EP3488082B1 - Steam turbine with flow shield - Google Patents

Description

The present invention relates to a steam turbine with a multi-part turbine housing.

Steam turbines are flow machines that are designed to convert the enthalpy of steam into kinetic energy. Conventional steam turbines have a turbine housing which surrounds a flow space for the steam to flow through. A rotationally mounted turbine shaft with a multiplicity of rotor blades is arranged in the flow space, which are held on the turbine shaft in the form of rotor blade rings arranged one behind the other. To optimize the flow of steam onto the rotor blades, steam turbines have guide vane rings which are each connected upstream of a rotor blade ring and are held on the turbine housing. A group of a guide vane ring with an associated rotor blade ring is also referred to as a turbine stage.

When flowing through the steam turbine, the steam releases part of its internal energy, which is converted into rotational energy of the turbine shaft via the rotor blades. Here, the steam is expanded so that the pressure and temperature of the steam as it flows through the steam turbine are reduced after each turbine stage. The turbine housing is thus exposed to a temperature gradient between a steam inlet and a steam outlet. In particular in the case of compact steam turbines, this leads to a very high load on the turbine housing.

In special embodiments, steam turbines have a high-pressure section and a medium-pressure section and / or low-pressure section. To improve the efficiency, such steam turbines can have a heating device for intermediate superheating of the steam, so that, for example, steam leaving the high-pressure section from the heating device can be heated before it is fed to the subsequent turbine sections. It can be provided that such a heating device is arranged between two turbine sections. In particular in the case of steam turbines with such reheating of the steam, strong temperature fluctuations occur along a longitudinal axis of the steam turbine. First of all, the temperature in the high-pressure section drops gradually, then rises suddenly in the transition area due to the reheating. A region of the turbine housing which is arranged adjacent to an outflow of the high-pressure section and an inflow to the following medium-pressure section or low-pressure section is exposed to particularly large temperature differences, particularly in the case of compactly constructed steam turbines.

In addition, for reasons of better manufacturability and ease of assembly, turbine housings have a plurality of housing parts which are connected to one another to form the turbine housing with the formation of parting lines. Turbine housings often have a lower housing part and an upper housing part. The turbine housing can also have a plurality of housing segments along the longitudinal axis of the turbine, so that the high-pressure section and the medium-pressure section are arranged, for example, in different housing segments. The connection is often made by screwing flanges of the housing parts or housing segments.

The greater the mechanical load on the connections of the housing parts or housing segments, the larger the fastening elements are required to compensate for forces that open the parting lines. In particular in the case of compactly constructed steam turbines, this represents a major problem, since the available installation space for the steam turbine is often very limited. Thus, the loading possibilities of these steam turbines are very limited.

From the DE 10 2008 045 657 A1 a steam turbine is known in which a parting line between two housing parts is completely covered by a shielding element. The shielding element is sealed off from the housing parts via a sealing device, so that a cavity formed between the shielding element and the turbine housing is sealed off from the flow space. The cavity is connected in a fluid-communicating manner via a pressure line to a region of the flow chamber which follows in the flow direction of the steam turbine and which is arranged behind a guide vane carrier. The pressure line can be shut off via a valve. Such a turbine is very complex and therefore costly to manufacture. Furthermore, the sealing device is exposed to high mechanical stress, in particular thermal stress, but also abrasion by the steam flow, and accordingly exhibits high wear. This causes a high maintenance effort and high maintenance costs due to the shutdown and start-up required for this and the high downtimes of the steam turbine required for maintenance.

It is therefore the object of the present invention to provide a steam turbine which improves or at least partially improves the above disadvantages. In particular, the object of the present invention is to create a steam turbine in a compact design with a multi-part housing, which ensures a reduced temperature gradient on the turbine housing with simple means and inexpensively and thus allows a larger steam mass flow with consistently dimensioned fastening elements for connecting the housing parts and thus also have improved efficiency.

The above problem is solved by the patent claims. Accordingly, the object is achieved by a steam turbine with a turbine housing having a plurality of turbine housing parts according to claim 1. Further features and details of the invention result from the subclaims, the description and the drawings.

According to a first aspect of the invention, the object is achieved by a steam turbine which has a turbine housing which has a plurality of turbine housing parts and which surrounds a flow space along a longitudinal axis of the turbine. The turbine housing has a housing wall, a parting line being formed between two adjacent turbine housing parts. On a housing wall side of the housing wall facing the flow space, at least one flow shield is arranged, which shields a wall section of the housing wall from a flow of the flow space. An intermediate space is formed between the flow shield and the wall section of the housing wall, the intermediate space having an opening to the flow space in at least one area. A fluid-communicating connection between the space and the flow space is formed via this opening. The opening is designed as a gap between the flow shield and the housing wall. According to the invention, the flow shield extends in the circumferential direction of the housing wall only over a partial circumferential area of the housing wall.

It is preferred here that the flow shield extends at least over parts of the turbine housing that are exposed to particularly large temperature differences and / or particularly high temperatures compared to other areas of the turbine housing. In this way it can be ensured that the steam turbine has a flow shield only in the areas of the turbine housing which are exposed to a particular thermal load in order to relieve these areas of the turbine housing. It is therefore no longer necessary to relieve these areas by reducing the steam mass flow and / or a steam temperature.

The turbine housing preferably has at least two turbine housing parts. The turbine housing preferably has a lower housing part and an upper housing part, each of which is divided into at least two housing segments along a longitudinal axis of the turbine. The turbine housing has a housing wall that is impermeable to steam. A parting line is formed between two adjacent turbine housing parts. The turbine housing parts preferably have at least one flange via which they are connected to one another, in particular screwed. As a result of the screwing, adjacent turbine housing parts are pressed against one another and the parting line is thus sealed. According to the invention, it is preferred that a sealing device, such as a sealing ring, is arranged in the parting line.

The turbine housing is designed along the turbine longitudinal axis and surrounding it. The turbine housing thus surrounds a flow space. For example, a turbine shaft with rotor blade rings is rotatably mounted in the flow space. Furthermore, the turbine housing preferably has at least one guide vane ring, which is assigned to at least one rotor blade ring of the turbine shaft. The flow space is designed for the passage of steam. The steam is deflected by the guide vanes and thus hits the rotor blades at an optimized angle of attack.

According to the invention, at least one flow shield is arranged on a housing wall side of the housing wall facing the flow space. The flow shield shields a wall section of the housing wall from a flow - in particular a steam mass flow - in the flow space. According to the invention, shielding is understood to mean a deflection of the flow so that the steam can hit the shielded wall section with a changed flow direction and / or reduced flow velocity. In the context of the invention, shielding does not mean that the wall section is completely isolated from the steam so that contact with the steam is no longer possible.

The flow shield is preferably designed in the form of a plate and is more preferably adapted to a curvature of the turbine housing in order to exert as little influence as possible on the rest of the steam flow flowing through the flow space. The turbine housing is preferably designed in such a way that the turbine wall and flow shield form an optimized flow space which is optimized for the flow to the turbine stages. For this purpose, the turbine housing preferably has a slight increase in cross section in the area of the flow shield in order to compensate for a reduction in the volume of the flow space caused by the flow shield.

An intermediate space is formed between the flow shield and the housing wall. For this purpose, the flow shield is preferably at least partially spaced from the housing wall. For this purpose, it is preferred that at least one spacer is arranged between the flow shield and the housing wall. The flow shield is preferably screwed to the housing wall, but it can also be welded or riveted to it. A spacer is preferably designed as a hollow cylinder which surrounds a screw of the screw connection. The fastening of the flow shield to the housing wall is preferably designed to be heat-movable in order to avoid tensions between the flow shield and the housing wall due to different thermal expansions.

In at least one area, the intermediate space has an opening to the flow space. A fluid-communicating connection between the intermediate space and the flow space is established via the opening. It is preferred that the opening is formed on a side of the space that faces in a flow direction of the steam. The intermediate space is preferably closed against the direction of flow of the steam. This prevents the steam flowing in the direction of flow from flowing directly into the space. In order to get into the flow space, the steam has to change its direction of flow and thus reduce its flow velocity. The opening is designed as a gap between the flow shield and the housing wall. The opening ensures that steam can get into the intermediate space from the rest of the flow space. Thus, during operation of the steam turbine, the same temperature or almost the same temperature and the same pressure or almost the same pressure as in the rest of the flow chamber or at the turbine stage, on the turbine longitudinal axis section of which the opening is formed, can be set in the space.

The steam turbine according to the invention has the advantage over conventional steam turbines that a thermal load on the turbine housing in the area of the flow shield is reduced with simple means and inexpensively. A temperature gradient in the housing is thus considerably reduced. In this way, when the steam turbine is in operation, fewer stresses are generated in the turbine housing, which occur as opening forces at the joints. As a result, a maximum load capacity and an efficiency of the steam turbine can be improved while the structural size remains unchanged.

It is preferred that the flow shield shield the parting line and a region of the housing wall surrounding the parting line from the flow. An area around the parting line is a structural weak point of the turbine housing and is particularly susceptible to thermal stress, in particular a high temperature gradient, since this can create forces at the parting line that open the parting line due to different thermal expansions. Targeted shielding of the parting line or an area around the parting line thus has the advantage that a thermal and mechanical stress on the parting line or the fastening means holding the parting line together can hereby be reduced with simple means.

More preferably, the flow shield extends in the circumferential direction by 1.5 times to 6 times the height of the joint flange of a joint flange of the steam turbine. At a parting line, adjacent turbine housing parts each have a parting line flange, via which the turbine housing parts are connected to one another, e.g. screwed. The parting line flange has a parting line flange height in the longitudinal direction of a connecting screw for connecting the parting line flanges. In the area of the joint flange, a thermal load on the turbine housing is particularly disadvantageous. In order to reduce the production costs of the steam turbine and at the same time ensure good shielding of the joint flange, it has been shown that an extension of the flow shield by 1.5 to 6 times the joint flange height is particularly advantageous for this.

The flow shield preferably has at least two flow shield parts which are arranged on adjacent turbine housing parts. The flow shields are thus each held on other turbine housing parts and can easily be mounted on the turbine housing parts before the turbine housing is installed. Assemblability of the steam turbine is thus improved. Furthermore, it is preferred that the flow shields are arranged on the turbine housing parts in such a way that when the turbine housing is assembled, at least two flow shields form a common flow shield.

It is further preferred that the flow shield is arranged in a flow space area of the flow space in which the flow space has a maximum temperature gradient. In these areas of the flow space there is a load on the turbine housing due to different thermal expansions extraordinary big. The flow shielding relieves these areas through reduced temperature input and the associated lower thermal expansion.

According to the invention, it can be provided that the flow shield has a terminating area in the flow direction, the intermediate space having a reduced height in the terminating area. Accordingly, the gap along the flow shield has different heights. The opening is formed in the closing area and consequently has an opening height which corresponds to the height of the space in the closing area. Such a flow shield is easy to manufacture and has the further advantage that the effect of the steam from the rest of the flow space into the intermediate space is reduced due to the lower height of the intermediate space. Thus, only a reduced heat exchange can take place on the housing wall in the area of the flow shield. The housing wall is thus better relieved.

More preferably, the steam turbine has at least one steam supply, which is designed for direct supply of steam into the intermediate space. The steam supply can be designed, for example, as a channel in the housing wall or as an independent line. The steam supply is preferably arranged in such a way that the steam is guided as close as possible to the parting line before it can be distributed within the interspace. The steam can be introduced into the intermediate space, for example in the direction of the parting line, via a corresponding nozzle. Alternatively or additionally, a steam inlet of the steam supply is arranged adjacent to the parting line. The steam supply is preferably designed to supply steam which has a higher temperature than the steam in the flow space on the flow shield. Such a steam supply has the advantage that the temperature gradient on the turbine housing can be further reduced with simple means. The turbine housing is thus less stressed exposed, so that, for example, a less resilient or less expensive turbine housing can be used for the steam turbine. Alternatively, the application of steam to the steam turbine, such as steam mass flow and / or steam temperature, can be increased and the efficiency of the steam turbine can thus be improved.

In an advantageous embodiment of the invention it can be provided that the steam supply connects a region of the flow space, which is arranged in the flow direction upstream of the flow shield, with the intermediate space in a fluid-communicating manner. According to the invention, this means in particular a region of the steam turbine which is arranged a turbine stage in front of the flow shield, that is to say an adjacent region. This has the advantage that, when the steam turbine is in operation, steam that is already present at an optimal or almost optimal temperature and an optimal or almost optimal pressure can be fed into the intermediate space. The steam does not have to be provided separately or conveyed over longer distances. As a result, operating costs of the steam turbine can be reduced further.

It is preferred that the steam supply has at least one actuator for setting a steam mass flow. The actuator is designed, for example, as a valve. Adjustability of the steam mass flow has the advantage that a temperature transition to the turbine housing in the area of the flow shield can be controlled. If, for example, it is determined, in particular by means of an infrared camera, that the turbine housing is too cold in the area of the flow shield, the actuator can be opened and the steam mass flow that penetrates into the space can be increased. Likewise, the actuator can be at least partially closed if the turbine housing has too high a temperature in the area of the flow shield in order to throttle the steam mass flow and thus reduce temperature exchange with the housing wall. According to the invention, the steam engine can have a regulating device for this purpose. The actuator is preferably designed to completely prevent the steam mass flow.

A side of the flow shield facing the housing wall preferably has at least one guide element which is designed to guide a steam mass flow within the intermediate space. The guide element can be designed, for example, as a wall which preferably extends between the housing wall and the flow shield and preferably contacts both the housing wall and the flow shield along its course. The guide element can be designed, for example, as a diverting element for diverting the steam mass flow once. Alternatively, the guide element is, for example, designed like a labyrinth. The guide element is preferably designed to divert the steam mass flow in the direction of the parting line. A guide element has the advantage that a flow direction of the steam mass flow in the intermediate space can be defined in order to optimize heat exchange between the steam mass flow and the housing wall. Furthermore, by means of the guide element, the steam mass flow directed into the intermediate space can be directed in a direction in which heating by the steam mass flow is particularly advantageous, e.g. in an area around a parting line.

It is preferred that the flow shield has a lower coefficient of thermal conductivity than the turbine housing. This is particularly advantageous in the case of high temperature differences in the turbine stage behind which the flow shield is arranged. Heat exchange with the intermediate space is thus reduced via the flow shield and the housing wall is thermally relieved as a result.

Figur 1

in einer Seitenansicht quer zur Strömungsrichtung eine bevorzugte Ausführungsform einer erfindungsgemäßen Dampfturbine,

Figur 2

in einer Seitenansicht quer zur Strömungsrichtung einen Ausschnitt der Dampfturbine aus Figur 1, und

Figur 3

in einer Seitenansicht in Strömungsrichtung einen Ausschnitt des Turbinengehäuses einer alternativen Ausführungsform einer erfindungsgemäßen Dampfturbine.

A steam turbine according to the invention with a flow shield is explained in more detail below with reference to drawings. They each show schematically:

Figure 1

in a side view transverse to the direction of flow, a preferred embodiment of a steam turbine according to the invention,

Figure 2

in a side view transverse to the direction of flow, a section of the steam turbine Figure 1 , and

Figure 3

in a side view in the flow direction a section of the turbine housing of an alternative embodiment of a steam turbine according to the invention.

In Fig. 1 a preferred embodiment of a steam turbine 1 according to the invention is shown schematically in a side view transverse to a flow direction 13 of a working fluid or a steam mass flow of the steam turbine 1. The steam turbine 1 has a turbine longitudinal axis 4 running in the flow direction 13 and a turbine housing 2 which is composed of four turbine housing parts 2a. The turbine housing parts 2a each have a joint flange 12 extending in the flow direction 13 and a joint flange height 11 extending in the circumferential direction around the turbine longitudinal axis 4. The turbine housing parts 2a are screwed to one another via the parting line flanges 12. A joint 6 is formed between two joint flanges 12 screwed together. The turbine housing 2 has a housing wall 5 which extends over the turbine housing parts 2a. The turbine housing 2 surrounds a flow space 3 for the passage of the working fluid or steam mass flow.

Fig. 2 shows a section of a lower part of the steam turbine 1 from Fig. 1 in a sectional view. A flow shield 7 is arranged on a wall section 5a of the housing wall 5, adjacent to a separating joint 6 extending parallel to the longitudinal axis 4 of the turbine. The flow shield 7 extends in the circumferential direction of the steam turbine 1 over a partial circumferential area 10. A flow shield 7 is preferably likewise arranged accordingly on an upper part of the steam turbine 1, not shown in this figure. An intermediate space 8 is formed between the flow shield 7 and the wall section 5a. In the flow direction 13, the intermediate space 8 is connected to the flow space 3 in a fluid-communicating manner via an opening 9. The flow shield 7 is arranged directly behind a guide vane carrier 19 in the flow direction 13. A plurality of steam supply lines 16 for supplying a steam mass flow into the intermediate space 7 are arranged in the guide vane carrier 19. Thus, steam from the flow space 3 can be supplied to the intermediate space 8 from an area in front of the guide vane carrier 19. To control the steam mass flow, the steam supply lines 16 each have an actuator 17. A plurality of guide elements 18 are arranged between the flow shield 7 and the wall section 5 a in order to deflect the steam mass flow supplied via the steam supply lines 16 or to guide it in the direction of the parting line 6. A vapor exchange between the intermediate space 8 and the flow space 3 can take place via the opening 9.

In Fig. 3 a section of the turbine housing 2 of the steam turbine 1 is shown in a side view and in the direction of flow 13. In this view, the space 8 formed between the flow shield 7 and the wall section 5a can be clearly seen. The flow shield 7 is formed from two shield parts 7a, one shield part 7a each being arranged on a turbine housing part 2a, for example on an upper housing part and a lower housing part. A parting line 6 formed between the turbine housing parts 2a can be clearly seen in this view. In this embodiment, the intermediate space 8 has an opening 9 which points downward. In the area of the opening 9, the interspace has a height 15 which is less than in other areas of the interspace 8.

Claims (11)

1. Steam turbine (1) having a turbine housing (2) having a plurality of turbine housing parts (2a), said turbine housing (2) surrounding a flow space (3) along a turbine longitudinal axis (4), wherein the turbine housing (2) has a housing wall (5), wherein a parting line (6) is formed between two adjacent turbine housing parts (2a) and wherein at least one flow shield (7) is arranged on a side of the housing wall (5) facing the flow space (3), said flow shield (7) shielding a wall portion (5a) of the housing wall (5) from a flow in the flow space (3), wherein an intermediate space (8) is formed between the flow shield (7) and the wall portion (5a) of the housing wall (5), wherein, in at least one region, the intermediate space (8) has an opening (9) to the flow space (3), wherein a fluid-communicating connection of the intermediate space (8) to the flow space (3) is formed via the opening (9), wherein the opening is in the form of a gap between the flow shield (7) and the housing wall (5),
   characterized
   in that the flow shield (7) extends in the circumferential direction of the housing wall (5) only over a partial circumferential region (10) of the housing wall (5).
2. Steam turbine (1) according to Claim 1,
   characterized
   in that the flow shield (3) shields the parting line (6) and a region, surrounding the parting line (6), of the housing wall (5) from the flow.
3. Steam turbine (1) according to Claim 2,
   characterized
   in that the flow shield (7) extends in the circumferential direction over 1.0 to 6.0 times, preferably 2.0 to 4.0 times, a parting line flange height (11) of a parting line flange (12) of the steam turbine (1).
4. Steam turbine (1) according to one of the preceding claims,
   characterized
   in that the flow shield (7) has at least two flow shield parts (7a), which are arranged on adjacent turbine housing parts (2a) .
5. Steam turbine (1) according to one of the preceding claims,
   characterized
   in that the flow shield (7) is arranged in a region of the flow space (3) in which the flow space (3) has a maximum temperature gradient.
6. Steam turbine (1) according to one of the preceding claims,
   characterized
   in that the flow shield (7) has an end region (14) in the direction of flow (13), wherein the intermediate space has a reduced height (15) in the end region (14).
7. Steam turbine (1) according to one of the preceding claims,
   characterized
   in that the steam turbine (1) has at least one steam feed (16), which is configured to directly feed steam into the intermediate space (8).
8. Steam turbine (1) according to Claim 7,
   characterized
   in that the steam feed (16) connects a region of the flow space (3) that is arranged upstream of the flow shield (7) in the direction of flow (13) to the intermediate space (8) in a fluid-communicating manner.
9. Steam turbine (1) according to Claim 7 or 8,
   characterized
   in that the steam feed (16) has at least one control member (17) for setting a steam mass flow.
10. Steam turbine (1) according to one of the preceding claims,
    characterized
    in that a side of the flow shield (7) that faces the housing wall (5) has at least one guide element (18), which is configured to guide a steam mass flow within the intermediate space (8).
11. Steam turbine (1) according to one of the preceding claims,
    characterized
    in that the flow shield (7) has a lower coefficient of thermal conductivity than the turbine housing (2).

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