Bridging macroscopic lubricant transport and surface tribochemical investigations in reciprocating engines

Abstract

Engine design studies are often conducted with one of two distinct focuses on two different scales: overall engine analysis or localized surface analysis. However, recent engine research requires a more combined approach. Classical tribological experiments and models have been developed usually for general contacting surfaces under specific operating conditions. They attempt to simulate the actual engine environment, which varies significantly with component design and engine operating conditions. Macroscopic engine studies, on the other hand, yield information pertaining to the overall engine system, such as component dynamics, lubricant flow, pressures, and temperatures. These macroscopic operating parameters serve as boundary conditions to the localized surface or tribochemical problem. This paper discusses the macroscopic oil transport processes in the engine and presents several current engine performance problems, such as in friction reduction, modelling wear with antiwear tribofilms, and minimizing deposit formation and emission of ash-related species. It also illustrates applications of the combined analysis of bulk oil transport in the engine with material surface phenomena and tribochemistry. A specific example involves the oil supply to the piston ring-pack and changes in oil and additive characteristics in that region.

Piston ring–liner lubrication and tribological performance evaluation: A review

“…Wong and his colleagues carried out a study using classical experiments and models to consider the effect of macroscopic operating parameters, instead of component design and operating conditions. 48 Engine component dynamics, lubricant flow rate, lubricant composition and temperature were considered as macroscopic operating factors to evaluate oil availability. The effect of these macroscopic parameters on chemical and rheological oil properties, and consequently on component lubrication and wear rate, was examined.…”

A new asperity interaction model considering transient flash temperature and inhomogeneous distribution of oil viscosity

“…In the regions of TDC and BDC, there is not only fluid-solid interaction but also asperity contact, which is the main source of friction and wear of piston ring and cylinder liner. 1 Hence, the phenomena occurring in mixed lubrication and boundary lubrication are worth of investigating in detail, e.g. an inverstigation of the elastic and plastic deformation of materials.…”