from those of0diesel soot particle (DS). Their complexity and variations of the surface functional groups bound to the soot particles have an impact on tribological behaviors of engine.Therefore, it was studied the dry tribological behaviors of biomass fuel soot and diesel soot using a multi-functional reciprocating tribometer under reciprocating motion conditions. By analyzing the different wear mechanisms of biomass fuel soot and diesel soot, it was expected to find a method to reduce the roles of friction and wear of biomass fuel soot. This can not only provide a reference for solving engine friction and wear under extreme conditions, also investigate structural changes of soot particles between the rubbing interfaces. The detailed contents are as follows:1. The BS particles and DS particles were produced using the soot trapping equipment and also were characterized using laser particle analyzer, Raman spectroscopy, elemental analysis and X-ray photoelectron spectroscopy. The results showed that the average particle diameter of biomass fuel soot particles (BS) was12.240μm, which is slightly lower than that of the diesel soot particles (DS)(17.409μm). The graphitization degree of BS (R=2.982) is higher than that of DS (R=3.647). Their components of BS and DS are same substantially. The oxygen content of BS is higher than that of DS. The functional groups of BS are more than those of DS because of the complexity of crude biomass fuel.2. It was investigated effects of BS and DS particles on their tribological properties of cast iron tribopairs under dry friction reciprocating conditions. The results showed that both soot particles could reduce the friction coefficient and wear weight loss; The anti-wear of BS is better than that of DS, because the degree of graphitization and oxygen content of BS were higher than those of DS; The anti-wear mechanism of both two soot particles were attributed to the friction-induced structure variation of soot particles from disorder to order, and the friction-induced oxidation of the cast iron tribopairs material. At the same time the iron oxide as produced and the soot particles formed a complex lubricating protective film together between the rubbing interfaces.3. It was studied the effect of surface texturing on tribological behaviors of BS under reciprocating dry friction conditions. The results showed that the suitable surface texturing could reduce the friction coefficient and improve the wear resistance. The coefficient friction decreases with increasing the share ratio of pit area; The coefficient friction between tribopairs with BS decreases with increasing load at the same texturing density. The effect of changing reciprocating frequency on the tribological behavior could be shown obviously; The role of friction-induced structure variation of soot particles was weak.4. It was investigated the effect of solid catalyst (T1F3) on the tribological performance with BS particles under dry friction reciprocating conditions. The results showed that BS with suitable catalyst made the boundary tribo-film more stable, which reduced the friction coefficient by18.3%when the content of solid catalyst (TiF3) was10wt%. The graphitization degree of soot particles and the relative contents of the metal oxide on the worn surface were reduced when the solid catalyst (TiF3) was introduced; Meanwhile the contents of functional groups (C-OH and C=O) increased significantly; On the worn surface there was an antiwear role with titanium dioxide (TiO2) and fluorides.