EP1136653A2 - Blading with damping elements - Google Patents

Abstract

The device has a rotor (5) with blades (6) and damper elements (9) between neighboring blades. Each damper element is in friction contact with a first section (1,2) of a first and a second section (3) of a second neighboring blade. The damper elements are positioned between the blades so that the first and the second sections are located in positions, which are at considerable radial distances from each other. Each damper element is prevented from executing a movement at right angles to a radial plane, by guide grooves formed in any of the sections.

Description

Technical application area

The present invention relates to blading with damping elements, a rotor and am The circumference of the rotor is inserted in the radial direction extending blades with blade platform and blade base includes. At least between some of each a damping element is arranged adjacent to blades, that with a rotation of the rotor via friction with at least a first area of a first and a second region of a second one of the neighboring ones Buckets communicates.

Such blading is used in particular at Turbomachines such as gas turbines are used. The single ones Blades consist of the blade, the bucket platform, the bucket neck and the Blade foot, which in corresponding recesses on the circumference of the rotor is used. When operating the blading arise due to various excitation mechanisms unwanted vibrations that lead to a early material fatigue and thus to a shortened Can lead to the lifespan of the blading. The present invention relates to blading with damping elements that reduce these vibrations.

State of the art

To reduce the vibrations of the blading damping elements are already used, the act between the individual blades. With these Damping elements are usually loose Bodies that are initially at rest between the blade necks rest on the rotor and when operating the rotor due to the acting centrifugal force in radial Direction against the blade platforms neighboring Buckets are pressed. This allows the kinetic energy of one caused by vibrations Relative movement between the blades in Frictional energy between the respective blade platforms and the frictionally applied damping element being transformed. This dampens the vibrations and leads to a reduced vibration load the blading.

Such blading with damping elements is described for example in US 5,156,528. With this arrangement, the edge regions form more adjacent ones Bucket platforms one in the radial direction tapering recess into which the damping element is pressed by the centrifugal force. The damping element is so similar to that in its geometric form Shape of this recess is adapted to that when operating the blading in this recess is present. The smallest distance between the neighboring ones Bucket platforms are of course smaller than the dimensions of the damping element, so that this cannot separate itself from the blading. At a relative movement between the neighboring showers the kinetic energy in at the contact surfaces friction energy occurring to the damping element implemented.

In addition to the triangular cross-sectional shape of the damping element shown in this publication, other geometric shapes are also known, with which frictional engagement can be produced with neighboring blade platforms. A disadvantage of this system, however, is that only certain higher vibration modes of the blading are converted into friction energy with sufficient effectiveness.
Blading usually consists of 30 to 200 blades. They can be excited in a variety of vibration modes. When there are blades with N blades, N / 2 + 1 there are different natural vibrations or modes in the circumferential direction of the rotor. The higher the vibration mode, the greater the difference in vibration between adjacent blades. For example, in the case of low vibration modes, there are only very small relative movements between adjacent blades, while these become very large in the case of high vibration modes. In the case of vibration damping by converting the vibration energy into friction, the strongest possible relative movement of the surfaces rubbing against one another is advantageous. The above-mentioned technique of the damping elements acting between two adjacent blades is therefore only effective if the oscillation difference between adjacent blades is large. For this reason, the systems known from the prior art in this context can only be used advantageously for high vibration modes. However, the resonances of rotating turbine blades that occur in practice are generally in the range of the lowest vibration modes, so that the above damping elements do not have a sufficient effect here.

The object of the present invention is in providing blading with damping elements, where the damping elements between neighboring blades work and even at low Vibration modes cause sufficient damping.

Presentation of the invention

The task is with the blading according to claim 1 solved. Advantageous embodiments of the Blading is the subject of the subclaims.

The present blading points in known Way a rotor and inserted on the circumference of the rotor, blades extending in the radial direction with shovel platform, shovel neck and shovel foot on, at least between some of each neighboring Paddles arranged a damping element is that when the rotor rotates via friction with at least a first area of a first and a second area of a second of the neighboring Buckets communicates. The blading is characterized in that the damping element so designed and between the first and the second Shovel is arranged that the first area and the second area clearly in the radial direction from each other spaced positions.

According to the invention, it was recognized that the Relative movement of the surfaces of the Damping element and the respective blades low vibration modes can be increased that the areas of contact, lines of contact or points of contact with the neighboring blades radially spaced apart. This radial distance increases the relative movements at low vibration modes, so one stronger energy dissipation and thus a better and more effective vibration damping can be achieved. This technique is therefore particularly useful for small relative movements adjacent blades or at low Vibration modes, as they often occur, of great Advantage. However, it goes without saying that with this technique also stronger relative movements or higher vibration modes can be damped well.

Below are the first and second area respectively to understand both surfaces, lines and points, because the type of contact between the damping element and the blades of the surface shape of each Partner and the operating status of the arrangement, i.e. of speed, temperature, wear and deposits, depends. The present damping element is as well as the known damping elements of the stand of technology, formed from a rigid body, the due to the centrifugal forces acting on the rotation pressed against the first and second area becomes. In this position, part of the energy becomes a vibration movement in friction work on the damping element implemented.

To achieve an optimal damping effect, that is, an effective dissipation of the vibration energy lower vibration modes, must be the first and the second area in the radial direction if possible be far apart. The distance in radial Direction should be at least a third of the distance from the top of one Bucket platform up to the surface of the rotor circumference is present. This gap is determined by the thickness of the Blade platform and an upper area of the blade root, the scoop neck. The lower area of the blade root is in the holder or recess inserted on the circumference of the rotor. One too small distance between the first and second area leads to low vibration modes the vibration energy is insufficient in friction energy can be converted.

It goes without saying that on the blades corresponding projections must be provided loosening of the damping element during rotation prevent the rotor from blading. For this the blade platform itself can serve on the one hand, on the other hand, however, could also be a separate lead be provided on the bucket for a shift of the damping element in the radial direction to prevent. Furthermore, the damping element be dimensioned so that it when operating the blading only in the desired Position pressed against the neighboring blades becomes. For this purpose, the damping element has a cross section preferably an elongated shape in the radial plane with a length that is greater than the distance between neighboring ones Blade feet in the circumferential direction of the rotor. As a result, the damping element can be between insert the blades that there is one end at the Underside of the platform that a bucket is resting on, while the other end is at a significantly different radial position against the blade root the other neighboring shovel pushes. The shape or Configuration of the damping elements in the axial direction, that is in the direction parallel to the axis of the rotor, can be both straight and curved. This applies to everyone in the arrangement according to the invention usable damping elements. In the radial position is the distance of one in the present application To understand the point to the rotor axis in a radial plane. A radial plane makes a plane perpendicular to the rotor axis.

It goes without saying that the exact form of the damping elements on the form, the dimensions and the spacing of the individual blades of the blading is dependent. The specialist is quite in the Able to find suitable forms of damping elements, that meet the requirements of the invention. Some Basic forms for suitable damping elements are in the shown below.

The damping elements can be particularly advantageous Use when your focus is close to first or second range. Through this required asymmetry of the damping element achieve that the vibration energy at a Relative movement between adjacent blades only at the contact area with the damping element converts into frictional energy, which is further from the center of gravity of the damping element is removed than the other Contact area. By choosing a focus of the damping element as close as possible to one of these Contact areas occur at this area no or very little frictional movement on. This leads to an increase in effectiveness of energy conversion.

In a further advantageous embodiment the damping element has a widened at one end Range on which between the operation of the rotor both platforms is pressed and thus like one Damping element according to the state mentioned at the beginning works. The dimensions of this widened area and the shape of the edge areas of the platforms should be suitably matched to one another. The invention Damping element has one of these widened area outgoing foothills on the up to one clearly in the radial direction from the Platforms spaced area of the blade root enough. The distribution of the center of gravity in the damping element is chosen so that the end of the foothills pressed against the blade root during operation of the rotor becomes. In this embodiment, the damping properties the known elements of the stand the technology combined with the damping properties, as with the damping elements shown above can be achieved.

At the first and / or second areas of the Blade feet or blade platforms are preferred Depressions or grooves provided in which the damping element can be used or in rotary operation engages, and the movement of the damping element prevent in the axial direction. For one optimal effect of the damping element should be the first and the second area as large a distance as possible have in the radial direction. The maximum distance is made possible by the first area at or just below the platform of the first blade and just above the rotor surface on the blade neck the second blade is in contact. The damping element extends quasi diagonally in the radial plane over the one present between adjacent blade roots Space. The best damping effect can can of course only be achieved if between all neighboring blades of the blading Damping elements are arranged. The mass, focus distribution, Shape and the material of the damping element depending on the desired damping properties and the properties of the rotor and the Number of blades selected.

Fig. 1

ein erstes Beispiel eines Ausschnitts einer erfindungsgemäßen Beschaufelung in zwei Querschnittsansichten;

Fig. 2

ein zweites Beispiel eines Ausschnitts einer erfindungsgemäßen Beschaufelung in zwei Querschnittsansichten; und

Fig. 3

ein drittes Beispiel eines Ausschnitts einer erfindungsgemäßen Beschaufelung in zwei Querschnittsansichten.

The invention is explained in more detail below on the basis of exemplary embodiments in conjunction with the drawings without restricting the general inventive concept. Here show:

Fig. 1

a first example of a section of a blading according to the invention in two cross-sectional views;

Fig. 2

a second example of a section of a blading according to the invention in two cross-sectional views; and

Fig. 3

a third example of a section of a blading according to the invention in two cross-sectional views.

Ways of Carrying Out the Invention

Figure 1 shows a first example of an embodiment of the blading according to the invention in the detail. Here, a section through the blading parallel to the rotor axis is shown in the left part of the figure. The cutting plane contains the rotor axis. In this partial illustration, the rotor 5 can be seen, into which the blade root 8 of a blade 6 is inserted in a manner known per se. The blade neck 14 and the blade platform 7 extend between the blade blade 10, which is only indicated, and the rotor 5. The same arrangement is shown in the right part of the figure in a section perpendicular to the rotor axis, that is to say in a radial plane. A section of the rotor 5 with two inserted blades 6 (blade i; adjacent blade i + 1) with the blade platforms 7 and the blade necks 14 protruding from the rotor can also be seen here.
In this example, a damping element 9 is arranged between the adjacent blades, which is shown again in a perspective view in the top right corner. This damping element has an elongated, stick-like shape in cross section in the radial plane, so that its center of gravity 12 is clearly shifted towards one end. In the right part of the figure, the arrangement of this damping element 9 during operation of the blading, that is to say when the rotor rotates, is shown. The centrifugal force acting on the center of gravity 12, which acts in the radial direction, presses the damping element 9 against the adjacent blades 6 in the orientation shown. One end of the damping element is pressed against the contact areas 1 and 2 of the blade neck or the blade platform of the right blade while the other end abuts the contact area 3 of the left blade. Depending on the surface shape of the damping element, these contact areas can be 9 surfaces, points or lines. In the present example it is a linear contact. In the left part of the figure, this linear contact is indicated by the connecting lines between points 1, 2 and 3 and points 1 ', 2' and 3 '. In this partial illustration, a groove 11 on the scoop neck 14 can also be seen, in which the damping element is arranged, thereby preventing axial movements of the damping element.
In the present example, the damping element 9 is designed such that it can only be in contact with the contact areas 1, 2 and 3 in the position shown when the rotor is in operation. In the idle state, the damping element initially rests on the rotor 5 with the widened region and is forced into the position shown by the centrifugal force during a rotational movement. For an optimal effect of the damping element in the sense of the present invention, the dimensions of the damping element are chosen such that the smallest possible distance 13 to the rotor surface remains. In this way, the desired position of the damping element is reliably ensured during operation of the rotor.
When operating the rotor, friction or reaction forces act on areas 1, 2 and 3. The magnitude of these forces depends on the mass, the dimensions and the radial position of the damping element and on the speed of rotation of the rotor. In the present case, in which the center of gravity of the damping element is close to the contact area 3, the reaction force acting there is greatest, so that at this point 3 there is hardly any relative movement between the damping element 9 and the blade neck 14. In the event of a vibration movement between the two blades shown, the vibration energy is converted into friction at the corresponding contact regions 1 and 2.

Of course, in the present example the transition between the bucket neck 14 and the bucket platform 7 also be rounded, so the damping element 9 in a form-fitting manner in these areas can concern.

Figure 2 shows a further embodiment of the blading according to the invention. The same views are shown in this representation as in the blading of FIG. 1.
In this example, the damping element 9 is designed with a widened region on one side, which is pressed between a recess formed by the spaced-apart blade platforms 7 during operation of the rotor. This can be seen in the right part of the figure, wherein in addition to a contact with the right vane platform in area 1, there is also a contact with the left vane platform in area 4. This achieves the effect of the damping elements known from the prior art, which act in the same way on the blade platforms at the same height. However, the present damping element does not only consist of this widened area which engages between the two blades. Rather, the damping element has an elongated shape or an extension in the radial plane, as shown, a lower region being in contact with the left vane neck in region 3. In order to enable this contact to the area 3, the center of gravity 12 of the damping element 9 must lie in the circumferential direction between the contact point 2 and the contact point 3, since the damping element is then only pressed against the left blade neck by the centrifugal force in the manner shown.
The geometric shape of the damping element 9 used in this exemplary embodiment is shown again in a perspective view in the upper right part of the figure. The recognizable asymmetry is necessary in this case in order to achieve the frictional connection with the illustrated contact points or contact surfaces 1, 3 and 4 under the action of the centrifugal force. In this case too, the damping element 9 is dimensioned such that it is only a short distance 13 from the rotor 5. In the present case, this small distance enables a large distance - in the radial direction - between the contact area 3 and the contact area 1. This clear distance is advantageous for achieving the effect according to the invention.

Of course, the effect of the damping element 9 known from the prior art on the two adjacent platforms 7 can also be achieved via the contact surfaces 1 and 4 by a different design of the edge regions of the platforms or the upper end of the damping element 9. It is essential in this embodiment that the damping element extends towards the rotor in order to achieve frictional contact with the contact surface 3 during operation.
In this example, the vibration of the blading is damped simultaneously in all three areas 1, 3 and 4. To prevent axial movement of the damping element, a groove 11 is provided in the blade platform 7, as is indicated in the left part of the figure.

FIG. 3 finally shows a further embodiment of the blading according to the invention, the same cross-sectional views being shown here as in FIG. 1. In this example, the damping element 9 has an angled shape which approximately corresponds to that of a golf club. With this shape, two essentially parallel surfaces are provided on the damping element 9, a first of which rests on the underside of the blade platform 7 in area 1, while a second rests on the underside of a projection on the adjacent shovel neck 14 (contact area 3). It goes without saying that the illustration relates to the operating state of the blading, in which the damping element 9 is pressed against the surfaces 1 and 3 by the centrifugal force. In this example too, the damping element 9 is dimensioned such that the smallest possible distances 13 to the rotor 5 or to the left blade neck 14 occur. By choosing the center of gravity 12 in the lower region of the damping element, that is to say close to the contact surface 3, the reaction force acting on the contact surface 3 when the two adjacent blades 6 move relative to one another is very much greater than the force acting on the contact surface 1. As a result, an oscillation of the blades at area 1 is converted into friction energy. For optimal damping, a frictional movement in area 3 should be prevented or minimized. This is achieved by the asymmetrical design for shifting the center of gravity as close as possible to area 3.
The reaction forces are shown in the lower part of the figure again on an enlarged view of the damping element 9 and the adjacent blade platforms or blade necks. The reaction force R1 acting on the contact surface 1 is substantially smaller than the reaction force R3 acting on the contact surface 3. This distribution of forces results from the position of the center of gravity 12, at which the centrifugal force N acts, in conjunction with the ratio of the dimensions a - d indicated in the figure.

With the illustrated embodiments, from which the specialist easily additional forms of damping elements can derive the properties shown have, a blade damper is realized, which is particularly effective when adjacent blades only small relative movements to each other To run. This is achieved in that the damping element on clearly different radial positions on the adjacent blades attacks.

Reference list

1/2

first contact area

3rd

second contact area

4th

third contact area

5

rotor

6

shovel

7

Bucket platform

8th

Blade root

9

Damping element

10th

Airfoil

11

Guide groove

12th

main emphasis

13

Distance to the rotor or airfoil

14

Bucket neck

Claims (11)

Blading with damping elements,
which comprises a rotor (5) and blades (6) with a blade platform (7), blade neck (14) and blade root (8) inserted in the radial direction and extending in the radial direction, at least between some of adjacent blades (6) a damping element (9) is arranged which, when the rotor (5) rotates, is connected via frictional engagement to at least a first region (1, 2) of a first and a second region (3) of a second one of the adjacent blades (6) ,
characterized in that the damping element (9) is designed and arranged between the first and the second blade (6) in such a way that the first region (1, 2) and the second region (3) lie at positions which are clearly spaced apart in the radial direction . Blading according to claim 1,
characterized in that the first area (1, 2) in the upper third of an area of the first blade extending from the blade platform (7) to the rotor (5) and the second area (3) in the lower third of an area extending from the blade platform ( 7) up to the rotor (5) extending area of the second blade. Blading according to claim 1 or 2,
characterized in that the first area (1, 2) lies on an underside of the blade platform (7) of the first and the second area (3) on the blade neck (14) of the second blade. Blading according to claim 1 or 2,
characterized in that the first area (1, 2) is located on the scoop neck (14) near the scoop platform (7) of the first and the second area (3) on the scoop neck (14) of the second scoop. Blading according to claim 1 or 2,
characterized in that the first region (1, 2) lies on an underside of the blade platform (7) of the first and the second region (3) on the blade neck (14) of the second blade, the damping element (9) being designed in such a way that when the rotor (5) rotates, it is additionally connected via frictional engagement to a third region (4) on the blade platform (7) of the second blade, which is opposite the first region (1, 2). Blading according to one of claims 1 to 5,
characterized in that a cross section of the damping element (9) has an elongated shape in a radial plane, the length of which is greater than the distance between adjacent blade necks (14). Blading according to one of claims 1 or 2,
characterized in that a cross section of the damping element (9) has an angled shape in a radial plane, wherein when the rotor (9) rotates, an end region of the damping element (9) with an underside of the blade platform (7) of the first blade as the first region (1) is in frictional contact and an opposite end region of the damping element (9) rests as a second region (3) on a bottom side of a projection formed on the blade neck (14) of the second blade. Blading according to one of claims 1 to 7,
characterized in that the damping element (9) is designed asymmetrically in such a way that its center of gravity (12) is close to the first (1, 2) or second region (3). Blading according to claim 5,
characterized in that a cross section of the damping element (9) in a radial plane has an elongated shape with a widened end region and with an asymmetry to the longitudinal axis, the widened end region being wider than the distance between the adjacent blade platforms (7). Blading according to one of claims 1 to 9,
characterized in that contact surfaces between the damping element (9) and the first (1, 2) and / or second region (3) are designed as flat surfaces. Blading according to one of claims 1 to 10,
characterized in that the damping element (9) is prevented from moving perpendicularly to a radial plane by guide grooves (11) formed on the first (1, 2) and / or second (3) and / or third region (4).

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