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The subject invention relates to turbines. More particularly, the subject invention relates to film cooling of turbine components.
Components in the hot gas path of turbines, for example, gas turbines, are subjected to high temperatures which leads to low cycle fatigue cracking, creep rupture, and/or oxidation and the like which causes premature failure of the components. One or more methods are often employed to cool the hot gas path components to extend their useful lives. One such method is film cooling. Film cooling is accomplished by injecting air through holes in the surface of the component, from a source such as compressor bleed flow which bypasses a combustor. The relatively cooler air enters the hot gas path and forms an insulating layer between the hot gas and the component and reduces heat flux into the component.
An increase in the volume of air bled from the compressor, however, has a negative impact on an overall turbine efficiency. It is therefore desirable to increase an effectiveness of film cooling such that less air needs to be bled from the compressor and injected through the holes in order to achieve an acceptable amount of cooling.
A turbine component includes a flow path surface and a trench disposed in the flow path surface. At least one cooling through hole is located in the trench and is capable of injecting a cooling flow onto the flow path surface of the turbine component. The cooling flow forms a cooling film on the flow path surface.
A method of cooling a turbine component includes injecting a cooling flow onto a flow path surface of the turbine component through at least one cooling through hole disposed in a trench in the turbine component. A cooling film is formed by the cooling flow between the flow path surface and a hot gas flow.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a partial perspective view of an embodiment of a turbine component having flow diverters for film cooling;
FIG. 2 is a cross-sectional view of the turbine component of FIG. 1;
FIG. 3 is an axial cross-sectional view of the turbine component of FIG. 1;
FIG. 4 is a partial perspective view of another embodiment of a turbine component having flow diverters for film cooling;
FIG. 5 is a partial perspective view of an alternative embodiment of the turbine component of FIG. 4; and
FIG. 6 is a partial perspective view of yet another embodiment of a turbine component having flow diverters for film cooling.
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
A partial view of a turbine component, for example, a turbine airfoil 10 is shown in FIG. 1. Hot gas flow 12 proceeds across an outer surface 14 of the turbine airfoil 10 in a flow direction 16. At least one trench 18 is disposed in the turbine airfoil 10 and is defined by an upstream trench wall 20 which, in some embodiments extends substantially radially outward from the turbine airfoil 10, and at least one downstream trench surface 22. At least one cooling through hole 24 is disposed in the trench 18. In FIG. 1, a plurality of cooling through holes 24 are arranged substantially in a line extending radially along the trench 18, but other arrangements of cooling through holes 24 in the trench 18 are contemplated within the scope of the present disclosure. The cooling through holes 24 may have an elliptical opening as shown in FIG. 1, or may have circular or other-shaped openings depending on desired flow from the cooling through holes 24. Further, as shown in FIG. 2, the cooling through holes 24 may have an axis 26 which is not perpendicular to the outer surface 14, to facilitate smoother flow through the cooling through holes 24.
Referring again to FIG. 1, the downstream trench surface 22 slopes radially outwardly from a trench floor 28. This prevents a cooling flow 30 exiting the cooling through holes 24 from blowing off of the outer surface 14 and into the hot gas flow 12. At least one flow diverter 32 is disposed at the downstream trench surface 22. Each flow diverter 32 includes a downstream wall 34 which, in the embodiment of FIG. 1, is disposed axially downstream from and substantially perpendicular to the flow direction 16 such that cooling flow 30 exiting the cooling through hole 24 is diverted or split as shown in FIG. 1. In some embodiments the downstream wall 34 is disposed at a substantially same lateral position as a corresponding cooling through hole 24. The cooling flow 30 divides and flows laterally around the downstream wall 34 and along the downstream trench surface 22. A portion of the cooling flow 30 may flow radially outboard of the downstream wall 34 and proceed along the outer surface 14. Each flow diverter 32 includes two diverter sidewalls 36. Each diverter sidewall 36 extends from the downstream wall 34 at a sidewall angle 38 which in some embodiments may be toward a diverter sidewall 36 of an adjacent flow diverter 32. In the embodiment shown in FIG. 1, the sidewall angles 38 are equal, but it is to be appreciated that embodiments where sidewall angles 38 differ for one or more sidewalls 36 are contemplated within the present scope. Utilizing flow diverters 32 causes the cooling flow 30 to spread over a greater portion of the turbine airfoil 10 thus providing more effective cooling of the turbine airfoil 10. A width 40 of the downstream wall 32 and/or the sidewall angle 38 can be varied to provide a desired amount of spread of the cooling flow 28. Further, as shown in FIG. 3, the diverter sidewalls 36 of adjacent flow diverters form a flow channel 42 preventing hot gas flow 12 from flowing between the cooling flow 30 and the downstream trench surface 22 thus preventing mixing of the hot gas flow 12 and the cooling flow 30.
Referring now to FIG. 4, in an alternative embodiment each flow diverter 32 comprises two diverter sidewalls 36 converging at a vertex 44 located axially downstream from, and at a substantially same lateral position as a corresponding cooling through hole 24 such that cooling flow 30 exiting the cooling through hole 24 is split or diverted as shown in FIG. 4. Each diverter sidewall 36 is disposed at a sidewall angle 38 and extends toward a diverter sidewall 36 of an adjacent flow diverter 32. The flow diverter 32 including a vertex 44 prevents a vortex from forming in the cooling flow 30 at an exit of the cooling through hole 24, as well as causes the cooling flow 30 to spread over a greater portion of the turbine airfoil 10. Referring now to FIG. 5, each vertex 44 may be disposed at least partially within a corresponding cooling through hole 24. A flow diverter 32 of this configuration is capable of splitting or diverting the cooling flow 30 as the cooling flow 30 exits the cooling through hole 24.
In an alternative embodiment shown in FIG. 6, each flow diverter 32 is disposed laterally substantially between two cooling through holes 24. As above, each flow diverter 32 includes a downstream wall 34 and two diverter sidewalls 36 disposed at a sidewall angle 38. In this embodiment, the sidewall angles 38 are such that each diverter sidewall 36 extends toward convergence with the other diverter sidewall 36 of the same flow diverter 32. In this embodiment, the cooling flow 30 does not split upon exit from the cooling through hole 24, but spreads across the flow channel 42 between adjacent flow diverters 32.
As stated above, the cooling through holes 24 may have a number of shapes. The cooling through holes 24 shown in FIG. 6 include a diffusion surface 46 located at a downstream exit portion of the cooling through hole 24 and which slopes radially inward below the trench floor 28. Cooling through holes 24 including the diffusion surface 46 provide additionally smooth transition of cooling flow 30 from the cooling through holes 24 to the outer surface 14 preventing blowing off of the cooling flow 30 into the hot gas flow 12. In the embodiment shown in FIG. 6, an edge 48 of the diffusion surface is coplanar with the diverter sidewall 36, but other configurations and alignments of the edge 48 relative to the diverter sidewall 36 are contemplated within the present scope.
In some embodiments, the turbine airfoil 10 comprises a substrate layer 50 and a coating layer 52, which may include a thermal barrier coating (TBC) to provide additional thermal protection of the substrate layer 50. As shown in FIG. 6, the cooling through holes 24 are disposed in the substrate layer 50 while the flow diverters 32, upstream trench wall 20 and downstream trench surface 22 are disposed in the coating layer 52 and may be formed from TBC.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.