Cooled airfoil, guide vane, and method for manufacturing the airfoil and guide vane

Abstract

Disclosed is a cooled airfoil having a hub end and tip, an airfoil height being defined between the hub end and the tip. The airfoil has a leading edge, trailing edge, suction side and pressure side. The airfoil has a first airfoil height section adjacent the hub end and extending towards the tip, wherein, in a meridional view, the leading edge and trailing edge are straight along the first airfoil height section. The airfoil has a second airfoil height section adjacent the tip and extending towards the hub end, wherein, in a meridional view, the airfoil is concavely shaped at the leading edge and is convexly shaped at the trailing edge along the second airfoil height section. At least one cooling channel has a length principally extending along the airfoil height, extends straight in a first cooling channel length section, and is bent in a second cooling channel length section.

Claims

1. A method for manufacturing an airfoil, the method comprising: providing a mold, the mold being provided to generate the outer surface shape at least of the airfoil in a casting process; providing at least one core, the core being provided to generate at least one internal cooling channel in the airfoil in the casting process; each of the mold and the core containing a hub end and a tip end, and an airfoil length extending between the hub end and the tip end; each of a cavity of the mold, and the core, containing a straight section provided adjacent the respective hub end and a bent section provided adjacent the respective tip end; placing the core inside the mold cavity; placing the core bent section inside the mold cavity bent section; placing the core straight section inside the mold cavity straight section; wherein the core is attached to the mold in a fixed bearing relationship at the core tip end; and wherein the core is attached to the mold in a floating bearing relationship at the core hub end such that the core hub end will displace relative to the mold along a lengthwise direction of the core straight section and is fixed relative to the mold in any direction across the lengthwise direction of the core straight section.

2. The method according to claim 1, comprising: manufacturing a vane with the airfoil.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The subject matter of the present disclosure is now to be explained in more detail by means of selected exemplary embodiments shown in the accompanying drawings. The figures show

(2) FIG. 1 a meridional view of a part of a hot gas path of an expansion turbine;

(3) FIG. 2 a cut through a cooled guide vane;

(4) FIG. 3 a diagram depicting the leading edge and trailing edge geometry in an axial direction; and

(5) FIG. 4 a schematic depiction of a casting process, or a mold for a casting process, respectively, as herein described.

(6) It is understood that the drawings are highly schematic, and details not required for instruction purposes may have been omitted for the ease of understanding and depiction. It is further understood that the drawings show only selected, illustrative embodiments, and embodiments not shown may still be well within the scope of the herein claimed subject matter.

EXEMPLARY MODES OF CARRYING OUT THE TEACHING OF THE PRESENT DISCLOSURE

(7) FIG. 1 shows a schematic view of some blades and vanes arranged in a part of the expansion turbine 1 of a gas turbine engine in a longitudinal cut, that is, in a meridional view. Gas turbine engine 1 comprises housing 2, or stator, respectively, and rotor shaft 3. Rotating turbine blades 5 and 7 are fixedly attached to the rotor shaft 3. A flow of hot working fluid flows through the turbine in a principal direction depicted at 4, and is expanded, while performing useful work at the rotating blades 5 and 7. Upstream of each blade, a stationary guide vane is provided, which directs the working fluid flow to the rotating blades with a circumferential velocity component. Shown in this embodiment is guide vane 6, which acts as a guide vane for blade 7. Guide vane 6 comprises an airfoil 61, which comprises a hub end or radially inner end 8, and a tip or radially outer end 9. A radial direction is shown at R. Hub end 8 faces the rotor shaft 3, while tip end 9 faces the housing 2. The guide vane 6 is fixedly attached to the housing 2. The working fluid flow channel in which the blades and vanes are arranged is strongly divergent. The flow thus also is not only axially oriented, as implied at 4, but also has a radial component, in particular at the radially outer side of the flow channel. In order to improve aerodynamics of the guide vane 6, the airfoil 61 is bent, such that, generally spoken, the airfoil in the meridional view is concave at the leading edge LE, and is convex at the trailing edge TE. The curvature is in particular chosen such that the leading edge LE at the airfoil hub end forms an angle a with a radially inner wall of the working fluid flow channel, and forms at the airfoil tip an angle c with a radially outer wall of the working fluid flow channel. Likewise, the geometry of the airfoil 61 at the trailing edge TE is chosen such that at the airfoil hub end forms an angle b with the radially inner wall of the flow channel, and forms at its tip an angle d with a radially outer wall of the flow channel. The radially inner wall of the flow channel may be provided by the rotor shaft 3, or by a hot gas side of a hub platform of the vane. The radially outer wall of the flow channel may be provided by the hot gas side of a vane tip platform. The angles a, b, c and d are 90°±15°. Vane 6 and the geometry of the airfoil 61 will be lined out in more detail below.

(8) FIG. 2 depicts a cut through an exemplary guide vane 6 in a meridional view. The vane 6 comprises an airfoil 61, wherein said airfoil comprises a hub end 8 and a tip 9. By virtue of the intended arrangement in the gas turbine engine, the hub end 8 may also be referred to as a radially inner end, and the tip 9 may be referred to as a radially outer end. The airfoil extends along a height h from the hub end 8 to the tip 9. A tip platform 62 is arranged at the tip of the airfoil 61. The tip platform 62 comprises a hot gas side 621. Furthermore, means 63 are arranged at the tip platform for fixedly attaching the guide vane to the turbine housing. At the hub end 8, vane hub platform 64 is provided. The vane hub platform comprises a hot gas side 641. The leading edge LE is straight at least in a first section H1 of the airfoil 61 extending from the hub end 8 and towards the tip 9. The leading edge LE is, in the meridional view, concavely bend in a second region H2 of the airfoil, starting from the tip 9 and extending towards the hub end 8. Likewise, the trailing edge TE is, in the meridional view, straight at least in the first section H1 of the airfoil 61, and is convexly bend in the second section of the airfoil adjacent the airfoil tip 9. A transitional section of the airfoil 61 may be interposed between the first section H1 and the second section H2. Moreover, cooling channels 65, 66 and 67 are provided in the airfoil 61, and extend along the height h of the airfoil 61 between the tip 9 and the hub end 8. The cooling channels 65, 66, 67 are arranged in series, and, in combination, form an airfoil internal coolant duct. Coolant 11 is received by a leading edge cooling channel 65 which is open towards the housing and is in fluid communication with a gas turbine cooling system, and is guided through leading edge cooling channel 65, through cooling channel 66, and finally into trailing edge cooling channel 67. From the trailing edge cooling channel 67, the coolant is discharged as a coolant discharge flow 12 through trailing edge cooling slots 68, and cooling holes 69. The coolant channels 65, 66, and 67 generally follow the geometry of the airfoil 61 in the meridional view, that is, the cooling channels run straight in the first section of the airfoil, and are bent in a second section of the airfoil, whereas walls delimiting the cooling channels are convexly shaped on a leading edge side of the cooling channels, and are concavely shaped on a trailing edge side of the cooling channels.

(9) With reference to FIG. 3, an exemplary geometry of the leading edge LE and the trailing edge TE is shown in an axial view of the guide vane, that is, along a gas turbine rotor axis. The leading edge and the trailing edge generally extend between the hub end 8 and the tip 9. Said radial direction R is also depicted at H, pointing towards the hub, and T, pointing towards the tip. The airfoil generally also comprises a pressure side PS and a suction side SS. The leading edge and the trailing edge extend straight, starting at the hub end 8, and in a first section H1, and are bent in the second section of the airfoil H2. The trailing edge TE is bent such that it is concave on the pressure side of the airfoil, while the leading edge LE is bent such that it is concave on the suction side of the airfoil.

(10) As is apparent, the airfoil is straight along its radial extent, or height extent, in a first airfoil section H1 starting at the hub end 8 in a meridional view as well as in an axial view.

(11) A method for manufacturing an airfoil, or vane, respectively, as described above by casting with high precision of the wall thickness is now lined out in relation with FIG. 4. A ceramic mold 21 is provided and is shaped such that the outer geometry of the airfoil may be manufactured by casting. A mold cavity 21a is provided inside the mold 21 as a space intended to receive molten material during the casting process, and is delimited by walls of the mold. The walls define the outer geometry of the member to be manufactured by casting. A core 22 is provided for manufacturing a cooling channel. Both, the mold cavity 21a and the core 22, are bent adjacent a tip end 91, and are straight adjacent a hub end 81. The core 22 is supported in a fixed bearing relationship at 23, adjacent the bent core section. It is furthermore supported in a floating bearing relationship at 24, adjacent the straight core section. Thus, during the casting process, the core 22 may displace inside the mold cavity 21a along the arrow depicted at 25 in response to differential thermal expansion. Said displacement, however, takes place along a lengthwise direction of the core 22, and thus the manufactured wall thickness of the airfoil is not impacted. Thermal expansion in the bent core section is restricted to a short level of expansion, and thus the influence of core displacement on the manufactured wall thickness is largely restricted. This allows the airfoil, or vane, respectively as disclosed above to be manufactured with highly precise thickness of the airfoil walls around the cooling channels.

(12) Summarizing, the geometry of the airfoil is chosen such that an aerodynamic efficiency gain is achieved while at the same time it may be manufactured applying a method allowing for high precision casting of the wall thickness, which in turn enable highly efficient use of the coolant provided to cool the airfoil.

(13) While the subject matter of the disclosure has been explained by means of exemplary embodiments, it is understood that these are in no way intended to limit the scope of the claimed invention. It will be appreciated that the claims cover embodiments not explicitly shown or disclosed herein, and embodiments deviating from those disclosed in the exemplary modes of carrying out the teaching of the present disclosure will still be covered by the claims.

LIST OF REFERENCE NUMERALS

(14) 1 turbine

(15) 2 housing, stator

(16) 3 rotor shaft

(17) 4 main working fluid flow direction

(18) 5 running blade, rotating blade

(19) 6 guide vane

(20) 7 running blade, rotating blade

(21) 8 hub end

(22) 9 tip

(23) 11 coolant supply flow

(24) 12 coolant discharge flow

(25) 21 ceramic mold

(26) 21a mold cavity

(27) 22 core

(28) 23 fixed bearing

(29) 24 floating bearing

(30) 25 thermal displacement direction

(31) 61 airfoil

(32) 62 vane tip platform

(33) 63 vane attachment means

(34) 64 vane hub platform

(35) 65 cooling channel

(36) 66 cooling channel

(37) 67 cooling channel

(38) 68 trailing edge coolant discharge slots

(39) 69 coolant discharge openings, cooling holes

(40) 81 hub end of mold

(41) 91 tip end of mold

(42) 621 vane tip platform hot gas side

(43) 641 vane hub platform hot gas side

(44) a angle

(45) b angle

(46) c angle

(47) d angle

(48) h airfoil height

(49) H hub

(50) T tip

(51) LE leading edge

(52) TE trailing edge

(53) PS pressure side

(54) SS suction side

(55) H1 first airfoil section, airfoil hub section

(56) H2 second airfoil section, airfoil tip section

(57) R radial direction