Abstract
Hybrid bearings (combinations of hydrostatic and hydrodynamic bearings) represent an attractive alternative to ball bearings for use in high-speed cryogenic turbopumps. However, the internally-developed cross-coupled forces can generate instabilitiesand are responsible for a speed limitation of the machine. To reduce the cross-coupledforces and raise the onset speed of instability, the use of deliberately-roughened stators has been proposed, and already successfully tested for liquid "damper" seals. This thesis presents experimental as well as theoretical static and dynamic results for a five-pocket orifice-compensated hole-pattern-land hybrid bearing. Experimental data show a significant improvement in stability compared to a smooth hybrid bearing, resulting in an elevation of the onset speed of instability. Poor correlation is found with a code developed by San Andres (I 994), especially for the direct and cross-coupled stiffness predictions. The use of the Moody friction-factor model is thought to be mainly responsible for these mediocre predictions, since it does not correctly account for the clearance influence on the friction factor.
Fayolle, Patrice Gerard (1997). Rotordynamic evaluation of a roughened-land hybrid bearing. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1997 -THESIS -F39.