Operating Characteristics of an Externally Pressurized Gas Lubricated Piston Ring

An analytical model is presented to obtain the film thickness profile of an externally pressurized gas lubricated piston ring which is applied to an air compressor. In order to examine the effects of the ends of the ring, the analysis is based on the two-dimensional, transient, compressible Reynolds equation accounting for the ring deflection and the equilibrium condition of the ring in the clearance space between the piston and the cylinder bore. In the numerical simulation, the Reynolds equation is discretized by using a cell method. The resulting nonlinear system of equations is solved by the Newton-Raphson iteration method. The obtained results show that the piston ring keeps the lubricating film thickness within a narrow range of the design clearance over the entire circumferential area throughout one cycle of compressor operation.