TURBOMACHINE, SUCH AS A TURBOJET OR A TURBOPROP ENGINE
This invention relates to a turbine engine, such as
a turbojet or a turboprop engine.
As is already known in particular in documents
FR 2 840 974, FR 2 937 098 and FR 2 921 463 in the name
5 of the Applicant, the annular combustion chamber of a
turbine engine conventionally comprises coaxial walls of
revolution that extend one inside the other, referred to
as inner shell and outer shell, and which are connected
at the upstream ends by a chamber bottom annular wall
10 comprising opening for mounting fuel injectors.
During operation, a portion of the airflow supplied
by a gas producer of the chamber passes through openings
of the chamber bottom wall and is mixed with the fuel
supplied by the injectors, with this air/fuel mixture
15 then being burnt inside the chamber. Another portion of
this airflow by-passes the combustion chamber then
penetrates into the chamber through multiperforations of
the inner and outer shells of the chamber.
A sectorised turbine inlet distributor is mounted at
20 the outlet of the combustion chamber and comprises
coaxial shells between which extend substantially radial
blades. The shells of the distributor are in the axial
extension of the inner and outer shells of the combustion
chamber.
Sealing means are provided between the combustion
5 chamber and the distributor, in particular between the
downstream ends of the inner and outer shells of the
combustion chamber and the upstream ends of the inner and
outer shells of the turbine distributor.
More precisely, the downstream end of each shell of
10 the combustion chamber comprises a rim of which a radial
portion is extended by a cylindrical portion extending
downstream. In addition, the upstream end of each shell
of the distributor comprises a radial rim of a smaller
dimension than the aforementioned radial portion of the
15 corresponding rim of the combustion chamber.
The sealing means comprise sealing strips extending
radially and circumferentially along each sector, each
bearing sealingly against a radial face of the
corresponding rim of the distributor and on the free end
20 of the axial portion of the corresponding rim of the
combustion chamber. The strips are maintained bearing
against the rims using means of elastic return.
Such sealing means have the disadvantages mentioned
hereinafter.
25 First of all, the rims of the shells of the
combustion chamber are located in the by-pass airflow, in
such a way that these portions of the combustion chamber
have relatively substantial exchange surfaces with the
cold airflow. These surfaces are therefore relatively
30 cold in relation to the rest of the combustion chamber.
The temperature differences within the shells of the
combustion chamber can generate bending stresses, which
negatively affect its lifespan.
Furthermore, such a structure requires providing on
the shells of the combustion chamber, rims that have
5 relatively substantial dimensions, which increases the
overall mass.
The axial displacements between the combustion
chamber and the turbine distributor can damage the strips
and/or generate leaks. Generally, such radial strips do
10 not have a good seal, which negatively affects the
overall performance of the turbine engine (fuel
consumption, pollution, relighting range, etc.) and
exposes the downstream end of the combustion chamber to
azimuth or circumferential thermal gradients.
15 Furthermore, in prior art, when the combustion
chamber is fastened upstream by a pin system or an
upstream retaining for example, it is necessary to
provide bearing members on the downstream ends of the
inner and outer shells of the combustion chamber. Each
20 bearing member is generally annular and has a section in
the shape of a U or a pin. Each bearing member extends
radially inwards or outwards, between the corresponding
rim of the inner shell or of the outer shell of the
combustion chamber and an inner casing or an outer casing
25 of the chamber. The bearing members limit the relative
displacements between the rims of the combustion chamber
and the rims of the distributor, and therefore also
damage to the strips.
These bearing members are required in order to
30 provide for the seal of the strips but have a substantial
mass. Furthermore, cracks or fissures caused by thermal
and/or mechanical stress can appear in the bearing
members. Finally, functional clearances must be defined
with precision between the bearing members and the inner
and outer casings on which they bear against.
The invention has in particular for purpose to
5 provide a simple, effective and economical solution to
these problems.
To this effect, it proposes a turbine engine, such
as a turbojet or a turboprop engine, comprising an
annular combustion chamber defined by an inner shell and
10 an outer shell, a turbine distributor arranged downstream
of the combustion chamber, with the downstream end of the
outer shell and/or of the inner shell of the chamber
comprising a radial rim arranged opposite a radial rim of
the upstream end of the distributor, sealing means
15 comprising at least one strip extending between said rims
in such a way as to provide the seal between the
combustion chamber and the distributor, characterised in
that the sealing strip extends axially and
circumferentially between said rims and bears sealingly
20 radially against the free ends of said rims.
In this way, the radial dimension of the rim of the
combustion chamber can be reduced, which has for effect
to reduce the overall mass and to reduce the exchange
surfaces with the by-pass air. The temperature of the
25 downstream end of the corresponding shell of the
combustion chamber is as such increased, in such a way
that the temperature differences within this shell and
the bending stresses that stem from it are substantially
reduced.
30 In addition, as the sealing strip is oriented
axially, at least in its bearing zones on the
aforementioned rims, it always provides a good seal, even
in the case of substantial axial displacement of the
combustion chamber in relation to the turbine distributor.
This makes it possible to obtain a high output of the
turbine engine and to be able to be free of the presence
5 of bearing members. The mass of the combustion chamber
can therefore be substantially reduced.
Advantageously, the free end of the rim of the
combustion chamber is axially opposite the free end of
the rim of the distributor.
10 Preferably, the turbine engine comprises means of
elastic return that tend to stress the sealing strip
bearing against the free ends of the rims.
According to a characteristic of the invention, the
distributor comprises at least one positioning lug of
15 which one end engages in a notch of a shape complementary
with the strip, in such a way as to immobilise the strip
in its circumferential direction and in its axial
direction.
Furthermore, the turbine engine can comprise a cover
20 extending circumferentially and axially, in such a way as
to cover, at least partially, the rims of the chamber and
of the distributor as well as the sealing strip.
The cover makes it possible to further reduce the
thermal exchanges between the downstream end of the
25 corresponding shell of the combustion chamber and the bypass
air.
In this case, the cover can be fastened using a
screw or a rivet that forms the positioning lug of which
the free end engages in the corresponding notch of the
30 sealing strip.
The cover can have a generally U-shaped section
comprising a base extending axially and two flanks
extending radially inwards from the base, respectively a
first flank extending radially upstream of the rim of the
combustion chamber and a second flank extending radially
downstream of the rim of the distributor.
5 According to a possibility of the invention, the
second flank is fastened to a flange of the distributor,
with the first flank being separated from the rim of the
downstream end of the combustion chamber by a determined
clearance, for example less than 3 rnrn.
10 Such a clearance makes it possible to offset any
dilatation effect and as well as prevents the cover from
being deformed by the bearing of the rim of the
combustion chamber on the first flank.
According to another characteristic of the invention,
15 the means of elastic return comprise at least one
radially acting elastic member bearing on the one hand
against the cover and on the other hand against the
sealing strip.
In addition, the turbine distributor can be
20 sectorised, with a strip and/or a cover extending
circumferentially along each turbine sector.
Furthermore, the free ends of the rims can comprise
grooves, with the strip having hollow zones that hug the
shapes of the free ends of the rims.
25 The invention shall be better understood and other
details, characteristics and advantages of the invention
shall appear when reading the following description
provided as a non-restricted example in reference to the
annexed drawings wherein:
30 - figure 1 is a longitudinal cross-section half-view
of a portion of a combustion chamber and of a turbine
distributor of a turbine engine of prior art,
- figure 2 is a perspective view of a portion of the
chamber and of the distributor of figure 1, provided with
sealing means,
- figure 3 is a detailed and cross-section view,
5 showing the sealing means of prior art located between
the outer shell of the combustion chamber and the outer
shell of the distributor,
- figure 4 is a detailed and cross-section view,
showing the sealing means of prior art located between
10 the inner shell of the combustion chamber and the inner
shell of the distributor,
- figure 5 is a view corresponding to figure 2,
showing an embodiment of the invention,
- figure 6 is a perspective view of a portion of the
15 outer shells of the chamber and of the distributor of
figure 4, provided with associated sealing means,
- figure 7 is a perspective view of a portion of the
inner shells of the chamber and of the distributor of
figure 4, provided with associated sealing means,
20 - figure 8 is a detailed and cross-section view, of
a portion of the outer shells of the chamber and of the
distributor of figure 4, provided with associated sealing
means,
- figure 9 is a detailed and cross-section view, of
25 a portion of the inner shells of the chamber and of the
distributor of figure 4, provided with associated sealing
means.
Reference is first made to figure 1 which shows a
portion of an annular combustion chamber 1 of a turbine
30 engine of prior art, such as a turbojet or a turboprop
engine, which is arranged downstream of a compressor and
of a diffuser (not shown), and upstream of an inlet
distributor 2 of a high-pressure turbine.
The combustion chamber 1 comprises inner and outer
walls of revolution, referred to respectively as inner
5 shell 3 and outer shell 4, which extend inside one
another and which are connected upstream to a chamber
bottom annular wall (not shown).
In order to limit the deformation of the inner 3 and
outer 4 shells, the latter are provided at their
10 downstream end with inner and outer bearing members 6.
Each bearing member 6 is annular and has a section in the
shape of a U or in the shape of a hairpin. Each bearing
member 6 extends radially inwards or outwards, between a
rim 7 of the inner shell 3 or of the outer shell 4 of the
15 combustion chamber 1 and an inner casing 8 or an outer
casing 9 of the chamber 1.
More particularly, the downstream end of each shell
3, 4 of the combustion chamber 1 comprises a rim 7
comprising a radial portion 7a extended by a cylindrical
20 portion 7b extending downstream.
The distributor 2 is fastened downstream of the
chamber 1 by suitable means and comprises annular inner
11 and outer 12 shells that extend inside one another and
which are connected together by substantially radial
25 blades 13. The outer shell 12 of the distributor 2 is
axially aligned riith the downstream end portion of the
outer shell 4 of the chamber 1, and its inner shell 11 is
axially aligned riith the downstream end portion of the
inner shell 3 of the chamber 1. The upstream end of each
30 shell 11, 12 of the distributor 2 comprises a radial rim
14 of a dimension that is more reduced than the radial
portion 7a of the corresponding rim 7 of the combustion
chamber 1.
This distributor 2 is sectorised and forms several
contiguous sectors on a circumference centred on the axis
5 of revolution A of the chamber 1. The distributor sectors
are for example in the number of fourteen.
The inner rims 7, 14 of the inner shells 3, 11 of
the chamber 1 and of the distributor 2 delimit an inner
annular space 15 that opens at one end in the chamber 1
10 and which is closed at its other end by sealing means 16.
Likewise, the outer rims 7, 14 of the outer shells 4,
12 of the chamber 1 and of the distributor 2 delimit an
external annular space 15 that opens at one end in the
chamber 1 and which is closed at its other end by sealing
15 means 16.
The sealing means 16 located on annular spaces 15
shall be described in what follows.
As can be seen better in figures 2 to 4, these
sealing means 16 comprise sealing strips 17 extending
20 radially and circumferentially along each distributor
sector 2. Each strip 17 bears sealingly against a radial
face of the corresponding rim 14 of the distributor 2 and
on the free end of the axial portion 7b of the
corresponding rim 7 of the combustion chamber 1. The
25 strips 17 are maintained against the rims 7, 14 using
means of elastic return.
These elastic means are helical springs 18 of
tapered shape, mounted around screws 19 which are screwed
into the brackets 20 or flanges extending radially from
30 the corresponding shell 11, 12 of the distributor 2. The
shrunk portion of each spring 18 bears against a radial
face of the corresponding bracket 20, with the widened
portion bearing against the sealing strip 17. The ends of
the screws 19 are engaged into the holes of the sealing
strip 17, in such a way as to provide for its maintaining
in position.
5 As indicated hereinabove, the use of such sealing
means 19 increases the overall mass, reduces the lifespan
of the combustion chamber 1 and penalises the overall
performance of the turbine engine.
Furthermore, the bearing members 6 have a
10 substantial mass and can be the location for the
appearance of cracks or fissures caused by thermal and/or
mechanical stresses. Finally, functional clearances must
be defined with precision between the bearing members 6
and the inner and outer casings 8, 9 against which they
15 bear.
Figures 5 to 9 show a portion of a turbine engine
according to the invention. In these figures, the bearing
members 6 are not necessarily shown, in order to
facilitate the comprehension of the drawings.
2 0 As can be seen better in figures 8 and 9 in the
invention, the rims 7 of the inner 3 and outer 4 shells
of the combustion chamber 1 extend radially and are
devoid of axial portion. The free end of each rim 7 is
located radially opposite the free end of the
25 corresponding radial rim 14 of the distributor 2. A
sealing strip 17 extends axially and circumferentially,
on each distributor sector 2, between said radial rims 7,
14 and bears sealingly against the faces of the free ends
of said rims 7, 14.
30 The sealing strip 17 comprises notches 21 that open
onto its downstream edge, wherein are engaged the ends of
the screws 19 fastened onto the brackets 20 of the
distributor 2, in such a way as to immobilise the strip
17.
These screws 19 are also used to fasten a cover 22
extending circumferentially and axially, in such a way as
5 to cover, at least partially, the corresponding rims 7,
14 of the chamber 1 and of the distributor 2 as well as
the sealing strip 17.
The cover 22 has a generally U-shaped section
comprising a base 22a extending axially and two flanks
10 22b, 22c extending radially inwards from the base 22a,
respectively a first flank 22b extending radially
upstream of the rim 7 of the combustion chamber 1 and a
second flank 22c extending radially downstream of the rim
14 of the distributor 1.
15 The second flank 22c is fastened to the brackets 20
of the distributor 2 using screws 19 and nuts 23. The
first flank 22b is separated from the rim of the
downstream end of the combustion chamber 1 by a
determined clearance j (figure 8), for example less than
20 3 mm. Such a clearance makes it possible to offset any
dilatation effects and as well as prevent the cover 22
from being deformed by the bearing of the rim 7 of the
combustion chamber 1 on the first flank 22b.
Means of elastic return that stresses the sealing
25 strip 17 to bear against the free ends of the rims 7, 14.
These means of return comprise helical compression
springs 18 of which one end is bearing against the strip
17 and of which the other end is bearing against the base
22a of the cover 22. The springs 18 are mounted around
30 screws or lugs 24 fastened in the base 22a of the cover
22.
The free ends of the rims 7 and/or 14 comprise
grooves. The strip 17 can extend only axially (embodiment
of figure 9) or comprises hollow zones 25 that hug the
shapes of the free ends of the rims 7, 14 having grooves
5 (embodiment of figure 8).
The presence of the grooves makes it possible to
prevent any deterioration of the strips 17.
Note that, in the embodiment of figure 9, the strips
17 allow for a grand axial displacement of the combustion
10 chamber 1 in relation to the distributor 2, without
penalising the performance of the sealing means 16. The
presence of hollow zones 25 makes it possible to better
support a radial offset between the rims 7, 14 and
therefore a slight pivoting of the strip 17 around the
15 ends that have the grooves.
Note that, in the invention, the radial dimensions
of the rims 7 of the combustion chamber 1 are reduced and
that the bearing members 6 are not necessarily reduced,
which has for effect to reduce the overall mass and to
20 reduce the exchange surfaces with the by-pass air 26
(figure 1). The temperature of the downstream end of the
corresponding shell 3, 4 of the combustion chamber 1 is
as such increased, in such a way that the temperature
differences within this shell 3, 4 and the bending
25 stresses that stem from it are substantially reduced.
In addition, as the sealing strip 17 is oriented
axially, at least in its bearing zones on the
aforementioned rims 7, 14, it always provides a good seal,
even in the case of axial displacement of the combustion
30 chamber 1 in relation to the turbine distributor 2. The
output of the turbine engine is as such increased.
The cover 22 makes it possible to further reduce the
thermal exchanges between the downstream end of the
corresponding shell 3, 4 of the combustion chamber 1 and
the by-pass air 26. This cover 22 can be perforated on
5 its base 22a and on its second flank 22c, as can be seen
in figures 5 to 7. On the contrary, the first flank 22b
is more preferably continuous and devoid of an opening,
in such a way as to limit the cooling of the downstream
end of the corresponding shell 3, 4 of the combustion
10 chamber 1 by the by-pass airflow 26 directed from the
upstream downstream and directly affecting the first
flank 22b.
CLAIMS
1. Turbomachine, such as a turbojet or a turboprop engine,
comprising an annular combustion chamber (1) defined by
an inner shell (3) and an outer shell (4), a turbine
distributor (2) arranged downstream of the combustion
5 chamber (I), the downstream end of the outer shell (4)
and/or of the inner shell (3) of the chamber (1)
comprising a radial rim (7) arranged opposite a radial
rim (14) of the upstream end of the distributor (2), and
sealing means (16) comprising at least one strip (17)
10 extending between said rims (7, 14) in such a way as to
provide the seal between the combustion chamber (1) and
the distributor ( 2 ) , characterised in that the sealing
strip (17) extends axially and circumferentially between
said rims (7, 14) and bears radially sealingly against
15 the free ends of said rims (7, 14).
2. Turbomachine according to claim 1, characterised in
that the free end of the rim (7) of the combustion
chamber (1) is axially opposite the free end of the rim
20 (14) of the distributor (2).
3. Turbomachine according to claim 1 or 2, characterised
in that it comprises means of elastic return (18) that
tend to stress the sealing strip (17) bearing against the
25 free ends of the rims (7, 14).
4. Turbomachine according to one of claims 1 to 3,
characterised in that the distributor (2) comprises at
least one positioning lug (19) of which one end engages
30 in a notch (21) with a shape complementary to the strip
(17), in such a way as to immobilise the strip (17) in
its circumferential direction and in its axial direction.
5. Turbomachine according to one of claims 1 to 4,
5 characterised in that it comprises a cover (22) extending
circumferentially and axially, in such a way as to cover
at least partially the rims (7, 14) of the chamber (1)
and of the distributor (2) as well' as the sealing strip
(17) -
10
6. Turbomachine according to claim 5, characterised in
that the cover (22) is fastened using a screw (19) or a
rivet that forms the positioning lug of which the free
end engages in the corresponding notch (21) of the
15 sealing strip (17).
7. Turbomachine according to claim 5 or 6, characterised
in that the cover (22) has a generally U-shaped section
comprising a base (22a) extending axially and two flanks
20 (22b, 22c) extending radially inwards from the base (22a),
respectively a first flank (22b) extending radially
upstream of the rim (7) of the combustion chamber (1) and
a second flank (22c) extending radially downstream of the
rim (14) of the distributor (2).

8. Turbomachine according to claim 7, characterised in
that the second flank (22c) is fastened to a flange (20)
of the distributor (2), with the first flank (22b) being
separated from the rim (7) of the downstream end of the
combustion chamber (1) by a determined clearance (j), for
example less than 3 mm.

9. Turbomachine according to the claims 3 and 5,
characterised in that the means of elastic return
comprise at least one radially acting elastic member (18)
bearing on the one hand against the cover (22) and on the
other hand adainst the sealing strip in).
10. Turboma4hine according to one of claims 1 to 9,
characterised in that the turbine distributor (2) is
sectorised, jwith a strip (17) and/or a cover (22)
extending ciicumferentially along each turbine sector.