Film Recession in Hydrostatic Thrust Bearings

Abstract

In general, hydrostatic thrust bearings are designed to operate with parallel bearing surfaces and it is assumed that the lubricant film completely fills the bearing clearance. In practice, bearings almost inevitably operate in a tilted condition and this modifies the behaviour of the bearing. In addition, when the surface approaching the bearing under sliding conditions is free of lubricant, recession of the film boundary can occur which further modifies the bearing characteristics. An experimental and theoretical investigation has been undertaken into the behaviour of tilted and parallel hydrostatic thrust pads operating under ‘dry’ sliding conditions. It has been shown that recession of the lubricant film can occur under quite modest operating conditions and that this results in a substantial modification of the bearing characteristics whether the bearing is parallel or tilted. Another feature of film recession revealed by the investigation is that it eliminates the occurrence of cavitation in the film. Boundary recession greatly complicates prediction of the bearing characteristics, but it is shown that this can be carried out successfully giving predicted characteristics that are in reasonable agreement with the experimental data.