Airfoil with customized convective cooling
An airfoil suitable for use in the turbine section of a jet engine. Said airfoil contains a core having a passage for conducting a coolant through said airfoil and discharging the coolant through a radially disposed slot at the trailing edge of the airfoil. A flow barrier is mounted adjacent to the discharge slot within the flow passage which contains openings for tailoring the coolant flow distribution profile in the trailing edge region based upon some identifiable airfoil property such as the airfoil's pressure and/or temperature profile, or a combination of the pressure and temperature profiles.
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The United States Government has certain rights in this invention pursuant to Contract No. N00019-02-C-3003 between the United States Navy and United Technologies Corporation.
FIELD OF THE INVENTIONThis invention relates to the internal cooling of an airfoil employed in a rotary machine and, in particular, to controlled internal cooling of a jet engine turbine blade. Background of the Invention
The term airfoil, as herein used, refers to either a rotor blade or a stator vane of the type employed in many types of rotary machine such as gas turbines, compressors, and the like. In the case of a jet engine turbine blade, for example, a coolant is typically introduced into the core of the blade through the blade root and is circulated through a core passage and finally discharged through a radially extended window or slotted opening located along the trailing edge of the airfoil. As disclosed in U.S. Pat. No. 6,637,500 to Shah et al., pedestals fabricated of core materials are placed in the coolant flow passage near the discharge slot to meter flow, augment the flow, provide convective surface area and provide additional strength in this area. The pedestals are generally spaced apart at the same distance and the coolant flow at the trailing edge of the blade is generally uniform over the radial span of the blade.
SUMMARY OF THE INVENTIONIt is therefore an object of this invention to improve the internal convective cooling of an airfoil employed in a rotary machine.
It is a further object of the present invention to improve the internal convective cooling of a turbine blade utilized in a jet engine.
A still further object of the present invention is to tailor the flow profile of a coolant moving through the core of an airfoil to provide controlled cooling to regions of the airfoil which require more or less cooling.
Another object of the present invention is to contour the trailing edge flow of a cooling that is moving internally through an airfoil with particular regard to the temperature or pressure profile over the span of the airfoil or a combination of the two.
These and other objects of the invention are attained by means of an airfoil having an internal flow passage for routing a coolant through the core of the airfoil and discharging the coolant through a slot or window radially extended along the trailing edge of the airfoil. In the practice of the present invention, the trailing edge flow is governed by the pressure ratio over the trailing edge of the airfoil and a control barrier that is placed in the edge flow to selectively distribute the flow over the radial span of the airfoil in response to some identifiable characteristic of the airfoil such as the radial pressure or temperature profile of the airfoil or both.
For a better understanding of these and other objects of the invention, reference will be made to the following detailed description of the invention, which is to be read in association with the following drawings, wherein:
Referring initially to
With further reference to
Blockage is the ratio of closed to open areas within the flow path in the trailing edge region. The external discharge pressure can vary significantly along the radial span of the airfoil, and as a result, the flow field along the trailing edge will be non-uniform where the blockage in the trailing edge region is relatively constant. The heat loading upon the airfoil can also vary significantly along the radial span. Accordingly, the amount of convective cooling required at various span locations will vary with respect to the temperature and pressure trailing edge profiles of the airfoil. Additionally, the amount of convective cooling potential, as a function of mass flow rates at various span locations, will vary with respect to the external trailing edge pressure profile. Typical pressure and temperature profiles are depicted in
With further reference to
In this embodiment of the invention, banks of cylindrical pedestals 50-50 that are fabricated of the core material extend perpendicularly across the trailing edge flow path adjacent to the discharge window or slots. As illustrated in
The profile of the trailing edge flow is tailored in the embodiment of the invention such that internal convection levels result in metal temperatures which meet oxidation, creep, and thermal mechanical fatigue life requirements. Conversely, the flow distribution may be varied to reduce convection so that coolant heatup along a passage is minimized, and thus allowing for more available heat flux potential in downstream regions.
Although cylindrical pedestals are employed in this embodiment of the invention to establish blockage within the trailing edge flow, any type of barrier may be used in the practice of the invention which serves to tailor the flow distribution into a desired profile. For example, a wall or a series of walls can be erected in the discharge flow path having openings of various sizes and/or shapes located within the wall which serve to tailor the flow distribution into a desired profile. Here again, the barrier or barriers may be fabricated of any known core material.
As illustrated in
Customizing of the above noted basic system provides for trailing edge flow reduction and Mach number benefits. As illustrated in
While this invention has been particularly shown and described with reference to the preferred embodiment in the drawings, it will be understood by one skilled in the art that various changes in its details may be effected therein without departing from the teachings of the invention.
Claims
1. An airfoil having a core containing passage for conducting a coolant through the airfoil and discharging the coolant through a slot extending radially along the trailing edge of the airfoil, wherein said airfoil further includes:
- a flow barrier mounted adjacent to said slot for presenting blockage to coolant moving through the trailing edge region of the airflow; and
- said flow barrier having openings therein for tailoring the coolant trailing edge flow profile along the radial span of the airfoil.
2. The airfoil of claim 1, wherein said barrier is fabricated of the same material as the airfoil core.
3. The airfoil of claim 1, wherein said barrier is fabricated of a material that is different from the core material.
4. The airfoil of claim 1, wherein said barrier is constructed of a ceramic material.
5. The airfoil of claim 1, wherein the barrier is constructed of a material containing a refractory metal.
6. The airfoil of claim 1, wherein said coolant is air.
7. The airfoil of claim 1, wherein the coolant trailing edge flow profile is based upon the pressure profile along the radial span of the airfoil.
8. The airfoil of claim 1, wherein the coolant trailing edge flow profile is based upon the temperature profile along the radial span of the airfoil.
9. The airfoil of claim 1, wherein said barrier contains a plurality of spaced apart cylindrical pedestals that are mounted perpendicularly to the coolant trailing edge flow.
10. The airfoil of claim 9, wherein the coolant flow profile is generated by varying the gap between the adjacent pedestals.
11. The airfoil of claim 9, wherein the coolant flow profile is generated by varying the pedestal diameters.
12. The airfoil of claim 1, wherein the coolant trailing edge flow profile is based upon both the pressure profile and the temperature profile along the radial span of the blade.
13. The airfoil of claim 1, wherein said barrier is at least one wall that is mounted adjacent to the trailing edge slot, said wall containing holes passing there through for tailoring the trailing edge flow distribution profile of the coolant.
14. The airflow of claim 13, wherein the coolant flow profile is generated by varying the size or shape of said openings.
Type: Application
Filed: Aug 1, 2006
Publication Date: Feb 7, 2008
Applicant:
Inventors: Matthew A. Devore (Manchester, CT), Corneil S. Paauwe (Manchester, CT)
Application Number: 11/497,094
International Classification: F01D 5/18 (20060101);