Abstract:

In order to explore the effect of soot particles on the friction pair interface of engine and the role of lubricating oil additives under extremely starved oil condition, a reciprocal friction and wear tester was performed to investigate the effect of nano-LaF₃ on the granular flow lubrication behavior of biomass fuel soot (BS) particles under reciprocating friction condition. The roles of the nano-LaF₃ between rubbing surfaces were analyzed by the Raman spectrometry, 3D laser scanning microscope and X-ray photoelectron spectrometer. Results showed that the wear resistance and friction reduction of friction pairs could been significantly improved under reciprocating sliding conditions as the addition mass fraction of the nano-LaF₃ was more than 20%. With the increasing of nano-LaF₃ content, the graphitization degree of soot was increased on the wear surface. Meanwhile, the graphite crystallite size was increased. The lubrication mechanisms of the nano-LaF₃ for BS granular flow lubrication under sliding condition were attributed to the formation of tribo-films including LaF₃ and other lanthanum compounds, carbon oxides and iron oxides on the wear surface. At the same time, the nano-LaF₃ would induce the more graphite transition of soot under the sliding condition which sequentially enhanced the antifriction ability of BS granular flow lubrication.

Key words: biomass fuel, soot, nano-LaF₃, granular flow, lubrication

摘要：

为探索极端乏油工况下碳烟颗粒在发动机摩擦副界面的功效及润滑油添加剂的作用，本文采用往复摩擦磨损试验机研究了纳米氟化镧（nano-LaF₃）颗粒对往复滑动条件下生物质燃油碳烟（BS）颗粒流润滑性能的影响。借助拉曼光谱仪、3D激光扫描显微镜、X射线光电子能谱仪等仪器探讨了滑动条件下nano-LaF₃对BS颗粒流润滑特性的影响作用机理。结果表明：当nano-LaF₃的添加质量分数大于20%时能显著改善往复滑动条件下BS颗粒的抗磨减摩性能，并且随着nano-LaF₃添加浓度的增大，摩擦表面碳烟石墨化程度和石墨微晶尺寸均增大。nano-LaF₃在含BS颗粒流润滑的摩擦界面形成了LaF₃摩擦膜以及含镧化合物、碳氧化合物及铁氧化合物的化学复合反应膜，同时nano-LaF₃会加大诱导碳烟的石墨化作用，从而增强了BS颗粒流润滑的减摩性。

关键词: 生物质燃油, 碳烟, 纳米氟化镧, 颗粒流, 润滑