Brush seal segment

Abstract: A brush seal segment (110) useful, when circumferentially arrayed with other such segments, to seal the gap between a rotor and a surrounding casing of a rotary machine such as a steam turbine. An annular backing plate (124) has a rim (140) radially-inwardly bounding together upstream-facing and downstream-facing surfaces (128,130). Canted bristles (150) abut the upstream-facing surface (128). The rim is designed to allow the bristles to recover from a rotor rub. In one design, the rim acts as a labyrinth-seal tooth (146) and is shaped to deform, under a radial force, longitudinally away from the upstream-facing surface. In another design, the rim has a more-inwardly projecting second portion near a radially-aligned edge, and only this second portion acts as a labyrinth-seal tooth.

Description: The present invention relates generally to seals, and more particularly to a brush seal segment. 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 includes an annular backing plate which may terminate in the shape of an annular labyrinth-seal tooth having a sloped downstream-facing surface and also includes bristles which are canted at typically a forty-five degree angle with respect to a radius line. A gas or steam turbine brush seal is made up of circumferentially-arrayed and radially-cut brush seal segments. The angled bristles create an exposed area at one circumferential edge of each segment. The labyrinth-seal tooth reduces leakage through this exposed area. Examples of such brush seals are described in US-A-5,749,584 and US-A-5,401,036. Unfortunately, Applicants have found that radial contact of the labyrinth-seal tooth with the rotor during startup deformed the annular tooth into large circumferential areas of bristles preventing recovery of these bristles once the rotor reached steady-state operating conditions. The unrecovered bristles allowed large leakage. The brush seal segment of the invention includes a brush-seal backing plate and brush-seal bristles. The backing plate has a shape of generally an annular segment of a circular ring which has a longitudinal axis. The backing plate has generally upstream-facing and downstream-facing surfaces with the upstream-facing surface aligned generally perpendicular to the axis. The backing plate has generally radially-aligned first and second edges circumferentially bounding together the upstream-facing and downstream-facing surfaces. The backing plate has a rim radially-inwardly bounding together the upstream-facing and downstream-facing surfaces, wherein the rim has first and second portions, wherein the first portion circumferentially extends from the first edge to the second portion, wherein the second portion is located near the second edge, and wherein the second portion extends radially inward further than the first portion. The bristles generally abut the upstream-facing surface and are each canted at a generally-identical angle with respect to a corresponding radius line extending outward to each of the bristles. The bristles are generally entirely circumferentially contained between a radius line extending outward to the first edge and a radius line extending outward to the second edge, and the bristles extend inwardly beyond said rim from generally the first portion only of the rim. Several benefits and advantages are derived from the invention. Only the small second portion of the rim will deform when the brush seal segment experiences a transient rotor rub. Since generally no bristles extend from the second portion of the rim because of the bristle angle, the deformed rim generally will not interfere with the bristles even if the rim deforms longitudinally toward the upstream-facing surface of the backing plate, and thus the bristles can recover from a rotor rub. Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic upstream-facing view of a first preferred embodiment of the brush seal segment of the invention shown circumferentially arrayed with other identical brush seal segments to define a brush seal; Figure 2 is a cross-sectional view taken along lines 2-2 of Figure 1; and Figure 3 is a cross-sectional view taken along lines 3-3 of Figure 1. Referring now to the drawings, Figures 1-3 schematically show a first preferred embodiment of the brush seal segment 110 of the present invention together with five other identical brush seal segments 112, 114, 116, 118, and 120 all circumferentially arrayed to define an annular brush seal 122. Preferably, the annular brush seal 122 is for use in a rotary machine (not shown in the figures) with the brush seal being disposed in the annular gap between a rotor and a surrounding casing of the rotary machine and with the brush seal being attached to the casing. A preferred rotary machine is a steam turbine or a gas turbine. The brush seal segment 110 includes a brush seal backing plate 124. As seen in Figure 1, the backing plate 124 has a shape of generally an annular segment of a circular ring (e.g., the brush seal 112) having a longitudinal axis 126 (seen on end as a dot in Figure 1 and seen as a dashed line in Figures 2 and 3). The backing plate 124 has generally upstream-facing and downstream-facing surfaces 128 and 130 with the upstream-facing surface 128 aligned generally perpendicular to the axis 126. For the purpose of describing the invention, an upstream-facing surface is defined as a surface which faces generally toward the higher-pressure side 132, and away from the lower-pressure side 134, of the seal segment 110, and a downstream-facing surface is defined as a surface which faces generally toward the lower-pressure side 134, and away from the higher-pressure side 132, of the seal segment 110. The backing plate 124 has generally radially-aligned first and second edges 136 and 138 circumferentially bounding (i.e., attaching) together the upstream-facing and downstream-facing surfaces 128 and 130. The backing plate 124 also has a rim 140 radially-inwardly bounding (i.e., attaching) together the upstream-facing and downstream-facing surfaces 128 and 130. The rim 140 circumferentially extends from the first edge 136 to the second edge 138. The rim 140 has first and second portions 142 and 144. The first portion 142 of the rim 140 circumferentially extends from the first edge 136 to the second portion 144. The second portion 144 is disposed proximate the second edge 138, and the second portion 144 extends radially inward further than the first portion 142. Preferably, the second portion 144 of the rim 140 of the backing plate 124 has a shape of a labyrinth-seal tooth 146 when the backing plate 124 is viewed in a first cross section (see Figure 2) taken by a cutting plane defined by the intersection of the axis 126 and a radius line which extends radially outward (from the axis 126) to the second portion 144. It is also preferred that the first portion 142 of the rim 140 of the backing plate 124 has a shape other than that of a labyrinth-seal tooth when the backing plate 124 is viewed in a second cross section (see Figure 3) taken by a cutting plane defined by the intersection of the axis 126 and a radius line (from the axis 126) which extends radially outward to the first portion 142. In an exemplary enablement, the first portion 142 of the rim 140 of the backing plate 124 has a shape of a line 148 which is generally parallel to the axis 126 when the backing plate 124 is viewed in the second cross section (see Figure 3). The brush seal segment 110 also includes brush-seal bristles 150 generally abutting the upstream-facing surface 128 of the backing plate 124. The bristles 150 are each canted at a generally-identical angle with respect to a corresponding radius line extending outward (from the axis 126) to each of the bristles 150. Preferably, the angle of the bristles 150 is generally forty-five degrees. The bristles 150 are generally entirely circumferentially contained between a radius line extending outward (from the axis 126) to the first edge 136 and a radius line extending outward (from the axis 126) to the second edge 138. Thus, the brush seal segment 110, including its just-described bristles 150 and previously-described backing plate 124, is said to be radially cut. The bristles 150 extend inwardly beyond the rim 140 from generally the first portion 142 only of the rim 140. Thus, generally no bristles 150 extend from the second portion 144 of the rim 140 because of the bristle angle. The brush seal segment 110 of the present invention offers advantages, as can be appreciated by those skilled in the art. Only the small second portion 144 of the rim 140 will deform when the brush seal segment 110 experiences a transient rotor rub. Since generally no bristles 150 extend from the second portion 144 of the rim 140 because of the bristle angle, the deformed rim generally will not interfere with the bristles 150 even if the rim 140 deforms longitudinally toward the upstream-facing surface 128 of the backing plate 124, and thus the bristles can recover from a rotor rub. In a typical construction, the backing plate 124 including the rim 140 is of monolithic construction and consists essentially of metal or metal alloy such as, but not limited to, stainless steel. The bristles 150 typically consist essentially of metal-wire or ceramic-wire bristles such as, but not limited to, cobalt-based-alloy wire bristles. Preferably, metal-wire bristles 150 are attached to the backing plate 124 by welding (such weldment omitted from the figures for clarity). Commonly, the brush seal segment 110 further includes an upstream plate 152 as is known to the artisan.

Claims: A brush seal segment (110) comprising: a) a brush-seal backing plate (124) having a shape of generally an annular segment of a circular ring, said ring having a longitudinal axis (126), said backing plate having generally upstream-facing (128) and downstream-facing surfaces (130), said upstream-facing surface being aligned generally perpendicular to said axis, said backing plate having generally radially-aligned first (136) and second edges (138) circumferentially bounding together said upstream-facing and downstream-facing surfaces, said backing plate having a rim (140) radially-inwardly bounding together said upstream-facing and downstream-facing surfaces, and b) brush-seal bristles (150) generally abutting said upstream-facing surface, said bristles each canted at a generally-identical angle with respect to a corresponding radius line extending outward to each of said bristles, said bristles generally entirely circumferentially contained between a radius line extending outward to said first edge (136) and a radius line extending outward to said second edge (138), and said bristles extending inwardly beyond said rim from generally said first portion only of said rim, characterised in that said rim has first (142) and second (144) portions, said first portion (142) circumferentially extending from said first edge to said second portion(144), and said second portion disposed only proximate said second edge, wherein said second portion extends radially inward further than said first portion. The brush seal segment (110) of claim 1, wherein said second portion (144) of said rim (140) of said backing plate (124) has a shape of a labyrinth-seal tooth (146) when said backing plate is viewed in a first cross section taken by a cutting plane defined by the intersection of said axis (126) and a radius line which extends radially outward to said second portion. The brush seal segment (110) of claim 2, wherein said first portion (142) of said rim (140) of said backing plate (124) has a shape other than that of a labyrinth-seal tooth (146) when said backing plate is viewed in a second cross section taken by a cutting plane defined by the intersection of said axis (126) and a radius line which extends radially outward to said first portion. The brush seal segment (110) of claim 3, wherein said first portion (142) of said rim (140) of said backing plate (124) has a shape of a line (148) which is generally parallel to said axis (126) when said backing plate is viewed in said second cross section. The brush seal segment (110) of claim 1, wherein said angle of said bristles (150) is generally forty-five degrees. The brush seal segment (110) of claim 1, wherein said second portion (144) of said rim is deformable, under a radial force, longitudinally away from said upstream-facing surface (128). The brush seal segment (110) of claim 6, wherein said second portion (144) of said rim (140) has a shape of a labyrinth-seal tooth (146) when said backing plate (124) is viewed in a cross section taken by a cutting plane defined by the intersection of said axis (126) and a radius line which extends radially outward to said rim. The brush seal segment (110) of claim 7, wherein said tooth has a tip (154) which is aligned generally parallel to said axis (126) when viewed in said cross section, wherein said tooth has a first surface (156) which extends generally radially outward from said tip to said downstream-facing surface (130) of said backing plate (124), and wherein said tooth has a second surface (158) which extends generally radially outward and longitudinally upstream from said tip to said upstream-facing surface (128) of said backing plate. The brush seal segment (110) of claim 8, wherein said second surface (158) has a shape of a straight line when viewed in said cross section. The brush seal segment of claim 1 wherein the brush seal segment further comprises a brush-seal upstream plate (152), said brush-seal bristles (150) being located between the brush-seal backing plate (124) and the brush-seal upstream plate. The brush seal segment (110) of claim 10, wherein said rim (140) has a shape of a labyrinth-seal tooth (146) when said backing plate (124) is viewed in cross section taken by a cutting plane defined by the intersection of said axis (126) and a radius line which extends radially outward to said rim. The brush seal segment (110) of claim 11, wherein said tooth (146) has a tip which is aligned generally parallel to said axis (126) when viewed in said cross section, wherein said tooth has a first surface (156) which extends generally radially outward from said tip to said downstream-facing surface of said backing plate, and wherein said tooth has a second surface (158) which extends generally radially outward and longitudinally upstream from said tip to said upstream-facing surface (130) of said backing plate (124) . The brush seal segment (110) of claim 12, wherein said second surface (158) has a shape of a straight line when viewed in said cross section.

Inventors: CROMER ROBERT HAROLD, DINC OSMAN SAIM, RELUZCO GEORGE ERNEST, SKINNER DAVID ROBERT, TURNQUIST NORMAN ARNOLD, WOLFE CHRISTOPHER EDWARD, CROMER, ROBERT HAROLD, DINC, OSMAN SAIM, RELUZCO, GEORGE ERNEST, SKINNER, DAVID ROBERT, TURNQUIST, NORMAN ARNOLD, WOLFE, CHRISTOPHER EDWARD
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 1999
Main classification: F16J15
IPC codes: F01D25, F16J15, F01D11, F01D1