A ROTOR WHEEL FOR A TURBINE ENGINE
The present invention relates to a rotor wheel for a
turbine engine such as an airplane turboprop or turbojet.
Conventionally, a rotor wheel, for example in a low-
5 pressure turbine, comprises a rotor disk with an outer
periphery having teeth that define slots for axially
mounting and radially retaining blade roots. The blades
are formed with platforms that are arranged
circumferentially side-by-side and that define the inside
10 of an annular passage for fluid flow.
The blades also include annular lips extending
substantially axially upstream from the platforms in
order to limit fluid passing out from the annular
passage.
15 Metal blades are made as single pieces by casting,
with the lips being formed together with the platforms
and the blade roots.
Fabricating blades by casting enables good
dimensional tolerances to be obtained, i.e. enables parts
20 to be obtained that have accurate dimensions
corresponding substantially to specifications.
Nevertheless, such blades are heavy.
In order to remedy that drawback, proposals have
been made to make blades in full or in part out of
25 ceramic matrix composite material (CMC). Nevertheless,
fabrication tolerances for blades made of CMC are greater
than tolerances for metal blades made by casting.
Furthermore, fabricating blades out of CMC is a complex
process since it makes use of weaving and requires two
30 layers of texture to be formed on the blade at platform
level, one of which constitutes the surface defining the
flow passage and the lip, and the other of which serves
to prevent the blade from tilting and to provide
downstream overlap. In patent application FR 10/54163,
35 the Applicant has already proposed making the lip in the
form of a separate fitting in order to simplify the
fabrication of blades out of CMC. Sealing means are
arranged between the lip and the platforms of the blades
in order to avoid leaks while also accommodating the
fabrication tolerances for blades made of CMC.
In that configuration, while the turbine engine is
5 in operation, the lip is centrifuged outwards and comes
to bear against the upstream ends of the platforms of the
blades, thereby leading to an increase in the radial
forces applied to the blades.
A particular object of the invention is to provide a
10 solution to this problem that is simple, effective, and
inexpensive.
For this purpose, the invention proposes a rotor
wheel for a turbine engine such as an airplane turboprop
or turbojet, the wheel comprising a rotor disk having
15 teeth at its outer periphery defining slots for axially
mounting and radially retaining blade roots, the blades
including platforms arranged circumferentially end to end
to define an annular flow passage for an air stream, an
annular lip extending substantially axially upstream
20 being fitted on an upstream face of the disk to limit air
passing out from the annular passage, sealing means being
provided between the annular lip and the upstream ends of
the platforms of the blades, the rotor wheel being
characterized in that the annular lip comprises an
25 annular rim extending axially downstream from and
radially towards the inside of radial retaining means for
retaining the annular lip on the disk, these retaining
means being formed to project axially from the upstream
face of the disk, the sealing means being arranged
30 radially inside the annular lip and upstream ends of the
platforms of the blades.
In operation, the radial retaining means of the
annular lip formed on the disk ensure that the upstream
ends of the blades are not subjected to additional radial
35 forces due to the annular lip being centrifuged.
The lip inay be of continuous annular shape over '
360". It could equally well be in the form of a
plurality of distinct sectors arranged end-to-end to form
a ring, thereby enabling differential expansion between
the disk and the lip to be well compensated.
According to a characteristic of the invention, the
5 radial retaining means are formed at the upstream and
radially outer ends of the teeth of the disk.
According to another characteristic of the
invention, the annular rim of the lip comprises a
substantially cylindrical wall bearing radially outwards
10 against the radial retaining means and connected at its
downstream end to a radial annular wall.
According to yet another characteristic pf the
invention, lugs are formed projecting axially from the
upstream face of the disk, substantially at the bases of
15 the teeth of the disk and facing the radially inner end
of the radial annular rim of the lip.
While the lip is being mounted on the disk, and also
while the turbine engine is stopped, the lugs serve to
position the annular lip on the upstream face of the
20 disk, and to hold it radially. In this way, the sealing
means are correctly positioned relative to the lip and to
the upstream ends of the platforms.
Advantageously, the radial annular wall of the rim
of the lip includes at least one anti-rotation finger
25 projecting radially inwards and engaged circumferentially
between two consecutive lugs, thereby making it possible
to guarantee that the annular lip is prevented from
turning on the disk.
According to a characteristic of the invention, the
30 annular lip includes an annular groove that is open
downstream to house sealing means, the groove being
defined internally by the cylindrical wall and externally
by a frustoconical annular wall of section that increases
going downstream.
3 5 In a particular embodiment of the invention, the
sealing means comprise an O-ring interposed radially
between the frustoconical wall and the radial retaining
means projecting from the upstream face of the disk, said
O-ring being suitable for moving radially outwards under
the centrifugal effect during rotation of the rotor wheel
and for pressing against the frustoconical wall and
5 against the upstream ends of the platforms.
The O-ring is radially movable relative to the lip,
thus making it possible by the centrifugal effect for the
O-ring to press properly against the frustoconical wall
and the upstream ends of the platforms.
10 Preferably, the O-ring is of substantially
triangular section and includes a frustoconical face for
.coming into contact with the frustoconical wall of the
lip and a substantially radial face for pressing axially
against radial faces of the upstream ends of the
15 platforms of the blades.
According to another characteristic of the
invention, the annular lip is clamped axially against the
rotor disk by an upstream cheek plate fastened to the
rotor disk.
2 0 In known manner, the inner end of the cheek plate
carries wipers forming a labyrinth seal by cooperating
with a block of abradable material on a stationary nozzle
arranged upstream.
In the preferred embodiment of the invention, the
25 blades are made of ceramic matrix composite material
(CMC) .
The invention also provides a turbine engine such as
an airplane turboprop or turbojet, the engine including
at least one rotor wheel as described above, in
30 particular in a low-pressure turbine.
Other details, characteristics, and advantages of
the invention appear on reading the following description
made by way of non-limiting example and with reference to
the accompanying drawings, in which:
35 Figure 1 is a perspective view of a portion of a
prior art rotor wheel;
Figure 2 is a diagrammatic axial section view of a
rotor wheel of the invention;
Figure 3 is a diagrammatic perspective view of the
annular lip of the invention;
5 Figure 4 is a diagrammatic perspective view from
upstream of the annular lip of the invention; and
Figure 5 is a diagrammatic axial section view of
the zone outlined by a dashed line in Figure 2.
Figure 1 shows a rotor wheel 10 as described in
10 document FR 10/54163. The rotor wheel 10 comprises a
rotor disk 12 with its outer periphery carrying teeth 14
defining dovetail slots 16 for axially mounting and
radially retaining blade roots 18 (Figures 3 and 4). The
downstream ends of the teeth 14 are provided with hooks
15 20 that are turned radially inwards. The tops of the
teeth 14 are substantially plane.
The turbine disk 12 is also provided with a
cylindrical rim 22 extending axially downstream in a zone
that is situated radially between the bottoms of the
20 slots 16 and the inner periphery of the disk 12. A
groove 24 situated radially substantially facing the
hooks 20 is formed in the rim 22. The groove 24 and the
hooks 20 are used for fastening axial stop means (not
shown) for stopping the roots 18 of the blades.
25 The blades 26 have airfoils 28 extending radially
and platforms 30 defining the inside of an annular fluid
flow passage, the platforms being formed at the bases of
the airfoils 28 and being connected to the roots 18 of
the blades 26.
30 Each platform 30 has a central portion 32 that
slopes relative to the axial direction, which portion is
extended by an upstream portion 34 that is curved
radially inwards.
The platforms 30 of the blades 26 are arranged side-
35 by-side and means are provided for providing sealing
between their facing circumferential lateral edges.
The rotor wheel 10 has a metal annular lip 36 fitted
onto the upstream face of the disk 12 of the rotor at the
outer periphery of the disk 12. The lip 36 has a
cylindrical wall 38 extending substantially axially
5 upstream level with the upstream ends of the platforms 30
and serving to limit any fluid passing out from the
annular passage. The lip 36 also has an annular wall 40
extending substantially radially and serving to press
against the upstream face of the rotor disk 12. Sealing
10 means 42 are provided between the lip 36 and the upstream
ends of the platforms 30 of the blades 26.
These sealing means comprise an O-ring 42 mounted in
a groove 44 of the lip 36, which groove includes a
frustoconical wall 46 of section that flares going
15 downstream so that the O-ring is pressed from upstream to
downstream against the upstream edges 34 of the platforms
30.
While the turbine engine is in operation, the lip 36
is centrifuged outwards and comes to bear via the O-ring
20 42 against the upstream edges 34 of the platforms 30,
thereby increasing the radial forces applied to the
blades 26.
The invention provides a solution to this problem by
means of a lip 48 that, in operation, bears radially
25 outwards against radial retaining means formed to project
from the upstream face of the disk 50.
In the embodiment shown, the lip 48 has an annular
rim 52 with a substantially cylindrical wall 54 connected
at its downstream end to an annular wall 56 that extends
30 radially inwards (Figures 2 and 3). The radial annular
wall 56 has at least one anti-rotation finger 58
projecting radially inwards (Figure 4). The lip 48 also
has a second cylindrical wall 60 extending axially
upstream between two stationary annular portions 62 and
35 64 of a stator nozzle 66 arranged upstream, thereby
limiting air passing out from the annular passage
(Figures 2 and 5).
The cylindrical wall 54 of the annular rim 52 of the
lip 48 co-operates with a frustoconical wall 68 of
section that increases going downstream, and together
they define an annular groove that is open downstream.
5 The radial retaining means comprise tabs 70 formed
at the upstream and radially outer ends of the teeth 14
of the disk 50. These tabs 70 constitute extra
thicknesses on the teeth 14 of the disk 50 and they
project axially from the upstream face of the disk 50.
10 Each tooth 14 of the disk 50 has a lug 72 formed
substantially at the base of the tooth and facing the
radially inner end of the radial annular wall 56 of the
annular rim 52 of the lip 48.
When the lip 48 is axially engaged downstream on the
15 upstream face of the disk 50, the annular rim 52 becomes
housed between the tabs 70 and the lugs 72 projecting
from the upstream face of the disk 50, thereby
positioning the lip 48 on the disk 50. In operation, the
lip 48 is retained radially by the tabs 70 of the disk 50
20 and no longer by the upstream edges 74 of the platforms,
thereby serving to reduce the radial forces that are
applied to the blades. Furthermore, the finger 58 of the
radial annular wall 56 is received circumferentially
between two consecutive lugs 72 of the disk 50, thereby
25 preventing the lip 48 from turning on the disk 50. The
lip 48 is clamped against the upstream face of the rotor
disk 50 by a cheek plate 76 that is bolted to a radial
flange 78 of the disk 50. At its inner end, the cheek
plate 76 has wipers 80 that form a labyrinth seal with a
30 block of abradable material 82 of the nozzle 66
(Figure 2).
Sealing means 84 are interposed between the tabs 70
of the teeth 14 of the disk 50 and the frustoconical wall
68 of the lip 48. I
3 5 In the embodiment shown, the sealing means comprise
an O-ring 84 of substantially triangular section, with a
frustoconical face 86 positioned substantially radially
facing the frustoconical wall 68 of the lip 48 and with
another face 88 that is radial and positioned facing the
corresponding radial faces of the upstream edges 74 of
the platforms.
5 While the turbine engine is in operation, the O-ring
84 moves along the frustoconical wall 68 under the effect
of centrifugal force until it becomes pressed against the
upstream edges 74 of the platforms (Figures 3 and 5).
The O-ring 84 is sufficientlydeformable to
10 accommodate the dimensional tolerances due to the method
of fabricating blades out of CMC.
The O-ring may also be split so as to make it easier
to expand under the effect of centrifugal force.
The upstream edge 74 of each platform includes a tip
15 90 extending substantially radially inwards and formed in
the substantially middle portion of the edge 74 of the
platform. While the blade roots 18 are being mounted
axially in the slots 16, each of the tips 90 of the
platforms engages axially between two consecutive tabs 70
20 of the disk 50. Each upstream edge of a platform has two
lateral portions 92 on either side of the tip 90 of the
platform, which portions are positioned radially facing a
tab 70 of the disk 50 with a predetermined clearance.
These lateral portions 92 are for bearing against the
25 tabs 70 of the disk 50 in order to limit tilting of the
blades in a circumferential direction (Figure 3).
When the lip 48 is sectorized, each lip sector may
include an anti-rotation finger 58 that co-operates
circumferentially with lugs 72 of the disk 50.
30
CLAIMS
1. A rotor wheel for a turbine engine such as an airplane
turboprop or turbojet, the wheel comprising a rotor disk
(50) having teeth (14) at its outer periphery defining
5 slots (18) for axially mounting and radially retaining
blade roots, the blades including platforms arranged
circumferentially end to end to define an annular flow
passage for an air stream, an annular lip (48) extending
substantially axially upstream being fitted on an
10 upstream face of the disk (50) to limit air passing out
from the annular passage, sealing means (48) being
provided between the annular lip (48) and the upstream
ends of the platforms of the blades, the rotor wheel
being characterized in that the annular lip (48)
15 comprises an annular rim (52) extending axially
downstream from and radially towards the inside of radial
retaining means (70) for retaining the annular lip (48)
on the disk (50), these retaining means (70) being formed
to project axially from the upstream face of the disk
20 (50), the sealing means (84) being arranged radially
inside the annular lip (48) and upstream ends of the
platforms of the blades.
2. A rotor wheel according to claim 1, characterized in
25 that the radial retaining means (70) are formed at the
upstream and radially outer ends of the teeth (14) of the
disk (50).
3. A rotor wheel according to claim 1 or claim 2,
30 characterized in that the annular rim (52) of the lip
(48) comprises a substantially cylindrical wall (54)
bearing radially outwards against the radial retaining
means (70) and connected at its downstream end to a
radial annular wall (56) . *
35
4. A rotor wheel according to claim 3, characterized in
that lugs (72) are formed projecting axially from the
upstream face of the disk (50), substantially at the
bases of the teeth (14) of the disk (50) and facing the
radially inner end of the radial annular rim (52) of the
lip (48).
5
5. A rotor wheel according to claim 4, characterized in
that the radial annular wall (56) of the rim (52) of the
lip (48) includes at least one anti-rotation finger (58)
projecting radially inwards and engaged circumferentially
10 between two consecutive lugs (72).
6. A rotor wheel according to any one of claims 3 to 5,
characterized in that the annular lip (48) includes an
annular groove that is open downstream to house sealing
15 means, the groove being defined internally by the
cylindrical wall (54) and externally by a frustoconical
annular wall (68) of section that increases going
downstream.
20 7. A rotor wheel according to claim 6, characterized in
that the sealing means comprise an O-ring (84) interposed
radially between the frustoconical wall (68) and the
radial retaining means (70) projecting from the upstream
face of the disk, said O-ring (84) being suitable for
25 moving radially outwards under the centrifugal effect
during rotation of the rotor wheel and for pressing
against the frustoconical wall (68) and against the
upstream ends of the platforms.
30 8. A rotor wheel according to claim 7, characterized in
that the O-ring (84) is of substantially triangular
section and includes a frustoconical face (86) for coming
into contact with the frustoconical wall (68) of the lip
(48) and a substantially radial face (88) for pressing
35 axially against radial faces of the upstream ends of the
platforms of the blades.
9. A rotor wheel according to any preceding claim,
characterized in that the annular lip (48) is cLamped
axially against the rofor disk' (50) by an upstream cheek
plate (46) fastened to the rotor disk. *
5
10. A rotor wheel according to any preceding claim,
characterized in that the blades are made of ceramic
matrix composite material
- 10 11. A turbine engine such as an airplane turboprop or
turbojet including at least one rotor wheel according to
any preceding claim, in particular in a low-pressure
turbine.