EP2045444B1 - Rotor blade, method for producing a rotor blade, and compressor with such a rotor blade - Google Patents

Description

TECHNICAL AREA

The present invention relates to the field of turbomachinery. It relates to a rotor of a turbomachine according to the preamble of claim 1, a method for producing a rotor, and a compressor with such a rotor.

STATE OF THE ART

The buckets of a compressor are part of an axial compressor system that moves and compresses large quantities of air needed for the proper and safe operation of a gas turbine system. The blades are on the outer circumference of the rotor of the Compressor mounted and are exposed to a variety of mechanical loads, which are particularly based on the type of blade attachment.

In order to safely avoid the systematically disassembling a blade from the rotor, various systems for mounting the blades to the rotor have been developed and proposed in the past. One of these systems to which the present invention relates is the fastening system with a T-shaped blade root and spacers as shown in FIGS Fig. 1 and 2 or in Fig. 6 simplified in the cutout is reproduced, and that for a long time, for example, from the document DE-PS-318 662 is known.

In this system, in one around the rotor axis (A2 in Fig. 5 ) of the rotor 10 circumferential groove 11 in the circumferential direction one behind the other intermediate pieces 12, 18 and held by means resting against undercuts 24 holding surfaces 20 in the groove 11. Between two adjacent intermediate pieces 12, 18, a rotor blade 13 or 27 is respectively arranged, which comprises an airfoil 14 and with a downwardly adjoining the airfoil 14 T-shaped blade root 15 and 25 (see Fig. 6 ) abuts the side surfaces of the adjacent intermediate pieces 12, 18 and engages with circumferentially protruding projections 16, 16 'and 26, 26' under the adjacent intermediate pieces 12, 18. The intermediate pieces 12, 18 and the blades 13 and 27 are arranged obliquely to the rotor axis A2 standing, so that the blade axis (A1 in Fig. 5 ) with the rotor axis A2 an angle of for example 25 ° includes (see Fig. 5 ).

Heretofore, the T-shaped blade roots 25 of the compressor blades 27 have been forged (forged) by upset forging so as to obtain a strength-determining grain structure as shown in FIG Fig. 6 is indicated by the dashed lines. Recently, due to new requirements in terms of costs, tools and logistics increasingly The idea was not to forge the blade roots, but to make them by milling (grain structure in Fig. 4 ). In order to achieve the same or better strength in the milled blade feet at the critical transitions to the projections 16, 16 'and 26, 26', as in the forged blade roots, a larger radius must be provided at the transitions. In the case of the forged blade roots 25, the forging radius 29 is approximately in the range between 0.5 and 1.0 mm (FIG. Fig. 6 ). Due to the notch factor, milled blade feet at the transitions require a radius that is about 1.5 to 2 times greater than the forging radius 29.

The previous forging method for the blade roots 25 had further consequences: bulging 31 causes bulges 31 on the shaft above the projections 26, 26 '(in FIG Fig. 6 this is indicated by the dotted lines), which are in the range of 0.3 to 0.5 mm. To ensure that the forged blade feet 25 still rest securely and immovably on the adjacent intermediate pieces 12, 18 despite the lateral bulges 31, they are provided on the side faces in the lower part with a long bevel 17, 19, the space for the bulges 31 creates (see also Fig. 3 ).

Although there is already a depending on the blade size, 0.3 to 0.5 mm wide gap between the adjacent intermediate pieces 12, 18 and the T-shaped blade root 25, would increase the radius in the corners of the projections 26, 26 'to the Factor 1.5 to 2 - which is necessary for milled blade feet - cause an unwanted and dangerous collision at the exact point where the reduction of mechanical stresses should actually be the goal.

On the other hand, it is possible for mechanical stresses in areas of machine parts in which, on the one hand, the risk of cracks is great, on the other hand, however, the space for attaching larger radii is limited to reduce the fact that suitably dimensioned and placed undercuts are provided in accordance with the ISO standard.

The publication JP-2005 220825 discloses a blade (for a steam turbine) having a foot with a T-shaped cross-sectional profile. The blade is inserted with the foot in a circumferential groove in the rotor so that the projections of the foot protrude in the axial direction. The geometry (orientation of the foot relative to the airfoil) is thus different than in the rotor of the present invention.

The publication DE 10 2005 048883 A1 cites a prior art in which the T-shaped foot of the blade is oriented with the laterally projecting protrusions in the axial direction. It is therefore the same as in the previous document.

The publication DE 437 049 C does not go beyond the ones already discussed above in Revelation DE-318 662 out.

The publication EP 1 698 758 A2 discloses simple upsetting blades, as they should not be used according to the present invention straight.

PRESENTATION OF THE INVENTION

It is an object of the invention to design a rotor of the type mentioned so that it is cheaper to produce and nevertheless reaches the usual forged blade roots life, and to provide a method for its preparation.

The object is solved by the entirety of the features of claims 1 and 7. Essential to the invention is that the T-shaped blade root of the blade is milled that to reduce the mechanical stresses on the transitions of the blade root to the projections in each case an extending in the axial direction undercut is provided, and that the undercut follows in the direction of the blade axis an elliptical curve.

The inventive compressor has a rotor which is equipped with blades according to the invention.

Basically, the undercut can be a standard undercut to ISO standard. In particular, the undercut is then an undercut type E or F according to DIN standard 509.

Particularly advantageous with regard to the reduction of the mechanical stresses is when the spacers each have a chamfer at their adjoining the blade root side surfaces, and the undercut has a deviating from a standard undercut to ISO standard, increased height, which the bevel exploits. In particular, the height of the undercut can correspond approximately to the height of the bevel.

Preferably, the undercut has a radius that is 1.5-2 times the radius of a comparable upset formed blade root. In particular, the radius is 1.5 mm with a compression radius of 0.8, or 1.75 mm with a compression radius of 1.0.

A preferred embodiment of the method according to the invention is characterized in that for milling the undercuts a deviating from the spherical shape milling tool is used.

BRIEF EXPLANATION OF THE FIGURES

Fig. 1

in Umfangsrichtung gesehen die der Erfindung zugrunde liegende Befestigungsart der Laufschaufeln mit T-förmigem Schaufelfuss zwischen zwei Zwischenstücken:

Fig. 2

die Befestigungsart der Fig. 1 in perspektivischer Darstellung;

Fig. 3

die Ausgestaltung des Schaufelfusses gemäss einem Ausführungsbeispiel der Erfindung;

Fig. 4

die Bearbeitung des Freistichs am Schaufelfuss mit einem grösseren Fräswerkzeug gemäss einem Ausführungsbeispiel der Erfindung;

Fig. 4a

die Bearbeitung des Freistichs am Schaufelfuss mit einem kleineren Fräswerkzeug mit Kugelkopf;

Fig. 5

einen Schaufelfuss gemäss einem Ausführungsbeispiel der Erfindung in perspektivischer Darstellung mit einem eingezeichneten elliptischen Bearbeitungspfad; und

Fig. 6

den in herkömmlicher Weise durch Stauchschmieden hergestellten T-förmigen Schaufelfuss.

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

Fig. 1

Seen in the circumferential direction, the invention underlying the mounting of the blades with T-shaped blade root between two intermediate pieces:

Fig. 2

the attachment of the Fig. 1 in perspective view;

Fig. 3

the embodiment of the blade root according to an embodiment of the invention;

Fig. 4

the machining of the undercut on the blade root with a larger milling tool according to an embodiment of the invention;

Fig. 4a

the machining of the undercut on the blade root with a smaller milling tool with ball head;

Fig. 5

a blade root according to an embodiment of the invention in perspective view with an indicated elliptical processing path; and

Fig. 6

the T-shaped blade root produced in a conventional manner by upset forging.

WAYS FOR CARRYING OUT THE INVENTION

It is essential for the present invention that the increased radius required for the milled blade root is produced by an undercut, which is preferably realized taking into account the lateral bevels formed on the intermediate pieces. As undercuts are first undercuts according to ISO standard in question, which are listed under the DIN standard 509 as undercuts form E and F. The undercut of type E only cuts into one of the two adjoining surfaces that are perpendicular to each other, while the undercut of type F cuts into both surfaces. Both undercut types have special outlet areas (32, 33 in Fig. 3 ), which serve the additional stress relief in the radius.

With such undercuts is achieved that with unchanged overall arrangement and mounting of the blades without problems, the blades with forged blade root can be replaced by the cheaper blades with milled blade root without losses in the Lifetime must be accepted. In particular, the adjacent intermediate pieces 12, 18 need not be changed or additionally processed. The contact surface between the blade root (15 in Fig. 3 ) and the adjacent intermediate pieces 12 and 18 is limited by the chamfers 17 and 19 on the side surfaces of the intermediate pieces 12, 18, but also determined, so that the type of undercut 21 within the region of the chamfers 17, 19 has no influence on the contact surface ( Fig. 3 ). Accordingly, the blades are always held in the same way between the intermediate pieces 12, 18, regardless of whether the blade root is forged ( Fig. 6 ) or milled ( Fig. 4 ). It also follows that the natural frequencies (resonances) of the blades do not change, so that there is complete interchangeability between the differently manufactured blades.

A standard undercut type F cuts - as already mentioned above - in both adjacent vertical surfaces in the corners of the projections 16, 16 'of the blade root 15 ( Fig. 4a ). This is the only way to achieve the increased radius for the desired equal or longer life over forged blade roots. However, such a standard F-cut can only be produced by means of a milling process if the undercut is simultaneously moved in the direction of the blade axis A1 along an elliptical processing path (23 in FIG Fig. 5 ). The undercut, however, can only be milled with a great deal of effort, since this is what the in Fig. 4a shown small milling tool 28 with a spherical milling head (head diameter (2 x radius R2): 2-3 mm, shank diameter: 1.5-2 mm) must be used.

It is therefore at the blade root 15 preferably in Fig. 3 . 4 and 5 shown modified undercut 21 used, which is characterized by an increased height h in the direction of the longitudinal axis of the blade. In particular, the height h of the undercut 21 may correspond to the entire length of the chamfer 17, 19 on the side surfaces of the intermediate pieces 12, 18. The increase in the height h compared to the standard undercut 30 makes it possible, according to Fig. 4 to use a larger milling tool 22 with a radius R1> R2 (R1 is eg 1.75 mm), which significantly reduces costs and processing times (dashed hatch in Fig. 4 indicates that the blade root 15 is milled and not forged).

The described increase in the height h of the undercut is not only allowed (because there is no contact between the blade root 15 and the intermediate pieces 12, 18 anyway due to the long bevel 17, 19), but also desirable because the stresses in the notch are thereby automatically reduced ,

LIST OF REFERENCE NUMBERS

10

rotor

11

groove

12.18

connecting piece

13.27

blade

14

airfoil

15.25

blade root

16.16 '

head Start

17.19

bevel

20

holding surface

21.30

Freeway

22.28

milling tool

23

elliptical machining path

24

undercut

26.26 '

head Start

29

wrought radius

31

bulge

32.33

discharge area

A1

blade axis

A2

rotor axis

H

Height (undercut)

R1, R2

Radius (undercut)

Claims (9)

1. Rotor (10) of a turbomachine, especially of a compressor of a gas turbine, comprising a slot (11) which is arranged on the outer periphery of the rotor 10 and encompasses a rotor axis (A2), and at least one rotor blade (13), which rotor blade (13) comprises a blade airfoil (14) and a blade root (15) which adjoins the lower end of the blade airfoil (14) and extends along a blade axis (A1), lying obliquely to the rotor axis (A2), and by which the rotor blade (13), in the slot (11), is retained between two spacers (12, 18) which follow each other in the circumferential direction and which in their turn are retained in the slot (11), wherein the blade root (15), due to shoulders (16, 16') which extend in the circumferential direction, is formed with a T-shape in cross section and by the shoulders (16, 16') fits under the adjacent spacers (12, 18), and the spacers (12, 18), in the direction of the blade axis (A1), engage by retaining surfaces (20) in undercuts (24) in the slot (11), characterized in that the T-shaped blade root (15) is milled, in that for reducing the mechanical stresses at the transitions of the blade root (15) to the shoulders (16, 16') a relief groove (21, 30), which extends in the direction of the blade axis (A1), is provided in each case, and in that the relief groove (21, 30) follows an elliptical curve shape (23) in the direction of the blade axis (A1).
2. Rotor according to Claim 1, characterized in that the relief groove (30) is a standard relief groove according to ISO standard.
3. Rotor according to Claim 2, characterized in that the relief groove (30) is a relief groove of type E or F according to DIN standard 509.
4. Rotor according to Claim 1, characterized in that the spacers (12, 18) have a chamfer (17, 19) in each case on their side surfaces which are adjacent to the blade root (15), and in that the relief groove (21) has an increased height (h) which deviates from a standard relief groove according to ISO standard.
5. Rotor according to Claim 4, characterized in that the height (h) of the relief groove (21) corresponds approximately to the height of the chamfer (17, 19).
6. Rotor according to either of Claims 4 or 5, characterized in that the relief groove (21) has a radius (R1) which corresponds to 1.5 - 2 times the radius of a comparable blade root which is formed by means of upset forging.
7. Method for producing a rotor according to one of Claims 1 to 6, characterized in that, in the production of the at least one rotor blade (13), in a first step the T-shape of the blade root (15) is created by means of a milling process, in that in a second step the relief grooves (21, 30) are milled into the blade root (15), and in that the relief grooves (21, 30) are milled along an elliptical machining path (23) in the direction of the blade axis (A1).
8. Method according to Claim 7, characterized in that for milling the relief grooves (21) a milling tool (22) which deviates from the spherical shape is used.
9. Compressor, especially for a gas turbine, characterized in that it has a rotor (10) according to one of Claims 1 to 6.

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