Turbine blade

Abstract

A turbine vane for a rotary turbomachine has a turbine blade delimited by a concave pressure-side wall and a convex suction-side wall which are connected in the region of a vane front edge which can be assigned to the turbine blade and enclose a cavity which extends in the longitudinal extent of the vane front edge and is delimited on the inner wall by the pressure-side wall and the suction-side wall in the region of the vane front edge and by an intermediate wall which extends in the longitudinal direction to the vane front edge and connects the suction-side wall and the pressure-side wall on the inner wall. The intermediate wall has a perforation at least in sections in the connecting region to the suction-side wall and/or pressure-side wall, in order to increase the elasticity of the intermediate wall.

Claims

1. A turbine blade for a rotating turbomachine, comprising: a blade airfoil including a concave pressure side wall and a convex suction side wall connected in a region of a leading edge of the blade airfoil; and a cavity extending in a longitudinal direction of the blade and delimited by the pressure side wall and suction side wall in the region of the leading edge and by an intermediate wall extending in the longitudinal direction of the blade and connecting the suction side wall and pressure side wall internally, wherein the intermediate wall having, at least in sections, a perforation wherein at least one of a connection of the intermediate wall to the suction side wall and a connection of the intermediate wall to the pressure side wall comprises a fillet and each perforation runs at least in part therethrough for increasing an elasticity of the intermediate wall in the connection region, wherein the intermediate wall has, extending from the suction side wall to the pressure side wall or vice versa, at least one curved wall section which deviates from a straight wall profile and the at least one curved wall section is configured to have a curvature-induced elasticity in a direction of the extent of the intermediate wall from the suction side wall to the pressure side wall or vice versa, the at least one curved wall section is V-shaped or U-shaped as seen in a cross section cutting through the leading edge, and a convex wall side of the at least one V-shaped or U-shaped wall section is formed and arranged substantially parallel to the suction side wall and pressure side wall which are connected at the blade leading edge and which bound the cavity.

2. The turbine blade as claimed in claim 1, wherein each perforation comprises a row of cylindrical holes.

3. The turbine blade as claimed in claim 1, wherein each perforation comprises a row of longitudinal holes or slits, a longer side of which extends parallel to the adjacent suction side wall and/or pressure side wall.

4. The turbine blade as claimed in claim 1, wherein the intermediate wall has a wall side which faces away from the cavity and which, together with the suction side wall and the pressure side wall, delimits at least one further cavity, and in that the cavities are cooling ducts into which a coolant can be introduced.

5. The turbine blade as claimed in claim 4, wherein openings of each perforation are created parallel to an internal surface of the suction side wall or, respectively, an internal surface of the pressure side wall in each connection region of the intermediate wall and, in operation, cooling air flows through these openings from the cavity into the at least one further cavity and an outlet jet of the respective opening runs tangentially to the internal surface of the respective suction side wall or, respectively, pressure side wall.

6. The turbine blade as claimed in claim 1, wherein at a base of the V-shaped or U-shaped cross section of the intermediate wall there is, at least in sections, a second perforation which runs parallel to each perforation in each connection region in order to increase elasticity.

7. The turbine blade as claimed in claim 1, wherein throughflow ducts are provided in the intermediate wall for impingement cooling of the suction side wall and pressure side wall which are connected at the leading edge.

8. The turbine blade as claimed in claim 1, wherein the turbine blade is a guide blade or a rotor blade of a turbine stage of a gas turbine arrangement.

9. The turbine blade as claimed in claim 1, wherein in a perforated region a hole length of an perforations represents at least 30% of the overall length of the perforated region.

10. A turbine blade for a rotating turbomachine, comprising: a blade airfoil including a concave pressure side wall and a convex suction side wall connected in a region of a leading edge of the blade airfoil; and a cavity extending in a longitudinal direction of the blade and delimited by the pressure side wall and suction side wall in the region of the leading edge and by an intermediate wall extending in the longitudinal direction of the blade and connecting the suction side wall and pressure side wall internally, wherein the intermediate wall having, at least in sections, a perforation wherein at least one of a connection of the intermediate wall to the suction side wall and a connection of the intermediate wall to the pressure side wall comprises a fillet and each perforation runs at least in part therethrough for increasing an elasticity of the intermediate wall in the connection region, wherein the intermediate wall has, extending from the suction side wall to the pressure side wall or vice versa, at least one curved wall section which deviates from a straight wall profile and the at least one curved wall section is configured to have a curvature-induced elasticity in a direction of the extent of the intermediate wall from the suction side wall to the pressure side wall or vice versa, throughflow ducts are provided in the intermediate wall for impingement cooling of the suction side wall and pressure side wall which are connected at the blade leading edge, and the throughflow ducts arranged in the intermediate wall are split into at least three groups with respect to their throughflow direction which is predetermined by a throughflow duct longitudinal extent which can be assigned to the throughflow ducts, wherein a first group of throughflow ducts having a throughflow direction is oriented toward the suction side wall, a second group of throughflow ducts having a throughflow direction is oriented toward the blade leading edge and a third group of throughflow ducts having a throughflow direction is oriented toward the pressure side wall.

11. The turbine blade as claimed in claim 10, wherein each perforation comprises a row of cylindrical holes.

12. The turbine blade as claimed in claim 10, wherein each perforation comprises a row of longitudinal holes or slits, a longer side of which extends parallel to the adjacent suction side wall and/or pressure side wall.

13. The turbine blade as claimed in claim 10, wherein the intermediate wall has a wall side which faces away from the cavity and which, together with the suction side wall and the pressure side wall, delimits at least one further cavity, and in that the cavities are cooling ducts into which a coolant can be introduced.

14. The turbine blade as claimed in claim 13, wherein openings of each perforation are created parallel to an internal surface of the suction side wall or, respectively, an internal surface of the pressure side wall in each connection region of the intermediate wall and, in operation, cooling air flows through these openings from the cavity into the at least one further cavity and an outlet jet of the respective opening runs tangentially to the internal surface of the respective suction side wall or, respectively, pressure side wall.

15. The turbine blade as claimed in claim 10, wherein the at least one curved wall section is V-shaped or U-shaped as seen in a cross section cutting through the leading edge.

16. The turbine blade as claimed in claim 10, wherein at a base of the V-shaped or U-shaped cross section of the intermediate wall there is, at least in sections, a second perforation which runs parallel to each perforation in each connection region in order to increase elasticity.

17. The turbine blade as claimed in claim 10, wherein the at least one curved wall section is V-shaped or U-shaped as seen in a cross section cutting through the leading edge, and wherein a convex wall side of the at least one V-shaped or U-shaped wall section is formed and arranged substantially parallel to the suction side wall and pressure side wall which are connected at the blade leading edge and which bound the cavity.

18. The turbine blade as claimed in claim 10, wherein the turbine blade is a guide blade or a rotor blade of a turbine stage of a gas turbine arrangement.

19. The turbine blade as claimed in claim 10, wherein in a perforated region a hole length of the perforations represents at least 30% of an overall length of the perforated region.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred embodiments of the disclosure will be described below with reference to the drawings which serve purely for illustrative purposes and are not to be interpreted as limiting, and in which:

(2) FIG. 1 is an illustration of the schematic arrangement of turbine guide blades and turbine rotor blades within a turbine stage,

(3) FIG. 2 shows a representative profile through a turbine blade and

(4) FIGS. 3a, b, c show alternative variants for forming a perforation in an intermediate wall in the region of the blade leading edge,

(5) FIG. 4a-d show alternative variants for forming an intermediate wall in the region of the blade leading edge.

DETAILED DESCRIPTION

(6) FIG. 1 shows, in a schematic representation, a guide blade 2 and a rotor blade 3 as they are arranged in a turbine stage (not illustrated in more detail) along a guide blade row and rotor blade row. It should be assumed that the guide blade 2 and the rotor blade 3 come into contact with a hot gas stream H which, in the illustration, flows from left to right over the respective blade airfoils 4 of the guide blade 2 and the rotor blade 3. The blade airfoils 4 of the guide blade 2 and rotor blade 3 project into the hot gas duct of the turbine stage 1 of a gas turbine arrangement, which hot gas duct is respectively bounded by radially inner shrouds 2i, 3i and by the radially outer shrouds 2a of the guide blades 2 and radially outer heat accumulation segments 3a. The rotor blade 3 is mounted on a rotor unit R (not shown in more detail) which is mounted such that it is able to rotate about an axis of rotation A.

(7) FIG. 2 shows a cross-sectional representation through a guide blade or rotor blade which results along a plane of section A-A shown in FIG. 1. The typical blade profile of a turbine guide blade or turbine rotor blade is distinguished by an aerodynamically profiled blade airfoil 4 which is delimited on its two sides by a convex suction side wall 7 and by a concave pressure side wall 6. The convex suction side wall 7 and the concave pressure side wall 6 unite in one piece in the region of the blade leading edge 5 which, as already explained in the introduction, is directly exposed to the hot gas stream passing through the turbine stage of a gas turbine arrangement. It is obvious that the turbine blade region along the blade leading edge 5 experiences a particularly high thermal load.

(8) In order to cool the turbine blade exposed to the hot gases, radially oriented cavities 9, 10, 11 etc., which are flooded with cooling air, are provided within the blade airfoil 4. The individual cavities 9, 10, 11 etc. are separated from one another by intermediate walls 8, 12, 13 etc. Depending on the form and configuration of the turbine blade, the individual cooling ducts 9, 10, 11 etc. communicate with one another.

(9) In order to solve the problem, noted in the introduction, of fatigue-induced crack formation in the suction side wall 7 and pressure side wall 6 close to the blade leading edge 5, the foremost intermediate wall 8 in the connection region to the suction side wall 7 and/or pressure side wall 6 is provided, at least in sections, with a perforation 16. Exemplary embodiments of perforations 16 are shown in FIGS. 3a, b and c.

(10) A first exemplary embodiment is shown in FIG. 3a. One perforation 16 is provided in each connection region of the intermediate wall 8 to the suction side wall 7 and pressure side wall 6. The perforations of the example shown are a row of cylindrical holes 18 which are arranged parallel to the suction side wall 7 and pressure side wall 6. In the example, the perforation 16 at the pressure side wall 6 runs only over a section of the intermediate wall 8.

(11) A second exemplary embodiment is shown in FIG. 3b. One perforation 16 is provided in each connection region of the intermediate wall 8 to the suction side wall 7 and pressure side wall 6. The perforations of this example are a row of longitudinal holes 19 which are arranged parallel to the suction side wall 7 and pressure side wall 6 and whose longer side extends parallel to the respective adjacent suction side wall 7 or pressure side wall 6.

(12) In the third exemplary embodiment of FIG. 3c, in addition to the perforation 16 of the example shown in FIG. 3b, a central perforation 20 is also provided, which runs parallel to the suction side wall 7 and pressure side wall 6 in the center of the intermediate wall 8. Together with the perforations 16 in the connection region to the suction side wall 7 and pressure side wall 6, this forms an intermediate wall 8 which is divided in two and can be flexibly folded together.

(13) In order to better illustrate the intermediate wall configuration, reference is made to the exemplary embodiment illustrated in detail in FIG. 4a, which shows the blade profile in the blade leading edge region. FIG. 4a shows a perforation 16 in the connection region of the suction side wall 7 and in the connection region of the pressure side wall 6. In the example, the principal direction of the tendency of the material of the side walls 6, 7 to expand or contract runs substantially parallel to the extent of the intermediate wall 8.

(14) In contrast to a straight configuration, as is the case in FIGS. 1, 2, 3 and 4a with the intermediate walls 8, 12, 13, FIG. 4b shows an exemplary embodiment with a curved intermediate wall 8. The intermediate wall 8 has a U-shaped wall cross section which is integrally connected internally on both sides both to the suction side wall 7 and to the pressure side wall 6. The U-shaped wall configuration of the intermediate wall 8 lends the blade profile region an additional elastic deformability such that it is possible to yield to the thermally induced tendency of the material of the suction side wall and pressure side wall to expand or contract, in that the wall distance W is not fixed as hitherto but is variable within certain limits which are determined by the shape and curvature elasticity of the intermediate wall 8 and the elasticity of the perforation 16.

(15) FIG. 4c shows, in detail, an exemplary embodiment having an additional central perforation 20. This divides the intermediate wall 8 into two legs which, proceeding from the connection region to the side walls 6, 7, run at an angle toward each other, it being possible for the angle to be flexibly changed by means of the central perforation 20, making it easy to compensate for expansion-induced changes in the separation between the pressure side wall and suction side wall.

(16) Further, FIG. 4c shows an example for a possible film cooling arrangement. Cooling air leaves the cavity 9 via the film cooling holes 14 and forms a film of cooling air on, respectively, the surface of the suction side outer wall 6 and pressure side outer wall 7. The U-shaped intermediate wall 8, which is integrally connected on its two sides with the internal wall of the suction side wall 7 and pressure side wall 6, preferably has a wall profile on the convex side which faces the blade leading edge 5 and is formed substantially parallel to the suction side wall 7 and pressure side wall 6 which bound the cavity 9 and are integrally connected at the blade leading edge 5. In this example, the cooling air enters the forward cavity 9 at least partially through the perforations 16 and central perforation 20.

(17) A further exemplary embodiment having details for the cooling is shown in FIG. 4d. Here, the intermediate wall has perforations 16 at the connection regions to the suction side wall 7 and pressure side wall 6. It also has, next to the perforation, cooling air throughflow ducts 15a, b, c which serve for the impingement cooling of the internal wall side 17 of the blade wall leading edge. Particularly advantageously, the throughflow ducts 15a, b, c can be split into at least three groups depending on their throughflow duct longitudinal extent and the throughflow direction which is predetermined thereby.

(18) A first group of throughflow ducts 15a is distinguished by a throughflow direction which is oriented toward the suction side wall 7, a second group of throughflow ducts 15b is distinguished by a throughflow direction which is oriented toward the blade leading edge and a third group of throughflow ducts 15c is distinguished by a throughflow direction which is oriented toward the pressure side wall 6. The throughflow ducts 15a, 15b and 15c are distributed along the entire radial extent in the intermediate wall 8 and thus provide effective and individual cooling of the blade leading edge region of the turbine blade. Further throughflow ducts may of course be created in the intermediate wall 8 for the purpose of an optimized impingement cooling.

(19) Furthermore, the impingement air cooling may be combined with a central perforation. Impingement air cooling air holes typically have a larger diameter than the perforation holes, for example twice as large.