Experimental study on multi-decked protuberant foil thrust bearing with different number of thrust pads

Thrust bearing is an important component in high speed rotor bearing system. For the thrust bearing, the pad circumferential partition is recognized as an essential factor for the foil thrust bearing in hydrodynamic lubrication. In this paper, performances of multi-decked protuberant foil thrust bearing (MDPFTB) with different pad numbers were experimentally studied on a thrust bearing test rig. Static deflection, transient start-up and transient loading performance of the thrust bearings of 3 pads, 4 pads and 6 pads were compared. The test results indicated that partition of thrust pad had a significant effect on the static and transient loading characteristics of the bearing. Radial vibration of the rotor-bearing system was coupled with the axial thrust bearing support condition. The axial supporting had limited effects on the lower order critical speeds in the radial direction. However, in higher speed range, more thrust pads could increase the second and higher critical speeds and suppress the vibration amplitude. The ultimate load capacity of the bearing increased with thrust pads. However, the available operational speed range was narrowed down. For the bearing with more thrust pads, load capacity decreased earlier in high speed range with softer static stiffness. The results may provide some design guides for application of protuberant foil thrust bearing.