Note: Descriptions are shown in the official language in which they were submitted.
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A SYSTEM AND METHOD FOR SUPPORTING STATOR COMPONENTS
BACKGROUND OF THE INVENTION
This invention relates generally to gas turbine engine components, and more
specifically to mounting of stators in turbine engines.
Gas turbine engines typically include a core engine having a compressor for
compressing air entering the core engine, a combustor where fuel is mixed with
the
compressed air and then burned to create a high energy gas stream, and a first
or high
pressure turbine which extracts energy from the gas stream to drive the
compressor. In
aircraft turbofan engines, a second turbine or low pressure turbine located
downstream
from the core engine extracts more energy from the gas stream for driving a
fan. The
fan provides the main propulsive thrust generated by the engine.
An annular turbine nozzle is located between the combustor and high
pressure turbine and between stages of the turbine. The turbine nozzle
includes a pair
of radially spaced inner and outer bands disposed concentrically about a
longitudinal
axis of the core engine and airfoils supported between the inner and outer
annular
bands. In the annular turbine nozzle assembly, the airfoils are arranged in
circumferentially spaced relation from one another and extend in radial
relation to the
core engine axis. The annular turbine nozzle assembly is formed by a plurality
of
arcuate segments (alternatively referred to herein as "stator vane" or "stator
vanes")
which fit end-to-end together to form the 360 degree circumferentially
extending
nozzle assembly. Each turbine nozzle segment includes arcuate segments of the
inner
and outer bands and one or more airfoils mounted between the inner and outer
band
segments.
The turbine nozzle provides the function of directing and/or re-directing hot
gas flow from the combustor into a more efficient direction for impinging on
and
effecting rotation of the rotor stages of the turbine. The directing process
performed by
the nozzle also accelerates gas flow resulting in a static pressure reduction
between
inlet and outlet planes and creates high pressure loads and moments on the
nozzle and
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its support system. Additionally, the turbine nozzle and its support systems
also
experience loads and moments due to the high thermal gradients from the hot
combustion gases and the coolant air at the radial support surfaces.
In conventional nozzle support systems, the nozzle segments are attached by
bolted joints or a combination of bolts and some form of clamping arrangement
to an
engine support structure. Such arrangements, however, create significant
bending
stresses in the nozzle and support due to mechanical loads and moments
experienced
by the nozzle airfoils and due to differential thermal expansion and
contraction.
Furthermore, holes required for receiving the bolts inherently create stress
concentrations and may provide potential leakage paths. And, the nuts and
bolts
required for the assembly add undesirable weight to the engine and increase
assembly
and disassembly time.
In some designs of smaller turbine engines, turbine nozzles are supported
only at their radially outer band in essentially a cantilever type arrangement
since their
radially inner band extends adjacent a rotating engine structure to which the
turbine
rotor stages are attached. In some stages, such as the first stage nozzle, the
nozzle is
attached to the engine stationary structure via a radially inner mount or
flange
structure coupled to the inner band. The radially outer band is not
mechanically
retained but is supported against axial forces by a circumferential engine
flange. In
other stages, such as stage 2 turbine of an engine, the turbine nozzle may be
attached
at its radially outer band but be free at its radially inner band. In either
design, the use
of bolts and clamps at circumferential locations about a turbine nozzle band
act as a
restriction to the band, which band is hotter than the structure to which it
is attached,
causing radial bowing of the outer band of the nozzle, causing out-of-
roundness and
stressing of the airfoils attached to the band. Such stressing of the airfoils
may lead to
formation of cracks in the airfoil.
A need exists for the development of alternative designs methods which will
provide improvements in mounting and supporting stator components such as
turbine
nozzle segments to the engine support structure. Accordingly, it would be
desirable to
have a method and system for mounting static components in a turbine engine,
such as
a stator vane, to the engine support structure that react the loads and
moments without
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using bolts and nuts. It is desirable to have a reaction mount system for a
turbine stator
component such that the stator can be easily replaced in an assembly.
BRIEF DESCRIPTION OF THE INVENTION
The above-mentioned need or needs may be met by exemplary embodiments
described herein which provide a method and system for supporting removable
static
components in a turbine engine. The method comprises the steps of engaging a
stator
hanger located at a first location on a first static component with a post
located on a
first static structure whereby the post supports at least a part of the weight
of the first
static component, engaging a stator stopper located at a second location on
the first
static component that is located circumferentially apart from the first
location with the
stator hanger that is located on a second static component, and engaging a
hook
located at a third location on the first static component with a second static
structure
whereby the second static structure supports at least a part of the weight of
the first
static component. A reaction mount system provides support for a stator vane,
comprising a stator hanger located on an outer band at a first location and a
stator
stopper located at a second location that is located circumferentially apart
from the
first location.
BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter which is regarded as the invention is particularly pointed
out and distinctly claimed in the concluding part of the specification. The
invention,
however, may be best understood by reference to the following description
taken in
conjunction with the accompanying drawing figures in which:
Figure 1 is a longitudinal cross sectional illustration of a portion of a gas
turbine showing the rotors and stators including an exemplary embodiment of
the
present invention.
Figure 2 is a longitudinal cross sectional illustration of the stator
components
in the gas turbine shown in Figure 1, including an exemplary embodiment of the
present invention.
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Figure 3 shows an isometric view of a stator assembly having an exemplary
embodiment of a stator mounting system according to the present invention.
Figure 4 shows an isometric view of a stator vane having a reaction mount
system according to an exemplary embodiment of the present invention.
Figure 5 shows an isometric view of a stator assembly having an alternative
embodiment of a stator mounting system according to the present invention.
Figure 6 shows an isometric view of a stator vane having a reaction mount
system according to an alternative embodiment of the present invention.
Figure 7 shows an isometric view of a shroud hanger shown in Figure 3.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings wherein identical reference numerals denote the
same elements throughout the various views, Figure 1 shows a longitudinal
cross
sectional illustration of a portion of an exemplary gas turbine 10 showing the
rotors
and stators including an exemplary embodiment of the present invention. The
exemplary gas turbine 10 shown in Figure 1 comprises a Stage 1 turbine rotor
21, a
Stage 2 turbine rotor 22, and a Stage 2 turbine nozzle 23 located axially in
between
them. Turbine blades 20 and 24 are circumferentially arranged around turbine
centerline 11 on the rims of the Stage 1 and Stage 2 rotors respectively. The
exemplary embodiments shown herein show support systems 300 in turbines for
supporting static components, such as turbine nozzles 23, using adjacent
static
structures 91, 92 such as shroud hangers 32, 90.
Figure 2 shows an enlarged view of the Stage 2 turbine nozzle that is shown
in Figure 1. The stage 2 turbine nozzle 23 comprises an inner band 51, an
outer band
52 and an airfoil 50 that extends between the inner band 51 and the outer band
52. The
turbine nozzles shown herein have one airfoil between the inner band and the
outer
band. However, in other embodiments of the present invention, it is possible
to have a
plurality of airfoils in a turbine nozzle segment, between the inner band and
the outer
band. The inner band 51 and the outer band 52 form the flow path for the
combustion
gases. The turbine nozzle airfoil 50 may be hollow (such as, for example,
shown in
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Figure 5) so that cooling air supplied from a spoolie 100 can be circulated
through the
hollow airfoil 50. The nozzle segment 23 including the outer band may be made
of a
single piece of casting having the vane airfoils, the outer band and the inner
band.
Alternatively the nozzle segment may be made by suitable conventional methods
of
joining, such as brazing, individual sub-components such as vane airfoils, the
outer
band and the inner band.
The outer band 52 and inner band 51 of each nozzle segment 23 have an
arcuate shape so as to form an annular flow path when multiple nozzle segments
are
assembled around the turbine centerline 11. The turbine nozzle segments 23,
when
assembled in the engine, form an annular turbine nozzle assembly, with the
inner and
outer bands 51, 52 forming the annular flow path through which the hot gases
pass. In
the turbine 10 shown in Figure 1, Stage 2 turbine nozzle receives the flow
coming out
of the stage 1 turbine and reorients its direction and flows it into the stage
2 turbine.
Referring to Figures 2 and 3, the exemplary embodiment of the stage 2
nozzle shown therein is held in position by a stator support system 300. An
exemplary
outer band cantilever mount system is shown in Figures 1 and 2. In the
exemplary
embodiments shown, the axially forward end 61 of the outer band 52 has a
forward
hook 56 which extends in the circumferential direction along the
circumferential
length of the nozzle segment 23. The forward hook 56 sits on an arcuate rail
40 which
protrudes axially from the aft end of the stage 1 shroud hanger 32.
Figure 3 shows an isometric view of a stator assembly 200 having an
exemplary embodiment of a stator components mounting system 300 according to
the
present invention. For illustration purposes, only two outer bands 52 that are
circumferentially to each other are shown in Figure 3. Each outer band 52 has
a
reaction mount system 205 comprising a stator hanger 210 located at a first
location
221, such as near the aft end location shown in Figure 3, and a stator stopper
220 at a
second location 222. The stator stopper 220 is shown located circumferentially
apart
from the stator hanger 210, near the aft end on the outer bands 52. The
support system
300 further comprises a hook 56 that is located at a third location 223, shown
in
Figures 2 and 3 near the axially forward end 61. As shown in Figure 3, the
forward
hook may be have arcuate shape that engages with an arcuate rail 40 on a
static
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structure 92 located near the forward hook 56. As shown in the figures herein,
the
arcuate rail 40 forms a part of a shroud hanger 32 located axially forward
from the
outer band 52.
Figure 4 shows an isometric view of a stator vane 53 having a reaction mount
system 205 according to an exemplary embodiment of the present invention. The
stator hanger 210 and the stator stopper 220 are located near the aft end 60
and the
forward hook 56 is located near the forward end 61 of the outer band 52. The
stator
hanger 210 comprises a stem 64, having a block of material shaped like a
hammer
(herein referred to as "hammer", identified as item 68) located at its
radially outer
end. The stator hanger has a hanger claw 71 located near the radially outer
end of the
stem 64. The stator stopper 220 is located circumferentially apart from the
stator
hanger 210. The stator stopper 220 comprises a paddle 80 having a paddle aft
face 83
and an end face 86.
During assembly, hanger claw 71 engages with a post 96 that is located on a
first support structure 91, such as for example, a shroud hanger 90. The
stator stopper
220 located on an outer band 52 engages, as shown in Figure 3, with the stator
hanger
210 located on the circumferentially adjacent outer band 52. Specifically the
paddle
aft face 83 is located adjacent to the stem 64 of the stator hanger 210. A
portion of the
top of the stator stopper 220 engages with a radially inner portion of the
hammer 68.
When the turbine is not operating, the hanger claw 71 rests on the post 96,
providing
support for the nozzle in the cold condition. In Figures 3 and 4, an anti-
rotation tab 72
is shown located near an end of the hanger claw 71. The anti-rotation tab 72
engages
with the post 96 to prevent rotation of the nozzle segements23 during
assembly.
During turbine operation the stem 64 of the hammer 68 reacts the nozzle
tangential loads against the post 96. The top of the stator stopper 220
located at the
second location 222 on the opposite slash face of the outer band 52 reacts the
radial
moment into the hammer 68 of the circumferentially adjacent outer band 52 of
the
adjacent nozzle segment 23. The top 70 of the hammer 68 reacts radially
against a
360 degree shroud support. In addition to the hammer 68, the radial load is
also
reacted into supporting structure 92 by the nozzle forward hook 56. The axial
moments are reacted by the paddle 80, into the hammer stem 64 of the adjacent
nozzle
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segment, and into the adjacent supporting structure 91. Axial loads are
reacted
against the adjacent static structures such as the stage 2 shroud hanger. When
the
nozzle segments 23 are assembled into a full nozzle assembly, all of the
nozzle
segments will react the radial moment against the 360 degree shroud support
and all
of the axial loads and moments, and circumferential loads against the adjacent
supporting structures. This feature of support system 300 improves the
roundness of
the nozzle assembly around the turbine axis 11 and results in a reduction of
the
relative gap between nozzle segments and is an improvement over prior art.
Figure 5 shows a stator assembly 200 having an alternative embodiment of a
stator mounting system 300 according to the present invention. Three nozzle
segments
are shown, each segment having a single vane. The nozzle vanes 53 shown have
hollow cavities through which cooling flow air is passed through. An
alternative
embodiment of the stator hanger 210 is shown in Figure 5 and 6.The hanger claw
engages with a post 96 located on an adjacent supporting structure 91, such as
a
shroud hanger. In this alternative embodiment, the reaction mount system 205
has an
anti-rotation tab 172 that is located on the reaction mount 63 (see Figure 6).
The
engagement of the stator hanger 210 and the stator stopper 220 with the
support
structure 91 is as described previously.
Figure 7 shows a shroud hanger 90 that can be used in the static component
mount system 300 described herein. The shroud hanger 90 has an inner rail 94
that is
arcuate in shape. The inner rail can support a conventional turbine shroud.
The shroud
hanger 90 has an outer rail that is also arcuate in shape. The outer rail
engages with a
casing 34 and reacts the loads against the casing 34. The shroud hanger has at
least
one post 96 that extends generally in an axial direction, as shown in Figures
3, 5 and
7. The post provides support for the stator vanes 23 as described previously
and
transmits the loads through the post 96 to the shroud hanger and the casing.
The
shroud hangers, and nozzles and other components shown herein are made of
conventional turbine materials such as for example Rene 80 and Inconel 718
that have
high temperature capabilities.
This written description uses examples to disclose the invention, including
the best mode, and also to enable any person skilled in the art to make and
use the
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invention. The patentable scope of the invention is defined by the claims, and
may
include other examples that occur to those skilled in the art in view of the
description.
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