DE102019202054A1 - Rotor blade for a thermal rotary machine and method for producing such a rotor blade - Google Patents

Abstract

The invention relates to a rotating blade (1) for a thermal rotary machine, comprising at least one blade area (3) forming a flow profile (2) and a blade root area (4) designed to attach the rotating blade (1) to a rotor. The rotor blade (1) is assembled from at least two prefabricated components (5, 6, 7) and has at least one cavity (8) which is formed by inner surfaces (9) of at least two components (5, 6, 7) of the rotor blade (1) is limited. The invention further comprises a method for producing such a rotor blade (1).

Description

The invention relates to a rotor blade for a thermal rotary machine according to the preamble of independent claim 1 and a method for producing such a rotor blade according to the preamble of independent method claim 7.

Rotating blades for thermal rotating machines, such as steam or gas turbines, are often exposed to high centrifugal forces as well as high thermal loads and must be designed accordingly. In particular, with large blade lengths and / or high speeds, the moving blades can only be made with high-strength materials or, ultimately, no longer at all. Blades for different speeds can be compared with each other by the quantity A · n ² , where A represents the swept area and n the speed.

At the moment, rotor blades are usually made in one piece, for example from forgings or semi-finished products. The rotor blades have a blade root with which they are inserted into a rotor groove formed in the rotor in order to form a row of blades. Each moving blade can be inserted into its own axial groove or all moving blades of a blade row can be inserted into a common circumferential groove. The most highly stressed areas of the blade are the blade root and the transition from the blade root to the blade area; the leaf itself is also highly stressed in large parts of its extension.

The stress on the blade root area and the airfoil area act as a combination of LCF Low Cycle Fatigue (LCF) and High Cycle Fatigue (HCF), which are made up of the start-stop load cycles (LCF) and vibration excitations (HCF). Due to the high centrifugal forces of the rotor blade, strong contact loads continue to act in the rotor slots at the blade root. For large blades, centrifugal forces can be up to 100 t per blade.

Due to the strength limits of today's materials, blades can only be built in a certain size at a given speed. As a result, the swept area A is limited, whereby the mass or volume flow that can be passed through a blade ring is also limited. This means a limitation of the performance of the rotary machine per flood due to the feasible blade size.

In addition to this limitation of the performance, the high centrifugal force-related LCF stress of the rotor blades used today often represents a limitation of the permissible number of load cycles of the components. When the permissible number of load cycles is reached, complex and expensive testing or repair work or the replacement of blades or rotor are necessary.

As a result, it would be highly desirable for rotary thermal machines to have blades with a larger swept area. Thus, a higher output could be achieved per flood, which would enable more compact and / or more powerful machines. In addition, a reduction in the centrifugal force (LCF) would be desirable in order to increase the tolerable number of load cycles.

The object of the present invention is to provide such a rotor blade. A further object of the present invention is to indicate a corresponding method for producing such a rotor blade.

With regard to the rotor blade, the object is achieved by the features of independent patent claim 1. With regard to the method for producing such a rotor blade, the object is achieved by the features of independent claim 7.

Further advantages and embodiments of the invention, which can be used individually or in combinations with one another, are the subject of the subclaims.

The rotor blade according to the invention for a thermal rotary machine, comprising at least one blade area forming a flow profile and a blade root area designed to attach the blade to a rotor, is characterized in that the blade is assembled from at least two prefabricated components and has at least one cavity , which is bounded by inner surfaces of at least two components of the rotor blades.

The mass of the rotor blade is reduced by the cavity or the cavities within the rotor blade, as a result of which the centrifugal load on the rotor blades is significantly reduced. In the context of the invention, an assembly is understood to be the joining of at least two prefabricated components in such a way that their surfaces delimit at least part of the subsequent cavity. The advantage of the assembly is that the surfaces of the later cavity are accessible before assembly and can be processed and / or measured. This allows high-quality surfaces of the cavity (higher HCF / LCF stresses) and / or more precise Wall thickness and geometry properties (load-bearing cross-sections, unbalance contributions and / or centrifugal force contributions) can be achieved. An inner contour of the cavity of fixed geometry and optionally machined surfaces is thus achieved. Such processing of the cavity is only possible by assembling the prefabricated components.

One embodiment of the invention provides that the blade area with the blade root area is formed by assembling one or more prefabricated components.

The blade root area, which is exposed to high contact loads and high tensile loads on the blade area, is preferably made of a high-strength, weldable material. In this way, high levels of stress are achieved, which has an advantageous effect on the implementable blade length and / or on the permissible number of starts (LCF stress).

Another embodiment of the invention provides that the prefabricated components are assembled by welding. By welding the components, it is possible to combine materials with different properties in an advantageous manner. For example, a high-strength blade root area can be combined with an erosion-resistant airfoil area, or (because less stressed) a less high-strength airfoil area. The airfoil area can also be joined from several (optionally) different materials. For example, the blade area can be protected by an erosion protection measure in the area of the blade edges. All known welding processes can be used for welding.

Another embodiment of the invention provides that the weld seam roots of the weld seams are arranged near the neutral fiber of the rotor blades with regard to their main bending moments. For this purpose, the inner contour of the rotor blade in the weld area can be designed in such a way that the weld seam root is spatially closer to the neutral fiber. In addition to flow-induced bending moments, the bending moments linked to the main eigenmodes are to be considered as the main bending moments. In order to achieve the required load-bearing capacity of the weld seam, it is also useful to position the weld seam in such a way that the weld seam root lies, if possible, in a stress-reduced area when the force flows across the weld seam. In order to increase the LCF stress, a cross-sectional thickening should preferably be formed. The spatial arrangement of the weld root near the neutral fiber significantly improves the HCF stress. In the case of a force flow along the weld seam, the stress on the weld seam root is not decisive and does not constitute a strength restriction. Here, too, the weld seam is advantageously positioned in such a way that shear stresses and main eigenmodes can be easily tolerated, ie. H. that the weld root is in turn arranged near the neutral fiber.

A further embodiment of the invention provides that the cavity / cavities are formed in the blade area. Due to the formation of the cavity or the cavities of the blade area, the center of gravity of the rotor blade is moved closer to the axis of rotation of the rotor, whereby the centrifugal force can be reduced more than it would bring about the same saving of mass, which is closer to the rotor axis.

A further embodiment of the invention provides that the cavity / cavities are formed in the blade area and in the blade root area. Because cavities are also formed in the blade root area, the total mass of the rotor blade can be further reduced, which means that even lower rotor blade masses can be implemented and the centrifugal force load can thus be further optimized. In this way, even greater blade lengths can be achieved without the permissible loads, in particular LCF and HCF loads, being exceeded.

• - Herstellen bzw. vorfertigen der einzelnen Bauteile der Laufschaufel mit einer vorgegebenen Innen- und Außenkontur;
• - Zusammenbau der einzelnen vorgefertigten Bauteile zur fertigen Laufschaufel.

The method according to the invention for producing a rotor blade according to the invention according to one of the preceding claims is characterized by the following method steps:

• - Manufacture or prefabricate the individual components of the rotor blade with a predetermined inner and outer contour;
• - Assembly of the individual prefabricated components to form the finished rotor blade.

Before assembling the individually prefabricated components, the geometry of the later inner and outer contour can optionally be checked with a 3D measuring process and the components can be post-treated if necessary. Another advantage of the assembly or the method according to the invention is that the surfaces of the subsequent cavity are accessible and can be processed during assembly. This enables high-quality surfaces (higher HCF / LCF resistance) and / or more precise wall thicknesses and geometric properties (load-bearing cross-sections, imbalance or centrifugal force contribution) to be achieved. As a result, an inner contour with a fixed geometry and optionally a machined surface is achieved. With the help of the process, prefabricated components can be made from various Material with different properties can be combined, for example a high-strength foot area can be combined with an erosion-resistant blade area, which is not possible with conventional rotor blades that are made in one piece, for example from forgings or semi-finished products.

An embodiment of the method according to the invention is characterized in that after the assembly of the guide vane, a 3D measurement and recording of the blade profile is carried out and a simulation is then carried out on the basis of the recorded blade profile, by means of which it is checked whether previously defined properties, in particular with regard to wall thicknesses , Blade geometry, blade position, blade dimensions and natural frequencies are adhered to. As a result, errors that would lead to damage to the thermal rotary machine during operation can already be ruled out during manufacture. The 3D measurement can measure the entire blade profile or just the flow profile of the blade area.

A further embodiment of the method according to the invention provides that if one or more specified properties are not adhered to based on the recorded blade profile, a machining geometry for the outer contour of the blade profile is determined and formed in which all specified properties, in particular with regard to wall thickness, blade geometry, blade position, blade mass and natural frequencies be respected. As a result, the scrap in the manufacture of rotor blades is significantly reduced and the production of the rotor blades is cost-optimized. Nevertheless, it is ensured that all of the required properties of the rotor blades are maintained.

By means of the method according to the invention, a reduced-mass rotor blade can thus be produced with a defined, highly stressable inner contour which, in spite of the integral (welding) assembly, meets the requirements for large rotor blades. By reducing the centrifugal force, this enables an increase in the relevant variable A · n ² and / or an increase in the number of load changes / start numbers (LCF or HCF stress).

• 1 eine Laufschaufel nach dem Stand der Technik;
• 2 eine erfindungsgemäße Laufschaufel in einer Seitenansicht;
• 3 die in 2 gezeigte erfindungsgemäße Laufschaufel entlang der Schnittlinie A-A;
• 4 die in 2 gezeigte erfindungsgemäße Laufschaufel in einer Detailansicht entlang der Schnittlinie B-B und
• 5 eine zweite Ausführungsform einer erfindungsgemäßen Laufschaufel.

Further embodiments and advantages of the invention are explained below with reference to the figures. It shows:

• 1 a prior art blade;
• 2 a rotor blade according to the invention in a side view;
• 3 in the 2 The rotor blade according to the invention shown along the section line AA;
• 4th in the 2 The rotor blade according to the invention shown in a detailed view along the section line BB and FIG
• 5 a second embodiment of a blade according to the invention.

The figures each represent, in some cases greatly simplified, schematic representations. The figures are not necessarily shown to scale. Identical or functionally identical components are provided with the same reference symbols across the figures.

1 shows a rotor blade 1 According to the state of the art. The rotor blade is made in one piece, for example from a forging or a semi-finished product. The blade 1 includes one in the form of an airfoil 2 trained, airfoil area 3 and one to attach the blade 1 formed on a rotor, blade root area 4th . Due to the massive, one-piece design of the rotor blade 1 During the operation of the thermal rotary machine, high centrifugal forces act. Particularly in the case of large blade lengths and / or high speeds, the rotor blades can only be manufactured with high-strength and therefore expensive materials, or ultimately no longer at all. The most highly stressed areas of the blade 1 are the blade root area 4th and the transition into the airfoil area 3 . Also the airfoil area 3 itself is highly stressed in large parts of its extension. The stress on the blade root and blade act as a combination of LCF and HCF stress, which result from the start-stop load cycles (LCF) and the vibration excitations (HCF). Due to the existing strength limits of today's materials, only rotor blades can 1 of a certain size.

2 shows a blade according to the invention 1 for a thermal rotary machine. The blade 1 again includes one, a flow profile 2 forming, airfoil area 3 , and one to attach the blade 1 formed on a rotor, blade root area 4th . The blade 1 is in the exemplary embodiment from a number of prefabricated components 5 , 6th , 7th assembled. The blade 1 has a cavity 8th on, which by inner surfaces 9 of the three components 5 , 6th , 7th of the blades 1 is limited. The cavity 8th extends only in the airfoil area 3 . In principle, it would also be conceivable to use the cavity 8th both in the airfoil area 3 as well as in the blade root area 4th to train. The formation of several cavities is also conceivable. Basically, the cavities lead 8th to a reduction in the mass of the rotor blade 1 , thereby reducing the centrifugal force on the blade 1 is reduced. By assembling the blades 1 The blade root area, which is exposed to high contact loads and high tensile loads, can be manufactured from a high-strength, weldable material from several prefabricated components. This achieves high levels of stress, which has an advantageous effect on the executable blade length and / or the permissible number of starts (LCF). The airfoil area 3 is made by assembling several prefabricated components with the blade root area 4th joined. The advantage of assembling is that the surface 9 of the cavity is still accessible during the joining and can thereby be processed and / or measured. This allows high quality surfaces 9 , higher HCF / LCF loading capacities and / or more precise wall thickness and geometry properties can be achieved. An inner contour of fixed geometry and optionally machined surfaces is thus achieved. The rotor blade shown in the exemplary embodiment 1 is assembled by welding.

3 shows the in 2 illustrated rotor blade 1 in a sectional view along the section line AA. The flow profile 2 the blade 1 has a print side 2 ' and a suction side 2 " on. In order to achieve the required load capacity of the weld seam, it is positioned in such a way that the root area is close to a stress-reduced area when the force flows across the weld seam. The root area should be as close as possible to the neutral fiber 11 the blade 1 , with regard to the main bending modes. In the case of a frictional connection along the weld seam, the stress on the roots is not decisive and does not constitute a strength restriction. However, the weld seam is advantageously positioned here so that it is close to the neutral fiber 11 so that shear stresses of the main mode can be tolerated well.

4th shows them off 2 well-known blade 1 in a sectional view along the section line BB. It can be seen from the illustration that the airfoil area 3 is assembled from several prefabricated components 5,6,7. Welding makes it possible to combine materials with different properties. For example, a high-strength foot area can be combined with a less high-strength blade area. Also, as in 4th shown can be assembled from several optionally different materials. As in 4th can be seen, is the inner contour of the blade 1 in the area of the weld seam 10 designed so that the weld root of the welds 10 spatially closer to the neutral fiber 11 is brought up, for this purpose the wall thickness has been thickened in the interior.

5 shows a second exemplary embodiment of a rotor blade according to the invention 1 . The blade 1 is essentially identical to the rotor blade according to 2 educated. Additionally includes the blade 1 in the airfoil area 3 a special erosion protection measure on the blade edge 12 . The erosion control measure 12 can be done by different measures. One possibility is the application of, for example, welding, welding, build-up welding or plating of an erosion-resistant material, e.g. titanium or nickel materials with a buffer layer (if necessary), another possibility is the hard material coating with an erosion-resistant material and a third possibility is surface hardening in the area exposed to erosion. Through the erosion control measure 12 a high level of erosion resistance is achieved, which is necessary in particular in steam turbines and here in the low-pressure range, since droplets often form here from the steam and hit the rotor blade at high speed 1 hit and here regularly to erosion damage to the rotor blade 1 to lead.

The rotor blades shown in the two exemplary embodiments are essentially manufactured by prefabricating the required components 5 , 6th , 7th with a given inner and outer contour and the subsequent assembly of the individual prefabricated components 5 , 6th , 7th to the finished blade 1 . As a result of the assembly, the surfaces of the later cavity remain 8th , still accessible during assembly and can therefore be edited and / or measured. The external and internal contours can optionally be measured using a 3D measurement process. After the assembly of the individual components, the generated geometry and a possible distortion due to the assembly can be measured. The warpage can be assessed, for example, by means of a simulation (eg FEM). If a distortion is detected or if the actual geometries deviate from the previously defined geometry, suitable machining geometries can be defined for the outer contour and, if necessary, also for the inner contour, so that despite a distortion, wall thickness, blade geometry, blade position, blade mass and Natural frequency requirements are met. This can result in a scrap of the rotor blade 1 can be avoided in many cases, resulting in significant cost savings.

In summary, it can thus be stated that the method according to the invention can produce a mass-reduced rotor blade with a defined, highly stressable inner contour which, despite the material / welded assembly, meets the requirements of large rotor blades. By reducing the centrifugal force, this enables an increase in the relevant variable A · n ² and / or an increase in the number of load cycles / start numbers (LCF or HCF stresses).

Claims (10)

A rotor blade (1) for a thermal rotary machine, comprising at least one blade area (3) forming a flow profile (2) and a blade root area (4) designed to fasten the blade (1) to a rotor, characterized in that the blade (1) is assembled from at least two prefabricated components (5, 6, 7) and has at least one cavity (8) which is delimited by inner surfaces (9) of at least two components (5, 6, 7) of the rotor blade (1). Blade (1) after Claim 1 , characterized in that the blade area (3) with the blade root area (4) is formed by assembling one or more prefabricated components (5, 6, 7). Blade (1) after Claim 1 or 2 , characterized in that the prefabricated components (5, 6, 7) are assembled by welding. Blade (1) after Claim 3 , characterized in that the weld seam roots of the weld seams (10) are arranged near the neutral fiber (11) of the rotor blade (1) with regard to the main bending moments. Rotating blade (1) according to one of the preceding claims, characterized in that the cavity / cavities are formed in the blade area (3). Blade (1) after one of the Claims 1 to 4th , characterized in that the cavity / cavities (8) are formed in the blade area (3) and in the blade root area (4). Method for producing a rotor blade (1) according to one of the Claims 1 to 6th Comprising the following method steps, - producing the individual components (5, 6, 7) of the rotor blade (1) with a predetermined inner and outer contour; - Assemble the individual prefabricated components (5, 6, 7) to form the rotor blade (1). Method for producing a rotor blade (1) according to Claim 7 , characterized in that the prefabricated components (5, 6, 7) are assembled by means of a welding process. Method for producing a rotor blade (1) according to Claim 7 or 8th , characterized in that - after the assembly of the rotor blade (1), a 3D measurement and recording of the rotor blade profile takes place and then, - a simulation is carried out on the basis of the recorded rotor blade profile, by means of which it is checked whether previously defined properties, in particular with regard to wall thicknesses, Blade geometry, blade position, blade dimensions and natural frequencies are observed. Method for producing a rotor blade (1) according to Claim 9 , characterized in that in the event of non-compliance with one or more specified properties on the basis of the recorded blade profile, a machining geometry for the outer contour of the blade profile is determined and formed in which all specified properties, in particular with regard to wall thicknesses, blade geometry, blade position, blade masses and natural frequencies are observed.

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