Cavitation between cylinder-liner and piston-ring in a new designed optical IC engine

Abstract

A new engine block with optical access has been designed and manufactured capable of running up to 3000 r/min with the same specification as the unmodified engine. The optical window allowed access to the full length of the liner over a width of 25 mm to investigate the lubricant flow and cavitation at contact point between the rings and cylinder-liner. In addition, it allowed good access into the combustion chamber to allow charged flow, spray and combustion visualisation and measurements using different optical methods. New custom engine management system with build in LabView allowed for the precise full control of the engine. The design of the new optical engine was a great success in producing high quality images of lubricant flow, cavitation formation and development at contact point at different engine speeds ranging from 208 to 3000 r/min and lubricant temperatures (30°C–70°C) using a high-speed camera. The results under motorised operation confirmed that there was no cavitation at contact points during the intake/exhaust strokes due to low in-cylinder presure, while during compression/expansion strokes, with high in-cylinder pressure, considerable cavities were observed, in particular, during the compression stroke. Lubricant temperatures had the effect of promoting cavities both in their intensity and covered ring area up to 50°C as expected. Beyond that, although the cavitation intensity increases further with temperature, its area reduces due to possible collapse of the cavitating bubbles at higher temperature. The change of engine speed from 208 to 800 r/min increased cavitating area considerably by 52% of the ring area and was further increased by 19% at 1000 r/min. After that, the results showed very small increase in cavitation area (1.3% at 2000 r/min) with similar intensity and distribution across the ring.

Piston ring performance II: measurement of cavitation shapes in different operating conditions and their link to lubricant properties

“…The Ricardo HYDRA engine test rig was fitted with a purpose-built visualisation window as in the case of the Lister-Petter engine. In this case, firing tests could be conducted (Vasilakos, 2017;Nouri et al, 2021). The engine, modifications and a drawing with the windows sections can be seen in Figure 4.…”

“…Video images captured with two high-speed cameras coupled with three high-intensity light sources were analysed, and the images were post-processed with the aid of a custom-IJSI 13,4 built algorithm to deliver cavitation statistics. The basic function of this algorithm is the extraction of matrices with elements of cavity length, cavity width, area of cavitation and number of cavities present under the piston ring and the cylinder liner (Vasilakos, 2017;Nouri et al, 2021). In this instance, after the initial evaluation of cavitation visualised through quartz sections in a Lister-Petter engine and the attempt to compare the imaging findings to the ones already identified in a simulating single ring test rig (Dellis, 2005(Dellis, , 2017(Dellis, , 2018a(Dellis, , b, 2020, a more detailed and controlled experiment was carried out, with new visualisation tools and a specially made optical internal combustion reciprocating engine.…”

“…Valuable information of lubricant flow properties under the specified circumstances is gathered, which, in turn, leads to understanding of the flow in an ordinary engine piston ring pack, and eventually, to characterisation of the lubricant transport phenomena in the piston ring pack of production engines (Vasilakos, 2017;Nouri et al, 2021) along with a link, via a parametric study, to the effect of lubricant properties in oil film characteristics (Dellis, 2010(Dellis, , 2017(Dellis, , 2020Dellis and Arcoumanis, 2013).…”

“…Special honing tools were used to smoothen out the surface of the cylinder to reach the same surface roughness as the original cylinder block Source(s): Dellis (2018b) of the Ricardo HYDRA engine. It was ensured that the new custom optical engine can stand extreme forces, temperatures and pressures, especially under firing operation, and at the same time, to allow for the thermal expansion and tolerances, which involved the identification of the materials that would be the best fit for the new optical cylinder (Nouri et al, 2021). Another stage is to process the images and move another step towards modifying the cavitation factor (CF), which was initially introduced to compare the Lister-Petter engine results with the ones already derived from the test rig, to the one that will be derived from image processing.…”

“…A single-ring simulating test rig provides the mechanism with the necessary measurement options to contribute to this study (Dellis and Arcoumanis, 2004;Dellis, 2005Dellis, , 2019aDellis, , 2020Vasilakos, 2017). Further on, engine applications in motored and firing engines have been conducted to assess the lubricant flow and compare the simplification study to the real engine results (Vasilakos, 2017;Dellis, 2018b;Nouri et al, 2021).…”