Information
-
Patent Grant
-
6439841
-
Patent Number
6,439,841
-
Date Filed
Saturday, April 29, 200024 years ago
-
Date Issued
Tuesday, August 27, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Lopez; F. Daniel
- Woo; Richard
Agents
- Herkamp; Nathan D.
- Rosen; Steven J.
-
CPC
-
US Classifications
Field of Search
US
- 415 142
- 415 180
- 415 189
- 415 190
- 415 115
- 415 116
- 415 174
- 415 177
- 415 178
- 415 176
- 415 175
- 415 2094
- 415 2093
- 060 3931
-
International Classifications
-
-
Disclaimer
Terminal disclaimer
Abstract
An annular turbine frame has ring disposed coaxially about an axial centerline axis and includes a plurality of circumferentially spaced apart ports. A plurality of circumferentially spaced apart struts are joined radially to the ring by devises on the ring. Each strut has radially opposite first and second ends, and a through channel extending therebetween. Each of the channels is aligned with a corresponding one of the ports. Each of the ports has a port counterbore though a radially outer portion of the port forming a shoulder in the port. A seal is disposed within the port counterbore between the shoulder and the strut.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to gas turbine engines and, more specifically, to frames therein for supporting bearings and shafts.
2. Discussion of the Background Art
Gas turbine engines include one or more rotor shafts supported by bearings which, in turn, are supported by annular frames. Frames include an annular casing spaced radially outwardly from an annular hub, with a plurality of circumferentially spaced apart struts extending therebetween. The struts may be integrally formed with the casing and hub in a common casting, for example, or may be suitable bolted thereto. In either configuration, the overall frame must have suitable structural rigidity for supporting the rotor shaft to minimize deflections thereof during operation.
The struts have a hollow cross section through which pressurized cooling air passes and is routed into a hub. The pressurized air provides rotor purge for the high pressure and low pressure turbines through holes in the hub. The air also provides cooling for the strut and hub in addition to tubes contained within the struts which service the aft high pressure turbine (HPT) bearing. It is important that the pressurized air within the strut and hub not be lost due to leakage. If leakage occurs, the rotor cavity temperatures will be adversely affected.
One example of a bolted turbine frame assembly is a GE90 turbine center frame (TCF) which has an outer strut end connected to the outer case by eight bolts at each of the twelve strut ends. To minimize relative movement between the case and strut end, a shear bolt is used at each location which bounds off the hole in the case and strut end. To assure concentricity between the case hole and strut hole during manufacture, each strut is located relative to the case and each hole is machined through the case and strut in a single pass. The struts are then separated from the case and each previously machined through hole is used as a pilot to machine a counterbore feature for subsequent thread tapping and insert installation.
The struts are connected to the hub with a clevis and with 2 expandable bolts which provide a secure shear connection preventing any relative motion between the strut and hub. The struts have a hollow cross section through which pressurized air passes and is routed into the hub. The pressurized air provides rotor purge for the high pressure and low pressure turbines through holes in the hub box. The air also provides cooling for the strut and hub in addition to tubes contained within the hollow struts which service the aft high pressure turbine (HPT) bearing. It is important that the pressurized air within the strut and hub not be lost due to leakage. If leakage occurs, the rotor cavity temperatures will be adversely affected. Since the expandable bolts do not seal the strut to the hub it is desirable to prevent leakage of the pressurized air between the struts and the hub.
SUMMARY OF THE INVENTION
An annular turbine frame has ring disposed coaxially about an axial centerline axis and includes a plurality of circumferentially spaced apart ports. A plurality of circumferentially spaced apart struts are joined radially to the ring by clevises on the ring. Each strut has radially opposite first and second ends, and a through channel extending therebetween. Each of the channels is aligned with a corresponding one of the ports. Each of the ports has a port counterbore though a radially outer portion of the port forming a shoulder in the port. A seal is disposed within the port counterbore between the shoulder and the strut.
BRIEF DESCRIPTION OF THE DRAWINGS
The novel features believed characteristic of the present invention are set forth and differentiated in the claims. The invention is more particularly described in conjunction with the accompanying drawings in which:
FIG. 1
is a longitudinal cross-sectional view illustration of a portion of a gas turbine engine having a turbine center frame assembly of an exemplary embodiment of the present invention.
FIG. 2
is a perspective view illustration of the turbine center frame assembly in FIG.
1
.
FIG. 3
is a perspective view illustration of a strut and casing inside of the turbine center frame assembly in FIG.
2
.
FIG. 4
is a radially outwardly looking perspective view illustration of a radially outer end of the strut in FIG.
3
.
FIG. 5
is a radially inwardly looking perspective view illustration of a radially outer end of the strut in FIG.
3
.
FIG. 6
is a cross-sectional view illustration of a portion of the casing and strut assembly taken though a bolt and threaded in an insert and a key used to secure the insert in a mounting hole in a strut base illustrated in FIG.
5
.
FIG. 7
is a cross-sectional view illustration of a portion of the casing and strut assembly taken though a bolt and threaded in the insert in the mounting hole in the strut base illustrated in FIG.
5
.
FIG. 8
is a radially inwardly looking perspective view illustration of a radially inner end of the strut and hub in FIG.
2
.
FIG. 9
is a radially inwardly looking perspective view illustration of the hub in
FIG. 8
with the radially inner end of the strut removed.
FIG. 10
is a diagrammatic cross-sectional perspective view illustration of the hub and the radially inner end of the strut and hub in FIG.
2
.
DETAILED DESCRIPTION
While there have been described herein what are considered to be preferred and exemplary embodiments of the present invention, other modifications of the invention shall be apparent to those skilled in the art from the teachings herein and, it is therefore, desired to be secured in the appended claims all such modifications as fall within the true spirit and scope of the invention.
Illustrated schematically in
FIG. 1
is a portion of an exemplary gas turbine engine
10
having an axial or longitudinal centerline axis
12
. Disposed about the centerline axis
12
in serial flow communication are a fan, compressor, and combustor (all not shown), high pressure turbine (HPT)
20
and low pressure turbine (LPT)
22
. A first shaft (not shown) joins the compressor to the HPT
20
, and a second shaft
26
joins the fan to the LPT. During operation, air enters the fan, a portion of which is compressed in the compressor to flow to the combustor wherein it is mixed with fuel and ignited for generating combustion gases
30
which flow downstream through the HPT
20
and the LPT which extract energy therefrom for rotating the first and second shafts.
An annular turbine frame
32
, illustrated as a turbine center frame in accordance with one embodiment of the present invention, supports a bearing
34
which, in turn, supports one end of the second shaft
26
for allowing rotation thereof. Turbine frames are also used to support aft ends of the HPT shaft (not shown). The turbine frame
32
is disposed downstream of the HPT
20
and, therefore, must be protected from the combustion gases
30
which flow therethrough.
The turbine frame
32
as illustrated in
FIGS. 1 and 2
includes a radially outer first structural ring, illustrated as a casing
36
for example, disposed coaxially about the centerline axis
12
. The frame
32
also includes a radially inner second structural ring illustrated as a hub
38
, for example, disposed coaxially with the first ring or casing
36
about the centerline axis
12
and spaced radially inwardly therefrom. A plurality of circumferentially spaced apart hollow struts
40
extend radially between the casing
36
and the hub
38
and are removably fixedly joined thereto.
The frame
32
also includes a plurality of conventional fairings
42
each of which surrounds a respective one of the struts
40
for protecting the struts from the combustion gases
30
which flow through the turbine frame
32
. A generally conical sump member
44
which supports the bearing
34
in its central bore is joined to the hub
38
. Each of the struts
40
includes a first or outer end
41
and a radially opposite second or inner end
43
with an elongate center portion
45
extending therebetween. The strut
40
is hollow and includes a through channel
46
extending completely through the strut
40
from the outer end
41
and through the center portion
45
to the inner end
43
.
The casing
36
includes a plurality of circumferentially spaced apart first ports
48
extending radially therethrough and the hub
38
includes a plurality of circumferentially spaced apart second ports
50
extending radially therethrough. In the exemplary embodiment illustrated herein, the inner ends
43
of the struts
40
are removably fixedly joined to the hub
38
with a bolted connection, other embodiments have the inner ends
43
of the struts
40
fixedly attached with welding to or integrally formed with the hub
38
in a common casting. In this embodiment, the outer ends
41
of the struts
40
are removably fixedly joined to the casing
36
. In alternate embodiments, the strut outer ends
41
may be integrally joined to the casing
36
in a common casting, for example, with the strut inner ends
43
being removably joined to the hub
38
also in accordance with the present invention.
A plurality of collars
52
surround and are integrally formed with the strut outer ends
41
and removably join the strut outer ends
41
to the casing
36
. Though the collar
52
is illustrated as being integrally formed with the strut outer end
41
, the collar can be separate in the form of a clevis as disclosed in U.S. Pat. Nos. 5,292,227 and 5,438,756 which are incorporated herein by reference. The collar
52
removably joins the strut outer ends
41
to the casing
36
. In alternative embodiments (not shown), collars
52
may be used to removably join the inner ends
43
to the hub
38
. In either configuration, each of the collars
52
is disposed between a respective one of the strut outer and inner ends
41
,
43
and the respective ring, i.e. casing
36
or hub
38
, in alignment with respective ones of the first or second ports
48
,
50
for removably joining the struts
40
to the first or second ring, i.e. casing
36
or hub
38
, for both carrying loads and providing access therethrough.
In the exemplary embodiment, referring to
FIG. 3
, each of the collars
52
is an arcuate base
54
disposed against the inner circumference of the casing
36
. A plurality of casing holes
55
are aligned with a plurality of collar mounting holes
56
in the base
54
, eight of each hole being shown for example, for receiving a respective plurality of mounting bolts
58
, therethrough to removably fixedly join the base
54
to the casing
36
. The base
54
includes a central aperture
60
aligned with a respective one of the first ports
48
.
Referring back to
FIG. 2
, the casing
36
includes a pair of axially spaced apart, annular stiffening ribs
72
disposed on opposite, axial sides of the collars
52
and the first ports
48
for carrying loads between the struts
40
and the casing
36
. The stiffening ribs
72
are continuous and uninterrupted annular members which carry loads in the hoop-stress direction without interruption by either the ports
48
or the struts
40
joined to the casing
36
so that loads may be transmitted from the hub
38
through the struts
40
and through the collars
52
to the casing
36
, with the stiffening ribs
72
ensuring substantially rigid annular members to which the struts
40
are connected.
Referring to
FIGS. 3
,
4
,
6
, and
7
, the base
54
is rigidly mounted to the casing
36
by the eight mounting bolts
58
, thus, rigidly connecting the strut
40
by way of the strut outer end
41
to the casing. Each collar mounting hole
56
through the arcuate base
54
of the collar
52
includes a hole counterbore
80
though a radially outer portion
82
of the mounting hole. A threaded hollow insert
84
having inner and outer threaded surfaces
86
and
88
, respectively, is used to secure the mounting bolt
58
. A radially inner portion
90
of the collar mounting hole
56
is threaded to receive and hold the insert
84
disposed therein. A washer
94
is disposed in the counterbore
80
with a press fit. The mounting bolts
58
are disposed through the in line-drilled casing holes
55
, washer
94
, and mounting holes
56
and screwed into the threaded inner surface
86
of the insert
84
. This assembly allows an assembler to screw in and tighten the bolts
58
from radially outboard of the casing
36
instead of radially inboard of the casing in a difficult to access area of the frame between the base
54
and the strut outer end
41
.
The mounting bolts
58
seals off the mounting holes
56
, thus, preventing leakage of the combustion gases
30
through the casing holes
55
and the casing
36
. The washer
94
should be made from a material with a higher coefficient of thermal expansion than the strut
40
and base
54
which it is press fit into. The difference in thermal expansion will assure that the washer interference with the hole counterbore
80
is always present during engine operation. One advantage of the present invention is that it enables the hole counterbore
80
and threads on the inner and outer threaded surfaces
86
and
88
to be machined from radially outboard of the casing
36
, a more accessible side of the outer strut end
41
. This is a more producible and less costly design of the turbine frame. The inserts are installed from radially outboard of the casing
36
. Referring to
FIGS. 5 and 6
, insert keys
120
are radially disposed through aligned radially extending matched key insert hole slots
122
in the insert
84
and hole slots
124
along the inner portion
90
of the casing holes
55
respectively. The insert keys
120
are trapped in place by the washer
94
which prevents them from backing out due to engine vibration. The washer has tight tolerance diameter and concentricity requirements and this helps the washer take circumferential and axial loads through the struts and transfer them to the annular stiffening ribs
72
on the casing
36
.
Another advantage of the present invention is that the washer will encounter the majority of the assembly/disassembly wear. The washer material has a lower hardness than the outer case and will yield/wear before the case if the parts are not aligned during assembly or they are distorted from long term operation. If the washer wears beyond desired limits, it can be easily replaced at a relative low cost as compared to prior art frame assemblies.
As an example of the method of the present invention reference may be had to a GE90 Turbine Center Frame (TCF) outer strut end which is connected to the outer casing by eight shear bolts at each of the twelve strut ends. To minimize relative movement between the case and strut end the shear bolt is used at each location. During manufacture each strut is placed in its assembled position relative to the casing
36
and each pair of the casing holes
55
collar mounting holes
56
is machined through the casing and the strut base
54
in a single pass to assure concentricity between holes in the casing and strut base and that they aligned properly during assembly. The struts are then separated from the casing and each previously machined through collar mounting hole
56
is used as a pilot to machine the counterbore
80
though the radially outer portion
82
of the collar hole to a specified depth relative to a reference plane on the strut end for subsequent thread tapping and insert installation. The radially inner portion
90
of the collar mounting hole
56
is then enlarged and threaded with a tapping procedure. The threaded hollow insert
84
is self broaching and keyed, having at least one key to prevent unwanted rotation. The threaded hollow insert
84
is installed flush with the bottom
102
of the counterbore
80
and the outer threaded surfaces
88
is screwed into the threaded radially inner portion
90
of the collar mounting hole
56
. The washer
94
is then press fit into the counterbore
80
and retained by the counterbore bottom
102
. Once all inserts and washers have been installed, the outer casing is assembled on to the outer strut ends
41
. The bolts
58
are then installed through the casing holes
55
and threaded into the inserts
84
.
Referring to
FIGS. 1
,
2
, and
8
, the inner end
43
of each of the struts
40
is removably connected to the hub
38
of the frame
32
. In the exemplary embodiment illustrated herein expandable bolts
140
are used to connect the inner end
43
to radially outwardly extending devises
144
mounted on the casing
36
as shown more particularly in FIG.
9
. The through channel
46
of the strut
40
is aligned with the first port
50
on the hub
38
. A racetrack shaped hub counterbore
148
is machined into the base
54
around the second ports
50
. A seal
150
, illustrated in
FIG. 10
, is disposed between the inner end
43
and a shoulder
156
of the hub counterbore
148
thereby sealing off any leakage of pressurized cooling air
160
from the hollow through channel
46
between the inner end
43
of each of the struts
40
and the hub
38
of the frame
32
. The seal
150
in the exemplary embodiment illustrated herein is metallic and deformable, and is able to withstand and function at temperatures up to 1000 degrees Fahrenheit. The racetrack shaped hub counterbore
148
is characterized by spaced apart straight parallel sides
142
disposed between rounded ends
146
. In the exemplary embodiment illustrated herein the rounded ends are
146
are semi-circular.
The racetrack shaped hub counterbore
148
is machined into the hub
38
at each strut end connection location
170
. The seal
150
is placed in the hub counterbore
148
using hand pressure. The seal
150
is bowed slightly outward at new part manufacture so that it is retained in the hub counterbore
148
in the absence of the strut
40
. This aids in the assembly of the struts
40
to the hub
38
. The strut
40
is attached to the hub
38
by first installing a forward one
172
of the expandable bolts
140
then rotating the strut about the forward bolt thus compressing the seal
150
between the strut and hub and then installing an aft one
174
of the expandable bolts. The expandable bolts are then torqued within a specified tolerance. Once the seal
150
is installed, a portion of the seal is visible allowing assembly personal to verify the seal is present. The seal is designed to function properly regardless of assembly orientation within the cavity (i.e. the seal can be installed upside down). Due to manufacturing tolerances, the gap between the strut end and hub counterbore can vary from frame to frame and from strut to strut within a given frame. The seal is designed to function properly (meet maximum leakage limits) given the variety of gaps. The seal will also function properly if it is initially installed into a cavity of minimum gap and later installed into a cavity of maximum allowable gap. Leakage between the strut and hub is minimized to acceptable levels. Manufacturing tolerances of the strut and hub are accommodated by the deformable nature of the seal. The seal will function properly regardless of assembly orientation, is reusable at other strut locations, and on other similar turbine center frames. Once installed, visual access exists to verify the a seal is present.
While there have been described herein, what are considered to be preferred and exemplary embodiments of the present invention, other modifications of the invention shall be apparent to those skilled in the art from the teachings herein and, it is, therefore, desired to be secured in the appended claims all such modifications as fall within the true spirit and scope of the invention.
Accordingly, what is desired to be secured by Letters Patent of the United States is the invention as defined and differentiated in the following claims.
Claims
- 1. An annular turbine frame comprising:a ring disposed coaxially about an axial centerline axis and having a plurality of circumferentially spaced apart ports; a plurality of circumferentially spaced apart struts joined radially to said ring by devises on said ring, each strut having radially opposite first and second ends, and a through channel extending therebetween; and each of said channels aligned with a corresponding one of said ports; each of said ports has a port counterbore though a radially outer portion of said port forming a shoulder in said port; and a seal is disposed within said port counterbore between said shoulder and said strut.
- 2. An annular turbine frame as claimed in claim 1 wherein said port counterbore is racetrack shaped having parallel sides extending between rounded ends.
- 3. An annular turbine frame as claimed in claim 1 wherein said seal is metallic and deformable.
- 4. An annular turbine frame as claimed in claim 3 wherein said seal withstand and function at temperatures up to 1000 degrees Fahrenheit.
- 5. An annular turbine frame comprising:a ring disposed coaxially about an axial centerline axis and having a plurality of circumferentially spaced apart ports; a plurality of circumferentially spaced apart struts joined radially to said ring by bolts, each strut having radially opposite first and second ends, and a through channel extending therebetween; and each of said channels aligned with a corresponding one of said ports; each of said ports has a port counterbore though a radially outer portion of said port forming a shoulder in said port; and a seal is disposed within said port counterbore between said shoulder and said strut.
- 6. An annular turbine frame as claimed in claim 5 wherein said port counterbore is racetrack shaped having parallel sides extending between rounded ends.
- 7. An annular turbine frame as claimed in claim 5 wherein said seal is metallic and deformable.
- 8. An annular turbine frame as claimed in claim 7 wherein said seal withstand and function at temperatures up to 1000 degrees Fahrenheit.
- 9. An annular turbine frame as claimed in claim 5 wherein said circumferentially spaced apart struts are joined radially by said bolts to devises on said ring.
- 10. An annular turbine frame as claimed in claim 9 wherein said port counterbore is racetrack shaped having parallel sides extending between rounded ends.
- 11. An annular turbine frame comprising:a radially outer structural ring disposed coaxially about an axial centerline axis and having a plurality of circumferentially spaced apart first ports extending radially therethrough, a radially inner structural ring disposed coaxially about said centerline axis, spaced radially inwardly from said outer structural ring, and having a plurality of circumferentially spaced apart second ports extending radially therethrough, a plurality of circumferentially spaced apart struts joined to said outer and inner structural rings, each of said struts having radially opposite inner and outer ends and a through channel extending therebetween; and said channel aligned with a corresponding one of said first and second ports; each of said second ports having a port counterbore though a radially outer portion of said second ports forming a shoulder in said second ports; and a seal disposed within said port counterbore between said shoulder and said inner end of said strut.
- 12. An annular turbine frame as claimed in claim 11 wherein said circumferentially spaced apart struts are joined radially by bolts to said inner ring.
- 13. An annular turbine frame as claimed in claim 12 wherein said circumferentially spaced apart struts are joined radially by said bolts to devises on said inner ring.
- 14. An annular turbine frame as claimed in claim 13 wherein said port counterbore is racetrack shaped having parallel sides extending between rounded ends.
- 15. An annular turbine frame as claimed in claim 14 wherein said seal is metallic and deformable.
- 16. An annular turbine frame as claimed in claim 15 wherein said seal withstand and function at temperatures up to 1000 degrees Fahrenheit.
- 17. An annular turbine frame as claimed in claim 11 wherein said seal is metallic and deformable.
US Referenced Citations (10)
Foreign Referenced Citations (1)
Number |
Date |
Country |
2084261 |
Apr 1982 |
GB |