Power plants – Combustion products used as motive fluid – Having expansible connection
Reexamination Certificate
2000-03-08
2004-06-22
Koczo, Michael (Department: 3746)
Power plants
Combustion products used as motive fluid
Having expansible connection
C060S752000
Reexamination Certificate
active
06751962
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a tail tube structure of gas turbine combustor. More particularly, this invention relates to a structure for enhancing the performance of gas turbine by increasing the cooling effect in the tail tube seal, decreasing the cooling air flow to save the air consumption, and decreasing the load of the compressor.
BACKGROUND OF THE INVENTION
FIG. 9
is a general structural diagram of a combustor of a gas turbine. Reference numeral
80
indicates a combustor. This combustor
80
is fixed in a casing
81
. Reference numeral
82
indicates a pilot fuel nozzle. Pilot fuel to be used for ignition is supplied to the pilot fuel nozzle
82
. Reference numeral
83
indicates a main fuel nozzle. A plurality of main fuel nozzles (for example eight in number) are arranged in a circle around the pilot fuel nozzle
82
. Reference numeral
84
indicates an inner tube, and
85
indicates a tail tube. The inner tube
84
and the tail tube
85
guide a high temperature combustion gas
200
towards an outlet
86
of the tail tube
85
(hereafter tail tube outlet). Reference numeral
87
indicates a bypass pipe, and
88
indicates a bypass valve. The bypass valve
88
gets opened when the combustion air becomes insufficient because of the fluctuations in the load. When the bypass valve
88
gets opened, a passage is created for guiding the air in the casing
81
into the combustor
80
. Reference numeral
89
indicates a seal section. This seal section
89
is provided at the peripheral end of the tail tube outlet
86
as described below. The seal section
89
is intended to seal the connection area with gas passage (alternatively the “gas pass”)
100
of the gas turbine. A plurality of such combustors
80
(for example sixteen in number) are disposed around the rotor in the casing
81
. Each combustor
80
supplies the high temperature combustion gas into the gas pass
100
. This combustion gas expands in the gas pass
100
to work and rotate the rotor.
In the combustor having such constitution, the fuel from the main fuel nozzle
83
is mixed with the air sucked from around. The mixture of fuel and air is ignited by the flame of the pilot fuel from the pilot fuel nozzle
82
. The mixture burns to form a high temperature combustion gas
200
. The high temperature combustion gas
200
is supplied from the tail tube outlet
86
into the gas pass
100
through the inner tube
84
and tail tube
85
. Since the wall of the inner tube
84
and the wall of the tail tube
85
always come in contact with the high temperature combustion gas
200
, a cooling passage for passing cooling air is provided in these walls in order to cool them. Moreover, the tail tube outlet
86
is connected to the periphery of the inlet of the gas pass
100
through the seal section
89
. This seal section
89
is also cooled using the cooling air.
FIG. 10
is a magnified sectional view of portion Y in FIG.
9
. This figure shows a detail structure of a conventional tail tube seal. Reference numeral
89
indicates the entire seal section. A flange
86
a
is formed around the tail tube outlet
86
. The wall of the tail tube is exposed to high temperature combustion gas
200
, for example, the temperature of the gas as high as 1500 degree centigrade. However, multiple passages (not shown) for cooling air are formed in the wall of the tail tube
85
, and the wall is cooled by the cooling air. Further, a groove
90
for cooling air is also formed around the tail tube outlet
86
. The tail tube outlet
86
is cooled by passing the cooling air in this groove
90
.
The tail tube outlet
86
is connected to the gas pass
100
through a tail tube seal
61
. One end of the tail tube seal
61
has a U-shaped groove
61
a.
A peripheral flange
86
a
of the tail tube outlet
86
is fitted into this groove
61
a.
The other end of the tail tube seal
61
has a pi-shaped groove
61
b.
Flange ends
102
a,
103
a
of an outer shroud
102
and an inner shroud
103
of a first stage stationary blade
101
in the gas pass
100
are fitted into this groove
61
b,
thereby sealing the connection area.
Since the tail tube seal
61
is also exposed to high temperature combustion gas
200
as mentioned above, multiple cooling holes
61
c
are drilled around the tail tube seal
61
in a direction which is perpendicular to the direction into which the gas flows at the inlet of the gas pass
100
. High pressure air
91
flows in from around the combustor in the casing and cools the wall of the tail tube seal
61
. After cooling, this air flows into the gas pass
100
. The amount of cooling air required to cool the tail tube seal
61
is about 1 to 2% of the amount of compressed air discharged from the compressor.
Thus, in the tail tube seal of the conventional gas turbine combustor, air holes
61
c
are drilled on the periphery of the tail tube seal
61
and the tail tube seal
61
is cooled by passing cooling air
91
in the air holes
61
c.
The periphery of the holes
61
c
is cooled by passing cooling air into the holes
61
c,
however, the side of the groove
61
b
connecting to the gas pass
100
side is not cooled sufficiently by passing cooling air into the holes
61
c
alone. As the cooling is insufficient, the flange ends
102
a,
103
a
towards the gas pass side expand due to thermal expansion. This thermal expansion of the flange ends
102
a,
103
a
generates a frictional force at the contact with the groove
61
b
and the groove
61
b
is worn. Thus, the performance of the tail tube seal
61
is impaired.
Moreover, the amount of air required to cool the tail tube seal
61
is about 1 to 2% of the entire amount of compressed air discharged from the compressor. However, it is desirable that this air consumption is as little as possible, because, when the air consumption is less, the efficiency of the compressor can be improved and the performance of the gas turbine can be enhanced. Such a decrease in the air consumption was in demand but was not realized till present.
SUMMARY OF THE INVENTION
It is an object of the present invention to present a tail tube seal structure of a combustor capable of improving the cooling structure of the tail tube seal of a combustor of gas turbine, raising the cooling effect, curtailing the amount of air by cooling by a smaller amount of air, and contributing to an upgraded performance of the entire gas turbine.
According to one aspect of the present invention, the air in the casing flows in from a plurality of inclined cooling holes and flows out obliquely into the gas pass, and cools the wall contacting with the gas passage in the groove in which the flange end of the gas pass is fitted by film effect, the cooling in this area is reinforced. Owing to this cooling, the conventional problem of wear due to difference in thermal expansion between the fitting section of the member and the gas pass side flange end to be fitted is decreased, and the reliability of the tail tube seal structure is enhanced.
Further, the gas pass is generally in a cylindrical shape, and the inclined cooling holes are formed at specific intervals in the entire peripheral direction. Therefore, the inner wall of the gas pass can be cooled uniformly and efficiently also in the peripheral direction.
Further, the air flowing out from the inclined cooling holes flows smoothly along the inner wall of the gas pass side formed of a smooth curvature. Therefore, the film cooling effect is enhanced, and the cooling of the flange end at the gas pass side is further effective.
According to one aspect of the present invention, the seal member is fitted outside to the flange of the outer circumference of the tail tube outlet, and also fitted to the protrusion at the gas pass side on the outer periphery of the tail tube outlet wall. Therefore, the member itself does not come in contact with the high temperature combustion gas. Hence, it is not necessary to cool the member itself, and hence cooling holes and cooling are not needed. Instead, to reinforce cooling of the tail tube outlet wall, inclined coo
Kataoka Masahito
Kuwabara Masamitsu
Sato Yoshichika
Suenaga Kiyoshi
Tomita Yasuoki
Koczo Michael
Mitsubishi Heavy Industries Ltd.
Sughrue & Mion, PLLC
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