Rotary kinetic fluid motors or pumps – With shaft connected fluid force subjected thrust balancing... – Motor shaft
Reexamination Certificate
2002-02-27
2004-02-24
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
With shaft connected fluid force subjected thrust balancing...
Motor shaft
C415S116000, C417S405000
Reexamination Certificate
active
06695575
ABSTRACT:
FIELD OF THE INVENTION
The invention generally relates to a turbine. In particular, it can relate to a steam turbine with a rotor, which has a bladed area for rotor blades and a thrust compensation piston. The thrust compensation piston may have a hot side, which faces the bladed area, and a cold side, which is remote from the bladed area. The invention also generally relates to a method for discharging leakage fluid which flows over the thrust compensation piston.
BACKGROUND OF THE INVENTION
German utility model 6809708 dated Dec. 12, 1968 has described a multishell axial, throttle-controlled steam turbine for high pressures and temperatures. The steam turbine in this case has an inner housing part and a guide-blade carrier, which are structurally combined to form a single inner shell which is split in the axial plane. The inner shell is surrounded by an outer housing, which is designed in the form of a pot. For its part, the inner shell surrounds a turbine shaft, also known as the rotor, which has a bladed area with rotor blades. Shaft seals between rotor and outer housing are provided at each of the opposite ends of the rotor. At one end of the rotor, the steam flowing through the steam turbine enters the bladed area and causes the rotor to rotate about its axis of rotation. At the opposite end, the steam, which is now at least partly expanded, escapes from the bladed area and the steam turbine. In the process, the steam exerts a thrust on the rotor. To counteract this thrust, the rotor has a compensation piston arrangement at the end at which the steam flows in. This arrangement is distinguished by an end face which faces the bladed area and has a larger surface area than an end face which is remote from the bladed area. A similar steam turbine of pot design is described in U.S. Pat. No. 3,754,833.
German Patent 281 253 has described a device for relieving the load on a ship's turbine. The turbine has a forward and a reverse turbine with constant-pressure and excess-pressure sets, which are accommodated in a single housing and are relieved by a drum wall. To relieve the load on the turbine, a divided load-relief surface is provided between the forward turbine and a shaft bearing. This makes it possible to relieve the blade thrust and the thrust of the ship's propeller both in forward and reverse mode.
DE 197 01 020 has described a steam turbine having a high-pressure part turbine and a medium-pressure part turbine with a degree of reaction which varies across the turbine stages. The medium-pressure and high-pressure part turbines may in this case be accommodated in a single housing, in which case each of the part turbines is of single-flow design. A thrust compensation piston is provided for the purpose of absorbing axial thrust of a medium-pressure part turbine which is of drum design. This pressure compensation piston is arranged between a shaft bearing and the high-pressure part turbine. On the side assigned to the shaft bearing, the thrust compensation piston is acted on by steam from the exhaust-steam area of the medium-pressure part turbine, and on the side assigned to the high-pressure part turbine, the thrust compensation piston is acted on by steam from the exhaust-steam area of the high-pressure part turbine. The part turbines may also be accommodated in two separate housings. In the case of a single-flow design, a thrust compensation piston is then likewise provided.
SUMMARY OF THE INVENTION
It is an object of an embodiment of the invention to provide a turbine having a thrust compensation arrangement for high temperat ures of a working medium which drives the turbine. A further object of an embodiment of the invention is to provi de a method for discharging leakage steam in a thrust compensation arrangement.
According to the invention, an object relating to a turbine may be achieved by a turbine having a rotor which has a bladed area for rotor blades and a thrust compensation piston. The thrust compensation piston may have a hot side, which faces the bladed area, and a cold side which is remote from the bladed area. Further, a mixing area may be included, into which a feed for sealing fluid, which is assigned to the cold side, and a leakage fluid feed, which is flow-connected to the bladed area, open out and from which a discharge line branches off.
In this context, the term thrust compensation piston is understood as meaning a thrust compensation arrangement which is mechanically connected to the rotor of the turbine, for example is produced integrally therewith, in particular by forging or casting, or is welded or screwed thereto or otherwise fixedly connected thereto in some other mechanical way. In particular, the thrust compensation piston includes sur faces which can be acted on by a medium, such as steam or gas, so that overall a force which is directed oppositely to the thrust which the wo rking medium imparts to the rotor in the direction of its axis of rotation is generated on the thrust compensation piston.
A flow connection between two parts or two areas refers to a fluid can flow from one area (part) to the other. A flow connection is produced, for example, by a fluid line, an opening or the like.
In this connection, an embodiment of the invention may be based on the consideration that the thrust compensation piston, referred to below as the piston for short, comes into contact with working medium. This working medium can flow through between the piston and a stationary turbine part, for example an inner housing. This results in a leakage flow of the working medium. Although this leakage flow can be reduced by seals, complete sealing is impossible to achieve by contact-free seals. The leakage flow may be at high temperatures, up to 600° C. in the case of steam turbines and even higher in the case of gas turbines. Therefore, the hot leakage steam flow can impinge on turbine parts which are not designed for such high temperatures. To avoid this, it would be necessary for even turbine parts which lie outside the flow area of the hot working medium to be made from materials which are suitable for such high temperatures, which materials are often expensive and relatively difficult to machine.
As an alternative, it would also be possible for a further sealing area to be arranged at the flow region of the end of the piston which is remote from the hot working medium, also referred to below as the cold side. In addition or as an alternative, a suction device could be provided for sucking out the leakage flow. In this case, the leakage flow over the piston would be inversely proportional to the flow resistances of the additional sealing area and of the suction pipe included in the suction device. Complete sealing, preventing hot leaking fluid from impinging on turbine components which lie outside the flow area of the working medium, however, cannot be achieved in this way.
According to an embodiment of the invention, the hot leakage fluid can be mixed with a cooler sealing fluid, so that after the two fluids have been mixed a fluid mixture is present. The fluid mixture can then escape from the mixing area via the discharge. This enables the fluid mixture, which is at a lower temperature than the leakage fluid, to be discharged in a controlled manner into appropriate turbine areas. Therefore, the piston is completely sealed with regard to the leakage fluid. In this way, a leakage flow outside the piston, e.g. along the rotor, is reliably avoided. The temperature of the fluid mixture is preferably below the permissible temperature of use of turbine parts outside the area of flow of the hot working medium.
The mixing area is preferably arranged on the cold side of the piston. As a result, a sealing area with, for example, a contact-free seal can be provided between the hot side of the piston and the mixing area in the leakage-fluid feed.
It is preferable for a delivery device for generating a flow of sealing fluid which is directed radially outward to be provided on the cold side of the piston, in which case the delivery device is flow-connected to
Sasse Stefan
Tamme Rainer
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