U.S. patent application number 13/679093 was filed with the patent office on 2014-05-22 for contoured stator shroud.
This patent application is currently assigned to General Electric Company. The applicant listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to JOSEPH CAPOZZI, Jeffrey Carnes, David Vickery Parker.
Application Number | 20140140822 13/679093 |
Document ID | / |
Family ID | 50002832 |
Filed Date | 2014-05-22 |
United States Patent
Application |
20140140822 |
Kind Code |
A1 |
CAPOZZI; JOSEPH ; et
al. |
May 22, 2014 |
Contoured Stator Shroud
Abstract
A contoured stator shroud has a stator chord overhang having a
surface which varies in elevation forming a plurality of surface
contours, wherein the contours reduce clearance between adjacent
vanes during off design performance positioning of the vanes.
Inventors: |
CAPOZZI; JOSEPH; (North
Reading, MA) ; Parker; David Vickery; (Medford,
MA) ; Carnes; Jeffrey; (Newton, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY |
Schenectady |
NY |
US |
|
|
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
50002832 |
Appl. No.: |
13/679093 |
Filed: |
November 16, 2012 |
Current U.S.
Class: |
415/160 |
Current CPC
Class: |
F01D 5/143 20130101;
F01D 9/00 20130101; F01D 17/162 20130101 |
Class at
Publication: |
415/160 |
International
Class: |
F01D 9/00 20060101
F01D009/00 |
Claims
1. A contoured stator shroud vane assembly in a gas turbine engine
having an inlet end, an outlet end and a plurality of propulsor
components, comprising: a stator shroud having a generally circular
cross-section; said shroud having a forward end, an aft end and at
least one surface extending between said first end and said second
end; said shroud having a plurality of pivots disposed
circumferentially about said shroud to support a trunnion of a
vane; said at least one surface of varying elevation adjacent to
said plurality of pivots, and extending in a circumferential
direction.
2. The contoured stator shroud vane assembly of claim 1, said
surface of varying elevation of at least one surface disposed
adjacent an edge of said vane.
3. The contoured stator shroud vane assembly of claim 2, said
surface of varying elevation being curved to approximate the
curvature defined by rotation of said edge of said vane.
4. The contoured stator shroud vane assembly of claim 3, wherein
said vane overhang and said surface of varying elevation inhibit
leakage when said vane pivots.
5. The contoured stator shroud vane assembly of claim 1, said
plurality of pivots each receiving buttons of a plurality of
vanes.
6. The contoured stator shroud vane assembly of claim 1, said axes
of curvature of said surface of varying elevation being generally
parallel to an engine axis.
7. A contoured stator shroud, comprising: a forward end, an aft end
and at least one surface extending between said forward end and
said aft end; said at least one surface being tapered from said
forward end to said aft end; a plurality of areas of varying
elevation disposed about said at least one surface, said plurality
of areas each having a peak and a valley; a plurality of pivot
apertures spaced about a forward end of said at least one
surface.
8. The contoured stator shroud of claim 7, said plurality of areas
of varying elevation being curved from a first elevation to a
second elevation in a circumferential direction.
9. The contoured stator shroud of claim 7, said plurality of
varying elevation being linear from a first elevation to a second
elevation in a circumferential direction.
10. The contoured stator shroud of claim 7, said shroud changing
elevation in an axial direction.
11. The contoured stator shroud of claim 10, said changing
elevation being curved.
12. The contoured stator shroud of claim 10, said changing
elevation being linear.
13. The contoured stator shroud of claim 7 further comprising a
vane having a lowermost edge.
14. The contoured stator shroud of claim 13, said lowermost edge
engaging said plurality of areas of varying elevation during
pivoting movement of said vane.
15. The contoured stator shroud vane assembly of claim 7, said
plurality of areas of varying elevation additionally being curved
to approximate the curvature defined by rotation of a lower edge of
a vane.
16. A contoured stator shroud, comprising: a forward end and an aft
end, at least one surface extending between said forward end and
said second end; said at least one surface having a scalloped chord
overhang area, said scalloped area extending in a circumferential
direction; a plurality of vane mounting locations disposed
circumferentially between said forward end and said aft end.
17. The contoured stator shroud of claim 16, said scalloped chord
overhang area being curved from a lower elevation of said stator
shroud to an upper elevation of said stator shroud.
18. The contoured stator shroud of claim 16 further comprising a
plurality of vanes operably connected to said plurality of vane
mounting locations.
19. The contoured stator shroud of claim 18, said plurality of
vanes each having an edge extending between a leading edge and a
trailing edge.
20. The contoured stator shroud of claim 19, said edge engaging a
scalloped chord overhang area during pivoting movement of said
vane.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] None
BACKGROUND
[0002] The disclosed embodiments generally pertain to gas turbine
engines. More particularly, present embodiments relate to shrouds
within gas turbine engines which are utilized with pivoting
vanes.
[0003] In a gas turbine engine a typical gas turbine engine
generally possesses a forward end and an aft end with its several
components following inline therebetween. An air inlet or intake is
at a forward end of the engine. Moving toward the aft end, in
order, the intake is followed by a compressor, a combustion
chamber, a turbine, and a nozzle at the aft end of the engine. It
will be readily apparent from those skilled in the art that
additional components may also be included in the engine, such as,
for example, low-pressure and high-pressure compressors,
high-pressure and low-pressure turbines, and an external shaft.
This, however, is not an exhaustive list. An engine also typically
has an internal shaft axially disposed through a center
longitudinal axis of the engine. The internal shaft is connected to
both the turbine and the air compressor, such that the turbine
provides a rotational input to the air compressor to drive the
compressor blades.
[0004] In operation, air is pressurized in a compressor and mixed
with fuel in a combustor for generating hot combustion gases which
flow downstream through turbine stages. These turbine stages
extract energy from the combustion gases. A high pressure turbine
first receives the hot combustion gases from the combustor and
includes a stator nozzle assembly directing the combustion gases
downstream through a row of high pressure turbine rotor blades
extending radially outwardly from a supporting rotor disk. In a two
stage turbine, a second stage stator nozzle assembly is positioned
downstream of the first stage blades followed in turn by a row of
second stage rotor blades extending radially outwardly from a
second supporting rotor disk. The turbine converts the combustion
gas energy to mechanical energy.
[0005] Vanes or airfoils are typically designed with a primary or
optimal position for operation. However, depending on the desired
operating condition of the turbine engine, the vanes may be
actuated to alternate positions. Current stator shroud designs
utilize a circular cross-section across which vanes are actuated.
As the vanes move from the open design position to off design
closed positions, clearance between the vane and shroud increases
due to the curvature of the shroud, the flow path geometry and the
lower edge shape of the vane, all of which are required to meet the
compressor operating requirements.
[0006] When this clearance increases, flow disruptions can affect
the intended purpose of the vane shape function and configuration.
It would be desirable to overcome these and other deficiencies so
that the clearance between the vane and shroud is reduced, for
example in the off design closed angular positions of the vane.
SUMMARY
[0007] According to at least some embodiments, a contoured stator
shroud vane assembly in a gas turbine engine having an inlet end,
an outlet end and a plurality of propulsor components comprises a
stator shroud having a generally circular cross-section, the shroud
having a forward end, an aft end and at least one surface extending
between said first end and said second end, the shroud having a
plurality of pivots disposed circumferentially about the shroud to
support a trunnion of a vane, the at least one surface of varying
elevation adjacent to said plurality of pivots and extending in a
circumferential direction.
[0008] According to at least some embodiments, a contoured stator
shroud, comprises a forward end, an aft end and at least one
surface extending between the forward end and the aft end, the at
least one surface being tapered from the forward end to the aft
end, a plurality of areas of varying elevation disposed about the
at least one surface, the plurality of areas each having a peak and
a valley, a plurality of pivot apertures spaced about a forward end
of the at least one surface.
[0009] According to still other embodiments, a contoured stator
shroud, comprises a forward end and an aft end, at least one
surface extending between the forward end and the second end, the
at least one surface having a scalloped chord overhang area, the
scalloped area extending in a circumferential direction, a
plurality of vane mounting locations disposed circumferentially
between the forward end and the aft end.
BRIEF DESCRIPTION OF THE ILLUSTRATIONS
[0010] Embodiments of the invention are illustrated in the
following illustrations.
[0011] FIG. 1 is a side section view of a gas turbine engine;
[0012] FIG. 2 is an exploded perspective view of a stator shroud
vane assembly;
[0013] FIG. 3 is a perspective view of the stator shroud vane
assembly;
[0014] FIG. 4 is a side section view of an exemplary stator shroud
vane assembly;
[0015] FIG. 5 is a detail perspective view of stator shroud vane
assembly;
[0016] FIG. 6 is an aft view of the stator shroud vane assembly in
a first position;
[0017] FIG. 7 is an aft view of the stator shroud vane assembly in
a second position;
[0018] FIG. 8 is an aft view of the stator shroud vane assembly in
a third position; and,
[0019] FIG. 9 is a graph of vane position as related to clearance
between the shroud and the vane.
DETAILED DESCRIPTION
[0020] Reference now will be made in detail to embodiments
provided, one or more examples of which are illustrated in the
drawings. Each example is provided by way of explanation, not
limitation of the disclosed embodiments. In fact, it will be
apparent to those skilled in the art that various modifications and
variations can be made in the present embodiments without departing
from the scope or spirit of the disclosure. For instance, features
illustrated or described as part of one embodiment can be used with
another embodiment to still yield further embodiments. Thus it is
intended that the present invention covers such modifications and
variations as come within the scope of the appended claims and
their equivalents.
[0021] Referring to FIGS. 1-9, various embodiments of a contoured
stator shroud capable of use with pivoting vanes. The stator shroud
includes a stator shroud overhang surface over which vanes are
pivoted during engine operation. The stator shroud overhang surface
has varying elevations to eliminate leakage between the vane and
the shroud which would normally occur when a vane pivots an outer
surface of the shroud. This reduces any flow disruptions or flow
disturbances along the vane or airfoil.
[0022] As used herein, the terms "axial" or "axially" refer to a
dimension along a longitudinal axis of an engine. The term
"forward" used in conjunction with "axial" or "axially" refers to
moving in a direction toward the engine inlet, or a component being
relatively closer to the engine inlet as compared to another
component. The term "aft" used in conjunction with "axial" or
"axially" refers to moving in a direction toward the engine nozzle,
or a component being relatively closer to the engine nozzle as
compared to another component.
[0023] As used herein, the terms "radial" or "radially" refer to a
dimension extending between a center longitudinal axis of the
engine and an outer engine circumference. The use of the terms
"proximal" or "proximally," either by themselves or in conjunction
with the terms "radial" or "radially," refers to moving in a
direction toward the center longitudinal axis, or a component being
relatively closer to the center longitudinal axis as compared to
another component. The use of the terms "distal" or "distally,"
either by themselves or in conjunction with the terms "radial" or
"radially," refers to moving in a direction toward the outer engine
circumference, or a component being relatively closer to the outer
engine circumference as compared to another component.
[0024] As used herein, the terms "lateral" or "laterally" refer to
a dimension that is perpendicular to both the axial and radial
dimensions.
[0025] Referring initially to FIG. 1, a schematic side section view
of a gas turbine engine 10 is shown having an engine inlet end 12
wherein air enters the propulsor 13 which is defined generally by a
compressor 14, a combustor 16 and a multi-stage high pressure
turbine 20. Collectively, the propulsor 13 provides thrust or power
during operation. The gas turbine 10 may be used for aviation,
power generation, industrial, marine or the like. Depending on the
usage, the engine inlet end 12 may alternatively contain
multi-stage compressors rather than a fan. The gas turbine 10 is
axis-symmetrical about engine axis 26 or shaft 24 so that various
engine components rotate thereabout. In operation air enters
through the air inlet end 12 of the engine 10 and moves through at
least one stage of compression where the air pressure is increased
and directed to the combustor 16. The compressed air is mixed with
fuel and burned providing the hot combustion gas which exits the
combustor 16 toward the high pressure turbine 20. At the high
pressure turbine 20, energy is extracted from the hot combustion
gas causing rotation of turbine blades which in turn cause rotation
of the shaft 24. The shaft 24 passes toward the front of the engine
to continue rotation of the one or more compressor stages 14, a
turbofan 18 or inlet fan blades, depending on the turbine
design.
[0026] The axis-symmetrical shaft 24 extends through the through
the turbine engine 10, from the forward end 12 to an aft end. The
shaft 24 is journaled along its length. The shaft 24 may be hollow
to allow rotation of a low pressure turbine shaft 28 therein and
independent of the shaft 24 rotation. Both shafts 24, 28 may rotate
about the centerline axis 26 of the engine. During operation the
shafts 24, 28 rotate along with other structures connected to the
shafts such as the rotor assemblies of the turbine 20 and
compressor 14 in order to create power or thrust depending on the
area of use, for example power, industrial or aviation.
[0027] Referring still to FIG. 1, the inlet 12 includes a turbofan
18 which has a plurality of blades. The turbofan 18 is connected by
the shaft 28 to the low pressure turbine 19 and creates thrust for
the turbine engine 10. The low pressure air may be used to aid in
cooling components of the engine as well.
[0028] Referring now to FIG. 2 an exploded perspective view of a
stator shroud vane assembly 30 is depicted. A plurality of vanes 40
are spaced about the shroud 32, most of which are not shown. Three
vanes 40 are shown exploded from the outer surface of the shroud.
For clarity sake, however, it should be understood that a plurality
of vanes 40 are disposed about the shroud 32. The shroud 32 of the
exemplary embodiment is circular in cross section and
frusto-conical in shape having a forward end 34, an aft end 36.
Within the hollow central portion of the shroud the propulsor
components 13 of the gas turbine engine 10 may pass through. The
exemplary shroud 32 is located in the compressor 14 area of the
engine. For example, a multi-stage compressor typically includes
several rows of rotating blades mounted on a rotor and several rows
of stator vanes 40 mounted between a stator casing and the shroud
32. The shroud is axisymmetric to the shaft 24 (FIG. 1) of engine
10.
[0029] Near the forward end 34 are a plurality of pivots 38, which
are represented in the exemplary embodiment as a number of circular
pockets wherein the vanes 40 are seated for rotation relative to
the shroud 32. The shroud 32 also tapers from a smaller diameter
near the forward end 34 to a larger diameter near the aft end 36.
As will be better understood upon further reading of this
disclosure, a clearance is created between a lower edge of the
vanes 40 and the outer surface of the shroud 32 when the vanes 40
are seated within the pivots 38. In a normal shroud, the circular
cross-section results in increased clearance between the vane and
the shroud when the vane is rotated to off design positions.
However, present embodiments provide for a wavy or variable surface
height to reduce clearance in the off-design positions of the vane
40.
[0030] The vane 40 includes an outer spindle 44 and an inner
spindle 45. The spindles 44, 45 may be formed as a vertical line or
at an angle to the vertical. For example, the depicted spindles are
at an angle of between 10 and 15 degrees from the vertical. At the
inner spindle 45 is a button 42 which along with the spindle 45 is
seated within the pivot 38. An upper button 56 also controls
rotation within the casing of the engine, through which the outer
spindle passes.
[0031] Referring now to FIG. 3, a perspective view of a stator
shroud vane assembly 30 is depicted. As previously described, the
instant shroud assembly 30 is located within the compressor 14 of
the turbine engine. However the principles embodied in the
contoured stator shroud 32 may be utilized in alternate locations
of the engine wherein shrouds and vanes or air foils are utilized,
such as the stator vanes of a turbine, for example. The stator
shroud 32 depicted is at an inner diameter of the vanes 40. An
engine casing (not shown) may be used to provide the outer diameter
pivot location for the vanes 40. The stator vane shroud assembly 30
utilizes a shroud 32 having a forward end 34 and aft end 36. The
shroud 32 is generally circular in cross section as partially shown
in the view depicted. The diameter at the forward end 34 may be
larger than the diameter at the aft end 36. The forward end
includes a plurality of pivots 38 wherein vanes 40 may be
positioned. The pivots 38 are recessed areas wherein the vane or
air foils 40 are positioned for pivoting utilizing buttons or
guides 42. At a radially outward position of the vane 40 is a
spindle 44 which may be utilized to mount the second end of the
vanes 40 to provide guided pivoting or rotation. The spindle 44 may
pass through an aperture in an engine casing to stabilize the
spindle and allow for pivoting motion. A lever arm (not shown)
guides the rotation through the desired angular displacement
providing the different positions for improved efficiency and
performance of the engine at multiple operating conditions. The
plurality of vanes 40 extend about the circumference of the shroud
32 near the forward end 34 of the shroud, although some are not
shown for clarity.
[0032] Extending rearwardly from the pivots 38 is at least one
shroud surface 46, for example a stator chord overhang surface 46.
The stator chord overhang surface 46 tapers from a smaller diameter
near the pivots 38 to a larger diameter near the aft end 36. This
axial direction taper or change in elevation may be curved or may
be linear.
[0033] In addition to this taper, the stator chord overhang surface
46 is contoured so that the elevation changes in the
circumferential direction. As shown with the broken lines 48
extending in the circumferential direction, the curvature 48 of the
broken lines depicts the contour of the stator chord overhang
surface 46 which varies between a lower elevation and an upper
elevation in a circumferential direction. Thus rather than having a
circular surface, the broken line depicts the contour 48 along wavy
or sinuous surface 46. According to one embodiment of the present
disclosure, the stator chord overhang surface 46 has a wavy contour
48 to reduce clearance between the vane 40 and the shroud 32 during
movement of the vane 40. According to alternate embodiments, the
variation in elevation in the circumferential direction may be
linear. In either embodiment, the surface 48 includes a plurality
of peaks and valleys. The axis of the peaks or valleys are
generally parallel to the axis of the engine 26 (FIG. 1) or at an
angle to engine axis 26 as the shroud tapers from forward to aft
end. As will be described further herein, the contour 48
significantly reduces the flow field disruptions created by the
clearance between the vanes 40 and shroud 32. These clearances
would normally adversely affect the intended purpose of the vane
airfoil shape, function and configuration when the vane moves
between open and closed angular positions.
[0034] The exemplary vane or air foil 40 includes a leading edge
50, and a trailing edge 52 and opposed surfaces extending between.
The opposed surfaces define a suction side and a pressure side
which will be understood by one skilled in the art. At a radially
outward end of the vane 40 an outer enlarged portion or button 56.
The spindle or trunion 44 may be connected to a lever arm or other
feature to actuate the vane 40 to a desired position. The rotation
of the vane 40 provides more than one optimal condition for the
vane or air foil to provide improved efficiency and performance at
differing operating conditions of the gas turbine engine 10.
[0035] Near a lower end of the vane 40, a fillet 54 connects the
vane 40 to the button 42 at the radially inner end. The lower edge
58 of the vane 40, or vane overhang, is curved and during movement
of the vane 40, the lower edge 58 moves away from the typical
shroud surface (FIG. 6) which is purely circular in cross section
and represented by line 70. This creates clearance between the
lower vane edge 58 and the chord overhang surface 46 due to the
divergent geometries of the two parts. The increased clearance
which occurs with prior art to systems reduces performance, air
flow turn and increases loss in this region which is undesirable
and inhibits improvements in engine performance. The contour
represented by the wavy or curved broken line 48 decreases
clearance between the shroud 32 and the vane 40 improving the air
turning performance and reducing loss in this region.
[0036] Referring now to FIG. 4, a side section view of the assembly
30 of FIG. 3 is depicted. The shroud 32 is shown sectioned
vertically between the forward end 34 and the aft end 36 so as to
depict the button 42 which is seated within the pivot 38. The vane
40 further includes a lower spindle or trunnion 45 which extends
downwardly into the pivot so that the vane 42 is pivotally secured
in the shroud 32 and, as previously described, the upper spindle 44
is pivotally retained through an engine casing. As also shown in
the figure, the stator chord overhang 46 is curved in the axial
direction between the forward end 34 and the aft end 36, and more
specifically aft of the pivots 38. According to alternative
embodiments, the surface 46 is tapered linearly in the axial
direction between forward end 34 and the aft end 36.
[0037] Referring now to FIG. 5, a detailed perspective view of the
shroud 32 and vanes 40 are depicted. The detailed view shows a
pivot 38 in both an empty condition and a filled by a vane 40. A
button 42 is seated within the generally circularly shaped pivot 38
and the vane 40 is connected to the button 42 by fillet 54. Between
a lower edge 58 of the vane and the stator chord overhang 46 a
clearance 60 is shown. The clearance is reduced relative to prior
art stators due to the curvature in the axial direction, between
the forward end 34 and the aft end 36. Similarly, the clearance is
decreased through the arcuate movement of the vane 40 within the
pivot 38 due to the contour 48 along the circumferential direction
of the overhang surface 46.
[0038] In the view of FIG. 5, the contour 48 is more clearly shown
due to the curvature of the broken line 48 which represents the
contour of the stator shroud 32. A plurality of axially extending
contour lines 49 also are shown on the stator chord overhang
surface 46 which depict another curvature of the stator 32. In
combination with the lower edge 58 of the vane 40 decrease
clearance between the vane 40 and stator 32 which improves engine
performance through multiple positions of the pivoting vane 40.
Relative to operation of the engine 10, the vanes 40 are closed
when the engine speed is at or very near zero. In this closed
position, the vanes 40 are near the uppermost elevation of the
contour surface 48. Alternatively, as engine speed increases and
approaches a maximum, the vane 40 approaches the lowermost
elevation of the contour surface 48.
[0039] Referring now to FIGS. 6-8, the shroud 32 is shown in an aft
view looking forward with a vane 40 shown move in multiple
positions. The contour of the stator chord overhang surface 46 is
best described in reference to this view. The wavy or sinuous
surface 48 is formed by a plurality of scallop-like humps which
change between first and second elevations. Although the term
sinuous is used, it should not be limited to mathematically exact
sin curve. The term is instead used in a general sense to indicate
a repeating change in elevation. A broken line 70 is shown in the
view to represent a circular reference shape of a prior art shroud.
The line 70 may also represent a base or first elevation of the
stator chord overhang surface 46. Alternatively, the line 70 of the
instant embodiment may be above or below the valley or lower
elevation of the stator chord overhang surface since, as shown, the
surface 46 also changes elevation in the axial direction. The
contour 48 elevation changes are shown by referencing the
difference between first elevation 70 and the second upper
elevation 72 of the contour. Thus the overhang surface 46 changes
elevation between a first elevation and a second elevation and with
such changing elevation, the clearance between the vane 40 is
reduced throughout the positions depicted in FIGS. 6-8.
[0040] The vane 40 may rotate from, for example, minus 3 degrees
and about 25 degrees. Thus the exemplary vane 40 may move about 14
degrees from the center position in either of two rotational
directions. However this is exemplary and alternate angular ranges
may be designed into the vane movement.
[0041] Referring now to FIG. 7, the vane is shown in a central
position which more clearly depicts the lower edge 58 of the vane.
The vane 40 is in the 11 degree position, according to the
exemplary range as previously described. This is generally a
central position. A pair of clearance arrows are shown in FIG. 7.
Clearance 60 depicts the clearance provided by the contoured 48 in
cooperation with the lower edge 58 of vane 40. Meanwhile the
clearance P is shown which depicts the larger clearance between the
lower edge 58 and the prior art circular shroud reference
previously described as line 70. From this embodiment, one skilled
in the art can clearly see the reduced differential that the
contour 48 provides.
[0042] Referring now to FIG. 8, a second extreme position of the
vane 40 is depicted, for example at the 25 degree position. Again
the clearance 60 is much smaller than the prior art clearance P as
related to the circular shroud reference 70.
[0043] It should be understood by one skilled in the art that vanes
may take various shapes and forms depending upon the design
characteristics of the engine. Accordingly, the shape of the
contours may be formed to correspond to the shape of the vane lower
edge through a preselected arcuate motion. The shroud surface,
spindle angle, amount of vane chord overhang and travel are all
designed/optimized with reduced clearance for reduced loss and
improved performance in mind when optimizing the variable vane
system.
[0044] Referring now to FIG. 9, a chart is shown depicting a
relationship between the vane's angle measured in degrees and the
clearance between the vane lower edge 58 and the shroud chord
overhang 46. As shown by the line 80, having diamond-shaped data
points, the clearance between an angle of minus 10 degrees and 25
increases rather constantly. The stator shroud 32 of this prior art
embodiment is circular in shape and is lacking the contour shape of
the instant embodiments. To the contrary, line 82 represented by
square-shaped data points begins at the previously defined range of
minus 3 degrees and moves to a position of 25 degrees. The
clearance represented by line 82 is generally constant from about 0
degrees to about 12 degrees, before increasing up to the 25 degree
position. Thus, by comparing the data points along the lines 80, 82
one skilled in the art will recognize the clearance is much less in
the contoured stator shroud than that of the prior art.
[0045] The foregoing description of structures and methods has been
presented for purposes of illustration. It is not intended to be
exhaustive or to limit the invention to the precise steps and/or
forms disclosed, and obviously many modifications and variations
are possible in light of the above teaching. Features described
herein may be combined in any combination. Steps of a method
described herein may be performed in any sequence that is
physically possible. It is understood that while certain forms of a
contoured stator shroud have been illustrated and described, it is
not limited thereto and instead will only be limited by the claims,
appended hereto.
* * * * *