TURBINE AIRFOIL COOLING SYSTEM WITH NONLINEAR TRAILING EDGE EXIT SLOTS
A cooling system for a turbine airfoil of a turbine engine having a trailing edge cooling channel formed from a central trailing edge cooling channel and at least one trailing edge exit slot with a nonlinear longitudinal axis is disclosed. The trailing edge exit slot may be defined by ribs having wavy side edges that form a jagged edge As such, the nonlinear longitudinal axis of the trailing edge exit slot reduces the effective flow area, generates impingement and turbulence to increase heat transfer and provides sufficient mechanical strength for better casting yield without overflowing for better performance The nonlinear trailing edge exit slot may be formed using a ceramic core and investment casting.
This invention is directed generally to turbine airfoils, and more particularly to trailing edge cooling systems in hollow turbine airfoils
BACKGROUNDTypically, gas turbine engines include a compressor for compressing air, a combustor for mixing the compressed air with fuel and igniting the mixture, and a turbine blade assembly for producing power. Combustors often operate at high temperatures that may exceed 2,500 degrees Fahrenheit. Typical turbine combustor configurations expose turbine blade assemblies to these high temperatures As a result, turbine blades must be made of materials capable of withstanding such high temperatures In addition, turbine blades often contain cooling systems for prolonging the life of the blades and reducing the likelihood of failure as a result of excessive temperatures.
Typically, turbine blades are formed from a root portion having a platform at one end and an elongated portion forming a blade that extends outwardly from the platform coupled to the root portion The blade is ordinarily composed of a tip opposite the root section, a leading edge, and a trailing edge The inner aspects of most turbine blades typically contain an intricate maze of cooling channels forming a cooling system The cooling channels in a blade receive air from the compressor of the turbine engine and pass the air through the blade. The cooling channels often include multiple flow paths that are designed to maintain all aspects of the turbine blade at a relatively uniform temperature However, centrifugal forces and air flow at boundary layers often prevent some areas of the turbine blade from being adequately cooled, which results in the formation of localized hot spots Localized hot spots, depending on their location, can reduce the useful life of a turbine blade and can damage a turbine blade to an extent necessitating replacement of the blade.
Typically, the trailing edge of turbine airfoils develop hot spots Trailing edges are thus often designed to be thin and include cooling channels that exhaust cooling fluids from the pressure side of the trailing edge. Often times, the trailing edge exhaust channels are formed via machining, which adds expense to the manufacturing process. Thus, a need exists for a more cost effective cooling system capable of providing sufficient cooling to trailing edge of turbine airfoils.
SUMMARY OF THE INVENTIONA cooling system for a turbine airfoil of a turbine engine having a trailing edge cooling channel formed from a central trailing edge cooling channel and at least one trailing edge exit slot with a nonlinear longitudinal axis is disclosed The trailing edge exit slot may be defined by ribs having wavy side edges that form a jagged edge. As such, the nonlinear longitudinal axis of the trailing edge exit slot reduces the effective flow area, generates impingement and turbulence to increase heat transfer and provides sufficient mechanical strength for better casting yield without overflowing for better performance. The nonlinear trailing edge exit slot may be formed using a ceramic core and investment casting.
The turbine airfoil may be formed from a generally elongated, hollow airfoil formed by an outer wall and having a leading edge, a trailing edge, a tip section at a first end, a root coupled to the airfoil at an end generally opposite the first end for supporting the airfoil and for coupling the airfoil to a disc, and a cooling system formed from at least one cavity in the elongated, hollow airfoil positioned in internal aspects of the generally elongated, hollow airfoil The cooling system may include at least one trailing edge cooling channel positioned within the generally elongated, hollow airfoil and proximate to the trailing edge, wherein the at least one trailing edge cooling channel comprises a central trailing edge cooling channel extending spanwise within the generally elongated, hollow airfoil and at least one trailing edge exit slot extending from the central trailing edge cooling channel to the trailing edge The trailing edge exit slot may have a nonlinear longitudinal axis with a plurality of turns In particular, the trailing edge exit slot may include a first linear line extending between a first ridge and a second ridge on a first side of the at least one trailing edge exit slot that is separated laterally from a second linear line extending between a first ridge and a second ridge on a second side of the at least one trailing edge slot on an opposite side from the first side A lateral distance between the first and second linear line may be more than one half of a distance from a first ridge on the first linear side and a valley opposite the first ridge on the second side. The first side of the trailing edge exit slot may be formed from at least two ridges and at least two valleys and the second side of the at least one trailing edge exit slot may be formed from at least one ridge and at least two valleys. The ridge on the second side may be aligned with a valley on the first side positioned between two ridges.
In at least one embodiment, the trailing edge exit slot extending from the central trailing edge cooling channel to the trailing edge may be formed from a plurality of trailing edge exit slots extending from the central trailing edge cooling channel to the trailing edge, wherein adjacent trailing edge exit slots are separated from each other by a trailing edge rib extend from the suction side to the pressure side. The trailing edge rib may include a pointed leading edge formed by two linear edges that intersect at a tip of the trailing edge rib. The tip of the trailing edge rib may be rounded. A downstream end of the trailing edge rib may be aligned with the trailing edge of the turbine airfoil The trailing edge exit slot may include a tapered mouth such that an opening of the mouth is wider than a width of the trailing edge exit slot at the intersection between the trailing edge exit slot and the mouth. A ratio of width of trailing edge exit slot to width of trailing edge rib separating adjacent trailing edge slots may be between about 2•3 and about 2:5. In another embodiment, a ratio of width of trailing edge exit slot to width of trailing edge rib separating adjacent trailing edge slots may be about 2:3.2.
An advantage of this invention is that the trailing edge exit slot reduces the effective flow area, generates impingement and turbulence to increase heat transfer and provides sufficient mechanical strength for better casting yield without overflowing for better performance.
Another advantage of this invention is that the design provides sufficient mechanical support while providing sufficient flow metering with quality heat transfer capability
Yet another advantage of this invention is that the mechanically supportive trailing edge exit slots may be form with investment casting rather than machining holes which saves costs
These and other embodiments are described in more detail below.
The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the presently disclosed invention and, together with the description, disclose the principles of the invention.
As shown in
In at least one embodiment, as shown in
The leading edge cooling channel 48 or the serpentine cooling channel 54, or both, may include one or more turbulators 58 that may extend from an inner surface of the suction side 60 or the pressure side 62, or both The turbulators 58 may be positioned nonlinear and nonorthogonal to the flow of cooling fluids through the cooling system 10 In at least one embodiment, the turbulators 58 may be positioned at about 45 degrees relative to a direction of flow 64 of cooling fluids through the cooling system 10. A plurality of film cooling orifices 53 may extend through the pressure and suction sides 62, 60 to exhaust cooling fluids from the serpentine cooling channel 54
The cooling system 10 may include one or more trailing edge cooling channels 16 positioned within the generally elongated, hollow airfoil 30 and proximate to the trailing edge 36 The trailing edge cooling channel 16 may include one or more impingement ribs 66 extending spanwise within the channel 16 In at least one embodiment, the trailing edge cooling channel 16 may include three impingement ribs 66.
The trailing edge cooling channel 16, as shown in
In at least one embodiment, the trailing edge exit slot 20 extending from the central trailing edge cooling channel 18 to the trailing edge 36 may be formed from a plurality of trailing edge exit slots 20 extending from the central trailing edge cooling channel 18 to the trailing edge 36. Adjacent trailing edge exit slots 20 may be separated from each other by a trailing edge rib 24 extend from the suction side 60 to the pressure side 62. The trailing edge rib 24 may include a pointed leading edge 90 formed by at two linear edges 92, 94 that intersect at a tip 96 of the trailing edge rib 24. In at least one embodiment, the tip 96 of the trailing edge rib 24 may be rounded A downstream end 98 of the trailing edge rib 24 may be aligned with the trailing edge 36 of the turbine airfoil 12. The trailing edge exit slot 20 may include a tapered mouth 100 such that an opening 102 of the mouth 100 is wider than a width of the trailing edge exit slot 20 at the intersection 104 between the tapered edge exit slot 20 and the mouth. A ratio of width of trailing edge exit slot 20 to width of trailing edge rib 24 separating adjacent trailing edge slots 20 may be between about 2•3 and about 2•5 In another embodiment, the ratio of width of trailing edge exit slot 20 to width of trailing edge rib 24 separating adjacent trailing edge slots 20 may be about 2•3 2. In yet another embodiment, the ratio of width of trailing edge exit slot 20 to width of trailing edge rib 24 separating adjacent trailing edge exit slots 20 may be about 2:3 17 In at least one embodiment, the trailing edge exit slot 20 may have a width extending from the suction side to the pressure side between about 0.5 millimeter and about 1.5 millimeters, a slot height between about 1 millimeter and about 3 millimeters and a pitch between about 4 millimeters and about 6 millimeters. In yet another embodiment, the trailing edge exit slot 20 may have a width extending from the suction side to the pressure side of about 1 millimeter, a slot height of about 2 millimeter, and a pitch of about 5.17 millimeters.
The turbine airfoil 12 may be formed via a method of investment casting whereby a die 110, as shown in
During use, cooling fluids may flow into the cooling system 10 from a cooling fluid supply source. At least a portion of the cooling fluids may flow into the leading edge cooling channel 48 and the serpentine cooling channel 54 in the midchord region 56. A portion of the cooling fluid flowing into the serpentine cooling channel 54 in the midchord region 56 may flow into the trailing edge cooling channel 18 The cooling fluid flowing into the trailing edge cooling channel 18 may flow through one or more impingement rib 66 and into one or more trailing edge exit slots 20. The fluid flowing through the trailing edge exit slots 20 follows a nonlinear longitudinal axis 22 Such nonlinear path within the trailing edge exit slot 20 reduces the effective flow area, generates impingement and turbulence to increase heat transfer and provides sufficient mechanical strength for better casting yield without overflowing for better performance.
The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of this invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention.
Claims
1. A turbine airfoil, comprising:
- a generally elongated, hollow airfoil formed by an outer wall and having a leading edge, a trailing edge, a tip section at a first end, a root coupled to the airfoil at an end generally opposite the first end for supporting the airfoil and for coupling the airfoil to a disc, and a cooling system formed from at least one cavity in the elongated, hollow airfoil positioned in internal aspects of the generally elongated, hollow airfoil;
- at least one trailing edge cooling channel positioned within the generally elongated, hollow airfoil and proximate to the trailing edge, wherein the at least one trailing edge cooling channel comprises a central trailing edge cooling channel extending spanwise within the generally elongated, hollow airfoil and at least one trailing edge exit slot extending from the central trailing edge cooling channel to the trailing edge; and
- wherein the at least one trailing edge exit slot has a nonlinear longitudinal axis whereby a first linear line extending between a first ridge and a second ridge on a first side of the at least one trailing edge exit slot is separated laterally from a second linear line extending between a first ridge and a second ridge on a second side of the at least one trailing edge exit slot on an opposite side from the first side
2. The turbine airfoil of claim 1, wherein a lateral distance between the first and second linear lines is more than one half of a distance from a first ridge on the first linear side and a valley opposite the first ridge on the second side.
3. The turbine airfoil of claim 1, wherein the first side of the at least one trailing edge exit slot is formed from at least two ridges and at least two valleys and the second side of the at least one trailing edge exit slot is formed from at least one ridge and at least two valleys.
4. The turbine airfoil of claim 3, wherein the at least one ridge on the second side is aligned with a valley on the first side positioned between two ridges.
5. The turbine airfoil of claim 1, wherein the at least one trailing edge exit slot extending from the central trailing edge cooling channel to the trailing edge is formed from a plurality of trailing edge exit slots extending from the central trailing edge cooling channel to the trailing edge, wherein adjacent trailing edge exit slots are separated from each other by a trailing edge rib extend from the suction side to the pressure side.
6. The turbine airfoil of claim 5, wherein the trailing edge rib includes a pointed leading edge formed by two linear edges that intersect at a tip of the trailing edge rib.
7. The turbine airfoil of claim 6, wherein the tip of the trailing edge rib is rounded.
8. The turbine airfoil of claim 6, wherein a downstream end of the trailing edge rib is aligned with the trailing edge of the turbine airfoil.
9. The turbine airfoil of claim 1, wherein the at least one trailing edge exit slot includes a tapered mouth such that an opening of the mouth is wider than a width of the at least one trailing edge exit slot at an intersection between the trailing edge exit slot and the mouth.
10. The turbine airfoil of claim 1, wherein a ratio of width of trailing edge exit slot to width of trailing edge rib separating adjacent trailing edge slots is between about 2:3 and about 2•5.
11. The turbine airfoil of claim 10, wherein the ratio of width of trailing edge exit slot to width of trailing edge rib separating adjacent trailing edge slots is about 2:3.2.
12. A turbine airfoil, comprising:
- a generally elongated, hollow airfoil formed by an outer wall and having a leading edge, a trailing edge, a tip section at a first end, a root coupled to the airfoil at an end generally opposite the first end for supporting the airfoil and for coupling the airfoil to a disc, and a cooling system formed from at least one cavity in the elongated, hollow airfoil positioned in internal aspects of the generally elongated, hollow airfoil;
- at least one trailing edge cooling channel positioned within the generally elongated, hollow airfoil and proximate to the trailing edge, wherein the at least one trailing edge cooling channel comprises a central trailing edge cooling channel extending spanwise within the generally elongated, hollow airfoil and at least one trailing edge exit slot extending from the central trailing edge cooling channel to the trailing edge;
- wherein the at least one trailing edge exit slot has a nonlinear longitudinal axis whereby a first linear line extending between a first ridge and a second ridge on a first side of the at least one trailing edge exit slot is separated laterally from a second linear line extending between a first ridge and a second ridge on a second side of the at least one trailing edge exit slot on an opposite side from the first side;
- wherein the first side of the at least one trailing edge exit slot is formed from at least two ridges and at least two valleys and the second side of the at least one trailing edge exit slot is formed from at least one ridge and at least two valleys;
- wherein the at least one ridge on the second side is aligned with a valley on the first side positioned between two ridges;
- wherein the at least one trailing edge exit slot extending from the central trailing edge cooling channel to the trailing edge is formed from a plurality of trailing edge exit slots extending from the central trailing edge cooling channel to the trailing edge, wherein adjacent trailing edge exit slots are separated from each other by a trailing edge rib extend from the suction side to the pressure side; and
- wherein the at least one trailing edge exit slot includes a tapered mouth such that an opening of the mouth is wider than a width of the at least one trailing edge exit slot at an intersection between the trailing edge exit slot and the mouth.
13. The turbine airfoil of claim 12, wherein a lateral distance between the first and second linear lines is more than one half of a distance from a first ridge on the first linear side and a valley opposite the first ridge on the second side.
14. The turbine airfoil of claim 12, wherein the trailing edge rib includes a pointed leading edge formed by two linear edges that intersect at a tip of the trailing edge rib.
15. The turbine airfoil of claim 14, wherein the tip of the trailing edge rib is rounded
16. The turbine airfoil of claim 12, wherein a downstream end of the trailing edge rib is aligned with the trailing edge of the turbine airfoil.
17. The turbine airfoil of claim 12, wherein a ratio of width of trailing edge exit slot to width of trailing edge rib separating adjacent trailing edge slots is between about 2•3 and about 2:5.
18. The turbine airfoil of claim 17, wherein the ratio of width of trailing edge exit slot to width of trailing edge rib separating adjacent trailing edge slots is about 2:3.2.
19. A method of forming a turbine airfoil, comprising:
- forming ceramic core a cooling system for a turbine airfoil, wherein the cooling system is formed at least one trailing edge cooling channel positioned within the generally elongated, hollow airfoil and proximate to the trailing edge, wherein the at least one trailing edge cooling channel comprises a central trailing edge cooling channel extending spanwise within the generally elongated, hollow airfoil and at least one trailing edge exit slot extending from the central trailing edge cooling channel to the trailing edge, wherein the at least one trailing edge exit slot has a nonlinear longitudinal axis whereby a first linear line extending between a first ridge and a second ridge on a first side of the at least one trailing edge exit slot is separated laterally from a second linear line extending between a first ridge and a second ridge on a second side of the at least one trailing edge exit slot on an opposite side from the first side;
- positioning the ceramic core within a wax die;
- filling the wax die with wax to form a wax blade having a form of the generally elongated, hollow airfoil;
- coating the wax blade with ceramic material to form an external shell;
- removing the wax to form a hollow casting mold;
- casting the generally elongated, hollow airfoil including by pouring an alloy into the external shell, wherein the generally elongated, hollow airfoil is formed by an outer wall and having a leading edge, a trailing edge, a tip section at a first end, a root coupled to the airfoil at an end generally opposite the first end for supporting the airfoil and for coupling the airfoil to a disc, and a cooling system formed from at least one cavity in the elongated, hollow airfoil positioned in internal aspects of the generally elongated, hollow airfoil; and
- removing the ceramic core to form the at least one trailing edge cooling channel, the central trailing edge cooling channel, and the at least one trailing edge exit slot.
Type: Application
Filed: Dec 26, 2013
Publication Date: Jul 2, 2015
Inventor: Ching-Pang Lee (Cincinnati, OH)
Application Number: 14/140,593