Seal for a joint or juncture – Seal between relatively movable parts – Brush seal
Reexamination Certificate
1998-11-30
2001-07-10
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Brush seal
C277S305000, C277S307000, C160S040000
Reexamination Certificate
active
06257588
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to seals, and, more particularly, to a brush seal for a rotary machine.
Rotary machines include, without limitation, turbines for steam turbines and compressors and turbines for gas turbines. A steam turbine has a steam path which typically includes, in serial-flow relationship, a steam inlet, a turbine, and a steam outlet. A gas turbine has a gas path which typically includes, in serial-flow relationship, an air intake (or inlet), a compressor, a combustor, a turbine, and a gas outlet (or exhaust nozzle). Gas or steam leakage, either out of the gas or steam path or into the gas or steam path, from an area of higher pressure to an area of lower pressure, is generally undesirable. For example, gas-path leakage in the turbine or compressor area of a gas turbine, between the rotor of the turbine or compressor and the circumferentially surrounding turbine or compressor casing, will lower the efficiency of the gas turbine leading to increased fuel costs. Also, steam-path leakage in the turbine area of a steam turbine, between the rotor of the turbine and the circumferentially surrounding casing, will lower the efficiency of the steam turbine leading to increased fuel costs.
Annular brush seals have been used, or proposed for use, between a rotor and a surrounding casing (i.e., stator casing) in gas and steam turbines. A gas or steam turbine brush seal is made up of circumferentially-arrayed brush seal segments. Each brush seal segment includes a plurality of flexible, metal-wire bristles attached to (e.g., welded to) a metal bristle holder which has a shape of an annular segment of a circular ring. The bristle holder has a fixed radius and a fixed circumferential length corresponding to the radius and circumferential length of the surface groove of the annular casing segment into which the bristle holder, with attached bristles, is inserted. The bristle holder may include a backing plate positioned between the bristles and the lower-pressure side of the seal with the free ends of the bristles radially-inwardly-extending beyond the radially-inward end of the backing plate.
BRIEF SUMMARY OF THE INVENTION
In a first embodiment, a brush seal of the invention includes manually-flexible, plastic-containing, brush-seal bristles and an elongated bristle holder. The bristles each have a fixed end and a free end. The fixed ends of the bristles are fixedly-attached to the bristle holder. In one construction, the bristle holder is manually flexible and hand-tool-cutable with the bristle holder and the bristles together being a monolithic unit and with the bristle holder with the fixedly-attached bristles being manually flexible to a shape of a multi-turn coil.
In a second embodiment, a rotary machine of the invention includes a rotor, stator casing segments, and brush seal segments. The rotor has a longitudinal axis. The stator casing segments are circumferentially arrayed together creating a stator casing which is generally coaxially aligned with the axis and which circumferentially surrounds and is radially spaced apart from the rotor. Each stator casing segment has a surface groove which together create a circumferential channel which is generally coaxially aligned with the axis and which is open to the rotor. Each brush seal segment includes manually-flexible, plastic-containing, brush-seal bristles and an elongated bristle holder. The bristles each have a fixed end and a free end. The fixed ends of the bristles are fixedly-attached to the bristle holder. The bristle holder is positioned in the surface groove of a corresponding stator casing segment. In one construction, the bristle holder is manually flexible with the positioned bristle holder being in a flexed state, and the bristle holder is hand-tool-cutable to a circumferential length with the positioned bristle holder having a hand-tool-cut circumferential end.
Several benefits and advantages are derived from the invention. It is noted that most plastics are electrically non-conductive and such plastic bristles can be used in applications in electrical generators for which prior-art brush seals were unsuitable. A flexible and hand-tool-cutable bristle holder allows the brush-seal to be wound with multiple turns on a spool, taken to the location of an existing rotary machine needing seal replacement, and then cut to the required circumferential length and flexibly inserted into a surface groove of arbitrary radius whereas prior-art brush seal segments were individually made at the factory to a specific radius and circumferential length. A monolithic plastic brush seal allows, in effect, the bristles to be created from an enlarged bristle holder and avoids the prior art difficulties of attaching the fixed ends of distinct bristles to the bristle holder.
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“Brush Seal Segment”, N.R. Turnquist et al, SN #09/131/485, filed Aug. 10, 1998, RD-26196.
“Brush Seal For Use On Rough Rotating Surfaces”, CE Wolfe et al, SN #08/942,887, filed Oct. 2, 1997, RD-25545.
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“Anti-Hysteresis Brush Seal”, NA Turnquist et al, SN #08/928,114, filed Sep. 12, 1997, RD-25199.
Aksit Mahmut Faruk
Bagepalli Bharat Sampathkumaran
Mayer Robert Russell
General Electric Company
Ingraham Donald S.
Knight Anthony
Stoner Douglas E.
Williams Mark
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