Fluid reaction surfaces (i.e. – impellers) – With heating – cooling or thermal insulation means – Changing state mass within or fluid flow through working...
Reexamination Certificate
1999-06-02
2001-07-10
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, C416S09700R, C415S115000
Reexamination Certificate
active
06257830
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a gas-turbine blade provided with a steam-cooled structure.
2. Related Art
In recent years, it has been thought of to use steam in place of air for cooling the blades of a gas turbine in a combined cycle power plant, and to recover the steam used for cooling the blades without discharging it into a main gas flow with a view to improving the thermal efficiency of the gas turbine, (see, for example, Japanese Patent Application Laid-open No. 8-319803)). However, such approach has not yet found practical application.
With such steam cooling system, heat energy from the gas turbine carried by the recovered steam can be utilized in a steam turbine, whereby efficiency of the plant on the whole can be protected against degradation. Further, by suppressing the amount of cooling medium or coolant fed to the gas turbine, turbine efficiency can be enhanced. Additionally, by using steam as the coolant instead of air, heat transfer performance can be significantly enhanced without the need for changing or altering the geometrical configuration of the existing coolant flow passages.
A typical internal cooling structure of a moving blade in a conventional heat recovery type steam-cooled gas turbine, such as mentioned above, is shown in
FIGS. 5
a
and
5
b
. Moreover,
FIG. 5
a
is a vertical section of a blade, and
FIG. 5
b
is a sectional view of same along the line
5
B—
5
B in
FIG. 5
a.
Steam for cooling the moving blade
1
is supplied through a cooling steam inlet port
8
provided in a lower end portion of the blade at a location close to a leading edge
5
of the blade, and the steam flows through a coolant flow passage
4
formed inside the moving blade
1
in a serpentine pattern, as indicated by the arrows. After having cooled the interior of the blade, the steam leaves the blade through a cooling steam outlet port
9
provided at a location close to the blade trailing edge
6
and is subsequently introduced into a recovery system not shown.
Further, a plurality of turbulence promoting fins
7
are formed on the inner surfaces of the coolant flow passage
4
in the blade, each extending in a direction substantially orthogonal to the flow of the coolant steam so as to promote internal heat transfer.
As mentioned previously, the coolant steam is recovered by equipment provided at a location downstream of the gas turbine. To this end, the pressure of the coolant steam within the blade is maintained higher than the pressure of gases flowing outside of the blade by, 2 to 4 MPa. Hence, the blade is subjected to internal pressures which may exceed a permissible limit predetermined by the strength of the hollow blade with a thin structure, thus involving deformation (bulging) of the blade and hence fluid delamination of the working gas flowing along the external surface of the blade, to incur such problems as degradation in the performance of the blade and the like. Thus, there exists a demand for a blade with a structure which can at least withstand the internal pressure mentioned above.
SUMMARY OF THE INVENTION
In order to meet the demand mentioned above, an object of the present invention is to provide a gas-turbine blade in which strength can be reliably ensured without impairing the advantages of the steam cooling system designed to improve the thermal efficiency of the gas turbine to thus be able to freely enjoy such advantages.
The present invention has been made to achieve the object described above and provides a gas-turbine blade having a coolant flow passage formed to extend longitudinally in an inner portion of the blade, wherein a reinforcing rib or ribs are provided within the coolant flow passage so as to extend in a flow direction of a coolant and connect a dorsal wall and a ventral wall of the blade.
By connecting the dorsal wall and the ventral wall of the blade by means of reinforcing rib or ribs, the blade can be imparted with sufficient strength for withstanding a force applied by a pressure difference between the high-pressure steam flowing inside of the blade and the gas flowing outside of the blade. Further, since the reinforcing rib or ribs are disposed so as to extend in the direction in which the coolant flows through the coolant flow passage, the high-pressure steam serving as the coolant encounters essentially no obstacle in flowing through the coolant flow passage. Thus, the flow of the coolant is not essentially effected by the presence (or absence) of the reinforcing rib or ribs, whereby the desired cooling effect as aimed can be achieved.
Further, the present invention provides a gas-turbine blade, in which the coolant flow passage is formed, being partitioned by a partition wall or walls, and in which the reinforcing rib is disposed at such a position that coolant flow passage portions located at right and left sides of the reinforcing rib or ribs, together with the partition walls located adjacent to the reinforcing rib are not blocked.
More specifically, by positioning and disposing the reinforcing rib or ribs between the adjacent partition walls defining the coolant flow passage, preferably at a central position between the adjacent partition walls which cooperate to form the coolant flow passage, so as not to block the coolant flow passage, the width of the coolant flow passage is correspondingly decreased, which is effective for preventing the deformation of the blade (bulging) by the pressure difference between the coolant steam pressure within the coolant flow passage and the main gas flow.
With the blade structure mentioned above, the blade can be protected against deformation even when a coolant steam of higher pressure than that of the main gas flow is used, whereby degradation of the blade performance which may otherwise be brought about by so-called fluid delamination due to blade deformation can be suppressed or prevented.
Furthermore, the present invention provides a gas-turbine blade, in which the coolant flow passage portions located at left and right sides of the reinforcing rib or ribs are each formed as independent structures, such that the coolant flow passage portions exhibit independent flow characteristics.
In other words, the reinforcing rib or ribs are not simply disposed within the coolant flow passage but disposed such that the coolant flow passage portions defined at the left and right sides thereof can be constructed independently according to the characteristics of the coolant steam flowing through the respective coolant flow passage portions. Hence, efficient heat exchange and heat recovery can be achieved.
Furthermore, the present invention provides a gas-turbine blade, in which the blade is structured so that the coolant steam fed to the coolant flow passage and recovered therefrom is fed through an inlet port projecting forwardly from a root portion of the blade and recovered through an outlet port projecting rearwardly from the blade root portion.
More specifically, in the inlet port for feeding the coolant steam into the coolant flow passage and the outlet port for recovering the coolant steam having performed a cooling operation and received the heat from the turbine blade, there is high possibility of steam leakage. Moreover, it is to be noted that these ports are formed so as to project forwardly and rearwardly, respectively, from the blade root as described above. Hence, the machining of these portions, including connecting structures, etc., is facilitated, while the leakage of the steam at the connecting portions which degrades the operating efficiency can be appropriately and reliably prevented.
Furthermore, the present invention provides a gas-turbine blade, in which the reinforcing rib or ribs are disposed only within a portion of the coolant flow passage which is located adjacent to the blade trailing edge, while the other portion of said coolant flow passage is partitioned a number of times at short intervals such that the cross-sections thereof are approximately circular.
More specifically, when the coolant flo
Aoki Sunao
Fukuno Hiroki
Matsuura Masaaki
Suenaga Kiyoshi
Tomita Yasuoki
Look Edward K.
Mitsubishi Heavy Industries Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Woo Richard
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