Centrifugal compressors are rotating machines. They are comprised of stationary portions referred to as stators and rotating portions known as rotors. The rotors are supported on journal bearings in the stator. Differential gas pressure in the axial direction along the shaft tends to cause leakage flow along the shaft from higher to lower pressure regions. This leakage flow is detrimental for various reasons. Hence, seals are positioned along the shaft to restrict this leakage flow. In centrifugal compressors, use of labyrinth seals and especially stepped labyrinth seals are well known. Stepped labyrinth seals provide a tortuous path along the shaft minimizing leakage flow. Generally, stepped labyrinth seals comprise a plurality of radial teeth extending from the stator with a small radial clearance at the tips of the teeth as shown in
Another type of seal is known as a damper seal. Damper seals have the ability to exert damping forces on the shaft that attenuate the vibration of the shaft. There are a number of types of damper seals. By in large, damper seals have a larger clearance than labyrinth seals and, therefore, are not as effective at preventing axial leakage flow.
It is an object according to this invention to provide a combination of damper seals and labyrinth seals associated in a way that they do not interfere with each other's function.
Briefly, according to this invention, there is provided an apparatus for restricting axial flow through the clearance between a rotating shaft and a seal stator and providing necessary damping to improve rotor stability. The shaft has a stepped surface with a plurality of sections of a first diameter and a plurality of grooved sections of a second lesser diameter. The sections of first and second diameter are interleaved and adjacent. The seal stator has a plurality of damper seal segments opposite the shaft sections of the first diameter and a plurality of labyrinth seal segments opposite the shaft sections of second diameter. The labyrinth seal segment comprises one or more annular teeth that extend from the stator toward the shaft terminating with a very small clearance.
Further features and other objects and advantages will become clear from the following detailed description made with reference to the drawings in which:
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Having thus described our invention with the detail and particularity required by the Patent Laws, what is desired protected by Letters Patent is set forth in the following claims.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US04/19495 | 6/18/2004 | WO | 11/14/2006 |
Number | Date | Country | |
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60480146 | Jun 2003 | US |