Patent Application
20140311466
The present disclosure relates generally to heat exchangers for the transfer of thermal energy in an exhaust gas recirculation system associated with an internal combustion engine and, more particularly, to devices and/or modifications for use in connection with such heat exchangers that contribute to the efficiency, manufacturability, reliability and/or longevity thereof.
Internal combustion engines burn a hydrocarbon-based fuel or another combustible fuel source to convert the potential or chemical energy therein to mechanical power that may be utilized for other work. The combustion of fuel produces byproducts and emissions that the U.S. Government and other governments regulate. To comply with these regulations, engine manufacturers have developed a number of methods for reducing or treating the emissions created by the internal combustion process. One such apparatus for reducing or treating the emissions is an exhaust gas recirculation (EGR) system. An EGR system is a system in which a portion of the exhaust gasses produced by the combustion process are recirculated and intermixed with the incoming intake air. The use of an EGR system lessens the creation of nitrogen oxides such as NO and NO2, commonly referred to as NOx, during combustion. Because the exhaust gasses are typically still hot after their initial combustion, however, they generally are cooled before being recirculated into the intake air. Accordingly, one of the purposes of EGR systems is to cool the exhaust gas prior to recirculation to avoid disrupting the combustion process and/or to gain additional performance advantages.
The cooling of the exhaust gas in an EGR system before introduction into the engine intake air may be accomplished through the use of heat exchangers. Consistent therewith, U.S. patent application Ser. No. 13/549,936, filed on Jul. 16, 2012, assigned to the assignee of the present application (the entire contents of which are herein incorporated and fully integrated by reference), discloses a heat exchanger of the type that may be used with an EGR system in accordance with the present disclosure as well as a coolant inlet structure for use therewith. Similarly, Japanese Patent Publication 200900131285912 (JP '912), entitled “Cooling Water Inlet Structure of Heat Exchanger for EGR Cooler,” also discloses an EGR heat exchanger and a coolant inlet structure thereof.
While both of these disclosures disclose heat exchangers and coolant inlet structures useable in EGR systems, in some applications, it may be desired to optimize certain aspects of the designs of heat exchangers used in such EGR systems, and in particular, structures located at or proximate coolant inlet sections of such heat exchangers. In particular, it may be desired to have inlet structures for heat exchangers operable for use in EGR systems that contribute to the thermal efficiency of the heat exchanger. Further, it may be desired that these inlet structures be capable of being manufactured in an efficient and cost-effective manner and that the manufactured inlet structures have the desired longevity.
In one aspect, the disclosure describes aspects of a heat exchanger for an EGR system associated with an internal combustion engine, and more specifically, to inlet structures for use in connection with such heat exchangers. Specifically, in accordance with one aspect of the disclosure, the disclosed inlet structures may comprise an inlet collar formed from at least two separate pieces that have been combined. More specifically, the inlet collar may be formed from at least two separate pieces that have been brazed, welded, or otherwise combined together
In another aspect of the disclosure, inlet structures in accordance with the disclosure may comprise an inlet channel to an inlet collar of an EGR system that has a geometry that increases the thermal efficiency of the EGR system. In particular, the inlet structure may comprise a coolant feed connection fitted with a flow deflector to direct coolant flow into and around a coolant inlet collar. Additionally, in accordance with other aspects of the disclosure, the inlet structure may comprise a coolant feed connection that is tapered outwardly to more smoothly and efficiently direct coolant flow into a coolant inlet collar.
In another aspect, the inlet structure may comprise structures for manipulating the flow of a coolant into an inlet collar for a heat exchanger used in an EGR system. In particular, in such an embodiment, an inlet flow splitter may be incorporated in a coolant feed elbow to create a more uniform inlet coolant flow thereby increasing the thermal efficiency of the EGR system. In accordance with aspects of the embodiments consistent therewith, the inlet flow splitter may be comprised of a bisecting wall in a coolant feed elbow.
Now referring to the drawings, wherein like reference numbers refer to like elements, there is illustrated a machine 100 powered by an internal combustion engine 102 adapted to combust a fuel to release the chemical energy therein and convert that energy to mechanical power. The machine 100 may be an “over-the-road” vehicle such as a truck used in transportation or may be any other type of machine that performs some type of operation associated with an industry such as mining, construction, farming, transportation, or any other industry known in the art. For example, the machine may be an off-highway truck, earth-moving machine, such as a wheel loader, excavator, dump truck, backhoe, motor grader, material handler or the like. The term “machine” may also refer to stationary equipment like a generator that is driven by an internal combustion engine to generate electricity. The specific machine 100 illustrated in
The internal combustion engine 102 may be a compression ignition engine that combusts diesel fuel, though in other embodiments, it may be a spark ignition engine that combusts gasoline or other fuels such as ethanol, bio-fuels, or the like. To store and supply the internal combustion engine 102 with fuel for the combustion process, the machine 100 may include a fuel reservoir 104 that is in fluid communication with a fuel rail 106 on the machine 100 by way of a fuel line 108. To direct intake air used in the combustion process to the internal combustion engine 102, an intake manifold 110 may be disposed over the engine 102 and in fluid communication with the combustion chambers disposed therein. The intake manifold 110 may receive intake air from an intake line 112 that may draw atmospheric air through an air intake filter 114. Similarly, to direct the exhaust gasses produced by the combustion process from the internal combustion engine 102, an exhaust manifold 120 may extend over the engine 102 and may be in fluid communication with the combustion cylinders. The intake manifold 110 and the exhaust manifold 120 are depicted in an overlapping fashion, but in other embodiments may be disposed in any suitable arrangement including being integrally formed into the internal combustion engine 102 itself. The exhaust manifold 120 may direct exhaust gasses to an exhaust line 122 that terminates at an exhaust orifice 124 that releases the gasses back to the atmosphere.
To assist in directing intake air into the internal combustion engine 102, the machine 100 may include a turbocharger 130. The turbocharger 130 may include a compressor 132 disposed in the intake line 112 that compresses intake air drawn from the atmosphere and directs the compressed air to the intake manifold 110. Although a single turbocharger 130 is shown, more than one such device connected in series and/or in parallel with another may be used. To power the compressor 132, a turbine 134 may be disposed in the exhaust line 122 and may receive pressurized exhaust gasses from the exhaust manifold 120. The pressurized exhaust gasses directed through the turbine 134 may rotate a turbine wheel having a series of blades thereon, which powers a shaft that causes a compressor wheel to rotate within a compressor housing pressurizing the intake air.
To remove heat produced by the internal combustion process and cool the internal combustion engine 102, the machine 100 may include a coolant system 140 that may direct a coolant such as water or radiator fluid through the engine 102. The coolant circulating through the engine 102 absorbs heat therein in the form of thermal energy and, upon exiting the engine 102, discharges the thermal energy to the atmosphere. The coolant system 140 may include a radiator 142, such as an air-cooled crossflow radiator disposed in a location where a sufficient amount of air will pass over and/or through it. To deliver cooled coolant to the internal combustion engine 102, the radiator 142 may communicate with a cold line or feed line 144, and to receive heated coolant returning from the engine 102, the radiator 142 may be operatively connected to a hot line or return line 146. To pressurize and forcibly direct the coolant through the coolant system 140, a coolant pump 148 may be disposed in the feed line 144, the return line 146 or elsewhere in the coolant system 140.
To reduce emissions produced by the combustion process, the internal combustion engine 102 may be operatively associated with an exhaust gas recirculation EGR system 150. An EGR system, as will be familiar to those of skill in the art, may redirect a portion of the exhaust gasses discharged from the combustion process back to the intake system and intermix the exhaust gasses with the intake air. The presence of exhaust gasses in the intake air lowers the relative proportion or amount of oxygen available for combustion in the combustion chamber, which results in a lower flame and/or combustion temperature. As a result, the combustion process generates less nitrogen oxides than would be produced in an oxygen rich environment that often results in higher combustion temperatures.
To redirect the exhaust gasses, the EGR system 150 may include an EGR line 152 that communicates with the exhaust line 122 and that may be in fluid communication to the intake manifold 110 or intake line 112. To selectively control the amount of exhaust gasses redirected to the EGR process, the EGR system 150 may include an adjustable EGR valve 154, such as a butterfly valve, disposed in the EGR line 152. Please note, that the illustration shows a “hot side” application wherein the EGR valve 154 is located between the cooler inlet and exhaust manifold. It is to be understood, however, that the present disclosure is equally applicable to a “cold side” valve arrangement where the EGR valve 154 is located between the cooler outlet and intake manifold, as well as many other configurations/set ups, consistent with the disclosure herein. In the illustrated embodiment, the EGR line 152 accesses the exhaust line 122 upstream of the turbine 134 so as to receive high-pressure exhaust gasses that have not lost pressure through the turbine 134 and is thus referred to as a high-pressure EGR system. In other embodiments, the EGR line 152 may intersect the exhaust line 122 downstream of the turbine 134 to receive depressurized exhaust gasses and may thus be considered a low-pressure EGR system.
To cool the redirected exhaust gasses prior to recirculation with the intake air, the EGR system 150 may include a heat exchanger 160 operatively associated with the internal combustion engine 102 and the coolant system 140. In the illustrated embodiment, the heat exchanger 160 may be attached to the side of the internal combustion engine 102 but, in other embodiments, it may be located elsewhere on the machine 100. Referring to
To receive the exhaust gasses, the heat exchanger 160 may have an exhaust gas inlet diffuser 170 disposed at the upstream end 162 and that may connect to the EGR line 152 downstream of the EGR valve 154 and upstream of the intake manifold 110. The inlet diffuser 170 may widen from its connection point to the EGR line 152 to its attachment to the elongated, rectangular main body 174 of the heat exchanger 160 to assist in slowing the incoming, high-pressure exhaust gasses. Additionally, in the illustrated embodiment, the inlet diffuser 170 may define an inlet axis line 172 aligned with the flow direction of the incoming exhaust gasses and that is generally perpendicular to the longitudinal axis line 166 of the heat exchanger 160. The inlet diffuser 170 may therefore direct the incoming exhaust gasses through a 90° turn or bend to realign flow with the longitudinal axis line 166 and uniformly aid in distributing the exhaust gasses to the internal components of the heat exchanger 160. In an embodiment, the inlet diffuser 170 may include a pivotal blade or baffle that may move within the diffuser 170 to increase or restrict the flow area therein and thus help control the flow of exhaust gasses. To return the exhaust gasses to the EGR system 150 after passing through the heat exchanger 160, the heat exchanger 160 may include a substantially identical exhaust gas exit diffuser 176 disposed at the downstream end 164 that may connect with the remainder of the EGR line 152 to communicate with the intake manifold 110. The exit diffuser 176 may define an exit axis line 178 that is substantially parallel to the inlet axis line 172 and perpendicular to the longitudinal axis line 166. However, alternative embodiments may include configurations wherein the inlet diffuser 170 and exit diffuser 176 have non-coplanar axis lines.
To receive cooled coolant from the coolant system 140, the heat exchanger 160 may include a coolant feed connection 180 disposed proximate to the upstream end 162 in fluid communication with the coolant feed line 144. The coolant feed connection 180 may be any suitable type of connection such as a hose bib, a threaded hose fitting, or a more complex connection such as a quick-release fitting, or a permanent connection such as done by welding or brazing.
The coolant feed inlet 180 may extend from the main body 174 of the heat exchanger 160 perpendicular to the longitudinal axis line 166 and parallel to the inlet axis line 172. To simplify connection with the coolant feed line 144, in one embodiment, a single coolant feed inlet 180 may be included on the heat exchanger 160.
To discharge the heated coolant from the heat exchanger 160, a coolant return connection 182 may be attached to the main body 174 proximate to the downstream end 164 and may be oriented perpendicular to the longitudinal axis line 166 and parallel to the exit axis line 178. In an alternative embodiment, the coolant feed inlet 180 may extend from the main body 174 of the heat exchanger 160 perpendicular to the longitudinal axis line 166 and substantially orthogonal to the inlet axis line 172. Similarly, in an alternative embodiment, the coolant return connection 182 may be oriented perpendicular to the longitudinal axis line 166 and substantially orthogonal to the exit axis line 178.
Because the exhaust gas inlet diffuser 170 and coolant feed connection 180 are located proximate to the upstream end 162, and the exhaust gas exit diffuser 176 and coolant return connection 182 are located proximate to the downstream end 164, flow of both mediums, exhaust gas and coolant, will be generally directed from the upstream end 162 to the downstream end 164. This arrangement is commonly referred to as a parallel flow-heat exchanger 160. In other embodiments of the disclosure, though, the inlets, exits and connections may be arranged for a counter-flow heat exchanger 160 wherein exhaust gasses and coolant enter and exit at opposite ends of the heat exchanger 160. Additionally, the described embodiment of the heat exchanger 160 is a single pass design in which the two conducting mediums make a single pass through the exchanger, but the disclosure is also applicable to multipass arrangements in which the mediums are directed to make multiple passes through the heat exchanger 160. The particular flow arrangement may depend in part upon size constraints, volume capacity and desired thermal efficiencies, and any suitable flow arrangement or variation thereof are contemplated as within the scope of the claims.
Referring to
In the present embodiment, the hollow tubes 190 may be designated to conduct the exhaust gasses and maintain separation of the exhaust gasses from the coolant flowing over and around the tubes 190. To define coolant channels 198 in the tube core 192 for flow of coolant between the tubes 190, the plurality of tubes 190 may be spaced apart from each other along their lengths so that elongated voids are created between and separate the tubes 190. To maintain the plurality of tubes 190 in a fixed, spaced-apart arrangement and thereby maintain the coolant channels 198, the elongated tubes 190 may be fixed at one end to an upstream header 200 and at the opposite end to a downstream header 202. Thus, the upstream header 200 demarcates the upstream face 194 of the tube core 192 and the downstream header 202 demarcates the downstream face 196. The headers 200, 202 may be relatively thick, flat plates of a metallic material like steel or aluminum arranged perpendicular to the longitudinal axis line 166. To provide access to the interior of the hollow tubes 190, a plurality of apertures 204 may be disposed through the headers 200, 202 with each aperture aligned to one corresponding tube. The tubes 190 may be welded, brazed or otherwise joined to the headers 200, 202 to align with their respective apertures 204. In the illustrated embodiment, the apertures 204 are oblong slots but, in other embodiments, could have other shapes.
The tube core 192 may be disposed in a hollow, outer housing or core shell 210. The core shell 210 may extend between a first rim 212 and an opposite second rim 214 and is generally disposed over and around the tube core 192 to retain the coolant within the coolant channels 198. The illustrated core shell 210 is a generally four-sided structure with four, integral longitudinal sides 216 to correspond to the rectangular or square arrangement of the tubes 190 in the tube core 192 but in other embodiments could have different shapes. Like the headers 200, 202, the core shell 210 may be made from a metal such as steel or aluminum. The coolant feed connection 180 and the coolant return connection 182 may be disposed through one side 216 of the core shell 210 slightly behind the headers 200, 202 to introduce and receive coolant to and from the tube core 192. Accordingly, the headers 200, 202 constrain coolant in the core shell 210 to prevent coolant from entering the inlet and exit diffusers 170,176 and intermixing with the exhaust gasses.
Referring to
In accordance therewith, the heat exchanger 160 may therefore be equipped with coolant inlet structures which may allow for improved distribution of coolant in the EGR system generally, and, specifically, to various components thereof, thereby addressing potential issues of inadequate distribution and localized heating. Non-limiting examples of such coolant inlet structures, all of which will be discussed in detail below, include coolant inlet lines (or the like) which provide multiple coolant introduction paths or ports for coolant into and around the tube core 192 (see, e.g.
Referring first to
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The inlet collar 300 may have a width provided by the integral first sidewall 302, second sidewall 304, third sidewall 306, and fourth sidewall to faun a first surface or first edge 312 and an opposing second surface or second edge 314, both of which follow the substantially square outline of the inlet collar 300. The first edge 312 may be joined to the correspondingly shaped first rim 212 of the core shell 210 by welding, brazing or the like. Constrained at the opposite second edge 314 of the inlet collar 300 and traversing the interior region 310 is the upstream header 200. For example, the header 200 and the second edge 314 may be joined along abutting flange structures by brazing, welding or the like. When the tube core 192 is included and interfaced at its upstream face 194 with the upstream header 200, the inlet collar 300 may be disposed about and surround the tube core 192 coextensively with the upstream face 194.
To distribute coolant substantially about the tube core 192, the inlet collar 300 may include a hollow, enclosed coolant duct 320 that is generally aligned along the loop 219 to circumscribe the interior region 310. The coolant duct 320 may be a generally flat, hollow void external of the first sidewall 302, second sidewall 304, third sidewall 306 and fourth sidewall that is enclosed by a duct cover 322 disposed about the exterior of the inlet collar 300. The coolant duct 320 may be separated from the interior region 310 by an inner barrier wall 324 that, in the illustrated embodiment, may be formed by portions of the first sidewall 302, second sidewall 304, third sidewall 306 and fourth sidewall.
Specific introduction points or paths may be disposed through the barrier wall 324 so that coolant flowing in the coolant duct 320 may flow or pass to the tube core 192. In the embodiment shown in
In another embodiment, rather than completely circumscribe the tube core 192, the coolant inlet line may partially circumscribe the tube core 192, for example, approximately halfway. Referring to
To communicate with the coolant system 140, the coolant feed connection 180 may be disposed on the inlet collar 300, for example, protruding from the bottom second side 306 of the inlet collar 300. The coolant duct 320 may be in fluid communication with the coolant feed connection 180. An advantage of this arrangement is that a single connection point such as a hose fitting may be made to the coolant system 140 and still distribute coolant substantially around and about the tube core 192 to provide multiple introduction paths in multiple directions radially inward toward the common longitudinal axis line 1.66. To recover heated coolant from the heat exchanger 160, in one exemplary embodiment a similar coolant outlet 182 collar may be disposed at the downstream end 164 so that coolant is uniformly removed from the downstream face 196 of the tube core 192. Alternative exemplary embodiments include configurations wherein the outlet 182 does not include a collar configuration. The inlet collar 300 may be made from metal or another suitable material and may be made as a cast part, for example, by lost wax or investment casting.
Referring to
To direct the coolant about the inlet collar 400 for uniform distribution into the tube core 192, the inlet collar 400 may include a coolant duct 420 disposed continuously about the exteriors of the first sidewall 402, second sidewall 404, third sidewall 406 and fourth sidewall so that the duct 420 circumscribes the centrally disposed longitudinal axis line 166. The coolant duct 420 may be a low, flat, void that is enclosed by an external duct cover 422 joined to and partially offset from the sidewalls 605. To separate the coolant duct 420 from the interior region 410, a barrier wall 424 may be formed from the portions of the first sidewall 402, second sidewall 404, third sidewall 406 and fourth sidewall underneath the duct cover 422 so that the barrier wall 424 serves as the interior of the duct 420. In the illustrated embodiment, the coolant duct 420 may trace the outline disposed around and circumscribing the longitudinal axis line 166 by the loop 219 in a substantially annular manner.
To introduce coolant from the coolant duct 420 into the interior region 410 and the upstream face 194 of the tube core 192 that will be disposed therein, an introduction path may be established by a slot 426 disposed through the barrier wall 424 continuously along the first sidewall 402, second sidewall 404, third sidewall 406 and fourth sidewall. The slot 426 therefore forms an inwardly directed flow path that is generally radially oriented toward the longitudinal axis line 166 so that at least a portion of the incoming coolant may converge at the central longitudinal axis line 166. Moreover, the slot 426 may be shifted closer to the second edge 414 than the first edge 412 so that radially incoming coolant may flow adjacent or proximate to the upstream header 200. The continuous or uninterrupted design of the slot 426 facilitates uniform distribution of coolant across the upstream header 200 and upstream face 194 of the tube core 192 that will be adjacent to the header 200. The width of the slot 426 may be dimensioned proportional to the width of the coolant duct 420 so that coolant is evenly distributed about the duct 420 for uniform introduction to the interior region 410 from substantially all directions. Alternative embodiments include configurations wherein the width of the slot 426 may be varied depending on a distance from the coolant feed connection 180; for example, the width of the slot 426 may be greatest at a location disposed furthest from the coolant feed connection 180.
Given the difficulty of forming the coolant inlet collar 300 from a single casting, as well as issues of reliability related thereto, it has been found that the coolant inlet collars 300, 400 may be formed from multiple pieces that are then brazed, welded or otherwise joined together in accordance with an aspect to of the disclosure as shown in
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As discussed above, coolant feed connections are provided which may improve coolant flow into the body of a coolant inlet line (such as coolant inlet collar 300, 400) or the heat exchanger 160 itself. Referring first to
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The present disclosure is applicable to coolant inlet structures for heat exchangers in general and, in particular to heat exchangers that may be used to cool exhaust gasses prior to incorporation with intake air in EGR systems. While coolant inlet structures for heat exchangers of this type have been used in the past, sometimes it may be desired to optimize certain aspects of the designs of these structures. In particular, it may be desired to have inlet structures for heat exchangers operable for use in EGR systems that contribute to the thermal efficiency of the heat exchanger 160. Further, it may be desired that these inlet structures be capable of being manufactured in an efficient and cost-effective manner and that the manufactured inlet structures have the desired longevity.
More specifically, it has been found that coolant inlet structures for heat exchangers, particularly those having complicated structural features (such as inlet orifices 326, channels, sidewalls 605, etc.) may be difficult to manufacture in single castings. Accordingly, it may be desirable in some applications, to produce a coolant inlet structure, such as a coolant inlet collar 300 in multiple pieces that are then, thereafter, joined together. Methods for joining could include, but are not limited to, welding, brazing, and the like.
It has also been found that some prior art tubes 190 have been known to fail due to heat stress. It has been found that such failures typically occur at a point or location most distant from the coolant ingress point into the coolant inlet structure along a coolant inlet face. Accordingly, it may be desirable, in some applications, to provide inlet structures that have geometries that increase the thermal efficiency of the EGR system 150 and the longevity of the cooler core itself. In particular, the inlet structure may comprise a coolant feed connection 180 fitted with a flow deflector to direct coolant flow into and around a coolant inlet collar 300. Additionally, in some applications, it may be desired to provide an inlet structure comprising a coolant feed connection 180 that is tapered outwardly to more smoothly and efficiently direct coolant flow into a coolant inlet collar 300. Finally, in other applications, it may be desired to correct non-uniform flow of coolant entering a coolant inlet collar 300 of a heat exchanger 160. In such applications, an inlet flow splitter 702 may be incorporated in a coolant feed elbow 700 to create a more uniform inlet coolant flow thereby increasing the thermal efficiency of the EGR system 150, as well as potential longevity of a coolant inlet collar 300 associated therewith.
The many features and advantages of the disclosure are apparent from the detailed specification, and, thus, it is intended by the appended claims to cover all such features and advantages of the disclosure which fall within its true spirit and scope. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the disclosure to the exact construction and operation illustrated and described, and, accordingly, all suitable modifications and equivalents may be resorted to that fall within the scope of the disclosure.
