FIELD OF THE INVENTION
The present disclosure relates to an annular
5 combustion chamber, and more particularly to an annular
combustion chamber having a first annular wall and a
second annular wall that are coaxial about an axis, a
chamber end wall connecting together the first and second
walls, and a plurality of injectors, the first wall
10 including first air feed holes downstream from the
injectors. Such a combustion chamber may be a turbine
engine combustion chamber.
TECHNOLOGICAL BACKGROUND
15 Combustion chambers of this type are known, e.g.
from Document EP 0 569 300 that describes a guillotine
device serving to modify the axial position of a member
for shutting primary feed holes. Thus, the distance
between the air feed passages and the chamber end wall
20 can be controlled while the combustion chamber is in
operation, thus making it possible to provide a
combustion chamber that pollutes little.
Nevertheless, such a system is complex and does not
provide good control over the temperature field at the
25 outlet from the combustion chamber. However, that
temperature field is very important for ensuring that the
burnt gas leaving the combustion chamber does not damage
the turbine adjacent to said chamber. There therefore
exists a need for a novel type of combustion chamber.
30
SUMMARY OF THE INVENTION
This object is achieved by the fact that for at
least a first one of said injectors, at least three, and
preferably at least four, of the first holes sharing the
35 first injector as their closest injector are situated at
equal distances from the first injector.
5
2
Since the at least three or four first holes are
situated at equal distances from the injector that is
closest to them, i.e. the first injector, said first
holes are arranged on a circular arc centered on the
first injector. A circular arc 1s a curve that is
strictly convex in a radial view, and specifically it has
its concave side facing towards the first injector. In
other words, in a radial projection, the curve defines a
surface that is strictly convex, with the injector being
10 situated inside said surface. It should be recalled that
a convex surface is a surface such that for any two
points lying on the convex surface, the straight line
segment connecting those two points together lies
entirely inside said convex surface. Furthermore, a
15 surface is strictly convex if the curve defining it does
not contain any straight line portion.
Thus, unlike the usual approach, which consists in
determining the positions of the first holes relative to
the chamber end wall and in putting them into alignment,
20 the present disclosure proposes determining the positions
of the first holes relative to the injector that is
closest to said holes. This gives rise to better control
over the flow and over the temperature field in the
combustion chamber.
25 The first injector, and preferably all of the
30
injectors, may be placed in the end wall of the chamber
or in one of the annular walls, in particular in the
first wall.
The term "axis of the combustion chamber" is used to
designate its axis of symmetry (or quasi~symmetry). The
axial direction corresponds to the direction of the axis
of the combustion chamber, and a radial direction is a
direction perpendicular to the axis of the combustion
chamber and intersecting that axis. Likewise, an axial
35 plane is a plane containing the axis of the combustion
chamber, and a radial plane is a plane perpendicular to
that axis. A circumference should be understood as a
3
circle lying in a radial plane and having its center
lying on the axis of the combustion chamber. A
tangential or circumferential direction is a direction
tangential to a circumference; it is perpendicular to the
~ axis of the combustion chamber but it does not intersect
the axis.
In some embodiments, the first holes may be primary
holes, l.e. holes configured to introduce fresh air, e.g.
coming from the compressor, so as to use turbulence to
10 define a zone for anchoring the flame between the
injectors and said holes in order to ensure that the
flame is stable and to ensure good combustion. This zone
is referred to as the "primary'' zone.
In some embodiments, the first holes may be dilution
15 holes, i.e. holes configured to introduce fresh air, e.g.
coming from the compressor, into the core of the
combustion chamber, at a distance downstream from the
flame of the injector.
In some embodiments, all of the first holes sharing
20 the same closest injector are situated at equal distances
from that injector. Thus, throughout the combustion
chamber, the first holes are positioned as a function of
their distances from the closest injector, thereby making
it possible to control the recirculation zones and
25 consequently the temperature field in the combustion
chamber.
In some embodiments, the second wall includes second
air feed holes downstream from the injectors. The second
holes may be positioned in similar manner to the first
30 holes, or in a different manner.
In some embodiments, the second holes, preferably
all of the second holes, sharing the same closest
injector, are situated at equal distances from the
injector. Thus, the positioning of the second holes can
35 likewise be determined, not relative to the chamber end
wall, but relative to the injectors that are respectively
the closest thereto. Also, the positions of the second
4
holes may be determined independently of the positions of
the first holes.
In some embodiments, the first holes and the second
holes sharing the same closest injector are situated at
5 equal distances from that injector. This makes it
possible to have a temperature field that is radially
uniform.
In some embodiments, all of the first and/or second
holes are situated respectively at equal distances from
10 the injector that is closest to them. By means of these
provisions, the temperature field presents axial symmetry
about the axis of the combustion chamber. It is thus
more stable and easier to control.
In some embodiments, the first holes and/or the
15 second holes are arranged on circular arcs centered on
the respective closest injectors.
20
25
In some embodiments, the first wall is a radially
outer wall, and the second wall is a radially inner wall.
The converse is also possible.
The present disclosure also relates to a turbine
engine including an annular combustion chamber as
described above.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention and its advantages can be better
understood on reading the following detailed description
of embodiments of the invention given as nonlimiting
examples. The description refers to the accompanying
drawings, in which:
30 · Figure 1 shows a longitudinal section of a sector
35
of a combustion chamber;
· Figure 2 is a radial view of a portion of the
first wall in a first embodiment, seen in direction II of
Figure 1;
Figure 3 is a diagram showing a longitudinal
section of a sector of a combustion chamber; and
5
· Figure 4 is a radial view of a portion of the
first wall in a second embodiment, seen in direction IV
of Figure 3.
5 DETAILED DESCRIPTION OF THE INVENTION
Figure 1 shows a longitudinal section of a sector of
a combustion chamber 10 of an aviation turbine engine.
The combustion chamber 10 is annular, of longitudinal
axis X. It is defined by a first wall 12 that is
10 substantially annular around the axis X, in this example
a radially outer wall, by a second wall 13 that is
substantially annular around the axis X, in this example
a radially inner wall, and by a chamber end wall 14 that
connects together the end of the first wall 12 and the
15 facing end of the second wall 13 so as to close the
upstream end of the combustion chamber 10. In this
example, the chamber end wall 14 is annular.
The annular combustion chamber 10 also has a
plurality of fuel injectors 16 that inject fuel into the
20 combustion chamber 10. The injectors 16 are distributed
around the longitudinal axis X. In the present
embodiment, the injectors are arranged through the
chamber end wall 14. ~ach injector 16 defines an
injection direction I.
25 Air penetrates into the combustion chamber 10
through the chamber end wall 14 via first primary holes
18, optionally via first dilution holes 20, and via
cooling holes (not ~hown), all of these holes being in
the first wall 12, and also via second primary holes 19,
30 optionally via second dilution holes 21, and cooling
holes (not shown), all of these holes being in the second
wall 13. In other words, the first wall 12 has first
holes formed by the first primary holes 18 and optionally
by the first dilution holes 20. The second wall 13 has
35 second holes formed by the second primary holes 19, and
optionally by the second dilution holes 21.
6
In a first embodiment shown in Figure 2, for at
least one first injector 16, at least three, and
preferably at least four, of the first holes 18 that
share the first injector 16 as their closest injector are
5 situated along a curve C Lhal is strictly convex in a
radial view, the concave side of the curve C facing
towards the first injector 16. These first holes 18 may
be holes that are consecutive, being adjacent to one
another, in particular in a circumferential direction.
10 More precisely, the figure shows six first holes 18,
which in this example are first primary holes 18, that
are arranged along the strictly convex curve C. In this
example, the curve C is a circular arc, specifically
centered on the first injector 16 and typically on the
15 injection point A of said first injector 16. Thus, the
first holes 18 that share the same closest injector,
namely the first injector 16, are situated at equal
distances D from the injector.
By means of these provisions, the flame 24 is
20 stabilized by the recirculation zone 26 and is fed by the
fuel 22 in suspension.
As can be seen in Figures 1 and 2, relative to the
orientation ot the chamber end wall, the injection
direction I is coplanar with the axis X of the combustion
25 chamber.
Figures 3 and 4 are views that are analogous
respectively to the views of Figures 1 and 2, in a second
embodiment. In the§e figures, elements that correspond
to or are identical with elements of the first embodiment
30 are given the same reference signs, apart from the
hundreds digit, and they are not described again.
In the second embodiment, the injectors 116 are not
arranged in the chamber end wall 114. Specifically, the
injectors 116 are arranged in the first wall 112. The
35 injectors 116 are also downstream from the chamber end
wall 114. Furthermore, as can be seen in Figure 3,
relative to the orientation of the chamber end wall, the
7
injection direction I is not coplanar with the axis X of
the combustion chamber. Thus, the injection direction I
possesses a nonzero component in the circumferential
direction around the axis X. Furthermore, the injection
5 direction I possesses an axial component towards the
chamber end wall 114.
In a combustion chamber in the second embodiment,
the stream is represented by arrows. The air comes from
an outlet 130 of a compressor and enters into the
10 combustion chamber 110 via the injectors 116, via the
first primary holes 118, via the second primary holes
119, via the first dilution holes 120, and via the second
dilution holes 121. The combustion gas is discharged
towards the inlet 132 of a turbine.
15 In this embodiment, and as shown in Figure 4, for at
least one first injector 116, at least three, and
preferably at least four, of the first holes 118 that
share the first injector 116 as their closest injector
are situated along a curve C that is strictly convex in a
20 radial view, the concave side of the curve C facing
towards the first injector 116. More precisely, the
figure shows six first holes 118, which in this example
are firsl primary holes 118, four of which are arranged
along the strictly convex curve C. The three first holes
25 118 shown in the bottom right corner of Figure 4 are in
alignment, so all three of them cannot lie on a single
strictly convex curve.
By means of these provisions, the positioning of the
feeds (in this example the first holes 118) is optimized,
30 with the first holes being positioned in a manner that is
consistent with the physical phenomena occurring within
the combustion chamber 110. Thus, in spite of the offaxis
orientation of the injector 116, the flame 124 is
stabilized by the recirculation zone 126, and is fed with
35 the fuel 122 in suspension. Positioning primary holes
118 along a curve that is strictly convex with its
concave side facing towards the first injector 118, such
8
as the curve C in Figure 4, serves to stop the
recirculation zone 126 and provides better recirculation
of the burnt gas and makes the temperature field in the
combustion chamber 110 more uniform.
5 Although the embodiments described are described
concerning a single injector 16, 116 with the first holes
18, 118 in the first wall 12, 112, similar examples could
describe the distribution of second holes in the second
wall. As mentioned above, the second holes 19, 119
10 sharing a closest injector 16, 116 could all be situated
at equal distances from the injector. This distance may
be different from the distance D between the first holes
18, 118 and the injector 16, 116, or else the same, as
shown in Figure 1. Also, the distance between the first
15 and/or second holes and their respective closest
injectors may vary from one injector to another, or it
may be identical for all of the injectors. It can also
be understood that the distance between the first and/or
second holes and their respective closest injectors may
20 vary depending on the type of the hole, for example it
may be different for the first primary holes 18, 118 and
for the first dilution holes 20, 120 that nevertheless
share the same closest injector 16, 116.
Although the arrangement of the first holes 18 in
25 the first embodiment is described with reference to a
combustion chamber of the type shown in Figure 1, and the
arrangement of the first holes 118 in the second
embodiment is desci~bed with reference to a combustion
chamber of the type shown in Figure 3, the first
30 embodiment could be applied to a combustion chamber of
the type shown in Figure 3 having injectors situated in
one of the annular walls, and the second embodiment could
be applied to a combustion chamber of the type shown in
Figure 1 having injectors situated in the chamber end
35 wall.
Although the present invention is described with
reference to specific embodiments, modifications may be
5
9
made to those 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 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, 110) having a first
annular wall (12, 112) and a second annular wall (13,
113) that are coaxial about an axis (X), a chamber end
5 wall (14, 114) connecting together the first and second
walls (12, 13, 112, 113), and a plurality of injectors
(16, 116), the first wall (12, 112) including first air
feed holes (18, 118) downstream from the injectors (16,
116), the combustion chamber (10, 110) being
10 characterized in that for at least a first one of said
injectors (16, 116), at least three of the first holes
(18, 118) sharing the first injector as their closest
injector are situated at equal distances (D) from the
first injector (16, 116).
15
2. A combustion chamber (110) according to claim 1,
wherein the first injector (116) is placed in the first
wall (112).
20 3. A combustion chamber (10) according to claim 1 or
claim 2, wherein at least four of the first holes (18)
sharing the first injector as their closest injector are
situated at equal distances (D) from that injector (16).
25 4. A combustion chamber (10) according to any one of
claims 1 to 3, wherein all of the first holes (18)
sharing the same closest injector (16) are situated at
equal distances (D] from that injector.
30 5. A combustion chamber (10) according to any one of
claims 1 to 4, wherein the second wall (13) includes
second air feed holes (19) downstream from the injectors
(16), and wherein the second holes (19), preferably all
of the second holes (16), sharing the same closest
35 injector (16), are situated at equal distances (D) from
that injector.
5
10
15
20
11
6. A combustion chamber (10) according to claim 5,
wherein the first holes (18) and the second holes (19)
sharing the same closest injector (16) are situated at
equal distances (D) from that injector.
7. A combustion chamber (10) according to any one of
claims 1 to 6, wherein all of the first and/or second
holes (18, 19) are situated respectively at equal
distances from the injector (16) that is closest to them.
8. A combustion chamber (10) according to any one of
claims 1 to 7, wherein the first holes (18) and/or the
second holes (19) are arranged on circular arcs centered
on the respective closest injectors.
9. A combustion chamber (10) according to any one of
claims 1 to 8, wherein the first wall (12) is a radially
outer wall, and the second wall (14) is a radially inner
wall.
10. A turbine engine including a combustion chamber (10)
according to any one of claims 1 to 9.