Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FINAL-STAGE INTERNAL COLLAR GASKET OF AN AXIAL TURBINE ENGINE
COMPRESSOR
Technical field
The invention relates to a turbine engine guide vane assembly. More
specifically, the
invention relates to a turbine engine compressor guide vane assembly fitted
with an
internal collar having a gasket ensuring airtightness with a casing of the
turbine
engine. The invention likewise relates to a turbine engine having a gasket
disposed
between a collar and a casing of the turbine engine.
Prior art
A turbojet engine comprises a plurality of levels such as a fan, compressors,
a
combustion chamber and turbines. These compartments are fixed to the
intermediate casing, such that they are all connected. The intermediate casing
is
crossed by annular flows that circulate in the turbine engine. In order to
limit leaks,
sealing devices are provided at the interfaces between the intermediate casing
and
the compartments. In particular, the low-pressure compressor which is fixed
directly
to the intermediate casing exhibits gaskets at its external casing and at the
internal
collar of its downstream guide vane assembly.
The internal collar of the upstream guide vane assembly is fixed to the
internal ends
of the blades and cooperates in an airtight manner with a planar surface of
the
intermediate casing. To this end, the guide vane assembly comprises a circular
silicon gasket pressed against the sealing surface of the casing.
Document EP 1 426 559 Al discloses an inner collar for the guide vane assembly
of
a low-pressure axial turbojet engine compressor. The compressor is fixed to
the
intermediate casing of the turbine engine, the internal collar of the last
stage of the
compressor being in contact with the intermediate casing by means of a
circular
gasket. During operation of the turbojet engine, the circular gasket is
subject to
vibrations due, for example, to the operation of the turbine engine itself, to
ingestion,
to a pumping phenomenon, to the existence of an unbalancing mass or to a "fan
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blade off" state. These vibrations deform the gasket radially and axially,
thereby
reducing the airtightness. The gasket may likewise become detached from the
intermediate housing, thereby creating a leak. The gasket no longer achieves
either
its contact pressure or its nominal position.
Brief description of the invention
The aim of the invention is to solve at least one of the problems presented by
the
former art. More precisely, the invention aims to preserve the airtightness of
a guide
vane assembly at the junction between its internal collar and a sealing
surface of a
casing when the guide vane assembly is subject to turbine engine vibrations.
The invention relates to a guide vane assembly of an axial turbine engine
compressor, the guide vane assembly comprising an annular row of blades which
extend radially, an internal collar disposed at the internal ends of the
blades which
comprises a circular gasket on one of the upstream or downstream sides of said
collar, so as to ensure airtightness with a sealing surface of an intermediate
casing
of the turbine engine, this being exceptional in that the internal collar
comprises a
cavity in which the gasket is housed.
According to an embodiment of the invention, the cavity is formed, possibly
integrally, in the material of the internal collar, said collar preferably
being realized in
a polymer material, more preferably in a composite material with an organic
matrix.
According to an embodiment of the invention, the cavity is formed by a portion
of the
collar and one or a plurality of members added to said collar and preferably
creating
a generally circular form, the internal collar and each added member
preferably
being realized in composite materials with an organic matrix.
According to an embodiment of the invention, the guide vane assembly comprises
a
hook which forms the cavity, so as to hold the gasket against the sealing
surface of
the casing and against the internal collar, the cavity preferably forming an
annular
throat essentially opened axially.
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According to an embodiment of the invention, the guide vane assembly comprises
an annular shoulder delimiting the cavity axially, the shoulder preferably
being
formed by an annular flange extending radially, the annular shoulder
preferably
being formed by the annular collar and/or by each added member.
According to an embodiment of the invention, the guide vane assembly comprises
a
generally tubular face delimiting the inside of the cavity radially, the
tubular face
possibly being formed on the annular collar and/or on each added member,
preferably at least one added member tubular face compressing the gasket
radially
against the internal surface of the internal collar.
According to an embodiment of the invention, the gasket is for the most part
disposed axially and/or radially inside the cavity,.the gasket preferably
comprising an
elastomer material such as a silicon material.
According to an embodiment of the invention, the gasket exhibits a generally
toroidal
form, the revolution profile of the gasket preferably generally being a
circle, a triangle
or a quadrilateral such as a parallelogram.
According to an embodiment of the invention, the gasket guarantees
airtightness
between the internal collar and each added member, preferably right around the
internal collar.
According to an embodiment of the invention, each added member is fixed to the
internal collar, each added member possibly being interlocked or bonded
adhesively
to the internal collar or fixed to the blades with the help of fixing means by
material
engagement.
According to an embodiment of the invention, each added member extends over
most of, possibly over all, the axial length of the internal collar, each
added member
preferably being placed against the internal surface of the internal collar.
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According to an embodiment of the invention, the length of the internal collar
is more
than twice the chord of each blade measured according to said chord, the
length of
each added member possibly being greater than the chord of each blade measured
according to said chord.
According to an embodiment of the invention, the guide vane assembly comprises
an annular layer of abradable material disposed on the upstream or downstream
side of the internal collar which is axially opposed to that which the
circular gasket
comprises, the abradable layer possibly extending axially up to the material
io delimiting the cavity.
According to an embodiment of the invention, the internal collar and at least
one
added member are realized in different materials, the density of each added
member
preferably being lower than the density of the internal collar.
According to an embodiment of the invention, each added member is fixed to the
internal collar with the help of fixing means by material engagement and/or
each
added member fits closely against the internal surface of the internal collar.
According to an embodiment of the invention, the tubular face is disposed
axially
and/or radially to the inside of the external surface of the internal collar.
According to an of the invention, the gasket extends axially beyond the
internal collar
and/or each added member.
According to an embodiment of the invention, the abradable layer is delimited
axially
with the help of the internal collar and/or by each added member.
According to an embodiment of the invention, the gasket fits closely against
most of
the internal surface of the cavity, preferably against all of it, and/or the
gasket fills
most of the internal volume of the cavity.
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The invention likewise relates to an axial turbine engine comprising a casing
provided with a sealing surface, at least one compressor with a guide vane
assembly
which cooperates in an airtight manner with the sealing surface, this being
exceptional in that the guide vane assembly conforms to the invention, the
gasket
5 preferably being compressed axially between the guide vane assembly and
the
sealing surface of the casing.
According to an embodiment of the invention, axial play J is conserved between
the
casing and the internal collar, the gasket extending axially over the entire
axial play
J, the turbine engine preferably comprises at least one turbine, at least one
fan, the
casing being the intermediate casing of the turbine engine, and withstands
most,
possibly all, of the forces of each compressor, each turbine and each fan.
The invention allows the gasket to be effectively held against the sealing
surface of
the casing. The cavity allows the gasket to be housed and held against the
casing
surface. The solution in which the cavity is integrally formed in the material
of the
internal collar allows a simple collar to be realized integrally. The collar
can be
realized by grinding, its cavity can be ground directly and/or fabricated,
which
enables production costs to be kept down.
Thanks to the added member, a radial compressive stress can be applied to the
gasket, which further improves the seal. The added member allows the gasket to
be
supported, it forms a support improving positioning, the gasket holding
position. It
further allows the contact between the gasket and the casing to be made rigid.
In
passing, the added member improves the rigidity of the internal collar and
limits its
axial and/or radial deformation, such as its out-of-roundness, significantly.
The
addition of the added member enables a cavity with a complex form to be
realized
without increasing the production cost of the internal collar.
The added member allows the lightness of the guide vane assembly to be
preserved. In fact, it can be realized in a lighter material than the internal
collar. For
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example, the internal collar can be realized in metal and the added member
perhaps
in a polymer, such as a composite material.
During production of the turbine engine, the compressor is assembled so as to
form
an assembly which is then placed against the intermediate casing. At this
point the
circular gasket is compressed axially against the sealing surface of the
turbine
engine casing. The compression of the gasket relies on a series of sides
including a
plurality of members including the blades of the guide vane assembly. Said
blades
may exhibit variations in position of more than 2.00 mm, which increases the
margin
that the circular gasket must be able to tolerate. Moreover, the circular
gasket must
likewise be adapted to a differential dilatation phenomenon.
Brief description of the drawings
Figure 1 depicts an axial turbine engine according to the invention.
Figure 2 is a schematic representation of a turbine engine compressor
according to
the invention.
Figure 3 illustrates the downstream guide vane assembly of the compressor in
contact with the casing of the turbine engine according to the invention.
Description of embodiments
In the following description, the terms "interior" or "internal" and
"exterior" or
"external" relate to a position in respect of the axis of rotation of an axial
engine
turbine. The axial direction relates to the axis of rotation.
Figure 1 depicts a simplified representation of an axial engine turbine. In
this
particular case, it is a double-flow turbojet engine. The turbojet engine 2
comprises a
plurality of communication levels, such as a first compression level referred
to as a
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low-pressure compressor 4, a second compression level referred to as a high-
pressure compressor 6, a combustion chamber 8 and one or a plurality of
turbine
levels 10.
During operation, the mechanical power of the turbine 10 transmitted via the
central
shaft up to the rotor 12 sets the two compressors 4 and 6 in operation. Gear
reduction means or concentric shafts may connect the turbines 8 to the
compressors
4 and 6. Said compressors comprise a plurality of rows of rotor blades
associated
with rows of stator blades. The rotation of the rotor about its axis of
rotation 14
thereby allows an air flow rate to be generated and progressively compressed
up to
the inlet of the combustion chamber 10, in order to increase the output of the
turbine
engine.
An input blower usually referred to as a fan 16 is coupled with the rotor 12
and
generates an air flow that divides up into a primary flow 18 crossing the
different
levels of the turbine engine mentioned above and a secondary flow 20 crossing
an
annular conduit (partially represented) along the engine, after which it joins
up with
the primary flow again at the turbine outlet. The turbine engine may comprise
a
plurality of fans. The primary 18 and secondary 20 flows are annular flows and
are
channelled through the casing of the turbine engine.
The turbine engine may comprise a casing, possibly an intermediate casing. The
intermediate casing guarantees a fixing structure function to which the
compressors
4 and 6, the turbines 8, the combustion chamber 10, the fan 16 and the shafts
are all
fixed or connected, so that at least most of the forces, preferably all of the
forces,
coming from it are withstood.
Figure 2 is a sectional view of a compressor of an axial turbine engine 2 such
as that
shown in Figure 1. The compressor may be a low-pressure compressor 4. This
shows part of the fan 16 and the separation spout 22 of the primary flow 18
and of
the secondary flow 20. The rotor 12 comprises a plurality of rows of rotor
blades 24,
in this case three.
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The low-pressure compressor 4 comprises a plurality of guide vane assemblies,
in
this case four, which each contain a row of stator blades 26. The stator
blades 26
extend essentially radially from an exterior casing 28 and can be fixed there
with the
help of an axle. They are regularly spaced relative to one another and exhibit
the
same angular orientation in the flow. The guide vane assemblies are linked to
the fan
16 or to a row of rotor blades to guide the flow of air, so as to convert the
flow speed
into pressure.
The blades in the same row are advantageously identical. The space between the
blades, just as their angular orientation, may possibly vary locally. Certain
blades
may differ from the rest of the blades in their row.
Each guide vane assembly comprises an internal collar 30 which is disposed at
the
internal ends of the stator blades 26 of the corresponding row. The internal
collars 30
allow the primary flow 18 to be guided during its compression. They likewise
allow
the ends of the blades 26 to be held in relation to one another. The guide
vane
assemblies may likewise comprise annular layers of abradable material 32,
possibly
applied to each internal surface of the internal collar 30. These abradable
layers 32
cooperate by abrasion with radial annular ribs of the rotor 12, in order to
guarantee
its airtightness.
Downstream, the compressor may be mounted, possibly directly, on the casing of
the turbine engine, possibly on the intermediate casing 34. The compressor may
be
mounted on any casing or any portion of the turbine engine casing. The
compressor
may be in contact with the intermediate casing 34 at its exterior casing 28
and at the
downstream side of the internal collar 30 of its downstream guide vane
assembly.
Annular seals are provided for at the interfaces.
In this perspective, the internal collar 30 comprises an annular gasket 36 or
a circular
gasket 36 which ensures airtightness with a sealing surface of the casing,
possibly
the intermediate casing 34 of the turbine engine 2. The gasket 36 may form a
sealing
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bead and may comprise, possibly for the most part or in its entirety, an
elastomer
material such as a silicon material. The silicon material may be organic or
made of
resin. The gasket 36 may be disposed at an opposite axial end to that
receiving the
abradable layer 32.
Figure 3 depicts the guide vane assembly downstream of the compressor and the
intermediate casing 34 of the turbine engine, as well as an enlargement at the
sealing interface between the internal collar 30 and the casing 34.
The intermediate casing 34 may be crossed by the primary flow 18, it guides it
with
the help of an external wall 38 and an internal wall 40 which are linked by
casing
arms 41 which cross the flow radially. The internal wall 40 may be formed by
an
internal hub 42 to which shafts of the turbine engine can be articulated.
Axially in
respect of the gasket 36 of the internal collar 30, the casing comprises a
sealing
surface 44, generally planar for example, in order to reduce rubbing in the
case of
axial vibration and to avoid hyperstatic assembly. The sealing surface 44 may
be
substantially conical. -
The internal collar 30 comprises a cavity 45 in which is housed the gasket 36,
for the
most part or completely, for example. The cavity 45 may be circular. The
cavity 45
may be formed, possibly integrally, in the material of the internal collar 30.
The cavity
45 may run right around the collar 30 or be formed in a discontinuous manner.
The
cavity 45 may form a hook, it may be open essentially axially towards the
sealing
surface 44 of the casing 34. It may exhibit a general U-shaped profile pivoted
towards the casing 34. The cavity 45 and the sealing surface 44 envelop the
gasket
for the most part or essentially completely. They may enclose it on at least
four
faces.
The internal collar 30 may comprise one or a plurality of added members 46.
The
added member or members 46 extend along the circular gasket 36 following its
circumference. Each added member 46 may exhibit a generally circular or
annular
form, the combination of added members 46 being generally circular. Each added
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member 46 may be disposed inside the internal collar 30 and may hold the
circular
gasket 36, possibly against the internal surface of the collar and/or against
the
intermediate casing 34. Each added member 46 may apply an axial and/or radial
pressure against the circular gasket 36, possibly in such a manner as to
increase the
5 axial length of the gasket 36 following compression.
The cavity 45 may be formed by combining a portion of the internal collar 30
and of
the added member or members 46, the cavity 45 exhibiting a circular
continuity.
Alternatively, the added members 46 may be inserted in the discontinuous
portions
10 of the internal collar, so as to form a generally continuously circular
cavity 45.
The guide vane assembly may comprise a shoulder 48. The shoulder 48 may be
formed on the internal collar 30 and/or on each added member 46. Each shoulder
48
extends radially, is in contact with the circular gasket 36 and can form an
axial stop
for the circular gasket 36. The shoulder 48 or the combination of shoulders
may
possibly extend over most or all of the radial thickness of the circular
gasket 36. At
least one or every shoulder 48 may be an annular flange extending radially.
Each
added member 46 may be fixed to the internal radial end of the shoulder of the
internal collar 30, by adhesive bonding for example. When the internal collar
30 and
each added member 46 each exhibit a shoulder, these are radial to one another
in
the extension. The added member 46 may allow the circular gasket to be held
axially.
The guide vane assembly may comprise a generally tubular 50 or substantially
conical face which is possibly disposed axially and/or radially to the inside
of the
internal collar 30. The tubular face 50 may extend over the majority,
preferably over
substantially the entirety, of the axial thickness of the circular gasket 36,
this applying
right around the gasket. The tubular face 50 may be formed on the internal
collar 30
and/or on each added member 46. It may exhibit material discontinuities and be
both
formed by the collar and also by the added member or members 46.
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The circular gasket 36 may be added and adhesively bonded to the internal
collar 30
or realized in the cavity and adhered there. The gasket 36 may exhibit a ring
or
toroidal form, it may exhibit a generally round or polygonal revolution
profile. It may
exhibit a revolution profile in triangular, quadrilateral ¨ such as a
parallelogram ¨ or
square form. The gasket 36 may guarantee airtightness between the internal
collar
30 and each added member 46.
The internal collar 30 may comprise an annular partition 52 with a generally
constant
thickness, for example. Its revolution profile may be inclined relative to the
axis of
rotation of the turbine engine, possibly by at least 5 , preferably by at
least 100, more
preferably by at least 15 . The internal collar 30 may comprise an annular row
of
openings (not shown) into which are introduced the internal ends of the blades
26 in
order to fix them. The internal collar 30 forms an axial annular junction
between a
portion of rotor and the intermediate casing 34. Its length is greater than
130%,
preferably greater than 250%, of the chord of the blade 26, both measured
according
to said chord at the junction between the blade 26 and the internal collar 30.
Axial play J is conserved between the sealing surface 44 of the casing 34 and
the
internal collar 30. The same equal axial play is preferably conserved between
the
sealing surface 44 of the casing and each added member. The circular gasket 36
extends axially right along the play J, so as to form an airtight barrier. The
material of
the gasket 36 likewise enables a cushioning of vibrations at the axial play J
to be
guaranteed.
At least one or each added member 46 can be fixed to the internal collar 30,
for
example by adhesive bonding and/or by interlocking. It may comprise an annular
platform 54 fitting closely against the inside of the partition 52 of the
internal collar
30. The internal collar 30 and/or each added member 46 and/or the blades 26
may
comprise fixing means by material engagement, resulting in the fixing of each
added
member 46 on the internal collar 30 and/or on the blades 26, the internal
collar 30
likewise being able to be fixed to the blades 26 by these means.
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The internal collar 30 and/or each added member 46 may be realized in metal
such
as titanium or aluminium. The internal collar 30 and/or each added member 46
may
be realized by injection of a polymer or a filled resin. At least one,
preferably both, of
these may be realized in composite materials with an organic matrix. They may
comprise a polyetherimide (PEI) or polyether ether ketone (PEEK) matrix. They
may
comprise carbon fibres, glass fibres, graphite fibres. The fibres may exhibit
a length
of less than 3.00 mm, preferably less than 1.00 mm, more preferably less than
0.30
mm. At least one of these members preferably comprises a fibrous preform with
an
epoxy matrix.
The invention may likewise be applied to a high-pressure compressor, for
example
an internal collar of a guide vane assembly upstream of the high-pressure
compressor. In this configuration, the upstream guide vane assembly comprises
an
elastomer gasket disposed upstream of its internal collar, the gasket
cooperating
with a sealing surface of the downstream face of the intermediate casing of
the
turbine engine. The gasket is likewise held against the collar and the sealing
surface
with the help of at least one added member.
