HEAT EXCHANGER OF AN INTERNAL COMBUSTION ENGINE

Abstract

A heat exchanger (18) is provided for an internal combustion engine (1) for heat transfer between a gas stream (8) and a working medium stream (10). The heat exchanger (18) comprises a housing (28), which encloses a gas path (38), and with at least one spiral tube (29), which carries a working medium path (30) and which is arranged in the gas path (38) and which extends helically in relation to the central longitudinal axis (31) of the housing (28). Increased fatigue strength is achieved with an elastic outer mounting layer (32). The elastic outer mounting layer (32) is arranged between the housing (28) and the at least one spiral tube (29).

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2013 201 465.1, filed on Jan. 30, 2013, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains to a heat exchanger for an internal combustion engine for heat transmission between a gas stream and a working medium stream.

BACKGROUND OF THE INVENTION

Heat exchangers are used for various applications in internal combustion engines, especially of motor vehicles. For example, a heat exchanger, through which ambient air can flow in order to remove heat from the cooling circuit into the environment, may be integrated into an engine cooling circuit. Furthermore, an interior space air stream can be admitted into a heat exchanger coupled thermally with the engine cooling circuit in order to heat the interior space air stream in this manner. Furthermore, applications are conceivable in which a heat exchanger is integrated into an exhaust system of the internal combustion engine in order to remove heat from the exhaust gas, for example, in order to heat the interior of the vehicle with it or to evaporate a working medium in a waste heat utilization circuit with it. A charge cooler as well as exhaust gas recirculation cooler, in which a gas stream is cooled by means of a working medium stream, are known as well.

Insofar as the heat exchanger is exposed to high temperatures and/or great temperature variations in connection with its particular use, there will also be high thermal and mechanical stresses for the heat exchanger as a result. High requirements are imposed in terms of the fatigue strength of the heat exchanger especially in cases in which the heat exchanger is exposed on the gas side to an exhaust gas stream or to a recirculated exhaust gas stream. Applications in vehicles are also associated with high stresses due to vibrations and shocks.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved embodiment, which is characterized especially by high fatigue strength, for a heat exchanger of the type mentioned in the introduction.

According to the invention, a heat exchanger is provided for an internal combustion engine for transferring heat between a gas stream and a working medium stream. The heat exchanger comprises a housing enclosing a gas path, a spiral tube carrying the working medium and an elastic outer mounting layer. The spiral tube provides at least a part of a working medium path. The spiral tube is arranged in the gas path and extends helically in relation to a central longitudinal axis of the housing. The elastic outer mounting layer is arranged between the housing and the spiral tube.

The present invention is based on the general idea of mounting the at least one spiral tube on the housing via such an elastic outer mounting layer. Such a spiral tube is arranged in this case in the gas path and extends helically in relation to a central longitudinal axis of the housing. A working medium path is led through the spiral tube, as a result of which the heat transfer between the gas stream and the working medium stream ultimately takes place via the spiral tube arranged in the gas path. The outer mounting layer is arranged radially between the housing and the at least one spiral tube. The outer mounting layer is preferably arranged all-round in the circumferential direction. Thermal expansion effects within the spiral tube can be absorbed in a comparatively simple manner due to the use of a spiral tube, because these effects lead to a change in the length of the spiral tube and act essentially only axially as a result. Furthermore, the outer mounting layer ensures that radial expansion effects can also be absorbed elastically. The fatigue strength of the heat exchanger can thus be increased correspondingly.

If the outer mounting layer is pressed radially in the mounted state between the housing and the at least one tube corresponding to an advantageous embodiment, the outer mounting layer can also be used to fix the spiral tube axially relative to the housing, as a result of which other fastening means are relieved or may even be eliminated.

A core tube, which extends coaxially with the central longitudinal axis of the housing, may be arranged in the preferably tubular housing in another advantageous embodiment. The gas path is now formed radially between the housing and the core tube. The at least one spiral tube correspondingly also extends radially between the housing and the core tube. The core tube encloses in its turn a bypass path, which bypasses the gas path in the area of the at least one spiral tube. Two gas paths extending in parallel, namely, the gas path proper for heat coupling with the working medium, on the one hand, and the bypass path for bypassing this heat coupling, on the other hand, are formed in this manner in the heat exchanger. The gas stream can thus be sent through the bypass path for operating states in which a heat coupling between the gas stream and the working medium stream is not desired, as a result of which the thermal load of the respective spiral tube is ultimately reduced. The bypass path may be connected fluidically with the gas path upstream and downstream of the at least one spiral tube according to an advantageous embodiment. The fluidic coupling between the gas path and the bypass path will still take place correspondingly within the housing of the heat exchanger. For example, the core tube may have an interruption or a perforation for the particular fluidic coupling with the gas path.

In another advantageous embodiment, an elastic inner mounting layer may be provided, which is arranged radially between the core tube and the at least one spiral tube. This inner mounting layer may be arranged especially such that it extends all-round. The respective spiral tube can thus be supported additionally via the inner mounting layer, and the elasticity of the inner mounting layer can compensate thermal expansion effects in this case as well. According to an advantageous embodiment, the inner mounting layer may be pressed between the core tube and the at least one spiral tube, as a result of which the inner mounting layer can be used to fix the position of the spiral tube relative to the core tube and hence within the housing.

In another advantageous embodiment, the core tube may contain a control means for controlling the cross section of the bypass path through which flow is possible. The gas stream can be divided by means of such a control means into the gas path in the annular space between housing and core tube and the bypass path. In a simple embodiment, the control means can at least release and block the cross section of the bypass path through which flow is possible. However, at least one intermediate position is possible in a preferred embodiment. In particular, a plurality of intermediate positions or any desired number of intermediate positions may be able to be set, especially continuously, in order to make it possible to divide the flow between the core tube and the annular space quasi as desired.

In another advantageous embodiment, the core tube may project over the housing at both longitudinal ends of the housing and form a gas inlet and a gas outlet of the housing. The heat exchanger can thus be integrated into a line carrying the gas stream via the gas inlet and the gas outlet, i.e., via the core tube. The housing can be carried by the core tube in this case.

According to another advantageous embodiment, the core tube may be composed axially of three tube sections, wherein an inlet section has the gas inlet, an outlet section has the gas outlet, and a control section arranged between the inlet section and the outlet section has the aforementioned control means. This leads to a design that can be manufactured in an especially simple manner, which facilitates the assembly of the heat exchanger.

The at least one spiral tube may have a plurality of ribs, which protrude into the gas path, in another advantageous embodiment. Such ribs may be embodied, for example, in the form of ring-shaped disks, a plurality of which can be pushed over a central tubular body of the spiral tube. It is also possible as an alternative hereto to embody the ribs by means of a web, which extends helically along the central tubular body. The heat transfer between gas and working medium is considerably improved by means of the ribs.

The respective elastic mounting layer may be a ceramic fiber mat or a wire mesh or a metal wire mesh or a metal foam or a ceramic foam structure or a swelling mat in another advantageous embodiment. Composite structures are conceivable as well. The respective mounting mat may be a single-layer or multilayer mat. The respective mounting mat may also be a one-part or multipart mat.

The respective mounting layer is preferably of a temperature-resistant design.

The respective mounting layer may be formed with spring elements and/or corrugated plates and/or by an elastic sheet metal layer in an alternative embodiment.

The respective mounting layer may have a supporting mount at least on a side exposed to the gas stream in another advantageous embodiment. In particular, the outer mounting layer can thus be provided on its inside facing the spiral tube with such a supporting mount. In addition or as an alternative, the inner mounting layer may be provided on its outside facing the spiral tube with such a supporting mount. It is also conceivable that the respective mounting layer is provided with such a supporting mount on its inside and on its outside. Furthermore, the respective mounting layer may be fully enveloped by such a supporting mount. The supporting mount can improve the mechanical strength of the mounting layer. In particular, the supporting mount can protect the respective mounting layer from mechanical wear.

Corresponding to an advantageous variant, the respective supporting mount may be, for example, a wire netting or a metal foil or a graphite foil or a graphite layer or a heat-resistant woven structure or a heat-resistant textile or a metal mesh or a wire mesh or a metal foam, especially a rolled one. Combinations of the above-mentioned embodiments are also conceivable.

The mounting layer may have a fiber material or consist entirely of such a fiber material in another advantageous embodiment. The supporting mount is now designed preferably as being impermeable to the fibers of the fiber material. Fibers can be prevented from being removed from the mounting layer due to this mode of construction, whereby the service life of the mount is improved.

The respective mounting layer may be designed in another advantageous embodiment as a mounting mat, which is closed in itself in the circumferential direction. Such a mounting mat is characterized in that it makes radial pressing possible, which can be used, for example, to fix the position of the respective spiral tube relative to the housing and relative to the core tube. Such pressing can be maintained permanently by means of such a mounting mat even at high temperature in order to make it possible to reversibly compensate thermal expansion effects. Such mounting mats are used, for example, to fix the position of ceramic monoliths in cylindrical metal housings of catalytic converters or particle filters.

The respective mounting layer may be in contact with the respective adjacent element radially on the inside and radially on the outside in another advantageous embodiment. In addition, the respective mounting layer may be pressed radially.

Moreover, the respective mounting layer may be designed such that it brings about heat insulation at the same time. The outer mounting layer now brings about heat insulation of the housing against the gas stream. The inner mounting layer brings about heat insulation of the core tube, so that the heat dissipation by radiation to the outside is reduced in bypass operation.

It is apparent that the above-mentioned features, which will also be explained below, can be used not only in the particular combination shown, but in other combinations or alone as well, without going beyond the scope of the present invention.

Preferred exemplary embodiments of the present invention are shown in the drawings and will be explained in more detail in the following description, in which identical reference numbers refer to identical or similar or functionally identical components. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a highly simplified, circuit diagram-like general view of an internal combustion engine with heat exchanger system according to the invention;

FIG. 2 is a longitudinal sectional view of a heat exchanger according to the invention; and

FIG. 3 is an isometric exploded view of the heat exchanger of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in particular, corresponding to FIG. 1, an internal combustion engine 1 comprises, in the usual manner, an engine block 2 with a plurality of combustion chambers 3, a fresh air feed unit 4 for feeding fresh air to the combustion chambers 3, an exhaust system 5 for removing exhaust gas from the combustion chambers 3 and a waste heat utilization unit 6 for utilizing the heat being carried in the exhaust gas. A fresh air stream 7 being carried in the fresh air feed unit 4 is indicated by an arrow. An exhaust gas stream 8 being carried in the exhaust system 5 is indicated by arrows. The waste heat utilization unit 6 comprises a waste heat utilization circuit 9, in which a working medium circulates, wherein a working medium stream 10 is indicated by arrows. A delivery means 11 for driving the working medium, an evaporator 12 for evaporating the working medium, an expansion engine 13 for expanding the working medium and a condenser 14 for condensing the working medium are arranged one after another in the direction of flow of the working medium 10 in the waste heat utilization circuit 9. The expansion engine 13 may drive, for example, a generator 15 for generating power. The condenser 14 may be integrated into a cooling circuit 16, which may be fluidically and/or thermally coupled with an engine cooling circuit 17 for cooling the engine block 2. Cooling circuit 16 may be formed, in particular, by a heat exchanger 18, which is installed in the exhaust system 5 in a suitable manner. The heat exchanger 18 is thus used in the exhaust system 5 for heat transfer between the exhaust gas stream 8 and the working medium stream 10. The waste heat utilization unit 6 may preferably operate according to the principle of a Clausius-Rankine cycle. The exhaust system 5 may contain, moreover, in the usual manner at least one exhaust gas treating means 19, for example, a catalytic converter or a particle filter, as well as at least one exhaust muffler 20. If the catalytic converter 19 is an oxidation catalytic converter, the heat exchanger 18 is preferably arranged, unlike in the simplified view in FIG. 1, downstream of the catalytic converter 19.

The internal combustion engine 1 shown purely as an example in FIG. 1 has, besides, an exhaust gas recirculating unit 21, by means of which exhaust gas can be recirculated from the exhaust system 5 to the fresh air feed unit 4. A corresponding exhaust gas recirculation stream is indicated in FIG. 1 by arrows and is designated by 22. An exhaust gas recirculation cooler 26, by means of which the recirculated exhaust gas can be cooled, may be arranged in an exhaust gas recirculating line 23 provided for this purpose, which fluidically connects an exhaust gas line 24 with a fresh air line 25. The exhaust gas recirculation cooler 26 may be integrated for this into a cooling circuit 27, which may likewise be formed by a branch of the engine cooling circuit 17 or by a separate cooling circuit. The exhaust gas recirculation cooler 26 is also a heat exchanger 18.

The design of such a heat exchanger 18, which may be used, in principle, as desired, but can preferably be used as an evaporator 12 or as an exhaust gas recirculation cooler 26, will be explained in more detail below with reference to FIGS. 2 and 3.

Corresponding to FIGS. 2 and 3, the heat exchanger 18 comprises a housing 28, which encloses a gas path 38 in the circumferential direction. Housing 28 is, for example, of a cylindrical shape and may consist according to FIG. 3 of two half shells. Furthermore, the heat exchanger 18 comprises at least one spiral tube 29, which contains in its interior a working medium path 30, so that the working medium is sent through the spiral tube 29. Spiral tube 29 is arranged in the gas path 38 and extends helically in relation to a central longitudinal axis 31 of the housing 28.

An elastic outer mounting layer 32 is arranged radially between the housing 28 and the spiral tube 29.

In addition, a core tube 33 is arranged in housing 28 such that it extends coaxially with the central longitudinal axis 31 of the tubular housing 28. An annular space 34 is formed hereby radially between the core tube 33 and the housing 28. The gas path 38 is now located in this annular space 34. The spiral tube 29 is likewise located in this annular space 34, i.e., radially between the housing 28 and the core tube 33. The core tube 33 encloses a bypass path 35, which bypasses the gas path 38 in the area of the spiral tube 29. The core tube 33 is fluidically connected with the gas path 38 upstream and downstream of the spiral tube 29. This is embodied in the example shown in FIGS. 2 and 3 by means of a perforation 36 each, which is formed in the core tube 33. For example, the perforation 36 comprises a plurality of axially oriented elongated holes or slots, which are arranged distributed in the circumferential direction. By means of such a perforation, the core tube 33 does not have to be interrupted in the area of the fluidic connection between the bypass path 35 and the exhaust gas path 38. It is thus possible, especially according to the example shown in FIGS. 2 and 3, to design the core tube 33 as a continuous tube. As an alternative to such perforations 36, an interruption of the core tube 33 is also conceivable, in principle, in order to establish the respective fluidic connection between the gas path 38 and the bypass path 35.

An elastic inner mounting layer 37 is arranged radially between the core tube 33 and the spiral tube 29.

Furthermore, a control means 39, by means of which the cross section of the bypass path 35, through which cross section flow is possible, can be controlled. The control means 39 is designed as a butterfly valve 40 in this case, which can be rotatingly actuated by means of a drive shaft 41. The drive shaft 41 extends at right angles to the central longitudinal axis 31 approximately centrally through the core tube 33 and may be connected for driving with an actuating drive 42 outside the core tube 33 and preferably outside the housing 28.

In the example according to FIGS. 2 and 3, the core tube 33 is arranged at both longitudinal ends of the housing 28 such that it projects over the housing 28, so that the core tube 33 forms a gas inlet 43 and a gas outlet 44 of the housing 28. Housing 28 also comprises, besides a cylindrical tubular body 45, an inlet funnel 46 and an outlet funnel 47. The inlet funnel 46 connects the core tube 33 in the area of the gas inlet 43 with the tubular body 45. The incoming flow-side perforation 36 is located in the area of the inlet funnel 46. The outlet funnel 47 connects the tubular body 45 with the core tube 33 in the area of the gas outlet 44. The discharge-side perforation 36 is located in the area of the outlet funnel 47. The core tube 33 is composed in the example of three axial tube sections, namely, an inlet section 48, an outlet section 49 and a control section 50. The inlet section 48 has the gas inlet 43 and the incoming flow-side perforation 36. The outlet section 49 has the gas outlet 44 and the discharge-side perforation 38. The control section 50 has the control means 39 and is arranged axially between the inlet section 48 and the outlet section 49.

The spiral tube 29 has a helically wound tubular body 51, which carries a plurality of ribs 52 on its outside. The ribs 52 thus protrude into the gas path 38.

The mounting layers 32, 37 may be made each of a heat-resistant and permanently elastic material. Various materials, especially fiber materials, may be used for this. The respective mounting layer 32, 37 may be especially a mounting mat, which extends as a closed mat in the circumferential direction. The two mounting layers 32, 37 are shown in FIG. 3 as such mounting mats extending as closed mats in the circumferential direction. There is a contact between the spiral tube 29 or the ribs 52 thereof and the two mounting layers 32, 37 in the mounted state according to FIG. 2. Furthermore, the outer mounting layer 32 is in contact with the housing 28, while the inner mounting layer 37 is in contact with the core tube 33. Mounting is preferably carried out such that the mounting mats 32, 37 are pressed radially, i.e., they generate a certain prestress radially between the spiral tube 29 and the core tube 33, on the one hand, and the housing 28, on the other hand.

Corresponding to an advantageous embodiment, the inner mounting layer 37 may be provided with a supporting mount 53 at least on its outside facing the spiral tube 29 according to FIG. 3. In addition or as an alternative, the outer mounting layer 32 may be provided with a supporting mount 53 at least on its inside facing the spiral tube 29. The respective supporting mount 53 is characterized in that it has a greater mechanical strength than the mounting layer 32, 37 provided with it.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

Claims

1. A heat exchanger for an internal combustion engine for transferring heat between a gas stream and a working medium stream, the heat exchanger comprising:

a housing enclosing a gas path;

a spiral tube carrying the working medium and defining at least a part of a working medium path, the spiral tube being arranged in the gas path and extending helically in relation to a central longitudinal axis of the housing; and

an elastic outer mounting layer arranged between the housing and the spiral tube.

2. A heat exchanger in accordance with claim 1, further comprising a core tube extending coaxially with the central longitudinal axis of the housing and arranged in the housing, wherein:

the gas path is formed radially between the housing and the core tube;

the spiral tube is arranged between the housing and the core tube; and

the core tube encloses a bypass path, which bypass path bypasses the gas path in the area of the at least one spiral tube.

3. A heat exchanger in accordance with claim 2, wherein the bypass path is fluidically connected with the gas path upstream of and downstream of the at least one spiral tube.

4. A heat exchanger in accordance with claim 2, further comprising an elastic inner mounting layer, which is arranged between the core tube and the spiral tube.

5. A heat exchanger in accordance with claim 3, wherein the core tube contains a control means for controlling a cross section of the bypass path, the flow passing through the cross section of the bypass path.

6. A heat exchanger in accordance with claim 5, wherein the core tube projects over the housing at both longitudinal ends of the housing and forms a gas inlet and a gas outlet of the housing.

7. A heat exchanger in accordance with claim 6, wherein the core tube is assembled axially from three tube sections, wherein an inlet section has the gas inlet, an outlet section has the gas outlet, and a control section has the control means.

8. A heat exchanger in accordance with claim 1, wherein the at least one spiral tube has a plurality of ribs protruding into the gas path.

9. A heat exchanger in accordance with claim 1, wherein the elastic mounting layer is at least one of: a ceramic fiber mat; a wire mesh; a metal wire mesh; a metal foam; a ceramic foam structure; a temperature-resistant material; a composite structure; and a swelling mat.

10. A heat exchanger in accordance with claim 4, wherein the elastic inner mounting layer is at least one of: a ceramic fiber mat; a wire mesh; a metal wire mesh; a metal foam; a ceramic foam structure; a temperature-resistant material; a composite structure; and a swelling mat.

11. A heat exchanger in accordance with claim 1, wherein the elastic mounting layer has a supporting mount at least on a side exposed to the gas stream.

12. A heat exchanger in accordance with claim 11, wherein the supporting mount is at least one of: a wire mesh; a metal foil; a graphite foil; a graphite layer; a heat-resistant woven structure; a heat-resistant textile; a metal mesh; a wire mesh; and a metal foam.

13. A heat exchanger in accordance with claim 10, wherein the elastic mounting layer has a fiber material, wherein the supporting mount is impervious to the fibers of the fiber material.

14. A heat exchanger in accordance with claim 1, wherein the elastic mounting layer comprises a mounting mat extending as a closed mat in the circumferential direction.

15. A heat exchanger in accordance with claim 1, wherein the elastic mounting layer is in contact with the adjacent housing and the spiral tube, respectively radially on the outside and radially on the inside.

16. A heat exchanger in accordance with claim 1, wherein the elastic mounting layer is pressed radially.

17. A heat exchanger system comprising:

an internal combustion engine with an exhaust system with an exhaust gas stream;

a heat exchanger for transferring heat between the exhaust gas stream and a working medium stream, the heat exchanger comprising:

a housing enclosing a gas path;

a spiral tube carrying the working medium and defining at least a part of a working medium path, the spiral tube being arranged in the gas path and extending helically in relation to a central longitudinal axis of the housing; and

an elastic outer mounting layer arranged between the housing and the spiral tube.

18. A heat exchanger system in accordance with claim 17, further comprising a core tube extending coaxially with the central longitudinal axis of the housing and arranged in the housing, wherein:

the gas path is formed radially between the housing and the core tube;

the spiral tube is arranged between the housing and the core tube; and

the core tube encloses a bypass path, which bypass path bypasses the gas path in the area of the at least one spiral tube, wherein the bypass path is fluidically connected with the gas path upstream of and downstream of the at least one spiral tube.

19. A heat exchanger system in accordance with claim 18, wherein the core tube contains a control means for controlling a cross section of the bypass path, the flow passing through the cross section of the bypass path.

20. A heat exchanger system in accordance with claim 18, further comprising an elastic inner mounting layer, which is arranged between the core tube and the spiral tube.