Rotary kinetic fluid motors or pumps – Bearing – seal – or liner between runner portion and static part – Resilient – flexible – or resiliently biased
Reexamination Certificate
1999-12-15
2001-10-16
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Bearing, seal, or liner between runner portion and static part
Resilient, flexible, or resiliently biased
C415S230000
Reexamination Certificate
active
06302646
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to rotary machines, and more particularly to a rotary machine having a brush seal.
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 proposed for use between a rotor and a surrounding casing in gas and steam turbines. The annular brush seal is made up of circumferentially-arrayed brush seal segments. Each brush seal segment is attached to the casing and includes a back (i.e., downstream) plate, a front (i.e., upstream) plate, and bristles which are positioned between the back and front plates with the free end of generally each bristle extending beyond the edges of the back and front plates. The bristles typically are canted at an angle of generally forty-five degrees in the direction of rotation of the rotor, and the free ends of the bristles are close to (and may even touch) the rotor. Typically, the front plate (and in some designs also portions of the back plate), near the free ends of the bristles, is spaced apart from the bristles to allow room for the bristles to flex and recover during transient encounters of the free ends of the bristles with the rotor.
Known rotary machine designs include a design having a stepped rotor, a first brush seal downstream of the step, and, in one example, a second brush seal upstream of the step. Applicants found that gas flow passing the step would swirl, and some of such flow would swirl between the front plate and the bristles of the first brush seal causing bristle flutter (i.e., instability) which quickly wore the bristles and lead to premature brush seal failure. Also, when there is turbulent gas flow upstream, some of such flow can swirl between the front plate and the bristles of the second brush seal causing bristle flutter which quickly wears the bristles leading to premature brush seal failure. What is needed is a design for a rotary machine which reduces bristle flutter in a brush seal located near a stepped area of the rotor.
BRIEF SUMMARY OF THE INVENTION
In a first expression of an embodiment of the invention, a rotary machine includes a rotor, a stator, and a first brush seal. The rotor has a longitudinal axis and an outer surface. The outer surface includes longitudinally extending first and second sections and a third section located longitudinally between, and connected to, the first and second sections. The first section is disposed upstream from the second section. The second section has a smaller radius than the first section, and the third section has at least one area located radially between the first and second sections and facing in a direction other than perpendicular or parallel to the axis. The stator circumferentially surrounds the rotor. The first brush seal is attached to the stator, has radially-inwardly-extending front and back plates, and has bristles positioned longitudinally between the back and front plates. The front plate has a radially inner edge and a portion extending to the edge with the portion longitudinally spaced apart from the bristles. The back plate is located longitudinally further downstream from the third section of the outer surface of the rotor than is the front plate, and the bristles have free ends positioned near the second section of the outer surface of the rotor.
In a second expression of an embodiment of the invention, a rotary machine includes a rotor, a stator, a first brush seal, and a second brush seal. The rotor has a longitudinal axis and an outer surface. The outer surface includes longitudinally extending first and second sections and a third section located longitudinally between, and connected to, the first and second sections. The first section is disposed upstream from the second section. The second section has a smaller radius than the first section, and the third section has at least one area located radially between the first and second sections and facing in a direction other than perpendicular or parallel to the axis. The stator circumferentially surrounds the rotor. The first brush seal is attached to the stator, has radially-inwardly-extending first front and first back plates, and has first bristles positioned longitudinally between the first back and first front plates. The first front plate has a first radially inner edge and a first portion extending to the edge with the first portion longitudinally spaced apart from the first bristles. The first back plate is located longitudinally further from the third section of the outer surface of the rotor than is the first front plate, and the first bristles have first free ends positioned near the second section of the outer surface of the rotor. The second brush seal is attached to the stator, has radially-inwardly-extending second front and second back plates, and has second bristles positioned longitudinally between the second back and second front plates. The second front plate has a second radially inner edge and a second portion extending to the edge with the second portion longitudinally spaced apart from the second bristles. The second front plate is located longitudinally further upstream from the second section of the outer surface of the rotor than is the second back plate, and the second bristles have second free ends positioned near the first section of the outer surface of the rotor. The second portion of the second front plate at the second radially inner edge has a ledge projecting generally away from the second bristles.
Several benefits and advantages are derived from the invention. In the first and second expressions of an embodiment of the invention, as shown by engineering analysis, the shape of the third section of the outer surface of the rotor (which acts to smooth the radial gap between the first and second sections of the outer surface of the rotor) reduces swirl in the gas flow approaching the first brush seal. This reduces swirl between the first front plate and the first bristles which reduces bristle flutter resulting in less bristle wear and increased seal life for the first brush seal. In the second expression of an embodiment of the invention, as shown by engineering analysis, the ledge of the second portion of the second front plate of the second brush seal acts to channelize gas flow reducing swirl in any turbulent gas flow found upstream near the first brush seal. This reduces swirl between the second front plate and the second bristles which reduces bristle flutter resulting in less bristle wear and increased seal life for the second brush seal.
REFERENCES:
patent: 5192084 (1993-03-01), Norbury
patent: 5400952 (1995-03-01), Hetico et al.
patent: 5961280 (1999-10-01), Turnquist et al.
patent: 5971400 (1999-10-01), Turnquist et al.
patent: 6010132 (2000-01-01), Bagepalli et al.
patent: 6139019 (2000-10-01), Dinc et al.
patent: 6168377 (2001-01-01), Wolfe et al.
patent: 6173958 (2001-01-01), Dinc et al.
“Brush Seal Segment”, filed Aug. 10, 1998, S.N. 09/131,485.
“Seal Assembly and Rotary Machine Containing Such Seal”, Jun. 8, 1999, S
Albers Robert Joseph
Dinc Osman Saim
Dogu Yahya
Zhou Ming
General Electric Company
Look Edward K.
McAleenan James M.
Patnode Patrick K.
Stoner Douglas E.
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