发动机润滑油使用中的组成变化和性能衰变特性

以市售全合成发动机润滑油为研究对象，通过实车运行10 000 km,研究润滑油使用过程中的性能及组成变化，并探究其衰变特性。研究结果表明：润滑油使用后运动黏度降低23.84%;总酸值和正戊烷不溶物增至3.53 mg/g和0.268%;磨损元素Fe、Al和污染物元素Si的量分别由<1、<1和2μg/g增加至11、 20和20μg/g;润滑油衰变过程中聚α烯烃(PAO)发生分解反应和聚合反应，使其组成分布趋于复杂；衰变过程以分子链断裂的分解反应为主，导致其黏度降低；润滑油发生氧化反应和硝化反应，添加剂被消耗，生成酮类、多环芳烃、胺类、酸类化合物，使润滑油颜色变深、酸值增加；润滑油的分子质量分布发生变化，说明润滑油衰变过程既发生分解反应也发生聚合反应，但以链断裂的分解反应为主。

Composition Change and Performance Decay Characteristics of Engine Lubricant During the Utilization

Taking the fully synthetic engine lubricant as the research object, the performance and composition changes were studied and its decay characteristics was also explored after 10 000 km running of real vehicle. The results showed that the kinematic viscosity of lubricant decreased by 23.84%. Meanwhile, the total acid value and n-pentane insoluble matter increased up to 3.53 mg/g and 0.268%, respectively, and the contents of wear elements(i.e, Fe and Al) and pollutant element(i.e, Si) increased from < 1, < 1, 2 μg/g to 11, 20, 20 μg/g, respectively. During the decay process of lubricant, the decomposition and polymerization reactions of poly α olefin(PAO) made the composition of lubricant complicated, while the decomposition process was dominated by the decomposition reaction of molecular chain fracture that led to the decrease of kinematic viscosity. In addition, the reaction of oxidation and nitration also occurred, and the ketones, polycyclic aromatic hydrocarbons, amines and acids were generated with the additives consumption, which led to the deepening color and increasing total acid value. The change of lubricant molecular weight distribution indicated that both decomposition and polymerization reactions occured during the decay process, while the chain-breaking decomposition reaction was dominated.