Information
-
Patent Grant
-
6196793
-
Patent Number
6,196,793
-
Date Filed
Monday, January 11, 199925 years ago
-
Date Issued
Tuesday, March 6, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Look; Edward K.
- Nguyen; Ninh
Agents
- Patnode; Patrick K.
- Snyder; Marvin
-
CPC
-
US Classifications
Field of Search
US
- 415 202
- 415 191
- 415 2082
- 415 2091
- 415 2093
- 415 193
-
International Classifications
-
Abstract
Apparatus and method for directing a flow of fluid to a turbine via a nozzle box mountable to encircle a shaft. The nozzle box includes a housing having an inner wall spaced from an outer wall and joined therewith so as to form a chamber therein. The housing also includes at least one inlet and at least one outlet in which each is in fluid flow communication with the chamber. A plurality of radially projecting nozzles are positioned between the inner and outer walls and located upstream of the outlet for directing the flow of fluid through the outlet. A flow distributor is positioned between the inner and outer walls and located upstream of the nozzles for directing the flow of fluid through the chamber and to the nozzles. The flow distributor is configured to obtain a substantially uniform flow of fluid to the nozzles.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to turbines, and more specifically, to a nozzle box for increasing the efficiency of a flow directed to a turbine.
By way of a more detailed background, and with reference to
FIG. 1
, a control or first stage
10
of a conventional turbine includes a nozzle box
12
surrounding a rotor
14
, the turbine control stage represented by a single bucket
16
. Nozzle box
12
generally includes a torus portion
18
, a bridge ring assembly
20
and a partition ring assembly
22
. In turbines of this type, steam is fed into torus portion
18
of nozzle box
12
, and is directed axially between outer bridge ring
24
and inner bridge ring
26
, and between a plurality of circumferentially spaced bridge elements
28
, which bridge elements
28
connect rings
24
and
26
. The steam then flows through partition ring assembly
22
towards bucket(s)
16
. Partition ring assembly typically comprises of radially inner and outer bands
30
and
32
(each formed in 180° segments which, when the turbine is fully assembled, form 360° rings), respectively, which hold between them a large number (for example, 100) of vane-shaped partition elements
34
, which partition elements
34
serve to direct the steam at a desired angle to the bucket blades. Steampath assembly
22
is welded in place between upper and lower rings
24
,
26
by circumferentially extending welds
36
,
38
. Rings
24
,
26
are, in turn, welded to torus
18
by means of circumferential welds
40
,
42
. Nozzle box
12
is supported within a turbine inner shell
44
by a plurality of lugs
46
(one shown) welded to the outside of torus
18
and bridge ring assembly
20
, in an area radially adjacent partition ring assembly
22
. Nozzle box
12
is also keyed to inner shell
44
at
48
.
Within conventional nozzle box designs, however, there exists significant circumferential variation in the cylindrical flow angle and a hub-strong velocity profile of the flow entering the first stage nozzle. This type of inlet distortion can lead to a significant loss in first stage efficiency.
Accordingly, there is a need in the art for an improved nozzle box.
SUMMARY OF THE INVENTION
An apparatus and method for directing a flow of fluid to a turbine via a nozzle box mountable to encircle a shaft is disclosed. The nozzle box includes a housing having an inner wall spaced from an outer wall and joined therewith so as to form a chamber. The housing also includes at least one inlet and at least one outlet, each in fluid flow communication with the chamber. A plurality of radially projecting nozzles are positioned between the inner and outer walls and located upstream of the outlet for directing the flow of fluid through the outlet. A flow distributor is positioned between the inner and outer walls and located upstream of the nozzles for directing the flow of fluid through the chamber and to the nozzles. The flow distributor is configured to maintain a substantially uniform flow of the fluid to the nozzles.
DESCRIPTION OF THE DRAWINGS
FIG. 1
is a partial cross-sectional, cutaway view of a conventional nozzle box construction;
FIG. 2
is an enlarged perspective view of a conventional available nozzle box.
FIG. 3
is a schematic view of the nozzle box of
FIG. 2
with a portion of the nozzle box enlarged and cut away to expose the configuration of a plurality of nozzles and a plurality of bridges located therein;
FIG. 4
is an enlarged perspective, partially cut-away view of an exemplary embodiment of a nozzle box of the invention;
FIG. 5
is a cross-sectional view of the nozzle box of
FIG. 4
taken along the line
5
—
5
;
FIG. 6
is an enlarged schematic view of a cut-away portion of the nozzle box of
FIG. 4
detailing a flow distributor and a plurality of radially projecting nozzles;
FIG. 6A
is a back view of the flow distributor of
FIG. 6
taken along the line
6
A—
6
A without the cut-away portion removed;
FIG. 7
is a view similar to
FIG. 6
but of an alternative embodiment of the flow distributor comprising a honeycomb structure;
FIG. 7A
is a back view of the flow distributor of
FIG. 7
taken along the line
7
A—
7
A without the cut-away portion removed;
FIG. 8
is a view similar to
FIG. 6
but of an alternative embodiment of the flow distributor comprising a holed plate;
FIG. 8A
is a back view of the flow distributor of
FIG. 8
taken along the line
8
A—
8
A without the cut-away portion removed;
FIG. 9
is a view similar to
FIG. 6
but of an alternative embodiment of the flow distributor comprising a slotted plate;
FIG. 9A
is a back view of the flow distributor of
FIG. 9
taken along the line
9
A—
9
A without the cut-away portion removed; and
FIG. 10
is an exploded view of a nozzle box similar to
FIG. 5
but of an alternative embodiment of the flow distributor comprising a retro-fit part separably connectable with the nozzle box and having a flow distributor configuration similar to FIG.
6
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to
FIG. 2
, a nozzle box
50
includes inlet pipes
52
and a torus
54
. Also referring to
FIG. 3
, within torus
54
are typically a ring of structural bridges
56
and a ring of nozzles or partitions
58
. Nozzles
58
can be connected at one end to outer wall
60
and at a second end to wall
62
. Bridges
56
are connected at both ends within torus
54
. Bridges
56
serve merely to mechanically maintain inner wall
62
and outer wall
60
in position against the outward stress of pressurized fluid, for example steam, exerted within chamber
64
during operation. Conventional design practice is that bridges
56
must be spaced far apart so as to not cause pressure loss within the system and serve the mechanical purpose intended for maintaining the structural integrity of inner wall
62
and outer wall
60
.
In operation, a flow of steam, represented schematically by flow arrows
66
,
68
and
70
, under pressure is received in torus
54
though inlets
52
in the direction of flow arrows
66
and forced into chamber
64
. By conventional pressure differential principles, the flow of steam is forced through chamber
64
, through bridges
56
, through nozzles
58
and through an outlet
72
in the direction of flow arrows
70
, which flow arrows
70
are generally perpendicular to flow arrows
66
. Steam flowing in direction
70
impacts and drives the turbine blades of the turbo machinery.
Still referring to
FIGS. 2 and 3
, experimentally and computationally, for example, using a conventional computational fluid dynamics code, such as CFX5.2 sold by AEA Technology, PLC headquartered in Great Britain, tests have determined that the efficiency of a high pressure section can be substantially increased if the uniformity of the flow of steam exiting nozzle box
50
is enhanced. As used herein, the phrase substantially increased means an increase in efficiency in the range between about 1% to about 2% above the 88% efficiency of a typical high pressure section of a steam turbine.
As determined in the manner discussed above, the configuration of nozzles
58
and bridges
56
in nozzle box
50
leads to significant circumferential non-uniformity characteristics in terms of a swirl angle and an axial velocity of the flow of steam passing through and out of nozzle box
50
. At least in part, the swirl angle and axial velocity components are created by flowing the steam into and out of nozzle box
50
, for example, the steam flowing into nozzle box
50
in a direction
66
but flowing out of nozzle box
50
in a direction
70
that is perpendicular to direction
66
. Also, for example, multiple inlets
52
, that enter chamber
64
from opposite directions, further contribute to creating the efficiency reducing non-uniformity characteristics.
As a result of these non-uniformity characteristics, it has been determined that the flow of steam leaving outlet
72
and impacting the turbo machinery, is not substantially circumferentially uniform. The energy provided by the flow of steam is a series of peaks and valleys over the circumference of outlet
72
. Consequently, the turbo machinery runs less efficiently than possible with a circumferentially uniform flow of steam.
Still referring to
FIGS. 2 and 3
, another factor considered was the critical constraint of bridges
56
that carry the tensile stress between inner wall
62
and outer wall
60
to prevent structural failure, for example, blow out of nozzle box
50
at inner wall
62
or outer wall
60
. Additionally, it is desirable to enhance the uniformity of the flow of steam without significantly increasing the total pressure loss or else any gain realized by uniformity will be canceled out by the loss of energy attributed to pressure loss.
FIGS. 4-5
illustrate a nozzle box
100
mountable to encircle a shaft of a turbine (not shown) for directing a flow of fluid, for example, steam, to a turbine. Nozzle box
100
includes a housing
102
having an inner wall
104
spaced from an outer wall
106
and joined therewith so as to form a chamber
108
. Housing
102
includes at least one inlet
110
and at least one outlet
112
in which each is in fluid flow communication with chamber
108
. A plurality of radially projecting nozzles
114
are fixedly positioned between inner wall
104
and outer wall
106
and located upstream of outlet
112
for directing the flow of fluid through outlet
112
. A flow distributor
116
is fixedly positioned between inner wall
104
and outer wall
106
and located upstream of nozzles
114
for directing the flow of fluid through chamber
108
to nozzles
114
. Flow distributor
116
is typically rigidly connected to both inner wall
104
and outer wall
106
. Nozzle box
100
and associated components are constructed of typical materials used to make similar components in nozzle box
50
(FIG.
2
). Flow distributor
116
is constructed of typical materials used for structural bridges
56
(FIG.
2
).
FIGS. 4 and 5
further illustrate nozzle box
100
as a single-flow nozzle box. Double-flow nozzle boxes can implement the invention and would generally be constructed and function similar to the single-flow box as shown and described. In particular, a double-flow nozzle box (not shown) also directs a flow of steam out the “back” of housing
102
, in a direction generally 180° opposite that of outlet
112
. Such a nozzle box would thus have a second flow distributor and a second ring of nozzles included therein for directing a second flow of steam to the turbo machinery.
Generally,
FIGS. 6-9A
, illustrate flow distributor
116
configured to obtain a substantially uniform flow of fluid, for example, steam, to nozzles
114
. Flow distributor
116
smooths out or reduces a circumferential variation of the flow velocity and straightens or reduces the swirl angle of the flow, thereby enhancing the uniformity of the flow of fluid exiting nozzle box
100
, without significantly increasing total pressure loss of the flow of fluid. For example, flow distributor
116
includes a plurality of flow members
118
. Each flow member
118
is at least partially spaced from an adjacent flow member
118
by a flow passage
120
formed therebetween. Flow passage
120
may be defined by at least a pair of spaced side walls
122
positioned axially relative to an axis of a shaft and extending parallel relative to each other for at least an upstream portion
124
of flow passage
120
. Flow passage
120
may have an axial length to width ratio greater than about 3.5:1.7, for example at the narrowest portion of flow passage
120
, and preferably has such a ratio of about 3.5:0.4.
FIGS. 6 and 6A
illustrate an exemplary embodiment including flow members
118
having an aerodynamically shaped nose
126
upstream of spaced side walls
122
. Also, along a length
128
of flow member
118
, flow member
118
has a thickness no greater than a greatest thickness of aerodynamically shaped nose
126
. Flow members
118
may also have an aerodynamically shaped tail
130
downstream of side walls
122
. Tail
130
may taper to a single edge
132
. An alternative way of defining the configuration of flow members
118
and flow passages
120
relative to nozzles
114
, for example, is where each nozzle
114
has at least one flow member
118
, and preferably two, corresponding thereto and located adjacent to and upstream thereof.
FIGS. 7 and 7A
illustrate an alternative embodiment of flow distributor
116
comprising a honeycomb structure
134
. In this embodiment, as well as that illustrated in
FIGS. 6 and 6A
, flow members
118
may also define a plurality of bridge struts
136
, similar to structural bridges
56
(FIG.
2
). Accordingly, flow members
118
of
FIGS. 6-7A
, are connected at opposite ends to inner wall
104
and outer wall
106
to provide the mechanical strength necessary to avoid blow out of nozzle box
100
during use.
FIGS. 8 and 8A
illustrate another embodiment of flow distributor
116
comprising a holed plate
138
. Holed plate
138
is positioned between inner wall
104
and outer wall
106
, fixed to both or either wall, upstream of a plurality of bridge struts
140
. Bridge struts
140
are fixedly connected between the inner and outer walls and provide the mechanical strength necessary to avoid blow out of nozzle box
100
during use.
FIGS. 9 and 9A
, illustrate yet another embodiment of flow distributor
116
comprising a slotted plate
142
. Slotted plate
142
is similar in all respects, other than its obvious configuration difference, to holed plate
138
. It should also be understood that the invention includes plates
138
and
142
located downstream of bridge struts
140
, although this configuration is not illustrated.
FIG. 10
illustrates an alternative embodiment of flow distributor
116
comprising a retro-fit flow distributor unit
144
. Unit
144
is separably connectable with nozzle box
100
and has a flow distributor
116
configuration similar to FIG.
6
. Unit
144
, however, could have any flow distributor configuration discussed above. Housing
146
is similar to that of
FIG. 4
except that housing
146
has an annular outlet
148
to which unit
144
is connectable. For example, housing
146
can be formed from a typical nozzle box
50
(
FIG. 2
) when torus
54
is altered by cutting or grinding a portion up to and including nozzles
58
and structural bridges
56
. Then, unit
144
can be welded or otherwise fixedly connected to torus
54
. In all other respects, the embodiment of
FIG. 10
is structurally and functionally similar to those embodiments discussed herein.
Nozzle box
100
and flow distributor
116
of
FIGS. 4-10
, inclusive, operate as follows, for example. A flow of fluid, for example, steam, represented generally by flow arrows
150
,
152
and
154
, under pressure is received in housings
102
,
146
though inlets
110
in the direction of flow arrows
150
and forced into chamber
108
. By pressure differential principles, the flow of steam is directed through chamber
108
, through flow distributor
116
, through nozzles
114
and through outlet
112
in the direction of flow arrows
154
, which flow arrows
154
are generally perpendicular to flow arrows
150
. As the flow is directed through flow distributor
116
, for example, a swirl angle of the flow is reduced and a circumferential variation of the flow is reduced to cause a substantially uniform flow of fluid to pass through nozzles
114
. The substantially uniform flow may be created before or after directing the flow of fluid through bridge struts
136
and
140
. The substantially uniform flow of fluid is then directed by nozzles
114
through outlet
112
and to, for example, turbo machinery.
As various possible embodiments may be made in the above invention for use for different purposes and as various changes might be made in the embodiments above set forth, it is understood that all matters here set forth or shown in the accompanying drawings are to be interpreted as illustrative and not in a limiting sense.
While only certain features of the invention have been illustrated and described, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
Claims
- 1. A nozzle box mountable to encircle a shaft for directing a flow of fluid to a turbine, comprising:a housing having an inner wall spaced from an outer wall and joined therewith so as to form a chamber therein, said housing including at least one inlet and at least one outlet in which each is in fluid flow communication with said chamber; a plurality of radially projecting nozzles positioned between said inner and said outer walls and located upstream of said outlet; a flow distributor positioned between said inner and said outer walls and located upstream of the nozzles for directing the flow of fluid through said chamber, said flow distributor being configured to obtain a substantially uniform flow of fluid and direct said flow to said nozzles, and wherein said nozzles then direct the substantially uniform flow of fluid through said outlet, said flow distributor comprising a slotted plate; and a holed plate or a honeycomb structure.
- 2. The nozzle box of claim 1, in which said flow distributor includes a plurality of flow members with each flow member being at least partially spaced from an adjacent flow member by a flow passage formed therebetween and said flow passage being defined by at least a pair of spaced side walls positioned axially relative to an axis of said shaft and extending parallel relative to each other for at least an upstream portion of each flow passage.
- 3. T he nozzle box of claim 2, in which said flow passage has an axial length to width ratio greater than about 3.5:1.7.
- 4. The nozzle box of claim 3, in which each of said plurality of flow members has an aerodynamically shaped nose upstream of said pair of spaced side walls, and along a length of said flow member said flow member has a thickness no greater than a greatest thickness of said aerodynamically shaped nose.
- 5. The nozzle box of claim 4, in which each of said plurality of flow members has an aerodynamically shaped tail downstream of said pair of spaced side walls and said aerodynamically shaped tail tapers to a single edge.
- 6. The nozzle box of claim 2, in which each of the plurality of nozzles has at least one of said plurality of flow members corresponding thereto and located adjacent to and upstream of each nozzle.
- 7. The nozzle box of claim 6, in which each of said plurality of nozzles has two of said plurality of flow members corresponding thereto and located adjacent to and upstream of each nozzle.
- 8. The nozzle box of claim 2, further comprising a plurality of bridge struts connected between said inner and said outer walls and located upstream of said nozzles and downstream of said flow distributor.
- 9. The nozzle box of claim 2, in which said plurality of flow members further define a plurality of bridge struts connected between said inner and said outer walls.
- 10. A flow distributor unit for use in a nozzle box mountable to encircle a shaft for directing a flow of fluid to a turbine, said nozzle box including an inlet and an annular outlet, said flow distributor unit comprising:a housing having an inner wall spaced from an outer wall and joined therewith where said housing is connectable with said nozzle box adjacent said annular outlet in which a chamber is formed by said inner and said outer walls and said nozzle box and in which said housing has an outlet; a plurality of radially projecting nozzles positioned between said inner and said outer walls and located upstream of said outlet; a flow distributor positioned between said inner and said outer walls and located upstream of said nozzles for directing said flow of fluid through said chamber, said flow distributor being configured to obtain and direct a substantially uniform flow of fluid to said nozzles, wherein said nozzles then direct the substantially uniform flow of fluid through said outlet; and said flow distributor comprising a slotted plate, a holed slate or a honeycomb structure.
- 11. A method for retro-fitting a nozzle box which directs a flow of fluid to a turbine, said nozzle box including an inlet and an outlet adjacent a plurality of radially projecting nozzles located between an inner wall spaced from an outer wall, comprising:removing said nozzles and a portion of said inner and said outer walls adjacent said nozzles to form an annular outlet of the nozzle box; joining a flow distributor adjacent said annular outlet; and locating a second plurality of radially projecting nozzles downstream of said flow distributor, wherein said flow distributor is configured to direct a substantially uniform flow of fluid to said nozzles; wherein said nozzle box further includes a plurality of structural bridges upstream of said nozzles and connected between said inner and said outer walls and said removing includes said structural bridges and a portion of said inner and said outer walls adjacent said structural bridges.
- 12. The method of claim 11, in which said nozzle box further includes a plurality of structural bridges upstream of said nozzles and connected between said inner and said outer walls and said removing includes said structural bridges and a portion of said inner and said outer walls adjacent said structural bridges.
- 13. The method of claim 11, in which the second plurality of radially projecting nozzles and said flow distributor are integrally formed as a flow distributor unit.
US Referenced Citations (4)
Foreign Referenced Citations (3)
Number |
Date |
Country |
61-053403 |
Mar 1986 |
JP |
61-129409 |
Jun 1986 |
JP |
61-132704 |
Jun 1986 |
JP |