U.S. patent application number 11/354514 was filed with the patent office on 2007-08-16 for methods and apparatus for turbine engine rotors.
Invention is credited to Mark E. Burnett, Lyle B. Spiegel, Samuel V. Thamboo, Gary E. Yehle.
Application Number | 20070189894 11/354514 |
Document ID | / |
Family ID | 38016976 |
Filed Date | 2007-08-16 |
United States Patent
Application |
20070189894 |
Kind Code |
A1 |
Thamboo; Samuel V. ; et
al. |
August 16, 2007 |
Methods and apparatus for turbine engine rotors
Abstract
A method for welding two sections of a rotor together, wherein
each rotor section includes a welding surface, is provided. The
method includes positioning the welding surface of the first rotor
section substantially flush against the welding surface of the
second rotor section. The method also includes positioning the
second section substantially flush against a flange circumscribing
the first section such that a rabbeted joint is defined
therebetween.
Inventors: |
Thamboo; Samuel V.; (Latham,
NY) ; Spiegel; Lyle B.; (Niskuyuna, NY) ;
Yehle; Gary E.; (Clifton Park, NY) ; Burnett; Mark
E.; (Barton, NY) |
Correspondence
Address: |
John S. Beulick;Armstrong Teasdale LLP
One Metropolitan Square
Suite 2600
St. Louis
MO
63102
US
|
Family ID: |
38016976 |
Appl. No.: |
11/354514 |
Filed: |
February 15, 2006 |
Current U.S.
Class: |
415/216.1 |
Current CPC
Class: |
F01D 5/026 20130101;
B23K 33/006 20130101; B23K 15/002 20130101; B23K 15/0053 20130101;
B23K 15/0093 20130101; B23K 15/0006 20130101; F05D 2230/233
20130101; B23K 2101/001 20180801 |
Class at
Publication: |
415/216.1 |
International
Class: |
F04D 29/04 20060101
F04D029/04 |
Claims
1. A method for welding two sections of a rotor together, wherein
each rotor section includes a welding surface, said method
comprising: positioning the welding surface of the first rotor
section substantially flush against the welding surface of the
second rotor section such that a welding joint is defined
therebetween; and positioning the second rotor section
substantially flush against a flange circumscribing the first rotor
section such that a rabbeted joint is defined therebetween.
2. A method in accordance with claim 1 further comprising: coupling
a casing to the rotor such that a chamber defined by the casing
circumscribes the welding joint; removing air from the chamber to
create a vacuum therein; and welding the welding joint with an
electron beam generator.
3. A method in accordance with claim 2 wherein welding the welding
joint further comprises welding the welding joint during a single
rotation of the electron beam generator around the welding
joint.
4. A method in accordance with claim 3 wherein welding the welding
joint further comprises adjusting an intensity of the electron beam
as the electron beam generator is rotated about the welding
joint.
5. A method in accordance with claim 1 wherein positioning the
second rotor section substantially flush against a flange
circumscribing the first rotor section further comprises
positioning the second rotor section substantially flush against
the flange such that a cavity is defined between the first rotor
section and the second rotor section.
6. A method in accordance with claim 1 wherein the first rotor
section and the second rotor section are fabricated from different
materials, said method further comprising inserting a shim between
the first rotor section surface and the second rotor section
surface to facilitate coupling the first rotor section and the
second rotor section.
7. A method in accordance with claim 6 further comprising: heating
the first rotor section surface and the second rotor section
surface to facilitate producing welded metal at each welding
surface; and melting the shim to facilitate mixing the material of
the shim with the welded metal to facilitate coupling the first
rotor section and the second rotor section.
8. A rotor for a turbine engine, said rotor comprising: a first
rotor section comprising a welding surface and a flange; a second
rotor section comprising a welding surface, said first rotor
welding surface is positioned substantially flush against said
second rotor welding surface such that a welding joint is defined
therebetween, said second rotor section is substantially flush
against said flange such that a rabbeted joint is defined
therebetween, said rabbeted joint facilitates coupling said first
rotor section and said second rotor section.
9. A rotor in accordance with claim 8 wherein a casing is coupled
to said rotor such that a chamber defined by the casing
substantially circumscribes said welding joint, said chamber
configured to maintain a vacuum pressure therein, said welding
joint configured to be welded with an electron beam generator
within said chamber.
10. A rotor in accordance with claim 9 wherein said welding joint
is configured to be welded by the electron beam generator during a
single rotation of the electron beam generator around said welding
joint.
11. A rotor in accordance with claim 9 further comprising a shim
inserted substantially flush between said first rotor section
surface and said second rotor section surface, said shim
facilitates coupling said first rotor section and said second rotor
section.
12. A rotor in accordance with claim 11 wherein said shim comprises
an alloy material.
13. A rotor in accordance with claim 8 wherein a cavity is defined
between said first rotor section and said second rotor section.
14. A system for welding two sections of a rotor, wherein each
rotor section includes a welding surface, said system comprising: a
welding joint defined between the first rotor section welding
surface and the second rotor section welding surface; a rabbeted
joint defined between the second rotor section and a flange
circumscribing the first rotor section; a casing coupled to the
rotor such that a chamber defined by said casing substantially
circumscribes the welding joint, said chamber configured to
maintain a vacuum pressure therein; and an electron beam generator
configured to weld said welding joint within said chamber.
15. A system in accordance with claim 14 wherein said electron beam
generator is configured to weld said welding joint during a single
rotation around said welding joint.
16. A system in accordance with claim 14 wherein an intensity of
said electron beam generator is adjustable to facilitate welding
said welding joint.
17. A system in accordance with claim 14 wherein said welding joint
includes an inner portion, an intensity of said electron beam
generator is adjustable to facilitate welding said inner
portion.
18. A system in accordance with claim 14 further comprising a shim
positioned substantially flush between said first rotor section
surface and said second rotor section surface, said shim
facilitates coupling said first rotor section and said second rotor
section.
19. A system in accordance with claim 18 wherein said shim
comprises an alloy material.
20. A system in accordance with claim 14 further comprising a
cavity defined between said first rotor section and said second
rotor section.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to turbine engines,
and, more particularly to methods for welding turbine engine
rotors.
[0002] At least some known turbine engine rotors include several
rotor sections, wherein each rotor section may operate at a
different temperature and/or at different operating conditions. For
example, such rotors may include a high pressure rotor section, an
intermediate pressure rotor section, and a low pressure rotor
section. Because the different rotor sections are subjected to
different operating temperatures and pressures, for example, within
a rotor, at least some known rotor sections are fabricated with
different materials. Known methods of coupling the different rotor
sections include bolting and/or welding the sections together.
Between the two coupling methods commonly employed, bolting the
sections together is generally the least desirable because the
flanges and bolts used generally result in the turbine rotor being
longer than desired and increase the original weight of the
rotor.
[0003] Known methods of welding rotor sections may subject the
rotor to flaws if such welding processes require multiple passes,
intermediate machining, and/or multiple heat treatments. In
particular, multiple welding passes may increase risks of defects
in the finished weld. For example, each pass may increase the risk
for slag entrapment, lack of fusion, or porosity, which may serve
as an initiation point for serious cracking.
[0004] To facilitate reducing risks associated with welding rotor
sections together, at least one welding method uses a welding
electrode to build up a layer on either side of the joint to be
welded. However, this welding technique increases the width of the
welding joint, which may increase the risk of slag entrapment
and/or porosity. An alternative welding technique uses layered
transition pieces fabricated from different composite materials.
However, generally, such transition pieces have lower material
strengths than other sections of the rotor. As a result, the rotor
must be handled with special care to avoid damaging or weakening
the transition pieces. Furthermore, the ends of such a rotor must
be heat treated, which may subject the composite transition
materials to excessive temperatures.
BRIEF DESCRIPTION OF THE INVENTION
[0005] In one aspect, a method for welding two sections of a rotor
together, wherein each rotor section includes a welding surface, is
provided. The method includes positioning the welding surface of
the first rotor section substantially flush against the welding
surface of the second rotor section. The method also includes
positioning the second section substantially flush against a flange
circumscribing the first section such that a rabbeted joint is
defined therebetween.
[0006] In another aspect, a rotor for a turbine engine is provided.
The rotor includes a first rotor section including a welding
surface and a flange. The rotor also includes a second rotor
section including a welding surface. The first rotor welding
surface is positioned substantially flush against the second rotor
welding surface and the second rotor section is substantially flush
against the flange such that a rabbeted joint is defined between
the first rotor section and the second rotor section.
[0007] In a further aspect, a system for welding two sections of a
rotor is provided. Both sections of the rotor include a welding
surface. The first rotor section welding surface is positioned
substantially flush against the second rotor section welding
surface, and the second rotor section is substantially flush
against a flange circumscribing the first rotor section such that a
rabbeted joint is defined therebetween. The system includes a
casing coupled to the rotor such that a chamber, defined by the
casing, substantially circumscribes the joint. The chamber is
vacuum pumped to create a vacuum therein or a partial vacuum. The
system also includes an electron beam generator to weld the joint
within the chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is an exemplary view of a turbine rotor including at
least two sections to be welded;
[0009] FIG. 2 is a view of an exemplary welding joint that may be
used in coupling the sections of the rotor shown in FIG. 1;
[0010] FIG. 3 is a sectional view of an exemplary weld joint
showing how the electron beam energy is profiled towards the end of
the weld cycle; and
[0011] FIG. 4 is a view of a portion of the joint shown in FIG. 2,
and including a shim inserted between the sections of the joint
welded together.
DETAILED DESCRIPTION OF THE INVENTION
[0012] FIG. 1 is an exemplary view of a turbine rotor 100 including
at least two rotor sections to be welded. Specifically, rotor 100
includes a first rotor section 102 and a second rotor section 104
to be coupled together at a weld joint 106. Joint 106 includes a
radially outer portion 107 and a radially inner portion 108 that is
radially inward from joint outer portion 107. A cavity 109 is
defined within joint 106 between rotor sections 102 and 104. A
casing 110 is coupled to rotor 100 such that casing 110 defines a
chamber 111 circumscribing joint 106 and extending
circumferentially about rotor 100. Any air in chamber 111 is
removed using a vacuum pump, such that a vacuum is induced within
chamber 111. A reduced pressure electron beam generator 112 is then
coupled to casing 110, within chamber 111, and is aligned such that
it can direct an electron beam towards joint outer portion 107 to
facilitate welding rotor sections 102 and 104.
[0013] FIG. 2 is a view of an exemplary welding joint 106 that may
be used in welding rotor sections 102 and 104. Joint 106 is formed
with a first section surface 114, and is aligned and pressed into
contact substantially flush against a second section surface 116. A
rabbet 118 extends outward along a first section inner surface 120,
and in the exemplary embodiment, is substantially perpendicular to
first section surface 114. Rabbet 118 includes a radially upper
surface 124 that is substantially parallel to first section inner
surface 120 and is substantially perpendicular to first section
surface 114. A second section inner surface 122 is substantially
flush against rabbet upper surface 124 such that a rabbeted joint
125 is defined along joint inner portion 108.
[0014] Prior to beginning a welding operation, rotor sections 102
and 104 are positioned together to define joint 106. Specifically,
second section surface 116 is positioned substantially flush
against first section surface 114, and second section inner surface
122 is positioned substantially flush against rabbet upper surface
124 to define rabbeted joint 125. Rabbeted joint 125 facilitates
coupling section 102 and section 104. The coupling of section 102
and section 104 also defines cavity 109. Alternatively, rotor 100
may include several joints 106 defined by multiple sections.
[0015] Casing 110 is coupled to rotor 100 such that casing 110
defines chamber 111 substantially circumscribing joint 106. The air
is removed from the chamber 111 to create a vacuum surrounding
joint 106. Because chamber 111 circumscribes a limited section of
rotor 100, the need for large vacuum housings is eliminated.
[0016] After a vacuum is established within chamber 111, the
welding process is performed. Specifically, in the exemplary
embodiment, the welding is performed by electron beam generator
112. Electron beam generator 112 is coupled to casing 110, within
chamber 111, such that it can be moved circumferentially around
rotor 100. Electron beam generator 112 is aligned relative to joint
106 to enable an electron beam to be directed towards joint outer
portion 107 with an intensity that enables it to penetrate to joint
inner portion 108.
[0017] Electron beam generator 112 is rotated around the
circumference of rotor 100 while directing the electron beam at
joint outer portion 107. Alternatively the electron beam is kept
stationary and the rotor is rotated to create a relative travel
between the beam and the rotor circumference. During the rotation,
the electron beam heats first section surface 114 and second
section surface 116 to produce welded metal. Welded metal from
surface 114 is fused with welded metal from surface 116 such that
section 102 and section 104 are bonded into a unitary piece.
Because electron beam generator 112 need only make one complete
rotation around the circumference of joint 106 to bond surfaces 114
and 116, welding defects are facilitated to be reduced in
comparison to welding techniques that require multiple passes.
Specifically, because rabbeted joint 125 facilitates a tighter fit
between sections 102 and 104, the electron beam is able to produce
a more structurally sound weld with only one pass of electron beam
generator 112. As a result, a structurally strong weld that is less
susceptible to weld defects and distortion, is produced.
[0018] During the welding process, rabbet 118 prevents materials,
including welded metal and/or slag, from falling into cavity 109
such that fusing between the welded metal of surface 114 and the
welded metal of surface 116 is facilitated to be optimized. As
such, the bond provided between section 102 and section 104 is
structurally sound, and brittleness and cracking within the weld is
facilitated to be reduced. Moreover, by preventing welded metal
from falling into cavity 109, a more complete bond can be obtained
between sections 102 and 104, resulting in fewer defects.
[0019] In the exemplary embodiment, electron beam generator 112 is
operable through a range of powers indicative of the intensity of
the electron beam. Because joint outer portion 107 has a greater
circumference than joint inner portion 108, the inner portion will
be welded 360 degrees before the outer portion is completed as
shown in FIG. 3. The power of the electron beam must be reduced as
electron beam generator 112 completes the welding of the inner
portion. This is done to facilitate a gradual change in the weld
penetration depth to the surface. This prevents weld defects like
porosity or voids which would be seen if the full beam intensity
were suddenly shutdown on completion of the outer portion of the
weld.
[0020] After completion of the weld a stress relieving heat treat
process is applied locally to the area near the joint. This is
needed because of two reasons. The first reason is that any weld
process will leave some residual stresses at the joint. The second
reason is that most materials will undergo metallurgical
transformation in the heat affected zone of the weld which may
change their mechanical properties. The selection of temperature
for this heat treatment is based on the materials being welded.
After the heat treat process the materials properties at the joint
are mostly restored close to the original base material
properties.
[0021] FIG. 4 is an enlarged view of a portion of joint 106
including a shim 130 inserted between welding sections 102 and 104.
In the exemplary embodiment, first section 102 and second section
104 are fabricated from different materials, which, because of
their material properties, cannot be welded directly against each
other without increasing the potential of brittleness or cracking
developing in joint 106. Shim 130 is inserted between first section
102 and second section 104 to facilitate proper fusing of the two
materials during welding. Specifically, when shim 130 is positioned
between sections 102 and 104, a shim first surface 132 is
substantially flush against first section surface 114, and an
opposite shim second surface 134 is substantially flush against
second section surface 116. Furthermore, when shim 130 is inserted
between sections 102 and 104, a shim inner surface 136 is
substantially flush against rabbet upper surface 124. Shim 130 has
a width 138 that is sized to enable second section inner surface
122 to be positioned substantially flush against rabbet upper
surface 124.
[0022] The material used in fabricating shim 130 is selected based
on the materials used in fabricating first section 102 and second
section 104. For example, if CrMoV steel were being welded to
NiCrMoV steel, a shim fabricated of an intermediate composition of
the two steel alloys could be used. Moreover, and for example, if
steel materials are being coupled to nickel-based alloys, an alloy
such as alloy 625 or alloy 617 could be used. In each embodiment,
the shim material of the appropriate thickness is selected to
facilitate preventing potentially harmful phases from forming in
the weld, while maintaining the properties of the weld metal. In
the exemplary embodiment, a similar process to the above-described
welding process and heat treat process is utilized when shim 130 is
inserted between section 102 and section 104.
[0023] Prior to beginning welding operations, rotor sections 102
and 104 and shim 130 are positioned together to define joint 106.
Specifically, shim first surface 132 is positioned substantially
flush against first section surface 114 and shim second surface 134
is positioned substantially flush against second section surface
116. Furthermore, shim inner surface 136 is positioned
substantially flush against rabbet upper surface 124. Shim width
138 is sized such that second section inner surface 122 is
positioned substantially flush against rabbet upper surface 124.
The coupling of sections 102 and 104 with shim 130 also defines
cavity 109. Alternatively, rotor 100 may include several joints 106
defined by multiple sections and multiple shims.
[0024] Casing 110 is coupled to rotor 100 such that chamber 111
substantially circumscribes joint 106. The air is removed from the
chamber 111 to create a vacuum surrounding joint 106. Because
chamber 111 circumscribes a limited section of rotor 100, the need
for large vacuum housings is eliminated. After a vacuum is
established within chamber 111, the welding process is performed
with electron beam generator 112 coupled to casing 110, within
chamber 111.
[0025] During the rotation of electron beam generator 112 around
rotor 100, the electron beam heats surface 114 and surface 116 to
produce welded metal. Furthermore, shim 130 is melted by the
electron beam. Melted shim 130 fuses with the rotor metal on either
side to bond section 102 and section 104 into a unitary piece. In
the exemplary embodiment electron beam generator 112 completes one
rotation around the circumference of joint 106. Moreover, the
intensity of electron beam generator 112 is reduced as the rotation
nears completion.
[0026] After completion of the weld a stress relieving heat treat
process is applied locally to the area near the joint. This is
needed relieve residual stresses at the joint and to restore the
material properties of the metal. The selection of temperature for
this heat treatment is based on the materials being welded. After
the heat treat process the material properties at the joint are
mostly restored close to the original base material properties.
[0027] The above-described methods and systems facilitate a turbine
rotor being efficiently welded with a weld joint that is subject to
less brittleness and/or cracking within the joint. Specifically,
the rabbeted joint facilitates coupling the rotor sections
together, such that they can be welded using only a single pass of
an electron beam generator. As such, two sections of the rotor are
welded using a technique which facilitates reducing defects, such
as slag entrapment or porosity, within the weld. Furthermore, the
methods and system described herein can be used to weld two rotor
sections fabricated from different materials. The shim described
herein enables at least two rotor sections being properly bonded
together despite each having different material properties.
Moreover, the shim does not effect the need for only one pass of
the electron beam generator. As a result, rotor sections can be
welded together with a structurally sound joint that is cost
effective and reliable.
[0028] As used herein, an element or step recited in the singular
and proceeded with the word "a" or "an" should be understood as not
excluding plural said elements or steps, unless such exclusion is
explicitly recited. Furthermore, references to "one embodiment" of
the present invention are not intended to be interpreted as
excluding the existence of additional embodiments that also
incorporate the recited features.
[0029] Although the methods and systems described herein are
described in the context of welding a turbine rotor, it is
understood that the welding methods and systems described herein
are not limited to turbine rotors. Likewise, the welding system
components illustrated are not limited to the specific embodiments
described herein, but rather, components of the welding system can
be utilized independently and separately from other components
described herein.
[0030] While the invention has been described in terms of various
specific embodiments, those skilled in the art will recognize that
the invention can be practiced with modification within the spirit
and scope of the claims.
* * * * *