Fluid reaction surfaces (i.e. – impellers) – With heating – cooling or thermal insulation means – Changing state mass within or fluid flow through working...
Reexamination Certificate
1998-03-24
2001-07-03
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...
C416S09600A, C415S115000
Reexamination Certificate
active
06254346
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a gas turbine cooling moving blade whose thickness is small and which has a cavity therein, and it is particularly applicable to a large-sized blade used in a rear stage of a gas turbine.
Recently, the gas turbine has been used at a higher temperature and the output of the gas turbine has been increased. Accordingly, a moving blade also tends to be large-sized. In particular, the moving blade used in a rear stage has become particularly large. For example, moving blades having a size from 50 to 60 cm have appeared. In such a large-sized moving blade, the weight of the moving blade itself increases and vibrations of the moving blade also increase so that stress generated by centrifugal force driving the rotation of the moving blade is greatly increased in comparison with conventional blades. Accordingly, in such moving blades, the thickness of a blade section is reduced as much as possible so as to make the moving blade light in weight. Further, the moving blade has a smaller width toward the blade tip by making the moving blade tapered.
FIG. 5
shows one example of the above-mentioned large-sized conventional moving blade. FIG.
5
(A) is a longitudinal sectional view of a central portion of this moving blade. FIG.
5
(B) is a cross-sectional view taken along line C—C in FIG.
5
(A). In FIG.
5
(A), reference numerals
10
,
11
and
12
respectively designate an entire moving blade, a hub portion and a blade portion. Reference numerals
13
and
14
respectively designate a cavity and a supporting rib within the cavity
13
. This supporting rib
14
is arranged to support a ceramic core used as a core for forming the cavity
13
at the time of casting and also has a reinforcing function.
As shown in FIG.
5
(B), many multiholes
15
within the blade
12
are bored toward a blade tip
16
. A shroud
17
is attached to the tip of the blade
12
. The blade base portion
18
occupies about 25% of axial length of the blade from the hub portion
11
to the blade tip. The cavity
13
is formed within the blade base portion
18
. A blade root portion
19
, together with the above-mentioned parts, forms the large-sized moving blade
10
.
In the moving blade of the above construction, when cooling air
20
is sent from an unillustrated turbine rotor, this cooling air
20
enters the cavity
13
and cools the entire moving blade
10
while the cooling air passes through the multiholes
15
. The cooling air is then discharged from an unillustrated opening formed in the blade tip
16
or the shroud
17
to a combustion gas passage.
However, in such a moving blade
10
having a cooling structure therein, it is difficult to manufacture a casting core for forming the cavity
13
at the time of manufacture and it is difficult to place a casting core within the moving blade
10
having the cavity
13
.
Further, since temperature and pressure are still increasing to improve efficiency of the gas turbine, the cooling of the moving blade
10
used in the gas turbine approximately having a turbine inlet temperature of 1500° C. becomes insufficient when the cavity
13
is simply formed in the above-mentioned blade base portion
18
and the cooling air
20
is introduced into the multiholes
15
within the moving blade
10
. The lack of sufficient cooling may cause reduced creep strength in this moving blade
10
.
Furthermore, when the cooling is done using only the multiholes
15
and the cooling air
20
merely passes through the multiholes
15
, cooling efficiency cannot be further improved. In addition, hollow space in the blade cannot be increased to make the moving blade light in weight, and a boring process is required in manufacturing the blade. Therefore, there is room for some consideration so as to make the processing easier.
OBJECT AND SUMMARY OF THE INVENTION
Therefore, to solve some of the problems associated with the conventional large-sized thin moving blade of the gas turbine, an object of the present invention is to provide a moving blade which can easily be processed without the conventional working process of multiholes and which has reduced weight to increase the proportion of hollow space in the blade and which is also applicable to a gas turbine having a higher inlet temperature by increasing further cooling efficiency in comparison with the blades having multiholes.
The present invention provides the following (1) and (2) means to achieve the above object.
(1) A cavity is formed in the entire interior of a moving blade from the blade root portion to the tip of the moving blade, and a plurality of turbulators are formed on an inner wall of this cavity.
(2) In a cooling moving blade of a gas turbine, a shroud is arranged at the tip of the moving blade and a passage for cooling air is formed from the blade root portion to the shroud, and the moving blade and the shroud are cooled by the cooling air flowing through this passage and by discharging the cooling air from the shroud. This passage for cooling air is formed by a cavity disposed in the interior of the moving blade from the blade root portion to the tip of the moving blade, and a plurality of turbulators are formed on an inner wall of the cavity.
In the gas turbine cooling moving blade of each of the above (1) and (2) according to the present invention, the cavity is formed in the interior of the moving blade from the blade root portion to the tip of the moving blade, and many turbulators are formed. Accordingly, a flow of the cooling air is disturbed by the turbulators as the cooling air flows into the cavity from the blade root portion and rises within the moving blade. Therefore, the frequency of the cooling air hitting the inner wall of the moving blade is increased so that the heat transfer rate is improved. Accordingly, cooling efficiency is improved in comparison with the cooling of a conventional multihole system. The cooled air is externally discharged from the tip portion of the moving blade. In the invention of the above (2), the cooled air is externally discharged from the shroud.
In accordance with the cooling moving blade of the gas turbine in each of the above (1) and (2) of the present invention, no conventional boring process of multiholes is required, and only the cavity and the turbulators need to be formed so that the moving blade is more easily manufactured. Since the moving blade becomes lighter due to a larger hollow space in the blade, low frequency vibrations are reduced and a bad influence of vibrational stress caused by centrifugal force is reduced.
As explained above, in the present invention, (1) a cavity is formed in the entire interior of the moving blade from the blade root portion to the tip of the moving blade, and a plurality of turbulators are formed on the inner wall of this cavity. Further, (2) in a cooling moving blade of a gas turbine, a shroud is arranged at the tip of the moving blade, and a passage for cooling air is formed from a blade root portion to the shroud, and the moving blade and the shroud are cooled by the cooling air flowing through this passage and by discharging the cooling air from the shroud. This passage for cooling air is formed by a cavity formed in the interior of the moving blade from said blade root portion to the end tip of the moving blade, and the turbulators are formed around an inner wall of the cavity. Accordingly, a flow of the cooling air flowing into the cavity is disturbed by the turbulators so that heat transfer becomes preferable and cooling efficiency is improved in comparison with cooling using the conventional multiholes.
Further, there is no such machining working process as boring of the multiholes, etc., so that the moving blade is manufactured easily. Since the cavity is formed, the proportion of hollow space in the blade increases. With this, the moving blade becomes lighter in weight and an influence of vibrations caused by centrifugal force is reduced. Thus, the moving blade of the high temperature gas turbine can be made thin and light in weight without d
Fukuno Hiroki
Suenaga Kiyoshi
Tomita Yasuoki
Alston & Bird LLP
Lopez F. Daniel
Mitsubishi Heavy Industries Ltd.
Woo Richard
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