ELLIPTICAL SEALING SYSTEM
TECHNICAL FIELD
[0101] The present application relates generally to seals for use with rotary
machines and more particularly relates to a compliant and an abradable labyrinth sealing
system having an elliptical shape for use with a rotary machine such as a rotary
compressor and the like.
BACKGROUND OF THE INVENTION
[0102] In a rotary machine, one or more seal generally extend along an interface
between the rotating and the stationary components. For example, compressors, turbines,
and the like may have one or more seals at the interface between a series of rotating
blades or buckets disposed within a casing or a vane. These seals are intended to
preserve a pressure differential across the rotating components between upstream and
downstream sides thereof. A smaller clearance dimension at the seal generally increases
the performance of the seal and the efficiency of the overall rotary machine by limiting
the leakage thereacross.
[0103] The seals and the components thereof, however, may be subject to
relatively high temperatures, thermal gradients, and thermal expansion and contraction
during various operational stages of the rotary machine such as during start-up and during
other types of transient operations. Typically, the seal includes an extra clearance
dimension to reduce the likelihood of contact and damage between the rotating and the
stationary components during such transient operations. This extra clearance dimension,
however, also may reduce the performance and efficiency of the seal and the overall
rotary machine because of the leakage flow across the seal. Fluid leakage between the
rotor and the casing may lower the efficiency of the compressor and hence lead to
increased fiiel costs.
[0104] There is thus a desire for an improved sealing system for a rotary machine
such as a compressor and the like that reduces leakage therethrough while maintaining
adequate clearance during transient operations as well as during steady state operating
conditions. Such reduced leakage should improved overall efficiency while preventing
damage to the components herein.
SUMMARY OF THE INVENTION
[0105] The present application thus provides an elliptical sealing system for use
with a rotor and a stator housing of a rotary machine. The elliptical sealing system may
include a number of sealing segments with an abradable coating thereon. The sealing
segments with the abradable coating thereon may have a substantially elliptical shape. A
number of biasing members may be in communication with the sealing segments and the
stator housing.
[0106] The present application further provides an elliptical sealing system for
use with a rotor and a stator housing of a rotary machine. The elliptical sealing system
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may include a pair of elliptical sealing segments with an abradable coating thereon. A
number of biasing members may be in communication with the elliptical sealing
segments and the stator housing so as to bias the pair of elliptical sealing segments with
the abradable coating thereon towards the rotor.
[0107] The present application further provides for a rotary machine. The rotary
machine may include a stator housing, a rotor, a pair of elliptical sealing segments
positioned therebetween with an abradable coating thereon, and a number of biasing
members in communication with the pair of elliptical sealing segments and the stator
housing so as to bias the pair of elliptical sealing segments with the abradable coating
thereon towards the rotor.
[0108] These and other features and improvements of the present application will
become apparent to one of ordinary skill in the art upon review of the following detailed
description when taken in conjunction with the several drawings and the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0109] Fig. 1 is a schematic view of a gas turbine engine.
[0110] Fig. 2 is a cross-sectional view of an elliptical sealing system as may be
described herein positioned within a rotary machine.
[0111] Fig. 3 is an axial view of the elliptical sealing system of Fig. 2 positioned
about a rotor of the rotary machine.
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DETAILED DESCRIPTION
[0112] Referring now to the drawings, in which like numerals refer to like
elements throughout the several views, Fig. 1 shows a schematic view of a rotary
machine such as gas turbine engine 10. The gas turbine engine 10 may include a
compressor 15. The compressor 15 compresses an incoming flow of air 20. The
compressor 15 delivers the compressed flow of air 20 to a combustor 25. The combustor
25 mixes the compressed flow of air 20 with a compressed flow of fuel 30 and ignites the
mixture to create a flow of combustion gases 35. Although only a single combustor 25 is
shown, the gas turbine engine 10 may include any number of combustors 25. The flow of
combustion gases 35 is delivered in turn to a turbine 40. The flow of combustion gases
35 drives the turbine 40 so as to produce mechanical work. The mechanical work
produced in the turbine 40 drives the compressor 15 and an external load 45 such as an
electrical generator and the like.
[0113] The gas turbine engine 10 may use natural gas, various types of syngas,
and/or other types of fuels. The gas turbine engine 10 may be one of any number of
different gas turbine engines offered by General Electric Company of Schenectady, New
York and the like. The gas turbine engine 10 may have other configurations and may use
other types of components. Other types of gas turbine engines also may be used herein.
Multiple gas turbine engines 10, other types of turbines, and other types of power
generation equipment also may be used herein together. Other types of rotary machines
also may be used herein.
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[0114] Gas leakage out of the gas path or into the gas path of the gas turbine
engine 10 from an area of higher pressure to an area of lower pressure generally is
undesirable. As described above, gas path leakage in the compressor 15 and/or in the
turbine 40 may lower the efficiency of the overall gas turbine engine 10 and lead to
increased fuel costs. The gas turbine engine 10 therefore may include a sealing system
50 provided in the compressor 15 and/or the turbine 40. The sealing system 50 facilitates
a minimum clearance between the stationary components and the rotating components
therein. As a result, fluid leakage through these components may be minimized so as to
enhance overall efficiency.
[0115] Fig. 2 shows a portion of rotary machine 100 as may be described herein.
In this example, the rotary machine 100 may include a compressor 110 similar to
compressor 15 described above. Generally described, the compressor 110 includes a
rotor 120 disposed inside a stator housing 130. The rotor 120 may be coupled to an input
device shaft (not shown) or otherwise. Likewise, the stator housing 130 may include a
number of suction ports and discharge ports (not shown) communicating fluid to and
fi-om the rotor 120 and the components thereof or otherwise. During rotation of the rotor
120, an incoming fluid may be sucked through the suction ports and a compressed fluid
may be discharged through the discharge ports. Other configurations and other
components may be used herein.
[0116] An elliptical sealing system 140 may be positioned between the rotor 120
and the stator housing 130. The elliptical sealing system 140 may be configured to
control the leakage of the fluid therethrough without damaging the components thereof
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Although described herein in the context of the compressor 110, the elliptical sealing
system 140 may be used with any type of rotary machine 100, including steam turbines,
gas turbines, and the like.
[0117] The elliptical sealing system 140 may include a retractable packing ring
150 positioned within a slot 160 of the stator housing 130. The packing ring 150 may be
generally I-shaped although other configurations may be used herein. The packing ring
150 may include an abradable coating 170 facing the rotor 120. The abradable coating
170 may include an alloy of cobalt, nickel, chromium, aluminum, yttrium, hexagonal
boron nitride, and polymers such as polyesters, polyimides, or the like. Alternatively, the
abradable coating 170 may include nickel, chromium, aluminum, and clay (bentonite).
Further, the abradable coating 170 may include nickel, graphite, and stainless steel.
Further, the abradable coating 170 may include nickel, chromium, iron, aluminum, boron
and nitrogen. Further, the abradable coating 170 may also include non-metallic materials
(e.g., polytetrafluoroethylene applied by electrostatic powder coating process or
polytetrafluoroethylene filled synthetic mica which may be attached by a mechanical
device). The abradable coating 170 may use any desired material in any desired size,
shape, and/or orientation.
[0118] A number of biasing members 180 such as springs 190 may be disposed
between the packing ring 150 and the stator housing 130. The biasing members 180 may
include leaf springs, coil springs, helical springs, hydraulic springs, pneumatic springs,
stacked washers, and the like. The biasing members 180 may be configured to bias the
packing ring 150 towards the rotor 120. In this example, the biasing members 180 may
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be positioned at about a 12 o'clock position and about a 6 o'clock position. Other
positions may be used herein. Any number or type of biasing members 180 may be used
herein. Other configurations and other components may be used herein.
[0119] The rotor 120 also may include a number of teeth 200 extending towards
the elliptical sealing system 140. The teeth 200 may be in the form of a number of "J"-
type strips 210 positioned within a number of slots 220 on the rotor 120. The J-strips 210
may be held in place within the rotor slots 220 via a number of wires 230 or other types
of connection means. The J-strips 210 may be made of out stainless steel or other types
of substantially rigid materials. Some or all of the J-strips 210 may be in contact with the
abradable coating 170 of the rotor 120. The J-strips 210 may be detachable from the
rotor 120 for replacement if damaged or worn via contact with the abradable coating 170.
Other configurations and other components may be used herein.
[0120] Fig. 3 shows an axial view of the elliptical sealing system 140. As is
shown, the elliptical sealing system 140 may have a largely elliptical shape 240.
Specifically, the packing ring 150 with the abradable coating 170 may largely form the
elliptical shape 240. By use of the term "elliptical", we also include various types of
hyperboloid, parabaloid, and other types of similar shapes. Other configurations may be
used herein. The elliptical sealing system 140 is shown as positioned about the rotor 120.
A horizontal arrow 250 shows the seal major axis that is substantially equal to the outside
diameter of the rotor 120 and the extended teeth 200 or the J-strips 210. Other
configurations may be used herein.
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[0121] The elliptical sealing system 140 also may have a number of segments
260. In this example the elliptical sealing system 140 may have only two (2) segments
260, a first half 270 and a second half 280. Any number of segments 260 may be used
herein. By only using the two (2) halves 270, 280, no additional end gap leakage may be
introduced through the elliptical sealing system 140. Likewise, the use of the biasing
members 180 at about the 12 o'clock position (shown at vertical arrows 290) and about at
the 6 o'clock position generally forces the halves 270, 280 towards the center and the
rotor 120 for contact therewith. Operating pressures also may provide additional sealing
force.
[0122] The use of the elliptical shape 240 allows for an interference engagement
300 between the abradable coating 170 of the elliptical sealing system 140 and the Jstrips
210 of the rotor 120. Specifically, the biasing members 180 allow for a deeper
interference engagement 300 at about the 6 o'clock position and about the 12 o'clock
position while providing for a line on line engagement 310 at about the 3 o'clock and
about the 9 o'clock position. The sealing system 140 thus acts as a wheel eye seal with
improved radial engagement. Likewise, no additional end gap leakage may be introduced
through the elliptical sealing system 140 given the use of a minimum number of segments
260, the first half 270 and the second half 280. Such reduced leakage flows therethrough
should increase overall compressor and rotary machine efficiency through the
combination herein of the elliptical shape 240, the biasing members 180, and/or the
abradable coating 170.
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[0123] It should be apparent that the foregoing relates only to certain
embodiments of the present application and that numerous changes and modifications
may be made herein by one of ordinary skill in the art without departing from the general
spirit and scope of the invention as defined by the following claims and the equivalents
thereof.

CLAIMS
We claim:
1. An elliptical sealing system (140) for use with a rotor (120) and a stator
housing (130) of a rotary machine (100), comprising:
a plurality of sealing segments (260);
each of the plurality of sealing segments (260) comprising an abradable coating
(170) thereon;
the plurality of sealing segments (260) with the abradable coating (170) thereon
comprising a substantially elliptical shape (240); and
a plurality of biasing members (180) in communication with the plurality of
sealing segments (260) and the stator housing (130).
2. The elliptical sealing system (140) of claim 1, wherein the plurality of
sealing segments (260) comprises a packing ring (150).
3. The elliptical sealing system (140) of claim 1, wherein the plurality of
sealing segments (260) comprises a first half (270) and a second half (280).
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4. The elliptical sealing system (140) of claim 1, wherein the rotor (120)
comprises a plurality of teeth (200) thereon and wherein the plurality of teeth (200)
engage the abradable coating (170) of the plurality of sealing segments (260).
5. The elliptical sealing system (140) of claim 4, wherein the plurality of i
teeth (200) comprising a plurality of J-strips (210) and wherein the plurality of J-strips
(210) engage the abradable coating (170) of the plurality of sealing segments (260). 6. The elliptical sealing system (140) of claim 1, wherein the plurality of t
biasing members (180) are positioned at about a 12 o'clock position and about a 6
o'clock position to bias the plurality of sealing segments (260) towards the rotor (120). 1. The elliptical sealing system (140) of claim 1, wherein the plurality of biasing members (180) comprises a plurality of springs (190) to bias the plurality of J
sealing segments (260) towards the rotor (120).
8. The elliptical sealing system (140) of claim 1, wherein the plurality of
sealing segments (260) with the abradable coating (170) thereon comprises an
interference engagement (300) with the rotor (120) at about a 12 o'clock position and
about a 6 o'clock position.
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9. The elliptical sealing system (140) of claim 1, wherein the plurality of
sealing segments (260) with the abradable coating (170) thereon comprises a line on line
engagement (310) with the rotor (120) at about a 3 o'clock position and about a 9 o'clock
position.
10. The elliptical sealing system (140) of claim 1, wherein the plurality of
sealing segments (260) with the abradable coating (170) thereon comprises a seal major
axis (250) of about an outer diameter of the rotor (120) and a plurality of teeth (200)
thereon.
11. The elliptical sealing system (140) of claim 1, wherein the rotary machine
(100) comprises a compressor (110).
12. An elliptical sealing system for use with a rotor and a stator housing of
a rotary machine, substantially as herein described with reference to accompanying
drawings and example.
Dated this|^''day of January 2012