Sliding wear under fluctuating load

摘要

In a low speed, two stroke, crosshead marine diesel engines, lubrication between piston ring and cylinder liner at the top dead centre .(TDC) is of the boundary type. When piston is moving from the TDC towards the bottom dead centre, the nature of lubrication between piston ring and cylinder liner is changing from boundary to mixed lubrication and eventually to full fluid film lubrication. Also, the load on the contact is fluctuating due to changeable gas pressure. In order to study wear in the contact between piston ring and cylinder liner under conditions outlined above, a pin-on-eccentric disc testing apparatus was constructed. Both the pin and disc were made of materials actually used in a slow speed, two-stroke, crosshead marine diesel engine. Also, the lubricant used in a real engine was employed in experiments. It was found that the wear of the pin is mainly of delamination type and the wear of the disc is proportional to the load on contact. When sliding speed is relatively high, there is no difference in wear performance for different lubricants. However, when sliding speed is low, the lubricants with a package of additives were found to minimise the wear.