U.S. patent application number 12/963206 was filed with the patent office on 2011-06-16 for two-part shroud or shroud section for a stator stage with vanes of an axial compressor.
Invention is credited to Andre Lhoest, Christophe Remy.
Application Number | 20110142651 12/963206 |
Document ID | / |
Family ID | 42332776 |
Filed Date | 2011-06-16 |
United States Patent
Application |
20110142651 |
Kind Code |
A1 |
Lhoest; Andre ; et
al. |
June 16, 2011 |
Two-Part Shroud or Shroud Section for a Stator Stage with Vanes of
an Axial Compressor
Abstract
A shroud or shroud section for a stator stage with vanes of an
axial compressor is made of composite material and is built in two
parts, each having a series of notches corresponding to a half of
the profile of the vanes, so as to form apertures that follow the
shape of the vanes when the two parts are assembled. The two parts
also include mutual fastening members or means adapted to ensure
their assembly.
Inventors: |
Lhoest; Andre; (Huy, BE)
; Remy; Christophe; (Fexhe-Le-Haut-Clocher, BE) |
Family ID: |
42332776 |
Appl. No.: |
12/963206 |
Filed: |
December 8, 2010 |
Current U.S.
Class: |
416/182 |
Current CPC
Class: |
F05D 2300/501 20130101;
F01D 11/125 20130101; Y02T 50/673 20130101; F04D 29/164 20130101;
F05D 2300/603 20130101; F05D 2260/30 20130101; F05D 2260/36
20130101; F01D 5/26 20130101; F01D 9/041 20130101; Y02T 50/60
20130101; Y02T 50/672 20130101 |
Class at
Publication: |
416/182 |
International
Class: |
F04D 29/38 20060101
F04D029/38 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 14, 2009 |
EP |
09179128.5 |
Claims
1. A shroud for a stator stage with vanes of an axial compressor,
comprising: at least one first curved element having at least one
first notch, each first notch corresponding to a first portion of a
contour of an end of one of the vanes; and at least one second
curved element having at least one second notch, each second notch
corresponding to a second portion of the contour of the end of the
vane, the first and second curved elements being adapted to be
arranged axially against one another, so as to confine the ends of
the vanes in corresponding pairs of first and second notches.
2. The shroud according to claim 1, wherein each of the first and
second curved elements comprises: an assembly edge in a plane that
is perpendicular to a main axis of the compressor, the assembly
edges being adapted to come into mutual contact during the assembly
of the two curved elements by becoming closer in a direction
generally corresponding to a flow direction through the
compressor.
3. The shroud according to claim 1, wherein each first portion of
the contour of the end of a vane generally corresponds to half of
the profile of the end of such vane in a flow direction of the
compressor.
4. The shroud according to claim 1, further comprising: a first
assembly edge disposed on the first curved element; and a second
assembly edge disposed on the second curved element; wherein the
first assembly edge cooperates by insertion with the second
assembly edge during assembly of the first curved element and the
second curved element by becoming closer in a direction
corresponding to a flow direction of the compressor.
5. The shroud according to claim 1, further comprising: a groove
disposed along the curved direction of one of the first assembly
edge and second assembly edge; and a projecting part disposed along
the curved direction of the other of the first assembly edge and
second assembly edge; wherein the groove and the projecting part
are interrupted by the respective first and second notches of the
first and second curved elements.
6. The shroud according to claim 1, further comprising: an internal
U-shaped section having an opening of the U-shape directed toward
the center of the shroud, so as to form a recess adapted to
received an abradable material.
7. The shroud according to claim 6, wherein the first and second
curved elements intersect at approximately the center of the
U-shape.
8. The shroud according to claim 1, further comprising: clip-type
fastening members disposed on the first and second assembly
edges.
9. The shroud according to claim 8, wherein the clip-type fastening
members cooperate by elastic engagement of positive contact
surfaces when the first and second curved elements become closer
together along a direction corresponding to a flow direction of the
compressor.
10. The shroud according to claim 8, wherein the clip-type
fastening members comprise: a plurality of spaced elements
projecting beyond one of the first and second curved elements along
a direction corresponding approximately to the direction for moving
the first and second curved elements closer together.
11. The shroud according to claim 8, wherein the clip-type
fastening members are arranged radially interior to the respective
assembly edges of the first and second curved elements.
12. The shroud according to claim 1, wherein the first curved
element and the second curved element are each formed by a
plurality of curved sections, the end of each section having a
profile that corresponds to the end of a vane, such that the
junction between adjacent curved sections corresponds to the vane
profile.
13. The shroud according to claim 1, wherein at least one of the
first curved element and the second curved element is formed by a
plurality of curved sections, the end of each section having a
profile that corresponds to a portion of the end of a vane, such
that the junction between adjacent curved sections corresponds to a
portion of the vane profile.
14. The shroud according to claim 13, wherein each end of each
curved section includes a means for connecting to an adjacent
section, each means for connecting including a positive contact on
both sides of the junction on each of the first and second curved
elements.
15. The shroud according to claim 1, wherein each of the first and
second curved elements is in the shape of a closed ring.
16. The shroud according to claim 1, wherein one of the first and
second curved elements forms a closed ring shape, and the other of
the first and second curved elements is formed by a plurality of
curved sections corresponding to the closed ring shape, each curved
section being successively arranged against the closed ring shape
so as to confine, over the entire perimeter of the closed ring
shape, the roots of the vanes in corresponding pairs of first and
second notches.
17. The shroud according to claim 1, wherein the shroud forms a
shroud section of the compressor.
18. The shroud according to claim 1, wherein the shroud is made of
a composite material.
Description
[0001] This application claims priority under 35 U.S.C. .sctn.119
to European Patent Application No. 09179128.5, filed 14 Dec. 2009,
which is incorporated herein by reference for all purposes.
BACKGROUND
[0002] 1. Field of the Application
[0003] The present application relates to a shroud for a stator
with vanes of an axial compressor, more particularly to an internal
shroud of a stator, more particularly still, to an internal shroud
made of composite material. Such compressors are typically present
in turbojet engines, jet prop engines, and gas generators.
[0004] 2. Description of Related Art
[0005] An axial compressor typically comprises a series of
compression stages, each being constituted of a circumferential
arrangement of vanes mounted on their bases on a rotor. A stator
serving as a casing surrounds the rotor and the blades. The ends of
the rotor blades move in the vicinity of the internal surface of
the stator. The fluid, typically air, is thus displaced and
compressed according to an annular jet, concentric to the rotation
axis of the rotor. The rotor thus comprises several rows of
circumferential blades, spaced apart from one another. Rows of
stationary vanes are mounted on the stator between the rows of
rotor blades for the purpose of rectifying the airflow between two
stages of the compressor. These stator vanes conventionally
comprise an internal shroud at their ends for the purpose of
delimiting the internal envelope of the fluid stream. This shroud
conventionally has an annular shape with an outer surface that is
shaped specifically for the defining of the flow. The outer surface
comprises a series of apertures or holes adapted to receive the
inner ends of the vanes which are fixed at their outer ends or
bases to the stator. This shroud also ensures that the vanes are
affixed to one another in the area of their inner ends. The
internal surface of the shroud is lined with a friable material or
else more conventionally called "abradable" from the English term.
This layer of abradable material is adapted to cooperate by
friction with one or several circumferential ribs on the rotor in
order to make it somewhat leak-proof. These ribs are more
conventionally called knife edges.
[0006] The patent document EP 1 213 484 A1 of the same applicant as
this application discloses an internal shroud and an external
shroud of a compressor stator stage, these shrouds being
conventionally made of metal. This document relates to a device for
connecting the vanes to the shrouds by means of a band which is
inserted in apertures made at each end of the vanes passing through
the holes of the shrouds, the band serving as a locking key with
respect to the outer and inner surfaces of the external and
internal shrouds, respectively.
[0007] As a function of the dimensions and materials used and also
to facilitate the assembly, it can be interesting to segment the
shroud into several sections. Indeed, in the case of a shroud made
of composite material, for example, it can be difficult to inject
the resin of the composite material over lengthy pieces, which
means that it is interesting to segment the shroud so as to reduce
the length of the sections. Segmenting the shroud can also prove to
be interesting to compensate for the differential expansions in the
area of the vanes themselves and of parts of the stator supporting
the vanes. The aerodynamic performance of a segmented composite
shroud is diminished for the following reasons.
[0008] The method of manufacture by plastic or resin injection
requires the use of a mold to give the final shape. The general
shape of a section is an arc of circle whereas the unmolding
direction on a surface of the section is axial and not radial. The
shroud holes have main axes which correspond to radii starting from
the rotation axis of the rotor; these axes are therefore inclined
with respect to the unmolding direction. Consequently, the holes
have an unnecessarily flared section toward the unmolding
direction. The adjustment between the holes of the shroud and the
vanes is unnecessarily large and unfavorable from an aerodynamic
standpoint. It is indeed desirable for the shroud surface in
contact with the fluid stream, particularly in the area of the
junction with the vanes, to be as continuous as possible.
[0009] Furthermore, independent of this requirement related to the
unmolding, the holes of a segmented composite shroud must be
provided to be slightly larger than the section of the vanes which
go through them because of the assembly process. Indeed, once a
first section is in place, it needs to be pulled up along the vanes
in order to leave minimum room for the adjacent end of the section
to be set in place next, so the first section can then be pulled
down toward its final position. The clearance increase between the
holes and the vanes, in particular in the area of the outer
surface, is detrimental to the aerodynamics of the stator
stage.
[0010] Although great strides have been made in the area of axial
compressors, many shortcomings remain.
DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a partial, cross-sectional view of an axial
compressor with, among other things, a shroud according to the
present application.
[0012] FIG. 2 is a perspective view of a shroud section according
to the present application.
[0013] FIG. 3 is a perspective view according to another angle of
the shroud section according to FIG. 1 mounted on a row of
vanes.
[0014] FIG. 4 is a bottom, perspective view of the shroud section
of FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] The present application discloses a shroud or shroud section
made of composite material for a stator stage with vanes of an
axial compressor, the shroud or shroud section being adapted to
receive an end of the vanes, comprising at least one first curved
element with at least one first notch corresponding to a first
portion of the contour of the end of the vanes, at least one second
curved element having a generally similar shape as the first curved
element with at least a second notch corresponding to a second
portion of the contour of the end of the vanes, the first and
second notch or notches forming one or several pair(s) of notches,
the first and second curved elements being adapted to be arranged
axially against one another so as to confine the profile of the end
of the vanes in each pair of first and second notches. The second
portion of the contour of the end of the vanes preferably
corresponds to the rest of the contour which is not concerned with
the first portion, so that the first and second notches surround
the entirety of the contour of the vanes. Such a construction has
numerous advantages, mostly from the standpoint of an ease of
assembly on the vanes and from the standpoint of aerodynamics of
the flow of the fluid stream into the stator.
[0016] Indeed, this modular construction with the pairs of notches
forming the apertures of the shroud enables a substantially easier
assembly in comparison with a conventional segmented shroud, each
section of which being required to be carefully placed in front of
the series of vanes to which it must be mounted and must then be
pulled up along the vanes in the area of one lateral end in order
to leave enough room for the adjacent end of the next section.
[0017] Furthermore, this modular construction makes it possible to
use another way of unmolding the segments made of composite
material by getting rid of the unavoidable requirement with the
segments of a conventional shroud of having to unmold in a
direction forming an angle with the main directions of some
apertures thus formed. The apertures of each segment of a
conventional shroud are indeed different from one another in order
to take into account the projection of the vane according to the
direction of assembly. These differences lead to assembly
adjustments which are too great, having a detrimental effect on the
aerodynamics of the flow.
[0018] Each curved element forming the shroud comprises at least
two, preferably three, even more preferably at least four,
notches.
[0019] According to an advantageous embodiment of the present
application, each of the first and second curved elements comprises
an assembly edge in a plane, perpendicular to the main axis of the
compressor, the assembly edges being adapted to come into contact
with one another during the assembly of the two curved elements,
preferably, by becoming closer together in a direction
corresponding approximately to the flow direction.
[0020] According to another advantageous embodiment of the present
application, the first and/or second portion of the contour of the
end of the vanes correspond(s) to approximately half of the profile
in the direction of the flow. This measure allows the apertures to
take on the shape of the barrel-shaped vanes.
[0021] According to yet another advantageous embodiment of the
present application, the first curved element comprises an assembly
edge adapted to cooperate by insertion with an assembly edge of the
second segment during the assembly of the two curved elements,
preferably by becoming closer in a direction corresponding
approximately to the direction of the flow.
[0022] According to yet another advantageous embodiment of the
present application, the assembly edge of one of the first and
second curved elements comprises a groove according to the curved
direction and the assembly edge of the other of the first and
second curved elements comprises a projecting portion, the groove
and the projecting portion being interrupted by the respective
notch or notches of the first and second curved elements.
[0023] According to yet another advantageous embodiment of the
present application, the shroud is an internal shroud with a
U-shaped section with the opening of the U-shape being directed
toward the center of the shroud so as to form a recess adapted to
receive some abradable material and where the limit between the
first and second curved elements is located approximately toward
the center of the U-shape.
[0024] According to another advantageous embodiment of the present
application, each of the first and second curved elements comprises
member or means for mutual fastening, these members or means being
preferably of the clip-type.
[0025] According to another advantageous embodiment of the present
application, the mutual fastening means or members are such that
they cooperate by elastic engagement of surfaces with positive
contact when the first and second curved elements move closer
together in a direction corresponding approximately to the flow
direction.
[0026] According to another advantageous embodiment of the present
application, the mutual fastening means or members comprise several
elements projecting over one of the first and second curved
elements in a direction corresponding approximately to the
direction for moving the first and second curved elements closer
together.
[0027] According to another advantageous embodiment of the present
application, the mutual fastening means or members are arranged on
the respective assembly edges of the first and second curved
elements.
[0028] According to another advantageous embodiment of the present
application, each end of the shroud section comprises a section
whose shape corresponds to that of the end of the vanes so that the
junction between two adjacent sections corresponds to the shape of
the vane.
[0029] According to another advantageous embodiment of the present
application, each end of the shroud section comprises means for
connecting to an adjacent section, these connection means having a
positive contact, preferably on both sides of the junction on each
of the first and second curved elements.
[0030] According to another advantageous embodiment of the present
application, the first and second curved elements are each
ring-shaped, preferably closed.
[0031] According to another advantageous embodiment of the present
application, one of the first and second curved elements is
ring-shaped, preferably closed, and comprises several second curved
elements corresponding to sections of the ring and adapted to be
arranged successively against the ring-shaped curved element so as
to confine, over the entire perimeter of the ring, the shape of the
vane roots in each pair of first and second notches.
[0032] The present application also comprises a shroud for a stator
stage with vanes of an axial compressor comprising several shroud
sections such as described hereinabove.
[0033] FIG. 1 shows a cross-sectional view of part of an axial
compressor, typically of a jet engine or turbine engine. The
compressor comprises a rotor 5 rotating about the axis 2. The rotor
comprises a series of blades 6 fixed onto its circumference,
corresponding to a stator stage. The flow direction of the fluid to
be compressed is shown by the arrow. The casing 3, or the stator,
of the compressor comprises a series of vanes 4 fixed at their
bases. This series of vanes constitutes a stator of the fluid
stream located between two blade rows of the mobile wheel, the
upstream row not being represented. A row of blades of the mobile
wheel and the guide vane downstream constitute a stage of the
compressor. The inner ends of the vanes 4 are connected to a shroud
8. The shroud has the general shape of a circular ring following
the shape of the rotor 5. The shroud 8 thus delimits the lower or
internal part of the annular fluid stream passing through the
stator. It is kept in place by the vanes and makes the rotor 5
leak-proof. The shroud comprises on its inner surface a layer of
abradable material 10. The rotor 5 comprises two circumferential
ribs, more commonly called knife edges 9, cooperating with the
layer of friable material 10. The abradable material 10 is applied
and then machined so as to present a sealing surface 11 cooperating
with the knife edges. This material has friction properties with
the metal of the knife edges and the ability to disintegrate into
fine dust in case of contact with the knife edges when the rotor is
in rotation. The knife edges 9 and the surface 11 made of friable
material thus constitute a labyrinth seal.
[0034] The shroud 8 is constituted of a series of sections shaped
in an arc-of-circle such as shown in FIG. 2. The section shown in
FIG. 2 is constituted of two elements in an arc-of-circle 12 and
14, each forming about a half, in a direction corresponding to that
of the axis of the machine, of the shroud section along to a median
arc-of-circle.
[0035] The curved element 12 comprises a series of notches 16
adapted to follow the shape of the corresponding end of the vanes.
The notches 16 are, in principle, identical, taking into account
the fact that all the vanes of a stator stage are generally
identical and uniformly distributed on the circumference of the
shroud. The notches 16 are such that they correspond to about half
of the profile of the vanes, the half being in a general direction
corresponding to the flow direction of the fluid, or to the
longitudinal direction of the section of a vane. The curved element
12 comprises an outer surface 22 of revolution, corresponding
generally to a segment or piece of a cylinder, that is, a surface
directed toward the outside of the circle or ring which forms the
complete shroud. This surface is the surface delimiting the inner
envelope of the fluid stream passing through the stator. It is
delimited on one side by a rounded edge 26 and on the other side by
an edge 27 crossing through the notches 16 and adapted to come into
contact with a corresponding edge 29 of the other curved element
14. This contact edge 27 comprises a groove 28 extending in
parallel to the outer surface 22 and below this surface. The groove
28, as the edge 27, is interrupted by the notches 16.
[0036] The curved element 14 opposite the curved element 12 is
generally similar. It comprises a series of notches 18
corresponding to the notches 16 of the opposite curved element 12
and adapted to form, when the two curved elements are arranged in
an adjacent and corresponding manner, a series of apertures or
openings which follow the shape of the vanes. The shape of the
notches 18 thus corresponds to the rest of the section of the
vanes, that is, to the portion of the contour of the vane which is
not covered by the notch 16 of the opposite curved element 12. As a
result, the notches 18 can have a slightly or even substantially
different profile than those of the opposite notches 16, as a
function of the section of the end of the vane to be surrounded.
Similar to the opposite curved element 12, the curved element 14
comprises an outer surface 22, generally cylindrical or
ring-shaped, that is, a surface directed toward the outside of the
circle or ring which forms the complete shroud. This surface is the
surface delimiting the inner envelope of the fluid stream passing
through the stator. It is delimited on one side by a rounded edge
24 and on the other side by an edge 29 passing through the notches
18 and adapted to come into contact with the corresponding edge 27
of the opposite curved element 12. This contact edge 29 comprises a
tongue 30 or lug extending in parallel to the outer surface 22 and
at a lower level of this surface. The tongue 30, as the edge 29, is
interrupted by the notches 18.
[0037] The curved element 14 also comprises in the area of its
contact edge 29, at a level that is lower than that of the outer
surface 22, a series of elastic hooks generally directed toward the
opposite curved element 12 during the assembly and adapted to
cooperate by flexion followed by a movement for returning to a
position close to the initial position with corresponding housings
provided in the area of the contact edge 27 of the opposite curved
element 12. These hooks are arranged by pairs with a generally
U-shaped profile directed toward the outside and where the ends of
the U-shaped legs each comprise a boss forming the hook as such
with a surface inclined with respect to the direction for inserting
the hooks in their housings 21 of the opposite curved elements and
with a surface that is generally perpendicular to this direction
and being able to come into positive contact with a corresponding
surface of the housings. The bosses in question are arranged at
each end of the two U-shaped legs and so as to be laterally
directed toward the outside of the U-shape.
[0038] The shroud section is provided to be mounted by assembling
the two elements about the vanes. In practice, the two elements 12
and 14 are arranged in front of one another, similar to the drawing
of FIG. 2, by first engaging each of the elements with the row of
vanes which is adapted to be fixed to this shroud section. Once
each element is engaged with the row of vanes, that is when the
notches of each element cooperate, at least partially, with the
vanes, moving the two elements closer together is very easy since
it is guided, at least in a plane generally at a tangent to the
outer surface 22 of the shroud, by the vanes. Putting the
respective contact edges 27 and 29 in correspondence can require
one or more movements in a direction that is perpendicular to the
plane at a tangent to the outer surface 22 of the shroud. The
tongue 30 of the element 14 is arranged facing the groove 28 of the
opposite element 12 so as to ensure an efficient guiding during the
assembly. The mutual fastening of the two elements is carried out
by applying a force for moving the contact edges closer together so
as to make the resilient hooks penetrate in the respective housings
up to the point where the parts with the positive contact surfaces
override the corresponding surfaces of the housings. The legs can
then return to a position close to that before insertion and where
the positive contact surfaces of the hooks mesh with the
corresponding surfaces of the housings.
[0039] Alternatively, the shroud section can be assembled before
the vanes are mounted. The elements 12 and 14 are thus assembled by
a similar movement to that described hereinabove, but without the
presence of the vanes. The section is then mounted pre-assembled on
the vanes. This principle of assembly, just like the previous
assembly principle described in detail in the previous paragraph,
provides the advantage of allowing a shroud with apertures and a
profile that is very adjusted to the profile of the vanes to be
made, while doing away with the requirements caused by the
unmolding of a conventional shroud section at the apertures. The
unmolding of a conventional shroud section is generally done by
moving away part of the mold corresponding to the outer surface and
to the apertures over at least part of the thickness of the shroud
from the outer surface. The curved nature of the shroud section
causes the axes of the apertures to correspond to radii of the
shroud and can thus form an angle with the unmolding direction.
This requirement calls for a section of the apertures that flares
more than what is required for the assembly. However, the previous
principle of assembly described in detail in the previous paragraph
has the added advantage to make it easier to assemble the shroud
and mount it on the vanes.
[0040] FIG. 3 shows the shroud section of FIG. 2 once assembled and
mounted on a row of vanes 4. One can see that the outer surface 22
of the shroud 8 remains continuous and regular in the junction
area. The mutual fastening is ensured by a pair of elastic hooks 20
between each pair of neighboring vanes. The vanes 4 can be fixed to
the shroud by applying glue or an elastomer serving as glue
ensuring a dual function, namely, that of ensuring a mechanical
connection and a tight sealing. To do so, the ends of the vanes
slightly project under the apertures so as to receive the glue or
the elastomer.
[0041] It must be noted that other methods for mechanically
connecting the vanes and the shroud can be provided. Indeed, it is
absolutely conceivable to provide for a band to be placed through
the holes made in the ends of the vanes so as to ensure a
mechanical connection preventing the vanes from exiting the shroud,
such as disclosed in the document EP 1213484 A1. In this case, it
would be more practical to provide for a band to be placed before
the shroud is mounted on the vanes.
[0042] FIG. 3 also shows the U-shaped section with the open portion
directed toward the center of the shroud, forming a recess adapted
to receive the abradable material in the form of a paste by
projection or by any other equivalent or similar method.
[0043] FIG. 4 is an enlarged view of a part of the bottom of the
shroud section mounted on the vanes shown in FIG. 3. It shows well
the precision of the adjustment between the apertures formed by the
pairs of notches 16 and 18 and the vanes 4. The fact that each
notch of a pair of notches 16 and 18 forming an aperture surrounds
the blade over approximately half of its length (according to the
flow direction) makes it possible to precisely adjust the apertures
on tunnel-section vanes, that is, vanes whose section is
substantially thicker in the middle than on the edges (leading or
trailing).
[0044] The shroud sections such as shown in FIGS. 2, 3, and 4 can
have ends with a profile corresponding to that of the end of the
vanes, so that the junction between two adjacent sections
corresponds to the profile of the blade (not shown). Preferably,
each shroud section end comprises means for connecting to an
adjacent section, these connection means being of the positive
contact type, preferably on both sides of the junction on each of
the curved elements forming a section. This positive contact
ideally cooperates with a relative sliding movement along vanes
between two adjacent sections.
[0045] It must be noted that the shape, number, and position of the
elastic hooks as mutual fastening means for curved elements are
given only by way of non-limiting example. Indeed, various
alternatives which are similar and/or equivalent to these fastening
means are possible, as a function of diverse parameters such as the
choice of materials, manufacturing requirements (molding/unmolding
for non-metallic materials), ease of assembly and disassembly,
desired resistance to disassembly.
[0046] It must also be noted that the shroud can be made of two
elements of the type previously described, namely the curved
elements 12 and 14, each forming a complete ring. These elements
will preferably form a closed ring. Alternatively, the shroud can
be composed of a first element forming a complete ring and
preferably closed, and a series of curved elements adapted to be
arranged against the first element and adjacent to one another
along the circumference of the first element.
[0047] It must also be noted that it is, of course, conceivable to
apply the shroud according to the present application to a stator
stage whose vanes are not necessarily identical and/or uniformly
distributed over the entire circumference. In this case, the
apertures formed by the pairs of notches will not be uniformly
distributed but rather according to the vanes of the stator.
[0048] It must also be noted that, although the embodiment of the
present application was described in relation to an internal
shroud, the present application is similarly applicable to an
external shroud.
[0049] The present application discloses a shroud that overcomes
the aforementioned drawbacks and has many benefits and advantages,
including a shroud that is easy to mount and has good aerodynamic
characteristics.
[0050] It is apparent that an invention with significant advantages
has been described and illustrated. The particular embodiments
disclosed above are illustrative only, as the invention may be
modified and practiced in different but equivalent manners apparent
to those skilled in the art having the benefit of the teachings
herein. It is therefore evident that the particular embodiments
disclosed above may be altered or modified, and all such variations
are considered within the scope and spirit of the invention.
Accordingly, the protection sought herein is as set forth in the
description. Although the present application is shown in a limited
number of forms, it is not limited to just these forms, but is
amenable to various changes and modifications without departing
from the spirit thereof.
* * * * *