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This research follows closely previous findings in flow characteristics and phenomena that take place in the piston ring and cylinder liner interface during motoring and firing engine operation, and also compares results between different optical engine set-ups. Cavitation visualisation in a simulating lubrication single-ring test rig and oil transport and cavitation visualisation in custom made cylinder assemblies of optical engines are the tools used to quantify the transport process under the piston ring and cylinder liner. Simplification of the interface is an essential technique that enhances the researcher's confidence in results interpretation. Engine complexity and severe oil starvation are impeding the analysis of the experimental results. Visualisation experiments constitute an effective way to test various lubricant types and assess their overall performance characteristics, including their properties and cavitation behaviour. The repeatability of the visualisation method establishes the parametric study effects and offers valuable experimental results. As a further step towards the lubricant composition effect, a link between the lubricant formulation and the operating conditions could be established as the oil performance is assessed with a view to its transport behaviour. Image processing is used to quantify the impact of cavitation on piston ring lubrication in conjunction with varied operating and lubricant parameters. The characteristics of the lubricant and the working environment have an impact on these types of cavities. Viscosity, cavitation, oil film thickness (OFT), lubricant shear-thinning characteristics and friction are all linked. [ABSTRACT FROM AUTHOR]

The lubricated interface at the piston-ring and liner and its interaction with different lubricants and testing conditions is examined in terms of experimental measurements that show the minimum oil film thickness developed at the lubricated or depending on conditions partly lubricated conjunction and the surface interaction intensity, as measured from the friction sensor. An analysis is carried out with the use of different parameters for the experiments as well as different lubricants in a simplified piston-ring simulation test rig. This analysis is further enhanced with the squeeze film effect investigations close to the stroke reversals and together with cavitation initiation and load-carrying effect results from previous experimental data, light is shed on the interacting surface's behaviour at the different lubrication regimes. Another parameter, the viscosity index of the lubricant is used as an indication of the effects of squeeze film shift and friction force measurements and how the load and temperature effect are influencing the squeeze film. [ABSTRACT FROM AUTHOR]

The importance of these investigations lies to the combination of experimental results with cavitation initiation investigations and its development after the dead centers of the stroke as well as rheological behavior of different chemical additives with a view to establishing the likely performance gains in new lubricant formulations. Lubricant formulation plays an important role because at higher temperatures lubricant additives have a different interaction with contacting surfaces and in this manner the resulting effect of asperity contact is either increased or reduced. [ABSTRACT FROM AUTHOR]

The laser-induced fluorescence technique is based on the excitation of molecules of a fluorescent material by a light source. The main advantage of this technique is that it has the potential to quantify the lubricant film thickness throughout the cycle. Similar to all the other optical techniques, it has this major advantage compared to the electrical techniques where the oil film can be measured only under the piston rings. In this work, experimental data from a simulating single-ring test rig are presented and further parametric analysis is given regarding cavitation in lubricants that was, at first, in the case of the single-ring test rig, evident in laser-induced fluorescence measurements. Different lubricants are used for the laser-induced fluorescence experiments and the different laser-induced fluorescence signals are analysed and interpreted compared to their physical and chemical properties and, furthermore, with the aid of imaging through a glass liner, a clearer picture is given regarding the cavitation shapes together with the respective laser-induced fluorescence measurements and cavitation initiation. [ABSTRACT FROM AUTHOR]

Oil film pressure, the driving force behind piston-ring lubrication phenomena, is measured in a single piston-ring simulating rig after the successful installation of a miniature pressure transducer. The partition of overall load-carrying capacity between direct surface interaction and hydrodynamic action is clearly of some significance if the characteristics of the piston seal are to be understood and predicted with any confidence. It is therefore important that the contribution of the fluid film lubrication to load support be adequately represented. This study presents an extensive load, speed, temperature and piston-ring curvature parametric study on how the measured pressure profile at mid-stroke is affected in terms of peak pressure, magnitude and shift in the trailing edge of the piston ring, taking into account cavitation appearance and lubricant viscosity variation. [ABSTRACT FROM AUTHOR]