Seal for a joint or juncture – Seal between relatively movable parts – Brush seal
Reexamination Certificate
1999-03-31
2002-10-29
Knight, Anthony (Department: 3676)
Seal for a joint or juncture
Seal between relatively movable parts
Brush seal
C277S416000
Reexamination Certificate
active
06471213
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a seal structure for a gas turbine, and more particularly to a seal separating surface connecting structure which reduces the amount of air leaking from a seal separating surface and improves sealing performance, and a structure which employs a brush seal so as to prevent a support plate of the brush seal from seriously contacting with a rotation side and which provides a small sealing interval so as to improve the sealing performance.
2. Description of Related Art
FIG. 9
is a cross sectional view which shows a general seal structure for a conventional gas turbine. In the drawing, reference numeral
61
denotes a stator blade, reference numeral
62
denotes an outer shroud thereof, and the outer shroud
62
is supported by a blade ring
70
. Reference numeral
63
denotes an inner shroud, reference numeral
64
denotes a flange portion thereof and reference numeral
65
denotes a seal ring holding ring. The seal ring holding ring
65
is held by the flange portion
64
of the inner shroud
63
, and supports a seal ring
66
in an inner side (a rotor side) thereof. Reference numerals
67
and
68
denote seal portions, and seal fins
67
a
and
67
b
are provided in a side of a rotor disc
69
, thereby constituting a seal portion in opposition to the seal portion of the seal ring
66
. Reference numeral
81
denotes a rotor blade, and reference numeral
82
denotes a platform thereof. The platform
82
is mounted on the rotor disc adjacent to the stator blade
61
and rotates together with the rotor. Reference numeral
71
denotes a tube for sealing air, which is provided within the stator blade
61
, extends through the inner shroud
63
from the outer shroud
62
and is structured so as to introduce the sealing air within a cavity
75
. Reference numerals
72
,
73
and
74
denote spaces formed with respect to the adjacent rotor blade.
In the stator blade having the structure mentioned above, air
40
, introduced from an inner portion of the sealing air tube
71
within the stator blade
61
to an inner portion of the cavity
75
, passes through a hole
65
a
in the seal ring holding ring
65
and flows into the space
72
as shown by reference symbol
40
a
, and a part thereof flows out from the space
72
to the space
73
as leaking air from the seal portion
68
as shown by reference symbol
40
b
, passes between the platforms of the rotor blade adjacent to the inner shroud
13
as shown by reference symbol
40
c
and flows out to a main current gas passage.
Further, the air also flows out to the space
74
from the space
72
through the portion between the seal ring
66
and the seal portions
67
a
and
67
b
as shown by reference symbol
40
e
, and flows out from there through the portion between the inner shroud
63
and the platform
82
of the adjacent rotary blade
81
as shown by reference symbol
40
f
. A pressure within the cavity
75
and the spaces
72
,
73
and
74
is increased in comparison with the outer main current gas passage due to the air flows mentioned above, thereby preventing the high temperature combustion gas from entering the inner portion. Accordingly, in order to increase sealing performance, it is necessary to increase the sealing performance of a labyrinth seal formed by the seal ring
66
, the seal portion
67
on the rotor side and the seal portion
68
so as to reduce the amount of leaking air represented by reference symbols
40
b
,
40
c
,
40
e
and
40
f
. When it is possible to reduce the flowing-out air amount, it is possible to reduce the sealing air amount, so that it will be possible to improve the performance of the gas turbine as a whole.
FIG.
10
(
a
) is a schematic view as seen from a line Z—Z in
FIG. 9
, which illustrates an upper half of the seal ring
66
. Further, FIG.
10
(
b
) is a schematic view taken along a line W—W in FIG.
10
(
a
). The seal ring
66
is formed in a circular ring shape and is separated into a plurality of portions, and in the drawing, the upper half portion is separated into three portions comprising portions (A), (B) and (C) (totally separated into four portions). Fins
66
a
,
66
b
and
66
c
are respectively mounted on the separated pieces (A), (B) and (C), which are opposed to the seal portions
67
a
and
67
b
in the side of the rotor disc
69
. In the separated structure of the seal ring
66
mentioned above, a gap
51
is disposed between the separated pieces (A) and (B), a gap
52
is disposed between the separated pieces (B) and (C), and air flows out from an upstream space
72
(see
FIG. 9
) to a downstream space
74
(see
FIG. 9
) as the leaking air
60
flows through gap
51
as shown in
FIG. 10B
, so that the seal performance of the seal ring
66
is lowered.
As mentioned above, the seal structure of the conventional gas turbine is structured such that the seal ring
66
is separated into a plurality of portions, as mentioned above, and has a gap at a connecting end surface between the separated pieces of each of the seal rings. It is necessary to structure the gap such that a certain degree of gap is kept in connection with the thermal expansion of the seal ring. The gap is formed in a straight shape from the upstream side of the main current gas to the downstream side, and the sealing air leaks from the upstream side to the downstream side, so that the performance of the labyrinth seal constituted by the seal portion of the seal ring
66
and the seal portion
67
of the rotor disc
69
is reduced, and the amount of sealing air is increased, thereby providing an effect on the performance of the whole of the gas turbine.
Further, in recent years, in order to improve the seal performance of the stator side and the rotor side in the gas turbine for a flying machine or an industrial machine, the brush seal is going to be used.
FIG. 11
is a representative cross sectional view of the industrial gas turbine, in which reference numeral
101
denotes a rotor blade, reference numeral
102
denotes a platform and reference numeral
103
denotes a seal pin within the platform
102
, which is constituted by portions
103
a
,
103
b
and
103
c
. Reference numerals
102
a
and
102
b
denote a seal portion at both end portions in front and rear with respect to the axial direction of the platform
102
. Reference numeral
104
denotes a shank portion and seal plates
106
and
107
are provided at the front and at the rear of the shank portion. Reference numeral
105
denotes a disc for a rotor, to which parts of each of the rotor blades
101
to
104
are mounted.
Reference numeral
91
denotes a stator blade, reference numeral
92
denotes an inner shroud and reference numeral
93
denotes an outer shroud. Reference numerals
92
a
and
92
b
denote the front and rear end portions with respect to an axial direction of the inner shroud
92
. Reference numeral
94
denotes a cavity formed within the inner shroud
92
, into which the sealing air is flowed through from the inner portion of the stator blade
91
. Reference numeral
95
denotes a seal box, which holds a labyrinth seal
100
at one portion and a brush seal
101
at the other portion. Reference numerals
96
and
97
denote honeycomb seals provided at both end portions
92
a
and
92
b
of the inner shroud
92
, respectively. Reference numerals
98
and
99
denote spaces formed with respect to each of the adjacent front and rear rotor blades, which correspond to flow passages for the sealing air.
In the gas turbine having the structure mentioned above, the sealing air is introduced into the cavity
94
from a sealing air passage (not shown) passing through the inner shroud
92
after passing from the side of the outer shroud
93
in the stator blade
91
through the inner portion of the blade. The air flows out into the space
99
from a hole (not shown) provided in the seal box
95
. The air then passes through the honeycomb seal
96
provided at the end portion
92
a
of a the inner shroud
92
, and flows out into the combustion gas p
Ai Toshishige
Yuri Masanori
Mitsubishi Heavy Industries Ltd.
Pickard Alison K.
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