Lift-off performance in flexure pivot pad and hybrid bearings

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Title: Lift-off performance in flexure pivot pad and hybrid bearings
Author: Mertz, David Hunter
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 .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -3197
Date: 2009-05-15

Citation

Lift-off performance in flexure pivot pad and hybrid bearings. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -3197 .

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