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

Abstract

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 four-cylinder, four-stroke gasoline engine operating at 1500 r/min with conditions pertaining to the New European Drive Cycle. The analysis shows the two main sources of starvation: first, due to a physical lack of inlet meniscus and second, due to reverse flow at the inlet wedge significantly affecting the prevailing conditions from the generally assumed idealised boundary conditions. Such an approach has not hitherto been reported in literature.

Evaluation on the tribological performance of ring/liner system under cylinder deactivation with consideration of cylinder liner deformation and oil supply

“…Furthermore, it should be pointed out that only a portion of oil film supplying to the compression ring-cylinder liner system will be transported into the lubrication zone [ 55 ], and some amount of oil film existing the lubrication zone will be remained at the outlet of the lubrication zone during the operation of the compression ring-cylinder liner system [ 56 ]. Hence, some amount of the oil film will be accumulated at the inlet and outlet of the lubrication zone [ 55 , 56 ].…”

“…Furthermore, it should be pointed out that only a portion of oil film supplying to the compression ring-cylinder liner system will be transported into the lubrication zone [ 55 ], and some amount of oil film existing the lubrication zone will be remained at the outlet of the lubrication zone during the operation of the compression ring-cylinder liner system [ 56 ]. Hence, some amount of the oil film will be accumulated at the inlet and outlet of the lubrication zone [ 55 , 56 ]. In order to predicted the transition between fully flooded and starved lubrication conditions in an engine cycle with consideration of the oil film accumulation, an oil transport model [ 56 ] with front and back control volumes at the inlet and outlet of the lubricated zone is employed to calculate the width of lubrication zone, as shown in Fig 5 .…”

Lubrication Performance of Engine Commercial Oils with Different Performance Levels: The Effect of Engine Synthetic Oil Aging on Piston Ring Tribology under Real Engine Conditions

“…They concluded a thermomixed lubrication model, showing that cavitation flow has a dominant role in load-carrying capacity under high engine speeds. Bewsher et al [16] also observed that oil availability can create starvation in the contact due to the reverse flow and the lack of oil. They found that this effect may lead to increased friction and low lubricant films.…”

Effect of surface texture on the improvement of tribological performance of ring‐deformed liner conjunction under different oil supplies

“…In this case, the ring cannot be completely covered by the oil film in the moving direction (ie, the axial direction). It means that a starved lubrication condition will be encountered in the engine cycle besides the fully flooded lubrication condition . Furthermore, when the ring‐liner conjunction is under the starved lubrication condition, the degree of oil starvation is time‐varying because the oil film supplied to the conjunction is non‐uniformly distributed on the liner and the clearance between the ring and liner is time‐varying .…”

“…Furthermore, during the operation of the textured ring‐liner conjunction, the oil film supplied to the conjunction does not flow into the lubrication zone adequately, and some amount of the oil film will be accumulated at the inlet of the lubrication zone . In particular, when the oil film supplied to the conjunction is sufficient, the leading edge of the textured ring is fully flooded, and the oil film accumulation will be observed at the leading edge of the textured ring (in this case, the inlet of lubrication zone is coincide with the leading edge of the textured ring), as shown in Figure a.…”