The present innovations generally pertain to apparatuses, methods, and/or systems for improving heat exchange. More particularly, but not by way of limitation, the present innovations relate to multi-branch furcating flow heat exchangers, which may be used, for example, in a gas turbine engine, for fluid-fluid heat exchange wherein the fluid thermal boundary layers within the heat exchanger are continually re-established while minimizing pressure drop through the heat exchanger. As one skilled in the art will understand, while various embodiments are described relative to a gas turbine engine, the apparatus, methods and/or systems may also be used in various alternative applications where it is desired that heat be exchanged between two fluids.
In a gas turbine engine, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases which flow downstream through turbine stages. A typical gas turbine engine generally possesses a forward end and an aft end with its several core or propulsion components positioned axially therebetween. An air inlet or intake is located at a forward end of the gas turbine engine. Moving toward the aft end, in order, the intake is followed by a compressor, a combustion chamber, and a turbine. It will be readily apparent from those skilled in the art that additional components may also be included in the gas turbine engine, such as, for example, low pressure and high pressure compressors, and low pressure and high pressure turbines. This, however, is not an exhaustive list.
It is necessary to manage heat generation within the gas turbine engine so as not to raise gas turbine engine temperatures to unacceptable levels. For example, it may be desirable to control oil temperatures within the gas turbine engine which lubricates bearings associated with the high pressure shaft and/or the low pressure shaft. Further, during operation, significant heat is generated by the high pressure compressor which generates high temperature flow. Therefore, it may also be desirable to cool air exiting one or both of the high pressure compressor and the low pressure compressor.
In order to cool these fluids, various methods have been used however, improvements are still desirable. For example, improvement of parameters which are continually sought for heat exchangers include, but are not limited to, decreased weight, decreased volume, decreased pressure drop across the heat exchangers and decreased resistivity to thermal exchange. Additionally, it would be desirable to manufacture such heat exchanger in a manner which overcomes limitations associated with more commonly utilized manufacturing techniques.
The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded subject matter by which the scope of the instant embodiments are to be bound.
According to an embodiment, a heat exchanger (e.g., fluid-to-fluid) is provided. The heat exchanger provides a first plurality of flow passages and a second plurality of flow passages which extend from first and second manifolds, respectively. The plurality of flow passages include tubes which furcate near at least one manifold into two or more furcated flow passages and subsequently converge for joining near the at least one manifold. The plurality of furcated flow passages are intertwined, reducing the distance between flow passages containing each fluid therebetween to improve thermal transfer. Further, the furcations create changes of direction of the fluid to re-establish new thermal boundary layers within the flow passages to further reduce resistance to thermal transfer.
According to another embodiment, a heat exchanger comprises a first manifold defining a first fluid inlet, a second manifold defining a second fluid inlet, a first plurality of flow passages in flow communication with the first manifold, the first plurality of flow passages including a first fluid inlet and a plurality of first furcated flow passages extending from the first fluid inlet, a second plurality of flow passages in flow communication with the second manifold, the second plurality of flow passages including a second fluid inlet and a plurality of second furcated flow passages extending from the second fluid inlet, some of the plurality of first furcated flow passages joining and being in a first flow communication and some of the plurality of second furcated flow passages joining and being in a second flow communication, the furcated first plurality of flow passages and the furcated second plurality of flow passages intertwined to provide improved heat transfer.
According to yet another embodiment, a heat exchanger comprises a first fluid header and a second fluid header, a first plurality of flow passages in flow communication with the first header, the first plurality of flow passages including a first fluid inlet and a plurality of first furcated flow passages extending from the first fluid inlet, a second plurality of flow passages in flow communication with the second header, the second plurality of flow passages including a second fluid inlet and a plurality of second furcated flow passages extending from the second fluid inlet, some of the plurality of first furcated flow passages joining and being in a first flow communication and some of the plurality of second furcated flow passages joining and being in a second flow communication, the furcated flow passages changing direction and reducing thermal boundary within the flow passages, the furcated first plurality of flow passages and the furcated second plurality of flow passages intertwined to provide improved heat transfer, the first and second plurality of flow passages further in flow communication with a second and third fluid headers, respectively.
All of the above outlined features are to be understood as exemplary only and many more features and objectives of the apparatus, method and systems of the multi-branch furcating flow heat exchanger may be gleaned from the disclosure herein. This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. A more extensive presentation of features, details, utilities, and advantages of the present invention is provided in the following written description of various embodiments of the invention, illustrated in the accompanying drawings, and defined in the appended claims. Therefore, no limiting interpretation of this Summary is to be understood without further reading of the entire specification, claims, and drawings included herewith.
The above-mentioned and other features and advantages of these exemplary embodiments, and the manner of attaining them, will become more apparent and the multi-branch furcating flow heat exchanger will be better understood by reference to the following description of embodiments taken in conjunction with the accompanying drawings, wherein:
Reference now will be made in detail to embodiments provided, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation, not limitation of the disclosed embodiments. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present embodiments without departing from the scope or spirit of the disclosure. For instance, features illustrated or described as part of one embodiment can be combined, integrated or otherwise used with additional or alternative embodiments to yield further embodiments. Thus it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Referring to
As used herein, the terms “axial” or “axially” refer to a dimension along a longitudinal axis of an engine. The term “forward” used in conjunction with “axial” or “axially” refers to moving in a direction toward the engine inlet, or a component being relatively closer to the engine inlet as compared to another component. The term “aft” used in conjunction with “axial” or “axially” refers to moving in a direction toward the engine outlet, or a component being relatively closer to the engine outlet as compared to an inlet. As used herein, the terms “radial” or “radially” refer to a dimension extending between a center longitudinal axis of the engine and an outer engine circumference. The term parallel flow(s) as used herein, unless otherwise stated, means that the flow divides into two or more paths in moving between a first location and a second location. This is meant in contrast to the term serial which is generally defined as a single path between two locations. The term furcate as used herein means that a tube or fluid flow passage splits apart into two or more tubes, fluid flow passages or branches.
Referring initially to
The gas turbine engine 10 further comprises a fan 18, a low pressure turbine 21, and a low pressure compressor 22. The fan 18 includes an array of fan blades 27 extending radially outward from a rotor disc. Opposite the engine inlet end 12 in the axial direction is an exhaust side 29. In these embodiments, for example, gas turbine engine 10 may be any engine commercially available from General Electric Company. Although the gas turbine engine 10 is shown in an aviation embodiment, such example should not be considered limiting as the gas turbine engine 10 may be used for aviation, power generation, industrial, marine or the like.
In operation air enters through the engine inlet end 12 of the gas turbine engine 10 and moves through at least one stage of compression in the low pressure compressor 22 and high pressure compressors 14 where the air pressure is increased and directed to the combustor 16. The compressed air is mixed with fuel and burned providing the hot combustion gas which exits the combustor 16 toward the high pressure turbine 20. At the high pressure turbine 20, energy is extracted from the hot combustion gas causing rotation of turbine blades 27 which in turn cause rotation of the high pressure shaft 24. The high pressure shaft 24 passes toward the front of the gas turbine engine 10 to cause rotation of the one or more high pressure compressor 14 stages and continue the power cycle. The low pressure turbine 21 may also be utilized to extract further energy and power additional compressor stages. The fan 18 is connected by the low pressure shaft 28 to a low pressure compressor 22 and the low pressure turbine 21. The connection may be direct or indirect, such as through a gearbox or other transmission. The fan 18 creates thrust for the gas turbine engine 10.
The gas turbine engine 10 is axi-symmetrical about centerline axis 26 so that various engine components rotate thereabout. An axi-symmetrical high pressure shaft 24 extends through the gas turbine engine 10 forward end into an aft end and is journaled by bearings along the length of the shaft structure. The high pressure shaft 24 rotates about the centerline axis 26 of the gas turbine engine 10. The high pressure shaft 24 may be hollow to allow rotation of a low pressure shaft 28 therein and independent of the high pressure shaft 24 rotation. The low pressure shaft 28 also may rotate about the centerline axis 26 of the engine. During operation the shafts 24, 28 rotate along with other structures connected to the shafts 24, 28 such as the rotor assemblies of the turbines 20, 21 in order to create power or thrust for various types of turbines used in power and industrial or aviation areas of use.
The gas turbine engine 10 further includes a multi-branch furcating flow heat exchanger 40. In the exemplary schematic view, the furcating heat exchangers 40 are shown in various locations for purpose of teaching. The furcating heat exchanger 40 may be utilized for a variety of fluid cooling functions including, but not limited to, liquid cooling and air cooling. In the instance of liquid cooling, it may be desirable to cool oil or other relatively higher temperature liquid lubricant with one or more relatively cooler temperature sources in the gas turbine engine 10. The oil may be cooled by air such that the cooling air is provided by a relatively lower temperature by-pass air flow 19. The axial location of the furcating heat exchanger 40 may also change depending on the fluid location to be cooled.
Further, the oil may be cooled by a liquid, for example fuel, which is often stored in wings and is exposed to the cold ambient conditions experienced at typical flight altitudes, for example. Therefore the relatively cooler temperature fuel may be used as the means for absorbing thermal energy from the relatively higher temperature cooling fluid or oil. In such embodiment, the furcating heat exchanger 40 may be positioned in a variety of locations, for non-limiting example as shown radially inward of an engine cowling 32. As with the previous embodiment, the furcating heat exchanger 40 may also be moved axially depending on the location of the, for example, fluid to be cooled.
In still further embodiments, the furcating heat exchanger 40 may be an air to air heat exchanger and may again be positioned in a variety of locations, for example in the by-pass air flow 19 so that the relatively cooler by-pass air flow 19 cools the relatively higher temperature compressor discharge air. Or according to other embodiments, the higher temperature compressor discharge air may be cooled by lower temperature air from the low pressure compressor 22. In this instance, the furcating heat exchanger 40 may be located within the engine cowling 32 or within the bypass air flow 19.
While gas-gas heat exchange is described according to some embodiments, according to other embodiments, gas-liquid heat exchange may also be within the scope of the instant disclosure. For example, the liquid may be sub-cooled, saturated, supercritical or partially vaporized. For example, the compressor discharge flow path may be cooled with water, water-based coolant mixtures, dielectric liquids, liquid fuels or fuel mixtures, refrigerants, cryogens, or cryogenic fuels such as liquefied natural gas (LNG) and liquid hydrogen. However, this list is not exhaustive and therefore, should not be considered limiting. Further, the lubricating fluids such as oil may be cooled in similar matters.
Thus, as depicted in
Referring now to
Within each manifold 42, 44 is a header 46, 48 which serves as a conduit for the flows of relatively higher temperature fluid and relatively lower temperature fluid, respectively. The two flows of fluid may both enter from the first manifold 42 and exit at the second manifold 44. Alternatively, the two flows may enter from opposite manifolds 42, 44 and exit at the opposite manifolds 42, 44. As a still further alternative, the two flows may be both entering and exiting at both of the first and second manifolds 42, 44. Such embodiment may be provided through the addition of more headers within each manifold.
The furcating heat exchanger 40 may further comprise a first plurality of fluid tubes or fluid flow passages 50, 52. Although the tubes 50, 52 are shown, it should be understood that the depiction is of a fluid domain because the furcating heat exchanger 40 is monolithic in nature and the fluid flow passages are surrounded by metal (solid domain), having no distinct outer boundary or surface. Therefore, while the term “tube(s)” is used and shown, the tubes may interchangeably be referred to as “fluid flow passages” since the monolithic structure does not provide for a true tube outer surface as is common with known tubes. Each fluid flow passage 50 having the first fluid includes an inlet 51 and an outlet 53, while each fluid flow passage 52 having the second fluid includes an inlet 54 and an outlet 56. In the exemplary embodiment, the flows of fluids are described as entering the furcating heat exchanger 40 at opposite manifolds 42, 44 and exiting at opposite manifolds 42, 44, rather than both moving in the same direction. Either flow direction may be used but it is believed that improved heat exchange occurs when the fluid enters the furcating heat exchangers 40 at opposite ends.
The furcating heat exchanger 40 further comprises furcating fluid flow passages 50, 52. Specifically, each of the first fluid passages 50 extends from the first manifold 42 and furcates or split apart into two or more first furcated flow passages 60. Similarly, each of the second fluid flow passages 52 extends from the second manifold 44 and furcates or splits apart into two or more second furcated flow passages 62.
The first plurality of fluid flow passages 50 and second plurality of fluid flow passages 52 may comprise various cross-sectional shapes. For example, the depicted embodiment shows that the fluid flow passages 50, 52 have a circular cross-section. However, this is not to be construed as limiting as will be shown in further non-limiting examples wherein the flow passages may be square or skewed square/diamond shaped. Still further cross-sections may be utilized, however it may be desirable to maximize external contact surface area between the first plurality of fluid flow passages 50 and the second plurality of fluid flow passages 52 when determining cross-section shape. Further, it may be desirable to minimize distance between the first plurality of fluid flow passages 50 and the second plurality of fluid flow passages 52 which may otherwise provide resistance to thermal transfer between the first and second pluralities of fluid flow passages 50, 52. Additionally, it may be desirable to vary the cross-sectional area of the flow passages or maintain constant cross-sectional area of the flow passages. Still further, it may be desirable to vary the cross-section between the first and second flow passages. In other words, the tubes or flow passages need not have the same cross-section.
Referring now to
Referring now to
Referring now to
In the exemplary embodiment of
Additionally, with reference to both
The furcated flow passages 60, 62 extending from the inlet flow passages 51, 61 and the joinders 63, 71 between furcated flow passages 60, 62. These provide division of flow and changes of direction of the fluid flows providing the thermal heat exchange. In linear tubes, thermal boundary layers and momentum boundary layers build. However, the flow division and change of direction corresponding to the furcated flow passages 60, 62 and joinders 63, 71 provide reduction of these boundary layers. The reduction of these boundary layers reduces resistivity to thermal transfer thereby allowing improved thermal transmission. Unfortunately, the changes of direction and entrance region of effects also create pressure drop across the furcating heat exchanger 40. Therefore, acceptable pressure drops may be determined and number of direction changes be designed to stay within an acceptable pressure drop limit or range.
The furcating heat exchanger 40 may be formed in a variety of manners. A housing (not shown) may be formed substantially hollow wherein the manifolds 42, 44 and the plurality of fluid flow passages 50, 52 may be disposed therein. In other embodiments, the furcating heat exchanger 40 may be formed in monolithic forms and the manifolds 42, 44 may be formed integrally and the flow passages be formed integrally. The flow passages and/or monolithic formed housing may be formed of a high thermally conductive material. For example, an aluminum or aluminum alloy may be utilized or alternatively a casting alloy, copper casting alloy (C81500) or cast aluminum bronze (C95400) may be utilized. According to other embodiments, nickel-cobalt or nickel-cobalt alloys may be utilized. Still further, the plurality of fluid flow passages 50, 52 may be formed of, but are not limited to, incoloy alloy, INCONEL alloy, titanium-aluminide alloy, stainless steel alloy or refractory metals. It may be desirable to as closely match coefficient of thermal expansion (CTE) in order to reduce stress build up during production and operation of the different materials utilized for the fluid flow passages 50, 52. Desirable features for the materials utilized include outstanding resistance to fatigue and oxidation resistance or corrosion resistance from air or seawater. Additionally, pressure tight castings, incorporation into welded assemblies of cast or wrought parts, highly effective vibration damping and machinability and weldability are all desirable characteristics. While the above list of characteristics is provided, such is not limiting as various materials may be utilized for the matching of flow passage and body components.
Additionally, if differing materials are used to form the furcating heat exchanger 40, portions of dissimilar materials, metals for example, the furcating heat exchanger 40 may be coated with a diffusion barrier between dissimilar regions of metal. For example, the surface area of the plurality of fluid flow passages 50, 52 may be coated in a single or multi-layer process if such are formed of differing materials. According to one exemplary embodiment, a three layer coating process may be utilized wherein a first layer may comprise an electro-coated nickel bond coat followed by a second gold overcoat for adhesion of the third layer. The third layer might be established by a physical vapor deposition (PVD) of sputtered material such as titanium nickel or titanium stabilized with W, Pt, Mo, NiCr, or NiV. In either of these embodiments, the third layer is intended to function as a diffusion barrier preventing alloy depletion of the fluid flow passages 50, 52.
Although a number of examples are provided for material usage, one skilled in the art will recognize that this description is not limiting and other materials and combinations may be utilized as required by the application. Some parameters include, but are not limited to, temperature, pressure, chemical compatibility with the fluid, and coefficient of thermal expansion. This list is non-exhaustive and other materials and compatibility features may be considered. For example, other plastics, polymers and ceramics may be desirable for some aspects of the heat exchanger.
The manufacturing of the instant furcating heat exchanger 40 may occur in a variety of manners; however, one exemplary manufacturing technique can include additive manufacturing wherein the fluid flow passages 50, 52 are formed within a matrix body defining the furcating heat exchanger 40 using one or more materials. The aforementioned technique allows the materials to be joined during the manufacturing process.
Referring now to
Referring now to
Referring now to
Referring now to
With reference now to
The unit cell first portion 191 includes a plurality of furcated flow passages 160 which furcate and intertwine with adjacent unit cell first portions 191 (
The unit cell first portion 191 includes three furcated flow passages 161, 162, 163 (which are represented by the inbound flows 192) feed flow into the unit cell first portion 191. The inbound flows are shown as arrows 192. The unit cell first portion 191 also includes three additional furcated flow passages 164, 165, 166 (also represented by outbound flows 193) for outbound flow from the unit cell first portion 191. The outbound flows are shown as arrows 193. In this way, the flow of one unit cell first portion 191 is in flow communication with an adjacent one or more unit cell first portions 191.
When constructed, the plurality of furcated flow passages 160 of the unit cell first portion 191 are intertwined with the furcated flow passages 180 of the unit cell second portion 194 (
Referring now to
The furcated flow passages 180 include a trifurcated arrangement similar to the unit cell first portion 191. The furcated flow passages 180 include three furcated flow passages 181, 182, 183 through which outbound fluid flows. In the exemplary embodiment, these provide a conduit for outbound fluid flow 187 from the unit cell second portion 194. The unit cell second portion 194 also includes three furcated flow passages 184, 185, 186. These flow passages provide a conduit for inbound fluid flow 188.
Referring now to
The solid domain 195 is shown with a plurality of arrows disposed about the solid domain 195 that depict the various fluid flows of
Additionally, the arrows of the unit cell second portion 194 (
With this unit cell 190 defined, additional unit cells are formed to define a larger heat exchanger core. For example, with reference to
One skilled in the art will realize that the ratios of hydraulic diameter or areas for the fluids is 1 to 1 since the flow passage 160, 180 are equivalent. However, these ratios may be varied by changing the cross-sectional area of the one fluid passage relative to the other fluid passage. This may be optimized for flow requirements, such as flow rate, pressure drop and heat transfer. Also this may be optimized for a given space wherein the heat exchanger 170 will be positioned.
Referring still to the embodiment of
In this view, one skilled in the art will also better understand how the flows of the unit cell first portion 191 and the unit cell second portion 194 are intertwined. The unit cell first portion 191 for example may flow through the interior of each solid domain 195. Further, the unit cell second portion 194 may be positioned along the exterior surfaces of the solid domain 195. In this way, the two flows represented by portions 191 and 195 are separated and do not become mixed. Further, since the flows are on both sides of the depicted solid domain 195, the heat transfer is improved.
The depicted view shows that the fluid flows are continually changing direction which continually resets the fluid boundary layers and therefore also improves heat transfer. In this view, it is clear that the fluid flows are changing direction in a zig-zag or saw-tooth pattern so that boundary layers are limited and so that turbulent flow is also created, which aids in heat exchange between the fluid flows. The unit cell first portion 191 and the unit cell second portion 194 are intertwined or otherwise formed so as to intertwine or weave together. The flat surfaces of the plurality of furcated flow passages 160 and the plurality of furcated flow passages 180 are in contact to aid improved thermal transfer and the flat exterior surfaces maximize contact surface area.
With this limited construction in mind, and with additional reference to
Referring now to
While various techniques may be used to construct the heat exchanger core 170, it may be desirable that the present embodiments, or variations thereof, be manufactured using additive manufacturing techniques. This limits the number of brazed or welded joints which in turn reduces the likelihood of leakage within the device. Additionally, the additive manufacturing technique allows for more complex geometries such as that of the instant embodiment and formation of such while limiting joints.
Referring now to
Additionally, in this embodiment, a manifold 142 is defined at one end of the heat exchanger so that the two or more headers 146, 148 are also disposed at one end of the furcating heat exchanger 140. Thus, as opposed to the previous embodiment where the fluids entered and exited the furcating heat exchanger 40 at opposite ends, in the instant embodiment the fluids may enter and exit at the same end of the furcating heat exchanger 140. Additionally, while a first and second header is shown, the embodiment may include third and fourth headers which are not shown so that a header exists for input and output for each of the two fluids.
Referring still further to
The present embodiments provide two desirable but unexpected results. First, the cross-sectional area for the fluid to flow remains constant during the straight, diverging/furcating, and converging portions, thus irreversible losses due to flow velocity change is limited, if at all an issue. Second, the shapes of the flow passages for each fluid may be varied in cross-sectional area throughout a given fluid domain as needed to optimize for various factors such as flow rate, pressure drop, heat exchange and volume required for the heat exchanger.
The foregoing description of structures and methods has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. Features described herein may be combined in any combination. Steps of a method described herein may be performed in any sequence that is physically possible. It is understood that while certain embodiments of methods and materials have been illustrated and described, it is not limited thereto and instead will only be limited by the claims, appended hereto.
This application is a continuation of U.S. patent application Ser. No. 15/517,310 filed Oct. 6, 2015, which claims the benefit of PCT application PCT/US2015/054115 filed Oct. 6, 2015, which claims priority to and benefit from provisional application with Ser. No. 62/060,719 filed Oct. 7, 2014, entitled “MULTI-BRANCH FURCATING FLOW HEAT EXCHANGER”, all of which is incorporated by reference herein.
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