Blade airfoil for an internally cooled turbine rotor blade, and method for producing the same

Abstract

A blade airfoil for an internally cooled turbine rotor blade has suction-side and pressure-side side walls, which, extending from a common leading edge to a common trailing edge and in a span direction from a root-side end to a tip-side end, at least partially enclose a cavity. The tip-side end includes a tip wall which delimits the cavity at the tip side. At least one cooling hole for the discharge of cooling fluid that can be caused to flow in the interior is provided. In the cavity, at least one rib which extends from the tip wall in the direction of the root-side end projects from the inner surface, surrounding the rib, of the suction-side side wall and/or from the inner surface of the pressure-side side wall. An inflow-side end, in relation to the cooling fluid, of the at least one cooling hole opens out laterally in the respective rib.

Claims

1. A blade airfoil for an internally cooled turbine rotor blade, comprising: a suction-side side wall and a pressure-side side wall, which, extending from a leading edge to a trailing edge and in a span direction from a root-side end to a tip-side end, at least partially enclose a cavity, wherein the tip-side end comprises a tip wall which delimits the cavity at the tip-side end, and at least one cooling hole adapted for discharge of cooling fluid that can be caused to flow in the interior, wherein, in the cavity, at least one rib which extends from the tip wall in a direction of the root-side end projects from an inner surface of the suction-side side wall or from an inner surface of the pressure-side side wall, wherein an inflow opening of the at least one cooling hole opens out laterally in the respective rib, wherein the at least one cooling hole comprises a channel axis which, at least in a region of the inflow opening of the at least one cooling hole, is inclined relative to a longitudinal extent of the at least one rib, wherein the respective rib is, from its tip-side end to its root side end, inclined in a direction of the leading edge or in a direction of the trailing edge, wherein the tip wall comprises at least one sealing tip on its outwardly pointing surface, and wherein the at least one cooling hole extends through the tip wall and the at least one sealing tip into the at least one rib.

2. The blade airfoil as claimed in claim 1, wherein the inflow opening comprises an elliptical shape comprising a relatively short axis and a relatively long axis, wherein the relatively short axis is shorter than a diameter of the at least one cooling hole.

3. The blade airfoil as claimed in claim 1, wherein the respective rib comprises, in a cross-sectional plane normal with respect to the span direction, a curved contour comprising a maximum rib height in relation to a rest of the inner surface, and the inflow opening of the respective cooling hole is arranged laterally with respect to a location of the maximum rib height.

4. The blade airfoil as claimed in claim 1, wherein the respective rib comprises, in a cross-sectional plane normal with respect to the span direction, a polygonal contour comprising a maximum rib height in relation to a rest of the inner surface, and the inflow opening of the respective cooling hole is arranged on a laterally arranged surface of the rib.

5. The blade airfoil as claimed in claim 1, wherein the cavity adjacent to the respective rib is such that a major supply of coolant to said cavity is arranged on that side of the respective rib which is averted from that surface of the rib which comprises the inflow opening of the at least one cooling hole.

6. A turbine rotor blade comprising: a blade airfoil as claimed in claim 1.

7. A method for producing a blade airfoil as claimed in claim 1, the method comprising: boring the at least one cooling hole such that the inflow opening opens out in one of the respective ribs.

8. The method of claim 7, further comprising casting the blade airfoil before boring the at least one cooling hole.

9. The method of claim 7, wherein the blade airfoil comprises multiple ribs.

10. The blade airfoil as claimed in claim 1, further comprising: multiple cooling holes.

11. The blade airfoil as claimed in claim 1, further comprising: multiple ribs.

12. The blade airfoil as claimed in claim 1, wherein the respective cooling hole extends through an entirety of the sealing tip.

13. A blade airfoil for an internally cooled turbine rotor blade, comprising: a suction-side side wall and a pressure-side side wall, which, extending from a leading edge to a trailing edge and in a span direction from a root-side end to a tip-side end, at least partially enclose a cavity, wherein the tip-side end comprises a tip wall which delimits the cavity at the tip-side end and which comprises sealing tip on an outwardly pointing surface of the tip wall, and a cooling hole adapted for discharge of cooling fluid that can be caused to flow in the interior, wherein, in the cavity, a rib extends from the tip wall in a direction of the root-side end farther than the rib projects from an inner surface of the suction-side side wall or from an inner surface of the pressure-side side wall, wherein an inflow opening of the cooling hole opens out laterally in the rib, and wherein the cooling hole extends through the tip wall and extends through the sealing tip into the rib.

14. The blade airfoil as claimed in claim 13, wherein the cooling hole extends through an uppermost surface of the sealing tip.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Here, the figures are illustrated merely schematically, and thus in particular do not give rise to any restriction of the practicability of the invention.

(2) In the figures:

(3) FIG. 1 shows a turbine rotor blade in a perspective schematic illustration,

(4) FIG. 2 shows the longitudinal section through the blade airfoil of the turbine rotor blade as per FIG. 1 as a first exemplary embodiment,

(5) FIG. 3 shows the side view of an inner surface of a side wall of the blade airfoil as per the view III-III,

(6) FIG. 4 shows the cross section as per the section line IV-IV through the blade airfoil as per FIG. 2, and

(7) FIG. 5 shows an alternative exemplary embodiment of a rib-cooling hole pairing according to the invention in a side view.

DETAILED DESCRIPTION OF INVENTION

(8) Below, identical technical features are denoted by the same reference designations in all of the figures. Furthermore, features of different exemplary embodiments may be combined with one another in any desired manner.

(9) FIG. 1 shows a turbine blade 10 in a perspective illustration. The turbine blade 10 is, as per FIG. 1, designed as a rotor blade. It comprises a fir-tree-shaped blade root 12 and a platform 14 arranged thereon. The platform 14 is then adjoined by a blade airfoil 16, which is aerodynamically curved. It is not of importance for the invention whether or not the blade airfoil 16 is covered by a thermal protective layer. The blade airfoil 16 comprises a suction side wall 22 and a pressure side wall 24. In relation to a hot gas flowing around the blade airfoil 16, said walls extend from a leading edge 18 to a trailing edge 20. Along the trailing edge 20 there are provided a multiplicity of openings 28 for the discharge of coolant, which openings are separated from one another by interposed webs 30. The blade airfoil 16 extends along a span direction, which coincides with a radial direction of a turbine, from a root-side end 26 to a tip-side end 27. The latter is also known as blade tip. When the turbine blade 10 shown is used in a gas turbine through which flow passes axially, the span direction coincides with the radial direction R of the gas turbine.

(10) FIG. 2 shows a sectional illustration through the blade airfoil 16 as per the section line II-II as a first exemplary embodiment of a blade airfoil 16 according to the invention. FIG. 2 illustrates only the radially outer end of the blade airfoil 16 in relation to the span or radial direction R of the gas turbine, that is to say the blade airfoil tip. Installed in a gas turbine, the blade airfoil 1 extends in the radial direction R. Further axes of the gas turbine are denoted by A and U, wherein A stands for axial direction and U represents the circumferential direction. Below, these will be used where required for the purposes of more easily describing the arrangement.

(11) The blade airfoil 16 has, on the tip-side end 27, a tip wall 34 which delimits a cavity 32 to the outside. The tip wall 34 is substantially at right angles to the suction-side side wall 22 and transitions into the latter. In the transition region, a rib 38 is arranged on an inner surface 40, pointing toward the cavity 32, of the suction-side side wall 22. The rib 38 extends rectilinearly from its end 46 arranged at the tip side to its end 44 arranged at the root side.

(12) A further rib 39, which runs in an axial direction, is provided so as to be adjacent to and spaced apart from the rib 38 in a radially inward direction, in order to divert particles in the case of a possible radially occurring cooling flow.

(13) On the radially outwardly pointing surface 52 of the tip wall 34, there is also arranged a sealing tip 48, which is part of said tip wall. Such sealing tips, also referred to in English as squealer tips, are normally realized as radial elongations of the side walls 22, 24 of the turbine rotor blade 10. They serve for reducing a gap between the blade tip and the hot-gas path delimitation, situated opposite said blade tip, of the gas turbine. The sealing tips 48 may be arranged without a step in relation to the outer side surfaces of the suction-side side wall 22 or pressure-side side wall 24, as shown.

(14) In the exemplary embodiment illustrated in FIG. 2, a cooling hole 36 extends through the tip wall 34 together with sealing tip 48 into the rib 38. The cooling hole 36 has an inflow opening 42 for a cooling fluid. A cooling fluid that can be supplied to the cavity 32 can flow into said opening 42, flow along the cooling hole 36, and emerge at the outer end. During this time, the cooling fluid cools the local region of the suction-side side wall 22, of the tip wall 34 and in particular the sealing tip 48. It is self-evident that several of the pairs of cooling holes 36 and ribs 38 as shown and described in more detail further below may be provided at the blade tip of a turbine blade 10. This is the case in particular if the sealing tip 48 extends along the entire boundary of the blade airfoil 16.

(15) The cooling hole 36 need not imperatively extend through the sealing tip 48. In an alternative embodiment, the cooling hole 36 may also end laterally with respect to the sealing tip 48. It may for example end on the hot gas side or in the tip clearance 39.

(16) FIG. 3 shows the plan view of the interior of the blade tip as per the section line III-III from FIG. 2. On the basis of the reference to the different directions in the installed blade airfoil 16 in a gas turbine, it can be seen that the rib 38 is designed to be inclined relative to the radial direction. The rib 38 as per the exemplary embodiment shown here extends rectilinearly from its tip-side end 46 to its root-side end 44. At the same time, the cooling hole 36, which extends through the sealing tip 48 and the tip wall 34 into the rib 38 is oriented parallel to the radial direction R, but here is inclined in the circumferential direction (FIG. 2). The depicted orientations of the cooling hole 36 and of the rib 37 are not imperatively necessary, but rather are in each case dependent on the orientation of the aerodynamically curved blade airfoil in space, on the one hand, and the location of the cooling hole, on the other hand. Advantageously, a channel axis 37 of the cooling hole 36 in the region of the inflow opening 42 is inclined at an obtuse angle relative to the longitudinal extent of the rib 38. To achieve this, it is for example possible for the cooling hole 36, and likewise the rib 38, to be inclined in the circumferential direction U and/or in the axial direction A. A cooling hole 36 inclined in the axial direction is illustrated as a second exemplary embodiment in FIG. 5, and opens out in the rib 38, which is designed to be curved in the radial direction. Furthermore, FIG. 5 shows, in addition to the features already described, an elliptical inflow opening 42, the relatively short axis 54 of which is shorter than the diameter of the rest of the cooling hole 36, which is of circular cross section.

(17) FIG. 4 shows the section through the blade-tip-side end 27 of the blade airfoil 16 as per the section line IV-IV from FIG. 2. In the exemplary embodiment shown, on the suction side, two ribs 38 according to the invention are provided, of which the first projects in asymmetrically curved form from the inner surface 40 of the suction-side side wall 22. By contrast, the second of the two ribs 38 according to the invention is of triangular shape in this cross-sectional view, which cross-sectional plane lies normally with respect to the radial direction R. It is not necessary for the rib to protrude from the inner surface in the manner of turbulators or the like; the transition from inner surface 40 to the side surface of the rib 38 may also, in particular on the incident-flow side thereof, be of stepless form and thus exhibit low aerodynamic losses.

(18) The cooling holes 36 open out in one of the side surfaces of the ribs 38. The position of the opening 42 is, according to the invention, in that side surface of the rib 38 which is arranged beyond a maximum rib height H. The rib height H is in relation to the rest of the inner surface 40 of the suction-side wall 22.

(19) During operation, a cooling fluid, advantageously cooling air, is supplied in the interior of the blade airfoil 16 of the internally cooled turbine rotor blade 10. The cavity 32 is accordingly flowed through by the cooling fluid, and the cooling fluid has a predefined main flow direction 50 owing to the topology of the cavity 32 and the position of a cooling air supply and the position of adjoining outflow channels. Said main flow direction is to be determined in the immediate vicinity of the rib 38 according to the invention. Since the cooling fluid can never be entirely free from dirt particles, it is advantageous if the inflow opening 42 of the cooling hole 36 is arranged on that side of the respective rib 38 which is averted from the cooling fluid flowing toward the respective rib. The inflow opening 42 of the cooling hole 36 is situated, as it were, more in the wind shadowin the leeof the maximum rib height H. Owing to the shape of the rib 38, particles entrained by the cooling fluid are diverted into a flow path in which, with increasing distance covered, said particles move progressively further away from the inner surfaces of the side walls 22, 24, to the point of the maximum rib height H. Subsequently, owing to their inertia and the flow direction pointing away from the inflow opening 42, said particles pass by the inflow opening; said particles can flow into the cooling hole 36 only under adverse conditions. This has the result that air with fewer particlesin relation to the prior artflows into the cooling holes 36, and thus the risk of blockage is reduced. This permits the use of cooling holes 36 with a particularly small diameter, for example even smaller than one millimeter, with a reduced risk of blockage of the inflow openings 42 or of the cooling holes 36 by entrained particles.

(20) Owing to the curved contour of the rib 38 and of the orientations, inclined either in the circumferential direction U and/or in the axial direction A relative to the radial direction R, of the, in principle, rectilinear cooling holes 36, the inflow opening 42 of the cooling holes 36 that open out in the rib 38 is not circular but rather is inclined in elliptical fashion, with a relatively long axis and a relatively short axis. This alone would make it more difficult, in the case of cooling air flowing in alignment with the rectilinear cooling hole 36, for particles to flow into the respective cooling hole 36.

(21) The cooling hole 36 may be produced retroactively, after the casting of the turbine blade 10, by boring. The orientation of the rib 38 inclined in relation to the radial direction R is particularly advantageous. For example in the case of a rectilinear cooling hole 36 bored in the radial direction R, the inclined rib 38 (FIG. 3) offers the advantage that the cooling hole 36 can be located in a relatively large axial section AB. As long as the cooling hole 36 is located in the section AB, it has an elliptically shaped inflow opening 42 which is always arranged in the lee on the side situated downstream of the incoming cooling fluid. This improves the producibility of a turbine blade 10 of said type, because the section AB in which the cooling hole is to be bored is relatively large, and thus easier to arrive at.

(22) Altogether, with the invention, a blade airfoil 16 for an internally cooled turbine rotor blade 10 is provided, comprising a suction-side side wall 22 and a pressure-side side wall 24, which, extending from a common leading edge 18 to a common trailing edge 20 and in a span direction from a root-side end 26 to a tip-side end 27, at least partially enclose a cavity, wherein the tip-side end 27 comprises a tip wall 34 which delimits the cavity 32 at the tip side and in which at least one cooling hole 36, advantageously multiple cooling holes 36, for the discharge of cooling fluid that can be caused to flow in the interior is or are provided. To provide a turbine blade in the case of which the risk of blockages of cooling holes is reduced and thus the service life of the turbine blade 10 can be lengthened, it is proposed that, in the cavity 32, at least one rib which extends from the tip wall 34 in the direction of the root-side end 42, advantageously multiple such ribs 38, projects from the inner surface 40, surrounding said rib, of the suction-side side wall 22 and/or from the inner surface 40 of the pressure-side side wall 24, and that an inflow opening 42, in relation to the cooling fluid, of the at least one cooling hole 36 opens out laterally in the respective rib 38.