摘要:

AbstractA 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 fluid‐film hydrodynamic lubrication, elastohydrodynamic lubrication, and boundary lubrication. With adequate configuration and appropriate test conditions, these bench tests are seen to simulate major friction losses in a typical internal 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 friction, 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 friction characteristics of crankcase lubricants and to develop superior fuel‐efficient engine oils.Major findings from this study can be summarised as follows:1The linear model predicts that 5 to 6% fuel economy improvement over the industry high reference oil HR‐4 is achievable with today's motor oil technology2Hydrodynamic friction losses in 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%.3Friction losses in the elastohydrodynamic (EHD) 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/high‐shear/high‐pressure viscosity, pressure‐viscosity coefficients) are important.4Increasing fuel economy improvement is in general in the order: SAE 10W–40

ISSN:0954-0075    

DOI:10.1002/ls.3010050402

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractTesting lubricants for fuel economy is a significant part of the drive for energy conservation. Generally, the small differences in fuel economy between lubricants make measurements inherently uncertain. Furthermore, precise engine tests for assessment of energy efficiency are expensive and time consuming. There has been a need, therefore, for the development of an effective laboratory screening technique to assess the energy efficiency of engine oils. With this objective in view, a new test technique consisting of two different tests has been developed for measuring lubricant‐related fuel economy.Fuel economy through the use of engine oil is achieved by reducing boundary friction and viscous friction. Whereas reduction in boundary friction is obtained through the use of friction modifiers in engine oil, viscous friction is reduced through the use of low viscosity oils and by multigrading.The efficacy of action of friction modifiers in reducing boundary friction has been assessed with a SRV‐Oscillating Friction and Wear Tester, using point and piston ring/liner segment contact. For the measurement of viscous friction, an attempt has been made to find out the reduction in viscous friction by using low viscosity oils and multigrade oils on a SAE No. 2 Machine, with all‐steel clutch p

ISSN:0954-0075    

DOI:10.1002/ls.3010050403

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractAn analysis of the rheological properties of various oils and their formulations with selected rheological additives (Visconyl‐200 and ECA‐6911) was performed. Base oils (OS and OU) obtained on a large laboratory scale were the primary subject of the investigation. They were produced according to classical and modified base oil technologies. The modification introduced an additional process of mild oxidation of atmospheric residue before vacuum distillation. Other oils, such as aromatic and saturated hydrocarbons separated from the OS and OU oils, as well as oil fractions (1S–5S and 1U‐5U) obtained from the base oils by vacuum distillation, have also been investigated.Using the rheological properties determined for the distillate oil fractions formulated with the Visconyl and ECA additives, the empirical formulae describing the dependence of kinematic viscosity v50, cand v100, cand of the pour point of the compositions, on the basic physico‐chemical properties of the base oils, and on the type and concentration of additive, have been found. The theoretical viscosity index values of the oil compositions were also characterised indirectly by using the empirical formulae describing kinematic viscosities of the compositions at 50 and 100°C. The formulae obtained were successfully tested with several selected

ISSN:0954-0075    

DOI:10.1002/ls.3010050404

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper discusses deep disconnected cavities (DDC), a concept first introduced by the author. Disconnected shallow cavities or pockets have been treated by other authors, but the consequences of the extreme depths involved with DDC have not been recognised. The introductory paper established the existence of DDC effects. The latter are partly expressible as a slightly modified Reynolds equation, in which the film thickness function refers to the local minimum rather than the local mean customary in roughness analysis. In addition, the equation involves modifying factors which are independent of film thickness and other aspects of the macro‐geometry of the bearing, generating what may be interpreted as effective viscosities. The present paper establishes, by numerical studies, more exact expressions for the effective viscosities for a certain class of cavity geometry and distribution. The interaction of macro‐ and micro‐geometry is studied, showing that the optimisation of the cavity distribution depends on the macro‐geometry of the bearing. It is further shown, by a combination of analytical and numerical means, that the minimum frictional coefficient obtainable for a DDC bearing is that of its smooth counterpart when the two are running at the same minimum film thickness. If the two are lubricated by the same fluid and take the same load, a well‐designed DDC bearing will have a lower coefficient of friction than a similar s

ISSN:0954-0075    

DOI:10.1002/ls.3010050405

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe use of oil‐soluble organo‐molybdenum compounds in engine oils can help in fuel conservation by reducing engine friction and increase durability by improving wear characteristics. The tribological behaviour of molybdenum dialkyldithiophosphate (MoDDP) was studied with a SRV Optimal tester under reciprocating sliding conditions. The studies were conducted under nonconformal contact conditions on En‐31 steel and conformal contact conditions on piston ring and liner materials. The results indicated that the frictional behaviour of these additives is shear sensitive. Shear sensitivity is influenced by materials, operating conditions and the interaction of MoDDP with additives present in the oil. MoDDP when used in base oil was found to increase the scuff resistance of ring and liner materials. The use of the additive reduced friction and wear (running in as well as normal) under nonconformal contact conditions, while under conformal contact conditions its effect was selective and li

ISSN:0954-0075    

DOI:10.1002/ls.3010050406

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0954-0075    

DOI:10.1002/ls.3010050401

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY