Thermoplastic last-stage blade
A turbine blade, a turbine and a method of manufacturing a damping zone of a turbine blade are provided. The turbine blade includes a damping zone with a damping layer and the damping layer has a fiber matrix system. The fiber matrix system has a thermoplastic matrix. Reinforcing fibers are embedded in the thermoplastic matrix.
This application claims priority of German Patent Application No. 10 2009 036 018.2 DE filed Aug. 4, 2009, which is incorporated by reference herein in its entirety.
FIELD OF INVENTIONThe present invention relates to a turbine blade. The present invention also relates to a turbine, in particular a steam turbine. The present invention further relates to a method for manufacturing a turbine blade.
BACKGROUND OF THE INVENTIONTurbine rotor blades made of steel are predominantly used nowadays in turbines, in particular in steam turbines. In particular in large stationary steam turbines having large diameters, the achievable rotational speeds for rotor blades made of steel are limited due to the high dead weight. In this case using rotor blades consisting of fiber-reinforced composite materials would be conceivable in order to reduce the mass of the blades significantly, which in turn enables the rotational speed to be increased.
Furthermore, in stationary steam turbines that have large diameters and consequently large blade lengths, undesirable vibrations occur which have to be damped. In present-day applications, therefore, vibration damping is produced by way of additional damping wires or shrouding bands on the surface of the blades. Owing to the blade geometry it is often extremely labor-intensive, time-consuming and difficult to apply said damping wires or shrouding bands to the blades, which in turn entails a deterioration in efficiency and necessitates a complex manufacturing overhead.
SUMMARY OF THE INVENTIONIt is an object of the present invention to provide a turbine blade having damping characteristics.
The object is achieved by means of a turbine blade, a turbine, in particular a steam turbine, and a method for manufacturing a turbine blade having the features recited in the independent claims.
According to a first exemplary embodiment variant, a turbine blade is provided wherein sub-regions of the turbine blade or the entire turbine blade constitute or have a damping zone consisting of a damping layer. The damping layer has a fiber matrix system. The fiber matrix system has a thermoplastic matrix, in which matrix reinforcing fibers are embedded.
According to a further exemplary embodiment variant, a turbine is provided which has the above-described turbine blade.
According to a further exemplary embodiment variant, a method for manufacturing a turbine blade is provided. According to the method, reinforcing fibers are initially embedded into a thermoplastic matrix in order to form a fiber matrix system of a damping layer. By means of the damping layer a damping zone of the turbine blade is formed. The damping zone can embody sub-regions of the turbine blade or the entire turbine blade.
By means of the term “damping zone” an area of a turbine blade is described in which damping characteristics of the turbine blade are integrated. The damping zone is installed in particular in such regions of the turbine blade in which mostly higher shearing or moment loads occur than in the remaining regions of the turbine blade, with the result that damping is desirable in said damping zones. Furthermore, greater vibrations can be damped in the damping zone than in the remaining regions of the turbine blade. The damping zone can define a specific section along the extension zone or, as the case may be, along the length of a turbine blade. The damping zone can also define a specific region in a cross-section of the turbine blade. Thus, for example, an outer region of a turbine blade can have a damping zone, while an inner region can define an arbitrary blade region. In the damping zone it is possible, for example, for high centrifugal forces, high bending loads, high shearing stresses, high torsional loads or undesirable vibrations to be applied which require damping and are damped in the damping zone. For a turbine blade, in particular a thermoplastic last-stage blade, the entire turbine blade forms the damping zone. This means that the entire turbine blade can be manufactured from a plurality of damping layers and consequently can consist of the damping layers themselves.
A “layer”, in particular a damping layer and/or a fiber layer, is understood to mean a stratum of a damping layer or, as the case may be, of a damping material and a stratum of a fiber layer or, as the case may be, of a reinforcing fiber layer. A layer can have a thickness of, for example, 0.1-1 mm, in particular a thickness of 0.2 mm, 0.25 mm and/or 0.3 mm, for example.
The term “fiber matrix system” can be understood to mean a fiber composite consisting of a matrix and reinforcing fibers. The fiber matrix system can constitute, for example, the damping layer in its entirety or a part thereof.
The term “reinforcing fibers” is understood to means fibers which can pass on and transfer forces that act on the fiber matrix system. In comparison with the matrix the fibers can exhibit a high rigidity, in particular in respect of tension. The force flow is mostly configured along the fiber in order to exploit the best rigidity characteristics of a reinforcing fiber.
The term “matrix” is understood to mean a raw material which embeds the reinforcing fibers. The term “embed” serves to define that the reinforcing fibers are present spatially fixed in the matrix and consequently can enable load to be introduced and load to be directed out. The matrix can also protect the reinforcing fibers, for example, against compression in the event of pressure parallel to the fibers. The reinforcing fibers and the matrix are, for example, glued or, as the case may be, fused to one another so that load can be transferred between the matrix and the reinforcing fiber, whereby shearing forces can also be transferred.
The term “thermoplastic” matrix serves to define the material of the matrix. A thermoplastic material or, as the case may be, a thermoplastic matrix has in particular damping characteristics. The thermoplastic material of the matrix has a lower rigidity and a higher damping value in relation to a reinforcing fiber that is subject to tension. Accordingly, the thermoplastic matrix can have a damping effect, whereas the reinforcing fiber has a stiffening effect. The thermoplastic matrix can also be reshaped or fused subsequently. The thermoplastic matrix can consist, for example, of polyetheretherketone (PEEK), of polyamide (PA), of polypropylene (PP), of polycarbonate (PC) or of polyethylene (PE).
The reinforcing fibers can consist, for example, of synthetic fibers, such as e.g. carbon fibers, aramid fibers, polyester fibers, polyamide fibers or polyethylene fibers. As well as these organic reinforcing fibers, inorganic fibers such as glass fibers, natural fibers or metallic fibers can equally well be used.
By means of the present invention a turbine blade which consists in particular of fiber composite materials can be selectively damped without the turbine blade's stability or rigidity being reduced to such an extent that an instability is created. Through the use of a thermoplastic matrix material a selectively adjustable, advantageous potential for vibration damping can be achieved by means of the material itself. In other words, the material-side vibration damping is improved through the use of a material combination consisting of thermoplastic and reinforcing fiber in the critical damping zones or in the entire turbine blade. Furthermore, different combinations of different thermoplastic fiber matrix systems can be provided for damping zones subject to different loads in order to adapt the turbine blade in a targeted manner to a predefined load.
Furthermore, owing to the use of the thermoplastic fiber matrix system the turbine blade can be subject to a subsequent reshaping of the profile of the turbine blade, this being achieved by reheating and consequently partly fusing or, as the case may be, melting the thermoplastic fiber matrix system. In this way a targeted subsequent deformation or, as the case may be, readjustment or fine adjustment to suit specific turbine blade profiles or to match different load stresses is possible. A targeted detuning or, as the case may be, deformation of individual blades on the blade ring can be achieved in this way.
According to a further exemplary embodiment variant, the damping zone has fiber layers, the fiber layers and the damping layer forming a laminar structure.
The term “laminar structure” is understood to mean, for example, a laminate which describes a stacking of the different layers, in particular the damping layers and the fiber layers, on top of one another. A laminar structure describes a layer-by-layer fabrication or, as the case may be, the layer-by-layer construction of the damping zone or also other regions of the turbine blade, such as the other blade regions, for example. The laminar structure or, as the case may be, the laminar structure materials consists or consist of layers superimposed on one another or, as the case may be, different numbers of layers. The individual strata or, as the case may be, the individual layers can be glued, for example, or they can mutually interlock due to the open-cell nature of the materials. For example, the laminar structure can be immersed in resin in order to bond the layers to one another. The laminar structure forms the integral configuration of a component such that forces that act on the component can be transferred via the laminar structure. The laminar structure additionally has the homogeneously running surface of the component. In other words, fixtures glued onto the surface of a component externally do not count as part of the laminar structure of the component or, as the case may be, of the turbine blade.
In this context the term “fiber layer” describes a layer consisting of fibers that can have no thermoplastic material. The fiber layers can, for example, exhibit a high rigidity or, as the case may be, a higher rigidity than the damping layers and consist of different reinforcing fiber materials, as described above.
According to another exemplary embodiment variant, the turbine blade has a blade region, the blade region consisting of a plurality of further fiber layers. The plurality of further fiber layers embodies a further laminar structure. The blade region or, as the case may be, the blade regions can adjoin the damping zone or zones of the turbine blade. The blade regions can consist of the plurality of further fiber layers that exhibit a higher rigidity and load-bearing capability by comparison with the damping zone. Vibrations can be transmitted, for example, from the blade region onto the damping zone, the damping zone being able to damp or, as the case may be, absorb the vibrations by means of the thermoplastic fiber matrix system. By means of the present exemplary embodiment a turbine blade can be provided which along its extension direction has, for example, a plurality of blade regions which in turn adjoin a plurality of damping zones. The damping zones can be arranged at predefined regions having a high loading or, as the case may be, having a high damping requirement. The blade regions can be arranged at areas at which vibration are non-critical or, as the case may be, at which a high rigidity is required. Thus, a turbine blade can be individually adapted to suit the loads to which it is subject and consequently tailored to a detailed requirements profile in terms of costs and efficiency.
According to a further exemplary embodiment variant, the reinforcing fibers are embedded into the matrix at an angle of between 1° (degree) and 90° (degrees) to one another. More particularly with complex loads or, as the case may be, load directions, individual reinforcing fibers can be arranged at different angles to one another. In this case the damping layer or the fiber layer can be produced, for example, as a woven fabric, as a knitted fabric or as a mesh having oriented reinforcing fibers. Depending on the alignment of the reinforcing fibers, the turbine blade can be adapted to predefined load directions, with the result that the turbine blade can be selectively matched to a predefined requirements potential.
According to another exemplary embodiment variant, the reinforcing fibers are embedded into the thermoplastic matrix parallel to one another. In areas in which the turbine blade is subject exclusively to tension, for example, reinforcing fibers arranged in parallel can suffice. Complex interweaves and alignments of reinforcing fibers are then unnecessary, so that a manufacturing method having low manufacturing costs can be created in these areas with parallel reinforcing fibers.
According to a further exemplary embodiment variant, at least one of the reinforcing fibers has a hybrid yarn. The hybrid yarn has a thermoplastic material and a carbon fiber material. Such a hybrid yarn can consist, for example, of many yarns which are twisted together with one another or interlaced with one another and which together form the hybrid yarn. One part of said yarns can consist of a thermoplastic material and the other of a reinforcing fiber material, such as e.g. carbon fibers. Furthermore it is also possible to form the hybrid yarn in such a way that the thermoplastic material is embodied as yarn and the fiber yarn is fused into the thermoplastic yarn. In this way a targeted damping of the turbine blade can be provided in a simple manner already by means of the use of the thermoplastic yarn as a reinforcing fiber.
According to another exemplary embodiment variant, the damping layer has a lower elastic rigidity and/or a higher damping value than the fiber layer.
The term “damping value” describes the damping characteristics of a material. The damping value ‘tan δ’ can lie between 0 and 1, for example.
The teen “rigidity” can describe the E modulus or G modulus, for example. Thus, for example, a fiber can have a rigidity of 130 GPa in the longitudinal direction and only 8 GPa along the transverse direction. In the case of a weft of fibers, rigidities of 65 GPa, for example, can be achieved in each main fiber direction. Each main fiber direction is aligned at an angle a relative to each other. The thermoplastic matrix can have a rigidity of 0.5 to 10 GPa, for example, yet in return exhibit better damping characteristics than the reinforcing fibers.
According to a further exemplary embodiment variant, the damping zone has a lower elastic rigidity and/or a higher damping value than the blade region.
According to a further exemplary embodiment variant, the turbine blade has an enveloping layer. The enveloping layer is wrapped around a surface or, as the case may be, a surface region of the turbine blade in such a way that the turbine blade is protected against external influences. The enveloping layer has a non-reinforced thermoplastic material which is identical to the matrix material. Owing to the high damping effect of a non-reinforced thermoplastic material the softness or, as the case may be, the elasticity of the thermoplastic material can be greater than the elasticity of the fiber layer. When external particles strike the surface of the turbine blade, a surface made of thermoplastic material erodes less than, for example, a fiber layer consisting of reinforcing fibers having a higher rigidity. Accordingly, the service life of a turbine blade can be increased, since damage due to impingement of external particles is reduced. Moreover, a thermoplastic material is generally more resistant to humidity than a reinforcing fiber, so corrosion is reduced.
According to another exemplary embodiment variant, the damping zone has a further fiber matrix system having a thermoplastic matrix. The further fiber matrix system is disposed in the damping zone and/or in the blade region such that said system is exposed to external influences of the turbine blade. The further fiber matrix system having a thermoplastic matrix has reinforcing fibers which are present as fiber mats in arbitrary main fiber directions. As a result of the arbitrary alignment of the main fiber directions of the reinforcing fibers, the rigidity characteristic of the further fiber matrix system is reduced and a better absorption characteristic and a greater resistance toward an impact of external particles are achieved. Moreover, the further fiber matrix system can also be extended over the other areas of the turbine blade, for example also over the blade regions. In comparison with a non-reinforced thermoplastic matrix, the further fiber matrix system having a fiber-reinforced matrix can have not only a high absorption capability in respect of impinging particles but also a higher rigidity, with the result that the further thermoplastic fiber matrix system can likewise contribute toward the overall rigidity of the turbine blade. Accordingly, a rigid material can be provided for a turbine blade while at the same time increasing the erosion resistance and also the corrosion resistance toward liquids of a surface of the turbine blade. With steam turbines in particular, erosion due to water droplets is critical. A surface or, as the case may be, an outer layer of the turbine blade consisting of non-reinforced thermoplastic or, as the case may be, of a terminating layer consisting of thermoplastic matrix material or, as the case may be, of a terminating layer of the further thermoplastic fiber matrix system can provide an integrated erosion layer without the necessity of applying additional sealing layers.
According to a further exemplary embodiment variant, a turbine, in particular a steam turbine, is equipped with the above-described turbine blades. Steam turbines in particular have large diameters, in particular in the first compressor stage and the last turbines stage. High centrifugal forces, bending moments and torsion forces act in particular in the case of blade wheels of a steam turbine having a large diameter. Specifically in that situation it is suitable to use the turbine blade according to the invention in order to achieve adequate rigidity while improving damping characteristics compared to conventional turbine blades. Accordingly, turbine blades consisting of a composite material can be employed even for steam turbines having large diameters.
According to a further exemplary embodiment variant of the method, the thermoplastic matrix is melted during the embedding process and the reinforcing fibers are pressed onto the matrix. Thus, an economical manufacture using the hot-press method can be provided in that the thermoplastic material present in the matrix is melted. Long infiltration and curing times as in the case of conventional fiber composite layers, for example, can be dispensed with.
According to a further exemplary embodiment variant of the method, the damping zone is reshaped by means of a further fusing or melting of the thermoplastic matrix in order to match a predefined shape of the turbine blade. Owing to this fusibility or meltability of the fiber matrix system or, as the case may be, of the thermoplastic matrix the definitive shaping of the turbine blade, e.g. a twisting of the turbine blade, can be carried out directly after the manufacturing process, e.g. a hot-press process. This can be useful above all in the case of special turbine requirements, in particular in the case of special requirements in terms of the twisting angle, etc. Furthermore, a subsequent reshaping or, as the case may be, readjustment helps in the case of specific problems with an oscillation frequency. By means of the remelting the damping zone can be subsequently reshaped or, as the case may be, fine-adjusted, for example, to a changed or, as the case may be, unanticipated oscillation frequency.
Furthermore, the property of the remeltability of the fiber matrix system also permits a subsequent blade repair. For example, an additional thermoplastic material can be applied in order to rectify damage to the fiber matrix system. Accordingly, the possibility of a repair is created. In other words, an additional thermoplastic can be applied locally in order to repair damage to the turbine blade.
It is pointed out that embodiment variants of the invention have been described with reference to different subject matters of the invention. In particular some embodiment variants of the invention are described by means of device-related claims and other embodiment variants of the invention by means of method-related claims. However, it will become immediately clear to the person skilled in the art when reading this application that, unless explicitly stated otherwise, in addition to a combination of features that belong to one type of inventive subject matter, an arbitrary combination of features that belong to different types of inventive subject matter is also possible.
Further advantages and features of the present invention will emerge from the following exemplary description of currently preferred embodiments.
The same or similar components are labeled with the same reference numerals throughout the figures. The depiction in the figures is schematic and not to scale.
The turbine blade 100 has, as shown in
The fiber layers 104 in the damping zone 101 can transition seamlessly into the blade regions 102. In the case of a seamless or, as the case may be, constant transition of the fiber layers 104 from the damping zone 102 into the blade regions 102, the fiber layers 104 together with the further fiber layers 105 form a continuously running layer. Furthermore, the damping zones 101 can be manufactured as semifinished products, wherein the fiber layers 104 do not run beyond the damping zone 101 or, as the case may be, do not protrude into the blade regions 102. The fiber layers 104 are truncated, for example, at the border regions of the damping zones 101.
In the damping zone 101, the vibration damping can be produced in that a laminar structure 106 forms the damping zone 101, the laminar structure 106 consisting of at least one damping layer 103 and of further fiber layers 104. Owing to the layer-by-layer structure by means of the damping layer 103 the damping zone 101 can be less rigid than the blade regions 102, with the result that in this case vibration damping is produced by means of the laminar structure 106, i.e. by means of the material itself
Furthermore, an enveloping layer 108 can be molded around the turbine blade 100, the enveloping layer 108 protecting at least the damping zone 101 but also in addition the blade regions 102 against external influences. In this arrangement the enveloping layer 108 can consist, for example, of a non-reinforced thermoplastic material. A non-reinforced thermoplastic material can embody a soft enveloping layer 108 such that impacts of foreign particles onto the turbine blade are cushioned and can rebound by virtue of the soft enveloping layer 108. As a result of the low rigidity of the thermoplastic enveloping layer 108, the impact of a foreign particle causes the enveloping layer 108 to deform slightly such that the impact energy is absorbed without this resulting in fissures or other forms of damage being produced.
Furthermore, the damping zone 101 or in addition also the blade regions 102 can have a further thermoplastic fiber matrix system 109 which can protect the turbine blade 100 against external influences. The further fiber matrix system 109 can have a thermoplastic matrix 201 into which reinforcing fibers 202 are embedded. If the reinforcing fibers 202 are arbitrarily present in the thermoplastic matrix 201, this can be referred to as a fiber mat. The fiber mats have a lower rigidity than fiber matrix systems with directed composite fibers, with the result that in turn a greater softness or, as the case may be, elasticity can be created with the further fiber matrix system 109. This leads in turn to a protection against external impacts of foreign particles and against erosion of the surface of the turbine blade 100.
For completeness it should be pointed out that “comprising” excludes no other elements or steps and “one” or “a” does not exclude a plurality. Let it furthermore be pointed out that features or steps that have been described with reference to one of the above exemplary embodiments can also be used in combination with other features or steps of other above-described exemplary embodiments. Reference signs in the claims are not to be regarded as limiting.
Claims
1.-15. (canceled)
16. A turbine blade, comprising:
- a damping zone including a damping layer with a fiber matrix system,
- wherein the fiber matrix system has a thermoplastic matrix comprising reinforcing fibers.
17. The turbine blade as claimed in claim 16, wherein the reinforcing fibers are embedded in the thermoplastic matrix.
18. The turbine blade as claimed in claim 16, wherein the damping zone includes fiber layers, the fiber layers together with the damping layer forming a laminar structure.
19. The turbine blade as claimed in claim 16, further comprising:
- a blade region,
- wherein the blade region comprises a plurality of further fiber layers, and
- wherein the plurality of further fiber layers embodies a further laminar structure.
20. The turbine blade as claimed in claim 16, wherein the reinforcing fibers are embedded in the thermoplastic matrix at an angle between 1 degree and 90 degrees to one another.
21. The turbine blade as claimed in claim 16, wherein the reinforcing fibers are embedded in the thermoplastic matrix parallel to one another.
22. The turbine blade as claimed in claim 16, wherein at least one of the reinforcing fibers includes a hybrid yarn, and wherein the hybrid yarn comprises a thermoplastic material and a carbon fiber material.
23. The turbine blade as claimed in claim 18, wherein the damping layer has a lower elastic rigidity or a higher damping value than the fiber layers.
24. The turbine blade as claimed in claim 18, wherein the damping layer has a lower elastic rigidity and a higher damping value than the fiber layers.
25. The turbine blade as claimed in claim 19, wherein the damping zone has a lower elastic rigidity or a higher damping value than the blade region.
26. The turbine blade as claimed in claim 19, wherein the damping zone has a lower elastic rigidity and a higher damping value than the blade region.
27. The turbine blade as claimed in claim 16, further comprising:
- an enveloping layer,
- wherein the enveloping layer is wrapped around a surface of the turbine blade such that the turbine blade is protected against external influences, and
- wherein the enveloping layer comprises non-reinforced thermoplastic material.
28. The turbine blade as claimed in claim 16, further comprising:
- a further fiber matrix system with a thermoplastic matrix,
- wherein the further fiber matrix system is disposed in the damping zone or the blade region such that the further fiber matrix system is exposed to external influences of the turbine blades, and
- wherein the further fiber matrix system comprises reinforcing fibers which are present as fiber mats with arbitrary main fiber directions.
29. The turbine blade as claimed in claim 16, further comprising:
- a further fiber matrix system with a thermoplastic matrix,
- wherein the further fiber matrix system is disposed in the damping zone and the blade region such that the further fiber matrix system is exposed to external influences of the turbine blades, and
- wherein the further fiber matrix system comprises reinforcing fibers which are present as fiber mats with arbitrary main fiber directions.
30. A turbine, comprising:
- a turbine blade, comprising: a damping zone including a damping layer with a fiber matrix system, wherein the fiber matrix system has a thermoplastic matrix comprising reinforcing fibers.
31. The turbine as claimed in claim 30, wherein the turbine is a steam turbine and the turbine blade is a rotor blade of the steam turbine.
32. A method of manufacturing a damping zone of a turbine blade, comprising:
- embedding reinforcing fibers into a thermoplastic matrix in order to form a fiber matrix system of a damping layer;
- forming the damping zone of the turbine blade by the damping layer.
33. The method as claimed in claim 32, wherein, during the embedding, the thermoplastic matrix is melted and the reinforcing fibers are pressed onto the thermoplastic matrix.
34. The method as claimed in claim 32, further comprising
- deforming the damping zone in order to match the damping zone to a predefined shape of the turbine blade by a further melting of the thermoplastic matrix.
Type: Application
Filed: Jul 30, 2010
Publication Date: Jan 6, 2011
Inventors: Christoph Ebert (Dresden), Detlef Haje (Gorlitz), Albert Langkamp (Dresden), Markus Mantei (Pulsnitz)
Application Number: 12/847,126
International Classification: F01D 5/14 (20060101);
