Rotary kinetic fluid motors or pumps – Method of operation
Reexamination Certificate
2000-03-17
2001-12-11
Ryznic, John E. (Department: 3745)
Rotary kinetic fluid motors or pumps
Method of operation
C415S027000, C415S149400
Reexamination Certificate
active
06328526
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gas turbine starting method, which includes to reduce an air amount to be discharged into the air and to avoid a fluid unstableness phenomenon occurring in a compressor both at the time of starting.
2. Description of the Prior Art
FIG. 3
is a cross sectional view of one example of a gas turbine compressor in the prior art. In
FIG. 3
, numeral
50
designates a compressor and numeral
10
designates a rotor. The rotor
10
has rotor vanes M
1
, M
2
, M
3
, M
4
, . . . (illustration shows an example of 10 stages) fitted to an outer circumferential periphery of a rotor disc so as to be rotated together with the rotor
10
. On the other hand, stator vanes C
1
, C
2
, C
3
, C
4
, . . . are fitted to an inner circumferential wall of a casing
14
so that the stator vanes and the rotor vanes are arranged alternately in an axial direction of the compressor
50
.
At an inlet of the compressor
50
, an IGV (Inlet Guide Vane)
11
is fitted to the inner circumferential wall of the casing
14
so as to adjustable of its opening by a driver portion
12
.
Of the stator vanes shown in the example of
FIG. 3
, those of C
1
, C
2
, C
3
and C
4
are variable vanes and their openings are adjustable by respective driver portions
13
-
1
,
13
-
2
,
13
-
3
and
13
-
4
. Air
20
is adjusted of a flow rate by the opening of the IGV
11
to enter the compressor
50
to be compressed while flowing through between the respective stator vanes and between the rotating rotor vanes and a compressed air
21
flows out of the compressor
50
to be supplied as a gas turbine combustion air or a turbine rotor or turbine blade cooling air. It is to be noted that while description is made with respect to
FIG. 3
on the example of the compressor
50
having the vanes of 10 stages in total in which four stages of the stator vanes C
1
, C
2
, C
3
and C
4
are variable, such a compressor as having vanes of 15 stages in total in which five stages of stator vanes C
1
to C
5
are variable is also developed.
FIG. 4
is a diagrammatic constructional view of stator vanes and their surrounding portion of the above-mentioned compressor in the prior art having five stages of variable stator vanes C
1
to C
5
. In
FIG. 4
, an IGV
11
is provided at an inlet of a compressor
50
and stator vanes C
1
to C
15
are arranged, although not all the stator vanes are illustrated. An opening
15
is provided immediately after the fifth stage stator vane C
5
so as to communicate with a piping
30
. The piping
30
is provided at its middle way with a bleed valve
60
for bleeding a compressed air. Likewise, an opening
16
is provided immediately after the eighth stage stator vane C
8
, and a piping
31
and a bleed valve
61
communicate therewith. Also, an opening
17
is provided immediately after the eleventh stage stator vane C
11
, and a piping
32
and a bleed valve
62
communicate therewith. It is to be noted that the openings
15
,
16
,
17
, respectively, are provided at four places on an outer circumferential periphery of a casing and four pipings each of the pipings
30
,
31
,
32
join together to communicate with the respective bleed valves
60
,
61
,
62
.
In the gas turbine compressor constructed as above, while the IGV
11
and the five stages of the stator vanes C
1
to C
5
are adjustable of their openings, the bleed valves
60
,
61
,
62
are so constructed as to be either fully opened or fully closed by an ON/OFF operation. At the time of starting, the IGV
11
and the stator vanes C
1
to C
5
are set to a predetermined opening, the bleed valves
60
,
61
,
62
are fully opened and air
20
is compressed. Until a rise of the gas turbine, the compressor is operated by a drive of a starter motor. At an initial slow speed operation and until the speed is elevated to about 90%, the bleed valves
60
,
61
,
62
are fully opened so that the air
20
is bled to be discharged into the ambient air for a matching of an air flow rate to the slow speed operation. When the speed comes to 90% of a rated speed and the operation rises up, the bleed valves
60
,
61
,
62
are fully closed and a steady operation starts. In such circumferences, there are problems in the prior art that a mismatching of the air flow rate occurs at the initial stage of the starting or a flow rate unstableness phenomenon occurs at the time when the bleed valves are closed while the speed is being elevated, etc. as well as the starter motor must have a large capacity in order to ensure a starting force at the time of operation start.
In the prior art gas turbine compressor, as mentioned above, when the operation is started, the starter motor is driven and the bleed valves are fully opened so that air is bled on the way for a matching to the operation state and when the speed is elevated to about 90%, the bleed valves are fully closed and the steady operation starts. In the mentioned operation method, while the speed is being elevated from the starting, a large amount of the air compressed halfway is discharged in vain into the ambient air.
Further, the starter motor is needed to have a sufficient capacity taking account of the air flow rate to be discharged into the ambient air at the time of starting. Also, the adjustment of the bleed valves to meet the air flow rate of the initial slow speed operation time and that of the compressor rated operation time is only done by the ON/OFF operation by which the bleed valves are either fully opened or fully closed, hence a phenomenon to cause an unstable fluid flow occurs at the starting time, which results in the obstruction in achieving a smooth speed elevation.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a gas turbine starting method in which bleed valves of a compressor are improved of their opening and closing operation so as to be adjustable of openings continuously and the starting operation is done such that a plurality of the bleed valves are first throttled and changed of their respective openings and when the speed comes to a predetermined level, the bleed valves are fully closed so that a rated speed is attained, thereby a bleed air amount which has so far been discharged in vain into the ambient air is reduced, a fluid unstableness phenomenon at the starting time is avoided and a smooth speed elevation is attained.
In order to achieve said object, the present invention provides methods of the following (1) to (7).
(1) A gas turbine starting method comprising a step of setting an inlet guide vane (IGV) and a variable stator vane of a gas turbine compressor to a predetermined opening during a starting time from a start initiation to a rated speed, characterized in that a plurality of bleed valves of said compressor are made variable of their openings and are controlled to a predetermined opening during said starting time.
(2) A gas turbine starting method as mentioned in (1) above, characterized in that an opening setting of said plurality of bleed valves is such that said plurality of bleed valves are throttled to a predetermined opening for a time from the start initiation to a half way of a speed elevation, are fully opened at said half way of the speed elevation and are fully closed immediately before the rated speed.
(3) A gas turbine starting method as mentioned in (2) above, characterized in that said opening setting of the plurality of bleed valves for the time from the start initiation to the half way of the speed elevation is such that said plurality of bleed valves are set to openings which are different from each other.
(4) A gas turbine starting method as mentioned in (3) above, characterized in that said opening setting of the plurality of bleed valves for the time from the start initiation to the half way of the speed elevation is such that at least one of said plurality of bleed valves is fully closed.
(5) A gas turbine starting method as mentioned in any one of (2) to (4) above, characterized in that a speed when said plurality of blee
Arimura Hisato
Seki Naoyuki
Mitsubishi Heavy Industries Ltd.
Ryznic John E.
Wenderoth , Lind & Ponack, L.L.P.
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