CA2377027A1

CA2377027A1 - Device for the treatment of exhaust gas

Info

Publication number: CA2377027A1
Application number: CA002377027A
Authority: CA
Inventors: Alfred Ernst Buck
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-06-29
Filing date: 2000-06-29
Publication date: 2001-01-11
Also published as: ATE293209T1; AU6425600A; EP1192336B1; DE19929911A1; WO2001002705A1; AU764496B2; DE50010050D1; DE19929911C2; JP2003505629A; EP1192336A1

Abstract

A device 1 for treating exhaust gases from internal combustion engines has a housing 2, in which an insert 5 is located, which is composed of two types of knit tubes 13, 14. One knit tube 13 consists exclusively of metal wire, while the other knit tube 14 is made completely of mineral fibers, or primarily consists of mineral fibers. The knit tube 13 made of metal wire forms a mesh, which protrudes on the inflow side past the knit tube 14 made of mineral fibers in order to absorb additional heat and to convey it into the interior of the insert 5. Because of this it is possible to arrange the insert at such a distance from the outlet of the engine, that overheating in the full load range is prevented while, on the other hand, the response of the catalytic material is also assured when employed in the partial load range of the internal combustion engine.

Description

Device for the Treatment of Exhaust Gas A catalytic converter for the exhaust flow of an internal combustion engine is described in DE-C-43 03 850. The catalytic converter consists of knit mineral fibers. The knit material is arranged in layers in that it is either folded in an accordion- like manner or rolled up. The flow through the body obtained in this way takes place in a direction parallel l0 with the individual layers. The fibers from which the knit material has been produced are coated with an appropriate catalytic material, for example platinum.
The great advantage of this arrangement lies in a highly effective purification of the exhaust flow while, on the other hand, because of the inherently resilient knit material, there is no danger of its destruction. Since the knit material is furthermore produced as a tubular fabric, there are no exposed edges where the knit material might start to unravel. Even if yarn breaks should occur within the body formed by the knit material, the structure of the knit material is still preserved because the broken yarn is held fast by means of the mesh on both sides of the break.
So-called monoliths are another embodiment of catalytic converters, wherein a porous, gas-permeable ceramic body is covered with the catalytic material. These ceramic bodies have the disadvantage that they possibly might be shattered in the exhaust gas flow.
Independently of the manner how the carrier for the catalytic material is embodied, the known catalytic converters encounter difficulties in their reaction under partial load conditions and at a low output of the internal combustion engine. The reason for this lies in that the exhaust gas flow has too small a volume at these low engine outputs and is not capable of bringing the catalytic converter up to the process temperature at which the catalytic material is capable of splitting the nitrogen monoxide. The low-volume exhaust gas flow is cooled too extensively in the exhaust pipe.
In order to be able to start the catalytic process perfectly at low engine output, the catalytic converter would have to be moved closer to the outlet openings of the internal combustion engine, so that cooling in the exhaust pipe does not become too strong. But this has the result that at a high S engine output the catalytic converter is destroyed thermally.
The large volume exhaust gas flow is not cooled so much. With a short distance between the outlet opening of the cylinder and the catalytic converter when they are connected in a way required for partial load operations, the exhaust gas flow of a large mass would heat the catalytic converter to relatively high temperatures, which are still further increased because of the catalytic decay of the NOX. Because of this, temperatures are reached inside the catalytic converter which will destroy it thermally, or at least damage the catalytic material.
1S Basically similar conditions are encountered with self-regenerating soot filters. Too large a distance of the soot filter from the outlet opening of the cylinder leads to low temperatures in the partial load range of the engine. Higher temperatures would be necessary so that the soot is burned catalytically in the filter. Too short a distance of the soot filter from the outlet opening results in too high temperatures at high engine output.
Based on the foregoing, it is the object of the invention to create a device for the exhaust gas treatment of internal combustion engines which also operates dependably in the lower output range, or partial load range, of internal combustion engines without there being the danger of it being thermally destroyed under full load operations of the engine.
In accordance with the invention, this object is attained by means of the device having the characteristics of claim i.
Flat textile str~~ctures, which are stacked in layers, are also used for the catalytic converter material with the device in accordance with the invention. In this case the body formed in this way is composed of two different types of layers, namely layers consisting exclusively of wire and layers which are either formed of mineral fibers alone, or of a combination of wires and mineral fibers. The layers consisting exclusively of wire are arranged in such a way that, on the inflow side, they protrude for a short distance, for example 3 to 10 mm, past the other layers.
In comparison with mineral fibers, wire is a very good heat conductor and it~is assumed that the protruding wire layers will heat up very rapidly in the exhaust gas flow and will convey the high temperatures into the interior, or between the layers made of mineral fibers. The catalytic process is i0 started by this and further heats the catalytic converter correspondingly. It is therefore possible to arrange the novel catalytic converter at such a distance from the outlet opening of the cylinder that there is no danger of overheating the catalytic converter, even if the engine is operated under full load.
Similar conditions basically exist in connection with a self-regenerating soot filter, wherein the soot deposited on the wire or the fibers with or without a catalytic coating can burn off, even if the vehicle is only operated under partial load.
A housing insert, which is very resistant to mechanical damage by the exhaust gas flow is achieved if at least the first and/or second layer consists of a knit fabric. One skilled in the art understands a knit fabric to be a material produced by knitting. The knit fabric is also very strong if it has been produced in the form of a tubular fabric or as a ribbon with a firm edge, because it is".then possible, for one, to create a double-layered structure, and furthermore, because no exposed borders occur at the edges where there would be a danger of the knit material beginning to unravel. The tubular fabric is endless in the circumferential direction, so that ro Wales are created which are not tied up between the neighboring wares.
The first layers are usefully connected in one piece with each other, which also applies to the second layers. To achieve this, the basic materials for the first and the second layers are placed on top of each other. The double-layered material obtained in this way is either pleated in an accordion fold or is rolled up. First and second layers then respectively alternate in the stack. Depending on the type of internal combustion engine with which the device is to be employed, the catalytic material is either a catalytic material for nitrogen monoxide, or a catalytic material for the oxidation of soot. Finally, the novel device can also be used as a self-regenerating filter arrangement for superfine particles which occur in connection with a Diesel engine as well as with a gasoline engine.
Further developments are the subject of the dependent claims. Exemplary embodiments of the subject of the invention are represented in the drawings; shown are in Fig. 1, the device in accordance with the invention in schematic longitudinal section, Fig. 2, the insert in accordance with Fig. 1 in a perspective schematic representation, and Fig. 3, a further embodiment of the insert of the device in accordance with Fig. 1, also in a partial schematic representation.
Fig. 1 shows in schematic form a device 1 for treating the exhaust gas from an internal combustion engine, for example a Diesel or gasoline engine.
The device 1 has a housing 2, which is provided with an inlet connector 3 and an outlet connector 4. The inlet connector 3 is provided, for example, for a connection to the exhaust manifold of the internal combustion engine, while the exhaust pipe is connected at 4.
An insert 5 is located in the interior of the housing 2.
As shown, the insert 5 completely fills the cross section of the housing 2. On the side facing the inlet connector 3, the insert S is secured by means of an annular collar 6, which is fastened on the housing 2. A perforated plate 7 is fastened in the housing 2 at a distance from the annular collar 6, which is used as a contact surface for the insert 5 and is intended to prevent the exhaust gas flow from displacing the insert 5 in the direction toward the outlet connector 4.

The perforated plate 7 contains a plurality of holes 8 and can also be constituted by a narrow-meshed screen, which is welded to the inside of the housing 2.
The flow through the device 1 occurs from the inlet S connector 3 to the outlet connector 4 in the direction of an arrow 9. In this way; an inflow side 11 and an outflow side 12 is created on the insert 5.
The structure of the insert 5 can be seen in Fig. 2.
The insert 5 consists of two knit tubes 13 and 14, wound in a drum-like manner. The knit tube 13 consists of metal wire 15, which is knit so that a mesh is formed. This results in a structure which, is endless in the circumferential direction, in which the wales 17 formed in the course of knitting extend in the direction of the generator line of the knit tube. The rows of mesh iie in the circumferential direction.
The second knit tube 14 also consists of a mesh 18, wherein the fibers from which the knit tube 14 is formed are mineral fibers. Depending on the type of use, these mineral fibers are coated with a catalytic material for soot, or with a catalytic material for NOx. Moreover, in the case of glass fibers, the latter are also thinned out, if required.
The created tubes 13, 14 of material are laid flat, which can be seen in Fig. 2, and have been wound together over the broad side. The drum-like structure 2 represented in Fig.
2S 2 is created in this way. The width of the knit tube 13 has been selected in respect to the width of the knit tube 14 in such a way that, when both knit tubes_1_3, 14 are pressed flat, the width of the knit tube 13 made of the metal wire 15 is slightly greater than the width of the knit tube 14 made of mineral fibers. Because of this, the knit tube 13 protrudes past the edge of the knit tube 14 at the one side of the insert S.
The insert 5 is produced in the following manner:
The knit tube 13 is knit from metal wire 15 on appropriate circular knitting machines. The knit tube 14 is created from mineral fiber yarn, also on a circular knitting machine. Then the knit tube 14 made of mineral fibers is placed on top of the knit tube made of metal wire in such a way that the knit tube 14, laid flat, is flush at the one edge with the corresponding edge of the knit tube 13 made of metal wire, also laid flat.
Because of the difference in width, one edge of the knit tube 13 made of metal'wire protrudes past the edge of the knit tube 14, as can be schematically seen in Fig. 2. Then the double- layered structure made of the two knit tubes 13 and 14, laid flat, is wound up over the broad side, as also seen in Fig. 2. Winding is continued until a lap roll of a diameter equal to the interior diameter of the housing 2 is created.
Thereafter the created lap roll is cut off from the supply of knit tunes 13 and 14. The lap roll which has been created now represents the insert 5, which is arranged in the housing 2.
1S It is placed into the housing 2 in such a way that the front of the lap roll at which the knit tube 13 of metal wire protrudes faces the inlet connector 3, i.e. constitutes the inflow side 11 of the insert 5.
As can be seen from the explanation of the invention, a first layer formed by the knit tube 14 respectively alternates, viewed in relation to the radial direction of the insert S, with a second layer formed from the knit tube 13 of metal wire.
Because of the arrangement of the lap roll, or of the insert 5, the flow through the insert 5 essentially takes place in a direction parallel with the approximately cylindrical (or more correctly helical) surfaces defined by the layers of the flattened knit tubes 13, 14. In relation to the main.
direction, namely the connection between the inlet connector 3 and the outlet connector 4, the flow takes place approximately parallel with the rows of the mesh 17, wherein in this definition of the flow-through direction only the macroscopic flow is considered. In a microscopical view it can easily occur that a thread of a stream passes through a layer because of turbulence.
Because the knit tube 13 made of metal wire protrudes past the knit tube 14 on the inflow side 11, the structure in this area is quite a bit looser. Moreover, the metal wire has better heat conducting properties than mineral fibers. The metal wire can absorb heat much faster on the flow-in side and convey this heat between the layers of mineral fibers, namely the layers formed by the knit tube 14. Because of this it also becomes possible in the partial load range of the engine to bring the insert 5 up to temperatures at which it can perform its catalytic functions. This occurs at a spatial distance from the outlet opening which prevents the thermal destruction of the insert 5.
The catalytic effects can possibly even be increased if, in addition the metal wire of the knit tube 13 is also coated with a catalytic material.
Instead of producing a cylindrical lap roll, such as represented in Fig. 2, there is also the option of producing a lap roll which has the shape of an oval in a view from above, so that the extension of the housing 2 matched to this is of different size in two directions placed perpendicularly on top of each other. Such a configuration has advantages, for example, when the arrangement must be placed underneath a vehicle.
With the previously explained exemplary embodiment the two knit tubes 13, 14 are wound in every case, i.e. they more or less follow a spiral.
Fig. 3 shows an embodiment wherein the two knit tubes 2S 13, 14 are folded in an accordion-like manner into a stack.
Because of the accordion-like arranged folds, respectively two layers constituted by the knit tube 14_rest directly on top of each other, which are followed, viewed in the stack direction, by two layers of a knit tube 13 placed directly on top of each other. The same effect as with the arrangement in accordance with rig. 2 can also be achieved with such a configuration of the insert 5.
A device 1 for treating exhaust gases from internal combustion engines has a housing 2, in which an insert 5 is located, which is composed of two types of knit tubes 13, 14.
One knit tube 13 consists exclusively of metal wire, while the other knit tube 14 is made completely of mineral fibers, or primarily consists of mineral fibers. The knit tube 13 made of metal wire forms a mesh, which protrudes on the inflow side past the knit tube 14 made of mineral fibers in order to absorb additional heat and to convey it into the interior of the insert 5. Because of this it is possible to arrange the insert 5 at such a distance~from the outlet of the engine, that overheating in the full load range is prevented while, on the other hand, the response of the catalytic material is also assured when employed in the partial load range of the internal combustion engine.
_g_

Claims

Claims:

1. A device (1) for the treatment of exhaust gases from internal combustion engines, having a housing (2) with an exhaust gas inlet (3) and an exhaust gas outlet (4), having at least one housing insert (5), which in accordance with the flow is arranged between the exhaust gas inlet (3) and the exhaust gas outlet (4), wherein the housing insert (5) has an inflow side (11) facing the exhaust gas, inlet (3) and an outflow side (12) facing the exhaust gas outlet (4), the housing insert (5) has at least one first layer (14) of a flat textile structure extending between the inflow side (11) and the outflow side (12), and the housing insert (5) has at least one second layer (13) of a flat textile structure extending between the inflow side (11) and the outflow side (12), contains a metal wire (15) and protrudes past the first layer (14) at least at the inflow side (11) in such a way that the exhaust gas flow passes through the housing insert (5) essentially parallel to the layers (13, 14).

2. The device in accordance with claim 1, characterized in that the housing insert (5) has several first layers (14) and several second layers (13) and at least one first layer (14) is located between neighboring second layers (13).

3. The device in accordance with claim 1, characterized in that the first and/or the second layer (13, 14) consist of a mesh material.

4. The device in accordance with claim 1, characterized in that the first and/or the second layer (13, 14) consist of a knit mesh tube material, laid flat, or of a knit ribbon, wherein the wales (17) lie in the longitudinal direction of the tube, or the longitudinal direction of the ribbon.

5. The device in accordance with claim 2, characterized in that at least the preponderant portion of the first layers (14), preferably all first layers (14), are connected in one piece with each other.

6. The device in accordance with claim 2, characterized in that at least the preponderant portion of the second layers (13), preferably all second layers (13), are connected in one piece with each other.

7. The device in accordance with claim 2, characterized in that the first and second layers (13, 14) are formed by accordion- folding of base products (13, 14) constituting the respective flat textile structures.

8. The device in accordance with claim 2, characterized in that the first and second layers (13, 14) are formed by mutually rolling up the base products (13, 14) constituting the respective flat textile structure.

9. The device in accordance with claim 3, characterized in that the wales (17) extend at right angles in respect to a connecting line from the exhaust inlet (3) to the exhaust gas outlet (4).

10. The device in accordance with claim 1, characterized in that the material for the first layer (14) is exclusively mineral fibers.

11. The device in accordance with claim 1, characterized in that the material for the first layer (14) is mineral fibers and metal wire.

12. The device in accordance with claim 11, characterized in that at least the mineral fibers are coated with a catalytic material.

13. The device in accordance with claim 1, characterized in that the material for the second layer (13) is exclusively metal wire.

14. The device in accordance with claim 13, characterized in that the metal wire is coated with a catalytic material.

15. The device in accordance with claim 12 or 14, characterized in that the catalytic material is used as a catalyst for soot.

16. The device in accordance with claim 12 or 14, characterized in that the catalytic material is used as a catalyst for NO x.

17. The device in accordance with claim 1, characterized in that the housing insert (5) acts as a soot filter.

18. The device in accordance with claim 1, characterized in that the housing insert (5) acts as a nitrogen monoxide catalyst.

19. The device in accordance with claim 1, characterized in that housing insert (5) acts as a filter for superfine particles.