U.S. patent application number 11/491924 was filed with the patent office on 2006-11-23 for turbine exhaust case and method of making.
This patent application is currently assigned to Pratt & Whitney Canada Corp.. Invention is credited to Mike Fontaine, Eugene Gekht, Martin Jutras.
Application Number | 20060260127 11/491924 |
Document ID | / |
Family ID | 35597964 |
Filed Date | 2006-11-23 |
United States Patent
Application |
20060260127 |
Kind Code |
A1 |
Gekht; Eugene ; et
al. |
November 23, 2006 |
Turbine exhaust case and method of making
Abstract
A structural turbine exhaust case of a gas turbine engine,
comprises inner and outer case portions; a bearing housing
connected to the inner case portion for supporting a main spool of
the gas turbine engine; and a plurality of airfoils extending
between the inner and outer case portions, airfoils structurally
connecting the inner case portion to the outer case portion.
Inventors: |
Gekht; Eugene; (Brossard,
CA) ; Fontaine; Mike; (Candlac, CA) ; Jutras;
Martin; (St. Amable, CA) |
Correspondence
Address: |
OGILVY RENAULT LLP (PWC)
1981 MCGILL COLLEGE AVENUE
SUITE 1600
MONTREAL
QC
H3A 2Y3
CA
|
Assignee: |
Pratt & Whitney Canada
Corp.
Longueuil
CA
|
Family ID: |
35597964 |
Appl. No.: |
11/491924 |
Filed: |
July 25, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10892497 |
Jul 16, 2004 |
7100358 |
|
|
11491924 |
Jul 25, 2006 |
|
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Current U.S.
Class: |
29/889.21 ;
29/889.2 |
Current CPC
Class: |
B23K 15/04 20130101;
Y02T 50/673 20130101; Y02T 50/60 20130101; F05D 2230/60 20130101;
F01D 9/065 20130101; B23K 15/0093 20130101; F02K 1/386 20130101;
Y10T 29/4932 20150115; Y02T 50/671 20130101; F01D 7/00 20130101;
F05D 2230/232 20130101; Y10T 29/49321 20150115; F01D 25/162
20130101; F01D 5/3061 20130101; B23K 2101/001 20180801; B23K 26/28
20130101; F02K 1/48 20130101 |
Class at
Publication: |
029/889.21 ;
029/889.2 |
International
Class: |
B23P 15/04 20060101
B23P015/04 |
Claims
1. A method of welding an end of a sheet metal airfoil to an
annular case of a gas turbine engine, comprising: inserting the end
of the airfoil into a matingly-profiled opening of the case wall;
and applying a weld fillet extending along an periphery of the
profiled opening and fully penetrating through an entire thickness
of the case wall, wherein the case wall thickness is adapted to
permit said full penetration.
2. The method as claimed in claim 1 wherein said end of the airfoil
protrudes through said opening by a predetermined amount to form a
protrusion, the predetermined amount being an amount which will be
substantially consumed in the weld, such that substantially no
protrusion remains after welding is completed.
3. The method as claimed in claim 1 wherein the weld fillet
penetrates through substantially an entire thickness of the sheet
metal of the case.
4. A method of fabricating a turbine exhaust case of a gas turbine
engine, comprising: providing inner and outer case portions with
profiled openings therein; providing a bearing housing for
supporting a main spool of the gas turbine engine; providing a
plurality of sheet metal airfoils; and brazing the bearing housing
to the inner case portion and welding the respective airfoils at
opposed ends thereof to the respective inner and outer case
portions, thereby structurally connecting the inner and outer case
portions to bear a load of the main spool of the engine supported
by the bearing housing.
5. A method as claimed in claim 4 comprising steps of inserting one
end of an airfoil into a corresponding profiled opening in the
respective inner and outer case portions and forming weld
penetrating through the an entire thickness of the respective case
portions and penetrating through an entire thickness of the sheet
metal of the airfoil.
6. A method as claimed in claim 5 wherein said end of the airfoil
is inserted into the corresponding profiled opening from one side
of the respective inner and outer case portions to have a
predetermined portion of the airfoil protruding from the other side
of the respective inner and outer case portions, the predetermined
protruding portion being substantially consumed in weld.
7. A method as claimed in claim 6 wherein one of the laser beam and
electron beam is applied to said end of the airfoil at said other
side of the respective inner and outer case portions.
8. A method of welding a profiled sheet metal element to a metal
host having a matingly-profiled opening therethrough, the method
comprising the step of: inserting an end profiled sheet metal
element into the matingly-profiled opening from a first face side
of the host such that a portion of the element protrudes through
the opening and extends a height above a second face side of the
host; and applying a weld fillet from the second face side along a
periphery of the opening; wherein the protrusion height is selected
so that the protruding portion is substantially consumed during the
step of applying a fillet weld.
9. The method of claim 8 wherein the metal host has a thickness
between the first and second face sides, and wherein the thickness
is selected such that the step of applying a fillet results in full
penetration through the host substantially around the opening.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 10/892,497, filed Jul. 16, 2004.
FIELD OF THE INVENTION
[0002] The present invention relates to gas turbine engines, and
more particularly to a turbine exhaust case of an gas turbine
engine.
BACKGROUND OF THE INVENTION
[0003] A "non-structural" turbine exhaust case typically used for
gas turbines and is basically little more than an aerodynamic
fairing, and carries no additional load other than its own weight
and any aerodynamic loading effecting thereon. A "structural"
turbine exhaust case on the other hand not only supports its own
weight and any aerodynamic loading, but also supports a bearing
housing and bearing for a main spool of the engine, typically, the
low pressure spool. Present state of the art structural turbine
exhaust cases, and in particular the bearing housing and the
airfoils components, are made of cast components. However, cast
components used in smaller airborne gas turbine engines (e.g. about
2000 lbs thrust and under) will increase the weight and thereby
cost of manufacturing. Thus it would be desirable to provide a
configuration with the strength-to-weight ratio.
SUMMARY OF THE INVENTION
[0004] One object of the present invention is to provide a improved
structural turbine exhaust case.
[0005] In accordance with one aspect of the present invention,
there is a turbine exhaust case of a gas turbine engine which
comprises inner and outer case portions defining an annual gas path
therebetween, the inner case portion including a bearing housing
portion adapted to support a main spool bearing of the gas turbine
engine, the outer case including a connection apparatus for
supportably connecting the turbine exhaust case to the gas turbine
engine and a plurality of sheet metal airfoils extending between
the inner and outer case portions, the sheet metal airfoils
structurally connecting the inner case portion to the outer case
portion and supporting inner case relative to outer case.
[0006] In accordance with another aspect of the present invention,
there is a turbine exhaust case of a gas turbine engine, which
comprises inner and outer case portions, a bearing housing
connected to and supported by the inner case portion for supporting
a main spool of the gas turbine engine, a plurality of airfoils
extending between the inner and outer case portions, the airfoils
structurally connecting and supporting the inner case portion to
the outer case portion and wherein the inner case portions are
sheet metal.
[0007] In accordance with a further aspect of the present
invention, there is a method provided for welding an end of a sheet
metal airfoil to an annular case of a gas turbine engine, which
comprises inserting the end of the airfoil into a matingly-profiled
opening of the case wall and applying a weld fillet extending along
an periphery of the profiled opening and fully penetrating through
an entire thickness of the case wall, wherein the case wall
thickness is adapted to permit said full penetration.
[0008] In accordance with a still further aspect of the present
invention, there is a method provided for fabricating a turbine
exhaust case of a gas turbine engine, which comprises providing
inner and outer case portions with profiled openings therein,
providing a bearing housing for supporting a main spool of the gas
turbine engine, providing a plurality of sheet metal airfoils, and
brazing the bearing housing to the inner case portion and welding
the respective airfoils at opposed ends thereof to the respective
inner and outer case portions, thereby structurally connecting the
inner and outer case portions to bear a load of the main spool of
the engine supported by the bearing housing.
[0009] In accordance with a yet further aspect of the present
invention, there is a method for welding a profiled sheet metal
element to a metal host having a matingly profiled opening
therethrough, which comprises the step of inserting an end profiled
sheet metal element into the matingly-profiled opening from a first
face side of the host such that a portion of the element protrudes
through the opening and extends a height above a second face side
of the host and applying a weld fillet from the second face side
along a periphery of the opening, wherein the protrusion height is
selected so that the protruding portion is substantially consumed
during the step of applying a fillet weld.
[0010] The present invention advantageously provides a structural
turbine exhaust case which is lighter in weight and more reliable
in operation, resulting from improved welding quality of the
airfoils connected to the inner and outer case portions.
[0011] Other advantages and features of the present invention will
be better understood with reference to a preferred embodiment
described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Reference will now be made to the accompanying drawings by
way of illustration showing a preferred embodiment of the present
invention in which:
[0013] FIG. 1 is a cross-sectional view of a bypass gas turbine
engine, as an exemplary application of the present invention;
[0014] FIG. 2A is a perspective view of a structural turbine
exhaust case incorporating one embodiment of the present invention
and used in the engine of FIG. 1, while FIG. 2B is a cross-section
of the same installed on the engine;
[0015] FIG. 3 is a cross-sectional view of a sheet metal airfoil of
the embodiment of FIG. 2A;
[0016] FIG. 4 is a cross-sectional view of a sheet metal strut of
the embodiment of FIG. 2A;
[0017] FIG. 5 is a partial top plan view of an outer case portion
of the embodiment of FIG. 2A, showing a profiled opening therein
for receiving an outer end of the airfoil before welding;
[0018] FIG. 6 is a schematic cross-sectional view of an airfoil
conventionally welded at an end thereof to a case wall;
[0019] FIG. 7 is a schematic cross-sectional view of an end of an
airfoil inserted into a profiled opening of a case wall before
welding according to the welding method of the present
invention;
[0020] FIG. 8 is a view similar to FIG. 7, showing a welded
configuration of the airfoil connected to the case wall according
to the welding method of the present invention.
[0021] It will be noted that throughout the appended drawings, like
features are identified by like reference numerals.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] A bypass gas turbine engine seen generally in FIG. 1
includes a housing or nacelle 10, a low pressure spool assembly
seen generally at 12 which includes a fan 11, low pressure
compressor 13 and low pressure turbine 15, a high pressure spool
assembly seen generally at 14 which includes a high pressure
compressor 17, high pressure turbine 19, a burner seen generally at
23 and fuel injecting means 21.
[0023] Referring to FIGS. 1 and 2A-2B, the bypass gas turbine
engine further includes a turbine exhaust case 25 which as an
example of the present invention, includes an annular inner case
portion 27 and an annular outer case portion 29 and a plurality of
airfoils 31 circumferentially spaced apart, and radially extending
between the inner and outer case portions 27, 29, thereby
structurally connecting same. A bearing housing 33 is co-axially
connected to the inner case portion 27 for supporting an aft end of
a main shaft 35 of the low pressure spool 12. Preferably, there is
a mixer 37 attached to the aft end of the outer case portion 29. A
mounting flange 39 is integrated with the outer case portion 29 at
the front end thereof for securing the turbine exhaust case 25 to
the engine case 41 which in turn is structurally connected to the
nacelle 10 through a plurality of radially extending struts 43.
[0024] In operation, combustion gases discharged from the burner 23
power the high and low pressure turbines 19 and 15, and then
exhausted into the annular gas path defined between the inner and
outer case portions 27, 29. The tangential components included in
the exhaust gases is deswirled by the airfoils 31 of the turbine
exhaust case 25, and then the exhaust gases are discharged into the
atmosphere through the mixer 17 which facilitates the mixing of the
exhaust gases with the bypass air flow. The bypass gas turbine
engine is supported by aircraft frame, for example suspending from
the wings by a mounting structure connected to the nacelle 10.
Therefore, the turbine exhaust case 25 is part of the mechanical
support chain for supporting the weight of the entire engine. In
particular, the turbine exhaust case 25 supports a major portion of
the weight of the low pressure spool 12, in addition to bearing its
own weight and the aerodynamic loads affecting thereon by the
exhaust gases.
[0025] In accordance with one embodiment of the present invention,
at least the airfoils 31 of the turbine exhaust case 25 are made of
sheet metal, preferably all components of the turbine exhaust case
25 are made from fabricating processes different from a casting
process thereby avoiding porosity defects formed therein. In other
words, the turbine exhaust case 25 includes no casting components,
for example, sheet metal airfoils, sheet metal inner and outer case
portions and machined bearing housing 33 made of a forged
component. The mixer 37 is also preferably made of sheet metal
fabricated in a pressing process.
[0026] The bearing housing 33 includes a cylindrical body (not
indicated) defining a bore 45 machined in an accurate size for
accommodating a bearing of the main shaft 35 of the low pressure
spool 12. The bearing housing 33 further includes a flange portion
47 radially and upwardly extending from the cylindrical body at the
aft end thereof. The flange portion 47 of the bearing housing 33 is
connected by a plurality of bolts (not indicated), or alternatively
by welding, to an inner support structure of the inner case portion
27 of the turbine exhaust case 25. The inner support structure of
the inner case portion 27 includes a truncated conical structure 49
(more clearly seen in FIG. 2B) extending inwardly, radially and
forwardly from the forward end of the inner case portion 27, to
connect the bearing housing 33. The truncated conical structure 49
is also made of sheet metal which can be integrated with the inner
case portion 27, or welded to the inner case portion 27 at their
adjoining aft ends. As can be seen in FIG. 2B, the cross sectional
profile of structure 49 is somewhat like a hair pin which, as the
skilled reader will understand in light of this disclosure, gives
the sheet metal structure 49 the desired stiffness to permit
adequate structural support for bearing housing 33. The smooth,
profiled bends of inner case portion 27, from gas path to bearing
chamber, provide the configuration desired to permit a sheet metal
construction to reliably support the bearing and spool
components.
[0027] Referring to FIGS. 2A-2B to 4. the airfoils 31 are made of
sheet metal bent in a forming process thereby form a hollow airfoil
configuration 31a or 31b as shown in respective FIGS. 3 and 4. The
opposed ends of the bent sheet metal(s) are joined by a line of
welding fillet (not indicated). The welding line is preferably
positioned at either a leading edge or a trailing edge of the
airfoil. Alternatively, each of the airfoils 31a and 31b can be
made of two pieces of sheet metal spaced apart to form the hollow
configuration. The two spaced pieces of sheet metal join together
at the leading edge and trailing edge of the airfoil in a welding
process. The hollow airfoil configuration 31b presents a thicker
profiled cross-section, providing a relatively big space to allow
services and pipes (shown in a circular broken line) to pass
through. One airfoil configured with the thicker configuration 31b
is provided in the turbine exhaust case 25 (see FIG. 2) for
permitting oil pipes (not shown) to pass through for delivering oil
to the bearing housing 33. The remaining airfoils provide only
aerodynamic functions and their inner space is not used, therefore
is configured with a thinner configuration 31a as shown in FIG. 3,
to present a relatively thin cross-sectional profile.
[0028] Each of the airfoils 31 is welded at opposed ends thereof to
the respective inner and outer case portions 27, 29 to form the
complete structure of the turbine exhaust case 25. The sheet metal
mixer 37 is connected by bolts fastening the adjoining flanges (not
shown) of the respective turbine exhaust case 25 and the mixer 37.
However, the mixer 37 can be alternatively welded at the front end
thereof to the aft end of the outer case portion 29 of the turbine
exhaust case 25. In a turbine exhaust case fabrication process, the
components thereof can be connected in any desired sequence, and
are not limited by the above described order
[0029] Referring to FIGS. 3-8, a method of improved welding process
in accordance with another aspect of the present invention is
described, particularly for welding the airfoils 31 to a case wall
50 of the respective inner and outer case portions 27, 29 of FIG.
1. During the fabrication, the case wall 50 of the respective inner
and outer case portions 27, 29 of FIG. 1 is provided with a
plurality of profiled openings 51 (only one shown in FIG. 5) in
locations where the airfoil 31 is to be connected. This can be
conducted by any well known means. The profiled opening 51
corresponds to the profiled cross section of an end of a
corresponding airfoil 31 to be welded to the case wall 50 such that
the airfoil 31 can be inserted from one side of the case wall 50
into the profiled opening 51 and fitly received therein with a
protruding end section H1 or H2 extending out of the case wall 50
at the other side thereof.
[0030] Conventionally, a welding fillet line 53 is formed at each
side of the case wall 50, surrounding the sectional profile of the
airfoil 31, securing the airfoil 31 to the case wall 50, as shown
in FIG. 6. The reason for welding the airfoil 31 at both sides of
the case wall 50 is that the welding fillet line 53 only partially
penetrates the case wall 50. Nevertheless, although welding fillet
lines 53 are provided at both sides of the case wall 50, which will
improve the quality of the connection of the airfoil 31 to the case
wall 50, there is still a possibility to leave an unwelded portion
55 of the interface between the welding fillet lines 53 at both
sides of the case wall 50. This unwelded portion 55 of the
interface functions as a crack in a component of the gas turbine
engine and thereby creates potential dangers to the safety of the
engine operation. When the airfoil is conventionally made of a cast
component, the airfoil may contain fine holes in the body thereof
resulting from fine bubbles in a casting process. When a fine hole,
as indicated at numeral 57 is located adjacent to the welding
fillet line 53, it creates another crack which is a unwelded
portion between welding fillet line 53 and the cast airfoil 31.
[0031] Another disadvantage of the conventional method of welding
airfoil 31 to case wall 50 of the respective inner and outer case
portions 27, 29 of FIG. 1 lies in that it is difficult to access
the welding location inside the annular exhaust past defined
between the inner and outer case portions 27, 29 of FIG. 1,
particularly with welding tools. In certain circumstances, such
inside welding has to be given up because of no access to the
desired location. This will more likely happen in manufacturing of
small gas turbine engines, and is apparently not desirable.
[0032] In accordance the present invention, the welding process is
conducted only at one side of the case wall 50 out of which side of
the case wall the airfoil end to be welded extends, the is, an
outer side opposite to the inner side defining the annular exhaust
gas path. The end of the airfoil 31 should be inserted into the
opening 51 of the case wall 50 with a protruding portion H2 which
is predetermined such that the protruding portion H2 of the end of
airfoil 31 will be substantially consumed in weld and will not
appear after the welding process.
[0033] The welding process begins with applying to the end of the
airfoil 31 either a laser beam or an electron beam at the side of
the case wall 50 having the protruding portion H2 of the end of the
airfoil 31. The laser beam or electro-beam is adjusted to have a
controlled size, resulting in the fillet 59 extending along a
periphery of the profiled opening 51 of the case wall 50 and
penetrating through an entire thickness of the case wall 50.
Preferably, the laser beam or electron beam is further adjusted to
have a controlled size such that the welding fillet 59 also
penetrates through the entire thickness of the sheet metal of the
airfoil 31. Therefore, the welding fillet 59 constitutes an
integral and complete joining portion of the end of the airfoil 31
and the case wall 50, which eliminates any possible unwelded
portions of the interface, thereby avoiding any possible cracks in
the welding area. The welding process is preferably conducted with
an automatic welding apparatus.
[0034] The welding method of the present invention advantageously
avoids welding the airfoils to the case wall of the respective
inner and outer case portions of FIG. 1 from the inside of the
annular exhaust gas path defined between the inner and outer case
portions. Therefore, it is convenient and efficient to conduct a
welding process for manufacturing the turbine exhaust case, thereby
saving the manufacturing cost. The turbine exhaust case
manufactured using the welding method of the present invention
provides more safety and reliability for engine operation.
[0035] It should be noted that although the welding method of the
present invention is described with reference to a fabricating
process of welding an airfoil to the respective inner and outer
case portions of the turbine exhaust case, it is applicable to use
the method of the present invention for welding any other
components, particularly of a gas turbine engine. For example, the
bearing housing 33 which may be made of sheet metal, machined
forging components or other metal components, can be welded to the
inner support structure of the inner case portion 27 in accordance
with the present invention.
[0036] Modifications and improvements to the above-described
embodiments of the present invention may become apparent to those
skilled in the art. The foregoing description is intended to be
exemplary rather than limiting. The scope of the invention is
therefore intended to be limited solely by the scope of the
appended claims.
* * * * *