Abstract

A series of journal bearing tests were conducted to acquire more detailed information on the behavior of individual pads in a tilting pad journal bearing and how the individual behavior may affect the performance and dynamic characteristics of the bearing. Load cells, proximity probes, and an array of capacitance and temperature probes were installed to measure pad motion, oil films, and hydrodynamic film forces of the individual pads. The test program was initiated to study differences in journal bearing designs, such as evacuated vs. flooded operation.

Unique information regarding the oil films and hydrodynamic forces were acquired during the course of the tests. Two results are particularly interesting. First, the oil films tend to cavitate at the axial edges in the case of insufficient flow rather than starve the leading edge (a typical assumption in direct lube bearing code development). Second is a tendency for an increase in temperature towards the axial edge rather than the centerline of the pad surface.

The side cavitation and increased temperature were difficult to envision until a recently published computational fluid dynamics (CFD) analysis of an elliptical bearing predicted similar behavior. The authors decided to collaborate on applying the CFD analysis to the tilt pad experimental test results, results of which are presented in this paper. The CFD method used was a multiphase fluid-structure interaction (FSI) analysis that accounts for: thermal conduction between the pads, the journal and the lubricant; tilting of the pads and loaded position of the staff; and phase distributions of air and lubricant within the film. Deformation is ignored in this work as the load was relatively low. The analysis was conducted in ANSYS CFX.