U.S. patent application number 11/517299 was filed with the patent office on 2008-03-13 for fan case abradable.
Invention is credited to Barry Barnett, David Denis, Andreas Eleftheriou.
Application Number | 20080063508 11/517299 |
Document ID | / |
Family ID | 39153717 |
Filed Date | 2008-03-13 |
United States Patent
Application |
20080063508 |
Kind Code |
A1 |
Barnett; Barry ; et
al. |
March 13, 2008 |
Fan case abradable
Abstract
A fan case and method of manufacturing a fan case, for a gas
turbine engine, where the fan case has a hollow tubular metal shell
with: a central axis of symmetry; an inlet; an outlet; and
peripheral wall about the axis to encompass the tips of a plurality
of rotary fan blades, and the shell wall includes an upstream
portion defining an annular abradable material recess that extends
axially having an upstream end at the shell inlet and a downstream
end located upstream from the shell outlet.
Inventors: |
Barnett; Barry; (Markham,
CA) ; Denis; David; (Burlington, CA) ;
Eleftheriou; Andreas; (Woodbridge, CA) |
Correspondence
Address: |
OGILVY RENAULT LLP (PWC)
1981 MCGILL COLLEGE AVENUE, SUITE 1600
MONTREAL
QC
H3A 2Y3
US
|
Family ID: |
39153717 |
Appl. No.: |
11/517299 |
Filed: |
September 8, 2006 |
Current U.S.
Class: |
415/9 |
Current CPC
Class: |
F01D 11/122 20130101;
F02K 3/06 20130101 |
Class at
Publication: |
415/9 |
International
Class: |
F01D 21/00 20060101
F01D021/00 |
Claims
1. A fan case, for a gas turbine engine, comprising: a hollow
tubular metal shell having: a central axis of symmetry; an inlet;
an outlet; and peripheral wall about the axis to encompass the tips
of a plurality of rotary fan blades, wherein: the shell wall
includes an upstream portion defining an annular abradable material
recess that extends axially having an upstream end at the shell
inlet and a downstream end located upstream from the shell
outlet.
2. A fan case according to claim 1 wherein the shell inlet has an
inlet diameter and wherein the recess has a recess diameter that is
no greater than the inlet diameter.
3. A fan case according to claim 2 wherein the recess diameter is
tapered in a downstream direction having a maximum recess diameter
at the upstream end that is equal to the inlet diameter and a
minimum recess diameter at the downstream end of the recess.
4. A fan case according to claim 1 including abradable material
filling said recess and defining an upstream edge of unsupported
abradable material radially inward of the shell inlet.
5. A fan case according to claim 1 wherein the shell includes a
front flange at the inlet and a rear flange at the outlet, and
wherein the front flange has an external diameter greater than an
external diameter of the rear flange.
6. A fan case according to claim 1 including molded abradable tiles
bonded to the shell and filling the recess.
7. A fan case according to claim 6 wherein the molded abradable
tiles have a molded upstream edge of unsupported abradable material
that is disposed radially inward of the shell inlet on
installation.
8. A method of manufacturing a fan case comprising the steps of:
fabricating a hollow tubular metal shell having: a central axis of
symmetry; an inlet; an outlet; and peripheral wall about the axis
to encompass the tips of a plurality of rotary fan blades, the
shell wall including an upstream portion defining an annular
abradable material recess that extends axially having an upstream
end at the shell inlet and a downstream end located upstream from
the shell outlet; and filling the recess with abradable material
filling said recess and defining an upstream edge of unsupported
abradable material radially inward of the shell inlet.
9. A method of manufacturing according to claim 8 wherein the step
of filling the recess includes: molding prefabricated abradable
material tiles apart from the shell; and bonding said tiles to the
recess in the shell.
10. A method of manufacturing according to claim 9 wherein the
prefabricated abradable material tiles are molded with an upstream
edge of unsupported abradable material for installation radially
inward of the shell inlet.
11. A method of manufacturing according to claim 8 wherein the step
of fabricating the hollow tubular metal shell consists of metal
fabrication procedures selected from the group consisting of:
pressing forming sheet metal; welding; rolling sheet metal; spin
forming.
12. A method of manufacturing according to claim 8 wherein the step
of fabricating the hollow tubular metal shell does not include
forging the metal shell as a single oversized forging and then
machining to remove excess metal material.
Description
TECHNICAL FIELD
[0001] The invention relates to a fan case for a gas turbine engine
having abradable material.
BACKGROUND OF THE ART
[0002] Typically, fan cases are constructed of a metal shell with
abradable material encapsulated or bounded by metal surfaces within
a recess machined into the metal shell surface. Since the abradable
material is relatively soft and fragile, placing the abradable
material in the recess between upstream and downstream walls of
relatively tough and resilient metal of the shell provides
protection. However, this approach is costly in time, labour, and
material use, and there is room for improvement.
[0003] Features that distinguish the present invention from the
background art will be apparent from review of the disclosure,
drawings and description of the invention presented below.
DISCLOSURE OF THE INVENTION
[0004] The invention provides a fan case, for a gas turbine engine,
where the fan case has a hollow tubular metal shell with: a central
axis of symmetry; an inlet; an outlet; and peripheral wall about
the axis to encompass the tips of a plurality of rotary fan blades,
and the shell wall includes an upstream portion defining an annular
abradable material recess that extends axially having an upstream
end at the shell inlet and a downstream end located upstream from
the shell outlet.
[0005] The invention also provides a method of manufacturing a fan
case comprising the steps of: fabricating a hollow tubular metal
shell having: a central axis of symmetry; an inlet; an outlet; and
peripheral wall about the axis to encompass the tips of a plurality
of rotary fan blades, the shell wall including an upstream portion
defining an annular abradable material recess that extends axially
having an upstream end at the shell inlet and a downstream end
located upstream from the shell outlet; and filling the recess with
abradable material filling said recess and defining an upstream
edge of unsupported abradable material radially inward of the shell
inlet.
DESCRIPTION OF THE DRAWINGS
[0006] In order that the invention may be readily understood, one
embodiment of the invention is illustrated by way of example in the
accompanying drawings.
[0007] FIG. 1 is an axial cross-sectional view through a prior art
gas turbine engine, showing the various components that are
assembled to produce an engine, and an example of a prior art fan
case with an encapsulated layer of abradable material.
[0008] FIG. 2 is a detailed axial cross-sectional view through
another example of a prior art fan case with an encapsulated layer
of abradable material having metal to metal contact in an upstream
portion with abradable material recess downstream.
[0009] FIG. 4 is a detailed sectional view of the embodiment shown
in FIG. 3.
[0010] FIG. 5 is an exploded isometric view of the metal fan case
shell bounded by front and rear flanges, and showing abradable
material tiles removed from the recess in which they are
bonded.
[0011] FIG. 6 is a like isometric view of the metal fan case shell
showing abradable material tiles installed in the recess.
[0012] Further details of the invention and its advantages will be
apparent from the detailed description included below.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0013] FIG. 1 shows an axial cross-section through a turbo-fan gas
turbine engine. It will be understood however that the invention is
equally applicable to any type of engine with a combustor and
turbine section such as a turbo-shaft, a turbo-prop, or auxiliary
power units. Air intake into the engine passes over fan blades 1 in
a fan case 2 and is then split into an outer annular flow through
the bypass duct 3 and an inner flow through the low-pressure axial
compressor 4 and high-pressure centrifugal compressor 5. Compressed
air exits the compressor 5 through a diffuser 6 and is contained
within a plenum 7 that surrounds the combustor 8. Fuel is supplied
to the combustor 8 through fuel tubes 9 which is mixed with air
from the plenum 7 when sprayed through nozzles into the combustor 8
as a fuel air mixture that is ignited. A portion of the compressed
air within the plenum 7 is admitted into the combustor 8 through
orifices in the side walls to create a cooling air curtain along
the combustor walls or is used for cooling to eventually mix with
the hot gases from the combustor and pass over the nozzle guide
vane 10 and turbines 11 before exiting the tail of the engine as
exhaust.
[0014] The prior art fan case 2 shown in FIG. 1 has a recessed
portion adjacent the tips of the fan blades 1 that includes an
encapsulated layer of abradable material 12 and some designs
include other impact absorbent materials such as ballistic fabric
or mesh and metal honeycomb structures. The recess to house the
abradable material in the prior art is radially outward of the
front flange 13 and the fan case 2 is bolted to the engine with the
rear flange 14. Due to the geometry of the recess, the fan case 2
is generally fabricated by machining the recess from an oversized
casting and abradable material 12 is plasma spray coated into the
recess.
[0015] FIG. 2 shows another example of a prior art fan case 2 with
an enclosed layer of abradable material 12. The upstream tip of the
blade 1 is in metal to metal contact with a circumferentially
grooved portion of the fan case shell 15 and the blade tips contact
the abradable material 12 housed in the recess downstream. Metal of
the fan case shell 15 axially bounds or encapsulates the relatively
softer abradable material 12 upstream and downstream in this prior
art example as well.
[0016] FIG. 3 shows an axial cross-section through the fan case 2
according to the invention with the fan case 2 being fabricated
with a hollow tubular metal shell 15 having a central axis 16 of
symmetry; an inlet surrounded by the front flange 13; an outlet
surrounded by the rear flange 14; and peripheral metal wall 17
about the axis 16 to encompass the tips of the rotary fan blades
1.
[0017] As better seen in the detail of FIG. 4, the shell wall 17
includes an upstream portion defining an annular abradable material
recess 18. The recess 18 fully extends axially from it's upstream
end at the shell inlet 19 surrounded by the front flange 13 to the
downstream end 21 located upstream from the shell outlet 20
surrounded by the rear flange 14.
[0018] The shell inlet 19 has an inlet diameter and the recess has
a recess diameter that is no greater than the inlet diameter.
Compared to the prior art examples shown in FIGS. 1-2, the prior
art examples show recess diameters greater than the inlet diameters
and hence the abradable material is axially bounded by the metal of
the fan case shell 15 in the prior art.
[0019] The recess diameter shown in the embodiment of FIGS. 3-4 is
tapered in a downstream direction having a maximum recess diameter
at the upstream end of the recess 18 that is equal to the shell
inlet diameter and a minimum recess diameter at the downstream end
21 of the recess 18. The abradable material 12 partially or fully
fills the recess and an upstream edge 22 of unsupported abradable
material 12 radially inward of the shell inlet 19.
[0020] The shell 15 includes a front flange 13 at the inlet 19 to
which an inlet cowl is bolted and a rear flange 14 at the outlet 20
to bolt the fan case 2 to the engine. Of advantage in
manufacturing, the front flange 13 has an external diameter greater
than an external diameter of the rear flange 14 as illustrated with
a dashed line parallel to the axis 16. This feature enables access
to use simple metal forming techniques and reduces the need to use
relatively expensive metal forging and machining methods of the
prior art. Fabricating the hollow tubular metal shell 15 can be
accomplished with less expensive metal fabrication procedures such
as: press forming sheet metal; welding; rolling sheet metal; and
spin forming and need not follow the prior art methods of forging
the metal shell 15 as a single oversized forging and then machining
to remove excess metal material.
[0021] As best seen in FIGS. 5-6 the metal fan case shell 15 may be
fabricated with the forwardly open recess 18 and prefabricated
molded abradable tiles 23 can slide into the recess 18 to be bonded
to the metal shell 15 thereby filling the recess 18. In the
embodiment illustrated there are four tiles 23 each covering one
quarter of the circumference of the recess 18, however various
other tile patterns can be used. The axial seam between the tiles
23 may be filled and bonded together to fill the entire recess 18.
The molded abradable tiles 23 also have a molded upstream edge 22
of unsupported abradable material 12 that is disposed radially
inward of the shell inlet on installation.
[0022] As a result of using prefabricated molded tiles 23 costs may
be reduced and a greater variety of materials can be used for the
abradable layer 12. Molding of the tiles 23 frees the choice of
abradable materials from materials that can be powdered and plasma
spray coated to materials that can be molded and then bonded to
metal.
[0023] Although the use of a particular abradable tile is described
and preferred, any suitable abradable provided in any suitable
format may be used with the present method and/or apparatus.
[0024] Recapping the process of manufacturing a fan case 2 in
accordance with the invention, the following steps are involved. A
hollow tubular metal shell 15 is fabricated having: a central axis
of symmetry 16; an inlet 19; an outlet 20; and peripheral wall 17
about the axis 16 to encompass the tips of a plurality of rotary
fan blades 1. The metal shell wall 17 includes an upstream portion
defining an annular abradable material recess 18 that extends
axially from the upstream end at the shell inlet 19 to the
downstream end 21 located upstream from the shell outlet 20. The
recess 18 is filled with abradable material 12 leaving an upstream
edge 22 of unsupported abradable material 12 radially inward of the
metal shell inlet 19.
[0025] Since the abradable material 12 can slide into the recess 18
as shown in FIGS. 5-6, the step of filling the recess 18 can
include molding prefabricated abradable material tiles 23 apart
from the metal shell 15 and then bonding the tiles 23 into the
recess 18 formed in the shell 15.
[0026] Although the above description relates to a specific
preferred embodiment as presently contemplated by the inventors, it
will be understood that the invention in its broad aspect includes
mechanical and functional equivalents of the elements described
herein.
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