WO1997025523A2

WO1997025523A2 - Bearing system for turbomachine assembly

Info

Publication number: WO1997025523A2
Application number: PCT/DE1996/002491
Authority: WO
Inventors: Klaus Nitsche; Helmut Maghon
Original assignee: Siemens Aktiengesellschaft
Priority date: 1996-01-08
Filing date: 1996-12-20
Publication date: 1997-07-17
Also published as: DE19600419A1; JP2000502776A; WO1997025523A3; EP0873467A2

Abstract

The invention concerns a machine assembly comprising a rotating shaft (3) and two machines (1, 2) connected to it which exchange energy with one another through rotation of the shaft (3), as well as a number of bearings (4, 5) supporting the shaft (3). There are only three bearings (4, 5) provided in this machine assembly. The first machine (1) is in particular a free-running gas turbine (1), and the second machine (2) is in particular a generator (2).

Description

description

STORAGE FOR A TURBO MACHINE SET

The invention relates to a machine set comprising a rotatable shaft train, two machines seated thereon, which exchange energy between one another by rotation of the shaft train, and a plurality of bearings, each of which supports the shaft train.

The invention relates in particular to a machine set with a first machine in the form of a turbine, in particular a free-running gas turbine, and a second machine in the form of a generator. In such a machine set, the rotating shaft train transmits mechanical energy, which is obtained from the turbine by relaxing a flow medium, to the generator, which converts the mechanical energy into electricity. In this context, a "free-running gas turbine" is understood to mean a turbine which is acted upon by a fluid in the manner of a hot flue gas, the fluid being not provided for condensation behind the turbine, and which turbine is not mechanically operatively connected to it another machine in the manner of a turbo compressor or the like; the turbine is only mechanically coupled to the other machine of the machine set. The use of the word "gas turbine" in the present context does not correspond to the widespread practice according to which a gas turbine comprises a unit comprising a compressor for providing compressed air, a combustion device for burning a fuel in the compressed air to form a flue gas and at least one turbine in the actual sense to relax the flue gas. Such a combination is referred to herein as a "gas turbine plant" for the purpose of differentiation. The invention relates in particular to a machine set with a turbine which is part of a gas turbine plant of the so-called "two-shaft type". A gas turbine system of the two-shaft type contains two turbines which are seated on different shaft trains. One of the turbines and a compressor, which is driven by the first shaft train, sit on a first shaft train. The other turbine is seated on a second shaft train, and this other turbine is connected via the second shaft train to an external driven machine, for example a generator. In this context, the other turbine, the second shaft train and the driven machine form a machine set which can be designed as stated in the introduction.

In a machine set of the type mentioned in the introduction, the shaft train is supported twice in each machine, so that a total of at least four bearings support the shaft train. This can be explained by the fact that, conventionally, each machine has its own shaft, which is supported at least twice, and the shaft train is formed by coupling the shafts together.

The object of the invention is to significantly simplify the machine set of the type mentioned.

To achieve this object, a machine set is specified, comprising a rotatable shaft train, two machines sitting on it, which exchange energy between one another by rotation of the shaft train, and a large number of bearings, each of which supports the shaft train, only three bearings being present.

The invention is based on the surprising finding that it is sufficient to load a shaft train intended for the exchange of energy between two machines only three times.

ERSÄΪZBLÄ1T (REGEL26) gladly. In fact, it turns out that in each machine set designed according to conventional technical expertise, one of a total of four bearings is superfluous.

The bearings in the machine set are preferably distributed such that a bearing is directly adjacent to a first machine of the machine set and two bearings are directly adjacent to a second machine of the machine set. Furthermore, the first machine preferably additionally has a guide ring which surrounds the shaft train, by means of which the shaft train can be supported in the event of a deformation from a normal shape. In particular, this further development ensures a high degree of security against undesired deformations of the shaft in the event of severe deformations and vibrations of the shaft train, for example in the context of an accident, and it ensures that the first machine can be carried out in a conventional manner , although it has only a single bearing for a piece of the shaft train provided in the first machine. During regular operation of the machine set, a small gap remains between the guide ring and the shaft train, so that no significant friction occurs between the guide ring and the shaft train. Contact between the shaft train and the guide ring only occurs in the event of an accident or during transport, although adequate storage can be guaranteed.

The bearing immediately adjacent to the first machine is, in particular, an internal bearing installed in the first machine. In this sense, the term "immediately adjacent" does not mean that the bearings and the machines in the machine set should be spaced apart. The bearings can very well be integral parts of the machines.

The first machine is preferably a turbine, in particular a free-running gas turbine, and the second machine is preferably a generator. However, this choice is by no means mandatory; depending on the circumstances of the individual case, the first machine can also be the generator and the second machine the turbine. However that may be, the turbine can be of such a type that when it is operating it exerts an axial thrust on the shaft train, that is to say a force directed in a longitudinal direction of the shaft train. This force has to be absorbed, and for this purpose one of the bearings in particular is a bearing that absorbs such an axial thrust, that is to say an axial bearing. This thrust bearing can be any of the three bearings; The positioning of the thrust bearing can be decided according to the circumstances of the individual case. The two other bearings can be simple radial bearings, which only absorb forces that are directed perpendicular to the longitudinal direction of the shaft train.

In a particularly preferred embodiment, the shaft train is formed from two partial shafts and an intermediate shaft coupled to the partial shafts between the partial shafts and between the machines, which has a bending stiffness which is significantly lower than the bending stiffness of the partial shafts, and in which each bearing is of the Intermediate shaft spaced supports the shaft train. In this configuration, a possible bearing offset between the machines is essentially compensated for by the intermediate shaft, in that it is bent accordingly. The load on the bearings and the load on couplings in the shaft train can be limited to an appropriate level by a suitable choice of the bending stiffness. The intermediate shaft can consist of a metal or a fiber-reinforced, in particular glass-fiber-reinforced, plastic.

In the case of a machine set with an intermediate shaft in the sense of the preceding explanations, which is designed for rotating the shaft train with a predetermined nominal frequency, each natural frequency that results in a bending vibration of the intermediate ridge wave belongs, significantly different from the nominal frequency or an integer multiple of the nominal frequency. This configuration prevents the intermediate shaft, which may have been bent, from being excited into a bending vibration when the machine set is operated as intended. With regard to any vibration, in particular any bending vibration, the intermediate shaft is to be regarded as a damped resonator. In order to excite the intermediate wave into a bending oscillation, an excitation therefore does not have to take place exactly with a natural frequency, but also an excitation with a frequency slightly different from a natural frequency can excite the intermediate wave into a forced bending oscillation. The extent to which this occurs a deviation from the natural frequency is possible is determined by corresponding parameters of the shaft train. "Substantially different" means that there is no significant excitation of a bending vibration with a corresponding excitation.

The bearings in the machine set of any configuration can be slide bearings or roller bearings, depending on the circumstances of the respective individual case, roller bearings in particular being considered as roller bearings.

The machine set of any configuration is designed in particular for exchanging the energy with a power between 25 megawatts and 250 megawatts, in particular of about 200 megawatts. This comes into consideration especially in the event that the machine is a free-running gas turbine and a generator. Such a machine set forms, for example, an essential component of a gas turbine power plant or a combination power plant, in which an exhaust gas released from the gas turbine is fed to a steam boiler, where it is used to provide a high-tension steam to be relaxed in a correspondingly provided steam turbine. Embodiments of the invention are explained below with reference to the drawing. The drawing contains several schematic representations, and the explanation of the drawing is limited to the features that are important in the present context. In detail show:

1, 2 and 3 show schematic drawings of exemplary embodiments for a machine set in the sense of the above embodiments; 4 shows a part of a longitudinal section through a gas turbine system with a turbine which is part of a corresponding machine set.

In all the figures of the drawing, corresponding partial features and components each have the same reference number. In view of this, the following explanations apply accordingly to all figures.

Reference is first made to FIGS. 1, 2 and 3. Each of which shows a machine set with a first machine 1 in the form of a free-running gas turbine 1, a second machine 2, namely a generator 2, and a shaft train 3 , on which machines 1 and 2 are seated and, when rotating, machines 1 and 2 exchange energy between them. The exchange of energy takes place in such a way that the free-running gas turbine 1 drives the generator 2 via the shaft train 3; the free-running gas turbine 1 converts thermodynamic energy into mechanical energy which flows along the shaft train 3 to the generator 2 and is converted there into electromagnetic energy.

The shaft train 3 is supported in three bearings 4 and 5, whereby a bearing 4 is arranged in the immediate vicinity of the first machine 1 and two bearings 4 and 5 are arranged in the immediate vicinity of the second machine 2. The bearings 4, 5 comprise two radial bearings 4 for absorbing forces perpendicular to a longitudinal direction of the shaft train 3 and an axial bearing 5 for receiving an axial thrust communicated to the shaft train 3. In the present examples, the thrust bearing 5 also has the same functions as a radial bearing 4.

The shaft train 3 is coupled together from an intermediate shaft 7 arranged between the machines 1, 2 and two other parts 6, each of which is a shaft crossing one of the machines 1 or 2. The parts 6 and 7 are coupled together on respective couplings 9. The arrangement of the single bearing 4 on the first machine 1 can also take into account the requirements of the respective individual case. According to FIG. 1, this bearing 4 is located on a side of the first machine 1 facing away from the intermediate shaft 7. According to FIG. 2, this bearing is located inside the first machine 1, and according to FIG side of the first machine 1.

The intermediate shaft 7 fulfills specific functions in each of the exemplary embodiments. First of all, by providing it, space can be created between the machines 1 and 2 in order to provide an exhaust gas routing system for discharging exhaust gas from the free-running gas turbine 1 in the vicinity of the shaft line 3. This is necessary in the sense of many known constructions, since gas turbines with a higher output in particular require an axial outflow of their exhaust gases. In the present context, it is also important that the intermediate shaft 7 can be designed in such a way that it is easily bendable and can essentially compensate for any misalignment between the different bearings 4 and 5 alone. For this purpose, the intermediate shaft 7 is designed with a comparatively low bending stiffness, measured on the bending stiffness of the other parts 6. It is also important to design the intermediate shaft 7 so that it does not tend to vibrate when the machine set is operated as intended; Such bending vibrations can occur in particular if the intermediate shaft 7 is slightly bent due to an offset between the bearings 4 and 5. For this purpose, the intermediate shaft 7 is designed in such a way that any natural frequency which corresponds to a possible bending vibration of the intermediate shaft 7 is significantly different in the sense of the statements made earlier of a nominal frequency or a multiple of the nominal frequency with which the shaft train 3 at intended operation of the machine set rotates. The load on the bearings 4 and 5 and the couplings 9 can also be set by selecting the bending stiffness and other parameters of the intermediate shaft 7, in particular their mass. it is possible and worthwhile, for example, to design the intermediate shaft 7 and possibly the other parts 6 of the shaft train 3 in such a way that at least one of the couplings 9 even with a certain bending of the shaft train 3, which possibly already when the Shaft strand 3 is to be expected due to the distribution of the mass, is not loaded with torque or bending moments. In the context of such considerations, a careful selection of the material for the production of the intermediate shaft 7 can be important; not only common metals, but also plastics, in particular carbon or glass fiber reinforced plastics, come into consideration for this purpose.

FIG. 4 shows part of a longitudinal section through a gas turbine system which contains a free-running gas turbine 1 which belongs to a machine set of the type just explained. In the immediate vicinity of the free-running gas turbine 1, a bearing 4 is provided in accordance with the exemplary embodiment according to FIG. A shaft 6 in the interior of the free-running gas turbine 1 is formed from disks screwed together and arranged one behind the other. The radial bearing 4 on the left side is assigned to this shaft 6.

REPLACEMENT BUTT (RULE 26) ken side of the free-running gas turbine 1 and a guide ring 8 on the right side of the free-running gas turbine 1, which guide ring 8 does not touch the shaft 6 during its intended operation, but leaves a small gap, not visible in Figure 4. The shaft 6 should only touch the guide ring 8 if it is severely deformed, for example in the context of an accident. Such a fault can occur, for example, if there is a break in the free-running gas turbine 1. The intermediate shaft 7 is coupled to the shaft 6 at a clutch 9.

To the left of the free-running gas turbine 1 there is another gas turbine 11 which drives a turbocompressor (not shown) from which compressed air is fed to an incinerator (also not shown), where a fuel burns in this air to form a flue gas, which flue gas first the other turbine 11 and then the free-running gas turbine 1 is delivered. A common bearing housing 10 is provided for mounting both gas turbines 1 and 11. Both gas turbines 1 and 11 are also surrounded by a common turbine housing 12.

The invention provides a machine set with two machines 1 and 2 coupled via a shaft train 3, which is particularly simple and therefore inexpensive in view of the necessary mounting of the shaft train 3.

FIG. 1

Claims

claims

l. Machine set comprising a rotatable shaft train (3), two machines (1, 2) seated thereon, which exchange energy between one another by rotation of the shaft train (3), and a large number of bearings (4, 5), each of which supports the shaft train (3) supports, characterized in that only three bearings (4, 5) are available.

2. Machine set according to claim 1, wherein the machines (1, 2) are a first machine (1) and a second machine (2), wherein the first machine (1) is a bearing (4, 5) immediately adjacent and wherein the second machine (2) has two bearings (4, 5) immediately adjacent.

3. Machine set according to claim 2, wherein the first machine (1) additionally has a guide ring (8) surrounding the shaft train (3), by means of which the shaft train (3) can be supported in the event of a deformation from a normal shape.

4. Machine set according to claim 2 or 3, in which the first machine (1) immediately adjacent bearing (4, 5) is an internal bearing (4, 5) attached in the first machine (1).

5. Machine set according to one of claims 2 to 4, wherein the first machine (1) is a turbine (1), in particular a free-running gas turbine (1), and the second machine (2) is a generator (2).

6. Machine set according to one of claims 1 to 4, wherein the machines (1, 2) are a turbine (1), in particular a free-running gas turbine (1), and a generator (2).

7. Machine set according to claim 5 or 6, wherein one of the bearings (4, 5) is an axial thrust bearing (5).

8. Machine set according to one of the preceding claims, in which the shaft train (3) is formed from two partial shafts

(6) and an intermediate shaft (7) coupled to the partial shafts (6) between the partial shafts (6) and between the machines (1, 2), which has a bending stiffness which is substantially lower than the bending stiffness of the partial shafts (6), and in which each bearing (4, 5) at a distance from the intermediate shaft (7) supports the shaft train (3).

9. Machine set according to claim 8, wherein the intermediate shaft

(7) consists of a metal or a fiber-reinforced, in particular glass-fiber-reinforced, plastic.

10. Machine set according to claim 8 or 9, which is designed to rotate the shaft train (3) with a predetermined nominal frequency, and at which each natural frequency belonging to a bending oscillation of the intermediate shaft (7) is substantially different from the nominal frequency or an integer multiple of the nominal frequency.

11. Machine set according to one of the preceding claims, wherein the bearings (4, 5) plain bearings (4, 5) or roller bearings (4, 5).

12. Machine set according to one of the preceding claims, in which the machines (1, 2) are designed to exchange the energy with a power between 25 MW and 250 MW, in particular approximately 200 MW.