EP0886722A1

EP0886722A1 - Prevention of encrustation of a steam turbine blade by injection of pure steam

Info

Publication number: EP0886722A1
Application number: EP97915337A
Authority: EP
Inventors: Heinrich Oeynhausen
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1996-03-14
Filing date: 1997-03-06
Publication date: 1998-12-30
Anticipated expiration: 2017-03-06
Also published as: CN1084823C; JP3863185B2; EP0886722B1; WO1997034075A1; DE59710616D1; CN1218533A; JP2000506246A

Abstract

The invention concerns a steam turbine (14) with a turbine blade (1) aligned along a principal axis (2) and provided with a curved flow surface (3) for steam. A fluid feed duct (5) is provided in the interior (4) of the turbine blade (1) and connected fluidically to a plurality of fluid outlets (6), each fluid outlet (6) opening out at the flow surface (3) to deliver pure steam. Feeding pure steam creates a protective fluid film, in particular of steam, over the flow surface and if necessary other areas of the turbine blade surface. The steam film forms a boundary layer around the turbine blade which to a large extent keeps the steam flowing through the steam turbine away from the blade surface. It is therefore possible to operate the steam turbine with a corrosive steam produced, for example, from drying brown coal or other combustible material. The steam film prevents impurities from becoming encrusted. The invention also relates to a use of the steam turbine (14) in a facility (17) for drying brown coal, in which the steam released in the drying process is fed into the steam turbine (14).

Description

description

PREVENTION OF SCALING A STEAM TURBINE BLADE BY PURE STEAM ^¬ SPRAYING.

The invention relates to a steam turbine, in particular a low-pressure steam turbine, with a turbine blade, which is directed along a main axis and has a curved inflow surface for steam, and a use of the steam turbine.

DE 43 35 598 AI deals with the subject of fouling on a compressor or a expansion gas turbine which is connected upstream of a gas turbine system. There is a risk that icing or accumulation of

Dirt particles take place since air is cooled from the compressor and fed to the expansion gas turbine. This is to be prevented by providing a central bore in the blades of the expansion gas turbine and radial bores branching from there and leading to the blade surface. The blades are heated by air heated in the compressor, which leads to melting of the egg. This creates a water protection film on the surface of the blades of the expansion gas turbine, through which dirt particles may also be removed. The expansion gas turbine is operated with the same medium, namely the air compressed by the compressor, with which the blades are already flowing.

From the book "Dampf urbinen" by F. Dietzel, 3rd edition,

1980, Carl Hanser Verlag Munich - Vienna, various steam turbines are known. Section 3.3.3 "Erosion of the blade edges" deals with the avoidance of erosion occurring at the trailing edges in large condensation steam turbines. To reduce the erosion that occurs, drainage of the steam turbine on the one hand and mechanical processing of the turbine blades specified. This mechanical processing consists of soldering wear-resistant materials or induction hardening of the turbine blade.

The object of the invention is to provide a steam turbine which is suitable for operation with aggressive steam. Another object is to specify the use of such a steam turbine.

The object directed to a steam turbine is achieved by a steam turbine, in particular a low-pressure steam turbine, which has a turbine blade which is directed along a main axis, a blade root for anchoring in a housing (guide blade) or a turbine shaft (Laufschaufei), a curved inflow surface for steam and in its interior has a fluid supply, which fluid supply is fluidly connected to a plurality of fluid outlets, each fluid outlet opening at the inflow surface, and which opens outward in the blade root is, a flow channel for supplying pure steam into the fluid supply is provided in a recess receiving the blade root.

By supplying pure steam or another contamination-free fluid through the blade root and the turbine blade to the inflow surface, a protective fluid film, in particular steam film, is generated over the inflow surface and possibly other areas of the surface of the turbine blade . This vapor film forms one

Boundary layer around the turbine blade, which largely keeps the steam flowing through the steam turbine away from the surface of the turbine blade. This makes it possible to operate the steam turbine with an aggressive steam, for example from the drying of brown coal or other combustible material, such as house or Industrial waste that becomes contaminated. In particular, sodium, potassium, calcium, magnesium, iron, chloride, nitrates and sulfates can occur as impurities. A steam generated during the drying of brown coal is called "vapor steam". The vapor film around the inflow surface avoids the accumulation of contaminants and significantly reduces the risk of corrosion and erosion.

By means of a turbine blade, which has a fluid supply with a fluidic connection to the inflow surface, during operation of a steam turbine with aggressive steam it is achieved that the fluid flowing through the fluid supply and exiting at the outflow surface largely removes the aggressive steam from the Surface of the turbine blade is kept away. Depending on the required throughput of fluid through the fluid supply, this is designed appropriately dimensioned. In this case, it can be designed as a bore or a plurality of bores, and can represent an inner hollow region of the turbine blade. The aggressive one

Steam, which originates, for example, from the drying of wet brown coal, can contain strong impurities, which can lead to erosion, corrosion or deposits in a normal turbine blade. Of course, the turbine blade can be provided with a special material, for example with a low stress state, or a special coating on the surface for further protection against erosion and corrosion.

The turbine blade preferably has a blade root

Anchoring in a housing (guide vane) or in a turbine shaft (rotor blade) of a steam turbine, the fluid supply in the blade root being open to the outside. A supply of fluid, in particular pure steam or air, is thus structurally simple through the blade root via the housing or the turbine shaft into the fluid supply into it. The supply of the fluid thus also leads to at most low flow resistances and efficiency losses in the steam turbine.

The fluid supply is essentially parallel to the main axis. The fluid supply can have an axial bore or a plurality of axial bores.

The fluid discharges are preferably directed essentially perpendicular to the main axis. As a result, they are particularly simple to manufacture, for example as bores or by casting. Forming the fluid supply and the fluid discharge as bores also allows them to be subsequently introduced into the turbine blade. As a result, the distribution of the fluid discharges on the inflow surface and in other surface areas of the turbine blade can also be subsequently changed in accordance with the steam conditions in a steam turbine. By supplying pure steam via the fluid discharges, the surface area and the surface areas lying further downstream are removed

Turbine blade creates a vapor film. This steam film reduces or completely prevents contact of the aggressive steam, which is contaminated with impurities, with the surface of the turbine blade. The steam film also prevents deposits from being carried in the aggressive steam

Contamination on the surface and thus also causes at least a significant reduction in erosion and corrosion on the inflow surface of the turbine blade.

The flow channel is preferably embodied in the recess as a groove which connects a plurality of turbine blades, ie their blade roots, to one another in terms of flow technology. The groove is preferably designed as an annular groove in the housing of the steam turbine or in the turbine shaft. The steam turbine is particularly suitable for use in a plant for drying fuel, in particular wet brown coal, for a power plant. By drying wet lignite, for example, the efficiency of a lignite-fired power plant can be increased. The lignite can be dried with low-quality steam, for example from a tap in a low-pressure partial tower. The moisture evaporating from the brown coal is collected in the steam and brought up to a saturated steam state. This saturated steam can be expanded to below 0.1 bar in a low-pressure turbine. As a result, at least part of the thermal energy that is used to dry the wet lignite is recovered. The steam generated from the wet lignite may contain strong impurities, in particular sodium, potassium, calcium, magnesium, iron, chloride, nitrates and sulfates. When a low-pressure steam turbine is operated, this could lead to increased corrosion and / or erosion of the turbine blades, which is largely avoided in the steam turbine according to the invention by the design of the turbine blades.

The steam turbine with turbine blade and the use of a steam turbine are explained in more detail with the aid of the exemplary embodiments shown in the drawing. Show it:

1 shows a detail of a steam turbine with turbine blades in a longitudinal section, FIG. 2 shows a cross section through a turbine blade according to FIGS

3 shows a schematic arrangement of a steam turbine in a drying plant for fuel or waste.

1 shows a section of a longitudinal section through a steam turbine 14, in particular a low-pressure steam turbine. In a housing 8 of the steam turbine 14 is one Turbine shaft 9 shown. The turbine shaft 9 has ring-shaped recesses 12 for receiving rotor blades la. Analogously, the housing 8 has annular recesses 12 for receiving guide vanes 1b. For the sake of clarity, only one rotor blade la and one guide blade lb are shown. Each turbine blade 1, ie each rotor blade 1 a and each guide blade 1 b, has a corresponding blade root 7. The shape of the respective recesses 12 is adapted to that of the blade root 7. Each turbine blade 1 is directed along a main axis 2. Starting from the blade root 7, in each turbine blade 1 shown there is a fluid supply 5, which runs parallel to the main axis 2 and penetrates the turbine blade 1 almost completely and is designed as a bore. A plurality of fluid outlets 6, likewise designed as bores, branch off vertically from the fluid supply 5. The fluid discharges 6 extend from the fluid feed 5 to one of the semicircular inflow surfaces 3 facing the steam flow 14 operating the steam turbine 14 (see FIG. 2). The fluid discharges 6 are distributed over the inflow surface 3 forming part of the surface of the turbine blade 1 such that the inflow surface 3 is covered with a vapor film 11. The steam film 11 is created by a steam flow 10 which is supplied via a flow channel 13 running in the recess 12. The inflow surface 3 and possibly further downstream surface areas of the turbine blade 1 are thus protected against the steam flow 21. Contaminants carried in the steam flow 21, for example from the drying of wet lignite, do not therefore accumulate on the inflow surface 3, nor do they lead to increased corrosion or erosion of the turbine blade 1. The flow duct 13 is a circumferential one in the recess 12 Groove 13a, through which all turbine blades 1 of a guide blade row or a rotor blade row are connected to one another in terms of flow. The groove 13a can, for example, via an axial bore (not shown) in the turbine shaft 9 or the housing 8 are supplied with pure steam 16, it being possible for a plurality of axially spaced grooves 13a to be connected to such a bore.

2 shows, on an enlarged scale, sections of a cross section through a row of moving blades with two moving blades 1a. Each rotor blade la has a semicircularly curved inflow surface 3 directed in the direction of the main axis 2. The fluid feed 5, which is designed as a bore with a circular cross section, is arranged approximately in the center of the semicircularly curved inflow surface 3. In the cross section shown, a fluid discharge 6 leads from the fluid supply 5 directly opposite the main direction of the steam flow 21 to the inflow surface 3. In a further cross section running in the direction of the main axis 2 above and below the cross section shown, there are two at an angle of Further fluid outlets 6 rotated about 45 ° relative to the fluid outlet 6 are shown. A particularly uniform formation of the vapor film 11 is achieved by an arrangement of fluid discharges 6 alternating in the direction of the main axis 2.

3 schematically shows an arrangement of a power plant 19 with a high-pressure turbine 22, a low-pressure turbine serving as a steam source 20 and a generator 15 connected to it. The low-pressure turbine is a steam source 20 for pure steam 16 and has a tap for discharge of low pressure steam. This pure steam 16 is fed to a plant 17 for drying a fuel 18 or waste. Drying produces an aggressive steam which contains impurities such as sodium, potassium, calcium, magnesium, iron, chloride, nitrates or sulfates. This steam is fed to a low-pressure steam turbine 14, which is also connected to a generator 15. This low-pressure steam turbine 14 has, analogously to FIG. 1 and FIG. 2

Turbmenschaufein 1, which through a m their interior horizontal fluid supply of pure steam 16 is supplied to the steam source 20. This clean steam 16 emerges at an inflow surface 3 of the turbine blades 1, as a result of which they are protected against the aggressive steam.

The invention is characterized by a steam turbine with a turbine blade, which has a fluid supply in its interior, in particular for pure steam, which is connected to an inflow surface via a plurality of fluid discharges. By supplying pure steam, in particular via the blade root of the turbine blade, into the fluid supply and thus to the inflow surface, a steam film covering the inflow surface is formed. This provides protection against aggressive steam with which the steam turbine in which the turbine blade is arranged is operated. A steam turbine with such a turbine blade is preferably suitable when using an aggressive steam from a drying process of wet lignite, in which steam with strong impurities is generated. The constructive supply of clean steam thus reliably prevents the aggressive impurities from being deposited on the surface of the turbine blade and at least significantly reduces erosion and corrosion of the turbine blade.

Claims

claims

1. steam turbine (14) for impinging contaminated steam, in particular low-pressure steam turbine, with a turbine blade (1) which is directed along a main axis (2), a blade root (7) for anchoring in a housing ( 8) or a turbine shaft (9), a curved inflow surface (3) for steam, and in its interior (4) a fluid feed (5) which fluid feed (5) a) with a plurality of fluid discharges (6) flow ¬ is technically connected, each fluid discharge (6) opening at the inflow surface (3), and b) the blade root (7) is open to the outside, with a flow channel (13) in a recess (12) receiving the blade root (7) for supplying pure steam (16) to the fluid supply (5) is provided.

2. Steam turbine (14) according to claim 1, in which the fluid discharges (6) of the turbine blade (1) are distributed over the inflow surface (3) in such a way that a steam stream (10) fed in via the fluid feed (5) is one steam film (11) which covers the inflow surface (5) in a protective manner.

3. Steam turbine (14) according to claim 1 or 2, wherein the fluid supply (5) of the turbine blade (1) runs essentially parallel to the main axis (2).

4. Steam turbine (14) according to one of the preceding claims, in which each fluid discharge (6) of the turbine blade (1) is directed substantially perpendicular to the main axis (2).

5. Steam turbine (14) according to one of the preceding claims, wherein the flow channel (13) is a m of the recess (12) with several Turbmenschaufein (1) fluidically connected groove (13a).

6. Use of a steam turbine (14) according to claim 4 or 5, in a system (17) for drying fuel (18), in particular lignite, for a power plant (19), which for the purpose of drying over the fuel ( 18) guided steam (10) is fed to the steam turbine (14) and pure steam (16) is fed to the flow duct (13) to protect the turbine blades (1) from a steam source (20), for example a steam turbine of the power plant (19) becomes.