EP1945911B1 - Steam turbine - Google Patents

Abstract

Steam turbine (1) has a casing (2,3), a turbine shaft (5) having a thrust-compensating piston (4) is arranged in a rotatably mounted manner inside the casing and is directed along a rotation axis (6). The cooling line (17) is connected to one outflow line (18) for directing cooling steam onto a lateral surface (19) of the thrust-compensating piston.

Description

The invention relates to a steam turbine having a housing, wherein a turbine shaft having a thrust balance piston rotatably mounted within the housing and directed along a rotation axis, wherein a flow channel between the housing and the turbine shaft is formed, wherein the turbine shaft in its interior a cooling pipe for guiding Has cooling steam in the direction of the axis of rotation and the cooling line is connected to at least one inflow line for the inflow of cooling steam from the flow channel in the cooling line.

To increase the efficiency of a steam turbine, the use of steam at higher pressures and temperatures helps. The use of steam with such a steam condition places increased demands on the corresponding steam turbine.

For the purposes of the present application, a steam turbine is understood to mean any turbine or sub-turbine through which a working medium in the form of steam flows. In contrast, gas turbines are traversed with gas and / or air as the working medium, which, however, is subject to completely different temperature and pressure conditions than the steam in a steam turbine. In contrast to gas turbines has steam turbines z. As the one part turbine incoming working fluid with the highest temperature at the same time the highest pressure. An open cooling system, as in gas turbines, is therefore not feasible without external supply.

A steam turbine typically includes a vaned rotatably mounted rotor disposed within a casing shell. When flowing through the flow space formed by the housing jacket with heated and pressurized steam, the rotor passes through the blades set the steam in rotation. The rotor-mounted blades are also referred to as blades. In addition, usually stationary guide vanes are mounted on the housing jacket, which engage in the intermediate spaces of the moving blades. A vane is typically held at a first location along an interior of the steam turbine casing. In this case, it is usually part of a vane ring, which comprises a number of vanes, which are arranged along an inner circumference on the inside of the steam turbine housing. Each vane has its blade radially inward. A vane ring at a location along the axial extent is also referred to as a vane row. Usually, a number of vane rows are arranged one behind the other.

An essential role in increasing the efficiency plays the cooling. In the previously known coolant methods for cooling a steam turbine housing, a distinction must be made between active cooling and passive cooling. In the case of active cooling, cooling is effected separately by a cooling medium supplied to the steam turbine housing, that is to say in addition to the working medium. In contrast, a passive cooling is done only by a suitable leadership or use of the working medium. A conventional cooling of a steam turbine housing is limited to a passive cooling. For example, it is known to flow around an inner casing of a steam turbine with cool, already expanded steam. However, this has the disadvantage that a temperature difference over the Innengehäusewandung must remain limited, otherwise the inner housing would thermally deform too much at too large a temperature difference. Although a heat dissipation takes place in a flow around the inner housing, the heat removal takes place relatively far away from the point of heat supply. Heat removal in the immediate vicinity of the heat supply has not been realized sufficiently. Another passive cooling can be achieved by means of a suitable design of the expansion of the working medium in a so-called diagonal stage become. However, this can only achieve a very limited cooling effect on the housing.

The steam turbine shafts, which are rotatably mounted in the steam turbines, are subjected to a great deal of thermal stress during operation. The development and production of a steam turbine shaft is both expensive and time consuming. Steam turbine shafts are considered to be the most stressed and expensive components of a steam turbine. This increasingly applies to high steam temperatures.

Sometimes due to the high masses of the steam turbine shafts these are thermally inert, which has a negative effect on thermal load changes of a turbine set. This means that the response of the entire steam turbine to a load change depends strongly on the speed of the steam turbine shaft to respond to thermally altered conditions depends. To monitor the steam turbine shaft, the temperature is monitored by default, which is complex and costly.

One characteristic of steam turbine shafts is that they have no significant heat sink. Therefore, the cooling of the blades arranged on the steam turbine shaft is difficult.

To improve the adaptation of a steam turbine shaft to a thermal stress, it is known to hollow out these in the inflow region or to form it as a hollow shaft. These cavities are usually completed and filled with air.

However, the high voltages that occur during operation, which largely consist of tangential stresses from the centrifugal force, have an adverse effect on the aforementioned steam turbine hollow shafts. These voltages are about twice as high as the voltages that would occur at corresponding full waves. This has a strong influence on the choice of material of the hollow shafts, which can lead to the fact that the hollow shafts for high steam conditions are not suitable or not feasible.

In gas turbine construction, it is known to carry air-cooled hollow shafts as thin-walled welded constructions. It is known, inter alia, to form the gas turbine shafts via a so-called Hirth toothing with discs. These gas turbine shafts have for this purpose a central tie rod.

However, a direct transfer of cooling principles in gas turbines on the steam turbine construction is usually not possible, since a steam turbine is operated in contrast to the gas turbine as a closed system. By this is meant that the working fluid is in a circuit and is not discharged into the environment. The working medium used in a gas turbine, which basically consists of air and exhaust gas, is released into the environment after passing through the turbine unit of the gas turbine.

In addition, steam turbines, in contrast to the gas turbine, have no compressor unit and, moreover, the shafts of the steam turbine are generally accessible only radially.

Steam turbines with a steam inlet temperature of about 600 ° C were developed and built in the 1950s. These steam turbines had a radial blading. The current state of the art in steam turbine construction includes shaft cooling with radial arrangement of the first row of vanes in the form of diagonal or control stages. A disadvantage of this embodiment, however, is the low cooling effect of these diagonal or control stages.

The piston and inflow areas are particularly thermally stressed in the steam turbine shafts. Piston area is to be understood as the area of a thrust balance piston. The thrust balance piston acts in a steam turbine such that caused by the working fluid force the shaft is formed in one direction a counter force in the opposite direction.

A cooling of a steam turbine shaft is inter alia in the EP 0 991 850 B1 described. In this case, a compact or high-pressure and medium-pressure turbine part is performed by a compound in the shaft through which a cooling medium can flow. A disadvantage here is felt that between two different expansion sections no controllable bypass can be formed. In addition, problems in transient operation are possible.

In the US 2005/0118025 A1 discloses a rotor for a steam turbine, wherein the rotor has a cooling channel.

The US 6,082,962 discloses a steam turbine having the features of the preamble of claim 1.

In he US 6,048,165 discloses a turbine rotor cooling, wherein the cooling is effected by means of a cooling steam, which is guided in the interior of the rotor.

It would be desirable to form a steam turbine that is suitable for high temperatures.

The object of the invention is therefore to provide a steam turbine, which can be operated at high steam temperatures.

This object is achieved by a steam turbine with a housing, wherein a turbine piston having a thrust balance piston rotatably mounted within the housing and directed along a rotation axis, wherein a flow channel between the housing and the turbine shaft is formed, wherein the turbine shaft in its interior a cooling pipe to Having leadership of cooling steam in the direction of the axis of rotation and the cooling line on the one hand at least one inflow line is connected to the inflow of cooling steam from the flow channel into the cooling line, the cooling line being connected to at least one outflow line for guiding cooling steam to a thrust-compensating piston skirt surface, the steam turbine having a return line for returning a mixed vapor formed from the cooling steam and a compensation piston leakage, formed, wherein the return flows into the flow channel.

It is thus proposed a steam turbine with a steam turbine shaft, which is in each case hollow in the hot during operation and is provided with an internal cooling. The invention is based on the aspect that during operation expanded steam is guided through the shaft interior to the balance piston and there cools the highly stressed compensation piston. With the proposed cooling option, especially those steam turbine shafts can be cooled, which have a balance piston. This would be z. B. high pressure, medium pressure and K-part turbines. Whereby a K partial turbine is to be understood as meaning a compact partial turbine which has a high-pressure and medium-pressure region located on a steam turbine shaft. The advantage of the invention is to be seen, inter alia, that the steam turbine shaft can be formed on the one hand creep stable and on the other hand reacts flexibly to thermal loads. For example, during a load change in which a higher thermal load can occur, the cooling causes the thermal load of the shaft to eventually decrease. This is especially true for the areas that are particularly thermally stressed, such. B. the inflow or the balance piston.

The invention is based on the aspect that the cooling steam is mixed with a compensation piston leakage steam and this mixed steam is again supplied to the flow channel to continue to work there. The efficiency of the steam turbine thereby increases.

This allows a quick start-up of the steam turbine, which is a special aspect for the present time, which is about providing energy quickly available. Furthermore, there is an advantage of the steam turbine according to the invention in that the costs for wave monitoring can be lower. A hollow steam turbine shaft has a lower mass compared to a solid shaft and thus also a lower heat capacity a solid shaft and a larger flowed surface. As a result, a rapid warm-up of the steam turbine shaft is possible.

Another aspect of the invention is that the creep strength of the material used for the steam turbine shaft is increased by the improved cooling. The creep rupture strength can be increased by a factor greater than 2 compared to a solid shaft, so that the above-described voltage increase is overcompensated. This leads to an extension of the field of application of the steam turbine shaft.

Another aspect of the invention is that the radial clearance can be reduced by the diameter of the hollow shaft is increased by radial centrifugal forces. The radial centrifugal force is proportional to the square of the speed. An increase in the speed thus causes a reduction of radial play, which leads to an increase in the overall efficiency of the steam turbine.

Another aspect of the invention is that hollow shafts can be produced inexpensively.

In an advantageous development, the housing comprises an inner housing and an outer housing. High-pressure turbine sections as well as medium-pressure and compact turbine sections are among the most thermally stable steam turbines. In general, high-pressure, medium-pressure and compact turbine sections with an inner housing, are arranged on the vanes and formed around the inner housing arranged outer housing.

In an advantageous development, the turbine shaft has at least two regions made of different materials in the axial direction.

This can save costs. In the thermally stressed areas is usually high quality material used. For example, 10% chromium steel can be used in the thermally stressed areas. Whereas in the areas of low thermal stress 1% chromium steel can be used.

Conveniently, the turbine shaft has three regions of different materials in the axial direction. In particular, the two outer regions are made of the same material. As a result, targeted material can be selected for the respective area of the steam turbine shaft of different thermal load.

Advantageously, the areas comprising different materials are welded together. The welding creates a stable turbine shaft.

In a further advantageous alternative embodiment, the regions consisting of different materials are connected to one another by means of a Hirth toothing. The main advantage of the Hirth toothing is the particularly high thermal flexibility of the turbine shaft. Another advantage is that this usually leads to the turbine shaft can be made quickly. In addition, the turbine shaft can be formed inexpensively.

In a further advantageous development, the two outer regions are designed as a solid shaft and the intermediate region lying between them as a hollow shaft. It is equally advantageous if the regions consisting of different materials are connected to one another by means of a flange connection. This can be helpful during revision work because the different areas can be easily separated from each other.

It is likewise advantageous if the inflow line and the outflow line are integrated in the flange connection.

Conveniently, the areas comprising different materials are welded together by at least one weld.

It is very advantageous if the inflow line and the outflow line are integrated in the Hirth toothing. In this case, the Hirth toothing, which may have a trapezoidal, rectangular or triangular toothing, be made with a recess formed as an inflow and / or outflow line. This has a very easy way to form an inflow and / or outflow line. For example, the recess in the trapezoidal, rectangular or triangular toothing can be adapted depending on the calculated passage volume of the cooling steam. The production of such recesses on a Hirth toothing is relatively simple and can also be carried out quickly. This results in cost advantages.

Advantageously, the return line is arranged within the outer housing. The return line can also be designed as a bore in the inner housing.

Embodiments of the invention will be explained in more detail with reference to the following drawings. In this case, components with the same reference numerals have the same functionality.

Show it

FIG. 1

a cross-sectional view of a high pressure turbine part according to the prior art,

FIG. 2

a section through a part of a sub-turbine,

FIG. 3

a section through a turbine shaft,

FIG. 4

a section through a turbine shaft in an alternative embodiment,

FIG. 5

a section through a turbine shaft in an alternative embodiment,

FIG. 6

a section through a turbine shaft in an alternative embodiment,

FIG. 7

a section through a turbine shaft in an alternative embodiment,

FIG. 8

an enlarged view of a flange connection,

FIG. 9

a perspective view of a part of the flange,

FIG. 10

a perspective view of the principle of a Hirth toothing,

FIG. 11

a sectional view of a Hirth toothing with passage channels in a triangular shape,

FIG. 12

a section through a Hirth toothing in trapezoidal shape with through holes,

FIG. 13

Curve showing relative creep rupture strength as a function of temperature.

In the FIG. 1 is a section through a high-pressure turbine part 1 according to the prior art shown. The high-pressure turbine part 1 as an embodiment of a steam turbine comprises an outer housing 2 and an inner housing 3 arranged therein. Within the inner housing 3, a turbine shaft 5 is rotatably mounted about an axis of rotation 6. The turbine shaft 5 includes blades 7 disposed in grooves on a surface of the turbine shaft 5. The inner case 3 has guide vanes 8 arranged in grooves on its inner surface. The guide 8 and blades 7 are arranged such that in a flow direction 13, a flow channel 9 is formed. The high-pressure turbine section 1 has an inflow region 10, through which live steam flows into the high-pressure turbine section 1 during operation. The live steam may have steam parameters above 300 bar and above 620 ° C. The relaxing in the flow direction 13 live steam flows alternately past the guide 8 and blades 7, relaxes and cools down. The steam loses in this case to internal energy, which is converted into rotational energy of the turbine shaft 5. The rotation of the turbine shaft 5 finally drives a generator, not shown, for power supply. Of course, the high pressure turbine part 1 may drive other plant components other than a generator, such as a compressor, a propeller, or the like. The steam flows through the flow channel 9 and flows out of the high-pressure turbine section 1 from the outlet 33. The steam exerts an action force 11 in the flow direction 13. The result is that the turbine shaft 4 would perform a movement in the flow direction 13. An actual movement of the turbine shaft 5 is prevented by the formation of a balance piston 4. This is done by 12 steam is flowed in a Ausgleichskolbenvorraum with a corresponding pressure, which leads to the fact that due to the building up pressure in Ausgleichskolbenvorraum 12 a force against the flow direction 13 is formed, which ideally should be just as large as the action force 11. Der in the Ausgleichskolbenvorraum 12 incoming steam is usually branched live steam, which has very high temperature parameters. As a result, the inflow region 10 and the compensating piston 4 of the turbine shaft are subjected to high thermal stress.

In the FIG. 2 a section of a steam turbine 1 is shown. The steam turbine has an outer casing 2, an inner casing 3 and a turbine shaft 5. The steam turbine 1 has moving blades 7 and guide vanes 8. live steam passes through the inflow region 10 via a diagonal stage 15 in the flow channel 9. The steam relaxes and cools down. The internal energy of the steam is converted into rotational energy of the turbine shaft 5.

After a certain number of turbine stages, which are formed by guide vanes 8 and rotor blades 7, the steam is fluidly connected to a cooling line 17 via an inflow line 16. The cooling line 17 is in this case formed as a cavity within the turbine shaft 5. Other embodiments are conceivable. So z. Example, instead of a cavity 17 form a line, not shown, within the turbine shaft 5.

The turbine shaft 5 is rotatably mounted within the housing 2, 3 and directed along a rotation axis 6. Between the housing 2, 3 and the turbine shaft 5, a flow channel 9 is formed. The cooling line 17 is in this case designed to guide cooling steam in the direction of the axis of rotation 6. The cooling line 17 is on the one hand fluidly connected to at least one inflow line 16. The inflow line 16 is designed for the inflow of cooling steam from the flow channel 9 into the cooling line 17.

The inflow line 16 may in this case be aligned radially with respect to the axis of rotation 6. Other embodiments of the inflow line 16 are conceivable. Thus, for example, the inflow line 16 can be designed to be inclined perpendicular to the axis of rotation 6. The cooling line 16 could run in a spiral shape from the flow channel 9 to the cooling line 17. The cross section of the cooling line 16 can vary from the flow channel 9 to the cooling line 17.

On the other hand, the cooling line 17 is connected to at least one outflow line 18 for guiding the cooling steam onto a thrust balance piston skirt surface 19.

The effluent from the discharge line 18 cooling steam is distributed on the thrust balance piston skirt surface 19 and cools this off.

The housing 2, 3 comprises an inner housing 3 and an outer housing 2. The cooling steam flowing out of the discharge line 18 flows in two directions. On the one hand in the direction of the main flow direction 13 and the other in one of the main flow 13 opposite direction. A portion of the live steam flows via the inflow region 10 between the inner casing 3 and the turbine shaft 5 in the direction of the thrust balance piston 4. This so-called piston leakage steam 20 mixes with the cooling steam flowing out of the outflow line and is returned to the flow channel 9 by means of a return line 21. It makes sense that this return line 21 begins between inflow 10 and the outlet of the discharge line 18. Thus, a partial flow of the cooling steam can be directed in the direction of the main flow 13 and lock the piston leakage 20. In this way, the above-described cooling of the piston surface 18 is ensured. This mixed steam formed from the cooling steam and a compensating piston leakage steam is flowed in at a suitable point in the flow channel 9 in order to perform work there.

The return line 21 may be formed as an external line within the outer housing 2. The return line 21 may also be formed as a bore within the inner housing 3.

In the FIG. 3 a turbine shaft 5 is shown. The turbine shaft 5 is made of a material that takes into account the thermal stresses. The disadvantage here, however, that the thermal stress is not uniformly distributed on the turbine shaft 5, but as shown earlier, in the region of the inflow 10 and the balance piston 4 is particularly strong. For clarity, the blades 7 are not shown.

By the hatching in the FIG. 3 is made clear that the turbine shaft 5 is formed of a material.

In the FIG. 4 a further turbine shaft 5 is shown, wherein this turbine shaft 5 in the flow direction 13 has at least two regions made of different materials. In alternative embodiments, the turbine shaft 5 in the axial flow direction 13 may comprise three regions 24, 23, 22 made of different materials. The central region 22 may for example be made of a temperature-resistant 10% chromium steel and the two outer regions 23 and 24 made of the same material such. B. 1% chromium steel. In the in FIG. 4 illustrated embodiment, the turbine shaft 5 is connected by means of welded joints 25 and 26.

The turbine shaft 5 can be designed as a hollow shaft in its central region 22 and in its outer regions 23, 24 as a solid shaft.

If the areas 22, 23, 24 are welded together, at least one weld is used.

The turbine shaft 5 can be made of different materials existing areas 22, 23, 24 by means of a flange 40 with each other, wherein the inflow line 16 and the discharge line 18 is integrated in the flange connection.

In the FIG. 5 an alternative embodiment of the turbine shaft 5 is shown. The difference to the in FIG. 4 shown turbine shaft is that in FIG. 5 shown turbine shaft 5 is composed by means of a Hirth toothing 27, 28. In this case, a tie rod 29 must be formed, which is arranged such that the two outer regions 23 and 24 are pressed against the central region 22. The central region 22 comprises one or more sections which are tubular or disk-shaped are and each may contain one or more blade stages:

In a further alternative embodiment, as in FIG. 6 represented, the turbine shaft 5 by means of a Hirth toothing 30, 31 connected to each other, wherein the inflow line 16 and the discharge line 18 in the Hirth toothing 30, 31 is integrated.

In the FIG. 7 a further alternative embodiment of the turbine shaft 5 is shown. The turbine shaft 5 comprises at least two regions 22 'and 23' formed of different materials. The area 23 'is flanged to the area 22'. The screwing takes place by means of suitable expansion shank bolts 39. The flange connection 40 is centered according to the prior art. Conveniently, a thread 41 for grasping the screw 39 is formed in the region 22 '. Furthermore, the screwing of the region 23 'with the region 22' preferably takes place from the cooler side.

In the FIG. 8 is a sectional view of the bolted connection from the FIG. 7 to see. It can also be seen in this illustration that the discharge line 18 integrates into the connection through recesses. This is in a perspective view of a part of the turbine shaft 5 in the FIG. 5 shown. By connecting the outflow line 18 with the screw hole 43 by means of an annular space 42, the cooling of the screws can be realized and an approximation of the temperatures of the flange (balance piston) with the screws.

In the FIG. 10 is a perspective view of a Hirth toothing 30, 31 to see. The middle region 2 in this case has one according to FIG. 10 illustrated Hirth toothing 30, 31 on. Likewise, the two outer regions 24 and 23 made of different materials likewise have a Hirth toothing 30, 31.

In the FIG. 11 is a cross-sectional view of the Hirth serration 30, 31 can be seen. The left part is, for example, the left region 24 and the right part of the central region 22 is connected to one another via the Hirth toothing 30. The inflow line 16 is integrated in the Hirth toothing. In the FIG. 11 illustrated cross-sectional illustration may also represent the discharge line 18. In this case, the left-hand region would be the middle region 22 and the right-hand region 23 connected via the Hirth toothing 31. The outflow line 18 is integrated in the Hirth toothing 30, 31. In the FIG. 11 illustrated embodiment has a triangular toothing.

The inflow line 16 or the outflow line 18 is formed via recesses 32 of the Hirth toothing 30, 31.

In the FIG. 12 illustrated embodiment of the Hirth toothing 30, 31, this has a trapezoidal toothing. Possible embodiments of the Hirth toothing are a trapezoidal, rectangular or triangular toothing. Other embodiments are possible.

In the FIG. 13 The relevant strength values for 1% and 10% chromium steels for steam turbine shafts are shown.

aufgetragen. Die obere Kurve 37 zeigt das Temperaturverhalten für den Werkstoff 30 CrMoNiV5-11 und die untere Kurve 38 zeigt das Temperaturverhalten für den Werkstoff X12CrMoWVNbN10-1-1.On the x-axis 35, the temperature is plotted in a linear scale of 400 to 600 ° C. On the y-axis 36, the creep rupture strength R _{m is 200,000 h} in a linear scale of 30 to 530 $\frac{\mathrm{<figure-callout\; id="2"\; label="N\; mm"\; filenames="imgf0001.png"\; state="\{\{state\}\}">N\; </figure-callout>}}{{\mathit{mm}}^{}}$

applied. The upper curve 37 shows the temperature behavior for the material 30 CrMoNiV5-11 and the lower curve 38 shows the temperature behavior for the material X12CrMoWVNbN10-1-1.

It has been found that in addition to the guidance of the cooling steam according to the invention, a plot of a thermal barrier coating on the surfaces of the thermally stressed components increases the effect of effective cooling.

Through the use of the tie rod 29, a part of the axial forces is taken. This allows the turbine shaft 5 are formed thin-walled, which has a positive effect on the thermal flexibility and the formation of radial play.

The invention is not limited to the formation of a high-pressure turbine section as an embodiment of a steam turbine 1, the turbine shaft 5 according to the invention can also be used in a medium-pressure or a compact turbine section (high pressure and medium pressure within a housing). Likewise, the turbine shaft 5 can be used in other types of steam turbine.

Claims (14)

1. Steam turbine (1) with a casing (2, 3),
   wherein a turbine shaft (5), which has a thrust compensating piston (4), is arranged in a rotatably mounted manner inside the casing (2, 3), and is oriented along a rotational axis (6),
   wherein a flow passage (9) is formed between the casing (2, 3) and the turbine shaft (5),
   wherein the turbine shaft (5) has a cooling line (17) within it for guiding cooling steam in the direction of the rotational axis (6), and the cooling line (17) is connected on one side to at least one inflow line (16) for inflow of cooling steam from the flow passage (9) into the cooling line (17), wherein
   the cooling line (17) is connected on the other side to at least one outflow line (18) for guiding cooling steam onto a generated surface (19) of the thrust compensating piston,
   characterized by
   a return line (21) for return of mixed steam which is formed from the cooling steam, which flows out of the outflow line (18), and some live steam, which as compensating piston leakage steam flows between the casing (2, 3) and the turbine shaft (5) in the direction of the thrust compensating piston (4),
   wherein the return line (21) leads into the flow passage (9).
2. Steam turbine (1) according to Claim 1,
   wherein the casing (2, 3) comprises an inner casing (3) and an outer casing (2).
3. Steam turbine (1) according to either of Claims 1 or 2,
   wherein the turbine shaft (5) in the axial direction (34) has at least two sections consisting of different materials.
4. Steam turbine (1) according to Claim 1, 2 or 3,
   wherein the turbine shaft (5) in the axial direction (34) has three sections (22, 23, 24) consisting of different materials.
5. Steam turbine (1) according to Claim 4,
   wherein the two outer sections (23, 24) consist of the same material.
6. Steam turbine (1) according to Claim 3, 4 or 5,
   wherein the sections consisting of different materials (22, 23, 24) are welded to each other.
7. Steam turbine (1) according to Claim 3, 4, 5 or 6,
   wherein the sections (23, 24) are formed as a solid shaft and the section (22) is formed as a hollow shaft.
8. Steam turbine (1) according to Claim 3, 4, 5 or 7,
   wherein the sections consisting of different materials (22, 23, 24) are interconnected by means of a Hirth toothing (30, 31).
9. Steam turbine (1) according to Claim 3, 4, 5 or 7,
   wherein the sections consisting of different materials (22, 23, 24) are interconnected by means of a flanged connection (40).
10. Steam turbine (1) according to Claim 8,
    wherein the inflow line (16) and the outflow line (18) are integrated in the Hirth toothing (30, 31).
11. Steam turbine (1) according to Claim 9,
    wherein the inflow line (16) and the outflow line (18) are integrated in the flanged connection (40).
12. Steam turbine (1) according to Claim 8,
    wherein the Hirth toothing (30, 31) has trapezoidal, rectangular or triangular serrations with a recess (32) which is formed as an inflow line (16) and/or outflow line (18).
13. Steam turbine (1) according to one of the preceding claims,
    wherein the return line (21) is arranged inside the outer casing (2).
14. Steam turbine (1) according to one of the preceding claims,
    wherein the return line (21) is formed as a bore in the inner casing (2).

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