EP0568909A1 - Rotating disc obturator for steam turbine - Google Patents

Abstract

The replacement of the regulating valves usually used to control the steam flow rate by rotary disc valves is only worthwhile if significant advantages can thereby be achieved. The object of the invention is to construct a steam turbine with a rotary disc valve in such a way that, on the one hand, the steam flow rate can be adapted sensitively and more efficiently to the respective part load and that, on the other hand, the actuating forces required to change the position of the rotary disc valve are kept as small as possible. For this purpose, at least one rolling bearing ring (10), which reduces the rotary friction, is provided between a fixed passage-containing body (2) and the rotary disc valve (1) and is inserted in such a way that it lies outside the area in which control ports (11) of the rotary disc valve (1) and passage inlets (12) of the passage-containing body (2) are situated. At least two control ports (11a, 11b) are arranged in such a way on separate pitch circles that, given the appropriate direction of rotation of the rotary disc valve (1), one of the passage inlets (12) - likewise arranged on these pitch circles but appropriately offset - opens while further passage inlets (12), which can likewise be opened, are still closed. <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, in which the use of a rotary valve with axial flow not only leads to favorable flow conditions, but also to a space-saving design.

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. Here, the 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 ", Maschinenbautechnik, Berlin, 38 (1989), pages 17 ff. Rotary vane controls are known. Here there is also an indication that rotary vane can be implemented both for throttle control and for 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. Both solutions are suitable However, only for throttle control, with the rotary valve from the fully open state to complete shutdown, only to be moved by one window division.

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 steam throughput per nozzle or nozzle group can be fine-tuned to the respective partial load with a high degree of efficiency and to change the position of the rotary slide valve actuating forces to be applied are as low as possible.

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.

A decisive improvement of the rotary valve with regard to a fine control of the steam throughput is achieved in that the control slots formed in the rotary valve lie on separate circular paths and the channel inputs associated with these circular paths and formed in a channel body leading to the nozzles are arranged so offset with respect to the control slots are that on each circular path a channel entrance is opened at the same time, while further channel entrances that are also to be opened are still closed. By arranging control slots and channel inputs on several different circular paths, it is possible to open a larger number of nozzles or nozzle groups one after the other without reducing the cross-section. Another important advantage of the invention is that it is possible with the aid of a roller bearing ring to significantly reduce the high friction which occurs in conventional rotary valves with slide bearings, one or more roller bearing rings having to be arranged in such a way that they do not obstruct the control area between the control slots and the Cause channel inputs.

In principle, it is possible to arrange several control slots on several circular paths at a certain angle to one another and to the channel inputs corresponding to them, and thereby to adapt the opening behavior of the rotary valve to the desired turbine control. With two lying on different circular paths Control slots, it is appropriate to offset them by 180 ° to each other, so that accordingly the angle of rotation when adjusting the rotary valve between closing and fully opening extends over 180 °.

In order to be able to easily assemble the rotary slide valve, it is advisable to divide it horizontally into two rotary slide valve halves, which can be individually placed on the channel body and connected to one another. The connection is made in an expedient manner with the aid of rotary slide joint flanges.

It is also advantageous to provide each of the two rotary slide halves with a control slot, the control slot of the first rotary slide half correspondingly having to run on a different circular path from that of the second rotary slide half.

The construction of the rotary slide valve according to the invention enables a large number of variants to control the steam throughput. A very advantageous variant is the combination of individually controllable nozzles or nozzle groups with the activation of a bypass, which is also provided, the latter being the last to be opened after opening the nozzles.

For uniform heating of the turbine housing, it is advantageous, starting from the lowest power level, to apply steam as uniformly as possible at different points along its circumference. A further development of the subject matter of the invention therefore provides for the control slots to be arranged with respect to the channel inputs in such a way that two or more channel inputs, each at the same distance from one another, simultaneously can be opened or closed through the control slots.

A wide-area, good support of the rotary valve on the roller bearing results if the control slots and the channel inputs are between two roller bearing rings.

A preferably electrically acting servo motor, which drives a drive pinion via a flexible cardan shaft and which engages in a toothed ring provided on the rotary slide valve, serves to drive the rotary slide valve for its actuating movement.

It is also provided that the channel body as well as the rotary slide valve be divided into two channel body halves and mounted in a corresponding manner above the shaft of the steam turbine.

Due to the channel entrances lying on different circular paths, different channel body halves are required. A simplified production can be achieved in that the two halves of the channel body are cast as identical parts and the channel inlets are only produced in the channel body by subsequent machining of the cast body.

In order to reduce the leakage flow, which is not entirely avoidable in rotary valves, as far as possible, the roller bearing rings are sunk so deep into the channel body that only a narrow gap remains between the rotary valve and the channel body, which can then be sealed well in a known manner by suitable measures.

Despite the greatly reduced friction due to the rolling bearing rings, wear in the area of the running surfaces must be expected at high contact pressures. So it is expedient to harden this area on the rotary valve or to temper it by detonation coating.

The rotary valve to be rotatably mounted on the channel body is expediently connected to it in such a way that the two parts engage behind one another by corresponding ring grooves and ring cams. The channel body, in turn, can be flanged to the guide vane carrier or hung into the housing like a guide vane carrier.

All of the measures described above can be used both in the case of an axial and also 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, which takes place uniformly 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 differential 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 teilweise ausgeschnittenem Blickfenster zur Sichtbarmachung der Kanaleingänge und der Wälzlagerringe in geschlossenem Zustand,

Figur 3

die Regelstufe einer Dampfturbine mit einem Axialdrehschieber zur Steuerung eines Bypasses,

Figur 4

die Regelstufe einer Dampfturbine mit einem Radialdrehschieber zur Düsengruppen- und Bypaßregelung mit Blick in Achsrichtung in einem Schnitt quer zur Drehachse,

Figur 5

die Regelstufe nach Figur 4 seitlich gesehen im Schnitt entlang der Drehachse,

Figur 6

den Radialdrehschieber mit zwei versetzt angeordneten auf unterschiedlichen Kreisbahnen liegenden Steuerschlitzen abgewickelt.

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

1 in the axial direction of view of the axial rotary slide valve with a partially cut-out viewing window to make the channel inputs and the roller bearing rings visible in the closed state,

Figure 3

the control stage of a steam turbine with an axial rotary valve to control a bypass,

Figure 4

the control stage of a steam turbine with a radial rotary valve for nozzle group and bypass control with a view in the axial direction in a section transverse to the axis of rotation,

Figure 5

the control stage according to Figure 4 seen laterally in section along the axis of rotation,

Figure 6

the radial rotary valve with two staggered control slots located on different circular paths.

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 regulate the steam throughput, a rotary slide valve 1 designed as an axial rotary slide valve is provided, which is rotatably mounted on a channel body 2, and this is in turn flange-mounted on a guide vane carrier 3 in a stationary manner. The entire arrangement is enclosed by a turbine housing 4.

The steam coming from the high-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 by it 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 the rotary slide valve 1 were moved clockwise, the control slot 11a would first meet the channel entrance 12f and the control slot 11b would 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 increasingly, with the channel inputs 12e, 12b next would be caught 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. Even outside the outer roller bearing ring 10a, in the area of the outer edge of the axial rotary valve 1, a ring gear 9 is provided, 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 on the turbine housing 4 is attached.

So that the rotary valve 1 and the channel body 2 can be joined together during assembly above the shaft, 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 part joint 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.

FIG. 3 shows the execution of a bypass in the case of an axial rotary slide valve, the channel body only having to allow flow around the control wheel 16 in the area of the bypass 24, but otherwise correspond to all other essential details of FIG. 1.

In the control stage shown in Figures 4 to 6, the rotary valve 1 is designed as a radial rotary valve and the channel body 2 is adapted to this. Because of the principle of operation, the same reference numerals have been used. In the representation according to FIG. 4, it can be seen relatively well that one can assign to the various channel inputs 12 either several nozzle groups comprising several nozzles 15 or a bypass 24.

Claims (16)

Steam turbine with a rotary slide valve (1) for controlling the steam throughput, in particular in connection with steam extraction, control slits (11) provided in the rotary slide valve (1) having channel inputs (12) formed in a fixed channel body (2) in such a way that they interact in accordance with respective directions of rotation of the rotary valve (1) are increasingly opened or closed, characterized in that at least one rolling bearing ring (10) which reduces the rotational friction is provided between the stationary channel body (2) and the rotary valve (1) and that this lies outside the area in which are the control slots (11) and the channel inputs (12) and that at least one control slot (11) is arranged on each of at least two separate circular paths so that with the corresponding direction of rotation of the rotary valve (1) from the channel inputs arranged on corresponding circular paths ( 12) one opens at a time, while others, eb any channel entrances (12) to be opened are still closed. Steam turbine according to claim 1, characterized in that in the case of two control slots (11) of the rotary valve (1) these extend over an angle of rotation of approximately 180 ° and between the closing and the fully opening of the rotary valve (1) also an angle of rotation of approximately 180 ° lies. Steam turbine according to one of the preceding claims, characterized in that the rotary slide valve (1) is horizontally divided into two rotary slide valve halves (1a, 1b) which are individually placed on the channel body (2) and connected to one another, and the connection is preferably made using a rotary slide valve Partial joint flanges (13). Steam turbine according to one of the preceding claims, characterized in that the two associated rotary slide halves (1a, 1b) each have at least one control slot (11) and the control slot (11) of the first rotary slide half (1a) runs on a different circular path from that of the second rotary slide half (1b). Steam turbine according to one of the preceding claims, characterized in that the channel inputs (12) lead to one or more nozzles (15) or nozzle groups and possibly also to at least one bypass (24). Steam turbine according to one of the preceding claims, characterized in that the control slots (11) are arranged with respect to the channel entrances (12) in such a way that nozzles (15) or groups of nozzles which are opposite each other at the same distance are simultaneously subjected to steam. Steam turbine according to one of the preceding claims, characterized in that the control slots (11) and the channel inputs (12) lie between two roller bearing rings (10). Steam turbine according to one of the preceding claims, characterized in that the rotary slide valve (1) is driven by a preferably electrically acting servo motor (6) in order to carry out its rotations. Steam turbine according to one of the preceding claims, characterized in that the rotary slide valve (1) is provided with a toothed ring (9) located in its outer region, into which a drive pinion (8) of the servomotor (6) engages and that the servomotor (6) stationary, is preferably mounted on the turbine housing (4) and is connected to the drive pinion (8) via a flexible cardan shaft (7). Steam turbine according to one of the preceding claims, characterized in that the channel body (2) is horizontally divided into two channel body halves (2a, 2b) and these are placed one above the other and connected to one another via the shaft (20) of the steam turbine. Steam turbine according to one of the preceding claims, characterized in that the two channel body halves (2a, 2b) are cast as identical parts and the channel inputs (12) of the channels of the channel body (2) are produced by subsequent machining of the cast body. Steam turbine according to one of the preceding claims, characterized in that the roller bearing rings (10) are sunk so far into the channel body (2) that only a narrow gap remains between the rotary valve (1) and the channel body (2), which gap is known can be sealed well using suitable measures. Steam turbine according to one of the preceding claims, characterized in that the rotary slide valve (1) is hardened or detonation-coated at least in the region of its running surfaces sliding over the roller bearing rings (10). Steam turbine according to one of the preceding claims, characterized in that the rotary slide valve (1) is rotatably mounted on the channel body (2) in such a way that the two parts engage behind one another by corresponding ring grooves and ring cams. Steam turbine according to one of the preceding claims, characterized in that the channel body (2) is fastened to the guide vane carrier (3). 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 channel body (2) is adapted accordingly.

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