Power plants – Combustion products used as motive fluid – With variable oxidizer control
Reexamination Certificate
2000-12-22
2001-12-11
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
With variable oxidizer control
Reexamination Certificate
active
06327845
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a by-pass valve device used in a gas turbine combustor and more specifically to a by-pass valve for controlling a compressed air flow rate to be supplied into a combustion area of a tail tube downstream side so as to obtain an appropriate fuel/air ratio for a good combustion efficiency and for preventing foreign matters from coming into the gas turbine combustor for a smooth operation thereof.
2. Description of the Prior Art
As shown in
FIG. 9
, in a gas turbine combustor
01
, fuel F is jetted into a combustor inner tube
02
from a fuel nozzle
03
to be led into a combustor tail tube
05
. At the same time, compressed air PA discharged from a compressor
04
is led into the combustor tail tube
05
for combustion in a combustion area downstream of the combustor tail tube
05
so that a high temperature high pressure combustion gas CG is generated. This combustion gas CG is set to a flow velocity and a flow direction of designed condition by a stationary blade
06
downstream of the combustion area to be supplied to a moving blade
07
. Thus, the compressor
04
is driven and a surplus drive force is used outside.
The compressed air PA from the compressor
04
is also supplied into the combustor inner tube
02
so as to form a mixture with the fuel F supplied from a fuel nozzle for flame holding in the fuel nozzle
03
. This mixture is fired as a holding flame.
Thus, the fuel F jetted from the fuel nozzle
03
is ignited by the holding flame in the combustor inner tube
02
and is supplied into the combustion area with a fuel rich concentration.
On the other hand, the compressed air PA, except that supplied into the combustor inner tube
02
as mentioned above, discharged from the compressor
04
into a turbine casing
010
is supplied into the combustor tail tube
05
via an opening provided within the turbine casing
010
. A by-pass valve
08
is provided in the opening near the combustor tail tube
05
and the compressed air PA supplied into the combustion area through the opening has its flow rate controlled by opening and closing of the by-pass valve
08
. Therefore, a mixing ratio of the fuel F supplied from the combustor inner tube
02
and the air PA is adjusted to such a ratio as is able to generate a combustion gas of the best combustion efficiency in the combustion area.
As shown in FIG.
10
(
b
), the combustor tail tube
05
is provided in 20 pieces along the circumferential direction of the turbine casing
010
, and the by-pass valve
08
is provided in one piece for each of the combustor tail tubes
05
. The by-pass valve
08
is operated to be opened and closed by rotation of a drive shaft
09
provided for each of the by-pass valves
08
.
That is, as shown in FIG.
9
and FIG.
10
(
a
), which is a partially cut out perspective view of a mounting portion of the by-pass valve
08
, the drive shaft
09
has its proximal end connected to an end portion of a stem of the by-pass valve
08
and the drive shaft
09
passes through the turbine casing
010
so that its distal end projects outside of the turbine casing
010
. As shown in FIG.
10
(
b
), the drive shaft
09
is arranged in 20 pieces radially around a central axis of the turbine casing
010
.
An inner ring
011
is fixed to an outer circumferential surface of the turbine casing
010
, and an outer ring
012
is provided on the inner ring
011
and is moveable by an actuator. The drive shaft
09
is connected at the distal end to a side surface of the outer ring
012
via a link mechanism. When the outer ring
012
is rotated on the inner ring
011
, all the drive shafts
09
are rotated so that all the by-pass valves
08
are opened and closed in unison. Thus, the compressed air PA is supplied uniformly into the combustion area downstream each of the combustor tail tubes
05
.
In the prior art gas turbine combustor
01
, the by-pass valves
08
are opened and closed in unison for controlling the flow rate of the compressed air PA to be flown into the combustor tail tubes
05
provided in 20 pieces along the circumferential direction of the turbine casing
010
so as to adjust the mixing ratio of the fuel F and the air PA to be supplied into the combustion area between the combustor tail tube
05
and the stationary blade
06
for a good generation of the high temperature high pressure combustion gas CG. As a result, the structure is made such that the drive shaft
09
for opening and closing the by-pass valve
08
projects outside of the turbine casing
010
and such that the drive shafts
09
of as many as 20 pieces are arranged with substantially equal pitches along the entire circumference of the-turbine casing
010
, as mentioned above, and this results in a problem.
That is, as shown in portion A of FIG.
10
(
b
), in a type of the gas turbine casing
010
which is formed by an upper portion and a lower portion fastened so as to be integrated, a turbine casing horizontal flange
013
for fastening the turbine casing
010
and other like portions on the outer side of the turbine casing
010
interfere with some of the drive shafts
09
so that there arises a case at some positions where the drive shaft
09
for opening and closing the by-pass valve
08
can not be provided.
That is, the turbine casing horizontal flange
013
, a by-pass pipe
014
, etc. on the outer side of the turbine casing
010
prevent some of the drive shaft
09
from projecting outside of the turbine casing
010
. Thus, the by-pass valve
08
provided in the corresponding portion within the turbine casing
010
can not be operated to be opened and closed by the drive shaft
09
which is operated from outside of the turbine casing
010
.
Accordingly, the by-pass valve
08
which is provided in the circumferential position where the turbine casing horizontal flange
013
and the like interfere and can not be opened and closed by the drive shaft is set to a predetermined opening position prior to operation of the gas turbine and the operation is done continuously with this predetermined opening. Hence, in the combustion area of the specific combustor tail tube
05
of the gas turbine combustor
01
, the combustion efficiency becomes worse which results in a problem that lower operation of the worse combustion efficiency is unavoidable for a whole of the gas turbine combustor
01
.
Also, in order to solve this problem, if all the by-pass valves
08
provided in 20 pieces with equal pitches along the circumferential direction of the turbine casing
010
are constructed to be opened and closed uniformly so that the combustion in all the combustion areas downstream of the combustor tail tubes
05
is done efficiently to enhance the combustion efficiency as a whole of the gas turbine combustor
01
, then such a structure in which all the drive shafts
09
for opening and closing the by-pass valves
08
are arranged so as to project outside of the turbine casing
010
is unavoidable. This results in the restrictions in the outside structure of the turbine casing
010
and creates a problem in the arrangement of a plant comprising the gas turbine combustor
01
.
Also, in the gas turbine combustor
01
, when the by-pass valve
08
is opened so that the air is led into the combustor tail tube
05
through a by-pass duct
015
, foreign matters are liable to flow through the by-pass valve
08
, which results in a problem that the gas turbine may be damaged thereby. That is, if supporting members of pipings and the like in the combustor are damaged by vibration, or if bolts, nuts and the like loosen to scatter, then foreign matters caused thereby enter the by-pass ducts
015
to be led into the gas turbine, which may result in serious damage in the gas turbine moving blade and stationary blade. In the prior art gas turbine, however, there has been taken no effective countermeasure for preventing the foreign matters from coming in the turbine while the by-pass valve
08
is opened.
SUMMARY OF THE INVENTION
As mentioned above, in the prior art, co
Akagi Koichi
Iwasaki Yoichi
Kubota Jun
Ojiro Yasuhiro
Umemura Sunao
Casaregola Louis J.
Mitsubishi Heavy Industries Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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