JP5781756B2 - EGR cooler - Google Patents

Description

  The present invention is used for cooling a part of exhaust gas (EGR gas) in an EGR (exhaust gas recirculation) device that recirculates a part of exhaust gas from a combustion apparatus such as an internal combustion engine into a combustion chamber and re-combusts it. Relating to the EGR cooler.

  Purifying the exhaust from the internal combustion engine to suppress the expansion of air pollution is an important issue, but as one of the systems (apparatus) for this purpose, a part of the exhaust from the internal combustion engine is returned to the combustion chamber. A so-called EGR (Exhaust Gas Recirculation) system is known for reducing the concentration (exhaust amount) of nitrogen oxides (hereinafter referred to as NOx) in exhaust gas by reducing the combustion temperature by recombusting the exhaust gas. ing.

  In such an EGR system, by cooling the EGR gas to be recirculated into the combustion chamber, the combustion temperature can be lowered, and thereby the NOx emission can be more effectively reduced.

  For this reason, for example, in the EGR system described in Patent Document 1, an EGR cooler that is a heat exchanger for cooling EGR gas is connected to an EGR passage that guides the EGR gas from the exhaust passage to the intake passage of the internal combustion engine. It has been done to intervene.

  In addition, since the expansion of the EGR gas is suppressed by providing the EGR cooler and lowering the EGR gas temperature, it is desired to increase the amount of EGR gas (exhaust gas recirculation amount) mixed in the intake air, that is, the EGR rate (= EGR This is also advantageous when there is a demand for further earning gas amount / (fresh air amount + EGR gas amount) × 100 (%)).

  Here, examples of the structure of a multi-tube EGR cooler having a large number of heat exchange pipes used in the EGR system are described in, for example, Patent Document 2, Patent Document 3, Patent Document 4, and Patent Document 5. There is something like that.

JP 2006-125356 A Japanese Patent Application Laid-Open No. 11-193992 Japanese Patent Laid-Open No. 11-193993 JP 2007-170271 A JP 2007-225137 A

  By the way, in the structure of the multi-tube type EGR cooler provided with a large number of heat exchange pipes, it is desirable to arrange the heat exchange pipes so that the cross section is cylindrical as shown in FIG.

  However, if the number of heat exchange pipes is increased in order to increase the cooling efficiency (cooling performance) in such a multi-tube EGR cooler, the size (outer diameter) increases as shown in FIG. In this case, the mountability to the vehicle is deteriorated, and there is a limit to the increase in the number of heat exchange pipes.

  Note that the cross-sectional shape of the EGR cooler substantially orthogonal to the longitudinal direction of the heat exchange pipe is changed from a cylindrical shape as shown in FIG. 6 or 7 to a box shape (polygonal shape such as a rectangle) as shown in FIG. ), It can be expected that both the increase in the number of heat exchange pipes and the ease of mounting on a vehicle or the like can be achieved, but at the corner (corner) of the box-shaped cross section compared to the case of the cylindrical cross section. It was confirmed that a stagnation was likely to occur in the flow of cooling water (refrigerant) or EGR gas.

  The presence of such stagnation causes a region where the heat exchange efficiency is locally lowered in the box-shaped cross section. Therefore, even with the same number of heat exchange pipes, the cooling efficiency ( It is assumed that the cooling performance is inferior to the EGR cooler having a cylindrical cross section.

  For this reason, in a multi-tube EGR cooler provided with a large number of heat exchange pipes, in which the cross section substantially perpendicular to the longitudinal direction of the heat exchange pipe has a polygonal shape such as a box shape, the object to be cooled ( It is desired to improve the cooling efficiency (cooling performance) by eliminating the stagnation at the corners (corners) while taking into account the relationship between the EGR gas) and the inlet diameter to the EGR cooler.

  In Patent Document 2, Patent Document 3, Patent Document 4, and Patent Document 5, the diameter of some heat exchange pipes is different from the diameter of heat exchange pipes in other parts, or the diameter of the heat exchange pipe in the longitudinal direction. Attempts have been made to partially change the flow of refrigerant and EGR gas by giving changes to the shape, but the cross section approximately perpendicular to the longitudinal direction of the heat exchange pipe has a polygonal shape such as a box shape. In fact, sufficient consideration has not been given to the flow (stagnation) in the corners of the EGR cooler having the above.

  The present invention has been made in view of such circumstances, and is a multi-tube EGR cooler having a plurality of heat exchange pipes (heat transfer pipes) while having a simple and inexpensive configuration. An object of the present invention is to provide an EGR cooler structure capable of improving the heat exchange performance in an EGR cooler having a polygonal shape such as a box shape in a cross section substantially perpendicular to the longitudinal direction.

For this reason, the EGR cooler according to the present invention is
An EGR cooler of an EGR device that recirculates a part of exhaust gas as EGR gas to a combustion chamber through an EGR passage, and guides the EGR gas in the EGR passage to the inside of a plurality of heat transfer tubes arranged side by side. In which the heat medium is guided to the outer peripheral side of the gas and heat exchange is performed between the EGR gas and the heat medium,
Cross-sectional shape of the EGR cooler have a corner in a direction substantially perpendicular to the longitudinal direction of the heat transfer tube, the inner and outer diameters of the heat transfer tubes in the vicinity of the corner portion, the inner diameter and smaller than the outer diameter of the heat transfer tube of the other part In this case, the heat transfer tubes are arranged at a higher density in the vicinity of the corners than in other portions .

  In the present invention, the vicinity of the corner portion may be outside the EGR gas inlet to the EGR cooler when viewed from the longitudinal direction of the heat transfer tube.

  According to the present invention, a multi-tube EGR cooler having a plurality of heat exchange pipes (heat transfer tubes) with a simple and inexpensive configuration, the cross section substantially orthogonal to the longitudinal direction of the heat exchange pipes is a box. It is possible to provide an EGR cooler structure that can improve heat exchange performance in an EGR cooler having a polygonal shape such as a shape.

1 is a schematic overall configuration diagram schematically showing a configuration example of an internal combustion engine provided with an EGR device according to an embodiment (Example 1) of the present invention. It is sectional drawing along the heat exchanger tube longitudinal direction for demonstrating the structural example of the EGR cooler utilized for the EGR apparatus which concerns on embodiment (Example 1) same as the above. It is sectional drawing in AA of FIG. 1 for demonstrating the structural example of the EGR cooler utilized for the EGR apparatus which concerns on embodiment (Example 1) same as the above. It is sectional drawing in AA of FIG. 1 for demonstrating the structural example of the EGR cooler utilized for the EGR apparatus which concerns on embodiment (Example 2) of this invention. It is sectional drawing for demonstrating the stagnation in the corner | angular part (corner | corner part) vicinity of the EGR cooler which made polygonal shape, such as a box shape, the cross section substantially orthogonal to a heat exchanger tube longitudinal direction. It is sectional drawing which shows the structural example of the EGR cooler whose cross section substantially orthogonal to the conventional heat exchanger tube longitudinal direction is cylindrical. It is sectional drawing for demonstrating the problem at the time of increasing the number of heat exchanger tubes in the EGR cooler which has the conventional cylindrical cross section.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

  As shown in FIG. 1, in the internal combustion engine 1 according to Example 1 of the present embodiment, outside air (fresh air) is drawn through an air cleaner or the like (not shown). Then, after being guided to a compressor (impeller) 3A of the supercharger 3 and compressed to a predetermined level, it is cooled to a predetermined level via an intercooler 4 interposed in the intake passage 2 and is put into a combustion chamber (cylinder) 5. Led.

  The combusted gas discharged from the combustion chamber 5 is guided to an exhaust passage (exhaust manifold portion) 6 through an exhaust port (not shown) opened facing the combustion chamber 5, and then the supercharger 3. After supplying rotational energy to the exhaust turbine 3B, the exhaust gas is purified by receiving predetermined processing in an exhaust treatment device (not shown) (an oxidation catalyst, a NOx reduction catalyst, a diesel particulate filter, etc.) disposed downstream of the exhaust passage 6. And discharged into the atmosphere.

  Here, in this embodiment, part of the gas after combustion (that is, the exhaust gas) is guided again to the combustion chamber 5 together with the intake air (fresh air), thereby reducing the combustion temperature and reducing NOx. Devices 100 and 200 are provided.

  An EGR device (system) 100 (HPL-EGR: High Pressure Loop-EGR) according to the present embodiment is an EGR passage (exhaust recirculation passage) that communicates with an exhaust passage (exhaust manifold portion) 6 on the upstream side of the exhaust turbine 3B. The EGR passage 101 is provided with an EGR cooler 110 for cooling the exhaust gas (EGR gas: recirculation exhaust gas) flowing through the EGR passage 101 in a predetermined manner.

  An EGR valve 120 is interposed in the vicinity of the connection portion between the EGR passage 101 and the intake passage 2, and in a predetermined operation state, a part of the exhaust flowing through the exhaust passage 6 is partially opened by EGR gas. As described above, while being cooled by the EGR cooler 110, it is guided to the intake passage 2 of the internal combustion engine 1.

  Further, an EGR device (system) 200 (LPL-EGR: Low Pressure Loop-EGR) according to the present embodiment is an EGR passage (exhaust gas recirculation) communicated with an exhaust passage (exhaust manifold portion) 6 on the downstream side of the exhaust turbine 3B. The EGR passage 201 is provided with an EGR cooler 210 for cooling the exhaust gas (EGR gas: recirculation exhaust gas) flowing through the EGR passage 201 in a predetermined manner.

  In the vicinity of the connection portion between the EGR passage 201 and the intake passage 2, a one-way valve (not shown) or the like is interposed, and while a part of the exhaust gas flowing through the exhaust passage 6 is cooled by the EGR cooler 210 as EGR gas, It is guided to an intake passage 2 (upstream side of the compressor (impeller) 3A) of the internal combustion engine 1 via an EGR valve 211 for LPL-EGR.

  Here, in this embodiment, the EGR cooler 110 and the EGR cooler 210 function as a heat exchanger, and a plurality of thin long tubular heat transfer tubes (heat exchange pipes) 111 are provided in parallel, and these heat transfer tubes An EGR gas flows inside 111, and a heat medium (for example, a cooling medium such as cooling water) of a cooling system of the internal combustion engine 1 flows outside the heat transfer pipe 111.

  That is, as shown in FIG. 2, a supply passage 110A for supplying cooling water of the internal combustion engine 1 to the EGR cooler 110 is supplied to the container 112 of the EGR cooler 110, and cooling water is supplied to the internal combustion engine 1 from the EGR cooler 110. The return passage 110B for returning is connected, and the cooling water of the internal combustion engine 1 is fed through these through a water pump or the like (not shown) between the partition 112A and the partition 112B of the container 112 of the EGR cooler 110. It comes to circulate.

  A plurality of thin long tubular heat transfer tubes (heat exchange pipes) 111 are arranged in parallel between the partition walls 112A and 112B of the container 112 of the EGR cooler 110, and the plurality of heat transfer tubes 111 include the partition walls 112A and 112B. 2 and is connected to the EGR passage 101 through, for example, EGR gas flowing through the EGR passage 101 from the left side in FIG. 2 into the heat transfer pipe 111 and from the right side in FIG. It flows out to the passage 101.

  Thereby, while the heat which EGR gas has is transmitted to the heat exchanger tube 111, the heat is transmitted to the cooling water touching the outer peripheral side of the heat exchanger tube 111, and, thereby, EGR gas is cooled to predetermined. become.

  Here, as described above, the present inventors changed the cross-sectional shape of the EGR cooler substantially perpendicular to the longitudinal direction of the heat exchange pipe from a cylindrical shape as shown in FIG. (Polygonal shape such as a rectangle) can be expected to achieve both an increase in the number of heat exchange pipes and a mounting property on a vehicle, etc. Phenomenon that stagnation tends to occur in the flow of cooling water (refrigerant) or EGR gas in the corner (corner) was confirmed.

  The present inventors have conducted various experiments, researches, etc., and as a result, a multi-tube EGR cooler having a plurality of heat exchange pipes, the cross section substantially orthogonal to the longitudinal direction of the heat exchange pipes being a box shape The structure of the EGR cooler which can eliminate the stagnation of the corners (corners) in the polygonal shape such as the shape and can improve the cooling efficiency (cooling performance) is obtained.

  That is, in the EGR cooler 110 according to the present embodiment, as shown in FIG. 3, the cross section substantially perpendicular to the longitudinal direction of the heat transfer pipe (heat exchange pipe) 111 housed in the container 112 has a box shape. The heat transfer tube 111B in the corner (corner) region (region outside the vicinity of the EGR gas inlet in FIG. 3) in the container 112 having a larger diameter (inner diameter or outer diameter) than the heat transfer tube 111A in the central region It is formed with.

  As a result, the gas in the region where the stagnation is likely to occur in the EGR gas flow inside the container 112 of the EGR cooler 110 (the corner (corner) region of the box-shaped cross section: the region outside the vicinity of the EGR gas inlet in FIG. 3). Since the pressure loss is reduced, the stagnation of the EGR gas flow in the region can be eliminated, and the reduction of the heat exchange efficiency in the heat transfer tube 111 at the corner can be suppressed, so that the cross section substantially orthogonal to the longitudinal direction of the heat transfer tube 111 However, the heat exchange performance of the EGR cooler 110 having a polygonal shape such as a box shape can be improved.

  Note that the EGR cooler 210 can also have the same configuration as the EGR cooler 110 described above.

  As described above, according to the present embodiment, it is a multi-tube EGR cooler having a plurality of heat exchange pipes (heat transfer pipes) with a simple and inexpensive configuration, and the longitudinal direction of the heat exchange pipes It is possible to provide an EGR cooler structure capable of improving the heat exchange performance in an EGR cooler having a polygonal shape such as a box shape in a cross section substantially orthogonal to the shape.

  In the EGR cooler 110 according to Example 2 of the present embodiment, a configuration as shown in FIG. 4 can be adopted. The basic configuration of the second embodiment is the same as that of the first embodiment, and only the arrangement of the heat transfer tubes of the EGR cooler is different. Therefore, the common portions are denoted by the same reference numerals and detailed description thereof is omitted and different. The part will be described in detail.

  As shown in FIG. 4, the EGR cooler 110 according to the present embodiment relates to a heat transfer pipe (heat exchange pipe) 111 housed in the container 112, and a container whose cross section substantially perpendicular to the longitudinal direction has a box shape. A heat transfer tube 111C in a corner (corner) region in 112 (region outside the vicinity of the EGR gas inlet in FIG. 4) is formed with a smaller diameter (inner diameter or outer diameter) than the heat transfer tube 111A in the central region. In addition, the heat transfer tube 111C is disposed at a higher density than the density at which the heat transfer tube 111A is disposed.

  Thereby, the region where the stagnation of the flow of the EGR gas or the cooling water inside the container 112 of the EGR cooler 110 is likely to occur (the corner (corner) region of the box-shaped cross section: outside the vicinity of the EGR gas inlet in FIG. The heat exchange area in the region) can be expanded and the cooling water flow is improved by reducing the outer diameter of the heat transfer tube 111C, so that the heat exchange efficiency of the heat transfer tube 111 in the region is reduced. Therefore, the heat exchange performance in the EGR cooler 110 in which the cross section substantially orthogonal to the longitudinal direction of the heat transfer tube 111 has a polygonal shape such as a box shape can be improved.

  Also in the present embodiment, the EGR cooler 210 can have the same configuration as the EGR cooler 110 described above.

  As described above, even in this embodiment, the multi-tube EGR cooler having a plurality of heat exchange pipes (heat transfer tubes) is provided in the longitudinal direction of the heat exchange pipes with a simple and inexpensive configuration. It is possible to provide an EGR cooler structure capable of improving the heat exchange performance in an EGR cooler having a polygonal shape such as a box shape in a substantially orthogonal cross section.

  By the way, in this embodiment, both EGR device (system) 100 (HPL-EGR: High Pressure Loop-EGR) and EGR device (system) 200 (LPL-EGR: Low Pressure Loop-EGR) are provided. However, the present invention is not limited to this, but can be applied to the case where any one of them is provided. Further, another EGR device (system) is added. It is also possible to apply it.

  In the present embodiment, the heat medium in the EGR cooler 110 or EGR cooler 210 (cooling medium such as cooling water. However, in the present invention, the heating medium may be used instead of the cooling medium in some cases). 1, 2, etc., the case where the flow is a forward flow that flows in the same direction as the flow direction of the EGR gas flowing in the heat transfer tube 111 is illustrated. Without being limited thereto, the flow of the heat medium in the EGR cooler 110 or the EGR cooler 210 can be configured as a reverse flow that flows in a direction opposite to the flow direction of the EGR gas flowing in the heat transfer tube 111.

  The cross-sectional shape substantially orthogonal to the longitudinal direction of the heat exchange pipe is a rectangle, pentagon, hexagon, triangle, or a shape surrounded by two corners and a curve, that is, at least one corner. The present invention is applicable to any cross-sectional shape having (a site where stagnation is likely to occur).

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

1 Internal combustion engine 2 Intake passage 5 Combustion chamber 6 Exhaust passage 100 EGR device (HPL-EGR)
101 EGR passage 110 EGR cooler 111 Heat transfer pipe (heat exchange pipe)
111A Heat transfer tube (heat exchange pipe) (standard size)
111B Heat Transfer Tube (Heat Exchange Pipe) (diameter enlarged)
111C Heat transfer tube (heat exchange pipe) (small diameter and high density)
112 Container 112A Partition 112B Partition 120 EGR valve (for HPL-EGR)
200 EGR equipment (LPL-EGR)
201 EGR passage 210 EGR cooler 211 EGR valve (for LPL-EGR)

Claims (2)

An EGR cooler of an EGR device that recirculates a part of exhaust gas as EGR gas to a combustion chamber through an EGR passage, and guides the EGR gas in the EGR passage to the inside of a plurality of heat transfer tubes arranged side by side. In which the heat medium is guided to the outer peripheral side of the gas and heat exchange is performed between the EGR gas and the heat medium,
Cross-sectional shape of the EGR cooler have a corner in a direction substantially perpendicular to the longitudinal direction of the heat transfer tube, the inner and outer diameters of the heat transfer tubes in the vicinity of the corner portion, the inner diameter and smaller than the outer diameter of the heat transfer tube of the other part In this case, the EGR cooler is characterized in that the heat transfer tubes are arranged at a higher density in the vicinity of the corner portion than in other portions . 2. The EGR cooler according to claim 1, wherein the vicinity of the corner is outside of an EGR gas inlet to the EGR cooler when viewed from the longitudinal direction of the heat transfer tube.

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