Fluid reaction surfaces (i.e. – impellers) – With fluid passage in working member communicating with... – Discharge solely at periphery normal to rotation axis
Patent
1999-02-23
2000-11-28
Look, Edward K.
Fluid reaction surfaces (i.e., impellers)
With fluid passage in working member communicating with...
Discharge solely at periphery normal to rotation axis
416 97R, 416191, B64C 1124
Patent
active
061526940
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a tip shroud for a gas turbine moving blade and, more particularly, to a tip shroud for a moving blade, which is used at a downstream stage and is made thin and light to have multi-holes therein for cooling purposes, and which is extended in its creep lifetime by cooling it effectively.
DESCRIPTION OF RELATED ART
FIGS. 8(a)-8(b) show one example of a prior art moving blade to be used at a downstream stage of the gas turbine. FIG. 8(a) is a longitudinal section, and FIG. 8(b) is a section taken in the direction of arrows D--D of FIG. 8(a). In order to enhance the effect of cooling the gas turbine, which in recent years is subject to hotter and hotter temperatures, there has been adopted a system in which a moving blade to be used at a downstream stage is made thin and light but long and in which multiple holes are formed to feed cooling air to cool the inside of the moving blade. FIG. 8 shows one example of the moving blade, in which reference numeral 60 designates a moving blade, numeral 61 a blade root, and numeral 62 a hub having an internal cavity 64 extending along a hub portion 63 by 25% of the total blade length and supported by core supporting ribs 65. Numeral 66 designates a plurality of holes or passages which are formed from the upper portion of the hub portion 63 to a blade end 67, as shown in FIG. 8(b). A tip shroud 68 is mounted on the leading end of the moving blade 60, and includes air holes for guiding the cooling air from the holes 66 so as to release the cooling air 70 to the outside.
In the moving blade 60 thus constructed, the cooling air 70 is guided from the blade root 61 into the cavity 64 to cool the cavity 64 and then flows through the holes 66 and the blade end 67 to cool the blade so that the cooling air is released, while cooling the tip shroud 68, from the air holes formed in the tip shroud 68 to a combustion gas passage.
FIGS. 7(a)-7(b) show another example of a gas turbine moving blade, which is used at the downstream stage of the gas turbine as in the example of FIG. 8. FIG. 7(a) is a longitudinal section, and FIG. 7(b) is a section taken in the direction of arrows C--C of FIG. 7(a). In FIG. 7, reference numeral 50 designates a moving blade, numeral 51 a blade root, and numeral 52 a hub having an internal cavity 54 extending along a hub portion 53 by 25% of the total-blade length and supported by core supporting ribs 55. Numeral 56 designates a plurality of holes or passages which are formed from the upper portion of the hub portion 53 to a blade end 57. A tip shroud 58 is mounted on the leading end of the moving blade 50. These structures are identical to those of the example shown in FIG. 8. In the example of FIG. 7, however, a number of pin fins 59 are provided in the cavity 54 by projecting them from the two inner wall faces or by connecting them to the two inner wall faces.
In the moving blade 50 thus constructed, the cooling air 70 flows from the blade root 51 into the cavity 54, and its flow is disturbed by the pin fins 59 to enhance the thermal conductivity and accordingly the cooling efficiency of the internal cooling air in the hub portion 53. After this, the cooling air 70 flows through the holes 56 to the blade end 57 to cool the blade 50 and the tip shroud 58. The cooling air is released from the air holes formed in the tip shroud 58 to the combustion gas passage.
As described hereinbefore, the moving blade to be used at the downstream stage of the gas turbine is made light and long, and its tip shroud is shaped so as to be exposed to the hot gas so that it is liable to crack. FIGS. 6(a)-6(b) show the moving blade and the tip shroud. FIG. 6(a) is a side elevation, and FIG. (b) is a top plan view of the tip shroud. On the leading end of a moving blade 10, as shown in FIG. 6(a), there is mounted a tip shroud 11, which is provided with flanges 14 and at its two end portions and a flange 16 at its central portion. However, the tip shroud 11 has portions at its circumferential end portions that are liable to have a
REFERENCES:
patent: 5464486 (1995-11-01), Rao
Look Edward K.
Mitsubishi Heavy Industries Ltd.
Rodriguez Hermes
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