EP1322838B1 - Moving blade for a turbo-machine and turbo-machine - Google Patents

Abstract

The invention relates to a novel blade design which does not exceed the permitted stresses for particular loads, especially as a result of the centrifugal force and which at the same time, allows the turbo-machine (3) to function with a high degree of efficiency. To this end, an inventive moving blade (1) for a turbo-machine (3) consists at least partially of a cellular material (5), especially a foamed metal (21). Said cellular material (5) can be provided e.g. in the hollowed-out part (7) of the moving blade (1).

Description

The invention relates to a blade for a turbomachine. The invention further relates to a turbomachine with a blade.

Blades for turbomachinery, such as blades for high, medium or low pressure turbine part of a steam turbine or gas turbine blades for compressor or turbine, are usually made of homogeneous metallic alloys. In addition to milling processes, casting and forging techniques are used. The metallic raw material is melted and then rolled as bar stock or forged as a blade blank.

Such a turbomachine comprises a single impeller or a number of impellers arranged one behind the other in the axial direction, the rotor blades of which are surrounded during operation by a gaseous or vaporous flow medium. The flow medium exerts a force on the blades, which causes a torque of the rotor or paddle wheel and thus the working power. For this purpose, the blades are usually arranged on a rotatable shaft of the turbomachine, whose vanes are arranged on corresponding guide wheels on the stationary, the shaft surrounding the formation of a flow channel housing, the housing of the turbomachine, are arranged.

While mechanical energy is supplied to the flow medium in a compressor or a compressor, in a turbine as a turbomachine mechanical energy is withdrawn from the flow medium flowing through. In a conventional turbomachine with a rotating shaft in operation and with resting housing generates the centrifugal force in the or each blade attached to the shaft has a tensile load superimposed on a bending load caused by the flow forces of the flow medium. This results in a critical load at those points in the blade root and in the shaft at which the bending tension and the tensile stress due to the centrifugal force overlap. Due to this critical load, the blade height is limited in its radial dimension and thus the efficiency of the turbomachine.

In particular, the blades of steam turbine low pressure parts (ND blades) are mainly loaded by centrifugal force due to the rotation of the shaft. The load is thus directly proportional to the density of the blade material used. Since the densities of the materials used are very similar to those of iron, the load on long ND blades is so great that a certain blade length can not be exceeded. This is particularly important for the higher stages of ND blading whose radial dimensions are limited by the limits of centrifugal load. Due to the limited blade length only a certain outlet cross section for the flow medium can be achieved, so that the flow medium, e.g. the exhaust steam of a low-pressure turbine part, leaves the turbomachine at high speed and consequently with high losses.

Previous solutions to ND blade problems require that titanium alloy materials be used for very long blade lengths. Titanium alloys have a lower density compared to alloys based on iron, cobalt or nickel, and rotor blades made of this material are therefore subject to less stress than blades made of the hitherto customary metallic materials with otherwise identical dimensions. The disadvantage of this problem solution, however, is that titanium alloys are very expensive and the problem of centrifugal load is still, albeit to a lesser extent.

Both US Pat. No. 3,695,778 and US Pat. No. 5,634,189 show components or a turbine blade having an outer wall made of a non-cellular material, wherein a cavity formed by the solid wall is filled with cellular material.

The object of the invention is to specify a blade design for a rotor blade for a turbomachine, which does not exceed the permissible stresses at the given loads in the turbomachine and nevertheless allows a high degree of efficiency. Another object of the invention is to provide a turbomachine for high loads with high efficiency.

According to the invention, the object directed to a blade is achieved by a blade for a turbomachine, wherein the blade forms an outer surface with a closed structure with respect to cells and a blade profile consists entirely of a cellular material.

Compared to the conventional embodiments of blades for turbomachines, such as gas or steam turbines, the invention takes a completely new approach. Hitherto, homogeneous metallic materials have been used for the moving blades, the concept of the invention is based on the structural design of the moving blade and the materials forming it. The use of cellular materials for the blade results in a significant reduction in the mean density of the blade. The cellular structure ensures a much lower density than previously common homogeneous materials. By targeted regional arrangement of the cellular material, blades according to the invention therefore cause much lower stresses due to the centrifugal force. Thus, when using cellular materials, it is possible to realize blades with a significantly larger blade length, so that a larger flow cross-section with lower losses when using the blade in a turbomachine can be realized.

Cellular materials also have a greater internal damping than homogeneous materials, so that they advantageously dampen possible vibrations particularly efficient. In addition, cellular materials show good stiffness properties, so that they have approximately the permissible load of comparable homogeneous materials due to the high specific strength. This is particularly advantageous when used in a turbomachine, where significant thermo-mechanical loads are recorded. By selectively selecting areas of the blade where the cellular material is provided, a load-adapted bucket design for the blade can be specified. Depending on the application, therefore, different areas of the blade may have the cellular material.

The blade preferably has an airfoil portion with the cellular material. Especially the blade blade area of a blade is exposed to particularly high blade stresses when using the blade in a turbomachine due to the centrifugal force, since the blade blade area relative to other areas of the blade has a greater radial distance from the axis of rotation. An airfoil region having the cellular material results in a correspondingly lower centrifugal load due to the significantly lower density.

The moving blade preferably has a fastening region, in particular a blade root, wherein the cellular material is provided in the fastening region. The attachment of a blade is usually carried out on a rotatable shaft, wherein a mounting region of the blade is connected to a corresponding receiving region of the shaft. Various blade attachment concepts are known, such as fir tree slot connections or hammer head connections, to which the new blade concept is applicable. By providing the cellular material in the mounting area of the blade, the blade stresses can be reduced accordingly also in the attachment area. By combining different areas of the blade, in which the cellular material is provided, is a targeted adjustment allows for the respective loads. For example, the cellular material may be provided both in the airfoil region and in the attachment region.

The blade can also consist as a whole of a cellular material, which is achieved due to the reduction in density over a comparable solid material, a lightweight construction of the blade as a whole. In terms of physical properties such as weight, hardness and flexibility, the cellular structure of the blade is far superior to the use of massive light metals, such as titanium alloys.

In a preferred embodiment, the blade has an inner region and a jacket region surrounding the inner region, wherein the cellular material is provided in the jacket region and in the inner region.

Further, the cellular material forms an outer surface with closed structure to the cells. This is particularly advantageous if the outer surface is a partial surface of the blade airfoil region of the rotor blade, wherein the airfoil region is subjected to a flow medium during operation. By forming a closed structure of the outer surface, a surface, eg a surface in the airfoil region, with correspondingly low roughness is provided. Advantageously, the cellular structure of the material provides an outer surface which also has a strong cushioning effect against secondary losses due to cross-flow, provided that the outer surface of the cellular structure is exposed to a flow medium. For this purpose, the surface has barriers for a possible transverse flow, which may be formed along adjacent cells of the cellular structure.

In a particularly preferred embodiment, the cellular material is a metal foam. Above all, metal foams are considered lightweight materials with high potential and a wide range of applications. Metal foams can be obtained in various manufacturing processes, for example by means of melting and powder metallurgy deposition and sputtering techniques. In a powder metallurgical process, a replacement material is produced by mixing a metal powder with a blowing agent, for example metal hydride, which is compacted after subsequent axial hot pressing or extrusion to form a prefabricated semi-finished product that can be conformed to shape by appropriate forming to a respective end product and by appropriate heating is foamed to just above the melting temperature of the metal. The blowing agent contained in the semifinished product, for which titanium hydride is typically used, decomposes on heating and splits off hydrogen gas. The gaseous hydrogen leads as a propellant gas in the molten metal to the corresponding pore formation. The porosity of the metal foam formed by the pores can be adjusted in a targeted manner over the duration of the foaming process.

Preferably, the density of the metal foam is between about 5% to 50%, more preferably between about 8% to 20%, of the density of the bulk material.

Preferably, the metal foam consists of a high-temperature-resistant material, in particular a nickel-based or cobalt-based alloy. The choice of a high-temperature resistant material is particularly advantageous for use in a gas turbine, with turbine inlet temperatures of up to 1200 ° C. The application in a steam turbine with high steam conditions of more than 600 ° C steam temperature is made possible by this choice of material for the metal foam.

Preferably, the blade is configured as a gas turbine blade, a steam turbine blade, particularly a low pressure steam turbine blade, or a compressor blade. In particular, the use of the blade in a low-pressure steam turbine appears to be particularly advantageous because the use of the cellular material, such as a metal foam, larger blade lengths at lower centrifugal load compared to the conventional blades can be realized. This has a directly favorable effect on the efficiency of the turbomachine, for example a low-pressure steam turbine.

The task directed towards a turbomachine is achieved according to the invention by a turbomachine with a moving blade according to the above statements.

Advantageously, the turbomachine is designed as a gas turbine, a steam turbine or a compressor.

The advantages of such a turbomachine arise in accordance with the comments on the blade.

FIG 1

in perspektivischer Ansicht eine Laufschaufel für eine Strömungsmaschine,

FIG 2

in perspektivischer Ansicht eine Laufschaufel für eine Strömungsmaschine, die bereichsweise aus einem zellularen Werkstoff besteht,

FIG 3

eine perspektivische Darstellung einer gegenüber FIG 2 modifizierten Laufschaufel,

FIG 4

eine Laufschaufel nach dem Stand der Technik,

FIG 5, FIG 6

jeweils eine Schnittansicht einer Laufschaufel in erfindungsgemäßer Ausgestaltung,

FIG 7

in vergrößerter Darstellung die Einzelheit VII der in FIG 6 gezeigten Laufschaufel, und

FIG 8

einen stark vereinfachten Längsschnitt eines Ausschnitts einer Strömungsmaschine mit Laufschaufeln.

The invention will be explained in more detail by way of example with reference to the drawing. It shows schematically and partially simplified:

FIG. 1

a perspective view of a blade for a turbomachine,

FIG. 2

3 is a perspective view of a blade for a turbomachine, which is partially made of a cellular material,

FIG. 3

3 a perspective view of a blade modified relative to FIG. 2, FIG.

FIG. 4

a blade according to the prior art,

FIG. 5, FIG. 6

each a sectional view of a blade in the inventive design,

FIG. 7

in an enlarged view, the detail VII of the rotor blade shown in FIG 6, and

FIG. 8

a highly simplified longitudinal section of a section of a turbomachine with blades.

Like reference numerals have the same meaning in the various figures.

1 shows a perspective view of a blade 1, which extends along a longitudinal axis 25. The blade has along the longitudinal axis successively a mounting region 9, an adjoining paddle platform 23 and an airfoil region 7. In the fastening region 9, a blade root 11 is formed, which serves for fastening the blade 1 to the shaft of a turbomachine, not shown in FIG 1 (see FIG 8). The blade root 11 is designed as a hammer head. Other configurations, for example as a Christmas tree or Schwalbenschwanzfuß are possible. In conventional blades 1 massive metal materials are used in all areas 9, 23, 7 of the blade 1. The blade 1 can be made by a casting process, by a forging process, by a milling process or combinations thereof.

A blade 1 according to the invention is shown in FIG. The moving blade 1 is partially made of a cellular material 5 in comparison to the conventional moving blade 1 shown in FIG. 1. The cellular material 5 is provided in the blade blade region 7 of the moving blade 1, the entire blade blade region 7 being the cellular material 5 has. The cellular material 5 has a plurality of cells 17, 17a, 17b. The cell structure of the cellular material 5 may be such that a closed porous structure is achieved with each of the cells 17, 17a, 17b closed. In an alternative embodiment of the cellular material, the cells 17, 17A, 17B may also form an at least partially non-closed porous structure. By providing the cellular material 5 in the airfoil region 7, a region 7 with a significantly reduced material density is provided in the airfoil region 7 compared to conventional blades 1 with a solid material insert (see FIG. This is achieved due to the cellular structure of the material 5. Due to the reduced density in the airfoil region 7, a considerable reduction in the load due to the centrifugal force F _z directed radially outward along the longitudinal axis 25 is achieved in the operating case, for example when using the blade 1 in a turbomachine. The region of the blade 1, which experiences a larger centrifugal force F _z due to the greater radial distance from the axis of rotation, namely the blade blade region 7, is specifically provided with the cellular material. With the invention, an adaptation to the respective requirements, which depend on the application and the resulting stresses on the blade 1, possible. For the first time, the structural properties of the materials are taken into account and used to advantage over conventional concepts.

The cellular material 5 may be provided in different regions 9, 23, 7 of the blade 1. In order to illustrate this flexibility, FIG. 3 shows a perspective view of a blade 1 with a modified embodiment with respect to the blade 1 shown in FIG. 2 with regard to the presence of the cellular material 5. For the sake of clarity and clarity, this is based on the details X1 and X2 of the blade 1 clarifies light. The cellular material 5 is present according to detail X1 in the attachment area 9 as well as in the area of the blade platform 23 according to detail X2. The details X1 and X2 represent exemplary subregions of the attachment region 9 or the blade platform 23. Of course, in an advantageous embodiment, the entire attachment region 9 and / or the region of the blade platform 23 can be made of the cellular material 5. The cellular material 5 comprises a plurality of cells 17.

4 shows a blade 1 according to the prior art. The rotor blade 1 has an inlet edge 31 and an outlet edge 33. Furthermore, the moving blade 1 has a pressure side 35 and a suction side 37 opposite the pressure side 35. A typical blade profile is given by this. The rotor blade 1 has an inner region 13 and a jacket region 15 surrounding the inner region 13. The jacket region 15 forms an outer surface 39 of the rotor blade 1, wherein the outer surface 39 is acted upon in the case of operation with a flow medium, for example a hot gas or steam. According to FIG. 4, the jacket region 15 consists of a conventional, unspecified, for example, metallic solid material 27. The inner region 13 consists, at least partially, of a cellular material 5, the cellular material 5 being formed of a metal foam 21 with a multiplicity of adjacent cells 17 is. In the inner region 13 cooling channels 29, 29 A, 29 B are provided, so that the blade 1 is designed in the case of operation for an interior cooling. Here, the cooling channels 29, 29 A, 29 B are acted upon by a coolant, for example cooling air or cooling steam. The cooling channel 29 serves for example for the supply of the coolant, while the cooling channels 29A, 29B serve for the removal of the coolant. The cooling channels 29, 29A, 29B are formed in the inner region 13 by corresponding recesses of the cellular material 5. The blade of FIG 3 can hereby For example, be prepared in that the thin-walled the blade profile forming shell portion 15 is ejected as a mold with the metal foam 21, wherein corresponding removable or leachable casting cores for forming the cooling channels 29, 29 A, 29 B are positioned prior to the injection of the metal foam 21 in the inner region 13. With the construction of the rotor blade 1 shown, a thin-walled jacket region 15 is produced, which is supported by the cellular material 5 in the inner region 13 as a support structure.

An inventive embodiment of a blade profile of a blade 1 is shown in FIG. Here, the jacket region 5 consists of a metal foam 21, which encloses an inner region 13. The inner region 13 forms a cavity of the rotor blade 1, so that an interior cooling is possible. The jacket region 15 has an outer surface 39, which in the case of operation is acted upon by a flow medium. Compared with the variant shown in FIG. 4, the metal foam 21 forms the outer surface 39.

Another variant of a blade 1 is shown in a sectional view in FIG. Here, the blade profile completely made of a cellular material 5, in which case a metal foam 21 is provided here again. At the same time forms, as discussed in connection with FIG 5, the metal foam 21 an outer surface 39. The inner region 13 and the cladding region 15 of the blade 1 thus consist of cellular material. 5

7 shows an enlarged detail of a detail VII of the rotor blade 1 shown in FIG. 6. The cellular structure of the material 5, which is provided here by a metal foam 21, is intended to be clarified hereby. A plurality of cells 17, 17A, 17B are shown with cells 17A, 17B contiguous and part of the surface 39 of the blade 1 form. In addition, cells 17 are also provided which do not form an outer surface 39. These cells 17 may also be referred to as inner cells 17. The cells 17, 17A, 17B have, in the sectional view, by way of example a polygon structure. In a three-dimensional view this corresponds to polyhedra or linear combinations of polyhedra. Due to the structure and arrangement of the cells 17A, 17B, the cellular material 5 forms an outer surface 39 with a closed structure with respect to the cells 17A, 17B. Thus, an outer surface 39 of the rotor blade 1 is provided, which has a sufficiently low surface roughness, so that accordingly correspondingly low flow losses are ensured when using the rotor blade 1 in a turbomachine (see FIG. Compared to conventional blades 1, a competitive, if not superior, solution is thus also shown with regard to the smoothest possible surface. Advantageously, the local surface structure in the region of adjoining near-surface cells 17A, 17B can in particular significantly reduce the secondary losses as a result of transverse flows.

In FIG. 8, a detail of a turbomachine 3 is shown in simplified representation in a longitudinal section using the example of a low-pressure steam turbine 59. The low-pressure steam turbine 59 has a rotor 43 which extends along the axis of rotation 41 of the steam turbine 59. Furthermore, the low-pressure steam turbine 59 has an inflow region 49, a blading region 51 and an outflow region 53 along the axis 41 in succession. In the blading area 51 rotatable blades 1 and fixed vanes 45 are arranged. The rotor blades 1 are fastened to the turbine rotor 43, while the stator blades 45 are arranged on a guide blade carrier 47 surrounding the turbine rotor 43. Through the shaft 43, the Beschaufelungsbereich 51 and the Leitschaufelträger 47 is an annular flow channel for a flow medium A, for example, superheated steam formed. The inflow region 49 serving to supply the flow medium A is bounded in the radial direction by an inflow housing 55 arranged upstream of the guide vanes carrier 59. An outflow housing 57 is disposed downstream of the vane support 47 and defines the outflow region 53 in the radial direction. During operation of the steam turbine 59, the flow medium A, here a superheated steam, flows from the inflow region 49 into the blading region 51, where the flow medium A performs work under expansion, and then leaves the steam turbine 59 via the outflow region 53 downstream of the outflow housing 57, not shown in detail in FIG 8, capacitor for the steam turbine 59 collected.

As it flows through the blading region 51, the flow medium A relaxes and performs work on the rotor blades 1, causing them to rotate. The rotor blades 1 of the low-pressure steam turbine 51 consist, at least in regions, of a cellular material 5, as described in FIGS. 2 to 7.

As a result, the rotor blades 1 have a lower density than conventional rotor blades 1 (see FIG. 1) and are not subjected to such high loads as a result of the centrifugal force. The rotor blades 1 form the low-pressure blading of the low-pressure steam turbine 59. By the use of a cellular material 5 for the rotor blades 1, blades 1 can be used with a larger radial dimension due to the density advantage, so that a larger flow cross-section with lower losses for the blades Steam turbine 59 is realized.

In addition to the rotor blades 1, the guide vanes 45 can also be made in regions of a cellular material 5, so that in the blading region 51 both rotor blades 1 and vanes 45 can be used in lightweight construction. Farther is an application of the new blade concept on other types of turbomachines 3 possible. Thus, the blading of a gas turbine, a compressor, a high-pressure or medium-pressure turbine part of a steam turbine plant rotor blades 1 and / or vanes 45 with the cellular material 5, in particular a metal foam 21 have.

Claims (9)

1. Moving blade (1) for a turbomachine (3), said moving blade consisting, at least in regions, of a cellular material (5), characterized in that the cellular material (5) forms an outer surface (39) with a structure which is closed with respect to cells (17, 17A, 17B), and in that the blade profile consists entirely of a cellular material.
2. Moving blade according to Claim 1, with a blade leaf region (7) having the cellular material (5).
3. Moving blade (1) according to Claim 1 or 2, said moving blade having a fastening region (9), in particular a blade foot (11), the cellular material (5) being provided in the fastening region (9).
4. Moving blade (1) according to one of the preceding claims, the cellular material (5) being a metal foam (21).
5. Moving blade (1) according to Claim 4, the density of the metal foam (21) being between about 5% and 50%, in particular between about 8% and 20%, of the density of the solid material (27).
6. Moving blade (1) according to Claim 4 or 5, the metal foam (21) consisting of a material resistant to high temperature, in particular a nickel-based or cobalt-based alloy.
7. Moving blade (1) according to one of the preceding claims, said moving blade being designed as a gas turbine moving blade, a steam turbine moving blade, in particular a low-pressure steam turbine moving blade, or a compressor moving blade.
8. Turbomachine (3) having a moving blade (1) according to one of the preceding claims.
9. Turbomachine (3) according to Claim 8, said turbomachine being designed as a gas turbine, a steam turbine (59), in particular a low-pressure steam turbine, or a compressor.

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