Turbine airfoil cooling system with near wall pin fin cooling chambers

Abstract

A cooling system for a turbine airfoil of a turbine engine having a suction side near wall cooling chamber extending from the leading edge to the trailing edge. The suction side near wall cooling chamber may include a plurality of pin fins for increasing the cooling effectiveness of the suction side near wall cooling chamber. The pin fins may be formed in two or more regions having varying sizes and quantities per unit area to accommodate different cooling requirements across the airfoil. In one embodiment, cooling fluids may flow in a counterflow manner through the suction side near wall cooling chamber relative to a pressure side near wall cooling chamber. In another embodiment, the cooling fluids may flow from the leading edge through the suction side near wall cooling chamber and be exhausted through slots in the trailing edge.

Description

FIELD OF THE INVENTION

This invention is directed generally to turbine airfoils, and more particularly to cooling systems in hollow turbine airfoils.

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 1-5 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. Thus, a need exists for a cooling system capable of providing sufficient cooling to turbine airfoils.

SUMMARY OF THE INVENTION

This invention relates to a cooling system for turbine airfoils used in turbine engines. In particular, the turbine airfoil cooling system may include an internal cavity positioned between outer walls of the turbine airfoil. The cooling system may include a suction side near wall cooling chamber immediately adjacent to the outer wall forming a suction side of the turbine airfoil. The cooling system may also include a pressure side near wall cooling chamber immediately adjacent to the outer wall forming a pressure side of the turbine airfoil. The suction and pressure side near wall cooling chambers may include a plurality of pin fins to increase the cooling effectiveness of the cooling system and to accommodate localized hot spots in the turbine blade.

The turbine airfoil may be formed, in general, from a generally elongated, hollow airfoil 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. The airfoil may include a cooling system formed from at least one cavity in the elongated, hollow airfoil. An inner wall may be positioned in close proximity to the outer wall and may form a pressure side near wall cooling chamber proximate to a pressure side of the generally elongated, hollow airfoil and may form a suction side near wall cooling chamber proximate to a suction side of the generally elongated, hollow airfoil. The airfoil may also include a leading edge cooling chamber positioned proximate to the leading edge of the generally elongated, hollow airfoil that may extend generally spanwise through the generally elongated, hollow airfoil. The airfoil may also include a trailing edge cooling chamber positioned proximate to the trailing edge of the generally elongated, hollow airfoil and extending generally spanwise through the generally elongated, hollow airfoil.

The suction side near wall cooling chamber may extend from the leading edge cooling chamber to the trailing edge cooling chamber and may include a plurality of pin fins extending from the outerwall to the inner wall. The plurality of pin fins in the suction side near wall cooling chamber may be formed from a first region having fin pins with a first cross-sectional area and a second region having pin fins with a second cross-sectional area that is greater than the first cross-sectional area. The plurality of pin fins in the suction side near wall cooling chamber may be formed from a first region in a first quantity per unit area and a second region having pin fins in a second quantity per unit area that is greater than the first quantity per unit area. The plurality of pin fins in the suction side near wall cooling chamber may be aligned into rows of pin fins extending generally spanwise or extending at an acute angle between a chordwise and spanwise directions. Trip strips may extend between the pin fins and may protrude from the outer wall toward the inner partition wall.

The pressure side near wall cooling chamber may extend from the leading edge cooling chamber to the trailing edge cooling chamber and may include a plurality of pin fins extending from the outerwall to the inner wall. The plurality of pin fins in the pressure side near wall cooling chamber may be formed from a first region having fin pins with a first cross-sectional area and a second region having pin fins with a second cross-sectional area that is greater than the first cross-sectional area. The plurality of pin fins in the pressure side near wall cooling chamber may be formed from a first region in a first quantity per unit area and a second region having pin fins in a second quantity per unit area that is greater than the first quantity per unit area. The plurality of pin fins in the pressure side near wall cooling chamber may be aligned into rows of pin fins extending generally spanwise or extending at an acute angle between chordwise and spanwise directions. Trip strips may extend between the pin fins and may protrude from the outer wall toward the inner partition wall.

In one embodiment, pin fins may be positioned in the trailing edge cooling chamber. The pressure side near wall cooling chamber may have at least one impingement orifice providing cooling fluids from proximate to the leading edge such that cooling fluids flow in a direction from the leading edge toward the trailing edge. The suction side near wall cooling chamber may be in communication with the pressure side near wall cooling chamber proximate to the trailing edge cooling chamber such that cooling fluids flow in a direction from the trailing edge toward the leading edge establishing a counterflow. The cooling system may also include, in one embodiment, a central cooling fluid supply channel positioned between the pressure side and suction side near wall cooling chambers and extending from the leading edge cooling chamber to the trailing edge cooling chamber.

During use, cooling fluids may flow from a cooling fluid supply source into the pressure side near wall cooling chamber. The cooling fluids flow through the pin fins and increase in temperature. The cooling fluids pass through the impingement orifices and impinge on the backside of the outer wall forming the leading edge. The cooling fluids then flow into the suction side near wall cooling chamber and contact the pin fins, which causes the cooling fluids to increase in temperature. The cooling fluids are released from the suction side near wall cooling chamber through the trailing edge slots.

In another embodiment, cooling fluids may flow from a cooling fluid supply source into the central cooling fluid supply chamber. The cooling fluids then flow through impingement orifices and impinge on a backside surface of the leading edge. The cooling fluids then flow into the pressure side near wall cooling chamber and contact the pin fins. The cooling fluids flow through the pressure side near wall cooling chamber toward the trailing edge to the intersection of the suction and pressure side near wall cooling chambers. A portion of the cooling fluids may be exhausted through the trailing edge slots, and a portion of the cooling fluids may flow from the trailing edge toward the leading edge through the suction side near wall cooling chamber. Another portion of the cooling fluids may be exhausted from the cooling system through the film cooling orifices. The cooling fluids may then flow from the trailing edge to the leading edge through the suction side near wall cooling chamber. The cooling fluids may increase in temperature by contacting the pin fins, the inner partition wall, and the outer wall. The cooling fluids may be exhausted from the system through the film cooling orifices proximate to the leading edge.

An advantage of this invention is that the near wall cooling chamber configuration maximizes usage of cooling fluids for a given airfoil inlet gas temperature and pressure profile.

Another advantage of this invention is that the combination of the pin fins and trip strips generate extremely high turbulence levels of cooling fluids that, in turn, generate high internal heat transfer coefficient values.

Yet another advantage of this invention is that the high internal convection and conduction areas created by the complex cooling system yields very high internal convection effectiveness in comparison to conventional single pass radial flow channels.

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 airfoil having features according to the instant invention.

FIG. 2 is a cross-sectional view of the turbine airfoil shown in FIG. 1 taken along line 2-2.

FIG. 3 is a detailed cross-sectional view of a portion of the vortex cooling chambers shown in FIG. 2 along line 3-3.

FIG. 4 is a cross-sectional view of an alternative configuration of a cooling system in the turbine airfoil shown in FIG. 2 taken along line 4-4.

FIG. 5 is a cross-sectional view of another alternative configuration of a cooling system in the turbine airfoil shown in FIG. 2 taken along line 5-5.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIGS. 1-5, this invention is directed to a turbine airfoil cooling system 10 for a turbine airfoil 12 used in turbine engines. In particular, the turbine airfoil cooling system 10 includes a plurality of internal cavities 14, as shown in FIG. 2, positioned between outer walls 16 of the turbine airfoil 12. The cooling system 10 may include a suction side near wall cooling chamber 18 immediately adjacent to the outer wall 16 forming a suction side 20 of the turbine airfoil 12. The cooling system 10 may also include a pressure side near wall cooling chamber 22 immediately adjacent to the outer wall 16 forming a pressure side 24 of the turbine airfoil 12. The suction and pressure side near wall cooling chambers 18, 22 may include a plurality of pin fins 26 to increase the cooling effectiveness of the cooling system 10 and to accommodate localized hot spots in the turbine blade 12.

The turbine airfoil 12 may be formed from a generally elongated, hollow airfoil 28 coupled to a root 30 at a platform 32. The turbine airfoil 12 may be formed from conventional metals or other acceptable materials. The generally elongated airfoil 28 may extend from the root 30 to a tip section 34 and include a leading edge 36 and trailing edge 38. Airfoil 28 may have an outer wall 16 adapted for use, for example, in a first stage of an axial flow turbine engine. Outer wall 16 may form a generally concave shaped portion forming the pressure side 24 and may form a generally convex shaped portion forming the suction side 20. The cavity 14, as shown in FIG. 2, may be positioned in inner aspects of the airfoil 28 for directing one or more gases, which may include air received from a compressor (not shown), through the airfoil 28 to reduce the temperature of the airfoil 28. The cavity 14 may be arranged in various configurations and is not limited to a particular flow path.

The cooling system 10, as shown in FIGS. 2-3, may include a suction side near wall cooling chamber 18 positioned in the outer wall 16 of the generally elongated, hollow airfoil 28 and defined by inner partition wall 42. The suction side near wall cooling chamber 18 may extend from a leading edge impingement chamber 44 to trailing edge slots 46 in a trailing edge cooling chamber 47 that extends through the trailing edge 38. The trailing edge cooling chamber 47 may be positioned proximate to the trailing edge 38 of the generally elongated, hollow airfoil 28 and may extend generally spanwise through the generally elongated, hollow airfoil 28. The suction side near wall cooling chamber 18 may extend from the root 30 to the tip section 34 or extend for any partial length therebetween. The size of trailing edge slots 46 may be varied to control the flow of cooling fluids from the airfoil 12. The leading edge impingement chamber 44 may extend from the root 30 to the tip section 34 or extend for any partial length therebetween.

The suction side near wall cooling chamber 18 may include a plurality of pin fins 26 for increasing the cooling effectiveness of the system 10 and for customizing portions of the suction side near wall cooling chamber 18 to accommodate localized pockets of increased heat loads. For instance, as shown in FIG. 3, the suction side near wall cooling chamber 18 may include a first region 48 of pin fins 26 having a first cross-sectional area for each pin fin 26 that is different from a second region 50 of pin fins 26 having a second cross-sectional area for each pin fin 26. In at least one embodiment, the second region 50 of pin fins 26 may have pin fins 26 with larger cross-sectional areas than the pin fins 26 of the first region 48, or vice versa. The cross-sectional shape of the pin fins 26 shown in FIG. 3 is generally circular; however, the pin fins 26 are not limited to this shape. Rather, the pin fins 26 may have other appropriate cross-sections, such as, but not limited to, elliptical, oval, triangular, rectangular, and other appropriate shapes. The quantity of pin fins 26 per unit area in the first region 48 may differ from the quantity of pin fins 26 per unit area in the second region 50. In one embodiment, the quantity of pin fins 26 in the second region 50 may be greater than the quantity of pin fins 26 in the first region 48, or vice versa. The pin fins 26 may extend from the outer wall 16 to the inner partition wall 42. In one embodiment, the pin fins 26 may extend generally orthogonally from the outer wall 16 to the inner partition wall 42.

As shown in FIG. 3, the pin fins 26 may be aligned into rows that extend in a general spanwise direction. Trip strips 52 may also extend between the pin fins 26 in a generally spanwise direction. The trip strips 52 may protrude from an inner surface 54 of the outer wall 16 toward the inner partition wall 42. As shown in FIG. 3, the first region 48 may include pin fins 26 aligned into rows that extend at an acute angle between the chordwise and spanwise directions. The trip strips 52 may extend between the pin fins 26 and may be aligned into the rows of pin fins 26 positioned at an acute angle relative to the chordwise and spanwise directions.

The cooling system 10 may include a pressure side near wall cooling chamber 22. The pressure side near wall cooling chamber 22 may be positioned in a mid chord region 56. As shown in FIGS. 2, 3 and 5, the pressure side near wall cooling chamber 22 may be in fluid communication with the leading edge impingement chamber 44 through one or more impingement orifices 58. Cooling fluids may be received from a cooling fluid supply source and exhausted through the impingement orifices 58 to supply cooling fluids to the leading edge impingement chamber 44 and to the suction side near wall cooling chamber 18. As shown in FIG. 4, the cooling system 12 may include one or more refresh holes 60 in the inner partition wall 42 to supply cooling fluids to the suction side near wall cooling chamber 18. The size and location of the refresh holes 60 may be varied according to the heat loads of the particular airfoil 12. The refresh holes 60 enables lower temperature cooling fluids at higher pressures to be injected into the suction side near wall cooling chamber 18, thereby enhancing the local internal heat transfer coefficient. The pressure side near wall cooling chamber 22 may include pin fins 26. The pin fins 26 increase the temperature of the inner partition wall 42 by conducting heat from the outer wall 16, thereby reducing the temperature gradient between the inner partition wall 42 and the outer wall 16. Reducing the temperature gradient reduces stresses on the turbine airfoil 12. The pin fins 26 may be positioned into two or more regions, such as previously set forth for the pin fins in the suction side near wall cooling chamber 18. In addition, the pin fins 26 in the pressure side near wall cooling chamber 22 may be sized and aligned into rows as previously described.

As shown in FIG. 5, the inner partition wall 42 and a second inner wall 70 may form a central cooling fluid supply chamber 62. The embodiment shown in FIG. 5 depicts a parallel flow design in which the cooling fluids flows inline with the airfoil external pressure and heat loads. The cooling air is channeled rearward, toward the trailing edge 38, and discharged immediately upstream from the trailing edge 38 for film cooling purposes. The central cooling fluid supply chamber 62 may be in fluid communication with a supply source (not shown). The central cooling fluid cooling fluid supply chamber 62 may be in fluid communication with the pressure side near wall cooling chamber 22 through one or more impingement orifices 58. The pressure side near wall cooling chamber 22 may extend to contact the suction side near wall cooling chamber 18 at inlet 61, where a portion of the cooling fluids are exhausted through the trailing edge slots 46 and a portion of the cooling fluids flow from the trailing edge 38 toward the leading edge 36 through the suction side near wall cooling chamber 18. This configuration established a counterflow of cooling fluids relative to the flow of cooling fluids through the pressure side near wall cooling chamber 22. The outer wall 16 may include a plurality of film cooling orifices 64 for exhausting the cooling fluids. At least one film cooling orifice 64 may extend through the pressure side 24 outer wall 16 at the intersection between the pressure side near wall cooling chamber 22 and the suction side near wall cooling chamber 18. Other film cooling orifices 64 may be positioned in the suction side 20 outer wall 16 at the leading edge 36 and at other locations between the leading and trailing edges 36, 38.

In the embodiments shown in FIGS. 2 and 4, during use, cooling fluids flow from a cooling fluid supply source (not shown) into the pressure side near wall cooling chamber 22. The cooling fluids flow through the pin fins 26 and increase in temperature. The cooling fluids pass through the impingement orifices 58 and impinge on the backside of the outer wall 16 forming the leading edge 36. The cooling fluids then flow into the suction side near wall cooling chamber 18 and contact the pin fins 26, which causes the cooling fluids to increase in temperature. The cooling fluids are released from the suction side near wall cooling chamber 18 through the trailing edge slots 46.

In the embodiment shown in FIG. 5, cooling fluids flow from a cooling fluid supply source (not shown) into the central cooling fluid supply chamber 62. The cooling fluids then flow through impingement orifices 58 and impinge on a backside surface of the leading edge 36. The cooling fluids then flow into the pressure side near wall cooling chamber 22 and contact the pin fins 26. The cooling fluids flow through the pressure side near wall cooling chamber 22 toward the trailing edge 38 to the intersection of the suction and pressure side near wall cooling chambers 18, 22. A portion of the cooling fluids may be exhausted through the trailing edge slots 46, and a portion of the cooling fluids may flow from the trailing edge 38 toward the leading edge 36 through the suction side near wall cooling chamber 18. Another portion of the cooling fluids may be exhausted from the cooling system 10 through the film cooling orifices 64. The cooling fluids may then flow from the trailing edge 38 to the leading edge 36 through the suction side near wall cooling chamber 18. The cooling fluids may increase in temperature by contacting the pin fins 26, the inner partition wall 42, and the outer wall 16. The cooling fluids may be exhausted from the system 10 through the film cooling orifices 64 proximate to the leading edge 36.

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 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;

an outer wall forming the generally elongated airfoil;

an inner wall positioned in close proximity to the outer wall forming a pressure side near wall cooling chamber proximate to a pressure side of the generally elongated, hollow airfoil and forming a suction side near wall cooling chamber proximate to a suction side of the generally elongated, hollow airfoil;

a leading edge cooling chamber positioned proximate to the leading edge of the generally elongated, hollow airfoil and extending generally spanwise through the generally elongated, hollow airfoil;

a trailing edge cooling chamber positioned proximate to the trailing edge of the generally elongated, hollow airfoil and extending generally spanwise through the generally elongated, hollow airfoil;

wherein the pressure side near wall cooling chamber extends from the leading edge cooling chamber to the trailing edge cooling chamber and includes a plurality of pin fins extending from the outerwall to the inner wall;

wherein the suction side near wall cooling chamber extends from the leading edge cooling chamber to the trailing edge cooling chamber and includes a plurality of pin fins extending from the outerwall to the inner wall; and

wherein the pressure side near wall cooling chamber has an inlet providing cooling fluids from proximate to the leading edge such that cooling fluids flow in a direction from the leading edge toward the trailing edge and the suction side near wall cooling chamber has an inlet proximate to the trailing edge cooling chamber from the pressure side near wall cooling chamber such that cooling fluids flow in a direction from the trailing edge toward the leading edge establishing a counterflow, wherein the pressure side and suction side near wall cooling chambers are separated by a rib at the leading edge.

2. The turbine airfoil of claim 1, wherein the plurality of pin fins in the pressure side near wall cooling chamber are formed from a first region having pin fins with first cross-sectional area with a shape and a second region having pin fins with a second cross-sectional area with the same shape that is greater than the first cross-sectional area.

3. The turbine airfoil of claim 1, wherein the plurality of pin fins in the pressure side near wall cooling chamber are formed from a first region in a first quantity per unit area and a second region having pin fins in a second quantity per unit area that is greater than the first quantity per unit area.

4. The turbine airfoil of claim 1, wherein the plurality of pin fins in the pressure side near wall cooling chamber are aligned in rows of pin fins extending generally spanwise.

5. The turbine airfoil of claim 4, further comprising trip strips extending between the pin fins.

6. The turbine airfoil of claim 1, wherein the plurality of pin fins in the pressure side near wall cooling chamber are aligned in rows of pin fins extending at an acute angle between a chordwise and spanwise directions.

7. The turbine airfoil of claim 6, further comprising trip strips extending between the pin fins.

8. The turbine airfoil of claim 1, wherein the plurality of pin fins in the suction side near wall cooling chamber are formed from a first region having pin fins with a first cross-sectional area with a shape and a second region having pin fins with a second cross-sectional area with the same shape that is greater than the first cross-sectional area.

9. The turbine airfoil of claim 1, wherein the plurality of pin fins in the suction side near wall cooling chamber are formed from a first region in a first quantity per unit area and a second region having pin fins in a second quantity per unit area that is greater than the first quantity per unit area.

10. The turbine airfoil of claim 1, wherein the plurality of pin fins in the suction side near wall cooling chamber are aligned in rows of pin fins extending generally spanwise.

11. The turbine airfoil of claim 10, further comprising trip strips extending between the pin fins.

12. The turbine airfoil of claim 1, wherein the plurality of pin fins in the suction side near wall cooling chamber are aligned in rows of pin fins extending at an acute angle between a chordwise and spanwise directions.

13. The turbine airfoil of claim 12, further comprising trip strips extending between the pin fins.

14. The turbine airfoil of claim 1, further comprising pin fins positioned in the trailing edge cooling chamber.

15. The turbine airfoil of claim 1, further comprising at least one refresh hole in the inner wall separating the leading edge cooling chamber from the trailing edge cooling chamber.

16. The turbine airfoil of claim 1, further comprising a central cooling fluid supply channel positioned between the pressure side and suction side near wall cooling chambers, formed by a second inner wall and extending from the leading edge cooling chamber to the trailing edge cooling chamber.

17. (canceled)

18. A turbine airfoil, comprising:

a generally elongated, hollow airfoil 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;

an outer wall forming the generally elongated airfoil;

an inner wall positioned in close proximity to the outer wall forming a suction side near wall cooling chamber proximate to a suction side of the generally elongated, hollow airfoil and a pressure side cooling chamber proximate to a pressure side of the generally elongated, hollow airfoil, wherein the pressure side cooling chamber is adjacent to the suction side near wall cooling chamber;

a leading edge cooling chamber positioned proximate to the leading edge of the generally elongated, hollow airfoil and extending generally spanwise through the generally elongated, hollow airfoil;

a trailing edge cooling slots positioned proximate to the trailing edge of the generally elongated, hollow airfoil;

wherein the suction side near wall cooling chamber extends from the leading edge cooling chamber to the trailing edge cooling slots and includes a plurality of pin fins extending from the outerwall to the inner wall;

wherein the pressure side near wall cooling chamber extends from the leading edge cooling chamber to the trailing edge cooling chamber and includes a plurality of pin fins extending from the outerwall to the inner wall; and

wherein the pressure side near wall cooling chamber has an inlet providing cooling fluids from proximate to the leading edge such that cooling fluids flow in a direction from the leading edge toward the trailing edge and the suction side near wall cooling chamber has an inlet proximate to the trailing edge cooling chamber from the pressure side near wall cooling chamber such that cooling fluids flow in a direction from the trailing edge toward the leading edge establishing a counterflow, wherein the pressure side and suction side near wall cooling chambers are separated by a rib at the leading edge.

19. The turbine airfoil of claim 18, wherein the plurality of pin fins in the suction side near wall cooling chamber are formed from a first region having fin pins with first cross-sectional area with a shape and a second region having pin fins with a second cross-sectional area with the same shape that is greater than the first cross-sectional area and wherein the plurality of pin fins in the second region of the suction side near wall cooling chamber are aligned in rows of pin fins extending generally spanwise and wherein the plurality of pin fins in the first region of the suction side near wall cooling chamber are aligned in rows of pin fins extending at an acute angle between a chordwise and spanwise directions.

20. The turbine airfoil of claim 18, wherein the plurality of pin fins in the pressure side cooling chamber are formed from a first region having fin pins with first cross-sectional area and a second region having pin fins with a second cross-sectional area that is greater than the first cross-sectional area.