Gas turbine cooling blade

Details Gas turbine cooling blade Gas turbine cooling blade

1998-03-05

2001-02-13

Lopez, F. Daniel (Department: 3745)

Fluid reaction surfaces (i.e., impellers)

With heating, cooling or thermal insulation means

Changing state mass within or fluid flow through working...

C416S09700R

Reexamination Certificate

active

06186740

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a cooling blade of a gas turbine.
Waste heat from a high-temperature gas turbine is recovered and utilized for a boiler of a steam turbine in some combined plants.
In one such combined plant, a cooling blade of the high-temperature gas turbine is cooled by internal cooling only. A refrigerant, having absorbed heat from the gas turbine by cooling it, is entirely recovered outside the gas turbine, and is fed into the steam turbine. By doing this, the performance of the whole plant is improved.
The cooling blade of the gas turbine has a recovery-type cooling structure. Thus, pneumatic power loss attributable to film-cooling that is applied to the high-temperature gas turbine can be reduced, and the turbine efficiency of the gas turbine can be improved.
Referring now to
FIGS. 1A and 1B
, a conventional turbine blade of the recovery type will be described. In the description to follow, a stationary blade is given as an example of the gas turbine cooling blade.
FIG. 1A
is a vertical sectional view of the cooling blade, and
FIG. 1B
is a sectional view taken along line A—A of FIG.
1
A.
A cooling blade
1
is supplied with a refrigerant
6
from a waste heat boiler or the like outside a casing (not shown) through supply pipes
4
that penetrate an outer shroud
3
. The refrigerant
6
fed into the blade
1
absorbs heat as it flows through a cooling passage
2
defined by a rib
7
toward a rear-side flow. The refrigerant
6
, having thus absorbed heat, is guided through a recovery pipe to the outside of the gas turbine system. Thereafter, the refrigerant is delivered to a steam turbine in a combined plant, whereupon heat is recovered from it.
FIG. 2A
shows a heat transfer rate distribution on the outer surface of the conventional turbine blade described above. Referring to
FIG. 2A
, a reference point O is settled on a front edge
8
(
FIG. 1B
) of the blade, and various points are settled on the outside and inside of the blade, corresponding individually to the ratios between X-direction distances from the reference point O, along the outside and inside of the blade, and a distance X
max
from the point O to the rear end edge of the blade. The curve of
FIG. 2A
represent a series heat transfer rates obtained at the individual points.
As seen from
FIG. 2A
, the heat transfer rate of the front edge
8
is relatively high, and the heat transfer area is narrower on the cooling side than on the gas side. Thus, the front edge
8
of the blade can be regarded as one of the most reluctant parts to be cooled.
Generally, in a cooling blade of this type, the refrigerant
6
is run through the cooling passage
2
therein, so that the passage
2
can be cooled at an average heat transfer rate throughout the area. Actually, however, high-temperature portions are formed in the cooling blade, as mentioned before. This implies that high-temperature portions will inevitably develop in part of the cooling blade if only the front edge of the blade, which displays relatively high heat transfer rates outside, is intensively cooled with use of a conventional serpentine passage.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to provide a long-life turbine cooling blade with a uniform metal temperature.
In order to achieve the above object, a gas turbine cooling blade according to the present invention comprises an insert fitted in a cooling passage at the front edge of the turbine blade, a plurality of nozzles formed in the front face of the insert and used to spray an impact jet of a refrigerant against the inner surface of the front edge of the blade, thereby cooling the inner surface, and a passage formed between the rear face of the insert and a rib on the inner surface of the blade and communicating with a rear-side flow.
In this arrangement, the refrigerant is ejected from the nozzles in the insert and runs against the inner surface of the turbine blade, thereby cooling the front edge portion of the blade from inside. Then, the refrigerant, run against the inner surface of the turbine blade, flows through a gap between the insert and the inner surface of the turbine blade, thereby effecting the so-called convection cooling. After flowing through the gap, the refrigerant finally flows through the passage defined by the rear face of the insert and the rib on the inner surface of the blade. Then, the refrigerant flows into the next cooling passage and gradually recovers heat energy.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.


REFERENCES:
patent: 3574481 (1971-04-01), Pyne, Jr.
patent: 3628885 (1971-12-01), Sidenstick et al.
patent: 4021139 (1977-05-01), Franklin
patent: 4297077 (1981-10-01), Durgin et al.
patent: 4461612 (1984-07-01), Dodd
patent: 4616976 (1986-10-01), Lings et al.
patent: 5120192 (1992-06-01), Ohtomo et al.
patent: 5762471 (1998-06-01), Cunha

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