Rotary kinetic fluid motors or pumps – With passage in blade – vane – shaft or rotary distributor...
Reexamination Certificate
1999-12-27
2001-05-08
Ryznic, John E. (Department: 3745)
Rotary kinetic fluid motors or pumps
With passage in blade, vane, shaft or rotary distributor...
Reexamination Certificate
active
06227799
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a turbine shaft of a steam turbine, in particular for accommodating the high-pressure and intermediate-pressure blading, and also to a method of cooling the turbine shaft of a steam turbine.
The use of steam at higher pressures and temperatures helps to increase the efficiency of a steam turbine. The use of such steam imposes increased requirements on the corresponding steam turbine. A single-line steam turbine having a high-pressure turbine section and an intermediate-pressure turbine section as well as a downstream low-pressure turbine section is suitable in the case of a steam turbine in a power range of several 100 MW. Both the high-pressure moving blades and the intermediate-pressure moving blades are accommodated by the turbine shaft, which if need be is composed of a plurality of segments. Each turbine section may have an inner casing and an outer casing, which in each case are, for example, split horizontally and bolted together. The live-steam state characterized by the high-pressure steam may be at around 170 bar and 540° C. In the course of increasing the efficiency, a live-steam state of up to 270 bar and 600° C. may be aimed at. The high-pressure steam is fed to the turbine shaft and flows through the high-pressure blading up to a discharge connection. The steam expanded and cooled down in the process may be fed to a boiler and heated up again there. The steam state at the end of the high-pressure turbine section is designated below as “cold reheating”, and the steam state after leaving the boiler is designated below as “hot reheating”. The steam issuing from the boiler is fed to the intermediate-pressure blading. The steam state may be around 30 bar up to 50 bar and 540° C., an increase to a steam state of about 50 bar up to 60 bar and 600° C. being aimed at. In a steam-inflow region, in particular of the intermediate-pressure turbine section, configuration measures in which the turbine shaft is protected from direct contact with the steam via a shaft screen may be carried out.
In Published, Non-Prosecuted German Patent Application DE 195 31 290 A1 there is specified a rotor for thermal turbo-engines, containing a compressor part, disposed on a shaft, a central part and a turbine part. The rotor is made up predominantly of individual welded-together bodies of rotation, the geometrical shape of which leads to the formation of axially symmetrical cavities between the respectively neighbouring bodies of rotation. The rotor has an axially directed cylindrical cavity, reaching from the end of the rotor on the inflow side to the last cavity on the upstream side. Placed in this cylindrical cavity are at least two tubes of diameters and lengths differing from one another. This is intended to allow the rotor of the turbo-engine to be brought to its operating state within the shortest time and to be easy to regulate thermally, i.e. according to requirements, heatable or coolable with relatively little effort.
U.S. Pat. No. 5,054,996 concerns a gas turbine rotor containing rotor discs interconnected by an axial tie rod. Air is directed through the gas turbine rotor, whereby the rotor and the rotor discs are heatable and coolable essentially uniformly.
U.S. Pat. No. 5,498,131 discloses a steam turbine installation with a system for reducing thermomechanical stresses, which may occur in a turbine shaft during the starting up or shutting down of the steam turbine installation. For this purpose, the steam turbine installation has a high-pressure turbine section and an intermediate-pressure turbine section with a single turbine shaft, which has a central bore passing right the way through. The central bore can be supplied with steam via a separate supply system for steam, respectively outside the casing of the turbine sections, during the starting up or shutting down of the steam turbine installation. Between the two turbine sections, i.e. approximately at the center of the turbine shaft, the steam is discharged again from the central bore. The system makes it possible for the transient starting-up or shutting-down state to be passed through in a short time in an improved and controlled manner.
In Patent Abstract of Japan N-303, Jun. 20, 1984, Vol. 8, No. 132, relating to Japanese Patent Application JP-A-59-34402, there is described a turbine shaft for a steam turbine. This turbine shaft of a single steam turbine has in its interior an axial bore, into which there is centrally introduced a cooling fluid, which flows out again on both sides at the ends of the bore.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a turbine shaft of a steam turbine having internal cooling, and also a method of cooling a turbine shaft, that overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, that withstands the, in particular locally occurring, high operational thermal loads in such a way that it exhibits long-term stability.
With the foregoing and other objects in view there is provided, in accordance with the invention, a turbine shaft for a steam turbine having a rotation axis, including:
a first blading region of a first turbine section disposed along the rotation axis;
a second blading region of a second turbine section disposed along the rotation axis;
a bearing region disposed between the first blading region and the second blading region, the first blading region, the second blading region and the bearing region together defining an interior therein functioning as a cooling line for passing cooling steam in a direction of the rotation axis and together defining a circumferential surface;
at least one outflow line connected to the cooling line for discharging the cooling steam; and
at least one inflow line connected to the cooling line for supplying an inflow of the cooling steam, the cooling steam cooling highly temperature-loaded regions of the bearing region and the first and second blading regions.
Through the cooling line running in the interior of the turbine shaft, cooling steam can be passed in the direction of the rotation axis through the turbine shaft and can be directed through the outflow line. In this way, both a highly thermally loaded region of the turbine shaft, in particular the steam-inflow region, can be cooled from inside and at the circumferential surface and in the region of fastenings for the moving blades. The cooling line can be inclined relative to the rotation axis or can run so as to be wound relative to the latter, in which case it permits a transport of cooling steam in the direction of the rotation axis. Furthermore, cooling of the moving blades, in particular their roots, which moving blades can be anchored in the turbine shaft, can also be carried out. It goes without saying that, depending on the manufacture of the cooling line, the outflow line and the inflow line may constitute part of the cooling line. It also goes without saying that more than one cooling line may be provided, in which case a plurality of cooling lines are connected to one another and can each be connected to one or more outflow lines and inflow lines respectively. It is likewise possible to dispose outflow lines, adjacent in the direction of the rotation axis, at predeterminable distances apart and to connect them to the cooling line. Cooling of shaft sections subjected to high thermal loads can therefore be effected without considerable outlay on pipelines, casing leadthroughs and integration in the turbine control system. Such a high configuration outlay would be necessary, for example, when cooling a turbine shaft by uses of cold steam from the outside through the casing and the guide blades up to the turbine shaft in order to directly cool the circumferential surface of the turbine shaft.
The turbine shaft is preferably suitable for a single-line steam turbine having a high-pressure turbine section and an intermediate-pressure turbine section. Here, the turbine shaft may consist of two turbine segments connected to one anothe
Feldmuller Andreas
Kuhn Ralf
Sasse Stefan
Ulma Andreas
Greenberg Laurence A.
Lerner Herbert L.
Ryznic John E.
Siemens Aktiengesellschaft
Stemer Werner H.
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