A Dynamic Theory of Piston-Ring Lubrication : 1st Report, Calculation

Near the TDC of the expansion stroke, the piston-ring speed is 0 and its load and temperature reach the maximum. If it were based on the steady-flow-hydrodynamics, the oil-film between the ring and the cylinder would have to be broken down. In practice, however, the fluid-film lubrication is achieved in the high speed region. These phenomena can be explained by a dynamic theory of the hydrodynamics, the pistion-ring speed and load vary so extremely that the oil-film thickness changes rapidly, and this rate of change in the oil-film thickness generates a load carrying capacity by the squeez action. This paper introduces the equations of the above-mentioned theory, and some calculations are carried out for a ring, the surface profile of which consists of the quadratic and the parallel line.