Measurements to Quantify the Effect of a Reduced Flow Rate On the Performance of a Tilting Pad Journal Bearing (LBP) with Flooded Ends

Operation of tilting pad journal bearings (TPJBs) with a reduced flow improves system energy efficiency by reducing drag power losses, albeit the temperature rise in both the bearing pads and the lubricating oil become a concern. This paper presents measurements of the static and dynamic load performance of a flooded ends TPJB with flowrates ranging from 150% to ~5% of a nominal supply condition. The test bearing is a four-pad, 102 mm diameter, center pivot, with single orifice feeds, and configured with end seals. Experiments include operation at two shaft speeds = 6 krpm and 12 krpm and under three specific loads = 0.345 MPa, 1.03 MPa and 2.07 MPa applied in between pads (LBP). The measurements show the bearing drag power loss decreases by nearly 20% when flow rate drops to 50% of nominal. However, halving the flow produces a raise in pad subsurface temperatures, ~7 °C for operation at 12 krpm. Flow reduction below 50% results in substantial power savings; however, it also produces too hot pad temperatures that approach a known limit for Babbitt material safe operation. Damping coefficients decrease by ~30% as the flow rate decreases from 150% to just a few % of nominal flow. The experimental results are first to quantify operation of a TPJB supplied with minute amounts of lubricant flow. A test with a very low flow rate at ~2% of nominal and under a light load produced the emergence of a broadband subsynchronous vibration frequency, albeit with very small amplitude.