Rotary kinetic fluid motors or pumps – With lubricating – sealing – packing or bearing means having...
Reexamination Certificate
1999-02-10
2001-04-17
Verdier, Christopher (Department: 3745)
Rotary kinetic fluid motors or pumps
With lubricating, sealing, packing or bearing means having...
C415S115000, C415S116000, C415S135000, C415S136000, C415S176000, C415S180000
Reexamination Certificate
active
06217279
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a stator blade for a gas turbine, which is enabled by improving the feed of sealing air to reduce leakage of the air thereby to feed the air to an inner shroud efficiently and by cooling the sealing air to reduce the clearance between a rotor side and a stationary side at a rated running time.
2. Description of Related Art
FIG. 14
is a general block diagram of a gas turbine, which is constructed to include a compressor
150
, a turbine
151
and a combustor
152
. A fuel is burned in the combustor
152
with the air coming from the compressor
150
so that a hot combustion gas is fed to the turbine
151
. This combustion gas flows through a combustion gas passage, in which moving blades mounted on a rotor and stator blades are alternately arranged in multiple stages, to rotate the rotor thereby to drive a power generator connected directly to the rotor. Since the turbine
151
is exposed to the hot combustion gas, the air from the compressor
150
is partially bled and fed to the turbine
151
to cool the stator blades, the moving blades and the rotor.
FIG. 15
is a sectional view showing a sealing air feed line to a representative stator blade of a prior art gas turbine, and shows the construction of the blades in the turbine
151
of FIG.
14
.
In
FIG. 15
, reference numeral
21
designates a moving blade including a platform
22
, a seal plate
23
under the platform
22
, two end portions
24
and
25
of the platform
22
, and a blade root
26
. A plurality of moving blades
21
each composed of those members, are arranged in the circumferential direction of the rotor.
Reference numeral
31
designates a stator blade which is arranged adjacent to the moving blade
21
. Numeral
32
designates an outer shroud, and numeral
33
designates an inner shroud. Numerals
34
and
35
designate two end portions of the inner shroud
33
, and numeral
36
designates a cavity under the inner shroud
33
. Numeral
37
designates a seal ring retaining, ring which has a labyrinth seal
37
a
at its end portion and which slides with respect to the rotating portion of the blade root
26
on the moving blade side. Numeral
38
designates an air hole that is formed through the seal ring retaining ring
37
to provide communication between the cavity
36
and a space at the blade root
26
of the adjoining moving blade
21
. Numerals
40
a
and
40
b
designate seal portions between the platform
22
and the inner shroud
33
. The seal portions adjoining each other and are constructed by fitting seal members between the end portions
24
and
34
, and the end portions
25
and
35
.
Numeral
50
designates a blade ring, on the inner side of which the outer shroud
32
of the stator blade
31
is fixed through heat insulating rings
32
a
and
32
b
. Numeral
51
designates an air hole, which is formed in the blade ring
50
. The air hole
51
communicates with a space
53
, which is formed by the blade ring
50
, the heat insulating rings
32
a
and
32
b
and the outer shroud
32
. The space
53
is connected at its leading end with an air source leading from the not-shown compressor. Numeral
52
designates a seal tube which extends from the outer shroud
32
in the stator blade
31
through the inner shroud
33
.
In the construction thus far described, cooling air
54
from the compressor is fed from the air hole
51
of the blade ring
50
and into a space
53
. This cooling air
54
flows on one side through the seal tube
52
into the cavity
36
under the inner shroud
33
. The cooling air from this cavity is blown from the air hole
38
, as indicated by arrow S
1
, into the trailing side space of the adjoining moving blade
21
at the upstream side and further through the labyrinth seal
37
a
into the leading side space of the moving blade
21
at the trailing stage, as indicated by arrow S
2
. These cooling air flows S
1
and S
2
emanate from the seal portions
40
a
and
40
b
, respectively, to prevent the combustion gas from entering the inside of the inner shroud
33
.
As shown in
FIG. 16
, the air that has entered the space
53
cools the face of the outer shroud
32
and enters the cooling passage in the stator blade, so that it is blown out of the holes of the trailing edge while cooling the blade inside, until it is released into the combustion gas passage.
In the sealing structure thus far described, the air hole
51
of the blade ring has a diameter of 2 to 50 mm, and the seal tube
52
is limited in its internal diameter by the thickness and the camber of the blades. As a result, the in flow of air is subjected to a pressure loss so that its pressure drops. In addition, the cooling air having entered the space
53
leaks from clearances between the outer shroud
32
and the heat insulating rings
32
a
and
32
b
, as indicated by arrows S
3
and S
4
.
One example of the pressure situations resulting from the aforementioned leakage will now be described. The cooling air
54
flowing into the air hole
51
of the blade ring
50
has a pressure of about 6 Kg /cm
2
. This pressure is lowered to about 5 Kg/cm
2
in the space
53
by the pressure loss and further to 3.5 Kg/cm
2
in the cavity
36
due to the pressure loss. This pressure level is equal to the pressure of 3.5 Kg/cm
2
between between the moving blade
21
and the stator blade
31
adjoining each other so that the sealing effect is deteriorated.
A first problem of the sealing structure for the prior art gas turbine stator blade thus far described, is that the cooling air fed from the air hole
51
of the blade ring
50
leaks from the clearances between the outer shroud
32
and the heat insulating rings
32
a
and
32
b
, even though it flows into the space
53
between the blade ring
50
and the outer shroud
32
and into the cavity
36
under the inner shroud
33
from the seal tube
52
. On the other hand, the cooling air is subjected to a pressure loss in the seal tube
52
so that its pressure drops when it flows into the cavity
36
of the inner shroud. As a result, the difference in the pressure of the combustion gas disappears to make it difficult for the cooling air to maintain sufficient pressure as the sealing air.
FIG. 16
is a sectional view showing a stator blade of the prior art gas turbine and explains the cooling of the stator blade mainly although the stator blade has the same structure as that of FIG.
15
. In the stator blade
31
, as shown in
FIG. 16
, air passages
80
A,
80
B and
80
C are sequentially formed to form a serpentine passage. Reference numeral
80
D designates the trailing edge of the blade, which has a number of film cooling air holes
60
. The seal tube
52
vertically extends through the stator blade
31
. The seal tube
52
opens at its lower end into cavity
36
. The seal ring retaining ring
37
retains the flange of the inner shroud
33
and the labyrinth seal
37
a
. The air hole
38
is formed in the retaining ring
37
to provide communication between the cavity
36
and a space
72
between the adjoining moving blade. The outer shroud
32
has a cooling air feeding hole
62
. Note the numeral
21
designates the adjoining moving blade
21
.
In the stator blade thus constructed, cooling air
70
is fed from the hole
62
of the outer shroud
32
to the air passage
80
A on the leading edge side of the stator blade
31
, and the air then flows at the inner side into the next air passage
80
B and then at the outer side into the adjoining air passage
80
C. The cooling air
70
then flows at the inner side to cool the stator blade
31
sequentially and eventually flows from the air holes
60
of the trailing edge
80
D along the outer surfaces of the trailing edge to provide a film cooling effect.
From the open end of the seal tube
52
of the outer shroud
32
, cooling air
71
for the cooling operation flows from the lower end of the seal tube
52
into the cavity
36
, as shown in
FIG. 16
, and this portion of the air flows from the air hole
38
formed in the cavity
36
into the
Ai Toshishige
Aoki Sunao
Fukuno Hiroki
Suenaga Kiyoshi
Tomita Yasuoki
Mitsubishi Heavy Industries Ltd.
Verdier Christopher
Wenderoth, Lind & Ponack L.L.P
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