EP2171238A1

EP2171238A1 - Continuous-flow or displacement machine with magnetic bearings

Info

Publication number: EP2171238A1
Application number: EP08774842A
Authority: EP
Inventors: Detlef Haje
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2007-07-26
Filing date: 2008-07-07
Publication date: 2010-04-07
Also published as: WO2009013119A1; PL2022950T3; EP2022950A1; EP2022950B1

Abstract

The present invention relates to a continuous-flow or displacement machine, in particular a steam turbine (1), having a flow area through which a flow medium flows in which at least one rotor (2) including shaft sections (3) with rotor bearing points revolves. The rotor (2) is borne in magnetic bearings (5, 6), with each magnetic bearing (5, 6) having a plurality of electromagnets which comprise a winding (15), a winding core (16) and at least one pole (17). In this case, the magnetic bearings (5, 6) are arranged within the flow area. Furthermore, at least the winding (15) of each electromagnet of the magnetic bearings (5, 6) is accommodated in a housing (18), hermetically sealed from the flow medium.

Description

description

Flow or extrusion machine

The invention relates to a flow or displacement machine, in particular a steam turbine with magnetic bearings according to the preamble of claim 1.

From storage technology is known to store rotors of flow or displacement machines by means of magnet assemblies in the radial and axial directions (magnetic bearing). In this case, the position of the rotor is continuously measured via position sensors using a position control device and counteracted any off-center position by rapid adjustment of the magnetic fields. These bearings have already been used with rotor weights of several tons successfully in turbomachines, such as feedwater pump or compressors. The magnetic bearings are used instead of the usual bearings outside the flow space, similar to so-called plummer block.

A use of magnetic bearings in steam turbines is not known from practice, but probably z. B. in EP 655 108 Bl described in principle. However, this does not adequately address the feasibility of designing the magnetic bearings in the vapor space, so that a technical solution is not yet available. Thus, a significant advantage of magnetic bearings is not yet exhausted, which provides with the arrangement of the magnetic bearing in the vapor space the opportunity to extend the active rotor length over the prior art on. The length of turbines or sub-turbines is determined inter alia by the dynamic behavior of the rotor and thus by the bearing distance. For reasons of thermodynamics and the Efficiency or the design of the expansion task, such as regulated steam extraction would be a higher overall length, however, desired in many cases.

The invention has for its object to increase the overall length of the generic turbomachine by designing the magnetic bearing.

The object is achieved in a generic flow or displacement machine according to the invention by the characterizing features of claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

The advantage of the inventive solution is to achieve a reliable use of magnetic bearings in the flow space of turbomachinery and to tap the benefits of magnetic bearing technology for a wide range of applications in fluid mechanics. Using steam turbines as an example, this can support a virtually unlimited length of steam turbine rotors and eliminate the length-to-diameter limitations of previous rotors. As a result, significant advantages in efficiency, flexibility, cost, size, etc. can be achieved.

An embodiment of the invention is illustrated in the drawing and will be explained in more detail below. Show it:

Fig. 1 is a longitudinal section through a steam turbine with a

Expansion section;

2 shows a cross section through a magnetic bearing. 3 to 6 different embodiments of a magnetic bearing and 7 shows a schematic diagram of a steam turbine with three expansion sections.

In Fig. 1 is shown as an embodiment of a turbomachine, a steam turbine with an expansion section. The exemplary embodiment described below with reference to a steam turbine can also be applied to other turbomachines and to displacement machines.

The steam turbine 1 comprises a rotatably mounted turbine rotor 2 including shaft sections 3 with bearings and a fixed turbine housing 4. The turbine rotor is mounted on the respective shaft sections 3 in two radial magnetic bearings 5 and 6. In this case, the magnetic bearing 6 is arranged on the high pressure side 7 and the magnetic bearing 5 on the exhaust steam side 8 of the steam turbine 1. In the steam turbine 1 according to FIG. 1, the shaft section 3 of the turbine rotor 2 is guided on the exhaust steam side 8 through the turbine housing 4.

On the high pressure side 7, a magnetic thrust bearing 9 is arranged, which holds the turbine rotor 2 in the axial direction via the shaft portion 3. The magnetic thrust bearing 9 absorbs the shear forces generated by the steam and acting on the turbine rotor 2.

On the high pressure side 7 also a fishing camp 10 is provided, which is arranged in the embodiment between the radial magnetic bearing 6 and the axial magnetic bearing 9. Another fishing camp 11 is disposed on the exhaust steam side 8 in the flow direction of the steam behind the radial magnetic bearing 5. In case of failure of the radial magnetic bearings 5 and 6 can the turbine rotor 2 with its shaft sections 3 in the backup bearings 10 and 11 expire.

The turbine housing 4 is vapor-tightly sealed on the high-pressure side 7 with a cover 12 fastened to the turbine housing 4, so that there is no longer any connection to the exterior space. On the exhaust steam side 8 of the turbine housing 4 is a non-contact shaft seal 13 behind the magnetic bearing 5 and the fishing camp 11 in the flow direction as indicated by an arrow on the shaft portion 3 of the turbine rotor 2. On the high pressure side 7 of the turbine housing 4, a labyrinth seal 14 is provided behind the magnetic bearing 6 in the direction of flow of the indicated arrow.

Thus, the shaft seal 13 is disposed on the side facing away from the interior of the turbine housing 4 side of the radial magnetic bearing 5, while the labyrinth seal 14 is mounted on the interior of the turbine housing 4 facing side of the radial magnetic bearing 6. The turbine housing 4 thus encloses the turbine rotor 2 with the shaft sections 3 over part of its length as well as the magnetic bearings 5, 6, 9, the backup bearings 10, 11 and the seals 13, 14.

In the interior of the turbine housing 4, a flow space is thus formed, in which the magnetic bearings 5, 6, 9 are arranged. The flow space is considered to be the entire space filled by the flow medium and not accessible to the surrounding medium during normal operation. The embodiment is also suitable for applications in which the bearings are surrounded to some extent by surrounding medium and to another part by flow medium. As shown in Fig. 2, each of the radial magnetic bearings 5, 6 of a plurality of electromagnets with the windings 15, the winding cores 16 and the poles 17 in the housing 18. The electromagnets are arranged at the rotor bearing point around the shaft portion 3. The electromagnets of the magnetic bearings 5, 6 arranged around the shaft section 3 in each case form radial annular gaps 23 between the shaft section 3 and the respective electromagnets as well as tangential gaps 24 between the individual electromagnets themselves.

As shown by way of example in FIGS. 3 to 6, each electromagnet contains a winding 15, which consists of conductors surrounded by an insulator and which encloses a winding core 16. At the winding core 16 close pole 17.

Alternatively, the poles 17 may also be formed by the winding core 16. It is considered as a pole: The bearing point opposite, a magnetic flux at the bearing point releasing form element.

From the intended arrangement of the magnetic bearings 5, 6 within the flow space of the flow or displacement machine, such as the illustrated steam turbine 1, arise in terms of ambient temperature, the flow medium and the ambient pressure, the following essential requirements.

With regard to the ambient temperature, the magnetic bearings 5, 6 are surrounded by a flow medium having a largely predetermined temperature. The temperature can reach, for example, several hundred degrees Celsius in thermal turbomachines. Cooling of the magnetic bearings 5, 6 down to an applicability of conventional plastic insulation would be associated with great expenditure on equipment and requires one Continuous use of energy through fan drives, pumps or similar machines.

With regard to the flow medium, the surrounding medium may be corrosive or abrasive, depending on the type of turbomachine. The flow medium could cause damage or destruction in direct contact with the magnetic bearings 5, 6. Water vapor as a flow medium or contained moisture in the flow medium can affect the effect of the insulation of the windings by penetrating into the windings 15 of the magnetic bearing 5,6 due to the conductivity of water.

With regard to the ambient pressure, the pressure of the flow medium is determined by the respective operating point of the turbomachine and varies, for example, between ambient pressure and a pressure at maximum energy conversion. A winding exposed to such pressure 15 would be soaked in flow medium within a few loading or unloading cycles of the turbomachine and potentially impaired in its effect. Rapid pressure changes could lead to a pressure difference between the winding 15 and the flow space and cause a mechanical overload of the winding 15.

For the use of the magnetic bearings 5, 6 under increased application temperatures, high-temperature-resistant power materials are preferably used for the electromagnets.

As insulation means for the electric materials, for example, high-temperature plastics, glass fiber mesh, mica tape, ceramic fiber braid and as a conductor material such as copper, nickel-plated copper, pure nickel or Special alloys used. For high temperatures, the insulation between individual turns of the windings 15 is ensured by ceramic fabric or wraps of tissue, so that the ambient temperatures that occur in the flow space of a turbomachine and by heating the magnetic bearings 5, 6, can be safely endured.

In such an embodiment, the cost of cooling the magnetic bearings 5, 6 and heat dissipation from the magnetic bearings 5, 6 is minimized. Furthermore, in such an embodiment, the cooling can take place even without external coolant supply. Such insulation means are known from electrical engineering, for example, ventilation systems for road tunnels. However, such insulating agents are generally not suitable for exposure to moisture or foreign media.

In order to ensure safe operation of the magnetic bearings 5, 6 within the flow space of the turbine housing 4, at least the winding 15 of the electromagnets is hermetically separated from the flow medium. For this purpose, several embodiments are given in FIGS. 3 to 6.

According to FIGS. 3 and 4, the entire magnetic bearing 5, 6 or each individual electromagnet of the magnetic bearing 5, 6 with winding 15 and winding core 16 and two poles 17 are accommodated in a housing 18. The housing 18 is under an internal pressure Pi and an external pressure Pa and is closed with an associated termination device 19 on the side facing the shaft portion 3 with the rotor bearing point. It is essential that the magnetic flux can reach the rotor bearing point despite the termination device 19 of the housing 18. For this purpose, the termination device 19 of the Housing 18 by a magnetically permeable material, eg. B. austenitic steel are formed.

In the embodiment shown in Fig. 6, only the winding 15 is enclosed with the winding core 16 by a housing 18 which is arranged between the two poles 17 of the electromagnet. The two poles 17 are outside the housing

18 and are the shaft section 3 with the rotor bearing directly opposite.

The entire housing 18 is pressure-resistant (FIGS. 3, 4, 5).

It can thus be the difference between the external pressure Pa of

Flow medium and the self-adjusting internal pressure Pi inside the housing 18 withstand.

The housing 18 can also be supported as shown in FIG. 5 by internal, pressure-bearing, non-magnetic components 20 of the magnetic bearings 5, 6 so that it can transfer the forces from the pressure difference to these components, for example, on a housing 18 with termination device

19 completely filling arrangement of the winding 15 with winding core 16th

Finally, as shown in FIG. 4, advantageously a supply line 21 can be connected to the housing 18, via which a pressure medium is introduced into the housing 18 with the aid of a compressor 22. The pressure of the pressure medium can be equal to or less than the pressure of the

Flow medium, so that the differential pressure across the housing 18 is reduced or canceled.

In Fig. 7, a steam turbine with three expansion sections in the block diagram is shown, a Turbine rotor 25 for high-pressure expansion, a turbine rotor 26 for medium-pressure expansion and a turbine rotor 27 for low-pressure expansion shows. The rotors 25, 26, 27 are each mounted with shaft sections 3 at bearings in radial magnetic bearings 5, 5 ', 5'',5'''. Furthermore, axial magnetic bearings 9 are arranged between the turbine rotor 25 of the high-pressure stage and the turbine rotor 26 of the medium-pressure stage, seen in front of the radial magnetic bearing 5 'in the flow direction of the turbine rotor 26 for medium-pressure expansion. The respective flow direction is again indicated by an arrow.

Claims

claims

1. flow or displacement machine, in particular steam turbine (1), with a flow medium flowed through by a flow space in which a rotor (2) including shaft sections (3) rotates with rotor bearings, which is mounted in magnetic bearings (5, 6), each Magnetic bearing (5, 6) comprises a plurality of electromagnets, consisting of a winding (15), a winding core (16) and at least one pole (17), characterized in that the magnetic bearings (5, 6) are arranged within the flow space and that at least the winding (15) of each electromagnet of the magnetic bearings (5, 6) is hermetically housed separate from the flow medium in a housing (18).

2. Turbomachine according to claim 1, characterized in that the entire electromagnet including the winding

(15), the winding core (16) and the poles (17) of the housing (18) is enclosed and that a terminating device (19) of the housing (18) on the rotor bearing of the shaft sections (3) facing side of a magnetically permeable Material is made.

3. Turbomachine according to claim 1, characterized in that the poles (17) of the electromagnet outside the housing

(18) lie.

4. Turbomachine according to one of claims 1 to 3, characterized in that the housing (18) is pressure-resistant with respect to the maximum pressure of the flow medium is designed.

5. Turbomachine according to one of claims 1 to 4, characterized in that the housing (18) is acted upon by a pressure medium whose pressure corresponds at most to the maximum pressure of the flow medium.

6. Turbomachine according to claim 1, characterized in that the electromagnets have a winding (15) and a winding core (16) with at least one integrated pole (17).