Analysis and computation of the oil film thickness between the piston ring and cylinder liner of an internal combustion engine

Abstract

A study of the essential features of piston rings in the cylinder liner of an internal combustion engine reveals that the lubrication problem posed by it is basically that of a slider bearing. According to steady-flow-hydrodynamics, viz. d dx (h 3 dp dx ) = 6μU dh dx the oil film thickness becomes zero at the dead centre positions as the velocity, U = 0. In practice, however, such a phenomenon cannot be supported by consideration of the wear rates of pistion rings and cylinder liners. This can be explained by including the “squeeze” action term in the hydrodynamic theory, viz. h 3 dp dx = 6μU dh dx + 12V . This article introduces the equations of the above theory along with the viscosity variation over the piston stroke length; the piston ring profile is assumed as a double parabola with a central straight portion. The results of this analysis as applied to internal combustion engines are presented and compared with other earlier analysis.