Reliable model of lubricant‐related friction in internal combustion engines

Abstract

A linear model of lubricant-related engine friction was developed. Based on lubrication fundamentals, the technique is comprised of three simple bench tests that respectively operate under thick fluidfilm hydrodynamic lubrication, elastohydrodynamic lubrication, and boundary lubrication. With adequate configunztion and appropriate test conditions, these bench tests are seen to simulate major friction losses in a typical intern1 combustion engine. Lubricant characteristics obtained in the bench tests were combined using SAS linear regression and correlated to ASTM Five-Car and Sequence VI engine tests. The linear model gave an excellent prediction of engine data. It further showed that hydrodynamic friction losses dominate lubricant-related engine fiction, followed by boundary friction losses, and elastohydrodynamic or mixed friction losses. This simple, reliable, and inexpensive technique can be used as a research tool to study fiction characteristics of crankcase lubricants and to develop superior fuel-efficient engine oils. Major findings fron this study can be summarised as f i h w s : I . The linear &l predicts that 5 to 6% fuel economy improvement over the industry high reference oil HR-4 is achievable with today's motor oil technology. both 'thick' and 'thin' fluid-film lubrication account for 63% of total friction losses caused by the engine oil while boundary friction losses amount to 37%. 3. Friction losses in the elastohydrodynamic mHD) engine are significant, up to 22% of total friction losses. This, combined with the fact that EHD film thickness is the most significant parameter in the linear model, suggests that pressure effects (ie, high-temperature I high-shear I high-pressure viscosity, pressure-viscosity coefficients) are important. Hydrodynamic friction losses in 4.Increasing fuel economy improvement is in general in the order: SAE lOW-40 < SAE low40 < SAE 5W-30, providing that base stock and additive systems are unchanged.

Biolubricants: Raw materials, chemical modifications and environmental benefits

“…In practice, the usable liquid range is limited by the pour point (PP) at low temperatures and the flash point at high temperatures. The PP should be low to ensure that the lubricant is pump‐able when the equipment is started from extremely low temperatures 22. The flash point should be high to allow the safe operation and minimum volatilization at the maximum operating temperature.…”

Finite Temperature Structure and Dynamics of Zinc Dialkyldithiophosphate Wear Inhibitors: A Density Functional Theory and ab Initio Molecular Dynamics Study

“…Given the great importance and utility of ZDDP additives, and the antiwear films derived from them, numerous studies have taken place in hopes of developing a clear description of the process of film formation and acquiring an understanding of the fundamental nature of the properties that these films exhibit. 1,[5][6][7][8][9][10][11][12][13][14] Although a large amount of attention has been devoted to exploring ZDDP film formation, many questions remain unanswered, 15,16 in part due to the difficulties encountered upon examining the formation of antiwear films under engine conditions or similar conditions in the lab. 17,18 Furthermore, the multidisciplinary nature of the study of ZDDP molecules and films complicates this task, 19 and there remains an obvious need to develop a model for the behavior of ZDDPs that is consistent with the wealth of available experimental data in order to optimize their effectiveness in current motor oils.…”

Common Properties of Lubricants that Affect Vehicle Fuel Efficiency: A North American Historical Perspective

“…As shown in Figure 7, there are cases where viscosity has no effect on fuel efficiency. For many years, researchers have tried to determine the relative effect of viscosity, boundary friction and EHD friction on efficiency in engines, transmissions and axles [42,45,[88][89][90][91][92][93]. In these research efforts, a series of lubricants with different tribological properties are developed.…”