EP3128135A1 - Turbine design in overload inlet area - Google Patents

Abstract

The invention relates to a turbomachine, in particular steam turbine (2) with an overload inflow region (17), which is designed for the inflow of overload steam, said overload steam is prevented from hitting the rotor surface (23) by a special design of the shrouds (37).

Description

The invention relates to a turbomachine, in particular steam turbine, comprising an inflow region, a rotatably mounted rotor, a housing which is arranged around the rotor, wherein between the rotor and the housing, a flow channel is formed, flows through the flow during operation, a flow medium in a flow direction wherein the rotor includes rotor blades and the housing includes vanes, the turbomachine comprising an inflow region, the housing having an additional overload inflow region disposed downstream of the inflow region and for flowing overload vapor into the flow channel, the vanes having shrouds ,

Furthermore, the invention relates to a method for preventing thermal overload in the overload inflow region of a turbomachine.

Modern power plants are equipped with turbomachines, such as Operated steam turbines, which must meet special requirements. Since the operation of fossil power plants requires increasing overload capacity, a flexibilization of such power plants is required. A power plant usually has a steam generator or a steam boiler. As a rule, the power plant operators demand that the pressure in the boiler in overload operation does not rise or only slightly increases. This allows the boiler to be designed cost-effectively to the pressure required in nominal operation. In a pure Gleitdruckbetrieb the steam boiler, a correspondingly high boiler pressure would be required.

For this purpose, it is known to use a control stage, which is operated in nominal operation with one or more closed nozzle groups. In an overload operation these become Valves open, allowing more mass flow can be enforced without the boiler pressure must be increased. The disadvantage here is that the control stage is structurally complex and thus represents a cost-intensive factor. In addition, in rated operation or in the nominal point, the aforementioned solution has an unfavorable efficiency. In addition, this solution requires a complex valve control with many individual valves.

A common approach is to use a so-called overload introduction. This means that additional steam is supplied within the blade path via a valve closed in nominal operation. As a result, the steam mass flow is increased only from one stage of the blade path. This is also referred to as the step lockup.

The boiler pressure can thus be kept constant.

In addition, a better efficiency can be achieved at the nominal point, since here the valves can be operated fully open at the nominal point. When operating the overload introduction, the temperature distribution changes in the blade path: in particular at the point of steam injection results in a temperature jump on the shaft. These temperatures typically result in thermal stresses in the shaft and adjacent blade grooves. This could lead to frequent damage changes between a rated operation and an overload operation due to the thermal stresses to permanent damage to the shaft.

Depending on the structural design of the steam inlet, the thermal load on the shaft can be adversely affected by further effects. If z. B. the introduction of steam through radial holes constructively realized, the thermal load is also increased. The supplied overload steam is injected radially inwardly into the main flow through the radial bores. The overload steam has a higher temperature than that coming from the entrance of the turbine Steam of the mainstream. As a result, the steam does not mix immediately with the vapor of the overload steam inflow but penetrates radially the entire flow path and impinges on the shaft surface. As a result of the prevailing pressure and the occurring steam velocity, a very high heat transfer coefficient between wave and Zudampf is achieved.

It is therefore known to limit the power of the overload introduction and thereby minimize the resulting temperature differences.

It is also known to limit the load gradient with which the overload introduction is driven to power in order to extend the temperature gradient and thereby limit the resulting voltages. However, limiting the load gradient is generally undesirable.

Moreover, it is known that the wave in the area of overload introduction, e.g. specially designed by relief grooves to thereby mitigate the thermal stresses in the shaft.

The invention has set itself the task of enabling a more flexible operation of a turbomachine in particular steam turbine.

This is achieved by using a structurally modified guide vane in the area of the overload discharge, which is designed to shield the shaft from incoming overload steam in the area of the overload discharge. For this purpose, the cover plate of the following guide row is extended upstream over the overload discharge.

The invention is not limited to overload inflow areas, but can at any point in the turbomachine be used, not only with the aim of overload operation.

The object is thus achieved by a turbomachine, in particular a steam turbine, comprising an inflow region, a rotatably mounted rotor, a housing which is arranged around the rotor, wherein between the rotor and the housing a flow channel is formed, through which in operation a flow medium in one Flow direction, wherein the rotor blades and the housing includes vanes, wherein the turbomachine has an inflow region, wherein the housing has an additional Überlasteinströmbereich, which is arranged in the flow direction downstream of the inflow and is formed for the inflow of overload steam in the flow channel, wherein the guide vanes Having shrouds, which is prevented in operation of the overload steam by the shrouds on Aufteffen on the rotor in Überlasteinströmbereich.

Advantageous developments are specified in the subclaims. Thus, in a first advantageous embodiment, the shroud is arranged on the vane tip.

In a further advantageous embodiment, the shroud is formed substantially to the rotor surface, which leads to a better aerodynamic effect, since the steam from the main flow and the steam from the overload device can be optimally guided by the shroud.

In a further advantageous development, the shroud is formed from the vane tip to the adjacent blade. As a result, the shaft surface is thermally well protected, especially in this area, resulting in a more flexible operation of the steam turbine.

In a further advantageous embodiment, the shroud is formed of the same material with the guide vane. This allows a more stable construction.

In a further advantageous embodiment, the entire stator blade ring as an integral component, for. B. in the form of two half-rings. As a result, a more stable construction is possible, which is also thermally decoupled from the housing, for example, is mounted thermally movable, can be performed.

In addition, a labyrinth seal is arranged between the shroud and the rotor surface. This has the advantage that a steam that passes between the shroud and the shaft surface, is slowed down, because such a vapor is usually a loss of steam and has a negative impact on the efficiency.

In addition, the object is achieved by a method for preventing a thermal overload in Überlasteinströmbereich a turbomachine, in particular steam turbine, wherein the flowing into the Überlasteinströmbereich overload steam is prevented by a arranged at the top of the vane shroud on hitting the rotor surface in Überlasteinströmbereich.

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 connection with the following description of the embodiments, which will be described in more detail in conjunction with the drawings.

The invention will be described below with reference to the drawings. These are not intended to represent the embodiments significantly, but rather the drawing is illustrative only, executed in a schematic 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 Kraftwerksanlage umfassend eine Dampfturbine;

Figur 2

schematische Darstellung eines Überlasteinströmbereiches gemäß dem Stand der Technik;

Figur 3

eine erfindungsgemäße Gestaltung des Einströmbereiches.

Show it:

FIG. 1

a schematic representation of a power plant including a steam turbine;

FIG. 2

schematic representation of a Überlasteinströmbereiches according to the prior art;

FIG. 3

an inventive design of the inflow.

The FIG. 1 shows a schematic representation of a power plant comprising a steam turbine 2, which is formed from a high-pressure turbine section 2a, a medium-pressure turbine section 2b, and a low-pressure turbine section 2c. Furthermore, the power plant 1 comprises a steam generator 3. In the steam generator 3 steam is generated, which is generated by the use of fossil fuels. The steam generated in the steam generator flows via a main steam line 4 via a main steam valve 5 into an inflow region 6 of the high-pressure partial turbine 2a. The steam then flows into a flow channel (in FIG. 1 not shown) through the high-pressure turbine section and flows at the outlet 7 of the high-pressure turbine section 2a in a cold reheater line 8. Subsequently, the steam flows to a reheater 9 and is brought there to a higher temperature. Subsequently, the steam flows via a hot reheater line 10 to the inflow region 11 of the medium-pressure turbine section 2b. There relaxes the steam, wherein the thermal energy of the steam is converted into rotational energy of the rotor. Subsequently, the steam flows via the medium-pressure outlet 12 into an overflow line 13 to the low-pressure turbine section 2c. From there, the steam flows via the outlet 14 of the low-pressure turbine section 2c to a condenser 15 and condenses there again to water. Subsequently, the water is returned via the pump 16 to the steam generator 3 and converted there back into steam.

In addition to the inflow region 6, the high-pressure part-turbine 2a has an overload inflow region 17. This Überlasteinströmbereich 17 is fluidly connected to an overload valve 18. The overload valve 18 is fluidically connected to an overload line 19. The main steam line 4 has a branch 20, wherein a portion of the steam in the main steam line 4 is deflected to the inflow region 6 and a further part is deflected into the overload line 19.

The FIG. 2 shows a schematic representation of a part of a steam turbine according to the prior art. In the FIG. 2 Steam turbine shown has a rotor 21 which is rotatably disposed about a rotation axis 22. On the rotor surface 23 24 blades 25 are arranged in so-called blade grooves. The blades 25 have blade feet 26 disposed in the blade grooves 24.

To the rotor 21 is a housing, here an inner housing 27 is arranged. Between the inner housing 27 and the rotor 21, a flow channel 28 is formed. In operation, a vapor flows in a flow direction 29 along the flow channel 28. On the inner housing 27 so-called vanes 30 are arranged. The guide vanes 30 have guide blade feet 31 which are arranged in blade grooves in the inner housing 27. The flow channel 28 leads along a blade path formed between the vanes 30 and blades 25.

The inflow area is in the FIG. 2 not shown in detail, in certain operating cases, it is necessary to divide the steam, which is then passed over the main steam line 4 to the overload line 19 and from there into a Überlasteinströmbereich 17 is performed. As in FIG. 2 shown, the overload steam comes from the overload line 19 in the flow channel 28. In this case, the overload steam 32 flows more or less in a radial direction 33 in the direction of Rotor surface 23. As a result, the rotor surface 23 is thermally heavily loaded. It is therefore common in the prior art, in the region of the inflow region 17, which is characterized by a distance between a first blade 34 and a second blade 35 to arrange relief grooves 36.

The FIG. 3 shows an inventive arrangement of the inflow 6 of the steam turbine. 2

Components with the same mode of operation have the same reference numerals.

The difference of the inflow area 6 as in the FIG. 3 is shown, with respect to the inflow 6 as in the FIG. 2 is shown, is that in operation, the overload steam 32 is prevented by a shroud 37, which is arranged on the vane tip 38, from hitting the rotor 21. The hot overload steam 32 thus no longer impinges directly on the rotor surface 23, but is prevented by the shroud 37 therefrom. The shroud 37 protrudes from the vane tip 38 to the next blade 34. The first blade 34 is disposed adjacent to the vane 30. The shroud is formed of the same material with the guide vane 30.

The shroud 37 is integrally connected to the guide vane 30.

Between the shroud 37 and the rotor surface 23, a labyrinth seal 39 is formed.

The Überlasteinströmbereich 17 is arranged downstream of the inflow 6 in the flow direction.

The turbomachine according to FIG. 3 is used to prevent thermal overload in Überlasteinströmbereich 17 a turbomachine, in particular steam turbine, wherein the overloading steam 32 flowing in the overload inflow region 17 is prevented from impinging on the rotor surface 23 in the overload inflow region 17 at the tip of the guide vane 38.

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 (10)

Flow machine,
in particular steam turbine (2) comprising an inflow region (6), a rotatably mounted rotor (21), a housing which is arranged around the rotor (21),
wherein a flow channel (28) is formed between the rotor (21) and the housing, through which in operation a flow medium flows in a flow direction (29), wherein the rotor (21) comprises moving blades (25) and the housing, guide vanes (30). includes,
the turbomachine having an inflow region (6), wherein the housing has an additional overload inflow region (17) which is arranged downstream of the inflow region (6) in the flow direction (29) and is designed to feed overload vapor into the flow channel (28),
the guide vanes (30) having shrouds (37), characterized in that
In operation, the overload steam (32) is prevented from hitting the rotor (21) in the overflow inflow region (17) by the shrouds (37). Turbomachine according to claim 1,
wherein the shroud (37) is disposed on the vane tip (38). Turbomachine according to claim 1,
wherein the guide vanes (30) and shrouds (37) are designed as an integral component. Turbomachine according to claim 1,
wherein the guide vanes (30) and shrouds (37) are designed as integral half-rings. Turbomachine according to one of the preceding claims,
wherein the shroud (37) is formed substantially parallel to the rotor surface (23). Turbomachine according to one of the preceding claims,
wherein the shroud (37) protrudes from the vane tip (38) to the adjacent blade (25). Turbomachine according to one of the preceding claims,
wherein the shroud (37) of the same material with the guide vane (30) is formed. Turbomachine according to one of claims 1 to 7,
wherein the shroud (37) is integrally connected to the guide vane (30). Turbomachine according to one of claims 1 to 8,
wherein between the shroud (37) and the rotor surface (23) a labyrinth seal (39) is arranged. Method for preventing thermal overload in the overload inflow region (17) of a turbomachine, in particular a steam turbine (2),
wherein the overload vapor (32) flowing into the overload inflow region (17) is prevented from hitting the rotor surface (23) in the overload inflow region (17) by a shroud (37) disposed at the tip of the vane (30).

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