EP1712740A1 - Blade for a turbo machine and turbo machine with a number of blades - Google Patents

Abstract

The blade has a base (12) that is connectable with a turbine shaft, where the base carries a profiled blade sheet. The profiled blade sheet is provided with a cover plate whose contour is formed such that the plate takes up a given position in an operating region. The cover plate is displaced tangentially and radially to a blade axis and turbine axis, respectively, where an inner housing and a rotor are arranged along the turbine axis.

Description

The invention relates to a blade for a turbomachine, z. B. for a steam turbine. The blade has a blade root connectable to a turbine shaft carrying a profiled airfoil provided with a cover plate. It further relates to a blade row with a number of blades and a turbomachine with a number of each combined into blade rows, arranged on a turbine shaft blades.

Turbomachines, z. As gas turbines, steam turbines are used in many areas for driving generators or work machines. In a turbomachine, for example, the energy content of a fuel is used to generate a rotational movement of a turbine shaft. The produced by the combustion of the fuel, under high pressure and high temperature working medium is passed through a turbine unit, where it relaxes work.

In order to generate the rotational movement of the turbine shaft, a number of rotor blades, which are usually combined into blade groups or blade rows and which drive the turbine shaft via a momentum transfer from the working medium, are arranged thereon. In this case, the rotor blades usually have a profiled airfoil extending along a blade axis for suitable guidance of the working medium, which blade is supported by a blade root that can be connected to the turbine shaft. To guide the working fluid in the turbine unit also usually connected between adjacent blade rows are connected to the turbine housing Leitschaufelreihen.

The blade has at the opposite end of the blade root an optionally slightly curved cover plate on which, for example, a sealing web is arranged as a sealing element, in particular welded or milled from the plate. When in a rotor of a turbomachine, in particular a steam turbine, circumferentially juxtaposed blades, the cover plates of the blades form an annular shroud and the substantially circumferentially directed sealing elements forming a circular sealing strip in a plane perpendicular to the main axis of the turbine shaft with circular cross-section. The sealing tape provides increased flow resistance and thus reduces leakage currents between the blades, both vanes and blades, and an inner shell or turbine shaft (also called a turbine runner or rotor). By improving the gap seal, the efficiency losses of the turbomachine can be reduced.

During operation of the turbomachine, it often happens with blades with cover plate as a result of centrifugal force to a deformation of the airfoil and a misalignment of the cover plate. This can lead to a misalignment and incorrect positioning of the sealing element located on the cover plate or the cover plate surfaces running against the stator-mounted sealing tips. In addition, cover plate surfaces can be placed in the water drop stream, resulting in increased erosion of these surfaces.

Usually, the blade to reduce the misalignment of the cover plate on a very rigid airfoil construction. This can lead to aerodynamically unfavorable blade blade contours and blade numbers. Also, an adapted cover plate mass distribution can reduce skewing in the operating speed range. However, this is of limited use because significant mass redistributions are required to achieve the desired effect.

The invention is therefore based on the object of specifying a blade for a turbomachine in which an unfavorable skewing in the working speed range is reduced with a comparatively simple construction. Furthermore, a blade row and a turbomachine with such a blade are to be specified.

With regard to the blade, the stated object is achieved according to the invention by providing a cover plate whose production contour is shaped such that the cover plate occupies a predetermined position in the working rotational speed range.

The invention is based on the consideration that an aerodynamic and simultaneously sealing position in the working or operating speed range should be made possible, especially for a blade that is comparatively highly loaded by centrifugal forces. The idea consists in the utilization of centrifugal forces for a variable-speed positioning of the cover plate, in particular mounted on the cover plate sealing elements to realize a sufficiently good tightness of the cover plate in stationary operation, especially in the working speed range. For this purpose, the manufacturing contour of the cover plate is shaped such that the changed manufacturing contour of the cover plate in the working speed range compensates for the centrifugal forces caused deformation of the cover plate and the cover plate assumes a predetermined position, in particular a sufficiently tight position. For a particularly tight final positioning of the blades along the flow path of the working fluid in the working speed range, each blade is made individually based on given specific requirements, wherein the cover plate has a predetermined manufacturing contour and manufacturing position. The production contour and production position is designed such that the cover plate occupies a working or target contour, in particular a desired position and correct position in the working speed range due to the centrifugal force and the gas power by unwinding or deformation of the airfoil. In the following, for the cover plates outer contour Production structure features described in more detail, which cause the employment of a working contour for the cover plate in the working speed range under the action of centrifugal and gas forces, which largely corresponds to a predetermined target contour.

In one possible embodiment, the cover plate is formed asymmetrically to the blade axis. For example, by a misalignment of the cover plate in production, the cover plate, until the rated speed is reached, brought by the centrifugal force in the desired position. The production-relevant misalignment is set depending on the strain state of the blade, in particular of the blade and the cover plate. Under an asymmetrical arrangement or misalignment of the cover plate to the blade axis in the production is understood in particular an eccentric arrangement of the cover plate, wherein the cover plate has an offset to the blade axis or blade center line. For example, the manufacturing contour of the cover plate on a rest or standstill centerline, which is offset by a predetermined offset to the blade axis and / or the turbine axis.

In a preferred embodiment, the cover plate is offset tangentially to the blade axis. With a tangential offset, the cover plate is offset in the circumferential direction and thus in the direction of adjacent blades. For example, the cover plate has a tangential offset, which is up to 30 mm depending on the associated strain state.

In addition, the cover plate may be offset radially to the turbine axis. For example, the cover plate has a radial offset, which is up to 10 mm, depending on the associated strain state.

For best possible shielding of trailing neighboring blades against drop impact erosion on the inner contour the cover plate and the most homogeneous outer contour of the cover plate, the inner radius of the cover plate on a relation to the outer radius of the cover plate greater radial offset relative to the turbine axis.

For example, the outer contour of the cover plate and the associated outer radius along the circumferential direction of the cover plate only a small radial offset relative to the turbine axis of up to 10 mm. This allows a substantially homogeneous alignment of the cover plate along the outer contour of the blades, so that they form an annular shroud. Preferably, the outer contour of the cover plate forms a cylinder section in the working speed range. Thus, the outer contour of the cover plate in the working speed range to ensure the sealing function sufficiently well.

In contrast, the inner contour and the associated inner radius along the circumferential direction of the cover plate may have a greater radial offset with respect to the turbine axis of up to 10 mm. Conveniently, the inner contour in the working speed range of the cover plate is shaped such that their inner side edges cause a shield. For example, the cover plate on the underside or inner contour with respect to the undersides of adjacent cover plates a jump, in particular along the circumferential direction of the cover plate on a sloping Sägezahnsprung on. This allows shading or shielding of erosion prone areas on the inside of the trailing neighbor blade. Also, depending on the degree of skewing or the tangential and possibly the radial offset over- or undercompensation on the inner and on the outer contour can be effected.

The blade is preferably a blade for a steam turbine, in particular for a medium-pressure and / or low-pressure turbine part. By using blades with a predetermined obliquely or eccentrically arranged cover plate is a reduction of Steam leakage flows achieved in a steam turbine, whereby an efficiency increase is achieved in particular in a low-pressure turbine section.

The task directed to the blade row is achieved in that the cover plates of the individual blades are shaped such that they occupy a predetermined position in the working speed range. Preferably, the outer contours of the cover plates are shaped such that the outer contours of all blades of a row of blades form a cylinder in the working speed range. For this purpose, the respective cover plate of adjacent blades on a production contour and manufacturing position with a predetermined tangential and / or a radial offset. In the case of a tangential offset, the outer contour of the cover plate protrudes as little as possible beyond the shroud. This allows in the working speed range due to the centrifugal force as homogeneous as possible outer contour, so that a sufficiently good orientation of the cover plate against stator-mounted sealing tips or located on the cover plate itself sealing points is made possible against the stator. Such a misalignment of the Au-βenkontur the individual cover plates is a high flow resistance for the guided in the turbomachine working medium, eg. As steam achieved, whereby a Leckdampfrate is significantly reduced.

In the case of a radial offset, the cover plate with its outer contour and inner contour protrudes at least partially beyond the annular shroud of the associated blade row or into it. With acting on the blade centrifugal and gas forces the cover plate is speed-dependent brought into a position which leads to a compensation of over- and / or undercoverage and thus to a compensation of the predetermined misalignment of the cover plate, so that the sealing function of the cover plate to the outside and the erosion protection of lagging neighboring blades is fulfilled inside.

Also, an over- and / or undercompensation of the predetermined misalignment can be effected by the individual cover plates in the manufacturing state more tangential and optionally radially offset or moved. Such overcompensation or, if appropriate, also an undercompensation can be used for shadowing erosion-prone areas on the inside and also on the outside of lagging neighboring blades. The flow medium, for. As drops of water, strike this at a very shallow angle to the inner or outer contour of the cover plate and erode these weak due to the flat angle.

The task directed to the turbomachine is achieved in that the cover plates of adjacent blades of a single row of blades and / or of adjacent blades of adjacent blade rows have a production contour which occupies a predetermined position in the working speed range. Each blade has an associated production contour and / or production position of the cover plate. Namely, the working medium flowing through the turbomachine continuously relaxes along its flow path as it flows through the turbomachine. The operating pressure of the working medium is thus dependent on the position along the longitudinal axis of the turbomachine. For this purpose, the blades are designed differently sized depending on the position within the turbomachine, so that different strong centrifugal forces act. This leads to an individual manufacturing contour of the cover plates and blades in order to absorb or reduce the respective positionally acting mechanical forces.

The advantages achieved by the invention are in particular that by a predetermined misalignment of the cover plates of individual blades for one or more rows of blades in the production as homogeneous as possible outer shape, in particular a cylindrical shape of the cover plates for the best possible sealing function and a reduction of Blatttitzenüberströmungen be effected. The inner contour of the cover plates has a serrated, in particular sawtooth-like shape, so that there is a shielding of trailing adjacent blades against impacting water droplets or solid particles.

FIG 1

einen Ausschnitt eines Längsschnitts durch eine Strömungsmaschine, insbesondere eine Dampfturbine,

FIG 2

einen Ausschnitt einer Draufsicht auf eine Schaufelreihe mit einer Anzahl von Schaufeln,

FIG 3

den Versatz der Koordinatensysteme für eine Schaufel mit einer schief gestellten Deckplatte, und

FIG 4

einen Ausschnitt eines Querschnitts durch schief gestellte Deckplatten von Schaufeln einer Schaufelreihe, und

FIG 5

einen vergrößerten Ausschnitt an einem Übergangsbereich von Deckplatten benachbarter Schaufeln gemäß FIG 4.

An embodiment of the invention will be explained in more detail with reference to a drawing. Show:

FIG. 1

a detail of a longitudinal section through a turbomachine, in particular a steam turbine,

FIG. 2

4 a section of a plan view of a row of blades with a number of blades,

FIG. 3

the offset of the coordinate systems for a blade with a slanted cover plate, and

FIG. 4

a section of a cross section through oblique cover plates of blades of a row of blades, and

FIG. 5

an enlarged section at a transition region of cover plates of adjacent blades according to FIG. 4

Identical parts are provided with the same reference numerals in all figures.

1 shows a section of a longitudinal section of a turbomachine 1, in particular a steam turbine with an inner housing 2 and a rotor 4 disposed within the inner housing 2. The inner housing 2 and the rotor 4 are directed along a turbine axis 6 and have at their circular inner circumference or outer circumference annular in the circumferential direction extending recesses 8a and 8b.

In the steam turbine, a plurality of blades 10 are arranged, wherein here for the sake of clarity, only one fixed in the inner housing 2 guide vane 10a and connected to the rotor 4 blade 10b are shown.

Each blade 10 has a blade root 12 with which it is anchored in the inner housing 2 or in the rotor 4. The blade 10 is directed along a longitudinal or blade axis 14. In the direction of the blade axis 14, a profiled blade 16 connects to the blade root 12 for deflecting the working medium, in particular a steam flow 18. The airfoil 16 has an end 20 opposite the blade root 12, on which a cover plate 22 is provided.

At the end 20 of each blade 10, a sealing web 26 is provided in the direction of the blade axis 14, which extends on the cover plate 22 along the circumferential direction. The sealing web 26 protrudes into the associated recess 8a or 8b without contact. In addition, on the outer circumference of the rotor 4 and on the inner circumference of the inner housing 2 also in the direction of the longitudinal or blade axis 14 directed a respective cover plate 22 opposite sealing tips 28 are provided. By a protrude of the sealing ridge 26 in the recess 8b of the rotor 4 and the recess 8a of the inner housing 2 is between the blade 10b and the inner housing 2 or between the vane 10a and the rotor 4, a direct radial gap for a flow of leakage steam from the Steam flow 18 avoided. For the best possible flow resistance and a high tightness and thus to reduce the leakage steam flow in the working speed range of the turbomachine 1, a sufficiently accurate positioning of the blades 10 is required.

Due to the forces acting on the blades 10 centrifugal forces, the cover plate 22 is in operation of the turbomachine 1 askew. To compensate for the misalignment the blades 10 in the working speed range, the manufacturing contour of the cover plate 22 of each blade 10, in particular the blade 10b is carried out such that the cover plate 22 occupies a predetermined position or position in the working speed range.

The vanes 10 secured in the circumferential direction on the rotor 4 or the inner housing 2 each form an annular blade row 30, wherein the cover plates 22 form an annular shroud. 2 shows a detail of a plan view of the cover plates 22 of a row of blades 30 with a number of blades 10. The blades 10b are annularly arranged on the turbine shaft, not shown, and thus form a number of blade rows. Furthermore, the turbomachine 1 comprises a number of fixed guide vanes 10 a, which are likewise fixed in a ring shape to the inner housing 2 with the formation of rows of guide vanes. The blades 10b serve to drive the turbine shaft by momentum transfer from the streaming machine 1 flowing through the steam flow 18. The vanes 10a, however, serve to guide the flow of the working medium 18 between two seen in the flow direction of the steam flow 18 successive blade rows or blade rings. A successive pair of a ring of vanes 10a or a row of vanes and a ring of blades 10b or a blade row is also referred to as a turbine stage.

FIG. 3 shows the offset V _T , V _{R of} the coordinate systems KS2, KS3 for the production contour of a cover plate 22 offset from the blade axis 14 to the coordinate system KS1 of the blade 10. The coordinate system KS1 shows a conventional blade 10 without a changed production contour of the cover plate 22, ie , the cover plate 22 is arranged symmetrically to the blade axis 14. The turbomachine 1 has an outer radius r _a and an inner radius r _i for the blade 10. The outer radius r _a extends from the turbine axis 6 to the outer contour 22a of the cover plate 22; the inner radius r _i extends from the turbine axis 6 to the inner contour 22b. To compensate for the centrifugal forces caused by misalignment of the cover plate 22 in the working speed range, the manufacturing contour and manufacturing position of the cover plate 22 is designed such that the cover plate 22 is arranged asymmetrically to the blade axis 14 and the blade coordinate system KS1.

The coordinate systems KS2 and KS3 show possible embodiments for a staggered cover plate 22. In one possible embodiment, the cover plate 22 is tangentially offset from the blade axis 14. The tangential offset V _T is the offset of the cover plate 22 in the circumferential direction. Optionally, in addition to the tangential offset V _T, the cover plate 22 may have a radial offset V _R. When the radial offset V _R , the cover plate 22 is offset radially to the turbine axis 6.

The coordinate system KS2 shows by way of example the tangential and radial offset V _T , V _{R of} the inner radius r _i ; the coordinate system KS3 shows an example of the tangential and radial offset V _T , V _{R of} the outer radius r _a . The size of the tangential and the radial offset V _T , V _R is determined as a function of the strain state and the position of the blade 10 in the turbomachine 1. That is, each blade 10 is manufactured individually as a result of the respective positionally acting mechanical forces. In this case, the tangential offset V _{T can} be up to 30 mm, for example. The radial offset V _R can be, for example, up to 10 mm.

4 shows a section of a cross section through the cover plates 22 of adjacent blades 10 of a blade row 30 during operation in the working speed range without strains and deformations. Each cover plate 22 forms a cylindrical portion of the annular shroud of all cover plates 22 of a row of blades 30. At the transition region B of two adjacent cover plates 22, the cover plates 22 offset in relation to each other in the outer contour 22a as well as in the inner contour 22b to form a step along the blade axis 14. Due to a relative to the outer radius r _{a of} the cover plate 22 larger radial displacement of the inner radius r _i , the inner contour 22b of the cover plates 22 has a larger heel or a larger step S1 in the transition region B from the pressure side DS of a first blade 10 to the suction side SS of the trailing adjacent Blade 10 as the outer contour 22a, as shown in more detail in FIG 5 in a larger section of FIG 4.

With regard to the annular blade row 30 with the outer plates forming a cover plates 22, the misalignment of the individual cover plates 22 takes place such that the center of the outer cylinder is tangentially and optionally radially offset.

The outer steps S2 formed by the tangential and optionally radial offset V _T and V _R in the transition regions B of adjacent cover plates 22 are shaped such that the outer contour 22a forms a homogeneous shape, in particular approximately a cylinder. As a result, a sufficiently good tightness is given. On the other hand, the inner steps S1 are shaped such that the inner side edges 22c cause shielding. For example, the inner contour 22b has a sawtooth shape. As a result, the erosion-prone area can be shaded by trailing neighboring blades.

Depending on the degree of skew, z. B. a stronger displacement of the cover plate 22, a stronger stage S1 and S2 may be formed, ie, the inclination of the cover plates 22 is not only compensated, but overcompensated and undercompensated. Such an overcompensation or possibly undercompensation can be used to shadow the erosion-prone area on the inside and also outside of the trailing blade 10. Beat the drops of water As a result, at a very shallow angle to the inner contour 22b and the outer contour 22a and erode this only weakly.

Claims (15)

A blade (10) for a turbomachine (1) having a turbine shaft connectable blade root (12) carrying a profiled airfoil (16) provided with a cover plate (22) whose manufacturing contour is shaped to be in the working speed range assumes a predetermined position. A blade according to claim 1, wherein the cover plate (22) is formed asymmetrically to the blade axis (14). A blade according to claim 1 or 2, wherein the cover plate (22) is offset tangentially to the blade axis (14). Blade according to one of claims 1 to 3, wherein the cover plate (22) has a tangential offset (V _T ), which is up to 30 mm, depending on the associated strain state. Blade according to one of claims 1 to 3, wherein the cover plate (22) is offset radially to the turbine axis (6). Blade according to one of claims 1 to 5, wherein the cover plate (22) has a radial offset (V _R ), which is up to 10 mm, depending on the associated strain state. Bucket according to one of claims 1 to 6, wherein the inner radius (r _i ) of the cover plate (22) relative to the outer radius (r _a ) of the cover plate (22) greater radial offset (V _R ) relative to the turbine axis (6). Blade according to one of claims 1 to 7, wherein in the working speed range, the outer contour (22a) of the cover plate (22) forms a cylinder portion. Blade according to one of claims 1 to 8, wherein in the working speed range, the inner contour (22b) of the cover plates (22) is shaped such that the inner side edges (22c) effect a shield. Use of the blade according to one of claims 1 to 9 as a moving blade (10b) for a turbomachine (1), in particular in the low pressure end stage of a steam turbine. A blade row (30) having a number of blades (10) according to any one of claims 1 to 10. A blade row according to claim 11, wherein the outer contours (22a) of the cover plates (22) form a cylinder in the working speed range. Blade row according to claim 11 or 12, wherein the inner contours (22b) of the cover plates (22) of adjacent blades (10) form a step shape in the working speed range. Turbomachine (1) with a number of each combined into rows of blades (30) blades (10) according to one of claims 1 to 10. Turbomachine according to claim 14, wherein one or more rows of blades (30) are formed as blade rows, the rotor blades (10b) are arranged on a turbine shaft.

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