U.S. patent application number 13/386496 was filed with the patent office on 2012-05-24 for outer shell sector for a bladed ring for an aircraft turbomachine stator, including vibration damping shims.
This patent application is currently assigned to SNECMA. Invention is credited to Laurent Gilles Dezouche, Patrick Edmond Kapala, Samir Zaidi.
Application Number | 20120128482 13/386496 |
Document ID | / |
Family ID | 41800367 |
Filed Date | 2012-05-24 |
United States Patent
Application |
20120128482 |
Kind Code |
A1 |
Dezouche; Laurent Gilles ;
et al. |
May 24, 2012 |
OUTER SHELL SECTOR FOR A BLADED RING FOR AN AIRCRAFT TURBOMACHINE
STATOR, INCLUDING VIBRATION DAMPING SHIMS
Abstract
An assembly forming an outer shell sector, for a bladed ring
sector configured to be used on a compressor or turbine stator in
an aircraft turbomachine, including a plurality of elementary
sectors and vibration damping shims each of them being inserted
between two elementary sectors associated with it. A profile of
each vibration damping shim is approximately the same as a profile
of the elementary sectors.
Inventors: |
Dezouche; Laurent Gilles;
(Le coudray Montceau, FR) ; Kapala; Patrick Edmond;
(Villevaude, FR) ; Zaidi; Samir; (Moissy Cramayel,
FR) |
Assignee: |
SNECMA
Paris
FR
|
Family ID: |
41800367 |
Appl. No.: |
13/386496 |
Filed: |
July 29, 2010 |
PCT Filed: |
July 29, 2010 |
PCT NO: |
PCT/EP10/61037 |
371 Date: |
January 23, 2012 |
Current U.S.
Class: |
415/209.2 |
Current CPC
Class: |
F01D 9/042 20130101;
F01D 11/001 20130101; F01D 25/06 20130101; F04D 29/542 20130101;
F04D 29/668 20130101; F04D 29/644 20130101; F01D 25/246
20130101 |
Class at
Publication: |
415/209.2 |
International
Class: |
F01D 9/04 20060101
F01D009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 2009 |
FR |
09 55439 |
Claims
1-7. (canceled)
8. A bladed ring sector configured to be installed on a compressor
stator of an aircraft turbomachine, comprising: an assembly forming
an outer shell sector; an inner shell sector; a plurality of blades
at a tangential spacing from each other and inserted between the
assembly forming the outer shell sector and the inner shell sector,
the blades being fixed to each assembly forming the outer shell
sector and the inner shell sector; and the assembly forming an
outer shell sector comprising firstly a plurality of elementary
sectors at a spacing from each other along a tangential direction
of the assembly, and secondly vibration damping shims each of them
being inserted between two elementary sectors associated with it,
placed directly consecutively along the tangential direction,
wherein a profile of each vibration damping shim is approximately a
same as a profile of the elementary sectors.
9. A sector according to claim 8, wherein the shim is forced in
contact with two parallel plane friction surfaces facing each other
along the tangential direction and provided respectively on the two
elementary sectors associated with the shim, and wherein the shim
has two complementary plane friction surfaces, parallel to each
other and cooperating with the two corresponding friction surfaces
of the elementary sectors.
10. A sector according to claim 8, wherein the shim includes hooks
to hold it in place on the compressor or turbine stator.
11. A sector according to claim 8, wherein the elementary sectors
are separated from each other by radial slits completely filled in
by the vibration damping shims.
12. A sector according to claim 8, wherein the vibration damping
shims extend approximately along an axial or oblique direction of
the assembly.
13. An aircraft turbomachine comprising: a compressor stator
including at least one bladed ring sector according to claim 8.
Description
DESCRIPTION
[0001] This invention generally relates to an aircraft
turbomachine, preferably of the turbojet or turboprop type.
[0002] More particularly, the invention relates to the compressor
or turbine stator of such a turbomachine, and more precisely to a
bladed ring sector comprising a plurality of stator blades and two
concentric shells supporting the blades and designed to radially
delimit a primary flow passing through the turbomachine, inwards
and outwards respectively. Such a bladed ring is usually made using
several sectors arranged end to end, is usually used in the
compressor or the turbine as a guide vane or a nozzle.
[0003] Turbomachines usually comprise a low pressure compressor, a
high pressure compressor, a combustion chamber, a high pressure
turbine and a low pressure turbine, in series. Compressors and
turbines comprise several rows of mobile blades at a
circumferential spacing, these rows being separated by rows of
fixed blades also at a circumferential spacing. In modern
turbomachines, high dynamic stresses are applied to the guide vanes
and nozzles. Technological progress leads to a reduction in the
number of stages for equal or better performances, resulting in a
higher load for each stage. Furthermore, changes to production
technologies have led to a reduction in the number of parts, which
reduces the damping effect of connections between parts. This is
the case particularly when an abradable cartridge brazing
technology is used which eliminates a large source of dissipation
of vibration energy.
[0004] Document FR-A-2 902 843 discloses a means of solving this
vibration problem by breaking the outer shell sector down into
elementary sectors at a fixed spacing from each other along the
tangential direction by the use of slits or radial cuts, oblique or
in another direction, each elementary sector supporting a single
blade of the bladed ring sector. Furthermore, damping inserts in
the form of strips are inserted between the elementary sectors. The
operating principle is based on the introduction of a stiffness
non-linearity in the dynamic behaviour of the structure. This
non-linearity is triggered by a threshold vibration level of the
system. This vibration activity causes a relative movement between
the elementary sectors of the blades and the damping inserts. This
relative movement causes successive loss and recovery of adhesion
of the damping inserts and consequently a continuous variation of
the local stiffness of the system. Consequently, the mode(s)
causing the vibration activity are disorganised by the permanent
variation of the associated natural frequencies. Resonance of the
system cannot be set up because of the continuous variation in the
state of the dynamic system. This reduces vibration amplitudes in
the system.
[0005] Nevertheless, even if this solution is satisfactory in terms
of reducing vibrations, it can be improved. Furthermore, in this
solution disclosed in document FR-A-2 902 843, the damping inserts
are held in contact against the friction surfaces of the elementary
sectors due to the effect of the pressure gradient between the
aerodynamic flowpath and the outside of the compressor, applying a
radially inwards force on these inserts. The disadvantage is that
this pressure gradient cannot be sufficient to satisfactorily force
the inserts into contact with the friction surfaces. In this case,
the result is firstly a reduction in the vibration damping
performances, but also a possible loss of leak tightness of the air
flowpath.
[0006] Another disadvantage with this solution is the fact that one
of the blades in the bladed ring sector will be overloaded.
Aerodynamic forces applied on the blades include a tangential
component that cannot be resisted in the outer shell sector, due to
its segmentation into tangentially spaced elementary sectors. Thus,
these tangential components are combined and pass through the inner
shell sector of the bladed ring sector before passing through the
blade located adjacent to the anti-rotation stop fitted on the ring
sector. Therefore, this blade is very highly loaded due to the
incapability of the outer shell sector to transmit static forces
along the tangential direction.
[0007] Therefore, the purpose of the invention is to at least
partially overcome the problems mentioned above that arise with
embodiments according to prior art.
[0008] The first purpose of the invention to achieve this is an
assembly forming an outer shell sector for a bladed ring sector
that will be used on a compressor or turbine stator in an aircraft
turbomachine, said outer shell sector comprising firstly a
plurality of elementary sectors at a spacing from each other along
a tangential direction of said assembly, and secondly vibration
damping shims, each of them being inserted between two elementary
sectors associated with it, placed directly consecutively along
said tangential direction.
[0009] According to the invention, the profile of each vibration
damping shim is approximately the same as the profile of the
elementary sectors.
[0010] Due to the particular profile of the shims, the friction
interface between the shims and the elementary sectors is large
which results in an improved damping effect.
[0011] Furthermore, the fact that the shims are forced into contact
with the friction surfaces of the elementary sectors can result in
a perfect seal between these elements, independent of the pressure
difference between the aerodynamic flowpath and the outside of the
compressor or the turbine. This seal is obtained by construction,
with shims applying forces on the friction surfaces of the
elementary sectors approximately along the tangential direction.
Note that this seal is further reinforced during operation, because
the forces bringing the friction surfaces and the shims into
contact with each other are accentuated by application of the
tangential component of aerodynamic forces applied on the stator
blades, on the elementary sectors.
[0012] Concerning the tangential component of the aerodynamic
forces applied on the blades, note that one of the essential
advantages of this invention lies in the fact that this component
can transit through the assembly forming an outer shell sector
because the outer shell sector is very much stiffened along the
tangential direction due to the particular positioning of vibration
damping shims, even though it is separated into sectors along this
direction. The result is that there is no overload of the blades
that are therefore loaded approximately uniformly.
[0013] Finally, note that by adopting approximately the same
profile as the profile of the elementary sectors, the outer radial
delimitation of the primary annular flow, also called the air
flowpath, is perfectly recreated between the elementary sectors at
a spacing from each other.
[0014] Preferably, said shim bears in contact with two parallel
plane friction surfaces facing each other along said tangential
direction and provided on said two elementary sectors associated
with said shim, and said shim has two complementary plane friction
surfaces parallel to each other and cooperating with the two
corresponding friction surfaces of the elementary sectors. The
plane contacts between the friction surfaces and the complementary
friction surfaces give satisfactory damping of vibrations by
friction. It is also possible to make the two friction surfaces
simultaneously during a single machining operation, for example by
a single cutting operation, in order to obtain straight slits, in
other words slits in a determined plane, inside which the
corresponding shims will subsequently be housed. This makes it very
much simpler to fabricate the assembly according to the invention,
which results in a significant cost and time saving.
[0015] Preferably, said shim is provided with hooks to hold it in
place on the compressor or turbine stator, therefore these hooks
have the same profile as the hooks fixed on the elementary
sectors.
[0016] Preferably, the elementary sectors are separated from each
other by radial slits completely filled in by said vibration
damping shims.
[0017] Preferably, said vibration damping shims extend
approximately along an axial or oblique direction of said
assembly.
[0018] Another purpose of this invention applies to a bladed ring
sector designed to be installed on a compressor or turbine stator
of an aircraft turbomachine comprising an assembly forming an outer
shell sector like that described above, an inner shell sector and a
plurality of blades at a tangential spacing from each other and
inserted between the assembly forming the outer shell sector and
the inner shell sector. In this case, each elementary sector will
carry a single stator blade, or possibly several blades, without
going outside the scope of the invention.
[0019] The bladed ring may form a guide vane of a compressor or a
nozzle of a turbine.
[0020] Furthermore, the ring sector preferably extends around an
angular range of between 5 and 60.degree., but can be as much as
360.degree. so as to form the entire bladed ring.
[0021] Another purpose of the invention is an aircraft turbomachine
comprising a compressor or turbine stator equipped with at least
one bladed ring sector like that described above.
[0022] Other advantages and characteristics of the invention will
appear in the detailed non-limitative description given below.
[0023] This description will be made with reference to the appended
drawings among which;
[0024] FIG. 1 shows a diagrammatic sectional view of a turbomachine
that will be equipped with one or several bladed ring sectors
according to this invention;
[0025] FIG. 2 shows a sectional view representing part of the high
pressure compressor of the turbomachine shown in FIG. 1, and
including a bladed ring sector according to this invention;
[0026] FIG. 3 shows a perspective view of the bladed ring sector
shown in the previous figure, the sector being in the form of a
preferred embodiment of this invention;
[0027] FIG. 4 shows an axial view of part of the bladed ring sector
shown in the previous figure;
[0028] FIG. 5 shows a profile view of the shims and the elementary
sectors of the bladed ring sector shown in the previous figures,
along line V-V in FIG. 4; and
[0029] FIGS. 6a to 6c show views diagrammatically showing the
different steps in a fabrication process of the bladed ring sector
shown in the previous figures.
[0030] With reference firstly to FIG. 1, the figure shows an
aircraft turbojet 100 to which the invention is applicable. It
comprises, in order along the upstream to downstream direction, a
low pressure compressor 2, a high pressure compressor 4, an annular
combustion chamber 6, a high pressure turbine 8 and a low pressure
turbine 10.
[0031] FIG. 2 shows part of the high pressure compressor 4. In a
known manner, the compressor comprises rows 14 of stator blades and
rows 16 of rotor blades alternating on an axial direction parallel
to the axis 12 of the compressor. The stator blades 18 distributed
circumferentially/tangentially around the axis 12, are included in
a part of the stator called the bladed ring 20, preferably
constructed in sectors along the circumferential direction 22.
Thus, in the following we will refer to a bladed ring sector 20, it
being understood that this sector 20 preferably extends over an
angular range of between 5 and 60.degree., but possibly as much as
360.degree. so as to form the entire bladed ring.
[0032] The sector 20, therefore forming all or part of a turbine
nozzle or a compressor guide vane, comprises an inner shell sector
24 forming the inner surface radially delimiting a primary annular
flow 26 passing through the turbomachine, this shell sector 24
supporting the fixed roots of the stator blades 18. In addition to
these blades 18, the sector 20 also comprises an assembly forming
an outer shell sector 28 forming the outer surface radially
delimiting the primary annular flow, and supporting the fixed heads
of the blades 18.
[0033] In this respect, note that the sector 20 also comprises
known additional elements fitted on the shell sector 24, such as a
radially internal abradable coating 29 forming the annular sealing
track contacted by a sealing device 31 supported by the rotor stage
16 supporting the rotating blades and arranged on the downstream
side of the sector 20 concerned. The rotating sealing device 31 is
a known labyrinth or lip seal type sealing device.
[0034] FIG. 3 shows the bladed ring sector 20. In the preferred
embodiment described, the entire turbine nozzle or compressor guide
vane is obtained by end to end placement of a plurality of these
sectors 20, therefore each forming an angular or circumferential
portion of this bladed ring. The angular sectors 20 (only one of
which can be seen in FIG. 3) are preferably deprived of any rigid
direct mechanical links connecting them to each other, their
adjacent ends being simply placed facing each other with or without
clearance.
[0035] More specifically with reference to FIGS. 3 and 4, the
figures show that the inner ring sector 24 is made in a single part
and is not segmented. On the other hand, the assembly 28 forming
the outer shell sector 28 is segmented into elementary sectors 30
at a spacing from each other along the tangential direction 22, by
straight radial or slightly oblique slits 32, therefore creating
clearances between the directly consecutive sectors 30. Each slit
32 is made along a median straight line between two directly
consecutive blades 18, such that each elementary sector 30 supports
a single fixed stator blade 18. One of the two elementary sectors
30 located at the ends of the sector 20 supports a rotation stop 33
projecting radially outwards and that will cooperate with another
part of the compressor stator in a known manner.
[0036] The assembly 28 also comprises vibration damping shims 34
housed between directly consecutive elementary sectors 30.
[0037] More precisely, each vibration damping shim is housed
between two plane parallel friction surfaces 38 facing each other
along the tangential direction 22, and provided on the
corresponding tangential ends facing each other on the two
elementary sectors associated with the shim. Similarly, each shim
has two complementary plane friction surfaces 40 parallel to each
other and also parallel and in contact with the two corresponding
plane friction surfaces 38 with which they cooperate.
[0038] Therefore, each shim 34 is squeezed between two directly
consecutive elementary sectors 30, having a shape complementary
with the shape of the friction surfaces 38.
[0039] The contact between the two friction surfaces 38, 40 of each
pair is preferably obtained as soon as the shim 34 is put into
position between its two associated elementary sectors 30. The
shims 34 thus apply forces oriented approximately along the
tangential direction in contact with the friction surfaces 38 of
the elementary sectors, with their complementary plane friction
surfaces 40. These forces are advantageously increased during
operation by the additional application of the tangential component
of aerodynamic forces applied on the stator blades, on the
elementary sectors.
[0040] As shown diagrammatically in FIG. 5, one of the special
features of this invention lies in the fact that the profile of the
shims 34 is approximately the same as the profile of the elementary
sectors, this same profile corresponding to the profile of the
outer shell sector. In this disclosure, profile refers to the
global shape of the element seen along the tangential direction 22,
although a sectional view is shown in FIG. 5.
[0041] Thus, the lower surface 46 of each shim 34, like the
elementary sectors 30, acts as the outer radial delimitation of the
air flowpath. Consequently, the global annular delimitation surface
of the air flowpath composed of the sequence of these surfaces 46
formed on the shims 34 and the sectors 30, is approximately
continuous from an aerodynamic point of view because there is no
step between the successive surfaces 46.
[0042] Each shim 34 and each sector 30 also comprises hooks to hold
it in place on another part of the compressor stator, and more
precisely a fixing hook 48 projecting forwards, and a fixing hook
50 projecting backwards. As shown in FIG. 2, the hooks 48, 50 are
housed in the corresponding annular slits 52, 54 provided in
another part of the compressor stator, to fix the sector 20 onto
this other part of the stator.
[0043] The shims 34, entirely filling in the slits 32, perform a
vibration damping function by friction in contact with the friction
surfaces 38, based on the physical principle described above for
the shims disclosed in document FR-A-2 902 843. They also perform a
seal function, and a function to allow the tangential component of
aerodynamic forces applied on the stator blades to pass through.
More generally in this respect, each shim 34 is capable of
transmitting tangential forces between the two elementary sectors
30 between which it is inserted.
[0044] The natures of the materials used for the elementary sectors
30 and for the shims 34 are approximately the same, preferably
metallic, and are chosen such that the shims wear preferentially
rather than the elementary sectors 30.
[0045] Note also that the ratio between the extent of each shim and
the extent of each elementary sector along the tangential direction
that also correspond to the thicknesses, is between 0.5 and 1.
[0046] FIGS. 6a to 6c diagrammatically show a process for
fabrication of the bladed ring sector 20. Firstly as can be seen in
FIG. 6a, a single-piece assembly 100 is made by pouring or
machining forming the inner shell sector 24, the outer shell sector
28 and the stator blades 18. The next step is to make straight
radial slits 32 on the outer shell sector 28 so as to obtain the
elementary sectors 30 as shown diagrammatically in FIG. 6b, by
simple and inexpensive machining. For example, these slits 32 can
be made simply by cutting the sector 28.
[0047] Finally, FIG. 6c shows the final step that consists of
putting the vibration damping shims 34 into position in the slits
32 forming the friction surfaces, simply by sliding the shims into
their corresponding holes.
[0048] Note that a precise sliding adjustment clearance is
preferred to make it relatively easy to insert of each shim in its
associated slit while holding this shim in its slit solely by the
squeezing force between the two friction surfaces 38.
[0049] Obviously, those skilled in the art could make various
modifications to the invention as described above, solely using
non-limitative examples.
* * * * *