Bearings – Rotary bearing – Plain bearing
Reexamination Certificate
1999-01-29
2001-07-24
Estremsky, Sherry (Department: 3681)
Bearings
Rotary bearing
Plain bearing
Reexamination Certificate
active
06264369
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to bearing assemblies and, more particularly, to bearing assembly materials.
Gas turbine engines generally include a high pressure compressor, a combustor, and a high pressure turbine. Compressed air flows through the engine while fuel is mixed with the compressed air and ignited to form a high energy gas steam in the high pressure compressor and combustor, respectively. The high pressure compressor, combustor, and high pressure turbine are sometimes collectively referred to as a core engine. Such gas turbine engines also may include a low pressure compressor for supplying compressed air, for further compression, to the high pressure compressor, and a fan for supplying air to the low pressure compressor.
The high pressure compressor typically includes a rotor surrounded by a casing. The casing is typically fabricated to be removable, such as by forming the casing into two halves that are then removably joined together. The high pressure compressor includes a plurality of stages and each stage includes a row of rotor blades and a row of stator vanes. The casing supports the stator vanes, and the rotor supports the rotor blades. The stator vane rows are between the rotor blade rows and direct air flow toward a downstream rotor blade row.
Variable stator vane assemblies are utilized to control the amount of air flowing through the compressor to optimize performance of the compressor. Each variable stator vane assembly includes a variable stator vane which extends between adjacent rotor blades. The variable stator vane is rotatable about an axis. The orientation of the variable stator vane affects air flow through the compressor.
A known variable vane assembly includes a variable vane, a trunnion seal, and a washer. The variable vane assembly is bolted onto a high pressure compressor stator casing and the trunnion seal and washer surround an opening that extends through the casing. The variable vane includes a vane stem that extends through the opening in casing and through the trunnion seal and washer. The seal and washer are referred to herein as a bearing assembly. The bearing assembly produces a low friction surface that prevents metal on metal contact. Such variable vane assemblies have possible air leakage pathways through the openings in the casing. Also, the high velocity and high temperature air causes oxidation and erosion of the bearing assemblies, which may lead to failure of fibers within the bearing assembly, and eventual failure of the variable vane assembly.
Once the bearing assembly fails, an increase in leakage through the opening occurs, which results in a performance loss. In addition, failure of the bearing assembly allows contact between the stator vane and the casing, which causes wear and increases overhaul costs of the engine.
Accordingly, it would be desirable to provide bearing assemblies fabricated from materials having performance characteristics that will reduce or eliminate air leakage between the stator vane stem and the compressor casing. In addition, it would be desirable to provide an increase in the durability of the seal and washer composition to increase part life.
BRIEF SUMMARY OF THE INVENTION
These and other objects may be attained by a multi-layer bearing assembly that provides a seal between a vane stem and a casing. In one embodiment, the bearing assembly includes a washer and a seal positioned on the casing to surround an opening. The vane stem extends through the opening and the bearing assembly. Outer layers of each element in the bearing assembly are fabricated from a combination of materials that provide a low coefficient of friction.
The seal prevents the stator vane from contacting the stator casing and prevents air flow from exiting the opening. The washer prevents contact between spacer and the casing and also prevents air flow from exiting the opening. The bearing assembly thus provides two barriers to air flow escaping through the opening in the stator casing.
The seal and washer are fabricated from a combination of materials, such as Teflon fibers and glass fibers impregnated with a polyimide resin, that have desirable performance characteristics and that provide a low coefficient of friction. In addition, the bearing assembly materials significantly improve the service life of the stator vane assembly and reduce air leakage through the opening in the stator casing. Further, the bearing assembly provides an efficiency improvement in the turbine engine while reducing overhaul costs caused by metal on metal contact between the stator casing, the stator vane, and the spacer.
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Bowen Wayne R.
Hester David B.
Mesing Thomas C.
Estremsky Sherry
General Electric Company
Herkamp Nathan D.
Hess Andrew C.
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