Rotary kinetic fluid motors or pumps – With passage in blade – vane – shaft or rotary distributor...
Reexamination Certificate
1999-10-21
2001-10-23
Ryznic, John E. (Department: 3745)
Rotary kinetic fluid motors or pumps
With passage in blade, vane, shaft or rotary distributor...
Reexamination Certificate
active
06305902
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a stationary blade of a steam turbine and more particularly to a stationary blade applied as a precision cast hollow blade which is used for a final stage of a steam turbine and has an enhanced drain removal efficiency of its blade surface.
2. Description of the Prior Art
As for a final stage stationary blade of a steam turbine, steam which has worked on a front stage side thereof passes through it and as the temperature of the steam becomes lower, the blade is not specifically cooled. Although drain comes out on a blade surface, it is a present situation that there are provided slits for recovering the drain through which the drain is led into a blade interior to be recovered through a hollow therein.
FIG. 5
is a perspective view of a precision cast hollow blade used in a steam turbine in the prior art, as mentioned above. In
FIG. 5
, numeral
2
designates an outer shroud, numeral
3
designates an inner shroud and numeral
31
designates a stationary blade, which is a precision cast blade to be used for a final stage of the steam turbine and has a hollow formed therein. Numeral
32
designates the hollow in the blade interior, which is formed as a single hollow. Numerals
33
,
34
, respectively, designate a plurality of ventral slits, which are provided in the blade surface linearly with a predetermined interval between each of the slits so that two rows of the ventral slits are arranged in parallel with each other. Numeral
35
designates a plurality of dorsal slits provided likewise in the blade surface. The ventral slits
33
,
34
and the dorsal slits
35
are provided to open at the blade surface and communicate with the hollow
32
so that the drain may flow therethrough into the blade interior.
FIG. 6
is a cross sectional view taken on line G—G of FIG.
5
. As mentioned above, the single hollow
32
is formed in the stationary blade
31
and the ventral slits
33
,
34
are provided in a ventral portion of the stationary blade
31
to pass through from the blade surface to the hollow
32
. Likewise, the dorsal slit
35
is provided in a dorsal portion of the stationary blade
31
to pass through from the blade surface to the hollow
32
.
In the steam turbine stationary blade constructed as mentioned above, drain
50
on the blade surface flows into the ventral slits
33
,
34
and the dorsal slits
35
to be led into the hollow
32
and then passes through the outer shroud
2
or the inner shroud
3
to be recovered into a condenser (not shown) via a pipe system (not shown). In the process of such flow of the drain
50
which has been led into the hollow
32
through the ventral slits
33
,
34
and the dorsal slits
35
, there is a problem in operation that the drain so led into the hollow
32
through the dorsal slits
35
moves along an inner wall of the hollow
32
to flow out again through the ventral slits
33
,
34
or a reverse case thereof occurs, and an improvement in terms of a drain removal efficiency is desired.
That is, in the precision cast hollow stationary blade of a steam turbine in the prior art as mentioned above, there occurs a case that the drain recovered into the hollow
32
through the dorsal slits
35
, or through the ventral slits
33
34
, moves along the inner wall of the hollow
32
to flow out again through the ventral slits
33
,
34
, or through the dorsal slits
35
, respectively, which results in lowering the drain recovery efficiency.
SUMMARY OF THE INVENTION
In view of the above-mentioned problem in the prior art, it is an object of the present invention to provide a steam turbine stationary blade comprising a structure to section a drain flow passage into two portions, one for recovering drain through dorsal slits and one for recovering drain through ventral slits so that the drain recovered into a hollow through the dorsal slits may not flow out again through the ventral slits or a reverse case thereof may not occur.
In order to achieve this object, the present invention provides the following means.
The steam turbine stationary blade comprises a hollow passing through an interior of the blade from an outer shroud to an inner shroud and a plurality of slits, formed on a ventral side and a dorsal side of the blade so as to communicate with the hollow from a surface of the blade, extending in a lengthwise direction of the blade with a predetermined interval between each of the slits. The hollow is characterized in that it is sectioned into a leading edge side hollow on a leading edge side of the blade and a trailing edge side hollow on a trailing edge side of the blade. The leading edge side hollow and the trailing edge side hollow are independent of each other so that the slits formed on the dorsal side communicate with the leading edge side hollow and the slits formed on the ventral side communicate with the trailing edge side hollow.
In the steam turbine stationary blade according to the present invention, the hollow in the blade is sectioned into the leading edge side and the trailing edge side so as to be independent of each other, thereby the drain entering the leading edge side hollow from the dorsal slits and that entering the trailing edge side hollow from the ventral slits are separated from each other. Due to this sectioning, no case occurs where the drain recovered through the dorsal slits flows out through the ventral slits or the drain flows out reversely thereof, and a secure recovery of the drain can be accomplished. In the prior art case, there is provided only a single hollow and there occurs a case where the drain recovered into the hollow through the dorsal slits flows out to the blade surface through the ventral slits or the drain flows out reversely thereof, but in the present invention, no such shortcomings occur.
REFERENCES:
patent: 1829674 (1931-10-01), Rosenlocher
patent: 3672787 (1972-06-01), Thorstenson
patent: 5342172 (1994-08-01), Coudray et al.
patent: 5352091 (1994-10-01), Sylvestro
patent: 5494402 (1996-02-01), Glezer et al.
patent: 0233332 (1987-08-01), None
patent: 1072483 (1967-06-01), None
patent: 62271905 (1987-11-01), None
patent: 01045904 (1989-02-01), None
patent: 06173607 (1994-06-01), None
Konishi Tetsu
Magoshi Ryotaro
Matsuo Takaaki
Toda Hideyuki
Watanabe Eiichiro
Mitsubishi Heavy Industries Ltd.
Ryznic John E.
Wenderoth , Lind & Ponack, L.L.P.
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