U.S. patent application number 12/209314 was filed with the patent office on 2010-03-18 for gas turbine vane attachment.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Roger Claude Beharrysingh, Christian Michael Hansen.
Application Number | 20100068050 12/209314 |
Document ID | / |
Family ID | 41258938 |
Filed Date | 2010-03-18 |
United States Patent
Application |
20100068050 |
Kind Code |
A1 |
Hansen; Christian Michael ;
et al. |
March 18, 2010 |
GAS TURBINE VANE ATTACHMENT
Abstract
Base hooks of a vane includes an approximate two times thicker
radial geometry, with dimensioning and tolerancing that results in
a line-line to loose fit on the forward OD hook surface and the aft
ID hook surface. Tolerances thus stack up on the opposite,
non-critical surfaces of the hooks (the forward ID hook surface and
the aft OD hook surface). The base of the vane is curved to match
that of the casing. An interface between the vane base and the
casing groove includes a metal alloy liner. Also, a wear coating is
provided on the vane attachment hooks. The liner protects the
casing groove from wear damage, while the hook coating and the
liner provide a wear coupling between the vane base and the casing
that provides a barrier between the vane bases and the casing to
decrease the wear rate.
Inventors: |
Hansen; Christian Michael;
(Simpsonville, SC) ; Beharrysingh; Roger Claude;
(Simpsonville, SC) |
Correspondence
Address: |
CANTOR COLBURN, LLP
20 Church Street, 22nd Floor
Hartford
CT
06103
US
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
41258938 |
Appl. No.: |
12/209314 |
Filed: |
September 12, 2008 |
Current U.S.
Class: |
415/209.3 |
Current CPC
Class: |
F01D 25/246 20130101;
F01D 9/042 20130101 |
Class at
Publication: |
415/209.3 |
International
Class: |
F01D 9/04 20060101
F01D009/04 |
Claims
1. An apparatus, comprising: a vane having a base with a hook
portion on both a forward facing portion of the base and an aft
facing portion of the base; and a casing having a groove that is
configured to receive the base of the vane; wherein the hook
portions each has an overall dimension with respect to a dimension
of the casing groove that provides for contact between the vane
base at a forward outer diameter (OD) hook surface and at an aft
inner diameter (ID) hook surface, thereby allowing tolerances to
stack up on a forward ID hook surface and an aft OD hook
surface.
2. The apparatus of claim 1, wherein the casing groove is curved at
a predetermined radial amount.
3. The apparatus of claim 2, wherein the vane base is curved at the
same predetermined radial amount as that of the casing groove.
4. The apparatus of claim 1, further comprising a material
interface between the vane base and the casing groove.
5. The apparatus of claim 4, wherein the material interface
includes a liner that interfaces between the vane base and the
casing groove.
6. The apparatus of claim 5, wherein the liner comprises a metal
alloy.
7. The apparatus of claim 6, wherein the metal alloy comprises a
cobalt-based metal alloy.
8. The apparatus of claim 6, wherein the metal alloy comprises a
stainless steel with a thermal spray coating on an inner surface of
the liner.
9. The apparatus of claim 4, wherein the material interface
comprises a wear coating disposed on the hook portions.
10. The apparatus of claim 9, wherein the wear coating comprises a
metal alloy.
11. The apparatus of claim 9, wherein the wear coating comprises a
cobalt-based metal alloy.
12. The apparatus of claim 9, wherein the wear coating comprises
tungsten carbide or chromium carbide.
13. An apparatus, comprising: a vane having a base with a hook
portion on both a forward facing portion of the base and an aft
facing portion of the base; a casing having a groove that is
configured to receive the base of the vane; and a liner disposed
between the vane base and the casing groove.
14. The apparatus of claim 13, further comprising a wear coating
disposed on the hook portions.
15. The apparatus of claim 14, wherein the wear coating comprises a
metal alloy.
16. The apparatus of claim 14, wherein the wear coating comprises a
cobalt-based metal alloy.
17. The apparatus of claim 13, wherein the casing groove is curved
at a predetermined radial amount.
18. The apparatus of claim 17, wherein the vane base is curved at
the same predetermined radial amount as that of the casing
groove.
19. The apparatus of claim 13, wherein the liner comprises a metal
alloy.
20. The apparatus of claim 13, wherein the liner comprises a
cobalt-based metal alloy.
Description
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to gas turbine
engines and, more particularly, to the attachment of vanes within a
casing of a compressor of a gas turbine engine.
[0002] Stator vanes located in the back-end stages of a compressor
are typically configured as singlets (one airfoil per attachment),
and have a square base that includes an attachment hook on the
forward and aft sides of the base. The hooks are commonly
constructed with a straight geometry such that when they are slid
into the radial compressor casing grooves, the resulting reaction
load distribution is concentrated at discrete (determinable) point
locations or contact zones. This is due in part to the fact that
the base of a vane is planar while the casing grooves are curved to
some extent. During operation at load, the stators are subject to
an unsteady aerodynamic vibratory environment that causes vibration
motion to be transmitted to the constraint points in the base
hooks. In addition, the responsive mode of vibration can result in
a concentration of vibratory stress near these same attachment
points. These hook attachment points experience fretting related
damage, including fretting wear and fretting fatigue, which
significantly shortens the design life of the vane.
[0003] Vanes and case hooks experience fretting wear damage as
indicated by stator rock-check measurements and pictures of case
hook material degradation upon top-halving a unit. If the stator
hook damage becomes excessive before repair, the stator airfoils
can clash into the rotating stages in front of the stators,
resulting in catastrophic damage to the flowpath components.
[0004] During an outage with the gas turbine not operating,
displacement measurements may be performed on the stator attachment
bases while pushing the airfoil in a specified direction. These
measurements, referred to as a "rock check", indicate the level of
hook deterioration associated with the fretting wear and fretting
fatigue experienced during operation. If the measured values exceed
a specified threshold, then the stators are removed from the
compressor. After the required inspection of the compressor
discharge casing (CDC) grooves and of the stator attachment hooks,
and depending upon the extent of the damage, the casing section can
be machined out. After machining, a custom patch ring may then be
retrofitted with a custom fit to provide a restored assembly groove
for the stators. New stators may then be installed in the patch
ring. However, while this solution may provide extended operation
capability, it does not address the root cause of the problem.
Another stopgap measure is to attach adjacent vanes together in
packs through welding or bolting, which again does not address the
root cause of the problem.
BRIEF DESCRIPTION OF THE INVENTION
[0005] According to one aspect of the invention, the base hooks of
a vane includes an approximate two times thicker radial geometry of
the hooks, with a dimensioning and tolerancing scheme that results
in a line-line to loose fit on the forward outer diameter (OD) hook
surface and the same on the aft inner diameter (ID) hook surface.
Tolerances are thus allowed to stack up on the opposite,
non-critical, surfaces of the hooks (i.e., the forward ID hook
surface and the aft OD hook surface). The base of the vane is
curved to match the curvature of the casing that the base resides
in.
[0006] According to another aspect of the invention, a material
interface is provided between the vane base and the casing groove.
The material interface includes a metal alloy liner that interfaces
between the base of the vane and the associated casing in which the
vane is disposed. Also, a wear coating is provided on the vane
attachment hooks. The liner protects the casing groove from wear
damage, while the combination of the hook coating and the liner
provide a wear coupling between the base of the vane and the
casing. The wear coupling provides a barrier between the vane bases
and the casing to decrease the wear rate.
[0007] These and other advantages and features will become more
apparent from the following description taken in conjunction with
the drawings.
BRIEF DESCRIPTION OF THE DRAWING
[0008] The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the claims at
the conclusion of the specification. The foregoing and other
objects, features, and advantages of the invention are apparent
from the following detailed description taken in conjunction with
the accompanying drawings in which:
[0009] FIG. 1 is a cross-section view of a compressor within a gas
turbine engine;
[0010] FIG. 2 illustrates the base of a vane according to an
embodiment of the invention overlaid with a vane of the prior
art;
[0011] FIG. 3 illustrates the casing for the base of the vane
according to an embodiment of the invention overlaid with the
casing for the vane within the prior art;
[0012] FIG. 4 illustrates a spring-loaded liner in accordance with
an aspect of the invention; and
[0013] FIG. 5 illustrates the base of a vane within a casing groove
with the liner of FIG. 4.
[0014] The detailed description explains embodiments of the
invention, together with advantages and features, by way of example
with reference to the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0015] Referring to FIG. 1, there illustrated is a cross-section
view of a compressor 100 within a gas turbine engine. The
compressor includes a discharge case 102 having a number of
circular rows or stages 104, wherein each stage 104 has a plurality
of vanes 106 that are located around the circumference of the
casing 102 within a groove on the inner periphery of the casing
102. As mentioned above, the vanes 106 commonly are slide-in
singlets with respect to the groove of the casing 102. Typically it
is the stages 104 located towards the back end of the compressor
100 (i.e., on the right hand side of the compressor 100 when
viewing FIG. 1) that experience the most fretting-related damage,
as discussed hereinabove. The material of the vanes 106
(particularly those in the back end of the compressor 100)
typically comprises a 403cb stainless steel, while the compressor
discharge case 102 may typically comprise a 2.25 CrlMo steel alloy
material.
[0016] Referring to FIGS. 2 and 3, according to one aspect of the
invention, a geometry change to the base hooks 110, 112 of a vane
106 from that of the prior art includes an approximate two times
thicker radial geometry of the hooks 110, 112, with a dimensioning
and tolerancing scheme that results in a line-line to loose fit on
the outer diameter (OD) of the forward hook surface 114 and the
same on the inner diameter (ID) of the aft hook surface 116.
Tolerances are thus allowed to stack up on the opposite,
non-critical, surfaces of the hooks 110, 112 (i.e., the forward ID
hook surface 118 and the aft OD hook surface 120). FIG. 2
illustrates the outline of a base of a vane 106 having the geometry
features of this aspect of the present invention. FIG. 2 also
illustrates the outline of a base of a vane 122 in the prior art,
where the vane 106 overlays the vane 122 to illustrate the contrast
between the size of the physical features of the hooks of both
vanes 106, 122.
[0017] Although not clearly seen in FIG. 2, the base of the vane
106, including the hooks 110, 112, according to an aspect of the
present invention has a slight radial curvature to better match the
normal curvature of the compressor casing 102. In contrast, the
base of the vane 122 of the prior art has no curvature and is
straight or planar. An attachment geometry based on curved or
radial hooks 110, 112 (instead of planar hooks as in the prior art)
with the critical load surfaces (i.e., the forward OD hook surface
118 and the aft ID hook surface 120) thereby achieves a line on
line assembly fit, such that the load surfaces of the vanes 106 are
established at assembly, minimizing any rigid body relative motion
of the hooks 110, 112 to the casing 102, and optimizing the load
pressure distribution on the surface of the hooks 110, 112. The
optimized load distribution results in the lowest possible pressure
placed on the hooks 110, 112, which is the primary parameter in
reducing fretting wear.
[0018] The hooks 110, 112 of the vanes 106 of this aspect of the
invention are thicker and longer than the prior art designs. The
dimensioning and tolerancing scheme for the vane hooks or rails
110, 112 are tighter, allowing for better fit-ups and reduced
manufacturing variation. Assembly clearances are increased over
that of the prior art for ease of assembly. Because durability of
the vanes 106 and the case 102 has been increased, customer down
time is reduced.
[0019] FIG. 2 also illustrates a groove 124 formed in the vane 106
of an embodiment of the invention. The groove 124 acts as an
error-proofing feature that ensures proper assembly of the vane 106
to the casing 102.
[0020] FIG. 3 illustrates the groove portion 128 of the casing 102
for the base of the vane 106 according to an embodiment of the
invention overlaid with the corresponding groove portion 130 of the
casing 132 for a vane within the prior art. FIG. 3 illustrates the
contrast in size between these features. From FIG. 3 it can be seen
that the groove portion 128 of the casing 102 that accommodates the
base of the vane 106 has been made larger to accommodate the now
larger hooks 110, 112 of the vane 106 according to an aspect of the
invention.
[0021] According to another aspect of the invention, a material
interface is provided between the base of the vane 106 and the
groove 128 of the casing 102. Referring to FIGS. 4 and 5, the
material interface includes a pair of spring-loaded liners 140 that
interface between the hooks 110, 112 of the base of the vane 106
and the associated groove portion 128 of the casing 102. FIG. 4
illustrates the liner 140 in an unloaded position. In an embodiment
of the invention, the liner 140 may comprise a cobalt-based metal
alloy that has a thickness of, e.g., 10 mils. The liners 140 may be
vanes per liner) contacts a single pair of liners 140 within the
compressor casing 102. In the alternative, the liner material may
comprise a stainless steel with a thermal spray coating on the
inner surface of the liner 140. The primary purpose of the liner
140 is to protect the casing groove 128 from wear damage, which is
accomplished by the material comprising the liner 140. As seen in
FIG. 5, two liners 140 are provided (one for each hook 110, 112)
and the liners 140, which are easily assembled in between the hooks
110, 1120 and the casing 102, completely surround the hooks or
rails 110, 112 of the base of the vane 106.
[0022] In further accord with an aspect of the invention, a
hard-face wear coating may be provided on the surface of the vane
attachment hooks 110, 112. The hook coating may comprise a metal
alloy, for example, a cobalt-based alloy that may comprise that
sold under the trademark Stellite.RTM.. The coating may be
approximately 5 mils thick and may comprise a thermal spray coating
applied by the high velocity oxygen fuel (EVOF) process.
[0023] The hook coating and the liner 140 together provide an
improved wear couple for the base of the vane 106 and the casing
groove 128. The cobalt-based wear couple provides a barrier between
the base of each vane 106 and the casing 102 to decrease the wear
rate when compared to the bare 403cb stainless steel vane and
2.25CrlMo steel alloy case materials used in the prior art. Also,
the improved wear couple provides a wear liner interface to protect
the casing material, and provide a load surface for the critical
hook surfaces of the vanes. The wear couple liner and the hard-face
coating on the hooks 110, 112 provides a long term durable
interface in a dynamic environment. Suitable alternative wear
coatings include tungsten carbide, chromium carbide, T800, T400,
T400C (all cobalt-based materials) or other cobalt-based
materials.
[0024] Embodiments of the present invention have been described and
illustrated herein for use with stator vanes that are located
within a compressor of a gas turbine engine. However, various
aspects of the present invention contemplate other types of vanes
for use therewith. Also, embodiments of the invention can be
retrofitted in the field onto older vanes.
[0025] While the invention has been described in detail in
connection with only a limited number of embodiments, it should be
readily understood that the invention is not limited to such
disclosed embodiments. Rather, the invention can be modified to
incorporate any number of variations, alterations, substitutions or
equivalent arrangements not heretofore described, but which are
commensurate with the spirit and scope of the invention.
Additionally, while various embodiments of the invention have been
described, it is to be understood that aspects of the invention may
include only some of the described embodiments. Accordingly, the
invention is not to be seen as limited by the foregoing
description, but is only limited by the scope of the appended
claims.
* * * * *