WO2003081027A1

WO2003081027A1 - Support and guide blades for a francis turbine

Info

Publication number: WO2003081027A1
Application number: PCT/EP2003/003007
Authority: WO
Inventors: Ernst-Ulrich Jaeger; Gerhard Wengert; Armin Otto; Ulrich Seidel
Original assignee: Voith Siemens Hydro Power Generation Gmbh & Co. Kg
Priority date: 2002-03-27
Filing date: 2003-03-22
Publication date: 2003-10-02
Also published as: DE10213774A1

Abstract

The invention relates to a Francis turbine or a machine which is constructed according to the Francis principle. According to the invention, said Francis turbine is provided with a blade wheel comprising moving blades, a spiral housing which surrounds said blade wheel, a ring of fixed support blades which is arranged downstream from the spiral housing, and a ring of rotatable guide blades which is arranged downstream from the ring of fixed guide blades. At least one guide blade can be displaced or the outer contour of said guide blade can be modified. A sensory mechanism for detecting the vibratory behaviour or other parameters of the entire machine or parts thereof is provided. A central processing unit (CPU) is provided, which commands the displacement of the guide blades or the modification of their outer contour if nominal values of the parameters are exceeded.

Description

SUPPORT AND GUIDE BLADES FOR FRANCIS TURBINE

The invention relates to a Francis turbine or pump or pump turbine, in particular the diffuser of such a turbine, which serves to supply the water to the impeller.

Water turbines such as Francis turbines are subject to increasingly higher requirements with regard to efficiency and the largest possible working area. A variable use with regard to the water flow rate from extreme part-load operation to overload operation is desirable. In all load ranges, the highest possible efficiency with vibration-free running of the turbine should be achieved.

Francis turbines are adapted to different operating conditions by adjusting the guide vanes. Nevertheless, unsteady flow conditions occur, especially under partial load, which lead to strong vibrations on the machine. Material damage as a result can occur in particular if the natural frequencies of components match these vibrations. Another negative consequence of turbine vibrations, especially for large machines, is the impact that these vibrations have on the power grid. Synchronous unrest is coupled into the power grid via the generator and there is unpleasantly noticeable as power fluctuations. This results in disadvantageous restrictions on the turbine operating range. Critical partial load areas can be passed through particularly quickly when the turbine is started up and avoided in continuous operation. In addition, there is an undesirable mutual influence of water-bearing systems.

When a Francis turbine is operating optimally, the water flows radially symmetrically from the inlet spiral into the impeller, where it is deflected by the rotor blades so that it flows almost axially into the intake manifold and is diverted to the underwater. With such ideal operation, the flow in the intake manifold is almost swirl-free. When the turbine is operating outside the best point this swirl freedom of the outflow after the impeller no longer exists. The causal relationship between the rotary component of the flow in the intake manifold and the machine vibrations is known. To stabilize the flow in the intake manifold and to suppress the swirl, baffles are introduced along the intake manifold according to the current state of the art. such

Baffles can be designed as fins, which are oriented in the axial direction. This shape leads to suppression of the swirl in the intake manifold, but this is associated with the disadvantage of reduced efficiency.

To solve this problem, variable baffles have been developed that can be swiveled around an axis parallel to the machine axis depending on the operating conditions. Further designs of baffles are oriented parallel to the wall surfaces of the intake manifold and thus prevent flow areas from becoming detached by stabilizing the flow between baffle and intake manifold wall. Like the aforementioned fin-like structures, this construction also reduces the energy yield of the turbines. Furthermore, such static or variable designs increase the effort for the manufacture and maintenance of turbines and are therefore a cost-relevant factor.

Further measures are also known, but these are either complex or impair the efficiency of the machine.

The invention has for its object to design a machine of the type mentioned in such a way that pressure fluctuations at any point in the machine are minimized under different operating conditions.

This object is solved by the features of claim 1.

The inventor has recognized the following: If the direction of flow of the water to the moving blade is changed when the guide blades are adjusted about their pivot axes, shock losses and deflection losses occur at certain angular positions of the guide blades. This means that the machine has only one certain operating area has the necessary smoothness, but vibrates in other operating areas.

According to a first alternative of the invention, it is provided that the support blades or the guide blades are not made stationary, but are displaceable, and preferably also during operation.

This means that the individual guide vane can still be pivoted in order to be able to adapt the operation to given conditions at any time, for example to a given surface water level. At the same time, however, the individual guide vane can be moved to counteract undesirable pressure fluctuations. It may be sufficient for only a few guide vanes of a guide vane ring to be displaceable, and in extreme cases only a single guide vane. By moving guide vanes, a vibration in the machine can be impaired or disturbed or superimposed by other vibrations so that it no longer appears.

What applies to adjustable guide vanes also applies to fixed support vanes.

A second alternative consists of at least one support blade and / or

To make the guide vane changeable in shape, again preferably during operation. This can be done in that the blade is divided into two parts, which are connected to one another in an articulated manner and which can be brought into specific angular positions relative to one another via the joint. The second alternative can also be realized in that at least one blade can be changed in volume, for example in that it is at least partially hollow and at least partially consists of an elastic material. For example, it can be inflated so that it changes its total volume. However, it can also be designed in such a way that only part of its wall consists of elastic material which bulges outwards when an overpressure is introduced into the hollow interior of the blade or pulls into the cavity when an underpressure is applied. A third alternative is to equip the machine with irregularities from the outset. Such irregularities can consist in the irregular arrangement of fixed or movable guide vanes. For example, the mutual distance between two adjacent ones

Guide vanes are chosen differently than between another pair of adjacent guide vanes. The geometry of certain guide vanes can also be different from the outset than that of the other guide vanes. Such irregularities can be determined constructively from the outset, without which they can be changed later.

The three variants mentioned can be used individually or in combination.

According to the invention, the machine is preferably equipped with a sensor and regulating or control device. The sensor device detects the vibration level of the machine or individual elements of the machine, for example in the blade-free space between the guide vane and the impeller. The measured value is then compared to a target value. If the vibration level deviates from a setpoint, a central process unit initiates it

(CPU) an intervention in the sense of a change in the guide vane designed according to the invention. This means - according to the first alternative - a displacement of at least one of the guide vanes, or - according to the second alternative - a change in the outer shape of at least one guide blade, or - when using both alternatives - both a displacement and a change in shape.

The first alternative can also be realized, for example, by making the swivel axis tiltable so that it can also take any course relative to the machine axis, thus inclined towards the machine axis. One way of realizing the first alternative can also be to place one or more support blades or guide vanes happens finely in the form of an oscillation or vibration. The deflections of the deplacement can thus be minimal and at high frequency.

The second alternative can be realized, for example, in that the guide vane has a telescopic structure. Accordingly, it consists of two or more parts which are telescopically fitted into one another and which can thus be moved into one another or moved away from one another.

The first alternative can also be realized in that the entire guide vane ring can be rotated in the radial direction about its own axis, or in that individual segments of the guide vane ring can be rotated around the axis of rotation.

An interesting variant of the first alternative is to set at least one guide vane to vibrate. Dislocation also takes place, albeit to a minimal extent. The idea of applying a vibration to guide vanes is known, but for a different purpose and not in conjunction with the other features mentioned here, namely a sensor system for detecting the actual vibration state and a CPU for initiating countermeasures against excessive vibrations.

The same measures according to the invention, which can be used in the case of pivotable guide vanes, can also be used in the case of fixed support vanes which are usually fixed and which are connected upstream of the guide vane ring. These fixed support blades are called the so-called truss ring.

The blades of the truss ring can thus also be dislocated according to the invention - first alternative - or change in shape - second alternative. Here, too, it may be sufficient if at least one blade which is fixed per se is designed in the manner according to the invention, and if a sensor system and a CPU are provided. The invention is explained in more detail with reference to the drawing. The following is shown in detail:

Figure 1 shows a Francis turbine in an axial section.

2-7 show support blades and pivotable guide blades of a Francis turbine each in a meridian section.

FIG. 8 shows a first embodiment of a guide vane with a changeable outer contour.

FIG. 9 shows a second embodiment of a guide vane with a variable outer contour.

FIG. 10 contains a diagram which illustrates the possibilities of compensating for undesired pressure pulsations by forced vibrations from rotatable guide vanes.

The Francis turbine shown in FIG. 1 is constructed as follows:

An impeller 1 comprises a plurality of blades 1.1. It is rotatable about an impeller axis 1.2.

The impeller 1 with its blades 1.1 is surrounded by a spiral housing 2. The impeller 1 is preceded by a ring of fixed support blades 3, followed by a ring of pivotable guide blades 4.

The turbine has a suction pipe 5. This includes an inlet diffuser 5.1 with an axis 5.1.1, an adjoining manifold 5.2, and an adjoining suction box 5.3. FIG. 2 shows a ring of fixed support blades 3, also called a “traverse ring”. Radially inside the crossbar ring is a ring of guide vanes 4. These can be rotated about an axis 4.1 in order to adjust the width between two respectively adjacent guide vanes 4, and thus at the same time the throughput of the incoming water flow.

As you can see, all rotatable guide vanes can be moved to a position shown in dashed lines. The shift takes place in the circumferential direction - see the double arrow.

In the present case, the displacement of all guide vanes 4 is the same. This could also be different. It is also conceivable to move only some of the rotatable guide vanes, or even just one. Despite the displacement, each guide vane can perform a rotary movement about the associated axis of rotation 4.1.

In the embodiment shown in FIG. 3, the rotatable guide vanes 4 are again displaceable, but not in the circumferential direction but in the radial direction. The same applies here as in the embodiment of FIG. 1: not all rotatable guide vanes 4 have to be displaceable.

In addition, the size of the displacement path can be freely selected. This applies to all of the examples shown here, in which a displacement of guide vanes is provided (first alternative). This applies to Figures 2 to 4.

FIG. 3 uses one of the rotatable guide vanes 4 to illustrate a displacement possibility that differs from that of FIGS. 2 and 3. See the blade 4 shown on the far left in FIG. 4. The double arrow A indicates the possibility of rotating this blade about its axis of rotation 4.1, and double arrow B indicates the displacement of the blade. As can be seen, double arrow B essentially runs in the direction of the longitudinal axis 4.2 of the blade profile. FIG. 5 again shows fixed support blades 3 and rotatable guide blades 4. A special structure can be seen from the fixed guide blade 3 shown on the left. This blade 3 is constructed from two components, namely from blade part 3.3 and from blade part 3.4. Blade part 3.3 forms a sleeve into which blade part 3.4 is inserted. Blade part 3.4 can be telescopically extended and retracted from blade part 3.3, in the direction of the double arrow B. This extends essentially in the direction of the longitudinal axis 3.2 of the blade profile. Bucket part 3.3 remains stationary during the sliding movement of bucket part 3.4.

The embodiment shown here differs from that according to FIGS. 2 to 4. Here, the outer contour of the blade 3 can be changed. This measure can be carried out with all fixed guide vanes 3, but also only with some or with a single one.

The same applies to the rotatable guide vanes 4. These can be designed in the same way or in a similar manner to the aforementioned fixed support vane 3 shown on the left.

FIG. 6 shows guide vanes in which the outer contour can also be changed. This is the case, for example, with one of the fixed support blades 3. This consists of two parts, namely a fixed part 3.3 and a pivotable part 3.4. The two parts are articulated to one another by an axis of rotation 3.1.

Also in the case of the rotatable guide vanes 4, various possibilities are given with which the outer contour of the guide vane 4 in question is changed. The rotatable guide vane 4 shown on the left thus comprises two parts 4.3, 4.4. These can be pivoted in different ways - see the double arrows C and D. While, for example, blade part 4.3 can execute a certain pivot angle, blade part 4.4 can execute a different pivot angle. In the case of the guide vane following the left rotatable guide vane, the tail region 4.4 of the vane profile can be bent such that it is pivoted out of the longitudinal axis 4.2.

In the embodiment according to FIG. 7, the rotatable guide vanes 4 are in turn divided into a front part 4.3 and a rear part 4.4. The entire blade 4 can be pivoted about an axis of rotation 4.1 in the manner shown above, but the rear part 4.4 of the rotatable guide blade can be pivoted through a different angle than the front part 4.3.

The guide vane 3 shown in Figure 8 is made of an elastic material and is hollow. The cavity has a compressed air connection. If compressed air is admitted into the cavity, the outer contour 3.8 of the blade 3 is changed to the outer contour 3.9.

In the embodiment according to FIG. 9, the head part 3.10 consists of elastic material, while the main part 3.11 consists of steel. The head part 3.10 is attached to the main part 3.11. There is a cavity in the area of the head part. This in turn has a compressed air connection. When initiating

Compressed air, the outer contour 3.8 is changed to the outer contour 3.9.

Any other medium can be used instead of compressed air.

An interesting thought is to realize the first alternative

- misplacing one or more guide vanes - causing the relevant guide vane 3 or 4 to vibrate. This means that the guide vane is also misplaced, either at very short or extremely short notice.

The diagram shown in Figure 10 shows the following:

Pressure pulsations are plotted on the ordinate, time on the abscissa. Three curves I, II and III can be seen. Curve I illustrates the pressure pulsations that the machine has.

Curve II illustrates vibrations that are applied in the area of the guide apparatus, for example in the case of one or more rotatable guide vanes.

Curve III illustrates the resulting pressure pulsations from the machine. As can be seen, the amplitudes of these pressure pulsations are greatly minimized compared to the amplitudes of curve I.

In practice, curve I will be determined by measurements at critical points on the machine, for example in the intake manifold, in the vane-free space, in the spiral, or at other locations.

Curve II can be generated, for example, by rotating one or more rotatable guide vanes, i. H. closed and opened again, namely by a minimum angle of, for example, 1 °. The opening and closing can take place at relatively high frequencies, for example at a frequency of 0.1-100 Hz, thus at a frequency somewhere between these two limit values. Deviations upwards and downwards are also possible.

Instead of rotating, it is also possible to move the rotatable guide vane in the axial or radial direction or in a direction inclined thereto.

As an alternative to applying a vibration to a rotatable guide vane, consideration can be given to applying a vibration to a stationary support vane. LIST OF REFERENCE NUMBERS

1 impeller

1.1 Blades 2 spiral casings

3 fixed support blades

3.1 Axes of rotation of the guide vanes

3.2 Longitudinal axes of the blade profile

3.3 Guide vane part 3.4 Guide vane part

3.8 outer contour, not inflated

3.9 outer contour, inflated

3.10 headboard

3.11 main part 4 rotatable guide vane

4.1 axis of rotation

4.2 Longitudinal axis of the blade profile

4.3 Bucket part

4.4 Bucket part 5 suction pipe

5.1 Entry diffuser

5.1.1 Axis of the single inlet diffuser

5.2 manifold

5.3 Suction box

Claims

claims

1. Francis turbine or another machine constructed according to the Francis principle 1.1 with an impeller (1) having blades (1.1);

1.2 with a spiral housing (2) which surrounds the impeller (1.1);

1.3 the spiral housing (2) is followed by a ring of fixed support blades (3);

1.4 the ring of fixed support blades (3) is followed by a ring of rotatable guide vanes (4);

1.5 at least one guide vane (3, 4) can be moved or its outer contour can be changed;

2. Machine according to claim 1, characterized by the following features:

2.1 sensors are provided for detecting the vibration behavior or other parameters of the entire machine or parts thereof;

2.2 A central process unit (CPU) is provided, which commands the guide vane to be moved or the outer contour to be changed when the setpoint values of the parameters are exceeded.

3. Machine according to claim 1 or 2, characterized in that the stationary support blades (3) and / or the rotatable guide blades (4) cannot be changed with regard to their irregularities

Have shape and / or their arrangement.

4. Machine according to one of claims 1 to 3, characterized in that at least one fixed support blade (3) and / or a rotatable guide blade (4) is displaceable in the circumferential direction.

5. Machine according to one of claims 1 to 4, characterized in that at least one fixed support blade (3) and / or a rotatable guide blade (4) is displaceable in the radial direction.

6. Machine according to one of claims 1 to 5, characterized in that at least one fixed support blade (3) and / or a rotatable guide blade (4) is displaceable in a direction deviating from the circumferential direction and from the radial direction.

7. Machine according to one of claims 1 to 6, characterized in that at least one fixed support blade (3) and / or a rotatable guide blade (4) from at least two parts (3.3, 3.4) is constructed, which are telescopically movable relative to each other.

8. Machine according to one of claims 1 to 7, characterized by the following features: 8.1 at least one fixed support blade (3) and / or at least one rotatable guide blade (4) is hollow;

8.2 the hollow blade has a wall area (3.10) which consists of an elastic material;

8.3 the elastic wall area (3.10) is inflatable, so that its outer contour (3.8) changes to the outer contour (3.9).

9. Machine according to claim 8, characterized in that the entire outer contour (3.8) of the hollow blade (3, 4) is formed from an elastic material.

10. Machine according to one of claims 1 to 9, characterized in that at least one blade (3, 4) can be set in vibration.

11. Francis turbine or another machine built according to the Francis principle

11.1 with an impeller (1) which has blades (1.1);

11.2 with a spiral housing (2) which surrounds the impeller (1.1);

11.3 the spiral housing (2) is followed by a ring of fixed support show (3);

11.4 the ring of stationary support blades (3) is followed by a ring of rotatable guide vanes (4);

11.5 at least one blade (3, 4) of the support blades or the guide blades has a thickness or length or a profile which differs from the other blades, or the

Support blades or the guide blades are arranged with an irregular division, or designed in such a way that a symmetrical structure is avoided.