EP0493627A1 - Device for regulating the effective cross-sectional area of a turbomachine - Google Patents

Abstract

In a device for regulating the free cross-section in the guide vanes of pass-out turbines, pins (13) can be introduced between in each case two adjacent vane lobes of the guide vanes (12a) of the first stage, being introduced radially from the vane root (15) of the guide vane as far as the vane tip opposite the rotor (4) of the turbomachine, in the narrowest cross-section between two guide vanes (12a). <IMAGE>

Description

Technical field

The invention relates to a device for regulating the free cross section in the diffuser of axially flowed through turbomachines, in particular extraction steam turbines.

State of the art

Such devices are usually 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 conventional, axially flow-through steam turbines, such controlled withdrawals are known in which the entire mass flow after flowing through a turbine part is led out of the turbine, regulated and then reintroduced into the subsequent sub-turbine. For each internally regulated removal, 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 removal pressure is thereby kept constant.

Devices of the type mentioned at the outset, in 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 lie on the front edge of the blade, within the blade profile or on the rear edge of the blade. In all of these variants, the cross-section through which the flow passes 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.

Presentation of the invention

The invention tries to avoid these disadvantages. It is the object of the invention to create an adjusting device with which the inflow conditions to the guide apparatus remain unchanged and the outflow conditions are only moderately influenced by the guide apparatus.

According to the invention, this is achieved in that a pin penetrating the blade carrier of the turbomachine can be inserted radially from the blade root of the guide blade to the blade tip opposite the rotor of the turbomachine between each two adjacent blade blades of the guide blades of the first stage.

The advantages of the invention can be seen, inter alia, in that the flow channel is narrowed over the height. This means among other things. that the unobstructed part of the blade profiles does not experience any aerodynamic deterioration. Furthermore, there is a division the prevailing pressure forces on the blades and pins. Finally, there are basically no unknown strength problems, since the guide vanes themselves remain immobile.

Brief description of the drawing

In the drawing, an embodiment of the invention is shown using a single-shaft, axially flow-through steam turbine.

Fig.1

einen schematischen Längsschnitt durch eine Doppelentnahmeturbine;

Fig.2

einen Teillängsschnitt durch eine stromabwärts einer Entnahme liegenden Teilturbine;

Fig.3

die teilweise Abwicklung eines Zylinderschnittes auf dem Durchmesser des Leitschaufelfusses;

Fig.4

einen Querschnitt durch die Turbine in der Ebene der ersten Leitreihe gemäss Linie 3-3 in Fig.2.

Show it:

Fig. 1

a schematic longitudinal section through a double extraction turbine;

Fig. 2

a partial longitudinal section through a turbine located downstream of a withdrawal;

Fig. 3

the partial development of a cylindrical section on the diameter of the guide blade root;

Fig. 4

a cross section through the turbine in the plane of the first guide row according to line 3-3 in Figure 2.

Only the elements essential for understanding the invention are shown. The system does not show, for example, the inlet elements, ie the quick-closing and regulating valves, the bearings and their bearing housings, the various taps, the exhaust part, etc. The direction of flow of the working fluid is indicated by arrows.

Way of carrying out the invention

The double extraction turbine shown in FIG. 1 is a single-shaft, 3-part turbine with controlled withdrawals 1 and 2 for process steam, for example, as is used to drive a generator (not shown) or for a mechanical drive. It consists of a high-pressure turbine 3 in the back-pressure type, a medium-pressure turbine 3 'also 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, in addition to the two regulated steam pressures in taps 1 and 2, the frequency also has to be maintained.

The rotor blades of the three turbine parts are arranged on a common rotor 4. The blade carriers 6, 6 ', 6''are suspended in the largely cylindrical turbine housing 5 so that they can be moved by heat. Via a valve housing block, not shown, which is flanged to the turbine housing 5, the live steam flows into the nozzle box 7 of the high-pressure turbine 3, 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 'and reaches the high-pressure exhaust steam 9. In contrast to the solution mentioned above with overflow control valves, the steam to be expanded remains within the turbine housing. The steam not removed in FIG. 1 flows through the medium-pressure turbine 3 ′ and reaches the medium-pressure exhaust steam 10. The steam not removed in FIG. 2 flows through the low-pressure turbine 3 ″. From the outlet, the steam arrives in 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, double extraction condensation turbines are known. The new regulating device, which regulates the respective extraction pressure and thus the extraction steam quantity downstream of a steam extraction via an intervention in the subsequent guide apparatus, can be used both on the medium-pressure turbine 3 'and on the low-pressure turbine 3' 'according to the dash-dotted line.

In Figure 2, the medium pressure turbine 3 'is partially shown in longitudinal section. For the sake of clarity, rotor 4 and blade carrier 6 'are not hatched. The blades 11a and 11b of the first two stages, which are used in the rotor 4, and the guide blades 12a, 12b and 12c of the first three stages, which are arranged in the blade carrier 6 ', are shown from the blading, the profiles of which are cylindrical throughout from the foot to the head.

The actual control device now consists of a number of pins 13 which can be inserted radially into the flow channel, specifically in the plane of the first guide row 12a. The number of pins corresponds to the number of guide vanes. Each pin is guided within a bush 14 seated in the blade carrier. This bush penetrates from the outside of the blade carrier and extends into the blade root 15. The pin is cylindrical in its upper guide part. The part that is intended to be introduced into the flow-through channel is tapered. This taper corresponds to the different distance between two adjacent blade profiles above the channel height. In the development in FIG. 3, this faning is shown to the extent that the simply hatched profiles represent the blade position and the fully inserted pin at the level of the blade root 15, while the cross-hatched parts represent the corresponding positions on the blade tips facing the rotor. The pin 13 fully retracted in the flow channel blocks the narrowest cross section between two adjacent blades. Since the profiles are cylindrical, this narrowest cross section is on a radial and is usually found in the area of the pressure-side trailing edge of the blades.

The radial movement of the pins is carried out by means of an overall drive. For this purpose, the principle of the known jaw chuck drive is used in its modification. A turntable 17 centered and supported on the blade carrier 6 'by means of three cams 16 (FIG. 4) is provided with guide grooves 18. In these guide grooves, the number of which corresponds to that of the pins, two locating pins 19 engage per pin, which are fastened to the pin in a suitable manner. The guide grooves are segments of an Archimedean spiral and extend from the outside diameter of the rotating ring to its inside diameter (Fig. 4). The guide grooves have the same distance from one another in the direction of the center axis of rotation in order to ensure a problem-free movement of the locating bolts. By rotating the turntable, the drive torque is thus converted into a vectorial rectilinear movement, and the drive force is transmitted to the pins to be inserted. In order to further improve the radial guidance of the pins, a retaining ring 20 is provided which is fastened to the blade carrier and provided with radial slots (not shown), the locating bolts 19 running in these slots.

The drive of the turntable 17 is shown in Fig.4. In this illustration, the retaining ring has been omitted for reasons of clarity. The drive is flanged to the outside of the turbine housing 5 and essentially consists of two hydraulically adjustable servomotors 21 with extending and retracting pistons. The opposing pistons are each connected via a linkage 22 to a pin 23 arranged on the turntable. Since, on the occasion of the piston movement and the associated rotational movement of the plate, the pins 23 also execute a slight radial movement take appropriate precautions at one or the other connection point of the linkage 22.

Of course, the invention is not limited to the exemplary embodiment described and shown. In deviation from the solution shown, it is just as possible to provide individual drives for the plurality of pins instead of the overall drive. Furthermore, the guide grooves can also have a circular arc shape instead of a spiral shape. Finally, the invention can also be used for guide vanes which are provided with cover strips or cover plates at the tip of the blade. With such blades, the fully retracted sift can be given additional guidance in the cover plate, which can have a favorable effect on the absorption of forces. Contrary to the illustration in FIG. 3, the diameter of the pins can also be selected such that, in the retracted state, a residual gap between the pin and the blades remains, which guarantees cooling of the blades downstream of the pins during operation.

Claims (4)

Device for regulating the free cross section in the guide apparatus of turbomachines with axial flow, in particular of extraction steam turbines,
characterized,
that between two adjacent blades of the guide blades (12a) of the first stage, a pin (13) penetrating the blade carrier (6 ', 6'') of the turbomachine radially from the blade root (15) of the guide blade to the rotor (4) of the turbomachine opposite Blade tip is insertable. Device according to claim 1, characterized in that the pin (13) can be inserted in the narrowest cross-section between two guide blades (12a). Apparatus according to claim 1, characterized in that the pin (13) is conical in accordance with the fan of the guide vanes (12a) in the radial plane of the pin. Device according to claim 1, characterized in that the radial feed movement of the pin (13) is carried out via a turntable (17) provided with guide grooves (18), at least one locating pin (19) connected to the pin (13) being preferably spiral-shaped engages in the rotating plate grooves.

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