Rotary kinetic fluid motors or pumps – With passage in blade – vane – shaft or rotary distributor...
Reexamination Certificate
1998-02-20
2001-07-24
Verdier, Christopher (Department: 3745)
Rotary kinetic fluid motors or pumps
With passage in blade, vane, shaft or rotary distributor...
C416S09600A, C416S09700R
Reexamination Certificate
active
06264426
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a stationary blade for a gas turbine in which cooling is effected by using both steam and air as cooling media.
The prior art will be described with reference to FIG.
4
.
FIG. 4
is a sectional view of a conventional cooled stationary blade for gas turbine.
A cooled stationary blade
51
is integrally formed together with outside and inside shrouds (not shown) by precision casting. Inserts
54
A and
54
B having many cooling holes
53
are inserted in the cooled stationary blade
51
, and cooling air is supplied into the inserts
54
A and
54
B through the outside shroud.
The cooling air flows out through the cooling holes
53
as indicated by arrows, and flows into a hollow chamber A after effecting impingement cooling by colliding with the inner wall of the cooled stationary blade
51
. Subsequently, the cooling air cools the cooled stationary blade
51
while flowing toward the trailing edge of blade. Part of the cooling air forms a cooling film on the blade surface by flowing out through film cooling holes
52
and
55
and flowing along the blade profile, whereby film cooling is effected.
The cooling air flowing out through a slit
56
at the blade trailing edge convection-cools the blade trailing edge including pin fins
57
. Also, the cooling air flowing out through a cooling hole
58
at the blade leading edge shower-cools the blade leading edge.
Although not shown in the figure, the outside and inside shrouds are provided with an impingement plate and pin fins, and impingement cooling and pin fin cooling are effected by the cooling air before it is supplied to the inserts
54
A and
54
B.
As the efficiency of gas turbine has increased recently, the inlet temperature has increased. An inlet temperature of about 1500° C. cannot be overcome by the air cooling only because air has a low heat capacity and the air cooling requires a large amount of air. For this reason, steam has begun to be used as a cooling medium because steam has a higher heat capacity than air and a smaller amount thereof is required.
In the process of development of technology for accommodating such a change of needs, it was thought that the stationary blade portions that can be air-cooled are cooled by air, and on the other hand, the stationary blade portions that are difficult to be air-cooled are cooled by steam.
However, in the case where steam cooling is effected in such a manner, extraction steam of a steam turbine constituting a combined cycle, waste heat boiler steam, and the like are used, so that the complete elimination of steam leakage into the gas turbine is required in view of the efficiency of steam cycle.
Therefore, the cooling medium passage must be closed to the outside and have supply and recovery ports of steam.
Also, because both of steam and air are used as cooling media, the whole system including the outside and inside shrouds, not to mention the blade itself is required to be cooled by using both cooling media without relying on either one cooling medium only in view of the control balance of the whole system etc.
OBJECT AND SUMMARY OF THE INVENTION
The present invention was made in view of this situation, and accordingly an object thereof is to provide a gas turbine stationary blade in which every necessary place is cooled by effectively using both cooling media of steam and air in a well-balanced manner, and the cooling steam is used without leakage.
Accordingly, the present invention for solving the above problems provides a gas turbine stationary blade provided with a steam cooling section at the rear from the leading edge of blade and an air cooling section at the trailing edge of blade, in which the steam cooling section comprises a cooling steam supply portion having an impingement plate, which is formed at the end of an outside shroud; a serpentine flow path extending in the blade length direction from the cooling steam supply portion and turns plural times; many turbulators arranged on the inner wall of the serpentine flow path so as to extend slantwise with respect to the flow; an inside impingement plate provided in an inside shroud at the final turning portion of the serpentine flow path; and a steam recovery port formed in the outside shroud at a downstream position of the serpentine flow path turned at the inside impingement plate, and the air cooling section comprises an air flow path extending at the rear of the steam cooling section from the outer edge of the outside shroud to the outer edge of the inside shroud and having many turbulators arranged on the inner wall so as to extend slantwise with respect to the flow; slot holes provided at the trailing edge of blade; and a cooling air supply portion for supplying the cooling air to the slot holes. The cooling steam cools the portion at the rear from the blade leading edge with a higher temperature. First, the cooling steam impingement-cools the outside shroud, and then cools the blade while flowing in the serpentine flow path in the lengthwise direction in a turbulent flow state by being turned. It impingement-cools the inside shroud during the flow, and is finally transferred to a predetermined recovery system from the outside shroud. On the other hand, the cooling air cools the trailing edge portion of blade. The cooling air flows in the air flow path in the blade length direction in a turbulent flow state to cool the blade, and effects slot cooling in which the cooling air passes through the slot holes to the gas flow path at the trailing edge of blade. Desirable blade cooling is effected by the cooperation of steam cooling and air cooling, and in steam cooling, the cooling steam is guided without leakage during the cooling process and recovered surely in a predetermined manner, by which the efficiency is improved variously.
According to the present invention, the gas turbine stationary blade is provided with a steam cooling section at the rear from the leading edge of blade and an air cooling section at the trailing edge of blade. The steam cooling section comprises a cooling steam supply portion having an impingement plate, which is formed at the end of an outside shroud; a serpentine flow path extending in the blade length direction from the cooling steam supply portion and turns plural times; many turbulators arranged on the inner wall of the serpentine flow path so as to extend slantwise with respect to the flow; an inside impingement plate provided in an inside shroud at the final turning portion of the serpentine flow path; and a steam recovery port formed in the outside shroud at a downstream position of the serpentine flow path turned at the inside impingement plate. The air cooling section comprises an air flow path extending at the rear of the steam cooling section from the outer edge of the outside shroud to the outer edge of the inside shroud and having many turbulators arranged on the inner wall so as to extend slantwise with respect to the flow; slot holes provided at the trailing edge of blade; and a cooling air supply portion for supplying the cooling air to the slot holes. The gas turbine stationary blade configured as described above has the following effects.
The gas turbine stationary blade, which has a high temperature in operation, is cooled by both of the steam cooling section and air cooling section. In the steam cooling section, the cooling steam flows in the serpentine flow path in the blade at the rear from the leading edge while impingement-cooling the outside and inside shrouds. In the air cooling section, the air flow path cooling and slot cooling are combined at the trailing edge. Moreover, in the steam cooling, the heated cooling steam is recovered surely and reused. Also, because steam has a high heat capacity, the total fluid flow of steam plus air is significantly decreased as compared with the case where cooling is effected by air only. Further, a great decrease in use of air as a cooling medium provides a margin for combustion air, resulting in the improvement in gas turbine efficiency.
Fukuno Hiroki
Suenaga Kiyoshi
Tomita Yasuoki
Alston & Bird LLP
Mitsubishi Heavy Industries Ltd.
Verdier Christopher
Woo Richard
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