The motion of a ring pack an oil film covering the cylinder liner has been considered. In the paper, equations, a numerical method, algorithm of solution and results of numerical simulations of this phenomena have been presented. The model presented takes into account hydrodynamic, spring and gas forces acting on each ring. The cases of motion with full and partial wetting of ring land have been considered. The influence of engine rotational speed, ring land curvature, oil viscosity on individual rings radial motion and oil film thickness have been analysed. The results of the calculations have been presented in graphical form.

In the paper, the author analyses a model of a ring pack motion on an oil film. The local thickness of the oil film can be compared to the height of the combined surface roughness of a cylinder liner and piston rings. Equations describing the mixed lubrication problem based on the empirical mathematical model formulated in works by Patir, Cheng [6, 7] and Greenwood, Tripp [3] have been combined [13] and used in this paper. A model of a gas flow through the labyrinth seal of piston rings has been developed [14,16]. In addition, models of ring twist effects and axial ring motion in piston grooves have been applied [15,16].

In contrast to the previous papers of the author, an experimental verification of the main parts of developed mathematical model and software has been presented. A relatively good compatibility between the experimental measurements and calculated results has been achieved.

The motion of a ring pack on a thin oil film covering a cylinder liner has been analysed. In contrast to the previous paper [8], which considered only hydrodynamic phenomena, in the present paper a mixed lubrication case is also taken into account. Equations describing the mixed lubrication problem based on the empirical mathematical model formulated in works of Patir, Cheng [5], [6] and Greenwood, Trip [2] have been combined and used in this paper. Results of numerical simulations of this phenomenon have been presented. The model of ring motion considered takes the following phenomena into account: hydrodynamic and contact forces, spring and gas forces and the local motion of each ring in piston grooves. Differences between the motion of the ring on a thick and thin oil film are analysed and discussed.