U.S. patent application number 13/557722 was filed with the patent office on 2013-08-08 for turbojet engine case, notably intermediate case.
This patent application is currently assigned to SNECMA. The applicant listed for this patent is Wouter BALK. Invention is credited to Wouter BALK.
Application Number | 20130202425 13/557722 |
Document ID | / |
Family ID | 44588083 |
Filed Date | 2013-08-08 |
United States Patent
Application |
20130202425 |
Kind Code |
A1 |
BALK; Wouter |
August 8, 2013 |
Turbojet engine case, notably intermediate case
Abstract
The present invention relates to an annular case (20) of a
multi-flow turbojet engine comprising a first element (22) forming
a hub, a second element (24) forming a cylindrical casing, radially
on the outside of and concentric with the first element, radial
arms (23) connecting the first element (22) to the second element
(24), at least part of said arms being structural and having an
aerodynamic flow straightener vane profile, characterized in that
it comprises a first ring sector (20C) of the case and a second
ring sector (20T), the first ring sector being made of composite
material and the second ring sector of metal, said radial arms
(23T) of the second ring sector (20T) being structural.
Inventors: |
BALK; Wouter; (Melun,
FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BALK; Wouter |
Melun |
|
FR |
|
|
Assignee: |
SNECMA
Paris
FR
|
Family ID: |
44588083 |
Appl. No.: |
13/557722 |
Filed: |
July 25, 2012 |
Current U.S.
Class: |
415/200 |
Current CPC
Class: |
Y02T 50/672 20130101;
F01D 9/065 20130101; F01D 9/041 20130101; Y02T 50/60 20130101; F05D
2240/128 20130101; F05D 2300/603 20130101; F01D 25/24 20130101;
Y02T 50/673 20130101 |
Class at
Publication: |
415/200 |
International
Class: |
F01D 25/24 20060101
F01D025/24 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 25, 2011 |
FR |
11 56769 |
Claims
1. An annular case of a multi-flow turbojet engine comprising a
first element forming a hub, a second element forming a cylindrical
casing, radially on the outside of and concentric with the first
element, radial arms connecting the first element to the second
element, at least part of said arms being structural and having an
aerodynamic flow straightener vane profile, said annular case
further comprising a first ring sector of the case and a second
ring sector, the first ring sector being made at least partially of
composite material and the second ring sector of metal, said radial
arms of the second ring sector being structural.
2. The case according to claim 1, in which the first ring sector
has a resin impregnated fibrous structure.
3. The case according to claim 2, in which the first ring sector is
of one piece and the radial arms of the first sector form flow
straightener vanes.
4. The case according to claim 3, in which the second ring sector
is of one piece.
5. The case according to claim 4, in which the second ring sector
is a casting.
6. The case according to claim 4, in which the second ring sector
is made of titanium alloy.
7. The case according to claim 6, in which the two ring sectors are
joined together by bolting.
8. The case according to claim 7, in which the two ring sectors are
joined together using fishplates.
9. The case according to claim 8, in which the second element of
the second ring sector comprises attachment means for fixing the
turbojet engine, on which the case is mounted, to the structure of
an aircraft; the angle subtended at the center of the second ring
sector being comprised between 30.degree. and 120.degree..
10. A multi-flow turbojet engine comprising an intermediate case at
least partially incorporating a case according to claim 1.
Description
[0001] The present invention relates to the field of multi-flow
turbojet engines and is aimed more particularly at a case element
which is usually termed the intermediate case.
PRIOR ART
[0002] A multi-flow turbojet engine such as a front fan twin spool
turbofan engine comprises an air intake fixed to a fan case itself
bolted to the outer shroud of the case known as the intermediate
case. The duct downstream of the fan communicates with two
concentric ducts: the primary flow duct and the secondary or bypass
flow duct. The primary flow duct leads to the compression stages
and to the combustion chamber. The latter opens into the flowpath
for the hot gases comprising the turbine wheels driving the
compressors including the fan rotor. Following expansion, the gases
of the primary flow are discharged via a central nozzle. The
secondary flow duct which is annularly on the outside of the duct
for the primary flow is straightened axially then passes between
the arms of the intermediate case before being ejected through a
secondary flow nozzle if the engine is of the type in which the
flows are kept separate.
[0003] The rotary parts of a turbojet engine are guided in their
rotation by rolling bearings generally supported by two case
elements, one of them positioned at the front and forming the
intermediate case and the other at the rear and forming the exhaust
case. Furthermore, the transmission of load between the engine and
the aircraft is performed by attachments secured to these two case
elements.
[0004] The intermediate case is a component which may be of large
diameter in so far as its external diameter is that of the fan. It
comprises a hub through which the rotary shafts of the engine pass
and which supports the bearings thereof, and through which the
primary flow duct also passes. Structural arms extend radially from
the hub as far as an outer cylindrical casing. The latter is formed
of a shroud on which fittings are formed for attachment to a strut
for suspending from an aircraft. Much of the load between the
engine and the aircraft thus passes through this case.
[0005] On account of its structural role and of its size, the case
makes a significant contribution toward the mass of the engine.
This characteristic is all the more pronounced in the case of high
bypass ratio engines in which the ratio between the cold secondary
or bypass flow and the hot primary flow is high, of the order of 12
to 16, which are the target of development work on account of their
low specific fuel consumption.
[0006] It would seem that the diameter of these components cannot
be appreciably increased simply by extrapolating from known
structures.
[0007] The problem is therefore that of finding an intermediate
case structure that is light enough in weight that it can be
incorporated notably by way of intermediate case in a high bypass
ratio engine without impairing the specific consumption
thereof.
[0008] According to one prior art, a bladed disk of fixed guide
vanes is arranged in the secondary or bypass flow duct, the vanes
being designed to straighten, before it is discharged into the
atmosphere, the flow of air set in rotation about the engine axis
by its passage through the fan. These vanes are often known by the
abbreviation OGV, which stands for Outlet Guide Vanes. These vanes
have only an aerodynamic role and are connected to the fan case by
bolted connections. In this case the intermediate case is a
one-piece metal component of all-welded construction. This solution
is undesirable for high bypass ratio engines because the structural
arms of the intermediate case introduce an aerodynamic pressure
drop and thus impair the propulsion efficiency of the engine.
[0009] According to another prior art, the vanes that form flow
straighteners are designed also to act as structural arms. They are
connected by bolted connections to the outer shroud and to the hub
of the case. However, despite the presence of the bolts, these
vanes cannot be removed without the engine being dismantled from
the wing structure of the airplane. The vanes are made of metal, as
too are the shroud and the hub of the case. The disadvantage of
this solution is that it adds the mass of the bolted connections.
In addition, the flow path has to be rebuilt over the bolt heads in
order to prevent the engine flow creating a drag effect.
[0010] One solution that improves on the previous one is described
in Patent Application WO 2010/122053 in the name of the present
applicant. The intermediate case comprises structural arms
connecting between the hub and the outer shroud. These arms combine
the mechanical function of transmitting load and the aerodynamic
function. To do so they comprise, on the one hand, a plurality of
metal ties extending radially along the length of the arms and, on
the other hand, a shell made of composite material surrounding the
ties and forming the aerodynamic exterior surface. However, the
bolted connections are present again in this embodiment too.
[0011] Another solution might make it possible to dispense with the
bolted connections of the previous solution and incorporate the
straightening blades into the hub and the outer shroud. This would
involve designing a one-piece case made of composite material which
would have the additional advantage of saving weight. However, this
solution would be complicated to produce and it would be difficult
to guarantee a quality that was repeatable from one case to
another. Further, if all the straightening vanes were made of
composite a greater thickness would be required between the hub and
the outer shroud. That would lead to a not-negligible pressure drop
within the flow path.
SUMMARY OF THE INVENTION
[0012] It is an object of the invention to improve on the existing
solutions in terms of weight and aerodynamic efficiency.
[0013] Thus, a subject of the invention is an annular case of a
multi-flow turbojet engine comprising a first element forming a
hub, a second element forming a cylindrical casing, radially on the
outside of and concentric with the first element, radial arms
connecting the first annular element to the second annular element,
at least part of said arms being structural and having an
aerodynamic flow straightener vane profile.
[0014] According to the invention, the annular case is
characterized that it comprises a first ring sector and a second
ring sector; the first ring sector is made at least partially of
composite material and the second ring sector is made of metal,
said arms of the second ring sector being structural.
[0015] More specifically, the first case ring sector has a resin
impregnated fibrous structure and notably is of one piece with the
arms that connect the annular elements configured to form flow
straightening vanes and which are incorporated into the two
elements, hub and cylindrical casing, of the first ring sector.
[0016] By means of the invention, most of the transmission of load
is concentrated into the metal part of the second ring sector.
Further, by making the first ring sector as one piece, the bolted
connections are avoided, and this is advantageous in terms of
mass.
[0017] According to another feature, the second ring sector is of
one piece; more specifically, it is a casting notably made of
titanium alloy.
[0018] According to another feature, the two ring sectors are
joined together by bolting; more specifically they are joined
together using fishplates.
[0019] According to another feature, the second element of the
second ring sector comprises attachment means for fixing the
turbojet engine to the structure of an aircraft. Advantageously, in
the context of this application, the angle subtended at the center
of the second ring sector is comprised between 30.degree. and
120.degree..
[0020] The invention also relates to the turbojet engine that
incorporates the new case by way of intermediate case.
BRIEF DESCRIPTION OF THE FIGURES
[0021] Other features and advantages will become apparent from the
following description of one nonlimiting embodiment given with
reference to the attached drawings in which:
[0022] FIG. 1 is half of an axial section through the front part of
a front fan twin spool turbofan engine, showing intermediate case
elements;
[0023] FIG. 2 is a three quarters front perspective view of a case
according to the invention, forming an intermediate case;
[0024] FIGS. 3 and 4 show the detail of the case of FIG. 2;
[0025] FIG. 5 is one step in the production of the first ring
sector according to one mode of manufacture.
DETAILED DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION
[0026] FIG. 1 is taken from Patent Application WO2010/122053 which
relates to an intermediate case structure with arms mechanically
connecting the hub to the outer cylindrical casing. These arms
combine the structural function of transmitting loads between the
hub and the casing and the aerodynamic function of straightening
the secondary or bypass flow. The present invention is aimed at a
case structure that forms an intermediate case that is an
improvement on the solution disclosed in that application.
[0027] Thus, the turbojet engine 1, of axis 3, in FIG. 1 comprises,
in the general direction F in which the air flows from left to
right in the figure, an air intake 2, a fan 4, a splitter 6, that
splits the flow between a annular duct 8 for the primary flow F1
and an annular duct 10 for the secondary or bypass flow F2,
radially on the outside of the primary flow duct 8. The primary
flow F1 is compressed by compression means 7 which lead to the
combustion chamber, not depicted, downstream. The fan is contained
in a fan case 5 which delimits the duct 10 for the secondary or
bypass flow F2 with the fairing of the primary flow duct. The fan
duct 5 is bolted to the outer shroud 14 of the intermediate case
12. This case 12 comprises a hub 15 centered on the axis 3 of the
engine and radial arms 13 mechanically connecting the hub 15 to the
shroud 14 and uniformly distributed about the axis of the engine.
The outer shroud 14 forms a cylindrical casing in aerodynamic
continuation of the internal wall of the fan duct 5. As can be seen
from the figure, the hub 15 comprises openings for the primary flow
duct 8 and a central opening for the shafts of the rotors of the
engine and their bearings.
[0028] In the structure set out in application WO2010/122053, each
arm 13 comprises a metal core formed of ties bolted at their two
ends to the hub and to the shroud and a shell made of composite
material, the exterior surface of which is of an aerodynamic shape
in order to act as a flow straightener.
[0029] The structure of the case of the invention is illustrated in
FIGS. 2 to 4. The case 20, of annular shape about an axis that may
coincide with that of the engine on which it is mounted, comprises
a first element forming a hub 22 and a second element forming a
cylindrical casing 24 leaving an annular space to the hub. Radial
arms 23 mechanically connect the hub and the casing 24 and are
circumferentially distributed about the axis of the case. These
arms 23 have an aerodynamic profile which allows them to straighten
an incident air flow rotating about the axis, i.e. which has an
axial direction with a circumferential component. The flow of air
that has passed through the annular space of the case finds itself
substantially along the axis of the case further downstream. The
number and profile of the arms are thus dictated by the flow
straightener vane function conferred upon them.
[0030] According to the invention, the case here is made up of two
ring sections centered on the axis of the case. The first ring
section 20C is of one piece in as much as the arms 23C are
incorporated into the parts of the first element forming the hub
22C and of the second element forming the casing 24C of the sector,
thereby forming a single piece; the sector is also mainly made of
composite material with a resin impregnated fiber structure. A
metal coating may potentially be applied to the leading edge of the
flow straightening vanes in order to increase their resistance to
erosion and to impact. This leading edge coating is preferably
added on in order to make it easier to replace in the event of
damage.
[0031] The second ring sector 20T is made of metal. Advantageously,
this sector is also of one piece. The radial arms 23T mechanically
connecting the hub and the casing are incorporated into the parts
of the first element forming a hub 22T and of the second element
forming a casing 24T of the ring sector 20T. The ring sector is
preferably obtained using the casting technique and is made of
titanium alloy. The function of the arms 23T is twofold:
aerodynamic and structural. Because of their aerodynamic profile,
the arms 23T act as flow straightening vanes in the same way as the
radial arms 23C. Because of their metal structure they transmit
load between the hub and the casing.
[0032] The two sectors 20C and 20T are fitted together to form the
case 20 and means of attachment between the two components may
consist of fishplates 26 joining the second casing elements 24C and
24T together. The hub elements may also potentially be joined
together. The fishplates are fixed for example by bolting.
[0033] When the case is used as an intermediate case, it comprises
a means of attachment 28 on the casing element 24T. This means of
attachment allows the engine to be suspended from an aircraft strut
for example. It may be cast in with the remainder of the second
ring sector. Through this contrivance, most of the load passes
through the radial arms 23T.
[0034] To ensure this transmission of load between the hub and the
casing, the angle subtended by the second ring sector is preferably
comprised between 30.degree. and 120.degree. with respect to
attachment 28, or even preferably between 15.degree. and 60.degree.
on each side of the attachment.
[0035] Regarding the way in which the first ring sector made of
composite material is manufactured.
[0036] One nonlimiting method of manufacture is to produce a
fibrous structure using, for example, a three dimensional weaving
technique using a weave of the interlock type covering several
layers of warp threads and weft threads. One application of this
three dimensional weaving technique is described in patent FR 2 913
053 in the name of the present applicant for the manufacture of a
fan case.
[0037] In the present application, two 3D textile cloths are woven
in such a way as to cause loops of warp thread to project out from
the plane of weaving. These loops form protrusions that project out
from the plane of weaving and will act as anchoring structures for
the straightener vanes. The arrangement and spacing of the loops
are thus determined by the vanes they are to accept.
[0038] FIG. 5 shows two cylindrical and concentric fibrous
structures 122c and 124c which have been formed from the cloths to
constitute the shrouds that form the first and second elements of
the case. On the cloth of the interior cylinder 122c, the
protrusions 122c' formed by the loops face outward. On the exterior
cylindrical cloth 124c the protrusions 124c' face inward. The
protrusions 122c' and 124c' are aligned in radial directions.
[0039] Fibrous structures 123, made up of fibers such as carbon
fibers which are braided and in the form of sleeves, are then
slipped around each pair of protrusions aligned on one and the same
radius. They form connections between the interior cylindrical
fibrous structure and the exterior cylindrical fibrous structure.
These sleeves are shaped so that, after molding, they will form the
straightening vanes. Once all the sleeves are in position on the
cylindrical structures the entire entity is placed in a suitable
mold, the volume of which corresponds to that of the shrouds, with
the first and second elements 22c and 24c joined together by flow
straightener vanes, and a resin is injected into the mold.
[0040] The component obtained is cut to form the first ring sector
with which the second ring sector is then combined, the assembly
constituting the composite case of the invention. In an alternative
form, the ring sector is formed directly by molding.
[0041] The case structure of the invention thus allows a
significant weight saving by comparison with the prior art, notably
when applied to the intermediate case of a high bypass ratio
engine.
* * * * *