Rotary kinetic fluid motors or pumps – With passage in blade – vane – shaft or rotary distributor...
Reexamination Certificate
2000-01-31
2001-05-15
Ryznic, John E. (Department: 3745)
Rotary kinetic fluid motors or pumps
With passage in blade, vane, shaft or rotary distributor...
C415S117000
Reexamination Certificate
active
06231303
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a gas turbine including a first stage having a first guide blade, a first moving blade and a cooling configuration for cooling the first guide blade with air through a first cooling-air feed at the guide blade to be cooled, the cooling-air feed having a first cooling-air supply at a first pressure.
In order to achieve a high efficiency in a gas turbine, it is attempted, on one hand, to achieve gas inlet temperatures which are as high as possible and, on the other hand, to keep the quantity of cooling air required for cooling guide blades and moving blades of a stage as small as possible due to an efficiency loss caused thereby. Guide and moving blades are each disposed in a corresponding blade ring.
The turbine guide blades are supplied with cooling air in stages. The cooling air originates from various bleeds from a compressor of the gas turbine. That is described, for example, in a company brochure entitled “Die 3A-Gasturbinen-Familie von Siemens” [The 3A Gas Turbine Family of Siemens], Siemens Aktiengesellschaft, order No. A96001-U10-A281, February 1995. Therefore, in order to cool the stage and in particular the turbine guide blade, a certain pressure gradient is required and that pressure gradient determines the requisite pressure of the respective bleed.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a gas is turbine having a turbine stage with cooling-air distribution, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which limits a cooling-air quantity for a turbine stage and in particular for a guide-blade ring in order to achieve a high efficiency of the gas turbine.
With the foregoing and other objects in view there is provided, in accordance with the invention, a gas turbine, comprising a first turbine stage including a first guide blade; a first moving blade; and a cooling configuration having a first cooling-air feed at the first guide blade for cooling the first guide blade to be cooled with air, a first cooling-air supply at a first pressure for supplying the first cooling-air feed, and a second cooling-air feed disposed downstream of the first cooling-air feed for cooling the first guide blade, the second cooling-air feed supplied with a second pressure lower than the first pressure.
It follows from this construction of the cooling configuration that a stage now has different cooling-air regions. It is thereby possible for there to be an increased pressure gradient of the cooling air only where it is required in the stage, namely in particular in the region of the cooling-air inlet into the turbine guide blade. In the other regions, in which the cooling air is mainly used to is perform the function of sealing air, a high pressure gradient is now no longer produced. On the contrary, the second cooling-air feed at the lower second pressure permits adequate cooling with less leakage-air mass flow. This leads to an increase in the efficiency of the gas turbine as compared with a cooling-air supply in which the first turbine stage after the combustion chamber from the inlet of the No. 1 turbine guide blade up to a rear hooking of the guide ring is operated completely with final compressor air and the following second turbine stage from the inlet of the No. 2 turbine guide blade up to a front hooking of the No. 3 turbine guide blade is cooled with air from a No. 3 bleed of the compressor. This is because, in this case, at both stages, the cooling-air inlet in each case lies upstream of the guide blade, i.e. at the high pressure that is still not reduced over the stage.
In accordance with another feature of the invention, it is especially advantageous if the second cooling-air feed is disposed after one-third, in particular after one-half, of the axial length of the guide-blade ring, i.e. as viewed in the direction of the axis of rotation of the gas turbine. The upstream guide-blade regions, which are subjected to especially high thermal loading, are sufficiently cooled through the first cooling-air feed in accordance with the mass flow originating from the first cooling-air supply. Therefore, downstream regions are sufficiently cooled through the second cooling-air feed at lower pressure without impairment of function.
In accordance with a further feature of the invention, to this end, the second cooling-air feed has a second cooling-air supply, which is separate from the first cooling-air supply. For example, the first cooling-air supply and the second cooling-air supply may each be different bleed points of the gas-turbine compressor.
In accordance with an added feature of the invention, the second cooling-air feed is connected through a pressure reducer to the first cooling-air supply. The pressure reducer ensures that the cooling-air mass flow of the second cooling-air feed is as small as possible but well proportioned. It is therefore expedient for the pressure reducer to be made controllable.
In accordance with an additional feature of the invention, this also makes it possible in particular for the second pressure to just still have a value such that the air fed through the second cooling-air supply still acts as sealing air. Due to this extremely small pressure difference between the cooling air and the hot-gas pressure in the interior of the gas turbine, the cooling-air mass flow used and the efficiency loss associated therewith therefore likewise turn out to be small. In this case, values of 2 bar, in particular values of around 1 bar or even lower, can be set as a pressure difference.
In accordance with yet another feature of the invention, the second cooling-air feed of the first stage also serves as a first cooling-air feed for a second stage following the first stage downstream. In this case, this cooling-air feed is preferably used for the cooling of a guide-blade ring of the second stage. On one hand, this enables the number of requisite bleeds and thus the construction cost to be kept down. On the other hand, the requisite cooling-air mass flow can in turn be kept small by reducing the pressure difference.
In accordance with yet a further feature of the invention, which is especially favorable for a gas turbine having an annular combustion chamber, the guide blade has a first chamber for the first cooling-air supply and a second chamber for the second cooling-air supply, which are adjacent one another and adjoin a carrier for the guide blade. In accordance with a concomitant feature of the invention, the first chamber and the second chamber are separated from one another by a wall, the wall being inserted into the guide-blade carrier and the guide blade. To this end, slots are preferably turned in the guide-blade carrier and a bead is integrally cast on the guide blade during the casting of the latter. An axial barrier plate can preferably be inserted as the wall between the chambers and can also be fitted subsequently for then subdividing a single chamber into a first and a second chamber.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a gas turbine having a turbine stage with cooling-air distribution, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
REFERENCES:
patent: 3377803 (1968-04-01), Prachar
patent: 3453825 (1969-07-01), May et al.
patent: 3635586 (1972-01-01), Kent et al.
patent: 3742706 (1973-07-01), Klompas
patent: 4497610 (1985-02-01), Richardson et al.
patent: 451271
Milazar Mirko
Tiemann Peter
Greenberg Laurence A.
Lerner Herbert L.
Ryznic John E.
Siemens Aktiengesellschaft
Stemer Werner H.
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