U.S. patent application number 13/979145 was filed with the patent office on 2013-11-21 for assembly and method of attaching stub shaft to drum of axial compressor rotor shaft.
This patent application is currently assigned to ELLIOTT COMPANY. The applicant listed for this patent is Andrew Paul Watson. Invention is credited to Andrew Paul Watson.
Application Number | 20130309087 13/979145 |
Document ID | / |
Family ID | 47558696 |
Filed Date | 2013-11-21 |
United States Patent
Application |
20130309087 |
Kind Code |
A1 |
Watson; Andrew Paul |
November 21, 2013 |
ASSEMBLY AND METHOD OF ATTACHING STUB SHAFT TO DRUM OF AXIAL
COMPRESSOR ROTOR SHAFT
Abstract
An assembly and method for an axial compressor includes an axial
shaft extending between an inlet casing and a discharge casing
along the longitudinal length of a compressor housing. The axial
shaft assembly includes a first stub shaft, a second stub shaft,
and a hollow shaft drum having a longitudinal axis. The first stub
shaft and the second stub shaft are coupled to opposing ends of the
shaft drum along its longitudinal axis. A plurality of keys is
disposed in a radial arrangement near the outer circumference of
the first and second stub shafts and the shaft drum. A plurality of
pins engage the plurality of keys, whereby the pins prevent the
shaft drum from rotating axially relative to the first stub shaft
and the second stub shaft and prevent the shaft drum from axially
and radially separating from the stub shafts.
Inventors: |
Watson; Andrew Paul;
(Export, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Watson; Andrew Paul |
Export |
PA |
US |
|
|
Assignee: |
ELLIOTT COMPANY
Jeannette
PA
|
Family ID: |
47558696 |
Appl. No.: |
13/979145 |
Filed: |
July 17, 2012 |
PCT Filed: |
July 17, 2012 |
PCT NO: |
PCT/US12/47005 |
371 Date: |
July 11, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61509262 |
Jul 19, 2011 |
|
|
|
Current U.S.
Class: |
415/229 ;
29/888.02 |
Current CPC
Class: |
Y10T 29/49236 20150115;
F04D 29/053 20130101; F04D 29/321 20130101; F04D 29/266
20130101 |
Class at
Publication: |
415/229 ;
29/888.02 |
International
Class: |
F04D 29/053 20060101
F04D029/053 |
Claims
1. A shaft assembly for an axial compressor, the shaft assembly
comprising: a first stub shaft; a second stub shaft; a hollow shaft
drum having a longitudinal axis, the first stub shaft and the
second stub shaft coupled to opposing ends of the shaft drum along
the longitudinal axis; a plurality of keys disposed in a radial
arrangement proximate to the outer circumference of the first and
second stub shafts and the shaft drum; and a plurality of pins
engaging the plurality of keys, wherein the pins prevent the shaft
drum from rotating axially relative to the first stub shaft and the
second stub shaft and prevent the shaft drum from axially and
radially separating from the stub shafts.
2. The shaft assembly according to claim 1, further comprising: a
plurality of shoulder structures provided on each of the first stub
shaft and the second stub shaft; and a plurality of shoulder
recesses provided at opposing ends of the shaft drum along the
longitudinal axis, wherein the plurality of shoulder structures are
operative for engaging the plurality of shoulder recesses to form a
rabbet fit between the first and second stub shafts and the shaft
drum for maintaining coaxial arrangement of the shaft assembly.
3. The shaft assembly according to claim 1, wherein each pin is
dimensioned to be larger than the corresponding key to allow for an
interference fit between the pin and the key.
4. The shaft assembly according to claim 1, wherein each key
comprises a slot formed on the first and second stub shafts and a
corresponding slot formed on the shaft drum.
5. The shaft assembly according to claim 1, wherein each pin
includes a recess substantially coaxial with a longitudinal axis of
the pin, the recess adapted for facilitating insertion of the pin
into the corresponding key.
6. The shaft assembly according to claim 1, further comprising one
or more through-bolts extending axially between the first and
second stub shafts through the shaft drum, the one or more
through-bolts providing a closing force to prevent relative
movement between the first and second stub shafts and the shaft
drum.
7. The shaft assembly according to claim 6, wherein each
through-bolt includes threaded ends and a nut is provided at each
threaded end to tighten the through-bolt and couple the first and
second stub shafts to the shaft drum.
8. An axial compressor comprising: a housing having an inlet casing
provided at one end and a discharge casing provided at an opposing
end; an axial shaft assembly rotatably disposed inside the housing,
the axial shaft assembly extending between the inlet casing and the
discharge casing along a longitudinal length of the housing; a
plurality of stator blades extending radially inward from an inner
surface of the housing; a plurality of rotor blades extending
radially outward from an outer surface of the axial shaft assembly,
wherein the axial shaft assembly comprises: a first stub shaft; a
second stub shaft; a hollow shaft drum having a longitudinal axis,
the first stub shaft and the second stub shaft coupled to opposing
ends of the shaft drum along the longitudinal axis; a plurality of
keys disposed in a radial arrangement proximate to the outer
circumference of the first and second stub shafts and the shaft
drum; and a plurality of pins engaging the plurality of keys,
wherein the pins prevent the shaft drum from rotating axially
relative to the first stub shaft and the second stub shaft and
prevent the shaft drum from axially and radially separating from
the stub shafts.
9. The axial compressor of claim 8, further comprising: a plurality
of shoulder structures provided on the first stub shaft and the
second stub shaft; and a plurality of shoulder recesses provided at
opposing ends of the shaft drum along its longitudinal axis,
wherein the plurality of shoulder structures are operative for
engaging the plurality of shoulder recesses to form a rabbet fit
between the first and second stub shafts and the shaft drum for
maintaining coaxial arrangement of the shaft assembly.
10. The axial compressor of claim 8, wherein each pin is
dimensioned to be larger than the corresponding key to allow for an
interference fit between the pin and the key.
11. The axial compressor of claim 8, wherein each key comprises a
slot formed on the first and second stub shafts and a corresponding
slot formed on the shaft drum.
12. The axial compressor of claim 8, wherein each pin includes a
recess substantially coaxial with a longitudinal axis of the pin,
the recess adapted for facilitating insertion of the pin into the
corresponding key.
13. The axial compressor of claim 8, further comprising one or more
through-bolts extending axially between the first and second stub
shafts through the shaft drum, the one or more through-bolts
providing a closing force to prevent relative movement between the
first and second stub shafts and the shaft drum.
14. The axial compressor of claim 13, wherein each through-bolt
includes threaded ends and a nut is provided at each threaded end
to tighten the through-bolt and couple the first and second stub
shafts to the shaft drum.
15. A method of attaching stub shafts to a shaft drum of an axial
compressor, the method comprising the steps of: providing an axial
shaft assembly comprising: a first stub shaft; a second stub shaft;
and a hollow shaft drum having a longitudinal axis, the first stub
shaft and the second stub shaft coupled to opposing ends of the
shaft drum along its longitudinal axis; providing a plurality of
keys disposed in a radial arrangement near the outer circumference
of the first and second stub shafts and the shaft drum; and
providing a plurality of pins engaging the plurality of keys,
wherein the pins prevent the shaft drum from rotating axially
relative to the first stub shaft and the second stub shaft and
prevent the shaft drum from axially and radially separating from
the stub shafts.
16. The method of claim 15, further comprising the steps of:
providing a plurality of shoulder structures provided on the first
stub shaft and the second stub shaft; and providing a plurality of
shoulder recesses provided at opposing ends of the shaft drum along
its longitudinal axis, wherein the plurality of shoulder structures
are operative for engaging the plurality of shoulder recesses to
form a rabbet fit between the first and second stub shafts and the
shaft drum for maintaining coaxial arrangement.
17. The method of claim 15, wherein each pin is dimensioned to be
larger than the corresponding key to allow for an interference fit
between the pin and the key.
18. The method of claim 15, wherein each key comprises a slot
formed on the first and second stub shafts and a corresponding slot
formed on the shaft drum.
19. The method of claim 15, further comprising the step of
providing one or more through-bolts extending axially between the
first and second stub shafts through the shaft drum, the one or
more through-bolts providing a closing force to prevent relative
movement between the first and second stub shafts and the shaft
drum.
20. The method of claim 19, wherein each through-bolt includes
threaded ends and a nut is provided at each threaded end to tighten
the through-bolt and couple the first and second stub shafts to the
shaft drum.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates, in general, to axial compressors
and, more particularly, to a method of attaching a stub shaft to a
drum of an axial flow compressor rotor shaft.
[0003] 2. Description of the Related Art
[0004] Turbo machines, such as centrifugal flow compressors, axial
flow compressors, and turbines are utilized in various industries.
Axial flow compressors, in particular, have a widespread use in
power stations, jet engine applications, gas turbines, and
automotive applications. Axial flow compressors are also commonly
used in large scale industrial applications, such as air separation
plants and hot gas expanders used in the oil refinery industry.
[0005] Axial flow compressors generally include a rotating shaft
coupled to a central drum having a number of airfoil blades
circumferentially arranged and spaced apart in multiple rows along
the axial length of the drum. The airfoil blades rotate between a
corresponding number of stationary blades attached to a stationary
tubular casing. The working fluid, such as air, enters and exits
the axial compressor in the axial direction of the rotating shaft.
Energy from the working fluid causes a relative motion of the
rotating airfoil blades with respect to stationary blades. The
cross-sectional area between the central drum and the casing
decreases from an inlet end to a discharge end, such that the
working fluid is compressed as it passes through the axial flow
compressor.
[0006] In the manufacture of axial flow compressors, one or more
solid stub shafts are operatively coupled to a hollow shaft drum by
way of an interference connection, such as a rabbet fit. Due to the
design of the stub shaft and the hollow drum, the two components
tend to grow apart both radially and axially during compressor
operation. The major change in dimension occurs in the radial
direction. The magnitude of radial expansion of the stub shaft is
usually smaller than the magnitude of radial expansion of the
hollow drum, which reduces the effectiveness of the interference
fit. In order to overcome this problem, prior art systems utilize
long through-bolts that extend between the inlet and discharge ends
of the stub shaft. The through-bolts extend in an axial direction
within an annular clearance space between the stub shaft and the
hollow shaft drum and prevent the shaft drum from radially growing
apart from the stub shaft.
[0007] Within the prior art, U.S. Pat. No. 1,142,069 to
Westinghouse discloses a marine turbine including a rotor element
having a drum to which an impulse wheel is bolted by means of a
plurality of bolts. The first shaft end is formed integrally with
the impulse wheel while the second shaft end is formed integrally
with the drum. FIGS. 1 and 3 of the Westinghouse patent illustrate
that the bolts are circumferentially arranged about the impulse
wheel.
[0008] U.S. Pat. No. 3,749,516 to Samurin et al. discloses a rotor
structure for turbo machines having stub shafts fixedly secured to
the ends of a through-bolt. A plurality of impellers is attached to
the stub shafts. The stub shafts are threaded onto the through-bolt
and compressed axially to form a rigid structure. A plurality of
driving means in the form of pins is positioned intermediate to the
impellers and between the impellers and the stub shafts. Radially
disposed keys are inserted between the impellers and the stub
shafts to engage the pins and provide a driving connection to the
impeller assembly from the stub shafts.
[0009] U.S. Pat. No. 7,335,108 to Lin et al. discloses a composite
drive shaft with captured end adapters. The drive shaft assembly
includes a composite tube captured by end adapters. The end
adapters are captured at the end portions of the composite tube.
Each end adapter includes an adapter tube interface configured to
engage the composite tube. A plurality of lugs protrudes radially
outward from the adapter tube interface to engage the composite
tube at its interior surface. The lugs function to transmit the
torque from the end adapters to the composite tube and vice
versa.
[0010] Numerous disadvantages are associated with the use of these
conventional devices to prevent relative movement between the stub
shaft and the shaft drum. In embodiments where through-bolts are
used, the bolts are subject to harmonic imbalance and resonance as
the axial flow compressor is brought up to operating speed because
the bolts must be of substantial length to extend along the entire
stub shaft length. High speeds at which stub shafts are usually
rotated further complicate these problems. Additionally, the
through-bolts are fastened under a very high pre-stretch condition,
which tends to weaken the bolts as the axial flow compressor is
operated in multiple cycles.
SUMMARY OF THE INVENTION
[0011] In view of the foregoing, a need exists for an assembly and
method for attaching the stub shaft to the shaft drum of the axial
flow compressor, whereby the need for through-bolts for preventing
relative motion of the stub shaft to the shaft drum is eliminated.
An additional need exists for providing an assembly and method for
attaching the stub shaft to the shaft drum of the axial flow
compressor, whereby the assembly and method lower manufacturing
costs and reduce maintenance expenses.
[0012] According to one embodiment, a shaft assembly for an axial
compressor includes a first stub shaft, a second stub shaft, and a
hollow shaft drum having a longitudinal axis. The first stub shaft
and the second stub shaft may be coupled to opposing ends of the
shaft drum along its longitudinal axis. A plurality of keys may be
disposed in a radial arrangement near the outer circumference of
the first and second stub shafts and the shaft drum. A plurality of
pins may engage the plurality of keys, wherein the pins prevent the
shaft drum from rotating axially relative to the first stub shaft
and the second stub shaft and prevent the shaft drum from axially
and radially separating from the stub shafts.
[0013] According to another embodiment, the shaft assembly may
further include a plurality of shoulder structures provided on the
first stub shaft and the second stub shaft and a plurality of
shoulder recesses provided at opposing ends of the shaft drum along
its longitudinal axis. The plurality of shoulder structures may be
operative for engaging the plurality of shoulder recesses to form a
rabbet fit between the first and second stub shafts and the shaft
drum for maintaining coaxial arrangement.
[0014] In accordance with yet another embodiment, each pin of the
axial shaft assembly may be dimensioned to be larger than the
corresponding key to allow for an interference fit between the pin
and the key. Additionally, each key may include a slot formed on
the first and second stub shafts and a corresponding slot formed on
the shaft drum. The shaft drum may further include a plurality of
recesses provided on its outer surface in axially-offset rows, each
of the plurality of recesses operative for receiving a rotor
blade.
[0015] In another embodiment of the axial shaft assembly, one or
more through-bolts may extend axially between the first and second
stub shafts through the shaft drum. The one or more through-bolts
desirably provides a closing force to prevent relative movement
between the first and second stub shafts and the shaft drum. Each
through-bolt may include threaded ends and a nut may be provided at
each threaded end to tighten the through-bolt and couple the first
and second stub shafts to the shaft drum.
[0016] According to another embodiment, an axial compressor may be
provided to include a housing having an inlet casing provided at
one end and a discharge casing provided at an opposing end and an
axial shaft assembly provided inside the housing. The axial shaft
assembly may extend between the inlet casing and the discharge
casing along the longitudinal length of the housing. A plurality of
stator blades may extend radially inward from an inner surface of
the housing and a plurality of rotor blades may extend radially
outward from the outer surface of the axial shaft assembly. The
axial shaft assembly may further include a first stub shaft, a
second stub shaft, and a hollow shaft drum having a longitudinal
axis. The first stub shaft and the second stub shaft may be coupled
to opposing ends of the shaft drum along its longitudinal axis. A
plurality of keys may be disposed in a radial arrangement near the
outer circumference of the first and second stub shafts and the
shaft drum. Additionally, a plurality of pins may engage the
plurality of keys, wherein the pins prevent the shaft drum from
rotating axially relative to the first stub shaft and the second
stub shaft and prevent the shaft drum from axially and radially
separating from the stub shafts.
[0017] According to a further embodiment, a method of attaching
stub shafts to a shaft drum of an axial compressor may include the
steps of providing an axial shaft assembly having a first stub
shaft, a second stub shaft, and a hollow shaft drum having a
longitudinal axis. The first stub shaft and the second stub shaft
are desirably coupled to opposing ends of the shaft drum along its
longitudinal axis. The method may additionally include the step of
providing a plurality of keys disposed in a radial arrangement near
the outer circumference of the first and second stub shafts and the
shaft drum. Furthermore, the method may include the step of
providing a plurality of pins engaging the plurality of keys,
wherein the pins prevent the shaft drum from rotating axially
relative to the first stub shaft and the second stub shaft and
prevent the shaft drum from axially and radially separating from
the stub shafts.
[0018] In another embodiment, the method may further include the
steps of providing a plurality of shoulder structures provided on
the first stub shaft and the second stub shaft and providing a
plurality of shoulder recesses provided at opposing ends of the
shaft drum along its longitudinal axis. Desirably, the plurality of
shoulder structures are operative for engaging the plurality of
shoulder recesses to form a rabbet fit between the first and second
stub shafts and the shaft drum for maintaining coaxial arrangement.
Each pin may be dimensioned to be larger than the corresponding key
to allow for an interference fit between the pin and the key.
Furthermore, each key may include a slot formed on the first and
second stub shafts and a corresponding slot formed on the shaft
drum.
[0019] In accordance with another embodiment, the method of
assembling stub shafts to a shaft drum of an axial compressor may
include the step of providing one or more through-bolts extending
axially between the first and second stub shafts through the shaft
drum. The one or more through-bolts may be operative for providing
a closing force to prevent relative movement between the first and
second stub shafts and the shaft drum. Each through-bolt may
include threaded ends and a nut is provided at each threaded end to
tighten the through-bolt and couple the first and second stub
shafts to the shaft drum.
[0020] Further details and advantages of the present invention will
become apparent from the following detailed description read in
conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a cross-sectional view of an axial flow compressor
showing the through-bolt arrangement according to the prior
art;
[0022] FIG. 2 is a cross-sectional view of internal components of
an axial flow compressor according to one embodiment of the present
invention;
[0023] FIG. 3 is a detailed cross-sectional view of another
embodiment of a pin in use with an axial shaft assembly in
accordance with the embodiment of FIG. 2;
[0024] FIG. 4 is a detailed cross-sectional view of a pin in use
with an axial shaft assembly shown in FIG. 2; and
[0025] FIG. 5 is an exploded view of internal components of an
axial flow compressor in accordance with another embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0026] For purposes of the description hereinafter, spatial
orientation terms, if used, shall relate to the referenced
embodiment as it is oriented in the accompanying drawing figures or
otherwise described in the following detailed description. However,
it is to be understood that the embodiments described hereinafter
may assume many alternative variations and embodiments. It is also
to be understood that the specific devices illustrated in the
accompanying drawing figures and described herein are simply
exemplary and should not be considered as limiting.
[0027] Referring to the drawings in which like reference characters
refer to like parts throughout the several views thereof, the
present invention is generally described in terms of an assembly
and method of attaching the stub shaft to the drum of the axial
compressor rotor shaft. With reference to FIG. 1, an axial
compressor 10 in accordance with a prior art embodiment is shown.
Axial compressor 10 includes an inlet end 20 provided opposite a
discharge end 30 along the axial direction of axial compressor 10.
Inlet end 20 includes an inlet casing 40 for directing the working
fluid into axial compressor 10. Desirably, inlet casing 40 is
secured to a first end of housing 50 of axial compressor 10 by a
plurality of mechanical fasteners 55. A discharge casing 60 is
provided at discharge end 30 for expelling the working fluid once
it is passed through axial compressor 10. Discharge casing 60 is
secured to the second end of housing 50 by a plurality of
mechanical fasteners 55.
[0028] With continuing reference to FIG. 1, an axial shaft assembly
70 is provided inside housing 50. Axial shaft assembly 70 is
rotatable about a longitudinal axis 80 of housing 50 to drive the
working fluid from inlet end 20 to discharge end 30. Axial shaft
assembly 70 includes a plurality of rotor vanes 90 extending
radially outward from its outer peripheral edge. A plurality of
stator blades 100 extend radially inward from an inner peripheral
edge of housing 50. Rotor vanes 90 and stator blades 100 are
arranged in one or more alternating rows along longitudinal axis
80. Working fluid is redirected between the alternating rows of
rotor vanes 90 and stator blades 100 as it is passed from inlet end
20 toward discharge end 30. A shaft seal 110 is provided at an
interface with the inlet and discharge casings, 40 and 60,
respectively, to seal axial shaft assembly 70 and prevent leakage
of the working fluid from axial compressor 10.
[0029] Axial shaft assembly 70 further includes an inlet end stub
shaft 120 and a discharge end stub shaft 130 connected to a hollow
shaft drum 140. Inlet end stub shaft 120 and discharge end stub
shaft 130 are connected to opposing ends of shaft drum 140 along
its longitudinal axis. Shoulder structures 150 are provided at
inlet end stub shaft 120 and discharge end stub shaft 130.
Complementary shoulder recesses 160 are provided at each end of
shaft drum 140 at the interface of shaft drum 140 with each of
inlet end stub shaft 120 and discharge end stub shaft 130. Shoulder
structures 150 and shoulder recesses 160 form a rabbet fit between
stub shafts 120, 130 and shaft drum 140 to maintain the coaxial
arrangement of these components. Stub shafts 120, 130 are further
secured to shaft drum 140 via a plurality of through-bolts 170
extending from inlet end stub shaft 120 to discharge end stub shaft
130 through shaft drum 140. A plurality of holes 180 are formed in
a radial pattern around the circumference of inlet end stub shaft
120 and discharge end stub shaft 130. Through-bolt 170 is inserted
through each of the plurality of holes 180 to securely connect the
stub shafts to shaft drum 140. Each through-bolt 170 must be
pre-stretched in order to provide a large closing force in the
rabbet fit between the stub shafts 120, 130 and shaft drum 140.
This arrangement keeps shaft drum 140 from slipping relative to
each of the stub shafts 120, 130 and prevents shaft drum 140 from
axially and radially growing apart from the stub shafts 120, 130
during operation of axial compressor 10.
[0030] With the basic structure of axial compressor 10 having an
axial shaft assembly 70 according to an embodiment of the prior art
now described with reference to FIG. 1, a shaft assembly 200 will
now be described with reference to FIGS. 2-5. In various
embodiments, shaft assembly 200 is utilized with axial compressor
10; however, it is to be understood that this described embodiment
is exemplary only, and that shaft assembly 200 may be utilized with
a plurality of other turbine devices.
[0031] Referring to FIG. 2, shaft assembly 200 includes an inlet
end stub shaft 210 and a discharge end stub shaft 220 connected to
a hollow shaft drum 230. Inlet end stub shaft 210 and discharge end
stub shaft 220 are connected to opposing ends of shaft drum 230
along its longitudinal axis 240. Shaft drum 230 may be manufactured
from the same material as the stub shafts 210 and 220.
Alternatively, shaft drum 230 may be manufactured from a different
material compared to stub shafts 210 and 220. Shaft drum 230,
desirably, has a plurality of recesses 250 for receiving rotor
blades 260 (shown in FIGS. 4-5). Each recess 250 is provided on the
outer surface of shaft drum 230. FIGS. 4 and 5, for example,
illustrate a dove-tail recess 250; however, other embodiments are
possible without departing from the scope and spirit of the
structure of shaft drum 230. As shown in FIGS. 4 and 5, each rotor
blade 260 is slidingly received inside recess 250, such that a
plurality of rotor blades 260 is arranged in rows extending axially
along the longitudinal length of shaft drum 230.
[0032] Referring back to FIG. 2, shoulder structures 270 are
provided at inlet end stub shaft 210 and discharge end stub shaft
220. Complementary shoulder recesses 280 are provided at each end
of shaft drum 230 at the interface of shaft drum 230 with each of
inlet end stub shaft 210 and discharge end stub shaft 220. Shoulder
structures 270 and shoulder recesses 280 form a rabbet fit between
stub shafts 210 and 220 and shaft drum 230 to maintain the coaxial
arrangement of these components. Shoulder structures 270 desirably
extend over shoulder recesses 280 in a radial direction of shaft
drum 230. This arrangement keeps shaft drum 230 from slipping
relative to each of the stub shafts 210 and 220 and prevents shaft
drum 230 from axially and radially growing apart from the stub
shafts 210 and 220 during operation of axial compressor 10.
[0033] With continuing reference to FIG. 2, stub shafts 210 and 220
are further secured to shaft drum 230 via a plurality of pins 290
secured inside a plurality of keys 300 provided on the stub shafts
210, 220, and shaft drum 230. Keys 300 are disposed in a radial
arrangement near the outer circumference of the stub shafts 210,
220 and shaft drum 230. Each key 300 includes a stub shaft slot 310
and a corresponding shaft drum slot 320 provided on the respective
components. Each key 300 may be rounded in cross-section; however,
one of ordinary skill in the art will recognize that other shapes,
such as square or rectangular, may also be possible. Each pin 290
is shaped such that it may be disposed inside a corresponding key
300. For example, each pin 290 may have an elongated cylinder shape
that corresponds to key 300. Desirably, each pin 290 is dimensioned
slightly larger than a corresponding key 300 to allow for an
interference fit between pin 290 and key 300. This arrangement
keeps shaft drum 230 from slipping relative to each of the stub
shafts 210 and 220 and prevents shaft drum 230 from axially and
radially growing apart from the stub shafts 210 and 220 during
operation of axial compressor 10.
[0034] With reference to FIG. 3, another embodiment of pin 290 is
illustrated. In this embodiment, pin 290 includes a recess 370
extending axially inward from one end of pin 290. Recess 370 is
desirably coaxial with a longitudinal axis of pin 290 and extends
through a portion of the body of pin 290. Recess 370 is shaped to
accommodate a pin insertion tool (not shown) for inserting pin 290
into corresponding key 300. In order to assemble pin 290 inside key
300 in an interference fit, it is desirable to cool pin 290 in
order to slightly reduce its outer dimension. Such cooling may be
accomplished, for example, using liquid nitrogen. Recess 370 is
provided to facilitate handling of pin 290 as it is moved from a
cooling station, such as a container with liquid nitrogen, and
positioned for insertion into key 300. The pin insertion tool is
inserted into recess 370 such that pin 290 may be cooled and
inserted into key 300. The pin insertion tool is then retracted
from recess 370. Recess 370 has a chamfered edge 380 to facilitate
insertion of the pin insertion tool.
[0035] With reference to FIG. 5, an exploded view of shaft assembly
200 is shown. Optionally, a plurality of through-bolts 330 may be
provided between inlet end stub shaft 210 and discharge end stub
shaft (not shown in FIG. 5). Through-bolt 330 desirably extends
through shaft drum 230 and includes threaded ends 335. A plurality
of holes 340 are formed in a radial pattern around the
circumference of inlet end stub shaft 210 and discharge end stub
shaft 220. Through-bolt 330 is inserted through each of the
plurality of holes 340 to securely connect the stub shafts 210 and
220 to shaft drum 230. A nut 350 is threaded onto each threaded end
335 of through-bolt 330 and tightened to couple the stub shafts 210
and 220 to shaft drum 230. A washer 360 may be provided at the
interface between nut 350 and hole 340.
[0036] With the basic structure of shaft assembly 200 according to
an embodiment of the present invention now described, a method of
attaching stub shafts 210 and 220 to shaft drum 230 will now be
described with reference to FIGS. 2-5. According to an embodiment
of shaft assembly 200 for axial compressor 10, the method of
attaching stub shafts 210 and 220 to shaft drum 230 begins at a
step where inlet end stub shaft 210 and discharge end stub shaft
220 are provided on opposing ends of shaft drum 230. At the next
step, shoulder structures 270 are provided at inlet end stub shaft
210 and discharge end stub shaft 220. At the following step,
complementary shoulder recesses 280 are provided at each end of
shaft drum 230 at the interface of shaft drum 230 with each of
inlet end stub shaft 210 and discharge end stub shaft 220. Shoulder
structures 270 and shoulder recesses 280 form a rabbet fit between
stub shafts 210 and 220 and shaft drum 230 to maintain the coaxial
arrangement of these components. Subsequently, a plurality of keys
300 are provided on the stub shafts 210, 220, and shaft drum 230.
Keys 300 are disposed in a radial arrangement near the outer
circumference of the stub shafts 210, 220, and shaft drum 230. At
the next step, a plurality of pins 290 are inserted into one of the
slots 310 or 320 formed on inlet end stub shaft 210 or shaft drum
230, respectively. Desirably, each pin 290 is dimensioned slightly
larger than a corresponding key 300 to allow for an interference
fit between pin 290 and key 300. At the final step, inlet end stub
shaft 210 and discharge end stub shaft 220 are secured to shaft
drum 230 by inserting and securing each pin 290 inside key 300. The
interference fit between each pin 290 and key 300 is sufficient to
prevent relative movement of the stub shafts 210 and 220 with
respect to shaft drum 230. Optionally, a plurality of through-bolts
330 may be inserted through the corresponding plurality of holes
340 provided on the stub shafts 210 and 220 to further secure the
shaft assembly 200.
[0037] While an embodiment of an axial compressor having a shaft
assembly and a method of attaching the stub shafts to the shaft
drum of the axial compressor is shown in the accompanying figures
and described herein in detail, other embodiments will be apparent
to, and readily made by those skilled in the art, without departing
from the scope and spirit of the invention. For example, while the
present disclosure generally discusses the shaft assembly 200
utilized with an axial compressor 10, it is contemplated that
embodiments of the shaft assembly and method may be applicable to
other gas turbine devices. The scope of the invention will be
measured by the appended claims and their equivalents.
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