U.S. patent application number 10/902781 was filed with the patent office on 2005-04-28 for abradable device on the blower casing of a gas turbine engine.
This patent application is currently assigned to SNECMA MOTEURS. Invention is credited to Brefort, Francois, Celerier, Eric, Gerain, Eric, Maillard, Pierre-Yves.
Application Number | 20050089390 10/902781 |
Document ID | / |
Family ID | 34089846 |
Filed Date | 2005-04-28 |
United States Patent
Application |
20050089390 |
Kind Code |
A1 |
Gerain, Eric ; et
al. |
April 28, 2005 |
Abradable device on the blower casing of a gas turbine engine
Abstract
The invention concerns a turbine engine with an axis of rotation
B comprising a blower casing (10) and a blower (V) with movable
blades (17). A clearance lies between the internal surface of the
casing and the free ends of the blades. A bearing of the blower is
connected to fixed parts of the turbine engine by connections such
that, in the event of a load on the blower blades, these
connections break and the axis of rotation of the blower oscillates
about the axis of rotation B. The casing comprises, bonded to its
internal surface and over at least part of the extent of the
clearance, a layer of thermoformable foam (19) placed opposite the
ends of the blades (17) of the blower (V). The layer of
thermoformable foam (19) is partly covered with a layer of
abradable substance (14), the thickness of the layer of abradable
substance (14) is such that the free ends of the blades of the
blower do not reach the layer of foam during the normal functioning
of the turbine engine, and, in the event of a load on the blower,
the free ends of the blades at least partly fragment the layer of
abradable substance.
Inventors: |
Gerain, Eric;
(Courcouronnes, FR) ; Celerier, Eric; (Boussy
Saint Antoine, FR) ; Brefort, Francois; (Bernay
Vilbert, FR) ; Maillard, Pierre-Yves; (La Chapelle
Gauthier, FR) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
SNECMA MOTEURS
Paris
FR
|
Family ID: |
34089846 |
Appl. No.: |
10/902781 |
Filed: |
August 2, 2004 |
Current U.S.
Class: |
415/9 |
Current CPC
Class: |
F01D 11/125 20130101;
F01D 21/045 20130101 |
Class at
Publication: |
415/009 |
International
Class: |
F01D 021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 18, 2003 |
FR |
0309989 |
Claims
What is claimed is:
1. Turbine engine with an axis of rotation B comprising a blower
casing (10) and a blower (V) with movable blades (17), a clearance
lying between the internal surface of the casing and the free ends
of the blades, a bearing of the blower being connected to fixed
parts of the turbine engine by connections such that, in the event
of a load on the blower blades, these connections break and the
axis of rotation of the blower oscillates about the axis of
rotation B, wherein the casing comprises, bonded to its internal
surface and over at least part of the extent of the clearance, a
layer of thermoformable foam (19) placed opposite the ends of the
blades (17) of the blower (V), the layer of thermoformable foam
(19) being partly covered with a layer of abradable substance (14),
the thickness of the layer of abradable substance (14) being such
that the free ends of the blades of the blower do not reach the
layer of foam during the normal functioning of the turbine engine,
and, in the event of a load on the blower, the free ends of the
blades at least partly fragment all the layers of abradable
material (14) and thermoformable foam (19).
2. Turbine engine according to claim 1, wherein the thickness of
the layer of foam and of the layer of abradable substance is such
that there exists a clearance remaining between the free ends of
the blades of the blower and the layer of abradable substance
during normal functioning of the engine, this remaining clearance
being sufficiently small to limit the passage of air in order to
preserve a dynamic flow of air whose path is forced by the blades
of the blower.
3. Turbine engine according to claim 1, wherein the layer of
thermoformable foam consists of preformed sectors.
4. Turbine engine according to claim 1, wherein the layer of
thermoformable foam is a layer of polyacrylic imide foam.
5. Turbine engine according to claim 1, wherein the layer of
abradable substance is made from epoxy resin filled with glass
balls.
6. Turbine engine according to claim 1, wherein the layer of
abradable substance is made from silicone filled with glass
balls.
7. Turbine engine according to claim 1, wherein the layer of
abradable substance adheres directly or indirectly to the layer of
thermoformable foam.
8. Blower casing able to form part of a turbine engine according to
claim 1, the casing comprising, bonded to its internal surface, a
layer of thermoformable foam intended to be placed opposite free
ends of the blades (17) of the blower (V), the layer of
thermoformable foam being partly covered with a layer of abradable
substance, the thickness of the layer of abradable substance being
such that the free ends of the blades of the blower do not reach
the layer of foam during the normal functioning of the turbine
engine, and, in the event of a load on the blower, the ends of the
blades at least partly fragment all the layers of abradable
material and thermoformable foam.
Description
FIELD OF THE INVENTION
[0001] The invention concerns the field of gas turbine engines, and
more particularly gas turbine engine blower casings.
BACKGROUND OF THE INVENTION
[0002] In the case of aircraft engines, a bladed blower disc is
situated on the rotor part at the inlet to the engine and precedes
the bladed discs of the compressor. This bladed blower disc
accelerates the air before entering the compressor stages. This
bladed blower disc is liable to receive foreign bodies such as ice,
birds or others. Because of this, this bladed disc is liable to
deform, to cause an imbalance on the blower support shaft and
cyclic loads and vibrations communicated by the blower shaft
support bearings to the fixed parts of the turbine engine, to which
these support bearings are connected.
[0003] To prevent communication of these loads and vibrations, it
is known from the application FR 2 752 024 how to fit a so-called
"fusible" bearing, that is to say the bearing supporting the blower
shaft is connected to the fixed parts of the turbine engine by
fairly weak connections so that they break as soon as a certain
load is exerted on the blower blades. These weak connections can be
screw connections for example. Once the connection is broken, the
bladed disc of the blower continues to turn freely, which avoids
transmitting forces onto the fixed parts of the turbine engine.
However, the axis of rotation of the bladed disc of the blower
oscillates about the fixed axis of rotation of the turbine engine.
This oscillation causes that of the blades, which then violently
touch the blower casing. The latter is thus greatly stressed
mechanically, or even torn, during these shocks.
[0004] To remedy this, panels adhesively bonded to the interior of
the blower casing have been developed, these panels being composed
of a Nomex honeycomb structure filled with an abradable material,
bonded to a glass cloth, itself bonded to an aluminium honeycomb,
the whole being bonded to the blower casing. Such a technology is
expensive and repairs must be carried out in specialist workshops,
particularly in the case of casings with a specific shape, for
example conical.
SUMMARY OF THE INVENTION
[0005] The present invention aims to improve the situation.
[0006] The invention concerns a turbine engine with an axis of
rotation comprising a blower casing and a blower with movable
blades, a clearance lying between the internal surface of the
casing and the free ends of the blades, a bearing of the blower
being connected to fixed parts of the turbine engine by connections
such that, in the event of a load on the blower blades, these
connections break and the axis of rotation of the blower oscillates
about the axis of rotation of the turbine engine.
[0007] According to a first characteristic of the invention, the
casing comprises, bonded to its internal surface and over at least
part of the extent of the clearance, a layer of thermoformable foam
placed opposite the ends of the blades of the blower, the layer of
thermoformable foam being partly covered with a layer of abradable
substance, the thickness of the layer of abradable substance being
such that the free ends of the blades of the blower do not reach
the layer of foam during the normal functioning of the turbine
engine, and, in the event of a load on the blower, the free ends of
the blades at least partly fragment all the layers of abradable
material and thermoformable foam.
[0008] Optional characteristics of the turbine engine according to
the invention, complementary or in substitution, are set out
below:
[0009] the thickness of the layer of foam and of the layer of
abradable substance is such that there exists a clearance remaining
between the free ends of the blades of the blower and the layer of
abradable substance during normal functioning of the engine, this
remaining clearance being sufficiently small to limit the passage
of air in order to preserve a dynamic flow of air whose path is
forced by the blades of the blower,
[0010] the layer of thermoformable foam consists of preformed
sectors,
[0011] the layer of thermoformable foam is a layer of polyacrylic
imide foam,
[0012] the layer of abradable substance is made from epoxy resin
filled with glass balls,
[0013] the layer of abradable substance is made from silicone
filled with glass balls,
[0014] the layer of abradable substance adheres directly or
indirectly to the layer of thermoformable foam.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The following figures non-limitingly illustrate embodiments
of the invention:
[0016] FIG. 1 depicts a view in section of a front part of a
turbine engine comprising a blower connected by a fusible bearing
to the fixed parts of the turbine engine,
[0017] FIG. 2A depicts in section part of the inlet to the gas
turbine engine comprising an example of a blower casing according
to the prior art,
[0018] FIG. 2B depicts in section part of the inlet of the gas
turbine engine comprising an example of a blower casing according
to the invention,
[0019] FIG. 3 is a detail of FIG. 2B representing the interaction
between a blower blade and the blower casing according to the
invention.
[0020] The drawings contain essentially elements of a certain
character. They can therefore not only serve to give a better
understanding of the description but also contribute to the
definition of the invention, where applicable.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0021] FIG. 1 depicts a section of a turbine engine T along its
axis of rotation. This section comprises a blower V for
accelerating the air before the entry to the stages of the
compressor C, and then a high-pressure compressor CC. The blower V
comprises a disc provided with blades 17 connected by screwing to
the front end BA of a blower shaft AV mounted on a front bearing
PAV and a rear bearing PAR as detailed in the application FR 2 752
024. The front and rear bearings are supported by support pieces
connected to a fixed part of the turbine engine (the stator), at
least one of the bearings being connected by connections which are
sufficiently fragile to break when there is an excessive load on a
blower blade. Such a bearing is referred to as a "fusible bearing".
These weak connections can be connections by screws whose
cross-section is reduced over part of the length of the screw for
example. Once the connection is broken, the bladed disc of the
blower continues to turn freely, which avoids transmitting forces
to the fixed parts of the turbine engine. However, the axis of
rotation of the bladed disc of the blower oscillates about the
fixed axis of rotation of the turbine engine. This oscillation
generates that of the blades, which then violently touch the blower
casing. The latter is thus greatly stressed mechanically, or even
torn, during these shocks.
[0022] As known to persons skilled in the art, FIG. 2A depicts a
part of the turbine engine T comprising a blower V followed by a
compressor C. This turbine engine part comprises a casing 10
forming the stator part S of the blower V and a casing forming the
rotor part R of the turbine engine. The shaft of the rotor part of
the turbine engine is driven in rotation by a turbine situated
downstream of the compressor. The axis of rotation is denoted B.
The external surface of the casing of the rotor part and the
internal surface of the casing of the stator part delimit a "flow
stream" for the air flow. The bladed disc 18 of the blower V
comprising blades 17 is fixed to the rotor R.
[0023] The bladed blower disc is situated at the inlet to the
engine and precedes the bladed discs of the compressor. In FIG. 2A,
the shaft of the blower is assumed to be supported by at least one
front bearing PAV forming a fusible bearing. To respond to the
impacts of the blades of the blower against the casing 8, there
have been developed panels 3 bonded to the inside of this blower
casing 10, these panels being composed of a Nomex honeycomb
structure filled with abradable material, bonded to a glass cloth,
itself bonded to an aluminium honeycomb, the whole being bonded to
the blower casing. The thickness of these panels makes it possible
to preserve the flow stream so that in normal functioning the ends
of the blades of the blower disc do not come into contact with
these panels. The technology of the panels in FIG. 2A have
drawbacks of cost, and the repair and fitting of these panels must
be carried out in equipped workshops. In addition, the materials
used are not isotropic, the manufacture of the honeycomb structure
for a casing of special shape (for example conical) is more complex
because of the mechanical characteristics of this structure and the
honeycombs are subject to buckling.
[0024] The invention makes it possible to remedy these
drawbacks.
[0025] As in FIG. 2A, FIG. 2B illustrates a part of a turbine
engine T comprising the blower V followed by the compressor C. The
bladed disc 18 of the blower V comprising blades 17 is fixed to the
rotor R. Reference will also be made to FIG. 3, showing in detail
the casing 10 positioned opposite the ends of the blades of the
bladed discs 18. In the example in FIG. 2B, the casing 10 has the
general shape of a truncated cone whose axis of symmetry coincides
with the axis of rotation B of the turbine engine. From upstream to
downstream, that is to say the direction of flow of the air flow or
from the blower inlet to the compressor inlet, the casing 10 of the
blower V comprises a first truncated cone part 20 connected to a
ring with a diametral step 21 itself connected to a second
truncated cone part 22. The internal surface of the first truncated
cone part 20 delimits the air flow stream. The ends of the blades
are placed opposite the internal surface of the second truncated
cone part 22 and are distant from this internal surface by an
internal annular space 15. A clearance e is spoken of, for example
of 20 mm between the internal surface of the blower casing and the
free ends of the blades.
[0026] Over at least part of the internal wall of the second
truncated cone part there is bonded a layer of thermoformable foam
19 by means of a film of adhesive 12. In the example in FIGS. 2B
and 3, the layer of thermoformable foam has a shape complementary
to that of the internal annular space so as to fill the latter.
Advantageously, the layer of foam has an axial width lg
corresponding at least to the axial width lc along the axis B of
the free end of the blades 17 of the blower V. The layer of
thermoformable foam 19 is covered with a layer of abradable
substance 14, over at least the axial width lc of the ends of the
blades. The thickness of the layer of abradable substance is such
that the free ends of the blades of the blower do not reach the
layer of foam during normal functioning of the engine.
Advantageously, the layer of thermoformable foam covered with
abradable substance entirely fills the internal annular space and
is machined so that there is no discontinuity with the internal
surface of the first cone part, the flow stream thus being
preserved. More particularly, the thickness of the layer of
abradable substance is such that there exists a clearance between
the free ends of the blades of the blower and the layer of
abradable substance during normal functioning of the engine, this
clearance being sufficiently small to limit the passage of air in
order to preserve a dynamic flow of the air whose path is forced by
the blower blades. Downstream of this layer acoustic panels 13 can
be positioned so as to preserve the continuity of the flow
stream.
[0027] In the example in FIGS. 2B and 3, the width lg is greater
than the width lc and the internal annular space 15 is delimited by
an upstream stop.
[0028] Other embodiments are possible: for example, the blower
casing can consist of a single piece (frustoconical, cylindrical or
other) with symmetry of revolution covered on its internal surface
with a protective screen consisting of a layer of thermoformable
foam, itself partly covered with an abradable substance. As
previously, the layers of thermoformable foam and abradable
substance, referred to as "large clearance" abradable layers, are
placed opposite the ends of the blades. The blower casing has a
clearance between its internal surface and the free ends of the
blades so as to a stick a certain thickness of layers on the
internal surface of the casing, for example around 20 mm. The flow
stream is preserved by the fitting, upstream and downstream of the
protective layers, of acoustic panels for example.
[0029] The protection of the casing, in the case of rupture of the
breaking connection of the fusible bearing, is effected by the
screen consisting of thermoformable foam and the abradable
substance. In this case, the bearings of the blower shaft are no
longer connected to the fixed parts of the turbine engine and the
axis of rotation of the blower oscillates about the axis of
rotation B of the turbine engine. The ends of the blades dig into
the screen by fragmentation of material. Advantageously, the
presence of the layer of thermoformable foam offers resistance to
the removal of material which is less than the layer of abradable
substance, which allows the pulverisation of all the "large
clearance" abradable layers in the event of rupture of the bearing
fuses.
[0030] To facilitate the fitting of the layer of thermoformable
foam, the latter consists of preformed sectors. By way of example,
the layer of thermoformable foam is a layer of polyacrylic imide
foam. Also by way of example, the layer of abradable substance can
be made from epoxy resin loaded with glass balls, silicone loaded
with glass balls or any other material having the abrasion
properties of an abradable substance.
[0031] More particularly, the layer of abradable substance adheres
to the layer of thermoformable foam through its adhesive properties
and by diffusion in the cells of the thermoformable foam.
[0032] By virtue of these layers of "large clearance" abradable,
the casing is not damaged during abnormal functioning (for example
in the case of ingestion of a foreign body). The use of
thermoformable foam allows simple shaping, the machining being able
to be carried out before the shaping, for example for a conical
blower casing part, with a changing profile. The layers of "large
clearance" abradable can be repaired without equipment requiring a
dedicated workshop, which offers a saving in time and money.
[0033] The thickness of these layers makes it possible to preserve
the flow stream so that, in normal functioning, the ends of the
blades of the blower disc do not come into contact with these
layers.
[0034] The invention is not limited to the embodiments of the
fixing device described above, solely by way of example, but
encompasses all variants which can be envisaged by a person skilled
in the art in the context of the following claims.
[0035] The invention does not apply solely to the
frustoconical-shaped casing but can also apply in the case of all
other casing shapes, for example cylindrical.
* * * * *