US20100154396A1

US20100154396A1 - Exhaust gas treatment device

Info

Publication number: US20100154396A1
Application number: US12/641,351
Authority: US
Inventors: Wolfgang Hahnl; Martin Adldinger; Marco Ranalli
Original assignee: Individual
Current assignee: Faurecia Emissions Control Technologies Germany GmbH
Priority date: 2008-12-19
Filing date: 2009-12-18
Publication date: 2010-06-24
Also published as: DE102008063861A1

Abstract

An exhaust gas treatment device, in particular for an internal combustion engine, is fitted with a housing including an entrance and an exit. At least one porous substrate is accommodated in the housing and has an exhaust gas flowing through the substrate. The porous substrate is arranged in the flow path from the entrance to the exit. At least one thermoelectric generator is provided on the housing.

Description

RELATED APPLICATION

This application claims priority to DE Application No. 10 2008 063 861.7, which was filed Dec. 19, 2008.

FIELD OF THE INVENTION

The present invention relates to an exhaust gas treatment device, in particular for an internal combustion engine of a vehicle.

BACKGROUND OF THE INVENTION

For the treatment, more particularly for the purification of exhaust gases of internal combustion engines, e.g., diesel engines of passenger automobiles, it is known to arrange porous, gas-permeable substrates in a closed metallic housing in an exhaust pipe so that the exhaust gas flows through the substrate.
Exhaust gas treatment devices of this type, which may involve, for example, diesel particulate filters or catalytic converters, such as, e.g., for NO_xreduction, are inserted in the exhaust pipe in such a way that all of the exhaust gas has to flow through the exhaust gas treatment device. In the process, the exhaust gas is forced to pass through the porous substrate which has a filter effect and/or effects a catalytically activated chemical reaction with a chemically active coating. An exhaust gas treatment occurs here, e.g., by chemical conversion, by mechanical deposition of particles carried along with the exhaust gas, e.g., soot particles, in the pores of the substrate, or a combination of different methods.
It is known to bring the substrate into the shape of a hollow body having one or more walls. The hollow body is arranged in the housing such that the exhaust gas must always flow through at least one wall of the hollow body to pass from an entrance of the housing to an exit thereof.
The exhaust gas stream that flows through the housing has a temperature of several hundred degrees Celsius.
It is the object of the invention to utilize the thermal energy of the exhaust gas stream.

SUMMARY OF THE INVENTION

The exhaust gas treatment device, which in particular is provided for an internal combustion engine, includes a housing with an entrance and an exit. At least one porous substrate is accommodated in the housing and has an exhaust gas flowing through the substrate. The substrate is arranged in a flow path from the entrance to the exit. Further, at least one thermoelectric generator is arranged on the housing. Thermoelectric generators are devices for converting thermal energy into electrical energy. They include thermocouple elements which operate on the so-called “Seebeck effect” and in which a thermoelectric voltage is generated based on the specific pairing of materials used and the temperature difference prevailing across the thermocouple element. In this way, the thermal energy of the exhaust gas stream can be utilized to generate electrical energy. In addition, a cooling effect on the housing is produced, which results in, e.g., a reduction in the differences in the thermal expansion between the housing and the substrate.
The thermoelectric generators employed may be known conventional thermoelectric generators.
The thermoelectric generator is preferably applied on an outside of the housing to be able to utilize a major part of the thermal energy given off by the exhaust gas stream to the housing. Thermoelectric generators are advantageously used in the form of sheets or strips and are preferably so flexible that they can be well adjusted to the surface of the housing. It is possible to cover essentially the entire outer surface of the housing with one or more thermoelectric generators.
The thermoelectric generators may be fastened to the housing in any suitable manner, such as, e.g., by soldering or brazing, it being of advantage here if a direct, large-area connection having good thermal conductivity exists between the thermoelectric generator and the outer surface of the housing.
Exhaust gas treatment devices in which the exhaust gas flows directly against an inner wall of the housing are advantageous to the configuration because a direct heat transfer from the exhaust gas to the housing, and thus a high yield of thermal energy, is ensured. The housing is designed, for example, in the form of a cylinder having connecting funnels applied at the entrance and at the exit. The cylindrical section has a larger diameter than an adjacent exhaust gas pipe. The inner wall is preferably the inner side of the cylindrical peripheral wall, which can be provided with a known, e.g. catalytically active, coating which has such a small thickness that it is normally of no consequence with regard to the heat conduction.
In one example, the substrates through which the exhaust gas flows are supported in the housing without the interposition of a support mat, as a result of which the housing is uninsulated from the inside.
Possible geometries to be used for the hollow body include, e.g., a pair of cone envelopes or truncated cone envelopes fitted inversely into each other, four- or multi-sided pyramid envelopes or truncated pyramid envelopes, or a pair of cylinder envelopes arranged concentrically in relation to each other.
Such envelopes may be simply produced by reshaped sheets.
In one example, the substrate consists of a metal foam, metal sponge and/or a metallic hollow sphere structure, or a wire mesh or wire knit. In contrast to ceramic substrates, which are wrapped in an elastic support mat and are accommodated in the housing, in the case of a body made of a porous metal substrate, in particular a hollow body, no such thermally insulating material is arranged on the inner wall of the housing, so that a high yield of thermal energy is ensured. In contrast to ceramic substrates, this special metal substrate has an inherent elasticity which allows a press fit in the housing, in particular without additional fastening means.
In another known form, the substrate consists of one or more porous ceramic blocks.
The difference in temperature necessary for operation of the thermoelectric generator or generators is implemented in a radial direction from an interior of the housing to the outside.
To increase the difference in temperature, heat conducting fins may be provided on the inside and/or on the outside of the exhaust gas treatment device, which preferably project radially from the housing. Inside fins serve to withdraw as much heat as possible from the exhaust gas stream to provide as high a temperature as possible on the radially inner side of the thermoelectric generator, whereas outside fins, preferably on the thermoelectric generator, serve to radiate as much heat as possible from the radially outer side of the thermoelectric generator to cause the temperature there to be as low as possible.
The difference in temperature may be further increased by making provision for a cooling device for the thermoelectric generator.
The cooling device may consist of a cooling body, for example, with cooling fins formed thereon, for instance, the cooling body being placed on the outside of the thermoelectric generator or generators.
In one example, the cooling device surrounds the thermoelectric generator on the outside to dissipate heat to the surroundings of the exhaust gas treatment device.
The cooling device may include at least one cooling duct having a cooling medium flowing through the cooling duct. The cooling duct or ducts is/are preferably formed between the thermoelectric generator and a wall of the cooling device and may extend in a longitudinal direction of the exhaust gas treatment device.
It is also possible to employ a cooling liquid. In this configuration, the cooling device may be connected to a conventionally provided cooling circuit of the internal combustion engine, for example.
It is, however, of advantage to use air as the cooling medium since in this way the weight of the exhaust gas treatment device may be reduced and the device may have a simpler structure.
The cooling device includes, for example, at least one inlet having a supply opening. Air from the surroundings of the exhaust gas treatment device flows through the supply opening into the cooling device. The inlet and the supply opening are preferably provided in the immediate vicinity of the housing to produce an effective air flow through the cooling device.
The inlet is advantageously oriented in a travel direction of a vehicle in which the internal combustion engine is arranged since in this way the relative wind can be made use of for producing the air flow.
In one example, provision is made for at least one inlet which widens in the travel direction towards the open end. A plurality of inlets of any desired shape may be distributed both over the periphery of the exhaust gas treatment device and over the longitudinal extent thereof. For example, it is possible to make provision for a plurality of inlets arranged one behind the other and each widening in the travel direction towards the open end. Here, the shape of the inlets may be selected such that a swirling of the air in the cooling device is obtained, for example by curved or obliquely extending walls, and that, where desired, outlets and subsequent inlets may be provided in approximately the same plane. This allows new cold cooling air flows to be supplied at all times along the assembly made up of thermoelectric generators, so that the cooling device is, as it were, subdivided into individual cooling air ducts, and the cooling air is divided up into individual cooling air flows.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic longitudinal section taken through an exhaust gas treatment device according to a first embodiment of the invention;

FIG. 2 shows a schematic longitudinal section taken through an exhaust gas treatment device according to a second embodiment of the invention;

FIG. 3 shows a front view of the exhaust gas treatment device according to the invention as shown in FIG. 2;

FIG. 4 shows a top view of the exhaust gas treatment device according to the invention as shown in FIG. 2;

FIG. 5 shows a schematic longitudinal section taken through an exhaust gas treatment device according to a third embodiment of the invention;

FIG. 6 shows a front view of the exhaust gas treatment device according to the invention as shown in FIG. 5;

FIG. 7 shows a schematic longitudinal section taken through an exhaust gas treatment device according to a fourth embodiment of the invention;

FIG. 8 shows a front view of the exhaust gas treatment device according to the invention as shown in FIG. 7;

FIG. 9 shows a top view of the exhaust gas treatment device according to the invention as shown in FIG. 7;

FIG. 10 shows a schematic longitudinal section taken through an exhaust gas treatment device according to a fifth embodiment of the invention;

FIG. 11 shows a top view of the exhaust gas treatment device according to the invention as shown in FIG. 10;

FIG. 12 shows a front view of the exhaust gas treatment device according to the invention as shown in FIG. 10; and

FIG. 13 shows a cross-section XIII-XIII taken through the exhaust gas treatment device according to the invention as shown in FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a first embodiment of an exhaust gas treatment device 10, in particular for an internal combustion engine of a vehicle, which includes a housing 12 having an entrance 14 and an exit 16. A porous substrate 20 is accommodated in the housing 12 and has an exhaust gas 18 flowing through the substrate 20. The substrate 20 is arranged in the flow path from the entrance 14 to the exit 16. At least one thermoelectric generator 22 is provided on the housing 12.
The exhaust gas treatment device 10 is, for example, a catalytic converter for a motor vehicle, a particulate filter for a motor vehicle, or a combination of a catalytic converter and a particulate filter. Preferably, the porous substrate used consists of a metal foam, a metal sponge and/or a metallic hollow sphere structure, and has an inner and an outer contour in the shape of a cone or a truncated cone.
Thermoelectric generators 22 utilize a difference in temperature between two points of a conductor to generate an electrical voltage. The structure and function of such generators 22 are known from the prior art and will not be discussed in further detail. In each of the Figures, the thermoelectric generator 22 is applied to the outside of the housing 12 and is illustrated merely schematically and greatly simplified.
Furthermore, an active cooling device 24 is provided which surrounds the thermoelectric generator 22 on the outside. The cooling device 24 includes at least one cooling duct 26 through which a cooling medium 28 flows. The cooling medium 28 is a liquid or, preferably, air.
The housing 12 has a largely cylindrical shape with an oval or polygonal base. In one example, the housing has a hexagonally shaped base. The thermoelectric generator 22 makes use of the temperature gradient that develops in a radial direction between the housing 12 and the cooling device 24 to generate an electrical voltage. The greater the temperature gradient between the housing 12 and the cooling device, the higher the electrical voltage generated by the generator 22. In a preferred variant, the hot exhaust gas 18 therefore flows directly against an inner side of the housing wall to reach as high a housing temperature as possible. The heat is absorbed especially well if the housing 12 has heat conducting fins 30 on the inside. Heat conducting fins 30 may also be provided on an outside of the housing 12 and/or on an inside of the generator 22 to achieve a particularly efficient heat transfer from the housing 12 to the inside of the generator 22. In a similar fashion, the thermoelectric generator 22 may also be provided with heat conducting fins 30 on its outside, which protrude into the cooling duct 26 and ensure a particularly efficient cooling of the outside of the generator 22.
Provision may also be made for a plurality of cooling ducts 26 spaced apart in the peripheral direction.
Further embodiments of the exhaust gas treatment device 10 are illustrated in FIGS. 2 to 13. Since there are no differences from the first embodiment with regard to the design and functioning in principle, reference is made in this respect to the above description in relation to FIG. 1, and only the special features of these exemplary embodiments will be discussed
FIG. 2 shows the exhaust gas treatment device 10 according to a second embodiment, in which the cooling device 24 includes at least one inlet 32 pointing in the travel direction and having a supply opening 34, so that cooling medium 28, preferably air from the surroundings of the exhaust gas treatment device 10, flows through the supply opening 34 into the cooling device 24. According to FIG. 2, the supply opening 34 is made to be very large to allow a good air intake, with the inlet 32 tapering inwardly towards the cooling duct 26. Since the inlet 32 is positioned in the region of a conical housing neck 35, the inflow cross-section is extremely large.
FIGS. 3 and 4 show the exhaust gas treatment device according to FIG. 2 in a front view and a top view, respectively. In this case, the housing 12 is of a cylindrical design with a hexagonal base, with a flat thermoelectric generator 22 having heat conducting fins 30 being fastened to each of the outer sides of the side surfaces of the cylinder.
FIGS. 5 and 6 show a longitudinal section and a front view, respectively, of the exhaust gas treatment device 10 according to a third embodiment, which differs from the second embodiment merely in that the inlet 32 of the cooling device 24 on a later bottom surface of the exhaust gas treatment device 10 does not extend beyond the cooling duct 26 in the radial direction. The inlet 32 is not widened or is less widened in this region in order to enlarge the supply opening 34, but is flattened (cf. FIG. 6) so as to restrict as little as possible the ground clearance of the vehicle in which the exhaust gas treatment device 10 is installed.
FIG. 7 shows a fourth embodiment of the exhaust gas treatment device 10, in which the cooling device 24 includes a plurality of inlets 32 arranged axially one behind the other in relation to a longitudinal axis A. The inlets 32 here are each formed such that they radially widen in the travel direction towards the open end, i.e. towards the supply opening. FIGS. 8 and 9 illustrate the associated front view and top view of the exhaust gas treatment device 10.
FIGS. 10 to 12 show a longitudinal section, a top view, and a front view, respectively, of the exhaust gas treatment device 10 in accordance with a fifth embodiment, the cooling device of which likewise includes a plurality of inlets 32, 32′ arranged axially one behind the other in relation to a longitudinal axis A. In this embodiment the thermoelectric generator 22 is however subdivided into two separate sections 36, 38, which are axially spaced apart from each other and are arranged one behind the other. In relation to the flow direction of the cooling medium 28, the cooling duct 26 has an undulating shape at the rear end of a front section 36.
At the front end of the rear section 38, the cooling duct 26 has a rear inlet 32′, which is likewise of an undulating shape. The front inlet 32 is rotated in relation to the rear inlet 32′ in the peripheral direction, so that a wave trough and a wave crest are always disposed axially behind each other (cf. FIG. 12). This allows cooling medium that has already been heated in the front section 36 to flow out of the cooling duct 26 into the surroundings between the sections 36, 38 of the thermoelectric generator 22 and “fresh” cooling medium from the surroundings to flow into the cooling duct 26 at the same time to cool the rear section 38 of the generator 22. Since the efficiency of the thermoelectric generator 22 would be very low in this inflow and outflow region, the generator 22 is recessed in this region, so that the axially forward section 36 and the axially rearward section 38 are produced.
FIG. 13 shows a cross-section XIII-XIII through the exhaust gas treatment device according to FIG. 11, the section being taken between the sections 36, 38 of the thermoelectric generator, and with the exhaust gas and cooling medium flows being indicated by arrows.
The exhaust gas 18 flows out radially through the substrate 20 at a high velocity and impinges as a turbulent flow onto the housing 12, in particular onto the fins 30 of the housing 12. Due to this turbulent flow, an especially good heat transfer is effected between the exhaust gas 18 and the housing 12.
With respect to the flow of the cooling medium 28, FIG. 13 again illustrates that cooling medium 28 that has already been heated in the front section 36 of the generator 22 can escape from the cooling duct 26 between the sections 36, 38 of the generator 22 (dashed arrows) and, at the same time, fresh cooling medium 28 can flow into the cooling duct 26.
In all of the embodiments, the hot exhaust gas flows directly against the inner side of the housing 12.
No elastic support mat for supporting the substrate is provided.
The substrate formed from the hollow metal spheres or the metal sponge is radially elastic and may also be directly clamped radially in the housing.
Also, the substrate need not necessarily be a hollow body, but may a solid body.
According to the illustrated embodiments, the substrates are fastened to a linkage or a holding mechanism in a region of their axial ends, the holding mechanism, for its part, being fitted to the housing.
Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims

1. An exhaust gas treatment device for an internal combustion engine, comprising:

a housing including an entrance and an exit;

at least one porous substrate accommodated in said housing wherein an exhaust gas flows through said at least one porous substrate, and wherein said at least one porous substrate is arranged in a flow path from said entrance to said exit; and

at least one thermoelectric generator provided on said housing.

2. The exhaust gas treatment device according to claim 1, wherein said at least one thermoelectric generator is applied on an outside of said housing.

3. The exhaust gas treatment device according to claim 1, wherein said exhaust gas flows against an inner wall of said housing.

4. The exhaust gas treatment device according to claim 1, wherein said at least one porous substrate consists of at least one of a metal foam, metal sponge, and a metallic hollow sphere structure.

5. The exhaust gas treatment device according to claim 1, including heat conducting fins provided on at least one of an inside and an outside of said exhaust gas treatment device.

6. The exhaust gas treatment device according to claim 1, including a cooling device for said thermoelectric generator.

7. The exhaust gas treatment device according to claim 6, wherein said cooling device surrounds an outside of said thermoelectric generator.

8. The exhaust gas treatment device according to claim 6, wherein said cooling device includes at least one cooling duct having a cooling medium flowing through said at least one cooling duct.

9. The exhaust gas treatment device according to claim 8, wherein said cooling medium is air.

10. The exhaust gas treatment device according to claim 9, wherein said cooling device includes at least one inlet having a supply opening so that air from surroundings of said exhaust gas treatment device flows through said supply opening into said cooling device.

11. The exhaust gas treatment device according to claim 10, wherein said at least one inlet widens in a vehicle driving direction towards an open end.

12. The exhaust gas treatment device according to claim 11, wherein said at least one inlet comprises a plurality of inlets arranged one behind each other, said plurality of inlets widening in the vehicle driving direction towards said open end.