GB2174615A

GB2174615A - Matrix for a catalytic reactor for waste gas cleaning

Info

Publication number: GB2174615A
Application number: GB08609487A
Authority: GB
Inventors: Bohumil Humpolik
Original assignee: Behr GmbH and Co KG
Current assignee: Mahle Behr GmbH and Co KG
Priority date: 1985-05-11
Filing date: 1986-04-18
Publication date: 1986-11-12
Also published as: GB2174615B; JPS61259735A; DE3517035C1; JPH0655258B2; GB8609487D0

Abstract

A matrix for a catalytic reactor for waste gas cleaning consists of a corrugated sheet steel strip which can be coated with catalyst material, the strip being folded in a superposed zig-zag form and held in a housing. Along fold planes 6 extending transversely to the longitudinal direction of the passages through which the waste gas flows, the sheet steel strip is provided with weakenings of its cross-section, in the form of scores which cut from one side through the sheet steel strip except for a gap which corresponds substantially to the thickness of the sheet steel strip material. The portions thus formed are folded around the remaining connecting strips and upwards through 180 DEG so that corresponding corrugations in each case form throughflow passages for the matrix which can then be pushed into a housing. The advantage of the new embodiment is the easier manufacture of a matrix for which no soldering process is required. <IMAGE>

Description

SPECIFICATION Matrix for a catalytic reactor for waste gas cleaning The invention relates to a matrix for a catalytic reactor for waste gas cleaning, particularly for internal combustion engines, consisting of a corrugated sheet steel strip which can be coated with catalyst material and which is folded in a superposed zig-zag to form a plurality of layers, being held in a housing through which waste gas flows in a longitudinal direction of the passages formed by the corrugations.

It is known to produce the matrix for reactors of the abovementioned type from corrugated sheet steel strips (German Patent Specification No. 2733640). In each case smooth steel strips and corrugated strips are wound up with one another. It is also known (DOS No. 2902779), in order to increase the turbulence of throughflow of such a matrix, to attach strips of corrugated sheet on smooth sheet steel strips or to roll them up with one another. In any case, after rolling up, the matrix must be soldered so that the individual layers do not slip in relation to one another.

A matrix of the type mentioned at the outset has likewise also been proposed. Where it is concerned, a sheet steel strip provided with a trapezoidal cross-section in its corrugations is folded zig-zag wise along its corrugation edges, in other words in a direction which extends parallel with the passage formed by the corrugations. The cross-sectional form of the corrugated strip is thereby so chosen that the adjacently positioned passage walls are in each case greater than the gaps present between them. This is intended to avoid any slipping of the individual layers into one another. Also with this matrix it is necessary to take precautions to secure the layers folded parallel with what will subsequently be the direction of flow in respect of one another in the direction of flow. This is generally carried out by soldering.

The invention is based on the problem of se developing a matrix of the type mentioned at the outset that no soldering process is needed and so that folding layers on one another already produces a sufficiently stable matrix which only needs to be coated with catalyst material.

In order to resolve this problem, the invention resides, in the case of a matrix of the type mentioned at the outset, in providing the sheet steel strip with cross-sectional weakenings along fold planes which extend transversely to the longitudinal direction of the passages and to fold it over through 1800 in these fold planes and at the remaining connecting points. By virtue of this construction, connection points which continue over the entire width of the matrix and which extend transversely to each layer and in each case on both end faces remain and are sufficiently stable to hold the matrix which is contained in a housing so that the layers are rigidly on one another without any additional working operation. The gap between the fold planes can thereby be chosen to be of equal size so that after folding the matrix acquires a cubic or block-shaped form.The new development is quite particularly suitable for forming non-circular matrix shapes which cannot or at least cannot easily be produced with strips which are rolled up or folded in the manner previously described.

In the case of one particularly simple embodiment of the invention, the cross-sectional weakenings take the form of scores which from one side cut through the sheet steel strip as far as a gap which corresponds substantially to its material thickness. The scores are thereby adapted to suit the material used and to suit its deformability so that whatever connecting strips are left and which forms parts of a passage wall, can be bent through 1800 and assume the axial securing of the superposed layers. With such an embodiment, it is naturally advantageous if the corrugations of the sheet steel strip form a trapezoidal cross-section for the passages so that in each case three passage walls are scored, the remaining passages wall forming the connecting strip.

It is also possible, in order to increase the turbulence, to provide the passage walls with stamped-out lugs which project into the interior of the passages or additionally to provide apertures in the passage walls through which some equalization of flow is possible between the individual passages. Such a compensation is also possible if the passages in the region of one layer are sub-divided in a longitudinal direction into zones of different height, at least two zones being provided with the greatest height to serve as a support for the adjacent layer. The zone of lower height can thereby by formed in that the sheet steel strip is presse flatter at this point than in the other zones. Manufacture of the new steel strip can for the rest be largely automated.

Firstly a flat steel strip is pulled through rolls and provided with the desired corrugations in the direction of drawing, after which specific portions are scored and then folded upon one another in zig-zag fashion. During this rolling process, it is also possible for the intermediate zones to be pressed flat so that no separate expenditure is required to produce the sheet steel strip and subsequently to fold it over to form the matrix.

The invention is described hereinafter with reference to two examples of embodiment which are shown in the accompanying drawings, in which: Figure 1 is a diagrammatic perspective view of a part of a new longitudinally corrugated sheet steel strip which is sub-divided into specific portions of fold planes; Figure 2 shows the sheet steel strip according to Fig. 1 but in which one portion has been raised up or folded in one fold plane in relation to the other; Figure 3 shows a section through the sheet steel strip in Fig. 2, in the direction of the plane III-ill; Figure 4 is a diagrammatic and perspective view of a block-shaped matrix formed by folding onto one another the various portions shown in Figs. 1 and 2;; Figure 5 is a view similar to Fig. 1 but in the case of another embodiment in which case only the region of the sheet strip corresponding to one portion is shown; Figure 6 shows a section through the portion of sheet steel strip in Fig. 5 in the direction of the plane VI-VI; Figure 7 is a diagrammatic plan view of a sheet steel strip suitable for forming a matrix which is not block-shaped; Figure 8 shows a section view, enlarged in relation to that in Fig. 7, through a matrix formed from a sheet steel strip shown in Fig.

7, and Figure 9 is the likewise diagrammatic plan view of the matrix in Fig. 8.

Fig. 1 shows a portion of sheet steel strip 1 which has in its longitudinal direction corrugations which form channels 2 of trapezoidal cross-section which are bounded by passage walls 3, 4 and 5. At interval a, the sheet steel strip 1 is sub-divided into portions 1a, 1b, etc., the boundaries of the portions being formed by fold planes 6 indicated by dashdotted lines which extend at a right-angle to the longitudinal direction of the channels 2. In these fold planes 6, the sheet steel strip 1 is provided from one side, in the case of the embodiment it is the under side, with scores 7 which extend as far as a distance b which corresponds substantially to the thickness of the material of the steel strip 1, the scores 7 parting the sheet steel strip 1 except for a strip 8 which is part of the upper passage wall 3 of each of the individual channels 2.

If, then, according to Figs. 2 and 3, a portion of steel strip, for example the portion 1 b, is folded over in relation to the other portion, for example 1a, through an angle of 1800 in the direction of the arrow 9, then the connecting strip 8 becomes correspondingly deformed but after being folded over and together with the other connecting strips on the other channels, constitutes a stable connecting point for the adjacently disposed layers la, 1b, 1c, etc., of the matrix 10 which, as indicated in Fig. 4, can be inserted into the block or cube-shaped housing 11 indicated by the dash-dotted lines.

During the folding over, which takes place in zig-zag fashion in one direction or the other, the superposition of the relevant channel walls 3, 3' results in the formation of passages 12 of honeycomb cross-section through which waste gas then passes in the longitudinal direction of the passages and in the direction of the arrow 13. The cross-section of the passages 12 therefore corresponds to twice the cross-section of the channels 2 which, after the folding over of the portions 1a, 1b, etc., supplement one another to form the honeycomb shaped cross-section of the passage.

The new embodiment of matrix 10 offers good utilization of the surface area which can be still further improved if the surface of the passage wall 3, 3' is kept as small as possible, Naturally, sheet steel strips of other corrugation cross-section can be provided so long as it is guaranteed that when the incisions or scores are made, there is still sufficient material left to be folded over and, after the folding over, to provide for stable cohesion of the individual layers which are folded onto one another.

Figs. 5 and 6 show another embodiment in which the sheet steel strip used as a starting material and which is shown here only in one portion la', is provided with channels 2' of different height in their longitudinal direction, according to arrow 13. In the case of the embodiment, this has been achieved in that the strip 1 in Fig. 1, when the corrugations are produced, is pressed flatter in the intermediate zones 14 than in the two zones 15 situated before and after these latter, so that, at these locations, the resultant portions of passage are broader in cross-section but are flatter in height, as can be seen from Fig. 6. The zone 15 of height h merges namely into an indeed broader zone 14 which has only the height i.When portions such as, for example, portions 1a' and 1b' are placed on each other, the latter being shown in broken lines in Fig. 6, there are created in the region of the adjacently disposed walls and extending transversely to the longitudinal direction, openings 16 which make it possible for waste gas to be transferred cross-wise to the flow direction 13 out of one passage 12 and into the other. This results in satisfactory mixing and regularization of the flow profile within the matrix, this being another decisive factor for catalytic efficiency of the reactor.

To improve the mixing process and in order to achieve the highest possible degree of turbulence conducive to this end, it is possible, as is also provided in other constructions, to stamp out of the side walls 4, 5 of the channels 2, 2', lugs 17 which project into the region of the passages 12 or channels 2, 2'.

At the stampee out locations, apertures 18 are formed which can likewise serve to allow gas to pass from one passage 12 into the neighbouring passage.

Figs. 7 to 9 show an embodiment of a matrix which, in contrast to the matrix in Fig. 4, is not of a block shape but which can be provided to form waste gas reactors of oval or possibly even round cross-section.

Fig. 7 shows thereby diagrammatically the construction of a sheet steel strip 20 which has the outer contours of two trapezia of which the greater base lines 21 coincide and of which the smaller base area 22 is in each case associated with the end of the sheet steel strip 20 and of which the side faces 23 and 24 in each case diverge from width At to the greatest width A2. The side faces 23' and 24' of the second trapezium which is constructed and disposed symmetrically of the trapezium 21, 20, 24, 22 in relation to the base line 21 extend in similar fashion. In each case at the distance a/2 from the base line 21 there are disposed in this sheet steel strip 20 the fold planes 6 which, as also with the previously described embodiments, are again distributed at equal distances a in respect of each other over the length of the sheet steel strip 20.The rest of the construction corresponds to the embodiment shown in Figs. 1 and 2. Folding at the fold planes 6 does not therefore create block-shaped bodies of which the cross-section is indicated, for example, in Fig. 8. It can be seen that the individual portions 20a, 20b are layered on one another by being folded over one another in this zig-zag fashion. Since their width becomes increasingly smaller due to the trapezoidal form of the steel strip portions, a matrix is created of which the cross-section substantially corresponds to the oval form 25 in Fig. 8. The greatest width of this oval cross-sectional form corresponds to the greatest width A2 of the sheet steel strip 20. The smallest width A1 is achieved in each case at the two outer ends. The smallest trapezoidal portions 20csee Fig. 9-are in each case on the outside of the matrix.The middle portion 20a is located in the middle.

As can also be seen clearly from Figs. 7 and 8, with this embodiment the pitch of the corrugation cross-sections of the strip varies from the greatest pitch t2 to the smallest pitch tl. Possibly, however, it might also be feasible to produce the strip 20 with the same corrugation pitch if in fact the starting point were a steel strip such as is shown in Fig. 1 and if only the outer contours were subsequently cut.

In principle, naturally, it is also possible instead of the trapezoidal cross-section of the corrugations shown and having pitch t or t2 to provide a different cross-section of corrugation such as was in principle envisaged also with other known forms of matrix. All that is important is that the cross-section of the corrugations must be so devices that after the scores 7 have been made, sufficient material is still to hold together the strip which then has to be folded.

Claims

1. Matrix for a catalytic reactor for waste gas cleaning, particularly for internal combustion engines, consisting of a corrugated sheet steel strip which can be coated with catalyst material and which is zig-zag folded and forms a plurality of layers, being held in a housing through which waste gas can flow along the passages formed by the corrugations, characterised in that the sheet steel strip is provided with cross-sectional weakenings along fold planes extending transverse to the passages and, in these fold planes, is folded over through 180 at the remaining connection points.

2. Matrix according to Claim 1, characterised in that the distance between fold planes is in each case identical.

3. Matrix according to Claim 1 and 2, characterised in that the fold planes extend at an angle of 90" to the longitudinal direction of the passages.

4. Matrix according to Claim 1, characterised in that the cross-sectional weakenings are constructed as scores which cut from one side through the sheet steel strip except for a gap which corresponds substantially to the thickness of the material.

5. Matrix according to Claim 4, characterised in that the scores are of a width which is adapted to the material used and to its deformability as well bs to the material thickness.

6. Matrix according to any one of Claims 1 to 5, characterised in that the corrugations form a trapezoidal cross-section for the channels which then supplement the passages and that in each case three passage walls in the fold planes are provided with the scores and in that the remaining connection point is a strip-like part of the fourth passage wall.

7. Matrix according to any one of Claims 1 to 6, characterised in that the passage walls are provided with stamped-out lugs which project into the interior of the passages.

8. Matrix according to Claim 7, characterised in that apertures are provided in the passage walls.

9. Matrix according to any one of Claims 1 to 8, characterised in that in the region of one layer the passages are sub-divided in a longitudinal direction into zones of different height, at least two zones of greatest height being provided as a support for the adjacent layer.

10. Matrix according to Claim 9, characterised in that between two zones of greatest height there is in each case one flattened zone of lesser height.

11. Matrix according to Claim 1 or 2, characterised in that the sheet steel strip has outer contours which diverge to a maximum width.

12. Matrix according to Claim 11, characterised in that the sheet steel strip has the outer contours of two symmetrically constructed trapezia of which the greater base lines coincide and in that the fold planes are in each case located at the same distance from this base line.

13. Matrix according to Claim 11, characterised in that the corrugations have a differ ent pitch over the length of the steel strip.