Fundamentals of lubrication and friction of piston ring contact

The piston ring-pack exhibits a complex dynamic behaviour, which includes the dynamics of the rings and related gas flow and oil flows, twisting of the piston rings and its influence on ring-liner and ring-groove lubrication and contact, and unsteady oil supply to upper piston rings and its effects on ring-liner lubrication. These dynamic phenomena play a crucial role in the piston assembly response such as blowby, friction, wear and oil consumption and it is of both theoretical and practical interest to understand and model them. In fact, a significant share of the total power loss in a modern automotive engine is due to the ring pack/cylinder wall friction. On this basis, the lubrication of the piston ring has been an important research matter for many years, because it is generally accepted that the interaction at the ring-cylinder wall interface provides substantial effects on friction, wear, oil consumption and power loss in internal combustion engines. This chapter aims to illustrate the physics of the piston rings lubrication and friction characteristics involving the fundamentals of their role in the complex engine system, the main mathematical and computer models about the theoretical reported investigations. The chapter is completed by a looking into the future trends and opportunities of research on piston ring modelling and improvements to its frictional behaviour