On Liquid Film Pressure Sealing

The dynamics of the thin film established, by oil injection, on the inside wall of the casing in certain rotary compressors are analyzed both experimentally and theoretically. The film may provide an effective pressure seal to prevent leakage of air from one side of a rotor lobe to the other. It is found that Reynolds’ bearing theory, corrected for Reynolds number and surface tension effects, gives reasonable results for the film thickness needed to sustain typical operational pressure differences in the machine. The theoretical predictions have been verified experimentally in a series of tests performed in a specially designed apparatus.