Counter-vortex paired film cooling hole design
An apparatus for use in a gas turbine engine includes a wall defining an exterior face, a first film cooling passage extending through the wall for providing film cooling to the exterior face of the wall, and a second film cooling passage extending through the wall adjacent to the first film cooling passage for providing film cooling to the exterior face of the wall. The first film passage includes a first vortex-generating structure for inducing a vortex in a first rotational direction in a cooling fluid passing therethrough, and the second film passage includes a second vortex-generating structure for inducing a vortex in a second rotational direction in a cooling fluid passing therethrough. The first and second rotational directions are substantially opposite one another.
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The present invention relates to film cooling, and more particularly to structures and methods for providing vortex film cooling flows along gas turbine engine components.
Gas turbine engines utilize hot fluid flows in order to generate thrust or other usable power. Modern gas turbine engines have increased working fluid temperatures in order to increase engine operating efficiency. However, such high temperature fluids pose a risk of damage to engine components, such as turbine blades and vanes. High melting point superalloys and specialized coatings (e.g., thermal barrier coatings) have been used to help avoid thermally induced damage to engine components, but operating temperatures in modern gas turbine engines can still exceed superalloy melting points and coatings can become damaged or otherwise fail over time.
Cooling fluids have also been used to protect engine components, often in conjunction with the use of high temperature alloys and specialized coatings. One method of using cooling fluids is called impingement cooling, which involves directing a relatively cool fluid (e.g., compressor bleed air) against a surface of a component exposed to high temperatures in order to absorb thermal energy into the cooling fluid that is then carried away from the component to cool it. Impingement cooling is typically implemented with internal cooling passages. However, impingement cooling alone may not be sufficient to maintain suitable component temperatures in operation. An alternative method of using cooling fluids is called film cooling, which involves providing a flow of relatively cool fluid from film cooling holes in order to create a thermally insulative barrier between a surface of a component and a relatively hot fluid flow. Problems with film cooling include flow separation or “liftoff”, where the film cooling flow lifts off the surface of the component desired to be cooled, undesirably allowing hot fluids to reach the surface of the component. Film cooling fluid liftoff can necessitate additional, more closely-spaced film cooling holes to achieve a given level of cooling. Cooling flows of any type can present efficiency loss for an engine. The more fluid that is redirected within an engine for cooling purposes, the less efficient the engine tends to be in producing thrust or another usable power output. Therefore, fewer and smaller cooling holes with less dense cooling hole patterns are desirable.
The present invention provides an alternative method and apparatus for film cooling gas turbine engine components.
SUMMARYAn apparatus for use in a gas turbine engine includes a wall defining an exterior face, a first film cooling passage extending through the wall for providing film cooling to the exterior face of the wall, and a second film cooling passage extending through the wall adjacent to the first film cooling passage for providing film cooling to the exterior face of the wall. The first film passage includes a first vortex-generating structure for inducing a vortex in a first rotational direction in a cooling fluid passing therethrough, and the second film passage includes a second vortex-generating structure for inducing a vortex in a second rotational direction in a cooling fluid passing therethrough. The first and second rotational directions are substantially opposite one another.
The present invention, in general, relates to structures and methods for generating a counter-rotating vortex film cooling flow along a surface of a component for a gas turbine engine exposed to hot gases, such as a turbine blade, vane, shroud, duct wall, etc. Such a film cooling flow can provide a thermally insulative barrier between the gas turbine engine component and the hot gases. According to the present invention, a pair of film cooling passages have closely-spaced outlets at an exterior surface (or face) of the component that is exposed to the hot gases. A vortex-generating structure is positioned within each film cooling passage of the pair to generate a vortex flow. The vortex flow generated within a first of the pair of film cooling passages rotates in a first rotational direction therein, prior to reaching an outlet, and the vortex flow generated within a second of the pair of film cooling passages rotates in a substantially opposite direction (i.e., counter-rotates with respect to the first rotational direction). In one embodiment of the present invention, the vortex-generating structures can comprise helical ribs (or rifling), with the helical ribs of the first and second film cooling passages winding in opposite directions. Additional features and benefits of the present invention will be recognized in light of the description that follows.
The first and second vortex-generating structures 40A and 40B respectively can have nearly any desired cross-sectional shape (or profile).
The following are descriptions of particular dimensions and proportions for exemplary embodiments of the present invention. These embodiments are provided merely by way of example and not limitation. The first and second film cooling passages 36A and 36B and the first and second vortex-generating structures 40A and 40B can be described as having vortex generating structures with a pitch P that is a multiple of a radius R, where P represents either the pitch PA or PB and R represents the corresponding radius RA or RB. The pitch P can be in the range of approximately 1 to 10 times the radius R, or alternatively in the range of approximately 1.5 to 3 times the radius R.
A ratio of the height of vortex-generating structure Ht over the diameter of the associated film cooling passage (i.e., two time the radius RA or RB) can be between approximately 0.05 and 0.5, or alternatively between approximately 0.1 and 0.3. A ratio of the width Wt over the height Ht of the vortex-generating structures 40A and 40B can be between approximately 0.5 and 4, or alternatively between approximately 0.5 and 1.5. The distance S between the axes 50A and 50B can be less than approximately ten times the radius R, or alternatively between approximately two to six times the radius R. Furthermore, a length of the first and second film cooling passages 36A and 36B respectively can be at least approximately three to ten times a hydraulic diameter at the respective first and second outlets 38A and 38B, or alternatively at least approximately 5 to ten times the hydraulic diameter at the respective first and second outlets 38A and 38B (where the hydraulic diameter is four times the area divided by the perimeter).
The present invention provides numerous advantages. For example, while mixing of film cooling fluid jets with hot gas flows represents an efficiency loss, that loss is balanced against improved film cooling effectiveness per film cooling passage. This can permit a given level of film cooling to be provided to a given component with a relatively small number of film cooling passages for a given film cooling fluid flow rate and/or increasing spacing between pairs of cooling hole outlets. Moreover, even with the presence of paired, closely spaced cooling hole outlets, the present invention can provide film cooling to a given surface area with a relatively low density of cooling holes and a relatively low total cooling hole area. Film cooling according to the present invention can help allow gas turbine engine components to operate in higher temperature environments with a relatively low risk of thermal damage.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For instance, the particular angle of film cooling passages relative to a film cooled surface can vary as desired for particular applications. Moreover, a cross-sectional area of film cooling passages of the present invention can vary over their length (e.g., with substantially conical film cooling passages).
Claims
1. An apparatus for use in a gas turbine engine, the apparatus comprising:
- a wall defining an exterior face;
- a first film cooling passage extending through the wall for providing film cooling to the exterior face of the wall, wherein the first film passage includes a first vortex-generating structure for inducing a vortex in a first rotational direction in a cooling fluid passing therethrough; and
- a second film cooling passage extending through the wall adjacent to the first film cooling passage for providing film cooling to the exterior face of the wall, wherein the second film passage includes a second vortex-generating structure for inducing a vortex in a second rotational direction in a cooling fluid passing therethrough, and wherein the first and second rotational directions are substantially opposite one another.
2. The apparatus of claim 1, wherein the first vortex-generating structure comprises a first helical rib disposed along an interior surface of the first film cooling passage.
3. The apparatus of claim 2, wherein the second vortex-generating structure comprises a second helical rib disposed along an interior surface of the second film cooling passage, and wherein the first and second helical ribs of the first and second vortex-generating structures wind about respective central axes in opposite directions.
4. The apparatus of claim 1, wherein the first and second vortex-generating structures are configured as mirror images of one another.
5. The apparatus of claim 1, wherein the first and second film cooling passages have respective first and second outlets closely spaced from each other along the exterior face of the wall.
6. The apparatus of claim 5, wherein the first and second film cooling passages define respective first and second central axes, wherein the first film cooling passage defines a first diameter, and wherein the first and second central axes are spaced from each other by a distance less than or equal to approximately ten times the first diameter.
7. The apparatus of claim 1, wherein the first and second film cooling passages are both substantially cylindrically-shaped.
8. The apparatus of claim 1, wherein the first and second film cooling passages are arranged substantially parallel to each other.
9. The apparatus of claim 1, wherein the first and second rotational directions are arranged to flow generally toward the exterior face of the wall at a location where the vortexes adjoin each other.
10. An apparatus for use in a gas turbine engine, the apparatus comprising:
- a wall defining an exterior face;
- a pair of closely spaced film cooling passages extending through the wall for providing film cooling to the exterior face of the wall, the pair comprising: a first film cooling passage extending to a first outlet on the exterior face of the wall, wherein the first film passage includes a first helically-shaped vortex-generating structure disposed along an interior surface of the first film cooling passage for inducing a vortex in a first rotational direction in a cooling fluid passing therethrough; and a second film cooling passage extending to a second outlet on the exterior face of the wall, wherein the second film passage includes a second helically-shaped vortex-generating structure disposed along an interior surface of the second film cooling passage for inducing a vortex in a second rotational direction in a cooling fluid passing therethrough.
11. The apparatus of claim 10, wherein the first and second vortex-generating structures are configured as substantially mirror images of each other.
12. The apparatus of claim 10, wherein the first and second rotational directions are arranged to flow generally toward the exterior face of the wall at a location where the vortexes adjoin each other.
13. The apparatus of claim 10, wherein the first and second film cooling passages define respective first and second central axes, wherein the first film cooling passage defines a first diameter, and wherein the first and second central axes are spaced from each other by a distance less than or equal to approximately ten times the first diameter.
14. The apparatus of claim 10, wherein the first and second film cooling passages are both substantially cylindrically-shaped.
15. The apparatus of claim 10, wherein the first and second film cooling passages extend substantially parallel to each other through the wall.
16. The apparatus of claim 10, wherein the first and second rotational directions are substantially opposite one another.
17. A method of film cooling a gas turbine engine component exposed to a hot fluid stream, the method comprising:
- directing a cooling fluid into a first film cooling passage of the component;
- passing the cooling fluid over at least one first vortex-generating structure to rotate a portion of the cooling fluid within the first film cooling passage in a first rotational direction;
- directing a cooling fluid into a second film cooling passage of the component;
- passing the cooling fluid over at least one second vortex-generating structure to rotate a portion of the cooling fluid within the second film cooling passage in a second rotational direction that counter-rotates with respect to the first rotational direction;
- ejecting the cooling fluid rotating in the first rotational direction out of a first outlet in fluid communication with the first film cooling passage;
- ejecting the cooling fluid rotating in the second rotational direction out of a second outlet in fluid communication with the second film cooling passage, wherein the counter-rotating cooling fluid ejected from the first and second outlets forms a contiguous cooling film jet; and
- passing the counter-rotating cooling film jet along an exterior surface of the component to provide film cooling therealong.
18. The method of claim 17, wherein the counter-rotation of the film cooling jet concentrates mixing with the hot fluid stream at a region spaced away from the exterior surface of the component.
Type: Application
Filed: Jun 6, 2008
Publication Date: Dec 10, 2009
Applicant: United Technologies Corporation (Hartford, CT)
Inventors: Christopher W. Strock (Kennebunk, ME), Paul M. Lutjen (Kennebunkport, ME)
Application Number: 12/157,115
International Classification: F01D 5/18 (20060101);