| dc.description.abstract | Three flexure pivot pad bearings (FPBs) with different preloads are evaluated for
use in high performance applications by comparing them to a hybrid hydrostatic bearing
(HHB). One application of these bearings is in turbopumps for liquid rocket engines.
To evaluate bearing performance, the lift-off speed of the shaft from the bearing surface
is experimentally determined. Experimental data of lift-off are collected using a circuit
running through the shaft and the designed bearing. Other methods for measuring liftoff
speeds were attempted but did not yield consistent results. Water is used as a
lubricant to simulate a low viscosity medium.
In comparison to load-capacity-based predictions for FPBs, the experimental
results showed lower lift-off speeds, higher load capacities, higher eccentricity ratios,
and lower attitude angles. The bearings’ predicted load capacity determined lift-off
speed predictions, but the experimental results show no clear trend relating lift-off speed
to load capacity. This was for a range of running speeds, with the design speed defined
as the final speed in a particular test case.
At 0.689 bar supply pressure and for a design speed of 3000 rpm, the HHB
showed greater load capacities and lower eccentricities than the FPBs, but the FPBs had
lower lift-off speeds and attitude angles. In fact, the FPBs in the load-between-pad
orientation outperformed the HHB in the load-on-pocket orientation with lower lift-off
speeds for the shaft weight-only case. An increased supply pressure lowered the lift-off
speeds in the HHB tests. If the load in the bearing application remains relatively small, a
FPB could be substituted for an HHB. | en |
