FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
& The Patent Rules, 2003
COMPLETE SPECIFICATION
1. TITLE OF THE INVENTION:
CONSTANT-VOLUME COMBUSTION SYSTEM FOR A TURBINE ENGINE OF AN AIRCRAFT
ENGINE
2. APPLICANT:
Name: SAFRAN HELICOPTER ENGINES
Nationality: France
Address: 64510 Bordes, France.
3. PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the invention and the manner in
which it is to be performed:
2
DESCRIPTION
TECHNICAL FIELD
The invention relates to a constant-volume combustion system, also
designated by the acronym CVC, or by the term combustion according to the Humphrey
cycle, this system being intended to equip a turbomachine of an aircraft engine.
STATE OF PRIOR ART
The combustion chamber of most of the current aircraft engines, of the
turbojet engine type, operates according to the Brayton cycle which is a constant
pressure continuous combustion cycle.
However, it is known that the replacement of a constant pressure
combustion system by a constant-volume combustion system, that is implementing the
Humphrey cycle, should bring about a specific consumption gain that can reach up to
twenty percents.
Generally, the Humphrey cycle imposes to preserve the load in a
physically closed volume for some part of the cycle, and it induces the implementation of
a pulsed type operating region.
In practice, a constant-volume combustion aircraft engine includes a
compressor, an exhaust pipe and a combustion chamber connected to the compressor
and to the pipe, by respectively injection and ejection valves.
Each constant-volume combustion cycle includes a phase of intake and
setting in the combustion chamber of a compressed air and fuel mixture, a phase of
ignition by a controlled system and combustion of the mixture, and a phase of expansion
and ejection of the combustion gas.
Valves are controlled in a synchronised manner to implement these
three phases of the Humphrey cycle: they are in particular all closed during the
combustion phase, after which the opening of the ejection valve(s) allows the expansion
and ejection of the combustion gases.
3
In known constant-volume combustion systems, it has been attempted
to date to reduce the general bulk of the system, in particular to integrate it in the
thickness of the aircraft wing.
The object of the invention is on the contrary to provide a constantvolume
combustion system architecture that can be simply integrated to a current
turbomachine architecture, having a generally cylindrical shape and with a large
diameter.
DISCLOSURE OF THE INVENTION
One object of the invention is a constant-volume combustion system for
an aircraft turbomachine, this system comprising:
– several combustion chambers evenly distributed about a longitudinal
axis;
– a compressed air manifold extending about the longitudinal axis and
comprising a radially oriented compressed air outlet for supplying compressed air from a
compressor of the turbomachine, to each combustion chamber;
– an exhaust pipe extending about the longitudinal axis and comprising
a radially oriented inlet to receive the combustion gases from the combustion chambers
as well as an axially oriented outlet, the combustion chambers being radially interposed
between the outlet of the manifold and the inlet of the exhaust pipe;
– timing means for timing the intake into each combustion chamber of
compressed air from the outlet of the manifold and the ejection out of each combustion
chamber of combustion gases to the exhaust pipe.
With this arrangement, the combustion system radially extends on a
small length along the longitudinal axis, which facilitates its integration to a current
turbomachine, where it can be installed in place of a continuous combustion chamber,
namely between the compression stages and the turbine stages.
The invention also relates to a combustion system thus defined,
comprising a combustion body carrying the combustion chambers, this combustion body
including at each combustion chamber, a radially oriented compressed air intake
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aperture, and a radially oriented combustion gas exhaust aperture, and a rotary feeder
with means for rotatably driving this rotary feeder, this rotary feeder including:
– an intake ring coaxial with the longitudinal axis and provided with
intake ports, this intake crown being radially interposed between the outlet of the
manifold and the combustion body;
– an exhaust ring coaxial with the longitudinal axis and provided with
exhaust ports, this exhaust ring being radially interposed between the inlet of the exhaust
pipe and the combustion body.
The invention also relates to a combustion system thus defined, wherein
the outlet of the manifold extends about the combustion chambers and wherein the
combustion chambers are located about the inlet of the exhaust pipe.
The invention also relates to a combustion system thus defined, wherein
the inlet of the exhaust pipe extends about the combustion chambers, and wherein the
combustion chambers are located about the outlet of the manifold.
The invention also relates to a combustion system thus defined, wherein
each combustion chamber includes an intake port and an exhaust port, and wherein each
combustion chamber is rotatably mounted about an axis which is central to the same to
be rotatable on itself, means for rotatably driving the combustion chambers, each intake
port allowing intake of compressed air into the chamber when this port is facing the
outlet of the compressed air manifold, each exhaust port allowing exhaust of combustion
gases out of the combustion chamber when this exhaust port is facing the inlet of the
exhaust pipe.
The invention also relates to a combustion system thus defined, wherein
the means for rotatably driving each combustion chamber comprise a toothed wheel
rotatably driven about the longitudinal axis and for each combustion chamber, a pinion
meshed with this toothed wheel by being radially spaced apart from the longitudinal axis,
each pinion being rigidly coupled to a corresponding combustion chamber.
The invention also relates to a turbomachine comprising a constantvolume
combustion system thus defined.
5
The invention also relates to a turbojet engine type aircraft engine
comprising a turbomachine thus defined.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic side cross-section view of a first embodiment of the
system according to the invention comprising a fixed combustion chamber and which is
integrated to an engine with a centrifugal compressor;
Fig. 2 is a transverse cross-section view showing the arrangement of the
combustion chambers for the first or the second embodiment of the invention;
Fig. 3 is a close-up view showing the arrangement of the intake and
ejection ports in the first embodiment of the invention;
Fig. 4 is a partial schematic side cross-section view of a second
embodiment of a system according to the invention also comprising a fixed combustion
chamber and which is integrated to an engine with an axial compressor;
Fig. 5 is a partial schematic side cross-section view of a third
embodiment of the system according to the invention comprising a rotary combustion
chamber and which is integrated to an engine with a centrifugal compressor.
DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS
Generally, the invention is applicable to a turbomachine comprising a
compressor that can be centrifugal or even axial, and a turbine that can be radial or even
axial.
In Fig. 1, an engine 1 equipped with the constant-volume combustion
system according to the invention has a general structure of a revolution about a main
axis AX which corresponds to its longitudinal axis.
This engine includes upstream thereof a compressor 2 which is herein a
centrifugal compressor, to supply a constant-volume combustion system generally
designated by reference 3, ejecting combustion gases at the inlet of an exhaust pipe 4
which is located downstream of this combustion system.
6
The compressor 2, the combustion system 3 and the exhaust pipe 4
have themselves revolution structures while being located behind each other along the
axis AX, being surrounded as a whole by a revolution case 6 represented symbolically.
The centrifugal compressor 2 is supplied with air from upstream of the
engine and which is conveyed in parallel to the longitudinal axis. When this air has passed
through the centrifugal compressor, it is radially ejected along a centrifugal direction, that
is moving away from the axis AX, to be received at the inlet of a manifold 7 in which it
first travels longitudinally to downstream of the engine. By continuing its travel in this
manifold 7, the air is then radially directed along a radial direction, that is to the axis AX,
to exit from the manifold 7 in order to enter the combustion system 3 itself.
After they have been burned in the constant-volume combustion
system 3, the combustion gases are ejected from this system 3 radially along a radial
direction by being taken in at the inlet of the exhaust pipe 4. During their travel in this
exhaust pipe, the gases are adjusted to be expanded in parallel to the axis AX. This
expansion can, according to the architecture retained, be used to directly generate a
thrust, or even drive a turbine not represented which is located downstream of the
exhaust pipe 4.
As visible in Fig. 1, the combustion system 3 itself has a general toric
structure. This system is surrounded by the outlet of the manifold 7, and it surrounds the
inlet of the exhaust pipe 4, while being located along the axis AX at the same level as the
outlet of the manifold 7 and as the inlet of the exhaust pipe 4.
This combustion system 3 includes a fixed combustion body 8 having
here four combustion chambers 11-14 evenly spaced apart from each other about the
axis AX.
Each combustion chamber 11-14 is a closed enclosure delimited by one
or more walls, but including an intake aperture 11a-14a at its outer peripheral face, and
an ejection aperture 11e-14e at its inner peripheral face.
The intake apertures 11a-14a enable the compressed air from the outlet
of the manifold 7 to be taken in the chambers 11-14, whereas the ejection apertures
enable the combustion gases to be discharged to the inlet of the exhaust pipe. These
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intakes and ejections occur in an independent and coordinated manner for each of the
chambers 11a-14a of the combustion body.
The gas intakes and ejections are insured and synchronised by a rotary
feeder 16 which comprises an intake ring 17 surrounding the combustion body 8 by
running along its outer face, and an ejection ring 18 running along the inner face of the
combustion body 8 by being surrounded by the same.
The intake ring 17 and the ejection ring 18 each have a truncated
cylinder shape, centred on the axis AX, and they join each other at a bottom 19 of the
feeder 16. This rotary feeder 16 thus has generally a U-shaped cross-section toric gutter
shape which covers the upstream, inner and outer faces of the combustion body 8.
The intake ring 17 surrounds the combustion body 8 by being
interposed between this combustion body 8 and the outlet of the manifold 7. In an
analogous way, the ejection ring 18 is surrounded by the combustion body 8 by being
interposed between this body and the inlet of the exhaust pipe 4.
As visible in Fig. 3, the intake wall 17 includes a series of four intake
apertures or ports referred to as 17a, evenly distributed along this intake wall, that is
evenly distributed about the axis AX.
In the same manner, the ejection wall 18 includes four ejection
apertures or ports 18e evenly distributed along this wall, that is about the axis of
revolution AX.
In use, the feeder 16 is rotatably driven about the axis AX, to sequence
gas intakes and ejections for the different chambers.
More particularly, when a port 17a of the feeder 16 is at least partially
facing the intake aperture 11a of the window 11, compressed air from the compressor is
taken in the chamber 11 via the outlet of the manifold 7.
Since the feeder 16 continues rotating, the port 17a spaces apart from
the intake aperture 11a until the latter is closed. Under this situation, the ejection
aperture 11e is also closed by the ejection wall 18, such that fuel can be injected into the
chamber 11 via an injector 21 visible in Fig. 1. After the fuel is injected, the combustion in
the closed chamber is triggered by a plug 22, or any other controlled ignition system.
8
Since the feeder 16 continues rotating, about the axis AX, an ejection
port 18e comes to face the ejection aperture 11e of the chamber 11, which enables the
combustion gases to be ejected into the exhaust pipe 4 via its inlet, to produce a thrust or
supply a turbine.
Since the feeder 16 continues rotating, a new window 17a comes in
registry with the intake aperture 11a, which enables a new compressed air intake to be
started.
It is to be noted that during the start of the compressed air intake, the
gas ejection is still open because there is an overlapping portion during which the intake
and the ejection ports are simultaneously open. This overlapping enables the combustion
gases to be flushed.
On the other hand, the cycle just described for the combustion
chamber 11 happens in the same way for the other chambers, that is chambers 12-14.
As visible in Fig. 1, the manifold 7 is delimited by two revolution walls,
namely an inner wall 23 and an outer wall 24, the inner space of this manifold thus having
a generally toric-shape centred on the axis AX. The inner wall 23 can be fixed, or be rigidly
integral with the rotary feeder 16 to rotate with the same, as is the case in the example of
Fig. 1.
The outer wall 24 is here fixed by being for example rigidly fastened to
the case 6. It includes an inner peripheral edge, located facing the ring for supplying the
feeder 16 which is on the contrary rotating. A circular sealing means 27 is interposed
between the inner edge of the outer wall 24 and the outer face of the supply wall 17 in
order to insure a satisfactory sealing at this junction, when the feeder 16 rotates relative
to the inner edge of the outer wall 24, that is when the engine is in use.
The exhaust pipe 4 is itself delimited by an outer revolution wall 28 and
an inner revolution wall 29, this pipe 4 having itself a toric architecture about the
longitudinal axis AX.
The inner wall 29 is here fixed. It includes an outer peripheral edge
which is located facing the ejection ring 18 along which it runs. A sealing means 31 is
interposed between this outer edge and the inner face of the ejection ring 18 to insure a
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satisfactory sealing of the junction of these two elements when the rotary feeder rotates,
that is when the engine is in use.
The outer wall 28 which is also fixed includes an outer peripheral edge
which is rigidly fastened to an internal portion of the combustion body 8 which is also
fixed.
The sealing of the rotary feeder with the combustion body is also
optimised by four circular sealing means.
Two circular sealing means 32 are interposed between the inner face of
the intake ring 17 which is rotary and the outer face of the combustion body 8 which is
fixed, by being disposed on either side of the intake ports 17a and the intake
apertures 11a-14a along the longitudinal axis AX. Both these means aim at limiting, or
even cancelling, the amount of air taken in by an intake port 17a which leaks before
reaching the corresponded intake aperture.
Analogously, two other circular sealing means 33 are also interposed
between the outer face of the ejection ring 18 which is rotary and the inner face of the
combustion body 8 which is fixed, by being disposed on either side of the ejection
ports 18e and the ejection apertures 11e-14e along the longitudinal axis AX.
According to the invention, the compressed air and combustion gas
stream passing through the combustion chambers is moving radially, that is
perpendicularly to the axis AX.
In the example of Fig. 1, this stream is radial, that is it is directed to the
axis, which is appropriate for an architecture with a centrifugal compressor, that is
delivering a compressed air radial stream remotely from the axis, this stream being also
possibly deviated to be redirected to the axis for the combustion thereof.
The invention is also applicable to an axial compressor engine
architecture, as in the example of Fig. 4, wherein the stream passes through the
combustion chambers by being oriented in a centrifugal manner, unlike the case of Fig. 1.
In the example of Fig. 4, the engine, referred to as 41 includes an axial
compressor, not represented, which delivers compressed air in an axial manifold 42
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delimited by an cylindrical inner wall 43 and an outer revolution wall 44 both of which are
fixed.
The compressed air first travels longitudinally in this manifold 42 to be
then radially deviated therein in order to exit from this manifold by following a centrifugal
radial direction, so as to enter the constant-volume combustion system 46 which
surrounds the outlet of this manifold 42.
The combustion gases are then radially ejected from the system 46
along a radial direction to come to the inlet of an exhaust pipe 47 which is also delimited
by an inner revolution wall 48 and an outer revolution wall 49. This exhaust pipe has a
toric shape the inlet of which surrounds the combustion system 46, and its inner wall as
well as its outer wall are both fixed.
The trajectory of the combustion gases which are taken radially in this
exhaust pipe 47 is adjusted in order that they travel longitudinally, so that these gases are
expanded along the direction AX so as to be able to supply a turbine not represented or
to generate directly a longitudinally oriented thrust.
The constant-volume combustion system 46 is quite analogous to the
combustion system 3 of the example of Figs. 1 and 3. It includes a combustion body 51
which is identical to the combustion body 8, and which comprises several combustion
chambers evenly distributed about the axis AX.
The gas intake and ejection is once again synchronised by a rotary
feeder 52 which is analogous to the feeder 16 of the example of Fig. 1, this feeder having
also a U-shaped cross-section toric gutter shape which partially covers the combustion
body.
But, the feeder 52 is herein oriented upstream, in opposition to that of
Fig. 1, that is it covers the downstream face of the combustion body, as well as the outer
and inner peripheral faces of this body.
This rotary feeder 52 includes also an outer ring, referred to as 53 as
well as an inner ring referred to as 54 which it is also cylindrical. Thus, the general
structure of the feeder 52 is identical to that of the feeder 16, but it is its inner ring 54
11
which is equipped with intake ports to make up the intake ring, and it is its outer ring 53
which is provided with ejection ports to make up the exhaust ring.
Analogously, the intake apertures are located at the inner cylindrical
wall of the combustion body 51, and the ejection apertures are formed at the outer wall
of this combustion body 51.
The operation of this other engine 41 is analogous to that of the
engine 1: the intakes and exhausts being synchronised here again by a circular rotary
feeder which surrounds the combustion body, but the gases taken in and ejected follow
here a trajectory which is centrifugal instead of being radial.
The sealing of the rotary feeder 52 with le combustion body 51 is here
again optimised by four circular sealing means.
Two circular sealing means are interposed between the outer face of
the rotary intake ring and the inner face of the fixed combustion body, by being disposed
on either side of the intake ports and apertures along the axis AX. Both means aim at
limiting, or even cancelling, the amount of air taken in by an intake port which leaks
before reaching the corresponding intake aperture.
Analogously, two other circular sealing means are interposed between
the inner face of the rotary ejection ring and the outer face of the fixed combustion body,
by being disposed along the axis AX on either side of the ejection ports and apertures.
In a complementary fashion, a circular sealing means is interposed
between the outer edge of the inner wall 43 of the manifold 42 and the inner face of the
supply ring in order to ensure a satisfactory sealing for this junction, when the feeder
rotates.
Another circular sealing means is interposed between the inner edge of
the inner wall 48 of the exhaust pipe 47 and the outer face of the ejection ring to ensure a
sealing of the junction of both these elements when the rotary feeder rotates.
In the embodiment of Figs. 1 to 4, the combustion body is fixed, and it is
a rotary feeder which synchronises the intakes and exhausts for each combustion
chamber, these intakes and exhausts occurring along radially oriented trajectories.
12
But the invention also relates to an architecture in which each
combustion chamber is provided rotary and rotatably driven to synchronise the air
intakes and combustion gas exhausts.
It is the case in the example of Fig. 5 where this solution is applied to an
engine 61 provided with a compressor which is centrifugal, this engine 61 thus having a
general structure identical to that of the engine of Fig. 1.
This engine which appears in Fig. 5 comprises much like that of Fig. 1, a
centrifugal compressor 2 upstream thereof to supply a constant-volume combustion
system 62 which ejects combustion gases at the inlet of the downstream exhaust pipe 4.
The compressor 2, the combustion system 62 and the exhaust pipe 4
have themselves revolution structures while being distributed behind each other along
the axis AX, being surrounded as a whole by a case 6.
The compressor 2 delivers air it radially ejects along a centrifugal
direction, this being received at the inlet of the manifold 7 in which it first travels
longitudinally to downstream before being radially adjusted along a radial direction at the
outlet of the manifold 7 to enter the system 62.
After being burned in the system 62, the gases are radially ejected along
a radial direction to be taken in at the inlet of the exhaust pipe 4 in which they are then
adjusted to be expanded in parallel to the axis AX.
The combustion system 62 houses in a general toric structure which is
surrounded by the outlet of the manifold 7 and which surrounds the inlet of the exhaust
pipe 4, while being located along the axis AX at the same level as the outlet of the
manifold 7 and as the inlet, the pipe 4.
The constant-volume combustion system includes here again several
distinct combustion chambers, for example four in number, which are evenly distributed
about the axis AX, one of these chambers appearing in the Fig. by being referred to as 63.
This combustion chamber 63 is surrounded by a fixed outer jacket 64 in
which there are rotatably mounted so as to be able to pivot about a longitudinal axis of
rotation AR which is radially spaced from the axis AX.
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The engine is still equipped with means for rotatably driving each inner
shroud of the combustion chamber. These driven means are here a gear train 66
comprising for example a main wheel 67 with a large diameter centred on the axis AX,
and for each combustion chamber, a pinion 68 driven by this main wheel and itself driving
the combustion chamber to which it is mated by being for example rigidly fastened
thereto.
The fixed jacket 64 includes an intake aperture 69 which is located at
the region of this jacket which is the farthest from the axis of revolution AX, this aperture
being thus facing the outlet of the manifold 7. Analogously, this fixed jacket 64 also
includes an ejection aperture 71 which is on the contrary located at the closest region
thereof to the axis AX, to directly open into the inlet of the exhaust pipe 4. The intake and
exhaust apertures are advantageously spaced apart from each other along the axis AX.
In a complementary fashion, the rotary combustion chamber 63
includes an intake port and an exhaust port, respectively located along the axis AX, at the
intake aperture 69, and at the ejection aperture 71. These ports can be spaced apart from
each other about the axis AR so as to optimise timing of the compressed air intakes and
combustion gas ejection.
Thus, during the rotation of the combustion chamber 63 about its
axis AR, when the intake port is facing the aperture 69, compressed air is taken in the
chamber, from the outlet of the manifold 7. When the intake port is no longer facing the
aperture 69, the chamber 63 is completely closed, which enables fuel to be injected and
combustion to be caused by a controlled ignition, implementing for example a plug.
Then, the rotational movement of the chamber 63 results in a situation
in which the ejection port is located facing the exhaust aperture 71, which enables the
combustion gases to be ejected into the inlet of the exhaust pipe 4 to be expanded in
order to drive a turbine or to generate a thrust.
The intake and exhaust ports can be located at the same level about the
axis AR by being spaced apart from each other along this axis, such that when the intake
port is facing the aperture 69, the exhaust port is sealed by the rest of the jacket. In the
same manner, when the exhaust port is facing the aperture 71, the intake port is sealed
14
by the rest of the jacket in this region. In this case, the intake and exhaust apertures are
then also spaced apart from each other along the axis AX by an appropriate value.
As will be understood, the other combustion chambers have the same
operation as the chamber 63, which enables these different chambers to deliver
combustion gases at the inlet of the exhaust pipe 4.
In the example that has been described, the invention is applied to a
turbomachine of an aircraft engine, but the invention is applicable as well to a
turbomachine being part of a different equipment, such as in particular a terrestrial
electrical power generation equipment or else.
15
We claim:
1. A constant-volume combustion system (3; 46; 62) for a turbomachine,
this system comprising:
– several combustion chambers (11-14) evenly distributed about a
longitudinal axis (AX);
– a compressed air manifold (7; 42) extending about the longitudinal
axis (AX) and comprising a radially oriented compressed air outlet for supplying
compressed air, from a compressor of the turbomachine, to each combustion chamber;
– an exhaust pipe (4; 47) extending about the longitudinal axis (AX) and
comprising a radially oriented inlet to receive the combustion gases from the combustion
chambers (11-14) as well as an axially oriented outlet, the combustion chambers (11-14)
being radially interposed between the outlet of the manifold (7; 42) and the inlet of the
exhaust pipe (4; 47);
– timing means for timing the intake into each combustion
chamber (11-14) of compressed air from the outlet of the manifold (7; 42) and the
ejection out of each combustion chamber (11-14) of combustion gases to the exhaust
pipe (4; 47).
2. The system according to claim 1 comprising a combustion body (8; 51)
carrying the combustion chambers (11-14), this combustion body including at each
combustion chamber (11-14), a radially oriented compressed air intake
aperture (11a-14a), and a radially oriented combustion gas exhaust aperture (11e-14e),
and a rotary feeder (16; 52) with means for rotatably driving this rotary feeder (16; 52),
this rotary feeder (16; 52) including:
– an intake ring (17) coaxial with the longitudinal axis (AX) and provided
with intake ports (17a), this intake crown (17) being radially interposed between the
outlet of the manifold (7; 42) and the combustion body (8; 51);
16
– an exhaust ring (18) coaxial with the longitudinal axis (AX) and
provided with exhaust ports (18e), this exhaust ring being radially interposed between
the inlet of the exhaust pipe (4) and the combustion body (8; 51).
3. The system according to claim 1 or 2, wherein the outlet of the
manifold (7) extends about the combustion chambers (11-14) and wherein the
combustion chambers (11-14) are located about the inlet of the exhaust pipe (4).
4. The system according to claim 1 or 2, wherein the inlet of the exhaust
pipe (47) extends about the combustion chambers (11-14), and wherein the combustion
chambers (11-14) are located about the outlet of the manifold (42).
5. The system according to claim 1, wherein each combustion
chamber (63) includes an intake port and an exhaust port, and wherein each combustion
chamber (63) is rotatably mounted about an axis (AR) which is central to the same to be
rotatable on itself, means (66) for rotatably driving the combustion chambers (63), each
intake port allowing intake of compressed air into the chamber (63) when this port is
facing the outlet of the compressed air manifold (7), each exhaust port allowing exhaust
of combustion gases out of the combustion chamber (63) when this exhaust port is facing
the inlet of the exhaust pipe (4).
6. The system according to claim 5, wherein the means for rotatably
driving each combustion chamber comprise a toothed wheel (67) rotatably driven about
the longitudinal axis (AX) and for each combustion chamber (63), a pinion (68) meshed
with this toothed wheel by being radially spaced apart from the longitudinal axis (AX),
each pinion being rigidly coupled to a corresponding combustion chamber (63).
7. A turbomachine comprising a constant-volume combustion system
according to one of the preceding claims.
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8. An aircraft engine comprising a turbomachine according to claim 7.