Shroud segment of a blade

[0001] The invention relates to a rotor blade bandage segment, in particular a gas turbine blade according to the preamble of claim 1. The invention further relates to a flow machine, and more particularly to a gas turbine of the type given in the preamble of claim 11.

[0002] Such a bandage segment is already known from the prior art. The bandage segment, which is located in the radial end area of ​​the blade, serves essentially to damp vibrations of the blade and is used in particular for the gas turbine blades in the rear turbine blades. In addition, the bandage segment reduces the flow of the tip of the vane and increases the degree of efficiency of the associated flow machine. The bandages of adjacent rotor blades form a continuous, unbroken bandage. To reduce stress concentrations, known bandage segments have a bulging stiffening structure with respect to the bandage segment surface, which is a so-called "dog-bone" or "dog-bone half".

[0003] As a disadvantage of the known bandage segments, the fact that they must be made relatively bulky to allow for sufficient reduction of stress concentration should be considered. As a result, the total weight of the bandage segment and the blade provided with it is considerable. During the operation of the blade in the associated flow machine, this results in high displaced masses.

[0004] A turbine blade with a bandage is known from GB 2 290 833 A.

[0005] WO2005 / 008032 discloses a rotor blade or a rotor blade segment for a gas turbine with a blade blade and a bandage.

[0006] From US 6 491 498 B1 a turbine blade for gas turbines with a bandage is known.

[0007] The object of the present invention is to create a bandage segment that allows weight reduction while good stress reduction. In addition, it is an object of the present invention to propose a flow machine with a rotor.

This object according to the invention has been achieved by a bandage segment having the characteristics of claim 1 and a flow machine having the features of claim 11. Preferred embodiments with purposeful improvements of the invention are given in the dependent claims, wherein preferred embodiments of the bandage segment should be considered as advantageous shaping of the flow machine and vice versa.

[0009] In the bandage segment according to the invention, which makes it possible to reduce the weight while simultaneously reducing the stress, the stiffening structure is at least in some areas of the cross-shaped configuration. By cross-shaped it is possible to significantly reduce the stress concentration in the bandage segment and improve the stiffness of the bandage segment while optimizing the weight.

[0010] The stiffening structure of the bandage segment according to the invention comprises at least two cross-ribs, the major axes of which are aligned with each other at a predetermined angle. This allows a simple and purposeful adjustment of the stress level within the bandage segment, with individual bandage segment types being necessary. Then, for example, it can be predicted that a given angle depending on the given geometry of the bandage segment, the material of the bandage segment and the subsequent application conditions will be determined in the associated flow machine.

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[0011] In a further embodiment, it has proven advantageous when the main axes of the ribs are positioned at an angle between 20 ° and 90 ° with respect to each other. Thanks to this, a particularly advantageous distribution of stresses inside the bandage segment with a high stiffness is guaranteed.

[0012] Further advantages arise from the fact that the stiffening structure comprises at least one rib that is longitudinal and / or perpendicular to the stress lines of the bandage segment. Thanks to the rigidity achieved in the bandage segment, a particularly low stress level within the bandage segment is obtained.

In a further embodiment of the invention, it is provided that the stiffening structure comprises at least one rib which, at its longitudinal extent in the profile, has a constant and / or point-dependent height. In other words, one or more ribs of the stiffening structure are predicted to have a uniform height profile for their respective longitudinal extent or variable for their respective longitudinal extent, thereby achieving a particularly precise possibility of adjusting the stiffening structure to a given configuration of the bandage segment and the individual stress line course inside the bandage segment.

[0014] An optimal possibility of adjusting the bandage segment in terms of minimum weight at maximum stress reduction in a further advantageous embodiment of the invention is made possible by the fact that at least one rib has a height between 0.1 cm and 10 cm.

[0015] In this case, it still remains advantageous if the stiffening structure comprises at least one rib which has a cross-sectional profile at its longitudinal extent, which is selected depending on the stress profile of the bandage segment without the rib. In other words, the cross-sectional profile of at least one rib is made on the longitudinal extent, taking into account the stress profiles that this bandage segment would have without the rib. For example, at least one rib in areas of potential high stress may have a thickened cross-sectional profile. Conversely, in areas of potentially low stress, a correspondingly reduced profile of the cross-section can be provided.

[0016] Increasing the durability of the bandage segment in a further embodiment is made possible by the fact that the stiffening structure comprises rounded surface transitions to the bandage segment surface, because it reliably avoids the occurrence of peak force values ​​at the edges of the stiffening structure, for example in the case of tensile or bending loads bandage segment.

[0017] Particularly high stiffness of the bandage segment with an optimized weight is obtained by the fact that the stiffening structure of the bandage segment according to the invention limits on the side at least one discontinuous surface area of ​​the bandage segment. In other words, the bandage segment has a recess, which is formed by a buckled stiffening structure.

A particularly uniform distribution of force and stress on the bandage segment is obtained by a further configuration in that the stiffening structure limits four and / or six discontinuous areas of the bandage on the sides.

[0019] In a further preferred embodiment of the invention, it is provided that the bandage segment has two oppositely disposed longitudinal cross-sections and substantially Z-shaped contact surfaces for connecting the matching contact surfaces of two successive bandage segments. Thanks to this, adjacent rotor blades, each of which is equipped with this kind of bandage segment, during operation

VP / 4842 / AG

An associated flow machine or rotor equipped with rotating blades can support each other in pairs, which provides a particularly mechanically stable reinforcement. In this way, undesirable bending or twisting of the rotating blades is also minimized.

[0020] Particularly high rigidity in the further embodiment is achieved by the fact that the stiffening structure comprises at least one rib that extends between the two contact surfaces. In this case, it can in particular be provided that the rib extends between the corresponding corner areas of both Z-shaped contact surfaces, because these corners usually have particularly high stress concentrations.

[0021] In certain embodiments of the invention, the rotor blade, and in particular the gas turbine blade for the flow machine, with the bandage segment located in the end region of the rotor blade, has a stiffening structure bulged with respect to the bandage segment surface. The reduction of the weight of the rotor blade while at the same time a good reduction in tension makes it possible for the stiffening structure to be in the form of a cross in at least some areas. The cross-shaped design can significantly reduce the stress concentration in the bandage segment and improve the stiffness of the bandage segment while optimizing the weight.

[0022] In this case, it has proven advantageous if the bandage segment is made according to one of the previous embodiments. The resulting advantages are found in the relevant descriptions. [0023] In a further embodiment, particularly high mechanical stability and loadability of the rotor blade is achieved in that the bandage segment is made in one piece with the rotating blade. Although the bandage segment and the rotor blade are generally made in two parts or in part, and can be connected in a suitable manner, the one-piece version can also be omitted from the necessary assembly stage, thus ensuring a corresponding reduction in costs.

A further aspect of the invention relates to a flow machine, in particular a thermal gas turbine with a rotor, which includes at least one rotating blade with a bandage segment arranged on the radial end area of ​​the rotor blade, wherein the bandage segment has a braced stiffening structure relative to the bandage surface area. At the same time, the weight reduction of the at least one rotor blade, while at the same time a good reduction of the voltage according to the invention, is made possible in that the bandage segment and / or the rotor blade are shaped according to one of the preceding embodiments. As a result, the weight of the rotor or the entire flow machine is optimized accordingly, while its load capacity is improved, which allows for longer service cycles. preferably, all segments of the bandage and / or the rotor blades are made according to one of the preceding embodiments to achieve the greatest reduction in weight and stresses. Furthermore, during the operation of the flow machine, the moving mass is correspondingly reduced, which results in further advantages, in particular in terms of fuel economy.

[0025] Further features of the invention result from the patent claims, embodiments and drawings. The features mentioned above and combinations of features, as well as the features and combinations of features listed below in the embodiments of the invention may be used not only in a given combination, but also in other combinations or separately without departing from the scope of the invention. At the same time, the figures show:

Fig. 1 a schematic plan view and sectional side view of a prior art bandage segment with a stiffening structure;

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EP 2 376 746 B1

Fig. 2 a schematic plan view and sectional side view of a prior art bandage segment with an alternative stiffening structure;

Fig. 3 a schematic perspective view of a rotor blade with a bandage segment according to the invention which has a stiffening structure according to a first embodiment;

Fig. 4 a schematic perspective view of a rotor blade with a bandage segment according to the invention which has a stiffening structure according to a second embodiment;

Fig. 5 a schematic, fragmentary and transparent top perspective view of the rotor blade shown in Fig. 4; and

Fig. 6 a schematic and fragmentary view of a construction grid of the rear side of a rotor blade according to the invention with a bandage segment that has a stiffening structure according to a third embodiment.

[0026] Fig. 1 shows a schematic plan view of the prior art bandage segment 10 for being placed on the impeller blade 12 (see Fig. 3) and a side section view of the bandage segment 10 along the intersection line II. The bandage segment 10 has a stiffening structure 16, bulged against the surface of the bandage 14, which - as can be seen from above - is substantially made in the shape of a bone and is therefore referred to as "dog-bone".

[0027] Fig. 2 shows a schematic plan view of a prior art bandage segment 10 for placement on the impeller blade 12 (see Fig. 3) and a side section view of the bandage segment 10 along the intersection line II. The segment 10 of the bandage, as compared to the segment 10 of the bandage shown in Fig. 1, has an alternative stiffening structure 16, which is flattened on one side and is therefore referred to as "half dog-bone".

[0028] The two banding segments 10 shown in Figures 1 and 2 have the disadvantage that their stiffening structures 16 must be made with a comparable volume in order to be able to guarantee a sufficient reduction in the stress concentration in the bandage segment. As a result, the weight of the 10 bandage segments and the rotor blade 12 connected to this type of bandage segment are increased.

[0029] Fig. 3 shows a schematic perspective view of a rotor blade 12 made as a gas turbine blade for a flow machine with a bandage segment 20 according to the invention that has a stiffening structure 22 according to a first embodiment. The stiffening structure 22 is also bulged in relation to the surface 24 of the bandage segment 20, but in contrast to the embodiments shown in Figures 1 and 2 in some areas is cross-shaped. By cross-shaped, it is possible to significantly reduce the stress concentration in the bandage segment and improve the stiffness of the bandage segment while optimizing the weight. The stiffening structure 22 includes here two ribs arranged cross-spaced 26, whose main axes H1, H2 are set at a given angle α with each other, and which have a fixed height on their longitudinal extent in the profile. In addition, both ribs 26 are arranged along or perpendicular to the tension line of the bandage segment 20. As a result, a particularly effective reduction in the stress level of the bandage segment 20 is obtained. The height of the ribs 26 and the angle α between the main axes H1, H2 of the ribs 26 can be precisely adjusted to the level of stress. The angle α and the profile of the ribs 26, and in particular their height, must be determined individually for each type of bandage segment, depending on the given stress line that would occur without the stiffening structure. a particularly effective reduction in the stress level of the bandage segment 20 is obtained. The height of the ribs 26 and the angle α between the main axes H1, H2 of the ribs 26 can be precisely adjusted to the level of stress. The angle α and the profile of the ribs 26, and in particular their height, must be determined individually for each type of bandage segment, depending on the given stress line that would occur without the stiffening structure. a particularly effective reduction in the stress level of the bandage segment 20 is obtained. The height of the ribs 26 and the angle α between the main axes H1, H2 of the ribs 26 can be precisely adjusted to the level of stress. The angle α and the profile of the ribs 26, and in particular their height, must be determined individually for each type of bandage segment, depending on the given stress line that would occur without the stiffening structure.

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[0030] The bandage section 20 further has two oppositely disposed longitudinal cross sections and substantially Z-shaped contact surfaces 28 ("Z shroud") for connecting the matching contact surfaces of two successive (not shown) bandage segments. One of the ribs 26 extends between the corners III of both Z of the shapely contact surfaces 28, whereby a particularly high stress reduction is achieved in otherwise stress-strained areas of the bandage segment 20. In addition to the ribs 26, the stiffening structure 22 is shaped such that it limits the discontinuous regions 24 of the surface of the bandage section on the sides. The areas of the 24th surface of the bandage segment are in other words the bottom surfaces of the four depressions,

[0031] The stiffening structure 22 may in principle be produced by separating the bandage segment from the blank. Alternatively, the bandage segment 20 can optionally be produced in one piece with the rotating blade 12 - using casting methods, in particular precision casting or generative methods.

[0032] Fig. 4 shows a schematic perspective view of a rotor blade 12 with a bandage segment 20 according to the invention which has a stiffening structure 22 according to a second embodiment. 4 is hereinafter explained in the joint observation of FIG. 5, which shows a schematic, fragmentary and transparent top perspective view of the rotor blade 12 shown in FIG. 4. In contrast to the embodiment shown in FIG. 3, the structure stiffening 22 includes three ribs 26a-c, which are respectively spaced in pairs and also extend along or perpendicular to the stress lines of the bandage segment 20. The angle α between the main axis H (not shown) of the rib 26c and the main axis H of the rib 26a and the angle α between the main axis H of the rib 26c and the main axis Hb of rib 26b are here chosen in the same way so that the main axes H of the ribs 26a, 26b run parallel to each other. Due to the additional rib 26b, the stiffening structure 22 now now limits the discontinuous areas 24 of the bandage segment surface.

[0033] Fig. 6 finally shows a schematic and fragmentary view of the construction grid of the rear side of the rotor blade 12 according to the invention, which is made in one piece with the bandage segment 20. The bandage segment 20 itself has a stiffening structure 22 according to the third embodiment. The stiffening structure 22, as in the first embodiment, comprises two cross-ribs 26. The ribs 26 are also arranged longitudinally or perpendicular to the stress lines of the bandage segment 20, only one of the ribs 26 being visible. The angles α between the main axes H of the ribs 26 and the height or course of the profile of the ribs 26 are, however, selected depending on the stress level of the bandage segment without these ribs 26.

The parameter values ​​given in the documents to define process and measurement conditions to characterize the specific properties of the subject matter of the invention should also be considered within deviations - e.g. caused by measurement errors, system errors, weighing errors, DIN tolerances and the like - as included in the frame. invention.

VP / 4842 / AG

EP 2 376 746 B1