Experimental investigation into surface texture effect on journal bearings performance

Hydrodynamic sliding bearings are designed to operate under fully flooded conditions to enable adequate film formation. In actual operating conditions, journal bearings could operate in a mixed or even boundary lubrication regime, for example, during the start-up/shut-down period. To prevent bearing destruction, a specific surface texture can be created on the sliding zones. One of the roles of surface irregularities is to maintain a certain amount of oil in the case of its shortage. The aim of this study was to identify the characteristic parameters, such as the sliding velocity, Hersey number, and friction torque or friction coefficient, when the transition of lubrication regimes occurs for different journal bearing types. The study demonstrates the results achieved in experimental investigations conducted on journal bearings, with the oil pockets on the journal surface mating with the smooth bearing and with the texture on the bearing surface co-acting with a standard smooth journal. The obtained results were also compared with the tested effects of the classical, smoothly finished journal bearing. It was found that, during shut-down, the textured journal bearings remained in hydrodynamic lubrication for longer and moved to mixed lubrication at lower speeds compared to the smooth journal bearing.