Spiral pertaining to a turbo-machine

A spiral for a turbomachine including reinforcing sheets which are partially located in the transition region between the spiral and parallel plate.

BACKGROUND OF THE INVENTION

The invention relates to a spiral pertaining to a turbomachine, the spiral having a number of interconnected segments and at least one parallel plate, and also relates to a use of such a spiral in a water power station.

The spirals of turbomachines, such as turbines, pumping turbines or pumps, are formed, as a rule, from individual segments welded to one another. In this case, the spiral becomes the more beneficial in terms of stress and flow, the more segments are provided. On the other hand, the more segments are provided, the more costly a spiral becomes. For this reason, spirals are manufactured, instead, with fewer segments, the stress peaks which occur at the transitions of the spiral to the parallel plate being absorbed by corresponding sheet metal thicknesses of the spiral skin. Flow-related disadvantages are in this case taken into account.

SUMMARY OF THE INVENTION

The object of the present invention, then, is to provide a spiral which makes it possible to use thinner metal sheets for the spiral and at the same time improve the spiral in terms of flow.

This object is achieved, according to the invention, in that a reinforcing sheet, which forms part of the casing of the spiral, is arranged at at least one connecting joint of two segments of the spiral and/or in the region of the transition of the spiral to the parallel plate.

Owing to the reinforcing sheet in the region of the transition, the spiral becomes more beneficial in terms of stress, and the stress peaks are reduced, with the result that thinner sheets can be used for the spiral itself. In practice, therefore, it was possible to achieve a reduction in the weight of a spiral of up to 10%, which is also reflected correspondingly in the production costs.

Moreover, the reinforcing sheets give rise to a less pronounced deflection of the liquid medium in a spiral, the consequence of this being that the flow contour in the spiral is improved.

An especially stress-reducing and flow-improving embodiment is obtained when the reinforcing sheet is of triangular design.

The reinforcing sheets are in this case advantageously used in such a way that, by virtue of the reinforcing sheet, the inner contour of the spiral is essentially preserved, thus improving the flow contour of the spiral due to the gentler deflections which occur. Consequently, the flow losses decrease and the efficiency is improved.

For reasons of efficiency and of cost, the reinforcing sheets are arranged only in the region of the spiral having the largest diameters, since the highest loads occur there and the reinforcing sheets can therefore also exert the greatest effect.

Since the loads occur essentially symmetrically about the mid-plane, beneficially at least one reinforcing sheet is arranged in each case on both sides of the transitions to the parallel plate.

A spiral according to the invention can be manufactured in a simple way by the segments being welded together and by the reinforcing sheets being welded into recesses of the spiral or by the reinforcing sheets being welded on.

For safety reasons, the locations on the spiral which are subjected to the highest load are left partially free in order to allow subsequent checks of these locations. This, then, is no longer necessary, since the stress level is lowered due to the reinforcing sheets, but, instead, the outer face of the spiral can be concreted in completely in the region of the reinforcing sheets, and this may considerably simplify the design of a water power station.

A spiral a turbomachine, the spiral comprising: a plurality of spiral segments arranged around a longitudinal axis of the spiral, the segments being hollow shapes in cross-section and each including an attachable region including a transition; each segment having opposite end faces and adjacent segments being interconnected at their opposing end faces; at least one parallel plate radially inward of the segments and to which the segments are connected at the transition; a reinforcing sheet, which forms part of a casing of the spiral and is arranged in the region of the transition of the spiral to the parallel plate, the reinforcing sheet connecting the spiral with the parallel plate in the direction of the longitudinal axis of the spiral and providing only a part of the connection at the transition. In the spiral, reinforcing sheet is shorter in the direction along the parallel plate than the transition from a segment to the plate. whereby the reinforcing sheet extends along part of the length of the connection of the transition to the plate. The spiral may be used as the spiral of a turbine or pumping turbine in a water power station including at least one turbine or pumping turbine, with a spiral feed of liquid medium and a generator.

DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1shows a detail of a spiral1pertaining to a turbomachine, such as, for example, a Francis turbine, a pumping turbine or a pump. The spiral has a plurality of segments2for manufacturing reasons. As seen in the example ofFIG. 2, the segments may be hollow and may be rounded in shape, in cross-section. In this exemplary embodiment, the segments2are welded to one another along the segment joints5. The segments of the spiral1are welded at their radially inward regions to a parallel plate3, to which other components of the turbomachine, such as a turbine cover, the guide wheel ring, etc., can be flanged. Supporting blades sufficiently known, but not illustrated here, or other suitable connection elements, such as spacer stays, etc., could likewise also be arranged between an upper and a lower parallel plate3.

In the region of the spiral1having the largest cross-sectional diameters, that is to say where the highest loads occur, then, reinforcing sheets4are arranged in the region of intersection of the segment joints5with the parallel plate3, that is to say in the region in which the highest stresses and loads normally occur. The reinforcing sheets4are of triangular design here and are welded in recesses in the casing of the spiral1, so that the bottom side of the triangle is connected to the parallel plate3and the two sides of the triangle converge at the segment joint5into a rounded vertex.

The shape of the reinforcing sheet is, of course, not restricted to a triangle, but any other desired shapes, such as, for example, an elliptic or oval reinforcing sheet, may also be envisaged. The reinforcing sheet is shorter in the direction along the parallel plate than the transition from a segment to the plate, whereby the reinforcing sheet extends along part of the length of the connection of the transition to the plate.

As may be gathered fromFIG. 2, the circular inner contour of the spiral is essentially preserved. Of course, for flow-related or stress-induced reasons, the inner contour could be varied by means of the reinforcing sheets4, for example the selected radius of the reinforcing sheet4could be somewhat greater than the inner spiral radius.

The reinforcing sheet4is thicker here than the rest of the spiral1or, expressed more pertinently, due to the stress-reducing effect of the reinforcing sheets4, the selected sheet thickness of the spiral1may be thinner than hitherto, thus affording a considerable weight saving of the spiral1.

In this exemplary embodiment, a reinforcing sheet4is used on both sides of the parallel plate3.

As may be gathered fromFIG. 1, with regard to the parallel plate3, the number of segments is doubled by the reinforcing sheets4, since the reinforcing sheet4actually functions as a segment in the region of the parallel plate3. As a result, the opening angle of the individual segments is reduced, thus leading, in turn, to lower stress peaks. Furthermore, the reinforcing sheets4also have an advantageous effect in terms of flow, since the reduced deflection of the medium reduces the risk of the breakaway of the medium from the spiral skin, the flow contour thus being improved.

The above statements refer only to inserted reinforcing sheets, but, of course, it may also be envisaged to weld reinforcing sheets onto the casing of the spiral at the appropriate locations, preferably on the outside, which would exert essentially the same effect.

Owing to the stress-reducing effect of the reinforcing sheets, it is in this case no longer necessary to leave these locations of the highest loads free when the spiral is concreted in, in order to make subsequent checks possible, but, instead, the entire spiral may be concreted in, if required, and this, of course, simplifies the construction of a water power station in which the spiral of the invention may be used. For safety reasons, however, these locations could, of course, be kept free, as before, if required.

FIG. 3schematically illustrates a water power station10including a turbine12with a turbine runner14, e.g. a Francis type turbine, including a spiral1according to the invention which is a spiral feed of a liquid medium. The spiral1conventionally includes a not shown inlet and an outlet16for liquid medium to be transferred from the inlet to the turbine runner14via the spiral1and the outlet16, as indicated inFIG. 3by the arrows. The turbine runner14and the generator18are arranged on a shaft24and the turbine runner14drives the generator18for generation of electrical energy. Such an arrangement is well known to a person skilled in the art. The spiral1has an outer face20on the exterior thereof at which the spiral1is concreted into the water power station10. The spiral1is completely surrounded by concrete22at least in the region of the reinforcing sheets.