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The engine power losses and sealing behaviour through compression rings have become a priority for engine manufactures in view of future stringent emissions standards. Historically, compression rings have great application in small road vehicles and high-performance engines. The sealing behaviour of the compression ring has a significant effect on generated friction. Therefore, the lubrication conditions in the compression ring-liner conjunction should be addressed. This study comprises ring-liner mixed hydrodynamics using a two-phase flow and a gas blow-by model. This is implemented to investigate the characteristics of a high-performance top compression ring for different engine conditions. Low, medium, and high driving speeds are examined according to world-wide harmonized light vehicles test cycle. Additionally, the impact of lubricant temperature and compression ring width on power loss and fuel consumption are investigated to display the better engine performance. [ABSTRACT FROM AUTHOR]

Here we consider melting of an ultrathin lubricant layer between two atomically smooth solid surfaces taking into account the stress dependence of the lubricant shear modulus and its decrease with increasing stress (strain). In the adiabatic approximation with the stress relaxation time far longer than strain and temperature relaxation times, a Langevin equation is written and its respective Fokker-Planck equation is derived using the Stratonovich calculus. Phase diagrams for the steady case are presented illustrating the effect of the system parameters on the lubricant behavior. A joint numerical and analytical analysis demonstrates a very close match between probability distributions at different parameters. It is shown that in a limited stress range, a self-similar mode of dry friction is established showing up in self-similar behavior of stress time series. [ABSTRACT FROM AUTHOR]

The paper deals with the design of the bearing assembly slide bearing crank pin of the crankshaft of boosted diesel engines. Selecting bearing diametrical clearance is an important matter in the design of the bearing assemblies. Then the assigned values clearances are checked with the help of the bearing and oil consumption hydrodynamic parameters of calculations. The magnitude of the clearance is one of the main indices. The final selection of clearance magnitude is carried out after the experimental operation or special experimental studies in case the latter is done. [ABSTRACT FROM AUTHOR]

The article presents experimental data on the influence of the roughness and the load on the mechano-chemical processes at the boundary sliding friction. It was found that the use of electrometric method for assessment of the mechano-chemical processes occurring in the frictional contact area allows one to determine the duration of plastic and elastic-plastic deformation and the electrical conductivity, and the product of these indicators was suggested to be taken as a criterion for anti-wear properties of lubricants allowing to estimate their propensity to form protective boundary layers. [ABSTRACT FROM AUTHOR]

This article describes the friction characteristics of zinc dialkyldithiophosphates (ZnDTPs) with different hydrocarbon moieties. A newly developed tribometer was used for the precise measurement of friction by alteration of the sliding speed from ultra-low to moderate. Four types of ZnDTPs (sec-C3C6, sec-C6, prim-C8, and prim-C12) were used as additives to measure friction between steel surfaces. Several phosphorus compounds were used as references. Auger electron spectroscopy analysis and micro-FT-IR reflection adsorption spec-troscopy analysis were employed to elucidate the chemical composition and chemical structure of tribochemically reacted films on steel surfaces. The results demonstrated that a remarkable difference between friction characteristics was observed among four ZnDTPs with different hydrocarbon moieties and that friction decreased with increasing alkyl chain length of ZnDTPs at lower speeds. These results accounted for the observation that the friction characteristics of ZnDTPs were influenced by their respective hydrocarbon moieties. [ABSTRACT FROM AUTHOR]