Description

TUBE DESIGN FOR AN AIR-TO-AIR AFTERCOOLER

Technical Field The present disclosure relates to air-to-air aftercoolers, and more particularly, to flow tube designs for air-to-air aftercoolers.

Background

Construction and earthmoving equipment, as well as many other types of work machines, are commonly used in a wide variety of applications. Generally, a work machine is powered by an internal combustion engine. In order to optimize the performance of the work machine, the engine must perform as efficiently as possible. Because many work machines are powered by internal combustion engines, various methods have been developed to increase internal combustion engine efficiency. One method has been to incorporate a turbocharger into the internal combustion engine. The turbocharger may compress air prior to entering an engine intake or combustion chamber. Supplying the engine intake with compressed air ("charged air") may allow for more complete combustion. This may result in lower emissions, improved performance, and better engine efficiency. However, compressing the air may also cause an increase in the intake air temperature. Supplying the engine intake with such heated charged air may lead to an undesirable increase in the amount of emissions exiting from the engine. Also, because engines generally produce large quantities of heat already, adding heated charged air to the engine intake or combustion chamber may increase the operating temperature of the engine, thus resulting in excessive wear on engine components.

An air-to-air aftercooler (ATAAC) may be used to reduce smoke and other engine emissions by cooling the charged air before it enters the engine intake manifold. Using the ATAAC may also result in lower combustion temperatures, thus improving engine component life by reducing thermal stress on the engine.

The ATAAC may include one or more tubes through which the heated charged air may pass. The outside of the tube may be subjected to some type of fluid, for example, ambient air, which may cool the tube. As the heated charged air passes through the tube, it may come into contact with the tube walls. Heat may be transferred from the charged air to the tube walls, and then from the tube walls into the ambient air, thus removing heat from the charged air. External fins may be added to the external surfaces of the tube walls to create greater surface area, which may provide improved heat transfer between the heated charged air and the ambient air. Additionally, improved heat transfer may be achieved by incorporating a turbulator within the interior of the tube. The turbulator may be an internal fin, which may increase the turbulence of the heated charged air flowing through the tube. By creating turbulence inside the tube, all of the heated charged air may mix together, keeping the temperature of the heated charged air touching the tube walls up so that more heat may be extracted.

U.S. Patent No. 5,730,213, issued to Kiser et al. ("Kiser") discloses a system for creating turbulence within heat exchanger tubes. In particular, Kiser describes a heat exchanger having an aluminum cooling tube including a plurality of cylindrical dimples projecting into the interior surface of the tube. The dimples may agitate tube flow through the tube to improve heat exchange by reducing the thermal resistance between the tube wall and the enclosed charged air. However, the tube in Kiser may not create enough turbulence for certain applications due to the geometry and size of the dimples. Furthermore, there is a concern that aluminum brazed ATAAC tubes may not

have the ability to provide adequate life for newer engines, which may have higher charged air temperatures than older models.

The present disclosure is directed towards overcoming one or more of the problems set forth above.

Summary of the Invention

In one aspect, the present disclosure may be directed to an air-to- air aftercooler. The air-to-air aftercooler may include a tube configured to direct a flow of charged air. The tube may include at least one first protrusion located on a first interior surface of the tube, and a first longitudinal plane may extend through the at least one first protrusion. The tube may also include at least one second protrusion located on a second interior surface of the tube, and a second longitudinal plane may extend through the at least one second protrusion. Furthermore, the first longitudinal plane and the second longitudinal plane may intersect. In another aspect, the present disclosure may be directed to a method of making an air-to-air aftercooler tube. The method may include deforming a metal plate to create at least one first protrusion and at least one second protrusion on a surface of the metal plate. A first longitudinal plane may extend through the at least one first protrusion, and a second longitudinal plane may extend through the at least one second protrusion. The first longitudinal plane may intersect with the second longitudinal plane. The method may also include rolling the plate into a tubular shape, and joining first and second edges of the plate to form a tube.

In yet another aspect, the present disclosure may be directed to an engine assembly. The engine assembly may include a turbocharger configured to compress intake air before it enters an engine air intake manifold. The engine assembly may also include an air-to-air aftercooler operatively connected between the turbocharger and the engine air intake manifold. The air-to-air aftercooler may include at least one tube configured to direct the compressed

intake air, the tube including at least one first protrusion located on a first interior surface of the tube, with a first longitudinal plane extending through the at least one first protrusion. The tube may also include at least one second protrusion located on a second interior surface of the tube, with a second longitudinal plane extending through the at least one second protrusion. Furthermore, the first longitudinal plane and the second longitudinal plane may intersect.

In yet another aspect, the present disclosure may be directed to a tube configured to direct a flow of charged air. The tube may include at least one first protrusion located on a first interior surface of the tube, and a first longitudinal plane may extend through the at least one first protrusion. The tube may also include at least one second protrusion located on a second interior surface of the tube, and a second longitudinal plane may extend through the at least one second protrusion. Furthermore, the first longitudinal plane and the second longitudinal plane may intersect and extend at an angle with respect to a longitudinal axis of the tube.

Brief Description of the Drawings

FIG. 1 provides a diagrammatic view of a work machine according to an exemplary disclosed embodiment.

FIG. 2 provides a diagrammatic view of an engine according to an exemplary disclosed embodiment.

FIG. 3 provides a diagrammatic view of an air-to-air aftercooler according to an exemplary disclosed embodiment.

FIG. 4 provides a diagrammatic view of tubes and fins according to an exemplary disclosed embodiment. FIG. 5 provides a diagrammatic view of a tube according to an exemplary disclosed embodiment.

FIG. 6 provides a diagrammatic view of a tube according to an exemplary disclosed embodiment.

FIG. 7 provides a diagrammatic view of a tube according to an exemplary disclosed embodiment.

FIGS. 8a-8d provide diagrammatic perspective views of a method of making a tube according to an exemplary disclosed embodiment.

Detailed Description

Referring to FIG. 1, a work machine 10, such as an off-highway truck, is illustrated. Work machine 10 may comprise a frame 12 and a dump body 14 pivotally mounted to the frame 12. An operator cab 16 may be mounted on the front of the frame 12 above an engine enclosure 18. Work machine 10 may be supported on the ground by a pair of front tires 20 (one shown), and a pair of rear tires 22 (one shown).

One or more engines 24 may be located within engine enclosure 18. An example of an engine 24 is shown in FIG. 2. Engine 24 may be used to provide power to a drive assembly of work machine 10, via a mechanical or electric drive train. As illustrated in FIG. 2, engine 24 may include an internal combustion engine. Internal combustion engine 24 may include a turbocharger 26 for compressing intake air 38a into heated charged air 38b, and an air-to-air aftercooler (ATAAC) 36 for cooling heated charged air 38b prior to entering an air intake manifold 32. Each of the engine sub-components may have a variety of configurations to suit a particular application. Exemplary sub-components of engine 24 will be discussed, but the presently disclosed embodiment is not limited to these specific configurations.

Turbocharger 26 may include a compressor 30, powered by a turbine 28 driven by engine exhaust flow 34. The compressor 30 may pressurize intake air 38a to allow a greater mass of fuel/air mixture in the engine cylinders of engine 24. The result may be an increase in power and improved engine efficiency. However, as a byproduct of pressurization, the temperature of intake air 38a may also increase, which may be undesirable. The compressed intake air exiting compressor 30 may be referred to as heated charged air 38b. As noted

above, heated charged air 38b may be cooled prior to entering air intake manifold by passing through ATAAC 36.

One exemplary disclosed embodiment of ATAAC 36 is shown in FIG. 3. Heated charged air 38b from compressor 30 of turbocharger 26 may be admitted into ATAAC 36 through an inlet port 40. Inlet port 40 forms a portion of an ATAAC inlet manifold 42 that directs heated charged air 38b into one or more tubes 44. After traversing ATAAC 36, and having undergone a heat exchange operation with respect to relatively cool ambient air simultaneously passing over and around ATAAC 36, the previously heated charged air 38b may be exhausted through an outlet port 46 of an ATAAC outlet manifold 48 as relatively cooled charged air 38 c, which may then be routed to engine air intake manifold 32. As shown in FIG. 2, engine air intake manifold 32 of engine 24 may include one or more passages or pipes which may be used to conduct cooled charged air 38c to one or more engine cylinders (not shown). ATAAC 36 may be constructed from suitable metals including copper, stainless steel, aluminum, or alloys thereof.

Tubes 44 are shown enlarged in FIG. 4. Tubes 44 may be separated by external fins 50, which may be bonded to tubes 44 to increase their external surface area, thus aiding in heat transfer. External fins 50 may be formed from thin strips of metal, bent or otherwise formed into desired configurations. The configurations may allow for the free flow of ambient air across external fins 50, resulting in the ambient air removing heat from tubes 44 and external fins 50. External fins 50 may have any number of different configurations, including, for example, serpentine, saw tooth, louver, and wave shapes. Tubes 44 and external fins 50 may be constructed out of copper and alloys thereof. Alternatively, tubes 44 and fins 50 may be made of other suitable materials, including, for example, stainless steel, aluminum, and other metals and alloys.

As shown in FIG. 5, each tube 44 may also include a turbulator 52 to promote mixing of heated charged air 38b passing through tube 44. Creating turbulent flow within tube 44 may provide increased heat transfer between heated charged air 38b and tube 44 and fins 50. In one embodiment, turbulator 52 may include one or more top protrusions 58 on a top interior surface 60 of tube wall 66, and/or one or more bottom protrusions 62 on a bottom interior surface 64 of tube wall 66. As will be described in more detail below, top and bottom protrusions 58 and 62 may be formed between noses (curved portions) 54 and 56 of tube 44 using known metal deformation processes, such as, for example, rolling, stamping, or other suitable methods. Also, while only one set of top protrusions 58 and bottom protrusions 62 is shown in FIG. 5, it should be understood that tube 44 may extend a greater distance in the longitudinal direction than shown, and the sets of top protrusions 58 and bottom protrusions 62 may repeat at spaced intervals along the entire longitudinal length of tube 44 (FIG. 4).

The dimensions of the above-identified structural elements may affect the degree to which tube 44 may turbulate and cool heated charged air 38. Two dimensions are shown in FIG. 6, including, for example, tube width "tw" which may range from 2-6 mm. Values for tw that are closer to the lower end of the range may be desirable because if tw has a smaller value, then protrusion depth "de" may also have a smaller value. Top protrusions 58 and bottom protrusions 62 with smaller de values may be easier to manufacture because they require a lesser degree of metal deformation processing. In one embodiment, values for de may fall in the range of 20%-60% of tw. For example, top protrusions 58 and bottom protrusions 62 may extend for equal distances such that both sets of protrusions 58 and 62 may have a de substantially equivalent to 50% of tw. Alternatively, top and bottom protrusions 58 and 62 may have de values less than 50% of tw, and so they will not contact each other. Alternatively still, one set of protrusions may have a de value greater than 50% of tw, and thus,

will have a greater de value than the remaining set of protrusions. Additionally, as shown in FIG. 7, values for protrusion width "dw" may range from 1-2 times the value for de. Protrusion angle "da" may also affect the degree of turbulation and/or cooling, and in one embodiment, da may range from 30-75 degrees. While ranges for elements of tube 44 have been described for exemplary purposes, it should be understood that other ranges are nonetheless contemplated. In one embodiment, top protrusions 58 and bottom protrusions 62 may each include a longitudinal axis 63 that may lie within a corresponding longitudinal plane extending normal to tube wall 66. Longitudinal axes 63 of top protrusions 58, as well as their corresponding longitudinal planes, may be parallel to one another, and may be oriented at an angle greater than 15 degrees with respect to a longitudinal axis 65 of tube 44. Similarly, longitudinal axes 63 of bottom protrusions 62, and their corresponding longitudinal planes, may also be parallel to one another oriented at an angle greater than 15 degrees with respect to longitudinal axis 65. When longitudinal axes 63 of top protrusions 58 and bottom protrusions 62 are superimposed, the apparent intersection of longitudinal axes 63 of top protrusions 58 and bottom protrusions 62 may form a chevron shape, including a vertex 63 a. In addition, the longitudinal plane containing longitudinal axis 63 of top protrusion 58 may intersect with the longitudinal plane containing longitudinal axis 63 of bottom protrusion 62 near vertex 63 a. It is also contemplated that top protrusions 58 and bottom protrusions 62 may contact each other in the vicinity of vertex 63 a. Furthermore, the chevrons may be arranged into a pattern, such that vertex 63a of each chevron may lie on a line extending perpendicular to the longitudinal axis 65 of tube 44. The chevron pattern may create the desired turbulence by changing the direction of heated charged air 38b passing through tube 44 without causing an excessive increase in pressure drop within tube 44. Additionally, or alternatively, top protrusions 58 and/or bottom protrusions 62 may be at least partially curvilinear, and may include sharp edges or rounded edges. Furthermore, it should be understood that the term "vertex"

may include not only a point of intersection, but also a high point of a curve. It is also contemplated that, top protrusions 58 and/or bottom protrusions 62 may have alternative geometries, sizes, and orientations, and furthermore, the number of top protrusions 58 and/or bottom protrusions 62 may be increased or decreased as desired. Alternatively, tube 44 may have only either top protrusions 58 or bottom protrusions 62, but not both. In yet another embodiment, tube 44 may include alternating sections of top protrusions 58 and bottom protrusions 62.

As shown in FIGS. 8a through 8d, tube 44 may be formed from a metal plate 68 having a first edge 70 and a second edge 72. Top protrusions 58 and bottom protrusions 62 may be created on metal plate 68 by stamping, rolling, or other suitable metal deformation process, thus producing the structure shown in FIG. 8b. After top and bottom protrusions 58 and 62 are formed, metal plate 68 may be rolled, thus bringing first edge 70 into close proximity with second edge 72, as shown in FIG. 8c. Alternatively, first edge 70 and second edge 72 may be brought into contact with one another. Finally, as shown in FIG. 8d, first edge 70 and second edge 72 may be welded together to produce tube 44. It is further contemplated that welding may be performed at any point of contact between opposing top protrusions 58 and bottom protrusions 62. Welding may provide structural strength to tube 44 by providing additional support to ensure that tube 44 will not deform undesirably due to high pressures within tube 44 and/or forces applied by loads outside of tube 44. The welds may be created by using high frequency induction welding, resistance welding, brazing, or other suitable processes.

Industrial Applicability The disclosed ATAAC may have applicability with internal combustion engines. In particular, and as shown in FIG. 2, ATAAC 36 may serve to cool a flow of intake air 38a exiting a compressor 30 of a turbocharger 26 before it enters an intake manifold 32 of an engine 24, thus decreasing the level of emissions and increasing the life of engine components.

In a work machine 10, exhaust 34 leaving engine 24 may be directed towards a turbine 28 of turbocharger 26. The flow of exhaust 34 may power turbine 28, causing it to rotate and drive compressor 30. Intake air 38a may be directed into compressor 30 where it may undergo compression, and as a byproduct of compression, intake air 38a may also be heated into heated charged air 38b. Heated charged air 38b may travel from compressor 30 into ATTAC 36 through an inlet 40, where it may be directed into an intake manifold 42. Tubes 44 may be in fluid communication with intake manifold 42 of ATAAC 36, and thus, heated charged air 38b may pass from intake manifold 42 into tubes 44. To assist in the heat transfer, tubes 44 may each have one or more turbulators 52 configured to provide turbulence to the flow of heated charged air 38b passing through tubes 44. Turbulence created by turbulators 52 may assist in preventing development of a radial temperature gradient within tubes 44 by mixing all of the regions of heated charged air 38b together, which my result in increased heat transfer between heated charged air 38b and tubes 44. Tubes 44 may direct cooled charged air 38c into outlet manifold 48 towards outlet 46. Upon exiting ATAAC 36, cooled charged air 38c may be mixed with fuel within one or more combustions chambers (not shown) within engine 24. Because cooler air has greater density than heated air, a volume of cooled charged air 38c at a certain pressure may contain a greater number of air molecules than the same volume of heated charged air 38b at that same pressure. Increasing the number of air molecules in combustion chambers of engine 24 assists combustion, which may decrease the amount of smoke and/or emissions exiting from engine 24. Also, reducing the temperature of heated charged air 38b may decrease the operating temperature of engine 24, thus resulting in less wear on engine components.

The use of turbulators 52 may also provide other advantages. For example, ATAAC 36 may preferably be constructed of copper or alloys thereof because copper brazed ATAAC tubes 44 may provide superior performance. A difficulty that may arise when using copper brazed ATAAC tubes 44 is that

disturbing braze paste or foil in the interior of copper brazed ATAAC tubes 44 may result in added manufacturing expense. Turbulators 52 may be formed from the outside of tube 44, and thus, may not require insertion of any devices into tube 44 that could damage or disturb the braze paste or foil in the interior of tubes 44. This characteristic of turbulators 52 may allow the use of copper brazed ATAAC tubes 44 for their performance capabilities, while avoiding the added expense associated with disturbing braze paste or foil during manufacturing. The same may hold true when making ATAAC 36 using stainless steel.

Turbulators 52 may also provide added structural strength. As discussed above, top protrusions 58 may contact bottom protrusions 62 in the vicinity of vertex 63a, and they may be joined together at any point of contact by one or more welds to reinforce the walls of tube 44. Contact between top protrusions 58 and bottom protrusions 62 may resist external forces on tube 44 that would otherwise cause tube 44 to inwardly deform. Additionally, internal pressure within tube 44 may be less likely to cause outward deformation of walls 66 of tube 44 when turbulators 52 are included. As a result, ATAAC 36 may be used in engine assemblies with high charge air pressures. The ability to use higher charge air pressures may provide the added benefits of more complete combustion of fuel, lower emissions, and greater overall engine efficiency. It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed ATAAC and methods without departing from the scope of the disclosure. Additionally, other embodiments of the ATAAC and methods will be apparent to those skill in the art from consideration of the specification. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.