METHOD FOR MACHINING A BLADE AND A BLADE FOR A TURBOMACHINE

Abstract

The invention refers to a method for machining a blade and a blade for a turbomachine comprising a shroud which is positioned on a tip side of the blade. The shroud has an outer surface with at least one circumferential fin arranged thereon, whereby at least one section of the outer surface beside the at least one fin is processed in at least two manufacturing steps. At least one first section of the outer surface is processed to have a first shape and at least one second section of the outer surface is processed to have a second shape.

Claims

1. A method for machining a blade for a turbomachine comprising a shroud which is positioned on a tip side of the blade having an outer surface with at least one circumferential fin arranged thereon, whereby at least one section of the outer surface beside the at least one fin is processed, comprising the manufacturing steps of: machining the outer surface along a first machining path; and machining the outer surface along a second machining path which is different to the first machining path.

2. The method for machining a blade for a turbomachine according to claim 1, wherein the first machining path or the second machining path runs circumferentially around a machining axis along a circular arc of a circle with a center on the rotation axis of the turbomachine.

3. The method for machining a blade for a turbomachine according to claim 2, wherein the machining axis corresponds to the rotation axis of the turbomachine.

4. The method for machining a blade for a turbomachine according to claim 1, wherein the first machining path and/or the second machining path is a linear machining path.

5. The method for machining a blade for a turbomachine according to claim 4, wherein the first machining path and/or the second machining path is running along or inclined to a plane arranged perpendicular to a center line of the blade.

6. The method for machining a blade for a turbomachine according to claim 5, wherein the inclination of the first machining path and/or the second machining path to the plane is between 0.1° and 6°.

7. The method for machining a blade for a turbomachine according to claim 1, wherein the first machining path and/or the second machining path is a freeform path.

8. The method for machining a blade for a turbomachine according to claim 1, wherein the machining area transverse to the first machining path and/or to the second machining path is inclined with regard to the axial direction of the rotation axis.

9. The method for machining a blade for a turbomachine according to claim 1, wherein the machining process along the first and/or second machining path is grinding.

10. A blade for a turbomachine, comprising a shroud which is positioned on a tip side of the blade having an outer surface with at least one circumferential fin arranged thereon, whereby at least one area of the outer surface beside the least one fin is machined such that at least one first section of the outer surface has a first shape and such that at least one second section of the outer surface has a second shape that is different to the shape of the first section.

11. The blade for a turbomachine according to claim 10, wherein the first section and or the second section has a cylindrical shape.

12. The blade for a turbomachine according to claim 11, wherein, in a circumferential direction section of the outer shroud having a cylindrical shape has an essentially constant wall thickness and the section of the outer shroud having a different than a cylindrical shape has different wall thicknesses.

13. The blade for a turbomachine according to claim 10, wherein the outer shroud comprises at least one recess, wherein at least two sections and/or ribs adjacent to the at least one recess have different wall thicknesses.

14. The blade for a turbomachine according to claim 10, wherein the shroud is positioned on a tip side of the blade having an outer surface with at least one circumferential fin arranged thereon, whereby at least one section of the outer surface beside the at least one fin is processed, comprising the manufacturing steps of: machining the outer surface along a first machining path; and machining the outer surface along a second machining path which is different to the first machining path.

15. The blade for a turbomachine according to claim 10, wherein the blade is configured and arranged in a turbomachine.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0036] Further advantages, features and possible applications of the present invention will be described in the accompanying drawing figures in which:

[0037] FIG. 1 is a schematic representation of an exemplary blade for a turbomachine having a shroud positioned on the tip side;

[0038] FIG. 2a is a top view on the surface of the shroud of the exemplary blade shown in FIG. 1;

[0039] FIG. 2b is a sectional view of the shroud of FIG. 2a along the intersection line B-B; and

[0040] FIG. 2c is a further sectional view of the shroud of FIG. 2a along the intersection line B-B having a different second machining path.

DESCRIPTION OF THE INVENTION

[0041] FIG. 1 shows a schematic representation of an exemplary blade 10 for a turbomachine having a shroud 12 positioned on the tip side of the blade 10. The shroud 12 comprises an outer surface 14 with two circumferential fins 16 arranged thereon. On the opposite side of the blade tip, where the shroud 12 is positioned, the blade root 18 is arranged. Between the blade root 18 and the shroud 12, the airfoil 17 of the blade 10 is arranged. In the exemplary embodiment of the blade 10, at least one area of the outer surface 14 of the shroud 12 beside the two fins 16 is processed in at least two manufacturing steps. FIG. 1 also shows the position of the rotation axis A of the turbomachine, where the radial distance of the rotation axis from the blade 10 is broken as in fact the radial distance is clearly larger than shown in FIG. 1.

[0042] FIG. 2a shows a top view on the outer surface 14 of the shroud 12 of the exemplary blade 10 shown in FIG. 1 which outer surface 14 is processed in at least two manufacturing steps beside the two fins 16. The arrow U indicates the circumferential direction of rotation. At the right hand side in FIG. 2a, the suction side of the blade 10 and shroud 12, respectively, is arranged and at the left hand side the pressure side is arranged. The outer shroud 12 comprises several recesses 30 in form of pockets and several reinforcement ribs 26, 27, 28, 29 adjacent to and also between the recesses 30. FIG. 2a also shows areas 20 in which possible hardfacing elements can be arranged in some embodiments.

[0043] As indicated by different hatchings, there are two differently machined sections 23, 24 arranged on the outer shroud 12: In the exemplary embodiment, one area of the outer surface 14 beside the fins 16 is machined such that at least one first section 23 of the outer surface 14 has a cylindrical shape and such that at least one second section 24 of the outer surface 14 has a shape that is different to the first section 23. In an embodiment of the invention, this is achieved by machining the outer surface 14 along a first machining path 33 running circumferentially around a machining axis C (see FIG. 2b). For example, axis C can correspond to the rotation axis A of the turbomachine. In a second manufacturing step, the outer surface 14 is machined along a second machining path 34 which is different to the first machining path 33. As is apparent in FIG. 2a, the machining area transverse to the second machining path 24 is inclined with regard to the axial direction of the rotation axis.

[0044] FIG. 2b shows a sectional view of the shroud 12 of FIG. 2a along the intersection line B-B, shown in FIG. 2a. FIG. 2b illustrates the shroud 12 at the sectional line B-B after the machining operation along the first machining path 33 in dashed lines and the shroud 12 at the sectional line B-B after the machining operation along the second machining path 34 in solid lines.

[0045] As can be seen in FIG. 2b, the first machining path 33 is a circumferential path and the second machining path 34 is a linear machining path, which is inclined with respect to a plane 32 arranged perpendicular to a center line D of the blade 10. For example, the inclination α can range from 0.1° to 6°. In FIG. 2b, for better understanding an inclination having a larger angle α than 6° is shown. The machining process used for manufacturing the exemplary embodiment of the blade 10 along the first machining path 33 and the second machining path 34 is grinding.

[0046] As is illustrated in FIG. 2b, after the machining step along the first machining path 33, the outer surface 14 of the outer shroud 12 has—beside the recesses 30—an essentially constant wall thickness t.sub.1. After machining along the second machining path 34, the outer surface 14 in the second section 24 of the outer shroud 12 has different wall thicknesses t.sub.2, t.sub.3 and t.sub.4. In the exemplary embodiment, reinforcement rib 27 has a wall thickness t.sub.2, reinforcement rib 28 has a wall thickness t.sub.3 and reinforcement rib 29 has a wall thickness t.sub.4, wherein the wall thickness t.sub.3 of reinforcement rib 28 is smaller than the wall thicknesses t.sub.2 and t.sub.4. As the rib bending moment of resistance is W.sub.b=b/6*t.sup.2, the wall thickness t of the rib determines the strength of the rib. For weight reduction, material is removed from the reinforcement ribs with less strength requirements. In the exemplary embodiment of the blade 10, more than two sections 23, 24 and/or reinforcement ribs 26, 27, 28, 29 adjacent to the recesses 30 have different wall thicknesses t.sub.2 to t.sub.4.

[0047] FIG. 2c shows a further sectional view of the shroud 12 of FIG. 2a along the intersection line B-B, shown in FIG. 2a having a different second machining path. FIG. 2c illustrates the shroud 12 at the sectional line B-B after the first machining operation along the first linear machining path 33 and after the machining operation along the second also linear machining path 34.

[0048] As can be seen in FIG. 2c, the first machining path 33 and the second machining path 34 are linear machining paths, which are inclined with respect to the plane 32 arranged perpendicular to a center line D of the blade 10. The inclination α1 of the first machining path 33 is arranged in opposite direction of the inclination α2 of the second machining path 34. In FIG. 2c the inclinations are shown having an angle α1, α2 of more than 6°. Also the machining process used for manufacturing the exemplary embodiment of the blade 10 of FIG. 2c is grinding.

[0049] It would be appreciated by those skilled in the art that various changes and modifications can be made to the illustrated embodiments without departing from the spirit of the present invention. All such modifications and changes are intended to be covered by the appended claims.