Power plants – Combustion products used as motive fluid – With variable oxidizer control
Reexamination Certificate
1999-09-21
2001-05-08
Freay, Charles G. (Department: 3746)
Power plants
Combustion products used as motive fluid
With variable oxidizer control
Reexamination Certificate
active
06226977
ABSTRACT:
TECHNICAL FIELD
This invention concerns a bypass air control device used to control the volume of air bypassed from the combustion engine in a gas turbine. More specifically, it concerns a bypass air control device which bypasses a volume of compressed air in the casing of the combustion engine, in which a number of combustion chambers are arranged with tail pipes, by diverting the compressed air into those tail pipes.
TECHNICAL BACKGROUND
The gas turbines used in electric power plants, nuclear power plants and various other industrial plants are velocity-type heat engines which employ as their operating medium their own operating gases, mainly air and combustion gases. These turbines basically comprise a compressor, which performs the adiabatic compression process; a combustor, which heats the air-fuel mixture under constant pressure; and a turbine, which performs the adiabatic expansion process.
The combustor has a number of combustion chambers, each with a tail pipe, in the space in the casing which is pressurized by the air from the compressor. The combustion gases generated in the combustion chambers are conducted via the tail pipes to the turbine, which they cause to rotate.
In this sort of combustor, the air pressurized by the compressor is conducted to the space in the combustor casing at all times. Since the amount of the pressured air for combustion is proportional to the state of combustion in the chambers (i.e., to the load fluctuation), and it fluctuates according to the state of combustion at all times, it is necessary to bypass the pressurized air in the space in the casing in order to maintain the air pressure at a constant level. In other words, a portion of the compressed air in the space is conducted via control valves or bypass channels into the tail pipes connected to the combustion chambers, mixed with the hot, high-pressure combustion gases in the pipes and released into the turbine, thus the pressure of the air in the space in the casing can be maintained at a constant level.
To be more specific, if the volume of air admitted to the bypass channels is controlled by a valve or a valve-adjusting mechanism, and a large volume of pressurized air is to be admitted to the combustion chamber, then the bypass valve can be constricted or closed by the valve-adjusting mechanism so that the volume of air flowing into the bypass channels is reduced or entirely cut off. If a small volume of pressurized air is to be admitted to the combustion chamber, the bypass valve can be opened more or opened all the way so that the volume of air flowing into the bypass channels is increased. In this way the air in the space in the casing can be maintained at a specified pressure.
The prior art design shown in
FIG. 7
is a bypass air control device for controlling the volume of air which is bypassed. It consists of a control valve for the bypass channel and a mechanism for adjusting the valve.
4
is the pressurized space inside casing
7
of the combustor. In the space
4
under casing
7
, a number of the combustion chambers (not shown) and the tail pipes
1
which are connected to them are arranged around the circumference of the casing. (In the drawing, only casing
7
and the essential portion of a single tail pipe
1
are shown.)
A bypass channel consisting of elbow pipe
3
and bypass pipe
2
is connected to the side of the tail pipe
1
. Opening
2
a
at the front of the bypass channel faces space
4
in casing
7
. Pressurized air can be bypassed into the tail pipe
1
via the opening
2
a.
A butterfly valve
5
is inside the bypass pipe
2
. This valve controls the volume of air which is bypassed. Valve stem
19
of the butterfly valve
5
extends upward from the valve and is connected via a spline to adjustment shaft
17
.
Shaft
17
is mounted to the outer surface of casing
7
. Its operating portion is inserted through casing
7
; its front end is connected via a spline to valve stem
19
of the butterfly valve
5
.
Annular inner ring
9
is fixed on the outer periphery of the exterior (i.e., the upper surface) of the casing
7
. The upper surface of the inner ring
9
is shaped into a rectangular depression. Shaft rollers
9
a
are mounted along the entire periphery of inner ring
9
, so that outer ring
11
can freely move in contact with them in the bottom of the depression.
The bottom of outer ring
11
has a rectangular protuberance which engages in the shaft rollers in the inner ring
9
in such a way that it is free to rotate. The inner surface of the outer ring
11
and the upper end of adjustment shaft
17
are connected by link
13
and lever
15
, which convert the rotational movement of the outer ring
11
to rotational movement of adjustment shaft
17
.
Thus when outer ring
11
rotates in the peripheral direction with inner ring
9
as a guide, adjustment shaft
17
is caused to rotate via link
13
and lever
15
.
Because adjustment shaft
17
is connected to valve stem
19
of butterfly valve
5
via a spline, the rotation of shaft
17
is linked to the rotation of valve stem
19
, and valve body
21
of valve
5
can be made to open and close.
Thus the rotation in of outer ring
11
the circumferential direction on the outer surface of the casing
7
can be converted to a force which drives valve body
21
of butterfly valve
5
in bypass channel
2
and
3
within casing
7
to open or close. In this way it is possible to adjust the rate at which the air bypass control valve is opened, and with it, the volume of air which is bypassed.
In this sort of prior art air bypass device for controlling the volume of air, valve body
21
of butterfly valve
5
is made of a lightweight material, so vibration resulting from combustion could be transmitted via the tail pipe from the combustion chamber to the bypass channel. When this happened, the resonant vibration of the pipe would cause the valve body in the channel to stutter. This would result in greatly accelerated abrasion of the valve body, the shaft and the bearings for the valve stem in the bypass channel.
DESCRIPTION OF THE INVENTION
The object of this invention is to provide a bypass air control device for controlling the volume of air bypassed used in the combustion engine of a gas turbine in which, even when the combustion vibration described above occurs, the structural components of the control valve and its related hardware would not experience vibration, and in which the opening and closing of the bypass could be controlled in a reliable and stable fashion.
Another object of this invention is to provide a bypass air control device for controlling the volume of air bypassed in which the links or other connectors between the valve in the bypass channel for controlling the volume of air and the mechanism for adjusting that valve, which is placed on the exterior surface of the casing, can easily absorb any thermal expansion or assembly error which might occur.
Still other objects of this invention will be made clear from the disclosure which follows.
To achieve these objects, the present invention has been designed as follows. It pertains to a combustion engine for a gas turbine which has, in a space within the casing pressurized by compressed air fed into it from a compressor, a number of combustors comprised of combustion chambers and the tail pipes connected to them. The invention applies to an air bypass control device which can bypass a portion of the compressed air in the space within the casing into the tail pipe connected to a combustion chamber via a control valve and a bypass channel.
The invention is distinguished in the following ways, it comprises a valve mechanism including a flat sliding ring, and a valve operating mechanism. The valve mechanism intersects a number of bypass air channels, each of which is connected to a pipe located in the space inside the casing. The bypass air channels are located at a circular position in the casing. A number of openings are arranged in the flat sliding ring of the valve mechanism corresponding to the number of bypass air channels for bypassing
Ichiryu Taku
Yashiki Tadao
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Freay Charles G.
Gartenberg Ehud
Mitsubishi Heavy Industries Ltd.
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