TURBOMACHINE ROTOR BLADE
FIELD OF THE INVENTION
The present description relates to a turbomachine
5 rotor blade.
Such a blade may be fitted to any type of
turbomachine whether terrestrial or for aviation, and in
particular it may be fitted to an airplane turbojet or to
a helicopter turboshaft engine.
10 STATE OF THE PRIOR ART
In the present description, "upstream" and
"downstream" are defined relative to the normal flow
direction of gas through the turbomachine (from upstream
to downstream) .
15 The terms "turbomachine axis" or "engine axis"
designate the axis of rotation of the rotor of the
turbomachine. The axial direction corresponds to the
direction of the axis of the engine and a radial
direction is a direction perpendicular to the axis of the
20 engine and intersecting said axis. Likewise, an axial
plane is a plane containing the axis of the engine, and a
radial plane is a plane perpendicular to said axis.
Unless otherwise specified, the adjectives "inner"
and "outer" are used relative to a radial direction such
25 that an inner portion of an element is closer in a radial
direction to the axis of the engine than is an outer
portion of the same element.
Typically, a rotor blade of a turbomachine comprises
an airfoil extending along a stacking axis of the blade
30 between proximal and distal (i.e. inner and outer) ends
of the blade. At its proximal end, the blade includes a
root for fastening it to a disk of the rotor of the
engine, the disk being common to a plurality of blades.
The blades serve to recover force from gas passing
through the turbomachine in order to transmit force to
the rotor disk. At its distal end, a blade may have a
transverse element referred to as an outer part. When a
5 plurality of rotor blades are fastened to a rotor disk,
their outer parts are arranged side by side so as to form
a circumferential band that serves in particular to
define the outside of the flow passage for gas passing
through the turbomachine, thereby limiting gas leaks at
10 that location. Rotor blades are generally fabricated with
a pre-twist angle. When the blades are assembled, they
are assembled while applying force to reduce this pretwist
angle to zero, thereby enabling the outer parts of
the blades to come into contact and imparting rigidity to
15 the bladed wheel and limiting vibration.
The stacking axis of a blade is the axis
perpendicular to the axis of the turbomachine that passes
through the center of gravity of the innermost section of
the airfoil of the blade (i.e. the section closest to the
20 axis of the engine).
The airfoil of the blade presents a pressure side
face and a suction side face. The pressure and suction
sides of the blade are defined correspondingly.
A conventional rotor blade is shown in Figure 1. A
25 blade of this type is described in patent document
FR 2 923 524 Al. The blade 10 comprises an airfoil 16
extending along the stacking axis X of the blade between
the proximal and distal ends 10A and 10B of the blade.
The airfoil 16 presents a pressure side face 15A and a
30 suction side face. At its proximal end 10A, the blade has
a root 12 whereby it is fastened to a disk of the rotor
(not shown). At its distal end 10B, the blade 10 has an
outer part 14. When a plurality of rotor blades 10 are
fastened to a rotor disk, their outer parts 14 are
arranged side by side so as to form a circumferential
band.
The outer part 14 comprises: a platform 20 defining
5 the outside of the flop1 passage for gas passing between
the airfoils 16 and presenting first and second opposite
side edges 21 and 22 respectively on the pressure side
and on the suction side of the blade 10; and upstream and
downstream sealing wipers 31 and 32 extending radially
10 outwards from the outside face of the platform 20. Each
of the first and second side edges of the platform
presents a substantially Z-shaped profile between the
upstream and downstream wipers 31 and 32, which profile
has a first portion 21A, 22A close to the upstream wiper
15 31, an intermediate second portion 21B, 22B, and a third
portion 21C, 22C close to the downstream wiper 32, the
first and third portions being substantially parallel to
each other and the second portion extending obliquely
between the first and third portions.
2 0 In order to damp the vibration to which blades 10
are subjected in operation, the blades are mounted on
their rotor disks with pre-stress in twisting about their
stacking axes X: the shape of the outer parts 14 is such
that each blade 10 is subjected to twisting stress by
25 pressing against the adjacent blades along the second
portions 218, 228 of the side edges 21, 22. The second
portions 21B, 22B thus define inter-blade contact
surfaces and they are subjected to large amounts of
friction while the turbomachine is in operation.
30 In order to protect them against wear, the second
portions 218, 22B are covered in a material that
withstands friction and that is sold under the trademark
"Stellite". Conventionally, this anti-wear material is
deposited on the second portions 218, 22B by welding.
This is a manual operation and the anti-wear material is
in liquid form while it is being deposited.
A first problem encountered with such blades 10
5 stems from the fact that when the second portions 21B,
22B of the outer part 14 are narrow (i.e. present limited
height along the stacking axis X), it is difficult to
deposit the anti-wear material on these portions 21B, 22B
only (i.e. it is difficult to avoid overflowing from
10 these portions), given that the deposition method used is
not sufficiently accurate. Unfortunately, depositing
anti-wear material outside the portions 21B, 22B, and in
particular on the fillet located between the airfoil 16
and the inside face of the platform 20 is harmful since
15 it may generate cracks in the part 'and give rise to
aerodynamic losses in the gas flow passage.
A solution to that problem consists in "overdimensioning"
the second portions 21B, 22B, i.e. in
increasing their height along the stacking axis X.
20 Nevertheless, that solution is not satisfactory since it
increases the weight and the size of the outer part 14.
Another problem encountered with such blades 10 is
overlapping between adjacent blades (i.e. the side edge
21 of a first blade passes over the side edge 22 of a
25 second blade adjacent to the first), during different
stages of operation of the turbomachine.
There therefore exists a need for another type of
rotor blade.
SUMMARY OF THE INVENTION
The present description provides a turbomachine
rotor blade presenting an outer part at its distal end,
the outer part comprising a platform defining the outside
surface of the passage for gas passing through the
turbomachine and the platform presenting first and second
opposite side edges. The outer part also comprises
upstream and downstream sealing wipers extending
(heightwise) outwards from said platform, each wiper
5 extending (lengthwise) between trio lateral faces situated
respectively at the first and second side edges. The
blade is such that the lateral faces of the upstream and
downstream wipers are covered at least in part in an
anti-wear material.
10 In this solution, the lateral faces of the upstream
and downstream wipers are configured to carry the antiwear
material and they thus serve as inter-blade contact
surfaces.
This solution makes it possible to comply with
15 functional and manufacturing criteria concerning the
outer part while also reducing its weight and size (given
that in terms of weight the outer part is the most
critical portion of the blade). In particular, there is
no longer any need to over-dimension the intermediate
20 portions of the side edges since they no longer act as
inter-blade contact surfaces. The side edges can
therefore be made as narrow as necessary. Furthermore,
the new inter-blade contact surfaces make use of the
wipers without there being any need to overdimension the
25 wipers.
This solution has the additional advantage of making
it easier to position the center of gravity of the outer
part of the blade, thereby improving the mechanical
behavior of the blade, both in vibration and statically.
30 In addition, the proposed solution makes it possible
to define an inter-blade contact surface of fairly large
area, thereby limiting the wear of that surface.
Finally, with this solution, the risk of blades
overlapping is reduced because the height of the interblade
contact surface is increased.
The anti-wear material that is used may be an alloy
5 based on cobalt, and in particular it may be an alloy of
the type sold under the trademark "Stellite" that
includes a significant content of chromium.
The lateral faces of the upstream or downstream
wiper may be covered with the anti-wear material in full
10 or in part. When they are covered in full, the layer of
anti-wear material extends heightwise all along the
wiper, from the inner face of the platform (i.e. the
anti-wear material covers the portion of the side edge
that is situated at the base of the wiper, in line with
15 the wiper) up to the outer (i.e. distal) end of the
wiper. The presence of anti-wear material at the outer
end of the wiper presents the advantage of reinforcing
it. When covered in part only, the layer of anti-wear
material may, for example, extend heightwise from the
20 inner face of the platform to an outer limit that is
spaced back from the outer end of the wiper. Under such
circumstances, the outer end portion of the wiper may be
made of the same material as the remainder of the outer
edge of the wiper. This solution may be advantageous when
25 the anti-wear material does not present the required
ties for coming into contact with the abradable material
present on the outer casing that surrounds the wiper on
its outside. The abradable material is typically a
material in honeycomb form, e.g. a metal. The outer edge
30 of the wiper penetrates into the abradable material
(which is stationary) in order to provide good sealing in
operation.
The anti-wear material may also cover portions of
the side edges that are adjacent to the base of the
wiper.
Furthermore, using the upstream wiper or the
5 downstream wiper to define the inter-blade contact
surfaces makes it possible to optimize the shape of the
outer part in terms of weight and size.
In certain embodiments, the wipers are inclined
upstream in an axial section plane at a non-zero angle
10 relative to the radial direction. This makes it possible
to improve performance while avoiding leaks of air out
from the flow passage in operation.
In other embodiments, the wipers are not inclined
relative to the radial direction, i.e. in an axial
15 section plane the wipers form an angle that is
substantially zero relative to the radial direction: they
extend substantially in this direction.
Thus, in certain embodiments of a first type, in
which the lateral faces of the upstream wiper are used as
20 inter-blade contact surfaces, and are therefore covered
for this purpose in the anti-wear material, it is
possible to use the following optimized shape for the
platform: each of the first and second side edges
presents a profile between the upstream and downstream
25 wipers, which profile is generally U-shaped with a first
portion close to the upstream wiper and forming a first
branch of the U-shape, an intermediate second portion,
forming the base of the U-shape, and a third portion
close to the downstream wiper and forming a second branch
30 of the U-shape, the first and third portions diverging.
In certain embodiments of the first type, the abovementioned
second portion extends substantially
perpendicularly to the wipers.
In certain embodiments of the first type, the third
portion is at least twice as long as the first portion.
In certain embodiments of the first type, the second
portion is smaller than the first portion.
5 In certain embodiments of a second type, in which
the lateral faces of the upstream wiper are used as
inter-blade contact surfaces and are therefore covered
for this purpose in the anti-wear material, it is
possible to use the following optimized shape for the
10 platform: each of the first and second side edges
presents a profile between the upstream and dorinstream
wipers, which profile has a first portion close to the
upstream wiper, an intermediate second portion, and a
third portion that is close to the downstream wiper, the
15 first and third portions being substantially parallel to
each other and the second portion extending obliquely
between the first and third portions from upstream to
downstream and from the suction side towards the pressure
side of the blade.
2 0 This type of profile with three flat portions is
sometimes said to be a Z-shaped profile even though the
angle formed between the first and second portions is an
angle that is obtuse (i.e. not acute) and the angle
formed between the second and third portions is likewise
25 an obtuse angle.
With this optimized shape for the outer part, it is
easier during fabrication of the blade to position the
center of gravity of the outer part correctly relative to
the center of gravity of the inner part of the airfoil.
30 It is generally sought to align these two centers of
gravity along the radial direction. Positioning the
center of gravity of the outer part better relative to
the center of gravity of the root part of the airfoil
makes it possible to obtain better mechanical behavior of
the blade in operation and in particular to improve the
ability of the blade to withstand megacyclic fatigue and
to withstand creep rupture.
5 Such an optimized shape presents a particular
advantage when the wipers slope upstream. The slope of
the wipers raises certain difficulties in aligning the
center of gravity of the outer part with that of the
inner part of the airfoil.
10 In certain embodiments of the second type, each of
the first and second side edges presents an upstream end
portion in line with the first portion and a downstream
end portion in line with the third portion.
These upstream and dorinstream end portions of the
15 side edges laterally define upstream and downstream end
portions of the platform, which portions are sometimes
referred to as upstream and downstream "lips".
Thus, the side edge of the platform presents a
profile with three flat portions that extends from the
20 upstream edge to the downstream edge of the platform, the
profile of each side edge thus presenting three flat
portions and no more. From a fabrication point of view,
such a profile made up of three flat portions is easy to
machine, in particular because the number of faces to be
25 machined is limited (only three). This design also makes
it possible to limit the weight of the unfinished part,
prior to machining, and thus to limit foundry costs.
Finally, this design limits the formation of sharp edges
and spikes that lead to difficulties when manipulating
30 blades.
In certain embodiments of the second type, the first
and third portions extend substantially perpendicularly
to the wipers.
In certain embodiments of the second type, the
upstream wiper flows upstream at a non-zero angle
relative to the radial direction, each of the lateral
faces of the upstream wiper joining the side edge of the
5 platform in its intermediate portion. Also, the anti-wear
material covers each of the lateral faces of the upstream
wiper, at least in part, and covers the intermediate
portion of each side edge at least in part, such that the
anti-wear material situated on the suction side of the
10 blade is exposed downstream whereas the anti-wear
material situated on the pressure side of the blade is
exposed upstream.
It should be observed that the exposure direction of
the anti-wear material is inverted relative to currently
15 existing solutions. Consequently, the pre-twist angle of
the blade is also inverted relative to conventional
solutions.
The present solution also provides a turbomachine
including a blade as described above.
20 BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings are diagrammatic and not
necessarily to scale, and above all they seek to
illustrate the principles of the invention.
In the drawings, from one figure to another,
25 elements (or element portions) that are identical are
identified using the same reference signs.
Figure 1 is a perspective view of a prior art rotor
blade.
Figure 2 is a perspective view of an embodiment of a
30 rotor blade of the present description.
Figure 3 is a detail view from above of the outer
part of the Figure 2 blade.
Figure 4 is a detail view from the side of the outer
part of the Figure 2 blade.
Figure 5 is a view analogous to the view of
Figure 4, showing another embodiment of a rotor blade of
5 the present description.
Figure 6 is a perspective view of another embodiment
of a rotor blade of the present description, with only
the outer portion of the blade being shown.
Figure 7 is a detail view from above of the outer
10 part of the Figure 6 blade.
Figure 8 is a detail view from the side of the outer
part of the Figure 6 blade.
Figure 9 is a view analogous to Figure 6, showing
another embodiment of a rotor blade of the present
15 description.
DETAILED DESCRIPTION OF EMBODIMENTS
Embodiments of a rotor blade with an outer part are
described in detail below with reference to the
accompanying drawings. These embodiments illustrate the
20 characteristics and advantages of the invention. It
should nevertheless be recalled that the invention is not
limited to these embodiments.
Figure 2 shows an embodiment of a turbomachine rotor
blade 110. Such a blade may be used in a low pressure
25 stage of an airplane turbojet.
The rotor blade 110 comprises an airfoil 116
extending along the stacking axis X of the blade between
the proximal and distal ends llOA and llOB of the blade
(i. e. its inner and outer ends) . At its proximal end
30 llOA, the blade has a root 112 whereby it is fastened to
a rotor disk (not shown) of a turbomachine (not shown).
This disk rotates about the axis A of the engine. At its
distal end llOB, the blade 110 has an outer part 114.
When a plurality of rotor blades 110 are fastened to
a rotor disk, their outer parts 114 are arranged side by
side so as to form a rotary circumferential band defining
a surface of revolution around the axis of rotation A of
5 the disk. A particular function of this band is to define
the outside surface of the flow passage for the gas
passing between the airfoils 116, and thus to limit leaks
of gas past the distal ends llOB of the blades 110.
The outer part 114 comprises a platform 120
10 defining the outside of the flow passage for the gas
passing between the airfoils 116, and presenting first
and second opposite side edges 151 and 152. The outer
part 114 also has upstream and downstream sealing wipers
131 and 132 that extend radially outwards from the
15 platform 120. Each wiper 131 (132) presents two lateral
faces 131L (132L) situated respectively at the first and
second side edges (151, 152), and each wiper 131 (132)
extends circumferentially between its two lateral faces
131L (132L).
20 When a plurality of rotor blades 110 are fastened on
a rotor disk, the upstream and downstream wipers 131 and
132 of the blades are arranged end to end so as to form
rotary rings of axis A, each ring being contained
substantially in a radial plane. A particular function of
25 such a ring is to limit the clearance that exists between
the blades 110 and the covering or casing that surrounds
them, in order to limit leaks of gas at this location.
The configuration of the platform 120 is optimized
in terms of weight and size.
30 The platform 120 has an upstream portion 124
referred to as an upstream "lip" that projects upstream
from the upstream wiper 131. The platform 120 also has a
downstream portion 128 commonly referred to as a
downstream "lip", extending downstream from the
downstream wiper 132. Finally, the platform presents a
central portion 126 extending between the upstream and
dormstream wipers 131 and 132. In this embodiment, the
5 central portion 126 has a comma-shaped rib 127 that
extends from the upstream wiper 131 to the downstream
wiper 132 and that is a result of the casting process
used for fabricating the blade.
As can be seen clearly in Figure 3, in the central
10 portion 126, each of the first and second side edges 151
(152) of the platform 120 presents a profile that is
generally U-shaped, having a first portion 151A (152A)
close to the upstream wiper 131 and forming a first
branch of the U-shape, a second portion 151B (152B) that
15 is intermediate forming the base of the U-shape, and a
third portion 151C (152C) close to the downstream wiper
132 and forming a second branch of the U-shape, the first
and third portions 151A, 151C (152A, 152C) being
divergent, i.e. these portions 151A, 151C (152A, 152C)
20 spread apart from each other on going away from the
second portion 151B (152B). In this embodiment, the
second portion 151B (152B) extends substantially
perpendicularly to the wipers 131 (132). Nevertheless, it
should be observed that the second portion 151B (152B)
25 could have a different slope, or that it could even be
omitted. Under such circumstances, the first and third
portions 151A, 151C (152A, 152C) would join together and
form a V-shape.
The first and second side edges 151 and 152 present
30 complementary shapes, the side edge 151 of a first blade
110 being suitable for being received in the side edge
152 of the blade that is adjacent to said first blade
110. Thus, the first portions 151A, 152A of the side
edges 151 and 152 are substantially parallel to each
other. The same applies to the second portions 151B, 152B
and to the third portions 151C, 152C. Furthermore, the Ushaped
profiles of the side edges 15.1, 152 are such that
5 the branches of the U-shapes point towards the pressure
side of the blade 110.
The third portion 151C (152C) of the side edges 151
(152) may be at least twice as large as the first portion
151A (152A). In this embodiment, the third portion 151C
10 (152C) is about three times as long as the first portion
151A (152A). Furthermore, the second portion 151B (152B)
may be smaller than the first portion 151A (152A). In
this embodiment, this second portion 151B (152B) is about
half as long as the first portion 151A (152A).
15 Furthermore, the first and third portions 151A, 151C
(152A, 152C) may form between them an angle that lies in
the range 15" to 150°, for example. In the embodiment
shown, this angle is about 65'.
In order to damp the vibration to which the blades
20 110 are subjected in operation, the blades 110 are
mounted on their rotor disks (not shown) with twist prestress
about their stacking axes X. Thus, the outer parts
114 are configured so that each blade 110 is subjected to
twisting stress by pressing against its neighbors, mainly
25 along the lateral faces 131L of the upstream wipers 131.
The upstream wiper 131 carries a layer 0-f anti-wear
material 160 on its lateral faces 131L, which layer is
obtained by building up each of these lateral faces 131L
with a cobalt-based alloy that presents good anti-wear
30 ties, e.g. such as an alloy of the type sold under the
trademark "Stellite". This anti-wear material 160 is
represented by shading in the figures.
As can be seen clearly in Figure 4, the layer of
anti-vrear material 160 extends radially along the wiper
131 from the inside face 1201 of the platform 120 to the
outer end 131E of the wiper. Each lateral face 131L of
5 the upstream wiper 131 is thus covered from bottom to top
in the anti-wear material 160, and the anti-wear material
160 also covers a portion 151P of the side edge 151 that
is adjacent to the base of the wiper. This portion 151P
comprises the edge portion situated radially in line with
10 the wiper and may also include edge portions adjacent
thereto, as in the configuration shown.
In another embodiment, as shown in Figure 5, each
lateral face 131L of the upstream wiper 131, or only one
of these lateral faces 131L (the other face 131L then
15 being covered from bottom to top as in the examples of
Figures 2 to 4), is covered in part only by the anti-wear
material 260'. More precisely, only the bottom portion of
the lateral face 131L is covered. The layer of anti-wear
material 260 extends radially along the wiper 131 from
20 the bottom face 1201 of the platform 120 out to an outer
limit 260E that is spaced apart from the outer end 131E
of the wiper. For example, the outer limit 260E is spaced
apart from the outer end 131E of the wiper by
2 millimeters (mm) to 3 rnm. The outer portion of the
25 lateral face 131L is thus not covered in anti-wear
material, and thus the outer edge of the wiper can be
made entirely out of a single material (i.e. the material
of the blade). The anti-wear material 260 also covers a
portion 151B of the side edge 151 that is adjacent to the
30 base of the wiper. In comparison with the example of
Figures 2 to 4, this portion 151P extends further
downstream towards the downstream wiper 132.
In the example of Figure 5, the face 131L that
carries the layer of material 260 may be locally enlarged
(i.e. its axial thickness may be increased) compared with
the remainder of the wiper 131 in order to maximize the
5 contact area between blades.
Figure 6 shows an embodiment of a turbomachine rotor
blade 310. Such a blade may be used in a low pressure
stage of an airplane turbojet.
Only the outer (distal) portion 310B of the blade
10 310 is shown in Figure 6. The inner (proximal) portion of
the blade 310 may be analogous to that of the blade in
Figure 1.
The rotor blade 310 has an airfoil 316 extending
along the stacking axis of the blade between the proximal
15 (i.e. inner) end and the distal (i.e. outer) end 310B of
the blade. The airfoil 316 presents a pressure side face
315A and a suction side face (not shown in Figure 6). At
its proximal end (not shown), the blade 310 has a root
whereby it is fastened to a rotor disk (not shown) of a
20 turbomachine (not shown). The disk rotates about the axis
A of the engine. At its distal end 310B, the blade 310
has an outer part 314.
When a plurality of rotor blades 310 are fastened on
a rotor disk, their outer parts 314 are arranged side by
25 side in such a manner as to form a rotary circumferential
band defining a surface of revolution around the axis of
rotation A of the disk. A particular function of the band
is to define the outside surface of the flow passage for
gas passing between the airfoils 316 so as to limit leaks
30 of gas past the distal ends 310B of the blades 310.
The outer part 314 comprises a platform 320
defining the outside of the flow passage for gas passing
between the airfoils 316, and presenting first and second
opposite side edges 351, 352 situated respectively on the
pressure side and on the suction side of the blade 310.
The outer part 314 also has upstream and downstream
sealing wipers 331 and 332 extending upwards from the
5 platform 320 in an outward direction. In this embodiment,
the wipers 331, 332 are inclined upstream relative to the
radial direction by respective non-zero angles A1 and A2.
The angles A1 and A2 are shown in Figure 8, these angles
being measured respectively in axial section planes
10 passing via the lateral faces 331L and 332L of the wipers
331, 332.
Each wiper 331 (332) presents two lateral faces 331L
(332L) situated respectively at the first and second side
edges (351, 352). One of the lateral faces 331L (332L) of
15 the wiper 331 (332) is thus situated on the pressure side
of the blade 310, and the other lateral face is situated
on the suction side. Each wiper 331 (332) thus extends
lengthwise from the pressure side towards the suction
side (i.e. in a circumferential direction) between its
20 two lateral faces 331L (332L).
When a plurality of rotor blades 310 are fastened on
a rotor disk, the upstream or downstream wipers 331 or
332 of the blades are arranged end to end so as to form
respective rotary rings of axis A, each ring being
25 contained substantially in a radial plane. Such a ring
serves in particular to limit the clearance that exists
between the blades 310 and the cover or casing that
surrounds them, in order to limit leaks of gas at that
location.
30 The configuration of the platform 320 is optimized
in terms of weight and size
The platform 320 presents an upstream end portion
324 referred to as the upstream "lip" that extends
upstream from the upstream wiper 331. The platform 320
also presents a downstream end portion 328 referred to as
the downstream "lip" that extends downstream from the
downstream wiper 332. Finally, the platform presents a
5 central portion 326 extending between the upstream and
downstream wipers 331 and 332. In this embodiment, the
central portion 326 has a comma-shaped rib 327 that
extends from the upstream wiper 331 to the dorinstream
wiper 332 and that is a result of the casting process
10 used for fabricating the blade 310.
As can be seen clearly in Figure 7, in the central
portion 326, each of the first and second side edges 351
(352) of the platform 320 presents a profile having three
flat portions with a first portion 351A (352A) close to
15 the upstream wiper 331, an intermediate second portion
351B (352B), and a third portion 351C (352C) that is
close to the downstream wiper 332. The second portion
351B (352B) extends obliquely between the first and third
portions, from upstream to downstream and from the
20 suction side CE towards the pressure side CI of the blade
(see Figure 7). Thus, in plan view, in the plane of the
central portion 326 of the platform 320, the directed
angle B1 (see Figure 7) between the second portion 351B
(352B) and the axial direction (i.e. the upstream-
25 downstream direction) lies strictly between 0 to +90°,
and is preferably greater than +50°.
In this embodiment, the first and third portions
351A, 351C (352A, 352C) are substantially parallel with
each other and oriented in the axial direction. They are
30 substantially perpendicular to the wipers 331 and 332,
respectively.
In addition, the first and second lateral edges 351,
352 present respective upstream end portions 351AA, 352AA
in alignment with the first portion 351A, 352A, and
respective downstream end portions 351CC, 352CC in
alignment with the third portion 351C, 352C. The upstream
end portions 351AA of the edges 351, 352 laterally define
5 the upstream lip 324, while the downstream end portions
351CC, 352CC of the edges 351, 352 laterally define the
downstream lip 328.
The first and second side edges 351 and 352 are
complementary in shape, the side edge 351 of a first
10 blade 310 being suitable for engaging in the side edge
352 of the blade adjacent to the first blade 310. Thus,
the first portions 351A, 352A of the side edges 351 and
352 are substantially parallel to each other. The same
applies to the second portions 351B, 352B and to the
15 third portions 351C, 352C.
In order to damp the vibration to which the blades
310 are subjected in operation, the blades 310 are
mounted on their rotor disks (not shown) with twist prestress
about their stacking axes. The outer parts 314 are
20 configured so that each blade 310 is put under twist prestress
by bearing against its neighbors, mainly along the
lateral faces 331L of the upstream wiper 331.
Thus, an upstream wiper 331 carries a layer of antiwear
material 360 on its lateral faces 331L, vrhich layer
25 is obtained by building out said lateral face 331L with a
cobalt-based alloy presenting good anti-wear ties, such
as for example an alloy of the type sold under the
trademark "Stellite". This anti-wear material 360 is
represented by shading in the figures.
30 In the example, the upstream wiper 331 flares (i.e.
its axial thickness increases) on approaching the
platform 320, such that the lateral face 331L of the
wiper flares as it comes up to the side edge 351 of the
platform 320, as shown in Figure 8. The lateral face 331L
joins the side edge 351 of the platform at its
intermediate portion 351B (see Figures 6 to 8).
As shown in Figure 8, the layer of anti-wear
5 material 360 extends upwards along the wiper 331 from the
inner face 3201 of the platform 320 to an outer limit
360E. In this embodiment, the outer limit 360E is spaced
apart from the outer end 331E of the wiper. The anti-wear
material thus covers only an inner zone of the lateral
10 face 331L. The anti-wear material 360 also covers a zone
of the identical portion 351B of the side edge 351, this
zone being adjacent to the base of the wiper 331.
In this embodiment, the layer of anti-wear material
360 extends from the base of the wiper 331 towards the
15 outer limit 360E in a direction that is substantially
radial, even though the wiper 331 slopes relative to the
radial direction. The anti-wear material 360 thus covers
only a portion of the lateral face 331L.
As shown in Figure 7, the anti-wear material 360
20 situated beside the suction side CE of the blade is
exposed downstream whereas the anti-wear material 360
situated beside the pressure side CI of the blade is
exposed upstream. The direction in which the anti-wear
material is exposed is thus inverted compared with
25 conventional solutions.
Another embodiment is shown in Figure 9, this
embodiment differing from that of Figures 6 to 8
essentially by the positioning of the anti-wear material
460, while the general shape of the platform 320 , of the
30 wipers 331, 332, and of the side edges 351, 352 is
analogous in both embodiments.
In the embodiment of Figure 9, the layer of antiwear
material 460 extends along the downstream wiper 332.
In addition, the anti-wear material 460 extends from the
inner face 3201 of the platform 320 to the outer end
3323 of the wiper. Each lateral face 332L of the
downstream wiper 332 is thus completely covered in anti-
5 wear material 460. The anti-wear material 460 also covers
the zone of the third portion 351C (352C) of the side
edge 351 (352) that is adjacent to the base of the wiper
332.
In general, the anti-wear material may be deposited
10 in various ways. For example, the anti-wear material may
be in the form of plates (made of a specific alloy
presenting high hardness) that are brazed onto the
lateral faces of the wipers. In another technique, the
surface that is to be protected is progressively built up
15 with an anti-wear material that is melted together with
the top layer of the substrate. The heat needed for
deposition is delivered by means of a suitable heat
source, such as for example an electric arc sheathed in
an inert gas, or indeed a laser beam.
2 0 Furthermore, in certain methods, the anti-wear
material is deposited on the substrate (i.e. the body of
the blade) after locally removing material from the
substrate by grinding to a determined depth. In other
methods, when fabricating the outer part (e.g. by
25 casting), the zones of the substrate that are to be
covered in the anti-wear material are "under-dimensioned"
relative to the desired final shape. Thereafter, the
anti-wear material is deposited on these zones and the
covered zones are then machined in order to obtain the
30 desired final shape.
The embodiments described in the present description
are given by way of non-limiting illustration, and in the
light of the present description, a person skilled in the
art can easily modify these embodiments or can envisage
others while remaining within the scope of the invention.
Furthermore, the various characteristics of these
embodiments may be used'singly or in combination with one
5 another. When they are combined, these characteristics
may be combined as described above or in other ways, the
invention not being limited t'o the specific combinations
described in the present description. In particular,
unless there is a major technical incompatibility, any of
10 the characteristics described with respect to any of the
embodiments may be applied in analogous manner to any
other embodiment.

CLAIMS
1. A turbomachine rotor blade having an outer part (114,
314) at its distal end (llOB, 310B), the outer part
5 comprising:
a platform (120, 320) defining the outside surface
of the passage for gas passing through the turbomachine
and presenting first and second opposite side edges (151,
152, 351, 352); and
10 upstream and downstream sealing wipers (131, 132,
331, 332) extending outwards from said platform (120,
320), each wiper extending between two lateral faces
(131L, 132L, 331L, 332L) situated respectively at the
first and second side edges (151, 152, 351, 352);
15 the blade (110, 310) being characterized in that the
lateral faces (131L, 132L, 331L, 332L) of the upstream
and downstream wipers (131, 132, 331, 332) are covered,
at least in part, in an anti-wear material (160, 360,
460) .
2 0
2. A blade according to claim 1, wherein each of the
first and second side edges (351, 352) presents a profile
between the upstream and downstream wipers (331, 332) ,
which profile has a first portion (351A; 352A) close to
25 the upstream wiper (331), an intermediate second portion
(351B; 352B), and a third portion (351C; 352C) that is
close to the downstream wiper (332), the first and third
portions (351A, 351C; 352A, 352C) being substantially
parallel to each other and the second portion (351B;
30 352B) extending obliquely between the first and third
portions from upstream to downstream and from the suction
side towards the pressure side of the blade.
3. A blade according to claim 2, wherein each of the
first and second side edges (351, 352) presents an
upstream end portion (351AA; 352AA) in line with the
first portion (351A; 352A) and a downstream end portion
5 (351CC; 352CC) in line with the third portion (351C;
352C).
4. A blade according to claim 2 or claim 3, wherein the
first and third portions (351A, 351C; 352A, 352C) extend
10 substantially perpendicularly to the wipers (331, 332).
5. A blade according to 'any one of claims 2 to 4, wherein
the upstream wiper (331) flows upstream at a non-zero
angle (Al) relative to the radial direction, each of the
15 lateral faces (331L) of the upstream wiper joining the
side edge (351, 352) of the platform in its intermediate
portion (351B, 352B), and wherein the anti-wear material
(360) covers each of the lateral faces (331L) of the
upstream wiper, at least in part, and covers the
20 intermediate portion (351B, 352B) of each side edge at
least in part, such that the anti-wear material (360)
situated on the suction side (CE) of the blade is exposed
downstream whereas the anti-wear material situated on the
pressure side (CI) of the blade is exposed upstream.
25
6. A blade according to claim 1, wherein each of the
first and second side edges (151, 152) presents a profile
between the upstream and downstream wipers (131, 132),
which profile is generally U-shaped with a first portion
30 (151A; 152A) close to the upstream wiper (131) and
forming a first branch of the U-shape, an intermediate
second portion (151B; 152B), forming the base of the Ushape,
and a third portion (151C; 152C) close to the
downstream wiper (132) and forming a second branch of the
U-shape, the first and third portions (151A, 151C; 152A;
152C) diverging.
5 7. A blade according to claim 6, wherein the second
portion (151B; 152B) extends substantially
perpendicularly to the wipers (131, 132).
8. A blade according to claim 6 or claim 7, wherein the
10 third portion (151C; 152C) is at least twice as long as
the first portion (151A, 152A).
9. A blade according to any one of claims 1 to 8, wherein
at least one of the lateral faces (131L, 132L, 331L,
15 332L) is completely covered in the anti-wear material
(160, 360, 460).
10. A blade according to any one of claims 1 to 9,
wherein at least one of the lateral faces (131L, 132L,
20 33lL, 332L) is covered in part in the anti-wear material
(160, 360), only the inner zone of said lateral face
(131L, 331L) being covered.
11. A blade according to any one of claims 1 to 10,
25 wherein the lateral faces (131L, 331L) of the upstream
riiper (131, 331) are covered in the anti-wear material
(160, 360).
12. A blade according to any one of claims 1 to 11,
30 wherein the upstream and/or downstream riiper (131, 331;
132, 332) slopes upstream in an axial section plane at a
non-zero angle (Al, A2) relative to the radial direction.
13. A blade according to any one of cl-aims 1 to 11, in
which the upstream and/or downstream wiper (131, 331;
132, 332) extends substantially in the radial direction.
5 14. A turbomachine including a blade (110, 310) according
to any preceding claim.
W J N A MEHTA-DUTT]
OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANT[S]
A B S T R A C T
A turbomachine rotor blade presenting an outer part
(314) at its distal end (310B), the outer part comprising
a platform (320) defining the outside surface of the
passage for gas passing through the turbomachine and
10 presenting first (351) and second opposite side edges;
and upstream and downstream sealing wipers (331, 332)
extending outwards from said platform (320), each wiper
extending between two lateral faces (331L, 332L) situated
respectively at the first (351) and second side edges.
15 The lateral faces (331L, 332L) of the upstream and
downstream wipers (331, 332) are covered at least in part
in an anti-wear material (360).