| dc.description.abstract | The lecture presents measurements of the static and dynamic load performance conducted with a tilting pad journal bearing running under flooded and evacuated conditions and lubricated with flow rates ranging from a nominal rate to over flooded (150% nominal), and then to a starved flow (25% or lesser of nominal). The 102 mm diameter test bearing has four pads; and with single orifice feeds for the flooded condition and spray bar injection for the evacuated condition. The lubricant is ISO VG 46 oil supplied at 60oC. The experiments include operation at two shaft speeds = 6 krpm and 12 krpm (= 64 m/s surface speed) and three applied specific loads = 0.345 MPa, 1.034 MPa and 2.068 MPa. The load is applied between pads (LBP). The lecture compares the measurements procured for the flooded bearing vis-à-vis those for the evacuated bearing and quantifies major similarities and differences. The first bearing configuration has single orifices for lubricant supply in-between pads, while the second bearing has spray bars for oil injection. A reduction in flow rate makes both bearings operate more eccentrically. The bearing under an evacuated condition operates at a larger eccentricity, which for the lowest flow rate (25% or so of nominal) does not align with the direction of the applied load, hence displaying a sizable attitude angle. Pad temperatures are similar for both bearing configurations though the evacuated bearing is colder by a few Celsius degrees and its oil exit temperature is much lower, in particular for the over flooded condition. Drag power losses derived from the oil exit temperatures show the bearing under an evacuated condition produces up to ~ 40% lesser power loss; the reduction is notable for operation with a flow rate 50% larger than the nominal flow. The bearings direct stiffnesses Kxx and Kyy increase with an applied load and show little dependency on shaft speed. The bearing operating as evacuated produces lower magnitude stiffnesses, 20% or so lesser, than the bearing running as flooded. Damping coefficients Cxx ~ Cyy reduce in magnitude as the supplied flowrate decreases; the differences become marked between both bearing configurations as the load decreases. In particular for flow rates at 35% or lower of nominal, the bearing operating as evacuated shows rather small (though highly uncertain) damping coefficients. For Copyright© 2021 by Turbomachinery Laboratory, Texas A&M Engineering Experiment Station 2 sufficiently small flow rates, operation at 6 krpm shaft speed and under the smallest load (0.345 MPa) produced subsynchronous shaft motions with a broad band spectrum (SSV hash). The bearing running evacuated produced SSV hash at flow rates equal to 30% or so of nominal, while the bearing operating as flooded demanded very low flow rates (~15% and lesser of nominal) to produce SSV hash. For both bearings, the SSV amplitude motions were rather small in amplitude. | |
