EP0508067B1 - Device for regulating the cross-sectional flow area of a turbomachine - Google Patents

Description

Technical field

The invention relates to a device for the regulated loading of the diffuser of axially flowed through turbomachines, in particular of extraction steam turbines, with a control slide arranged at least two inlet windows for the working medium and arranged upstream of the diffuser.

State of the art

In the case of steam turbines, the nozzle group control is particularly suitable for systems in which high partial load efficiency is required. The first turbine stage, which is usually equipped with a constant pressure or Curtis blading, also called a control stage, has a plurality of admission sectors, the steam inflow from the steam generator to each of the admission sectors having one special control valve is set. It is customary to open one control valve after the other with increasing output of the steam turbine. For a given load condition, therefore, a more or less large number of control valves is generally fully open and therefore does not cause throttling. Only one of the control valves will be partially open and cause an additional throttle loss. This loss can, however, be kept to a modest extent, because it only affects the partial mass flow flowing through the respective control valve. And this subset will be the smaller, the greater the number of impact sectors. The result of this is that ideally an infinite number of control valves and pressurization sectors are to be provided. In practice, machines are known which have up to 10 pressurization sectors and associated control valves and thus permit very fine-level control. The arrangement with 4 segments is the most common; almost all reheater turbines work in this way today. With 4 valves it is possible to distribute the nozzle area over the circumference by 20%, 20%, 30%, 30%. This means that valve points with approximately the following outputs can be moved during machine operation: 30%, 60%, 90%, 100%. At today's high steam temperatures, the first opening nozzle surfaces are usually arranged symmetrically in the lower and upper part of the housing, so that asymmetrical temperature distributions are avoided when starting up.

Devices for regulating the cross-section through which a turbomachine flows are also used in steam extraction turbines. They allow a variable steam mass flow to be branched out of the turbine, for example for process purposes. In the case of conventional steam turbines with axial flow, such controlled withdrawals are known in which the entire mass flow after flowing through a turbine part led out of the turbine, regulated and then reintroduced into the subsequent sub-turbine. For each internally controlled withdrawal, several successively opening overflow control valves are flanged onto the turbine housing, with which the steam quantity flowing into the subsequent turbine part is controlled and the extraction pressure is thereby kept constant.

Furthermore, devices with which the free cross-section through which flow is changed in the guide apparatus for regulating the steam mass flow are also known in the form of adjustable guide vanes. For example, the guide vanes can be rotated about their own longitudinal axis in order to reduce the cross section. The fulcrum can be on the front edge of the blade, within the blade profile or on the rear edge of the blade. With all these variants, the cross-section through which the flow is flowing can be completely blocked on the occasion of an adjustment. The aerodynamically important blade geometry is also retained. However, with these solutions, the inflow and outflow of the guide vanes are changed to a greater or lesser extent, which impairs the operation of at least the immediately following rotor blades.

Devices of the type mentioned are known from the magazine article "For the development of low-pressure steam control elements, current status and future possibilities", Machinenbautechnik, Berlin, 38 (1989), pages 17 ff. In a first variant, the working medium, here low-pressure steam, passes over Radial rotary valve with a large number of lockable entry windows into an annular chamber in front of the guide grille. In a second variant, the working medium enters the guide blading directly via axial rotary valves with a large number of lockable entry windows. Both solutions are suitable for throttle control, whereby from the fully open state to complete shut-off Rotary sliders are to be moved by one window division.

Presentation of the invention

The invention has for its object to provide a simple adjusting device for nozzle group control, while avoiding the above-mentioned number of control valves, with which the inflow conditions to the guide device and the outflow conditions from the guide device remain unchanged.

According to the invention, this is achieved in that a channel element is arranged between the control slide and the guide apparatus, with a plurality of inflow channels which connect the inlet windows of the control slide to the nozzles of the guide apparatus, the control slide being rotatable by 180 ° in the circumferential direction for increasing opening and closing of the inflow channels .

It is expedient if each individual nozzle of the diffuser is acted on via its own inflow channel.

Apart from the simplicity of the measure, the advantages of the invention can be seen in particular in the high efficiency that can be achieved. On the one hand, a large number of lossless operating points can be driven, and on the other hand, there is an optimal inflow for the nozzles in question.

Brief description of the drawing

In the drawing, two exemplary embodiments of the invention are shown using an extraction steam turbine through which there is an axial flow.

Fig.1

einen schematischen Längsschnitt durch eine Entnahme-Damptturbine;

Fig.2

einen Querschnitt durch eine erste Ausführungsvariante der Erfindung im Hochdruck-Eintrittsteil der Turbine gemäss Linie 2-2 in Fig.1;

Fig.3

einen Querschnitt durch den Hochdruck-Eintrittsteil der Turbine gemäss Linie 3-3 in Fig.1;

Fig.4

einen Teilquerschnitt durch die Regelvorrichtung gemäss Detail Z in Fig.2, jedoch in geschlossenem Zustand;

Fig.5

die teilweise Abwicklung eines Zylinderschnittes in der Ebene gemäss Linie 5-5 in Fig.1 auf halber Höhe der Leitbeschaufelung;

Fig.6

die Abwicklung des Verstellelementes im Hochdruck-Eintrittsteil der Turbine;

Fig.7

einen Querschnitt durch eine zweite Ausführungsvariante der Erfindung im Niederdruck-Eintrittsteil der Turbine gemäss Linie 7-7 in Fig.1.

Show it:

Fig. 1

a schematic longitudinal section through a removal steam turbine;

Fig. 2

a cross section through a first embodiment of the invention in the high pressure inlet part of the turbine according to line 2-2 in Figure 1;

Fig. 3

a cross section through the high pressure inlet part of the turbine according to line 3-3 in Figure 1;

Fig. 4

a partial cross section through the control device according to detail Z in Figure 2, but in the closed state;

Fig. 5

the partial development of a cylindrical cut in the plane according to line 5-5 in Figure 1 halfway up the guide blading;

Fig. 6

the handling of the adjusting element in the high-pressure inlet part of the turbine;

Fig. 7

a cross section through a second embodiment of the invention in the low-pressure inlet part of the turbine according to line 7-7 in Fig.1.

Only the elements essential for understanding the invention are shown. The system does not show, for example, the actual inlet elements, the bearings and their bearing housings, the various taps, the exhaust part and the driven element, for example a generator. The direction of flow of the working fluid is indicated by arrows.

Way of carrying out the invention

The extraction turbine shown in FIG. 1 is a single-shaft, two-part turbine with internally controlled extraction 1, for example for process steam. It consists of a high pressure turbine 3 in the back pressure type and a low pressure turbine 3 'in the condensation type. The latter is necessary to compensate for the fluctuations in the power requirement of the company if, for example, the frequency must also be maintained in addition to the regulated steam pressure in the extraction 1.

The rotor blades of the two partial turbines are arranged on a common rotor 4. The blade carriers 6, 6 'are suspended in the largely cylindrical turbine housing 5 so that they can be moved by heat. The live steam flows into the diffuser 7 of the high-pressure turbine 3 via an inlet housing 2 connected to the turbine housing 5, from where it acts on the control stage blading of the control wheel 8. This control stage blading usually works according to the constant pressure principle and is carried out in one stage in the case shown. The steam then flows through the reaction blading of the high-pressure turbine 3, which is only shown symbolically, and reaches the high-pressure exhaust steam 9. In contrast to the above-mentioned solution with overflow control valves, the steam to be expanded remains within the turbine housing 5. The steam not removed in 1 flows through the low-pressure turbine 3 '. From the outlet, the steam reaches the exhaust steam housing, not shown, and from there into a condenser, on the cooled pipes of which the now relaxed steam is deposited.

So far extraction condensation turbines are known. The new regulating device can be used both on the high-pressure turbine 3 for fresh steam regulation and on the low-pressure turbine 3 'for regulating the extraction.

According to FIG. 1, the guide apparatus 7 on the high-pressure turbine consists of a nozzle box, which is integrated in a channel element 10 designed as a ring. Depending on the steam data, the individual nozzles, in this case 42 in number, can either be inserted and caulked in the channel ring or welded into the channel ring. The two-part channel ring, which will generally be designed with a horizontal partial plane, is on the one hand suspended in the inlet housing 2 and, on the other hand, surrounds the compensating piston 11 of the high-pressure turbine with its radially inner diameter. On its inner circumference, it is provided with a labyrinth 12 over its axial extent in order to form the piston seal.

2, the channel ring 10 is provided over its circumference with two symmetrically arranged sectors of inflow channels 13. These inflow channels, of which each sector has 20 pieces, each open into a nozzle of the guide apparatus (FIG. 5). This ensures optimal inflow to the nozzles. In the present case, only the inflow channel 13a opening when the machine starts up extends over two nozzle divisions in order to keep the mechanical stresses on the control wheel within limits. The dimensions of the inflow channels are unchanged. The adaptation to the swallowing capacity of the blading is advantageously done via the geometry of the nozzles. For example, their width can be adapted to the prevailing conditions over the circumference and / or their radial height. At the inlet end, the inflow channels 13 are guided radially out of the channel ring. The actual inlet openings of the channels of the upper sector and the lower sector are offset from one another in the axial direction (FIG. 1) and are accordingly located on two different levels.

The steam enters the inflow channels 13 via a control slide 14 provided with two entry windows 15. In the simplest case, this two-part radial slide, which is also formed with a horizontal partial plane, is a ring which surrounds the channel ring 10 with its inner diameter and seals against it. The ring must be able to operate in the closed state, i.e. without the inflow of steam into the inflow channels, to be able to absorb the maximum pressure drop without great deformation. Since the permanently open entry windows are acted upon by the working medium even in the non-flowed state, the radial slide is equipped with sealing strips (not shown) for sealing purposes in its axial extension on both sides of the entry window. The two inlet windows 15, which have the same axial displacement relative to one another as the corresponding inlet openings of the inflow channels 13, extend in the circumferential direction over an angular range which corresponds to that of the 20 associated inflow channels. It follows from this that the radial slide should be rotatable by 180 ° from the fully closed to the fully open position. Since a seal is required not only at the side of the inlet window but also in the circumferential direction when the position is closed, the channel ring according to FIG .

The aforementioned rotation of the radial slide by 180 ° can be done in a simple manner according to FIG. 3. On one of its end faces, the slide is provided over the circumference with a toothing 17 (only partially shown) into which a pinion inserted from the outside and driven through the upper part of the inlet housing 2 engages. The radial slide valve, which is only shown schematically, is provided by four roller bolts 18, which are evenly distributed over the circumference.

On the occasion of the rotation from the closed state (FIG. 4), the two opposite inflow channels 13a first open, and with increasing rotation of the radial slide, further opposite inflow channels 13 are flowed through by the working medium. In the present case, so-called valve points, i.e. almost lossless operating points, can be driven with the system. The new solution thus corresponds to the effect of 20 of the control valves mentioned at the beginning. In addition, the simultaneous loading of opposite inflow channels enables the subsequent turbine part to be warmed up evenly and avoids any additional bearing load.

The right part of FIG. 1 and FIG. 7 show an exemplary embodiment of the invention in the area of internally regulated steam extraction. Since there are significantly lower vapor pressures and thus pressure drops in this area, a simplified variant can be used. This has the additional advantage that the axial flow direction of the steam is not interrupted at the point of withdrawal. In addition, it is characterized by a short axial length.

The channel element here is a channel disk 19, in which the control device 20 of the control stage is integrated. The two-part channel disk, which will also generally be designed with a horizontal partial plane, is on the one hand suspended in the turbine housing 5 and, on the other hand, surrounds the low-pressure rotor 4 of the turbine with its radially inner diameter. On its inner circumference, it is provided with a labyrinth over its axial extent to form a seal.

The channel disk 19 is provided with two symmetrically arranged sectors of inflow channels 21 over its circumference. These inflow channels, each sector having 20 pieces, each lead into a nozzle of the control apparatus 20. Only the inflow channels 21a opening or closing last, in the present case, extend over two nozzle divisions in order to keep the mechanical loads on the downstream control wheel within limits.

At the inlet end, the inflow channels 21 are guided axially or obliquely axially out of the channel disk 19. The actual inlet openings of the channels of the upper sector and the lower sector are offset from one another in the radial direction and are therefore located in two different radial planes.

In the inflow channels 21, the non-extracted steam passes through a control slide 23 provided with two entry windows 22. In the simplest case, this two-part axial slide, which is also formed with a horizontal partial plane, is a disk which rests against the end face of the channel disk, is guided there and seals against it. The two entry windows 22, which have the same radial displacement relative to one another as the corresponding inlet openings of the inflow channels 21, extend in the circumferential direction over an angular range which corresponds to that of the 20 associated inflow channels. This means that the axial slide must be rotatable by 180 ° from the fully closed to the fully open position.

Claims (4)

1. Arrangement for controlled admission to the nozzle assembly (7,20) of axial flow turbomachines, in particular of extraction steam turbines (3,3'), having a control valve (14,23) which is located upstream of the nozzle assembly and has at least two inlet windows (15,22) for the working medium, characterized in that a duct element (10,19) is located between control valve (14,23) and nozzle assembly (7,20), which duct element has a plurality of inlet flow ducts (13,21) which connect the inlet windows (15,22) of the control valve (14,23) to the nozzles of the nozzle assembly (7,20), the control valve being rotatable by 180°C in the peripheral direction for the increasing opening or closing of the inlet flow ducts.
2. Arrangement according to Patent Claim 1, characterized in that the duct element is a duct ring (10) and the control valve is a radial valve (14), the radially inner diameter of the duct ring (10) surrounding the balance piston (11) of the turbine (3) and being surrounded on its radially outer diameter by the radial valve (14) and the at least two inlet windows (15) in the radial valve being offset in the axial direction relative to one another.
3. Arrangement according to Patent Claim 1, characterized in that the duct element is a duct disc (21) and the control valve is an axial valve (23), the at least two inlet windows (22) in the axial valve (23) being offset in the radial direction relative to one another.
4. Arrangement according to Patent Claim 1, characterized in that working medium is admitted to each nozzle of the nozzle assembly (7,20) via its own inlet flow duct (13,21).

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