Power plants – Combustion products used as motive fluid – Combustion products generator
Reexamination Certificate
2000-09-05
2001-09-25
Thorpe, Timothy S. (Department: 3746)
Power plants
Combustion products used as motive fluid
Combustion products generator
C415S174500, C416S09600A
Reexamination Certificate
active
06293089
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a gas turbine which supplies and discharges a cooling medium to and from a high temperature section of the gas turbine.
Recently, a high temperature gas turbine has been developed and improved, and the temperature of the gas turbine is becoming 1500° C. or more from a temperature ranging from 700° C. or 900° C. to 1000° C. or 1300° C. in the prior art technology.
Under such circumstances that the temperature of the gas turbine is rapidly made high, a superalloy steel (heat resisting alloy steel) has been developed, and the superalloy steel has applied to a high temperature section such as a turbine stationary blade and a turbine rotor blade of the gas turbine. However, the superalloy steel has exceeded its usable limit, and for this reason, there has been employed an air cooling technique of compensating for lack of material strength with the use of air. Further, in a recent gas turbine, in order to achieve a high power generation and a high heat efficiency of the gas turbine, there is a plan to make 1500° C. or more a gas turbine combustion gas temperature (gas turbine inlet combustion gas temperature). In the case where a test (trial) calculation of plant heat efficiency is made with the use of the air cooling technique applied, a disadvantage occurs therein, and for this reason, a cooling medium is transferred from the air to a steam.
There have been proposed many gas turbines which use a steam as a cooling medium and one example of such gas turbines is disclosed in Japanese Patent Laid-Open Publication No. HEI 8-277725, in which
FIG. 1
shows an general arrangement of the gas turbine composed a compressor, a combustor and a turbine main body including a plurality of rotors formed with discs and movable blades arranged in stages along an axial direction of the gas turbine.
As shown in FIG.
17
and
FIG. 18
, a steam supply passages
3
and steam recovery passages
4
are formed in a gas turbine disc
2
molded integrally with a gas turbine rotor
1
which is formed in a sectional type, a plurality of the gas turbine rotors being arranged in an axial direction thereof. A steam supplied from a rear shaft (not shown) is supplied to a gas turbine rotor blade
6
with the use of a cavity
5
, and then, is cooled, and thereafter, the steam is recovered to the rear shaft via the recovery passage
4
.
Meanwhile, as shown in
FIG. 19
, in the gas turbine, the gas turbine disc
2
including a final stage gas turbine rotor blade
6
is provided with a rear shaft
8
, and a partition
14
is formed so as to divide an interior of the rear shaft
8
into the steam supply passage
3
on the center side and the steam recovery passage
4
on the opposite side. Further, the rear shaft
8
is provided a journal bearing
12
which includes a bearing housing
9
, a pad
10
, a retainer
11
or the like, at the outer side thereof, and is provided with a recovery pipe
13
for recovering a steam.
As described above, in Japanese Patent Laid-open Publication No. HEI 8-277725 shown in
FIG. 17
, FIG.
18
and
FIG. 19
, the cooling steam is supplied and discharged by way of the rear shaft
8
so as to reduce a thermal stress generated in the gas turbine rotor
1
, the gas turbine disc
2
and the gas turbine rotor blade
6
, and thus, it is possible to cope with the gas turbine from being made high temperature. Incidentally, in
FIG. 18
, a portion shown with oblique lines is a stacking bolt hole
7
for fixing the gas turbine disc
2
which is formed in a sectional type.
In the arrangement of the Japanese Patent Laid-open Publication No. HEI 8-277725 shown in
FIGS. 17
,
18
and
19
, a temperature of the cooling steam supplied to the high temperature section of the gas turbine and a temperature of the recovery steam are respectively set to 250° C. , and 450° C. in order to restrict the temperature of these steams less than the allowable temperature of each material of the gas turbine rotor
1
and the gas turbine disc
2
.
However, both the temperature 250° C. of the cooling steam supplied to the high temperature section of the gas turbine and the temperature 450° C. of the recovery steam far exceeds a allowable temperature of the journal bearing
12
supporting the rear shaft
8
.
In general, in the journal bearing
12
, a temperature of each metal component is restricted so as to be 100° C. to 150° C. even if a radiation heat of gas turbine combustion gas is added to a radiation heat of lubricating oil. However, in the case where the cooling and recovery steam temperatures are high, white metal adhered on a sliding surface of an inner ring of the bearing is melted, and for this reason, there is the possibility that the gas turbine falls into a dangerous state during operation.
Therefore, in the gas turbine, the steam temperature required for cooling the high temperature section of the gas turbine is secured, and there is the need of taking measures for stably operating the journal bearing
12
.
SUMMARY OF THE INVENTION
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a gas turbine provided with an improved structure for stably operating a journal bearing of a turbine rear shaft and effectively cooling a high temperature section of the gas turbine while effectively recovering a cooling medium.
This and other objects can be achieved according to the present invention, by providing a gas turbine having the general structure comprising a compressor, a combustor and a turbine body operatively connected to the compressor through a rotation shaft, the turbine body being composed of a plurality of rotors formed with turbine discs and movable blades which are arranged in plural stages along an axial direction of the turbine body, in which a rear shaft is connected to a downstream side of a final stage disc of the turbine discs so as to extend rearward from the final stage turbine disc and supported by means of a bearing.
In one aspect, the rear shaft is formed with a cooling medium supply passage for supplying a cooling medium to the turbine disc and a cooling medium recovery passage for recovering the cooling medium from the turbine disc, and a further cooling medium passage is formed between the rear shaft and either one of the cooling medium supply passage and the cooling medium recovery passage.
The further cooling medium passage is composed of an air passage, and the air passage is provided at an inlet thereof with an air guide portion and is formed at an outlet thereof with an air flow outlet extending along a radial direction of the rear shaft. The air guide portion is formed of a circular hole including a notched groove at an inlet portion thereof, and the air guide portion is composed of a disc-shaped retaining member and a ring member and includes guide vanes arranged annularly between the retaining member and the ring member.
In another aspect, the rear shaft is formed with a cooling medium supply passage for supplying a cooling medium to the gas turbine disc and a cooling medium recovery passage for recovering the cooling medium from the gas turbine disc, and a labyrinth seal is provided between the gas turbine disc and the bearing, the labyrinth seal being formed with a cooling medium supply hole which communicates with the cooling medium supply passage and a cooling medium recovery hole which communicates with the cooling medium recovery passage.
In a further aspect, the rear shaft is formed with a cooling medium supply passage for supplying a cooling medium to the turbine disc and a cooling medium recovery passage for recovering the cooling medium from the turbine disc, and a labyrinth seal is provided between the gas turbine disc and the bearing, the labyrinth seal being formed with a cooling medium supply hole which communicates with the cooling medium supply passage and a cooling medium recovery hole which communicates with the cooling medium recovery passage, and a cooling medium passage is further formed in the rear shaft sup
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Thorpe Timothy S.
Torrente David J.
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