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The emissions control regulations introduced by governments are set to improve engine quality and reduce the impact automobiles have on the planet. The regulations imposed on the manufactures have proven very difficult to meet. To this effect some of the leading names in the industry were pushed to invest significant funding in research, development and optimisation of combustion, powertrain and tribology inside the ICE. Their goal is reduction of fuel consumption and emissions while increasing performance and durability. The piston-ring and cylinder-liner interaction is the major source of frictional losses for reciprocating ICEs and so, it is important to avoid any failure of piston-rings to effectively control lubricant transport from the sump onto the cylinder walls and further to the combustion chamber. This lubricant will participate in the emissions through absorption and desorption of fuel in the oil film at the cylinder walls, also resulting in lubricant contamination and consumption. The objective of this project is to assist with the investigation of phenomena occurring in the cylinder liner and piston-ring interaction under different operating conditions. The following investigations have been carried out, flow and cavitation visualisation in a model lubricant rig and cavitation visualisation in a newly designed optical engine.

Both in engines and test rigs, cavitation in piston-ring lubrication is a subject studied by many researchers in the past. Although there is no sufficient evidence of cavitation erosion on the surface of the liner, this phenomenon is studied as part of the lubricant transport process. During the transport process the lubricant enters the combustion chamber. The combustion products of consumed oil might contribute to exhaust gas emissions and with emission legislation becoming more stringent, it is important that oil consumption is reduced to the lowest level possible. The role of the piston-rings is becoming more complex with the imposed requirements for lower oil consumption and friction. The piston-ring pack role on engine performance, durability and wear, is becoming on the other hand, more demanding. Between the piston-ring and cylinder liner, cavitation occurs as a result of two-phase liquid flow. Cavitation has long been recognized to degrade performances in most engineering applications and its effect in piston-ring lubrication is that it alters the oil film pressure profile, generated at the converging-diverging wedge of the piston-ring. An area of the piston-ring surface is void, corresponds to subatmospheric pressures and thus, the piston-ring load capacity is altered. Two experimental rigs were used, a simplified single-ring test rig that simulates the piston-ring liner movement at speeds corresponding to idle but the movement is reversed and a single cylinder diesel engine that was used for visualization results only, after the necessary modifications.

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 well-established oil condition monitoring tool of spectrometric oil analysis is used to expand previous published experimental analysis with a view to enhancing multiple wear metal elements study in numerous different applications. This study includes gas turbine engines, piston engines, turboprop and turboshaft engines and helicopter gearbox assemblies. The database used in the original study was enhanced with numerous applications that were used to establish the credibility of spectrometric oil analysis as an important diagnostic tool. The importance of the method lies in its ability to locate unusual concentrations of a metal element that is translated as an indication of abnormal wear of the equipment under scrutiny. The operator benefits from major failures avoidance and taking correct decisions regarding equipment maintenance and servicing or repairing, can also profit from economic factors rationality during equipment operation. Lubricant quality, identification or imminent failures, prolonged life cycle and acquisition of statistical data are conditions that emanate from the correct interpretation of the results that in turn, can avoid human lives and equipment losses due to major incidents. [ABSTRACT FROM AUTHOR]