Rotor-Bearing System Stability Performance Comparing Hybrid versus Conventional Bearings
New closed-form expressions for calculating the linear stability thresholds for rigid and flexible Jeffcott systems and the imbalance response for a rotor supported on a hybrid bearing are presented. For typical bearings characteristics, expressions yield stability thresholds practically equal to th...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Wiley
2005-01-01
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| Series: | International Journal of Rotating Machinery |
| Subjects: | |
| Online Access: | http://dx.doi.org/10.1155/IJRM.2005.16 |
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| Summary: | New closed-form expressions for calculating the linear
stability thresholds for rigid and flexible Jeffcott systems and
the imbalance response for a rotor supported on a hybrid bearing
are presented. For typical bearings characteristics, expressions yield stability thresholds practically equal to those reported by
Lund (1966). The hybrid bearing design has a single injection
port whose location is so chosen to stabilize the bearing
performance and to reduce the steady equilibrium attitude angle.
Rotordynamics coefficients graphs for conventional and
pressurized bearings, as functions of bearing equilibrium
eccentricity and/or Sommerfeld number, are presented. Using the
rotordynamics coefficients into the expressions for the
corresponding velocity thresholds and the imbalance response, the
system stability and vibration performances are estimated and
analyzed. When comparing the Jeffcott flexible shaft supported on
two journal bearings of the conventional type with the hybrid
type, the results show a clear superiority of the pressurized
design as far as stability behavior is concerned. Specifically
for cases of flexible shafts with similar characteristics to
those used in industry, the analysis shows that this design yields
velocity thresholds 25%–40% higher compared to the
conventional circular ones. Also this bearing displays nonlinear
feeding pressure behavior, and it is capable of reducing the
synchronous vibration amplitude in most speed ranges, except
around the critical speed; moreover, for certain Jeffcott
configurations the amplitude reduction can be substantial. |
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| ISSN: | 1023-621X 1542-3034 |