Annular honeycomb body with variable corrugation height

Abstract

The invention relates to an annular honeycomb body (5) that is usable in particular as a catalytic converter (1) for the aftertreatment of a fluid flow in a spatially constricted flow path. The honeycomb body (5) is constructed from a number of first metal foils (6) and a number of second metal foils (7) which are stacked one on top of the other and which are wound, along their length, around an inner pipe, wherein the honeycomb body (5) is arranged in an annular gap (4) between the inner pipe (2) and a casing formed by an outer pipe (3), wherein the second metal foils (7) are at least partially structured, wherein at least one of the second metal foils (7) has a corrugation (8) which is configured to vary, in terms of its corrugation height (9), along the length of the second metal foil (7).

Description

[0001] Ring-shaped honeycomb body with variable corrugation height

[0002] The invention relates to an annular honeycomb body formed from a number of first metal foils and a number of second metal foils that are stacked one upon the other and wound lengthwise around an inner tube. The honeycomb body is arranged in an annular gap between the inner tube and a casing formed by an outer tube, the second metal foils being at least partially structured. Such a honeycomb body can form a carrier body for a catalyst for the aftertreatment of a fluid flow in a spatially limited flow path.

[0003] Catalysts for exhaust gas aftertreatment are available in a wide variety of designs on the market. Among them are catalysts that comprise a metallic honeycomb body formed from a plurality of smooth and at least partially structured metal foils stacked on top of each other to form a layer stack and wound around at least one rotational axis.

[0004] Between the smooth metal foils and the at least partially structured metal foils, cells are formed through which flow can take place along a main flow direction from an end face of the honeycomb body acting as a gas inlet side to an end face of the honeycomb body acting as a gas outlet side.

[0005] The honeycomb structures known in the prior art comprise, in addition to the smooth metal foils, corrugated metal foils, which exhibit a corrugation of constant amplitude and corrugation frequency across their entire length. This is disadvantageous because the number of metal foils used is limited, thus reducing the load-bearing cross-section of the honeycomb structure. Furthermore, the metal foils are subject to severe deformation and sometimes damage, particularly in areas with small bending radii.

[0006] These tight radii and the resulting severe deformation are particularly problematic for so-called ring catalysts. The most severe deformations occur in the area of ​​the inner tube, around which the layer stack is wrapped.

[0007] Therefore, the object of the present invention is to at least partially solve the problems described with reference to the prior art. In particular, an annular honeycomb body or catalyst for exhaust gas aftertreatment is to be provided that undergoes less deformation during production, particularly in the area of ​​the inner tube, and is thus more resistant to damage.

[0008] The objects are achieved by a honeycomb body having the features of claim 1. Further advantageous embodiments are specified in the dependent claims. It should be noted that the features recited in the claims can be combined with one another in any desired manner and can also be supplemented by features of the description, if necessary. The description, particularly in conjunction with the figures, provides further preferred embodiments of the invention.

[0009] This is achieved by an annular honeycomb body which is formed from a number of first metal foils and a number of second metal foils which are stacked on top of one another and wound lengthwise around an inner tube, wherein the honeycomb body is arranged in an annular gap between the inner tube and a casing formed by an outer tube, wherein the second metal foils are at least partially structured, wherein at least one of the second metal foils has a corrugation which is formed differently along the length of the second metal foil with regard to the respective corrugation height.

[0010] The annular honeycomb body can (co-)form a catalyst for the aftertreatment of a fluid flow in a spatially limited flow path. For this purpose, it is possible that a catalytically active substance is at least partially applied to the honeycomb body or its metal foils. The honeycomb body or catalyst can be a so-called ring catalyst. This is characterized by a central tubular flow channel through which an exhaust gas can flow, i.e., it is free of any internals, so that the exhaust gas can flow freely therethrough. Connected to or behind the tubular flow channel (downstream) is a deflection chamber which deflects the exhaust gas flow into an annular flow channel (outer or surrounding the central flow channel), usually by 180 degrees. The annular flow channel is formed between the inner tube forming the tubular flow channel and an outer tube. Such a honeycomb body orA catalytic converter has the advantage that a flow path for exhaust gas aftertreatment can be achieved approximately twice as long over a given length. Honeycomb structures with a catalytically active coating can be arranged in both the tubular and annular sections, thus chemically converting the flowing exhaust gas.

[0011] The honeycomb body, which is arranged in the annular section, is formed from a plurality of metal foils that are stacked on top of one another and wound or layered to form the honeycomb body. The honeycomb body is finally accommodated between the inner tube and the outer tube. The number of metal foils can vary; this means, in particular, that a single first and a single second metal foil can be provided, but also a plurality of first and a (possibly identical) plurality of second metal foils. Likewise, the honeycomb body (in particular second) can have metal foils with different structures, in particular corrugations. Depending on the type of corrugation, in particular the corrugation height (in the thickness direction of the metal foil) and / or corrugation frequency (in the longitudinal direction of the metal foil), the metal foils can be wound more or less tightly, thus, in particular, forming different numbers of windings around the inner tube.The angle at which a metal foil lying against the inner tube protrudes or runs away from it can therefore also vary and can vary from approximately 90 degrees relative to a tangent at the outer radius of the inner tube to approximately 0 degrees relative to a tangent at the outer radius of the inner tube. According to the invention, at least one of the second metal foils, which are the at least partially structured metal foils, has a corrugation which has at least different corrugation heights. A metal foil is characterized in that it has an extension in two spatial directions which are significantly greater than its extension in the third spatial direction. In particular, this third spatial direction, the thickness, of a metal foil is very small, for example a few millimeters or less, in particular less than 1.0 mm and preferably less than 0.5 mm. The extension of the metal foil in the other two spatial directions is significantly greater in comparison.By definition, the length of the metal foil is the direction that later represents the circumferential direction of the honeycomb when wound, or runs in the circumferential direction. The width of the metal foil is the extension of the flow channels created by winding, which corresponds to the axial extension of the wound honeycomb. Length and width are therefore regularly arranged at right angles to each other. The corrugation height is determined particularly in the third spatial direction and can also be described as the amplitude of the structure in the thickness direction (perpendicular to the length and width of the metal foil).

[0012] The second metal foils preferably have a corrugation that runs along the length of the metal foils. The individual corrugation peaks and troughs are thus arranged adjacent to one another along the length of the metal foil, while they preferably extend along the width to form flow channels.

[0013] The honeycomb body according to the invention comprises at least one second metal foil having a corrugation with varying corrugation heights along the length of the second metal foil. The corrugation height can vary both continuously along the length and in sections. The change in corrugation height can occur abruptly or continuously.

[0014] Such a design of the second metal foil is advantageous in particular in that it facilitates the assembly of the honeycomb body, since an adapted corrugation height, particularly in the area directly adjacent to the inner tube, results in less deformation occurring during winding, thus resulting in less deformation and thus a lower risk of damage to the metal foils.

[0015] The inventive design of the second metal foil also allows a larger number of metal foils to be stacked on top of one another, whereby in particular the load-bearing cross section is increased in the soldering areas in which the permanently durable connection of the honeycomb body is finally created by soldering the metal foils together.

[0016] Furthermore, a more even flow distribution across the cross-section of the honeycomb body in the radial direction is achieved, as the backpressure in the edge area, in particular, is reduced relative to the backpressure in the center. This allows the air to flow more effectively through the honeycomb body, thus improving the exhaust gas conversion.

[0017] In a simple embodiment, the first metal foils can be smooth, so that they form a plurality of flow channels with the at least partially structured metal foils when wound up. Alternatively, the first metal foils can also be structured, for example corrugated. Here, the type of structuring can prevent the metal foils from sliding into one another and thus causing snagging between the metal foils. In an advantageous embodiment, the structures of the first metal foils and the second metal foils can be set at an angle to one another, for example, so that sliding into one another is effectively prevented. In a further alternative embodiment, the metal foils can have so-called herringbone structures or fishbone structures, which are characterized in that the structures are formed into the metal foils in a type of zigzag pattern.A molded wave crest or a molded wave trough thus extends along the width of the metal foil in a zigzag pattern. A plurality of parallel wave crests and wave troughs create the herringbone structure along the width of the metal foil. At least one second metal foil can have a corrugation that has a minimum corrugation height at the (inner or first) end region facing the inner tube and a maximum corrugation height at the (outer or second) end region facing the outer tube.

[0018] The metal foils of the honeycomb body, which are stacked in particular to form a layer stack, are in contact with the inner tube at one end and with the outer tube at the opposite end in the final assembled state in the formed annular gap. Since the deformation of the metal foils in the inner tube area is significantly greater than in the outer tube area due to the small bending radii, low corrugation heights in the inner tube area are advantageous to prevent damage to the metal foils. In the outer tube area, the bending radii are naturally larger, so a higher corrugation height can be provided there without risking excessive deformation of the metal foils.

[0019] It is also advantageous if the corrugation height of the at least one second metal foil increases continuously from the end region facing the inner tube to the end region facing the outer tube. A continuous increase in the corrugation height is advantageous in order to minimize sudden changes in the stress in the metal foils. A continuously increasing corrugation height along the length of the metal foil can be created using a specially designed tool that imprints the corrugation into the metal foil with a correspondingly varying corrugation height.

[0020] A preferred embodiment is characterized in that the corrugation height of the at least one second metal foil increases in sections in steps from the end region facing the inner tube to the end region facing the outer tube. Increasing the corrugation height in steps is advantageous for creating defined zones of uniform corrugation height. This can be advantageously used to create defined zones across the cross-section of the honeycomb body that have a specific corrugation height. This allows the flow properties of the honeycomb body to be influenced, thus creating an optimal honeycomb body depending on the application.

[0021] The ratio of the corrugation height on the outer pipe to the corrugation height on the inner pipe can be greater than 1.

[0022] The ratio of the corrugation height on the outer pipe to the corrugation height on the inner pipe can be less than or equal to the ratio of the inner diameter on the outer pipe to the outer diameter of the inner pipe.

[0023] Furthermore, it is advantageous if the at least one second metal foil has no corrugation in the area of ​​the inner tube. A second metal foil without corrugation in the area of ​​the inner tube can ensure that the metal foil protrudes at an approximately right angle to a tangent on the outer radius of the inner tube. This is advantageous for implementing as many layers of metal foil as possible in the honeycomb body. Furthermore, bending of the second metal foils, especially with very small bending radii, is avoided.

[0024] Advantageous further developments of the present invention are described in the subclaims and in the following description of the figures.

[0025] The invention is explained in detail below using an exemplary embodiment with reference to the drawing. In the drawings:

[0026] Fig. 1 is a sketch to illustrate the size ratios and the wave heights of an exemplary ring catalyst,

[0027] Fig. 2 shows a detail of a variant of the structure of a honeycomb body.

[0028] Figure 1 shows a sketched sectional view through a ring catalyst 1 or ring-shaped honeycomb body 5 with an inner tube 2, which has an outer diameter d ka and an outer tube 3 arranged concentrically with the inner tube 2, which has an inner diameter d gi The annular gap 4 resulting between the inner tube 2 and the outer tube 3 is the receiving space for the honeycomb body not shown in Figure 1.

[0029] For example, the ring catalyst shown in Figure 1 shows:

[0030] - The outer diameter of the inner tube d ka to 52 mm with a tolerance of + / - 0.9 mm

[0031] - The inner diameter of the outer tube d gi to 129 mm with a tolerance of 1.09 mm

[0032] The scope is therefore:

[0033] - Outside circumference of the inner tube U ka to 163.4 mm

[0034] - Circumference inside the outer tube U gi to 405.33 mm

[0035] This results in the area of ​​the annular gap being:

[0036] VRin g spait — 109460.1 mm 2

[0037] The extreme case, in which no corrugation is formed on the inner tube and therefore the layers (n) are at a right angle to a tangent on the outer circumference of the inner tube, can now be calculated as follows:

[0038] - n = U ka / s, where s is the foil thickness (thickness of the metal foil) and is 0.04 mm and thus n = 163.4 mm / 0.04 mm = 4085

[0039] This results in the corrugation height on the outer pipe w h = U gi / n to 0.1 mm.

[0040] Alternatively, if a desired wave height of w is present, the following results: h = 1 .09 mm on the inner pipe for the outer pipe a corrugation height of:

[0041] - n = U ka / tubs = 163.4 mm / 1 ,09 mm = 150 and W hau ssen = U gi / n = 405.3 mm / 150 = 2.7 mm

[0042] If a desired corrugation height is present on the outer pipe of W haussen = 1 .09 mm results in a corrugation height on the inner pipe of:

[0043] - n = U gi / Wh aus s e n = 405.3 mm / 1 ,09 mm = 372 and Wonnen = Uka / n = 163.4 mm / 372 = 0.44 mm Using Figure 1 and the calculation methods listed, an ideal corrugation height on the inner tube and on the outer tube can be calculated for any dimensioning of the honeycomb body.

[0044] Figure 2 illustrates a portion of a honeycomb body 5 comprising a plurality of first metal foils 6 (smooth, having a foil thickness s) and second metal foils 7 (structured, having a foil thickness s), so that a plurality of flow channels 10 (extending rectilinearly in the width direction B) are formed. The second metal foils 7 have a corrugation 8 with a varying corrugation height 9 in the longitudinal direction.

[0045] The embodiments of Figures 1 and 2 are in particular not restrictive in nature and serve to clarify the inventive concept.

[0046] List of reference symbols

[0047] 1 ring catalyst

[0048] 2 inner tube

[0049] 3 Outer tube

[0050] 4 Annular gap

[0051] 5 honeycomb bodies

[0052] 6 first metal foil

[0053] 7 second metal foil

[0054] 8 Corrugation

[0055] 9 Wave height

[0056] 10 Flow channel d ka Outer diameter inner tube d gi Inner diameter outer tube

[0057] U ka outer circumference inner tube

[0058] U gi inner circumference outer tube

[0059] Whaussen Corrugation height on the outer pipe Wonnen Corrugation height on the inner pipe s Film thickness n Number of layers

[0060] L Length direction

[0061] B Width direction

Claims

Claims 1. Annular honeycomb body (5) formed from a number of first metal foils (6) and a number of second metal foils (7) which are stacked on top of one another and wound lengthwise around an inner tube (2), wherein the honeycomb body (5) is arranged in an annular gap (4) between the inner tube (2) and a casing formed by an outer tube (3), wherein the second metal foils (7) are at least partially structured, characterized in that at least one of the second metal foils (7) has a corrugation (8) which is formed differently along the length of the second metal foil (7) with regard to the respective corrugation height (9).

2. Honeycomb body (5) according to claim 1, characterized in that the at least one second metal foil (7) has a corrugation (8) which has a minimum corrugation height (9) at the end region facing the inner tube (2) and which has a maximum corrugation height (9) at the end region facing the outer tube (3).

3. Honeycomb body (5) according to claim 2, characterized in that the corrugation height (9) of the at least one second metal foil (7) increases continuously from the end region facing the inner tube (2) to the end region facing the outer tube (3).

4. Honeycomb body (5) according to claim 2, characterized in that the corrugation height (9) of the at least one second metal foil increases in sections in jumps from the end region facing the inner tube (2) to the end region facing the outer tube (3).

5. Honeycomb body (5) according to one of the preceding claims, characterized in that the ratio of the corrugation height (9) on the outer tube (3) to the corrugation height (9) on the inner tube (2) is greater than 1.

6. Honeycomb body (5) according to one of the preceding claims, characterized in that the ratio of the corrugation height (9) at the outer outer pipe (3) to the corrugation height (9) on the inner pipe (2) is less than or equal to the ratio of the inner diameter on the outer pipe (d gi )to the outer diameter of the inner tube (d ka ). Honeycomb body (5) according to one of the preceding claims, characterized in that the at least one second metal foil (7) has no corrugation in the region of the inner tube (2).

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