Opaque heating matrix in flow path

Abstract

The invention relates to a device for post-treating exhaust gases of an internal combustion engine, having a flow path (11) that is spatially delimited by a housing (2) and through which exhaust gas can flow, having a heating matrix (1) that has a plurality of flow channels (20) for the exhaust gas, wherein the heating matrix (1) can be connected to a voltage source and can be heated by utilising the ohmic resistance, wherein the heating matrix (1) has at least one air gap (5, 7) that extends transversely through the heating matrix (1) with respect to the flow path (11), and having a support structure (8) that fixes the heating matrix (1) on the housing (2), wherein the support structure (8) is designed such that the at least one air gap (5, 7) is covered by the support structure (8) in the flow direction.

Description

[0001] 202301301

[0002] 1

[0003] Description

[0004] Opaque heating matrix in flow path

[0005] Technical field

[0006] The invention relates to a device for the aftertreatment of exhaust gases from an internal combustion engine, comprising a flow path spatially limited by a housing through which exhaust gas can flow, a metallic heating matrix which has a plurality of flow channels formed between a plurality of stacked metal foils wound around at least one axis of rotation, wherein the flow channels can be traversed by the exhaust gas along a main flow direction from a gas inlet side to a gas outlet side, wherein the heating matrix can be connected to a voltage source and heated by utilizing the ohmic resistance, wherein the heating matrix has air gaps between the individual windings or foil packs, and a support structure which is arranged as a connecting element between the housing and the heating matrix.

[0007] State of the art

[0008] Electric heating elements are now regularly used to heat exhaust gases in the exhaust system downstream of a combustion engine, or the exhaust gas flowing within the exhaust system itself. The aim is to reach a temperature threshold more quickly, above which effective conversion of the pollutants carried in the exhaust gas can occur. This is necessary because the catalytically active surfaces of the catalysts used for exhaust aftertreatment in the exhaust system only enable sufficient conversion of the respective pollutants above a minimum temperature, the so-called light-off temperature.

[0009] Known solutions in the prior art include so-called heating catalysts, which consist of a metallic element connected to a voltage source.

[0010] 2

[0011] exhibit a structure or have a metallic-coated ceramic structure which can be heated by utilizing ohmic resistance.

[0012] The heatable metallic structures can, for example, consist of a honeycomb structure created from metal foils. For this purpose, a plurality of smooth and / or at least partially structured metal foils are stacked on top of each other and wound around at least one pivot point to form a honeycomb structure. The matrix formed from the metal foils can be electrically contacted and heated by utilizing its ohmic resistance.

[0013] For this purpose, the matrix must be arranged in an exhaust gas path and be positioned upstream or downstream of a catalyst designed for exhaust gas aftertreatment in the direction of exhaust gas flow.

[0014] The heating elements are often arranged in a spiral or meandering pattern within the exhaust gas path. A disadvantage of the solutions known in the prior art is that, due to their design, air gaps form between the individual sections of the heating element, preventing the flowing exhaust gas from being actively heated by the element. This applies both to the air gaps between the individual sections of the heating element and to the air gap between the heating element and the housing in which it is located. Depending on the cross-sectional area of ​​these air gaps, the heating of the flowing medium can be significantly impaired, or even a flow bypass can occur, which considerably reduces or almost completely prevents the flow through the actual heating element.Besides the insufficient heating of the flowing medium, this also has the disadvantage that the heating element experiences practically no cooling, which can lead to local overheating and potentially damage to the heating element. 202301301.

[0015] 3

[0016] Description of the invention, problem, solution, advantages

[0017] Therefore, the object of the present invention is to provide a heating element which is improved, particularly with regard to the resulting air gaps, in such a way as to ensure a uniform and as complete as possible flow through the heating element. In particular, the heating element should alleviate or solve at least some of the problems described above.

[0018] The problem with regard to the device is solved by a device having the features of claim 1.

[0019] One embodiment of the invention relates to a device for the aftertreatment of exhaust gases from an internal combustion engine, comprising a flow path spatially limited by a housing, through which exhaust gas can flow, a (metallic) heating matrix which has a plurality of flow channels for the exhaust gas, wherein the heating matrix can be connected to a voltage source and can be heated by utilizing the ohmic resistance, wherein the heating matrix has at least one air gap which runs transversely to the flow path through the heating matrix, and a support structure which fixes the heating matrix to the housing, wherein the support structure is designed such that the at least one air gap is covered by the support structure.

[0020] The housing can be designed as part of a (mobile or stationary) exhaust system or exhaust duct. The housing can form an approximately tubular flow channel, which may be straight and / or curved. Exhaust gas introduced into the housing flows through it in a preferred direction (main flow direction), particularly away from a connected internal combustion engine. A predetermined, spatially limited flow path is provided within the housing, through which exhaust gas can flow. The flow path can be axially limited, for example, by the axial extent of the heating matrix or a small multiple thereof (e.g., 2 times to a maximum of 4 times). 202301301

[0021] 4

[0022] The heating matrix is ​​also permeable to exhaust gas due to the integral design of multiple or many flow channels. The heating matrix can form a honeycomb structure. The flow channels and the flow path run essentially parallel from one exhaust gas inlet side to an (opposite) exhaust gas outlet side. The heating matrix can be designed to divide the flow path into many small flow channels.

[0023] The heating matrix can be formed with at least one partially structured metal foil. It is possible that several (e.g., corrugated and / or smooth) metal foils are (alternately) assembled into a stack or package, with the corrugated / smooth metal foil surfaces forming the flow channel walls along which the exhaust gas flows.

[0024] By winding and / or coiling the at least one metal foil or stacked metal foils, air gaps can be created between the individual foil stacks or windings. This is advantageous for forming an electrical current path that flows in a controlled and limited manner along these foils, foil stacks, or foil bundles without arcing. If an undesired voltage arc were to occur, the heating matrix would either be only partially energized and / or so-called hot spots would form, in which the heating matrix would be heated significantly more. Such an air gap can be characterized by having a profile perpendicular to the flow channels or perpendicular to the axial extent of the heating matrix, which corresponds to at least three times, in particular at least five times, or even at least five times the axial extent of the heating matrix / flow channels.Such an air gap can (further) be characterized by the fact that it has a gap thickness perpendicular to the flow channels or perpendicular to the axial extent of the heating matrix (and in particular also perpendicular to its own course), which corresponds to at least 3 times, in particular at least 5 times, the mean opening width (diameter) of the flow channels.

[0025] Such an air gap, due to its larger dimensions, can be problematic for the exhaust gas 202301301

[0026] 5. The cross-sections are very easily or preferentially permeable because the flow resistance is not increased by the heating matrix there. A significant portion of the exhaust gas can therefore flow past the heating matrix and not through the flow channels formed by the heating matrix. This can lead to suboptimal heating of the exhaust gas and, at the same time, to a very inhomogeneous flow through the heating matrix.

[0027] Since the heating matrix extends essentially (radially) over the entire flow path, but itself has only a comparatively small axial extent, a support structure is provided on which the heating matrix is ​​supported at a multitude of support or suspension points. Separate support pins can be provided for this purpose, which are attached on the one hand to the support structure and on the other hand (in the flow channels) to the heating matrix. The support structure can also extend essentially (radially) over the entire flow path and be positioned upstream and / or axially downstream of the heating matrix. The support structure can comprise a central support area, an outer support frame, and a plurality of support beams connecting these elements. The support structure is preferably at least 80% open to allow exhaust gas flow through it.

[0028] The support structure, which is also designed to electrically insulate and fix the heating matrix within the exhaust gas system housing, is shaped to follow the contours of the heating matrix's air gap and, if applicable, any air space between the heating matrix and the housing, completely covering it. The support structure can be adapted to the specific air gap configuration of different heating matrix designs, ensuring that the air gaps are covered in the direction of exhaust gas flow. Coverage of the air gap is particularly evident when the heating matrix's air gap is not visible from an axial view of the support structure. Coverage is especially evident when exhaust gas flowing towards the support structure during operation of the internal combustion engine is predominantly deflected away from the air gap (towards the flow channels).Full coverage is present in particular when at least 90% of the course and gap thickness of at least one air gap is covered 202301301.

[0029] 6 is.

[0030] The support structure does not completely seal the air gaps fluid-tight because, by design, it must be positioned at a distance from the heating matrix in the main flow direction of the exhaust gas to create electrical insulation between the heating matrix and the support structure. However, the support structure presents a barrier to the otherwise freely flowing exhaust gas, which the gas must at least flow around. Consequently, the exhaust gas is deflected and directed towards the areas filled by the heating matrix or its flow channels. This significantly increases the proportion of exhaust gas that actually flows through the flow channels, resulting in improved heating of the exhaust gas and a more uniform flow through the heating matrix.

[0031] The support structure can include at least one gap cover element that does not cover any flow channels. The gap cover element can (additionally) be attached, connected, and / or mounted to the support structure. The gap cover element can be designed to cover, in particular, (only) the at least one air gap in the heating matrix or between the foil packs. The gap cover element can be designed to correspond, in particular, to the shape and thickness of the at least one air gap in the heating matrix. This allows the freely flowing exhaust gas to be guided through the gap cover elements, past the at least one air gap, and towards the flow channels.

[0032] The at least one gap cover element can have a continuous profile from a housing-adjacent area to a central area of ​​the heating matrix. In particular, the gap cover element can be attached to the support structure as a continuous, uninterrupted element. The gap cover element can also have a spiral or meandering profile (corresponding to the air gap).

[0033] The support structure can consist of a plurality of struts or support beams extending from the central area towards the housing and an outer (support) frame. 202301301

[0034] 7, wherein at least one gap cover element is attached to or integrated with it. In other words, this means in particular that the gap cover element is designed to overlap with the support elements or to connect them (repeatedly). It is possible that the gap cover element primarily serves only the function of covering, and the support elements primarily the function of stabilizing and securing the heating matrix. In particular, the support elements may allow thermal deformation of the heating matrix, which can also be transferred to the gap cover element via the support elements, so that even in this case (thermal displacement of the air gap), a cover can be maintained (independently).

[0035] It is also advantageous if the support structure has initial sections (especially the struts or support beams) that each have at least one connecting element to the heating matrix. These initial sections at least partially cover the heating matrix and offer the possibility of connecting the heating matrix to the support structure, for example by means of support pins. The support pins provide an electrically insulated connection between the support structure and the heating matrix.

[0036] Furthermore, it is preferable if the support structure has at least one second section (in particular the gap-covering element) that does not have any connecting elements to the heating matrix. These second sections can, in particular, be the gap-covering elements that cover the air gaps. Advantageously, no connecting elements are provided between the heating matrix and the support structure in these second sections, since the known support pins would engage in the air gaps and thus a durable connection to the heating matrix cannot be established. Connecting two adjacent foil packs or windings should be avoided, as this can lead to unwanted current bridges, which alter the current path through the heating matrix.

[0037] The second section can begin at the housing or support frame and "wind" inwards to the center of the device. It is possible that the second section extends from the outside of the support structure to its 202301301.

[0038] 8

[0039] The center extends. It is possible that the second section has two elements, both starting at the housing and projecting to the center of the support structure, but not touching. The two elements may be intertwined and together cover the entire air gap formed in the heating matrix.

[0040] The support structure can be mechanically supported by the elements of the second section. It is possible that the support structure is mechanically reinforced and stiffened by the second section.

[0041] A preferred embodiment is characterized in that a first support structure is arranged upstream of the heating matrix when viewed in the direction of exhaust gas flow, and a second support structure is arranged downstream of the heating matrix in the direction of exhaust gas flow. This enables a particularly stable and durable fixation of the heating matrix in the housing.

[0042] It is also preferable if the arrangement of the first support structure upstream of the heating matrix creates an opacity along the main flow direction of the exhaust gas. This opacity, i.e., the covering of the open air gaps, is preferably created in the flow direction upstream of the heating matrix, as this allows the exhaust gas flowing onto the heating matrix to be successfully deflected from the air gaps onto the flow channels.

[0043] Furthermore, it is advantageous if the first and second support structures are not identical. Advantageously, the two support structures are not identical; in particular, the second support structure can have a simpler design, since it only performs the function of positioning the heating matrix, but not the flow-guiding function.

[0044] Furthermore, it is advantageous if the first support structure has flow-guiding elements that direct the exhaust gas flowing onto the first support structure towards the heating matrix. Flow-guiding elements can be, in particular, surface-mounted guide elements such as blades, grooves, or similar contoured features.

[0045] There can be nine generating elements. However, the support structure can also have a special shape that promotes the deflection of the exhaust gas flowing onto the support structure in a specific direction. For example, it is advantageous if the individual sections of the first support structure have wedge-shaped cross-sections, with the individual sections of the first support structure widening conically in the direction of exhaust gas flow. This improves the deflection of the exhaust gas from the support structure into the flow channels of the heating matrix.

[0046] The support structure can have (at least) three covering zones. Preferably, the support structure can be designed such that no further gap covering elements are required, but rather the air gap can be covered (exclusively) by the support structure itself. The covering zones are preferably formed by parts of the support structure that serve a purely supporting function. It is possible for at least three covering zones to be provided. It is possible for circumferential struts to form a first covering zone. It is possible for the central area to form a second covering zone. It is possible for the area near the housing to form a third covering zone. It is possible for the three covering zones to cover practically 100% of the air gap. Preferably, it is possible for at least 75% of the air gap to be covered by the covering zones.It is particularly advantageous that at least 50% of the air gap is covered by the cover zones. The support structure, comprising the three cover zones, can thus fulfill a dual function, eliminating the need for additional structures, especially gap cover elements. This allows for advantageous material savings. It is also possible for the three cover zones to redirect the flow path towards the air gap. This is advantageous because it modifies the flow distribution across the cross-section of the heating matrix.

[0047] Advantageous embodiments of the present invention are described in the dependent claims and in the following description of the figures. 202301301

[0048] 10

[0049] Brief description of the drawings

[0050] The invention will now be explained in detail using exemplary embodiments and with reference to the drawings. The drawings show:

[0051] Fig. 1 shows a perspective view of a heating matrix that is inserted into a casing tube as a housing.

[0052] Fig. 2 shows a perspective view of a heating matrix with a support structure according to the invention, wherein the support structure is designed such that the air gaps in the heating matrix and between the heating matrix and the housing are covered by the support structure.

[0053] Fig. 3 Detail view of the air gap, and

[0054] Fig. 4 alternative design of the support structure.

[0055] Preferred embodiment of the invention

[0056] Figure 1 shows a heating matrix 1 arranged in a casing pipe 2, which serves as a housing and forms a flow path 11 for the exhaust gas. The heating matrix 1 is formed from a honeycomb structure. The honeycomb structure is formed from a plurality of corrugated and smooth metal foils 12, which are stacked on top of each other and wound around two winding mandrels. The metal foils 12 form at least one foil pack 13. Honeycomb structures of this type are known in various forms in the prior art.

[0057] The heating matrix 1 is connected to a voltage source (not shown) via two electrical contacts 3, 4. By applying a voltage to the heating matrix 1, it can be heated by utilizing its ohmic resistance.

[0058] The heating matrix forms air gaps 5 between its individual foil packs 13. Furthermore, air gaps 7 are formed between the heating matrix 1 and the outer casing 2. Exhaust gas flowing through the outer casing 2 can thus flow through flow channels 20 of the honeycomb structure, but also through the air gaps 5 and 7.

[0059] 11

[0060] Following the principle of least resistance, a large portion of the flow will occur along the air gaps 5, 7. The exhaust gas flowing through the air gaps 5, 7 cannot be heated, or only insufficiently. Furthermore, this results in an uneven flow distribution across the cross-section of the casing pipe 2. This uneven flow distribution can lead to reduced flow through individual flow channels 20 in certain areas, potentially creating unwanted hot spots, which in extreme cases can cause structural damage to the heating matrix 1.

[0061] Figure 2 shows the structure of Figure 1 supplemented by a support structure 8, which is located upstream of the heating matrix 1 in the direction of exhaust gas flow. The support structure 8 is characterized by the fact that, in addition to first sections 9, which accommodate the support pins engaging with the heating matrix 1 and serving to connect the support structure 8 and the heating matrix 1 (not shown in Figure 2), it also has second sections 10, which, in particular, act as gap cover elements 14, covering the air gaps 5, 7. These second sections 10 have no other designated function with regard to connecting the support structure 8 to the heating matrix 1. The second sections 10 cover the air gaps 5, 7, and therefore no retaining connections between the heating matrix 1 and the support structure 8 can be created in these sections. The second sections 10 have a continuous extension 15 from a housing-adjacent region 16 to a central region 17.The second sections 10 are attached to the support structure 8. The support structure 8 has an outer frame 19 and struts 18. The struts 18 are attached to the outer frame 19 and span the heating matrix 1.

[0062] The support structure 8 fulfills the function of creating a durable connection to the heating matrix 1 and the jacket tube 2. In addition, the main objective of the invention is to cover the air gaps 5, 7 in order to significantly reduce the bypass of the exhaust gas at the heating matrix 1 and thus significantly increase the proportion of exhaust gas flowing through the flow channels 20.

[0063] 12

[0064] The support structure 8 can be formed from flat sheets, so that the cross-section through the support structure 8 along the main flow direction of the exhaust gas can essentially correspond to a rectangle. In an advantageous embodiment, the cross-section can also be conical, widening in the flow direction, or, in the extreme case, triangular, with the apex of the triangle oriented towards the flowing exhaust gas and the base of the triangle oriented towards the heating matrix 1.

[0065] Figure 3 shows a detailed view of the air gap 5. The support structure 8 with the gap cover elements 14 is not shown here (see Figure 2). The air gap 5 is formed between two foil packs 13. The foil packs 13 are each composed of metal foils 12. Smooth and corrugated metal foils 12 are stacked alternately on top of each other. Flow channels 20 are formed between the metal foils 12 and their structures / surfaces. A channel 21 extends along the length of the foil packs 13. The foil packs 13 may have a curved profile. The air gap 5 also has a curved profile at curved sections of the foil packs 13 (see also Figures 1 and 2). The foil packs 13 form a gap thickness 6. The gap thickness 6 is measured between the facing inner surfaces of adjacent foil packs 13.Preferably, the gap thickness 6 remains essentially constant along the path 21 of the air gap 5. Finally, the flow path 11 is indicated. This runs perpendicular to the foil packs 13 through the flow channels 20 and the air gap 5.

[0066] Figure 4 shows a further embodiment of the support structure 8. The support structure has three cover zones in which the air gap 5 is covered. The cover zones are each formed by the struts 18 of the support structure 8, the central area 17 of the support structure 8, and the area 16 of the support structure 8 near the housing. In particular, no further gap cover elements 14 are provided on the support structure 8 whose sole purpose is to cover the air gap 5. All cover zones are formed in particular by parts of the support structure 8 that have only a supporting function.

[0067] 13. The struts 18 of the support structure are designed to follow the path 21 of the air gap 5. In particular, circumferential struts 18 are designed according to the path 21 of the air gap 5. The support structure has struts 18 that extend from the area 16 near the housing to the central area 17. Perpendicular to these, circumferential struts 18 extend. These struts 18 are arranged in particular to follow the path 21 of the air gap 5 and cover the air gap 5. In the area 16 near the housing, the support structure 8 has transverse areas that follow the path 21 of the air gap 5 and cover the air gap 5. In the central area 17, the support structure 8 has an area that covers a central area of ​​the air gap 5. In other words, the support structure 8 has at least three covering zones, each of which is part of the support structure 8.

[0068] The embodiments shown in Figures 1 to 4 are not restrictive in any way and serve to illustrate the inventive concept.

[0069] 202301301

[0070] 14

[0071] Reference symbol list

[0072] 1. Heating matrix

[0073] 2. Casing tube / housing

[0074] 3. electrical contacting

[0075] 4. electrical contacting

[0076] 5. Air gap

[0077] 6. Gap thickness

[0078] 7. Air gap

[0079] 8. Support structure

[0080] 9. First section of the support structure

[0081] 10. Second section of the support structure

[0082] 11. Flow path

[0083] 12. Metal foil

[0084] 13. Slide package

[0085] 14. Gap cover element

[0086] 15. continuous course

[0087] 16. Area near the housing

[0088] 17. Central area

[0089] 18th strut

[0090] 19. Outer frame

[0091] 20. Flow channel

[0092] 21. Course

Claims

202301301 15 Patent claims 1. Device for the aftertreatment of exhaust gases from an internal combustion engine, comprising a flow path (11) spatially limited by a housing (2) through which exhaust gas can flow, a heating matrix (1) which has a plurality of flow channels (20) for the exhaust gas, wherein the heating matrix (1) can be connected to a voltage source and can be heated by utilizing the ohmic resistance, wherein the heating matrix (1) has at least one air gap (5, 7) which runs transversely to the flow path (11) through the heating matrix (1), and a support structure (8) which fixes the heating matrix (1) to the housing (2), characterized in that the support structure (8) is designed such that the at least one air gap (5) is covered by the support structure (8).

2. Device according to claim 1, characterized in that the heating matrix (1) is formed with at least one at least partially structured metal foil (12).

3. Device according to claim 2, characterized in that at least one foil package (13) is formed with the at least one metal foil (12), between which at least one air gap is formed.

4. Device according to one of the preceding claims, characterized in that the support structure (8) comprises at least one gap cover element (14) which does not cover any flow channels (20).

5. Device according to claim 4, characterized in that the at least one gap cover element (14) has a continuous progression (15) from a housing-adjacent area (16) to a central area (17) of the heating matrix (1 ). 202301301 16 6. Device according to one of the preceding claims, characterized in that the support structure has a plurality of struts (18) extending from the central area (17) towards the housing and an outer frame (19), wherein the at least one gap cover element (14) is attached to it or integrated therein.

7. Device according to one of the preceding claims, characterized in that the support structure (8) at least partially covers the heating matrix (1) when viewed in the direction of the exhaust gas flow.

8. Device according to one of the preceding claims, characterized in that the support structure (8) has first sections (9) which each have at least one connecting element to the heating matrix (1 ), and second sections (10) which do not have any connecting elements to the heating matrix (1 ).

9. Device according to claim 8, characterized in that the individual sections (9, 10) of the support structure (8) have wedge-shaped cross-sections, wherein the individual sections of the support structure (8) widen conically in the direction of flow of the exhaust gas.

10. Device according to one of the preceding claims, characterized in that a support structure (8) is arranged in the direction of flow of the exhaust gas in front of the heating matrix (1) and a second support structure (8') is arranged in the direction of flow of the exhaust gas behind the heating matrix (1).

11. Device according to claim 9, characterized in that the first support structure (8) and the second support structure are not identical in design. 202301301 17 12. Device according to one of the preceding claims, characterized in that the support structure (8) has flow-guiding elements which direct the exhaust gas flowing onto the support structure (8) towards the heating matrix (1 ).

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