Note: Descriptions are shown in the official language in which they were submitted.
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RADIAL FIXING AND POSITIONING FLANGES FOR SHELLS OF AXIAL TURBINE
COMPRESSOR HOUSINGS
Field
[0001] The present disclosure relates to the housing of an axial turbomachine.
More
particularly, the disclosure relates to contiguous shells in the housing of an
axial turbomachine. More particularly, the disclosure relates to fixing
brackets between the shells in the housing of an axial turbomachine. The
disclosure relates to the concentricity between two shells of a turbomachine
fixed with radial flanges. The disclosure relates also to an axial
turbomachine.
Prior art
[0002] Turbomachines generally include a plurality of annular passages through
which flows of air pass in order to generate a driving force. The airflow
passes through a fan, a compressor, a combustion chamber, and turbines.
In or between these elements, the housing of the turbomachine helps to
guide the flow by constraining it within the turbomachine itself.
[0003] The housing is made up of annular walls mirroring the changes in
section of
the stream. To this end, it comprises shells having a generally tubular shape
arranged along the engine's axis of rotation. The shells have functional
surfaces in contact with the stream. They can form internal and/or external
surfaces that physically define the stream. The shells may be cylinders or
parts of cylinders. Where they join roughly forms a cylinder or the base of a
cone of the desired length.
[0004] The functional surfaces of the shells generally match the theoretical
geometry of the airstream, in particular its continuity. This results in the
requirement that the various shells follow a general concentricity, without
which steps or discontinuities may occur in the stream. These defects lead to
a reduction in the efficiency of the turbomachine. Uncontrolled modes of
operation can occur.
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[0005] Patent EP123645 A1 discloses an assembly of two adjacent shells with
flanges connected by axial screws for fixing them. One of the shells has a
female cylindrical surface inside which a male cylindrical surface on the
other shell is located, so as to form a shaft-bore assembly. The male and
female cylindrical surfaces are located at the bases of the flanges. This type
of assembly makes it possible to optimise the position and orientation of the
shells relative to one another. However, the screws require an unobstructed
locating surface. This surface may be greater than the inherent size of the
screws to improve the distribution of mechanical stresses. The superposition
of the cylindrical bearing face and the locating surface for the screw means
that the radius of the outer flange has to be increased. The radius between
the flange and the cylindrical bearing surface further increases the outer
radius of the flange. This flange size is cumbersome and increases the
weight of the shell. Such a radial flange can be difficult to implement in a
splitter nose with a given lift/drag ratio. The presence of equipment in the
nose may make it impossible to assemble.
[0006] Patent EP2077183 B1 discloses a junction between two shells of a
turbomachine positioned with respect to each other using their flanges.
These are located at the axial ends of the shells. The radial ends of the
flanges have male and female surfaces. This solution allows optimum
positioning while avoiding any constraints imposed by locating surfaces for
screws. However, it requires a cylindrical portion at the top of one of the
flanges, thereby increasing the radius of the latter.
Summary of the disdosure
The technical problem
[0007] The present disclosure aims to solve at least one of the problems
presented
by the prior art. The disclosure aims to reduce the radius of the fixing
flanges
of the two shells of the housing of an axial turbomachine. The disclosure
also aims to simplify the assembly of two shells of the housing of an axial
turbomachine.
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Technical solution
[0008] The disclosure relates to an axial turbomachine housing capable of
directing
an annular flow in the said turbomachine, the housing comprising a first shell
and a second shell designed to be contiguous and coaxial, the first shell
comprising a flange and a surface substantially cylindrical and the second
comprising a flange and means of centring designed to mate with the
centring surface, wherein the flange of the first shell includes cut-outs
distributed along its circumference and the centring means extend axially
from the flange of the second shell through the said cut-outs to the centring
surface where the two flanges are in contact.
[0009] According to one embodiment of the disclosure, the cut-outs of the
flange of
the first shell are scallop-shaped or openings.
[0010] According to yet another embodiment of the disclosure, the axial
extension
of the cut-outs intersects the centring surface.
[0011] According to yet another embodiment of the disclosure, the centring
surface
forms a thickened layer on the first shell.
[0012] According to yet another advantageous embodiment of the disclosure, the
radius R2 of the centring surface is smaller than the radius R3 of the radial
extremity of the flange on the first shell.
[0013] According to yet another embodiment of the disclosure, the first shell
includes an annular bead adjacent to the flange of the first shell, the
centring
surface being at the top of annular bead or the centring surface forms an
annular groove in the first shell.
[0014] According to yet another embodiment
of the disclosure, the centring
surface is less than 30 mm from the flange of the first shell, preferably less
than 20 mm, more preferably less than 5 mm or possibly the centring surface
and the flange of the first shell are contiguous.
[0015] According to yet another embodiment of the disclosure, the cut-outs
have a
closed outline in the flange or an open outline on the free edge of the
flange.
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[0016] According to yet another embodiment of the disclosure, the centring
means
are radially some distance away from the profile of the cut-outs of the flange
of the first shell.
[0017] According to yet another embodiment of the disclosure, the centring
surface
and the means of centring are machined by turning.
[0018] According to yet another embodiment of the disclosure, the cross-
section of
the centring means is generally curved, and the cut-outs are wider than the
centring means in a circumferential direction.
[0019] According to yet another embodiment of the disclosure, the centring
means
include contact surfaces designed to contact the centring surface.
[0020] According to yet another embodiment of the disclosure, each contact
surface
is angled at more than 5 , preferably more than 15 , even more preferably
more than 30 to the circumference of the flange of the first shell.
[0021] This feature improves the strength imparted to each contact surface.
Thus,
the radial dimensions of the centring means can be reduced, as can the
thickness of the shells. Ultimately, the dimensions of the flanges can be
reduced. The angle in question is measured in the plane of the flange
relative to the central axis of the shells.
[0022] According to yet another embodiment of the disclosure, the shells are
fixed
to each using means of fastening on the flanges of the first and second
shells, between the cut-outs on the flange of the first shell.
[0023] According to yet another embodiment of the disclosure, the flanges of
the
first and second shells have equal outer radii R3.
[0024] According to yet another embodiment of the disclosure, in combination,
the
centring means physically cover more than 10% of the circumference of the
second shell, preferably more than 30%, even more preferably more than
50%.
[0025] According to yet another embodiment of the disclosure, the housing is a
stator housing of a turbine or a compressor.
[0026] According to yet another embodiment of the disclosure, the compressor
is a
low-pressure compressor.
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[0027] According to yet another embodiment of the disclosure, the shells are
made
of metal or a composite material.
[0028] According to yet another embodiment of the disclosure, the first and
second
shells are each formed integrally.
[0029] According to yet another embodiment of the disclosure, the shells are
essentially the same diameter and the same thickness.
[0030] According to yet another embodiment of the disclosure, the shells are a
surface of revolution with a curved profile.
[0031] According to yet another embodiment of the disclosure, at the centring
means the base of the cut-outs is radially recessed in relation to the
centring
surface.
[0032] According to yet another embodiment of the disclosure, the second shell
is in
planar contact with the radial flange.
[0033] According to yet another embodiment of the disclosure, the radius of
the
centring surface R2 is closer to the mean radius R1 of the first shell than
the
radius R3 of the extremities of the flanges.
[0034] The mean radius is the mean thickness of the tube formed by the first
shell.
[0035] According to yet another embodiment of the disclosure, the centring
means
are materially continuous from the second shell to the centring surface.
[0036] The disclosure also relates to an axial turbomachine including a
turbofan, at
least one compressor, at least one turbine in which the streams flow as
directed by the housings, wherein at least one of the housings is in
accordance with the disclosure.
[0037] Embodiments thus enable the radius of the flange to be reduced. The
disclosure uses discontinuous centring taking advantage of the areas
between the screws. This space allows positioning the two shells with
respect to each other while reducing the radial size of the assembly. Thanks
to this the reduction in radius substantial weight savings are possible.
[0038] The manufacturing processes required use standard tooling for shells.
The
precautions needed to ensure concentricity remain unchanged. The
disclosure can enable combined turning and milling operations to create the
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shapes for which the geometric tolerances are optimal. The machining
processes are simple and can permit a reduced number of operations. Costs
are moderate.
[0039] The outside diameter of a radial flange located in a splitter nose may
be
reduced. This feature means there need be fewer or no constraints on the
design of the splitter nose. This may be thinned if necessary, for example to
better serve a desired flow geometry.
[0040] The disclosure requires no spacers to achieve its compactness and
precision. This feature means there can be a small number of mechanical
interfaces so that the effects of mechanical play are reduced and the
associated metrology costs remain low.
Brief description of the drawings
[0041] Figure 1 shows a turbomachine in accordance with the disclosure
[0042] Figure 2 shows a diagram of a turbomachine compressor according to the
disclosure.
[0043] Figure 3 illustrates a junction between two housing shells in
accordance with
a first embodiment of the disclosure.
[0044] Figure 4 shows a section of the junction between two shells of the
housing of
Figure 3 sectioned at 4-4 in accordance to the first embodiment of the
disclosure.
[0045] Figure 5 illustrates a junction between two housing shells in
accordance with
a second embodiment of the disclosure.
Description of the embodiments
[0046] In the following description, the terms inner and outer refer to a
position
relative to the axis of rotation of an axial turbomachine.
[0047] Figure 1 shows an axial turbomachine. In this case it is a double-flow
turbojet. The turbojet 2 comprises a first compression stage, a so-called low-
pressure compressor 6, a second compression stage, a so-called high
pressure compressor 8, a combustion chamber 10 and one or more turbine
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stages 12. In operation, the mechanical power of the turbine 12 transmitted
through the central shaft to the rotor 14 drives the two compressors 6 and 8.
Reduction mechanisms may increase the speed of rotation transmitted to the
compressors. Alternatively, the different turbine stages can each be
connected to compressor stages through concentric shafts. These latter
comprise several rotor blade rows associated with stator blade rows. The
rotation of the rotor around its axis of rotation 16 generates a flow of air
and
gradually compresses it up to the inlet of the combustion chamber 12.
[0048] An inlet fan, commonly designated a "turbofan" 18, is coupled to the
rotor 14
and generates an airflow which is divided into a primary flow 20 passing
through the various above-mentioned levels of the turbomachine, and a
secondary flow 22 passing through an annular conduit (shown in part) along
the length of the machine and then rejoining the main flow at the turbine
outlet. The primary flow 20 and secondary flow 22 are annular flows and are
channelled through the casing of the turbomachine. To this end, the housing
has cylindrical walls or shells that can be internal or external. These shells
can be fitted at the turbofan 18, compressors (6, 8) between the
compressors, at a turbine 12 or between the turbines.
[0049] Figure 2 is a sectional view of a low-pressure compressor 6 of an axial
turbomachine 2 such as that of Figure 1. Part of the turbofan 18 can be
seen, as can the splitter nose 24 between the primary 20 and secondary 22
airflows. The rotor 14 comprises several rows of rotor blades 26, for example
three, and several rows of stator blades 28, for example four. Each row of
stator blades 28 is associated with a row of rotor blades 26 for straightening
the airflow so as to convert the velocity of the flow into pressure. Each pair
of
rotor blade rows with the associated stator form a stage of the compressor 6.
[0050] The housing comprises annular surfaces which delimit the interior and
exterior of the primary stream 20. The housing delimits the outside of the
primary flow along the length of the low pressure compressor 6, and also the
inside and outside between the compressors (6, 8).
[0051] The housing includes several shells (32, 34, 36, 38, 40). The housing
may
include, for example, a first external or upstream shell 32 that is located at
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the front and which, for example is contact with the splitter nose 24. It can
be
connected to the first row of stator blades. The housing may include a
second outer or central shell 34. This can be connected to the stator vanes
28 of the second and third stage of the compressor 6. The housing may
include a third outer or downstream shell 36. This may be in contact with the
blades of the final compressor stage. lt can be connected to an outer
connecting shell 38, guiding the primary flow 20 to the compressor in
combination with an internal shell 40.
[0052] According to an alternative of the disclosure, the second shell may be
formed of a plurality of axial shell sections. This alternative can be
advantageous when the compressor has more than four rows of stator
blades. Alternatively, the first shell and the third shell may each be
connected to more than one row of stator blades.
[0053] The shells are attached to each other at junctions (42, 44, 46) with
radial
flanges. Fixing means such as screws can be inserted into axial holes. The
radial flanges are formed on at least one axial end of the shells. Preferably,
the second shell is fixed by means of two radial flanges: an upstream one
and a downstream one. Some of the shells are connected to structural parts
of the turbomachine 2 by their radial flanges. Preferably, an axial assembly
of shells is essentially fixed to the structural parts of the turbomachine
using
the radial flanges at the extremities of the assembly.
[0054] The shells comprise a tubular body formed by a tubular wall. The shells
generally are circularly symmetrical, with profiles of revolution about axes
of
revolution. Preferably, the axes of revolution coincide with the axis 16 of
rotation. Their profiles can be arched or angled. The wall thickness is less
than 5.00 mm, preferably less than 3.00 mm, even more preferably less than
1.50 mm. The shells are preferably made of titanium.
[0055] Each shell may comprise angular sectors of the outer shell, each
defining a
part of a perimeter of the outer shell. These angular sectors are joined
axially, for example by means of axial screwed flanges.
[0056] The shells can be used to fix the stator blades 28. They can be fixed
by
welding or screwing. The shells form walls designed to guide the flow in the
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turbomachine. They are preferably sealed. In combination they form a
continuous sealed surface to achieve a high compression ratio. Locally,
holes may be provided for tapping off air into the stream, or for injecting
it.
The shells may have annular grooves for housing layers of abradable
material.
[0057] Figure 3 is a junction between two adjacent shells, such as the
junction 42
between the first shell 32 and the second shell 34. The first shell 32 has a
radial flange called the first flange 48. Preferably, the second shell has a
second radial flange 50. Each of the radial flanges has a planar bearing
surface which is perpendicular to the axis of rotation 16 of the turbomachine
2. The bearing surfaces enable a planar joint to be made. These bearing
surfaces are used to align the two shells with respect to each other and, in
particular, to enable their axes of revolution to be parallel. The radial
flanges
(48, 50) are extensions of the bodies of the shells and are in continuous
contact, so as to ensure the junction between them is sealed.
[0058] To ensure the positioning of the shells (32, 34) in the plane of their
flanges
(48, 50), the second shell 34 has a radial centring means 52 engaging with
complementary centring means. Additional means of centring may include a
centring surface 54 or reference surface. The centring surface 54 is
generally cylindrical and coaxial with the first sleeve. The centring means
comprise contact surfaces 56 being in contact with the centring surface 54.
[0059] The centring means 52 are in contact with the centring surface 54 on at
least
three unaligned points. Preferably, the centring means 52 are in contact with
the centring surface 54 on at least two separate surfaces, preferably
distributed around the circumference of the centring surface.
[0060] The centring surface 54 is formed by turning so as to provide optimum
cylindricity and adequate perpendicularity with the plane of the first flange
48. The first flange 48 has cut-outs 58 that are the full depth of the
material.
The cut-outs 58, which may be straight-sided or wave-shaped, extend
radially into the first flange 48. In order to reduce the outside radius R3 of
the
flanges of the shells, the centring means 52 are moved closer to the axis 16
and pass through the cut-outs. The centring surface 54 is located at the base
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of the first flange 48, opposite the second shell with respect to the first
flange
48.
[0061] To ensure that the contact surfaces 56 are substantially in abutment
against
a reference surface having a defined shape, in particular the centring surface
54 which is formed by turning, the bases 62 of the voids of the cut-outs 58
are radially recessed relative to the centring surface 54. An arched tunnel is
bounded by the bottom 62 of the cut-outs 58 and the centring means 52.
[0062] Figure 4 is a sectional view of the first shell and the second shell
sectioned
along 4-4 in Figure 3. This section passes through the interface between
centring means 52 and the centring surface 54.
[0063] The centring means 52 are discontinuous in order to fit into the cut-
outs 58
between the residual portions of the first flange 48. Their cross-sections
correspondent to curved segments.
[0064] The centring means 52 contain the secondary contact surfaces 56 which
are
made by tuming. This embodiment can benefit, from a shape standpoint,
from the same advantages as the centring surface 54. The reference and
contact surfaces (54, 56) are complementary. Preferably, the contact
surfaces are located on the angled portions of the tube. When the contact
and centring surfaces are fitted, they allow precise positioning and
concentricity between the shells. Concentricity is less than 0.10 mm,
preferably less than 0.05 mm, even more preferably less than 0.02 mm. This
fitting takes advantage of the mating accuracy between a shaft and a bore.
[0065] The fixing means are arranged in the residual parts of the first flange
48.
They pass through fixing holes 60 passing through both flanges. The
required clearance around the fastening means does not conflict with the
centring means 52 as they are offset tangentially. Therefore, the radial
thickness of the centring means can be increased regardless of the
configuration of the centring means. This increased thickness can strengthen
the junction between the two shells (32, 34).
[0066] The disclosure is particularly suitable for an extemal junction between
two
shells of the low-pressure compressor 6. The mechanical strength of flanges
thus produced is consistent both with the pressure of the primary flow as well
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as the thermal stress, vibration and shock to which a low pressure
compressor can be subjected.
[0067] Figure 5 shows a junction between two shells in accordance with a
second
embodiment of the disclosure. Figure 5 has the same numbering scheme as
in previous figures for the same or similar elements, but the numbering is
incremented by 100.
[0068] The shells (132, 134) may be located at the turbofan 18 and define a
secondary flow. The shells can be internal shells defining the outside of the
secondary flow. They have radial flanges extending inwardly toward the axis
of rotation 16 of the turbomachine. They are located at the junction between
the two shells (132, 134).
[0069] The first sleeve 132 has a first radial flange 148 which has a cut-out
158 that
is the full depth of the material. This latter may be an opening whose contour
is included in that of the first radial flange 148. The inner material
continuity
is advantageous for stiffening the first flange and hence the junction between
the shells. The free extremity of the first flange essentially describes a
circle.
[0070] The first shell also has a centring surface 154 oriented in the radial
direction
of the first radial flange 148. This surface is located in the thickness of
the
first shell 132. It is generally cylindrical. It forms a reduction in the
thickness
of the first shell 132. The bottom of the cut-out 162 is raised relative to
the
centring surface 154. At this point, the first shell 132 is even thinner than
at
the centring surface 154.
[0071] The second shell 134 has a second radial flange 150 on which are
located
the centring means 152. They have contact surfaces 156 matching the
centring surface 154. The centring means 152 pass through the cut-outs
until they reach the centring surface 154. On the first radial flange 148 the
centring means 152 have a thickness less than that of the openings so as to
be substantially in radial contact with the centring surface 154.
[0072] One skilled in the art can easily reverse the orientation of the
technical
features that have an orientation towards the inside or outside. The technical
features of a shaped cut-out opening can be applied to a radially outwardly
directed flange, as can a centring surface located in the body of a shell.
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