Background of the invention
The invention relates to gas turbine casings, and
more particularly, but not exclusively, to gas turbine
5 fan casings for aeroengines.
In a gas turbine aeroengine, the fan casing performs
several functions. It defines the inlet passage for
admitting air into the engine, and it supports an
abradable material facing khe tips of the fan blades, the
10 abradable material generally itself being supported by a
cellular structure.
Casing such as fan casings used to be made out of
metal material, but they are now made out of composite
material, i.e. from a fiber preform densified by an
15 organic matrix, thus making it possible to make parts of
overall weight that is less than that of the same parts
when they are made out of metal, while still presenting
mechanical strength that is at least equivalent if not
stronger: ,-Fabri-catinga fan casing out of organic matrix
20 composite material is described in particular in Document
EP 1 961 923.
A fan casing is one of the parts defining a "fire"
zone in the meaning of aviation certification. In this
context, it must be considered as being a fire wall
25 between the nacelle compartment situated on the outside
of the casing and the flow passage defined on the inside
of the casing, and it must satisfy the associated
regulatory requirements.
Nevertheless, during fire testing, it has been found
30 that extinguishing flames present on the outside of the
casing, i.e. in the nacelle compartment of the engine,
can be difficult, even after switching off the burner.
Object and summary of the invention
35 It would thus be desirable to have available a
solution enabling fire on the outside of the casing to be
extinguished reliably.
Fire tests carried out by the Proprietor on test
pieces made of organic matrix composite material have
shown that the resin degrades while giving off gas. That
gas is flammable, and it can lead to maintaining a flame
5 even after the burner has been switched off.
For an aeroengine casing, structural parts, such as
abradable and/or acoustic panels are fastened against the
inside face of the casing by adhesive. Tests likewise
carried out by the Proprietor have shown that, in the
10 event of a fire, these parts bonded against the inside
face of the casing have the effect of preventing
discharge of the gas that results from degradation of the
resin beside the passage, so that such gas is
consequently discharged mainly on the outside of the
15 casing, i.e. into the nacelle compartment where the fire
is present. Since the gas is flammable, discharging it
beside the flame can lead to the flame being maintained
even after the engine has been shut down and extinction
systems have been triggered. Thus, when in the presence
20 of a part made of organic matrix composite material, it
is desirable to give preference to discharging the gas
that results from the resin degrading away from the flame
zone.
To this end, the invention provides a gas turbine
25 casing made of organic matrix composite material
comprising reinforcement densified by an organic matrix,
said casing defining an inside volume having on its
inside face a structural part having a first face facing
the inside face of the casing and an opposite second face
30 defining a portion of the flow passage, the casing being
characterized in that the face of the structural part
facing the inside face of the casing includes grooves
opening out directly or indirectly into the inside volume
of the casing, and in that these grooves extend at least
35 in the axial direction of the casing.
Thus, because of the presence of grooves opening out
into the inside volume of the casing, gas resulting from
degradation of the matrix of the casing in the presence
of flames on the outside of the casing can be discharged
into the passage, thereby avoiding disturbing extinction
of the fire on the outside of the casing.
5 Additional grooves may extend in a direction
perpendicular to these axial first grooves. In an aspect
of the casing of the invention, the grooves open out at
least at one axial end of the structural part. In
another aspect of the casing of the invention, the
10 grooves stop before the axial ends of the structural part
and communicate with perforations opening out into the
second face of the structural part.
In another embodiment of the casing of the
invention, the structural part is bonded to the inside
15 face of the casing via spacer studs, thereby making it
possible to have recesses or spaces between the inside
face of the casing and the structural part and enabling
the gas given off during fire degradation of the matrix
of the .cas,ing to be discharged into the passage.
2 0 In yet another embodiment of the casing of the
invention, the inside face of the casing includes grooves
that open out beyond the structural part.
In an aspect of the casing of the invention, the
structural part comprises a cellular structure facing the
25 inside face of the casing. Under such circumstances, the
presence of recesses between the structural part and the
inside space of the casing enables the gas given off
during degradation of the matrix of the casing to pass
through the cellular structure in order to be discharged
30 into the passage. The structural part may also include a
layer of abradable coating supported by the cellular
structure.
Furthermore, the grooves may include gutters, e.g.
made of a fiber texture consolidated by a matrix. This
35 serves to seal the cellular structure in zones where it
is no longer in contact with the wall of the casing.
Still in another embodiment of the casing of the
invention, the structural part comprises a cellular
structure facing the inside face of the casing, a skin
closing the cells of the cellular structure beside the
5 face of said cellular structure that is opposite from its
f?ace facing the inside face of the casing, the walls of
the cells of the cellular structure including at least
one perforation, the skin further including perforations
opening out into the inside volume of the casing.
10 The invention also provides a gas turbine aeroengine
having a fan retention casing of the invention, and an
aircraft including one or more such engines.
Brief description of the drawings
15 Other characteristics and advantages of the
invention appear from the following description of
particular embodiments of the invention given as nonlimiting
examples, and with reference to the accompanying
drawingsi- in which:
2 0 Figures 1A and 1B are respectively a perspective
view and a section view of a prior art aeroengine ffan
casing;
Figure 2A is a perspective view of a structural
part in accordance with an embodiment of the invention;
2 5 Figure 2B is a section view of an organic matrix
composite material casing fitted with the structural part
of Figure 2A;
Figure 3 is a perspective view of a structural
part in accordance with an embodiment of the invention;
3 0 Figure 4A is a perspective view of a structural
part in accordance with an embodiment of the invention;
Figure 4B is a section view of an organic matrix
composite material casing fitted with the structural part
of Figure 4A;
35 Figure 5A is a section view of an organic matrix
composite material casing fitted with the structural part
in accordance with an embodiment of the invention;
Figure 5B is a perspective view of the Figure 5A
structural part; and
Figure 6 is a section view of an organic matrix
composite material casing fitted with a structure in
5 accordance with an embodiment of the invention.
Detailed description of embodiments
The invention applies in general manner to any
organic matsrix composite material casing for a gas
10 t.urbine and having on its inside face at least one
structural part.
The invention is described below in the context of
its application to a fan casing of a gas turbine
aeroengine.
15 Such an engine, as shown very diagrammatically in
Figure lA, comprises from upstream to downstream in the
gas stream flow direction: a fan 1 arranged at the inlet
of the engine; a compressor 2; a combustion chamber 3; a
high pressure turbine 4; and a low pressure turbine 5.
20 The engine is housed inside a casing made up of a
plurality of portions corresponding to the various
elements of the engine. Thus, the fan 1 is surrounded by
a fan casing 10.
Figure 1B shows the profile of the fan casing 10,
25 which is made of organic matrix composite material, i.e.
from fiber reinforcement, e.g. made of carbon, glass,
aramid, or ceramic fibers, and densified by a polymer
matrix, e.g. of epoxy, bismaleimide, or polyimide.
Fabricating such a casing is described in particular in
30 Document EP 1 961 923.
In the presently-described example, the inside face
11 of the casing 10 is provided with a structural part 20
made up of a cellular structure 21 and a layer of
abradable material 23 fastened to the cellular structure
35 by a skin 22, e.g. constituted by a layer of resin, and
serving also to close the bottom portions of the cells
210 of the cellular structure 21, with the top portions
of the cells being closed by the inside face 11 of the
casing with which they are in contact. The structural
part 20 comprises a first face 20a facing the inside face
11 of the casing 10, with the face 20a in this example
5 corresponding to the high portions of the cells 210 of
the cellular structure 21. The structural part has a
second face20b opposite from its face 20a and of shape
that defines a portion of the flow passage 14.
In the presence of a flame beside the outside face
10 1~2 of t,he casing, the gas given off (arrows GD in
~~igur1eB ) during degradation constituting the matrix of
the casing beside the inside face 11 of the casing cannot
pass through the part 20 in order to reach the passage 14
through which it ought to be discharged. This gas is
15 thus discharged mainly beside the outside face 12 of the
casing 10, i.e. beside the flame, which then runs the
risk of being sustained by the flammable degradation gas.
In accordance with an embodiment of the invention,
as shown in Figures 2A and 2B, a casing 100 similar to
20 the above-described casing 10 has on its inside face 101
a structural part 120 that differs from the abovedescribed
structural part 20 in that it includes grooves
or corridors 130 in its first face 120a facing the inside
face 101 of the casing 100, which grooves or corridors
25 130 are formed in the walls 1211 of the cells 1210 of the
cellular structure 121, the grooves 130 extending in a
direction parallel to the axial direction of the casing
100. The second face 120b opposite from the face 120a is
constituted by the layer of abradable material 123 that
30 is fastened to the cellular structure 121 via the skin
122. This second face 120b defines a portion of the flow
passage 102. The grooves 130 enable the gas given off
(arrows GD in Figure 2B) during degradation of the
organic matrix of the material of the casing to flow
35 towards the downstream portion of the part 120 so as to
be discharged via perforations 140, as shown in
Figure 2B. In the presently-described example, the
perforations 140 are present in the layer of abradable
material 123 at the downstream end of the part 120, and
they enable the gas flowing in the grooves 130 to be
discharged into the passage 102 situated in the inside
5 volume of the casing 100.
In the presently-described embodiment, the grooves
130 comprise gutters 131 made of fiber texture, e.g. made
of carbon fibers, consolidated by a matrix, e.g. an epoxy
maerix. The gutters 131 may be made by using a fiber
10 texture that has been pre-impregnated with a precursor
resin for the matrix and that is shaped in the grooves so
as to form a web 131a of the gutter from which there
extend two gutter flanges or side walls 131b and 131c.
The gutters 131 serve to seal the cellular structure in
15 zones where it is no longer in contact with the wall of
the casing, and they thus avoid allowing any moisture to
penetrate into the cells of the cellular structure.
In a variant embodiment shown in Figure 3, the
structurl--pa-rt-12a0l so has additional grooves 150 in
20 its face 120a that extends perpendicularly relative to
the grooves 130, which themselves extend in the axial
direction of the casing 1'00. Degradation gas from the
casing 100 can thus flow both in the grooves 130 and in
the grooves 150 so as to be discharged via the
25 perforations 140, i.e. into the flow passage situated in
the inside volume of the casing 100. In the presentlydescribed
embodiment, the grooves 130 and 150 comprise
respective gutters 131 and 151 that are formed by a fiber
texture, e.g. made of carbon fibers consolidated by a
30 matrix, e.g. an epoxy matrix. The gutters 131 and 151
may be made using a fiber texture that has been preimpregnated
with a resin precursor for the matrix and
that is shaped in the grooves so as to form respective
gutter webs 131a and 151a, from which there extend
35 respective pairs of side walls 131b & 131c and 151b &
151c. The gutters 131 and 151 serve to seal the cellular
structure in zones where it is no longer in contact with
the wall of-the casing, and they thus avoid allowing any
moisture to penetrate into the cells of the cellular
structure.
In another embodiment of the invention, as shown in
5 Figures 4A and 4B, a casing 200 similar to the abovedescribed
casing 10 has a structural part 220 on its
inside face 201 that differs from the above-described
structural part 20 in that it includes grooves or
corridors 230 in its first face 220ajfacing the inside
10 . face 201 of the casing 200, which grooves or corridors
230 are formed in the walls 2211 of the cells 2210 of the
cellular structure 221, the grooves 230 extending in a
direction parallel to the axial direction of the casing
100. The second face 220b opposite from the face 220a is
15 constituted by the layer of abradable material 223 that
is fastened to the cellular structure 221 via the skin
222. This second face 220b defines a portion of the flow
passage 202. The grooves 230 enable the gas given off
(arrows- GD in.-.Fligure4 B) during degradation of the
20 organic matrix of the material of the casing to flow
towards the downstream portion of the part 220 so as to
be discharged via openings 240 formed at the downstream
end 230b of the grooves 230, the upstream ends 230a of
the grooves 230 being closed. The degradation gas
25 flowing in the grooves 230 is then discharged into the
passage 202 situated in the inside volume of the casing
200. In the presently-described embodiment, the grooves
230 comprise gutters 231 that are made of a fiber
texture, e.g. of carbon iibers consolidated by a matrix,
30 e.g. an epoxy matrix. The gutters 231 may be made by
using a fiber texture that has been pre-impregnated with
a resin precursor for the matrix that is shaped in the
grooves in order to form a gutter web 231a from which
there extend two side walls 231b and 231c. The gutters
35 231 serve to seal the cellular structure in the zone
where it isno longer in contact with the wall of the
casing, and thus avoid allowing any moisture to penetrate
into the cells of the cellular structure, in particular
via the openings 240. In a variant embodiment of the
protection against moisture, the cells present in the
vicinity of the grooves 230 may be densified with an
5 intumescent adhesive or a potting resin.
In another embodiment of the invention, shown in
Figures 5A and 5B, a casing 300 similar to the abovedescribed
casing 10 has a structural part 320 on its
inside face 301 that differs from the above-described
.I0 structural part 20 in that each of the walls 3211 of the
cells 3210 of the cellular structure 321 includes one or
more perforations 3212. The second face 320b opposite
from the face 320a and constituted by the layer of
abradable material 323 defines a portion of the flow
15 passage 302. The perforations 3212 enable the gas given
off (arrows GD in Figure 5B) during degradation of the
organic matrix of the material of the casing and entering
into the cells 3210 beside the face 320a of the part 320
to flow-eowards the downstream portion of the part 320 in
20 order to be discharged via the perforations 340 as shown
in Figure 58. In the presently-described example, the
perforations 340 are present in the skin 322 and the
abradable material layer 323 at the downstream end of the
part 320, and they enable the gas flowing through the
25 perforations 3212 formed in the cells 3210 to be
discharged into the passage situated in the inside volume
of the casing 300.
In the embodiments described above with reference to
Figures 2, 3, 4, 5, and 6, the perforations are made at
30 the downstream end of the structural part. Nevertheless,
perforations could equally well be made at other
locations in the structural part.
In yet another embodiment of the invention, shown in
Figure 6, a casing 400 includes beside its inside face
35 401 a structural part 420 that is constituted by a
cellular structure 421 and a layer of abradable material
423 fastened on the cellular structure by a first skin
422-, e.g. made of carbon plies, that also serves to close
the bottom portions of the cells 4210 of the cellular
structure 421, which cells are closed in their top
portions by a second skin 424, e.g. formed by carbon
5 plies. The structural part 420 has a first face 420a
facing the inside face 401 of the casing 410, the face
420a in this example corresponding to the top portion of
the cells of the cellular structure 421. The structural
part has a second face 420b opposite from the face 420a
10 of shape that defines a portion of the flow passage 402.
In this embodiment, the structural part 420 is
fastened to the casing via spacer studs 430 that are
adhesively bonded firstly to the inside face 401 of the
casing 400 and secondly to the face 420a of the part 420,
15 which in this example is constituted by the second skin
424. The spacer studs 430 are preferably adjustable in
height so as to control clearances and interaction with
the tips of the turbine blades. By using spacer studs
430, a eorridor or recess 430 is formed between the face
20 420a of the part 420 and the inside face 401 of the
casing 400, thus enabling the gas give off (arrows GD in
Figure 6) during degradation of the organic matrix of the
casing material to flow towards the downstream portion of
the part 420 in order to be discharged into the passage
25 402.
In still another embodiment, the inside face of the
casing includes grooves that open out beyond the
structural part. This embodiment may optionally be
combined with the other embodiments described above.
CLAIMS
1. A gas turbine casing (100; 200; 300; 400) made of
organic matrix composite material comprising
reinforcement densified by an organic matrix, said casing
5 defining an inside volume having on its inside face (101;
201; 301; 401 ) a structural part (120; 220; 320; 420)
having a first face (120a; 220a; 320a; 420a) facing the
inside face of the casing and an opposite second face
(120b; 220b; 320b; 420b) defining a portion of the flow
10 passage (102; 202; 302; 402), the casing being
characterized in that the first face (120a; 220a) of the
structural part (120; 220) facing the inside face (101;
201) of the casing includes grooves (130; 230) opening
out directly or indirectly into the inside volume of the
15 casing, and in that said grooves (130; 230) extend at
least in the axial direction of the casing (100).
2. A casing according to claim 1, characterized in that
the grooves (230) open out at least at one axial end of
20 the structural part (220).
3. A casing according to claim 1 or claim 2,
characterized in that the grooves (130) stop before the
axial ends of the structural part (120), the grooves
25 including perforations (140) opening out in the second
face (120b) of the structural part.
4. A casing according to any one of claims 1 to 3,
characterized in that first grooves (130) extend in the
30 axial direction of the casing (loo), and in that second
grooves (150) extend perpendicularly to the first grooves
(130) .
5. A casing according to any one of claims 1 to 4,
35 characterized in that the inside face of the casing
includes grooves that open out beyond the structural
part.
6. A casing according to any one of claims 1 to 4,
characterized in that the structural part (120; 220; 320;
420) comprises a cellular structure (121; 221; 321; 421)
5 facing the inside face (101; 201; 301; 401) of the casing
(I 00; 200; 300; 400).
7. A casing according to claim 6, characterized in that
the grooves comprise gutters.
10
8. A casing according to claim 6 or claim 7,
characterized in that the structural part (120;-220; 320;
420) further includes an abradable coating layer (123;
223; 323; 423).
15
9. A gas turbine aeroengine having a fan retention casing
according to any one of claims 1 to 8.
10. An aizeraft,including one or more engines according
20 to claim 9.