EP0568905A1 - Rotating disc obturator for steam turbine - Google Patents

Abstract

Steam turbines with a rotary disc valve are so constructed that control ports (11) provided in the rotary disc valve (1) and duct inlets (12) formed in a fixed duct body (2) interact in such a way that according to the respective direction of rotation of the rotary disc valve (1), the duct inlets (12) are increasingly opened or closed. Simplified manufacture and improved adaptation to different control requirements can be achieved by means of the duct body in that this comprises at least two parts. Accordingly an adapter part (2a) is provided, in which the duct inlets (12) are located and which is matched to a base part (2b), in which the steam ducts (14), required for conducting the steam and leading especially to nozzles (15), are located. The adapter part (2a) thereby defines the duct inlets (12) to be determined in accordance with the proposed control characteristic and connects the control ports (11) to the steam ducts (14). <IMAGE>

Description

The invention relates to a steam turbine according to the preamble of claim 1.

In steam turbine construction, valves are used almost exclusively to control the steam, while slides are used relatively rarely as control elements. One reason for this is probably the high reliability and the exact mechanism of action of valves and, on the other hand, the problems that have to be solved in the practical use of valves. So z. B. the static relief of slide valves which is almost a matter of course in today's valves is not readily possible. Furthermore, the sliding of ungreased, hot and possibly distorted components is fundamentally disadvantageous.

Nevertheless, there have already been a number of attempts to use rotary valves at least where, in the case of axially flow-through steam turbines, when using control valves, not only very complicated constructions arise, but also quite unfavorable flow conditions. This applies in particular to extraction steam turbines, where the use of an axially flowed rotary valve can not only lead to favorable flow conditions, but also to a space-saving construction.

To control the steam throughput in steam turbines, one works with a throttle control or a nozzle group control. The latter is particularly suitable for systems in which high partial load efficiency is to be achieved. The first control stage has a plurality of nozzle groups, the steam flow to each of the nozzle groups being adjusted using a special control valve. It is customary to apply steam to one nozzle group after the other as the power requirement increases, which is done with the help of appropriately controlled control valves or through the control slots of a rotary valve. For a given load condition, therefore, a more or less large number of nozzle groups is generally fully charged, so that this does not result in throttling and the respective nozzles work with a favorable efficiency. Only one group of nozzles is only subjected to partial loading in accordance with the respective position of the control valve or of the rotary slide valve, and as a result work with lower efficiency. However, the greater the number of nozzle groups, the smaller this loss will be, which means that as many nozzle groups as possible should be provided and ideally each individual nozzle would be controllable. A corresponding multiplication of the control valves would quickly reach constructional limits, while a corresponding design of a rotary valve is more in the area of technical possibilities.

From the magazine article "On the development of low-pressure steam control units, current status and future possibilities", mechanical engineering, Berlin, 38 (1989), pages 17 ff, rotary valve controls are known. Here you will also find an indication that rotary valves can be used for both throttle control and nozzle group control. A first variant, designed as a radial slide valve, is described, in which a large number of lockable individual windows lead into a channel body with an annular chamber located in front of the guide vane. In a second variant designed as an axial rotary slide valve, a large number of lockable individual windows are also provided, which lead directly to the guide blading via a channel body. However, both solutions are only suitable for throttle control, whereby the rotary valve can only be moved by one window division from fully open to complete shut-off.

In another magazine article "The rotary slide valve as a control device for extraction steam turbines", Maschinenbautechnik, Berlin, 15 (1966), pages 185 ff, it is stated that it is possible to arrange the cross sections of the individual groups somewhat offset in the nozzle group control. With a rotary valve designed in this way, however, it is possible to arrange only up to four nozzle groups, despite a disadvantageous reduction in cross-section. Such a small number of nozzle groups would, however, also be controllable with control valves, so that an improvement with regard to the efficiency in the part-load range of the steam turbine cannot be achieved here.

The object of the invention is to construct a steam turbine according to the type mentioned in the preamble of claim 1 in such a way that the channel body interacting with the rotary valve can be produced in a simple manner and can easily be adapted to different control tasks.

This object is achieved by the features characterized in claim 1. Appropriate refinements and developments of the subject matter of the invention are mentioned in the subclaims.

The division of the channel body into a base part and an adapter part results in a significant simplification of production. This makes it possible to have a base part that is the same for all applications, e.g. to produce as a casting and to produce different channel bodies by means of a variable adapter part adapted to different applications. The adapter part is designed as a ring which is relatively easy to manufacture and which connects the channels of the base part which have been expanded to form nozzle chambers via the channel inputs formed therein with the control slots of the rotary slide valve, provided that these are in a corresponding position. The position and size of the respective channel inputs can be adapted to a desired control characteristic in such a way that several nozzles are combined to form a nozzle group or only very specific nozzles or nozzle groups are activated. This is achieved through their interaction with the control slots provided in the rotary valve.

In an advantageous embodiment of the subject matter of the invention, it is provided that the control slots cover an angle of rotation that is at least as large as the channel inputs corresponding to them and that between the closing and opening of all channel inputs there is an angle of rotation which corresponds approximately to the angle of rotation that the channel inputs of a circular path cover. The amount of this angle of rotation can be increased or decreased, depending on the size of the number of circular paths used by control slots and channel inputs. The arrangement enables the simultaneous opening of several, at a uniform distance from each other over a rotation angle of 360 ° arranged nozzles. This means that a nozzle group is formed here, in which, however, it is not, as usual, several nozzles lying next to one another that are combined to form a group, but rather several nozzles uniformly distributed over the entire circumference. This requires a very even heating of the turbine housing and all other parts that are exposed to steam. It is disadvantageous, however, that with an increasing number of circular orbits to be provided with control slots, the arrangement becomes more complicated and with an increasing number of nozzle groups formed, the control characteristic becomes correspondingly coarser.

In a second variant it is provided that between the opening and closing of all the channel inputs there is an angle of rotation which corresponds approximately to the sum of all angles of rotation which are covered by all the channel inputs arranged on their respective circular paths. Here, the channel inputs are offset from one another on their circular path with respect to the control slots corresponding to them, so that after all the channel inputs of the first circular path have been completely opened, those of the second and subsequently any further circular paths are opened. This enables a very fine-tuned control characteristic, since only one nozzle or one nozzle group is opened one after the other. A disadvantage of this arrangement is that there is a loss of cross-section, since it is not possible to open nozzles in succession over a rotation angle of 360 ° with only one rotary valve. The angle of rotation that cannot be used for the nozzle control could, however, be made usable by opening a bypass after opening all the nozzles, which could be opened by a correspondingly offset control slot.

In a further variant it is provided that the rotary slide valve is designed as a double slide valve with two mutually overlapping partial slide valves, each of which is provided with control slots, and, starting from the closed position, a first partial slide valve driven to a rotary movement over a non-driven second partial slide valve rotates a predetermined first angle of rotation. At the end of this angle of rotation, the first slide element must grasp the second slide element and take it over a predetermined second angle of rotation. The control slots of the first slide element and the control slots of the second slide element are arranged with respect to one another and correspond to the channel inputs in such a way that one channel input after the other is opened when the first slide element rotates. The channel inputs are closed in the reverse order. With this arrangement, all of the nozzles or groups of nozzles provided can thus be controlled individually, so that a particularly fine-level control characteristic is achieved.

The adapter part, which is relatively easy to manufacture, must be adapted to the structural conditions of its surroundings. It must be anchored to the base part as precisely and tightly as possible. If necessary, it can extend into the area of the roller bearing rings provided for the rotary slide valve, so that it is then expedient to harden it at least in the area of the receptacles provided for the roller bearing rings.

So that all of the parts mentioned, such as adapter part, base part and rotary slide valve, can be installed above the shaft of the turbine, they must be radially divided into two halves and finally connected again. This can be done with the help of parting flanges.

All of the measures provided can be applied to both an axial and a radial rotary slide valve, only the channel body having to be adapted accordingly. The radial rotary valve has the advantage that it is statically relieved when steam is applied evenly over its entire circumference and thus the wear is kept within limits even with a plain bearing. A disadvantage, however, is the steam deflection required in an axially flow-through turbine. In this regard, preference is given to the axial rotary slide valve, although this can only be relieved of static load by relatively complicated designs and the bearings generally have to absorb the full mass pressure.

Embodiments of the invention are shown in the drawings and are described in more detail below.

Figur 1

eine Dampfturbinenregelstufe mit einem Axialdrehschieber zur Düsengruppenregelung in geöffnetem Zustand im Axialschnitt gesehen,

Figur 2

die Regelstufe nach Figur 1 in axialer Blickrichtung auf den Axialdrehschieber mit einem teilweise ausgeschnittenen Blickfenster zur Sichtbarmachung der Kanaleingänge in geschlossenem Zustand,

Figur 3

eine erste Variante des Drehschiebers in bestimmter Konstellation der Steuerschlitze zu den Kanaleingängen,

Figur 4

eine zweite Variante des Drehschiebers in einer gegenüber Fig. 3 anderen Konstellation der Steuerschlitze zu den Kanaleingangen,

Figur 5

einen ersten Teilschieber eines als Doppelschieber aufgebauten Drehschiebers,

Figur 6

einen zweiten Teilschieber eines als Doppelschieber aufgebauten Drehschiebers,

Figur 7

ein Adapterteil mit den Kanaleingängen,

Figur 8

ein Basisteil mit den Kanälen,

Figur 9

die geöffneten Kanaleingänge des Doppeldrehschiebers nach einer Öffnungsdrehung von 90°,

Figur 10

die geöffneten Kanaleingänge nach einer Öffnungsdrehung des Doppelschiebers von 180°,

Figur 11

die Kanaleingänge nach einer Öffnungsdrehung des Doppelschiebers von 270°,

Figur 12

die Kanaleingänge nach einer Öffnungsdrehung des Doppelschiebers von 360°.

Show it:

Figure 1

seen a steam turbine control stage with an axial rotary valve for nozzle group control in the open state in axial section,

Figure 2

2 the control stage according to FIG. 1 in the axial direction of view of the axial rotary slide valve with a partially cut-out viewing window to make the channel entrances visible in the closed state,

Figure 3

a first variant of the rotary valve in a specific constellation of the control slots to the channel inputs,

Figure 4

3 shows a second variant of the rotary slide valve in a different constellation of the control slots to the channel inputs compared to FIG. 3,

Figure 5

a first slide valve of a rotary valve constructed as a double valve,

Figure 6

a second slide valve of a rotary valve constructed as a double valve,

Figure 7

an adapter part with the channel inputs,

Figure 8

a base part with the channels,

Figure 9

the open channel inputs of the double rotary valve after an opening rotation of 90 °,

Figure 10

the opened channel entrances after the opening of the double slide by 180 °,

Figure 11

the channel inputs after an opening rotation of the double slide of 270 °,

Figure 12

the channel inputs after the opening of the double slide by 360 °.

The control stage of a steam turbine shown in FIGS. 1 and 2 lies at the interface between two turbine parts with different pressures. This is an extraction steam turbine in which the extraction takes place via an extraction channel 5 before the control stage. To control the steam flow rate is an as Radial rotary valve trained rotary valve 1 is provided, which is rotatably mounted on a channel body 2, and this in turn is flange-mounted on a fixed guide vane carrier 3. The entire arrangement is enclosed by a turbine housing 4.

The steam coming from the low-pressure part of the steam turbine flows through the rotary valve 1 in the area of a control slot 11 and passes via a channel inlet 12 of the channel body 2 into a nozzle chamber 14 and from here to a nozzle 15, in order to be directed from there to a control wheel 16 with control wheel blades 17 and finally to drive the rotor blades 19 lying between guide blades 18 and thus the turbine rotor 20.

As can be seen in particular in FIG. 2, the special design of both the rotary slide valve 1 and the channel body 2 enables a very fine-tuned nozzle group control. For this purpose, the rotary slide valve 1 has two control slots 11a, 11b which are arranged on adjacent circular paths and are offset by 180 ° to one another and correspond to the channel inputs 12 of the channel body 2. In this case, three channel inputs 12a, 12b, 12c lie on a corresponding circular path provided with the same radius as the control slot 11b, but offset by an angle of rotation of 180 °. Correspondingly, three further channel inputs 12d, 12e, 12f lie on a circular path with the same radius as the control slot 11a, again offset by an angle of rotation of 180 °.

1 shows a position of the rotary valve in which it has opened the channel inputs 12, the rotary valve 1 according to FIG. 2 is in a position rotated by 180 ° in which all the channel inputs 12 are closed. However, if you were to turn the rotary valve 1 clockwise, the control slot would be first 11a meet the channel entrance 12f and the control slot 11b meet the channel entrance 12a. The nozzle groups connected to the channel inlets 12a, 12f would therefore be the first to be supplied with steam. With increasing power requirements, the rotary slide valve could be opened more and more, the channel inputs 12e, 12b next being captured by the control slots 11a, 11b. After moving the rotary valve 1 over a rotation angle of 180 °, all the channel inputs 12 would be fully open.

As can easily be seen, two diametrically opposed channel entrances are always supplied with steam at the same time. This results in a correspondingly uniform heating of the turbine housing. Of course, it is possible to assign a different rotation angle length to the individual channel inputs 12. It would be conceivable to assign a nozzle group consisting of two or three nozzles to each of the first two channel inputs, and to provide only one nozzle per channel input for the further increase in output in order to achieve the finest possible control.

In order to enable a smooth rotary movement, two roller bearing rings 10 are provided, which can be constructed as axial needle rims for an axial rotary valve or as radial needle rings for a radial rotary valve. The roller bearing rings 10 are arranged so that the control slots 11 on the one hand and the channel inputs on the other come to lie between them and this results in the best possible support for the rotary valve. In the case of an axial rotary slide valve, an inner roller bearing ring 10b lying near the axis and an outer roller bearing ring 10a lying outside are therefore required. A toothed ring 9 is provided in the area of the outer edge of the axial rotary slide valve 1 even outside the outer roller bearing ring 10a. into which a drive pinion 8 engages, which is connected via a flexible cardan shaft 7 to a servo motor 6, which enables the rotary movement of the rotary valve 1 and is fastened to the turbine housing 4.

So that the rotary valve 1 and also the channel body 2 can be assembled with its adapter part 2a and its base part 2b over the shaft during assembly, these are horizontally divided into rotary valve halves 1a, 1b and channel body halves. Thus, the roller bearing rings, which can otherwise correspond to commercially available designs, must be divided horizontally. Parting joint flanges, such as the rotary slide joint part flange 13 shown here, make it possible to connect the two halves that belong together.

FIG. 1 also shows how the rotary valve 1 is anchored to the channel body 2 with a cam or collar 22 on the one hand and in an annular groove 21 of the channel body 2. The channel body in turn is flanged to the guide vane carrier 3 with screws 23. The two roller bearing rings 10a, 10b are largely sunk in the channel body 2.

By dividing the channel body 2 into a base part 2b and an adapter part 2a, the latter forms with the channel inputs 12 provided in it a connection between the control slots 11 of the rotary valve 1 and the channels of the base part 2b widened into nozzle chambers 14. The insertion and connection of the adapter part 2a on the base part 2b must be done in a known manner so that there is no leakage between the two parts. Otherwise, the adapter part can be adapted to the design environment, taking into account a design suitable for production. So it can possibly extend into the area of the rolling bearing rings, in which case it makes sense the adapter part 2a would be subjected to a limited or complete hardening.

FIGS. 3 to 12 show purely schematic representations of certain constellations of the control slots arranged on several circular paths, indicated only by lines, and of the channel inputs corresponding to them. In the rotary slide valves 1 shown in FIGS. 3 and 4, the channel inputs are also made visible, although these are actually covered when the rotary slide valve is viewed from above. In both examples, the rotary valve 1 is in the closed position.

If the rotary valve 1 according to FIG. 3 is moved clockwise, the first control slot S1, which extends over an angle of rotation of 270 °, will meet the first channel inputs K1 and open them one after the other. After a rotation of 90 °, the second control slot S2, which extends over an angle of rotation of 180 °, will meet the second channel inputs K2 and also open them one after the other. Finally, the third control slot S3, which only extends over an angle of rotation of 90 °, opens the third channel inputs K3. When the rotary valve 1 is fully opened, the channel inputs K1, K2, K3, which extend together over an angle of 270 °, are opened.

4 also open the control slots, SS1 to SS 4, which are arranged on four circular paths, which are offset by 90 ° to each other and extend over an angle of rotation of 90 °, so that they form an angle overall cover from 360 °, the first channel entrance of the channel inputs KA1 to KA4. So two opposite channel entrances are opened twice, which leads to the application of four symmetrically arranged nozzles or nozzle groups.

Figures 5 and 6 show two slide valves 1a, 1b of a rotary valve 1 designed as a double slide valve as separate parts next to each other in their closed position. The two slide elements 1a, 1b, the adapter part 2a shown in FIG. 7 and the base part 2b shown in FIG. 8 are actually mounted one above the other and are shown next to one another only to clarify their respective positions. The channels or nozzle chambers 14 in the base part 2b must cover all circular paths on which control slots SL or channel inputs KE are located, that is to say they must be correspondingly wide. FIGS. 9 to 12 show the various opening positions of the rotary valve 1 after a further 90 ° rotation in order to open the rotary valve in the clockwise direction.

The first slide valve 1a is driven clockwise by a servo motor, while the second slide valve 1b remains in its position. As a result, the first control slot SL1 first meets a third control slot SL3 of the second slide element 1b and opens the channel inputs KE1 arranged underneath, as shown in FIGS. 9 and 10. After a rotation of 180 °, all channel inputs KE1 below the control slots SL3 are opened. The two slide elements 1a and 1b are now connected to one another and rotated further together by a driver designed in a known manner, the control slots SL1 and SL2 being located above the control slots SL3 and SL4. The opening of the second channel inputs KE2 now beginning, as shown in FIGS. 11 and 12, is easily understandable.

With the double slide it is possible to control all the nozzles or groups of nozzles individually one after the other. The driver must be designed so that when the rotary slide 1 is turned back into the closed position, it only releases the connection of the two slide members 1a, 1b after an angle of rotation of 180 °.

Claims (9)

Steam turbine with a rotary valve (1) for controlling the steam throughput, in particular in connection with a steam extraction, and for this purpose in the rotary valve (1) provided control slots (11) and in a fixed channel body (2) formed channel inputs (12), which cooperate so that The channel inputs (12) are increasingly opened or closed in accordance with the respective direction of rotation of the rotary slide valve (1), characterized in that the channel body (2) consists of at least two parts, with an adapter part (2a) in which the channel inputs (12) are formed and with a base part (2b) in which the steam channels (14) required for the steam line, in particular leading to nozzles (15), and that the channel inputs (12) to be defined according to the intended control characteristic, the control slots (11) with the steam channels Connect (14). Steam turbine according to Claim 1, characterized in that the control slots (11) cover an angle of rotation which is at least as large as the channel inputs (12) corresponding to them and between the closing and opening of all channel inputs (12) there is an angle of rotation which corresponds approximately to the angle of rotation , which the channel inputs (12) cover a circular path and the amount of this angle of rotation is 360 ° divided by the number of circular paths. Steam turbine according to claim 1, characterized in that between the opening and closing of all the channel inputs (12) there is an angle of rotation which corresponds approximately to the sum of all angles of rotation which are covered by all the channel inputs (12) arranged on their respective circular paths, and the channel inputs (12) with respect to the control slots (11) corresponding to them on their circular path are offset from one another in such a way that after all the channel inputs (12) of the first circular path have been completely opened, the second and then possibly further circular paths are opened. Steam turbine according to Claim 1, characterized in that the rotary slide valve (1) is designed as a double slide valve with two mutually overlapping partial slide valves (1a, 1b), each of which is provided with control slots (11) and, starting from the closed position, a first to one Rotary movement of the driven partial slide (1a) rotates relative to a non-driven second partial slide (1b) over a predetermined first angle of rotation, preferably by approximately 180 °, and at the end of this angle of rotation detects the second partial slide (1b) and over a predetermined second angle of rotation, preferably again by about 180 °, and the control slots (11) of the first slide valve (1a) and the control slots (11) of the second slide valve (1b) are arranged in relation to each other and correspond to the channel inputs (12) so that when the the first slide valve (1a) opens one channel input (12) after the other and closes the channel inputs (1 2) happens in reverse order. Steam turbine according to one of the preceding claims, characterized in that the channel inlets (12) are fixed in their dimensions and positioned so that their cross-section is one or more Detect channels and thus also define the number of nozzles (15) forming a nozzle group, wherein a bypass (24) can also be provided instead of at least one nozzle (15) or nozzle group. Steam turbine according to one of the preceding claims, characterized in that the adapter part (2a) is anchored to the base part (2b) in a leakproof manner. Steam turbine according to one of the preceding claims, characterized in that the adapter part (2a) is hardened or detonation-coated completely or only in the running area of a roller bearing ring (10). Steam turbine according to one of the preceding claims, characterized in that the adapter part (2a), like the base part (2b) and the rotary slide valve (1), is horizontally divided into two halves, and these parts are placed over the shaft (20) of the turbine and together are connected. Steam turbine according to one of the preceding claims, characterized in that the rotary valve (1) is constructed as an axial or radial rotary valve and the adapter part (2a) and the base part (2b) belonging to the channel body (2) are adapted accordingly.

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