EP1705339B1 - Rotor shaft, in particular for a gas turbine - Google Patents

Description

TECHNICAL AREA

The present invention relates to the field of rotary machines. It relates to a rotor shaft, in particular for a gas turbine, according to the preamble of claim 1.

STATE OF THE ART

In thermally and mechanically highly loaded machines, such as compressors, gas turbines or steam turbines represent, it is desirable to reduce mechanical stress by a suitable structural design of the individual machine and system parts.

For example, it is known from the prior art (see the EP-A1-0 945 594 or the US B1-6,478,539 ) in the blades of gas turbines to form the transition from the blade to the underlying, subsequent platform of the blade with a predetermined, preferably elliptical curve contour, wherein the major axis is in the radial direction and the small main axis is oriented parallel to the surface of the platform.

Furthermore, it is from the US B1-6,237,558 Known to provide certain, critical with respect to mechanical stress points of the crankcase of an internal combustion engine with a curvature following a conic (ellipse, hyperbola, parabola).

Not only the blades of turbines are exposed to high mechanical loads due to the high rotational speeds, but also the rotor shaft itself. Critical places are mainly on the outer circumference arranged groove in the rotor shaft, extending in the axial direction or annularly rotating, for example, for receiving the blade roots of the blades or may be provided as part of a shaft seal. In such grooves, the stresses occurring in the groove depend significantly on the cross-sectional contour. From the GB-A-2 265 671 or the US-A-4,818,182 annular circumferential grooves for mounting of blades are known which have a rounded cross-sectional contour. Information about the type of curvature or the influence of the contour on the stresses in the groove are not made.

From the DE3047514 For example, a rotor disk with an elliptical cooling air opening arranged in the rotor disk is known. In the thermally particularly stressed part of the rotor, the turbine part, additional cooling measures are often provided in order to achieve a sufficient service life of the material used at the high hot gas temperatures. Such cooling measures include cooling air ducts which extend approximately in the radial direction from the inside to the outside through the rotor shaft and cooling air from an internal cooling air supply to the surface lead the rotor shaft. However, such cooling air ducts represent mechanical weakenings of the rotor shaft, which can have a negative effect on the high temperatures and centrifugal forces and the changing loads.

PRESENTATION OF THE INVENTION

It is an object of the invention to design such a rotor shaft equipped with radial cooling air ducts in such a way that the weakenings of the rotor shaft are minimized or at least significantly reduced by the cooling air ducts.

The object is solved by the entirety of the features of claim 1. An essential point of the present solution is that the cooling air ducts for reducing mechanical stresses have an elliptical cross-section.

The rotor shaft further has a compressor part and a turbine part and the cooling air passages are arranged in the turbine part. In addition, the turbine part has a plurality of rotor disks arranged one behind the other in the axial direction for fastening rotor blades, wherein the cooling air ducts are arranged between adjacent rotor disks. An embodiment of the invention is characterized in that the cooling air ducts are arranged distributed over the circumference of the rotor shaft, and that the elliptical cross section of the cooling air ducts is oriented in each case so that the large main axis in the circumferential direction and the small main axis are aligned in the axial direction.

In particular, it is conceivable that cavities are formed concentrically to the rotor axis in the interior of the rotor shaft, and that the cooling air channels emanate from at least one of the cavities and via this cavity with the Cooling air supply communicate. It is then particularly favorable for the cavities to have at least sections an elliptical cross-sectional contour to reduce mechanical stresses on the outer circumference, wherein the cross-sectional contour is preferably composed on the outer circumference of two elliptical sections of two mutually tilted ellipses whose major axes are oriented approximately in the radial direction are.

BRIEF EXPLANATION OF THE FIGURES

Fig. 1

in einer perspektivischen Seitenansicht eine Rotorwelle (ohne Beschaufelung) mit Kühlluftkanälen im Turbinenteil gemäss einem Ausführungsbeispiel der vorliegenden Erfindung;

Fig. 2

einen Längsschnitt durch die Rotorwelle aus Fig. 1 im Bereich des Turbinenteils;

Fig. 3

den Blick auf einen mit herkömmlichen Kühlluftkanälen ausgestatteten Turbinenteil einer Rotorwelle;

Fig. 4

in einer zu Fig. 3 vergleichbaren Darstellung eine Rotorwelle gemäss einem Ausführungsbeispiel der Erfindung; und

Fig. 5

im Längsschnitt eine Rotorwelle mit innenliegenden Hohlräumen, die gemäss einem anderen Ausführungsbeispiel der Erfindung am äusseren Umfang mit einer abschnittsweise elliptischen Querschnittskontur versehen sind.

The invention will be explained in more detail with reference to embodiments in conjunction with the drawings. Show it

Fig. 1

in a perspective side view of a rotor shaft (without blading) with cooling air ducts in the turbine part according to an embodiment of the present invention;

Fig. 2

a longitudinal section through the rotor shaft Fig. 1 in the area of the turbine part;

Fig. 3

the view of a equipped with conventional cooling air ducts turbine part of a rotor shaft;

Fig. 4

in one too Fig. 3 comparable representation of a rotor shaft according to an embodiment of the invention; and

Fig. 5

in longitudinal section a rotor shaft with internal cavities, which are provided according to another embodiment of the invention on the outer periphery with a sectionally elliptical cross-sectional contour.

WAYS FOR CARRYING OUT THE INVENTION

In Fig. 1 in a perspective side view, a rotor shaft 10 (without blading) reproduced a gas turbine. The to the rotor axis (17 in Fig. 2 The rotationally symmetrical rotor shaft 10 is subdivided into a compressor part 11 and a turbine part 12. Between the two parts 11 and 12, the combustion chamber is arranged inside the gas turbine into which the air compressed in the compressor part 11 is introduced and from which the hot gas through the turbine part 12 flows. The turbine part 12 has a plurality of rotor disks 13 arranged one behind the other in the axial direction, in which Fig. 3, 4 Axially aligned receiving slots 21 are formed around the circumference for receiving corresponding blades. The support of the blade roots in the receiving slots 21 in the usual manner by positive engagement by means of a fir tree-like cross-sectional contour. In the compressor part 11 are according to Fig. 5 circumferential circumferential grooves 18 are provided, in which the blading of the compressor part is fixed.

In the thermally heavily loaded turbine part 12 is distributed over the circumference between adjacent rotor disks a plurality of cooling air channels 14 are provided, which approximately radially outwardly depart from a formed inside the rotor shaft 10 cavity 15 and open at the surface of the rotor shaft 10 in the outer space ( Fig. 2 ). The cavity 15 is in communication with a central, axially extending cooling air supply 16. While in earlier constructions ( Fig. 3 ) the cooling air channels (14 ') had a circular cross section, the cooling air channels 14 in the new configuration of Fig. 4 for reasons of mechanical stability an elliptical cross-section. The elliptical cross section of the cooling air ducts 14 can already be predetermined during the casting of the rotor shaft. However, it is also conceivable to introduce such a cross section into the rotor shaft 10 by special machining methods such as eroding.

As in Fig. 4 is clearly visible, the ellipses of the channel cross-section of the cooling air channels 14 are oriented so that the major major axes are oriented in the circumferential direction, while the small main axes are parallel to the rotor axis 17. As a result, a maximum reduction of the mechanical stresses is achieved. It goes without saying that the advantages of an elliptical cross section are not limited to cooling air channels in the rotor shaft itself, but also apply to cooling air channels, which are arranged on other parts of the rotor such as blades or the like.

The concentric to the rotor axis 17 formed cavity 15 is also optimized in its cross-sectional profile in view of the mechanical stresses occurring. The optimization of the cross-sectional profile takes place in the in Fig. 5 for further cavities 19, 20 in the compressor part 11 illustrated manner such that the edge contour on the outer circumference of the cavity 15, 19, 20 is formed at least partially elliptical. In particular, the cross-sectional contour is at the outer periphery - as for the cavity 20 in Fig. 5 is shown - from two elliptical sections of two mutually tilted ellipses E1, E2 (in Fig. 5 dashed lines drawn together) whose major axes are oriented approximately in the radial direction. Such a shape for the cavities present in the interior of the rotor shaft 10 is advantageous not only in connection with the cooling air channels 14 in the turbine part, but can also be used for other cavities 19, 20 which are located, for example, in the compressor part 11 of the rotor shaft 10.

LIST OF REFERENCE NUMBERS

10

Rotor shaft (gas turbine)

11

compressor part

12

turbine part

13

rotor disc

14, 14 '

Cooling air duct

15

cavity

16

Cooling air supply

17

rotor axis

18

Circumferential groove (circumferential)

19.20

cavity

21

Receiving slot (axial)

E1, E2

ellipse

Claims (5)

1. Rotor shaft (10), in particular for a gas turbine, in which cooling air channels (14) are provided which run substantially in a radial direction from inside to outside and are connected to a cooling air supply (16) present inside the rotor shaft (10), wherein the cooling air channels (14) have an elliptical cross-section to reduce mechanical stresses, and the rotor shaft (10) comprises a compressor part (11) and a turbine part (12), and the cooling air channels (14) are arranged in the turbine part (12), characterised in that the turbine part (12) comprises a plurality of rotor discs (13) arranged behind each other in the axial direction for fixing of rotor vanes, and that the cooling air channels (14) are arranged between adjacent rotor discs (13).
2. Rotor shaft according to claim 1, characterised in that the cooling air channels (14) are distributed over the circumference of the rotor shaft (10), and that the elliptical cross-section of the cooling channels (14) is oriented in each case such that the long main axis is oriented in the circumferential direction and the small main axis in the axial direction.
3. Rotor shaft according to one of claims 1 and 2, characterised in that cavities (15, 19, 20) are formed inside the rotor shaft (10) concentrically to the rotor axis (17), and that the cooling air channels (14) start from at least one of the cavities (15, 19, 20) and are connected to the cooling air supply (16) via said cavity (15).
4. Rotor shaft according to claim 3, characterised in that to reduce mechanical stresses on the outer periphery, the cavities (15, 19, 20) at least in portions have an elliptical cross-section contour (E1, E2).
5. Rotor shaft according to claim 4, characterised in that on the outer periphery, the cross-section contour is composed of two elliptical portions of two ellipses (E1, E2) tilted relative to each other, the long main axes of which are oriented approximately in the radial direction.

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