Abstract
The contribution of internal friction in the boundary layer flow of lube oil feed grooves to the power loss of high-speed journal bearings is a function of the rotor speed and the flow regime in which the bearing operates. The literature shows that the portion of power loss in the groove region can exceed 30% of the overall power loss. This paper investigates the impact of gas phases in the feed groove region on the reduction of the internal friction in the lubricant. For this purpose, existing measurement data for two fixed-pad bearings with different bore geometries is evaluated for different lubrication conditions including flooded lubrication of all grooves and a deactivation of the oil supply in one groove. The latter configuration involves a significant reduction of measured power loss with increasing bearing unit load. Comparisons with thermo-elasto-hydrodynamic (TEHD) calculations indicate that the partial filling of deactivated lube oil feed grooves leads to a significant reduction of frictional power loss. Different approaches for the theoretical approximation of the impact of the gas phase in the groove region are investigated and validated with the test data to provide improved understanding of friction in high-speed bearings.
