An investigation into the oil transport and starvation of piston-ring pack

In order to accurately predict the lubricant film thickness and generated friction in any tribological contact, it is important to determine appropriate boundary conditions, taking into account the oil availability and extent of starvation. This paper presents a two-dimensional hydrodynamic model of a piston ring pack for prediction of lubricant film thickness, friction and total power loss. The model takes into account starvation caused by reverse flow at the conjunctional inlet wedge, and applied to a ring-pack, comprising a compression and scraper ring. Inlet boundaries are calculated for an engine cycle of a 4-cylinder, 4-stroke gasoline engine operating at 1500rpm with conditions pertaining to the New European Drive Cycle (NEDC). The analysis shows that the two main sources of starvation; firstly due to a physical lack of inlet meniscus and secondly due to reverse flow at the inlet wedge, significantly affect the prevailing conditions from the generally assumed idealised boundary conditions. Such an approach has not hitherto been reported in literature.