FIELD OF THE INVENTION
The invention relates to the field of turbomachine
5 combustion chambers, and more particularly to the field
of annular combustion chambers for a turbomachine, and
particularly but not exclusively for a helicopter
turboshaft engine.
The term "turbomachine" is used to mean any gas
10 turbine apparatus that generates driving power, including
in particular turbojets that provide thrust needed for
propulsion in reaction to ejecting hot gas at high speed,
and turboshaft engines where the driving power is
delivered by rotating a drive shaft. For example,
15 turboshaft engines are used as engines in helicopters,
ships, trains, and indeed as industrial power plants.
Turboprops (a turboshaft engine driving a propeller) are
likewise turboshaft engines used as aeroengines.
20 STATE OF THE PRIOR ART
A conventional annular combustion chamber for a
turbomachine presents an axial direction, a radial
direction, and an azimuth direction, and it generally
comprises five annular walls, each annular wall
25 delimiting at least a portion of the volume of the
combustion chamber.
Those annular walls are conventionally assembled
together by welding or by bolting. Assembling them
together by welding makes it impossible to disassemble a
30 first wall from a second wall, e.g. for maintenance or
for the purpose of replacing one of the walls. Assembly
by bolting presents the drawback of encouraging cracks to
appear in the vicinity of the holes in which the bolts
are engaged because of the blocking that is generated,
35 thereby weakening the combustion chamber. In addition,
assembling in those ways is complex, lengthy, and
expensive.
SUMMARY OF THE INVENTION
An embodiment provides an annular combustion chamber
for a turbomachine, the combustion chamber presenting an
axial direction, a radial direction, and an azimuth
direction, and comprising a first annular wall and a
second annular wall, each wall delimiting at least a
portion of the volume of the annular combustion chamber,
the first and second walls presenting complementary
fitting elements, the first wall presenting at least one
first through hole, while the second wall presents at
least one second through hole, the combustion chamber
also having at least one pin engaged in a pair of holes
comprising a first hole and a second hole, said pin
locking the fitting of the first and second walls.
It can be understood that the first annular wall has
first fitting elements while the second annular wall has
second fitting elements, the first and second fitting
elements being respectively complementary to one another
so as to be able to co-operate by fitting in the axial
and/or azimuth direction of the combustion chamber. In
other words, the first and second fitting elements are
fitted or mutually engaged by moving them relative to
each other along the axial and/or azimuth direction of
the combustion chamber.
The combustion chamber may have two or more annular
walls. With more than two walls, the assembly of the
plurality of annular walls can be locked by the pin. For
example, a single pin can lock together the assembly of
at least three (or more) distinct walls. In another
example, a pin may lock together the assembly of two
walls, namely a first wall and a second wall, while
another pin locks together the assembly of the first or
the second wall with a third wall.
It can be understood that the first wall presents
one or more first holes, and that the second wall
presents one or more second holes. Naturally, in a
variant, there are as many first holes as there are
second holes, each first hole being paired with a second
hole (or vice versa). Below, and unless specified to the
contrary, the terms "first hole" and "second hole"
5 designate either the only first hole or all of the first
holes or the only second hole or all of the second holes.
The combustion chamber has one or more pins. Below,
and unless specified to the contrary, the term "pin" is
used to mean the only pin or all of the pins. By way of
10 example, the pin may be a rod or a clip configured to be
engaged simultaneously in a first hole and in a second
hole forming a pair of holes. The pin is engdged with or
without clearance in a pair comprising a first hole and a
second hole. Such a pin co-operates only by fitting in
15 or engaging with the pair of holes so as to couple
together the first and second walls relative to one or
more degrees of freedom, e.g. in axial translation and/or
in rotation about the axial direction of the combustion
chamber, while nevertheless not blocking all degrees of
20 freedom. Such a pin makes it possible to avoid, or to
reduce significantly, the risk of cracks appearing in
comparison with the conventional use of bolts. Thus,
such a pin enables the walls of the combustion chamber to
be assembled together without any need for welding and/or
25 for crimping together the two walls, as is done with
combustion chambers in the prior art.
Naturally, when the combustion chamber presents a
plurality of pairs of first and second holes, said
combustion chamber may present a plurality of pins, each
30 pin being engaged in a pair of holes. In a variant, when
a pin is provided in a pair of holes, that pair of holes
receives a single pin. In a variant, there are as many
pins as there are pairs of first and second holes. In a
variant, the pins are similar.
35 The pin blocks relative movements axially and/or in
azimuth between the first and second walls. Thus, when
the pins are engaged in the hole pair(s), the fitting
between the first and second walls is locked. In order
to separate the first and second walls from each other,
it is therefore necessary to begin by withdrawing the
pin(s) from the first and second hole pair(s) .
Thus, the combustion chamber can be assembled
easily, quickly, and at low cost compared with combustion
chambers of the prior art, and without requiring a
welding operation. Furthermore, such a combustion
chamber can just as easily be disassembled, thereby
facilitating maintenance operations.
In some embodiments, the first hole and the second
hole of the pair of holes are disposed substantially
facing each other.
It can also be understood that the term "facing" is
used to mean that the first hole is in alignment axially
and in azimuth with the second hole, presenting the same
angular position. In other words, the first and second
holes of the pair of holes are not diametrically
opposite. Such a facing configuration makes it possible
to use pins that are simple and enables assembly to be
easy and effective.
In some embodiments, the pin is formed by an
injector.
Naturally, the combustion chamber may present other
pins formed by other elements. In a variant, the
combustion chamber may present a plurality of pins, each
pin being formed by an injector.
Using an injector as a pin leads to a saving in
weight for the combustion chamber, where saving weight is
a major concern in turbomachines used in aviation. This
also simplifies the structure of the combustion chamber,
which can contribute to facilitating assembly and/or
disassembly. Furthermore, by using injectors as pins, it
is possible to fasten and position the combustion chamber
directly in this way within a turbomachine.
In some embodiments, the pin extends substantially
radially.
The term "substantially radial direction" is used to
mean a direction that is parallel to a radial plane and
that forms an angle lying in the range 60" to 120'
relative to the axis of the combustion chamber.
Such an orientation for the pinis) serves to
facilitate assembly of the combustion chamber and the
locking of the fitting is even more satisfactory.
In some embodiments, the complementary fitting
elements comprise a plurality of axial tongues extending
from one wall from among the first and second walls, and
a plurality of openings provided in the other wall from
among the first and second walls, said openings receiving
the tongues. Under such circumstances, the complementary
fitting elements form complementary elements for axial
fitting.
It can be understood that the first wall and/or the
second wall has/have one or more tongues. Thus, the
first wall may present tongues while the second wall does
not present any tongue, the first wall may present no
tongues while the second wall presents tongues, or indeed
the first wall may present a plurality of first tongues
while the second wall presents a plurality of second
tongues.
The other wall has openings arranged facing the
tongues, so as to be capable of receiving the tongues and
of co-operating with them by axial fitting. Thus, if
only the first wall presents tongues, then the second
wall presents openings, if only the second wall presents
tongues, then the first wall presents openings, whereas
if the first wall presents first tongues and the second
wall presents second tongues, then the first wall
presents first openings for receiving the second tongues
and the second wall presents second openings for
receiving the first tongues.
In a variant, the tongues and the openings are
regularly distributed (or spaced apart) in azimuth. It
can thus be understood that the angular spacing between
adjacent tongues and adjacent openings is equal. Such a
distribution makes it possible to obtain a degree of
symmetry of revolution for the complementary fitting
elements, thereby facilitating operations of fitting the
5 walls together, and thus of assembling the combustion
chamber.
In some embodiments, the hole of one of the walls
from among the first and second walls is provided in a
projecting blade.
10 It can be understood that the blade is a portion
projecting from the first wall if the hole is the first
hole, or that the blade is a portion projecting from the
second wall if the hole is a second hole. Such a
configuration makes it possible to reduce the weight of a
15 wall while reducing the overall size of the combustion
chamber in the vicinity of the blade. Furthermore, such
a configuration makes it possible to confine the location
of the hole to a particular position that is well
controlled within the combustion chamber, thereby
20 reducing any risk of leaks, such leaks being penalizing
from the point of view of the performance of the
combustion chamber.
In some embodiments, a projection arranged in the
vicinity of the other hole from among the first hole and
25 the second hole extends substantially parallel of the
axis of said other hole so as to co-operate with the
blade by snap-fitting.
For example, the vicinity of a hole includes an
annular portion of the wall that extends around the hole
30 over three times the diameter (or maximum dimension) of
the hole. For example, the projection is formed by a
projection machined directly on the wall, e.g. by diestamping,
or by a separate part fastened to the wall.
Snap-fitting (or clipping) is a technique for
35 assembling together two portions by mutual engagement and
elastic deformation (in general local deformation, e.g.
of the blade, or by deforming all of the parts involved
in the assembly). When the two portions are engaged in
the snap-fitting position, they have generally returned
to their initial shapes and no longer present any elastic
deformation (or they present less elastic deformation).
5 When the two portions are engaged with each other in the
snap-fitting position, they co-operate with each other so
as to oppose, or indeed block, relative movements between
said parts in the disengagement direction (the direction
opposite to the engagement direction). In the snap-
10 fitting position, the two portions can also co-operate in
such a manner as to oppose, or indeed block, relative
movements between them in the direction for extending the
engagement beyond the snap-fitting position.
Such snap-fitting enables the first and second walls
15 to be held in an fitted position prior to locking the
fitting by using the pin.
In some embodiments, the border of said other hole
forms a projection extending substantially parallel to
the axis of said other hole so as to co-operate with the
20 blade by snap-fitting.
In some embodiments, one of the walls from among the
first wall and the second wall presents an axial annular
shoulder co-operating in abutment with the other wall
from among the first wall and the second wall.
25 Such a shoulder makes it possible to form a join
plane between the first and second walls whereby leaks
from within the combustion chamber are minimized or
reduced to zero.
In some embodiments, the combustion chamber has only
30 two annular walls delimiting the volume of the combustion
chamber, namely the first annular wall and the second
annular wall.
The first and second walls thus suffice on their own
to define the volume of the combustion chamber. Such a
35 combustion chamber presents a particularly small number
of walls, thereby making it that much easier, faster, and
inexpensive to assemble. Furthermore, disassembly
operations for maintenance purposes are also made easier.
Furthermore, a combustion chamber presenting such a small
number of walls presents particularly low risks of leaks
in the vicinity of the joins between the various walls.
5 An embodiment provides a turbomachine including a
combustion chamber according to any of the embodiments
described in the present description.
BRIEF DESCRIPTION OF THE DRAWINGS
10 The invention and its advantages can be better
understood on reading the following detailed description
of various embodiments of the invention giver1 as nonlimiting
examples. The description refers to the
accompanying sheets of figures, in which:
15 Figure 1 shows a turbomachine having a combustion
chamber;
Figure 2 shows the annular walls of the Figure 1
combustion chamber seen in perspective;
Figure 3 is a detail view of the annular walls of
20 Figure 1; and
Figure 4 shows the annular walls of Figure 1 when
assembled together.
DETAILED DESCRIPTION OF EMBODIMENTS
2 5 Figure 1 shows a turbomachine 100 having an annular
combustion chamber 10, while Figures 2 to 4 show the two
annular walls 12 and 14 of the combustion chamber 10 in
greater detail. It should be observed that the
combustion chamber 10 is an annular chamber of the
30 reverse flow type, but that the invention is not limited
to this particular type of combustion chamber.
The combustion chamber 10 presents an axial
direction (along the axis X), a radial direction R, and
an azimuth direction Y. The combustion chamber 10
35 presents symmetry of revolution about the axis X. In
this example, the first wall 12 forms a flame tube
delimiting the volume in which the fuel ignites, i.e.
where combustion takes place. The second wall 14 forms
an outer bend and serves as a deflector for guiding the
flow of gas coming from the flame tube. This combustion
chamber example 10 has only two annular walls 12 and 14
5 for delimiting the volume 10a of the combustion chamber
10.
More particularly, each of the first wall 12 and the
second wall 14 presents a general shape that is
substantially half a torus, the torus being split
10 perpendicularly to its axis of revolution, like a donut
mold, the two half-toruses being placed facing each
other. Thus, each wall 12 and 14 has an outer portion
12a, 14a that. is substantially axial, an inner portion
12b, 14b that is substantially axial, and a bottom 12c,
15 14c that is substantially radial interconnecting the
outer and inner portions 12a and 12b of the first wall
12, or the outer and inner portions 14a and 14b of the
second wall 14. It should be recalled that in general,
and unless specified to the contrary, the adjectives
20 "inner" and "outer" are used with reference to a radial
direction such that an inner portion (i.e. a radially
inner portion) of an element is closer to the axis X than
is an outer portion (i.e. radially outer portion) of the
same element.
2 5 In this example, the radius of the outer portion 12a
of the first wall 12 is substantially equal to, but less
than, the radius of the outer portion 14a of the second
wall 14, while the radius of the inner portion 12b of the
first wall 12 is greater than the radius 14b of the
30 second wall 14. It is thus possible to assemble the
first wall 12 with the second wall 14 via their outer
walls 12a and 14a, the outer portion 12a of the first
wall 21 being arranged inside the outer portion 14a of
the second wall 14, while the difference in radius of the
35 inner portions 12b and 14b serves to create an exhaust
duct for the combustion gas.
The first wall 12 presents a plurality of axial
tongues 12d, while the second wall 14 presents a
plurality of openings 14d configured to receive the
tongues 12d of the first wall 12. The tongues 12d and
5 the openings 14d in this example form complementary axial
fitting elements of the first and second walls 12 and 14.
Naturally, in a variant that is not shown, tongues could
form complementary elements for fitting in azimuth, or
for fitting both axially and in azimuth.
10 The axial tongues 12d extend axially from the outer
portion 12a of the first wall 12. The openings 14d are
arranged in an annular shoulder 14e that extends radially
and that connects the outer portion 14a to the bottom 14c
of the second wall 14. In this example, there are as
15 many tongues 12d as there are openings 14d, each opening
14d receiving one tongue 12d.
When the first wall 12 is fitted axially with the
second wall 14, the tongues 12d are caused to penetrate
into the openings 14d, while the free axial end of the
20 outer portion 12a of the first wall co-operates with the
shoulder 14e by coming axially into abutment therewith.
The first wall 12 presents a plurality of first
through holes 12f, with the axes of these holes 12f
extending radially. These holes 12f are arranged in the
25 outer portion 12a of the wall 12. The second wall 14
presents second through holes 14f with axes that extend
radially. The holes 14f are arranged in blades 149 that
project axially from the outer portion 14a of the second
wall 14. In this example, the holes 12f and 14f are
30 substantially circular, however they could naturally
present some other shape. When the first and second
walls 12 and 14 are fitted, the holes 12f and 14f face
one another. In this example, there are as many first
holes 12f as there are second holes 14f.
3 5 A sleeve 16 configured to receive an injector 18 is
fastened in each first hole 12f, e.g. by welding or
crimping. The sleeve 16 forms a border that projects
outwardly along the axis of each first hole 12f. The
maximum radius of the sleeve 16 is less than the radius
of the second hole 14f. Thus, during fitting of the
first and second walls 12 and 14, each blade 149 cooperates
by snap-fitting with a sleeve 16.
In order to block the blades 149 snap-fitting with
the sleeves 16, after the first and second walls 12 and
14 have been fitted, a rim 20 is installed on the outside
of the outer portion 12a of the first wall 12. By way of
example, the rim 20 is welded on. Such a rim 20 provides
intermediate blocking of the fitting of the walls 12 and
14 prior to installation of the injectors 18 that are
described below and that form pins for locking the
fitting. One or more rims may be provided. In this
example, there are as many rims 20 as there are blades
149. Naturally, these rims 20 are optional and they may
thus be omitted in some combustion chamber variants.
When the first and second walls 12 and 14 are
axially fitted, the first holes 12f face the second holes
14f. An injector 18 is then inserted into each facing
pair of first and second holes 12f and 14f, the injector
forming a pin that locks the fitting of the first and
second walls 12 and 14. The injectors 18 extend radially
through each pair of holes 12f and 14f. The injectors 18
are engaged with clearance in each pair of holes so as to
allow relative movements between each of the elements due
to differential thermal expansion, but nevertheless they
couple together the first and second walls 12 and 14 in
translation along the axial direction X and in rotation
in the azimuth direction Y. Naturally, the sleeve 16
also contributes to coupling together the first and
second walls 12 and 14, but this coupling is relatively
fragile, in particular because of thermal expansion
differences that, under some circumstances, can cause the
blades 149 to cease co-operating effectively with the
sleeve 16, and in spite of the rims 20. Thus, the
essential part of the locking of the fitting between the
first and second walls 12 and 14 is provided by the pins
formed by the injectors 18.
Although the present invention is described with
reference to specific embodiments, it is clear that
5 modifications and changes may be made to these
embodiments without going beyond the general ambit of the
invention as defined by the claims. In particular,
individual characteristics of the various embodiments
shown and/or mentioned may be combined in additional
10 embodiments. Consequently, the description and the
drawings should be considered in a sense that is
illustrative rather than restrictive.

CLAIMS
1. An annular combustion chamber (10) for a turbomachine
(100) presenting an axial direction (X), a radial
direction (R), and an azimuth direction (Y), and
5 comprising a first annular wall (12) and a second annular
wall (14), each wall delimiting at least a portion of the
volume (10a) of the annular combustion chamber (10) , the
first and second walls (12, 14) presenting complementary
fitting elements (12d, 14d), the first wall (12)
10 presenting at least one first through hole (12f), while
the second wall (14) presents at least one second through
hole (14f) , the combustion chamber (10) also having at
least one pin (18) engaged in a pair of holes comprising
a first hole (12f) and a second hole (14f), said pin (18)
15 locking the fitting of the first and second walls (12,
14), said pin being formed by an injector (18).
2. A combustion chamber (10) according to claim 1,
wherein the first hole (12f) and the second hole (14f) of
20 the pair of holes are disposed substantially facing each
other.
3. A combustion chamber (10) according to claim 1 or
claim 2, wherein the pin (18) extends substantially
25 radially.
4. A combustion chamber (10) according to any one of
claims 1 to 3, wherein the complementary fitting elements
comprise a plurality of axial tongues (12d) extending
30 from one wall from among the first wall (12) and the
second wall (14), and a plurality of openings (14d)
provided in the other wall from among the first wall (12)
and the second wall (14), said openings (14d) receiving
the tongues (12d).
35
5. A combustion chamber (10) according to any one of
claims 1 to 4, wherein one of the holes from among the
first hole (12f) and the second hole (14f) is provided in
a projecting blade (149) .
6. A combustion chamber (10) according to claim 5,
5 wherein a projection (16) arranged in the vicinity of the
other hole from among the first hole (12f) and the second
hole (14f) extends substantially parallel of the axis of
said other hole so as to co-operate with the blade (149)
by snap-fitting.
10
7. A combustion chamber (10) according to any one of
claims 1 to 6, wherein one of the walls from among the
first wall (12) and the second wall (14) presents an
annular shoulder (14e) that co-operates axially in
15 abutment with the other wall from among the first wall
(12) and the second wall (14).
8. A combustion chamber (10) according to any one of
claims 1 to 7, having only two annular walls, delimiting
20 the volume (10a) of the combustion chamber (lo), namely
the first annular wall (12) and the second annular wall
(14).
9. A turbomachine (100) including a combustion chamber
25 (10) according to any one of claims 1 to 8.