EP3183426B1 - Controlled cooling of turbine shafts - Google Patents

Description

The invention relates to a turbomachine, in particular a steam turbine, with an inflow region for supplying steam, a rotatably mounted rotor, a housing which is arranged around the rotor, wherein between the rotor and the housing, a flow channel is formed, wherein the flow channel with the Inlet region is fluidly connected to each other, with a shield which is designed such that during operation, a flowing into the inflow steam is deflected into the flow channel, wherein the shield has a coolant supply, which is designed such that in operation a cooling steam in a cooling region which is disposed between the shield and the rotor, is flowable.

Turbomachines such as steam turbines are flowed through a flow medium, which usually has high temperatures and pressures. Thus, steam is used as a flow medium in a steam turbine as an embodiment of a turbomachine. The steam parameters in the live steam inflow region are so high that the steam turbine is subjected to a high thermal load at various points. Thus, for example, in the inflow region of the steam turbine, the materials are thermally heavily loaded. A steam turbine essentially comprises a turbine shaft, which is rotatably mounted, and a housing arranged around the turbine shaft. The turbine shaft is thermally heavily loaded by the temperature of the incoming steam. The higher the temperature, the higher the thermal load. Turbine blades are arranged in so-called grooves on the rotor. During operation, the grooves experience a high mechanical load. However, the thermal load reduces the tolerable mechanical load due to rotation and additional load due to the blades attached to the rotor.

From a thermodynamic point of view, it makes sense to increase the input temperature of the steam, since the efficiency increases with higher inlet temperature. In order to expand the load capacity of the materials used in the steam turbine at high temperatures, the inflow regions of the shaft are cooled. If a suitable cooling method can be developed, one can do without the change to a higher quality, but more expensive material.

A steam turbine plant comprises at least one steam generator and a first steam turbine formed as a high-pressure turbine part, as well as further partial turbines, which are designed as medium-pressure or low-pressure turbine parts. After flowing through the live steam through the high-pressure turbine section, the steam is reheated to a high temperature in a reheater and fed into the medium-pressure turbine section. The steam that comes from the high-pressure turbine part is called a cold reheater steam and is comparatively cool compared to live steam. This cold reheater steam is used as a cooling medium.

This means that the cold reheater steam is led into the inlet area of the steam turbine where it lowers the material temperature. However, it is the case that the cold reheater steam in the inlet region, for example, of a medium-pressure turbine section leads to very large temperature differences. This leads to the disadvantage that, despite the cooling locally high temperature gradients and thus high thermal stresses occur. In addition, there may be local changes in shape, which is forced by thermal distortion by unequal thermal expansion, since highly cooled and uncooled areas are arranged side by side. Furthermore, in the case of failure of the cooling, ie that the cold reheater steam is not available and thus forms a fault, thermal shocks occur which lead to extremely high thermal stresses.

In the event of a fault, this means that if the cooling fails, the previously cooled shaft expands significantly. This thermal expansion must be considered constructively and complicates the coolant supply and sealing of the cooled area.
The document DE 34 06 071 A1 discloses a shield wherein the shield has only one cooling steam duct but no additional duct.
At this point, the invention begins. The object of the invention is to provide an improved cooling for a steam turbine.
This object is achieved by a turbomachine, in particular steam turbine, with an inflow region for supplying steam, a rotatably mounted rotor, a housing which is arranged around the rotor, wherein between the rotor and the housing, a flow channel is formed, wherein the flow channel with the inflow area is fluidly connected to each other, with a shield which is designed such that during operation, a flowing into the inflow steam is deflected into the flow channel, wherein the shield has a coolant supply, which is designed such that in operation a cooling steam in a Cooling region, which is arranged between the shield and the rotor, flows, wherein the shield additionally comprises a conduit which establishes a fluidic connection between the cooling region and the inflow region.
The invention thus relates to turbomachines, in particular steam turbines, which comprise a shield, which is arranged in the inflow region and shields the shaft from the hot flow medium. For cooling, a coolant supply is used, which leads a cooling steam to the rotor during operation. The invention has the following idea: So far, a comparatively strong cooling of the rotor in the cooling area, ie between the shield and the rotor surface it acts. It is cooled with a cold reheater steam, which, however, leads to a very strong cooling of the rotor in the inflow area. In the case of a failure of the coolant, the rotor heats up very strongly in this area, which leads to undesirable extreme thermal cycling. To avoid this, it is proposed according to the invention, in addition to the coolant supply, to form the shield with a line through which the live steam can flow into the space between the rotor and the shield. The flow rate of the coolant and the flow rate of live steam through the line is selected such that the temperature of the rotor heats up to a limit value in the inflow region. This limit value is chosen such that in the event of failure of the cooling medium, heating to the maximum temperature, ie to heating without coolant, is moderate.

According to the invention it is thus proposed to realize a passive mixing cooling, fed through holes that can be made small, in the shield the cooling steam from the coolant supply a certain amount of live steam. This allows a suitable mixing temperature can be adjusted by a suitable choice of the lines.

The term vapor is to be understood as meaning a flow medium which, in addition to water vapor, may be ammonia or a vapor-CO ₂ mixture.

The invention thus avoids that the shaft causes damage due to unsafe failure behavior during cooling with very cold reheater steam or complex process engineering implementation with temperature-controlled cooling steam. Such a new cooling arrangement is advantageous because it is passive. This means that no complex control technology and no control valves for temperature control of the cooling medium are required. Due to the low temperature differences in the component is a low thermal stress, a small additional local distortion by cooling and a more robust behavior with short-term failure of the cooling achieved.

Advantageous developments are specified in the subclaims.

In a first advantageous development, the turbomachine is designed to be double-flowed. This means that the shield covers an area that allows the incoming steam to flow into a first flood and a second flood.

In an advantageous development, the coolant supply is designed such that, during operation, the cooling steam impinges tangentially on the rotor. Thus, the coolant supply is not achieved radially through the shield, but guided substantially in the circumferential direction, so that the cooling steam undergoes a twist in the region between the shield and the rotor.

Likewise, in an advantageous embodiment, the line can be designed such that, during operation, a vapor from the inflow area tangentially impinges on the rotor. Here it is also proposed not to form the conduit radially through the shield, but to take into account a tangential component, which leads to a swirl of the vapor from the inflow into the space between the shield and rotor.

In the tangential arrangement of the coolant supply, a residual cooling effect can be obtained by the swirling inflow of live steam in case of failure of the cooling.

The above-described characteristics, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in the context of the following description of the embodiments, which will be described in more detail in conjunction with the drawings.

Embodiments of the invention will be described below with reference to the drawings. This is not intended to represent the embodiments significantly, but the drawing, where appropriate for explanation, executed in a schematized and / or slightly distorted form. With regard to additions to the teachings directly recognizable in the drawing reference is made to the relevant prior art.

Figur 1

eine schematische Darstellung einer Dampfkraftanlage

Figur 2

eine schematische Darstellung der Erfindung in Betrieb

Figur 3

eine schematische Darstellung der Erfindung bei Ausfall der Kühlmittelzuführung

Figur 4

eine Seitenansicht der erfindungsgemäßen Anordnung

Figur 5

eine Seitenansicht der erfindungsgemäßen Anordnung in einer alternativen Ausführungsform.

Show it

FIG. 1

a schematic representation of a steam power plant

FIG. 2

a schematic representation of the invention in operation

FIG. 3

a schematic representation of the invention in case of failure of the coolant supply

FIG. 4

a side view of the arrangement according to the invention

FIG. 5

a side view of the inventive arrangement in an alternative embodiment.

The FIG. 1 shows a steam power plant 1 in a schematic overview. The steam power plant 1 comprises a high-pressure turbine part 2, which has a live steam feed 3 and a high-pressure steam outlet 4. By the live steam supply 3, a live steam flows from a main steam line 5, wherein the live steam was generated in a steam generator 6. In the main steam line 5, a live steam valve 7 is arranged, which regulates the flow of the live steam through the high pressure turbine part 2. Furthermore, in the main steam line 5, a quick-acting valve is arranged (not shown), which closes the steam supply to the high-pressure turbine section 2 in the event of an error. After flowing through the Vapor through the high pressure turbine part 2, where the steam in the high pressure turbine part 2 converts the thermal energy into rotational energy of the rotor 21, the steam from the high pressure steam outlet 4 flows into a cold reheater line 8. The steam in the cold reheater line 8 is compared to the steam parameters of the Main steam in the main steam line 5 such that this cold reheater steam can be used as a coolant, which in the FIG. 1 is shown schematically by the coolant line 9. The cold reheater steam is heated in a reheater 10 and passed through a hot reheater line 11 to a medium pressure turbine section 12. The coolant line 9 can be led to the medium-pressure turbine part 12 in the inflow region (not shown). The rotor of the medium-pressure turbine part 12 is connected to transmit torque to the rotor of the high-pressure turbine part 2 and to the rotor 21 of a low-pressure turbine part 13. Likewise, an electric generator 14 is torque transmitting connected to the rotor 21 of the low pressure turbine section 13. After the flow of steam through the medium-pressure turbine section 12, the steam flows from medium-pressure steam outlets 15 to the low-pressure turbine section 13 FIG. 1 selected medium-pressure turbine section 12 includes a first 29 and a second 30 flood. The steam from the medium pressure steam outlets 15 is guided in an overflow line 16 to the low pressure turbine section 13. After flowing through the low-pressure turbine part 13, the steam flows into a condenser 17 and will condense there to water. Subsequently, the vapor converted into water in the condenser 17 flows via a line 18 to a pump 19 and from there the water is led to the steam generator 6.

The high-pressure turbine part 2, the medium-pressure turbine part 12 and the low-pressure turbine part 13 is referred to as a steam turbine and represents an embodiment of a turbomachine.

In FIG. 2 is an illustration of the inventive arrangement to see. The FIG. 2 in particular shows an inflow region 20 of the medium-pressure turbine section 12. The medium-pressure turbine part 12 comprises a rotor 21 which is rotatably mounted about a rotation axis 22. The rotor 21 includes a plurality of blades 23 disposed in grooves (not shown) on the rotor surface 24. Between the blades 23 vanes 25 are arranged, which are held on a housing (not shown). A first vane row 26 is formed such that this vane row 26 holds a shield 27. The shield 27 is designed in such a way that, during operation, a steam flowing into the inflow region 20 can be diverted into a flow channel 28. Since the in FIG. 2 shown medium-pressure turbine section 12 has a first flow 29 and a second flow 30, the flow channel 28 is divided into a first flow channel 31 and a second flow channel 32. The incoming steam 33 is thus diverted to a first steam 34 and a second steam 35. The first vapor 34 flows into the first flow channel 31. The second vapor 35 flows into the second flow channel 32.

The medium-pressure turbine part 12 comprises a housing (not shown) which is arranged around the rotor 21, wherein the first flow channel 31 and the second flow channel 32 are formed between the rotor 21 and the housing, wherein the first flow channel 31 and the second flow channel 32 with the inflow region 20 are fluidically connected to each other.

The term vapor is to be understood as meaning a flow medium which, in addition to water vapor, may be ammonia or a vapor-CO ₂ mixture.

The shield 27 has a coolant supply 36, which is designed such that, during operation, a cooling steam flows into a cooling region 37, which is arranged between the shield 27 and the rotor 21. As cooling steam is a vapor used from the coolant line 9, which comes from the cold reheater line 8. It can be used in alternative embodiments, another cooling steam. The cooling steam from the coolant supply 36 thus flows to the rotor surface 24 and cools a thermally stressed area, which is represented by a parabolic gray zone 38. The temperature is shown in shades of gray. As in FIG. 2 The gray tone in the parabolic gray zone 38 is a little darker than the gray tones of the rotor 21. This means that the temperature in the parabolic gray zone 38 is greater than the temperature of the rotor 21.

In addition to the coolant supply 36, a line 39 is now arranged according to the invention in the shield 27. This line 39 establishes a fluidic connection between the cooling region 37 and the inflow region 20. The line 39 may be designed as a bore or with multiple holes. These holes can be executed distributed on the circumference. The line 39 may be arranged symmetrically to the parabolic gray zone 38, which means that the line 39 is arranged in the direction of a central inflow direction 40. In FIG. 2 the line 39 is not shown in the same direction as the central inflow 40, but a small distance further to the right.

The FIG. 3 shows substantially the same arrangement as in FIG. 2 , On a repetition of the name and mode of action of the components is therefore omitted. The difference in the presentation of the FIG. 3 is that a failure of the coolant supply 36 is symbolized by a cross. The failure of the coolant supply 36 leads to a heating of the cooling region 37. This leads to a change in the temperature in the parabolic gray zone 38. In the FIG. 3 It can be seen that the gray tones are even darker than the gray area in FIG. 2 , This means that the temperature is higher than the normal operation in FIG. 2 you can see. However, the temperature difference between the normal operation, as in FIG. 2 can be seen, and the Disturbance operation in FIG. 3 is shown, moderate. This means that the material of the rotor 21 undergoes a comparatively small temperature jump.

The FIG. 4 shows a side view of the arrangement according to the invention. The coolant supply 36 is formed in a first embodiment in the radial direction 41 towards the axis of rotation. This means that during operation the cooling steam strikes the rotor 21 radially. Similarly, the line 39 according to FIG. 4 such that, during operation, a vapor from the inflow region strikes the rotor 21 radially.

The FIG. 5 shows an alternative embodiment to the embodiment according to FIG. 4 , The FIG. 5 shows that the coolant supply 36 is formed such that during operation of the cooling steam tangentially impinges on the rotor 21. For this purpose, the coolant supply 36 is carried out substantially in such a way that the shield receives a bore through which the steam can strike the rotor 21 tangentially. This leads to a twist of the vapor located in the cooling region 37. The conduit 39 is also formed in an alternative embodiment in such a way that in operation, a steam from the inflow 20 strikes tangentially to the rotor 21. This leads to a better mixing in the cooling area 37.

Although the invention has been further illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims (11)

1. Turbomachine, especially steam turbine (2, 12, 13), having an inlet region (20) for feeding steam,
   a rotatably mounted rotor (21),
   a casing, which is arranged around the rotor (21), wherein a flow passage (28) is formed between the rotor (21) and the casing,
   wherein the flow passage (28) and the inlet region (20) are fluidically interconnected,
   having a shield (27) which is designed in such a way that during operation steam which flows into the inlet region (20) can be deflected into the flow passage (28),
   wherein the shield (27) has a cooling medium feed (36) which is designed in such a way that during operation cooling steam flows into a cooling region (37) which is arranged between the shield (27) and the rotor (21), characterized in that
   the shield (27) additionally has a line (39) which creates a fluidic connection between the cooling region (37) and the inlet region (20).
2. Turbomachine according to Claim 1,
   wherein the turbomachine is of double-flow design.
3. Turbomachine according to Claim 2,
   wherein during operation steam which flows into the inlet region (20) can be deflected by means of the shield (27) partly into a first flow (29) and partly into a second flow (30).
4. Turbomachine according to one of the preceding claims, wherein the shield (27) is arranged upstream of a first blade stage.
5. Turbomachine according to one of the preceding claims, wherein the shield (27) is arranged around the rotor (21).
6. Turbomachine according to one of the preceding claims, wherein the cooling medium feed (36) is designed in such a way that during operation the cooling steam impinges radially upon the rotor (21).
7. Turbomachine according to one of Claims 1 to 5,
   wherein the cooling medium feed (36) is designed in such a way that during operation the cooling steam impinges tangentially upon the rotor (21).
8. Turbomachine according to one of the preceding claims, wherein the line (39) is designed in such a way that during operation steam from the inlet region (20) impinges radially upon the rotor (21).
9. Turbomachine according to one of Claims 1 to 7,
   wherein the line (39) is designed in such a way that during operation steam from the inlet region (20) impinges tangentially upon the rotor (21).
10. Turbomachine according to one of the preceding claims, having a cooling medium line which is directly connected to the cooling medium feed (36),
    wherein during operation the cooling steam can flow in the cooling medium line.
11. Steam power plant having a turbomachine according to one of the preceding claims,
    wherein the cooling medium feed (36) is connected to a cool reheat line (8).

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