Turbine blade having a shroud and a cutting tooth

Abstract

A turbine blade (100) having an airfoil (1). In its radially outer region, the turbine blade (100) has at least one shroud (200) or at least one shroud segment, as well as at least one cutting tooth (300) which is intended to engage at least once into portions of a turbine casing during use of the turbine blade (100). The cutting tooth (300) is connected to the shroud (200) or the shroud segment.

Claims

1. A turbine blade comprising: an airfoil; at least one shroud or shroud segment in a radially outer region; and at least one cutting tooth for engaging at least once into at least one abradable coating of a turbine casing during operation of the turbine blade, the cutting tooth connected to the shroud or the shroud segment; wherein the cutting tooth is a portion of the airfoil.

2. The turbine blade as recited in claim 1 wherein the cutting tooth is integral with the shroud or of the shroud segment.

3. The turbine blade as recited in claim 1 wherein the cutting tooth is a stiffening element for the shroud or the shroud segment.

4. The turbine blade as recited in claim 1 wherein at least one portion of the shroud is extended beyond a shroud cutback.

5. The turbine blade as recited in claim 4 wherein the portion of the shroud extended beyond the shroud cutback is inclined at least 10 degrees relative to a longitudinal blade axis against a main direction of flow of the turbine blade.

6. The turbine blade as recited in claim 1 wherein the shroud has a leading sealing lip and a trailing sealing lip, the leading and trailing sealing lips extending radially beyond a top surface of the shroud, and wherein the leading sealing lip is longer than the trailing sealing lip.

7. The turbine blade as recited in claim 1 wherein the shroud has a leading sealing lip and a trailing sealing lip, the leading and trailing sealing lips extending radially beyond a top surface of the shroud, and wherein the shroud, with the leading and trailing sealing lips, has the shape of a trapezoid or rectangular trapezoid in a cross-sectional plane through the turbine blade perpendicular to the shroud top surface and extending in the axial direction of the turbine blade.

8. A turbine blade comprising: an airfoil; at least one shroud or shroud segment in a radially outer region; and at least one cutting tooth for engaging at least once into at least one abradable coating of a turbine casing during operation of the turbine blade, the cutting tooth connected to the shroud or the shroud segment; the airfoil having a curved extension extending along a front side of the shroud or shoud segment, the cutting tooth being a portion of the extension.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which identical or similar components are indicated by the same reference numerals. The figures are, in part, greatly simplified views, of which:

(2) FIG. 1a is a schematic simplified perspective view of a turbine blade according to the present invention having a shroud and a cutting tooth;

(3) FIG. 1b is an enlarged view of a detail of FIG. 1, showing the radial end portion of the turbine blade according to the present invention;

(4) FIG. 2 is a side view showing the shroud with the cutting tooth;

(5) FIG. 3 is a further side view showing the shroud of FIG. 2 with the cutting tooth;

(6) FIG. 4 is a cross-sectional view through the shroud shown in FIG. 1b.

DETAILED DESCRIPTION

(7) FIG. 1a depicts, in a simplified schematic perspective view, a turbine blade 100 according to the present invention, including a shroud 200, a cutting tooth 300, an airfoil 1 and a main direction of flow incidence 3 extending in the x-direction.

(8) Shroud 200 is located at the radial end of airfoil 1.

(9) The entire turbine blade 100 including shroud 200, cutting tooth 300, and a blade root 400 may be manufactured as a casting.

(10) FIG. 1b is a detail of FIG. 1a, showing an enlarged view of the radial end portion of the turbine blade 100 according to the present invention, including shroud 200 and cutting tooth 300.

(11) Shroud 200 has a top surface 5, which is bounded by a sealing lip 7a located upstream (with respect to the main direction of flow; i.e., in the x-direction) and a downstream trailing sealing lip 7b. Sealing lips 7a, 7b are intended to prevent the medium passing through from flowing past the radially outer edge of turbine blade 100 between the turbine blade and the turbine casing, but rather to cause it to flow against airfoil 1, thereby contributing to the transfer of energy by turbine blade 100.

(12) FIG. 2 shows shroud 200 including leading sealing lip 7a and trailing sealing lip 7b, cutting tooth 300, as well as a portion of airfoil 1. FIG. 2 is a side view. In certain embodiments of the present invention, the cutting tooth is intended to cut into a portion of the turbine casing lining 101, shown schematically.

(13) Airfoil 1 is connected to cutting tooth 300 by an airfoil extension 9. Hence, cutting tooth 300 may be referred to as a portion or integral portion of airfoil 1.

(14) Furthermore, both cutting tooth 300 and airfoil 1 are also connected by airfoil extension 9 to shroud 200 via leading sealing lip 7a, which is a portion of shroud 200. The unit including cutting tooth 300, blade portion 9, and leading sealing lip 7a may be configured as an integral portion of turbine blade 100.

(15) FIG. 3 shows shroud 200 including leading sealing lip 7a, cutting tooth 300, as well as a portion of airfoil 1. FIG. 3 shows a detail from FIG. 2 in a further view.

(16) In FIG. 3, a shroud cutback 11 is shown as the distance between leading edge 13 of the base area of shroud 200 and the leading end of airfoil 1 (located upstream with respect to the main direction of flow in the x-direction). In accordance with the present invention, leading sealing lip 7a is inclined or tilted forwardly (i.e., against the x-direction), in the embodiment shown in FIG. 3, for example, by an angle of inclination 15 of about 33 degrees. Moreover, in accordance with the present invention, leading sealing lip 7a is not only inclined forwardly, but also extends beyond shroud cutback 11. In FIG. 3, this extent beyond shroud cutback 11 is illustrated by distance 17.

(17) The extent of leading sealing lip 7a beyond shroud cutback 11, together with the integration or merging of airfoil 1 with cutting tooth 300 via airfoil extension 9, provides an advantageous structural design, for example, in terms of stiffness. Airfoil extension 9 may also be understood to be a supporting rib under leading sealing lip 7a of shroud 200.

(18) FIG. 4 shows a cross section through the shroud 200 of turbine blade 100 shown in FIG. 1b. Leading sealing lip 7a and trailing sealing lip 7b of shroud 200 both extend radially beyond top surface 5 of shroud 200. In a cross-sectional plane which corresponds to the plane of the drawing of FIG. 4 and which is perpendicular to shroud top surface 5 and extends in the axial direction of turbine blade 100, shroud top surface 5 and the leading and trailing sealing lips 7a, 7b together form the shape of a trapezoid or of a rectangular trapezoid, as shown in FIG. 4.

(19) TABLE-US-00001 List of Reference Numerals Reference Numeral Description 100 turbine blade 101 turbine casing lining 200 Shroud 300 cutting tooth 400 blade root 1 Airfoil 3 main direction of flow incidence 5 shroud top surface 7a leading sealing lip 7b trailing sealing lip 9 airfoil extension 11 shroud cutback 13 outer edge of the base area of the shroud 14 leading end of the airfoil 15 inclination angle 17 distance; extent beyond the shroud cutback