Heat exchanging structure

Abstract

Provided are heat exchanging structures 12 for use in transferring heat energy between an exchange fluid 22 and a working fluid 14. An exemplary structure 12 has a face sheet 30, a back sheet 36 and first and a second interior sheets 32, 38. The first and second interior sheets 32, 38 are undulant and are bonded to one another at a plurality of interior joints 42. The first interior sheet 32 is bonded to the face sheet 30 at a face joint 34 and the second interior sheet 38 is bonded to the back sheet 36 at a back joint 40. A fluid passage 44 is formed between the first and second interior sheets 32, 38. The exchange fluid 22 circulates about the structure 12 and exchanges heat with the working fluid 14.

Description

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present disclosure generally relates to a structure for exchanging heat between fluids and more specifically to such structures used in aerospace applications.

(2) Description of the Related Art

Aerospace propulsion systems such as gas turbines, scramjets and rockets produce high temperature gases by burning a fuel and oxidizer mixture for powering vehicles. After the fuel and oxidizer mixture ignites in a combustion chamber, the high-temperature combustion gases travel downstream to a drive a turbine, or are exhausted through a nozzle. During the combustion process, the combustion chamber walls encounter extremely high temperatures, which can reduce the chamber's strength. Since some aerospace vehicles utilize the combustion chamber as a structural member, any reduction in strength may compromise the vehicle and/or the mission.

A light weight propulsion system is important for enabling the maximum payload carrying capacity of an aerospace vehicle. Thick combustion chambers and high density materials add weight to the vehicle and reduce the payload capacity. For small aerospace vehicles it is particularly important to have a durable, light-weight combustion chamber to enable the vehicle to carry adequate payload.

Combustion chambers made from various materials, coatings, and cooling systems are known. For example, a ceramic combustion chamber liner, such as disclosed in United States Patent Application Publication Number US20060242965 ‘Compliant metal support for ceramic combustor liner in a gas turbine engine’, teaches a liner wall made entirely of ceramic material. A cooled combustion chamber, such as disclosed in unpublished U.S. patent application Ser. No. 11/843,743 ‘Heat exchanger panel and manufacturing method thereof using transient liquid phase bonding agent and vacuum compression brazing’, teaches combustion chamber walls having milled channels and a bonded cover to allow a coolant to circulate through the wall itself. Published United States Patent Application 20070029369 ‘Transient Liquid Phase Bonding of Dissimilar Metals’, teaches a method of bonding a structure made of dissimilar materials.

BRIEF SUMMARY OF THE INVENTION

Provided are heat exchanging structures for use in transferring heat energy between two fluids. An exemplary structure has a face sheet, a back sheet, a first interior sheet, and a second interior sheet. The interior sheets are undulant and are bonded to one another at a plurality of interior joints. The first interior sheet is bonded to the face sheet at a face joint and the second interior sheet is bonded to the back sheet at a back joint. A fluid passage is formed between the first and second interior sheets.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an isometric view of an annular combustion chamber formed from a heat exchanging structure according to an embodiment of the present invention;

FIG. 2 is an isometric view of a three dimensional, heat exchanging structure according to another embodiment of the present invention;

FIG. 3 is a fragmented sectional view of the heat exchanging structure of FIG. 1 and FIG. 2;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 3;

FIG. 5 is a sectional view taken along line 5-5 of FIG. 3;

FIG. 6 is an alternate embodiment of the sectional view of FIG. 5;

FIG. 7 is sectional view taken along line 7-7 of FIG. 3; and

FIG. 8 is an exploded view of a die set and a formed interior sheet.

DETAILED DESCRIPTION OF THE INVENTION

An annular combustion chamber 10 of the type used in aerospace propulsion systems is illustrated in FIG. 1. A heat exchanging structure 12, also referred to as a structure 12, encloses a working fluid 14, such as a hot combustion gas. In this example, an ambient air stream 16 surrounds the structure 12. The structure 12 extends circumferentially about a longitudinal, central axis 18 and may be a constant or varying diameter along the axis 18. A manifold 20 allows an exchange fluid 22 to enter and exit the structure 12. A structural joint 24 may be included at one or more locations to secure adjacent structures 12. In this manner, combustion chambers 10 or other systems of complex geometries may be formed. While an annular structure 12 is illustrated here for brevity, rectangular, polygonal, elliptical, or other enclosed shaped structures 12 are similarly contemplated.

Referring now to FIG. 2, a three-dimensional structure 12 with a non-enclosed shape is illustrated. In this particular embodiment, a working fluid 14, such as a hot combustion gas, is proximate the structure 12 and an exchange fluid 22 enters and exits the structure 12 via a manifold 20. In this embodiment, several, three dimensional structures 12 may be joined together to form a combustion chamber 10 or other system for use in aerospace propulsion systems. Of course, planar structures 12 (not shown) are also possible.

The structure 12 transfers heat from the working fluid 14 to the exchange fluid 22 or vice versa. In other words, the exchange fluid 22 functions as a heat sink, absorbing heat from the working fluid 14, or a heat source, providing heat to the working fluid 14. Additionally, each of the working fluid x14 and exchange fluid 22 may be in a liquid or a gas state. In some embodiments, the exchange fluid 22 is fuel.

Now, the various elements of the structure 12 will be discussed in detail with reference to FIGS. 3-5. A face sheet 30 is bonded to a first interior sheet 32 at a face joint 34. A back sheet 36 is bonded to a second interior sheet 38 at a back joint 40. The first interior sheet 32 is bonded to the second interior sheet 38 at a plurality of interior joints 42. A fluid passage 44 between the first and second interior sheets 32, 38 forms a grid-like pattern and directs the exchange fluid 22 throughout the structure 12. The fluid passage 44 is coupled to a manifold 20, thus allowing the exchange fluid 22 to enter and exit the structure 12.

In order to form complex shaped combustion chambers 10 or other systems, a structural joint 24, such as a lap joint (shown), butt joint or other style joint is used to bond adjacent structures 12. A side wall 46 bonded between the face sheet 30 and back sheet 36 provides further strength and design flexibility.

The face sheet 30 and back sheet 36 are generally featureless and create an aerodynamic surface for directing the working fluid 14 and/or ambient air stream 16. The first and second interior sheets 32, 38 are undulant, having a plurality of convex features or undulations 50 formed in their surfaces. Each undulation 50 has an upper rim 52 and a lower base 54. The rims 52 of the first interior sheet 32 are bonded to the face sheet 30 at a face joint 34, while the rims 52 of the second interior sheet 38 are bonded to the back sheet 36 at a back joint 40. The bases 54 of the first and second interior sheets 32, 38 are bonded to each other at interior joints 42. The undulations 50 may be cup shaped with larger bases 54 as illustrated in FIGS. 3-5, or dish shaped with smaller bases 54 as illustrated in FIG. 6; however, other shaped bases 54 may also be used if bondable.

In a preferred embodiment, the materials of the face sheet 30 and first interior sheet 32 are different than the materials of the back sheet 36 and second interior sheet 38. With different material properties, the structure 12 can exchange sufficient heat while maintaining adequate structural strength for aerospace applications. In this regard, it's preferable to have a material for the face sheet 30 and first interior sheet 32 with a thermal conductivity that differs from the thermal conductivity of the back sheet 36 and the second interior sheet 38. Most preferably, the thermal conductivity of the face sheet 30 and first interior sheet 32 material is greater than the thermal conductivity of the back sheet 36 and the second interior sheet 38 material. For example, a face sheet 30 and first interior sheet 32 made of a Copper based alloy and a back sheet 36 and second interior sheet 38 made of a Nickel based alloy provide excellent heat transfer capability without compromising the strength of the structure 12.

With specific attention now given to FIG. 4, the undulations 50 of the first and second interior sheets 32,38 are opposed to one another and bonded at their bases 54 by interior joints 42. The space between the undulations 50 forms an approximately grid shaped fluid passage 44. The fluid passage 44 can also be seen in FIG. 7. The exchange fluid 22 circulates within the fluid passage 44 in multiple directions for enhanced heat transfer. The undulations 50 also form a plurality of enclosed chambers 56 as best seen in FIG. 5. The chambers 56 are formed between the face sheet 30 and the first interior sheet 32, and between the back sheet 36 and the second interior sheet 38. Each of the chambers 56 is sealed about the rim 52 at the face joint 34 or back joint 40, and the exchange fluid 22 cannot enter the chambers 56 because of this seal. The undulations 50 in FIGS. 4 and 5 are cup shaped with larger bases 54, while the undulations 50 of FIG. 6 are dish shaped with smaller bases 54. Of course, other undulation 50 shapes may be used as long as sufficient rim 52 and base 54 areas are provided for bonding the structure 12 together.

FIG. 7 schematically illustrates the flow of exchange fluid 22 as it circulates within the passage 44. The undulations 50 form a grid-like pattern in the fluid passage 44, and the exchange fluid 22 circulates in approximately orthogonal directions. The exchange fluid 22 either absorbs heat from, and/or provides heat to, the face and back sheets 30, 36. The exchange fluid 22 may be in a liquid or a gas state as it circulates through the fluid passage 44.

The first and second interior sheets 32, 38 are readily formed using a die set as illustrated in FIG. 8. While only the first interior sheet 32 is shown, the second interior sheet 38 is similarly formed. A male die half 60 has a plurality of spaced pins 62 that are forced into a plurality of complementary pockets 64 in a female die half 66. By placing an first or second interior sheet 32, 38 between the dies 60, 66, while forcing them together, the undulations 50 are formed. The complementary pins 62 and pockets 64 form cup shaped undulations 50 (see FIG. 5), while complementary conical features will create cup shaped undulations 50 (see FIG. 6).

With the first and second interior sheets 32, 38 formed as described above, the structure 12 is assembled and then bonded together using a suitable bonding method. A transient liquid phase, vacuum compression bonding method is preferable for bonding different materials. A complete description of the preferred bonding method is disclosed in published United States Patent Application 20070029369 ‘Transient Liquid Phase Bonding of Dissimilar Metals’, which is incorporated herein by reference as if included at length.

The bonded structure 12 is next shaped as required for the aerospace vehicle application. Planar, non-planar, annular or other shapes may be created by die forming, rolling or other shaping means. Multiple structures 12 may also be bonded together at structural joints 24 to form the complex shapes required for certain applications.

Other alternatives, modifications and variations will become apparent to those skilled in the art having read the foregoing description. The dimensions provided herein are merely exemplary and describe but a single embodiment of the present invention. Accordingly, the invention embraces those alternatives, modifications and variations as fall within the broad scope of the appended claims.

Claims

1. A heat exchanging structure comprising:

a face sheet;

a back sheet;

a first interior sheet bonded to said face sheet at a face joint;

a second interior sheet bonded to said back sheet at a back joint; and

wherein the first and second interior sheets are bonded to each other at a plurality of interior joints such that a fluid passage is formed between the interior sheets.

2. The heat exchanging structure as recited in claim 1, wherein the first and second interior sheets have undulant surfaces.

3. The heat exchanging structure as recited in claim 2, wherein each surface undulation has a rim and a base.

4. The heat exchanging structure as recited in claim 3, wherein at least one of the surface undulations is cup shaped.

5. The heat exchanging structure as recited in claim 3, wherein at least one of the surface undulations is dish shaped.

6. The heat exchanging structure as recited in claim 3, wherein each of the face and back joints are disposed at the undulation rims.

7. The heat exchanging structure as recited in claim 3, wherein the plurality of interior joints are disposed at the undulation bases.

8. The heat exchanging structure as recited in claim 1, further comprising a plurality of enclosed chambers disposed between said face sheet and said first interior sheet and between said back sheet and said second interior sheet.

9. The heat exchanging structure as recited in claim 8, wherein each enclosed chamber is sealed by one of a face joint or a back joint.

10. The heat exchanging structure as recited in claim 1, wherein the fluid passage is approximately grid shaped.

11. The heat exchanging structure as recited in claim 10, further comprising a manifold coupled to the fluid passage.

12. The heat exchanging structure as recited in claim 1, wherein the face and back sheets have different thermal conductivities.

13. The heat exchanging structure as recited in claim 12, wherein the material of the face sheet has a thermal conductivity that is greater than the thermal conductivity of the back sheet material.

14. The heat exchanging structure as recited in claim 13, wherein the face sheet is made of a Copper based alloy material.

15. The heat exchanging structure as recited in claim 13, wherein the back sheet is made of a Nickel based alloy material.

16. The heat exchanging structure as recited in claim 13, wherein said first interior sheet is made of the same material as the face sheet and the second interior sheet is made of the same material as the back sheet.

17. The heat exchanging structure as recited in claim 1, wherein the face sheet is nonplanar.

18. The heat exchanging structure as recited in claim 17, wherein the face sheet is annular.

19. The heat exchanging structure as recited in claim 1, wherein the joints are made by a transient liquid phase, vacuum compression brazing method.

20. The heat exchanging structure as recited in claim 1, wherein the structure is part of a combustion chamber for an aerospace propulsion system.