AN ANNULAR COMBUSTION CHAMBER IN A TURBINE ENGINE
The present invention relates to an annulas
combustion chamber of a turbine engine such as an
airplane turbojet or turboprop.
5 In known manner, an annular combustion chamber of a
turbine engine receives a stream of air from an upstream
high pressure compressor and it delivers a stream of hot
gas downstream for driving rotors of high pressure and
low pressure turbines.
10 An annular combustion chamber comprises two coaxial
walls forming surfaces of revolution that extend one
inside the other and that are connected together and
their upstream ends by an annular chamber end wall that
includes openings for mounting fuel injection systems.
15 Each injection system has means for supporting the
head of a fuel injector and at least one swirler, which
is arranged downstream from the injector head, coaxially
about its axis, and which delivers a stream of air that
is rotating in order to form a mixture of air and fuel
20 that is to be burnt in the combustion chamber.
The swirlers of the injection systems are fed with
air coming from an annular diffuser mounted at the outlet
from the high pressure compressor that is arranged
upstream from the combustion chamber.
25 Each swirler opens out downstream into the inside of
a mixer bowl having a substantially Erustoconical
. . ~ - . . ~ . ... - ~ ~ . . . . . . . . . . .
downstream wall that flares downstream and that is formed
with an annular row of air injection orifices that are
regularly distributed around the axis of the bowl.
30 At least one ignition spark plug is mounted in an
orifice in the outer annular wall of the combustion
chamber, downstream from the fuel injection systems.
In operation, the air leaving the high pressure
compressor flows inside each injection system. The
35 air/fuel mixture is ejected from each injection system
and forms a substantially frustoconical rotating sheet of
air and fuel that flares downstream. The flare angle of
the sheet is a function of the flare angle of the
frustoconical wall of the mixer bowl, and of the
dimensions of the air injection orifices formed in said
frustoconical wall. Thus, the larger the diameter of the
5 orifices in the mixer bowl, the greater the flow rate of
air passing each through each of these orifices and the
smaller the extent to which the air/fuel mixture sheet
flares. Likewise, the further upstream the holes are
positioned along the frustoconical wall, the greater the
10 aerodynamic blocking and the less the extent to which the
air/fuel mixture sheet flares.
In the prior art, the injection systems of the
combustion chamber produce air/fuel mixture sheets that
all rotate in the same direction. The direction of
15 rotation may equally well be clockwise or
counterclockwise when looking at the injection systems
from downstream.
In order to improve ignition of the air/fuel mixture
sheets, it is known to arrange a spark plug on the axis
20 of an injection system.
In its application FR 2 943 199, the Applicant
proposes increasing the flare angle of the fuel sheet
produced by the injection system situated closest to the
spark plug. That type of configuration is found to be
25 effective, but it can lead to the inside end of the spark
plug being wetted by droplets of fuel, and that is not
~ ~
desirable in order to conserve optimum operation of the
spark plug.
An object of the invention is to improve the
30 ignition of the fuel mixture sheets compared with
combustion chambers of the prior art while avoiding the
drawbacks of the prior art.
To this end, the invention proposes an annular
combustion chamber of a turbine engine, the chamber
35 having inner and outer coaxial walls forming two surfaces
of revolution connected together at their upstream ends
by an annular chamber end wall including openings for
mounting injection systems, each comprising an injector
and at least one swirler for producing a rotating air
stream that mixes downstream with fuel coming from the
injector, and at least one ignition spark plug mounted in
5 an orifice in the outer wall downstream from the
injection systems, the chamber being characterized in
that the spark plug is situated circumferentially between
two adjacent injection systems that are configured so as
to produce two air/fuel mixture sheets rotating in
10 opposite directions.
Unlike the prior art, the spark plug is mounted
between two injectors and the injection systems on either
side of the spark plug are configured to produce sheets
of fuel that are contrarotating. This ensures good
15 interpenetration of the fuel sheets on the axis of the
spark plug, thereby increasing the time spent by the
droplets of fuel in the vicinity of the inside end of the
spark plug compared with the prior art. The
effectiveness with which the combustion chamber is
20 ignited or re-ignited is thus improved.
Advantageously, as seen from downstream, a first of
the two injection systems that is situated
circumferentially to the left of the spark plug produces
an air/fuel mixture sheet rotating clockwise and a second
25 of the two injection systems situated circumferentially
to the right of the spark plug produces an air/fuel
mixture sheet rotating counterclockwise.
With such a configuration, a fuel droplet
recirculation zone is observed to form in the vicinity of
30 the inside end of the spark plug, and the droplets of
fuel within this recirculation zone are smaller, thereby
further improving ignition or re-ignition of the
combustion chamber.
This configuration is more advantageous than the
35 configuration in which, seen from downstream, a first of
the two injection systems situated circumferentially to
the left of the spark plug produces an air/fuel mixture
sheet rotating counterclockwise and a second of the two
injection systems situated circumferentially to the right
of the spark plug produces an air/fuel mixture sheet
rotating clockwise, since the recirculation zone would
5 then tend to be created beside the annular wall defining
the inside of the combustion chamber.
In an embodiment of the invention, each of the two
above-specified adjacent injection systems comprises a
bowl having a substantially frustoconical wall downstream
10 from the swirler and formed with an annular row of air
injection orifices fqr producing a substantially
frustoconical and rotating sheet of air/fuel mixture,
these orifices being distributed and dimensioned in such
a manner that the resulting air/fuel mixture sheet
15 presents a local enlargement crossing the axis of the
spark plug.
With such a configuration, the same flare angle is
conserved for both bowls situated on either side of the
spark plug, and modifications to the orifices in the
20 bowls make it possible to form a local enlargement of
their fuel sheets crossing the axis of the spark plug.
These enlargements of the fuel sheets enable the
fuel sheets to be projected locally as close as possible
to the inside end of the spark plug, thereby further
25 increasing the time spent by the droplets in the vicinity
of the inside end of the spark plug . .. and improving
ignition of the air/fuel mixture.
According to another characteristic of the
invention, the bowl of at least one of the two injection
30 has orifices of diameter smaller than the diameter of the
other orifices of said bowl, these smaller-diameter
orifices being formed over an angular sector of size and
angular position that are predetermined so as to form the
enlargement crossing the axis of the spark plug.
3 5 Reducing the diameter of the orifices over a given
sector of the bowl makes it possible to reduce the flow
rate of air passing through these orifices. The air
leaving via these orifices has less impact on the
airlfuel mixture coming from the upstream swirler,
thereby leading to a local increase in the flare angle of
the air/fuel mixture and forming a local enlargement of
the sheet of fuel.
According to another characteristic of the
invention, the orifices of the above-mentioned angular
sector of each above-mentioned bowl present a diameter
that is at least 40% smaller than the diameter of the
other orifices in the bowl.
In another embodiment of the invention, the bowl of
at least one of the two injection systems has no orifices
over an angular sector of dimension and position that are
predetermined in such a manner as to form the enlargement
crossing the axis of the spark plug.
Eliminating orifices in the frustoconical wall of
the bowl over a sector makes it possible to increase
locally the ejection angle of the air/fuel mixture sheet,
and to form a local enlargement of said sheet that
crosses the axis of the spark plug.
The angular sectors of the two injection systems are
preferably symmetrical to each other about a radial plane
containing the axis of the spark plug.
In a practical embodiment of the invention, the or
each above-mentioned angular sector extends over an angle
of about 20' to 50".
The spark plug is advantageously positioned at
substantially equal circumferential distances from the
two adjacent injection systems.
The invention also proposes a turbine engine, such
as an airplane turbojet or turboprop that includes a
combustion chamber as described above.
Other advantages and characteristics of the
invention appear on reading the following description
made by way of non-limiting example and with reference to
the accompanying drawings, in which:
Figure 1 is a fragmentary diagrammatic half-view
in axial section of an annular combustion chamber of
known type;
Figure 2 is a fragmentary diagrammatic view on a
5 larger scale of the zone in the dashed-line box of
Figure 1;
Figure 3 is a diagrammatic view in cross-section
of the primary swirler of the Figure 2 injection system;
Figure 4 is a diagrammatic view from downstream
10 and in cross-section showing injection systems producing
contrarotating sheets of air/fuel mixture, which systems
are situated on either side of a spark plug in a
combustion chamber of the invention;
Figure 5 is a diagrammatic view in cross-section
15 of the primary swirler of the Figure 4 injection system
situated circumferentially immediately to the left of the
spark plug;
Figure 6 is a diagrammatic view in cross-section
of a variant embodiment of the invention showing two
20 injection systems situated on either side of the spark
plug;
Figure 7 is a diagrammatic view on a cross-section
plane containing the axis of the spark plug and showing
the sheets of fuel from the injection systems of
25 Figure 6; and
Figure 8 is a diagrammatic view in cross-section
of another variant embodiment of the invention showing
injection systems situated on either side of the spark
plug.
30 Reference is made initially to Figure 1, which shows
an annular combustion chamber 10 of a turbine engine such
as an airplane turboprop or turbojet, the combustion
chamber being arranged at the outlet from a centrifugal
diffuser 12 mounted at the outlet from a high pressure
35 compressor (not shown). The combustion chamber 10 is -
followed by a high pressure turbine 14 with only its
inlet nozzle 16 being shown.
The combustion chamber 10 comprises c o a x i a l i n n e r
and outer walls 18 and 20 c o n s t i t u t i n g two frustoconical
surfaces of revolution arranged one inside the other and
of section t h a t tapers going downstream. Such a
5 combustion chamber is s a i d t o be convergent. The inner
and outer annular walls 18 and 20 are connected a t t h e i r
upstream ends t o an annular chamber end wall 22 and they
are secured downstream via inner and outer annular
flanges 24 and 26. The outer annular flange 26 bears
10 r a d i a l l y outwardly against an outer casing 28 and bears
a x i a l l y a g a i n s t a r a d i a l flange 30 f o r fastening the
nozzle 16 of the high pressure turbine t o the outer
casing 28. The inner annular flange 24 of the combustion
chamber bears r a d i a l l y and a x i a l l y against an inner
15 annular p a r t 32 f o r fastening the nozzle 16 t o an inner
annular wall 34.
The chamber end wall 22 has openings for mounting
i n j e c t i o n systems f o r i n j e c t i n g an a i r - f u e l mixture i n t o
the chamber, the a i r coming from the c e n t r i f u g a l d i f f u s e r
20 12 and t h e f u e l being delivered by i n j e c t o r s 36.
The i n j e c t o r s 36 have t h e i r r a d i a l l y outer ends
fastened t o the outer casing 28 and they are r e g u l a r l y
d i s t r i b u t e d along a circumference around t h e a x i s of
revolution 38 of the chamber. Each i n j e c t o r 36 has an
25 i n j e c t i o n head 40 a t its r a d i a l l y inner end f o r i n j e c t i n g
f u e l , which head is i n alignment with a correspondingopening
i n the chamber end wall 22.
The mixture of a i r and f u e l t h a t is i n j e c t e d i n t o
the chamber 10 is ignited by means of a t l e a s t one
30 i g n i t i o n spark plug 42 t h a t extends r a d i a l l y t o the
outside of the chamber 1 0 . The r a d i a l l y outer end of the
spark plug is held t o the outer casing 28 by s u i t a b l e
means, it is connected t o e l e c t r i c a l power supply means
(not shown) s i t u a t e d outside the casing 28, and i t s inner
35 end is engaged i n an o r i f i c e i n the outer wall 20 of the
chamber.
As can be seen in Figure 2, each injection system
includes an upstream primary swirler 44 and a downstream
secondary swirler 46, which swirlers are on the same axis
and are connected upstream to means for centering and
5 guiding the head of the injector, and downstream to a
mixer bowl 48 that is mounted axially in the opening in
the chamber end wall 22.
The swirlers 44 and 46 are spaced apart from each
other by a radial wall 50 having its radially inner end
10 connected to a Venturi 52 that extends axially downstream
inside the downstream swirler and that separates the
flows of air coming from the upstream and downstream
swirlers 44 and 46. A first annular air flow stream is
formed inside the Venturi 52 and a second annular air
15 flow stream is formed outside the Venturi 52.
The mixer bowl 48 has a substantially frustoconical
wall 54 that flares downstream and that is connected at
its downstream end to a cylindrical rim 56 extending
upstream and mounted axially in the opening in the
20 chamber end wall 22. The upstream end of the
frustoconical wall of the bowl is fastened by an
intermediate annular part 58 to the downstream secondary
swirler 46.
The frustoconical wall 54 of the bowl has an annular
25 row of air injection orifices 60 that are regularly
distributed around the axis 62 of the bowl 48. The air
passing through these orifices and the air flowing in the
streams inside and outside the Venturi 54 become mixed
with the fuel that is sprayed by the injector so as to
30 form a rotating sheet 64 of an air and fuel mixture
having a substantially frustoconical shape that flares
downstream. The axes 66 of each of the air injection
orifices 60 of the bowl 48 slope relative to the axis 62
of the bowl and converge towards said axis going
35 downstream. A second annular row of orifices 68 is
formed at the downstream end of the cylindrical rim 56.
In operation, the upstream and downstream swirlers
44 and 46 of the injection system cause the stream of air
and sprayed fuel to rotate, and the air injection
orifices 60 in the frustoconical wall 54 of the bowl 48
5 apply shear to the air/fuel mixture. Thus, the greater
the diameter of the air injection orifices 60 of the bowl
48, the greater the flow of air passing through these
orifices, thereby diminishing the flare angle 64 of the
frustoconical sheet of the air/fuel mixture.
10 Figure 3 is a diagrammatic view of the primary
swirler 44 shown in cross-section asseen from
downstream, the section being on a line 111-111 of the
injection system shown in Figure 2.
The primary swirler 44 has a plurality of vanes 70
15 regularly distributed around the axis 62 of the swirler
44. These vanes 70 extend radially and
circumferentially, and between them they define airpassing
channels 72 opening out into the inside of the
swirler 44. The inner openings of the channels 72 are
20 all oriented in directions 74 that are inclined relative
to the axis 62 of the swirler 44 so as to produce a
stream of air that is rotating in a counterclockwise
direction (arrow A).
With such a primary swirler 44, the mixture of air
25 and fuel leaving the injection system forms a sheet of a
mixture of air and fuel that rotates counterclockwise.
The secondary swirler 46 also has a plurality of
vanes regularly distributed around the axis of the
swirler. These vanes extend radially and
30 circumferentially and between them they define air
passage channels. In a manner similar to the primary
swirler, the inner openings of the channels in the
secondary swirler are all oriented in directions that are
inclined relative to the axis of the secondary swirler so
35 as to produce a stream of air rotating in the
counterclockwise direction.
In a variant of the invention, the inner openings of
the channels in the secondary swirler 46 may be oriented
in directions that are inclined relative to the axis of
the secondary swirler so as to produce a stream of air
5 rotating in the clockwise direction, i.e. a stream of air
that is rotating in the opposite direction to the stream
of air from the primary swirler.
The secondary swirler serves to accelerate expansion
of the air/fuel mixture leaving the injection system. It
10 also serves to generate shear with the slowed-down outlet
flow from the Venturi, thereby contributing to improving
the spraying of the air/fuel mixture.
The injection system may thus have primary and
secondary swirlers that are co-rotating, i.e. both of
15 them lead to forming a respective stream of air rotating
in the same direction, or else it has primary and
secondary swirlers producing streams of air that are
rotating in opposite directions. Under such
circumstances, the direction of rotation of the air/fuel
20 mixture leaving the injection system is driven mainly by
the pitch angles of the outlets of the channels of the
primary and secondary swirlers and also by the flow rates
passing through the primary and secondary swirlers.
In the combustion chamber shown in Figure 1, all of
25 the injection systems are configured in the same way and
they produce sheets of~~air/fuemli xture that all rotate
in the same counterclockwise direction.
The invention serves to improve ignition or reignition
of the combustion chamber by mounting the
30 ignition spark plug 42 circumferentially between two
adjacent injection systems S1, S, that produce respective
air/fuel mixture sheets N,, N, rotating in opposite
directions (arrows B and C in Figure 4).
The injection system S, arranged circumferentially
35 immediately to the left of the spark plug when seen from
downstream has a primary swirler similar to that
described with reference to Figure 3. This swirler 76
differs in that the vanes 78 define between them channels
80 that have their inner openings all oriented in
directions that are inclined relative to the axis 82 of
the swirler 76 in such a manner as to produce a stream of
5 air rotating in the clockwise direction (Figure 5).
The injection system S, arranged circumferentially
immediately to the right of the spark plug has a primary
swirler 44 that is identical to that described with
reference to Figure 3.
10 The other injection systems S3, i.e. those that are
not situated circumferentially immediately beside the
spark plug 42, all produce air fuel mixture sheets N, that
are rotating in the same direction. This direction of
rotation may either be clockwise or counterclockwise
15 (Figure 4).
Mounting the spark plug 42 between two adjacent
injection systems S,, S, that produce contrarotating
air/fuel mixture sheets N,, N, makes it possible to form a
recirculation zone 84 of fuel droplets very close to the
20 inside end of the spark plug 42. The flow directions of
the droplets within the recirculation zone 84 are very
varied, thus contributing to increasing the length of
time the droplets of fuel spend in the vicinity of the
spark plug and improving ignition of the combustion
25 chamber. Furthermore, the droplets of fuel in the
recirculation zone 84 are fine-r, thus further
facilitating the formation of a combustion flame.
Figure 7 is a diagrammatic view from downstream of
two adjacent injection systems S4, 5, circumferentially on
30 either side of the spark plug 42, and Figure 8 shows the
air/fuel mixture sheets N, and N, produced by the
respective injection systems S, and S,.
The injection system S, situated circumferentially to
the left of the spark plug 42 has a primary swirler 76
35 matching that described with reference to Figure 5 so as
to produce an air/fuel mixture sheet N, rotating clockwise
(arrow D in Figure 7). This injection system S, has a
mixer bowl 86 with a plurality of air injection orifices
88 regularly distributed around the axis of the bowl 90.
The bowl 86 has an angular sector 92 in which the
orifices 94 are of diameter smaller than the diameter of
5 the other orifices 88 of the bowl 86 (Figure 6).
When the air/fuel mixture penetrates into the inside
of the bowls 86, the flow rate of air passing through the
orifices 94 of the angular sector 92 is smaller than the
flow rate of air passing through the other orifices 88 of
10 the bowl 86. As a result, the particles of air and of
fuel passing in the vicinity of this sector 92 leave the
bowl 86 with a trajectory that is more flared than that
of the particles passing in the vicinity of the other
orifices 88 of the bowl 86. This leads to a local
15 enlargement 96 of the sheet of sprayed fuel (Figure 7).
Because of the frustoconical and rotating shape of
the air/fuel mixture sheet, each particle of air and of
fuel follows a path that is substantially in the form of
a frustoconical helix. The local enlargement thus takes
20 on a shape corresponding to those frustoconical helical
paths.
In order to ensure that the enlargement 96 crosses
the axis 98 of the spark plug 42 and comes as close as
possible to the inside end of the spark plug 42, the
25 sector 92 of the bowl 86 needs to be angularly offset by
an angle IY. in the direction opposite to the direction of
rotation of the air/fuel mixture, i.e. counterclockwise,
relative to a plane 100 containing the axis of the bowl
90 and passing through the angular position around the
30 axis 90 of the bowl at which it is desired for the
enlargement to cross the axis 98 of the spark plug 42.
In Figure 6, the plane 100 is represented by a line and
it is perpendicular to the plane of the sheet.
The injection system S, situated circumferentially to
35 the right of the spark plug has a primary swirler
matching that described with reference to Figure 3 so as
to produce an air/fuel mixture sheet rotating
counterclockwise (arrow E in Figure 7). This injection
system S, has a mixer bowl 102 with a plurality of
orifices 88 that are regularly distributed around the
axis of the bowl and that are identical to the orifices
5 of the bowl 86 of the injection system S,. The bowl 102
has an angular sector 104 in which the orifices 96 are of
a diameter smaller than the diameter of the other
orifices in the bowl 88, thus making it possible to form
a local enlargement 105 of the fuel sheet N, (Figure 7).
10 The angular sector 104 of the bowl 102 is angularly
offset by an angle P in the direction opposite to the
direction of rotation of the air/fuel mixture, i.e. in
the clockwise direction, relative to a plane 106
containing the axis 108 of the bowl 102 and passing
15 through the angular position about the axis 108 of the
bowl 102 where it is desired that the enlargement crosses
the axis 98 of the spark plug 42. The angles u and P are
measured from the middles of each of the sectors 92, 104
of the bowls 86, 102 having the orifices of smaller
20 diameter.
The angular extents of the sectors 92, 104 of the
bowls 86, 102 of the injection systems S, and S, determine
the angular extent of each of the enlargements 96, 105 of
the air/fuel mixture sheets N,, N, around the respective
25 axes 90, 108 of the bowls 86, 102.
With such a configuration, the local deformations
96, 105 of the air/fuel mixture sheets N,, N, as produced
by the injection systems S, and S, situated on either side
of the spark plug enable droplets of fuel to be projected
30 as close as possible to the inside end of the spark plug
42, thereby increasing the time spent by the particles in
the vicinity of the inside end of the spark plug 42 and
facilitating ignition of the combustion chamber.
In the embodiment shown in Figure 6, the angular
35 sectors 92, 104 of the trio injection systems S, and S, are
symmetrical relative to each other about a radial plane
containing the axis of the spark plug. Under such
circumstances, the angles a and P are identical.
In another embodiment of the invention, as shown in
Figure 8, the sectors of the bowls that have orifices of
5 reduced diameter are replaced by sectors 110, 112 that
have no air injection orifices. These bowls 114, 116
serve to obtain fuel sheets having substantially the same
shapes as those obtained using the bowls 86, 102 having
respective sectors 92, 104 with orifices 94, 96 of
10 smaller diameter. Only the widths of the enlargements of
the fuel sheets in the radial direction are larger
because there is no flow of air passing through the
sectors 110, 112 of the bowls 114, 116.
It is possible to combine an injection system having
15 a bowl with a sector having orifices of smaller diameter
and an injection system having a bowl with a sector
having no orifices.
In a practical embodiment of the invention, the
sectors 91, 104 of the bowls 86, 102 with orifices 94, 96
20 of smaller diameter, and,the sectors 110, 112 of the
bowls 114, 116 having no orifices, all extend angularly
over about 50°, and the angles a and P are of the order
of 80". The angles a and P may lie in the range 0" to
180".
25 In practice, the positioning and the angular extents
of the two angular sectors 92, 104 having orifices of
smaller diameter or of the two sectors 110, 112 having no
orifices are determined by three-dimensional simulation.
Such simulation takes account of numerous parameters such
30 as the shape and the angle of inclination of the vanes of
the swirlers, the flow rate of air from the high pressure
compressor, the flov~ rate of fuel from the injectors,
etc.
In the various embodiments of the invention, the
35 spark plug 42 may be positioned at substantially equal
circumferential distances from the two adjacent injection
systems .
CLAIMS
1. An annular combustion chamber (10) of a turbine
engine, the chamber having inner and outer coaxial walls
(18, 20) forming two surfaces of revolution connected
5 together at their upstream ends by an annular chamber end
wall (22) including openings for mounting injection
systems, each comprising an injector (36) and at least
one swirler (76, 44) for producing a rotating air stream
that mixes downstream with fuel coming from the injector
10 (36), and at least one ignition spark plug (42) mounted
in an orifice in the outer wall (20) downstream from the
injection systems, the chamber being characterized in
that the spark plug (42) is situated circumferentially
between two adjacent injection systems (S,, S,) that are
15 configured so as to produce two air/fuel mixture sheets
(B, C) rotating in opposite directions.
2. A chamber according to claim 1, characterized in that,
as seen from downstream, a first (S,) of the two injection
20 systems that is situated circumferentially to the left of
the spark plug (42) produces an air/fuel mixture sheet
(N,) rotating clockwise and a second (S,) of the two
injection systems situated circumferentially to the right
of the spark plug (42) produces an air/fuel mixture sheet
25 (N,) rotating counterclockvrise.
3. A chamber according to claim 2, characterized in that
each of the two adjacent injection systems (S,, S,)
comprises a bowl (86, 102) having a substantially
30 frustoconical wall downstream from the swirler and formed
with an annular row of air injection orifices (88) for
producing a substantially frustoconical and rotating
sheet of air/fuel mixture, these orifices (88, 94) being
distributed and dimensioned in such a manner that the
35 resulting air/fuel mixture sheet presents a local
enlargement crossing the axis of the spark plug.
4. A chamber according to claim 3, characterized in that
the bowl of at least one of the two injection (S,, S5) has
orifices (94) of diameter smaller than the diameter of
the other orifices (88) of said bowl (861, these smaller-
5 diameter orifices (94) being formed over an angular
sector (92, 104) of size and angular position that are
predetermined so as to form the enlargement crossing the
axis of the spark plug (42) .
10 5. A chamber according to claim 4, characterized in that
the orifices (94) of the above-mentioned angular sector
(92, 104) of each bowl (86, 102) present a diameter that
is at least 40% smaller than the diameter of the other
orifices in the bowl.
15
6. A chamber according to any one of claims 3 to 5,
characterized in that the bowl (114, 116) of at least one
of the two injection systems has no orifices over an
angular sector (110, 112) of dimension and position that
20 are predetermined in such a manner as to form the
enlargement crossing the axis of the spark plug (42).
7. A chamber according to any one of claims 4 to 6,
characterized in that the angular sectors (92, 104, 110,
25 112) of the two injection systems are syr~unetrical to each
other about a radial plane containing the axis of the
spark plug (42).
8. A chamber according to any one of claims 4 to 7,
30 characterized in that the or each above-mentioned angular
sector (92, 104, 110, 112) extends over an angle of about
20" to 50'.
9. A chamber according to any preceding claim,
35 characterized in that the spark plug (42) is positioned
at substantially equal circumferential distances from the
two adjacent injection systems.
10. A turbine engine, such as an airplane turbojet or
turboprop, having a combustion chamber according to any
preceding claim.