SYSTEM AND METHOD FOR ADAPTIVE IMPINGEMENT COOLING
An adaptive cooling structure comprises a mounting support, a liner, and a spacer. The mounting support has a coolant aperture for directing cooling air through the support. The liner has a first surface facing away from the mounting support and a second surface facing towards the support. The liner is coupled to the mounting support, and the spacer is positioned between the support and the liner. The positioning of the spacer creates a chamber between the mounting support and the liner, thus allowing the cooling air to impinge on the second surface of the liner. The liner wall is configured to deflect away from the mounting support to expand the chamber, thus allowing the cooling air to further impinge on the second surface of the liner.
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The present invention relates to cooling systems, and in particular, to a system and method for adaptive impingement cooling for use in hot environments such as those found in gas turbine engines.
Gas turbine engines operate according to a continuous Brayton cycle where a pressurized air and fuel mixture is ignited in a combustor to produce a flowing stream of hot gas. The air is compressed, used for combustion, expands through a turbine, and finally exits the engine. Some gas turbine engines also include an augmentation system downstream of the turbine, where fuel is also introduced and ignited to increase thrust. Most often, the temperature of the primary air is higher than the melting temperatures of the materials that form the combustor, turbine, and augmentation system components. As a result, adequate cooling is integral to the function of gas turbine engines.
It is common to combine the benefits of both impingement cooling and film cooling in gas turbine engines. This combination of impingement and film cooling is particularly useful in parts such as combustors and augmentation systems where local hot spots develop. Current practice is to design impingement cooling structures neglecting the deformation that occurs in local hot spots as the temperature in the hot spots increases. As a result, impingement cooling effectiveness decreases as the deformation develops, causing hot spots to become even hotter. Cooling effectiveness should be the highest at local hot spots.
SUMMARYAn adaptive cooling structure comprises a mounting support, a liner, and a spacer. The mounting support has a coolant aperture for directing cooling air through the support. The liner has a first surface facing away from the mounting support and a second surface facing towards the support. The liner is coupled to the mounting support, and the spacer is positioned between the support and the liner. The positioning of the spacer creates a chamber between the mounting support and the liner, thus allowing the cooling air to impinge on the second surface of the liner. The liner wall is configured to deflect away from the mounting support to expand the chamber, thus allowing the cooling air to further impinge on the second surface of the liner.
Ambient air AAmbient enters turbofan engine 10 at inlet 38 through drive fan 16. Drive fan 16 is rotated by low pressure turbine 26 to accelerate AAmbient thereby producing a major portion of the thrust output of turbofan engine 10. Accelerated AAmbient is divided into two streams of air: primary air AP and secondary air AS. Secondary air AS, also known as bypass air, passes into fan duct 14 where it passes on to augmentation system 12. Primary air AP, also known as hot air, is a stream of air that is directed first into low pressure compressor 18 and then into high pressure compressor 20. Pressurized primary air AP is then passed into combustor 22 where it is mixed with a fuel supply and ignited to produce the high energy gases used to turn high pressure turbine 24 and low pressure turbine 26. Combusted primary air AP and secondary air AS are passed through augmentor duct 34 and into augmentation system 12 where a secondary combustion process can be carried out. Augmentation liner 36 prevents heat damage to augmentation system 12 and turbofan engine 10. Exhausted air AEx exits turbofan engine 10 through exhaust nozzle 28. The adaptive cooling structure of the present invention can be used in combustor 22 or augmentation system 12.
Referring now to
Coolant apertures 62 in mounting support 44 direct cooling air AC, such as pressurized air bled from compressor 18 or 20 (
The present invention combines the benefits of both impingement cooling and film cooling and is particularly useful in parts such as combustor 22 and augmentation system 12 (
Adaptive cooling structure 40 is directly exposed to hot air Ap. Cooling air AC flows through coolant apertures 62 and enters chamber 70, impinging on second surface 54. Cooling air AC exits first surface 52 through film apertures 50 in liner wall 48, forming a film. Film apertures 50 have a circular cross section, but can have a non-circular cross section or can be flared. Film apertures 50 are angled with the flow of hot air AP. In alternative embodiments, film apertures 50 can be at another angle or can be perpendicular to the flow. The location of coolant apertures 62 is staggered in relation to film apertures 50. In alternative embodiments, the location of coolant apertures 62 can be aligned with film apertures 50 or completely independent of the location of film apertures 50.
In impingement cooling a ratio L/D of distance L to diameter D of approximately three provides a preferred impingement heat transfer coefficient. When hot spot location 60 causes liner wall 48 to deflect away from mounting support 44 (as seen in
Cooling air AC flows through coolant apertures 62 and enters chamber 70, impinging on second surface 54. Cooling air AC exits first surface 52 through film apertures 50 in liner wall 48, forming a film. Impingement effectiveness is increased at hot spot location 60 as a result of the deflection of liner 48 away from mounting support 44. As discussed in relation to
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims
1. A structure for adaptive cooling comprising:
- a mounting support having a coolant aperture for directing cooling air through the mounting support;
- a liner coupled to the mounting support, including a wall having a first surface facing away from the mounting support and a second surface facing toward the mounting support;
- a spacer positioned between the mounting support and the liner, the spacer creating a chamber between the mounting support and the liner, thus allowing the cooling air to impinge on the second surface of the liner; and
- wherein the liner wall is configured to deflect away when exposed to hot air from the mounting support to expand the chamber, thus allowing the cooling air to further impinge on the second surface of the liner.
2. The structure of claim 1, wherein the spacer positions the liner a distance away from the mounting support to provide impingement cooling at a first rate, and wherein the liner is configured to deflect an amount to increase the distance such that impingement cooling is provided at a second, greater rate.
3. The structure of claim 1, wherein the liner permits the cooling air to pass through and exit the first surface, forming a film.
4. The structure of claim 1, wherein the coolant aperture has a diameter D, the chamber has a distance L between the liner and the support that is less than three times the value of D, and the liner wall deflects away from the mounting support when exposed to hot air, increasing L to approximately three times the value of D.
5. The structure of claim 1, wherein a mounting post with a threaded stud extends from the second surface of the liner wall and through the support, the mounting post is surrounded by a washer acting as the spacer between the support and the liner, and a nut secures the mounting post to the support.
6. The structure of claim 1, wherein the first surface is a hot surface with a hot spot location, and the hot spot location causes the liner wall to deflect away from the mounting support.
7. The structure of claim 1, wherein the liner is an impingement film cooled panel acting as a heat shield in a gas turbine combustor.
8. The structure of claim 1, wherein the liner is an impingement film cooled liner in a gas turbine augmenter.
9. A method of adaptively cooling a liner coupled to a support with a spacer positioned between the liner and the support, the method comprising:
- introducing cooling air into a coolant aperture in the support;
- directing the cooling air into a chamber between the support and the liner and impinging the cooling air against the liner at a first rate;
- deflecting the liner away from the mounting support, expanding the chamber; and
- directing the cooling air into the chamber and further impinging the cooling air against the liner at a second rate.
10. The method of claim 9, wherein the spacer positions the liner a distance away from the mounting support to provide impingement cooling at the first rate, and wherein the liner is configured to deflect an amount to increase the distance such that impingement cooling is provided at the second rate.
11. The method of claim 10, wherein the second rate is greater than the first rate.
12. The method of claim 9, wherein the coolant aperture has a diameter D, the chamber has a distance L between the liner and support that is less than three times the value of D, and the deflecting step causes the liner to deflect away from the mounting support, increasing L to between approximately one to four times the value of D.
13. The method of claim 10, wherein the deflecting step causes the liner to deflect away from the mounting support, increasing L to between approximately two to four times the value of D.
14. The method of claim 10, wherein the deflecting step causes the liner to deflect away from the mounting support, increasing L to approximately three times the value of D.
15. The method of claim 10, wherein the chamber has a distance L between the liner and support that is between approximately two to three times the value of D, and the deflecting step causes the liner to deflect away from the mounting support, increasing L to between approximately two to four times the value of D.
16. The method of claim 13, wherein the deflecting step causes the liner to deflect away from the mounting support, increasing L to between approximately 2.5 to 3.5 times the value of D.
17. The method of claim 13, wherein the deflecting step causes the liner to deflect away from the mounting support, increasing L to approximately three times the value of D.
18. The method of claim 9, and further comprising:
- directing the cooling air to pass through the liner and exit the first surface, forming a film.
19. The method of claim 9, wherein a hot spot location on the liner causes the deflecting step.
20. The method of claim 9, wherein the liner is an impingement film cooled panel acting as a heat shield in a gas turbine combustor and the liner is exposed directly to hot air.
21. The method of claim 9, wherein the liner is an impingement film cooled liner in a gas turbine augmenter and the liner is exposed directly to hot air.
Type: Application
Filed: Jun 30, 2011
Publication Date: Jan 3, 2013
Applicant: UNITED TECHNOLOGIES CORPORATION (Hartford, CT)
Inventor: James A. Dierberger (Hebron, CT)
Application Number: 13/174,166
International Classification: F23R 3/42 (20060101); F28F 9/007 (20060101);