WO2007050205A2

WO2007050205A2 - Serpentine cooling circuit and method for cooling a gas turbine part

Info

Publication number: WO2007050205A2
Application number: PCT/US2006/036523
Authority: WO
Inventors: Paul M. Lutjen; Gary L. Grogg
Original assignee: United Technologies Corporation
Priority date: 2005-09-19
Filing date: 2006-09-19
Publication date: 2007-05-03
Also published as: WO2007050205A3; US20070227706A1

Abstract

A compact heat exchanger for providing coolant gas flow through a gas turbine component is provided. The compact heat exchanger reduces internal pressure losses through the compact heat exchanger. The compact heat exchanger has at least one inlet through which a coolant gas may enter, a circuit channel in fluid communication with the at least one inlet, and at least one outlet in fluid communication with the circuit channel through which the coolant gas may- exit the circuit channel. The circuit channel is formed from superimposition of a plurality of alternating serpentine circuits, where at least one crossover of the circuit channel has a flow stabilizer that is formed in the channel and reduces internal pressure losses in the circuit channel.

Description

COMPACT HEAT EXCHANGER

GOVERNMENT RIGHTS IN THE INVENTION

[0001] The invention was made by or under contract with the Air Force of the United States Government under contract number F33615-03-D-2354.

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0002] This invention relates to a compact heat exchanger or microcircuit for providing heat dissipation and film protection. More specifically, the invention relates to a linked compact heat exchanger or microcircuit with low levels of internal pressure loss.

2. Description of the Related Art

[0003] As a result of moving at high speeds through gas or having high-speed gas passing over static parts, parts such as turbines employ various techniques to dissipate internal heat, as well as provide a protective cooling film over the surface of the part. One such technique involves the integration of cooling channels into the part through which cool gas can flow, absorbing heat energy, and exiting so as to form a protective film.

[0004] With reference to FIG. 1 , there is illustrated a cooling channel fabricated as a linked microcircuit. This linked microcircuit is the subject of U.S. Patent 6,705,831 to Draper, which is commonly owned with the present application and the disclosure of which is incorporated herein by reference. The linked microcircuit provides coolant gas flow through a part, such as, for example, combustor liners, turbine vanes, turbine blades, turbine BOAS, vane endwalls, and/or airfoil edges. The exemplary embodiment i of the Draper linked microcircuit comprises an inlet through which a coolant gas may enter, a circuit channel extending from the inlet through which the coolant gas may flow and an outlet appended to the circuit channel through which the coolant gas may exit the circuit channel (as depicted in the two sets of arrows). The circuit channel is formed from the superimposition of a plurality of alternating serpentine circuits.

[0005] The linked microcircuit of Draper provides improved thermal coverage while reducing the incongruity of coolant gas properties present at the junctions or crossover points of the component serpentine microcircuits. This is due at least in part to the property that similar points along the circuit channel of the Draper linked microchannel would end up coincident, and the properties of the coolant gases present at any one such point joining after traveling through adjacent circuit channels would be nearly identical. The resulting mixing of gases in the Draper microchannel occurs with a reduction of incongruities in gas temperature or pressure.

[0006] However, the use of serpentine circuit channels having an abrupt 180° turn therein (e.g., adjacent 90° turns), creates internal pressure losses. Thus, there is a need for a microcircuit that reduces internal pressure losses while maintaining the efficiency of heat exchange.

BRIEF SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to provide an improved system and method for heat dissipation and film protection.

[0008] It is a further object of the present invention to provide such a system and method that reduces internal pressure losses.

[0009] It is another object of the present invention to provide such a system and method that improves thermal coverage, while reducing the incongruity of coolant gas properties flowing therein. [0010] A compact heat exchanger for providing coolant gas flow through a part is provided. The compact heat exchanger comprises at least one inlet through which a coolant gas may enter; a circuit channel in fluid communication with the at least one inlet, wherein the circuit channel is formed from superimposition of a plurality of alternating serpentine circuits; and at least one outlet in fluid communication with the circuit channel through which the coolant gas may exit the circuit channel. The at least one crossover of the circuit channel has a flow stabilizer that is formed in the circuit channel. The flow stabilizer reduces internal pressure losses in the circuit channel.

[0011] In another aspect, a method of dispensing heat in a part is provided. The method comprises providing a compact heat exchanger in thermal communication with the part, with the microcircuit being formed from superimposition of a plurality of alternating serpentine circuits that provide adjacent flow paths that converge and/or diverge at crossovers; and directing at least two of the adjacent flow paths to converge or diverge at an angle with respect to each other at one or more of the crossovers.

[0012] The flow stabilizer may direct the flow along a non-orthogonal path. The at least one crossover can be adjacent to the at least one inlet. The flow stabilizer may be positioned along a downstream portion of the at least one crossover. The flow stabilizer can reduce a cross-sectional area of the at least one crossover. The at least one crossover may be positioned along a portion of the part that is in proximity to a low- pressure ratio area.

[0013] The downstream portion of the at least one crossover can be substantially convex. The upstream portion of the at least one crossover may be substantially convex. The upstream and downstream portions of the at least one crossover can be substantially symmetrical. The circuit channel can have a first-cross-sectional area, and the at least one crossover can have a second cross-sectional area that is twice as large as the first cross-sectional area.

[0014] The circuit channel can have a third cross-sectional area, and the first cross- sectional area can be twice as large as the third cross-sectional area. The inner geometry of the first crossover can direct flow in a non-orthogonal path. The downstream portion of the first crossover may be convex. The downstream portion of the second crossover can be planar. The method may further comprise directing one or more of the flow paths to eliminate 90° turns along a portion of the compact heat exchanger that is subject to a low-pressure ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Other uses and advantages of the present invention will become apparent to those skilled in the art upon reference to the specification and the drawings, in which:

[0016] Figure 1 is a schematic view of a linked microcircuit as depicted in U.S. Patent 6,705,831.

[0017] Figure 2 is a cross-sectional view of a gas turbine engine that may employ a compact heat exchanger in accordance with the present invention;

[0018] Figure 3 is a schematic view of an exemplary embodiment of the compact heat exchanger of the present invention; and

[0019] Figure 4 is a schematic view of another exemplary embodiment of a compact heat exchanger of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Figure 2 shows a portion of a gas turbine engine 1 that may employ a compact heat exchanger or linked microcircuit of the present invention. The gas turbine has numerous components known in the art including, but not limited to, a blade 2 and a blade outer air seal 3 with a gas flow path shown by arrow 5 and cooling path or supply shown by arrows 6. Figure 3 provides a schematic view of an exemplary embodiment of a microcircuit heat exchanger of the present invention generally represented by reference numeral 10. The microcircuit 10 is usable with various parts or components moving at high speeds through gas or having high-speed gas passing thereover to dissipate internal heat, as well as provide a protective cooling film over the surface of the part. Such parts or components can be, but are not limited to, components of the gas turbine of Figure 2.

[0021] Microcircuit 10 is a compact heat exchanger, which is a superimposition of alternating serpentine microcircuits or heat exchangers, where the pitch of the alternating serpentine microcircuits has been reduced such that adjacent alternating serpentine microcircuits touch. The pitch is the distance between each of the parallel paths of the circuit channel 20 of the alternating serpentine microcircuits. The degree to which the pitch may be reduced to cause superimposition of the alternating serpentine microcircuits when creating compact heat exchanger 10 is variable, and depends upon the desired coolant gas flow characteristics.

[0022] The circuit channels 20 are in communication with one or more inlets 30 and one or more outlets 40 for the flow of a cooling medium or fluid therethrough along the flow path indicated by arrows 25. In a gas turbine engine, the cooling fluid is typically compressed ambient air. However, the present disclosure contemplates the use of other cooling fluids such as, for example, ethylene glycol, propylene glycol, steam or the like that are used in the cooling of parts or components such as, for example, internal combustion engines, steam turbines and/or heat exchanger applications.

[0023] Referring to Figure 4, the circuit channels 120 converge and/or diverge at crossover points 150. In the exemplary embodiment of compact heat exchanger 100, the microcircuit is used within a component or part that is subjected to a pressure differential. In Figure 2, the cooling passages of the blade outer air seal 3 are supplied from a single supply chamber. Region 60 has a higher pressure than does region 70. From the supply chamber, coolant flow 6, which exits to the region upstream of the blade 2, is at a lower pressure ratio than that of flow 6 which exits to the downstream region 70. The use of a compact heat exchanger 100 would require a lower supply pressure to drive cooling flow than would the configuration described in the prior art. At locations where pressure ratio is limited, it is preferred to have internal cooling features with lower pressure losses. This minimizes the supply pressure needed and reduces leakage resulting in a more efficient system.

[0024] Referring back to Figure 3, to reduce the internal pressure losses along the microcircuit 10, the crossovers 50 in the low-pressure ratio area 60 are provided with flow stabilizers 80. The flow stabilizers 80 provide a change of geometry to the turn in the circuit channel 20 to reduce the internal pressure loss. The flow stabilizers 80 preferably have a concave shape. In the exemplary embodiment of microcircuit 10, the flow stabilizers are positioned along a downstream portion of the crossover 50 and are adjacent to each of the inlets 30. The flow stabilizers 80 eliminate the 90° turns that the cooling fluid must accomplish to pass through these crossovers 50 by deflecting or directing the flow along a substantially non-orthogonal and/or curved path.

[0025] In the exemplary embodiment of microcircuit 100 of Figure 4, the crossovers 150 in the low-pressure ratio area 60 are reduced in cross-sectional area by the flow stabilizers 180 so as to maintain a substantially uniform total cross-sectional area through which the cooling fluid flows. This is more evident by comparing the crossovers 150 of the low-pressure ratio areas 60 of the exemplary embodiment, with the expanded crossover points of Figure 1. Maintaining a substantially uniform total cross-sectional area along the flow path 125, eliminates any region for expansion of the fluid as it passes through the crossover 150. The cross-sectional area of the crossover 150 is preferably substantially equal to twice the cross-sectional area of the circuit channel 120. This reduces internal pressure loss by maintaining a uniform volume through which the cooling fluid is flowing.

[0026] In contrast, the crossovers of the prior art of Figure 1 , which do not have flow stabilizers 180, are larger in cross-sectional area than cross-overs 150. Use of this geometry in locations with high pressure ratios 70 compensates for the higher internal pressure losses. [0027] In the alternative exemplary embodiment of Figure 4, microcircuit 100 has a circuit channel 120 with one or more inlets 130 and one or more outlets 140 for the flow of a cooling medium or fluid therethrough along the flow path indicated by arrows 125. Flow stabilizers 180 are positioned at substantially each of the crossovers 150, where the adjacent flow paths 125 converge and/or diverge. The number of flow stabilizers 180 that are used in the circuit channel 120, and how far along the microcircuit 100 that the flow stabilizers are positioned, depends upon the pressure ratios to which the microcircuit 180, and its component, are subjected.

[0028] The flow stabilizers 180 are concave at the upstream and downstream portions of the crossovers 150. In this embodiment, the flow stabilizers 180 are symmetrical. However, the present disclosure also contemplates the use of non-symmetrical flow stabilizers 180. The crossovers 150 are reduced in cross-sectional area by the flow stabilizers 180 so as to maintain a substantially uniform total cross-sectional area through which the cooling fluid flows. Maintaining a substantially uniform total cross- sectional area along the flow path 125, eliminates any region for expansion of the fluid as it passes through the crossover 150. The cross-sectional area of the crossover 150 is preferably substantially equal to twice the cross-sectional area of the circuit channel 120. This reduces internal pressure loss by maintaining a uniform volume through which the cooling fluid is flowing.

[0029] The flow stabilizers 180 also eliminate the 90° turns that the cooling fluid must accomplish to pass through these crossovers 50 by deflecting or directing the flow along a substantially non-orthogonal and/or curved path. Also, the flow stabilizers 180 direct adjacent flow paths 125 so that when they converge at the crossovers 150, they are not moving in directly opposite directions to each other. The flow stabilizers 180 converge and diverge the adjacent flow paths 125 at an angle to each other, which reduces the internal pressure loss at the crossover 150.

[0030] The microcircuit 100 was subjected to testing with respect to the internal pressure loss. It was determined from this testing that the flow stabilizers 80 and 180 reduce internal pressure losses at the crossovers 50 and 150, respectively. The prior art crossovers having adjacent 90° turns and expanded crossover regions, provided inherent instability where the adjacent flow paths were convergihg and/or diverging, including increased pressure loss and a higher heat transfer coefficient. It has been determined that the changing of the geometry of the crossovers 50 and 150, including eliminating adjacent 90° turns, utilizing a substantially uniform cross-sectional area (approximately twice the cross-sectional area of the circuit channels 20 and 120), and eliminating directly opposite convergence of adjacent flow paths, has reduced internal pressure losses for the compact heat exchangers.

[0031] Compact heat exchangers 10 and 100 may be placed in thermal communication with a part, such as a turbine or airfoil, utilizing an array of small channels. The microcircuits 10 and 100 and their corresponding circuit channels 20 and 120 can be tailored for the local heat load and geometry requirements of the part. Compact heat exchangers 10 and 100 offer advantages during fabrication. Because the linked serpentine circuit channels 20 or 120 are linked, the core body used to create them will also be linked. This linking will make a more rigid structure for the casting process greatly increasing the chances of casting success.

[0032] While the instant disclosure has been described with reference to one or more exemplary embodiments, 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 thereof. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

What is claimed is:

1. A compact heat exchanger for providing coolant gas flow through a part, comprising: at least one inlet through which a coolant gas may enter; a circuit channel in fluid communication with said at least one inlet, wherein said circuit channel is formed from superimposition of a plurality of alternating serpentine circuits; and at least one outlet in fluid communication with said circuit channel through which said coolant gas may exit said circuit channel, wherein at least one crossover of said circuit channel has a flow stabilizer that is formed in said circuit channel, and wherein said flow stabilizer reduces internal pressure losses in said circuit channel.

2. The compact heat exchanger of claim 1 , wherein said flow stabilizer directs the flow along a non-orthogonal path.

3. The compact heat exchanger of claim 1 , wherein said at least one crossover is adjacent to said at least one inlet.

4. The compact heat exchanger claim 1 , wherein said flow stabilizer is positioned along a downstream portion of said at least one crossover, and wherein said flow stabilizer reduces a cross-sectional area of said at least one crossover.

5. The compact heat exchanger of claim 1 , wherein said at least one crossover is positioned along a portion of the part that is in proximity to a low-pressure ratio area.

6. The compact heat exchanger of claim 1 , wherein a downstream portion of said at least one crossover is substantially convex.

7. The compact heat exchanger of claim 6, wherein an upstream portion of said at least one crossover is substantially convex.

8. The compact heat exchanger of claim 7, wherein said upstream and downstream portions of said at least one crossover are substantially symmetrical.

9. The compact heat exchanger of claim 1 , wherein said circuit channel has a first-cross-sectional area, and wherein said at least one crossover has a second cross-sectional area that is twice as large as said first cross-sectional area.

10. The compact heat exchanger of claim 9, wherein said at least one crossover is adjacent to said at least one inlet.

11. A compact heat exchanger for providing coolant gas flow through a part, comprising: at least one inlet through which a coolant gas may enter; a circuit channel in fluid communication with said at least one inlet, wherein said circuit channel is formed from superimposition of a plurality of alternating serpentine circuits; and at least one outlet in fluid communication with said circuit channel through which said coolant gas may exit said circuit channel, wherein said circuit channel has a first crossover positioned at a portion of the part in proximity to a low-pressure ratio area and a second crossover positioned at a portion of the part in proximity to a high-pressure ratio area, wherein a first cross-sectional area of said first crossover is smaller than a second cross-sectional area of said second crossover.

12. The compact heat exchanger of claim 11, wherein said circuit channel has a third cross-sectional area, and where said first cross-sectional area is twice as large as said third cross-sectional area.

13. The compact heat exchanger of claim 11 , wherein said first crossover is adjacent to said at least one inlet.

14. The compact heat exchanger of claim 11 , wherein an inner geometry of said first crossover directs flow in a non-orthogonal path.

15. The compact heat exchanger of claim 11 , wherein a downstream portion of said first crossover is convex.

16. The compact heat exchanger of claim 11 , wherein a downstream portion of said second crossover is planar.

17. A method of dispensing heat in a part comprising: providing a compact heat exchanger in thermal communication with the part, said compact heat exchanger being formed from superimposition of a plurality of alternating serpentine circuits that provide adjacent flow paths of fluid that converge and/or diverge at crossovers; and directing at least two of said adjacent flow paths to converge or diverge at an angle with respect to each other at one or more of said crossovers.

18. The method of claim 17, further comprising directing one or more of said flow paths to eliminate 90° turns along a portion of the compact heat exchanger that is in proximity to a low-pressure ratio area.

19. The method of claim 18, further comprising directing at least two of said adjacent flow paths to converge or diverge at substantially opposite directions at one or more of said crossovers.

20. The method of claim 18, further comprising reducing expansion of said fluid at said one or more crossovers.