Note: Descriptions are shown in the official language in which they were submitted.
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STEAM TURBINE, BLADE, AND METHOD
BACKGROUND
TECHNICAL FIELD
The present invention relates generally to steam turbines and, more
specifically,
to a stator blade ring for a steam turbine and a method of making a stator
blade
ring.
DISCUSSION OF THE BACKGROUND
A steam turbine is a turbo machine which converts thermal and pressure energy
of steam into rotary motion which may be used to perform work. Steam turbines
may be used, for example, to drive electrical generators or compressors.
To enhance steam turbine efficiency, steam is often expanded through a number
of stages. Each stage typically includes a stator blade diaphragm and a
bearing
mounted rotor assembly including at least one impeller.
As steam progresses through the latter stages of the steam turbine, sufficient
energy may be absorbed from the steam to cause portions of the steam to
condense, and thus, to become so called, wet steam. In addition to having a
potential corrosive effect, when wet steam impinges against the stator blade
diaphragm, the condensate tends to violently impact the stator blades and
other
parts of the diaphragm. As a result, the stator blades and other portions of
each
stator blade diaphragm in the latter stages of the steam turbine may be
damaged, for example, during prolonged exposure to wet steam having a high
proportion of condensate.
In modern steam turbines, the manufacture of stator blade diaphragms
represents a significant cost, particularly in multi stage steam turbines
having
three or more stages each of which may include one or more separate stator
blade diaphragms.
If a stator blade diaphragm is damaged, the steam turbine may need to be shut
down and the damaged stator diaphragm removed for servicing. If on site repair
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is not possible, the entire diaphragm may need to be sent for repair or
alternatively, an entire new stator diaphragm must be installed. Worse yet, if
a
replacement is available, a new stator blade diaphragm must be fabricated.
Thus, in addition to the cost of the stator diaphragm, costs associated with
the
extended downtime of the steam turbine are also incurred.
Accordingly, what is needed is a replacement for the conventional stator blade
diaphragm, which is easily serviced and/or replaced, which is capable of
successful operation in the presence of wet steam, and which provides a simple
design which is easier manufactured.
SUMMARY
According to an exemplary embodiment, a stator blade ring for a steam turbine
includes a plurality of stator blade modules defining an annular chamber, each
stator blade module including an elongated blade portion including a first
blade
shell portion and a second blade shell portion brazed to the first blade shell
portion. The elongated blade portion further includes a longitudinal
passageway
and at least one opening extending through one of the first blade shell
portion
and the second blade shell portion to the longitudinal passageway. An inner
portion brazed to a first longitudinal end of the blade portion, the inner
portion
including a through hole forming a portion of the annular chamber, the inner
portion further including an inner passageway extending from the through hole
to
the longitudinal passageway. An outer portion brazed to a second longitudinal
end of the blade portion and engaged to the steam turbine, the outer portion
including an outer passageway open to a surface of the steam turbine and the
longitudinal passageway.
According to another exemplary embodiment, a turbo machine includes a rotor
assembly including at least one impeller, a bearing connected to, and for
rotatably supporting, the rotor assembly, and a stator blade ring having a
plurality
of stator blade modules defining an annular chamber. Each blade module
includes at least one elongated blade portion including a first blade shell
portion
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and a second blade shell portion brazed to the first blade shell portion, an
inner
portion brazed to a first longitudinal end of the at least one blade portion,
the
inner portion including a through hole forming a portion of the annular
chamber,
and an outer portion brazed to a second longitudinal end of the at least one
blade
portion and engaged to a surface of the steam turbine. At least one of the
blade
modules includes a longitudinal passageway and at least one opening in the at
least one blade portion for liquid to enter the longitudinal passageway and an
inner passageway in the inner portion extending from the through hole to the
longitudinal passageway for allowing the liquid to flow between the annular
chamber and the longitudinal passageway. At least one of the blade modules
includes a longitudinal passageway in the at least one blade portion, an inner
passageway in the inner portion extending from the through hole to the
longitudinal passageway for allowing the liquid to flow between the annular
chamber and the longitudinal passageway and an outer passageway in the outer
portion extending from the longitudinal passageway and opening to the surface
of
the turbo machine for allowing the liquid to flow out of the stator blade
ring.
According to another exemplary embodiment, a method of making a blade
module for a stator blade ring can include the steps of brazing first and
second
edges of a first blade shell portion to first and second edges of a second
blade
shell portion to provide an elongated blade portion having a longitudinal
passageway, forming a through hole in the inner portion, forming an inner
passageway in the inner portion extending from a surface of the inner portion
to
the through hole, brazing a first longitudinal end of the blade portion to the
surface of the inner portion such that the longitudinal passageway is open to
the
inner passageway, forming an outer passageway in the outer portion extending
from a first surface to a second surface of the outer portion, and, brazing a
second longitudinal end of the blade portion to the first surface of the outer
portion such that the longitudinal passageway is open to the outer passageway.
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BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of
the specification, illustrate one or more embodiments and, together with the
description, explain these embodiments. In the drawings:
Figure 1 depicts a steam turbine.
Figure 2 shows a perspective view of an exemplary embodiment.
Figure 3 shows a side view of the exemplary embodiment of Figure 2.
Figure 4 shows a cross-sectional view of the exemplary embodiment shown in
Figure 2.
Figures 5 to 7 show an inner portion of the exemplary embodiment shown in Fig.
2.
Figures 8 to 10 show an outer portion of the exemplary embodiment shown in
Fig. 2.
Figure 11 is a flowchart illustrating a method of making a blade module for a
stator blade ring according to an exemplary embodiment.
DETAILED DESCRIPTION
The following description of the exemplary embodiments refers to the
accompanying drawings. The same reference numbers in different drawings
identify the same or similar elements. The following detailed description does
not
limit the invention. Instead, the scope of the invention is defined by the
appended
claims. The following embodiments are discussed, for simplicity, with regard
to the
terminology and structure of a turbo machine that has a stator and a rotor.
However, the embodiments to be discussed next are not limited to these
exemplary
systems, but may be applied to other systems.
Reference throughout the specification to "one embodiment" or "an embodiment"
means that a particular feature, structure, or characteristic described in
connection
with an embodiment is included in at least one embodiment of the subject
matter
disclosed. Thus, the appearance of the phrases "in one embodiment" or "in an
embodiment" in various places throughout the specification is not necessarily
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referring to the same embodiment. Further, the particular features, structures
or
characteristics may be combined in any suitable manner in one or more
embodiments.
To provide some context for the subsequent discussion relating to stator
blades
according to these exemplary embodiments, Figure 1 schematically illustrates a
turbo machine in the form of a multistage steam turbine 400. Therein, the
steam
turbine 400 includes a housing (stator) 420 within which a number of stator
blade
diaphragms 430 are disposed along with a rotor shaft 450 provided with a
plurality of impeller rotors 440. The shaft 450 is supported radially and
axially
through bearings 480.
During operation, the steam turbine takes a steam input from an inlet 460
through
various stages of expansion, to an outlet 470 leading to a condensor. At each
turbine stage, steam is directed by a stator diaphragm 430 onto an impeller
rotor
440 thereby converting the temperature and pressure energy of the steam into
rotating energy available for work at the rotor shaft 450.
Figure 2 shows a portion of a stator blade ring 12 according to an exemplary
embodiment of the present invention. Stator blade ring 12 includes a plurality
of
individual stator blade modules 14 extending around rotor 28 (Fig. 3) in steam
turbine 10. Figure 2 shows two such blade modules 14a and 14b.
Each stator blade module 14a, 14b includes an elongated blade portion 16, as
shown in Figs. 2 and 3. Fig. 4 shows a cross-sectional view of an elongated
blade portion 16 having a longitudinal reinforcing rib 24 and longitudinal
passageways 26. As is further shown in Fig. 4, a blade portion 116 may also be
provided without reinforcing rib 24 and may thus have a single longitudinal
passageway 26. As will be discussed in further detail below, each blade
portion
16 is made by brazing a first blade shell portion 18 to a second blade shell
portion 22 along the upstream edge 32 and the downstream edge 34 thereof.
As further shown in Figs. 2 to 4, each blade portion 16 includes a plurality
of
openings 36 in at least one of blade shell portion 22 and blade shell portion
24.
In the embodiment of Figs. 2 to 4, each opening 36 is a slot formed by
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discharge machining. Alternatively, openings 36 may be formed by other
machining processes such as drilling or milling, or, openings 36 may be formed
during the initial manufacture of blade shell portion 22 and blade shell
portion 24,
for example, by a mold insert.
Each blade module 14 includes an inner portion 38 connected to a first
longitudinal end of at least one blade portion 16, as shown in Fig. 2. In the
embodiment shown in Figs. 2 to 4, inner portion 38 is brazed to blade portion
16,
as will be discussed further below. Each inner portion 38 includes a through
hole
42 extending transversely to the longitudinal axis 46 (Fig. 3) of blade
portion 16.
Through hole 42 forms a part of an annular chamber 20 in stator blade ring 12
when each of the blade modules are installed into the steam turbine 10. In
order
to enhance the seal between through holes 42 in adjacent blade modules 14, at
least one end of each through hole 42 may be provided with a groove 48
configured to receive a sealing gasket. In the embodiment of Figs. 2 to 4,
groove
48 is configured to receive an 0-ring.
Each inner portion 38 also includes at least one inner passageway 44, as shown
in Fig. 3, extending from through hole 42 to each longitudinal passageway 26.
Alternatively, if reinforcement rib 24 is terminated prior to the longitudinal
end of
blade portion 16, then a single inner passageway 44 may be open to both
longitudinal passageways 26.
Each stator blade module 14 also includes an outer portion 52 connected to a
second longitudinal end of at least one blade portion 16, as shown in Figs. 2
and
3. Each outer portion 52 includes at least one outer passageway 54 which is
open to each longitudinal passageway 26 and to an interior surface of steam
turbine 10, as shown in Figs. 2, 9 and 10. Further, in the embodiment of Figs.
2 to
4 and 8-10, each outer portion may include a groove 74 on at least one side
thereof. Groove 74 may be configured to receive a gasket for sealing adjacent
outer portions 52 to each other and/or for providing a dampening effect to
stator
blade ring 12. Stator blade ring 12 may be used in one of the latter stages of
the
steam turbine 10, as shown in Fig. 2. During operation, condensate from the
wet
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steam impinging against each blade portion 14 may enter the longitudinal
passageway 26 of a blade portion 16 through one of the openings 36. Multiple
paths are available for the condensate to travel within the blade modules 14
before exiting outside stator blade ring 12 at a location where the condensate
may be less likely to cause damage to the components of steam turbine 10. In
one path, which may include stator blade modules 14 above the rotor shaft, the
condensate may travel downwardly through each longitudinal passageway 26
and inner passageway 44 into through hole 42. The open through holes 42 in
adjacent blade modules 14 that form the annular chamber 20 extending around
stator blade ring 12 allow the condensate to continue flowing downwardly with
gravity. The condensate may exit the annular chamber 20 and continue on a
downward path through an inner passageway 44 of a blade module 14 below the
rotor shaft of steam turbine 10. Finally, the condensate may flow through an
outer passageway 54 to a surface of steam turbine outside of blade ring 12.
In another path, condensate may enter a longitudinal passageway 26 of a blade
portion 16 below the rotor shaft of steam turbine 10 and flow out through
outer
passageway 54 without first travelling through the annular chamber 20 formed
by
through holes 42.
The removal of condensate from the wet steam progressing through the latter
stages of steam turbine 10 may prevent damage to the stator blade ring 12 as
well as to the turbine blades 16 and other downstream components of steam
turbine 10. Moreover, stator blade ring 12 allows for the collection of
condensate
which may include residual heat for use in other processes.
Some blade modules, for example, blade modules above the rotor shaft of steam
turbine 10, may be provided without an outer passageway 54, for example, to
reduce manufacturing costs, since the downward flow of condensate may obviate
the need for outer passageways 54 in blade modules 14 above the rotor shaft.
Further, some blade modules 14 may be provided with blade portions 16 without
slots, for example, to further reduce manufacturing costs. Alternatively, and
as
shown in the embodiment of Figs. 2-3 and 5-10, each of the blade modules 14
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may be identical to one another. This feature provides a number of benefits.
For
example, the manufacturing process is rendered more uniform. Also, servicing
of
steam turbine 10 is also more convenient in that, during repair or replacement
of
a single blade module 14 which is made possible by the exemplary embodiment,
only a single part number is necessary since all blade modules 14 are
identical
within the stator blade ring 12.
In addition to providing cost savings over stator blade diaphragms which may
need to be serviced or replaced as a unit, blade modules 14 provide a simple
one
piece design which is easier to install and/or replace than conventional
stator
blade diaphragm rings. As shown in Figs. 2, 3 and 8 to 10, the outer portion
52
of each stator blade module 14 is engaged directly to steam turbine 10.
Specifically, each outer portion 52 includes an upstream groove 56 and a
downstream groove 58. Steam turbine 10 includes an upstream ridge 62
engaging groove 56 and a downstream ridge 64 engaging groove 58. Groove 56
is offset closer to inner portion 38 than groove 58. The offset between
grooves
56 and 58 may allow each stator blade module to better conform to the desired
flow path of the steam through steam turbine 10, and may also prevent a
technician from inadvertently installing a blade module 14 in an improper
orientation during construction or servicing of stator blade ring 12.
As shown in Figs. 2 and 3, outer passageway 54 opens to a surface of steam
turbine 10 between ridge 62 and ridge 64. Note that a chamber 76 is formed
between the outer surface of blade ring 12 and the surface of steam turbine
10.
Chamber 76 may facilitate convenient collection of condensate which flows out
of
outer passageways 54.
A groove 66 in each inner portion 38 forms a continuous circumferential groove
facing a center of stator blade ring 12, as shown in Figs. 2, 3, and 5-7. As
shown
in Fig. 3, each groove 66 is engaged by a metal ring 68 which locks the stator
blade modules 14 together.
As further shown in Figs. 2, 3 and 5 to 7, the inner portion 38 of each stator
blade
module 14 defines an inner brazing platform 72 surrounding the first
longitudinal
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end of each blade portion 16. Also, as shown in Figs. 2, 3 and 8 to 10, the
outer
portion 52 of each stator blade module defines an outer brazing platform 74
surrounding the second longitudinal end of each blade portion 16.
Brazing platform 72 and brazing platform 74 provide a convenient surface for
brazing the longitudinal ends of each blade portion 16 as well as defining a
portion of a stage and/or steam flow path within steam turbine 10. Note from
Figs. 2 and 3 that the brazing platform 74 of each outer portion 52
transitions
evenly to the surrounding surfaces of steam turbine 10.
In the embodiment of Figs. 2 to 4, blade shell portion 18 may be vacuum brazed
to blade shell portion 22. The first and second longitudinal ends of the
resulting
blade portion 16 may then be vacuum brazed to the inner portion 38 and outer
portion 52 of each stator blade module 14. The vacuum brazing equipment used
to perform the vacuum brazing of diaphragm 14 can be standard vacuum brazing
equipment as, for example, disclosed in U.S. Patent Nos. 4,874,918 and
4,401,254.
Thus, according to an exemplary embodiment shown in Fig. 11, a method (1000)
of making a blade module for a stator blade ring, the blade module including
an
elongated blade portion, an inner portion, and an outer portion, can include
the
steps of brazing (1002) first and second edges of a first blade shell portion
to first
and second edges of a second blade shell portion to form a longitudinal
passageway in the elongated blade portion, forming (1004) a through hole in
the
inner portion, forming (1006) an inner passageway in the inner portion
extending
from a surface of the inner portion to the through hole, brazing (1008) a
first
longitudinal end of the blade portion to the surface of the inner portion such
that
the longitudinal passageway is open to the inner passageway, forming (1010) an
outer passageway in the outer portion extending from a first surface to a
second
surface of the outer portion, and, brazing (1012) a second longitudinal end of
the
blade portion to the first surface of the outer portion such that the
longitudinal
passageway is open to the outer passageway.
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The above-described exemplary embodiments are intended to be illustrative in
all
respects, rather than restrictive, of the present invention. Thus the present
invention is capable of many variations in detailed implementation that can be
derived from the description contained herein by a person skilled in the art.
All
such variations and modifications are considered to be within the scope of the
present invention as defined by the following claims. No element, act, or
instruction
used in the description of the present application should be construed as
critical or
essential to the invention unless explicitly described as such. Also, as used
herein,
the article "a" is intended to include one or more items.
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