Research About Effect Of Viscosity Index Improvers On Base Oil Film Forming Characteristic

The basis of energy-saving lubrication is low-viscosity and high-viscosity index energy-saving lubricating oil formed by selecting base oil adding viscosity index improver.Viscosity index improver is an oil soluble high-molecular polymer. It is an indispensible additive of lubricating oil. It can improve viscosity index of base oil, makes the viscosity of base oil declines with the variance of temperature so as to improve viscosity temperature property of base oil. However, the oil film thickness calculation value based on the classical theory of EHL is found serious deviates from the actual film thickness in the study of lubrication performance of the energy-saving lubricants, which is mainly due to after adding viscosity index improver in the lubricant base oil, the oil show the characteristics of non-Newtonian and viscosity-temperature effect. The actual working condition of the EHL hydrodynamic theory calculation of the base oil containing viscosity index improver is more complex than the base oil and the classic EHL theory can not accurately predict the film-forming properties.In lubricating design, people often concern about the thickness of lubricating film and variable rule of film thickness with the variation of working condition. At present, the relation between the performance of viscosity index improver and lubricating oil film-forming property still remains at the qualitative description level and without determined theory and calculation method to calculate it correctly. In the paper, the effect rules of viscosity index improver on base oil film is studied based on the theoretical calculation and experimental test. Major research work includes:1. Based on film elasto-hydrodynamic lubrication velocity pressure theory and on the premise of considering viscosity temperature effect and non-Newton shear thinning effect, the paper creates elasto-hydrodynamic lubrication mathematic model of base oil containing viscosity index improver through applying Carreau-Yasuda to revise constitutive equations and WLF viscosity temperature equation.2. It writes number calculation program by applying FORTRAN90 assembly language.The program can get the value of oil thickness, shape and pressure through changing input parameters.3. Based on principle of light interferometry, the paper utilizes NGY-4 nanometer lubricating film comprehensive gauge to design related test and complete actural film thickness measurement experiment of base oil containing index improver with different viscosities,under different working conditions.4. It compares number analysis calculated value and measured value in the experiment.The research indicates that the film forming ability of base oil containing viscosity index improver is lower than theoretical value of classic elasto-hydrodynamic lubrication theory,while the number of this paper can predict the effect rule of viscosity index improver on film forming characteristic of base oil.5. The paper studies the change rule of base oil containing index improver with different viscosities under different working conditions such as different speeds,temperatures and loads and discloses the influence relation between use property of viscosity index improver and lubricating oil film forming characteristic.