Journal
INTERNATIONAL JOURNAL OF ENGINE RESEARCH
Volume 23, Issue 7, Pages 1144-1158Publisher
SAGE PUBLICATIONS LTD
DOI: 10.1177/14680874211008007
Keywords
New optical engine design; lubricant flow; piston ring-liner interaction; cavitation; high-speed CCD visualisation
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The new optical engine design successfully produced high-quality images of lubricant flow, cavitation formation, and development at different engine speeds and lubricant temperatures. Results showed that in-cylinder pressure and lubricant temperatures had significant effects on cavitation formation and distribution. Increasing the engine speed also impacted the extent of cavitation, with a notable increase in cavitation area as the speed increased.
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 degrees C-70 degrees 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 degrees 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.
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