WO2003076797A1

WO2003076797A1 - Device for stabilizing the flow in hydraulic turbomachines

Info

Publication number: WO2003076797A1
Application number: PCT/EP2003/002373
Authority: WO
Inventors: Frank Simon; Thomas Scherer; Ulrich Seidel
Original assignee: Voith Siemens Hydro Power Generation Gmbh & Co.Kg
Priority date: 2002-03-09
Filing date: 2003-03-07
Publication date: 2003-09-18
Also published as: DE10210426A1

Abstract

Disclosed is a hydraulic turbomachine which is characterized by the fact that it comprises a runner that is provided with a plurality of rotor blades and other flow-influencing components which have leading edges and trailing edges. The area of the leading edges and/or the area of the trailing edges display/s geometric irregularities which locally influence the flow velocity.

Description

Device for flow stabilization in hydraulic flow machines

The invention relates to hydraulic flow machines. It primarily affects water turbines and pump turbines.

The machines mentioned have been known for a long time. However, they were further developed until modern times. The developments are primarily concerned with increasing efficiency and reducing manufacturing and operating costs.

Important issues are general operating behavior, wear resistance and smoothness.

It is desirable to be able to vary the operating parameters such as the water flow rate or the external pressure conditions in the inlet and outlet in a wide range. Even in extreme partial load or overload operation, high efficiency and vibration-free running should be achieved.

Under operating conditions that deviate far from the best point, unsteady flow conditions can occur in hydraulic fluid machines, which lead to strong vibrations. Particularly when exciting natural frequencies of components, mechanical vibrations can also result from mechanical vibrations as a result of the machine vibrations. In addition, with the appropriate machine size, a reduction in smoothness has a negative impact on the energy supply with which we operate a hydraulic fluid machine.

To adapt to different operating conditions, adjustable structures such as movable guide plates or adjustable impeller blades are used in hydraulic turbomachines. Furthermore, passive and active methods are used to stabilize the flow outside of the optimal operating points in hydraulic turbomachines, such as rigid ones or flexible baffles or the injection of compressed air or water into the main water flow. A disadvantage of the known methods, however, is the high design and manufacturing outlay and their limitation to certain operating states.

The invention has for its object to improve the operating behavior of a hydraulic fluid machine. This applies in particular to increasing efficiency and minimizing pressure fluctuations and cavitation.

The invention is based on the finding that it is possible to influence the recirculation zone which forms in front of or behind an inflow or outflow edge by an irregularity in the shape of the inflow and / or outflow edge in such a way that the vortex detachment, and as a result thereof z. B. the formation of a Kärman vortex road is significantly delayed.

According to the current state of the art, the leading edges are shaped as round as possible and the trailing edges are tapered. The roundness of the leading edge allows varying angles of attack in a certain range. The tapered trailing edges used today limit the size of the circulation zone and thus reduce the area of formation of coherent vortex structures. This prevents the formation of a Karman vortex street up to a critical point in the flow velocity. In particular under partial load conditions, however, flow conditions can occur in which such eddy streets are formed.

The inventors have recognized that irregularities in the shape of the leading and / or trailing edge stabilize the wake flow behind components in hydraulic flow machines, in which no coherent flow structures such as vortex braids can arise due to the structurally pre-shaped spatial variation of the trailing edge. Irregularities in the shape of the leading edge influence the boundary layer along the entire course up to to the trailing edge and also dampen the formation of large swirl structures. For the design of the irregularities in the shape of the leading and / or trailing edge, wave-like changes are particularly suitable.

Furthermore, the merging of the leading and / or trailing edge, which is varied in a wave-like manner, has a positive influence on the merging of the top and bottom flow at different speeds, since the boundary region between these two flow regions is stabilized in the wake by a disturbance predefined on the varied edge.

The disadvantages of the prior art are overcome by the solution according to the invention. Structures around which the vortex is detached are caused to vibrate at frequencies close to their natural frequencies, which has a further destabilizing effect on the flow. This is achieved according to the invention in that the wave-shaped structuring in the vicinity of the leading and / or trailing edge in an advantageous embodiment includes wave-shaped thickness variations, which leads to a locally variable natural frequency. Thus, an element structured in this way cannot be excited as a whole from a certain flow state to natural vibrations.

The wavy variations near the edges are small with regard to the dimensions of the leading and / or trailing edge. However, they are larger than the roughness and waviness caused by the machining and are adjusted to the flow and dimensional conditions as a target.

In a particularly advantageous embodiment of the invention, the thickness variations near the edge are extended to the leading and / or trailing edge in such a way that they lead to a wavy length variation at the edge. This shape is particularly advantageous in production, since these variations can be applied to the leading and / or trailing edge by milling in a subsequent processing step. The invention is explained in more detail with reference to the drawings. The following is shown in detail. Show it:

Figure 1 wing of a Kaplan turbine with an irregular trailing edge

Figure 2 impeller blade of a Francis turbine with an irregular

trailing edge

Figure 3 impeller blade of a Francis turbine with an irregular leading and trailing edge

Figure 4 impeller blade of a Francis turbine with an irregular

trailing edge

5, a, b, c geometrically irregular edge regions of a component which influences the flow

6, a, b, c further geometrical irregularities in the edge region of flow-influencing components

FIG. 7 shows a geometric irregularity in the form of a block function

Figure 8 shows a geometric irregularity in the form of a sawtooth structure

Fig. 9 -11 top views on edges of flow-influencing components, in development

Fig. 12 -14 top views on edges of blades of Francis

turbines; Figure 15 shows a nozzle with a needle on a Pelton turbine in longitudinal section

Figure 16 shows the subject of Figure 15 in a perspective view

Figure 17 shows the object of Figure 15 in a front view

Figure 18 shows the subject of Figure 15 a sectional view according to the

Section line A-A

Figure 19 shows a suction pipe of a Francis turbine in a longitudinal section

Figure 20 shows the upper part of the object of Figure 19 in perspective

Figure 21 shows the object of Figure 19 in plan view

Figure 22 segments of a Pelton wheel.

The expression "flow-influencing components" denotes the following

components:

Blades, e.g. B. Francis turbines

Kaplan turbine blades

vanes

Guide vanes (so-called traverses)

Suction Tubes

volute

Ring pipes (for Pelton turbines).

FIG. 1 shows a top view of the wing of a Kaplan turbine as an example of a flow-around element in a hydraulic fluid machine. In the outlines of this open space form are shown in a highly simplified manner. On the right is the inlet area of the flow and thus the leading edge, on the left the outlet of the flow and the trailing edge. The irregularity in the shape of the trailing edge is shown schematically simplified. The dashed line marks the middle course of this trailing edge. The design of the trailing edge in this exemplary embodiment varies in waves in this course.

The blade shown in Figure 2 is the blade through a Francis turbine in a meridian section. The trailing edge on the pressure side shows several discrepancies. These discontinuities extend over the entire course of the trailing edge of the blade.

The blade of a Francis turbine shown in Figure 3 also has irregularities, namely along the leading edge and the trailing edge. The irregularities are only planned locally. The variations in their periodicity can change, which is exemplarily outlined along the trailing edge.

Changes in the amplitudes are not shown in the simplified schematic diagrams. However, these are possible in a particularly advantageous embodiment of the invention, which also includes a variation in the thickness of the leading and trailing edges.

The leading edge describes an elongated sine line with two turning points.

In the blade of a Francis turbine according to FIG. 4, the trailing edge has a course in which five turning points are provided in the area of the bottom of the turbine, and six turning points in the area of the ring of the turbine. FIGS. 5a, 5b and 5c illustrate the geometric irregularity at the edge region of a component of any type which influences the flow. This can be, for example, the edge profile in a Francis turbine - see the meridian view shown in FIG. 2. It can also be a matter of variations in the thickness curve or the length curve.

In the present case, the irregularity is an undamped harmonic vibration. As you can see, the irregularities can take the form of a sine curve. Attenuated frequencies are also possible. In the embodiment according to FIG. 5c, the tops of the amplitudes are cut off.

Figures 6a, 6b and 6c also show numerous variants. Note the turning points in Figure 6a and Figure 6b. Note also the tangent discontinuities in Figure 6b.

There is a frequency variation in FIG. 6c.

The irregularity shown in Figure 7 is trapezoidal.

FIG. 8 illustrates geometric irregularities in the form of a sawtooth profile.

FIGS. 9, 10 and 11 show the course of the thickness of a blade edge. This can be the leading or trailing edge of a hydraulic profile, i. H. a flow-influencing component such as the blade of a Francis impeller.

As can be seen, the thickness is reduced on one side along a sine curve in FIG. The material removal compared to the prior art is shown hatched. At the end of the blade edge, as you can see, it runs sinusoidally. Viewed at the end of the edge, it runs steadily. That is, the flow areas have no discontinuities such as jumps or kinks. FIG. 10 illustrates an irregularity in which material is removed on both sides of the flow surfaces, in the present case symmetrically.

In FIG. 11, material is also removed on both sides, but asymmetrically. The edge in the end region thus has the shape of a sinusoidal band of constant thickness.

Figures 12 to 14 illustrate variations of possible geometric irregularities.

In FIGS. 15 to 18, the design of the nozzle opening of a Pelton turbine is important. In the state of the art, this is rotationally symmetrical today. According to the invention, it deviates from the rotationally symmetrical shape. In the present case, it is approximately hexagonal. Oval, two, three, four, five or polygonal shapes are also possible and can be useful.

Figures 19 to 21 relate to a suction pipe and thus to a stationary component, which, however, strongly influences the flow.

Here, too, a non-rotationally symmetrical shape, namely a hexagon, can be seen in the inlet area. You can also see that the trailing edges have geometric irregularities. This also applies to an apron and apron-supporting bars.

The segments of a Pelton wheel shown in FIG. 22 show a length variation of the trailing edge. The trailing edge has four turning points. Compared to the conventional design, material is removed at the trailing edge, so that the trailing edge in the embodiment now shown is below the radial line.

Claims

claims

1. Hydraulic fluid machine

1.1 with an impeller that has a plurality of blades;

1.2 with other flow-influencing components;

1.3 the flow-influencing components have leading edges and trailing edges; characterized by the following features:

1.4 the area of the leading edges and / or the area of the trailing edges is provided with geometric irregularities which locally influence the flow velocity.

2. Hydraulic flow machine according to claim 1, characterized in that the geometric irregularities relate to the course of the length and / or the thickness of a leading edge and / or a trailing edge.

3. Hydraulic flow machine according to claim 1 or 2, characterized in that the contour of the leading and / or trailing edge varies at least in part of its course several times wave-shaped around an average course.

4. Hydraulic flow machine according to claim 3, characterized in that the multiple wave-shaped course varies in the direction of the flow by an average course.

5. Hydraulic flow machine according to claim 3, characterized in that the multiple wave-shaped course varies perpendicular to the direction of the flow by an average course.

6. Hydraulic flow machine according to one of claims 1 to 5, characterized in that thickness and / or length variations of the arrival and / or trailing edge or a region close to the edge lead to a wavy structure on the top or the bottom or on the top and bottom of the leading and / or trailing edge.

7. Hydraulic flow machine according to one of claims 1 to 6, characterized in that thickness and / or length variations of a region close to the edge lead to a wavy structure on the top or the bottom or on the top and bottom of the leading and / or trailing edge ,

8. Hydraulic fluid flow machine according to one of claims 1 to 7, characterized in that the undulating deviation from the central course line is greater than the manufacturing tolerances and smaller than the length dimension of the leading and / or trailing edge.

9. Hydraulic flow machine according to one of claims 1 to 7, characterized in that the undulating variations around a central profile section line correspond to a harmonic vibration or a superposition of harmonic vibrations.

10. Hydraulic fluid flow machine according to one of claims 1 to 7, characterized in that the undulating variations around a central profile section line correspond to a harmonic vibration or a superposition of harmonic vibrations which are trimmed by an enveloping function.

11. Hydraulic flow machine according to one of claims 9 or 10, characterized in that the undulating variations around a central profile section line correspond to the amount of a harmonic vibration or the amount of a superposition of harmonic vibrations, which can also be trimmed by an enveloping function.

12. Hydraulic flow machine according to one of claims 1 to 7, characterized in that the undulating variations around a central profile section line have a variable frequency.

13. Hydraulic flow machine according to one of claims 1 to 7, characterized in that the size of the undulating variations change by a central profile cut line along the course of this profile cut line.

14. Hydraulic flow machine according to one of claims 1 to 12, characterized in that different areas of the leading and / or trailing edge have different undulating shapes.

15. Hydraulic fluid flow machine according to one of claims 1 to 13, characterized in that the inflow and / or outflow edge with an identical mean profile with respect to their placement or their design have different wavy shapes.

16. Hydraulic flow machine according to one of claims 1 to 15, characterized in that only some of the leading edges and / or trailing edges is designed according to one of claims 1 to 15.

17. Machine set with a plurality of hydraulic flow machines;

17.1 each machine has an impeller that has a plurality of blades;

17.2 each machine has other flow-influencing components;

17.3 the components influencing the flow have leading edges and trailing edges;

17.4 some or all leading edges or trailing edges are designed according to one of claims 1 to 14.