WO2010043666A1

WO2010043666A1 - Axial turbomachine comprising a rotor blade ring and a damping device

Info

Publication number: WO2010043666A1
Application number: PCT/EP2009/063458
Authority: WO
Inventors: Detlef Haje
Original assignee: Siemens Aktiengesellschaft
Priority date: 2008-10-16
Filing date: 2009-10-15
Publication date: 2010-04-22
Also published as: DE102008052021A1

Abstract

An axial turbine comprises a rotor blade ring formed from a plurality of rotor blades, each of which comprises a vane, and a damping device comprising a coupling device and a respective contact element fastened thereto for each vane, said contact elements fastening the corresponding vane to the coupling device so that the vanes are coupled together mechanically in the peripheral direction of the rotor blade ring by way of the coupling device, resulting in a reduction of the vane vibrations of the vanes.

Description

description

AXIAL TURBINE MACHINE WITH A RUNNING SHAFT AND A STEAMING DEVICE

The invention relates to an axial turbine with a blade ring, which is formed by a plurality of blades, each having an airfoil, and a damping device, are reduced by the blade leaf vibrations of the airfoils.

An axial turbine is, for example, a steam turbine with a rotor having a plurality of rotor blade rows lined up on the rotor. The blade rings are each formed by a plurality of blades, each having an airfoil. In the direction of flow through the steam turbine, the length of the blades generally increases, so that in the high-pressure region of the steam turbine the shortest blades and in the low-pressure region of the steam turbine the longest blades are arranged. During operation of the steam turbine, the low-pressure rotor blades are mechanically highly stressed components due to centrifugal forces and vibration excitation, wherein they are adapted as a function of the respectively expected boundary conditions during operation of the steam turbine. Here are used as a measure of the expected vibration excitation of the blades, the amount of the expected Abdampfdrucks and the operation of the steam turbine at a constant or variable speed. As a measure of the stress level and as a selection criterion for the choice of running turbine blade materials, the size of the required outflow surface and the intended maximum speed of the rotor are taken.

Freestanding low-pressure blades are usually found at constant speeds and moderate exhaust steam pressures

Steel application. In the steam turbine, which is designed for operation at variable speed and / or increased exhaust steam pressure, conventionally an additional damping of the blade provided against excessive vibration excitation leaves. This is typically realized by a damping connection between the blades of a rotor blade ring. This connection is conventionally a damper wire, coupling elements inserted between the airfoils, integral coupling elements of the rotor blades ("snubber") or cover plates. When operating the steam turbine at a high Abdampfdruck the low pressure blades are exposed to increased vibration stress by an amplified excitation, which is counteracted by the provision of the damping acting connecting elements. Furthermore, during variable-speed operation of the steam turbine, excitation in resonance or at least in the vicinity of the resonance of the blades of the low-pressure blades may occur, this stimulus being counteracted by the damping elements acting as damping elements.

If the low-pressure blade ring is provided with a high outflow area, or if the steam turbine is operated at high speeds, in particular the blades of the low-pressure blade ring are made of light metal materials, in particular titanium. Due to the poor damping properties of the light metal materials, the damping effect connecting elements are essential.

The use of dampening connecting elements leads in particular to the Laufschaufein made of light metal to friction damage, such as scrubbing. A remedy for this could be a coating of the contact surfaces of the blades, on which the damping elements rest. Such coatings may adversely affect the fatigue life of the low pressure impeller since, for example, the coating material has a different coefficient of thermal expansion than the blade material, which may result in internal stresses in the rotor during operation of the steam turbine. This results in a limited wear resistance of Niederdrucklaufschaufein, whereby their Dauer- durability is reduced. Also, the coating process may cause residual stresses or structural changes.

The object of the invention is to provide an axial turbine with a blade ring, which is formed by a plurality of blades, in which the blades are damped effectively and only with minor signs of wear during operation of the axial turbine.

The axial turbine according to the invention comprises a blade ring, which is formed by a plurality of blades, each having an airfoil, and a damping device which has a coupling device and for each blade a fastened thereto contact element, via which the corresponding blade on the Coupling device is set so that in the circumferential direction of the blade ring, the blades are mechanically coupled to each other by the coupling means, whereby blade blade vibrations of the blades are reduced.

Thus, in each case a separate contact element is provided between the coupling device and each blade, which is engaged by the coupling device. Due to the fact that the contact element is fastened to the corresponding airfoil, forces can be transmitted from the coupling device to the corresponding airfoil via the contact element. In this case, a contact contact is formed on a contact surface of the contact element with the coupling device to which a relative movement between the coupling device and the contact element may occur during operation of the axial turbine, whereby the coupling device can scrub with a corresponding pressure force on the contact element on the contact surface of the contact element. By providing the contact element on the respective airfoil this is not directly exposed to the scrubbing, so that a mechanical damage caused by the rubbing against the airfoil is prevented. Furthermore, at the Airfoil possibly measures to be envisaged, such as a coating of the airfoil in the area of the contact surface to reduce the wear caused by the scouring accounts. Thus, the base material of the blades remains protected from the friction damage mechanisms such as scrubbing.

The contact element is typically made of a material which, by its nature or nature, can sufficiently withstand the damage mechanisms caused by friction. In this case, the contact element may have been subjected to a corresponding treatment or a corresponding surface treatment.

It is preferred that at the same point each airfoil has a through hole into which a respective contact bush is formed as the contact element, through which a damper wire is formed as the coupling device. In this case, it is further preferred that the airfoil is formed on the through-hole as an eye which has a thickening of the airfoil through which the through-hole extends. As a result, the blade is designed in its structure adapted to the forces that are transmitted from the damper wire to the blade during operation of the axial turbine.

Preferably, the contact bush is fixed in the longitudinal direction of the through hole at the thickening. As a result, it is advantageously prevented that the contact bush can move in the longitudinal direction of the damper wire.

Preferably, the thickening has a first annular surface and a second annular surface, which are raised away from the blade and perpendicular to the longitudinal direction of the through hole, wherein the contact socket is supported on the annular surfaces, so that the contact socket is fixed in the longitudinal direction of the through hole. Furthermore, it is preferred that the contact bushing has a first support projection and a second support projection at their end-side longitudinal ends, wherein the first support projection abuts the first annular surface and the second support projection abuts the second annular surface. As a result, the contact bushing is fixed in the longitudinal direction of the damper wire and thus stably inserted into the eye of the airfoil.

It is preferable that the first and second support protrusions are respectively supported at a location of the first annular surface and the second annular surface, the location being spaced from the through hole. As a result, the point is advantageously not arranged directly on the through hole of the thickening, wherein the occurrence of voltage peaks in the thickening caused by a load on the female connector in the longitudinal direction of the damper wire during operation of the axial turbine is prevented.

Preferably, the support projections and / or the cylindrical portion of the contact socket are slotted. As a result, advantageously, the mounting of the contact socket can be carried out analogously to a mounting of a blind rivet, wherein the contact socket is inserted into the through hole and reshaped so that the contact socket is fixed to the annular surfaces. Preferably, the slot is made narrow, so that no significant movements between the contact socket and the blade can occur in the radial direction of the contact socket. Further, it is possible that the contact bush provided with the slotted supporting projections can yield to thermal expansions of the airfoil.

Alternatively, it is preferred that at the same point each blade has on its pressure side a first recess and on its suction side a second recess, wherein in the first recess formed as the contact element, provided with a receiving trough, the first contact socket and in the second recess as the contact element formed a damper rod with its one longitudinal end in the receiving trough of the first contact base of a blade and at its other longitudinal end in the receiving trough of the second contact base of the other blade of the blade adjacent one blade intervenes. The receiving trough may be formed, for example, as a depression, a hollow sphere or a blind hole.

It is preferred that the airfoil is formed as a web between the two recesses. As a result, the two contact sockets are stably supported on the airfoil, and the airfoil has a high-strength structure.

Furthermore, it is preferred that the web has a first support surface, on which the first contact socket is supported perpendicular to the pressure side, and a second support surface facing away from the first support surface, on which the second contact socket is supported perpendicular to the suction side.

It is preferred that the contact sockets are soldered, latched and / or screwed into the recesses. As a result, the contact socket with the blades are connected so that the majority of the relative movements occur directly on the contact sockets. Thus, the support surfaces are at most exposed to minimal relative movements.

Preferably, an internal thread is provided in the recesses, in each of which the contact socket is screwed. Furthermore, the contact base is preferably equipped with an anti-twist device. In addition, it is preferred that the internal thread is notch designed, for example, the placement of the internal thread is outside the zone with the maximum stress. It is also preferred that the blades are made of a light metal. Affected here are in particular low-pressure turbine blades, final stage blades and the power stages upstream blade rows, so-called precursors.

Preferably, the contact element is made of a steel, wherein preferably the steel is hardened. As a result, the contact element is sufficiently resistant to the friction caused by the coupling device damage mechanisms.

In the following, preferred embodiments of the axial turbine according to the invention are explained with reference to the accompanying schematic drawings. Show it:

1 shows a detail of the cross section of an airfoil of a blade of a first embodiment of the axial turbine according to the invention and

FIG. 2 shows a detail of the cross section of an airfoil of a rotor blade of a second embodiment of the axial turbine according to the invention.

An axial turbine shown in Figures 1 and 2 has a

Rotor blade on with a circumferentially juxtaposed blades that form a blade grid. Each blade has an airfoil 2 which, together with the blades of the other blades in the blade ring 1, is aerodynamically effective in the operation of the axial turbine. In FIGS. 1 and 2, a longitudinal cross section 3 of the blade 2 is shown.

According to a first embodiment according to FIG. 1, the airfoil 2 has an eye 4. The eye 4 is formed by a thickening 5 of the airfoil 2, which extends to each side of the airfoil 2, wherein a through hole 8 extends through the thickening 5 in the circumferential direction. The thickening 5 is designed to be flat on both sides of the blade 2 so that on each side of the blade 2 a first annular surface 6 and a second annular surface 7 facing away from the first annular surface 6 are formed on the thickening 5 the annular surfaces 6 and 7 are arranged substantially perpendicular to the through hole 8. The through hole 8 is located approximately in the middle of the thickening 5, so that the annular surfaces 6 and 7 are rotationally symmetrical.

Further, the blade ring 1 has a damper wire 9 which extends in the circumferential direction of the blade ring 1 and extends through the through holes 8 of the individual blades 2 of the rotor blade 1 in the run. Further, the blade ring 1 in each eye 4 each have a contact socket 10 with which the damper wire 9 is mounted in the through hole 8.

The female contact 10 has a cylindrical portion 11 which encloses the damper wire 9 and is arranged in the through-hole 8, so that the damper wire 9 has only indirect contact with the airfoil 2 on the inside of the through-hole 8. The contact socket 10 has on its one longitudinal side a first collar 12 and on its other longitudinal side a second collar 13, which faces away from the first collar 12. The collars 12 and 13 are arranged outside the eye 4, so that the first collar 12 protrudes from the first annular surface 6 and the second collar 13 from the second annular surface 7. At the radially outer end, both the first collar 12 and the second collar 13 have a first support projection 14 which in each case contacts the corresponding annular surface 6 or 7 with its free longitudinal end. The first collar 12 and the second collar 13 are semicircular in cross section, so that in the region of the cylindrical portion 11 of the contact bushing 10, both the first collar 12 and the second collar 13 protrude from the annular surfaces 6 and 7 and from the through hole 8 extend radially outwards, with the first Ab- supporting projection 14 of the first collar 12 is supported on the first annular surface 6 and the second supporting projection 15 of the second collar 13 on the second annular surface 7 in the axial direction of the through hole 8.

The first support projection 14 is free of play on the first annular surface 6 and the second support projection 15 is free of play on the second annular surface 7, so that in the axial direction of the through hole 8, the contact socket 10 is fixed without play on the thickening 5 of the eye 4.

The wall thickness of the contact socket 10 is selected on the cylindrical portion 11 such that the damper wire 9 with its predetermined outer diameter in the cylindrical portion 11 has a corresponding clearance fit. Further, the female contact 10 is formed on its cylindrical portion 11 and on its collar 12, 13 with a longitudinal slot, which can yield in eventual clamping of the damper wire 9 in the contact socket 9. Upon rotation of the rotor blade ring 1, the damper wire 9 applies by the action of centrifugal force to the contact socket 10, so that when a relative movement of the damper wire 9 and the blade 2 during operation of the axial turbine occurs, this can be accomplished only under a frictional resistance.

The blade 2 shown in Figure 2 with its longitudinal section 3 also has an eye 4, which is formed by a thickening 5 with a first annular surface 6 and a second annular surface 7.

The embodiment shown in Figure 2 differs from the embodiment shown in Figure 1 in that in the through hole 8 in Figure 1, a web 24 is provided, which continues the longitudinal cross section 3 of the airfoil 2 in the eye 4, so that on the airfoil. 2 two mutually remote recesses 16 and 17 are formed. The recesses 16 and 17 are formed as cylindrical blind holes, wherein in the first recess 16 a first contact socket 18 and in the second recess 17, a second contact socket 19 is inserted.

The rotor blade ring 1 according to FIG. 2 has damper rods between its rotor blades with which the individual rotor blades are mechanically coupled. A first damper rod 20 is with its designed as a rounded tip longitudinal end in a first receiving trough 22 of the first contact socket

18 used. A second damper rod 21, which lies on the other side of the airfoil 2 of the first damper rod 20, is inserted into a second receiving recess 23 of the second contact socket 18 with its longitudinal end, also designed as a rounded tip. The damper rods 20, 21 are arranged over the circumference of the rotor blade ring 1, so that between the blade blades 2 of the rotor blade ring 1 is always a respective damper rod 20, 21 is arranged.

The contact bases 18, 19 are provided on their outer cylindrical wall with a thread 27 which engages in a thread 27 provided in the cylindrical inner wall of the recesses 16, 17.

The first recess 16 is formed at its base with a first support surface 25 and the second recess 17 at its base with a second support surface 26, wherein the support surfaces 25, 26 are formed by the web 24. The contact bases 18 and 19 are screwed with their threads 27 in the recesses 16, 17 such that the contact socket 18,

19 are supported on the support surfaces 25, 26. Thereby, a longitudinal force of the damper rods 20, 21 on the

Contact base 18, 19 is transmitted in the direction of the airfoil 2, received by the web 24.

Claims

claims

An axial turbomachine comprising a blade ring (1) formed by a plurality of blades each having an airfoil (2) and a damping device comprising a coupling device (9, 20, 21) and for each airfoil (2 ) has a contact element (10, 18, 19), via which the corresponding blade (2) on the coupling device (9, 20, 21) is fixed, so that in the circumferential direction of the blade ring (1) the blades (2) mechanically through each other the coupling means (9, 20, 21) are coupled, whereby blade vibrations of the blades (2) are reduced.

2. Axialturbumaschine according to claim 1, wherein at the same point each airfoil (2) has a through hole (8) in which each formed as the contact element is a contact bushing (10) is inserted through which formed as the coupling means a damper wire (9) is.

An axial turbomachine according to claim 2, wherein at the through-hole (8), the airfoil (2) is formed as an eye (4) having a thickening (5) of the airfoil (2) through which the through-hole (8) extends ,

4. Axial turbine according to claim 3, wherein at the thickening (5), the contact bush (10) in the longitudinal direction of the through hole

(8).

5. axial turbine according to claim 4, wherein the thickening (5) has a first annular surface (6) and a second annular surface (7), of the airfoil (2) raised, facing away from each other and perpendicular to the longitudinal direction of the passage hole (8 ), wherein the contact socket (10) on the annular surfaces (6, 7) is supported, so that the contact socket (10) in the longitudinal direction of the through hole (8) is fixed.

6. Axial turbine according to claim 5, wherein the contact bush (10) at their end-side longitudinal ends in each case a first

Support projection (14) and a second support projection (15), wherein the first support projection (14) abuts the first annular surface (6) and the second support projection (15) to the second annular surface (7).

7. axial turbine according to claim 6, wherein the first and the second support projection (14, 15) are each supported at a position of the first annular surface (6) and the second annular surface (7), wherein the location of the through hole (8). is spaced apart.

8. Axial turbine according to claim 6 or 7, wherein the support projections (14, 15) and / or the cylindrical portion (11) of the contact socket (10) are designed slotted.

9. Axial turbine according to claim 1, wherein at the same point each blade (2) on its pressure side a first recess (16) and on its suction side a second recess (17), wherein in the first recess (16) designed as a contact element , a first contact base (18) provided with a receiving trough (22) and a second contact base (19) designed as the contact element, designed as the contact element and provided with a receiving trough (23), and designed as the coupling device Damper rod (20, 21) with its one longitudinal end into the receiving trough (22) of the first contact socket (18) of the one blade (2) and with its other longitudinal end in the receiving trough (23) of the second contact socket (19) of the one blade ( 2) adjacent other airfoil (2) engages.

10. Axial turbine according to claim 9, wherein between the two recesses (16, 17), the blade (2) is designed as a web (24).

11. axial turbine according to claim 10, wherein the web (24) a first support surface (25) on which the first contact socket (18) is supported perpendicular to the pressure side, and one of the first support surface (25) facing away, second support surface (26), on which the second contact socket (19) is supported perpendicular to the suction side.

12. axial turbine according to one of claims 9 to 11, wherein the contact elements (18, 19) in the recesses (16, 17) soldered, latched and / or are screwed.

13. Axial turbine according to one of claims 1 to 12, wherein the blade (2) are made of a light metal.

14. Axial turbine according to one of claims 1 to 13, wherein the contact element (9, 18, 19) is made of a steel.

15. Axial turbine according to claim 14, wherein the steel is hardened.