US20120034101A1

US20120034101A1 - Turbine blade squealer tip

Info

Publication number: US20120034101A1
Application number: US12/852,679
Authority: US
Inventors: Allister W. James; Anand A. Kulkarni
Original assignee: Siemens Energy Inc
Current assignee: Siemens Energy Inc
Priority date: 2010-08-09
Filing date: 2010-08-09
Publication date: 2012-02-09

Abstract

A turbine blade having a squealer tip coupled to a radially outer end of the turbine blade that is usable in a gas turbine engine is disclosed. The squealer tip may require less cooling air and may therefore be more efficient than conventional configurations. The squealer tip may be formed from one or more materials such as oxide dispersion strengthened alloys and FeCrAl alloys. The squealer tip may be formed from a plurality of segmented tips extending radially outward and spaced apart from each other. For example, the squealer tip may be formed from two rails extending radially outward and spaced apart from each other. The two rails may be formed from outer and inner rails that each form a continuous ring. The squealer tip may be attached to the tip with a transient liquid phase bond or an additive manufacturing process, such as, a selective laser melting process.

Description

FIELD OF THE INVENTION

This invention is directed generally to turbine blades, and more particularly to tip sealing systems for turbine blades.

BACKGROUND

Typically, 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 at one end and an elongated portion forming an airfoil that extends outwardly from a platform coupled to the root portion at an opposite end of the turbine blade. The blade is ordinarily composed of a tip opposite the root section, a leading edge, and a trailing edge. The tip of a turbine blade often has a tip seals to reduce the gap between ring segments and blades in the gas path of the turbine. The tip seals are often referred to as squealer tips and are frequently incorporated onto the tips of blades to help reduce pressure losses between turbine stages. These features are designed to minimize the gap between the blade tip and the ring segment. The material at the tip is exposed to the hot gas path because there is not a ceramic thermal barrier coating on the squealer tips. Squealer tips are integrally cast with the turbine blade. Turbine engines are being run at higher and higher temperatures in an effort to create increasing amounts of power from the engines. These higher temperatures are creating increased thermal stress levels on the turbine airfoils.
The inner aspects of most turbine blades typically contain an intricate maze of cooling channels forming a cooling system. 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.

SUMMARY OF THE INVENTION

A turbine blade having a squealer tip coupled to a radially outer end of the turbine blade that is usable in a gas turbine engine is disclosed. The squealer tip may be configured such that the squealer tip requires less cooling fluids than conventional squealer tips, therefore increasing the efficiency of the turbine engine in which the squealer tip is used. In at least one embodiment, the squealer tip may use about 1.5 percent less cooling fluids than conventional turbine blades. In addition, the squealer tip may also be configured to be used in turbine engines that are designed to operate at higher operating temperatures than conventional turbine engines. The squealer tip may be formed from a material that is different than the material forming the turbine blade.
The turbine blade may be formed from a generally elongated blade having a leading edge, a trailing edge, a tip wall at a first end, a root coupled to the blade at an end generally opposite the first end for supporting the blade and for coupling the blade to a disc, and at least one cavity forming a cooling system in the blade. The squealer tip may be coupled to the tip at the first end. The squealer tip may be formed from a material selected from the group consisting of oxide dispersion strengthened alloys and FeCrAl alloys. The oxide dispersion strengthened alloys may include, but are not limited to, PM2000 and ODM 751, and the FeCrAl alloy may include, but are not limited to, APMT.
The squealer tip may be formed from a plurality of segmented tips extending radially outward and spaced apart from each other to relieve thermal stress at the tip. To relieve thermal stress in the squealer tip, the squealer tip may be formed from two rails extending radially outward and spaced apart from each other. The two rails may be formed from outer and inner rails that each form a continuous ring.
The squealer tip may be attached to the tip using a joining method such as transient liquid phase bonding. Alternatively, the squealer tip may be attached to the tip with an additive manufacturing process. The additive manufacturing process may be a selective laser melting process or a direct metal laser sintering process.
An advantage of this invention is that the squealer tip may enable turbine blade tips to be exposed to higher temperatures without an increased risk of failure.
Another advantage of this invention is that the squealer tip may be made with materials that would reduce cooling requirements at the tip and improve blade clearance while increasing the operating efficiency of the turbine engine by about ½ percent.
Yet another advantage of this invention is that the squealer tip may be formed from segmented tips to alleviate thermal stress in the squealer tip.
These and other embodiments are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

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.

FIG. 1 is a perspective view of a turbine blade having features according to the instant invention.

FIG. 2 is top view of the turbine blade.

FIG. 3 is a detailed, side view of a squealer tip.

FIG. 4 is a partial side of a squealer tip being formed in a mechanical attachment system.

FIG. 5 is a partial side view of a squealer tip attached to a tip of the turbine blade.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIGS. 1-5, this invention is directed to a turbine blade 10 having a squealer tip 12 for use in turbine engines. The squealer tip 12 may be configured such that the squealer tip 12 requires less cooling fluids than conventional squealer tips, thereby increasing the efficiency of the turbine engine in which the squealer tip 12 is used. In at least one embodiment, the squealer tip 12 may use about 1.5 percent less cooling fluids than conventional turbine blades. In addition, the squealer tip 12 may also be configured to be used in turbine engines that are designed to operate at higher operating temperatures than conventional turbine engines without an increased risk of failure.
The squealer tip 12 may be attached to a radially outward tip 14 of a turbine blade 10. The turbine blade 10 may be formed from a generally elongated airfoil 16 having a leading edge 18, a trailing edge 20, the tip 14 at a first end 24, a root 26 coupled to the blade 10 at an end 28 generally opposite the first end 24 for supporting the blade 10 and for coupling the blade 10 to a disc, and one or more cavities forming a cooling system in the blade 10. The cooling system may have any appropriate configuration within internal aspects of the elongated blade 16.
The squealer tip 12 may be coupled to the tip 14 at the first end 24. The squealer tip 12 may be formed from a material having high temperature oxidation and corrosion properties. The squealer tip 12 may be formed from materials that are different from the turbine blade 10. The material may be, but is not limited to, an oxide dispersion strengthened alloy, such as, but not limited to, PM2000 and ODM 751. The material may also be an advanced dispersion strengthened powder metallurgy FeCrAl alloy, such as, but not limited to Kanthal APMT. These materials are capable of withstanding temperatures in excess of 1200 degrees Celsius in an uncoated condition.
The squealer tip 12 may be configured such that the squealer tip 12 is formed from a plurality of segmented tips 32 extending radially outward and spaced apart from each other, as shown FIG. 3. The tips 32 may include channels 34 between each adjacent tip 32. The segments tips 32 may be aligned with each other or otherwise positioned. The channels 34 may extend any appropriate depth into the squealer tip 12 but not completely through the squealer tip 12 and into the tip 14 of the turbine blade 10. The channels 34 may be square, rectangular, or have any other appropriate cross-sectional configuration.
In one embodiment, as shown in FIG. 2, the squealer tip 12 may be formed from two rails 36, 38 extending radially outward and spaced apart from each other. The rails 36, 38 may be formed from inner and outer rails 36, 38 that each form a continuous ring.
The squealer tip 12 may be formed using powder manufacturing systems that enable easy buildup of different structures on the tip 14 of the turbine blade 10. The squealer tip 12 may be manufactured using an additive manufacturing technique such as selective laser melting (SLM), direct metal laser sintering (DMLS) or via the attachment of a preform by techniques such as transient liquid phase (TLP) bonding. Such a system enables multiple rails, such as rails 36, 38, to be formed, which may have increased efficiencies. In particular, these manufacturing systems enable the formation of the inner and outer rails 36, 38 that follow the exterior shape of the turbine blades 10.
As shown in FIGS. 4 and 5, the squealer tip 12 may be attached to the tip 14 via a mechanical attachment system 36. The mechanical attachment system 36 may be any cavity having a ledge under which the squealer tip 12 may be attached. As shown in FIG. 4, a powder may be placed in a cavity and sintered therein to build the squealer tip 12. As shown in FIG. 5, the squealer tip 12 may extend radially outward from the tip 14. The mechanical attachment system 36 may be a dovetail attachment system 38, as shown in FIG. 5.
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 blade, comprising:

a generally elongated airfoil having a leading edge, a trailing edge, a tip 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 blade to a disc, and at least one cavity forming a cooling system in the blade; and

a squealer tip coupled to the tip at the first end, wherein the squealer tip is formed from a material selected from the group consisting of oxide dispersion strengthened alloys and FeCrAl alloys.

2. The turbine blade of claim 1, wherein the oxide dispersion strengthened alloys comprise PM2000 and ODM 751.

3. The turbine blade of claim 1, wherein the FeCrAl alloys comprise APMT.

4. The turbine blade of claim 1, wherein the squealer tip is comprised of a plurality of segmented tips extending radially outward and spaced apart from each other.

5. The turbine blade of claim 1, wherein the squealer tip is comprised of two rails extending radially outward and spaced apart from each other.

6. The turbine blade of claim 5, wherein the two rails are formed from outer and inner rails that each form a continuous ring.

7. The turbine blade of claim 1, wherein the squealer tip is attached to the tip with a transient liquid phase bond.

8. The turbine blade of claim 1, wherein the squealer tip is attached to the tip with an additive manufacturing process.

9. The turbine blade of claim 8, wherein the additive manufacturing process is a selective laser melting process.

10. The turbine blade of claim 8, wherein the additive manufacturing process is a direct metal laser sintering.

11. The turbine blade of claim 1, wherein the squealer tip is attached to the tip with a mechanical attachment system.

12. The turbine blade of claim 11, wherein the mechanical attachment system is a dovetail attachment system.

13. A turbine blade, comprising:

a generally elongated blade having a leading edge, a trailing edge, a tip 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 blade to a disc, and at least one cavity forming a cooling system in the blade; and

a squealer tip coupled to the tip at the first end, wherein the squealer tip is formed from two rails extending radially outward and spaced apart from each other.

14. The turbine blade of claim 13, wherein the two rails are formed from outer and inner rails that each form a continuous ring.

15. The turbine blade of claim 13, wherein the squealer tip is formed from a material selected from the group consisting of oxide dispersion strengthened alloys PM2000 and ODM 751 and FeCrAl alloys of APMT.

16. The turbine blade of claim 13, wherein the squealer tip is attached to the tip with a transient liquid phase bond.

17. The turbine blade of claim 13, wherein the squealer tip is attached to the tip with an additive manufacturing process selected from the group consisting of a selective laser melting process and a direct metal laser sintering.

18. The turbine blade of claim 13, wherein the squealer tip is attached to the tip with a mechanical attachment system.

19. A turbine blade, comprising:

a generally elongated blade having a leading edge, a trailing edge, a tip at a first end, a root coupled to the blade at an end generally opposite the first end for supporting the blade and for coupling the blade to a disc, and at least one cavity forming a cooling system in the blade; and

a squealer tip coupled to the tip at the first end, wherein the squealer tip is formed from a material selected from the group consisting of oxide dispersion strengthened alloys and FeCrAl alloys;

wherein the squealer tip is attached to the tip with a transient liquid phase bond.

20. The turbine blade of claim 19, wherein the oxide dispersion strengthened alloys comprise PM2000 and ODM 751, and the FeCrAl alloy comprises APMT.

21. The turbine blade of claim 19, wherein the squealer tip is comprised of a plurality of segmented tips extending radially outward and spaced apart from each other.