Fluid reaction surfaces (i.e. – impellers) – With heating – cooling or thermal insulation means – Changing state mass within or fluid flow through working...
Reexamination Certificate
2001-03-08
2003-06-03
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
With heating, cooling or thermal insulation means
Changing state mass within or fluid flow through working...
C416S09600A
Reexamination Certificate
active
06572335
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a gas turbine cooled stationary blade and more particularly to a gas turbine cooled stationary blade which is suitably applied to a second stage stationary blade and is improved so as to have an enhanced strength against thermal stresses and an enhanced cooling effect.
2. Description of the Prior Art
FIG. 10
is a cross sectional view showing a gas path portion of front stages of a gas turbine in the prior art. In
FIG. 10
, a combustor
30
comprises a fitting flange
31
, to which an outer shroud
33
and inner shroud
34
of a first stage stationary blade (
1
c
)
32
are fixed. The first stage stationary blade
32
has its upper and lower ends fitted to the outer shroud
33
and inner shroud
34
, respectively, so as to be fixed between them. The first stage stationary blade
32
is provided in plural pieces arranged in a turbine circumferential direction and fixed to a turbine casing on a turbine stationary side. A first stage moving blade (
1
s
)
35
is provided on the downstream side of the first stage stationary blade
32
in plural pieces arranged in the turbine circumferential direction. The first stage moving blade
35
is fixed to a platform
36
, and this platform
36
is fixed around a turbine rotor disc, so that the moving blade
35
rotates together with a turbine rotor. A second stage stationary blade (
2
c
)
37
is provided, having its upper and lower ends fitted likewise to an outer shroud
38
and inner shroud
39
, respectively, on the downstream side of the first stage moving blade
35
. The second stage stationary blade is provided in plural pieces arranged in the turbine circumferential direction on the turbine stationary side. Further downstream thereof, a second stage moving blade (
2
s
)
40
is provided, being fixed to the turbine rotor disc via a platform
43
. Such a gas turbine as having the mentioned blade arrangement is usually constructed of four stages. A high temperature combustion gas
50
generated by combustion in the combustor
30
flows through the first stage stationary blades (
1
c
)
32
and, while flowing through between the blades of the second to fourth stages, the gas expands to rotate the moving blades
35
,
40
, etc. to thus give rotational power to the turbine rotor, The gas
50
is then discharged.
FIG. 11
is a perspective view of the second stage stationary blade
37
mentioned with respect to FIG.
10
. In
FIG. 11
, the second stage stationary blade
37
is fixed to the outer shroud
38
and inner shroud
39
. The outer shroud
38
is formed in a rectangular shape having the periphery thereof surrounded by end flanges
38
a
,
38
b
,
38
c
, and
38
d
and a bottom plate
38
e
in a central portion thereof. Likewise, the inner shroud
39
is formed in a rectangular shape having a lower side (or inner side) peripheral portion thereof surrounded by end flanges
39
a
and
39
c
and fitting flanges
41
and
42
and a bottom plate
39
e
in a central portion thereof. Cooling of the second stage stationary blade
37
is done such that cooling air flows in from the outer shroud
38
side via an impingement plate (not shown) to enter an interior of the shroud
38
for cooling the shroud interior and then to enter an opening of an upper portion of the blade
37
to flow through blade inner passages for cooling the blade
37
. The cooling air, having so cooled the blade
37
, flows into an interior of the inner shroud
39
for cooling thereof and is then discharged outside.
FIG. 12
is a cross sectional view of the second stage stationary blade. In
FIG. 12
, numeral
61
designates a blade wall, which is usually formed to have a wall thickness of 4 mm. Within the blade, there is provided a rib
62
to form two sectioned spaces on blade leading edge and trailing edge sides. An insert
63
is inserted into the space on the blade leading edge side and an insert
64
is inserted into the space on the blade trailing edge side. Both of the inserts
63
and
64
are inserted into the spaces with a predetermined gap being maintained from an inner wall surface of the blade wall
61
. A plurality of air blow holes
66
are provided in and around each of the inserts
63
and
64
so that cooling air in the blade may flow out therethrough into the gap between the blade wall
61
and the inserts
63
and
64
. Also, a plurality of cooling holes
60
for blowing out the cooling air are provided in the blade wall
61
at a plurality of places of a blade leading edge portion and blade concave and convex side portions, so that the cooling air which has flowed into the gap between the blade wall
61
and the inserts
63
,
64
may be blown outside of the blade for effecting shower head cooling of the blade leading edge portion and film cooling of the blade concave and convex side portions to thereby minimize the influences of the high temperature therearound.
In the gas turbine stationary blade as described above, the cooling structure is made such that cooling air flows in from the outer shroud side for cooling the interior of the outer shroud and then flows into the interior of the stationary blade for cooling the inner side and outer side of the blade, and further flows into the interior of the inner shroud for cooling the interior of the inner shroud. However, the second stage stationary blade is a blade which is exposed to high temperature, and there are problems caused by the high temperature, such as deformation of the shroud, thinning of the blade due to oxidation, peeling of the coating, the occurrence of cracks at a blade trailing edge fitting portion or a platform end face portion, etc.
SUMMARY OF THE INVENTION
In view of the problems in the gas turbine stationary blade, especially the second stage stationary blade, in the prior art, it is an object of the present invention to provide a gas turbine cooled stationary blade which is suitably applied to the second stage stationary blade and is improved in the construction and cooling structure such that a shroud or blade wall, which is exposed to a high temperature to be in a thermally severe state, may be enhanced in strength and cooling effect so that deformation due to thermal influences and the occurrence of cracks may be suppressed.
In order to achieve the object, the present invention provides the following structures (1) to (7).
(1) A gas turbine cooled stationary blade comprises an outer shroud, an inner shroud and an insert of a sleeve shape, having air blow holes, inserted into an interior of the blade between the outer and inner shrouds. The blade is constructed such that cooling air entering the outer shroud flows through the insert to be blown through the air blow holes, to be further blown outside of the blade through cooling holes provided so as to pass through a blade wall of the blade, to be led into the inner shroud for cooling thereof, and to then be discharged to the outside. A blade wall thickness in an area of 75% to 100% of a blade height of a blade leading edge portion of the blade is made thicker toward the insert than a blade wall thickness of other portions of the blade. The blade is provided therein with a plurality of ribs arranged up and down between 0% and 100% of the blade height on a blade inner wall on a blade convex side. The plurality of ribs extend in a blade transverse direction and protrude toward the insert. The outer and inner shrouds are provided therein with cooling passages arranged in shroud both side end portions on blade convex and concave sides of the respective shrouds so that cooling air may flow therethrough from a shroud front portion, or a blade leading edge side portion, of the respective shrouds to a shroud rear portion, or a blade trailing edge side portion, of the respective shrouds to then be discharged outside through openings provided in the shroud rear portion. The inner shroud is further provided therein with a plurality of cooling holes arranged along the cooling passages on the blade convex and concave sides of the inner shrou
Ito Eisaku
Kuwabara Masamitsu
Shirota Akihiko
Tomita Yasuoki
Look Edward K.
Mitsubishi Heavy Industries Ltd.
Wenderoth , Lind & Ponack, L.L.P.
White Dwayne
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