WO2009148236A2

WO2009148236A2 - Filter element for subsequent treatment of exhaust gases from internal combustion engines

Info

Publication number: WO2009148236A2
Application number: PCT/KR2009/002868
Authority: WO
Inventors: David Meister; Armen Markarian; Sebastian Schurholz
Original assignee: Alantum Corporation
Priority date: 2008-06-02
Filing date: 2009-05-29
Publication date: 2009-12-10
Also published as: EP2131018B1; CN102046937A; CN102046937B; EP2131018A1; WO2009148236A3; KR20110028318A; JP2011522156A

Abstract

The invention relates to filter elements for the subsequent treatment of exhaust gases from internal combustion engines. In addition to a separation of particles contained in the exhaust gas, if necessary, a subsequent catalytic treatment can also be implemented with a filter element. It is an object of the invention to make filter elements available that have improved properties for a subsequent treatment of exhaust gases in which the thermal properties are thereby improved. A filter element according to the invention is formed with an open-pore material. It has inlet channels that are sealed on one side and outlet channels that are sealed on the diametrically opposite side. The exhaust gas to be subsequently treated flows into inlet channels, through separating walls formed with an open-pore metallic material into an adjacently disposed outlet channel, and out of the latter from the filter element. The free cross-section in the interior of the inlet and outlet channels changes in the inflow and outflow directions into or out of the inlet and outlet channels. The wall thickness of the separating walls separating the inlet and outlet channels from each other is thereby maintained constant in the region through which exhaust gas flows.

Description

FILTER ELEMENT FOR SUBSEQUENT TREATMENT OF EXHAUST GASES FROM INTERNAL COMBUSTION ENGINES

The invention relates to filter elements for subsequent treatment of exhaust gases from internal combustion engines. In addition to separation of particles contained in the exhaust gas, if necessary, a subsequent catalytic treatment can also be implemented with a filter element.

Particle filters and catalysts in many varied forms and made of various materials have been used to date. As is known, specific minimum temperatures are required, for example for regeneration or catalytic effectiveness. These are partially achieved or are achieved only with a delay during operation of internal combustion engines (cold start, partial load, or short journey) with the hot exhaust gas so that the effect is achieved in a temporarily restricted manner or a pressure increase results since porosity is reduced by deposited carbon. In order to counteract this, different measures, such as supplementary heating, have been adopted. However, costs and complexity are consequently increased.

It is known from DE 10 2006 009 164 A1 to use a filter medium which is formed from a metallic open-pore foam. The filter medium through which the exhaust gas flows in the throughflow direction is intended to be formed with at least two layers and a reducing thickness, and average porosity and/or average pore size is intended to be present in the layers.

In the case of this known device, inlet and outlet channels for exhaust gas are present and are separated from each other by the filter medium. In one embodiment, inlet channels are intended to have a reducing free cross-section in the flow direction of the exhaust gas, as a result of which the deflection of the flowing exhaust gas in the narrowed region, and also at the gas-tight sealed end of inlet channels, is intended to be assisted so that improved flow rates for the exhaust gas flowing through the filter medium can be achieved.

The multilayer filter medium through which the exhaust gas is to flow has, however, because of the multilayer construction, no constant properties across the entire volume, which not only applies to permeability but also to electrical and in particular thermal parameters.

It is the object of the invention to make filter elements available that have improved properties for a subsequent treatment of exhaust gases, and the thermal properties are thereby improved.

According to the invention, this object is achieved with a filter element that has the features of claim 1. Advantageous embodiments and developments can be achieved with features described in the subordinate claims.

In the case of the filter element according to the invention, inlet and outlet channels for exhaust gas are present, and said channels are sealed at respectively diametrically opposite sides so that exhaust gas flowing into inlet channels flows through separating walls into respectively adjacent outlet channels, and from there further in the direction of the external environment. At least the separating walls are formed from an open-pore material. The inlet openings for exhaust gas that flows into inlet channels are thereby situated in the main flow direction of the exhaust gas at an end-side of a filter element, and the outlet openings are formed at outlet channels on the oppositely situated end-side.

Although the inlet channels and the outlet channels have changing free cross-sections, the separating walls that separate them are intended, in the region through which the exhaust gas flows, to have a constant wall thickness. The separating walls in this region are also preferably intended to have a completely homogeneous configuration, i.e., constant average porosity, average pore size, and thickness, and to be formed from the same material.

This is not only advantageous for the flow behaviour, but the same thermal properties are thereby provided. As a result of constant heat conductivity, heat bridges and heat sinks can be avoided, and more uniform heating within a shorter time can be achieved in the total volume of the separating walls through which exhaust gas flows.

Metal alloys can preferably be used as a material thereof, and in particular, iron or nickel alloys can be used.

As a particular preference, filter elements according to the invention are formed with plate-like elements that are integrally connected to each other. These plate-like elements are formed at least in the region through which the exhaust gas flows from the open-pore metallic material. Openings that form the inlet and outlet channels in the stack that is formed with the plate-like elements are configured in the individual plate-like elements.

Openings are configured in the individual plate-like elements. The free cross-sections change, however, from one plate-like element to an adjacent plate-like element so that a change in the free cross-sections of the inlet and outlet channels can be achieved.

The plate-like elements can be produced for example analogously to the Schwarzwald method which is known per se. The openings can be cut from the individual plate-like elements with a laser beam. Further, non-perpendicular cut edges can thereby be formed in order to achieve continuous transitions in the channels from one plate-like element to an adjacently disposed plate-like element.

The thusly prepared plate-like elements can then be stacked one above the other in a prescribed sequence and then be integrally connected to each other during a heat treatment. Sintering is thereby implemented, preferably, and on the surfaces of the plate-like elements that are in contact with each other, a sinterable powder of the material used for production of the plate-like element can thereby be applied. During the heat treatment, the plate-like and stacked elements that are to be connected to each other can be pressed together.

The free cross-sections of inlet and outlet channels can have the most varied of geometries and dimensions. As a result, adaptation to different internal combustion engines and respective exhaust gas volume flows can be undertaken. The free cross-sections can be round, square, triangular, rectangular, or polygonal. However, they can also have the form of circular ring segments.

It can be advantageous that inlet and outlet channels on one filter element have the same geometry and possibly also the same dimensioning, wherein the dimensioning of the free cross-sections, viewed in the main flow direction, change respectively in an opposite manner. If the free cross-section of inlet channels is reduced, starting from their inlet opening up to the closed end-side, then an increase in the free cross-section of outlet channels, starting from their closed end-side up to their outlet opening, should be provided.

This is the case in particular when inlet and outlet channels are configured in the form of truncated cones or pyramids.

The gas-tight sealing of inlet and outlet channels can be achieved with plate-like elements that are suitable for this purpose and are disposed on both end-sides relative to the main flow direction of the exhaust gas. Non-porous plate-like elements made of the respective metals can be used for this purpose. However, the possibility also exists of using plate-like elements with significantly less porosity or closed porous structures. This also can be achieved in the heat treatment which is used to configure the integral connection or with an additional heat treatment. Pores that are present can thereby be at least extensively closed by means of infiltration or with a suitable metallic powder.

The gas-tight sealing can however also be achieved with a housing that is suitable for this purpose and in which corresponding openings for the inflow and outflow of exhaust gas are configured. This can be achieved in the cover region, i.e., where no inlet and outlet openings for exhaust gas are disposed, and also by infiltration or with a metallic powder by means of heat treatment, as explained already. Sufficiently less porosity can thus be present there or pores can be completely closed.

For a subsequent catalytic treatment of exhaust gas, the surface of separating walls can be provided with a catalytically effective coating and/or a catalytically effective material. This can and should also be possible in the inner porous region thereof. Solutions known per se and suitable materials can be resorted to here.

The wall thickness of the separating walls should have, at least in the region through which the exhaust gas flows, a thickness in the range of 1.0 mm to 25 mm, preferably in the range 2 mm to 20 mm. Small deviations in the wall thickness in the region of the inlet and outlet channels through which exhaust gas can flow can, however, be tolerated if the volume flows flowing through separating walls can be maintained approximately constant.

In one embodiment, intermediate channels can also be present in addition on a filter element according to the invention, said intermediate channels being able to form chambers and the exhaust gas thereby being able to flow out of an inlet channel through a separating wall into an intermediate channel and from there through a further separating wall into an outlet channel. Such an embodiment can be produced with a type of series arrangement that is formed with two regions connected to each other. For example, two such regions with plate-like elements can be used for this purpose, in the case of which channels, with the openings on one side sealed in a gas-tight manner, are configured in the form of truncated cones or pyramids. Orientated opposite each other, these can then be placed one upon the other, and just like the individual plate-like elements, connected to each other. Intermediate channels thereby have then, in the main flow direction of the exhaust gas through the filter element, a firstly increasing and then reducing free cross-section. In this case also, the separating walls have a constant wall thickness.

Filter elements according to the invention can be adapted specifically to the respective requirements of subsequent treatment of exhaust gases. The filter efficiency and/or the catalytic efficiency can then be influenced. The production costs can thereby be significantly reduced since, in the case of a subsequent catalytic treatment, the use of catalytically effective materials (in particular noble metals) can be reduced without reducing efficiency during the catalysis.

The invention is intended to be explained subsequently in more detail with reference to examples.

There are thereby shown:

Figure 1 an example of a filter element in a sectional representation;

Figure 2 a further example of a filter element in a sectional representation;

Figure 3 a further example of a filter element in a sectional representation;

Figure 4 a plan view of a filter element; and

Figure 5 a perspective representation of a filter element.

Three examples of filter elements according to the invention, which are formed with plate-like filter elements that are integrally connected to each other, are represented in Figures 1 to 3. The plate-like filter elements are formed from a metallic open-pore material and sintered to each other by a heat treatment. In the examples shown in Figures 1 and 2, there are 25 such plate-like filter elements. All of them have the same densities, porosities, and average pore sizes. The metallic material can be provided with a catalytically effective coating or a catalytically effective material (e.g. by doping) at least in the region of separating walls 4.

Openings have been formed in the plate-like filter elements by laser cutting. The inlet channels 2 and the outlet channels 3 have again been configured with the openings in the individual plate-like filter elements, and also with intermediate channels 5 in the example shown in Figure 3.

It also becomes clear in the illustrations that the free cross-section through which exhaust gas can flow changes in the inlet channels 2 and the outlet channels 3. The wall thickness of separating walls 4 is maintained constant at 2.75 mm over the entire length of inlet and outlet channels.

The plate-like filter elements have a constant thickness of 3 mm.

In the example of a filter element 1 shown in Figure 1, the openings have been configured such that uniform conical tapering occurs on two sides of the inlet and outlet channels. The end-edges on the openings are configured to be inclined at an angle for this purpose. In other cases, some of the inlet and outlet channels are configured as circular ring segments with their free cross-section on a cylindrical filter element 1, as can be deduced from the illustration in Figure 4. The section line A-A can also be deduced from the plan view shown there, said section line corresponding to the sectional representations of Figure 1 to 3.

In the example shown in Figure 2, separating walls 4 of inlet and outlet channels are curved convexly in the direction of the respective channels, which applies at least to the regions that are disposed on radii of the filter element 1. In contrast to this represented shape, a concave curve is also possible.

Figure 3 shows an example of a filter element 1 that is formed with two regions A and B that are connected to each other. Exhaust gas can enter here into inlet openings of inlet channels 2. It then flows through the inlet channels 2, the separating walls 4 into intermediate channels 5, and from there again through further separating walls 4 into outlet channels 3.

In this example, the regions A and B are separated by a plate-like filter element that has no openings so that the latter can form an additional separating wall in the intermediate channels 5. This is indicated with the arrows in this part of the intermediate channels 5.

When exhaust gas flows through separating walls 4, firstly a separation of particles contained in the exhaust gas and then a subsequent catalytic treatment can be implemented.

For reasons of clarity, the number of reference numbers for separating walls 4 has been limited in the illustrations, and the representation of an outer housing has also been dispensed with.

Figure 5 is intended, with the perspective representation, to clarify a possible embodiment of a filter element 1 with an arrangement and geometric configuration of inlet channels 2. The side that is not visible here with the outlet openings of outlet channels 3 can then have a complementary configuration.

Claims

A filter element for subsequent treatment of exhaust gases from internal combustion engines, which is formed with an open-pore material and inlet channels that are sealed on one side and outlet channels that are sealed on the diametrically opposite side, the exhaust gas to be subsequently treated flows thereby into the inlet channels, flows through the separating walls formed with the open-pore metallic material into the adjacently disposed outlet channels, and flows out of the latter from the filter element,

characterised in that the free cross-section in the interior of the inlet and outlet channels (2, 3) changes in the inflow and outflow direction into or out of the inlet and outlet channels (2, 3) and the wall thickness of the separating walls (4) separating the inlet and outlet channels (2, 3) from each other is maintained constant in the region through which exhaust gas flows.
The filter element according to claim 1, characterised in that it is formed from plate-like filter elements that are integrally connected to each other and form a stack, the inlet and outlet channels (2, 3) and the separating walls (4) being configured by means of openings configured in the plate-like filter elements.
The filter element according to claim 1 or 2, characterised in that the free cross-section of the inlet and outlet channels (2, 3) has a round, square, rectangular, or polygonal geometric shape, or is configured in the form of circular ring segments.
The filter element according to one of the preceding claims, characterised in that the inlet and outlet channels (2, 3) are configured in the form of a truncated cone or pyramid.
The filter element according to one of the preceding claims, characterised in that plate-like filter elements are sintered to each other.
The filter element according to one of the preceding claims, characterised in that gas-tight plate-like filter elements are disposed on both end-sides, in which filter elements openings for inlet channels (2) are configured on one end-side and openings for outlet channels (3) are configured on the other end-side.
The filter element according to one of the preceding claims, characterised in that the surface of separating walls (4) is provided with a catalytically effective coating and/or a catalytically effective material.
The filter element according to one of the preceding claims, characterised in that a filter element (1) with two regions (A, B) that are connected to each other is formed, said regions forming a series arrangement, with inlet channels (2), intermediate channels (5), and outlet channels (3) being present, and exhaust gas entering through the inlet channels (2) flows through a separating wall (4) into the intermediate channels (5) and through a further separating wall (4) into the outlet channels (3).
The filter element according to one of the preceding claims, characterised in that the separating walls (4) in the region through which exhaust gas flows have a constant porosity, pore size, and density.
The filter element according to one of the preceding claims, characterised in that the region of the filter element (1) through which exhaust gas flows is surrounded by a gas-tight housing, and less porosity is present in an outer region thereof or the pores are closed in this region.
The filter element according to one of the preceding claims, characterised in that the filter element (1) is formed with an open-pore metallic material.