EP1154125A2 - Blading with damping elements - Google Patents

Abstract

The present invention relates to a blade arrangement with damping elements and a method for vibration damping of a blade arrangement. The blade arrangement comprises a rotor and blades arranged on the circumference of the rotor. Damping elements (2, 3) are arranged between the blades and are in contact with the blades when the rotor rotates due to a centrifugal force acting in the radial direction. Between adjacent blades, at least two damping elements (2, 3) are arranged one behind the other in the circumferential direction of the rotor, which come into contact when the rotor rotates via a contact surface (6) and of which a first damping element (2) with a first friction surface (4) one and a second damping element (3) come into contact with a second friction surface (5) of the other blade. A multitude of different vibration conditions can be effectively damped with the blade arrangement. <IMAGE>

Description

Technical application area

The present invention relates to a blade arrangement with damping elements. The damping elements serve the vibration damping of the blade arrangement. The blade arrangement includes a rotor as well blades arranged on the circumference of the rotor, wherein between the blades damping elements loosely arranged are when the rotor rotates about a rotor axis by a centrifugal force acting in the radial direction be in contact with the blades.

Such blade arrangements are particularly used in turbomachines such as gas turbines. The individual blades usually consist of the airfoil, a blade platform and the Blade foot, which in corresponding recesses on the circumference of the rotor is attached. When operating the blade arrangement arise from various causes of stimulation undesirable bending and torsional vibrations, which leads to early material fatigue and thus lead to a shortened lifespan of the blade arrangement can. The present invention relates to a Blade arrangement with damping elements for damping of these unwanted vibrations.

State of the art

To reduce the vibrations of blade assemblies damping elements are already used, that work between the individual blades. At these damping elements are usually loose body, which at first between at rest the blade roots of the blades on the rotor or on corresponding Support structures are in place and in operation of the rotor due to the acting in the radial direction Centrifugal force against the bottom of the blade platforms adjacent blades are pressed. Each Damping element is at the same time two adjacent blade platforms in contact. As a result, the kinetic energy can be due relative motion between vibrations the blades in frictional energy between each Bucket platforms and the adjacent damping element being transformed. This dampens the Vibrations and overall leads to a decreased Vibration load on the blade arrangement.

Such a blade arrangement with damping elements is known for example from US 4,917,574. With this arrangement, the blade platforms are more adjacent Blades with their underside recesses, into that during rotation by centrifugal force spherical bodies are pressed as damping elements.

Another way of designing the Damping elements consists of these as rod-shaped Form elements with a round cross-section that are parallel arranged to the rotor axis between adjacent blades are. The arrangement can, for example in a corresponding lateral recess of the Blade base or the blade platform of one of the neighboring ones Shovels take place. Such an arrangement is described, for example, in A. J. Scalzo, Journal of Engineering for Gas Turbines and Power, Vol. 114, April 1992, on pages 289 and 290. This frequently used shape of the damping elements with circular Cross-section also creates a seal the gas flow of a gas turbine with respect to the rotor and is therefore also referred to as a "seal-pin damper". However, there is a disadvantage of these damping elements in that under certain conditions the damping element can jam. This makes relative movements prevented, causing great tension at the transition points arise from the damping element to the blades. These tensions lead to premature Material fatigue and the formation of cracks favor in the blades. These continue to work circular cross-sectional damping elements not all occurring vibrations of a blade arrangement in the same way so that certain vibrational states can occur almost undamped. In particular it comes with these circular cross-sectional damping elements before that no relative movement between the contact surfaces or the damping elements roll on the contact surface instead of sliding perform.

Another blade arrangement with damping elements is described for example in US 5,156,528. In this arrangement, edge areas form opposite one another neighboring blade platforms one recess or tapering in the radial direction Guide in which the damping element by centrifugal force is pressed. The damping element is here formed with a wedge-shaped cross section, wherein the wedge angle is the angle through the two edge areas of the vane platforms formed Recess corresponds. With this wedge-shaped design the damping elements can be others Vibration modes of the blade arrangement efficient dampen than those with the damping elements described above be effectively influenced. In particular these wedge-shaped damping elements are not for the Damping in-phase vibration modes suitable. Farther there is a problem with these damping elements, that they're in use under certain conditions can tilt, making the damping effect strong is reduced.

The object of the present invention is therein, a blade arrangement with damping elements and a method for damping vibrations of a blade arrangement specify with which good damping a variety of different vibration conditions can be achieved.

Presentation of the invention

The task is performed according to the blade arrangement Claim 1 or solved with the method according to claim 19. Advantageous configurations of the blade arrangement are the subject of the subclaims.

The blade arrangement includes damping elements a rotor and arranged on the circumference of the rotor Shovels. There are damping elements between the blades arranged to rotate the rotor around the rotor axis through the one acting in the radial direction Centrifugal force brought into contact with the blades become. The blade arrangement is characterized by this from that at least between two adjacent blades several damping elements in the circumferential direction of the Rotors are arranged one behind the other. These damping elements are designed and arranged in such a way that when the rotor rotates one after the other arranged damping elements over one or more Touch the touch surfaces and a first one in a row arranged damping elements with a first Friction surface of one and a second one behind the other arranged damping elements with a second friction surface of the other of the neighboring ones Get in contact with the blades.

In contrast to the known arrangements of the prior art, one or more further surfaces, the contact surfaces between the two or more damping elements, are available in the present arrangement for converting kinetic vibration energy into friction energy. This additional contact surface (s) further reduces the risk of the damping elements becoming stuck, as can occur under certain vibration conditions in the case of the circular cross-sectional damping elements of the prior art. The present arrangement offers, in particular, the possibility of designing the two or more damping elements in mutually different shapes in order to be able to optimally adapt them to the respective damping requirements. There are no limits to the variety of shapes as long as the mutual frictional contacts and the frictional contacts to the blades or blade platforms can be maintained during operation.
The mass center of gravity of the group of damping elements arranged one behind the other can be selected such that it does not lie symmetrically between the two adjacent blades or friction surfaces in the circumferential direction of the rotor. As a result, the load can be distributed unevenly over the damping elements, particularly when using two damping elements arranged one behind the other. The asymmetry can be set in a targeted manner by a different geometric configuration or by different masses of the two damping elements. Due to the multitude of possible combinations, the groups of damping elements can be optimally configured for every application. In particular, the suitable choice of the friction or contact surfaces, the mass and the position of the center of mass can ensure that the damping elements do not get stuck.
The damping elements should also have a high rigidity / weight ratio. This can also be achieved by a hollow shape of these elements.

The damping elements of a group can consist of different ones Materials exist. For example as base material one of two damping elements Cobalt, as the base material of the other damping element Nickel can be chosen. this makes possible different coefficients of friction on the respective Frictional surfaces with the blades so that through the choice of materials is another option for customization Achieving optimal vibration damping available stands.

The damping elements here, as well in the known arrangements of the prior art, by the centrifugal force during the rotation of the rotor for example against the underside of the blade platforms pressed. The blade platforms should be on their Subpages for this in adaptation to the shape of the Damping elements be suitably shaped or guide grooves form. However, it goes without saying that other areas besides the bucket platforms of the blade root by means of suitable shaping for receiving the damping elements can be formed. in the The damping elements can be used to idle the rotor also be held by suitable restraint systems.

In a preferred embodiment of the present blade arrangement, a combination of a rod-shaped damping element with a circular cross-section and a wedge-shaped damping element, i. h, a rod-shaped damping element with a wedge-shaped cross section. This combination of two damping elements with different effects can effectively dampen a large number of different vibration states. While the rod-shaped damping element with a circular cross-section primarily dampens in-phase vibrations effectively, the wedge-shaped damping element primarily acts on vibrations that do not occur in phase.
Due to the additional contact surface between the damping elements for absorbing vibrational energy, the problem of locking that occurs when only a rod-shaped damping element with a circular cross section is used can be avoided. This increases the life of the blade assembly.

Of course, you can also have more than two Arrange damping elements one behind the other. So can for example three damping elements, one of which a circular cross section and the other two have a wedge-shaped cross section - or vice versa - be used.

The group according to the invention arranged one behind the other Damping elements can only be used between individual or also between all neighboring blades of the blading be used. Lately has been also pointed out that through a mismatch (mistuning) the damper reduces the flutter or can be avoided. The possibility of an asymmetrical Damper configuration of the present invention offers clear advantages. For example the damping elements arranged one behind the other a group consist of different materials and / or have different geometric shapes, this material or shape pattern in in a mixed up way across the entire blading repeated. The relative can also be used, for example Position of a damping element with a wedge-shaped Cross section to a damping element with a circular Swap cross section from bucket to bucket, to achieve the desired mismatch.

You can also choose between neighboring ones Shovel two or more groups in a row arranged damping elements in identical or different Design over the axial extent arrange the blades. This gives you the opportunity various forms of vibration effectively dampen. The damper configurations of the individual groups are each in the form and / or the mass ratio and / or according to the geometric dimensions optimized the shape of the vibration to be damped.

Fig. 1

ein erstes Beispiel für eine Ausgestaltung und Anordnung der Dämpfungselemente bei der erfindungsgemäßen Schaufelanordnung;

Fig. 2

ein zweites Beispiel für eine Ausgestaltung und Anordnung der Dämpfungselemente bei der erfindungsgemäßen Schaufelanordnung;

Fig. 3

ein drittes Beispiel für eine Ausgestaltung und Anordnung der Dämpfungselemente bei der erfindungsgemäßen Schaufelanordnung; und

Fig. 4

ein Beispiel für die Anordnung von zwei Gruppen von Dämpfungselementen über die axiale Erstreckung der Schaufeln.

The blade arrangement according to the invention is explained again below by way of example using exemplary embodiments in conjunction with the drawings without restricting the general inventive concept. Here show:

Fig. 1

a first example of an embodiment and arrangement of the damping elements in the blade arrangement according to the invention;

Fig. 2

a second example of an embodiment and arrangement of the damping elements in the blade arrangement according to the invention;

Fig. 3

a third example of an embodiment and arrangement of the damping elements in the blade arrangement according to the invention; and

Fig. 4

an example of the arrangement of two groups of damping elements over the axial extension of the blades.

Ways of Carrying Out the Invention

Figure 1 shows a first embodiment for an embodiment of the damping elements in the invention Blade arrangement. The figure shows one Section of the blade arrangement in a sectional plane perpendicular to the rotor axis. Here are the blade platforms 1 to recognize neighboring blades, which - not shown - are attached to the rotor blade and have a small distance from each other. The subpages of the two blade platforms 1 form friction surfaces 4, 5, against which the two damping elements 2, 3 when the rotor is rotated by the centrifugal force be pressed. The friction surfaces 4, 5 are at an angle of approx. 45 ° in this example to the plane by the radial direction and the Rotor axis is clamped, inclined. In this example becomes a damping element 2 with a wedge-shaped Cross section - hereinafter referred to as a wedge-shaped damping element designated - together with a damping element 3 with a circular cross section - hereinafter as called circular damping element - used. Both damping elements are rod-shaped in the axial direction trained as this from the prior art is known.

If the entire system vibrates, a Relative movement between the two neighboring ones Bucket platforms 1, which in turn lead to a relative movement between the wedge-shaped damping element 2 and the friction surface 4, between the circular damping element 3 and the friction surface 5 and to one Relative movement between the two damping elements leads on the contact surface 6. At all three touch or contact points can thus vibrational energy be converted into frictional energy so that a effective vibration damping is achieved.

Such a design and arrangement enables a relative movement of the damping elements to each other and to the blade platforms in the radial direction for optimal damping of the in-phase bending vibrations. At the same time, this will be the case with damping elements problem with circular cross section of fixing without avoiding a specific one Tilt angle of the friction surface 5 on the To have to adhere to the bucket platform.

FIG. 2 shows a further example of the configuration and arrangement of the damping elements in the present blade arrangement. In this embodiment, which otherwise corresponds to the embodiment of FIG. 1, the surface of the wedge-shaped damping element 2, which comes into contact with the friction surface 4 of the blade platform, is provided with elevations or raised areas 7. These raised areas serve to prevent the wedge-shaped damping element from tilting relative to the friction surface 4, as might occur under certain vibration conditions. This configuration therefore prevents possible tilting of the damping element, which leads to a deterioration in the damping behavior.
The inclination of the friction surface 4 on the side of the wedge-shaped damping element 2 to a plane running perpendicular to the radial direction can be between 45 ° and 80 ° in this, as in the other exemplary embodiments, and is chosen such that the damping element 2 is prevented from becoming stuck. The angle α between the contact surface 6 of the wedge-shaped 2 and circular damping element 3 and the plane running perpendicular to the radial direction can be chosen as desired in order to achieve the required stability and to prevent the damping element 3 from becoming stuck. This angle α can in particular also be chosen to be significantly smaller than 90 °. The angle  between the friction surface 5 and the plane running perpendicular to the radial direction results at α = 90 ° from the condition µ ≤ cos / (1 + sin) in order to prevent the damping element 3 from becoming fixed, where µ is the coefficient of friction on the contact surface 6. At an angle α <90 °, such a condition can be derived for α and .

Another example of a configuration of the damping elements of the present blade arrangement is shown in FIG. 3. In this arrangement, the first damping element 2 - again wedge-shaped - is designed such that it comes into contact with both friction surfaces 4, 5 of the two adjacent vane platforms 1 when the rotor rotates. Here, too, another damping element with a circular cross section 3 is used, which also comes into frictional contact with the friction surface 5 of the one blade platform 1. The diameter of the circular damping element 4 must of course be smaller than in the embodiments of FIGS. 1 and 2 under otherwise identical geometric conditions.
The wedge-shaped damping element 2 is in turn provided with raised areas 7 in order to avoid the tilting instability already described.

In contrast to the embodiments of the figures 1 and 2 occurs in the embodiment of Figure 3 additional frictional contact between the first damping element 2 and the friction surface 5. There are therefore an additional contact point for receiving Vibration energy available. In this example too causes the circular damping element 3 a efficient damping of radial relative movements during the wedge-shaped damping element damping the other vibration modes takes over.

Figure 4 finally shows an example schematically for the arrangement of two groups of damping elements about the axial extension of the blades. In the Figure is the airfoil 8, the airfoil platform 1 and to recognize the blade root 9. About the axial Extent of the blade (axial direction 12) are here the positions of two groups 10, 11 from one another arranged damping elements indicated, which according to the claims, for example as in the preceding Examples are designed. The first group 10 is located on the front edge in this example 14 of the shovel, the second group 11 on the rear edge 15. The flow direction 13 is through a Arrow indicated. Through an asymmetrical arrangement or configuration of the groups in the axial direction can effectively dampen different vibration modes become.

The configurations of the present blade arrangement are possible for the damping of a variety resonant and non-resonant vibration excitations suitable, such as fluttering, shaking or stochastic excitation. The possibility of each other deviating geometric design of the two Damping elements enable optimal adjustment to the respective circumstances. Also regarding The inclined platforms of the rotor axis can Damping elements in a correspondingly inclined position or orientation can be used.

The damping elements are both when used in Low pressure as well as in high pressure turbines and for compressor blades suitable. You can as simple Damping elements or for additional sealing as Damping and sealing elements are used.

Reference list

1

Bucket platform

2nd

first damping element

3rd

second damping element

4th

first friction surface

5

second friction surface

6

Level of contact

7

Surveys

8th

Airfoil

9

Blade root

10th

first group

11

second group

12th

axial direction

13

Flow direction

14

Leading edge

15

Trailing edge

Claims (22)

Blade arrangement with damping elements, which comprises a rotor and blades arranged on the circumference of the rotor, damping elements (2, 3) being arranged between the blades, which come into contact with the blades when the rotor rotates about a rotor axis by a centrifugal force acting in the radial direction stand,
characterized in that at least between two adjacent blades, a plurality of damping elements (2, 3) are arranged one behind the other in the circumferential direction of the rotor, so that when the rotor rotates, the damping elements (2, 3) arranged one behind the other touch via one or more contact surfaces (6) and a first (2) of the damping elements arranged in series come into contact with a first friction surface (4) of one and a second (3) of the damping elements arranged in series with a second friction surface (5) of the other of the adjacent blades. Blade arrangement according to claim 1,
characterized in that the damping elements arranged one behind the other comprise the first (2), the second (3) and a third damping element which is arranged in the circumferential direction of the rotor between the first (2) and second damping element (3). Blade arrangement according to claim 1,
characterized in that the damping elements arranged one behind the other only comprise the first (2) and the second damping element (3). Blade arrangement according to claim 3,
characterized in that the contact surface (6) between the first (2) and the second damping element (3) runs approximately parallel to the radial direction. Blade arrangement according to claim 3 or 4,
characterized in that the first (2) and the second damping element (3) differ in their geometric shape. Blade arrangement according to claim 5,
characterized in that the first damping element (2) has a wedge-shaped cross section and the second damping element (3) has a circular or elliptical cross section. Blade arrangement according to claim 6,
characterized in that the wedge angle of the wedge-shaped cross section of the first damping element (2) corresponds to the angle between the first friction surface (4) and the plane spanned by the radial direction and the rotor axis. Blade arrangement according to one of claims 3 to 6,
characterized in that the first damping element (2) is designed and arranged such that it also comes into contact with the second friction surface (5) when the rotor rotates. Blade arrangement according to claim 8,
characterized in that in a configuration of the first damping element (2) with a wedge-shaped cross section, the wedge angle of the wedge-shaped cross section corresponds to the angle between the first friction surface (4) and the second friction surface (5). Blade arrangement according to one of claims 6, 7 and 9,
characterized in that surfaces of the first damping element (2) which come into contact with the friction surface or surfaces (4, 5) have elevations (7). Blade arrangement according to claim 2,
characterized in that the third damping element differs in geometry from the first (2) and second damping element (3). Blade arrangement according to claim 11,
characterized in that the third damping element has a wedge-shaped cross section and the first (2) and the second damping element (3) have a circular or elliptical cross section. Blade arrangement according to claim 11,
characterized in that the third damping element has a circular or elliptical cross-section and the first (2) and the second damping element (3) have a wedge-shaped cross-section. Blade arrangement according to one of claims 1 to 13,
characterized in that the first (4) and the second friction surface (5) are each formed by an underside of a blade platform (1) of the respective blade, the friction surfaces (4, 5) thus spanning the radial direction and the rotor axis Are inclined plane that together they form a V-shaped guide into which the damping elements (2, 3) are pressed by the centrifugal force. Blade arrangement according to one of claims 1 to 14,
characterized in that the center of mass of the group of damping elements (2, 3) arranged one behind the other does not lie symmetrically between the two adjacent blades or friction surfaces (4, 5) in the circumferential direction of the rotor. Blade arrangement according to one of claims 1 to 15,
characterized in that two or more groups of damping elements (2, 3) arranged one behind the other are arranged in an identical or different configuration over the axial extension of the blades. Blade arrangement according to one of claims 1 to 16,
characterized in that one or more groups of the damping elements (2, 3) arranged one behind the other are arranged between further adjacent blades. Blade arrangement according to claim 17,
characterized in that some of the groups of damping elements (2, 3) arranged one behind the other differ in their design between different adjacent blades. Method for vibration damping of a blade arrangement, which comprises a rotor and blades arranged on the circumference of the rotor, in which damping elements (2, 3) are arranged between the blades, which are rotated by a centrifugal force acting in the radial direction when the rotor rotates about a rotor axis Blades contact
characterized in that at least between two adjacent blades, a plurality of damping elements (2, 3) are arranged one behind the other in the circumferential direction, so that when the rotor rotates, the damping elements arranged one behind the other touch and a first (2) of the damping elements arranged one behind the other with a first friction surface ( 4) one and a second (3) of the damping elements arranged one behind the other come into contact with a second friction surface (5) of the other of the adjacent blades. Method according to claim 19,
characterized in that two or three of the damping elements (2, 3) are arranged one behind the other. A method according to claim 19 or 20,
characterized in that two or more groups of damping elements (2, 3) arranged one behind the other are arranged in identical or different configurations over the axial extension of the blades. Method according to one of claims 19 to 21,
characterized in that one or more groups of the damping elements (2, 3) arranged one behind the other are arranged in an identical or different configuration between further adjacent blades.

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