Blade and gas turbine

This application is the US National Stage of International Application No. PCT/EP2004/005753, filed May 27, 2004 and claims the benefit thereof. The International Application claims the benefits of European Patent application No. 03013857.2 EP filed Jun. 18, 2003, both of the applications are incorporated by reference herein in their entirety.

The invention relates to a blade for use in turbomachines, having a blade root, a platform region and a main blade part, which main blade part has a blade length from a blade leading edge to a blade trailing edge and a blade height from the platform region to a main blade part tip, and which is formed from at least one base body segment and, in the region of at least one of the two blade edges, from at least one edge segment which is connected in a positively locking manner to the base body segment.

A corresponding turbine blade of modular construction is known from U.S. Pat. No. 4,786,234. The main blade part disclosed in that document is composed of a plurality of components or segments. In this case, the different segments are divided over the blade height. In a variant, U.S. Pat. No. 4,786,234 shows a main blade part which is divided in the direction of the blade length, with in particular the leading edge and the trailing edge of the main blade part being designed as separate, radially movable components.

To apply, for example, the latter embodiment of U.S. Pat. No. 4,786,234 to a guide vane with a base body segment and two cast-on platforms, at least one of the two platforms must have an opening through which the radially displaceable blade edge can be pushed onto the main blade part. In this case, special design measures, such as for example sealing measures in the transition region between main blade part and platform, are required, and these measures are disadvantageous for production and operation.

The invention is therefore based on the object of providing an alternative, simplified design of a modular blade while at the same time increasing the service life. A further object of the invention is to provide a turbomachine with reduced maintenance and production costs.

The object relating to the blade is achieved by the features of the claims. Advantageous configurations are given in the subclaims.

As a solution, it is proposed that the positively locking connection is produced by means of projections which are formed integrally on one of the segments and are spaced apart from one another in the direction of the blade height, with the other segment at least partially arranged projecting in between the projections.

This connection allows particularly simple fitting of the blade trailing edge and/or the blade leading edge, since the edge segments are formed such that they can be displaced transversely with respect to the blade edge. Therefore, with the blade according to the invention, the edge segment can be exchanged without having to dismantle the blade, which shortens the repair time. Furthermore, the modular structure allows the blade edges of the main blade part, which are subject to higher stresses and are accordingly more vulnerable, to be selectively exchanged. This increases the service life of the base body segment, which is subject to less wear. Furthermore, the exchangeable regions can be deliberately matched to the mechanical and thermal demands, which leads to cost savings.

Furthermore, the segmentation allows production of standard segments for the individual blade sizes, with the result that, based on use and wear, the costs can be reduced further by standardization. It is in this context advantageous if the segments have different dimensions, so that the regions of the individual wear levels can be optimally combined. The connection can be effected by a press fit, soldering, welding, adhesive bonding or pinned connections. In this context, it is advantageous for the segment connecting surfaces to be oriented horizontally and/or vertically.

In an advantageous configuration, a particularly effective connection can be achieved if the base body segment and the edge segment each have a plurality of projections with recesses between them. Then, the projections arranged on one of the two segments can project in a positively locking manner into the opposite recesses in the other segment, forming positively locking toothing. This allows secure attachment of the blade edges in particular in the case of rotor blades, since the centrifugal forces acting on the edge segments in the radial direction during operation can be compensated for by a segment connecting surface of the base body segment running transversely with respect thereto.

According to a particularly advantageous configuration, a holding pin which runs in the direction of the blade edge secures the segments against relative movements by virtue of this holding pin penetrating transversely through the projections of both segments. The toothed arrangement of the projections results in overlapping, intermeshing regions through which an aligned bore, in which the holding pin is fitted, can extend.

A further advantageous configuration provides for the segments which form the main blade part to be made from different materials. This is advantageous since there are regions which are subject to higher mechanical stress and regions which are subject to higher thermal stresses, with the result that the main blade part can be optimally matched in its segmented structure to the individual wear conditions by virtue of the different materials. According to further teaching of the invention, some of the segments may be made from a particularly thermally conductive material, and others may be made from a material which is resistant to high temperatures.

Suitable materials in this context are ceramic material, metals, metal alloys and plastics materials. In addition, further teaching of the invention provides for the segments to be coated. This allows the properties of the segments to be deliberately influenced further.

To reduce weight, the segments may have cavities. These cavities may in this case be filled with a material which is different from the segment material. This material may, for example, be foams. It is in this way possible to deliberately influence strength properties of the segments.

It is expedient for the blade to be designed as a guide vane or as a rotor blade. It is particularly advantageous for a blade of this type to be used in a gas turbine.