EP2675999B1 - Steam turbine with dummy piston sealing arrangement for blocking saturated steam - Google Patents

Description

The invention relates to a steam turbine comprising a steam turbine having a rotatably mounted rotor, an inner housing and a high-pressure flow passage arranged between the rotor and the inner housing, the rotor having a thrust balance piston, wherein the steam turbine has a thrust balance piston line, wherein the thrust balance piston line opens into a thrust balance piston antechamber wherein the steam turbine has a wet steam line that establishes a fluidic connection between a gap space and a first pressure space, wherein the gap space between the rotor and the inner housing is arranged, wherein the thrust balance piston line is fluidly connected to a steam source, wherein the steam source disposed outside of the steam turbine wherein the steam turbine has a second flow channel and an inflow region assigned to the second flow channel, the thrust balance piston line being connected to the E inströmbereich is fluidically connected.

Conventionally, steam turbines are divided into several sub-turbines, such as a high-pressure, medium-pressure and low-pressure turbine part. The aforementioned sub-turbines differ essentially in that the steam parameters such as temperature and pressure of the incoming steam are different. Thus, a high-pressure turbine part experiences the highest steam parameters and is thus subjected to the highest thermal load. The effluent from the high-pressure turbine section steam is reheated via a reheater and forwarded to a medium-pressure turbine section, the steam usually flows without intermediate reheating after flowing through the medium-pressure turbine section in the low-pressure turbine section.

As a rule, the turbine sections are formed separately. This means that each turbine part has its own housing. However, there are also known designs in which the high-pressure turbine section and the medium-pressure turbine section are housed in a common outer housing. Likewise, sub-turbines are known in which the medium-pressure part and the low-pressure part are arranged together in an outer housing.

Particularly in the high-pressure and medium-pressure range, the turbine sections are formed with a rotor, an inner housing arranged around the rotor and an outer housing. The rotor comprises moving blades, which form a flow channel with the guide vanes arranged in the inner housing. As a rule, the high-pressure turbine sections are designed to be single-flow, with the result that a comparatively high thrust as a result of the steam pressure on the rotor leads in one direction. Therefore, the rotors are usually formed with thrust balance piston. By flow of the thrust balance piston at a defined location, a pressure is generated, which leads to a counter thrust, which holds the rotor substantially force-free in the axial direction.

The components of a steam turbine must be designed to be relatively resistant to corrosion, since some components are flown with wet steam at the same time high flow velocity of the steam. Such components would result in corrosion and erosion upon exposure to wet steam coupled with high flow velocity. This issue is currently addressed by taking relatively costly measures.

One of the measures would be, for example, the use of high-chromium materials or the use of coatings that are applied to the components and thus avoid corrosion and erosion.

Particularly in high-pressure turbine sections, the steam flowing out of the flow channel is essentially a wet steam. This means that small water particles are formed in the steam which impinge on components of the steam turbine and cause damage, such as damage to the steam turbine. lead to corrosion or erosion of the component. It is known to keep this wet steam away from the components by means of protective shields.

The object of the invention is to avoid corrosion and erosion damage caused by wet steam.

The object is achieved by a steam turbine comprising a rotatably mounted rotor, an inner housing and a high-pressure flow channel arranged between the rotor and the inner housing, the rotor having a thrust balance piston, the steam turbine having a thrust balance piston line, wherein the thrust balance piston line opens into a thrust balance piston antechamber, the steam turbine has a wet steam line which produces a fluidic connection between a gap space and a first pressure space, the gap space being arranged between the rotor and the inner housing, the thrust balance piston line being fluidically connected to a steam source, the steam source being arranged outside the steam turbine, wherein the steam turbine has a second flow channel and an inflow region assigned to the second flow channel, wherein the thrust balance piston line flows with the inflow region is not connected technically, wherein the first pressure chamber is arranged in the inflow region.

The thrust balance steam line directs steam into a thrust balance piston anvil which, as a result of the pressure, exerts a force on the rotor to compensate for thrust. The thrust balance piston is usually a section of the rotor with an ideally for the purpose desired thrust balance selected radius at an axial point corresponding pressure levels. The vestibule is located in front of a radial lateral surface. The thrust balance steam line is connected to a source of steam having a particular vapor at a pressure and a temperature. This steam mixes with the effluent from the high-pressure turbine section steam and passes between the thrust balance piston and the inner housing in a space between the inner housing and the outer housing. At the point where the steam flows out between the rotor and the inner housing, the outer housing is heavily stressed in terms of erosion and corrosion. According to the invention, the steam turbine is now carried out with a wet steam line. This wet steam line opens into a gap, which is located between the inner housing and the rotor. At this point, the wet steam flowing out of the high-pressure turbine part flow channel flows in the direction of the thrust balance piston. This wet steam line is fluidically connected to a first pressure chamber, wherein in this first pressure chamber, a lower pressure prevails than in the gap. According to the invention, this first pressure chamber is located in an inflow region. As a result, the wet steam present in this gap space is virtually completely sucked off and removed in the wet steam line. The mixing of the wet steam with the steam in the thrust balance piston antechamber is thereby drastically reduced. An outflow of a mixed vapor formed from the wet steam and the steam in the thrust balance piston antechamber is thereby almost prevented, so that virtually no mixing steam flows between the thrust balance piston and the inner housing to the outer housing. The turbine has a second flow channel, wherein the thrust balance piston steam line is fluidically connected to the second inflow region or another pressure chamber. Thus, a vapor, which may be superheated steam, passes from the second flow passage via the thrust balance piston steam line to the thrust balance piston antechamber. The outer housing can thus be made of a material having a lower corrosion and erosion resistance having. This will lead to a cheaper version of the outer housing. In addition, the leakage losses are reduced. As a result, the steam turbine efficiency increases and the wet steam line costs are lower because of simplified interconnection.

Advantageous developments are specified in the subclaims.

The invention will now be described with reference to an embodiment. Components with the same reference numbers have essentially the same functionality.

Figur 1

einen Querschnitt durch eine erfindungsgemäße Dampfturbine;

Figur 2

einen vergrößerter Ausschnitt im Bereich des Schubausgleichskolbens der Dampfturbine aus Fig. 1.

Show it:

FIG. 1

a cross section through a steam turbine according to the invention;

FIG. 2

an enlarged section in the region of the thrust balance piston of the steam turbine Fig. 1 ,

The FIG. 1 shows a cross-section of a steam turbine 1. The steam turbine 1 comprises a combined high-pressure and medium-pressure turbine part 2. An essential feature of the steam turbine 1 is that a common outer housing 3 is arranged around the high-pressure and medium-pressure turbine section 2. The steam turbine 1 comprises a rotor 4, on which a first Beschaufelungsbereich 5, which is arranged in a high-pressure flow channel 6. The rotor 4 further comprises a second blading region 7, which is arranged in a medium-pressure flow channel 8. Both the high-pressure flow channel 6 and the medium-pressure flow channel 8 comprise a plurality of rotor blades 4, which are not provided with reference numerals, and guide vanes, which are not provided with reference symbols, arranged in an inner housing 9. The terms high pressure and medium pressure turbine parts refer to the steam parameters of the incoming steam. Thus, the pressure of the steam flowing into the high-pressure turbine part is greater than the pressure of the steam flowing into the medium-pressure turbine section. The terms high-pressure and medium-pressure turbine part differ in the feature that the steam flowing out of the high-pressure turbine section is reheated in a reheater and then flows into the medium-pressure turbine section.

A common definition of high pressure and medium pressure turbine parts is not used in the art.

In the FIG. 1 shown steam turbine 1 is characterized by a common inner housing 9 for the first blading region 5 and the second blading region 7. In operation, steam flows into a high-pressure inflow region 10. From there, the steam flows through the first impingement region 5 in a first flow direction 11. After flowing through the first blading region 5, the steam flows out into a high-pressure outflow region 12 out of the steam turbine. The steam present in the high-pressure outflow region 12 has temperature and pressure values which differ from the temperature and pressure values of the steam in the high-pressure inflow region 10. In particular, the temperature and pressure values have become lower due to expansion of the steam. The steam present in the high-pressure outflow region 12 has such temperature and pressure values that this steam can be referred to as wet steam. This means that this wet steam is the smallest condensed water particles contains. These smallest water particles in the wet steam at high speeds in an impact on a component of the steam turbine 1 lead to erosion and corrosion damage. The majority of the wet steam flows out of the steam turbine 1 via the high-pressure outflow region 12. However, a residual leakage flow remains, which is arranged in a gap 13 between the rotor 4 and the inner housing 9. This wet steam located in the gap 13 flows in the first flow direction 11 and strikes a thrust balance piston 14. The thrust balance piston 14 has a thrust balance piston antechamber 15, in which a superheated steam flows. This superheated steam is located in the thrust balance piston antechamber 15 which is disposed between the thrust balance piston 14 and a rear wall 16 of the inner housing 9. The superheated steam located in the thrust balance piston antechamber 15 leads to an axially acting force on the thrust balance piston 14 and thus on the rotor 4.

Between the inner housing 9 and the rotor 4 in the region of the thrust balance piston 14 is a gap 17. Through this gap, a vapor can flow, which passes into a gap 18 which is located between the outer housing 3 and the inner housing 9. A wet steam present in the gap 17 could lead to an increased risk of corrosion and erosion of the outer housing 3.

According to the invention, a wet steam line 19 is now arranged in the steam turbine 1, which establishes a fluidic connection between the gap space 13 and a first pressure space 20, the gap space 13 being arranged between the rotor 4 and the inner housing 9. The first pressure chamber 20 is arranged in the inflow region 26. This in FIG. 1 illustrated embodiment shows that the wet steam line 19 opens into the inflow 26. The inflow region 26 has the shape of a bubble and is therefore also referred to as a medium-pressure bladder.

In operation, the wet steam arising from the first blading area 5 flows to a reheater unit (not shown). This vapor flowing out of the first blading area 5 is therefore also referred to as a cold reheater steam. In the reheater, this steam is reheated and flows from the reheater to the inflow region 26. Therefore, this steam is also referred to as a hot reheater steam.

According to the invention, a large part of the wet and cold reheater steam is thus conducted into the medium-pressure bladder. The remaining, smaller portion of the wet steam continues to flow at low speed and is dried with superheated hot reheater steam flowing over the piston equalization line. As a result, the thrust balance piston 14 and the outer housing 3 are protected from wet steam.

Also, the pressure in this first pressure chamber 20 should be such that the pressure for the wet steam in the gap 13 is greater than in the first pressure chamber 20, so that a pressure gradient in the wet steam line 19 prevails, which causes the wet steam from the gap 13 to first pressure chamber 20 passes.

The thrust balance piston 14 extends in a radial direction 22, which is formed substantially perpendicular to the rotation axis 23.

The thrust balance piston steam line 24 is fluidly connected to a steam source 25. As in FIG. 1 the inflow region 26 forms the steam source 25. This steam, which flows into the medium-pressure turbine section in the inflow region 26, is a superheated steam which enters the thrust balance piston antechamber 15. In an alternative embodiment, the steam source 25 is also arranged outside the steam turbine 1.

The inner housing 9 has a feed opening 27, with which the wet steam line 19 can be connected.

The FIG. 2 shows an enlarged section of the high pressure Ausströmbereichs 12 of the high pressure turbine section. The inner housing 9 is designed such that a high-pressure outflow region 12 is enclosed and rests in the region of the gap space 13 with respect to the rotor 4. The gap 13 should be as small as possible so that the wet steam located in the high-pressure outflow region 12 does not flow out over the gap 13. The majority of the wet steam will pass through the high-pressure discharge area 12 to a reheater. A lesser part passes as leakage flow between the rotor 4 and the inner housing 9 in the gap space 13. Therefore, a not-shown cavity is arranged in the inner housing 9, which is connected to the gap space 13. About this cavity and the wet steam line 19, the leakage flow is sucked out, so to speak. The first pressure chamber 20, which has a lower pressure than the pressure in the gap space 13, serves as the drive for this extraction. Further flow of the leakage flow formed in the gap 13 in the direction of the thrust balance piston chamber 15 is prevented by the greater part of the wet steam flowing in the wet steam line 19 is sucked off. In operation, the superheated steam, which enters the thrust balance piston antechamber 15 via a thrust balance piston line 24, spreads in two directions. A portion of the superheated steam propagates in the direction of the gap 17 and strikes the outer housing 3. Another part of the superheated steam flows in the direction of the gap 13 and is sucked as well as the wet steam through the wet steam line 19 to the first pressure chamber 20 through.

Claims (8)

1. Steam turbine (1) comprising a rotatably mounted rotor (4), an inner casing (9) and a high-pressure flow duct (6) arranged between the rotor (4) and the inner casing (9), wherein the rotor (4) has a dummy piston (14),
   wherein the steam turbine (1) has a dummy piston line (24),
   wherein the dummy piston line (24) opens into a dummy piston prechamber (15),
   the steam turbine (1) has a wet steam line (19), which establishes a fluidic connection between a gap space (13) and a first pressure space (20),
   wherein the gap space (13) is arranged between the rotor (4) and the inner casing (9),
   wherein the dummy piston line (24) is connected fluidically to a steam source (25) wherein the steam source (25) is arranged outside the steam turbine, wherein the steam turbine (1) has a second flow duct (21) and an inflow zone (26) assigned to the second flow duct (21),
   wherein the dummy piston line (24) is connected fluidically to the inflow zone (26),
   characterized in that
   the first pressure space (20) is arranged in the inflow zone (26),
   wherein the second flow duct (21) has the first pressure space (20) and a feed opening (27) for feeding steam into the first pressure space (20),
   wherein the second flow duct (21) has a plurality of blade stages arranged in series in a direction of flow and comprising guide and rotor blades.
2. Steam turbine (1) according to Claim 1,
   wherein the wet steam line (19) opens into the inflow zone (26).
3. Steam turbine (1) according to Claim 1 or 2,
   wherein the dummy piston (14) is designed to compensate for the thrust of the rotor (4) which occurs during operation.
4. Steam turbine (1) according to Claim 1, 2 or 3
   wherein the dummy piston (14) extends in a radial direction (22).
5. Steam turbine (1) according to Claim 4,
   wherein the dummy piston prechamber (15) is formed between the dummy piston (14) and the inner casing (9).
6. Steam turbine (1) according to one of the preceding claims,
   wherein the gap space (13) is arranged between the dummy piston prechamber (15) and a high-pressure outflow zone (12) of the high-pressure flow duct (6).
7. Steam turbine (1) according to one of the preceding claims,
   wherein the inner casing (9) has a cavity open toward the gap space (13).
8. Steam turbine (1) according to one of the preceding claims,
   wherein the high-pressure duct (6) and the second flow duct (21) are arranged in a common inner casing (9).

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