Effect of friction force between piston rings and liner: a parametric study of speed, load, temperature, piston-ring curvature, and high-temperature, high-shear viscosity

Efficient engine operation is combined with effective lubrication in the ring/cylinder interface. On the one hand, there should be enough lubricant on the surfaces and, on the other hand, the lubricant contribution to combustion and, thus, to hydrocarbons and particulate emissions should be minimized. These requirements present a challenge to formulate new additives that would enable the lubricant to operate in the demanding circumstances inside the internal combustion engine and at the same time contribute to an environmentally friendly operation. This study is focused on parametric friction force measurements, their appearance close to the dead centres of the stroke, and how load, speed, and temperature affect the friction maxima. An approach is also attempted to the role of high-temperature, high-shear viscosity for a group of CASTROL lubricants. Piston rings with different curvatures were also tested, and friction power losses for each testing case are presented.