FR2938051A1 - Heat exchange unit for use in exhaust gas recirculation circuit of internal combustion engine of motor vehicle, has fixing unit to fix filter element with respect to case such that element is placed near collecting chamber of conduits - Google Patents

Abstract

The unit (1) has a set of conduits (9) for circulation of primary fluid, and extension channels for circulation of secondary fluid, where the channels are defined by the conduits. A case (3) accommodates the conduits. A fixing unit fixes a filter element i.e. particle filter (16), with respect to the case in a selected position such that the filter element is placed near an collecting chamber (13) of the conduits. The channels are opened at vicinity of the filter element. The filter element is coupled with an open surface of the case.

Description

Heat exchange unit for use, for example, in an exhaust gas recirculation circuit

The invention relates to a heat exchange unit and more particularly to a heat exchange unit for use in an exhaust gas recirculation circuit.

In a combustion air circuit for an internal combustion engine, it is known to create a bypass of the line leading the gases from combustion outward to bring some of these gases back to the engine. This flue gas recirculation, or exhaust gas, reduces the amount of nitrogen oxide (NOx) created during internal combustion. The amount of nitrogen oxide generated can be further reduced by cooling the combustion gases before reinjection into the engine.

At the engine outlet, the combustion gases carry solid particles, in potentially quite hard materials. For example, metal particles may come from the aging of the various elements of the exhaust line, and ceramic particles from the aging of the particulate filter. These particles can damage mechanical elements of the combustion gas circuit, in particular the compressor located upstream of the engine. This compressor indeed incorporates moving mechanical parts, which can be damaged by these solid particles.

To overcome this drawback, it is known, for example from US 2008/0141671 A1, to connect a gas filtering device in the recirculation line, upstream of the exhaust gas cooler. Such a device comprises in particular one or more particulate filters.

This solution has only partially satisfied, so that the Applicant has set itself the goal of improving the situation.

The invention relates to a heat exchange unit of the type comprising a bundle of pipes intended for the circulation of a first fluid, intermediate channels intended for the circulation of a second fluid, delimited by the bundle of pipes, and a housing housing the pipe bundle, remarkable in that it further comprises at least one filter element and means for fixing this filter element relative to the housing, at a position chosen in such a way that the filter element is disposed near an extreme face of the bundle of pipes in the vicinity of which open at least some of the intermediate channels. The heat exchange unit according to the invention consists of an exhaust gas heat exchanger for cooling the latter to reintroduce them at least partially into the combustion engine. This results in a heat exchange unit incorporating a filter element that allows the capture of harmful solid particles.

This configuration of the heat exchange unit makes it possible to reduce the overall volume of the combustion air / recirculated gas circuit, in particular with respect to the state of the art, which provides for the integration into the cooling circuit. a cooling device and a filtering device, separate from each other. In this configuration also, the filter element may have a large passage section without a significant increase in the volume of the heat exchange unit. In particular, a large portion, if not all, of the end face through which the air to be cooled enters through the bundle of pipes can be covered by the filter element. The filter element can thus have a section of extent close to the extent of this end face. This makes it possible to have very little loss of charge in the heat exchange unit, and consequently in the entire recirculation circuit of the combustion gases. The installations of the state of the art have a major disadvantage in that they are very bulky and difficult to integrate into a vehicle when they include a large cross section filter, while they generate strong losses when the filter section to facilitate the integration in question.

In addition, the heat exchange unit according to the invention is economically more advantageous than the installations of the state of the art.

Other features and advantages of the invention will appear on reading the detailed description below, and the attached drawings in which:

FIG. 1 schematically represents a heat exchange unit 30 according to a first embodiment of the invention, seen in longitudinal section,

FIG. 2 diagrammatically represents an alternative embodiment of the heat exchange unit of FIG. 1, seen in longitudinal section; FIG. 3 schematically represents a heat exchange unit according to a second embodiment of FIG. 4 is a schematic representation of a first embodiment of the heat exchange unit of FIG. 3, seen in longitudinal section,

FIG. 5 diagrammatically represents a second variant embodiment of the heat exchange unit of FIG. 3, seen in longitudinal section;

FIG. 6 diagrammatically represents a third variant embodiment of the heat exchange unit of FIG. 3, seen in longitudinal section;

FIG. 7 represents a combustion air circulation circuit capable of integrating the heat exchange unit 20 of FIGS. 1 to 6, and

FIG. 8 schematically represents an integration variant of the heat exchange unit of FIG. 5.

The accompanying drawings may serve not only to supplement the invention, but also to assist in its definition, as appropriate.

FIG. 1 schematically represents a heat exchange unit 1 for use in cooling gas, in particular combustion gases of a motor vehicle.

The heat exchange unit 1 comprises an elongated housing 3 having a gas inlet 5, arranged at a longitudinal end of the housing 3, and a gas outlet 7, arranged at the longitudinal end of the housing 3 opposite the gas inlet 5.

The housing 3 houses a bundle of tubes 9, or bundle of 5 pipes for the circulation of gases to be cooled.

The tubes of the bundle 9 are for example generally rectilinear and parallel to each other, and extend in the longitudinal direction of the case 3. The tubes of the bundle 9 delimit between them fluid circulation channels, which generally extend according to the longitudinal direction of the housing 3.Typically, the exhaust gas circulates in the tubes of the bundle 9, 15 while the cooling fluid, for example water, circulates in the channels.

On both sides of the tube bundle 9, in the longitudinal direction, the housing 3 delimits respectively an inlet collecting chamber 11 and an outlet collecting chamber 13.

The gas inlet 5 opens into the inlet collecting chamber 11, while the gas outlet 7 opens into the outlet collecting chamber 13.

Each of the tubes of the bundle 9 opens into both the inlet collecting chamber 11 and the outlet collecting chamber 13. The bundle of tubes 9 has a first end face 14 extending longitudinally, forming an inlet face for the gases to cool, and a second end face 15, opposite to the first end face 14, forming an outlet face for the cooled gases.

The tubes of the bundle 9 open in the vicinity of each of the first end face 14 and the second end face 15.

In operation, the gases to be cooled enter the heat exchange unit 1 through the inlet 5 and reach the inlet collecting chamber 11. From there, the gases to be cooled take the tubes of the bundle 9 while making an exchange thermal with the coolant circulating in said circulation channels defined by said tubes. The gases thus cooled reach the outlet collection chamber 13, and leave the heat exchange unit 1 through the outlet 7.

In other words, the coolant flows externally to the tubes of the bundle 9.

The tubes of the bundle 9 can be made in very different shapes, such as a stack of plates, a bundle of round, oval, flat section tubes, and other forms of sections.

The heat exchange unit 1 comprises a particle filter 16 held in position relative to the housing 3, here in the inlet collecting chamber 11, by suitable fixing means.

The particulate filter 16 is disposed near the first end face 14 of the tube bundle 9, so that at least a portion of the gas entering the bundle of tubes 9 passes through it. The particulate filter 16 has a first large face, or input face, and a second large face, or exit face, opposite to the first major face and disposed facing the first end face 14.

The particulate filter 16 has a generally flat shape and is similar to the cross-sectional area of the inlet collecting chamber 11 at the location where the particulate filter 16 is held. This particulate filter 16 is fixed on the inner wall 17 of the heat exchange unit 1.

The particle filter 16 thus divides the inlet collecting chamber 11 into an upstream part, connected to the gas inlet 5, and a downstream part, close to the first end face 14 of the tube bundle 9.

In this configuration, the entire gas flow entering the heat exchange unit passes through the particulate filter 16. The pressure losses between the particulate filter 16 and the tube bundle 9 are thus minimized.

In an alternative embodiment not shown, the particulate filter 16 is attached to the first end face 14. In particular, the second large face of the particulate filter 16 is substantially against the first end face 14. The particulate filter 16 can then be fixed directly to the tube bundle 9, for example by welding on the tube bundle 9 already assembled, or during a soldering operation assembling the constituent elements of the latter.

The particulate filter 16 may be welded to the inner wall 17 of the housing 3.

The housing 3 can be made of at least two mutually assembled parts to form the latter: a first part 19 mainly comprising the gas inlet 5 and the inlet collecting chamber 11, and a second part 21 housing the tube bundle 9 and delimiting the outlet collecting chamber 13 as well as the gas outlet 7. In this configuration of the housing 3, the particulate filter 16 can be fixed in the collecting chamber 11, for example by welding or soldering, before this first part 19 of the housing 3 is fixed to the second part 21 of the housing 3.

Preferably, the second part 21 is itself made of two mutually assembled elements for said part: a first element 21A of second part 21, housing the tube bundle 9, and a second element 21B of second part 21, delimiting the chamber output collector 13.

The particulate filter 16 may also be brazed to the inner wall 17 of the housing 3, for example during the same brazing operation which fixes the other elements of the heat exchange unit 1 between them.

In an alternative embodiment of the embodiment of Figure 1, the particulate filter 16, or an additional particulate filter, may be disposed at the output of the tube bundle 9, for example attached to the second end face 15 of said bundle.

FIG. 2 illustrates an alternative embodiment in which the heat exchange unit 1 integrates two particle filters 16.

The particulate filters 16 are maintained in the inlet collecting chamber 11 and are shaped so as to each realize a partitioning thereof.

The particle filters 16 coincide here in the vicinity of the first end face 14 of the tube bundle 9. The particle filters 16 jointly define, and in combination with the inner wall 17 of the housing 3, an upstream portion 23 of the collecting chamber 11, in which opens the gas inlet 5. Each of the particulate filters 16 further delimits a downstream portion 25 of the inlet collecting chamber 11, adjacent to the first end face 14 of the tube bundle 9, together with the inner wall 17 of the housing 3.

In this configuration, the entire gas stream to be cooled entering the heat exchange unit 1 passes through the particle filters 16. The filtering surface is increased with respect to the arrangement of FIG. The losses generated by the filtering are even smaller. The pressure drops are minimized.

Particle filters 16 may be adapted to capture particles of different types.

Typically, a particulate filter 16 may take the form of a metal grid whose fineness of mesh is adapted to the capture of particles of 100 micrometers in diameter. However, the material used for the realization and the smoothness of the mesh, or its porosity, depend on the envisaged applications.

FIG. 3 illustrates a heat exchange unit 27 comprising an elongate housing 29, housing a bundle of rectilinear tubes 31 and arranged parallel to each other, in the longitudinal direction of the elongated housing 29.

The housing 29 has a junction face 34 at a longitudinal end thereof. The junction face 34 is open to allow both the gas inlet to cool and the gas outlet cooled.

Fluid circulation channels are here delimited by the tubes of the beam 31. The tubes of the bundle 31 open at the same time on a first end face 32 and a second end face 33 of the bundle of tubes 31, opposite one to the other. another according to the length of this bundle of tubes 31. The first end face 32 is close to the junction face 34 of the housing 29.

The tubes of the bundle 31 are separated into a first set of tubes 35, forming a first part (bottom part in FIG. 3) of the bundle of tubes 31, and a second set of tubes 37, forming a second part (upper part on the FIG. 3) of the bundle of tubes 31.

The housing 29 delimits a collecting chamber 39, adjacent to the second end face 33 of the tube bundle 31. Each of the tubes of the bundle 31 opens into this collecting chamber 39.

In this configuration of the heat exchange unit 27, the gases flow in a U-shaped or two-pass path. The gases to be cooled penetrate through the junction face 34 into the housing 29 and pass through the tube bundle 31 through the tubes of said first set of tubes 35. The partially cooled gases reach the collection chamber 39. From there, these partially cooled gases pass through the bundle of tubes 31 through the tubes of said second set of tubes 37. The cooled gases leave the housing 29 through the junction face 34.20 The junction face 34 of the housing 29 forms both a face of the gas inlet to be cooled and a cooled gas outlet face. The first end face 32 also forms both a gas inlet face to be cooled and a cooled gas outlet face for the tube bundle 31. The second end face 33 forms both an inlet face and a outlet face of the tube bundle 31 for the partially cooled gases.

The heat exchange unit 27 incorporates a particle filter 41, similar to the particulate filters 16 of FIGS. 1 and 2, and means for fixing this particulate filter 41 with respect to the housing 29.

The particulate filter 41 is disposed near the first end face 32 of the tube bundle 31.

The particle filter 41 has a generally flat shape and is similar to the junction face 34. The particle filter 41 is attached to the junction face 34 and is fixed on the housing 29, for example by means of a weld bead or by brazing. In particular, the second large face of the particulate filter 41 comes into substantially contact with the junction face 34.

The heat exchange unit 27, including the particle filter 41, can be connected to a gas circulation duct 43. The heat exchange unit 1 is connected to this gas duct 43 so that the face junction 34 is disposed transversely to said gas flow.

A bypass valve 45 is here disposed in the conduit 43, in the vicinity of the separation of the first set of channels 35 and the second set of channels 37. In the closed position, the valve 45 closes the conduit 43 so that the gas flowing in an upstream portion 43A of the duct 43 penetrate through the junction face 34, after having passed through the particle filter 41, in the housing 29, to reach the first set of tubes 35. The gases thus pass through the filter a first time with particles 41.

The cooled gases leave the housing 29 through the junction face 34, pass through the particulate filter and open into a downstream portion 43B of the pipe 43. The cooled gases thus pass through the particle filter 41 a second time.

In an alternative embodiment, not shown, the particulate filter 41 is attached to the first end face 32 of the tube bundle 31. In particular, the second large face of the particulate filter 41 may come into substantial contact with this first end face. 32. The particle filter 41 can be housed in the housing 29 or disposed outside the latter. In such an embodiment, the particulate filter may be attached to the tube bundle 31, for example by clipping, clamping, soldering or soldering, in particular before introduction of this bundle of tubes 31 into the housing 29. The particulate filter 41 may be provided with a frame to facilitate its attachment, allowing for example fixing by screw, gluing or crimping. In particular, this frame can be made of plastic material, for example by overmolding.

According to the variant embodiments, the first end face 32 of the tube bundle 31, and / or the particle filter 41 may be flush with the junction face 34 of the case 29.

The gas conduit 43, the particulate filter 41 and the housing 29 may be brazed together, for example during a brazing operation also linking the other constituent elements of the heat exchange unit 1 to each other. The particulate filter can also be maintained on the gas pipe 43 and then welded to the housing 29.

In a particular embodiment, not shown, the valve 45 and the filter 41 could be assembled into a unitary cheek, to be reported on the housing 29, opposite the junction face 34.

In an alternative embodiment illustrated in FIG. 4, the particle filter 41 is fixedly held in the vicinity of the second end face 33 of the tube bundle 31. Here, the particle filter 41 is attached to this second end face 33.

The particulate filter 41 may be attached to the housing 29, in its portion defining the collection chamber 39. Optionally, this part of the housing 29 may be attached to a portion of the housing 29 housing the tube bundle 31. The particulate filter 41 can then be fixed to the housing 29, for example by brazing or by means of a weld bead, prior to assembling the two housing parts together.

The particulate filter 41 may also be attached directly to the bundle of tubes 31, for example by means of flanges, a brazing operation, screwing, clipping or the like.

In the variant embodiment of FIG. 5, the particulate filter 41 is arranged in the collecting chamber 39 and shaped so as to form a partitioning of the latter.

The particulate filter 41 thus separates a first portion 45 from the collection chamber 39, or upstream portion, into which each of the tubes of said first set of tubes 35, a second portion 47, or downstream portion of the collection chamber 39 opens. in which each of the tubes of said second set of tubes 37 opens.

In this variant, the gases pass through the particle filter 41 once.

The particulate filter 41 may be attached to the housing 29 and / or the tube bundle 31 adjacent the second end face 33.

FIG. 8 shows an integration variant of the heat exchange unit 27 in the exhaust gas circuit.

The gas duct is here devoid of bypass valve 45. In other words, the upstream portion 43A of the gas duct 43 is connected to the junction face 34 of the heat exchange unit 27, opposite the first set 35, while the downstream portion 43B of this gas conduit 43 is connected to the same junction face 34, facing the second set of tubes 37.

The gases to be cooled are thus always filtered.

In the variant embodiment illustrated in FIG. 6, the heat exchange unit 1 incorporates two particulate filters 41, held in the collection chamber 39. Each of the particulate filters 41 partitions this collection chamber 39. The particulate filters 41 converge near the second end face 33. One of the particulate filters 41 defines an inlet portion 49 of the collection chamber 39, into which the tubes of said first set of tubes 35, in combination with the inner wall of the housing 29. The other of the particulate filters 41 35 defines an outlet portion 53 of the collection chamber 39, into which the tubes of said second set of tubes 37, in combination with the inner wall of the housing 29, open. two particle filters 41 jointly delimit an intermediate portion 51 of the collection chamber 39 in combination with the inner wall of the housing 29.

Each of the particulate filters 41 may be provided with a fineness mesh different from the other particle filter 41. For example, the first particle filter 41 encountered by the gases to be cooled may have a coarser mesh than the mesh of the second particulate filter 41. This improves the filtering of the recirculation gases.

FIG. 7 represents a cooling circuit 55 associated with an internal combustion engine M of a motor vehicle. The engine M comprises a motor unit 57 provided with an intake manifold 59 and an exhaust manifold 61. An intake line 63, supplied with external air, is connected to the intake manifold 59, while an exhaust line 65 is connected to the exhaust manifold 61 for exhausting the exhaust gases to the outside. The air is compressed by a turbocharger consisting of a compressor 67 mounted on the intake line 63 and a turbine 69 mounted on the exhaust line 65. The compressed air, also called supercharging air, comes from compressor 67 is cooled by a first cooler 71, also called a charge air cooler (abbreviated to RAS).

The exhaust gases from the turbine 69 pass through a three-way valve 73, which makes it possible to return part of the exhaust gas in the intake line 63 upstream of the compressor 76, via a line 75. line 75 incorporates the heat exchange unit 1. The gases flowing in the line 75, at low pressure, are both filtered and cooled before reinjection into the intake manifold 59.

The integration of a particulate filter in the heat exchange unit 1 is advantageous, in particular with regard to the overall volume of the air circulation system, the total cost of the installation, and the Losses of charge caused by the particulate filter are very small.

The invention takes advantage of the fact that the performances with regard to the heat exchange in the unit increase with the surface of the end face of the tube bundle forming the inlet or gas inlet / outlet to be cooled, just as the performance of the filter particles increase with the surface of the inlet section of the latter. The invention allows a surface of the end face of the tube bundle and a large filter inlet section surface for a rather small space, and in any case limited.

The invention is not limited to the embodiments described above, by way of example only.

The particulate filter could be fixed, for example by gluing, into a plastic or aluminum header, to which would be added later a bundle of tubes surrounded by a housing.

In the second embodiment, the particulate filter 41 could take the form of a cheek intended to be affixed against the bundle of tubes 31. Said cheek could then be disposed between the flue gas pipe 43 and the tube bundle and attached together with the valve 45 to the remainder of the heat exchange unit 1. The particulate filter 41, in particular embodiments of FIGS. 1, 3, 4 and 5, although shown in a unitary manner may comprise two or more filter elements, contiguous mesh finesse different for example.

Particulate filters may be provided in addition to the filters shown and described above. For example, an additional particulate filter 41 could be provided, in the embodiments of FIGS. 1 and 2, in the second collection chamber 13, in particular contiguous to the second end face 15. Likewise, in the embodiment of FIG. 3, an additional particle filter 41 could be attached to the second end face 33, and in the embodiments of FIGS. 4, 5, 6 and 8, on the first end face 32 or the junction face 34.

In all cases, it is advantageous that the particle filter 41 located upstream has a mesh coarser than a particle filter 41 located further downstream.

The integration of the heat exchange unit 27, as shown in FIG. 8, can be implemented with each of the embodiments of the heat exchange unit 27 described above as well as with all variants that result, directly or indirectly, from the description of these embodiments.

The bundle of tubes 9 is not limited to producing a bundle of tubular elements or to that of a stack of plates delimiting said tubes, but encompasses all the variants that can be envisaged for the production of a part

Claims (13)

Revendications1. Heat exchange unit (1,27) of the type comprising a bundle of pipes (9,31) intended for the circulation of a first fluid, interposed channels intended for the circulation of a second fluid, delimited by the bundle of pipes (9,31), and a housing (3,29) housing the bundle of pipes (9,31), characterized in that it further comprises at least one filter element (16,41) and means for fixing said filter element (16, 41) with respect to the housing (3.29) at a position chosen in such a way that the filtering element (16, 41) is disposed near an end face (13, 32). 33) of the bundle of pipes (9,31) in the vicinity of which at least some of the intermediate channels open. 2. Unit according to claim 1, wherein the filter element (16,41) has a large face shaped similarly to said end face (13,32,33) of the bundle of pipes (9,31). 3. Unit according to claim 2, wherein the large face of the filter element (16,41) is attached to said end face (13,32,33). 4. Unit according to one of the preceding claims, wherein the filter element (41) has a large face shaped similarly to an open face (33) of said housing (29). 5. Unit according to claim 4, wherein the large face of the filter element (41) is contiguous to the open face (41) of said housing (29). 6. Unit according to one of the preceding claims, wherein the housing (3,29) defines at least one collecting chamber (11,13,39) adjacent to the end face (14,15,33) of the bundle of pipes ( 9.31) and into which the intermediate channels open, the filter element (16.41) being arranged across the collecting chamber (14, 15, 33). The unit of claim 6, wherein the filter element (16,41) forms a septum in the collection chamber (11,13,39). 8. Unit according to claim 7, wherein the partition separates a first portion (25, 49) of the collecting chamber (11, 13, 39) into which some of the intermediate ducts of a second portion (25, 53) open. in which the remaining intermediate channels open. 9. Unit according to claim 6, wherein the filter element (41) is arranged in interface between the pipe bundle (31) and the collecting chamber (39). 10. Unit according to one of the preceding claims, wherein the filter element (16,41) is fixed inside said housing (3,29). 25 11. Unit according to one of claims 1 to 10, wherein the filter element (41) is fixed on said housing (29). 30 12. Unit according to one of the preceding claims, wherein the filter element (41) is fixed to the pipe bundle {31). 13. Unit according to one of the preceding claims, comprising several filter elements (16, 41) fineness of different mesh.