FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
& The Patent Rules, 2003
COMPLETE SPECIFICATION
1. TITLE OF THE INVENTION:
SEALING DEVICE BETWEEN AN INJECTION SYSTEM AND A FUEL
INJECTION NOZZLE OF AN AIRCRAFT TURBINE ENGINE
2. APPLICANT:
Name: SAFRAN AIRCRAFT ENGINES
Nationality: France
Address: 2 boulevard du Général Martial Valin, 75015 Paris, 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 DOMAIN
The invention relates to the domain of combustion chambers for aircraft turbine
engines. More specifically, the invention relates to fuel injectors and injection systems to
inject an air-fuel mix for such turbine engine combustion chambers.
STATE OF PRIOR ART
A classical injection system of an air-fuel mix into an aircraft turbine engine
combustion chamber is known for example through document EP 1 731 837 A2.
The injection system comprises a part fixed relative to the combustion chamber.
The fixed part comprises a mixer bowl fixed to a combustion chamber bottom, and a
venturi and an air swirler. The venturi and the air swirler are located upstream from the
mixer bowl.
The injection system also comprises a sliding cross member free to move relative
to the fixed part. The sliding cross-member, also called the "injection nozzle guide", is
configured to mechanically connect the fuel injector to the injection system. This guide is
intended particularly to at least partially compensate for misalignments of the injector
relative to the injection system during operation and/or during assembly of the injector
and the injection system in the combustion chamber.
The guide has an inner surface delimiting a centring orifice in which the injector
nozzle is centred. The nozzle comprises an outer casing centred on a longitudinal axis of
the injector nozzle. The guide and the outer casing of the injector nozzle are thus subject
to wear at their contact surface, corresponding to said inner surface of the guide. This
wear is generated particularly by engine vibrations and is aggravated by misalignments of
the injector relative to the injection system.
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An undesirable clearance is then created between the guide and the injector
nozzle during the life of the installation. The main consequence of this clearance is the
generation of an additional uncontrolled air flow towards the bottom of the combustion
chamber. In general, the result is a reduction in the performances of the combustion
chamber. This unwanted air flow could create important disturbances to operation of the
combustion chamber, particularly in terms of flame stability, risk of flameout of the
chamber or the in-flight reignition capability.
Furthermore, excessive wear can make major repairs to the injector nozzle
necessary, such as replacement of its outer casing, with a non-negligible impact on the
global cost of the solution.
SUMMARY OF THE INVENTION
The invention is aimed at at least partially solving problems encountered in
solutions according to prior art.
To achieve this, the first subject of the invention is an arrangement for an aircraft
turbine engine combustion chamber, the arrangement comprising a system for injection
of an air-fuel mix into the combustion chamber, and a fuel injector, comprising a spray
nozzle, the injection system comprising a spray nozzle guide, the inner surface of which
delimits a centring opening in which there is the injector nozzle that is composed of an
outer casing centred on a longitudinal axis of the injector nozzle.
According to the invention, the arrangement also comprises a sealing device
between the inner surface of the guide and the outer casing of the injector nozzle, the
sealing device comprising:
- a first part accommodated in a groove in the outer casing, said groove extending
around said longitudinal axis and being delimited partly by a downstream delimiting
surface, the first part having a first sealing surface and bearing axially against said
downstream delimiting surface of the groove; and
- a second part having a second sealing surface bearing radially against said inner
surface of the injector nozzle guide.
4
Therefore the invention has the special feature that a sealing device is implanted
between the injector nozzle and the guide, to avoid/limit risks of generation of an
additional air flow towards the bottom of the combustion chamber. In general, the result
is an increase in the performances and life of the combustion chamber.
This sealing device limits wear between the guide and the injector nozzle, and can
judiciously be used as a wear indicator to avoid extensive operations to repair the injector
nozzle necessary with solutions according to prior art. Since a clearance is preferably
provided between the outer casing of the injector nozzle and the inside surface of the
guide, the sealing device specific to the invention will be consumed in priority, like a
sacrificial part acting as a wear meter. It can thus be easily replaced before excessive
damage occurs to the injector nozzle.
Finally, note that the solution proposed by the invention is particularly
advantageous because the mass of the sealing device can be negligible.
The invention also preferably has at least one of the following additional
characteristics, taken in isolation or in combination.
Said first and second parts of the sealing device are arranged to be approximately
orthogonal with a connecting radius between the two, said second part extending
backwards in the axial direction from said connecting radius. Preferably, the first and
second parts are made from a single piece. The orthogonal layout between these two
parts of the sealing device can advantageously form a hollow in which air under pressure
from the compressor unit applies combined axial and radial pressure reinforcing contact
forces at said first and second sealing surfaces of the sealing device.
Said second part comprises an upstream axial end and a downstream axial end
located at the connecting radius, said upstream axial end being folded radially inwards.
Such an annular fold makes it easier to extract the sealing device in the upstream
direction, using an appropriate tool.
Said sealing device is in the form of a global split ring. The slit in the ring is
preferably straight and is inclined relative to an axis of this ring. This causes rotation of
the air leak generated by the slit in the ring. The direction of rotation and the angle are
thus chosen so as to optimise integration into the air flow in the combustion chamber.
5
Said groove is partly delimited by an upstream delimiting surface facing said
downstream delimiting surface, and the upstream delimiting surface extends radially
outwards from an inner end of the first part of the sealing device. This arrangement limits
risks that the sealing device might escape from its groove during insertion of the injector
nozzle into the guide. The device can then be retained by the stop at the inner end of the
first part of the sealing device, in contact with the upstream delimiting surface of the
groove.
The sealing device is preferably metallic, and preferably has approximately
constant thickness.
Said outer casing of the injection nozzle has a globally spherical outer surface, in
other words its shape is conventional.
Another purpose of the invention is an aircraft turbine engine comprising at least
one such arrangement.
Finally, the purpose of the invention is a method of assembling such an
arrangement, including the following steps:
- placement of the sealing device in the groove formed on the outer casing of the
injector nozzle;
- insertion of the injector nozzle fitted with the sealing device in the centring
opening, by movement of the nozzle along the direction of its longitudinal axis.
Other advantages and characteristics of the invention will appear in the nonlimitative
detailed description given below.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood after reading the description of example
embodiments, given purely for information and in no way limitative, with reference to
the appended drawings on which:
- figure 1 shows a partial diagrammatic longitudinal half-sectional view of a
combustion chamber for a turbine engine, including an arrangement according to a
preferred embodiment of the invention;
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- figure 2 shows a perspective view of the arrangement shown on the previous
figure;
- figure 3 shows a longitudinal sectional view of the arrangement shown on the
previous figure;
- figure 4 shows a perspective view of the fuel injector forming an integral part of
the arrangement shown on figures 2 and 3;
- figure 5 shows an enlarged perspective view of part of the arrangement shown
on the previous figure;
- figure 6 shows a longitudinal sectional view of the part of the arrangement
shown on the previous figure;
- figure 7a is a perspective view of a first embodiment of the sealing device fitted
on the arrangement shown on the previous figures;
- figure 7b is an elevation view of the view in the previous figure;
- figure 8a is a perspective view of a second embodiment of the sealing device
fitted on the arrangement shown on the previous figures; and
- figure 8b is an elevation view of the view in the previous figure;
DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS
Figure 1 diagrammatically represents a combustion chamber 2 of an aircraft
turbine engine 1, that is annular in shape about an axis of the turbine engine. The
combustion chamber 2 comprises a fixed inner casing wall 4 and an outer casing wall 6.
The outer casing wall 6 and an outer chamber wall 12 delimit an air flow passage 14. The
inner casing wall 4 and an inner chamber wall 8 delimit a second air flow passage 10. The
inner chamber wall 8 and the outer chamber wall 12 are connected through the chamber
bottom 16 of the combustion chamber 2.
Throughout this document, the "upstream" and "downstream" directions are
defined with regard to the general direction of air and fuel flow in the combustion
chamber 2, diagrammatically represented by the arrow 5. This direction also corresponds
approximately to the flow direction of exhaust gases in the turbine engine 1.
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A plurality of injection systems 18 are fitted on the chamber bottom 16, only one
of which is visible on figure 1. The injection system 18 comprises a sliding crossing 26, also
called the "injector nozzle guide" and also includes a fixed downstream part 25 of the
injection system 18. The injection system 18 is connected to a fuel injector 80 that is
installed in the guide 26 at an injector nozzle 82.
With reference to figures 1 to 3, the fixed downstream part 25 of the injection
system 18 comprises a venturi 27, a swirler 24 and a mixer bowl 28 fixed to the chamber
bottom 16. The fixed downstream part 25 is generally symmetrical in revolution about an
axis 3 of revolution of the mixer bowl 28. The axis 3 of revolution of the mixer bowl 28 is
usually coincident with the axis of revolution 3 of the injection system 18, and particularly
with that of the guide 26. This axis 3 also corresponds to the longitudinal axis of the
injector nozzle 82.
The swirler 24 is mounted fixed to the mixer bowl 28. It comprises a first stage of
blades 30 and a second stage of blades 32 that have the function of driving air in rotation
about the axis 3 of the mixer bowl 28. The blades in the first stage of blades 30 can rotate
in the same direction as the blades in the second stage of blades 32, or in the opposite
direction.
The mixer bowl 28 is tapered in an approximate shape of revolution about the axis
3 of the mixer bowl 28. It is connected to the bottom of the chamber 16 through a split
ring 22 and possibly a deflector 20.
The guide 26 is free to move relative to the fixed downstream part 25 of the
injection system 18. More precisely, the guide 26 is mounted free to slide on a housing
ring 35 of the fixed downstream part 25.
The housing ring 35 comprises a wall 34 in contact with which the guide 26 can
slide. The wall 34, in cooperation with an edge 44 of the fixed downstream part 25 of the
injection system 18, defines a housing 29 for the sliding crossing shoe 36. The wall 34 and
the edge 44 can possibly be monoblock, so as to form a single part.
The guide 26 is annular around the longitudinal axis 3. It comprises a shoe 36
configured to bear in contact with the fixed downstream part 25, and a tapered
precentring portion 38 designed to precentre a fuel injector 80 such that the injector
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nozzle 82 can be subsequently be housed in the centring portion 39 of the guide 26. For
example, the general shape of the precentring portion 38 is tapered. It opens up in the
centring portion 39 that has a cylindrical inner surface 40 with centre line 3, delimiting a
centring opening 40’ in which the injector nozzle will be housed.
The guide 26 is preferably monoblock, such that the precentring portion 38, the
shoe 36 and the centring portion 39 only form a single part.
The guide 26 comprises purge holes 33 distributed circumferentially close to the
junction of the shoe 36 and the centring portion 39, these holes being used to introduce a
bleed air flow into the injection system 18. The function of the bleed air flow is to prevent
fuel from stagnating around the injector nozzle 82.
The injector nozzle 82 is located at the end of the injector body 81, at the annular
terminal part of the injector 80, that has an aeromechanical or aerodynamic type design.
The injector nozzle 82 comprises an outer casing 85 centred on the axis 3 and with a
globally spherical shaped outer centring surface 84 and more precisely defining a
segment in the shape of a sphere.
An operating clearance is preferably selected between the inner surface 40
defining the centring opening 40’, and the outer centring surface 84 of the injector nozzle
82. The mechanical connection between the guide 26 and the injector nozzle 82 at least
partially compensates for misalignments, caused particularly by manufacturing tolerances
for the injector 80 and the injection system 18, assembly tolerances of the injector 80 and
the injection system 18 in the combustion chamber 2, and differential expansions of the
injector 80 relative to the injection system 18.
During operation, the combustion chamber 2, and particularly each injection
system 18, are supplied in the direction of the arrow 48 by air under pressure at the
passage 46. This air under pressure from the compressor unit arranged on the upstream
side is used for combustion or cooling of the combustion chamber 2. Part of this air is
added into the combustion chamber 2 at the central opening of a cover 50 as shown
diagrammatically by the arrow 52, while another part of the air flows to the air flow
passages 10 and 14 along directions 54 and 56 respectively and then along direction 60.
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The air flow shown diagrammatically by the arrows 60 then penetrates into the
combustion chamber 2 through primary openings and dilution openings.
It is required to minimise the air flow between the inner surface 40 defining the
centring opening 40’, and the outer centring surface 84 of the injector nozzle 82. This
parasite air flow could generate important disturbances to the operation of the
combustion chamber, particularly in terms of flame stability, risk of flameout of the
chamber and the in-flight reignition capability. This parasite air flow is limited by
construction, due to the small operating clearance between the guide 26 and the injector
nozzle 82. Nevertheless, if there is any wear of these parts, the clearance could increase
and therefore reinforce the parasite air flow. To prevent this situation, the invention
ingeniously includes the insertion of a sealing device 100 between the injector nozzle 82
and its guide 26, this device 100 being assembled on the outer casing 85 of the nozzle 82,
as shown on figure 4.
We will now describe this metallic sealing device 100 in more detail with reference
to figures 5 and 6, designed to resist the high ambient temperatures close to the
combustion chamber.
The device 100 is annular in shape, centred on axis 3. It globally corresponds to a
split ring to enable easy assembly on the outer casing 85 of the injector nozzle 82. It is
made in a single piece, preferably with an approximately constant thickness. It comprises
essentially two parts 102, 104, each in the form of an annular band, these parts 102, 104
being connected to each other through a connecting radius 106. The two parts 102, 104
are arranged approximately orthogonal to each other, the first 102 extending in the radial
direction while the second 104 extends in the axial direction. More precisely, the first part
102 of the device 100 comprises an outer end 102a and an inner end 102b housed in a
groove 108. The second part 104 has a downstream axial end 104a and an upstream axial
end 104b. The ends 102a, 104a are connected through the connecting radius 106, such
that the second part 104 of the device extends in the axially backwards direction from
this connecting radius. The half-sections of the first and second parts 102, 104 thus form a
rounded corner at the right angle. The angle also defines a recess 110 open in the
upstream direction between its two flanges.
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The upstream axial end 104b of the second part 104 is folded down radially
inwards to facilitate gripping of the device 100 when it is to be extracted in the upstream
direction, using an appropriate tool.
The inner end 102b of the first part 102 is housed in the groove 108 formed on the
casing 85, this groove opening up radially outwards and being centred on the axis 3. It is
delimited by a bottom 112 at a radial spacing from the inner end 102b of the first part
102, so as to enable thermal expansion of this first part. The groove 108 is also delimited
by a downstream delimiting surface 108a and an upstream delimiting surface 108b
arranged facing each other in the axial direction.
The first part 102 has a first sealing surface 114 bearing axially against the
downstream delimiting surface 108a of the groove, to create a seal between the guide 26
and the injector nozzle 82. The first sealing surface 114 corresponds to the downstream
surface of the first band shaped part 102. Similarly, the second part 104 has a second
sealing surface 116 bearing radially against the inner surface 40 of the guide 26. The
second sealing surface 116 corresponds to the radially outer surface of the second band
shaped part 104.
When air under pressure output from the compressor unit penetrates into the
recess 110 defined by the sealing device 100, the contact forces at the sealing surfaces
114, 116 are reinforced to obtain an even higher performance seal. Furthermore, the
device 100 wears earlier than the outer casing 85 of the injector nozzle 82, such that it
forms a sacrificial part also acting as a wear indicator. Therefore it is easy to replace it
before wear between the guide and the other casing 85 becomes problematic and
requires major action. In this respect, note that leak tightness is not affected by wear of
the casing 85 at the downstream limitation surface 108a of the groove resulting from
contact with the device 100. Air pressure in the hollow 110 forces the device 100 into
contact with the surface 108a of the groove, thus compensating for the wear clearance
that might arise between the downstream delimiting surface 108a and the first sealing
surface 114.
The first step in assembling the assembly 200 comprising the injector and the
injection system is to install the sealing device 100 in the groove formed on the outer
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casing of the injector nozzle, as shown in figure 4. It is put into place by opening the
segmented ring 100, and then closing it once it is in position radially facing the groove.
The injector nozzle 82 fitted with the sealing device 100 is then inserted in the
centring opening 40', by movement of the nozzle 82 along the direction of its longitudinal
axis 3. This insertion is facilitated by the connecting radius 106, that precentres the
assembly. Furthermore, the risk that the device 100 should escape from the groove 108 is
extremely low because the upstream delimiting surface 108b extends radially outwards
beyond the inner end 102b of the first part 102 of the sealing device 100. During the
insertion, the device 100 can then be retained by the stop at this inner end 102b in
contact with the upstream delimiting surface 108b of the groove.
A first embodiment of the split ring 100 is now illustrated with reference to figures
7a and 7b. In this case, the slit 120 in the ring is straight and is inclined relative to an axis
3 of this ring. This causes rotation of the air leak generated by the slit in the ring, the
direction of rotation and the angle being chosen so as to blend as well as possible into the
air flow in the combustion chamber. According to a second embodiment represented on
figures 8a and 8b, the slit is generally Z-shaped with the central portion of this slit 120
extending circumferentially and corresponding to an axial overlap zone of the two ends of
the ring 100.
Obviously, an expert in the subject could make various modifications to the
invention that has just been described without going outside the framework of the
presentation of the invention.
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WE CLAIM:
1. Arrangement (200) for a combustion chamber (2) for an aircraft turbine engine
(1), the arrangement comprising a system (18) for injection of an air-fuel mix into the
combustion chamber (2), and a fuel injector (80) comprising an injector nozzle (82), the
injection system (18) comprising a spray nozzle guide (26), the inner surface (40) of which
delimits a centring opening (40') in which there is the injector nozzle (82) that is
composed of an outer casing (85) centred on a longitudinal axis (3) of the injector nozzle,
characterised in that the arrangement also comprises a sealing device (100)
between the inner surface (40) of the guide (26) and the outer casing (85) of the injector
nozzle, the sealing device (100) comprising:
- a first part (102) accommodated in a groove (108) in the outer casing (85), said
groove extending around said longitudinal axis (3) and being delimited partly by a
downstream delimiting surface (108a), the first part (102) having a first sealing surface
(114) and bearing axially against said downstream delimiting surface (108a) of the groove;
and
- a second part (104) having a second sealing surface (116) bearing radially against
said inner surface (40) of the injector nozzle guide (26).
2. Arrangement according to claim 1, characterised in that said first and second
parts (102, 104) of the sealing device (100) are arranged to be approximately orthogonal
with a connecting radius (106) between the two, said second part (104) extending
backwards in the axial direction from said connecting radius (106).
3. Arrangement according to claim 2, characterised in that said second part (104)
comprises an upstream axial end (104b) and a downstream axial end (104a) located at the
connecting radius (106), said upstream axial end (104b) being folded radially inwards.
4. Arrangement according to any one of the previous claims, characterised in that
said sealing device (100) is in the global form of a split ring
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5. Arrangement according to claim 4, characterised in that the slit (120) in the ring
is straight and is inclined relative to an axis of this ring.
6. Arrangement according to any one of the previous claims, characterised in that
said groove (108) is partly delimited by an upstream delimiting surface (108b) facing said
downstream delimiting surface (108a), and in that this upstream delimiting surface (108b)
extends radially outwards from an inner end (102b) of the first part (102) of the sealing
device.
7. Arrangement according to any one of the previous claims, characterised in that
sealing device (100) is metallic and that its thickness is preferably approximately constant
8. Arrangement according to any one of the previous claims, characterised in that
said outer casing (85) of the injection nozzle (82) has a globally spherical outer surface
(84).
9. Aircraft turbine engine (1) comprising at least one arrangement (200) according
to any one of the previous claims.
10. Method of assembling an arrangement (200) according to any one of claims 1
to 8, characterised in that it comprises the following steps:
- placement of the sealing device (100) in the groove (108) formed on the outer
casing (85) of the injector nozzle (82); and
- insertion of the injector nozzle (82) fitted with the sealing device (100) in the
centring opening (40'), by movement of the nozzle (82) along the direction of its
longitudinal axis (3).