Rotary kinetic fluid motors or pumps – With passage in blade – vane – shaft or rotary distributor...
Reexamination Certificate
1999-02-16
2001-05-01
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
With passage in blade, vane, shaft or rotary distributor...
C415S114000, C416S095000, C416S09600A
Reexamination Certificate
active
06224327
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a steam-cooling type gas turbine and more particularly to an improved cooling structure therefor which can effectively prevent leakage of coolant steam.
2. Description of Related Art
A combined cycle power plant comprised of a combination of a gas turbine plant and a steam turbine plant is designed such that the gas turbine is operated in a high temperature region with the steam turbine operated in a low temperature region in a sharing mode to efficiently recover thermal energy for effective utilization thereof. In recent years, this type of power generating system has been attracting public attention from the standpoint of high thermal efficiency.
In conjunction with the cooling of moving blades of the gas turbine in the combined cycle power plant such as mentioned above, it is noted that in the present state of the art, a steam cooling system is replacing an air cooling system. Parenthetically, in the steam cooling system, a part of steam generated in the steam turbine is extracted to be led to the gas turbine for cooling the moving blades thereof, and the steam having a temperature raised after cooling of the moving blades of the gas turbine is recovered to be fed back to the steam turbine cycle to achieve more effective utilization of thermal energy. Thus, it is expected that the steam cooling system can contribute to improvement of the operation efficiency of the combined cycle power plant. For this reason, the steam cooling system is attracting attention in these years.
FIG. 13
is a sectional view showing schematically a portion of a typical one of the conventional steam-cooling type gas turbines. In the figure, reference numerals
50
and
51
denote casings of a compressor and the gas turbine, respectively, wherein a rotor
60
having a large number of moving blades mounted therearound in rows and designated representatively by reference numerals
71
,
72
and
73
is disposed within the turbine casing
51
. A high temperature combustion gas discharged from the associated combustor is introduced through a combustion gas passage
52
into spaces defined between stationary blades
83
;
84
;
85
disposed on the inner wall surface of the turbine casing
51
and the moving blades
71
;
72
;
73
to undergo expansion, to thereby force the rotor
60
to rotate.
On the other hand, there are formed in a disk
61
of the rotor
60
a plurality of circumferentially distributed steam passages
63
which extend axially through the disk. The coolant or cooling steam
80
is introduced into the individual steam passages
63
from a steam inlet
65
disposed in a turbine shaft
64
to flow through other passages
62
formed similarly in the disk
61
, wherein a part of the cooling steam
80
enters a cavity
66
and hence flows into moving blades
72
of the second stage by way of steam feeding passages
67
to cool the second-stage moving blades
72
. Thereafter, the cooling steam
80
reaches a cavity
69
by way of steam recovering passages
68
. Further, another part of the cooling steam
80
flows into steam feeding passages
91
by way of a cavity
90
to enter the moving blades
71
of the first stage for cooling the interior of these moving blades. Thereafter, the steam reaches the cavity
69
by way of steam recovering passages
92
. Thus, within the cavity
69
, the flows of the steam recovered after cooling of the first-stage moving blades
71
and the second-stage moving blades
72
join together to enter another cavity
93
. Thereafter, the steam flows through a center passage of the rotor
60
to be recovered at the side of the turbine shaft
64
. Additionally, a part of the steam flowing through the steam passage
62
is supplied to the compressor
50
as well by way of a cavity
94
to be used for cooling the compressor
50
. At this juncture, it should be mentioned that each of the steam passages
62
and
63
may defined by a pipe.
As is apparent from the above description, the conventional steam cooling system is so designed that the steam of low temperature and high pressure flows through the passages implemented internally of the rotor. Consequently, there are many locations where the steam leakage may occur to the external low-pressure environment, giving rise to a serious problem in the steam cooling system with regards to prevention of the leakage of the feed steam, i.e., steam to be fed to the moving blades of the gas turbine.
FIGS. 11 and 12
are sectional views showing fragmentally another example of the conventional gas turbines in which the steam cooling system is adopted. More specifically,
FIG. 11
shows a rear portion of a fourth stage of moving blades in the conventional gas turbine. Referring to the figures, a rear disk (journal bearing)
102
is mounted onto a fourth-stage disk
100
through interposition of a seal disk
101
, wherein an outer rotatable shaft
103
and an inner rotatable shaft
108
are mounted on the rear disk
102
so that the fourth-stage disk
100
can rotate together with the outer rotatable shaft
103
and the inner rotatable shaft
108
. Rear end portions of the outer rotatable shaft
103
and the inner rotatable shaft
108
are enclosed by a stationary housing
104
which is disposed in opposition to both the rotatable shafts by means of a bearing portion
105
serving as a seal portion for the outer rotatable shaft
103
and a bearing portion
107
serving as a seal portion for the inner rotatable shaft
108
. A high-pressure chamber
106
is defined between the rear end portion of the outer rotatable shaft
103
and the housing
104
, while an annular steam passage
109
is defined between the outer rotatable shaft
103
and the inner rotatable shaft
108
.
In the steam-cooling type gas turbine of the structure mentioned above, feed steam
120
(see
FIG. 12
) flows through the steam passage
109
from the high-pressure chamber
106
to enter an annular high-pressure chamber
110
from which the steam flows into a cavity
112
by way of a passage
111
. From the cavity
112
, the feed steam is introduced into the moving blades of the first and second stages (not shown either) via relevant passages (not shown) provided in the fourth-stage disk
100
. The steam having done work of cooling the moving blades is recovered as the recovery-destined steam as indicated by an arrow
121
by way of a passage (not shown) formed in the inner rotatable shaft
108
.
FIG. 12
is an enlarged view of the rear disk
102
shown in FIG.
11
. Referring to
FIG. 12
, the portion of the rear disk
102
which lies adjacent to the seal disk
101
is heated by the recovery-destined steam
121
having a raised temperature and has a higher temperature than the other portion of the rear disk
102
. Consequently, the portion of the rear disk
102
located adjacent to the seal disk is subjected to the influence of thermal expansion, as a result of which a disk coupling bolt
113
tends to be tilted under tension, as indicated by an arrow in FIG.
12
. Consequently, a part
120
a
of the feed steam
120
will leak to the exterior through a clearance making appearance due to the tilting of the disk coupling bolt
113
.
As is apparent from the foregoing description, in the typical steam-cooling type gas turbine known heretofore, the steam extracted from the steam turbine is introduced into the moving blades of the gas turbine via the disks from a plurality of steam passages provided internally of the rotor for cooling the moving blades. The steam heated to a high temperature after cooling of the moving blades is collected into the steam collecting cavity and fed to the center passage formed in the rotor, from which the steam is recovered to be fed back to the steam turbine. Owing to such cooling scheme effective utilization of the steam can certainly be achieved. However, with the conventional steamcooling system in which the steam of low temperature and high pressure is fed along the peripheral portion of the rotor, there exist many locations where the s
Aoki Sunao
Chikami Rintaro
Hirokawa Kazuharu
Tanaka Katsunori
Look Edward K.
Mitsubishi Heavy Idustries, Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Woo Richard
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